ANATOMY 


DESCRIPTIVE  AND  SURGICAL 


BY 


HENRY  (GRAY,  F.B.S. 

1  1,     '—  ' 

FELLOW  OF  THK   ROYAL  COLLEGE  OF  SURGEONS;   LECTURER  OX  ANATOMY   AT  ST.   GEORGE  8 
HOSPITAL  MEDICAL  SCHOOL,   LONDON 


SEVENTEENTH  EDITION 


THOROUGHLY  REVISED  AND  RE-EDITED  WITH  ADDIT1OXS 


BY 


JOHN  CHALMERS  DACOSTA,  M.I). 

PROFESSOR  OF  T«K  PRINCIPLKS  OF  SURGERY  AND  OF  CLINICAL  SURGERY  IN  THE  JEFFERSON  MEDICAL  COI.I.1.CK 

PHILADELPHIA 


EDWARD  ANTHONY  SPITZKA,  M.D. 

PROFESSOR  OF  GENERAL  ANATOMY  IN  THE  JEFFERSON  MEDICAL  COLLEGE,   PHILADELPHIA 


Illustrate*)  witb  1149  Engravings 


LEA  &  FEBIGER 
PHILADELPHIA  AND  NEW  YORK 

1908 


Entered  according  to  the  Act  of  Congress,  in  the  year  1908,  by 

LEA   &   FEBIGER, 
in  the  Office  of  the  Librarian  of  Congress.      All  rights  reserved. 


THIS 


NEW  AMERICAN  EDITION  OF  GRAY'S  ANATOMY 


IS  DEDICATED    TO 


WILLIAM  W.  KEEN,  M.D,  LL.D,  HON.  F.KC.S.  [ENG.  AND  EDIN.] 

THE    DISTINGUISHED    PROFESSOR    OF    SURGERY    IN    JEFFERSON 
MEDICAL    COLLEGE 


AS    AN    EVIDENCE    OF 


THE    ADMIRATION,    THE    AFFECTION    AND    THE    GRATITUDE    OF    HIS    COLLEAGUE 


AND    FORMER    ASSISTANT 


THE  EDITOR 


EDITORS'  PREFACE. 


THE  fact  that  this  new  edition  has  been  demanded  so  soon  after  the  publication 
of  the  sixteenth  edition  is  gratifying  evidence  of  the  continued  popularity  and 
usefulness  of  "Gray." 

In  this  edition  there  have  been  many  alterations,  a  number  of  eliminations,  and 
additions  of  important  anatomical  facts.  One  hundred  and  thirty-three  new 
illustrations  have  been  inserted  and  thirty-eight  old  ones  have  been  improved 
and  re-engraved,  and  it  is  hoped  and  believed  that  the  cuts  will  warrant  more 
than  ever  the  approbation  of  students  and  teachers.  In  the  illustrations  of  the 
Nerve  System  special  effort  has  been  bestowed  on  combining  the  features  visible 
to  the  naked  eye  with  those  seen  only  under  high  magnifying  powers.  By  the 
knowledge  of  macroscopic  and  microscopic  structures  the  attentive  student  is 
enabled  to  resolve  or  reconstruct,  in  the  three  dimensions  of  space,  and  with  his 
mental  eye  see  the  opaque  interior  resolved  into  intricate  yet  well-defined  pro- 
jecting and  associating  mechanisms.  Such  study  is  assisted  by  new  illustrations 
depicting  hidden  structures  in  accordance  with  this  principle.  Much  that  could 
not  be  described  in  detail  within  the  confines  of  a  text-book  has  been  summarized 
in  such  way  as  to  be  of  assistance  even  to  advanced  students. 

Histology  and  embryology  have  been  treated  by  resumes,  as  heretofore.  Free 
quotations  have  been  made  from  numerous  treatises,  monographs,  and  reports, 
the  invariable  intention  being  to  give  proper  credit  to  the  authors. 

A  universally  accepted  international  nomenclature  of  anatomical  items  is 
eminently  desirable.  A  transition  from  the  old  to  the  new  will  of  necessity  be 
gradual,  because  in  the  minds  of  many  the  older  names  are  not  only  fixed  but 
also  cherished.  The  Latin  or  international  nomenclature  is  in  many  respects  a 
distinct  advance  in  accuracy  and  simplicity.  It  has  gained  many  advocates,  but 
has  not  as  yet  completely  displaced  older  designations  to  the  degree  its  enthu- 
siastic advocates  would  wish.  In  this  edition  the  custom  previously  adopted  is 
still  pursued,  and  the  names,  according  to  the  new  nomenclature,  have  been 
introduced  in  parentheses,  following  those  still  in  current  use  in  English-speaking 
countries. 

The  section  on  the  Nerve  System,  which  has  been  largely  rewritten  by  Dr. 
Spitzka,  has  been  prepared  with  due  regard  to  the  advances  recently  made  in  the 
morphological  and  embryological  aspects  of  the  subject.  The  more  important 
physiological  and  pathological  data  have  been  presented  in  their  anatomical 
bearings,  in  order  to  demonstrate  with  greater  clearness  the  mutual  relations  of 
the  structure  and  functions  of  the  nerve  system. 

The  Digestive  System,  the  Ductless  Glands,  and  the  Female  Organs  of  Gener- 
ation have  also  received  careful  consideration  by  the  editors,  and  they  trust  these 
portions  of  the  book  will  be  found  to  merit  the  approval  of  students  and  teachers. 

The  editors  wish  to  thank  Mr.  William  A.  Hassett,  of  Lea  &  Febiger,  for 
indexing  the  book,  for  seeing  it  through  the  press,  and  for  the  valuable  aid  he 
has  ungrudgingly  given. 

JOHN  CHALMERS  DA  COSTA, 
EDWARD  ANTHONY  SPITZKA. 

(v) 


PUBLISHERS'  NOTE  TO  SEVENTEENTH  EDITION. 


A  NEW  edition  of  Grays  Anatomy  is  always  an  event  of  importance  to  the 
English-speaking  world  of  medicine.  For  fifty  years  it  has  been  easily  the  leading 
work  in  all  medical  literature,  broadly  considered,  and,  a  fortiori,  preeminent  in  its 
own  field,  a  position  which  the  many  excellent  treatises  that  have  appeared  from 
time  to  time  have  only  rendered  more  conspicuous.  During  its  first  half-century 
it  has  given  hundreds  of  thousands  of  students  their  foundation  in  medicine,  and 
has  been  the  one  book  carried  from  college  for  guidance  in  the  basic  questions 
underlying  the  practice  of  medicine  and  surgery.  Its  value  for  reference  leads  to  a 
large  absorption  of  each  new  edition  on  the  part  of  practitioners  desiring  to  be 
posted  on  the  most  recent  developments  and  bearings  of  anatomy.  This  double 
demand  brings  about  three  important  results  for  its  readers:  In  the  first  place, 
rendering  possible  frequent  new  editions,  whereby  Gray  may  always  be  consulted 
for  the  latest  knowledge;  secondly,  warranting  an  otherwise  impossible  expense 
for  revisions  and  improvements;  and  thirdly,  combining  these  advantages  with  a 
low  price.  A  glance  at  the  intrinsic  causes  which  have  led  to  these  conditions  may 
not  be  amiss. 

Henry  Gray's  genius  was  twofold.  He  united  a  profound  understanding  of 
human  structure  with  equal  insight  into  the  best  methods  of  imparting  knowledge 
to  other  minds.  Reflecting  this  unique  combination  of  powers,  his  Anatomy 
sprang  to  the  front  and  has  never  lost  its  precedence.  It  joins  a  text  of  inimitable 
didactic  quality  with  engravings  of  equal  force  and  clearness.  If  Gray  had  dis- 
cerned nothing  else  than  the  great  advantage  to  his  readers  of  having  the  names  of 
the  various  parts  engraved  directly  on  the  body  of  an  illustration,  he  would  have 
performed  a  notable  service.  His  work,  still  unique  in  this  respect,  was  also  the 
first  to  employ  colors.  It  is  hardly  to  be  wondered  at  that  students  and  teachers 
alike  find  their  labors  cut  in  half  and  the  permanence  of  knowledge  doubled  by 
the  use  of  such  a  book. 

The  early  death  of  Henry  Gray  has  enlisted  in  successive  revisions  of  this 
work  the  services  of  many  leading  anatomists.  Passing  over  the  intervening 
editions,  and  bearing  in  mind  the  close  relations  between  anatomy  and  surgery, 
it  is  scarcely  necessary  to  allude  to  the  advantage  of  uniting  in  this  new  issue  the 
knowledge  of  so  eminent  a  surgeon  as  Dr.  Da  Costa,  and  of  Dr.  Spitzka,  equally 

eminent  as  a  specialist  in  anatomy.     Professor  Spitzka  also  possesses  the  ability 

(vii) 


viii  PUBLISHERS'  NOTE 

of  a  skilful  artist,  and  his  delineations  therefore  convey  his  grasp  of  structure 
directly  to  the  eye  of  the  reader. 

As  ample  directions  are  given  for  dissecting,  this  single  volume  will  serve  everv 
requirement  of  the  student  throughout  his  course.  The  new  nomenclature  and 
that  still  in  common  use  have  been  introduced  in  a  manner  rendering  the  work 
universal  in  the  prime  essential  of  terminology.  The  Table  of  Contents  is  so 
arranged  as  to  give  a  complete  conspectus  of  anatomy,  a  feature  of  obvious 
value.  The  whole  book  is  thoroughly  organized  in  its  headings  and  the  sequence 
•of  subjects,  so  that  the  student  receives  his  knowledge  of  the  parts  in  their 
anatomical  dependence. 

As  a  teaching  instrument  the  new  Gray's  Anatomy  embodies  all  that  careful 
thought  and  unstinted  expenditure  can  combine  in  book  form,  and  it  now  enters 
its  second  half-century  well  equipped  to  excel  even  its  own  record. 


CONTENTS. 


DESCRIPTIVE  AND  SURGICAL  '  ANATOMY, 


OSTEOLOGY— THE   SKELETON. 


PAGE 

The  Skeleton 33 

Number  of  the  Bones 33 

Form  of  Bones 33 

Long  Bones 33 

Short  Bones 33 

Flat  Bones 34 

Irregular  Bones 34 

Surfaces  of  Bones 34 

Structure  of  Bone 34 

Bloodvessels  of  Bone 39 

Chemical  Composition  of  Bone   ....  41 

Ossification  and  Growth  of  Bone      ...  42 

THE  VERTEBRAL  OR  SPINAL  COLUMN. 

General  Characters  of  a  Vertebra. 
The  Cervical  Vertebrae 

Atlas 

Axis 

Seventh  Cervical 

The  Thoracic  or  Dorsal  Vertebra?     . 

Peculiar  Dorsal  Vertebrae     .... 

The  Lumbar  Vertebra? 

Structure  of  the  Vertebrae 

Development  of  the  Vertebrae      .... 

Development  of  the  Atlas 

Development  of  the  Axis 

Development  of  the  Seventh  Cervical    . 
Development  of  the  Lumbar  Vertebrae 
Progress  of  Ossification  in  the  Spine  Gener- 
ally       

The  Sacral  and  Coccygeal  Vertebra; 

Sacrum 

Differences  in  the   Sacrum  of  the 
Male  and  Female        .... 
Peculiarities  of  the  Sacrum 

Coccyx        

The  Vertebral  Column  or  Spine  in  General  . 
Surface  Form  of  the  Vertebral  Column  . 
Surgical  Anatomy  of  the  Vertebral  Column 

THE  SKULL. 
The  Cerebral  Cranium. 

The  Occipital  Bone 

The  Parietal  Bone 

The  Frontal  Bone 

Vertical  Portion  of  the  Frontal  Bone  . 
Horizontal   or  Orbital   Portion   of   the 

Frontal  Bone 

The  Temporal  Bone 

Squamous    Portion    of    the    Temporal 

Bone 

The  Mastoid  Portion  of  the  Temporal 

Bone 

The  Petrous  Portion  of  the  Temporal 
Bone 


49 
50 
52 
53 
53 
55 
5(5 
58 
58 
59 
59 
60 
60 

60 
61 
61 

64 
64 
65 
07 
69 


71 
76 
79 
79 

SI 
83 

83 

85 


PAGE 

The  Sphenoid  Bone 92 

The  Body  of  the  Sphenoid  Bone    .       .  92 
The  Greater  or  Temporal  Wings  of  the 

Sphenoid  Bone 95 

The    Lesser   or   Orbital    Wings    of    the 

Sphenoid  Bone 96 

The  Pterygoid  Processes  of  the  Sphe- 
noid Bone 96 

The  Sphenoidal  Spongy  Bone   ...  97 

The  Ethmoid  Bone 98 

The  Horizontal   Lamina  or  Cribriform 

Plate  of  the  Ethmoid  Bone   .       .      .99 
The  Vertical  or  Perpendicular  Lamina 

or  Plate  of  the  Ethmoid  Bone    .       .  100 
The  Lateral  Mass  or  Labyrinth  of  the 

Ethmoid  Bone 100 

Development  of  the  Cranium      ....  102 

The  Fontanelles 102 

Supernumerary  or  W'ormian  Bones      .  103 

Congenital  Fissures  and  Gaps   .      .       .  104 

Bones  of  the  Face. 

The  Nasal  Bones   . 104 

The  Superior  Maxillary  Bones    ....  105 
The  Body  of  the  Superior  Maxilla  .       .  105 
The  Processes  of  the  Superior  Maxillae  109 
Malar  Process  of  the  Superior  Max- 
illa           109 

Nasal  Process  of  the  Superior  Max- 
illa           109 

Alveolar   Process   of   the   Superior 

Maxilla 109 

Palate    Process    of    the    Superior 

Maxilla 110 

Changes  Produced  in  the  Upper  Jaw  by  Age  112 

The  Lachrymal  Bone 112 

The  Malar  Bone 113 

The  Palate  Bone 115 

The    Horizontal    Plate   of    the    Palate 

Bone 116 

The  Vertical  or  Perpendicular  Plate  of 

the  Palate  Bone 117 

The  Inferior  Turbinated  Bone     .      .             .  119 

The  Vomer 120 

The  Maxillary  Bone,  Inferior  Maxilla,  Man- 
dible or  Lower  Jaw 122 

The  Horizontal  Portion  or  Body  of  the 

Mandible 122 

The  Perpendicular  Portion  or  Kami  of 

the  Mandible 124 

Changes   Produced   in    the    Lower   Jaw   by 

Age '.125 

The  Sutures  127 


The  Skull  as  a  Whole. 


The  Vertex  of  the  Skull 
88  ;  The  Base  of  the  Skull 


129 
130 


(ix) 


CONTENTS 


PAGE 

The  Lateral  Region  of  the  Skull      ...  136 

The  Temporal  Fossa 137 

The  Mastoid  Portion 138 

The  Zygomatic  or  Infra  temporal  Fossa  138 
The  Spheno-maxillary  or  Pterygo-pala- 

tine  Fossa 139 

The  Anterior  Region  of  the  Skull    ...  139 

Orbits,  Orbital  Cavities  or  Orbital  Fossae  140 

The  Nasal  Cavity 142 

Shape  of  the  Skull     ' 146 

Dimensions  of  the  Skull 147 

Surface  Form  of  the  Skull 148 

Fixed  Points  for  Measurement  of  the  Skull  150 

Surgical  Anatomy  of  the  Skull     ....  150 

The  Hyoid  or  Lingual  Bone 155 

THE  THCRAX. 

The  Sternum 1 57 

The  Ribs 161 

Common  Characters  of  the  Ribs    .      .  161 

Peculiar  Ribs 163 

The  Costal  Cartilages 165 

Surface  Form  of  the  Chest 166 

Surgical  Anatomy  of  the  Chest  ....  167 

THE  UPPER  EXTREMITY. 
The  Shoulder  Girdle. 

The  Clavicle 169 

Surface  Form  of  the  Clavicle  .  .  .  172 

Surgical  Anatomy  of  the  Clavicle  .  .  172 

The  Scapula 172 

Surface  Form  of  the  Scapula  .  .  .  178 

Surgical  Anatomy  of  the  Scapula  .  .  178 

The  Arm. 

The  Humerus    .7 179 

Surface  Form  of  the  Humerus  .       .       .  185 

Surgical  Anatomy  of  the  Humerus      .  185 

The  Forearm. 

The  Ulna '.      .  186 

Surface  Form  of  the  Ulna    .      .      .      .191 

The  Radius 192 

Surface  Form  of  the  Radius      .       .      .  194 
Surgical  Anatomy  of  the   Radius  and 

Ulna 194 

The  Hand. 

The  Carpus 195 

Common  Characters  of  the  Carpal  Bones  195 

Bones  of  the  Upper  Row      ....  197 

Scaphoid  or  Navicular  Bone    .       .  197 

Semilunar  Bone 198 

Cuneiform  Bone 199 

Pisiform  Bone 199 

Bones  of  the  Lower  Row     ....  200 

Trapezium 200 

Trapezoid 200 

Os  Magnum 201 

Unciform  201 


PAGE 

The  Metacarpus 202 

Common  Characters  of  the  Metacarpal 

Bones 202 

Peculiar  Characters  of  the  Metacarpal 

Bones 203 

The  Phalanges  of  the  Hand 206 

Surface  Form  of  the  Bones  of  the  Hand  206 

Surgical  Anatomy  of  the  Bones  of  the  Hand  207 

Development  of  the  Bones  of  the  Hand      .  207 

THE  LOWER  EXTREMITY. 
The  Pelvic  Girdle. 

The  Pelvis 209 

The  False  Pelvis 209 

The  True  Pelvis 209 

Position  of  the  Pelvis 211 

Axes  of  the  Pelvis 211 

Differences  Between  the  Male  and  the 

Female  Pelvis 212 

The  Os  Innominatum 213 

The  Ilium 215 

The  Ischium 217 

The  Pubis 219 

The  Cotyloid  Cavity  or  Acetabulum      .  220 

The  Obturator  or  Thyroid  Foramen     .  220 

Surface  Form  of  the  Pelvis  ....  222 

Surgical  Anatomy  of  the  Pelvis      .      .  222 

The  Thigh. 

The  Femur  or  Thigh  Bone 223 

Surface  Form  af  the  Femur      .       .      .231 

Surgical  Anatomy  of  the  Femur     .      .  232 

The  Leg. 

The  Patella  or  Knee-cap 233 

Surface  Form  of  the  Patella  .  .  .  234 

Surgical  Anatomy  of  the  Patella  .  .  234 

The  Tibia  or  Shin  Bone 234 

Surface  Form  of  the  Tibia  ....  239 

The  Fibula  or  Calf  Bone 239 

Surface  Form  of  the  Fibula  .  .  .  241 

Surgical  Anatomy  of  Bones  of  the  Leg  244 

The  Foot. 

The  Tarsus 244 

The  Calcaneus  or  Heel  Bone      .      .      .  244 

The  Astragalus  or  Ankle  Bone  .       .      .  246 

The  Cuboid 248 

Scaphoid  or  Navicular  Bone     .      .      .  249 

Cuneiform  or  Wedge  Bones  ....  249 

The  Metatarsal  Bones 252 

Common  Characters  of  Metatarsal  Bones  252 

Peculiar  Characters  of  Metatarsal  Bones  252 

The  Phalanges  of  the  Foot 255 

Development  of  the  Foot 255 

Construction  of  the  Foot  as  a  Whole     .  256 

Surface  Form  of  the  Foot      ....  258 

Surgical  Anatomy  of  the  Foot    ....  258 

Sesamoid  Bones 259 


THE  ARTICULATIONS  OR  JOINTS. 


Structures  Composing  the  Joints       .       .       .  261 

Bone 261 

Cartilage 261 

Ligaments 263 

Synovial  Membranes 264 

Forms  of  Articulation: 

Synarthrosis 266 

Amphiarthrosis .  266 

Diarthrosis 267 

The    "Kinds    of     Movement    Admitted     in 

Joints 268 

Ligamentous  Action  of  Muscles  ....  270 


ARTICULATIONS  OF  THE  TRUNK. 

Articulations  of  the  Vertebral  Column  . 
Articulations  of  the  Atlas  with  the  Axis      .      276 

Articulations  of  the  Spine  with  the  Cranium. 
Articulation  of  the  Atlas  with  the  Occipital 

Bone 

Articulation  of  the  Axis  with  the  Occipital 

Bone          . 280 

Surgical   Anatomy   of   Articulations   of   the 

Spine          .........  281 


CONTENTS 


XI 


Articulation  of  the  Lower  Jaw  or  the  Tem- 

poro-mandibiilar  Articulation       .       .  282 

Surface  Form 284 

Surgical  Anatomy 284 

Articulations  of  the  Ribs  with  the  Vertebrae 

or  the  Costo-vertebral  Articulations  .       .  285 
Articulation  of  the  Cartilages  of  the   Ribs 
with  the  Sternum,  etc.,  or  the  Costo- 

stornal  Articulations 289 

Articulations  of  the  Cartilages  of  the 
Ribs  with  Each  Other  or  the  Inter- 
chondral  Articulations  ....  291 
Articulations  of  the  Ribs  with  their  Car- 
tilages or  the  Costo-chondral  Artic- 
ulations    292 

Articulations  of  the  Sternum       ....  292 
Articulations  of  the  Vertebral  Column  with 

tlio  Pelvis 292 

Articulations  of  the  Pelvis 294 

Articulation  of  the  Sacrum  and  Ilium  .  294 
Ligaments  passing  between  the  Sacrum 

and  Ischium 294 

Articulation  of  the  Sacrum  and  Coccyx  296 

Articulation  of  the  Ossa  Pubis  .       .      .  298 

ARTICULATIONS  OF  THE  UPPER  EXTREMITY. 

Sterno-clavicular  Articulation      ....  299 

Surface  Form 301 

Surgical  Anatomy 301 

Acromio-clavicular  Articulation  or  Scapulo- 

clavicular  Articulation       ....  301 

Surface  Form 303 

Surgical  Anatomy 303 

Proper  Ligaments  of  the  Scapula     .       .      .  303 

The  Shoulder-joint 305 

Surface  Form  of  the  Shoulder-joint     .  309 
Surgical    Anatomy    of    the    Shoulder- 
joint        309 

The  Elbow-joint 310 

Surface  Form  of  the  Elbow-joint   .       .  314 

Surgical  Anatomy  of  the  Elbow-joint  .  314 

Radio-ulnar  Articulation 315 

Superior  or  Proximal  Radio-ulnar  Artic- 
ulation          316 

Surface  Form 316 

Surgical  Anatomy 316 

Middle  Radio-ulnar  Ligaments  .       .       .  316 
Inferior   or   Distal    Radio-ulnar    Artic- 
ulation          317 

Surface  Form 319 

Radio-carpal  or  Wrist-joint 319 

Surface  Form  of  wrist-joint      .      .      .  320 

Surgical  Anatomy  of  Wrist-joint     .       .  320 

Articulations  of  the  Carpus 321 

Articulations  of  the  First  Row  of  Carpal 

Bones 321 

Articulations  of  the  Second  Row  of  Car- 
pal Bones 321 

Articulations  of  the  Two  Rows  of  Car- 
pal Bones 322 


PAGE 

Carpo-metacarpal  Articulations  ....  323 
Articulation  of  the  Metacarpal  Bone  of 

the  Thumb  with  the  Trapezium       .  323 
Articulations  of  the  Metacarpal  Bones  of 

the  Four  Inner  Fingers  with  the  Carpus  324 
Articulations  of  the  Metacarpal  Bones 

with  Each  Other    .  ....  326 

Metacarpo-phalangeal  Articulations        .       .  326 
Surface  Form  of  Metacarpo-phalangeal 

Articulations 327 

Articulations  of  the  Phalanges     ....  327 

ARTICULATIONS  OF  THE  LOWER  EXTREMITY. 

The  Hip-joint 327 

Surface  Form  of  the  Hip-joint  .       .       .  335 

Surgical  Anatomy  of  the  Hip-joint      .  335 

The  Knee-joint 336 

Surface  Form  of  the  Knee-joint     .      .  345 

Surgical  Anatomy  of  the  Knee-joint   .  345 

Tibio-fibular  Articulation 347 

Superior  Tibio-fibular  Articulation       .  347 
Middle  Tibio-fibular  Ligament  or  Inter- 
osseous  Membrane        .             ...  348 
Inferior  Tibio-fibular  Articulation  .       .  348 
The  Tibi-o-tarsal  Articulation  or  Ankle-joint  349 
Surface  Form  of  Ankle-joint     .      .      .  353 
Surgical  Anatomy  of  Ankle-joint   .       .  353 

Articulations  of  the  Tarsus 354 

Articulation  of  the  Os  Calcis  and  As- 
tragalus or  the  Calcaneo-astragaloid 

Articulation 354 

Articulation  of  the  Os  Calcis  with  the 
Cuboid  or  the  Calcaneo-cuboid  Artic- 
ulation    355 

The  Ligaments  connecting  the  Os  Calcis 
and  Scaphoid    or   the  Calcaneo- 

scaphoid  Articulation  Ligaments  355 

Surgical  Anatomy 356 

Articulation  of  the  Astragalus  with  the 
Scaphoid  Bone  or  the  Astragalo- 

scaphoid  Articulation         ....  356 
The  Articulation  of  the  Scaphoid  with 

the  Cuneiform  Bones 357 

The  Articulation  of  the  Scaphoid  with 

the  Cuboid 357 

The    Articulations    of    the    Cuneiform 
Bones  with  Each  Other  or  the  Inter- 
cuneiform  Articulations     ....  357 
The  Articulation  of  the  External  Cunei- 
form Bone  with  the  Cuboid      .  358 

Surgical  Anatomy 358 

Tarso-metatarsal  Articulations     ....  359 
Articulations  of  the  Metatarsal  Bones  with 

Each  Other 360 

The  Sy  no  vial  Membranes  in  the  Tarsal 

and  Metatarsal  Joints 360 

Metatarso-phalangeal  Articulations         .      .  361 

Articulations  of  the  Phalanges     ....  361 

Surface  Form 362 

Surgical  Anatomy 362 


THE  MUSCLES  AND  FASCLE. 


General  Description  of  Muscles    ....  363 

General  Description  of  Tendons         .       .      .  366 

General  Description  of  Aponeuroses       .       .  366 

General  Description  of  Fasciae     ....  366 

MUSCLES  AND  FASCIAE  OF  THE  CRANIUM  AND 
FACE. 

Subdivision  into  Groups 368 

The  Cranial  Region  368 

Dissection 368 

Superficial  Fascia 368 

Surgical  Anatomy 369 

The  Occipito-frontalis 369 

Surgical  Anatomy 371 


The  Auricular  Region 371 

Dissection 371 

Attrahens  Auriculam  or  Aurem  .  .  372, 

Attollens  Auriculam  or  Aurem.  .  .  372 

Retrahens  Auriculam  or  Aurem  .  .  372 

The  Palpebral  Region 372 

Dissection 372 

Orbicularis  Palpebrarum  ....  372 

Corrugator  Supercilii 373 

Levator  Palpebrse 373 

Tensor  Tarsi  or  Horner's  Muscle  .  .  373 

The  Orbital  Region 374 

Levator  Palpebra  Superioris  .  .  .  375 

Superior  Rectus 375 

Inferior  Rectus  375 


Xll 


CONTENTS 


PAGE 

The  Orbital  Region — 

External  Rectus 375 

Superior  Oblique 

Inferior  Oblique    ..'..... 

Fasciae  of  the  Orbit 377 

Surgical  Anatomy 377 

The  Nasal  Region 373 

Pyramidalis  Nasi 37g 

Levator  Labii  Superiorly  Alaeque  Nasi  378 

Dilator  Naris  Posterior    .....  378 

Dilator  Naris  Anterior 378 

Compressor  Nasi         378 

Compressor  Narium  Minor   ....  378 

Depressor  Alse  Nasi 378 

The  Superior  Maxillary  Region   ....  379 

Levator  Labii  Superions       ....  379 

Levator  Anguli  Oris 379 

Zygomaticus  Major 379 

Zygomaticus  Minor 379 

The  Mandibular  Region 380 

Dissection 380 

Levator  .Labii    Inferioris    or    Levator 

Menti 380 

Depressor  Labii  Inferioris  or  Quadratus 

Menti 380 

Depressor  Anguli  Oris  or  Triangularis 

Menti 380 

The  Intermaxillary  Region     .....  381 

Dissection 381 

Orbicularis  Oris 381 

Buccinator 382 

Risorius  or  Santorini's  Muscle    .       .       .  383 

The  Temporo-mandibular  Region      .       .       .  383 

Masseteric  Fascia 383 

Masseter  Muscle 383 

Temporal  Fascia 384 

Dissection 384 

Temporal  Muscle 384 

The  Pterygo-mandibular  Region        .       .       .  385 

Dissection 385 

External  Pterygoid  Muscle   ....  386 

Internal  Pterygoid  Muscle    ....  386 

Surface  Form  of  Muscles  of  Head  and  Face  387 

MUSCLES  AND  FASCI.E  OF  THE  NECK. 

Subdivision  in  Groups 387 

The  Superficial  Cervical  Region  ....  388 

Dissection 388 

Superficial  Cervical  Fascia  ....  388 

Platysma  Myoides 388 

Deep  Cervical  Fascia 389 

Surgical  Anatomy 391 

Sterno-mastoid  orSterno-cleido-mastoid  391 

Surface  Form 393 

Surgical  Anatomy    .'....  393 

The  Infra-hyoid  Region 393 

Dissection 393 

Sterno-hyoid 394 

Sterno-thyroid 394 

Thyro-hyoid 395 

Omo-hyoid 395 

The  Supra-hyoid  Region 396 

Dissection 396 

Digastric 396 

Stylo-hyoid 396 

Mylo-hyoid 397 

Dissection 397 

Genio-hyoid 397 

The  Lingual  Region 398 

Dissection 399 

Genio-hyo-glossus 399 

Hyo-glossus 399 

Chondro-glossus 399 

Stylo-glossus 399 

Palato-glossus    or    Constrictor    Isthmi 

Faucium 400 

Muscular  Substance  of  the  Tongue      .  400 

Surgical  Anatomy 402 


The  Pharyngeal  Region 

Dissection         .       .       .       .t 

Inferior  Constrictor    .       . 

Middle  Constrictor     .... 

Superior  Constrictor  .... 

Stylo-pharyngeus         .... 
The  Palatal  Region 

Dissection         .... 

Levator  Palati 

Circumflexus  or  Tensor  Palati 

Palatine  Aponeurosis 

Azygos  Uvulae 

Palato-glossus     or    Constrictor    Isthmi 
Faucium 

Palato-pharyngeus 

Salpingo-pharyngeus        .... 

Surgical  Anatomy 

The  Anterior  Vertebral  Region   .... 

Rectus  Capitis  Anticus  Major  or  Lorigus 
Capitis 

Rectus  Capitis  Anticus  Minor  . 

Rectus  Capitis  Lateralis        .... 

Longus  Colli 

The  Lateral  Vertebral  Region     .... 

Scalenus  Anticus 

Scalenus  Medius .         

Scalenus  Post ic us 

Surface  Form  of  Muscles  of  the  Neck 

MUSCLES  AND  FASCIAE  OF  THE  TRUNK. 
Subdivision  into  Groups 

Muscles  of  the  Back. 

Subdivision  into  Groups 

The  First  Layer 

Dissection 

Superficial  Fascia 

Deep  Fascia 

Trapezius 

Ligamentum  Nuchae 

Latissimus  Dorsi 

The  Second  Layer 

Dissection 

Levator  Anguli  Scapulas 

Rhomboideus  Minor 

Rhomboideus  Major 

The  Third  Layer 

Dissection 

Serratus  Posticus  Superior    .... 
Serratus  Posticus  Inferior     .... 

Vertebral  Aponeurosis 

Lumbar  Fascia  or  Aponeurosis 

Splenius 

Splenius  Capitis 

Splenius  Colli 

The  Fourth  Layer        .      ! 

Dissection         .      . 

Erector  Spinae 

Ilio-costalis  or  Sacro-lumbalis    . 

Musculus    Accessorius   ad  Ilio-cos- 

talem 

Cervicalis  Ascendens      .... 

Longissimus  Dorsi 

Transversalis    Cervicis    or    Trans- 

versalis  Colli 

Trachelo-mastoid 

Spinalis  Dorsi 

Spinalis  Colli 

Complexus 

The  Fifth  Layer      . 

Dissection 

Semispinalis  Dorsi 

Semispinalis  Colli 

Multifidus  Spinae         .... 

Rotatores  Spinae 

Supraspinales 

Interspinales 

Extensor  Coccygis 

Intertransversales        .  ... 

Rectus  Capitis  Posticus  Major  . 


PAGE 

402 
402. 
402 
403 
403 
405 
405 
40& 
405 
406 
40C, 
407 

407 
407 
407 
408 
408 


412 


412 
412 
412 
413 
413 
413 
415 
415 
416 
416 
416 
416 
416 
417 
417 
417 
417 
418 
418 
418 
418 
418 
419 
419 
419- 
421 

421 
421 
421 

421 
421 
421 
422 
422 
422 
422 
423 
423 
423 
423 
423 
423 
424 
424 
424 


CONTEXTS 


Xlll 


The  Fifth  Layer — 

Rectus  Capitis  Posticus  Minor  .      .      .  424 

Obliquus  Capitis  Inferior      ....  424 

Obliquus  Capitis  Superior     ....  424 

Surface  Form  of  Muscles  of  the  Back   .       .  426 

Muscles  and  Fascice  oj  the  Thorax. 

Intercostal  Fascia 426 

Intercostal  Muscles 427 

External  Intercostals 427 

Internal  Intercostals 427 

Infracostales 427 

Triangularis  Sterni 427 

Levatores  Costarum 428 

Diaphragm 429 

Ligamentum  Arcuatum  Internum  .       .  429 

Ligamentum  Arcuatum  Externum       .  429 

Central  Tendon  of  the  Diaphragm  .       .  431 

The  Openings  of  the  Diaphragm     .       .  431 

Muscles  of  Inspiration  and  Expiration  434 

Muscles  of  the  Abdomen, 

The  Superficial  Muscles  of  the  Abdomen     .  434 

Dissection 434 

Superficial  Fascia 435 

Deep  Fascia 435 

External  or  Descending  Oblique  .  .  435 
Aponeurosis  of  External  Oblique  .  436 
External  Abdominal  Ring  .  .  .  437 
External  Pillar  or  Inferior  Crus  .  438 
Internal  Pillar  or  Superior  Crus  .  438 
Intercolumnar  Fibres  ....  438 
Poupart's  Ligament  ....  438 
Gimbernat's  Ligament  .  .  .  439 
Triangular  Fascia  or  Colles's  Liga- 
ment    439 

Ligament  of  Cooper       ....  439 

Suspensory  Ligament  of  the  Penis  439 

Suspensory  Ligament  of  the  Clitoris  439 

Internal  or  Ascending  Oblique  .       .       .  439 

Aponeurosis  of  Internal  Oblique    .  441 

Cremaster  Muscle 441 

Transversalis 444 

Dissection 444 

Rectus  Abdominis 444 

Pyramidalis 446 

The  Linea  Alba 446 

The  Lineae  Semilunares       .       .       .  447 

The  Lineae  Transversse  ....  447 

The  Transversalis  Fascia      ....  447 

Internal  or  Deep  Abdominal  Ring      .  448 

The  Inguinal  or  Spermatic  Canal   .       .  450 

The  Deep  Crural  Arch 450 

Cooper's  Ligament 450 

Surface  Forms  of  Muscles  of  the  Abdomen  450 

The  Deep  Muscles  of  the  Abdomen        .       .  451 

The    Fascia    Covering    the    Quadratus 

Lumborum 451 

Quadratus  Lumborum 451 

Muscles  of  the  Pelvic  Outlet. 

The  Muscles  of  the  Ischio-rectal  Region      .  451 

The  Corrugator  Cutis  Ani     ....  451 

External  Sphincter  Ani 452 

Internal  Sphincter  Ani 453 

Levator  Ani 453 

Pubococcygeus  Muscle  ....  454 

Iliococcygeus  Muscle      ....  456 

foccygeus 457 

The  Muscles  and  Fascia?  of  the  Perinaeum  in 

the  Male 457 

Superficial  Fascia 457 

The    Central    Tendinous    Point    of    the 

Perinaeum 458 

Transversus  Perinei  Superficialis     .       .  459 

Accelerator  LTrina? 459 

Erector  Penis 460 

Triangular  Ligament      ....  460 

Compressor  or  Constrictor  LTrethrae      .  462 


PAGE 

The  Muscles  of  the  Perinn-um  in  the  Female  462 

Transversus  Perinei  Superficialis     .       .  462 

Sphincter  Vaginae 463 

Erector  Clitoridis 463 

Triangular  Ligament      ....  464 

Compressor  Urethras 4(14 

MUSCLES  AND  FASCI.K  OF  THE  UPPER 
EXTREMITY. 

Subdivision  into  Groups 464 

Dissection  of  Pectoral  Region  and  Axilla     .  465 

The  Muscles  and  Fasciae  of  the  Thoracic  ' 
Region. 

The  Anterior  Thoracic  Region     ....  465 

Superficial  Fascia 465 

Deep  Fascia 465 

Pectoralis  Major 466 

Dissection 469 

Costo-coracoid  Membrane  or  Clavipec- 

toral  Fascia 469 

Pectoralis  Minor 470 

Subclavius 470 

The  Lateral  Thoracic  Region       .       .      .      .471 

Serratus  Magnus         471 

Surgical  Anatomy 471 

Dissection  471 


Muscles  and  Fascia?  oj  Shoulder  and 

Superficial  Fascia 

Deep  Fascia ' .       .  •    . 

The  Acromial  Region 

Deep  Fascia 

Deltoid 

Surgical   Anatomy    . 
The  Anterior  Scapular  Region    . 

Dissection 

The  Subscapular  Fascia  .... 

Subscapularis 

The  Posterior  Scapular  Region    . 

Dissection 

Supraspinatus  Fascia       .... 

Supraspinatus  Muscle      .       ... 

Infraspmatus  Fascia        .... 

Infraspinatus  Muscle        .... 

Teres  Minor 

Teres  Major 


The  Muscles  and  Fascice  of  the  Arm. 

The  Anterior  Humeral  Region    . 

Dissection 

Deep  Fascia 

Coraco-brachialis 

Biceps  or  Biceps  Flexor  Cubiti  . 

Brachialis  Anticus 

The  Posterior  Humeral  Region   . 

Triceps  or  Triceps  Extensor  Cubiti 

Subanconeus    

Surgical  Anatomy 

Muscles  and  Fascice  of  the  Form r in. 

Dissection     . 

Deep  Fascia 

The  Anterior  Radio-ulnar  Region     . 
The  Superficial  Layer 

Pronator  Radii  Teres     . 
Surgical  Anatomy  . 
Flexor  Carpi  Radialis     . 
Palmaris  Longus       .... 
Flexor  Carpi  Ulnaris 
Flexor  Sublimis  Digit orum 

The  Deep  Layer 

Dissection 

Flexor  Profundus  Digitorum    . 
Flexor  Longus  Pollicis  . 
Pronator  Quadratus       ... 
Surgical  Anatomy 


\rm. 


472 
472 
472 
472 
472 
473 
473 
473 
473 
473 
474 
474 
474 
474 
474 
474 
475 
475 


476 
476 
476 

477 
477 
478 
479 
479 
480 
480 


480 
480 
481 
481 
481 
481 
481 
482 
482 
483 
484 
484 
484 
484 
485 
486 


XIV 


CONTENTS 


PAGE 

The  Radial  Region 486 

Dissection 486 

Supinator  Longus 486 

Extensor  Carpi  Radialis  Longior     .      .  487 

Extensor  Carpi  Radialis  Brevior     .      .  487 

The  Posterior  Radio-ulnar  Region   .      .      .  488 

The  Superficial  Layer 48S 

Extensor  Communis  Digitorum     .  488 

Extensor  Minimi  Digiti       .      .      .  489 

Extensor  Carpi  Ulnaris       .      .      .  489 

Anconeus 489 

The  Deep  Layer 489 

Supinator  Radii  Brevis       .      .      .  489 

Extensor  Ossis  Metacarpi  Pollicis  491 

Extensor  Brevis  Pollicis     .      .      .  491 

Extensor  Longus  Pollicis    .      .      .  491 

Extensor  Indicis 492 

Surgical  Anatomy 493 

Muscles  and  Fasciae  of  the  Hand. 

Dissection 493 

Ligamentum  Carpi  Volare 493 

Anterior  Annular  Ligament 493 

The  Synovial  Membranes  of  the  Flexor  Ten- 
dons at  the  Wrist 494 

Surgical  Anatomy 494 

Burssc  about  the  Hand  and  Wrist   .      .      .  494 

Posterior  Annular  Ligament 495 

The  Deep  Palmar  Fascia 495 

The  Superficial  Transverse  Ligament  of 

the  Fingers 496 

Surgical  Anatomy 496 

The  Radial  Region 497 

Abductor  Pollicis 497 

Opponens  Pollicis 498 

Flexor  Brevis  Pollicis 499 

Adductor  Obliquus  Pollicis  ....  499 

Adductor  Transversus  Pollicis  .       .      .  499 

The  Ulnar  Region  ........  500 

Palmaris  Brevis 500 

Abductor  Minimi  Digiti 500 

Flexor  Brevis  Minimi  Digiti       ...      .  500 

Opponens  Minimi  Digiti        ....  500 

The  Middle  Palmar  Region 501 

Lumbricales 501 

Interossei          501 

Surface  Form  of  Muscles  of  the  Upper  Ex- 
tremity    ...             502 

Surgical  Anatomy  of  Muscles  of  the  Upper 

Extremity 505 

MUSCLES  AND   FASCIAE  OF  THE   LOWER 

EXTREMITY. 

Subdivision  into  Groups 509 

Muscles  and  Fasciae  of  the  Iliac  Region. 

Dissection 510 

Iliac  Fascia 510 

Psoas  Magnus 512 

Psoas  Parvus 512 

Iliacus 512 

Surgical  Anatomy 513 


Muscles  and  Fasciae  of  the  Thigh. 
The  Anterior  Femoral  Region     . 

Dissection 

Superficial  Fascia 

Deep  Fascia  or  Fascia  Lata 

Surgical  Anatomy    .... 
Tensor  Fascia?  Femoris    .... 

Sartorius 

Quadriceps  Extensor       .... 

Rectus  Femoris 

Vastus  Externus 

Vastus  Internus        .... 

Crureus     

Subcrureus 

Surgical  Anatomy 


514 
514 
514 
515 
517 
517 
518 
518 
518 
520 
520 
520 
521 
521 


The  Internal  Femoral  Region     . 

Dissection 

Gracilis 

Pectineus 

Adductor  Longus        .... 

Adductor  Brevis 

Adductor  Magnus 

Hunter's  Canal 

Surgical  Anatomy 

The  Muscles  and  Fasciae  of  the  Hip 
The  Gluteal  Region 

Dissection 

Gluteus  Maximus 

Gluteus  Medius 

Gluteus  Minimus 

Pyriformis 

Obturator  Internus 

Gemelli 

Gemellus  Superior    .... 
Gemellus  Inferior     .... 

Quadratus  Femoris    .      .      .      . 

Obturator  Externus 

Surgical   Anatomy 

The  Posterior  Femoral  Region   . 

Dissection 

Biceps  or  Biceps  Flexor  Cruris  . 

Semitendinosus 

Semimembranosus 

Surgical  Anatomy 


PAGE 
522 
522 
522 
522 
522 
523 
523 
524 
525 


525 
525 
525 
526 
526 
527 
528 
529 
529 
530 
530 
531 
531 
532 
532 
532 
533 
533 
534 


Muscles  and  Fasciae  of  the  Leg. 

The  Anterior  Tibio-fibular  Region    .      .      .  534 

Dissection         535 

Deep  Fascia  of  the  Leg  .      .  '   .      .      .  535 

Tibialis  Anticus 535 

Extensor  Proprius  Hallucis  .             .      .  535 

Extensor  Longus  Digitorum       .      .      .  536 

Peroneus  Tertius         537 

The  Posterior  Tibio-fibular  Region  .      .      .  537 

Dissection 537 

The  Superficial  Layer 537 

Gastrocnemius 537 

Soleus 538 

Tendo-Achillis 538 

Plantaris 539 

The  Deep  Layer 540 

Deep  Transverse  Fascia     .      .      .  540 

Popliteus        .             540 

Flexor  Longus  Hallucis       .      .      .541 

Flexor  Longus  Digitorum  .      .      .  541 

Tibialis  Posticus 541 

The  Fibular  Region 542 

Dissection 542 

Peroneus  Longus 542 

Peroneus  Brevis 543 

Surgical  Anatomy  of  Tendons  around  Ankle  544 

Muscles  and  Fasciae  of  the  Foot. 

Dissection 544 

Anterior  Annular  Ligament 544 

Internal   Annular  Ligament 545 

External  Annular  Ligament 545 

Dissection  of  the  Sole  of  the  Foot    .      .      .  545 

Plantar  Fascia         ....             ...  545 

Central  Portion  of  Plantar  Fascia  .      .  545 

Lateral  Portions  of  Plantar  Fascia      .  546 

Bursa?  about  the  Ankle  and  Foot    .      .      .  546 

Surgical  Anatomy 546 

The  Dorsal  Region       .      .      .      .      .      .      .  546 

Fascia 546 

Extensor  Brevis  Digitorum  ....  54*3 

The  Plantar  Region 547 

The  First  Layer 547 

Dissection 547 

Abductor  Hallucis 547 

Flexor  Brevis  Digitorum     .       .      .  547 
Fibrous  Sheaths  of  the  Flexor 

Tendons 548 

Abductor  Minimi   Digiti      .      .      .  548 


CONTENTS 


xv 


The  Plantar  Region — 

Tin-  Second  Layer     ......  549 

Flexor  Accessorius   .      .      .      .      .  549 

Lumbricales         549 

The  Third  Layer 549 

Flexor  Brevis  Hallucis  ....  549 

Adductor  Obliquus   Hallucis    .      .  549 

Flexor  Brevis  Minimi  Digiti     .       .  550 

Adductor  Transversus  Hallucis     .  551 


The  Plantar  Region — 

The  Fourth  Layer 551 

Interossei  Muscles 551 

Dorsal   Interossei    .       .       .      .551 
Plantar  Interossei         .   •  .      .  551 
Surface  Form  of  Muscles  of  the  Lower  Ex- 
tremity       552 

Surgical  Anatomy  of  Muscles  of  the  Lower 

Extremity 554 


THE  BLOOD-VASCULAR  SYSTEM. 


The  Circulation  of  the  Blood      ....  557 

The  Cavity  of  the  Thorax  ....  558 

The  Upper  Opening  of  the  Thorax  .       .       .  558 

The  Lower  Opening  of  the  Thorax  .       .      .  558 

THE  PERICARDIUM. 

Structure  of  the  Pericardium  ....  560 

Fibrous  Layer 560 

Serous  Pericardium 562 

Arteries  of  the  Pericardium  ....  563 

Nerves  of  the  Pericardium  ....  563 

The  Vestigial  Fold  of  the  Pericardium  563 

Surgical  Anatomy  of  the  Pericardium  .      .  563 

THE  HEART. 

Position  of  the  Heart 564 

Size  and  Weight  of  the  Heart     ....  566 

Capacity  of  the  Cavities  of  the  Heart    .      .  566 

Fat  upon  the  Heart 566 


Component  Parts  of  the  Heart     ....  567 

Right  Forechamber  or  Auricle    .       .       .  567 

Left  Forechamber  or  Auricle      .      .      .  570 

Right  Ventricle 571 

Left  Ventricle 573 

Structure  of  the  Heart       .       .  ...  576 

Endocardium 576 

Myocardium 576 

Muscular  Structure  of  the  Heart      .      .  577 
The    Auriculo-ventricular     Fasciculus    or 

Bundle  of  His 579 

Vessels  and  Nerves  of  the  Heart      .      .      .  580 

Surface  Form  of  the  Heart 580 

Surgical  Anatomy  of  the  Heart  ....  580 

Peculiarities  of  Vascular  System  in  Fostus.  581 

The  Foramen  Ovale 581 

The  Eustachian  Valve 581 

The  Ductus  Arteriosus 582 

The  Umbilical  Arteries 583 

Fretal  Circulation 583 

Changes  in  the  Vascular  System  at  Birth  .  584 


THE  ARTERIES. 


Distribution  of  the  Arteries  77.".      .  585 

Anastomosis  of  the  Arteries 585 

Histology  of  the  Capillaries  and  Arteries    .  586 

Blood-vessels  of  the  Blood-vessel  Wall       .  588 

Lymphatics  of  Arteries 588 

Nerves  of  Arteries 588 

Arterial  Sheath 588 

PULMONARY  ARTERY. 

Right  Pulmonary  Artery 589 

Left  Pulmonary  Artery 589 

THE  AORTA. 
The  Ascending  Aorta. 

Relations  of  the  Ascending  Aorta     .       .       .591 

Branches  of  the  Ascending  Aorta    .       .       .  592 

The  Coronary  Arteries 592 

Right  Coronary  Artery 592 

Left  Coronary  Artery 593 

Peculiarities  of  Coronary  Arteries  .       .  593 

The  Arch  of  the  Aorta. 

Relations  of  the  Arch  of  the  Aorta  .      .       .  594 

Peculiarities  of  the  Arch  of  the  Aorta    .       .  594 

Surgical  Anatomy  of  the  Arch  of  the  Aorta  594 

Branches  of  the  Arch  of  the  Aorta  .      .       .  595 

Peculiarities  of  the  Branches     .       .       .  595 

The  Innominate  Artery 596 

Relations 596 

Branches 596 

Thyroidea  Ima 596 

Peculiarities 597 

Surgical  Anatomy 697 

ARTERIES  OF -THE  HEAD  AND  NECK. 

The  Common  Carotid  Artery. 

Relations  of  the  Common  Carotid  Artery  .  600 

Peculiarities  of  the  Common  Carotid  Artery  601 


Surface    Marking   of   the    Common   Carotid 

Artery 

Surgical  Anatomy  of  the  Common  Carotid 

Artery 

The  External  Carotid  Artery       .... 

Relations 

Surface  Marking 

Surgical  Anatomy 

Branches    

Superior  Thyroid  Artery     . 

Branches      

Surgical  Anatomy  .... 

Lingual  Artery 

Relations 

Branches      

Surgical  Anatomy  .... 
Facial  or  External  Maxillary  Artery 

Relations 

Branches      

Peculiarities 

Surgical  Anatomy  .... 

Occipital  Artery 

Branches      

Posterior  Auricular  Artery 

Branches      

Ascending  Pharyngeal  Artery 

Branches      

Surgical  Anatomy  .... 
Superficial  Temporal  Artery    . 


Surgical  Anatomy  ....  613 

Internal  Maxillary  Artery  .       .       .  613 

Branches  of  First  Portion      .  615 

Surgical  Anatomy       .       .  615 

Branches  of  Second  Portion   .  616 

Branches  of  Third  Portion     .  616 

Surgical  Anatomy      .      .  617 

Surgical  Anatomy  of  the  Triangles  of  the 

Neck        . 618 

Anterior  Triangle  of  the  Neck   .       .      .  618 

Posterior  Triangle  of  the  Neck  .      .      .  620 


XVI 


CONTENTS 


PAGE 

The  Internal  Carotid  Artery  .....  620 

Cervical  Portion 621 

Relations 622 

Petrous  Portion 622 

Cavernous  Portion 622 

Cerebral  Portion 623 

Peculiarities 623 

Surgical  Anatomy 623 

Branches 623 

Tympanic 623 

Arterise  Receptaculi       ....  623 

Predural  or  Anterior  Meningeal      .  623 

Ophthalmic 624 

Branches 624 

Precerebral  or  Anterior  Cerebral    .  628 

Branches 628 

Medicerebral  or  Middle  Cerebral    .  629 

Branches 629 

Postcommunicant     or     Posterior 

Communicating 630 

Prechoroid  or  Anterior  Choroid      .  630 

The  Bloodvessels  of  the  Brain. 

The  Central  Ganglionic  System    ....  632 

The  Cortical  Arterial  System        ....  632 

ARTERIES  OF  THE  UPPER  EXTREMITY. 

The  Subclavian  Artery. 

First  Part  of  the  Right  Subclavian  Artery  .  633 

Relations 633 

First  Part  of  the  Left  Subclavian  Artery     .  635 

Relations 635 

Second  and  Third  Parts  of  Subclavian  Artery  635 

Relations 635 

Third  Portion  of  the  Subclavian  Artery      .  636 

Peculiarities  of  the  Subclavian  Artery  .      .  636 

Surface  Marking  of  the  Subclavian  Artery  .  637 

Surgical  Anatomy  of  the  Subclavian  Artery  637 

Branches  of  the  Subclavian  Artery  .      .      .  639 

Vertebral  Artery 639 

Relations 639 

Branches 640 

Surgical  Anatomy 641 

Basilar  Artery 641 

Branches 641 

Circulus  or  Circle  of  Willis  .      .      .  642 

Thyroid  Axis 642 

Branches 643 

Internal  Mammary  Artery   ....  645 

Relations 646 

Branches 646 

Surgical  Anatomy 647 

Superior  Intercostal  Artery  ....  647 

Deep  Cervical  Branch   ....  647 

Surgical  Anatomy  of  the  Axilla   ....  647 

Boundaries 647 

Contents 648 

Surgical  Anatomy 648 

The  Axillary  Artery. 

Relations  of  the  Axillary  Artery      7      .      .  650 

Peculiarities  of  the  Axillary  Artery       .      .  651 

Surface  Marking  of  the  Axillary  Artery    ' .  651 

Surgical  Anatomy  of  the  Axillary  Artery    .  651 

Branches  of  the  Axillary  Artery       .       .       .  652 

Superior  Thoracic  Artery      ....  652 

Acromial  Thoracic  Artery  or  Thoracic 

Axis 653 

Branches         653 

Long  Thoracic  or  External  Mammary 

Artery 653 

Alar  Thoracic  Artery 653 

Subscapular  Artery 653 

Circumflex  Arteries 653 

The  Brachial  Artery. 

Relations  of  the  Brachial  Artery      .      .      .  654 

Surgical  Anatomy  of  the  Bend  of  the  Elbow  655 

Peculiarities  of  the  Brachial  Artery      .      .  655 

Surface  Marking  of  the  Brachial  Artery      .  656 

Surgical  Anatomy  of  the  Brachial  Artery    .  656 


Branches  of  the  Brachial  Artery 
Superior  Profunda  Artery  . 
Nutrient  Artery  .... 
Inferior  Profunda  Artery  . 
Anastomotica  Magna 
Muscular  Branches  . 


PAGE 

.      :  657 

.      .  657 

.      .  658 

.      .  658 

.      .  658 

.      .  658 
The  Anastomosis  around  the  Elbow-joint    659 

The  Radial  Artery 659 

Relations 659 

The  Deep  Palmar  Arch  ...  660 

Peculiarities 660 

Surface  Marking 660 

Surgical  Anatomy 660 

Branches 661 

Radial  Recurrent 661 

Muscular  Branches 661 

Anterior  Radial  Carpal       .      .      .661 

Superficialis  Volae 661 

Posterior  Radial  Carpal      .      .      .  661 

Dorsalis  Pollicis 661 

Dorsalis  Indicis 661 

Princeps  Pollicis 662 

Radialis  Indicis 662 

Perforating  Arteries       ....  662 

Palmar  Interosseous      ....  6G2 

Palmar  Recurrent  Branches    .      .  662 

The  Ulnar  Artery '.      .  662 

Relations 663 

Peculiarities 663 

Surface  Marking 663 

Surgical  Anatomy      .      .      .      .      .      .  663 

Branches    . 664 

Anterior  Ulnar  Recurrent  .      .      .  664 

Posterior  Ulnar  Recurrent       .      .  664 

Interosseous  Artery       ....  664 

Muscular  Branches 665 

Anterior  Carpal 665 

Posterior  Carpal 665 

Deep  Palmar  Arch 666 

Superficial  Palmar  Arch      .      .      .  666 

Relations 666 

Branches 666 

Surface  Marking     ....  667 

Surgical  Anatomy  ....  667 

ARTERIES  OF  THE  TRUNK. 

The  Descending  Aorta. 

The  Thoracic  Aorta 667 

Relations 667 

Surface  Marking 668 

Surgical  Anatomy 668 

Branches 668 

Bronchial  Arteries 668 

(Esophageal  Arteries      ....  668 

Pericardiac  Arteries       ....  668 

Posterior  Mediastinal  Arteries       .  668 

Intercostal  Arteries  and  Branches  669 

Surgical  Anatomy  ....  670 

The  Abdominal  Aorta 670 

Relations 671 

Surface  Marking 672 

Surgical  Anatomy 672 

Branches 673 

The  Creliac  Axis  or  Artery      .      .  673 

Relations 673 

Branches 673 

Surgical  Anatomy  ....  676 

The  Superior  Mesenteric  Artery    .  677 

Branches      ....  .  677 

Blood-supply  of  the  Right  Iliac 

Fossa 678 

The  Inferior  Mesenteric  Artery      .  679 

Suprarenal  Artery 680 

The  Renal  Arteries 680 

The  Spermatic  Arteries       .      .      .  681 
The  Ovarian  Arteries     .      .      .      .681 

The  Inferior  Phrenic  Arteries    .      .  682 

The  Lumbar  Arteries      ....  682 

Branches  ....  682 


CONTENTS 


xvn 


The  Common  Iliac  Arteries. 

Branches  of  Common  Iliac  Arteries       .       .  683 

Peculiarities  of  Common  Iliac  Arteries.      .  684 

Surface  Marking  of   Common  Iliac  Arteries  684 

Surgical  Anatomy  of  Common  Iliac  Arteries  684 

The  Internal  Iliac  Artery 685 

Relations          685 

Peculiarities 686 

Surgical  Anatomy 687 

Branches 687 

Superior  Vesical  Artery      .      .      .  687 

Middle  Vesical  Artery   ....  688 

Inferior  Vesical  Artery  ....  688 

Middle  Hsemorrhoidal   Artery        .  688 

Uterine  Artery 688 

Vaginal  Artery 688 

Surgical  Anatomy  ....  689 

Obturator  Artery 689 

Branches 689 

Peculiarities       .      .      .      .       .  690 

Internal  Pudic  Artery  ....  690 

Relations 691 

Peculiarities 691 

Surgical  Anatomy  .      .      .      .691 

Branches 691 

Sciatic  Artery 603 

Branches 694 

Lateral  Sacral  Artery   ....  694 

Branches 694 

Gluteal  Artery 695 

Branches 695 

Surface  Marking 695 

Surgical  Anatomy  ....  695 

The  External  Iliac  Artery 695 

Relations 695 

Surface  Marking 696 

Surgical  Anatomy 696 

Branches 697 

Internal  or  Deep  Epigastric  Artery  697 

Branches      .      .    • .      .      .      .  697 

Peculiarities 697 

Surgical  Anatomy  ....  698 

Deep  Circumflex  Iliac  Artery  .       .  698 

ARTERIES  OF  THE  LOWER  EXTREMITY. 
The  Femoral  Artery. 

Scarpa's  Triangle 698 

Hunter's  Canal  or  the  Adductor  Canal         .  699 

The  Common  Femoral  Artery     ....  700 

Relations 701 

The  Superficial  Femoral  Artery  ....  701 

Relations 701 

Peculiarities 702 

Surface  Marking 702 

Surgical  Anatomy 702 

Branches 704 

Superficial  Epigastric    ....  704 

Superficial  Circumflex  Iliac      .      .  704 

Superficial  External  Pudic        .      .  704 

Deep  External  Pudic     ....  704 

Deep  Femoral  or  Prof  unda  Femoris  704 

Relations 705 

Branches  ....  705 


The  Superficial  Femoral  Artery — 

Muscular  Branches 706 

Anastomotica  Magna     ....  706 

Branches 706 

The  Popliteal  Artery. 

The  Popliteal  Space 707 

Dissection 707 

Boundaries 707 

Position  of  Contained  Parts       .       .      .  708 

Peculiarities 708 

Surface  Marking 709 

Surgical  Anatomy 709 

Branches 709 

Superior  Muscular  Branches     .       .  709 

Inferior  Muscular  Branches     .      .  709 
Cutaneous  Branches       .      .       .      .710 

Superior   Articular  Arteries      .      .  710 
Azygos  Articular  Artery     .       .      .710 

Inferior  Articular  Arteries  .      .      .  71Q 

Circumpatellar  Anastomosis     .      .  710 

The  Anterior  Tibial  Artery 710 

Relations 71 1 

Peculiarities 71 1 

Surface  Marking 711 

Surgical  Anatomy 7n 

Branches 712 

Posterior  Recurrent  Tibial       .      .  712 

Superior  Fibular 712 

Anterior  Recurrent  Tibial  .       .      .  713 

Muscular  Branches 713 

Malleolar  Arteries 713 

The  Dorsalis  Pedis  Artery 713 

Relations 713 

Peculiarities 713 

Surface  Marking 714 

Surgical  Anatomy 714 

Branches 714 

Cutaneous  Branches       ....  714 

Tarsal  Artery 714 

Metatarsal  Artery 715 

Communicating  Artery        .      .      .715 

The  Posterior  Tibial  Artery 715 

Relations 715 

Peculiarities 716 

Surface  Marking 716 

Surgical  Anatomy 716 

Branches 716 

Peroneal  Artery 717 

Relations 717 

Peculiarities       '."  .      .      .717 

Branches 717 

Cutaneous  Branches      ....  718 

Nutrient  Artery 718 

Muscular  Branches 718 

Communicating  Branch       .       .      .  718 
Malleolar     or    Internal    Malleolar 

Artery 718 

Internal  Calcanean  Arteries     .      .718 

Internal  Plantar  Artery      .      .      .718 

External  Plantar  Artery     .       .      .  719 

Surface  Marking     .      .      .      .719 

Surgical  Anatomy  ....  719 

Branches 719 


THE  VEINS. 


Subdivisions  of  the  Veins 

Anastomosis  of  Veins 

Histology  of  the  Veins  .... 
The  Superficial  or  Cutaneous  Veins  . 
The  Deep  Veins 


THE  PULMONARY  VEINS. 

THE  SYSTEMIC  VEINS. 
Veins  of  the  Head  and  Neck. 
Veins  of  the  Exterior  of  the  Head  and  Face 


721 
722 
722 
723 
723 


725 


Veins  of  the  Exterior  of  the  Head  and  Face — 

Frontal  Vein 725 

Supraorbital  Vein       .      .*    .      .      .      .  726 

Angular  Vein 726 

Anterior  Facial  Vein 726 

Common  Facial  Vein 726 

Superficial  Temporal  Vein     ....  727 
The  Pterygoid  Plexus  and  the  Internal 

Maxillary  Vein 727 

Temporo-maxillary  Vein       ....  727 

Posterior  Auricular  Vein       ....  727 

Occipital  Vein 727 


CONTENTS 


PAGE 

The  Veins  of  the  Neck     .      .      .      .      .      .  728 

External  Jugular  Vein 728 

Posterior  External  Jugular  Vein     .       .  728 

Anterior  Jugular  Vein 728 

Internal  Jugular  Vein     .       .      .      .      .  729 

Lingual  Veins 729 

Pharyngeal  Veins 730 

Superior  Thyroid  Vein  ....  730 

Middle  Thyroid  Vein     ....  730 

Veins  of  the  Thyroid  Gland     .       .  73-1 

Surgical  Anatomy 732 

Vertebral  Vein 732 

Anterior    Vertebral     or    Anterior 

Deep  Cewical  Vein    ....  733 
Posterior   Vertebral    or   Posterior 

Deep  Cervical  Vein    ....  733 

The  Veins  of  the  Diploe 733 

The  Dural  or  the  Meningeal  Veins  .      .  734 

The  Cerebral  Veins 734 

Superficial  or  Cortical  Cerebral  Veins      .  735 
Supercerebral     or     Superior      Cerebral 

Veins 735 

Medicerebral  or  Median  Cerebral  Veins  735 
Subcerebral  or  Inferior  Cerebral  Veins  .  735 
Velar,  Deep  Cerebral,  Central  or  Ven- 
tricular Veins,  Veins  of  Galen    .  735 
Vena  Corporis  Striati     |.      .      .      .  735 

Choroid  Vein       '..'....  735 

Basilar  Vein  .......  735 

Superficial  Cerebellar  Veins         .      .       .  736 

Deep  Cerebellar  Veins 736 

Veins  of  the  Pons 736 

Veins  of  the  Oblongata  ....  736 
The  Sinuses  of  the  Dura,  Ophthalmic  Veins 

and  Emissary  Veins 736 

Longitutinal  or  Superior  Longitudinal 

Sinus 736 

Torcular  Herophili 737 

Falcial  or  Inferior  Longitudinal  Sinus  .  738 

Tentorial  or  Straight  Sinus    ....  738 

Lateral  Sinus 738 

Surgical  Anatomy 739 

Occipital  Sinus 739 

Cavernous  Sinus 739 

Surgical  Anatomy 740 

Sphenoparietal  Sinus  or  Sinus  Alae  Parvae  740 

Ophthalmic  Veins 740 

Circular  Sinus 742 

Superpetrosal  or  Superior  Petrosal  Sinus  742 

Subpetrosal  or  Inferior  Petrosal  Sinus  742 

Transverse  or  Basilar  Sinus  ....  743 

Emissary  Veins 743 

Surgical  Anatomy 743 

Veins  of  the  Upper  Extremity  and  Thorax. 

The  Superficial  Veins  of  Upper  Extremity   .  745 
Superficial  Veins  of  the  Hand  and  Fin- 
gers    745 

Anterior  Ulnar  Vein 745 

Posterior  or  Dorsal  Ulnar  Vein        .       .  745 

Common  Ulnar  Vein 745 

Radial  Vein 745 

Median  Vein 745 

Median  Cephalic  Vein 746 

Median  Basilic  Vein       ....  746 

Basilic  Vein 746 

Cephalic  Vein 747 

The  Deep  Veins  of  the  Upper  Extremity     .  747 

Interosseous  Veins 747 

Deep  Palmar  Veins 747 

Brachial  Veins 747 

Axillary  Vein  .........  747 

Branches 748 

Surgical  Anatomy 748 

Subclavian  Vein 749 

Innominate  or  Brachio-cephalic   Veins  750 

Right  Innominate  Vein 750 

Left  Innominate  Vein    • 750 

Peculiarities  750 


The  Deep  Veins  of  the  Upper  Extremity — 
Internal  Mammary  Vein 
Inferior  Thyroid  Veins     . 

Intercostal  Veins 

Precava  or  Superior  Vena  Cava 

Relations 

Azygos  Veins          

Surgical  Anatomy     . 

Bronchial  Veins 

The  Spinal  Veins 

Dorsi-spinal  Veins 
Meningo-rachidian  Veins 
Veins  of  the  Bodies  of  the  Vertebra  or 
Venae  Basis  Vertebrarum   .... 
Veins  of  the  Spinal  Cord  or  Medulli- 
spinal  Veins 

Veins  of  the  Lower  Extremity,  Abdomen 
and  Pelvis. 

The  Superficial  Veins  of  the  Lower  Extrem- 
ity      

The  Superficial  Veins  of  the  Foot  . 
Internal  or  Long  Saphenous  Vein 
External  or  Short  Saphenous  Vein 

Surgical  Anatomy 

The  Deep  Veins  of  the  Lower  Extremity 
The  Deep  Veins  of  the  Foot 

Posterior  Tibial  Veins 

Anterior  Tibial  Veins 

Popliteal  Vein 

Femoral  Vein 

External  Iliac  Vein 

Deep  Epigastric  Vein 

Deep  Circumflex  Iliac  Vein 
Hypogastric  or  Internal  Iliac  Vein 

Surgical  Anatomy 

Obturator  Vein 

Sciatic  Veins 

Gluteal  Veins         .      .      .      .  '    . 
Superior  Vesical  Plexus         .... 
Prostatic  or  Prostatico-vesical  Plexus  . 
Inferior  Vesical  Plexus 

Surgical  Anatomy 

The  Dorsal  Veins  of  the  Penis  . 
The  Vaginal  Plexuses  and  Veins    . 
The  Uterine  Plexuses  and  Veins 
Common  Iliac  Vein 

Peculiarities 

Postcava,   Ascending  or  Inferior  Vena 
Cava 

Relations 

Peculiarities 

Lumbar  Veins 

Spermatic  Veins 

Ovarian  Veins 

Renal  Veins 

Suprarenal  Veins 

Phrenic  Veins 

Hepatic  Veins     : 


THE  PORTAL  SYSTEM  OF  VEINS. 


Superior  Mesenteric  Vein 
Splenic  Vein  .  .  .  . 
Inferior  Mesenteric  Vein  , 
Gastric  Veins  .  .  .  . 
Cystic  Vein  . 
Portal  Vein 


The  Cardiac  Veins. 

Great  Cardiac  or  Left  Coronary  Vein 
Posterior  or  Middle  Cardiac  Vein 

Left  Cardiac  Vein 

Anterior  Cardiac  Vein        .... 
Right  Cardiac  or  Small  Coronary  Vein 

Coronary  Sinus 

Vena?  Thebesii 


PAGE 

750 
751 
752 
752 
752 
752 
753 
753 
753 
753 
754 

755 
755 


756 
756 
756 
756 
757 
758 
758 
758 
758 
758 
758 
759 
759 
759 
760 
761 
761 
761 
761 
761 
761 
762 
762 
762 
763 
763 
764 
764 

764 
764 
764 
765 
765 
766 
767 
767 
767 
767 


768 
768 
768 
768 
769 
769 


770 
771 
771 
771 
771 
771 
771 


CONTENTS 


xix 


THE  LYMPHATIC  SYSTEM. 


Subdivision  into  Superficial  and  Deep  Sets  773 

Lymphatic  or  Conglobate  Glands       .      .      .  774 

Hemolymph  nodes 774 

Surgical  Anatomy 775 

THE  THORACIC  DUCT  AND  THE  RIGHT 

LYMPHATIC  DUCT. 

Radicals  of  Origin  and  Tributaries  of  Tho- 
racic Duct 776 

Structure  of  the  Thoracic  Duct    ....      777 

The  Right  Lymphatic  Duct 777 

Tributaries 778 

LYMPHATICS  OF  THE  CRANIAL  REGION,  FACE 

AND  NECK. 

The  Lymphatic  Glands  of  the  Head  and  Face     778 
The  Occipital  or  Suboccipital  Glands    .      779 
The  Posterior  Auricular,  Retro-auricu- 
lar or  Mastoid  Glands        ....      779 

Parotid  Lymph  Glands 779 

The  Subparotid  Glands  .  ...      781 

The  Internal   Maxillary  or  Zygomatic 

Glands .  781 

The  Facial  Glands  or  Genial  Glands    .      781 
The  Lymphatic  Vessels  of  the  Cranial  Region     781 
The  Lymphatic  Vessels  of  the  Face,  the  In- 
terior of  the  Nose,  Tongue,  Floor  of  the 
Mouth,    Pharynx,    Larynx    and    Thyroid 

Gland 782 

The  Lymphatic  Glands  of  the  Neck  .  .  783 
The  Superficial  Cervical  Glands  .  .  783 
The  Submaxillary  or  Lateral  Supra- 

hyoid  Glands 784 

The  Submental  or  Median  Suprahyoid 

Glands 784 

The  Retro-pharyngeal  or  Post-pharyn- 

geal  Glands 784 

The  Deep  Cervical,  Carotid,  or  Sterno- 

mastoid  Glands 785 

The  Lymphatic  Vessels  of  the  Neck  .  .  786 
Surgical  Anatomy 786 

THE  LYMPHATICS  OF  THE  UPPER  EXTREMITY. 

The  Lymphatic  Glands  of  the   Upper  Ex- 
tremity   787 

The  Superficial   Lymphatic   Glands      .     787 
The  Deep  Lymphatic  or  the   Axillary 

Glands 787 

The  Lymphatic  Vessels  of  the  Upper  Ex- 
tremity          790 

The   Superficial   Lymphatic   Vessels   of 

the  Upper  Extremity 790 

The    Deep   Lymphatic   Vessels   of   the 

Upper  Extremity        ....     790 
Surgical  Anatomy 791 

THE  LYMPHATICS  OF  THE  LOWER  EXTREMITY. 

The  Lymphatic  Glands  of  the   Lower  Ex- 
tremity   791 

The    Superficial    Inguinal     Lymphatic 

Glands 791 

Surgical  Anatomy 794 

The    Deep    Lymphatic    Glands    of    the 

Lower  Extremity              .      .      .     794 
The  Deep  Inguinal  or  Deep  Fem- 
oral Lymphatic  Glands  .      .      .     794 
The  Anterior  Tibial  Gland       .      .      794 
The  Popliteal  Glands     ....      794 
The  Gluteal  and  Ischiatic  Glands     794 
The  Lymphatic  Vessels  of  the  Lower  Ex- 
tremity   794 

The  Superficial  Lymphatic  Vessels  of 

the  Lower  Extremity 795 

The    Deep    Lymphatic    Vessels   of   the 

Lower  Extremity 795 


THE  LYMPHATICS  OF  THE  PELVIS  AND 
ABDOMEN. 

The  Iliac  or  Ilio-pelvic  Glands  ....  795 
The  External  Iliac  Glands  ....  795 
The  Internal  Iliac  or  Hypogastric  Glands  796 
The  Common  Iliac  Gland  ....  796 
The  Abdomino-aortic  Glands  ....  797 
The  Right  Juxta-aortic  Glands  .  .  797 
The  Left  Juxta-aortic  Glands  .  .  .  798 
The  Retro-aortic  Glands  ....  798 
The  Pre-aortic  Glands 798 

The  Glands  along  the  Mesenteric 
Arteries 798 

The  Glands  connected  with  the 
Cosliac  Axis  and  its  Branches  .  798 

The  Gastric  Glands 793 

The  Splenic  Glands 798 

The  Hepatic  Glands       ....     798 
The  Lymphatic  Vessels  of  the  Abdomen  and 

Pelvis 799 

The  Superficial    Lymphatic    Vessels  of 

the  Walls  of  the  Abdomen    .       .     799 

The  Superficial  Lymphatic  Vessels 
of  the  Gluteal  Region  .  .  .  799 

The  Superficial  Lymphatic  Vessels 

of  the  Scrotum  and  Perinaeum  .     799 

The  Superficial  Lymphatic  Vessels 

of  the  Penis 799 

The    Deep    Lymphatic    Vessels   of   the 

Abdominal  Wall   ...  .     799 

The  Lymphatic  Vessels  of  the  Um- 
bilicus   799 

The  Lymphatic  Vessels  of  the  Peri- 
toneum   800 

The     Lymphatic     Vessels    of    the 

Bladder 800 

The  Lymphatic  Vessels  of  the  Pros- 
tate Gland 800 

The  Lymphatic  Vessels  of  the  Male 

Urethra 801 

The  Lymphatic  Vessels  of  the  Fe- 
male Urethra 801 

The     Lymphatic     Vessels    of    the 

Uterus         .  801 

The  Lymphatic  Vessels  of  the  Fal- 
lopian Tube 801 

The  Lymphatic  Vessels  of  the 
Ovary 801 

The     Lymphatic     Vessels    of    the 

Vagina 802 

The     Lymphatic     Vessels    of    the 

Testicle 802 

The     Lymphatic     Vessels    of    the 

Vas  Deferens          802 

The     Lymphatic     Vessels    of    the 

Seminal  Vesicles 802 

The  Lymphatic  Vessels  of  the 
Kidney,  Ureter,  and  Suprarenal 
Capsule 802 

The  Lymphatic  Vessels  of  the  Liver     802 

The    Lymphatic    Vessels    of    the 

Bile-ducts 803 

The    Lymphatic    Vessels    of    the 

Stomach 804 

The     Lymphatic     Vessels     of    the 

Pancreas 804 

The     Lymphatic     Vessels    of    the 

Spleen         804 

THE  LYMPHATIC  SYSTEM  OF  THE  INTESTINES. 

The  Lymphatic  Glands  of  the  Small  Intestine  805 

The  Lymphatic  Vessels  of  the  Small  Intestine  806 

The  Lymphatic  Glands  of  the  Large  Intestine  806 

The  Colic  Glands 806 

The  Rectal  Glands     .  806 


XX 


CONTENTS 


The  Lymphatic  Vessels  of  the  Large  Intestine 
Lymphatics  of  the  Anus  and  Rectum 

THE  LYMPHATICS  OF  THE  THORAX. 


PAGE 
806 
807 


The  Lymphatic  Glands  of  the  Thoracic  Wall 

or  the  Parietal  Lymphatics    .      .      .  807 

The  Internal  Mammary  Glands        .      .  807 

The  Intercostal  Glands 808 

The  Diaphragmatic  Lymphatics       .      .  808 

The  Visceral  Lymphatics       ....  808 

The  Anterior  Mediastinal 'Glands  .  808 

The  Posterior  Mediastinal  Glands  .  808 

The  Peritracheo-bronchial   Glands  809 


PAGE 

The  Lymphatic  Vessels  of  the  Thoracic  Wall  810 

The  Cutaneous  Lymphatics  ....  810 

Lymphatics  of  the  Mammary  Gland     .  810 
Lymphatics  of  the  Great  Pectoral 

Muscle 811 

Surgical  Anatomy 811 

The  Pulmonary  Lymphatics       .      .      .  812 
The  Pleural  Lymphatics      .      .      .  812 
The  Cardiac  Lymphatics        ....  812 
The  Thymic  Lymphatic  Vessels        .      .  813 
The  Lymphatic  Vessels  of  the  (Esoph- 
agus     813 

The  Lymphatic  Vessels  of  the  Thoracic 

Trachea 813 


THE  NERVE  SYSTEM. 


THE  SPINAL  CORD  AND  BRAIN  WITH  THEIR 
MENINGES. 

Fundamental    Facts   regarding   the    Devel- 

opment of  the  Nerve  System      ....  816 

Development  of  Nerve  Tissue  .....  818 

In  the  Wall  of  the  Neural  Tube    .      .      .  818 

In  the  Neural-crest  Tissue      ....  819 

Structure  of  the  Nerve  System       ....  819 

The  Neurone    ........  820 

Nerve-cell  Body  ......  820 

Unipolar  cells     .....  820 

Bipolar  cells  ......  820 

Multipolar  cells         ....  820 

Nerve-cell    Body.      Internal    Mor- 

phology      .......  822 

TheDendrites        .......  822 

TheAxone        ........  823 

The  Collaterals       .......  823 


NERVE-FIBRES  AND  NERVES. 


827 


Origin  and  Termination  of  Nerves       .      .      . 
The    Supporting    Tissue    Elements    of    the 

Nerve  System    .......      832 

The  Neuroglia        .......      832 

Chemical  Composition  of  Nerves    ....      833 

THE  CENTRAL  NERVE  SYSTEM. 

Preliminary  Considerations      .....      833 

The   Spinal   Cord. 

External  Morphology  of  the  Spinal  Cord         .      835 
The  Enlargements  of  the  Spinal  Cord        .      .      837 

Conus    ..........      838 

Filum    ......  ...      838 

Fissures  and  Grooves  of  the  Spinal  Cord  .      .      838 
Columns  of  the  Spinal  Cord      .....      839 

Development  of  the  Spinal  Cord    ....      840 

Muscular   Supply  from   Motor  Segments  of 
the  Cord    .......... 

Internal  Structure  of  the  Spinal  Cord  .       .      . 

Gray  Substance  of  the  Cord    .... 

White  Substance  of  the  Cord        .      .      . 

Longitudinal  Fibres  of  the  Cord  .      .      . 

Marginal  Tract  of  the  Cord     .... 

Ground  Bundles  of  the  Dorsal  Column    . 

Ground  Bxindles  of  the  Lateral  Column 

Ground  Bundles  of  the  Ventral  Column 

Myelinization  of  the  Axones  of  the  Cord 


843 
843 
843 


851 
852 
853 
854 
855 


Dissection  of  the  Spinal  Cord   .....      856 


The  Membranes  of  the  Cord. 


The  Spinal  Dura 

Structure 
The  Arachnoid 

Structure 
The  Pia  of  the  Cord  . 


856 

858 
858 
859 
859 


The  Pia  of  the  Cord — 
Structure    . 
Surgical  Anatomy . 


860 
860 


The  Brain  or  Encephalon. 


General    Appearance    and    Topography    of 

the  Brain ,     .  860 

Dimensions  of  the  Brain '  862 

The    Development    of    the    Brain    and    the 

Usual  Classifications  of  its  Subdivisions   .  863 

Brief  Consideration  of  the  Phases  of  Devel-  ' 

opment  of  the  Brain-tube  ....  865 

The  Fore-brain 865 

The  Mid-brain 869 

The  Hind-brain 869 

Flexures  of  the  Brain-tube 869 

Dorsal  and  Ventral  Lamina?  or  Longitudinal 

Zones  of  the  Brain 870 

Descriptive  Anatomy  of  the  Adult  Human  Brain. 

Parts  derived  from  Hind-brain   (Rhomben- 

cephalon) 874 

The  Oblongata 874 

Fissures  of  Oblongata 874 

Areas  of  Oblongata 875 

The  Pyramids 875 

Lateral  Area 876 

Dorsal  Area 876 

The  Pons  and  Pre-obloiigata 877 

The  Ventral  Surf  ace 877 

The  Pre-oblongata 878 

The  Fourth  Ventricle  of  the  Brain       .      .      .  878 

"Floor"  of  the  Fourth  Ventricle        .       .  879 
Membranous  Portion  of  the  "Roof"  of 

the  Fourth  Ventricle 881 

Internal  Structure  of  the  Postoblongata  .       .  881 

Pyramidal  Decussation 881 

Decussation  of  the  Lemnisci  ....  882 

The  Formatio  Reticularis       ....  884 

TheRaphe 885 

TheRestis 885 

The    Nucleus  of    the  Olive   or  Inferior 

Olivary  Nucleus 885 

The  Arcuate  Fibre  Systems    ....  886 

Internal    Structure  of    the  Pons  and    Pre- 
oblongata 887 

The  Transverse  Fibres 887 

The  Longitudinal  Fibres 887 

The  Nuclei  Pontis 887 

The  Pre-oblongata             887 

The  Superior  Olivary  Nucleus      .      .      .  887 

The  Nucleus  Incertus 888 

Fibre-tracts  in  the  Pre-oblongata        .      .      .  888 

The  Medial  Lemniscus 888 

The  Lateral  Lemniscus 888 

The  Medial  Longitudinal  Bundle       .       .  888 

The  Cerebellar  Peduncle 888 

Summary  of  Gray  Masses  in  the  Pre-oblon- 
gata       888 


CONTENTS 


xxi 


PAGE 

Central  Connections  of  the  Cranial  Nerves 

attached  to  the  Hind-brain       .      .      . .  888 

The  Nuclei  of  Origin 889 

The  Nuclei  of  Termination     ....  889 

The  Hypoglossal  Nerve 889 

The  Accessory  Nerve 890 

The  Vagus  and  Glosso-pharyngeal  Nuclei  890 

The  Acoustic  Nerve 892 

The  Facial  Nerve 893 

The  Abducent  Nerve 894 

The  Trigeminal  Nerve 894 

The  Cerebellum 895 

Lobes  and  Fissures  of  the  Cerebellum     .  896 

TheLingula 897 

The  Central  Lobe 897 

The  Culminal  Lobe    .....  897 

The  Clival  Lobe 898 

The  Cacuminal  Lobe       ....  898 

The  Tuberal  Lobe 898 

The  Gracile  Lobe        .      .      .      .      .898 

The  Pyramidal  Lobe        ....  898 

The  Uvular  Lobe 898 

The  Nodular  Lobe 898 

The    Internal    Structure    of    the    Cere- 
bellum       899 

Isolated  Gray  Masses  or  Nuclei  of  the 

Cerebellum 899 

The  Cerebellar  Peduncles 900 

The  Medullary  Vela 901 

The  Fibres  Proper  of  the  Cerebellum       .  902 
Microscopic  Appearance  of  the  Cerebel- 
lar Cortex      902 

Weight  of  the  Cerebellum       ....  903 

The  Mid-brain -   ...  904 

External  Morphology 905 

ThePregemina 905 

The  Prebrachium 905 

The  Postgeniculum 905 

TheCrura 905 

The  Tamia  Pontis 906 

The  Cimbia    or  Tractus    Peduncu- 

laris  Transversus 906 

Internal  Structures  of  the  Mid-brain       .  906 
The  Aqueduct  and    Central    Gray 

Aqueduct 907 

The    Substantia    Nigra  or  Interca- 

latum 907 

The  Quadrigemina 907 

The  Tegmen  turn 908 

Fountain  Decussation     .      .      .      .910 

The  Crusta  or  Pes             ....  910 
Summary  of    the  Gray  Masses    in    the 

Mid-brain 910 

Deep  Origin  of  Cranial  Nerves  Arising 

in  the  Mid-brain     .       .      .      .      .910 

The  Trochlear-nerve  Nucleus     .       .  910 

The  Oculomotor-nerve  Nucleus       .  911 

Parts  Derived  from  the  Fore-brain      .      .      .911 

External  Morphology 911 

TheThalami  .... 

The  Tuberculum  Anterius         .  913 
Internal      Structure     of      the 
Thalamus  and    its    Connec- 
tions      914 

The  Connections  of  the  Thala- 
mus        914 

TheEpiphysis 915 

Structure 915 

Postcommissure       .      .      .      .  915 

Postperforatum        .      .      .      •  916 

The  Albicantia 916 

Third  Ventricle 916 

External  Morphology  of  the  Optic  Por- 
tion of  the  Hypothalamus      .      .  917 

TheTuber 917 

The  Hypophysis 

TheTerma 917 

The  Optic    Tract  and   its    Central 

Connections 917 

Chiasni 919 


The  Cerebral  Hemispheres 919 

External  Morphology 919 

Configuration    of    Each  Hemicere- 

brum 922 

Cerebral  Fissures  and  Gyres       .      .  922 

Cerebral  Lobes  and  Fissures       .       .  923 

The  Interlobar  Fissures        .      .      .  924 

The   Sylvian    Fissure  and    its 

Kami 924 

The  Central  Fissure       ...  926 

The  Occipital  Fissure    ...  926 

The  Calcarine  Fissure    ...  926 

The  Frontal  Lobe 926 

The  Parietal  Lobe 930 

Gyres  of  the  Parietal  Lobe 

The  Occipital  Lobe 931 

The  Temporal  Lobe 931 

Gyres  of  the  Temporal  Lobe     .  932 

Thelnsula      ....             .       .  933 

The    Rhinencephalon  or  Olfactory 

Lobe 934 

Internal  Configuration  of  the  Cerebral 

Hemispheres 938 

The  Cortex 939 

TheCallosum 939 

Development  of        .      .      .      .941 
The  Lateral  Ventricles    .      .       .      .941 

The  Choroid  Fissure  or  Rima     .      .  946 

The  Paraplexus  and  Velum         .       .  946 

The  Hippocampus  and  Fornix  .      .  947 

The  Septum  Lucidum     ....  952 

The  Precommissure 952 

The  Gray  Masses  in  the  Hemicere- 

brum 952 

TheCaudatum 

The  Lenticula 

The  Amygdala 

TheClaustrum 

The  Internal  Capsule       .... 
The  External  Capsule      .... 
Intimate    Structure    of    the  Cere- 
bral Cortex  and  its  Special  Type 

in  Different  Regions    ....  958 

Special  Types  of  Gray  Substance     .  959 
Summary    of    the    Cerebral    Fibre 

Systems 961 

Connections  of  the  Striatum       .       .  964 
The  Olfactory  Pathways  . 

Peripheral  Pathway         ....  964 

Central  Pathway 964 

Weight  of  the  Brain       ....             .       .  965 

Cortical  Localization  and  Function. 

Motor  Area  .      .      . 

Sensor  Area 

The  Language  Areas 968 

The  Association  Areas 969 

Cranio-cerebral  Topography    ....  970 

The  Meninges  or  Meningeal  Membranes  of 
the  Brain. 


Dissection 

The  Dura  of  the  Brain 

Structure 

The  Arteries  of  the  Dura 
The  Veins  of  the  Dura     . 
The  Lymphatics  of  the  Dura 
The  Nerves  of  the  Dura  . 
Processes  of  the  Dura        .... 

TheFalx 

TheTentorium 

TheFalcula 

The  Diaphragma  Sellse    . 
The  Arachnoid  of  the  Brain      .... 
The  Subarachnoid  Space  .... 

Structure 

The  Arachnoid  Villi  or  Pacchionian  Bodies 


972 
972 
973 
974 
974 
974 
974 
975 
975 
975 
976 
976 
976 
977 
977 
979 


XX11 


CONTENTS 


PAGE 

The  Pia  of  the  Brain 980 

The    Velum    or    the    Fela    Chorioidea 

Superior 981 

THE  SPINAL  NERVES. 

The  Roots  of  the  Spinal  Nerves    .      .  982 

The  Ventral  Root       .....'.  982 

The  Dorsal  Root 982 

The  Ganglia  of  the  Spinal  Nerves       .      .       .  983 

Distribution  of  the  Spinal  Nerves      .      .      .  984 

Points  of  Emergence  of  the  Spinal  Nerve       .  985 

The  Cervical  Nerves. 

The  Roots  of  the  Cervical  Nerves       .      .      .  986 

The  Dorsal  Division  of  the  Cervical  Nerves  986 
The    Ventral     Division     of     the     Cervical 

Nerves 988 

The  Cervical  Plexus 989 

Superficial  Branches 989 

Deep  Branches,  Internal  Series        .       .  992 

Surgical  Anatomy 993 

Deep.  Branches,  External  Series       .       .  993 

Surgical  Anatomy 994 

The  Brachial  Plexus 994 

Relations 998 

Branches 998 

Surgical  Anatomy 1009 

The  Thoracic  or  Dorsal  Nerves. 

The  Roots  of  the  Thoracic  Nerves  .  .  .  1010 

The  Dorsal  Divisions  of  the  Thoracic  Nerves  1010 

The  Medial  Branches 1010 

The  Lateral  Branches 1010 

The  Cutaneous  Branches  ....  1010 
The  Ventral  Divisions  of  the  Thoracic 

Nerves  or  the  Intercostal  Nerves  .  101 1 
The  Ventral  Division  of  the  First 

Thoracic  Nerve 1011 

The  Ventral  Divisions  of  the  Upper 

Thoracic  Nerves 1011 

The  Ventral  Divisions  of  the  Lower 

Thoracic  Nerves 1013 

The  Last  Thoracic  Nerve  ....  1014 

Surgical  Anatomy 1014 

The  Lumbar  Nerves. 

The  Roots  of  the  Lumbar  Nerves       .       .      .  1015 

The  Dorsal  Divisions  of  the  Lumbar  Nerves  1015 

Medial  Branches 1015 

Lateral  Branches 1015 

The  Ventral  Divisions  of  the  Lumbar  Nerves  1015 

The  Lumbar  Plexus 1016 

Branches 1017 

The  Sacral  and  Coccygeal  Nerves. 

The  Roots  of  the  Upper  Sacral  Nerves    .      .  1023 

The  Dorsal  Divisions  of  the  Sacral  Nerves    .  1023 

The  Upper  Sacral  Nerves      ....  1023 

The  Lower  Sacral  Nerves      ....  1023 

The  Ventral  Divisions  of  the  Sacral  Nerves  1025 

The    Dorsal    Divisions    of    the    Coccygeal 

Nerve 1025 

The  Ventral  Division  of  the  Coccygeal 

Nerve 1025 

The  Sacral  or  Sciatic  Plexus  and  the  Pudic 

or  Pudendal  Plexus 1026 

Branches 1027 

The  Coccygeal  Plexus 1034 

Surgical  Anatomy 1034 

THE  CRANIAL  NERVES. 

The  First  or  Olfactory  Nerve. 

Surgical  Anatomy 1038 


The  Second  or  Optic  Nerve. 

TheChiasm 

Surgical  Anatomy        .... 


1038 
1038 


The  Third  or  Oculomotor  Nerve. 

Surgical  Anatomy        .  1040 

The  Fourth  or  Trochlear  Nerve. 

Branches  of  Communication         ....  1041 

Branches  of  Distribution 1041 

Surgical  Anatomy 1041 

The  Fifth,  Trigeminal  or  Trifacial  Nerve. 

The  Gasserian  or  Semilunar  Ganglion  .  .  1042 

Ophthalmic  Nerve 1043 

Branches 1043 

The  Superior  Maxillary  Nerve  ....  1046 

Branches 1046 

The  Mandibular  or  Inferior  Maxillary  Nerve  1050 

Branches 1051 

Surface  Marking 1055 

Surgical  Anatomy 1055 

The  Sixth  or  Abducent  Nerve. 

Branches  of  Communication 1057 

Surgical  Anatomy 1058 

The  Seventh  or  Facial  Nerve. 

Branches  of  Communication 1060 

Branches  of  Distribution 1060 

Surgical  Anatomy 1064 

The  Eighth  or  Acoustic  Nerve. 

The  Cochlear  Nerve 1064 

The  Vestibular  Nerve 1065 

Surgical  Anatomy 1065 

The  Ninth  or  Glosso-Pharyngeal  Nerve. 

The  Superior  or  Jugular  Ganglion      .       .      .  1066 

The  Inferior  or  Petrous  Ganglion       .      .      .  1066 

Branches  of  Communication       .       .      .  1067 

Branches  of  Distribution       ....  1067 

The  Gustatory  Path 1067 

Surgical  Anatomy 1067 

The  Tenth,  Vagus  or  Pneumogastric  Nerve. 

The   Ganglion   of    the  Root  of    the  Vagus 

Nerve 1069 

Connecting  Branches 1069 

The  Ganglion  of  the  Trunk  of  the  Vagus 

Nerve 1069 

Connecting  Branches 1069 

Surgical  Anatomy 1072 

The  Eleventh  or  Accessory  Nerve. 

The  Bulbar  or  Vagal  Part  of  the  Accessory 

Nerve ".  1073 

The  Spinal  Portion  of  the  Accessory  Nerve  1074 

Surgical  Anatomy 1074 

The  Twelfth  or  Hypoglossal  Nerve. 

Branches  of  Communication         ....  1075 

Branches  of  Distribution 1076 

Surgical  Anatomy 1077 

THE  SYMPATHETIC  NERVE  SYSTEM. 

Structure  of  the  Sympathetic  System      .      .  1079 

The  Gangliated  Cord. 

The  Cervical  Portion  of  the  Gangliated  Cord  1081 
The  Superior  Cervical  Ganglion        .      .  1081 
The  Middle  Cervical  or  Thyroid  Gan- 
glion         1085 

The  Inferior  Cervical  Ganglion  .      .      .  1086 

Surgical  Anatomy 1087 


CONTENTS 


XXlll 


The  Thoracic  Portion  of  the  Gangliated  Cord  1087    The  Cardiac  Plexus — 
The  Lumbar  Portion  of  the  Gangliated  Cord  1089  The    Superficial    or 
The  Pelvic  or  Sacral  Portion  of  the  Gangli- 
ated Cord                                                           .  1089 


The  Great  Plexuses  of  the  Sympathetics. 

The  Cardiac  Plexus 1090 

The  Great  or  Deep  Cardiac  Plexus     .    1090 


Ventral     Cardiac 


Plexus 

The  Pulmonary  Plexus 
The  CEsophageal  Plexus    . 
The  Epigastric  or  Solar  Plexus 
The  Hypogastric  Plexus   . 
The  Pelvic  or  Sacral  Plexus 


1090 
1091 
1091 
1091 
1095 
1095 


THE  ORGANS  OF  SPECIAL  SENSE. 


THE  TONGUE. 

The  Body 1097 

The  Base  or  Root 1097 

The  Apex  or  Tip 1097 

The  Dorsum  of  the  Tongue 1097 

The  Margin  of  the  Tongue 1097 

The  Under  or  Inferior  Surface      ....  1097 

Structure  of  the  Tongue 1098 

THE  NOSE. 
The  Outer  Nose. 

Structure 1106 

The  Nasal  Fossae. 

The  Anterior  Nares 1108 

The  Posterior  Nares 1108 

Outer  Wall 1109 

The  Inner  Wall 1110 

Surgical  Anatomy 1112 

THE  EYE. 
The  Fascia  or  Capsule  of  Te"non      .      .      .1113 

The  Tunics  of  the  Eye. 
The  Fibrous  or  External  Coat :  The  Sclerotic 

and  Cornea 1117 

The  Sclera  or  Sclerotic  Coat      .      .       .1117 

The  Cornea      .             1118 

The  Choroid,  Ciliary  Body,  and  Iris;    the 

Tunica  Media ;  the  Uveal  Tract    .       .  1121 

The  Choroid    .       .       .    ' 1121 

Tapet.um 1124 

The  Ciliary  Body 1125 

The  Iris 1127 

The  Tunica  Interna  or  Retina     ....  1130 

The  Refracting  Media. 

The  Aqueous  Humor 1138 

The  Vitreous  Body 1139 

The  Crystalline  Lens .  1140 

Surgical  Anatomy  of  the  Eye     ....  1144 

The  Appendages  of  the  Eye. 

The  Eyebrow 1147 

The  Eyelid .      .  1147 

The  Meibomian  or  Tarsal  Glands    .      .  1 149 


The  Conjunctiva 

The  Lachrymal  Apparatus  . 

The  Lachrymal  Glands   . 

The  Lachrymal  Sac   . 

The  Nasal"  Duct  .... 

Surface  Form 

Surgical  Anatomy  .... 

THE  EAR. 
The  External  Ear. 
The  Pinna  or  Auricle  .... 

Structure  of  the  Pinna   . 
The  External  Auditory  Canal 
The  Cartilaginous  Portion     . 
The  Osseous  Portion 
Surface  Form    . 


1150 
1151 
1151 
1152 
1152 
1152 
1153 


1154 
1156 
1158 
1158 
1159 
1160 


The  Middle  Ear,  Drum  or  Tympanum. 

The  Tympanic  Cavity 1160 

The  Drumhead  or  Membrana  Tympani      .    1165 

The  Ossicles  of  the  Tympanum  .       .      .      .1168 

The  Malleus  or  Hammer       ....    1168 

The  Incus  or  Anvil 1169 

The  Stapes  or  Stirrup 1170 

The  Internal  Ear  or  Labyrinth. 

The  Osseous  Labyrinth 1174 

The  Vestibule 1174 

The  Semicircular  Canals  .  .  .  .1175 
The  Cochlea 1175 

The  Membranous  Labyrinth 1179 

The  Utricle 1179 

The  Saccule 1180 

The  Membranous  Semicircular  Canals  .  1180 

Surgical  Anatomy 1186 

THE  SKIN. 

The  Corium,  Cutis  Vera,   Dermis  or  True 

Skin H90 

The  Cuticle,  Scarf  Skin  or  Epidermis     .      .    1191 
The  Appendages  of  the  Skin       .       .      .      .1195 

The  Nails 1195 

The  Hairs 1197 

The  Sudoriferous  or  Sweat-glands  .  .  1200 
The  Sebaceous  Glands  .  .1201 


THE  ORGANS  OF  DIGESTION. 


THE  ALIMENTARY  CANAL. 

The  Mouth,  Oral  or  Buccal  Cavity. 

The  Vestibule 1204 

The  Cavity  of  the  Mouth  Proper      .      .      .  1204 

The  Lips 1204 

The  Cheeks 1205 

The  Gums 1205 

The  Teeth 1205 

General  Characters 1205 

Temporary,  Deciduous  or  Milk  Teeth   .  1206 

Permanent  Teeth 1206 

Arrangement  of  the  Teeth   ....  1208 

Structure  of  the  Teeth 1210 

Development  of  the  Teeth  .       .      .      .1214 

The  Palate 1220 

The  Hard  Palate                                         .  1220 


The  Palate — 

The  Soft    Palate  or  Velum  Pendulum 

Palati 1221 

The  Tonsil  or  Amygdala       ....  1223 

The  Salivary  Glands 1224 

The  Parotid  Gland 1224 

Surface  Form 1225 

The  Submaxillary  Gland      ....  1226 

The  Sublingual  Gland 1227 

Structure  of  Salivary  Glands     .      .      .  1227 

Surface  Form                                               .  1229 


The  Pharynx. 
The  Nasal  Part      .... 

The  Oral  Part 

The  Laryngeal  Part 
Structure 


1231 
1231 
1232 
1232 


XXIV 


CONTENTS 


Surgical  Anatomy  of  the  Mouth,  Cheeks, 
Lips,  Gums,  Tonsils,  Palate,  Salivary 
Glands  and  Pharynx 1234 

The  (Esophagus. 

Relations 1237 

Anomalies 1238 

Structure 1238 

Movements  and  Innervations  of  the  (Esoph- 
agus    1240 

Surgical  Anatomy 1240 

THE  ABDOMEN. 

Boundaries 1241 

Development  of  the  Alimentary  Canal,  Vis- 
cera and  Peritoneum 1245 

Development  of  the  Alimentary  Canal  .      .  1247 

The  Peritoneum. 

Structure '  of  the  Peritoneum       ....    1256 

Retro-peritoneal  Fossae 1270 

Surgical  Anatomy 1274 

The  Stomach. 

Relations  of  the  Stomach       .... 

Surfaces 

The  Cardia 

The  Pylorus 

Alterations  in  Position 

Supports  of  the  Stomach       .... 

Structure 

Movements  and  Innervation  of  Stomach 

Surface  Form 

Surgical  Anatomy 

The  Small  Intestine. 

The  Duodenum 

The  First  or  Superior  Portion  . 
The  Second  or  Descending  Portion 
The    Third,    Pre-aortic,    Horizontal    or 

Transverse  Portion 

The   Fourth  or  Ascending  Portion 

The  Jejunum  and  Ileum 

Differences  between  the  Jejunum  and 

Ileum 

The  Jejunum         

The  Ileum 

Structure  of  the  Small  Intestine,  including 
the  Duodenum  . 


1277 
1277 

1278 
1279 
1280 
1281 
1281 
1288 
1288 
1288 


1290 
1292 
1293 

1293 
1294 
1297 

1297 
1297 
1297 

1298 


The  Large  Intestine. 

The  Caecum 1308 

The  Vermiform  Appendix     .      .      .      .1311 
The  Ileo-ca3cal  Valve  or  the  Valve  of 

Bauhin 1315 

The  Colon 1317 

The  Ascending  Colon 1317 

The  Transverse  Colon 1317 

The  Descending  Colon 1317 

The  Sigmoid  Flexure,  Pelvic  Colon  or 
Sigmoid  Colon 1317 

The  Rectum 1320 

The  Common  Anal  Canal     ....   1323 

Structure  of  the  Large  Intestine      .      .      .   1324 

Movements  and  Innervations  of  the  Intes- 
tines     1330 

Surface  Form  of  the  Intestines   .       .      .      .1331 

Surgical  Anatomy  of  the  Intestines       .      .1331 

The  Liver. 

The  Superior  Area  or  Surface      ....  1336 

The  Anterior  Area  or  Surface      ....  1336 

The  Lateral  or  Right  Area  or  Surface   .      .  1336 

The  Under  or  Visceral  Area  or  Surface       .  1336 

The  Posterior  Area  or  Surface     ....  1337 

Fissures  of  the  Liver 1338 

Lobes  of  the  Liver 1339 

Supports  and  Movability  of  the  Liver  .      .  1342 

Abnormalities  of  the  Liver 1342 

Structure  of  the  Liver 1345 

The  Excretory  Apparatus  of  the  Liver       .  1349 

The  Hepatic  Duct 1350 

The  Gall-bladder 1350 

The  Cystic  Duct         1351 

Surface  Relations  of  the  Liver    ....  1353 

Surgical  Anatomy  of  the  Liver  ....  1354 


The  Pancreas. 

Dissection 

The  Right  Extremity  or  Head  of  the  Pan- 
creas    

The  Neck  of  the  Pancreas 

The  Body  and  Tail  of  the  Pancreas 

Structure  of  the  Pancreas 

Surface  Form 

Surgical  Anatomy 


1355 


The  Spleen. 

Surface  of  the  Spleen 

Supports  and  Movability  of  the  Spleen 

Surface  Form 

Surgical  Anatomy 


1357 
1357 
1357 
1359 
1360 
1360 


1361 
1363 
1366 
1366 


ORGANS  OF  VOICE  AND  RESPIRATION. 


THE  LARYNX. 

The  Cartilages  of  the  Larynx      .      .      .      .1370 

The  Thyroid  Cartilage 1370 

The  Cricoid  Cartilage 1371 

The  Arytenoid  Cartilages     .      .      .      .1372 
The  Cornicula  Laryngis  or  Cartilages 

of  Santorini 1373 

The  Cuneiform  Cartilages  or  Cartilages 

of  Wrisberg 1373 

The  Epiglottis  or  the  Cartilage  of  Epi- 
glottis      1373 

Structure  of  the  Larynx 1373 

Interior  of  the  Larynx 1376 

THE  TRACHEA  AND  BRONCHI. 

Relations 1384 

The  Right  Bronchus 1384 

The  Left  Bronchus 1386 

Structure  of  the  Trachea 1386 

Surface  Form  of  Larynx 1389 

Surgical  Anatomy  of  Larynx  and  Trachea  .  1389 


THE  PLEURAE. 

Reflections  of  the  Pleura 1392 

Structure  of  the  Pleura 1395 

Surgical  Anatomy 1395 

THE  MEDIASTINAL  SPACE,  INTERPLEURAL  SPACE 
OR  MEDIASTINUM. 

The  Superior  Mediastinum 1 

The  Anterior  Mediastinum 1 

The  Middle  Mediastinum 1396 

The  Posterior  Mediastinum 1397 


THE  LUNGS. 

Apex  of  the  Lungs •   1 

Base  of  the  Lungs 1398 

Surfaces  of  the  Lungs 1 

Borders  of  the  Lungs 1 

Lobes  of  the  Lungs 1402 


CONTENTS 


xxv 


The  Root  of  the  Lung 
The  Foetal  Lung     . 
Structure  of  the  Lung 
The  Bronchus  . 


PAGE 
1402 
1402 
1403 
1403 


Changes  in  the  Structure  of  the  Bronchi  in 

the  Lungs 1403 

Surface  Form  of  the  Lungs 1405 

Surgical  Anatomy  of  the  Lungs   ....  1406 


THE  DUCTLESS  GLANDS. 


THE  THYROID  BODY  OR  GLAND. 

Accessory  Thyroids 1409 

Structure  of  the  Thyroid 1409 

Surgical  Anatomy 1411 

THE  PARATHYROID  GLANDS 1412 

Structure T  1413 

Surgical  Anatomy 1413 


THE  THYMUS  GLAND. 
Structure  of  the  Thymus  Gland  ....      1414 

THE  CAROTID  GLAND  OR  CAROTID  BODY. 


Surgical  Anatomy 

THE  COCCYGEAL  GLAND  OR  COCCYGEAL 


BODY 


THE  PARASYMPATHETIC  BODIES 


1417 


1417 
1417 


THE  URINARY  ORGANS. 


THE  KIDNEYS. 

Surfaces  of  the  Kidneys    .      .      .      .      .      .  1420 

Borders  of  the  Kidneys 1423 

General  Structure  of  the  Kdney       .      .      .  1423 

Surface  Form ,  1434 

Surgical  Anatomy 1434 

THE  URETER. 

The  Ureter  Proper 1435 

Relations  of  the  Ureter 1435 

Structure  of  the  Ureter 1436 

Surgical  Anatomy 1437 

THE  SUPRARENAL  CAPSULE  OR  GLAND. 

Relations  of  the  Suprarenal  Capsule      .      .  1437 

Accessory  Suprarenal  Glands       ....  1438 

Structure  of  Suprarenal  Glands                       '.  1438 


THE  CAVITY  OF  THE  PELVIS. 


Boundaries 
Contents 


1440 
1440 


The  Urinary  Bladder. 

Surfaces        .      .  - 1442 

The  Fundus  or  Base 1443 

The  Summit  or  Apex 1445 

The  Urachus  or  Middle  Umbilical  Ligament  1445 

Structure  of  the  Bladder 1446 

Objects  Seen  on  the  Inner  Surface  of  Bladder  1447 

Surface  Form 1449 

Surgical  Anatomy 1449 

The  Male  Urethra. 

The  First  or  Prostatic  Portion     ....  1450 
The  Second,  Muscular  or  Membranous  Por- 
tion       1451 

The  Third,  Penile,  Pendulous,  Cavernous  or 

Spongy  Portion 1452 

Structure  of  Male  Urethra 1453 

Surgical  Anatomy 1454 

The  Female  Bladder  and  Urethra. 

The  Female  Urethra 1455 

Structure 1455 


THE  MALE  ORGANS  OF  GENERATION. 


THE  PROSTATE  GLAND. 

The  Base  , 1461 

The  Apex 1461 

Surfaces 1461 

The  Lateral  Lobes 1461 

The  So-called  Middle  Lobe 1461 

Structure 1462 

Surgical  Anatomy 1462 

COWPER'S  GLANDS. 

Structure 1463 

THE  PENIS. 

The  Root 1464 

The  Body  of  the  Penis 1465 

Structure  of  the  Penis 1465 

Surgical  Anatomy 1470 

THE  TESTICLES  AND  THEIR  COVERINGS. 

Descent  of  the  Testis. 

Surgical  Anatomy 1472 


The  Coverings  of  the  Testicle. 

The  Testicular  Bag  or  Scrotum    ....  1472 

The  Intercolumnar  or  Spermatic  Fascia       .  1474 

The  Cremasteric  Fascia 1474 

The  Infundibuliform  Fascia 1475 

The  Tunica  Vaginalis 1476 

The  Spermatic  Cord. 

Structure 1476 

Surgical  Anatomy 1478 

The  Testicles. 

The  Tunics  of  the  Testicle 1481 

Structure  of  the  Testicle  and  Epididymis      .  1482 

THE  SEMINAL  VESICLES. 

The  Ejaculatory  Ducts 1487 

Structure          1487 

Surgical  Anatomy 1487 


THE  FEMALE  ORGANS  OF  GENERATION. 


EXTERNAL  ORGANS. 

The  Large  Lips  or  Labia  Majora  .  .       .  1489 

The  Small  Lips,  Nympha;  or  Labia  Minora  .  1490 

The  Vestibule  .  1491 


The  Clitoris       .       . 
Glands  of  Bartholin 
The  Vaginal  Bulb  . 


1493 
1495 
1495 


XXVI 


CONTENTS 


Relations 
Structure 


INTERNAL  ORGANS. 
The  Vagina. 

The  Womb  or  Uterus. 


1496 
1496 


The  Fundus 1499 

The  Body  of  the  Uterus 1499 

The  Neck  or  Cervix  Uteri 1500 

Folds  and  Ligaments 1501 

The  Cavity  of  the  Uterus 1503 

The  Cavity  of  the  Cervix  or  Cervical  Canal  1503 

Surgical  Anatomy 1508 

THE  ADNEXA  OR  APPENDAGES  OF  UTERUS. 

The  Fallopian  Tube. 
Structure  of  the  Fallopian  Tube      .      .      7  1510 


The  Epo-ophoron,  Parovarium  or  Organ  of 

Rosenmiiller 

The  Paro-ophoron 

The  Ovary. 

Supports  and  Connections  of  the  Ovary 
Descent  of  the  Ovary 

The  Ovary  at  Different  Ages     . 

Structure 

Surgical  Anatomy  of  the  Appendages 

The  Mammary  Gland. 
Description  of  a  Well-developed  Breast 
The  Nipple         ....  ..'.-'* 

Prolongation  of  Mammary  Tissue    . 
Structure  of  Mammary  Gland  and  Nipple    . 

Surgical  Anatomy  .      . 

The  Male  Breast 

Surgical  Anatomy 


1511 
1512 


1513 
1513 
1513 
1514 
1515 


1516 
1516 
1518 
1518 
1520 
1522 
1522 


THE   SURGICAL  ANATOMY  OF  INGUINAL  AND  FEMORAL 

HERNIA. 


Dissection 1523 

Inguinal  Hernia. 

Oblique  Inguinal  Hernia 1532 

Congenital  Hernia 1535 

Infantile  and  Encysted  Hernia  .  .  1535 


Hernia  into  Funicular  Process 
Direct  Inguinal  .Hernia     . 


Femoral  Hernia. 
Varieties  of  Femoral  Hernia 


1535 
1535 


1536 


SURGICAL  ANATOMY  OF  THE  PERINEUM. 


Dissection    .  ......      77.    1537  1  Surgical  Anatomy 

Ischio-rectal  Region. 
Dissection    ......      ....    1538 

„,     D     . 

The  Permaeum  Proper  ^n  the  Male. 

Position  of  the  Viscera  at  the  Outlet  of  the 

Pelvis        ..........    1552 


1553 


The   Female  Perineum. 
The  Pelvic  Fascia  ........   1556 

The  obturator  Fascia       ......   1558 

The   Recto-vesical   Fascia  or  the   Visceral 

Layer  of  the  Pelvic  Fascia       ....   1558 


CHRONOLOGICAL  TABLE  OF  THE  DEVELOPMENT  OF  THE  FOSTUS      ....     .""     .      .      .      .  1559 
INDEX .   1561 


DESCRIPTIVE  AND  SURGICAL 

ANATOMY. 


OSTEOLOGY-THE  SKELETON. 


T 


HE  entire  skeleton  in  the  adult  consists  of  200  distinct  bones.    These  are: 

The  spine  or  vertebral  column  (sacrum  and  coccyx  included)     ....  26 

Cranium 8 

Face 14 

Hyoid  bone,   sternum,   and   ribs 26 

Upper  extremities 64 

Lower  extremities 62 

200 

In  this  enumeration  the  patellae  are  included  as  separate  bones,  but  the  smaller 
sesamoid  bones  and  the  ossicula  auditus  are  not  reckoned.  The  teeth  belong  to 
the  tegumentary  system.  Different  anatomists  make  different  computations  as 
to  the  number  of  bones  in  the  skeleton.  Some  describe  the  skeleton  as  containing 
206  distinct  bones,  adding  the  ossicles  of  the  ear  to  the  previously  stated  number. 
By  adding  the  epipteric  bones,  the  sphenoidal  turbinal  bones,  the  sesamoid  bones, 
and  others,  the  number  may  be  greatly  augmented. 

Bones  are  divisible,  according  to  their  shape,  into  four  classes:  long,  short,  flat, 
and  irregular. 

Long  Bones. — The  long  bones  are  found  in  the  limbs,  where  they  form  a 
system  of  levers,  which  sustain  the  weight  of  the  trunk  and  confer  the  power 
of  locomotion.  A  long  bone  consists  of  a  shaft  and  two  extremities.  The  shaft 
is  a  hollow  cylinder,  contracted  and  narrowed  to  afford  greater  space  for  the 
bellies  of  the  muscles;  the  walls  consist  of  dense,  compact  tissue  of  great  thick- 
ness in  the  middle,  but  becoming  thinner  toward  the  extremities;  the  spongy 
tissue  is  scanty,  and  the  bone  is  hollowed  out  in  its  interior  to  form  the  medullary 
canal.  The  extremities  are  generally  somewhat  expanded  for  greater  convenience 
of  mutual  connection,  for  the  purpose  of  articulation,  and  to  afford  a  broad 
surface  for  muscular  attachment.  Here  the  bone  is  made  up  of  spongy  tissue 
with  only  a  thin  coating  of  compact  substance.  The  long  bones  are  not  straight, 
but  curved,  the  curve  generally  taking  place  in  two  directions,  thus  affording 
greater  strength  to  the  bone.  The  bones  belonging  to  this  class  are  the  clavicle, 
humerus,  radius,  ulna,  femur,  tibia,  fibula,  metacarpal  and  metatarsal  bones,  and 
the  phalanges. 

Short  Bones. — Where  a  part  of  the  skeleton  is  intended  for  strength  and  com- 
pactness, and  its  motion  is  at  the  same  time  slight  and  limited,  it  is  divided  into 
a  number  of  small  pieces  united  together  by  ligaments,  and  the  separate  bones 
are  short  and  compressed,  such  as  the  bones  of  the  carpus  and  tarsus.  These 
bones,  in  their  structure,  are  spongy  throughout,  excepting  at  their  surface,  where 

3  (  33  ) 


34  THE  SKELETON 

there  is  a  thin  crust  of  compact  substance.    The  patellae  also,  together  with  the 
other  sesamoid  bones,  are  by  some  regarded  as  short  bones. 

Flat  Bones. — Where  the  principal  requirement  is  either  extensive  protection 
or  the  provision  of  broad  surfaces  for  muscular  attachment,  we  find  the  osseous 
structure  expanded  into  broad,  flat  plates,  as  is  seen  in  the  bones  of  the  skull 
and  the  shoulder-blades.  Flat  bones  are  composed  of  two  thin  layers  of  com- 
pact tissue  enclosing  between  them  a  variable  quantity  of  cancellous  tissue.  In 
the  cranial  bones  these  layers  of  compact  tissue  are  familiarly  known  as  the  tables 
of  the  skull ;  the  outer  table  is  thick  and  tough ;  the  inner  table  is  thinner,  denser, 
and  more  brittle,  and  hence  is  termed  the  vitreous  table.  The  intervening  can- 
cellous tissue  is  called  the  diploe.  The  flat  bones  are:  the  occipital,  parietal,  frontal, 
nasal,  lachrymal,  vomer,  scapula,  os  innominatum,  sternum,  ribs,  and  patella. 

Irregular  Bones.  —The  irregular  or  mixed  bones  are  such  as,  from  their  pecu- 
liar form,  cannot  be  grouped  under  either  of  the  preceding  heads.  Their  structure 
is  similar  to  that  of  other  bones,  consisting  of  a  layer  of  compact  tissue  externally 
and  of  spongy,  cancellous  tissue  within.  The  irregular  bones  are:  the  vertebrae, 
sacrum,  coccyx,  temporal,  sphenoid,  ethmoid,  malar,  superior  maxilla,  inferior  maxilla, 
palate,  inferior  turbinated,  and  hyoid. 

Surfaces  of  Bones. — If  the  surface  of  any  bone  is  examined,  certain  eminences 
and  depressions  are  seen,  to  which  descriptive  anatomists  have  given  the  following 
names. 

These  eminences  and  depressions  are  of  two  kinds:  articular  and  non-articular. 
Well-marked  examples  of  articular  eminences  are  found  in  the  heads  of  the 
humerus  and  femur  and  of  articular  depressions  in  the  glenoid  cavity  of  the 
scapula  and  the  acetabulum.  Non-articular  eminences  are  designated  according 
to  their  form.  Thus  a  broad,  rough,  uneven  elevation  is  called  a  tuberosity;  a 
small,  rough  prominence,  a  tubercle;  a  sharp,  slender,  pointed  eminence,  a  spine; 
a  narrow,  rough  elevation,  running  some  way  along  the  surface,  a  ridge,  line,  or 
crest. 

The  non-articular  depressions  are  also  of  very  variable  form,  and  are  described 
as  fossae,  grooves,  furrows,  fissures,  notches,  sulci,  etc.  These  non-articular  emi- 
nences and  depressions  may  receive  blood-vessels,  nerves,  tendons,  ligaments,  or 
portions  of  organs,  or  may  serve  to  increase  the  extent  of  surface  for  the  attach- 
ment of  ligaments  and  muscles.  They  are  usually  well  marked  in  proportion  to 
the  muscular  development  of  the  subject. 

A  prominent  process  projecting  from  the  surface  of  a  bone  which  it  has  never 
been  separate  from  or  movable  upon  is  termed  an  apophysis  (from  d^ot/'Uffa;,  an 
excrescence) ;  but  if  such  process  is  developed  as  a  separate  piece  from  the  rest  of 
the  bone,  to  which  it  is  afterward  joined,  it  is  termed  an  epiphysis  (from  iKiyufftz, 
an  accretion).  The  main  part  of  the  bone,  or  shaft,  which  is  formed  from  the 
primary  centre  of  ossification,  is  termed  the  diaphysis,  and  is  separated,  during 
growth,  from  the  epiphysis  by  a  layer  of  cartilage,  at  which  growth  in  length  of 
the  bone  takes  place.  Some  bones  are  hollow  and  contain  sinuses,  which  are 
spaces  for  air.  Canals  or  foramina  are  channels  or  openings  in  bone  through 
which  nerves  or  vessels  pass. 

Structure  of  Bone. — Bone  is  a  highly  specialized  form  of  connective  tissue. 
In  reality,  it  is  white  fibrous  tissue,  calcified  and  structurally  modified  until  it 
becomes  osseous  tissue.  Bone  is  not  simply  a  crude  mass  resulting  from  the 
calcification  of  cartilage  or  fibrous  tissue;  it  is  a  distinct  tissue,  of  a  definite  struc- 
ture, the  constituent  parts  of  which  are  arranged  symmetrically.  Its  structure 
varies  somewhat  in  different  vertebrates.1 

1  Arquitectura  del  Aparato  de  Sustentacion  en  los  Vertebrados.     Por  el  Dr.  Saturnine  Garcia  Hurtado.     Our 
description  applies  to  human  bone. 


STRUCTURE    OF  BONE 


35 


There  are  two  varieties  of  bone:  dense  or  compact  bone  (substantia  compacta], 
and  cancellous,  loose,  or  spongy  bone  (substantia  spongiosa). 

Compact  Bone  is  dense,  like  ivory,  and  is  always  placed  upon  the  exterior  of 
bones.  Even  this  apparently  compact  tissue  is  porous;  it  differs  from  cancellous 
bone  in  the  greater  density  of  its  tissue  and  in  the  arrangement  of  its  osseous 
plates  into  Haversian  systems.  Compact  bone  is  surrounded  by  periosteum. 


OSTEOGENETIC 
CELLS 


LAMELL/E 

LACUN/E 

CANALIOUL 

HAVERSIAN 

CANAL 


COMPLETE 
HAVERSIAN 
SYSTEM 


FIG.  1. — Diagram  of  the  structure  of  osseous  tissue.  A  small  part  of  a  transverse  section  of  the  shaft  of  a  long 
bone  is  shown.  At  the  uppermost  part  is  the  periosteum  covering  the  outside  of  the  bone  ;  at  the  lowermost  part 
is  t  he  endosteum  lining  the  marrow-cavity.  Between  these  is  the  compact  tissue,  consisting  largely  of  a  series  of 
Haversian  systems,  each  being  circular  in  outline  and  perforated  by  a  central  canal.  In  the  first  one  is  shown 
only  the  area  occupied  by  a  system;  in  the  second  is  seen  the  concentric  arrangement  of  the  lamellae;  and  in  the 
others,  respectively,  canaliculi;  lacuna1;  lacunae  and  canaliculi;  the  contents  of  the  canal,  artery,  vein,  lymphatic 
and  areolar  tissue;  lamellae,  lacunae,  and  canaliculi;  and,  finally,  all  of  the  structures  composing  a  complete  sys- 
tem. Between  the  systems  are  circumferential  and  intermediate  lamellae,  only  a  few  of  which  are  represented  as 
lodging  lacunae,  though  it  is  to  be  understood  that  the  lacunae  are  in  all  parts.  The  periosteum  is  seen  to  be 
made  up  of  a  fibrous  layer  and  a  vascular  layer,  and  to  have  upon  its  attached  surface  a  stratum  of  cells.  From 
the  fibrous  layer  project  inward  the  rivet-like  fibres  of  Sharpey.  (F.  H.  Gerrish.) 

The  outer  portion  of  the  wall  of  a  long  bone,  the  cortex  of  the  head  of  a  bone, 
and  the  outer  and  inner  layers  of  a  flat  bone  are  composed  of  compact  osseous 
tissue,  which  is  the  hardest  substance  in  the  body  with  the  exception  of  dentine 
and  enamel ;  it  is  tough  and  elastic,  and  much  force  is  required  to  break  it. 

Cancellous  Bone  is  found  in  the  interior  of  bones.  The  name,  which  means 
lattice-work,  indicates  the  structure,  which  consists  of  slender  fibres  and  lamellse 
joined  to  form  a  reticulum,  the  small  meshes  of  which  are  marrow-spaces.  The 


36  THE  SKELETON 

spicules  of  cancellous  bone  contain  lacunae  and  canaliculi,  but  no  Haversian 
systems.  In  some  regions  the  inner  portion  of  the  wall  of  a  long  bone,  about  the 
marrow-cavity,  is  composed  of  cancellous  bone.  Toward  each  extremity  of  the 
shaft  the  amount  of  cancellous  tissue  increases,  the  marrow-cavity  diminishes  in 
size,  and  the  cancellous  tissue  is  arranged  in  lines  that  approach  each  other  toward 
the  extremity,  like  the  sides  of  an  arch,  and  form  a  support  for  the  epiphysis 
(Fig.  131).  In  the  epiphysis  the  bone-plates  are,  as  a  rule,  at  right  angles  to 
the  plane  of  the  articular  surface  (the  lines  of  greatest  pressure) ;  and  they  are 
bound  together  or  strengthened  by  other  bone-fibres,  which  are  usually  in  corre- 
spondence with  the  planes  of  the  articulation  (the  lines  of  greatest  tension)  (Fig. 
164).  The  nearer  the  bone-spicules  are  to  the  medullary  cavity  the  stronger  they 
are  (Hurtado). 

In  the  flat  and  the  irregular  bones,  the  cancellous  tissue  is  between  the  layers 
of  compact  bone,  and  is  called  the  diploe. 

A  Short  Bone  is  composed  chiefly  of  cancellous  tissue,  which  is  encased  in  a 
thin  coat  of  compact  substance  (substantia  corticalis). 

A  Long  Bone  consists  of  a  shaft,  or  diaphysis,  and  two  extremities,  or  epiphyses. 
The  shaft  is  an  osseous  tube,  the  outer  layer  of  which  is  compact,  and  the  inner 
layer  of  which  is  cancellous.  It  surrounds  the  medullary  cavity  (cavum  medullare), 
which,  in  the  recent  condition,  contains  the  medulla,  or  marrow  (medulla  ossium), 
which  substance  enters  into  the  nearest  Haversian  canals.  This  cavity  is  widest 
at  the  centre  of  the  shaft,  and  narrows  toward  the  ends,  where  it  is  encroached 
upon  by  the  cancellous  layer  which  lies  within  the  compact  layer. 

There  are  two  varieties  of  marrow:  Yellow  marrow  (medulla  ossium  flava)  is 
found  in  the  medullary  cavities  of  the  shafts  of  the  long  bones.  It  is  composed 
of  a  network  of  fibrous  tissue  carrying  many  blood-vessels,  fat-cells,  and  a  few 
large  nucleated  masses  of  protoplasm — the  true  marrow-cells,  or  myelocytes. 
The  yellow  color,  of  the  marrow  is  due  to  fat.  Yellow  marrow  is  derived  from 
red  marrow  by  an  increase  in  fat  and  diminution  in  marrow  elements;  it  plays 
no  part  in  blood-formation.  At  the  periphery  of  the  marrow  cavity  the  fibrous 
tissue  of  the  network  forms  a  firm,  fibrous  membrane  lining  the  cavity.  This 
represents  an  inner  periosteum,  and  is  called  the  endosteum. 

Red  marrow  (medulla  ossium  rubra)  is  found  in  the  diploe  of  the  cranial  bones,  in 
the  cancellous  tissue  of  the  vertebrae,  ribs,  and  sternum,  and  in  the  articular  ends 
of  the  long  bones.  Red  marrow  contains  much  less  fat  and  is  less  solid  than  yellow 
marrow.  It  consists  of  a  delicate  network  of  connective  tissue,  supporting  a 
dense  capillary  plexus ;  some  fat;  and  numerous  cellular  elements.  The  delicate 
fibrous  membrane  surrounding  red  marrow  is  called  the  endosteum.  The 
cellular  elements  of  red  marrow  (Fig.  2)  comprise,  first,  marrow-cells,  or  myelocytes, 
which  are  protoplasmic  masses,  capable  of  amoeboid  movements,  and  containing 
large  nuclei.  They  are  not  found  in  normal  blood,  but  are  abundant  in  leukaemia; 
second,  small,  nucleated,  reddish  cells  called  erythroblasts,  resembling  the  nucleated 
red  cells  of  the  blood  of  the  embryo,  and  eventually  by  the  loss  of  their  nuclei 
becoming  red  blood-corpuscles;  third,  non-nucleated  red  blood-corpuscles;  fourth, 
giant-cells  containing  one  or  more  nuclei.  They  are  varieties  of  leukocytes.  The 
leukocyte  group  also  contains  the  osteoclasts,  eosinophiles,  and  mast-cells. 

Gelatinous  or  mucoid  marrow  is  formed  by  the  absorption  of  the  fat  and  the 
cellular  elements  of  yellow  marrow,  and  by  the  serous  infiltration  of  the  inter- 
cellular substance.  It  is  produced  by  starvation,  old  age,  and  certain  pathological 
conditions. 

Each  extremity  of  a  long  bone  is  separated  from  the  shaft  by  a  layer  of  car- 
tilage known  as  the  cambium  layer,  the  epiphysial  cartilage,  or  the  epiphysial 
disk  (Fig.  8).  Growth  from  the  cartilages  causes  an  increase  in  the  length  of 
the  bone.  The  cartilages  ossify  during  development,  and  effect  a  bony  union 


STRUCTURE    OF  BONE 


37 


between    the   shaft    and  the   head  of   the    bone.     Certain    bony   processes   are 
separated  from  the  bone  by  cartilage,  which  later  ossifies. 

A  Flat  Bone  is  composed  of  two  layers  of  compact  bone  with  a  layer  of  can- 
cellous  bone  (the  diploe)  interposed.  There  is  no  general  marrow-cavity;  but 
the  spaces  between  the  bone-spicules  intercommunicate  and  contain  marrow. 


FIG.  2. — Cells  of  red  marrow  of  the  guinea-pig,     a-d.  Myelo-plaques.     e-i.  Marrow-cells  proper,    j-t.  Erythro- 
blasts — some  in  process  of  division.     (Schiifer.) 

The  Periosteum  is  a  fibrous  membrane  adhering  to  the  surface  of  the  bone  in 
nearly  every  .part  except  at  the  cartilage-covered  extremities.  When  strong  ten- 
dons or  ligaments  are  attached  to  the  bone,  the  periosteum  is  incorporated  with 
them.  By  means  of  the  periosteum  many  vessels  reach  and  enter  the  hard  bone 
through  Volkmann's  canals.  This  is  shown  by  stripping  the  periosteum  from  the 
surface  of  living  bone,  when  small  bleeding  points  are  seen,  each  of  which 
marks  the  entrance  of  a  vessel  from  the  periosteum.  It  thus  becomes  obvious 
that  the  loosening  of  the  periosteum,  by  depriving  a  portion  of  the  bone  of  its 
nourishment,  may  produce  necrosis.  The  membrane  is  firmly  attached  to  the 
bone  by  trabeculse  of  fibrous  tissue,  which  pene- 
trate the  bone  at  right  angles  to  its  surface,  and 
carry  blood-vessels.  These  trabeculse  are  called 
the  fibres  of  Sharpey  (Fig.  3).  They  do  not  di- 
rectly enter  the  Haversian  systems,  but  only  the 
circumferential  and  intermediate  lamellae — parts 
that  are  formed  by  periosteal  action.  Prolonga- 
tions from  some  of  these  vessels  reach  the  Haver- 
sian canals,  and  even  the  bone-marrow.  In  the 
extremities  of  a  long  bone,  vessels  from  the  peri- 
osteum penetrate  the  layer  of  compact  bone  and 
reach  the  cancellous  tissue.  In  the  newborn  and 
in  the  young  the  periosteum  is  composed  of  three 
layers:  an  outer  or  fibrous  layer,  containing  some 
blood-vessels,  and  composed  of  bundles  of  white 
fibrous  tissue;  a  middle  or  fibro-elastic  layer,  con- 
taining some  blood-vessels,  fibrous  tissue,  and 
much  elastic  tissue ;  and  an  inner  or  osteogenetic  layer,  which  is  very  vascular  and 
contains  numerous  cells,  which  are  converted  into  osteoblasts.  These  are  the 
cells  that  form  osseous  tissue. 


m 


FIG.  3. — Fibres  of  Sharpey  from  the 
parietal  bone  (adult  man)  isolated  by 
dissociation.  (After  Kolliker.) 


38 


THE  SKELETON 


Transverse  Section  of  Compact  Bone  (Figs.  1,  4,  and  6). — As  previously  stated, 
dense  bone  differs  from  cancellous  bone  in  the  fact  that  the  bone-plates  of  the 
former  are  arranged  in  Haversian  systems,  so  named  from  the  anatomist 
Havers.  A  Haversian  system  consists  of  a  central  canal,  running  in  a  more  or 
less  longitudinal  or  slightly  curved  or. spiral  direction  and  called  the  Haversian 
canal ;  from  five  to  ten  bone-plates,  or  lamellae,  arranged  concentrically  around  the 
canal;  gaps,  called  lacunae,  between  the  lamellae,  which  spaces  contain  bone-cor- 
puscles; minute  channels,  or  canaliculi,  radiating  from  the  lacunae  and  passing 
through  the  lamella? — some  reaching  other  lacunae,  some  reaching  the  Haver- 
sian canal,  and  others  passing  to  adjacent  Haversian  systems.  The  canaliculi 
contain  processes  from  the  bone-corpuscle.  From  a  study  of  transverse  sections 
it  would  be  thought  that  the  lamellae  always  run  longitudinally  in  straight  lines 
or  in  curves  determined  by  pressure  and  tension;  but  Prof.  Dixon  proved  that 
in  the  human  femur  many  of  the  bone-plates  are  arranged  spirally,  and  thus 
increased  strength  is  obtained.  The  same  is  probably  true  of  other  bones. 


FIG.  4. — Transverse  section  of  compact  tissue  of  bone.     Magnified  about  150  diameters.     (Sharpey.) 


There  are  four  varieties  of  lamellae:  (1)  the  periosteal,  peripheral,  superficial, 
or  external;  (2)  the  Haversian,  or  concentric;  (3)  the  interstitial,  ground,  or  inter- 
mediate; and  (4)  the  perimedullary,  or  internal.  The  periosteal  lamellae  are  some- 
times called  primary,  as  they  are  the  first  to  appear,  and  are  formed  by  the  direct 
transformation  of  the  inner  layer  of  the  periosteum  into  bone.  In  the  shaft  of 
a  long  bone  there  are  several  layers  of  periosteal  lamellae,  but  no  one  layer  is 
extensive  enough  to  surround  the  bone  completely. 

In  the  outer  surface  of  the  layer  of  periosteal  lamellae  depressions  exist  that 
are  known  as  Howship's  foveolae,  or  lacunas.  These  depressions  are  made  by 
large  cells,  called  osteoclasts,  which  destroy  bone.  There  are  no  Haversian 
canals  in  this  outer  layer,  but  there  are  some  large  channels  that  convey  blood- 
vessels into  the  bone,  and  are  known  as  Volkmann's  canals.  Many  small  arteries 
from  the  periosteum  enter  the  periphery  of  the  shaft,  and  also  of  the  epiphyses. 
A  large  trunk  enters  the  shaft  by  the  nutrient  foramen  (foramen  nutricius),  pass 
along  the  nutrient  canal  (canalis  nutricius),  and  reaches  the  medullary  canal. 
This  vessel  is  called  the  nutrient  artery. 

The  Haversian  or  concentric  lamellae  are  circular  layers  arranged  around  a 
central  space,  or  canal,  known  as  the  Haversian  canal.  There  is  no  fixed  num- 
ber of  these  layers,  there  being  usually  from  five  to  ten.  The  layers  of  each  system 
are  parallel  to  one  another,  but  the  layers  of  different  systems  cross  at  various 


BLOOD-VESSELS  OF  BONE 


39 


angles.  Between  these  layers  are  small,  irregular  spaces,  called  lacunae;  and 
extending  radially  out  from  the  lacunae  and  piercing  the  various  lamellae  are 
delicate  canals,  known  as  canaliculi,  which  connect  the  lacunae.  The  lacuna 
nearest  to  the  Haversian  canal  communicates  with  it  by  means  of  canaliculi; 
and  canaliculi  also  communicate  with  other  Haversian  systems.  The  Haversian 
canal  contains  blood-vessels — an  artery  or  a  vein,  or  both  an  artery  and  a  vein — 
and  a  nerve.  The  vessel  in  the  canal  is  covered  with  endothelial  cells,  and  the 
canal  itself  is  lined  with  them.  The  space  thus  formed  is  a  lymph-space,  and 
into  these  lymph-spaces  the  canaliculi  empty.  Beneath  the  periosteum  and  at 
the  periphery  of  the  medullary  cavity  there  are  lymph-spaces  that  are  in  direct 
communication  with  the  canaliculi  of  the  Haversian  systems.  In  each  lacuna  is 
a  bone-cell— a  corpuscle  that  almost  fills  the  space,  and  sends  arms,  or  processes, 
out  into  the  canaliculi  (Fig.  5).  This  bone-cell  is  an  osteoblast. 

The  interstitial  or  intermediate  lamellae  occupy  the  spaces  between  the 
Haversian  systems.  They  represent  the  remains  of  peripheral  lamellae.  They 
are  usually  short  and  very 

-Spe 


lacunae 


irregular,    but    possess 

i  1*1*1*1 

and  canaliculi,  which  are  ar- 
ranged as  in  the  Haversian 
systems.  The  perimedullary 
lamellae  are  irregular  and  few 
in  number. 


FIG.  5. — Nucleated  bone-cells  and  their 
processes,  contained  in  the  bone-lacunae  and 
their  canaliculi,  respectively.  From  a  section 
through  the  vertebra  of  an  adult  mouse. 
(Klein  and  Noble  Smith.) 


FIG.  6. — Combined  transverse  and  longitudinal  section  of 
compact  bone.  Off.  Longitudinal  Haversian  canal  and 
anastomosing  canals,  o.  Communicating  with  medullary 
cavity.  Si.  Intermediate  systems.  Spe.  Circumferential 
lamellae.  Spi.  Perimedullary  lamella;.  os.  Osteoblasts. 
(Poirier  and  Charpy.) 


The  osteoblasts  are  irregular,  flattened,  stellate  masses  of  protoplasm,  pos- 
sessing a  number  of  processes.  The  protoplasm  is  granular,  and  each  cell  con- 
tains a  large  and  distinct  nucleus.  Osteoblasts  are  met  with  in  the  deeper  layer 
of  the  periosteum,  in  the  endosteum,  and  in  the  lacunae. 

Longitudinal  Section  of  Compact  Bone  (Figs.  6  and  7). — We  do  not  see  con- 
centric rings,  as  in  a  transverse  section,  but  rows  of  lacunae  parallel  to  the  course 
of  the  Haversian  canals — and  these  canals  appear  like  half-tubes  instead  of 
circular  spaces.  The  tubes  are  seen  to  branch  and  communicate,  so  that  each 
separate  Haversian  canal  runs  only  a  short  distance.  In  other  respects  the 
structure  closely  resembles  that  of  a  transverse  section. 

Lamellae  of  Cancellous  Bone. — There  are  no  Haversian  canals,  and  canaliculi 
open  into  the  medullary  spaces,  which  act  as  do  the  Haversian  canals  in  com- 
pact bone. 

Blood-vessels  of  Bone. — Small  arteries  derived  from  the  periosteum  enter 
the  minute  orifices  of  the  compact  bone  (Volkmann's  canals)  and  reach  the 


40 


THE   SKELETON 


Haversian  canals  of  the  bony  substance.  Prolongations  from  these  vessels 
reach  the  marrow  and  communicate  with  branches  from  the  nutrient  artery. 
The  cancellous  tissue  is  supplied  by  fewer  but  larger  vessels,  which  are  derived 
from  the  periosteum,  and  which  often  penetrate  the  cortex  of  compact  bone 
and  ramify  in  the  cavities  of  the  spongy  tissue. 


FIG.  7.— From  a  ground  longitudinal  section  through  the  diaphysis  of  the  human   ulna.     All  canals  are  filled 
with  pigment,  which  is  here  black.     Haversian  canals  are  cut  longitudinally.      X  90..     (Szymonowicz.) 

The  medullary  canal  of  a  long  bone  is  supplied  by  a  large  artery  (sometimes 
more  than  one)  called  the  nutrient  artery.  It  enters  the  bone  by  {he  nutrient 
foramen,  which  is  usually  near  the  centre  of  the  shaft,  runs  in  an  oblique  canal 
through  the  compact  structure,  giving  off  branches  to  this  structure,  and  enters 
the  medullary  cavity,  and  sends  branches  upward  and  downward.  These  branches 
communicate  with  branches  from  the  periosteal  vessels  and  subdivide  into  capil- 
laries, which  pass  into  comparatively  large  vessels.  The  walls  of  the  vessels  are 
very  thin,  and  in  some  places  deficient;  the  venous  blood  enters  the  spaces  of 
the  red  marrow,  and  the  current  becomes  extremely  slow.  Small  veins  collect 
the  venous  blood  and  emerge  from  the  bone. 

In  the  humerus  the  nutrient  canal  is  directed  toward  the  elbow-joint;  in  the 
radius  and  the  ulna  the  nutrient  canals  are  directed  toward  the  elbow-joint;  in 
the  femur,  the  canal  is  directed  toward  the  hip-joint;  and  in  the  tibia  and  the 
fibula,  the  canals  are  directed  toward  the  ankle-joint.  As  Professor  Cunningham 
states  it:  "In  the  upper  limb  the  vessels  flow  toward  the  elbow;  while  in  the 


CHEMICAL   COMPOSITION  OF  BONE  41 

lower  limb  they  pass  from  the  knee."  The  red  marrow  of  the  extremities  and 
the  medulla  of  the  entire  shaft,  and  the  bone  of  the  shaft,  except  the  circum- 
ferential lamellae,  are  supplied  by  the  nutrient  artery.  The  circumferential 
lamellae,  wholly,  and  the  cancellous  tissue  of  the  extremities,  in  part,  and  the 
medulla  of  the  shaft  to  a  very  small  extent  are  supplied  by  vessels  from  the 
periosteum.  The  extremities  of  a  bone  also  receive  articular  arteries.  In  most 
of  the  flat  bones,  and  in  some  of  the  short  bones,  one  or  more  large  apertures  exist 
for  the  passage  of  blood-vessels  to  the  central  parts  of  the  bone. 

Veins  emerge  from  the  long  bones  in  three  places:  1.  One  or  two  large  veins 
accompany  the  nutrient  artery.  2.  Numerous  veins  emerge  at  the  articular 
extremities.  3.  Many  small  veins  arise  in  and  emerge  from  compact  substance. 
The  latter  two  classes  do  not  accompany  arteries.  The  veins  in  the  marrow 
and  in  the  bone  are  devoid  of  valves;  but  immediately  after  emerging  from  the 
bone  they  have  numerous  valves. 

In  the  flat  cranial  bones  the  veins  are  numerous  and  large;  as  seen  in  diploic 
canals,  the  walls  of  which  are  composed  of  osseous  tissue,  perforated,  here  and 
there,  for  branches  from  adjacent  cancelli.  In  all  cancellous  tissue  the  venous 
channels  are  similarly  arranged,  and  the  veins  have  very  thin  coats  and  are 
without  valves.  When  the  bone  is  divided,  the  vessels  remain  open;  they  do 
not  retract  into  their  bony  canals,  and  readily  absorb  any  septic  matter  that 
may  be  present. 

The  lymphatics  are  chiefly  periosteal;  but  some  enter  the  bone,  along  with  the 
vessels.  Cruikshank  has  traced  them  into  the  substance  of  the  bone  and  Klein 
has  described  them  as  running  in  the  Haversian  canals.  The  perivascular  spaces 
of  the  Haversian  canals  are  lymph-spaces. 

Nerves,  medullated  (myelinic]  and  non-medullated  (amyelinic'),  are  found  in 
bone.  They  are  distributed  freely  to  the  periosteum,  and  some  of  the  fibres  ter- 
minate in  this  structure  as  Pacinian  corpuscles.  Nerves  accompany  the  nutrient 
arteries  into  the  interior  of  the  bone,  and  also  reach  the  marrow  from  the  peri- 
osteum by  way  of  Volkmann's  canals  and  the  Haversian  canals.  They  certainly 
supply  the  arterial  coats.  It  is  not,  as  yet,  determined  whether  nerves  do  or  do 
not  terminate  in  bone-tissue.  Stroh  maintains  that  occasionally  they  terminate 
in  bone-corpuscles.  According  to  Kolliker  nerves  are  most  numerous  in  the 
articular  extremities  of  the  long  bones,  in  the  vertebrae,  and  the  large  flat  bones. 

Chemical  Composition  of  Bone. — Bone  consists  of  an  animal  and  an  earthy 
part  intimately  combined. 

The  animal  part  may  be  obtained  by  immersing  the  bone  for  a  considerable 
time  in  dilute  mineral  acid,  after  which  process  the  bone  comes  out  exactly  the 
same  shape  as  before,  but  perfectly  flexible,  so  that  a  long  bone  (one  of  the  ribs, 
for  example)  can  easily  be  tied  into  a  knot.  If  now  a  transverse  section  is  made, 
the  same  general  arrangement  of  the  Haversian  canals,  lamellae,  lacunae,  and 
canaliculi  is  seen,  though  not  so  plainly,  as  in  the  ordinary  section. 

The  earthy  part  may  be  obtained  separate  by  calcination,  by  which  the  animal 
matter  is  completely  burned  out.  The  bone  will  still  retain  its  original  form,  but 
it  will  be  white  and  brittle,  will  have  lost  about  one-third  of  its  original  weight, 
and  will  crumble  with  the  slightest  force.  The  earthy  matter  confers  on  bone 
its  hardness  and  rigidity,  and  the  animal  matter  its  tenacity. 

The  mineral  matter  consists  of  phosphate,  carbonate,  and  fluoride  of  calcium, 
chloride  of  sodium,  and  phosphate  of  magnesium. 

The  animal  basis  is  largely  composed  of  ossein,  or  fat  collagen.  When  boiled 
with  water,  especially  under  pressure,  fat  collagen  is  almost  entirely  resolved 
into  gelatin. 

The  organic  matter  of  bone  forms  about  one-third;  the  inorganic  matter, 
two-thirds.  The  exact  composition,  according  to  Professor  Cunningham,  is,  of 


42 


THE   SKELETON 


organic  matter,  31.04  parts;  of  inorganic  matter,  68.97  parts.  Of  the  earthy 
matter,  five-sixths  is  calcium  phosphate.  Even  after  the  removal  of  all  the 
marrow  a  small  percentage  of  fat  is  still  found  in  bone. 

Some  of  the  diseases  to  which  bones  are  liable  mainly  depend  on  the  dispro- 
portion between  the  two  constituents  of  bone.  Thus  in  the  disease  called  rickets, 
so  common  in  the  children  of  the  poor,  the  bones  become  bent  and  curved,  either 
from  the  superincumbent  weight  of  the  body  or  under  the  action  of  certain  mus-^ 
cles.  This  depends  upon  some  defect  of  nutrition  by  which  bone  becomes  deprived 
of  its  normal  proportion  of  earthy  matter,  while  the  animal  matter  is  of  unhealthy 
quality.  In  the  vertebra  of  a  rickety  subject  Bostock  found  in  100  parts  79.75 
animal  and  20.25  earthy  matter.  Osteomalacia  is  a  disease  of  adults  charac- 
terized by  the  decalcification  of  existing  bone  and  by  the  failure  in  calcification 
of  new  osteoid  material.  In  this  disease  the  bone  shows  a  diminution  in 
inorganic  and  an  increase  in  organic  material.  Senile  atrophy  renders  bones 
porous  and  brittle,  and  portions  of  bone  may  actually  be  absorbed,  as  is  seen  in 
the  disappearance  of  the  alveolae  in  old  age.  In  senile  atrophy  of  the  calvaria 
the  outer  table  becomes  very  thin,  porous,  and  brittle,  and  the  inner  table  often 
becomes  rough  and  thicker  from  the  formation  of  new  bone.  In  senile  atrophy 
of  a  long  bone  there  is  absorption  of  bone  from  the  surface  by  osteoclasts  in 
Howship's  lacunae,  and  absorption  of  the  inner  surface.  The  bone  becomes 
porous  and  the  medulla  becomes  more  fatty.  This  change  is  not,  as  was  so 

long  taught,  a  decrease  in  organic  matter 
and  an  increase  in  mineral  matter,  but  is  an 
actual  alteration  in  the  structure  of  the  bone. 
Ossification  and  Growth  of  Bone. — For 
the  early  development  of  the  skeleton  the 
reader  is  referred  to  text-books  on  embry- 
ology. Embryonic  connective-tissue  cells  of 
the  mesoblast  develop  membrane.  Membrane 
may  become  bone  directly  or  cartilage  may  be 
deposited,  which  cartilage  by  the  process  of 
ossification  is  formed  into  bone.  The  tissue 
which  is  eventually  to  become  bone  contains 
cellular  elements  which  evolve  into  osteoblasts, 
or  bone-forming  cells.  Osteoblasts  exist  in  the 
connective  tissues  which  become  bone  by  in- 
tramembranous  ossification,  and  in  the  deeper 
layers  of  the  tissue  called  perichondrium  which 
invests  cartilage  and  which  becomes  the  osteo- 
genetic  layer  of  the  periosteum.  In  view  of 
the  fact  that  in  the  total  skeleton  some  bones 

are  preceded  by  membrane  (parietal  bones,  frontal  bone,  upper  part  of  tabular 
surface  of  occipital  bone,  most  of  bones  of  the  face),  and  others  are  preceded  by 
rods  of  cartilage  (the  long  bones),  two  kinds  of  ossification  are  described — viz., 
the  intramembranous  and  the  intracartilaginous.  Professor  Cunningham  says  all 
true  bone  may  be  correctly  regarded  as  of  membranous  origin,  though  its  appear- 
ance is  preceded  in  some  instances  by  the  deposition  of  cartilage ;  in  this  case 
calcification  of  the  cartilage  is  an  essential  stage  in  the  process  of  bone  forma- 
tion, but  the  ultimate  conversion  into  true  bone,  with  characteristic  Haversian 
systems,  leads  to  the  absorption  and  disappearance  of  this  primitive  calcified 
cartilage.  Intramembranous  ossification  forms  membrane  bones,  that  is,  forms 
bone  directly  from  fibrous  tissue,  there  being  no  intermediate  cartilaginous 
stage. 

Intracartilaginous  ossification  consists  in  the  ossification  of  cartilage. 


FIG.  8. — Schematic  diagram,  showing  epi- 
physis  and  diaphysis  and  line  of  ossification. 
Ep.  Epiphysis  of  endochondral  bone.  zpt. 
Zone  of  proliferation,  zc.  Zone  of  calcifica- 
tion, ca.  Cartilage.  (Poirier  and  Charpy.) 


OSSIFICATION  AND   GROWTH  OF  BONE 


43 


Intramembranous  Ossification. — In  the  case  of  bones  which  are  developed  in 
membrane  no  cartilaginous  mould  precedes  the  appearance  of  the  bone-tissue. 
The  membrane,  which  occupies  the  place  of  the  future  bone,  is  of  the  nature  of 
connective  tissue,  and  ultimately  forms  the  periosteum.  At  this  stage  it  is  seen 
to  be  composed  of  fibres  and  granular  cells  in  a  matrix.  The  outer  portion  is 
more  fibrous,  while  internally  the  cells  or  osteoblasts  predominate;  the  whole 
tissue  is  richly  supplied  with  blood-vessels.  At  the  outset  of  the  process  of  bone- 
formation  a  little  network  of  bony  spiculre  is  first  noticed  radiating  from  the  point 
or  centre  of  ossification.  When  these  rays  of  growing  bone  are  examined  with  a 
microscope,  they  are  found  to  consist  at  their  growing  point  of  a  network  of  fine, 
clear  fibres  and  granular  corpuscles,  with  an  intervening  ground  substance 
(Fig.  9).  The  fibres  are  termed  osteogenetic  fibres,  and  are  made  up  of  fine  fibrils 


I'ninn  of 

adjacent 
spicnlcs. 


Osteoblasts.< 


Jsteogenetic 

fibres. 


Calcific  depdtit 

between  the 
fibres. 


Bony 
spicules. 


FIG.  9. — Part  of  the  growing  edge  of  the  developing  parietal  bone  of  a  foetal  cat.     (After  J.  Lawrence.) 


differing  little  from  those  of  white  fibrous  tissue.  Like  them,  they  are  probably 
deposited  in  the  matrix  through  the  influence  of  the  cells — in  this  case  the  osteo- 
blasts. The  osteogenetic  fibres  soon  assume  a  dark  and  granular  appearance  from 
the  deposition  of  calcareous  granules  in  the  fibres  and  in  the  intervening  matrix, 
and  as  they  calcify  they  are  found  to  enclose  some  of  the  granular  corpuscles  or 
osteoblasts.  By  the  fusion  of  the  calcareous  granules  the  bony  tissue  again  assumes 
a  more  transparent  appearance,  but  the  fibres  are  no  longer  so  distinctly  seen. 
The  involved  osteoblasts  form  the  corpuscles  of  the  future  bone,  the  spaces  in 
which  they  are  enclosed  constituting  the  lacuna?.  As  the  osteogenetic  fibres  grow 
out  to  the  periphery  they  continue  to  calcify,  and  give  rise  to  fresh  bone-spicules. 
Thus  a  network  of  bone  is  formed,  the  meshes  of  which  contain  the  blood-vessels 
and  a  delicate  connective  tissue  crowded  with  osteoblasts.  The  bony  trabecula? 
thicken  by  the  addition  of  fresh  layers  of  bone  formed  by  the  osteoblasts  on  their 
surface,  and  the  meshes  are  correspondingly  encroached  upon.  Subsequently 
successive  layers  of  bony  tissue  are  deposited  under  the  periosteum  and  around 
the  larger  vascular  channels,  which  become  the  Haversian  canals,  so  that  the  bone 
increases  much  in  thickness. 

Intracartilaginous  Ossification. — Just  before  ossification  begins  the  bone  is 
entirely  cartilaginous,  and  in  the  long  bone,  which  may  be  taken  as  an  example,  the 
process  commences  in  the  centre  and  proceeds  toward  the  extremities,  which  for 
some  time  remain  cartilaginous.  Subsequently  a  similar  process  commences  in  one 


44 


THE  SKELETON 


or  more  places  in  those  extremities  and  gradually  extends  through  them.  The 
extremities  do  not,  however,  become  joined  to  the  shaft  by  bony  tissue  until  growth 
has  ceased,  but  are  attached  to  it  by  a  layer  of  cartilaginous  tissue  termed  the 
epiphyseal  cartilage  (Fig.  8). 

The  first  step  in  the  ossification  of  the  cartilage  is  that  the  cartilage-cells,  at 
the  point  where  ossification  is  commencing  and  which  is  termed  a  centre  of  ossifica- 
tion, enlarge  and  arrange  themselves  in  rows  (Fig.  10).  The  matrix  in  which  they 
are  embedded  increases  in  quantity,  so  that  the  cells  become  further  separated 
from  each  other.  A  deposit  of  calcareous  material  now  takes  place  in  this  matrix, 


FIG.  11. — Part  of  a  longitudinal  section  of 
the  developing  femur  of  a  rabbit,  a.  Flat- 
tened cartilage-cells,  b.  Enlarged  cartilage- 
cells,  c,  d.  Newly  formed  bone.  e.  Osteo- 
blasta.  /.  Giant-cells  or  osteoclasts.  g,  h. 
Shrunken  cartilage-cells.  (From  Atlas  of  His- 
tology, Klein  and  Noble  Smith.) 

between  the  rows  of  cells,  so  that  they  become  separated  from  each  other  by  longi- 
tudinal columns  of  calcified  matrix,  presenting  a  granular  and  opaque  appearance. 
Here  and  there  the  matrix  between  two  cells  of  the  same  row  also  becomes  calci- 
fied, and  transverse  bars  of  calcified  substance  stretch  across  from  one  calcareous 
column  to  another.  Thus  there  are  longitudinal  groups  of  the  cartilage-cells 
enclosed  in  oblong  cavities,  the  walls  of  which  are  formed  of  calcified  matrix, 
which  cuts  off  all  nutrition  from  the  cells,  and  they,  in  consequence,  waste,  leav- 
ing spaces  called  the  primary  areolae  (Sharpey). 

At  the  same  time  that  this  process  is  going  on  in  the  centre  of  the  solid  bar  of 
cartilage  of  which  the  foetal  bone  consists,  certain  changes  are  taking  place  on 


OSSIFICATION  AND   GROWTH  OF  BONE 


45 


its  surface.  This  is  covered  by  a  very  vascular  membrane,  the  perichondrium, 
entirely  similar  to  the  embryonic  connective  tissue  already  described  as  constituting 
the  basis  of  membrane-bone,  on  the  inner  surface  of  which,  that  is  to  say,  on  the 
surface  in  contact  with  the  cartilage,  are  gathered  the  formative  cells,  the  osteo- 
blasts.  By  the  agency  of  these  cells  a  thin  layer  of  bony  tissue  is  being  formed 
between  the  perichondrium  and  the  cartilage,  by  the  intramembranous  mode  of 
ossification  just  described.  There  are,  then,  in  this  first  stage  of  ossification,  two 
processes  going  on  simultaneously:  in  the  centre  of  the  cartilage  the  formation 
of  a  number  of  oblong  spaces,  formed  of  calcified  matrix  and  containing  the 
withered  cartilage-cells,  and  on  the  surface  of  the  cartilage  the  formation  of  a 
layer  of  true  membrane-bone.  The  second  stage  consists  in  the  prolongation 
into  the  cartilage  of  processes  of  the 
deeper  or  osteogenetic  layer  of  the 
perichondrium,  which  has  now  be- 
come periosteum  (Fig.  10,  ir).  The 
processes  consist  of  blood-vessels  and 
cells — osteoblasts,  or  bone -formers,  and 
osteoclasts,  or  bone -destroyers.  The 
latter  are  similar  to  the  giant-cells 
(myelo-plaques)  found  in  marrow, 
and  they  excavate  passages  through 


FIG.  12. — transverse  section  from  t  he  femur  of  a 
human  embryo  about  eleven  weeks  old.  o.  A  med- 
ullary sinus  cut  transversely,  and  6,  another,  longi- 
tudinally, c.  Osteoblasts.  d.  Newly  formed  osseous 
substance  of  a  lighter  color,  e.  That  of  greater  age. 
/.  Lacunce  with  their  cells,  g.  A  cell  still  united  to 
an  osteoblast. 


FIG.  13. — Vertical  section  from  the  edge  of  the 
ossifying  portion  of  the  diaphysis  of  a  metatar- 
sal  bone  from  a  foetal  calf.  a.  Ground-mass  of 
the  cartilage.  6.  Of  the  bone.  c.  Newly  formed 
bone-cells  in  profile,  more  or  less  embedded  in  in- 
tercellular substance,  d.  Medullary  canal  in  pro- 
cess of  formation,  with  vessels  and  medullary 
cells.  e,f.  Bone-cells  on  their  broad  aspect,  g. 
Cartilage-capsules  arranged  in  rows,  and  partly 
with  shrunken  cell-bodies.  (After  Miiller.) 


the  new-formed  bony  layer  by  absorption,  and  pass  through  it  into  the  cal- 
cified matrix  (Fig.  10).  Wherever  these  processes  come  in  contact  with  the 
calcified  walls  of  the  primary  areolre  they  absorb  it,  and  thus  cause  a  fusion 
of  the  original  cavities  and  the  formation  of  larger  spaces,  which  are  termed 
the  secondary  areolae  (Sharpey),  or  medullary  spaces  (Miiller).  In  these  second- 
ary spaces  the  original  cartilage-cells,  having  disappeared,  become  filled 
with  embryonic  marrow,  consisting  of  osteoblasts  and  vessels,  and  derived  in 


46 


THE  SKELETON 


the    manner  described   above,  from   the  osteogenetic  layer  of   the  periosteum 
(Fig.  11). 

Thus  far  there  has  been  traced  the  formation  of  enlarged  spaces  (secondary 
areolae),  the  perforated  walls  of  which  are  still  formed  by  calcified  cartilage- 
matrix,  containing  an  embryonic  marrow,  derived  from  the  processes  sent  in 
from  the  osteogenetic  layer  of  the  periosteum,  and  consisting  of  blood-vessels 
and  round-cells,  osteoblasts  (Fig.  11).  The  wails  of  these  secondary  areolae  are 
at  this  time  of  only  inconsiderable  thickness,  but  they  become  thickened  by 
the  deposition  of  layers  of  new  bone  on  their  interior.  This  process  takes  place 
in  the  following  manner:  Some  of  the  osteoblasts  of  the  embryonic  marrow, 
after  undergoing  rapid  division,  arrange  themselves  as  an  epithelioid  layer  on 
the  surface  of  the  wall  of  the  space  (Fig.  12).  This  layer  of  osteoblasts  form  a 
bony  stratum,  and  thus  the  wall  of  the  space  becomes  gradually  covered  with  a 
layer  of  true  osseous  substance.  On  this  a  second  layer  of  osteoblasts  arrange 
themselves,  and  in  their  turn  form  an  osseous  layer.  By  the  repetition  of  this 
process  the  original  cavity  becomes  very  much  reduced  in  size,  and  at  last  only 
remains  as  a  small  circular  hole  in  the  centre,  containing  the  remains  of  the 
embryonic  marrow — that  is,  a  blood-vessel  and  a  few  osteoblasts.  This  small 
cavity  constitutes  the  Haversian  canal  of  the  perfectly  ossified  bone.  The  successive 
layers  of  osseous  matter  which  have  been  laid  down  and  which  encircle  this  central 

canal  constitute  the  lamellae  of 
which,  as  we  have  seen,  each 
Haversian  system  is  made  up. 
As  the  successive  layers  of  os- 
teoblasts form  osseous  tissue, 
certain  of  the  osteoblastic  cells 
remain  included  between  the 
various  bony  layers.  These 
persist  as  the  corpuscles  of  the 
future  bone,  the  spaces  enclos- 
ing them  forming  the  lacunae 
(Figs.  12  and  14).  The  canal- 
iculi,  at  first  extremely  short,  are 
supposed  to  be  extended  by  ab- 
sorption, so  as  to  meet  those  of 
neighboring  lacunae. 

FIG.  14. — Osteoblasts  from  the  parietal  bone  of  a  human  embryo  G5iir>Vi    arp  thp   pVmncrpc;  whirli 

thirteen  weeks  old.     a.  Bony  septa  with  the  cells  of  the  lacunas. 

b.  Layers  of  osteoblasts.     c.   The   latter  in  transition  to  bone-  may  be  observed  at  One  partlC- 
corpuscles.     (After  Gegenbauer.)  <f         .  •    •       •« 

ular  point,  the  centre  of  ossifi- 
cation. While  they  have  been  going  on  here  a  similar  process  has  been  set  up 
in  the  surrounding  parts  and  has  been  gradually  proceeding  toward  the  end  of 
the  shaft,  so  that  in  the  ossifying  bone  all  the  changes  described  above  may  be 
seen  in  different  parts,  from  the  true  bone  in  the  centre  of  the  shaft  to  the  hyaline 
cartilage  at  the  extremities.  The  bone  thus  formed  differs  from  the  bone  of  the 
adult  in  being  more  spongy  and  less  regularly  lamellated. 

Thus  far,  then,  we  have  followed  the  steps  of  a  process  by  which  a  solid  bony 
mass  is  produced,  having  vessels  running  into  it  from  the  periosteum,  Haversian 
canals  in  which  those  vessels  run,  medullary  spaces  filled  with  foetal  marrow, 
lacunae  with  their  contained  bone-cells,  and  canaliculi  growing  out  of  these 
lacunae. 

This  process  of  ossification,  however,  is  not  the  origin  of  the  whole  of  the 
skeleton,  for  even  in  those  bones  in  which  the  ossification  proceeds  in  a  great 
measure  from  a  single  centre,  situated  in  the  cartilaginous  shaft  of  a  long  bone,  a 
considerable  part  of  the  original  bone  is  formed  by  intramembranous  ossification 


OSSIFICATION  AND  GROWTH  OF  BONE  47 

beneath  the  perichondrium  or  periosteum ;  so  that  the  girth  of  the  bone  is  increased 
by  bony  deposit  from  the  deeper  layer  of  this  membrane.  The  shaft  of  the  bone 
is  at  first  solid,  but  a  tube  is  hollowed  out  in  it  by  absorption  around  the  vessels 
passing  into  it,  which  becomes  the  medullary  canal.  This  absorption  is  supposed 
to  be  brought  about  by  large  "giant-cells,"  the  so-called  osteoclasts  of  Kolliker 
(Fig.  11).  They  vary  in.  shape  and  size,  and  are  known  by  containing  a  large 
number  of  clear  nuclei,  sometimes  as  many  as  twenty.  The  occurrence  of 
similar  cells  in  some  tumors  of  bones  has  led  to  such  tumors  being  denominated 
"myeloid." 

As  more  and  more  bone  is  removed  by  this  process  of  absorption  from  the 
interior  of  the  bone  to  form  the  medullary  canal,  so  more  and  more  bone  is 
deposited  on  the  exterior  from  the  periosteum,  until  at  length  the  bone  has  attained 
the  shape  and  size  which  it  is  destined  to  retain  during  adult  life.  As  the  ossifi- 
cation of  the  cartilaginous  shaft  extends  toward  the  articular  ends  it  carries  with 
it,  as  it  were,  a  layer  of  cartilage,  or  the  cartilage  grows  as  it  ossifies,  and  thus  the 
bone  is  increased  in  length.  During  this  period  of  growth  the  articular  end,  or 
epiphysis,  remains  for  some  time  entirely  cartilaginous ;  then  a  bony  centre  appears 
in  it,  and  it  commences  the  same  process  of  intracartilaginous  ossification;  but 
this  process  never  extends  to  any  great  distance.  The  epiphyses  remain  separated 
from  the  shaft  by  a  narrow  cartilaginous  layer  for  a  definite  time  (Fig.  8). 
This  layer  ultimately  ossifies,  the  distinction  between  shaft  and  epiphysis  is 
obliterated,  and  the  bone  assumes  its  completed  form  and  shape.  The  same 
remarks  also  apply  to  the  processes  of  bone  which  are  separately  ossified,  such  as 
the  trochanters  of  the  femur.  The  bones,  having  been  formed,  continue  to 
grow  until  the  body  has  acquired  its  full  stature.  They  increase  in  length  by 
ossification  continuing  to  extend  in  the  epiphyseal  cartilage,  which  goes  on  grow- 
ing in  advance  of  the  ossifying  process.  They  increase  in  circumference  by 
deposition  of  new  bone,  from  the  deeper  layer  of  the  periosteum,  on  their  external 
surface,  and  at  the  same  time  an  absorption  takes  place  within,  by  which  the 
medullary  cavity  is  increased. 

The  medullary  spaces  which  characterize  the  cancellous  tissue  are  produced  by 
the  absorption  of  the  original  foetal  bone  in  the  same  way  as  the  original  medul- 
lary canal  is  formed.  The  distinction  between  the  cancellous  and  compact  tissue 
appears  to  depend  essentially  upon  the  extent  to  which  this  process  of  absorption 
has  been  carried ;  and  we  may  perhaps  remind  the  reader  that  in  morbid  states  of 
the  bone  inflammatory  absorption  produces  exactly  the  same  change,  and  con- 
verts portions  of  bone  naturally  compact  into  cancellous  tissue. 

The  number  of  ossific  centres  is  different  in  different  bones.  In  most  of  the 
short  bones  ossification  commences  by  a  single  point  in  the  centre,  and  proceeds 
toward  the  circumference.  In  the  long  bones  there  is  a  central  point  of  ossifica- 
tion for  the  shaft  or  diaphysis;  and  one  or  more  for  each  extremity,  the  epiphysis. 
That  for  the  shaft  is  the  first  to  appear.  The  union  of  the  epiphyses  with  the 
shaft  takes  place  in  the  reverse  order  to  that  in  which  their  ossification  began,  with 
the  exception  of  the  fibula,  and  appears  to  be  regulated  by  direction  of  the  nutrient 
artery  of  the  bone.  Thus  the  nutrient  arteries  of  the  bones  of  the  arm  and  fore- 
arm are  directed  toward  the  elbow,  and  the  epiphyses  of  the  bones  forming  this 
joint  become  united  to  the  shaft  before  those  at  the  shoulder  and  wrist.  In  the 
lower  limb,  on  the  other  hand,  the  nutrient  arteries  pass  in  a  direction  from  the 
knee;  that  is,  upward  in  the  femur,  downward  in  the  tibia  and  fibula;  and  in 
them  it  is  observed  that  the  upper  epiphysis  of  the  femur  and  the  lower  epiphysis 
of  the  tibia  and  fibula  become  first  united  to  the  shaft. 

Where  there  is  only  one  epiphysis,  the  medullary  artery  is  directed  toward 
that  end  of  the  bone  where  there  is  no  additional  centre,  as  toward  the  acromial 
end  of  the  clavicle,  toward  the  distal  end  of  the  metacarpal  bone  of  the  thumb 


48  THE  SKELETON 

and  great  toe,  and  toward  the  proximal  end  of  the  other  metacarpal  and  meta- 
tarsal  bones. 

Besides  these  epiphyses  for  the  articular  ends,  there  are  others  for  projecting 
parts  or  processes,  which  are  formed  separately  from  the  bulk  of  the  bone.  For 
an  account  of  these  the  reader  is  referred  to  the  description  of  the  individual 
bones  in  the  sequel.  , 

A  knowledge  of  the  exact  periods  when  the  epiphyses  become  joined  to  the 
shaft  is  often  of  great  importance  in  medico-legal  inquiries.  It  also  aids  the  sur- 
geon in  the  diagnosis  of  many  of  the  injuries  to  which  the  joints  are  liable;  for  it 
not  infrequently  happens  that  on  the  application  of  severe  force  to  a  joint  the 
epiphysis  becomes  separated  from  the  shaft,  and  such  an  injury  may  be 
mistaken  for  a  fracture  or  dislocation. 

THE  VERTEBRAL  OR  SPINAL  COLUMN  OR  THE  SPINE 
(COLUMNA  VERTEBRALIS). 

The  spine  is  a  flexuous  and  flexible  column  formed  of  a  series  of  bones  called 
vertebrae  (from  verier  e,  to  turn). 

The  vertebrae  are  thirty-three  in  number,  and  have  received  the  names  cervical, 
dorsal  or  thoracic,  lumbar,  sacral,  and  coccygeal,  according  to  the  position  which 
they  occupy;  seven  being  found  in  the  cervical  region,  twelve  in  the  thoracic,  five 
in  the  lumbar,  five  in  the  sacral,  and  four  in  the  coccygeal. 

This  number  is  sometimes  increased  by  an  additional  vertebra  in  one  region,  or 
the  number  may  be  diminished  in  one  region,  the  deficiency  being  supplied  by 
an  additional  vertebra  in  another.  These  observations  do  not  apply  to  the  cervical 
portion  of  the  spine,  the  number  of  bones  forming  which  is  seldom  increased  or 
diminished. 

The  vertebrae  in  the  upper  three  regions  of  the  spine  remain  separate  through- 
out life,  and  are  known  as  true  or  movable  vertebrae;  but  those  found  in  the 
sacral  and  coccygeal  regions  are  in  the  adult  firmly  united,  so  as  to  form  two 
bones — five  entering  into  the  formation  of  the  upper  bone  or  sacrum,  and  four  into 
the  terminal  bone  of  the  spine  or  coccyx.  The  fused  vertebrae  are  known  as 
false  or  immovable  vertebrae. 

GENERAL  CHARACTERS  OF  A  VERTEBRA. 

•Each  vertebra  consists  of  two  essential  parts — an  anterior  solid  segment,  the 
body,  or  centrum,  and  a  posterior  segment,  the  arch  (arcus  vertebra;),  or  the  neural 
arch.  The  neural  arch  is  formed  of  two  pedicles  and  two  laminae,  supporting 
seven  processes — viz.,  four  articular,  two  transverse,  and  one  spinous. 

The  bodies  of  the  vertebrae  are  piled  one  upon  the  other,  forming  a  strong 
pillar  for  the  support  of  the  cranium  and  trunk;  the  arches  forming  a  hollow 
cylinder  behind  the  bodies  for  the  protection  of  the  spinal  cord  (spinal  canal  or 
neural  canal).  The  different  vertebrae  are  connected  together  by  means  of  the 
articular  processes  and  the  intervertebral  fibrocartilages ;  while  the  transverse 
and  spinous  processes  serve  as  levers  for  the  attachment  of  muscles  which 
move  the  different  parts  of  the  spine.  Lastly,  between  each  pair  of  vertebrae 
apertures  exist  through  which  the  spinal  nerves  pass  from  the  cord.  Each  of 
these  constituent  parts  must  now  be  separately  examined. 

Body,  or  Centrum  (corpus  vertebra'). — The  body  is  the  largest  part  of  a  vertebra. 
Above  and  below  it  is  flattened;  its  upper  and  lower  surfaces  are  rough  for  the 
attachment  of  the  intervertebral  fibro-cartilages,  and  each  presents  a  rim  around 
its  circumference.  In  front  it  is  convex  from  side  to  side,  concave  from  above 
downward.  Behind  it  is  flat  from  above  downward  and  slightly  concave  from 


THE    CERVICAL    VERTEBRAE  49 

side  to  side.  Its  anterior  surface  is  perforated  by  a  few  small  apertures,  for 
the  passage  of  nutrient  vessels;  while  on  the  posterior  surface  is  a  single  large, 
irregular  aperture,  or  occasionally  more  than  one,  for  the  exit  of  veins  from  the 
body  of  the*  vertebra — the  venae  basis  vertebrae. 

Pedicles. — The  pedicles  are  two  short,  thick  pieces  of  bone,  which  project 
backward,  one  on  each  side,  from  the  upper  part  of  the  body  of  the  vertebra,  at 
the  line  of  junction  of  its  posterior  and  lateral  surfaces.  Each  pedicle  (radix 
arcus  vertebra)  is  a  root  of  the  vertebral  arch.  The  concavities  above  and  below 
the  pedicles  are  the  superior  and  inferior  intervertebral  notches  or  grooves  (incisura 
vertebralis  superior  et  inferior) ;  they  are  four  in  number,  two  on  each  side,  the 
inferior  ones  being  generally  the  deeper.  When  the  vertebra?  are  articulated  the 
notches  of  each  contiguous  pair  of  bones  form  the  intervertebral  foramina  (fora- 
mina intervertebralia) ,  which  communicate  with  the  spinal  canal  and  transmit 
the  spinal  nerves  and  bloodvessels. 

Laminae. — The  laminae  are  two  broad  plates  of  bone  which  complete  the  neural 
arch  by  fusing  together  in  the  middle  line  behind.  They  enclose  a  foramen,  the 
spinal  or  vertebral  foramen  (foramen  vertebrate),  which  serves  for  the  protection  of 
the  spinal  cord.  When  the  vertebrae  are  joined  they  form,  with  their  ligaments, 
the  vertebral  canal  (spinal  or  neural  canal,  canalis  vertebralis).  The  lamina?  are 
connected  to  the  body  by  means  of  the  pedicles.  Their  upper  and  lower  borders 
are  rough,  for  the  attachment  of  the  ligamenta  subflava. 

Processes.  Spinous  Process  (processus  spinosus). — The  spinous  process  projects 
backward  from  the  junction  of  the  two  laminae,  and  serves  for  the  attachment  of 
muscles  and  ligaments. 

Articular  Processes. — The  articular  processes  (zygapophyses],  four  in  number, 
two  on  each  side,  spring  from  the  junction  of  the  pedicles  with  the  laminae.  Each 
superior  process  (processus  articularis  superior)  projects  upward,  its  articular 
surface  (fades  articularis  superior)  being  directed  more  or  less  backward;  each 
inferior  process  (processus  articularis  inferior)  projects  downward,  its  articular 
surface  (fades  articularis  inferior)  looking  more  or  less  forward.1 

Transverse  Processes  (processus  transversi). — The  transverse  processes,  two  in 
number,  project  one  at  each  side  from  the  point  where  the  lamina  joins  the 
pedicle,  between  the  superior  and  inferior  articular  processes.  They  also  serve 
for  the  attachment  of  muscles  and  ligaments. 

The  Cervical  Vertebrae  (Vertebrae  Cervicales)  (Fig.  15). 

The  cervical  vertebrae  are  smaller  than  those  in  any  other  region  of  the  spine, 
and  may  be  readily  distinguished  by  the  foramen  in  the  transverse  process,  which 
does  not  exist  in  the  transverse  process  of  either  a  dorsal  or  lumbar  vertebra. 

Body. — The  body  (centrum)  is  small,  comparatively  dense,  and  broader  from 
side  to  side  than  from  before  backward.  The  anterior  and  posterior  surfaces 
are  flattened  and  of  equal  depth;  the  former  is  placed  on  a  lower  level  than  the 
latter,  and  its  inferior  border  is  prolonged  downward,  so  as  to  overlap  the  upper 
and  fore  part  of  the  vertebra  below.  Its  upper  surface  is  concave  transversely, 
and  presents  a  projecting  lip  on  each  side;  its  lower  surface  is  convex  from  side 
to  side,  concave  from  before  backward,  and  presents  laterally  a  shallow  concavity 
which  receives  the  corresponding  projecting  lip  of  the  adjacent  vertebra. 

Pedicles. — The  pedicles  are  directed  outward  and  backward,  and  are 
attached  to  the  body  midway  between  the  upper  and  lower  borders,  so  that 
the  superior  intervertebral  notch  is  as  deep  as  the  inferior,  but  it  is,  at  the  same 
time,  narrower. 

1  It  may,  perhaps,  be  as  well  to  remind  the  reader  that  the  direction  of  a  surface  is  determined  by  that  of  a 
line  drawn  at  right  angles  to  it. — ED.  of  15th  English  Edition. 


50 


THE  SKELETON 


Laminae. — The  laminae  are  narrow,  long,   thinner  above  than  below,  and 
overlap  each  other,  enclosing  the  spinal  foramen,  which  is  very  large,  and  of  a 


triangular  form. 


Processes.  Spinous  Process. — The  spinous  process  is  short,  and  bifid  at  the 
extremity,  to  afford  greater  extent  of  surface  for  the  attachment  of  muscles,  the 
two  divisions  being  often  of  unequal  size.  They  increase  in  length  from  the  fourth 
to  the  seventh  vertebra. 


Anterior  tubercle  of  trans- 
verse process. 

Costo-transverse  foramen  for 

vertebral  artery  and  vein  and 

sympathetic  plexus.^ 

Posterior  tubercle,  of 
transverse  process. 


Costal  cartilage. 


Transverse  process. 


^-Superior  articular 

process. 
Inferior  articular  process. 


FIG.  15. — Cervical  vertebra. 

Articular  Processes. — The  articular  processes  are  flat,  oblique,  and  of  an  oval 
form:  the  superior  are  directed  backward  and  upward;  the  inferior  forward  and 
downward. 

Transverse  Processes. — The  transverse  processes  are  short,  directed  down- 
ward, outward,  and  forward,  bifid  at  their  extremity,  and  marked  by  a 
groove  along  their  upper  surface,  which  runs  downward  and  outward  from  the 
superior  intervertebral  notch  and  serves  for  the  transmission  of  one  of  the  cer- 
vical nerves.  They  are  situated  in  front  of  the  articular  processes  and  on  the 
outer  side  of  the  pedicles.  The  transverse  processes  are  pierced  at  their  base  by 
a  foramen,  for  the  transmission  of  the  vertebral  artery,  vein,  and  a  plexus  of 
sympathetic  nerves.  This  foramen  is  known  as  the  transverse  foramen,  the  costo- 
transverse  foramen,  and  the  vertebrarterial  foramen  (foramen  transversarium) . 
Each  process  is  formed  by  two  roots:  the  anterior  root,  sometimes  called  the 
costal  process,  arising  from  the  side  of  the  body,  and  the  homologue  of  the  rib 
in  the  thoracic  region  of  the  spine;  the  posterior  root  springs  from  the  junction  of 
the  pedicle  with  the  lamina,  and  corresponds  with  the  transverse  process  in  the 
thoracic  region.  It  is  by  the  junction  of  the  two  that  the  foramen  for  the  vertebral 
vessels  is  formed.  The  extremity  of  each  of  the  anterior  roots  forms  the  anterior 
tubercle  (tuberculum  anterius)  and  the  extremity  of  each  of  the  posterior  roots  the 
posterior  tubercle  (tubercidum  posterius)  of  the  transverse  processes.1 

The  peculiar  vertebrae  in  the  cervical  regions  are  the  first,  or  atlas;  the  second, 
or  axis;  and  the  seventh,  or  vertebra  prominens.  The  great  modifications  in  the 
form  of  the  atlas  and  axis  are  designed  to  admit  of  the  nodding  and  rotatory 
movements  of  the  head. 

Atlas. — The  atlas  (Fig.  16)  is  so  named  from  supporting  the  globe  of  the  head. 
The  chief  peculiarities  of  this  bone  are  that  it  has  neither  body  nor  spinous  process. 
The  body  is  detached  from  the  rest  of  the  bone,  and  forms  the  odontoid  process  of 

1  The  anterior  tubercle  of  the  transverse  process  of  the  sixth  cervical  vertebra  is  of  large  size,  and  is  some- 
times known  as  "Chassaignac's"  or  the  "carotid  tubercle"  (tuberculum  caroticum).  It  is  in  close  relation  with 
the  carotid  artery,  which  lies  in  front  and  a  little  external  to  it;  so  that,  as  was  first  pointed  out  by  Chassaignac, 
the  vessel  can  with  ease  be  compressed  against  it. — ED.  of  15th  English  Edition. 


THE    CERVICAL    VERTEBRAE 


51 


the  second  vertebra;  while  the  parts  corresponding  to  the  pedicles  join  in  front  to 
form  the  anterior  arch.  The  atlas  is  ring-like,  and  consists  of  an  anterior  arch,  a 
posterior  arch,  and  two  lateral  masses.  The  anterior  arch  (arcus  anterior)  forms  about 
one-fifth  of  the  ring;  its  anterior  surface  is  convex,  and  presents  about  its  centre  a 
tubercle  (tuberculum  anterius),  for  the  attachment  of  the  Longus  colli  muscle;  pos- 
teriorly it  is  concave,  and  marked  by  a  smooth,  oval  facet,  called  the  circular  facet 
(fovea  dentis),  covered  with  cartilage,  for  articulation  with  the  odontoid  process  of  the 


Tubercle. 


Transverse 
process. 


Diagram  of  section  of  odontoid 
process. 

Diagram  of  section  of 
transverse  ligament. 

Foramen  for 
vertebral  artery. 


Groove  for  vertebral  artery 
and  1st  cervical  nerve. 


Rudimentary  spinous  process. . 

FIG.  16.— First  cervical  vertebra,  or  atlas. 

axis.  The  upper  and  lower  borders  give  attachment  to  the  anterior  occipito-atlantal 
and  the  anterior  atlanto-axial  ligaments,  which  connect  it  with  the  occipital  bone 
above  and  the  axis  below.  The  posterior  arch  (arcus  posterior)  forms  about  two- 
fifths  of  the  circumference  of  the  bone;  it  terminates  behind  in  a  tubercle  (tuber- 
culum posterius) ,  which  is  the  rudiment  of  a  spinous  process,  and  gives  origin  to 
the  Rectus  capitis  posticus  minor.  The  diminutive  size  of  this  process  prevents 
any  interference  in  the  movements  between  the  atlas  and  the  cranium.  The  pos- 
terior part  of  the  arch  presents  above  and  behind  a  rounded  edge  for  the  attach- 
ment of  the  posterior  occipito-atlantal  ligament,  while  in  front,  immediately 
behind  each  superior  articular  process,  is  a  groove  (sulcus  arteries  vertebralis] , 
sometimes  converted  into  a  foramen  by  a  delicate  bony  spiculum,  which  arches 
backward  from  the  posterior  extremity  of  the  superior  articular  process.  These 
grooves  represent  the  superior  intervertebral  notches,  and  are  peculiar  from  being 
situated  behind  the  articular  processes,  instead  of  in  front  of  them,  as  in  the 
other  vertebrae.  They  serve  for  the  transmission  of  the  vertebral  artery,  which, 
ascending  through  the  foramen  in  the  transverse  process,  winds  round  the  lateral 
mass  in  a  direction  backward  and  inward.  They  also  transmit  the  suboccipital 
(first  spinal)  nerve.  On  the  under  surface  of  the  posterior  arch,  in  the  same 
situation,  are  two  other  grooves,  placed  behind  the  lateral  masses,  and  repre- 
senting the  inferior  intervertebral  notches  of  other  vertebrae.  They  are  much 
less  marked  than  the  superior.  The  lower  border  also  gives  attachment  to  the 
posterior  atlanto-axial  ligament,  which  connects  it  with  the  axis.  The  lateral 
masses  (masses  laterales)  are  the  most  bulky  and  solid  parts  of  the  atlas,  in  order 
to  support  the  weight  of  the  head;  they  present  two  articulating  surfaces  above, 
and  two  below.  Each  superior  process  (fovea  articularis  superior)  is  of  large  size, 
oval,  concave,  and  approaches  its  companion  in  front,  but  diverges  from  it 
behind;  it  is  directed  upward,  inward,  and  a  little  backward,  forming  a  kind  of 
cup  for  the  corresponding  condyle  of  the  occipital  bone.  The  two  processes  are 
admirably  adapted  to  the  nodding  movements  of  the  head.  Not  infrequently 
they  are  partially  subdivided  by  a  more  or  less  deep  indentation,  which  encroaches 
upon  each  lateral  margin.  Each  inferior  articular  process  (fades  articularis  inferior) 


52  THE  SKELETON 

is  circular  in  form,  flattened  or  slightly  concave,  and  directed  downward  and 
inward,  articulating  with  the  axis.  The  inferior  processes  permit  the  rotatory 
movements.  Just  below  the  inner  margin  of  each  superior  articular  surface  is 
a  small  tubercle,  for  the  attachment  of  the  transverse  ligament,  which,  stretching 
across  the  ring  of  the  atlas,  divides  it  into  two  unequal  parts  or  arches;  the  anterior 
or  smaller  segment  receiving  the  odontoid  process  of  the  axis,  the  posterior  allow- 
ing the  transmission  of  the  spinal  cord  and  its  membranes.  This  part  of  the 
spinal  canal  is  of  considerable  size,  to  afford  space  for  the  spinal  cord ;  and  hence 
lateral  displacement  of  the  atlas  may  occur  without  compression  of  this  structure. 
The  transverse  processes  are  of  large  size,  project  directly  outward  and  down- 
ward from  the  lateral  masses,  and  serve  for  the  attachment  of  special  muscles 
which  assist  in  rotating  the  head.  They  are  long,  not  bifid,  and  perforated  at 
their  base  by  a  canal  for  the  vertebral  artery,  which  is  directed  from  below, 
upward,  and  backward. 

Odontoid  process. 

Rough  surface  for  check  ligaments. — 

_Articular  surface  for 

atlas. 

Articular  surface  for  transverse  ligament. . 


Spinous  process.-! 

mrunr-  •^p,  _ 

i  Transverse  process. 
i 
Inferior  articular  process. 

FIG.  17. — Second  cervical  vertebra,  or  axis. 

Axis. — The  axis  (epistropheus)  (Fig.  17)  is  the  pivot  upon  which  the  first 
vertebra,  carrying  the  head,  rotates,  hence  the  name,  axis.  The  most  distinctive 
character  of  this  bone  is  the  strong,  prominent  process,  tooth-like  in  form  (hence 
the  name  odontoid  process,  or  dens),  which  rises  perpendicularly  from  the  upper 
surface  of  the  body.  The  body  is  deeper  in  front  than  behind,  and  prolonged 
downward  anteriorly  so  as  to  overlap  the  upper  and  fore  part  of  the  next 
vertebra.  It  presents  in  front  a  median  longitudinal  ridge,  separating  two 
lateral  depressions,  for  the  attachment  of  the  Longus  colli  muscle  of  either  side. 
The  odontoid  process  presents  two  articulating  surfaces  covered  with  cartilage: 
one  in  front,  of  an  oval  form,  for  articulation  with  the  atlas  (fades  articularis 
anterior) ;  another  behind  (fades  articularis  posterior),  for  the  transverse  ligament 
— the  latter  frequently  encroaching  on  the  sides  of .  the  process.  The  apex  is 
pointed,  and  gives  attachment  to  the  middle  odontoid  ligament  (ligamentum 
apids  dentis).  Below  the  apex  the  process  is  somewhat  enlarged,  and  presents 
on  either  side  a  rough  impression  for  the  attachment  of  the  lateral  fasciculi  of 
the  odontoid  or  check  ligaments,  which  connect  it  to  the  occipital  bone;  the  base 
of  the  process,  where  it  is  attached  to  the  body,  is  constricted,  so  as  to  prevent 
displacement  from  the  transverse  ligament,  which  binds  it  in  this  situation  to  the 
anterior  arch  of  the  atlas.  Sometimes,  however,  this  process  does  become  dis- 
placed, especially  in  children,  in  whqm  the  ligaments  are  more  relaxed:  instant 
death  is  the  result  of  this  accident.  The  internal  structure  of  the  odontoid  process 
is  more  compact  than  that  of  the  body.  The  pedicles  are  broad  and  strong,  espe- 
cially their  anterior  extremities,  which  coalesce  with  the  sides  of  the  body  and  the 


THE    THORACIC    OR    DORSAL    VERTEBRA 


53 


root  of  the  odontoid  process.  The  laminae  are  thick  and  strong,  and  the  spinal 
foramen  large,  but  smaller  than  that  of  the  atlas.  The  transverse  processes  are  very 
small,  not  bifid,  and  each  is  perforated  by  the  foramen  for  the  vertebral  artery, 
which  is  directed  obliquely  upward  and  outward.  The  superior  articular  surfaces 
(fades  articulares  superiores)  are  round,  slightly  convex,  directed  upward  and 
outward,  and  are  peculiar  in  being  supported  on  the  body,  pedicles,  and  trans- 
verse processes.  The  inferior 

articular   surfaces   (fades  articu-  Body, 

lares  inferior es)  have  the  same 
direction  as  those  of  the  other 
cervical  vertebra3.  The  superior 
intervertebral  notches  are  very 
shallow,  and  lie  behind  the  artic- 
ular processes ;  the  inferior  in 
front  of  them,  as  in  the  other 
cervical  vertebrae.  The  spinous 
process  is  of  large  size,  very 
strong,  deeply  channelled  on  its 
under  surface,  and  presents  a 
bifid,  tubercular  extremity  for 
the  attachment  of  muscles  which 
serve  to  rotate  the  head  upon 
the  spine. 

Seventh  Cervical  (Fig.  18).— 
The  most  distinctive  character 
of  this  vertebra  is  the  existence 
of  a  very  long  and  prominent 
spinous  process;  hence  the  name  vertebra  prominens.  This  process  is  thick,  nearly 
horizontal  in  direction,  not  bifurcated,  and  has  attached  to  it  the  lower  end  of  the 
ligamentum  nuchae.  The  transverse  process  is  usually  of  large  size,  its  posterior 
tubercles  are  large  and  prominent,  while  the  anterior  are  small  and  faintly  marked ; 
its  upper  surface  has  usually  a  hollow  groove,  and  it  seldom  presents  more  than  a 
trace  of  bifurcation  at  its  extremity.  The  foramen  in  the  transverse  process  is 
sometimes  as  large  as  in  the  other  cervical  vertebrae,  but  is  usually  smaller  on  one 
or  both  sides,  and  is  sometimes  wanting.  On  the  left  side  it  occasionally  gives 
passage  to  the  vertebral  artery;  more  frequently  the  vertebral  vein  traverses  it  on 
both  sides;  but  the  usual  arrangement  is  for  both  artery  and  vein  to  pass  in  front 
of  the  transverse  process,  and  not  through  the  foramen.  Occasionally  the  anterior 
root  of  the  transverse  process  exists  as  a  separate  bone,  and  attains  a  large  size. 
It  is  then  known  as  a  cervical  rib. 


Spinous  process. 
FIG.  18. — Seventh  cervical  vertebra,  or  vertebra  prominens. 


The  Thoracic  or  Dorsal  Vertebrae  (Vertebrae  Thoracales). 

The  thoracic  vertebrae  are  intermediate  in  size  between  those  in  the  cervical  and 
those  in  the  lumbar  region,  and  increase  in  size  from  above  downward,  the  upper 
vertebra?  in  this  segment  of  the  spine  being  much  smaller  than  those  in  the 
lower  part  of  the  region.  A  thoracic  vertebra  may  be  at  once  recognized  by  the 
presence  on  each  side  of  the  body  of  one  or  more  facets  or  half-facets  for  the  heads 
of  the  ribs. 

Bodies. — The  bodies  of  the  thoracic  vertebra?  resemble  those  in  the  cervical  and 
lumbar  regions  at  the  respective  ends  of  this  portion  of  the  spine;  but  in  the  middle 
of  the  thoracic  region  their  form  is  very  characteristic,  being  heart-shaped ,  and  as 
broad  in  the  antero-posterior  as  in  the  lateral  direction.  They  are  thicker  behind 
than  in  front,  flat  above  and  below,  convex  and  prominent  in  front,  deeply  con- 


54 


THE  SKELETON 


cave  behind,  slightly  constricted  in  front  and  at  the  sides,  and  marked  on  each 
side,  near  the  root  of  the  pedicle,  by  two  demi-facets,  one  above,  the  other  below 
(fovea  costalis  superior  et  inferior).  These  are  covered  with  cartilage  in  the  recent 
state,  and,  when  articulated  with  the  adjoining  vertebrae,  form,  with  the  inter- 
vening fibro-cartilage,  oval  surfaces  for  the  reception  of  the  heads  of  the  corre- 
sponding ribs.  The  tenth,  eleventh,  and  twelfth  thoracic  vertebrae  each  possesses 
one  complete  facet  for  the  head  of  the  rib,  instead  of  two  demi-facets. 


Superior  articular  process. 


Demi-facet  for  head  of  rib. 


Facet  for  tubercle  of  rib. 


Demi-facet  for  head  of  rib. 


Inferior  articular  process. 


FIG.  19. — A  thoracic  vertebra. 

Pedicles. — The  pedicles  are  directed  backward,  and  the  inferior  intervertebral 
notches  are  of  large  size,  and  deeper  than  in  any  other  region  of  the  spine. 

Laminae. — The  laminae  are  broad,  thick,  and  imbricated — that  is  to  say,  over- 
lapping one  another  like  tiles  on  a  roof.  The  spinal  foramen  is  small,  and  of  a 
circular  form. 

Processes.  Spinous  Processes. — Each  spinous  process  is  long,  triangular  on 
transverse  section,  directed  obliquely  downward,  and  terminates  in  a  tubercular 
extremity.  They  overlap  one  another  from  the  fifth  to  the  eighth  vertebra,  but 
are  less  oblique  in  direction  above  and  below. 

Articular  Processes. — The  articular  processes  are  flat,  nearly  vertical  in 
direction,  and  project  from  the  upper  and  lower  part  of  the  pedicles;  the 
superior  being  directed  backward  and  slightly  outward  and  upward,  the  inferior 
forward  and  a  little  inward  and  downward. 

Transverse  Processes. — The  transverse  processes  arise  from  the  same  parts 
of  the  arch  as  the  posterior  roots  of  the  transverse  processes  in  the  neck,  and 
are  situated  behind  the  articular  processes  and  pedicles;  they  are  thick,  strong, 
and  of  great  length,  directed  obliquely  backward  and  outward,  presenting  a 
clubbed  extremity,  which  is  tipped  on  its  anterior  part  by  a  small  concave  surface, 
for  articulation  with  the  tubercle  of  a  rib  (fovea  costalis  transversalis] .  The 
twelfth,  the  eleventh,  and  sometimes  the  tenth  thoracic  vertebra  has  no  facet  on 
the  transverse  process.  Besides  the  articular  facet  for  the  rib,  three  indistinct 
tubercles  may  be  seen  arising  from  the  transverse  processes:  one  at  the  upper 
border,  one  at  the  lower  border,  and  one  externally.  In  man  they  are  compara- 
tively of  small  size,  and  serve  only  for  the  attachment  of  muscles.  But  in  some 
animals  they  attain  considerable  magnitude,  either  for  the  purpose  of  more  closely 


THE   THORACIC    VERTEBRAE 


55 


connecting  the  segments  of  this  portion  of  the  spine  or  for  muscular  and  liga- 
mentous  attachment. 

The  peculiar  thoracic  vertebrae  are  the  first,  ninth,  tenth,  eleventh,  and  twelfth 
(Fig.  20). 


f  An  entire  facet  above; 
\     a  demi-facet  below. 


'-A  demi-facet  above. 


— One  entire  facet. 


(  An  entire  facet. 
J  No  facet  on  transverse 
process,  which  is  ru- 
|_     dimentary. 


An  entire  facet. 

(No facet  on  trans- 
verse process. 
Inferior  articular 
process,  convex 
and  turned  out- 
ward. 


FIG.  20. — Peculiar  thoracic  vertebrae. 


First  Thoracic  Vertebra. — The  first  thoracic  vertebra  presents,  on  each  side  of 
the  body,  a  single  entire  articular  facet  for  the  head  of  the  first  rib  and  a  half- 
facet  for  the  upper  half  of  the  second.  The  body  is  like  that  of  a  cervical  vertebra, 
being  broad  transversely,  its  upper  surface  is  concave,  and  lipped  on  each  side. 
The  articular  surfaces  are  oblique,  and  the  spinous  process  thick,  long,  and  almost 
horizontal. 

Ninth  Thoracic  Vertebra. — The  ninth  thoracic  vertebra  has  no  demi-facet 
below.  In  some  subjects,  however,  the  ninth  has  two  demi-facets  on  each  side; 
when  this  occurs  the  tenth  has  only  a  demi-facet  at  the  upper  part. 


56  THE  SKELETON 

Tenth  Thoracic  Vertebra. — The  tenth  thoracic  vertebra  has  (except  in  the 
cases  just  mentioned)  an  entire  articular  facet  on  each  side,  above,  which  is 
partly  placed  on  the  outer  surface  of  the  pedicle.  It  has  no  demi-facet  below. 

Eleventh  Thoracic  Vertebra. — In  the  eleventh  thoracic  vertebra  the  body  ap- 
proaches in  its  form  and  size  to  the  lumbar.  The  articular  facets  for  the  heads 
of  the  ribs,  one  on  each  side,  are  of  large  size,  and  placed  chiefly  on  the  pedicles, 
which  are  thicker  and  stronger  in  this  and  the  next  vertebra  than  in  any  other 
part  of  the  thoracic  region.  The  spinous  process  is  short,  and  nearly  horizontal 
in  direction.  The  transverse  processes  are  very  short,  tubercular  at  their  extrem- 
ities, and  have  no  articular  facets  for  the  tubercles  of  the  ribs. 

Twelfth  Thoracic  Vertebra. — The  twelfth  thoracic  vertebra  has  the  same 
general  characters  as  the  eleventh,  but  may  be  distinguished  from  it  by  the  in- 
ferior articular  processes,  being  convex  and  turned  outward,  like  those  of  the 
lumbar  vertebrae;  by  the  general  form  of  the  body,  laminae,  and  spinous  process, 
approaching  to  that  of  the  lumbar  vertebrae;  and  by  the  transverse  processes 
being  shorter,  and  marked  by  three  elevations,  the  superior,  inferior,  and  external 
tubercles,  which  correspond  to  the  mammillary,  accessory,  and  transverse  pro- 
cesses of  the  lumbar  vertebrae.  Traces  of  similar  elevations  are  usually  to  be  found 
upon  the  other  thoracic  vertebrae  (vide  ut  supra). 

The  Lumbar  Vertebrae  (Vertebrae  Lumbales)  (Fig.  21). 

The  lumbar  vertebrae  are  the  largest  segments  of  the  vertebral  column,  and  can 
at  once  be  distinguished  by  the  absence  of  the  foramen  in  the  transverse  process, 
the  characteristic  point  of  the  cervical  vertebrae,  and  by  the  absence  of  any  articu- 
lating facet  on  the  side  of  the  body,  the  distinguishing  mark  of  the  thoracic 
vertebrae. 


Superior  articular  process 


FIG.  21. — Lumbar  vertebra. 


Body. — The  body  is  large,  and  has  a  greater  diameter  from  side  to  side  than 
from  before  backward,  slightly  thicker  in  front  than  behind,  flattened  or  slightly 
concave  above  and  below,  concave  behind,  and  deeply  constricted  in  front  and  at 
the  sides,  presenting  prominent  margins,  which  afford  a  broad  basis  for  the  sup- 
port of  the  superincumbent  weight. 

Pedicles. — The  pedicles  are  very  strong,  directed  backward  from  the  upper 
part  of  the  bodies;  consequently,  the  inferior  intervertebral  notches  are  of  con- 
siderable depth. 

Laminae.— The  laminae  are  broad,  short,  and  strong,  and  the  spinal  fora- 
men triangular,  larger  than  in  the  thoracic,  smaller  than  in  the  cervical,  region. 


THE   LUMBAR    VERTEBRAE  57 

Processes.  Spinous  Processes. — The  spinous  processes  are  thick  and  broad, 
somewhat  quadrilateral,  horizontal  in  direction,  thicker  below  than  above,  and 
terminating  by  a  rough,  uneven  border. 

Articular  Processes. — The  superior  articular  processes  are  concave,  and  look 
backward  and  inward;  the  inferior  are  convex,  and  look  forward  and  outward; 
the  former  are  separated  by  a  much  wider  interval  than  the  latter,  embracing 
the  lower  articulating  processes  of  the  vertebra  above. 

Transverse  Processes. — The  transverse  processes  are  long,  slender,  directed 
transversely  outward  in  the  upper  three  lumbar  vertebrae,  slanting  a  little  upward 
in  the  lower  two.  They  are  situated  in  front  of  the  articular  processes,  instead 
of  behind  them,  as  in  the  thoracic  vertebrae,  and  are  homologous  with  the  ribs.  Of 
the  three  tubercles  noticed  in  connection  with  the  transverse  processes  of  the 
twelfth  thoracic  vertebra,  the  superior  one  on  each  side  becomes  connected  in  this 
region  with  the  back  part  of  the  superior  articular  process,  and  has  received  the 


Inf.  articular  process. 
/ 

Costal  process.  ^      .-      '^L^^        Mammillary  process. 

Accessory  process. 


Sup.  articular  process. 


FIG.  22. — Lumbar  vertebra. 


name  of  mammillary  process  (processus  mammillaris) ;  the  inferior  is  represented 
by  a  small  process  pointing  downward,  situated  at  the  back  part  of  the  base  of 
the  transverse  process,  and  called  the  accessory  process  (processus  accessorius): 
these  are  the  true  transverse  processes,  which  are  rudimental  in  this  region  of 
the  spine.  The  external  one  is  the  so-called  transverse  process,  the  homologue 
of  the  rib,  and  hence  sometimes  called  the  costal  process  (processus  costarius) 
(Fig.  22).  Although  in  man  the  costal  processes  are  comparatively  small,  in  some 
animals  they  attain  considerable  size,  and  serve  to  lock  the  vertebrae  more 
closely  together. 

Fifth  Lumbar  Vertebra. — The  fifth  lumbar  vertebra  is  characterized  by  having 
the  body  much  thicker  in  front  than  behind,  which  accords  with  the  prominence 
of  the  sacro- vertebral  articulation;  by  the  smaller  size  of  its  spinous  process;  by 
the  wide  interval  between  the  inferior  articulating  processes;  and  by  the  greater 
size  and  thickness  of  its  transverse  processes,  which  spring  from  the  body  as  well 
as  from  the  pedicles. 


58 


THE  SKELETON 


Structure  of  the  Vertebrae. — The  body  is  composed  of  light,  spongy,  cancel- 
Ions  tissue,  having  a  thin  coating  of  compact  tissue  on  its  external  surface  per- 
forated by  numerous  orifices,  some  of  large  size,  for  the  passage  of  vessels;  its 
interior  is  traversed  by  one  or  two  large  canals,  for  the  reception  of  veins,  which 
converge  toward  a  single  large,  irregular  aperture  or  several  small  apertures  at  the 
posterior  part  of  the  body  of  each  bone.  The  arch  and  processes  projecting  from 
it  have,  on  the  contrary,  an  exceedingly  thick  covering  of  compact  tissue  (Fig.  23). 


FIG  23. — Bony  structure  of  a  lumbar  vertebra.     (Poirier  and  Charpy.) 

Development-. — Each  vertebra  is  formed  of  four  primary  centres  of  ossification 
(Fig.  24),  one  for  each  lamina  and  its  processes,  and  two  for  the  body.1  Ossifica- 
tion commences  in  the  lamina;  about  the  sixth  week  of  foetal  life,  in  the  situation 
where  the  transverse  processes  afterward  project,  the  ossific  granules  shooting 
backward  to  the  spine,  forward  into  the  pedicles,  and  outward  into  the  transverse 
and  articular  processes.  Ossification  in  the  body  commences  in  the  middle  of 
the  cartilage  about  the  eighth  week  by  two  closely  approximated  centres,  which 

By  4  primary  centres. 

\2for  body  (8th  week). 


1  for  each  trans- 
verse process, 
16  years. 


Ifor  each  lamina  (6th  week). 
FIG.  24. — Development  of  a  vertebra. 


By  2  additional  plates. 

)-•!  for  upper  surface 
of  body, 

1  for  under  surface 

of  body, 
FIG.  25. 


21  years. 


2  (sometimes  1)  for  spinous  process  (16  years). 
FIG.  26. 


speedily  coalesce  to  form  one  central  ossific  point.  According  to  some  authors, 
ossification  commences  in  the  lamina?  only  in  the  upper  vertebrae — i.  e.,  in  the 
cervical  and  upper  thoracic.  The  first  ossific  points  in  the  lower  vertebra?  are  those 
which  are  to  form  the  body,  the  osseous  centres  for  the  lamina;  appearing  at  a 
subsequent  period.  At  birth  these  three  pieces  are  perfectly  separate.  During 
the  first  year  the  lamina?  become  united  behind,  the  union  taking  place  first  in 
the  lumbar  region  and  then  extending  upward  through  the  thoracic  and  lower  cer- 
vical regions.  About  the  third  year  the  body  is  joined  to  the  arch  on  each  side  in 
such  a  manner  that  the  body  is  formed  from  the  three  original  centres  of  ossifica- 

1  By  many  observers  it  is  asserted  that  the  bodies  of  the  vertebra  are  developed  from  a  single  centre  which 
speedily  becomes  bilobed,  so  as  to  give  the  appearance  of  two  nuclei ;  but  that  there  are  two  centres,  at  all  events 
sometimes,  is  evidenced  by  the  fact  that  the  two  halves  of  the  body  of  the  vertebra  may  remain  distinct  through- 
out life  and  be  separated  by  a  fissure  through  which  a  protrusion  of  the  spinal  membrane  may  take  place,  con- 
stituting an  anterior  spina  bifida. — ED.  of  the  15th  English  Edition. 


THE  LUMBAR    VERTEBRA 


59 


By  S  centres. 


"or  anterior  arch  (1st  year), 

not  constant. 


tion,  the  amount  contributed  by  the  pedicles  increasing  in  extent  from  below 
upward.  Thus  the  bodies  of  the  sacral  vertebrae  are  formed  almost  entirely  from 
the  central  nuclei ;  the  bodies  of  the  lumbar  are  formed  laterally  and  behind  by  the 
pedicles ;  in  the  thoracic  region  the  pedicles  advance  as  far  forward  as  the  articular 
depressions  for  the  head  of  the  ribs,  forming  these  cavities  of  reception;  and  in 
the  neck  the  lateral  portions  of  the  bodies  are  formed  entirely  by  the  advance  of 
the  pedicles.  The  line  along  which  union  takes  place  between  the  body  and  the 
neural  arch  is  named  neuro-central  suture.  Before  puberty  no  other  changes  occur, 
excepting  a  gradual  increase  in  the  growth  of  these  primary  centres;  the  upper 
and  under  surfaces  of  the  bodies  and  the  ends  of  the  transverse  and  spinous  pro- 
cesses being  tipped  with  cartilage,  in  which  ossific  granules  are  not  as  yet  deposited. 
At  sixteen  years  (Fig.  26)  three  secondary  centres  appear,  one  for  the  tip  of 
each  transverse  process,  and  one  for  the  extremity  of  the  spinous  process.  In 
some  of  the  lumbar  vertebra?,  especially  the  first,  second,  and  third,  a  second 
ossifying  centre  appears  at  the  base  of  the  spinous  process.  At  twenty-one  years 
(Fig.  25)  a  thin,  circular,  epiphyseal  plate  of  bone  is  formed  in  the  layer  of  cartilage 
situated  on  the  upper  and  under  surfaces  of  the  body,  the  former  being  the  thicker 
of  the  two.  All  these  become  joined,  and  the  bone  is  completely  formed  between 
the  twenty-fifth  and  thirtieth  year  of  life. 

Exceptions  to  this  mode  of  development  occur  in  the  first,  second,  and  seventh 
cervical,  and  in  the  vertebra?  of  the  lumbar  region. 

Atlas  (Fig.  27). — The  number  of  centres  of  ossification  of  the  atlas  is  very  vari- 
able. It  may  be  developed  from  two,  three,  four,  or  five  centres.  The  most 
frequent  arrangement  is  by  three 
centres.  Two  of  these  are  destined 
for  the  two  lateral  or  neural  masses, 
the  ossification  of  which  commences 
about  the  seventh  week  near  the 
articular  processes,  and  extend 
backward;  these  portions  of  bone 
are  separated  from  one  another  be- 
hind, at  birth,  by  a  narrow  interval 
filled  in  with  cartilage.  Between 
the  third  and  fourth  years  they  unite 
either  directly  or  through  the  me- 
dium of  a  separate  centre  developed 
in  the  cartilage  in  the  middle  line. 
The  anterior  arch,  at  birth,  is  al- 
together cartilaginous,  and  in  this 
a  separate  nucleus  appears  about 
the  end  of  the  first  year  after  birth, 
and,  extending  laterally,  joins  the 
neural  processes  in  front  of  the  pedi- 
cles. Sometimes  there  are  two  nu- 
clei developed  in  the  cartilage,  one 
on  either  side  of  the  median  line, 
which  join  to  form  a  single  mass. 
And  occasionally  there  is  no  sepa- 
rate centre,  but  the  anterior  arch  is  formed  by  the  gradual  extension  forward 
and  ultimate  junction  of  the  two  neural  processes. 

Axis. — The  axis  (Fig.  28)  is  developed  by  seven  centres.  The  body  and  arch 
of  this  bone  are  formed  in  the  same  manner  as  the  corresponding  parts  in  the  other 
vertebrae:  one  centre  (or  two,  which  speedily  coalesce)  for  the  lower  part  of  the 
body,  and  one  for  each  lamina.  The  centres  for  the  laminae  appear  about  the 


FIG.  27.— Atlas. 


By  7  centres. 


2d  year. 


6th  month. 

1  for  each  lateral  mass. 


- —  1  for  body  (4th  month). 
1  for  under  surface  of 
body. 


FIG.  28.— Axis. 
S  additional  centres. 


for  tubercles  on  superior  articular  process. 
FIG.  29. — Lumbar  vertebra. 


60  THE  SKELETON 

seventh  or  eighth  week,  that  for  the  body  about  the  fourth  month.  The  odontoid 
process  consists  originally  of  an  extension  upward  of  the  cartilaginous  mass  in 
which  the  lower  part  of  the  body  is  formed.  At  about  the  sixth  month  of  foetal 
life  two  osseous  nuclei  make  their  appearance  in  the  base  of  this  process;  they 
are  placed  laterally,  and  join  before  birth  to  form  a  conical  bilobed  mass  deeply 
cleft  above;  the  interval  between  the  cleft  and  the  summit  of  the  process  is  formed 
by  a  wedge-shaped  piece  of  cartilage,  the  base  of  the  process  being  separated 
from  the  body  by  a  cartilaginous  interval,  which  gradually  becomes  ossified  at 
its  circumference,  but  remains  cartilaginous  in  its  centre  until  advanced  age.1 
Finally,  as  Humphry  has  demonstrated,  the  apex  of  the  odontoid  process  has 
a  separate  nucleus,  which  appears  in  the  second  year  and  joins  about  the  twelfth 
year.  In  addition  to  these  there  is  a  secondary  centre  for  a  thin  epiphysial  plate 
on  the  under  surface  of  the  body  of  the  bone.  J.  Bland  Sutton  and  others  main- 
tain that  the  odontoid  process  is  the  "dissociated  body  of  the  atlas."2 

Seventh  Cervical. — The  anterior  or  costal  part  of  the  transverse  process  of  the 
seventh  cervical  is  developed  from  a  separate  osseous  centre  at  about  the  sixth 
month  of  foetal  life,  and  joins  the  body  and  posterior  division  of  the  transverse 
process  between  the  fifth  and  sixth  years.  Sometimes  this  process  continues  as 
a  separate  piece,  and,  becoming  lengthened  outward,  constitutes  what  is  known 
as  a  cervical  rib.  This  separate  ossific  centre  for  the  costal  process  has  also  been 
found  in  the  fourth,  fifth,  and  sixth  cervical  vertebrae. 

Lumbar  Vertebrae. — The  lumbar  vertebra  (Fig.  29)  have  two  additional  centres 
(besides  those  peculiar  to  the  vertebrae  generally)  for  the  mammillary  tubercles, 
which  project  from  the  back  part  of  the  superior  articular  processes.  The  trans- 
verse process  of  the  first  lumbar  is  sometimes  developed  as  a  separate  piece,  which 
may  remain  permanently  unconnected  with  the  remaining  portion  of  the  bone, 
thus  forming  a  lumbar  rib — a  peculiarity  that  is  rarely  met  with. 

Progress  of  Ossification  in  the  Spine  Generally. — Ossification  of  the  laminae  of 
the  vertebras  commences  in  the  cervical  region  of  the  spine,  and  proceeds  gradually 
downward.  Ossification  of  the  bodies,  on  the  other  hand,  commences  a  little 
below  the  centre  of  the  spinal  column  (about  the  ninth  or  tenth  thoracic  vertebra), 
and  extends  both  upward  and  downward.  Although  the  ossific  nuclei  make  their 
first  appearance  in  the  lower  thoracic  vertebrae,  the  lumbar  and  first  sacral  ver- 
tebras are  those  in  which  these  nuclei  are  largest  at  birth. 

Attachment  of  Muscles. — To  the  Atlas  are  attached  nine  pairs:  the  Longus 
colli,  Rectus  capitis  anticus  minor,  Rectus  lateralis.,  Obliquus  capitis  superior  and 
inferior,  Splenius  colli,  Levator  anguli  scapulae,  First  Intertransverse,  and  Rectus 
capitis  posticus  minor. 

To  the  Axis  are  attached  eleven  pairs:  the  Longus  colli,  Levator  anguli  scapulae, 
Splenius  colli,  Scalenus  medius,  Transversalis  colli,  Intertransversales,  Obliquus 
capitis  inferior,  Rectus  capitis  posticus  major,  Semispinalis  colli,  Multifidus  spinae, 
Interspinales. 

To  the  remaining  vertebrae,  generally,  are  attached  thirty-five  pairs  and  a 
single  muscle:  anteriorly,  the  Rectus  capitis  anticus  major,  Longus  colli,  Scalenus 
anticus  medius  and  posticus,  Psoas  magnus  and  parvus,  Quadratus  lumborum, 
Diaphragm,  Obliquus  abdominis  internus,  and  Transversalis  abdominis;  pos- 
teriorly, the  Trapezius,  Latissimus  dorsi,  Levator  anguli  scapulae,  Rhomboideus 
major  and  minor,  Serratus  posticus  superior  and  inferior,  Splenius,  Erector  spinae, 
Ilio-costalis,  Longissimus  dorsi,  Spinalis  dorsi,  Cervicalis  ascendens,  Transversalis 
colli,  Trachelo-mastoid,  Complexus,  Biventer  cervicis,  Semispinalis  dorsi  and  colli, 
Multifidus  spinae,  Rotatores  spinae,  Interspinales,  Supraspinales,  Intertransversales, 
Levatores  costarum. 

1  See  Cunningham,  Jour.  Anat.,  vol.  xx.  p.  238. — ED.  of  the  15th  English  Edition. 

2  Ligaments:  their  Nature  and  Morphology. 


THE  SACRAL    AND    COCCYGEAL    VERTEBRAE 
The  Sacral  and  Coccygeal  Vertebrae  (False  or  Immovable  Vertebrae). 


61 


The  sacral  and  coccygeal  vertebrae  consist,  at  an  early  period  of  life,  of  nine 
separate  pieces,  which  are  united  in  the  aduli  so  as  to  form  two  bones,  five  enter- 
ing into  the  formation  of  the  sacrum,  four  into  that  of  the  coccyx.  Occasionally, 
the  coccyx  consists  of  five  bones.1 

Sacrum  (os  sacrum). — The  os  sacrum  (sacer,  sacred),  the  sacred  bone. 
So  called,  according  to  some,  because  it  was  the  part  selected  in  sacrifices. 
Another  view  is  that  the  name  is  derived  from  an  opinion  of  the  Jewish  rabbis, 
that  this  part  of  the  skeleton  strongly  resists  decay  and  becomes  the  germ  from 
which  the  new  body  will  be  raised.  The  sacrum  is  a  large,  triangular  bone  (Fig. 
30),  situated  at  the  lower  part  of  the  vertebral  column,  and  at  the  upper  and 
back  part  of  the  pelvic  cavity,  where  it  is  inserted  like  a  wedge  between  the  two 
innominate  bones;  its  upper  part  or  base  articulating  with  the  last  lumbar  ver- 
tebra, its  apex  with  the  coccyx.  It  is  composed  of  five  segments  of  bone  (sacral 
vertebrae,  or  vertebra  sacrales}.  The  sacrum  is  curved  upon  itself,  and  placed 
very  obliquely,  its  upper  extremity  projecting  forward,  and  forming,  with  the 
last  lumbar  vertebra,  a  very  prominent  angle,  called  the  promontory  (promontorium) , 
or  sacro-vertebral  angle;  while  its  central  part  is  directed  backward,  so  as  to  give 
increased  capacity  to  the  pelvic  cavity.  It  presents  for  examination  an  anterior  and 
posterior  surface,  two  lateral  surfaces,  a  base,  an  apex,  and  a  central  canal. 


FIG.  30.— Sacrum,  anterior  surface. 

Surfaces.  Anterior  or  Pelvic  Surface  (fades  pelvina). — The  anterior  surface 
is  concave  from  above  downward,  and  slightly  so  from  side  to  side.  In  the 
middle  are  seen  four  transverse  ridges  (lineoe  transversce) ,  indicating  the  original 
division  of  the  bone  into  five  separate  pieces.  The  portions  of  bone  intervening 

1  Sir  George  Humphry  describes  this  as  the  usual  composition  of  the  coccyx.     On  the  Skeleton,  p.  456. 


62 


THE   SKELETON 


between  the  ridges  correspond  to  the  bodies  of  the  vertebrae.  The  body  of  the  first 
segment  is  of  large  size,  and  in  form  resembles  that  of  a  lumbar  vertebra;  the  suc- 
ceeding ones  diminish  in  size  from  above  downward,  are  flattened  from  before 
backward,  and  curved  so  as  to  accommodate  themselves  to  the  form  of  the  sacrum, 
being  concave  in  front,  convex  behind.  At  each  end  of  the  ridges  above  men- 
tioned are  seen  the  anterior  sacral  foramina  (foramina  sacralia  anteriora),  analogous 
to  the  intervertebral  foramina,  four  in  number  on  each  side,  somewhat  rounded 
in  form,  diminishing  in  size  from  above  downward,  and  directed  outward  and 
forward;  they  transmit  the  anterior  branches  of  the  sacral  nerves  and  the  lateral 
sacral  arteries.  External  to  these  foramina  is  the  lateral  mass  (pars  lateralis), 
consisting  at  an  early  period  of  life  of  separate  segments;  these  become  blended, 

in  the  adult,  with  the  bodies,  with  each 
other,  and  with  the  posterior  transverse 
processes.  Each  lateral  mass  is  traversed 
by  four  broad,  shallow  grooves,  which 
lodge  the  anterior  sacral  nerves  as  they 
pass  outward,  the  grooves  being  sepa- 
rated by  prominent  ridges  of  bone,  which 
give  attachment  to  the  slips  of  the 
Pyriformis  muscle. 

If  a  vertical  section  is  made  through 
the  centre  of  the  sacrum  (Fig.  31),  the 
bodies  are  seen  to  be  united  at  their  cir- 
cumference by  bone,  a  wide  interval  being 
left  centrally,  which,  in  the  recent  state, 
is  filled  by  intervertebral  substance.  In 
some  bones  this  union  is  more  complete 
between  the  lower  segments  than  between 
the  upper  ones. 

Posterior  or  Dorsal  Surface  (fades  dor- 
salis) . — The  posterior  surface  (Fig.  32)  is 
convex  and  much  narrower  than  the  ante- 
rior. In  the  middle  line  are  three  or  four 
tubercles,  which  represent  the  rudimen- 
tary spinous  processes  of  the  sacral  verte- 
brae. Of  these  tubercles,  the  first  is 
usually  prominent,  and  perfectly  distinct 
from  the  rest;  the  second  and  third  are 
either  separate  or  united  into  a  tubercular 
ridge  (crista  sacralis  media],  which  dimin- 
ishes in  size  from  above  downward;  the 
fourth  usually,  and  the  fifth  always, 
remaining  undeveloped.  The  gap  which  results  from  failure  of  the  laminae  to 
meet  in  the  mid-line  is  called  the  hiatus  sacralis.  External  to  the  spinous  pro- 
cesses on  each  side  are  the  laminae,  broad  and  well  marked  in  the  first  three 
pieces;  sometimes  the  fourth,  and  generally  the  fifth,  are  only  partially  developed 
and  fail  to  meet  in  the  middle  line.  These  partially  developed  laminae  are  prolonged 
downward  as  rounded  processes,  the  sacral  cornua  (cornua  sacralia),  and  are  con- 
nected to  the  cornua  of  the  coccyx.  Between  them  the  bony  wall  of  the  lower  end 
of  the  sacral  canal  is  imperfect.  External  to  the  laminae  is  a  linear  series  of 
indistinct  tubercles  representing  the  articular  processes  (cristce  sacrales  articulares) ; 
the  upper  pair  are  large,  well  developed,  and  correspond  in  shape  and  direction 
to  the  superior  articulating  processes  of  a  lumbar  vertebra;  the  second  and  third 
are  small;  the  fourth  and  fifth  (usually  blended  together)  are  situated  on  each 


FIG.  31. — Vertical  section  of  the  sacrum. 


THE  SACRAL    AND    COCCYQEAL    VERTEBRA 


63 


side  of  the  sacral  canal  and  assist  in  forming  the  sacral  cornua.  External  to  the 
articular  processes  are  the  four  posterior  sacral  foramina  (foramina  sacralia  pos- 
teriora);  they  are  smaller  in  size  and  less  regular  in  form  than  the  anterior, 
and  transmit  the  posterior  branches  of  the  sacral  nerves.  On  the  outer  side  of 


Erector  spime. 


Latissimus  dorsi. 


Erector  spiwe. 


_   Upper  half  of  fifth 
posterior  sacral  foramen. 


FIG.  32. — Sacrum,  posterior  surface. 


the  posterior  sacral  foramina  is  a  series  of  tubercles,  the  rudimentary  transverse 
processes  of  the  sacral  vertebrae  (cristce  sacrales  laterales] .  The  first  pair  of  trans- 
verse tubercles  are  large,  very  distinct,  and  correspond  with  each  superior  angle  of 
the  bone;  they  together  with  the  second  pair,  which  are  of  small  size,  give  attach- 
ment to  the  horizontal  part  of  the  sacro-iliac  ligament;  the  third  gives  attachment 
to  the  oblique  fasciculi  of  the  posterior  sacro-iliac  ligaments ;  and  the  fourth 
and  fifth  to  the  great  sacro-sciatic  ligaments.  The  interspace  between  the  spinous 
and  transverse  processes  on  the  back  of  the  sacrum  presents  a  wide,  shallow 
concavity,  called  the  sacral  groove:  it  is  continuous  above  with  the  vertebral 
groove,  and  lodges  the  origin  of  the  Multifidus  spinae. 

Lateral  Surface. — The  lateral  surface,  broad  above,  becomes  narrowed  into  a 
thin  edge  below.  Its  upper  half  presents  in  front  a  broad,  ear-shaped  surface  for 
articulation  with  the  ilium.  This  is  called  the  auricular  surface  (fades  auricularis) , 
and  in  the  fresh  state  is  coated  with  fibro-cartilage.  It  is  bounded  posteriorly  by 
deep  and  uneven  impressions,  for  the  attachment  of  the  posterior  sacro-iliac  liga- 
ments. The  chief  prominence  is  called  the  tuberosity  (tuberositas  sacralis) .  The 
lower  half  is  thin  and  sharp,  and  terminates  in  a  projection  called  the  inferior  lateral 
angle;  below  this  angle  is  a  notch,  which  is  converted  into  a  foramen  by  articula- 
tion with  the  transverse  process  of  the  upper  piece  of  the  coccyx,  and  transmits 
the  anterior  division  of  the  fifth  sacral  nerve.  This  lower,  sharp  border  gives 
attachment  to  the  greater  and  lesser  sacro-sciatic  ligaments,  and  to  some  fibres 
of  the  Glutens  maximus  posteriorly,  and  to  the  Coccygeus  in  front. 


64  THE  SKELETON 

Base  (basis  oss.  sacri). — The  base  of  the  sacrum,  which  is  broad  and  expanded,  is 
directed  upward  and  forward.  In  the  middle  is  seen  a  large  oval  articular  surface, 
which  is  connected  with  the  under  surface  of  the  body  of  the  last  lumbar  vertebra 
by  a  fibre-cartilaginous  disk.  It  is  bounded  behind  by  the  large,  triangular  orifice 
of  the  sacral  canal.  The  orifice  is  formed  behind  by  the  laminae  and  spinous  process 
of  the  first  sacral  vertebra:  the  superior  articular  processes  project  from  it  on  each 
side;  they  are  oval,  concave,  directed  backward  and  inward,  like  the  superior 
articular  processes  of  a  lumbar  vertebra;  and  in  front  of  each  articular  process  i§ 
an  intervertebral  notch,  which  forms  the  lower  part  of  the  foramen  between  the 
last  lumbar  and  first  sacral  vertebra.  Lastly,  on  each  side  of  the  large  oval  articular 
plate  is  a  broad  and  flat  triangular  surface  of  bone,  which  extends  outward, 
supports  the  Psoas  magnus  muscle  and  lumbo-sacral  cord,  and  is  continuous 
on  each  side  with  the  iliac  fossa.  This  is  called  the  ala  of  the  sacrum  (ala 
sacralis) ,  and  gives  attachment  to  a  few  of  the  fibres  of  the  Iliacus  muscle.  The 
posterior  part  of  the  ala  represents  the  transverse  process  of  the  first  sacral 
segment. 

Apex  (apex  oss.  sacri). — The  apex,  directed  downward  and  slightly  forward, 
presents  a  small,  oval,  concave  surface  for  articulation  with  the  coccyx. 

Spinal  Canal. — The  spinal  canal  in  this  region  is  called  the  sacral  canal  (canalis 
sacralis).  It  runs  throughout  the  greater  part  of  the  bone;  it  is  large  and  tri- 
angular in  form  above,  small  and  flattened,  from  before  backward,  below.  In 
this  situation  its  posterior  wall  is  incomplete,  from  the  •  non-development  of  the 
laminae  and  spinous  processes  (hiatus  sacralis).  It  lodges  the  sacral  nerves, 
and  is  perforated  by  the  anterior  and  posterior  sacral  foramina,  through  which 
these  pass  out. 

Structure. — It  consists  of  much  loose,  spongy  tissue  within,  invested  externally 
by  a  thin  layer  of  compact  tissue. 

Differences  in  the  Sacrum  of  the  Male  and  Female. — The  sacrum  in  the 
female  is  shorter  and  wider  than  in  the  male;  the  lower  half  forms  a  greater 
angle  with  the  upper,  the  upper  half  of  the  bone  being  nearly  straight,  the  lower 
half  presenting  the  greatest  amount  of  curvature.  The  bone  is  also  directed  more 
obliquely  backward,  which  increases  the  size  of  the  pelvic  cavity;  but  the  sacro- 
vertebral  angle  projects  less.  In  the  male  the  curvature  is  more  evenly  dis- 
tributed over  the  whole  length  of  the  bone,  and  is  altogether  greater  than  in 
the  female. 

Peculiarities  of  the  Sacrum. — This  bone,  in  some  cases,  consists  of  six  pieces; 
occasionally,  the  number  is  reduced  to  four.  Sometimes  the  bodies  of  the  first 
and  second  segments  are  not  joined  or  the  laminae  and  spinous  processes  have  not 
coalesced.  Occasionally,  the  upper  pair  of  transverse  tubercles  are  not  joined  to 
the  rest  of  the  bone  on  one  or  both  sides;  and,  lastly,  the  sacral  canal  may  be  open 
for  nearly  the  lower  half  of  the  bone,  in  consequence  of  the  imperfect  development 
of  the  laminae  and  spinous  processes.  The  sacrum,  also,  varies  considerably  with 
respect  to  its  degree  of  curvature.  From  the  examination  of  a  large  number  of 
skeletons  it  would  appear  that  in  one  set  of  cases  the  anterior  surface  of  this  bone 
was  nearly  straight,  the  curvature,  which  was  very  slight,  affecting  only  its  lower 
end.  In  another  set  of  cases  the  bone  was  curved  throughout  its  whole  length, 
but  especially  toward  its  middle.  In  a  third  set  the  degree  of  curvature  was  less 
marked,  and  affected  especially  the  lower  third  of  the  bone. 

Development  (Fig.  33). — The  sacrum,  formed  by  the  union  of  five  vertebrae, 
has  thirty-five  centres  of  ossification. 

The  bodies  of  the  sacral  vertebrae  have  each  three  ossific  centres:  one  for  the 
central  part,  and  one  for  the  epiphyseal  plates  on  its  upper  and  under  surface. 
Occasionally  the  primary  centres  for  the  bodies  of  the  first  and  second  piece  of  the 
sacrum  are  double. 


65 


The  arch  of  each  sacral  vertebra  is  developed  by  two  centres,  one  for  each 
lamina.  These  unite  with  each  other  behind,  and  subsequently  join  the  body. 

The  lateral  masses  have  six  additional  centres,  two  for  each  of  the  first  three 
vertebrae.  These  centres  make  their  appearance  above  and  to  the  outer  side  of 
the  anterior  .sacral  foramina  (Fig.  33),  and  are  developed  into  separate  segments 
(Fig.  34);  they  are  subsequently  blended  with  each  other,  and  with  the  bodies 
and  transverse  processes  to  form  the  lateral  mass. 

Lastly,  each  lateral  surface  of  the  sacrum  is  developed  by  two  epiphyseal  plates 
(Fig.  35):  one  for  the  auricular  surface,  and  one  for  the  remaining  part  of  the 
thin  lateral  edge  of  the  bone. 


Additional  centres 
for  the  first  three  pieces.* 


At  birth. 


Two  epiphyseal  laminx 
for  each  lateral  surface.® 


At 
25th  year. 


At  4k  years. 


FIG.  33. — Development  of  the  sacrum. 


FIG.  34. 


FIG.  35. 


Period  of  Development.— At  about  the  eighth  or  ninth  week  of  fetal  life  ossifi- 
cation of  the  central  part  of  the  bodies  of  the  first  three  vertebrae  commences, 
and  at  a  somewhat  later  period  that  of  the  last  two.  Between  the  sixth  and 
eighth  months  ossification  of  the  laminae  takes  place;  and  at  about  the  same 
period  the  centres  for  the  lateral  masses  for  the  first  three  sacral  vertebrae  make 
their  appearance.  The  period  at  which  the  arch  becomes  completed  by  the  junc- 
tion of  the  laminae  with  the  bodies  in  front  and  with  each  other  behind  varies  in 
different  segments.  The  junction  between  the  laminae  and  the  bodies  takes  place 
first  in  the  lower  vertebrae  as  early  as  the  second  year,  but  is  not  affected  in  the 
uppermost  until  the  fifth  or  sixth  year.  About  the  sixteenth  year  the  epiphyses 
for  the  upper  and  under  surfaces  of  the  bodies  are  formed,  and  between  the  eigh- 
teenth and  twentieth  years  those  for  each  lateral  surface  of  the  sacrum  make  their 
appearance.  The  bodies  of  the  sacral  vertebrae  are,  during  early  life,  separated 
from  each  other  by  intervertebral  disks.  But  about  the  eighteenth  year  the  two 
lowest  segments  become  joined  together  by  ossification  extending  through  the 
disk.  This  process  gradually  extends  upward  until  all  the  segments  become 
united,  and  the  bone  is  completely  formed  from  the  twenty-fifth  to  the  thirtieth 
year  of  life. 

Articulations. — With  four  bones':  the  last  lumbar  vertebra,  coccyx,  and  the 
two  innominate  bones. 

Attachment  of  Muscles.— To  eight  pairs:  in  front,  the  Pyriformis  and  Coc- 
cygeus,  and  a  portion  of  the  Iliacus  to  the  base  of  the  bone;  behind,  the  Gluteus 
maximus,  Latissimus  dorsi,  Multifidus  spinae,  and  Erector  spinae,  and  sometimes 
the  Extensor  coccygis. 

Coccyx  (os  coccygis}. — The  coccyx  (xoxxoz,  cuckoo],  so  called  from  having 
been  compared  to  a  cuckoo's  beak  (Fig.  36),  is  usually  formed  of  four  small 
segments  of  bone,  the  most  rudimentary  parts  of  the  vertebral  column  (vertebrae 
coccygeae  or  caudate  vertebrae).  In  each  of  the  first  three  segments  may  be  traced 
a  rudimentary  body,  articular  and  transverse  processes;  the  last  piece  (some- 

5 


66 


THE  SKELETON 


times  the  third)  is  a  mere  nodule  of  bone,  without  distinct  processes.  All  the 
segments  are  destitute  of  pedicles,  lamina?,  and  spinous  processes,  and,  conse- 
quently, of  intervertebral  foramina  and  spinal  canal.  The  first  segment  is  the 
largest;  it  resembles  the  lowermost  sacral  vertebra,  and  often  exists  as  a  separate 


Cornua. 


Anterior  surface. 


Posterior  surface. 


FIG.  36. — Coccyx. 


piece;  the  last  three,  diminishing  in  size  from  above  downward,  are  usually 
blended  together  so  as  to  form  a  single  bone.  The  gradual  diminution  in  the  size 
of  the  pieces  gives  this  bone  a  triangular  form,  the  base  of  the  triangle  joining 
the  end  of  the  sacrum.  It  presents  for  examination  an  anterior  and  posterior  sur- 
face, two  borders,  a  base,  and  an  apex. 

Surfaces.  Anterior  Surface. — The  anterior  surface  is  slightly  concave,  and 
marked  with  three  transverse  grooves,  indicating  the  points  of  junction  of  the 
different  pieces.  It  has  attached  to  it  the  anterior  sacro-coccygeal  ligament  and 
Levator  ani  muscle,  and  supports  the  lower  end  of  the  rectum. 

Posterior  Surface. — The  posterior  surface  is  convex,  marked  by  transverse  grooves 
similar  to  those  on  the  anterior  surface;  and  presents  on  each  side  a  lineal  row 
of  tubercles,  the  rudimentary  articular  processes  of  the  coccygeal  vertebrae.  Of 
these,  the  superior  pair  are  large,  and  are  called  the  cornua  of  the  coccyx  (cornua 
coccygea) ;  they  project  upward,  and  articulate  with  the  cornua  of  the  sacrum,  the 
junction  between  these  two  bones  completing  the  fifth  posterior  sacral  foramen  for 
the  transmission  of  the  posterior  division  of  the  fifth  sacral  nerve. 

Borders. — The  lateral  borders  are  thin,  and  present  a  series  of  small  eminences, 
which  represent  the  transverse  processes  of  the  coccygeal  vertebrae.  Of  these, 
the  first  on  each  side  is  the  largest,  flattened  from  before  backward,  and  often 
ascends  to  join  the  lower  part  of  the  thin  lateral  edge  of  the  sacrum,  thus  com- 
pleting the  fifth  anterior  sacral  foramen  for  the  transmission  of  the  anterior 
division  of  the  fifth  sacral  nerve;  the  others  diminish  in  size  from  above  down- 
ward, and  are  often  wanting.  The  borders  of  the  coccyx  are  narrow,  and  give 
attachment  on  each  side  to  the  sacro-sciatic  ligaments,  to  the  Coccygeus  muscles 
in  front  of  the  ligaments,  and  to  the  Gluteus  maximus  behind  them. 

Base. — The  base  presents  an  oval  surface  for  articulation  with  the  sacrum. 
This  articulation  is  known  as  the  sacro-coccygeal  symphysis  (symphysis  sacro- 
coccygea) . 

Apex. — The  apex  is  rounded,  and  has  attached  to  it  the  tendon  of  the  external 
Sphincter  muscle.  It  is  occasionally  bifid,  and  sometimes  deflected  to  one  or 
other  side. 

Development. — The  coccyx  is  developed  by  four  centres,  one  for  each  piece. 
Occasionally  one  of  the  first  three  pieces  of  this  bone  is  developed  by  two  centres, 
placed  side  by  side.  The  ossific  nuclei  make  their  appearance  in  the  following 
order:  in  the  first  segment,  shortly  after  birth;  in  the  second  piece,  at  from  five 


THE    VERTEBRAL    COLUMN 


67 


to  ten  years;  in  the  third,  from  ten  to  fifteen 
years;  in  the  fourth,  from  fifteen  to  twenty 
years.  As  age  advances  these  various  seg- 
ments become  united  with  each  other  from 
below  upward,  the  union  between  the  first 
;in<l  second  segments  being  frequently  delayed 
until  after  the  age  of  twenty-five  or  thirty. 
At  a  late  period  of  life,  especially  in  females, 
the  coccyx  often  becomes  joined  to  the  end 
of  the  sacrum. 

Articulation. — With  the  sacrum. 

Attachment  of  Muscles. — To  four  pairs 
and  one  single  muscle :  on  either  side,  the 
Coccygeus ;  behind,  the  Gluteus  maximus 
and  Extensor  coccygis,  when  present ;  at  the 
apex,  the  Sphincter  ani ;  and  in  front,  the 
Levator  ani. 


1st  cervical ' 
or  Atlas. 

2nd  cervical ' 
or  Axis. 


6- 
7-1 

1st  thoracic. -\ 


The  Vertebral  Column  or  Spine  in  General. 

The  spinal  column  (columna  vertebralis) , 
formed  by  the  junction  of  the  vertebrae,  is 
situated  in  the  median  line,  at  the  posterior 
part  of  the  trunk;  its  average  length  is  about 
two  feet  two  or  three  inches,  measuring  along 
the  curved  anterior  surface  of  the  column. 
Of  this  length  the  cervical  part  measures 
about  five,  the  thoracic  about  eleven,  the  lum- 
bar about  seven  inches,  and  the  sacrum  and 
coccyx  the  remainder.  The  female  spine  is 
about  one  inch  less  than  that  of  the  male. 

Viewed  in  front,  the  ventral  surface  presents 
two  pyramids  joined  together  at  their  bases, 
the  upper  one  being  formed  by  all  the  verte- 
brae from  the  second  cervical  to  the  last  lum- 
bar, the  lower  one  by  the  sacrum  and  coccyx. 
When  examined  more  closely,  the  upper 
pyramid  is  seen  to  be  formed  of  three  smaller 
pyramids.  The  uppermost  of  these  consists 
of  the  six  lower  cervical  vertebrae,  its  apex 
being  formed  by  the  axis  or  second  cervical, 
its  base  by  the  first  thoracic.  The  second 
pyramid,  which  is  inverted,  is  formed  by  the 
four  upper  thoracic  vertebrae,  the  base  being 
at  the  first  thoracic,  the  smaller  end  at  the 
fourth.  The  third  pyramid  commences  at  the 
fourth  thoracic,  and  gradually  increases  in 
size  to  the  fifth  lumbar. 

Viewed  laterally  (Fig.  37),  the  spinal  col- 
umn presents  several  curves  which  correspond 
to  the  different  regions  of  the  column,  and  are 
called  cervical,  thoracic,  lumbar,  and  pelvic. 
The  cervical  curve  commences  at  the  apex  of 
the  odontoid  process,  and  terminates  at  the 


1st  lumbar.- 


r, 


Sacrum. 


Coccyx. 
FIG.  37. — Lateral  view  of  the  spine. 


68  THE  SKELETON 

middle  of  the  second  thoracic  vertebra;  it  is  convex  in  front,  and  is  the  least 
marked  of  all  the  curves.  The  thoracic  curve,  which  is  concave  forward,  com- 
mences at  the  middle  of  the  second,  and  terminates  at  the  middle  of  the  twelfth 
thoracic  vertebra.  Its  most  prominent  point  behind  corresponds  to  the  spine 
of  the  seventh  thoracic  vertebra.  The  lumbar  curve  commences  at  the  middle 
of  the  last  thoracic  vertebra,  and  terminates  at  the  sacro-vertebral  angle.  It  is 
convex  anteriorly;  the  convexity  of  the  lower  three  vertebrae  being  much  greater 
than  that  of  the  upper  two.  The  pelvic  curve  commences  at  the  sacro-verte- 
bral articulation  and  terminates  at' the  point  of  the  coccyx.  It  is  concave  ante- 
riorly. The  thoracic  and  pelvic  curves  are  the  primary  curves,  and  begin  to  be 
formed  at  an  early  period  of  foetal  life,  and  are  due  to  the  shape  of  the  bodies 
of  the  vertebrae.  The  cervical  and  lumbar  curves  are  compensatory  or  secondary, 
and  are  developed  after  birth  in  order  to  maintain  the  erect  position.  They  are 
due  mainly  to  the  shape  of  the  intervertebral  disks. 

Some  writers  teach  that  the  spine  has  a  normal  deviation  to  the  right  side. 
Quain,  Hyrtl,  and  others  maintain  this  view.  The  curve  is  said  to  be  in  the 
thoracic  region.  Bichat  assigned  muscular  action  as  the  chief  cause  of  the  curve. 
Most  persons  use  the  right  arm  in  preference  to  the  left,  especially  in  making 
long-continued  efforts,  when  the  body  is  curved  to  the  right  side.  In  support 
of  this  explanation  is  the  observation  made  by  Beclard  that  in  some  individuals 
who  were  left-handed  the  lateral  curvature  was  directed  to  the  left  side.  Sappey 
and  others  deny  the  existence  of  this  curve. 

The  movable  part  of  the  spinal  column  presents  for  examination  an  anterior, 
a  posterior,  and  two  lateral  surfaces;  a  base,  a  summit,  and  the  spinal  canal. 

Surfaces.  Anterior  Surface. — The  anterior  or  ventral  surface  presents  the  bodies 
of  the  vertebrae  separated  in  the  recent  state  by  the  intervertebral  disks.  The  bodies 
are  broad  in  the  cervical  region,  narrow  in  the  upper  part  of  the  thoracic,  and 
broadest  in  the  lumbar  region.  The  whole  of  this  surface  is  convex  transversely, 
concave  from  above  downward  in  the  thoracic  region,  and  convex  in  the  same 
direction  in  the  cervical  and  lumbar  regions. 

Posterior  Surface. — The  posterior  or  dorsal  surface  presents  in  the  median  line 
the  spinous  processes.  These  are  short,  horizontal,  with  bifid  extremities,  in  the 
cervical  region.  In  the  thoracic  region  they  are  directed  obliquely  above,  assume 
almost  a  vertical  direction  in  the  middle,  and  are  horizontal  below,  as  are  also 
the  spines  of  the  lumbar  vertebrae.  They  are  separated  by  considerable  intervals 
in  the  loins,  by  narrower  intervals  in  the  neck,  and  are  closely  approximated  in 
the  middle  of  the  thoracic  region.  Occasionally  one  of  these  processes  deviates  a 
little  from  the  median  line — a  fact  to  be  remembered  in  practice,  as  irregularities 
of  this  sort  are  attendant  also  on  fractures  or  displacements  of  the  spine.  On 
either  side  of  the  spinous  processes,  extending  the  whole  length  of  the  column, 
is  the  vertebral  groove  formed  by  the  laminae  in  the  cervical  and  lumbar  regions, 
where  it  is  shallow,  and  by  the  laminae  and  transverse  processes  in  the  thoracic 
region,  where  it  is  deep  and  broad.  In  the  recent  state  these  grooves  lodge  the 
deep  muscles  of  the  back.  External  to  each  vertebral  groove  are  the  articular 
processes,  and  still  more  externally  is  the  transverse  process.  In  the  thoracic  region 
the  latter  processes  stand  backward,  on  a  plane  considerably  posterior  to  that 
of  like  processes  in  the  cervical  and  lumbar  regions.  In  the  cervical  region  the 
transverse  processes  are  placed  in  front  of  the  articular  processes,  and  on  the 
outer  side  of  the  pedicles,  between  the  intervertebral  foramina.  In  the  thoracic 
region  they  are  posterior  to  the  pedicles,  intervertebral  foramina,  and  articular 
processes.  In  the  lumbar  region  they  are  placed  also  in  front  of  the  articular 
processes,  but  behind  the  intervertebral  foramina. 

Lateral  Surfaces. — The  lateral  surfaces  are  separated  from  the  posterior  surface 
by  the  articular  processes  in  the  cervical  and  lumbar  regions,  and  by  the  trans- 


THE    VERTEBRAL    COLUMN  69 

verse  processes  in  the  thoracic  region.  These  surfaces  present  in  front  the  sides  of 
the  bodies  of  the  vertebrae,  marked  in  the  thoracic  region  by  the  facets  for  articula- 
tion with  the  heads  of  the  ribs.  More  posteriorly  are  the  intervertebral  foramina, 
formed  by  the  juxtaposition  of  the  intervertebral  notches,  oval  in  shape,  smallest 
in  the  cervical  and  upper  part  of  the  thoracic  regions,  and  gradually  increasing  in 
size  to  the  last  lumbar  vertebra.  They  are  situated  between  the  transverse  pro- 
cesses in  the  neck,  and  in  front  of  them  in  the  back  and  loins,  and  transmit  the 
spinal  nerves. 

Base. — The  base  of  that  portion  of  the  vertebral  column  formed  by  the  twenty- 
four  movable  vertebrte  is  formed  by  the  under  surface  of  the  body  of  the  fifth 
lumbar  vertebra;  and  the  summit  by  the  upper  surface  of  the  atlas. 

Spinal  Canal  (canalis  vertebralis). — The  vertebral  or  spinal  canal  follows  the 
different  curves  of  the  spine;  it  is  largest  in  those  regions  in  which  the  spine 
enjoys  the  greatest  freedom  of  movement,  as  in  the  neck  and  loins,  where  it  is 
wide  and  triangular;  and  is  narrow  and  rounded  in  the  back,  where  motion  is 
more  limited.  The  centre  of  gravity  of  the  spine  is  in  the  upper  lumbar  region, 
slightly  to  the  right  of  the  median  plane  (Struthers). 

Surface  Form. — The  only  parts  of  the  vertebral  column  which  lie  closely  under  the  skin,  and 
so  directly  influence  surface  form,  are  the  apices  of  the  spinous  processes.  These  are  always  distin- 
guishable at  the  bottom  of  a  median  furrow,  which,  more  or  less  evident,  runs  down  the  mesial 
line  of  the  back  from  the  external  occipital  protuberance  above  to  the  middle  of  the  sacrum  below. 
In  the  cervical  region  the  furrow  is  between  the  Trapezii  muscles ;  in  the  back  and  loins  it  is  between 
the  Erector  spinae  muscles.  In  the  neck  the  furrow  is  broad,  and  terminates  in  a  conspicuous 
projection,  which  is  caused  by  the  spinous  process  of  the  seventh  cervical  vertebra  (vertebra 
prominens).  Above  this  the  spinous  process  of  the  sixth  cervical  vertebra  may  sometimes  be 
seen  to  form  a  projection;  the  other  cervical  spines  are  sunken,  and  are  not  visible,  though  the 
spine  of  the  axis  can  be  felt,  and  generally  also  the  spines  of  the  third,  fourth,  and  fifth  cervical 
vertebrae.  In  the  thoracic  region  the  furrow  is  shallow,  and  during  stooping  disappears,  and  then 
the  spinous  processes  become  more  or  less  visible.  The  markings  produced  by  these  spines  are 
small  and  close  together.  In  the  lumbar  region  the  furrow  is  deep,  and  the  situation  of  the  lumbar 
spines  is  frequently  indicated  by  little  pits  or  depressions,  especially  if  the  muscles  in  the  loins 
are  well  developed  and  the  spine  incurved.  They  are  much  larger  and  farther  apart  than  in  the 
thoracic  region.  In  the  sacral  region  the  furrow  is  shallower,  presenting  a  flattened  area  which 
terminates  below  at  the  most  prominent  part  of  the  posterior  surface  of  the  sacrum,  formed  by 
the  spinous  process  of  the  third  sacral  vertebra.  At  the  bottom  of  the  furrow  may  be  felt  the 
irregular  posterior  surface  of  the  bone.  Below  this,  in  the  deep  groove  leading  to  the  anus,  the 
coccyx  may  be  felt.  The  only  other  portions  of  the  vertebral  column  which  can  be  felt  from  the 
surface  are  the  transverse  processes  of  three  of  the  cervical  vertebrae — viz.,  the  first,  the  sixth, 
and  the  seventh.  The  transverse  process  of  the  atlas  can  be  felt  as  a  rounded  nodule  of  bone 
just  below  and  in  front  of  the  apex  of  the  mastoid  process,  along  the  anterior  border  of  the  sterno- 
mastoid.  The  transverse  process  of  the  sixth  cervical  vertebra  is  of  surgical  importance.  If 
deep  pressure  be  made  in  the  neck  in  the  course  of  the  carotid  artery,  opposite  the  cricoid  carti- 
lage, the  prominent  anterior  tubercle  of  the  transverse  process  of  the  sixth  cervical  vertebra  can 
be  felt.  This  has  been  named  Chassaignac's  tubercle,  and  against  it  the  carotid  artery  may  be 
most  conveniently  compressed  by  the  finger.  The  transverse  process  of  the  seventh  cervical 
vertebra  can  also  often  be  felt.  Occasionally  the  anterior  root,  or  costal  process,  is  large  and 
segmented  off,  forming  a  cervical  rib. 

Surgical  Anatomy. — It  is  frequently  necessary  to  locate  certain  vertebrae.  Several  of  them 
can  be  easily  found  and  identified.  The  seventh  cervical  spine  is  conspicuously  prominent,  and 
when  the  skin  above  it  has  been  marked  with  a  blue  pencil  the  spine  of  the  sixth  cervical  above 
and  of  the  first  thoracic  below  may  be  located.  The  spine  of  the  third  thoracic  vertebra  is  on  a 
level  with  the  root  of  the  spine  of  the  scapula.  The  spine  of  the  fourth  lumbar  vertebra  is  on  a  level 
with  the  highest  point  of  the  iliac  crest.  When  one  or  two  vertebrae  have  been  definitely  recog- 
nized the  other  ones  can  be  found  by  counting  the  spines  from  a  fixed  point  or  from  fixed  points. 
Over  the  fifth  lumbar  spine  there  is  no  prominence,  but  a  depression.  The  third  sacral  spine 
is  on  a  level  with  the  posterior  superior  spines  of  the  ilium.  The  level  at  which  the  spinal  cord 
terminates  should  be  known  to  the  surgeon  if  he  proposes  to  tap  the  spinal  theca  (lumbar  punc- 
ture), for  diagnostic  or  therapeutic  purposes  or  as  a  preliminary  to  the  injection  of  cocaine  or 
eucaine  (spinal  anaesthesia).  In  an  adult  the  cord  terminates  at  the  lower  border  of  the  first 
lumbar  vertebra,  and  the  theca  terminates  opposite  the  body  of  the  third  sacral  vertebra.  In  a 
child  the  cord  terminates  opposite  the  body  of  the  third  lumbar  vertebra,  and  the  theca  ends  at 


70  THE  SKELETON 

about  the  same  level  as  in  an  adult.  Hence,  in  either  a  child  or  an  adult,  a  puncture  below  the 
level  of  the  fourth  lumbar  vertebra  will  inflict  no  injury  upon  the  cord.  In  children  the  puncture 
is  made  just  beneath  the  vertebral  spine,  and  in  adults  about  one-half  an  inch  to  either  side  of 
the  vertebral  spine,  although,  even  in  adults,  the  needle  is  made  to  enter  the  dura  in  the  middle 
line.  In  either  case  the  needle  is  directed  upward  and  forward.  As  previously  pointed  out,  the 
surgical  anatomy  of  an  infant's  spine  is  not  identical  with  the  surgical  anatomy  of  an  adult's 
spine.  An  infant's  spine  is  larger  comparatively  than  an  adult's  spine,  because  the  lower  limbs 
are  less  developed  in  the  former  (A.  H.  Tubby).  The  umbilicus  of  an  infant  is  opposite  the  body 
of  the  fourth  lumbar  vertebra;  in  an  adult  it  is  opposite  the  spine  of  the  third  lumbar  vertebra. 
In  an  infant  the  base  of  the  sternum  is  on  a  level  with  the  top  of  the  seventh  cervical  spine,  and 
in  an  adult  of  the  second  thoracic  spine  (A.  H.  Tubby). 

Occasionally  the  coalescence  of  the  laminae  is  not  completed,  and  consequently  a  cleft  is  left 
in  the  arches  of  the  vertebrae  and  in  the  dura,  through  which  a  protrusion  of  the  arachnoid 
membrane  and  sometimes  of  the  spinal  cord  itself  takes  place,  constituting  a  malformation 
known  as  spina  bifida  or  hydrorrhachitis.  This  disease  is  most  common  in  the  lumbo-sacral 
region;  but  it  may  occur  in  the  thoracic  or  cervical  region,  or  the  arches  throughout  the  whole 
length  of  the  canal  may  remain  unapproximated.  In  some  rare  cases,  in  consequence  of  the 
non-coalescence  of  the  two  primary  centres  from  which  the  body  is  formed,  a  similar  condition 
may  occur  in  front  of  the  canal,  the  bodies  of  the  vertebrae  being  found  cleft  and  the  tumor  pro- 
jecting into  the  thorax,  abdomen .  or  pelvis,  between  the  lateral  halves  of  the  bodies  affected. 

The  construction  of  the  spinal  column  of  a  number  of  pieces,  securely  connected  together 
and  enjoying  only  a  slight  degree  of  movement  between  any  two  individual  pieces,  though  per- 
mitting of  a  very  considerable  range  of  movement  as  a  whole,  allows  a  sufficient  degree  of 
mobility  without  any  material  diminution  of  strength.  The  main  joints  of  which  the  spine  is 
composed,  together  with  the  very  varied  movements  to  which  it  is  subjected,  render  it  liable  to 
sprains,  which  may  complicate  other  injuries  or  may  exist  alone;  but  so  closely  are  the  individual 
vertebrae  articulated  that  these  sprains  are  seldom  severe,  and  an  amount  of  violence  sufficiently 
great  to  produce  tearing  of  the  ligaments  would  tend  to  cause  a  dislocation  or  fracture.  The 
further  safety  of  the  column  and  its  less  liability  to  injury  is  provided  for  by  its  disposition 
in  curves  instead  of  in  one  straight  line.  For  it  is  an  elastic  column,  and  must  first  bend  before 
it  breaks :  under  these  circumstances,  being  made  up  of  three  curves,  it  represents  three  columns, 
and  greater  force  is  required  to  produce  bending  of  a  short  column  than  of  a  longer  one  that  is 
equal  to  it  in  breadth  and  material.  Again,  the  safety  of  the  column  is  provided  for  by  the  inter- 
position of  the  intervertebral  disks  between  the  bodies  of  the  vertebrae,  which  act  as  admirable 
buffers  in  counteracting  the  effects  of  violent  jars  or  shocks.  Fracture  dislocation  of  the  spine 
may  be  caused  by  direct  or  indirect  violence,  or  by  a  combination  of  the  two,  as  when  a  person, 
falling  from  a  height,  strikes  against  some  prominence  and  is  doubled  over  it.  The  fractures 
from  indirect  violence  are  the  more  common,  and  here  the  bodies  of  the  vertebrae  are  compressed, 
whilst  the  arches  are  torn  asunder;  whilst  in  fractures  from  direct  violence  the  arches  are  com- 
pressed and  the  bodies  of  the  vertebrae  separated  from  each  other.  It  will  therefore  be  seen  that 
in  both  classes  of  injury  the  spinal  marrow  is  the  part  least  likely  to  be  injured,  and  may  escape 
damage  even  where  there  has  been  considerable  lesion  of  the  bony  framework.  For,  as  Mr. 
Jacobson  states,  "being  lodged  in  the  centre  of  the  column,  it  occupies  neutral  ground  in  respect 
to  forces  which  might  cause  fracture.  For  it  is  a  law  in  mechanics  that  when  a  beam,  as  of  timber, 
is  exposed  to  breakage  and  the  force  does  not  exceed  the  limits  of  the  strength  of  the  material, 
one  division  resists  compression,  another  laceration  of  the  particles,  while  the  third,  between 
the  two,  is  in  a  negative  condition."1  Applying  this  principle  to  the  spine  it  will  be  seen  that, 
whether  the  fracture  dislocation  be  produced  by  direct  violence  or  by  indirect  force,  one  segment, 
either  the  anterior  or  posterior,  will  be  exposed  to  compression,  the  other  to  laceration,  and  the 
intermediate  part,  where  the  cord  is  situated,  will  be  in  a  neutral  state.  When  a  fracture  dis- 
location is  produced  by  indirect  violence  the  displacement  is  almost  always  the  same,  the  upper 
segment  being  driven  forward  on  the  lower,  so  that  the  cord  is  compressed  between  the  body  of 
the  vertebra  below  and  the  arch  of  the  vertebra  above. 

The  parts  of  the  spine  most  liable  to  be  injured  are  (1)  the  dorso-lumbar  region,  for  this  part 
is  near  the  middle  of  the  column,  and  there  is  therefore  a  greater  amount  of  leverage,  and  more- 
over the  portion  above  is  comparatively  fixed,  and  the  vertebrae  which  form  it,  though  much 
smaller,  have  nevertheless  to  bear  almost  as  great  a  weight  as  those  below;  (2)  the  cervico-tho- 
racic  region,  because  here  the  flexible  cervical  portion  of  the  spine  joins  the  more  fixed  thoracic 
region;  and  (3)  the  atlanto-axial  region,  because  it  enjoys  an  extensive  range  of  movement,  and, 
being  near  the  skull,  is  influenced  by  violence  applied  to  the  head.  In  fracture-dislocation  spinous 
processes  and  portions  of  the  laminae  may  be  removed  (laminectomy}  in  order  to  free  the  cord 
from  pressure,  and  to  permit  the  surgeon  to  explore,  to  arrest  hemorrhage,  to  remove  bone 
fragments,  or  to  apply  sutures.  Laminectomy  is  also  resorted  to  in  some  cases  of  paraplegia  due 
to  Pott's  disease  of  the  spine. 

i  Holmes's  System  of  Surgery,  1883,  vol.  i.  p.  529. — ED.  of  the  15th  English  Edition. 


THE    OCCIPITAL    BONE 


71 


THE  SKULL. 

The  skeleton  of  the  head  is  called  the  skull.  The  cranium  is  the  skull  without 
the  mandible.  The  calvaria  or  cerebral  cranium  is  the  skull  without  the  bones  of 
the  face.  The  skull  is  supported  on  the  summit  of  the  vertebral  column,  and  is 
of  an  oval  shape,  wider  behind  than  in  front.  It  is  composed  of  a  series  of  flat- 
tened or  irregularly  shaped  bones  which,  with  one  exception  (the  lower  jaw),  are 
immovably  joined  together.  It  is  divided  into  two  parts,  the  cerebral  cranium  or 
calvaria  and  the  visceral  cranium  or  face,  the  former  of  which  constitutes  a  case 
for  the  accommodation  and  protection  of  the  brain,  while  opening  on  the  face 
are  the  orifices  of  the  nose  and  mouth;  between  the  cerebral  cranium  above  and 
the  face  below  the  orbital  cavities  are  situated.  The  cerebral  cranium  (xpdvos,  a 
helmet)  is  composed  of  eight  bones — viz.,  the  occipital,  two  parietal,  frontal,  two 
temporal,  sphenoid,  and  ethmoid.  The  face  is  composed  of  fourteen  bones — 
viz.,  the  two  nasal,  two  superior  maxillary,  two  lachrymal,  two  malar,  two  palate, 
two  inferior  turbinated,  vomer,  and  inferior  maxillary  or  mandible.  The  ossiculi 
auditus,  the  teeth,  and  Wonnian  bones  are  not  included  in  this  enumeration. 


Cranium,  8  bones 


Skull,  22  bones 


Face,  14  bones 


ital. 

!  Two"  Parietal. 
Frontal. 

Two  Temporal. 
Sphenoid. 
Ethmoid. 
Two  Nasal. 

Two  Superior  Maxillary. 
Two  Lachrymal. 
Two  Malar. 
Two  Palate. 

Two  Inferior  Turbinated. 
Vomer. 
Inferior  Maxillary  or  Mandible. 

The  Hyoid  Bone,  situated  at  the  root  of  the  tongue  and  attached  to  the  base 
of  the  skull  by  ligaments,  has  also  to  be  considered  in  this  section. 

THE  CEREBRAL  CRANIUM  (CRANIUM  CEREBRALE)  (THE  CALVARIA). 

The  Occipital  Bone  (Os  Occipitale). 

The  occipital  bone  (ob,  caput,  against  the  head)  is  situated  at  the  back  part 
and  base  of  the  cranium,  is  trapezoid  in  shape  and  is  much  curved  on  itself  (Fig. 
38).  It  presents  at  its  front  and  lower  part  a  large  oval  aperture,  the  foramen 
magnum  (foramen  occipitale  magnum) ,  by  which  the  cranial  cavity  communicates 
with  the  spinal  canal.  The  portion  of  bone  behind  this  opening  is  flat  and 
expanded  and  forms  the  tabula,  tabular  portion,  or  squamous  part  (squama 
occipitalis) ;  the  portion  in  front  is  a  thick,  el  ngated  mass  of  bone,  the  basilar 
process  (pars  basilaris) ;  while  on  each  side  of  the  foramen  is  situated  a  lateral 
or  condylic  portion  (pars  lateralis),  bearing  the  condyle,  by  which  the  bone  articu- 
lates with  the  atlas.  The  bone  presents  for  examination  two  surfaces,  four  borders, 
and  four  angles. 

Surfaces.  External  Surface.— The  external  surface  is  convex.  Midway  between 
the  summit  of  the  bone  and  the  posterior  margin  of  the  foramen  magnum  is  a 
prominent  tubercle,  the  inion  or  external  occipital- protuberance  (protuberantia 


72 


THE   SKELETON 


occipitalis  externa),  and,  descending  from  it  as  far  as  the  foramen,  a  vertical 
ridge,  the  external  occipital  crest  (crista  occipitalis  externa).  This  protuberance 
and  crest  give  attachment  to  the  ligamentum  nuchte,  and  vary  in  prominence 
in  different  skulls.  Passing  outward  from  the  occipital  protuberance  is  a  semi- 
circular ridge  on  each  side,  the  superior  curved  or  superior  nuchal  line  (linea 
nuchca  superior).  Above  this  line  there  is  often  a  second  less  distinctly 
marked  ridge,  called  the  highest  curved  line  (linea  nuchce  suprema);  to  it  the  epi- 
cranial  aponeurosis  is  attached.  The  bone  between  these  two  lines  is  smoother 
and  denser  than  the  rest  of  the  surface.  Running  parallel  with  these  from  the 
middle  of  the  crest  is  another  semicircular  ridge  on  each  side,  the  inferior  curved 
or  inferior  nuchal  line  (linea  nuchae  inferior}.  The  surface  of  the  bone  above  the 
linea  suprema  is  rough  and  porous,  and  in  the  recent  state  is  covered  by  the 


Linea 
suprema 


SUPERIOR 
CONSTRICTOR 

of  Pharynx. 


FIG.  38.— Occipital  bone.     Outer  surface. 

Occipito-frontalis  muscle.  It  is  called  the  occipital  portion  or  the  planum 
occipitale.  The  superior  and  inferior  curved  li-nes,  together  with  the  surfaces  of 
bone  between  and  below  them,  serve  for  the  attachment  of  several  muscles. 
The  superior  curved  line  gives  attachment  internally  to  the  Trapezius,  externally 
to  the  muscular  origin  of  the  Occipito-frontalis,  and  to  the  Sterno-cleido-mastoid 
to  the  extent  shown  in  Fig.  38;  the  depressions  between  the  curved  lines  to  the 
Cornplexus  internally,  the  Splenius  capitis  and  Obliquus  capitis  superior  exter- 
nally. The  inferior  curved  line  and  the  depressions  below  it  afford  insertion  to 
the  Rectus  capitis  posticus,  major  and  minor.  The  portion  of  the  tabula  below 
the  superior  curved  line  is  called  the  nuchal  plane  (planum  nuchale),  and  it  gives 
attachment  to  certain  of  the  neck  muscles. 

The  foramen  magnum  (foramen  occipitale  magnum)  is  a  large,  oval  aperture,  its 
long  diameter  extending  from  before  backward.    It  transmits  the  lower  portion 


THE   OCCIPITAL   BONE  73 

of  the  oblongata  and  its  membranes,  the  accessory  nerves,  the  vertebral 
arteries,  the  anterior  and  posterior  spinal  arteries,  and  the  occi  pi  to-axial 
ligaments.  Its  back  part  is  wide  for  the  transmission  of  the  oblongata,  and  the 
corresponding  margin  rough  for  the  attachment  of  the  dura  enclosing  it;  the 
fore  part  is  narrower,  being  encroached  upon  by  the  condyles;  it  has  projecting 
toward  it,  from  below,  the  odontoid  process,  and  its  margins  are  smooth  and 
bevelled  internally  to  support  the  oblongata.  The  middle  of  the  anterior 
wall  of  the  foramen  magnum  is  called  by  Broca  the  basion.  The  lateral  or 
condylic  portions  (partes  laterales}  are  on  either  side  of  the  foramen  magnum 
and  bear  the  condyles  for  articulation  with  the  atlas.  Each  condyle  (condylus 
occipitalis)  is  convex,  oval,  or  reniform  in  shape,  and  directed  downward  and 
outward.  The  condyles  converge  in  front,  and  encroach  slightly  upon  the  anterior 
segment  of  the  foramen.  On  the  inner  border  of  each  condyle  is  a  rough  tubercle 
for  the  attachment  of  the  ligaments  (check)  which  connect  this  bone  with  the 
odontoid  process  of  the  axis;  while  external  to  them  is  a  rough  tubercular  promi- 
nence, the  transverse  or  jugular  process  (processus  jugularis),  channelled  in  front 
by  a  deep  notch  (incisura  jugularis),  which  forms  part  of  the  jugular  foramen 
or  foramen  lacerum  posterius.  The  under  surface  of  this  process  presents  an 
eminence  (processus  intrajugularis)  which  represents  the  paramastoid  process  of 
some  mammals.  The  eminence  is  occasionally  large,  and  extends  as  low  as  the 
transverse  process  of  the  atlas.  This  surface  affords  attachment  to  the  Rectus 
capitis  lateralis  muscle  and  to  the  lateral  occipito-atlantal  ligament;  its  upper  or 
cerebral  surface  presents  a  deep  groove  which  lodges  part  of  the  lateral  sinus, 
while  its  external  surface  is  marked  by  a  quadrilateral  rough  facet,  covered  with 
cartilage  in  the  fresh  state,  and  articulating  with  a  similar  surface  on  the  petrous 
portion  of  the  temporal  bone.  On  the  outer  side  of  each  condyle,  near  its  fore 
part,  is  a  foramen,  the  anterior  condyloid  foramen  (canalis  hypoglossi  or  the  hypo- 
glossal  canal) ;  it  is  directed  downward,  outward,  and  forward,  and  transmits  the 
hypoglossal  nerve,  and  occasionally  a  meningeal  branch  of  the  ascending  pharyn- 
geal  artery.  This  foramen  is  sometimes  double.  Behind  each  condyle  is  a 
fossa1  (fossa  condyloideus),  sometimes  perforated  at  the  bottom  by  a  foramen, 
the  posterior  condyloid  foramen  (canalis  condyloideus),  for  the  transmission  of  a 
vein  to  the  lateral  sinus.  The  basilar  process  (pars  basilaris)  is  a  strong  quadri- 
lateral plate  of  bone,  which  is  wider  behind  than  in  front,  and  is  situated  in  front 
of  the  foramen  magnum.  Its  under  surface,  which  is  rough,  presents  in  the 
median  line  a  tubercular  ridge,  the  pharyngeal  spine  or  tubercle  (tuberculum 
pharyngeum),  for  the  attachment  of  the  tendinous  raphe*  and  Superior  con- 
strictor of  the  pharynx;  and  on  each  side  of  it  rough  depressions  for  the  attach- 
ment of  the  Rectus  capitis  anticus,  major  and  minor. 

Internal  Surface. — The  internal  or  cerebral  surface  (Fig.  39)  is  deeply  concave. 
The  posterior  or  tabular  part  is  divided  by  a  crucial  ridge  into  four  fossae.  The 
two  superior  fossae  receive  the  occipital  lobes  of  the  cerebrum,  and  present  slight 
eminences  and  depressions  corresponding  to  their  convolutions.  The  two  inferior, 
which  receive  the  hemispheres  of  the  cerebellum,  are  larger  than  the  former,  and 
comparatively  smooth;  both  are  marked  by  slight  grooves  for  the  lodgement  of 
arteries.  At  the  point  of  meeting  of  the  four  divisions  of  the  crucial  ridge  is  an 
eminence,  the  internal  occipital  protuberance  (protuberantia  occipitalis  interna).  It 
nearly  corresponds  to  that  on  the  outer  surface,  though  it  is  often  on  a  slightly 
higher  level,  and  is  perforated  by  one  or  more  large  vascular  foramina.  From 
this  eminence  the  superior  division  of  the  crucial  ridge  runs  upward  to  the  supe- 
rior angle  of  the  bone;  it  presents  a  deep  groove,  the  sagittal  sulcus  (sulcus  sagit- 

1  This  fossa  presents  many  variations  in  size.  It  is  usually  shallow,  and  the  foramen  small:  occasionally 
wanting  on  one  or  both  sides.  Sometimes  both  fossa  and  foramen  are  large,  but  confined  to  one  side  only;  more 
rarely,  the  fossa  and  foramen  are  very  large  on  both  sides. — ED.  of  15th  English  Edition. 


74 


THE  SKELETON 


talis) ,  for  the  superior  longitudinal  sinus.  The  margins  of  the  groove  give  attach- 
ment to  the  falx  cerebri.  The  inferior  division,  the  internal  occipital  crest  (crista 
occipitalis  internet) ,  runs  to  the  posterior  margin  of  the  foramen  magnum,  on  the 
edge  of  which  it  becomes  gradually  lost;  this  ridge,  which  is  bifurcated  below, serves 


Superior  angle. 


Lateral 
Angle. 


Inferior  angle. 
FIG.  39. — Occipital  bone.     Inner  surface. 

for  the  attachment  of  the  falcula.  It  is  usually  marked  by  a  single  groove,  which 
commences  at  the  back  part  of  the  foramen  magnum  and  lodges  the  occipital 
sinus.  Occasionally  the  groove  is  double  where  two  sinuses  exist.  A  transverse 
groove  (sulcus  transversus)  passes  outward  on  each  side  to  the  lateral  angle. 
The  grooves  are  deep  channels  for  the  lodgement  of  the  lateral  sinuses,  their 
prominent  margins  affording  attachment  to  the  tentorium.1  At  the  point  of 
meeting  of  these  grooves  is  a  depression,  the  torcular,2  placed  a  little  to  one  or 
the  other  side  of  the  internal  occipital  protuberance.  More  anteriorly  is  the  fora- 
men magnum,  and  on  each  side  of  it,  but  nearer  its  anterior  than  its  posterior 
part,  the  internal  openings  of  the  anterior  condyloid  foramen.  On  the  supe- 
rior aspect  of  the  lateral  portion  of  the  bone  the  jugular  tubercle  (tuberculum 
jugulare)  is  seen.  This  corresponds  to  the  portion  of  bone  which  roofs  in  the 
anterior  condyloid  foramen.  The  internal  openings  of  the  posterior  condyloid 

1  Usually  one  of  the  transverse  grooves  is  deeper  and  broader  than  the  other;  occasionally,  both  grooves  are 
of  equal  depth  and  breadth,  or  both  equally  indistinct.     The  broader  of  the  two  transverse  grooves  is  nearly 
always  continuous  with  the  vertical  groove  for  the  superior  longitudinal  sinus. — ED.  of  15th  Knglish  Edition. 

2  The  columns  of  blood  coming  in   different   directions  were  supposed  to  be  pressed  together  at  this  point 
(torcular,  a  wine-press). — ED.  of  15th  English  Edition. 


THE    OCCIPITAL    BONE  75 

foramina  are  a  little  external  and  posterior  to  the  openings  of  the  anterior  con- 
dyloid foramina,  protected  by  a  small  arch  of  bone.  At  this  part  of  the  internal 
surface  there  is  a  very  deep  groove  in  which  the  posterior  condyloid  foramen, 
when  it  exists,  has  its  termination.  This  groove  is  continuous,  in  the  complete 
skull,  with  the  transverse  groove  on  the  posterior  part  of  the  bone,  and  lodges 
the  end  of  the  same  sinus,  the  lateral.  In  front  of  the  foramen  magnum  is  the 
basilar  process,  presenting  a  shallow  depression,  the  basilar  groove  (clivus),  which 
slopes  from  behind,  upward  and  forward,  and  supports  the  oblongata  and  part 
of  the  pons  Varolii,  and  on  each  side  of  the  basilar  process  is  a  narrow  channel, 
which,  when  united  with  a  similar  channel  on  the  petrous  portion  of  the  temporal 
bone,  forms  a  groove  (sulcus  petrosus  inferior)  which  lodges  the  inferior  petrosal 
sinus. 

Borders.  Superior  Border. — The  superior  border,  lambdoidal  margin  (margo 
lambda ideus) ,  extends  on  each  side  from  the  superior  to  the  lateral  angle,  is 
deeply  serrated  for  articulation  with  the  parietal  bone,  and  forms,  by  this  union, 
the  lambdoid  suture. 

Inferior  Border. — The  inferior  border  extends  from  the  lateral  to  the  inferior 
angle;  its  upper  half,  mastoid  margin  (margo  mastoideus},  is  rough,  and  articu- 
lates with  the  mastoid  portion  of  the  temporal,  forming  the  masto-occipital  suture ; 
the  inferior  half  articulates  with  the  petrous  portion  of  the  temporal,  forming 
the  petro-occipital  suture;  these  two  portions  are  separated  from  one  another  by 
the  jugular  process.  In  front  of  this  process  is  a  deep  notch,  which,  with  a 
similar  one  on  the  petrous  portion  of  the  temporal,  forms  the  jugular  foramen 
(foramen  lacerum  posterius).  This  notch  is  occasionally  subdivided  into  two 
parts  by  a  small  process  of  bone  (processus  intraj ugularis) ,  and  it  generally 
presents  an  aperture  at  its  upper  part,  the  internal  opening  of  the  posterior 
condyloid  foramen. 

Angles.  Superior  Angle. — The  superior  angle  is  received  into  the  interval 
between  the  posterior  superior  angles  of  the  two  parietal  bones;  it  corresponds 
with  that  part  of  the  skull  in  the  foetus  which  is  called  the  posterior  fontanelle 
(lambda). 

Inferior  Angle. — The  inferior  angle  is  represented  by  the  square-shaped  surface 
of  the  basilar  process.  At  an  early  period  of  life  a  layer  of  cartilage  separates  this 
part  of  the  bone  from  the  sphenoid, 
but  in  the  adult  the  union  between 
them  is  osseous. 

Lateral  Angles. — The  lateral  an-  ___ 

gles  correspond  to  the  outer  ends  of  1^4  for  occipital 

the  transverse  grooves,  and  are  re-  ^      "^HlF    P°rtion- 

ceived  into  the  interval  between  the 
posterior  inferior  angles  of  the  pari- 
etal and  the  mastoid  portion  of  the    the* pieces  j^ffi         ^%\~~1  f°r  each  condyloid  •) 
temporal.     The  junction  of  the  oc-      separate.    ufr\          )l]u  portion. 

cipital,  parietal,  and  temporal  bones  ^^^d&^&^  \  & 

was  named  the  asterion  by  Broca.  \^jj       — i  for  basilar  portion,    j  "? 

Structure. The    Occipital    bone    FIG.  40. — Development  of  occipital  bone.     By  seven  centres. 

consists  of    two    compact    lamina?, 

called  the  outer  and  inner  tables,  having  between  them  the  diploic  tissue;  this  bone 
is  especially  thick  at  the  ridges,  protuberances,  condyles,  and  anterior  part  of  the 
basilar  process;  while  at  the  bottom  of  the  fossa?,  especially  the  inferior,  it  is  thin, 
semitransparent,  and  destitute  of  diploe. 

Development  (Fig.  40). — At  birth  the  bone  consists  of  four  distinct  parts:  a 
tabular  squamous  or  expanded  portion,  which  lies  behind  the  foramen  magnum ;  two 
condylic  parts,  which  form  the  sides  of  the  foramen;  and  a  basilar  part,  which  lies 


76  THE  SKELETON 

in  front  of  the  foramen.  The  number  of  nuclei  for  the  tabular  part  vary.  As 
a  rule,  there  are  four,  but  there  may  be  only  one  (Blandin)  or  as  many  as  eight 
(Meckel).  They  appear  about  the  eighth  week  of  foetal  life,  and  soon  unite  to 
form  a  single  piece,  which  is,  however,  fissured  in  the  direction  indicated  in 
Fig.  40.  The  basilar  and  two  condyloid  portions  are  each  developed  from  a  single 
nucleus,  which  appears  a  little  later.  The  upper  portion  of  the  tabular  surface 
— that  is  to  say,  the  portion  above  the  transverse  fissure— is  developed  from  mem- 
brane, and  may  remain  separated  from  the  rest  of  the  bone  throughout  life,  when 
it  constitutes  the  interparietal  bone,  which  is  called  the  os  incae,  because  of  its  fre- 
quent occurrence  in  Peruvian  skulls.  The  rest  of  the  bone  is  developed  from 
cartilage.  At  about  the  fourth  year  the  tabular  and  the  two  condyloid  pieces 
join,  and  about  the  sixth  year  the  bone  consists  of  a  single  piece.  At  a  later  period, 
between  the  eighteenth  and  twenty-fifth  years,  the  occipital  and  sphenoid  become 
united,  forming  a  single  bone. 

Articulations. — With  six  bones:  two  parietal,  two  temporal, sphenoid, and  atlas. 

Attachment  of  Muscles. — To  twelve  pairs:  to  the  superior  curved  line  are 
attached  the  Occipito-frontalis,  Trapezius,  and  Sterno-cleido-mastoid.  To  the 
space  between  the  curved  lines,  the  Complexus,1  Splenius  capitis,  and  Obliquus 
capitis  superior;  to  the  inferior  curved  line,  and  the  space  between  it  and  the 
foramen  magnum,  the  Rectus  capitis  posticus,  major  and  minor;  to  the  transverse 
process,  the  Rectus  capitis  lateralis;  and  to  the  basilar  process,  the  Rectus  capitis 
anticus,  major  and  minor,  and  Superior  constrictor  of  the  pharynx. 

The  Parietal  Bone  (Os  Parietale). 

The  parietal  bones  (paries,  a  wall)  are  paired  bones  and  form,  by  their  union,  the 
sides  and  roof  of  the  cerebral  cranium.  Each  bone  is  of  an  irregular  quadrilateral 
form,  and  presents  for  examination  two  surfaces,  four  borders,  and  four  angles. 

Surfaces.  External  Surface  (fades  parietalis). — The  external  surface  (Fig.  41) 
is  convex,  smooth,  and  marked  about  its  centre  by  an  eminence  called  the 
parietal  eminence  (tuber  parietale),  which  indicates  the  point  where  ossification 
commenced.  Crossing  the  middle  of  the  bone  in  an  arched  direction  are  two 
well-marked  curved  lines  or  ridges,  the  upper  and  lower  temporal  lines  or  ridges 
(linea  temporalis  superior  et  inferior);  the  former  gives  attachment  to  the  tem- 
poral fascia,  while  the  latter  indicates  the  upper  limit  of  the  origin  of  the 
Temporal  muscle.  These  lines  form  the  temporal  crest.  Above  these  ridges 
the  surface  of  the  bone  is  rough  and  porous,  and  covered  by  the  aponeurosis 
of  the  Occipito-frontalis ;  between  them  the  bone  is  smoother  and  more  polished 
than  the  rest;  below  them  the  bone  forms  part  of  the  temporal  fossa.  This 
portion  of  bone  is  called  the  planum  temporale,  and  affords  attachment  to  the 
Temporal  muscle.  The  superior  stephanion  is  the  intersection  of  the  upper 
temporal  ridge  with  the  coronal  suture.  The  inferior  stephanion  is  the  intersec- 
tion of  the  lower  temporal  ridge  with  the  coronal  suture.  At  the  back  part  of 
the  superior  border,  close  to  the  sagittal  suture,  is  a  small  foramen,  the  parietal 
foramen  (foramen  parietale),  which  transmits  the  emissary  vein  of  Santorini  from 
the  scalp  to  the  superior  longitudinal  sinus.  It  sometimes  also  transmits  a 
small  branch  of  the  occipital  artery.  Its  existence  is  not  constant,  and  its 
size  varies  considerably.  The  point  on  the  sagittal  suture,  between  the  parietal 
foramina,  is  the  obelion. 

Internal  or  Cerebral  Surface  (fades  cerebralis) . — The  internal  surface  (Fig.  42)  is 
concave,  presents  depressions  for  lodging  the  convolutions  of  the  cerebrum  and 
numerous  furrows,  for  the  ramifications  of  the  middle  meningeal  artery;  the 

1  To  these  the  Biventer  cervicis  should  be  added,  if  it  is  regarded  as  a  separate  muscle. — ED.  of  15th  English 
Edition. 


THE  PARIETAL    BONE 

with  opposite  pariet 


77 


Squamous  portion  of 
temporal  bone. 


FIG.  41. — Left  parietal  bone.     External  surface. 


Posterior 

superior 

angle. 


^Anterior 
superior 
angle. 


Posterior 

inferior 

angle. 


FIG.  42. — Left  parietal  bone.     Internal  surface. 


Anterior 

inferior 

angle. 


78  THE  SKELETON 

latter  runs  upward  and  backward  from  the  anterior  inferior  angle  and  from  the 
central  and  posterior  part  of  the  lower  border  of  the  bone.  The  depression  for 
the  middle  meningeal  artery  at  the  anterior  and  inferior  portions  of  the  cerebral 
surface  of  the  bone  is  called  the  sulcus  arteriosus.  Sometimes  a  distinct  canal 
exists  for  the  artery,  but  it  never  remains  a  canal  for  a  long  distance.  Along 
the  upper  margin  of  the  bone  is  part  of  a  shallow  groove,  which,  when  joined 
to  the  opposite  parietal,  forms  a  channel  for  the  superior  longitudinal  sinus  (the 
sulcus  sagittalis).  The  elevated  edges  of  the  groove  afford  attachment  to  the 
falx.  Near  the  groove  are  seen  several  depressions,  Pacchionian  depressions  (foveolae 
granulares  [Pacchioni]}.  They  are  most  frequently  found  in  the  skulls  of  old  per- 
sons, and  lodge  the  arachnoid  villi  (Pacchionian  bodies}.  The  internal  opening  of 
the  parietal  foramen  is  also  seen  when  that  aperture  exists.  On  the  inner  surface 
of  the  posterior  inferior  portion  of  the  bone  is  a  portion  of  the  groove  for  the  lodge- 
ment of  the  lateral  sinus. 

Borders.  Superior  Border. — The  superior  border,  sagittal  margin  (margo  sagit- 
talis), the  longest  and  thickest,  is  dentated  to  articulate  with  its  fellow  of  the 
opposite  side,  forming  the  sagittal  suture. 

Inferior  Border. — The  inferior  border,  squamous  margin  (margo  squamosus),  is 
divided  into  three  parts:  of  these,  the  anterior  is  thin  and  pointed,  bevelled  at 
the  expense  of  the  outer  surface,  and  overlapped  by  the  tip  of  the  great  wing 
of  the  sphenoid;  the  middle  portion  is  arched,  bevelled  at  the  expense  of  the 
outer  surface,  and  overlapped  by  the  squainous  portion  of  the  temporal;  the 
posterior  portion  is  thick  and  serrated  for  articulation  with  the  mastoid  portion 
of  the  temporal. 

Anterior  Border. — The  anterior  border,  frontal  margin  (margo  frontalis),  deeply 
serrated,  is  bevelled  at  the  expense  of  the  outer  surface  above  and  of  the  inner 
below;  it  articulates  with  the  frontal  bone,  forming  the  coronal  suture. 

Posterior  Border. — The  posterior  border,  occipital  margin  (margo  occipitalis), 
deeply  denticulated,  articulates  with  the  occipital,  forming  the  lambdoid  suture. 

Angles.  Anterior  Superior  Angle  (angulus  frontalis). — The  anterior  superior 
or  frontal  angle,  thin  and  pointed,  corresponds  with  that  portion  of  the  skull 
which  in  the  foetus  is  membranous,  and  is  called  the  anterior  fontanelle  (bregma). 

Anterior  Inferior  Angle  (angulus  sphenoidalis) . — The  anterior  inferior  or 
sphenoidal  angle  is  thin  and  lengthened,  being  received  in  the  interval  between 
the  great  wing  of  the  sphenoid  and  the  frontal.  Its  inner  surface  is  marked  by  a 
deep  groove,  sometimes  a  canal,  for  the  anterior  branch  of  the  middle  meningeal 
artery.  At  the  anterior  inferior  angle  the  parietal,  temporal,  and  frontal  bones 
and  the  greater  wing  of  the  sphenoid  bone  meet.  This  spot  is  called  the 
pterion. 

Posterior  Superior  Angle  (angulus  occipitalis) . — The  posterior  superior  or  occip- 
ital angle  corresponds  with  the  junction  of  the  sagittal  and  lambdoid  sutures.  In 
the  foetus  this  part  of  the  skull  is  membranous,  and  is  called  the  posterior  fonta- 
nelle (lambda). 

Posterior  Inferior  Angle  (angulus  mastoideus. — The  posterior  inferior  or  mas- 
toid angle  articulates  with  the  mastoid  portion  of  the  temporal  bone,  and 
generally  presents  on  its  inner  surface  a  broad,  shallow  groove  for  lodging  part 
of  the  lateral  sinus. 

Development. — The  parietal  bone  is  formed  in  membrane,  being  developed 
by  one  centre,  which  corresponds  with  the  parietal  eminence,  and  makes  its  first 
appearance  about  the  seventh  or  eighth  week  of  foetal  life.  Ossification  gradually 
extends  from  the  centre  to  the  circumference  of  the  bone:  the  angles  are  conse- 
quently the  parts  last  formed,  and  it  is  in  their  situation  that  the  fontanelles  exist 
previous  to  the  completion  of  the  growth  of  the  bone.  Occasionally  the  parietal 
bone  is  divided  into  two  parts,  upper  and  lower,  by  an  antero-posterior  suture. 


THE    FRONTAL    BONE 


79 


Articulations. — With  five  bones:  the  opposite  parietal,  the  occipital,  frontal, 
temporal,  and  sphenoid. 
Attachment  of  Muscles. — One  only,  the  Temporal. 

The  Frontal  Bone  (Os  Frontale). 

The  frontal  bone  (frons,  the  forehead)  resembles  a  cockle-shell  in  form,  and 
consists  of  two  portions — a  vertical  or  frontal  portion,  situated  at  the  anterior 
part  of  the  cranium,  forming  the  forehead;  and  a  horizontal  or  orbital  portion, 
which  enters  into  the  formation  of  the  roof  of  the  orbits  and  nasal  fossae. 

Vertical  Portion  of  the  Frontal  Bone  (Pars  Frontalis). 

Surfaces.  External  Surface  (fades  Jrontalis]  (Fig.  43). — In  the  median  line, 
traversing  the  bone  from  the  upper  to  the  lower  part,  is  occasionally  seen  a 
slightly  elevated  ridge,  and  in  young  subjects  a  suture,  the  frontal  (metopic) 
suture,  which  represents  the  line  of  union  of  the  two  lateral  halves  of  which  the 


-  ,  External 

angular  process.        angvlar  proceS8. 

Nasal  I  spine. 
FIG.  43. — Frontal  bone.     Outer  surface. 

bone  consists  at  an  early  period  of  life;  in  the  adult  this  suture  is  usually  oblit- 
erated and  the  bone  forms  one  piece;  traces  of  the  obliterated  suture  are,  how- 
ever, generally  perceptible  at  the  lower  part.  On  either  side  of  this  ridge,  a  little 
below  the  centre  of  the  bone,  is  a  rounded  eminence,  the  frontal  eminence  (tuber 
frontale).  These  eminences  vary  in  size  in  different  individuals,  and  are  occa- 
sionally unsymmetrical  in  the  same  subject.  They  are  especially  prominent  in 
cases  of  well-marked  cerebral  development.  The  whole  surface  of  the  bone 
above  this  part  is  smooth,  and  covered  by  the  aponeurosis  of  the  Occipito- 
frontalis  muscle.  Below  the  frontal  eminence  and  separated  from  it  by  a  slight 


80  THE   SKELETON 

groove  is  the  superciliary  ridge  (arcus  superciliaris} ,  broad  internally,  where  it 
is  continuous  with  the  nasal  eminence,  but  less  distinct  as  it  arches  outward. 
These  ridges  are  caused  by  the  projection  outward  of  the  frontal  air  sinuses,1 
and  give  attachment  to  the  Orbicularis  palpebrarum  and  Corrugator  supercilii. 
Between  the  two  superciliary  ridges  is  a  smooth,  flat  surface,  the  glabella. 
Nearly  corresponding  with  the  glabella  is  the  ophryon,  a  point  in  the  mid-line 
on  a  level  with  the  upper  border  of  the  eyebrows,  which  is  the  centre  of  the 
narrowest  transverse  diameter  of  the  forehead.  Beneath  the  superciliary  ridge 
is  the  orbital  margin  or  supraorbital  arch  (mar go  supraorbitalis),  a  curved  and 
prominent  margin,  which  forms  the  upper  boundary  of  the  orbit  and  separates 
the  vertical  from  the  horizontal  portion  of  the  bone.  The  outer  part  of  the 
arch  is  sharp  and  prominent,  affording  to  the  eye,  in  that  situation,  considerable 
protection  from  injury;  the  inner  part  is  less  prominent.  At  the  junction  of  the 
internal  and  middle  third  of  this  arch  is  a  notch,  sometimes  converted  into  a 
foramen,  and  called  the  supraorbital  notch  or  foramen  (incisura  supraorbitalis  or 
foramen  supraorbitale) .  It  transmits  the  supraorbital  artery,  vein,  and  nerve.  A 
small  aperture  is  seen  in  the  upper  part  of  the  notch,  which  transmits  a  vein 
from  the  diploe  to  join  the  supraorbital  vein.  To  the  median  side  of  the 
supraorbital  notch  there  is  often  a  notch  (incisura  frontalis)  for  the  passage 
of  the  frontal  artery  and  frontal  nerve.  The  supraorbital  arch  terminates 
externally  in  the  external  angular  process  (processus  zygomaticus)  and  internally 
in  the  internal  angular  process.  The  external  angular  process  is  strong,  prominent, 
and  articulates  with  the  malar  bone;  running  upward  and  backward  from  it  are 
two  well-marked  lines,  which,  commencing  together  from  the  external  angular 
process  as  the  temporal  ridge,  crest  or  line  (linea  temporalis),  soon  diverge  from 
each  other  and  run  in  a  curved  direction  across  the  bone.  These  are  the 
upper  and  lower  temporal  ridges;  the  upper  gives  attachment  to  the  temporal 
fascia,  the  lower  to  the  Temporal  muscle.  Beneath  them  is  a  slight  concavity 
that  forms  the  anterior  part  of  the  temporal  fossa  and  gives  origin  to  the 
Temporal  muscle.  The  internal  angular  processes  are  less  marked  than  the 
external,  and  articulate  with  the  lachrymal  bones.  Between  the  internal  angular 
processes  is  a  rough,  uneven  interval,  the  nasal  notch,  which  articulates  in  the 
middle  line  with  the  nasal  bone,  and  on  either  side  with  the  nasal  process  of  the 
superior  maxillary  bone.  From  the  concavity  of  this  notch  projects  a  process, 
the  nasal  process,  which  extends  beneath  the  nasal  bones  and  nasal  processes  of 
the  superior  maxillary  bones  and  supports  the  bridge  of  the  nose.  On  the  under 
surface  of  this  is  a  long,  pointed  process,  the  nasal  or  frontal  spine  (spina  nasalis 
or  frontalis),  and  on  either  side  a  small  grooved  surface  enters  into  the  formation 
of  the  roof  of  the  nasal  fossa.  The  nasal  spine  forms  part  of  the  septum  of  the 
nose,  articulating  in  front  with  the  nasal  bones  and  behind  with  the  perpen- 
dicular plate  of  the  ethmoid.  The  junction  of  the  nasal  and  frontal  bones  is 
called  the  nasion. 

Internal  Surface  (cerebral  surface,  fades  cerebralis)  (Fig.  44). — Along  the  middle 
line  is  a  vertical  groove,  the  sulcus  sagittalis,  the  edges  of  which  unite  below  to 
form  a  ridge,  the  frontal  crest  (crista  frontalis) ;  the  groove  lodges  the  superior 
longitudinal  sinus,  whilst  its  margins  afford  attachment  to  the  falx.  The  crest 
terminates  below  at  a  small  notch  which  is  converted  into  a  foramen  by  artic- 
ulation with  the  ethmoid.  It  is  called  the  foramen  caecum,  and  varies  in  size  in 
different  subjects:  it  is  sometimes  partially  or  completely  impervious,  lodges  a 

1  Some  confusion  is  occasioned  to  students  commencing  the  study  of  anatomy  by  the  name  "sinuses"  having 
been  given  to  two  perfectly  different  kinds  of  spaces  connected  with  the  skull.  It  may  be  as  well,  therefore,  to 
state  here  at  the  outset,  that  the  "sinuses"  in  the  interior  of  the  cranium  which  produce  the  grooves  on  the 
inner  surface  of  the  bones  are  venous  channels  along  which  the  blood  runs  in  its  passage  back  from  the  brain, 
while  the  "sinuses"  external  to  the  cranial  cavity  (the  frontal  sphenoidal,  ethmoidal,  and  maxillary)  are  hollow 
spaces  in  the  bones  themselves  which  communicate  with  the  nostrils,  and  contain  air. — ED.  of  15th  English 
Edition. 


THE  FRONTAL   BONE 


81 


process  of  the  falx,  and  when  open  transmits  a  vein  from  the  lining  membrane  of 
the  nose  to  the  superior  longitudinal  sinus.  On  either  side  of  the  groove  the  bone 
is  deeply  concave,  presenting  depressions  for  the  convolutions  of  the  brain,  and 
numerous  small  furrows  for  lodging  the  ramifications  of  the  anterior  branches 
of  the  middle  meningeal  arteries.  Several  small  irregular  fossae  are  seen  also  on 
either  side  of  the  groove,  for  the  reception  of  the  arachnoid  villi. 


With  superior  maxillary. 

With  nasal'. 


Frontal  sinus. 


\Under  surface  of  nasal  process, 

With  perpendicular  plate  of  ethmoid.   '       forming  part  of  roof  of  nose. 
Fio.  44. — Frontal  bone.     Inner  surface. 

Border. — The  border  of  the  vertical  portion  is  thick,  strongly  serrated,  bevelled 
at  the  expense  of  the  internal  table  above,  where  it  rests  upon  the  parietal  bones, 
and  at  the  expense  of  the  external  table  at  each  side,  where  it  receives  the  lateral 
pressure  of  those  bones;  this  border  is  continued  below  into  a  triangular  rough 
surface  which  articulates  with  the  great  wing  of  the  sphenoid. 

Structure. — The  vertical  portion  and  external  angular  processes  are  very  thick, 
consisting  of  diploic  tissue  contained  between  two  compact  laminae. 

Horizontal  or  Orbital  Portion  of  the  Frontal  Bone  (Pars  Orbitalis). 

This  portion  of  the  bone  consists  of  two  thin  plates,  the  orbital  plates,  which 
form  the  vault  of  the  orbit,  separated  from  one  another  by  a  median  gap,  the 
ethmoidal  notch. 

Surfaces.  External  Surface. — The  inferior  or  external  surface  of  each  orbital 
plate  (fades  orbitalis)  consists  of  a  smooth,  concave,  triangular  lamina  of  bone, 
marked  at  its  anterior  and  external  part  (immediately  beneath  the  external 
angular  process)  by  a  shallow  depression,  the  lachrymal  fossa  (fossa  glandidae 
lacrimalis)  for  lodging  the  lachrymal  gland;  and  at  its  anterior  and  internal  part 

6 


82 


THE  SKELETON 


by  a  depression  (sometimes  a  small  tubercle),  the  trochlear  fossa  (fovea  trochlearis), 
for  the  attachment  of  the  cartilaginous  pulley  of  the  Superior  oblique  muscle  of 
the  eye.  The  ethmoidal  notch  (incisura  ethmoidalis)  separates  the  two  orbital 
plates;  it  is  quadrilateral,  and  filled  up,  when  the  bones  are  united,  by  the  cribri- 
form plate  of  the  ethmoid.  The  margins  of  this  notch  present  several  half-cells, 
which,  when  united  with  corresponding  half-cells  on  the  upper  surface  of  the  eth- 
moid, complete  the  ethmoidal  cells;  two  grooves  are  also  seen  crossing  these  edges 
transversely;  they  are  converted  into  canals  by  articulation  with  the  ethmoid,  and 
are  called  the  anterior  and  posterior  ethmoidal  foramina  or  canals  (foramen  ethmoi- 
dale  anterius  and  foramen  ethmoidale  postering) :  they  open  on  the  inner  wall  of  the 
orbit.  The  anterior  one  transmits  the  nasal  nerve  and  anterior  ethmoidal  vessels, 
the  posterior  one  the  posterior  ethmoidal  vessels.  In  front  of  the  ethmoidal 
notch,  on  each  side  of  the  nasal  spine,  is  the  opening  of  the  frontal  air  sinus  (sinus 
frontalis).  These  are  two  irregular  cavities,  which  extend  upward  and  outward,  a 
variable  distance,  between  the  two  tables  of  the  skull,  and  are  separated  from  one 
another  by  a  thin,  bony  septum  (septum  sinuum  frontalium),  which  is  often  dis- 
placed to  one  side.  Within  the  sinuses  imperfect  trabeculae  of  bone  often  exist.  The 
sinuses  are  beneath  and  give  rise  to  the  prominences  above  the  supraorbital  arches 
called  the  superciliary  ridges  (arcus  superciliares) .  The  frontal  air  sinuses  are  absent 
at  birth,  become  apparent  about  the  seventh  year  of  life,  and  from  this  period  until 
the  age  of  twenty  increase  gradually  in  size.  Sometimes,  however,  the  sinuses 
remain  very  small  or  never  develop  at  all — or  one  side  may  be  large  and  the  other 
small — or  one  may  exist  on  one  side  and  be  absent  on  the  other.1  The  right  sinus 
is  usually  the  larger.  These  cavities  are  larger  in  men  than  in  women.  The  floor 
of  each  sinus  is  very  thin  and  is  over  the  orbit  and  the  upper  border  of  the  lateral 
mass  of  the  ethmoid.  The  thinnest  portion  of  the  floor  is  at  the  upper  and 
inner  angle  of  the  orbit,  and  at  this  point  pus  is  apt  to  point  in  cases  of 
empyema  of  the  sinus.  The  frontal  sinuses  are  lined  by  mucous  membrane 
and  each  sinus  communicates  with  the  middle  meatus  of  the  nose  by  the  infun- 
dibulum  and  part  of  the  semilunar  hiatus.  In  some  cases  the  sinuses  commu- 
nicate with  each  other  by  means  of  an  aperture  in  the  septum  and  occasionally 
join  the  sinus  in  the  crista  galli  of  the  ethmoid.2 

Internal  Surface  (cerebral  surface,  fades  cerebralis). — The  internal  surface  of 
the  horizontal  portion  presents  the  convex  upper  surfaces  of  the  orbital   plates, 

separated  from  each  other  in  the  mid- 
dle line  by  the  ethmoidal  notch,  and 
marked  by  eminences  and  depressions  for 
the  convolutions  of  the  frontal  lobes  of 
the  brain. 

Border. — The  border  of  the  horizontal 
portion  is  thin,  serrated,  and  articulates 
with  the  lesser  wing  of  the  sphenoid. 

Structure. — The  horizontal  portion  is 
thin,  translucent,  and  composed  entirely 
of  compact  tissue;  hence  the  facility  with 
which  instruments  can  penetrate  the 
cranium  through  this  part  of  the  orbit. 

Development  (Fig.  45). — The  frontal 
bone  is  formed  in  membrane,  being 

developed  by  two  centres,  one  for  each  lateral  half,  which  make  their  appearance 
about  the  seventh  or  eighth  week,  above  the  orbital  arches.  From  this  point 
ossification  extends,  in  a  radiating  manner,  upward  into  the  forehead  and  back- 


FIG.  45. — Frontal  bone  at  birth, 
two  lateral  halves. 


Developed  by 


1  Dr.  D.  Kerfoot  Shute.     Article  on  the  Skull,  in  Reference  Handbook  of  the  Medical  Sciences. 


2  Ibid. 


THE  TEMPORAL  BONE 


83 


ward  over  the  orbit.  At  birth  the  bone  consists  of  two  pieces,  which  afterward 
become  united,  along  the  middle  line,  by  a  suture  which  runs  from  the  vertex 
to  the  root  of  the  nose.  This  suture  usually  becomes  obliterated  within  a  few 
years  after  birth;  but  it  occasionally  remains  throughout  life,  constituting  the 
metopic  suture.  Secondary  centres  of  ossification  appear  for  the  nasal  spine — 
one  on  either  side  of  the  internal  angular  process  where  it  articulates  with  the 
lachrymal  bone;  and  sometimes  there  is  one  on  either  side  at  the  lower  end  of 
the  coronal  suture.  This  latter  centre  sometimes  remains  ununited,  and  is 
known  as  the  pterion  ossicle,  or  it  may  join  with  the  parietal,  sphenoid,  or  tem- 
poral bone. 

Articulations. — With  twelve  bones:  two  parietal,  the  sphenoid,  the  ethmoid, 
two  nasal,  two  superior  maxillary,  two  lachrymal,  and  two  malar. 

Attachment  of  Muscles. — To  three  pairs:  the  Corrugator  supercilii,  Orbicu- 
laris  palpebrarum,  and  Temporal,  on  each  side. 

The  Temporal  Bone  (Os  Temporale). 

The  temporal  bones  (tempus,  time)  are  paired  bones,  situated  at  the  sides  and 
base  of  the  skull.  Each  presents  for  examination  a  squamous,  mastoid,  and  petrous 
portion. 

Squamous  Portion  of  the  Temporal  Bone  (Squama  Temporalis) . 

The  squamous  portion  (squama,  a  scale),  the  anterior  and  upper  part  of  the 
'  bone,  is  scale-like  in  form,  and  thin  and  translucent  in  texture  (Fig.  46). 


MOUS 
If      TE 


SQUAMOUS SUTURE 

TEMPORAL  FASCIA 


SULCUS    FOR   MIDDLE 
TEMPORAL  ARTERY 


REMAINS  OF 

SQUAMOSO- 

MASTOID 

SUTURE 

MASTOID 

FOSSA 

SUPRA- 

MEATAL 

SPINE 


APEX  OF  PETROUS 
PORTION 


MASTOID 
FORAMEN      f 

MASTOID 
PORTION 


PETROTYMPANIC  OH 
GLASERIAN    FISSURE 

VAGINAL  PORTION 

OF  STYLOID 


EXTERNAL  AUDITORY  MEATUS      TYMPANIC  PORTION 

FIG.  46. — Right  temporal  bone,  from  without.     (Spaltekolz.) 

Surfaces.  Outer  Surface  (fades  temporalis) . — Its  outer  surface  is  smooth,  convex, 
and  grooved  at  its  back  part  for  the  middle  or  deep  temporal  artery  (sulcus  a. 
temporalis  mediae);  it  affords  attachment  to  a  portion  of  the  Temporal  muscle  and 
forms  part  of  the  temporal  fossa.  At  its  back  part  may  be  seen  a  curved  ridge — 
part  of  the  temporal  ridge  or  line;  it  serves  for  the  attachment  of  the  temporal 


84  THE  SKELETON 

fascia  and  limits  the  origin  of  the  Temporal  muscle.  The  boundary  between  the 
squamous  and  mastoid  portions  of  the  bone,  as  indicated  by  traces  of  the  original 
suture,  lies  fully  half  an  inch  below  this  ridge.  Projecting  from  the  lower  part  of 
the  squamous  portion  is  a  long,  arched  process  of  bone,  the  zygoma  or  zygomatic 
process  (processus  zygomaticus) .  This  process  is  at  first  directed  outward,  its 
two  surfaces  looking  upward  and  downward;  it  then  appears  as  if  twisted 
upon  itself,  and  runs  forward,  its  surfaces  now  looking  inward  and  outward. 
The  superior  border  of  the  process  is  long,  thin,  and  sharp,  and  serves  for  the 
attachment  of  the  temporal  fascia.  The  inferior,  short,  thick,  and  arched,  has 
attached  to  it  some  fibres  of  the  Masseter  muscle.  Its  outer  surface  is  convex 
and  subcutaneous;  its  inner  is  concave,  and  also  affords  attachment  to  the 
Masseter.  The  extremity,  broad  and  deeply  serrated,  articulates  with  the  malar 
bone.  The  zygomatic  process  is  connected  to  the  temporal  bone  by  three  divi- 
sions, called  its  roots — an  anterior,  middle,  and  posterior.  The  anterior,  wrhich 
is  short,  but  broad  and  strong,  is  directed  inward,  to  terminate  in  a  rounded 
eminence,  the  eminentia  articularis  or  articular  eminence  (tuberculum  articulare) 
(Fig.  46).  This  eminence  forms  the  front  boundary  of  the  glenoid  or  mandibular 
fossa  (fossa  mandibular  is),  and  in  the  recent  state  is  covered  with  cartilage. 
The  middle  root  is  known  as  the  post-glenoid  process  or  tubercle,  and  is  very 
prominent  in  young  bones.  It  separates  the  mandibular  portion  of  the  glenoid 
fossa  from  the  external  auditory  meatus,  and  terminates  at  the  commencement 
of  a  well-marked  fissure,  the  Glaserian  (petro-tympanic)  fissure  (fissura  petro- 
tympanica  [Glaseri]).  The  posterior  root,  which  is  strongly  marked,  runs  from 
the  upper  border  of  the  zygoma  backward  over  the  external  auditory  meatus. 
It  is  termed  the  supramastoid  or  temporal  crest,  and  forms  part  of  the  lower 
temporal  ridge.  At  the  junction  of  the  anterior  root  with  the  zygoma  is  a 
projection,  called  the  tubercle,  for  the  attachment  of  the  external  lateral  liga- 
ment of  the  lower  jaw;  and  between  the  anterior  and  middle  roots  is  an  oval 
depression,  forming  part  of  the  glenoid  (mandibular)  fossa  (fAyvy,  a  socket),  for 
the  reception  of  the  condyle  of  the  lower  jaw.  This  fossa  is  bounded,  in  front, 
by  the  eminentia  articularis;  behind,  by  the  tympanic  plate,  which  separates  it 
from  the  external  auditory  meatus;  it  is  divided  into  two  parts  by  a  narrow  slit, 
the  Glaserian  or  petro-tympanic  fissure.  The  anterior  or  mandibular  part,  formed 
by  the  squamous  portion  of  the  bone,  is  smooth,  covered  in  the  recent  state  with 
cartilage,  and  articulates  with  the  condyle  of  the  lower  jaw.  This  part  of  the 
glenoid  fossa  presents  posteriorly  a  small  conical  eminence,  the  post-glenoid 
process,  already  referred  to.  This  process  is  the  representative  of  a  prominent 
tubercle  which,  in  some  of  the  mammalia,  descends  behind  the  condyle  of  the 
jaw,  and  prevents  it  being  displaced  backward  during  mastication  (Humphry). 
The  posterior  part  of  the  glenoid  fossa,  which  lodges  a  portion  of  the  parotid 
gland,  is  formed  chiefly  by  the  tympanic  plate,  which  constitutes  the  anterior 
wall  of  the  tympanum  and  external  auditory  meatus.  The  plate  of  bone  termi- 
nates above  in  the  Glaserian  fissure,  and  below  forms  a  sharp  edge,  the  vaginal 
process  of  the  styloid  (vagina  processus  styloidei),  which  gives  origin  to  some  of 
the  fibres  of  the  Tensor  palati  muscle.  The  Glaserian  fissure,  which  leads  into 
the  tympanum,  lodges  the  processus  gracilis  of  the  malleus,  and  transmits  the 
tympanic  branch  of  the  internal  maxillary  artery.  The  chorda  tympani  nerve 
passes  through  a  separate  canal,  parallel  to  the  Glaserian  fissure,  the  canal  of 
Huguier  (canaliculus  chordcp  tympani),  on  the  outer  side  of  the  Eustachian 
tube,  in  the  retiring  angle  between  the  squamous  and  petrous  portions  of  the 
temporal  bone.1  Between  the  posterior  bony  wall  of  the  external  auditory  meatus 

1  This  small  fissure  must  not  be  confounded  with  the  large  canal  which  lies  above  the  Eustachian  tube  and 
transmits  the  Tensor  tympani  muscle. 


THE    TEMPORAL    BONE 


85 


and  the  posterior  root  of  the  zygoma  is  the  area  called  the  suprameatal  triangle  of 
Prof.  Macewen.  Through  this  space  the  surgeon  pushes  the  gouge  in  order  to 
carry  it  into  the  antrum  of  the  mastoid  process. 

Internal  Surface  (cerebral  surface,  fades  cerebralis}. — The  internal  surface  of 
the  squamous  portion  (Fig.  47)  is  concave,  presents  numerous  eminences  and 
depressions  for  the  convolutions  of  the  cerebrum,  and  two  well-marked  grooves 
for  the  branches  of  the  middle  meningeal  artery. 


parietal 


Aquseductus  vestibuli. 

Depression  for  dura. 

Meatus  auditorius  internus. 


Eminence  for  superior  semicircular  canal. 
Hiatus  Fallopii. 

Opening  for.  smaller  petrosal  nerve. 

Depression  for  Gasserian  Ganglion. 

— Bristle  passed  through  carotid  canal. 


FIG.  47. — Left  temporal  bone.     Inner  surface. 

Borders.  Superior  Border. — The  superior  border,  parietal  margin  (margo 
parietalis),  is  thin,  bevelled  at  the  expense  of  the  internal  surface,  so  as  to 
overlap  the  lower  border  of  the  parietal  bone,  forming  the  squamous  suture. 

Anterior  Inferior  Border. — The  anterior  inferior  border,  sphenoidal  margin  (margo 
sphenoidalis),  is  thick,  serrated,  and  bevelled,  alternately  at  the  expense  of  the 
inner  and  outer  surfaces,  for  articulation  with  the  great  wing  of  the  sphenoid. 

Posterior  Inferior  Border. — The  posterior  inferior  border,  occipital  margin 
(margo  occipitalis),  is  serrated  and  articulates  with  the  occipital  bone. 

The  Mastoid  Portion  of  the  Temporal  Bone  (Pars  Mastoidea). 

The  mastoid  portion  (/jtaaroz,  a  nipple  or  teat)  is  situated  at  the  posterior  part 
of  the  bone  (Figs.  46,  48,  and  49). 

Surfaces.  Outer  Surface. — The  outer  surface  of  the  mastoid  is  rough,  and 
gives  attachment  to  the  Occipito-frontalis  and  Retrahens  aurem  muscles.  It 
is  perforated  by  numerous  foramina;  one  of  these,  of  large  size,  situated  at  the 
posterior  border  of  the  bone,  is  termed  the  mastoid  foramen  (foramen  mastoideum} ; 
it  transmits  a  vein  to  the  lateral  sinus  and  a  small  artery  from  the  occipital  to 
supply  the  dura.  The  position  and  size  of  this  foramen  are  very  variable.  It 
is  not  always  present;  sometimes  it  is  situated  in  the  occipital  bone  or  in  the 
suture  between  the  temporal  and  the  occipital.  The  mastoid  portion  is  con- 


86 


THE   SKELETON 


tinned  below  into  a  conical  projection,  the  mastoid  process  (processus  mastoideus) , 
the  size  and  form  of  which  vary  somewhat.  The  mastoid  process  begins  to 
develop  during  the  second  year  and  does  not  attain  full  size  until  after  puberty. 
This  process  serves  for  the  attachment  of  the  Sterno-mastoid,  Splenius  capitis, 
and  Trachelo-mastoid  muscles.  On  the  inner  side  of  the  mastoid  process  is  a 
deep  groove,  the  digastric  fossa  (incisura  mastoidea),  for  the  attachment  of  the 
Digastric  muscle;  and,  running  parallel  with  it,  but  more  internal,  the  occipital 
groove  (sulcus  a.  occipitalis) ,  which  lodges  the  occipital  artery.  The  suprameatai 
triangle  of  Prof.  Macewen  is  bounded  by  the  posterior  root  of  the  zygoma,  the 
posterior  bony  wall  of  the  external  auditory  meatus,  and  an  imaginary  line  join- 
ing these  two.  Through  this  triangle  the  surgeon  enters  his  instrument  in  order 
to  reach  the  mastoid  antrum.  Behind  the  suprameatai  spine  is  a  depression 
known  as  the  mastoid  fossa  (fossa  mastoidea),  which  contains  numerous  small 
openings  for  bloodvessels. 


Tensor  tympani. 
•Proc.  cochleariformis. 
'Eustachian  tube. 

'Carotid  canal. 


Carotid  cana 
Fenestra  rotunda. 

Pyramid. 

FIG.  48. ^-Section  through  the 


•Styloid  process. 

Aqueductus  Fallopii. 
'Marrow  cells. 


,tion 


the  petrous  and  mastoid  portions  of  the  temporal  bone,  showing  the  communicati 
of  the  cavity  of  the  tympanum  with  the  mastoid  antrum. 


Internal  Surface. — The  internal  surface  of  the  mastoid  portion  presents  a  deep, 
curved  groove,  the  sigmoid  fossa  or  sulcus  (sulcus  sigmoideus),  which  lodges  part 
of  the  lateral  sinus;  and  into  it  may  be  seen  opening  the  mastoid  foramen, 
which  transmits  an  emissary  vein  from  the  lateral  sinus  to  the  posterior  auricular 
or  occipital  vein  and  a  small  artery,  the  mastoid  branch  of  the  occipital  artery 
(ramus  mastoideus).  The  groove  for  the  lateral  sinus  is  separated  from  the  inner- 
most of  the  mastoid  air-cells  by  only  a  thin  lamina  of  bone,  and  even  this  may  be 
partly  deficient.  A  section  of  the  mastoid  process  (Figs.  48  and  49)  shows  it  to  be 
hollowed  out  into  a  number  of  cellular  spaces,  communicating  with  each  other, 
called  the  mastoid  cells  (cellulae  mastoideae),  which  exhibit  the  greatest  possible 
variety  as  to  their  size  and  number,  and  which  do  not  exist  at  birth,  but  develop 
with  the  growth  of  the  mastoid  process.  At  the  upper  and  front  part  of  the 
bone  these  cells  are  large  and  irregular,  and  contain  air.  They  diminish  in  size 
toward  the  lower  part  of  the  bone,  those  situated  at  the  apex  of  the  mastoid 
process  being  quite  small  and  usually  containing  marrow.  These  pneumatic 
cells  extend  far  beyond  the  mastoid.  Some  may  reach  the  floor  of  the  Eustachian 


THE    TEMPORAL    BONE 


87 


canal;  others  the  jugular  portion  of  the  occipital  bone;  others  the  roof  of  the 
external  auditory  canal,  and  some  pass  up  toward  the  squamous  portion.1  Occa- 
sionally they  are  entirely  absent,  and  the  mastoid  is  solid  throughout.  In  addi- 
tion to  these  pneumatic  cells  may  be  seen  a  large,  irregular  cavity  (Figs.  48  and 
49),  situated  at  the  upper  and  front  part  of  the  section.  It  is  called  the  mastoid  or 
tympanic  antrum  (antrum  tympanicum) ,  and  must  be  distinguished  from  the  mas- 
toid cells,  though  it  communicates  with  them.  The  mastoid  cells  are  not  developed 
until  after  puberty,  but  the  mastoid  antrum  is  almost  as  large  at  birth  as  it  is  in 
the  adult. 

It  is  filled  with  air,  and  is  lined  with  a  prolongation  of  the  mucous  membrane 
of  the  tympanum,  which  extends  into  it  through  an  opening,  by  which  it  com- 
municates with  the  cavity  of  the  tympanum.  The  mastoid  antrum  is  bounded 
above  by  a  thin  plate  of  bone,  the  tegmen  tympani,  which  separates  it  from  the 
middle  fossa  of  the  base  of  the  skull  on  the  anterior  surface  of  the  petrous  portion 


PROMINENCE  OVER 
SEMICIRCULAR   CANAL 


FENESTRA  OVALIS 
OR  VESTIBULI 


PROCESSUS 
COCHLEARIFORMIS 


SEPTUM    OF 
EUSTACHIAN  TUBE 


PROBE  IN 
TYMPANIC 
CANAL 


SEMI  CANAL  FOR 
TENSOR  TYMPANI 


PROBE    IN 
TYMPANIC  CANAL 


FIG.  49. — Right  temporal  bone  cut  open.     Lateral  view  of  medial  half  of  bone.     X  2.     (Spalteholz.) 


of  the  temporal  bone ;  below  by  the  mastoid  process ;  externally  by  the  squamous 
portion  of  the  bone  just  below  the  supramastoid  crest;  and  internally  by  the 
external  semicircular  canal  of  the  internal  ear,  which  projects  into  its  cavity. 
The  opening  by  which  it  communicates  with  the  tympanum  is  situated  at  the 
superior  internal  angle  of  the  posterior  wall  of  that  cavity;  it  is  a  triangular 
ope.iing  into  that  portion  of  the  tympanic  cavity  which  is  known  as  the  tu  mptnic 
attic  or  epitympanic  recess  or  space  (aditus  ad  antrum) — that  is  to  say,  that 
portion  of  the  tympanum  which  is  above  the  level  of  the  membrana  tympani. 

In  consequence  of  the  communication  which  exists  between  the  tympanum  and  mastoid  cells, 
inflammation  of  the  lining  membrane  of  the  former  cavity  may  easily  travel  backward  to  that 
of  the  antrum,  leading  to  caries  and  necrosis  of  their  walls  and  the  risk  of  transference  of  the 
inflammation  to  the  lateral  sinus  or  encephalon. 


1  Dr.  D.  Kerfoot  Shute,  in  Reference  Handbook  of  the  Medical  Science's. 


88  THE   SKELETON 

Borders.  Superior  Border.  —  The  superior  border  of  the  mastoid  portion  is 
broad  and  rough,  its  serrated  edge  sloping  outward,  for  articulation  with  the 
posterior  inferior  angle  of  the  parietal  bone. 

Posterior  Border.  —  The  posterior  border,  also,  uneven  and  serrated,  articu- 
lates with  the  inferior  border  of  the  occipital  bone  between  its  lateral  angle  and 
jugular  process. 

The  Petrous  Portion  of  the  Temporal  Bone  (Pars  Petrosa  [Pyramis])  (Fig.  47). 


The  petrous  portion  (nerpoz,  a  stone),  so  named  from  its  extreme  density  and 
hardness,  is  a  pyramidal  process  of  bone  wedged  in  at  the  base  of  the  skull 
between  the  sphenoid  and  occipital  bones.  Its  direction  from  without  is  inward, 
forward,  and  a  little  downward.  It  presents  for  examination  a  base,  an  apex, 
three  surfaces,  and  three  borders,  and  contains,  in  its  interior,  the  essential  parts 
of  the  organ  of  hearing. 

Base.  —  The  base  is  applied  against  the  internal  surface  of  the  squamous  and 
mastoid  portions,  its  upper  half  being  concealed;  but  its  lower  half  is  exposed 
by  the  divergence  of  those  two  portions  of  the  bone,  which  brings  into  view  the 
oval,  expanded  orifice  of  a  canal  leading  'into  the  tympanum,  the  meatus  audi- 
torius  externus  (meatus  acusticus  externus).  The  curved  tympanic  plate  or  part 
(pars  tympanica)  forms  the  anterior  wall,  the  floor,  and  a  part  of  the  posterior 
wall  of  this  meatus,  while  the  squamous  portion  of  the  temporal  completes  it 
above  and  behind.  The  entrance  to  the  meatus  is  bounded  throughout  the 
greater  part  of  its  circumference  by  the  auditory  process,  which  is  the  name 
applied  to  the  free  rough  margin  of  the  tympanic  plate,  and  which  gives  attach- 
ment to  the  cartilaginous  portion  of  the  meatus.  Superiorly  the  entrance  to 
the  meatus  is  limited  by  the  posterior  root  of  the  zygoma.  At  the  upper  and 
posterior  portion  of  the  bony  meatus  is  a  spine  of  bone  known  as  the  suprameatal 
spine  or  spine  of  Henle  (spina  suprameatum)  ,  which  is  a  valuable  surgical  land- 
mark. In  most  skulls  it  is  distinctly  marked. 

Apex  (apex  pyramidis).  —  The  apex  of  the  petrous  portion,  rough  and  uneven, 
is  received  into  the  angular  interval  between  the  posterior  border  of  the  greater 
wing  of  the  sphenoid  and  the  basilar  process  of  the  occipital;  it  presents  the  anterior 
or  internal  orifice  of  the  carotid  canal  (foramen  caroticum  internum),  and  forms 
the  posterior  and  external  boundary  of  the  foramen  lacerum  medium. 

Surfaces.  Anterior  Surface  (fades  anterior  pyramidis).  —  The  anterior  surface 
of  the  petrous  portion  (Fig.  47)  forms  the  posterior  part  of  the  middle  fossa  of 
the  skull.  This  surface  is  continuous  with  the  squamous  portion,  to  which  it  is 
united  by  a  suture,  the  petro-squamous  suture,  the  remains  of  which  are  distinct  even 
at  a  late  period  of  life.  It  presents  six  points  for  examination  :  (1)  An  eminence 
(eminentia  arcuata)  near  the  centre,  which  indicates  the  situation  of  the 
superior  semicircular  canal.  (2)  In  front  and  a  little  to  the  outer  side  of  this 
eminence  a  depression  indicating  the  position  of  the  tympanum;  here  the  layer 
of  bone  which  separates  the  tympanum  from  the  cranial  cavity  is  extremely  thin, 
and  is  known  as  the  tegmen  tympani.  (3)  A  shallow  groove,  sometimes  double, 
leading  outward  and  backward  to  an  oblique  opening,  the  hiatus  Fallopii  (hiatus 
canalis  facialis)  ,  for  the  passage  of  the  greater  petrosal  nerve  and  the  petrosal 
branch  of  the  middle  meningeal  artery.  (4)  A  smaller  opening  (apertura  superior 
canaliculi  tympanici),  occasionally  seen  external  to  the  latter,  for  the  passage  of 
the  smaller  petrosal  nerve.  (5)  Near  the  apex  of  the  bone,  the  termination  of  the 
carotid  canal,  the  internal  carotid  foramen  (foramen  caroticum  internum),  the  wall 
of  which  in  this  situation  is  deficient  in  front.  (6)  Above  the  canal  a  shallow 
depression,  the  trigeminal  depression  (impressio  trigemini),  for  the  reception  of  the 
Gasserian  ganglion. 


THE    TEMPORAL    BONE 


89 


Posterior  Surface  (fades  posterior  pyramidis), — The  posterior  surface  forms  the 
front  part  of  the  posterior  fossa  of  the  skull,  and  is  continuous  with  the  inner 
surface  of  the  mastoid  portion  of  the  bone.  It  presents  three  points  for  exami- 
nation: 1.  About  its  centre,  a  large  orifice,  the  meatus  auditorius  interims  (meatus 
acusticus  interims),  whose  size  varies  considerably;  its  margins  are  smooth  and 
rounded,  and  it  leads  into  a  short  canal,  about  four  lines  in  length,  which  runs 
directly  outward  and  is  closed  by  a  vertical  plate,  the  lamina  cribrosa,  which  is 
divided  by  a  horizontal  crest,  the  falciform  crest  (crista  faldformis) ,  into  two  unequal 
portions  ( Fig.  50) .  Each  portion  is  subdivided  by  a  little  vertical  crest  into  two  parts, 
named,  respectively,  anterior  and  posterior.  The  lower  portion  presents  three  sets 
of  foramina :  one  group  just  below  the  poste- 
rior part  of  the  crest,  the  area  cribrosa  media, 
consisting  of  a  number  of  small  openings 
for  the  nerves  to  the  saccule;  below  and 
posterior  to  this,  the  foramen  singulare,  or 
opening  for  the  nerve  to  the  posterior  semi- 
circular canal ;  in  front  and  below  the  first, 
the  tractus  spiralis  foraminosus,  consisting 
of  a  number  of  small,  spirally  arranged 
openings  which  terminate  in  the  canalis 
centralis  cochleae  and  transmit  the  nerve  to 
the  cochlea;  the  upper  portion,  that  above 
the  crista,  presents  behind  a  series  of  small 
openings  the  area  cribrosa  superior,  for  the 
passage  of  filaments  to  the  utricle  and  supe- 
rior and  external  semicircular  canal,  and,  in 
front,  one  large  opening,  the  commence- 
ment of  the  aquseductus  Fallopii  (canalis 
facialis),  for  the  passage  of  the  facial  nerve. 

2.  Behind  the  rneatus  auditorius,  a  small 
slit  (apertura  externa  aquceductus  vestibuli), 
almost  hidden  by  a  thin  plate  of  bone,  lead- 
ing to  a  canal,  the   aquseductus    vestibuli, 
which  transmits  the  ductus  endolymphaticus 
together  with  a  small  artery  and  vein.     3. 

In  the  interval  between  these  two  openings,  but  above  them,  is  an  angular  depres- 
sion (fossa  subarcuata)  which  lodges  a  process  of  the  dura,  and  transmits  a 
small  vein  into  the  cancellous  tissue  of  the  bone.  In  the  child  this  depression 
is  represented  by  a  large  fossa,  the  floccular  fossa,  which  extends  backward  as  a 
blind  tunnel  under  the  superior  semicircular  canal. 

Inferior  Surface  (fades  inferior  pyramidis) . — The  inferior  or  basilar  surface  (Fig. 
51)  is  rough  and  irregular,  and  forms  part  of  the  base  of  the  skull.  Passing  from 
the  apex  to  the  base,  this  surface  presents  eleven  points  for  examination:  1.  A 
rough  surface,  quadrilateral  in  form,  which  serves  partly  for  the  attachment  of 
the  Levator  palati  and  Tensor  tympani  muscles.  2.  The  large,  circular  aperture 
of  the  carotid  canal,  the  external  carotid  foramen  (foramen  caroticum  externum) ;  the 
canal  ascends  at  first  vertically,  and  then,  making  a  bend,  runs  horizontally  for- 
ward and  inward;  it  transmits  the  internal  carotid  artery  and  the  carotid  plexus. 
Within  the  carotid  canal  are  several  openings  (canaliculi  carotico  tympanici)  which 
transmit  tympanic  branches  of  the  internal  carotid  artery  and  of  the  carotid  plexus. 

3.  The  opening  of  the  aquaeductus  cochleae  (apertura  externa  canaliculi  cochlea),  a 
small  triangular  opening,  lying  on  the  inner  side  of  the  latter,  close  to  the  posterior 
and  inner  border  of  the  petrous  portion;  it  transmits  a  vein  from  the  cochlea, 
which  joins  the  internal  jugular.  4.  Behind  these  openings  a  deep  depression,  the 


FIG.  50. — Diagrammatic  view  of  the  fundus 
of  the  internal  auditory  meatus:  1.  Falciform 
crest.  2.  Anterior  superior  cribriform  area.  2'. 
Internal  opening  of  the  aqutcductus  Fallopii. 
3.  Vertical  crest  which  separates  the  anterior 
and  posterior  superior  cribriform  areas.  4.  Pos- 
terior superior  cribriform  area,  with  (4')  open- 
ings for  nerve-filaments.  5.  Anterior  inferior 
cribriform  area.  5'.  Spirally  arranged,  sieve-like 
openings  for  the  nerves  to  the  cochlea.  5".  Open- 
ing of  the  central  canal  of  the  cochlea.  6.  Crest 
which  separates  the  anterior  and  posterior  infe- 
rior cribriform  areas.  7.  Posterior  inferior  crib- 
riform area.  7'.  Orifices  for  the  branches  of  the 
nerve  to  the  saccule.  8.  Foramen  singulare  of 
Morgagni,  with  the  anterior  portion  of  the  canal 
which  give^  passage  to  the  nerve  to  the  posterior 
semicircular  canal.  (Testut) 


90 


THE  SKELETON 


jugular  fossa  (fossa  jugularis],  which  varies  in  depth  and  size  in  different  skulls;  it 
lodges  the  lateral  sinus,  and,  with  a  similar  depression  on  the  margin  of  the  jugular 
process  of  the  occipital  bone,  forms  the  foramen  lacerum  posterius  or  jugular  fora- 
men. 5.  A  foramen  which  is  the  opening  of  a  small  canal  (canaliculus  tympanicus}, 


Canals  for  Eustachian  tube  and 

TENSOR  TYMPANI  MUSCLE. 


Rough  quadrilateral  surface. 

Opening  of  carotid  canal. 

Canal  for  Jacobson's  nerve. 

Aquseductus  cochlese. 

Canal  for  Arnold's  nerve. 

Jugular  fossa. 

Vaginal  process. 

Styloid  process. 
Stylo-mastoid  foramen. 
Jugular  surface. 
Auricular  fissure. 


STYLO-PHARYNQEU8. 


^PB^^~ 

FIG.  51. — Petrous  portion  of  the  left  temporal  bone.      Inferior  surface. 


for  the  passage  of  Jacobson's  nerve  (the  tympanic  branch  of  the  glosso-pharyn- 
geal);  this  foramen  is  seen  in  front  of  the  bony  ridge  dividing  the  carotid  canal 
from  the  jugular  fossa.  6.  A  small  foramen  on  the  wall  of  the  jugular  fossa,  for 
the  entrance  of  the  auricular  branch  of  the  vagus  (Arnold's)  nerve.  7.  Behind 
the  jugular  fossa  a  smooth,  square-shaped  facet,  the  jugular  surface;  it  is  covered 
with  cartilage  in  the  recent  state,  and  articulates  with  the  jugular  process  of 
the  occipital  bone.  8.  The  vaginal  process  (vagina  processus  styloidea],  a  very 
broad,  sheath-like  plate  of  bone,  which  extends  backward  from  the  carotid  canal, 
gives  attachment  to  part  of  the  Tensor  palati  muscle;  this  plate  divides  behind 
into  two  laminae,  the  outer  of  which  is  continuous  with  the  tympanic  plate,  the 
inner  with  the  jugular  process.  9.  Between  these  laminae  is  the  ninth  point  for 
examination,  the  styloid  process  (processus  styloideus},  a  sharp  spine,  about  an 
inch  in  length;  it  is  directed  downward,  forward,  and  inward,  varies  in  size  and 
shape,  and  sometimes  consists  of  several  pieces  united  by  cartilage;  it  affords 
attachment  to  three  muscles,  the  Stylo-pharyngeus,  Stylo-hyoideus,  and  Stylo- 
glossus,  and  two  ligaments,  the  stylo-hyoid  and  stylo-maxillary.  10.  The  stylo- 
mastoid  foramen  (foramen  stylomasloideum],  a  rather  large  orifice,  placed  between 
the  styloid  and  mastoid  processes;  it  is  the  termination  of  the  aquseductus  Fallopii, 
and  transmits  the  facial  nerve  and  stylo-mastoid  artery.  11.  The  auricular  fissure 
(fissura  tympanomasloidea),  situated  between  the  tympanic  plate  and  mastoid 
process,  for  the  exit  of  the  auricular  branch  of  the  vagus  nerve.  This  fissure  is  the 


THE    TEMPORAL   BONE 


91 


external  opening  of  the  canaliculus  mastoideus,  which  passes  to  the  aqueduct  of 
Fallopius. 

Borders.  Superior  Border  (angulus  superior  pyramidis}. — The  superior,  the 
longest,  is  grooved  for  the  superior  petrosal  sinus,  and  has  attached  to  it  the  ten- 
torium;  at  its  inner  extremity  is  a  semilunar  notch,  upon  which  the  trigeminal 
nerve  lies. 

Posterior  Border  (angulus  posterior  pyramidis} . — The  posterior  border  is  inter- 
mediate in  length  between  the  superior  and  the  anterior.  Its  inner  half  is  marked 
by  a  groove,  which,  when  completed  by  its  articulation  with  the  occipital,  forms 
the  channel  for  the  inferior  petrosal  sinus.  Its  outer  half  presents  a  deep  excava- 
tion, the  jugular  fossa  (fossa  jugularis),  which,  with  a  similar  notch  on  the  occipital, 
forms  the  foramen  lacerum  posterius.  A  projecting  eminence  of  bone  occasionally 
stands  out  from  the  centre  of  the  notch,  and  divides  the  foramen  into  two  parts. 

Anterior  Border  (angulus  anterior  pyramidis) . — The  anterior  border  is  divided 
into  two  parts — an  outer,  joined  to  the  squamous  portion  by  a  suture,  the  remains 
of  which  are  distinct;  an  inner,  free,  articulating  with  the  spinous  process  of  the 
sphenoid.  At  the  angle  of  junction  of  the  petrous  and  squamous  portions  is 
seen  the  opening  of  the  canalis  musculotubarius.  This  canal  is  completely  or 
partially  divided  into  two  canals,  separated  from  one  another  by  a  thin  plate  of 
bone,  the  processus  cochleariformis  (septum  canalis  musculotubarii) ;  they  both  lead 
into  the  tympanum,  the  upper  one  (semicanalis  m.  tensoris  tympani}  transmitting 
the  Tensor  tympani  muscle,  the  lower 
one  (semicanalis  tubce  auditivce)  form- 
ing the  bony  part  of  the  Eustachian 
tube  or  canal. 

Structure. — The  squamous  portion 
is  like  that  of  the  other  cranial  bones: 
the  mastoid  portion,  cellular;  and  the 
petrous  portion,  dense  and  hard. 

Development  (Fig.  52). — The  tem- 
poral bone  is  developed  by  ten  centres,  1  for  tympanic 
exclusive  of  those  for  the  internal  ear 
and  the  ossicula  —  viz.,  one  of  the 
squamous  portion  including  the  zygo- 
ma, one  for  the  tympanic  plate,  six  for 
the  petrous  and  mastoid  parts,  and  two 
for  the  styloid  process.  Just  before  the 
close  of  foetal  life  the  temporal  bone 
consists  of  four  parts:  1.  The  squamo- 
zygomatic  part,  ossified  in  membrane 
from  a  single  nucleus,  which  appears 


If  or 
squamous 
portion, 
including 
zygoma : 
2d  month. 


plate. 


6  for  petrous 

and  mastoid 

portions. 


2  for  styloid  process. 


By 


FIG.  52. — Development  of  the  temporal  bone, 
ten  centres. 

at  its  lower  part  about  the  second 
month.  2.  The  tympanic  plate,  an  imperfect  ring,  in  the  concavity  of  which  is 
a  groove,  the  sulcus  tympanicus,  for  the  attachment  of  the  circumference  of  the 
tympanic  membrane.  This  is  also  ossified  from  a  single  centre,  which  appears 
about  the  third  month.  3.  The  petro -mastoid  part  is  developed  from  six  cen- 
tres, which  appear  about  the  fifth  or  sixth  month.  Four  of  these  are  for  the 
petrous  portion,  and  are  placed  around  the  labyrinth,  and  two  for  the  mastoid 
(Vrolik).  According  to  Huxley,  the  centres  are  more  numerous,  and  are  dis- 
posed so  as  to  form  three  portions:  (1)  including  most  of  the  labyrinth,  with  a 
part  of  the  petrous  and  mastoid,  he  has  named  prootic;  (2)  the  rest  of  the  petrous, 
the  opisthotic;  and  (3)  the  remainder  of  the  mastoid,  the  epiotic.  The  petro- 
mastoid  is  ossified  in  cartilage.  4.  The  styloid  process  is  also  ossified  in  cartilage 
from  two  centres:  one  for  the  base,  which  appears  before  birth,  and  is  termed  the 


92  THE  SKELETON 

tympanohyal;  the  other,  comprising  the  rest  of  the  process,  is  named  the  stylohyal, 
and  does  not  appear  until  after  birth.  Shortly  before  birth  the  tympanic  plate  joins 
with  the  squarnous.  The  petrous  and  mastoid  join  with  the  squamous  during 
the  first  year,  and  the  tympanohyal  portion  of  the  styloid  process  about  the  same 
time.  The  stylohyal  does  not  join  the  rest  of  the  bone  until  after  puberty,  and 
in  some  skulls  never  becomes  united.  The  subsequent  changes  in  this  bone  are, 
that  the  tympanic  plate  extends  outward  and  backward,  so  as  to  form  the  meatus 
auditorius.  The  extension  of  the  tympanic  plate,  however,  does  not  take  place  at 
an  equal  rate  all  around  the  circumference  of  the  ring,  but  occurs  most  rapidly 
on  its  anterior  and  posterior  portions,  and  these  outgrowths  meet  and  blend,  and 
thus,  for  a  time,  there  exists  in  the  floor  of  the  meatus  a  foramen,  the  foramen  of 
Huschke;  this  foramen  may  persist  throughout  life.  The  glenoid  cavity  is  at  first 
extremely  shallow,  and  looks  outward  as  well  as  downward;  it  becomes  deeper 
and  is  ultimately  directed  downward.  Its  change  in  direction  is  accounted  for 
as  follows:  the  part  of  the  squamous  temporal  which  supports  it  lies  at  first  below 
the  level  of  the  zygoma.  As,  however,  the  base  of  the  skull  increases  in  width, 
this  lower  part  of  the  squama  is  directed  horizontally  inward  to  contribute  to 
the  middle  fossa  of  the  skull,  and  its  surfaces  therefore  come  to  look  upward  and 
downward.  The  mastoid  portion  is  at  first  quite  flat,  and  the  stylo-mastoid  fora- 
'men  and  rudimentary  styloid  process  lie  immediately  behind  the  entrance  to  the 
auditory  meatus.  With  the  development  of  the  air-cells  the  outer  part  of  the 
mastoid  portion  grows  downward  and  forward  to  form  the  mastoid  process,  and 
the  styloid  process  and  stylo-mastoid  foramen  now  come  to  lie  on  the  under  sur- 
face. The  descent  of  the  foramen  is  necessarily  accompanied  by  a  corresponding 
lengthening  of  the  aqueduct  of  Fallopius. 

The  downward  and  forward  growth  of  the  mastoid  process  also  pushes  forward 
the  tympanic  plate,  so  that  the  portion  of  it  which  formed  the  original  floor  of 
the  meatus  and  containing  the  foramen  of  Huschke  is  ultimately  found  in  the 
anterior  wall.  With  the  gradual  increase  in  size  of  the  petrous  portion  the  floc- 
cular  fossa  or  tunnel  under  the  superior  semicircular  canal  becomes  filled  up 
and  almost  obliterated. 

Articulations. — With  five  bones — occipital,  parietal,  sphenoid,  inferior  maxil- 
lary, and  malar. 

Attachment  of  Muscles. — To  fifteen  :  to  the  squamous  portion,  the  Tem- 
poral; to  the  zygoma,  the  Masseter;  to  the  mastoid  portion,  the  Occipito- 
frontalis,  Sterno-mastoid,  Splenius  capitis,  Trachelo-mastoid,  Digastricus,  and 
Retrahens  aurem;  to  the  styloid  process,  the  Stylo-pharyngeus,  Stylo-hyoideus, 
and  Stylo-glossus  ;  and  to  the  petrous  portion,  the  Levator  palati,  Tensor 
tympani,  Tensor  palati,  and  Stapedius. 

The  Sphenoid  Bone  (Os  Sphenoidale) . 

The  sphenoid  bone  (oyyv,  a  wedge)  is  situated  at  the  anterior  part  of  the  base 
of  the  skull,  articulating  with  all  the  other  cranial  bones,  which  it  binds  firmly 
and  solidly  together.  In  its  form  it  somewhat  resembles  a  bat  with  its  wings 
extended;  and  is  divided  into  a  central  portion  or  body,  two  greater  and  two  lesser 
wings  extending  outward  on  each  side  of  the  body,  and  two  processes — the  ptery- 
goid  processes — which  project  from  it  below. 

The  Body  of  the  Sphenoid  Bone. 

The  body  (corpus)  is  of  large  size  and  hollowed  out  in  its  interior  so  as  to  form  a 
mere  shell  of  bone.  It  presents  for  examination  four  surfaces — a  superior,  an 
inferior,  an  anterior,  and  a  posterior. 


THE  SPHENOID    BONE 


93 


Surfaces.  Superior  Surface  (fades  cerebralis)  (Fig.  53). — In  front  is  seen  a  promi- 
nent spine,  the  ethmoidal  spine,  for  articulation  with  the  cribriform  plate  of  the  eth- 
moid ;  behind  this  a  smooth  surface  presenting,  in  the  median  line,  a  slight  longi- 
tudinal eminence,  with  a  depression  on  each  side  for  lodging  the  olfactory  lobes. 
This  surface  is  bounded  behind  by  a  ridge,  which  forms  the  anterior  border  of  a 
narrow,  transverse  groove,  the  optic  groove  (sulcus  chiasmatis),  behind  which  lies  the 
optic  chiasm;  the  groove  is  continuous  on  each  side  with  the  optic  foramen  (foramen 
opticum) ,  for  the  passage  of  the  optic  nerve  and  ophthalmic  artery.  Behind  the 

Middle  cJnioid  process.  Ethmoidal 

_  Posterior  dinoid  process.  \  „_ .,_  spine. 


Foramen  opticum. 
Foramen  lacerum  anie- 
rius  or  Sphenoidal 
fissure. 

Foramen  rotundum. 

Foramen  Vesalii; 

Foramen  orate: 

Foramen  .spinosum. 


FIG.  53. — Sphenoid  bone.     Superior  surface. 


optic  groove  is  a  small  eminence,  olive-like  in  shape,  the  olivary  process  or  eminence 
(tuberculum  sellce) ;  and  still  more  posteriorly,  a  deep  depression,  the  pituitary  fossa, 
or  sella  turcica  (fossa  hypophyseos) ,  which  lodges  the  circular  sinus  and  the  pituitary 
body  (hypophysis).  This  fossa  is  perforated  by  numerous  foramina,  for  the  trans- 
mission of  nutrient  vessels  into  the  substance  of  the  bone.  It  is  bounded  in  front 
by  the  olivary  eminence,  and  also  by  two  small  eminences,  one  on  either  side,  called 
the  middle  clinoid  processes  (processus  clinoidei  medii)  (xkivq,  a  bed),  which  are 
sometimes  connected  by  a  spiculum  of  bone  to  the  anterior  clinoid  processes.  It 
is  bounded  behind  by  a  square-shaped  plate  of  bone,  the  dorsum  ephippii  or  dorsum 
sellae,  terminating  at  each  superior  angle  in  a  tubercle,  the  posterior  clinoid  process 
(processus  clinoideus  posterior) .  The  size  and  form  of  these  processes  vary  con- 
siderably in  different  individuals.  They  deepen  the  pituitary  fossa,  and  serve  for 
the  attachment  of  prolongations  from  the  tentorium.  The  sides  of  the  dorsum 
ephippii  are  notched  for  the  passage  of  the  abducent  nerves,  and  below  present 
a  sharp  process,  the  petrosal  process,  which  is  joined  to  the  apex  of  the  petrous 
portion  of  the  temporal  bone,  forming  the  inner  boundary  of  the  middle  lacerated 
foramen.  Behind  this  plate  the  bone  presents  a  shallow  depression,  which  slopes 
obliquely  backward,  and  is  continuous  with  the  basilar  groove  of  the  occipital 
bone;  it  is  called  the  clivus,  and  supports  the  upper  part  of  the  pons.  On  either 
side  of  the  body  is  a  broad  groove,  curved  something  like  the  italic  letter  /;  it 
lodges  the  internal  carotid  artery  and  the  cavernous  sinus,  and  is  called  the  carotid 
or  cavernous  groove  (sulcus  caroticus).  Along  the  outer  margin  of  this  groove, 
at  its  posterior  part,  is  a  ridge  of  bone  in  the  angle  between  the  body  and  greater 
wing,  called  the  lingula  (lingula  sphenoidalis). 

Posterior  Surface. — The  posterior  surface,  quadrilateral  in  form,  is  joined  to  the 
basilar  process  of  the  occipital  bone.    During  childhood  these  bones  are  separated 


94 


THE  SKELETON 


by  a  layer  of  cartilage;  but  in  after-life  (between  the  eighteenth  and  twenty-fifth 
years)  this  becomes  ossified,  ossification  commencing  above  and  extending  down- 
ward; and  the  two  bones  then  form  one  piece. 

Anterior  Surface. — The  anterior  surface  (Fig.  54)  presents,  in  the  middle  line,  a 
vertical  ridge  of  bone,  the  ethmoidal  or  sphenoidal  crest  (crista  sphenoidalis) ,  which 
articulates  in  front  with  the  perpendicular  plate  of  the  ethmoid,  forming  part  of 
the  septum  of  the  nose.  On  either  side  of  it  are  irregular  openings  leading  into 
the  sphenoidal  cells  or  sinuses  (sinus  sphenoidales) .  These  are  two  large,  irregular 
cavities  hollowed  out  of  the  interior  of  the  body  of  the  sphenoid  bone,  often 


'erygo-  \     \Artic.  with 

ine    I      \    vomer. 
ma/.     ' 
Groove  for  alal 
of  vomer.  7 
m~S 


Pterygoid  ridge. 


Internal  pterygoid  plate.- 
Hamular  process.- 

FIG.  54.  —  Sphenoid  bone.    Anterior  surface.1 

extending  into  the  pterygoid  processes  and  base  of  the  greater  wings  of  the  bone, 
and  separated  from  one  another  by  a  more  or  less  complete  perpendicular  bony 
septum  (septum  sinuum  sphenoidalium)  .  Occasionally  they  extend  into  the  basilar 
process  of  the  occipital  nearly  as  far  as  the  foramen  magnum.  Their  form  and 
size  vary  considerably;  they  are  seldom  symmetrical,  and  are  often  partially  sub- 
divided by  irregular,  osseous  lamime.  One  sinus  or  both  sinuses  may  be  absent. 
The  septum  is  seldom  quite  vertical,  being  commonly  bent  to  one  or  the  other 
side.  These  sinuses  do  not  exist  in  very  young  children,  but  appear,  according 
to  Laurent,  in  the  seventh  year,  and,  according  to  Tillaux,  not  until  the  twen- 
tieth year.  After  once  appearing  they  increase  in  size  as  age  advances.  They 
are  partially  closed,  in  front  and  below,  by  two  thin,  curved  plates  of  bone, 
the  sphenoidal,  spongy,  or  turbinated  bones  (conches  sphenoidales}.  At  the  upper 
part  of  each  is  a  round  opening  (apertura  sinus  sphenoidalis)  by  which  the  sinus 
communicates  with  the  upper  and  back  part  of  the  nose,  and  occasionally  with 
the  posterior  ethmoidal  cells  or  sinuses.  The  lateral  margins  of  this  surface 
present  a  serrated  edge,  which  articulates  with  the  os  planum  of  the  ethmoid, 
completing  the  posterior  ethmoidal  cells;  the  lower  margin,  also  rough  and  ser- 
rated, articulates  with  the  orbital  process  of  the  palate  bone,  and  the  upper 
margin  with  the  orbital  plate  of  the  frontal  bone. 

Inferior  Surface.  —  The  inferior  surface  presents,  in  the  middle  line,  a  triangular 
spine,  the  rostrum  (rostrum  sphenoidalis),  which  is  continuous  with  the  sphenoidal 
crest  on  the  anterior  surface,  and  is  received  into  a  deep  fissure  between  the  alae 


1  In  this  ficcure,  both  the  anterior  and  inferior  surfaces  of  the  body  of  the  sphenoid  bone  are  shown,  the  bone 
being  held  with  the  pterygoid  processes  almost  horizontal.  —  ED.  of  15th  English  Edition. 


THE  SPHENOID  BONE  95 

of  the  voraer.  On  each  side  may  be  seen  a  projecting  lamina  of  bone,  which  runs 
horizontally  inward  from  near  the  base  of  thepterygoid  process:  these  plates,  termed 
the  vaginal  processes,  articulate  with  the  edges  of  the  vomer.  Close  to  the  root  of 
the  pterygoid  process  is  a  groove  (sidcus  pterygopalatinus) ,  formed  into  a  complete 
canal  when  articulated  with  the  sphenoidal  process  of  the  palate  bone ;  it  is  called 
the  pterygo-palatine  canal,  and  transmits  the  pterygo-palatine  vessels  and  pharyngeal 
nerve. 

The  Greater  or  Temporal  Wings  of  the  Sphenoid  Bone  (Alae  Magnae ) . 

The  greater  wings  are  two  strong  processes  of  bone  which  arise  from  the  sides 
of  the  body,  and  are  curved  in  a  direction  upward,  outward,  and  backward,  each 
being  prolonged  behind  into  a  sharp-pointed  extremity,  the  alar  or  sphenoidal 
spine  (spina  angularis) .  Each  wing  presents  three  surfaces  and  a  circumference. 

Surfaces.  Superior  Surface  (fades  cerebralis). — The  superior  or  cerebral  surface 
(Tig.  53)  forms  part  of  the  middle  fossa  of  the  skull;  it  is  deeply  concave,  and  pre- 
sents eminences  and  depressions  for  the  convolutions  of  the  brain.  At  its  anterior 
and  internal  part  is  seen  a  circular  aperture,  the  foramen  rotundum,  for  the  transmis- 
sion of  the  second  division  of  the  trigeminal  nerve.  Behind  and  external  to  this  is  a 
large,  oval  foramen,  the  foramen  ovale,  for  the  transmission  of  the  third  division  of 
the  trigeminal  nerve,  the  small  meningeal  artery,  and  sometimes  the  small  petrosal 
nerve.1  At  the  inner  side  of  the  foramen  ovale  a  small  aperture  may  occasionally 
be  seen  opposite  the  root  of  the  pterygoid  process;  it  is  the  foramen  Vesalii,  trans- 
mitting a  small  vein.  Lastly,  in  the  posterior  angle,  near  to  the  spine  of  the  sphe- 
noid, is  a  short  canal,  sometimes  double,  the  foramen  spinosum;  it  transmits  the 
middle  meningeal  artery. 

External  Surface. — The  external  surface  (Fig.  54)  is  convex  and  divided  by  a 
transverse  ridge,  the  pterygoid  ridge  or  infratemporal  crest  (crista  infratemporalis) , 
into  two  portions.  The  superior  or  larger,  convex  from  above  downward,  concave 
from  before  backward,  enters  into  the  formation  of  the  temporal  fossa,  and  gives 
attachment  to  part  of  the  Temporal  muscle.  The  inferior  portion,  smaller  in  size 
and  concave,  enters  into  the  formation  of  the  zygomatic  fossa,  and  affords  attach- 
ment to  the  External  pterygoid  muscle.  It  presents,  at  its  posterior  part,  a  sharp- 
pointed  eminence  of  bone,  the  spine,  to  which  are  connected  the  internal  lateral 
ligament  of  the  lower  jaw  and  the  Tensor  palati  muscle.  The  pterygoid  ridge, 
dividing  the  temporal  and  zygomatic  portions,  gives  attachment  to  part  of  the 
External  pterygoid  muscle.  At  its  inner  and  anterior  extremity  is  a  triangular 
spine  of  bone,  which  serves  to  increase  the  extent  of  origin  of  this  muscle. 

Anterior  Surface  (fades  orbitalw] . — The  anterior  or  orbital  surface,  smooth  and 
quadrilateral  in  form,  assists  in  forming  the  outer  wall  of  the  orbit.  It  is  bounded 
above  by  a  serrated  edge,  for  articulation  with  the  frontal  bone;  below,  by  a  rounded 
border  which  enters  into  the  formation  of  the  spheno-maxillary  fissure.  Internally,  it 
presents  a  sharp  border,  which  forms  the  lower  boundary  of  the  sphenoidal  fissure, 
and  has  projecting  from  about  its  centre  a  little  tubercle  of  bone,  which  gives 
origin  to  one  head  of  the  External  rectus  muscle  of  the  eye;  and  at  its  upper  part 
is  a  notch  for  the  transmission  of  a  recurrent  branch  of  the  lachrymal  artery; 
externally  it  presents  a  serrated  margin  for  articulation  with  the  malar  bone.  One 
or  two  small  foramina  may  occasionally  be  seen  for  the  passage  of  branches  of 
the  deep  temporal  arteries;  they  are  called  the  external  orbital  foramina. 

Circumference  (Fig.  53). — Commencing  from  behind,  that  portion  of  the  cir- 
cumference from  the  body  of  the  sphenoid  to  the  spine  is  serrated  and  articulates 
by  its  outer  half  with  the  petrous  portion  of  the  temporal  bone,  while  the  inner 
half  forms  the  anterior  boundary  of  the  foramen  lacerum  medium,  and  presents 

1  The  small  petrosal  nerve  sometimes  passes  through  a  special  forame  j  between  the  foramen  ovale  and  foramen 
spinosum. — ED.  of  15th  English  Edition. 


96  THE   SKELETON 

the. posterior  aperture  of  the  Vidian  canal  (canalis  pterygoideus)  for  the  passage  of  the 
Vidian  nerve  and  artery.  In  front  of  the  spine,  the  circumference  of  the  great  wing 
presents  a  serrated  edge,  bevelled  at  the  expense  of  the  inner  table  below  and  of  the 
external  above,  which  articulates  with  the  squamous  portion  of  the  temporal  bone. 
At  the  tip  of  the  great  wing  a  triangular  portion  is  seen,  bevelled  at  the  expense  of 
the  internal  surface,  for  articulation  with  the  anterior  inferior  angle  of  the  parietal 
bone.  Internal  to  this,  is  a  triangular,  serrated  surface,  for  articulation  with  the 
frontal  bone;  this  surface  is  continuous  internally  with  the  sharp  inner  edge  of 
the  orbital  plate,  which  assists  in  the  formation  of  the  sphenoidal  fissure,  and 
externally  with  the  serrated  margin  for  articulation  with  the  malar  bone. 

The  Lesser  or  Orbital  Wings  of  the  Sphenoid  Bone  (Alse  Parvse). 

The  lesser  wings  (processes  of  Ingrassias)  are  two  thin,  triangular  plates  of 
bone  which  arise  from  the  upper  and  lateral  parts  of  the  body  of  the  sphenoid, 
and,  projecting  transversely  outward,  terminate  in  a  sharp  point  (Fig.  53).  The 
superior  surface  of  each  is  smooth,  flat,  broader  internally  than  externally,  and 
supports  part  of  the  frontal  lobe  of  the  brain.  The  inferior  surface  forms  the 
back  part  of  the  roof  of  the  orbit  and  the  upper  boundary  of  the  orbital  or  sphe- 
noidal fissure  or  foramen  lacerum  anterius  (fissura  orbitalis  superior) .  This  fissure  is 
of  a  triangular  form,  and  leads  from  the  cavity  of  the  cranium  into  the  orbit;  it  is 
bounded  internally  by  the  body  of  the  sphenoid — above,  by  the  lesser  wing; 
below,  by  the  internal  margin  of  the  orbital  surface  of  the  great  wing — and  is 
converted  into  a  foramen  by  the  articulation  of  this  bone  with  the  frontal.  It 
transmits  the  third,  the  fourth,  the  three  branches  of  the  ophthalmic  division 
of  the  trigeminal,  the  abducent  nerve,  some  filaments  from  the  cavernous  plexus 
of  the  sympathetic,  the  orbital  branch  of  the  middle  meningeal  artery,  a  recur- 
rent branch  from  the  lachrymal  artery  to  the  dura  and  the  ophthalmic  vein. 
The  anterior  border  of  the  lesser  wing  is  serrated  for  articulation  with  the 
frontal  bone;  the  posterior  border,  smooth  and  rounded,  is  received  into  the  fissure  of 
Sylvius  of  the  brain.  Each  inner  extremity  of  this  border  forms  an  anterior  clinoid 
process  (processus  clinoideus  anterior).  The  lesser  wing  is  connected  to  the  side 
of  the  body  by  two  roots,  the  upper  thin  and  flat,  the  lower  thicker,  obliquely 
directed,  and  presenting  on  its  outer  side,  near  its  junction  with  the  body,  a  small 
tubercle,  for  the  attachment  of  the  common  tendon  of  origin  of  three  of  the  muscles 
of  the  eye.  Between  the  two  roots  is  the  optic  foramen  (foramen  opticum),  for 
the  transmission  of  the  optic  nerve  and  ophthalmic  artery. 

The  Pterygoid  Processes  of  the  Sphenoid  Bone  (Processus  Pterygoidei) . 

The  pterygoid  processes  (xrepus,  a  wing;  e?&>c,  likeness),  one  on  each  side, 
descend  perpendicularly  from  the  point  where  the  body  and  greater  wing  unite 
(Fig.  55).  Each  process  consists  of  an  external  and  an  internal  lamina  or  plate, 
which  are  joined  together  by  their  anterior  borders  above,  but  are  separated  below, 
leaving  an  angular  cleft,  the  pterygoid  notch  or  fissure  (fissura  pterygoidea) ,  in  which 
the  pterygoid  process  or  tuberosity  of  the  palate  bone  is  received.  The  two  plates 
diverge  from  each  other  from  their  line  of  connection  in  front,  so  as  to  form  a  V-- 
shaped fossa,  the  pterygoid  fossa  (fossa  pterygoidea) .  The  external  pterygoid  plate 
(lamina  later  alls  processus  pterygoidei)  is  broad  and  thin,  turned  a  little  outward, 
and,  by  its  outer  surface,  forms  part  of  the  inner  wall  of  the  zygomatic  fossa,  giving 
attachment  to  the  External  pterygoid ;  its  inner  surface  forms  part  of  the  pterygoid 
fossa,  and  gives  attachment  to  the  Internal  pterygoid.  The  internal  pterygoid  plate 
(lamina  medialis  processus  pterygoidei)  is  much  narrower  and  longer,  curving 
outward,  at  its  extremity,  into  a  hook-like  process  of  bone,  the  hamular  process 


THE   SPHENOID    BONE 


97 


(hamulus  pterygoideus},  around  which  turns  the  tendon  of  the  Tensor  palati 
muscle.  The  outer  surface  of  this  plate  forms  part  of  the  pterygoid  fossa,  the 
inner  surface  forming  the  outer  boundary  of  the  posterior  aperture  of  the  nares. 
On  the  posterior  surface  of  the  base  of  the  process,  above  the  pterygoid  fossa,  is  a 
small,  oval,  shallow  depression,  the  scaphoid  fossa  (fossa  scaphoidea),  from  which 
arises  the  Tensor  palati,  and  above  which  is  seen  the  posterior  orifice  of  the  Vidian 
canal  (canal  is  pterygoideus  [Vidii]).  Below  and  to  the  inner  side  of  the  Vidian 


FIG.  55. — Sphenoid  bone.     Posterior  surface. 

canal,  on  the  posterior  surface  of  the  base  of  the  internal  plate,  is  a  little  promi- 
nence, which  is  known  by  the  name  of  the  pterygoid  tubercle.  The  Superior 
constrictor  of  the  pharynx  is  attached  to  the  posterior  edge  of  the  internal  plate. 
The  anterior  surface  of  the  pterygoid  process  is  very  broad  at  its  base,  and  forms 
the  posterior  wall  of  the  spheno-maxillary  fossa.  It  supports  Meckel's  ganglion. 
It  presents,  above,  the  anterior  orifice  of  the  Vidian  canal ;  and  below,  a  rough 
margin,  which  articulates  with  the  perpendicular  plate  of  the  palate  bone. 


The  Sphenoidal  Spongy  Bone. 

The  sphenoidal  spongy,  turbinal  or  turbinated  bones  (the  bones  of  Bertin,  conches 
sphenoidales)  are  two  thin,  curved  plates  of  bones,  which  exist  as  separate  pieces 
until  puberty,  and  occasionally  are  not  joined  to  the  sphenoid  in  the  adult.  They 
are  situated  at  the  anterior  and  inferior  part  of  the  body  of  the  sphenoid,  an 
aperture  (apertura  sinus  sphenoidalis)  of  variable  size  being  left  in  the  anterior  wall 
of  each,  through  which  the  sphenoidal  sinuses  open  into  the  nasal  fossae.  They  are 
irregular  in  form  and  taper  to  a  point  behind,  being  broader  and  thinner  in  front. 
Their  upper  surface,  which  looks  toward  the  cavity  of  the  sinus,  is  concave;  their 
under  surface  convex.  Each  bone  articulates  in  front  with  the  ethmoid,  exter- 
nally with  the  palate;  its  pointed  posterior  extremity  is  placed  above  the  vom^r, 
and  is  received  between  the  root  of  the  pterygoid  process  on  the  outer  side  and 
the  rostrum  of  the  sphenoid  on  the  inner.1 

Development. — Up  to  about  the  eighth  month  of  fcetal  life  the  sphenoid  bone 
consists  of  two  distinct  parts:  a  posterior  or  post-sphenoid  part,  which  comprises 
the  pituitary  fossa,  the  greater  wings,  and  the  pterygoid  processes;  and  an  anterior 
or  pre-sphenoid  part,  to  which  the  anterior  part  of  the  body  and  lesser  wings 
belong.  It  is  developed  by  fourteen  centres:  eight  for  the  posterior  sphenoid 
division,  and  six  for  the  anterior  sphenoid.  The  eight  centres  for  the  posterior 

1  A  small  portion  of  the  sphenoidal  turbinated  bone  sometimes  enters  into  the  formation  of  the  inner  wall  of 
the  orbit,  between  the  os  planum  of  the  ethmoid  in  front,  the  orbital  plate  of  the  palate  below,  and  the  frontal 
above.— Cleland,  Roy.  Soc.  Trans..  1862. 


98  THE   SKELETON 

sphenoid  are:  one  for  each  greater  wing  and  external  pterygoid  plate,  one  for 
each  internal  pterygoid  plate,  two  for  the  posterior  part  of  the  body,  and  one  on 
each  side  for  the  lingula.  The  six  for  the  anterior  sphenoid  are:  one  for  each 
lesser  wing,  two  for  the  anterior  part  of  the  body,  and  one  for  each  sphenoidal 
turbinated  bone. 

Post-sphenoid  Division. — The  first  nuclei  to  appear  are  those  for  the  greater 
wings  (ali-sphenoids).  They  make  their  appearance  between  the  foramen  rotun- 

dum  and  foramen  ovale  about  the  eighth 
one  for  each    two  for  anterior  week,  and  from  them  the  external  ptervgoid 

lesser  wing,    gart  of  body.  pjates    are    a]so    formed.       Soon    after,    the 

nuclei  for  the  posterior  part  of   the  body 
appear,  one  on  either  side  of  the  sella  turcica, 
and    become   blended   together   about   the 
middle  of   foetal  life.      About   the  fourth 
month  the  remaining  four  centres  appear, 
one  for  each  inte^alA'?''      ^     \         tho.se  for ;  the"  internal  pterygoid  plates  being 
pterygoid  plate.     ''•'  \        ossified  in  membrane  and  becoming  joined 

one  for       for°each  lingula.        \      to  the  external  pterygoid  plate  about  the 

each  great  wing  and  external  ptery-      sixth    month.     The    centres  for    the    Ungulte 

one  for  each  Sphenoidal  turbinated  bSedplate'     speedily  become  joined  to  the  rest  of  the 

FIG.  56. — Plan  of  development  of  the  sphenoid. 

By  fourteen  centres.  Pre-sphenoid  Division. — The  first  nuclei 

to  appear  are  those  for  the  lesser  wings 

(orbito-sphenoids).  They  make  their  appearance  about  the  ninth  week,  at  the 
outer  borders  of  the  optic  foramina.  A  second  pair  of  nuclei  appear  on  the  inner 
side  of  the  foramina  shortly  after,  and,  becoming  united,  form  the  front  part  of 
the  body  of  the  bone.  The  remaining  two  centres  for  the  sphenoidal  turbinated 
bones  make  their  appearance  about  the  fifth  month.  At  birth  they  consist  of  small 
triangular  laminae,  and  it  is  not  till  the  third  year  that  they  become  hollowed  out 
and  cone-shaped.  About  the  fourth  year  they  become  fused  with  the  lateral 
masses  of  the  ethmoid,  and  hence,  from  an  embryo  logical  point  of  view,  may  be 
regarded  as  belonging  to  the  ethmoid. 

The  pre-sphenoid  is  united  to  the  body  of  the  post-sphenoid  about  the  eighth 
month,  so  that  at  birth  the  bone  consists  of  three  pieces — viz.,  the  body  in  the 
centre,  and  on  each  side  the  great  wings  with  the  pterygoid  processes.  The  lesser 
wings  become  joined  to  the  body  at  about  the  time  of  birth.  At  the  first  year 
after  birth  the  greater  wings  and  body  are  united.  From  the  tenth  to  the  twelfth 
year  the  spongy  bones  are  partially  united  to  the  sphenoid,  their  junction  being 
complete  by  the  twentieth  year.  Lastly,  the  sphenoid  joins  the  occipital  from  the 
eighteenth  to  the  twenty-fifth  year. 

Articulations. — The  sphenoid  articulates  with  all  the  bones  of  the  cranium, 
and  five  of  the  face— the  two  malar,  the  two  palate,  and  vomer;  the  exact  extent 
of  articulation  with  each  bone  is  shown  in  the  accompanying  figures.1 

Attachment  of  Muscles. — To  eleven  pairs:  the  Temporal,  External  ptervgoid, 
Internal  pterygoid,  Superior  constrictor,  Tensor  palati,  Levator  palpebrse,  Ob- 
liquus  oculi  superior,  Superior  rectus,  Internal  rectus,  Inferior  rectus,  External 
rectus. 

The  Ethmoid  Bone  (Os  Ethmoidale). 

The  ethmoid  (/}#//oc,  a  sieve)  is  an  exceedingly  light,  spongy  bone,  of  a  cubical 
form,  situated  at  the  anterior  part  of  the  base  of  the  cranium,  between  the  two 
orbits  at  the  root  of  the  nose,  and  contributing  to  form  each  of  these  cavities. 

1  It  also  sometimes  articulates  with  the  tuberosity  of  the  superior  maxilla. — ED.  of  15th  English  Edition. 


THE   ETHMOID    BONE 


99 


It  consists  of  three  parts:  a  horizontal  plate,  which  forms  part  of  the  base  of  the 
cranium;  a  perpendicular  plate,  which  forms  part  of  the  septum  nasi;  and  two 
lateral  masses  of  cells. 

The  Horizontal  Lamina  or  Cribriform  Plate  (lamina  cribrosa)  (Fig.  57)  forms 
part  of  the  anterior  fossa  of  the  base  of  the  skull,  and  is  received  into  the  ethmoid 
notch  of  the  frontal  bone  be- 
tween the  two  orbital  plates. 
Projecting  upward  from  the 
middle  line  of  this  plate  is  a 
thick,  smooth,  triangular  pro- 
cess of  bone,  the  crista  galh',  so 
called  from  its  fancied  resem- 
blance to  a  cock's  comb.  Its 
base  joins  the  cribriform  plate. 
Its  posterior  border,  long,  thin, 
and  slightly  curved,  serves  for 
the  attachment  of  the  falx. 
Its  anterior  border,  short  and 
thick,  articulates  with  the 
frontal  bone,  and  presents  two 
small  projecting  alse  (processus 

alares] ,  which  are  received  in-  mth  inferior  lurbinated  b~°™- 

to  corresponding  depressions 
in  the  frontal,  completing  the 
foramen  caecum  behind.  Its  sides  are  smooth  and  sometimes  bulging;  in  which 
case  it  is  found  to  enclose  a  small  sinus.1  On  each  side  of  the  crista  galli  the  cribri- 
form plate  is  narrow  and  deeply  grooved,  to  support  the  bulb  of  the  olfactory  tract, 
and  is  perforated  by  foramina  for  the  passage  of  the  olfactory  nerves.  These  fora- 


FIG.  57. — Ethmoid  bone.     Outer  surface  of  right   lateral   mass 
(enlarged). 


LAMINA  CRIBROSA 


CRISTA  GALLI 

ALAR   PROCESS 

LAMINA   CRIBROSA 


UNCIFORM 
PROCESS 


ETHMOIDAL       PERPENDICU- 
LABYRINTH          LAR   LAMINA 

FIG.  58. — Ethmoid  bone  from  behind,  somewhat 
schematic.     (Spalteholz.) 


POSTERIOR 
ETHMOIDAL 
FORAMEN 


ANTERIOR 

ETHMOIDAL 

FORAMEN 


CRISTA  GALLI 


ALAR    PROCESS 


FIG.  59. — Ethmoid  bone  from  above.     (Spalteholz.) 


mina  are  arranged  in  three  rows:  the  innermost,  which  are  the  largest  and  least 
numerous,  are  lost  in  grooves  on  the  upper  part  of  the  septum;  the  foramina  of  the 
outer  row  are  continued  on  to  the  surface  of  the  upper  spongy  bone.  The  fora- 
mina of  the  middle  row  are  the  smallest;  they  perforate  the  bone  and  transmit 
nerves  to  the  roof  of  the  nose.  At  the  front  part  of  the  cribriform  plate,  on  each 


1  Sir  George  Humphry  states  that  the  crista  galli  is  commonly  inclined  to  one  side,  usually  the  opposite  to 
that  toward  which  the  lower  part  of  the  perpendicular  plate  is  bent. — The  Human  Skeleton,  1858,  p.  277. 


100 


THE  SKELETON 


with  Ethmoidal 


side  of  the  crista  galli,  is  a  small  fissure,  which  transmits  the  nasal  branch  of  the 
ophthalmic  nerve;  and  at  its  posterior  part  a  triangular  notch,  which  receives  the 
ethmoidal  spine  of  the  sphenoid. 

The  Vertical  or  Perpendicular  Lamina  or  Plate  (lamina  perpendicular™  or 
mesethmoid)  (Fig.  60)  is  a  thin,  flattened  lamella  of  bone,  which  descends  from  the 
under  surface  of  the  cribriform  plate,  and  assists  in  forming  the  septum  of  the  nose. 
It  is  much  thinner  in  the  middle  than  at  the  circumference,  and  is  generally  deflected 
a  little  to  one  side.  Its  anterior  border  articulates  with  the  nasal  spine  of  the  frontal 
bone  and  crest  of  the  nasal  bones.  Its  posterior  border,  divided  into  two  parts, 

articulates  by  its  upper 
half  with  the  sphenoidal 
crest  of  the  sphenoid,  by 
its  lower  half  with  the 
vomer.  The  inferior  bor- 
der serves  for  the  attach- 
ment of  the  triangular  car- 
tilage of  the  nose.  On 
each  side  of  the  perpen- 
dicular plate  numerous 
grooves  and  canals  are 
seen,  leading  from  the  for- 
amina on  the  cribriform 
plate;  they  lodge  filaments 
of  the  olfactory  nerves. 

The  Lateral  Mass  or 
Labyrinth  (labyrinthus 
ethmoidalis)  of  the  ethmoid 
consists  of  a  number  of 

thin-walled  cellular  cavities,  the  ethmoidal  cells  (cellulw  ethmoidales)  interposed  be- 
tween two  vertical  plates  of  bone,  the  outer  one  of  which  forms  part  of  the  orbit, 
and  the  inner  one  part  of  the  nasal  fossa  of  the  corresponding  side.  There  are  two 
lateral  masses,  one  on  each  side.  The  ethmoidal  cells  are  not  present  at  birth, 
but  appear  during  the  fifth  year.  In  the  disarticulated  bone  many  of  these  cells 
appear  to  be  broken;  but  when  the  bones  are  articulated  they  are  closed  in  at 
every  part,  except  where  they  open  into  the  nasal  fossse.  The  upper  surface  of 
each  lateral  mass  presents  a  number  of  apparently  half-broken  cellular  spaces; 
these  are  closed  in,  when  articulated,  by  the  edges  of  the  ethmoidal  notch  of  the 
frontal  bone.  Crossing  this  surface  are  two  grooves  on  each  side,  converted  into 
canals  by  articulation  with  the  frontal;  they  are  the  anterior  and  posterior  ethmoidal 
canals  (canalis  ethmoidale  anterius  and  posterius),  and  open  on  the  inner  wall  of 
the  orbit.  The  posterior  surface  also  presents  large,  irregular  cellular  cavities, 
which  are  closed  in  by  articulation  with  the  sphenoidal  turbinated  bones  and 
the  orbital  process  of  the  palate.  The  cells  at  the  anterior  surface  are  completed 
by  the  lachrymal  bone  and  nasal  process  of  the  superior  maxillary,  and  those 
below  also  by  the  superior  maxillary.  The  outer  surface  of  each  lateral  mass  is 
formed  of  a  thin,  smooth,  oblong  plate  of  bone,  called  the  os  planum  (lamina 
papyracea) ;  it  forms  part  of  the  inner  wall  of  the  orbit,  and  articulates,  above, 
with  the  orbital  plate  of  the  frontal;  below,  with  the  superior  maxillary;  in 
front,  with  the  lachrymal;  and  behind,  with  the  sphenoid  and  orbital  process  of 
the  palate. 

From  the  inferior  part  of  each  lateral  mass,  immediately  beneath  the  os  planum, 
there  projects  downward  and  backward  an  irregular  lamina  of  bone,  called  the 
unciform  process  (processus  uncinatus),  from  its  hook-like  form;  it  serves  to  close 
in  the  upper  part  of  the  orifice  of  the  antrum,  and  articulates  with  the  ethmoidal 


FIG.  60. — Perpendicular  plate  of  ethmoid  (enlarged),  shown  by 
removing  the  right  lateral  mass. 


THE   ETHMOID    BONE  101 

process  of  the  inferior  turbinated  bone.  It,  is  often  broken  in  disarticulating  the 
bones. 

The  inner  surface  of  each  lateral  mass  forms  part  of  the  outer  wall  of  the  nasal 
fossa  of  the  corresponding  side.  It  is  formed  of  a  thin  lamella  of  bone,  which 
descends  from  the  under  surface  of  the  cribriform  plate,  and  terminates  below  in 
a  free,  convoluted  margin,  the  middle  turbinated  or  the  inferior  ethmoidal  turbinate 
bone  (concha  nasalis  media).  The  middle  turbinated  bone  may  contain  a  cell  or 
cells,  which  are  really  ethmoidal  cells.  Howard  A.  Lothrop1  studied  1000  speci- 
mens, and  found  cells  in  9  per  cent, 
of  them.  He  never  found  cells  in 
children.  As  a  rule,  a  turbinate  cell 
communicates  with  a  posterior  eth- 
moidal cell,  but  may  join  an  anterior 
ethmoidal  cell.  The  cells  may  open 
into  the  superior  meatus  or  into  the 
middle  meatus.  The  whole  of  this 
surface  is  rough  and  marked  above 
by  numerous  grooves,  which  run  nearly 
vertically  downward  from  the  cribri- 
form plate;  they  lodge  branches  of  the 

IP  i  •    i  !•    .    -i  j      FIG.  61. — Ethmoid  bone.     Inner  surface  of  right  lateral 

olfactory  nerve,  which  are  distributed  mass  (enlarged). 

on  the  mucous  membrane  covering  the 

bone.  The  back  part  of  this  surface  is  subdivided  by  a  narrow  oblique  fissure,  the 
superior  meatus  of  the  nose  (meatus  nasi  superior) ,  bounded  above  by  a  thin,  curved 
plate  of  bone,  the  superior  turbinated  bone  (concha  nasalis  superior}.  By  means  of  an 
orifice  at  the  upper  part  of  this  fissure  the  posterior  ethmoidal  cells  open  into  the 
superior  meatus.  Below,  and  in  front  of  the  superior  meatus,  is  seen  the  convex  sur- 
face of  the  middle  turbinated  bone.  It  extends  along  the  whole  length  of  the  inner 
surface  of  each  lateral  mass;  its  lower  margin  is  free  and  thick,  and  its  concavity, 
directed  outward,  assists  in  forming  the  middle  meatus.  It  is  by  a  large  orifice 
at  the  upper  and  front  part  of  the  middle  meatus  that  the  anterior  ethmoidal  cells, 
and  through  them  the  frontal  sinuses,  communicate  with  the  nose  by  means  of  a 
funnel-shaped  canal,  the  infundibulum  (infundibulum  ethmoidale).  The  cellular 
cavities  of  each  lateral  mass,  thus  walled  in  by  the  os  planum  on  the  outer  side  and 
by  the  other  bones  already  mentioned,  are  divided  by  a  thin  transverse  bony  parti- 
tion into  two  sets,  which  do  not  communicate  with  each  other;  they  are  termed 
the  anterior  and  posterior  ethmoidal  cells  or  sinuses.  The  former,  more  numerous, 
communicate  with  the  frontal  sinuses  above  and  the  middle  meatus  below  by 
means  of  a  long,  flexuous  canal,  the  infundibulum;  the  posterior,  less  numerous, 
open  into  the  superior  meatus  and  communicate  (occasionally)  with  the  sphe- 
noidal  sinuses.  In  some  cases  the  ethmoidal  sinuses  communicate  with  the  maxil- 
lary sinus.  In  some  cases  the  os  planum  never  develops,  and  the  ethmoidal 
sinuses  are  separated  from  the  orbit  merely  by  membrane. 

Development. — By  three  centres:  one  for  the  perpendicular  lamella,  and  one 
for  each  lateral  mass.  The  lateral  masses  are  first  developed,  ossific  granules 
making  their  appearance  in  the  os  planum  between  the  fourth  and  fifth  months 
of  fretal  life,  and  extending  into  the  spongy  bones.  At  birth  the  bone  consists  of 
the  two  lateral  masses,  which  are  small  and  ill-developed.  During  the  first  year 
after  birth  the  perpendicular  plate  and  crista  galli  begin  to  ossify,  from  a  single 
nucleus,  and  become  joined  to  the  lateral  masses  about  the  beginning  of  the  second 
year.  The  cribriform  plate  is  ossified  partly  from  the  perpendicular  plate  and 
partly  from  the  lateral  masses.  The  formation  of  the  ethmoidal  cells,  which  com- 
pletes the  bone,  does  not  commence  until  the  end  of  the  fourth  year. 

1  Annals  of  Surgery,  May,  1903. 


102  THE   SKELETON 

Articulations. — With  fifteen  bones:  the  sphenoid,  two  sphenoidal  turbinated, 
the  frontal,  and  eleven  of  the  face — the  two  nasal,  two  superior  maxillary,  two 
lachrymal,  two  palate,  two  inferior  turbinated,  and  the  vomer.  No  muscles  are 
attached  to  this  bone. 

DEVELOPMENT  OF  THE  CRANIUM. 

The  cerebral  vesicles  became  enclosed  by  an  envelope  of  membrane  derived  from  the  em- 
bryonic connective  tissue  about  the  head  end  of  the  chorda.  This  sac  from  the  mesoderm 
is  converted  into  fibrous  tissue,  and  is  known  -as  the  membranous  cranium.  In  adult  life 
the  dura  mater  represents  the  membranous  cranium. 

In  mammals  the  base  and  part  of  the  sides  of  the  membranous  cranium  become  cartilaginous, 
but  the  roof  and  the  remaining  part  of  the  sides  remain  membranous.  Ossification  com- 
mences in  the  roof  and  begins  at  a  later  period  in  the  base.  Although  ossification  begins  in 
the  membrane  bones  before  it  does  in  the  cartilage  bones,  and  the  bones  of  the  roof  appear 
before  the  bones  of  the  base  and  make  considerable  progress  in  their  growth,  at  birth  ossification 
is  more  advanced  in  the  base,  this  portion  of  the  skull  forming  a  solid,  immovable  groundwork. 

The  Skull  at  Different  Ages. — The  skull  at  birth  is  relatively  of  large  size  as  compared 
with  the  body.  The  cerebral  cranium  is  large  and  the  face  is  small.  The  fontanelles  are 
open  (see  below).  There  are  no  sutures,  but  the  margins  of  adjacent  bones  are  widely  sepa- 
rated by  fibrous  tissue  which  runs  from  the  periosteum  to  the  dura  mater.  The  bones  of  the 
vault  have  no  diploe  and  digital  impressions  are  absent  on  the  cranial  surfaces.  The  parietal 
eminences  and  the  frontal  eminences  are  very  distinct.1 

The  orbits  and  parietal  bones  are  large.  If  the  base  is  examined  it  is  noted  that  the 
mastoid  processes  are  absent,  that  the  lower  border  of  the  symphysis  of  the  jaw  is  on  a  level 
with  the  condyles  of  the  occipital  bone,  and  that  the  pterygoid  plates  form  "  a  large  angle  with 
the  skull  base,  whereas  in  the  adult  the  angle  is  almost  a  right  one,"  2  The  lower  jaw  at  birth 
is  shown  in  Fig.  91 . 

The  development  of  individual  bones  is  considered  under  the  appropriate  headings.  At 
puberty  various  pneumatic  cells  develop  in  bone  and  alter  the  form  of  the  head  and  face. 

After  the  eruption  of  the  first  set  of  teeth  the  age  can  be  determined  with  reasonable  cer- 
tainty, and  the  degree  of  obliteration  of  the  sutures  will  also  give  valuable  information.  In 
the  vast  majority  of  individuals  the  metopic  suture  becomes  a  mere  trace  during  the  fifth  or 
sixth  years.  Ossification  at  the  junction  of  the  coronal  and  sagittal  sutures  and  osseous  union 
of  the  sphenoid  and  basilar  portion  of  the  occipital  occur  during  maturity.  The  lower  jaw  of 
an  adult  is  shown  in  Fig.  93.  7 

In  old  age  much  of  the  diploe  disappears  and  the  bones  become  thinner  and  more  porous. 
The  alveolar  surfaces  of  the  jaws  are  absorbed  if  the  teeth  are  lost,  and  the  lower  jaw  alters 
its  form  (Fig.  94). 

Sexual  Differences. — It  is  not  always  possible  to  tell  with  certainty  a  woman's  skull  from 
a  man's,  but  certain  features  are  of  value  in  reaching  a  conclusion.  Virchow  maintained  that 
in  non-European  races  it  is  very  difficult  to  determine  the  sex  from  the  skull,  though  among 
some  savage  races  the  differences  may  be  great.3  It  is  always  to  be  borne  in  mind  that  a 
woman's  skull  may  be  of  the  masculine  type  and  a  man's  skull  may  be  of  the  feminine  type. 
There  is  no  constant  characteristic  significant  of  the  male  or  female  skull.  As  a  general  rule, 
the  female  skull  is  smaller  and  lighter  than  the  male;  the  muscular  ridges  and  processes 
are  less  distinct,  the  mastoid  processes  are  of  less  size,  the  orbital  margins  are  thin  and 
sharp,  the  forehead  is  more  vertical  and  the  vertex  is  more  flattened,  and  the  edge 
of  the  tympanic  plate  is  "  rounder  and  more  tuberculous "  (Cunningham).  The  frontal 
air  sinuses  are  smaller  in  women  than  in  men,  one  reason  why  the  glabella  is  more  promi- 
nent in  men.  The  flattening  of  the  vertex  in  women,  previously  referred  to,  causes  the  top 
of  the  head  to  be  at  a  more  marked  angle  with  the  forehead  than  in  men  (Ecker).  This 
characteristic  was  recognized  by  the  Greek  sculptors  (Havelock  Ellis).  The  cephalic  index, 
which  shows  the  relation  of  skull  breadth  to  skull  length,  is  of  doubtful  value  in  determin- 
ing sex. 

The  Fontanelles  (Fonticuli). 

Before  birth  the  bones  at  the  vertex  and  side  of  the  skull  are  sep'arated  from  each  other  by 
membranous  intervals  in  which  bone  is  deficient.  These  intervals  are  principally  found  at  the 
four  angles  of  the  parietal  bones.  Hence  there  are  six  fontanelles.  Their  formation  is  due  to 
the  wave  of  ossification  being  circular  and  the  bones  quadrilateral ;  the  ossific  matter  first  meets 
at  the  margins  of  the  bones,  at  the  points  nearest  to  their  centres  of  ossification,  and  vacuities 

1  J.  Bland  Sutton  in  Henry  Morris'  Human  Anatomy.  2  Ibid. 

3  Man  and  Woman,  by  Havelock  Ellis. 


SUPERNUMERARY,.  WORMIAN  OR  SUTURAL  BONES 


103 


or  spaces  are  left  at  the  angles,  which  are  called  fontanelles,  so  named  from  the  pulsations  of  the 
brain,  which  are  perceptible  at  the  anterior  fontanelle,  and  have  been  likened  to  the  rising  of  water 
in  a  fountain.  The  anterior  or  bregmatic  fontanelle  (fonticulusfrontalis}  (Fig.  62),  is  the  largest ; 
it  is  lozenge-shaped,  and  corresponds  to  the  junction  of  the  sagittal  and  coronal  sutures ;  the  poste- 
rior fontanelle  (fonticulus  occipitali.?)  (Fig-  62),  of  smaller  size,  is  triangular,  and  is  situated  at  the 
junction  of  the  sagittal  and  lambdoid  sutures ;  the  remaining  ones,  the  antero-lateral  and  the  pos- 
tero-lateral  fontanelles  (fonticulus  sphenoidalis  etfoniiculus  Ihastoidens}  (Fig.  63) , are  situated  at 
the  inferior  angles  of  each  parietal  bone.  The  antero-lateral  fontanelle  is  closed  in  from  one  to  two 
months  after  birth;  the  postero-lateral  is  not  completely  closed  until  the  end  of  the  first  year.  The 
posterior  fontanelle  is  closed  in  one  or  two  months  after  birth ;  the  anterior  fontanelle  remains  open 
until  the  middle  of  the  first  or  the  beginning  of  the  second  year.  Sometimes  the  anterior  fontanelle 
remains  open  beyond  two  years,  and  is  occasionally  persistent  throughout  life.  Each  space  is  grad- 
ually filled  in  by  an  extension  of  the  ossifying  process  or  by  the  development  of  a  Wormian  bone. 

Supernumerary,  Wormian,1  Sutural  or  Epactal  Bones  (Ossa  Triquetra). 

In  addition  to  the  constant  centres  of  ossification  of  the  skull,  additional  ones  are  occasion- 
ally found  in  the  course  of  the  sutures.  These  form  irregular,  isolated  bones,  interposed  between 
the  cranial  bones,  and  have  been  termed  Wormian  bones  or  Ossa  triquetra.  They  are  most 


FIG.  62. — Skull  at  birth,  showing  the  anterior  and 
posterior  fontanelles. 


FIG.  63.— The  lateral  fontanelles. 


frequently  found  in  the  course  of  the  lambdoid  suture,  but  occasionally  also  occupy  the  situation 
of  the  fontanelles,  especially  the  posterior  and,  more  rarely,  the  anterior.  Frequently  one  is 
found  between  the  anterior  inferior  angle  of  the  parietal  bone  and  the  greater  wing  of  the 


FIG.  64. — Wormian  bones. 


FIG.  65. 


FIG.  66. 


sphenoid,  the  epicteric  bone  or  the  pterion  ossicle  (Fig.  63).  They  have  a  great  tendency  to  be 
symmetrical  on  the  two  sides  of  the  skull,  and  they  vary  much  in  size,  being  in  some  cases  not 
larger  than  a  pin's  head,  and  confined  to  the  outer  table;  in  other  cases  so  large  that  one  pair  of 
these  bones  may  form  the  whole  of  the  occipital  bone  above  the  superior  curved  lines,  as  described 

1  Wormius,  a  physician  of  Copenhagen,  is  said  to  have  given  the  first  detailed  description  of  these  bones. 


104 


THE  SKELETON 


by  Beclard  and  Ward.  Their  number  is  generally  limited  to  two  or  three,  but  more  than  a 
hundred  have  been  found  in  the  skull  of  an  adult  hydrocephalic  skeleton.  In  their  development, 
structure,  and  mode  of  articulation  they  resemble  the  other  cranial  bones. 

Congenital  Fissures  and  Gaps. 

An  arrest  in  the  ossifying  process  may  give  rise  to  deficiencies  or  gaps;  or  to  fissures,  which 
are  of  importance  in  a  medico-legal  point  of  view,  as  they  are  liable  to  be  mistaken  for  fractures. 
The  fissures  generally  extend  from  the  margins  toward  the  centre  of  the  bone,  but  the  gaps 
may  be  found  in  the  middle  as  well  as  at  the  edges.  In  course  of  time  they  may  become  covered 
with  a  thin  lamina  of  bone. 

BONES  OF  THE  FACE    (OSSA  FACIEI  . 

The  Facial  Bones  are  fourteen  in  number — viz.,  the 
Two  Nasal.  Two  Palate. 

Two  Superior  Maxillae.  Two  Inferior  Turbinated. 

Two  Lachrymal.  Vomer. 

Two  Malar.  Inferior  Maxilla  or  Mandible. 

,  "  Of  these,  the  upper  and  lower  jaws  are  the  fundamental  bones  for  mastication, 
and  the  others  are  accessories;  for  the  chief  function  of  the  facial  bones  is  to 
provide  an  apparatus  for  mastication,  while  subsidiary  functions  are  to  provide  for 
the  sense  organs  (eye,  nose,  tongue)  and  a  vestibule  to  the  respiratory  and  vocal 
organs.  Hence  the  variations  in  the  shape  of  the  face  in  man  and  the  lower 
animals  depend  chiefly  on  the  question  of  the  character  of  their  food  and  their 
mode  of  obtaining  it."1 

The  Nasal  Bones  (Ossa  Nasalia). 

The  nasal  (nasus,  the  nose)  are  two  small  oblong  bones,  varying  in  size  and 
form  in  different  individuals;  they  are  placed  side  by  side  at  the  middle  and  upper 


Nasal  bone. 
Nasal  proc. 


Infra-orbital 
foramen. 


Ant.  nasal  spine. 


Lachrymal  bone. 


Orbital  surface. 
Infra-orbital 
groove. 


Artie,  with  malar. 


Post,  dental 
canals. 


Maxillary 
tuberosity. 


FIG.  67. — Nasal  and  lachrymal  bones  in  situ. 


part  of  the  face,  forming,  by  their  junction,  "the  bridge"  of  the  nose  (Fig.  67). 
Each  bone  presents  for  examination  two  surfaces  and  four  borders. 


1  W.  W.  Keen,  American  edition,  1887,  p.  185. 


THE  SUPERIOR    MAXILLARY   BOXES 


105 


Surfaces.  Outer  Surface. — The  outer  surface  is  concave  from  above  downward, 
convex  from  side  to  side;  it  is  covered  by  the  Pyramidalis  and  Compressor  nasi 
muscles,  and  gives  attachment  at  its  upper  part  to  a  few  fibres  of  the  Occipito- 
frontalis  muscle  (Theile).  It  is  marked  by  numerous  small  arterial  furrows,  and 
perforated  about  its  centre  by  a  foramen  (foramen  nasale),  sometimes  double, 
for  the  transmission  of  a  small  vein. 

Inner  Surface. — The  inner  surface  is  concave  from  side  to  side,  convex  from 
above  downward;  in  which  direction  it  is  traversed  by  a  longitudinal  groove 
(sometimes  a  canal),  for  the 

With  frontal  bone. 

With 


With 
'opposite  bone. 


Outer  Surface. 

FIG.  68. — Right  nasal  bone. 


frontal  spine. 

Crest. 

With 

perpendicular 
plate  of 
ethmoid. 


Groove  for  nasal  nerve. 


Inner  Surface. 

FIG.  69. — Left  nasal  bone. 


passage  of  a  branch  of  the  nasal 
nerve. 

Borders.  Superior  Border.— 
The  superior  border  is  narrow, 
thick,  and  serrated,  for  articula- 
tion with  the  nasal  notch  of  the 
frontal  bone. 

Inferior  Border. — The  inferior 
border  is  broad,  thin,  sharp,  in- 
clined  obliquely  downward,  out- 
ward, and  backward,  and  serves 
for  the  attachment  of  the  lateral 
cartilage  of  the  nose.    This  bor- 
der presents,  about  its  middle,  a  notch,  through  which  passes  the  branch  of  the 
nasal  nerve  above  referred  to,  and  is  prolonged  at  its  inner  extremity  into  a  sharp 
spine,  which,  when  articulated  with  the  opposite  bone,  forms  the  nasal  angle. 

External  Border. — The  external  border  is  serrated,  bevelled  at  the  expense  of 
the  internal  surface  above  and  of  the  external  below,  to  articulate  with  the  nasal 
process  of  the  superior  maxillary. 

Internal  Border. — The  internal  border,  thicker  above  than  below,  articulates 
with  its  fellow  of  the  opposite  side,  and  is  prolonged  behind  into  a  vertical  crest, 
which  forms  part  of  the  septum  of  the  nose;  this  crest  articulates  above  down- 
ward with  the  nasal  spine  of  the  frontal  above,  and  the  perpendicular  plate  of 
the  ethmoid,  and  the  triangular  septal  cartilage  of  the  nose. 

Development. — By  one  centre  for  each  bone,  which  appears  about  the  eighth  week. 

Articulations. — With  four  bones:  two  of  the  cranium,  the  frontal  and  ethmoid, 
and  two  of  the  face,  the  opposite  nasal  arid  the  superior  maxillary. 

Attachment  of  Muscles. — A  few  fibres  of  the  Occipito-frontalis  muscle. 

The  Superior  Maxillary  Bones  (Upper  Jaw  Bones  or  Maxillae). 

The  superior  maxillae  (maxilla,  the  jaw  bone)  are  the  most  important  bones 
of  the  face  from  a  surgical  point  of  view,  on  account  of  the  number  of  diseases  to 
which  some  of  their  parts  are  liable.  Their  careful  examination  becomes,  there- 
fore, a  matter  of  considerable  interest.  They  are  the  largest  bones  of  the  face, 
excepting  the  lower  jaw,  and  form,  by  their  union,  the  whole  of  the  upper  jaw. 
Each  maxilla  assists  in  the  formation  of  three  cavities,  the  roof  of  the  mouth,  the 
floor  and  outer  wall  of  the  nasal  fossae,  and  the  floor  of  the  orbit,  and  also  enters 
into  the  formation  of  two  fossae,  the  zygomatic  and  spheno-maxillary,  and  two 
fissures,  the  spheno-maxillary  and  pterygo-m axillary.  The  bone  presents  for  exam- 
ination a  body  and  four  processes — malar,  nasal,  alveolar,  and  palate. 

The  Body  of  the  Superior  Maxilla  (Corpus  Maxillae). 

The  body  is  somewhat  cuboid  and  is  hollowed  out  in  its  interior  to  form  a 
large  cavity,  the  antnun  of  Highmore  (sinus  maxillaris).  Its  surfaces  are  four — 


100 


THE  SKELETON 


an  external  or  facial,  a  posterior  or  zygoraatic,  a  superior  or  orbital,  and  an 
internal  or  nasal. 

Surfaces.  External  Surface  (fades  anterior}. — The  external  anterior  or  facial 
surface  (Fig.  70)  is  directed  forward  and  outward.  It  presents  at  its  lower  part  a 
series  of  eminences  corresponding  to  the  position  of  the  anterior  five  alveoli  (juga 
alveolaria) .  Just  above  those  for  the  incisor  teeth  is  a  depression,  the  incisive  or 
myrtiform  fossa,  which  gives  origin  to  the  Depressor  ahe  nasijand  below  it  to  the 
alveolar  border  is  attached  a  slip  of  the  Orbicularis  oris.  Above  and  a  little  exter- 
nal to  it  the  Compressor  nasi  arises.  More  external  is  another  depression,  the 
canine  fossa  (fossa  canina),  larger  and  deeper  than  the  incisive  fossa,  from  which  it 
is  separated  by  a  vertical  ridge,  the  canine  eminence,  corresponding  to  the  socket  of 
the  canine  tooth.  The  canine  fossa  gives  origin  to  the  Levator  anguli  oris.  Above 
the  canine  fossa  is  the  infraorbital  foramen  (foramen  infraorbitale) ,  the  termination 

Outer  Surface. 


TENDO    OCUL 


Incisive  fossa. 


Posterior  dental 
canals. 


Maxillary  tuberosity. 


FIG.  70. — Left  superior  maxilla.     Outer  surface. 

of  the  infraorbital  canal ;  it  transmits  the  infraorbital  vessels  and  nerve.  Some- 
times the  infraorbital  canal  opens  by  two,  very  rarely  by  three,  orifices  on  the 
face.  Above  the  infraorbital  foramen  is  the  margin  of  the  orbit  (margo  infraor- 
bitalis),  which  affords  partial  attachment  to  the  Levator  labii  superioris  proprius. 
To  the  sharp  margin  of  bone  which  bounds  this  surface  in  front  and  separates 
it  from  the  internal  surface  is  attached  the  Dilator  naris  posterior. 

Posterior  Surface  (fades  infratemporalis) . — The  posterior  or  zygomatic  or  infra- 
temporal  surface  is  convex,  directed  backward  and  outward,  and  forms  part  of  the 
zygomatic  fossa.  It  is  separated  from  the  facial  surface  by  a  strong  ridge  of  bone, 
the  malar  process,  which  extends  upward  from  the  socket  of  the  second  molar 
tooth.  It  presents  about  its  centre  several  apertures  leading  to  canals  in  the 
substance  of  the  bone;  they  are  termed  the  posterior  dental  canals  (foramina  alveo- 
laria), and  transmit  the  posterior  dental  vessels  and  nerves.  At  the  lower  part  of 
this  surface  is  a  rounded  eminence,  the  maxillary  tuberosity  (tuber  maxillare), 
especially  prominent  after  the  growth  of  the  wisdom-tooth,  rough  on  its  inner 


THE  SUPERIOR    MAXILLARY  BONES  107 

side  for  articulation  with  the  tuberosity  of  the  palate  bone,  and  sometimes  with 
the  external  pterygoid  plate.  It  gives  attachment  to  a  few  fibres  of  origin  of 
the  Internal  pterygoid  muscle.  Immediately  above  this  is  a  smooth  surface, 
which  forms  the  anterior  boundary  of  the  spheno-maxillary  fossa;  it  presents  a 
groove  which,  running  obliquely  downward,  is  converted  into  a  canal  by  articu- 
lation with  the  palate  bone,  forming  the  posterior  palatine  or  palato-maxillary  canal 
for  the  descending  palatine  artery  and  great  palatine  nerve. 

Superior  Surface  (fades  orbitalis). — The  superior  or  orbital  surface  is  thin, 
smooth,  triangular,  and  forms  part  of  the  floor  of  the  orbit.  It  is  bounded  in- 
ternally by  an  irregular  margin  which  in  front  presents  a  notch,  the  lachrymal  notch 
(incisura  lacrimalis),  which  receives  the  lachrymal  bone;  in  the  middle  articulates 
with  the  os  planum  of  the  ethmoid,  and  behind  with  the  orbital  process  of  the 
palate  bone;  bounded  externally  by  a  smooth,  rounded  edge  which  enters  into  the 
formation  of  the  spheno-maxillary  fissure,  and  which  sometimes  articulates  at  its 
anterior  extremity  with  the  orbital  plate  of  the  sphenoid;  bounded  in  front  by  part 
of  the  circumference  of  the  orbit,  which  is  continuous  on  the  inner  side  with  the 
nasal,  on  the  outer  side  with  the  malar  process.  Along  the  middle  line  of  the  orbital 
surface  is  a  deep  groove,  the  infraorbital  groove  (sulcus  infraorbitalis) ,  for  the  pas- 
sage of  the  infraorbital  vessels  and  nerve.  The  groove  commences  at  the  middle 
of  the  outer  border  of  this  surface,  and,  passing  forward,  terminates  in  a  canal, 
which  subdivides  into  two  branches.  One  of  the  canals,  the  infraorbital  canal 
(canalis  infraorbitalis},  opens  just  below  the  margin  of  the  orbit;  the  other,  which 
is  smaller,  runs  downward  in  the  substance  of  the  anterior  wall  of  the  antrum; 
it  is  called  the  anterior  dental  canal,  and  transmits  the  anterior  dental  vessels 
and  nerve  to  the  front  teeth  of  the  upper  jaw.  From  the  back  part  of  the 
infraorbital  canal  a  second  small  canal  is  sometimes  given  off,  which  runs  down- 
ward in  the  outer  wall  of  the  antrum,  and  conveys  the  middle  dental  nerve  to 
the  bicuspid  teeth.  Occasionally  this  canal  is  derived  from  the  anterior  dental. 
At  the  inner  and  fore  part  of  the  orbital  surface,  just  external  to  the  lachrymal 
groove  for  the  nasal  duct,  is  a  depression  which  gives  origin  to  the  Inferior  oblique 
muscle  of  the  eye. 

Internal  Surface. — The  internal  surface  (Figs.  71  and  81)  is  unequally  divided 
into  two  parts  by  a  horizontal  projection  of  bone,  the  palate  process  (processus 
palatinus) :  the  portion  above  the  palate  process  is  known  as  the  nasal  surface  (fades 
namlis}.  It  forms  part  of  the  outer  wall  of  the  nasal  fossa.  Below  the  palate 
process  is  the  cavity  of  the  mouth.  The  superior  division  of  the  nasal  surface 
presents  a  large,  irregular  opening,  the  maxillary  hiatus  (hiatus  maxillaris),  leading 
into  the  antrum  of  Highmore.  At  the  upper  border  of  this  aperture  are  numerous 
broken  cellular  cavities,  which  in  the  articulated  skull  are  closed  in  by  the  ethmoid 
and  lachrymal  bones.  Below  the  aperture  is  a  smooth  concavity  which  forms  part 
of  the  inferior  meatus  of  the  nasal  fossae,  and  behind  it  is  a  rough  surface  which 
articulates  with  the  perpendicular  plate  of  the  palate  bone,  traversed  by  a  groove 
which,  commencing  near  the  middle  of  the  posterior  border,  runs  obliquely  down- 
ward and  forward,  and  forms,  when  completed  by  its  articulation  with  the  palate 
bone,  the  posterior  palatine  or  palato-maxillary  canal.  In  front  of  the  opening  of  the 
antrum  is  a  deep  groove,  converted  into  a  canal  (canalis  nasolacrimalis)  by  the 
lachrymal  and  inferior  turbinated  bones.  The  groove  is  called  the  lachrymal  groove 
(sulcus  lacrimalis),  and  lodges  the  nasal  duct.  More  anteriorly  is  a  well-marked 
rough  ridge,  the  inferior  turbinated  crest  (crista  conchalis),  for  articulation  with  the 
inferior  turbinated  bone.  The  shallow  concavity  above  this  ridge  forms  part  of  the 
middle  rneatus  of  the  nose,  while  that  below  it  forms  part  of  the  inferior  meatus. 
The  portion  of  this  surface  below  the  palate  process  is  concave,  rough,  and  uneven, 
and  perforated  by  numerous  small  foramina  for  the  passage  of  nutrient  vessels. 
It  enters  into  the  formation  of  the  roof  of  the  mouth. 


108 


THE   SKELETON 


The  Antrum  of  Highmore,  Maxillary  Antrum,  or  Maxillary  Sinus  (sinus  maxil- 
laris),  is  a  pyramidal  cavity  hollowed  out  of  the  body  of  the  maxillary  bone. 
It  varies  much  in  size.  It  is  in  most  cases  a  large  cavity,  but  in  some  is  very 
small.  The  apex  of  the  antrum,  directed  outward,  is  formed  by  the  malar  process; 


Bones  partially  dosing  orifice  of  antrum 
marked  in  outline. 


Ethmoid. 

Inferior  turbinated. 
Palate. 


Anterior  nasal  spine. 


Bristle  passed 
through  anterior 
palatine  canal. 


FIG.  71. — Left  superior  maxilla.     Internal  surface. 


its  base  by  the  outer  wall  of  the  nose.  Its  walls  are  everywhere  exceedingly  thin, 
and  correspond  to  the  orbital,  facial,  and  zygomatic  surfaces  of  the  body  of  the 
bone.  The  antral  floor  is,  in  most  persons,  on  a  level  with  the  floor  of  the  nasal 
fossa,  but  in  some  individuals  it  is  on  a  lower  level.  Not  unusually  the  inner 
wall  of  the  antrum  will  be  found  to  contain  depressions  or  pockets.  In  rare 
instances  an  antral  cavity  is  made  into  two  by  a  bony  septum.  Its  inner  wall  or 
base  presents,  in  the  disarticulated  bone,  a  large,  irregular  aperture  (hiatus 
maxillaris),  which  communicates  with  the  nasal  fossa.  The  margins  of  this 
aperture  are  thin  and  ragged,  and  the  aperture  itself  is  much  contracted  by  its 
articulation  with  the  ethmoid  above,  the  inferior  turbinated  below,  and  the 
palate  bone  behind.1  In  the  articulated  skull  this  cavity  communicates  with 
the  middle  meatus  of  the  nasal  cavity,  generally  by  two  small  apertures  left 
between  the  above-mentionsd  bones.  In  the  recent  state  usually  only  one  small 
opening  exists,  near  the  upper  part  of  the  cavity,  sufficiently  large  to  admit  the 
end  of  a  probe,  the  other  being  closed  by  the  lining  membrane  of  the  sinus.  That 
the  opening  into  the  nasal  fossa  does  not  afford  the  best  drainage  is  demon- 
strated, when  we  note  that  it  is  at  the  highest  and  not  at  the  lowest  point  of  the 
antrum.  "In  rare  instances  the  antrum  communicates  with  the  anterior  eth- 
moidal  cells,  or  the  orbital  and  posterior  ethmoidal  cells  and  sphenoidal  sinuses."2 
At  birth  the  antrum  exists,  though  in  a  rudimentary  state.  It  attains  its  full 
size  from  the  twelfth  to  the  fourteenth  year. 

Crossing  the  cavity  of  the  antrum  are  often  seen  several  projecting  laminae  of 
bone,  similar  to  those  seen  in  the  sinuses  of  the  cranium;  and  on  its  posterior  wall 


1  In  some  cases,  at  any  rate,  the  lachrymal  bone  encroaches  slightly  on  the  anterior  superior  portion  of  the 
opening,  and  assists  in  forming  the  inner  wall  of  the  antrum. — ED.  of  15th  English  Edition. 

2  D.  Kerfoot  Shute,  in  the  Reference  Handbook  of  the  Medical  Sciences. 


THE  SUPERIOR    MAXILLARY  BONES  109 

arc  the  posterior  dental  canals,  transmitting  the  posterior  dental  vessels  and  nerves 
to  the  teeth.  Projecting  into  the  floor  are  several  conical  processes,  corresponding 
to  the  roots  of  the  first  and  second  molar  teeth;1  in  some  cases  the  floor  is  per- 
forated by  the  teeth  in  this  situation. 

It  is  from  the  extreme  thinness  of  the  walls  of  this  cavity  that  we  are  enabled  to  explain  how 
a  tumor  growing  from  the  antrum  encroaches  upon  the  adjacent  parts,  pushing  up  the  floor  of 
the  orbit,  and  displacing  the  eyeball,  projecting  inward  into  the  nose,  protruding  forward  on 
to  the  cheek,  and  making  its  way  backward  into  the  zygomatic  fossa  and  downward  into  the 
mouth. 

The  Processes  of  the  Superior  Maxillae. 

Malar  Process  (processus  zygomaticus). — The  malar  process  is  a  rough,  trian- 
gular eminence,  situated  at  the  angle  of  separation  of  the  facial  from  the  zygo- 
matic surface.  In  front  it  is  concave,  forming  part  of  the  facial  surface;  behind 
it  is  also  concave,  and  forms  part  of  the  zygomatic  fossa;  above  it  is  rough  and 
serrated  for  articulation  with  the  riialar  bone;  whilst  below  a  prominent  ridge 
marks  the  division  between  the  facial  and  zygomatic  surfaces.  A  small  part  of 
the  Masseter  muscle  arises  from  this  process. 

Nasal  Process  (processus  frontalis). — The  nasal  process  is  a  strong,  triangular 
plate  of  bone,  which  projects  upward,  inward,  and  backward  by  the  side  of  the 
nose,  forming  part  of  its  lateral  boundary.  Its  external  surface  is  concave,  smooth, 
perforated  by  numerous  foramina,  and  gives  attachment  to  the  Levator  labii 
superioris  alseque  nasi,  the  Orbicularis  palpebrarum,  and  Tendo  oculi.  Its 
internal  surface  forms  part  of  the  outer  wall  of  the  nasal  fossae;  at  its  upper 
part  it  presents  a  rough,  uneven  surface,  which  articulates  with  the  ethmoid 
bone,  closing  in  the  anterior  ethmoidal  cells;  below  this  is  a  transverse  ridge,  the 
superior  turbinated  crest  (crista  ethmoidalis),  for  articulation  with  the  middle  tur- 
binated  bone  of  the  ethmoid,  bounded  below  by'  a  shallow,  smooth  concavity 
which  forms  part  of  the  middle  meatus;  below  this  again  is  the  inferior  turbinated 
crest  (already  described),  where  the  process  joins  the  body  of  the  bone.  Its  upper 
border  articulates  with  the  frontal  bone.  The  anterior  border  of  the  nasal  process 
is  thin,  directed  obliquely  downward  and  forward,  and  presents  a  serrated  edge  for 
articulation  with  the  nasal  bone;  its  posterior  border  is  thick,  and  hollowed  into 
a  groove,  the  lachrymal  groove  (sulcus  lacrimalis) ,  for  the  naso-lachrymal  duct:  of 
the  two  margins  of  this  groove,  the  inner  one  articulates  with  the  lachrymal  bone; 
the  outer  one  forms  part  of  the  circumference  of  the  orbit.  Just  where  the  latter 
joins  the  orbital  surface  is  a  small  tubercle,  the  lachrymal  tubercle ;  this  serves  as 
a  guide  to  the  position  of  the  lachrymal  sac  in  the  operation  for  fistula  lachrymalis. 
The  lachrymal  groove  in  the  articulated  skull  is  converted  into  a  canal  (canalis 
lacrimalis)  by  the  lachrymal,  bone  and  lachrymal  process  of  the  inferior  turbin- 
ated; it  is  directed  downward,  and  a  little  backward  and  outward,  is  about  the 
diameter  of  a  goose-quill,  slightly  narrower  in  the  middle  than  at  either  extremity, 
and  terminates  below  in  the  inferior  meatus.  It  lodges  the  nasal  duct. 

Alveolar  Process  (processus  alveolaris). — The  alveolar  process  is  the  thickest 
and  most  spongy  part  of  the  bone,  broader  behind  than  in  front,  and  excavated 
into  deep  cavities  for  the  reception  of  the  teeth  (alveoli  dentales).  These  cavities 
are  eight  in  number,  and  vary  in  size  and  depth  according  to  the  teeth  they  con- 
tain. That  for  the  canine  tooth  is  the  deepest;  those  for  the  molars  are  the 
widest,  and  subdivided  into  minor  cavities  by  septa;  those  for  the  incisors  are 
single,  but  deep  and  narrow.  The  limbus  alveolaris  is  the  broad  inferior  margin 
of  the  alveolar  process.  On  the  anterior  surface  are  five  projections  correspond- 

1  The  number  of  teeth  whose  fangs  are  in  relation  to  the  floor  of  the  antrum  is  variable.  The  antrum  '  'may 
extend  so  as  to  be  in  relation  to  all  the  teeth  of  the  true  maxilla,  from  the  canine  to  the  dens  sapienlice.''  (See  Mr. 
Salter  on  Abscess  of  the  Antrum,  in  a  System  of  Surgery,  edited  by  T.  Holmes,  2d  ed.,  vol.  iv.  p.  356.) — ED.  of 
15th  English  Edition. 


110 


THE   SKELETON 


Foramen  of  Stenson. 


Palate  process  of 
maxillary  bone 


ior  palatine  canal. 


ing  to  the  five  anterior  alveoli.  They  are  called  juga  alveolaria.  The  cavities 
for  the  teeth  are  separated  by  septa  inter  alveolaria.  The  Buccinator  muscle  arises 
from  the  outer  surface  of  this  process  as  far  forward  as  the  first  molar  tooth. 

Palate  Process  (processus  palatinus}. — The  palate  process,  thick  and  strong, 
projects  horizontally  inward  from  the  inner  surface  of  the  bone.    It  is  much  thicker 

in  front  than  behind,  and 

Ant  nor  palatine  canal.  forms  a  considerable  part 

of  the  floor  of  the  nostril 
and  the  roof  of  the  mouth. 
^Foramen  of  Scarpa.  Its  inferior  surface  (Fig. 
72)  is  concave,  rough  and 
uneven,  contains  numer- 
ous little  cavities  for  the 
glands  of  the  mucous 
membrane,  and  forms 
part  of  the  roof  of  the 
mouth.  This  surface  is 
perforated  by  numerous 
foramina  for  the  passage 
of  the  nutrient  vessels, 
channelled  at  the  back 
part  of  its  alveolar  bor- 
der by  a  longitudinal 

Horizontal  plate'    \      Xv"    /    /  groo ve, sometimes  a  canal, 

of  palate  bone.       \       \J/  /  for   the    transmission   of 

the  posterior  palatine 
vessels,  and  the  great  pos- 
terior palatine  nerve  from 
Meckel's  ganglion,  and 
presents  little  depressions 
for  the  lodgement  of  the  palatine  glands.  When  the  two  superior  maxillte 
bones  are  articulated  together,  a  large  orifice  may  be  seen  in  the  middle 
line,  immediately  behind  the  incisor  teeth.  This  is  the  anterior  palatine  fossa 
(foramen  incisivum}.  On  examining  the  bottom  of  this  fossa  four  canals  are 
seen :  two  branch  off  laterally  to  the  right  and  left  nasal  fossfe,  and  two,  one  in 
front  and  one  behind,  lie  in  the  middle  line.  The  former  pair  of  these  openings 
are  named  the  incisor  foramina  or  foramina  of  Stenson ;  they  are  the  openings  of 
the  forking  incisor  canal  (canalis  incisivus),  through  which  pass  the  anterior  or 
terminal  branches  of  the  descending  or  posterior  palatine  arteries,  which  ascend 
from  the  mouth  to  the  nasal  fossae,  and  they  contain  the  remains  of  Jacobson's 
organ.  The  canals  in  the  middle  line  are  termed  the  foramina  of  Scarpa,  and 
transmit  the  naso-palatine  nerves,  the  left  passing  through  the  anterior,  and  the 
right  through  the  posterior,  canal.  Occasionally  in  adults'  skulls,  often  in  chil- 
dren's skulls,  on  the  palatal  surface  of  the  process  a  delicate  linear  suture  may 
sometimes  be  seen  extending  from  the  anterior  palatine  fossa  to  the  interval 
between  the  lateral  incisor  and  the  canine  tooth.  This  marks  out  the  inter- 
maxillary or  pre-maxillary  bones  or  the  incisive  bone  (os  incisivum)  on  each  side. 
It  is  the  portion  of  the  upper  jaw  which  is  in  front  of  the  anterior  palatine 
foramen,  and  which  in  some  animals  exists  permanently  as  a  separate  piece. 
It  includes  the  whole  thickness  of  the  alveolus,  the  corresponding  part  of  the  floor 
of  the  nose,  and  the  anterior  nasal  spine,  and  contains  the  sockets  of  the  incisor 
teeth.  The  pre-maxillary  bone  has  a  separate  centre  of  ossification  and  develops 
in  association  with  the  vertical  plate  of  the  ethmoid  and  the  vomer.  The  incisive 
bones,  which  are  always  present  in  the  fretus,  usually  join  the  rest  of  the  bone 


Accessory  palatine  foramen. 
FIG.  72. — The  palate  and  alveolar  arch. 


THE   SUPERIOR  MAXILLARY  BONES 


111 


ENDO-GNATHION 


ENDO-GNATHION 


MCSO-GNATHION 


EXO-GNATHION 


ENDO-MESO-GNATHION 
SUTURE 


ENDO-EXO-GNATHION 
SUTURE 


MESO- EXO-GNATHION 
SUTURE 


early  in  development,  more  or  less  well-marked  sutures  (sutura  incisiva)  indi- 
cating the  lines  of  union.  In  double  hare-lip  the  incisive  bones  covered  by  the 
median  part  of  the  lip  are  frequently  not  joined  to  the  palate  processes  of  the 
superior  maxillary  bones,  but  are  fixed  to  the  nasal  septum.  Albrecht  maintains 
that  instead  of  two  intermaxillary  seg- 
ments or  incisive  bones,  each  carrying 
two  incisor  teeth,  there  are  originally 
four,  each  carrying  the  rudiment  of 
one  tooth  and  each  of  a  triangular 
shape,  the  apices  approaching  at  the 
anterior  palatine  canal.  The  seg- 
ments are  separated  by  five  sutures. 
The  maxilla  is  called  the  exo-gnathion, 
each  mesial  segment  is  called  an  endo- 
gnathion,  and  each  lateral  segment 
a,  meso-gnathion.  In  hare-lip  the  cleft 

may  be  purely  in  the  soft  parts,  but  may  pass  into  the  nostril,  the  alveolar  portion 
of  the  maxilla,  or  through  the  palate  bone  (cleft  palate).  In  hare-lip  with  cleft 
palate  (alveolar  hare-lip)  Kolliker  believes  that  the  cleft  is  between  the  maxilla  and 
the  intermaxillary  bone;  that  is,  between  the  exo-gnathion  and  the  meso-gnathion. 
Albrecht  is  of  the  opinion  that  the  cleft  is  between  the  endo-gnathion  and  the  meso- 
gnathion.  In  some  cases  of  double  hare-lip  the  pre-maxillary  segment  contains  the 
germs  of  four  incisors,  and  in  such  a  case  the  cleft  must  be  between  the  exo- 
gnathion  and  the  meso-gnathion.  In  other  cases  it  contains  but  two,  and  in  such 
a  case  the  cleft  must  be  as  indicated  by  Albrecht,  as  Fergusson's  explanation  is 
not  in  accordance  with  our  knowledge  of  development.  Fergusson  believed  that 
if  the  germs  of  four  incisors  are  not  present  the  missing  ones  were  lost  in  the  gap. 
The  upper  surface  of  the  palate  process  is  concave  from  side  to  side,  smooth,  and 
forms  part  of  the  floor  of  the  nose.  It  presents  the  upper  orifices  of  the  foramina  of 


FIG.  73. — The  pre-maxilla  and  its  sutures.     (Albrecht.) 


FIG.  74. — Kolliker's  theory  of  alveolar  hare-lip. 
(Poirier  and  Charpy.) 


FIG.  75. — Alveolar  hare-lip  according  to  the  theory  of 
Albrecht.     (Poirier  and  Charpy.) 


Stenson  and  Scarpa,  the  former  being  on  each  side  of  the  middle  fine,  the  latter 
being  situated  in  the  intermaxillary  suture,  and  therefore  not  visible  unless  the  two 
bones  are  placed  in  apposition.  The  outer  border  of  the  palate  process  is  incorpor- 
ated with  the  rest  of  the  bone.  The  inner  border  is  thicker  in  front  than  behind,  and 
is  raised  above  into  a  ridge,  the  nasal  crest  (crista  nasalis),  which,  with  the  corre- 
sponding ridge  in  the  opposite  bone,  forms  a  groove  for  the  reception  of  the  vomer. 
In  front  this  crest  rises  to  a  considerable  height,  and  this  portion  is  named  the  incisor 
crest.  The  anterior  margin  is  bounded  by  the  thin,  concave  border  of  the  opening 
of  the  nose,  prolonged  forward  internally  into  a  sharp  process,  forming,  with  a 
similar  process  of  the  opposite  bone,  the  anterior  nasal  spine  (spina  nasalis  anterior}. 
The  posterior  border  is  serrated  for  articulation  with  the  horizontal  plate  of  the 
palate  bone. 


112 


THE   SKELETON 


Anterior  Surface. 


Inferior  Surface. 


Development. — This  bone  commences  to  ossify  at  a  very  early  period,  and 
ossification  proceeds  in  it  with  great  rapidity,  so  that  it  is  difficult  to  ascertain  with 
certainty  its  precise  number  of  centres.  It  appears,  however,  probable  that  it  is 
ossified  from  four  centres,  which  are  deposited  in  membrane.  1.  One  which  forms 
that  portion  of  the  body  of  the  bone  which  lies  internal 
to  the  infraorbital  canal,  including  the  floor  of  the  orbit, 
the  outer  wall  of  the  nasal  fossa,  and  the  nasal  process. 
2.  A  second  which  gives  origin  to  that  portion  of  the 
bone  which  lies  external  to  the  infraorbital  canal  and  the 
malar  process.  3.  A  third  from  which  is  developed  the 
palatine  process  posterior  to  Stenson's  canal  and  the  ad- 
joining part  of  the  nasal  wall.  4.  And  a  fourth  for  the 
front  part  of  the  alveolus  which  carries  the  incisor  teeth 
and  corresponds  to  the  pre-maxillary  bone  of  the  lower 
animals.  These  centres  appear  about  the  eighth  week, 
and  by  the  tenth  week  the  three  first-named  centres 
have  become  fused  together  and  the  bone  consists  of  two 
portions,  one  the  maxilla  proper,  and  the  other  the  pre- 
maxillary  portion.  The  suture  between  these  two  por- 
tions on  the  palate  persists  till  middle  life,  but  is  not  to 
be  seen  on  the  facial  surface.  This  is  believed  by  Cal- 
lender  to  be  due  to  the  fact  that  the  front  wall  of  the 
sockets  of  the  incisive  teeth  is  not  formed  by  the  pre- 
FIG.  76.  —  Development  of  maxillary  bone,  but  by  an  outgrowth  from  the  facial  part 

•superior    maxillary    bone.     At         .    ,  *        .  ...»         „, 

birth.  ot  the  superior  maxilla.  1  he  antrum  appears  as  a  shal- 

low groove  on  the  inner  surface  of  the  bone  at  an  earher 

period  than  any  of  the  other  nasal  sinuses,  its  development  commencing  about 
the  fourth  month  of  foatal  life.  The  sockets  for  the  teeth  are  formed  by  the 
growing  downward  of  two  plates  from  the  dental  groove,  which  subsequently 
becomes  divided  by  partitions  jutting  across  from  the  one  to  the  other.  If  the 
two  palate  processes  fail  to  unite  partially  or  completely,  a  partial  or  complete 
cleft  palate  results. 

Articulations. — With  nine  bones :  two  of  the  cranium,  the  frontal  and  ethmoid, 
and  seven  of  the  face — viz.,  the  nasal,  malar,  lachrymal,  inferior  jturbinated,  palate, 
vomer,  and  its  fellow  of  the  opposite  side.  Sometimes  it  articulates  with  the  orbital 
plate  of  the  sphenoid,  and  sometimes  with  its  external  pterygoid  plate. 

Attachment  of  Muscles. — To  twelve:  the  Orbicularis  palpebrarum,  Obliquus 
oculi  inferior,  Levator  labii  superioris  alaeque  nasi,  Levator  labii  superioris  pro- 
prius,  Levator  anguli  oris,  Compressor  nasi,  Depressor  ahe  nasi,  Dilatator  naris 
posterior,  Masseter,  Buccinator,  Internal  pterygoid,  and  Orbicularis  oris. 

CHANGES  PRODUCED  IN  THE  UPPER  JAW  BY  AGE. 

At  birth  and  during  infancy  the  diameter  of  the  bone  is  greater  in  an  antero-posterior  than 
in  a  vertical  direction.  Its  nasal  process  is  long,  its  orbital  surface  large,  and  its  tuberosity 
well  marked.  In  the  adult  the  vertical  diameter  is  the  greater,  owing  to  the  development  of 
the  alveolar  process  and  the  increase  in  size  of  the  antrum.  In  old  age  the  bone  approaches 
again  in  character  to  the  infantile  condition:  its  height  is  diminished,  and  after  the  loss  of  the 
teeth  the  alveolar  process  is  absorbed,  and  the  lower  part  of  the  bone  contracted  and  diminished 
in  thickness. 

The  Lachrymal  Bone  (Os  Lacrimale). 

The  lachrymal  (lachryma,  a  tear)  is  the  smallest  and  most  fragile  bone  of 
the  face.  There  are  two  lachrymal  bones.  They  are  situated  at  the  front  part 
of  the  inner  wall  of  the  orbit  (Fig.  67),  and  resemble  somewhat  in  form,  thinness, 


THE    MALAR    BONE  113 

and  size  a  finger-nail;  hence  they  are  termed  theossa  unguis.    Each  bone  presents 
for  examination  two  surfaces  and  four  borders. 

Surfaces.  External  Surface. — The  external  or  orbital  surface  (Fig.  77)  is  divided 
by  a  vertical  ridge,  the  lachrymal  crest  (crista  lacrimalis  posterior},  into  two  parts. 
The  portion  of  bone  in  front  of  this  ridge,  the  lachrymal  sulcus  (sulcus  lacrimalis}, 
presents  a  smooth,  concave,  longitudinal  groove,  the  free  margin  of  which  unites 
with  the  nasal  process  of  the  superior  maxillary  bone,  completing  the  lachrymal 
groove.  The  upper  part  of  this  groove  (fossa  sacci  lacrimalis} 
lodges  the  lachrymal  sac;  the  lower  part  (sulcus  lacrimalis) 
lodges  the  nasal  duct.  The  portion  of  bone  behind  the  ridge 
is  smooth,  slightly  concave,  and  forms  part  of  the  inner  wall 
of  the  orbit.  The  ridge,  with  a  part  of  the  orbital  surface 
immediately  behind  it,  affords  attachment  to  the  Tensor  tarsi 
muscle:  it  terminates  below  in  a  small,  hook-like  projection, 
the  hamular  process  (hamulus  lacrimalis),  which  articulates 
with  the  lachrymal  tubercle  of  the  superior  maxillary  bone, 
and  completes  the  upper  orifice  of  the  lachrymal  groove. 
It  sometimes  exists  as  a  separate  piece,  which  is  then  called 
the  lesser  lachrymal  bone. 

Internal  Surface. — The  internal  or  nasal  surface  presents 

I  ip  !•  il  *     1  •  j  Illitl     UOiie.  J\Alfc!I  Ilcll     »ur- 

a  depressed  furrow,  corresponding  to  the  ridge  on  its  outer    face.    (Slightly  enlarged.) 
surface.    The  surface  of  bone  in  front  of  this  forms  part  of 
the  middle  meatus,  and  that  behind  it  articulates  with  the  ethmoid  bone,  fill- 
ing in  the  anterior  ethmoidal  cells. 

Borders. — Of  the  four  borders,  the  anterior  is  the  longest,  and  articulates  with 
the  nasal  process  of  the  superior  maxillary  bone.  The  posterior,  thin  and  uneven, 
articulates  with  the  os  planum  of  the  ethmoid.  The  superior,  the  shortest  and 
thickest,  articulates  with  the  internal  angular  process  of  the  frontal  bone.  The 
inferior  is  divided  by  the  lower  edge  of  the  vertical  crest  into  two  parts;  the  poste- 
rior part  articulates  with  the  orbital  plate  of  the  superior  maxillary  bone;  the 
anterior  portion  is  prolonged  downward  into  a  pointed  process,  which  articulates 
with  the  lachrymal  process  of  the  inferior  turbinated  bone  and  assists  in  the  forma- 
tion of  the  lachrymal  groove. 

Development. — By  a  single  centre,  which  makes  its  appearance  soon  after  ossifi- 
cation of  the  vertebne  has  commenced. 

Articulations. — With  four  bones :  two  of  the  cranium,  the  frontal  and  ethmoid, 
and  two  of  the  face,  the  superior  maxillary  and  the  inferior  turbinated. 

Attachment  of  Muscles. — To  one  muscle,  the  Tensor  tarsi. 

The  Malar  Bone  (Os  Zygomaticum). 

The  name  malar  is  derived  from  mala,  the  cheek.  The  malar  or  yoke  bone  is 
also  called  the  cheek  bone.  There  are  two  malar  bones.  Each  is  a  small,  quad- 
rangular bone,  situated  at  the  upper  and  outer  part  of  the  face.  They  form 
the  prominence  of  the  cheek,  part  of  the  outer  wall  and  floor  of  the  orbit,  and 
part  of  the  temporal  and  zygomatic  fossae  (Fig.  78).  Each  bone  presents  for 
examination  an  external  and  an  internal  surface;  four  processes,  the  frontal, 
orbital,  maxillary,  and  zygomatic  processes;  and  four  borders. 

Surfaces.  External  or  Malar  Surface  (fades  malaris). — The  external  surface 
(Fig.  79)  is  smooth,  convex,  perforated  near  its  centre  by  a  small  aperture,  the 
malar  foramen  (foramen  zygomaticofaciale),  for  the  passage  of  nerves  and  vessels 
from  the  orbit.  The  malar  surface  is  covered  by  the  Orbicularis  palpebrarum 
muscle,  and  affords  attachment  to  the  Zygomaticus  major  and  minor  muscles. 

8 


114 


THE   SKELETON 


Internal  or  Temporal  Surface  (fades  temporalis) . — The  internal  surface  (Fig.  80), 
directed  backward  and  inward,  is  concave,  presenting  internally  a  rough, 
triangular  surface,  for  articulation  with  the  superior  maxillary  bone;  and  exter- 
nally, a  smooth  concave  surface,  which  above  forms  the  anterior  boundary  of 

Frontal  process    Ext.  angular  process 


Zygoma- 
tic  proc. 


FIG.  78. — Right  malar  bone  in  situ. 


the  temporal  fossa,  and  below,  where  it  is  wider,  forms  part  of  the  zygomatic 
fossa.  This  surface  presents,  a  little  above  its  centre,  the  aperture  of  a  malar 
canal  (foramen  zygomaticotemporale) ,  and  affords  attachment  to  a  portion  of  the 
Masseter  muscle  at  its  lower  part. 


With  frontal. 


FIG.  79. — Left  malar  bone.     Outer  surface. 


FIG.  80. — Left  malar  bone.     Inner  surface. 


Processes.  Frontal  Process  (processus  frontosphenoidalis). — Of  the  four 
processes,  the  frontal  is  thick  and  serrated,  and  articulates  with  the  external 
angular  process  of  the  frontal  bone.  To  its  orbital  margin  is  attached  the 
external  tarsal  ligament. 

Orbital  Process. — The  orbital  process  is  a  thick  and  strong  plate,  which  projects 
backward  from  the  Orbital  margin  of  the  bone.  Its  supero-internal  surface  (fades 


THE   PALATE   BONE  115 

orbilalis),  smooth  and  concave,  forms,  by  its  junction  with  the  orbital  surface  of  the 
superior  maxillary  bone  and  with  the  great  wing  of  the  sphenoid,  part  of  the  floor 
and  outer  wall  of  the  orbit.  Its  infero-external  surface,  smooth  and  convex,  forms  part 
of  the  zygomatic  and  temporal  fossse.  Its  anterior  margin  is  smooth  and  rounded, 
forming  part  of  the  circumference  of  the  orbit.  Its  superior  margin,  rough  and 
directed  horizontally,  articulates  with  the  frontal  bone  behind  the  external  angular 
process.  Its  posterior  margin  is  rough  and  serrated  for  articulation  with  the 
sphenoid;  internalli/  it  is  also  serrated  for  articulation  with  the  orbital  surface  of 
the  superior  maxillary.  At  the  angle  of  junction  of  the  sphenoidal  and  maxillary 
portions  a  short,  rounded,  non-articular  margin  is  generally  seen;  this  forms  the 
anterior  boundary  of  the  spheno-maxillary  fissure:  occasionally  no  such  non- 
articular  margin  exists,  the  fissure  being  completed  by  the  direct  junction  of  the 
maxillary  and  sphenoid  bones  or  by  the  interposition  of  a  small  Wormian  bone  in 
the  angular  interval  between  them.  On  the  upper  surface  of  the  orbital  process 
are  seen  a  single  or  double  temporo -malax  foramen  (foramen  zygomaticoorbitale), 
the  entrance  of  the  temporo-malar  canal.  This  canal  may  be  bifurcated,  or 
there  may  be  two  canals  from  the  beginning;  one  of  these  usually  opens  on  the 
posterior  surface,  the  other  (occasionally  two)  on  the  facial  surface:  they  transmit 
filaments  (temporo-malar)  of  the  orbital  branch  of  the  superior  maxillary  nerve. 

Maxillary  Process. — The  maxillary  process  is  a  rough,  triangular  surface  which 
articulates  with  the  malar  process  of  the  superior  maxillary  bone. 

Zygomatic  Process  (processus  temporalis). — The  zygomatic  process,  long,  narrow, 
and  serrated,  articulates  with  the  zygomatic  process  of  the  temporal  bone. 

Borders. — Of  the  four  borders,  the  antero-superior  or  orbital  border  is  smooth, 
arched,  and  forms  a  considerable  part  of  the  circumference  of  the  orbit.  The 
antero-inferior  or  maxillary  border  is  rough,  and  bevelled  at  the  expense  of  its 
inner  table,  to  articulate  with  the  superior  maxillary  bone;  affording  attachment 
by  its  margin  to  the  Levator  labii  superioris  proprius,  just  at  its  point  of  junction 
with  the  superior  maxillary.  The  postero-superior  or  temporal  border,  curved  like 
an  italic  letter  /,  is  continuous  above  with  the  commencement  of  the  temporal 
ridge;  below,  with  the  upper  border  of  the  zygomatic  arch:  it  affords  attachment 
to  the  temporal  fascia.  The  postero-inferior  or  zygomatic  border  is  continuous 
with  the  lower  border  of  the  zygomatic  arch,  affording  attachment  by  its  rough 
edge  to  the  Masseter  muscle. 

Development. — The  malar  bone  ossifies  generally  from  three  centres,  which 
appear  about  the  eighth  week — one  for  the  zygomatic  and  two  for  the  orbital 
portion — and  fuse  about  the  fifth  month  of  foetal  life.  The  bone  is  sometimes, 
after  birth,  seen  to  be  divided  by  a  horizontal  suture  into  an  upper  and  larger 
and  a  lower  and  smaller  division.  In  some  quadrumana  the  malar  bone  consists 
of  two  parts,  an  orbital  and  a  malar,  which  are  ossified  by  separate  centres. 

Articulations. — With  four  bones:  three  of  the  cranium,  frontal,  sphenoid,  and 
temporal;  and  one  of  the  face,  the  superior  maxillary. 

Attachment  of  Muscles. — To  four:  the  Levator  labii  superioris  proprius, 
Zygomaticus  major  and  minor,  and  Masseter. 

The  Palate  Bone  (Os  Palatinum). 

The  palate  bones  (palatum,  the  palate)  are  situated  at  the  back  part  of  the 
nasal  fossae:  they  are  wedged  in  between  the  superior  maxillary  bones  and  the 
pterygoid  processes  of  the  sphenoid  (Fig.  81).  Each  bone  assists  in  the  formation 
of  three  cavities:  the  floor  and  outer  wall  of  the  nose,  the  roof  of  the  mouth,  and 
the  floor  of  the  orbit,  and  enters  into  the  formation  of  two  fossie,  the  spheno- 
maxillary  (fossa  pterygopalatina)  and  pterygoid  fossae  (fossa  pterygoidea) ;  and  one 
fissure,  the  spheno-maxillary  fissure  (fissura  orbitalis  inferior).  In  form  the  palate 


116 


THE    SKELETON 


bone  somewhat  resembles  the  letter  L,  and  may  be  divided  into  an  inferior  or 
horizontal  plate  and  a  superior  or  vertical  plate. 


Spheno-palatine  for. 
Sup.  turbinated  crest. 
Inf.  turbinated  crest. 


Sup.  turbinated  crest. 


Inf.  turbinated  crest. 


'Ant.  nasal  spine. 


FIG.  81. — Internal  surface  of  left  maxilla. 

The  Horizontal  Plate  of  the  Palate  Bone  (Pars  Horizontalis)  (Figs.  72,  82,  83). 

The  horizontal  plate  is  of  a  quadrilateral  form,  and  presents  two  surfaces  and 
four  borders. 

Surfaces.  Superior  Surface  (fades  nasalis). — The  superior  or  nasal  surface, 
concave  from  side  to  side,  forms  the  back  part  of  the  floor  of  the  nasal  cavity. 

Inferior  Surface  (fades  palatina). — The  inferior  or  palatine  surface,  slightly 
concave  and  rough,  forms  the  back  part  of  the  hard  palate.  At  its  posterior  part 
may  be  seen  a  transverse  ridge,  more  or  less  marked,  for  the  attachment  of  part 
of  the  aponeurosis  of  the  Tensor  palati  muscle.  At  the  outer  extremity  of  this 
ridge  is  a  deep  groove,  the  pterygopalatine  groove  (sulcus  pterygopalatinus), 
converted  into  a  canal  by  its  articulation  with  the  tuberosity  of  the  superior 
maxillary  bone,  and  forming  the  lower  end  of  the  posterior  palatine  canal  (canalis 
pterygopalatinus) ,  the  opening  of  which  is  called  the  great  palatine  foramen  (fora- 
men palatinummajus).  Near  this  groove  the  orifices  (foramina  palatina  minora) 
of  one  or  two  small  canals,  accessory  posterior  palatine  canals  (canales  palatini) 
may  be  seen.  Through  the  posterior  palatine  canal  emerge  the  descending 
-  palatine  artery  and  the  great  posterior  palatine  nerve. 

Borders. — The  anterior  border  is  serrated,  bevelled  at  the  expense  of  its  inferior 
surface,  and  articulates  with  the  palate  process  of  the  superior  maxillary  bone. 
The  posterior  border  is  concave,  free,  and  serves  for  the  attachment  of  the  soft 
palate.  Its  inner  extremity  is  sharp  and  pointed,  and,  when  united  with  the 
opposite  bone,  forms  a  projecting  process,  the  posterior  nasal  or  palatine  spine 
(spina  nasalis  posterior},  for  the  attachment  of  the  Azygos  uvulae  muscle.  The 
external  border  is  united  with  the  lower  part  of  the  perpendicular  plate  almost 
at  right  angles.  The  internal  border,  the  thickest,  is  serrated  for  articulation  with 
its  fellow  of  the  opposite  side;  its  superior  edge  is  raised  into  a  ridge,  which,  united 
with  the  opposite  bone,  forms  a  crest  (crista  nasalis)  into  which  the  vomer  is 
received. 


THE    PALATE    BONE 


117 


The  Vertical  or  Perpendicular  Plate  of  the  Palate  Bone  (Pars  Perpendicularis). 

The  vertical  or  perpendicular  plate  (Figs.  82  and  83)  is  thin,  of  an  oblong 
form,  and  directed  upward  and  a  little  inward.  It  presents  two  surfaces,  an 
external  and  an  internal,  and  four  borders. 

Surfaces.  Internal,  Medial,  or  Nasal  Surface  (fades  nasalis). — The  internal  sur- 
face presents  at  its  lower  part  a  broad,  shallow  depression,  which  forms  part  of 
the  inferior  meatus  of  the  nose. 

Orbital  process. 

Orbital  surface. 


Maxillary  surface. 


Maxillary 
process. 


Horizontal  Plate. 

FIG.  82. — Left  palate  bone.     Internal  view. 


(Enlarged.) 


' 

I 


Immediately  above  this  is  a 
well-marked  horizontal  ridge, 
the  inferior  turbinated  crest 
(crixta  conchalis),  for  articula- 
tion with  the  inferior  turbin-  Superior  m 

ated  bone ;  above  this,  a  Second    Spheno-palaKne  foramen.— 

broad,  shallow  depression, 
which  forms  part  of  the  mid- 
dle meatus,  surmounted  above 
by  a  horizontal  ridge  less 
prominent  than  the  inferior, 
the  superior  turbinated  crest 
(crista  ethmoidalis) ,  for  articu- 
lation with  the  middle  turbin- 
ated bone.  Above  the  superior 
turbinated  crest  is  a  narrow, 
horizontal  groove,  which  forms 
part  of  the  superior  meatus. 

External,  Lateral,  or  Maxillary 
Surface    (fades  maxillaris). — 
The  external  surface  is  rough  and  irregular  throughout  the  greater  part  of  its  extent, 
for  articulation  with  the  inner  surface  of  the  superior  maxillary  bone,  its  upper 

and  back  part  being  smooth  where  it  enters 
into  the  formation  of  the  spheno-maxillary 
fossa;  it  is  also  smooth  in  front,  where  it 
covers  the  orifice  of  the  antrum.  Toward 
the  back  part  of  this  surface  is  a  deep  groove, 
the  pterygo-palatine  groove,  converted  into 
a  canal,  the  posterior  palatine  canal  (canalis 
pterygopalatinus) ,  by  its  articulation  with 
the  superior  maxillary  bone.  It  transmits 
the  posterior  or  descending  palatine  vessels 
and  the  great  or  anterior  palatine  nerve 
from  Meckel's  ganglion. 

Borders.  Anterior  Border  (Fig.  82).— The 
anterior  border  is  thin,  irregular,  and  pre- 
sents opposite  the  inferior  turbinated  crest 
a  pointed,  projecting  lamina,  the  maxillary 
process  (processus  maxillaris),  which  is  di- 
rected forward,  and  closes  in  the  lower  and 
back  part  of  the  opening  of  the  antrum. 

Posterior  Border. — The  posterior  border 
(Fig.  83)  presents  a  deep  groove,  the  edges 
of  which  are  serrated  for  articulation  with 

the  pterygoid  process  of  the  sphenoid.  At  the  lower  part  of  this  border  is  seen  a 
pyramidal  process  of  bone,  the  pterygoid  process  or  tuberosity  of  the  palate  (processus 
pyramidalis),  which  is  received  into  the  angular  interval  between  the  two  pterygoid 


Orbital  proceso. 
.10J,  surface. 
* 


Sphenoidal  palatine 
foramen. 

Sphenoidal  process. 
Articular  portion. 
Ron-articular  portion. 


External  Surface. 


QOS  UVUL/E.J 

Horizontal 
Plate. 


Posterior 
nasal  spine. 


FIG.  83.— Left  palate  bone. 
(Enlarged.) 


Posterior  view. 


118  THE   SKELETON 

plates  of  the  sphenoid  at  their  inferior  extremity.  This  process  presents  at  its  back 
part  a  median  groove  and  two  lateral  surfaces.  The  groove  is  smooth,  and  forms 
part  of  the  pterygoid  fossa,  affording  attachment  to  the  Internal  pterygoid  muscle ; 
whilst  the  lateral  surfaces  are  rough  and  uneven,  for  articulation  with  the  anterior 
border  of  each  pterygoid  plate.  A  few  fibres  of  the  Superior  constrictor  arise  from 
the  tuberosity  of  the  palate  bone.  The  base  of  this  process,  continuous  with  the 
horizontal  portion  of  the  bone,  presents  the  aperture  of  the  accessory  descending 
palatine  canals,  through  which  pass  the  two  smaller  descending  branches  of 
Meckel's  ganglion  ;  whilst  its  outer  surface  is  rough  for  articulation  with  the 
inner  surface  of  the  body  of  the  superior  maxillary  bone. 

Superior  Border.— The  superior  border  of  the  vertical  plate  presents  two  well- 
marked  processes  separated  by  an  intervening  notch  or  foramen.  The  anterior, 
or  larger,  is  called  the  orbital  process;  the  posterior,  the  sphenoidal  process. 

Processes.  Orbital  Process  (processus  orbitalis). — The  orbital  process,  directed 
upward  and  outward,  is  placed  on  a  higher  level  than  the  sphenoidal.  It  presents 
five  surfaces,  which  enclose  a  hollow  cellular  cavity,  and  is  connected  with  the  per- 
pendicular plate  by  a  narrow,  constricted  neck.  Of  these  five  surfaces,  three  are 
articular,  two  non-articular  or  free  surfaces.  The  three  articular  are  the  anterior  or 
maxillary  surface,  which  is  directed  forward,  outward,  and  downward,  is  of  an 
oblong  form,  and  rough  for  articulation  with  the  superior  maxillary  bone.  The  pos- 
terior or  sphenoidal  surface  is  directed  backward,  upward,  and  inward.  It  ordinarily 
presents  a  small,  open  cell,  the  orbital  sinus  (sinus  orbitalis) ,  which  communicates 
with  the  sphenoidal  cells,  and  the  margins  of  which  are  serrated  for  articulation  with 
the  vertical  part  of  the  sphenoidal  turbinated  bone.  "The  orbital  may  communicate 
not  only  with  the  sphenoidal  sinus  and  the  ethmoidal  cells,  but,  in  rare  instances, 
with  the  maxillary  antrum."1  The  internal  or  ethmoidal  surface  is  directed  inward, 
upward,  and  forward,  and  articulates  with  the  lateral  mass  of  the  ethmoid  bone. 
In  some  cases  the  cellular  cavity  opens  on  the  internal  surface  of  the  bone ;  it  then 
communicates  with  the  posterior  ethmoidal  cells.  More  rarely  it  opens  on  both 
surfaces,  and  then  communicates  with  both  the  posterior  ethmoidal  and  the 
sphenoidal  cells.  The  non-articular  or  free  surfaces  are  the  superior  or  orbital 
surface,  directed  upward  and  outward,  of  triangular  form,  concave,  smooth,  and 
forming  the  back  part  of  the  floor  of  the  orbit ;  and  the  external  or  zygomatic  surface, 
directed  outward,  backward,  and  downward,  of  an  oblong  form,  smooth,  lying  in 
the  spheno-maxillary  fossa,  and  looking  into  the  zygomatic  fossa.  The  latter 
surface  is  separated  from  the  orbital  by  a  smooth,  rounded  border,  which  enters 
into  the  formation  of  the  spheno-maxillary  fissure. 

Sphenoidal  Process  (processus  sphenoidalis) . — The  sphenoidal  process  of  the 
palate  bone  is  a  thin,  compressed  plate,  much  smaller  than  the  orbital,  and 
directed  upward  and  inward.  It  presents  three  surfaces  and  two  borders.  The 
superior  surface,  the  smallest  of  the  three,  articulates  with  the  under  surface  of 
the  sphenoidal  turbinated  bone;  it  presents  a  groove,  which  contributes  to  the 
formation  of  the  pterygo-palatine  canal.  The  internal  surface  is  concave,  and 
forms  part  of  the  outer  wall  of  the  nasal  fossa.  The  external  surface  is  divided 
into  an  articular  and  a  non-articular  portion:  the  former  is  rough,  for  articulation 
with  the  inner  surface  of  the  internal  pterygoid  plate  of  the  sphenoid;  the  latter  is 
smooth,  and  forms  part  of  the  spheno-maxillary  fossa.  The  anterior  border  forms 
the  posterior  boundary  of  the  spheno-palatine  notch.  The  posterior  border, 
serrated  at  the  expense  of  the  outer  table,  articulates  with  the  inner  surface  of 
the  internal  pterygoid  plate. 

The  orbital  and  sphenoidal  processes  are  separated  from  one  another  by  a  deep 
notch,  the  spheno-palatine  notch  (incisura  sphenopalatinum) ,  which  is  converted 

1  Dr.  D.  Kerfoot  Shute,  in  the  Reference  Handbook  of  the  Medical  Sciences. 


THE    INFERIOR    TURBINATED    BONE 


119 


into  a  foramen,  the  spheno-palatine  foramen  (foramen  sphenopalatinum) ,  by  articu- 
lation with  the  under  surface  of  the  body  of  the  sphenoid  bone.  Sometimes  the 
two  processes  are  united  above,  and  form  between  them  a  complete  foramen  (Figs. 
82  and  83) ,  or  the  notch  is  crossed  by  one  or  more  spiculae  of  bone,  so  as  to  form 
two  or  more  foramina.  In  the  articulated  skull  this  foramen  is  seen  to  pass  from 
the  spheno-maxillary  fossa  into  the  back  part  of  the  superior  meatus.  It  trans- 
mits the  spheno-palatine  vessels  and  the  superior  nasal  and  naso-palatine  nerves. 

Development. — From  a  single  centre,'  which  makes  its  appearance  about  the 
second  month  at  the  angle  of  junction  of  the  two  plates  of  the  bone.  From  this 
point  ossification  spreads  inward  to  the  horizontal  plate,  downward  into  the 
tuberosity,  and  upward  into  the  vertical  plate.  In  the  foetus  the  horizontal  plate 
is  much  larger  than  the  vertical,  and  even  after  it  is  fully  ossified  the  whole  bone 
is  at  first  remarkable  for  its  shortness. 

Articulations. — With  six  bones:  the  sphenoid,  ethmoid,  superior  maxillary, 
inferior  turbinated,  vomer,  and  opposite  palate. 

Attachment  of  Muscles.- -To  four:  the  Tensor  palati,  Azygos  uvulae,  Internal 
pterygoid,  and  Superior  constrictor  of  the  pharynx. 

The  Inferior  Turbinated  Bone  ( Concha  Nasalis  Inferior). 

The  inferior  turbinal  or  turbinated  bones  (turbo,  a  whirl)  are  situated  one  on 
each  side  of  the  outer  wall  of  the  nasal  fossse.  Each  inferior  turbinated  bone 
(concha  nasalis  inferior]  consists  of  a  layer  of  thin,  spongy  bone,  curled  upon 


NASO-PHARYNGEAL 

MEATUS 


FTG.  84. — Nasal  cavity,  right  lateral  wall,  from  the  left.      (Spalteholz.) 


itself  like  a  scroll — hence  its  name  "  turbinated  "—  and  extends  horizontally 
along  the  outer  wall  of  the  nasal  fossa,  immediately  below  the  orifice  of  the 
antrum  (Fig.  84).  Each  bone  presents  two  surfaces,  two  borders,  and  two 
extremities. 


120 


THE    SKELETON 


Surfaces. — The  internasal  surface  (Fig.  85)  is  convex,  perforated  by  numerous 
apertures,  and  traversed  by  longitudinal  grooves  and  canals  for  the  lodgement 
of  arteries  and  veins.  In  the  recent  state  it  is  covered  by  the  lining  membrane  of 
the  nose.  The  external  surface  is  concave  (Fig.  86),  and  forms  part  of  the  inferior 
meatus. 


FIG.  85. — Right  inferior  turbinated  bone.     Internal 
surface. 


FIG.  86.— Right  inferior  turbinated  bone. 
External  surface. 


Borders. — Its  upper  border  is  thin,  irregular,  and  connected  to  various  bones 
along  the  outer  wall  of  the  nose.  It  may  be  divided  into  three  portions :  of  these, 
the  anterior  articulates  with  the  inferior  turbinated  crest  of  the  superior  maxillary 
bone;  the  posterior  with  the  inferior  turbinated  crest  of  the  palate  bone;  the  middle 
portion  of  the  superior  border  presents  three  well-marked  processes,  which  vary 
much  in  their  size  and  form.  Of  these,  the  anterior  and  smallest  is  situated  at 
the  junction  of  the  anterior  fourth  with  the  posterior  three-fourths  of  the  bone: 
it  is  small  and  pointed,  and  is  called  the  lachrymal  process  (processus  lacrimalis) ; 
it  articulates  by  its  apex  with  the  anterior  inferior  angle  of  the  lachrymal  bone, 
and  by  its  margins  with  the  groove  on  the  back  of  the  nasal  process  of  the  supe- 
rior maxillary,  and  thus  assists  in  forming  the  canal  for  the  nasal  duct.  At  the 
junction  of  the  two  middle  fourths  of  the  bone,  but  encroaching  on  its  posterior 
fourth,  a  broad,  thin  plate,  the  ethmoidal  process  (processus  ethmouLalis) ,  ascends 
to  join  the  unciform  process  of  the  ethmoid;  from  the  lower  border  of  this  pro- 
cess a  thin  lamina  of  bone  curves  downward  and  outward,  hooking  over  the 
lower  edge  of  the  orifice  of  the  antrum,  which  it  narrows  below:  it  is  called  the 
maxillary  process  (processus  maxillaris) ,  and  fixes  the  bone  firmly  to  the  outer  wall 
of  the  nasal  fossa.  The  inferior  border  is  free  and  thick,  more  especially  in  the 
middle  of  the  bone.  Bone  extremities  are  more  or  less  narrow  and  pointed,  the 
posterior  being  the  more  tapering.  If  the  bone  is  held  so  that  its  outer  concave 
surface  is  directed  backward  (i.  e.,  toward  the  holder),  and  its  superior  border,  from 
which  the  lachrymal  and  ethmoidal  processes  project,  upward,  the  lachrymal  pro- 
cess will  be  directed  to  the  side  to  which  the  bone  belongs.1  In  a  study  of  1000  speci- 
mens, Howard  A.  Lothrop2  did  not  discover  cells  in  the  inferior  turbinated  bone. 

Development. — By  a  single  centre,  which  makes  its  appearance  about  the 
middle  of  fcetal  life. 

Articulations. — With  four  bones:  one  of  the  cranium,  the  ethmoid,  and  three 
of  the  face,  the  superior  maxillary,  lachrymal,  and  palate. 

No  muscles  are  attached  to  this  bone. 

The  Vomer  (Ploughshare  Bone). 

The  vomer  (vomer,  a  ploughshare)  is  a  single  bone,  situated  vertically  at  the 
back  part  of  the  nasal  fossae,  forming  part  of  the  septum  of  the  nose  (Fig.  87). 
It  is  thin,  somewhat  like  a  ploughshare  in  form;  but  it  varies  in  different  indi- 
viduals, being  frequently  bent  to  one  or  the  other  side;  it  presents  for  examination 
two  surfaces  and  four  borders. 


1  If  the  lachrymal  process  is  broken  off,  as  is  often  the  case,  the  side  to  which  the  bone  belongs  may  be  known 
by  recollecting  that  the  maxillary  process  is  nearer  the  back  than  the  front  of  the  bone. — Ki>.  of  15th  English 
Edition.  2  Annals  of  Surgery,  May,  1903. 


THE    VOMER 


121 


Surfaces. — The  lateral  surfaces  are  smooth,  marked  by  small  furrows  for  the 
lodgement  of  blood-vessels,  and  by  a  groove  on  each  side,  sometimes  a  canal,  the 
naso-palatine  groove  or  canal,  which  runs  obliquely  downward  and  forward  to  the 
intermaxillary  suture;  it  transmits  the  naso-palatine  nerve. 


Space  for  triangular 
cartilage  of  septum. 


Rostrum  of  sphenoid. 


A\x. 


FIG.  87. — Vomer  in  situ. 

Borders. — The  superior  border,  the  thickest,  presents  a  deep  groove,  bounded 
on  each  side  by  a  horizontal  projecting  leaf  of  bone;  these  leaves  are  the  alae 
(alee  vomeris).  The  groove  formed  by  the  alae  receives  the  rostrum  of  the 
sphenoid,  while  the  alae  are  overlapped  and  retained  by  the  vaginal  processes,  which 
project  from  the  under  surface  of  the  body  of  the  sphenoid  at  the  base  of  the 
pterygoid  processes.  At  the  front 
of  the  groove  a  fissure  is  left  for 
the  transmission  of  blood-vessels 
to  the  substance  of  the  bone.  The 
inferior  border,  the  longest,  is 
broad  and  uneven  in  front,  where 
it  articulates  with  the  two  supe- 
rior maxillary  bones ;  thin  and 
sharp  behind,  where  it  joins  with 
the  palate  bones.  The  upper 
half  of  the  anterior  border  usually 
consists  of  two  laminae  of  bone, 
in  the  groove  between  which  is 
received  the  perpendicular  plate 
of  the  ethmoid;  the  lower  half, 

also  separated  into  two  lamella?,  receives  between  them  the  lower  margin  of  the 
septal  cartilage  of  the  nose.  The  posterior  border  is  free,  concave,  and  separates 
the  nasal  fossae  behind.  It  is  thick  and  bifid  above,  thin  below. 

The  surfaces  of  the  vomer  are  covered  by  mucous  membrane,  which  is  inti- 
mately connected  with  the  periosteum,  with  the  intervention  of  very  little,  if  any, 


With  sup.  maxill.  bones  and  palate. 

FIG.  88. — The  vomer. 


122 


THE   SKELETON 


submucous  connective  tissue.  Hence  polypi  are  rarely  found  growing  from  this 
surface,  though  they  frequently  grow  from  the  outer  wall  of  the  nasal  fossae, 
where  the  submucous  tissue  is  abundant. 

Development. — The  vomer  at  an  early  period  consists  of  two  laminae,  separated 
by  a  very  considerable  interval,  and  enclosing  between  them  a  plate  of  cartilage, 
the  vomerine  cartilage,  which  is  prolonged  forward  to  form  the  remainder  of  the 
septum.  Ossification  commences  in  the  membrane  at  the  postero-inferior  part  of 
this  cartilage  by  two  centres,  one  on  each  side  of  the  middle  line,  which  extend 
to  form  the  two  lamimie.  They  begin  to  coalesce  at  the  lower  part,  but  their 
union  is  not  complete  until  after  puberty. 

Articulations.--  With  six  bones:  two  of  the  cranium,  the  sphenoid  and  ethmoid; 
and  four  of  the  face,  the  superior  maxillary  and  the  two  palate  bones;  and  with 
the  cartilage  of  the  septum. 

The  vomer  has  no  muscles  attached  to  it. 

The  Maxillary  Bone,  Inferior  Maxilla,  Mandible  or  Lower  Jaw  (Mandibula). 

The  mandible,  the  largest  and  strongest  bone-  of  the  face,  serves  for  the 
reception  of  the  lower  teeth.  It  consists  of  a  curved,  horizontal  portion,  the 
body,  and  two  perpendicular  portions,  the  rami,  which  join  the  back  part  of 
the  body  nearly  at  right  angles. 

The  Horizontal  Portion  or  Body  of  the  Mandible   (Corpus  Mandibulae). 

The  horizontal  portion  or  body  (Fig.  89)  is  convex  in  its  general  outline,  and 
curved  somewhat  like  a  horseshoe.  It  presents  for  examination  two  surfaces  and 
two  borders. 

Coronoid  process.  Condyle. 


Groove  for  facial  artery. 
FIG.  89. — The  mandible.     Outer  surface.     Side  view. 


— Angle. 


Surfaces.  External  Surface.— The  external  surface  is  convex  from  side  to  side,, 
concave  from  above  downward.  In  the  median  line  is  a  vertical  ridge,  the  symphy- 
sis,  which  extends  from  the  upper  to  the  lower  border  of  the  bone,  and  indicates 
the  point  of  junction  of  the  two  pieces  of  which  the  bone  is  composed  at  an  early 
period  of  life.  The  lower  part  of  the  ridge  terminates  in  a  prominent  triangular 
eminence,  the  mental  process  or  protuberance  (protuberantia  mentalis) .  This  emi- 
nence is  rounded  below,  and  often  presents  a  median  depression  separating  two 
processes,  the  mental  tubercles  (tubera  mentalia).  It  forms  the  chin,  a  feature 
peculiar  to  the  human  skull.  On  either  side  of  the  symphysis,  just  below  the 


THE   MAXILLARY  BONE 


123 


cavities  for  the  incisor  teeth,  is  a  depression,  the  incisive  or  incisor  fossa,  for  the 
attachment  of  the  Levator  menti  (or  Levator  labii  inferioris) ;  more  externally  is 
attached  a  portion  of  the  Orbicularis  oris  (accessorii  orbicularis  inferioris),  and, 
still  more  externally,  a  foramen,  the  mental  foramen  (foramen  mentale),  for  the 
passage  of  the  mental  vessels  and  nerve.  This  foramen  is  placed  just  below  the 
interval  between  the  two  bicuspid  teeth.  Running  outward  from  the  base  of  the 
mental  process  on  each  side  is  a  ridge,  the  external  oblique  line  (linea  obliqud). 
The  ridge  is  at  first  nearly  horizontal,  but  afterward  inclines  upward  and  back- 
ward, and  is  continuous  with  the  anterior  border  of  the  ramus:  it  affords  attach- 
ment to  the  Depressor  labii  inferioris  and  Depressor  anguli  oris;  below  it  the 
Platysma  myoides  is  attached. 

Internal  Surface. — The  internal  surface  (Fig.  90)  is  concave  from  side  to  side, 
convex  from  above  downward.    In  the  middle  line  is  an  indistinct  linear  depres- 


QENIO-HYO-QLOSS 


GENIO-HYOIDEUS. 


Mylo-hyoid  ridge. 

Body. 

FIG.  90. — The  mandible.     Inner  surface.     Side  view. 

sion,  corresponding  to  the  symphysis  externally;  on  either  side  of  this  depression, 
just  below  its  centre,  are  four  prominent  tubercles,  placed  in  pairs,  two  above  and 
two  below;  they  are  called  the  genial  tubercles  or  mental  spines  (spince  mentales) ,  and 
afford  attachment,  the  upper  pair  to  the  Genio-hyo-glossi,  the  lower  pair  to  the 
Genio-hyoidei,  muscles.  Sometimes  the  tubercles  on  each  side  are  blended  into 
one;  at  others  they  all  unite  into  an  irregular  eminence;  or,  again,  nothing  but  an 
irregularity  may  be  seen  on  the  surface  of  the  bone  at  this  part.  On  either  side  of 
the  genial  tubercles  is  an  dval  depression,  the  sublingual  fossa  (fovea  sublingualis) , 
for  lodging  the  sublingual  gland;  and  beneath  the  fossa  a  rough  depression  on 
each  side  which  gives  attachment  to  the  anterior  belly  of  the  Digastric  muscle, 
the  digastric  fossa  (fossa  digdstrica).  At  the  back  part  of  the  sublingual  fossa  the 
internal  oblique  line  or  mylo-hyoid  ridge  (linea  mylohyoidea)  commences;  it  is  at 
first  faintly  marked,  but  becomes  more  distinct  as  it  passes  upward  and  outward, 
and  is  especially  prominent  opposite  the  last  two  molar  teeth ;  it  affords  attach- 
ment throughout  its  whole  extent  to  the  Mylo-hyoid  muscle;  the  Superior  con- 
strictor of  the  pharynx  with  the  pterygo-m  axillary  ligament  being  attached  above 
its  posterior  extremity,  near  the  alveolar  margin.  The  portion  of  the  bone  above 
this  ridge  is  smooth  and  covered  by  the  mucous  membrane  of  the  mouth;  the 
portion  below  presents  an  oblong  depression,  the  submaxillary  fossa  (fovea  sub- 
maxillaris),  wider  behind  than  in  front,  for  the  lodgement  of  the  submaxillary 


124  THE   SKELETON 

gland.  The  external  oblique  line  and  the  internal  or  mylo-hyoidean  line  divide 
the  body  of  the  bone  into  a  superior  or  alveolar  and  an  inferior  or  basilar  portion. 
Borders. — The  superior  or  alveolar  portion  of  the  body  (pars  alveolaris)  has 
above  a  narrow  border  which  is  wider  and  the  margins  of  which  are  thicker 
behind  than  in  front.  Its  narrow  margin  is  called  the  limbus  alveolaris.  It  is 
hollowed  into  numerous  cavities  (alveoli  dentales) ,  for  the  reception  of  the  teeth ; 
these  cavities  are  sixteen  in  number,  and  vary  in  depth  and  size  according  to  the 
teeth  which  they  contain.  The  cavities  are  separated  from  one  another  by  septa 
inter  alveolar  ia.  The  juga  alveolaria  are  prominences  on  the  outer  surface  over  the 
three  front  alveoli.  To  the  outer  side  of  the  alveolar  border  the  Buccinator  muscle 
is  attached  upon  the  buccinator  crest  (crista  buccinatoria)  as  far  forward  as  the 
first  molar  tooth.  The  inferior  or  basilar  portion  (basis  mandibidce)  is  rounded, 
longer  than  the  superior,  and  thicker  in  front  than  behind;  it  presents  a  shallow 
groove,  just  where  the  body  joins  the  ramus,  over  which  tjie  facial  artery  turns. 

The  Perpendicular  Portions  or  Kami  of  the  Mandible  (Kami  Mandibolse). 

The  perpendicular  portions  or  rami  are  of  a  quadrilateral  form.  Each  presents 
for  examination  two  surfaces,  four  borders,  and  two  processes. 

Surfaces.  External  Surface. — The  external  surface  is  flat,  marked  with  ridges, 
and  gives  attachment  throughout  nearly  the  whole  of  its  extent  to  the  Masseter 
muscle. 

Internal  Surface. — The  internal  surface  presents  about  its  centre  an  oblique 
foramen  (foramen  mandibulare)  of  the  inferior  dental  canal  (canalis  mandibulce) ,  for 
the  passage  of  the  inferior  dental  vessels  and  nerve.  The  margin  of  this  opening 
is  irregular;  it  presents  in  front  a  prominent  ridge,  surmounted  by  a  sharp  spine, 
the  lingula  (lingula  mandibulae) ,  which  gives  attachment  to  the  internal  lateral 
ligament  of  the  lower  jaw,  and  at  its  lower  and  back  part  a  notch  leading  to 
a  groove,  the  mylo-hyoidean  groove  (sulcus  mylohyoideus) ,  which  runs  obliquely 
downward  to  the  back  part  of  the  submaxillary  fossa,  and  lodges  the  mylo-hyoid 
vessels  and  nerve.  Behind  the  groove  is  a  rough  surface,  for  the  insertion  of  the 
Internal  pterygoid  muscle.  The  inferior  dental  canal  runs  obliquely  downward 
and  forward  in  the  substance  of  the  ramus,  and  then  horizontally  forward  in  the 
body ;  it  is  here  placed  under  the  alveoli,  with  which  it  communicates  by  small 
openings.  On  arriving  at  the  incisor  teeth,  it  turns  back  to  communicate  with 
the  mental  foramen,  giving  off  two  small  canals,  which  run  forward,  to  be  lost  in 
the  cancellous  tissue  of  the  bone  beneath  the  incisor  teeth.  This  canal,  in  the 
posterior  two-thirds  of  the  bone,  is  situated  nearer  the  internal  surface  of  the 
jaw;  and  in  the  anterior  third,  nearer  its  external  surface.  Its  walls  are  com- 
posed of  compact  tissue  at  either  extremity,  and  of  cancellous  in  the  centre.  It 
contains  the  inferior  dental  vessels  and  nerve,  from  which  branches  are  distributed 
to  the  teeth  through  small  apertures  at  the  bases  of  the.  alveoli. 

Borders. — The  lower  border  of  the  ramus  is  thick,  straight,  and  continuous 
with  the  body  of  the  bone.  At  its  junction  with  the  posterior  border  is  the  angle 
of  the  jaw  (angulus  mandibulce).  The  outer  portion  of  the  angle  is  called  the 
gonion.  The  angle  is  either  inverted  or  everted,  and  marked  by  rough,  oblique 
ridges  on  each  side,  for  the  attachment  of  the  Masseter  externally,  and  the 
Internal  pterygoid  internally ;  the  stylo-maxillary  ligament  is  attached  to  the  angle 
between  these  muscles.  'The  anterior  border  is  thin  above,  thicker  below,  and 
continuous  with  the  external  oblique  line.  The  posterior  border  is  thick, 
smooth,  rounded,  and  covered  by  the  parotid  gland.  The  upper  'border  of  the 
ramus  is  thin,  and  presents  two  processes,  separated  by  a  deep  concavity,  the 
sigmoid  notch  (incisura  mandibulce).  Of  these  processes,  the  anterior  is  the 
coronoid,  the  posterior  the  condyloid. 


THE    MAXILLARY  BONE  125 

Coronoid  Process  (processus  coronoideus) . — The  coronoid  process  is  a  thin,  flat- 
tened, triangular  eminence  of  bone,  which  varies  in  shape  and  size  in  different 
subjects,  and  serves  chiefly  for  the  attachment  of  the  Temporal  muscle.  Its  external 
surface  is  smooth,  and  affords  attachment  to  the  Temporal  and  Masseter  muscles. 
Its  internal  surface  gives  attachment  to  the  Temporal  muscle  and  presents  the 
commencement  of  a  longitudinal  ridge,  which  is  continued  to  the  posterior  part 
of  the  alveolar  process.  On  the  outer  side  of  this  ridge  is  a  deep  groove,  con- 
tinued below  on  the  outer  side  of  the  alveolar  process;  this  ridge  and  part  of  the 
groove  afford  attachment,  above,  to  the  Temporal;  below,  to  the  Buccinator 
muscle. 

Condyloid  Process  (processus  condyloideus) . — The  condyloid  process,  shorter  but 
thicker  than  the  coronoid,  consists  of  two  portions:  the  condyle  (capitulum  man- 
dibulce) ,  and  the  constricted  portion  which  supports  the  condyle,  the  neck  (collum 
mandibulcB).  The  condyle  is  of  an  oblong  form,  its  long  axis  being  transverse,  and 
set  obliquely  on  the  neck  in  such  a  manner  that  its  outer  end  is  a  little  more 
forward  and  a  little  higher  than  its  inner.  It  is  convex  from  before  backward 
and  from  side  to  side,  the  articular  surface  extending  farther  on  the  posterior 
than  on  the  anterior  aspect.  At  its  outer  extremity  is  a  small  tubercle  for  the 
attachment  of  the  external  lateral  ligament  of  the  temporo-mandibular  joint. 
The  neck  of  the  condyle  is  flattened  from  before  backward,  and  strengthened 
by  ridges  which  descend  from  the  fore  part  and  sides  of  the  condyle.  Its  lateral 
margins  are  narrow,  the  external  one  giving  attachment  to  part  of  the  external 
lateral  ligament.  Its  posterior  surface  is  convex;  its  anterior  is  hollowed  out  on 
its  inner  side  by  a  depression,  the  pterygoid  depression  (fovea  pterygoidea) ,  for  the 
attachment  of  the  External  pterygoid  muscle. 

The  Sigmoid  Notch  (incisura  maridibuloe),  separating  the  two  processes,  is  a 
deep  semilunar  depression,  crossed  by  the  masseteric  vessels  and  nerve. 

Development. — The  lower  jaw  is  developed  principally  from  membrane,  but 
partly  from  cartilage.  The  process  of  ossification  commences  early — earlier  than 
in  any  other  bone  except  the  clavicle.  The  greater  part  of  the  bone  is  formed  from 
a  centre  of  ossification  (dentary),  which  appears  between  the  fifth  and  sixth  week 
in  the  membrane  on  the  outer  surface  of  Meckel's  cartilage.  A  second  centre 
(splenial)  appears  in  the  membrane  on  the  inner  surface  of  the  cartilage,  and 
from  this  centre  the  inner  wall  of  the  sockets  of  the  teeth  is  formed;  this  termi- 
nates above  in  the  lingula.  The  anterior  extremity  of  Meckel's  cartilage  becomes 
ossified,  forming  the  body  of  the  bone  on  each  side  of  the  syrnphysis.  Two  supple- 
mental patches  of  cartilage  appear  at  the  condyle  and  at  the  angle,  in  each  of 
which  a  centre  of  ossification  for  these  parts  appears;  the  coronoid  process  is  also 
ossified  from  a  separate  centre.  At  birth  the  bone  consists  of  two  halves,  united 
by  a  fibrous  symphysis,  in  which  ossification  takes  place  during  the  first  year. 

Articulation. — With  the  glenoid  (mandibular)  fossae  of  the  two  temporal  bones. 

Attachment  of  Muscles. — To  fifteen  pairs:  to  its  external  surface,  commencing 
at  the  symphysis,  and  proceeding  backward :  Levator  menti,  Depressor  labii  infe- 
rioris,  Depressor  anguli  oris,  Platysma  myoides,  Buccinator,  Masseter;  a  portion 
of  the  Orbicularis  oris  (Accessorii  orbicularis  inferioris)  is  also  attached  to  this 
surface.  To  its  internal  surface,  commencingat  the  same  point :  Genio-hyo-glossus, 
Genio-hyoideus,  Mylo-hyoideus,  Digastric,  Superior  constrictor,  Temporal,  Inter- 
nal pterygoid,  External  pterygoid. 

CHANGES  PRODUCED  IN  THE  LOWER  JAW  BY  AGE. 

The  changes  which  the  lower  jaw  undergoes  after  birth  relate  (1)  to  the  alterations  effected 
in  the  body  of  the  bone  by  the  first  and  second  dentitions,  the  loss  of  the  teeth  in  the  aged,  and 
the  subsequent  absorption  of  the  alveoli;  (2)  to  the  size  and  situation  of  the  dental  canal;  and 
(3)  to  the  angle  at  which  the  ramus  joins  with  the  body. 


126 


THE   SKELETON 


SIDE  VIEW  OF  THE  LOWER  JAW  AT  DIFFERENT  PERIODS  OF  LIFE. 

At  birth  (Fig.  91)  the  bone  consists  of  lateral  halves,  united  by  fibrous  tissue.  The  body  is 
a  mere  shell  of  bone,  containing  the  sockets  of  the  two  incisor,  the  canine,  and  the  two  tem- 
porary molar  teeth,  imperfectly  partitioned  from  one  another.  The  dental  canal  is  of  large  size, 
and  runs  near  the  lower  border  of  the  bone,  the  mental  foramen  opening  beneath  the  socket  of 
the  first  molar.  The  angle  is  obtuse  (175  degrees),  and  the  condyloid  portion  nearly  in  the 
same  horizontal  line  with  the  body;  the  neck  of  the  condyle  is  short,  and  bent  backward.  The 
coronoid  process  is  of  comparatively  large  size,  and  situated  at  right  angles  with  the  rest  of 
the  bone. 


FIG.  91. — Lower  jaw  bone  in  newborn.  (Spalteholz.) 


FIG.  92. — In  child  six  to  seven  years  of  age. 
(Spalteholz.) 


After  birth  (Fig.  92)  the  two  segments  of  the  bone  become  joined  at  the  symphysis,  from 
below  upward,  in  the  first  year;  but  a  trace  of  separation  may  be  visible  in  the  beginning  of  the 
second  year  near  the  alveolar  margin.  The  body  becomes  elongated  in  its  whole  length,  but 
more  especially  behind  the  mental  foramen,  to  provide  space  for  the  three  additional  teeth 
developed  in  this  part.  The  depth  of  the  body  becomes  greater,  owing  to  increased  growth  of 
the  alveolar  part,  to  afford  room  for  the  fangs  of  the  teeth,  and  by  thickening  of  the  subdental 
portion,  which  enables  the  jaw  to  withstand  the  powerful  action  of  the  masticatory  muscles ;  but 
the  alveolar  portion  is  the  deeper  of  the  two,  and,  consequently,  the  chief  part  of  the  body  lies 
above  the  oblique  line.  The  dental  canal  after  the  second  dentition  is  situated  just  above  the 
level  of  the  mylo-hyoid  ridge,  and  the  mental  foramen  occupies  the  position  usual  to  it  in  the 
adult.  The  angle  becomes  less  obtuse,  owing  to  the  separation  of  the  jaws  by  the  teeth.  (About 
the  fourth  year  it  is  140  degrees.) 


FIG.  93. — In  the  adult.     (Spalteholz.) 


In  the  adult  (Fig.  93)  the  alveolar  and  basilar  portions  of  the  body  are  usually  of  equal 
depth.    The  mental  foramen  opens  midway  between  the  upper  and  lower  border  of  the  bone, 


THE  SUTURES  127 

and  the  dental  canal  runs  nearly  parallel  with  the  mylo-hyoid  line.    The  ramus  is  almost  vertical 
in  direction,  and  joins  the  body  nearly  at  right  angles. 

In  old  age  (Fig.  94)  the  bone  becomes  greatly  reduced  in  size;  for  with  the  loss  of  the  teeth 
the  alveolar  process  is  absorbed,  and  the  basilar  part  of  the  bone  alone  remains,  consequently, 


FIG.  94. — In  old  age.     (Spalteholz.) 

the  chief  part  of  the  bone  is  below  the  oblique  line.  The  dental  canal,  with  the  mental  foramen 
opening  from  it,  is  close  to  the  alveolar  border.  The  rami  are  oblique  in  direction,  the  angle 
obtuse,  and  the  neck  of  the  condyle  more  or  less  bent  backward. 

The  Sutures. 

The  bones  of  the  cranium  and  face  are  connected  to  each  other  by  means  of 
sutures.  That  is,  the  articulating  surfaces  or  edges  of  the  bones  are  more  or  less 
roughened  or  uneven,  and  are  closely  adapted  to  each  other,  a  small  amount  of 
intervening  fibrous  tissue,  the  sutural  ligament,  fastening  them  together.  The 
cranial  sutures  may  be  divided  into  three  sets:  1.  Those  at  the  vertex  of  the 
skull.  2.  Those  at  the  side  of  the  skull.  3.  Those  at  the  base. 

The  sutures  at  the  vertex  of  the  skull  are  four:  the  metopic,  the  sagittal,  the 
coronal,  and  the  lambdoid. 

The  Metopic  or  Frontal  Suture  (sutura  frontalis)  is  usually  noted  in  adults  as  a 
trivial  fissure,  just  above  the  glabella.  At  birth  the  two  halves  of  the  frontal 
bone  are  separated  by  the  suture.  This  suture  is,  as  a  rule,  almost  completely 
or  completely  closed  during  the  fifth  or  sixth  year,  but  occasionally  it  remains 
intact. 

The  Interparietal  or  Sagittal  Suture  (sutura  sagittalis)  is  formed  by  the  junction 
of  the  two  parietal  bones,  and  extends  from  the  middle  of  the  frontal  bone  back- 
ward to  the  superior  angle  of  the  occipital.  This  suture  is  sometimes  perforated, 
near  its  posterior  extremity,  by  the  parietal  foramen ;  and  in  front,  where  it  joins 
the  coronal  suture,  a  space  is  occasionally  left  which  encloses  a  large  Wormian 
bone. 

The  Fronto -parietal  or  Coronal  Suture  (sutura  coronalis]  extends  transversely 
across  the  vertex  of  the  skull,  and  connects  the  frontal  with  the  parietal  bones. 
It  commences  at  the  extremity  of  the  greater  wing  of  the  sphenoid  on  one  side, 
and  terminates  at  the  same  point  on  the  opposite  side.  The  dentations  of  the 
suture  are  more  marked  at  the  sides  than  at  the  summit,  and  are  so  constructed 
that  the  frontal  rests  on  the  parietal  above,  whilst  laterally  the  frontal  supports 
the  parietal. 


128  THE  SKELETON 

The  Occipito-parietal  or  Lambdoid  Suture  (sutura  lambdoidea),  so  called  from 
its  resemblance  to  the  Greek  letter  A,  connects  the  occipital  with  the  parietal 
bones.  It  commences  on  each  side  at  the  mastoid  portion  of  the  temporal  bone, 
and  inclines  upward  to  the  end  of  the  sagittal  suture.  The  dentations  of  this 
suture  are  very  deep  and  distinct,  and  are  often  interrupted  by  several  small 
Wormian  bones. 

The  sutures  at  the  side  of  the  skull  extend  from  the  external  angular  process  of 
the  frontal  bone  to  the  lower  end  of  the  lambdoid  suture  behind.  The  anterior  portion 
is  formed  between  the  lateral  part  of  the  frontal  bone  above  and  the  malar  and  great 
wing  of  the  sphenoid  below,  forming  the  fronto-xnalar  suture  (sutura  zygomatico- 
frontalis)  and  fronto-sphenoidal  suture  (sutura  sphenofrontalis) .  These  sutures 
can  also  be  seen  in  the  orbit,  and  form  part  of  the  so-called  transverse  facial 
suture.  The  posterior  portion  is  formed  between  the  parietal  bone  above  and 
the  great  wing  of  the  sphenoid,  the  squamous  and  mastoid  portions  of  the  temporal 
bone  below,  forming  the  spheno-parietal,  squamo-parietal,  and  masto-parietal  sutures. 

The  spheno-parietal  (sutura  sphenoparietalis)  is  very  short;  it  is  formed  by  the 
tip  of  the  great  wing  of  the  sphenoid,  which  overlaps  the  anterior  inferior  angle 
of  the  parietal  bone. 

The  squamo-parietal  or  squamous  suture  (sutura  squamosa)  is  arched.  It  is 
formed  by  the  squamous  portion  of  the  temporal  bone  overlapping  the  middle 
division  of  the  lower  border  of  the  parietal. 

The  masto-parietal  (sutura  parietomastoidea)  is  a  short  suture,  deeply  dentated, 
formed  by  the  posterior  inferior  angle  of  the  parietal  and  the  superior  border  of 
the  mastoid  portion  of  the  temporal. 

The  sutures  at  the  base  of  the  skull  are  the  basilar  in  the  centre,  and  on  each 
side  the  petro-occipital,  the  masto-occipital,  the  petro-sphenoidal,  and  the  squamo- 
sphenoidal. 

The  Basilar  Suture  (fissura  sphenooccipitalis)  is  formed  by  the  junction  of  the 
basilar  surface  of  the  occipital  bone  with  the  posterior  surface  of  the  body  of 
the  sphenoid.  At  an  early  period  of  life  a  thin  plate  of  cartilage  exists  between 
these  bones,  but  in  the  adult  they  become  fused  into  one  (synchondrosis  spheno- 
occipitalis) .  Between  the  outer  extremity  of  the  basilar  suture  and  the  termina- 
tion of  the  lambdoid  an  irregular  suture  exists,  which  is  subdivided  into  two  por- 
tions. The  inner  portion,  formed  by  the  union  of  the  petrous  part  of  the  temporal 
with  the  occipital  bone,  is  termed  the  petro-occipital  fissure  (fissura  petrooccipitalis) . 
The  outer  portion,  formed  by  the  junction  of  the  mastoid  part  of  the  temporal 
with  the  occipital,  is  called  the  masto-occipital  suture  (sutura  occipitomastoidea) . 
Between  the  bones  forming  the  petro-occipital  suture  a  thin  plate  of  cartilage 
exists;  in  the  masto-occipital  is  occasionally  found  the  opening  of  the  mastoid 
foramen.  Between  the  outer  extremity  of  the  basilar  suture  and  the  spheno- 
parietal  an  irregular  suture  may  be  seen,  formed  by  the  union  of  the  sphenoid 
with  the  temporal  bone.  The  inner  and  smaller  portion  of  this  suture  is  termed 
the  petro-sphenoidal  fissure  (fissura  sphenopetrosa) ;  it  is  formed  between  the 
petrous  portion  of  the  temporal  and  the  great  wing  of  the  sphenoid;  the  outer 
portion,  of  greater  length  and  arched,  is  formed  between  the  squamous  portion 
of  the  temporal  and  the  great  wing  of  the  sphenoid ;  it  is  called  the  squamo- 
sphenoidal  suture  (sutura  sphenosquamosa) . 

The  cranial  bones  are  connected  with  those  of  the  face,  and  the  facial  bones 
with  each  other,  by  numerous  sutures,  which,  though  distinctly  marked,  have 
received  no  special  names.  The  only  remaining  suture  deserving  especial  con- 
sideration is  the  transverse  suture.  This  extends  across  the  upper  part  of  the  face, 
and  is  formed  by  the  junction  of  the  frontal  with  the  facial  bones:  it  extends  from 
the  external  angular  process  of  one  side  to  the  same  point  on  the  opposite  side, 
and  connects  the  frontal  with  the  malar,  the  sphenoid,  the  ethmoid,  the  lachrymal, 


THE    VERTEX   OF    THE  SKULL  129 

the  superior  maxillary,  and  the  nasal  bones  on  each  side  (sutura  zygomatico- 
jrontalis;  the  orbital  portion  of  the  sutura  sphenofrontalis,  sutura  fronto- 
ethmoidalis,  sutura  frontolacrimalis,  sutura  frontomaxillaris,  sutura  nasojrontalis) . 
The  sutures  remain  separate  for  a  considerable  period  after  the  complete  for- 
mation of  the  skull.  It  is  probable  that  they  serve  the  purpose  of  permitting  the 
growth  of  the  bones  at  their  margins,  while  their  peculiar  formation,  together 
with  the  interposition  of  the  sutural  ligament  between  the  bones  forming  them, 
prevents  the  dispersion  of  blows  or  jars  received  upon  the  skull.  Humphry 
remarks,  "that,  as  a  general  rule,  the  sutures  are  first  obliterated  at  the  parts  in 
which  the  ossification  of  the  skull  was  last  completed — viz.,  in  the  neighborhood 
of  the  fontanelles;  and  the  cranial  bones  seem  in  this  respect  to  observe  a  similar 
law  to  that  which  regulates  the  union  of  the  epiphyses  to  the  shafts  of  the  long 
bones."  The  same  author  remarks  that  the  time  of  their  disappearance  is  ex- 
tremely variable:  they  are  sometimes  found  well  marked  in  skulls  edentulous 
with  age,  while  in  others  wrhich  have  only  just  reached  maturity  they  can  hardly 
be  traced.  The  obliteration  of  the  sutures  takes  place  sooner  on  the  inner  than 
on  the  outer  surface  of  the  skull.  The  sagittal  and  coronal  sutures  are  as  a  rule 
the  first  to  become  ossified — the  process  starting  near  the  posterior  extremity  of 
the  former  and  the  lower  ends  of  the  latter. 

THE  SKULL  AS  A  WHOLE. 

The  skull,  formed  by  the  union  of  the  several  cranial  and  facial  bones  already 
described,  when  considered  as  a  whole  is  divisible  into  five  regions:  a  superior 
region  or  vertex,  an  inferior  region  or  base,  two  lateral  regions,  and  an  anterior 
region,  the  face. 

The  Vertex  of  the  Skull. 

The  superior  region,  or  vertex,  presents  two  surfaces,  an  external  and  an 
internal. 

Surfaces.  External  Surface.  (This  surface  as  seen  from  above  is  called  the 
norma  verticalis.) — The  external  surface  is  bounded,  in  front,  by  the  glabella 
and  supraorbital  ridges;  behind,  by  the  occipital  protuberance  and  superior 
curved  lines  of  the  occipital  bone;  laterally,  by  an  imaginary  line  extending  from 
the  outer  end  of  the  superior  curved  line,  along  the  temporal  ridge,  to  the  exter- 
nal angular  process  of  the  frontal  bone.  This  surface  includes  the  greater  part  of 
the  vertical  portion  of  the  frontal,  the  greater  part  of  the  parietal,  and  the  superior 
third  of  the  occipital  bone;  it  is  smooth,  convex,  of  an  elongated  oval  form,  crossed 
transversely  by  the  coronal  suture,  and  from  before  backward  by  the  sagittal, 
which  terminates  behind  in  the  lambdoid.  The  point  of  junction  of  the  coronal 
and  sagittal  sutures  is  named  the  bregma,  and  is  represented  by  a  line  drawn  verti- 
cally upward  from  the  external  auditory  meatus,  the  head  being  in  its  normal  posi- 
tion. The  point  of  junction  of  the  sagittal  and  lambdoid  sutures  is  called  the 
lambda,  and  is  about  2f  inches  above  the  external  occipital  protuberance.  From 
before  backward  may  be  seen  the  frontal  eminences  and  remains  of  the  suture 
connecting  the  two  lateral  halves  of  the  frontal  bone;  on  each  side  of  the  sagittal 
suture  are  the  parietal  foramen  and  parietal  eminence,  and  still  more  posteriorly 
the  convex  surface  of  the  occipital  bone.  In  the  neighborhood  of  the  parietal 
foramen  the  skull  is  often  flattened,  and  the  name  of  obelion  is  sometimes  given 
to  that  point  of  the  sagittal  suture  which  lies  exactly  opposite  to  the  parietal 
foramen. 

Internal  or  Cerebral  Surface. — The  internal  surface  is  concave,  presents  depres- 
sions for  the  convolutions  of  the  cerebrum,  and  numerous  furrows  for  the  lodge- 
ment of  branches  of  the  meningeal  arteries.  Along  the  middle  line  of  this 


130  THE  SKELETON 

surface  is  a  longitudinal  groove,  narrow  in  front,  where  it  commences  at  the 
frontal  crest,  but  broader  behind,  where  it  lodges  the  superior  longitudinal 
sinus,  and  by  its  margin  affords  attachment  to  the  falx.  On  either  side  of  it  are 
several  depressions  for  the  arachnoid  villi,  and  at  its  back  part  the  internal  open- 
ings of  the  parietal  foramina.  This  surface  is  crossed,  in  front,  by  the  coronal 
suture;  from  before  backward  by  the  sagittal;  behind,  by  the  lambdoid. 


The  Base  of  the  Skull  (the  Skull  being  without  the  Mandible). 

The  inferior  region,  or  base  of  the  skull,  presents  two  surfaces — an  internal 
or  cerebral,  and  an  external  or  basilar. 

Surfaces.  Internal  Upper  or  Cerebral  Surface. — The  internal  or  cerebral  surface 
(Fig.  95)  presents  three  fossie,  called  the  anterior,  middle,  and  posterior  fossae  of  the 
cranium. 

ANTERIOR  FOSSA  (fossa  cranii  anterior). — The  anterior  fossa  is  formed  by  the 
orbital  plates  of  the  frontal,  the  cribriform  plate  of  the  ethmoid,  the  anterior 
third  of  the  superior  surface  of  the  body,  and  the  upper  surface  of  the  lesser  wings 
of  the  sphenoid  bone.  It  is  the  most  elevated  of  the  three  fossae,  convex  exter- 
nally where  it  corresponds  to  the  roof  of  the  orbit,  concave  in  the  median  line  in 
the  situation  of  the  cribriform  plate  of  the  ethmoid.  It  is  traversed  by  three  sutures, 
the  ethmo-frontal,  ethmo-sphenoidal,  and  fronto-sphenoidal,  and  lodges  the  frontal 
lobes  of  the  cerebrum.  It  presents,  in  the  median  line,  from  before  backward,  the 
commencement  of  the  groove  for  the  superior  longitudinal  sinus  and  the  frontal 
crest  for  the  attachment  of  the  falx;  the  foramen  caecum,  an  aperture  formed 
between  the  frontal  bone  and  the  crista  galli  of  the  ethmoid,  which,  if  pervious, 
transmits  a  small  vein  from  the  nose  to  the  superior  longitudinal  sinus;  behind  the 
foramen  caecum,  the  crista  galli,  the  posterior  margin  of  which  affords  attachment 
to  the  falx;  on  either  side  of  the  crista  galli,  the  cribriform  plate,  which  supports  the 
olfactory  bulb,  and  presents  three  rows  of  foramina  for  the  transmission  of  its 
nervous  filaments,  and  in  front  a  slit-like  opening  for  the  nasal  branch  of  the 
ophthalmic  division  of  the  trigeminal  nerve.  On  the  outer  side  of  each  olfactory 
groove,  transmits  the  anterior  ethmoidal  vessels  and  the  nasal  nerve,  which  latter 
runs  in  a  depression  along  the  surface  of  the  ethmoid  to  the  slit-like  opening  above 
mentioned;  while  the  posterior  ethmoidal  foramen  opens  at  the  back  part  of  this 
margin  under  cover  of  the  projecting  lamina  of  the  sphenoid,  and  transmits  the 
posterior  ethmoidal  vessels.  Farther  back  in  the  middle  line  is  the  ethmoidal  spine, 
bounded  behind  by  a  slight  elevation,  separating  two  shallow  longitudinal  grooves 
which  support  the  olfactory  lobes.  Behind  this  is  a  transverse  sharp  ridge,  run- 
ning outward  on  either  side  to  the  anterior  margin  of  the  optic  foramen,  and  sepa- 
rating the  anterior  from  the  middle  fossa  of  the  base  of  the  skull.  The  anterior 
fossa  presents,  laterally,  depressions  for  the  convolutions  of  the  brain  and  grooves 
for  the  lodgement  of  the  anterior  meningeal  arteries. 

MIDDLE  FOSSA  (fossa  cranii  media). — The  middle  fossa,  deeper  than  the  pre- 
ceding, is  narrow  in  the  middle  line,  but  becomes  wider  at  the  side  of  the  skull.  It 
is  bounded  in  front  by  the  posterior  margin  of  the  lesser  wing  of  the  sphenoid,  the 
anterior  clinoid  process,  and  the  ridge  forming  the  anterior  margin  of  the  optic 
groove;  behind,  by  the  superior  border  of  the  petrous  portion  of  the  temporal  and 
the  dorsum  sellae ;  externally  by  the  squamous  portion  of  the  temporal  and  the 
anterior  inferior  angle  of  the  parietal  bone,  and  greater  wing  of  the  sphenoid.  It  is 
traversed  by  four  sutures,  the  squamo-parietal,  spheno-parietal,  squamo-sphenoidal, 
and  petro-sphenoidal.  In  the  middle  line,  from  before  backward,  is  the  optic  groove, 


THE  BASE  OF  THE  SKULL 


131 


behind  which  lies  the  chiasma  (optic  commissure) ;  the  groove  terminates  on  each 
side  in  the  optic  foramen,  for  the  passage  of  the  optic  nerve  and  ophthalmic  artery; 


Groove  for  superior  longitudinal  sinus. 

Grooves  for  anterior  meningeal  artery. 

Foramen  csecum. 

Crista  galli. 

Slit  for  nasal  nerve. 

Groove  for  nasal  nerve. 

Anterior  ethmoidal  foramen. 

Orifices  for  olfactory  nerves. 

Posterior  ethmoidal  foramen. 

Ethmoidal  spine. 


Olfactory  grooves. 

Optic  foramen. 

Optic  groove. 

Olivary  process. 

Anterior  clinoid  process. 

Middle  clinoid  process. 

Posterior  clinoid  process. 

Groove  for  6th  nerve. 

Foramen  lacerum  medium. 

Orifice  of  carotid  canal. 

Depression  for  Gasserian  ganglion. 


Meatus  auditorius  internus. 

Slit  for  dura  mater. 

Superior  petrosal  groove. 

Foramen  lacerum  posterius. 

Antenor  condyloid  foramen. 

Aquxductus  vestibuli. 

Posterior  condyloid  foramen. 


Mastoid  foramen 
Posterior  meningeal  grooves. 


FIG.  95.  —  Base  of  the  skull.     Inner  or  cerebral  surface. 


behind  the  optic  groove  is  the  olivary  process  and  laterally  the  anterior  clinoid  pro- 
cesses, to  which  are  attached  processes  of  the  tentorium.  Farther  back  is  the  sella 
turcica,  a  deep  depression  which  lodges  the  pituitary  gland,  bounded  in  front  by  a 


132  THE  SKELETON 

small  eminence  on  either  side,  the  middle  clinoid  process,  and  behind  by  a  broad, 
square  plate  of  bone,  the  dorsum  sellae  or  dorsum  ephippii,  surmounted  at  each  supe- 
rior angle  by  a  tubercle,  the  posterior  clinoid  process ;  beneath  the  latter  process  is 
a  notch,  for  the  abducent  nerve.  On  each  side  of  the  sella  turcica  is  the  cavernous 
groove:  it  is  broad,  shallow,  and  curved  somewhat  like  the  italic  letter  /;  it  com- 
mences behind  at  the  foramen  lacerum  medium,  and  terminates  on  the  inner 
side  of  the  anterior  clinoid  process,  and  presents  along  its  outer  margin  a  ridge 
of  bone.  This  groove  lodges  the  cavernous  sinus,  the  internal  carotid  artery, 
and  the  nerves  of  the  orbit.  The  sides  of  the  middle  fossa  are  of  considerable 
depth;  they  present  depressions  for  the  convolutions  of  the  brain  and  grooves 
for  the  branches  of  the  middle  meningeal  artery;  the  latter  commence  on  the 
outer  side  of  the  foramen  spinosum,  and  consist  of  two  large  branches,  an  anterior 
and  a  posterior;  the  former  passing  upward  and  forward  to  the  anterior  inferior 
angle  of  the  parietal  bone,  the  latter  passing  upward  and  backward.  The  fol- 
lowing foramina  may  also  be  seen  from  before  backward:  Most  anteriorly  is  the 
foramen  lacerum  anterius,  or  sphenoidal  fissure  (fissura  orbitalis  superior),  formed 
above  by  the  lesser  wing  of  the  sphenoid ;  below,  by  the  greater  wing;  internally,  by 
the  body  of  the  sphenoid ;  and  sometimes  completed  externally  by  the  orbital  plate 
of  the  frontal  bone.  It  transmits  the  third,  the  fourth,  the  three  branches  of  the 
ophthalmic  division  of  the  trigeminal,  the  abducent  nerve,  some  filaments  from  the 
cavernous  plexus  of  the  sympathetic,  the  orbital  branch  of  the  middle  meningeal 
artery,  a  recurrent  branch  from  the  lachrymal  artery  to  the  dura,  and  the  ophthal- 
mic vein.  Behind  the  inner  extremity  of  the  sphenoidal  fissure  is  the  foramen 
rotundum,  for  the  passage  of  the  second  division  of  the  trigeminal  or  the  superior 
maxillary  nerve;  still  more  posteriorly  is  seen  a  small  orifice,  the  foramen  Vesalii, 
an  opening  situated  between  the  foramen  rotundum  and  ovale,  a  little  internal  to 
both:  it  varies  in  size  in  different  individuals,  and  is  often  absent;  when  present  it 
transmits  a  small  vein.  It  opens  below  into  the  pterygoid  fossa,  just  at  the  outer 
side  of  the  scaphoid  depression.  Behind  and  external  to  the  latter  opening  is  the 
foramen  ovale,  which  transmits  the  third  division  of  the  trigeminal  or  the  inferior 
maxillary  nerve,  the  small  meningeal  artery,  and  the  small  petrosal  nerve.1  On  the 
outer  side  of  the  foramen  ovale  is  the  foramen  spinosum,  for  the  passage  of  the  middle 
meningeal  artery;  and  on  the  inner  side  of  the  foramen  ovale  is  the  foramen  lacerum 
medium.  The  lower  part  of  this  aperture  is  filled  with  cartilage  in  the  recent  state. 
The  Vidian  nerve  and  a  meningeal  branch  from  the  ascending  pharyngeal  artery 
pierce  this  cartilage.  On  the  anterior  surface  of  the  petrous  portion  of  the  temporal 
bone  is  seen,  from  without  inward,  the  eminence  caused  by  the  projection  of  the 
superior  semicircular  canal;  in  front  of  and  a  little  outside  this  is  a  depression  cor- 
responding to  the  roof  of  the  tympanum;  the  groove  leading  to  the  hiatus  Fallopii, 
for  the  transmission  of  the  petrosal  branch  of  the  Vidian  nerve  and  the  petrosal 
branch  of  the  middle  meningeal  artery;  beneath  it,  the  smaller  groove,  for  the  pas- 
sage of  the  lesser  petrosal  nerve;  and,  near  the  apex  of  the  bone,  the  depression  for 
the  Gasserian  ganglion;  and  the  internal  orifice  of  the  carotid  canal  (foramen 
caroticum  internum),  for  the  passage  of  the  internal  carotid  artery  and  carotid 
plexus  of  nerves. 

POSTERIOR  FOSSA  (fossa  cranii*  posterior). — The  posterior  fossa,  deeply  con- 
cave, is  the  largest  of  the  three,  and  situated  on  a  lower  level  than  either  of  the  pre- 
ceding. It  is  formed  by  the  posterior  third  of  the  superior  surface  of  the  body  of  the 
sphenoid,  by  the  occipital,  the  petrous  and  mastoid  portions  of  the  temporal,  and 
the  posterior  inferior  angle  of  the  parietal  bone;  it  is  crossed  by  four  sutures,  the 
petro-occipital,  the  mas  to-occipital,  the  masto-parietal,  and  the  basilar;  and  lodges 
the  cerebellum,  pons,  and  oblongata.  It  is  separated  from  the  middle  fossa  in 

1  See  footnote,  p.  95. 


THE  BASE  OF  THE  SKULL  133 

the  median  line  by  the  dorsum  sellae,  and  on  each  side  by  the  superior  border 
of  the  petrous  portion  of  the  temporal  bone.  This  border  serves  for  the  attach- 
ment of  the  tentorium,  is  grooved  for  the  superior  petrosal  sinus,  and  at  its 
inner  extremity  presents  a  notch,  upon  which  rests  the  trigeminal  nerve.  The 
circumference  of  the  fossa  is  bounded  posteriorly  by  the  grooves  for  the  lateral 
sinuses.  In  the  centre  of  this  fossa  is  the  foramen  magnum,  bounded  on  either 
side  by  a  rough  tubercle,  which  gives  attachment  to  the  odontoid  or  check  liga- 
ments; and  a  little  above  these  are  seen  the  internal  openings  of  the  anterior 
condyloid  foramina,  through  which  pass  the  hypoglossal  nerves  and  meningeal 
branches  from  the  ascending  pharyngeal  arteries.  In  front  of  the  foramen  mag- 
num is  a  grooved  surface,  formed  by  the  basilar  process  of  the  occipital  bone  and 
by  the  posterior  third  of  the  superior  surface  of  the  body  of  the  sphenoid,  which 
supports  the  oblongata  and  pons,  and  articulates  on  each  side  with  the  petrous 
portion  of  the  temporal  bone,  forming  the  petro-occipital  suture,  the  anterior  half 
of  which  is  grooved  for  the  inferior  petrosal  sinus,  the  posterior  half  being 
encroached  upon  by  the  foramen  lacerum  posterius  or  jugular  foramen  (foramen 
jugulare).  This  foramen  presents  three  compartments:  through  the  anterior 
passes  the  inferior  petrosal  sinus;  through  the  posterior,  the  lateral  sinus  and 
some  meningeal  branches  from  the  occipital  and  ascending  pharyngeal  arteries; 
and  through  the  middle,  the  glosso-pharyngeal,  vagus,  and  accessory  nerves. 
Above  the  jugular  foramen  is  the  internal  auditory  meatus,  for  the  facial  and  audi- 
tory nerves  and  auditory  artery;  behind  and  external  to  this  is  the  slit-like  opening 
leading  into  the  aquaeductus  vestibuli,  which  lodges  the  ductus  endolymphaticus; 
while  between  the  two  latter,  and  near  the  superior  border  of  the  petrous  portion, 
is  a  small,  triangular  depression,  the  remains  of  the  floccular  fossa,  which  lodges  a 
process  of  the  dura  and  occasionally  transmits  a  small  vein  into  the  substance  of 
the  bone.  Behind  the  foramen  magnum  are  the  inferior  occipital  fossae,  which 
lodge  the  hemispheres  of  the  cerebellum,  separated  from  one  another  by  the  inter- 
nal occipital  crest,  which  serves  for  the  attachment  of  the  falcula  (falx  cerebelli)  and 
lodges  the  occipital  sinus.  The  posterior  fossae  are  surmounted  above  by  the  deep 
transverse  grooves  for  the  lodgement  of  the  lateral  sinuses.  These  channels,  in 
their  passage  outward,  groove  the  occipital  bone,  the  posterior  inferior  angle  of 
the  parietal,  the  mastoid  portion  of  the  temporal,  and  the  jugular  process  of  the 
occipital,  and  terminate  at  the  back  part  of  the  jugular  foramen.  Where  the  lateral 
sinus  grooves  the  mastoid  portion  of  the  temporal  bone  the  orifice  of  the  mastoid 
foramen  may  be  seen.  Just  previous  to  the  termination  of  the  groove  the  posterior 
condyloid  foramen  opens  into  it.  Neither  foramen  is  constant. 

External  Under  or  Basilar  Surface  (the  view  from  below  is  called  the  norma 
basalis). — The  external  surface  of  the  base  of  the  skull  (Fig.  96)  is  extremely 
irregular.  It  is  bounded  in  front  by  the  incisor  teeth  in  the  upper  jaw;  behind 
by  the  superior  curved  lines  of  the  occipital  bone;  and  laterally  by  the  alve- 
olar arch,  the  lower  border  of  the  malar  bone,  the  zygoma,  and  an  imaginary  line 
extending  from  the  zygoma  to  the  mastoid  process  and  extremity  of  the  superior 
curved  line  of  the  occiput.  It  is  formed  by  the  palate  processes  of  the  superior 
maxillary  and  palate  bones,  the  vomer,  the  pterygoid  processes,  under  surface 
of  the  great  wing,  spinous  processes  and  part  of  the  body  of  the  sphenoid,  the 
under  surface  of  the  squamous,  mastoid,  and  petrous  portions  of  the  temporal, 
and  the  under  surface  of  the  occipital  bone.  The  anterior  part  of  the  base  of  the 
skull  is  raised  above  the  level  of  the  rest  of  this  surface  (when  the  skull  is  turned 
over  for  the  purpose  of  examination),  surrounded  by  the  alveolar  process,  which  is 
thicker  behind  than  in  front,  and  excavated  by  sixteen  depressions  for  lodging  the 
teeth  of  the  upper  jaw,  the  cavities  varying  in  depth  and  size  according  to  the  teeth 
they  contain.  Immediately  behind  the  incisor  teeth  is  the  anterior  palatine  fossa 
(foramen  incisivum) .  At  the  bottom  of  this  fossa  may  usually  be  seen  four  apertures : 


134 


THE    SKELETON 


two  placed  laterally,  the  foramina  of  Stenson,  which  open  above,  one  in  the  floor  of 
each  nostril,  and  transmit  the  anterior  branch  of  the  posterior  palatine  vessels,  and 


Anterior  palatine  fossa. 

Transmits  left  naso-palatine  nerve. 
Transmits  anterior  palatine  vessel. 
Transmits  right  naso-palatine  nerve. 


Accessory  palatine  foramina. 
Posterior  nasal  spine. 

AZYQOS   UVUL/E. 

Hamular  process. 


•Sphenoid  process  of  palate. 
Ptery go-palatine  canal. 


-TENSOR    TVMPANI. 

Pharyngeal  spine  for 

SUPERIOR    CONSTRICTOR. 

Situation  of  Eustachian  tube  and, 
canal  for  TENSOR  TVMPANI. 

TENSOR    PALATI. 

Canal  for  Jacobson's  nerve. 
Aquseductus  cochlex. 
Foramen  lacerum  postering. 
Canal  for  Arnold's  nerve. 
Auricular  fissure. 


FIG.  96.— Base  of  the  skull.     External  surface. 


THE   BASE    OF    THE  SKULL  135 

two  in  the  median  line  in  the  intermaxillary  suture,  the  foramina  of  Scarpa,  one 
in  front  of  the  other,  the  anterior  transmitting  the  left,  and  the  posterior  (the 
larger)  the  right,  naso-palatine  nerve.  These  two  lateral  canals  are  sometimes 
wanting,  or  they  may  join  to  form  a  single  one,  or  one  of  them  may  open  into  one 
of  the  lateral  canals  above  referred  to.  The  palatine  vault  is  concave,  uneven, 
perforated  by  numerous  foramina,  marked  by  depressions  for  the  palatine  glands, 
and  crossed  by  a  crucial  suture,  formed  by  the  junction  of  the  four  bones  of  which 
it  is  composed.  At  the  front  part  of  this  surface  a  delicate  linear  suture  may 
frequently  be  seen,  passing  outward  and  forward  from  the  anterior  palatine  fossa 
to  the  interval  between  the  lateral  incisor  and  canine  teeth,  and  marking  off  the 
pre -maxillary  portion  of  the  bone.  At  each  posterior  angle  of  the  hard  palate  is 
the  posterior  palatine  foramen,  for  the  transmission  of  the  posterior  palatine  vessels 
and  great  descending  palatine  nerve;  and  running  forward  and  inward  from  it  a 
groove,  for  the  same  vessels  and  nerve.  Behind  the  posterior  palatine  foramen 
is  the  tuberosity  of  the  palate  bone,  perforated  by  one  or  more  accessory  posterior 
palatine  canals,  and  marked  by  the  commencement  of  a  ridge  which  runs  trans- 
versely inward,  and  serves  for  the  attachment  of  the  tendinous  expansion  of  the 
Tensor  palati  muscle.  Projecting  backward  from  the  centre  of  the  posterior 
border  of  the  hard  palate  is  the  posterior  nasal  spine,  for  the  attachment  of  the 
Azygos  uvulae  muscle.  Behind  and  above  the  hard  palate  is  the  posterior  aper- 
ture of  the  nares,  divided  into  two  parts  by  the  vomer,  bounded  above  by  the 
body  of  the  sphenoid,  below  by  the  horizontal  plate  of  the  palate  bone,  and  lat- 
erally by  the  internal  pterygoid  plate  of  the  sphenoid.  Each  aperture  measures 
about  an  inch  in  the  vertical  and  about  half  an  inch  in  the  transverse  direction. 
At  the  base  of  the  vomer  may  be  seen  the  expanded  aloe  of  this  bone,  receiving 
between  them,  on  each  side,  the  rostrum  of  the  sphenoid.  Near  the  lateral  margins 
of  the  vomer,  at  the  root  of  the  pterygoid  processes,  are  the  pterygo-palatine  canals. 
The  pterygoid  process,  which  bounds  the  posterior  nares  on  each  side,  presents 
near  its  base  the  pterygoid  or  Vidian  canal  (canalis  pterygoideus) ,  for  the  Vidian  nerve 
and  artery.  Each  process  consists  of  two  plates,  which  bifurcate  at  the  extremity  to 
receive  the  tuberosity  of  the  palate  bone,  and  are  separated  behind  by  the  ptery- 
goid fossa,  which  lodges  the  Internal  pterygoid  muscle.  The  internal  plate  is 
long  and  narrow,  presenting  on  the  outer  side  of  its  base  the  scaphoid  fossa,  for 
the  origin  of  the  Tensor  palati  muscle,  and  at  its  extremity  the  hamular  process, 
around  which  the  tendon  of  this  muscle  turns.  The  external  pterygoid  plate  is 
broad,  forms  the  inner  boundary  of  the  zygomatic  fossa,  and  affords  attachment 
by  its  outer  surface  to  the  External  pterygoid  muscle. 

Behind  the  nasal  fossae  in  the  middle  line  is  the  basilar  surface  of  the  occipital 
bone,  presenting  in  its  centre  the  pharyngeal  spine,  for  the  attachment  of  the 
Superior  constrictor  muscle  of  the  pharynx,  with  depressions  on  each  side  for 
the  insertion  of  the  Rectus  capitis  anticus  major*and  minor.  At  the  base  of  the 
external  pterygoid  plate  is  the  foramen  ovale,  for  the  transmission  of  the  third  divi- 
sion of  the  trigeminal  nerve,  the  small  meningeal  artery,  and  sometimes  the  small 
petrosal  nerve;  behind  this,  the  foramen  spinosum,  which  transmits  the  middle 
meningeal  artery,  and  the  prominent  spinous  process  of  the  sphenoid,  which  gives 
attachment  to  the  internal  lateral  ligament  of  the  lower  jaw  and  the  Tensor  palati 
muscle.  External  to  the  spinous  process  is  the  glenoid  fossa,  divided  into  two  parts 
by  the  Glaserian  fissure  (page  84),  the  anterior  portion  concave,  smooth,  bounded 
in  front  by  the  eminentia  articularis,  and  serving  for  the  articulation  of  the  condyle 
of  the  lower  jaw;  the  posterior  portion  rough,  bounded  behind  by  the  tympanic 
plate,  and  serving  for  the  reception  of  part  of  the  parotid  gland.  Emerging  from 
between  the  laminae  of  the  vaginal  process  of  the  tympanic  plate  is  the  styloid 
process,  and  at  the  base  of  this  process  is  the  stylo-mastoid  foramen,  for  the  exit  of 
the  facial  nerve  and  entrance  of  the  stylo-mastoid  artery.  External  to  the  stylo- 


136  THE  SKELETON 

mastoid  foramen  is  the  auricular  fissure,  for  the  exit  of  the  auricular  branch  of  the 
vagus,  bounded  behind  by  the  mastoid  process.  Upon  the  inner  side  of  the  mas- 
toid process  is  a  deep  groove,  the  digastric  fossa;  and  a  little  more  internally  the 
occipital  groove,  for  the  occipital  artery.  At  the  base  of  the  internal  pterygoid  plate 
is  a  large  and  somewhat  triangular  aperture,  the  foramen  lacerum  medium,  bounded 
in  front  by  the  great  wing  of  the  sphenoid,  behind  by  the  apex  of  the  petrous  por- 
tion of  the  temporal  bone,  and  internally  by  the  body  of  the  sphenoid  and  basilar 
process  of  the  occipital  bone :  it  presents  in  front  the  posterior  orifice  of  the  Vidian 
canal;  behind,  the  aperture  of  the  carotid  canal.  The  basilar  surface  of  this  open- 
ing is  filled  in  the  recent  state  by  fibre-cartilaginous  substance;  across  its  upper 
or  cerebral  aspect  passes  the  internal  carotid  artery.  External  to  this  aperture  the 
petro-sphenoidal  suture  is  observed,  at  the  outer  termination  of  which  is  seen  the 
orifice  of  the  canal  for  the  Eustachian  tube  and  that  for  the  Tensor  tympani 
muscle.  Behind  this  suture  is  seen  the  under  surface  of  the  petrous  portion  of  the 
temporal  bone,  presenting,  from  within  outward,  the  quadrilateral,  rough  surface, 
part  of  which  affords  attachment  to  the  Levator  palati  and  Tensor  tympani  mus- 
cles; posterior  to  this  surface  is  the  orifice  of  the  carotid  canal  (foramen  caroticum 
externum)  and  the  orifice  of  the  aquaeductus  cochleae,  the  former  transmitting  the 
internal  carotid  artery  and  the  ascending  branches  of  the  superior  cervical  ganglion 
of  the  sympathetic,  the  latter  serving  for  the  passage  of  a  small  artery  to  and  a 
small  vein  from  the  cochlea.  Behind  the  carotid  canal  is  a  large  aperture,  the 
jugular  foramen,  formed  in  front  by  the  petrous  portion  of  the  temporal,  and  behind 
by  the  occipital;  it  is  generally  larger  on  the  right  than  on  the  left  side,  and  is 
divided  into  three  compartments  by  processes  of  dura.  The  anterior  is' for  the 
passage  of  the  inferior  petrosal  sinus;  the  posterior,  for  the  lateral  sinus  and 
some  meningeal  branches  from  the  occipital  and  ascending  pharyngeal  arteries; 
the  central  one,  for  the  glosso-pharyngeal,  vagus,  and  accessory  nerves.  On 
the  ridge  of  bone  dividing  the  carotid  canal  from  the  jugular  foramen  is  the 
small  foramen  for  the  transmission  of  Jacobson's  nerve;  and  on  the  wall  of  the 
jugular  foramen,  near  the  root  of  the  styloid  process,  is  the  small  aperture  for 
the  transmission  of  the  vagus  nerve.  Behind  the  basilar  -surface  of  the 
occipital  bone  is  the  foramen  magnum,  bounded  on  each  side  by  the  condyles, 
rough  internally  for  the  attachment  of  the  check  or  odontoid  ligaments,  and 
presenting  externally  a  rough  surface,  the  jugular  process,  which  serves  for  the 
attachment  of  the  Rectus  capitis  lateralis  muscle  and  the  lateral  occipito-atlantal 
ligament.  On  either  side  of  each  condyle  anteriorly  is  the  anterior  condyloid  fossa, 
perforated  by  the  anterior  condyloid  foramen,  for  the  passage  of  the  hypoglossal 
nerve  and  often  a  meningeal  branch  of  the  ascending  pharyngeal  artery.  Behind 
each  condyle  is  the  posterior  condyloid  fossa,  perforated  by  the  posterior  condyloid 
foramen,  for  the  transmission  of  a  vein  to  the  lateral  sinus.  Behind  the  foramen 
magnum  is  the  external  occipital  crest,  terminating  above  at  the  external  occipital 
protuberance,  whilst  on  each  side  are  seen  the  superior  and  inferior  curved  lines; 
these,  as  well  as  the  surfaces  of  bone  between  them,  are  rough  for  the  attachment 
of  the  muscles,  which  are  enumerated  on  page  76. 

The  Lateral  Region  of  the  Skull. 

The  view  of  the  lateral  region  of  the  skull  from  the  side  is  known  as  the  norma 
lateralis.  The  lateral  region  is  of  a  somewhat  triangular  form,  the  base  of  the  tri- 
angle being  formed  by  a  line  extending  from  the  external  angular  process  of  the 
frontal  bone  along  the  temporal  ridge  backward  to  the  outer  extremity  of  the  supe- 
rior curved  line  of  the  occiput;  and  the  sides  by  two  lines,  the  one  drawn  down- 
ward and  backward  from  the  external  angular  process  of  the  frontal  bone  to  the 
angle  of  the  lower  jaw,  the  other  from  the  angle  of  the  jaw  upward  and  back- 


THE  LATERAL    REGION   OF   THE  SKULL 


137 


ward  to  the  outer  extremity  of  the  superior  curved  line.  This  region  is  divisible  into 
three  portions — temporal  fossa,  mastoid  portion,  and  zygomatic  or  infratemporal  fossa. 
The  Temporal  Fossa  (fossa  temporalis) . — The  temporal  fossa  is  bounded  above 
and  behind  by  the  temporal  ridges,  which  extend  from  the  external  angular  process 
of  the  frontal  upward  and  backward  across  the  frontal  and  parietal  bones,  curving 
downward  behind  to  terminate  in  the  posterior  root  of  the  zygomatic  process,  supra- 


FIG.  97. — Side  view  of  the  skull.     (Cryer.) 


mastoid  crest.  In  front  it  is  bounded  by  the  frontal,  malar,  and  great  wing  of  the 
sphenoid;  externally  by  the  zygomatic  arch  formed  conjointly  by  the  malar  and 
temporal  bones;  below,  it  is  separated  from  the  zygomatic  fossa  by  the  pterygoid 
ridge,  seen  on  the  outer  surface  of  the  great  wing  of  the  sphenoid.  This  fossa  is 
formed  by  five  bones,  part  of  the  frontal,  great  wing  of  the  sphenoid,  parietal,  squa- 
mous  portion  of  the  temporal  and  malar  bones,  and  is  traversed  by  six  sutures,  part  of 
the  transverse  facial,  spheno-malar,  coronal,  spheno-parietal,  squamo-parietal,  and 
squamo-sphenoidal.  The  point  where  the  coronal  suture  crosses  the  superior  tem- 
poral ridge  is  sometimes  named  the  stephanion ;  and  the  region  where  the  four  bones, 
the  parietal,  the  frontal,  the  squamous,  and  the  greater  wing  of  the  sphenoid,  meet, 
at  the  anterior  inferior  angle  of  the  parietal  bone,  is  named  the  pterion.  This  point 
is  about  on  a  level  with  the  external  angular  process  of  the  frontal  bone  and  about 
one  and  a  half  inches  behind  it.  This  fossa  is  deeply  concave  in  front,  convex 
behind,  traversed  by  grooves  which  lodge  branches  of  the  deep  temporal  arteries, 
and  filled  by  the  Temporal  muscles. 


138 


THE   SKELETON 


The  Mastoid  Portion. — The  mastoid  portion  of  the  side  of  the  skull  is  bounded 
in  front  by  the  tubercle  of  the  zygoma ;  above,  by  a  line  which  runs  from  the  pos- 
terior root  of  the  zygoma  to  the  end  of  the  mastoid-parietal  suture;  behind  and 
below  by  the  masto-occipital  suture.  It  is  formed  by  the  mastoid  and  part  of  the 
squamous  and  petrous  portions  of  the  temporal  bone;  its  surface  is  convex  and 
rough  for  the  attachment  of  muscles,  and  presents,  from  behind  forward,  the 
mastoid  foramen,  the  mastoid  process,  the  external  auditory  meatus  surrounded  by 
the  tympanic  plate,  and,  most  anteriorly,  the  temporo-maxillary  articulation.  The 
point  where  the  posterior  inferior  angle  of  the  parietal  meets  the  occipital  bone 
and  mastoid  portion  of  the  temporal  is  named  the  asterion. 

The  Zygomatic  or  Infratemporal  Fossa  (fossa  infratemporalis) . — The  zygo- 
matic  fossa  is  an  irregularly  shaped  cavity,  situated  below  and  on  the  inner  side 
of  the  zygoma;  bounded  in  front  by  the  zygomatic  surface  of  the  superior  maxil- 
lary bone  and  the  ridge  which  descends  from  its  malar  process;  behind,  by  the 
posterior  border  of  the  external  pterygoid  plate  and  the  eminentia  articularis; 
above,  by  the  pterygoid  ridge  on  the  outer  surface  of  the  great  wing  of  the 
sphenoid  and  the  under  part  of  the  squamous  portion  of  the  temporal;  below, 
by  the  alveolar  border  of  the  superior  maxilla;  internally,  by  the  external  pterygoid 
plate;  and  externally,  by  the  zygomatic  arch  and  ramus  of  the  lower  jaw  (Fig.  98). 


process 


FIG.  98. — Zygomatic  fossa. 

It  contains  the  lower  part  of  the  Temporal,  the  External  and  Internal  pterygoid 
muscles,  the  internal  maxillary  artery  and  vein,  and  inferior  maxillary  nerve  and 
their  branches.  At  its  upper  and  inner  part  may  be  observed  two  fissures,  the 
spheno-maxillary  and  pterygo-maxillary  fissures. 

The  Spheno-maxillary  Fissure  (fissura  orbitalis  inferior),  horizontal  in  direction, 
opens  into  the  outer  and  back  part  of  the  orbit.  It  is  formed  above  by  the  lower 
border  of  the  orbital  surface  of  the  great  wing  of  the  sphenoid ;  below,  by  the  exter- 
nal border  of  the  orbital  surface  of  the  superior  maxilla  and  a  small  part  of  the 
palate  bone;  externally,  by  a  small  part  of  the  malar  bone:1  internally,  it  joins  at 

i  Occasionally  the  superior  maxillary  bone  and  the  sphenoid  articulate  with  each  other  at  the  anterior  extremity 
of  this  fissure;  the  malar  is  then  excluded  from  entering  into  its  formation. — ED.  of  15th  English  Edition. 


THE  ANTERIOR    REGION    OF    THE  SKULL  139 

t 

right  angles  with  the  pterygo-maxillary  fissure.  This  fissure  opens  a  communication 
from  the  orbit  into  three  fossae — the  temporal,  zygomatic,  and  spheno-maxillary  fossa ; 
it  transmits  the  superior  maxillary  nerve  and  its  orbital  branch,  the  infraorbital 
vessels,  and  ascending  branches  from  the  spheno-palatine  or  Meckel's  ganglion. 

The  Pterygo-maxillary  Fissure  is  vertical,  and  descends  at  right  angles  from  the 
inner  extremity  of  the  preceding;  it  is  a  V-shaped  interval,  formed  by  the  diver- 
gence of  the  superior  maxillary  bone  from  the  pterygoid  process  of  the  sphenoid. 
It  serves  to  connect  the  spheno-maxillary  fossa  with  the  zygomatic  fossa,  and 
transmits  the  internal  maxillary  artery. 

The  Spheno-maxillary  or  Pterygo-palatine  Fossa  (fossa  pterygopalatina).— 
The  spheno-maxillary  fossa  is  a  small,  triangular  space  situated  at  the  angle 
of  junction  of  the  spheno-maxillary  and  pterygo-maxillary  fissures,  and  placed 
beneath  the  apex  of  the  orbit.  It  is  formed  above  by  the  under  surface  of  the 
body  of  the  sphenoid  and  by  the  orbital  process  of  the  palate  bone;  in  front, 
by  the  superior  maxillary  bone;  behind,  by  the  anterior  surface  of  the  base  of 
the  pterygoid  process  and  lower  part  of  the  anterior  surface  of  the  great  wing  of 
the  sphenoid;  internally,  by  the  vertical  plate  of  the  palate.  This  fossa  has 
three  fissures  terminating  in  it — the  sphenoidal,  spheno-maxillary,  and  pterygo- 
maxillary  ;  it  communicates  with  the  orbit  by  the  spheno-maxillary  fissure ;  with  the 
nasal  fossie  by  the  spheno-palatine  foramen,  and  with  the  zygomatic  fossa  by  the 
pterygo-maxillary  fissure.  It  also  communicates  with  the  cavity  of  the  cranium, 
and  has  opening  into  it  five  foramina.  Of  these,  there  are  three  on  the  posterior 
wall:  the  foramen  rotundum  above;  below  and  internal  to  this,  the  Vidiah  canal;  and 
still  more  inferiorly  and  internally,  the  pterygo-palatine  canal.  On  the  inner  wall 
is  the  spheno-palatine  foramen,  by  which  the  spheno-maxillary  communicates  with 
the  nasal  fossa;  and  below  is  the  superior  orifice  of  the  posterior  palatine  canal, 
besides  occasionally  the  orifices  of  the  accessory  posterior  palatine  canals.  The 
fossa  contains  the  superior  maxillary  nerve  and  Meckel's  ganglion,  and  the  termi- 
nation of  the  internal  maxillary  artery. 

The  Anterior  Region  of  the  Skull. 

> 

The  view  of  the  anterior  region  of  the  skull  from  the  front  is  known  as  the 
norma  frontalis.  It  forms  the  face,  is  of  an  oval  form,  presents  an  irregular 
surface,  and  is  excavated  for  the  reception  of  two  of  the  organs  of  sense,  the 
eye  and  the  nose.  It  is  bounded  above  by  the  glabella  and  margins  of  the 
orbit;  below,  by  the  prominence  of  the  chin;  on  each  side  by  the  malar  bone 
and  anterior  margin  of  the  ramus  of  the  jaw.  In  the  median  line  are  seen  from 
above  downward  the  glabella,  and  diverging  from  it  are  the  superciliary  ridges, 
which  indicate  the  situation  of  the  frontal  sinuses  and  supports  the  eyebrow. 
Beneath  the  glabella  is  the  fronto-nasal  suture,  the  mid-point  of  which  is  termed 
the  nasion,  and  below  this  is  the  arch  of  the  nose,  formed  by  the  nasal  bones,  and 
the  nasal  processes  of  the  superior  maxillary.  The  nasal  arch  is  convex  from  side 
to  side,  concave  from  above  downward,  presenting  in  the  median  line  the  inter- 
nasal  suture  (sutura  internasalis) ,  formed  between  the  nasal  bones,  laterally  the 
naso-maxillary  suture  (sutura  nasomaxillaris) ,  formed  between  the  nasal  bone  and 
the  nasal  process  of  the  superior  maxillary  bone.  Below  the  nose  is  seen  the 
opening  of  the  anterior  nares,  which  is  heart-shaped,  with  the  narrow  end 
upward,  and  presents  laterally  the  thin,  sharp  margins  serving  for  the  attach- 
ment of  the  lateral  cartilages  of  the  nose,  and  in  the  middle  line  below  a 
prominent  process,  the  anterior  nasal  spine,  bounded  by  two  deep  notches. 
Below  this  is  the  intermaxillary  suture  (sutura  intermaxillaris) ,  and  on  each  side 
of  it  the  incisive  fossa.  Beneath  this  fossa  are  the  alveolar  processes  of  the 
upper  and  lower  jaws,  containing  the  incisor  teeth,  and  at  the  lower  part  of  the 


140 


THE   SKELETON 


median  line  the  symphysis  of  the  chin,  the  mental  process,  with  its  two  mental 
tubercles,  separated  by  a  median  groove,  and  the  incisive  fossa  of  the  lower  jaw. 

On  each  side,  proceeding  from  above  downward,  is  the  supraorbital  ridge, 
terminating  externally  in  the  external  angular  process  at  its  junction  with  the 
malar,  and  internally  in  the  internal  angular  process;  toward  the  inner  third  of 
this  ridge  is  the  supraorbital  notch  or  foramen,  for  the  passage  of  the  supraorbital 
vessels  and  nerve.  Beneath  the  supraorbital  ridge  is  the  opening  of  the  orbit, 
bounded  externally  by  the  orbital  ridge  of  the  malar  bone;  below,  by  the  orbital 
ridge  formed  by  the  malar  and  superior  maxillary  bones;  internally,  by  the  nasal 
process  of  the  superior  maxillary  arid  the  internal  angular  process  of  the  frontal 
bone.  On  the  outer  side  of  the  orbit  is  the  quadrilateral  anterior  surface  of  the 
malar  bone,  perforated  by  one  or  two  small  malar  foramina.  Below  the  inferior 
margin  of  the  orbit  is  the  infraorbital  foramen,  the  termination  of  the  infraorbital 
canal,  and  beneath  this  the  canine  fossa,  which  gives  attachment  to  the  Levator 
anguli  oris;  still  lower  are  the  alveolar  processes,  containing  the  teeth  of  the  upper 
and  lower  jaws.  Beneath  the  alveolar  arch  of  the  lower  jaw  is  the  mental  foramen, 
for  the  passage  of  the  mental  vessels  and  nerve,  the  external  oblique  line,  and  at 
the  lower  border  of  the  bone,  at  the  point  of  junction  of  the  body  with  the  ramus, 
a  shallow  groove  for  the  passage  of  the  facial  artery. 

Orbits,  Orbital  Cavities,  or  Orbital  Fossae. — The  orbits  (from  orbis,  a  circle) 
(Fig.  99)  are  two  quadrilateral  pyramidal  cavities,  situated  at  the  upper  and  anterior 


TENDO  OOULI 


Groove  for 
facial  artery 


FIG.  99. — Antero-lateral  region  of  the  skull.     (Cryer.) 


THE   ANTERIOR    REGION   OF   THE  SKULL  141 

part  of  the  face,  their  bases  being  directed  forward  and  outward,  and  their  apices 
backward  and  inward,  so  that  the  axes  of  the  two,  if  continued  backward,  would 
meet  over  the  body  of  the  sphenoid  bone.  The  wide  orbital  opening  or  mouth  is 
called  the  aditus  orbitce.  The  orbit  is  lined  with  periosteum,  the  periorbita.  Each 
orbit  (orbitd)  is  formed  of  seven  bones,  the  frontal,  sphenoid,  ethmoid,  superior 
maxillary,  malar,  lachrymal,  and  palate;  but  three  of  these,  the  frontal,  ethmoid, 
and  sphenoid,  enter  into  the  formation  of  both  orbits,  so  that  the  two  cavities  are 
formed  of  eleven  bones  only.  Each  cavity  presents  for  examination  a  roof,  a  floor, 
an  inner  and  an  outer  wall,  four  angles,  a  circumference  or  base,  and  an  apex. 

The  Roof  (paries  superior). — The  roof  is  concave,  directed  downward  and 
slightly  forward,  and  formed  in  front  by  the  orbital  plate  of  the  frontal;  behind, 
by  the  lesser  wing  of  the  sphenoid.  This  surface  presents  internally  the  depres- 
sion for  the  cartilaginous  pulley  of  the  Superior  oblique  muscle;  externally,  the 
depression  for  the  lachrymal  gland;  and  posteriorly,  the  suture  connecting  the 
frontal  and  lesser  wing  of  the  sphenoid. 

The  Floor  (paries  inferior). — The  floor  is  directed  upward  and  outward,  and 
is  of  less  extent  than  the  roof;  it  is  formed  chiefly  by  the  orbital  process  of 
the  superior  maxillary;  in  front,  to  a  small  extent,  by  the  orbital  process  of  the 
rnalar,  and  behind,  by  the  superior  surface  of  the  orbital  process  of  the  palate. 
This  surface  presents  at  its  anterior  and  internal  part,  just  external  to  the  lachrymal 
groove,  a  depression  for  the  attachment  of  the  Inferior  oblique  muscle;  externally, 
the  suture  between  the  malar  and  superior  maxillary  bones ;  near  its  middle,  the  infra- 
orbital  groove ;  and  posteriorly,  the  suture  between  the  maxillary  and  palate  bones. 

Inner  or  Medial  Wall  (paries  medialis). — The  inner  wall  is  flattened,  nearly 
vertical,  and  formed  from  before  backward  by  the  nasal  process  of  the  superior 
maxillary,  the  lachrymal,  os  planum  of  the  ethmoid,  and  a  small  part  of  the  body  of 
the  sphenoid.  This  surface  presents  the  lachrymal  groove  and  crests  of  the  lachrymal 
bone,  and  the  sutures  connecting  the  lachrymal  with  the  superior  maxillary,  the 
ethmoid  with  the  lachrymal  in  front,  and  the  ethmoid  with  the  sphenoid  behind. 

Outer  or  Lateral  Wall  (paries  lateralis). — The  outer  wall  is  directed  forward 
and  inward,  and  is  formed  in  front  by  the  orbital  process  of  the  malar  bone; 
behind,  by  the  orbital  surface  of  the  greater  wing  of  the  sphenoid.  On  it  are 
seen  the  orifices  of  one  or  two  malar  canals,  and  the  suture  connecting  the  sphenoid 
and  malar  bones. 

Angles. — The  superior  external  angle  is  formed  by  the  junction  of  the  upper 
and  outer  walls;  it  presents  from  before  backward,  the  suture  connecting  the 
frontal  with  the  malar  in  front  and  with  the  great  wing  of  the  sphenoid  behind; 
quite  posteriorly  is  the  foramen  lacerum  anterius,  or  sphenoidal  fissure,  which 
transmits  the  third,  the  fourth,  the  three  branches  of  the  ophthalmic  division  of  the 
trigeminal,  the  abducent  nerve,  some  filaments  from  the  cavernous  plexus  of  the 
sympathetic,  the  orbital  branch  of  the  middle  meningeal  artery,  a  recurrent 
branch  from  the  lachrymal  artery  to  the  dura,  and  the  ophthalmic  vein.  The 
superior  internal  angle  is  formed  by  the  junction  of  the  upper  and  inner  wall,  and 
presents  the  suture  connecting  the  frontal  bone  with  the  lachrymal  in  front  and 
with  the  ethmoid  behind.  The  point  of  junction  of  the  anterior  border  of  the 
lachrymal  with  the  frontal  has  been  named  the  dacryon.  This  angle  presents  two 
foramina,  the  anterior  and  posterior  ethmoidal  foramina,  the  former  transmitting  the 
anterior  ethmoidal  vessels  and  nasal  nerve,  the  latter  the  posterior  ethmoidal  vessels. 
The  inferior  external  angle,  formed  by  the  junction  of  the  outer  wall  and  floor,  pre- 
sents the  spheno-maxillary  fissure,  which  transmits  the  superior  maxillary  nerve  and 
its  orbital  branches,  the  infraorbital  vessels,  and  the  ascending  branches  from  the 
spheno-palatine  or  Meckel's  ganglion.  The  inferior  internal  angle  is  formed  by 
the  union  of  the  lachrymal  bone  and  the  os  planum  of  the  ethmoid  with  the 
superior  maxillary  and  palate  bones. 


142 


THE   SKELETON 


Circumference. — The  circumference  or  base  of  the  orbit,  quadrilateral  in  form, 
is  bounded  above  (mar go  supraorbitalis)  by  the  supraorbital  ridge;  below  (margo 
infraorbitalis) ,  by  the  anterior  border  of  the  orbital  plate  of  the  malar  and  supe- 
rior maxillary  bones;  externally,  by  the  external  angular  process  of  the  frontal 
and  malar  bones;  internally,  by  the  internal  angular  process  of  the  frontal  and  the 
nasal  process  of  the  superior  maxillary.  The  circumference  is  marked  by  three 
sutures,  the  fronto-maxillary  internally,  the  fronto-malar  externally,  and  the  malo- 
maxillary  below;  it  contributes  to  the  formation  of  the  lachrymal  groove,  and 
presents,  above,  the  supraorbital  notch  (or  foramen),  for  the  passage  of  the  supra- 
orbital  vessels  and  nerve. 

Apex. — The  apex,  situated  at  the  back  of  the  orbit,  corresponds  to  the  optic 
foramen,1  a  short  circular  canal  which  transmits  the  optic  nerve  and  ophthalmic 
artery.  It  will  thus  be  seen  that  there  are  nine  openings  communicating  with  each 
orbit— viz.,  the  optic  foramen,  sphenoidal  fissure,  spheno-maxillary  fissure,  supra- 
orbital  foramen,  infraorbital  canal,  anterior  and  posterior  ethmoidal  foramina, 
malar  foramina,  and  the  canal  for  the  nasal  duct. 


PROBE  FROM    FRONTAL 

SINUS  IN  THE 

INFUNDIBULUM 


PROBE   IN    N 
LACHRYMAL   CANAL  PALATE   BONE 

FIG.  100. — Nasal  cavity,  right  lateral  wall,  from  the  left.      (Spalteholz.) 

The  Nasal  Cavity  (cavum  nasi). — The  nasal  cavities  or  nasal  fossae  (Figs. 
84  and  100)  are  two  large,  irregular  cavities  situated  on  either  side  of  the  middle 
line  of  the  face,  extending  from  the  base  of  the  cranium  to  the  roof  of  the 
mouth,  and  separated  from  each  other  by  a  thin  vertical  septum,  the  septum  of 
the  nose  (septum  nasi  osseum),  formed  by  the  perpendicular  plate  of  the  ethmoid 
and  by  the  vomer.  Each  cavity  communicates  by  a  large  aperture,  the  anterior 
nasal  aperture  (apertura  pyriformis),2  with  the  front  of  the  face,  and  by  the  two 
posterior  nares  (choanoe)  with  the  naso-pharynx  behind.  These  fossae  are  much 

1  Quain,  Testut,  and  others  give  the  apex  of  the  orbit  as  corresponding  with  the  inner  end  of  the  sphenoidal 
fissure.     It  seems  better,  however,  to  adopt  the  statement  in  the  text,  since  the  muscles  of  the  eyeball  take 
origin  around  the  optic  foramen,  and  diverge  from  it  to  the  globe  of  the  eye. — ED.  of  15th  English  Edition. 

2  In  the  skull  freed  of  soft  parts,  the  anterior  nasal  cavities  open  in  front  by  the  apertura  pyriformis.     In  the 
skull  with  the  soft  parts  in  place  they  open  by  the  anterior  nares. 


THE    ANTERIOR   REGION    OF    THE  SKULL  143 

narrower  above  than  below,  and  in  the  middle  than  at  the  anterior  or  posterior 
openings;  their  depth,  which  is  considerable,  is  much  greater  in  the  middle  than  at 
either  extremity.  "  The  nasal  fossae  are  surrounded  by  four  other  fossae — above  is 
the  cranial  fossa;  laterally,  the  orbital  fossae;  and  below,  the  cavity  of  the  mouth."1 
Each  nasal  fossa  communicates  with  four  sinuses,  the  frontal  above,  the  sphenoidal 
behind,  and  the  maxillary  and  ethmoidal  on  the  outer  wall.  Each  fossa  also  com- 
municates with  four  cavities:  with  the  orbit  by  the  lachrymal  groove,  with  the 
mouth  by  the  anterior  palatine  canal,  with  the  cranium  by  the  olfactory  foramina, 
and  with  the  spheno-maxillary  fossa  by  the  spheno-palatine  foramen ;  and  they  occa- 
sionally communicate  with  each  other  by  an  aperture  in  the  septum.  The  bones 
entering  into  their  formation  are  fourteen  in  number:  three  of  the  cranium,  the 
frontal,  sphenoid,  and  ethmoid,  and  all  the  bones  of  the  face,  excepting  the  malar 
and  lower  jaw.  Each  cavity  is  bounded  by  a  roof,  a  floor,  an  inner  and  an  outer  wall. 

Upper  Wall. — The  upper  wall,  or  roof  (Fig.  101),  is  long,  narrow,  and  horizontal 
in  its  centre,  but  slopes  downward  at  its  anterior  and  posterior  extremities;  it  is 
formed  in  front  by  the  nasal  bones  and  nasal  spine  of  the  frontal,  which  are 
directed  downward  and  forward;  in  the  middle,  by  the  cribriform  plate  of  the 
ethmoid,  which  is  horizontal;  and  behind,  by  the  under  surface  of  the  body  of  the 
sphenoid  and  sphenoidal  turbinated  bones,  the  ala  of  the  vomer  and  the  sphenoidal 
process  of  the  palate  bone,  which  are  directed  downward  and  backward.  This 
surface  presents,  from  before  backward,  the  internal  aspect  of  the  nasal  bones; 
on  their  outer  side,  the  suture  formed  between  the  nasal  bone  and  the  nasal  process 
of  the  superior  maxillary;  on  their  inner  side,  the  elevated  crest  which  receives  the 
nasal  spine  of  the  frontal  and  the  perpendicular  plate  of  the  ethmoid,  and  articu- 
lates with  its  fellow  of  the  opposite  side;  whilst  the  surf  ace  of  the  bones  is  perforated 
by  a  few  small  vascular  apertures,  and  presents  the  longitudinal  groove  for  the 
nasal  nerve;  farther  back  is  the  transverse  suture,  connecting  the  frontal  with  the 
nasal  in  front,  and  the  ethmoid  behind,  the  olfactory  foramina  and  nasal  slit  on 
the  under  surface  of  the  cribriform  plate,  and  the  suture  between  it  and  the  sphe- 
noid behind;  quite  posteriorly  are  seen  the  sphenoidal  turbinated  bones,  the  ori- 
fices of  the  sphenoidal  sinuses,  and  the  articulation  of  the  alae  of  the  vomer  with 
the  under  surface  of  the  body  of  the  sphenoid. 

Floor  (Figs.  84,  100,  and  101). — The  floor  is  flattened  from  before  backward, 
concave  from  side  to  side,  and  wider  in  the  middle  than  at  either  extremity.  It 
is  formed  in  front  by.  the  palate  process  of  the  superior  maxillary;  behind,  by  the 
palate  process  of  the  palate  bone.  This  surface  presents,  from  before  backward, 
the  anterior  nasal  spine ;  behind  this,  the  upper  orifices  of  the  anterior  palatine  canal ; 
internally,  the  elevated  crest  which  articulates  with  the  vomer;  and  behind,  the 
suture  between  the  palate  and  superior  maxillary  bones,  and  the  posterior  nasal  spine. 

Inner  or  Medial  Wall. — The  inner  wall,  or  septum  (Figs.  101  and  103),  is  a  thin 
vertical  partition  which  separates  the  nasal  fossae  from  each  other;  it  is  occasionally 
perforated,  so  that  the  fossae  communicate,  and  it  is  frequently  deflected  consid- 
erably to  one  side.2  It  is  formed,  in  front,  by  the  crest  of  the  nasal  bones  and 
nasal  spine  of  the  frontal;  in  the  middle,  by  the  perpendicular  plate  of  the  ethmoid ; 
behind,  by  the  vomer  and  rostrum  of  the  sphenoid;  below,  by  the  crests  of  the 
superior  maxillary  and  palate  bones.  It  presents,  in  front,  a  large,  triangular 
notch,  which  receives  the  septal  cartilage  of  the  nose;  and  behind,  the  grooved 
edge  of  the  vomer.  Its  surface  is  marked  by  numerous  vascular  and  nervous 
canals  and  the  groove  for  the  naso-palatine  nerve,  and  is  traversed  by  sutures 
connecting  the  bones  of  which  it  is  formed. 

Outer  or  Lateral  Wall. — The  outer  wall  (Figs.  84  and  101)  is  formed,  in  front, 
by  the  nasal  process  of  the  superior  maxillary  and  lachrymal  bones;  in  the  middle, 

1  Howard  A.  Lothrop,  in  Annals  of  Surgery,  May,  1903.  2  See  footnote,  p.  99. 


144 


THE    SKELETON 


by  the  ethmoid  and  inner  surface  of  the  body  of  the  superior  maxillary  and  inferior 
turbinated  bones;  behind,  by  the  vertical  plate  of  the  palate  bone  and  the  internal 
pterygoid  plate  of  the  sphenoid.  Upon  this  outer  wall  are  two  marked  projections 


UNCIFORM 

PROCESS  OF 

ETHMOID 

INFERIOR 
TURBINATED 


MIDDLE 
TURBINATED 


THIRD  MOLAR 
TOOTH 


FIG.  101. — Coronal  section  of  the  face,  passing  through  the  third  molar  tooth.     (Poirier  and  Charpy.) 

of  bone  (Figs.  84  and  101).    One  is  known  as  the  inferior  turbinated  bone  and  the 
other  as  the  middle  turbinated  bone.    The  superior  turbinated  bones  or  bodies  appear 


BRISTLE   PASSED  THROUGH 
INFUNDIBULUM    FROM 
FRONTAL  SINUS  TO 
MIDDLE  MEATUS 


ANTRUM  O 
HIGHMOR 


PROBE  PASSED 
THROUGH  LACH- 
RYMAL CANAL 


RONTAL  CANAL 


if—  NASAL  CANAL 


FIG.  102. — Cranial  section  through  the  frontal  sinus  and  nasal  fossa.      (Poirier  and  Charpy.) 


as  less  distinct  bony  projections.  This  surface  presents  three  irregular  longitudinal 
passages,  or  meatuses,  termed  the  superior,  middle,  and  inferior  meatuses  of  the 
nose  (Figs.  84,  101,  and  102).  The  superior  meatus  (meatus  nasi  superior),  the 


THE  ANTERIOR  REGION  OF  THE  SKULL 


145 


smallest  of  the  three,  is  situated  at  the  upper  and  back  part  of  each  nasal  fossa,  occu- 
pying the  posterior  third  of  the  outer  wall.  It  is  situated  between  the  superior  and 
middle  turbinated  bones,  and  has  opening  into  it  two  foramina,  the  spheno-palatine 
foramina  at  the  back  of  its  outer  wall,  and  the  posterior  ethmoidal  cells  at  the  front 
part  of  the  outer  wall.  The  sphenoidal  sinus  opens  into  a  recess,  the  spheno- 
ethmoidal  recess  (recessus  sphenoethmoidalis) ,  which  is  situated  above  and  behind 
the  superior  turbinated  bone.  The  middle  meatus  (meatus  nasi  medius)  is  situated 
external  to  the  middle  turbinated  bone,  and  above  the  inferior  turbinated  bone, 
ami  extends  from  the  anterior  end  of  the  inferior  turbinated  bone  to  the  spheno- 
palatine  foramen  of  the  outer  wall  of  the  nasal  fossa.  Anteriorly  it  terminates  in 
a  depression,  the  atrium  of  the  nasal  meatus.  The  bulla  ethmoidalis,  an  elevated 
area  disclosed  by  removing  the  middle  turbinated  bone.  Below  and  in  front  of  the 
bulla  is  a  groove,  the  semilunar  hiatus  (hiatus  semilunaris),  into  which  open  the 
antrum  and  the  anterior  ethmoidal .  cells.  The  middle  meatus  presents  in  front 
the  orifice  of  the  infundibulum  (infundibulum  ethmoidale) ,  by  which  the  middle 
meatus  communicates  with  the  anterior  ethmoidal  cells,  and  through  these  with 


Crest  of  nasal  bone, 

Nasal  spine  of 
frontal  bone. 


Space  for  triangular ; 
cartilage  of  septum 


Crest  of  palate  bone, 
•est  of  superior  maxilla. 


FIG.  103. — Inner  wall  of  nasal  fossae,  or  septum  ol  nose. 

the  frontal  sinuses.  The  middle  ethmoidal  cells  also  open  into  this  meatus,  while 
at  the  centre  of  the  outer  wall  is  the  orifice  of  the  maxillary  antrum  (hiatus  maxil- 
laris),  which  varies  somewhat  as  to  its  exact  position  in  different  skulls.  The 
inferior  meatus  (meatus  nasi  inferior),  the  largest  of  the  three,  is  the  space  between 
the  inferior  turbinated  bone  and  the  floor  of  the  nasal  fossa.  It  extends  along 
the  entire  length  of  the  outer  wall  of  the  nose,  is  broader  in  front  than  behind, 
and  presents  anteriorly  the  lower  orifice  of  the  canal  for  the  nasal  duct  (canalis 
nasolacrimalis}.  The  anterior  nares  present  a  heart-shaped  or  pyriform  opening 
(apertura  piriformis}  whose  long  axis  is  vertical  and  narrow  extremity  upward. 
This  opening  in  the  recent  state  is  much  contracted  by  the  cartilages  of  the  nose. 
It  is  bounded  above  by  the  inferior  border  of  the  nasal  bone;  laterally  by  the  thin, 
sharp  margin  which  separates  the  facial  from  the  nasal  surface  of  the  superior 

10 


146 


THE  SKELETON 


maxillary  hone;  and  below  by  the  same  border,  where  it  slopes  inward  to  join  its 
fellow  of  the  opposite  side  at  the  anterior  nasal  spine.  The  posterior  nares,  or 
choanoe,  are  the  two  posterior  oval  openings  of  the  nasal  fossae,  by  which  they 
communicate  with  the  upper  part  of  the  naso-pharynx.  They  are  situated  imme- 
diately in  front  of  the  basilar  process,  and  are  bounded  above  by  the  under 
surface  of  the  body  of  the  sphenoid  and  alee  of  the  vomer;  below,  by  the  posterior 
border  of  the  horizontal  plate  of  the  palate  bone;  externally,  by  the  inner  surface 
of  the  internal  pterygoid  plate;  and  internally,  in  the  middle  line,  they  are 
separated  from  each  other  by  the  posterior  border  of  the  vomer. 

Shape  of  the  Skull. — Great  variations  in  shape  occur.  There  is  a  notable  con- 
trast between  the  oval  or  elliptical  skull  of  a  Caucasian,  the  pyramidal  skull  of  an 
Esquimaux,  and  the  prognathous  skull  of  a  Negro.  There  are  also  wide  differences 
in  skulls  of  persons  of  the  same  race.  The  skull  may  be  dolichocephalic,  that  is,  long 
and  narrow  (Figs.  105  and  107);  it  may  be  brachycephalic,  that  is,  short  and  round 
(Figs.  104  and  106) ;  it  may  be  acrocephalic,  that  is,  shaped  like  a  sugar  loaf.  There 
may  be  great  bulging  of  the  occiput  or  forehead,  the  forehead  may  be  vertical  or 
sloped  backward,  and  may  be  high  or  low.  In  many  dolichocephalic  skulls  there  is 
a  distinct  elevation  over  the  sagittal  suture.  A  skull  possessed  of  such  a  longitudinal 
ridge  is  called  scaphoid.  The  shape  of  a  dolichocephalic  skull  is  due  to  early  closure 
of  the  sagittal  and  metopic  sutures.  A  skull  becomes  short  and  round  because  of 
early  closure  of  the  coronal  and  lambdoidal  sutures.  The  sugar  loaf  skull  results 
from  early  obliteration  of  the  transverse  and  longitudinal  sutures.  An  individual 


FIG.  104. — Brachycephalic  cranium. 
(Poirier  and  Charpy.) 


FIG.  105. — Dolichocephalic  cranium. 
(Poirier  and  Charpy.) 


FIG.  106. — Brachycephalic  cranium. 
(Poirier  and  Charpy.) 


TIG.  107. — Dolichocephalic  cranium. 
Poirier  and  Charpy.) 


THE  ANTERIOR  REGION  OF  THE  SKULL  147 

with  a  long  and  narrow  skull  usually  has  a  long,  narrow  face;  an  individual  with  a 
short  and  round  skull  usually  has  a  short  and  broad  face.  The  head  is  practically 
always  asymmetrical,  the  left  side,  especially  the  frontal  region  of  the  left  side,  being 
the  larger,  and  the  right  side  being  the  higher  in  a  large  majority  of  persons.  The 
right  orbit  is  usually  higher,  and  the  right  side  of  the  jaw  is  stronger,  than  the  left. 
This  asymmetry  results  from  the  habitual  assumption  of  some  one  position. 

Dimensions  of  the  Skull. — The  diameters  of  different  skulls,  even  of  those  of 
the  same  race,  vary  greatly.  Broca  estimated  the  mean  diameters  of  the  skull  as 
follows  :l 

MALES.  FEMALES. 

MEAN.  Millimetres.       Millimetres. 

Length 182 

Breadth 145 

Height 132 

Cranial  Capacity. — Capacity  is  in  direct  ratio  to  dimensions.  According  to 
AVelcker  the  average  capacity  in  males  is  1450  c.c.,  and  in  females  is  1300  c.c. 
A  microcephalic  skull  has  a  capacity  of  less  than  1350  c.c. ;  a  mesocephalic  skull  has 
a  capacity  of  from  1350  to  1450  c.c.;  a  megacephalic  skull  has  a  capacity  of  over 
1450  c.c. 

Indices  and  Angles. — The  length  of  a  diameter  is  of  slight  importance;  the 
relation  which  this  length  bears  to  other  measurements  may  be  of  considerable 
importance. 

The  Cephalic  Index. — The  cephalic  index  is  the  proportion  borne  by  the  greatest 
breadth  of  the  skull  to  the  greatest  length.  It  is  used  to  determine  the  form  of  the 
skull.  The  formula  is  as  follows: 

Maximum  breadth  XI 00 

— = 1 — Hu =  Cephalic  index. 

maximum  length 

The  greatest  length  is  obtained  by  measuring  from  the  glabella  to  the  occipital 
point;  the  greatest  breadth,  by  measuring  the  widest  distance  just  above  the 
supramastoid  ridge.  A  dolichocephalic  skull  (long  antero-posterior  diameter  and 
short  transverse  diameter)  has  a  cephalic  index  of  under  75.  The  mesaticephalic 
skull  (median  head)  has  a  cephalic  index  from  75  to  80.  The  brachycephalic 
skull  (short  antero-posterior  diameter)  has  a  cephalic  index  over  80. 

Index  of  Height. — This  is  the  ratio  of  height  to  length.  The  line  of  height  is 
from  the  basion  to  the  bregma.  The  formula  for  this  index  is  as  follows : 

Height  x  100  * 

— ~. — — r =  Index  of  height. 

The  Facial  Index. — This  is  the  ratio  between  the  length  and  the  breadth  of  the 
face.  The  length  is  measured  from  the  nasion  to  the  mental  point;  the  breadth 
between  the  zygomatic  arches.  The  formula  is  as  follows: 

Length  x  100  .... 

•j-r =  Facial  index. 

breadth 

We  have  also  the  nasal  index,  the  orbital  index,  and  the  palatal  index.  Camper's 
facial  angle  has  been  abandoned  because  of  inaccuracy.  This  angle  was  obtained 
by  drawing  one  line  from  the  middle  of  the  external  auditory  meatus  to  the  inferior 
margin  of  the  nasal  septum  (from  the  auricular  point  to  the  nasal  spine),  the  other 
from  the  most  prominent  point  in  the  midline  of  the  forehead  to  the  nasal  spine. 
The  angle  formed  by  the  meeting  of  these  two  lines  varies  between  62  degrees 
and  85  degrees  (Cunningham).  The  more  the  lower  part  of  the  face  projects  the 
less  the  angle.  This  projection  is  marked  in  the  negro  races.  Such  a  projecting 
face  is  called  prognathous. 

1  Quoted  by  Prof.  Dwight  in  PiersoPs  Human  Anatomy. 


148  THE  SKELETON 

Flower's  Gnathic  Index. — This  is  now  employed  instead  of  Camper's  facial  angle. 
A  line  is  drawn  from  the  basion  to  the  alveolar  point,  and  another  line  is  drawn 
between  the  basion  and  nasion.  We  estimate  the  ratio  which  the  measurement 
of  the  first  line  bears  to  the  second.  The  formula  is  as  follows: 

Basi-alveolar  line  X  100 

— r — • —      ,  ,.         —  =  Gnathic  index, 
basi-nasal  line 

Dwight1  tells  us  that  an  orthognathous  skull  has  an  index  below  98;  a  mesogna- 
thous  skull  has  an  index  from  90  to  103;  a  prognathous  skull  has  an  index  above  103. 

For  the  Skull  at  Different  Ages,  see  p.  102;  Sexual  Differences  in  the  Skull, 
p.  102;  the  Fontanelles,  p.  102. 

Surface  Form. — The  various  bony  prominences  or  landmarks  which  are  to  be  easily  felt  and 
recognized  in  the  head  and  face,  and  which  afford  the  means  of  mapping  out  the  important 
structures  comprised  in  this  region,  are  as  follows: 

1.  Supraorbital  arch.  8.  Parietal  eminences. 

2.  Internal  angular  process.  9.  Temporal  ridge. 

3.  External  angular  process.  10.  Frontal  eminences. 

4.  Zygomatic  arch.  11.  Superciliary  ridges. 
-5.  Mastoid  process.  12.  Nasal  bones. 

6.  External  occipital  protuberance.  13.  Lower  margin  of  orbit. 

7.  Superior  curved  line  of  occipital  bone.  14.  Lower  jaw. 

1 .  The  Supraorbital  arches  are  to  be  felt  throughout  their  entire  extent,  covered  by  the  eye- 
brows. They  form  the  upper  boundary  of  the  circumference  or  base  of  the  orbit,  and  separate 
the  face  from  the  forehead.  They  are  strong  and  arched,  and  terminate  internally  on  each  side 
of  the  root  of  the  nose  in  the  internal  angular  process,  which  articulates  with  the  lachrymal 
bone.  Externally  they  terminate  in  the  external  angular  process,  which  articulates  with  the 
malar  bone,  This  arched  ridge  is  sharper  and  more  defined  in  its  outer  than  in  its  inner  half, 
and  forms  an  overhanging  process  which  protects  and  shields  the  lachrymal  gland.  It  thus  pro- 
tects the  eye  in  its  most  exposed  situation  and  in  the  direction  from  which  blows  are  most  likely 
to  descend.  The  Supraorbital  arch  varies  in  prominence  in  different  individuals.  It  is  more 
marked  in  the  male  than  in  the  female,  and  in  some  races  of  mankind  than  others.  In  the  less 
civilized  races,  as  the  forehead  recedes  backward,  the  Supraorbital  arch  becomes  more  prominent, 
and  approaches  more  to  the  characters  of  the  monkey  tribe,  in  which  the  supraorbital  arches  are 
very  largely  developed,  and  acquire  additional  prominence  from  the  oblique  direction  of  the 
frontal  bone.  2.  The  internal  angular  process  is  scarcely  to  be  felt.  Its  position  is  indicated 
by  the  angle  formed  by  the  supraorbital  arch  with  the  nasal  process  of  the  superior  maxillary 
bone  and  the  lachrymal  bone  at  the  inner  side  of  the  orbit.  Between  the  internal  angular  pro- 
cesses of  the  two  sides  is  a  broad  surface  which  assists  in  forming  the  root  of  the  nose,  and 
immediately  above  this  a  broad,  smooth,  somewhat  triangular  surface,  the  glabella,  situated 
between  the  superciliary  ridges.  3.  The  external  angular  process  is  much  more  strongly  marked 
than  the  internal,  and  is  plainly  to  be  felt.  It  is  formed  by  the  junction  or  confluence  of  the  supra- 
orbital  and  temporal  ridges,  and,  articulating  with  the  malar  bone,  it  serves  to  a  very  consider- 
able extent  to  support  the  bones  of  the  face.  In  carnivorous  animals  the  external  angular  pro- 
cess does  not  articulate  with  the  malar,  and  therefore  this  lateral  support  to  the  bones  of  the  face 
is  not  present.  4.  The  zygomatic  arch  is  plainly  to  be  felt  throughout  its  entire  length,  being 
situated  almost  immediately  under  the  skin.  It  is  formed  by  the  malar  bone  and  the  zygomatic 
process  of  the  temporal  bone.  At  its  anterior  extremity,  where  it  is  formed  by  the  malar  bone, 
it  is  broad  and  forms  the  prominence  of  the  cheek;  the  posterior  part  is  narrower,  and  termi- 
nates just  in  front  and  a  little  above  the  tragus  of  the  external  ear.  The  lower  border  is 
more  plainly  to  be  felt  than  the  upper,  in  consequence  of  the  dense  temporal  fascia  being 
attached  to  the  latter,  which  somewhat  obscures  its  outline.  Its  shape  differs  very  much  in  indi- 
viduals and  in  different  races  of  mankind.  In  the  most  degraded  type  of  skull — as,  for  instance, 
in  the  skull  of  the  negro  of  the  Guinea  Coast — the  malar  bones  project  forward  and  not  outward, 
and  the  zygoma  at  its  posterior  extremity  extends  farther  outward  before  it  is  twisted  on  itself  to 
be  prolonged,  forward.  This  makes  the  zygomatic  arch  stand  out  in  bold  relief,  and  affords 
greater  space  for  the  Temporal  muscle.  In  skulls  which  have  a  more  pyramidal  shape,  as  in  the 
Esquimaux  or  Greenlander,  the  malar  bones  do  not  project  forward  and  downward  under  the 
eyes,  as  in  the  preceding  form,  but  take  a  direction  outward,  forming  with  the  zygoma  a  large, 
rounded  sweep  or  segment  of  a  circle.  Thus  it  happens  that  if  two  lines  are  drawn  from  the 
zygomatic  arches,  touching  the  temporal  ridges,  they  meet  above  the  top  of  the  head,  instead  of 
being  parallel,  or  nearly  so,  as  in  the  European  skull,  in  which  the  zygomatic  arches  are  not 

>  Piersol's  Human  Anatomy. 


THE  ANTERIOR  REGION  OF  THE  SKULL  149 

nearly  so  prominent.  This  gives  to  the  face  a  more  or  less  oval  type.  5.  Behind  the  ear  is  the 
mastoid  portion  of  the  temporal  bone,  plainly  to  he  felt,  and  terminating  below  in  a  nipple- 
shaped  process.  Its  anterior  border  can  be  traced  immediately  behind  the  concha,  and  its  apex 
is  on  about  a  level  with  the  lobule  of  the  ear.  It  is  rudimentary  in  infancy,  but  gradually 
develops  in  childhood,  and  is  more  marked  in  the  negro  than  in  the  European.  6.  The  external 
occipital  protuberance  is  always  plainly  to  be  felt  just  at  the  level  where  the  skin  of  the  neck 
joins  that  of  the  head.  At  this  point  the  skull  is  thick  for  the  purposes  of  safety,  while  radiating 
from  it  are  numerous  curved  arches  or  buttresses  of  bone  which  give  to  this  portion  of  the 
skull  further  security.  7.  Running  outward  on  either  side  from  the  external  occipital  protu- 
berance is  an  arched  ridge  of  bone,  which  can  be  more  or  less  plainly  perceived.  This  is  the 
superior  curved  line  of  the  occipital  bone,  and  gives  attachment  to  some  of  the  muscles  which 
keep  the  head  erect  on  the  spine;  accordingly,  we  find  it  more  developed  in  the  negro  tribes,  in 
whom  the  jaws  are  much  more  massive,  and  therefore  require  stronger  muscles  to  prevent  their 
extra  weight  carrying  the  head  forward.  Below  this  line  the  surface  of  bone  at  the  back  of  the 
head  is  obscured  by  the  overlying  muscles.  Above  it,  the  vault  of  the  cranium  is  thinly  covered 
with  soft  structures,  so  that  the  form  of  this  part  of  the  head  is  almost  exactly  that  of  the  upper 
portion  of  the  occipital,  the  parietal,  and  the  frontal  bones  themselves;  and  in  bald  persons, 
even  the  lines  of  junction  of  the  bones,  especially  the  junction  of  the  occipital  and  parietal  at 
the  lambdoid  suture,  may  be  defined  as  a  slight  depression,  caused  by  the  thickening  of  the 
borders  of  the  bones  in  ihis  situation.  8.  In  the  line  of  the  greatest  transverse  diameter  of  the 
head,  on  each  side  of  the  middle  line,  are  generally  to  be  found  the  parietal  eminences,  one  on 
each -side  of  the  middle  line,  though  sometimes  these  eminences  are  not  situated  at  the  point  of 
the  greatest  transverse  diameter,  which  is  at  some  other  prominent  part  of  the  parietal  region. 
They  denote  the  point  where  ossification  of  the  parietal  bone  began.  They  are  much  more 
prominent  and  well-marked  in  early  life,  in  consequence  of  the  sharper  curve  of  the  bone  at 
this  period,  so  that  it  describes  the  segment  of  a  smaller  circle.  Later  in  life,  as  the  bone  grows, 
the  curve  spreads  out  and  forms  the  segment  of  a  larger  circle,  so  that  the  eminence  becomes 
less  distinguishable.  In  consequence  of  this  sharp  curve  of  the  bone  in  early  life,  the  whole  of 
the  vault  of  the  skull  has  a  squarer  shape  than  it  has  in  later  life,  and  this  appearance  may  per- 
sist in  some  rickety  skulls.  The  eminence  is  more  apparent  in  the  negro's  skull  than  in  that  of 
the  European.  This  is  due  to  greater  flattening  of  the  temporal  fossa  in  the  former  skull  to 
accommodate  the  larger  Temporal  muscle  which  exists  in  these  races.  The  parietal  eminence 
is  particularly  exposed  to  injury  from  blows  or  falls  on  the  head,  but  fracture  is  to  a  certain 
extent  prevented  by  the  shape  of  the  bone,  which  forms  an  arch,  so  that  the  force  of  the  blow 
is  diffused  over  the  bone  in  every  direction.  9.  At  the  side  of  the  head  may  be  felt  the  temporal 
ridge.  Commencing  at  the  external  angular  process,  it  may  be  felt  as  a  curved  ridge,  passing 
upward  and  then  curving  backward,  on  the  frontal  bone,  separating  the  forehead  from  the 
temporal  fossa.  It  may  then  be  traced  passing  backward  in  a  curved  direction,  over  the  parietal 
bone,  and,  though  less  marked,  still  generally  to  be  recognized.  Finally,  the  ridge  curves  down- 
ward, and  terminates  in  the  posterior  root  of  the  zygoma,  which  separates  the  squamous  from 
the  subcutaneous  mastoid  portion  of  the  temporal  bone.  Sir  Victor  Horsley  has  recently  shown 
in  an  article  on  the  "Topography  of  the  Cerebral  Cortex,"  that  the  second  temporal  ridge  (see 
page  76)  can  be  made  out  on  the  living  body.  10.  The  frontal  eminences  vary  a  good  deal  in 
different  individuals,  being  considerably  more  prominent  in  some  than  in  others,  and  they  are 
often  not  symmetrical  on  the  two  sides  of  the  body,  the  one  being  much  more  pronounced  than 
the  other.  This^  is  often  especially  noticeable  in  the  skull  of  the  young  child  or  infant,  and 
becomes  less  marked  as  age  advances.  The  prominence  of  the  frontal  eminences  depends 
more  upon  the  general  shape  of  the  whole  bone  than  upon  the  size  of  the  protuberances  them- 
selves. As  the  skull  is  more  highly  developed  in  consequence  of  increased  intellectual  capacity, 
s:)  the  frontal  bone  becomes  more  upright  and  the  frontal  eminences  stand  out  in  bolder  relief. 
Thus  they  may  be  considered  as  affording,  to  a  certain  extent,  an  indication  of  the  development 
of  the  hemispheres  of  the  brain  beneath,  and  of  the  mental  powers  of  the  individual.  They 
are  not  so  much  exposed  to  injury  as  the  parietal  eminences.  In  falls  forward  the  upper  extrem- 
ities are  involuntarily  thrown  out,  and  break  the  force  of  the  fall,  and  thus  shield  the  frontal 
bone  from  injury.  1 1 .  Below  the  frontal  eminences  on  the  forehead  are  the  superciliary  ridges, 
which  denote  the  position  of  the  frontal  sinuses,  and  vary  according  to  the  size  of  the  sinuses 
in  different  individuals,  being,  as  a  rule,  small  in  the  female,  absent  in  children,  and  some- 
times unusually  prominent  in  the  male,  when  the  frontal  sinuses  are  largely  developed.  They 
commence  on  either  side  of  the  glabella,  and  at  first  present  a  rounded  form,  which  gradually 
fades  away  at  their  outer  ends.  12.  The  nasal  bones  form  the  prominence  of  the  nose.  They 
vary  much  in  size  and  shape,  and  to  them  is  due  the  varieties  in  the  contour  of  this  organ  and 
much  of  the  character  of  the  face.  Thus,  in  the  Mongolian  or  Ethiopian  they  are  flat,  broad, 
and  thick  at  their  base,  giving  to  these  races  the  flattened  nose  by  which  they  are  characterized, 
and  differing  very  decidedly  from  the  Caucasian,  in  whom  the  nose,  owing  to  the  shape  of  the 
nasal  bones,  is  narrow,  elevated  at  the  bridge,  and  elongated  downward.  Below,  the  nasal 
bones  are  thin  and  connected  with  the  cartilages  of  the  nose,  and  the  angle  or  arch  formed  by 


150  THE  SKELETON 

their  union  serves  to  throw  out  the  bridge  of  the  nose,  and  is  much  more  marked  in  some  indi- 
viduals than  others.  13.  The  lower  margin  of  the  orbit,  formed  by  the  superior  maxillary  bone 
and  the  malar  bone,  is  plainly  to  be  felt  throughout  its  entire  length.  It  is  continuous  inter- 
nally with  the  nasal  process  of  the  superior  maxillary  bone,  which  forms  the  inner  boundary 
of  the  orbit.  At  the  point  of  junction  of  the  lower  margin  of  the  orbit  with  the  nasal  process 
is  to  be  felt  a  little  tubercle  of  bone,  which  can  be  plainly  perceived  by  running  the  finger  along 
the  bone  in  this  situation.  This  tubercle  serves  as  a  guide  to  the  position  of  the  lachrymal  sac, 
which  is  situated  above  and  behind  it.  14.  The  outline  of  the  lower  jaw  is  to  be  felt  throughout 
its  entire  length.  Just  in  front  of  the  tragus  of  the  external  ear,  and  below  the  zygomatic  arch, 
the  condyle  can  be  made  out.  When  the  mouth  is  opened  this  prominence  of  bone  can  be  per- 
ceived advancing  out  of  the  glenoid  fossa  on  to  the  eminentia  articularis,  and  receding  again 
when  the  mouth  is  closed.  From  the  condyle  the  posterior  border  of  the  ramus  can  be  felt 
extending  down  to  the  angle.  A  line  drawn  from  the  condyle  to  the  angle  would  indicate  the 
exact  position  of  this  border.  From  the  angle  to  the  symphysis  of  the  chin  the  lower,  rounded 
border  of  the  body  of  the  bone  is  plainly  to  be  felt.  At  the  point  of  junction  of  the  two  halves 
of  the  bone  is  a  well-marked  triangular  eminence,  the  mental  process,  which  forms  the  promi- 
nence of  the  chin. 

Fixed  Points  for  Measurement.— In  order  to  determine  the  location  of  regions  of  surgical 
importance  within  the  skull  (bony  spaces,  vessels,  fissures,  centres,  and  convolutions  of  the 
brain)  and  in  order  to  estimate  cranial  capacity,  measurements  are  made  and  these  measure- 
ments are  taken  from  fixed  points.  The  following  are  the  chief  fixed  points: 

The  ALVEOLAH  POINT.   The  lowest  mid-point  of  the  alveolar  process  of  the  upper  jaw. 

The  ASTERION.  The  region  of  the  postero-lateral  fontanelle,  at  the  posterior  inferior  margin 
of  the  parietal  bone. 

The  AURICULAR  POINT.    The  centre  of  the  external  auditory  meatus. 

The  BASION.    The  middle  of  the  anterior  edge  of  the  foramen  magnum. 

The  BREGMA.    The  site  of  the  anterior  fontanelle,  where  the  sagittal  and  coronal  sutures  meet. 

The  DACRYON.  The  point  where' the  frontal,  the  lachrymal,  and  the  superior  maxillary  bones 
come  in  contact. 

The  GLABELLA.    Midway  between  the  two  superciliary  ridges. 

The  GLENOID  POINT.    The  centre  of  the  glenoid  cavity. 

The  GONION.    The  outer  surface  of  the  angle  of  the  mandible. 

The  INION.    The  external  occipital  protuberance. 

The  LAMBDA.    The  point  of  junction  of  the  sagittal  and  lambdoid  sutures. 

The  MALAR  POINT.    The  most  prominent  portion  of  the  malar  bone. 

The  MENTAL  POINT.    The  point  on  the  symphysis  menti  which  projects  most  forward. 

The  NASION.    The  middle  of  the  naso-frontal  suture. 

The  OBELION.    A  point  in  the  sagittal  suture  between  the  parietal  foramina. 

The  OCCIPITAL  POINT.  The  most  prominent  midpoint  posterior.  It  is  situated  above  the 
inion. 

The  OPHRYON.  The  point  where  a  line  joining  the  summits  of  the  orbits  touches  the  median 
line.  It  is  the  middle  of  the  narrowest  transverse  diameter  of  the  forehead. 

The  OPISTHION.    The  mid-point  of  the  posterior  margin  of  the  foramen  magnum. 

The  PTERION.  The  site  of  the  antero-lateral  fontanelle,  where  the  frontal,  parietal,  squamous 
portion  of  the  temporal  and  greater  wing  of  the  sphenoid  are  in  relation. 

The  INFERIOR  STEPHANION.  The  point  where  the  inferior  temporal  ridge  meets  the  coronal 
suture. 

The  SUPERIOR  STEPHANION.  The  point  where  the  superior  temporal  ridge  meets  the  coronal 
suture. 

The  SUBNASAL  POINT.    At  Jhe  root  of  the  anterior  nasal  spine  in  the  mid-line. 

The  VERTEX.    The  highest  point  of  the  vault  of  the  skull. 

Besides  these  points  we  use  the  mastoid  process,  the  nasal  spine,  the  zygomatic  arch,  the 
frontal  eminences,  the  parietal  eminences,  the  supraorbital  ridges,  the  superciliary  ridges,  the 
mental  process,  suprameatal  spine,  the  external  and  internal  angular  processes,  and  the  canine 
fossa. 

Surgical  Anatomy. — The  thickness  of  the  skull  varies  greatly  in  different  regions  of  the  same 
skull  and  in  different  individuals.  The  average  thickness  of  the  skull-cap  is  about  one-fifth 
of  an  inch.  The  thickest  portions  are  the  occipital  protuberance,  the  inferior  portion  of  the 
frontal  bone,  and  the  mastoid  process.  The  thinnest  portions  are  the  occipital  fossa?,  the  squa- 
mous portion  of  the  temporal  bone,  and  over  certain  sinuses  and  arteries.  An  arrest  in  the 
ossifying  process  may  give  rise  to  deficiencies  or  gaps,  or  to  fissures,  which  are  of  importance 
in  a  medico-legal  point  of  view,  as  they  are  liable  to  be  mistaken  for  fractures.  The  fissures 
generally  extend  from  the  margin  toward  the  centre  of  the  bone,  but  gaps  may  be  found  in  the 
middle  as  well  as  at  the  edges.  In  course  of  time  they  may  become  covered  with  a  thin  lamina 
of  bone. 

Occasionally  a  protrusion  of  the  brain  or  its  membranes  may  take  place  through  one  of  these 


THE  ANTERIOR  REGION  OF  THE  SKULL  151 

gaps  in  an  imperfectly  developed  skull.  When  the  protrusion  consists  of  membranes  only,  and 
is  filled  with  cerebro-spinal  fluid,  it  is  called  a  meningocele  ;  when  the  protrusion  consists  of  brain 
as  well  as  membranes,  it  is  termed  an  encephalocele  and  when  the  protruded  brain  is  a  prolonga- 
tion from  one  of  the  ventricles,  and  is  distended  by  a  collection  of  fluid  from  an  accumulation  in 
the  ventricle,  it  is  termed  an  hydrencephalocele.  This  latter  condition  is  sometimes  found  at  the 
root  of  the  nose,  where  a  protrusion  of  the  anterior  horn  of  the  lateral  ventricle  takes  place 
through  a  deficiency  of  the  fronto-nasal  suture.  These  malformations  are  usually  found  in  the 
middle  line,  and  most  frequently  at  the  back  of  the  head,  the  protrusion  taking  place  through 
the  fissures  which  separate  the  four  centres  of  ossification  from  which  the  tabular  portion  of  the 
occipital  bone  is  originally  developed  (see  page  75).  They  most  frequently  occur  through  the 
uppef  part  of  the  vertical  fissure,  which  is  the  last  to  ossify,  but  not  uncommonly  through  the 
lower  part,  when  the  foramen  magnum  may  be  incomplete.  More  rarely  these  protrusions 
have  been  met  with  in  other  situations  than  those  above  mentioned,  both  through  normal 
fissures,  as  the  sagittal,  lambdoid,  and  other  sutures,  and  also  through  abnormal  gaps  and 
deficiencies  at  the  sides,  and  even  at  the  base  of  the  skull.  Force  may  be  responsible  in  a  young 
person  for  separating  a  suture.  This  accident,  seldom  met  with  even  in  the  young,  is  only  occa- 
sionally encountered  in  older  persons. 

Fractures  of  the  skull  may  be  divided  into  those  of  the  vault  and  those  of  the  base.  Frac- 
tures of  the  vault  are  usually  produced  by  direct  violence.  This  portion  of  the  skull  varies  in 
thickness  and  strength  in  different  individuals,  but,  as  a  rule,  is  sufficiently  strong  to  resist  a  very 
considerable  amount  of  violence  without  being  fractured.  This  is  due  to  several  causes:  the 
rounded  shape  of  the  head  and  its  construction  of  a  number  of  secondary  elastic  arches,  each 
made  up  of  a  single  bone;  the  fact  that  it  consists  of  a  number  of  bones,  united,  at  all  events  in 
early  life,  by  a  sutural  ligament,  which  acts  as  a  sort  of  buffer  and  interrupts  the  continuity  of 
any  violence  applied  to  the  skull;  the  presence  of  arches  or  ridges,  both  on  the  inside  and  outside 
of  the  skull,  which  materially  strengthen  it;  and  the  mobility  of  the  head  upon  the  spine,  which 
further  enables  it  to  withstand  violence.  The  elasticity  of  the  bones  of  the  head  is  especially 
marked  in  the  skull  of  the  child,  and  this  fact,  together  with  the  wide  separation  of  the  indi- 
vidual bones  from  each  other,  and  the  interposition  between  them  of  other  and  softer  structures 
render  fracture  of  the  bones  of  the  head  a  very  uncommon  event  in  infants  and  quite  young 
children;  as  age  advances  and  the  bones  become  joined,  fracture  is  more  common,  though  still 
less  liable  to  occur  than  in  the  adult.  Fractures  of  the  vault  may,  and  generally  do,  involve  the 
whole  thickness  of  the  bone;  but  sometimes  one  table  may  be  fractured  without  any  correspond- 
ing injury  to  the  other.  Thus,  the  outer  table  of  the  skull  may  be  splintered  and  driven  into  the 
diploe,  or  in  the  frontal  or  mastoid  regions  into  the  frontal  or  mastoid  cells,  without  any  injury 
to  the  internal  table.  And  on  the  other  hand,  the  internal  table  has  been  fractured,  and  por- 
tions of  it  depressed  and  driven  inward,  without  any  fracture  of  the  outer  table.  As  a  rule,  in 
fractures  of  the  skull  the  inner  table  is  more  splintered  and  comminuted  than  the  outer,  and 
this  is  due  to  several  causes.  It  is  thinner  and  more  brittle;  the  force  of  the  violence  as  it  passes 
inward  becomes  broken  up,  and  is  more  diffused  by  the  time  it  reaches  the  inner  table;  the 
bone,  being  in  the  form  of  an  arch,  bends  as  a  whole  and  spreads  out,  and  thus  presses  the 
particles  together  on  the  convex  surface  of  the  arch — i.e.,  the  outer  table — and  forces  them 
asunder  on  the  concave  surface  or  inner  table;  and,  lastly,  there  is  nothing  firm  under  the  inner 
table  to  support  it  and  oppose  the  force.  Fractures  of  the  vault  may  be  simple  fissures  or  starred 
and  comminuted  fractures,  and  these  may  be  depressed  or  elevated.  These  latter  cases  of 
fracture  with  elevation  of  the  fractured  portion  are  uncommon,  and  can  only  be  produced  by 
direct  wound.  In  comminuted  fracture  a  portion  of  the  skull  is  broken  into  several  pieces, 
the  lines  of  fracture  radiating  from  a  centre  where  the  chief  impact  of  the  blow  was  felt;  if 
depressed,  a  fissure  circumscribes  the  radiating  line,  enclosing  a  portion  of  skull.  If  this  area 
is  circular,  it  is  termed  a  pond  fracture,  and  would  in  all  probability  have  been  caused  by 
a  round  instrument,  as  a  life-preserver  or  hammer;  if  elliptical  in  shape,  it  is  termed  a  gutter 
fracture,  and  would  owe  its  shape  to  the  instrument  which  had  produced  it,  as  a  poker.  A 
fracture  may  take  place  along  the  line  of  an  ossified  or  partly  ossified  suture.  When  a  surgeon 
explores  the  vault  of  the  skull  through  a  wound  he  must  not  mistake  a  Wormian  bone  for  a  frag- 
ment produced  by  a  fracture.  A  Wormian  bone  which  may  lead  to  mistake  is  encountered  at 
the  anterior  inferior  angle  of  the  parietal  bone.  Wormian  bones  are  most  frequently  found 
along  the  lambdoid  suture. 

Fractures  of  the  base  are  most  frequently  produced  by  the  extension  of  a  fissure  from  the 
vault,  as  in  falls  on  the  head,  where  the  fissure  starts  from  the  part  of  the  vault  which  first 
struck  the  ground.  Sometimes,  however,  they  are  caused  by  direct  violence,  when  foreign 
bodies  have  been  forced  through  the  thin  roof  of  the  orbit,  through  the  cribriform  plate  of  the 
ethmoid  from  being  thrust  up  the  nose,  or  through  the  roof  of  the  pharynx.  Other  cases  of 
fracture  of  the  base  occur  from  indirect  violence,  as  in  fracture  of  the  occipital  bone  from  impac- 
tion  of  the  spinal  column  against  its  condyles  in  falls  on  the  buttocks,  knees,  or  feet,  or  in  cases 
where  the  glenoid  cavity  has  been  fractured  by  the  violent  impact  of  the  condyle  of  the  lower  jaw 
against  it  from  blows  on  the  chin. 


152  THE  SKELETON 

The  most  common  place  for  fracture  of  the  base  to  occur  is  through  the  middle  fossa,  and 
here  the  fissure  usually  takes  a  fairly  definite  course.  Starting  from  the  point  struck,  which  is 
generally  somewhere  in  the  neighborhood  of  the  parietal  eminence,  it  runs  downward  through  the 
parietal  bone  and  the  squamous  portion  of  the  temporal  bone  and  across  the  petrous  portion  of  this 
bone,  frequently  traversing  and  implicating  the  internal  auditory  meatus,  to  the  middle  lacerated 
foramen.  From  this  it  may  pass  across  the  body  of  the  sphenoid,  through  the  pituitary  fossa  to 
the  middle  lacerated  foramen  of  the  other  side,  and  may  indeed  travel  round  the  whole  cranium, 
so  as  to  completely  separate  the  anterior  from  the  posterior  part.  The  course  of  the  fracture 
should  be  borne  in  mind,  as  it  explains  the  symptoms  to  which  fracture  in  this  region  may  give 
rise;  thus,  if  the  fissure  pass  across  the  internal  auditory  meatus,  injury  to  the  facial  and  auditory 
nerves  may  result,  with  consequent  facial  paralysis  and  deafness;  or  the  tubular  prolongation 
of  the  arachnoid  around  these  nerves  in  the  meatus  may  be  torn,  and  thus  permit  of  the  escape 
of  the  cerebro-spinal  fluid  should  there  be  a  communication  between  the  internal  ear  a'nd  the 
tympanum  and  the  membrana  tympani  be  ruptured,  as  is  frequently  the  case;  again,  if  the 
fissure  passes  across  the  pituitary  fossa  and  the  muco-periosteum  covering  the  under  surface 
of  the  body  of  the  sphenoid  is  torn,  blood  will  find  its  way  into  the  pharynx  and  be  swallowed, 
and  after  a  time  vomiting  of  blood  will  result.  Fractures  of  the  anterior  fossa,  involving  the 
bones  forming  the  roof  of  the  orbit  and  nasal  fossa,  are  generally  the  results  of  blows  on  the  fore- 
head ;  but  fracture  of  the  cribriform  plate  of  the  ethmoid  may  be  a  complication  of  fracture  of 
the  nasal  bone.  When  the  fracture  implicates  the  roof  of  the  orbit,  the  blood  finds  its  way 
into  this  cavity,  and,  travelling  forward,  appears  as  a  subconjunctival  ecchymosis.  Subcon- 
junctival  ecchymosis  can  also  be  caused  by  fracture  of  the  malar  bone.  If  the  roof  of  the  nasal 
fossa  be  fractured,  the  blood  escapes  from  the  nose.  In  rare  cases  there  may  be  also  escape 
of  cerebro-spinal  fluid  from  the  nose  where  the  dura  and  arachnoid  have  been  torn.  In  frac- 
tures of  the  posterior  fossa  extravasation  of  blood  takes  place  beneath  the  deep  fascia  and 
discoloration  of  the  skin  is  soon  observed  in  the  course  of  the  posterior  auricular  artery,  the  dis- 
coloration first  appearing  in  the  skin  over  the  tip  of  the  mastoid  process  of  the  temporal  bone 
(Battle's  sign).  Some  of  the  blood  which  was  extra vasated  beneath  the  deep  fascia  approaches 
the  surface  through  the  openings  in  the  deep  fascia  for  the  passage  of  vessels  and  nerves. 

The  bones  of  the  skull  are  frequently  the  seat  of  nodes,  and  not  uncommonly  necrosis  results 
from  this  cause,  also  from  injury.  Necrosis  may  involve  the  entire  thickness  of  the  skull,  but 
is  usually  confined  to  the  external  table.  Necrosis  of  the  internal  table  alone  is  rarely  met  with. 
The  bones  of  the  skull  are  also  sometimes  the  seat  of  sarcomatous  tumor. 

The  skull  in  rickets  is  peculiar:  the  forehead  is  high,  square,  and  projecting,  and  the  antero- 
posterior  diameter  of  the  skull  is  long  in  relation  to  the  transverse  diameter.  The  bones  of  the 
face  are  small  and  ill-developed,  and  this  gives  the  appearance  of  a  larger  head  than  actually 
exists.  The  bones  of  the  head  are  often  thick,  especially  in  the  neighborhood  of  the  sutures, 
and  the  anterior  fontanelle  is  late  in  closing,  sometimes  remaining  unclosed  till  the  fourth  year. 
The  condition  of  craniotabes  has  by  some  been  also  believed  to  be  the  result  of  rickets,  by  others 
is  believed  to  be  due  to  inherited  syphilis.  In  all  probability  it  is  due  to  both.  In  these  cases 
the  bone  undergoes  atrophic  changes  in  patches,  so  that  it  becomes  greatly  thinned  in  places, 
generally  where  there  is  pressure,  as  from  the  pillow  or  nurse's  arm.  It  is,  therefore,  usually 
met  with  in  the  parietal  bone  and  vertical  plate  of  the  occipital  bone. 

In  congenital  syphilis  deposits  of  porous  bone  are  often  found  at  the  angles  of  the  parietal 
bones  and  two  halves  of  the  frontal  bone  which  bound  the  anterior  fontanelle.  These  deposits 
are  separated  by  the  coronal  and  sagittal  sutures,  and  give  to  the  skull  an  appearance  like  a  hot 
Cross  bun.  They  are  known  as  Parrot's  nodes,  and  such  a  skull  has  received  the  name  of  nati- 
form,  from  its  fancied  resemblance  to  the  buttocks.  When  the  surgeon  wishes  to  effect  an  entrance 
into  the  interior  of  the  -mastoid  antrum  (Fig.  108)  he  applies  his  bur  or  gouge  in  the  suprameatal 
triangle  1  cm.  posterior  to  the  suprameatal  spine,  being  careful  to  keep  below  the  posterior  root  of 
the  zygoma  and  the  level  of  the  superior  wall  of  the  bony  meatus.  If  the  instrument  is  entered 
at  a  higher  level  it  will  open  the  cerebral  cavity;  the  instrument  should  be  carried  inward,  for- 
ward, and  a  little  upward,  that  is,  in  the  direction  of  the  auditory  canal.  The  antrum  is  usually 
reached  after  the  penetration  of  from  1  to  1£  cm.  of  bone.  The  depth  at  which  the  antrum  is  sit- 
uated is  not  constant.  "It  is  safe  to  say  that  if  the  instrument  penetrates  deeper  than  1  \  cm.  and 
be  directed  too  far  forward  or  downward,  the  horizontal  semicircular  canal  or  the  aquseductus 
Fallopii  will  be  encountered.  If  the  former  were  opened  in  a  purulent  otitis  media  the  pus 
would  travel  along  it  to  the  vestibule  and  from  there  into  the  internal  auditory  meatus,  pro- 
ducing a  pachymeningitis  or  extradural  (epidural)  abscess  of  the  posterior  fossa  of  the  skull ; 
or  from  the  vestibule  through  the  perpendicular  semicircular  canal,  which  if  accompanied  by 
erosion  of  its  bony  covering  would  lead  to  involvement  of  the  meninges  of  the  middle  fossa; 
the  same  would  hold  good  for  the  posterior  semicircular  canal,  affecting  the  posterior  fossa.  If 
the  latter  (the  aquaeductus  Fallopii)  were  opened  an  inflammation  of  the  facial  nerve  which  is 
contained  therein  would  result,  producing  paralysis  of  that  side  of  the  face.  The  inflammatory 
process  might  also  find  its  way  through  the  entire  canal  to  the  internal  auditory  meatus,  caus- 
ing a  pachymeningitis  or  extradural  abscess  as  mentioned  above;  or,  travelling  along  the  nerve 


THE  ANTERIOR  REGION  OF  THE  SKULL 


153 


to  its  cerebral  attachment,  would  produce  a  meningitis  or  subdural  (intradural)  abscess.     The 

direction  of  the  penetrating  instrument  must  also  be  forward,  in  order  to  avoid  injuring  the 

lateral  sinus"  ("Anatomy  and  Surgery  of 

the  Temporal  Bone,"  by  A.  E.  Schmitt, 

M.D.,  American  Journal  of  the  Mcilii-al 

Sciences,  April,  1903).     In  the  operation 

for  infective   thrombosis  of    the    lateral 

sinus   the  sinus  is  .deliberately   exposed 

and  opened  (Fig.  108). 

Hartley  divides  the  mastoid  process 
into  four  parts  as  follows:  The  upper 
margin  is  the  posterior  root  of  the  zygoma. 
The  anterior  margin  is  the  anterior 
border  of  the  mastoid.  The  posterior 
margin  is  a  vertical  line  dropped  from 
the  masto-occipital  junction.  The  lower 
margin  is  an  imaginary  line  backward 
from  the  mastoid  tip.  This  space  is 
divided  into  four  equal  parts.  Points 
upon  it  may  be  designated  as  on  a  map. 
Take  the  left  side  for  demonstration. 
An  opening  in  the  N.  W.  quadrant  enters 
the  antrum,  one  into  the  N.  E.  quad- 


rant exposes  the  lateral  sinus,  one  into 


FIG.  108.— -Division  of  the  mastoid  process  into  four  equal 

the  b.  W.  quadrant  enters  mastoid  cells,  parts.  An  opentog  in  th«npper»nterior  quadrant  reachee  the 

and    a     superficial    one      into    the    S     E.  mastoid  antrum ;  into  the  upper  posterior  quadrant  reaches 

.  ,       11      i  j       '  the  lateral  sinus;  the  lower  anterior  quadrant  into  mastoid 

quadrant  enters  mastoid  cells,  but  a  deep  cells;  a  superficial  opening  into  the  lower  posterior  quadrant 

one    exposes    the    descending    Portion    of  reaches  mastoid  cells;  a  deep  opening  reaches  the  descending 

,  limb  of  the  lateral  sinus.     (A.  E.  Schmitt.) 

the    lateral    sinus.      When    pus    breaks 

through  the  mastoid  process  it  may  enter  the  sheath  of  the  Digastric  or  Sterno-cleido-mastoid 

muscle  and  point  a  considerable  distance  away  from  the  bone,  Bezold's  abscess. 

In  connection  with  the  bones  of  the  face  a  common  malformation  is  cleft  palate,  owing  to 
the  non-union  of  the  palatal  processes  of  the  maxillary  or  pre-oral  arch.  This  cleft  may  involve 
the  whole  or  only  a  portion  of  the  hard  palate,  and  usually  involves  the  soft  palate  also.  The 
cleft  is  in  the  middle  line,  except  it  involves  the  alveolus  in  front,  when  it  follows  the  suture 
between  the  main  portion  of  the  bone  and  the  pre-maxillary  bone.  Sometimes  the  cleft  runs 
on  either  side  of  the  pre-maxillary  bone,  so  that  this  bone  is  quite  isolated  from  the  maxillary 
bones  and  hangs  from  the  end  of  the  vomer.  In  such  a  case  the  pre-maxillary  bone  usually 
contains  the  germs  of  the  central  incisors  only.  In  some  cases  there  is  no  pre-maxillary  bone 
and  the  great  gap  in  the  lip  is  in  the  median  line.  Cleft  palate  (Fig.  92)  is  usually  associated 
with  hare-lip,  which,  when  single,  is  almost  always  on  one  side,  corresponding  to  the  position 
of  the  suture  between  the  lateral  incisor  and  canine  tooth.  Some  few. cases  of  median  hare- 
lip have  been  described.  In  double  hare-lip  there  is  a  cleft  on  each  side  of  the  middle  line  (see 
page  111). 

The  outlines  and  the  height  of  the  arch  of  the  palate  vary  greatly  in  different  persons.  A 
narrow  palate  with  a  high  arch  is  common  in  idiots  and  certain  degenerates. 

The  bones  of  the  face  are  sometimes  fractured  as  the  result  of  direct  violence.  The  two 
most  commonly  broken  are  the  nasal  bone  and  the  mandible,  and  of  these  the  latter  is  by 
far  the  most  frequently  fractured  of  all  the  bones  of  the  face.  Fracture  of  the  nasal  bone  is 
for  the  most  part  transverse,  and  takes  place  about  half  an  inch  from  the  free  margin.  The 
broken  portion  may  be  displaced  backward  or  more  generally  to  one  side  by  the  force  which 
produced  the  lesion,  as  there  are  no  muscles  here  which  can  cause  displacement.  The  malar 
bone  is  probably  never  broken  alone;  that  is  to  say,  unconnected  with  a  fracture  of  the  other 
bones  of  the  face.  The  zygomatic  arch  is  occasionally  fractured,  and  when  this  occurs  from 
direct  violence,  as  is  usually  the  case,  the  fragments  may  be  displaced  inward.  This  lesion  is 
often  attended  with  great  difficulty  or  even  inability  to  open  and  shut  the  mouth,  and  this  has 
been  stated  to  be  due  to  the  depressed  fragments  perforating  the  temporal  muscle,  but  would 
appear  rather  to  be  caused  by  the  injury  done  to  the  bony  origin  of  the  Masseter  muscle. 
Fractures  of  the  superior  maxilla  may  vary  much  in  degree,  from  the  chipping  off  of  a  portion 
of  the  alveolar  arch,  a  frequent  accident  when  the  "old  key"  instrument  was  used  for  the 
extraction  of  teeth,  to  an  extensive  comminution  of  the  whole  bone  from  severe  violence,  as 
the  kick  of  a  horse.  The  most  common  situation  for  a  fracture  of  the  mandible  bone  is  in  the 
neighborhood  of  the  canine  tooth,  as  at  this  spot  the  jaw  is  weakened  by  the  deep  socket  for 
the  fang  of  this  tooth;  it  is  next  most  frequently  fractured  at  the  angle;  then  at  the  symphysis, 
and  finally  the  neck  of  the  condyle  or  the  coronoid  process  may  be  broken.  Occasionally  a 
double  fracture  may  occur,  one  in  either  half  of  the  bone.  The  fractures  are  usually  compound, 


154  THE  SKELETON 

from  laceration  of  the  mucous  membrane  covering  the  gums.  The  displacement  is  mainly  the 
result  of  the  same  violence  as  produced  the  injury,  but  may  be  further  increased  by  the  action 
of  the  muscles  passing  from  the  neighborhood  of  the  symphysis  to  the  hyoid  bone. 

The  superior  and  inferior  maxillary  bones  are  both  of  them  frequently  the  seat  of  necrosis, 
though  the  disease  affects  the  lower  much  more  frequently  than  the  upper  jaw.  It  may  be  the 
result  of  periostitis,  from  tooth  irritation,  injury,  or  the  action  of  some  specific  poison,  as  syphilis, 
or  from  salivation  by  mercury;  it  not  infrequently  occurs  in  children  after  attacks  of  the  exan- 
thematous  fevers,  and  a  special  form  occurs  from  the  action  of  the  fumes  of  phosphorus  in 
persons  engaged  in  the  manufacture  of  matches. 

Tumors  attack  the  jaw  bones  not  infrequently,  and  these  may  be  either  innocent  or  malig- 
nant: in  the  upper  jaw  cysts  may  occur  in  the  antrum,  constituting  the  so-called  dropsy  of  the 
antrum;  or,  again,  cysts  may  form  in  either  jaw  in  connection  with  the  teeth:  either  cysts  con- 
nected with  the  roots  of  fully  developed  teeth,  the  "dental  cyst;"  or  cysts  connected  with  im- 
perfectly developed  teeth,  the  "dentigerous  cyst."  Solid  innocent  tumors  include  the  fibroma, 
the  chondroma,  and  the  osteoma.  Of  malignant  tumors  there  are  the  endotheliomata,  the 
sarcomata,  and  the  epitheliomata.  The  sarcomata  are  of  various  kinds,  the  spindle-celled, 
the  round-celled,  which  are  of  a  very  malignant  character,  and  the  myeloid  sarcomata,  prin- 
cipally affecting  the  alveolar  margin  of  the  bone.  Of  the  epitheliomata  we  find  the  squamous 
variety  spreading  to  the  bone  from  the  palate  or  gum,  and  the  cylindrical  epithelioma  origin- 
ating in  the  antrum  or  nasal  fossae. 

Both  superior  and  inferior  maxillary  bones  occasionally  require  excision  for  tumors  and  in 
some  other  conditions.  The  upper  jaw  is  removed  by  an  incision  from  the  inner  canthus  of  the 
eye,  along  the  side  of  the  nose,  round  the  ala,  and  down  the  middle  line  of  the  upper  lip.  A 
second  incision  is  carried  outward  from  the  inner  canthus  of  the  line  along  the  lower  margin  of 
the  orbit  as  far  as  the  prominence  of  the  malar  bone.  The  flap  thus  formed  is  reflected  outward 
and  the  surface  of  the  bone  exposed,  and  the  central  incisor  of  the  diseased  side  is  removed. 
The  connections  of  the  bone  to  the  other  bones  of  the  face  are  then  divided  with  a  narrow  saw  and 
bone-cutting  forceps.  They  are  (1)  the  junction  with  the  malar  bone,  passing  into  the  spheno- 
maxillary  fissure;  (2)  the  nasal  process;  a  small  portion  of  its  upper  extremity,  connected  with  the 
nasal  bone  in  front,  the  lachrymal  bone  behind,  and  the  frontal  bone  above,  being  left;  (3)  the 
connection  with  the  bone  on  the  opposite  side  and  the  palate  in  the  roof  of  the  mouth.  The 
bone  is  now  firmly  grasped  with  lion-jaw  forceps,  and  by  means  of  a  rocking  movement  upward 
and  downward  the  remaining  attachments  of  the  orbital  plate  with  the  ethmoid  and  the 
back  of  the  bone  with  the  palate,  broken  through.  The  soft  palate  is  first  separated  from 
the  hard  with  a  scalpel,  and  is  not  removed.  Occasionally  in  removing  the  upper  jaw  it 
will  be  found  that  the  orbital  plate  can  be  spared,  and  this  should  always  be  done  if  possible. 
A  horizontal  saw-cut  is  to  be  made  just  below  the  infraorbital  foramen  and  the  bone  cut  through 
with  a  chisel  and  mallet.  Lockwood  has  pointed  out  that  in  removing  the  upper  jaw  the  sur- 
geon must  be  careful  in  dividing  the  nasal  process  of  the  superior  maxilla  to  preserve  the  inter- 
nal orbital  or  palpebral  ligament  (Tendo  oculi),  because  this  ligament  arises  from  the  palpebral 
fascia,  and  if  it  is  interfered  with  the  eye  will  inevitably  drop  downward.  Removal  of  one-half 
of  the  lower  jaw  is  sometimes  required.  If  possible,  the  section  of  the  bone  should  be  made 
to  one  side  of  the  symphysis,  so  as  to  save  the  genial  tubercles  and  the  origin  of  the  genio-hyo- 
glossus  muscle,  as  otherwise  the  tongue  tends  to  fall  backward  and  may  produce  suffocation. 
Having  extracted  the  central  or  preferably  the  lateral  incisor  tooth,  a  vertical  incision  is  made 
down  to  the  bone,  commencing  at  the  free  margin  of  the  lip,  and  carried  to  the  lower  border 
of  the  bone;  it  is  then  carried  along  its  lower  border  to  the  angle  and  up  the  posterior  margin 
of  the  ramus  to  a  level  with  the  lobule  of  the  ear.  The  flap  thus  formed  is  raised  by  separating 
all  the  structures  attached  to  the  outer  surface  of  the  bone.  The  jaw  is  now  sawn  through 
at  the  point  where  the  tooth  has  been  extracted,  and  the  knife  passed  along  the  inner  side  of 
the  jaw,  separating  the  structures  attached  to  this  surface.  The  jaw  is  then  grasped  by  the 
surgeon  and  strongly  depressed,  so  as  to  bring  down  the  coronoid  process  and  enable  the  operator 
to  sever  the  tendon  of  the  Temporal  muscle.  The  jaw  can  be  now  further  depressed,  care  being 
taken  not  to  evert  it  nor  rotate  it  outward,  which  would  endanger  the  internal  maxillary  artery, 
and  the  External  pterygoid  muscle  is  torn  through  or  divided.  The  capsular  ligament  is  now 
opened  in  front  and  the  lateral  ligaments  divided,  and  the  jaw  removed  with  a  few  final  touches 
of  the  knife. 

The  antrum  of  Highmore  occasionally  requires  tapping  for  suppuration.  This  may  be  done 
through  the  socket  of  a  tooth,  preferably  the  first  molar,  the  fangs  of  which  are  most  intimately 
connected  with  the  antrum,  or  through  the  facial  aspect  of  the  bone  above  the  alveolar  process. 
This  latter  method  does  not  perhaps  afford  such  efficient  drainage,  but  there  is  less  chance  of 
food  finding  its  way  into  the  cavity.  The  operation  may  be  performed  by  incising  the  mucous 
membrane  above  the  second  molar  tooth,  and  driving  a  trocar  or  any  sharp-pointed  instrument 
into  the  cavity. 


155 


THE  HYOID  OR  LINGUAL  BONE  (OS  HYOIDEUM). 

The  hyoid  bone  (Fig.  109)  is  named  from  its  resemblance  to  the  Greek  upsilon; 
it  is  also  called  the  lingual  bone,  because  it  supports  the  tongue  and  gives  attach- 
ment to  its  numerous  muscles.  It  is  a  bony  arch,  shaped  like  a  horseshoe,  and 
consisting  of  five  segments :  a  body,  two  greater  cornua,  and  two  lesser  cornua.  It 
is  suspended  from  the  tip  of  the  styloid  processes  of  the  temporal  bone  by  liga- 
mcntous  bands,  the  stylo-hyoid  ligaments. 

Body  (corpus  ossei  hyoidei). — The  body,  or  basi-hyal,  forms  the  central  part 
of  the  bone,  and  is  of  a  quadrilateral  form. 

Surfaces. — Its  anterior  surface  (Fig.  109),  convex,  directed  forward  and  upward, 
is  divided  into  two  parts  by  a  vertical  ridge  which  descends  along  the  median 
line  and  is  crossed  at  right  angles  by  a  horizontal  ridge,  so  that  this  surface  is 
divfded  into  four  spaces  or  depressions.  At  the  point  of  meeting  of  these  two  lines 
is  a  prominent  elevation,  the  tubercle.  The  portion  above  the  horizontal  ridge  is 
directed  upward,  and  is  sometimes  described  as  the  superior  border.  The  anterior 
surface  gives  attachment  to  the  Genio-hyoid  in  the  greater  part  of  its  extent ;  above, 
to  the  Genio-hyo-glossus;  below,  to  the  Mylo-hyoid,  Stylo-hyoid,  and  aponeurosis  of 
the  Digastric  (suprahyoid  aponeurosis);  and  between  these  to  part  of  the  Hyo- 
glossus.  The  posterior  surface  is  smooth,  concave,  directed  backward  and  down- 
ward, and  separated  from  the  epiglottis  by  the  thyro-hyoid  membrane  and  by  a 
quantity  of  loose  areolar  tissue.  The  lateral  surfaces  after  middle  life  are  joined 
to  the  greater  cornua.  In  early  life  they  are  connected  to  the  cornua  by  carti- 
laginous surfaces,  and  held  together  by  ligaments,  and  occasionally  a  synovial 
membrane  is  found  between  them. 

Borders. — The  superior  border  is  rounded,  and  gives  attachment  to  the  thyro- 
hyoid  membrane,  part  of  the  Genio-hyo-glossi  and  Chondro-glossi  muscles.  The 
inferior  border  gives  attachment,  in  front,  to  the  Sterno-hyoid ;  behind,  to  the  Omo- 
hyoid  and  to  the  part  of  the  Thyro- 
hyoid  at  its  junction  with  the  great 
cornu.  It  also  gives  attachment  to 
the  Levatore  glandular  thyroideae 
when  this  muscle  is  present. 

Greater  Gornua  (cornua  major  a) . 
-The  greater  cornua  or  thyro-hyals 
project  backward  from  the  lateral 
surfaces  of  the  body;  they  are  flat- 
tened  from  above  downward,  di- 
minish  in  size  from  before  back- 
ward, and  terminate  posteriorly  in 
a  tubercle  for  the  attachment  of 

,l  |  1,1  1  •    1       !•  GENIO-HYOID.  STERNO-HYOID. 

the    lateral    thyro-hyoid    ligament.  FIG.  109.-Hyoid  bone.     Anterior  surface.     (Enlarged.) 

The  outer  surf  ace  gives  attachment 

to  the  Hyo-glossus,  their  upper  border  to  the  Middle  constrictor  of  the  pharynx, 

their  lower  border  to  part  of  the  Thyro-hyoid  muscle. 

Lesser  Gornua  (cornua  minora). — The  lesser  cornua,  or  cerato-hyals,  are  two 
small,  conical-shaped  eminences  attached  by  their  bases  to  the  angles  of  junc- 
tion between  the  body  and  greater  cornua,  and  giving  attachment  by  their  apices 
to  the  stylo-hyoid  ligaments.1  The  smaller  cornua  are  connected  to  the  body  of 
the  bone  by  a  distinct  diarthrodial  joint,  which  usually  persists  throughout  life, 
but  occasionally  becomes  ankylosed. 

1  These  ligaments  in  many  animals  are  distinct  bones,  and  in  man  are  occasionally  ossified  to  a  certain  extent. — 
ED.  of  15th  English  Edition. 


MYLO-HYOID. 


156  THE  SKELETON 

Development. — By  five  centres:  one  for  the  body,  and  one  for  each  cornu. 
Ossification  commences  in  the  body  about  the  eighth  month,  and  in  the  greater 
cornua  toward  the  end  of  foetal  life.  Ossification  of  the  lesser  cornua  commences 
some  years  after  birth.  Sometimes  there  are  two  centres  for  the  body. 

Attachment  of  Muscles. — Sterno-hyoid,  Thyro-hyoid,  Omo-hyoid,  aponeurosis 
of  the  Digastric,  Stylo-hyoid,  Mylo-hyoid,  Genio-hyoid,  Genio-hyo-glossus,  Chon- 
dro-glossus,  Hyo-glossus,  Middle  constrictor  of  the  pharynx,  and  occasionally  a 
few  fibres  of  the  Inferior  lingualis.  It  also  gives  attachment  to  the  thyro-hyoidean 
membrane  and  the  stylo-hyoid,  thyro-hyoid,  and  hyo-epiglottic  ligaments. 

Surface  Form. — The  hyoid  bone  can  be  felt  in  the  receding  angle  below  the  chin,  and  the 
finger  can  be  carried  along  the  whole  length  of  the  bone  to  the  greater  corhu,  which  is  situated 
just  below  the  angle  of  the  jaw.  This  process  of  bone  is  best  perceived  by  making  pressure  on 
one  cornu,  and  so  pushing  the  bone  over  to  the  opposite  side,  when  the  cornu  of  this  side  will 
be  distinctly  felt  immediately  beneath  the  skin.  This  process  of  bone  is  an  important  landmark 
in  ligature  of  the  lingual  artery. 

Surgical  Anatomy. — The  hyoid  bone  is  occasionally  fractured,  generally  from  direct  vio- 
lence, as  in  the  act  of  garroting  or  throttling.  It  is  frequently  found  broken  in  those  who  have 
been  hung.  The  great  cornu  is  the  part  of  the  bone  most  frequently  broken,  but  sometimes 
the  fracture  takes  place  through  the  body  of  the  bone.  In  consequence  of  the  muscles  of  the 
tongue  having  important  connections  with  this  bone,  there  is  great  pain  upon  any  attempt  being 
made  to  move  the  tongue,  as  in  speaking  or  swallowing. 

THE  THORAX. 

The  thorax,  or  chest,  is  an  osseo-cartilaginous  cage  the  cavity  of  which  (cavwn 
thoracis)  contains  and  protects  the  principal  organs  of  respiration  and  circula- 
tion. It  is  conical  in  shape,  being  narrow  above  and  broad  below,  flattened 
from  before  backward,  and  longer  behind  than  in  front.  It  is  somewhat 
reniform  on  transverse  section. 

Boundaries. — The  posterior  surf  ace  is  formed  by  the  twelve  thoracic  vertebrae  and 
the  posterior  part  of  the  ribs.  It  is  concave  from  above  downward,  and  presents 
on  each  side  of  the  middle  line  a  deep  groove,  the  vertebral  groove,  in  conse- 
quence of  the  direction  backward  and  outward  which  the  ribs  take  from  their 
vertebral  extremities  to  their  angles.  The  anterior  surface  is  flattened  or  slightly 
convex,  and  inclined  forward  from  above  downward.  It  is  formed  by  the  sternum 
and  costal  cartilages.  The  lateral  surfaces  are  convex;  they  are  formed  by  the 
ribs,  separated  from  each  other  by  spaces.  Each  space  is  called  an  intercostal 
space  (spatium  inter costale).  These  are  eleven  in  number,  and  are  occupied  by 
the  intercostal  muscles. 

The  superior  or  upper  opening  or  aperture  of  the  thorax,  the  inlet  (apertura 
thoracis  superior},  is  reniform  in  shape,  being  broader  from  side  to  side  than 
from  before  backward.  It  is -formed  by  the  first  thoracic  vertebra  behind,  the 
upper  margin  of  the  sternum  in  front,  and  the  first  rib  on  each  side.  It  slopes 
downward  and  forward,  so  that  the  anterior  part  of  the  ring  is  on  a  lower  level 
than  the  posterior.  The  antero-posterior  diameter  is  about  two  inches,  and  the 
transverse  about  four.  The  inferior  or  lower  opening  (apertura  thoracis  inferior] 
is  formed  by  the  twelfth  thoracic  vertebra  behind,  by  the  twelfth  ribs  at  the  sides, 
and  in  front  by  the  cartilages  of  the  eleventh,  tenth,  ninth,  eighth,  and  seventh 
ribs,  which  ascend  on  either  side  and  form  an  angle,  the  subcostal  angle  (angulus 
infrasternalis) ,  from  the  apex  of  which  the  ensiform  cartilage  projects.  It  is 
wider  transversely  than  from  before  backward.  It  slopes  obliquely  downward 
and  backward,  so  that  the  cavity  of  the  thorax  is  much  deeper  behind  than  in 
front.  The  Diaphragm  closes  in  the  opening  forming  the  floor  of  the  thorax. 

In  the  female  the  thorax  differs  as  follows  from  the  male:  1.  Its  general  capa- 
city is  less.  2.  The  sternum  is  shorter.  3.  The  upper  margin  of  the  sternum 


THE  STERN&M  157 

is  on  a  level  with  the  lower  part  of  the  body  of  the  third  thoracic  vertebra,  whereas 
in  the  male  it  is  on  a  level  with  the  lower  part  of  the  body  of  the  second  thoracic 
vertebra.  4.  The  upper  ribs  are  more  movable,  and  so  allow  a  greater  enlarge- 
ment of  the  upper  part  of  the  thorax  than  in  the  male. 

The  Sternum  or  Breast  Bone. 

The  sternum  (arepvov,  the  chest),  or  breast  bone  (Figs.  110,  111),  is  a  flat, 
narrow  bone,  situated  in  the  median  line  of  the  front  of  the  chest,  and  con- 
sisting, in  the  adult,  of  three  portions.  It  has  been  likened  to  an  ancient 
sword;  the  upper  piece,  representing  the  handle,  is  termed  the  manubrium 
sterni  (presternum);  the  middle  and  largest  piece,  which  represents  the  chief 
part  of  the  blade,  is  termed  the  gladiolus  (mesosternum  or  corpus  sterni);  and 
the  inferior  piece,  which  is  likened  to  the  point  of  the  sword,  is  termed  the 
ensiform  or  xiphoid  process  or  appendix  (processus  xiphoideus  or  metasternum) . 
In  early  youth  the  sternum  is  composed  of  six  pieces  or  sternebra.  In  adult  life 
the  upper  piece  remains  as  the  manubrium;  the  inferior  piece  remains  as  the 
xiphoid;  and  the  other  four  pieces  fuse  together  to  form  the  gladiolus.  In  its 
natural  position  its  inclination  is  oblique  from  above  downward  and  forward.  It 
is  slightly  convex  in  front,  concave  behind,  broad  above,  becoming  narrowed  at 
the  point  where  the  first  and  second  pieces  are  connected,  after  which  it  again 
widens  a  little,  and  is  pointed  at  its  extremity.  Its  average  length  in  the  adult  is 
about  seven  inches,  being  rather  longer  in  the  male  than  in  the  female.  At  the 
junction  of  the  manubrium  and  gladiolus  is  a  distinct  angle,  the  angulus  sterni 
(angle  of  Ludovic  or  angle  of  Louis),  the  manubrium  looking  forward,  the 
gladiolus  also  looking  forward,  but  to  a  less  degree.  •  This  angle  is  on  a  level 
with  the  second  rib,  and  is  produced  by  retraction  of  the  upper  portion  of  the 
thorax. 

First  Piece. — The  first  piece  of  the  sternum,  or  the  manubrium  sterni  (pre- 
sternum), is  of  a  somewhat  triangular  form,  broad  and  thick  above,  narrow 
below  at  its  junction  with  the  middle  piece. 

Surfaces. — Its  anterior  surface,  convex  from  side  to  side,  concave  from  above 
downward,  is  smooth,  and  affords  attachment  on  each  side  to  the  Pectoralis 
major  and  sternal  origin  of  the  Sterno-cleido-mastoid  muscle.  In  well-marked 
bones  the  ridges  limiting  the  attachment  of  these  muscles  are  very  distinct.  Its 
posterior  surface,  concave  and  smooth,  affords  attachment  on  each  side  to  the 
Sterno-hyoid  and  Sterno- thyroid  muscles. 

Borders. — The  superior  border,  the  thickest,  presents  at  its  centre  the  pre-sternal 
notch  (incisura  jugularis),  and  on  each  side  an  oval  articular  surface,  the 
clavicular  facet  (incisura  clavicularis) ,  directed  upward,  backward,  and  outward, 
for  articulation  with  the  sternal  end  of  the  clavicle.  The  inferior  border  presents 
an  oval,  rough  surface,  covered  in  the  recent  state  with  a  thin  layer  of  cartilage, 
for  articulation  with  the  second  portion  of  the  bone  (synchondrosis  sternalis). 
The  junction  of  the  manubrium  with  the  gladiolus  is  marked  by  a  transverse 
ridge,  which  corresponds  to  the  attachment  on  each  side  of  the  cartilage  of 
the  second  rib.  The  lateral  borders  are  marked  above  by  a  depression  (incisura 
costalis  I)  for  the  first  costal  cartilage,  and  below  by  a  small  facet,  which,  with  a 
similar  facet  on  the  upper  angle  of  the  middle  portion  of  the  bone,  forms  a 
notch  (incisura  costalis  II)  for  the  reception  of  the  costal  cartilage  of  the  second 
rib.  These  articular  surfaces  are  separated  by  a  narrow,  curved  edge,  which 
slopes  from  above  downward  and  inward. 

Second  Piece. — The  second  piece  of  the  sternum,  the  corpus  sterni  or  gladiolus 
(mesosternum),  considerably  longer,  narrower,  and  thinner  than  the  first  piece,  is 
broader  below  than  above. 


158 


THE   SKELETON 


STERNO-CLEIDOMASTOID."^ 
SUBOLAVIU8. 


FIG.  110. — Sternum  and  costal  cartilages. 


FIG.  111. — Posterior  surface  of  sternum. 


THE  STERNUM  159 

Surfaces. — Its  anterior  surface  (planum  sternale)  is  nearly  flat,  directed  upward 
and  forward,  and  marked  by  three  transverse  lines  which  cross  the  bone  opposite 
the  third,  fourth,  and  fifth  articular  depressions.  These  lines  are  produced  by  the 
union  of  the  four  separate  pieces  of  which  this  part  of  the  bone  consists  at  an  early 
period  of  life.  At  the  junction  of  the  third  and  fourth  pieces  is  occasionally  seen 
an  orifice,  the  sternal  foramen;  it  varies  in  size  and  form  in  different  individuals, 
and  pierces  the  bone  from  before  backward.  This  surface  affords  attachment 
on  each  side  to  the  sternal  origin  of  the  Pectoralis  major.  The  posterior  surface, 
slightly  concave,  is  also  marked  by  three  transverse  lines,  but  they  are  less  dis- 
tinct than  those  in  front:  this  surface  affords  attachment  below,  on  each  side, 
to  the  Triangularis  sterni  muscle,  and  occasionally  presents  the  posterior  opening, 
of  the  sternal  foramen. 

Borders. — The  superior  border  presents  an  oval  surface  for  articulation  with  the 
manubrium.  The  inferior  border  is  narrow,  and  articulates  with  the  ensiform 
appendix.  Each  lateral  border  presents,  at  each  superior  angle,  a  small  facet, 
which,  with  a  similar  facet  on  the  manubrium,  forms  a  cavity  for  the  cartilage  of 
the  second  rib;  the  four  succeeding  angular  depressions  receive  the  cartilages  of 
the  third,  fourth,  fifth,  and  sixth  ribs;  whilst  each  inferior  angle  presents  a  small 
facet,  which,  with  a  corresponding  one  on  the  ensiform  appendix,  forms  a  notch 
for  the  cartilage  of  the  seventh  rib.  These  articular  depressions  are  known  as 
incisurce  costales.  They  are  separated  by  a  series  of  curved  interarticular  inter- 
vals, which  diminish  in  length  from  above  downward,  and  correspond  to  the 
intercostal  spaces.  Most  of  .the  cartilages  belonging  to  the  true  ribs,  as  will  be 
seen  from  the  foregoing  description,  articulate  with  the  sternum  at  the  line  of 
junction  of  two  of  its  primitive  component  segments.  This  is  well  seen  in  many 
of  the  lower  animals,  where  the  separate  parts  of  the  bone  remain  ununited 
longer  than  in  man.  In  this  respect  a  striking  analogy  exists  between  the  mode 
of  connection  of  the  ribs  with  the  vertebral  column  and  the  connection  of  the 
costal  cartilages  with  the  sternum. 

Third  Piece. — The  third  piece  of  the  sternum,  the  ensiform  or  xiphoid  appendix 
(processus  xiphoideus  or  metasternum) ,  is  the  smallest  of  the  three;  it  is  thin  and 
elongated  in  form,  cartilaginous  in  structure  in  youth,  but  more  or  less  ossified 
at  its  upper  part  in  the  adult. 

Surfaces. — Its  anterior  surface  affords  attachment  to  the  chondro-xiphoid 
ligament;  its  posterior  surface,  to  some  of  the  fibres  of  the  Diaphragm  and 
Triangularis  sterni  muscles;  its  lateral  borders,  to  the  aponeurosis  of  the  abdom- 
inal muscles.  Above  it  articulates  with  the  lower  end  of  the  gladiolus,  and  at  each 
superior  angle  presents  a  facet  (incisura  costalis  VII),  for  the  lower  half  of  the 
cartilage  of  the  seventh  rib;  below,  by  its  pointed  extremity,  it  gives  attachment 
to  the  linea  alba.  This  portion  of  the  sternum  is  very  various  in  appearance, 
being  sometimes  pointed,  broad,  and  thin,  sometimes  bifid  or  perforated  by  a 
round  hole,  occasionally  curved  or  deflected  considerably  to  one  or  the  other  side. 

Structure. — The  bone  is  composed  of  delicate  cancellous  structure,  covered  by 
a  thin  layer  of  compact  tissue,  which  is  thickest  in  the  manubrium  between  the 
articular  facets  for  the  clavicles. 

Development. — The  cartilaginous  sternum  originally  consists  of  two  bars,  situ- 
ated one  on  either  side  of  the  mesial  plane  and  connected  with  the  rib  cartilages  of 
its  own  side.  These  two  bars  fuse  with  each  other  along  the  middle  line,  and 
the  bone,  including  the  ensiform  appendix,  is  developed  by  six  centres:  one  for  the 
first  piece  or  manubrium,  four  for  the  second  piece  or  gladiolus,  and  one  for  the 
ensiform  appendix.  Up  to  the  middle  of  fretal  life  the  sternum  is  entirely  car- 
tilaginous, and  when  ossification  takes  place  the  ossific  granules  are  deposited  in 
the  middle  of  the  intervals  between  the  articular  depressions  for  the  costal  car- 
tilages, in  the  following  order  (Fig.  112):  In  the  first  piece,  between  the  fifth  and 
sixth  months;  in  the  second  and  third,  between  the  sixth  and  seventh  months;  in 


160 


THE  SKELETON 


the  fourth  piece,  at  the  ninth  month;  in  the  fifth,  within  the  first  year  or  between 
the  first  and  second  years  after  birth;  and  in  the  ensiform  appendix,  between  the 
second  and  the  seventeenth  or  eighteenth  years,  by  a  single  centre  which  makes 
its  appearance  at  the  upper  part  and  proceeds  gradually  downward.  To  these 
may  be  added  the  occasional  existence,  as  described  by  Breschet,  of  two  small 
episternal  centres,  which  make  their  appearance  one  on  each  side  of  the  pre-sternal 
notch.  They  are  probably  vestiges  of  the  episternal  bone  of  the  monotremata 
and  lizards.  It  occasionally  happens  that  some  of  the  segments  are  formed  from 
more  than  one  centre,  the  number  and  position  of  which  vary  (Fig.  114).  Thus, 
the  first  piece  may  have  two,  three,  or  even  six  centres.  When  two  are  present, 
they  are  general y  situated  one  above  the  other,  the  upper  one  being  the  larger;1 
the  second  piece  has  seldom  more  than  one;  the  third,  fourth,  and  fifth  pieces 
are  often  formed  from  two  centres  placed  laterally,  the  irregular  union  of  which 
will  serve  to  explain  the  occasional  occurrence  of  the  sternal  foramen  (Fig.  113), 


1  for  1st  piece  \  5_fi<ft  monthfoetal. 
or  manubnum ) 


4  for  2nd  piece 
or  gladiolus 


6-7th  month. 


4  9th  month. 

5  1st  year  after 

birth. 


1  for  ensiform  \2ndtol8thye 
cartilage       ) 


FIG.  112. — Development  of  the  sternum  by  six 
centres.     Time  of  appearance. 


)  Rarely  unite, 

}    except  in  old  age. 


and  the  25th  year. 
Soon  after  puberty. 


Partly  cartilaginous  to 
advanced  life. 


FIG.  113. — Time  of  union  of  sternum. 


for  first  piece,  two  or  more  centres. 

for  second  piece,  usually  one. 
for  third    "I 

for  fourth  }•  2,  placed  laterally, 
for  fifth     J 


Arrest  of  development 
of  lateral  pieces,  producing 


FIG.  114. — Peculiarities  in  number  of  centres  of 
sternum. 


-Sternal  fissure,  and 
.Sternal  foramen. 


FIG.  115. — Peculiarities  in  mode  of  union 
of  sternum. 


or  of  the  vertical  fissure  which  occasionally  intersects  this  part  of  the  bone  (Fig.  113) , 
and  which  is  further  explained  by  the  manner  in  which  the  cartilaginous  matrix, 
in  which  ossification  takes  place,  is  formed.  Union  of  the  various  centres  of  the 
gladiolus  commences  about  puberty,  from  below,  and  proceeds  upward,  so  that  by 
the  age  of  twenty-five  they  are  all  united,  and  this  portion  of  bone  consists  of  one 
piece.  The  ensiform  cartilage  becomes  joined  to  the  gladiolus  about  forty.  The 
manubrium  is  occasionally  but  seldom  joined  to  the  gladiolus  in  advanced  life 

1  Sir  George  Humphry  states  that  this  is  "probably  the  more  complete  condition." — ED.  of  15th  English  Edition. 


THE  RIBS  161 

by  bone.  When  this  union  takes  place,  however,  it  is  generally  only  superficial, 
a  portion  of  the  centre  of  the  sutural  cartilage  remaining  unossified. 

Articulations. — With  the  clavicles  and  seven  costal  cartilages  on  each  side. 

Attachment  of  Muscles. — To  nine  pairs  and  one  single  muscle:  the  Pectoralis 
major,  Sterno-cleido-mastoid,  Sterno-hyoid,  Stern o-thyroid,  Triangularis  sterni, 
aponeuroses  of  the  Obliquus  externus,  Obliquus  internus,  Transversalis,  Rectus 
muscles,  and  Diaphragm. 

The  Eibs  (Costae). 

The  ribs  are  elastic  arches  of  bone,  which  form  the  chief  part  of  the  thoracic 
walls.  They  are  twelve  in  number  on  each  side;  but  this  number  may  be  in- 
creased by  the  development  of  a  cervical  or  lumbar  rib,  or  may  be  diminished 
to  eleven.  The  first  seven  are  connected  behind  with  the  spine  and  in  front 
with  the  sternum,  through  the  intervention  of  the  costal  cartilages;  they  are 
called  true,  sternal,  or  vertebro-sternal  ribs  (costae  verae).1  The  remaining  five  are 
false  ribs  (costae  spuriae) ;  of  these,  the  first  three  have  their  cartilages  attached  to 
the  cartilage  of  the  rib  above,  and  are  called  the  vertebro-chondral  ribs;  the  last 
two  are  free  at  their  anterior  extremities;  they  are  termed  floating  or  vertebral 
ribs.  The  ribs  vary  in  their  direction,  the  upper  ones  being  less  oblique  than 
the  lower.  The  extent  of  obliquity  reaches  its  maximum  at  the  ninth  rib,  and 
gradually  decreases  from  that  rib  to  the  twelfth.  The  ribs  are  situated  one  be- 
low the  other  in  such  a  manner  that  spaces  are  left  between  them.  Each  space 
is  called  an  intercostal  space  (spatium  intercostale) .  The  length  of  these  spaces 
corresponds  to  the  length  of  the  ribs  and  their  cartilages;  their  breadth  is  greater 
in  front  than  behind,  and  between  the  upper  than  between  the  lower  ribs.  The 
ribs  increase  in  length  from  the  first  to  the  seventh,  when  they  again  diminish 
to  the  twelfth.  In  breadth  they  decrease  from  above  downward;  in  the  upper 
ten  the  greatest  breadth  is  at  the  sternal  extremity. 

Common  Characters  of  the  Ribs. 

A  rib  from  the  middle  of  the  series  should  be  taken  in  order  to  study  the 
common  characters  of  the  ribs  (Figs.  116,  117,  and  11'8).  Each  rib  presents  two 
extremities,  a  posterior  or  vertebral,  an  anterior  or  sternal,  and  an  intervening 
portion — the  body  or  shaft. 

Posterior  Extremity. — The  posterior  or  vertebral  extremity  presents  for  ex- 
amination a  head,  neck,  and  tuberosity. 

The  Head  (capitidum  costae}. — The  head  (Fig.  118)  is  marked  by  a  kidney 
shaped  articular  surface,  divided  by  a  horizontal  ridge  (crista  capituli)  into  two 
facets  for  articulation  with  the  costal  cavity  formed  by  the  junction  of  the  bodies 
of  two  contiguous  thoracic  vertebrae;  the  upper  facet  is  small,  the  inferior  one 
of  larger  size;  the  ridge  separating  them  serves  for  the  attachment  of  the  inter- 
articular  ligament. 

The  Neck  (collum  costae). — The  neck  is  that  flattened  portion  of  the  rib  which 
extends  outward  from  the  head;  it  is  about  an  inch  long,  and  is  placed  in  front 
of  the  transverse  process  of  the  lower  of  the  two  vertebra?  with  which  the  head 
articulates.  Its  anterior  surface  is  flat  and  smooth,  its  posterior  surface  is  rough 
for  the  attachment  of  the  middle  costo-transverse  ligament,  and  is  perforated  by 
numerous  foramina,  the  direction  of  which  is  less  constant  than  those  found  on 
the  inner  surface  of  the  shaft.  Of  its  two  borders  the  superior  border  presents 
a  rough  crest  (crista  colli  costae)  for  the  attachment  of  the  anterior  costo-trans- 
verse ligament;  its  inferior  border  is  rounded.  On  the  'posterior  surface  of  the 

1  Sometimes  the  eighth  rib  cartilage  articulates  with  the  sternum;  this  condition  occurs  more  frequently  on  the 
right  than  on  the  left  side. — ED.  of  15th  English  Edition. 

11 


THE  SKELETON 


neck,  just  where  it  joins  the  shaft,  and  nearer  the  lower  than  the  upper  border, 
is  an  eminence — the  tuberosity,  or  tubercle. 


Angle.- 


— ^ 


/Tuberosity, 


Articular  part  of  tuberosity.'' 


iNeck. 


-Subcostal  groove 


Head.' 

Tuberosity  (tuberculum  costae). — The  tuber- 
osity, or  tubercle,  consists  of  an  articular  and  a 
non-articular  portion.  The  articular  portion 
(fades  articularis  tuberculi  costae),  the  more  in- 
ternal and  inferior  of  the  two,  presents  a  small, 
oval  surface  for  articulation  with  the  extremity 
of  the  transverse  process  of  the  lower  of  the  two 
vertebrae  to  which  the  head  is  connected.  The 
non-articular  portion  is  a  rough  elevation,  which 
affords  attachment  to  the  posterior  costo-trans- 
verse  ligament.  The  tubercle  is  much  more 
prominent  in  the  upper  than  in  the  lower  ribs. 


or  shaft. 


FIG.  117. — Ribs  and  articulations  of  the  vertebrae.      (Sappey.) 

Anterior  Extremity. — The  anterior  or  ster- 
nal extremity  is  flattened,  and  presents  a  porous, 
oval,  concave  depression,  into  which  the  costal 
cartilage  is  received. 

The  Shaft  (corpus  costae). — The  shaft  is  thin 
and  flat,  so  as  to  present  two  surfaces,  an  ex- 
FIG.  lie.— A  central  rib  of  right  side,     ternal    and    an    internal,    and    two    borders,    a 

superior  and  an  inferior. 

Surfaces. — The  external  surface  is  convex,  smooth  and  marked  at  its  back  part,  a 
little  in  front  of  the  tuberosity,  by  a  prominent  line,  directed  obliquely  from  above 


PECULIAR  RIBS 


163 


downward  and  outward;  this  gives  attachment  to  a  tendon  of  the  Ilio-costalis 
muscle  or  of  one  of  its  accessory  portions,  and  is  called  the  angle  (angulus  costce). 
At  this  point  the  rib  is  bent  in  two  directions.  If  the  rib  is  laid  upon  its  lower 
border,  it  will  be  seen  that  the  portion  of  the  shaft  in  front  of  the  angle  rests  upon 
this  border,  while  the  portion  of  the  shaft  behind  the  angle  is  bent  inward  and  at 
the  same  time  tilted  upward.  The  interval  between  the  angle  and  the  tuberosity 
increases  gradually  from  the  second  to  the  tenth  rib.  The  portion  of  bone  between 
these  two  parts  is  rounded,  rough,  and  irregular,  and  serves  for  the  attachment  of 
the  Longissimus  dorsi  muscle.  The  portion  of  bone  between  the  tubercle  and 
sternal  extremity  is  also  slightly  twisted  upon  its  own  axis,  the  external  surface 
looking  downward  behind  the  angle,  a  little  upward  in  front  of  it.  This  surface 
jresents,  toward  its  sternal  extremity,  an  oblique  line,  the  anterior  angle.  The 
internal  surface  is  concave,  smooth,  directed  a  little  upward  behind  the  angle,  a 
little  downward  in  front  of  it.  This  surface  is  marked  by  a  ridge  which  corn- 
Facet  for  body  of  upper  dorsal  vertebra. 
Ridge  for  interarticular  ligament. 
Facet  for  body  of  lower  dorsal  vertebra. 


Articular  part  of  tuberosity. 


Non-articular  part  of  tuberosity. 
FIG.  118. — Vertebral  extremity  of  a  rib.     External  surface. 

mences  at  the  lower  extremity  of  the  head;  it  is  strongly  marked  as  far  as  the 
inner  side  of  the  angle,  and  gradually  becomes  lost  at  the  junction  of  the  anterior 
with  the  middle  third  of  the  bone.  The  interval  between  it  and  the  inferior  border 
presents  a  groove,  subcostal  groove  (sulcus  costce),  for  the  intercostal  vessels  and 
nerve.  At  the  back  part  of  the  bone  this  groove  belongs  to  the  inferior  border, 
but  just  in  front  of  the  angle,  where  it  is  deepest  and  broadest,  it  corresponds  to 
the  internal  surface.  The  superior  edge  of  the  groove  is  rounded;  it  serves  for 
the  attachment  of  the  Internal  intercostal  muscle.  The  inferior  edge  corresponds 
to  the  lower  margin  of  the  rib  and  gives  attachment  to  the  External  intercostal 
muscle.  Within  the  groove  are  seen  the  orifices  of  numerous  small  foramina 
which  traverse  the  wall  of  the  shaft  obliquely  from  before  backward. 

Borders. — The  superior  border,  thick  and  rounded,  is  marked  by  an  external 
md  an  internal  lip,  more  distinct  behind  than  in  front;  they  serve  for  the  attach- 
lent  of  the  External  and  Internal  intercostal  muscles.  The  inferior  border,  thin 
md  sharp,  has  attached  to  it  the  External  intercostal  muscle. 

Peculiar  Ribs. 

The  ribs  which  require  especial  consideration  are  five  in  number — viz.,  the 
first,  second,  tenth,  eleventh,  and  twelfth. 
First  Rib. — The  first  rib  (Fig.  119)  is  the  shortest  and  the  most  curved  of 

ill  the  ribs;  it  is  broad  and  flat,  its  surface  looking  upward  and  downward,  and 
its  borders  inward  and  outward.  The  head  is  of  small  size,  rounded,  and  presents 
only  a  single  articular  facet  for  articulation  with  the  body  of  the  first  thoracic  ver- 
tebra. The  neck  is  narrow  and  rounded.  The  tuberosity,  thick  and  prominent, 
rests  on  the  outer  border.  There  is  no  angle,  but  in  this  situation  the  rib  is  slightly 
bent,  with  the  convexity  of  the  bend  upward,  so  that  the  head  of  the  bone  is 

lirected  downward.     The  upper  surface  of  the  shaft  is  marked  by  two  shallow 


164 


THE  SKELETON 


depressions,  separated  by  a  small  rough  surface  (tuberculum  scaleni)  for  the 
attachment  of  the  Scalenus  anticus  muscle — the  shallow  groove  in  front  of  it 
transmitting  the  subclavian  vein,  the  deeper  groove  behind  it  (sulcus  subclaviae) 
the  subclavian  artery.  Between  the  groove  for  the  subclavian  artery  and 
the  tuberosity  is  a  rough  surface,  for  the  attachment  of  the  Scalenus  medius 
muscle.  The  under  surface  is  smooth,  and  destitute  of  the  groove  observed  on  the 
other  ribs.  The  outer  border  is  convex,  thick,  and  rounded,  and  at  its  posterior 


Angle 

slightly  marked 

and  close  to 

tuberosity. 


Single  articular  facet.— 


Single  articular  facet 


Single  articular  facet. 


FIGS.  119-123.— Peculiar  ribs. 


part  gives  attachment  to  the  first  serration  of  the  Serratus  inagnus;  the  inner  is 
concave,  thin,  and  sharp,  and  marked  about  its  centre  by  the  commencement  of 
the  rough  surface  for  the  Scalenus  anticus.  The  anterior  extremity  is  larger  and 
thicker  than  any  of  the  other  ribs. 

Second  Rib. — The  second  rib  (Fig.  120)  is  much  longer  than  the  first,  but  bears 
a  very  considerable  resemblance  to  it  in  the  direction  of  its  curvature.  The  non- 
articular  portion  of  the  tuberosity  is  occasionally  only  slightly  marked.  The  angle 


THE  COSTAL  CARTILAGES  165 

is  slight  and  situated  close  to  the  tuberosity,  and  the  shaft  is  not  twisted,  so  that 
both  ends  touch  any  plane  surface  upon  which  it  may  be  laid;  but  there  is  a  similar 
though  slighter  bend,  with  its  convexity  upward,  to  that  found  in  the  first  rib.  The 
shaft  is  not  horizontal,  like  that  of  the  first  rib,  its  outer  surface,  which  is  convex, 
looking  upward  and  a  little  outward.  It  presents,  near  the  middle,  a  rough  emi- 
nence, tuberositas  costae  II,  for  the  attachment  of  the  second  and  third  digitations 
of  the  Serratus  magnus;  behind  and  above  which  is  attached  the  Scalenus 
posticus.  The  inner  surface,  smooth  and  concave,  is  directed  downward  and  a 
little  inward;  it  presents  a  short  groove  toward  its  posterior  part. 

Tenth  Rib. — The  tenth  rib  (Fig.  121)  has  only  a  single  articular  facet  on  its  head. 

Eleventh  and  Twelfth  Ribs.— The  eleventh  and  twelfth  ribs  (Figs.  122  and 
123)  have  each  a  single  articular  facet  on  the  head,  which  is  of  rather  large  size; 
they  have  no  neck  or  tuberosity,  and  are  pointed  at  the  extremity.  The  eleventh 
has  a  slight  angle  and  a  shallow  groove  on  the  lower  border.  The  twelfth  has 
neither,  and  is  much  shorter  than  the  eleventh,  and  the  head  has  a  slight  inclina- 
tion downward.  Sometimes  the  twelfth  rib  is  even  shorter  than  the  first. 

Structure. — The  ribs  consist  of  cancellous  tissue  enclosed  in  a  thin,  compact 
layer. 

Development. — Each  rib,  with  the  exception  of  the  last  two,  is  developed  by 
three  centres :  one  for  the  shaft,  one  for  the  head,  and  one  for  the  tubercle.  The 
last  two  have  only  two  centres,  that  for  the  tubercle  being  wanting.  Ossification 
commences  in  the  shaft  of  the  ribs  at  a  very  early  period,  before  its  appearance  in 
the  vertebrae.  The  epiphysis  of  the  head,  which  is  of  slightly  angular  shape,  and 
that  for  the  tubercle,  of  a  lenticular  form,  make  their  appearance  between  the  six- 
teenth and  twentieth  years,  and  are  not  united  to  the  rest  of  the  bone  until  about 
the  twenty-fifth  year. 

Attachment  of  Muscles. — To  nineteen :  The  Internal  and  External  intercostals, 
Scalenus  anticus,  Scalenus  medius,  Scalenus  posticus,  Pectoralis  minor,  Serratus 
magnus,  Obliquus  externus,  Quadratus  lumborum,  Diaphragm,  Latissimus  dorsi, 
Serratus  posticus  superior,  Serratus  posticus  inferior,  Ilio-costalis,  Musculus  acces- 
sorius  ad  ilio-costalem,  Longissimus  dorsi,  Cervicalis  ascendens,  Levatores  costa- 
rum,  and  Infracostales. 

The  Costal  Cartilages. 

The  costal  cartilage  (cartilago  costalis)  (Fig.  1 10)  is  white,  hyaline  cartilage.  The 
cartilages  serve  to  prolong  the  ribs  forward  to  the  front  of  the  chest,  and  they 
contribute  very  materially  to  the  elasticity  of  its  walls.  The  first  seven  are  con- 
lected  with  the  sternum,  the  next  three  with  the  lower  border  of  the  cartilage  of 
the  preceding  rib.  The  cartilages  of  the  last  two  ribs  have  pointed  extremities, 
which  terminate  in  free  ends  in  the  walls  of  the  abdomen.  Like  the  ribs,  the 
costal  cartilages  vary  in  their  length,  breadth,  and  direction.  They  increase  in 
length  from  the  first  to  the  seventh,  then  gradually  diminish  to  the  last.  They 
diminish  in  breadth,  as  well  as  the  intervals  between  them,  from  the  first  to  the 
last.  They  are  broad  at  their  attachment  to  the  ribs,  and  taper  toward  their  sternal 
extremities,  excepting  the  first  two,  which  are  of  the  same  breadth  throughout, 
and  the  sixth,  seventh,  and  eighth,  which  are  enlarged  where  their  margins  are 
in  contact.  In  direction  they  also  vary :  the  first  descends  a  little,  the  second  is 
horizontal,  the  third  ascends  slightly,  while  all  the  rest  follow  the  course  of  the 
ribs  for  a  short  extent,  and  then  ascend  to  the  sternum  or  preceding  cartilage. 
Each  costal  cartilage  presents  two  surfaces,  two  borders,  and  two  extremities. 

Surfaces. — The  anterior  surface  is  convex,  and  looks  forward  and  upward:  that 
of  the  first  gives  attachment  to  the  costo-clavicular  ligament  and  the  Subclavius 
muscle;  that  of  the  second,  third,  fourth,  fifth,  and  sixth,  at  their  sternal  ends, 


166  THE  SKELETON 

to  the  Pectoralis  major.1  The  others  are  covered  by,  and  give  partial  attachment 
to,  some  of  the  great  flat  muscles  of  the  abdomen.  The  posterior  surface  is  con- 
cave, and  directed  backward  and  downward,  the  first  giving  attachment  to  the 
Sterno-thyroid,  the  third  to  the  sixth  inclusive  to  the  Triangularis  sterni,  and 
the  six  or  seven  inferior  ones  to  the  Transversalis  muscle  and  the  Diaphragm. 

Borders. — Of  the  two  borders,  the  superior  border  is  concave,  the  inferior  con- 
vex; they  afford  attachment  to  the  internal  Intercostal  muscles,  the  upper  border 
of  the  sixth  giving  attachment  to  the  Pectoralis  major  muscle.  The  contiguous 
borders  of  the  sixth,  seventh,  and  eighth,  and  sometimes  the  ninth  and  tenth, 
costal  cartilages  present  small,  smooth,  oblong-shaped  facets  at  the  points  where 
they  articulate. 

Extremities. — Of  the  two  extremities,  the  outer  extremity  is  continuous  with  the 
osseous  tissue  of  the  rib  to  which  it  belongs.  The  inner  extremity  of  the  first  is 
continuous  with  the  sternum;  the  six  succeeding  ones  have  rounded  extremities, 
which  are  received  into  shallow  concavities  on  the  lateral  margins  of  the  sternum. 
The  inner  extremities  of  the  eighth,  ninth,  and  tenth  costal  cartilages  are  pointed, 
and  are  connected  with  the  cartilage  above.  Those  of  the  eleventh  and  twelfth 
are  free  and  pointed. 

The  costal  cartilages  are  most  elastic  in  youth,  those  of  the  false  ribs  being 
more  so  than  the  true.  In  old  age  they  become  of  a  deep  yellow  color,  and  are 
prone  to  calcify. 

Attachment  of  Muscles. — To  nine:  the  Subclavius,  Sterno-thyroid,  Pectoralis 
major,  Internal  oblique,  Transversalis,  Rectus,  Diaphragm,  Triangularis  sterni, 
and  Internal  intercostals. 

Surface  Form. — The  bones  of  the  chest  are  to  a  very  considerable  extent  covered  by  mus- 
cles, so  that  in  the  strongly  developed  muscular  subject  they  are  for  the  most  part  concealed. 
In  the  emaciated  subject,  on  the  other  hand,  the  ribs,  especially  in  the  lower  and  lateral  region, 
stand  out  as  prominent  ridges  with  the  sunken,  intercostal  spaces  between  them. 

In  the  middle  line,  in  front,  the  superficial  surface  of  the  sternum  is  to  be  felt  throughout 
its  entire  length,  at  the  bottom  of  a  deep  median  furrow  situated  between  the  two  great  pectoral 
muscles  and  called  the  Sternal  furrow.  These  muscles  overlap  the  anterior  surface  somewhat,  so 
that  the  whole  of  the  sternum  in  its  entire  width  is  not  subcutaneous;  and  this  overlapping  is 
greater  opposite  the  centre  of  the  bone  than  above  and  below,  so  that  the  furrow  is  wider  at  its 
upper  and  lower  parts,  but  narrower  in  the  middle.  The  centre  of  the  upper  border  of  the  ster- 
num is  visible,  constituting  the  pre-sternal  notch,  but  the  lateral  parts  of  this  border  are  obscured 
by  the  tendinous  origins  of  the  Sterno-mastoid  muscles,  which  present  themselves  as  oblique 
tendinous  cords,  which  narrow  and  deepen  the  notch.  Lower  down  on  the  subcutaneous  surface 
a  well-defined  transverse  ridge,  the  angle  of  Ludovic,  is  always  to  be  felt.  This  denotes  the  line 
of  junction  of  the  manubrium  and  body  of  the  bone,  and  is  a  useful  guide  to  the  second  costal 
cartilage,  and  thus  to  the  identity  of  any  given  rib.  The  second  rib  being  found  through  its 
costal  cartilage,  it  is  easy  to  count  downward  and  find  any  other.  From  the  middle  of  the 
sternum  the  furrow  spreads  out,  and,  exposing  more  of  the  surface  of  the  body  of  the  bone, 
terminates  below  in  a  sudden  depression,  the  infrasternal  depression  or  pit  of  the  stomach 
(scrobiculus  cordis),  which  corresponds  to  the  ensiform  cartilage.  This  depression  lies  between 
the  cartilages  of  the  seventh  ribs,  and  in  it  the  ensiform  cartilage  may  be  felt.  The  sternum  in 
its  vertical  diameter  presents  a  general  convexity  forward,  the  most  prominent  point  of  which 
is  at  the  joint  between  the  manubrium  and  gladiolus. 

On  each  side  of  the  sternum  the  costal  cartilages  and  ribs  on  the  front  of  the  chest  are  par- 
tially obscured  by  the  great  pectoral  muscles;  through  which,  however,  they  are  to  be  felt  as 
ridges,  with  yielding  intervals  between  them,  corresponding  to  the  intercostal  spaces.  Of  these 
spaces,  the  one  between  the  second  and  third  ribs  is  the  widest,  the  next  two  somewhat  nar- 
rower, and  the  remainder,  with  the  exception  of  the  last  two,  comparatively  narrow. 

The  lower  border  of  the  Pectoralis  major  muscle  corresponds  to  the  fifth  rib,  and  below 
this,  on  the  front  of  the  chest,  the  broad,  flat  outline  of  the  ribs,  as  they  begin  to  ascend,  and 
the  more  rounded  outline  of  the  costal  cartilages,  are  often  visible.  The  lower  boundary  of 
the  front  of  the  thorax,  the  abdomino-thoracic  arch,  which  is  most  plainly  seen  by  arching  the 
body  backward,  is  formed  by  the  ensiform  cartilage  and  the  cartilages  of  the  seventh,  eighth, 
ninth,  and  tenth  ribs,  and  the  extremities  of  the  eleventh  and  twelfth  ribs  or  their  cartilages. 

1  The  first  and  seventh  also,  occasionally,  give  origin  to  the  same  muscle. — ED.  of  15th  English  Edition. 


SURGICAL  ANATOMY  OF  THORAX  167 

On  each  side  of  the  chest,  from  the  axilla  downward,  the  flattened  external  surfaces  of  the 
ribs  may  be  defined  in  the  form  of  oblique  ridges,  separated  by  depressions  corresponding  to  the 
intercostal  spaces.  They  are,  however,  covered  by  muscles,  which  obscure  their  outline  to  a 
certain  extent  in  the  strongly  developed.  Nevertheless,  the  ribs,  with  the  exception  of  the  first, 
can  generally  be  followed  over  the  front  and  sides  of  the  chest  without  difficulty.  The  first  rib, 
being  almost  completely  covered  by  the  clavicle  and  scapula,  can  only  be  distinguished  in  a 
small  portion  of  its  extent.  At  the  back  the  angles  of  the  ribs  form  a  slightly-marked  oblique 
line  on  each  side  of  and  some  distance  from  the  vertebral  spines.  This  line  diverges  some- 
what as  it  descends,  and  external  to  it  is  a  broad,  convex  surface  caused  by  the  projection  of 
the  ribs  beyond  their  angles.  Over  this  surface,  except  where  covered  by  the  scapula,  the 
individual  ribs  can  be  distinguished. 

Surgical  Anatomy. — Malformations  of  the  sternum  present  nothing  of  surgical  importance 
beyond  the  fact  that  abscesses  of  the  mediastinum  may  sometimes  escape  through  the  sternal 
foramen.  Fractures  of  the  sternum  are  by  no  means  common,  owing,  no  doubt,  to  the  elasticity 
of  the  ribs  and  their  cartilages,  which  support  it  like  so  many  springs.  When  broken  it  is  fre- 
quently associated  with  fracture  of  the  spine,  and  may  be  caused  by  forcibly  bending  the  body 
either  backward  or  forward  until  the  chin  becomes  impacted  against  the  top  of  the  sternum.  It 
may  also  be  fractured  by  direct  violence  or  by  muscular  action.  The  fracture  usually  occurs  in 
the  upper  half  of  the  body  of  the  bone.  Dislocation  of  the  gladiolus  from  the  manubrium  also 
takes  place,  and  is  sometimes  described  as  a  fracture. 

The  bone,  cancellous  in  structure  and  being  subcutaneous,  is  frequently  the  seat  of  gummatous 
tumors,  and  not  uncommonly  is  affected  with  caries.  Occasionally  the  bone,  and  especially 
its  ensiform  appendix,  becomes  altered  in  shape  and  driven  inward  by  the  pressure,  in  work- 
men, of  tools  against  the  chest. 

The  ribs  are  frequently  broken,  though  from  their  connections  and  shape  they  are  able  to 
withstand  great  force,  yielding  under  the  injury  and  recovering  themselves  like  a  spring.  The 
middle  of  the  series  are  the  ones  most  liable  to  fracture.  The  first,  and  to  a  less  extent  the 
second,  being  protected  by  the  clavicle,  are  rarely  fractured;  and  the  eleventh  and  twelfth,  on 
account  of  their  loose  and  floating  condition,  enjoy  a  like  immunity.  The  fracture  generally 
occurs  from  indirect  violence,  from  forcible  compression  of  the  chest-wall,  and  the  bone  then 
gives  way  at  its  weakest  part — i.  e.,  just  in  front  of  the  angle.  But  the  ribs  may  also  be  broken 
by  direct  violence,  when  the  bone  gives  away  and  is  driven  inward  at  the  point  struck,  or  they 
may  be  broken  by  muscular  action.  It  seems  probable,  however,  that  in  the  latter  case  the 
bone  has  undergone  some  atrophic  changes.  Fracture  of  the  ribs  is  frequently  complicated  with 
some  injury  to  the  viscera  contained  within  the  thorax  or  upper  part  of  the  abdominal  cavity, 
and  this  is  most  likely  to  occur  in  fractures  from  direct  violence.  Occasionally  supernumerary  ribs 
exist.  They  may  come  from  the  lumbar  vertebrae  or  from  the  cervical  vertebrae.  A  lumbar  rib 
does  not  cause  discomfort.1  A  cervical  rib  is  due  to  freedom  of  the  costal  element  of  the  seventh 
cervical  vertebra.2  In  nearly  two-thirds  of  the  reported  cases  the  condition  is  double.  It  rarely 
produces  symptoms  until  after  the  twentieth  year.  The  symptoms  are  a  superficial  pulsation  of 
the  subclavian  artery,  a  prominence  which  can  be  felt,  and  evidences  of  pressure  in  the  brachial 
plexus  (Carl  Beck).  Beck  divides  the  different  types  of  the  condition  as  follows:  "(a)  Slight 
degree:  The  cervical  rib  reaches  beyond  the  transverse  process,  (b)  More  advanced:  The  cervical 
rib  reaches  beyond  the  transverse  process,  either  with  a  free  end  or  touching  the  first  rib.  (c) 
Almost  complete:  The  connection  between  the  cartilage  of  the  first  rib  is  formed  either  by  means 
of  a  distinct  band  or  by  the  end  of  its  long  body,  (d)  Complete:  It  has  become  a  true  rib  and 
possesses  a  true  cartilage  which  unites  with  the  cartilage  of  the  first  rib."3  A  very  rare  condition 
is  a  rib  from  the  sixth  cervical  vertebra.  The  diagnosis  is  confirmed  by  the  ar-rays.  The  treatment 
of  cervical  rib  is  excision. 

Fracture  of  the  costal  cartilages  may  also  take  place,  though  it  is  a  comparatively  rare  injury. 

The  thorax  is  frequently  found  to  be  altered  in  shape  in  certain  diseases. 

The  shape  of  the  rickety  thorax  is  produced  chiefly  by  atmospheric  pressure.  The  balance 
between  the  air  on  the  inside  of  the  chest  and  the  outside  during  some  stage  of  respiration  is  not 
equal,  the  preponderance  being  in  favor  of  the  air  outside;  and  this,  acting  on  the  softened  ribs, 
causes  them  to  be  forced  in  at  the  junction  of  the  cartilages  with  the  bones,  which  is  the  weakest 
part.  In  consequence  of  this  the  sternum  projects  forward,  with  a  deep  depression  on  either  side 
caused  by  the  sinking  in  of  the  softened  ribs.  The  depression  is  less  on  the  left  side,  on  account 
of  the  ribs  being  supported  by  the  heart.  The  condition  is  known  as  pigeon-breast.  The 
lower  ribs,  however,  are  not  involved  in  this  deformity,  as  they  are  prevented  from  falling  in  by 
the  presence  of  the  stomach,  liver,  and  spleen.  And  when  the  liver  and  spleen,  are  enlarged, 
as  they  sometimes  are  in  rickets,  the  lower  ribs  may  be  pushed  outward:  this  causes  a  trans- 
verse constriction  just  above  the  costal  arch.  The  anterior  extremities  of  the  ribs  are  usually 
enlarged  in  rickets,  giving  rise  to  what  has  been  termed  the  rickety  rosary.  The  phthisical 


i  Carl  Beck,  in  Jour.  Amer.  Med.  Assoc.,  June  17,  1905. 

1  Piersol's  Human  Anatomy,  p.  155. 

3  Jour.  Amer.  Med.  Aaeoc.,  June  17,  1905. 


168  THE  SKELETON 

chest  is  often  long  and  narrow,  flattened  from  before  backward,  and  with  great  obliquity  of  the 
ribs  and  projection  of  the  scapulae.  In  pulmonary  emphysema  the  chest  is  enlarged  in  all  its 
diameters,  and  presents  on  section  an  almost  circular  outline.  It  has  received  the  name  of  the 
barrel-shaped  chest.  In  severe  cases  of  lateral  curvature  of  the  spine  the  thorax  becomes 
much  distorted.  In  consequence  of  the  rotation  of  the  bodies  of  the  vertebrae  which  takes 
place  in  this  disease  the  ribs  opposite  the  convexity  of  the  thoracic  curve  become  extremely  con- 
vex behind,  being  thrown  out  and  bulging,  and  at  the  same  time  flattened  in  front,  so  that  the 
two  ends  of  the  same  rib  are  almost  parallel.  Coincident  with  this,  the  ribs  on  the  opposite 
side,  on  the  concavity  of  the  curve,  are  sunk  and  depressed  behind  and  bulging  and  convex  in 
front.  In  addition  to  this  the  ribs  become  occasionally  welded  together  by  bony  material. 

The  ribs  are  frequently  the  seat  of  caries  leading  to  abscesses  and  sinuses,  which  may 
burrow  to  a  considerable  extent  over  the  wall  of  the  chest.  The  only  special  anatomical  point 
in  connection  with  abscesses  and  sinuses  is  that  care  must  be  taken  in  dealing  with  them  that 
the  intercostal  space  is  not  punctured  and  the  pleural  cavity  opened  or  the  intercostal  vessels 
wounded,  as  the  necrosed  portion  of  bone  is  generally  situated  on  the  internal  surface  of  the  rib. 

In  cases  of  empyema  the  chest  requires  opening  t-»  evacuate  the  pus.  There  is  consider- 
able difference  of  opinion  as  to  the  best  position  to  do  this.  Probably  the  best  place  for  inter- 
costal drainage  is  between  the  fifth  and  sixth  ribs,  in  or  a  little  in  front  of  the  mid-axillary  line. 
This  is  the  last  part  of  the  cavity  to  be  closed  by  the  expansion  of  the  lung;  it  is  not  thickly 
covered  by  soft  parts;  the  space  between  the  two  ribs  is  sufficiently  great  to  allow  of  the  intro- 
duction of  a  fair-sized  drainage-tube,  and  when  the  patient  is  confined  to  bed  he  does  not  lie 
upon  the  drainage-tube  as  he  does  when  the  opening  is  posterior.  Better  than  intercostal  drain- 
age in  the  vast  majority  of  cases  is  rib  resection  and  drainage.  A  portion  of  the  fifth  or  sixth 
rib  should  be  removed  in  the  mid-axillary  line.  In  chronic  empyema  the  lung  becomes  shrunken 
and  adherent  and  simple  drainage  will  not  bring  about  a  cure.  It  is  necessary  in  such  cases 
to  do  an  operation  that  will  permit  of  collapse  of  the  chest  wall.  Esllander's  operation  consists 
in  resecting  a  portion  of  every  rib  which  overlies  the  cavity  of  the  empyema.  Schede's  opera- 
tion consists  in  removing  ribs  from  the  second  rib  down  over  the  empyema  cavity.  The  ribs 
are  removed  from  cartilages  to  angles,  and  intercostal  muscles  and  the  parietal  layer  of  the 
pleura  are  also  taken  away.  Fowler  and  de  Lorme  not  only  practice  extensive  rib  resection 
and  remove  the  parietal  layer  of  the  pleura,  but  also  remove  the  pulmonary  pleura  (total  pleu- 
rectomy  or  pulmonary  decortication). 

THE  EXTREMITIES. 

The  extremities,  or  limbs,  are  those  long,  jointed  appendages  of  the  body 
which  are  connected  with  the  trunk  by  one  end  and  free  in  the  rest  of  their  extent. 
They  are  jour  in  number:  an  upper  or  thoracic  pair,  connected  with  the  thorax 
through  the  intervention  of  the  shoulder,  and  subservient  mainly  to  prehension; 
and  a  lower  pair,  connected  with  the  pelvis,  intended  for  support  and  locomotion. 
Both  pairs  of  limbs  are  constructed  after  one  common  type,  so  that  they  present 
numerous  analogies,  while  at  the  same  time  certain  differences  are  observed 
between  the  upper  and  lower  pair,  dependent  on  the  peculiar  offices  they  have 
to  perform. 

The  bones  by  which  the  upper  and  lower  limbs  are  attached  to  the  trunk  are 
named  respectively  the  shoulder  and  pelvic  girdles,  and  they  are  constructed  on  the 
same  general  type,  though  presenting  certain  modifications  relating  to  the  different 
uses  to  which  the  upper  and  lower  limbs  are  respectively  applied.  The  shoulder 
girdle  is  formed  by  the  scapulae  and  clavicles,  and  is  imperfect  in  front  and  behind. 
In  front,  however,  the  girdle  is  completed  by  the  upper  end  of  the  sternum,  with 
which  the  inner  extremities  of  the  clavicle  articulate.  Behind,  the  girdle  is  widely 
imperfect  and  the  scapula  is  connected  to  the  trunk  by  muscles  only.  The  pelvic 
girdle  is  formed  by  the  innominate  bones,  and  is  completed  in  front  through  the 
symphysis  pubis,  at  which  the  two  innominate  bones  articulate  with  each  other. 
It  is  imperfect  behind,  but  the  intervening  gap  is  filled  in  by  the  upper  part  of 
the  sacrum.  The  pelvic  girdle,  therefore,  presents,  with  the  sacrum,  a  complete 
ring,  comparatively  fixed,  and  presenting  an  arched  form  which  confers  upon  it  a 
solidity  manifestly  intended  for  the  support  of  the  trunk,  and  in  marked  contrast 
to  the  lightness  and  mobility  of  the  shoulder  girdle. 


THE  CLAVICLE  169 

With  regard  to  the  morphology  of  these  girdles,  the  blade  of  the  scapula  is 
gnu-rally  believed  to  correspond  to  the  ilium;  but  with  regard  to  the  clavicles 
there  is  some  difference  of  opinion:  formerly  it  was  believed  that  they  corre- 
sponded to  the  ossa  pubis,  meeting  at  the  syrnphysis,  but  it  is  now  generally 
taught  that  trie  clavicle  has  no  homologue  in  the  pelvic  girdle,  and  that  the  os 
pubis  and  ischium  are  represented  by  the  small  coracoid  process  in  man  and 
most  mammals. 

THE  UPPER  EXTREMITY. 

The  bones  of  the  upper  extremity  consist  of  those  of  the  shoulder  girdle,  of  the 
arm,  the  forearm,  and  the  hand. 

THE  SHOULDER  GIRDLE. 

The  shoulder  girdle  consists  of  the  clavicle  and  the  scapula. 

The  Clavicle  or  Collar  Bone  (Clavicula). 

The  clavicle  or  key  bone  (clavis,  a  key)  obtains  it  name  from  its  supposed 
resemblance  to  the  key  used  by  the  Romans.  It  forms  the  anterior  portion  of  the 
shoukler  girdle.  It  is  a  long  bone,  curved  somewhat  like  the  italic  letter  /,  and 
placed  nearly  horizontally  at  the  upper  and  anterior  part  of  the  thorax,  imme- 
diately above  the  first  rib.  It  articulates  by  its  inner  extremity  with  the  upper 
border  of  the  sternum,  and  by  its  outer  extremity  with  the  acromion  process  of  the 
scapula,  serving  to  sustain  the  upper  extremity  in  the  various  positions  which  it 
assumes,  whilst  at  the  same  time  it  allows  of  great  latitude  of  motion  in  the  arm.1 
It  presents  a  double  curvature  when  looked  at  in  front,  the  convexity  being  for- 
ward at  the  sternal  end  and  the  concavity  at  the  scapular  end.  Its  outer  third  is 
flattened  from  above  downward,  and  extends,  in  the  natural  position  of  the  bone, 
from  a  point  opposite  the  coracoid  process  to  the  acromion.  Its  inner  two-thirds 
are  of  a  prismatic  form,  and  extend  from  the  sternum  to  a  point  opposite  the  cora- 
coid process  of  the  scapula. 

Outer,  External,  or  Flattened  Portion. — The  outer  third  is  flattened  from  above 
downward,  so  as  to  present  two  surfaces,  an  upper  and  a  lower;  and  two  borders, 
an  anterior  and  a  posterior. 

Surfaces. — The  upper  surface  is  flattened,  rough,  marked  by  impressions  for  the 
attachment  of  the  Deltoid  in  front  and  the  Trapezius  behind;  between  these  two 
impressions,  externally,  a  small  portion  of  the  bone  is  subcutaneous.  The  under 
surface  is  flattened.  At  its  posterior  border,  a  little  external  to  the  point  where  the 
prismatic  joins  with  the  flattened  portion,  is  a  rough  eminence,  the  conoid  tubercle 
(tuberositas  coracoidea) ;  this,  in  the  natural  position  of  the  bone,  surmounts  the 
coracoid  process  of  the  scapula  and  gives  attachments  to  the  conoid  ligament. 
From  this  tubercle  an  oblique  line,  occasionally  a  depression,  passes  forward 
and  outward  to  near  the  outer  end  of  the  anterior  border;  it  is  called  the  oblique 
line  or  trapezoid  ridge,  and  affords  attachment  to  the  trapezoid  ligament. 

Borders. — The  anterior  border  is  concave,  thin,  and  rough,  and  gives  attachment 
to  the  Deltoid;  it  occasionally  presents,  at  its  inner  end,  at  the  commencement  of 
the  deltoid  impression,  a  tubercle,  the  deltoid  tubercle,  which  is  sometimes  to  be 
felt  in  the  living  subject.  The  posterior  border  is  convex,  rough,  broader  than  the 
anterior,  and  gives  attachment  to  the  Trapezius. 

i  The  clavicle  acts  especially  as  a  fulcrum  to  enable  the  muscles  to  give  lateral  motion  to  the  arm.  It  is 
accordingly  absent  in  those  animals  whose  fore  limbs  are  used  only  for  progression,  but  is  present  for  the  most 
part  in  those  animals  whose  anterior  extremities  are  clawed  and  used  for  prehension,  though  in  some  of  them — 
as,  for  instance,  in  a  large  number  of  the  carnivora — it  is  merely  a  rudimentary  bone  suspended  among  the 
muscles,  and  not  articulating  with  the  scapula  or  sternum. — ED.  of  15th  English  Edition. 


170  THE  SKELETON 

Inner,  Internal,  or  Prismatic  Portion. — The  prismatic  portion  forms  the  inner 
two-thirds  of  the  bone.  It  is  curved  so  as  to  be  convex  in  front,  concave  behind, 
and  is  marked  by  three  borders,  separating  three  surfaces. 

Borders. — The  anterior  border  is  continuous  with  the  anterior  margin  of  the  flat 
portion.  At  its  commencement  it  is  smooth,  and  corresponds  to  the  interval 
between  the  attachment  of  the  Pectoralis  major  and  Deltoid  muscles;  at  the  inner 
half  of  the  clavicle  it  forms  the  lower  boundary  of  an  elliptical  space  for  the 
attachment  of  the  clavicular  portion  of  the  Pectoralis  major,  and  approaches  the 
posterior  border  of  the  bone.  The  superior  border  is  continuous  with  the  posterior 
margin  of  the  flat  portion,  and  separates  the  anterior  from  the  posterior  surface. 
At  its  commencement  it  is  smooth  and  rounded,  becomes  rough  toward  the  inner 
third  for  the  attachment  of  the  Sterno-mastoid  muscle,  and  terminates  at  the 
upper  angle  of  the  sternal  extremity.  The  posterior  or  subclavian  border  separates 
the  posterior  from  the  inferior  surface,  and  extends  from  the  conoid  tubercle  to 
the  rhomboid  impression.  It  forms  the  posterior  boundary  of  the  groove  for  the 
Subclavius  muscle,  and  gives  attachment  to  a  layer  of  cervical  fascia  covering 
the  Omo-hyoid  muscle. 

Surfaces. — The  anterior  surface  is  included  between  the  superior  and  anterior 
borders.  It  is  directed  forward  and  a  little  upward  at  the  sternal  end,  outward 
and  still  more  upward  at  the  acromial  extremity,  where  it  becomes  continuous 
with  the  upper  surface  of  the  flat  portion.  Externally,  it  is  smooth,  convex, 
nearly  subcutaneous,  being  covered  only  by  the  Platysma;  but,  corresponding 
to  the  inner  half  of  the  bone,  it  is  divided  by  a  more  or  less  prominent  line  into 
two  parts:  a  lower  portion,  elliptical  in  form,  rough,  and  slightly  convex,  for  the 
attachment  of  the  Pectoralis  major;  and  an  upper  part,  which  is  rough,  for  the 
attachment  of  the  Sterno-cleido-mastoid.  Between  the  two  muscular  impressions 
is  a  small  subcutaneous  interval.  The  posterior  or  cervical  surface  is  smooth, 
flat,  and  looks  backward  toward  the  root  of  the  neck.  It  is  limited,  above,  by  the 
superior  border;  below,  by  the  subclavian  border;  internally,  by  the  margin  of  the 
sternal  extremity;  externally,  it  is  continuous  with  the  posterior  border  of  the  flat 
portion.  It  is  concave  from  within  outward,  and  is  in  relation,  by  its  lower  part, 
with  the  suprascapular  vessels.  This  surface,  at  about  the  junction  of  the  inner 
and  outer  curves,  is  also  in  close  relation  with  the  brachial  plexus  and  subclavian 
vessels.  It  gives  attachment,  near  the  sternal  extremity,  to  part  of  the  Sterno-hyoid 
muscle;  and  presents,  at  or  near  the  middle,  a  foramen,  nutrient  foramen  (foramen 
nutricium).  It  opens  into  a  canal,  nutrient  canal  (canalis  nutricius),  which  is 
directed  obliquely  outward  and  transmits  the  chief  nutrient  artery  of  the  bone. 
Sometimes  there  are  two  foramina  on  the  posterior  surface,  or  one  on  the 
posterior,  and  one  on  the  inferior  surface.  The  inferior  or  subclavian  surface 
is  bounded,  in  front,  by  the  anterior  border;  behind,  by  the  subclavian  border. 
It  is  narrow  internally,  but  gradually  increases  in  width  externally,  and  is 
continuous  with  the  under  surface  of  the  flat  portion.  Commencing  at  the 
sternal  extremity  may  be  seen  a  small  facet,  the  costal  facet,  for  articulation 
with  the  cartilage  of  the  first  rib.  This  is  continuous  with  the  articular  surface 
at  the  sternal  end  of  the  bone.  External  to  this  is  a  broad,  rough  surface,  the 
rhomboid  impression  (tuberositas  costalis),  rather  more  than  an  inch  in  length,  for 
the  attachment  of  the  costo-clavicular  (rhomboid)  ligament.  The  remaining  part 
of  this  surface  is  occupied  by  a  longitudinal  groove,  the  subclavian  groove,  broad 
and  smooth  externally,  narrow  and  more  uneven  internally;  it  gives  attachment  to 
the  Subclavius  muscle,  and  by  its  margins  to  the  costo-coracoid  membrane, 
which  splits  to  enclose  the  muscle.  Not  infrequently  this  groove  is  subdivided 
into  two  parts  by  a  longitudinal  line,  which  gives  attachment  to  the  intermuscular 
septum  of  the  Subclavius  muscle. 


THE  CLAVICLE 


171 


Internal  or  Sternal  Extremity  (extremitas  sternalis). — The  internal  or  sternal 
extremity  of  the  clavicle  is  triangular  in  form,  directed  inward  and  a  little  down- 
ward and  forward;  and  presents  an  articular  facet  (fades  articularis  sternalis), 
concave  from  before  backward,  convex  from  above  downward,  which  articulates 
with  the  sternum  through  the  intervention  of  an  interarticular  fibro-cartilage; 
the  circumference  of  the  articular  surface  is  rough,  for  the  attachment  of 
numerous  ligaments.  The  posterior  border  of  this  surface  is  prolonged  back- 
ward, so  as  to  increase  the  size  of  the  articular  facet;  the  upper  border  gives 
attachment  to  the  interarticular  fibro-cartilage,  and  the  lower  border  is  con- 
tinuous with  the  costal  facet  on  the  inner  end  of  the  inferior  or  subclavian  sur- 
face, which  articulates  with  the  cartilage  of  the  first  rib. 

Outer  or  Acromial  Extremity  (extremitas  acromialis) . — The  outer  or  acromial 
extremity,  directed  outward  and  forward,  presents  a  small,  flattened,  oval  facet, 


Acromial  extremity. 


Sternal  extremity. 


FIG.  124. — Left  clavicle.     Superior  surface. 


FIG.  125.— Left  clavicle.     Inferior  surface. 

acromial  surface  (fades  articularis  acromialis) ,  which  looks  obliquely  downward, 
for  articulation  with  the  acromion  process  of  the  scapula.  The  circumference 
of  the  articular  facet  is  rough,  especially  above,  for  the  attachment  of  the 
acromio-clavicular  ligaments. 

Peculiarities  of  the  Bone  in  the  Sexes  and  in  Individuals.— In  the  female  the 
clavicle  is  generally  shorter,  thinner,  less  curved,  and  smoother  than  in  the  male. 
In  those  persons  who  perform  considerable  manual  labor,  which  brings  into  con- 
stant action  the  muscles  connected  with  this  bone,  it  becomes  thicker  and  more 
curved,  its  ridges  for  muscular  attachment  become  prominently  marked.  The 
right  clavicle  is  generally  longer,  thicker,  and  rougher  than  the  left. 

Structure. — The  shaft,  as  well  as  the  extremities,  consists  of  cancellous  tissue, 
invested  in  a  compact  layer  much  thicker  in  the  middle  than  at  either  end.  The 
clavicle  is  highly  elastic,  by  reason  of  its  curves.  From  the  experiments  of  Mr. 
Ward  it  has  been  shown  that  it  possesses  sufficient  longitudinal  elastic  force  to 
project  its  own  weight  nearly  two  feet  on  a  level  surface  when  a  smart  blow  is 
struck  on  it;  and  sufficient  transverse  elastic  force,  opposite  the  centre  of  its 


172  THE  SKELETON 

anterior  convexity,  to  throw  its  own  weight  about  a  foot.  This  extent  of  elastic 
power  must  serve  to  moderate  very  considerably  the  effect  of  concussions  received 
upon  the  point  of  the  shoulder. 

Development.— By  two  centres:  one  for  the  shaft  and  outer  extremity  and 
one  for  the  sternal  extremity.  The  centre  for  the  shaft  appears  very  early, 
before  any  other  bone — according  to  Beclard,  as  early  as  the  thirtieth  day. 
The  centre  for  the  sternal  end  makes  its  appearance  about  the  eighteenth  or 
twentieth  year,  and  unites  with  the  rest  of  the  bone  about  the  twenty-fifth  year. 

Articulations. — With  the  sternum,  scapula,  and  cartilage  of  the  first  rib. 

Attachment  of  Muscles. — To  six  :  the  Sterno-cleido-mastoid,  Trapezius, 
Pectoralis  major,  Deltoid,  Subclavius,  and  Sterno-hyoid. 

Surface  Form. — The  clavicle  can  be  felt  throughout  its  entire  length,  even  in  persons  who 
are  very  fat.  Commencing  at  the  inner  end,  the  enlarged  sternal  extremity,  where  the  bone 
projects  above  the  upper  margin  of  the  sternum,  can  be  felt,  forming  with  the  sternum  and  the 
rounded  tendon  of  the  Sterno-mastoid  a  V-shaped  notch,  the  pre-sternal  notch.  Passing  out- 
ward, the  shaft  of  the  bone  can  be  felt  immediately  under  the  skin,  with  its  convexity  forward 
in  the  inner  two-thirds,  the  surface  partially  obscured  above  and  below  by  the  attachments  of 
the  Sterno-mastoid  and  Pectoralis  major  muscles.  In  the  outer  third  it  forms  a  gentle  curve 
backward,  and  terminates  at  the  outer  end  in  a  somewhat  enlarged  extremity  which  articulates 
with  the  acromial  process  of  the  scapula.  The  direction  of  the  clavicle  is  almost,  if  not  quite, 
horizontal  when  the  arm  is  lying  quietly  by  the  side,  though  in  well-developed  subjects  it  may 
incline  a  little  upward  at  its  outer  end.  Its  direction  is,  however,  very  changeable,  altering 
with  the  varying  movements  of  the  shoulder-joint. 

Surgical  Anatomy. — The  clavicle  is  the  most  frequently  fractured  of  any  single  bone  in  the 
body.  This  is  due  to  the  fact  that  it  is  much  exposed  to  violence,  and  is  the  only  bony  connec- 
tion between  the  upper  limb  and  the  trunk.  The  bone,  moreover,  is  slender,  and  is  very  super- 
ficial. The  bone  may  be  broken  by  direct  or  indirect  violence  or  by  muscular  action.  The  most 
common  cause  is,  however,  from  indirect  violence,  and  the  bone  then  gives  way  at  the  junction 
of  the  fixed  outer  one-third  with  the  movable  inner  two-thirds  of  the  bone.  This  is  the  weakest 
and  most  slender  part  of  the  bone.  The  fracture  is  generally  oblique,  and  the  displacement 
of  the  outer  fragments  is  inward,  away  from  the  surface  of  the  body;  hence  compound 
fracture  of  the  clavicle  is  of  rare  occurrence.  The  inner  fragment  as  a  rule  is  little  displaced 
(page  505).  Beneath  the  bone  the  main  vessels  of  the  upper  limb  and  the  great  nerve-cords  of 
the  brachial  plexus  lie  on  the  first  rib,  and  are  liable  to  be  wounded  in  fracture,  especially  in 
fracture  from  direct  violence,  when  the  force  of  the  blow  drives  the  broken  ends  inward.  For- 
tunately, the  Subclavius  muscle  is  interposed  between  these  structures  and  the  clavicle,  and 
this  often  protects  them  from  injury. 

The  clavicle  is  not  uncommonly  the  seat  of  sarcomatous  tumors,  rendering  the  operation 
of  excision  of  the  entire  bone  necessary.  This  operation  is  best  performed  by  exposing  the 
bone  freely,  disarticulating  at  the  acromial  end,  and  turning  it  inward.  The  removal  of 
the  outer  part  is  comparatively  easy,  but  resection  of  the  inner  part  is  fraught  with  difficulty,  the 
main  danger  being  the  risk  of  wounding  the  great  veins  which  are  in  relation  with  its  under 
surface. 

The  Scapula  or  Shoulder  Blade. 

The  scapula  (axaxdvr] ,  a  spade),  or  blade  bone,  forms  the  back  part  of 
the  shoulder  girdle.  It  is  a  large,  flat  bone,  triangular  in  shape,  situated  at 
the  posterior  aspect  and  side  of  the  thorax,  between  the  second  and  seventh,  or 
sometimes  the  eighth,  ribs,  its  internal  border  or  base  being  about  an  inch  from 
and  nearly  but  not  quite  parallel  with  the  spinous  processes  of  the  vertebrae,  so 
that  it  is  rather  closer  to  them  above  than  below.  It  presents  for  examination- 
two  surfaces,  three  borders,  and  three  angles. 

Surfaces.  Anterior  or  Costal  Surface,  Ventral  Aspect  or  Venter  (fades  costalis). — 
The  anterior  surface  (Fig.  126)  presents  a  broad  concavity,  the  subscapular 
fossa  (fossa  subscapularis) .  It  is  'marked,  in  the  inner  two-thirds,  by  several 
oblique  ridges  (linecB  musculares) ,  which  pass  from  behind  outward  and  upward ; 
the  outer  third  is  smooth.  The  oblique  ridges  give  attachment  to  the  tendinous 
intersections,  and  the  surfaces  between  them  to  the  fleshy  fibres,  of  the  Sub- 
scapularis muscle.  The  anterior  third  of  the  fossa,  which  is  smooth,  is  covered 


THE  SCAPULA 


173 


by,  but  does  not  afford  attachment  to,  the  fibres  of  this  muscle.  The  venter  is 
separated  from  the  internal  border  by  a  smooth,  triangular  margin  at  the  supe- 
rior and  inferior  angles/and  in  the  interval  between  these  by  a  narrow  edge  which 
is  often  deficient.  This  marginal  surface  affords  attachment  throughout  its  entire 
extent  to  the  Serratus  magnus  muscle.  The  subscapular  fossa  presents  a  trans- 
verse depression  at  its  upper  part,  where  the  bone  appears  to  be  bent  on  itself, 
forming  a  considerable  angle,  called  the  subscapular  angle  (angulus  subscapularis) , 
thus  giving  greater  strength  to  the  body  of  the  bone  from  its  arched  form,  whilst 
the  summit  of  the  arch  serves  to  support  the  spine  and  acromion  process.  It  is  in 


FIG.  126. — Left  scapula.     Anterior  surface  or  venter. 

this  situation  that  the  fossa  is  deepest,  so  that  the  thickest  part  of  the  Subscapu- 
laris  muscle  lies  in  a  line  perpendicular  to  the  plane  of  the  glenoid  cavity,  and. 
must  consequently  operate  most  effectively  on  the  head  of  the  humerus,  which 
is  contained  in  that  cavity.  The  portion  of  bone  between  the  suprascapular 
notch  and  the  infraglenoid  tubercle  is  sometimes  called  the  surgical  neck. 

Posterior  or  Dorsal  Surface  or  Dorsum  (fades  dorsalis). — The  posterior  or  dorsal 
surface  (Fig.   127)  is    arched    from   above   downward,  alternately  concave   and 


174 


THE  SKELETON 


convex  from  side  to  side.  It  is  subdivided  unequally  into  two  parts  by  the 
spine ;  the  portion  above  the  spine  is  called  the  supraspinous  fossa,  and  that  below 
it  the  infraspinous  fossa. 

The  supraspinous  fossa  (fossa  supraspinata) ,  the  smaller  of  the  two,  is  concave, 
smooth,  and  broader  at  the  vertebral  than  at  the  humeral  extremity.  It  affords 
attachment  by  its  inner  two-thirds  to  the  Supraspinatus  muscle. 


Cor  a co 


Groove  for  Dorsalis 
Scapulx  Artery 


Inferior 
FIG.  127. — Left  scapula.     Posterior  surface  or  dorsum. 

The  infraspinous  fossa  (fossa  infraspinata)  is  much  larger  than  the  preceding; 
toward  its  vertebral  margin  a  shallow  concavity  is  seen  at  its  upper  part ;  its  centre 
presents  a  prominent  convexity,  whilst  toward  the  axillary  border  is  a  deep  groove 
which  runs  from  the  upper  toward  the  lower  part.  The  inner  two-thirds  of  this 
surface  affords  attachment  to  the  Infraspinatus  muscle;  the  outer  third  is  only  cov- 
ered by  it,  without  giving  origin  to  its  fibres.  This  surface  is  separated  from  the 
axillary  border  by  an  elevated  ridge,  which  runs  from  the  lower  margin  of  the  glenoid 
cavity  downward  and  backward  to  the  posterior  border,  about  an  inch  above  the  in- 


THE  SCAPULA  175 

ferior  angle.  The  ridge  serves  for  the  attachment  of  a  strong  aponeurosis  which 
separates  the  Inf raspinatus  from  the  two  Teres  muscles.  The  surface  of  bone  between 
this  line  and  the  axillary  border  is  narrow  in  the  upper  two-thirds  of  its  extent, 
and  traversed  near  its  centre  by  a  groove  for  the  passage  of  the  dorsalis  scapulae 
vessels;  it  affords  attachment  to  the  Teres  minor  muscle.  Its  lower  third  presents  a 
broader,  somewhat  triangular  surface,  which  gives  origin  to  the  Teres  major,  and 
over  which  the  Latissimus  dorsi  glides;  sometimes  the  latter  muscle  takes  origin 
by  a  few  fibres  from  this  part.  The  broad  and  narrow  portions  of  bone  above 
alluded  to  are  separated  by  an  oblique  line  which  runs  from  the  axillary  border, 
downward  and  backward,  to  meet  the  elevated  ridge:  to  it  is  attached  the 
aponeurosis  separating  the  two  Teres  muscles  from  each  other. 

The  spine  (spina  scapula?)  is  a  prominent  plate  of  bone  which  crosses  obliquely 
the  inner  four-fifths  of  the  dorsum  of  the  scapula  at  its  upper  part,  and  separates  the 
supra- from  the  infraspinous  fossa :  it  commences  at  the  vertebral  border  by  a  smooth, 
triangular  surface,  over  which  the  Trapezius  glides,  separated  from  the  bone  by  a 
bursa,  and,  gradually  becoming  more  elevated  as  it  passes  outward,  terminates  in 
the  acromion  process,  which  overhangs  the  shoulder-joint.  The  spine  is  triangular 
and  flattened  from  above  downward,  its  apex  corresponding  to  the  vertebral 
border,  its  base  (which  is  directed  outward)  to  the  neck  of  the  scapula.  It  pre- 
sents two  surfaces  and  three  borders.  Its  superior  surface  is  concave,  assists 
in  forming  the  supraspinous  fossa,  and  affords  attachment  to  part  of  the  Supra- 
spinatus  muscle.  Its  inferior  surface  forms  part  of  the  infraspinous  fossa,  gives 
origin  to  part  of  the  Infraspinatus  muscle,  and  presents  near  its  centre  the  orifice 
of  a  nutrient  canal.  Of  the  three  borders,  the  anterior  is  attached  to  the  dorsum 
of  the  bone;  the  posterior,  or  crest  of  the  spine,  is  broad,  and  presents  two  lips 
and  an  intervening  rough  interval.  To  the  superior  lip  is  attached  the  Trapezius 
to  the  extent  shown  in  the  figure.  A  rough  tubercle  is  generally  seen  occupying 
that  portion  of  the  spine  which  receives  the  insertion  of  the  middle  and  inferior 
fibres  of  this  muscle.  To  the  inferior  lip,  throughout  its  whole  length,  is  attached 
the  Deltoid.  The  intervals  between  the  lips  is  also  partly  covered  by  the  tendinous 
fibres  of  these  muscles.  The  external  border,  or  base,  the  shortest  of  the  three,  is 
slightly  concave,  its  edge  thick  and  round,  continuous  above  with  the  under  sur- 
face of  the  acromion  process,  below  with  the  neck  of  the  scapula.  The  narrow 
portion  of  bone  external  to  this  border,  and  separating  it  from  the  glenoid  cavity, 
is  called  the  great  scapular  notch,  and  serves  to  connect  the  supra-  and  infraspinous 
fossae. 

The  acromion  process  (acromion),  so  called  from  forming  the  summit  of  the 
shoulder  (dxpov,  a  summit;  dtpo^,  the  shoulder),  is  a  large  and  somewhat  triangular 
or  oblong  process,  flattened  from  behind  forward,  directed  at  first  a  little  outward, 
and  then  curving  forward  and  upward,  so  as  to  overhang  the  glenoid  cavity.  Its 
upper  surface,  directed  upward,  backward,  and  outward,  is  convex,  rough,  and 
gives  attachment  to  some  fibres  of  the  Deltoid,  and  in  the  rest  of  its  extent  it  is 
subcutaneous.  Its  under  surface  is  smooth  and  concave.  Its  outer  border  is  thick 
and  irregular,  and  presents  three  or  four  tubercles  for  the  tendinous  origins  of  the 
Deltoid  muscle.  Its  inner  margin,  shorter  than  the  outer,  is  concave,  gives  attach- 
ment to  a  portion  of  the  Trapezius  muscle,  and  presents  about  its  centre  a  small 
oval  surface  for  articulation  with  the  acrornial  end  of  the  clavicle.  Its  apex,  which 
corresponds  to  the  point  of  meeting  of  these  two  borders  in  front,  is  thin,  and 
has  attached  to  it  the  coraco-acromial  ligament. 

Margins  or  Borders  of  the  Scapula.  Superior  Border  (margo  superior) . — Of  the 
three  borders  of  the  scapula,  the  superior  is  the  shortest  and  thinnest;  it  is  concave 
and  extends  from  the  internal  angle  to  the  coracoid  process.  At  its  outer  part  is  a 
deep,  semicircular  notch,  the  suprascapular  notch  (incisura  scapulae) ,  formed  partly 
by  the  base  of  the  coracoid  process.  The  notch  is  converted  into  a  foramen  by  the 


178  THE  SKELETON 

transverse  ligament,  and  serves  for  the  passage  of  the  suprascapular  nerve.  Some- 
times this  foramen  is  entirely  surrounded  by  bone.  The  adjacent  margin  of  the 
superior  border  affords  attachment  to  the  Omo-hyoid  muscle. 

External  or  Axillary  Border  (mar go  axillaris). — The  external  or  axillary  border 
is  the  thickest  of  the  three.  It  commences  above  at  the  lower  margin  of  the 
glenoid  cavity,  and  inclines  obliquely  downward  and  backward  to  the  inferior 
angle.  Immediately  below  the  glenoid  cavity  is  a  rough  impression,  the  infra- 
glenoid  tubercle  (tuberositas  infraglenoidalis),  about  an  inch  in  length,  which 
affords  attachment  to  the  long  head  of  the  Triceps  muscle;  in  front  of  this  is 
a  longitudinal  groove,  which  extends  as  far  as  the  lower  third  of  the  axillary 
border  and  affords  origin  to  part  of  the  Subscapularis  muscle.  The  inferior 
third  of  this  border,  which  is  thin  and  sharp,  serves  for  the  attachment  of  a  few 
fibres  of  the  Teres  major  behind  and  the  Subscapularis  in  front. 

Internal  or  Vertebral  Border  (margo  vertebralis) . — The  internal  or  vertebral  bor- 
der, also  named  the  base,  is  the  longest  of  the  three,  and  extends  from  the  internal  to 
the  inferior  angle  of  the  bone.  It  is  arched,  is  intermediate  in  thickness  between  the 
superior  and  the  external  borders,  and  the  portion  of  it  above  the  spine  is  bent  con- 
siderably outward,  so  as  to  form  an  obtuse  angle  with  the  lower  part.  The  vertebral 
border  presents  an  anterior  lip,  a  posterior  lip,  and  an  intermediate  space.  Theemfe- 
rior  lip  affords  attachment  to  the  Serratus  magnus ;  the  posterior  lip,  to  the  Supra- 
spinatus  above  the  spine,  the  Infraspinatus  below;  the  interval  between  the  two  lips, 
to  the  Levator  anguli  scapulae  above  the  triangular  surface  at  the  commencement 
of  the  spine,  the  Rhomboideus  minor  to  the  edge  of  that  surface;  the  Rhomboideus 
major  being  attached  by  means  of  a  fibrous  arch  connected  above  to  the  lower 
part  of  the  triangular  surface  at  the  base  of  the  spine,  and  below  to  the  lower  part 
of  the  posterior  border. 

Angles.  Internal  or  Medial  Angle  (anguine  medialis). — Of  the  three  angles,  the 
internal,  formed  by  the  junction  of  the  superior  and  internal  borders,  is  thin, 
smooth,  rounded,  somewhat  inclined  outward,  and  gives  attachment  to  a  few 
fibres  of  the  Levator  anguli  scapulae  muscle. 

Inferior  Angle  (angulus  inferior}.  —  The  inferior  angle,  thick  and  rough,  is 
formed  by  the  union  of  the  vertebral  and  axillary  borders,  its  outer  surface  afford- 
ing attachment  to  the  Teres  major  and  frequently  to  a  few  fibres  of  the  Latissimus 
dorsi. 

External  or  Lateral  Angle  (angulus  lateralis). — The  external  angle  is  the  thickest 
part  of  the  bone,  and  forms  what  is  called  the  head  of  the  scapula.  The  head 
presents  a  shallow,  pyriform,  articular  surface,  the  glenoid  surface  or  cavity  (cav- 
itas  glenoidalis,  from  ftyvir},  a  socket),  whose  longest  diameter  is  from  above 
downward,  and  its  direction  outward  and  forward.  It  is  broader  below  than 
above.  Just  above  it  is  a  rough  surface,  the  supraglenoid  tubercle  or  tuberosity 
(tuberositas  supraglenoidalis) ,  to  which  is  attached  the  long  tendon  of  the  Biceps 
muscle.  The  glenoid  cavity  is  covered  with  cartilage  in  the  recent  state;  and 
its  margins  are  slightly  raised  and  give  attachment  to  a  fibre-cartilaginous  struc- 
ture, the  glenoid  ligament,  by  which  its  cavity  is  deepened.  The  anatomical  neck 
of  the  scapula  (collum  scapula)  is  the  slightly  depressed  surface  which  surrounds 
the  head;  it  is  more  distinct  on  the  posterior  than  on  the  anterior  surface,  and 
below  than  above.  In  the  latter  situation  it  has  arising  from  it  a  thick  prominence, 
the  coracoid  process. 

The  coracoid  process  (processus  coracoideus) ,  so  called  from  its  fancied  resemblance 
to  a  crow's  beak  (xopaz,  a  crow),  is  a  thick,  curved  process  of  bone  which  arises  by 
a  broad  base  from  the  upper  part  of  the  neck  of  the  scapula;  it  is  directed  at  first 
upward  and  inward,  then,  becoming  smaller,  it  changes  its  direction  and  passes  for- 
ward and  outward.  The  ascending  portion,  flattened  from  before  backward,  pre- 
sents in  front  a  smooth,  concave  surface  over  which  passes  the  Subscapularis 


THE  SCAPULA 


177 


muscle.  The  horizontal  portion  is  flattened  from  above  downward,  its  upper 
surface  is  convex  and  irregular,  and  gives  attachment  to  the  Pectoralis  minor; 
its  under  surface  is  smooth;  its 
inner  border  is  rough,  and  gives 
attachment  to  the  Pectoralis 
minor;  its  outer  border  is  also 
rough  for  the  coraco-acromial 
ligament,  while  the  apex'  is 
embraced  by  the  conjoined 
tendon  of  origin  of  the  short 
head  of  the  Biceps  and  of  the 
Coraco-brachialis  and  gives  at- 
tachment to  the  costo-coracoid 
ligament.  At  the  inner  side  of 
the  root  of  the  coracoid  process 
is  a  rough  impression  for  the 
attachment  of  the  conoid  liga- 
ment; and  running  from  it 
obliquely  forward  and  outward 
on  the  upper  surface  of  the 
horizontal  portion,  an  elevated 
ridge  for  the  attachment  of  the 
trapezoid  ligament. 

Structure. — In  the  head,  pro- 
cesses, and  all  the  thickened 
parts  of  the  bone  the  scapula 
is  composed  of  cancellous  tis- 
sue, while  in  the  rest  of  its  ex- 
tent it  is  composed  of  a  thin 
layer  of  dense,  compact  tissue. 
The  centre  part  of  the  supra- 
spinous  fossa  and  the  upper 
part  of  the  infraspinous  fossa,  but  especially  the  former,  are  usually  so  thin  as  to 
be  semitransparent ;  occasionally  the  bone  is  found  wanting  in  this  situation, 
and  the  adjacent  muscles  come  into  contact. 

Development  (Fig.  128). — By  seven  or  more  centres:  one  for  the  body,  two  for 
the  coracoid  process,  two  for  the  acromion,  one  for  the  vertebral  border,  and  one 
for  the  inferior  angle.  Ossification  of  the  body  of  the  scapula  commences  about 
the  second  month  of  foetal  life  by  the  formation  of  an  irregular  quadrilateral 
plate  of  bone  immediately  behind  the  glenoid  cavity.  This  plate  extends  itself  so 
as  to  form  the  chief  part  of  the  bone,  the  spine  growing  up  from  its  posterior, 
surface  about  the  third  month.  At  birth  a  large  part  of  the  scapula  is  osseous, 
but  the  glenoid  cavity,  coracoid  and  acromion  processes,  the  posterior  border,  and 
inferior  angle  are  cartilaginous.  From  the  fifteenth  to  the  eighteenth  month  after 
birth  ossification  takes  place  in  the  middle  of  the  coracoid  process,  which  usually 
becomes  joined  with  the  rest  of  the  bone  at  the  time  when  the  other  centres  make 
their  appearance.  Between  the  fourteenth  and  twentieth  years  ossification  of  the 
remaining  centres  takes  place  in  quick  succession,  and  in  .the  following  order: 
first,  in  the  root  of  the  coracoid  process,  in  the  form  of  a  broad  scale;  secondly, 
near  the  base  of  the  acromion  process;  thirdly,  in  the  inferior  angle  and  contigu- 
ous part  of  the  posterior  border;  fourthly,  near  the  extremity  of  the  acromion; 
fifthly,  in  the  posterior  border.  The  acromion  process,  besides  being  formed  of 
two  separate  nuclei,  has  its  base  formed  by  an  extension  into  it  of  the  centre  of 
ossification  which  belongs  to  the  spine,  the  extent  of  which  varies  in  different 

12 


& 


FIG.  128. — Plan  of  the  development  of  the  scapula.  By  seven 
centres.  The  epiphyses  (except  one  for  the  coracoid  process) 
appear  from  fifteen  to  seventeen  years,  and  unite  between  twenty- 
two  and  twenty-five  years  of  age. 


178  THE  SKELETON 

cases.  The  two  separate  nuclei  unite  and  then  join  with  the  extension  from  the 
spine.  These  various  epiphyses  become  joined  to  the  bone  between  the  ages  of 
twenty-two  and  twenty-five  years.  Sometimes  failure  of  union  between  the 
acromion  process  and  spine  occurs,  the  junction  being  effected  by  fibrous  tissue 
or  by  an  imperfect  articulation ;  in  some  cases  of  supposed  fracture  of  the  acromion 
with  ligamentous  union  it  is  probable  that  the  detached  segment  was  never  united 
to  the  rest  of  the  bone.  The  upper  third  of  the  glenoid  cavity  is  usually  ossified 
from  a  separate  centre  (subcoracoid)  which  makes  its  appearance  between  the 
tenth  and  eleventh  years.  Very  often,  in  addition,  an  epiphysis  appears  for  the 
lower  part  of  the  glenoid  cavity. 

Articulations. — With  the  humerus  and  clavicle. 

Attachment  of  Muscles. — To  seventeen:  to  the  anterior  surf  ace,  the  Subscapu- 
laris;  posterior  surface,  Supraspinatus,  Infraspinatus;  spine,  Trapezius,  Deltoid; 
superior  border,  Omo-hyoid;  vertebral  border,  Serratus  magnus,  Levator  anguli 
scapulae,  Rhomboideus  minor  and  major;  axillary  border,  Triceps,  Teres  minor, 
Teres  major;  apex  of  glenoid  cavity,  long  head  of  the  Biceps;  coracoid  process, 
short  head  of  the  Biceps,  Coraco-brachialis,  Pectoralis  minor;  and  to  the  inferior 
angle  occasionally  a  few  fibres  of  the  Latissimus  dorsi. 

Surface  Form. — The  only  parts  of  the  scapula  which  are  truly  subcutaneous  are  the  spine 
and  acromion  process,  but,  in  addition  to  these,  the  coracoid  process,  the  internal  or  vertebral 
border  and  inferior  angle,  and,  to  a  less  extent,  the  axillary  border,  may  be  defined.  The  acro- 
mion process  and  spine  of  the  scapula  are  easily  felt  throughout  their  entire  length,  forming, 
with  the  clavicle,  the  arch  of  the  shoulder.  The  acromion  can  be  ascertained  to  be  connected 
to  the  clavicle  at  the  acromio-clavicular  joint  by  running  the  finger  along  it,  its  position  being 
often  indicated  by  an  irregularity  or  bony  outgrowth  from  the  clavicle  close  to  the  joint.  The 
acromion  can  be  felt  forming  the  point  of  the  shoulder,  and  from  this  can  be  traced  backward  to 
join  the  spine  of  the  scapula.  The  place  of  junction  is  usually  denoted  by  a  prominence,  which  is 
sometimes  called  the  acromial  angle.  From  here  the  spine  of  the  scapula  can  be  felt  as  a  promi- 
nent ridge  of  bone,  marked  on  the  surface  as  an  oblique  depression,  which  becomes  less  and  less 
distinct,  and  terminates  a  little  external  to  the  spinous  processes  of  the  vertebrae.  Its  termination  is 
usually  indicated  by  a  slight  dimple  in  the  skin  on  a  level  with  the  interval  between  the  third  and 
fourth  thoracic  spines.  Below  thi?  point  the  vertebral  border  of  the  scapula  may  be  traced,  run- 
ning downward  and  outward,  and  thus  diverging  from  the  vertebral  spines,  to  the  inferior  angle 
of  the  bone,  which  can  be  recognized,  although  covered  by  the  Latissimus  dorsi  muscle.  From 
this  angle  the  axillary  border  can  usually  be  traced  through  this  thick  muscular  covering,  form- 
ing, with  the  muscles,  the  posterior  fold  of  the  axilla.  The  coracoid  process  may  be  felt  about 
an  inch  below  the  junction  of  the  middle  and  outer  thirds  of  the  clavicle.  Here  it  is  covered  by 
the  anterior  border  of  the  deltoid  and  lies  a  little  to  the  outer  side  of  a  slight  depression  which 
corresponds  to  the  interval  between  the  Pectoralis  major  and  Deltoid  muscles.  When  the  arms 
are  hanging  by  the  side,  the  upper  angle  of  the  scapula  corresponds  to  the  upper  border  of  the 
second  rib  or  the  interval  between  the  first  and  second  thoracic  spines,  the  inferior  angle  to  the 
upper  border  of  the  eighth  rib  or  the  interval  between  the  seventh  and  eighth  thoracic  spines. 

Surgical  Anatomy. — Fractures  of  the  body  of  the  scapula  are  rare,  owing  to  the  mobility  of  the 
bone,  the  thick  layer  of  muscles  by  which  it  is  encased  on  both  surfaces,  and  the  elasticity  of  the 
ribs  on  which  it  rests.  Fracture  of  the  neck  of  the  bone  is  also  uncommon.  The  most  frequent 
course  of  a  line  of  fracture  of  the  neck  is  from  the  suprascapular  notch  to  the  infraglenoid 
tubercle  (surgical  neck],  and  it  derives  its  principal  interest  from  its  simulation  to  a  subglenoid 
dislocation  of  the  humerus.  The  diagnosis  can  be  made  by  noting  the  alteration  in  the  position 
of  the  coracoid  process.  A  fracture  of  the  neck  external  to,  and  not  including,  the  coracoid 
process  (anatomical  neck}  is  said  to  occur,  but  it  is  exceedingly  doubtful  whether  such  an 
accident  ever  takes  place.  The  acromion  process  is  more  frequently  broken  than  any  other 
part  of  the  bone,  and  there  is  sometimes,  in  young  subjects,  a  separation  of  the  epiphysis.  It 
is  believed  that  many  of  the  cases  of  supposed  fracture  of  the  acromion,  with  fibrous  union, 
which  have  been  found  on  post-mortem  examination  are  really  cases  of  imperfectly  united 
epiphysis.  Sir  Astley  Cooper  believed  that  most  fractures  of  this  bone  united  by  fibrous 
tissue,  and  the  cause  of  this  mode  of  union  was  the  difficulty  there  was  in  keeping  the  frac- 
tured ends  in  constant  apposition.  The  coracoid  process  is  occasionally  broken  off,  either  from 
direct  violence  or  perhaps,  rarely,  from  muscular  action. 

Tumors  of  various  kinds  grow  from  the  scapula.  Of  the  innocent  form  of  tumors  probably 
the  osteomata  are  the  most  common.  When  an  osteoma  grows  from  the  venter  of  the  scapula,  as  it 
sometimes  does,  it  is  of  the  compact  variety,  such  as  usually  grows  from  membrane-formed  bones, 


THE  HUMERUS  179 

as  the  bones  of  the  skull.  This  would  appear  to  afford  evidence  that  this  portion  of  the  bone 
is  formed  from  membrane,  and  not,  like  the  rest  of  the  bone,  from  cartilage.  Sarcomatous 
tumors  sometimes  grow  from  the  scapula,  and  may  necessitate  removal  of  the  bone,  with  or 
without  amputation  of  the  upper  limb.  Removal  of  the  upper  limb  with  the  scapula  and  the 
outer  two-thirds  of  the  clavicle  is  known  as  the  interscapulo-thoracic  amputation.  The 
scapula  may  be  partially  resected  or  completely  excised.  There  are  several  methods  of  com- 
plete excision.  The  bone  may  be  excised  by  a  T-shaped  incision,  and,  the  flaps  being  reflected, 
the  removal  is  commenced  from  the  posterior  or  vertebral  border,  so  that  the  subscapular 
vessels  which  lie  along  the  axillary  border  are  among  the  last  structures  divided,  and  can  be 
at  once  secured. 

THE  ARM. 

The  arm  is  that  portion  of  the  upper  extremity  which  is  situated  between  the 
shoulder  and  the  elbow.  Its  skeleton  consists  of  a  single  bone,  the  humerus. 

The  Humerus  or  Upper  Arm  Bone  (Figs.  129,  130). 

The  humerus  (from  humerus,  or  more  correctly  umerus,  the  shoulder)  is  the 
longest  and  largest  bone  of  the  upper  extremity;  it  presents  for  examination  a 
shaft  and  two  extremities. 

Upper  Extremity. — The  upper  extremity  presents  a  large,  rounded  head, 
joined  to  the  shaft  by  a  constricted  portion,  called  the  neck,  and  two  other  emi- 
nences, the  greater  and  lesser  tuberosities. 

The  Head  (caput  humeri). — The  head,  nearly  hemispherical  in  form,1  is  directed 
upward,  inward,  and  slightly  backward,  and  articulates  with  the  glenoid  cavity 
of  the  scapula;  its  surface  is  smooth  and  coated  with  cartilage  in  the  recent  state. 
The  circumference  of  its  articular  surface  is  slightly  constricted,  and  is  termed 
the  anatomical  neck,  in  contradistinction  to  the  constriction  which  exists  below  the 
tuberosities.  The  latter  is  called  the  surgical  neck  (collum  chirurgicum) ,  f rom  its 
often  being  the  seat  of  fracture.  It  should  be  remembered,  however,  that  frac- 
ture of  the  anatomical  neck  does  sometimes,  though  rarely,  occur. 

ANATOMICAL  NECK  (collum  anatomicum). — The  anatomical  neck  is  obliquely 
directed,  forming  an  obtuse  angle  with  the  shaft.  It  is  more  distinctly  marked  in 
the  lower  half  of  its  circumference  than  in  the  upper  half,  where  it  presents  a  nar- 
row groove,  separating  the  head  from  the  tuberosities.  Its  circumference  affords 
attachment  to  the  capsular  ligament  and  is  perforated  by  numerous  vascular 
foramina. 

Greater  Tuberosity  (tuberculum  majus}. — The  greater  tuberosity  is  situated  on 
the  outer  side  of  the  head  and  lesser  tuberosity.  Its  upper  surface  is  rounded  and 
marked  by  three  flat  facets,  separated  by  two  slight  ridges:  the  highest  facet  gives 
attachment  to  the  tendon  of  the  Supraspinatus;  the  middle  one,  to  the  Infra- 
spinatus;  the  inferior  facet  and  the  shaft  of  the  bone  below  it,  to  the  Teres  minor. 
The  outer  surface  of  the  great  tuberosity  is  convex,  rough,  and  continuous  with 
the  outer  side  of  the  shaft. 

Lesser  Tuberosity  (tuberculum  minus). — The  lesser  tuberosity  is  more  promi- 
nent, although  smaller  than  the  greater:  it  is  situated  in  front  of  the  head,  and 
is  directed  inward  and  forward.  Its  summit  presents  a  prominent  facet  for 'the 
insertion  of  the  tendon  of  the  Subscapularis  muscle.  The  tuberosities  are  sepa- 
rated from  one  another  by  a  deep  groove,  the  bicipital  groove  (sulcus  intertuber- 
cularis).  This  groove  lodges  the  long  tendon  of  the  Biceps  muscle,  with  which 

1  Though  the  head  is  nearly  hemispherical  in  form,  its  margin,  as  Sir  G.  Humphry  has  shown,  is  by  no  means 
a  true  circle.  Its  greatest  measurement  is  from  the  top  of  the  bicipital  groove  in  a  direction  downward,  inward, 
and  backward.  Hence  it  follows  that  the  greatest  elevation  of  the  arm  can  be  obtained  by  rolling  the  articular 
surface  in  this  direction — that  is  to  sa^,  obliquely  upward,  outward,  and  forward. — ED.  of  15th  English  Edition. 


180 


THE  SKELETON 


Common  origin  of 

FLEXOR    CARPI    RADIALIS. 
PALMARIS    LONGUS. 
FLEXOR    SUBLIMIS    DIGITORUM 
FLEXOR    CARPI    ULNARIS. 


SUPINATOR    RADII    LONQUS. 


EXTENSOR    CARPI    RADIALIS 
LONQIOR. 


Common  origin  of 

EXTENSOR    CARPI    RADIALIS    BREVIS, 
"       COMMUNIS    DIGITORUM. 
"        MINIMI     DIGITI. 
'         CARPI    ULNARIS. 

SUPINATOR    BREVIS. 


FIG.  129. — Left  humerus.     Anterior  v«w. 


THE  HUMER  US  1 81 

runs  a  branch  of  the  anterior  circumflex  artery.  It  commences  above  between 
the  two  tuberosities,  passes  obliquely  downward  and  a  little  inward,  and  termin- 
ates at  the  junction  of  the  upper  with  the  middle  third  of  the  bone.  It  is  deep 
and  narrow  at  the  commencement,  and  becomes  shallow  and  a  little  broader  as 
it  descends.  Its  borders  are  called,  respectively,  the  external  or  posterior  bicipital 
ridge  (crista  tuberculi  majoris)  and  the  internal  or  anterior  bicipital  ridge  (crista 
fnhcrculi  minoris},  and  form  the  upper  part  of  the  anterior  and  internal  borders  of 
the  shaft  of  the  bone.  In  the  recent  state  it  is  covered  with  a  thin  layer  of  car- 
tilage, lined  by  a  prolongation  of  the  synovial  membrane  of  the  shoulder-joint, 
and  receives  the  tendon  of  insertion  of  the  Latissimus  dorsi  muscle. 

The  Shaft  (corpus  humeri}. — The  shaft  of  the  humerus  is  almost  cylindrical 
in  the  upper  half  of  its  extent,  prismatic  and  flattened  below,  and  presents  three 
borders  and  three  surfaces  for  examination. 

Anterior  Border. — The  anterior  border  runs  from  the  front  of  the  great  tuber- 
osity  above  to  the  coronoid  depression  below,  separating  the  internal  from  the 
external  surface.  Its  upper  part  is  very  prominent  and  rough,  and  forms  the 
outer  lip  of  the  bicipital  groove.  It  is  sometimes  called  the  posterior  bicipital, 
external  bicipital,  or  pectoral  ridge  (crista  tuberculi  majoris},  and  serves  for  the 
attachment  of  the  tendon  of  the  Pectoralis  major.  About  its  centre  it  forms 
the  anterior  boundary  of  the  rough  deltoid  eminence  or  impression  (tuberositas 
deltoidea};  below,  it  is  smooth  and  rounded,  affording  attachment  to  the  Brachialis 
anticus  muscle. 

External  Border  (margo  lateralis}. — The  external  border  runs  from  the  back 
part  of  the  greater  tuberosity  to  the  external  condyle,  and  separates  the  external 
from  the  posterior  surface.  It  is  rounded  and  indistinctly  marked  in  its  upper 
half,  serving  for  the  attachment  of  the  lower  part  of  the  insertion  of  the  Teres 
minor  muscle,  and  below  this  of  the  external  head  of  the  Triceps  muscle;  its 
centre  is  traversed  by  a  broad,  but  shallow,  oblique  depression,  the  musculo -spiral 
groove  (sulcus  nervi  radialis} ;  its  lower  part  is  marked  by  a  prominent,  rough 
margin,  a  little  curved  from  behind  forward,  the  external  supracondylar  or  epicon- 
dylic  ridge  (margo  lateralis},  which  presents  an  anterior  lip  for  the  attachment  of 
the  Supinator  longus  above  and  Extensor  carpi  radialis  longior  below,  a  posterior 
lip  for  the  Triceps,  and  an  intermediate  space  for  the  attachment  of  the  external 
intermuscular  septum. 

Internal  Border  (margo  medialis}. — The  internal  border  extends  from  the  lesser 
tul)erosity  to  the  internal  condyle.  Its  upper  third  is  marked  by  a  prominent 
ridge,  forming  the  posterior  lip  of  the  bicipital  groove,  and  gives  attachment  to 
the  tendon  of  the  Teres  major.  About  its  centre  is  an  impression  for  the  attach- 
ment of  the  Coraco-brachialis,  and  just  below  this  is  seen  the  entrance  of  the 
nutrient  canal,  directed  downward.  Sometimes  there  is  a  second  canal  situated 
at  the  commencement  of  the  musculo-spiral  groove,  for  a  nutrient  artery  derived 
from  the  superior  profunda  branch  of  the  brachial  artery.  The  inferior  third 
of  this  border  is  raised  into  a  slight  ridge,  the  internal  supracondylar  or  epicon- 
dylic  ridge  (margo  medialis},  which  becomes  very  prominent  below;  it  presents 
an  anterior  lip  for  the  attachment  of  the  Brachialis  anticus  muscle,  a  posterior 
lip  for  the  internal  head  of  the  Triceps  muscle,  and  an  intermediate  space  for 
the  attachment  of  the  internal  intermuscular  septum. 

External  Surface  (fades  anterior  lateralis}. — The  external  surface  is  directed 
outward  above,  where  it  is  smooth,  rounded,  and  covered  by  the  Deltoid  muscle; 
forward  and  outward  below,  where  it  is  slightly  concave  from  above  downward, 
and  gives  origin  to  part  of  the  Brachialis  anticus  muscle.  About  the  middle  of 
this  surface  is  seen  a  rough,  triangular  impression  for  the  insertion  of  the  Del- 
toid muscle,  deltoid  impression  (tuberositas  deltoidea);  and  below  it  the  musculo- 


182 


THE  SKELETON 


spiral  groove,  directed  obliquely  from  behind, 
forward  and  downward,  and  transmitting  the 
musculo-spiral  nerve  and  superior  profunda 
artery. 

Internal  Surface  (fades  anterior  medialis). — 
The  internal  surface,  less  extensive  than  the 
external,  is  directed  inward  above,  forward  and 
inward  below;  at  its  upper  part  it  is  narrow  and 
forms  the  floor  of  the  bicipital  groove:  to  it  is 
attached  the  Latissimus  dorsi.  The  middle 
part  of  this  surface  is  slightly  rough  for  the 
attachment  of  some  of  the  fibres  of  the  tendon 
of  insertion  of  the  Coraco-brachialis ;  its  lower 
part  is  smooth,  concave  from  above  downward, 
and  gives  attachment  to  the  Brachialis  anticus 
muscle.1  A  little  below  the  middle  of  the  shaft 
is  the  nutrient  foramen  (foramen  nidricium). 
This  leads  into  a  nutrient  canal  (canalis  nutri- 
dus),  which  is  directed  toward  the  elbow-joint 
(distally). 

Posterior  Surface  (fades  posterior). — The  pos- 
terior surface  (Fig.  130)  appears  somewhat 
twisted,  so  that  its  upper  part  is  directed  a  little 
inward,  its  lower  part  backward  and  a  little  out- 
ward. Nearly  the  whole  of  this  surface  is 
covered  by  the  external  and  internal  heads  of 
the  Triceps,  the  former  of  which  is  attached 
to  its  upper  and  outer  part,  the  latter  to  its  inner 
and  back  part,  the  two  being  separated  by  the 
musculo-spiral  groove. 

Lower  Extremity. — The  lower  extremity  is 
flattened  from  before  backward,  and  curved 
slightly  forward;  it  terminates  below  in  a 
broad,  articular  surface  which  is  divided  into 
two  parts  by  a  slight  ridge.  Projecting  on 
either  side  are  the  external  and  internal  condyles 
(epicondylus  lateralis  and  epicondylus  medi- 
alis^.  By  some  anatomists  the  external  con- 
dyle  is  called  the  external  epicondyle  and  the 
internal  condyle  is  called  the  internal  epicondyle. 


i  A  small,  hook-shaped  process  of  bone,  the  aupracondylar 
process,  varying  from  '/IQ  to  3/4  of  an  inch  in  length,  is  not  infre- 
quently found  projecting  from  the  inner  surface  of  the  shaft  of 
the  humerus  two  inches  above  the  internal  condyle.  It  is  curved 
downward,  forward,  and  inward,  and  its  pointed  extremity  is 
connected  to  the  internal  border,  just  above  the  inner  condyle, 
by  a  ligament  or  fibrous  band,  which  gives  origin  to  a  portion 
of  the  Pronator  radii  teres;  through  the  arch  completed  by  this  . 
fibrous  band  the  median  nerve  and  brachial  artery  pass  when 
these  structures  deviate  from  their  usual  course.  Sometimes  the 
nerve  alone  is  transmitted  through  it,  or  the  nerve  may  be  ac- 
companied by  the  ulnar  artery  in  cases  of  high  division  of  the 
brachial.  A  well-marked  groove  is  usually  found  behind  the 
process  in  which  the  nerve  and  artery  are  lodged.  This  space 
is  analogous  to  the  supracondyloid  foramen  in  many  animals, 
and  probably  serves  in  them  to  protect  the  nerve  and  artery 
from  compression  during  the  contraction  of  the  muscles  in  this 
region.  A  detailed  account  of  this  process  is  given  by  Dr. 
Struthers,  in  his  Anatomical  and  Physiological  Observations,  p. 

202.     An  accessory  portion   of  the  Coraco-brachialis  muscle  is  

frequently  connected  with  this  process,  according  to  Mr.  J.  Wood  _  T    fi  ,  „     ,     •  fo/,0 

(Journal  of  Anat.  and  Phys.,  No.  1,  November,  1866,  p.  47).—  Fl°-  130.— Left  humerus.    Posterior  surface. 
ED.  of  15th  English  edition. 


THE  HUMERUS  183 

Others  call  the  internal  condyle  the  epitrochlea.  The  articular  surface  extends  a 
little  lower  than  the  condyles,  and  is  curved  slightly  forward,  so  as  to  occupy  the 
more  anterior  part  of  the  bone;  its  greatest  breadth  is  in  the  transverse  diameter, 
and  it  is  obliquely  directed,  so  that  its  inner  extremity  occupies  a  lower  level  than 
the  outer.  The  outer  portion  of  the  articular  surface  presents  a  smooth,  rounded 
eminence,  which  has  received  the  name  of  the  capitellum,  or  radial  head  of  the 
humerus  (capitulum  humeri};  it  articulates  with  the  cup-shaped  depression  on 
the  head  of  the  radius,  and  is  limited  to  the  front  and  lower  part  of  the  bone, 
not  extending  as  far  back  as  the  other  portion  of  the  articular  surface.  On  the 
inner  side  of  this  eminence  is  a  shallow  groove,  in  which  is  received  the  inner 
margin  of  the  head  of  the  radius.  Above  the  front  part  of  the  capitellum  is  a 
slight  depression,  the  radial  fossa  (fossa  radialis),  which  receives  the  anterior 
border  of  the  head  of  the  radius  when  the  forearm  is  flexed.  The  inner  por- 
tion of  the  articular  surface,  the  trochlea  (trochlea  humeri),  presents  a  deep 
depression  between  two  well-marked  borders.  This  surface  is  convex  from 
before  backward,  concave  from  side  to  side,  and  occupies  the  anterior,  lower, 
and  posterior  parts  of  the  bone.  The  external  border,  less  prominent  than  the 
internal,  corresponds  to  the  interval  between  the  radius  and  the  ulna.  The 
internal  border  is  thicker,  more  prominent,  and  consequently  of  greater  length, 
than  the  external.  The  grooved  portion  of  the  articular  surface  fits  accurately 
within  the  greater  sigmoid  cavity  of  the  ulna:  it  is  broader  and  deeper  on  the  pos- 
terior than  on  the  anterior  aspect  of  the  bone,  and  is  inclined  obliquely  from 
behind  forward  and  from  without  inward.  Above  the  front  part  of  the  trochlear 
surface  is  seen  a  smaller  depression,  the  coronoid  fossa  (fossa  coronoidea),  which 
receives  the  coronoid  process  of  the  ulna  during  flexion  of  the  forearm.  Above 
the  back  part  of  the  trochlear  surface  is  a  deep,  triangular  depression,  the 
olecranon  fossa  (fossa  olecrani),  in  which  is  received  the  summit  of  the  olecranon 
process  in  extension  of  the  forearm.  These  fossae  are  separated  from  one  another  by 
a  thin,  transparent  lamina  of  bone,  which  is  sometimes  perforated  by  a  foramen, 
the  supratrochlear  foramen;  their  upper  margins  afford  attachment  to  the  anterior 
and  posterior  ligaments  of  the  elbow-joint,  and  they  are  lined,  in  the  recent  state, 
by  the  synovial  membrane  of  this  articulation.  The  articular  surfaces,  in  the 
recent  state,  are  covered  with  a  thin  layer  of  cartilage.  The  external  epicon- 
dyle  (epicondylus  lateralis)  is  a  small,  tubercular  eminence,  less  prominent 
than  the  internal,  curved  a  little  forward,  and  giving  attachment  to  the  external 
lateral  ligament  of  the  elbow-joint,  and  to  a  tendon  common  to  the  origin  of  some 
of  the  extensor  and  supinator  muscles.  The  internal  epicondyle  (epitrochlea  or 
epicondylus  medialis),  larger  and  more  prominent,  and  therefore  more  liable  to 
fracture,  than  the  external,  is  directed  a  little  backward:  it  gives  attachment  to 
the  internal  lateral  ligament,  to  the  Pronator  radii  teres,  and  to  a  tendon  common 
to  the  origin  of  some  of  the  flexor  muscles  of  the  forearm.  The  ulnar  nerve  runs 
in  a  groove,  the  ulnar  groove  (sulcus  nervi  ulnaris),  at  the  back  of  the  internal 
condyle,  or  between  it  and  the  olecranon  process.  These  condyles  are  directly 
mtinuous  above  with  the  external  and  internal  supracondylar  ridges. 
Structure. — The  extremities  consist  of  cancellous  tissue,  covered  with  a  thin 
compact  layer;  the  shaft  is  composed  of  a  cylinder  of  compact  tissue,  thicker  at 
the  centre  than  at  the  extremities,  and  hollowed  out  by  a  large  medullary  canal, 
which  extends  along  its  whole  length.  In  the  head  of  the  humerus  the  plates 
of  the  cancellous  tissue  are  arranged  in  curves  (Fig.  131)  known  as  pressure 
curves.  Most  of  the  bone-plates  are  at  right  angles  to  the  plane  of  the  articular 
surface  (the  lines  of  greatest  pressure),  and  they  are  bound  together  by  other 
bone-fibres,  which  usually  correspond  to  the  plane  of  the  articulation  (the  lines 
of  greatest  tension).  This  arch-like  arrangement  strengthens  the  head  of  the 
bone,  and  it  is  further  strengthened  by  the  binding  fibres. 


184 


THE  SKELETON 


Development. — By  seven,  or  occasionally  eight,  centres  (Fig.  133):  one  for  the 
shaft,  one  for  the  head,  one  for  the  tuberosities,  one  for  the  radial  head,  one  for 
the  trochlear  portion  of  the  articular  surface,  and  one  for  each  condyle.  The 
nucleus  for  the  shaft  appears  near  the  centre  of  the  bone  in  the  eighth  week,  and 
soon  extends  toward  the  extremities.  At  birth  the  humerus  is  ossified  nearly  in 
its  whole  length,  the  extremities  remaining  cartilaginous.  During  the  first  year, 


FIG.  131. — Diagram  showing  the  architecture  of  the  supe- 
rior extremity  of  the  humerus.     (Poirier  and  Charpy.) 


FIG.  132. — The  architecture  of  the  superior 
extremity  of  the  humerus  (x-ray  picture). 


Epiphyses  of  head  and 
tuberosities  blend   at 
5th  year,  and  unite 
with   shaft    at    20th  \ 
year. 


Unites  with  shaft  \ 
at  18th  year,      j 


FIG.  133. — Plan  of  the  development  of  the 
humerus  by  seven  centres. 


sometimes  even  before  birth,  ossification 
commences  in  the  head  of  the  bone,  and 
during  the  third  year  the  centre  for  the 
tuberosities  makes  its  appearance,  usually 
by  a  single  ossific  point,  but  sometimes, 
according  to  Beclard,  by  one  for  each 
tuberosity,  that  for  the  lesser  being  small 
and  not  appearing  until  the  fifth  year.  By 
the  sixth  year  the  centres  for  the  head  and 
tuberosities  have  increased  in  size  and  be- 
come joined,  so  as  to  form  a  single  large 
epiphysis. 

The  lower  end  of  the  humerus  is  devel- 
oped in  the  following  manner:  At  the  end 
of  the  second  year  ossification  commences 
in  the  capitellum,  and  from  this  point  ex- 
tends inward,  so  as  to  form  the  chief  part 
of  the  articular  end  of  the  bone,  the  centre 
for  the  inner  part  of  the  trochlea  not 
appearing  until  about  the  age  of  twelve. 
Ossification  commences  in  the  internal 
condyle  about  the  fifth  year,  and  in  the 
external  one  not  until  about  the  thirteenth 
or  fourteenth  year.  About  sixteen  or  seven- 
teen years  the  outer  condyle  and  both  por- 
tions of  the  articulating  surface  (which 
have  already  joined)  unite  with  the  shaft; 


THE  HUMERUS  185 

at  eighteen  years  the  inner  condyle  becomes  joined;  while  the  upper  epiphysis, 
although  the  first  formed,  is  not  united  until  about  the  twentieth  year. 

Articulations. — With  the  glenoid  cavity  of  the  scapula  and  with  the  ulna  and 
radius. 

Attachment  of  the  Muscles. — To  twenty-four:  to  the  greater  tuberosity,  the 
Supraspinatus,  Infraspinatus,  and  Teres  minor;  to  the  lesser  tuberosity,  the 
Subscapularis ;  to  the  anterior  bicipital  ridge,  the  Pectoralis  major;  to  the  posterior 
bicipital  ridge,  the  Teres  major;  to  the  bicipital  groove,  the  Latissimus  dorsi;  to 
the  shaft,  the  Deltoid,  Coraco-brachialis,  Brachialis  anticus,  external  and  internal 
heads  of  the  Triceps ;  to  the  internal  condyle,  the  Pronator  radii  teres,  and  common 
tendon  of  the  Flexor  carpi  radialis,  Palmaris  longus,  Flexor  sublimis  digitorum, 
and  Flexor  carpi  ulnaris;  to  the  external  condyloid  ridge,  the  Supinator  longus 
and  Extensor  carpi  radialis  longior;  to  the  external  condyle,  the  common  tendon 
of  the  Extensor  carpi  radialis  brevier,  Extensor  communis  digitorum,  Extensor 
minimi  digiti,  Extensor  carpi  ulnaris,  and  Supinator  brevis;  to  the  back  of  the 
external  condyle,  the  Anconeus. 

Surface  Form. — The  humerus  is  almost  entirely  clothed  by  the  muscles  which  surround  it, 
and  the  only  parts  of  this  bone  which  are  strictly  subcutaneous  are  small  portions  of  the 
internal  and  external  condyles.  In  addition  to  these,  the  tuberosities  and  a  part  of  the  head 
of  the  bone  can  be  felt  under  the  skin  and  muscles  by  which  they  are  covered.  Of  these  the 
greater  tuberosity  forms  the  most  prominent  bony  point  of  the  shoulder,  extending  beyond  the 
acromion  process  and  covered  by  the  Deltoid  muscle.  It  influences  materially  the  surface  form 
of  the  shoulder.  It  is  best  felt  while  the  arm  is  lying  loosely  by  the  side;  if  the  arm  be  raised, 
it  recedes  from  under  the  finger.  The  lesser  tuberosity,  directed  forward  and  inward,  is  to  be 
felt  to  the  inner  side  of  the  greater  tuberosity,  just  below  the  acromio-clavicular  joint.  Between 
the  two  tuberosities  lies  the  bicipital  groove.  This  can  be  defined  by  placing  the  finger  and 
making  firm  pressure  just  internal  to  the  greater  tuberosity;  then,  by  rotating  the  humerus,  the 
groove  will  be  felt  to  pass  under  the  finger  as  the  bone  is  rotated.  With  the  arm  abducted  from 
the  side,  by  pressing  deeply  in  the  axilla  the  lower  part  of  the  head  of  the  bone  is  to  be  felt. 
On  each  side  of  the  elbow-joint,  and  just  above  it,  the  internal  and  external  condyles  of  the 
bone  are  to  be  felt.  Of  these  the  internal  is  the  more  prominent,  but  the  ridge  passing  upward 
from  it,  the  internal  condyloid  ridge,  is  much  less  marked  than  the  external,  and,  as  a  rule,  is 
not  to  be  felt.  Occasionally,  however,  we  find  along  this  border  the  hook-shaped  process  men- 
tioned above.  The  external  eondyle  is  most  plainly  to  be  seen  during  semiflexion  of  the  fore- 
arm, and  its  position  is  indicated  by  a  depression  between  the  attachment  of  the  adjacent  mus- 
cles. From  it  is  to  be  felt  a  strong  bony  ridge  running  up  the  outer  border  of  the  shaft  of  the 
bone.  This  is  the  external  supracondylar  ridge;  it  is  concave  forward,  and  corresponds  with 
the  curved  direction  of  the  lower  extremity  of  the  humerus. 

Surgical  Anatomy. — There  are  several  points  of  surgical  interest  connected  with  the 
humerus.  First,  as  regards  its  development.  The  upper  end,  though  the  first  to  ossify,  is  the 
last  to  join  the  shaft,  and  the  length  of  the  bone  is  mainly  due  to  growth  from  this  upper 
epiphysis.  Hence,  in  cases  of  amputation  of  the  arm  in  young  subjects  the  humerus  continues 
to  grow  considerably,  and  the  end  of  the  bone,  which  immediately  after  the  operation  was  cov- 
ered with  a  thick  cushion  of  soft  tissue,  begins  to  project,  thinning  the  soft  parts  and  rendering 
the  stump  conical.  This  may  necessitate  another  operation,  which  consists  in  the  removal  of  a 
couple  of  inches  or  so  of  the  bone,  and  even  after  this  operation  a  recurrence  of  the  conical  stump 
may  take  place. 

There  are  several  points  of  surgical  interest  in  connection  with  fractures.  First,  as  regard 
their  causation :  the  bone  may  be  broken  by  direct  or  indirect  violence  like  the  other  long  bones, 
but,  in  addition  to  this,  it  is  probably  more  frequently  fractured  by  muscular  action  than  any 
other  of  this  class  of  bone  in  the  body.  It  is  usually  the  shaft,  just  below  the  insertion  of  the 
Deltoid,  which  is  thus  broken.  Mr.  Pick  has  seen  the  accident  happen  from  throwing  a  stone,  and 
in  an  apparently  healthy  adult  from  cutting  a  piece  of  hard  "cake  tobacco"  on  a  table.  In  this 
latter  case  there  was  no  disease  of  the  bone  that  could  be  discovered.  Fractures  of  the  upper 
end  may  take  place  through  the  anatomical  neck,  through  the  surgical  neck,  or  separation  of  the 
gmiter  tuberosity  may  occur.  Fracture  of  the  anatomical  neck  is  a  very  rare  accident;  in  fact, 
it  is  doubted  by  some  whether  it  ever  occurs.  These  fractures  are  usually  considered  to  be 
uitnicapsular,  but  they  are  probably  partly  within  and  partly  without  the  capsule,  as  the  lower 
part  of  the  capsule  is  inserted  some  little  distance  below  the  anatomical  neck,  while  the  upper 
part  is  attached  to  it.  They  may  be  impacted  or  non-impacted.  In  most  cases  there  is  little  or 


186  THE  SKELETON 

no  displacement  on  account  of  the  capsule,  in  whole  or  in  part,  remaining  attached  to  the  lower 
fragment.  But  occasionally  a  very  remarkable  alteration  in  position  takes  place;  the  upper 
fragment  turns  on  its  own  axis,  so  that  the  cartilaginous  surface  of  the  head  rests  against  the 
upper  end  of  the  lower  fragment.  When  the  fractured  end  is  entirely  separated  from  all  its 
surroundings,  its  vascular  supply  must  be  entirely  cut  off,  and  one  would  expect  it,  theoretically, 
to  necrose.  But  this  must  be  exceedingly  rare,  for  Gurlt  was  unable  to  find  a  single  authenti- 
cated case  recorded.  Separation  of  the  upper  epiphysis  of  the  humerus  sometimes  occurs  in  the 
young  subject,  and  is  marked  by  a  characteristic  deformity  by  which  the  lesion  may  be  at  once 
recognized.  This  consists  in  the  presence  of  an  abrupt  projection  at  the  front  of  the  joint  some 
short  distance  below  the  coracoid  process,  caused  by  the  upper  end  of  the  lower  fragment.  In 
fractures  of  the  shaft  of  the  humerus  the  lesion  may  take  place  at  any  point,  but  appears  to  be 
more  common  in  the  lower  than  in  the  upper  part  of  the  bone.  The  points  of  interest  in  con- 
nection with  these  fractures  are:  (1)  That  the  musculo-spiral  nerve  may  be  injured  as  it  lies  in  the 
groove  on  the  bone,  or  may  become  involved  in  the  callus  which  is  subsequently  thrown  out; 
and  (2)  the  frequency  of  non-union.  This  ic  believed  to  be  more  common  in  the  humerus  than 
in  any  other  bone,  and  various  causes  have  been  assigned  for  it.  It  would  seem  most  probably 
to  be  due  to  the  difficulty  that  there  is  in  fixing  the  shoulder-joint  and  the  upper  fragment,  and 
possibly  the  elbow-joint  and  lower  fragment  also.  Other  causes  which  have  been  assigned 
for  the  non-union  are:  (1)  That  in  attempting  passive  motion  of  the  elbow-joint  to  overcome 
any  rigidity  which  may  exist,  the  movement  does  not  take  place  at  the  articulation,  but  at  the 
seat  of  fracture;  or  that  the  patient,  in  consequence  of  the  rigidity  of  the  elbow,  in  attempting 
to  flex  or  extend  the  forearm  moves  the  fragment  and  not  the  joint.  (2)  The  presence  of  small 
portions  of  muscular  tissue  between  the  broken  ends.  (3)  Want  of  support  to  the  elbow,  so 
that  the  weight  of  the  arm  tends  to  drag  the  lower  fragment  away  from  the  upper.  An  impor- 
tant distinction  to  make  in  fractures  of  the  lower  end  of  the  humerus  is  between  those  that 
involve  the  elbow-joint  and  those  which  do  not ;  the  former  are  always  serious,  as  they  may  lead 
to  stiffness  of  the  joint  and  impairment  of  the  utility  of  the  limb.  They  include  the  T-shaped 
fracture  and  oblique  fractures  which  involve  the  articular  surface.  The  fractures  which  do  not 
involve  the  joint  are  the  transverse  above  the  condyles  and  the  so-called  epitrochlear  fracture, 
in  which  the  tip  of  the  internal  condyle  is  broken  off,  generally  by  direct  violence. 

Under  the  head  of  separation  of  the  lower  epiphysis  two  separate  injuries  have  been  described : 
One  where  the  whole  oi  the  four  ossific  centres  which  form  the  lower  extremity  of  the  bone  are 
separated  from  the  shaft;  and  secondly,  w7here  the  articular  portion  is  alone  separated,  the  two 
condyles  remaining  attached  to  the  shaft  of  the  bone.  The  epiphysial  line  between  the  shaft 
and  lower  end  runs  across  the  bone  just  above  the  tips  of  the  condyles,  a  point  to  be  borne  in 
mind  in  performing  the  operation  of  excision. 

Tumors  originating  from  the  humerus  are  of  frequent  occurrence.  A  not  uncommon  place 
for  a  chondroma  tc  grow  from  is  the  shaft  of  the  bone  somewhere  in  the  neighborhood  of  the 
insertion  of  the  deltoid.  Sarcomata  frequently  grow  from  this  bone. 


THE  FOREARM. 

The  forearm  is  that  portion  of  the  upper  extremity  which  is  situated  between 
the  elbow  and  the  wrist.  Its  skeleton  is  composed  of  two  bones,  the  ulna  and 
radius. 

%         The  Ulna  or  Elbow  Bone. 

The  ulna  (Figs.  134  and  135),  so  called  from  its  forming  the  elbow  ((btevy},  is  a 
long  bone,  prismatic  in  form,  placed  at  the  inner  side  of  the  forearm,  parallel  with 
the  radius.  It  is  the  larger  and  longer  of  the  two  bones.  Its  upper  extremity,  of 
great  thickness  and  strength,  forms  a  large  part  of  the  articulation  of  the  elbow- 
joint;  it  diminishes  in  size  from  above  downward,  its  lower  extremity  being  very 
small,  and  excluded  from  the  wrist-joint  by  the  interposition  of  an  interarticular 
fibro-cartilage.  It  is  divisible  into  a  shaft  and  two  extremities. 

Upper  Extremity.— The  upper  extremity,  the  strongest  part  of  the  bone, 
presents  for  examination  two  large,  curved  processes,  the  olecranon  process  and 
the  coronoid  process;  and  two  concave,  articular  cavities,  the  greater  and  lesser 
sigmoid  cavities. 

Olecranon  Process  (olecranon). — The  olecranon  process  (ioXivr],  elbow;  xixwiov, 
head)  is  a  large,  thick,  curved  eminence  situated  at  the  upper  and  back  part  of 


THE    ULNA 


187 


Ulna. 


Radius. 


FLEXOR    DIQITORUM 
SUBLIMIS. 


PBONATOR 
RADII    TERES. 


Occasional  origin  of 

FLEXOR    LONQUS    POLLIOIS. 


Styloid  process. 


Radial  origin  of  FLEXOR 

DIQITORUM    SUBLIMIS. 


SUPINATOR    LONQUS. 

Groove  for  EXT.  ossis 

METACAR?!    POLLICIS 
and  EXT     BREV.   POLL 


process. 
FIG.  134. — Bones  of  the  left  forearm.     Anterior  surface. 


188  THE  SKELETON 

the  ulna.  It  is  curved  forward  at  the  summit  so  as  to  present  a  prominent  tip 
which  is  received  into  the  olecranon  fossa  of  the  humerus  in  extension  of  the  fore- 
arm ;  its  base  being  contracted  where  it  joins  the  shaft.  This  is  the  narrowest  part 
of  the  upper  end  of  the  ulna,  and,  consequently,  the  most  usual  seat  of  fracture. 
The  posterior  surface  of  the  olecranon,  directed  backward,  is  triangular,  smooth, 
subcutaneous,  and  covered  by  a  bursa.  Its  upper  surface  is  of  a  quadrilateral 
form,  marked  behind  by  a  rough  impression  for  the  attachment  of  the  Triceps 
muscle;  and  in  front,  near  the  margin,  by  a  slight  transverse  groove  for  the 
attachment  of  part  of  the  posterior  ligament  of  the  elbow-joint.  Its  interior  sur- 
face is  smooth,  concave,  covered  with  cartilage  in  the  recent  state,  and  forms  the 
upper  and  back  part  of  the  great  sigmoid  cavity.  The  lateral  borders  present 
a  continuation  of  the  same  groove  that  was  seen  on  the  margin  of  the  superior 
surface;  they  serve  for  the  attachment  of  ligaments — viz.,  the  back  part  of  the 
internal  lateral  ligament  internally,  the  posterior  ligament  externally.  To  the 
inner  border  is  also  attached  a  part  of  the  Flexor  carpi  ulnaris,  while  to  the  outer 
border  is  attached  the  Anconeus  muscle. 

Coronoid  Process  (processus  coronoideus) . — The  coronoid  process  (xopcbvy,  any- 
thing hooked  like  a  crow's  beak)  is  a  triangular  eminence  of  bone  which  projects 
horizontally  forward  from  the  upper  and  front  part  of  the  ulna.  Its  base  is  con- 
tinuous with  the  shaft,  and  of  considerable  strength;  so  much  so  that  fracture  of 
it  is  an  accident  of  rare  occurrence.  Its  apex  is  pointed,  slightly  curved  upward, 
and  is  received  into  the  coronoid  depression  of  the  humerus  in  flexion  of  the  forearm. 
Its  upper  surface  is  smooth,  concave,  and  forms  the  lower  part  of  the  greater  sig- 
moid cavity.  The  under  surface  is  concave.  At  the  junction  of  this  surface  with 
the  shaft  is  a  rough  eminence,  the  tubercle  of  the  ulna  (tuberositas  ulnae],  for  the 
attachment  of  the  oblique  ligament  of  the  superior  radio-ulnar  articulation  and  the 
Brachialis  anticus  muscle.  Its  outer  surface  presents  a  narrow,  oblong,  articular 
depression,  the  lesser  sigmoid  cavity.  The  inner  surface,  by  its  prominent,  free 
margin,  serves  for  the  attachment  of  part  of  the  internal  lateral  ligament.  At 
the  front  part  of  this  surface  is  a  small,  rounded  eminence  for  the  attachment  of 
one  head  of  the  Flexor  sublimis  digitorum;  behind  the  eminence,  a  depression  for 
part  of  the  origin  of  the  Flexor  profundus  digitorum;  and,  descending  from  the 
eminence,  a  ridge  which  gives  attachment  to  one  head  of  the  Pronator  radii  teres. 
Generally,  the  Flexor  longus  pollicis  has  an  origin  from  the  lower  part  of  the 
coronoid  process  by  a  rounded  bundle  of  muscular  fibres. 

Greater  Sigmoid  Cavity  (incisura  semilunaris). — The  greater  sigmoid  cavity,  so 
called  from  its  resemblance  to  the  old  shape  of  the  Greek  letter  2',  is  a  semi- 
lunar  depression  of  large  size,  formed  by  the  olecranon  and  coronoid  processes, 
and  serving  for  articulation  with  the  trochlear  surface  of  the  humerus.  About 
the  middle  of  either  lateral  border  of  this  cavity  is  a  notch  which  contracts  it 
somewhat,  and  serves  to  indicate  the  junction  of  the  two  processes  of  which  it  is 
formed.  The  cavity  is  concave  from  above  downward,  and  divided  into  two 
lateral  parts  by  a  smooth,  elevated  ridge  which  runs  from  the  summit  of  the 
olecranon  to  the  tip  of  the  coronoid  process.  Of  these  two  portions,  the  internal 
is  the  larger,  and  is  slightly  concave  transversely;  the  external  portion  is  convex 
above,  slightly  concave  below.  The  articular  surface,  in  the  recent  state,  is 
covered  with  a  thin  layer  of  cartilage. 

Lesser  Sigmoid  Cavity  (incisura  radialis}. — The  lesser  sigmoid  cavity  is  a  narrow, 
oblong,  articular  depression,  placed  on  the  outer  side  of  the  coronoid  process,  and 
receives  the  lateral  articular  surface  of  the  head  of  the  radius.  It  is  concave  from 
before  backward,  and  its  extremities,  which  are  prominent,  serve  for  the  attach- 
ment of  the  orbicular  ligament.  In  the  recent  state  it  is  covered  with  a  thin  layer 
of  cartilage. 


THE     ULNA 

Ulna. 


189 


FLEXOR   SUBLIMI3    DlGITORUM. 


EXTENSOR    CARPI    ULNARI9. 
EXTENSOR    MINIMI     D;QITI. 


For 

EXTENSOR  CARPI  RADIALIS  BREVI'OR. 

EXTENSOR  LONQUS  POLL1CIS. 

FIG.  135. — Bones  of  the  left  forearm.     Posterior  surface. 


Fnr 


fEXTEN 
\  EXTEN 


SOR    INDICIS. 

SOR    COMMUNIS    DlGITORUM. 


190  THE  SKELETON 

The  Shaft(corpws  ulnae). — The  shaft,  at  its  upper  part,  is  prismatic  in  form,  and 
curved  from  behind  forward  and  from  without  inward,  so  as  to  be  convex  behind 
and  externally;  its  central  part  is  quite  straight;  its  lower  part  rounded,  smooth, 
and  bent  a  little  outward ;  it  tapers  gradually  from  above  downward,  and  presents 
for  examination  three  borders  and  three  surfaces. 

Anterior  or  Palmar  Border  (mar go  volaris). — The  anterior  border  commences 
above  at  the  prominent  inner  angle  of  the  coronoid  process,  and  terminates  below 
in  front  of  the  styloid  process.  It  is  well  marked  above,  smooth  and  rounded  in 
the  middle  of  its  extent,  and  affords  attachment  to  the  Flexor  profundus  digitorum : 
its  lower  fourth,  marked  off  from  the  rest  of  the  border  by  the  commencement  of 
an  oblique  ridge  on  the  anterior  surface,  serves  for  the  attachment^of  the  Pronator 
quadratus.  It  separates  the  anterior  from  the  internal  surface. 

Posterior  or  Dorsal  Border  (margo  dorsalis). — The  posterior  border  commences 
above  at  the  apex  of  the  triangular  subcutaneous  surface  at  the  back  part  of  the 
olecranon,  and  terminates  below  at  the  back  part  of  the  styloid  process;  it  is  well 
marked  in  the  upper  three-fourths,  and  gives  attachment  to  the  aponeurosis  com- 
mon to  the  Flexor  carpi  ulnaris,  the  Extensor  carpi  ulnaris,  and  the  Flexor  pro- 
fundus digitorum  muscles;  its  lower  fourth  is  smooth  and  rounded.  This  border 
separates  the  internal  from  the  posterior  surface. 

External  or  Interosseous  Border  (crista  interossea). — The  external  or  interosseous 
border  commences  above  by  the  union  of  two  lines,  which  converge  one  from  each 
extremity  of  the  lesser  sigmoid  cavity,  enclosing  between  them  a  triangular  space 
for  the  attachment  of  part  of  the  Supinator  brevis.  The  external  line  is  the 
crista  ra.  supinatoris.  The  interosseous  border  of  the  ulna  terminates  below  at 
the  middle  of  the  head  of  the  ulna.  Its  two  middle  fourths  are  very  prominent; 
its  lower  fourth  is  smooth  and  rounded.  This  border  gives  attachment  to  the 
interosseous  membrane,  and  separates  the  anterior  from  the  posterior  surface. 

Anterior  or  Palmar  Surface  (fades  volaris) . — The  anterior  surface,  much  broader 
above  than  below,  is  concave  in  the  upper  three-fourths  of  its  extent,  and  affords 
attachment  to  the  Flexor  profundus  digitorum;  its  lower  fourth,  also  concave,  is 
covered  by  the  Pronator  quadratus.  The  lower  fourth  is  separated  from  the 
remaining  portion  of  the  bone  by  a  prominent  ridge,  directed  obliquely  from 
above  downward  and  inward;  this  ridge,  the  oblique  or  pronator  ridge,  marks  the 
extent  of  attachment  of  the  Pronator  quadratus.  At  the  junction  of  the  upper 
with  the  middle  third  of  the  bone  is  the  nutrient  foramen  (foramen  nutricium). 
It  opens  into  the  nutrient  canal  (canalis  nutricius),  which  is  directed  obliquely 
upward  and  inward  (proximally) . 

Posterior  or  Dorsal  Surface  (fades  dorsalis) . — The  posterior  surface,  directed  back- 
ward and  outward,  is  broad  and  concave  above,  somewhat  narrower  and  convex  in 
the  middle  of  its  course,  narrow,  smooth,  and  rounded  below.  It  presents,  above,  an 
oblique  ridge,  which  runs  from  the  posterior  extremity  of  the  lesser  sigmoid  cavity, 
downward  to  the  posterior  border;  the  triangular  surface  above  this  ridge  receives 
the  insertion  of  the  Anconeus  muscle,  whilst  the  upper  part  of  the  ridge  itself  affords 
attachment  to  the  Supinator  brevis.  The  surface  of  bone  below  this  is  subdivided 
by  a  longitudinal  ridge,  sometimes  called  the  perpendicular  line,  into  two  parts; 
the  internal  part  is  smooth,  and  covered  by  the  Extensor  carpi  ulnaris;  the  exter- 
nal portion,  wider  and  rougher,  gives  attachment  from  above  downward  to  part 
of  the  Supinator  brevis,  the  Extensor  ossis  metacarpi  pollicis,  the  Extensor  longus 
pollicis,  and  the  Extensor  indicis  muscles. 

Internal  Surface  (fades  medialis). — The  internal  surface  is  broad  and  concave 
above,  narrow  and  convex  below.  It  gives  attachment  by  its  upper  three-fourths 
to  the  Flexor  profundus  digitorum  muscle:  its  lower  fourth  is  subcutaneous. 
The  anterior  and  the  inner  surfaces  constitute  the  flexor  surface. 


THE  ULNA 


191 


Olecranon. 
Appears  at^ 
10th  year. 


rins  shaft  at 
16th  year. 


Lower  Extremity. — The  lower  extremity  of  the  ulna  is  of  small  size,  and 
excluded  from  the  articulation  of  the  wrist-joint.  It  presents  for  examination  two 
eminences,  the  outer  and  larger  of  which  is  a  rounded,  articular  eminence,  termed 
the  head  of  the  ulna  (capitulum  ulnae],  the  inner,  narrower  and  more  projecting, 
is  a  non-articular  eminence,  the  styloid  process  (processus  styloideus) .  The  head 
presents  an  articular  facet,  part  of  which,  of  an  oval  or  semilunar  form,  is 
directed  downward,  and  articulates  with  the  upper  surface  of  the  interarticular 
fibro-cartilage  which  separates  it  from  the  wrist-joint;  the  remaining  portion, 
directed  outward,  is  narrow,  convex,  and  received  into  the  sigmoid  cavity  of  the 
radius.  The  peripheral  margin  of  the  portion  of  the  head  which  articulates  with 
the  ulna  is  called  the  articular  circumference  (circumferentia  articularis).  The 
styloid  process  projects  from  the  inner  and  back  part  of  the  bone,  and  descends 
a  little  lower  than  the  head,  terminating  in  a  rounded  summit,  which  affords 
attachment  to  the  internal  lateral  ligament  of  the  wrist.  The  head  is  separatee! 
from  the  styloid  process  by  a  depression  for  the  attachment  of  the  triangular 
interarticular  fibro-cartilage;  and  behind,  by  a  shallow  groove  for  the  passage  of 
the  tendon  of  the  Extensor  carpi  ulnaris. 

Structure. — Similar  to  that  of  the  other  long  bones. 

Development. — By  three  centres :  one  for  the  shaft,  one  for  the  inferior  extrem- 
ity, and  one  for  the  olecranon  (Fig.  136).  Ossification  commences  near  the 
middle  of  the  shaft  about  the  eighth  week,  and 
soon  extends  through  the  greater  part  of  the  bone. 
At  birth  the  ends  are  cartilaginous.  About  the 
fourth  year  a  separate  osseous  nucleus  appears  in 
the  middle  of  the  head,  which  soon  extends  into  the 
styloid  process.  About  the  tenth  year  ossific  matter 
appears  in  the  olecranon  near  its  extremity,  the  chief 
part  of  this  process  being  formed  from  an  extension 
of  the  shaft  of  the  bone  into  it.  At  about  the  six- 
teenth year  the  upper  epiphysis  becomes  joined,  and 
at  about  the  twentieth  year  the  lower  one. 

Articulations. — With  the  humerus  and  radius. 

Attachment  of  Muscles. — To  sixteen :  to  the  ole- 
cranon, the  Triceps,  Anconeus,  and  one  head  of  the 
Flexor  carpi  ulnaris.  To  the  coronoid  process,  the 
Brachialis  anticus,  Pronator  radii  teres,  Flexor  sub- 
limis  digitorum,  and  Flexor  profundus  digitorum; 
generally  also  the  Flexor  longus  pollicis.  To  the 
shaft,  the  Flexor  profundus  digitorum,  Pronator 
quadratus,  Flexor  carpi  ulnaris,  Extensor  carpi 
ulnaris,  Anconeus,  Supinator  brevis,  Extensor  ossis 
metacarpi  pollicis,  Extensor  longus  pollicis,  and 

Extensor  indicis.  Inferior  extremity. 

FIG.  136. — Plan  of  the  development 

Surface  Form.— The  most  prominent  part  of  the  ulna  on        of  the  ulna-    By  three  centres- 
the  surface  of  the  body  is  the  olecranon  process,  which  can 

always  be  felt  at  the  back  of  the  elbow-joint.  When  the  forearm  is  flexed,  the  upper  quadri- 
lateral surface  can  be  felt,  directed  backward;  during  extension  it  recedes  into  the  olecranon 
fossa,  and  the  contracting  fibres  of  the  triceps  prevent  its  being  perceived.  At  the  back  of 
the  olecranon  is  the  smooth,  triangular,  subcutaneous  surface,  which  below  is  continuous 
with  the  posterior  border  of  the  shaft  of  the  bone,  and  felt  in  every  position  of  the  forearm. 
During  extension  the  upper  border  of  the  olecranon  is  slightly  above  the  level  of  the  internal 
condyle,  and  the  process  itself  is  nearer  to  this  condyle  than  the  outer  one.  Running  down 
the  back  of  the  forearm,  from  the  apex  of  the  triangular  surface  which  forms  the  posterior 
surface  of  the  olecranon,  is  a  prominent  ridge  of  bone,  the  posterior  border  of  the  ulna. 
This  is  to  be  felt  throughout  the  entire  length  of  the  shaft  of  the  bone,  from  the  olecranon 
above  to  the  styloid  process  below.  As  it  passes  down  the  forearm  it  pursues  a  sinuous  course 


Appears  at 
4th  year. 


_Joins  shaft  at 
20th  year. 


192  THE  SKELETON 

and  inclines  to  the  inner  side,  so  that,  though  it  is  situated  in  the  middle  of  the  back  of 
the  limb  above,  it  is  on  the  inner  side  of  the  wrist  at  its  termination.  It  becomes  rounded  off 
in  its  lower  third,  and  may  be  traced  below  to  the  small,  subcutaneous  surface  of  the  stvloid 
process.  Internal  to  this  border  the  lower  fourth  of  the  inner  surface  is  to  be  felt.  The  styloid 
process  is  to  be  felt  as  a  prominent  tubercle  of  bone,  continuous  above  with  the  posterior  sub- 
cutaneous border  of  the  ulna,  and  terminating  below  in  a  blunt  apex,  which  lies  a  little  internal 
and  behind,  but  on  a  level  with,  the  wrist-joint.  The  styloid  process  is  best  felt  when  the  hand 
is  in  the  same  line  as  the  bones  of  the  forearm,  and  in  a  position  midway  between  supination 
and  pronation.  If  the  forearm  is  pronated  while  the  finger  is  placed  on  the  process,  it  will  be 
felt  to  recede,  and  another  prominence  of  bone  will  appear  just  behind  and  above  it.  This 
is  the  head  of  the  ulna,  which  articulates  with  the  lower  end  of  the  radius  and  the  triangular 
interarticular  fibre-cartilage,  and  now  projects  between  the  tendons  of  the  Extensor  carpi  ulnaris 
and  the  Extensor  minimi  digiti  muscles. 


The  Radius. 

The  radius  (radius,  a  ray,  or  spoke  of  a  wheel)  is  so  called  because  it  is  the 
rotary  bone  of  the  forearm.  It  is  situated  on  the  outer  side  of  the  forearm,  lying 
side  by  side  with  the  ulna,  which  exceeds  it  in  length  and  size  (Figs.  134  and 
135).  Its  upper  end  is  small,  and  forms  only  a  small  part  of  the  elbow-joint; 
but  its  lower  end  is  large,  and  forms  the  chief  part  of  the  wrist.  It  is  one  of  the 
long  bones,  prismatic  in  form,  slightly  curved  longitudinally,  and,  like  other 
long  bones,  has  a  shaft  and  two  extremities. 

Upper  Extremity. — The  upper  extremity  presents  a  head,  neck,  and  tuberosity. 

The  Head. — The  head  (capitulum  radii)  is  of  a  cylindrical  form,  depressed  on 
its  upper  surface  into  a  shallow  cup  (fovea  capituli  radii),  which  articulates  with 
the  capitellum  or  radial  head  of  the  humerus.  In  the  recent  state  it  is  covered 
with  a  layer  of  cartilage  which  is  thinnest  at  its  centre.  Around  the  circumference 
of  the  head  is  a  smooth,  articular  surface  (circumferentia  articularis),  broad  inter- 
nally where  it  articulates  with  the  lesser  sigmoid  cavity  of  the  ulna;  narrow  in 
the  rest  of  its  circumference,  where  it  rotates  within  the  orbicular  ligament.  It 
is  coated  with  cartilage  in  the  recent  state.  The  head  is  supported  on  a  round, 
smooth,  and  constricted  portion  of  bone,  called  the  neck  (collum  radii),  which 
presents,  behind,  a  slight  ridge,  for  the  attachment  of  part  of  the  Supinator  brevis. 
Beneath  the  neck,  at  the  inner  and  front  aspect  of  the  bone,  is  a  rough  eminence, 
the  bicipital  tuberosity  (tuberositas  radii).  Its  surface  is  divided  into  two  parts  by 
a  vertical  line — a  posterior,  rough  portion,  for  the  insertion  of  the  tendon  of  the 
Biceps  muscle;  and  an  anterior,  smooth  portion,  on  which  a  bursa  is  interposed 
between  the  tendon  and  the  bone. 

The  Shaft  (corpus  radii). — The  shaft  of  the  bone  is  prismoid  in  form,  narrower 
above  than  below,  and  slightly  curved,  so  as  to  be  convex  outward.  It  presents 
three  surfaces,  separated  by  three  borders. 

Anterior  or  Palmar  Border  (margo  volaris) . — The  anterior  border  extends  from 
the  lower  part  of  the  tuberosity  above  to  the  anterior  part  of  the  base  of  the  styloid 
process  below.  It  separates  the  anterior  from  the  external  surface.  Its  upper 
third  is  very  prominent;  and  from  its  oblique  direction,  downward  and  outward, 
has  received  the  name  of  the  oblique  line  of  the  radius.  It  gives  attachment  exter- 
nally to  the  Supinator  brevis,  internally  to  the  Flexor  longus  pollicis,  and  between 
these  to  the  Flexor  sublimis  digitorum.  The  middle  third  of  the  anterior  border 
is  indistinct  and  rounded.  Its  lower  fourth  is  sharp,  prominent,  affords  attach- 
ment to  the  Pronator  quadratus  and  to  the  posterior  annular  ligament  of  the  wrist, 
and  terminates  in  a  small  tubercle  at  the  base  of  the  styloid  process,  into  which 
is  inserted  the  tendon  of  the  Supinator  longus. 

Posterior  or  Dorsal  Border  (margo  dorsalis). — The  posterior  border  commences 
above  at  the  back  part  of  the  neck  of  the  radius,  and  terminates  below  at  the 


THE  RADIUS  193 

posterior  part  of  the  base  of  the  styloid  process;  it  separates  the  posterior  from 
t IK-  external  surface.  It  is  indistinct  above  and  below,  but  well  marked  in  the 
middle  third  of  the  bone. 

Internal  or  Interosseous  Border  (crista  interossea). — The  internal  or  interosseous 
border  commences  above  at  the  back  part  of  the  tuberosity,  where  it  is  rounded 
and  indistinct,  becomes  sharp  and  prominent  as  it  descends,  and  at  its  lower  part 
divides  into  two  ridges,  which  descend  to  the  anterior  and  posterior  margins  of 
the  sigmoid  cavity.  This  border  separates  the  anterior  from  the  posterior  sur- 
face, and  has  the  interosseous  membrane  attached  to  it  throughout  the  greater 
part  of  its  extent. 

Anterior  or  Palmar  or  Flexor  Surface  (fades  volaris). — The  anterior  surface  is 
concave  for  its  upper  three-fourths,  and  gives  attachment  to  the  Flexor  longus 
pollicis  muscle;  it  is  broad  and  flat  for  its  lower  fourth,  and  gives  attachment  to 
the  Pronator  quadratus.  A  prominent  ridge  limits  the  attachment  of  the  Pro- 
nator  quadratus  below,  and  between  this  and  the  inferior  border  is  a  triangular 
rough  surface  for  the  attachment  of  the  anterior  ligament  of  the  wrist-joint.  At 
the  junction  of  the  upper  and  middle  third  of  this  surface  is  the  nutrient  foramen 
(foramen  nutridum),  the  opening  of  the  nutrient  canal  (canalis  nutridus),  which 
is  directed  obliquely  upward  (proximally) . 

Posterior  or  Dorsal  or  Extensor  Surface  (fades  dorsalis). — The  posterior  surface 
is  rounded,  convex,  and  smooth  in  the  upper  third  of  its  extent,  and  covered  by 
the  Supinator  brevis  muscle.  Its  middle  third  is  broad,  slightly  concave,  and  gives 
attachment  to  the  Extensor  ossis  metacarpi  pollicis  above,  the  Extensor  brevis  pol- 
licis below.  Its  lower  third  is  broad,  convex,  and  covered  by  the  tendons  of  the 
muscles,  which  subsequently  run  in  the  grooves  on  the  lower  end  of  the  bone. 

External  Surface  (fades  lateralis) . — The  external  surface  is  rounded  and  convex 
throughout  its  entire  extent.  Its  upper  third  gives  attachment  to  the  Supinator 
brevis  muscle.  About  its  centre  is  seen  a  rough  ridge,  for  the  insertion  of  the  Pro- 
nator radii  teres  muscle.  Its  lower  part  is  narrow,  and  covered  by  the  tendons 
of  the  Extensor  ossis  metacarpi  pollicis  and  Extensor  brevis  pollicis  muscles. 

Lower  Extremity. — The  lower  extremity  of  the  radius  is  large,  of  quadri- 
lateral form,  and  provided  with  two  articular  surfaces — one  at  the  extremity,  for 
articulation  with  the  carpus,  and  one  at  the  inner  side  of  the  bone,  for  articulation 
with  the  ulna.  The  carpal  articular  surface  (fades  articularis  carped)  is  of  tri- 
angular form,  concave,  smooth,  and  divided  by  a  slight  antero-posterior  ridge 
into  two  parts.  Of  these,  the  external  is  of  a  triangular  form,  and  articulates  with 
the  scaphoid  bone;  the  inner  is  quadrilateral  and  articulates  with  the  semilunar 
bone.  The  articular  surface  for  the  head  of  the  ulna  is  called  the  sigmoid  cavity 
of  the  radius  (indsura  ulnaris};  it  is  narrow,  concave,  smooth,  and  articulates 
with  the  head  of  the  ulna.  The  circumference  of  this  end  of  the  bone  presents 
three  surfaces — an  anterior,  external,  and  posterior.  The  anterior  surface,  rough 
and  irregular,  affords  attachment  to  the  anterior  ligament  of  the  wrist-joint.  The 
external  surface  is  prolonged  obliquely  downward  into  a  strong,  conical  projec- 
tion, the  styloid  process  (processus  styloideus),  which  gives  attachment  by  its  base 
to  the  tendon  of  the  Supinator  longus,  and  by  its  apex  to  the  external  lateral  liga- 
ment of  the  wrist-joint.  The  outer  surface  of  this  process  is  marked  by  a  flat 
groove,  which  runs  obliquely  downward  and  forward,  and  gives  passage  to  the 
tendons  of  the  Extensor  ossis  metacarpi  pollicis  and  the  Extensor  brevis  pollicis. 
The  posterior  surface  is  convex,  affords  attachment  to  the  posterior  ligament  of 
the  wrist,  and  is  marked  by  three  grooves.  Proceeding  from  without  inward,  the 
first  groove  is  broad  but  shallow,  and  subdivided  into  two  by  a  slightly  elevated 
ridge:  the  outer  of  these  two  transmits  the  tendon  of  the  Extensor  carpi  radialis 
longior,  the  inner  the  tendon  of  the  Extensor  carpi  radialis  brevior.  The  second, 

13 


194 


THE  SKELETON 


Head. 
Appears  «<j^S^^\  Unites  with  shaft 


5th  year. 


about  puberty. 


which  is  near  the  centre  of  the  bone,  is  a  deep  but  narrow  groove,  bounded  on  its 
outer  side  by  a  sharply-defined  ridge;  it  is  directed  obliquely  from  above,  down- 
ward and  outward,  and  transmits  the  tendon  of  the  Extensor  longus  pollicis. 
The  third,  lying  most  internally,  is  a  broad  groove,  for  the  passage  of  the  tendons 
of  the  Extensor  indicis  and  Extensor  communis  digitorum. 
Structure. — Similar  to  that  of  the  other  long  bones. 

Development  (Fig.  137). — By  three  centres:  one  for  the  shaft  and  one  for  each 
extremity.  That  for  the  shaft  makes  its  appearance  near  the  centre  of  the  bone, 

about  the  eighth  week  of  foetal  life.  About 
the  end  of  the  second  year  ossification  com- 
mences in  the  lower  epiphysis,  and  about  the 
fifth  year  in  the  upper  end  At  the  age  of 
seventeen  or  eighteen  the  upper  epiphysis  be- 
comes joined  to  the  shaft,  the  lower  epiphysis 
becoming  united  about  the  twentieth  year. 

Articulation. — With  four  bones :  thehumerus, 
ulna,  scaphoid,  and  semilunar. 

Attachment  of  Muscles. — To  nine:  to  the 
tuberosity,  the  Biceps,  to  the  oblique  ridge,  the 
Supinator  brevis,  Flexor  sublimis  digitorum, 
and  Flexor  longus  pollicis:  to  the  shaft  (its 
anterior  surface),  the  Flexor  longus  pollicis 
and  Pronator  quadratus;  (its  posterior  surface), 
the  Extensor  ossis  metacarpi  pollicis  and  Exten- 
sor brevis  pollicis;  (its  outer  surface),  the  Pro- 
nator radii  teres;  and  to  the  styloid  process, 
the  Supinator  longus. 

*¥"?  S?  ataft       Surface  Form.— Just  below  and  a  little  in  front  of 
about  zOth  year.     .,  ,     .  ,  , ,  ,  ,  ,  , 

the  posterior  surtace  of  the  external  condyle  a  part  ot 

the  head  of  the  radius  may  be  felt,  covered  by  the 
orbicular  and  external  lateral  ligaments.  There  is  in 
this  situation  a  little  dimple  in  the  skin,  which  is  most 
visible  when  the  arm  is  extended,,  and  which  marks  the 

position  of  the  head  of  the  bone.  If  the  finger  is  placed  on  this  dimple  and  the  forearm  pro- 
nated  and  supinated,  the  head  of  the  bone  will  be  distinctly  perceived  rotating  in  the  lesser 
sigmoid  cavity.  The  upper  half  of  the  shaft  of  the  radius  cannot  be  felt,  as  it  is  surrounded  by 
the  fleshy  bellies  of  the  muscles  arising  from  the  external  condyle.  The  lower  half  of  the  shaft 
can  be  readily  examined,  though  covered  by  tendons  and  muscles  and  not  strictly  subcutaneous. 
If  traced  downward,  the  shaft  will  be  felt  to  terminate  in  a  lozenge-shaped,  convex  surface 
on  the  outer  side  of  the  base  of  the  styloid  process.  This  is  the  only  subcutaneous  part  of  the 
bone,  and  from  its  lower  extremity  the  apex  of  the  styloid  process  will  be  felt  bending  inward 
toward  the  wrist.  About  the  middle  of  the  posterior  aspect  of  the  lower  extremity  of  the  bone 
is  a  well-marked  ridge,  best  perceived  when  the  hand  is  slightly  flexed  on  the  wrist.  It  forms 
the  outer  boundary  of  the  oblique  groove  on  the  posterior  surface  of  the  bone,  through  which 
the  tendon  of  the  Extensor  longus  pollicis  runs,  and  serves  to  keep  that  tendon  in  place. 

Surgical  Anatomy  of  the  Radius  and  Ulna. — The  two  bones  of  the  forearm  are  more  often 
broken  together  than  is  either  the  radius  or  ulna  separately.  It  is  therefore  convenient  to  consider 
fractures  of  both  bones  in  the  first  instance,  and  subsequently  to  mention  the  principal  fractures 
which  take  place  in  each  bone  individually.  These  fractures  may  be  produced  by  either  direct 
or  indirect  violence,  though  more  commonly  by  direct  violence.  When  indirect  force  is  applied 
to  the  forearm  the  radius  generally  alone  gives  way,  though  both  bones  may  suffer.  The 
fracture  from  indirect  force  generally  takes  place  somewhere  about  the  middle  of  the  bones; 
fracture  from  direct  violence  may  occur  at  any  part,  more  often,  however,  in  the  lower  half  of 
the  bone.  The  fracture  is  usually  transverse,  but  may  be  more  or  less  oblique.  A  point  of 
interest  in  connection  with  these  fractures  is  the  tendency  that  there  is  for  the  two  bones  to  unite 
across  the  interosseous  membrane;  the  limb  should  therefore  be  put  up  in  a  position  midway 
between  supination  and  pronation,  which  is  not  only  the  most  comfortable  position,  but  also  sep- 
arates the  bones  most  widely  from  each  other,  and  therefore  diminishes  the  risk  of  the  bones 


Appears  at 
2d  year. 


Lower  extremity. 


FIG.  137. — Plan  of  the  development  of  the 
radius.     By  three  centres. 


THE    CARPUS  195 

becoming  united  across  the  interosseous  membrane.  The  splints,  anterior  and  posterior,  which 
are  applied  in  these  cases  should  be  rather  wider  than  the  limb,  so  as  to  prevent  any  lateral 
pressure  on  the  bones.  In  these  cases  there  is  a  greater  liability  to  gangrene  from  the  pressure 
of  the  splints  than  in  other  parts  of  the  body.  This  is  no  doubt  due  principally  to  two  causes: 
(1)  the  flexion  of  the  forearm  compressing  to  a  certain  extent  the  brachial  artery  and  retarding 
the  flow  of  blood  to  the  limb;  and  (2)  the  superficial  position  of  the  two  main  arteries  of  the 
forearm  in  a  part  of  their  course,  and  their  liability  to  be  compressed  by  the  splints.  The  special 
fractures  of  the  ulna  are  —  (1)  Fracture  of  the  olecranon.  This  may  be  caused  by  direct  violence, 
falls  on  the  elbow,  with  the  forearm  flexed,  or  by  muscular  action  by  the  sudden  contraction  of 
the  triceps  The  most  common  place  for  the  fracture  to  occur  is  at  the  constricted  portion 
where  the  olecranon  joins  the  shaft  of  the  bone,  and  the  fracture  may  be  either  transverse  or 
oblique;  but  any  part  may  be  broken,  even  a  thin  shell  may  be  torn  off.  Fractures  from  direct 
violence  are  occasionally  comminuted.  The  displacement  is  sometimes  very  slight,  owing  to  the 
fibrous  structures  around  the  process  not  being  torn.  (2)  Fracture  of  the  coronoid  process  some- 
times occurs  as  a  complication  of  dislocation  backward  of  the  bones  of  the  forearm,  but  it  is 
doubtful  if  it  ever  occurs  as  an  uncomplicated  injury.  (3)  Fractures  of  the  shaft  of  the  ulna 
may  occur  at  any  part,  but  usually  takes  place  at  the  middle  of  the  bone  or  a  little  below  it. 
They  are  almost  always  the  result  of  direct  violence.  (4)  The  styloid  process  may  be  knocked 
off  by  direct  violence.  Fractures  of  the  radius  consist  of  —  (1)  Fracture  of  the  head  of  the  bone; 
this  generally  occurs  in  conjunction  with  some  other  lesion,  but  may  occur  as  an  uncomplicated 
injury.  (2)  Fracture  of  the  neck  may  also  take  place,  but  is  generally  complicated  with  other 
injury.  (3)  Fractures  of  the  shaft  of  the  radius  are  very  common,  and  may  take  place  at  any 
part  of  the  bone.  They  may  take  place  from  either  direct  or  indirect  violence.  In  fractures  of  the 
upper  third  of  the  shaft  of  the  bone,  that  is  to  say,  above  the  insertion  of  the  Pronator  radii  teres, 
the  displacement  is  very  great.  The  upper  fragment  is  strongly  supinated  by  the  Biceps  and  Supi- 
nator  brevis,  and  flexed  by  the  Biceps,  while  the  lower  fragment  is  pronated  and  drawn  toward 
the  ulna  by  the  two  pronators  If  such  a  fracture  is  put  up  in  the  ordinary  position,  midway 
between  supination  and  pronation,  the  fracture  will  unite  with  the  upper  fragment  in  a  position 
of  supination,  and  the  lower  one  in  the  mid  -position,  and  thus  considerable  impairment  of  the 
movements  of  the  hand  will  result.  The  limb  should  be  put  up  with  the  forearm  supinated.  (4) 
The  most  important  fracture  of  the  radius  is  that  of  the  lower  end  (Colics'  's  fracture).  The 
fracture  is  transverse,  and  generally  takes  place  about  an  inch  from  the  lower  extremity.  It  is 
caused  by  falls  on  the  palm  of  the  hand,  and  is  an  injury  of  advanced  life,  occurring  more  fre- 
quently in  the  female  than  the  male.  In  consequence  of  the  manner  in  which  the  fracture  is 
caused,  the  upper  fragment  becomes  driven  into  the  lower,  and  impaction  is  the  result;  or  else 
the  lower  fragment  becomes  split  up  into  two  or  more  pieces,  so  that  no  fixation  occurs.  Sepa- 
ration of  the  lower  epiphysis  of  the  radius  may  take  place  in  the  young.  This  injury  and  Colles's 
fracture  may  be  distinguished  from  other  injuries  in  this  neighborhood  —  especially  dislocation, 
with  which  it  is  liable  to  be  confounded—  by  observing  the  relative  positions  of  the  styloid 
processes  of  the  ulna  and  radius.  In  the  natural  condition  of  parts,  with  the  arm  hanging  by  the 
side,  the  styloid  process  of  the  radius  is  on  a  lower  level  than  that  of  the  ulna;  that  is  to  say, 
learer  the  ground.  After  fracture  or  separation  of  the  epiphysis  this  process  is  on  the  same  or 
a  higher  level  than  that  of  the  ulna,  whereas  it  would  be  unaltered  in  position  in  dislocation. 

THE  HAND. 

The  skeleton  of  the  hand  is  subdivided  into  three  segments  —  the  carpus  or  wrist 
ines  ;  the  metacarpus  or  bones  of  the  palm  ;  and  the  phalanges  or  bones  of  the  digits  . 

The  Carpus  (Ossa  Carpi)  (Figs.  138,  139). 


The  bones  of  the  carpus  (xapxoz,  the  wrist),  eight  in  number,  are  arranged 
in  two  rows.  Those  of  the  upper  row,  enumerated  from  the  radial  to  the  ulnar 
side,  are  the  scaphoid,  semilunar,  cuneiform,  and  pisiform;  those  of  the  lower 
row,  enumerated  in  the  same  order,  are  the  trapezium,  trapezoid,  os  magnum, 
and  unciform. 

Common  Characters  of  the  Carpal  Bones.  —  Each  bone  (excepting  the  pisiform) 
presents  six  surfaces.  Of  these  the  anterior,  palmar,  or  volar,  and  the  posterior  or 
dorsal  are  rough  for  ligamentous  attachment,  the  dorsal  surface  being  the  broader, 
except  in  the  scaphoid  and  semilunar.  The  superior  or  proximal  and  inferior  or 
distal  are  articular,  the  superior  generally  convex,  the  inferior  concave;  and  the 


196 


THE  SKELETON 


internal  and  external  are  also  articular  when  in  contact  with  contiguous  bones, 
otherwise  rough  and  tubercular.     The  structure  in  all  is  similar,  consisting  of 


Carpus. 


EXTENSOR    CARPI 
RADIALIS    LONQI 


EXTENSOR    CARPI 
RADIALIS    BREVIOR. 


EXTENSOR    BR 

POLLIC1S. 


EXTENSOR    LONGU 
PO1.LICIS. 


EXTENSOR    DIGITORUM 

COMMUNIS  and 

EXTENSOR    INDICIS. 


Metacarpus. 


FIG.  138. — Bones  of  the  left  hand.     Dorsal  surface. 


cancelious  tissue  enclosed  in  a  layer  of  compact  bone.    Each  bone  is  also  developed 
from  a  single  centre  of  ossification. 


THE    CARPUS 


197 


Bones  of  the  Upper  Row. 

Scaphoid  or  Navicular  Bone  (os  namculare  manus,  the  boat-like  bone]  (Fig. 
140). — The  scaphoid  (axdyrj,  a  boat,  ecdoc; ,  like)  is  the  largest  bone  of  the  first 


Carpus. 


Groove  for  tendon  of 


FLEXOR    CARPI     ULNARIS 


FLEXOR     BREVIS    MINIMI     DlGITI. 


FLEXOR    OSSIS    METACARPI 
MINIMI    OIQITI. 


FLEXOR    OSSIS 
METACARPI     POLLICIS. 

LEXOR    BREVIS    POLL. 
EXTEN.   OS.   METACARP.   POLL. 
EXTENSOR    OSSIS 


Metacarpus 


FLEXOR 

DIGITORUM 
PROFUNDUS. 


FIG.  139. — Bones  of  the  left  hand.     Palmar  surface. 


Sesamoid 
bones. 


ABDUCTOR 
POLLICIS. 


row.     It  has  received  its  name  from  its  fancied  resemblance  to  a  boat,  being 
broad  at  one  end  and  narrowed  like  a  prow  at  the  opposite.     It  is  situated  at 


198  .  ,  THE  SKELETON 

the  upper  and  outer  part  of  the  carpus,  its  long  axis  being  from  above  down- 
ward, outward,  and  forward. 

Surfaces. — The  superior  surface  is  convex,  smooth,  of  triangular  shape,  and 

articulates  with  the  lower  end  of  the  radius.    The  inferior  surface,  directed 


For  radius. 
Tuberosity. 


For  trapezium.^    

\  For  os  magnum. 

For  trapezoid. 

FIG.  140.— The  left  scaphoid. 

downward,  outward,  and  backward,  is  smooth,  convex,  also  triangular,  and 
divided  by  a  slight  ridge  into  two  parts,  the  external  of  which  articulates  with 
the  trapezium,  the  inner  with'  the  trapezoid.  The  posterior  or  dorsal  surface 
presents  a  narrow,  rough  groove  which  runs  the  entire  length  of  the  bone  and 
serves  for  the  attachment  of  ligaments.  The  anterior  or  palmar  surface  is  concave 
above,  and  elevated  at  its  lower  and  outer  part  into  a  prominent  rounded  tuber- 
osity  (tuberculum  ossis  navicularis) ,  which  projects  forward  from  the  front  of  the 
carpus  and  gives  attachment  to  the  anterior  annular  ligament  of  the  wrist  and 
sometimes  a  few  fibres  of  the  Abductor  pollicis.  The  external  surface  is  rough 
and  narrow,  and  gives  attachment  to  the  external  lateral  ligament  of  the  wrist. 
The  internal  surface  presents  two  articular  facets :  of  these,  the  superior  or  smaller 
one  is  flattened,  of  semilunar  form,  and  articulates  with  the  semilunar;  the  inferior 
or  larger  is  concave,  forming,  with  the  semilunar  bone,  a  concavity  for  the  head 
of  the  os  magnum. 

To  ascertain  to  which  side  the  bone  belongs,  hold  it  with  the  superior  or  radial 
convex,  articular  surface  upward,  and  the  posterior  surface — i.  e.,  the  narrow, 
non-articular,  grooved  surface — toward  you.  The  tubercle  on  the  outer  surface 
points  to  the  side  to  which  the  bone  belongs.1 

Articulations. — With  five  bones:  the  radius  above,  trapezium  and  trapezoid 
below,  os  magnum  and  semilunar  internally. 

Attachment  of  Muscles. — Occasionally  a  few  fibres  of  the  Abductor  pollicis. 

Semilunar  (os  lunatum)  (Fig.  141). — The  semilunar  (semi,  half;  luna,  moon) 
bone  may  be  distinguished  by  its  deep  concavity  and  crescentic  outline.  It  is 

For  cuneiform.  For  radius. 


For 

For  unciform.    \  scaphoid. 

For  os  magnum. 
FIG.  141. — The  left  semilunar. 

situated  in  the  centre  of  the  upper  row  of  the  carpus,  between  the  scaphoid  and 
cuneiform. 

Surfaces. — The  superior  surface,  convex,  smooth,  and  bounded  by  four  edges, 
articulates  with  the  radius.  The  inferior  surface  is  deeply  concave,  and  of  greater 

1  In  these  directions  each  bone  is  supposed  to  be  placed  in  its  natural  position — that  is,  such  a  position  as  it 
would  occupy  when  the  arm  is  hanging  by  the  side,  the  forearm  in  a  position  of  supination,  the  thumb  being 
directed  outward,  and  the  palm  of  the  hand  looking  forward. — ED.  of  15th  English  Edition. 


199 


For  semilunar. 
For  pisiform. 


For  unciform. 

FIG.  142.— The  left  cunei- 
form. 


extent  from  before  backward  than  transversely :  it  articulates  with  the  head  of  the 
os  magnum  and  by  a  long,  narrow,  facet  (separated  by  a  ridge  from  the  general 
surface)  with  the  unciform  bone.  The  anterior  or  palmar  and  posterior  or  dorsal 
surfaces  are  rough,  for  the  attachment  of  ligaments,  the  former  being  the  broader 
and  of  a  somewhat  rounded  form.  The  external  surface  presents  a  narrow,  flat- 
tened, semilunar  facet  for  articulation  with  the  scaphoid.  The  internal  surface 
is  marked  by  a  smooth,  quadrilateral  facet,  for  articulation  with  the  cuneiform. 

Hold  it  with  the  convex  articular  surface  for  the  radius  upward,  and  the  nar- 
rowest non-articular  surface  toward  you.  The  semilunar  facet  for  the  scaphoid 
will  be  on  the  side  to  which  the  bone  belongs. 

Articulations. — With  five  bones:  the  radius  above,  os  magnum  and  unciform 
below,  scaphoid  and  cuneiform  on  either  side. 

Cuneiform  (os  triquetrum,  the  wedge-shaped  bone)  (Fig.  142). — The  cuneiform 
(cuneus,  a   wedge;   forma,   likeness)   may  be    distinguished    by   its    pyramidal 
shape,  and  by  its  having  an  oval,  isolated  facet  for  articu- 
lation with  the  pisiform  bone.    It  is  situated  at  the  upper 
and  inner  side  of  the  carpus. 

Surfaces. — The  superior  surface  presents  an  internal,  rough, 
non-articular  portion,  and  an  external  or  articular  portion, 
which  is  convex,  smooth,  and  articulates  with  the  triangular 
interarticular  fibro-cartilage  of  the  wrist.  The  inferior  sur- 
face, directed  outward,  is  concave,  sinuously  curved,  and 
smooth  for  articulation  with  the  unciform.  The  posterior 
or  dorsal  surface  is  rough,  for  the  attachment  of  ligaments.  The  anterior  or 
palmar  surface  presents,  at  its  inner  side,  an  oval  facet,  for  articulation  with 
the  pisiform;  and  is  rough  externally,  for  ligamentous  attachment.  The  exter- 
nal surface,  the  base  of  the  pyramid,  is  marked  by  a  flat,  quadrilateral,  smooth 
facet,  for  articulation  with  the  semilunar.  The  internal  surface,  the  summit  of 
the  pyramid,  is  pointed  and  roughened,  for  the  attachment^  the  internal  lateral 
ligament  of  the  wrist. 

Hold  the  bone  with  the  surface  supporting  the  pisiform  facet  away  from  you, 
and  the  concavo-convex  surface  for  the  unciform  downward.  The  base  of  the 
wedge  (i.  e.,  the  broad  end  of  the  bone)  will  be  on  the  side  to  which  it  belongs. 

Articulations. — With  three  bones:  the  semilunar  externally,  the  pisiform  in 
front,  the  unciform  below;  and  with  the  triangular,  interarticular  fibro-cartilage 
which  separates  it  from  the  lower  end  of  the  ulna. 

Pisiform  (os  pisifarme)  (Fig.  143). — The  pisiform  (pisum,  a  pea;  forma,  like- 
ness) may  be  known  by  its  small  size  and  by  its  presenting  a  single  articular 
facet.     It  is  situated  on  a  plane  anterior  to  the  other  bones  of 
the  carpus;  it  is   spheroidal  in  form,  with  its  long  diameter 
directed  vertically. 

Surfaces. — Its  posterior  surface  is  a  smooth,  oval  facet,  for 
articulation  with  the  cuneiform.  This  facet  approaches  the 
superior,  but  not  the  inferior  border  of  the  bone.  The  anterior 
or  palmar  surface  is  rounded  and  rough,  and  gives  attachment 
to  the  anterior  annular  ligament  and  to  the  Flexor  carpi 
ulnaris  and  Abductor  minimi  digiti  muscles.  The  outer  and  inner  surfaces  are 
ilso  rough,  the  former  being  concave,  the  latter  usually  convex. 

Hold  the  bone  with  the  posterior  surface — that  which  presents  the  articular 
facet — toward  you,  in  such  a  manner  that  the  faceted  portion  of  the  surface  is 
ippermost.  The  outer,  concave  surface  will  point  to  the  side  to  which  it  belongs. 

Articulations. — With  one  bone,  the  cuneiform. 

Attachment  of  Muscles. — To  two:    the    Flexor  carpi    ulnaris  and    Abductor 
linimi  digiti;  and  to  the  anterior  annular  ligament. 


For 
cuneiform. 


FIG.  143.— The  left 
pisiform. 


200  THE   SKELETON 

Bones  of  the  Lower  Row.  \ 

Trapezium  (os  multangulum  majus)  (Fig.  144). — The  trapezium  (rpd^s^a,  a 
table)  is  of  very  irregular  form.    It  may  be  distinguished  by  a  deep  groove,  for 


For  trapezoid.  _ L        Ridge 


Groove.  For  scaphoid. 

For  trapezoid. 


For  3d 
metacarpal.' 

For  1st  metacarpal.  For2d  metacarpal. 

FIG.  144. — The  left  trapezium. 

the  tendon  of  the  Flexor  carpi  radialis  muscle.  It  is  situated  at  the  external  and 
inferior  part  of  the  carpus  between  the  scaphoid  and  first  metacarpal  bone. 

Surfaces. — The  superior  surface,  concave  and  smooth,  is  directed  upward  and 
inward,  and  articulates  with  the  scaphoid.  The  inferior  surface,  directed  down- 
ward and  inward,  is  oval,  concave  from  side  to  side,  convex  from  before  backward, 
so  as  to  form  a  saddle-shaped  surface,  for  articulation  with  the  base  of  the  first 
metacarpal  bone.  The  anterior  or  palmar  surface  is  narrow  and  rough.  At  its 
upper  part  is  a  deep  groove  running  from  above  obliquely  downward  and  inward ; 
it  transmits  the  tendon  of  the  Flexor  carpi  radialis,  and  is  bounded  externally 
by  a  prominent  ridge,  the  oblique  ridge  of  the  trapezium  (tuberculum  ossis  mul- 
tanguli  majoris).  This  surface  gives  attachment  to  the  Abductor  pollicis,  Flexor 
ossis  metacarpi  pollicis,  and  Flexor  brevis  pollicis  muscles,  and  the  anterior 
annular  ligament.  The  posterior  or  dorsal  surface  is  rough.  The  external  sur- 
face is  also  broad  and  rough,  for  the  attachment  of  ligaments.  The  internal 
surface  presents  two  articular  facets:  the  upper  one,  large  and  concave,  articu- 
lates with  the  trape»oid;  the  lower  one,  small  and  oval,  with  the  base  of  the 
second  metacarpal  bone. 

Hold  the  bone  with  the  saddle-shaped  surface  downward  and  the  grooved 
surface  away  from  you.  The  prominent,  rough,  non-articular  surface  points  to 
the  side  to  which  the  bone  belongs. 

Articulations. — With  four  bones:  the  scaphoid  above,  the  trapezoid  and  second 
metacarpal  bones  internally,  the  first  metacarpal  below. 

Attachment  of  Muscles. — Abductor  pollicis,  Flexor  ossis  metacarpi  pollicis,  and 
part  of  the  Flexor  brevis  pollicis. 

Trapezoid  (05  multangulum  minus)  (Fig.  145). — The  trapezoid  is  the  smallest 
bone  in  the  second  row.  It  may  be  known  by  its  wedge-shaped  form,  the  broad 

Anterior  surface. 
For  scaphoid.  I    For  trapezium. 


For  os  magnum. 
Post,  surface. 

For  2d  metacarpal. 

FIG.  145. — The  left  trapezoid. 


end  of  the  wedge  forming  the  dorsal,  the  narrow  end  the  palmar,  surface,  and  by 
its  having  four  articular  surfaces  touching  each  other  and  separated  by  sharp 
edges. 

Surfaces. — The  superior  surface,  quadrilateral  in  form,  smooth,  and  slightly  con- 
cave, articulates  with  the  scaphoid.    The  inferior  surface  articulates  with  the  upper 


THE   CARPUS  201 

end  of  the  second  metacarpal  bone ;  it  is  convex  from  side  to  side,  concave  from  before 
backward,  and  subdivided  by  an  elevated  ridge  into  two  unequal  lateral  facets. 
The  posterior  or  dorsal  and  anterior  or  palmar  surfaces  are  rough,  for  the  attach- 
ment of  ligaments,  the  former  being  the  larger  of  the  two.  The  external  surface, 
convex  and  smooth,  articulates  with  the  trapezium.  The  internal  surface  is  con- 
cave and  smooth  in  front,  for  articulation  with  the  os  magnum;  rough  behind, 
for  the  attachment  of  an  interosseous  ligament. 

Hold  the  bone  with  the  larger,  non-articular  surface  toward  you,  and  the 
smooth,  quadrilateral  articular  surface  upward.  The  convex  articular  surface 
will  point  to  the  side  to  which  the  bone  belongs.1 

Articulations. — With  four  bones:  the  scaphoid  above,  second  metacarpal  bone 
below,  trapezium  externally,  os  magnum  internally. 

Os  Magnum  (os  capitatum)  (Fig.  146). — The  os  magnum  is  the  largest  bone 
of  the  carpus,  and  occupies  the  centre  of  the  wrist.  It  presents,  above,  a  rounded 

_For  semilunar.  For  semilunar. 

For  scaphoid.* 


For  unciform. 

For  3d 
metacarpal.-^—j^^H    «A 

^as^*jjm^  For  4th 

/          x^^^P  metacarpal. 

For  3d    For  4th  metacarpal. 
metacarpal. 

FIG.  146. — The  left  os  magnum. 

portion  or  head,  which  is  received  into  the  concavity  formed  by  the  scaphoid  and 
semilunar  bones;  a  constricted  portion  or  neck;  and,  below,  the  body. 

Surfaces. — The  superior  surface  is  rounded,  smooth,  and  articulates  with  the  semi- 
lunar.  The  inferior  surface  is  divided  by  two  ridges  into  three  facets  for  articulation 
with  the  second,  third,  and  fourth  metacarpal  bones,  that  for  the  third  (the  middle 
facet)  being  the  largest  of  the  three.  The  posterior  or  dorsal  surface  is  broad  and 
rough;  the  anterior  or  palmar,  narrow,  rounded,  and  also  rough,  for  the  attachment 
of  ligaments  and  a  part  of  the  Adductor  obliquus  pollicis.  The  external  surface 
articulates  with  the  trapezoid  by  a  small  facet  at  its  anterior  inferior  angle,  behind 
which  is  a  rough  depression  for  the  attachment  of  an  interosseous  ligament. 
Above  this  is  a  deep  and  rough  groove,  which  forms  part  of  the  neck  and  serves 
for  the  attachment  of  ligaments,  bounded  superiorly  by  a  smooth,  convex  surface, 
for  articulation  with  the  scaphoid.  The  internal  surface  articulates  with  the  unci- 
form by  a  smooth,  concave,  oblong  facet  which  occupies  its  posterior  and  superior 
parts,  and  is  rough  in  front,  for  the  attachment  of  an  interosseous  ligament. 

Hold  the  bone  with  the  broader,  non-articular  surface  toward  you,  and  the 
head  upward.  The  small,  articular  facet  at  the  anterior  inferior  angle  of  the 
external  surface  will  point  to  the  side  to  which  the  bone  belongs. 

Articulations. — With  seven  bones:  the  scaphoid  and  semilunar  above;  the 
second,  third,  and  fourth  metacarpal  below;  the  trapezoid  on  the  radial  side;  and 
the  unciform  on  the  ulnar  side. 

Attachment  of  Muscles. — Part  of  the  Adductor  obliquus  pollicis. 

Unciform  (os  hamatum)  (Fig.  147). — The  unciform  or  hook  bone  (uncus,  a  hook; 
forma,  likeness)  may  be  readily  distinguished  by  its  wedge-shaped  form  and  the 
hook-like  process  that  projects  from  its  palmar  surface.  It  is  situated  at  the  inner 

1  Occasionally  in  a  badly  marked  bone  there  is  some  difficulty  in  ascertaining  to  which  side  the  bone  belongs; 
the  following  method  will  sometimes  be  found  useful:  Hold  the  bone  with  its  broader,  non-articular  surface 
upward,  so  that  its  sloping  border  i.s  directed  toward  you.  The  border  will  slope  to  the  side  to  which  the  bone 
belongs. — ED.  of  15th  English  Edition. 


202  THE  SKELETON 

and  lower  angle  of  the  carpus,  with  its  base  downward,  resting  on  the  two  inner 
metacarpal  bones,  and  its  apex  directed  upward  and  outward. 

Surfaces. — The  superior  surface,  the   apex  of  the  wedge,  is   narrow,  convex, 
smooth,  and  articulates  with  the  semilunar.    The  inferior  surface  articulates  with 

For  semilunar. 

For  os  magnum. 


'  *  *•     -For  cuneiform. 


For  fourth  meta 
carpal. 


Unciform  process.  ^*V    JetLarpal. 

FIG.  147. — The  left  unciform. 

the  fourth  and  fifth  metacarpal  bones,  the  concave  surface  for  each  being  sepa- 
rated by  a  ridge  which  runs  from  before  backward.  The  posterior  or  dorsal 
surface  is  triangular  and  rough,  for  ligamentous  attachment.  The  anterior  or 
palmar  surface  presents,  at  its  lower  and  inner  side,  a  curved,  hook-like  pro- 
cess of  bone,  the  unciform  process  (hamulus  ossis  hamati),  directed  from  the 
palmar  surface  forward  and  outward.  It  gives  attachment  by  its  apex  to  the 
annular  ligament  and  Flexor  carpi  ulnaris;  by  its  inner  surface  to  the  Flexor  brevis 
minimi  digiti  and  the  Opponens  minimi  digiti;  and  is  grooved  on  its  outer 
side,  for  the  passage  of  the  Flexor  tendons  into  the  palm  of  the  hand.  This  is 
one  of  the  four  eminences  on  the  front  of  the  carpus  to  which  the  anterior 
annular  ligament  is  attached,  the  others  being  the  pisiform  internally,  the  oblique 
ridge  of  the  trapezium  and  the  tuberosity  of  the  scaphoid  externally.  The  internal 
surface  articulates  with  the  cuneiform  by  an  oblong  facet  cut  obliquely  from  above, 
downward  and  inward.  The  external  surface  articulates  with  the  os  magnum  by 
its  upper  and  posterior  part,  the  remaining  portion  being  rough,  for  the  attach- 
ment of  ligaments. 

Hold  the  bone  with  the  hooked  process  away  from  you,  and  the  articular  sur- 
face, divided  into  two  parts,  for  the  metacarpal  bones,  downward  The  concavity 
of  the  process  will  be  on  the  side  to  which  the  bone  belongs. 

Articulations. — With  five  bones:  the  semilunar  above,  the  fourth  and  fifth 
metacarpal  below,  the  cuneiform  internally,  the  os  magnum  externally. 

Attachment  of  Muscles. — To  three:  the  Flexor  brevis  minimi  digiti,  the  Opponens 
minimi  digiti,  the  Flexor  carpi  ulnaris. 

The  Metacarpus  (Ossa  Metacarpalia)  (Figs.  138,  139). 

The  metacarpal  bones  are  five  in  number,  and  they  are  numbered  from  1  to 
5  inclusive,  the  first  being  the  metacarpal  bone  of  the  thumb,  the  fifth  the 
metacarpal  bone  of  the  index  finger.  They  are  long,  cylindrical  bones,  pre- 
senting for  examination  a  shaft  and  two  extremities. 

Common  Characters  of  the  Metacarpal  Bones.  The  Shaft  (corpus). — The 
shaft  is  prismoid  in  form  and  curved  longitudinally,  so  as  to  be  convex  in  the 
longitudinal  direction  behind,  concave  in  front.  It  presents  three  surfaces: 
two  lateral  and  one  posterior.  The  two  lateral  surfaces  constitute  the  palmar  or 
volar  surface.  The  lateral  surfaces  are  concave,  for  the  attachment  of  the  Inter- 
ossei  muscles,  and  separated  from  one  another  by  a  prominent  anterior  ridge. 
The  posterior  or  dorsal  surface  presents  in  its  distal  half  a  smooth,  triangular,  flat- 
tened area  which  is  covered,  in  the  recent  state,  by  the  tendons  of  the  Extensor 
muscles.  This  triangular  surface  is  bounded  by  two  lines,  which  commence  in 


THE  METACARPUS 


203 


small  tubercles  situated  on  the  dorsal  aspect  on  either  side  of  the  digital  extremity, 
and,  running  backward,  converge  to  meet  together  a  little  behind  the  centre  of 
the  bone  and  form  a  ridge  which  runs  along  the  rest  of  the  dorsal  surface  to  the 
carpal  extremity.  This  ridge  separates  two  lateral,  sloping  surfaces  for  the 
attachment  of  the  Dorsal  interossei  muscles.1  To  the  tubercles  on  the  digital 
extremities  are  attached  the  lateral  ligaments  of  the  metacarpo-phalangeal  joints. 
On  the  palmar  surface  of  each  metacarpal  bone  is  a  nutrient  foramen  (foramen 
nutricium),  which  opens  into  a  nutrient  canal  (canalis  nutricius).  '  In  the  thumb 
metacarpal  the  direction  of  this  foramen  is  toward  the  periphery  (distally).  In 
each  of  the  other  metacarpals  it  is  from  the  periphery  (proximally) . 

Carpal  or  Proximal  Extremity  or  Base  (basis) . — The  carpal  extremity,  or  base, 
is  of  a  cuboidal  form,  and  broader  behind  than  in  front;  it  articulates  above 
with  the  carpus,  and  on  each  side  with  the  adjoining  metacarpal  bones ;  its  dorsal 
and  palmar  surfaces  are  rough,  for  the  attachment  of  tendons  and  ligaments. 

Digital  or  Distal  Extremity  or  Head  (capitulum). — The  digital  extremity,  or  head, 
presents  an  oblong  surface,  markedly  convex  from  before  backward,  less  so  from 
side  to  side,  and  flattened  laterally;  it  articulates  with  the  proximal  phalanx;  it  is 
broader  and  extends  farther  forward  on  the  palmar  than  on  the  dorsal  aspect.  It 
is  longer  in  the  antero-posterior  than  in  the  transverse  diameter.  On  either  side  of 
the  head  is  a  tubercle  for  the  attachment  of  the  lateral  ligament  of  the  metacarpo- 
phalangeal  joint.  The  posterior  surface,  broad  and  flat,  supports  the  Extensor 
tendons;  the  anterior  surface  is  grooved  in  the  middle  line  for  the  passage  of  the 
Flexor  tendons,  and  marked  on  each  side  by  an  articular  eminence  continuous  with 
the  terminal  articular  surface.  The  metacarpal  spaces  (spatia  interossea  metacarpi) 
are  the  intervals  between  the  metacarpal  bones.  They  are  occupied  by  the 
Interossei  muscles.  The  broadest  space  is  between  the  metacarpal  bones  of  the 
thumb  and  index  finger. 

Peculiar  Characters  of  the  Metacarpal  Bones. — The  Metacarpal  Bone  of  the 
Thumb  (os  metacarpale  I)  (Fig.  148)  is  shorter  and  wider  than  the  rest,  diverges  to  a 
greater  degree  from  the  carpus,  and  its  palmar  sur- 
face is  directed  inward  toward  the  palm.  The  shaft 
is  flattened  and  broad  on  its  dorsal  aspect,  and 
does  not  present  the  ridge  which  is  found  on  the 
other  metacarpal  bones ;  it  is  concave  from  above 
downward,  on  its  palmar  surface.  The  carpal 
extremity,  or  base,  presents  a  concavo-convex  sur- 
face, for  articulation  with  the  trapezium;  it  has 
no  lateral  facets,  but  presents  externally  a  tubercle 
for  the  insertion  of  the  Extensor  ossis  metacarpi 
pollicis.  The  digital  extremity  is  less  convex  than 
that  of  the  other  metacarpal  bones,  broader  from 
side  to  side  than  from  before  backward.  It  pre- 
sents on  its  palmar  aspect  two  distinct  articular 
eminences  for  the  two  sesamoid  bones  in  the  ten- 
dons of  the  Flexor  brevis  pollicis,  the  outer  one 
being  the  larger  of  the  two. 

The  side  to  which  this  bone  belongs  may  be  known  by  holding  it  in  the  position 
it  occupies  in  the  hand,  with  the  carpal  extremity  upward  and  the  dorsal  surface 
backward;  the  tubercle  for  the  Extensor  ossis  metacarpi  pollicis  will  point  to  the 
side  to  which  it  belongs. 

Attachment  of  Muscles. — To  four:  the  Flexor  ossis  metacarpi  pollicis,  the  Extensor 
ossis  metacarpi  pollicis,  the  Flexor  brevis  pollicis,  and  the  First  dorsal  interosseous. 

1  By  these  sloping  surfaces  the  metacarpal  bones  of  the  hand  may  be  at  once  differentiated  from  the  meta- 
tarsal  bone  of  the  foot. — ED.  of  15th  English  Edition. 


Tubercle. 

For  trapezium.        For  trapezium. 
FIG.  148.— The  first  metacarpal.    (Left.) 


204 


THE  SKELETON 


The  Metacarpal  Bone  of  the  Index  Finger  (os  metacarpale  II)  (Fig.  149)  is  the 
longest  and  its  base  the  largest  of  the  other  four.  Its  caxpal  extremity  is  prolonged 
upward  and  inward,  forming  a  prominent  ridge.  The  dorsal  and  palmar  surfaces 
of  this  extremity  are  rough,  for  the  attachment  of  tendons  and  ligaments.  It  pre- 
sents four  articular  facets:  three  on  the  upper  aspect  of  the  base:  the  middle  one  of 
the  three  is  the  largest,  concave  from  side  to  side,  convex  from  before  backward,  for 
articulation  with  the  trapezoid;  the  external  one  is  a  small,  flat,  oval  facet,' for 
articulation  with  the  trapezium ;  the  internal  one  on  the  summit  of  the  ridge  is  long 
and  narrow,  for  articulation  with  the  os  magnum.  The  fourth  facet  is  on  the  inner 
or  ulnar  side  of  the  extremity  of  the  bone,  and  is  for  articulation  with  the  third 
metacarpal  bone. 

The  side  to  which  this  bone  belongs  is  indicated  by  the  absence  of  the  lateral 
facet  on  the  outer  (radial)  side  of  its  base,  so  that  if  the  bone  is  placed  with  the 
base  toward  the  student  and  the  palmar  surface  upward,  the  side  on  which  there 
is  no  lateral  facet  will  be  that  to  which  it  belongs. 


trapezium.  j    For  third  metacarpaL 

For  trapesoid.  For  os  magnum. 

FIG.  149. — The  second  metacarpal.     (Left.) 


For  fourth 
metacarpal. 


Styloid   For  second 
process,  metacarpal. 

For  os  magnum. 

FIG.  150. — The  third  metacarpal.     (Left.) 


Attachment  of  Muscles. — To  six:  Flexor  carpi  radialis,  Extensor  carpi  radialis 
longior,  Adductor  obliquus  pollicis,  First  and  Second  dorsal  interosseous,  and 
First  palmar  interosseous. 

The  Metacarpal  Bone  of  the  Middle  Finger  (os  metacarpale  III)  (Fig.  150)  is  a 
little  smaller  than  the  preceding:  it  presents  a  pyramidal  eminence,  the  styloid 
process  (processus  styloideus) ,  on  the  radial  side  of  its  base  (dorsal  aspect),  which 
extends  upward  behind  the  os  magnum;  immediately  below  this,  on  the  dorsal 
aspect,  is  a  rough  surface  for  the  attachment  of  the  Extensor  carpi  radialis  brevior. 
The  carpal,  articular  facet  is  concave  behind,  flat  in  front,  and  articulates  with  the 
os  magnum.  On  the  radial  side  is  a  smooth,  concave  facet,  for  articulation  with 
the  second  metacarpal  bone,  and  on  the  ulnar  side  two  small,  oval  facets,  for  articu- 
lation with  the  fourth  metacarpal. 

The  side  to  which  this  bone  belongs  is  easily  recognized  by  the  styloid  process 
on  the  radial  side  of  its  base.  With  the  palmar  surface  uppermost  and  the  base 
toward  the  student,  this  process  points  toward  the  side  to  which  the  bone  belongs. 


THE  METACARPUS 


205 


Attachment  of  Muscles. — To  six:  Extensor  carpi  radialis  brevior,  Flexor  carpi 
radialis,  Adductor  transversus  pollicis,  Adductor  obliquus  pollicis,  and  Second  and 
Third  dorsal  interosseous. 

The  Metacarpal  Bone  of  the  Ring  Finger  (os  metacarpale  IV)  (Fig.  151)  is  shorter 
and  smaller  than  the  preceding,- and  its  base  small  and  quadrilateral;  the  carpal 
surface  of  the  base  presenting  two  facets,  a  large  one  externally,  for  articulation 
with  the  unciform,  and  a  small  one  internally,  for  the  os  magnum.  On  the  radial 
side  are  two  oval  facets,  for  articulation  with  the  third  metacarpal  bone;  and  on 
the  ulnar  side  a  single  concave  facet,  for  the  fifth  metacarpal. 

If  this  bone  is  placed  with*  the  base  toward  the  student  and  the  palmar  surface 
upward,  the  radial  side  of  the  base,  which  has  two  facets  for  articulation  with  the 
third  metacarpal  bone,  will  be  on  the  side  to  which  it  belongs.  If,  as  sometimes 
happens  in  badly  marked  bones,  one  of  these  facets  is  indistinguishable,  the  side 
may  be  known  by  selecting  the  surface  on  which  the  larger  articular  facet  is  present. 
This  facet  is  for  the  fifth  metacarpal  bone,  and  would  therefore  be  situated  on  the 
ulnar  side — that  is,  the  one  to  which  the  bone  does  not  belong. 


For  third  I  For  fifth  metn- 

metacarpal.      For  os  carpal 

For  unciform. 
FIG.  151. — The  fourth  metacarpal.      (Left.) 


,v 


For  fourth  For  cuneiform, 

metacarpal. 
FIG.  152. — The  fifth  metacarpal.     (Left.) 


Attachment  of  Muscles. — To  three:  the  Third  and  Fourth  dorsal  and  Second 
palmar  interosseous. 

The  Metacarpal  Bone  of  the  Little  Finger  (os  metacarpale  V)  (Fig.  152)  presents  on 
its  base  one  facet,  which  is  concavo-convex,  and  which  articulates  with  the  unciform 
bone,  and  one  lateral,  articular  facet,  which  articulates  with  the  fourth  metacarpal 
bone.  On  its  ulnar  side  is  a  prominent  tubercle,  for  the  insertion  of  the  tendon  of 
the  Extensor  carpi  ulnaris.  The  dorsal  surface  of  the  shaft  is  marked  by  an  oblique 
ridge  which  extends  from  near  the  ulnar  side  of  the  upper  extremity  to  the  radial 
side  of  the  lower.  The  outer  division  of  this  surface  serves  for  the  attachment  of 
the  Fourth  dorsal  interosseous  muscle;  the  inner  division  is  smooth  and  covered 
by  the  Extensor  tendons  of  the  little  finger. 

If  this  bone  is  placed  with  its  base  toward  the  student  and  its  palmar  surface 
upward,  the  side  of 'the  head  which  has  a  lateral  facet  will  be  that  to  which  the 
bone  belongs. 

Attachment  of  Muscles. — To  five:  the  Extensor  carpi  ulnaris,  Flexor  carpi 
ulnaris,  Flexor  ossis  metacarpi  minimi  digiti,  Fourth  dorsal,  and  Third  palmar 
interosseous. 


206  THE   SKELETON 

Articulations. — Besides  the  phalangeal  articulations,  the  first  metacarpal  bone 
articulates  with  the  trapezium;  the  second  with  the  trapezium,  trapezoid,  os 
magnum,  and  third  metacarpal  bones;  the  third  with  the  os  magnum  and  second 
and  fourth  metacarpal  bones;  the  fourth  with  the  os  magnum,  unciform,  and 
third  and  fifth  metacarpal  bones;  and  the  fifth  with  the  unciform  and  fourth 
metacarpal. 

The  first  has  no  lateral  facets  on  its  carpal  extremity;  the  second  has  no  lateral 
facet  on  its  radial  side,  but  one  on  its  ulnar  side;  the  third  has  one  on  its  radial 
and  two  on  its  ulnar  side;  the  fourth  has  two  on  its  radial  and  one  on  its  ulnar 
side;  and  the  fifth  has  only  one  on  its  radial  side. 

The  Phalanges  of  the  Hand  (Phalanges  Digitorum  Manus). 

The  phalanges  (internodia)  are  the  bones  of  the  fingers;  they  are  fourteen  in 
number,  three  for  each  finger,  and  two  for  the  thumb.  In  numbering  them  the 
proximal  bone  is  designated  as  the  first  phalanx  (phalanx  I) .  They  are  long  bones, 
and  present  for  examination  a  shaft  and  two  extremities.  The  shaft  (corpus 
phalangis)  tapers  from  above  downward,  is  convex  posteriorly,  concave  in  front 
from  above  downward,  flat  from  side  to  side,  and  marked  laterally  by  rough 
ridges,  which  give  attachment  to  the  fibrous  sheaths  of  the  Flexor  tendons.  A 
nutrient  foramen  on  the  palmar  surface  leads  into  a  nutrient  canal  which  runs 
toward  the  periphery  (distalward) .  The  metacarpal  extremity  or  base  (basis 
phalangis)  of  each  phalanx  in  the  first  row  presents  an  oval,  concave,  articular 
surface,  broader  from  side  to  side  than  from  before  backward;  and  the  same 
extremity  in  the  other  two  rows,  a  double  concavity,  separated  by  a  longitudinal 
median  ridge,  extending  from  before  backward.  The  distal  extremity  of  the  first 
phalanx  of  the  thumb  and  of  the  first  and  second  phalanx  of  each  of  the  fingers  is 
smaller  than  the  base,  and  terminates  in  two  small,  lateral  condyles,  separated 
by  a  slight  groove  (trochlea  phalangis) ;  the  articular  surface  being  prolonged  far- 
ther forward  on  the  palmar  than  on  the  dorsal  surface,  especially  in  the  first  row. 

The  Ungual  Phalanges  (distal)  are  convex  on  their  dorsal,  flat  on  their  palmar, 
surfaces;  they  are  recognized  by  their  small  size  and  by  a  roughened,  elevated 
surface  of  a  horseshoe  form  on  the  palmar  aspect  of  their  ungual  extremity 
(tuberositas  unguicularis) ,  which  serves  to  support  the  sensitive  pulp  of  the  finger. 

Articulations. — The  first  row,  with  the  metacarpal  bones  and  the  second  row  of 
phalanges;  the  second  row,  with  the  first  and  third;  the  third,  with  the  second  row. 

Attachment  of  Muscles. — To  the  base  of  the  first  phalanx  of  the  thumb,  five 
muscles:  the  Extensor  brevis  pollicis,  Flexor  brevis  pollicis,  Abductor  pollicis, 
Adductor  transversus  and  Obliquus  pollicis.  To  the  second  phalanx,  two:  the 
Flexor  longus  pollicis  and  the  Extensor  longus  pollicis.  To  the  base  of  the  first 
phalanx  of  the  index  finger,  the  First  dorsal  and  the  First  palmar  interosseous;  to 
that  of  the  middle  finger,  the  Second  and  Third  dorsal  interosseous;  to  that  of 
the  ring  finger,  the  Fourth  dorsal  and  the  Second  palmar  interosseous ;  and  to  that 
of  the  little  finger,  the  Third  palmar  interosseous,  the  Flexor  brevis  minimi  digiti, 
and  Abductor  minimi  digiti.  To  the  second  phalanges,  the  Extensor  sublimis  digi- 
torum,  Extensor  communis  digitorum,  and,  in  addition,  the  Extensor  indicis  to 
the  index  finger,  the  Extensor  minimi  digiti  to  the  little  finger.  To  the  third 
phalanges,  the  Flexor  profundus  digitorum  and  Extensor  communis  digitorum. 

Surface  Form. — On  the  front  of  the  wrist  are  two  subcutaneous  eminences,  one  on  the 
radial  side,  the  larger  and  flatter,  due  to  the  tuberosity  of  the  scaphoid  and  the  ridge  on  the 
trapezium;  the  other,  on  the  ulnar  side,  caused  by  the  pisiform  bone.  The  tubercle  of  the 
scaphoid  is  to  be  felt  just  below  and  in  front  of  the  apex  of  the  styloid  process  of  the  radius.  It 
is  best  perceived  by  extending  the  hand  on  the  forearm.  Immediately  below  is  to  be  felt 
another  prominence,  better  marked  than  the  tubercle;  this  is  the  ridge  on  the  trapezium  which 
gives  attachment  to  some  of  the  short  muscles  of  the  thumb.  On  the  inner  side  of  the  front  of 


DEVELOPMENT  OF  THE  BONES  OF  THE  HAND  207 

.e  wrist  the  pisiform  bone  is  to  be  felt,  forming  a  small  but  prominent  projection  in  this  situa- 
jn.  It  is  some  distance  below  the  styloid  process  of  the  ulna,  and  may  be  said  to  be  just  below 
ic  level  of  the  styloid  process  of  the  radius.  The  rest  of  the  front  of  the  carpus  is  covered  by 
•ndons  and  the  annular  ligament,  and  entirely  concealed,  with  the  exception  of  the  hooked 
process  of  the  unciform,  which  can  only  be  made  out  with  difficulty.  The  back  of  the  carpus  is 
convex  and  covered  by  the  Extensor  tendons,  so  that  none  of  the  posterior  surfaces  of  the  bones 
arc  to  be  felt,  with  the  exception  of  the  cuneiform  on  the  inner  side.  Below  the  carpus  the 
dorsal  surfaces  of  the  metacarpal  bones,  except  the  fifth,  are  covered  by  tendons,  and  are  scarcely 
visible  except  in  very  thin  hands.  The  dorsal  surface  of  the  fifth  is,  however,  subcutaneous 
throughout  almost  its  whole  length,  and  is  plainly  to  be  perceived  and  felt.  In  addition  to  this, 
slightly  external  to  the  middle  line  of  the  hand,  is  a  prominence,  frequently  well  marked,  but 
occasionally  indistinct,  formed  by  the  base  of  the  metacarpal  of  the  middle  finger.  The  heads  of 
thr  metacarpal  bones  are  plainly  to  be  felt  and  seen,  rounded  in  contour  and  standing  out  in  bold 
relict'  under  the  skin,  when  the  fist  is  clenched.  It  should  be  borne  in  mind  that  when  the  fin- 
gers are  flexed  on  the  hand,  the  articular  surfaces  of  the  first  phalanges  glide  off  the  heads  of  the 
metacarpal  bones  on  to  their  anterior  surfaces,  so  that  the  head  of  these  bones  form  the  prom- 
inence of  the  knuckles  and  receive  the  force  of  any  blow  which  may  be  given.  The  head  of  the 
third  metacarpal  bone  is  the  most  prominent,  and  receives  the  greater  part  of  the  shock  of  the 
blow.  This  bone  articulates  with  the  os  magnum,  so  that  the  concussion  is  carried  through  this 
bone  to  the  scaphoid  and  semilunar,  with  which  the  head  of  the  os  magnum  articulates,  and  by 
these  bones  is  transferred  to  the  radius,  along  which  it  may  be  carried  to  the  capitellum  of  the 
humerus.  The  enlarged  extremities  of  the  phalanges  are  to  be  plainly  felt:  they  form  the 
joints  of  the  fingers.  When  the  digits  are  bent  the  proximal  phalanges  of  the  joints  form 
prominences,  which  in  the  joint  between  the  first  and  second  phalanges  is  slightly  hollowed,  in 
accordance  with  the  grooved  shape  of  their  articular  surfaces,  whilst  at  the  last  row  the  prom- 
inence is  flattened  and  square-shaped.  In  the  palm  of  the  hand  the  four  inner  metacarpal  bones 
are  covered  by  muscles,  tendons,  and  the  palmar  fascia,  and  no  part  of  them  but  their  heads 
is  to  be  distinguished.  With  regard  to  the  thumb,  on  the  dorsal  aspect  the  base  of  the  meta- 
carpal bone  forms  a  prominence  below  the  styloid  process  of  the  radius;  the  shaft  is  to  be  felt, 
covered  by  tendons,  terminating  at  its  head  in  a  flattened  prominence,  in  front  of  which  can  be 
felt  the  sesamoid  bones. 

Surgical  Anatomy. — The  carpal  bones  are  not  very  liable  to  fracture,  except  from  extreme 
violence,  when  the  parts  may  be  so  comminuted  as  to  necessitate  amputation.  Occasionally  they 
are  the  seat  of  tuberculous  disease.  The  metacarpal  bones  and  the  phalanges  are  not  unfrequently 
broken  by  direct  violence.  The  first  metacarpal  bone  is  the  one  most  commonly  fractured; 
then  the  second,  the  fourth,  and  the  fifth,  the  third  being  the  one  least  frequently  broken.  There 
are  two  diseases  of  the  metacarpal  bones  and  phalanges  which  require  special  mention  on 
account  of  the  frequency  of  their  occurrence.  One  is  tuberculous  dactylitis,  consisting  in  a 
deposit  of  tuberculous  material  in  the  medullary  canal,  expanding  the  bone,  with  subsequent 
caseation  and  resulting  necrosis.  The  other  is  chondroma,  which  is  perhaps  more  frequently 
found  in  connection  with  the  metacarpal  bones  and  phalanges  than  with  any  other  bones.  When 
chondromatous  growth  takes  place  there  are  usually  multiple  tumors,  and  they  may  spring 
either  from  the  medullary  canal  or  from  the  periosteum. 

Development  of  the  Bones  of  the  Hand. 

The  Carpal  Bones  are  each  developed  by  a  single  centre.  At  birth  they  are 
all  cartilaginous.  Ossification  proceeds  in  the  following  order  (Fig.  153) :  In  the 
os  magnum  and  unciform  an  ossific  point  appears  during  the  first  year,  the  former 
preceding  the  latter;  in  the  cuneiform,  at  the  third  year;  in  the  trapezium  and 
semilunar,  at  the  fifth  year,  the  former  preceding  the  latter;  in  the  scaphoid,  at 
the  sixth  year;  in  the  trapezoid,  during  the  eighth  year;  and  in  the  pisiform,  about 
the  twelfth  year. 

Occasionally  an  additional  bone,  the  os  centrale,  is  found  in  the  carpus,  lying 
between  the  scaphoid,  trapezoid,  and  os  magnum.  During  the  second  month  of 
foetal  life  it  is  represented  by  a  small  cartilaginous  nodule,  which,  however, 
fuses  with  the  cantilaginous  scaphoid  about  the  third  month.  Sometimes  the 
styloid  process  of  the  third  metacarpal  is  detached  and  forms  an  additional 
ossicle. 

The  Metacarpal  Bones  are  each  developed  by  two  centres:  one  for  the  shaft 
and  one  for  the  digital  extremity  for  the  four  inner  metacarpal  bones;  one  for  the 
shaft  and  one  for  the  base  for  the  metacarpal  bone  of  the  thumb,  which  in  this 


208 


THE  SKELETON 


respect  resembles  the  phalanges.1  Ossification  commences  in  the  centre  of  the 
shaft  about  the  eighth  or  ninth  week,  and  gradually  proceeds  to  either  end  of  the 
bone:  about  the  third  year  the  digital  extremities  of  the  four  inner  metacarpal 
bones  and  the  base  of  the  first  metacarpal  begin  to  ossify,  and  they  unite  about 
the  twentieth  year. 


Carpus. 

One  centre  for  each  bone. 
All  cartilaginous  at  birth. 


Metacarpus. 

Two  centres  for  each  bone  : 
One  for  shaft, 
One  for  digital  extremity, 
except  first. 


Phalanges. 

Two  centres  for  each  bone  : 
One  for  shaft, 
One  for  metacarpal 
extremity. 


At^A     .Appears  3rd  year. 

•  i  *-  y  .  \ 

Unite  20th  year. 
.Appears  8th  week. 


)  Unite 
20th,  year. 

,  \Appears  3rd  year 
ad  i 


•s  Uh-5th  year. 
I  Unite  ISth^ZOlh  year. 
Appears  8th  week. 

Appears  Uh-Sth  year. 
I  Unite  18th-20  year. 
'^Appears  8th  week. 

FIG.  153. — Plan  of  the  development  of  the  hand. 

The  Phalanges  are  each  developed  by  two  centres;  one  for  the  shaft  and  one 
for  the  base.  Ossification  commences  in  the  shaft,  in  all  three  rows,  at  about  the 
eighth  week,  and  gradually  involves  the  whole  of  the  bone  excepting  the  upper 
extremity.  Ossification  of  the  base  commences  in  the  first  row  between  the  third 
and  fourth  years,  and  a  year  later  in  those  of  the  second  and  third  rows.  The  two 
centres  become  united,  in  each  row,  between  the  eighteenth  and  twentieth  years. 

In  the  ungual  phalanges  the  centre  for  the  shaft  appears  at  the  distal  extremity 
of  the  phalanx,  instead  of  at  the  middle  of  the  shaft,  as  is  the  case  with  the  other 
phalanges. 

THE  LOWER  EXTREMITY. 


The  bones  of  the  lower  extremity  consist  of  those  of  the  pelvis,  of  the  thigh,  of 
the  leg,  and  of  the  foot. 


THE  PELVIS 


209 


THE  PELVIS  (Figs.  154,  155). 

The  pelvis,  so  called  from  its  resemblance  to  a  basin  (L.  pelvis},  is  stronger 
and  more  massively  constructed  than  either  the  cranial  or  thoracic  cavity;  it  is  a 
bony  ring,  interposed  between  the  lower  end  of  the  spine,  which  it  supports,  and 
the  lower  extremities,  upon  which  its  rests.  It  is  composed  of  four  bones:  the  two 
ossa  innominata,  which  bound  it  on  either  side  and  in  front,  and  the  sacrum  and 
coccyx,  which  complete  it  behind.  The  pelvis  is  divided  by  an  oblique  plane 
passing  through  the  prominence  of  the  sacrum,  the  linea  ilio-pectinea,  and  the 
upper  margin  of  the  symphysis  pubis  into  the  false  and  true  pelvis. 

The  False  Pelvis  (pelvis  major) . — The  false  pelvis  is  the  expanded  portion  of 
the  pelvic  cavity  which  is  situated  above  this  plane.  It  is  bounded  on  each  side 
by  the  ossa  ilii;  in  front  it  is  incomplete,  presenting  a  wide  interval  between  the 
spinous  processes  of  the  ilia  on  either  side,  which  is  filled  up  in  the  recent  state  by 
the  parietes  of  the  abdomen;  behind,  in  the  middle  line,  is  a  deep  notch.  This 
broad,  shallow  cavity  is  fitted  to  support  the  t  intestines  and  to  transmit  part  of 
their  weight  to  the  anterior  wall  of  the  abdomen,  and  is,  in  fact,  really  a  portion 
of  the  abdominal  cavity.  The  term  false  pelvis  is  incorrect,  and  this  space  ought 


FIG.  154. — Male  pelvis  (adult). 

more  properly  to  be  regarded  as  part  of  the  hypogastric  and  iliac  regions  of  the 
abdomen. 

The  True  Pelvis  (pelvis  minor), — The  true  pelvis  is  that  part  of  the  pelvic 
cavity  which  is  situated  beneath  the  plane.  It  is  smaller  than  the  false  pelvis, 
but  its  walls  are  more  perfect.  For  convenience  of  description  it  is  divided 
into  a  superior  circumference  or  inlet,  an  inferior  circumference  or  outlet,  and  a 
cavity. 

The  Superior  Circumference  or  Inlet  (apertura  pelvis  superior}. — The  superior  cir- 
cumference forms  the  brim  of  the  pelvis,  the  included  space  being  called  the  inlet. 
It  is  formed  by  the  linea  ilio-pectinea,  completed  in  front  by  the  crests  of  the 
pubic  bones,  and  behind  by  the  anterior  margin  of  the  base  of  the  sacrum  and 
sacro-vertebral  angle.  The  brim  of  the  pelvis  is  the  name  often  given  to  the 

14 


210 


THE  SKELETON 


margin  of  the  inlet.  The  inlet  of  the  pelvis  is  somewhat  heart-shaped,  obtusely 
pointed  in  front,  diverging  on  either  side,  and  encroached  upon  behind  by  the 
projection  forward  of  the  promontory  of  the  sacrum.  It  has  three  principal 
diameters:  antero-posterior  (sacro-pubic),  transverse,  and  oblique.  The  antero- 
posterior  or  conjugate  diameter  (conjugata)  extends  from  the  sacro-vertebral  angle 
to  the  symphysis  pubis.  The  anatomical  conjugate  (conjugata  anatomica)  is  the 
distance  between  the  sacro-vertebral  angle  and  the  top  of  the  symphysis  pubis. 
Its  average  measurement  is  four  inches  in  the  male  and  four  and  three-fifths  inches 
in  the  female.  The  true,  available,  or  obstetric  conjugate  (conjugata  gynascologica] 
is  the  distance  between  the  sacro-vertebral  angle  and  the  nearest  point  upon  the 
symphysis.  This  point  is  a  little  behind  and  below  the  upper  margin  (Webster). 


FIG.  155.— Female  pelvis  (adult). 

The  average  distance  in  women  is  four  and  three-eighths  inches.  The  diagonal 
conjugate  (diagonalconjugata)  is  measured  from  the  sacro-vertebral  angle  to  the 
subpubic  ligament.  The  distance  exceeds  the  true  conjugate  by  one-half  or  two- 
thirds  of  an  inch.  The  transverse  diameter  (diameter  transversa)  extends  across 
the  greatest  width  of  the  inlet,  from  the  middle  of  the  brim  on  one  side  to  the 
same  point  on  the  opposite;  its  average  measurement  is  five  inches  in  the  male, 
five  and  one-fourth  inches  in  the  female.  The  oblique  diameter  (diameter  obliqua) 
extends  from  the  margin  of  the  pelvis,  corresponding  to  the  ilio-pectineal  eminence 
on  one  side,  to  the  sacro-iliac  articulation  on  the  opposite  side;  its  average 
measurement  is  four  and  a  quarter  inches  in  the  male  and  five  in  the  female.  The 
oblique  diameters  are  named  right  or  left  oblique,  according  to  the  sacro-iliac 
joint  from  which  the  measurement  is  taken. 

The  Cavity. — The  cavity  of  the  true  pelvis  is  bounded  in  front  by  the  symphysis 
pubis;  behind,  by  the  concavity  of  the  sacrum  and  coccyx,  which,  curving  forward 
above  and  below,  contracts  the  inlet  and  outlet  of  the  canal;  and  laterally  it  is 
bounded  by  a  broad,  smooth,  quadrangular  surface  of  bone,  corresponding  to  the 
inner  surface  of  the  body  of  the  ischium  and  that  part  of  the  ilium  which  is  below 
the  ilio-pectineal  line.  The  cavity  is  shallow  in  front,  measuring  at  the  symphy- 
sis an  inch  and  a  half  in  depth,  three  inches  and  a  half  in  the  middle,  and  four 
inches  and  a  half  posteriorly.  From  this  description  it  will  be  seen  that  the  cavity 
of  the  pelvis  is  a  short,  curved  canal,  considerably  deeper  on  its  posterior  than 
on  its  anterior  wall.  This  cavity  contains,  in  the  recent  subject,  the  rectum, 
bladder,  and  part  of  the  organs  of  generation.  The  rectum  is  placed  at  the  back 


THE  PELVIS 


211 


of  the  pelvis,  and  corresponds  to  the  curve  of  the  sacro-coccygeal  column;  the 
bladder  in  front,  behind  the  symphysis  pubis.  In  the  female  the  uterus  and 
vagina  occupy  the  interval  between  these  viscera. 

The  Lower  Circumference  or  Outlet  (apertura  pelvis  inferior). — The  lower  cir- 
cumference of  the  pelvis  is  very  irregular,  and  forms  what  is  called  the  outlet. 
It  is  bounded  by  three  prominent  eminences:  one  posterior,  formed  by  the  point 
of  the  coccyx;  and  one  on  each  side,  the  tuberosities  of  the  ischia.  These  emi- 
nences are  separated  by  three  notches ;  one  in  front,  the  pubic  arch  (arcus  pvbis) , 
formed  by  the  convergence  of  the  rami  of  the  ischia  and  pubic  bones  on  each 
side.  The  other  notches,  one  on  each  side,  are  formed  by  the  sacrum  and  coccyx 
behind,  the  ischium  in  front,  and  the  ilium  above;  they  are  called  the  sacro-sciatic 
notches ;  in  the  natural  state  they  are  converted  into  foramina  by  the  lesser  and 
greater  sacro-sciatic  ligaments.  In  the  recent  state,  when  the  ligaments  are  in 
situ,  the  outlet  of  the  pelvis  is  lozenge-shaped,  bounded  in  front  by  the  subpubic 
ligament  and  the  rami  of  the  os  pubis  and  ischium;  on  each  side  by  the  tuber- 
osities of  the  ischia;  and  behind  by  the  great  sacro-sciatic  ligaments  and  the  tip 
of  the  coccyx. 

The  diameters  of  the  outlet  of  the  pelvis  are  two,  antero-posterior  and  trans- 
verse. The  antero-posterior  (conjugate]  diameter  (diameter  recta  of  the  outlet) 
extends  from  the  tip  of  the  coccyx  to  the  lower  part  of  the  symphysis  pubis;  its 
average  measurement  is  three  and  three-quarter  inches  in  the  male  and  four  and 
one-half  inches  in  the  female.  The  antero-posterior  diameter  varies  with  the 
length  of  the  coccyx,  and  is  capable  of  increase  or  diminution  on  account  of  the 
mobility  of  that  bone.  During  labor  the  coccyx  may  be  bent  back  so  that  the 
conjugate  is  increased  one  inch,  or  even  one  and  one-fourth  inches.  The  trans- 
verse diameter  extends  from  the  posterior  part  of  one  ischiatic  tuberosity  to  the 
same  point  on  the  opposite  side:  the  average  measurement  is  three  and  a  half 
inches  in  the  male  and  four  and  three-fourths  in  the  female.1 

Oblique  diameters  are  not  employed,  as  there  are  no  fixed  points  from  which 
to  measure  them. 

Position  of  the  Pelvis. — In  the  erect  posture  the  pelvis  is  placed  obliquely  with 
regard  to  the  trunk  of  the  body:  the  bony  ring,  which  forms  the  brim  of  the  true 
pelvis,  is  placed  so  as  to  form  an  angle  of  about  60  to  65  degrees  with  the  ground 
on  which  we  stand  (inclinatio  pelvis).  The  pelvic  surface  of  the  symphysis  pubis 
looks  upward  and  backward,  the  concavity  of  the  sacrum  and  coccyx  downward 
and  forward,  the  base  of  the  sacrum  in  well-formed  female  bodies  being  nearly 
four  inches  above  the  upper  border  of  the  symphysis  pubis,  and  the  apex  of  the 
coccyx  a  little  more  than  half  an  inch  above  its  lower  border.  In  consequence 
of  the  obliquity  of  the  pelvis  the  line  of  gravity  of  the  head,  which  passes  through 
the  middle  of  the  odontoid  process  of  the  axis  and  through  the  points  of  junc- 
tion of  the  curves  of  the  vertebral  column  to  the  sacro-vertebral  angle,  descends 
toward  the  front  of  the  cavity,  so  that  it  bisects  a  line  drawn  transversely  through 
the  middle  of  the  heads  of  the  thigh  bones.  And  thus  the  centre  of  gravity  of 
the  head  is  placed  immediately  over  the  heads  of  the  thigh  bones  on  which  the 
trunk  is  supported. 

Axes  of  the  Pelvis  (Fig.  .156) . — The  plane  of  the  inlet  of  the  true  pelvis  will 
be  represented  by  a  line  drawn  from  the  base  of  the  sacrum  to  the  upper  margin 

1  The  measurements  of  the  pelvis  given  above  are,  I  believe,  fairly  accurate,  but  different  measurements  are 
tfiven  by  various  authors,  no  doubt  due  in  a  great  measure  to  differences  in  the  physique  and  stature  of  the 
population  from  whom  the  measurements  have  been  taken.  The  accompanying  chart  has  been  formulated  to 
show  the  measurements  of  the  pelvis  which  are  adopted  by  many  obstetricians. — ED. 


Of  inlet 
Of  outlet 


DIAMETERS  OF  THE  TRUE  PELVIS  IN  WOMAJJ. 

Antero-posterior.                            Oblique.  Transverse. 

43/s  inches  (118  mm.)               5  inches  (127  mm.)  5%  inches  (135  mm.) 

4%  inches  (115  mm. )  4%  inches  (120  mm.} 


212 


THE  SKELETON 


of  the  symphysis  pubis.  A  line  carried  at  right  angles  with  this  at  its  middle 
would  correspond  at  one  extremity  with  the  umbilicus,  and  at  the  other  with  the 
middle  of  the  coccyx:  the  axis  of  the  inlet  is  therefore  directed  downward  and 
backward.  The  axis  of  the  outlet,  prolonged  upward,  would  touch  the  base  of 

the  sacrum,  and  is  therefore  directed  downward 
and  forward.  The  axis  of  the  cavity  is  curved 
like  the  cavity  itself;  this  curve  corresponds  to 
the  concavity  of  the  sacrum  and  coccyx,  the 
extremities  being  indicated  by  the  central  points 
of  the  inlet  and  outlet.  A  knowledge  of  the 
direction  of  these  axes  serves  to  explain  the 
course  of  the  foetus  in  the  passage  through  the 
pelvis  during  parturition.  It  is  also  important 
to  the  surgeon,  as  indicating  the  direction  of 
the  force  required  in  the  removal  of  calculi  from 
the  bladder  by  the  sub-pubic  operation,  and  as 
determining  the  direction  in  which  instruments 
should  be  used  in  operations  upon  the  pelvic 
viscera. 

Differences  between  the  Male  and  the 
Female  Pelvis. — The  female  pelvis,  looked  at 
as  a  whole,  is  distinguished  from  the  male  by 
the  bones  being  more  delicate,  by  its  width 
being  greater  and  its  depth  smaller.  The  whole 
pelvis  is  less  massive,  and  its  bones  are  lighter  and  more  slender,  and  its  muscu- 
lar impressions  are  slightly  marked.  The  iliac  fossa?  are  shallow,  and  the  anterior 
iliac  spines  widely  separated;  hence  the  greater  prominence  of  the  hips.  The 
inlet  in  the  female  is  larger  than  in  the  male;  it  is  more  nearly  circular,  and  the 


Plane  o. 


FIG.  156. — Vertical  section  of  the  pelvis, 
with  lines  indicating  the  axis  of  the  pelvis. 


FIG.  157. — Diameters  of  the  pelvic  inlet. 


sacro- vertebral  angle  projects  less  forward.  The  cavity  is  shallower  and  wider; 
the  sacrum  is  shorter,  wider,  and  less  curved;  the  obturator  foramina  are  tri- 
angular, and  smaller  in  size  than  in  the  male.  The  outlet  is  larger  and  the 
coccyx  more  movable.  The  spines  of  the  ischia  project  less  inward.  The  tuber- 


THE  OS  INNOMINATUM 


213 


cities  of  the  ischia  and  the  acetabula  are  wider  apart.  The  pubic  arch  is  wider 
and  more  rounded  than  in  the  male,  where  it  is  an  angle  rather  than  an  arch. 
En  consequence  of  this  the  width  of  the  fore  part  of  the  pelvic  outlet  is  much  in- 
creased and  the  passage  of  the  foetal  head  facilitated. 

The  size  of  the  pelvis  varies  not  only  in  the  two  sexes,  but  also  in  different 
aembers  of  the  same  sex.     This  does  not  appear  to  be  influenced  in  any  way  by 


FIG.  158.— Diameters  of  the  pelvic  outlet. 

the  height  of  the  individual.    Women  of  short  stature,  as  a  rule,  have  broad  pelves. 

)ccasionally  the  pelvis  is  equally  contracted  in  all  its  dimensions,  so  much  so  that 
ill  its  diameters  measure  an  inch  less  than  the  average,  and  this  even  in  women 
)f  average  height  and  otherwise  well  formed.  The  principal  divergences,  however, 
ire  found  at  the  inlet,  and  affect  the  relation  of  the  antero-posterior  to  the  trans- 
verse diameter.  Thus  we  may  have  a  pelvis  the  inlet  of  which  is  elliptical  either 
in  a  transverse  or  antero-posterior  direction;  the  transverse  diameter  in  the  former 
ind  the  antero-posterior  in  the  latter  greatly  exceeding  the  other  diameters.  Again, 

le  inlet  of  the  pelvis  in  some  instances  is  seen  to  be  almost  circular.  The  same 
lifferences  are  found  in  various  races.  European  women  are  said  to  have  the 

lost  roomy  pelves.  That  of  the  negress  is  smaller,  circular  in  shape,  and  with  a 
larrow  pubic  arch.  The  Hottentots  and  Bushwomen  possess  the  smallest  pelves. 
In  the  foetus  and  for  several  years  after  birth  the  pelvis  is  small  in  proportion 
that  of  the  adult.  The  cavity  is  deep,  and  the  projection  of  the  sacro-vertebral 
ingle  less  marked.  The  generally  accepted  opinion  that  the  female  pelvis  does 
lot  acquire  its  sexual  characters  until  after  puberty  has  been  shown  by  recent 
observations1  to  be  erroneous,  the  characteristic  differences  between  the  male  and 
female  pelvis  being  distinctly  indicated  as  early  as  the  fourth  month  of  fcetal  life. 
At  birth  these  differences  are  distinct  (Romiti),  the  female  pelvis  possessing  less 
straight  ilia,  a  broader  subpubic  arch,  and  less  height  than  the  male. 

The  Os  Innominatum,  called  also  Os  Coxae,  Hip  Bone,  Haunch  Bone, 
the  Nameless  Bone  (Figs.  159,  160). 

The  os  innominatum  (in,  not;  nomino,  I  name)  is  so  called  from  bearing  no 
resemblance  to  any  known  object.  It  is  a  large,  irregularly  shaped,  flat  bone, 
constricted  in  the  centre  and  expanded  above  and  below.  With  its  fellow  of  the 

1  Fehling,  Zeitschr.  fur  Geburt.  u.  Gynaek.,  Bd.  ix.  und  x.;  and  Arthur  Thomson,  Journal  of  Anatomy  and 
Physiology,  vol.  xxxiii. 


214 


THE  SKELETON 


opposite  side  it  forms  the  sides  and  anterior  wall  of  the  pelvic  cavity.  In  young 
subjects  it  consists  of  three  separate  parts,  which  meet  and  form  the  large,  cup- 
like  cavity,  the  acetabulum,  situated  near  the  middle  of  the  outer  surface  of  the 
bone;  and,  although  in  the  adult  these  have  become  united,  it  is  usual  to  describe 
the  bone  as  divisible  into  three  portions — the  ilium,  the  ischium,  and  the  pubis. 


nterior  superior 
spine. 


Ilio-pectineal  line 
for  Gimbernat's  LIGAMENT. 


OEMELLUS    SUPERIOR. 

/Spine  of  ischium. 


QEMELLUS    INFERIOR 


*^LxRECTUS    ABOOMINIS. 


DDUCTOR  LONQUS. 


FIG.  159. — Right  os  innominatum.     External  surface. 

The  ilium,  so  called  from  its  supporting  the  flank  (ilium  or  ileum,  the  flank), 
is  the  superior,  broad,  and  expanded  portion  which  runs  upward  from  the 
acetabulum  and  forms  the  prominence  of  the  hip. 

The  ischium  (iayiov,  the  hip)  is  the  inferior  and  strongest  portion  of  the  bone; 
it  proceeds  downward  from  the  acetabulum,  expands  into  a  large  tuberosity,  and 
then,  curving  forward,  forms,  with  the  descending  ram  us  of  the  os  pubis,  a  large 
aperture,  the  obturator  foramen. 


THE  OS  INNOMINATUM 


215 


The  os  pubis  is  that  portion  which  extends  inward  and  downward  from  the 
?etabulum  to  articulate  in  the  middle  line  with  the  bone  of  the  opposite  side:  it 
forms  the  front  of  the  pelvis,  supports  the  external  organs  of  generation,  and  has 
?ived  its  name  from  the  skin  over  it  being  covered  with  hair  (pubes). 


COMPRESSOR    URETHR/C./ 


TRANSVERSUS    PERINEI. 
ERECTOR    PENIS. 


Crus  penis. 
FIG.  160. — Right  os  innominatum.     Internal  surface. 

The  Hium  (os  ilium). — The  lower  or  constricted  part  of  the  ilium  is  thick, 
though  narrower  than  the  expanded  portion.  It  aids  in  the  formation  of  the 

Jtabulum  and  is  called  the  body  (corpus  ossis  ilium).     The  broad  expanded 

>rtion  of  the  ilium  is  thin  in  many  places.  It  is  called  the  ala  (ala  ossis  ilium) . 
lie  ilium  presents  for  examination  two  surfaces,  an  external  and  an  internal;  a 
?rest,  and  two  borders,  an  anterior  and  a  posterior. 

External  Surface  or  Dorsum  of  the  Ilium  (Fig.  159). — The  posterior  part  of  this 
surface  is  directed  backward  and  outward;  its  front  part,  downward  and  outward. 
It  is  smooth,  convex  in  front,  deeply  concave  behind ;  bounded  above  by  the  crest, 


216  THE  SKELETON 

below  by  the  upper  border  of  the  acetabulum;  in  front  and  behind  by  the  anterior 
and  posterior  borders.  This  surface  is  crossed  in  an  arched  direction  by  three 
semicircular  lines — the  superior,  middle,  and  inferior  curved  lines.  The  superior 
curved  line,  or  the  posterior  gluteal  line  (linea  glutcea  posterior),  the  shortest  of  the 
three,  commences  at  the  crest,  about  two  inches  in  front  of  its  posterior  extremity; 
it  is  at  first  distinctly  marked,  but  as  it  passes  downward  and  backward  to  the 
upper  part  of  the  great  sacro-sciatic  notch,  where  it  terminates,  it  becomes  less 
marked,  and  is  often  altogether  lost.  Behind  this  line  is  a  narrow  semilunar 
surface,  the  upper  part  of  which  is  rough  and  affords  attachment  to  part  of 
the  Gluteus  maximus;  the  lower  part  is  smooth  and  has  no  muscular  fibres 
attached  to  it.  The  middle  curved  line,  or  the  anterior  gluteal  line  (linea  glutcea 
anterior),  the  longest  of  the  three,  commences  at  the  crest,  about  an  inch 
behind  its  anterior  extremity,  and,  taking  a  curved  direction  downward  and 
backward,  terminates  at  the  upper  part  of  the  great  sacro-sciatic  notch.  The 
space  between  the  superior  and  middle  curved  lines  and  the  crest  is  concave, 
and  affords  attachment  to  the  Gluteus  medius  muscle.  Near  the  central  part 
of  this  line  may  often  be  observed  the  orifice  of  a  nutrient  foramen.  The  inferior 
curved  or  inferior  gluteal  line  (linea  glutcea  inferior},  the  least  distinct  of  the  three, 
commences  in  front  at  the  notch  on  the  anterior  border,  and,  taking  a  curved 
direction  backward  and  downward,  terminates  at  the  middle  of  the  great  sacro- 
sciatic  notch.  The  surface  of  bone  included  between  the  middle  and  inferior 
curved  lines  is  concave  from  above  downward,  convex  from  before  backward,  and 
affords  attachment  to  the  Gluteus  minimus  muscle.  Beneath  the  inferior  curved 
line,  and  corresponding  to  the  upper  part  of  the  acetabulum,  is  a  roughened  sur- 
face (sometimes  a  depression),  to  which  is  attached  the  reflected  tendon  of  the 
Rectus  femoris  muscle. 

Internal  Surface. — The  internal  surface  (Fig.  160)  of  the  ilium  is  bounded  above 
by  the  crest;  below  it  is  continuous  with  the  pelvic  surface  of  the  os  pubis  and 
ischium,  a  faint  line  only  indicating  the  place  of  union;  and  before  and  behind  it 
is  bounded  by  the  anterior  and  posterior  borders.  It  presents  a  large,  smooth, 
concave  surface,  called  the  iliac  fossa,  or  venter  ilii  (fossa  iliaca) ,  which  lodges  the 
Iliacus  muscle,  and  presents  at  its  lower  part  the  orifice  of  a  nutrient  canal  (fora- 
men nutricium) ;  and  below  this  a  smooth,  rounded  border,  the  ilio-pectineal  line 
or  the  linea  ilio-pectinea  (linea  arcuata) ,  which  separates  the  iliac  fossa  from  that 
portion  of  the  internal  surface  which  enters  into  the  formation  of  the  true  pelvis, 
and  which  gives  attachment  to  part  of  the  Obturator  internus  muscle.  Behind 
the  iliac  fossa  is  a  rough  surface  divided  into  two  portions,  an  anterior  and 
a  posterior.  The  anterior  or  auricular  surface  (fades  auricularis) ,  so  called  from 
its  resemblance  in  shape  to  the  ear,  is  coated  with  cartilage  in  the  recent  state, 
and  articulates  with  a  surface  of  similar  shape  on  the  side  of  the  sacrum.  The 
posterior  portion  (tuberositas  iliaca)  is  rough,  for  the  attachment  of  the  posterior 
sacro-iliac  ligaments  and  for  a  part  of  the  origin  of  the  Erector  and  Multifidus 
spinse.  In  many  bones  a  furrow  exists  in  front,  under  and  behind  the  auricular 
surface.  This  furrow  is  the  paraglenoid  sulcus  (sulcus  paraglenoidalis) ,  and  it 
affords  attachment  to  the  sacro-sciatic  ligaments. 

The  Crest  of  the  Ilium  (crista  iliaca). — The  crest  of  the  ilium  is  convex  in  its 
general  outline  and  sinuously  curved,  being  concave  inward  in  front,  concave 
outward  behind.  It  is  longer  in  the  female  than  in  the  male,  very  thick  behind, 
and  thinner  at  the  centre  than  at  the  extremities.  It  terminates  at  either  end  in 
a  prominent  eminence,  the  anterior  superior  and  posterior  superior  spinous  process 
(spina  iliaca  anterior  superior  et  spina  iliaca  posterior  superior) .  The  surface  of 
the  crest  is  broad,  and  divided  into  an  external  lip  (labium  externum),  an  inter- 
nal lip  (labium  internum),  and  an  intermediate  space  (linea  intermedia).  About 
two  inches  behind  the  anterior  superior  spinous  process  there  is  a  prominent 


THE  OS  INNOMINATUM  217 

tul>ercle  on  the  outer  lip.  To  the  external  lip  is  attached  the  Tensor  fasciae 
femoris,  Obliquus  externus  abdominis,  and  Latissimus  dorsi,  and  along  its 
ole  length,  the  fascia  lata;  to  the  space  between  the  lips,  the  Internal  oblique; 
the  internal  lip,  the  Transversalis,  Quadratus  lumborum,  and  Erector  spinse, 
the  Iliacus,  and  the  fascia  iliaca. 

Anterior  Border. — The  anterior  border  of  the  ilium  is  concave.  It  presents  two 
>rojections,  separated  by  a  notch.  Of  these,  the  uppermost,  situated  at  the  junc- 
tion of  the  crest  and  anterior  border,  is  called  the  anterior  superior  spinous  process 
>f  the  ilium  (spina  iliaca  anterior  superior),  the  outer  border  of  which  gives 
ittachment  to  the  fascia  lata  and  the  origin  of  the  Tensor  fasciae  femoris  (tensor 
iginas  femoris};  its  inner  border,  to  the  Iliacus;  while  its  extremity  affords  attach- 
lent  to  Poupart's  ligament  and  the  origin  of  the  Sartorius.  Beneath  this  emi- 
icnce  is  a  notch  which  gives  attachment  to  the  Sartorius  muscle,  and  across 
fhich  passes  the  external  cutaneous  nerve.  Below  the  notch  is  the  anterior 
iferior  spinous  process  (spina  iliaca  anterior  inferior},  which  terminates  in  the 
ipper  lip  of  the  acetabulum;  it  gives  attachment  to  the  straight  tendon  of 
the  Rectus  femoris  muscle  and  the  ilio-femoral  ligament.  On  the  inner  side  of  the 
interior  inferior  spinous  process  is  a  broad,  shallow  groove,  over  which  passes 
ic  Ilio-psoas  muscle.  This  groove  is  bounded  internally  by  an  eminence,  the 
lio-pectineal  eminence  (eminentia  iliopectinea) ,  which  marks  the  point  of  union 
)f  the  ilium  and  os  pubis. 

Posterior  Border. — The  posterior  border  of  the  ilium,  shorter  than  the  anterior, 
ilso  presents  two  projections  separated  by  a  notch,  the  posterior  superior  spinous 
rocess  (spina  iliaca  posterior  superior)  and  the  posterior  inferior  spinous  process 
(spina  iliaca  posterior  inferior).     The  former  corresponds  with  that  portion  of 
le  inner  surface  of  the  ilium  which  serves  for  the  attachment  of  the  oblique 
>rtion  of  the  sacro-iliac  ligaments  and  the  Multifidus  spinse  muscle ;  the  latter, 
the  auricular  portion  which  articulates  with    the   sacrum.     Below  the   pos- 
srior  inferior  spinous  process  is  a  deep  notch,  the  great  sciatic,  ilio-sciatic,  or 
the  great  sacro-sciatic  notch  (incisura  ischiadica  major). 

The  Ischium  (os  ischii). — The  ischium  forms  the  lower  and  back  part  of  the 
)s  innominatum.  It  is  divisible  into  a  thick  and  solid  portion — the  body;  a  large, 
>ugh  eminence,  on  which  the  trunk  rests  in  sitting — the  tuberosity;  and  a  thin 
>art  which  passes  forward  and  slightly  upward — the  ramus. 
The  Body  (corpus  ossis  ischii). — The  body,  somewhat  triangular  in  form,  pre- 
ints  three  surfaces,  external,  internal,  and  posterior;  and  three  borders,  external, 
iternal,  and  posterior.  The  external  surface  corresponds  to  that  portion  of  the 
?etabulum  formed  .by  the  ischium;  it  is  smooth  and  concave,  and  forms  a 
little  more  than  two-fifths  of  the  acetabular  cavity;  its  outer  margin  is  bounded 
:>y  a  prominent  rim  or  lip,  the  external  border,  to  which  the  cotyloid  fibro- 
?artilage  is  attached.  Below  the  acetabulum,  between  it  and  the  tuberosity,  is 
a  deep  groove,  along  which  the  tendon  of  the  Obturator  externus  muscle  runs 
as  it  passes  outward  to  be  inserted  into  the  digital  fossa  of  the  femur.  The 
internal  surface  is  smooth,  concave,  and  enters  into  the  formation  of  the  lateral 
boundary  of  the  true  pelvic  cavity.  This  surface  is  perforated  by  two  or  three 
large,  vascular  foramina,  and  affords  attachment  to  part  of  the  Obturator  inter- 
mis  muscle.  The  posterior  surface  is  quadrilateral  in  form,  broad  and  smooth. 
Below,  where  it  joins  the  tuberosity,  it  presents  a  groove,  the  obturator  groove 
(sulcus  obturatorius) ,  continuous  with  that  on  the  external  surface,  for  the  tendon 
of  the  Obturator  externus  muscle.  The  lower  edge  of  this  groove  is  formed  by 
the  tuberosity  of  the  ischium,  and  affords  attachment  to  the  Gemellus  inferior 
muscle.  This  surface  is  limited,  externally,  by  the  margin  of  the  acetabulum; 
behind,  by  the  posterior  border;  it  supports  the  Pyriformis,  the  two  Gemelli,  and 
the  Obturator  internus  muscles  in  their  passage  outward  to  the  great  trochanter. 


218  THE  SKELETON 

The  external  border  forms  the  prominent  rim  of  the  acetabulum,  and  separates 
the  posterior  from  the  external  surface.  To  it  is  attached  the  cotyloid  fibro- 
cartilage.  The  internal  border  is  thin,  and  forms  the  outer  circumference  of  the 
obturator  foramen.  The  posterior  border  of  the  body  of  the  ischium  presents,  a 
little  below  the  centre,  a  thin  and  pointed,  triangular  eminence,  the  spine  of  the 
ischium  (spina  ischiadica),  more  or  less  elongated  in  different  subjects;  its  exter- 
nal surface  gives  attachment  to  the  Gemellus  superior,  its  internal  surface  to 
the  Coccygeus  and  Levator  ani;  whilst  to  the  pointed  extremity  is  connected  the 
lesser  sacro-sciatic  ligament.  Above  the  spine  is  a  notch  of  large  size,  the  great 
sacro-sciatic  notch  (incisura  ischiadica  major),  converted  into  a  foramen,  the  great 
sacro-sciatic  foramen  (foramen  ischiadicum  majus) ,  by  the  lesser  sacro-sciatic  liga- 
ment; it  transmits  the  Pyriformis  muscle,  the  gluteal  vessels,  and  superior  and 
inferior  gluteal  nerves;  the  sciatic  vessels,  the  greater  and  lesser  sciatic  nerves, 
the  internal  pudic  vessels  and  nerve,  and  the  nerves  to  the  Obturator  internus  and 
Quadratus  femoris.  Of  these,  the  gluteal  vessels  and  superior  gluteal  nerve  pass 
out  above  the  Pyriformis  muscle,  the  other  structures,  below  it.  Below  the  spine 
is  a  smaller  notch,  the  lesser  sacro-sciatic  notch  (incisura  ischiadica  minor) ;  it  is 
smooth,  coated  in  the  recent  state  with  cartilage,  the  surface  of  which  presents 
two  or  three  ridges  corresponding  to  the  subdivisions  of  the  tendon  of  the  Obtu- 
rator internus,  which  winds  over  it.  It  is  converted  into  a  foramen,  the  lesser 
sacro-sciatic  foramen  (foramen  ischiadicum  minus),  by  the  sacro-sciatic  ligaments, 
and  transmits  the  tendon  of  the  Obturator  internus,  the  nerve  which  supplies 
that  muscle,  and  the  internal  pudic  vessels  and  nerve. 

The  Tuberosity  of  the  Ischium  (tuber  ischiadicum). — The  tuberosity  of  the 
ischium  is  the  portion  of  bone  between  the  body  and  the  ascending  ramus. 
Some  anatomists  name  this  portion  of  bone  the  descending  or  superior  ramus 
(ramus  superior  ossis  ischii),  and  restrict  the  term  tuberosity  to  the  surface  of 
the  bone  which  is  rough,  and  is  directed  backward  and  outward.  The  tuber- 
osity presents  for  examination  three  surfaces:  external,  internal,  and  posterior. 
The  external  surface  is  quadrilateral  in  shape,  and  rough  for  the  attachment  of 
muscles.  It  is  bounded  above  by  the  groove  for  the  tendon  of  the  Obturator 
externus;  in  front  it  is  limited  by  the  posterior  margin  of  the  obturator  foramen, 
and  below  it  is  continuous  with  the  ramus  of  the  bone;  behind,  it  is  bounded  by 
a  prominent  margin  which  separates  it  from  the  posterior  surface.  In  front  of 
this  margin  the  surface  gives  attachment  to  the  Quadratus  femoris,  and  anterior 
to  this  to  some  of  the  fibres  of  origin  of  the  Obturator  externus.  The  lower  part 
of  the  surface  gives  origin  to  part  of  the  Adductor  magnus.  The  internal  sur- 
face forms  part  of  the  bony  wall  of  the  true  pelvis.  In  front  it  is  limited  by  the 
posterior  margin  of  the  obturator  foramen.  Behind,  it  is  bounded  by  a  sharp 
ridge,  for  the  attachment  of  a  falciform  prolongation  of  the  great  sacro-sciatic 
ligament;  it  sometimes  presents  a  groove  on  the  inner  side  of  this  ridge  for  the 
lodgement  of  the  internal  pudic  vessels  and  nerve;  and,  more  anteriorly,  has 
attached  the  Transversus  perinsei .  and  Erector  penis  muscles.  The  posterior 
surface  is  divided  into  two  portions — a  lower  rough,  somewhat  triangular  part, 
and  an  upper  smooth,  quadrilateral  portion.  The  anterior  portion  is  subdivided 
by  a  prominent  vertical  ridge,  passing  from  base  to  apex,  into  two  parts;  the 
outer  one  gives  attachment  to  the  Adductor  magnus;  the  inner  to  the  great  sacro- 
sciatic  ligament.  The  upper  portion  is  subdivided  into  two  facets  by  an  oblique 
ridge  which  runs  downward  and  outward;  from  the  upper  and  outer  facet  arises 
the  Semimembranosus;  from  the  lower  and  inner,  the  Biceps  and  Semitendinosus. 

The  Ramus  or  Inferior  Ramus  or  Ascending  Ramus  of  the  Ischium  (ramus  inferior 
ossis  ischii). — The  ramus  is  the  thin,  flattened  part  of  the  ischium  which  ascends 
from  the  tuberosity  upward  and  inward,  and  joins  the  descending  ramus  of  the 
os  pubis,  their  point  of  junction  being  indicated  in  the  adult  by  a  rough  line. 


THE  OS  INNOMINATUM  219 

outer  surface  of  the  ramus  is  rough,  for  the  attachment  of  the  Obturator 
sxternus  muscle,  and  also  some  fibres  of  the  Adductor  magnus;  its  inner  sur- 
face forms  part  of  the  anterior  wall  of  the  pelvis.  Its  inner  border  is  thick, 
)iigh,  slightly  everted,  forms  part  of  the  outlet  of  the  pelvis,  and  presents  two 
ridges  and  an  intervening  space.  The  ridges  are  continuous  with  similar  ones 
>n  the  descending  ramus  of  the  os  pubis:  to  the  outer  one  is  attached  the  deep 
iver  of  the  superficial  perineal  fascia,  and  to  the  inner,  the  superficial  layer  of 
the  triangular  ligament  of  the  urethra.  If  these  two  ridges  are  traced  downward, 
icy  will  be  found  to  join  with  each  other  just  behind  the  point  of  origin  of  the 
^ransversus  perinrei  muscle;  here  the  two  layers  of  fascia  are  continuous  behind 
ic  posterior  border  of  the  muscle.  To  the  intervening  space,  just  in  front  of  the 
)int  of  junction  of  the  ridges,  is  attached  the  Transversus  perinaei  muscle,  and 
front  of  this  a  portion  of  the  crus  penis  vel  clitoridis  and  the  Erector  penis  vel 
^litoridis  muscle.  Its  outer  border  is  thin  and  sharp,  and  forms  part  of  the  inner 
largin  of  the  obturator  foramen. 

The  Pubis  (os  pubis) . — The  os  pubis  forms  the  anterior  part  of  the  os  innomi- 
latum,  and,  with  the  bone  of  the  opposite  side,  forms  the  front  boundary  of  the 
rue  pelvic  cavity.    It  is  divisible  into  a  body,  a  superior  or  ascending  and  an  inferior 
descending  ramus. 

The  Body  (corpus  ossis  pubis). — The  body  is  the  broad  portion  of  bone  formed 
the  junction  of  the  two  rami.  It  is  somewhat  quadrilateral  in  shape,  and 
>resents  for  examination  two  surfaces  and  three  borders.'  The  anterior  surface 
rough,  directed  downward  and  outward,  and  serves  for  the  attachment  of 
various  muscles.  To  the  upper  and  inner  angle,  immediately  below  the  crest, 
attached  the  Adductor  longus ;  lower  down,  from  without  inward,  are  attached 
the  Obturator  externus,  the  Adductor  brevis,  and  the  upper  part  of  the  Gracilis. 
he  posterior  surface,  convex  from  above  downward,  concave  from  side  to  side, 
smooth,  and  forms  part  of  the  anterior  wall  of  the  pelvis.  It  gives  attach- 
icnt  to  the  Levator  ani,  Obturator  internus,  a  few  muscular  fibres  prolonged 
)m  the  bladder,  and  the  pubo-prostatic  ligaments.  The  upper  border  presents 
for  examination  a  prominent  tubercle,  which  projects  forward  and  is  called  the 
spine  (tuberculum  pubicum);  to  it  are  attached  the  outer  pillar  of  the  external 
abdominal  ring  and  Poupart's  ligament.  Passing  upward  and  outward  from 
this  is  a  prominent  ridge,  forming  part  of  the  ilio-pectineal  line  (linea  arcuata), 
and  called  the  pecten  ossis  pubis.  It  marks  the  brim  of  the  true  pelvis:  to  it  are 
attached  a  portion  of  the  conjoined  tendon  of  the  Internal  oblique  and  Trans- 
versalis  muscles,  Gimbernat's  ligament,  and  the  triangular  fascia  of  the  abdomen. 
Internal  to  the  spine  of  the  os  pubis  is  the  crest,  which  extends  from  this  process 
to  the  inner  extremity  of  the  bone.  It  affords  attachment,  anteriorly,  to  the  con- 
joined tendon  of  the  Internal  oblique  and  Transversalis ;  and  posteriorly,  to  the 
Rectus  and  Pyramidalis  muscles.  The  point  of  junction  of  the  crest  with  the 
inner  border  of  the  bone  (symphysis)  is  called  the  angle;  to  it,  as  well  as  to  the 
symphysis,  is  attached  the  internal  pillar  of  the  external  abdominal  ring.  The 
internal  border  is  articular;  it  is  oval,  covered  by  eight  or  nine  transverse  ridges, 
or  a  series  of  nipple-like  processes  arranged  in  rows,  separated  by  grooves;  they 
serve  for  the  attachment  of  a  thin  layer  of  cartilage,  placed  between  it  and  the 
central  fibro-cartilage.  The  outer  border  presents  a  sharp  margin,  which  forms 
part  of  the  circumference  of  the  obturator  foramen  and  affords  attachment  to 
the  obturator  membrane. 

The  Ascending  or  Superior  Ramus  of  the  Pubis  (ramus  superior  ossis  pubis). — 
The  ascending  or  superior  ramus  extends  from  the  body  to  the  point  of  junction 
of  the  os  pubis  with  the  ilium,  and  forms  the  upper  part  of  the  circumference  of 
the  obturator  foramen.  It  presents  for  examination  a  superior,  inferior,  and 
posterior  surface,  and  an  outer  extremity.  The  superior  surface  presents  a  con- 


220  1HE  SKELETON 

tinuation  of  the  ilio-pectineal  line,  already  mentioned  as  commencing  at  the 
pubic  spine.  In  front  of  this  ridge  the  surface  of  bone  is  triangular  in  form, 
wider  externally  than  internally,  smooth,  and  is  covered  by  the  Pectineus  muscle. 
The  surface  is  bounded  externally  by  a  rough  eminence,  the  ilio-pectineal  emi- 
nence (eminentia  iliopectinea) ,  which  serves  to  indicate  the  point  of  junction  of 
the  ilium  and  os  pubis,  and  gives  attachment  to  the  Psoas  parvus,  when  this 
muscle  is  present.  The  triangular  surface  is  bounded  below  by  a  prominent 
ridge,  the  obturator  crest  (crista  obturatoria) ,  which  extends  from  the  cotyloid 
notch  to  the  spine  of  the  os  pubis.  The  inferior  surface  forms  the  upper  bound- 
ary of  the  obturator  foramen,  and  presents  externally  a  broad  and  deep  oblique 
groove,  the  obturator  groove  (sulcus  obturatorius) ,  for  the  passage  of  the  obturator 
vessels  and  nerve;  and  internally  a  sharp  margin  which  forms  part  of  the  cir- 
cumference of  the  obturator  foramen,  and  to  which  the  obturator  membrane  is 
attached.  The  posterior  surface  forms  part  of  the  anterior  boundary  of  the  true 
pelvis.  It  is  smooth,  convex  from  above  downward,  and  affords  attachment  to 
some  fibres  of  the  Obturator  internus.  The  outer  extremity,  the  thickest  part  of 
the  ramus,  forms  one-fifth  of  the  cavity  of  the  acetabulum. 

The  Descending  or  Inferior  Ramus  of  the  Pubis  (ramus  inferior  ossis  pubis). — 
The  descending  or  inferior  ramus  of  the  os  pubis  is  thin  and  flattened.  It  passes 
outward  and  downward,  becoming  narrower  as  it  descends,  and  joins  with  the 
ramus  of  the  ischium.  Its  anterior  surface  is  rough,  for  the  attachment  of  muscles 
— the  Gracilis  along  its  inner  border;  a  portion  of  the  Obturator  externus  where  it 
enters  into  the  formation  of  the  foramen  of  that  name;  and  between  these  two 
muscles  the-  Adductores  brevis  and  magnus  from  within  outward.  The  posterior 
surface  is  smooth,  and  gives  attachment  to  the  Obturator  internus,  and,  close  to 
the  inner  margin,  to  the  Compressor  urethrse.  The  inner  border  is  thick,  rough, 
and  everted,  especially  in  females.  It  presents  two  ridges,  separated  by  an  inter- 
vening space.  The  ridges  extend  downward,  and  are  continuous  with  similar 
ridges  on  the  ascending  ramus  of  the  ischium;  to  the  external  one  is  attached 
the  deep  layer  of  the  superficial  perineal  fascia,  and  to  the  internal  one  the  super- 
ficial layer  of  the  triangular  ligament  of  the  urethra.  The  outer  border  is  thin 
and  sharp,  forms  part  of  the  circumference  of  the  obturator  foramen,  and  gives 
attachment  to  the  obturator  membrane. 

The  Cotyloid  Cavity  or  Acetabulum. — The  cotyloid  cavity,  or  acetabulum,  is 
a  deep,  cup-shaped,  hemispherical  depression,  directed  downward,  outward,  and 
forward;  formed  internally  by  the  os  pubis,  above  by  the  ilium,  behind  and  below 
by  the  ischium,  a  little  less  than  two-fifths  being  formed  by  the  ilium,  a  little  more 
than  two-fifths  by  the  ischium,  and  the  remaining  fifth  by  the  pubic  bone.  It  is 
bounded  by  a  prominent,  uneven  rim,  which  is  thick  and  strong  above,  and  serves 
for  the  attachment  of  the  cotyloid  ligament,  which  contracts  its  orifice  and  deepens 
the  surface  for  articulation.  It  presents  below  a  deep  notch,  the  cotyloid  notch 
(incisura  acetabuli),  which  is  continuous  with  a  circular  depression,  the  fossa  of 
the  acetabulum  (fossa  acetabuli),  at  the  bottom  of  the  cavity:  this  depression  is 
perforated  by  numerous  apertures,  lodges  a  mass  of  fat,  and  its  margins,  as  well 
as  those  of  the  notch,  serve  for  the  attachment  of  the  ligamentum  teres.  In  front, 
above  and  behind  the  fossa  acetabuli,  is  a  concave  rim  of  bone  (fades  lunata) .  The 
cotyloid  notch  is  converted,  in  the  natural  state,  into  a  foramen  by  a  dense  liga- 
mentous  band  which  passes  across  it.  Through  this  foramen  the  nutrient  vessels 
and  nerves  enter  the  joint. 

The  Obturator  or  Thyroid  Foramen  (foramen  obturatum). — The  obturator  or 
thyroid  foramen  is  a  large  aperture  situated  between  the  ischium  and  os  pubis. 
In  the  male  it  is  large,  of  an  oval  form,  its  longest  diameter  being  obliquely  from 
before  backward ;  in  the  female  it  is  smaller  and  more  triangular.  It  is  bounded 
by  a  thin,  uneven  margin,  to  which  a  strong  membrane  is  attached,  and  presents, 


THE  OS  INNOMINATUM 


221 


anteriorly,  a  deep  groove,  the  obturator  groove  (sulcus  obturatorius) ,  which  runs 

from  the  pelvis  obliquely  inward  and  downward.     This  groove  is  converted  into 

foramen  by  the  obturator  membrane,  and  transmits  the  obturator  vessels  and 


lerve. 


Structure.  —  This  bone  consists  of  much  cancellous  tissue,  especially  where  it 
thick,  enclosed  between  two  layers  of  dense,  compact  tissue.     In  the  thinner 
>arts  of  the  bone,  as  at  the  bottom  of  the  acetabulum  and  centre  of  the  iliac 
fossa,  it  is  usually  semitransparent,  and  composed  entirely  of  compact  tissue. 

Development  (Fig.  161).  —  By  eight  centres:  three  primary  —  one  for  the  ilium, 
me  for  the  ischium,  and  one  for  the  os  pubis;  and  five  secondary  —  one  for  the 


Three  primary  (Ilium,  Ischium,  and  Os  Pubis). 
^^  secondary 


"^ 


8.  Symphysis  pubis. 


The  three  primary  centres  unite  through  a  \-shaped  piece  about  puberty. 
Epiphyses  appear  about  puberty,  and  unite  about  the  twenty-fifth  year. 

FIG.  161. — Plan  of  the  development  of  the  os  innominatum. 

st  of  the  ilium,  one  for  the  anterior  inferior  spinous  process  (said  to  occur  more 
frequently  in  the  male  than  in  the  female),  one  for  the  tuberosity  of  the  ischium, 
>ne  for  the  symphysis  pubis  (more  frequent  in  the  female  than  the  male),  and  one 
3r  more  for  the  Y-shaped  piece  at  the  bottom  of  the  acetabulum.  These  various 
centres  appear  in  the  following  order:  First,  in  the  ilium,  at  ihe  lower  part  of 
the  bone,  immediately  above  the  sciatic  notch,  at  about  the  eighth  or  ninth  week; 
secondly,  in  the  body  of  the  ischium,  at  about  the  third  month  of  foetal  life; 
thirdly,  in  the  body  of  the  os  pubis,  between  the  fourth  and  fifth  months.  At 
birth  the  three  primary  centres  are  quite  separate,  the  crest,  the  bottom  of  the 
acetabulum,  the  ischial  tuberosity,  and  the  rami  of  the  ischium  and  pubes  being 
still  cartilaginous.  At  about  the  seventh  or  eighth  year  the  rami  of  the  os  pubis 
and  ischium  are  almost  completely  united  by  bone.  About  the  thirteenth  or 
fourteenth  year  the  three  divisions  of  the  bone  have  extended  their  growth  into 
the  bottom  of  the  acetabulum,  being  separated  from  each  oth^r  by  a  Y-shaped 
portion  of  cartilage,  which  now  presents  traces  of  ossification,  often  by  two  or 


222  THE  SKELETON 

more  centres.  One  of  these,  the  os  acetabuli,  appears  about  the  age  of  twelve, 
between  the  ilium  and  os  pubis,  and  fuses  with  them  about  the  age  of  eighteen. 
It  forms  the  pubic  part  of  the  acetabulum.  The  ilium  and  ischium  then  become 
joined,  and  lastly  the  os  pubis  to  the  ischium,  through  the  intervention  of  this 
Y-shaped  portion.  At  about  the  age  of  puberty  ossification  takes  place  in  each 
of  the  remaining  portions,  and  they  become  joined  to  the  rest  of  the  bone 
between  the  twentieth  and  twenty-fifth  years.  Separate  centres  are  frequently 
found  for  the  pubic  and  ischial  spines 

Articulations. — With  its  fellow  of  the  opposite  side,  the  sacrum,  and  femur. 

Attachment  of  Muscles. — To  the  ilium,  sixteen.  To  the  outer  lip  of  the  crest, 
the  Tensor  vaginje  femoris,  Obliquus  externus  abdominis,  and  Latissiinus  dorsi; 
to  the  internal  lip,  the  Iliacus,  Transversalis,  Quadratus  lumborum,  and  Erector 
spinse;  to  the  interspace  between  the  lips,  the  Obliquus  interims.  To  the  outer 
surface  of  the  ilium,  the  Gluteus  maximus,  Gluteus  medius,  Glutens  minimus, 
reflected  tendon  of  the  Rectus;  to  the  upper  part  of  the  great  sacro-sciatic  notch,  a 
portion  of  the  Pyriformis;  to  the  internal  surface,  the  Iliacus;  to  that  portion  of 
the  internal  surface  below  the  linea  ilio-pectinea,  the  Obturator  internus  to  the 
internal  surface  of  the  posterior  superior  spine,  and  the  Multifidus  spinse;  to  the 
anterior  border,  the  Sartorius  and  straight  tendon  of  the  Rectus.  To  the  ischium, 
thirteen.  To  the  outer  surface  of  the  ramus,  the  Obturator  externus  and  Adductor 
magnus;  to  the  internal  surface,  the- Obturator  internus  and  Erector  penis.  To  the 
spine,  the  Gemellus  superior,  Levator  ani,  and  Coccygeus.  To  the  tuberosity,  the 
Biceps,  Semitendinosus,  Semimembranosus,  Quadratus  femoris,  Adductor  mag- 
nus, Gemellus  inferior,  Transversus  perinnei,  Erector  penis.  To  the  pubis, 
sixteen:  Obliquus  externus,  Obliquus  internus,  Transversalis,  Rectus,  Pyramid- 
alis,  Psoas  parvus,  Pectineus,  Adductor  magnus,  Adductor  longus,  Adductor 
brevis,  Gracilis,  Obturator  externus  and  internus,  Levator  ani,  Compressor 
urethne,  and  occasionally  a  few  fibres  of  the  Accelerator  urinse. 

Surface  Form. — The  pelvic  bones  are  so  thickly  covered  with  muscles  that  it  is  only  at 
certain  points  that  they  approach  the  surface  and  can  be  felt  through  the  skin.  In  front, 
the  anterior  superior  spinous  process  is  easily  recognized;  a  portion  of  it  is  subcutaneous, 
and  in  thin  subjects  may  be  seen  to  stand  out  as  a  prominence  at  the  outer  extremity  of  the  fold 
of  the  groin.  In  fat  subjects  its  position  is  marked  by  an  oblique  depression  amongst  the  sur- 
rounding fat,  at  the  bottom  of  which  the  bony  process  may  be  felt.  Proceeding  upward  and 
outward  from  this  process,  the  crest  of  the  ilium  may  be  traced  throughout  its  whole  length, 
sinuously  curved.  It  is  represented,  in  muscular  subjects,  on  the  surface,  by  a  groove  or  fur- 
row, the  iliac  furrow,  caused  by  the  projection  of  fleshy  fibres  of  the  External  oblique  muscles 
of  the  abdomen;  the  iliac  furrow  lies  slightly  below  the  level  of  the  crest.  It  terminates  behind 
in  the  posterior  superior  spinous  process,  the  position  of  which  is  indicated  by  a  slight  depression 
on  a  level  with  the  spinous  process  of  the  second  sacral  vertebra.  Between  the  two  posterior 
superior  spinous  processes,  but  at  a  lower  level,  is  to  be  felt  the  spinous  process  of  the  third 
sacral  vertebra  (see  page  69).  Another  part  of  the  bony  pelvis  easily  accessible  to  touch  is  the 
tuberosity  of  the  ischium,  situated  beneath  the  gluteal  fold,  and,  when  the  hip  is  flexed,  it  is 
easily  felt,  as  it  is  then  to  a  great  extent  uncovered  by  muscle.  Finally,  the  spine  of  the  os 
pubis  can  always  be  readily  felt,  and  constitutes  an  important  surgical  guide,  especially  in  con- 
nection with  the  subject  of  hernia.  It  is  nearly  in  the  same  horizontal  line  with  the  upper  edge 
of  the  great  trochanter.  In  thin  subjects  it  is  very  apparent,  but  in  the  obese  it  is  obscured  by 
the  pubic  fat.  It  can,  however,  be  detected  by  following  up  the  tendon  of  origin  of  the 
Adductor  longus  muscle. 

Surgical  Anatomy. — There  is  arrest  of  development  in  the  bones  of  the  pelvis  in  cases 
of  extroversion  of  the  bladder ;  the  anterior  part  of  the  pelvic  girdle  being  deficient,  the  bodies 
of  the  pubic  bones  imperfectly  developed,  and  the  symphysis  absent.  The  pubic  bones  are 
separated  to  the  extent  of  from  two  to  four  inches,  the  superior  rami  shortened  and  directed 
forward,  and  the  obturator  foramen  diminished  in  size,  narrowed,  and  turned  outward.  The 
iliac  bones  are  straightened  out  more  than  normal.  The  sacrum  is  very  peculiar.  The  lateral 
curve,  instead  of  being  concave,  is  flattened  out  or  even  convex,  with  the  ilio-sacral  facets  turned 
more  outward  than  normal,  while  the  vertical  curve  is  straightened.1 

i  Wood.    Heath's  Dictionary  of  Practical  Surgery,  i.,  426. — ED.  of  15th  English  Edition. 


THE  FEMUR,    OR   THIGH  BONE  223 

Fractures  of  the  pclvix  are  divided  into  fractures  of  the  false  pelvis  and  of  the  true  pelvis, 
.ctures  of  the  false  pelvis  vary  in  extent:  a  small  portion  of  the  iliac  crest  may  be  broken  or 

ie  of  the  spinous  processes  may  be  torn  off,  and  this  may  be  the  result  of  muscular  action ;  or 

ie  bone  may  be  extensively  comminuted.  This  latter  accident  is  the  result  of  some  crushing 
violence,  and  may  be  complicated  with  fracture  of  the  true  pelvis.  These  cases  may  be  accom- 
panied by  injury  to  the  intestine  as  it  lies  in  the  hollow  of  the  bone,  or  to  the  iliac  vessels  as 
they  course  along  the  margin  of  the  true  pelvis.  Fractures  of  the  true  pelvis  generally  occur 
through  the  ascending  ramus  of  the  os  pubis  and  the  ramus  of  the  ischium,  as  this  is  the  weakest 
part  of  the  bony  ring,  and  may  be  caused  either  by  crushing  violence  applied  in  an  antero- 
posterior  direction,  when  the  fracture  occurs  from  direct  force,  or  by  compression  laterally, 
when  the  acetabula  are  pressed  together,  and  the  bone  gives  way  in  the  same  place  from  indirect 
violence.  Occasionally  the  injury  may  be  double,  a  break  occurring  on  both  sides  of  the  body. 
In  fracture  of  the  true  pelvis  the  contained  viscera  are  liable  to  be  damaged:  the  small  intestines, 
the  urethra,  the  bladder,  the  rectum,  the  vagina,  and  even  the  uterus,  in  the  female,  have  all 
been  lacerated  by  a  displaced  fragment.  Fractures  of  the  acetabulum  are  occasionally  met  with: 
either  a  portion  of  the  rim  may  be  broken  off,  or  a  fracture  may  take  place  through  the  bottom 
of  the  cavity,  and  the  head  of  the  femur  may  be  driven  inward  and  project  into  the  pelvic  cavity. 
Separation  of  the  Y-shaped  cartilage  at  the  bottom  of  the  acetabulum  may  also  occur  in  the 
young  subject,  dispersing  the  bone  into  its  three  anatomical  portions. 

The  sacrum  is  seldom  broken.  The  cause  is  direct  violence — i.  e.,  blows,  kicks,  or  falls 
on  the  part.  The  lesion  may  be  complicated  with  injury  to  the  nerves  of  the  sacral  plexus, 
leading  to  paralysis  and  loss  of  sensation  in  the  lower  extremity  or  to  incontinence  of  faeces  from 
paralysis  of  the  Sphincter  ani. 

Fracture  of  the  coccyx  is  a  very  rare  injury,  but  does  occasionally  take  place.  Some  sup- 
posed dislocations  of  this  bone  have  been  fractures  and  so  have  some  of  the  cures  diagnosti- 
cated as  coccygodynia.  A  fracture  of  the  coccyx  is  diie  to  direct  force. 

The  pelvic  bones  often  undergo  important  deformity  in  rickets,  the  effect  of  which  in  the 
adult  woman  may  interfere  seriously  with  childbearing.  The  deformity  is  due  mainly  to  the 
weight  of  the  spine  and  trunk,  which  presses  on  the  sacro-vertebral  angle  and  greatly  increases 
it,  so  that  the  antero-posterior  diameter  of  the  pelvis  is  diminished.  But,  in  addition  to  this, 
the  weight  of  the  viscera  on  the  venter  ilii  causes  those  bones  to  expand  and  the  tuberosities  of 
the  ischia  to  incurve.  In  osteomalacia  also  great  deformity  may  occur.  The  weight  of  the 
trunk  causes  an  increase  in  the  sacro-vertebral  angle  and  a  lessening  of  the  antero-posterior 
diameter  of  the  inlet,  and  at  the  same  time  the  pressure  of  the  acetabula  on  the  heads  of  the 
thigh-bones  causes  these  cavities,  with  the  adjacent  bone,  to  be  pushed  upward  and  backward, 
so  that  the  oblique  diameters  of  the  pelvis  are  also  diminished,  and  the  cavity  of  the  pelvis 
assumes  a  triradiate  shape,  with  the  symphysis  pubis  pushed  forward. 

THE  THIGH. 

The  thigh  is  that  portion  of  the  lower  extremity  which  is  situated  between  the 
pelvis  and  the  knee.  It  consists  in  the  skeleton  of  a  single  bone,  the  femur. 

The  Femur,  or  Thigh  Bone  (Figs.  162,  163). 

The  femur  (femur,  the  thigh)  is  the  longest,1  largest,  and  strongest  bone  in  the 
skeleton,  and  almost  perfectly  cylindrical  throughout  the  greater  part  of  its  extent. 
In  the  erect  posture  it  is  not  vertical,  being  separated  from  its  fellow  above  by 
a  considerable  interval,  which  corresponds  to  the  entire  breadth  of  the  pelvis,  but 
inclining  gradually  downward  and  inward,  so  as  to  approach  its  fellow  toward 
its  lower  part,  for  the  purpose  of  bringing  the  knee-joint  near  the  line  of  gravity 
of  the  body.  The  degree  of  this  inclination  varies  in  different  persons,  and 
is  greater  in  the  female  than  the  male,  on  account  of  the  greater  breadth  of 
the  pelvis.  The  femur,  like  other  long  bones,  is  divisible  into  a  shaft  and  two 
extremities. 

Upper  Extremity. — The  upper  extremity  presents  for  examination  a  head, 
a  neck,  and  a  great  and  lesser  trochanters. 

Head  of  the  Femur  (caput  femoris). — The  head,  which  is  globular,  and 
forms  rather  more  than  a  hemisphere,  is  directed  upward,  inward,  and  a  little 

J  In  a  man  six  feet  high  it  measures  eighteen  inches — one-fourth  of  the  whole  body. — ED.  of  15th  English 
Edition. 


224 


THE  SKELETON 


OBTURATOR    INTERNUS 

and  GEMELLI. 

PYRIFORMIS. 


.Shaft 


a 


SUB-CRUREUS. 


•N*. 


*NS 

Wjtftit.  **> 


FIG.  162. — Right  femur.     Anterior  surface. 


forward,  the  greater  part  of  its 
convexity  being  above  and  in  front. 
£  Its  surface  is  smooth,  coated  with 
cartilage  in  the  recent  state,  ex- 
cept at  a  little  behind  and  below  its  centre, 
where  is  an  ovoid  depression  (fovea  capitis 
femoris),  for  the  attachment  for  the  Ligamen- 
turn  teres. 

The  Neck  of  the  Femur  (collum  femoris) . — The 
neck  is  a  flattened  pyramidal  process  of  bone 
which  connects  the  head  with  the  shaft.  It 
varies  in  length  and  obliquity  at  various  periods 
in  life  and  under  different  circumstances.  The 
angle  is  widest  in  infancy,  and  becomes  lessened 
during  growth,  so  that  at  puberty  it  forms  a 
gentle  curve  from  the  axis  of  the  shaft.  In  the 
adult  it  forms  an  angle  of  about  1 30  degrees 
with  the  shaft,  but  varies  in  inverse  proportion 
to  the  development  of  the  pelvis  and  the  stature. 
In  consequence  of  the  prominence  of  the  hips 
and  widening  of  the  pelvis  in  the  female,  the 
neck  of  the  thigh  bone  forms  more  nearly  a  right 
angle  with  the  shaft  than  it  does  in  man.  It  has 
been  stated  that  the  angle  diminishes  in  old  age 
and  the  direction  of  the  neck  becomes  hori- 
zontal, but  this  statement  is  founded  on  insuffi- 
cient evidence.  Sir  George  Humphry  states 
that  the  angle  decreases  during  the  period  of 
growth,  but  after  full  growth  has  been  attained 
it  does  not  usually  undergo  any  change,  even 
in  old  age.  He  further  states  that  the  angle 
varies  considerably  in  different  persons  of  the 
same  age.  It  is  smaller  in  short  than  in  long 
bones,  and  when  the  pelvis  is  wide.1  The  neck 
is  flattened  from  before  backward,  contracted  in 
the  middle,  and  broader  at  its  outer  extremity, 
where  it  is  connected  with  the  shaft,  than  at 
its  summit,  where  it  is  attached  to  the  head. 
The  vertical  diameter  of  the  outer  half  is  in- 
creased by  the  thickening  of  the  lower  edge, 
which  slopes  downward  to  join  the  shaft  at  the 
lesser  trochanter,  so  that  the  outer  half  of  the 
neck  is  flattened  from  before  backward,  and  its 
vertical  diameter  measures  one-third  more  than 
the  antero-posterior.  The  inner  half  is  smaller 
and  of  a  more  circular  shape.  The  anterior 
surface  of  the  neck  is  perforated  by  numerous 
vascular  foramina.  The  posterior  surface  is 
smooth,  and  is  broader  and  more  concave  than 
the  anterior;  it  gives  attachment  to  the  posterior 
part  of  the  capsular  ligament  of  the  hip-joint, 
about  half  an  inch  above  the  posterior  intertro- 
chanteric  line.  The  superior  border  is  short  and 

1  Journal  of  Anatomy  and  Physiology. 


THE  FEMUR,   OR    THIGH  BONE  225 

lick,  and  terminates  externally  at  the  great  trochanter;  its  surface  is  perforated 
y  large  foramina.  The  inferior  border,  long  and  narrow,  curves  a  little  back- 
ward, to  terminate  at  the  lesser  trochanter. 

The  Trochanters. — The  trochanters  (Tpo%d&,  to  run  or  roll)  are  prominent  pro- 
ssses  of  bone  which  afford  leverage  to  the  muscles  which  rotate  the  thigh  on  its 
axis.    They  are  two  in  number,  the  greater  and  the  lesser. 

The  great  trochanter  (trochanter  major) is  a  large,  irregular,  quadrilateral  eminence, 
situated  at  the  outer  side  of  the  neck,  at  its  junction  with  the  upper  part  of  the  shaft. 
It  is  directed  a  little  outward  and  backward,  and  in  the  adult  is  about  three-quarters 
of  an  inch  lower  than  the  head.  It  presents  for  examination  two  surfaces  and  four 
borders.  The  external  surface,  quadrilateral  in  form,  is  broad,  rough,  convex,  and 
marked  by  a  prominent  diagonal  impression,  which  extends  from  the  posterior 
superior  to  the  anterior  inferior  angle,  and  serves  for  the  attachment  of  the  tendon 
of  the  Gluteus  medius.  Above  the  impression  is  a  triangular  surface,  sometimes 
rough  for  part  of  the  tendon  of  the  same  muscle,  sometimes  smooth  for  the  inter- 
position of  a  bursa  between  that  tendon  and  the  bone.  Below  and  behind  the 
diagonal  line  is  a  smooth,  triangular  surface,  over  which  the  tendon  of  the  Gluteus 
maximus  muscle  plays,  a  bursa  being  interposed.  The  internal  surface  is  of  much 
less  extent  than  the  external,  and  presents  at  its  base  a  deep  depression,  the  digital 
or  trochanteric  fossa  (fossa  trochant erica) ,  for  the  attachment  of  the  tendon  of  the 
Obturator  externus  muscle :  above  and  in  front  of  this  an  impression  for  the  attach- 
ment of  the  Obturator  internus  and  Gemelli.  The  superior  border  is  free;  it  is  thick 
and  irregular,  and  marked  near  the  centre  by  an  impression  for  the  attachment  of 
the  Pyriformis.  The  inferior  border  corresponds  to  the  point  of  junction  of  the  base 
of  the  trochanter  with  the  outer  surface  of  the  shaft;  it  is  marked  by  a  rough,  promi- 
nent, slightly  curved  ridge,  which  gives  attachment  to  the  upper  part  of  the  Vastus 
externus  muscle.  The  anterior  border  is  prominent,  somewhat  irregular,  as  well 
as  the  surface  of  bone  immediately  below  it;  it  affords  attachment  at  its  outer 
part  to  the  Gluteus  minimus.  The  posterior  border  is  very  prominent,  and  appears 
as  a  free,  rounded  edge,  which  forms  the  back  part  of  the  digital  fossa. 

The  lesser  trochanter  (trochanter  minor)  is  a  conical  eminence  which  varies  in  size 
in  different  subjects;  it  projects  from  the  lower  and  back  parts  of  the  base  of  the  neck. 
Its  base  is  triangular,  and  connected  with  the  adjacent  parts  of  the  bone  by  three 
well-marked  borders:  two  of  these  are  above — the  internal  border,  continuous  with 
the  lower  border  of  the  neck,  the  external  border  with  the  posterior  intertrochan- 
teric  line — while  the  inferior  border  is  continuous  with  the  middle  division  of  the 
linea  aspera.  Its  summit,  which  is  directed  inward  and  backward,  is  rough,  and 
gives  insertion  to  the  tendon  of  the  Ilio-psoas.  The  Iliacus  is  also  inserted  into 
the  shaft  below  the  lesser  trochanter  between  the  Vastus  internus  in  front  and  the 
Pectineus  behind. 

A  well-marked  prominence  of  variable  size,  which  projects  from  the  upper  and 
front  part  of  the  neck  at  its  junction  with  the  great  trochanter,  is  called  the  tuber- 
cle of  the  femur;  it  is  the  point  of  meeting  of  five  muscles:  the  Gluteus  minimus 
externally,  the  Vastus  externus  below,  and  the  tendon  of  the  Obturator  internus 
and  Gemelli  above.  Running  obliquely  downward  and  inward  from  the  tubercle 
is  the  spiral  line  of  the  femur,  or  anterior  intertrochanteric  line  (linea  intertrochan- 
terica) ;  it  winds  round  the  inner  side  of  the  shaft,  below  the  lesser  trochanter,  and 
terminates  in  the  linea  aspera,  about  two  inches  below  this  eminence.  Its  upper 
half  is  rough,  and  affords  attachment  to  the  ilio-femoral  ligament  of  the  hip-joint; 
its  lower  half  is  less  prominent,  and  gives  attachment  to  the  upper  part  of  the 
Vastus  internus.  Running  obliquely  downward  and  inward  from  the  summit  of 
the  great  trochanter  on  the  posterior  surface  of  the  neck  is  a  very  prominent, 
well-marked  ridge,  the  posterior  intertrochanteric  line  (crista  intertrochanterica}. 
Its  upper  half  forms  the  posterior  border  of  the  great  trochanter,  and  its  lower 

15 


226 


THE  SKELETON 


Groove  for  tendon  of 

POPLITEUS. 
%£ 


FIG.  163. — Right  femur.     Posterior  surface. 


half  runs  downward  and  inward 
to  the  upper  and  back  part  of 
the  lesser  trochanter.  A  slight 
ridge  sometimes  commences  about 
the  middle  of  the  posterior  inter- 
trochanteric  line,  and  passes  ver- 
tically downward  for  about  two 
inches  along  the  back  part  of  the 
shaft:  it  is  called  the  linea  quadrati, 
and  gives  attachment  to  the 
Quadratus  femoris  and  a  few 
fibres  of  the  Adductor  magnus 
muscles.1 

The  Shaft  of  the  Femur  (corpus 
femoris} . — The  shaft,  almost  cylin- 
drical in  form,  is  a  little  broader 
above  than  in  the  centre,  and 
somewhat  flattened  below,  from 
before  backward.  It  is  slightly 
arched,  so  as  to  be  convex  in  front 
and  concave  behind,  where  it  is 
strengthened  by  a  prominent  lon- 
gitudinal ridge,  the  linea  aspera. 
It  presents  for  examination  three 
borders,  separating  three  surfaces. 
Of  the  three  borders,  one,  the  linea 
aspera,  is  posterior;  the  other  two 
are  placed  laterally. 

The  Linea  Aspera.  —  The  linea 
aspera  (Fig.  163)  is  a  prominent 
longitudinal  ridge  or  crest,  on  the 
middle  third  of  the  bone,  present- 
ing an  external  lip  (labium  laterale) , 
an  internal  lip  (labium  mediale), 
and  a  rough  intermediate  space. 
Above,  this  crest  is  prolonged  by 
three  ridges.  The  most  external 
ridge  is  very  rough,  and  is  con- 
tinued almost  vertically  upward  to 
the  base  of  the  great  trochanter. 
It  is  sometimes  termed  the  gluteal 
ridge  (tuberositas  glutcea) ,  and  gives 
attachment  to  part  of  the  Gluteus 
maximus  muscle ;  its  upper  part  is 
sometimes  elongated  into  a  rough- 
ened crest,  on  which  is  a  more  or 
less  well-marked,  rounded  tuber- 
cle, a  rudimental  third  trochanter 
(trochanter  tertius).  The  middle 
ridge  (linea  pectinea) ,  the  least  dis- 


1  Generally  there  is  merely  a  slight  thickening 
about  the  centre  of  the  intertrochanteric  line, 
marking  the  point  of  attachment  of  the  Quad- 
ratus femoris.  This  is  termed  by  some  anato- 
mists the  tubercle  of  the  Quadratus. — ED.  of 
15th  English  Edition. 


THE   FEMUR,    OR    THIGH  BONE  227 

inct,  is  continued  to  the  base  of  the  trochanter  minor,  and  the  internal  ridge  is 
)st  above  in  the  spiral  line  of  the  femur.  Below,  the  linea  aspera  is  prolonged 
two  ridges,  which  pass  to  the  condyles  and  enclose  between  them  a  triangular 
the  popliteal  surface  (planum  popliteum),  upon  which  rests  the  popliteal 

tery.  Of  these  two  ridges,  the  outer  one  is  the  more  prominent,  and  descends 
to  the  summit  of  the  outer  condyle.  The  inner  one  is  less  marked,  especially  at 
its  upper  part,  where  it  is  crossed  by  the  femoral  artery.  It  terminates,  below, 
at  the  summit  of  the  internal  condyle,  in  a  small  tubercle,  the  adductor  tubercle, 
which  affords  attachment  to  the  tendon  of  the  Adductor  magnus.  To  the  inner 
lip  of  the  linea  aspera  and  its  inner  prolongation  above  and  below  is  attached 
the  Vastus  interims,  and  to  the  outer  lip  and  its  outer  prolongation  above  is 
attached  the  Vastus  externus.  The  Adductor  magnus  is  attached  to  the  linea 
nsj>era,  to  its  outer  prolongation  above  and  its  inner  prolongation  below.  Be- 
tween the  Vastus  externus  and  the  Adductor  magnus  are  attached  two  muscles 
— viz.,  the  Gluteus  maximus  above,  and  the  short  head  of  the  Biceps  below. 
Between  the  Adductor  magnus  and  the  Vastus  interims  four  muscles  are  attached : 
the  Iliacus  and  Pectineus  above,  the  Adductor  brevis  and  Adductor  longus  below. 
A  little  below  the  centre  of  the  linea  aspera  is  the  nutrient  foramen  (foramen 
nutricium),  the  orifice  of  the  nutrient  canal  (canalis  nutricius),  which  is  directed 
obliquely  upward  (proximally) . 

Lateral  Borders. — The  two  lateral  borders  of  the  femur  are  only  slightly  marked, 
the  outer  one  extending  from  the  anterior  inferior  angle  of  the  great  trochanter 
to  the  anterior  extremity  of  the  external  condyle ;  the  inner  one  from  the  spiral  line 
at  a  point  opposite  the  trochanter  minor,  to  the  anterior  extremity  of  the  internal 
condyle.  The  internal  border  marks  the  limit  of  attachment  of  the  Crureus  muscle 
internally. 

Anterior  Surface. — The  anterior  surface  includes  that  portion  of  the  shaft  which 
is  situated  between  the  two  lateral  borders.  It  is  smooth,  convex,  broader  above 
and  below  than  in  the  centre,  slightly  twisted,  so  that  its  upper  part  is  directed 
forward  and  a  little  outward,  its  lower  part  forward  and  a  little  inward.  To  the 
upper  three-fourths  of  this  surface  the  Crureus  is  attached;  the  lower  fourth  is 
separated  from  the  muscle  by  the  intervention  of  the  synovial  membrane  of  the 
knee-joint  and  a  bursa,  and  affords  attachment  to  the  Subcrureus  to  a  small  extent. 

External  Surface. — The  external  surface  includes  the  portion  of  bone  between 
the  external  border  and  the  outer  lip  of  the  linea  aspera :  it  is  continuous  above 
with  the  outer  surface  of  the  great  trochanter,  below  with  the  outer  surface  of 
the  external  condyle;  to  its  upper  three-fourths  is  attached  the  outer  portion  of 
the  Crureus  muscle. 

Internal  Surface. — The  internal  surface  includes  the  portion  of  bone  between 
the  internal  border  and  the  inner  lip  of  the  linea  aspera;  it  is  continuous  above 
with  the  lower  border  of  the  neck,  below  with  the  inner  side  of  the  internal  con- 
dyle: it  is  covered  by  the  Vastus  internus  muscle. 

Lower  Extremity. — The  lower  extremity,  larger  than  the  upper,  is  of  a  cuboid 
form,  flattened  from  before  backward,  and  divided  into  two  large  eminences, 
the  condyles  (condyli,  from  xovr7u/oc,  a  knuckle),  by  an  interval  which  presents  a 
smooth  depression  in  front  called  the  trochlea  (fades  patellaris) ,  and  a  notch  of  con- 
siderable size  behind — the  intercondyloid  notch  (fossa  intercondyloidea).  The  exter- 
nal condyle  (condylus  lateralis]  is  the  more  prominent  anteriorly,  and  is  the  broader 
both  in  the  antero-posterior  and  transverse  diameters.  The  internal  condyle  (con- 
<l//lns  medialis)  is  the  narrower,  longer,  and  more  prominent  inferiorly.  This 
difference  in  the  length  of  the  two  condyles  is  only  observed  when  the  bone  is 
perpendicular  and  depends  upon  the  obliquity  of  the  thigh  bones,  in  consequence 
of  their  separation  above  at  the  articulation  with  the  pelvis.  If  the  femur  is 
held  obliquely,  the  surfaces  of  the  two  condyles  will  be  seen  to  be  nearly  hori- 


228 


THE  SKELETON 


zontal.  The  two  condyles  are  directly  continuous  in  front,  and  form  a  smooth, 
trochlear  surface,  the  trochlea,  which  articulates  with  the  patella.  It  presents 
a  median  groove,  which  extends  downward  and  backward  to  the  intercondyloid 
notch;  and  two  lateral  convexities,  of  which  the  external  is  the  broader,  more 
prominent,  and  prolonged  farther  upward  upon  the  front  of  the  outer  condyle. 
The  external  border  of  this  articular  surface  is  also  more  prominent,  and  ascends 
higher  than  the  internal  one.  The  intercondyloid  notch  lodges  the  crucial  liga- 
ments; it  is  bounded  laterally  by  the  opposed  surfaces  of  the  two  condyles,  and 
in  front  by  the  lower  end  of  the  shaft.  Between  the  popliteal  surface  and  the 
floor  of  the  intercondyloid  notch  is  an  elevation  (linea  intercondyloidea)  ,  which 
affords  attachment  to  the  posterior  ligament  of  the  knee-joint. 

Outer  or  External  Condyle  (condylus  lateralis).  —  The  outer  surface  of  the  external 
condyle  presents,  a  little  behind  its  centre,  an  eminence,  the  outer  tuberosity  or  outer 
epicondyle  (epicondylus  lateralis);  it  is  less  prominent  than  the  inner  tuberosity, 
and  gives  attachment  to  the  external  lateral  ligaments  of  the  knee.  Immediately 
beneath  it  is  a  groove,  the  popliteal  groove  (sulcus  popliteus),  which  commences.  at  a 
depression  a  little  behind  the  centre  of  the  lower  border  of  this  surface:  the  front 
part  of  this  depression  gives  origin  to  the  Popliteus  muscle,  the  tendon  of  which  is 
lodged  in  the  groove  during  flexion  of  the  knee.  The  groove  is  smooth,  covered 
with  cartilage  in  the  recent  state,  and  runs  upward  and  backward  to  the  posterior 
extremity  of  the  condyle.  The  inner  surface  of  the  outer  condyle  forms  one  of 
the  lateral  boundaries  of  the  intercondyloid  notch,  and  gives  attachment,  by  its 
posterior  part,  to  the  anterior  crucial  ligament.  The  inferior  surface  is  convex, 
smooth,  and  broader  than  that  of  the  internal  condyle.  The  posterior  extremity 
is  convex  and  smooth:  just  above  and  to  the  outer  side  of  the  articular  surface 
is  a  depression  for  the  tendon  of  the  outer  head  of  the  Gastrocnemius,  above 
which  is  the  origin  of  the  Plantaris. 

Inner  or  Internal  Condyle  (condylus  medialis).  —  The  inner  surface  of  the  inner 
condyle  presents  a  convex  eminence,  the  inner  tuberosity  or  inner  epicondyle  (epi- 
condylus medialis),  rough  for  the  attachment  of  the  internal  lateral  ligament.  The 

outer  side  of  the  inner  condyle  forms  one  of  the 
lateral  boundaries  of  the  intercondyloid  notch, 
and  gives  attachment,  by  its  anterior  part,  to  the 
posterior  crucial  ligament.  Its  inferior  or  articu- 
lar surface  is  convex,  and  presents  a  less  exten- 
sive surface  than  the  external  condyle.  Just 
above  the  articular  surface  of  the  condyle, 
behind,  is  a  depression  for  the  tendon  of  origin 
of  the  inner  head  of  the  Gastrocnemius. 

Structure.  —  The  shaft  of  the  femur  is  a 
cylinder  of  compact  tissue,  hollowed  by  a 
large  medullary  canal.  The  cylinder  is  of  great 
thickness  and  density  in  the  middle  third  of 
the  shaft,  where  the  bone  is  narrowest  and  the 
medullary  canal  well  formed;  but  above  and 
below  this  the  cylinder  gradually  becomes 
thinner,  owing  to  a  separation  of  the  layers  of 
the  bone  into  cancelli,  which  project  into  the 

.n^l..^.-.,  ~nnal  anrl  firmllv  nHlitprfltp  it  SO 
medullary  Canal  anc  mail/  II,  » 

that  the  upper  and  lower  ends  of  the  shaft,  and 
the  articular  extremities  more  especially,  consist  of  cancellated  tissue  invested 
by  a  thin,  compact  layer. 

The  arrangement  of  the  cancelli  in  the  ends  of  the  femur  is  remarkable.  In 
the  upper  end  they  are  arranged  in  two  sets.  One,  starting  from  the  top  of  the 


FIG.  164.  —  Diagram  showing  the  arrangement 
of  the  bone-fibres  of  the  neck  of  the  femur. 


THE   FEMUR,    OR    THIGH  BONE 


229 


lead,  the  upper  surface  of  the  neck,  and  the  great  trochanter,  converge  to  the  inner 
3ircumference  of  the  shaft  (Figs.  164  and  165);  these  are  placed  in  the  direction  of 
satest  pressure,  and  serve  to  support  the  vertical  weight  of  the  body.    The  second 
are  planes  of  lamellae  intersecting  the  former  nearly  at  right  angles,  and  are 


FIG.  165. — Right  femur,  upper  extremity,  ground  frontal  section,  from  in  front.     (Spalteholz.) 

situated  in  the  line  of  the  greatest  tension — that  is  to  say,  along  the  lines  in  which 
the  muscles  and  ligaments  exert  their  traction.  In  the  head  of  the  bone  these 
planes  are  arranged  in  a  curved  form,  in  order  to  strengthen  the  bone  when  exposed 
to  pressure  in  all  directions.  In  the  midst  of  the  cancellous  tissue  of  the  neck  is 
a  vertical  plane  of  compact  bone,  the  femoral  spur  (calcar  femorale),  which  com- 


230 


THE  SKELETON 


mences  at  the  point  where  the  neck  joins  the  shaft  midway  between  the  lesser 
trochanter  and  th^  internal  border  of  the  shaft  of  the  bone,  and  extends  in  the 
direction  of  the  digital  fossa  (Fig.  167).  This  materially  strengthens  this  portion 
of  the  bone.  Another  point  in  connection  with  the  structure  of  the  neck  of  the 
femur  requires  mention,  especially  on  account  of  its  influence  on  the  production 


FIG.  166. — Architecture  of  head  of  femur  as  shown  by  the  x-ray. 

of  fracture  in  this  situation.  It  will  be  noticed  that  a  considerable  portion  of  the 
great  trochanter  lies  behind  the  level  of  the  posterior  surface  of  the  neck;  and  if  a 
section  be  made  through  the  trochanter  at  this  level,  it  will  be  seen  that  the  pos- 
terior wall  of  the  neck  is  prolonged  into  the  trochanter.  This  prolongation  is 
termed  by  Bigelow  the  true  neck,1  and  forms  a  thin,  dense  plate  of  bone,  which 
passes  beneath  the  posterior  intertrochanteric  ridge  toward  the  outer  surface  of 
the  bone.  In  the  lower  end  the  cancelli  spring  on  all  sides  from  the  inner  surface 
of  the  cylinder,  and  descend  in  a  perpendicular  direction  to  the  articular  surface, 
the  cancelli  being  strongest  and  having  a  more  accurately  perpendicular  course 
above  the  condyles.  In  addition  to  this,  however,  horizontal  planes  of  cancellous 
tissue  are  to  be  seen,  so  that  the  spongy  tissue  in  this  situation  presents  an  appear- 
ance of  being  mapped  out  into  a  series  of  rectangular  areas. 

'  Bigelow  on  the  Hip,  p.  121. 


Articulations. — With  three  bones:  the  os  innominatum,  tibia,  and  patella. 
Development  (Fig.  168). — The  femur  is  developed  by  five  centres:  one  for  the 
shaft,  one  for  each  extremity,  and  one  for  each  trochanter.     Of  all  the  long  bones, 
ccept  the  clavicle,  it  is  the  first  to  show  traces  of  ossification :  this  commences  in 
le  shaft,  at  about  the  seventh  week  of  foetal  life,  the  centres  of  ossification  in  the 
-piphyses  appearing  in  the  following  order:     First,  in  the  lower  end  of  the  bone, 
it  the'  ninth  month  of  foetal  life1  (from  this  the  condyles  and  tuberosities  are 


Great  trochanter. 


_  Digital  fossa. 


THE  FEMUR,    OR  THIGH  BONE 


231 


Appears  at    4th 
year ;  joins  shaft  ^ 
about  18th  year. 


Lesser 
trochanter. 


Appears  at 
9th  month 
(festal). 


Appears  at  end 

of  1st  year; 

joins  shaft  about 

18th  year. 


Appears  13th-14th  year  ; 
&    joins  shaft  about  18th 
year. 


Joins  shaft  at  20th 
year. 


FIG.  167. — Calcar  femorale. 


Lower  extremity. 

FIG.  168. — Plan  of  the  development  of  the  femur, 
five  centres. 


By 


formed);  in  the  head  at  the  end  of  the  first  year  after  birth;  in  the  great  tro- 
chanter, during  the  fourth  year;  and  in  the  lesser  trochanter,  between  the  thir- 
teenth and  fourteenth.  The  order  in  which  the  epiphyses  are  joined  to  the  shaft 
is  the  reverse  of  that  of  their  appearance:  their  junction  does  not  commence  until 
after  puberty,  the  lesser  trochanter  being  first  joined,  then  the  great,  then  the 
head,  and,  lastly,  the  inferior  extremity  (the  first  in  which  ossification  commenced), 
which  is  not  united  until  the  twentieth  year. 

Attachment  of  Muscles. — To  twenty-three.  To  the  great  trochanter:  the  Glu- 
teus  medius,  Gluteus  minimus,  Pyriformis,  Obturator  internus,  Obturator  externus, 
Gemellus  superior,  Gemellus  inferior,  and  Quadratus  femoris.  To  the  lesser 
trochanter:  the  Psoasmagnus  and  the  Iliacus  below  it.  To  the  shaft:  the  Vastus 
externus,  Gluteus  maximus,  short  head  of  the  Biceps,  Vastus  internus,  Adductor 
magnus,  Pectineus,  Adductor  brevis,  Adductor  longus,  Crureus,  and  Subcrureus. 
To  the  condyles:  the  Gastrocnemius,  Plantaris,  and  Popliteus. 

Surface  Form. — The  femur  is  covered  with  muscles,  so  that  in  fairly  muscular  subjects  the 
shaft  is  not  to  be  detected  through  its  fleshy  covering,  and  the  only  parts  accessible  to  the  touch 
are  the  outer  surface  of  the  great  trochanter  and  the  lower  expanded  end  of  the  bone.  The 
external  surface  of  the  great  trochanter  is  to  be  felt,  especially  in  certain  positions  of  the  limb.  Its 

1  This  is  said  to  be  the  only  epiphysis  in  which  ossification  begins  before  birth;  though  according  to  some 
observers,  the  centre  for  the  upper  epiphysis  of  the  tibia  also  appears  before  birth. — ED.  of  15th  English 
Edition. 


232  THE  SKELETON 

position  is  generally  indicated  by  a  depression,  owing  to  the  thickness  of  the  Gluteus  medius  and 
minimus,  which  project  above  it.  When,  however,  the  thigh  is  flexed,  and  especially  if  crossed 
over  the  opposite  one,  the  trochanter  produces  a  blunt  eminence  on  the  surface.  The  upper 
border  is  about  on  a  line  with  the  spine  of  the  os  pubis,  and  its  exact  level  is  indicated  by  a 
line  drawn  from  the  anterior  superior  spinous  process  of  the  ilium,  over  the  outer  side  of  the 
hip,  to  the  most  prominent  point  of  the  tuberosity  of  the  ischium.  This  is  known  as  Nelaton's 
line.  The  outer  and  inner  condyles  of  the  lower  extremity  are  easily  to  be  felt.  The  outer  one 
is  more  subcutaneous  than  the  inner  one  and  readily  felt.  The  tuberosity  on  it  is  comparatively 
little  developed,  but  can  be  more  or  less  easily  recognized.  The  inner  condyle  is  more  thickly 
covered,  and  this  gives  a  general  convex  outline  to  this  part,  especially  when  the  knee  is  flexed. 
The  tuberosity  on  it  is  easily  felt,  and  at  the  upper  part  of  the  condyle  the  sharp  tubercle  for  the 
insertion  of  the  tendon  of  the  Adductor  magnus  can  be  recognized  without  difficulty.  When 
the  knee  is  flexed,  and  the  patella  situated  in  the  interval  between  the  condyles  and  the  upper 
end  of  the  tibia,  a  part  of  the  trochlear  surface  of  the  femur  can  be  made  out  above  the  patella. 

Surgical  Anatomy. — There  are  one  or  two  points  about  the  ossification  of  the  femur  bear- 
ing on  practice  to  which  allusion  must  be  made.  It  has  been  stated  above  that  the  lower  end 
of  the  femur  is  the  only  epiphysis  in  which  ossification  has  commenced  at  the  time  of  birth. 
The  presence  of  the  ossific  centre  in  newly  born  children  found  dead  is,  therefore,  a  proof 
that  the  child  has  arrived  at  the  full  period  of  utero-gestation,  and  is  always  relied  upon  in 
medico-legal  investigations.  The  position  of  the  epiphysial  line  should  be  carefully  noted.  It 
is  on  a  level  with  the  adductor  tubercle,  and  the  epiphysis  does  not,  therefore,  form  the  whole 
of  the  cartilage-clad  portion  of  the  lower  end  of  the  bone.  It  is  essential  to  bear  this  point  in 
mind  in  performing  excision  of  the  knee,  since  growth  in  length  of  the  femur  takes  place  chiefly 
from  the  lower  epiphysis,  and  any  interference  with  the  epiphysial  cartilage  in  a  young  child 
would  involve  such  ultimate  shortening  of  the  limb,  from  want  of  growth,  as  to  render  it  almost 
useless.  Separation  of  the  lower  epiphysis  may  take  place  up  to  the  age  of  twenty,  at  which 
time  it  becomes  completely  joined  to  the  shaft  of  the  bone;  but,  as  a  matter  of  fact,  few  cases 
occur  after  the  age  of  sixteen  or  seventeen.  The  epiphysis  of  the  head  of  the  femur  is  of  interest 
principally  on  account  of  its  being  the  seat  of  origin  of  a  large  number  of  cases  of  tuberculous 
disease  of  the  hip-joint.  The  disease  commences  in  the  majority  of  cases  in  the  highly  vascular 
and  growing  tissue  in  the  neighborhood  of  the  epiphysis,  and  from  here  extends  into  the  joint. 
In  the  condition  known  as  coxa  vara  the  head  of  the  femur  falls  to  a  lower  level  than  normal. 
The  angle  between  the  neck  and  shaft  is  greatly  diminished  and  may  become  a  right  angle  or 
the  head  may  actually  descend  to  a  lower  level  than  that  of  the  trochanter.  The  neck  is  also 
bent  with  a  convexity  forward ;  coxa  vara  is  due  to  rickets. 

Fractures  of  the  femur  are  divided,  like  those  of  the  other  long  bones,  into  fractures  of  the 
upper  end;  of  the  shaft;  and  of  the  lower  end.  The  fractures  of  the  upper  end  may  be  classi- 
fied into  (1)  fracture  of  the  neck;  (2)  fracture  at  the  junction  of  the  neck  with  the  great  trochanter; 
(3)  fracture  of  the  great  trochanter;  and  (4)  separation  of  the  epiphysis,  either  of  the  head  or 
of  the  great  trochanter.  The  first  of  these,  fracture  of  the  neck,  is  usually  termed  intracapsular 
fracture,  but  this  is  scarcely  a  correct  designation,  as  owing  to  the  attachment  of  the  capsular 
ligament,  the  fracture  may  be  partly  within  and  partly  without  the  capsule,  when  the  fracture 
occurs  at  the  lower  part  of  the  neck.  It  generally  occurs  in  old  people,  principally  women,  and 
usually  from  a  very  slight  degree  of  indirect  violence.  Probably  the  main  cause  of  the  fracture 
taking  place  in  old.  people  is  in  consequence  of  the  degenerative  changes  which  the  bone  has 
undergone.  Merkel  believes  that  it  is  mainly  due  to  the  absorption  of  the  calcar  femorale. 
These  fractures  are  occasionally  impacted.  As  a  rule  they  unite  by  fibrous  tissue,  and  frequently 
iio  union  takes  place,  and  the  surfaces  of  the  fracture  become  smooth  and  eburnated.  The 
lack  of  reparative  power  in  intracapsular  fracture  is  due  to  lack  of  apposition  of  the  fragments  and 
diminution  in  the  amount  of  blood  sent  to  the  smaller  fragment.  The  head  of  the  bone  receives 
blood  from  the  neck  through  the  reflected  portions  of  the  capsule  and  through  the  Ligamentum 
teres.  A  fracture  cuts  off  the  supply  by  the  neck  and  by  the  reflected  portions  of  the  capsule. 

Fractures  at  the  junction  of  the  neck  with  the  great  trochanter  are  usually  termed  extra- 
capsular,  but  this  designation  is  also  incorrect;  as  the  fracture  is  partly  within  the  capsule, 
owing  to  its  attachment  in  front  to  the  anterior  intertrochanteric  line,  which  is  situated  below 
the  line  of  fracture.  These  fractures  are  produced  by  direct  violence  to  the  great  trochanter,  as 
from  a  blow  or  fall  laterally  on  the  hip.  From  the  manner  in  which  the  accident  is  caused,  the 
neck  of  the  bone  is  driven  into  the  trochanter,  where  it  may  remain  impacted  or  the  trochanter 
may  be  split  up  into  two  or  more  fragments,  and  thus  no  fixation  takes  place. 

Fractures  of  the  great  trochanter  may  be  either  'oblique  fracture  through  the  trochanter 
major,  without  implicating  the  neck  of  the  bone"  (Astley  Cooper),  or  separation  of  the  great 
trochanter.  Most  of  the  recorded  cases  of  this  latter  injury  occurred  in  young  persons,  and 
were  probably  cases  of  separation  of  the  epiphysis  of  the  great  trochanter.  Separation  of  the 
epiphysis  of  the  head  of  the  femur  has  been  said  to  occur,  but  has  probably  never  been  verified 
by  post-mortem  examination. 

Fractures  of  the  shaft  may  occur  at  any  part,  but  the  most  usual  situation  is  at  or  near  the 


THE  PATELLA,    OR  KNEE-CAP 


233 


entre  of  the  bone.  They  may  be  caused  by  direct  or  indirect  violence  or  by  muscular  action. 
Fractures  of  the  upper  third  of  the  shaft  are  almost  always  the  result  of  indirect  violence,  whilst 
lose  of  the  lower  third  are  the  result,  for  the  most  part,  of  direct  violence.  In  the  middle  third 
•actures  occur  from  both  forms  of  injury  in  about  equal  proportions.  Fractures  of  the  shaft 
generally  oblique,  but  they  may  be  transverse,  longitudinal,  or  spiral.  The  transverse 
eture  occurs  most  frequently  in  children.  The  fractures  of  the  lower  end  of  the  femur  include 
insverse  fracture  above  the  condyles,  the  most  common;  and  this  may  be  complicated  by  a 
jrtical  fracture  between  the  condyles,  constituting  the  T-shaped  fracture.  In  these  cases  the 
pliteal  artery  is  in  danger  of  being  wounded.  Oblique  fracture,  separating  either  the  internal 
external  condyle,  and  a  longitudinal  incomplete  fracture  between  the  condyles,  may  also  take 
alace. 

The  femur  and  also  the  bones  of  the  leg  are  frequently  the  seat  of  acute  osteomyelitis  in  young 
lildren.  This  is  no  doubt  due  to  their  greater  exposure  to  injury,  which  is  often  the  exciting 
luse  of  this  disease.  Tumors  not  unfrequently  are  found  growing  from  the  femur:  the  most 
3mmon  forms  being  sarcoma,  which  may  grow  either  from  the  periosteum  or  from  the  medullary 
tissue  within  the  interior  of  the  bone;  and  exostosis,  which  is  commonly  found  originating  in 
le  neighborhood  of  the  epiphysial  cartilage  of  the  lower  end. 

Genii  varum  is  a  form  of  bow-leg  in  which  the  tibia  and  femur  are  curved  outward,  the  knees 
ging  widely  separated.  Both  extremities  are  usually  affected.  In  early  life  the  disease  is  due 
rickets.  In  elderly  people  it  may  be  due  to  arthritis  deformans.  Genu  valgum  (knock-knee] 
a  condition  in  which  the  knees  are  close  together,  the  feet  are  wide  apart,  and  the  internal 
iteral  ligament  of  the  knee-joint  is  stretched.  It  is  due  to  excessive  growth  of  the  inner  con- 
lyle  of  the  femur,  the  shaft  of  the  femur  curving  inward.  It  may  be  due  to  rickets,  attitude  of 
in  occupation,  or  flat-foot,  and  one  or  both  knees  may  be  affected. 

THE  LEG. 

The  skeleton  of  the  leg  consists  of  three  bones;  the  patella,  a  large  sesamoid 
>ne,  placed  in  front  of  the  knee;  the  tibia;  and  the  fibula. 

The  Patella,  or  Knee-cap  (Fig.  169). 

The  patella  (patella,  a  small  pan),  the  knee-cap  or  knee-pan,  is  a  flat,  triangular 
>ne,  situated  at  the  anterior  part  of  the  knee-joint.    It  is  usually  regarded  as  a 
jsamoid  bone,  developed  in  the  tendon  of  the  Quadriceps  extensor.    It  resembles 
icse  bones  (1)  in  its  being  developed  in  a  tendon;  (2)  in  its  centre  of  ossification 
^resenting  a  knotty  or  tuberculated  outline;  (3)  in  its  structure  being  composed 
minly  of  dense  cancellous  tissue,  as  in  the  other  sesamoid  bones.    It  serves  to 
protect  the  front  of  the  joint,  and  increases  the  leverage  of  the  Quadriceps  extensor 
by  making  it  act  at  a  greater  angle.    It  presents  an  anterior  and  a  posterior  sur- 
face, three  borders,  and  an  apex. 

Surfaces.     Anterior  Surface. — The  anterior  surface  is  convex,  perforated  by 
small  apertures,  for  the  passage  of  nutrient  vessels,  and  marked  by  numerous 
rough,  longitudinal  striae.     This  surface  is  covered,  in  the  recent  state,  by  an 
expansion  from  the  tendon  of 
the  Quadriceps  extensor, which 
is  continuous  below  with  the 
superficial  fibres  of  the   liga- 
inentum  patellae.     It  is  sepa- 
rated from  the  integument  by 
a  bursa. 

Posterior  Surface. — The  pos- 
terior surface  presents  a 
smooth,  oval-shaped,  articular 

surface  (fades  articularis) ,  cov-  FlG  169._Right  patella.  a>  anterior  surface.  6,  poster-or  8urface. 
ered  with  cartilage  in  the  re- 
cent state,  and  divided  into  two  facets  by  a  vertical  ridge,  which  descends  from 
the  superior  border  toward  the  inferior  angle  of  the  bone.  The  ridge  corresponds 
to  the  groove  on  the  trochlear  surface  of  the  femur,  and  the  two  facets  to  the 
articular  surfaces  of  the  two  condyles;  the  outer  facet,  for  articulation  with  the 


234  THE  SKELETON 

outer  condyle,  being  broader  and  deeper.  This  character  serves  to  indicate 
the  side  to  which  the  bone  belongs.  Below  the  articular  surface  is  a  rough,  convex, 
non-articular  depression,  the  lower  half  of  which  gives  attachment  to  the  liga- 
mentum  patellte,  the  upper  half  being  separated  from  the  head  of  the  tibia  by 
adipose  tissue. 

Borders.  Superior  Border. — The  superior  border  (basis  patella)  is  thick,  and 
sloped  from  behind,  downward  and  forward:  it  gives  attachment  to  that  portion 
of  the  Quadriceps  extensor  which  is  derived  from  the  Rectus  and  Crureus  muscles. 

Lateral  Borders. — The  lateral  borders  are  thinner,  converging  below.  They 
give  attachment  to  that  portion  of  the  Quadriceps  extensor  derived  from  the 
external  and  internal  Vasti  muscles. 

The  Apex  (apex  patellae). — The  apex  is  pointed,  and  gives  attachment  to  the 
ligamentum  patellae. 

Structure. — It  consists  of  a  nearly  uniform,  dense  cancellous  tissue  covered 
by  a  thin  compact  lamina.  The  cancelli  immediately  beneath  the  anterior  surface 
are  arranged  parallel  with  it.  In  the  rest  of  the  bone  they  radiate  from  the  pos- 
terior articular  surface  toward  the  other  parts  of  the  bone. 

Development. — By  a  single  centre,  which  makes  its  appearance,  according  to 
Be*clard,  about  the  third  year.  In  two  instances  Mr.  Pick  has  seen  this  bone  car- 
tilaginous throughout,  at  a  much  later  period  (six  years).  More  rarely,  the  bone  is 
developed  by  two  centres,  placed  side  by  side.  Ossification  is  completed  about 
the  age  of  puberty. 

Articulations. — With  the  two  condyles  of  the  femur. 

Attachment  of  Muscles. — To  four:  the  Rectus,  Crureus,  Vastus  internus,  and 
Vastus  externus.  These  muscles,  joined  at  their  insertion,  constitute  the  Quadri- 
ceps extensor  cruris. 

Surface  Form. — The  external  surface  of  the  patella  can  be  seen  and  felt  in  front  of  the 
knee.  In  the  extended  position  of  the  limb  the  internal  border  is  a  little  more  prominent  than 
the  outer,  and  if  the  Quadriceps  extensor  is  relaxed  the  bone  can  be  moved  from  side  to  side  and 
appears  to  be  loosely  fixed.  If  the  joint  is  flexed,  the  patella  recedes  into  the  hollow  between  the 
condyles  of  the  femur  and  the  upper  end  of  the  tibia,  and  becomes  firmly  fixed  against  the  femur. 

Surgical  Anatomy. — The  main  surgical  interest  about  the  patella  is  in  connection  with 
fractures,  which  are  of  common  occurrence.  They  may  be  produced  by  muscular  action;  that 
is  to  say,  by  violent  contraction  of  the  Quadriceps  extensor  while  the  limb  is  in  a  position  of 
semi-flexion,  so  that  the  bone  is  snapped  across  the  condyles;  or  by  direct  violence,  such  as 
falls  on  the  knee.  Most  fractures  are  due  to  muscular  action ;  in  fact,  the  patella  is  more  often 
broken  by  muscular  action  than  is  any  other  bone.  In  fractures  by  muscular  action  the  line  of 
fracture  is  transverse.  In  fractures  by  direct  force  the  line  of  fractuure  may  be  oblique,  longi- 
tudinal, stellate,  or  the  bone  variously  comminuted.  The  principal  interest  in  these  cases 
attaches  to  their  treatment.  Owing  to  the  wide  separation  of  the  fragments,  and  the  diffi- 
culty there  is  in  maintaining  them  in  apposition,  union  takes  place  by  fibrous  tissue,  and  this 
may  subsequently  stretch,  producing  wide  separation  of  the  fragments  and  permanent  lame- 
ness. Various  plans,  including  opening  the  joint  and  suturing  the  fragments,  have  been  advo- 
cated for  overcoming  this  difficulty.  In  many  cases  a  portion  of  fascia  or  capsule  gets  between 
the  fragments.  In  such  a  condition  operation  is  necessary. 

In  the  larger  number  of  cases  of  fracture  of  the  patella  the  knee-joint  is  involved,  the  car- 
tilage which  covers  its  posterior  surface  being  torn,  the  synovial  membrane  lacerated,  the  lateral 
fibrous  expansions  ruptured,  and  the  patellar  bursa  torn  open.  In  cases  of  fracture  from 
direct  violence,  however,  this  need  not  necessarily  happen,  the  lesion  may  involve  only  the 
superficial  part  of  the  bone;  and,  as  Morris  has  pointed  out,  it  is  an  anatomical  possibility,  in 
complete  fracture,  if  the  lesion  involve  only  the  lower  and  non-articular  part  of  the  bone,  for 
it  to  take  place  without  injury  to  the  synovial  membrane. 

The  Tibia,  or  Shin  Bone  (Figs.  170,  171). 

The  tibia  (tibia,  a  flute  or  pipe)  is  situated  at  the  front  and  inner  side  of  the 
leg,  and,  excepting  the  femur,  is  the  longest  and  largest  bone  in  the  skeleton.  It 
is  prismoid  in  form,  expanded  above,  where  it  enters  into  the  knee-joint,  more 


THE  TIBIA,    OR  SHIN  BONE 


235 


Head 
Styloid  process. 


Tibia. 


Internal  malleolus. 
External  malleolus. 

FIG.  170. — Bones  of  the  right  leg.     Anterior  surface.          FIG.  171. — Bones  of  the  right  leg.     Posterior  surface. 


Styloid  process. 


Fibula. 


236  THE  SKELETON 

slightly  enlarged  below.  In  the  male  its  direction  is  vertical  and  parallel  with 
the  bone  of  the  opposite  side ;  but  in  the  female  it  has  a  slightly  oblique  direction 
downward  and  outward,  to  compensate  for  the  oblique  direction  of  the  femur 
inward.  It  presents  for  examination  a  shaft  and  two  extremities. 

Upper  Extremity. — The  upper  extremity,  or  head,  is  large,  and  expanded 
on  each  side  into  two  lateral  eminences,  the  internal  and  external  tuberosities 
(condylus  medialis  and  condylus  lateralis}.  Superiorly,  each  tuberosity  presents 
a  smooth,  concave  surface  (fades  articularis  superior),  which  articulates  with 

ATTACHMENT  OF  POSTERIOR    «_._....    -,_  poQTrBlOB    ATTACHMENT  OF  POSTERIOR 

EXTREMITY   OF  EXTERNAL  Q p      ,!T  °R  J " ' ° "    EXTREMITY   OF  INTERNAL 

SEMI  LUNAR  CARTILAGE,       CRUC,  A  L  LIGAMENT      ?EMILUNAR  CART.LAGE 


ATTACHMENT  OF  ANTERIOR'   -_.-...   __      '__      ^ATTACHMENT  OF  ANTERIOR 

EXTREMITY   OF  EXTERNAL    _?"''„   rvT     =       Ii     "TH  EM  ITY  OF  I NTERN  AL 

SEMILUNAH   CARTILAGE    J!?"  *?   .^T^^2   SEMILUNAR   CARTILAGE 


FIG.  172. — Upper  articular  surface  of  the  tibia,  showing  the  attachments  of  the  ligaments. 

(Poirier  and  Charpy.) 

a  condyle  of  the  femur.  The  internal,  articular  surface  is  longer,  deeper,  and 
narrower  than  the  external,  oval  from  before  backward,  to  articulate  with  the  in- 
ternal condyle;  the  external  one  is  broader  and  more  circular,  concave  from  side 
to  side,  but  slightly  convex  from  before  backward,  especially  at  its  posterior  part, 
where  it  is  prolonged  on  to  the  posterior  surface  for  a  short  distance,  to  articulate 
with  the  external  condyle.  Between  the  two  articular  surfaces,  and  nearer  the  pos- 
terior than  the  anterior  aspect  of  the  bone,  is  an  eminence,  the  spinous  process 
of  the  tibia  (eminentia  intercondyloidea) ;  surmounted  by  a  prominent  tubercle  on 
each  side  (the  tuberculum  intercondyloideum  mediate  and  the  tuberculum  inter- 
condyloideum  laterale) ,  on  to  the  lateral  aspect  of  which  the  facets  just  described 
are  prolonged;  in  front  and  behind  the  spinous  process  is  a  rough  depression 
(fossa  intercondyloidea  anterior  and  the  fossa  intercondyloidea  posterior)  for  the 
attachment  of  the  anterior  and  posterior  crucial  ligaments  arid  the  semilunar 
fibro-cartilages  (Fig.  172). 

The  anterior  surfaces  of  the  tuberosities  are  continuous  with  one  another,  form- 
ing a  single  large  surface,  which  is  somewhat  flattened:  it  is  triangular,  broad 
above,  and  perforated  by  large  vascular  foramina;  narrow  below,  where  it  ter- 
minates in  a  prominent  oblong  elevation  of  large  size,  the  tubercle  of  the  tibia 
(tuberositas  tibae);  the  lower  half  of  this  tubercle  is  rough,  for  the  attachment  of 
the  ligamentum  patellae;  the  upper  half  presents  a  smooth  facet  supporting,  in  the 
recent  state,  a  bursa  which  separates  the  ligament  from  the  bone.  Posteriorly  the 
tuberosities  are  separated  from  each  other  by  a  shallow  depression,  the  popliteal 
notch  (indsura  poplitea) ,  which  gives  attachment  to  part  of  the  posterior  crucial 
ligament  and  part  of  the  posterior  ligament  of  the  knee-joint.  The  inner  tuberosity 
presents  posteriorly  a  deep  transverse  groove,  for  the  insertion  of  one  of  the  fas- 
ciculi of  the  tendon  of  the  Semi-membranosus.  Its  lateral  surface  is  convex, 
rough,  and  prominent,  and  gives  attachment  to  the  internal  lateral  ligament.  The 
outer  tuberosity  presents  posteriorly  a  flat  articular  facet  (fades  articularis  fibularis), 
nearly  circular  in  form,  directed  downward,  backward,  and  outward,  for  articu- 
lation with  the  fibula.  Its  lateral  surface  is  convex  and  rough,  more  prominent 
in  front  than  the  internal,  and  presents  a  prominent  rough  eminence,  situated  on 


THE  TIBIA,    OR  SHIN  BONE  237 

a  level  with  the  upper  border  of  the  tubercle  of  the  tibia  at  the  junction  of  its 
anterior  and  outer  surfaces,  for  the  attachment  of  the  ilio-tibial  band.  Just  below 
this  the  Extensor  longus  digitorum  and  a  slip  from  the  Biceps  are  attached.  The 
infraglenoid  margin  (margo  infraglenoidalis)  is  at  the  outer  edge  of  the  superior 
articular  surface.  From  this  point  the  bone  rapidly  narrows  distally. 

Shaft  of  the  Tibia  (corpus  tibice). — The  shaft  of  the  tibia  is  of  a  triangular 
prismoid  form,  broad  above,  gradually  decreasing  in  size  to  its  most  slender  part, 
at  the  commencement  of  its  lower  fourth,  where  fracture  most  frequently  occurs; 
it  then  enlarges  again  toward  its  lower  extremity.  It  presents  for  examination 
three  borders  and  three  surfaces. 

Anterior  Border. — The  anterior  border,  the  most  prominent  of  the  three,  is 
called  the  crest  of  the  tibia  (crista  anterior) ,  or,  in  popular  language,  the  shin ;  it 
commences  above  at  the  tubercle,  and  terminates  below  at  the  anterior  margin 
of  the  inner  malleolus.  This  border  is  very  prominent  in  the  upper  two-thirds  of 
its  extent,  smooth  and  rounded  below.  It  presents  a  very  flexuous  course,  being 
usually  curved  outward  above  and  inward  below;  it  gives  attachment  to  the 
deep  fascia  of  the  leg. 

Internal  Border  (margo  medialis). — The  internal  border  is  smooth  and  rounded 
above  and  below,  but  more  prominent  in  the  centre;  it  commences  at  the  back 
part  of  the  inner  tuberosity,  and  terminates  at  the  posterior  border  of  the  inter- 
nal malleolus ;  its  upper  part  gives  attachment  to  the  internal  lateral  ligament  of 
the  knee  to  the  extent  of  about  two  inches,  and  to  some  fibres  of  the  Popliteus 
muscle,  and  its  middle  third  to  some  fibres  of  the  Soleus  and  Flexor  longus 
digitorum  muscles. 

External  Border  (crista  inter  ossea}. — The  external  border,  or  interosseous  ridge, 
is  thin  and  prominent,  especially  its  central  part,  and  gives  attachment  to  the 
interosseous  membrane ;  it  commences  above  in  front  of  the  fibular  articular  facet, 
and  bifurcates  below,  to  form  the  boundaries  of  a  triangular  rough  surface,  for 
the  attachment  of  the  interosseous  ligament  connecting  the  tibia  and  fibula. 

Internal  Surface  (fades  medialis). — The  internal  surface  is  smooth,  convex, 
and  broader  above  than  below;  its  upper  third,  directed  forward  and  inward,  is 
covered  by  the  aponeurosis  derived  from  the  tendon  of  the  Sartorius,  and  by  the 
tendons  of  the  Gracilis  and  Semitendinosus,  all  of  which  are  inserted  nearly  as 
far  forward  as  the  anterior  border;  in  the  rest  of  its  extent  it  is  subcutaneous. 

External  Surface  (fades  lateralis). — The  external  surface  is  narrower  than  the 
internal;  its  upper  two-thirds  presents  a  shallow  groove  for  the  attachment  of 
the  Tibialis  anticus  muscle;  its  lower  third  is  smooth,  convex,  curves  gradually 
forward  to  the  anterior  aspect  of  the  bone,  and  is  covered  from  within  outward  by 
the  tendons  of  the  following  muscles:  Tibialis  anticus,  Extensor  proprius  hallucis, 
Extensor  longus  digitorum. 

Posterior  Surface  (jades  posterior). — The  posterior  surface  (Fig.  171)  presents, 
at  its  upper  part,  a  prominent  ridge,  the  popliteal  line  or  the  oblique  line  of  the 
tibia  (linea  poplitea),  which  extends  from  the  back  part  of  the  articular  facet 
for  the  fibula  obliquely  downward,  to  the  internal  border,  at  the  junction  of 
its  upper  and  middle  thirds.  It  marks  the  lower  limit  for  the  insertion  of  the 
Popliteus  muscle,  and  serves  for  the  attachment  of  the  popliteal  fascia  and  part 
of  the  Soleus,  Flexor  longus  digitorum,  and  Tibialis  posticus  muscles;  the  tri- 
angular concave  surface,  above  and  to  the  inner  side  of  this  line,  gives  attach- 
ment to  the  Popliteus  muscle.  The  middle  third  of  the  posterior  surface  is 
divided  by  a  vertical  ridge  into  two  lateral  halves:  the  ridge  is  well  marked  at 
its  commencement  at  the  oblique  line,  but  becomes  gradually  indistinct  below; 
the  inner  and  broader  half  gives  attachment  to  the  Flexor  longus  digitorum,  the 
outer  and  narrower  to  part  of  the  Tibialis  posticus.  The  remaining  part  of  the 
bone  presents  a  smooth  surface  covered  by  the  Tibialis  posticus,  Flexor  longus 


238  THE  SKELETON 

digitorum,  and  Flexor  longus  hallucis  muscles.  Immediately  below  the  oblique 
line  is  the  nutritive  foramen  (foramen  nutridum),  which  is  large  and  directed 
obliquely  downward.  It  is  the  opening  of  the  nutrient  canal,  which  is  directed 
toward  the  periphery. 

Lower  Extremity. — The  lower  extremity,  much  smaller  than  the  upper, 
presents  five  surfaces;  it  is  prolonged  downward,  on  its  inner  side,  to  a  strong 
process,  the  internal  malleolus  (malleolus  medialis). 

Inferior  Surface  (fades  articularis  inferior). — The  inferior  surface  of  the  bone 
is  quadrilateral,  and  smooth  for  articulation  with  the  astragalus.  This  surface 
is  concave  from  before  backward,  and  broader  in  front  than  behind.  It  is  trav- 
ersed from  before  backward  by  a  slight  elevation,  separating  two  lateral  depres- 
sions. It  is  narrow  internally,  where  the  articular  surface  becomes  continuous 
with  that  on  the  inner  malleolus  (fades  articularis  malleolaris) . 

Anterior  Surface. — The  anterior  surface  of  the  lower  extremity  is  smooth  and 
rounded  above,  and  covered  by  the  tendons  of  the  Extensor  muscles  of  the  toes; 
its  lower  margin  presents  a  rough  transverse  depression,  for  the  attachment  of 
the  anterior  ligament  of  the  ankle-joint. 

Posterior  Surface. — The  posterior  surface  presents  a  superficial  groove  directed 
obliquely  downward  and  inward,  continuous  with  a  similar  groove  on  the  posterior 
surface  of  the  astragalus,  and  serving  for  the  passage  of  the  tendon  of  the  Flexor 
longus  hallucis. 

External  Surface. — The  external  surface  presents  a  triangular  rough  depression 
for  the  attachment  of  the  interior  interosseous  ligament,  connecting  it  with  the 
fibula;  the  lower  part  of  this  depression,  the  fibular  notch  (incisura  fibularis),  is 
smooth,  covered  with  cartilage  in  the  recent  state,  and  articulates  with  the  fibula. 
This  surface  is  bounded  by  two  prominent  borders,  continuous  above  with  the 
interosseous  ridge;  they  afford  attachment  to  the  anterior  inferior  and  posterior 
inferior  tibio-fibular  ligaments. 

Internal  Surface. — The  internal  surface  of  the  lower  extremity  is  prolonged 
downward  to  form  a  strong  pyramidal  process,  flattened  from  without  inward — 
the  internal  malleolus  (malleolus  medialis).  The  inner  surface  of  this  process  is 
convex  and  subcutaneous;  its  outer  surface  is  smooth  and  slightly  concave,  and 
articulates  with  the  astragalus;  its  anterior  border  is  rough,  for  the  attachment  of 
the  anterior  fibres  of  the  internal  lateral  or  Deltoid  ligament;  its  posterior  border 
presents  a  broad  and  deep  groove  (sulcus  malleolaris),  directed  obliquely  down- 
ward and  inward,  which  is  occasionally  double:  this  groove  transmits  the  tendons 
of  the  Tibialis  posticus  and  Flexor  longus  digitorum  muscles.  The  summit  of  the 
internal  malleolus  is  marked  by  a  rough  depression  behind,  for  the  attachment  of 
the  internal  lateral  ligament  of  the  ankle-joint. 

Structure. — Like  that  of  the  other  long  bones.  At  the  junction  of  the  middle 
and.  lower  third,  where  the  bone  is  smallest,  the  wall  of  the  shaft  is  thicker  than 
in  other  parts,  in  order  to  compensate  for  the  smallness  of  the  calibre  of  the  bone. 

Development. — By  three  centres  (Fig.  173) :  one  for  the  shaft  and  one  for 
each  extremity.  Ossification  commences  in  the  centre  of  the  shaft  about  the 
seventh  week,  and  gradually  extends  toward  either  extremity.  The  centre  for  the 
upper  epiphysis  appears  before  or  shortly  after  birth;  it  is  flattened  in  form,  and 
has  a  thin,  tongue-shaped  process  in  front  which  forms  the  tubercle.  That  for 
the  lower  epiphysis  appears  in  the  second  year.  The  lower  epiphysis  joins  the 
shaft  at  about  the  eighteenth,  and  the  upper  one  about  the  twentieth  year.  Two 
additional  centres  occasionally  exist — one  for  the  tongue-shaped  process  of  the 
upper  epiphysis,  which  forms  the  tubercle,  and  one  for  the  inner  malleolus. 

Articulations. — With  three  bones:  the  femur,  fibula,  and  astragalus 

Attachment  of  Muscles. — To  twelve:  to  the  inner  tuberosity,  the  Semimem- 
branosus;  to  the  outer  tuberosity,  the  Tibialis  anticus  and  Extensor  longus  digi- 


THE  FIBULA,   OR  CALF  BONE 


239 


Upper  extremity. 


Appears  at 
birth. 


roins  shaft  about 
20th  year. 


torum  and  Biceps;  to  the  shaft,  its  internal  surface,  the  Sartorius,  (Jracilis,  and 
Semitendinosus;  to  its  external  surface,  the  Tibialis  anticus;  to  its  posterior  sur- 
face, the  Popliteus,  Soleus,  Flexor  longus  digi torum,  and  Tibialis  posticus;  to  the 
tubercle,  the  ligamentum  patellae,  by  which  the  Quadriceps  extensor  muscle  is 

inserted  into  the  tibia.  In  addition  to 
these  muscles,  the  Tensor  fasciae  femoris 
is  inserted  indirectly  into  the  tibia,  through 
the  ilio-tibial  band,  and  the  Peroneus  lon- 
gus occasionally  derives  a  few  fibres  of 
origin  from  the  outer  tuberosity. 

Surface  Form. — A  considerable  portion  of  the 
tibia  is  subcutaneous  and  easily  to  be  felt.  At 
the  upper  extremity  the  tuberosities  are  to  be 
recognized  just  below  the  knee.  The  internal 
one  is  broad  and  smooth,  and  merges  into  the 
subcutaneous  surface  of  the  shaft  below.  The 
external  one  is  narrower  and  more  prominent, 
and  on  it,  about  midway  between  the  apex  of  the 
patella  and  the  head  of  the  fibula,  may  be  felt  a 
prominent  tubercle  for  the  insertion  of  the  iiio- 
tibial  band.  In  front  of  the  upper  end  of  the 
bone,  between  the  tuberosities,  is  the  tubercle  of 
the  tibia,  forming  an  oval  eminence  which  is  con- 
tinuous below  with  the  anterior  border  or  crest 
of  the  bone.  This  border  can  be  felt,  forming 
the  prominence  of  the  shin,  in  the  upper  two- 
thirds  of  its  extent  as  a  sharp  and  flexuous  ridge, 
curved  outward  above  and  inward  below.  In 
the  lower  third  of  the  leg  the  border  disappears, 
and  the  bone  is  concealed  by  the  tendons  of  the 
muscles  on  the  front  of  the  leg.  Internal  to  the 
anterior  border  is  to  be  felt  the  broad  internal 
surface  of  the  tibia,  slightly  encroached  upon  by  the  muscles  in  front  and  behind.  It  com- 
mences above  at  the  wide  expanded  inner  tuberosity,  and  terminates  below  at  the  internal 
malleolus.  The  internal  malleolus  is  a  broad  prominence  situated  on  a  higher  level  and  some- 
what farther  forward  than  the  external  malleolus.  It  overhangs  the  inner  border  of  the  arch 
of  the  foot.  Its  anterior  border  is  nearly  straight;  its  posterior  border  presents  a  sharp  edge 
which  forms  the  inner  margin  of  the  groove  for  the  tendon  of  the  Tibialis  posticus  muscle. 


Appears  at  2nd_ 
year. 


Joins  shaft  about 
18th  year. 


Lower  extremity. 

FIG.  173. — Plan  of  the  development  of  the  tibia. 
By  three  centres. 


The  Fibula,  or  Calf  Bone  (Figs.  170,  171). 

The  fibula  (fibula,  a  clasp)  is  situated  at  the  outer  side  of  the  leg.  It  is  the 
smaller  of  the  two  bones,  and,  in  proportion  to  its  length,  the  most  slender  of  all 
the  long  bones;  it  is  placed  on  the  outer  side  of  the  tibia,  with  which  it  is  con- 
nected above  and  below.  Its  upper  extremity  is  small,  placed  toward  the  back  of 
the  head  of  the  tibia  and  below  the  level  of  the  knee-joint,  and  excluded  from  its 
formation;  the  lower  extremity  inclines  a  little  forward,  so  as  to  be  on  a  plane 
anterior  to  that  of  the  upper  end,  projects  below  the  tibia,  and  forms  the  outer 
ankle.  It  presents  for  examination  a  shaft  and  two  extremities. 

Upper  Extremity. — The  upper  extremity,  or  head  (capitulum  fibulae],  is  of 
an  irregular  quadrate  form,  presenting  above  a  flattened  articular  facet,  directed 
upward,  forward,  and  inward,  for  articulation  with  a  corresponding  facet  on  the 
external  tuberosity  of  the  tibia.  On  the  outer  side  is  a  thick  and  rough  promi- 
nence, continued  behind  into  a  pointed  eminence,  the  styloid  process  of  the  fibula 
(apex  capituli  fibula?),  which  projects  upward  from  the  posterior  part  of  the 
head.  The  prominence  gives  attachment  to  the  tendon  of  the  Biceps  muscle 
and  to  the  long  external  lateral  ligament  of  the  knee,  the  ligament  dividing  the 
tendon  into  two  parts.  The  summit  of  the  styloid  process  gives  attachment  to 


240  THE  SKELETON 

the  short  external  lateral  ligament.  The  remaining  part  of  the  circumference  of  the 
head  is  rough,  for  the  attachment  of  muscles  and  ligaments.  It  presents  in  front 
a  tubercle  for  the  origin  of  the  upper  and  anterior  part  of  the  Peroneus  longus,  and 
the  adjacent  surface  gives  attachment  to  the  anterior  superior  tibio-fibular  liga- 
ment; and  behind,  another  tubercle  for  the  attachment  of  the  posterior  superior 
tibio-fibular  ligament  and  the  upper  fibres  of  the  Soleus  muscle. 

Shaft  of  the  Fibula  (corpus  fibulw). — The  shaft  presents  four  borders — 
the  antero-external,  the  antero-internal,  the  postero-external,  and  the  postero- 
internal;  and  four  surfaces — anterior,  posterior,  internal,  and  external. 

Antero-external  Border  (crista  anterior) . — The  antero-external  border  commences 
above  in  front  of  the  head,  runs  vertically  downward  to  a  little  below  the  middle  of 
the  bone,  arid  then,  curving  somewhat  outward,  bifurcates  so  as  to  embrace  the 
triangular  subcutaneous  surface  immediately  above  the  outer  surface  of  the  exter- 
nal malleolus.  This  border  gives  attachment  to  an  intermuscular  septum,  which 
separates  the  extensor  muscles  on  the  anterior  surface  of  the  leg  from  the  Peroneus 
longus  and  brevis  muscles  on  the  outer  surface. 

Antero-internal  Border  (crista  interossea)  .—The  antero-internal  border,  or  inter- 
osseous  ridge,  is  situated  close  to  the  inner  side  of  the  preceding,  and  runs  nearly 
parallel  with  it  in  the  upper  third  of  its  extent,  but  diverges  from  it  so  as  to 
include  a  broader  space  in  the  lower  two-thirds.  It  commences  above,  just 
beneath  the  head  of  the  bone  (sometimes  it  is  quite  indistinct  for  about  an 
inch  below  the  head),  and  terminates  below  at  the  apex  of  a  rough  triangular 
surface  immediately  above  the  articular  facet  of  the  external  malleolus.  It  serves 
for  the  attachment  of  the  interosseous  membrane,  which  separates  the  extensor 
muscles  in  front  from  the  flexor  muscles  behind. 

Postero-external  Border  (crista  lateralis) . — The  postero-external  border  is  promi- 
nent ;  it  commences  above  at  the  base  of  the  styloid  process,  and  terminates  below 
in  the  posterior  border  of  the  outer  malleolus.  It  is  directed  outward  above,  back- 
ward in  the  middle  of  its  course,  backward  and  a  little  inward  below,  and  gives 
attachment  to  an  aponeurosis  which  separates  the  Peronei  muscles  on  the  outer 
surface  of  the  shaft  from  the  flexor  muscles  on  its  posterior  surface. 

Postero-internal  Border  (crista  medialis). — The  postero-internal  border,  some- 
times called  the  oblique  line,  commences  above  at  the  inner  side  of  the  head, 
and  terminates  by  becoming  continuous  with  the  antero-internal  border  or  inter- 
osseous  ridge  at  the  lower  fourth  of  the  bone.  It  is  well  marked  and  promi- 
nent at  the  upper  and  middle  parts  of  the  bone.  It  gives  attachment  to  an 
aponeurosis  which  separates  the  Tibialis  posticus  from  the  Soleus  above  and  the 
Flexor  longus  hallucis  below. 

Anterior  Surface  (fades  anterior) , — The  anterior  surface  is  the  interval  between 
the  antero-external  and  antero-internal  borders.  It  is  extremely  narrow  and  flat 
in  the  upper  third  of  its  extent;  broader  and  grooved  longitudinally  in  its  lower 
third;  it  serves  for  the  attachment  of  three  muscles,  the  Extensor  longus  digitorum, 
Peroneus  tertius,  and  Extensor  proprius  hallucis. 

External  Surface  (fades  lateralis). — The  external  surface  is  the  space  between 
the  antero-external  and  postero-external  borders.  It  is  much  broader  than  the 
preceding,  and  often  deeply  grooved,  is  directed  outward  in  the  upper  two-thirds 
of  its  course,  backward  in  the  lower  third,  where  it  is  continuous  with  the  poste- 
rior border  of  the  external  malleolus.  This  surface  is  completely  occupied  by 
the  Peroneus  longus  and  brevis  muscles. 

Internal  Surface  (facies  medialis). — The  internal  surface  is  the  interval  included 
between  the  antero-internal  and  the  postero-internal  borders.  It  is  directed 
inward,  and  is  grooved  for  the  attachment  of  the  Tibialis  posticus  muscle. 

Posterior  Surface  (facies  posterior). — The  posterior  surface  is  the  space  included 
between  the  postero-external  and  the  postero-internal  borders,  it  is  continuous 


THE  FIBULA,    OR   CALF  BONE 


241 


below  with  the  rough  triangular  surface  above  the  articular  facet  of  the  outer 
malleolus;  it  is  directed  backward  above,  backward  and  inward  at  its  middle, 
directly  inward  below.  Its  upper  third  is  rough,  for  the  attachment  of  the  Soleus 
muscle;  its  lower  part  presents  a  triangular  rough  surface,  connected  to  the  tibia 
by  a  strong  interosseous  ligament,  and  between  these  two  points  the  entire  surface 
is  covered  by  the  fibres  of  origin  of  the  Flexor  longus  hallucis  muscle.  At  about 
the  middle  of  this  surface  is  the  nutrient  foramen  (foramen  nutricium).  It  opens 
into  the  nutrient  canal  (canalis  nutricius) ,  which  is  directed  downward. 

Lower  Extremity. — The  lower  extremity,  or  external  malleolus  (malleolus 
lateralis],  is  of  a  pyramidal  form,  somewhat  flattened  from  without  inward,  and 
is  longer,  and  descends  lower  than  the  internal  malleolus.  Its  external  surface  is 
convex,  subcutaneous,  and  continuous  with  the  triangular  (also  subcutaneous) 
surface  on  the  outer  side  of  the  shaft.  The  internal  surface  presents  in  front  a 
smooth  triangular  facet  (fades  articularis  malleoli).  broader  above  than  below,  and 
convex  from  above  downward,  which  articulates  with  a  corresponding  surface  on 
the  outer  side  of  the  astragalus.  Behind  and  beneath  the  articular  surface  is  a 
rough  depression  which  gives  attachment  to  the  posterior  fasciculus  of  the  external 
lateral  ligament  of  the  ankle.  The  anterior  border  is  thick  and  rough,  and  marked 
below  by  a  depression  for  the  attachment  of  the  anterior  fasciculus  of  the  external 
lateral  ligament.  The  posterior  border  is  broad  and  marked  by  a  shallow  groove 
(sulcus  malleolaris) ,  for  the  passage  of  the  tendons  of  the  Peroneus  longus  and 
brevis  muscles.  The  summit  is  rounded,  and  gives  attachment  to  the  middle 
fasciculus  of  the  external  lateral  ligament. 

In  order  to  distinguish  the  side  to  which  the  bone  belongs,  hold  it  with  the 
lower  extremity  downward  and  the  broad  groove  for  the  Peronei  tendons  back- 
ward— i.e.,  toward  the  holder;  the  triangular  subcutaneous  surface  will  then  be 
directed  to  the  side  to  which  the  bone  belongs. 

Articulations.— With  two  bones:  the  tibia  and 
astragalus. 

Development. — By  three  centres  (Fig.  174):  one 
for  the  shaft,  and  one  for  each  extremity.  Ossification 
commences  in  the  shaft  about  the  eighth  week  of  foetal 
life,  a  little  later  than  in  the  tibia,  and  extends  gradu- 
ally toward  the  extremities.  At  birth  both  ends  are 
cartilaginous.  Ossification  commences  in  the  lower 
end  in  the  second  year,  and  in  the  upper  one  about  the 
fourth  year.  The  lower  epiphysis,  the  first  in  which 
ossification  commences,  becomes  united  to  the  shaft 
about  the  twentieth  year;  the  upper  epiphysis  joins 
about  the  twenty-fifth  year.  Ossification  appearing 
first  in  the  lower  epiphysis  is  contrary  to  the  rule 
which  prevails  with  regard  to  the  commencement  of 
ossification  in  epiphyses — viz.,  that  epiphysis  toward 
which  the  nutrient  artery  is  directed  commences  to 
ossify  last;  but  it  follows  the  rule  which  prevails  with 
regard  to  the  union  of  epiphyses,  by  uniting  first. 

Attachment  of  Muscles. — To  nine:   to  the  head, 
the  Biceps,  Soleus,  and  Peroneus  longus;  to  the  shaft, 
its  anterior  surface,  the  Extensor  longus  digitorum, 
Peroneus  tertius,  and  Extensor  proprius  hallucis;  to  Flo  174._PiaTof'heTevdopment 
the  internal  surface,  the  Tibiahs  posticus;  to  the  pos-     of  the  fibula.    By  three  centres. 
terior  surface,  the  Soleus  and  Flexor  longus  hallucis,  to  the  external  surface,  the 
Peroneus  longus  and  brevis. 

Surface  Form. — The  only  parts  of  the  fibula  which  are  to  be  felt  are  the  head  and  the  lower 
part  of  the  external  surface  of  the  shaft  and  the  external  malleolus.  The  head  is  to  be  seen 

16 


Upper  extremity. 


Appears  about    , 
4th  year. 


I'n  it  en  about 
25th  year. 


Appears  at 
2nd  year.  ~ 


Unites  about 
20th  year. 


242 


THE  SKELETON 


Groove  for  PERONEUS  LONQUS 
Groove  for  PERONEUS  BREVIS. 


PERONEUS  TERTIUS 
PERONEUS  BREVIS, 


Groove  for  tendon  of 

FLEXOR    LONQUS    HALLUCIS. 


Tarsus. 


Metatarsus. 


Innermost  tendon  of 

EXTENSOR    BREVIS    DIQITORUM. 


'Tiaftl    Phalanges. 


EXTENSOR    LONQUS    HALUICIS. 


FIG.   175  — Bones  of  the  right  foot.     Dorsal  surface. 


THE    FOOT 


243 


OUTER    HEAD    OF    ACCESSORIUS, 


FLEXOR    LONQUS    OIQITORUM. 


FIG.  176. — Bones  of  the  right  foot.     Plantar  surface. 


244  THE  SKELETON 

and  felt  behind  and  to  the  outer  side  of  the  outer  tuberosity  of  the  tibia.  It  presents  a  small, 
prominent  triangular  eminence  slightly  above  the  level  of  the  tubercle  of  the  tibia.  The  exter- 
nal malleolus  presents  a  narrow  elongated  prominence,  situated  on  a  plane  posterior  to  the 
internal  malleolus  and  reaching  to  a  lower  level.  From  it  may  be  traced  the  lower  third  or 
half  of  the  external  surface  of  the  shaft  of  the  bone  in  the  interval  between  the  Peroneus  tertius 
in  front  and  the  other  two  Peronei  tendons  behind. 

Surgical  Anatomy. — In  fractures  of  the  bones  of  the  leg  both  bones  are  usually  fractured,  but 
either  bone  may  be  broken  separately,  the  fibula  more  frequently  than  the  tibia.  Fracture  of 
both  bones  may  be  caused  either  by  direct  or  indirect  violence.  When  it  occurs  from  indirect 
force,  the  fracture  in  the  tibia  is  usually  at  the  junction  of  the  middle  and  lower  third  of  the  bone. 
Many  causes  conduce  to  render  this  the  weakest  part  of  the  bone.  The  fracture  of  the  fibula 
is  usually  at  rather  a  higher  level  These  fractures  present  great  variety,  both  as  regards 
their  direction  and  condition.  They  may  be  oblique,  transverse,  longitudinal,  or  spiral.  When 
oblique,  they  are  usually  the  result  of  indirect  violence,  and  the  direction  of  the  fracture  is  from 
behind,  downward,  forward,  and  inward  in  many  cases,  but  may  be  downward  and  outward 
or  downward  and  backward.  When  transverse,  the  fracture  is  often  at  the  upper  part  of  the 
bone,  and  is  the  result  of  direct  violence.  The  spiral  fracture  usually  commences  as  a  vertical 
fissure,  involving  the  ankle-joint,  and  is  associated  with  fracture  of  the  fibula  higher  up.  It  is 
the  result  of  torsion,  from  twisting  of  the  body  whilst  the  foot  is  fixed. 

Fractures  of  the  tibia  alone  are  almost  always  the  result  of  direct  violence,  except  where  the 
malleolus  is  broken  off  by  twists  of  the  foot.  Fractures  of  the  fibula  alone  may  arise  from  indi- 
rect or  direct  force,  those  of  the  lower  end  being  usually  the  result  of  the  former,  and  those 
higher  up  being  caused  by  a  direct  blow  on  the  part. 

The  tibia  and  fibula,  like  the  femur,  are  frequently  the  seat  of  acute  osteomyelitis.  Tuberculous 
abscess  is  more  frequently  met  with  in  the  cancellous  tissue  of  the  head  and  lower  end  of  the 
tibia  than  in  any  other  bone  of  the  body.  The  abscess  is  of  small  size;  very  chronic,  and  prob- 
ably the  result  of  tuberculous  osteitis  in  the  highly  vascular  growing  tissue  at  the  end  of  the  shaft 
near  the  epiphysial  cartilage  in  the  young  subject.  Such  an  abscess  in  bone  is  called  Brodie's 
abscess. 

The  tibia  is  the  bone  which  is  most  frequently  and  most  extensively  distorted  in  rickets.  It 
gives  way  at  the  junction  of  the  middle  and  lower  third,  its  weakest  part,  and  presents  a  curve 
forward  and  outward.  Bow-leg  is  due  to  outward  curvature  of  the  femur,  tibia,  and  fibula, 
the  bend  being  about  the  junction  of  the  shafts  and  lower  extremities. 

THE  FOOT  (Figs.  175,  176). 

The  skeleton  of  the  foot  consists  of  three  divisions:  the  tarsus,  metatarsus,  and 
phalanges. 

The  Tarsus  (Ossa  Tarsi). 

The  bones  of  the  tarsus  are  seven  in  number — viz.,  the  calcaneus  or  os  calcis, 
astragalus,  cuboid,  scaphoid,  internal,  middle,  and  external  cuneiform. 

The  Calcaneus,  or  Heel  Bone  (Fig.  177). — It  is  also  called  the  os  calcis.  The 
name  is  derived  from  calx,  the  heel.  The  heel  bone  is  the  largest  and  strongest  of 
the  tarsal  bones.  It  is  irregularly  cuboidal  in  form,  having  its  long  axis  directed  for- 
ward and  outward.  It  is  situated  at  the  lower  and  back  part  of  the  foot,  serving  to 
transmit  the  weight  of  the  body  to  the  ground,  and  forming  a  strong  lever  for  the 
muscles  of  the  calf.  It  is  composed  of  a  body  (corpus  calcanei) ,  an  anterior  extremity 
or  greater  process,  and  a  posterior  extremity  or  tuberosity  (tuber  calcanei).  It  pre- 
sents for  examination  six  surfaces:  superior,  inferior,  external,  internal,  anterior, 
and  posterior. 

Superior  Surface. — The  superior  surface  is  formed  behind  by  the  upper  aspect 
of  that  part  of  the  os  calcis  which  projects  backward  to  form  the  heel.  It  varies 
in  length  in  different  individuals;  is  convex  from  side  to  side,  concave  from  before 
backward,  and  corresponds  above  to  a  mass  of  adipose  substance  placed  in 
front  of  the  tendo  Achillis.  In  the  middle  of  the  superior  surface  are  two  (some- 
times three)  articular  facets,  separated  by  a  broad  shallow  groove  (sulcus  cal- 
canei), which  is  directed  obliquely  forward  and  outward,  and  is  rough  for  the 
attachment  of  the  interosseous  ligament  connecting  the  astragalus  and  os  calcis. 
When  the  calcaneus  is  in  contact  with  the  astragalus  this  groove  is  converted  into 


THE  TARSUS  245 

a  canal  (sinus  tarsi).  Of  the  articular  surfaces,  the  external  or  posterior  articular 
surface  (fades  articidaris  calcanea  posterior)  is  the  larger,  and  is  situated  on  the  body 
of  the  bone:  it  is  of  an  oblong  form,  wider  behind  than  in  front,  and  convex  from 
before  backward.  The  internal  or  anterior  articular  surface  is  usually  divided  into 
two  facets.  The  anterior  facet  is  the  fades  articularls  calcanea  anterior,  and  it 
supports  the  head  of  the  astragalus.  The  more  posteriorly  situated  facet  is  the 
fades  articularis  calcanea  media.  It  articulates  with  the  middle  facet  on  the 
under  surface  of  the  astragalus.  The  internal  articular  surface  is  supported  on 
a  projecting  process  of  bone,  called  the  lesser  process  of  the  calcaneus  (sustcn- 
taculum  tali] ;  if  is  also  oblong,  concave  longitudinally,  and  sometimes  subdivided 
into  two  parts,  which  dift'er  in  size  and  shape.  More  anteriorly  is  seen  the  upper 
surface  of  the  greater  process  of  the  calcaneus,  marked  by  a  rough  depression 
for  the  attachment  of  numerous  ligaments,  and  a  tubercle  for  the  origin  of  the 
Extensor  brevis  digitorum  muscle. 

A 

Peroneal  tubercle. 
Groove  for 
Peroneus  brevis. 


Groove  for  ^^^^f^^For  tendo 

Peroneus  longus.  Tubercle  for  ext.  lat.  lig.       Achillis. 


For  astragalus. 


Sustentaciilum         For  cuboid. 
/  tali. 

Groore  for  Flex, 
long,  hallucis. 

FIG.  177. — The  left  calcaneus.     A.  Postero-external  view.     B.  Antero-internal  view. 

Inferior  Surface. — The  inferior  surface  is  narrow,  rough,  uneven,  wider  behind 
than  in  front  and  convex  from  side  to  side;  it  is  bounded  posteriorly  by  two  tuber- 
cles separated  by  a  rough  depression;  the  external  tubercle  (processus  lateralis  tuber  is 
calcanei),  small,  prominent,  and  rounded,  gives  attachment  to  part  of  the  Abductor 
minimi  digiti :  the  internal  tubercle  (processus  medialis  tuberis  calcanei) ,  broader 
and  larger,  for  the  support  of  the  heel,  gives  attachment,  by  its  prominent  inner 
margin,  to  the  Abductor  hallucis,  and  in  front  to  the  Flexor  brevis  digitorum 
muscles  and  plantar  fascia;  the  depression  between  the  tubercles  gives  attach- 
ment to  the  Abductor  minimi  digiti.  The  rough  surface  in  front  of  the  tubercles 
gives  attachment  to  the  long  plantar  ligament  and  to  the  outer  head  of  the  Flexor 
accessorius  muscle;  while  to  a  prominent  tubercle  nearer  the  anterior  part  of 


246  THE  SKELETON 

this  surface,  as  well  as  to  a  transverse  groove  in  front  of  it,  is  attached  the 
short  plantar  ligament. 

External  Surface. — The  external  surface  is  broad,  flat,  and  almost  subcutaneous; 
it  presents  near  its  centre  a  tubercle,  for  the  attachment  of  the  middle  fasciculus 
of  the  external  lateral  ligament.  At  its  upper  and  anterior  part  this  surface 
gives  attachment  to  the  external  calcaneo-astragaloid  ligament;  and  in  front  of 
the  tubercle  it  presents  a  narrow  surface  marked  by  two  oblique  grooves,  sepa- 
rated by  an  elevated  ridge  which  varies  much  in  size  in  different  bones;  it  is 
named  the  peroneal  spine  or  tubercle  (processus  trochlearis) ,  and  gives  attachment 
to  a  fibrous  process  from  the  external  annular  ligament.  The  superior  groove 
transmits  the  tendon  of  the  Peroneus  brevis;  the  inferior  groove  the  tendon  of 
the  Peroneus  longus. 

Internal  Surface. — The  internal  surface  is  deeply  concave;  it  is  directed  obliquely 
downward  and  forward,  and  serves  for  the  transmission  of  the  plantar  vessels 
and  nerves  into  the  sole  of  the  foot;  it  affords  attachment  to  part  of  the  Flexor 
accessorius  muscle.  At  its  upper  and  fore  part  it  presents  an  eminence  of  bone, 
the  lesser  process  of  the  calcaneum  (sustentaculum  tali),  which  projects  horizon- 
tally inward,  and  to  it  a  slip  of  the  tendon  of  the  Tibialis  posticus  is  attached. 
This  process  is  concave  above,  and  supports  the  anterior  articular  surface  of 
the  astragalus;  below,  it  is  grooved  for  the  tendon  of  the  Flexor  longus  hallucis. 
Its  free  margin  is  rough,  for  the  attachment  of  part  of  the  internal  lateral  liga- 
ment of  the  ankle-joint. 

Anterior  Surface  (fades  articularis  cuboidea). — The  anterior  surface,  of  a  some- 
what triangular  form,  articulates  with  the  cuboid.  It  is  concave  from  above 
downward  and  outward,  and  convex  in  the  opposite  direction.  Its  inner  border 
gives  attachment  to  the  inferior  calcaneo-scaphoid  ligament. 

Posterior  Surface. — The  posterior  surface  is  rough,  prominent,  convex,  and 
wider  below  than  above.  The  posterior  extremity  is  the  projection  of  the  heel. 
It  is  called  the  tuberosity  (tuber  calcanei).  Its  lower  part  is  rough,  for  the  attach- 
ment of  the  tendo  Achillis  and  the  tendon  of  the  Plantaris  muscle ;  its  upper  part 
is  smooth,  and  is  covered  by  a  bursa  which  separates  the  tendons  from  the  bone. 

Articulations. — With  two  bones:  the  astragalus  and  cuboid. 

Attachment  of  Muscles. — To  eight :  part  of  the  Tibialis  posticus,  the  tendo 
Achillis,  Plantaris,  Abductor  hallucis,  Abductor  minimi  digiti,  Flexor  brevis  digi- 
torum,  Flexor  accessorius,  and  Extensor  brevis  digitorum. 

The  Astragalus,  or  Ankle  Bone  (talus)  (Fig.  178). — The  astragalus  (da-pdjaXo;;, 
a  die)  is  the  largest  of  the  tarsal  bones,  next  to  the  os  calcis.  It  occupies  the 
middle  and  upper  part  of  the  tarsus,  supporting  the  tibia  above,  articulating 
with  the  malleoli  on  either  side,  resting  below  upon  the  os  calcis,  and  joined  in 
front  to  the  scaphoid.  This  bone  may  easily  be  recognized  by  its  large  rounded 
head,  by  the  broad  articular  facet  on  its  upper  convex  surface,  and  by  the  two 
articular  facets  separated  by  a  deep  groove  on  its  under  concave  surface.  It 
is  divided  into  a  body  (corpus  tali),  which  supports  the  trochlear  surface;  the 
head  (caput  tali),  which  is  in  front  of  the  body;  and  the  neck  (collum  tali),  the 
constricted  part  between  the  head  .and  body.  The  astragalus  presents  six 
surfaces  for  examination. 

Superior  Surface. — The  superior  surface  presents,  behind,  a  broad  smooth 
trochlear  surface  (trochlea  tali)  for  articulation  with  the  tibia.  The  trochlea  is 
broader  in  front  than  behind,  convex  from  before  backward,  slightly  concave 
from  side  to  side;  in  front  of  it  is  the  upper  surface  of  the  neck  of  the 
astragalus,  rough  for  the  attachment  of  ligaments. 

Inferior  Surface. — The  inferior  surface  presents  two  articular  facets  separated 
by  a  deep  groove  (sulcus  tali).  The  groove  runs  obliquely  forward  and  outward, 
becoming  gradually  broader  and  deeper  in  front:  it  corresponds  with  a  similar 


THE  TARSUS 


247 


groove  upon  the  upper  surface  of  the  calcaneus,  and  forms,  when  articulated  with 
that  bone,  a  canal  (sinus  tarsi),  filled  up  in  the  recent  state  by  the  interosseous 
calcaneo-astragaloid  ligament.  Of  the  two  articular  facets,  the  posterior  articular 
facet  (fades  articularis  calcanea  posterior)  is  the  larger,  of  an  oblong  form  and 
deeply  concave  from  side  to  side;  the  anterior  articular  facet  is  shorter  and  nar- 
rower, of  an  elongated  oval  form,  convex  longitudinally,  and  often  subdivided  into 
two  by  an  elevated  ridge ;  of  these,  the  posterior  (fades  articularis  calcanea  media) 
articulates  with  the  lesser  process  of  the  os  calcis ;  the  anterior  (fades  articularis 
calcanea  (interior) ,  with  the  upper  surface  of  the  inferior  calcaneo-scaphoid  ligament. 

Internal  Surface. — The  internal  surface  presents  at  its  upper  part  a  pear-shaped 
articular  facet  (fades  malleolaris  medialis)  for  the  inner  malleolus,  continuous 
above  with  the  trochlear  surface;  below  the  articular  surface  is  a  rough 
depression,  for  the  attachment  of  the  deep  portion  of  the  internal  lateral  ligament. 

External  Surface. — The  external  surface  presents  a  large  triangular  facet  (fades 
malleolaris  lateralis),  covered  with  cartilage  and  concave  from  above  downward 


for 
navicular.    Neck. 


Sup.  surface 
for  tibia. 


For  inner 
malleolus. 

For  navicular. 


For  ext.- 
malleolus. 


^For  inferior 
calc.  name.  lig. 


Groove  for 
Flex.  long.  hall. 

FIG.   178. — The  left  astragalus.     A.  Superior  and  external  view.     B.  Inferior  and  internal  view. 


for  articulation  with  the  external  malleolus ;  it  is  called  the  external  process  (pro- 
cessus  lateralis  tali),  and  passes  outward  and  downward  from  the  triangular  facet. 
The  triangular  facet  is  continuous  above  with  the  trochlear  surface;  and  in  front 
of  it  is  a  rough  depression  for  the  attachment  of  the  anterior  fasciculus  of  the 
external  lateral  ligament  of  the  ankle-joint. 

Anterior  Surface  (fades  articularis  navicularis) . — The  anterior  surface  of  the 
head  of  the  astragalus  is  convex  and  rounded,  smooth,  of  an  oval  form,  and 
directed  obliquely  inward  and  downward;  it  articulates  with  the  scaphoid.  On 
its  under  and  inner  surface  is  a  small  facet,  continuous  in  front  with  the  articular 
surface  of  the  head,  and  behind  with  the  smaller  facet  for  the  os  calcis.  This 
rests  on  the  inferior  calcaneo-scaphoid  ligament,  being  separated  from  it  by  the 
sy  no  vial  membrane,  which  is  prolonged  from  the  anterior  calcaneo-astragaloid 
joint  to  the  astragalo-scaphoid  joint.  The  head  is  surrounded  by  a  constricted 
portion,  the  neck  of  the  astragalus  (collum  tali). 

Posterior  Surface. — The  posterior  surface  is  narrow,  and  traversed  by  a  groove 
(sulcus  m.  ftexoris  halluds  longi),  which  runs  obliquely  downward  and  inward, 
and  transmits  the  tendon  of  the  Flexor  longus  hallucis,  external  to  which  is 
the  prominent  external  tubercle  (processus  posterior  tali),  to  which  the  posterior 
fasciculus  of  the  external  lateral  ligament  is  attached.  This  tubercle  is  some- 
times separated  from  the  rest  of  the  astragalus,  and  is  then  known  as  the  os 
trigonum.  To  the  inner  side  of  the  groove  is  the  less  marked  internal  tubercle. 

To  ascertain  to  which  foot  the  bone  belongs,  hold  it  with  the  broad  articular 
surface  upward,  and  the  rounded  head  forward;  the  lateral  triangular  articular 
surface  for  the  external  malleolus  will  then  point  to  the  side  to  which  the  bone 
belongs. 


248 


THE  SKELETON 


Articulations. — With  four  bones:  tibia,  fibula,  os  calcis,  and  scaphoid. 
The   Cuboid    (os  cuboideum)    (Fig.  179). — The  cuboid,  from  xu/9oc,  a  cube; 
tidos,  like,  is  placed  on  the  outer  side  of  the  foot,  in  front  of  the  os  calcis,  and 


For  ext. 
cuneiform. 


For  fourth 
metatarsal. 


Occasional  facet 
for  navicular. 


Groove  for 

Peroneus  longus.    For  os  calcis. 
For  fifth  metatarsal. 
FIG.  179. — The  left  cuboid.     A.  Antero-internal  view.     B.  Postero-external  view. 

behind  the  fourth  and  fifth  metatarsal  bones.  It  is  of  a  pyramidal  shape,  its 
base  being  directed  inward,  its  apex  outward.  It  may  be  distinguished  from 
the  other  tarsal  bones  by  the  existence  of  a  deep  groove  on  its  under  surface, 
for  the  tendon  of  the  Peroneus  longus  muscle.  It  presents  for  examination  six 
surfaces:  three  articular  and  three  non-articular. 

Non-articular  Surfaces. — The  non-articular  surfaces  are  the  superior,  inferior,  and 
external.  The  superior  or  dorsal  surface,  directed  upward  and  outward,  is  rough, 
for  the  attachment  of  numerous  ligaments.  The  inferior  or  plantar  surface  presents 
in  front  a  deep  groove,  the  peroneal  groove  (sulcus  m.  peronoei  longi),  which 
runs  obliquely  from  without,  forward  and  inward ;  it  lodges  the  tendon  of  the 
Peroneus  longus,  and  is  bounded  behind  by  a  prominent  ridge,  to  which  is 
attached  the  long  calcaneo-cuboid  ligament.  The  ridge  terminates  externally 
in  an  eminence,  the  tuberosity  of  the  cuboid  (tuberositas  ossis  cuboidei),  the  sur- 
face of  which  presents  a  convex  facet,  for  articulation  with  the  sesamoid  bone 
of  the  tendon  contained  in  the  groove.  The  surface  of  bone  behind  the  groove 
is  rough,  for  the  attachment  of  the  short  plantar  ligament,  a  few  fibres  of  the 
Flexor  brevis  hallucis,  and  a  fasciculus  from  the  tendon  of  the  Tibialis  posticus. 
The  external  surface,  the  smallest  and  narrowest  of  the  three,  presents  a  deep 
notch  formed  by  the  commencement  of  the  peroneal  groove. 

Articular  Surfaces. — The  articular  surfaces  are  the  posterior,  anterior,  and 
internal.  The  posterior  surface  is  smooth,  triangular,  and  concavo-conyex,  for 
articulation  with  the  anterior  surface  of  the  os  calcis.  The  anterior  surface,  of 
smaller  size,  but  also  irregularly  triangular,  is  divided  by  a  vertical  ridge  into 
two  facets;  the  inner  one,  quadrilateral  in  form,  articulates  with  the  fourth 
metatarsal  bone;  the  outer  one,  larger  and  more  triangular,  articulates  with 
the  fifth  metatarsal.  The  internal  surface  is  broad,  rough,  irregularly  quadri- 
lateral, presenting  at  its  middle  and  upper  part  a  smooth  oval  facet,  for  articula- 
tion with  the  external  cuneiform  bone;  and  behind  this  (occasionally)  a  smaller 
facet,  for  articulation  with  the  navicular;  it  is  rough  in  the  rest  of  its  extent,  for 
the  attachment  of  strong  interosseous  ligaments.  . 

To  ascertain  to  which  foot  the  bone  belongs,  hold  it  so  that  its  under  surface, 
marked  by  the  peroneal  groove,  looks  downward,  and  the  large  concavo-convex 
articular  surface  backward  toward  the  holder:  the  narrow  non-articular  surface, 
marked  by  the  commencement  of  the  peroneal  groove,  will  point  to  the  side  to 
wrhich  the  bone  belongs. 

Articulations. — With  four  bones: 'the  os  calcis,  external  cuneiform,  and  the 
fourth  and  fifth  metatarsal  bones;  occasionally  with  the  scaphoid. 

Attachment  of  Muscles. — Part  of  the  Flexor  brevis  hallucis  and  a  slip  from 
the  tendon  of  the  Tibialis  posticus. 


THE  TARSUS 


249 


Scaphoid  or  Navicular  Bone  (os  naviculare  pedis)  (Fig.  180). — The  scaphoid 
is  situated  at  the  inner  side  of  the  tarsus,  between  the  astragalus  behind   and 


For  mid.  cuneiform. 

For  int.  / 

For  ext. 

/cuneiform. 


For  cuboid 
(occasional).  For  attragalua, 

FIG.  180. — The  left  scaphoid.     A.  Antero-external  view.     B.  Postero-internal  view. 


the  three  cuneiform  bones  in  front.  It  may  be  distinguished  by  its  form,  being 
concave  behind,  convex  and  subdivided  into  three  facets  in  front. 

Surfaces. — The  anterior  surface,  of  an  oblong  form,  is  convex  from  side  to  side, 
and  subdivided  by  two  ridges  into  three  facets,  for  articulation  with  the  three 
cuneiform  bones.  The  posterior  surface  is  oval,  concave,  broader  externally 
than  internally,  and  articulates  with  the  rounded  head  of  the  astragalus.  The 
superior  surface  is  convex  from  side  to  side,  and  rough  for  the  attachment  of 
ligaments.  The  inferior  is  irregular,  and  also  rough  for  the  attachment  of  liga- 
ments. The  internal  surface  presents  a  rounded  tubercular  eminence,  the 
tuberosity  (tuberositas  ossis  navicularis) ,  the  lower  part  of  which  projects,  and 
gives  attachment  to  part  of  the  tendon  of  the  Tibialis  posticus.  The  external 
surface  is  rough  and  irregular,  for  the  attachment  of  ligamentous  fibres,  and 
occasionally  presents  a  small  facet  for  articulation  with  the  cuboid  bone. 

To  ascertain  to  which  foot  the  bone  belongs,  hold  it  with  the  concave  articular 
surface  backward,  and  the  convex  dorsal  surface  upward;  the  external  surface — 
i.  e.,  the  surface  opposite  the  tubercle — will  point  to  the  side  to  which  the  bone 
belongs. 

Articulations. — With  four  bones:  astragalus  and  three  cuneiform;  occasionally 
also  with  the  cuboid. 

Attachment  of  Muscles. — Part  of  the  Tibialis  posticus. 

Cuneiform  or  Wedge  Bones. — The  cuneiform  bones  have  received  their 
name  from  their  wedge-like  shape  (cuneus,  a  wedge;  forma,  likeness).  They 
form,  with  the  cuboid,  the  anterior  row 

of  the  tarsus,  being  placed  between  the 

scaphoid  behind,  the  three  innermost 
metatarsal  bones  in  front,  and  the  cu- 
boid externally.  They  are  called  the 
first,  second,  and  third,  counting  from 
the  inner  to  the  outer  side  of  the  foot, 
and,  from  their  position,  internal,  mid- 
dle, and  external. 

Internal  or  First  Cuneiform  (os 
cuneiforme  primum)  (Fig.  181). — The 
internal  cuneiform  is  the  largest  of  the  ^r  tendon  of 
three.  It  is  situated  at  the  inner  side 
of  the  foot,  between  the  scaphoid  behind 
and  the  base  of  the  first  metatarsal  in  front.  It  may  be  distinguished  from  the 
other  two  by  its  large  size,  and  by  its  not  presenting  such  a  distinct  wedge-like 
form.  Without  the  others  it  may  be  known  by  the  large,  kidney-shaped  anterior 


For  middle 
cuneiform. 


For  navicular. 


FIG.   181. — The  left  internal  cuneiform.     A,  Antero- 
internal  view.     B,  Postero-external  view. 


250 


THE  SKELETON 


articulating  surface  and  by  the  prominence  on  the  inferior  or  plantar  surface  for 
the  attachment  of  the  Tibialis  posticus.  It  presents  for  examination  six  surfaces. 

Surfaces. — The  internal  surface  is  subcutaneous,  and  forms  part  of  the  inner 
border  of  the  foot;  it  is  broad,  quadrilateral,  and  presents  at  its  anterior  inferior 
angle  a  smooth  oval  facet,  into  which  the  tendon  of  the  Tibialis  anticus  is 
partially  inserted;  in  the  rest  of  its  extent  it  is  rough,  for  the  attachment  of 
ligaments.  The  external  surface  is  concave,  presenting,  along  its  superior  and 
posterior  borders,  a  narrow,  reversed,  L-shaped  surface,  for  articulation  with  the 
middle  cuneiform  behind  and  second  metatarsal  bone  in  front;  in  the  rest  of  its 
extent  it  is  rough,  for  the  attachment  of  ligaments  and  part  of  the  tendon  of  the 
Peroneus  longus.  The  anterior  surface,  kidney-shaped,  much  larger  than  the  poste- 
rior, articulates  with  the  metatarsal  bone  of  the  great  toe.  The  posterior  surface 
is  triangular,  concave,  and  articulates  with  the  innermost  and  largest  of  the  three 
facets  on  the  anterior  surface  of  the  scaphoid.  The  inferior  or  plantar  surface 
is  rough,  and  presents  a  prominent  tuberosity  at  its  back  part  for  the  attachment 
of  part  of  the  tendon  of  the  Tibialis  posticus.  It  also  gives  attachment  in  front 
to  part  of  the  tendon  of  the  Tibialis  anticus.  The  superior  surface  is  the  narrow- 
pointed  end  of  the  wedge,  which  is  directed  upward  and  outward;  it  is  rough 
for  the  attachment  of  ligaments. 

To  ascertain  to  which  side  the  bone  belongs,  hold  it  so  that  its  superior  narrow 
edge  looks  upward,  and  the  long,  kidney-shaped,  articular  surface  forward;  the 
external  surface,  marked  by  its  vertical  and  horizontal  articular  facets,  will 
point  to  the  side  to  which  it  belongs. 

Articulations. — With  four  bones:  scaphoid,  middle  cuneiform,  first  and  second 
metatarsal  bones. 

Attachment  of  Muscles. — To  three :  the  Tibialis  anticus  and  posticus,  and 
Peroneus  longus. 

Middle  or  Second  Cuneiform  (os  cuneiforme  secundum)  (Fig.  182). — The 
middle  cuneiform,  the  smallest  of  the  three,  is  of  very  regular  wedge-like  form, 
the  broad  extremity  being  placed  upward,  the  narrow  end  downward.  It  is 
situated  between  the  other  two  bones  of  the  same  name,  and  articulates  with  the 
scaphoid  behind  and  the  second  metatarsal  in  front.  It  is  smaller  than  the  external 
cuneiform  bone,  from  which  it  may  be  further  distinguished  by  the  L-shaped 
articular  facet,  which  runs  round  the  upper  and  back  part  of  its  inner  surface. 


For  int.  cuneiform 


For  navicular. 

1 


For  navicular. 

For  mid.  cuneiform. 


For  fourth     For  cuboid, 
metatarsal. 


For  For  third 

second  metatarsal.  metatarsal. 

FIG.  182. — The  left  middle  cuneiform.  A.  Antero-       FIG.  183. — The  left  external  cuneiform.  A.  Postero-internal 
internal  view.     B.  Postero-external  view.  view.     B.  Antero-external  view. 

Surfaces. — The  anterior  surface,  triangular  in  form  and  narrower  than  the  poste- 
rior, articulates  with  the  base  of  the  second  metatarsal  bone.  The  posterior  sur- 
face, also  triangular,  articulates  with  the  scaphoid .  The  internal  surface  presents 
a  reversed  L-shaped  articular  facet,  running  along  the  superior  and  posterior 
borders,  for  articulation  with  the  internal  cuneiform,  and  is  rough  in  the  rest 
of  its  extent,  for  the  attachment  of  ligaments.  The  external  surface  presents 
posteriorly  a  smooth  facet  for  articulation  with  the  external  cuneiform  bone. 
The  superior  surface  forms  the  base  of  the  wedge;  it  is  quadrilateral,  broader 
behind  than  in  front,  and  rough  for  the  attachment  of  ligaments.  The  inferior 


THE  TARSUS  251 

surface,  pointed  and  tubercular,  is  also  rough  for  ligamentous  attachment  and 
for  the  insertion  of  a  slip  from  the  tendon  of  the  Tibialis  posticus. 

To  ascertain  to  which  foot  the  bone  belongs,  hold  its  superior  or  dorsal  surface 
upward,  the  broadest  edge  being  toward  the  holder:  the  smooth  facet  (limited 
to  the  posterior  border)  will  then  point  to  the  side  to  which  it  belongs. 

Articulations. — With  four  bones:  scaphoid,  internal  and  external  cuneiform, 
and  second  matatarsal  bone. 

Attachment  of  Muscles. — A  slip  from  the  tendon  of  the  Tibialis  posticus  is 
attached  to  this  bone. 

External  or  Third  Cuneiform  (os  cuneiforme  tertium)  (Fig.  183). — The  exter- 
nal cuneiform,  intermediate  in  size  between  the  two  preceding,  is  of  a  very 
regular  wedge-like  form,  the  broad  extremity  being  placed  upward,  the  narrow 
end  downward.  It  occupies  the  centre  of  the  front  row  of  the  tarsus,  between 
the  middle  cuneiform  internally,  the  cuboid  externally,  the  scaphoid  behind,  and 
the  third  metatarsal  in  front.  It  is  distinguished  from  the  internal  cuneiform 
bone  by  its  more  regular  wedge-like  shape  and  by  the  absence  of  the  kidney- 
shaped  articular  surface:  from  the  middle  cuneiform,  by  the  absence  of  the 
reversed  L-shaped  facet,  and  by  the  two  articular  facets  which  are  present  on 
both  its  inner  and  outer  surfaces.  It  has  six  surfaces  for  examination. 

Surfaces. — The  anterior  surface,  triangular  in  form,  articulates  with  the  third 
metatarsal  bone.  The  posterior  surface  articulates  with  the  most  external  facet 
of  the  scaphoid,  and  is  rough  below  for  the  attachment  of  ligamentous  fibres. 
The  internal  surface  presents  two  articular  facets,  separated  by  a  rough  depres- 
sion ;  the  anterior  one,  sometimes  divided  into  two,  articulates  with  the  outer  side 
of  the  base  of  the  second  metatarsal  bone;  the  posterior  one  skirts  the  posterior 
border  and  articulates  with  the  middle  cuneiform;  the  rough  depression  between 
the  two  gives  attachment  to  an  interosseous  ligament.  The  external  surface  also 
presents  two  articular  facets,  separated  by  a  rough  non-articular  surface;  the 
anterior  facet,  situated  at  the  superior  angle  of  the  bone,  is  small,  and  articulates 
with  the  inner  side  of  the  base  of  the  fourth  metatarsal;  the  posterior  and  larger 
one  articulates  with  the  cuboid;  the  rough,  non-articular  surface  serves  for  the 
attachment  of  an  interosseous  ligament.  The  three  facets  for  articulation  with 
the  three  metatarsal  bones  are  continuous  with  one  another,  and  covered  by  a 
prolongation  of  the  same  cartilage;  the  facets  for  articulation  with  the  middle 
cuneiform  and  scaphoid  are  also  continuous,  but  that  for  articulation  with  he 
cuboid  is  usually  separate.  The  superior  or  dorsal  surface  is  of  an  oblong  square 
form,  its  posterior  external  angle  being  prolonged  backward.  The  inferior  or 
plantar  surface  is  an  obtuse  rounded  margin,  and  serves  for  the  attachment  of 
part  of  the  tendon  of  the  Tibialis  posticus,  part  of  the  Flexor  brevis  hallucis, 
and  ligaments. 

To  ascertain  to  which  side  the  bone  belongs,  hold  it  with  the  broad  dorsal 
surface  upward,  the  prolonged  edge  backward;  the  separate  articular  facet  for 
the  cuboid  will  point  to  the  proper  side. 

Articulations. — With  six  bones:  the  scaphoid,  middle  cuneiform,  cuboid,  and 
second,  third,  and  fourth  metatarsal  bones. 

Attachment  of  Muscles. — To  two:  part  of  the  Tibialis  posticus,  and  Flexor 
brevis  hallucis. 

The  number  of  tarsal  bones  may  be  reduced  owing  to  congenital  ankylosis 
which  may  occur  between  the  os  calcis  and  cuboid,  the  os  calcis  and  scaphoid, 
the  os  calcis  and  astragalus,  or  the  astragalus  and  scaphoid. 


252 


THE  SKELETON 


The  Metatarsal  Bones  (Ossa  Metatarsalia). 

The  metatarsal  bones  are  five  in  number,  and  are  numbered  one  to  five,  in 
accordance  with  their  position  from  within  outward;  they  are  long  bones,  and 
present  for  examination  a  shaft  and  two  extremities. 

Common  Characters. — The  shaft  (corpus)  is  prismoid  in  form,  tapers  gradually 
from  the  tarsal  to  the  phalangeal  extremity,  and  is  slightly  curved  longitudinally, 
so  as  to  be  concave  below,  slightly  convex  above.  On  the  plantar  surface  of  the 
shaft  of  each  bone  is  a  nutrient  foramen  corresponding  to  the  nutrient  foramen 
in  each  metacarpal  bone.  The  posterior  or  proximal  extremity,  or  base  (basis) , 
is  wedge-shaped,  articulating  by  its  terminal  surface  with  the  tarsal  bones,  and 
by  its  lateral  surfaces  with  the  contiguous  metatarsal  bones,  its  dorsal  and  plantar 
surfaces  being  rough  for  the  attachment  of  ligaments.  The  anterior  or  distal 
extremity,  or  head  (capitulum) ,  presents  a  terminal  rounded  articular  surface, 
oblong  from  above  downward,  and  extending  farther  backward  below  than 
above.  Its  sides  are  flattened  and  present  a  depression,  surmounted  by  a 
tubercle,  for  ligamentous  attachment.  Its  under  surface  is  grooved  in  the 
middle  line  for  the  passage  of  the  Flexor  tendon,  and  marked  on  each  side  by 
an  articular  eminence  continuous  with  the  terminal  articular  surface. 

Peculiar  Characters.  First  Metatarsal  Bone  or  the  Metatarsal  Bone  of  the  Great 
Toe  (os  metatarsale  I) . — The  first  (Fig.  184)  is  remarkable  for  its  great  thickness, 
but  is  the  shortest  of  all  the  metatarsal  bones.  The  shaft  is  strong  and  of  well- 
marked  prismoid  form.  The  posterior  extremity  presents,  as  a  rule,  no  lateral 
articular  facet,  but  occasionally  on  the  outer  side  there  is  an  oval  facet  by  which 
it  articulates  with  the  second  metatarsal  bones.  Its  terminal  articular  surface  is  of 
large  size  and  kidney-shaped;  its  circumference  is  grooved,  for  the  tarso-metatarsal 
ligaments,  and  internally  gives  attachment  to  part  of  the  tendon  of  the  Tibialis 
anticus  muscle;  its  inferior  angle  presents  a  rough  oval  prominence,  the  tuberosity 
(tuberositas  ossis  metatarsalis  I),  for  the  insertion  of  the  tendon  of  the  Peroneus 
longus.  The  head  is  of  large  size;  on  its  plantar  surface  are  two  grooved  facets, 
over  which  glide  sesamoia  bones ;  the  facets  are  separated  by  a  smooth  elevated 
ridge. 

This  bone  is  known  by  the  single  kidney-shaped  articular  surface  on  its  base, 
the  deeply  grooved  appearance  of  the  plantar  surface  of  its  head,  and  its  great 

thickness  relatively  to  its  length. 
When  it  is  placed  in  its  natural 
position,  the  concave  border  of 
the  kidney-shaped  articular  sur- 
face on  its  base  points  to  the 
side  to  which  the  bone  belongs. 
Attachment  of  Muscles. — To 
three:  part  of  the  Tibialis  anti- 
cus, the  Peroneus  longus,  and 
the  First  dorsal  interosseous. 

Second  Metatarsal  (os  metatar- 
sale II).— The  second  (Fig.  185) 
is  the  longest  and  largest  of  the 
remaining  metatarsal  bones,  be- 
ing prolonged  backward  into  the 
recess  formed  between  the  three 
cuneiform  bones.  Its  tarsal  ex- 
tremity is  broad  above,  narrow 
and  rough  below.  It  presents 
four  articular  surfaces:  one  be- 


Occasional  facet  for 
second  metatarsal. 


For  internal  cuneiform. 

FIG.  184.— The  first  metatarsal.      (Left.) 


THE  METATARSAL  BONES 


253 


hind,  of  a  triangular  form,  for  articulation  with  the  middle  cuneiform;  one  at  the 
upper  part  of  its  internal  lateral  surface,  for  articulation  with  the  internal  cunei- 


Occasionnl 
facet  for  first 
metatarsal.          For 
For  middle  cuneiform. 

FIG.  185. — The  second  metatarsal.     (Left.) 


For  second  metnlarsal. 
For  middle  cuneiform. 


For  fourth 
metatarsal. 


FIG.  186. — The  third  metatarsal.     (Left.) 


form ;  and  two  on  its  external  lateral  surface — an  upper  and  a  lower,  separated  by 
a  rough  non-articular  interval.  Each  of  these  articular  surfaces  is  divided  by  a 
vertical  ridge  into  two  facets,  thus  making  four  facets;  the  two  anterior  of  these 
articulate  with  the  third  metatarsal ;  the  two  posterior  (sometimes  continuous)  with 
the  external  cuneiform.  In  addition  to  these  articular  surfaces  there  is  occasion- 
ally a  fifth  when  this  bone  articulates  with  the  first  metatarsal  bone.  It  is  oval  in 
shape,  and  is  situated  on  the  inner  side  of  the  shaft  near  the  base. 

The  facets  on  the  tarsal  extremity  of  the  second  metatarsal  bone  serve  at  once 
to  distinguish  it  from  the  rest,  and  to  indicate  the  foot  to  which  it  belongs;  there 
being  one  facet  at  the  upper  angle  of  the  internal  surface,  and  two  facets,  each 
subdivided  into  two  parts,  on  the  external  surface,  pointing  to  the  side  to  which 
the  bone  belongs.  The  fact  that  the  two  posterior  subdivisions  of  these  external 
facets  sometimes  run  into  one  should  not  be  forgotten. 

Attachment  of  Muscles. — To  four:  the  Adductor  obliquus  hallucis,  First  and 
Second  dorsal  interosseous,  and  a  slip  from  the  tendon  of  the  Tibialis  posticus; 
occasionally  also  a  slip  from  the  Peroneus  longus. 

Third  Metatarsal  (os  metatarsale  III) . — The  third  metatarsal  (Fig.  186)  articu- 
lates behind,  by  means  of  a  triangular  smooth  surface,  with  the  external  cunei- 
form; on  its  inner  side,  by  two  facets,  with  the  second  metatarsal;  and  on  its 
outer  side,  by  a  single  facet,  with  the  fourth  metatarsal.  The  latter  facet  is  of 
circular  form  and  situated  at  the  upper  angle  of  the  base. 

The  third  metatarsal  is  known  by  its  having  at  its  tarsal  end  two  undivided 
facets  on  the  inner  side,  and  a  single  facet  on  the  outer.  This  distinguishes  it 
from  the  second  metatarsal,  in  which  the  two  facets,  found  on  one  side  of  its 
tarsal  end,  are  each  subdivided  into  two.  The  single  facet  (when  the  bone  is  put 
in  its  natural  position)  is  on  the  side  to  which  the  bone  belongs. 

Attachment  of  Muscles. — To  five :  Adductor  obliquus  hallucis,  Second  and 
Third  dorsal,  and  First  plantar  interosseous,  and  a  slip  from  the  tendon  of  the 
Tibialis  posticus. 


254 


THE  SKELETON 


Fourth  Metatarsal  (os  metatarsale  IV}.—  The  fourth  metatarsal  (Fig.  187)  is 
smaller  in  size  than  the  preceding;  its  tarsal  extremity  presents  a  terminal  quad- 


For  third 
metatarsal. 


For  cuboid. 
For  ext.  cuneiform. 


For  fifth 
metatarsal,. 


Tuberosity. 


FIG.  187. — The  fourth  metatarsal.     (Left.) 


For  fourth 
metatarsal. 

For  cuboid. 
FIG.  188.— The  fifth  metatarsal.     (Left.) 


rilateral  surface,  for  articulation  with  the  cuboid;  a  smooth  facet  on  the  inner 
side,  divided  by  a  ridge  into  an  anterior  portion  for  articulation  with  the  third 
metatarsal,  and  a  posterior  portion  for  articulation  with  the  external  cuneiform; 
on  the  outer  side  a  single  facet,  for  articulation  with  the  fifth  metatarsal. 

The  fourth  metatarsal  is  known  by  its  having  a  single  facet  on  either  side  of 
the  tarsal  extremity,  that  on  the  inner  side  being  divided  into  two  parts.  If  this 
subdivision  be  not  recognizable,  the  fact  that  its  tarsal  end  isjbent  somewhat 
outward  will  indicate  the  side  to  which  it  belongs. 

Attachment  of  Muscles. — To  five:  Adductor  obliquus  hallucis,  Third  and 
Fourth  dorsal,  and  Second  plantar  interosseous,  and  a  slip  from  the  tendon  of  the 
Tibialis  posticus. 

Fifth  Metatarsal  Bone,  or  the  Metatarsal  Bone  of  the  Little  Toe  (os  metatarsale  V). 
—The  fifth  metatarsal  (Fig.  188)  is  recognized  by  the  tubercle  (tuberositas  ossis 
metatarsalis  V)  on  the  outer  side  of  its  base.  It  articulates  behind,  by  a  tri- 
angular surface  cut  obliquely  from  without  inward,  with  the  cuboid,  and  inter- 
nally with  the  fourth  metatarsal. 

The  projection  on  the  outer  side  of  this  bone  at  its  tarsal  end  at  once  distin- 
guishes it  from  the  others,  and  points  to  the  side  to  which  it  belongs. 

Attachment  of  Muscles. — To  six :  the  Peroneus  brevis,  Peroneus  tertius, 
Flexor  brevis  minimi  digiti,  Adductor  trarisversus  hallucis,  Fourth  dorsal,  and 
Third  plantar  interossei. 

Articulations. — Each  bone  articulates  with  the  tarsal  bones  by  one  extremity, 
and  by  the  other  with  the  first  row  of  phalanges.  The  number  of  tarsal  bones 
with  which  each  metatarsal  articulates  is  one  for  the  first,  three  for  the  second, 
one  for  the  third,  two  for  the  fourth,  and  one  for  the  fifth. 


DEVELOPMENT  OF  THE  FOOT  255 


The  Phalanges  of  the  Foot  (Phalanges  Digitorum  Pedis). 

The  phalanges  of  the  foot,  both  in  number  and  general  arrangement,  resemble 
those  in  the  hand;  there  being  two  in  the  great  toe  and  three  in  each  of  the 
other  toes.  The  nutritive  foramina  correspond  to  those  in  the  phalanges  of  the 
hand. 

The  first  or  proximal  phalanx  (phalanx  prima)  resembles  closely  the  correspond- 
ing bone  of  the  hand.  The  shaft  also  is  compressed  from  side  to  side,  convex 
above,  concave  below.  The  posterior  extremity  is  concave;  and  the  anterior 
extremity  presents  a  trochlear  surface,  for  articulation  with  the  second  phalanx. 

The  second  phalanx  (phalanx  secunda)  is  remarkably  small  and  short,  but 
rather  broader  than  the  first  phalanx. 

The  ungual  or  distal  phalanx  (phalanx  tertia)  in  form  resembles  the  bone  of  the 
corresponding  finger,  but  is  smaller,  flattened  from  above  downward,  presenting  a 
broad  base  for  articulation  with  the  second  phalanx,  and  an  expanded  extremity 
for  the  support  of  the  nail  and  end  of  the  toe. 

Articulation. — The  first  row,  with  the  metatarsal  bones  behind  and  second 
phalanges  in  front;  the  second  row  of  the  four  outer  toes,  with  the  first  and  third 
phalanges;  of  the  great  toe,  with  the  first  phalanx;  the  third  row  of  the  four  outer 
toes,  with  the  second  phalanges. 

Attachment  of  Muscles. — To  the  first  phalanges.  Great  toe,  five  muscles: 
innermost  tendon  of  Extensor  brevis  digitorum,  Abductor  hallucis,  Adductor 
obliquus  hallucis,  Flexor  brevis  hallucis,  Adductor  transversus  hallucis.  Second 
toe,  three  muscles:  First  and  Second  dorsal  interosseous  and  First  lumbrical. 
Third  toe,  three  muscles :  Third  dorsal  and  First  plantar  interosseous  and  Second 
lumbrical.  Fourth  toe,  three  muscles:  Fourth  dorsal  and  Second  plantar  inter- 
osseous and  Third  lumbrical.  Fifth  toe,  four  muscles:  Flexor  brevis  minimi 
digiti,  Abductor  minimi  digiti,  and  Third  plantar  interosseous,  and  Fourth 
lumbrical. — Second  phalanges.  Great  toe;  Extensor  longus  hallucis,  Flexor 
longus  hallucis.  Other  toes;  Flexor  brevis  digitorum,  one  slip  of  the  common 
tendon  of  the  Extensor  longus  and  brevis  digitorum.1 — Third  phalanges:  two  slips 
from  the  common  tendon  of  the  Extensor  longus  and  Extensor  brevis  digitorum, 
and  the  Flexor  longus  digitorum. 

Development  of  the  Foot  (Fig.  189). 

The  Tarsal  Bones  are  each  developed  by  a  single  centre,  excepting  the  os  calcis 
which  has  an  epiphysis  for  its  posterior  extremity.  The  centres  make  their  appear- 
ance in  the  following  order:  os  calcis,  at  the  sixth  month  of  foetal  life;  astragalus, 
about  the  seventh  month;  cuboid,  at  the  ninth  month;  external  cuneiform,  dur- 
ing the  first  year;  internal  cuneiform  in  the  third  year;  middle  cuneiform  and 
scaphoid  in  the  fourth  year.  The  epiphysis  for  the  posterior  tuberosity  of  the 
os  calcis  appears  at  the  tenth  year,  and  unites  with  the  rest  of  the  bone  soon 
after  puberty. 

The  Metatarsal  Bones  are  each  developed  by  two  centres:  one  for  the  shaft 
and  one  for  the  digital  extremity  in  the  four  outer  metatarsal;  one  for  the  shaft 
and  one  for  the  base  in  the  metatarsal  bone  of  the  great  toe.2  Ossification  com- 
mences in  the  centre  of  the  shaft  about  the  ninth  week,  and  extends  toward 
either  extremity.  The  centre  in  the  proximal  end  of  the  first  metatarsal  bone 
appears  about  the  third  year,  the  centre  in  the  distal  end  of  the  other  bones 

1  Except  the  second  phalanx  of  the  fifth  toe,  which  receives  no  slip  from  the  Extensor  brevis  digitorum. — 
ED.  of  15th  English  Edition. 

2  As  was  noted  in  the  first  metacarpal   bone,  so  in  the  first  metatarsal,  there  is  often  to  be  observed  a  ten- 
dency to  the  formation  of  a  second  epiphysis  in  the  distal  extremity. — ED.  of  15th  English  Edition. 


256 


THE  SKELETON 


between  the  fifth  and  eighth  years;  they  become  joined  between  the  eighteenth 
and  twentieth  years. 

The  Phalanges  are  developed  by  two  centres  for  each  bone:  one  for  the  shaft 
and  one  for  the  metatarsal  extremity.  The  centre  for  the  shaft  appears  about  the 
tenth  week,  that  for  the  epiphysis  between  the  fourth  and  tenth  years;  they  join 
the  shaft  about  the  eighteenth  year. 


y  sis. 


Appears  10th  year  ; 
'    unites  after  puberty. 


Tarsus. 

One  centre  for  each  bone, 
except  os  calcis. 


Metatarsus. 
Two  centres  for  each  bone : 
One  for  shaft, 
One  for  digital  extremity 
except  1st. 


Appears  7th  week.  ~ 


Unite  18th-20th  year. 
Appears  3rd  year. 

Appears  4th  year. 
Unite  17-18th  year,  j 
Phalanges.    Appears  2nd-4th  month.- 
Two  centres  for  each  bone  : 
One  for  shaft, 
One  for  metatarsal       Appears  6th-7th  year. 


Appears  5th  year. 
Unite  18th-20  year. 


-Appears  7th  week. 


extremity. 


Unite  17th-18th  year. 


,.-Cl 


Appears  2nd~4th  month 

Appears  6th  year.-^       s          (W 
Unite  17.th-18th  year.-{^  2 
Appears  7th  joeefc.  — 5J>  jj 

FIG.  189. — Plan  of  the  development  of  the  foot. 

Construction  of  the  Foot  as  a  Whole  (Figs.  190,  191). 

The  foot  is  constructed  on  the  same  principles  as  the  hand,  but  modified  to  form 
a  firm  basis  of  support  for  the  rest  of  the  body  when  in  the  erect  position.  It 
is  more  solidly  constructed,  and  its  component  parts  are  less  movable  on  each 
other  than  in  the  hand.  This  is  especially  the  case  with  the  great  toe,  which  has 
to  assist  in  supporting  the  body,  and  is  therefore  constructed  with  greater  solidity; 
it  lies  parallel  with  the  other  toes,  and  has  a  very  limited  degree  of  mobility, 
whereas  the  thumb,  which  is  occupied  in  numerous  and  varied  movements,  is 
constructed  in  such  a  manner  as  to  permit  of  great  mobility.  Its  metacarpal  bone 
is  directed  away  from  the  others,  so  as  to  form  an  acute  angle  with  the  second, 
and  it  enjoys  a  considerable  range  of  motion  at  its  articulation  with  the  carpus. 
The  foot  is  placed  at  right  angles  to  the  leg — a  position  which  is  almost  peculiar 
to  man,  and  has  relation  to  the  erect  position  which  he  maintains.  In  order  to 


CONSTRUCTION  OF  THE  FOOT  AS  A    WHOLE 


257 


allow  of  its  supporting  the  weight  of  the  whole  body  in  this  position  with  the 
least  expenditure  of  material,  it  is  constructed  in  the  form  of  an  arch.  This 
antero-posterior  or  longitudinal  arch  is  made  up  of  two  unequal  limbs.  The 


FIG.  190. — Skeleton  of  the  foot,  internal  border.     (Poirier  and  Charpy.) 


SECOND  CUNEIFORM 


SECOND  MCTATARSAL 


FIG.  191. — Skeleton  of  the  foot,  external  border.     (Poirier  and  Charpy.) 

hinder  one,  which  is  made  up  of  the  os  calcis  and  the  posterior  part  of  the 
astragalus,  is  about  half  the  length  of  the  anterior  limb,  and  measures  about 
three  inches.  The  anterior  limb  consists  of  the  rest  of  the  tarsal  and  the  meta- 
tarsal  bones,  and  measures  about  seven  inches.  It  may  be  said  to  consist  of  two 
parts,  an  inner  segment  made  up  of  the  head  of  the  astragalus,  the  scaphoid, 
the  three  cuneiform,  and  the  three  inner  metatarsal  bones;  and  an  outer  segment 
composed  of  the  os  calcis,  the  cuboid,  and  the  two  outer  metatarsal  bones.  The 
summit  of  the  arch  is  at  the  superior  articular  surface  of  the  astragalus;  and  its 
two  extremities — that  is  to  say,  the  two  piers  on  which  the  arch  rests  in  standing 
— are  the  tubercles  on  the  under  surface  of  the  os  calcis  posteriorly,  and  the  heads 
of  the  metatarsal  bones  anteriorly.  The  weakest  part  of  the  arch  is  the  joint 
between  the  astragalus  and  scaphoid,  and  here  it  is  more  liable  to  yield  in  those 
who  are  overweighted,  and  in  those  in  whom  the  ligaments  which  complete  and 
preserve  the  arch  are  relaxed.  This  weak  point  in  the  arch  is  braced  on  its  con- 
cave surface  by  the  inferior  calcaneo-scaphoid  ligament,  which  is  more  elastic 
than  most  other  ligaments,  and  thus  allows  the  arch  to  yield  from  jars  or  shocks 
applied  to  the  anterior  portion  of  the  foot  and  quickly  restores  it  to  its  pristine 
condition.  This  ligament  is  supported  internally  by  blending  with  the  Deltoid 
ligament,  and  inferiorly  by  the  tendon  of  the  Tibialis  posticus  muscle,  which  is 
spread  out  into  a  fan-shaped  insertion,  and  prevents  undue  tension  of  the  ligament 
or  such  an  amount  of  stretching  as  would  permanently  elongate  it. 

In  addition  to  this  longitudinal  arch  the  foot  presents  a  transverse  arch,  at  the 
anterior  part  of  the  tarsus  and  hinder  part  of  the  metatarsus.  This,  however,  can 
scarcely  be  described  as  a  true  arch,  but  presents  more  the  character  of  a  half- 
dome.  The  inner  border  of  the  central  portion  of  the  longitudinal  arch  is  elevated 

17 


258  THE  SKELETON 

from  the  ground,  and  from  this  point  the  bones  arch  over  to  the  outer  border, 
which  is  in  contact  with  the  ground,  and,  assisted  by  the  longitudinal  arch,  pro- 
duce a  sort  of  rounded  niche  on  the  inner  side  of  the  foot,  which  gives  the  appear- 
ance of  a  transverse  as  well  as  a  longitudinal  arch. 

The  line  of  the  foot,  from  the  point  of  the  heel  to  the  toes,  is  not  quite  straight, 
but  is  directed  a  little  outward,  so  that  the  inner  border  is  a  little  convex  and  the 
outer  border  concave.  This  disposition  of  the  bones  becomes  more  marked  when 
the  longitudinal  arch  of  the  foot  is  lost,  as  in  the  disease  known  under  the  name 
of  "flat-foot." 

Surface  Form.—  On  the  dorsum  of  the  foot  the  individual  bones  are  not  to  be  distinguished 
with  the  exception  of  the  head  of  the  astragalus,  which  forms  a  rounded  projection  in  front  of 
the  ankle-joint  when  the  foot  is  forcibly  extended.  The  whole  surface  forms  a  smooth  convex 
outline,  the  summit  of  which  is  the  ridge  formed  by  the  head  of  the  astragalus,  the  scaphoid, 
the  middle  cuneiform,  and  the  second  metatarsal  bones;  from  this  it  gradually  inclines  outward 
and  more  rapidly  inward.  On  the  inner  side  of  the  foot,  the  internal  tuberosity  of  the  OS  calcis 
and  the  ridge  separating  the  inner  from  the  posterior  surface  of  the  bone  may  be  felt  most  poste- 
riorly. In  front  of  this,  and  below  the  internal  malleolus,  may  be  felt  the  projection  of  the 
SUStentaculum  tali.  Passing  forward  is  the  well-marked  tuberosity  of  the  scaphoid  bone,  situ- 
ated about  an  inch  or  an  inch  and  a  quarter  in  front  of  the  internal  malleolus.  Further  toward 
the  front,  the  ridge  formed  by  the  base  of  the  first  metatarsal  bone  can  be  obscurely  felt,  and 
from  this  the  shaft  of  the  bone  can  be  traced  to  the  expanded  head  articulating  with  the  base 
of  the  first  phalanx  of  the  great  toe.  Immediately  beneath  the  base  of  this  phalanx,  the  internal 
sesamoid  bone  is  to  be  felt.  Lastly,  the  expanded  ends  of  the  bones  forming  the  last  joint  of 
the  great  toe  are  to  be  felt.  On  the  outer  side  of  the  foot  the  most  posterior  bony  point  is  the 
outer  tuberosity  of  the  os  calcis,  with  the  ridge  separating  the  posterior  from  the  outer  surface 
of  the  bone.  In  front  of  this  the  greater  part  of  the  external  surface  of  the  os  calcis  is  subcu- 
taneous; on  it,  below  and  in  front  of  the  external  malleolus,  may  be  felt  the  peroneal  ridge,  when 
this  process  is  present.  Farther  forward,  the  base  of  the  fifth  metatarsal  bone  forms  a  prom- 
inent and  well-defined  landmark,  and  in  front  of  this  the  shaft  of  the  bone,  with  its  expanded 
head,  and  the  base  of  the  first  phalanx  may  be  defined.  The  sole  of  the  foot  is  almost  entirely 
covered  by  soft  parts,  so  that  but  few  bony  parts  are  to  be  made  out,  and  these  somewhat 
obscurely.  The  hinder  part  of  the  under  surface  of  the  os  calcis  and  the  heads  of  the  metatarsal 
bones,  with  the  exception  of  the  first,  which  is  concealed  by  the  sesamoid  bones,  may  be  recog- 
nized. 

Surgical  Anatomy. — Considering  the  injuries  to  which  the  foot  is  subjected,  it  is  surpris- 
ing how  seldom  the  tarsal  bones  are  fractured.  This  is  no  doubt  due  to  the  fact  that  the  tarsus 
is  composed  of  a  number  of  bones,  articulated  by  a  considerable  extent  of  surface  and  joined 
together  by  very  strong  ligaments,  which  serve  to  mitigate  the  intensity  of  violence  applied  to  this 
part  of  the  body.  When  fracture  does  occur,  these  bones,  being  composed  for  the  most  part 
of  a  soft  cancellous  structure,  covered  only  by  a  thin  shell  of  compact  tissue,  are  often  extensively 
comminuted,  especially  as  most  of  the  fractures  are  produced  by  direct  violence.  As  the  bones 
have  only  a  very  scanty  amount  of  soft  parts  over  them,  fractures  are  very  often  compound,  and 
amputation  is  frequently  necessary. 

When  fracture  occurs  in  the  anterior  group  of  tafsal  bones,  it  is  almost  invariably  the  result 
of  direct  violence;  but  fractures  of  the  posterior  group,  that  is,  of  the  calcaneum  and  astrag- 
alus, are  most  frequently  produced  by  falls  from  a  height  on  to  the  feet;  though  fracture  of  the 
os  calcis  may  be  caused  by  direct  violence  or  by  muscular  action.  The  posterior  part  of  the 
bone,  that  is,  the  part  behind  the  articular  surfaces,  is  almost  always  the  seat  of  the  fracture, 
though  some  few  cases  of  fracture  of  the  sustentaculum  tali  and  of  vertical  fracture  between 
the  two  articulating  facets  have  been  recorded.  The  neck  of  the  astragalus,  being  the  weakest 
part  of  the  bone,  is  most  frequently  fractured,  though  fractures  may  occur  in  any  part  and 
almost  in  any  direction,  either  associated  or  not  with  fracture  of  other  bones. 

In  cases  of  club-foot,  especially  in  congenital  cases,  the  bones  of  the  tarsus  become  altered 
in  shape  and  size,  and  displaced  from  their  proper  positions.  This  is  especially  the  case  in  con- 
genital equino-varus,  in  which  the  astragalus,  particularly  about  the  head,  becomes  twisted  and 
atrophied,  and  a  similar  condition  may  be  present  in  the  other  bones,  more  especially  the  sca- 
phoid. The  tarsal  bones  are  peculiarly  liable  to  become  the  seat  of  tuberculous  caries,  and  this 
condition  may  arise  after  comparatively  trivial  injuries.  There  are  several  reasons  to  account 
for  this.  They  are  composed  of  a  delicate  cancellated  structure,  surrounded  by  intricate  synovial 
membranes.  They  are  situated  at  the  farthest  point  from  the  central  organ  of  the  circulation 
and  exposed  to  vicissitudes  of  temperature;  and,  moreover,  on  their  dorsal  surface  are  thinly 
clad  with  soft  parts  which  have  but  a  scanty  blood-supply.  And  finally,  after  slight  injuries, 
they  are  not  maintained  in  a  condition  of  rest  to  the  same  extent  as  structures  suffering  from 


SESAMOID  BONES  259 

similar  injuries  in  some  other  parts  of  the  body.  Caries  of  the  calcaneus  or  astragalus 
may  remain  limited  to  the  one  bone  for  a  long  period,  but  when  one  of  the  other  bones  is 
affected,  the  remainder  frequently  become  involved,  in  consequence  of  the  disease  spreading 
through  the  large  and  complicated  synovial  membrane  which  is  more  or  less  common  to  these 
bones. 

Amputation  of  the  whole  or  a  part  of  the  foot  is  frequently  required  either  for  injury  or 
disease.  The  principal  amputations  are  as  follows:  (1)  Syme's :  amputation  at  the  ankle-joint 
by  a  heel-flap,  with  removal  of  the  malleoli  and  a  thin  slice  from  the  lower  end  of  the  tibia. 
(2)  Roux's :  amputation  at  the  ankle-joint  by  a  large  internal  flap.  (3)  Pirogofi's  amputa- 
tion :  removal  of  the  whole  of  the  tarsal  bones,  except  the  posterior  part  of  the  os  calcis..  A  thin 
slice  is  sawn  from  the  tibia  and  fibula,  including  the  two  malleoli.  The  sawn  surface  of  the  os 
calcis  is  then  turned  up  and  united  to  the  similar  surface  of  the  tibia.  (4)  Subastragaloid 
amputation :  removal  of  the  foot  below  the  astragalus  through  the  joint  between  it  and  the  os 
calcis.  This  operation  has  been  modified  by  Hancock,  who  leaves  the  posterior  third  of  the  os 
calcis  and  turns  it  up  against  the  denuded  surface  of  the  astragalus.  This  latter  operation  is  of 
doubtful  utility  and  is  rarely  performed.  (5)  Chopart's  or  medio-tarsal :  removal  of  the  ante- 
rior part  of  the  foot  with  all  the  tarsal  bones  except  the  os  calcis  and  astragalus;  disarticula- 
tion  being  effected  through  the  astragalo-scaphoid  and  calcaneo-cuboid  joints.  (6)  Lisfranc's  : 
amputation  of  the  anterior  part  of  the  foot  through  the  tarso-metatarsal  joints.  This  was 
modified  by  Hey,  who  disarticulated  through  the  joints  of  the  four  outer  metatarsal  bones  with 
the  tarsus,  and  sawed  off  the  projecting  internal  cuneiform ;  and  by  Skey,  who  sawed  off  the  base 
of  the  second  metatarsal  bone  and  disarticulated  the  others. 

The  bones  of  the  tarsus  occasionally  require  removal  individually.  This  is  especially  the 
case  with  the  astragalus  and  os  calcis  for  disease  limited  to  the  one  bone,  or  again  the  astragalus 
may  require  excision  in  cases  of  subastragaloid  dislocation,  or,  as  recommended  by  M.r  Lund, 
in  cases  of  inveterate  talipes.  The  cuboid  has  been  removed  for  the  same  reason  by  Mr.  Solly. 
But  the  latter  two  operations  have  fallen  into  disuse,  and  have  been  superseded  by  resection 
of  a  wedge-shaped  piece  of  bone  from  the  outer  side  of  the  tarsus.  Finally,  Mickulicz  and 
Watson  have  devised  operations  for  the  removal  of  more  extensive  portions  of  the  tarsus. 
Mickulicz's  operation  consists  in  the  removal  of  the  os  calcis  and  astragalus,  along  with  the 
articular  surfaces  of  the  tibia  and  fibula,  and  also  of  the  scaphoid  and  cuboid.  The  remain- 
ing portion  of  the  tarsus  is  then  brought  into  contact  with  the  sawn  surfaces  of  the  tibia  and 
fibula,  and  fixed  there.  The  result  is  a  position  of  the  shortened  foot  resembling  talipes 
equinus.  Watson's  operation  is  adapted  to  those  cases  where  the  disease  is  confined  to  the 
anterior  tarsal  bones.  By  two  lateral  incisions  he  saws  through  the  bases  of  the  metatarsal 
bones  in  front  and  opens  up  the  joints  between  the  scaphoid  and  astragalus,  and  the  cuboid  and 
os  calcis,  and  removes  the  intervening  bones. 

Fractures  of  the  metatarsal  bones  and  phalanges  are  nearly  always  due  to  direct  violence,  and 
in  many  cases  the  injury  is  the  result  of  severe  crushing  accidents,  necessitating  amputation. 
The  metatarsal  bones,  and  especially  the  metatarsal  bone  of  the  great  toe,  are  frequently  dis- 
eased, either  in  tuberculous  subjects  or  in  perforating  ulcer  of  the  foot. 

Sesamoid  Bones  (Ossa  Sesamoidea)  (Figs.  192,  193). 

These  are  small  rounded  masses,  cartilaginous  in  early  life,  osseous  in  the  adult, 
which  are  developed  in  those  tendons  which  exert  a  great  amount  of  pressure  upon 
the  parts  over  which  they  glide.  It  is  said  that  they  are  more  commonly  found  in 
the  male  than  in  the  female,  and  in  persons  of  an  active  muscular  habit  than  in 
those  who  are  weak  and  debilitated.  They  are  invested  throughout  their  whole 
surface  by  the  fibrous  tissue  of  the  tendon  in  which  they  are  found,  excepting  upon 
that  side  which  lies  in  contact  with  the  part  over  which  they  play,  where  they 
present  a  free  articular  facet.  They  may  be  divided  into  two  kinds:  those  which 
glide  over  the  articular  surfaces  of  the  joints,  and  those  which  play  over  the  cartilag- 
inous facets  found  on  the  surfaces  of  certain  bones. 

The  sesamoid  bones  of  the  joints  in  the  upper  extremity  are  two  on  the  palmar 
surface  of  the  metacarpo-phalangeal  joint  in  the  thumb,  developed  in  the  tendons 
of  the  Flexor  brevis  pollicis;  one  on  the  palmar  surface  of  the  interphalangeal 
joint  of  the  thumb;  occasionally  one  or  two  opposite  the  metacarpo-phalangeal 
articulations  of  the  fore  and  little  fingers;  and,  still  more  rarely,  one  opposite 
the  same  joints  of  the  third  and  fourth  fingers.  In  the  lower  extremity,  the 
patella,  which  is  developed  in  the  tendon  of  the  Quadriceps  extensor;  two 
small  sesamoid  bones,  found  in  the  tendons  of  the  flexor  brevis  hallucis,  opposite 


260 


THE  SKELETON 


the  metatarso-phalangeal  joint  of  the  great  toe ;  one  sometimes  over  the  inter- 
phalangeal  joint  of  the  great  toe;  and  occasionally  one  in  the  metatarso-phalan- 
•geal  joint  of  the  second  toe,  the  little  toe,  and,  still  more  rarely,  the  third  and 
fourth  toes. 


FIG.  192. — Sesamoid  bones  of  the  hand, 
and  Charpy.) 


(Poirier 


FIG.  193. — Sesamoid  bones  of  the 
foot.     (Poirier  and  Charpy.) 


Those  found  in  the  tendons  which  glide  over  certain  bones  occupy  the  following 
situations:  one  sometimes  found  in  the  tendon  of  the  Biceps  cubiti,  opposite  the 
tuberosity  of  the  radius :  one  in  the  tendon  of  the  Peroneus  longus,  where  it  glides 
through  the  groove  in  the  cuboid  bone;  one  appears  late  in  life  in  the  tendon  of  the 
Tibialis  anticus,  opposite  the  smooth  facet  of  the  internal  cuneiform  bone;  one  is 
found  in  the  tendon  of  the  Tibialis  posticus,  opposite  the  inner  side  of  the  head 
of  the  astragalus;  one  in  the  outer  head  of  the  Gastrocnemius,  behind  the  outer 
condyle  of  the  femur;  and  one  in  the  conjoined  tendon  of  the  Psoas  and  Iliacus, 
where  it  glides  over  the  os  pubis.  Sesamoid  bones  are  found  occasionally  in  the 
tendon  of  the  Gluteus  maximus,  as  it  passes  over  the  great  trochanter,  and  in 
the  tendons  which  wind  round  the  inner  and  outer  malleoli. 


THE  ARTICULATIONS  OR  JOINTS. 


THE  various  bones  of  which  the  Skeleton  consists  are  connected  together  at 
different  parts  of  their  surfaces,  and  such  a  connection  is  designated  by  the 
name  of  joint  or  articulation.  Arthrology  is  the  branch  of  anatomy  which  treats  of 
the  joints.  Certain  joints  are  immovable,  as  those  between  the  cranial  bones  and 
most  of  those  between  the  facial  bones.  In  an  immovable  joint  the  adjacent 
margins  of  the  bones  are  applied  in  almost  close  contact,  a  thin  layer  of  fibrous 
membrane,  the  sutural  ligament,  or,  as  at  the  base  of  the  skull,  in  certain  situa- 
tions, a  thin  layer  of  cartilage,  being  interposed.  Where  slight  movement  is 
required,  combined  with  great  strength,  the  osseous  surfaces  are  united  by  tough 
and  elastic  fibro-cartilages,  as  in  the  joints  between  the  vertebral  bodies  and  in  the 
interpubic  articulation;  but  in  the  movable  joints  the  bones  forming  the  articula- 
tion are  generally  expanded  for  greater  convenience  of  mutual  connection,  covered 
by  cartilage,  held  together  by  strong  bands  or  capsules  of  fibrous  tissue  called  liga- 
ments, and  partially  lined  by  a  membrane,  the  synovial  membrane,  which  secretes 
a  fluid  to  lubricate  the  various  parts  of  which  the  joint  is  formed;  so  that  the 
structures  which  enter  into  the  formation  of  a  joint  are  bone,  cartilage,  fibro- 
cartilage,  ligament,  and  synovial  membrane. 

Bone. — Bone  constitutes  the  fundamental  element  of  all  the  joints.  In  the 
long  bones  the  extremities  are  the  parts  which  form  the  articulations;  they  are 
generally  somewhat  enlarged  and  consist  of  spongy,  cancellous  tissue,  with  a  thin 
coating  of  compact  substance.  The  layer  of  compact  bone  which  forms  the 
articular  surface,  and  to  which  the  cartilage  is  attached,  is  called  the  articular 
lamella.  It  is  of  a  white  color,  extremely  dense,  and  varies  in  thickness.  Its 
structure  differs  from  ordinary  bone-tissue  in  this  respect,  that  it  contains  no 
Haversian  canals,  and  its  lacunae  are  much  larger  than  in  ordinary  bone  and 
have  no  canaliculi.  The  vessels  of  the  cancellous  tissue,  as  they  approach  the 
articular  lamella,  turn  back  in  loops,  and  do  not  perforate  it;  this  layer  is  conse- 
quently more  dense  and  firmer  than  ordinary  bone,  and  is  evidently  designed  to 
form  a  firm  and  unyielding  support  for  the  articular  cartilage.  In  the  flat  bones 
the  articulations  usually  take  place  at  the  edges,  and,  in  the  short  bones,  at  various 
parts  of  their  surface. 

Cartilage. — Cartilage  is  material  which  is  a  transition  stage  of  connective  tissue 
into  bone.  When  boiled  it  yields  chondrin.  Cartilage  is  not  vascular  and  is  found 
in  various  parts  of  the  body;  in  adult  life  chiefly  in  the  joints,  in  the  parietes  of 
the  thorax,  and  in  various  tubes,  which  are  to  be  kept  permanently  open,  such  as 
the  air  passages,  nostrils,  and  ears.  In  the  foetus  at  an  early  period  the  greater 
part  of  the  skeleton  is  cartilaginous.  Because  this  cartilage  is  replaced  by  bone, 
it  is  called  temporary  in  contradistinction  to  that  which  remains  unossified  during 
life,  and  which  is  called  permanent.  Unless  active  growth  is  in  progress  or  cal- 
cification is  going  on,  cartilage  does  not  contain  blood-vessels;  if  there  is  either 
active  growth  or  calcification  it  may  contain  them.  The  investing  membrane  of 
cartilage  is  called  the  perichondrium.  It  consists  of  connective-tissue  fibres  and 
a  few  elastic  fibres.  The  perichondrium  carries  blood-vessels,  which  may  grow 
into  the  cartilage  during  active  growth  or  ossification.  Cartilage  is  divided  into: 

1.  Hyaline  cartilage.  2.  Elastic  cartilage.  3.  Fibro-cartilage. 

The  cells  of  these  three  varieties  of  cartilage  are  similar. 

(261) 


262 

Hyaline  Cartilage. — This  structure  is  found  in  embryos  in  regions  where  bone 
is  to  be  formed,  in  the  nose,  larynx,  trachea,  bronchi,  .and  in  symphyses,  epi- 
physes,  and  synchondroses.  Costal  cartilage  and  epiphyseal  cartilage  are  com- 
posed of  it,  and  as  articular  cartilage  (cartilago  articularis)  it  covers  joint  surfaces. 
It  is  a  bluish  or  pearly  hued  substance,  in  reality  a  modified  connective  tissue,, 
but  much  harder  than  most  connective  tissues.  The  investing  membrane,  the 
perichondrium,  is  composed  chiefly  of  connective-tissue  fibres,  although  a  few  elastic 
fibres  are  present.  The  peripheral  layers  of  the  cartilage  pass  into  the  perichon- 
drium. The  perichondrium  carries  blood-vessels  which  may,  if  there  be  active 
growth  or  ossification  in  progress,  grow  down  into  the  cartilage.  During  growth 
the  fibres  of  connective  tissue  may  become  the  ground  substance  of  cartilage  and 
the  cells  of  connective  tissue  may  become  cartilage  cells;  hence,  the  connective- 
tissue  cells  of  the  perichondrium  are  called  chondroblasts. 

Hyaline  cartilage  is  composed  of  round  or  oval  cells  and  intercellular  substance. 
Each  cell  contains  granular  protoplasm  and  a  nucleus,  and  the  nucleus  contains 
one  or  two  nucleoli.  The  cells  are  placed  in  the  so-called  cartilage  spaces  of  the 
ground  substance,  and  the  ground  substance  immediately  surrounding  a  space  is 
called  a  cartilage  capsule.  The  cells  are  placed  in  groups  and  near  the  surface  are 
arranged  in  rows,  and  in  some  regions  are  flattened  by  pressure.  The  intercellular 
or  ground  substance  (matrix)  is  an  apparently  homogeneous  and  structureless 
material  between  the  cartilage  spaces.  By  certain  methods,  however,  fibrils  can 
be  demonstrated  in  it.  These  fibrils  in  general  are  parallel.  In  some  of  the 
lower  animals  canals  have  been  demonstrated.  In  man  it  has  not  been  proved 
that  canals  exist,  and  it  has  been  suggested  that  the  fibrils  act  as  paths  for  the 
conduction  of  nutritive  fluid. 

Articular  cartilage  forms  a  thin  incrustation  upon  the  joint-surfaces  of  the  bones, 
and  its  elasticity  enables  it  to  break  the  force  of  any  concussion,  while  its  smooth- 
ness affords  ease  and  freedom  of  movement.  It  varies  in  thickness  according 
to  the  shape  of  the  articular  surface  on  which  it  lies;  where  this  is  convex  the 
cartilage  is  thickest  at  the  centre,  where  the  greatest  pressure  is  received;  and  the 
reverse  is  the  case  on  the  concave  articular  surfaces.  Articular  cartilage  appears 
to  derive  its  nutriment  partly  from  the  vessels  of  the  neighboring  synovial  mem- 
brane and  partly  from  those  of  the  bone  upon  which  it  is  implanted.  Toynbee 
has  shown  that  the  minute  vessels  of  the  cancellous  tissue  as  they  approach  the 
articular  lamella  dilate  and  form  arches,  and  then  return  into  the  substance  of 
the  bone. 

The  hyaline  cartilages,  especially  in  adult  and  advanced  life,  are  prone  to 
calcify — that  is  to  say,  to  have  their  matrix  permeated  by  the  salts  of  lime  without 
any  appearance  of  true  bone.  The  process  of  calcification  occurs  also,  and  still 
more  frequently,  according  to  Rollett,  in  such  cartilages  as  those  of  the  trachea 
and  in  the  costal  cartilages,  which  are  prone  afterward  to  conversion  into  true 
bone.  The  ossification  may  occur  in  old  age. 

Elastic  Cartilage. — In  this  structure  there  are  elastic  fibres  in  the  matrix,  which 
fibres  at  the  periphery  of  the  cartilage  enter  into  the  perichondrium.  Such  carti- 
lage is  not  blue-white  in  color,  but  is  a  very  light  yellow,  and  is  not  to  be  regarded 
as  identical  with  elastic  fibrous  tissue.  Elastic  cartilage  is  found  in  the  epiglottis, 
the  external  ear,  the  Eustachian  tube,  the  vocal  processes  of  the  arytenoid  carti- 
lages, the  corniculate  and  cuneiform  cartilages,  and  the  cartilages  of  the  larynx. 

Fibro-cartilage  is  composed  of  white  fibrous  tissue  and  cartilage  in  varying  pro- 
portions ;  it  is  to  the  first  of  these  two  constituents  that  its  flexibility  and  toughness 
are  chiefly  owing,  and  to  the  latter  its  elasticity ;  the  cells  are  fewer  in  number,  but 
are  possessed  of  more  definite  capsules  than  are  those  of  hyaline  cartilage,  and  they 
are  usually  arranged  in  groups  surrounded  by  small  islands  of  hyaline  matrix, 
which  may  be  concentrically  striated.  The  hyaline  islands  are  separated  from 


CARTILAGE  263 

one  another  by  bundles  of  white  fibrous  tissue  that  pursue  a  markedly  wavy 
course. 

Fibro-cartilage  is  found  at  the  point  of  insertion  of  the  ligamentum  teres  into 
the  head  of  the  femur,  in  the  intervertebral  disks,  in  the  pubic  symphysis,  and  in 
the  interarticular  cartilages. 

The  fibro-cartilages  admit  of  arrangement  into  four  groups:  interarticular,  con- 
necting, circumferential,  and  stratiform. 

1.  The    interarticular    fibro-cartilages    (menisci    interarticulares}    are    flattened, 
fibre-cartilaginous  plates,  of  a  round,  oval,  triangular,  or  sickle-like  form,  inter- 
posed between  the  articular  cartilages  of  certain  joints.     They  are  free  on  both 
surfaces,  thinner  toward  their  centre  than  at  their  circumference,  and  held  in 
position  by  the  attachment  of  their  margins  and  extremities  to  the  surrounding 
ligaments.     The  synovial  membrane  of  the  joint  is  prolonged  over  them  a  short 
distance  from  their  attached  margins.     They  are  found  in  the  temporo-mandib- 
ular,  sterno-clavicular,  acromio-clavicular,  wrist-  and  knee-joints.     These  carti- 
lages are  usually  found  in  those  joints  which  are  most  exposed  to  violent  concussion 
and  subject  to  frequent  movement.     Their  use  is  to  maintain  the  apposition  of  the 
opposed  surfaces  in  their  various  motions;  to  increase  the  depth  of  the  articular 
surfaces  and  give  ease  to  the  gliding  movement;  to  moderate  the  effects  of  great 
pressure  and  deaden  the  intensity  of  the  shocks  to  which  the  parts  may  be  sub- 
jected.    Humphry  has  pointed  out  that  these  interarticular  fibro-cartilages  serve 
an  important  purpose  in  increasing  the  variety  of  movements  in  a  joint.     Thus, 
in  the  knee-joint  there  are  two  kinds  of  motion — viz.,  angular  movement  and 
rotation — although  it  is  a  hinge-joint,  in  which,  as  a  rule,  only  one  variety  of  motion 
is  permitted;  the  former  movement  takes  place  between  the  condyles  of  the  femur 
and  the  interarticular  cartilage,  the  latter  between  the  cartilage  and  the  head  of 
the  tibia.     So,  also,  in  the  temporo-mandibular  joint,  the  upward  and  downward 
movement  of  opening  and  shutting  the  mouth  takes  place  between  the  fibro- 
cartilage  and  the  jaw-bone,  the  grinding  movement  between  the  glenoid  cavity 
and  the  fibre-cartilage,  the  latter  moving  with  the  jaw-bone. 

Interarticular  cartilages  may  divide  the  joint  into  two  distinct  cavities,  as  in  the 
temporo-maxillary  articulation.  The  periphery  of  an  articular  cartilage  is  attached 
particularly  to  the  capsule  and  may  also  be  attached  to  the  non-articular  portion 
of  the  bone.  The  semilunar  cartilages  of  the  knee  resemble  tendon  more  than 
they  do  cartilage.  The  fibres  are  arranged  in  dense,  more  or  less  parallel  bundles, 
separated  by  small,  scattered  hyaline  cells,  and  the  disks  are  attached  to  the  bone 
by  thin  layers  of  hyaline  cartilage. 

2.  The  connecting  fibro-cartilages  are  interposed  between  the  bony  surfaces  of 
those  joints  which  admit  of  only  slight  mobility,  as  between  the  bodies  of  the 
vertebrae  and  between  the  pubic  bones.    They  form  disks  which  adhere  closely  to 
both  of  the  opposed  surfaces,  and  are  composed  of  concentric  rings  of  fibrous 
tissue,  with  cartilaginous  laminae  interposed,  the  former  tissue  predominating 
toward  the  circumference,  the  latter  toward  the  centre. 

3.  The  circumferential  fibro-cartilages  consist  of  a  rim  of  fibro-cartilage,  which 
surrounds  the  margin  of  some  of  the  articular  cavities,  as  the  cotyloid  cavity  of 
the  hip  and  the  glenoid  cavity  of  the  shoulder;  they  serve  to  deepen  the  articular 
surface,  and  to  protect  its  edges. 

4.  The  stratiform  fibro-cartilages  are  those  which  form  a  thin  coating  to  osseous 
grooves  through  which  the  tendons  of  certain  muscles  glide.     Small  masses  of 
fibro-cartilages  are  developed  also  in  the  tendons  of  some  muscles,  where  they 
glide  over  bones,  as  in  tendons  of  the  Peroneus  longus  and  the  Tibialis  posticus. 

Ligaments. — Ligaments  consist  of  bands  of  various  forms,  serving  to  connect 
together  the  articular  extremities  of  bones,  and  are  composed  mainly  of  coarse 
bundles  of  very  dense  white  fibrous  tissue  placed  parallel  with,  or  closely  inter- 


264  THE  ARTICULATIONS  OR  JOINTS 

laced  with,  one  another,  and  presenting  a  white,  shining,  silvery  aspect.  These 
bundles  are  called  fasciculi.  They  are  held  together  by  a  cement  substance 
containing  cells  which  resemble  those  of  tendon.  A  ligament  is  pliant  and 
flexible,  so  as  to  allow  of  the  most  perfect  freedom  of  movement,  but  it  is 
strong,  tough,  and  inextensile,  so  as  not  readily  to  yield  under  the  most 
severely  applied  force;  it  is  consequently  well  adapted  to  serve  as  the  connecting 
medium  between  the  bones.  Some  ligaments  consist  entirely  of  yellow  elastic 
tissue  (elastic  -fibrous  tissue) ,  the  elastic  fibres  branching  considerably,  but  main- 
taining in  general  a  parallel  course.  The  fibres  are  in  bundles,  between  which 
areolar  connective  tissue  lies.  The  ligamenta  subflava,  which  connect  together 
the  adjacent  arches  of  the  vertebrae  in  man  and  the  ligamentum  nuchae  in  the 
lower  animals  are  composed  of  yellow  elastic  tissue.  In  these  cases  it  will  be 
observed  that  the  elasticity  of  the  ligament  is  intended  to  act  as  a  substitute  for 
muscular  power. 

Synovial  Membranes. — These  membranes  are  serous  in  character.  Asynovial 
membrane  consists  of  loose  connecting  tissue  (subendothelial  tissue),  containing  fat, 
vessels,  and  nerves,  its  inner  surface  being  lined  with  a  single  layer  of  flat  endothelial 
cells.  The  endothelial  cells  are  polyhedral,  and  each  cell  possesses  a  flattened  oval 
nucleus.  The  cells  are  held  together  by  intercellular  cement.  It  is  believed  by  some 
that  little  openings  occur  at  intervals  in  the  intercellular  cement,  but  it  is  held  by 
many  that  the  supposed  openings  are  artifacts.  Synovial  cavities  contain  a  little 
fluid.  A  non-articular  synovial  membrane  does  not  actually  secrete  fluid,  but  it  is 
moistened  by  lymph  which  passes  through  the  membrane  and  into  the  cavity  by 
osmosis. 

Joint  cavities  and  bursse  communicating  with  joints  contain  a  characteristic 
fluid  which  is  a  secretion  of  the  membrane.  It  is  yellowish-white  or  slightly  red- 
dish, somewhat  cloudy,  viscid  like  the  white  of  an  egg,  having  a  strongly  alkaline 
reaction  and  a  slightly  saline  taste.  It  consists  of  fats,  salts,  albumins,  extract- 
ives from  lymph,  a  mucinous  body  known  as  synovin,1  and  another  mucin-like 
body,  which  is  rich  in  phosphorus  (Simon).  The  synovial  membranes  found 
in  the  body  admit  of  subdivision  into  three  kinds — articular,  bursal,  and  vaginal. 

Articular  Synovial  Membrane. — Articular  synovial  membrane  is  found  in  every 
freely  movable  joint.  It  lines  the  capsule  of  the  joint  and  is  reflected  upon  the 
non-articular  intrascapular  portion  of  the  bones  which  enter  into  the  formation 
of  the  joint.  In  the  foetus  this  membrane  is  said,  by  Toynbee,  to  be  continued 
over  the  surface  of  the  cartilages;  but  in  the  adult  it  merely  encroaches  for  a  short 
distance  upon  the  margins  of  the  cartilages,  to  which  it  is  firmly  attached;  it 
then  invests  the  inner  surface  of  the  capsular  or  other  ligaments  enclosing  the 
joint,  and  is  reflected  over  the  surface  of  any  tendons  passing  through  its  cavity,  as 
the  tendon  of  the  Popliteus  in  the  knee  and  the  tendon  of  the  Biceps  in  the  shoulder. 
Hence  the  articular  synovial  membrane  may  be  regarded  as  a  short  wide  tube, 
attached  by  its  open  ends  to  the  margins  of  the  articular  cartilages,  and  covering 
the  inner  surface  of  the  various  ligaments  which  connect  the  articular  surfaces, 
so  that  along  with  the  cartilages  it  completely  encloses  the  joint-cavity.  In  some 
of  the  joints  the  synovial  membrane  is  thrown  into  folds,  which  pass  across  the 
cavity.  They  are  called  synovial  ligaments,  and  are  especially  distinct  in  the  knee. 
These  folds,  when  large,  frequently  contain  considerable  quantities  of  fat,  which 
acts  as  a  cushion  between  the  two  articular  surfaces  and  which  serves  a  valuable 
purpose  in  filling  up  gaps.  In  some  joints  there  are  flattened  folds,  subdivided 
at  their  margins  into  fringe-like  processes  (synovial  villi),  the  vessels  of  which 
have  a  convoluted  arrangement.  These  latter  generally  project  from  the  synovial 
membrane  near  the  margin  of  the  cartilage  and  lie  flat  upon  its  surface.  They 
consist  of  connective  tissue  covered  with  endothelium,  and  contain  fat-cells  in 
variable  quantities,  and,  more  rarely,  isolated  cartilage-cells.  They  were  described 

1  Simon's  Physiological  Chemistry. 


SYNOVIAL  MEMBRANES  265 

by  Clopton  Havers  as  mucilaginous  glands,  and  as  the  source  of  the  synovial  secre- 
tion. Under  certain  diseased  conditions  similar  processes  are  found  covering 
the  entire  surface  of  the  synovial  membrane,  forming  a  mass  of  pedunculated 
fibro-fatty  growths  which  project  into  the  joint.  Similar  structures  are  also 
found  in  some  of  the  bursal  and  vaginal  synovial  membranes. 

Bursal  Synovial  Membrane. — The  bursal  synovial  membranes  are  sacs  inter- 
posed between  surfaces  which  move  upon  each  other,  producing  friction,  as  in  the 
gliding  of  a  tendon  or  of  the  integument  over  projecting  bony  surfaces.  There  are 
two  groups  of  synovial  bursae  designated  according  to  situation:  (1)  Those 
situated  between  the  integument  and  a  prominent  process  of  bone.  Such  a  bursa 
is  called  a  subcutaneous  synovial  bursa  (bursa  mucosa  subcutanea)  (Fig.  246).  Sub- 
cutaneous bursse  are  found  between  the  integument  and  the  front  of  the  patella, 
over  the  olecranon,  the  malleoli,  and  other  prominent  parts.  (2)  Those  situated 
between  tendons  or  muscles  and  the  bony  or  cartilaginous  surfaces  over  which 
the  tendons  or  muscles  glide  (Fig.  194).  Such  a  bursa  is  called  a  subtendinous 


FIG.  194. — Scheme  of  a  serous  bursa.     (Poirier  and  Charpy.) 

.synovial  bursa  (bursa  mucosa  subtendinea).  For  example,  a  bursa  is  placed  be- 
tween the  Glutei  muscles  and  the  surface  of  the  great  trochanter.  Subtendinous 
bursae  are  found  often  about  joints  and  not  unusually  communicate  directly 
with  the  cavity  of  the  joint  by  means  of  an  opening  in  the  joint  capsule,  the  syno- 
vial membrane  of  the  joint  being  continuous  with  the  synovial  membrane  of  the 
tursa.  For  instance,  the  bursa  between  the  tendon  of  the  Psoas  and  Iliacus 
muscles  and  the  capsular  ligament  of  the  hip  communicates  with  the  hip-joint; 
:and  the  bursa  between  the  under  surface  of  the  Subscapularis  muscle  and  the  neck 
of  the  scapula  communicates  with  the  shoulder-joint.  Bursse  consist  of  a  thin  wall 
of  connective  tissue,  partially  covered  by  patches  of  cells,  and  contain  a  viscid  fluid. 

Vaginal  Synovial  Membrane  (Figs.  232  and  324). — A  vaginal  synovial  membrane 
which  is  the  synovial  sheath  or  the  thecal  synovial  bursa  (vagina  mucosa  tendinis} 
serves  to  facilitate  the  gliding  of  a  tendon  in  the  osseo-fibrous  canal  through  which 
it  passes.  The  membrane  is  here  arranged  in  the  form  of  a  sheath,  one  layer  of 
which  adheres  to  the  wall  of  the  canal,  and  the  other  is  reflected  upon  the  surface  of 
the  contained  tendon,  the  space  between  the  two  free  surfaces  of  the  membrane 
containing  synovia.  These  sheaths  are  chiefly  found  surrounding  the  tendons  of 
the  Flexor  and  Extensor  muscles  of  the  fingers  and  toes  as  they  pass  through  the 
osseo-fibrous  canals  in  the  hand  or  foot.  A  vaginal  sheath  covers  the  long  head 
of  the  Biceps  muscle  from  its  origin  to  the  surgical  neck  of  the  humerus  (Fig.  222). 

Pads  of  adipose  tissue  (synovial  fat  pads]  are  found  in  certain  joints  between 
folds  of  the  synovial  membrane  or  between  the  synovial  membrane  and  the 
surface  beneath  it.  These  pads  fill  up  certain  joint  intervals,  and  by  adapting 
themselves  to  changes  of  position  maintain  the  form  of  the  joint  during  movement. 

The  articulations  are  divided  into  three  classes:  synarthrosis,  or  immovable; 
amphiarthrosis,  or  mixed;  and  diarthrosis,  or  movable  joints. 


266  THE  ARTICULATIONS    OR    JOINTS 

Synarthrosis  (Immovable  Articulation). 

Synarthrosis  includes  all  those  articulations  in  which  the  surfaces  of  the  bones 
are  in  almost  direct  contact,  being  fastened  together  by  an  intervening  mass  of 
connective  tissue,  and  in  which  there  is  no  joint  cavity  and  no  appreciable  motion. 
Examples  of  Synarthrosis  are  the  joints  between  the  bones  of  the  cranium  and 
of  the  face,  excepting  those  of  the  lower  jaw.  The  varieties  of  Synarthrosis  are 
four  in  number:  sutura,  schindylesis,  gomphosis,  and  synchondrosis. 

Sutura. — Sutura  (a  seam)  is  that  form  of  articulation  met  with  only  in  the 
skull,  where  the  contiguous  margins  of  flat  bones  are  apparently  but  not  really 
in  immediate  contact,  a  thin  layer  of  fibrous  tissue,  sutural  membrane,  being 
interposed.  This  membrane  is  continuous  externally  with  the  pericranium  and 
internally  with  the  dura.  In  some  of  the  sutures  the  sutural  membrane  gradu- 
ally disappears  as  age  advances  and  the  two  bones  form  an  osseous  fusion.  Where 
the  articulating  surfaces  are  connected  by  a  series  of  processes  arid  indenta- 
tions interlocked  together,  it  is  termed  a  true  suture  or  sutura  vera,  of  which  there 
are  three  varieties :  sutura  dentata,  serrata,  and  limbosa.  The  sutura  dentata  (dens, 
a  tooth)  is  so  called  from  the  tooth-like  form  of  the  projecting  articular  processes, 
as  in  the  suture  between  the  parietal  bones.  In  the  sutura  serrata  (serra,  a  saw) 
the  edges  of  the  two  bones  forming  the  articulation  are  serrated  like  the  teeth 
of  a  fine  saw,  as  between  the  two  portions  of  the  frontal  bone.  In  the  sutura 
limbosa  (limbus,  a  selvage),  besides  the  dentated  processes,  there  is  a  certain 
degree  of  bevelling  of  the  articular  surfaces,  so  that  the  bones  overlap  one  another, 
as  in  the  suture  between  the  parietal  and  frontal  bones.  AVhen  the  articulation 
is  formed  by  roughened  surfaces  placed  in  apposition  with  one  another,  it  is 
termed  the  false  suture  (sutura  nothd),  of  which  there  are  two  kinds:  the  sutura 
squamosa  (squama,  a  scale),  formed  by  the  overlapping  of  two  contiguous  bones 
by  broad  bevelled  margins,  as  in  the  squamo-parietal  (squamous)  suture;  and 
the  sutura  harmonia  (bpfiovta,,  a  joining  together),  where  there  is  simple  apposition 
of  two  contiguous,  rough,  bony  surfaces,  as  in  the  articulation  between  the  two 
superior  maxillary  bones  or  of  the  horizontal  plates  of  the  palate  bones. 

Schindylesis. — Schindylesis  (a-^cvd(jXYja:<;,  a  fissure)  is  that  form  of  articulation 
in  which  a  thin  plate  of  bone  is  received  into  a  cleft  or  fissure  formed  by  the  sep- 
aration of  two  laminae  in  another  bone,  as  in  the  articulation  of  the  rostrum  of  the 
sphenoid  and  perpendicular  plate  of  the  ethmoid  with  the  vomer,  or  in  the  recep- 
tion of  the  latter  in  the  fissure  between  the  superior  maxillary  and  palate  bones. 

Gomphosis. — Gomphosis  (rbfjupot;,  a  nail)  is  an  articulation  formed  by  the 
insertion  of  a  cofiical  process  into  a  socket,  as  a  nail  is  driven  into  a  board;  this 
is  not  illustrated  by  any  articulation  between  bones,  properly  so  called,  but  is 
seen  in  the  articulation  of  the  teeth  with  the  alveoli  of  the  maxillary  bones. 

Synchondrosis. — Where  the  connecting  medium  is  cartilage  the  joint  is  termed 
a  synchondrosis.  This  is  a  temporary  form  of  joint,  because  the  hyaline  cartilage 
becomes  converted  into  bone  before  adult  life.  Such  a  joint  is  found  between 
the  epiphyses  and  shafts  of  long  bones.  Another  example  of  a  synchondrosis  is 
the  occipito-sphenoid  articulation. 

Amphiarthrosis  (Mixed  Articulation). 

In  this  form  of  articulation  the  contiguous  osseous  surfaces  may  be  connected 
together  by  broad  flattened  disks  of  fibro-cartilage,  of  a  more  or  less  complex 
structure,  which  adhere  to  the  end  of  each  bone,  as  in  the  articulation  between 
the  bodies  of  two  vertebrae  and  that  between  the  pubic  bones  at  the  symphysis. 
This  is  termed  symphysis.  In  a  symphysis  there  is  a  partial  joint-cavity  which  may 
exhibit  an  incomplete  synovial  membrane.  Each  constituent  bone  is  coated  with 
hyaline  cartilage  and  the  bones  are  held  together  by  ligaments  and  intervening 


DIARTHROSIS  267 

fibre-cartilage.  The  bony  surfaces  of  an  amphiarthrodial  joint  may  be  united 
by  an  interosseous  ligament,  as  in  the  inferior  tibio-fibular  articulation.  To  such 
an  articulation  the  term  syndesmosis  is  applied.  A  mixed  articulation  permits 
limited  motion. 

Diarthrosis  (Movable  Articulation). 

This  form  of  articulation  includes  the  greater  number  of  the  joints  in  the  body, 
mobility  being  their  distinguishing  character.  They  are  formed  by  the  approxi- 
mation of  two  contiguous  bony  surfaces  covered  with  cartilage,  connected  by 
ligaments  and  lined  by  synovia!  membrane.  The  varieties  of  joints  in  this  class 
have  been  determined  by  the  kind  of  motion  permitted  in  each.  There  are  two 
varieties  in  which  the  movement  is  uniaxial;  that  is  to  say,  all  movements  take 
place  around  one  axis.  In  one  form,  the  ginglymus  or  hinge-joint,  this  axis  is, 
practically  speaking,  transverse;  in  the  other,  the  trochoid  or  pivot-joint,  it  is 
longitudinal.  There  are  two  varieties  where  the  movement  is  biaxial  or  around 
two  horizontal  axes  at  right  angles  to  each  other  or  at  any  intervening  axis 
between  the  two.  These  are  the  condyloid -joint  and  the  saddle -joint.  There  is 
one  form  of  joint  where  the  movement  is  polyaxial,  the  enarthrosis  or  ball-and- 
socket  joint.  And  finally  there  are  the  arthrodia  or  gliding  joints.  In  a  diarthrosis 
there  is  always  a  joint  cavity  lined  with  synovial  membrane — the  articular  sur- 
faces of  the  bones  are  covered  with  hyaline  cartilage  and  the  bones  are  held  in 
contact  by  ligaments. 

Ginglymus  or  Hinge- joint  (jifftopo?,  a  hinge). — In  this  form  of  joint  the 
articular  surfaces  are  moulded  to  each  other  in  such  a  manner  as  to  permit  motion 
only  in  one  plane,  forward  and  backward ;  the  extent  of  motion  at  the  same  time 
being  considerable.  The  direction  which  the  distal  bone  takes  in  this  motion  is 
never  in  the  same  plane  as  that  of  the  axis  of  the  proximal  bone,  and  there  is 
always  a  certain  amount  of  alteration  from  the  straight  line  during  flexion.  The 
articular  surfaces  are  connected  together  by  strong  lateral  ligaments,  which  form 
their  chief  bond  of  union.  The  most  perfect  forms  of  ginglymus  are  the  inter- 
phalangeal  joints  and  the  joint  between  the  humerus  and  ulna;  the  knee  and 
ankle  are  less  perfect,  as  they  allow  a  slight  degree  of  rotation  or  lateral  move- 
ment in  certain  positions  of  the  limb. 

Trochoid  or  Pivot-joint  or  Rotary-joint. — Where  the  movement  is  limited  to 
rotation,  the  joint  is  formed  by  a  pivot-like  process  turning  within  a  ring,  or  the 
ring  on  the  pivot,  the  ring  being  formed  partly  of  bone,  partly  of  ligament.  In 
the  superior  radio-ulnar  articulation  the  ring  is  formed  partly  by  the  lesser  sig- 
moid  cavity  of  the  ulna;  in  the  rest  of  its  extent,  by  the  orbicular  ligament;  here 
the  head  of  the  radius  rotates  within  the  ring.  In  the  articulation  of  the  odontoid 
process  of  the  axis  with  the  atlas  the  ring  is  formed  in  front  by  the  anterior  arch 
of  the  atlas;  behind,  by  the  transverse  ligament;  here  the  ring  rotates  round  'the 
odontoid  process. 

Condyloid  or  Biaxial  Articulation. — In  this  form  of  joint  an  ovoid  articular 
head,  or  condyle,  is  received  into  an  elliptical  cavity  in  such  a  manner  as  to  per- 
mit of  flexion  and  extension,  adduction  and  abduction  and  circumduction,  but 
no  axial  rotation.  The  articular  surfaces  are  connected  together  by  anterior, 
posterior,  and  lateral  ligaments.  An  example  of  this  form  of. joint  is  found  in 
the  wrist. 

Articulation  by  Reciprocal  Reception  or  Saddle-joint. — In  this  variety  the 
articular  surfaces  are  concavo-convex;  that  is  to  say,  they  are  inversely  convex  in 
one  direction  and  concave  in  the  other.  The  movements  are  the  same  as  in  the 
preceding  form;  that  is  to  say,  there  is  flexion,  extension,  adduction,  abduction, 
and  circumduction,  but  no  axial  rotation.  The  articular  surfaces  are  connected 


268 


THE   ARTICULATIONS    OR    JOINTS 


by  a  capsular  ligament.  The  best  example  of  this  form  of  joint  is  the  carpo- 
metacarpal  joint  of  the  thumb. 

Enarthrosis,  or  Ball-and-socket-joint,  is  that  form  of  joint  in  which  the  distal 
bone  is  capable  of  motion  around  an  indefinite  number  of  axes  which  have  one 
common  centre.  It  is  formed  by  the  reception  of  a  globular  head  into  a  deep 
cup-like  cavity  (hence  the  name  "ball-and-socket"),  the  parts  being  kept  in 
apposition  by  a  capsular  ligament  strengthened  by  accessory  ligamentous  bands. 
Examples  of  this  form  of  articulation  are  found  in  the  hip  and  shoulder. 

Arthrodia. — Arthrodia  is  that  form  of  joint  which  admits  of  a  gliding  move- 
ment; it  is  formed  by  the  approximation  of  plane  surfaces  or  of  one  slightly  con- 
cave to  one  slightly  convex,  the  amount  of  motion  between  them  being  limited 
by  the  ligaments,  or  osseous  processes,  surrounding  the  articulation;  as  in  the 
articular  processes  of  the  vertebrae,  the  carpal  jointr,  except  that  of  the  os  magnum 
with  the  scaphoid  and  semilunar  bones,  and  the  tarsal  joints  with  the  exception 
of  the  joint  between  the  astragalus  and  the  scaphoid. 

Below,  in  tabular  form,  are  the  names,  distinctive  characters,  and  examples 
of  the  different  kinds  of  articulations. 

The  Kinds  of  Movement  Admitted  in  Joints. 

The  movements  admissible  in  joints  may  be  divided  into  four  kinds:  gliding, 
angular  movement,  circumduction,  and  rotation.  These  movements  are  often, 
however,  more  or  less  combined  in  the  various  joints,  so  as  to  produce  an  infinite 
variety,  and  it  is  seldom  that  we  find  only  one  kind  of  motion  in  any  particular  joint. 

Dentata,  having 
tooth-like  processes. 

As  in  interparietal 
suture. 

Serrata,  having  ser- 
rated edges  like  the 
teeth  of  a  saw. 

As  in  interfrontal 
suture. 

Limbosa,  having 

Sutura.  A.r-  bevelled    margins    and 

ticulation    by  dentated  processes, 

processes  and  As    in    fronto-parie- 

indentations  1  l^tal  suture, 

interlocked  f     Squamosa,       formed 

together.  by  thin  bevelled  mar- 

gins, overlapping  each 
other. 

As  in  squamo-parie- 
tal  suture. 

Harmonia,  formed  by 
the  apposition  of  con- 
tiguous rough  surfaces. 
As  in  intermaxillary 
suture. 

Schindylesis. — Articulation  formed  by  the  reception  of  a 
thin  plate  of  one  bone  into  a  fissure  of  another. 

As  in  articulation  of  rostrum  of  sphenoid  with  vomer. 
Gomphosis. — Articulation  formed  by  the  insertion  of  a 
conical  process  into  a  socket:  the  teeth. 


Synarthrosis,  or 
Immovable  Joint. 
Surfaces  separated 
by  fibrous  mem- 
brane or  by  line 
of  cartilage,  with- 
out any  interven- 
ing  synovial 
cavity,  and  im- 
movably  con- 
nected  with  each 
other.  • 

As  in  joints  of 
cranium  and  face 
(except  lower 
jaw). 


Sutura  vera 
(true),  articulate 
by  indented  bor- 
ders. 


Sutura   notha 

(false)  „    articulate 

.by  rough  surfaces. 


THE   KINDS    OF  MOVEMENT  ADMITTED    IN   JOINTS        269 


Amphiarthrosis,  \ 
Mixed  Articula--j 
tion. 


Diarthrosis, 
Movable  Joint. 


Symphysis. — Surfaces  connected  by  fibro-cartilage.  There 

is  a  Partial  Joint  ca?'lty  and  mav  be  an  incomplete  synovia! 
membrane.  Has  limited  motion.  As  in  joints  between 
bodies  of  vertebrae. 

Syndesmosis. — Surfaces  united  by  an  interosseous  liga- 
Lment.  As  in  the  inferior  tibio-fibular  articulation. 

Ginglymus. — Hinge-joint;  motion  limited  to  two  directions, 
forwaid  and  backward.  Articular  surfaces  fitted  together 
so  as  to  permit  of  movement  in  one  plane.  As  in  the  inter- 
phalangeal  joints  and  the  joint  between  the  humerus  and  the 
ulna. 

Trochoides,  or  Pivot-joint. — Articulation  by  a  pivot  process 
turning  within  a  ring  or  ring  around  a  pivot.  As  in  superior 
radio-ulnar  articulation  and  atlanto-axial  joint. 

Condyloid. — Ovoid  head  received  into  elliptical  cavity. 
Movements  in  every  direction  except  axial  rotation.  As  the 
wrist-joint. 

Reciprocal  Reception  (saddle-joint). — Articular  surfaces 
inversely  convex  in  one  direction  and  concave  in  the  other. 
Movement  in  every  direction  except  axial  rotation.  As  in 
the  carpo-metacarpal  joint  of  the  thumb. 

Enarthrosis. — Ball-and-socket  joint;  capable  of  motion  in 
all  directions.  Articulations  by  a  globular  head  received 
into  a  cup-like  cavity.  As  in  hip-  and  shoulder-joints. 

Arthrodia. — Gliding  joint;  articulations  by  plane  surfaces, 
which  glide  upon  each  other.  As  in  carpal  and  tarsal  articu- 
^  lations. 

Gliding  movement  is  the  most  simple  kind  of  motion  that  can  take  place  in  a 
joint,  one  surface  gliding  or  moving  over  another  without  any  angular  or  rotatory 
movement.  It  is  common  to  all  movable  joints,  but  in  some,  as  in  the  articu- 
lations of  the  carpus  and  tarsus,  it  is  the  only  motion  permitted.  This  movement 
is  not  confined  to  plane  surfaces,  but  may  exist  between  any  two  contiguous 
surfaces,  of  whatever  form,  limited  by  the  ligaments  which  enclose  the  articu- 
lation. Gliding  over  a  wide  range,  as  is  seen  in  the  sliding  of  the  patella  over 
the  femur,  is  called  coaptation. 

Angular  movement  occurs  only  between  the  long  bones,  and  by  it  the  angle 
between  the  two  bones  is  increased  or  diminished.  It  may  take  place  in  four 
directions:  forward  and  backward,  constituting  flexion  or  bending  and  extension 
or  straightening,  or  inward  toward  and  outward  from  the  medial  line  of  the  body, 
constituting  adduction  and  abduction.  Abduction  of  a  limb  is  movement  away 
from  the  medial  line  of  the  body.  Adduction  of  a  limb  is  movement  toward  the 
medial  line  of  the  body.  In  the  fingers  and  toes  the  significance  of  the  terms  are 
different;  abduction  means  movement  of  the  fingers  away  from  the  middle  finger 
or  of  the  toe  away  from  the  second  toe;  adduction  means  movement  of  fingers 
toward  the  middle  finger  or  of  the  toes  toward  the  second  toe.  The  strictly  gingly- 
moid  or  hinge-joints  admit  of  flexion  and  extension  only.  Abduction  and  adduc- 
tion, combined  with  flexion  and  extension,  are  met  with  in  the  more  movable 
joints;  as  in  the  hip-,  shoulder-,  and  metacarpal-joint  of  the  thumb,  and  partially 
in  the  wrist.  When  two  anterior  surfaces  are  brought  nearer  together,  as  by 
bending  the  elbow  or  wris£,  we  speak  of  the  movement  as  ventral  or  anterior 
flexion.  Ventral  flexion  of  the  wrist  is  also  called  volar  or  palmar  flexion.  If 
two  posterior  surfaces  are  brought  nearer  together,  as  by  bending  the  knee  or 
extending  the  wrist,  we  speak  of  the  movement  as  posterior  or  dorsal  flexion. 


270  THE   ARTICULATIONS    OR    JOINTS 

At  the  wrist-joint  the  bending  of  the  ulnar  margin  of  the  hand  toward  the 
ulnar  side  of  the  forearm  is  ulnar  flexion;  the  bending  of  the  radial  margin  of 
the  hand  toward  the  radial  side  of  the  forearm  is  radial  flexion. 

Circumduction  is  that  limited  degree  of  motion  which  takes  place  between  the 
head  of  the  bone  and  its  articular  cavity,  whilst  the  extremity  and  sides  of  the  limb 
are  made  to  circumscribe  a  conical  space,  the  base  of  which  corresponds  with  the 
inferior  extremity  of  the  limb,  the  apex  with  the  articular  cavity;  this  kind  of 
motion  is  best  seen  in  the  shoulder-  and  hip-joints. 

Rotation  is  the  movement  of  a  bone  upon  an  axis,  which  is  the  axis  of  the  pivot 
on  which  the  bone  turns,  as  in  the  articulation  between  the  atlas  and  axis,  when 
the  odontoid  process  serves  as  a  pivot  around  which  the  atlas  turns;  or  else  is  the 
axis  of  a  pivot-like  process  which  turns  within  a  ring,  as  in  the  rotation  of  the 
radius  upon  the  humerus. 

Ligamentous  Action  of  Muscles. — The  movements  of  the  different  joints  of 
a  limb  are  combined  by  means  of  the  long  muscles  which  pass  over  more  than  one 
joint,  and  which,  when  relaxed  and  stretched  to,  their  greatest  extent,  act  as 
elastic  ligaments  in  restraining  certain  movements  of  one  joint,  except  when 
combined  with  corresponding  movements  of  the  other,  these  latter  movements 
being  usually  in  the  opposite  direction.  Thus  the  shortness  of  the  hamstring 
muscles  prevents  complete  flexion  of  the  hip,  unless  the  knee-joint  is  also  flexed, 
so  as  to  bring  their  attachments  nearer  together.  The  uses  of  this  arrangement 
are  threefold:  1.  It  co-ordinates  the  kinds  of  movement  which  are  the  most 
habitual  and  necessary,  and  enables  them  to  be  performed  with  the  least  expendi- 
ture of  power.  "Thus  in  the  usual  gesture  of  the  arms,  whether  in  grasping  or 
rejecting,  the  shoulder  and  the  elbow  are  flexed  simultaneously,  and  simultane- 
ously extended,"  in  consequence  of  the  passage  of  the  Biceps  and  Triceps  cubiti 
over  both  joints.  2.  It  enables  the  short  muscles  which  pass  over  only  one  joint 
to  act  upon  more  than  one.  "Thus,  if  the  Rectus  femoris  remain  tonically  of 
such  length  that,  when  stretched  over  the  extended  hip,  it  compels  extension  of 
the  knee,  then  the  Glutens  maximus  becomes  not  only  an  extensor  of  the  hip,  but 
an  extensor  of  the  knee  as  well."  3.  It  provides  the  joints  with  ligaments  which, 
while  they  are  of  very  great  power  in  resisting  movements  to  an  extent  incom- 
patible with  the  mechanism  of  the  joint,  at  the  same  time  spontaneously  yield 
when  necessary.  "Taxed  beyond  its  strength,  a  ligament  will  be  ruptured, 
whereas  a  contracted  muscle  is  easily  relaxed;  also,  if  neighboring  joints  be 
united  by  ligaments,  the  amount  of  flexion  or  extension  of  each  must  remain  in 
constant  proportion  to  that  of  the  other;  while,  if  the  union  be  by  muscles,  the 
separation  of  the  points  of  attachment  of  those  muscles  may  vary  considerably 
in  different  varieties  of  movement,  the  muscles  adapting  themselves  tonically 
to  the  length  required."  The  quotations  are  from  a  very  interesting  paper  by 
Dr.  Cleland  iij  the  Journal  of  Anatomy  and  Physiologij,  No.  1,  1866,  p.  85;  by 
whom  I  believe  this  important  fact  in  the  mechanism  of  joints  was  first  clearly 
pointed  out,  though  it  has  been  independently  observed  afterward  by  other 
anatomists.  Dr.  W.  W.  Keen  points  out  how  important  it  is  "that  the  surgeon 
should  remember  this  ligamentous  action  of  muscles  in  making  passive  motion— 
for  instance,  at  the  wrist  after  Colles's  fracture.  If  the  fingers  be  extended,  the 
wrist  can  be  flexed  to  a  right  angle.  If,  however,  they  be  first  flexed,  as  in 
'making  a  fist/  flexion  at  the  wrist  is  strictly  limited  to  from  40  to  50  degrees  in 
different  persons,  and  is  very  painful  beyond  that  point.  Hence  passive  motion 
here  should  be  made  with  the  fingers  extended.  In  the  leg,  when  flexing  the  hip, 
the  knee  should  be  flexed."  Dr.  Keen  further  points  out  that  "a  beautiful  illus- 
tration of  this  is  seen  in  the  perching  of  birds,  whose  toes  are  forced  to  clasp  the 
perch  by  just  such  a  passive  ligamentous  action  so  soon  as  they  stoop.  Hence 
they  can  go  to  sleep  and  not  fall  off  the  perch." 


ARTICULATIONS    OF   THE    VERTEBRAL    COLUMN  271 

The  articulations  may  be  arranged  into  those  of  the  trunk,  those  of  the  upper 
extremity,  and  those  of  the  lower  extremity. 

ARTICULATIONS  OF  THE  TRUNK. 

These  may  be  divided  into  the  following  groups,  viz. : 


I.  Of  the  vertebral  column. 
II.  Of  the  atlas  with  the  axis. 

III.  Of   the   atlas   with   the   occipital 

bone. 

IV.  Of  the  axis  with  the  occipital  bone. 
V.  Of  the  lower  jaw. 

VI.  Of  the  ribs  with  the  vertebrae. 


VII.  Of  the  cartilages  of  the  ribs  with 
the  sternum  and  with  each  other. 
VIII.  Of  the  sternum. 
IX.  Of  the  vertebral  column  with  the 

pelvis. 
X.  Of  the  pelvis. 


I.  Articulations  of  the  Vertebral  Column. 

The  different  segments  of  the  spine  are  connected  together  by  spinal  ligaments 
(ligamenta  columnar  vertebralis) ,  which  may  be  divided  into  five  sets:  1.  Those 
connecting  the  bodies  of  the  vertebrae.  2.  Those  connecting  the  laminae. 
3.  Those  connecting  the  articular  processes.  4.  Those  connecting  the  spinous 
processes.  5.  Those  of  the  transverse  processes. 

The  articulations  of  the  bodies  of  the  vertebrae  with  each  other  form  a  series  of 
amphiarthrodial  joints;  those  between  the  articular  processes  form  a  series  of 
arthrodial  joints. 

1.  THE  LIGAMENTS  OF  THE  VERTEBRAL  BODIES  OR  CENTRA  (!NTERCENTRAL 

LIGAMENTS). 

Anterior  Common  Ligament  (anterior  longitudinal  ligament). 
Posterior  Common  Ligament  (posterior  longitudinal  ligament). 
Intervertebral  Substance  (intervertebral  disk,  fibro-cartilage). 

The  Anterior  Common  or  Anterior  Longitudinal  Ligament  (ligamentum  longitu- 
dinale  anterius)  (Figs.  197,  199,  and  203)  is  a  broad  and  strong  band  of  longi- 
tudinal fibres  which  extends  along  the  anterior  (ventral)  surface  of  the  bodies  of 
the  vertebrae  from  the  axis  to  the  sacrum.  It  is  broader  below  than  above,  thicker 
in  the  thoracic  than  in  the  cervical  or  lumbar  regions,  and  somewhat  thicker 
opposite  the  front  of  the  body  of  each  vertebra  than  opposite  the  intervertebral 
substance.  It  is  attached,  above,  to  the  body  of  the  axis  by  a  pointed  process, 
where  it  is  continuous  with  the  anterior  atlanto-axial  ligament,  is  connected 
with  the  tendon  of  insertion  of  the  Longus  colli  muscle,  and  extends  down  as  far 
as  the  upper  bone  of  the  sacrum.  It  consists  of  dense  longitudinal  fibres,  which 
are  intimately  adherent  to  the  intervertebral  substance  and  the  prominent  margins 
of  the  vertebrae,  but  less  closely  to  the  middle  of  the  bodies.  In  the  latter 
situation  the  fibres  are  exceedingly  thick,  and  serve  to  fill  up  the  concavities 
on  their  front  surface  and  to  make  the  anterior  surface  of  the  spine  more  even. 
This  ligament  is  composed  of  several  layers  of  fibres,  which  vary  in  length,  but 
are  closely  interlaced  with  each  other.  The  most  superficial  or  longest  fibres 
extend  between  four  or  five  vertebrae.  A  second  subjacent  set  extends  between 
two  or  three  vertebrae,  whilst  a  third  set,  the  shortest  and  deepest,  extends  from 
one  vertebra  to  the  next.  At  the  side  of  the  bodies  the  ligament  consists  of  a 
few  short  fibres,  which  pass  from  one  vertebra  to  the  next,  separated  from  the 
median  portion  by  large  oval  apertures  for  the  passage  of  vessels. 


272 


THE  ARTICULATIONS    OR    JOINTS 


The  Posterior  Common  or  Posterior  Longitudinal  Ligament  (ligamentum  longi- 
tudinale  posterius)  (Figs.  195,  197,  202,  and  203)  is  situated  within  the  spinal 
canal,  and  extends  along  the  posterior  (dorsal)  surface  of  the  bodies  of  the  ver- 
tebrae from  the  body  of  the  axis  above,  where  it  is  continuous  with  the  posterior 


INTERVERTE- 
BRAL  FIBRO- 
CARTILAGE 


ROOT  OF 

VERTEBRAL 

ARCH 


POSTERIOR  COMMON 
LIGAMENT 

FIG.  195. — Vertebral    bodies   with   ligaments,    from 
behind.     (Spalteholz.) 


FIG.  196. — Interyertebral    disk,  with  the    adjacent 
vertebral  bodies,  from  in  front.     (Spalteholz.) 

occipito-axial  ligament,  to  the  sacrum 
below.  It  can  be  separated  from  the 
posterior  occipito-axial  ligament,  as  is 
shown  in  Fig.  203,  and  maybe  regarded 
as  really  arising  from  the  clivus.  It  is. 
broader  above  than  below,  and  thicker  in 
the  thoracic  than  in  the  cervical  or  lumbar 
regions.  In  the  situation  of  the  intervertebral  substance  and  contiguous  margins 
of  the  vertebrae,  where  the  ligament  is  more  intimately  adherent,  it  is  broad,  and 
presents  a  series  of  dentations  with  intervening  concave  margins;  but  it  is  narrow 
and  thick  over  the  centre  of  the  bodies,  from  which  it  is  separated  by  the  vena? 
basis  vertebra?.  This  ligament  is  composed  of  smooth,  shining,  longitudinal 
fibres,  denser  and  more  compact  than  those  of  the  anterior  ligament,  and  formed 
of  a  superficial  layer  occupying  the  interval  between  three  or  four  vertebrae,  and 
of  a  deeper  layer  which  extends  between  one  vertebra  and  the  next  adjacent 
to  it.  It  is  separated  from  the  dura  of  the  spinal  cord  by  some  loose  connective 
tissue,  which  is  very  liable  to  serous  infiltration. 

The  Intervertebral  Fibro-cartilages,  Disks,  or  Substances  (fibrocartilagines  inter- 
vertebrales)  (Figs.  196  and  197). — Each  fibro-cartilaginous  disk  is  of  lenticular 
form  and  of  composite  structure.  The  disks  are  interposed  between  the  adjacent 
surfaces  of  the  bodies  of  the  vertebras  from  the  axis  to  the  sacrum,  and  form 
the  chief  bonds  of  connection  between  those  bones.  In  young  children  inter- 
vertebral substance  exists  in  the  coccyx.  These  disks  vary  in  shape,  size,  and 
thickness  in  different  parts  of  the  spine.  In  shape  they  accurately  correspond 
with  the  surfaces  of  the  bodies  between  which  they  are  placed,  being  oval  in  the 
cervical  arid  lumbar  regions,  and  circular  in  the  thoracic.  Their  size  is  greatest 
in  the  lumbar  region.  In  thickness  they  vary  not  only  in  the  different  regions 
of  the  spine,'  but  in  different  parts  of  the  same  disk:  thus,  they  are  thicker  in 
front  than  behind  in  the  cervical  and  lumbar  regions,  while  they  are  uniformly 
thick  in  the  thoracic  region.  The  intervertebral  disks  form  about  one-fourth  of 
the  spinal  column,  exclusive  of  the  first  two  vertebrae;  they  are  not  equally  dis- 
tributed, however,  between  the  various  bones;  the  thoracic  portion  of  the  spine 


ARTICULATIONS    OF    THE    VERTEBRAL    COLUMN 


273 


having,  in  proportion  to  its  length,  a  much  smaller  quantity  than  in  the  cervical 
and  lumbar  regions,  which  necessarily  gives  to  the  latter  parts  greater  pliancy 
and  freedom  of  movement.  The  intervertebral  disks  are  adherent,  by  their  sur- 
faces, to  a  thin  layer  of  hyaline  cartilage  which  covers  the  upper  and  under  sur- 
faces of  the  bodies  of  the  vertebrae,  and  in  which,  in  early  life,  the  epiphysial 
plate  develops,  and  by  their  circumference  are  closely  connected  in  front  to  the 
anterior,  and  behind  to  the  posterior  common  ligament;  whilst  in  the  thoracic 
region  they  are  connected  laterally,  by  means  of  the  interarticular  ligament,  to 
the  heads  of  those  ribs  which  articulate  with  two  vertebrae;  they,  consequently, 
form  part  of  the  articular  cavities  in  which  the  heads  of  these  bones  are  received. 


POSTERIOR  COMMON 
LIGAMENT 


FIG.  197. — Median  section  of  a  piece  of  the  lumbar  spinal  column,  right  half  of  sections  viewed  from  the 

left.     (Spalteholz.) 

Structure  of  the  Intervertebral  Substance. — The  outer  portion  of  the  intervertebral 
substance  is  composed  of  many  layers  of  fibrous  connective  tissue.  This  envel- 
oping portion  is  called  the  annulus  fibrosus.  The  central  portion  of  the  disk  is 
composed  of  soft,  pulpy,  highly  elastic  fibre-cartilage,  containing  some  bands  of 
connective  tissue.  It  is  called  the  nucleus  pulposus,  is  of  a  yellowish  color,  and 
rises  up  considerably  above  the  surrounding  level  when  the  disk  is  divided  hori- 
zontally. This  pulpy  substance,  which  is  especially  well  developed  in  the  lumbar 
region,  is  the  remains  of  the  chorda  dorsalis,  and,  according  to  Luschka,  contains  a 
small  synovial  cavity  in  its  centre.  The  outer  layers  of  the  disk  are  arranged  con- 
centrically one  within  the  other,  the  outermost  consisting  of  ordinary  fibrous  tissue, 
but  the  others  and  more  numerous  consisting  of  white  fibre-cartilage.  These 
plates  are  not  quite  vertical  in  their  direction,  those  near  the  circumference  being 
curved  outward  and  closely  approximated;  whilst  those  nearest  the  centre  curve 
in  the  opposite  direction,  and  are  somewhat  more  widely  separated.  The  fibres  of 
which  each  plate  is  composed  are  directed,  for  the  most  part,  obliquely  from  above 
downward,  the  fibres  of  adjacent  plates  passing  in  opposite  directions  and  varying 
in  every  layer;  so  that  the  fibres  of  one  layer  are  directed  across  those  of  another, 
like  the  limbs  of  the  letter  X.  This  laminar  arrangement  belongs  to  about  the 
outer  half  of  each  disk.  The  pulpy  substance  presents  no  concentric  arrangement, 
and  consists  of  a  fine  fibrous  matrix,  containing  angular  cells,  united  to  form  a 

18 


274 


THE   ARTICULATIONS    OR    JOINTS 


reticular  structure.  J.  Bland  Sutton1  calls  attention  to  the  fact  that  in  the  human 
foetus  a  transverse  ligamentous  band  crosses  the  dorsal  aspect  of  the  intervertebral 
disk  and  is  continuous  with  the  interosseous  ligaments  of  the  heads  of  the  ribs; 
and  also  that  a  foetal  ligamentous  band  exists  in  the  ventral  surface  of  the  inter- 
vertebral  disk  which,  after  development,  becomes  the  middle  fasciculus  of  the 
stellate  ligament.  These  bands  are  named  by  Sutton  the  posterior  conjugal 
ligaments  and  the  anterior  conjugal  ligaments. 

Interneural  Articulations  include  the  ligaments  of  the  laminae;  articular 
processes,  spinous  processes,  and  transverse  processes. 

2.  LIGAMENTS  CONNECTING  THE  LAMINAE. 
Ligamenta  Subflava. 

The  Ligamenta  Subflava  (ligamenta  flava,  ligamenta  intercruralia)  (Figs.  197 
and  198)  are  interposed  between  the  laminae  of  the  vertebra,  from  the  axis  to 
the  sacrum.  They  are  most  distinct  when  seen  from  the  interior  of  the  spinal 
canal;  when  viewed  from  the  outer  surface  they  appear  short,  being  over- 
lapped by  the  laminae.  Each  ligamentum  subflavum  consists  of  two  lateral 
portions,  which  commence  on  each  side  at  the  root  of  either  articular  process, 
and  pass  backward  to  the  point  where  the  laminae  converge  to  form  the  spi- 
nous process,  where  their  margins  are  in  contact  and  to  a  certain  extent  united; 
slight  intervals  being  left  for  the  passage  of  small  vessels.  These  ligaments 

consist  of  yellow  elastic  tissue,  the 
fibres  of  which,  almost  perpendic- 
ular in  direction,  are  attached  to 
the  anterior  surface  of  the  laminae 
above,  some  distance  from  its  in- 
ferior margin,  and  to  the  posterior 
surface,  as  well  as  to  the  margin 
of  the  lamina  below.  In  the  cer- 
vical region  they  are  thin  in  tex- 
ture, but  very  broad  and  long; 
they  become  thicker  in  the  thoracic 
region,  and  in  the  lumbar  acquire 
very  considerable  thickness.  Their 
highly  elastic  property  serves  to 
preserve  the  upright  posture  and 
to  assist  in  resuming  it  after  the 
spine  has  been  flexed.  These  liga- 
ments do  not  exist  between  the 
occiput  and  atlas  or  between  the 
atlas  and  axis. 

3.  LIGAMENTS  CONNECTING   THE 
ARTICULAR  PROCESSES. 

Capsular  Ligaments. 
The  Capsular  Ligaments  (capsulae 

FIG.  198.— Vertebral  arches  with  ligamenta  flava.  artlCulares]  (FifiT.  199)  are  thin  and 

(Spalteholz.)  IT  u    J 

loose   ligamentous  sacs,  attached 

to  the  contiguous  margins  of  the  articulating  processes  of  each  vertebra  through 
the  greater  part  of  their  circumference,  and  completed  internally  by  the  ligamenta 


1  J.  Bland  Sutton.     Ligaments:  Their  Nature  and  Morphology. 


ARTICULATIONS  Of   THE   VERTEBRAL  COLUMN  275 

subflava.  They  are  longer  and  looser  in  the  cervical  than  in  the  thoracic  or  lumbar 
regions.  The  capsular  ligaments  are  lined  on  their  inner  surface  by  synovial 
membrane. 

4.  LIGAMENTS    CONNECTING    THE    SPINOUS    PROCESSES. 
Supraspinous  Ligament     Interspinous  Ligaments. 

The  Supraspinous  Ligament  (ligamentum  supraspinale)  (Fig.  197)  is  a  strong 
fibrous  cord,  which  connects  together  the  apices  of  the  spinous  processes  from  the 
seventh  cervical  to  the  spinous  processes  of  the  sacrum.  It  is  thicker  and  broader 
in  the  lumbar  than  in  the  thoracic  region,  and  intimately  blended,  in  both  situa- 
tions, with  the  neighboring  aponeurosis.  The  most  superficial  fibres  of  this 
ligament  connects  three  or  four  vertebrae;  those  deeper-seated  pass  between  two 
or  three  vertebrae;  whilst  the  deepest  connect  the  contiguous  extremities  of 
neighboring  vertebras.  It  is  continued  upward  to  the  external  occipital  protu- 
berance as  the  ligamentum  nuchae,  which,  in  the  human  subject,  is  thin  and  forms 
merely  an  intermuscular  septum. 

The  Interspinous  Ligaments  (ligamenta  interspinalia)  (Fig.  197),  thin  and 
membranous,  are  interposed  between  the  spinous  processes.  Each  ligament 
extends  from  the  root  to  the  summit  of  each  spinous  process  and  connects  together 
their  adjacent  margins.  They  meet  the  ligamenta  subflava  in  front  and  the 
Supraspinous  ligament  behind.  They  are  narrow  and  elongated  in  the  thoracic 
region;  broader,  quadrilateral  in  form,  and  thicker  in  the  lumbar  region;  and 
only  slightly  developed  in  the  neck. 

5.  LIGAMENTS  CONNECTING  THE  TRANSVERSE  PROCESSES. 

In tertrans verse  Ligaments. 

The  Intertxansverse  Ligaments  (Ligamenta  intertransversaria)  (Fig.  210)  consist 
of  bundles  of  fibres  interposed  between  the  transverse  processes.  In  the  cervical 
region  they  consist  of  a  few  irregular,  scattered  fibres;  in  the  thoracic,  they  are 
rounded  cords  intimately  connected  with  the  deep  muscles  of  the  back;  in  the 
lumbar  region  they  are  thin  and  membranous. 

Actions. — The  movements  permitted  in  the  spinal  column  are,  flexion,  exten- 
sion, lateral  movement,  circumduction,  and  rotation. 

In  flexion  (forward  flexion),  or  movement  of  the  spine  forward,  the  anterior 
common  ligament  is  relaxed,  and  the  intervertebral  substances  are  compressed 
in  front,  while  the  posterior  common  ligament,  the  ligamenta  subflava,  and  the 
inter-  and  supra-spinous  ligaments  are  stretched,  as  well  as  the  posterior  fibres 
of  the  intervertebral  disks.  The  interspaces  between  the  laminae  are  widened, 
and  the  inferior  articular  processes  of  the  vertebrae  above  glide  upward  upon 
the  articular  processes  of  the  vertebrae  below.  Flexion  is  the  most  extensive  of 
all  the  movements  of  the  spine. 

In  extension  (backward  flexion),  or  movement  of  the  spine  backward,  an  exactly 
opposite  disposition  of  the  parts  takes  place.  This  movement  is  not  extensive, 
being  limited  by  the  anterior  common  ligament  and  by  the  approximation  of  the 
spinous  processes. 

Flexion  and  extension  are  free  in  the  lower  part  of  the  lumbar  region  between 
the  third  and  fourth  and  fourth  and  fifth  lumbar  vertebras;  above  the  third 
they  are  much  diminished,  and  reach  their  minimum  in  the  middle  and  upper 
part  of  the  back.  They  increase  again  in  the  neck,  the  capability  of  motion 
backward  from  the  upright  position  being  in  this  region  greater  than  that  of  the 
motion  forward,  whereas  in  the  lumbar  region  the  reverse  is  the  case. 

In  lateral  flexion,  the  sides  of  the  intervertebral  disks  are  compressed,  the 
extent  of  motion  being  limited  by  the  resistance  offered  by  the  surrounding  liga- 


276  THE   ARTICULATIONS    OR   JOINTS 

ments  and  by  the  approximati6n  of  the  transverse  processes.  This  movement 
may  take  place  in  any  part  of  the  spine,  but  is  most  free  in  the  neck  and  loins. 

Circumduction  is  very  limited,  and  is  produced  merely  by  a  succession  of  the 
preceding  movements. 

Rotation  is  produced  by  the  twisting  of  the  intervertebral  substances;  this, 
although  only  slight  between  any  two  vertebne,  produces  a  considerable  extent  of 
movement  when  it  takes  place  in  the  whole  length  of  the  spine,  the  front  of  the 
upper  part  of  the  column  being  turned  to  one  or  the  other  side.  This  movement 
takes  place  only  to  a  slight  extent  in  the  neck,  but  is  freer  in  the  upper  part  of 
the  thoracic  region,  and  is  altogether  absent  in  the  lumbar  region. 

It  is  thus  seen  that  the  cervical  region  enjoys  the  greatest  extent  of  each  variety 
of  movement,  flexion  and  extension,  especially  being  very  free.  In  the  thoracic 
region  the  three  movements  of  flexion,  extension,  and  circumduction  are  per- 
mitted only  to  a  slight  extent,  while  rotation  is  very  free  in  the  upper  part  and 
ceases  below.  In  the  lumbar  region  there  is  free  flexion,  extension,  and  lateral 
movement,  but  no  rotation. 

As  Sir  George  Humphry  has  pointed  out,  the  movements  permitted  are  mainly 
due  to  the  shape  and  position  of  the  articulating  processes.  In  the  loins  the  infe- 
rior articulating  processes  are  turned  outward  and  are  embraced  by  the  superior; 
this  renders  rotation  in  this  region  of  the  spine  impossible,  while  there  is  nothing- 
to  prevent  a  sliding  upward  and  downward  of  the  surfaces  on  each  other,  so  as  to 
allow  of  flexion  and  extension.  In  the  thoracic  region,  on  the  other  hand,  the 
articulating  processes,  by  their  direction  and  mutual  adaptation,  especially  at  the 
upper  part  of  the  series,  permit  of  rotation,  but  prevent  extension  and  flexion, 
while  in  the  cervical  region  the  greater  obliquity  and  lateral  slant  of  the  articular 
processes  allow  not  only  flexion  and  extension,  but  also  rotation. 

The  principal  muscles  which  produce  flexion  are  the  Sterno-mastoid,  Rectus 
capitis  anticus  major,  and  Longus  colli;  the  Scaleni;  the  abdominal  muscles  and 
the  Psoas  magnus.  Extension  is  produced  by  the  fourth  layer  of  the  muscles 
of  the  back,  assisted  in  the  neck  by  the  Splenius,  Semispinalis  dorsi  et  colli,  and 
the  Multifidus  spinae.  Lateral  motion  is  produced  by  the  fourth  layer  of  the 
muscles  of  the  back,  by  the  Splenius  and  the  Scaleni,  the  muscles  of  one  side  only 
acting;  and  rotation  by  the  action  of  the  following  muscles  of  one  side  only — viz. 
the  Sterno-mastoid,  the  Rectus  capitis  anticus  major,  the  Scaleni,  the  Multifidus 
spinse,  the  Complexus,  and  the  abdominal  muscles. 

II.  Articulation  of  the  Atlas  with  the  Axis  (Articulatio  Atlantoepistrophica). 

The  articulation  of  the  atlas  with  the  axis  is  of  a  complicated  nature,  compris- 
ing no  fewer  than  four  distinct  joints.  There  is  a  pivot  articulation  between  the 
odontoid  process  of  the  axis  and  the  ring  formed  between  the  anterior  arch  of  the 
atlas  and  the  transverse  ligament  (see  Fig.  201).  Here  there  are  two  joints:  one  in 
front  between  the  posterior  surface  of  the  anterior  arch  of  the  atlas  and  the  front 
of  the  odontoid  process,  the  atlanto-odontoid  joint  of  Cruveilhier ;  the  other  between 
the  anterior  surface  of  the  transverse  ligament  and  the  back  of  the  process,  the 
syndesmo-odontoid  joint.  Between  the  articular  processes  of  the  two  bones  there 
is  a  double  arthrodia  or  gliding  joint.  The  ligaments  which  connect  these  bones 
are  the 

Anterior  Atlanto-axial.  Transverse. 

Posterior  Atlanto-axial.  Two  Capsular. 

The  Anterior  Atlanto-axial  or  the  Anterior  Atlo-axoid  Ligament  (Figs.  199  and  203) 
is  a  strong,  membranous  layer,  attached,  above,  to  the  lower  border  of  the  anterior 
arch  of  the  atlas;  below,  to  the  base  of  the  odontoid  process  and  to  the  front  of 


ARTICULATION   OF    THE  ATLAS    WITH    THE  AXIS 


277 


the  body  of  the  axis.  It  is  strengthened  in  the  middle  line  by  a  rounded  cord,  which 
is  attached,  above,  to  the  tubercle  on  the  anterior  arch  of  the  atlas,  and  below  to 
the  body  of  the  axis,  being  a  continuation  upward  of  the  anterior  common  liga- 
ment of  the  spine.  Some  anatomists  regard  this  ligament  as  being  a  part  of  the 
anterior  common  ligament.  The  ligament  is  in  relation,  in  front,  with  the  Recti 
antici  majores. 

The  Posterior  Atlanto-axial  or  the  Posterior  Atlo-axoid  Ligament  (Figs.  200  and 
203)  is  a  broad  and  thin  membranous  layer,  attached,  above,  to  the  lower  border 
of  the  posterior  arch  of  the  atlas;  below,  to  the  upper  edge  of  the  laminse  of 
the  axis.  This  ligament  supplies  the  place  of  the  ligamenta  subflava,  and  is 
in  relation,  behind,  with  the  Inferior  oblique  muscles. 

The  Transverse  Ligament  of  the  Atlas1  (ligamentum  transversum  atlantis]  (Figs. 
201,  202,  and  203)  is  a  thick,  strong  band,  which  arches  across  the  ring  of  the 
atlas,  and  serves  to  retain  the  odontoid  process  in  firm  connection  with  its  anterior 
arch.  This  ligament  is  flattened  from  before  backward,  broader  and  thicker  in 
the  middle  than  at  either  extremity,  and  firmly  attached  on  each  side  to  a  small 
tubercle  on  the  inner  surface  of  the  lateral  mass  of  the  atlas.  As  it  crosses  the 
odontoid  process,  a  small  fasciculus  is  derived  from  its  upper,  and  another  from 
its  lower,  border;  the  former  passing  upward,  to  be  inserted  into  the  anterior  sur- 


PHARYNGEAL 

TUBERCLE  BASILAR  PORTION  Or 

OCCIPITAL  BONE 


ANTERIOR  OCCIPITO- 
ATLANTAL  LIGAMENT 


JOINT  BETWEEN 

BODY  OF  VERTEBRA 

AND   INTERVER-. 

TCBRAL  FIBRO- 

CARTILAGE 


ANTERIOR    CONDYLOID 
FORAMEN 


OCCIPITO-ATLANTAL 
ARTICULATION 


TRANSVERSE 
PROCESS  OF 
ATLAS 

ANTERIOR    ATLANTO- 
AXIAL  LIGAMENT 


TRANSVERSE 
PROCESS  OF 
AXIS 


TRANSVERSE  PROCESS 
OF  THIRD  CERVICAL 
VERTEBRA 


INTCRVERTEBRAL 

FIBROCARTI  LAGE 


ANTERIOR  COMMON 
LIGAMENT 


FIG.  199. — Occipital  bone  and  first  three  cervical  vertebrae  with  ligaments,  from  in  front.     (Spalteholz.) 

face  of  the  foramen  magnum  of  the  occipital  bone;  the  latter,  downward,  to  be 
attached  to  the  posterior  surface  of  the  body  of  the  axis;  hence,  the  whole  ligament 
has  received  the  name  of  cruciform  ligament  (ligamentum  cruciatum  atlantis). 
A  synovial  surface  is  interposed  between  the  odontoid  process  and  the  trans- 
verse ligament,  and  one  is  placed  between  the  anterior  surface  of  the  odontoid 
process  and  the  anterior  arch  of  the  atlas.  The  transverse  ligament  divides  the 


1  It  has  been  found  necessary  to  describe  the  transverse  ligament  with  those  of  the  atlas  and  axis;  but  the 
student  must  remember  that  it  is  really  a  portion  of  the  mechanism  by  which  the  movements  of  the  head  on 
the  spine  are  regulated;  so  that  the  connections  between  the  atlas  and  axis  ought  always  to  be  studied 
together  with  those  between  the  latter  bones  and  the  skull. — ED.  of  15th  English  Edition. 


278  THE  ARTICULATIONS  OR  JOINTS 

ring  of  the  atlas  into  two  unequal  parts :  of  these,  the  posterior  and  larger  serves 
for  the  transmission  of  the  cord  and  its  membranes  and  the  accessory  nerves ;  the 
anterior  and  smaller  contains  the  odontoid  process.  Since  the  space  between 
the  anterior  arch  of  the  atlas  and  the  transverse  ligament  is  smaller  at  the  lower 
part  than  the  upper  (because  the  transverse  ligament  embraces  tightly  the  narrow 
neck  of  the  odontoid  process),  this  process  is  retained  in  firm  connection  with  the 
atlas  after  all  the  other  ligaments  have  been  divided. 

The  Capsular  Ligaments  (capsidae  articulares)  (Figs.  199,  200,  and  202)  are  two- 
thin  an.d  loose  capsules,  connecting  the  lateral  masses  of  the  atlas  with  the  superior 
articular  surfaces  of  the  axis,  the  fibres  being  strengthened  at  the  posterior  and 
inner  part  of  each  articulation  by  an  accessory  ligament,  which  is  attached  below 
to  the  body  of  the  axis  near  the  base  of  the  odontoid  process. 

Synovial  Membranes  (Fig.  201). — There  are  four  synovial  membranes  in  this 
articulation:  one  lining  the  inner  surface  of  each  of  the  capsular  ligaments;  one 
between  the  anterior  surface  of  the  odontoid  process  and  the  anterior  arch  of 
the  atlas,  the  atlanto-odontoid  joint;  and  one  between  the  posterior  surface  of 
the  odontoid  process  and  the  transverse  ligament,  the  syndesmo-odontoid  joint. 
The  latter  often  communicates  with  those  between  the  condyles  of  the  occipital 
bone  and  the  articular  surfaces  of  the  atlas. 

Actions. — This  joint  allows  the  rotation  of  the  atlas  (and,  with  it,  of  the  cra- 
nium) upon  the  axis,  the  extent  of  rotation  being  limited  by  the  odontoid  ligaments. 

The  principal  muscles  by  which  this  action  is  produced  are  the  Sterno-mastoid 
and  Complexus  of  one  side,  acting  with  the  Rectus  capitis  anticus  major,  Sple- 
nius,  Trachelo-mastoid,  Rectus  capitis  posticus  major,  and  Inferior  oblique  of  the 
other  side. 


ARTICULATIONS  OF  THE  SPINE  WITH  THE  CRANIUM. 

The  ligaments  connecting  the  spine  with  the  cranium  may  be  divided  into  two 
sets — those  connecting  the  occipital  bone  with  the  atlas,  and  those  connecting  the 
occipital  bone  with  the  axis. 

III.  Articulation  of  the  Atlas  with  the  Occipital  Bone  (Articulatio 

Atlantooccipitalis) . 

This  articulation  is  a  double  condyloid  joint.    Its  ligaments  are  the 

Anterior  Occipito-atlantal.  Posterior  Occipito-atlantal. 

Two  Capsular. 

The  Anterior  Occipito-atlantal  Ligament  or  Membrane  (membrana  atlantooccipitalis 
anterior,  anterior  occipito-atloid  ligament)  (Figs.  199  and  203)  is  a  broad  membra- 
nous layer,  composed  of  densely  woven  fibres,  which  passes  between  the  anterior 
margin  of  the  foramen  magnum  above,  and  the  whole  length  of  the  upper  border 
of  the  anterior  arch  of  the  atlas  below.  Laterally,  it  is  continuous  with  the  cap- 
sular ligaments.  In  the  middle  line  in  front  it  is  strengthened  by  a  strong,  narrow, 
rounded  cord,  which  is  attached,  above,  to  the  basilar  process  of  the  occiput,  and, 
below,  to  the  tubercle  on  the  anterior  arch  of  the  atlas,  and  which  is  a  continua- 
tion of  the  anterior  common  ligament.  This  ligament  is  in  relation,  in  front, 
with  the  Recti  antici  minores ;  behind,  with  the  odontoid  ligaments. 

The  Posterior  Occipito-atlantal  Ligament  or  Membrane  (membrana  atlantooccipitalis 
posterior,  posterior  occipito-atloid  ligament)  (Figs.  200  and  203)  is  a  very  broad  but 
thin  membranous  lamina  intimately  blended  with  the  dura.  It  is  connected, 
above,  to  the  posterior  margin  of  the  foramen  magnum;  below,  to  the  upper  border 


ARTICULATION  OF  THE  ATLAS  WITH  THE  OCCIPITAL  BONE    279 


of  the  posterior  arch  of  the  atlas.  This  ligament  is  incomplete  at  each  side,  and 
forms,  with  the  superior  intervertebral  notch,  an  opening  for  the  passage  of  the 
vertebral  artery  and  suboccipital  nerve.  The  fibrous  band  which  arches  over  the 
artery  and  nerve  sometimes  becomes  ossified.  The  ligaments  are  in  relation, 
behind,  with  the  Recti  postici  minores  and  Obliqui  superiores;  in  front,  with  the 
dura  of  the  spinal  canal,  to  which  they  are  intimately  adherent. 


POSTERIOR  OC- 

CIPITO-ATLAIMTAL 

LIGAMENT 


POSTERIOR  OC- 

CIPITO-ATLANTAL 

LIGAMENT 


POSTERIOR 

ATLANTO-AXIAL' 

LIGAMENT 


TRANSVERSE 
PROCESS  OF 
ATLAS 


TRANSVERSE 
PROCESS  OF 
AXIS 


FIG.  200. — Occipital  bone,  first  and  second  cervical  vertebrae  with  ligaments  from  behind.     (Spalteholz.) 


The  Capsular  Ligaments  (capsules  articulares)  (Fig.  202)  surround  the  condyles 
of  the  occipital  bone,  and  connect  them  with  the  articular  processes  of  the  atlas; 
they  consist  of  thin  and  loose  capsules,  which  enclose  the  synovial  membranes 
of  the  articulations. 

Synovial  Membranes. — There  are  two  synovial  membranes  in  this  articulation, 
one  lining  the  inner  surface  of  each  of  the  capsular  ligaments.  These  occasionally 
communicate  with  that  between  the  posterior  surface  of  the  odontoid  process  and 
the  transverse  ligament. 


FIG.  201. — Articulation  between  odontoid  process  and  atlas. 

Actions. — The  movements  permitted  in  this  joint  are  flexion  and  extension, 
which  give  rise  to  the  ordinary  forward  and  backward  nodding  of  the  head.  Slight 
lateral  motion  to  one  or  the  other  side  may  also  take  place.  When  either  of  these 
actions  is  carried  beyond  a  slight  extent,  the  whole  of  the  cervical  portion  of  the  spine 
assists  in  its  production.  Flexion  is  mainly  produced  by  the  action  of  the  Rectus 
capitis  anticus  major  et  minor  and  the  Sterno-mastoid  muscles;  extension  by  the 


280 


THE  ARTICULATIONS    OR    JOINTS 


Rectus  capitis  posticus  major  et  minor,  the  Superior  oblique,  the  Complexus,  Sple- 
nius,  and  upper  fibres  of  the  Trapezius.  The  Recti  laterales  are  concerned  in  the 
lateral  movement,  assisted  by  the  Trapezius,  Splenius,  Complexus,  and  the  Sterno- 
mastoid  of  the  same  side,  all  acting  together.  According  to  Cruveilhier,  there  is 
a  slight  motion  of  rotation  in  this  joint. 

IV.  Articulation  of  the  Axis  with  the  Occipital  Bone. 

The  ligaments  of  this  articulation  are  the 

Occipito-axial.         Three  Odontoid. 

To  expose  these  ligaments  the  spinal  canal  should  be  laid  open  by  removing 
the  posterior  arch  of  the  atlas,  the  laminae  and  spinal  process  of  the  axis,  and  the 
portion  of  the  occipital  bone  behind  the  foramen  magnum,  as  seen  in  Fig.  193. 

The  Posterior  Occipito-axial  Ligament  (posterior  occipito-axoid  ligament,  membrana 
tectoria,  apparatus  ligamentosus  colli)  (Figs.  202  and  203)  is  situated  within  the  spinal 
canal.  It  is  a  broad,  strong  band,  which  covers  the  odontoid  process  and  its  liga- 
ments, and  appears  to  be  a  prolongation  upward  of  or  a  membrane  due  to  fusion 
with  the  posterior  common  ligament  of  the  spine.  It  is  attached,  below,  to  the 
posterior  surface  of  the  body  of  the  axis,  and,  becoming  expanded  as  it  ascends, 
is  inserted  into  the  basilar  groove  of  the  occipital  bone,  in  front  of  the  foramen 
magnum,  where  it  becomes  blended  with  the  dura  of  the  skull. 


The  vertical  portion  of 

ODONTOID    LIGAMENTS. 


(CAPSULAR     LIGAMENT 

1  <       and  synovial 
(_        membrane. 


fCAPSULAH     LIGAMENT 

<       and  synovial 
(_        membrane. 


FIG.  202. — Occipito-axial  and  atlanto-axial  ligaments.     Posterior  view,  obtained  by  removing  the  arches  of 
the  vertebrae  and  the  posterior  part  of  the  skull. 

t 

Relations. — By  its  anterior  surface  with  the  transverse  ligament;  by  its  posterior 
surface  with  the  posterior  common  ligament. 

The  Lateral  Odontoid  or  Check  Ligaments  (ligamenta  alaria]  (Figs.  202  and  203) 
are  strong,  rounded,  fibrous  cords,  which  arise  one  on  either  side  of  the  upper 
part  of  the  odontoid  process,  and,  passing  obliquely  upward  and  outward,  are 
inserted  into  the  rough  depressions  on  the  inner  side  of  the  condyles  of  the 


ARTICULATION  OF  THE  AXIS   WITH  THE  OCCIPITAL   BONE    281 

occipital  bone.  In  the  triangular  interval  left  between  these  ligaments  another 
strong  fibrous  cord,  ligamentum  suspensorium,  or  middle  odontoid  ligament  (liga- 
mentum  apicis  dentis),  may  be  seen,  which  passes  almost  perpendicularly  from 
the  apex  of  the  odontoid  process  to  the  anterior  margin  of  the  foramen  mag- 
num, being  intimately  blended  with  the  deep  portion  of  the  anterior  occipito- 
atlantal  ligament  and  upper  fasciculus  of  the  transverse  ligament  of  the  atlas. 

Actions. — The  odontoid  ligaments  serve  to  limit  the  extent  to  which  rotation 
of  the  cranium  may  be  carried;  hence,  they  have  received  the  name  of  check 
ligaments. 

In  addition  to  these  ligaments,  which  connect  the  atlas  and  axis  to  the  skull, 
the  ligamentum  nuchae  must  be  regarded  as  one  of  the  ligaments  by  which  the 
spine  is  connected  with  the  cranium.  It  is  described  on  page  275. 

Surgical  Anatomy. — The  ligaments  which  unite  the  component  parts  of  the  vertebrae 
together  are  so  strong,  and  these  bones  are  so  interlocked  by  the  arrangement  of  their  articu- 
lating processes,  that  dislocation  is  very  uncommon,  and,  indeed,  unless  accompanied  by  fracture, 
seldom  occurs,  except  in  the  upper  part  of  the  neck.  Dislocation  of  the  occiput  from  the  atlas 


THIN   LAYER  OF  POSTERIOR  COMMON 
LIGAMENT  SEPARATED    FROM  THE 
POSTERIOR  OCCIPITO-AXIAL  LIGAMENT 


HYPOGLOSSAL 
NERVE 


ANTERIOR  OCCIPITO--1 

ATLOID  LIGAMENT 

POSTERIOR   OCCIPITO- 
AXIAL  LIGAMENT 
CRUCIFORM 
LIGAMENT 
MIDDLE  ODONTOID 
LIGAMENT 

ANTERIOR  ARCH 
OF  ATLAS 
ODONTOID  PROC- 
ESS OF  AXIS 
ARTICULAR 
CAVITY 

TRANSVERSE   LIGA- 
MENT OF  ATLAS 
ANTERIOR  ATLO- 
AXOID    LIGAMENT 


POSTERIOR    OCCIP- 
ITO- ATLANTAL 
LIGAMENT 


•POSTERIOR 
ARCH  OF 
ATLAS 

SUBOCCI  PITAL 
NERVE 

JNTERVERTE- 
BRAL  FORAMEN 


1NTERVERTEBRAL 
FIBRO-CARTILAGE 


ANTERIOR  COMMON 
LIGAMENT 


POSTERIOR    COMMON 
LIGAMENT 

FIG.  203. — Median  section  through  the  occipital  bone  and  first  three  cervical  vertebrae  with  ligaments. 

(Spalteholz.) 

has  only  been  recorded  in  one  or  two  .cases;  but  dislocation  of  the  atlas  from  the  axis,  with  rup- 
ture of  the  transverse  ligament,  is  much  more  common :  it  is  the  mode  in  which  death  is  produced 
in  many  cases  of  execution  by  hanging.  Occipito-atloid  dislocation  is  certainly  fatal.  Recoveries 
are  on  record  after  atlo-axoid  dislocation.  Immediate  death  occurs  if  the  transverse  ligament 
is  torn  or  the  odontoid  process  is  broken.  In  the  lower  part  of  the  neck — that  is,  below  the 
third  cervical  vertebra — dislocation  unattended  by  fracture  occasionally  takes  place. 


282 


THE    ARTICULATIONS    OR    JOINTS 


V.  Articulation  of  the  Lower  Jaw,  or  the  Temporo-mandibular  Articulation 

(Articulatio  Mandibularis). 

This  is  a  ginglymo-arthrodial  joint:  the  parts  entering  into  its  formation  on 
each  side  are,  above,  the  anterior  part  of  the  glenoid  cavity  of  the  temporal  bone 
and  the  eminentia  articularis;  and,  below,  the  condyle  of  the  lower  jaw.  The 
ligaments  are  the  following: 

External  Lateral.  Stylo-mandibular. 

Internal  Lateral.  Capsular. 

Interarticular  Fibro-cartilage. 

The  External  Lateral  Ligament  (ligamentum  temporomandibulare}  (Fig.  204)  is  a, 
short,  thin,  and  narrow  fasciculus,  attached,  above,  to  the  outer  surface  of  the  zygoma 
and  to  the  tubercle  on  its  lower  border;  below,  to  the  outer  surface  and  posterior 
border  of  the  neck  of  the  lower  jaw.  It  is  broader  above  than  below;  its  fibres  are 


FIG.  204. — Temporo-mandibular  articulation. 


placed  parallel  with  one  another,  and  directed  obliquely  downward  and  backward. 
Externally,  it  is  covered  by  the  parotid  gland  and  by  the  integument.  Internally 
it  is  in  relation  with  the  capsular  ligament,  of  which  it  is  an  accessory  band,  and 
from  which  it  is  not  separable. 

The  Internal  Lateral  Ligament  (ligamentum  sphenomandibulare]  (Fig.  205)  is  a 
flat,  thin  band  which  is  attached  above  to  the  spinous  process  of  the  sphenoid 
bone,  and,  becoming  broader  as  it  descends,  is  inserted  into  the  margin  of  the 
mandibular  or  dental  foramen  and  the  portion  of  bone,  the  lingula,  which  over- 
hangs the  foramen  in  front.  Its  outer  surface  is  in  relation,  above,  with  the 
External  pterygoid  muscle;  lower  down  it  is  separated  from  the  neck  of  the 
condyle  by  the  internal  maxillary  artery;  and  still  more  inferiorly,  the  inferior 
dental  vessels  and  nerve  separate  it  from  the  ramus  of  the  jaw.  The  inner  surface 
is  in  relation  with  the  Internal  pterygoid.  It  is  really  the  fibrous  covering  of  a 
part  of  Meckel's  cartilage. 


ARTICULATION   OF   THE   LOWER   JAW 


283 


-•^•^^'••gyte  f  •  •?'•".•>-••.--•'•-*•'*>•'-•*••  ~-v& 


FIG.  205. — Temporo-mandibular  articulation.     Internal  view 


The  Stylo-mandibular  or  Stylo  -maxillary  Ligament  (ligamentum  stylomandibulare) 

(Fig.  205)  is  a  specialized  band  of  the  cervical  fascia,  which  extends  from  near  the 

apex  of  the  styloid  process  of  the  temporal  bone  to  the  angle  and  posterior  border 

of  the  ramus  of  the  lower  jaw,  between  the  Masseter  and  Internal  pterygoid  mus- 

cles.    This  ligament  separates  the  parotid  from  the  submaxillary  gland,  and  has 

attached  to  its  inner  side  part  of 

the  fibres  of  origin  of  the  Stylo- 

glossus  muscle.    Although  usually 

classed  among  the  ligaments  of  the 

jaw,  it  can  be  considered  only  as 

an  accessory  to  the  articulation. 
The  Capsular  Ligament  (capsula 

articular  is)    (Figs.  204    and    205) 

forms  a  thin  and   loose  capsule, 

passing  from  the  circumference  of 

the  glenoid  cavity  and  the  articular 

surface  immediately  in  front  to  the 

upper  margin  of  the  articular  disk, 

and  from  the  lower  margin  of  the 

articular  disk  to  the  neck  of  the 

coridyle  of  the  lower  jaw.     It  con- 

sists of  very  thin  fibres,  and  is  com- 

plete.   It  forms  two  joint  cavities, 

distinct  from  each  other,  and  sepa- 

rated  by  the  articular  disk.     So 

thin  is  it  that  it  is  hardly  to  be 

considered  as  a  distinct  ligament;  it  is  thickest  at  the  back  part,  and  thinnest 

on  the  inner  side  of  the  articulation.1 

The  Interarticular  Fibro-cartilage  or  Meniscus  (discus  articularis)  (Fig.  206)  is  a 

thin  plate  of  an  oval  form,  placed  horizontally  between  the  condyle  of  the  jaw  and 

the  glenoid  cavity.  Its  upper  surface 
is  concavo-convex  from  before  back- 
ward, and  a  little  convex  transversely, 
to  accommodate  itself  to  the  form  of 
the  glenoid  cavity.  Its  under  surface, 
where  it  is  in  contact  with  the  con- 
dyle, is  concave.  Its  circumference  is 
connected  to  the  capsular  ligament, 
and  in  front  to  the  tendon  of  the  Ex- 
ternal pterygoid  muscle.  It  is  thicker 
at  its  circumference,  especially  be- 
hind, than  at  its  centre.  The  fibres 
of  which  it  is  composed  have  a  con- 
centric  arrangement,  more  apparent 
at  the  circumference  than  at  the 

centre.     Its  surfaces  are  smooth.     It  divides  the  joint  into  two  cavities,  each 

of  which  is  furnished  with  a  separate   synovial   membrane  from  the  capsular 

ligament. 

Synovial  Membranes  (Fig.  206).  —  The  synovial  membranes,  two  in  number,  are 

placed,  one  above,  and  the  other  below,  the  fibro-cartilage.    The  upper  one,  the 

larger  and  looser  of  the  two,  is  continued  from  the  margin  of  the  cartilage  covering 


FIG.  206.—  Vertical  section  of  temporo-mandibuiar 


i  Sir  G.  Humphry  describes  the  internal  portion  of  the  capsular  ligament  separately  as  the  short  internal 
lateral  ligament:  and  it  certainly  seems  as  deserving  of  a  separate  description  as  is  the  external  lateral  liga- 
ment.— ED.  of  15th  English  Edition. 


284  THE  ARTICULATIONS    OR   JOINTS 

the  glenoid  cavity  and  eminentia  articularis  on  to  the  upper  surface  of  the  fibro- 
cartilage.  The  lower  one  passes  from  the  under  surface  of  the  fibre-cartilage  to 
the  neck  of  the  condyle  of  the  jaw,  being  prolonged  downward  a  little  farther 
behind  than  in  front.  The  interarticular  cartilage  is  sometimes  perforated  in  its 
centre;  the  two  sy  no  vial  sacs  then  communicate  with  each  other. 

The  nerves  of  this  joint  are  derived  from  the  auriculo-temporal  and  masseteric 
branches  of  the  inferior  maxillary.  The  arteries  are  derived  from  the  temporal 
branch  of  the  external  carotid. 

Actions. — The  movements  possible  in  this  articulation  are  very  extensive.  Thus, 
the  jaw  may  be  depressed  or  elevated,  or  it  may  be  carried  forward  or  backward. 
It  must  be  borne  in  mind  that  there  are  two  distinct  joints  in  this  articula- 
tion— that  is  to  say,  one  between  the  condyle  of  the  jaw  and  the  interarticular 
fibre-cartilage,  and  another  between  the  fibro-cartilage  and  the  glenoid  fossa; 
when  the  jaw  is  depressed,  as  in  opening  the  mouth,  the  movements  which  take 
place  in  these  two  joints  are  not  the  same.  In  the  lower  compartment,  that  between 
the  condyle  and  the  fibro-cartilage,  the  movement  is  of  a  ginglymoid  or  hinge-like 
character,  the  condyle  rotating  on  a  transverse  axis  on  the  fibro-cartilage;  while  in 
the  upper  compartment  the  movement  is  of  a  gliding  character,  the  fibro-cartilage, 
together  with  the  condyle,  gliding  forward  on  to  the  eminentia  articularis.  These 
two  movements  take  place  simultaneously — the  condyle  and  fibro-cartilage  move 
forward  on  the  eminence,  and  at  the  same  time  the  condyle  revolves  on  the  fibro- 
cartilage.  In  the  opposite  movement  of  shutting  the  mouth  the  reverse  action  takes 
place ;  the  fibro-cartilage  glides  back,  carrying  the  condyle  with  it,  and  this  at  the 
same  time  revolves  back  to  its  former  position.  When  the  jaw  is  carried  horizon- 
tally forward,  as  in  protruding  the  lower  incisors  in  front  of  the  upper,  the  move- 
ment takes  place  principally  in  the  upper  compartment  of  the  joint:  the  fibro- 
cartilage,  carrying  with  it  the  condyle,  glides  forward  on  the  glenoid  fossa.  This 
is  because  this  movement  is  mainly  effected  by  the  External  pterygoid  muscles, 
which  are  inserted  into  both  condyle  and  interarticular  fibro-cartilage.  The  grind- 
ing or  chewing  movement  is  produced  by  the  alternate  movement  of  one  condyle, 
with  its  fibro-cartilage,  forward  and  backward,  while  the  other  condyle  moves 
simultaneously  in  the  opposite  direction;  at  the  same  time  the  condyle  undergoes  a 
vertical  rotation  on  its  own  axis  on  the  fibro-cartilage  in  the  lower  compartment. 
One  condyle  advances  and  rotates,  the  other  condyle  recedes  and  rotates,  in  alter- 
nate succession. 

The  lower  jaw  is  depressed  by  its  own  weight,  assisted  by  the  Platysma,  the 
Digastric,  the  Mylo-hyoid,  and  the  Genio-hyoid  muscles.  It  is  elevated  by  the 
anterior  part  of  the  Temporal,  Masseter,  and  Internal  pterygoid.  It  is  drawn  for- 
ward by  the  simultaneous  action  of  the  External  pterygoid  and  the  superficial  fibres 
of  the  Masseter;  and  it  is  drawn  backward  by  the  deep  fibres  of  the  Masseter  and 
the  posterior  fibres  of  the  Temporal  muscle.  The  grinding  movement  is  caused  by 
the  alternate  action  of  the  two  External  pterygoids. 

Surface  Form. — The  temporo-mandibular  articulation  is  quite  superficial,  situated  below  the 
base  of  the  zygoma,  in  front  of  the  tragus  and  external  auditory  meatus,  and  behind  the  poste- 
rior border  of  the  upper  part  of  the  Masseter  muscle.  Its  exact  position  can  be  at  once  ascer- 
tained by  feeling  for  the  condyle  of  the  jaw,  the  working  of  which  can  be  distinctly  felt  in  the 
movements  of  the  lower  jaw  in  opening  and  shutting  the  mouth.  When  the  mouth  is  opened 
wide,  the  condyle  advances  out  of  the  glenoid  fossa  on  to  the  eminentia  articularis,  and  a  depres- 
sion is  felt  in  the  situation  of  the  joint. 

^  Surgical  Anatomy. — Genuine  dislocation  of  the  lower  jaw  is  almost  always  forward.  Croker 
King  and  Theim,  however,  have  reported  posterior  displacement.  Dislocation  is  caused  by 
violence  or  muscular  action.  When  the  mouth  is  open,  the  condyle  is  situated  on  the  eminentia 
articularis,  and  any  sudden  violence,  or  even  a  sudden  muscular  spasm,  as  during  a  convulsive 
yawn,  may  displace  the  condyle  forward  into  the  zygomatic  fossa.  The  displacement  may  be 
unilateral  or  bilateral,  according  as  one  or  both  of  the  condyles  is  displaced.  The  latter  of 


ARTICULATIONS   OF   THE  RIBS    WITH   THE    VERTEBRAE    285 

the  two  is  the  more  common.     The  interarticular  fibro-cartilage  adheres  to  the  condyle  till  it 
passes  over  the  eminentia  articularis,  but  at  this  point  remains  behind. 

Sir  Astley  Cooper  described  a  condition  which  he  termed  "  subluxation."  It  occurs  princi- 
pally in  delicate  women,  and  is  believed  by  some  to  be  due  to  the  relaxation  of  the  ligaments, 
permitting  too  free  movement  of  the  bone.  Others  believe  it  is  due  to  displacement  of  the  inter- 
articular  fibro-cartilage.  Still  others  attribute  the  symptoms  to  gouty  or  rheumatic  changes  in 
the  joint.  In  close  relation  to  the  condyle  of  the  jaw  is  the  external  auditory  meatus  and  the 
tympanum;  any  force,  therefore,  applied  to  the  bone  is  liable  to  be  attended  with  damage  to 
these  parts,  or  inflammation  in  the  joint  may  extend  to  the  ear,  or  on  the  other  hand  inflam- 
mation of  the  middle  ear  may  involve  the  articulation  and  cause  its  destruction,  thus  leading 
to  ankylosis  of  the  joint.  In  children,  arthritis  of  this  joint  may  follow  the  exanthemata,  and 
in  adults  it  occurs  as  the  result  of  some  constitutional  conditions,  as  rheumatism  or  gout.  The 
temporo-mandibular  joint  is  also  occasionally  the  seat  of  osteo-arthrilis,  leading  to  great  suffer- 
ing during  efforts  of  mastication.  A  peculiar  affection  sometimes  attacks  the  neck  and  condyle 
of  the  lower  jaw,  consisting  in  hypertrophy  and  elongation  of  these  parts  and  consequent  protru- 
sion of  the  chin  to  the  opposite  side. 

VI.  Articulations  of    the  Ribs  with  the  Vertebrae  or  the  Costo-vertebral 
Articulations  (Articulationes  Costovertebrales). 

The  articulations  of  the  ribs  with  the  vertebral  column  may  be  divided  into 
two  sets:  1.  Those  which  connect  the  heads  of  the  ribs  with  the  bodies  of  the 
vertebrae;  costo-central.  2.  Those  which  connect  the  necks  and  tubercles  of  the 
ribs  with  the  transverse  processes;  costo-trans verse. 

1.  ARTICULATIONS   BETWEEN  THE  HEADS  OF  THE  RIBS  AND  THE  BODIES  OF 
THE  VERTEBRAE  OR  THE  COSTO-CENTRAL  ARTICULATIONS  (ARTICU- 
LATIONES CAPITULORUM)  (Figs.  207  and  208). 

These  constitute  a  series  of  arthrodial  joints,  formed  by  the  articulation  of  the 
heads  of  the  ribs  with  the  cavities  on  the  contiguous  margins  of  the  bodies  of  the 


FOVCA  COSTALIS 
TRANSVERSALIS 


INTERVERTEBRAL 

FIBROCARTILAGE 


Fio.  207. — Spinal  column  with  ligament,  from  in  front.     (Spalteholz.) 


286 


THE  ARTICULATIONS  OR  JOINTS 


INTERARTICULAR  LIGA- 
MENT OF  HEAD  OF  RIB 


thoracic  vertebra  and  the  intervertebral  substance  between  them,  except  in  the  case 
of  the  first,  tenth,  eleventh,  and  twelfth  ribs,  where  the  cavity  is  formed  by  a  single 
vertebra.  The  bones  are  connected  by  the  following  ligaments: 

Anterior  Costo-vertebral  or  Stellate. 
Capsular.  Interarticular. 

The  Anterior  Costo-vertebral  or  Stellate  Ligament  (ligamentum  capituli  costce  radi- 
atum)  (Figs.  207  and  210)  connects  the  anterior  part  of  the  head  of  each  rib  with  the 
sides  of  the  bodies  of  two  vertebrae  and  the  intervertebral  disk  between  them.  It. 
consists  of  three  flat  bundles  of  ligamentous  fibres,  which  are  attached  to  the  ante- 
rior part  of  the  head  of  the  rib,  just  beyond  the  articular  surface.  The  superior 

fibres  pass  upward  to  be  con- 
nected with  the  body  of  the 
vertebra  above;  the  inferior 
one  descends  to  the  body  of 
the  vertebra  below;  and  the 
middle  one,  the  smallest  and 
least  distinct,  passes  horizon- 
tally inward,  to  be  attached 
to  the  intervertebral  sub- 
stance. 

Relations. — In  front,  with 
the  thoracic  ganglia  of  the 
sympathetic,  the  pleura,  and, 
on  the  right  side,  with  the  vena 
azygos  major;  behind,  with 
the  interarticular  ligament 
and  synovial  membranes. 

On  the  first  rib,  which 
articulates  with  a  single  ver- 
tebra, this  ligament  does  not 
present  a  distinct  division 
into  three  fasciculi ;  its  fibres, 
however,  radiate,  and  are  at- 
tached to  the  body  of  the  last  cervical  vertebra,  as  well  as  to  the  body  of  the 
vertebra  with  which  the  rib  articulates.  In  the  tenth,  eleventh,  and  twelfth  ribs 
also,  which  likewise  articulate  with  a  single  vertebra,  the  division  does  not  exist; 
but  the  fibres  of  the  ligament  in  each  case  radiate  and  are  connected  with  the 
vertebra  above,  as  well  as  that  with  which  the  ribs  articulate. 

The  Capsular  Ligament  (capsula  articularis)  is  a  thin  and  loose  ligamentous  bag, 
which  surrounds  the  joint  between  the  head  of  the  rib  and  the  articular  cavity 
formed  by  the  intervertebral  disk  and  the  adjacent  vertebra.  It  is  very  thin, 
firmly  connected  with  the  anterior  ligament,  and  most  distinct  at.  the  upper  and 
lower  parts  of  the  articulation.  Behind,  some  of  its  fibres  pass  through  the  inter- 
vertebral foramen  to  the  back  of  the  intervertebral  disk.  This  is  the  analogue  of 
the  ligamentum  conjugate  of  some  mammals,  which  unites  the  heads  of  opposite 
ribs  across  the  back  of  the  intervertebral  disk. 

The  Interarticular  Ligament  (ligamentum  capituli  costce  interarticulare)  (Figs.  208 
and  209)  is  situated  in  the  interior  of  the  joint.  It  consists  of  a  short  band  of 
fibres,  flattened  from  above  downward,  attached  by  one  extremity  to  the  sharp 
crest  which  separates  the  two  articular  facets  on  the  head  of  the  rib,  and  by  the 
other  to  the  intervertebral  disk.  It  divides  the  joint  into  two  cavities,  which 
have  no  communication  with  each  other.  In  the  first,  tenth,  eleventh,  and 


FIG.  208. — Ribs  and  corresponding  vertebral  bodies  with  their 
ligaments,  viewed  from  the  right.    (Spalteholz.) 


ARTICULATIONS    OF    THE  RIBS    WITH   THE    VERTEBRA    287 

twelfth  ribs  the  interarticular  ligament  does  not  exist;  consequently  there  is  but 
one  synovial  membrane. 

Synovial  Membranes  (Figs.  208  and  209). — There  are  two  synovial  membranes 
in  each  of  the  articulations  in  which  there  is  an  interarticular  ligament,  one  on 
each  side  of  this  structure. 

2.  ARTICULATIONS  OF  THE  NECKS  AND  TUBERCLES  OF  THE  RIBS  WITH   THE 

TRANSVERSE  PROCESSES  OR  THE  COSTO-TRANSVERSE  ARTICULATIONS 

(ARTICULATIONES  COSTOTRANSVERSARIAE)  (Fig.  209). 

The  articular  portion  of  the  tubercle  of  the  rib  and  adjacent  transverse  process 
form  an  arthrodial  joint. 

In  the  eleventh  and  twelfth  ribs  this  articulation  is  wanting. 
The  ligaments  connecting  these  parts  are  the 

Anterior  Superior  Costo-transverse.  Posterior  Costo-transverse 

Middle  Costo-transverse  (Interosseous).      Capsular. 

The  Anterior  Superior  or  Long  Costo-transverse  Ligament  (ligamentum  costo- 
transversarium  anterius)  (Figs.  207,208,209,  and  210)  consists  of  two  sets  of  fibres: 
the  one  (anterior)  is  attached  below  to  the  sharp  crest  on  the  upper  border 


INTERARTICULAR 
LIGAMENT 


ANTERIOR    COSTO-THANSVERSE 
UIQAMENT    DIVIDED. 


MIDDLE    COSTO-TRANSVERSE 

Or    INTEROSSEOUS 
POSTERIOR    COSTO- 
TRANSVERSE    LIGAMENT. 


FIG.  209. — Costo-transverse  articulation.     Seen  from  above. 

of  the  neck  of  each  rib,  and  passes  obliquely  upward  and  outward  to  the  lower 
border  of  the  transverse  process  immediately  above;  the  other  (posterior)  is 
attached  below  to  the  neck  of  the  rib,  and  passes  upward  and  inward  to  the  base 
of  the  transverse  process  and  outer  border  of  the  lower  articular  process  of  the 
vertebra  above.  This  ligament  is  in  relation,  in  front,  with  the  intercostal  vessels 
and  nerves;  behind,  with  the  Longissimus  dorsi  muscle.  Its  internal  border  is 
thickened  and  free,  and  bounds  an  aperture  through  which  pass  the  posterior 
branches  of  the  intercostal  vessels  and  nerves.  Its  external  border  is  continuous 
with  a  thin  aponeurosis  which  covers  the  External  intercostal  muscle. 

The  first  rib  has  no  anterior  costo-transverse  ligament.    In  the  twelfth  rib  the 
ligament  is  absent  or  is  a  mere  vestige. 


288 


THE   ARTICULATIONS    OR    JOINTS 


The  Middle  Costo-transverse  or  Interosseous  Ligament  (ligamentum  colli  costae) 
(Fig.  209)  consists  of  short  but  strong  fibres  which  pass  between  the  rough  sur- 
face on  the  posterior  part  of  the  neck  of  each  rib  and  the  anterior  surface  of  the 
adjacent  transverse  process.  In  order  fully  to  expose  this  ligament,  a  horizontal 
section  should  be  made  across  the  transverse  process  and  corresponding  part  of 
the  rib;  or  the  rib  may  be  forcibly  separated  from  the  transverse  process  and  the 
fibres  of  the  ligament  put  on  the  stretch. 

In  the  eleventh  and  twelfth  ribs  this  ligament  is  quite  rudimentary  or  wanting. 

The  Posterior  Costo-transverse  Ligament  (ligamentumcostotransversarium  posterius) 

(Fig.  209)  is  a  short  but  thick  and  strong  fasciculus  which  passes  obliquely  from  the 

summit  of  the  transverse 
process  to  the  rough  non- 
articular  portion  of  the 
tubercle  of  the  rib.  This 


ARTICULAR  SURFACE  £ 
FOR   TUBERCLE  at 
OF  RIB 


o  SUPERIOR  ARTICULAR 
SURFACE   FOR   HEAD 
RIB 


ANTERIOR 
COSTO-TRANS- 
VERSE   LIGAMENT 
INTERTRANS- 
VERSE   LIGAMENT 


ligament    is  shorter   and 


INTERVERTC- 
BRAL  FIBRO- 
CARTILAGE 


more  oblique  in  the  upper 
than  in  the  lower  ribs. 
Those  corresponding  to 
the  superior  ribs  ascend, 
while  those  of  the  inferior 
ribs  descend  slightly. 

In  the  eleventh  and 
twelfth  ribs  this  ligament 
is  wanting. 

The  Capsular  Ligament 
(capsula  articularis)  is  a 
thin,  membranous  sac  at- 
tached to  the  circumfer- 
ence of  the  articulari  sur- 
faces, and  enclosing  a 
small  synovial  membrane. 
In  the  eleventh  and 
twelfth  ribs  this  ligament 
is  absent. 

Actions.— The  heads  of 
the  ribs  are  so  closely 
connected  to  the  bodies 
of  the  vertebrae  by  the 
stellate  and  interarticular 
ligaments,  and  the  necks 
and  tubercles  of  the  ribs  to  the  transverse  processes,  that  only  a  slight  sliding 
movement  of  the  articular  surfaces  on  each  other  can  take  place  in  these  articula- 
tions. The  result  of  this  gliding  movement  with  respect  to  the  six  upper  ribs  con- 
sists in  an  elevation  of  the  front  and  middle  portion  of  the  rib,  the  hinder  part 
being  prevented  from  performing  any  upward  movement  by  its  close  connection 
with  the  spine.  In  this  gliding  movement  the  rib  rotates  on  an  axis  corresponding 
with  a  line  drawn  through  the  two  articulations,  costo-central  and  costo-transverse, 
which  the  rib  forms  with  the  spine.  With  respect  to  the  seventh,  eighth,  ninth,  and 
tenth  ribs,  each  one,  besides  rotating  in  a  similar  manner  to  the  upper  six,  also 
rotates  on  an  axis  corresponding  with  a  line  drawn  from  the  head  of  the  rib  to  the 
sternum.  By  the  first  movement — that  of  rotation  of  the  rib  on  an  axis  correspond- 
ing with  a  line  drawn  through  the  two  articulations  which  this  bone  forms  with 
the  spine — an  elevation  of  the  anterior  part  of  the  rib  takes  place,  and  a  consequent 
enlargement  of  the  antero-posterior  diameter  of  the  chest.  None  of  the  ribs  lie  in 


INFERIOR  ARTICULAR 
SURFACE    FOR   HEAD 
OF  RIB 

INFERIOR  ARTIC- 
ULAR   PROCESS 

FIG.  210. — Ribs  and  corresponding  vertebra  with  ligaments,  viewed 
from  the  right.      (Spalteholz.) 


ARTICULATION   OF   CARTILAGES    OF  RIBS  WITH  STERNUM    289 


a  truly  horizontal  plane;  they  are  all  directed  more  or  less  obliquely,  so  that  their 
anterior  extremities  lie  on  a  lower  level  than  their  posterior,  and  this  obliquity 
increases  from  the  first  to  the  seventh,  and  then  again  decreases.  If  we  examine 
any  one  rib — say,  that  in  which  there  is  the  greatest  obliquity — we  shall  see  that 
it  is  obvious  that  as  its  sternal  extremity  is  carried  upward,  it  must  also  be  thrown 
forward ;  so  that  the  rib  may  be 
regarded  as  a  radius  moving  on 
the  vertebral  joint  as  a  centre,  and 
causing  the  sternal  attachment  to 
describe  an  arc  of  a  circle  in  the 
vertical  plane  of  the  body.  Since 
all  the  ribs  are  oblique  and  con- 
nected in  front  to  the  sternum  by 
the  elastic  costal  cartilages,  they 
must  have  a  tendency  to  thrust 
the  sternum  forward,  and  so  in- 
crease the  antero-posterior  diam- 
eter of  the  chest.  By  the  second 
movement — that  of  the  rotation 
of  the  rib  on  an  axis  correspond- 
ing with  a  line  drawn  from  the 
head  of  the  rib  to  the  sternum — 
an  elevation  of  the  middle  portion 
of  the  rib  takes  place,  and  conse- 
quently an  increase  in  the  trans- 
verse diameter  of  the  chest.  For 
the  ribs  not  only  slant  downward 
and  forward  from  their  vertebral 
attachment,  but  they  are  also  ob- 
lique in  relation  to  their  transverse 
plane — that  is  to  say,  their  middle 
is  on  a  lower  level  than  either 
their  vertebral  or  sternal  extremi- 
ties. It  results  from  this  that  when 
the  ribs  are  raised,  the  centre  por- 
tion is  thrust  outward,  somewhat 
after  the  fashion  in  which  the 
handle  of  a  bucket  is  thrust  away 
from  the  side  when  raised  to  a 
horizontal  position,  and  the  lateral 
diameter  of  the  chest  is  increased 

(see  Fig.  211).  The  mobility  of  the  different  ribs  varies  very  much.  The  first  rib 
is  more  fixed  than  the  others,  on  account  of  the  weight  of  the  upper  extremity  and 
the  strain  of  the  ribs  beneath ;  but  on  the  freshly  dissected  thorax  it  moves  as  freely 
as  the  others.  From  the  same  causes  the  movement  of  the  second  rib  is  also  not 
very  extensive.  In  the  other  ribs  this  mobility  increases  successively  down  to  the 
last  two,  which  are  very  movable.  The  ribs  are  generally  more  movable  in  the 
female  than  in  the  male. 

VII.  Articulation  of  the  Cartilages  of  the  Ribs  with  the  Sternum,  etc.,  or 

the  Costo-sternal  Articulations  (Articulationes 

Sternocostales)   (Fig.  212). 

The  articulations  of  the  cartilages  of  the  true  ribs  with  the  sternum  are  arthro- 
dial  joints,  with  the  exception  of  the  first,  in  which  the  cartilage  is  almost  always 

19 


FIG.  211. — Diagrams  showing  the  axis  of  rotation  of  the 
ribs  in  the  movements  of  respiration.  The  one  axis  of  rota- 
tion corresponds  with  the  line  drawn  through  the  two  articu- 
lations which  the  rib  forms  with  the  spine  (a,  b),  and  the  other 
with  a  line  drawn  from  the  head  of  the  rib  to  the  sternum 
(A,  B).  (From  Kirke's  Handbook  of  Physiology.) 


290  THE   ARTICULATIONS    OR   JOINTS 

directly  united  with  the  sternum,  and  which  must  therefore  be  regarded  as  a 
synarthrodial  articulation.     The  ligaments  connecting  them  are  the 

Anterior  Chondro-sternal.  Capsular. 

Posterior  Chondro-sternal.  Interarticular  Chondro-sternal. 

Chondro-xiphoid. 

The  Anterior  Chondro-sternal  or  Sterno-costal  Ligament  (ligamentum  sternocostale 
radiatum)  (Fig.  212)  is  a  broad  and  thin  membranous  band  that  radiates  from 
the  front  of  the  inner  extremity  of  the  cartilages  of  the  true  ribs  to  the  anterior 
surface  of  the  sternum.  It  is  composed  of  fasciculi  which  pass  in  different  direc- 
tions. The  superior  fasciculi  ascend  obliquely,  the  inferior  fasciculi  pass  obliquely 
downward,  and  the  middle  fasciculi  pass  horizontally.  The  superficial  fibres  of  this 
ligament  are  the  longest:  they  intermingle  with  the  fibres  of  the  ligaments  above 
and  below  them,  with  those  of  the  opposite  side,  and  with  the  tendinous  fibres  of 
origin  of  the  Pectoralis  major,  forming  a  thick  fibrous  membrane  which  covers 
the  surface  of  the  sternum  (membrana  sterni}.  This  is  more  distinct  at  the  lower 
than  at  the  upper  part.  According  to  the  modern  nomenclature,  this  ligament 
and  the  posterior  chondro-sternal  ligament  are  called  ligamenta  sternocostalia 
radiata.  The  two  chondro-sternal  ligaments  form  a  sheath  for  the  sternum 
anteriorly  and  posteriorly,  the  membrana  sterni. 

The  Posterior  Chonjiro-sternal  or  Sterno-costal  Ligament  (ligamentum  sterno- 
costale radiatum),  less  thick  and  distinct  than  the  anterior,  is  composed  of  fibres 
which  radiate  from  the  posterior  surface  of  the  sternal  end  of  the  cartilages  of 
the  true  ribs  to  the  posterior  surface  of  the  sternum,  becoming  blended  with  the 
periosteum. 

The  Capsular  Ligament  (capsula  articidaris)  surrounds  the  joint  formed  between 
the  cartilage  of  a  true  rib  and  the  sternum.  It  is  very  thin,  intimately  blended 
with  the  anterior  and  posterior  ligaments,  and  strengthened  at  the  upper  and  lower 
part  of  the  articulation  by  a  few  fibres  which  pass  from  the  cartilage  to  the  side 
of  the  sternum.  These  ligaments  protect  the  synovial  membranes. 

The  Interarticular  Chondro-sternal  or  Sterno-costal  Ligament  (ligamentum  sterno- 
costale inter  articular  e]  (Fig.  212). — This  is  found  between  the  second  costal  car- 
tilage and  the  sternum.  The  cartilage  of  the  second  rib  is  connected  with  the 
sternum  by  means  of  an  interarticular  ligament  attached  by  one  extremity  to  the 
cartilage  of  the  second  rib,  and  by  the  other  extremity  to  the  cartilage  which  unites 
the  first  and  second  pieces  of  the  sternum.  This  articulation  is  provided  with  two 
synovial  membranes.  The  cartilage  of  the  third  rib  is  also  connected  with  the  ster- 
num by  means  of  an  interarticular  ligament  which  is  attached  by  one  extremity  to 
the  cartilage  of  the  third  rib,  and  by  the  other  extremity  to  the  point  of  junction 
of  the  second  and  third  pieces  of  the  sternum.  This  articulation  may  be  provided 
with  two  synovial  membranes.  In  the  other  joints  interarticular  ligaments  may 
exist,  but  they  rarely  completely  divide  the  joint  into  two  cavities. 

The  Anterior  Chondro-xiphoid  or  Costo-xiphoid  Ligament  (ligamentum  costo- 
xiphoidea)  (Fig.  212).— This  is  a  band  of  ligamentous  fibres  which  connects 
the  anterior  surface  of  the  seventh  costal  cartilage,  and  occasionally  also  that 
of  the  sixth,  to  the  anterior  surface  of  the  ensiform  appendix.  It  varies  in 
length  and  breadth  in  different  subjects.  A  similar  band  of  fibres  on  the  inter- 
nal or  posterior  surface,  though  less  thick  and  distinct,  may  be  demonstrated. 
It  is  spoken  of  as  the  posterior  chondro-xiphoid  or  costo -xiphoid  ligament. 

Synovial  Membranes  (Fig.  212). — There'  is  no  synovial  membrane  between  the 
first  costal  cartilage  and  the  sternum,  as  this  cartilage  is  directly  continuous  with 
the  sternum.  There  are  two  synovial  membranes,  both  in  the  articulation  of  the 
second  and  third  costal  cartilages  to  the  sternum.  There  is  generally  one  syno- 
vial membrane  in  each  of  the  joints  between  the  fourth,  fifth,  sixth,  and  seventh 


ARTICULATION   OF   CARTILAGES    OF  RIBS  WITH  STERNUM    291 

costal  cartilages  to  the  sternum;  but  it  is  sometimes  absent  in  the  sixth  and 
seventh  chondro-sternal  joints.  Thus  there  are  usually  eight  synovial  cavities  on 
each  side  in  the  articulations  between  the  costal  cartilages  of  the  true  ribs  and 
the  sternum.  After  middle  life  the  articular  surfaces  lose  their  polish,  become 


FIG.  212. — Sternum  and  ribs  with  ligaments,  from  in  front.  In  the  left  half  of  the  figure  the  most  anterior 
layer  has  been  removed  and  the  joint  slits  have  been  opened  ;  the  parts  are  separated  somewhat  from  one 
another  on  the  left  side.  (Spalteholz.) 

roughened,  and  the  synovial  membranes  appear  to  be  wanting.  In  old  age  the 
articulations  do  not  exist,  the  cartilages  of  most  of  the  ribs  becoming  continuous 
with  the  sternum. 

Actions. — The  movements  which  are  permitted  in  the  chondro-sternal  articu- 
lations are  limited  to  elevation  and  depression,  and  these  only  to  a  slight  extent. 

Articulations  of  the  Cartilages  of  the  Ribs  with  Each  Other  or  the  Inter- 
chondral  Articulations  (articidationes  interchondrales)  (Fig.  212). — The  con- 


292  THE   ARTICULATIONS    OR   JOINTS 

tiguous  borders  of  the  sixth,  seventh,  and  eighth,  and  sometimes  the  ninth  and 
tenth,  costal  cartilages  articulate  with  each  other  by  small,  smooth,  oblong-shaped 
facets.  Each  articulation  is  enclosed  in  a  thin  capsular  ligament  lined  by  syno- 
vial  membrane,  and  strengthened  externally  and  internally  by  ligamentous  fibres, 
external  and  internal  interchondral  ligaments  (ligamenta  intercostalia  externa  et 
internet),  which  pass  from  one  cartilage  to  the  other.  Sometimes  the  fifth  costal 
cartilage,  more  rarely  that  of  the  ninth,  articulates,  by  its  lower  border,  with  the 
adjoining  cartilage  by  a  small  oval  facet;  more  frequently  they  are  connected 
together  by  a  few  ligamentous  fibres.  Occasionally  the  articular  surfaces'  above 
mentioned  are  wanting. 

Articulations  of  the  Ribs  with  their  Cartilages  or  the  Costo-chondral 
Articulations  (Fig.  212). — The  outer  extremity  of  each  costal  cartilage  is  re- 
ceived into  a  depression  in  the  sternal  ends  of  the  ribs,  and  the  two  are  held 
together  by  the  periosteum.  There  is  no  real  joint.  Occasionally  a  synovial 
membrane  exists  between  the  first  rib  and  the  corresponding  cartilage. 

VIII.  Articulations  of  the  Sternum  (Fig.  212). 

The  first  piece  of  the  sternum  is  united  to  the  second  either  by  an  amphi- 
arthrodial  joint — a  single  piece  of  true  fibre-cartilage  uniting  the  segments — or 
by  a  diarthrodial  joint,  in  which  each  bone  is  clothed  with  a  distinct  lamina  of 
cartilage,  adherent  on  one  side,  free  and  lined  with  synovial  membrane  on  the 
other.  In  the  latter  case  the  cartilage  covering  the  gladiolus  is  continued  without 
interruption  on  to  the  cartilages  of  the  second  ribs.  Mr.  Rivington  has  found  the 
diarthrodial  form  of  joint  in  about  one-third  of  the  specimens  examined  by  him ; 
Mr.  Maisonneuve  more  frequently.  It  appears  to  be  rare  in  childhood,  and  is 
formed,  in  Mr.  Rivington's  opinion,  from  the  amphiarthrodial  form  by  absorption. 
The  diarthrodial  joint  seems  to  have  no  tendency  to  ossify  at  any  age,  while  the 
amphiarthrodial  is  more  liable  to  do  so,  and  has  been  found  ossified  as  early  as 
thirty-four  years  of  age.  Professor  Cunningham1  says :  "  It  is  not  usual  to  find  the 
manubri-gladiolar  joint  obliterated  by  the  ossification  of  the  two  bony  segments. 
Even  in  advanced  life  it  remains  open,  and  the  joint  partakes  of  the  nature  of" 
an  amphiarthrosis,  although  a  joint  cavity  is  not  found  under  any  circumstances 
in  the  plate  of  fibro-cartilage  which  intervenes  between  the  manubrium  and  the 
gladiolus.''  The  two  segments  are  further  connected  by  an 

Anterior  Intersternal  Ligament.         Posterior  Intersternal  Ligament. 

The  Anterior  Intersternal  Ligament  consists  of  a  layer  of  fibres,  having  a  longi- 
tudinal direction;  it  blends  with  the  fibres  of  the  anterior  chondro-sternal  liga- 
ments on  both  sides  (membrani  sterni),  and  with  the  tendinous  fibres  of  origin 
of  the  Pectoralis  major  muscle.  This  ligament  is  rough,  irregular,  and  much 
thicker  below  than  above. 

The  Posterior  Intersternal  Ligament  is  disposed  in  a  somewhat  similar  manner 
on  the  posterior  surface  of  the  articulation. 

IX.  Articulation  of  the  Vertebral  Column  with  the  Pelvis. 

The  ligaments  connecting  the  last  lumbar  vertebra  with  the  sacrum  are  similar 
to  those  which  connect  the  segments  of  the  spine  with  each  other— viz.:  1.  The 
continuation  downward  of  the  anterior  and  posterior  common  ligaments.  2.  The 
intervertebral  substance  connecting  the  flattened  oval  surfaces  of  the  two  bones 

1  Text-book  of  Anatomy,  p.  264. 


ARTICULATION  OF    VERTEBRAL    COLUMN  WITH   PELVIS    293 

and  forming  an  amphiarthrodial  joint.  3.  Ligamenta  subflava,  connecting  the 
arch  of  the  last  lumbar  vertebra  with  the  posterior  border  of  the  sacral  canal. 
4.  Capsular  ligaments  connecting  the  articulating  processes  and  forming  a  double 
arthrodia.  5.  Inter-  and  supraspinous  ligaments. 

The  two  proper  ligaments  connecting  the  pelvis  with  the  spine  are  the  lumbo- 
sacral  and  ilio-lumbar. 

The  Lumbo -sacral  Ligament  (Fig.  213)  is  a  short,  thick,  triangular  fascic- 
ulus, which  is  connected  above  to  the  lower  and  front  part  of  the  trans- 
verse process  of  the  last  lumbar  vertebra,  passes  obliquely  outward,  and  is 
attached  below  to  the  lateral  surface  of  the  base  of  the  sacrum.  It  is  closely 
blended  with  the  anterior  sacro-iliac  ligament  and  with  the  ilio-lumbar 
ligament,  and  is  to  be  regarded  as  a  portion  of  the  ilio-lumbar  ligament. 
This  ligament  is  in  relation,  in  front,  with  the  Psoas  muscle.  The  in- 
ternal border  of  the  lumbo-sacral  ligament  margins  the  foramen  of  the  last 
lumbar  nerve. 

The  Ilio-lumbar  Ligament  (ligamentum  iliolumbale)  (Fig.  213)  passes  horizon- 
tally outward  from  the  apex  of  the  transverse  process  of  the  last  lumbar  vertebra 


Aperture  of  communication 

with 
PSOAS  anil  ILIACUS. 


Femur. 

FIG.  213. — Articulations  of  the  pelvis  and  hip.     Anterior  view. 

to  the  crest  of  the  ilium  immediately  in  front  of  the  sacro-iliac  articulation.  It 
is  of  a  triangular  form,  thick  and  narrow  internally,  broad  and  thinner  exter- 
nally. It  is  in  relation,  in  front,  with  the  Psoas  muscle ;  behind,  with  the 
muscles  occupying  the  vertebral  groove;  above,  with  the  Quadratus  lum- 
borum.  It  blends  in  places  with  the  lumbo-sacral  ligament,  and  its  cres- 
centic  inner  margin  marks  the  limit  of  the  foramen  for  the  fourth  lumbar  nerve. 
These  ligaments  are  thick  prolongations  from,  the  anterior  layer  of  the  lumbar 
fascia. 


294  THE  ARTICULATIONS    OB,    JOINTS 

X.  Articulations  of  the  Pelvis. 

The  ligaments  connecting  the  bones  of  the  pelvis  with  each  other  may  be 
divided  into  four  groups:  1.  Those  connecting  the  sacrum  and  ilium.  2.  Those 
passing  between  the  sacrum  and  ischium.  3.  Those  connecting  the  sacrum  and 
coccyx.  4.  Those  between  the  two  pubic  bones. 

1.  ARTICULATION  OF  THE  SACRUM  AND  ILIUM  (ARTICULATIO  SACROILIACA.) 

The  sacro-iliac  articulation  is  an  amphiarthrodial  joint,  formed  between  the 
lateral  surfaces  of  the  sacrum  and  ilium.  The  anterior  or  auricular  portion  of  each 
articular  surface  is  covered  with  a  thin  plate  of  cartilage,  thicker  on  the  sacrum 
than  on  the  ilium.  These  are  in  close  contact  with  each  other,  and  to  a  certain 
extent  united  together  by  irregular  patches  of  softer  fibro-cartilage,  and  at  their 
upper  and  posterior  part  by  fine  fibres  of  interosseous  fibrous  tissue.  Throughout 
a  considerable  part  of  their  extent,  especially  in  advanced  life,  they  are  not 
connected  together,  but  are  separated  by  a  space  containing  a  synovial-like  fluid, 
and  hence  the  joint  presents  the  characters  of  a  diarthrosis. 

The  ligaments  connecting  these  surfaces  are  the 

Anterior  Sacro-iliac.  Posterior  Sacro-iliac. 

Interosseous. 

The  Anterior  Sacro-iliac  Ligaments  (lig  amenta  sacroiliaca  anterior  a)  (Fig.  213) 
consists  of  numerous  thin  bands  which  connect  the  anterior  surfaces  of  the  sacrum 
and  ilium. 

The  Posterior  Sacro-iliac  Ligament  (ligamentum  sacroiliacum  posterius)  (Fig.  214) 
is  a  strong  interosseous  ligament,  situated  in  a  deep  depression  between  the  sacrum 
and  ilium  behind,  and  forming  the  chief  bond  of  connection  between  those  bones. 
It  consists  of  numerous  strong  fasciculi  which  pass  between  the  bones  in  various 
directions.  Three  of  these  are  of  large  size:  the  two  superior  fasciculi  constitute 
the  short  sacro-iliac  ligament  (ligamentum  sacroiliacum  posterius  breve) .  They  are 
nearly  horizontal  in  direction,  arise  from  the  first  and  second  transverse  tuber- 
cles on  the  posterior  surface  of  the  sacrum,  and  are  inserted  into  the  rough, 
uneven  surface  at  the  posterior  part  of  the  inner  surface  of  the  ilium.  The 
third  fasciculus,  oblique  in  direction,  is  attached  by  one  extremity  to  the  third 
transverse  tubercle  on  the  posterior  surface  of  the  sacrum,  and  by  the  other  to 
the  posterior  superior  spine  of  the  ilium;  it  is  sometimes  called  the  long  or  oblique 
sacro-iliac  ligament  (ligamentum  sacroiliacum  posterius  longum). 

The  Interosseous  Ligaments  (ligamenta  sacroiliaca  interossed)  are  completely 
covered  by  the  posterior  sacro-iliac  ligament,  and  are  not  visible  when  the  joint 
is  unopened.  The  fibres  are  short  and  run  obliquely  and  completely  fill  the 
hollow  which  exists  posterior  to  the  joint. 

The  position  of  the  sacro-iliac  joint  is  indicated  by  the  posterior  superior  spine  of  the  ilium. 
This  process  is  immediately  behind  the  centre  of  the'  articulation. 

2.  LIGAMENTS  PASSING  BETWEEN  THE  SACRUM  AND  ISCHIUM  (Fig.  214). 

The  Great  Sacro-sciatic  (Posterior). 
The  Lesser  Sacro-sciatic  (Anterior). 

The  Great  or  Posterior  Sacro-sciatic  Ligament  (ligamentum  sacroiuberosum}  (Figs. 
214  and  215)  is  situated  at  the  lower  and  back  part  of  the  pelvis.  It  is  flat,  and 
triangular  in  form;  narrower  in  the  middle  than  at  the  extremities;  attached  by  its 
broad  base  to  the  posterior  inferior  spine  of  the  ilium,  to  the  fourth  and  fifth  trans- 


ARTICULATIONS    OF    THE   PELVIS 


295 


verse  tubercles  of  the  sacrum,  and  to  the  lower  part  of  the  lateral  margin  of  that  bone 
and  the  coccyx.  Passing  obliquely  downward,  outward,  and  forward,  it  becomes 
narrow  and  thick,  and  at  its  insertion  into  the  inner  margin  of  the  tuberosity  of 
the  ischium  it  increases  in  breadth,  and  is  prolonged  forward  along  the  inner 
margin  of  the  ramus,  forming  what  is  known  as  the  falciform  process  of  the 
great  sacro-sciatic  ligament  or  the  falciform  ligament  (processus  falciformis) .  The 
free  concave  edge  of  this  prolongation  has  attached  to  it  the  obturator  fascia, 
with  which  it  forms  a  kind  of  groove,  protecting  the  internal  pudic  vessels  and 
nerve.  One  of  its  surfaces  is  turned  toward  the  perinosum,  the  other  toward 
the  Obturator  internus  muscle. 


r 

S^. 

•emur, 

FIG.  214. — Articulations  of  pelvis  and  hip.     Posterior  view. 

The  posterior  surface  of  this  ligament  gives  origin,  by  its  whole  extent,  to  fibres 
of  the  Gluteus  maximus  muscle.  Its  anterior  surface  is  united  to  the  lesser  sacro- 
sciatic  ligament.  Its  external  border  forms,  above,  the  posterior  boundary  of  the 
great  sacro-sciatic  foramen,  and,  below,  the  posterior  boundary  of  the  lesser  sacro- 
sciatic  foramen.  Its  lower  border  forms  part  of  the  boundary  of  the  perinaeum.  It 
is  pierced  by  the  coccygeal  branch  of  the  sciatic  artery  and  the  coccygeal  nerve. 

The  Lesser  or  Anterior  Sacro-sciatic  Ligament  (ligamentum  sacrospinosum)  (Figs. 
214  and  215),  much  shorter  and  smaller  than  the  preceding,  is  thin,  triangular  in 
form,  attached  by  its  apex  to  the  spine  of  the  ischium,  and  internally,  by  its  broad 
base,  to  the  lateral  margin  of  the  sacrum  and  coccyx,  anterior  to  the  attachment 
of  the  great  sacro-sciatic  ligament,  with  W7hich  its  fibres  are  intermingled. 

It  is  in  relation,  anteriorly,  with  the  Coccygeus  muscle;  posteriorly,  it  is  covered 
by  the  great  sacro-sciatic  ligament  and  crossed  by  the  intecnal  pudic  vessels  and 
nerve.  Its  superior  border  forms  the  lower  boundary  of  the  great  sacro-sciatic 
foramen;  its  inferior  border,  part  of  the  lesser  sacro-sciatic  foramen. 


296 


THE    ARTICULATIONS    OR    JOINTS 


These  two  ligaments  convert  the  sacro-sciatic  notches  into  foramina.  The 
superior  or  great  sacro-sciatic  foramen  (foramen  ischiadicum  majus)  (Figs.  214  and 
215)  is  bounded,  in  front  and  above,  by  the  posterior  border  of  the  os  innominatum; 
behind,  by  the  great  sacro-sciatic  ligament;  and  below,  by  the  lesser  sacro-sciatic 
ligament.  It  is  partially  filled  up,  in  the  recent  state,  by  the  Pyriformis  muscle, 
which  passes  through  it.  Above  this  muscle  the  gluteal  vessels  and  superior  gluteal 
nerve  emerge  from  the  pelvis,  and,  below  it,  the  sciatic  vessels  and  nerves,  the  inter- 
nal pudic  vessels  and  nerve,  the  inferior  gluteal  nerve,  and  the  nerves  to  the  obtu- 
rator internus  and  quadratus  femoris.  The  inferior  or  lesser  sacro-sciatic  foramen 
(foramen  ischiadicum  minus)  (Figs.  214  and  215)  is  bounded,  in  front,  by  the 


POUPART'S 
LIGAMENT 


ANT.   SACRO-ILIAC 
LIGAMENT. 


GREAT   SACRO- 
SCIATIC    LIGA- 
MENT. 


LESSER  SACRO- 
SCIATIC  LIGA- 
MENT. 


GREAT   SACRO- 
SCIATIC    LIGA- 
MENT. 


Obturato 
membrane. 


FIG.  215. — Side  view  of  pelvis,  showing  the  greater  and  lesser  sacro-sciatic  ligaments. 

tuber  ischii;  above,  by  the  spine  and  lesser  sacro-sciatic  ligament;  behind,  by  the 
greater  sacro-sciatic  ligament.  It  transmits  the  tendon  of  the  Obturator  internus 
muscle,  its  nerve,  and  the  internal  pudic  vessels  and  nerve. 

3.  ARTICULATION  OF  THE  SACRUM  AND  COCCYX  (SYMPHYSIS  SACROCOCCYGEA)  . 

This  articulation  is  an  amphiarthrodial  joint,  formed  between  the  oval  surface 
at  the  apex  of  the  sacrum  and  the  base  of  the  coccyx.  It  is  analogous  to  the 
joints  between  the  bodies  of  the  vertebrae.  The  ligaments  are  the 


Anterior  Sacro-coccygeal. 
Posterior  Sacro-coccygeal. 


Lateral  Sacro-coccygeal. 
Interposed  Fibro-cartilage. 


The  Anterior  Sacro-coccygeal  Ligament  (ligamentum  sacrococcygeum  anterius) 
consists  of  a  few  irregular  fibres  which  descend  from  the  anterior  surface  of  the 
sacrum  to  the  front  of  tfre  coccyx,  becoming  blended  with  the  periosteum.  It  is 
a  continuation  of  the  anterior  common  ligament. 

The  Posterior  Sacro-coccygeal  Ligament  (ligamentum  sacrococcygeum  posterius) 
(Fig.  216)  is  divided  into  two  portions,  the  deep  and  the  superficial.  The  deep 


ARTICULATIONS    OF   THE  PELVIS  297 

portion  of  the  posterior  sacro-coccygeal  ligament  (ligamentum  sacrococcygeum  posterius 
profundwn) ,  which  is  a  continuation  of  the  posterior  common  ligament,  is  a  flat 
band  of  a  pearly  tint,  which  arises  from  the  margin  of  the  lower  orifice  of  the  sacral 
canal,  and  descends  to  be  inserted  into  the  posterior  surface  of  the  coccyx.  This 
ligament  completes  the  lower  and  back  part  of  the  sacral  canal.  Its  superficial 
fibres  are  much  longer  than  the  more  deeply  seated.  This  ligament  is  in  rela- 
tion, behind,  with  the  Gluteus  maximus. 

The  superficial  portion  of  the  posterior  sacro-coccygeal  ligament  (ligamentum 
sacrococcygeum  posterius  superficiale)  is  composed  of  longitudinal  fibrous  bands 
which  extend  from  the  lower  portion  of  the  middle  sacral  ridge  to  the  posterior 
surface  of  the  coccyx  and  closes  partly  the  hiatus  sacralis ;  and  of  fibrous  bands 
which  extend  from  the  sacral  cornua  to  the  coccygeal  cornua.  A  portion  of  this 
ligament  corresponds  to  the  ligamenta  subflava  and  the  balance  to  the  capsular 
ligament. 

A  Lateral  Sacro-coccygeal  or  Intertransverse  Ligament  (ligamentum  sacrococcygeum 
later  ale)  (Fig.  216)  connects  the  transverse  process  of  the  coccyx  to  the  lower 
lateral  angle  of  the  sacrum  on  each  side. 


APEX  OF  SACRUM 
LATERAL   SACRO- 
COCCYGEAL    LIGAMENT 
SUPERFICIAL    PORTION   OF    POST 
SACRO-COCCYGEAL  LIGAMENT 
DEEP  PORTION  OF  POSTERIOR 
SACRO-COCCYGEAL    LIGAMENT 


FIG.  216. — Ligaments  between  the  sacrum  and  the  coccyx.     (Spalteholz.) 

A  Fibro-cartilage  is  interposed  between  the  contiguous  surfaces  of  the  sacrum 
and  coccyx;  it  differs  from  that  interposed  between  the  bodies  of  the  vertebrae  in 
being  thinner,  and  its  central  part  firmer  in  texture.  It  is  somewhat  thicker  in 
front  and  behind  than  at  the  sides.  Occasionally,  a  synovial  membrane  is  found 
and  the  coccyx  is  freely  movable.  This  is  especially  the  case  during  pregnancy. 

The  different  segments  of  the  coccyx  are  connected  together  by  an  extension 
downward  of  the  anterior  and  posterior  sacro-coccygeal  ligaments,  a  thin  annular 
disk  of  fibro-cartilage  being  interposed  between  each  of  the  bones.  In  the  adult 
male  all  the  pieces  become  ossified,  but  in  the  female  this  does  not  commonly 
occur  until  a  later  period  of  life.  The  separate  segments  of  the  "coccyx  are  first 
united,  and  at  a  more  advanced  age  the  joint  between  the  sacrum  and  coccyx  is 
obliterated. 

Actions. — The  movements  which  take  place  between  the  sacrum  and  coccyx, 
and  between  the  different  pieces  of  the  latter  bone,  are  forward  and  backward, 
and  are  very  limited.  Their  extent  increases  during  pregnancy. 


298 


THE  ARTICULATIONS    OR   JOINTS 


Hyaline  cartilage  covering  lone. 


Intermediate  fibro-cartilage. 
Cavity  at  upper 
and  back  part 


4.  ARTICULATION  OF  THE  OSSA  PUBIS  (SYMPHYSIS  OSSIUM  PUBIS)  (Figs.  213, 217). 

The  articulation  between  the  pubic  bones  is  an  amphiarthrodial  joint,  formed 
by  the  junction  of  the  two  oval  articular  surfaces  of  the  ossa  pubis.  The  liga- 
ments of  this  articulation  are  the 

Anterior  Pubic.  Superior  Pubic. 

Posterior  Pubic.  Inferior  Pubic. 

Interpubic  Disk. 

The  Anterior  Pubic  Ligament  (ligamentum  pubicum  anterius)  (Fig.  213)  consists 
of  several  superimposed  layers  which  pass  across  the  front  of  the  articulation.  The 
superficial  fibres  pass  obliquely  from  one  bone  to  the  other,  decussating  and  form- 
ing an  interlacement  with  the  fibres  of  the  aponeurosis  of  the  External  oblique  and 
the  tendon  of  the  Rectus  muscles.  The  deep  fibres  pass  transversely  across  the 
symphysis,  and  are  blended  with  the  fibro-cartilage. 

The"  Posterior  Pubic  Ligament  (ligamentum  pubicum  posterius)  consists  of  a 
few  thin,  scattered  fibres  which  unite  the  two  pubic  bones  posteriorly. 

The  Superior  Pubic  Ligament  (liga- 
mentum pubicum  super ius)  (Fig.  213) 
is  a  band  of  fibres  which  connects  to- 
gether the  two  pubic  bones  superiorly. 
The  Inferior  Pubic  or  Subpubic 
Ligament  (ligamentum  arcuatum 
pubis)  (Fig.  213)  is  a  thick,  tri- 
angular arch  of  ligamentous  fibres, 
connecting  together  the  two  pubic 
bones  below  and  forming  the  upper 
boundary  of  the  pubic  arch.  Above, 
it  is  blended  with  the  interarticular 
fibro-cartilage;  laterally  it  is  united 
with  the  descending  rami  of  the 
pubis.  Its  fibres  are  closely  con- 
nected and  have  an  arched  direction. 
Its  lower  margin  is  separated  from 
the  triangular  ligament  of  the  per- 
imeum  by  a  gap,  through  which  runs 
the  dorsal  vein  of  the  penis. 
The  Interpubic  Disk  (lamina  fibrocartilaginea  interpubicd)  (Fig.  217)  consists  of  a 
disk  of  cartilage  and  fibro-cartilage  connecting  the  surfaces  of  the  pubic  bones  in 
front.  Each  of  the  two  surfaces  is  covered  by  a  thin  layer  of  hyaline  cartilage  which 
is  firmly  connected  to  the  bone  by  a  series  of  nipple-like  processes  which  accu- 
rately fit  within  corresponding  depressions  on  the  osseous  surfaces.  These  opposed 
cartilaginous  surfaces  are  connected  together  by  an  intermediate  stratum  of  fibrous 
tissue  and  fibro-cartilage  which  varies  in  thickness  in  different  subjects.  It  often 
contains  a  cavity  (cavum  articulare)  in  its  centre,  probably  formed  by  the  soften- 
ing and  absorption  of  the  fibro-cartilage,  since  it  rarely  appears  before  the  tenth 
year  of  life,  and  is  not  lined  by  synovial  membrane.  It  is  larger  in  the  female 
than  in  the  male,  but  it  is  very  questionable  whether  it  enlarges,  as  was  formerly 
supposed,  during  pregnancy.  It  is  most  frequently  limited  to  the  upper  and  back 
part  of  the  joint,  but  it  occasionally  reaches  to  the  front,  and  may  extend  the 
entire  length  of  the  cartilage.  This  cavity  may  be  easily  demonstrated  by  making 
a  vertical  section  of  the  symphysis  pubis  near  its  posterior  surface  (Fig.  217). 

The  Obturator  Ligament  is  more  properly  regarded  as  analogous  to  the  muscular 
fasciae,  with  which  it  will  be  described. 


FIG.  217. — Vertical  section  of  the  symphysis  pubis. 
Made  near  its  posterior  surface. 


STERNO-CLA  VICULAR  ARTICULA TION 


299 


ARTICULATIONS  OF  THE  UPPER  EXTREMITY. 

The  articulations  of  the  upper  extremity  may  be  arranged  in  the  following 


groups : 

I.  Sterno-clavicular  Articulation. 
II.  Acromio-clavicular  Articulation. 

III.  Ligaments  of  the  Scapula. 

IV.  Shoulder-joint. 
V.  Elbow-joint. 

VI.  Radio-ulnar  Articulations. 


VII.  Wrist-joint. 

VIII.  Articulations  of  the  Carpal  Bones. 
IX.  Carpo-metacarpal  Articulations. 
X.  Metacarpo-phalangeal    Articula- 
tions. 
XI.  Articulations  of  the  Phalanges. 


I.  Sterno-clavicular  Articulation  (Articulatio  Sternoclavicularis)  (Fig.  218). 

The  sterno-clavicular  is  regarded  by  most  anatomists  as  an  arthrodial  joint, 
but  Cruveilhier  considers  it  to  be  an  articulation  by  reciprocal  reception.  Probably 


FIG.  218. — Sterno-clavicular  articulation.     Anterior  view. 


the  former  opinion  is  the  correct  one,  the  varied  movement  which  the  joint  enjoys 
being  due  to  the  interposition  of  an  interarticular  fibro-cartilage  between  the 
joint  surfaces.  The  parts  entering  into  its  formation  are  the  sternal  end  of  the 
clavicle,  the  upper  and  lateral  part  of  the  first  piece  of  the  sternum,  and  the 
cartilage  of  the  first  rib.  The  articular  surface  of  the  sternum  is  covered  with 
cartilage.  The  articular  surface  of  the  clavicle  is  much  larger  than  that  of  the 
sternum,  and  invested  with  a  layer  of  cartilage1  which  is  considerably  thicker  than 
that  on  the  latter  bone.  The  ligaments  of  this  joint  are  the 


Capsular. 

Anterior  Sterno-clavicular. 

Posterior  Sterno-clavicular. 


Interclavicular. 
Costo-clavicular. 
Interarticular  Fibro-cartilage. 


The  Capsular  Ligament  (capsida  articularis)  completely  surrounds  the  articula- 
tion, consisting  of  fibres  of  varying  degrees  of  thickness  and  strength.  Those  in 
front  and  behind  are  of  considerable  thickness,  and  form  the  anterior  and  posterior 
sterno-clavicular  ligaments;  but  those  above  and  below,  especially  in  the  latter 
situation,  are  thin  and  scanty,  and  partake  more  of  the  character  of  connective 
tissue  than  true  fibrous  tissue. 


1  Accprding  to  Bruch,  the  sternal  end  of  the  clavicle  is  covered  by  a  tissue  which  is  rather  fibrous  than 
cartilaginous  in  structure. — ED.  of  15th  English  Edition. 


300  THE  ARTICULATIONS    OR    JOINTS 

The  Anterior  Sterno -clavicular  Ligament  (ligamentum  sternoclaviculare)  (Fig.  218) 
is  a  part  of  the  capsule.  It  is  a  broad  band  of  fibres  which  covers  the  anterior  sur- 
face of  the  articulation,  being  attached,  above,  to  the  upper  and  front  part  of  the 
inner  extremity  of  the  clavicle,  and,  passing  obliquely  downward  and  inward, 
is  attached,  below,  to  the  upper  and  front  part  of  the  first  piece  of  the  sternum. 
This  ligament  is  covered,  in  front,  by  the  sternal  portion  of  the  Sterno-cleido- 
mastoid  and  the  integument;  behind,  it  is  in  relation  with  the  interarticular 
fibre-cartilage  and  the  two  synovial  membranes. 

The  Posterior  Sterno -clavicular  Ligament,  also  a  part  of  the  capsule,  is  a  band  of 
fibres  which  covers  the  posterior  surface  of  the  articulation,  being  attached,  above, 
to  the  upper  and  back  part  of  the  inner  extremity  of  the  clavicle,  and,  passing 
obliquely  downward  and  inward,  is  attached,  below,  to  the  upper  and  back  part 
of  the  first  piece  of  the  sternum.  It  is  in  relation,  in  front,  with  the  interartic- 
ular fibro-cartilage  and  synovial  membranes;  behind,  with  the  Sterno-hyoid  and 
Sterno-thyroid  muscles. 

The  Interclavicular  Ligament  (ligamentum  interdaviculare)  (Fig.  218)  is  a  flat- 
tened band  which  varies  considerably  in  form  and  size  in  different  individuals;  it 
passes  in  a  curved  direction  from  the  upper  part  of  the  inner  extremity  of  one 
clavicle  to  the  other,  and  is  also  attached  to  the  upper  margin  of  the  sternum.  It 
is  in  relation,  in  front,  with  the  integument;  behind,  with  the  Sterno-thyroid 
muscles. 

The  Costo-clavicular  or  Rhomboid  Ligament  (ligamentum  costoclaviculare) 
(Fig.  218)  is  short,  flat,  and  strong;  it  is  of  a  rhomboid  form,  attached,  below,  to 
the  upper  and  inner  part  of  the  cartilage  of  the  first  rib :  it  ascends  obliquely  back- 
ward and  outward,  and  is  attached,  above,  to  the  rhomboid  depression  on  the 
under  surface  of  the  clavicle.  It  is  in  relation,  in  front,  with  the  tendon  of 
origin  of  the  Subclavius;  behind,  with  the  subclavian  vein. 

The  Interarticular  Fibro-cartilage  (discus  articularis)  (Fig.  218)  is  a  flat  and  nearly 
circular  meniscus,  interposed  between  the  articulating  surfaces  of  the  sternum  and 
clavicle.  It  is  attached,  above,  to  the  upper  and  posterior  border  of  the  articular 
surface  of  the  clavicle;  below,  to  the  cartilage  of  the  first  rib,  at  its  junction  with  the 
sternum ;  and  by  its  circumference,  to  the  anterior  and  posterior  sterno-clavicular 
and  the  interclavicular  ligaments.  It  is  thicker  at  the  circumference,  especially 
its  upper  and  back  part,  than  at  its  centre  or  below.  It  divides  the  joint  into  two 
cavities,  each  of  which  is  furnished  with  a  separate  synovial  membrane. 

Synovial  Membrane. — Of  the  two  synovial  membranes  found  in  this  articulation, 
one  is  reflected  from  the  sternal  end  of  the  clavicle  over  the  adjacent  surface  of  the 
fibro-cartilage  and  cartilage  of  the  first  rib ;  the  other  is  placed  between  the  articular 
surface  of  the  sternum  and  adjacent  surface  of  the  fibro-cartilage;  the  latter  is  the 
larger  of  the  two. 

Actions. — This  articulation  is  the  centre  of  the  movements  of  the  shoulder,  and 
admits  of  a  limited  amount  of  motion  in  nearly  every  direction — upward,  down- 
ward, backward,  forward — as  well  as  circumduction.  When  these  movements  take 
place  in  the  joint,  the  clavicle  in  its  motion  carries  the  scapula  with  it,  this  bone 
gliding  on  the  outer  surface  of  the  chest.  This  joint  therefore  forms  the  centre 
from  which  all  movements  of  the  supporting  arch  of  the  shoulder  originate,  and 
is  the  only  point  of  articulation  of  this  part  of  the  skeleton  with  the  trunk.  "The 
movements  attendant  on  elevation  and  depression  of  the  shoulder  take  place 
between  the  clavicle  and  the  interarticular  fibro-cartilage,  the  bone  rotating  upon 
the  ligament  on  an  axis  drawn  from  before  backward  through  its  own  articular 
facet.  When  the  shoulder  is  moved  forward  and  backward,  the  clavicle,  with 
the  interarticular  fibro-cartilage,  rolls  to  and  fro  on  the  articular  surface  of  the 
sternum,  revolving,  with  a  sliding  movement,  round  an  axis  drawn  nearly  vertically 
through  the  sternum.  In  the  circumduction  of  the  shoulder,  which  is  compounded 


ACROMIO-CLAVICULAR    ARTICULATION  301 

of  these  two  movements,  the  clavicle  revolves  upon  the  interarticular  fibre-carti- 
lage, and  the  latter,  with  the  clavicle,  rolls  upon  the  sternum."1  Elevation  of  the 
clavicle  is  principally  limited  by  the  costo-clavicular  ligament;  depression  by  the 
interclavicular.  The  muscles  which  raise  the  clavicle,  as  in  shrugging  the  shoulder, 
are  the  upper  fibres  of  the  Trapezius,  the  Levator  anguli  scapula*,  the  clavicular 
head  of  the  Sterno-mastoid,  assisted  to  a  certain  extent  by  the  two  Rhomboids, 
which  pull  the  vertebral  border  of  the  Scapula  backward  and  upward,  and  so 
raise  the  clavicle.  The  depression  of  the  clavicle  is  principally  effected  by  gravity, 
assisted  by  the  Subclavius,  Pectoralis  minor,  and  lower  fibres  of  the  Trapezius. 
It  is  drawn  backward  by  the  Rhomboids  and  the  middle  and  lower  fibres  of  the 
Trapezius;  and  forward  by  the  Serratus  magnus  and  Pectoralis  minor. 

Surface  Form. — The  position  of  the  sterno-clavicular  joint  may  be  easily  ascertained  by  feel- 
ing the  enlarged  sternal  end  of  the  collar-bone  just  external  to  the  long,  cord-like,  sternal  origin 
of  the  Sterno-mastoid  muscle.  If  this  muscle  is  relaxed  by  bending  the  head  forward,  a  depres- 
sion just  internal  to  the  end  of  the  clavicle,  and  between  it  and  the  sternum,  can  be  felt,  indi- 
cating the  exact  position  of  the  joint,  which  is  subcutaneous.  When  the  arm  hangs  by  the  side, 
the  cavity  of  the  joint  is  V-shaped.  If  the  arm  is  raised,  the  bones  become  more  closely  approx- 
imated, and  the  cavity  becomes  a  mere  slit. 

Surgical  Anatomy. — The  strength  of  this  joint  mainly  depends  upon  its  ligaments,  and 
it  is  because  of  the  ligaments  and  because  the  force  of  a  blow  is  generally  transmitted  along  the 
long  axis  of  the  clavicle,  that  dislocation  so  rarely  occurs,  and  that  the  bone  is  generally  broken 
rather  than  displaced.  When  dislocation  does  occur,  the  course  which  the  displaced  bone  takes 
depends  more  upon  the  direction  in  which  the  violence  was  applied  than  upon  the  anatomical 
construction  of  the  joint;  it  may  be  either  forward,  backward,  or  upward.  A  complete  upward 
dislocation  is  also  inward.  A  complete  forward  or  backward  dislocation  is  also  inward  and 
downward.  The  chief  point  worthy  of  note,  as  regards  the  construction  of  the  joint,  in  regard 
to  dislocations,  is  the  fact  that,  owing  to  the  shape  of  the  articular  surfaces  being  so  little 
adapted  to  each  other,  and  that  the  strength  of  the  joint  mainly  depends  upon  the  ligaments, 
the  displacement  when  reduced  is  very  liable  to  recur,  and  hence  it  is  extremely  difficult  to 
keep  the  end  of  the  bone  in  its  proper  place,  and  it  may  be  necessary  to  incise  the  soft  parts 
and  wire  the  bone  in  place. 

II.  Acromio-clavicular  Articulation  or  Scapulo-clavicular  Articulation 
(Articulatio  Acromioclavicularis)  (Fig.  219). 

The  acromio-clavicular  IT  an  arthrodial  joint  formed  between  the  outer  extrem- 
ity of  the  clavicle  and  the  inner  margin  of  the  acromion  process  of  the  scapula. 
The  ligaments  which  surround  the  joint  form  a  capsule.  The  ligaments  of  this 
articulation  are  the 

Superior  Acromio-clavicular.  f  Trapezoid. 

Inferior  Acromio-clavicular.  Coraco-clavicular  <       and 

Interarticular  Fibro-cartilage.  (  Conoid. 

The  Superior  Acromio-clavicular  Ligament  (lig amentum  acromioclaviculare}  (Figs. 
219  and  220)  is  a  portion  of  the  joint  capsule.  It  is  a  quadrilateral  band  which 
covers  the  superior  part  of  the  articulation,  extending  between  the  upper  part  of 
the  outer  end  of  the  clavicle  and  the  adjoining  part  of  the  upper  surface  of  the 
acromion.  It  is  composed  of  parallel  fibres  which  interlace  with  the  aponeurosis 
of  the  Trapezius  and  Deltoid  muscles;  below,  it  is  in  contact  with  the  inter- 
articular  fibro-cartilage  (when  it  exists)  and  the  synovial  membranes. 

The  Inferior  Acromio-clavicular  Ligament,  somewhat  thinner  than  the  pre- 
ceding, and  like  it  a  portion  of  the  capsule,  covers  the  under  part  of  the  articula- 
tion, and  is  attached  to  the  adjoining  surfaces  of  the  two  bones.  It  is  in  relation, 
above,  with  the  synovial  membranes,  and  in  rare  cases  with  the  interarticular 
fibro-cartilage;  below,  with  the  tendon  of  the  Supraspinatus.  These  two  liga- 

1  Humphry.    On  the  Human  Skeleton,  p.  402. 


302 


THE    ARTICULATIONS    OR    JOINTS 


ments  are  continuous  with  each  other  in  front  and  behind,  and  form  a  complete 
capsule  round  the  joint. 

The  Interarticular  Fibro-cartilage  (discus  articularis)  is  frequently  absent  in  this 
articulation.  When  the  meniscus  exists  it  is  generally  incomplete  and  only  par- 
tially separates  the  articular  surfaces,  and  occupies  the  upper  part  of  the  articu- 
lation. More  rarely  it  completely  separates  the  joint  into  two  cavities. 


^"•'-•.mrt  x-^ 
'IG.  219. — The  left  shoulder-joint,  scapulo-clavicular  articulations,  and  proper  ligaments  of  scapula. 


The  Synovial  Membrane. — There  is  usually  only  one  sy  no  vial  membrane  in 
this  articulation,  but  when  a  complete  interarticular  fibre-cartilage  exists  there  are 
two  synovial  membranes. 

The  Coraco-clavicular  Ligament  (ligamentum  coracoclaviculare)  (Figs.  219  and 
220)  serves  to  connect  the  clavicle  with  the  coracoid  process  of  the  scapula.  It  does 
not  properly  belong  to  this  articulation,  but  as  it  forms  a  most  efficient  means  in 
retaining  the  clavicle  in  contact  with  the  acromial  process,  it  is  usually  described 
with  it.  It  consists  of  two  fasciculi,  called  the  trapezoid  and  conoid  ligaments. 

The  trapezoid  ligament  (ligamentum  trapezoideum] ,  the  anterior  and  external 
fasciculus,  is  broad,  thin,  and  quadrilateral;  it  is  placed  obliquely  between  the 
coracoid  process  and  the  clavicle.  It  is  attached,  below,  to  the  upper  surface 
of  the  coracoid  process ;  above,  to  the  oblique  line  on  the  under  surface  of  the 
•clavicle.  Its  anterior  border  is  free ;  its  posterior  border  is  joined  with  the  conoid 
ligament,  the  two  forming  by  their  junction  a  projecting  angle. 

The  conoid  ligament  (ligamentum  conoideum),  the  posterior  and  internal  fas- 
ciculus, is  a  dense  band  of  fibres,  conical  in  form,  the  base  being  directed  upward, 
the  summit  downward.  It  is  attached  by  its  apex  to  a  rough  impression  at  the 
base  of  the  coracoid  process,  internal  to  the  preceding;  above,  by  its  expanded 


PROPER   LIGAMENTS    OF   THE  SCAPULA  393 

base,  to  the  conoid  tubercle  on  the  under  surface  of  the  clavicle,  and  to  a  line 
proceeding  internally  from  it  for  half  an  inch.  These  ligaments  are  in  relation, 
in  front,  with  the  Subclavius  and  Deltoid;  behind,  with  the  Trapezius.  They 
serve  to  limit  rotation  of  the  scapula,  the  Trapezoid  limiting  rotation  forward, 
and  the  Conoid  backward. 

Actions. — The  movements  of  this  articulation  are  of  two  kinds:  1.  A  gliding 
motion  of  the  articular  end  of  the  clavicle  on  the  acromion.  2.  Rotation  of  the 
scapula  forward  and  backward  upon  the  clavicle,  the  extent  of  this  rotation  being 
limited  by  the  two  portions  of  the  coraco-clavicular  ligament. 

The  acromio-clavicular  joint  has  important  functions  in  the  movements  of  the 
upper  extremity.  It  has  been  well  pointed  out  by  Sir  George  Humphry  that  if 
there  had  been  no  joint  between  the  clavicle  and  scapula  the  circular  movement  of 
the  scapula  on  the  rfbs  (as  in  throwing  both  shoulders  backward  or  forward)  would 
have  been  attended  with  a  greater  alteration  in  the  direction  of  the  shoulder  than  is 
consistent  with  the  free  use  of  the  arm  in  such  position,  and  it  would  have  been 
impossible  to  give  a  blow  straight  forward  with  the  full  force  of  the  arm;  that  is  to 
say,  with  the  combined  force  of  the  scapula,  arm,  and  forearm.  "This  joint,"  as 
he  happily  says,  "is  so  adjusted  as  to  enable  either  bone  to  turn  in  a  hinge-like 
manner  upon  a  vertical  axis  drawn  through  the  other,  and  it  permits  the  surfaces 
of  the  scapula,  like  the  baskets  in  a  roundabout  swing,  to  look  the  same  way  in 
every  position  or  nearly  so."  Again,  when  the  whole  arch  formed  by  the  clavicle 
and  scapula  rises  and  falls  (in  elevation  or  depression  of  the  shoulders),  the  joint 
between  these  two  bones  enables  the  scapula  still  to  maintain  its  lower  part  in 
contact  with  the  ribs. 

Surface  Form. — The  position  of  the  acromio-clavicular  joint  can  generally  be  ascertained  by 
the  slightly  enlarged  extremity  of  the  outer  end  of  the  clavicle,  which  causes  it  to  project  above 
the  level  of  the  acromion  process  of  the  scapula.  Sometimes  this  enlargement  is  so  considerable 
as  to  form  a  rounded  eminence,  which  is  easily  to  be  felt.  The  joint  lies  in  the  plane  of  a  ver- 
tical line  passing  up  the  middle  of  the  front  of  the  arm. 

Surgical  Anatomy. — Owing  to  the  slanting  shape  of  the  articular  surfaces  of  this  joint, 
the  commonest  dislocation  is  the  passing  of  the  acromion  process  of  the  scapula  under  the 
outer  end  of  the  clavicle;  but  dislocations  in  the  opposite  direction  have  been  described.  The 
first  form  of  dislocation  is  produced  by  violent  force  applied  to  the  scapula  so  as  to  drive  the 
shoulder  forward.  The  displacement  in  acromio-clavicular  dislocation  is  often  incomplete,  on 
account  of  the  strong  coraco-clavicular  ligaments  which  remain  untorn.  The  same  difficulty 
exists,  as  in  the  sterno-clavicular  dislocation,  in  maintaining  the  ends  of  the  bone  in  apposition  after 
reduction,  and  it  may  become  necessary  to  wire  them  in  place  after  incision  of  the  soft  parts. 

HI.  Proper  Ligaments  of  the  Scapula  (Figs.  219, 220). 

The  proper  ligaments  of  the  scapula  pass  between  portions  of  that  bone,  but 
are  not  parts  of  an  articulation.  They  are  the 

Coraco-acromial.  Superior  Transverse. 

Inferior  Transverse. 

The  Coraco-acromial  Ligament  (ligamentum  coracoacromiale)  is  a  strong  trian- 
gular band,  extending  between  the  coracoid  and  acromial  processes.  It  is  attached, 
by  its  apex,  to  the  summit  of  the  acromion  just  in  front  of  the  articular  surface 
for  the  clavicle,  and  by  its  broad  base  to  the  whole  length  of  the  outer  border  of 
the  coracoid  process.  Its  posterior  fibres  are  directed  inward,  its  anterior  fibres 
forward  and  inward.  This  ligament  completes  the  vault  formed  by  the  coracoid  and 
acromion  processes  for  the  protection  of  the  head  of  the  humerus.  It  is  in  relation, 
above,  with  the  clavicle  and  under  surface  of  the  Deltoid  muscle ;  below,  with  the 
tendon  of  the  Supraspinatus  muscle,  a  bursa  being  interposed.  Its  outer  border  is 
continuous  with  a  dense  lamina  that  passes  beneath  the  Deltoid  upon  the  tendons 


304 


THE   ARTICULATIONS    OR    JOINTS 


of  the  Supra-  and  Infraspinatus  muscles.  This,ligament  is  sometimes  described  as 
consisting  of  two  marginal  bands  and  a  thinner  intervening  portion,  the  two  bands 
being  attached  respectively  to  the  apex  and  base  of  the  coracoid  process,  and  join- 
ing together  at  their  attachment  into  the  acromion  process.  When  the  Pectoralis 
minor  is  inserted,  as  sometimes  is  the  case,  into  the  capsule  of  the  shoulder-joint 
instead  of  into  the  coracoid  process,  it  passes  between  these  two  bands,  and  the 
intervening  portion  is  then  deficient. 

The  Superior  Transverse,  Coracoid  or  Suprascapular  Ligament  (ligamentum  trans- 
versum  scapulae  superius)  (Figs.  219,  220,  and  222)  converts  the  suprascapular 


SUPERIOR 

ACROMIOCLAVICULAR 
LIGAMENT 


GLENOID 
LIGAMENT 


FIG.  220. — Right  clavicle  and  shoulder-blade  with  ligament,  from  without  and  somewhat  from  in  front. 

(Spalteholz.,) 

notch  into  a  foramen.  It  is  a  thin  and  flat  fasciculus,  narrower  at  the  middle 
than  at  the  extremities,  attached  by  one  end  to  the  base  of  the  coracoid  process, 
and  by  the  other  to  the  inner  extremity  of  the  scapular  notch.  The  suprascapular 
nerve  passes  through  the  foramen;  the  suprascapular  vessels  pass  over  the  liga- 
ment. 

An  additional  ligament,  the  Inferior  Transverse  or  Spino-glenoid  Ligament  (liga- 
mentum transversum  scapulae  inferius),  is  sometimes  found  on  the  scapula,  stretch- 
ing from  the  outer  border  of  the  spine  to  the  margin  of  the  glenoid  cavity.  When 
present,  it  forms  an  arch  under  which  the  suprascapular  vessels  and  nerve  pass  as 
they  enter  the  infraspinous  fossa. 

Movements  of  Scapula. — The  scapula  is  capable  of  being  moved  upward  and 
downward,  forward  and  backward,  or,  by  a  combination  of  these  movements,  cir- 
cumducted  on  the  wall  of  the  chest.  The  muscles  which  raise  the  scapula  are  the 
upper  fibres  of  the  Trapezius,  the  Levator  anguli  scapulre,  and  the  two  Rhom- 
boids; those  which  depress  it  are  the  lower  fibres  of  the  Trapezius,  the  Pectoralis 
minor,  and,  through  the  clavicle,  the  Subclavius.  The  scapula  is  drawn  backivard 
by  the  Rhomboids  and  the  middle  and  lower  fibres  of  the  Trapezius,  and  forward 


THE  SHOULDER- JOINT 


305 


by  the  Serratus  magnus  and  Pectoralis  minor,  assisted,  when  the  arm  is  fixed,  by 
the  Pectoralis  major.  The  mobility  of  the  scapula  is  very  considerable,  and 
greatly  assists  the  movements  of  the  arm  at  the  shoulder-joint.  Thus,  in  raising 
the  arm  from  the  side  the  Deltoid  and  Supraspinatus  can  only  lift  it  to  a  right 


CORACO-ACRO 

LIGAME 
DELTOID 


MOID    LIGAMENT. 


BICEPS. 
MIAL    1      GLS 

"LaW^- 

M^V§S§£ 

V  £ .-  • :. 


DELTOID.      SUPRA-SPINATUS. 


TERES     MAJOR. 


SUB- 
SCAPULA- 

RIS. 
TRICEPS. 


TRICEPS. 


TERES  MAJOR.      Circumflex  vessels.  •  Circumflex  vessels.  SCAPULARIS. 

FIG.  221. — Vertical  sections  through  the  shoulder-joint,  the  arm  being  vertical  and  horizontal.     (After  Henle.) 

angle  with  the  trunk,  the  further  elevation  of  the  limb  being  effected  by  the 
Trapezius  and  Serratus  magnus  moving  the  scapula  on  the  wall  of  the  chest. 
This  mobility  is  of  special  importance  in  ankylosis  of  the  shoulder-joint,  the 
movement  of  this  bone  compensating  to  a  very  great  extent  for  the  immobility 
of  the  joint. 

IV.  The  Shoulder-joint  (Articulatio  Humeri)  (Figs.  219,  220,  221,  222). 

The  shoulder  is  an  enarthrodial  or  ball-and-socket  joint.  The  bones  entering 
into  its  formation  are  the  large  globular  head  of  the  humerus,  which  is  received 
into  the  shallow  glenoid  cavity  of  the  scapula — an  arrangement  which  permits  of 
very  considerable  movement,  whilst  the  joint  itself  is  protected  against  displace- 
ment by  the  tendons  which  surround  it  and  by  atmospheric  pressure.  The  liga- 
ments do  not  maintain  the  joint  surfaces  in  apposition,  because  when  they  alone 
remain  the  humerus  can  be  separated  to  a  considerable  extent  from  the  glenoid 
cavity ;  their  use,  therefore,  is  to  limit  the  amount  of  movement.  Above,  the  joint 
is  protected  by  an  arched  vault,  formed  by  the  under  surfaces  of  the  coracoid  and 
acromion  processes,  and  the  coraco-acromial  ligament.  The  articular  surfaces 
are  covered  by  a  layer  of  cartilage :  that  on  the  head  of  the  humerus  is  thicker  at 
the  centre  than  at  the  circumference,  the  reverse  being  the  case  in  the  glenoid 
cavity.  The  ligaments  of  the  shoulder  are  the 

Capsular.  Transverse  humeral. 

Coraco-humeral.  Glenoid.1 

The  Capsular  Ligament  (capsida  articularis)  (Figs.  219,  220,  and  222)  completely 
encircles  the  articulation,  being  attached,  above,  to  the  circumference  of  the  glenoid 
cavity  beyond  the  glenoid  ligament,  below,  to  the  anatomical  neck  of  the  humerus, 
approaching  nearer  to  the  articular  cartilage  above  than  in  the  rest  of  its  extent. 
It  is  thicker  above  and  below  than  elsewhere,  and  is  remarkably  loose  and  lax,  and 

1  The  long  tendon  of  origin  of  the  Biceps  muscle  also  acts  as  one  of  the  ligaments  of  this  joint.  See  the 
observations  on  p.  270  on  the  function  of  the  muscles  passing  over  more  than  one  joint. — ED.  of  15th  English 
Edition. 

20  . 


306 


THE  ARTICULATIONS    OR    JOINTS 


much  larger  and  longer  than  is  necessary  to  keep  the  bones  in  contact,  allowing 
them  to  be  separated  from  each  other  more  than  an  inch — an  evident  provision 
for  that  extreme  freedom  of  movement  which  is  peculiar  to  this  articulation.  Its 
superficial  surface  is  strengthened,  above,  by  the  Supraspinatus ;  below,  by  the 
long  head  of  the  Triceps;  behind,  by  the  tendons  of  the  Infraspinatus  and  Teres 
minor;  and  in  front,  by  the  tendon  of  the  Subscapularis.  The  capsular  ligament 
usually  presents  three  openings:  One  anteriorly,  below  the  coracoid  process, 
establishes  a  communication  between  the  synovial  membrane  of  the  joint  and  a 


ARTICULAR 
CAPSULE 


LONG  HEAD  OF 
BICEPS  MUSCLE 


SUPERIOR 

TRANSVERSE 

LIGAMENT 


SPINE  OF   SCAPULA       „„„ 

(sawed  off  at  its  origin)  % 


FIG.  222. — Right  shoulder- joint,  frontal  section,  from  behind.     (Spalteholz.) 

bursa  beneath  the  tendon  of  the  Subscapularis  muscle.  The  second,  which  is 
not  constant,  is  at  the  posterior  part,  where  a  communication  sometimes  exists 
between  the  joint  and  a  bursal  sac  belonging  to  the  Infraspinatus  muscle.  The 
third  is  seen  between  the  two  tuberosities,  for  the  passage  of  the  long  tendon 
of  the  Biceps  muscle.  It  transmits  a  sac-like  prolongation  of  the  synovial 
membrane,  which  ends  as  a  blind  pouch  opposite  the  surgical  neck  of  the  bone. 
This  synovial  sac  is  called  the  vagina  mucosa  intertubercularis. 

The  Coraco-humeral  Ligament  (ligamentum  coracohumerale)  (Fig.  219)  is  a  broad 
band  which  strengthens  the  upper  part  of  the  capsular  ligament.  It  arises  from 
the  outer  border  of  the  coracoid  process,  and  passes  obliquely  downward  and  out- 
ward to  the  front  of  the  great  tuberosity  of  the  humerus,  being  blended  with  the 
tendon  of  the  Supraspinatus  muscle.  This  ligament  is  intimately  united  to  the 
capsular  ligament  throughout  the  greater  part  of  its  extent. 

Supplemental  Bands  of  the  Capsular  Ligament. — In  addition  to  the  coraco- 
humeral  ligament,  the  capsular  ligament  is  strengthened  by  supplemental  bands  in 
the  interior  of  the  joint.  One  of  these  bands  is  situated  on  the  inner  side  of  the 
joint,  and  passes  from  the  inner  edge  of  the  glenoid  cavity  to  the  lower  part  of  the 
lesser  tuberosity  of  the  humerus.  This  is  sometimes  known  as  Flood's  ligament, 


THE  SHOULDER -JOINT  307 

and  is  supposed  to  correspond  with  the  ligamentum  teres  of  the  hip-joint.  A 
second  of  these  bands  is  situated  at  the  lower  part  of  the  joint,  and  passes  from  the 
under  edge  of  the  glenoid  cavity  to  the  under  part  of  the  neck  of  the  humerus,  and 
is  known  as  Schlemm's  ligament.  A  third,  called  the  gleno-humeral  ligament,  is 
situated  at  the  upper  part  of  the  joint,  and  projects  into  its  interior,  so  that  it  can 
be  seen  only  when  the  capsule  is  opened.  It  is  attached  above  to  the  apex  of  the 
glenoid  cavity,  close  to  the  root  of  the  coracoid  process,  and,  passing  downward 
along  the  inner  edge  of  the  tendon  of  the  Biceps,  is  attached  below  to  the  lesser 
tuberosity  of  the  humerus,  where  it  forms  the  inner  boundary  of  the  upper  part  of 
the  bicipital  groove.  It  is  a  thin,  ribbon-like  band,  occasionally  quite  free  from 
the  capsule. 

The  Transverse  Humeral  Ligament  is  a  prolongation  of  the  capsular  ligament. 
It  is  a  broad  band  of  fibrous  tissue  passing  from  the  lesser  to  the  greater  tuber- 
osity of  the  humerus,  and  always  limited  to  that  portion  of  the  bone  which  lies 
above  the  epiphysial  line.  It  converts  the  bicipital  groove  into  an  osseo-aponeu- 
rotic  canal,  and  is  the  analogue  of  the  strong  process  of  bone  which  connects  the 
summits  of  the  two  tuberosities  in  the  musk  ox. 

The  Glenoid  Ligament  (labrum  glenoidale)  (Figs.  220  and  222)  is  a  fibro- 
cartilaginous  rim,  attached  round  the  margin  of  the  glenoid  cavity.  It  is  trian- 
gular on  section,  the  thickest  portion  being  fixed  to  the  circumference  of  the  cavity, 
the  free  edge  being  thin  and  sharp.  It  is  continuous  above  with  the  long  tendon 
of  the  Biceps  muscle,  which  bifurcates  at  the  upper  part  of  the  cavity  into  two 
fasciculi,  and  becomes  continuous  with  the  fibrous  tissue  of  the  glenoid  ligament. 
This  ligament  deepens  the  cavity  for  articulation,  and  protects  the  edges  of  the 
bone.  It  is  lined  by  the  synovial  membrane. 

Synovial  Membrane  (Fig.  222). — The  synovial  membrane  is  reflected  from  the 
margin  of  the  glenoid  cavity  over  the  fibro-cartilaginous  rim  surrounding  it:  it  is 
then  reflected  over  the  internal  surface  of  the  capsular  ligament,  covers  the  lower 
part  and  sides  of  the  anatomical  neck  of  the  humerus  as  far  as  the  cartilage  cover- 
ing the  head  of  the  bone.  The  long  tendon  of  the  Biceps  muscle  which  passes 
through  the  capsular  ligament  is  enclosed  in  a  tubular  sheath  of  synovial  membrane 
(vagina  mucosa  intertubercularis) ,  which  is  reflected  upon  it  at  the  point  where  it 
perforates  the  capsule,  and  is  continued  around  it  as  far  as  the  level  of  the  surgical 
neck  of  the  humerus.  The  tendon  of  the  Biceps  is  thus  enabled  to  traverse  the 
articulation,  but  it  is  not  contained  in  the  interior  of  the  synovial  cavity. 

Bursae. — A  large  bursa  exists  between  the  joint  capsule  and  the  tendon  of  the 
Subscapularis  muscle.  It  is  called  the  subscapular  bursa.  This  sac  communicates 
with  the  shoulder-joint  by  means  of  an  opening  at  the  inner  side  of  the  capsular 
ligament.  The  subscapular  bursa  is  constant.  Occasionally  another  and  smaller 
bursa  exists  beneath  the  tendon  of  the  infraspinatus.  It  is  called  the  infraspinatus 
bursa,  and  communicates  with  the  shoulder-joint  by  means  of  an  opening  in  the  outer 
surface  of  the  capsule.  The  subdeltoid  or  subacromial  bursa  is  placed  between  the 
under  surface  of  the  Deltoid  muscle  and  the  outer  surface  of  the  capsule.  It  does 
not  communicate  with  the  joint.  The  subcutaneous  acromial  bursa  is  between  the 
surface  and  the  summit  of  the  acromion  process.  There  is  a  bursa  beneath 
the  Coraco-brachialis  muscle — one  beneath  the  teres  major — and  one  beneath 
the  tendinous  portion  of  the  latissimus  dorsi.  There  is  also  a  bursa  between  the 
tendon  of  insertion  of  the  Pectoralis  major  muscle  and  the  long  head  of  the 
biceps. 

The  Muscles  in  relation  with  the  joint  are,  above,  the  Supraspinatus ;  below,  the 
long  head  of  the  Triceps;  in  front,  the  Subscapularis;  behind,  the  Infraspinatus 
and  Teres  minor;  within,  the  long  tendon  of  the  Biceps.  The  Deltoid  is  placed 
most  externally,  and  covers  the  articulation  on  its  outer  side,  as  well  as  in  front 
and  behind. 


308  THE   ARTICULATIONS    OR    JOINTS 

The  Arteries  supplying  the  joint  are  articular  branches  of  the  anterior  and 
posterior  circumflex,  and  the  suprascapular. 

The  Nerves  are  derived  from  the  circumflex  and  suprascapular. 

Actions. — The  shoulder-joint  is  capable  of  movement  in  every  direction,  forward, 
backward,  abduction,  adduction,  circumduction,  and  rotation.  The  humerus  is 
drawn  forward  by  the  Pectoralis  major,  anterior  fibres  of  the  Deltoid,  Coraco- 
brachialis,  and  by  the  Biceps  when  the  forearm  is  flexed ;  backward,  by  the  Latis- 
simus  dorsi,  Teres  major,  posterior  fibres  of  the  Deltoid,  and  by  the  Triceps  when 
the  forearm  is  extended;  it  is  abducted  (elevated)  by  the  Deltoid  and  Supraspinatus; 
it  is  adducted  (depressed)  by  the  Subscapularis,  Pectoralis  major,  Latissimus  dorsi, 
and  Teres  major;  it  is  rotated  outward  by  the  Infraspinatus  and  Teres  minor; 
and  it  is  rotated  inward  by  the  Subscapularis,  Latissimus  dorsi,  Teres  major,  and 
Pectoralis  major. 

The  most  striking  peculiarities  in  this  joint  are:  1.  The  large  size  of  the  head 
of  the  humerus  in  comparison  with  the  depth  of  the  glenoid  cavity,  even  when 
supplemented  by  the  glenoid  ligament.  2.  The  looseness  of  the  capsule  of  the 
joint.  3.  The  intimate  connection  of  the  capsule  with  the  muscles  attached  to  the 
head  of  the  humerus.  4.  The  peculiar  relation  of  the  biceps  tendon  to  the  joint. 

It  is  in  consequence  of  the  relative  size  of  the  two  articular  surfaces  that  the 
joint  enjoys  such  free  movement  in  every  possible  direction.  When  these  move- 
ments of  the  arm  are  arrested  in  the  shoulder-joint  by  the  contact  of  the  bony  sur- 
faces and  by  the  tension  of  the  corresponding  fibres  of  the  capsule,  together  with 
that  of  the  muscles  acting  as  accessory  ligaments,  they  can  be  carried  considerably 
farther  by  the  movements  of  the  scapula,  involving,  of  course,  motion  at  the 
acromio-  and  sterno-clavicular  joints.  These  joints  are  therefore  to  be  regarded 
as  accessory  structures  to  the  shoulder-joint.1  The  extent  of  these  movements  of 
the  scapula  is  very  considerable,  especially  in  extreme  elevation  of  the  arm,  which 
movement  is  best  accomplished  when  the  arm  is  thrown  somewhat  forward  and 
outward,  because  the  margin  of  the  head  of  the  humerus  is  by  no  means  a  true 
circle;  its  greatest  diameter  is  from  the  bicipital  groove  downward,  inward,  and 
backward,  and  the  greatest  elevation  of  the  arm  can  be  obtained  by  rolling  its 
articular  surface  in  the  direction  of  the  measurement.  The  great  width  of  the 
central  portion  of  the  humeral  head  also  allows  of  very  free  horizontal  movement 
when  the  arm  is  raised  to  a  right  angle,  in  which  movement  the  arch  formed  by  the 
acromion,  the  coracoid  process,  and  the  coraco-acromial  ligament  constitutes  a 
sort  of  supplemental  articular  cavity  for  the  head  of  the  bone. 

The  looseness  of  the  capsule  is  so  great  that  the  arm  will  fall  about  an  inch 
from  the  scapula  when  the  muscles  are  dissected  from  the  capsular  ligament  and 
an  opening  made  in  it  to  remove  the  atmospheric  pressure.  The  movements  of 
the  joint,  therefore,  are  not  regulated  by  the  capsule  so  much  as  by  the  surrounding 
muscles  and  by  the  pressure  of  the  atmosphere — an  arrangement  which  "renders 
the  movements  of  the  joint  much  more  easy  than  they  would  otherwise  have  been, 
and  permits  a  swinging,  pendulum-like  vibration  of  the  limb  when  the  muscles 
are  at  rest"  (Humphry).  The  fact,  also,  that  in  all  ordinary  positions  of  the  joint 
the  capsule  is  not  put  on  the  stretch  enables  the  arm  to  move  freely  in  all  direc- 
tions. Extreme  movements  are  checked  by  the  tension  of  appropriate  portions  of 
the  capsule,  as  well  as  by  the  interlocking  of  the  bones.  Thus  it  is  said  that 
"  abduction  is  checked  by  the  contact  of  the  great  tuberosity  with  the  upper  edge  of 
the  glenoid  cavity,  adduction  by  the  tension  of  the  coraco-humeral  ligament" 
(Beaunis  et  Bouchard).  Cleland2  maintains  that  the  limitations  of  movement  at 
the  shoulder-joint  are  due  to  the  structure  of  the  joint  itself,  the  glenoid  ligament 
fitting,  in  different  positions  of  the  elevated  arm,  into  the  anatomical  neck  of  the 
humerus. 

1  See  p.  303.  2  Journal  of  Anatomy  and  Physiology,  1884,  vol.  xviii. 


THE  SHOULDER -JOINT  399 

Cathcart1  has  pointed  out  that  in  abducting  the  arm  and  raising  it  above  the 
head,  the  scapula  rotates  throughout  the  whole  movement  with  the  exception  of 
a  short  space  at  the  beginning  and  at  the  end;  that  the  humerus  moves  on  the 
scapula  not  only  from  the  hanging  to  the  horizontal  position,  but  also  in  passing 
upward  as  it  approaches  the  vertical  above;  that  the  clavicle  moves  not  only 
during  the  second  half  of  the  movement  but  in  the  first  as  well,  though  to  a  less 
extent — i.  e.,  the  scapula  and  clavicle  are  concerned  in  the  first  stage  as  well  as  in 
the  second;  and  that  the  humerus  is  partly  involved  in  the  second  as  well  as 
chiefly  in  the  first. 

The  intimate  union  of  the  tendons  of  the  four  short  muscles  with  the  capsule 
converts  these  muscles  into  elastic  and  spontaneously  acting  ligaments  of  the  joint, 
and  it  is  regarded  as  being  also  intended  to  prevent  the  folds  into  which  all  portions 
of  the  capsule  would  alternately  fall  in  the  varying  positions  of  the  joint  from  being 
driven  between  the  bones  by  the  pressure  of  the  atmosphere. 

The  peculiar  relations  of  the  Biceps  tendon  to  the  shoulder-joint  appear  to  sub- 
serve various  purposes.  In  the  first  place,  by  its  connection  with  both  the  shoulder 
and  elbow  the  muscle  harmonizes  the  action  of  the  two  joints,  and  acts  as  an 
elastic  ligament  in  all  positions,  in  the  manner  previously  adverted  to.2  Next,  it 
strengthens  the  upper  part  of  the  articular  cavity,  and  prevents  the  head  of  the 
humerus  from  being  pressed  up  against  the  acromion  process,  when  the  Deltoid 
contracts,  instead  of  forming  the  centre  of  motion  in  the  glenoid  cavity.  By  its 
passage  along  the  bicipital  groove  it  assists  in  rendering  the  head  of  the  humerus 
steady  in  the  various  movements  of  the  arm.  When  the  arm  is  raised  from  the 
side  it  assists  the  Supra-  and  Infraspinatus  in  rotating  the  head  of  the  humerus  in 
the  glenoid  cavity.  It  also  holds  the  head  of  the  bone  firmly  in  contact  with  the 
glenoid  cavity,  and  prevents  its  slipping  over  its  lower  edge,  or  being  displaced  by 
the  action  of  the  Latissimus  dorsi  and  Pectoralis  major,  as  in  climbing  and  many 
other  movements. 

Surface  Form. — The  direction  and  position  of  the  shoulder-joint  may  be  indicated  by  a  line 
drawn  from  the  middle  of  the  coraco-acromial  ligament,  in  a  curved  direction,  with  its  con- 
vexity inward,  to  the  innermost  part  of  that  portion  of  the  head  of  the  humerus  which  can  be 
felt  in  the  axilla  when  the  arm  is  forcibly  abducted  from  the  side.  When  the  arm  hangs  by  the 
side,  not  more  than  one-third  of  the  head  of  the  bone  is  in  contact  with  the  glenoid  cavity,  and 
three-quarters  of  its  circumference  is  in  front  of  a  vertical  line  drawn  from  the  anterior  border 
of  the  acromion  process. 

Surgical  Anatomy. — Owing  to  the  construction  of  the  shoulder-joint  and  the  freedom  of 
movement  which  it  enjoys,  as  well  as  in  consequence  of  its  exposed  situation,  it  is  more  frequently 
dislocated  than  any  other  joint  in  the  body.  Dislocations  of  the  shoulder  contribute  about  forty 
per  cent,  of  the  cases  in  tables  of  dislocations.  Dislocation  occurs  when  the  arm  is  thrown  into 
extreme  abduction,  and  when,  therefore,  the  head  of  the  humerus  presses  against  the  lower  and 
front  part  of  the  capsule,  which  is  the  thinnest  and  least  supported  part  of  the  ligament.  The 
rent  in  the  capsule  almost  invariably  takes  place  in  this  situation,  between  the  tendon  of  the  Sub- 
scapularis  and  the  Triceps,  and  through  it  the  head  of  the  bone  escapes,  so  that  the  dislocation 
in  most  instances  is  primarily  subglenoid.  The  head  of  the  bone  does  not  usually  remain  in  this 
situation,  but  generally  assumes  some  other  position,  which  varies  according  to  the  direction  and 
amount  of  force  producing  the  dislocation  and  the  relative  strength  of  the  muscles  in  front  and 
behind  the  joint.  In  consequence  of  the  muscles  at  the  back  being  weaker  than  those  in  front, 
and  especially  on  account  of  the  long  head  of  the  Triceps  preventing  the  bone  passing  backward, 
dislocation  forward  is  much  more  common  than  backward.  The  most  frequent  position  which 
the  head  of  the  humerus  ultimately  assumes  is  on  the  front  of  the  neck  of  the  scapula,  beneath 
the  coracoid  process,  and  hence  named  subcoracoid  dislocation.  Occasionally,  in  consequence 
probably  of  a  greater  amount  of  force  being  brought  to  bear  on  the  limb,  the  head  is  driven 
farther  inward,  and  rests  on  the  upper  part  of  the  front  of  the  chest,  beneath  the  clavicle  (sub- 
clavicular).  If  the  head  of  the  bone  passes  under  the  Subscapularis  muscle  and  also  under 
the  Teres  major  or  the  lower  border  of  the  Pectoralis  major,  the  arm  remains  abducted,  or  even 
with  the  elbow  raised  above  the  head  (hixatio  erecta).  Sometimes  the  humerus  remains  in  the 
position  in  which  it  was  primarily  displaced,  resting  on  the  axillary  border  of  the  scapula  (sub- 

1  Journal  of  Anatomy  and  Physiology,  1884,  vol.  xviii.  2  See  p.  270. 


310  THE  ARTICULATIONS   OR   JOINTS 

glenoid),  and  rarely  it  passes  backward  and  remains  in  the  infraspinatous  fossa  beneath  the 
spine  (subspinous).  If  dislocation  frequently  recurs  the  condition  may  be  amended  in  some 
cases  by  exposing  the  capsule  and  putting  tucks  in  it  by  means  of  sutures. 

An  old  unreduced  dislocation  is  sometimes  treated  by  incising  the  soft  parts  and  returning 
the  head  of  the  humerus  into  the  glenoid  cavity.  In  other  cases  the  head  of  the  humerus  is 
excised.  Dislocation  of  the  long  tendon  of  the  Biceps  muscle  from  the  bicipital  groove  is  a  rare 
accident.  When  it  occurs  the  arm  is  rigid  in  abduction,  but  the  head  of  the  humerus  is  found 
to  be  in  the  glenoid  cavity.  It  is  reduced  by  flexion  of  the  elbow  and  rotation  of  the  arm. 
Rupture  of  the  long  tendon  of  the  biceps  is  more  common  than  dislocation  of  the  tendon. 

After  this  injury  the  belly  of  the  muscle  is  relaxed  and  is  nearer  than  normal  to  the  elbow; 
flexion  of  the  forearm  is  much  weakened,  and  is  weaker  in  supination  than  it  is  in  pronation. 
The  head  of  the  humerus  passes  forward  and  inward,  and  the  condition  is  often  mistaken  for 
dislocation  of  the  bone. 

If  we  desire  to  aspirate  the  shoulder-joint,  place  the  arm  against  the  side,  flex  the  forearm  at 
a  right  angle  to  the  arm,  carry  the  forearm  across  the  front  of  the  chest,  and  enter  the  trocar 
below  the  acromion  (De  Vos). 

The  shoulder-joint  is  sometimes  the  seat  of  all  those  inflammatory  affections,  both  acute  and 
chronic,  which  attack  joints,  though  perhaps  it  suffers  less  frequently  than  some  other  joints  of 
equal  size  and  importance.  Acute  synovitis  may  result  from  injury,  rheumatism,  or  pyaemia,  or 
may  follow  secondarily  on  the  so-called  acute  epiphysitis  of  infants.  It  is  attended  with  effusion 
into  the  joint,  and  when  this  occurs  the  capsule  is  evenly  distended  and  the  contour  of  the  joint 
rounded.  Special  projections  may  occur  at  the  site  of  the  openings  in  the  capsular  ligament. 
Thus  a  swelling  may  appear  just  in  front  of  the  joint,  internal  to  the  lesser  tuberosity,  from  effu- 
sion into  the  bursa  beneath  the  Subscapularis  muscle;  or,  again,  a  swelling  which  is  sometimes 
bilobed  may  be  seen  in  the  interval  between  the  Deltoid  and  Pectoralis  major  muscles,  from  effu- 
sion into  the  diverticulum,  which  runs  down  the  bicipital  groove  with  the  tendon  of  the  biceps. 
The  effusion  into  the  synovial  membrane  can  be  best  ascertained  by  examination  from  the  axilla, 
where  a  soft,  elastic,  fluctuating  swelling  can  usually  be  felt.  The  bursa  beneath  the  deltoid  is 
sometimes  ruptured  by  violence,  and  sometimes  inflames,  suppurates,  or  becomes  tuberculous. 

Tuberculous  arthritis  not  unfrequently  attacks  the  shoulder-joint,  and  may  lead  to  total 
destruction  of  the  articulation,  when  ankylosis  may  result  or  long-protracted  suppuration  may 
necessitate  excision.  This  joint  is  also  one  of  those  which  is  most  liable  to  be  the  seat  of  osteo- 
arthritis,  and  may  also  be  affected  in  gout  and  rheumatism;  or  in  locomotor  ataxia,  when  it 
occasionally  becomes  the  seat  of  Charcot's  disease. 

Excision  of  the  shoulder-joint  may  be  required  in  cases  of  arthritis  (especially  the  tuber- 
culous form)  which  have  gone  on  to  destruction  of  the  articulation;  in  compound  dislocations  and 
fractures,  particularly  those  arising  from  gunshot  injuries,  in  which  there  has  been  extensive 
injury  to  the  head  of  the  bone;  in  some  cases  of  old  unreduced  dislocation,  where  there  is  much 
pain;  and  possibly  in  some  few  cases  of  growth  connected  with  the  upper  end  of  the  bone.  The 
operation  is  best  performed  by  making  an  incision  from  the  middle  of  the  coraco-acromial  liga- 
ment down  the  arm  for  about  three  inches:  this  will  expose  the  bicipital  groove  and  the  tendon 
of  the  Biceps,  which  may  be  either  divided  or  hooked  out  of  the  way,  according  as  to  whether  it 
is  implicated  in  the  disease  or  not.  The  capsule  is  then  freely  opened,  and  the  muscles  attached 
to  the  greater  and  lesser  tuberosities  of  the  humerus  divided.  The  head  of  the  bone  can  then 
be  thrust  out  of  the  wound  and  sawn  off,  or  divided  with  a  narrow  saw  in  situ  and  subsequently 
removed.  The  section  should  be  made,  if  possible,  just  below  the  articular  surface,  so  as  to 
leave  the  bone  as  long  as  possible.  The  glenoid  cavity  must  then  be  examined,  and  gouged 
if  carious. 

V.  The  Elbow-joint  (Articulatio  Cubiti)  (Figs.  223,  224,  225,  226). 

The  elbow  is  a  ginglymus  or  hinge-joint.  The  bones  entering  into  its  forma- 
tion are  the  trochlea  of  the  humerus,  which  is  received  into  the  greater  sigmoid 
cavity  of  the  ulna  (articulatio  humeroulnaris) ,  and  admits  of  the  movements 
peculiar  to  this  joint — viz.,  flexion  and  extension;  whilst  the  capitellum  or  radial 
head  of  the  humerus  articulates  with  the  cup-shaped  depression  on  the  head  of 
the  radius  (articulatio  humeroradialis) ;  the  circumference  of  the  head  of  the 
radius  articulates  with  the  lesser  sigmoid  cavity  of  the  ulna  (articulatio  radio- 
ulnaris  proximalis) ,  allowing  of  the  movement  of  rotation  of  the  radius  on  the 
ulna,  the  chief  action  of  the  superior  radio-ulnar  articulation.  The  articular 
surfaces  are  covered  with  a  thin  layer  of  cartilage,  and  connected  together  by  a 
capsular  ligament  (capsula  articularis)  (Fig.  225)  of  unequal  thickness,  being 
especially  thickened  on  its  two  sides  and,  to  a  less  extent,  in  front  and  behind. 


THE  ELBOW -JOINT 


311 


These  thickened  portions  are  usually  described  as  distinct  ligaments  under  the 

following  names: 

Anterior.  Internal  Lateral 

Posterior.  External  Lateral. 

The  orbicular  ligament  of  the  upper  radio-ulnar  articulation  must  also  be 
reckoned  among  the  ligaments  of  the  elbow. 

The  Anterior  Ligament  (Fig.  223)  is  a  broad  and  thin  fibrous  layer  which  covers 
the  anterior  surface  of  the  joint.  It  is  attached  to  the  front  of  the  internal  condyle 
and  to  the  front  of  the  humerus  immediately  above  the  coronoid  and  radial  fossae; 
below,  to  the  anterior  surface  of  the  coronoid  process  of  the  ulna  and  to  the 
orbicular  ligament,  being  continuous  on  each  side  with  the  lateral  ligaments.  Its 


FIG.  223. — Left  elbow-joint,  showing  anterior 
and  internal  ligaments. 


FIG.  224. — Left  elbow-joint,  showing  posterior 
and  external  ligaments. 


superficial  fibres  pass  obliquely  from  the  inner  condyle  of  the  humerus  outward  to 
the  orbicular  ligament.  The  middle  fibres,  vertical  in  direction,  pass  from  the 
upper  part  of  the  coronoid  depression  and  become  partly  blended  with  the  pre- 
ceding, but  are  mainly  inserted  into  the  anterior  surface  of  the  coronoid  process. 
The  deep  or  transverse  set  intersects  these  at  right  angles.  This  ligament  is  in 
relation,  in  front,  with  the  Brachialis  anticus  muscle,  except  at  its  outermost 
part;  behind,  it  is  in  relation  with  the  synovial  membrane. 

The  Posterior  Ligament  (Fig.  224)  is  a  thin  and  loose  membranous  fold,  attached, 
above,  to  the  lower  end  of  the  humerus.  above  and  at  the  sides  of  the  olecranon 


312 


THE   ARTICULATIONS    OR    JOINTS 


CORONOID 
PROCESS 


OLECRANON 
FOSSA 


ARTICULAR 
CAPSULE 


fossa;  below,  to  the  groove  on  the  upper  and  outer  surfaces  of  the  olecranon.  The 
superficial  or  transverse  fibres  pass  between  the  adjacent  margins  of  the  olecranon 
fossa.  The  deeper  portion  consists  of  vertical  fibres,  some  of  which,  thin  and 
weak,  pass  from  the  upper  part  of  the  olecranon  fossa  to  the  margin  of  the  olec- 
ranon ;  others,  thicker  and  stronger,  pass  from  the  back  of  the  capitellum  of  the 
humeras  to  the  posterior  border  of  the  lesser  sigmoid  cavity  of  the  ulna.  This 
ligament  is  in  relation,  behind,  with  the  tendon  of  the  Triceps  muscle  and  the 
Anconeus  muscle;  in  front,  with  the  synovial  membrane. 

The  Internal  Lateral  Ligament  (ligamentum  collaterale  ulnare)  (Fig.  223)  is  a 
thick  triangular  band  consisting  of  two  portions,  an  anterior  and  posterior,  united 
by  a  thinner  intermediate  portion.  The  anterior  portion,  directed  obliquely  forward, 

is  attached,  above,  by  its  apex, 
to  the  front  part  of  the  in- 
ternal condyle  of  the  humerus ; 
and,  below,  by  its  broad  base, 
to  the  inner  margin  of  the 
coronoid  process.  The  poste- 
rior portion,  also  of  triangular 
form,  is  attached,  above,  by 
its  apex,  to  the  lower  and  back 
part  of  the  internal  condyle; 
below,  to  the  inner  margin  of 
the  olecranon.  Between  these 
two  bands  a  few  intermediate 
fibres  descend  from  the  inter- 
nal condyle  to  blend  with  a 
transverse  band  of  ligament- 
ous  tissue  which  bridges 
across  the  notch  between  the 
olecranon  and  coronoid  pro- 
cesses. This  ligament  is  in 
relation,  internally,  with  the 
Triceps  and  Flexor  carpi 
ulnaris  muscles  and  the  ulnar 
nerve,  and  gives  origin  to  part 
of  the  Flexor  sublimis  digi- 
torum  muscle. 

The  External  Lateral  Liga- 
ment (ligamentum  collaterale 
radiale)  (Fig.  224)  is  a  short 
and  narrow  fibrous  band  less 
distinct  than  the  internal,  at- 
tached, above,  to  a  depression 
below  the  external  condyle  of 
the  humerus;  below,  to  the 
orbicular  ligament,  some  of  its 
most  posterior  fibres  passing  over  that  ligament,  to  be  inserted  into  the  outer 
margin  of  the  ulna.  This  ligament  is  intimately  blended  with  the  tendon  of 
origin  of  the  Supinator  brevis  muscle. 

Synovial  Membrane  (Fig.  225) . — The  'synovial  membrane  is  very  extensive.  It 
covers  the  margin  of  the  articular  surface  of  the  humerus,  and  lines  the  coronoid 
and  olecranon  fossa  on  that  bone;  from  these  points  it  is  reflected  over  the  anterior, 
posterior,  and  lateral  ligaments,  and  forms  a  pouch  (recessus  sacciformis)  between 
the  lesser  sigmoid  cavity,  the  internal  surface  of  the  orbicular  ligament,  and  the 


EPIPHYSEAL 
JUNCTION 


EPIPHYSEAL 
JUNCTION 


FIG.  225. — Right  elbow-joint,  cut  through  at  right  angles  to  the 
axis  of  the  trochlea  humeri,  from  the  ulnar  side.      (Spalteholz.) 


THE  ELBOW- JOINT 


313 


circumference  of  the  head  of  the  radius.  Projecting  into  the  cavity  is  a  crescentic 
fold  of  synovial  membrane,  between  the  radius  and  ulna,  suggesting  the  division  of 
the  joint  into  two :  one  the  humero-radial,  the  other  the  humero-ulnar. 

Between  the  capsular  ligament  and  the  synovial  membrane  are  three  masses 
of  fat :  one,  the  largest,  above  the  olecranon  fossa,  which  is  pressed  into  the  fossa  by 
the  Triceps  during  flexion;  a  second,  over  the  coronoid  fossa;  and  a  third,  over 
the  radial  fossa.  The  two  last-named  pads  are  pressed  into  their  respective  fossre 
during  extension. 

The  muscles  (Fig.  226)  in  relation  with  the  joint  are,  in  front,  the  Brachialis 
anticus;  behind,  the  Triceps  and  Anconeus;  externally,  the  Supinator  brevis  and 
the  common  tendon  of  origin  of  the  Ex- 
tensor muscles  ;   internally,  the  common 
tendon  of  origin  of  the  Flexor  muscles,  and 
the  Flexor  carpi  ulnaris,  with  the  ulnar 
nerve. 

The  arteries  supplying  the  joint  are  de- 
rived from  the  anastomosis  between  the 
superior  profunda,  inferior  profunda,  and 
anastomotica  magna,  bi  inches  of  the 
brachial,  with  the  anterior,  posterior,  and 
interosseous  recurrent  branches  of  the 
ulnar  and  the  recurrent  branch  of  the 
radial.  These  vessels  form  a  complete 
chain  of  inosculation  around  the  joint. 

The  nerves  are  derived  from  the  ulnar 
as  it  passes  between  the  internal  condyle 
and  the  olecranon  ;  a  filament  from  the 
musculo-cutaneous  (Rudinger),  and  two 
filaments  from  the  median  (Macalister). 

Bur sae. — The  olecranon  bursa  (bursa  sub- 
cutaneous olecrani)  is  placed  between  the 
olecranon  process  and  the  cutaneous  sur- 
face. A  bursa  exists  between  the  tendon 
of  the  Biceps  and  the  tubercle  of  the 
radius  (bursa  bicipitoradialis)  —  another 
between  the  Triceps  tendon  and  the  olec- 
ranon process  (bursa  subtendinea  olecrani) 
— another  between  the  cutaneous  surface 
and  the  external  condyle  (bursa  subcutanea  epicondyli  humeri  lateralis) — another 
between  the  cutaneous  surface  and  the  internal  condyle  (bursa  subcutanea 
epicondyli  humeri  medialis — another  within  the  Triceps  tendon  at  its  insertion  on 
the  olecranon  (bursa  intratendinea  olecrani). 

Actions. — The  elbow-joint  comprises  three  different  portions — viz.,  the  joint 
between  the  ulna  and  humerus,  that  between  the  head  .of  the  radius  and  the 
humerus,  and  the  superior  radio-ulnar  articulation,  described  below.  All  these 
articular  surfaces  are  invested  by  a  common  synovial  membrane,  and  the  move- 
ments of  the  whole  joint  should  be  studied  together.  The  combination  of  the 
movements  of  flexion  and  extension  of  the  forearm  with  those  of  pronation  and 
supination  of  the  hand,  which  is  ensured  by  the  two  being  performed  at  the 
same  joint,  is  essential  to  the  accuracy  of  the  various  minute  movements  of  the 
hand. 

The  portion  of  the  joint  between  the  ulna  and  humerus  is  a  simple  hinge- 
joint,  and  allows  of  movements  of  flexion  and  extension  only.  Owing  to  the 
obliquity  of  the  trochlear  surface  of  the  humerus,  this  movement  does  not  take 


FIG.  226. — Sagittal  section  of  the  right  elbow- 
joint,  taken  somewhat  obliquely  and  seen  from  the 
radial  aspect.  (After  Braune.) 


314  THE  ARTICULATIONS  OR  JOINTS 

place  in  a  straight  line.  When  the  forearm  is  extended  and  supinated  the  axis 
of  the  arm  is  not  in  the  same  line  as  the  axis  of  the  forearm,  but  the  axis  of  the  arm 
forms  an  angle  with  the  axis  of  the  forearm,  and  the  hand,  with  the  forearm,  is 
directed  outward.  During  flexion,  on  the  other  hand,  the  forearm  and  the  hand 
tend  to  approach  the  middle  line  of  the  body,  and  thus  enable  the  hand  to  be  easily 
carried  to  the  face.  The  shape  of  the  articular  surface  of  the  humerus,  with  its 
prominences  and  depressions  accurately  adapted  to  the  opposing  surface  of  the 
olecranon,  prevents  any  lateral  movement.  Flexion  is  produced  by  the  action 
of  the  Biceps  and  Brachialis  anticus,  assisted  by  the  muscles  arising  from  the  in- 
ternal condyle  of  the  humerus  and  the  Supinator  longus;  extension,  by  the  Triceps 
and  Anconeus,  assisted  by  the  extensors  of  the  wrist  and  by  the  Extensor  communis 
digitorum  and  Extensor  minimi  digiti. 

The  joint  between  the  head  of  the  radius  and  the  capitellum  or  radial  head  of  the 
humerus  is  an  arthrodial  joint.  The  bony  surfaces  would  of  themselves  constitute 
an  enarthrosis,  and  allow  of  movement  in  all  directions  were  it  not  for  the  orbicular 
ligament  by  which  the  head  of  the  radius  is  bound  down  firmly  to  the  lesser 
sigmoid  cavity  of  the  ulna,  and  which  prevents  any  separation  of  the  two  bones 
laterally.  It  is  to  the  same  ligament  that  the  head  of  the  radius  owes  its  security 
from  dislocation,  which  would  otherwise  constantly  occur  as  a  consequence  of  the 
shallowness  of  the  cup-like  surface  on  the  head  of  the  radius.  In  fact,  but  for 
this  ligament  the  tendon  of  the  biceps  would  be  liable  to  pull  the  head  of  the 
radius  out  of  the  joint.1  In  complete  extension  the  head  of  the  radius  glides  so 
far  back  on  the  outer  condyle  that  its  edge  is  plainly  felt  at  the  back  of  the  articu- 
lation. Flexion  and  extension  of  the  elbow-joint  are  limited  by  the  tension  of 
the  structures  on  the  front  and  back  of  the  joint,  the  limitation  of  flexion  being 
also  aided  by  the  soft  structures  of  the  arm  and  forearm  coming  in  contact. 

In  combination  with  any  position  of  flexion  or  extension  the  head  of  the  radius 
can  be  rotated  in  the  upper  radio-ulnar  joint,  carrying  the  hand  with  it.  The 
hand  is  directly  articulated  to  the  lower  surface  of  the  radius  only,  and  the  concave 
or  sigmoid  surface  on  the  lower  end  of  the  radius  travels  round  the  lower  end  of 
the  ulna.  The  latter  bone  is  excluded  from  the  wrist-joint  (as  will  be  seen  in 
the  sequel)  by  the  interarticular  fibro-cartilage.  Thus,  rotation  of  the  head  of  the 
radius  round  an  axis  which  passes  through  the  centre  of  the  radial  head  of  the 
humerus  imparts  circular  movement  to  the  hand  through  a  very  considerable 
arc. 

Surface  Form. —  If  the  forearm  be  slightly  flexed  on  the  arm,  a  curved  crease  or  fold  with 
its  convexity  downward  may  be  seen  running  across  the  front  of  the  elbow,  extending  from  one 
condyle  to  the  other.  The  centre  of  this  fold  is  some  slight  distance  above  the  line  of  the  joint. 
The  position  of  the  radio-humeral  portion  of  the  joint  can  be  at  once  ascertained  by  feeling  for  a 
slight  groove  or  depression  between  the  head  of  the  radius  and  the  capitellum  of  the  humerus  at 
the  back  of  the  articulation. 

Surgical  Anatomy. — From  the  great  breadth  of  the  joint,  and  the  manner  in  which  the 
articular  surfaces  are  interlocked,  and  also  on  account  of  the  strong  lateral  ligaments  and 
the  support  which  the  joint  derives  from  the  mass  of  muscles  attached  to  each  condyle  of  the 
humerus,  lateral  displacement  of  the  bones  is  very  uncommon,  whereas  antero-posterior  disloca- 
tion, on  account  of  the  shortness  of  the  antero-posterior  diameter,  the  weakness  of  the  anterior 
and  posterior  ligaments,  and  the  want  of  support  of  muscles,  much  more  frequently  takes  place, 
dislocation  backward  taking  place  when  the  forearm  is  in  a  position  of  extension,  and  forward 
when  in  a  position  of  flexion.  For,  in  the  former  position,  that  of  extension,  the  coronoid  process 
is  not  interlocked  into  the  coronoid  fossa,  and  loses  its  grip  to  a  certain  extent,  whereas  the 
olecranon  process  is  in  the  olecranon  fossa,  and  entirely  prevents  displacement  forward.  On 
the  other  hand,  during  flexion,  the  coronoid  process  is  in  the  coronoid  fossa,  and  prevents  dis- 
location backward,  while  the  olecranon  loses  its  grip  and  is  not  so  efficient,  as  during  extension, 
in  preventing  a  forward  displacement.  When  lateral  dislocation  does  take  place,  it  is  generally 
incomplete. 

1  Humphry,  op  cit.,  p.  419. 


RADIO-  ULNAR   ARTICULATION  315 

Dislocation  of  the  elbow-joint  is  of  common  occurrence  in  children,  far  more  common  than 
dislocation  of  any  other  articulation,  for,  as  a  rule,  fracture  of  a  bone  more  frequently  takes 
place,  under  the  application  of  any  severe  violence,  in  young  persons  than  dislocation.  In 
lesions  of  this  joint  there  is  often  very  great  difficulty  in  ascertaining  the  exact  nature  of  the 
injury.  Sprain  of  the  elbow  is  a  very  common  injury  in  childhood.  Injury  to  the  radio- 
humeral  joint  is  frequently  produced  by  lifting  a  child  by  the  hand,  as  in  swinging  it  over  a 
gutter.  The  supinator  brevis,  which  under  normal  circumstances  would  retain  the  head  of  the 
radius  against  the  capitellum  of  the  humerus,  is  unable  to  do  so,  the  radio-humeral  articulation 
receives  the  force  and  the  orbicular  ligament  undergoes  upward  displacement,  is  caught 
between  the  head  of  the  radius  and  the  capitellum  and  jams  the  joint.1  This  injury  is  often 
called  subluxation  of  the  head  of  the  radius. 

The  elbow-joint  is  occasionally  the  seat  of  acute  synovitis.  The  synovial  membrane  then 
becomes  distended  with  fluid,  the  bulging  showing  itself  principally  around  the  olecranon  process; 
that  is  to  say,  on  its  inner  and  outer  sides  and  above,  in  consequence  of  the  laxness  of  the  poste- 
rior ligament.  Occasionally  a  well-marked,  triangular  projection  may  be  seen  on  the  outer 
side  of  the  olecranon,  from  bulging  of  the  synovial  membrane  beneath  the  Anconeus  muscle. 
Again,  there  is  often  some  swelling  just  above  the  head  of  the  radius,  in  the  line  of  the  radio- 
humeral  joint.  There  is  generally  not  much  swelling  at  the  front  of  the  joint,  though  sometimes 
deep-seated  fulness  beneath  the  Brachialis  anticus  may  be  noted.  When  suppuration  occurs  the 
abscess  usually  points  at  one  or  other  border  of  the  Triceps  muscle;  occasionally  the  pus  dis- 
charges itself  in  front,  near  the  insertion  of  the  Brachialis  anticus  muscle.  Chronic  synovitis, 
usually  of  tuberculous  origin,  is  of  common  occurrence  in  the  elbow-joint:  under  these  circum- 
stances the  forearm  tends  to  assume  the  position  of  semi-flexion,  which  is  that  of  greatest  ease 
and  relaxation  of  ligaments.  It  should  be  borne  in  mind  that  should  ankylosis  occur  in  this  or 
the  extended  position,  the  limb  will  not  be  nearly  so  useful  as  if  it  becomes  ankylosed  in  a  position 
of  rather  less  than  a  right  angle.  Loose  cartilages  are  sometimes  met  with  in  the  elbow-joint,  not 
so  commonly,  however,  as  in  the  knee;  nor  do  they,  as  a  rule,  giVe  rise  to  such  urgent  symptoms. 
They  rarely  require  operative  interference.  The  elbow-joint  is  also  sometimes  affected  with 
osteo-arthritis,  but  this  affection  is  less  common  in  this  articulation  than  in  some  other  of  the 
larger  joints.  Bursitis  about  the  elbow  is  not  uncommon.  Enlargement  of  the  subcutaneous 
bursa  over  the  olecranon  is  known  as  miners'  elbow.  Enlargement  of  any  one  of  the  bursse 
may  occur. 

Excision  of  the  elbow  is  principally  required  for  one  of  three  conditions — viz.,  tuberculous 
arthritis,  injury  and  its  results,  and  ankylosis  in  a  position  which  greatly  impairs  the  .useful- 
ness of  the  limb;  but  may  be  necessary  for  some  other  rarer  conditions,  such  as  disorganizing 
arthritis  after  pyamia,  unreduced  dislocation,  and  osteo-arthritis.  The  results  of  the  opera- 
tion are,  as  a  rule,  more  favorable  than  those  of  excision  of  any  other  joint,  and  it  is  one, 
therefore,  that  the  surgeon  should  never  hesitate  to  perform,  especially  in  the  first  three  of 
the  conditions  mentioned  above.  The  operation  is  best  performed  by  a  single  vertical  incision 
down  the  back  of  the  joint,  a  transverse  incision,  over  the  outer  condyle,  being  added  if  the 
parts  are  much  thickened  and  fixed.  A  straight  incision  is  made  about  four  inches  long,  the 
mid-point  of  which  is  on  a  level  with  and  a  little  to  the  inner  side  of  the  tip  of  the  olecra- 
non. This  incision  is  made  down  to  the  bone,  through  the  substance  of  the  Triceps  muscle. 
The  operator  with  the  point  of  his  knife,  and  guarding  the  soft  parts  with  his  thumb-nail, 
separates  them  from  the  bone.  In  doing  this  there  are  two  structures  which  he  should 
carefully  avoid:  the  ulnar  nerve,  which  lies  parallel  to  his  incision,  but  a  little  internal,  as  it 
courses  down  between  the  internal  condyle  and  the  olecranon  process,  and  the  prolongation  of 
the  Triceps  into  the  deep  fascia  of  the  forearm  over  the  Anconeus  muscle.  Having  cleared  the 
bones  and  divided  the  lateral  and  posterior  ligaments,  the  forearm  is  strongly  flexed  and  the 
ends  of  the  bone  turned  out  and  sawn  off.  The  section  of  the  humerus  should  be  through 
the  base  of  the  condyles,  that  of  the  ulna  and  radius  should  be  just  below  the  level  of  the  lesser 
sigmoid  cavity  of  the  ulna  and  the  neck  of  the  radius.  In  this  operation  the  object  is  to  obtain 
such  fibrous  union  as  shall  allow  free  motion  of  the  bones  of  the  forearm;  and,  therefore,  passive 
motion  must  be  commenced  early,  that  is  to  say,  about  the  tenth  day. 

VI.  Radio-ulnar  Articulation  (Articulatio  Radioulnaris). 

The  articulation  of  the  radius  with  the  ulna  is  effected  by  ligaments  which 
connect  together  both  extremities  as  well  as  the  shafts  of  these  bones.  It  may, 
consequently,  be  subdivided  into  three  articulations:  (1)  the  superior  radio-ulnar, 
which  is  a  portion  of  the  elbow-joint;  (2)  the  middle  radio-ulnar;  and  (3)  the  infe- 
rior radio-ulnar  articulations. 

1  Mr.  Jonathan  Hutchinson,  Jr.,  in  Annals  of  Surgery,  August,  1885. 


316  THE  ARTICULATIONS    OR   JOINTS 

1.  SUPERIOR  OR  PROXIMAL  RADIO-ULNAR  ARTICULATION  (ARTICULATIO 
RADIOULNARIS  PROXIMALIS)  . 

This  articulation  is  a  trochoid  or  pivot-joint.  The  bones  entering  into  its  forma- 
tion are  the  inner  side  of  the  circumference  of  the  head  of  the  radius  rotating  within 
the  lesser  sigmoid  cavity  of  the  ulna.  Its  only  ligament  is  the  annular  or  orbicular. 

The  Orbicular  or  Annular  Ligament  (ligamentum  annulare  radii)  (Figs.  223,  224, 
and  227)  is  a  strong,  flat  band  of  ligamentous  fibres  which  surrounds  the  head  of 
the  radius  and  retains  it  in  firm  connection  with  the  lesser  sigmoid  cavity  of  the 
ulna.  It  forms  about  four-fifths  of  an  osseo-fibrous  ring,  attached  by  each  end  to 
the  extremities  of  the  lesser  sigmoid  cavity,  and  is  smaller  at  the  lower  part  of  its 
circumference  than  above,  by  which  means  the  head  of  the  radius  is  more  securely 
held  in  its  position.  Its  outer  surface  is  strengthened  by  the  external  lateral 
ligament  of  the  elbow,  and  affords  origin  to  part  of  the  Supinator  brevis  muscle. 
Its  inner  surface  is  smooth,  and  lined  by  synovial  membrane.  The  synovial 
membrane  is  continuous  with  that  which  lines  the  elbow-joint. 

Actions. — The  movement  which  takes  place  in  this  articulation  is  limited  to 
rotation  of  the  head  of  the  radius  within  the  orbicular  ligament,  and  upon  the 
lesser  sigmoid  cavity  of  the  ulna,  rotation  forward  being  called  pronation;  rotation 
backward,  supination.  Supination  is  performed  by  the  Biceps  and  Supinator 
brevis,  assisted  to  a  slight  extent  by  the  Extensor  muscles  of  the  thumb  and, 
in  certain  positions,  by  the  Supinator  longus.  Pronation  is  performed  by  the 
Pronator  radii  teres  and  the  Pronator  quadratus,  assisted,  in  some  positions,  by 
the  Supinator  longus. 

Surface  Form. — The  position  of  the  superior  radio-ulnar  joint  is  marked  on  the  surface  of 
the  body  by  the  little  dimple  on  the  back  of  the  elbow  which  indicates  the  position  of  the  head 
of  the  radius. 

Surgical  Anatomy. — Dislocation  of  the  head  of  the  radius  alone  is  not  an  uncommon  acci- 
dent, and  occurs  most  frequently  in  young  persons  from  falls  on  the  hand  when  the  forearm  is 
extended  and  supinated,  the  head  of  the  bone  being  displaced  forward.  It  is  attended  by  rup- 
ture of  the  orbicular  ligament.  Occasionally  a  peculiar  injury,  which  is  supposed  to  be  a  sub- 
luxation,  occurs  in  young  children  in  lifting  them  from  the  ground  by  the  hand  or  forearm.  It 
is  believed  that  the  head  of  the  radius  is  displaced  downward  or  the  orbicular  ligament  upward, 
and  the  upper  border  of  the  ligament  becomes  folded  over  the  head  of  the  radius,  between  it  and 
the  capitellum  of  the  humerus. 

2.  MIDDLE  RADIO-ULNAR  LIGAMENTS. 

The  interval  between  the  shafts  of  the  radius  and  ulna  is  occupied  by  two 
ligaments. 

Oblique.  Interosseous. 

The  Oblique  or  Round  Ligament  (chorda  obliqua)  (Figs.  223  and  225)  is  a  small, 
flattened  fibrous  band  which  extends  obliquely  downward  and  outward  from  the 
tubercle  of  the  ulna  at  the  base  of  the  cororioid  process  to  the  radius  a  little  below 
the  bicipital  tuberosity.  Its  fibres  run  in  the  opposite  direction  to  those  of  the 
interosseous  ligament,  and  it  appears  to  be  placed  as  a  substitute  for  it  in  the 
upper  part  of  the  interosseous  interval.  This  ligament  is  sometimes  wanting. 

The  Interosseous  Membrane  (membrana  interossea  antibrachii)  (Fig.  227)  is  a 
broad  and  thin  plane  of  fibrous  tissue  descending  obliquely  downward  and  inward, 
from  the  interosseous  ridge  on  the  radius  to  that  on  the  ulna.  It  is  deficient  above, 
commencing  about  an  inch  beneath  the  tubercle  of  the  radius;  is  broader  in  the 
middle  than  at  either  extremity;  and  presents  an  oval  aperture  just  above  its 
lower  margin  for  the  passage  of  the  anterior  interosseous  vessels  to  the  back  of 
the  forearm.  This  ligament  serves  to  connect  the  bones  and  to  increase  the 
extent  of  surface  for  the  attachment  of  the  deep  muscles.  Between  its  upper 


RADIO-  ULNAR    ARTICULATION 


317 


ANNULAR  LIGAMENT 
OF  RADIUS 


border  and  the  oblique  ligament  an  interval  exists  through  which  the  posterior 
interosseous  vessels  pass  to  the  dorsum  of  the  forearm.  Two  or  three 
fibrous  bands  are  occasionally  found 
on  the  posterior  surface  of  this  mem- 
brane which  descend  obliquely  from 
the  ulna  toward  the  radius,  and  which 
have  consequently  a  direction  contrary 
to  that  of  the  other  fibres.  It  is  in 
relation,  in  front,  by  its  upper  three- 
fourths  with  the  Flexor  longus  pollicis 
on  the  outer  side,  and  with  the  Flexor 
profundus  digitorum  on  the  inner,  lying 
upon  the  interval  between  which  are 
the  anterior  interosseous  vessels  and 
nerve  ;  by  its  lower  fourth,  with  the 
Pronator  quadratus;  behind,  with  the 
Supinator  brevis,  Extensor  ossis  meta- 
carpi  pollicis,  Extensor  brevis  pollicis, 
Extensor  longus  pollicis,  Extensor  in- 
dicis;  and,  near  the  wrist,  with  the 
anterior  interosseous  artery  and  poste- 
rior interosseous  nerve. 


3.  INFERIOR  OR  DISTAL  RADIO-ULNAR 

ARTICULATION  (ARTICULATIO  RA- 

DIOULNARIS  DlSTALIS). 


TENDON  OF 
BICEPS  MUSCLE 

(cut  through) 


OBLIQUE 
LIGAMENT" 


INTEROSSEOUS 
MEMBRANE' 


This  is  a  pivot-joint,  formed  by  the 
sigmoid  cavity  at  the  inner  side  of  the 
lower  end  of  the  radius  receiving  the 
head  of  the  ulna.  The  articular  sur- 
faces are  covered  by  a  thin  layer  of 
cartilage,  and  connected  together  by  a 
capsule  (capsula  articularis)  ,  portions 
of  which  are  usually  described  as  dis- 
tinct ligaments.  The  ligaments  of  the 
articulation  are: 

Anterior  Radio-ulnar. 
Posterior  Radio-ulnar. 
Triangular   Interarticular   Fibro- 
cartilage. 

The  Anterior  Radio-ulnar  Ligament 
(Fig.  228)  is  a  narrow  band  of  fibres 
extending  from  the  anterior  margin  of 
the  sigmoid  cavity  of  the  radius  to  the 
anterior  surface  of  the  head  of  the  ulna. 

The  Posterior  Radio-ulnar  Ligament 
(Fig.  229)  extends  between  similar 
points  on  the  posterior  surface  of  the 
articulation. 

The  Triangular  Interarticular  Fibro-cartilage  (discus  articularis]  (Figs.  227  and  231) 
is  triangular  in  shape,  and  is  placed  transversely  beneath  the  head  of  the  ulna, 
binding  the  lower  end  of  this  bone  and  the  radius  firmly  together.  Its  periphery 


STYLO  ID 

.PROCESS 
OF  ULNA 

[TRIANGULAR 
INTCRARTICULAR 
FIBROCARTILAGE 
_STYLOID  PROCESS 
OF  RADIUS 


FIG.  227. — Bones  of  the  right  forearm,  with  ligaments 
from  the  volar  surface.     (Spalteholz.) 


318 


THE    ARTICULATIONS    OR    JOINTS 


is  thicker  than  its  centre,  which  is  thin  and  occasionally  perforated.  It  is  attached 
by  its  apex  to  a  depression  which  separates  the  styloid  process  of  the  ulna  from 
the  head  of  that  bone;  and  by  its  base,  which  is  thin,  to  the  prominent  edge  of 


Wrist-joint. 


Inferior  radio-ulnar 
articulation. 


Carpal  articulations. 


Carpo-metacarpal 
articulations. 


FIG.  228.— Ligaments  of  wrist  and  hand.     Anterior  view. 

the  radius,  which  separates  the  sigmoid  cavity  from  the  carpal  articulating  sur- 
face. Its  margins  are  united  to  the  ligaments  of  the  wrist-joint.  Its  upper  sur- 
face, smooth  and  concave,  articulates  with  the  head  of  the  ulna,  forming  an 


Inferior  radio-ulnar 

articulation. 


Wrist-joint. 
Carpal  articulations. 


Carpo-metacarpal 

articulations 


FIG.  229. — Ligaments  of  wrist  and  hand.     Posterior  view. 

arthrodial  joint;  its  under  surface,  also  concave  and  smooth,  forms  part  of  the 
wrist-joint  and  articulates  with  the  cuneiform  and  inner  part  of  the  semilunar 
bone.  Both  surfaces  are  lined  by  a  synovial  membrane — the  upper  surface,  by 


RADIO -CARPAL    OR    WRIST -JOINT 


319 


one  peculiar  to  the  radio-ulnar  articulation;  the  under  surface,  by  the  synovial 
membrane  of  the  wrist. 

Synovial  Membrane. — The  synovial  membrane  (Fig.  231)  of  this  articulation 
has  been  called,  from  its  extreme  looseness,  the  membrana  sacciformis.  It  projects 
horizontally  inward  between  the  head  of  the  ulna  and  the  interarticular  fibro- 
cartilage,  and  upward  between  the  radius  and  the  ulna,  forming  a  very  loose 
cul-de-sac  (recessus  sacciformis).  The  quantity 
of  synovia  which  it  contains  is  usually  consider- 
able. The  inferior  radio-ulnar  joint  does  not 
communicate  with  the  wrist-joint. 

Actions. — The  movement  in  the  inferior  radio- 
ulnar  articulation  is  just  the  reverse  of  that  in 
the  superior  radio-ulnar  joint.  It  consists  of  a 
movement  of  rotation  of  the  lower  end  of  the 
radius  round  an  axis  which  corresponds  to  the 
centre  of  the  head  of  the  ulna.  When  the  radius 
rotates  forward,  pronation  of  the  forearm  and 
hand  is  the  result;  and  when  backward,  supina- 
tion.  It  will  thus  be  seen  that  in  pronation  and 
supination  of  the  forearm  and  hand  the  radius 
describes  a  segment  of  a  cone,  the  axis  of  which 
extends  from  the  centre  of  the  head  of  the  radius 
to  the  middle  of  the  head  of  the  ulna.  In  this 
movement,  however,  the  ulna  is  not  quite  sta- 
tionary, but  rotates  a  little  in  the  opposite  direc- 
tion. So  that  it  also  describes  the  segment  of  a 
cone,  though  of  smaller  size  than  that  described 
by  the  radius.  The  movement  which  causes  this 
alteration  in  the  position  of  the  head  of  the  ulna 
takes  place  principally  at  the  shoulder-joint  by  a 
rotation  of  the  humerus,  but  possibly  also  to  a 
slight  extent  at  the  elbow-joint.1 

Surface  Form. — The  position  of  the  inferior  radio- 
ulnar  joint  may  be  ascertained  by  feeling  for  a  slight 
groove  at  the  back  of  the  wrist,  between  the  prominent 
head  of  the  ulna  and  the  lower  end  of  the  radius,  when 
the  forearm  is  in  a  state  of  almost  complete  pronation. 

VII.  Radio-carpal  or  Wrist-joint  (Articulatio 
Radiocarpea)  (Figs.  228,  229,  231). 

The  wrist  is  a  condyloid  articulation.  The 
parts  entering  into  its  formation  are  the  lower  ^  230  _Longitudinal  section  of  the 

end    Of     the    radius     and     Under     Surface    Of     the      right    forearm,    hand,     and    third   finger, 
..  ,  .   ,    ,  ,  viewed    from    the   ulnar    aspect.       (Alter 

interarticular  fibro-cartilage,  which  lorm  together    Braune.) 
the  receiving  cavity,  and  the  scaphoid,  semilunar, 

and  the  cuneiform  bones,  which  form  the  condyle.  The  articular  surface  of  the 
radius  and  the  under  surface  of  the  interarticular  fibro-cartilage  are  the  receiving 
cavity,  forming  together  a  transversely  elliptical  concave  surface.  The  articular 
surfaces  of  the  scaphoid,  semilunar,  and  cuneiform  bones  form  together  a  smooth, 
convex  surface,  the  condyle,  which  is  received  into  the  concavity  above  men- 
tioned. All  the  bony  surfaces  of  the  articulation  are  covered  with  cartilage,  and 


1  See  Journal  of  Anatomy  and  Physiology,  vol.  xix.,  parts  ii.,  iii.,  and  iv. 


THE  ARTICULATIONS    OR   JOINTS 

connected  together  by  a  loose  capsule  (capsula  articularis) ,  which  is  divided  into 
the  following  ligaments : 

External  Lateral.  Anterior. 

Internal  Lateral.  Posterior. 

The  External  Lateral  Ligament  ( ligamentum  collaterale  carpi  radiate)  (Fig.  228) 
extends  from  the  summit  of  the  styloid  process  of  the  radius  to  the  outer  side  of 
the  scaphoid,  some  of  its  fibres  being  prolonged  to  the  trapezium  and  annular 
ligament. 

The  Internal  Lateral  Ligament  (ligamentum  collaterale  carpi  ulnare)  (Fig.  228) 
is  a  rounded  cord,  attached,  above,  to  the  extremity  of  the  styloid  process  of  the 
ulna,  and  dividing  below  into  two  fasciculi,  which  are  attached,  one  to  the  inner 
side  of  the  cuneiform  bone,  the  other  to  the  pisiform  bone  and  annular  ligament. 

The  Anterior  or  Volar  Ligament  (ligamentum  radiocarpeum  volare)  (Fig.  228) 
is  a  broad,  membranous  band,  attached,  above,  to  the  anterior  margin  of  the 
lower  end  of  the  radius,  its  styloid  process,  and  the  ulna :  its  fibres  pass  downward 
and  inward  to  be  inserted  i^to  the  palmar  surface  of  the  scaphoid,  semilunar, 
and  cuneiform  bones,  some  of  the  fibres  being  continued  to  the  os  magnum.  In 
addition  to  this  broad  membrane  there  is  a  distinct  rounded  fasciculus,  superficial 
to  the  rest,  which  passes  from  the  base  of  the  styloid  process  of  the  ulna  to 
the  semilunar  and  cuneiform  bones.  This  ligament  is  perforated  by  numerous 
apertures  for  the  passage  of  vessels,  and  is  in  relation,  in  front,  with  the  tendons 
of  the  Flexor  profundus  digitorum  and  Flexor  longus  pollicis;  behind,  with  the 
synovial  membrane  of  the  wrist-joint. 

The  Posterior  or  Dorsal  Ligament  (ligamentum  radiocarpeum  dorsale)  (Fig.  229), 
less  thick  and  strong  than  the  anterior,  is  attached,  above,  to  the  posterior  border 
of  the  lower  end  of  the  radius ;  its  fibres  pass  obliquely  downward  and  inward,  to 
be  attached  to  the  dorsal  surface  of  the  scaphoid,  semilunar,  and  cuneiform  bones, 
being  continuous  with  those  of  the  dorsal  carpal  ligaments.  This  ligament  is  in 
relation,  behind,  with  the  extensor  tendons  of  the  fingers;  in  front,  with  the  syno- 
vial membrane  of  the  wrist. 

Synovial  Membrane. — The  synovial  membrane  (Fig.  231)  lines  the  inner  sur- 
face of  the  ligaments  above  described,  extending  from  the  lower  end  of  the  radius 
and  interarticular  fibro-cartilage  above  to  the  articular  surfaces  of  the  carpal  bones 
below.  It  is  loose  and  lax,  and  presents  numerous  folds,  especially  behind. 

Relations. — The  wrist-joint  is  covered  in  front  by  the  flexor  and  behind  by  the 
extensor  tendons  (Fig.  230) ;  it  is  also  in  relation  with  the  radial  and  ulnar 
arteries. 

The  arteries  supplying  the  joint  are  the  anterior  and  posterior  carpal  branches 
of  the  radial  and  ulnar,  the  anterior  and  posterior  interosseous,  and  some  ascend- 
ing branches  from  the  deep  palmar  arch. 

The  nerves  are  derived  from  the  ulnar  and  posterior  interosseous. 

Actions. — The  movements  permitted  in  this  joint  are  flexion,  extension,  abduc- 
tion, adduction,  and  circumduction.  Its  actions  will  be  further  studied  with  those 
of  the  carpus,  with  which  they  are  combined. 

Surface  Form. — The  line  of  the  radio-carpal  joint  is  on  a  level  with  the  apex  of  the  styloid 
process  of  the  ulna. 

Surgical  Anatomy. — The  wrist-joint  is  rarely  dislocated,  its  strength  depending  mainly 
upon  the  numerous  strong  tendons  which  surround  the  articulation.  Its  security  is  further  pro- 
vided for  by  the  number  of  small  bones  of  which  the  carpus  is  made  up,  and  which  are  united 
by  very  strong  ligaments.  The  slight  movement  which  takes  place  between  the  several  bones 
serves  to  break  the  jars  that  result  from  falls  or  blows  on  the  hand.  Dislocation  backward, 
which  is  the  more  common  dislocation,  simulates  to  a  considerable  extent  Colles's  fracture  of  the 
radius,  and  is  liable  to  be  mistaken  for  it.  The  diagnosis  can  be  easily  made  out  by  observing 
the  relative  position  of  the  styloid  processes  of  the  radius  and  the  ulna.  In  the  natural  condition 


ARTICULATIONS   OF    THE    CARPUS  321 

the  styloid  process  of  the  radius  is  on  a  lower  level — i.  e.,  nearer  the  ground — when  the  arm  hangs 
by  the  side,  than  that  of  the  ulna,  and  the  same  would  be  the  case  in  dislocation.  In  Collcs's 
fracture,  on  the  other  hand,  the  styloid  process  of  the  radius  is  on  the  same  or  even  a  higher 
level  than  that  of  the  ulna. 

The  wrist-joint  is  occasionally  the  seat  of  acute  synovitis,  the  result  of  traumatism  or  arising 
in  the  rheumatic  or  pysemic  state.  When  the  synovial  sac  is  distended  with  fluid,  the  swelling 
is  greatest  on  the  dorsal  aspect  of  the  wrist,  showing  a  general  fulness,  with  some  bulging  between 
the  tendons.  The  inflammation  is  prone  to  extend  to  the  intercarpal  joints  and  to  attack  also 
the  sheaths  of  the  tendons  in  the  neighborhood.  Chronic  inflammation  of  the  wrist  is  generally 
tuberculous,  and  often  leads  to  similar  disease  in  the  synovial  sheaths  of  adjacent  tendons  and  of 
the  intercarpal  joints.  The  disease,  therefore,  when  progressive,  often  leads  to  necrosis  of  the 
carpal  bones,  and  the  result  is  often  unsatisfactory. 

VIII.  Articulations  of  the  Carpus  (Articulatio  Intercarpea) 

(Figs.  228,  229,  231). 

These  articulations  may  -be  subdivided  into  three  sets : 

1.  The  Articulations  of  the  First  Row  of  Carpal  Bones. 

2.  The  Articulations  of  .the  Second  Row  of  Carpal  Bones. 

3.  The  Articulations  of  the  Two  Rows  with  each  other. 

1.  ARTICULATIONS  OF  THE  FIRST  Row  OF  CARPAL  BONES. 

These  are  arthrodial  joints.  The  ligaments  connecting  the  scaphoid,  semi- 
lunar,  and  cuneiform  bones  are — 

Dorsal.  Palmar. 

Two  Interosseous 

The  Dorsal  Ligaments  (ligamenta  intercarpea  dorsalia)  are  placed  transversely 
behind  the  bones  of  the  first  row;  they  connect  the  scaphoid  and  sernilunar  and 
the  semilunar  and  cuneiform. 

The  Palmar  or  Volar  Ligaments  (ligamenta  intercarpea  volaria)  connect  the 
scaphoid  and  semilunar  and  the  semilunar  and  cuneiform  bones;  they  are  less 
strong  than  the  dorsal,  and  placed  very  deeply  below  the  anterior  ligament  of 
the  wrist. 

The  Interosseous  Ligaments  (ligamenta  intercarpea  interossea)  (Fig.  231)  are  two 
narrow  bundles  of  fibrous  tissue  connecting  the  semilunar  bone  on  one  side  with 
the  scaphoid,  and  on  the  other  with  the  cuneiform.  They  are  on  a  level  with 
the  superior  surfaces  of  these  bones,  and  close  the  upper  part  of  the  spaces 
between  them.  Their  upper  surfaces  are  smooth,  and  form  with  the  bones  the 
convex  articular  surfaces  of  the  wrist-joint. 

The  ligaments  connecting  the  pisiform  bone  are — 

Capsular.  Two  Palmar  Ligaments. 

The  Capsular  Ligament  (capsida  articularis}  is  a  thin  membrane  which  con- 
nects the  pisiform  bone  to  the  cuneiform.  It  is  lined  with  a  separate  synovial 
membrane. 

The  Two  Palmar  Ligaments  are  two  strong  fibrous  bands  which  connect  the 
pisiform  to  the  unciform,  the  piso-uncinate  ligament  (ligamentum  pisohamatum) , 
and  to  the  base  of  the  fifth  metacarpal  bone,  the  piso-metacarpal  ligament  (liga- 
mentum pisometacarpeum) . 

2.  ARTICULATIONS  OF  THE  SECOND  Row  OF  CARPAL  BONES. 

These  are  also  arthrodial  joints.  The  articular  surfaces  are  covered  with 
cartilage,  and  connected  by  the  following  ligaments: 

Dorsal.  Palmar. 

Three  Interosseous. 

21 


322  THE   ARTICULATIONS    OR    JOINTS 

The  Dorsal  Ligaments  (ligamenta  inter  car  pea  dor  solid)  extend  transversely  from 
one  bone  to  another  on  the  dorsal  surface,  connecting  the  trapezium  with  the  trape- 
zoid,  the  trapezoid  with  the  os  magnum,  and  the  os  magnum  with  the  unciform. 

The  Palmar  or  Volar  Ligaments  (ligamenta  intercarpea  volaria)  have  a  similar 
arrangement  on  the  palmar  surface. 

The  Three  Interosseous  Ligaments  (ligamenta  intercarpea  interossea)  (Fig.  231) 
much  thicker  than  those  of  the  first  row,  are  placed  one  between  the  os  magnum 
and  the  unciform,  a  second  between  the  os  magnum  and  the  trapezoid,  and  a 
third  between  the  trapezium  and  trapezoid.  The  first  of  these  is  much  the 
strongest,  and  the  third  is  sometimes  wanting. 

3.  ARTICULATIONS  OF  THE  Two  Rows  OF  CARPAL  BONES  WITH  EACH  OTHER 

(Figs.  228,  229,  231). 

The  joint  between  the  scaphoid,  semilunar,  and  cuneiform,  and  the  second  row 
of  the  carpus,  or  the  mid-carpal  joint,  is  made  up  of  three  distinct  portions;  in  the 
centre  the  head  of  the  os  magnum  and  the  superior  surface  of  the  unciform 
articulate  with  the  deep,  cup-shaped  cavity  formed  by  the  scaphoid  and  s,emi- 
lunar  bones,  and  constitute  a  sort  of  ball-and-socket  joint.  On  the  outer  side 
the  trapezium  and  trapezoid  articulate  with  the  scaphoid,  and  on  the  inner  side 
the  unciform  articulates  with  the  cuneiform,  forming  gliding  joints. 

The  ligaments  are : 

Anterior.  External  Lateral. 

Posterior.  Internal   Lateral. 

The  Anterior,  Palmar,  or  Volar  Ligaments  (ligamenta  intercarpea  volaria)  consist 
of  short  fibres,  which  pass,  for  the  most  part,  from  the  palmar  surface  of  the  bones 
of  the  first  row  to  the  front  of  the  os  magnum. 

The  Posterior  or  Dorsal  Ligaments  (ligamenta  intercarpea  dorsalid)  consist  of 
short,  irregular  bundles  of  fibres  passing  between  the  bones  of  the  first  and  second 
row  on  the  dorsal  surface  of  the  carpus. 

The  Lateral  Ligaments  are  very  short:  they  are  placed,  one  on  the  radial,  the 
other  on  the  ulnar  side  of  the  carpus ;  the  former,  the  stronger  and  more  distinct, 
connecting  the  scaphoid  and  trapezium  bones,  the  latter  the  cuneiform  and  unci- 
form; they  are  continuous  with  the  lateral  ligaments  of  the  wrist-joint.  In  addi- 
tion to  these  ligaments,  a  slender  interosseous  band  sometimes  connects  the  os 
magnum  and  the  scaphoid. 

Synovial  Membrane  (Fig.  231). — The  sy  no  vial  membrane  of  the  carpus  is  very 
extensive:  it  passes  from  the  under  surface  of  the  scaphoid,  semilunar,  and  cunei- 
form bones  to  the  upper  surface  of  the  bones  of  the  second  row,  sending  upward 
two  prolongations — between  the  scaphoid  and  semilunar  and  the  semilunar  and 
cuneiform ;  sending  downward  three  prolongations  between  the  four  bones  of  the 
second  row,  which  are  further  continued  onward  into  the  carpo-metacarpal 
joints  of  the  four  inner  metacarpal  bones,  and  also  for  a  short  distance  between 
the  metacarpal  bones.  There  is  a  separate  synovial  membrane  between  the 
pisiform  and  cuneiform  bones. 

Actions. — The  articulation  of  the  hand  and  wrist,  considered  as  a  whole,  is 
divided  into  three  parts:  (1)  the  radius  and  the  interarticular  fibre-cartilage; 
(2)  the  meniscus,  formed  by  the  scaphoid,  semilunar,  and  cuneiform,  the  pisiform 
bone  having  no  essential  part  in  the  movements  of  the  hand;  (3)  the  hand  proper, 
the  metacarpal  bones  with  the  four  carpal  bones  on  which  they  are  supported — viz., 
the  trapezium,  trapezoid,  os  magnum,  and  unciform.  These  three  elements  form 
two  joints:  (1)  the  superior,  wrist-joint  proper,  between  the  meniscus  and  bones 
of  the  forearm;  (2)  the  inferior,  between  the  hand  and  meniscus,  transverse  or 
mid-carpal  joint. 


CARPO- METACARPAL    ARTICULATIONS  323 

(1)  The  articulation  between  the  forearm  and  carpus  is  a  true  condyloid  artic- 
ulation, and  therefore  all  movements  but  rotation  are  permitted.     Flexion  and 
extension  are  the  most  free,  and  of  these  a  greater  amount  of  extension  than 
flexion  is  permitted  on  account  of  the  articulating  surfaces  extending  farther  on 
the  dorsal  than  on  the  palmar  aspect  of  the  carpal  bones.    In  this  movement  the 
carpal  bones  rotate  on  a  transverse  axis  drawn  between  the  tips  of  the  styloid 
processes  of  the  radius  and  ulna.     A  certain  amount  of  adduction  (or  ulnar 
flexion)  and  abduction  (or  radial  flexion)  is  also  permitted.    Of  these  the  former 
is  considerably  greater  in  extent  than  the  latter.     In  this  movement  the  carpus 
revolves  upon  an  antero-posterior  axis  drawn  through  the  centre  of  the  wrist. 
Finally,  circumduction  is  permitted  by  the  consecutive  movements  of  adduction, 
extension,  abduction,  and  flexion,  with  intermediate  movements  between  them. 
There  is  no  rotation,  but  this  is  provided  for  By  the  supination  and  pronation 
of  the  radius  on  the  ulna.    The  movement  of  flexion  is  performed  by  the  Flexor 
carpi   radialis,  the   Flexor  carpi   ulnaris,  and   the   Palmaris  longus;  extension, 
by  the   Extensor    carpi    radialis  longior   et    brevior    and    the   Extensor    carpi 
ulnaris;    adduction  (ulnar    flexion),  by  the   Flexor  carpi  ulnaris  and   the  Ex- 
tensor carpi   ulnaris ;   and  abduction  (radial   flexion),  by  the   Extensors  of  the 
thumb  and  the  Extensor  carpi  radialis  longior  et  brevior  and  the  Flexor  carpi 
radialis. 

(2)  The  chief  movements  permitted  in  the  transverse  or  mid-carpal  joint  are 
flexion  and  extension  and  a  slight  amount  of  rotation.    In  flexion  and  extension, 
Avhich  is  the  movement  most  freely  enjoyed,  the  trapezium  and  trapezoid  on  the 
radial  side  and  the  unciform  on  the  ulnar  side  glide  forward  and  backward  on  the 
scaphoid  and  cuneiform  respectively,  while  the  head  of  the  os  magnum  and  the 
superior  surface  of  the  unciform  rotate  in  the  cup-shaped  cavity  of  the  scaphoid 
and  semilunar.     Flexion  at  this  joint  is  freer  than  extension.     A  very  trifling 
amount  of  rotation  is  also  permitted,  the  head  of  the  os  magnum  rotating  round  a 
vertical  axis  drawn  through  its  own  centre,  while  at  the  same  time  a  slight  gliding 
movement  takes  place  in  the  lateral  portions  of  the  joint. 

IX.  Garpo-metacarpal  Articulations  (Articulationes  Carpometacarpeae) 

(Figs.  228,  229,  231). 

1.  ARTICULATION  OF  THE  METACARPAL  BONE  OF  THE  THUMB  WITH  THE 
TRAPEZIUM  (ARTICULATIO  CARPOMETACARPEA  POLLICIS). 

This  is  a  joint  of  reciprocal  reception,  and  enjoys  great  freedom  of  movement, 
on  account  of  the  configuration  of  its  articular  surfaces,  which  are  saddle-shaped, 
so  that,  on  section,  each  bone  appears  to  be  received  into  a  cavity  in  the  other, 
according  to  the  direction  in  which  they  are  cut.  The  joint  is  surrounded  by  a 
capsular  ligament. 

The  Capsular  Ligament  (capsula  articularis)  is  thick  and  fibrous,  but  loose, 
and  passes  from  the  circumference  of  the  upper  extremity  of  the  meta- 
carpal bone  to  the  rough  edge  bounding  the  articular  surface  of  the  trape- 
zium; it  is  thickest  externally  and  behind,  and  lined  by  a  separate  synovial 
membrane. 

Movements. — In  the  articulation  of  the  metacarpal  bone  of  the  thumb  with  the 
trapezium  the  movements  permitted  are  flexion,  extension,  adduction,  abduction, 
and  circumduction.  When  the  joint  is  flexed  the  metacarpal  bone  is  brought  in 
front  of  the  palm  and  the  thumb  is  gradually  turned  to  the  fingers.  It  is  by  this 
peculiar  movement  that  the  tip  of  the  thumb  is  opposed  to  the  other  digits;  for 
by  slightly  flexing  the  fingers  the  palmar  surface  of  the  thumb  can  be  brought  in 
contact  with  their  palmar  surfaces  one  after  another. 


324 


THE  ARTICULATIONS    OR    JOINTS 


2.  ARTICULATIONS  OF  THE  METACARPAL  BONES  OF  THE  FOUR  INNER  FINGERS 
WITH  THE  CARPUS  (ARTICULATIONES  CARPOMETACARPEAE). 

The  joints  formed  between  the  carpus  and  four  inner  metacarpal  bones  are 
arthrodial  joints.     The  ligaments  are — 

Dorsal.  Palmar. 

Interosseous. 

The  Dorsal  Ligaments  (ligamenta  carpometacarpea  dorsalia),  the  strongest  and 
most  distinct,  connect  the  carpal  and  metacarpal  bones  on  their  dorsal  surface. 


EPIPHYSEAL 
JUNCTION 

MCMBRANA    SACCI- 

FORMIS  OF  INFERIOR 

RADIO-ULNAR 

ARTICULATION 


TRIANGULAR 
FIBRO-CARTILAGE 

STYLOID  PROCESS 
OF  ULNA 


EPIPHYSEAL 
JUNCTION 


RADIO-CARPAL 
ARTICULATION 


INTEROSSEOUS 
LIGAMENT 


INTEROSSEOUS 
LIGAMENT 


INTERMETACAR 

ARTICULATIO 


INTERCARPAL 
ARTICULATION 


ARTICULATION  OF 
TRAPEZIUM  AND 
METACARPAL  BONE 
OF  THUMB 

CARPO-METACARPAL 
ARTICULATION 


METACARPAL  BONES 

FIG.  231. — Joints  of  the  right  hand,  from  the  back  of  the  hand.      (Spalteholz.) 


The  second  metacarpal  bone  receives  two  fasciculi — one  from  the  trapezium, 
the  other  from  the  trapezoid;  the  third  metacarpal  receives  two — one  from 
the  trapezoid  and  one  from  the  os  magnum;  the  fourth  two — one  from  the  os 
magnum  and  one  from  the  unciform;  the  fifth  receives  a  single  fasciculus  from 
the  unciform  bone,  which  is  continuous  with  a  similar  ligament  on  the  palmar 
surface,  forming  an  incomplete  capsule. 

The  Palmar  or  Volar  Ligaments  (ligamenta  carpometacarpea  volaria)  have  a 
somewhat  similar  arrangement  on  the  palmar  surface,  with  the  exception  of 
the  third  metacarpal,  which  has  three  ligaments — an  external  one  from  the 


CARPO-METACARPAL    ARTICULATIONS 


325 


trapezium,  situated  above  the  sheath  of  the  tendon  of  the  Flexor  carpi  radialis; 
a  middle  one,  from  the  os  magnum;  and  an  internal  one,  from  the  unciform. 

The  Interosseous  Ligaments  consist  of  short,  thick  fibres,  which  are  limited  to 
one  part  of  the  carpo-metacarpal  articulation ;  they  connect  the  contiguous  inferior 
angles  of  the  os  magnum  and  unciform  with  the  adjacent  surfaces  of  the  third 
and  fourth  metacarpal  bones. 

Synovial  Membrane. — The  synovial  membrane  is  a  continuation  of  that  between 
the  two  rows  of  carpal  bones.  Occasionally,  the  articulation  of  the  unciform 
with  the  fourth  and  fifth  metacarpal  bones  has  a  separate  synovial  membrane. 

The  synovial  membranes  of  the  wrist  and  carpus  (Fig.  231)  are  thus  seen  to 
be  five  in  number.  The  first,  the  membrana  sacciformis  or  the  recessus  sacciformis 
of  the  inferior  radio-ulnar  articulation,  passes  from  the  lower  end  of  the  ulna  to 


TENDON  OF  FLEXOR 
SUBLIMIS  DIGITORUM 


TENDON  OF  FLEXOR 
PROFUNDUS    DIGITORUM 


ANTERIOR 

OR  VAGINAL 

LIGAMENT 


TRANSVERSE 

METACARPAL 

LIGAMENT 


LATERAL 
LIGAMENT 


SECOND  LUM- 
BRICAL  MUSCLE 


ANTERIOR  OR  SECOND 

VAGINAL  LIGAMENT  PALMAR 

INTEROSSEOUS 
MUSCLE 


TRANSVERSE  META- 
CARPAL LIGAMENT 


ANTERIOR  OR 
VAGINAL  LIGAMENT 


FIG.  232. — Metacarpal  bones  and  first  phalanges  of  the  second  to  the  fifth  finger  of  the  right  hand,  with 
ligaments,  from  the  volar  surface.     (Spalteholz.) 

the  sigmoid  cavity  of  the  radius,  and  lines  the  upper  surface  of  the  interarticular 
fibro-cartilage.  The  second  passes  from  the  lower  end  of  the  radius  and  inter- 
articular  fibro-cartilage  above  to  the  bones  of  the  first  row  below,  The  third, 
the  most  extensive,  passes  between  the  contiguous  margins  of  the  two  rows  of 
carpal  bones — between  the  bones  of  the  second  row  to  the  carpal  extremities  of 
the  four  inner  metacarpal  bones.  The  fourth,  from  the  margin  of  the  trapezium 
to  the  metacarpal  bone  of  the  thumb.  The  fifth,  between  the  adjacent  margins 
of  the  cuneiform  and  pisiform  bones. 

Actions. — The  movement  permitted  in  the  carpo-metacarpal  articulations  of  the 
four  inner  fingers  is  limited  to  a  slight  gliding  of  the  articular  surfaces  upon  each 
other,  the  extent  of  which  varies  in  the  different  joints.  Thus  the  articulation  of  the 
metacarpal  bone  of  the  little  finger  is  most  movable,  then  that  of  the  ring  finger. 
The  metacarpal  bones  of  the  index  and  middle  fingers  are  almost  immovable. 


326 


THE   ARTICULATIONS    OR    JOINTS 


3.  ARTICULATIONS  OF  THE  METACARPAL  BONES  WITH  EACH  OTHER  (ARTICU- 
LATIONES  INTERMETACARPEAE  (Figs.  228,  229,  231). 

The  carpal  extremities  of  the  four  inner  metacarpal  bones  articulate  with 
one  another  at  each  side  by  small  surfaces  covered  with  cartilages,  and  connected 
together  by  dorsal,  palmar,  and  interosseous  ligaments. 

The  Dorsal  Ligaments  (ligamenta  basium  oss.  metacarp.  dorsalia)  and  Palmar 
Ligaments  (ligamenta  basium  oss.  metacarp.  volarid)  pass  transversely  from  one 

bone  to  another  on  the  dorsal  and  palmar  sur- 

»O   P& 

faces. 

The  Interosseous  Ligaments  (ligamenta  basium 
oss.  metacarp.  interossea)  pass  between  their  con- 
tiguous surfaces,  just  beneath  their  lateral  artic- 
ular facets. 

Synovial  Membrane  (Fig.  231). — The  synovial 
membrane  between  the  lateral  facets  is  a  reflec- 
tion from  that  between  the  two  rows  of  carpal 
fiii  bones. 

The  Transverse  Metacarpal  Ligament  (liga- 
mentum  capitulorum  oss.  metacarpalium  trans- 
versum]  (Fig.  232)  is  a  narrow,  fibrous  band 
which  passes  transversely  across  the  anterior  sur- 
faces of  the  digital  extremities  of  the  four  inner 
metacarpal  bones,  connecting  them  together.  It 
is  blended  anteriorly  with  the  palmar  ligaments 
of  the  metacarpo-phalangeal  articulations.  To 
its  posterior  border  is  connected  the  fascia  which 
covers  the  Interossei  muscles.  Its  anterior  sur- 
face is  concave  where  the  flexor  tendons  pass 
over  it.  Behind  it  the  tendons  of  the  Interossei 
muscles  pass  to  their  insertion. 


ARTICULAR 
CAPSULE 


ARTICULAR. 
CAPSULE 


ARTICULAR 
CAPSULE" 


LATERAL 
"LIGAMEM 


X.  Metacarpo-phalangeal  Articulations  ( Artic- 

ulationes  Metacarpophalangeae) 

(Figs.  232,  233). 

These  articulations  are  of  the  condyloid  kind, 
formed  by  the  reception  of  the  rounded  head  of 
the  metacarpal  bone  into  a  shallow  cavity  in  the 
extremity  of  the  first  phalanx.  The  expansion 
of  the  extensor  tendon  acts  as  a  dorsal  ligament. 
There  is  a  capsular  ligament  which  at  certain 
points  has  strengthening  ligaments.  The  liga- 
.ments  are — 


Anterior. 


Two   Lateral. 


The    Anterior,    Palmar,    or    Vaginal    Ligament 

(glenoid    ligament    of     Cruveilhier,    ligamentnm 
vaqinale)    is    a    thick,    dense,   fibrous   structure, 

FIG.   233.  —  Metacarpal  bones  and  first        i  i      '       .1  i  <>  j>     -r       •    •     ,     •       ±1 

halanges  of  the  third  finger  of  the  right  placed  on  the  palmar  surrace  ot  the  joint  in  the 


interval  between  the  lateral  ligaments,  to  which 
it  is  connected;  it  is  loosely  united  to  the  meta- 

carpal bone,  but  very  firmly  to  the  base  of  the  first  phalanx.      Its  palmar  surface 
is  intimately  blended  with  the  transverse  metacarpal  ligament,  and  presents  a 


THE  HIP -JOINT 


327 


groove  for  the  passage  of  the  flexor  tendons,  the  sheath  surrounding  which  is 
connected  to  each  side  of  the  groove.  By  its  deep  surface  it  forms  part  of  the 
articular  surface  for  the  head  of  the  metacarpal  bone,  and  is  lined  by  a  synovial 
membrane. 

The  Lateral  or  Collateral  Ligaments  (ligamenta  collateralid)  are  strong,  rounded 
cords  placed  one  on  each  side  of  the  joint,  each  being  attached  by  one  extremity 
to  the  posterior  tubercle  on  the  side  of  the  head  of  the  metacarpal  bone,  and  by 
the  other  to  the  contiguous  extremity  of  the  phalanx. 

Actions.  —  The  movements  which  occur  in  these  joints  are  flexion,  extension, 
adduction,  abduction,  and  circumduction;  the  lateral  movements  are  very  limited. 

Surface  Form. — The  prominences  of  the  knuckles  do  not  correspond  to  the  position  of  the 
joints  either  of  the  metacarpo-phalangeal  or  interphalangeal  articulations.  These  prominences 
are  invariably  formed  by  the  distal  ends  of  the  proximal  bone  of  each  joint,  and  the  line  indi- 
cating the  position  of  the  joint  must  be  sought  considerably  in  front  of  the  middle  of  the  knuckle. 
The  usual  rule  for  finding  these  joints  is  to  flex  the  distal  phalanx  on  the  proximal  one  to  a  right 
angle;  the  position  of  the  joint  is  then  indicated  by  an  imaginary  line  drawn  along  the  middle  of 
the  lateral  aspect  of  the  proximal  phalanx. 

XI.  Articulations  of  the  Phalanges  (Articulationes  Digitorum  Maims 

(Fig.  233). 

These  are  ginglymus  joints.  Each  joint  has  a  capsule,  and  certain  accentuated 
portions  are  regarded  as  definite  ligaments.  These  ligaments  are — 

Anterior  or  Palmar.  Two  Lateral  (ligamenta  collateralia). 

The  arrangement  of  these  ligaments  is  similar  to  those  in  the  metacarpo- 
phalangeal  articulations;  the  extensor  tendon  supplies  the  place  of  a  dorsal 
ligament. 

Actions. — The  only  movements  permitted  in  the  phalangeal  joints  are  flexion 
and  extension;  these  movements  are  more  extensive  between  the  first  and  second 
phalanges  than  between  the  second  and  third.  The  movement  of  flexion  is  very 
considerable,  but  extension  is  limited  by  the  anterior  and  lateral  ligaments. 


ARTICULATIONS  OF  THE  LOWER  EXTREMITY. 

The  articulations  of  the  Lower  Extremity  comprise  the  following  groups: 


I.  The  Hip-joint. 
II.  The  Knee-joint. 

III.  The    Articulations    between    the 

Tibia  and  Fibula. 

IV.  The  Ankle-joint. 

V.  The  Articulations  of  the  Tarsus. 


VI.  The  Tarso-metatarsal  Articulations. 
VII.  Articulations    of     the     Metatarsal 

Bones  with  each  other. 
VIII.  The    Metatarso-phalangeal   Artic- 
ulations. 
IX.  The  Articulations  of  the  Phalanges. 


I.  The  Hip-joint  (Articulatio  Coxae)  (Figs.  234,  235,  236,  237,  238,  239). 

This  articulation  is  an  enarthrodial  or  ball-and-socket  joint,  formed  by  the 
reception  of  the  head  of  the  femur  into  the  cup-shaped  cavity  of  the  acetabulum. 
The  articulating  surfaces  are  covered  with  cartilage,  that  on  the  head  of  the  femur 
being  thicker  at  the  centre  than  at  the  circumference,  and  covering  the  entire 
surface,  with  the  exception  of  a  depression  just  below  its  centre  for  the  ligamen- 
tum  teres;  that  covering  the  acetabulum  is  much  thinner  at  the  centre  than  at 
the  circumference.  It  forms  an  incomplete  cartilaginous  ring  of  a  horseshoe 
shape,  being  deficient  below,  where  there  is  a  circular  depression,  which  is  occu- 


328 


THE  ARTICULATIONS    OR    JOINTS 


pied  in  the  recent  state  by  a  mass  of  fat  covered  by  synovial  membrane.    The 
ligaments  of  the  joints  are  the 


Capsular. 
Ilio-femoral. 


Transverse. 


Teres. 
Cotyloid. 


The  Capsular  Ligament  (capsula  articularis)  (Figs.  234,  235,  237,  and  239)  is  a 
strong,  dense,  ligamentous  capsule,  embracing  the  margin  of  the  acetabulum 
above  and  surrounding  the  neck  of  the  femur  below.  Its  upper  circumference 


ANTERIOR 

INTERTRO 

CHANTERIC    LINE 


FIG.  234.— Right  hip-joint,  from  in  front.     (Spalteholz.) 

is  attached  to  the  acetabulum,  above  and  behind,  two  or  three  lines  external 
to  the  cotyloid  ligament;  but  in  front  it  is  attached  to  the  outer  margin  of 
this  ligament,  and  opposite  to  the  notch,  where  the  margin  of  this  cavity  is 
deficient,  it  is  connected  to  the  transverse  ligament,  and  by  a  few  fibres  to 
the  edge  of  the  obturator  foramen.  Its  lower  circumference  surrounds  the  neck 
of  the  femur,  being  attached,  in  front,  to  the  spiral  or  anterior  intertrochanteric 
line;  above,  to  the  base  of  the  neck;  behind,  to  the  neck  of  the  bone,  about  half 


THE   HIP-JOINT 


329 


an  inch  above  the  posterior  intertrochanteric  line.  From  this  insertion  the  fibres 
are  reflected  upward  over  the  neck  of  the  femur,  forming  a  sort  of  tubular  sheath, 
the  cervical  reflection,  which  blends  with  the  periosteum  and  can  be  traced  as  fur 
as  the  articular  cartilage.  On  the  surface  of  the  neck  of  the  femur  some  of  these 
reflected  fibres  are  raised  into  longitudinal  folds,  termed  retinacula.  It  is  much 
thicker  at  the  upper  and  forepart  of  the  joint,  where  the  greatest  amount  of 


FIG.  235. — Right  hip-joint,  from  behind.     (The  joint  capsule,  except  for  the  strengthening  ligaments,  has 

been  removed.)     (Spalteholz.) 


resistance  is  required,  than  below  and  internally,  where  it  is  thin,  loose,  and 
longer  than  in  any  other  part.  It  consists  of  two  sets  of  fibres,,  circular  and  lon- 
gitudinal. The  circular  fibres,  zona  orbicularis  (Fig.  237) ,  are  most  abundant  at  the 
lower  and  back  part  of  the  capsule,  and  form  a  sling  or  collar  around  the  neck  of 
the  femur.  Anteriorly  they  blend  with  the  deep  surface  of  the  ilio-femoral  .liga- 
ment, and  through  its  medium  reach  the  anterior  inferior  spine  of  the  ilium.  The 
longitudinal  fibres  are  greatest  in  amount  at  the  upper  and  front  part  of  the  cap- 
sule, where  they  form  distinct  bands  or  accessory  ligaments,  of  which  the  most 
important  is  the  ilio-femoral.  Other  accessory  bands  are  known  as  the  pubo- 


330 

femoral  or  pubo-capsular  ligament  (ligamentum  pubocapsulare) ,  passing  from  the 
outer  portion  of  the  horizontal  pubic  ramus,  the  ilio-pectineal  eminence,  the 
obturator  crest  and  the  obturator  membrane,  to  the  front  of  the  capsule;  and 
ischio-capsular  ligament  or  ligament  of  Bertin  (ligamentum  ischiocapsulare) , 
passing  from  the  ischium,  just  below  the  acetabulum,  to  blend  with  the  circular 
fibres  at  the  lower  part  of  the  joint.  The  external  surface  is  rough,  covered  by 
numerous  muscles,  and  separated  in  front  from  the  Psoas  and  Iliacus  muscles  by 
a  synovial  bursa,  which  not  infrequently  communicates,  by  a  circular  aperture, 
with  the  cavity  of  the  joint.  It  differs  from  the  capsular  ligament  of  the  shoulder 
in  being  much  less  loose  and  lax,  and  in  not  being  perforated  for  the  passage  of 
a  tendon. 


ANTERIOR 

INFERIOR 

SPINE  OF  ILIUM 


SPINE  OF 
ISCHIUM 


TRANSVERSE 
LIGAMENT  OF 
ACETABULUM 


TUBEROSITV 
'OF  ISCHIUM 


FIG.  236. — Right  hip-joint  from  the  medial  side.     (The  bottom  of  the  acetabulum  has  been  chiselled  away 
sufficiently  to  make  the  head  of  the  femur  visible.)     (Spalteholz.) 

The  Ilio-femoral  or  Y-ligament  or  Ligament  of  Bigelow  (ligamentum  ilio- 
femorale)  (Figs.  234,  235,  237,  and  238)  is  an  accessory  band  of  fibres  extending 
obliquely  across  the  front  of  the  joint;  it  is  intimately  connected  with  the  cap- 
sular ligament,  and  serves  to  strengthen  it  in  this  situation.  It  is  attached, 
above,  to  the  lower  part  of  the  anterior  inferior  spine  of  the  ilium  and  the 
adjacent  rim  of*  the  acetabulum;  and,  diverging  below,  forms  two  bands,  of 
which  one  passes  downward  to  be  inserted  into  the  lower  part  of  the  anterior 
intertrochanteric  line;  the  other  passes  downward  and  outward  to  be  inserted 
into  the  upper  part  of  the  same  line  and  the  adjacent  part  of  the  neck  of  the 
femur.  Between  the  two  bands  is  a  thinner  part  of  the  capsule.  Sometimes 
there  is  no  division,  but  the  ligament  spreads  out  into  a  flat,  triangular  band, 
which  is  attached  below  into  the  whole  length  of  the  anterior  intertrochanteric 
line.  This  ligament  is  frequently  called  the  Y-shaped  ligament  of  Bigelow;  and 


THE   HIP -JOINT 


331 


the  outer  or  upper  of  the  two  bands  is  sometimes  described  as  a  separate  liga- 
ment, under  the  name  of  the  ilio-trochanteric  ligament. 

The  Ligamentum  Teres,  or  the  Interarticular  Ligament  (ligamentum  teres  femoris) 
(Figs.  236,  237,  and  239)  is  a  triangular  band  implanted  by  its  apex  into  the 
depression  a  little  behind  and  below  the  centre  of  the  head  of  the  femur,  and  by 
its  broad  base  into  the  margins  of  the  cotyloid  notch,  becoming  blended  with  the 
transverse  ligament.  It  is  formed  of  connective  tissue,  surrounded  by  a  tubular 
sheath  of  synovial  membrane.  Sometimes  only  the  synovial  fold  exists.  Very 
rarely  it  is  absent.  The  ligament  is  made  tense  when  the  hip  is  semiflexed, 


ILIOLUMBAR  LIGAMENT 


ANTERIOR  SACRO- 
ILIAC  LIGAMENT 


CAPSULAR   LIGAMENT. 

FIBROUS  PORTION 

CAPSULAR    LIGAMENT, 

SYNOVIAL  PORTION 


ILIOYEMORAL 
LIGAMENT 


ZONA 
ORBICULARIS 

GREAT 
TROCHANTER 


COOPER'S  LIGAMENT 
SPINE  OF  PUBIS 


PUBOFEMORAL 
LIGAMENT 


OBTURATOR   LIGAMENT 
ZONA  ORBICULARIS 
SMALL  SYNOVIAL  MEMBRANE  COVERING 

TROCHANTER  NECK  OF  FEMUR 


FIG.  237. — The  right  hip-joint,  seen  from  before.     (Toldt.) 

and  the  limb  adducted  and  rotated  outward;  it  is,  on  the  other  hand,  relaxed 
when  the  limb  is  abducted.  It  has,  however,  but  little  influence  as  a  ligament, 
though  it  may  to  a  certain  extent  limit  movement,  and  would  appear  to  be 
merely  a  "vestigial  and  practically  useless  ligament."1  It  is  probably  a  modifi- 
cation of  the  folds  which  in  other  joints  fringe  the  margins  of  reflection  of  synovial 
membranes. 

The  Cotyloid  Ligament  (labrum  glenoidale]  (Fig.  239)  is  a  fibro-cartilaginous  rim 
attached  to  the  margin  of  the  acetabulum,  the  cavity  of  which  it  deepens;  at  the 


1  J.  Bland  Sutton.     Ligaments:  Their  Nature  and  Morphology. 


332 


THE  ARTICULATIOS    OR   JOINTS 


same  time  it  protects  the  edges  of  the  bone  and  fills  up  the  inequalities  on  its  sur- 
face.   It  bridges  over  the  notch  as  the  transverse  ligament  of  the  acetabulum,  and 

thus  forms  a  complete  circle,  which  closely  sur- 
rounds the  head  of  the  femur,  and  assists  in 
holding  it  in  its  place,  acting  as  a  sort  of  valve. 
It  is  prismoid  on  section,  its  base  being  attached 
to  the  margin  of  the  acetabulum  and  its  op- 
posite edge  being  free  and  sharp;  whilst  its 
two  surfaces  are  invested  by  synovial  mem- 
brane, the  external  one  being  in  contact  with 
the  capsular  ligament,  the  internal  one  being 
inclined  inward,  so  as  to  narrow  the  acetab- 
ulum and  embrace  the  cartilaginous  surface 
of  the  head  of  the  femur.  It  is  much  thicker 
above  and  behind  than  below  and  in  front, 
and  consists  of  close,  compact  fibres,  which 
arise  from  different  points  of  the  circumference 
of  the  acetabulum  and  interlace  with  each  other 
at  very  acute  angles. 

The  transverse  ligament  of  the  acetabulum 
(ligamentum  tramversum  acetabuli)  (Figs.  236 
and  239)  is  in  reality  a  portion  of  the  cotyloid 
ligament,  though  differing  from  it  in  having 
no  cartilage-cells  amongst  its  fibres.  It  con- 
sists of  strong,  flattened  fibres,  which  cross  the 
notch  at  the  lower  part  of  the  acetabulum  and 
convert  it  into  a  foramen.  Thus  an  interval 
is  left  beneath  the  ligament  for  the  passage  of 
nutrient  vessels  to  the  joint. 
Synovial  Membrane  (Figs.  237  and  239). — The  synovial  membrane  is  very 
extensive.  Commencing  at  the  margin  of  the  cartilaginous  surface  of  the  head 
of  the  femur,  it  covers  all  that  portion  of  the  neck  which  is  contained  within  the 
joint;  from  the  neck  it  is  reflected  on  the  internal  surface  of  the  capsular  liga- 
ment, covers  both  surfaces  of  the  cotyloid  ligament  and  the  mass  of  fat  contained 
in  the  depression  at  the  bottom  of  the  acetabulum,  and  is  prolonged  in  the  form 
of  a  tubular  sheath  around  the  ligamentum  teres,  as  far  as  the  head  of  the  femur. 
It  sometimes  communicates  through  a  hole  in  the  capsular  ligament  between 
the  inner  band  of  the  Y-shaped  ligament  and  the  pubo-femoral  ligament  with 
a  bursa  situated  on  the  under  surface  of  the  Ilio-psoas  muscle. 

The  muscles  in  relation  with  the  joint  (Fig.  240)  are,  in  front,  the  Psoas  and 
Iliacus,  separated  from  the  capsular  ligament  by  a  synovial  bursa;  above,  the 
reflected  head  of  the  Rectus  and  Glutens  minimus,  the  latter  being  closely  adherent 
to  the  capsule ;  internally,  the  Obturator  externus  and  Pectineus ;  behind,  the  Pyri- 
formis,  Gemellus  superior,  Obturator  internus,  Gemellus  inferior,  Obturator  exter- 
nus, and  Quadratus  femoris. 

The  arteries  supplying  the  joint  are  derived  from  the  obturator,  sciatic,  internal 
circumflex,  and  gluteal. 

The  nerves  are  articular  branches  from  the  sacral  plexus,  great  sciatic,  obtu- 
rator, accessory  obturator,  and  a  filament  from  the  branch  of  the  anterior  crural 
supplying  the  rectus. 

Bursse. — Numerous  bursse  exist  in  the  neighborhood  of  the  hip-joint.  Some 
anatomists  have  counted  twenty-one  (Synnestredt).  The  chief  ones  are :  1.  The 
ilio-pectineal  bursa  (bursa  iliopectinea)  (Fig.  240),  between  the  ilio-psoas  tendon 
and  the  capsule  of  the  joint.  It  often  communicates  with  the  hip-joint.  2.  The 


FIG.  238. — Hip-joint,  showing  the  ilio-femoral 
ligament.      (After  Bigelow.) 


THE  HIP -JOINT 


333 


subtendinous  iliac  bursa  (bursa  iliaca  subtendinea) ,  between  the  tendon  of  the  psoas 
and  iliacus  and  the  lesser  trochanter.  3.  The  ischio-gluteal  bursa  (bursa  ischiadica 
m.  glutaei  maximi) ,  between  the  Gluteus  maximus  muscle  and  the  tuberosity  of  the 
ischium  (not  constant).  4.  The  bursa  of  the  great  trochanter  (bursa  trochanterica  m. 
glutcei  maximi),  between  the  great  trochanter  and  the  Gluteus  maximus  muscle 
near  the  muscular  insertion,  o.  Two  or  three  gluteo-femoral  bursae  (bursce 
glutccofemorales)  below.  6.  The  obturator  bursa  (bursa  m.  obturatorii  interni), 
between  the  margin  of  the  great  sacro-sciatic  notch  and  the  tendon  of  the 
Obturator  internus  muscle.  7.  The  subcutaneous  trochanteric  bursa  (bursa  tro- 


GREAT 
TROCHANTER 


EPIPHYSEAL 
JUNCTION 


FIG.  239. — Right  hip-joint.     Frontal  section.     Posterior  half,  viewed  from  in  front.     (The  joint  surfaces 
have  been  somewhat  pulled  apart.)     (Spalteholz.) 


chanterica  subcutanea) ,  between  the  cutaneous  surface  and  the  great  trochanter. 
Besides  these  there  is  a  bursa  between  the  great  trochanter  and  the  anterior  part 
of  the  Gluteus  medius — between  the  great  trochanter  and  the  posterior  part  of 
the  Gluteus  medius — between  the  great  trochanter  and  the  Gluteus  minimus — 
beneath  the  Pyriformis  muscle — between  the  small  trochanter  and  the  Quad- 
ratus  femoris  muscle,  and  there  are  bursae  beneath  the  Biceps  femoris  muscle. 

Actions. — The  movements  of  the  hip  are  very  extensive,  and  consist  of  flexion, 
extension,  adduction,  abduction,  circumduction,  and  rotation. 


334 


THE   ARTICULATIONS    OR    JOINTS 


The  hip-joint  presents  a  very  striking  contrast  to  the  shoulder-joint  in  the 
much  more  complete  mechanical  arrangements  for  its  security  and  for  the  limita- 
tion of  its  movements.  In  the  shoulder,  as  we  have  seen,  the  head  of  the  humerus 
is  not  adapted  at  all  in  size  to  the  glenoid  cavity,  and  is  hardly  restrained  in  any 
of  its  ordinary  movements  by  the  capsular  ligament.  In  the  hip-joint,  on  the 
contrary,  the  head  of  the  femur  is  closely  fitted  to  the  acetabulum  for  a  distance 
extending  over  nearly  half  a  sphere,  and  at  the  margin  of  the  bony  cup  it  is  still 
more  closely  embraced  by  the  cotyloid  ligament,  so  that  the  head  of  the  femur 
is  held  in  its  place  by  that  ligament  even  when  the  fibres  of  the  capsule  have  been 
quite  divided  (Humphry).  The  anterior  portion  of  the  capsule,  described  as  the 
ilio-femoral  ligament,  is  the  strongest  of  all  the  ligaments  in  the  body,  and  is  put 
on  the  stretch  by  any  attempt  to  extend  the  femur  beyond  a  straight  line  with  the 
trunk.  That  is  to  say,  this  ligament  is  the  chief  agent  in  maintaining  the  erect 
position  without  muscular  fatigue;  for  a  vertical  line  passing  through  the  centre 
of  gravity  of  the  trunk  falls  behind  the  centres  of  rotation  in  the  hip-joints,  and 


Ileo-fem.  ligament 


Isch.  caps, 
ligament. 


Pub.  fern,  ligament 


FIG.  240. — Relation  of  muscles  to  hip-joint.     (Henle.) 

therefore  the  pelvis  tends  to  fall  backward,  but  is  prevented  by  the  tension  of 
the  ilio-femoral  and  capsular  ligaments.  The  security  of  the  joint  may  be  also 
provided  for  by  the  two  bones  being  directly  united  through  the  ligamentum 
teres;  but  it  is  doubtful  whether  this  so-called  ligament  can  have  much  influence 
upon  the  mechanism  of  the  joint.  Flexion  of  the  hip-joint  is  arrested  by  the  soft 
parts  of  the  thigh  and  abdomen  being  brought  into  contact  when  the  leg  is  flexed 
on  the  thigh;  and  by  the  action  of  the  hamstring  muscles  when  the  leg  is  extended;1 
extension,  by  the  tension  of  the  ilio-femoral  ligament  and  front  of  the  capsule; 
adduction,  by  the  thighs  coming  into  contact;  adduction,  with  flexion  by  the 
outer  band  of  the  ilio-femoral  ligament,  the  outer  part  of  the  capsular  ligament: 

1  The  hip-joint  cannot  be  completely  flexed,  in  most  persons,  without  at  the  same  time  flexing  the  knee,  on 
account  of  the  shortness  of  the  hamstring  muscles. — Cleland,  Jour,  of  Anat.  and  Phys.,  No.  1,  Old  Series,  p.  87. 


DR'  M'  LEWIS  EMERSON  . 
THE  HIP -JOINT  335 

abduction,  by  the  inner  band  of  the  ilio-femoral  ligament  and  the  pubo-femoral 
band;  rotation  outward,  by  the  outer  band  of  the  ilio-femoral  ligament;  and 
rotation  inward,  by  the  ischio-capsular  ligament  and  the  hinder  part  of  the  cap- 
sule. The  muscles  which  flex  the  femur  on  the  pelvis  are  the  Psoas,  Iliacus, 
Rectus,  Sartorius,  Pectineus,  Adductor  longus  and  brevis,  and  the  anterior  fibres 
of  the  Gluteus  medius  and  minimus.  Extension  is  mainly  performed  by  the 
Gluteus  maximus,  assisted  by  the  hamstring  muscles.  The  thigh  is  adducted  by 
the  Adductor  magnus,  longus,  and  brevis,  the  Pectineus,  the  Gracilis,  and  lower 
part  of  the  Gluteus  maxirnus,  and  abducted  by  the  Gluteus  medius  and  minimus 
and  upper  part  of  the  Gluteus  maximus.  The  muscles  which  rotate  the  thigh 
inward  are  the  anterior  fibres  of  the  Gluteus  medius,  the  Gluteus  minimus,  and  the 
Tensor  fascia  femoris;  while  those  which  rotate  it  outward  are  the  posterior  fibres 
of  the  Gluteus  medius,  the  Pyriformis,  Obturator  externus  and  internus,  Gemellus 
superior  and  inferior,  Quadratus  femoris,  Iliacus,  Gluteus  maximus,  the  three 
Adductors,  the  Pectineus,  and  the  Sartorius. 

Surface  Form. — A  line  drawn  from  the  anterior  superior  spinous  process  of  the  ilium  to 
the  most  prominent  part  of  the  tuberosity  of  the  ischium  (Nelaton's  line)  runs  through  the 
centre  of  the  acetabulum,  and  would,  therefore,  indicate  the  level  of  the  hip-joint;  or,  in  other 
words,  the  upper  border  of  the  great  trochanter,  which  lies  on  Nelaton's  line,  is  on  a  level  with 
the  centre  of  the  hip-joint. 

Surgical  Anatomy. — Inflammation  of  bursce  about  the  hip-joint  gives  rise  to  confusing 
symptoms.  Inflammation  of  one  of  the  bursse  over  the  great  trochanter  is  not  uncommon. 
Great  pain  is  produced  if  any  movement  of  the  gluteal  muscles  is  permitted. 

Enlargement  of  the  bursa  over  the  ischial  tuberosity  was  long  called  weaver's  button.  Enlarge- 
ment of  the  bursa  beneath  the  ilio-psoas  may  produce  a  large  swelling.  Bursal  inflammation  is 
not  unusually  mistaken  for  hip-joint  disease 

In  dislocation  of  the  hip  "the  head  of  the  thigh  bone  may  rest  at  any  point  around  its  socket" 
(Bryant);  but  whatever  position  the  head  ultimately  assumes,  the  primary  displacement  is 
generally  downward  and  inward,  the  capsule  giving  way  at  its  weakest — that  is,  its  lower  and 
inner — part.  The  situation  that  the  head  of  the  bone  subsequently  assumes  is  determined 
by  the  degree  of  flexion  or  extension,  and  of  outward  or  inward  rotation  of  the  thigh  at  the 
moment  of  luxation,  influenced,  no  doubt,  by  the  ilio-femoral  ligament,  which  is  not  easily 
ruptured.  When,  for  instance,  the  head  is  forced  backward,  this  ligament  forms  a  fixed  axis, 
round  which  the  head  of  the  bone  rotates,  and  the  head  is  thus  driven  on  to  the  dorsum  of  the  ilium. 
The  ilio-femoral  ligament  also  influences  the  position  of  the  thigh  in  the  various  dislocations: 
in  the  dislocations  backward  it  is  tense,  and  produces  inversion  of  the  limb;  in  the  dislocation 
on  to  the  pubes  it  is  relaxed,  and  therefore  allows  the  external  rotators  to  evert  the  thigh;  while 
in  the»thyroid  dislocation  it  is  tense  and  produces  flexion.  The  muscles  inserted  into  the  upper 
part  of  the  femur,  with  the  exception  of  the  Obturator  internus,  have  very  little  direct  influence 
in  determining  the  position  of  the  bone.  But  Bigelow  has  endeavored  to  show  that  the  Obtu- 
rator internus  is  the  principal  agent  in  determining  whether  in  the  backward  dislocations  the 
head  of  the  bone  shall  be  ultimately  lodged  on  the  dorsum  of  the  ilium  or  in  or  near  the  sciatic 
notch.  In  both  dislocations  the  head  passes,  in  the  first  instance,  in  the  same  direction;  but, 
as  Bigelow  asserts,  in  the  displacement  on  to  the  dorsum,  the  head  of  the  bone  travels  up  behind 
the  acetabulum,  in  front  of  the  muscle;  while  in  the  dislocation  into  the  sciatic  notch,  the  head 
passes  behind  the  muscle,  and  is  therefore  prevented  from  reaching  the  dorsum,  in  consequence 
of  the  tendon  of  the  muscle  arching  over  the  neck  of  the  bone,  and  so  remains  in  the  neighbor- 
hood of  the  sciatic  notch.  Bigelow,  therefore,  distinguishes  these  two  forms  of  dislocation  by 
describing  them  as  dislocations  backward,  "above  and  below,"  the  Obturator  internus. 

The  ilio-femoral  ligament  is  rarely  torn  in  dislocations  of  the  hip,  and  this  fact  is  taken 
advantage  of  by  the  surgeon  in  reducing  these  dislocations  by  manipulation.  It  is  made  to  act 
as  a  fulcrum  to  a  lever,  of  which  the  long  arm  is  the  shaft  of  the  femur,  and  the  short  arm  the 
neck  of  the  bone. 

The  hip-joint  is  rarely  the  seat  of  acute  synovitis  from  injury,  on  account  of  its  deep  position 
and  its  thick  covering  of  soft  parts.  Acute  inflammation  may,  and  does,  frequently  occur  as 
the  result  of  constitutional  conditions,  as  rheumatism,  pyaemia,  etc.  When,  in  these  cases, 
effusion  takes  place,  and  the  joint  becomes  distended  with  fluid,  the  swelling  is  not  very  easy 
to  detect  on  account  of  the  thickness  of  the  capsule  and  the  depth  of  the  articulation.  It  is 
principally  to  be  found  on  the  front  of  the  joint,  just  internal  to  the  ilio-femoral  ligament;  or 
behind,  at  the  lower  and  back  part.  In  these  two  places  the  capsule  is  thinner  than  elsewhere. 
Disease  of  the  hip-joint  is  much  more  frequently  of  a  chronic  character  and  is  usually  of  tuber- 
culous origin.  It  begins  either  in  the  bones  or  in  the  synovial  membrane,  more  frequently  in  the 


336  THE   ARTICULATIONS    OR   JOINTS 

formef,  and  probably,  in  most  cases,  in  the  growing,  highly  vascular  tissue  in  the  neighborhood' 
of  the  epiphysial  cartilage.  In  this  respect  it  differs  very  materially  from  tuberculous  arthritis- 
of  the  knee,  where  the  disease  often  commences  in  the  synovial  membrane.  The  reasons  why 
hip-disease  so  frequently  begins  near  the  epiphysial  cartilage  are  twofold:  first,  this  part  being 
the  centre  of  rapid  growth,  its  nutrition  is  unstable  and  inflammation  is  easily  awakened;, 
and,  secondly,  great  strain  is  thrown  upon  it,  from  the  frequency  of  falls  and  blows  upon  the  hip, 
which  causes  crushing  of  the  epiphysial  cartilage  or  the  cancellous  tissue  in  its  neighborhood, 
with  the  results  likely  to  follow  such  an  injury.  In  addition  to  these,  the  depth  of  the  joint 
protects  it  from  the  causes  of  synovitis. 

In  chronic  hip-disease  the  affected  limb  assumes  an  altered  position,  the  cause  of  which  it 
is  important  to  understand.  In  the  early  stage  of  a  typical  case  the  limb  is  flexed,  abducted, 
and  rotated  outward.  In  this  position  all  the  ligaments  of  the  joint  are  relaxed:  the  front  of 
the  capsule  by  flexion;  the  outer  band  of  the  ilio-femoral  ligament  by  abduction;  and  the  inner 
band  of  this  ligament  and  the  back  of  the  capsule  by  rotation  outward.  It  is,  therefore,  the 
position  of  the  greatest  ease.  The  condition  is  not  quite  obvious  at  first  upon  examining  a- 
patient.  If  the  patient  is  laid  in  the  supine  position,  the  affected  limb  will  be  found  to  be 
extended  and  parallel  with  the  other.  But  it  will  be  found  that  the  pelvis  is  tilted  downward 
on  the  diseased  side  and  the  limb  apparently  longer  than  its  fellow,  and  that  the  lumbar  spine 
is  arched  forward  (lordosis).  If  now  the  thigh  is  abducted  and  flexed,  the  tilting  down- 
ward and  the  arching  forward  of  the  pelvis  disappears.  The  condition  is  thus  explained.  A 
limb  which  is  flexed  and  abducted  is  obviously  useless  for  progression,  and,  to  overcome  the 
difficulty,  the  patient  depresses  the  affected  side  of  his  pelvis  in  order  to  produce  parallelism 
of  his  limbs,  and  at  the  same  time  rotates  his  pelvis  on  its  transverse  horizontal  axis,  so  as  to 
direct  the  limb  downward  instead  of  forward.  In  the  latter  stages  of  the  disease  the  limb 
becomes  flexed,  adducted,  and  inverted.  The  position  probably  depends  upon  muscular 
action,  at  all  events  as  regards  the  adduction.  The  Adductor  muscles  are  supplied  by  the 
obturator  nerve,  which  also  largely  supplies  the  joint.  These  muscles  are  therefore  thrown  into 
reflex  action  by  the  irritation  of  the  peripheral  terminations  of  this  nerve  in  the  inflamed  artic- 
ulation. Osteo-arthritis  is  not  uncommon  in  the  hip-joint,  and  it  is  said  to  be  more  common  in 
the  male  than  in  the  female,  in  whom  the  knee-joint  is  more  frequently  affected.  It  is  a  disease 
of  middle  age  or  more  advanced  period  of  life. 

Congenital  dislocation  is  more  commonly  met  with  .in  the  hip-joint  than  in  any  other  articula- 
tion. The  displacement  usually  takes  place  on  to  the  dorsum  ilii.  It  gives  rise  to  extreme 
lordosis,  and  a  waddling  gait  is  noticed  as  soon  as  the  child  commences  to  walk. 

Excision  of  the  hip  may  be  required  for  disease  or  for  injury,  especially  for  gunshot  wound. 
It  may  be  performed  either  by  an  anterior  or  an  external  incision.  The  former  one  entails 
less  interference  with  important  structures,  especially  muscles,  than  the  posterior  one,  but  permits 
of  less  efficient  drainage.  In  these  days,  however,  when  the  surgeon  aims  at  securing  healing 
of  his  wound  without  suppuration,  this  second  advantage  is  not  of  so  much  importance.  In 
the  operation  in  front  the  surgeon  makes  an  incision  three  or  four  inches  in  length,  starting 
immediately  below  and  external  to  the  anterior  superior  spinous  process  of  the  ilium,  down- 
ward and  inward  between  the  Sartorius  and  Tensor  fasciae  femoris,  to  the  neck  of  the^bone, 
dividing  the  capsule  at  its  upper  part.  A  narrow-bladed  saw  now  divides  the  neck  of  the  femur, 
and  the  head  of  the  bone  is  extracted  with  sequestrum  forceps.  All  diseased  tissue  is  carefully 
removed  with  a  sharp  spoon  or  scissors,  and  the  cavity  thoroughly  flushed  with  a  hot  aseptic 
fluid. 

The  external  method  consists  in  making  an  incision  three  or  four  inches  long,  commencing 
midway  between  the  top  of  the  great  trochanter  and  the  anterior  superior  spine,  and  ending 
over  the  shaft,  just  below  the  trochanter.  The  muscles  are  detached  from  the  great  trochanter, 
and  the  capsule  opened  freely.  The  head  and  neck  are  freed  from  the  soft  parts  and  the  bone 
sawn  through  just  below  the  top  of  the  trochanter  with  a  narrow  saw.  The  head  of  the  bone  is 
then  levered  out  of  the  acetabulum.  In  both  operations,  if  the  acetabulum  is  eroded,  it  must  be 
freely  gouged. 

II.  The  Knee-joint  (Articulatio  Genu). 

The  knee-joint  was  formerly  described  as  a  ginglymus  or  hinge-joint,  but  is 
really  of  a  much  more  complicated  character.  It  must  be  regarded  as  consist- 
ing of  three  articulations  in  one :  one  between  each  condyle  of  the  femur  and  the 
corresponding  tuberosity  of  the  tibia,  which  are  condyloid  joints,  and  one  between 
the  patella  and  the  femur,  which  is  partly  arthrodial,  but  not  completely  so,  since 
the  articular  surfaces  are  not  mutually  adapted  to  each  other,  so  that  the  movement 
is  not  a  simple  gliding  one.  This  view  of  the  construction  of  the  knee-joint  receives 
confirmation  from  the  study  of  the  articulation  in  some  of  the  lower  mammals, 


THE   KNEE-JOINT 


337 


where  three  synovial  membranes  are  sometimes  found,  corresponding  to  these 
three  subdivisions,  either  entirely  distinct  or  only  connected  together  by  small 
communications.  This  view  is  further  rendered  probable  by  the  existence 
of  the  two  crucial  ligaments  within  the  joint,  which  must  be  regarded  as  the 
external  and  internal  lateral  ligaments  of  the  inner  and  outer  joints  respectively. 
The  existence  of  the  ligamentum  mucosum  would  further  indicate  a  tendency 
to  separation  of  the  synovial  cavity  into  two  minor  sacs,  one  corresponding  to 
each  joint. 

The  bones  entering  into  the  formation  of  the  knee-joint  are  the  condyles  of  the 
femur  above,  the  head  of  the  tibia  below,  and  the  patella  in  front.  The  bones  are 
connected  together  by  ligaments,  some  of  which  are  placed  on  the  exterior  of  the 
joint,  while  others  occupy  its  interior. 


External  Ligaments. 

Anterior,  or  Ligamentum  Patellae. 

Posterior. 

Internal  Lateral. 

Two  External  Lateral.  (The  long 
external  ligament  is  constant.  The 
short  external  ligament  is  not  always 
present.) 

Capsular. 


Interior  Ligaments. 

Anterior,  or  External  Crucial. 
Posterior,  or  Internal  Crucial. 
Two  Semilunar  Fibro-cartilages. 
Transverse. 
Coronary. 

T  -  f  Processes  of 

Ligamentum  mucosum.  c         .  , 

,     .  bvnovial 

Ligarnenta  alarm.  Membrane. 


The  Anterior  Ligament,  or  Ligamentum  Patellae  (Figs.  241,  245,  and  246),  is  the 
central  portion  of  the  common  tendon  of  the  Extensor  muscles  of  the  thigh,  which 
is  continued  from  the  patella  to  the  tubercle  of  the  tibia,  supplying  the  place  of  an 
anterior  ligament.  It  is  a  strong,  flat,  ligamentous  band  about  three  inches  in 
length,  attached,  above,  to  the  apex  of  the  patella  and  the  rough  depression  on  its 
posterior  surface ;  below,  to  the  lower  part  of  the  tubercle  of  the  tibia,  its  superficial 
fibres  being  continuous  over  the  front  of  the  patella  with  those  of  the  tendon  of  the 
Quadriceps  extensor.  The  lateral  portions  of  the  tendon  of  the  Extensor  muscles 
pass  down  on  either  side  of  the  patella,  and  are  attached  to  the  borders  of  this  bone. 
The  deep  fascia  and  the  quadriceps  extensor  muscle  are  inserted  into  the  patella. 
Prolongations  from  the  fascia  and  from  the  fibrous  expansion  of  the  muscle  pass 
from  the  edges  of  the  patella  and  from  the  ligament  of  the  patella  to  the  upper 
extremity  of  the  tibia  on  each  side  of  the  tubercle;  externally,  and  to  the  head  of 
the  fibula.  They  are  termed  lateral  patellar  ligaments  (retinaculum  patellae  mediate 
and  retinaculum  patellae  laterale),  and  merge  into  the  capsule.  The  posterior 
surface  of  the  ligamentum  patellae  is*  separated  from  the  front  of  the  capsular 
ligament  by  a  mass  of  fat. 

The  Posterior  Ligament  (ligamentum  popliteum  obliquum)  (Fig.  241)  is  a  broad, 
flat,  fibrous  band,  formed  of  fasciculi  separated  from  one  another  by  apertures 
for  the  passage  of  vessels  and  nerves.  It  is  attached,  above,  to  the  upper  margin 
of  the  intercondyloid  notch  of  the  femur,  and,  below,  to  the  posterior  margin  of 
the  head  of  the  tibia.  Superficial  to  the  main  part  of  the  ligament  and  forming 
a  portion  of  it  is  a  strong  fasciculus  derived  from  the  tendon  of  the  Semi- 
membranosus,  and  passing  from  the  back  part  of  the  inner  tuberosity  of  the  tibia 
obliquely  upward  and  outward  to  the  back  part  of  the  outer  condyle  of  the  femur. 
This  expansion  from  the  tendon  of  the  Semimembranosus  muscle  is  called  the 
posterior  ligament  of  Winslow  (ligamentum  posticum  Winslowii),  and  it  merges 
with  the  posterior  ligament.  The  posterior  ligament  forms  part  of  the  floor  of 
the  popliteal  space,  and  the  popliteal  artery  rests  upon  it. 

The  Internal  Lateral  Ligament  (ligamentum  collateral  tibiale)  (Figs.  241  and  242) 
is  a  broad,  flat,  membranous  band,  thicker  behind  than  in  front,  and  situated 

22 


338 


THE   ARTICULATIONS    OR    JOINTS 


nearer  to  the  back  than  the  front  of  the  joint.  It  is  attached,  above,  to  the  inner 
tuberosity  of  the  femur;  below,  to  the  inner  tuberosity  and  inner  surface  of  the 
shaft  of  the  tibia  to  the  extent  of  about  two  inches.  It  is  crossed,  at  its  lower 
part,  by  the  tendons  of  the  Sartorius,  Gracilis,  and  Semitendinosus  muscles,  a 
synovial  bursa  being  interposed.  Its  deep  surface  covers  the  anterior  portion  of 
the  tendon  of  the  Semimembranosus,  with  which  it  is  connected  by  a  few  fibres, 
the  synovial  membrane  of  the  joint,  and  the  inferior  internal  articular  vessels  and 
nerve;  it  is  intimately  adherent  to  the  internal  semilunar  fibro-cartilage. 


FIG.  241. — Right  knee-joint.     Anterior  view. 


FIG.  242. — Right  knee-joint.     Posterior  view. 


The  External  Lateral  or  Long  External  Lateral  Ligament  ( ligamentum  collaterale 
fibulare)  (Figs.  242  and  246)  is  a  strong,  rounded,  fibrous  cord  situated  nearer 
to  the  back  than  the  front  of  the  joint.  It  is  attached,  above,  to  the  back  part 
of  the  outer  tuberosity  of  the  femur;  below,  to  the  outer  part  of  the  head  of  the 
fibula.  Its  outer  surface  is  covered  by  the  tendon  of  the  Biceps,  which  divides  at 
its  insertion  into  two  parts,  separated  by  the  ligament.  The  ligament  has,  pass- 
ing beneath  it,  the  tendon  of  the  Popliteus  muscle  and  the  inferior  -external 
articular  vessels  and  nerve. 

The  Short  External  Lateral  Ligament  (ligamentum  later  ale  externum  breve  sen 
posticum)  (Fig.  242)  is  not  a  constant  structure.  It  is  an  accessory  bundle  of 
fibres  placed  behind  and  parallel  with  the  preceding,  attached,  above,  to  the 
lower  and  back  part  of  the  outer  tuberosity  of  the  femur;  below,  to  the  summit 
of  the  styloid  process  of  the  fibula.  This  ligament  is  intimately  connected  with 
the  capsular  ligament,  and  has,  passing  beneath  it,  the  tendon  of  the  Popliteus 
muscle  and  the  inferior  external  articular  vessels  and  nerve. 


THE  KNEE-JOINT 


339 


The  Capsular  Ligament  (capsula  articularis)  (Fig.  241)  consists  of  an  exceedingly 
thin  but  strong,  fibrous  membrane  which  fills  in  the  intervals  left  between  the 
stronger  bands  above  described,  and  is  inseparably  connected  with  them.  In  front 
it  blends  with  and  forms  part  of  the  lateral  Femur. 

patellar  ligaments  and  fills  in  the  interval 
between  the  anterior  and  lateral  ligaments  of 
the  joints,  with  which  latter  structures  it  is 
closely  connected.  It  is  deficient  above  the 
joint  and  beneath  the  tendon  of  the  quadri- 
ceps extensor.  Behind,  it  is  formed  chiefly 
of  vertical  fibres,  which  arise  above  from 
the  condyles  and  intercondyloid  notch  of 
the  femur,  and  is  connected  below  with  the 
back  part  of  the  head  of  the  tibia,  being 
closely  united  with  the  origins  of  the  Gas- 
trocnemius,  Plantaris,  and  Popliteus  muscles. 
It  passes  in  front  of,  but  is  inseparably  con- 
nected with,  the  posterior  ligament. 

The  Crucial  Ligaments  (ligamenta  cruciata 
genii)  (Figs.  172,  243,  and  244)  are  two  inter- 
osseous  ligaments  of  considerable  strength 
situated  in  the  interior  of  the  joint,  nearer  its 
posterior  than  its  anterior  part.  They  are 
called  crucial  because  they  cross  each  other 
somewhat  like  the  lines  of  the  letter  X;  and 
have  received  the  names  anterior  crucial  and 
posterior  crucial,  from  the  position  of  their  at- 
tachment to  the  tibia. 

The  anterior  or  external  crucial  ligament 
(ligamentum  cruciatum  anterius)  (Fig.  243)  is 
attached  to  the  depression  in  front  of  the 
spine  of  the  tibia,  being  blended  with  the  anterior  extremity  of  the  external 
semilunar  fibro-cartilage,  and,  passing  obliquely  upward,  backward,  and  out- 
ward, is  inserted  into  the  inner  and  back  part  of  the  outer  condyle  of  the  femur. 
The  posterior  or  internal  crucial  ligament  (ligamentum  cruciatum  posterius) 
is  stronger,  but  shorter  and  4ess  oblique  in  its  direction  than  the  anterior.  It 

is  attached  to  the  back  part 
of  the  depression  behind  the 
spine  of  the  tibia,  to  the  pop^ 
liteal  notch,  and  to  the  poste- 
rior extremity  of  the  external 
semilunar  fibro-cartilage;  and 
passes  upward,  forward,  and 
inward,  to  be  inserted  into 
the  outer  and  forepart  of  the 
inner  condyle  of  the  femur. 
It  is  in  relation,  in  front,  with 
the  anterior  crucial  ligament ; 
behind,  with  the  capsular  liga- 
ment. 

The  Semilunar  Fibro-cartil- 
ages(menmc)  (Figs.  172,  243, 
244,  245,  and  246)  are  two  crescentic  lamellae  which  serve  to  deepen  the  surface 
of  the  head  of  the  tibia,  for  articulation  with  the  condyles  of  the  femur.  The 


FIG.  243. — Right  knee-joint, 
ligaments. 


Showing  internal 


FIG.  244. — Head  of  tibia,  with  semilunar  cartilages,  etc. 
from  above.     Right  side. 


Seen 


340 


THE   ARTICULATIONS    OR    JOINTS 


circumference  of  each  cartilage  is  thick,  convex,  and  attached  to  the  inside  of  the 
capsule  of  the  knee ;  the  inner  border  is  thin,  concave,  and  free.  Their  upper 
surfaces  are  concave,  and  in  relation  with  the  condyles  of  the  femur;  their  lower 
surfaces  are  flat,  and  rest  upon  the  head  of  the  tibia.  Each  cartilage  covers 
nearly  the  outer  two-thirds  of  the  corresponding  articular  surface  of  the  tibia, 
leaving  the  inner  third  uncovered ;  both  surfaces  are  smooth  and  invested  by 
synovial  membrane. 


SUPRAPATELLAR 

BURSA 


TENDON    OF  QUADRICEPS 
EXTENSOR    FEMORIS 


EXTERNAL 

SEMILUNAR 

FIBRO-CARTILAGE 


EPIPHYSEAL. 
JUNCTION 


ARTICULAR 
CAVITY 


LIGAMENTA 
ALARIA 


LIGAMENTUM 
PATELLA: 


DEEP  INFRA- 
PATELLAR  BURSA 


TUBEROSITY 
OF  TIBIA 


FIG.  245. — Right  knee-joint.  Sagittal  section  through  the  external  condyle  of  the  femur.  Medial  half  of 
section,  from  the  lateral  side.  (The  knee  is  slightly  flexed;  the  joint  surfaces  have  been  pulled  a  little  apart.) 
(Spalteholz.) 


The  internal  semilunar  fibro-cartilage  (meniscus  medialis]  is  nearly  semicircular 
in  form,  a  little  elongated  from  before  backward,  and  broader  behind  than  in  front; 
its  anterior  extremity,  thin  and  pointed,  is  attached  to  a  depression  on  the  anterior 
margin  of  the  head  of  the  tibia,  in  front  of  the  anterior  crucial  ligament;  its 
posterior  extremity  is  attached  to  the  depression  behind  the  spine,  between  the 
attachments  of  the  external  semilunar  fibro-cartilage  and  the  posterior  crucial 
ligaments. 


THE  KNEE-JOINT 


341 


The  external  semilunar  fibro-cartilage  (meniscus  lateralis)  forms  nearly  an 
entire  circle,  covering  a  larger  portion  of  the  articular  surface  than  the  internal 
one.  It  is  grooved  on  its  outer  side  for  the  tendon  of  the  Popliteus  muscle.  Its 
extremities,  at  their  insertion,  are  interposed  between  the  two  extremities  of  the 
internal  semilunar  fibro-cartilage;  the  anterior  extremity  being  attached  in  front 
of  the  spine  of  the  tibia  to  the  outer  side  of,  and  behind,  the  anterior  crucial 


TENDON  OF  QUAD- 
RICEPS EXTENSOR 
FEMORIS 

SUPRAPATELLAR 

BURSA 


ARTICULAR 
CAVITY 


SHWFT  OF  THE,/ 

/fl    , 

T  I  B  I  A 


LONG  EXTERNAL 

LATERAL 

LIGAMENT 

TENDON  OF 

POPLITEUS 

MUSCLE 


POPLITEAL 
BURSA 


HEAD  OF 
FIBULA 


PREPATELLAR 
BURSA 


EXTERNAL   SEMI- 
LUNAR   FIBRO- 
CARTILAGE 

LIGAMENTUM 

PATELL/E 

DEEP   INFRAPATEL- 
LAR   BURSA 


TUBEROSITV 

OF  TIBIA 


FIG.  246. — Right  knee-joint,  from  the  lateral  surface.       (The  joint  cavity  and  several  bursse  have  been  injecteu 
with  a  stiffening  medium  and  then  dissected  out.)     (Spalteholz.) 

ligament,  with  which  it  blends ;  the  posterior  extremity  being  attached  behind  the 
spine  of  the  tibia,  in  front  of  the  posterior  extremity  of  the  internal  semilunar 
fibro-cartilage.  Just  before  its  insertion  posteriorly  it  gives  off  a  strong  fasciculus, 
the  ligament  of  Wrisberg,  which  passes  obliquely  upward  and  outward,  to  be 
inserted  into  the  inner  condyle  of  the  femur,  close  to  the  attachment  of  the  poste- 
rior crucial  ligament.  Occasionally  a  small  fasciculus  is  given  off  which  passes 
forward  to  be  inserted  into  the  back  part  of  the  anterior  crucial  ligament.  The 


342  THE  ARTICULATIONS    OR   JOINTS 


external  semilunar  fibro-cartilage  gives  off  from  its  anterior  convex  margin  a 
fasciculus  which  forms  the  transverse  ligament. 

The  Transverse  Ligament  (ligamentum  transversum  genu)  (Fig.  244)  is  a  band  of 
fibres  which  passes  transversely  from  the  anterior  convex  margin  of  the  external 
semilunar  fibro-cartilage  to  the  anterior  convex  margin  of  the  internal  semilunar 
fibro-cartilage ;  its  thickness  varies  considerably  'in  different  subjects,  and  it  is 
sometimes  absent  altogether. 

The  Coronary  Ligaments  (ligamenta  coronaria)  are  merely  portions  of  the  cap- 
sular  ligament,  which  connect  the  circumference  of  each  of  the  semilunar  fibro- 

~ 

cartilages  with  the  margin  of  the  head  of  the  tibia. 

Synovial  Membrane  (Figs.  245  and  246) . — The  synovial  membrane  encloses  the 
articular  cavity  (cavum  articulare)  of  the  knee-joint.  It  is  the  largest  and  most 
extensive  synovial  membrane  in  the  body.  Commencing  above  the  upper  border 
of  the  patella,  it  forms  a  short  cul-de-sac  beneath  the  Quadriceps  extensor  tendon  of 
the  thigh,  on  the  lower  part  of  the  front  of  the  shaft  of  the  femur;  this  communi- 
cates, by  an  orifice  of  variable  size,  with  a  synovial  bursa  interposed  between  the 
tendon  and  the  front  of  the  femur  (bursa  suprapatellaris) .  On  each  side  of  the 
patella  the  synovial  membrane  extends  beneath  the  aponeurosis  of  the  Vasti 
muscles,  and  more  especially  beneath  that  of  the  Vastus  internus.  Below  the 
patella  it  is  separated  from  the  anterior  ligament  by  the  anterior  part  of  the 
capsule  and  a  considerable  quantity  of  adipose  tissue,  known  as  the  infrapatellar 
pad  (Fig.  245) .  In  this  situation  the  synovial  membrane  sends  off  a  triangular 
prolongation,  containing  a  few  ligamentous  fibres,  which  extends  from  the  ante- 
rior part  of  the  joint  below  the  patella  to  the  front  of  the  intercondyloid  notch. 
This  fold  has  been  termed  the  ligamentum  mucosum  (plica  synomalis  patellaris}. 
It  also  sends  off  two  fringe-like  folds,  called  the  ligamenta  alaria  (pliccs  alares) 
(Fig.  245),  which  extend  from  the  sides  of  the  ligamentum  mucosum,  upward 
and  laterally  between  the  patella  and  femur.  On  either  side  of  the  joint  it  passes 
downward  from  the  femur,  lining  the  capsule  to  its  point  of  attachment  to  the 
semilunar  cartilages;  it  may  then  be  traced  over  the  upper  surfaces  of  these  car- 
tilages to  their  free  borders,  and  from  thence  along  their  under  surfaces  to  the 
tibia.  At  the  back  part  of  the  external  one  it  forms  a  cul-de-sac  between  the 
groove  on  its  surface  and  the  tendon  of  the  Popliteus;  it  surrounds  the  crucial 
ligaments  and  lines  the  inner  surface  of  the  ligaments  which  enclose  the  joint. 
The  pouch  of  synovial  membrane  between  the  Extensor  tendon  and  front  of  the 
femur  is  supported,  during  the  movements  of  the  knee,  by  a  small  muscle,  the 
Subcrureus,  which  is  inserted  into  the  upper  part  of  the  capsular  ligament. 

The  folds  of  synovial  membrane  and  the  fatty  processes  contained  in  them  act, 
as  it  seems,  mainly  in  padding  to  fill  up  interspaces  and  obviate  concussions. 
Sometimes  the  bursa  beneath  the  Quadriceps  extensor  is  completely  shut  off  from 
the  rest  of  the  synovial  cavity,  thus  forming  a  closed  sac  between  the  Quadriceps 
and  the  lower  part  of  the  front  of  the  femur;  sometimes  it  communicates  with  the 
synovial  cavity  by  a  minute  aperture;  usually  the  two  cavities  are  incompletely 
separated  by  a  synovial  fold. 

Bursse. — The  bursse  about  the  knee-joint  are  the  following:  In  front  there 
are  four  bursae:  one  is  interposed  between  the  patella  and  the  skin.  It  is 
known  as  the  prepatellar  bursa  (bursa  prcepatellaris  subcutanea);  another,  of 
small  size,  between  the  upper  part  of  the  tuberosity  of  the  tibia  and  the 
ligamentum  patellae  is  called  the  deep  infrapatellar  bursa  (bursa  infrapatellaris- 
profunda);  and  a  third  between  the  lower  part  of  the  tuberosity  of  the  tibia 
and  the  skin,  the  subcutaneous  tibial  bursa  (bursa  subcutanea  tuberositatis  tibice). 
A  fourth  bursa  exists  in  front,  the  suprapatellar  bursa  (bursa  suprapatellaris). 
It  lies  between  the  anterior  surface  of  the  lower  end  of  the  femur  and  the 
posterior  surface  of  the  quadriceps  femoris.  Spalteholz  says  that  the  supra- 


THE   KNEE-JOINT  343 

patellar  bursa  is  closely  connected  with  the  quadriceps  tendon  and  is  usually 
incompletely  shut  off  from  the  cavity  of  the  joint.1  Occasionally  there  is  a 
bursa  between  the  expansion  of  the  fascia  lata  and  the  Quadriceps  and'  the 
patella  (bursa  pracpatellaris  subfascialis) ,  and  sometimes  one  between  the  tendon 
of  the  quadriceps  and  the  anterior  surface  of  the  patella  (bursa  prcppatellaris 
subtendinea) .  On  the  outer  side  there  are  four  bursae:  (1)  one  beneath  the.  outer 
head  of  the  Gastrocnemius  (which  sometimes  communicates  with  the  joint); 
(2)  one  above  the  external  lateral  ligament  between  it  and  the  tendon  of  the 
Biceps;  (3)  one  beneath  the  external  lateral  ligament  between  it  and  the  tendon 
of  the  Popliteus  (this  is  sometimes  only  an  expansion  from  the  next  bursa); 

(4)  one  beneath  the  tendon  of  the  Popliteus  (bursa  musculi  poplitei)  between  it 
and  the  condyle  of  the  femur,  which  is  almost  always  an  extension  from  the  syno- 
vial  membrane  of  the  joint.     On  the  inner  side  there  are  five  bursae:  (1)  one 
beneath  the  inner  head  of  the  Gastrocnemius,  which  sends  a  prolongation  between 
the  tendons  of  the  Gastrocnemius  and  Semimembranosus :  this  bursa  often  com- 
municates with  the  joint;  (2)  one  above  the  internal  lateral  ligament  between  it 
and  the  tendons  of  the  Sartorius,  Gracilis,  and  Semitendinosus;  (3)  one  beneath 
the  internal  lateral  ligament  between   it   and  the  tendon  of  the  Semimembra- 
nosus: this  is  sometimes  only  an  expansion  from  the  next  bursa;  (4)  one  beneath 
the  tendon  of  the  Semimembranosus,  between  it  and   the   head   of  the  tibia; 

(5)  sometimes  there  is  a  bursa  between  the  tendons  of  the  Semimembranosus 
and  of  the  Semitendinosus. 

Structures  around  the  Joint. — In  front  and  at  the  sides,  the  Quadriceps  extensor; 
on  the  outer  side,  the  tendons  of  the  Biceps  and  the  Popliteus  and  the  external 
popliteal  nerve;  on  the  inner  side,  the  Sartorius,  Gracilis,  Semitendinosus,  and 
Semimembranosus;  behind,  an  expansion  from  the  tendon  of  the  Semimembra- 
nosus, the  popliteal  vessels,  and  the  internal  popliteal  nerve,  the  Popliteus,  the 
Plantaris,  and  the  inner  and  outer  heads  of  the  Gastrocnemius,  some  lymphatic 
glands,  and  fat. 

The  arteries  supplying  the  joint  are  derived  from  the  anastomotica  magna 
branch  of  the  femoral,  articular  branches  of  the  popliteal,  anterior  and  posterior 
recurrent  branches  of  the  anterior  tibial,  and  a  descending  branch  from  the 
external  circumflex  of  the  Profunda. 

The  nerves  are  derived  from  the  obturator,  anterior  crural,  and  external  and 
internal  popliteal. 

Actions. — The  knee-joint  permits  of  movements  of  flexion  and  extension,  and, 
in  certain  positions,  of  slight  rotation  inward  and  outward.  The  movement  of 
flexion  and  extension  does  not,  however,  take  place  in  a  simple,  finger-like  man- 
ner, as  in  other  joints,  but  is  a  complicated  movement,  consisting  of  a  certain 
amount  of  gliding  and  rotation;  so  that  the  same  part  of  one  articular  surface  is 
not  always  applied  to  the  same  part  of  the  other  articular  surface,  and  the  axis 
of  motion  is  not  a  fixed  one.  If  the  joint  is  examined  while  in  a  condition  of 
extreme  flexion,  the  posterior  part  of  the  articular  surfaces  of  the  tibia  will  be 
found  to  be  in  contact  with  the  posterior  rounded  extremities  of  the  condyles  of 
the  femur;  and  if  a  simple  hinge-like  movement  were  to  take  place,  the  axis, 
round  which  the  revolving  movement  of  the  tibia  occurs,  would  be  in  the  back 
part  of  the  condyle.  If  the  leg  is  now  brought  forward  into  a  position  of  semi- 
flexion,  the  upper  surface  of  the  tibia  will  be  seen  to  glide  over  the  condyles  of 
the  femur,  so  that  the  middle  part  of  the  articular  facets  are  in  contact,  and  the 
axis  of  rotation  must  therefore  have  shifted  forward  to  nearer  the  centre  of  the 
condyles.  If  the  leg  is  now  brought  into  the  extended  position,  a  still  further 
gliding  takes  place  and  a  further  shifting  forward  of  the  axis  of  rotation.  This 

1  Spalteholz's  Hand  Atlas  of  Human  Anatomy.     Translated  by  Lewellys  F.  Barker. 


344  THE   ARTICULATIONS    OR    JOINTS 

is  not,  however,  a  simple  movement,  but  is  accompanied  by  a  certain  amount  of 
rotation  outward  round  a  vertical  axis  drawn  through  the  centre  of  the  head  of 
the  tibia.  This  rotation  is  due  to,  the  greater  length  of  the  internal  condyle,  and 
to  the  fact  that  the  anterior  portion  of  its  articular  surface  is  inclined  obliquely 
outward.  In  consequence  of  this  it  will  be  seen  that  toward  the  close  of  the 
movement  of  extension — that  is  to  say,  just  before  complete  extension  is  effected 
— the  tibia  glides  obliquely  upward  and  outward  over  this  oblique  surface  on  the 
inner  condyle,  and  the  leg  is  therefore  necessarily  rotated  outward.  In  flexion 
of  the  joint  the  converse  of  these  movements  takes  place:  the  tibia  glides  backward 
round  the  end  of  the  femur,  and  at  the  commencement  of  the  movement  the  tibia 
is  directed  downward  and  inward  along  the  oblique  curve  of  the  inner  condyle, 
thus  causing  an  inward  rotation  to  the  leg. 

During  flexion  and  extension  the  patella  moves  on  the  lower  end  of  the  femur, 
but  this  movement  is  not  a  simple  gliding  one;  for  if  the  articular  surface  of  this 
bone  is  examined,  it  will  be  found  to  present  on  each  side  of  the  central  vertical 
ridge  two  less  marked  transverse  ridges,  which  divide  the  surface,  except  a  small 
portion  along  the  inner  border,  which  is  cut  off  by  a  slight  vertical  ridge  into 
six  facets  (see  Fig.  247),  and  therefore  does  not  present  a  uniform  curved  surface 

as  would  be  the  case  if  a  simple  gliding  movement  took 
place.  These  six  facets — three  on  each  side  of  the 
median  vertical  ridge — correspond  to  and  denote  the 
parts  of  the  bone  respectively  in  contact  with  the  con- 
dyles of  the  femur  during  flexion,  semiflexion,  and  exten- 
sion. In  flexion  only  the  upper  facets  on  the  patella  are 
in  contact  with  the  condyles  of  the  femur;  the  lower 
two-thirds  of  the  bone  rests  upon  the  mass  of  fat  which 
occupies  the  space  between  the  femur  and  tibia.  In  the 
semiflexed  position  of  the  joint  the  middle  facets  on  the 

FIG  247  —view  of  the  pos-     patella  rest  upon  the  most  prominent  portion  of  the  con- 
terior  surface  of  the  patella,     dyles,  and  thus  afford  greater  leverage  to  the  Quadriceps 

showing  diagrammatically  the        •       •  •         •         T  p  *  « 

areas  of  contact  with  the  femur     by  increasing  its  distance  trom  the  centre  ot  motion.     In 

in    different   positions   of    the  ,  .,  n      .       ,  Al  , 

knee.  complete  extension  the  patella  is  drawn  up,  so  that  only 

the  lower  facets  are  in  contact  with  the  articular  sur- 
faces of  the  condyles.  The  narrow  strip  along  the  inner  border  is  in  contact 
with  the  outer  aspect  of  the  internal  condyle  when  the  leg  is  fully  flexed  at 
the  knee-joint.  As  in  the  elbow,  so  it  is  in  the  knee — the  axis  of  rotation  in 
flexion  and  extension  is  not  precisely  at  right  angles  to  the  axis  of  the  bone,  but 
during  flexion  there  is  a  certain  amount  of  alteration  of  plane;  so  that,  whereas  in 
flexion  the  femur  and  tibia  are  in  the  same  plane,  in  extension  the  one  bone  forms 
an  angle  of  about  10  degrees  with  ithe  other.  There  is,  however,  this  difference 
between  the  two  extremities:  that  in  the  upper,  during  extension,  the  humeri  are 
parallel  and  the  bones  of  the  forearm  diverge;  in  the  lower,  the  femora  converge 
below  and  the  tibia  are  parallel. 

In  addition  to  the  slight  rotation  during  flexion  and  extension,  the  tibia  enjoys 
an  independent  rotation  on  the  condyles  of  the  femur  in  certain  positions  of  the 
joint.  This  movement  takes  place  between  the  interarticular  fibro-cartilages  and 
the  tibia,  whereas  the  movement  of  flexion  and  extension  takes  place  between  the 
interarticular  fibro-cartilages  and  the  femur.  So  that  the  knee  may  be  said  to 
consist  of  two  joints,  separated  by  the  fibro-cartilages:  an  upper,  menisco-femoral, 
in  which  flexion  and  extension  take  place;  and  a  lower,  menisco-tibial,  allowing 
of  a  certain  amount  of  rotation.  This  latter  movement  can  only  take  place  in  the 
semiflexed  position  of  the  limb,  when  all  the  ligaments  are  relaxed. 

During  flexion  the  ligamentum  patellae  is  put  upon  the  stretch,  as  is  also  the 
posterior  crucial  ligament  in  extreme  flexion.  The  other  ligaments  are  all  relaxed 


THE   KNEE-JOINT  345 

by  flexion  of  the  joint,  though  the  relaxation  of  the  anterior  crucial  ligament  is 
very  trifling.  During  life  flexion  is  checked  by  the  contact  of  the  leg  with  the 
thigh.  In  the  act  of  extending  the  leg  upon  the  thigh  the  ligamentum  patella  is 
tightened  by  the  Quadriceps  extensor;  but  when  the  leg  is  fully  extended,  as  in  the 
erect  posture,  the  ligament  becomes  relaxed,  so  as  to  allow  free  lateral  movement  to 
the  patella,  which  then  rests  on  the  front  of  the  lower  end  of  the  femur.  The  other 
ligaments,  with  the  exception  of  the  posterior  crucial,  which  is  partly  relaxed,  are  all 
on  the  stretch.  When  the  limb  has  been  brought  into  a  straight  line,  extension  is 
checked  mainly  by  the  tension  of  all  the  ligaments  except  the  posterior  crucial  and 
ligamentum  patella?.  The  movements  of  rotation  of  which  the  knee  is  capable  are 
permitted  in  the  semiflexed  condition  by  the  partial  relaxation  of  both  crucial  liga- 
ments, as  well  as  of  the  lateral  ligaments.  Rotation  inward  appears  to  be  limited 
by  the  tension  of  the  anterior  crucial  ligament,  and  by  the  interlocking  of  the  two 
ligaments;  but  rotation  outward  does  not  appear  to  be  checked  by  either  crucial 
ligament,  since  they  uncross  during  the  execution  of  this  movement,  but  it  is 
checked  by  the  lateral  ligaments,  especially  the  internal.  The  main  function  of 
the  crucial  ligaments  is  to  act  as  a  direct  bond  of  union  between  the  tibia  and 
femur,  preventing  the  former  bone  from  being  carried  too  far  backward  or 
forward.  Thus  the  anterior  crucial  ligament  prevents  the  tibia  being  carried 
too  far  forward  by  the  extensor  tendons,  and  the  posterior  crucial  checks  too 
great  movement  backward  by  the  flexors.  They  also  assist  the  lateral  ligaments 
in  resisting  any  lateral  bending  of  the  joint.  The  interarticular  cartilages  are 
intended,  as  it  seems,  to  adapt  the  surface  of  the  tibia  to  the  shape  of  the  femur 
to  a  certain  extent,  so  as  to  fill  up  the  intervals  which  would  otherwise  be  felt 
in  the  varying  positions  of  the  joint,  and  to  interrupt  the  jars  which  would  be 
so  frequently  transmitted  up  the  limb  in  jumping  or  falls  on  the  feet;  also  to 
permit  of  the  two  varieties  of  motion,  flexion  and  extension,  and  rotation,  as 
explained  above.  The  patella  is  a  great  defence  to  the  knee-joint  from  any 
injury  inflicted  in  front,  and  it  distributes  upon  a  large  and  tolerably  even  sur- 
face during  kneeling  the  pressure  which  would  otherwise  fall  upon  the  prominent 
ridges  of  the  condyles ;  it  also  affords  leverage  to  the  Quadriceps  extensor  muscle 
when  it  acts  upon  the  tibia;  and  Mr.  Ward  has  pointed  out1  how  this  leverage 
varies  in  the  various  positions  of  the  joint,  so  that  the  action  of  the  muscles  pro- 
duces velocity  at  the  expense  of  force  in  the  commencement  of  extension,  and,  on 
the  contrary,  at  the  close  of  extension  tends  to  diminish  velocity,  and  therefore 
the  shock  to  the  ligaments  at  the  moment  tension  of  the  structures  takes  place. 
Extension  of  the  leg  on  the  thigh  is  performed  by  the  Quadriceps  extensor; 
flexion  by  the  hamstring  muscles,  assisted  by  the  Gracilis  and  Sartorius,  and, 
indirectly,  by  the  Gastrocnemius,  Popliteus,  and  Plantaris;  rotation  outward,  by 
the  Biceps ;  and  rotation  inward  by  the  Popliteus,  Semitendinosus,  and,  to  a  slight 
extent,  the  Semimembranosus,  the  Sartorius,  and  the  Gracilis. 

Surface  Form. — The  interval  between  the  two  bones  entering  into  the  formation  of  the  knee- 
joint  can  always  easily  be  felt.  If  the  limb  is  extended,  it  is  situated  on  a  slightly  higher  level 
than  the  apex  of  the  patella ;  but  if  the  limb  is  slightly  flexed,  a  knife  carried  horizontally  back- 
ward immediately  below  the  apex  of  the  patella  would  pass  directly  into  the  joint.  When  the 
knee-joint  is  distended  with  fluid,  the  outline  of  the  synovial  membrane  at  the  front  of  the  knee 
may  be  fairly  well  mapped  out. 

Surgical  Anatomy. — The  bursts  about  the  knee  are  frequently  the  seat  of  inflammation. 
Enlargement  of  the  prepatellar  bursa  constitutes  housemaid'  s  knee.  The  bursa  beneath  the 
Semimembranosus  may  enlarge  greatly.  It  communicates  with  the  knee-joint  and  can  frequently 
be  made  to  disappear  by  pressure  when  the  knee  is  flexed.  Treves  points  out  that  enlargement 
of  the  bursa  between  the  biceps  tendon  and  the  external  lateral  ligament  causes  great  pain 
because  the  peroneal  nerve  crosses  the  sac.2 

From  a  consideration  of  the  construction  of  the  knee-joint  it  would  at  first  sight  appear  to  be 

1  Human  Osteology,  p.  405.  *  Applied  Anatomy. 


346  THE  ARTICULATIONS    OR   JOINTS 

one  of  the  least  secure  of  any  of  the  joints  in  the  body.  It  is  formed  between  the  two  longest 
bones,  and  therefore  the  amount  of  leverage  which  can  be  brought  to  bear  upon  it  is  very  con- 
siderable; the  articular  surfaces  are  but  ill  adapted  to  each  other,  and  the  range  and  variety  of 
motion  which  it  enjoys  is  great.  All  these  circumstances  tend  to  render  the  articulation  very 
insecure;  but,  nevertheless,  on  account  of  the  very  powerful  ligaments  which  bind  the  bones 
together,  the  joint  is  one  of  the  strongest  in  the  body,  and  dislocation  from  traumatism  is  of 
very  rare  occurrence.  When,  on  the  other  hand,  the  ligaments  have  been  softened  or  destroyed 
by  disease,  partial  displacement  is  very  liable  to  occur,  and  is  frequently  brought  about  by  the 
mere  action  of  the  muscles  displacing  the  articular  surfaces  from  each  other.  The  tibia  may 
be  dislocated  in  any  direction  from  the  femur — forward,  backward,  inward,  or  outward;  or  a 
combination  of  two  of  these  dislocations  may  occur — that  is,  the  tibia  may  be  dislocated  for- 
ward and  laterally,  or  backward  and  laterally,  and  any  of  these  dislocations  may  be  complete 
or  incomplete.  As  a  rule,  however,  the  antero-posterior  dislocations  are  complete,  the  lateral 
ones  incomplete. 

One  or  other  of  the  semilunar  cartilages  may  become  displaced  and  nipped  between  the 
femur  and  tibia.  The  accident  is  produced  by  a  twist  of  the  leg  when  the  knee  is  flexed,  and  is 
accompanied  by  a  sudden  pain  and  fixation  of  the  knee  in  a  flexed  position.  The  cartilage  may 
be  displaced  either  inward  or  outward:  that  is  to  say,  either  inward  toward  the  tibial  spine,  so 
that  the  cartilage  becomes  lodged  in  the  intercondyloid  notch;  or  outward,  so  that  the  car- 
tilage projects  beyond  the  margin  of  the  articular  surface.  Acute  synovitis,  the  result  of  trau- 
matism or  exposure  to  cold,  is  very  common  in  the  knee,  on  account  of  its  superficial  position. 
When  distended  with  fluid,  the  swelling  shows  itself  above  and  at  the  sides  of  the  patella,  reach- 
ing about  an  inch  or  more  above  the  trochlear  surface  of  the  femur,  and  extending  a  little  higher 
under  the  Vastus  internus  than  the  Vastus  externus.  Occasionally  the  swelling  may  extend 
two  inches  or  more.  At  the  sides  of  the  patella  the  swelling  extends  lower  at  the  inner  side 
than  it  does  on  the  outer  side.  The  lower  level  of  the  synovial  membrane  is  just  above  the 
level  of  the  upper  part  of  the  head  of  the  fibula.  In  the  middle  line  it  covers  the  upper  third 
of  the  ligamentum  patellae,  being  separated  from  it,  however,  by  the  capsule  and  a  pad  of  fat. 
Chronic  synovitis  principally  shows  itself  in  the  form  of  pulpy  degeneration  of  the  synovial  mem- 
brane, the  result  of  tuberculous  arthritis.  The  reasons  why  tuberculous  disease  of  the  knee 
so  often  commences  in  the  synovial  membrane  appear  to  be  the  complex  and  extensive  nature  of 
this  sac;  the  extensive  vascular  supply  to  it;  and  the  fact  that  injuries  are  generally  diffused 
and  applied  to  the  front  of  the  joint  rather  than  to  the  ends  of  the  bones.  Syphilitic  disease 
not  unfrequently  attacks  the  knee-joint.  In  the  hereditary  form  of  the  disease  it  is  usually 
symmetrical,  attacking  both  joints,  which  become  filled  with  synovial  effusion,  and  is  very  intract- 
able and  difficult  to  cure.  In  the  tertiary  stage  of  acquired  syphilis  gummatous  infiltration  of 
the  synovial  membrane  may  take  place.  The  knee  is  one  of  the  joints  most  commonly  affected  with 
osteo-arthritis,  and  is  said  to  be  more  frequently  the  seat  of  this  disease  in  wromen  than  in  men. 
The  occurrence  of  the  so-called  loose  cartilage  is  almost  confined  to  the  knee,  though  loose  cartilages 
are  occasionally  met  with  in  the  elbow,  and,  rarely,  in  some  other  joints.  Many  of  them  occur  in 
cases  of  osteo-arthritis,  in  which  calcareous  or  cartilaginous  material  is  formed  in  one  of  the  synovial 
fringes  and  constitutes  the  foreign  body,  and  may  or  may  not  become  detached,  in  the  former 
case  only  meriting  the  usual  term,  "  loose"  cartilage.  In  other  cases  they  have  their  origin  in  the 
exudation  of  inflammatory  lymph,  and  possibly,  in  some  rare  instances,  a  portion  of  the  articular 
cartilage  or  one  of  the  semilunar  cartilages  becomes  detached  and  constitutes  the  foreign  body. 

Genu  valgum,  or  knock-knee,  is  a  common  deformity  of  childhood,  in  which,  owing  to 
changes  in  and  about  the  joint,  the  angle  between  the  outer  border  of  the  tibia  and  femur  is 
diminished,  so  that  as  the  patient  stands  the  two  internal  condyles  of  the  femora  are  in  contact, 
but  the  two  internal  malleoli  of  the  tibiae  are  more  or  less  widely  separated  from  each  other. 
When,  however,  the  knees  are  flexed  to  a  right  angle,  the  two  legs  are  practically  parallel  with 
each  other.  At  the  commencement  of  the  disease  there  is  a  yielding  of  the  internal  lateral  liga- 
ment and  other  fibrous  structures  on  the  inner  side  of  the  joint;  as  a  result  of  this  there  is  a 
constant  undue  pressure  of  the  outer  tuberosity  of  the  tibia  against  the  outer  condyle  of  the 
femur.  This  extra  pressure  causes  arrest  of  growth  and,  possibly,  wasting  of  the  outer  con- 
dyle, and  a  consequent  tendency  for  the  tibia  to  become  separated  from  the  internal  condyle. 
To  prevent  this  the  internal  condyle  becomes  depressed;  probably,  as  was  first  pointed  out  by 
Mikulicz,  by  an  increased  growth  of  the  lower  end  of  the  diaphysis  on  its  inner  side,  so  that  the 
line  of  the  epiphysis  becomes  oblique  instead  of  transverse  to  the  axis  of  the  bone,  with  a  direc- 
tion downward  and  inward.  It  is  often  said  that  the  deformity  is  produced  by  undue  length 
of  the  inner  condyle,  but  in  reality  the  condyle  grows  as  the  deformity  progresses. 

Excision  of  the  knee-joint  is  most  frequently  required  for  tuberculous  disease  of  this  articula- 
tion, but  is  also  practised  in  cases  of  disorganization  of  the  knee  after  rheumatic  fever,  pyaemia, 
etc.,  in  osteo-arthritis,  and  in  ankylosis.  It  is  also  occasionally  called  for  in  cases  of  injury,  gun- 
shot or  otherwise.  The  operation  is  best  performed  either  by  a  horseshoe  incision,  starting  from 
one  condyle,  descending  as  low  as  the  tubercle  of  the  tibia,  where  it  crosses  the  leg,  and  is  then 
carried  upward  to  the  other  condyle;  or  by  a  transverse  incision  across  the  patella.  In  this 


TIBIO  -  FIB  ULAR    ARTICULA  TION 


TUBEROSITV 
'OF  TIBIA 


latter  incision  the  patella  is  either  removed  or  sawn  across,  and  the  halves  subsequently  sutured 
together.  The  bones  having  been  cleared,  and  in  those  cases  where  the  operation  is  performed 
for  tuberculous  disease  all  pulpy  tissue  having  been  carefully  removed,  the  section  of  the  femur 
is  first  made.  This  should  never  include,  in  children,  more  than,  at  the  most,  two-thirds  of 
the  articular  surface,  otherwise  the  epiphysial  cartilage  will  be  involved,  with  disastrous  results 
as  regards  the  growth  of  the  limb.  Afterward  a  thin  slice  should  be  removed  from  the  upper 
end  of  the  tibia,  not  more  than  half  an  inch.  If  any  diseased  tissue  still  appears  to  be  left  in  the 
bones,  it  should  be  removed  with  the  gouge  rather  than  by  making  a  further  section  of  the  bones. 

III.     Tibio-fibular    Articulation 
(Articulatio  Tibiofibularis) . 

The  articulations  between  the  tibia 
and  fibula  are  effected  by  ligaments 
which  connect  both  extremities,  as 
well  as  the  shafts  of  the  bones.  It 
may,  consequently,  be  subdivided 
into  three  articulations:  1.  The 
superior  tibio-fibular  articulation,  2. 
The  middle  tibio-fibular  ligament  or 
interosseous  membrane.  3.  The 
inferior  tibio-fibular  articulation. 


1.  SUPERIOR  TIBIO-FIBULAR  ARTIC- 
ULATION   (ARTICULATIO 
TIBIOFIBULARIS). 

This  articulation  is  an  arthrodial 
joint.  The  contiguous  surfaces  of 
the  bones  present  two  flat,  oval 
facets  covered  -with  cartilage,  and 
connected  together  by  the  following 
ligaments : 

Capsular. 

Anterior  Superior  Tibio-fibular. 

Posterior  Superior  Tibio-fibular. 

The  Capsular  Ligament  (capsula 
articularis)  consists  of  a  membra- 
nous bag  which  surrounds  the  artic- 
ulation, being  attached  around  the 
margins  of  the  articular  facets  on 
the  tibia  and  fibula,  and  is  much 
thicker  in  front  than  behind. 

The  new  nomenclature  considers 
the  anterior  and  posterior  ligaments 
as  one  ligament  (ligamentum  capituli 
fibulce). 

The  Anterior  Superior  Ligament 
(Fig.  248)  consists  of  two  or  three 
broad  and  flat  bands  which  pass 
obliquely  upward  and  inward  from 
the  front  of  the  head  of  the  fibula 
to  the  front  of  the  outer  tuberosity 
of  the  tibia. 

The  Posterior  Superior  Ligament 
(Fig.  241)  is  a  single  thick  and 


INNER 
MALLEOLUS 


OUTER 
MALLEOLUS 


ANTERIOR     LIGAMENT 
OF   OUTER 
MALLEOLUS 


FIG.  248. — Ligaments  of  the  right  leg,  from  in  front. 
(Spalteholz.) 


348  THE   ARTICULATIONS    OR    JOINTS 

broad  band  which  passes  upward  and  inward  from  the  back  part  of  the  head  of 
the  fibula  to  the  back  part  of  the  outer  tuberosity  of  the  tibia.  It  is  covered  by 
the  tendon  of  the  Popliteus  muscle. 

Synovial  Membrane. — A  sy  no  vial  membrane  lines  this  articulation,  which  at  its 
upper  and  back  part  is  occasionally  continuous  with  that  of  the  knee-joint. 

2.  MIDDLE  TIBIO-FIBULAR  LIGAMENT  OR  INTEROSSEOUS  MEMBRANE 
(MEMBRANA  INTEROSSEA  CRURIS)  (Fig.  248). 

An  interosseous  membrane  extends  between  the  contiguous  margins  of  the 
tibia,  and  fibula  and  separates  the  muscles  on  the  front  from  those  on  the  back 
of  the  leg.  It  consists  of  a  thin,  aponeurotic  lamina  composed  of  oblique  fibres 
which  for  the  most  part  pass  downward  and  outward  between  the  interosseous 
ridges  on  the  two  bones ;  some  few  fibres,  however,  pass  in  the  opposite  direction, 
downward  and  inward.  It  is  broader  above  than  below.  Its  upper  margin  does 
not  quite  reach  the  superior  tibio-fibular  joint,  but  presents  a  free  concave  border, 
above  which  is  a  large,  oval  aperture  for  the  passage  of  the  anterior  tibial  vessels 
forward  to  the  anterior  aspect  of  the  leg.  At  its  lower  part  is  an  opening  for  the 
passage  of  the  anterior  peroneal  vessels.  It  is  continuous  below  with  the  inferior 
interosseous  ligament,  and  is  perforated  in  numerous  places  for  the  passage  of  small 
vessels.  It  is  in  relation,  in  front,  with  the  Tibialis  anticus,  Extensor  longus  digi- 
torum,  Extensor  proprius  hallucis,  Peroneus  tertius,  and  the  anterior  tibial  vessels 
and  nerve;  behind,  with  the  Tibialis  posticus  and  Flexor  longus  hallucis. 

3.  INFERIOR  TIBIO-FIBULAR  ARTICULATION  (SYNDESMOSIS  TIBIOFIBULARIS) 

(Figs.  250,  251,  252). 

This  articulation  is  formed  by  the  rough,  convex  surface  of  the  inner  side  of 
the  lower  end  of  the  fibula,  connected  with  a  concave  rough  surface  on  the  outer 
side  of  the  tibia.  Below,  to  the  extent  of  about  two  lines,  these  surfaces  are  smooth, 
and  covered  with  cartilage,  which  is  continuous  with  that  of  the  ankle-joint.  The 
ligaments  of  this  joint  are — 

Anterior  Inferior  Tibio-fibular.  Transverse  or  Inferior. 

Posterior  Inferior  Tibio-fibular.  Inferior  Interosseous. 

The  Anterior  Inferior  Ligament  (ligamentum  malleoli  later  alls  anterius)  (Figs.  248 
and  252)  is  a  flat,  triangular  band  of  fibres,  broader  below  than  above,  which  extends 
obliquely  downward  and  outward,  between  the  adjacent  margins  of  the  tibia  and 
fibula,  on  the  front  aspect  of  the  articulation.  It  is  in  relation,  in  front,  with  the 
Peroneus  tertius,  the  aponeurosis  of  the  leg,  and  the  integument;  behind,  with 
the  inferior  interosseous  ligament;  and  lies  in  contact  with  the  cartilage  covering 
the  astragalus. 

The  Posterior  Inferior  Ligament  (ligamentum  malleoli  lateralis  posterius)  (Fig. 
252) ,  smaller  than  the  preceding,  is  disposed  in  a  similar  manner  on  the  posterior 
surface  of  the  articulation. 

The  Transverse  Ligament  or  Inferior  Ligament  lies  under  cover  of  the  posterior 
ligament,  and  is  a  strong,  thick  band  of  yellowish  fibres  which  passes  transversely 
across  the  back  of  the  joint,  from  the  external  malleolus  to  the  posterior  border  of 
the  articular  surface  of  the  tibia,  almost  as  far  as  its  malleolar  process.  This  liga- 
ment projects  below  the  margin  of  the  bones,  and  forms  part  of  the  articulating 
surface  for  the  astragalus. 

The  Inferior  Interosseous  Ligament  (Fig.  250)  consists  of  numerous  short,  strong, 
fibrous  bands  which  pass  between  the  contiguous  rough  surfaces  of  the  tibia  and 
fibula,  and  constitute  the  chief  bond  of  union  between  the  bones.  This  ligament 
is  continuous  above  with  the  interosseous  membrane. 


THE    TIBIO-TARSAL    ARTICULATION 


349 


Synovial  Membrane. — The  synovial  membrane  lining  the  articular  surface  is 
derived  from  that  of  the  ankle-joint  (Fig.  250). 

Actions. — The  movement  permitted  in  these  articulations  is  limited  to  a  very 
slight  gliding  of  the  articular  surfaces  one  upon  another. 

IV.  The  Tibio-tarsal  Articulation  or  Ankle-joint  (Articulatio  Talocruralis) 

(Figs.  249,  250,  251,  252). 

The  ankle  is  a  ginglymus  or  hinge-joint.  The  bones  entering  into  its  formation 
are  the  lower  extremity  of  the  tibia  and  its  malleolus  and  the  external  malleolus 


Ta  rso-  metatarsal 
articulations,  N- 


Tarsal  articulations. 


FIG.  249. — Ankle-joint:  tarsal  and  tarso-metatarsal  articulations.     Internal  view.     Right  side. 


of  the  fibula,  which  forms  a  mortise  (Fig.  248)  to  receive  the  upper  convex  surface 
of  the  astragalus  and  its  two  lateral  facets.  The  bony  surfaces  are  covered  with  car- 
tilage and  connected  together  by  a  capsule  (capsula  articularis) ,  which  in  places 
forms  thickened  bands  constituting  the  following  ligaments: 

Anterior.  Internal  Lateral. 

Posterior.  External  Lateral. 

The  Anterior  Tibio-tarsal  Ligament  (ligamentum  talotibiale  anterius)  is  a  broad, 
thin,  membranous  layer,  attached,  above,  to  the  anterior  margin  of  the  lower 
extremity  of  the  tibia;  below,  to  the  margin  of  the  astragalus,  in  front  of  its  artic- 
ular surface.  It  is  in  relation,  in  front,  with  the  Extensor  tendons  of  the  toes,  with 
the  tendons  of  the  Tibialis  anticus  and  Peroneus  tertius,  and  the  anterior  tibial 
vessels  and  nerve;  behind,  it  lies  in  contact  with  the  synovial  membrane. 

The  Posterior  Tibio-tarsal  Ligament  (ligamentum  talotibiale  posterius)  is  very 
thin,  and  consists  principally  of  transverse  fibres.  It  is  attached,  above,  to  the 
margin  of  the  articular  surface  of  the  tibia,  blending  with  the  transverse  tibio- 
fibular  ligament;  below,  to  the  astragalus,  behind  its  superior  articular  facet. 
Externally,  where  a  somewhat  thickened  band  of  transverse  fibres  is  attached  to 
the  hollow  on  the  inner  surface  of  the  external  malleolus,  it  is  thicker  than  inter- 
nally. 


350 


THE  ARTICULATIONS    OR   JOINTS 


The  Internal  Lateral  or  Deltoid  Ligament  (ligamentum  calcaneotibiale  or  ligamentum 
deltoideum)  (Figs.  249,  250,  and  251)  is  a  strong,  flat,  triangular  band,  attached, 
above,  to  the  apex  and  anterior  and  posterior  borders  of  the  inner  malleolus. 
The  most  anterior  fibres  pass  forward  to  be  inserted  into  the  scaphoid  bone  and 
the  inferior  calcaneo-scaphoid  ligament;  the  middle  descend  almost  perpendicu- 
larly to  be  inserted  into  the  sustentaculum  tali  of  the  os  calcis;  and  the  posterior 
fibres  pass  backward  and  outward  to  be  attached  to  the  inner  side  of  the  astragalus. 
This  ligament  is  covered  by  the  tendons  of  the  Tibialis  posticus  and  Flexor  longus 
digitorum  muscles. 

The  External  Lateral  Ligament  (ligamenta  talofibularia  et  calcaneofibulare)  (Figs. 
251  and  252)  consists  of  three  distinctly  specialized  fasciculi  of  the  capsule, 
taking  different  directions  and  separated  by  distinct  intervals;  for  which  reason 
it  is  described  by  some  anatomists  as  three  distinct  ligaments.1 

The  anterior  fasciculus  (ligamentum  talofibulare  anterius),  the  shortest  of  the 
three,  passes  from  the  anterior  margin  of  the  external  malleolus  forward  and 
inward  to  the  astragalus,  in  front  of  its  external  articular  facet. 


INTEROSSEOUS, 
LIGAMENT 


SYNOVIAL 
ADIPOSE    PAD 


PERONEUS 
BREVIS  MUSCLE 


PERONEU 
LONGUS  MUSCLE 


INTERNAL  LATERAL 
LIGAMENT 
TIBIALIS    POSTICUS 

INTEROSSEOUS  CAL- 

CANEO-ASTRAGALOID 

LIGAMENT 

FLEXOR  LONGUS 

DIGITORUM 

FLEXOR   LONGUS 

HALLUCIS 

POSTERIOR 

TIBIAL  VESSELS 


FIG.  250. — Frontal  section  through  the  ankle-joint  and  the  calcaneo-astragaloid  articulation. 
(Pcirier  and  Charpy). 

The  posterior  fasciculus  (ligamentum  talofibulare  posterius),  the  most  deeply  seated, 
passes  inward  from  the  depression  at  the  inner  and  back  part  of  the  external  mal- 
leolus to  a  prominent  tubercle  on  the  posterior  surface  of  the  astragalus.  Its  fibres 
are  almost  horizontal  in  direction. 

The  middle  fasciculus  (ligamentum  calcaneofibulare)  (Figs.  251  and  252),  the 
longest  of  the  three,  is  a  narrow,  rounded  cord  passing  from  the  apex  of  the 
external  malleolus  downward  and  slightly  backward  to  a  tubercle  on  the  outer 
surface  of  the  os  calcis.  It  is  covered  by  the  tendons  of  the  Peroneus  longus  and 
brevis. 

Synovial  Membrane.— The  synovial  membrane  (Fig.  250;  invests  the  inner 
surface  of  the  ligaments,  and  sends  a  duplicature  upward  between  the  lower 
extremities  of  the  tibia  and  fibula  for  a  short  distance. 


1  Humphry.     On  the  Skeleton,  p.  559. 


THE    TIBIO-TARSAL    ARTICULATION 


351 


Relations. — The  tendons,  vessels,  and  nerves  in  connection  with  the  joint  are, 
in  front,  from  within  outward,  the  Tibialis  anticus,  Extensor  proprius  hallucis, 
anterior  tibial  vessels,  anterior  tibial  nerve,  Extensor  longus  digitorum,  and  Pero- 
neus  tertius;  behind,  from  within  outward,  the  Tibialis  posticus,  Flexor  longus 


n. 


in. 


INTERNAL 

INTEROSSEOUS 

LIGAMENT 


TARSO- 

METATARSAL 
ARTICULATIONS 


INTEROSSEOUS 
LIGAMENT 


ASTRAGALO- 

SCAPHOIO 

ARTICULATION 


TENDON   OF   POS- 
TERIOR TIBIAL 
MUSCLE 


INTEROSSEOUS 
LIGAMENTS 


INTERMETATARSAL 
ARTICULATIONS 


INTEROSSEOUS 
LIGAMENT 


CALCANEO-SCAPHOID 
LIGAMENT 


CALCANEO-CUBOIO 
ARTICULATION 


INTEROSSEOUS 
LIGAMENT 


ASTRAGALO-CALCANEAL 
— ARTICULATION 


ANKLE-JOINT 

MIDDLE   FASCICULUS 
OF  THE   EXTERNAL 
LATERAL  LIGAMENT 

INFERIOR  TIBIO- 
FI8ULAR  ARTICULATION 


FIG.  251. — Joints  of  the  right  foot,  from  the  back  of  the  foot.     (Spalteholz.) 

digitorum,  posterior  tibial  vessels,  posterior  tibial  nerve,  Flexor  longus  hallucis; 
and  in  the  groove  behind  the  external  malleolus,  the  tendons  of  the  Peroneus 
longus  and  brevis. 

The  arteries  supplying  the  joint  are  derived  from  the  malleolar  branches  of 
the  anterior  tibial  and  the  peroneal. 


352 

The  nerves  are  derived  from  the  anterior  and  posterior  tibial. 

Actions. — The  movements  of  the  joint  are  those  of  flexion  and  extension. 
Flexion  consists  in  the  approximation  of  the  dorsum  of  the  foot  to  the  front  of  the 
leg,  while  in  extension  the  heel  is  drawn  up  and  the  toes  pointed  downward.  The 
malleoli  tightly  embrace  the  astragalus  in  all  positions  of  the  joint,  so  that  any 
slight  degree  of  lateral  movement  which  may  exist  is  simply  due  to  stretching 
of  the  inferior  tibio-fibular  ligaments  and  slight  bending  of  the  shaft  of  the  fibula. 
Of  the  ligaments,  the  internal,  or  deltoid,  is  of  very  great  power — so  much  so 
that  it  usually  resists  a  force  which  fractures  the  process  of  bone  to  which  it  is 
attached.  Its  middle  portion,  together  with  the  middle  fasciculus  of  the  external 
lateral  ligament,  binds  the  bones  of  the  leg  firmly  to  the  foot  and  resists  displace- 
ment in  every  direction.  Its  anterior  and  posterior  fibres  limit  extension  and 
flexion  of  the  foot  respectively,  and  the  anterior  fibres  also  limit  abduction.  The 
posterior  portion  of  the  external  lateral  ligament  assists  the  middle  portion  in 
resisting  the  displacement  of  the  foot  backward,  and  deepens  the  cavity  for  the 


Inferior  tibio-fibidar  articulation. 


Ankle-joint. 

Tarsal  articulations. 


FIG.  252. — Ankle-joint:  tarsal  and  tarso-metatarsal  articulations.     External  view.     Right  side. 


reception  of  the  astragalus.  The  anterior  fasciculus  is  a  security  against  the  dis- 
placement of  the  foot  forward,  and  limits  extension  of  the  joint.  The  movements 
of  inversion  and  eversion  of  the  foot,  together  with  the  minute  changes  in  form  by 
which  it  is  applied  to  the  ground  or  takes  hold  of  an  object  in  climbing,  etc.,  are 
mainly  effected  in  the  tarsal  joints,  the  one  which  enjoys  the  greatest  amount  of 
motion  being  that  between  the  astragalus  and  os  calcis  behind  and  the  scaphoid 
and  cuboid  in  front.  This  is  often  called  the  transverse  or  medio-tarsal  joint,  and 
it  can,  with  the  subordinate  joints  of  the  tarsus,  replace  the  ankle-joint  in  a  great 
measure  when  the  latter  has  become  ankylosed. 

Extension  of  the  tarsal  bones  upon  the  tibia  and  fibula  is  produced  by  the 
Gastrocnemius,  Soleus,  Plantaris,  Tibialis  posticus,  Peroneus  longus  and  brevis, 
Flexor  longus  digitorum,  and  Flexor  longus  hallucis;  flexion,  by  the  Tibialis  anti- 
cus,  Peroneus  tertius,  Extensor  longus  digitorum,  and  Extensor  proprius  hallucis1 


1  The  student  must  bear  in  mind  that  the  Extensor  longus  digitorum  and  Extensor  proprius  hallucis  are 
extensors  of  the  toes,  but  flexors  of  the  ankle,  and  that  the  Flexor  longus  digitorum  and  Flexor  longus  hallucis 
are  flexors  of  the  toes,  but  extensors  of  the  ankle. — ED.  of  15th  English  Edition. 


THE    TIBIO-TARSAL    ARTICULATION 


353 


(Fig.  251);  inversion,  in  the  extended  position,  is  produced  by  theTibialis  anticus 
and  posticus;  and  eversion  by  the  Peronei. 


FIG.  253. — Section  of  the  right   foot  near  its  inner  border,  dividing  the  tibia,  astragalus,  calcaneus,  scaphoid, 
internal  cuneiform,  and  first  metatarsal  bone,  and  the  first  phalanx  of  the  great  toe.      (After  Braune.) 

Surface  Form. — The  line  of  the  ankle-joint  may  be  indicated  by  a  transverse  line  drawn 
across  the  front  of  the  lower  part  of  the  leg,  about  half  an  inch  above  the  level  of  the  tip  of  the 
internal  malleolus. 

Surgical  Anatomy. — Displacement  of  the  trochlear  surface  of  the  astragalus  from  the  tibio- 
fibular  mortise  is  not  of  common  occurrence,  as  the  ankle-joint  is  a  very  strong  and  powerful 
articulation,  and  great  force  is  required  to  produce  dislocation.  Nevertheless,  dislocation  does 
occasionally  occur,  both  in  an  antero-posterior  and  a  lateral  direction.  In  the  latter,  which  is  the 
most  common,  fracture  is  a  necessary  accompaniment  of  the  injury.  The  dislocation  in  these  cases 
is  somewhat  peculiar,  and  is  not  a  displacement  in  a  horizontally  lateral  direction,  such  as  usually 
occurs  in  lateral  dislocations  of  ginglymoid  joints,  but  the  astragalus  undergoes  a  partial  rotation 
round  an  antero-posterior  axis  drawn  through  its  own  centre,  so  that  the  superior  surface,  instead 
of  being  directed  upward,  is  inclined  more  or  less  inward  or  outward  according  to  the  variety  of 
the  displacement. 

The  ankle-joint  is  more  frequently  sprained  than  any  joint  in  the  body,  and  this  may  lead 
to  acute  synovitis.  In  these  cases,  when  the  synovial  sac  is  distended  with  fluid,  the  bulging 
appears  principally  in  the  front  of  the  joint,  beneath  the  anterior  tendons,  and  on  either  side, 
between  the  tibialis  anticus  and  the  internal  lateral  ligament  on  the  inner  side,  and  between  the 
Peroneus  tertius  and  the  external  lateral  ligament  on  the  outer  side.  In  addition  to  this,  bulging 
frequently  occurs  posteriorly,  and  a  fluctuating  swelling  may  be  detected  on  either  side  of  the 
tendo  Achillis. 

Chronic  synovitis  may  result  from  frequent  sprains,  and  when  once  this  joint  has  been 
sprained  it  is  more  liable  to  a  recurrence  of  the  injury  than  it  was  before;  chronic  synovitis 
may  be  tuberculous  in  its  origin,  the  disease  usually  commencing  in  the  astragalus  and  extending 
to  the  joint,  though  it  may  commence  as  a  synovitis  the  result  probably  of  some  slight  strain  in 
a  tuberculous  subject. 

Excision  of  the  ankle-joint  is  not  often  performed  for  two  reasons.  In  the  first  place,  disease 
of  the  articulation  for  which  this  operation  is  indicated  is  frequently  associated  with  disease  of 
the  tarsal  bones,  which  prevents  its  performance;  and,  secondly,  the  foot  after  excision  is  fre- 
quently of  very  little  use;  far  less,  in  fact,  than  after  a  Syme's  amputation,  which  is  often,  there- 
fore, a  preferable  operation  in  these  cases.  Excision  may,  however,  be  attempted  in  a  case  of 
tuberculous  arthritis  in  a  young  and  otherwise  healthy  subject,  where  the  disease  is  limited  to 
the  bones  forming  the  joint.  It  may  also  be  required  after  injury  where  the  vessels  and  nerves 
have  not  been  damaged  and  the  patient  is  young  and  free  from  visceral  disease.  The  excision  is 
best  performed  through  two  lateral  incisions.  One  commencing  two  and  a  half  inches  above  the 
external  malleolus,  carried  down  the  posterior  border  of  the  fibula,  round  the  end  of  the  bone, 
and  then  forward  and  downward  as  far  as  the  calcaneo-cuboid  joint,  midway  between  the  tip 
of  the  external  malleolus  and  the  tuberosity  on  the  fifth  metatarsal  bone.  Through  this  incision 

23 


354  THE   ARTICULATIONS    OR    JOINTS 

the  fibula  is  cleared,  the  external  lateral  ligament  is  divided,  and  the  bone  sawn  through  about 
half  an  inch  above  the  level  of  the  ankle-joint  and  removed.  A  similar  curved  incision  is  now 
made  on  the  inner  side  of  the  foot,  commmencing  two  and  a  half  inches  above  the  lower  end  of 
the  tibia,  carried  down  the  posterior  border  of  the  bone,  round  the  internal  malleolus,  and  for- 
ward and  downward  to  the  tuberosity  of  the  scaphoid  bone.  Through  this  incision  the  tibia  is 
cleared  in  front  and  behind,  the  internal  lateral,  the  anterior  and  posterior  ligaments  divided, 
and  the  end  of  the  tibia  protruded  through  the  wound  by  displacing  the  foot  outward,  and  sawn 
off  sufficiently  high  to  secure  a  healthy  section  of  bone.  The  articular  surface  of  the  astragalus 
is  now  to  be  sawn  off  or  the  whole  bone  removed.  In  cases  where  the  operation  is  performed 
for  tuberculous  arthritis  the  latter  course  is  probably  preferable,  as  the  injury  done  by  the  saw  is 
frequently  the  starting  point  of  fresh  caries;  and  after  removal  of  the  whole  bone  the  shortening 
is  not  appreciably  increased,  and  the  result  as  regards  union  appears  to  be  as  good  as  when  two 
sawn  surfaces  of  bone  are  brought  into  apposition. 

V.  Articulations  of  the  Tarsus  (Articulationes  Intertarseae)  (Figs.  249, 

251,  252,  254,  255). 

1.    ARTICULATION  OF  THE  Os  CALCIS  AND  ASTRAGALUS   OR  THE    CALCANEO- 
ASTRAGALOID  ARTICULATION  (ARTICULATIO  TALOCALCANEA)    (Fig.  251). 

The  articulations  between  the  os  calcis  and  astragalus  are  two  in  number — 
anterior  and  posterior.  They  are  arthrodial  joints.  The  bones  are  connected 
together  by  a  capsule  (capsula  articularis) ,  which  is  at  certain  points  accentuated 
into  definite  ligaments.  There  are  five  ligaments  in  this  articulation: 

External  Calcaneo-astragaloid.          Anterior  Calcaneo-astragaloid. 
Internal  Calcaneo-astragaloid.  Posterior  Calcaneo-astragaloid. 

Interosseous. 

The  External  Calcaneo-astragaloid  Ligament  (ligamentum  talocalcaneum  laterale) 
(Fig.  252)  is  a  short,  strong,  fasciculus  passing  from  the  outer  surface  of  the 
astragalus,  immediately  beneath  its  external  malleolar  facet,  to  the  outer  surface 
of  the  os  calcis.  It  is  placed  in  front  of  the  middle  fasciculus  of  the  external 
lateral  ligament  of  the  ankle-joint,  with  the  fibres  of  which  it  is  parallel. 

The  Internal  Calcaneo-astragaloid  Ligament  (ligamentum  talocalcaneum  mediate) 
is  a  band  of  fibres  connecting  the  internal  tubercle  of  the  back  of  the  astragalus 
with  the  back  of  the  sustentaculum  tali.  Its  fibres  blend  with  those  of  the  inferior 
calcaneo-scaphoid  ligament. 

The  Anterior  Calcaneo-astragaloid  Ligament  (ligamentum  talocalcaneum  anterius) 
passes  from  the  front  and  outer  surface  of  the  neck  of  the  astragalus  to  the  supe- 
rior surface  of  the  os  calcis. 

The  Posterior  Calcaneo-astragaloid  Ligament  (ligamentum  talocalcaneum  posterius) 
connects  the  external  tubercle  of  the  astragalus  with  the  upper  and  inner  part 
of  the  os  calcis ;  it  is  a  short  band,  the  fibres  of  which  radiate  from  their  narrow 
attachment  to  the  astragalus. 

The  Interosseous  Ligament  (ligamentum  talocalcaneum  interosseum)  (Figs.  250, 
251,  and  255)  forms  the  chief  bond  of  union  between  the  bones.  It  consists  of 
numerous  vertical  and  oblique  fibres  attached  by  one  extremity  to  the  groove 
between  the  articulating  facets  on  the  under  surface  of  the  astragalus;  by  the 
other  to  a  corresponding  depression  on  the  upper  surface  of  the  os  calcis.  It 
is  very  thick  and  strong,  being  at  least  an  inch  in  breadth  from  side  to  side, 
and  serves  to  unite  the  os  calcis  and  astragalus  solidly  together. 

Synovial  Membrane. — The  synovial  membranes  (Fig.  255)  are  two  in  num- 
ber: one  for  the  posterior  calcaneo-astragaloid  articulation;  a  second  for  the 
anterior  calcaneo-astragaloid  joint.  The  latter  synovial  membrane  is  con- 
tinued forward  between  the  contiguous  surfaces  of  the  astragalus  and  scaphoid 
bones. 


ARTICULATIONS    OF    THE    TARSUS  355 

Actions. — The  movements  permitted  between  the  astragalus  and  os  calcis  are 
limited  to  a  gliding  of  the  one  bone  on  the  other  in  a  direction  from  before  back- 
ward, and  from  side  to  side. 

2.   ARTICULATION  OF  THE  Os  CALCIS  WITH  THE  CUBOID  OR  THE  CALCANEO- 
CUBOID  ARTICULATION  (ARTICULATIO  CALCANEOCUBOIDEA)  (Fig.  251). 

In  this  joint  the  articular  capsule  (capsula  articularis)  is  strengthened  at 
certain  points  by  definite  ligaments. 

The  ligaments  connecting  the  os  calcis  with  the  cuboid  are  four  in  number: 

Dorsal  or  Superior  Calcaneo-cuboid.         „       p.  (  Long  Calcaneo-cuboid. 

The  Internal  Calcaneo-cuboid.  T\  Short  Calcaneo-cuboid. 

The  Superior  Calcaneo-cuboid  Ligament  (ligamentum  calcaneocuboideum  dorsale) 
(Fig.  252)  is  a  broad  portion  of  the  capsule  which  passes  between  the  contiguous 
surfaces  of  the  os  calcis  and  cuboid  on  the  dorsal  surface  of  the  joint. 

The  Internal  Calcaneo-cuboid  or  the  Interosseous  Ligament  (pars  calcaneo- 
cuboidea  ligamenti  bifurcati)  is  a  short  but  thick  and  strong  band  of  fibres 
arising  from  the  os  calcis,  in  the  deep  hollow  which  intervenes  between  it  and 
the  astragalus,  and  closely  blended,  at  its  origin,  with  the  superior  calcaneo- 
scaphoid  ligament.  These  two  ligaments  are  often  regarded  as  a  single  bifur- 
cated ligament  (ligamentum  bifurcatum).  The  internal  calcaneo-cuboid  liga- 
ment is  inserted  into  the  inner  side  of  the  cuboid  bone.  This  ligament  forms 
one  of  the  chief  bonds  of  union  between  the  first  and  second  rows  of  the  tarsus. 

The  Long  Galcaneo-cuboid  or  Long  Plantar  or  Superficial  Long  Plantar  Ligament 
(ligamentum  plantar e  longum)  (Fig.  254),  the  more  superficial  of  the  two  plantar 
ligaments,  is  the  longest  of  all  the  ligaments  of  the  tarsus:  it  is  attached  to 
the  under  surface  of  the  os  calcis,  from  near  the  tuberosities,  as  far  forward  as 
the  anterior  tubercle;  its  fibres  pass  forward  to  be  attached  to  the  ridge  on  the 
under  surface  of  the  cuboid  bone,  the  more  superficial  fibres  being  continued 
onward  to  the  bases  of  the  second,  third,  and  fourth  metatarsal  bones.  This 
ligament  crosses  the  groove  on  the  under  surface  of  the  cuboid  bone,  converting 
it  into  a  canal  for  the  passage  of  the  tendon  of  the  Peroneus  longus. 

The  Short  Calcaneo-cuboid  or  Short  Plantar  Ligament  (ligamentum  calcaneo- 
cuboideum plantare)  (Fig.  254)  lies  nearer  the  bones  than  the  preceding,  from 
which  it  is  separated  by  a  little  areolar  tissue.  It  is  exceedingly  broad,  about 
an  inch  in  length,  and  extends  from  the  tubercle  and  the  depression  in  front  of 
it,  on  the  forepart  of  the  under  surface  of  the  os  calcis,  to  the  inferior  surface  of 
the  cuboid  bone  behind  the  peroneal  groove. 

Synovial  Membrane  (Fig.  255). — The  synovial  membrane  in  this  joint  is  distinct. 
It  lines  the  inner  surface  of  the  ligaments. 

Actions. — The  movements  permitted  between  the  os  calcis  and  cuboid  are 
limited  to  a  slight  gliding  upon  each  other. 

3.  THE  LIGAMENTS  CONNECTING  THE  Os  CALCIS  AND  SCAPHOID  OR  THE 
CALCANEO-SCAPHOID  ARTICULATION  LIGAMENTS. 

Though  these  two  bones  do  not  directly  articulate,  they  are  connected  together 
by  two  ligaments: 

Superior  or  External  Calcaneo-scaphoid. 
Inferior  or  Internal  Calcaneo-scaphoid. 

The  Superior  or  External  Calcaneo-scaphoid  or  Calcaneo-navicular  (pars  cal- 
caneonavicularis  ligamenti  bifurcati)  arises,  as  already  mentioned,  with  the 
internal  calcaneo-cuboid  in  the  deep  hollow  between  the  astragalus  and  os  calcis, 


356 


THE   ARTICULATIONS    OR    JOINTS 


constituting  a  part  of  the  ligamentum  bifurcaturn ;  it  passes  forward  from  the 
upper  surface  of  the  anterior  extremity  of  the  os  calcis  to  the  outer  side  of  the 
scaphoid  bone.  These  two  ligaments  resemble  the  letter  Y,  being  blended  together 
behind,  but  separated  in  front. 

The  Inferior  or  Internal  Calcaneo-scaphoid  or  Calcaneo-navicular  (ligamentum 
calcaneonavicidare  plantare)  (Fig.  254)  is  by  far  the  larger  and  stronger  of  the  two 
ligaments  between  these  bones;  it  is  a  broad  and  thick  band  of  fibres,  which 

passes  forward  and  inward  from  the  anterior 
margin  of  the  sustentaculum  tali  of  the  os 
calcis  to  the  under  surface  of  the  scaphoid 
bone.  This  ligament  not  only  serves  to 
connect  the  os  calcis  and  scaphoid,  but  sup- 
ports the  head  of  the  astragalus,  forming 
part  of  the  articular  cavity  in  which  it  is 
received.  The  upper  surface  presents  a 
fibro-cartilaginous  facet,  lined  by  the  syn- 
ovial  membrane  continued  from  the  ante- 
rior calcaneo-astragaloid  articulation,  upon 
which  a  portion  of  the  head  of  the  astragalus 
rests.  Its  under  surface  is  in  contact  with 
the  tendon  of  the  Tibialis  posticus  muscle;1 
its  inner  border  is  blended  with  the  forepart 
of  the  Deltoid  ligament,  thus  completing 
the  socket  for  the  head  of  the  astragalus. 

Surgical  Anatomy. — The  inferior  calcaneo- 
scaphoid  ligament,  by  supporting  the  head  of  the 
astragalus,  is  principally  concerned  in  maintaining 
the  arch  of  the  foot,  and  when  it  yields  the  head  of 
the  astragalus  is  pressed  downward,  inward,  and 
forward  by  the  weight  of  the  body,  and  the  foot 
becomes  flattened,  expanded,  and  turned  outward, 
constituting  the  disease  known  as  flat-foot.  This 
ligament  contains  a  considerable  amount  of  elastic 
fibre,  so  as  to  give  elasticity  to  the  arch  and  spring  to 
the  foot;  hence  it  is  sometimes  called  the  "spring" 
ligament.  It  is  supported,  on  its  under  surface,  by 
the  tendon  of  the  Tibialis  posticus,  which  spreads 
out  at  its  insertion  into  a  number  of  fasciculi  which 
are  attached  to  most  of  the  tarsal  and  metatarsal 
bones;  this  prevents  undue  stretching  of  the  ligament 
and  is  a  protection  against  the  occurrence  of  flat-foot. 


FIG.  254. — Ligaments  of  the  plantar  surface 
of  the  foot. 


4.    ARTICULATION  OF  THE   ASTRAGALUS  WITH  THE  SCAPHOID   BONE  OR  THE 
ASTRAGALO-SCAPHOID  ARTICULATION  (ARTICULATI.O  TALONAVICULARIS) 

(Fig.  251). 

The  articulation  between  the  astragalus  and  scaphoid  is  an  arthrodial  joint: 
the  rounded  head  of  the  astragalus  being  received  into  the  concavity  formed  by 
the  posterior  surface  of  the  scaphoid,  the  anterior  articulating  surface  of  the 
calcaneum,  and  the  upper  surface  of  the  inferior  calcaneo-scaphoid  ligament, 
which  fills  up  the  triangular  interval  between  these  bones.  The  only  ligament  of 
this  joint  is  the  superior  astragalo-scaphoid  (Fig.  249).  It  is  a  broad  band, 
which  passes  obliquely  forward  from  the  neck  of  the  astragalus  to  the  superior 
surface  of  the  scaphoid  bone.  It  is  thin,  and  weak  in  texture,  and  covered  by  the 
Extensor  tendons.  The  inferior  calcaneo-scaphoid  ligament  supplies  the  place  of 
an  inferior  astragalo-scaphoid  ligament. 

1  Mr.  Hancock  describes  an  extension  of  this  ligament  upward  on  the  inner  side  of  the  foot,  which  com- 
pletes the  socket  of  the  joint  in  that  direction  (Lancet,  1866,  vol.  i,  p.  618). — ED.  of  15th  English  Edition. 


ARTICULATIONS   OF   THE    TARSUS  357 

Synovial  Membrane  (Fig.  255). — The  synovial  membrane  which  lines  the  joint 
is  continued  forward  from  the  anterior  calcaneo-astragaloid  articulation. 

Actions. — This  articulation  permits  of  considerable  mobility,  but  its  feebleness 
is  such  as  to  allow  occasionally  of  dislocation  of  the  other  bones  of  the  tarsus 
from  the  astragalus. 

The  transverse  tarsal  or  medio-tarsal  joint  (articulatio  tarsi  transversa  [Choparti]) 
(Figs.  251  and  256)  is  formed  by  the  articulation  of  the  os  calcis  with  the  cuboid, 
and  by  the  articulation  of  the  astragalus  with  the  scaphoid.  The  movement  which 
takes  place  in  this  joint  is  more  extensive  than  that  in  the  other  tarsal  joints,  and 
consists  of  a  sort  of  rotation  by  means  of  which  the  sole  of  the  foot  may  be 
slightly  flexed  and  extended  or  carried  inward  (inverted)  and  outward  (everted). 

5.  THE  ARTICULATION  OF  THE  SCAPHOID  WITH  THE  CUNEIFORM  BONES 
(ARTICULATIO  CUNEONAVICULARIS)  (Fig.  251). 

The  scaphoid  is  connected  to  the  three  cuneiform  bones  by 
Dorsal  and  Plantar  ligaments. 

The  Dorsal  Ligaments  (ligamenta  navicularicuneiformia  dorsalia)  (Figs.  249  and 
251)  are  small,  longitudinal  bands  of  fibrous  tissue  arranged  as  three  bundles,  one 
to  each  of  the  cuneiform  bones.  That  bundle  of  fibres  which  connects  the  scaphoid 
with  the  internal  cuneiform  is  continued  round  the  inner  side  of  the  articulation  to 
be  continuous  with  the  plantar  ligament  which  connects  these  two  bones. 

The  Plantar  Ligaments  (ligamenta  navicularicuneiformia  plantaria)  (Fig.  254) 
have  a  similar  arrangement  to  those  on  the  dorsum.  They  are  strengthened  by 
processes  given  off  from  the  tendon  of  the  Tibialis  posticus. 

Synovial  Membrane  (Fig.  255). — The  synovial  membrane  of  these  joints  is 
part  of  the  great  tarsal  synovial  membrane. 

Actions. — The  movements  permitted  between  the  scaphoid  and  cuneiform 
bones  are  limited  to  a  slight  gliding  upon  each  other. 

6.  THE  ARTICULATION  OF  THE  SCAPHOID  WITH  THE  CUBOID  (ARTICULATIO 

CUBONAVICULARIS) . 

The  scaphoid  bone  is  connected  with  the  cuboid  by 

Dorsal,  Plantar,  and  Interosseous  ligaments. 

The  Dorsal  Ligament  (ligamentum  cuboideonaviculare  dor  sale)  (Fig.  252)  con- 
sists of  a  band  of  fibrous  tissue  which  passes  obliquely  forward  and  outward 
from  the  scaphoid  to  the  cuboid  bone. 

The  Plantar  Ligament  (ligamentum  cuboideonaviculare  plantare)  consists  of  a 
band  of  fibrous  tissue  which  passes  nearly  transversely  between  these  two  bones. 

The  Interosseous  Ligament  (Figs.  251  and  255)  consists  of  strong  transverse 
fibres  which  pass  between  the  rough  non-articular  portions  of  the  lateral  sur- 
faces of  these  two  bones. 

Synovial  Membrane  (Fig.  255). — The  synovial  membrane  of  this  joint  is  part 
of  the  great  tarsal  synovial  membrane. 

Actions. — The  movements  permitted  between  the  scaphoid  and  cuboid  bones 
are  limited  to  a  slight  gliding  upon  each  other. 

7.    THE  ARTICULATIONS  OF  THE   CUNEIFORM  BONES  WITH  EACH  OTHER  OR 
THE  INTERCUNEIFORM  ARTICULATIONS  (Fig.  251). 

These  bones  are  connected  together  by 

Dorsal,  Plantar,  and  Interosseous  ligaments. 


358 


THE   ARTICULATIONS    OR    JOINTS 


The  Dorsal  Ligaments  (ligamenta  inter  cuneiformia  dorsalia)  consist  of  two  bands 
of  fibrous  tissue  which  pass  transversely,  one  connecting  the  internal  with  the 
middle  cuneiform,  and  the  other  connecting  the  middle  with  the  external  cunei- 
form. 

The  Plantar  Ligaments  (ligamenta  inter  cuneiformia  plantarid)  have  a  similar 
arrangement  to  those  on  the  dorsum.  They  are  strengthened  by  the  processes 
given  off  from  the  tendon  of  the  Tibialis  posticus. 

The  Interosseous  Ligaments  (ligamenta  inter  cuneiformia  interossea)  consist  of 
strong  transverse  fibres  which  pass  between  the  rough  non-articular  portions  of 
the  lateral  surfaces  of  the  first  and  second  and  the  second  and  third  cuneiform 
bones.  The  outer  portion  of  the  third  cuneiform  is  attached  to  the  cuboid  by 
the  ligamentum  cuneocuboideum,  interosseum. 

Synovial  Membrane  (Fig.  255). — The  synovial  membrane  of  these  joints  is  part 
of  the  great  tarsal  synovial  membrane. 

Actions. — The  movements  permitted  between  the  cuneiform  bones  are  limited 
to  a  slight  gliding  upon  each  other. 

8.  THE  ARTICULATION  OF  THE  EXTERNAL  CUNEIFORM  BONE  WITH  THE 

CUBOID  (Fig.  251). 

These  bones  are  connected  together  by 

Dorsal,  Plantar,  and  Interosseous  ligaments. 

The  Dorsal  Ligament  (ligamentum  cuneocuboideum  dorsale)  (Fig.  252)  consists 
of  a  band  of  fibrous  tissue  which  passes  transversely  between  these  two  bones. 

The  Plantar  Ligament  (ligamentum  cuneocuboideum  plantare)  has  a  similar 
arrangement.  It  is  strengthened  by  a  process  given  off  from  the  tendon  of  the 
Tibialis  posticus. 

The  Interosseous  Ligament  (ligamentum  cuneocuboideum  interosseum)  (Fig.  251) 
consists  of  strong  transverse  fibres  which  pass  between  the  rough  non-articular 
portions  of  the  lateral  surfaces  of  the  adjacent  sides  of  these  two  bones. 

Synovial  Membrane  (Fig.  255). — The  synovial  membrane  of  this  joint  is  part 
of  the  great  tarsal  synovial  membrane. 

Actions. — The  movements  permitted  between  the  external  cuneiform  and 
cuboid  are  limited  to  a  slight  gliding  upon  each  other. 

Nerve-supply.— All  the  joints  of  the  tarsus  are  supplied  by  the  anterior  tibial 
nerve. 

Surgical  Anatomy. — In  spite  of  the  great  strength  of  the  ligaments  which  connect  the  tarsal 
bones  together,  dislocation  at  some  of  the  tarsal  joints  does  occasionally  occur;  though,  on 
account  of  the  spongy  character  of  the  bones,  they  are  more  frequently  broken  than  dislocated, 
as  the  result  of  violence.  When  dislocation  does  occur,  it  is  most  commonly  in  connection  with 
the  astragalus;  for  not  only  may  this  bone  be  dislocated  from  the  tibia  and  fibula  at  the  ankle- 
joint,  but  the  other  bones  may  be  dislocated  from  it,  the  trochlear  surface  of  the  bone  remaining 
in  situ  in  the  tibio-fibular  mortise.  This  constitutes  what  is  known  as  the  subastragaloid  dis- 
location. Or,  again,  the  astragalus  may  be  dislocated  from  all  its  connections — from  the  tibia 
and  fibula  above,  the  os  calcis  below,  and  the  scaphoid  in  front — and  may  even  undergo  a 
rotation,  either  on  a  vertical  or  horizontal  axis.  In  the  former  case  the  long  axis  of  the  bone 
becoming  directed  across  the  joint,  so  that  the  head  faces  the  articular  surface  on  one  or  other 
malleolus;  or,  in  the  latter,  the  lateral  surfaces  becoming  directed  upward  and  downward,  so 
that  the  trochlear  surface  faces  to  one  or  the  other  side.  Finally,  dislocation  may  occur  at 
the  medio-tarsal  joint,  the  anterior  tarsal  bones  being  luxated  from  the  astragalus  and  cal- 
caneum.  The  other  tarsal  bones  are  also,  occasionally,  though  rarely,  dislocated  from  their 
connections. 

Pes  planus,  flat-foot,  or  splay-foot  is  a  condition  in  which  there  is  abduction,  eversion,  and 
loss  of  both  the  longitudinal  and  the  transverse  arch.  The  head  of  the  astragalus  passes  down- 
ward and  inward ;  the  anterior  portion  of  the  foot  is  turned  outward  and  the  inner  side  of  the 
foot  is  lengthened  and  broadened.  Deformity  is  increased  when  standing.  In  severe  cases 


TARSO  -  METATARSAL    ARTICULATIONS  359 

the  patient  walks  on  the  inner  side  of  the  foot.  The  condition  is  due  to  yielding  of  the  tarsal 
ligaments.  Abduction  is  permitted  by  yielding  of  the  internal  lateral  and  calcaneo-astragaloid 
ligaments.  Yielding  of  the  calcaneo-scaphoid  ligament  permits  the  head  of  the  astragalus  to  pass 
downward  and  forward,  and  the  entire  arch  falls.  Further  deformity  is  induced  by  the  yielding 
of  the  ligaments. 

VI.  Tarso-metatarsal  Articulations  (Articulationes  Tarsometatarseae 
[Lisfranci])  (Figs.  249,  251,  252,  254,  257). 

These  are  arthrodial  joints.  The  bones  entering  into  their  formation  are  four 
tarsal  hones — viz.,  the  internal,  middle,  and  external  cuneiform  and  the  cuboid — 
which  articulate  with  the  metatarsal  bones  of  the  five  toes.  The  metatarsal  bone 
of  the  great  toe  articulates  with  the  internal  cuneiform;  that  of  the  second  is 
deeply  wedged  in  between  the  internal  and  external  cuneiform,  resting  against  the 
middle  cuneiform,  and  being  the  most  strongly  articulated  of  all  the  metatarsal 
bones;  the  third  metatarsal  articulates  with  the  extremity  of  the  external  cunei- 
form; the  fourth,  with  the  cuboid  and  external  cuneiform;  and  the  fifth,  with 
the  cuboid.  The  articular  surfaces  are  covered  with  cartilage,  lined  by 
synovial  membrane,  and  connected  together  by  capsules  and  by  the  following 
ligaments : 

Dorsal.  Plantar.  Interosseous. 

The  Dorsal  Ligaments  (ligamenta  tarsometatarsea  dorsalia)  consist  of  strong, 
flat,  fibrous  bands,  which  connect  the  tarsal  with  the  metatarsal  bones.  The 
first  metatarsal  is  connected  to  the  internal  cuneiform  by  a  single  broad,  thin, 
fibrous  band;  the  second  has  three  dorsal  ligaments,  one  from  each  cuneiform 
bone;  the  third  has  one  from  the  external  cuneiform;  the  fourth  has  two,  one 
from  the  external  cuneiform  and  one  from  the  cuboid;  and  the  fifth,  one  from 
the  cuboid. 

The  Plantar  Ligaments  (ligamenta  tarsometatarsea  plantaria)  consist  of  longi- 
tudinal and  oblique  fibrous  bands  connecting  the  tarsal  and  metatarsal  bones, 
but  disposed  with  less  regularity  than  on  the  dorsal  surface.  Those  for  the  first 
and  second  metatarsal  are  the  most  strongly  marked;  the  second  and  third  meta- 
tarsal receive  strong  fibrous  bands  which  pass  obliquely  across  from  the  internal 
cuneiform;  the  plantar  ligaments  of  the  fourth  and  fifth  metatarsal  consist  of  a 
few  scanty  fibres  derived  from  the  cuboid. 

The  Interosseous  Ligaments  (ligamenta  cuneometatarsea  interossea)  are  three  in 
number — internal,  middle,  and  external.  The  internal  one  is  the  strongest  of  the 
three,  and  passes  from  the  outer  extremity  of  the  internal  cuneiform  to  the 
adjacent  angle  of  the  second  metatarsal.  The  middle  one,  less  strong  than  the 
preceding,  connects  the  external  cuneiform  with  the  adjacent  angle  of  the  second 
metatarsal.  The  external  interosseous  ligament  connects  the  outer  angle  of  the 
external  cuneiform  with  the  adjacent  side  of  the  third  metatarsal. 

Synovial  Membrane  (Fig.  255). — The  synovial  membrane  between  the  internal 
cuneiform  bone  and  the  first  metatarsal  bone  is  a  distinct  sac.  The  synovial 
membrane  between  the  middle  and  external  cuneiform  behind,  and  the  second 
and  third  metatarsal  bones  in  front,  is  part  of  the  great  tarsal  synovial  membrane. 
Two  prolongations  are  sent  forward  from  it — one  between  the  adjacent  sides  of 
the  second  and  third  metatarsal  bones,  and  one  between  the  third  and  fourth 
metatarsal  bones.  The  synovial  membrane  between  the  cuboid  and  the  fourth 
and  fifth  metatarsal  bones  is  a  distinct  sac.  From  it  a  prolongation  is  sent  for- 
ward between  the  fourth  and  fifth  metatarsal  bones. 

Actions. — The  movements  permitted  between  the  tarsal  and  metatarsal  bones 
are  limited  to  a  slight  gliding  upon  each  other. 


360  THE  ARTICULATIONS   OR   JOINTS 

VII.  Articulations  of  the  Metatarsal  Bones  with  Each  Other 
(Articulationes  Intermetatarseae)  (Figs.  251,  252,  254). 

The  base  of  the  first  metatarsal  bone  is  not  connected  with  the  second  meta- 
tarsal  bone  by  any  ligaments;  in  this  respect  it  resembles  the  thumb. 

The  bases  of  the  four  outer  metatarsal  bones  are  connected  together  by  dorsal, 
plantar,  and  interosseous  ligaments. 

The  Dorsal  Ligaments  (ligamenta  basium  [oss.  metatars.]  dorsalia)  consist  of 
bands  of  fibrous  tissue  which  pass  transversely  between  the  adjacent  metatarsal 
bones. 

The  Plantar  Ligaments  (ligamenta  basium  [oss.  metatars,]  plantaria)  have  a 
similar  arrangement  to  those  on  the  dorsum. 

The  Interosseous  Ligaments  (ligamenta  basium  [oss.  metatars.]  interossea)  con- 
sist of  strong  transverse  fibres  which  pass  between  the  rough  non-articular  portions 
of  the  lateral  surfaces. 

Synovial  Membrane. — The  synovial  membrane  between  the  second  and  third 
and  the  third  and  fourth  metatarsal  bones  is  part  of  the  great  tarsal  synovial  mem- 
brane. The  synovial  membrane  between  the  fourth  and  fifth  metatarsal  bones  is 
a  prolongation  of  the  synovial  membrane  of  the  cubo-metatarsal  joint  (Fig.  255) . 

Actions. — The  movement  permitted  in  the  tarsal  ends  of  the  metatarsal  boneS 
is  limited  to  a  slight  gliding  of  the  articular  surfaces  upon  one  another. 

THE  SYNOVIAL  MEMBRANES  IN  THE  TARSAL  AND  METATARSAL  JOINTS. 

The  synovial  membranes  (Fig.  255)  found  in  the  articulations  of  the  tarsus 
and  metatarsus  are  six  in  number;  one  for  the  posterior  calcaneo-astragaloid 


FIG.  255. — Oblique  section  of  the  articulations  of  the  tarsus  and  metatarsus.     Showing  the  six  synovial 

membranes. 

articulation;  a  second  for  the  anterior  calcaneo-astragaloid  and  astragalo- 
scaphoid  articulations;  a  third  for  the  calcaneo-cuboid  articulation;  and  a  fourth 
for  the  articulations  of  the  scaphoid  with  the  three  cuneiform,  the  three  cunei- 
form with  each  other,  the  external  cuneiform  with  the  cuboid,  and  the  middle  and 
external  cuneiform  with  the  bases  of  the  second  and  third  metatarsal  bones,  and 
the  lateral  surfaces  of  the  second,  third,  and  fourth  metatarsal  bones  with  each 
other;  a  fifth  for  the  internal  cuneiform  with  the  metatarsal  bone  of  the  great  toe; 
and  a  sixth  for  the  articulation  of  the  cuboid  with  the  fourth  and  fifth  metatarsal 
bones.  A  small  synovial  membrane  is  sometimes  found  between  the  contiguous 
surfaces  of  the  scaphoid  and  cuboid  bones. 


ARTICULATIONS    OF    THE  PHALANGES  361 

Nerve-supply. — The  nerves  supplying  the  tarso-metatarsal  joints  are  derived 
from  the  anterior  tibial. 

The  digital  extremities  of  all  the  metatarsal  bones  are  connected  together  by 
the  transverse  metatarsal  ligament. 

The  Transverse  Metatarsal  Ligament  is  a  narrow  fibrous  band  which  passes 
transversely  across  the  anterior  extremities  of  all  the  metatarsal  bones,  connecting 
them  together.  It  is  blended  anteriorly  with  the  plantar  (glenoid}  ligament  of 
each  metatarso-phalangeal  articulation.  To  its  posterior  border  is  connected  the 
fascia  covering  the  Interossei  muscles.  Its  inferior  surface  is  concave  where  the 
Flexor  tendons  pass  over  it.  Above  it  the  tendons  of  the  Interossei  muscles  pass 
to  their  insertion.  It  differs  from  the  transverse  metacarpal  ligament  in  that  it 
connects  the  metatarsal  bone  of  the  great  toe  with  the  rest  of  the  metatarsal  bones. 

VIII.  Metatarso-phalangeal  Articulations  (Articulationes  Metatarso- 

phalangeae). 

The  metatarso-phalangeal  articulations  are  of  the  condyloid  kind,  formed  by 
the  reception  of  the  rounded  head  of  the  metatarsal  bone  into  a  superficial  cavity 
in  the  extremity  of  the  first  phalanx.  Each  joint  has  a  capsule  and  certain 
other  ligaments. 

These  ligaments  are — 

Plantar.  Two  Lateral. 

The  Plantar  Ligaments  or  the  Glenoid  Ligaments  of  Cruveilhier  (ligamenta 
accessoria  plantaria)  are  thick,  dense,  fibrous  structures.  Each  is  placed  on 
the  plantar  surface  of  the  joint  in  the  interval  between  the  lateral  ligaments, 
to  which  it  is  connected.  The  plantar  ligaments  are  loosely  united  to  the  meta- 
tarsal bones,  but  very  firmly  to  the  bases  of  the  first  phalanges.  The  plantar 
surface  of  each  is  intimately  blended  with  the  transverse  metatarsal  ligament, 
and,  except  in  the  great  toe,  presents  a  groove  for  the  passage  of  the  Flexor 
tendons,  the  sheath  surrounding  which  is  connected^  to  each  side  of  the  groove. 
The  plantar  ligament  of  the  great  toe  contains  two  large  sesamoid  hones.  By 
their  deep  surface  they  form  part  of  the  articular  surface  for  the  head  of  the 
metatarsal  bone,  and  are  lined  by  synovial  membrane. 

The  Lateral  Ligaments  (ligamenta  collateralia)  are  strong,  rounded  cords,  placed 
one  on  each  side  of  the  joint,  each  being  attached,  by  one  extremity,  to  the  poste- 
rior tubercle  on  the  side  of  the  head  of  the  metatarsal  bone;  and,  by  the  other,  to 
the  contiguous  extremity  of  the  phalanx. 

The  place  of  a  Posterior  Ligament  is  supplied  by  the  extensor  tendon  over  the 
back  of  the  joint. 

Actions. — The  movements  permitted  in  the  metatarso-phalangeal  articulations 
are  flexion,  extension,  abduction,  and  adduction. 

IX.  Articulations  of  the  Phalanges  (Articulationes  Digitorum  Pedis). 

The  articulations  of  the  phalanges  are  ginglymoid  joints.  Besides  the  cap- 
sular  the  ligaments  are — 

Plantar.  Two  Lateral  (ligamenta  collateralia). 

The  arrangement  of  these  ligaments  is  similar  to  those  in  the  metatarso-phalan- 
geal articulations;  the  extensor  tendon  supplies  the  place  of  a  posterior  ligament. 

Actions. — The  only  movements  permitted  in  the  phalangeal  joints  are  flexion 
and  extension;  these  movements  are  more  extensive  between  the  first  and  second 
phalanges  than  between  the  second  and  third.  The  movement  of  flexion  is  very 
considerable,  but  extension  is  limited  by  the  plantar  and  lateral  ligaments. 


362 


THE  ARTICULATIONS    OR    JOINTS 


Surface  Form. — The  principal  joints  which  it  is  necessary  to  distinguish,  with  regard  to 
the  surgery  of  the  foot,  are  the  medio-tarsal  and  the  tarso-metatarsal.  The  joint  between  the 
astragalus  and  the  scaphoid  is  best  found  by  means  of  the  tubercle  of  the  scaphoid,  for 
the  line  of  the  joint  is  immediately  behind  this  process.  If  the  foot  is  grasped  and  forcibly 
extended,  a  rounded  prominence,  the  head  of  the  astragalus,  will  appear  on  the  inner  side  of 
the  dorsum  in  front  of  the  ankle-joint,  and  if  a  knife  is  carried  downward,  just  in  front  of  this 
prominence  and  behind  the  line  of  the  scaphoid  tubercle,  it  will  enter  the  astragalo-scaphoid 
joint.  The  calcaneo-cuboid  joint  is  situated  midway  between  the  external  malleolus  and  the 
prominent  end  of  the  fifth  metatarsal  bone.  The  plane  of  the  joint  is  in  the  same  line  as  that 
of  the  astragalo-scaphoid.  The  position  of  the  joint  between  the  fifth  metatarsal  bone  and  the 
cuboid  is  easily  found  by  the  projection  of  the  fifth  metatarsal  bone,  which  is  the  guide  to  it. 
The  direction  of  the  line  of  the  joint  is  very  oblique,  so  that,  if  continued  onward,  it  would 
pass  through  the  head  of  the  first  metatarsal  bone.  The  joint  between  the  fourth  metatarsal 
bone  and  the  cuboid  and  external  cuneiform  is  the  direct  continuation  inward  of  the  previous 
joint,  but  its  plane  is  less  oblique;  it  would  be  represented  by  a  line  drawn  from  the  outer  side 
of  the  articulation  to  the  middle  of  the  first  metatarsal  bone.  The  plane  of  the  joint  between 
the  third  metatarsal  bone  and  the  external  cuneiform  is  almost  transverse.  It  would  be  repre- 


CALCANEUS 


FIFTH-f- 
METATARSAL 


EXTERNAL 
CUNEIFORM 


FIRST 
METATARSAL 


FIG.  256. — Line  of  Chopart's  amputation. 
(Poirier.) 


FIG.  257.— Line  of  Lisfranc's  amputation. 
(Poirier.) 


sented  by  a  line  drawn  from  the  outer  side  of  the  joint  to  the  base  of  the  first  metatarsal  bone. 
The  tarso-metatarsal  articulation  of  the  great  toe  corresponds  to  a  groove  which  can  be  felt  by 
making  firm  pressure  on  the  inner  side  of  the  foot  one  inch  in  front  of  the  tubercle  on  the 
scaphoid  bone;  and  the  joint  between  the  second  metatarsal  bone  and  the  middle  cuneiform  is 
to  be  found  on  the  dorsum  of  the  foot,  half  an  inch  behind  the  level  of  the  tarso-metatarsal  joint 
of  the  great  toe.  The  line  of  the  joints  between  the  metatarsal  bones  and  the  first  phalanges 
is  about  an  inch  behind  the  webs  of  the  corresponding  toes. 

Surgical  Anatomy. — Chopart's  amputation  passes  through  the  middle  tarsal  joint  (astragalo- 
scaphoid  and  calcaneo-cuboid  articulation).  Fig.  256  shows  the  line  of  Chopart.  Lisfranc 
amputated  at  the  tarso-metatarsal  articulation.  Fig.  257  shows  the  line  of  Lisfranc.  In  Key's 
amputation  the  fifth,  fourth,  third,  and  second  metatarsal  bones  are  disarticulated  from  the 
tarsus  and  the  internal  cuneiform  is  sawn  through.  In  the  operation  of  Forbes,  of  Toledo,  the 
cuneiform  bones  are  disarticulated  from  the  scaphoid,  the  cuboid  is  sawn  through  on  a  line 
with  the  surface  exposed  by  the  disarticulation. 


THE  MUSCLES  AND  FASCLE.1 


MYOLOGY  is  the  branch  of  anatomy  which  treats  of  the  muscles.  The 
muscles  are  formed  of  bundles  of  reddish  fibres,  endowed  notably  with  the 
property  of  contractility  in  the  direction  of  the  long  axes  of  the  muscle  cells. 
Contractions  of  muscle  fibres  induce  motion.  The  two  principal  kinds  of  muscu- 
lar tissue  found  in  the  body  are  the  more  highly  differentiated,  or  voluntary,  and 
the  less  highly  differentiated,  or  involuntary.  The  former  of  these,  from  the  char- 
acteristic appearances  which  its  fibres  exhibit  under  the  microscope,  is  known  as 
striated  or  striped  muscle.  Striped  muscle  is  called  voluntary  because  of  the  fact 
that  it  is  capable  of  being  put  into  action  and  controlled  by  the  will.  The  fibres 
of  involuntary  muscle  do  not  present  any  cross-striped  appearance,  and  for  the 
most  part  are  not  under  the  control  of  the  will ;  such  muscles  are  known  as  unstri- 
ated,  unstriped  or  vegetative.  The  muscular  fibres  of  the  heart  differ  in  certain 
particulars  from  both  these  groups,  and  they  are  therefore  separately  described 
as  cardiac  muscular  fibres. 

Thus  it  will  be  seen  that  there  are  three  varieties  of  muscular  fibres:  (1)  Trans- 
versely striated  muscular  fibres,  which  are  for  the  most  part  voluntary  and  under 
the  control  of  the  will,  but  some  of  which  are  not  so  (for  example,  the  muscles  of 
the  pharynx  and  upper  part  of  the  resophagus).  This  variety  of  muscle  is  some- 
times called  skeletal.  (2)  Transversely  striated  muscular  fibres,  which  are  not 
under  the  control  of  the  will — -i.  e.,  the  cardiac  muscles.  The  cardiac  muscle 
occupies  a  midposition  in  the  scale  between  the  cells  of  involuntary  and  the  striated 
fibres  of  voluntary  muscle.  (3)  Plain  or  unstriped  muscular  fibres,  which  are 
involuntary  and  controlled  by  a  different  part  of  the  nervous  system  from  that 
which  controls  the  activity  of  the  voluntary  muscles.  Such  are  the  muscular  walls 
of  the  stomach  and  intestine,  of  the  uterus  and  bladder,  of  the  blood-vessels,  of 
certain  canals  and  ducts,  etc.  The  statement  that  striated  muscle  is  always  vol- 
untary, and  that  non-striated  muscle  is  always  involuntary  cannot  be  accepted  as 
invariably  and  inevitably  true.  There  are  animals  in  which  some  voluntary 
muscle  is  free  from  distinct  striation. 

In  this  section  we  treat  of  the  skeletal  or  striated  muscles  only.  The  skeletal 
muscles  act  upon  the  bones,  and  thus  produce  movement.  The  primitive  con- 
tractile elements  of  a  muscle  are  the  fibres.  Fibres  are  gathered  into  groups 
known  as  fasciculi,  and  fasciculi  are  aggregated  into  masses  called  bundles.  In 
coarse  muscles  the  fasciculi  are  of  considerable  size;  in  fine  muscles  they  are  of 
trivial  size.  Fasciculi  may  be  long  or  short,  and  the  length  does  not  depend  on  the 
length  of  the  muscle.  If  a  muscle  has  an  insertion  only  at  each  end,  the  fasciculi 
are  sure  to  be  long  and  may  reach  from  the  tendon  of  origin  to  the  tendon  of 

1  The  Muscles  and  Fascise  are  described  conjointly,  in  order  that  the  student  may  consider  the  arrangement 
of  the  latter  in  his  dissection  of  the  former.  It  is  rare  for  the  student  of  anatomy  in  this  country  to  have 
the  opportunity  of  dissecting  the  fasciae  separately;  and  it  is  for  this  reason,  as  well  as  from  the  close  con- 
nection that  exists  between  the  muscles  and  their  investing  sheaths,  that  they  are  considered  together.  Some 
general  observations  are  first  made  on  the  histology  and  anatomy  of  the  muscles  and  fasciae,  the  special 
description  being  given  in  connection  with  the  different  regions. 

(363  ) 


364  THE  MUSCLES  AND  FASCIAE 

insertion.    If  a  muscle  takes  attachments  to  the  side  or  to  septa  within  the  muscle, 
the  fasciculi  may  be  very  short  even  when  the  muscle  is  very  long. 

Structure  of  Striated  Muscle. — The  striated  muscle  fibre  is  a  development  of 
a  muscle  cell.  Each  cell  is  long  and  narrow  and  is  called  a  fibre,  and  by  shorten- 
ing of  these  fibres  the  muscle,  as  a  whole,  is  shortened. 

A  fibre  is  more  or  less  cylindrical  in  outline,  is  usually  spindle-shaped,  and  in 
some  regions  the  fibres  branch.  The  diameter  is  very  variable,  and  does  not  depend 
in  any  degree  upon  the  size  of  the  muscle,  and  in  the  same  muscle  are  found  fibres 
varying  widely  in  diameter.  As  a  rule,  the  diameter  varies  between  0.01  and 
0.1  mm. 

The  fibres  are  usually  short,  being  seldom  over  5  cm.  in  length.  In  some  muscles, 
as  in  the  Sartorius,  they  are  much  longer,  and  may  be  10  or  12  cm.  in  length.  Some- 
times a  fibre  extends  the  entire  length  of  a  small  muscle.  A  muscle  fibre  is  surrounded 
by  a  sheath  or  wall,  the  sarcolemma.  Muscle  fibres  are  gathered  into  masses  known 
as  primary  bundles,  which  are  held  to  each  other  by  scanty  connective  tissue 
called  the  endomysium.  Each  primary  bundle  is  surrounded  by  the  perimysium. 
Primary  bundles  are  aggregated  into  groups,  the  secondary  bundles,  and  each 
secondary  bundle  is  invested  by  the  epimysium  which  is  derived  from  the  muscle 
sheath. 

Structure  of  the  Muscle  Fibre. — The  muscle  fibre  is  an  elongated  cell  containing 
numerous  nuclei  and  terminating  by  blending  of  the  sarcolemma  with  tendon 
aponeurosis  or  fibrous  septum,  or  else,  after  becoming  rounded  or  tapering,  joining 
another  cell  by  fusion  of  the  sarcolemma  of  both.  The  sarcolemma  completely 
invests  the  muscle  fibre  and  attaches  the  fibre  to  tendon,  aponeurosis,  or  the  sar- 
colemma of  another  fibre,  as  the  case  may  be. 

The  muscular  substance  within  the  sheath  of  sarcolemma  is  composed  of  pro- 
toplasm. One  part  is  unchanged  protoplasm,  and  is  called  sarcoplasm.  This  con- 
tains the  muscle  nuclei.  Another  part  is  highly  differentiated;  it  contains  the 
contractile  fibrillse  and  is  striated.  Transverse  striation  is  due  to  alteration  in  the 
parts  of  the  fibre,  so  that  the  altered  material  has  a  different  refractive  index  and 
stains  differently  from  the  unaltered  portions  of  the  fibre.  In  man  most  muscles 
are  of  the  red  type,  but  some  (mixed  muscles)  contain  red  and  white  fibres.  A  red 
muscle  fibre  contains  a  considerable  quantity  of  sarcoplasm,  and  the  nuclei  are 
toward  the  centre  of  the  cell;  in  a  white  muscle  fibre  there  is  less  sarcoplasm,  the 
nuclei  are  toward  the  periphery,  and  striation  is  very  distinct.1 

The  Arteries  of  voluntary  muscle  are  numerous.  They  pierce  the  epimysium, 
pass  along  the  septa  from  the  epimysium,  and  divide  into  small  branches,  which 
enter  between  the  fasciculi.  These  small  branches  pass  into  capillaries  which  lie 
around  the  fibres.  The  capillaries  form  a  network  between  and  upon  the  fibres. 
Capillary  plexuses  here  and  there  possess  dilatations  for  the  relief  of  tension  during 
muscular  action. 

Veins  accompany  the  arteries,  and  even  the  smaller  ones  possess  valves 
(Spalteholz). 

The  Nerve  Endings  in  voluntary  muscle  comprise  both  motor  and  sensory  ter- 
minations. A  motor  nerve  pierces  the  epimysium  and  breaks  up  into  numerous 
branches  to  form  an  interfascicular  plexus  in  the  perimysium.  From  this  plexus 
nerve  fibrils  arise  and  usually  one  nerve  fibril  passes  to  each  muscle  fibre.  The 
nerve  fibril  pierces  the  sarcolemma,  the  neurilemma  and  medullary  sheath  dis- 
appearing before  the  nerve  fibril  reaches  the  muscle  fibre,  and  probably  being 
lost  by  fusing  with  the  sarcolemma.  The  naked  axis-cylinder  beneath  the  sar- 
colemma of  a  fibre  continues  to  the  surface  of  the  muscle  fibre  and  undergoes 
arborization  to  form  an  end  organ.  Around  the  end  organ  is  a  quantity  of  granular 

'•A  Text-book  of  Histology.  By  Dr.  Ladislaus  Szymonowicz.  Translated  and  edited  by  Dr.  John  Bruce 
MacCallum. 


THE  STRUCTURE  OF  MUSCLE  365 

sarcoplasm,  which,  with  the  nerve  end  organ,  constitutes  a  sole-plate.  A  sensory 
nerve  takes  origin  from  a  muscle  spindle,  which  consists  of  a  bundle  of  encapsuled 
muscle  fibre  about  sensory  nerve  twigs.  From  a  muscle  spindle  arise  from  two  to 
eight  large  myelinic  nerve  fibres. 

The  muscles  are  connected  with  the  bones,  cartilages,  ligaments,  and  skin, 
either  directly  or  through  the  intervention  of  fibrous  structures  called  tendons 
or  aponeuroses.  Where  a  muscle  is  attached  to  bone  or  cartilage,  the  fibres  ter- 
minate in  blunt  extremities  upon  the  periosteum  or  perichondrium,  and  do  not 
come  into  direct  relation  with  the  osseous  or  cartilaginous  tissue.  Where  muscles 
are  connected  with  the  skin,  they  either  lie  as  a  flattened  layer  beneath  it,  or  are 
connected  with  its  areolar  tissue  by  larger  or  smaller  bundles  of  fibres,  as  in  the 
muscles  of  the  face.  The  direct  continuation  of  the  tendon  of  a  muscle  is  known 
as  the  belly  or  venter.  The  origin  of  a  muscle  is  its  head  (caput). 

The  muscles  vary  extremely  in  their  form.  In  the  limbs  they  are  of  consid- 
erable length,  especially  the  more  superficial  ones,  the  deep  ones  being  generally 
broad;  they  surround  the  bones  and  form  an  important  protection  to  the  various 
joints.  In  the  trunk  they  are  broad,  flattened,  and  expanded,  forming  the  parietes 
of  the  cavities  which  they  enclose;  hence  the  reason  of  the  terms  long,  broad, 
short,  etc.,  used  in  the  description  of  a  muscle. 

There  is  a  considerable  variation  in  the  arrangement  of  the  fibres  of  certain 
muscles  with  reference  to  the  tendons  to  which  they  are  attached.  In  some,  the 
fibres  are  parallel  and  run  directly  from  their  origin  to  their  insertion;  these  are 
quadrilateral  muscles,  such  as  the  Thyro-hyoid.  A  modification  of  these  is  found  in 
the  fusiform  muscles  (m.  fusiformis) ,  in  which  the  fibres  are  not  quite  parallel,  but 
slightly  curved,  so  that  the  muscle  tapers  at  each  end;  in  their  action,  however,  they 
resemble  the  quadrilateral  muscles.  Secondly,  in  other  muscles  the  fibres  are  con- 
vergent; arising  by  a  broad  origin,  they  converge  to  a  narrower  pointed  insertion. 
This  arrangement  of  fibres  is  found  in  the  triangular  muscles — e.  g.,  the  Temporal. 
In  some  muscles,  which  otherwise  would  belong  to  the  quadrilateral  or  triangular 
type,  the  origin  and  insertion  are  not  in  the  same  plane,  but  the  plane  of  the  line 
of  origin  intersects  that  of  their  insertion ;  such  is  the  case  in  the  Pectineus  muscle. 
Thirdly,  in  some  muscles  the  fibres  are  oblique  and  converge,  like  the  plumes 
of  a  pen,  to  one  side  of  a  tendon,  which  runs  the  entire  length  of  the  muscle. 
Such  a  muscle  is  rhomboidal  or  penniform  (m.  unipennatus) ,  as  the  Peronei.  A 
modification  of  these  rhomboidal  muscles  is  found  in  those  cases  where  oblique 
fibres  convero-e  to  both  sides  of  a  central  tendon  which  runs  down  the  middle  of 

O 

the  muscle ;  these  are  called  bipenniform  (m.  bipennatiis) ,  and  an  example  is  afforded 
MI  the  Rectus  femoris.  Finally,  we  have  muscles  in  which  the  fibres  are  arranged 
in  curved  bundles  in  one  or  more  planes,  as  in  an  orbicular  muscle  (m.  orbicularis) 
and  in  that  variety  of  orbicular  muscle  called  a  sphincter  muscle  (m.  sphincter). 
The  arrangement  of  the  muscular  fibres  is  of  considerable  importance  in  respect 
to  their  relative  strength  and  range  of  movement.  Those  muscles  where  the 
fibres  are  long  and  few  in  number  have  great  range,  but  diminished  strength; 
where,  on  the  other  hand,  the  fibres  are  short  and  more  numerous,  there  is 
great  power,  but  lessened  range. 

Muscles  differ  much  in  size:  the  Gastrocnemius  forms  the  chief  bulk  of  the 
back  of  the  leg;  the  Sartorius  is  very  long;  the  Stapedius,  a  small  muscle  of  the 
internal  ear,  weighs  about  a  grain,  and  its  fibres  are  not  more  than  two  lines  in 
length. 

The  names  applied  to  the  various  muscles  have  been  derived — 1,  from  their 
situation,  as  the  Tibialis,  Radialis,  Ulnaris,  Peroneus;  2,  from  their  direction,  as 
the  Rectus  abdominis,  Obliquus  capitis,Transversalis;  3,  from  their  uses,  as  Flexors, 
Extensors,  Abductors,  etc.;  4,  from  their  shape,  as  the  Deltoid,  Trapezius,  Rhom- 
boideus;  5,  from  the  number  of  their  divisions,  as  the  Biceps,  the  Triceps;  6, 


366  THE  MUSCLES  AND  FASCIAE 

from  their  points  of  attachment,  as  the  Sterno-cleido-mastoid,  Sterno-hyoid, 
Sterno-thyroid. 

In  the  description  of  a  muscle  the  term  origin  is  meant  to  imply  its  more  fixed 
or  central  attachment,  and  the  term  insertion,  the  movable  point  to  which  the 
force  of  the  muscle  is  directed;  but  the  origin  is  absolutely  fixed  in  only  a  very 
small  number  of  muscles,  such  as  those  of  the  face,  which  are  attached  by  one 
extremity  to  the  bone  and  by  the  other  to  the  movable  integument;  the  greater 
number  of  muscles  can  be  made  to  act  from  either  extremity. 

In  the  dissection  of  the  muscles  the  student  should  pay  especial  attention  to 
the  exact  origin,  insertion,  and  actions  of  each,  and  its  more  important  relations 
with  surrounding  parts.  An  accurate  knowledge  of  the  points  of  attachment  of 
the  muscles  is  of  great  importance  in  the  determination  of  their  action.  By  a 
knowledge  of  the  action  of  the  muscles  the  surgeon  is  able  to  explain  the  causes 
of  displacement  in  various  forms  of  fracture  and  the  causes  which  produce  dis- 
tortion in  various  deformities,  and,  consequently,  to  adopt  appropriate  treatment 
in  each  case.  The  relations,  also,  of  some  of  the  muscles,  especially  those  in 
immediate  apposition  with  the  larger  blood-vessels,  and  the  surface-markings  they 
produce,  should  be  especially  remembered,  as  they  form  useful  guides  to  the 
surgeon  who  operates  to  expose  and  ligate  them. 

Tendons. — Tendons  are  white,  glistening,  fibrous  cords,  varying  in  length  and 
thickness,  sometimes  round,  sometimes  flattened,  of  considerable  strength,  and 
devoid  of  elasticity.  They  consist  almost  entirely  of  white  fibrous  tissue.,  the  fibrils 
of  which  have  an  undulating  course  parallel  with  each  other  and  are  firmly  united 
together.  They  are  very  sparingly  supplied  with  blood-vessels,  the  smaller  ten- 
dons presenting  in  their  interior  not  a  trace  of  them.  Nerves  also  are  not  present 
in  the  smaller  tendons,  but  the  larger  ones,  as  the  tendo  Achillis,  receive  nerves 
which  accompany  nutrient  vessels.  The  tendons  consist  principally  of  a  sub- 
stance which  yields  gelatin. 

Aponeuroses. — Aponeuroses  are  flattened  or  ribbon-shaped  tendons,  of  a 
pearly-white  color,  iridescent,  glistening,  and  similar  in  structure  to  the  tendons. 
They  are  destitute  of  nerves,  and  the  thicker  ones  are  only  sparingly  supplied 
with  blood-vessels. 

The  tendons  and  aponeuroses  are  connected,  on  the  one  hand,  with  the  mus- 
cles, and,  on  the  other  hand,  with  movable  structures,  as  the  bones,  cartilages, 
ligaments,  fibrous  membranes  (for  instance,  the  sclerotic).  Where  the  muscular 
fibres  are  in  a  direct  line  with  those  of  the  tendon  or  aponeurosis,  the  two  are 
directly  continuous,  the  muscular  fibre  being  distinguishable  from  that  of  the 
tendon  only  by  its  striation.  But  where  the  muscular  fibres  join  the  tendon  or 
aponeurosis  at  an  oblique  angle  the  former  terminate,  according  to  Kolliker,  in 
rounded  extremities,  which  are  received  into  corresponding  depressions  on  the 
surface  of  the  latter,  the  connective  tissue  between  the  fibres  being  continuous 
with  that  of  the  tendon.  The  latter  mode  of  attachment  occurs  in  all  the  penni- 
form  and  bipenniform  muscles,  and  in  those  muscles  the  tendons  of  which  com- 
mence in  a  membranous  form,  as  the  Gastrocnemius  and  Soleus. 

Fasciae. — The  fasciae  (fascia,  a  bandage)  are  fibro-areolar  or  aponeurotic 
laminae  of  variable  thickness  and  strength,  found  in  all  regions  of  the  body, 
investing  the  softer  and  more  delicate  organs.  The  fascia  have  been  sub- 
divided, from  the  situation  in  which  they  are  found,  into  two  groups,  superficial 
and  deep. 

Superficial  Fascia  (panniculus  adiposus}. — The  superficial  fascia  is  found  imme- 
diately beneath  the  integument  over  almost  the  entire  surface  of  the  body.  It 
connects  the  skin  with  the  deep  or  aponeurotic  fascia,  and  consists  of  fibro-areolar 
tissue,  containing  in  its  meshes  pellicles  of  fat  in  varying  quantity.  In  the  eyelids 
and  scrotum,  where  adipose  tissue  is  rarely  deposited,  this  tissue  is  very  liable  to 


MUSCLES  AND  FASCIA  OF  THE  CRANIUM  AND  FACE       367 

serous  inflammation.  The  superficial  fascia  varies  in  thickness  in  different  parts 
of  the  body:  in  the  groin  it  is  so  thick  as  to  be  capable  of  being  subdivided  in 
several  lamina*.  Beneath  the' fatty  layer  of  the  superficial  fascia,  which  is  imme- 
diately subcutaneous,  there  is  generally  another  layer  of  the  same  structure,  com- 
paratively devoid  of  adipose  tissue,  in  which  the  trunks  of  the  subcutaneous  vessels 
and  nerves  are  found,  as  the  superficial  epigastric  vessels  in  the  abdominal  region, 
the  radial  and  ulnar  veins  in  the  forearm,  the  saphenous  veins  in  the  leg  and 
thigh,  and  the  superficial  lymphatic  glands;  certain  cutaneous  muscles  also  are 
situated  in  the  superficial  fascia,  as  the  Platysma  myoides  in  the  neck,  and  the 
Orbicularis  palpebrarum  around  the  eyelids.  This  fascia  is  most  distinct  at  the 
lower  part  of  the  abdomen,  the  scrotum,  perinaeum,  and  extremities;  is  very  thin 
in  those  regions  where  muscular  fibres  are  inserted  into  the  integument,  as  on 
the  side  of  the  neck,  the  face,  and  around  the  margin  of  the  anus.  It  is  very 
dense  in  the  scalp,  in  the  palms  of  the  hands  and  soles  of  the  feet,  forming  a  fibro- 
fatty  layer  which  binds  the  integument  firmly  to  the  subjacent  structure.  The 
superficial  fascia  connects  the  skin  to  the  subjacent  parts,  facilitates  the  move- 
ment of  the  skin,  serves  as  a  soft  medium  for  the  passage  of  vessels  and  nerves 
to  the  integument,  and  retains  the  warmth  of  the  body,  since  the  fat  contained  in 
its  areolse  is  a  bad  conductor  of  heat. 

Deep  Fascia. — The  deep  or  aponeurotic  fascia  is  a  dense,  inelastic,  unyielding 
fibrous  membrane,  forming  sheaths  for  the  muscles  and  affording  them  broad 
surfaces  for  attachment.  It  consists  of  shining  tendinous  fibres,  placed  parallel 
with  one  another,  and  connected  together  by  other  fibres  disposed  in  a  rectilinear 
manner.  It  is  usually  exposed  on  the  removal  of  the  superficial  fascia,  forming  a 
strong  investment,  which  not  only  binds  down  collectively  the  muscles  in  each 
region,  but  gives  a  separate  sheath  to  each,  as  well  as  to  the  vessels  and  nerves. 
The  fasciae  are  thick  in  unprotected  situations,  as  on  the  outer  side  of  a  limb,  and 
thinner  on  the  inner  side.  The  deep  fasciae  assist  the  muscles  in  their  action  by 
the  degree  of  tension  and  pressure  they  make  upon  their  surface;  and  in  certain 
situations  this  is  increased  and  regulated  by  muscular  action;  as,  for  instance,  by 
the  Tensor  fasciae  femoris  and  Gluteus  maximus  in  the  thigh,  by  the  Biceps  in 
the  upper  and  lower  extremities,  and  Palmaris  longus  in  the  hand.  In  the  limbs 
the  fasciae  not  only  invest  the  entire  limb,  but  give  off  septa  which  separate  the 
various  muscles,  and  are  attached  beneath  to  the  periosteum :  these  prolongations 
of  fasciae  are  usually  spoken  of  as  intermuscular  septa. 

The  Muscles  and  Fasciae  may  be  arranged,  according  to  the  general  division 
of  the  body,  into  those  of  the  cranium,  face,  and  neck;  those  of  the  trunk;  those  of 
the  upper  extremity;  and  those  of  the  lower  extremity. 


MUSCLES  AND  FASCLffl  OF  THE  CRANIUM  AND  FACE. 

The  muscles  of  the  cranium  and  face  consist  of  ten  groups,  arranged  according 
to  the  region  in  which  they  are  situated: 

1.  Cranial  Region.  6.  Maxillary  Region. 

2.  Auricular  Region.  7.  Mandibular  Region. 

3.  Palpebral  Region.  8.  Intermaxillary  Region. 

4.  Orbital  Region.  9.  Temporo-mandibular.  Region. 

5.  Nasal  Region  10.  Pterygo-mandibular  Region. 


368 


THE  MUSCLES  AND  FASCIA 


The  muscles  contained  in  each  of  these  groups  are  the  following: 


1.  Cranial  Region. 
Occipito-frontalis. 

2.  Auricular  Region. 

Attrahens  auriculam. 
Attollens  auriculam. 
Retrahens  auriculam. 

3.  Palpebral  Region. 

Orbicularis  palpebrarum. 
Corrugator  supercilii. 
Tensor  tarsi. 

4.  Orbital  Region. 

Levator  palpebrse. 
Rectus  superior. 
Rectus  inferior. 
Rectus  internus. 
Rectus  externus. 
Obliquus  superior. 
Obliquus  inferior. 

5.  Nasal  Region. 

Pyramidalis  nasi. 

Levator  labii  superioris  alseque 

nasi. 

Dilator  naris  posterior. 
Dilator  naris  anterior. 
Compressor  nasi. 
Compressor  narium  minor. 
Depressor  alre  nasi. 


6.  Maxillary  Region. 

Levator  labii  superioris. 
Levator  anguli  oris. 
Zygomaticus  major. 
Zygomaticus  minor. 


7.  Mandibular  Region. 

Levator  labii  inferioris. 
Depressor  labii  inferioris. 
Depressor  anguli  oris. 


8.  Intermaxillary  Region. 

Buccinator. 
Risorius. 
Orbicularis  oris. 


9.  Temporo-mandibular  Region. 

Masseter. 
Temporal. 

10.  Pterygo-mandibular  Region. 

Pterygoideus  externus. 
Pterygoideus  internus. 


1.  The  Cranial  Region. 

Occipito-frontalis. 

Dissection  (Fig.  258). — The  head  being  shaved,  and  a  block  placed  beneath  the  back  of 
the  neck,  make  a  vertical  incision  through  the  skin  from  before  backward,  commencing  at 
the  root  of  the  nose  in  front,  and  terminating  behind  at  the  occipital  protuberance;  make  a 
second  incision  in  a  horizontal  direction  along  the  forehead  and  round  the  side  of  the  head, 
from  the  anterior  to  the  posterior  extremity  of  the  preceding.  Raise  the  skin  in  front,  from 
the  subjacent  muscle,  from  below  upward;  this  must  be  done  with  extreme  care,  removing 
the  integument  from  the  outer  surface  of  the  vessels  and  the  nerves  which  lie  immediately 
beneath  the  skin. 

The  Skin  of  the  Scalp. — This  is  thicker  than  in  any  other  part  of  the  body.  It 
is  intimately  adherent  to  the  superficial  fascia,  which  attaches  it  firmly  to  the 
underlying  aponeurosis  and  muscle.  Movements  of  the  muscle  move  the  skin. 
The  hair-follicles  are  very  closely  set  together,  and  extend  throughout  the  whole 
thickness  of  the  skin.  It  also  contains  a  number  of  sebaceous  glands. 

Superficial  Fascia. — The  superficial  fascia  in  the  cranial  region  is  a  firm, 
dense,  fibro-fatty  layer,  intimately  adherent  to  the  integument,  and  to  the  occipito- 
frontalis  and  its  tendinous  aponeurosis;  it  is  continuous,  behind,  with  the  super- 
ficial fascia  at  the  back  part  of  the  neck;  and,  laterally,  is  continued  over  the 
temporal  fascia.  It  contains  between  its  layers  the  superficial  vessels  and  nerves 
and  much  granular  fat. 


THE  CRANIAL  REGION 


369 


Surgical  Anatomy.— The  subcutaneous  tissue  is  composed  of  bands  of  fibrous  tissue  enclos- 
ing spaces  filled  with  fat.  The  fibrous  character  of  this  tissue  greatly  limits  discoloration  and 
swelling  when  inflammation  occurs.  The  edges  of  a  wound  which  does  not  involve  the  apon- 
eurosis  or  muscle  do  not  retract,  hence  the  wound  does  not  gap.  The  blood-vessels  run  practi- 
cally in  the  skin,  and  as  they  lie  in  very  dense  tissue  and  are  adherent  to  it,  wounds  bleed 
profusely,  the  arteries  being  unable  to  freely  contract  and  retract.  It  is  very  difficult  or 
impossible  to  pick  up  with  forceps  a  vessel  in  the  skin  of  the  scalp,  and  bleeding  must  be 
arrested  by  suture  ligatures  or  by  the  stitches  which  close  the  wound.  Sebaceous  glands  in 
the  skin  of  the  scalp  may  develop  into  sebaceous  cysts  (wens). 


1.  Dissection  of  scalp. 

3,  5,  of  auricular  region. 

4,  5,  6,  of  face. 

7,  8,  of  neck. 


FIG.  258. — Dissection  of  the  head,  face,  and  neck. 


The  Occipito-frontalis   (m.  epicranius)   (Fig.   260). — The    Occipito-frontalis 
is  a  broad  musculo-fibrous  layer,  which  covers  the  whole  of  one  side  of  the 


SUBCUTANEOUS  ADI- 
SE  TISSUE 

APONEUROSIS  OF 

CCIPITO-FRONTALIS 
MUSCLE 


OCCIPITO-FRONTA 
MUSCLE 


BAPONEUROTIC 
SSUE 


ERIOSTEUM 


OCCIPITO-FRONTALIS 
MUSCLE 


FIG.  259. — Epicrar.ial  aponeurosis.     Antero-posterior  section.     (Schematic.)     (Poirier  and  Charpy.) 


vertex  of  the  skull,  from  the  occiput  to  the  eyebrow.  It  consists  of  two  mus- 
cular slips,  separated  by  an  intervening  tendinous  aponeurosis.  The  occipital 
portion,  the  occipitalis  muscle  (m.  occipitalis),  is  thin,  quadrilateral  in  form,  and 
about  an  inch  and  a  half  in  length;  it  arises  from  the  outer  two-thirds  of  the 
superior  curved  line  of  the  occipital  bone,  and  from  the  mastoid  portion  of  the 
temporal  bone.  Its  fibres  of  origin  are  tendinous,  but  they  soon  become  muscular, 
and  ascend  in  a  parallel  direction  to  terminate  in  a  tendinous  aponeurosis.  The 
frontal  portion,  the  frontalis  muscle  (m.  frontalis),  is  thin,  of  a  quadrilateral 
form,  and  intimately  adherent  to  the  superficial  fascia.  It  is  broader,  its  fibres 
are  longer,  and  their  structure  paler  than  the  occipital  portion.  Its  internal 
fibres  are  continuous  with  those  of  the  Pyramidalis  nasi.  Some  anatomists  con- 

24 


370 


THE  MUSCLES  AND  FASCIA 


sider  the  Pyramidalis  muscle  as  simply  the  lower  fibres  of  the  frontalis,  and 
give  these  bundles  of  muscle  fibre  the  name  of  musculus  procerus.  Its  middle 
fibres  become  blended  with  the  Corrugator  supercilii  and  Orbicularis  palpebra- 
rum ;  and  the  outer  fibres  are  also  blended  with  the  latter  muscle  over  the  external 
angular  process.  According  to  Theile,  the  innermost  fibres  are  attached  to  the 
nasal  bones,  the  outer  to  the  external  angular  process  of  the  frontal  bone.  From 
these  attachments  the  fibres  are  directed  upward,  and  join  the  aponeurosis  below 
the  coronal  suture.  The  inner  margins  of  the  frontal  portions  of  the  two  muscles 
are  joined  together  for  some  distance  above  the  root  of  the  nose;  but  between  the 
occipital  portions  there  is  a  considerable,  though  variable,  interval,  which  is  occu- 
pied by  the  aponeurosis. 

The  middle  portion  of  the  Occipito-frontalis  muscle  or  the  aponeurosis  (epi- 
cranial  aponeurosis,  Galea  aponeurotica)  covers  the  upper  part  of  .the  vertex 
of  the  skull,  being  continuous  across  the  middle  line  with  the  aponeurosis  of  the 


CORRUGATOR    SUPERCILII 


DILATOR  NAHIS    ANTERIOR. 

DILATOR     NARIS    POSTERIOR 

COMPRESSOR    NARIUM     MINOR. 

DEPRESSOR    AL/t    NASI. 


LEVATOR    MENTI. 


FIG.  260. — Muscles  of  the  head,  face,  and  neck. 


THE  A  URICULAR  REGION  371 

opposite  muscle.  Behind,  it  is  attached,  in  the  interval  between  the  occipital 
origins,  to  the  occipital  protuberance  and  highest  curved  lines  of  the  occipital 
bone;  in  front,  it  forms  a  short  and  narrow  prolongation  between  the  frontal  por- 
tions; and  on  each  side  it  has  connected  with  it  the  Attollens  and  Attrahens 
auriculam  muscles.  This  aponeurosis  is  closely  connected  to  the  integument  by 
the  firm,  dense,  fibre-fatty  layer  which  forms  the  superficial  fascia;  it  is  connected 
with  the  pericranium  by  loose  cellular  tissue,  which  allows  of  a  considerable 
degree  of  movement  of  the  integument.  It  is  continuous  with  the  temporal 
fascia  below  the  temporal  ridge,  and  it  is  in  reality  the  representative  of  the 
deep  fascia. 

Nerves. — The  frontal  portion  of  the  Occipito-frontalis  is  supplied  by  the  facial 
nerve;  its  occipital  portion  by  the  posterior  auricular  branch  of  the  facial. 

Actions. — The  frontal  portion  of  the  muscle  raises  the  eyebrows  and  the  skin 
over  the  root  of  the  nose,  and  at  the  same  time  draws  the  scalp  forward,  throwing 
the  integument  of  the  forehead  into  transverse  wrinkles.  The  posterior  portion 
draws  the  scalp  backward.  By  bringing  alternately  into  action  the  frontal  and 
occipital  portions  the  entire  scalp  may  be  moved  forward  and  backward.  In  the 
ordinary  action  of  the  muscles,  the  eyebrows  are  elevated,  and  at  the  same  time 
the  aponeurosis  is  fixed  by  the  posterior  portion,  thus  giving  to  the  face  the 
expression  of  surprise:  if  the  action  is  more  exaggerated,  the  eyebrows  a're  still 
further  raised,  and  the  skin  of  the  forehead  thrown  into  transverse  wrinkles,  as  in 
the  expression  of  fright  or  horror. 

Surgical  Anatomy. — The  skull  is  covered  by  the  scalp  (Fig.  259).  This  consists  of  five  layers: 
(1)  the  pericranium;  (2)  a  layer  of  connective  tissue  beneath  the  Occipito-frontalis  aponeurosis 
(subaponeurotic  tissue);  (3)  the  Occipito-frontalis  muscle  and  aponeurosis;  (4)  subcutaneous  fat; 
(5)  skin.  If  a  wound  involves  the  muscle  or  aponeurosis,  it  gaps  widely,  the  greatest  amount 
of  gaping  being  observed  in  transverse  wounds.  The  space  between  the  aponeurosis  and  the 
pericranium  is  called  by  Treves  the  dangerous  area  of  the  scalp.  It  contains  a  layer  of  con- 
nective tissue  and  suppuration  in  this  tissue  spreads  widely.  An  abscess  in  the  dangerous  area 
should  be  opened  above  the  superior  curved  line  of  the  occipital  bone,  above  the  eyebrow 
or  above  the  zygoma.  In  a  wound  or  contusion  above  the  aponeurosis  but  little  blood  can  be, 
effused  in  the  tissue  because  the  fibrous  structure  prevents  it,  and  abscesses  do  not  tend  to 
spread  widely.  Between  the  aponeurosis  and  the  pericranium  a  great  amount  of  blood  can  be 
effused.  An  effusion  of  blood  beneath  the  pericranium  is  called  a  cephalhoEmatoma.  Such 
a  condition  may  occur  from  pressure  during  birth.  An  extravasation  beneath  the  pericranium 
is  limited  to  the  surface  of  one  bone.  The  pericranium  is  tightly  attached  to  the  sutures,  but 
adheres  lightly  to  the  surface  of  the  bone,  and  abscess  beneath  the  pericranium  is  restricted 
to  the  surface  of  one  bone. 

2.  The  Auricular  Region  (Fig.  260). 

Attrahens  auriculam.  Attollens  auriculam. 

Retrahens  auriculam. 

These  three  small  muscles  are  placed  immediately  beneath  the  skin  around  the 
external  ear.  In  man,  in  whom  the  external  ear  is  almost  immovable,  they  are 
rudimentary.  They  are  the  analogues  of  large  and  important  muscles  in  some 
of  the  mammalia. 

Dissection. — This  requires  considerable  care,  and  should  be  performed  in  the  following 
manner:  To  expose  the  Attollens  auriculam,  draw  the  pinna,  or  broad  part  of  the  ear,  downward, 
when  a  tense  band  will  be  felt  beneath  the  skin,  passing  from  the  side  of  the  head  to  the  upper 
part  of  the  concha;  by  dividing  the  skin  over  this  band  in  a  direction  from  below  upward, 
and  then  reflecting  it  on"  each  side,  the  muscle  is  exposed.  To  bring  into  view  the  Attrahens 
auriculam,  draw  the  helix  backward  by  means  of  a  hook,  when  the  muscle  will  be  made 
tense,  and  may  be  exposed  in  a  similar  manner  to  the  preceding.  To  expose  the  Retrahens 
auriculam,  draw  the  pinna  forward,  when  the  muscle,  being  made  tense,  may  be  felt  beneath 
the  skin  at  its  insertion  into  the  back  part  of  the  concha,  and  may  be  exposed  in  the  same 
manner  as  the  other  muscles. 


372  THE  MUSCLES  AND  FASCIA 

The  Attrahens  Auriculam  or  Aurem  (m.  auricularis  anterior) ,  the  smallest  of  the 
three,  is  thin,  fan-shaped,  and  its  fibres  pale  and  indistinct;  they  arise  from  the 
lateral  edge  of  the  aponeurosis  of  the  Occipito-frontalis,  and  converge  to  be  inserted 
into  a  projection  on  the  front  of  the  helix. 

Relations. — Superficially,  with  the  skin;  deeply,  with  the  areolar  tissue  derived 
from  the  aponeurosis  of  the  Occipito-frontalis,  beneath  which  are  the  temporal 
artery  and  vein  and  the  temporal  fascia. 

The  Attollens  Auriculam  or  Aurem  (m.  auricularis  superior),  the  largest  of  the 
three,  is  thin  and  fan-shaped :  its  fibres  arise  from  the  aponeurosis  of  the  Occipito- 
frontalis  and  converge  to  be  inserted  by  a  thin,  flattened  tendon  into  the  upper 
part  of  the  cranial  surface  of  the  pinna. 

Relations. — Superficially,  with  the  integument;  deeply,  with  the  areolar  tissue 
derived  from  the  aponeurosis  of  the  Occipito-frontalis,  beneath  which  is  the  tem- 
poral fascia. 

The  Retrahens  Auriculam  or  Aurem  (m.  auricularis  posterior)  consists  of  two  or 
three  fleshy  fasciculi,  which  arise  from  the  mastoid  portion  of  the  temporal  bone 
by  short  aponeurotic  fibres.  They  are  inserted  into  the  lower  part  of  the  cranial 
surface  of  the  concha. 

Relations. — Superficially,  with  the  integument;  deeply,  with  the  mastoid  portion 
of  the  temporal  bone  and  the  posterior  auricular  artery  and  nerve. 

Nerves. — The  Attrahens  and  Attollens  auriculam  are  supplied  by  the  temporal 
branch  of  the  facial ;  the  Retrahens  auriculam  is  supplied  by  the  posterior  auricu- 
lar branch  of  the  same  nerve. 

Actions. — In  man,  these  muscles  possess  very  little  action:  the  Attrahens  auric- 
ulam draws  the  ear  forward  and  upward;  the  Attollens  auriculam  slightly  raises 
it;  and  the  Retrahens  auriculam  draws  it  backward. 

3.  The  Palpebral  Region  (Fig.  260). 

Orbicularis  palpebrarum.  Levator  palpebrse. 

Corrugator  supercilii.  Tensor  tarsi. 

Dissection  (Fig.  258). — In  order  to  expose  the  muscles  of  the  face,  continue  the  longi- 
tudinal incision  made  in  the  dissection  of  the  Occipito-frontalis  down  the  median  line  of  the 
face  to  the  tip  of  the  nose,  and  from  this  point  onward  to  the  upper  lip;  and  carry  another 
incision  along  the  margin  of  the  lip  to  the  angle  of  the  mouth,  and  transversely  across  the  face 
to  the  angle  of  the  jaw.  Then  make  an  incision  in  front  of  the  external  ear,  from  the  angle  of 
the  jaw  upward,  to  join  the  transverse  incision  made  in  exposing  the  Occipito-frontalis.  These 
incisions  include  a  square-shaped  flap,  which  should  be  removed  in  the  direction  marked  in 
the  figure,  with  care,  as  the  muscles  at  some  points  are  intimately  adherent  to  the  integument. 

The  Orbicularis  Palpebrarum  (TO.  orbicularis  oculi)  is  a  sphincter  muscle,  which 
surrounds  the  circumference  of  the  orbit  and  eyelids.  It  arises  from  the  internal 
angular  process  of  the  frontal  bone,  from  the  nasal  process  of  the  superior  maxil- 
lary bone  in  front  of  the  lachrymal  groove  for  the  nasal  duct,  and  from  the  anterior 
surface  and  borders  of  a  short  tendon,  the  tendo  oculi,  or  internal  tarsal  ligament, 
placed  at  the  inner  angle  of  the  orbit.  From  this  origin  the  fibres  are  directed 
outward,  forming  a  broad,  thin,  and  flat  layer,  which  covers  the  eyelids,  surrounds 
the  circumference  of  the  orbit,  and  spreads  out  over  the  temple  and  downward  on 
the  cheek.  The  internal  or  palpebral  portion  (pars  palpebralis)  of  the  Orbicularis  is 
thin  and  pale;  it  arises  from  the  bifurcation  of  the  tendo  palpebrarum,  and  forms 
a  series  of  concentric  curves,  which  are  on  the  outer  side  of  the  eyelids  inserted  into 
the  external  tarsal  ligament.  The  external  or  orbital  portion  (pars  orbitalis)  is 
thicker  and  of  a  reddish  color:  its  fibres  are  well  developed,  and  form  complete 
ellipses.  The  upper  fibres  of  this  portion  blend  with  the  Occipito-frontalis  and 
Corrugator  supercilii. 


THE  PALPEBRAL  REGION  373 

Relations. — By  its  superficial  surface,  with  the  integument.  By  its  deep  surface, 
above,  with  the  Occipito-frontalis  and  Corrugator  supercilii,  with  which  it  is  inti- 
mately blended,  and  with  the  supraorbital  vessels  and  nerve;  below,  it  covers  the 
lachrymal  sac,  and  the  origin  of  the  Levator  labii  superioris  alreque  nasi,  the 
Levator  labii  superioris,  and  the  Zygomaticus  minor  muscles.  Internally,  it  is 
occasionally  blended  with  the  Pyramidalis  nasi.  Externally,  it  lies  on  the  temporal 
fascia.  On  the  eyelids  it  is  separated  from  the  conjunctiva  by  the  Levator  palpe- 
brte,  the  tarsal  ligaments,  the  tarsal  plates,  and  the  Meibomian  glands. 

The  tendo  oculi  or  internal  tarsal  ligament  (ligamentum  palpebrale  mediate)  is  a 
short  tendon,  about  two  lines  in  length  and  one  in  breadth,  attached  to  the  nasal 
process  of  the  superior  maxillary  bone  in  front  of  the  lachrymal  groove.  Crossing 
the  lachrymal  sac,  it  divides  into  two  parts,  each  division  being  attached  to  the 
inner  extremity  of  the  corresponding  tarsal  plate.  As  the  tendon  crosses  the  lach- 
rymal sac,  a  strong  aponeurotic  lamina  is  given  off  from  the  posterior  surface, 
which  expands  over  the  sac,  and  is  attached  to  the  ridge  on  the  lachrymal  bone. 
This  is  the  reflected  aponeurosis  of  the  tendo  oculi. 

The  external  tarsal  ligament  (raphe  palpebralis  lateralis)  is  a  much  weaker  struc- 
ture than  the  tendo  oculi.  It  is  attached  to  the  margin  of  the  frontal  process  of 
the  malar  bone,  and  passes  inward  to  the  outer  commissure  of  the  eyelids;  it 
connects  together  the  outer  extremities  of  the  two  tarsal  cartilages. 

USE  OF  TENDO  OCULI. — Besides  giving  attachment  to  part  of  the  Orbicularis 
palpebrarum  and  to  the  tarsal  plates,  it  serves  to  suck  the  tears  into  the  lachrymal 
sac,  by  its  attachment  to  the  sac.  Thus,  each  time  the  eyelids  are  closed,  the  tendo 
oculi  becomes  tightened,  through  the  action  of  the  Orbicularis,  and  draws  the  wall 
of  the  lachrymal  sac  outward  and  forward,  so  that  a  vacuum  is  made  in  the  sac, 
and  the  tears  are  sucked  along  the  lachrymal  canals  into  it. 

The  Corrugator  Supercilii  (Figs.  259  and  260)  is  a  small  narrow,  pyramidal 
muscle,  placed  at  the  inner  extremity  of  the  eyebrow,  beneath  the  Occipito- 
frontalis  and  Orbicularis  palpebrarum  muscles.  It  arises  from  the  inner  extrem- 
ity of  the  superciliary  ridge,  from  whence  its  fibres  pass  upward  and  outward, 
and  are  inserted  into  the  deep  surface  of  the  skin,  opposite  the  middle  of  the 
orbital  arch. 

Relations. — By  its  anterior  surface  with  the  Occipito-frontalis  and  Orbicularis 
palpebrarum  muscles;  by  its  posterior  surface,  with  the  frontal  bone  and  supra- 
trochlear  nerve. 

The  Levator  Palpebrse  will  be  described  with  the  muscles  of  the  orbital  region. 

The  Tensor  Tarsi  or  Homer's  Muscle  (pars  lacrimalis  of  the  orbicularis  pal- 
pebrarum) (Fig.  261)  is  a  small  thin  muscle  about  three  lines  in  breadth  and  six 
in  length,  situated  at  the  inner  side  of  the  orbit,  behind  the  tendo  oculi.  It  is 
usually  considered  to  be  composed  of  fibres  derived  from  the  Orbicularis  palpe- 
brarum. It  arises  from  the  crest  and  adjacent  part  of  the  orbital  surface  of  the 
lachrymal  bone,  and,  passing  across  the  lachrymal  sac,  divides  into  two  slips, 
which  cover  the  lachrymal  canals  and  are  inserted  into  the  tarsal  plates  internal 
to  the  puncta  lachrymalia.  Its  fibres  appear  to  be  continuous  with  those  of  the 
palpebral  portion  of  the  Orbicularis  palpebrarum;  it  is  occasionally  very  indistinct. 

Nerves. — The  Orbicularis  palpebrarum,  Corrugator  supercilii,  and  Tensor  tarsi 
are  supplied  by  the  facial  nerve.  Recent  investigations  tend  to  show  that  the 
Orbicularis  palpebrarum,  Corrugator  supercilii,  and  frontal  part  of  the  Occipito- 
frontalis  are  in  reality  supplied  by  fibres  of  the  motor  oculi  nerve,  which  descend 
through  the  pons  to  join  the  facial  nerve. 

Actions. — The  Orbicularis  palpebrarum  is  the  sphincter  muscle  of  the  eyelids. 
The  palpebral  portion  acts  involuntarily,  closing  the  lids  gently,  as  in  sleep  or  in 
blinking;  the  orbicular  portion  is  subject  to  the  will.  When  the  entire  muscle  is 
brought  into  action,  the  skin  of  the  forehead,  temple,  and  cheek  is  drawn  inward 


374 


THE  MUSCLES  AND  FASCIA 


toward  the  inner  angle  of  the  orbit,  and  the  eyelids  are  firmly  closed  as  a  photo- 
phobia. .When  the  skin  of  the  forehead,  temple,  and  cheek  is  thus  drawn  inward 
by  the  action  of  the  muscle  it  is  thrown  into  folds,  especially  radiating  from  the 
outer  angle  of  the  eyelids,  which  give  rise  in  old  age  to  the  so-called  "crow's  feet." 
The  Levator  palpebrse  is  the  direct  antagonist  of  this  muscle;  it  raises  the  upper 
eyelid  and  exposes  the  globe.  The  Corrugator  supercilii  draws  the  eyebrow 
downward  and  inward,  producing  the  vertical  wrinkles  of  the  forehead.  It  is  the 
"frowning"  muscle,  and  may  be  regarded  as  the  principal  agent  in  the  expression 
of  suffering.  The  Tensor  tarsi  draws  the  eyelids  inward  and  compresses  the  eye- 
lids and  the  extremities  of  the  lachrymal  canals  against  the  surface  of  the  globe 
of  the  eye ;  thus  placing  the  canals  in  the  most  favorable  situation  for  receiving 
the  tears.  It  serves,  also,  to  compress  the  lachrymal  sac. 


FRONTAL  SINUS 


CORRUGATOR 
SUPERCILII 


PALPEBRAL PORTION 

OF  ORBICULARIS 

PALPEBRARUM 


IPUNCTA 
LACHRYMALIA 


ORBITAL  PORTION   OF 
ORBICULARIS  PALPEBRARUM 


ANTRUM   OF 
HIGHMORE 


FIG.  261. — The  three  portions  of  the  Orbicularis  palpebrarum  muscle,  and  the  relation  of  this  muscle  to  the 
Corrugator  supercilii  muscle,  seen  from  behind.     (Left  side.)     (Toldt.) 

4.  The  Orbital  Region  (Fig.  262). 

Levator  palpebrse  superioris.  Rectus  internus. 

Rectus  superior.  Rectus  externus. 

Rectus  inferior.  Obliquus  oculi  superior. 

Obliquus  oculi  inferior. 

Dissection. — To  open  the  cavity  of  the  orbit,  remove  the  skull-cap  and  brain;  then  saw 
through  the  frontal  bone  at  the  inner  extremity  of  the  supraorbital  ridge,  and  externally  at  its 
junction  with  the  malar.  Break  in  pieces  the  thin  roof  of  the  orbit  by  a  few  slight  blows  of 
the  hammer,  and  take  it  away;  drive  forward  the  superciliary  portion  of  the  frontal  bone 
by  a  smart  stroke,  but  do  not  remove  it,  as  that  would  destroy  the  pulley  of  the  Obliquus 
superior.  When  the  fragments  are  cleared  away,  the  periosteum  of  the  orbit  will  be  exposed; 
this  being  removed,  together  with  the  fat  which  fills  the  cavity  of  the  orbit,  the  several  muscles 
of  this  region  can  be  examined.  The  dissection  will  be  facilitated  by  distending  the  globe 
of  the  eye.  In  order  to  effect  this,  puncture  the  optic  nerve  near  the  eyeball  with  a  curved 
needle,  and  push  the  needle  onward  into  the  globe;  insert  the  point  of  a  blowpipe  through 
this  aperture,  and  force  a  little  air  into  the  cavity  of  the  eyeball;  then  apply  a  ligature  round 
the  nerve  so  as  to  prevent  the  air  escaping.  The  globe  being  now  drawn  forward,  the  muscles 
will  be  put  upon  the  stretch. 


THE  ORBITAL  REGION 


375 


The  Levator  Palbebrae  Superioris  is  thin,  flat,  and  triangular  in  shape.  It 
arises  from  the  under  surface  of  the  lesser  wing  of  the  sphenoid,  above  and  in 
front  of  the  optic  foramen,  from  which  it  is  separated  by  the  origin  of  the  Superior 
rectus  (Fig.  263).  At  its  origin  it  is  narrow  and  tendinous,  but  soon  becomes 
broad  and  fleshy,  and  finally  terminates  in  a  wide  aponeurosis,  which  is  inserted 
into  the  upper  margin  of  the  superior  tarsal  plate.  From  this  aponeurosis  a  thin 
expansion  is  continued  onward,  passing  between  the  fibres  of  the  Orbicularis 


FIG.  262. — Muscles  of  the  right  orbit. 

to  be  inserted  into  the  skin  of  the  lid,  and  some  deeper  fibres  blend  with  an 
expansion  from  the  sheath  of  the  Superior  rectus  muscle,  and  are  with  it  pro- 
longed into  the  conjunctiva. 

Relations. — By  its  upper  surface,  with  the  frontal  nerve  and  supraorbital 
artery,  the  periosteum  of  the  orbit  and  lachrymal  gland;  and,  in  the  lid,  with  the 
inner  surface  of  the  tarsal  ligament;  by  its  under  surface,  with  the  Superior  rectus, 
and,  in  the  lid,  with  the  conjunctiva.  A  small  branch  of  the  motor-oculi  nerve 
enters  its  under  surface. 

The  Superior  Rectus  (TO.  rectus  superior),  the  thinnest  and  narrowest  of  the 
four  Recti,  arises  from  the  upper  margin  of  the  optic  foramen  (Fig.  263)  beneath 
the  Levator  palpebrse,  and  from  the  fibrous  sheath  of  the  optic  nerve;  and  is 
inserted  by  a  tendinous  expansion  into  the  sclerotic  coat,  about  three  or  four 
lines  from  the  margin  of  the  cornea. 

Relations. — By  its  upper  surface,  with  the  Levator  palpebrse;  by  its  under  sur- 
face, with  the  optic  nerve,  the  ophthalmic  artery,  the  nasal  nerve,  and  the  branch 
of  the  motor-oculi  nerve  which  supplies  it;  and,  in  front,  with  the  tendon  of  the 
Superior  oblique  and  the  globe  of  the  eye. 

The  Inferior  Rectus  (TO.  rectus  inferior)  and  the  Internal  Rectus  (TO.  rectus 
medialis)  arise  by  a  common  tendon,  the  ligament  of  Zinn1  (annulus  tendineus 
commnnis).  which  is  attached  round  the  circumference  of  the  optic  foramen, 
except  at  its  upper  and  outer  part  (Fig.  263). 

The  External  Rectus  (TO.  rectus  lateralis)  has  two  heads:  the  upper  one  arises 
from  the  outer  margin  of  the  optic  foramen  immediately  beneath  the  Superior 
rectus;  the  lower  head,  partly  from  the  ligament  of  Zinn  and  partly  from  a  small 

1  The  ligament  of  Zinn  ought,  perhaps  more  appropriately,  to  be  termed  the  apnneurosis  or  tendon  of  Zinn, 
Mr.  C.  B.  Lockwood  has  described  a  somewhat  similar  structure  on  the  under  surface  of  the  Superior  rectus 
muscle,  which  is  attached  to  the  lesser  wing  of  the  sphenoid,  forming  the  upper  and  outer  margin  of  the  optic 
foramen.  This  superior  tendon  gives  origin  to  the  Rectus  superior,  the  superior  head  of  the  External  rectus. 
and  the  upper  part  of  the  Internal  rectus. — Journal  of  Anatomy  and  Physiology,  vol.  xx.  part  i.  p.  1. 


376  THE  MUSCLES  AND  FASCIA 

pointed  process  of  bone  on  the  lower  margin  of  the  sphenoidal  fissure  (Fig.  263). 
Each  muscle  passes  forward  in  the  position  implied  by  its  name,  to  be  inserted  by 
a  tendinous  expansion,  the  tunica  albuginea,  into  the  sclerotic  coat,  about  three  or 
four  lines  from  the  margin  of  the  cornea.  Between  the  two  heads  of  the  External 

rectus  is  a  narrow  interval  through  which  passes 

superior.  the  motor-oculi,  the  nasal  branch  of  the  ophthal- 

m^c  division  of  tne  trigemiiial,  and  the  abducent 
nerve,  and  the  ophthalmic  vein.  Although 
nearly  all  of  these  muscles  present  a  common 
origin  and  are  inserted  in  a  similar  manner 
into  the  sclerotic  coat,  there  are  certain  differ- 
ences to  be  observed  in  them  as  regards  their 
length  and  breadth.  The  Internal  rectus  is  the 
broadest,  the  External  is  the  longest,  and  the 
JIB**,  inferior,  y  Superior  is  the  thinnest  and  narrowest. 

FIG.  263. — The  relative  position  and  attach-          T^o  Sn-narinr  fthlimiP  ( *n    nhliniiiia  <ntv\0nrw\ 
ment  of  the  muscles  of  the  left  eyeball.  L  ne  pUperiOI  UDliqUC   (m.  OOliqUUS  Superior) 

is  a  fusiform  muscle  placed  at  the  upper  and 

inner  side  of  the  orbit,  internal  to  the  Levator  palpebrse.  It  arises  about  a  line 
above  the  inner  margin  of  the  optic  foramen  (Fig.  263),  and,  passing  forward  to 
the  inner  angle  of  the  orbit,  terminates  in  a  rounded  tendon,  which  plays  in  a  ring 
or  pulley,  the  trochlea  (trochlea  m.  obliqui  superior-is) ,  formed  by  a  cartilaginous 
tissue  attached  to  a  depression  beneath  the  internal  angular  process  of  the  frontal 
bone,  the  contiguous  surfaces  of  the  tendon  and  ring  being  lined  by  a  delicate 
synovial  membrane  and  enclosed  in  a  thin  fibrous  investment.  The  tendon  is 
reflected  backward,  outward,  and  downward  beneath  the  Superior  rectus  to  the 
outer  part  of  the  globe  of  the  eye,  and  is  inserted  into  the  sclerotic  coat,  behind 
the  equator  of  the  eyeball,  the  insertion  of  the  muscle  lying  between  the  Superior 
and  External  recti. 

Relations. — By  its  upper  surface,  with  the  periosteum  covering  the  roof  of  the 
orbit  and  the  trochlear  nerve:  the  tendon,  where  it  lies  on  the  globe  of  the  eye, 
is  covered  by  the  Superior  rectus;  by  its  under  surface,  with  the  nasal  nerve, 
ethmoidal  arteries,  and  the  upper  border  of  the  internal  rectus. 

The  Inferior  Oblique  (m.  obliquus  inferior}  is  a  thin,  narrow  muscle  placed  near 
the  anterior  margin  of  the  orbit.  It  arises  from  a  depression  on  the  orbital  plate 
of  the  superior  maxillary  bone,  external  to  the  lachrymal  groove  (Fig.  262). 
Passing  outward,  backward,  and  upward  between  the  Inferior  rectus  and  the 
floor  of  the  orbit,  and  then  between  the  eyeball  and  the  External  rectus,  it  is 
inserted  into  the  outer  part  of  the  sclerotic  coat  between  the  Superior  and  External 
recti,  near  to,  but  somewhat  behind,  the  tendon  of  insertion  of  the  Superior  oblique. 

Relations.— By  its  ocular  surface,  with  the  globe  of  the  eye  and  with  the  Inferior 
rectus  ;  by  its  orbital  surface,  with  the  periosteum  covering  the  floor  of  the  orbit, 
and  with  the  External  rectus.  Its  borders  look  forward  and  backward;  the  poste- 
rior one  receives  a  branch  of  the  motor  oculi  nerve. 

The  orbital  muscle  or  Miiller's  muscle  (musculus  orbitalis),  which  spans  the 
spheno-maxillary  fissure  and  infraorbital  groove,  is  composed  of  non-striated 
fibres,  and  is  a  rudimentary  structure  continuous  with  the  periosteum  of  the  orbit.1 

Nerves. — The  Levator  palpebrse,  Inferior  oblique,  and  all  the  Recti  excepting 
the  External,  are  supplied  by  the  motor  oculi  nerve;  the  Superior  oblique,  by  the 
trochlear;  the  External  rectus,  by  the  abducent. 

Actions. — The  Levator  palpebrse  raises  the  upper  eyelid,  and  is  the  direct 
antagonist  of  the  Orbicularis  palpebrarum.  The  four  Recti  muscles  are  attached 
in  such  a  manner  to  the  globe  of  the  eye  that,  acting  singly,  they  will  turn  it  either 

1  See  F.  Groyer,  in  the  Vienna  Siztungsberiehte  der  Kaiserlichen  Akademie  der  Wissenschaften,  1903,  Band  cxii. 
—Bo.  of  15th  English  Edition. 


THE  ORBITAL  REGION  377 

upward,  downward,  inward,  or  outward,  as  expressed  by  their  names.  The 
movement  produced  by  the  Superior  or  Inferior  rectus  is  not  quite  a  simple  one, 
for,  inasmuch  as  they  pass  obliquely  outward  arid  forward  to  the  eyeball,  the 
elevation  or  depression  of  the  cornea  must  be  accompanied  by  a  certain  deviation 
inward,  with  a  slight  amount  of  rotation,  which,  however,  is  corrected  by  the 
Oblique  muscles,  the  Inferior  oblique  correcting  the  deviation  inward  of  the 
Superior  rectus,  and  the  Superior  oblique  that  of  the  Inferior  rectus.  The  con- 
traction of  the  External  and  Internal  recti,  on  the  other  hand,  produces  a  purely 
horizontal  movement.  If  any  two  contiguous  recti  of  one  eye  act  together,  they 
carry  the  globe  of  the  eye  in  the  diagonal  of  these  directions — viz.,  upward  and 
inward,  upward  and  outward,  downward  and  inward,  or  downward  and  outward. 
The  movement  of  circumduction,  as  in  looking  round  a  room,  is  performed  by 
the  alternate  action  of  the  four  Recti.  The  Oblique  muscles  rotate  the  eyeball 
on  its  antero-posterior  axis,  this  kind  of  movement  being  required  for  the  correct 
viewing  of  an  object  when  the  head  is  moved  laterally,  as  from  shoulder  to  shoulder, 
in  order  that  the  picture  may  fall  in  all  respects  on  the  same  part  of  the  retina  of 
each  eye.1  It  should  be  noted  that  sometimes  the  corresponding  Recti  and  some- 
times the  opposite  ones  of  the  two  eyes  act  together;  for  instance,  the  two  superior 
and  inferior  Recti  carry  both  eyeballs  upward  and  downward,  respectively.  In 
looking  toward  the  right  the  right  External  and  left  Internal  recti  act  together, 
the  reverse  being  the  case  in  looking  toward  the  left.  In  turning  both  eyes  toward 
the  middle  line,  as  in  directing  our  vision  toward  an  object  less  than  twenty  feet 
distant,  the  two  internal  recti  act  together. 

Fasciae  of  the  Orbit. — The  connective  tissue  of  the  orbit  is  in  various  places 
condensed  into  thin  membranous  layers,  which  may  be  conveniently  described  as 
(1)  the  orbital  fascia;  (2)  the  sheaths  of  the  muscles;  and  (3)  the  covering  of  the 
eyeball. 

(1)  The  Orbital  Fascia. — This  forms  the  periosteum  of  the  orbit.     It  is  loosely 
connected  to  the  bones,  from  which  it  can  be  readily  separated.     Behind,  it  is 
connected  with  the  dura  by  processes  which  pass  through  the  optic  foramen 
and  sphenoidal  fissure,  and  with  the  sheath  of  the  optic  nerve.     In  front  it  is 
connected  with  the  periosteum  at  the  margin  of  the  orbit,  and  sends  off  a  process 
which  assists  in  forming  the  palpebral  fascia.     From  its  internal  surface  two 
processes  are  given  off — one  to  enclose  the  lachrymal  gland,  the  other  to  hold  the 
pulley  of  the  Superior  oblique  muscle  in  position. 

(2)  The  Sheaths  of  the  Muscles. — The  sheaths  of  the  muscles  give  off  expansions 
to  the  margins  of  the  orbit  which  limit  the  action  of  the  muscles. 

(3)  The  Covering  of  the  Eyeball — Tenon's  capsule — surrounds  the    posterior 
two- thirds  of  the  eyeball;  it  will  be  described  in  the  sequel. 

Surgical  Anatomy. — The  position  and  exact  point  of  insertion  of  the  tendons  of  the 
Internal  and  External  recti  muscles  into  the  globe  should  be  carefully  examined  from  the  front 
of  the  eyeball,  as  the  surgeon  is  often  required  to  divide  the  one  or  the  other  muscle  for  the  cure 
of  strabismus  (squint).  In  convergent  strabismus,  which  is  the  more  common  form  of  the  disease, 
the  eye  is  turned  inward,  requiring  the  division  of  the  Internal  rectus.  In  the  divergent  form, 
which  is  more  rare,  the  eye  is  turned  outward,  the  External  rectus  being  especially  implicated. 
The  deformity  produced  in  either  case  is  to  be  remedied  by  division  of  one  or  the  other  muscle. 
The  operation  is  thus  performed :  The  lids  are  to  be  well  separated ;  the  eyeball  being  rotated 
outward  or  inward,  the  conjunctiva  should  be  raised  by  a  pair  of  forceps  and  divided  immediately 
beneath  the  lower  border  of  the  tendon  of  the  muscle  to  be  divided,  a  little  behind  its  insertion 
into  the  sclerotic;  the  submucous  areolar  tissue  is  then  divided,  and  into  the  small  aperture 
,  thus  made  a  blunt  hook  is  passed  upward  between  the  muscle  and  the  globe,  and  the  tendon  of 
the  muscle  and  conjunctiva  covering  it  divided  by  a  pair  of  blunt-pointed  scissors.  Or  the 
tendon  may  be  divided  by  a  subconjunctival  incision,  one  blade  of  the  scissors  being  passed 

1  On  the  Oblique  Muscles  of  the  Eye  in  Man  and  Vertebrate  Animals,  by  John  Struthers,  M.D.,  in  Anatom- 
ical and  Physiological  Observations.  For  a  fuller  account  of  the  various  co-ordinate  actions  ot  the  muscles  of 
a  single  eye  and  of  both  eyes  than  our  space  allows  see  Dr.  M.  F'oster's  Text-book  of  Physiology. — ED.  of  loth 
English  edition. 


378  THE  MUSCLES  AND  FASCIA 

upward  between  the  tendon  and  the  conjunctiva,  and  the  other  between  the  tendon  and  the 
sclerotic.  The  student,  when  dissecting  these  muscles,  should  remove  on  one  side  of  the  subject 
the  conjunctiva  from  the  front  of  the  eye,  in  order  to  see  more  accurately  the  position  of  the 
tendons,  while  on  the  opposite  side  the  operation  may  be  performed.  Inflammation  of  the 
synovial  membrane  lining  the  trochlea  of  the  Superior  oblique  may  lead  to  the  formation  of 
a  cyst  of  considerable  size. 

In  performing  enucleation  of  the  eyeball  the  conjunctiva  is  clipped  with  scissors  near  the 
cornea  and  the  capsule  of  Tenon  is  divided  with  it.  One  rectus  muscle  after  another  is  caught 
up  on  a  blunt  hook  and  divided.  The  scissors  are  now  pushed  well  in  along  the  outer  orbital 
wall. and  the  optic  nerve  is  divided.  Finally  the  oblique  muscles,  the  ciliary  vessels  and  nerves, 
and  fragments  of  tissue  helping  to  retain  the  globe  are  cut  and  the  eyeball  is  enucleated. 

An  orbital  abscess  is  evacuated  by  making  an  incision  close  to  the  border  of  the  orbit,  above 
or  below  the  eyeball. 

5.  The  Nasal  Region  (Fig.  260). 

Pyramidalis  nasi.  Dilator  naris  anterior. 

Levator  labii  superioris  alseque  nasi.  Compressor  nasi. 

Dilator  naris  posterior.  Compressor  narium  minor. 

Depressor  alse  nasi. 

The  Pyramidalis  Nasi  is  a  small  pyramidal  slip  placed  over  the  nasal  bone. 
Its  origin,  is  by  tendinous  fibres  from  the  fascia'covering  the  lower  part  of  the  nasal 
bone  and  upper  part  of  the  cartilage,  where  it  blends  with  the  Compressor  nasi, 
and  it  is  inserted  into  the  skin  over  the  lower  part  of  the  forehead  between  the 
two  eyebrows,  its  fibres  decussating  with  those  of  the  Occipito-frontalis  (see 
page  371). 

Relations. — By  its  upper  surface,  with  the  skin;  by  its  under  surface,  with  the 
frontal  and  nasal  bones. 

The  Levator  Labii  Superioris  Alaeque  Nasi  is  a  thin  triangular  muscle  placed 
by  the  side  of  the  nose,  and  extending  between  the  inner  margin  of  the  orbit  and 
upper  lip.  It  arises  by  a  pointed  extremity  from  the  upper  part  of  the  nasal 
process  of  the  superior  maxillary  bone,  and,  passing  obliquely  downward  and 
outward,  divides  into  two  slips,  one  of  which  is  inserted  into  the  cartilage  of  the 
ala  of  the  nose  and  the  under  surface  of  the  skin  over  the  ala;  the  other  is  pro- 
longed into  the  upper  lip,  becoming  attached  to  the  under  surface  of  the  skin 
and  blended  with  the  Orbicularis  oris  and  Levator  labii  superioris  proprius. 

Relations. — In  front,  with  the  integument,  and  with  a  small  part  of  the  Orbicu- 
laris palpebrarum  above. 

The  Dilator  Naris  Posterior  is  a  small  muscle  which  is  placed  partly  beneath 
the  elevator  of  the  nose  and  lip.  It  arises  from  the  margin  of  the  nasal  notch  of 
the  superior  maxilla  and  from  the  sesamoid  cartilages,  and  is  inserted  into  the 
skin  near  the  margin  of  the  nostril. 

The  Dilator  Naris  Anterior  is  a  thin  delicate  fasciculus  passing  from  the 
cartilage  of  the  ala  of  the  nose  to  the  integument  near  its  margin.  This  muscle  is 
situated  in  front  of  the  preceding. 

The  Compressor  Nasi  is  a  small,  thin,  triangular  muscle  arising  by  its  apex 
from  the  superior  maxillary  bone,  above  and  a  little  external  to  the  incisive  fossa; 
its  fibres  proceed  upward  and  inward,  expanding  into  a  thin  aponeurosis  which 
is  attached  to  the  fibro-cartilage  of  the  nose  and  is  continuous  on  the  bridge  of 
the  nose  with  that  of  the  muscle  of  the  opposite  side  and  with  the  aponeurosis  of 
the  Pyramidalis  nasi.  His  uses  the  term  musculus  nasalis  to  include  the  Com- 
pressor nasi  (transverse  portion  of  the  nasal  muscle),  and  the  Dilatator  naris 
posterior  and  the  Dilatator  naris  anterior  (alar  portion  of  the  nasal  muscle). 

The  Compressor  Narium  Minor  is  a  small  muscle  attached  by  one  end  to  the 
alar  cartilage,  and  by  the  other  to  the  integument  at  the  end  of  the  nose. 

The  Depressor  Alae  Nasi  (depressor  septi)  is  a  short  radiated  muscle  arising 
from  the  incisive  fossa  of  the  superior  maxilla;  its  fibres  ascend  to  be  inserted  into 


379 

the  septum  and  back  part  of  the  ala  of  the  nose.  This  muscle  lies  between  the 
mucous  membrane  and  muscular  structure  of  the  lip. 

Nerves. — All  of  the  muscles  of  this  group  are  supplied  by  the  facial  nerve. 

Actions. — The  Pyramidalis  nasi  draws  down  the  inner  angle  of  the  eyebrows 
and  produces  transverse  wrinkles  over  the  bridge  of  the  nose.  The  Levator  labii 
superioris  alaeque  nasi  draws  upward  the  upper  lip  and  ala  of  the  nose ;  its  most 
important  action  is  upon  the  nose,  which  it  dilates  to  a  considerable  extent.  The 
action  of  this  muscle  produces  a  marked  influence  over  the  countenance,  and  it  is 
the  principal  agent  in  the  expression  of  contempt  and  disdain.  The  two  Dilatatores 
nasi  enlarge  the  aperture  of  the  nose.  Their  action  in  ordinary  breathing  is  to 
resist  the  tendency  of  the  nostrils  to  close  from  atmospheric  pressure,  but  in 
difficult  breathing  they  may  be  noticed  to  be  in  violent  action,  as  well  as  .in  some 
emotions,  as  anger.  The  Depressor  alae  nasi  is  a  direct  antagonist  of  the  other 
muscles  of  the  nose,  drawing  the  ala  of  the  nose  downward,  and  thereby  constrict- 
ing the  aperture  of  the  nares.  The  Compressor  nasi  depresses  the  cartilaginous 
part  of  the  nose  and  compresses  the  alae  together. 

6.  The  Superior  Maxillary  Region  (Fig.  260). 

Levator  labii  superioris.  Zygomaticus  major. 

Levator  anguli  oris.  Zygomaticus  minor. 

By  the  term  musculus  quadratus  labii  superioris,  His  includes  three  muscles. 
The  caput  angulare  is  called  in  this  book  the  Levator  labii  superioris  alseque  nasi. 
The  caput  infraorbitale  is  called  the  Levator  labii  superioris.  The  caput  zygomati- 
cum  is  called  the  Zygomaticus  minor. 

The  Levator  Labii  Superioris  (proprius)  is  a  thin  muscle  of  a  quadrilateral 
form.  It  arises  from  the  lower  margin  of  the  orbit  immediately  above  the  infra- 
orbital  foramen,  some  of  its  fibres  being  attached  to  the  superior  maxilla,  others 
to  the  malar  bone;  its  fibres  converge  to  be  inserted  into  the  muscular  substance 
of  the  upper  lip. 

Relations.— By  its  superficial  surface  above,  with  the  lower  segment  of  the 
Orbictilaris  palpebrarum;  below,  it  is  subcutaneous.  By  its  deep  surface  it  con- 
ceals the  origin  of  the  Compressor  nasi  and  Levator  anguli  oris  muscles,  and  the 
infraorbital  vessels  and  nerve,  as  they  escape  from  the  infraorbital  foramen. 

The  Levator  Anguli  Oris  (TO.  caninus]  arises  from  the  canine  fossa  immediately 
below  the  infraorbital  foramen ;  its  fibres  incline  downward  and  a  little  outward,  to 
be  inserted  into  the  deep  surface  of  the  skin  and  into  the  subcutaneous  tissue 
near  the  angle  of  the  mouth  and  intermingles  with  the  fibres  of  the  Zygomaticus 
major,  the  Depressor  anguli  oris,  and  the  Orbicularis. 

Relations. — By  its  superficial  surface,  with  the  Levator  labii  superioris  and 
the  infraorbital  vessels  and  nerves;  by  its  deep  surface,  with  the  superior  maxilla, 
the  Buccinator,  and  the  mucous  membrane. 

The  Zygomaticus  Major  (TO.  Zygomaticus}  is  a  slender  fasciculus  which 
arises  from  the  malar  bone,  in  front  of  the  zygomatic  suture,  and,  descending 
obliquely  downward  and  inward,  is  inserted  into  the  deep  surface  of  the  skin 
and  subcutaneous  tissue  at  the  outer  portion  of  the  upper  lip  and  into  the  angle 
of  the  mouth,  where  it  blends  with  the  fibres  of  the  Levator  anguli  oris,  the 
Orbicularis  oris,  and  the  Depressor  anguli  oris. 

Relations. — By  its  superficial  surface,  with  the  subcutaneous  adipose  tissue; 
by  its  deep  surface,  with  the  Masseter  and  Buccinator  muscles  and  the  facial  artery 
and  vein. 

The  Zygomaticus  Minor,  which  is  often  absent,  arises  from  the  malar  bone 
immediately  behind  the  maxillary  suture,  and,  passing  downward  and  inward,  is 
inserted  into  the  deep  surface  of  the  skin  and  the  adjacent  muscles  at  the  upper 
margin  of  the  exposed  vermilion  surface  of  the  lip  midway  between  the  middle 


380  THE  MUSCLES  AND  FASCIAE 

line  of  the  lip  and  the  angle  of  the  mouth.  It  is  continuous  with  the  Orbicularis 
oris  at  the  outer  margin  of  the  Levator  labii  superioris.  It  lies  in  front  of  the 
preceding. 

Relations. — By  its  superficial  surface,  with  the  integument  and  the  Orbicularis 
palpebrarum  above;  by  its  deep  surface,  with  the  Masseter,  Buccinator,  and 
Levator  anguli  oris,  and  the  facial  artery  and  vein. 

Nerves. — This  group  of  muscles  is  supplied  by  the  facial  nerve. 

Actions. — The  Levator  labii  superioris  is  the  proper  elevator  of  the  upper  lip, 
carrying  it  at  the  same  time  a  little  forward.  It  assists  in  forming  the  naso-labial 
ridge,  which  passes  from  the  side  of  the  nose  to  the  upper  lip  and  gives  to  the 
face  an  expression  of  sadness.  The  Levator  anguli  oris  raises  the  angle  of  the 
mouth  and  draws  it  inward,  and  assists  the  Levator  labii  superioris  in  producing 
the  naso-labial  ridge.  The  Zygomaticus  major  draws  the  angle  of  the  mouth 
backward  and  upward,  as  in  laughing;  whilst  the  Zygomaticus  minor,  being 
inserted  into  the  outer  part  of  the  upper  lip  and  not  into  the  angle  of  the 
mouth,  draws  it  backward,  upward,  and  outward,  and  thus  gives  to  the  face 
an  expression  of  sadness. 

7.  The  Mandibular  Region  (Fig.  260). 

Levator  labii  inferioris.  Depressor  labii  inferioris. 

Depressor  anguli  oris. 

Dissection. — The  muscles  in  this  region  may  be  dissected  by  making  a  vertical  incision 
through  the  integument  from  the  margin  of  the  lower  lip  to  the  chin;  a  second  incision  should 
then  be  carried  along  the  margin  of  the  lower  jaw  as  far  as  the  angle,  and  the  integument  care- 
fully removed  in  the  direction  shown  in  Fig.  258. 

The  Levator  Labii  Inferioris  or  Levator  Menti  (m.  mentalis)  is  to  be  dissected 
by  everting  the  lower  lip  and  raising  the  mucous  membrane.  It  is  a  small  conical 
fasciculus  placed  on  the  side  of  the  frsenum  of  the  lower  lip.  It  arises  from  the 
incisive  fossa,  external  to  the  symphysis  of  the  lower  jaw;  its  fibres  descend  to 
be  inserted  into  the  integument  of  the  chin. 

Relation. — On  its  inner  surface,  with  the  mucous  membrane;  in  the  median 
line,  it  is  blended  with  the  muscle  of  the  opposite  side;  and  on  its  outer  side,  with 
the  Depressor  labii  inferioris. 

The  Depressor  Labii  Inferioris  or  Quadratus  Menti  (m.  quadratus  labii 
inferioris}  (Fig.  264)  is  a  small  quadrilateral  muscle.  It  arises  from  the  external 
oblique  line  of  the  lower  jaw,  between  the  symphysis  and  mental  foramen,  and 
passes  obliquely  upward  and  inward,  to  be  inserted  into  the  integument  of  the 
lower  lip,  its  fibres  blending  with  the  Orbicularis  oris  and  with  those  of  its  fellow 
of  the  opposite  side.  It  is  continuous  with  the  fibres  of  the  Platysma  at  its  origin. 
This  muscle  contains  much  yellow  fat  intermingled  with  its  fibres. 

Relations. — By  its  superficial  surface,  with  part  of  the  Depressor  anguli  oris 
and  with  the  integument,  to  which  it  is  closely  connected;  by  its  deep  surface, 
with  the  mental  vessels  and  nerves,  the  mucous  membrane  of  the  lower  lip,  the 
labial  glands,  and  the  Levator  menti,  with  which  it  is  intimately  united. 

The  Depressor  Anguli  Oris  or  Triangularis  Menti  (m.  triangularis)  (Fig.  260) 
is  triangular  in  shape,  arising,  by  its  broad  base,  from  the  external  oblique  line  of 
the  lower  jaw,  from  whence  its  fibres  pass  upward,  to  be  inserted,  by  a  narrow 
fasciculus,  into  the  angle  of  the  mouth.  It  is  continuous  with  the  Platysma  at 
its  origin  and  with  the  Orbicularis  oris  and  Risorius  at  its  insertion,  and  some  of 
its  fibres  are  directly  continuous  with  those  of  the  Levator  anguli  oris.  Muscular 
fibres  connecting  the  two  muscles  below  the  chin  are  occasionally  met  with;  they 
constitute  the  Musculus  transversus  menti  of  His  and  Waldeyer. 


THE  INTERMAXILLARY  REGION  381 

Relations. — By  its  superficial  surface,  with  the  integument;  by  its  deep  surface, 
with  the  Depressor  labii  inferioris  and  Buccinator. 

Nerves. — This  group  of  muscles  is  supplied  by  the  facial  nerve. 

Actions. — The  Levator  labii  inferioris  raises  the  lower  lip  and  protrudes  it 
forward,  and  at  the  same  time  wrinkles  the  integument  of  the  chin,  expressing 
doubt  or  disdain.  The  Depressor  labii  inferioris  draws  the  lower  lip  directly 
downward  and  a  little  outward,  as  in  the  expression  of  irony.  The  Depressor 
anguli  oris  depresses  the  angle  of  the  mouth,  being  the  antagonist  to  the  Levator 
anguli  oris  and  Zygomaticus  major;  acting  with  these  muscles,  it  will  draw  the 
angle  of  the  mouth  directly  backward. 

8.  The  Intermaxillary  Region. 
Orbicularis  oris.  Buccinator.  Risorius. 

Dissection. — The  dissection  of  these  muscles  may  be  considerably  facilitated  by  filling  the 
cavity  of  the  mouth  with  tow,  so  as  to  distend  the  cheeks  and  lips;  the  mouth  should  then  be 
closed  by  a  few  stitches  and  the  integument  carefully  removed  from  the  surface. 

The  Orbicularis  oris  (Figs.  260  and  264)  is  not  a  sphincter  muscle,  like  the  Orbic- 
ularis palpebrarum,  but  consists  of  numerous  strata  of  muscular  fibres,  having  dif- 
ferent directions,  which  surround  the  orifice  of  the  mouth.  These  fibres  are  par- 
tially derived  from  the  other  facial  muscles  which  are  inserted  into  the  lips,  and  are 
partly  fibres  proper  to  the  lips  themselves.  Of  the  former,  a  considerable  number 
are  derived  from  the  Buccinator  and  form  the  deeper  stratum  of  the  Orbicularis. 
Some  of  them — namely,  those  near  the  middle  of  the  muscle — decussate  at  the 
angle  of  the  mouth,  those  arising  from  the  upper  jaw  passing  to  the  lower  lip,  and 
those  from  the  lower  jaw  to  the  upper  lip.  Other  fibres  of  the  muscle,  situated  at 
its  upper  and  lower  part,  pass  across  the  lips  from  side  to  side  without  decussation. 
Superficial  to  this  stratum  is  a  second,  formed  by  the  Levator  and  Depressor 
anguli  oris,  which  cross  each  other  at  the  angle  of  the  mouth,  those  from  the 
Depressor  passing  to  the  upper  lip,  and  those  from  the  Levator  to  the  lower  lip, 
along  which  they  run  to  be  inserted  into  the  skin  near  the  median  line.  In  addi- 
tion to  these  there  are  fibres  from  the  other  muscles  inserted  into  the  lips — the 
Levator  labii  superioris,  the  Levator  labii  superioris  alseque  nasi,  the  Zygomatici, 
and  the  Depressor  labii  inferioris;  these  intermingle  with  the  transverse  fibres 
above  described,  and  have  principally  an  oblique  direction.  The  proper  fibres  of 
the  lips  are  oblique,  and  pass  from  the  under  surface  of  the  skin  to  the  mucous 
membrane  through  the  thickness  of  the  lip.  And  in  addition  to  these  are  fibres 
by  which  the  muscle  is  connected  directly  with  the  maxillary  bones  and  the 
septum  of  the  nose.  These  consist,  in  the  upper  lip,  of  four  bands,  two  of 
which  (m.  incisivus  superior}  arise  from  the  alveolar  border  of  the  superior 
maxilla,  opposite  the  lateral  incisor  tooth,  and,  arching  outward  on  each  side, 
are  continuous  at  the  angles  of  the  mouth  with  the  other  muscles  inserted  into 
this  part.  The  two  remaining  muscular  slips,  called  the  Nasolabialis,  connect 
the  upper  lip  to  the  back  of  the  septum  of  the  nose:  as  they  descend  from  the 
septum  an  interval  is  left  between  them.  It  is  this  interval  which  forms  the  depres- 
sion seen  on  the  surface  of  the  skin  beneath  the  septum  of  the  nose,  which  is 
called  the  philtrum.  The  additional  fibres  for  the  lower  segment  (m.  incisivus 
inferior)  arise  from  the  inferior  maxilla,  externally  to  the  Levator  labii  inferioris, 
and  arch  outward  to  the  angles  of  the  mouth,  to  join  the  Buccinator  and  the  other 
muscles  attached  to  this  part. 

Relations. — By  its  superficial  surface,  with  the  integument,  to  which  it  is  closely 
connected;  by  its  deep  surface,  with  the  buccal  mucous  membrane,  the  labial 
glands,  and  coronary  vessels;  by  its  outer  circumference  it  is  blended  with  the 


382 


THE  MUSCLES  AND  FASCIA 


numerous  muscles  which  converge  to  the  mouth  from  the  various  parts  of  the  face. 
Its  inner  circumference  is  free,  and  covered  by  the  mucous  membrane. 

The  Buccinator  (Fig.  264)  is  a  broad,  thin  muscle,  quadrilateral  in  form, 
which  occupies  the  interval  between  the  jaws  at  the  side  of  the  face.  It  arises 
from  the  outer  surface  of  the  alveolar  processes  of  the  upper  and  lower  jaws, 


FIG.  264. — Temporal  and  deep  muscles  about  the  mouth.     (Testut.) 

corresponding  to  the  three  molar  teeth,  and,  behind,  from  the  anterior  border  of 
the  ptery go-maxillary  ligament.  The  fibres  converge  toward  the  angle  of  the 
mouth,  where  the  central  fibres  intersect  each  other,  those  from  below  being 
continuous  with  the  upper  segment  of  the  Orbicularis  oris,  and  those  from  above 
with  the  inferior  segment ;  the  highest  and  lowest  fibres  continue  forward  uninter- 
ruptedly into  the  corresponding  segment  of  the  lip,  without  decussation. 


THE  TEMPORO-MANDIBULAR  REGION  383 

Relations. — By  its  superficial  surface,  behind,  with  a  large  mass  of  fat,  the  sucking 
or  suctorial  pad  (corpus  adiposum  buccac) ,  which  separates  it  from  the  ramus  of  the 
lower  jaw,  the  Masseter,  and  a  small  portion  of  the  Temporal  muscle.  The  suck- 
ing pad  is  much  more  developed  relatively  in  children  than  in  adults.  It  assists 
sucking  by  aiding  the  cheek  to  resist  atmospheric  pressure.  The  buccinator 
muscle  is  in  relation,  anteriorly,  with  the  Zygomatici,  Risorius,  Levator  anguli 
oris,  Depressor  anguli  oris,  and  Stenson's  duct,  which  pierces  it  opposite  the 
second  molar  tooth  of  the  upper  jaw;  the  facial  artery  and  vein  cross  it  from  below 
upward;  it  is  also  crossed  by  the  branches  of  the  facial  and  buccal  nerves;  by 
its  internal  surface,  with  the  buccal  glands  and  mucous  membrane  of  the  mouth. 

The  Ptery go-maxillary  or  Pterygo-mandibular  Ligament  (raphe  pterygomandib- 
ularis)  separates  the  Buccinator  muscle  from  the  Superior  constrictor  of  the 
pharynx.  It  is  a  tendinous  thickening  of  the  bucco-pharyngeal  fascia,  attached  by 
one  extremity  to  the  apex  of  the  internal  pterygoid  plate,  and  by  the  other  to  the 
posterior  extremity  of  the  internal  oblique  line  of  the  lower  jaw.  Its  inner  surface 
corresponds  to  the  cavity  of  the  mouth,  and  is  lined  by  mucous  membrane.  Its 
outer  surface  is  separated  from  the  ramus  of  the  jaw  by  a  quantity  of  adipose 
tissue.  Its  posterior  border  gives  attachment  to  the  Superior  constrictor  of  the 
pharynx;  its  anterior  border,  to  the  fibres  of  the  Buccinator. 

The  Bucco-pharyngeal  fascia  (fascia  buccopharyngea)  is  a  thin  fascia  covering 
the  external  surface  of  the  Buccinator  muscle.  It  is  gradually  lost  in  front  of  the 
angle  of  the  mouth.  Posteriorly  it  is  continued  over  the  external  surface  of  the 
throat  muscles.  Its  thickened  cord-like  portion  is  the  stylo-mandibular  ligament. 

The  Risorius  or  Santorini's  Muscle  (ra.  risorius)  (Fig.  260)  consists  of  a 
narrow  bundle  of  fibres  which  arises  in  the  fascia  over  the  Masseter  muscle, 
and,  passing  horizontally  forward,  is  inserted  with  the  Depressor  anguli  oris  into 
the  subcutaneous  and  muscular  tissue  at  the  angle  of  the  mouth.  It  is  placed 
superficial  to  the  Platysma,  and  is  broadest  at  its  outer  extremity.  This  muscle 
varies  much  in  its  size  and  form. 

Nerves. — The  muscles  in  this  group  are  all  supplied  by  the  facial  nerve.  The 
buccal  branch  of  the  inferior  maxillary  nerve  pierces  the  Buccinator  muscle,  and 
by  some  anatomists  is  regarded  as  partly  supplying  this  muscle.  Probably  it 
merely  pierces  it  on  its  way  to  the  mucous  membrane  of  the  cheek. 

Actions. — The  Orbicularis  oris  in  its  ordinary  action  produces  the  direct  closure 
of  the  lips;  by  its  deep  fibres,  assisted  by  the  oblique  ones,  it  closely  applies  the 
lips  to  the  alveolar  arch.  The  superficial  part,  consisting  principally  of  the  decus- 
sating fibres,  brings  the  lips  together  and  also  protrudes  them  forward.  The  Buc- 
cinators contract  and  compress  the  cheeks,  so  that,  during  the  process  of  mastica- 
tion, the  food  is  kept  under  the  immediate  pressure  of  the  teeth.  When  the  cheeks 
have  been  previously  distended  with  air,  the  Buccinator  muscles  expel  it  from 
between  the  lips,  as  in  blowing  a  trumpet.  Hence  the  name  (buccina,  a  trumpet). 
The  Risorius  retracts  the  angles  of  the  mouth,  and  produces  'the  unpleasant 
expression  which  is  sometimes  seen  in  tetanus,  and  is  known  as  risus  sardonicus,  the 
sardonic  laugh. 

9.  The  Temporo-mandibular  Region. 
Masseter.  Temporal. 

The  Masseteric  Fascia  (fascia  parotideomassetericd)  covers  the  outer  and  inner 
surfaces  of  the  parotid  gland  as  a  thick  membrane,  called  the  parotid  fascia.  It 
passes  forward,  and  becomes  thinner  to  cover  the  Masseter  muscle,  to  which  it 
is  firmly  connected.  It  is  derived  from  the  deep  cervical  fascia.  Above,  this 
fascia  is  attached  to  the  lower  border  of  the  zygoma.  It  is  lost  in  front  below 
the  Risorius  and  Platysma. 

The  Masseter  Muscle  is  exposed  by  the  removal  of  this  fascia  (Fig.  260) ;  it  is  a 
short,  thick  muscle,  somewhat  quadrilateral  in  form,  consisting  of  two  portions, 


384  THE  MUSCLES  AND  FASCIA 

superficial  and  deep.  The  superficial  portion,  the  larger,  arises  by  a  thick,  tendinous 
aponeurosis  from  the  malar  process  of  the  superior  maxilla,  and  from  the  anterior 
two-thirds  of  the  lower  border  of  the  zygomatic  arch:  its  fibres  pass  downward 
and  backward,  to  be  inserted  into  the  angle  and  lower  half  of  the  outer  surface 
of  the  ramus  of  the  jaw.  The  deep  portion  is  much  smaller  and  more  muscular 
in  texture;  it  arises  from  the  posterior  third  of  the  lower  border  and  the  whole  of 
the  inner  surface  of  the  zygomatic  arch;  its  fibres  pass  downward  and  forward, 
to  be  inserted  into  the  upper  half  of  the  ramus  and  outer  surface  of  the  coronoid 
process  of  the  jaw,  The  deep  portion  of  the  muscle  is  partly  concealed,  in  front 
by  the  superficial  portion;  behind,  it  is  covered  by  the  parotid  gland.  The  fibres 
of  the  two  portions  are  united  at  their  insertion. 

Relations. — By  its  superficial  surface,  with  the  Zygomatici,  the  parotid  gland 
and  Socia  parotidis,  and  Stenson's  duct;  the  branches  of  the  facial  nerve  and 
the  transverse  facial  vessels,  which  cross  it;  the  masseteric  fascia;  the  Risorius, 
Platysma  myoides,  and  the  integument;  by  its  deep  surface,  with  the  Temporal 
muscle  at  its  insertion,  the  ramus  of  the  jaw,  the  Buccinator  and  the  long 
buccal  nerve,  from  which  it  is  separated  by  a  mass  of  fat  (suctorial  or  sucking  pad). 
The  masseteric  nerve  and  artery  enter  in  on  its  under  surface.  Its  posterior  margin 
is  overlapped  by  the  parotid  gland.  Its  anterior  margin  projects  over  the  Bucci- 
nator muscle,  and  the  facial  vein  lies  on  it  below. 

Temporal  Fascia  (fascia  temporalis). — The  temporal  fascia  is  seen,  at  this  stage 
of  a  dissection,  covering  in  the  Temporal  muscle.  It  is  a  strong,  fibrous  invest- 
ment, covered,  on  its  outer  surface,  by  the  Attrahens  and  Attollens  auricularn  mus- 
cles, the  aponeurosis  of  the  Occipito-frontalis,  and  by  part  of  the  Orbicularis  palpe- 
brarum.  The  temporal  vessels  and  the  auriculo-ternporal  nerve  cross  it  from  below 
upward.  Above,  it  is  a  single  layer,  attached  to  the  entire  extent  of  the  upper  tem- 
poral ridge;  but  below,  where  it  is  attached  to  the  zygoma,  it  consists  of  two  layers, 
one  of  which  is  inserted  into  the  outer,  and  the  other  into  the  inner,  border  of  the 
zygomatic  arch.  A  small  quantity  of  fat,  the  orbital  branch  of  the  temporal  artery, 
and  a  filament  from  the  orbital,  or  temporo-rnalar,  branch  of  the  superior  maxillary 
nerve  are  contained  between  these  two  layers.  It  affords  attachment  by  its  inner 
surface  to  the  superficial  fibres  of  the  Temporal  muscle. 

Dissection. — In  order  to  expose  the  Temporal  muscle,  remove  the  temporal  fascia,  which 
may  be  effected  by  separating  it  at  its  attachment  along  the  upper  border  of  the  zygoma,  and 
dissecting  it  upward  from  the  surface  of  the  muscle.  The  zygomatic  arch  should  then 
be  divided  in  front  at  its  junction  with  the  malar  bone,  and  behind  near  the  external  auditory 
meatus,  and  drawn  downward  with  the  Masseter,  which  should  be  detached  from  its  inser- 
tion into  the  ramus  and  angle  of  the  jaw.  The  whole  extent  of  the  Temporal  muscle  is  then 
exposed. 

The  Temporal  Muscle  (m.  temporalis)  (Figs.  264  and  265)  is  a  broad,  radiating 
muscle  situated  at  the  side  of  the  head  and  occupying  the  entire  extent  of  the  tem- 
poral fossa.  It  arises  from  the  whole  of  the  temporal  fossa  except  that  portion  of  it 
that  is  formed  by  the  malar  bone.  Its  attachment  extends  from  the  external  angular 
process  of  the  frontal  in  front  to  the  mastoid  portion  of  the  temporal  behind,  and 
from  the  curved  line  on  the  frontal  and  parietal  bones  above  to  the  pterygoid  ridge 
on  the  great  wing  of  the  sphenoid  below.  It  is  also  attached  to  the  inner  surface  of 
the  temporal  fascia.  Its  fibres  converge  as  they  descend,  and  terminate  in  an  apon- 
eurosis, the  fibres  of  which,  radiated  at  its  commencement,  converge  into  a  thick 
and  flat  tendon,  which  is  inserted  into  the  inner  surface,  apex,  and  anterior  border 
of  the  coronoid  process  of  the  jaw,  nearly  as  far  forward  as  the  last  molar  tooth. 

Relations. — By  its  superficial  surface,  with  the  integument,  the  Attrahens  and 
Attollens  auriculam  muscles,  the  temporal  vessels  and  nerves,  the  aponeurosis  of 
the  Occipito-frontalis,  the  temporal  fascia,  the  zygoma,  and  Masseter;  by  its 
deep  surface,  with  the  temporal  fossa,  the  External  pterygoid  and  part  of  the 
Buccinator  muscles,  the  internal  maxillary  artery  and  its  deep  temporal  branches, 


THE  PTERYGO-MANDIBULAR  REGION 


385 


and  the  deep  temporal  nerves.  Behind  the  tendon  are  the  masseteric  vessels  and 
nerve,  and  in  front  of  it  the  buccal  vessels  and  nerve.  Its  anterior  border  is  sepa- 
rated from  the  malar  bone  by  a  mass  of  fat. 

Nerves. — Both  muscles  are  supplied  by  the  inferior  maxillary  nerve. 


FIG.  265. — The  Temporal  muscle,  the  zygoma  and  Masseter  having  been  removed. 

10.  The  Pterygo-mandibular  Region  (Figs.  266,  267). 


External  pterygoid. 


Internal  pterygoid. 


Dissection. — The  Temporal  muscle  having  been  examined,  saw  through  the  base  of  the 
coronoid  process,  and  draw  it  upward,  together  with  the  Temporal  muscle,  which  should  be 
detached  from  the  surface  of  the  temporal  fossa.  Divide  the  ramus  of  the  jaw  just  below  the 
condyle,  and  also,  by  a  transverse  incision  extending  across  the  middle,  just  above  the  dental 
foramen;  remove  the  fragment,  and  the  Pterygoid  muscles  will  be  exposed. 


FIG.  266. — The  Pterygoid  muscles,  the  zygomatic  arch,  and  a  portion  of  the  ramus  of  the  jaw  having 

been  removed. 

25 


386 


THE  MUSCLES  AND  FASCIA 


The  External  Pterygoid  Muscle  (m.  pterygoideus  externus)  is  a  short,  thick 
muscle,  somewhat  conical  in  form,  which  extends  almost  horizontally  between  the 
zygomatic  fossa  and  the  condyle  of  the  jaw.  It  arises  by  two  heads,  separated 
by  a  slight  interval:  the  upper  head  arises  from  the  inferior  surface  of  the  greater 
wing  of  the  sphenoid  and  from  the  pterygoid  ridge,  which  separates  the  zygo- 
matic from  the  temporal  fossa;  the  lower  head  from  the  outer  surface  of  the  external 
pterygoid  plate.  'Its  fibres  pass  horizontally  backward  and  outward,  to  be  inserted 
into  a  depression  in  front  of  the  neck  of  the  condyle  of  the  lower  jaw  and  into  the 
corresponding  part  of  the  interarticular  fibre-cartilage. 


FIG.  267. — Pterygoid  muscles,  viewed  from  behind,  the  back  portion  of  the  skull  having  been  removed. 

(Testut.) 

Relations. — By  its  external  surface,  with  the  ramus  of  the  lower  jaw,  the  internal 
maxillary  artery,  which  crosses  it,1  the  tendon  of  the  Temporal  muscle,  arid  the 
Masseter;  by  its  internal  surface  it  rests  against  the  upper  part  of  the  Internal 
pterygoid  muscle,  the  internal  lateral  ligament,  the  middle  meningeal  artery,  and 
inferior  maxillary  nerve;  by  its  upper  border  it  is  in  relation  with  the  temporal  and 
masseteric  branches  of  the  inferior  maxillary  nerve;  by  its  lower  border  it  is  in 
relation  with  the  inferior  dental  and  gustatory  nerves.  Through  the  interval 
between  the  two  portions  of  the  muscle,  the  buccal  nerve  emerges  and  the  internal 
maxillary  artery  passes,  when  the  trunk  of  this  vessel  lies  on  the  muscle. 

The  Internal  Pterygoid  Muscle  (m.  pterygoideus  internus)  is  a  thick,  quadri- 
lateral muscle,  and  resembles  the  Masseter  in  form.  It  arises  from  the  pterygoid 
fossa,  being  attached  to  the  inner  surface  of  the  external  pterygoid  plate  and  to 
the  grooved  surface  of  the  tuberosity  of  the  palate  bone,  and  by  a  second  slip  from 

1  This  is  the  usual  relation,  but  in  many  cases  the  artery  will  be  found  below  the  muscle. — ED.  of  15th  English 
edition. 


MUSCLES  AND  FASCIA  OF  THE  NECK  387 

the  outer  surface  of  the  tuberosities  of  the  palate  and  superior  maxillary  bones; 
its  fibres  pass  downward,  outward,  and  backward,  to  be  inserted,  by  a  strong,  ten- 
dinous lamina,  into  the  lower  and  back  part  of  the  inner  side  of  the  ramus  and 
angle  of  the  lower  jaw,  as  high  as  the  dental  foramen. 

Relations. — By  its  external  surface,  with  the  ramus  of  the  lower  jaw,  from 
which  it  is  separated,  at  its  upper  part,  by  the  External  pterygoid  muscle,  the 
internal  lateral  ligament,  the  internal  maxillary  artery,  the  dental  vessels  and 
nerves,  and  the  lingual  nerve,  and  a  process  of  the  parotid  gland.  By  its  internal 
surface,  with  the  Tensor  palati,  being  separated  from  the  Superior  constrictor  of 
the  pharynx  by  a  cellular  interval. 

Nerves. — These  muscles  are  supplied  by  the  inferior  maxillary  nerve. 

Actions. — The  Temporal  and  Masseter  and  Internal  pterygoid  raise  the  lower 
jaw  against  the  upper  with  great  force.  The  superficial  portion  of  the  Masseter 
assists  the  External  pterygoid  in  drawing  the  lower  jaw  forward  upon  the  upper, 
the  jaw  being  drawn  back  again  by  the  deep  fibres  of  the  Masseter  and  posterior 
fibres  of  the  Temporal.  The  External  pterygoid  muscles  are  the  direct  agents  in 
the  trituration  of  the  food,  drawing  the  lower  jaw  directly  forward,  so  as  to  make 
the  lower  teeth  project  beyond  the  upper.  If  the  muscle  of  one  side  acts,  the 
corresponding  side  of  the  jaw  is  drawn  forward,  and,  the  other  condyle  remaining 
fixed,  the  symphysis  deviates  to  the  opposite  side.  The  alternation  of  these  move- 
ments on  the  two  sides  produces  trituration. 

Surface  Form. — The  outline  of  the  muscles  of  the  head  and  face  cannot  be  traced  on  the 
surface  of  the  body,  except  in  the  case  of  two  of  the  masticatory  muscles.  Those  of  the  head 
are  thin,  so  that  the  outline  of  the  bone  is  perceptible  beneath  them.  Those  in  the  face  are 
small,  covered  by  soft  skin,  and  often  by  a  considerable  layer  of  fat,  so  that  their  outline  is  con- 
cealed, but  they  serve  to  round  off  and  smooth  prominent  borders  and  to  fill  up  what  would  be 
otherwise  unsightly  angular  depressions.  Thus,  the  Orbicularis  palpebrarum  rounds  off  the 
prominent  margin  of  the  orbit,  and  the  Pyramidalis  nasi  fills  in  the  sharp  depression  beneath 
the  glabella,  and  thus  softens  and  tones  down  the  abrupt  depression  which  is  seen  on  the 
unclothed  bone.  In  like  manner,  the  labial  muscles,  converging  to  the  lips  and  assisted  by  the 
superimposed  fat,  fill  in  the  sunken  hollow  of  the  lower  part  of  the  face.  Although  the  muscles 
of  the  face  are  usually  described  as  arising  from  the  bones  and  inserted  into  the  nose,  lips,  and 
corners  of  the  mouth,  they  have  fibres  inserted  into  the  skin  of  the  face  along  their  whole 
extent,  so  that  almost  every  point  of  the  skin  of  the  face  has  its  muscular  fibre  to  move  it; 
hence  it  is  that  when  in  action  the  facial  muscles  produce  alterations  in  the  skin-surface, 
giving  rise  to  the  formation  of  various  folds  or  wrinkles,  or  otherwise  altering  the  relative 
position  of  the  parts,  so  as  to  produce  the  varied  expressions  with  which  the  face  is  endowed; 
hence  these  muscles  are  termed  the  muscles  of  expression.  The  only  two  muscles  in  this 
region  which  greatly  influence  surface  form  are  the  Masseter  and  the  Temporal.  The  Masseter 
is  a  quadrilateral  muscle,  which  imparts  fulness  to  the  hinder  part  of  the  cheek.  When  the 
muscle  is  firmly  contracted,  as  when  the  teeth  are  clenched,  its  outline  is  plainly  visible; 
the  anterior  border  forms  a  prominent  vertical  ridge,  behind  which  is  a  considerable  fulness, 
especially  marked  at  the  lower  part  of  the  muscle;  this  fulness  is  entirely  lost  when  the 
mouth  is  opened  and  the  muscle  no  longer  in  a  state  of  contraction.  The  Temporal  muscle 
is  fan-shaped,  and  fills  the  Temporal  fossa,  substituting  for  it  a  somewhat  convex  form,  the 
anterior  part  of  which,  on  account  of  the  absence  of  hair  over  the  temple,  is  more  marked  than 
the  posterior,  and  stands  out  in  strong  relief  when  the  muscle  is  in  a  state  of  contraction. 

MUSCLES  AND  FASCLE  OF  THE  NECK. 

The  muscles  of  the  neck  may  be  arranged  into  groups  corresponding  with  the 
region  in  which  they  are  situated. 
These  groups  are  nine  in  number: 

1.  Superficial  Cervical  Region.  5.  Muscles  of  the  Pharynx. 

2.  Depressors  of  the  Os  Hyoideum          6.  Muscles  of  the  Soft  Palate. 

and  Larynx.  7.  Muscles  of  the  Anterior  Ver- 

3.  Elevators  of  the  Os  Hyoideum  tebral  Region. 

and  Larynx.  8.  Muscles  of  the  Lateral  Ver- 

4.  Muscles  of  the  Tongue.  tebral  Region. 

9.  Muscles  of  the  Larynx. 


388 


THE  MUSCLES  AND  FASCIA 


The  muscles  contained  in  each  of  these  groups  are  the  following: 


I.  Superficial  Region. 

Platysma  myoides. 
Sterno-cleido-mastoid . 


Infra-hyoid  Region. 

2.  Depressors  of  Os  hyoideum  and 

Larynx. 

Sterno-hyoid. 
Sterno-thyroid. 
Thyro-hyoid. 
Omo-hyoid. 

Supra-hyoid  Region. 

3.  Elevators  of  Os  hyoideum  and  Larynx. 

Digastric. 
Stylo-hyoid. 
Mylo-hyoid. 
Genio-hyoid. 

Lingual  Region. 

4.  Muscles  of  the  Tongue. 

Genio-hyo-glossus. 

Hyo-glossus. 

Chondro-glossus. 

Stylo-glossus. 

Palato-glossus. 


5.  Muscles  of  the  Pharynx. 

Inferior  constrictor. 
Middle  constrictor. 
Superior  constrictor. 
Stylo-pharyngeus. 
Palato-pharyngeus. 

6.  Muscles  of  the  Soft  Palate. 

Levator  palati. 
Tensor  palati. 
Azygos  uvula?. 
Palato-glossus. 
Palato-pharyngeus. 
Salpingo-pharyngeus. 

7.  Muscles  of  the  Anterior  Vertebral 

Region. 

Rectus  capitis  anticus  major. 
Rectus  capitis  anticus  minor. 
Rectus  capitis  lateralis. 
Longus  colli. 

8.  Muscles   of   the  Lateral  Vertebral 

Region. 

Scalenus  anticus. 
Scalenus  medius. 
Scalenus  posticus. 

9.  Muscles  of  the  Larynx. 

Included   in   description   of    the 
Larynx. 


1.  The  Superficial  Cervical  Region. 

Platysma  myoides.  Sterno-cleido-mastoid. 

Dissection. — A  block  having  been  placed  at  the  back  of  the  neck,  and  the  face  turned  to 
the  side  opposite  that  to  be  dissected,  so  as  to  place  the  parts  upon  the  stretch,  make  two  trans- 
verse incisions:  one  from  the  chin,  along  the  margin  of  the  lower  jaw,  to  the  mastoid  process, 
and  the  other  along  the  upper  border  of  the  clavicle.  Connect  these  by  an  oblique  incision 
made  in  the  course  of  the  Sterno-mastoid  muscle,  from  the  mastoid  process  to  the  sternum;  the 
two  flaps  of  integument  having  been  removed  in  the  direction  shown  in  Fig.  258,  the  superficial 
fascia  will  be  exposed. 

Superficial  Cervical  Fascia. — The  superficial  cervical  fascia  is  a  thin,  apon- 
eurotic  lamina  which  is  hardly  demonstrable  as  a  separate  membrane.  Beneath 
it  is  found  the  Platysma  myoides  muscle. 

The  Platysma  Myoides  (m.  platysma)  (Fig.  260)  is  a  broad,  thin  plane  of  mus- 
cular fibres  placed  immediately  beneath  the  superficial  fascia  on  each  side  of  the 
neck.  It  arises  by  thin,  fibrous  bands  from  the  fascia  covering  the  upper  part  of  the 
Pectoral  and  Deltoid  muscles ;  its  fibres  pass  over  the  clavicle  and  proceed  obliquely 
upward  and  inward  along  the  side  of  the  neck.  The  anterior  fibres  interlace, 
below  and  behind  the  symphysis  menti,  with  the  fibres  of  the  muscle  of  the  oppo- 
site side ;  the  posterior  fibres  pass  over  the  lower  jaw,  some  of  them  being  attached 
to  the  bone  below  the  external  oblique  line,  others  passing  on  to  be  inserted  into 
the  skin  and  subcutaneous  tissue  of  the  lower  part  of  the  face,  many  of  these  fibres 
blending  with  the  muscles  about  the  angle  and  lower  part  of  the  mouth.  Some- 


THE  SUPERFICIAL  CER  VICAL  REGION  389 

times  fibres  can  be  traced  to  the  Zygomatic  muscles  or  to  the  margin  of  the 
Orbicularis  oris.  Beneath  the  Platysma  the  external  jugular  vein  may  be  seen 
descending  in  a  line  from  the  angle  of  the  jaw  to  the  middle  of  the  clavicle. 

Relations. — By  its  external  surface,  with  the  integument,  to  which  it  is  united 
more  closely  below  than  above;  by  its  internal  surface,  with  the  Pectoralis  major 
and  Deltoid,  and  with  the  clavicle.  In  the  neck,  with  the  external  and  anterior 
jugular  veins,  the  deep  cervical  fascia,  the  superficial  branches  of  the  cervical 
plexus,  the  Sterno-mastoid,  Sterno-hyoid,  Omo-hyoid,  and  Digastric  muscles; 
behind  the  Sterno-mastoid  muscle  it  covers  in  the  posterior  triangle  of  the  neck. 
On  the  face  it  is  in  relation  with  the  parotid  gland,  the  facial  artery  and  vein, 
and  the  Masseter  and  Buccinator  muscles. 

Nerves. — The  lower  division  of  the  facial  nerve  chiefly  innervates  this  muscle, 
and  superficial  branches  from  the  cervical  plexus  also  reach  it. 

Action. — The  Platysma  myoides  produces  a  slight  wrinkling  of  the  surface  of 
the  skin  of  the  neck,  in  an  oblique  direction,  when  the  entire  muscle  is  brought 
into  action.  Its  anterior  portion,  the  thickest  part  of  the  muscle,  depresses  the 
lower  jaw;  it  also  serves  to  draw  down  the  lower  lip  and  angle  of  the  mouth  on 
each  side,  being  one  of  the  chief  agents  in  the  expression  of  melancholy.  In  the 
pressure  upon  the  blood-vessels  of  the  neck  induced  by  strong  inspiratory  effort, 
this  muscle  draws  away  the  skin  and  fascia,  and  by  so  doing,  greatly  diminishes 
the  pressure  on  the  veins. 

Deep  Cervical  Fascia  (fascia  colli)  (Fig.  268). — The  deep  cervical  fascia 
lies  under  cover  of  the  Platysma  myoides  muscle  and  constitutes  a  complete 
investment  for  the  neck.  It  also  forms  a  sheath  for  the  carotid  vessels,  and,  in 
addition,  is  prolonged  deeply  in  the  shape  of  certain  processes  or  lamellae,  which 
come  into  close  relation  with  the  structures  situated  in  front  of  the  vertebral  column. 

The  investing  portion  of  the  fascia  is  attached,  behind,  to  the  ligamentum 
nuchae  and  to  the  spine  of  the  seventh  cervical  vertebra.  Along  this  line  it  splits 
to  enclose  the  Trapezius  muscle,  at  the  anterior  border  of  which  the  two  enclosing 
lamellae  unite  and  form  a  strong  membrane,  which  extends  forward  so  as  to  roof 
in  the  posterior  triangle  of  the  neck.  Along  the  hinder  edge  of  the  Sterno-mastoid 
the  membrane  divides  to  enclose  this  muscle,  at  the  anterior  edge  of  which  it  once 
more  forms  a  single  lamellae,  which  roofs  in  the  anterior  triangle  of  the  neck, 
and,  reaching  forward  to  the  middle  line,  is  continuous  with  the  corresponding 
part  from  the  opposite  side  of  the  neck.  In  the  middle  line  of  the  neck  it  is  attached 
to  the  symphysis  menti  and  to  the  body  of  the  hyoid  bone. 

Above,  the  fascia  is  attached  to  the  superior  curved  line  of  the  occiput,  to  the 
mastoid  process  of  the  temporal,  and  to  the  whole  length  of  the  body  of  the  jaw. 
Opposite  the  angle  of  the  jaw  the  fascia  is  very  strong,  and  binds  the  anterior 
edge  of  the  Sterno-mastoid  firmly  to  that  bone.  Between  the  jaw  and  the  mastoid 
process  it  ensheaths  the  parotid  gland — the  layer  which  covers  the  gland  extending 
upward  under  the  name  of  the  parotid  fascia  to  be  fixed  to  the  zygomatic  arch. 
The  parotid  fascia  is  prolonged  forward  to  cover  the  masseter  muscle,  the  masse- 
teric  fascia.  From  the  layer  which  passes  under  the  parotid  a  strong  band, 
the  stylo-mandibular  ligament,  reaches  from  the  styloid  process  to  the  angle  of 
the  jaw.  The  parotid  and  masseteric  fasciae  constitute  the  fascia  parotideo- 
masseterica. 

Below,  the  cervical  fascia  is  attached  to  the  acromion  process,  the  clavicle,  and 
to  the  manubrium  sterni.  Some  little  distance  above  the  last-named  point,  how- 
ever, it  splits  into  two  layers,  superficial  and  deep.  The  former  is  attached  to 
the  anterior  border  of  the  manubrium,  the  latter  to  its  posterior  border  and  to 
the  interclavicular  ligament.  Between  these  two  layers  is  a  slit-like  interval,  the 
suprasternal  space  or  space  of  Burns  (spatium  supr aster nale).  It  contains  a  small 
quantity  of  areolar  tissue,  and  sometimes  a  lymphatic  gland;  the  lower  portions 


390 


THE  MUSCLES  AND  FASCIAE 


of  the  anterior  jugular  veins  and  their  transverse  connecting  branch;  and  also 
the  sternal  heads  of  the  Sterno-mastoid  muscles. 

The  fascia  which  lines  the  deep  aspect  of  the  Sterno-mastoid  gives  off  certain 
important  processes,  viz. :  (1)  A  process  to  envelop  the  tendon  of  the  Omo-hyoid, 
and  bind  it  down  to  the  sternum  and  first  costal  cartilage.  (2)  A  strong  sheath, 
the  carotid  sheath,  for  the  large  vessels  of  the  neck,  enclosed  within  which  are  the 
carotid  artery,  internal  jugular  vein,  the  vagus,  and  descendens  hypoglossi  nerves. 
(3)  The  prevertebral  fascia  (fascia  praevertebralis),  which  extends  inward  behind 


SPACE   BETWEEN   THE 
TWO  LAYERS  OF  FASCIA 


CESOPHAGUS 


PREVERTEBRAL 
FASCIA 


STERNOTHYROID 

DEEP  FASCIA   OF  NECK 
STERNOHYOIO 
OMOHYOID 

COMMON  CAROTID 
ARTERY 

DESCENDENS  HYPO- 
iLOSSI   NERVE 

PNEUMOGASTRIC 
'NERVE 

^LYMPHATIC 
GLANDS 

.SYMPATHETIC 

NERVE 
.PHRENIC 

NERVE 
.INTERNAL 
JUGULAR 


SUPERFICIAL 
FASCIA  OF 
NECK 


FIG.  268.— Transverse  section  through  the  neck  at  the  level  of  the  seventh  cervical  vertebra.     (Spalteholz.) 

the  carotid  vessels,  where  it  assists  in  forming  their  sheath,  and  passes  in  front 
of  the  prevertebral  muscles..  It  thus  forms  the  posterior  limit  of  a  fibrous  com- 
partment which  contains  the  larynx  and  trachea,  the  thyroid  gland,  and  the 
pharynx  and  oesophagus.  The  prevertebral  fascia  is  fixed  above  to  the  base  of 
the  skull,  while  below  it  is  continued  into  the  thorax  in  front  of  the  Longus  colli 
muscles.  Parallel  to  the  carotid  vessels  and  along  their  inner  aspect  it  gives  off 
a  thin  lamina,  the  bucco-pharyngeal  fascia  (fascia  buccopharyngea) ,  which  closely 
invests  the  constrictor  muscles  of  the  pharynx,  and  is  continued  forward  from 
the  Superior  constrictor  on  to  the  Buccinator.  It  is  attached  to  the  prever- 


THE  SUPERFICIAL   CERVICAL  REGION  391 

tebral  layer  by  loose  connective  tissue  only,  and  thus  an  easily  distended  space, 
the  retro-pharyngeal  space  (xp:itium  retropharynged),is  found  between  them.  This 
space  is  limited  above  by  the  base  of  the  skull,  while  below  it  extends  behind  the 
u-sophagus  into  the  thorax,  where  it  is  continued  into  the  posterior  mediastinum. 
The  prevertebral  fascia  is  prolonged  downward  and  outward  behind  the  carotid 
vessels  and  in  front  of  the  Scaleni  muscles,  and  forms  a  sheath  for  the  brachial 
plexus  of  nerves  and  for  the  subclavian  vessels  in  the  posterior  triangle  of  the  neck, 
and,  continuing  under  the  clavicle  as  the  axillary  sheath,  is  attached  to  the  deep 
surface  of  the  costo-coracoid  membrane.  Immediately  above  the  clavicle  an 
areolar  space  exists  between  the  investing  layer  and  the  sheath  of  the  subclavian 
vessels,  and  in  it  are  found  the  lower  part  of  the  external  jugular  vein,  the  descend- 
ing clavicular  nerves,  the  suprascapular  and  transversalis  colli  vessels,  and  the 
posterior  belly  of  the  Omo-hyoid  muscle.  This  space  extends  downward  behind 
the  clavicle,  and  is  limited  below  by  the  fusion  of  the  costo-coracoid  membrane 
with  the  anterior  wall  of  the  axillary  sheath.  (4)  The  pre-tracheal  fascia,  which 
extends  inward  in  front  of  the  carotid  vessels,  and  assists  in  forming  the  carotid 
sheath.  It  is  further  continued  behind  the  Depressor  muscles  of  the  hyoid  bone, 
and,  after  enveloping  the  thyroid  body,  is  prolonged  in  front  of  the  trachea  to 
meet  the  corresponding  layer  of  the  opposite  side.  Above,  it  is  fixed  to  the  hyoid 
bone,  while  below  it  is  carried  downward  in  front  of  the  trachea  and  large  vessels 
at  the  root  of  the  neck,  and  ultimately  blends  with  the  fibrous  pericardium. 

Surgical  Anatomy. — The  cervical  fascia  is  of  considerable  importance  from  a  surgical 
point  of  view.  As  will  be  seen  from  the  foregoing  description,  it  may  be  divided  into  three 
layers:  (1)  A  superficial  layer;  (2)  a  layer  passing  in  front  of  the  trachea,  and  forming  with 
the  superficial  layer  a  sheath  for  the  depressors  of  the  hyoid  bone;  (3)  a  prevertebral  layer 
passing  in  front  of  the  bodies  of  the  cervical  vertebrae,  and  forming  with  the  second  layer  a 
space  in  which  are  contained  the  trachea,  oesophagus,  etc.  The  superficial  layer  forms  a  com- 
plete investment  for  the  neck.  It  is  attached  behind  to  the  ligamentum  nuchae  and  the  spine 
of  the  seventh  cervical  vertebra;  above  it  is  attached  to  the  external  occipital  protuberance,  to 
the  superior  curved  line  of  the  occiput,  to  the  mastoid  process,  to  the  zygoma  and  the  lower 
jaw;  below  it  is  attached  to  the  manubrium  sterni,  the  clavicle,  the  acromion  process,  and 
the  spine  of  the  scapula;  in  front  it  blends  with  the  fascia  of  the  opposite  side.  This  layer 
opposes  the  extension  of  abscesses  or  new-growths  toward  the  surface,  and  pus  forming  beneath 
it  has  a  tendency  to  extend  laterally.  If  pus  is  in  the  posterior  triangle,  it  might  extend 
backward  under  the  Trapezius,  forward  under  the  Sterno-mastoid,  or  downward  under  the 
clavicle  for  some  distance,  until  stopped  by  the  junction  of  the  cervical  fascia  to  the  Costo- 
coracoid  membrane.  If  the  pus  is  contained  in  the  anterior  triangle,  it  might  find  its  way  into 
the  anterior  mediastinum,  being  situated  in  front  of  the  layer  of  fascia  which  passes  down  into 
the  thorax  to  become  continuous  with  the  pericardium;  but  owing  to  the  lesser  density  and 
thickness  of  the  fascia  in  this  situation  it  more  frequently  finds  its  way  through  it  and  points 
above  the  sternum.  The  second  layer  of  fascia  is  connected  above  with  the  hyoid  bone.  It 
passes  down  beneath  the  depressors  and  in  front  of  the  thyroid  body  and  trachea  to  become 
continuous  with  the  fibrous  layer  of  the  pericardium.  Laterally  it  invests  the  great  vessels  of 
the  neck  and  is  connected  with  the  superficial  layer  beneath  the  Sterno-mastoid.  Pus  forming 
beneath  this  layer  would  in  all  probability  find  its  way  into  the  posterior  mediastinum.  The 
third  layer  (the  prevertebral  fascia)  is  connected  above  to  the  base  of  the  skull.  Pus  forming 
beneath  this  layer,  in  cases,  for  instance,  of  caries  of  the  bodies  of  the  cervical  vertebrae,  might 
extend  toward  the  posterior  and  lateral  part  of  the  neck  and  point  in  this  situation,  or  might 
perforate  this  layer  of  fascia  and  the  pharyngeal  fascia  and  point  into  the  pharynx  (retro- 
pharyngeal  abscess). 

In  cases  of  cut  throat  the  cervical  fascia  is  of  considerable  importance.  When  the  wound 
involves  only  the  superficial  layer  the  injury  is  usually  trivial,  the  only  special  danger  being 
injury  to  the  external  jugular  vein,  and  the  only  special  complication  being  diffuse  cellulitis. 
But  where  the  second  of  the  two  layers  has  been  opened  up,  important  structures  may  have 
been  injured,  which  may  lead  to  serious  results. 

It  may  be  worth  while 'mentioning  that  in  Burns's  space  is  contained  the  sternal  head  of 
origin  of  the  Sterno-mastoid  muscle,  so  that  this  space  is  opened  in  division  of  this  tendon. 
The  anterior  jugular  vein  is  also  contained  in  the  same  space. 

The  Sterno-mastoid  or  Sterno-cleido-mastoid  (m.  sternocleidomastoideus) 
(Fig.  269)  is  a  large,  thick  muscle,  which  passes  obliquely  across  the  side  of  the 


392 


THE  MUSCLES  AND  FASCIA 


neck,  being  enclosed  between  two  layers  of  the  deep  cervical  fascia.  It  is  thick 
and  narrow  at  its  central  part,  but  is  broader  and  thinner  at  each  extremity.  It 
arises,  by  two  heads,  from  the  sternum  and  clavicle.  The  sternal  portion  is  a 
rounded  fasciculus,  tendinous  in  front,  fleshy  behind,  which  arises  from  the 
upper  and  anterior  part  of  the  first  piece  of  the  sternum,  and  is  directed 
upward,  outward,  and  backward.  'The  clavicular  portion  arises  from  the  inner 
third  of  the  superior  border  and  anterior  surface  of  the  clavicle,  being  com- 
posed of  fleshy  and  aponeurotic  fibres;  it  is  directed  almost  vertically  upward. 
These  two  portions  are  separated  from  one  another,  at  their  origin,  by  a  triangular 
cellular  interval,  but  become  gradually  blended,  below  the  middle  of  the  neck/ 
into  a  thick,  rounded  muscle,  which  is  inserted,  by  a  strong  tendon,  into  the  outer 
surface  of  the  mastoid  process  of  the  temporal  bone,  from  its  apex  to  its  superior 
border,  and  by  a  thin  aponeurosis  into  the  outer  half  of  the  superior  curved  line  of 
the  occipital  bone.  The  Sterno-mastoid  varies  much  in  its  extent  of  attachment 
to  the  clavicle:  in  one  case  the  clavicular  may  be  as  narrow  as  the  sternal  portion; 
in  another,  the  former  may  be  as  much  as  three  inches  in  breadth.  When  the 
clavicular  origin  is  broad,  it  is  occasionally  subdivided  into  numerous  slips  separ- 
ated by  narrow  intervals.  More  rarely,  the  corresponding  margins  of  the  Sterno- 
mastoid  and  Trapezius  have  been  found  in  contact.  In  the  application  of  a  ligature 


FIG.  269. — Muscles  of  the  neck  and  boundaries  of  the  triangles. 

to  the  third  part  of  the  subclavian  artery  it  will  be  necessary,  where  the  Sterno- 
mastoid  and  Trapezius  come  close  together,  to  divide  a  portion  of  one  or  of  both. 
This  muscle  divides  the  quadrilateral  space  at  the  side  of  the  neck  into  two 
triangles,  an  anterior  and  a  posterior.  The  boundaries  of  the  anterior  triangle 
are,  in  front,  the  median  line  of  the  neck;  above,  the  lower  border  of  the  body  of 
the  jaw,  and  an  imaginary  line  drawn  from  the  angle  of  the  jaw  to  the  mastoid 
process;  behind,  the  anterior  border  of  the  Sterno-mastoid  muscle.  The  apex  of 
the  triangle  is  at  the  upper  border  of  the  sternum.  The  boundaries  of  the  posterior 


THE  INFRA-HYOID  REGION  393 

triangle  are,  in  front,  the  posterior  border  of  the  Sterno-mastoid ;  below,  the  middle 
third  of  the  clavicle ;  behind,  the  anterior  margin  of  the  Trapezius.1  The  apex  corre- 
sponds with  the  meeting  of  the  Sterno-mastoid  and  Trapezius  on  the  occipital  bone. 

Relations. — By  its  superficial  surface,  with  the  integument  and  Platysma, 
from  which  it  is  separated  by  the  external  jugular  vein,  the  superficial  branches 
of  the  cervical  plexus,  and  the  anterior  layer  of  the  deep  cervical  fascia.  By  its 
deep  surface  it  is  in  relation  with  the  Sterno-clavicular  articulation;  a  process  of 
the  deep  cervical  fascia;  the  Sterno-hyoid,  Sterno-thyroid,  Omo-hyoid,  posterior 
belly  of  the  Digastric,  Levator  anguli  scapulae,  Splenius  and  Scaleni  muscles; 
common  carotid  artery,  internal  and  anterior  jugular  veins,  commencement  of  the 
internal  and  external  carotid  arteries,  the  occipital,  subclavian,  transversalis  colli, 
and  suprascapular  arteries  and  veins;  the  phrenic,  vagus,  hypoglossal,  descen- 
dens  and  communicans  hypoglossi  nerves;  the  accessory  nerve,  which  pierces 
its  upper  third;  the  cervical  plexus,  parts  of  the  thyroid  and  parotid  gLnds,  and 
deep  lymphatic  glands. 

Nerves. — The  Sterno-cleido-mastoid  is  supplied  by  the  accessory  nerve  and 
deep  branches  of  the  cervical  plexus. 

Actions. — When  only  one  Sterno-mastoid  muscle  acts,  it  draws  the  head  toward 
the  shoulder  of  the  same  side,  assisted  by  the  Splenius  and  the  Obliquus  capitis 
inferior  of  the  opposite  side.  At  the  same  time  it  rotates  the  head  so  as  to  carry 
the  face  toward  the  opposite  side.  When  the  two  muscles  act  together  they 
flex  the  head  upon  the  neck.  If  the  head  is  fixed,  the  two  muscles  assist  in 
elevating  the  thorax  in  forced  inspiration. 

Surface  Form. — The  anterior  edge  of  the  muscle  forms  a  very  prominent  ridge  beneath  the 
skin,  which  it  is  important  to  notice,  as  it  forms  a  guide  to  the  surgeon  in  making  the  necessary 
incisions  for  ligature  of  the  common  carotid  artery  and  for  cesophagotomy. 

Surgical  Anatomy. — The  relations  of  the  sternal  and  clavicular  parts  of  the  Sterno-mastoid 
should  be  carefully  examined,  as  the  surgeon  is  sometimes  required  to  divide  one  or  both  portions 
of  the  muscle  in  wry-neck  (torticollis).  One  variety  of  this  distortion  is  produced  by  spasmodic 
contraction  or  rigidity  of  the  Sterno-mastoid;  the  head  being  carried  down  toward  the  shoulder 
of  the  same  side,  and  the  face  turned  to  the  opposite  side  and  fixed  in  that  position.  When  there 
is  permanent  shortening,  subcutaneous  division  of  the  muscle  is  resorted  to  by  some  surgeons. 
This  is  performed  by  introducing  a  tenotomy  knife  beneath  it,  close  to  its  origin,  and  dividing 
it  from  behind  forward  whilst  the  muscle  is  put  well  upon  the  stretch.  There  is  seldom  any 
difficulty  in  dividing  the  sternal  portion  by  making  a  puncture  on  the  inner  side  of  the  tendon, 
and  then  pushing  a  blunt  tenotome  behind  it,  and  cutting  forward.  In  dividing  the  clavicular 
portion  care  must  be  taken  to  avoid  wounding  the  external  jugular  vein,  which  runs  parallel 
with  the  posterior  border  of  the  muscle  in  this  situation,  or  the  anterior  jugular  vein,  which 
crosses  beneath  it.  If  the  external  jugular  vein  lies  near  the  muscle,  it  is  safer  to  make  the 
first  puncture  at  the  outer  side  of  the  tendon,  and  introduce  a  blunt  tenotome  from  without 
inward.  Many  surgeons  prefer  dividing  the  muscle  by  open  incision,  because  by  this  method 
all  of  the  contracted  fibres,  muscular  and  facial,  can  be  certainly  and  safely  divided.  An  incision 
is  made  over  the  origin  of  the  muscle,  the  origin  is  exposed,  a  director  is  passed  underneath  it, 
and  it  is  then  divided.  With  care  and  attention  to  asepsis  this  plan  of  treatment  is  devoid  of 
risk,  and  in  this  way  the  accidental  division  of  vessels  can  be  avoided.  Some  of  the  fibres  of 
the  Sterno-mastoid  muscle  are  occasionally  torn  during  birth,  especially  in  breech  presenta- 
tions; this  is  accompanied  by  hemorrhage  and  formation  of  a  swelling  within  the  substance  of 
the  muscle.  This  by  some  is  believed  to  be  one  of  the  causes  of  wry-neck,  the  scar  tissue 
which  is  formed  contracting  and  shortening  the  muscle. 

2.  The  Infra-hyoid  Region  (Figs.  269,  270). 
DEPRESSORS  OF  THE  Os  HYOIDEUM  AND  LARYNX. 

Sterno-hyoid.  Thyro-hyoid. 

Sterno-thyroid.  Omo-hyoid. 

Dissection. — The  muscles  in  this  region  may  be  exposed  by  removing  the  deep  fascia  from  the 
front  of  the  neck.  In  order  to  see  the  entire  extent  of  the  Omo-hyoid  it  is  necessary  to  divide 
the  sterno-mastoid  at  its  centre,  and  turn  its  ends  aside,  and  to  detach  the  Trapezius  from  the 
clavicle  and  scapula.  This,  however,  should  not  be  done  until  the  Trapezius  has  been  dissected. 

1  The  anatomy  of  these  triangles  will  be  more  exactly  described  with  that  of  the  vessels  of  the  neck. — ED.  of 
15th  English  edition. 


THE  MUSCLES  AND  FASCIA 

The  Sterno-hyoid  (m.  sternohyoideus)  is  a  thin,  narrow,  ribbon-like  muscle, 
which  arises  from  the  inner  extremity  of  the  clavicle,  the  posterior  sterno- 
clavicular  ligament,  and  the  upper  and  posterior  part  of  the  first  piece  of  the 
sternum ;  passing  upward  and  inward,  it  is  inserted,  by  short,  tendinous  fibres, 
into  the  lower  border  of  the  body  of  the  hyoid  bone.  This  muscle  is  separated, 
below,  from  its  fellow  by  a  considerable  interval ;  but  the  two  muscles  come  into 
contact  with  one  another  in  the  middle  of  their  course,  and  from  this  upward 
lie  side  by  side.  It  sometimes  presents,  immediately  above  its  origin,  a  trans- 
verse tendinous  intersection,  like  those  in  the  Rectus  abdominis.  As  a  rule, 
two  bursse,  the  sterno-hyoid  bursse  (bursae  sternokyoidii) ,  lie  between  the  crico- 
thyroid  membrane,  on  one  hand,  and  the  Sterno-hyoid  muscle  and  the  cervical 
fascia,  on  the  other.  Sometimes  there  is  one  large  median  bursa  instead  of  two 
lateral  bursse.  Not  unusually  there  is  no  bursa  at  all. 

Relations. — By  its  superficial  surface,  below,  with  the  sternum,  the  sternal  end 
of  the  clavicle,  and  the  Sterno-mastoid ;  and  above,  with  the  Platysma  and  deep 
cervical  fascia;  by  its  deep  surface,  with  the  Sterno-thyroid,  Crico-thyroid,  and 

Symphysis 
of  jaw. 


FIG.  270. — Muscles  of  the  neck.     Anterior  view. 

Thyro-hyoid  muscles,  the  thyroid  gland,  the  superior  thyroid  vessels,  the  thyroid 
cartilage,  the  crico-thyroid  and  thyro-hyoid  membranes. 

The  Sterno-thyroid  (m.  sternothyreoideus)  is  situated  beneath  the  preceding 
muscle,  but  is  shorter  and  wider  than  it.  It  arises  from  the  posterior  surface  of 
the  first  piece  of  the  sternum,  below  the  origin  of  the  Sterno-hyoid,  and  from  the 
edge  of  the  cartilage  of  the  first  rib,  occasionally  of  the  second  rib  also,  and  is 
inserted  into  the  oblique  line  on  the  side  of  the  ala  of  the  thyroid  cartilage. 
This  muscle  is  in  close  contact  with  its  fellow  at  the  lower  part  of  the  neck,  and 
is  occasionally  traversed  by  a  transverse  or  oblique  tendinous  intersection,  like 
those  in  the  Rectus  abdominis. 


THE  INFRA-HYOID  REGION  395 

Relations. — By  its  anterior  surface,  with  the  Stern o-hyoid,  Omo-hyoid,  and 
Sterno-mastoid ;  by  its  posterior  surface,  from  below  upward,  with  the  trachea, 
vena  innominata,  common  carotid  (and  on  the  right  side  the  arteria  innominata), 
the  thyroid  gland  and  its  vessels,  and  the  lower  part  of  the  larynx  and  pharynx. 
The  inferior  thyroid  vein  lies  along  its  inner  border,  a  relation  which  it  is  impor- 
tant to  remember  in  the  operation  of  tracheotomy.  On  the  left  side  the  deep 
surface  of  the  muscle  is  in  relation  to  the  o?sophagus. 

The  Thyro-hyoid  (m.  ihyreohyoideus)  is  a  small,  quadrilateral  muscle  appear- 
ing like  a  continuation  of  the  Sterno-thyroid.  It  arises  from  the  oblique  line  on 
the  side  of  the  thyroid  cartilage,  and  passes  vertically  upward  to  be  inserted  into 
the  lower  border  of  the  body  and  greater  cornu  of  the  hyoid  bone.  The  thyro- 
hyoid  bursae  (bursae  thyreohyoidii)  lie  inferior  to  the  greater  cornua  of  the  hyoid 
bone  and  upon  the  thyro-hyoid  membrane.  There  is  one  bursa  on  each  side 
beneath  the  corresponding  Thyro-hyoid  muscle. 

Relations. — By  its  external  surface,  with  the  Sterno-hyoid  and  Omo-hyoid 
muscles;  by  its  internal  surface,  with  the  thyroid  cartilage,  the  thyro-hyoid  mem- 
brane, and  the  superior  laryngeal  vessels  and  nerve. 

The  Omo-hyoid  (m.  omohyoideus)  passes  across  the  side  of  the  neck,  from 
the  scapula  to  the  hyoid  bone.  It  consists  of  two  fleshy  bellies,  united  by  a 
central  tendon.  It  arises  from  the  upper  border  of  the  scapula,  and  occasionally 
from  the  transverse  ligament  which  crosses  the  suprascapular  notch,  its  extent  of 
attachment  to  the  scapula  varying  from  a  few  lines  to  an  inch.  From  this  origin 
the  posterior  belly  (venter  inferior)  forms  a  flat,  narrow  fasciculus,  which  inclines 
forward  and  slightly  upward  across  the  lower  part  of  the  neck,  behind  the  Sterno- 
mastoid  muscle,  where  it  becomes  tendinous;  it  then  changes  its  direction,  forming 
an  obtuse  angle,  and  terminates  in  the  anterior  belly  (venter  superior),  which 
passes  almost  vertically  upward,  close  to  the  outer  border  of  the  Sterno-hyoid, 
to  be  inserted  into  the  lower  border  of  the  body  of  the  hyoid  bone,  just  external  to 
the  insertion  of  the  Sterno-hyoid.  The  central  tendon  of  this  muscle,  which  varies 
much  in  length  and  form,  is  held  in  position  by  a  process  of  the  deep  cervical 
fascia,  which  includes  it  in  a  sheath.  This  process  is  prolonged  down,  to  be 
attached  to  the  clavicle  and  first  rib.  It  is  by  this  means  that  the  angular  form  of 
the  muscle  is  maintained. 

This  muscle  subdivides  each  of  the  two  large  triangles  at  the  side  of  the  neck 
into  two  smaller  triangles;  the  two  posterior  ones  being  the  posterior  superior  or 
occipital  triangle,  and  the  posterior  inferior  or  subclavian  triangle;  the  two  anterior, 
the  anterior  superior  or  superior  carotid  triangle,  and  the  anterior  inferior  or  inferior 
carotid  triangle. 

Relations. — By  its  superficial  surface,  with  the  Trapezius,  the  Sterno-mastoid, 
deep  cervical  fascia,  Platysma,  and  integument;  by  its  deep  surface,  with  the 
Scaleni  muscles,  phrenic  nerve,  lower  cervical  nerves,  which  go  to  form  the  brachial 
plexus,  the  suprascapular  vessels  and  nerve,  sheath  of  the  common  carotid  artery 
and  internal  jugular  vein,  the  Sterno-thyroid  and  Thyro-hyoid  muscles. 

Nerves. — The  Thyro-hyoid  is  supplied  by  the  hypoglossal;  the  other  muscles 
of  this  group  by  branches  from  the  loop  of  communication  between  the  descendens 
and  communicans  hypoglossi. 

Actions. — These  muscles  depress  the  larynx  and  hyoid  bone,  after  they  have 
been  drawn  up  with  the  pharynx  in  the  act  of  deglutition.  The  Omo-hyoid 
muscles  not  only  depress  the  hyoid  bone,  but  carry  it  backward  and  to  one  side. 
It  is  concerned  especially  in  prolonged  inspiratory  efforts;  for  by  tensing  the 
lower  part  of  the  cervical  fascia  it  lessens  the  inward  suction  of  the  soft  parts, 
wrhich  would  otherwise  compress  the  great  vessels  and  the  apices  of  the  lungs. 
This  action  is  synergistic  with  that  of  the  Platysma.  The  Thyro-hyoid  may  act 
as  an  elevator  of  the  thyroid  cartilage  when  the  hyoid  bone  ascends,  drawing 


396  THE  MUSCLES  AND  FASCIA 

upward  the  thyroid  cartilage,  behind  the  hyoid  bone.     The  Sterno-thyroid  acts  as 
a  depressor  of  the  thyroid  cartilage. 

3.  The  Supra-hyoid  Region  (Figs.  269,  270). 
ELEVATORS  OF  THE  Os  HYOIDEUM — DEPRESSORS  OF  THE  LOWER  JAW. 

Digastric.  Mylo-hyoid. 

Stylo-hyoid.  Genio-hyoid. 

Dissection. — To  dissect  these  muscles  a  block  should  be  placed  beneath  the  back  of  the 
neck,  and  the  head  drawn  backward  and  retained  in  that  position.  On  the  removal  of  the  deep 
fascia  the  muscles  are  at  once  exposed. 

The  Digastric  (TO.  digastricus)  consists  of  two  fleshy  bellies  united  by  an  inter- 
mediate, rounded  tendon.  It  is  a  small  muscle,  situated  below  the  side  of  the 
body  of  the  lower  jaw,  and  extending,  in  a  curved  form,  from  the  side  of  the 
head  to  the  symphysis  of  the  jaw.  The  posterior  belly  (venter  posterior),  longer 
than  the  anterior,  arises  from  the  digastric  groove  on  the  inner  side  of  the  mas- 
toid  process  of  the  temporal  bone,  and  passes  downward,  forward,  and  inward. 
The  anterior  belly  (venter  anterior)  arises  from  a  depression  on  the  inner  side 
of  the  lower  border  of  the  jaw,  close  to  the  symphysis,  and  passes  downward 
and  backward.  The  two  bellies  terminate  in  the  central  tendon  which  per- 
forates the  Stylo-hyoid,  and  is  held  in  connection  with  the  side  of  the  body 
and  the  greater  cornu  of  the  hyoid  bone  by  a  fibrous  loop,  lined  by  a  synovial 
membrane.  A  broad  aponeurotic  layer  is  given  off  from  the  tendon  of  the 
Digastric  on  each  side,  which  is  attached  to  the  body  and  great  cornu  of  the 
hyoid  bone:  this  is  termed  the  supra-hyoid  aponeurosis.  It  forms  a  strong  layer 
of  fascia  between  the  anterior  portion  of  the  two  muscles,  and  a  firm  investment 
for  the  other  muscles  of  the  supra-hyoid  region  which  lie  deeper. 

The  Digastric  muscle  divides  the  anterior  superior  triangle  of  the  neck  into 
two  smaller  triangles;  the  upper,  or  submaxillary  triangle,  being  bounded,  above,  by 
the  lower  border  of  the  body  of  the  jaw,  and  a  line  drawn  from  its  angle  to  the 
mastoid  process;  below,  by  the  posterior  belly  of  the  Digastric  and  the  Stylo- 
hyoid  muscles;  in  front,  by  the  middle  line  of  the  neck  and  the  anterior  belly  of  the 
Digastric,  the  lower  or  superior  carotid  triangle  being  bounded  above  by  the  poste- 
rior belly  of  the  Digastric,  behind  by  the  Sterno-mastoid,  below  by  the  anterior 
belly  of  the  Omo-hyoid. 

Relations. — By  its  superficial  surface,  with  the  mastoid  process,  the  Platysma, 
Sterno-mastoid,  part  of  the  Splenius,  Trachelo-mastoid,  and  Stylo-hyoid  muscles, 
and  the  parotid  gland.  By  its  deep  surface,  the  anterior  belly  lies  on  the  Mylo- 
hyoid;  the  posterior  belly  oh  the  Stylo-glossus,  Stylo-pharyngeus,  and  Hyo-glossus 
muscles,  the  external  carotid  artery  and  its  occipital,  lingual,  facial,  and  ascending 
pharyngeal  branches,  the  internal  carotid  artery,  internal  jugular  vein,  and  hypo- 
glossal  nerve. 

The  Stylo-hyoid  (m.  stylohyoideus)  is  a  small,  slender  muscle,  lying  in  front 
of,  and  above,  the  posterior  belly  of  the  Digastric.  It  arises  from  the  back  and 
outer  surface  of  the  styloid  process  of  the  temporal  bone,  near  the  base;  and, 
passing  downward  and  forward,  is  inserted  into  the  body  of  the  hyoid  bone, 
just  at  its  junction  with  the  greater  cornu,  and  immediately  above  the  Omo- 
hyoid.  This  muscle  is  perforated,  near  its  insertion,  by  the  tendon  of  the 
Digastric. 

Relations. — By  its  superficial  surface  above  with  the  parotid  gland  and  deep 
cervical  fascia;  below  it  is  superficial,  being  situated  immediately  beneath  the  deep 
cervical  fascia.  By  its  deep  surface,  with  the  posterior  belly  of  the  Digastric,  the 
external  carotid  artery,  with  its  lingual  and  facial  branches,  the  Hyo-glossus 
muscle,  and  the  hypoglossal  nerve. 


THE  8UPRA-HYOID  REGION 


397 


The  Stylo-hyoid  Ligament  (ligamentum  stylohyoideus) . — In  connection  witli  the 
Stylo-hyoid  muscle  may  be  described  a  ligamentous  band,  the  styh-hyoid  ligament. 
It  is  a  fibrous  cord,  often  containing  a  little  cartilage  in  its  centre,  which  continues 
the  styloid  process  down  to  the  hyoid  bone,  being  attached  to  the  tip  of  the  former 
and  the  small  cornu  of  the  latter.  It  is  often  more  or  less  ossified,  and  in  many 
animals  forms  a  distinct  bone,  the  epihyal. 

The  anterior  belly  of  the  Digastric  should  be  removed,  in  order  to  expose  the  next  muscle. 

The  Mylo-hyoid  (m.  mylohyoideus)  (Fig.  271)  is  a  flat,  triangular  muscle, 
situated  immediately  beneath  the  anterior  belly  of  the  Digastric,  and  forming, 
with  its  fellow  of  the  opposite  side,  a  muscular  floor  for  the  cavity  of  the  mouth. 
It  arises  from  the  whole  length  of  the  mylo-hyoid  ridge  of  the  lower  jaw,  extend- 
ing from  the  symphysis  in  front  to  the  last  molar  tooth  behind.  The  posterior 
fibres  pass  inward  and  slightly  downward,  to  be  inserted  into  the  body  of  the 
hyoid  bone.  The  middle  and  anterior  fibres  are  inserted  into  a  median  fibrous 
raphe,  extending  from  the  symphysis  of  the  lower  jaw  to  the  hyoid  bone,  where 
they  join  at  an  angle  with  the  fibres  of  the  opposite  muscle.  The  median  raphe 


HYOID  BONE 


FIG.  271. — Mylo-hyoid  muscle.     (Poirier  and  Charpy.) 

is  sometimes  wanting;  the  muscular  fibres  of  the  two  sides    are  then  directly 
continuous  with  one  another. 

Relations. — By  its  cutaneous  or  under  surface,  with  the  Platysma,  the  anterior 
belly  of  the  Digastric,  the  supra-hyoid  aponeurosis,  the  submaxillary  gland,  sub- 
mental  vessels,  and  mylo-hyoid  vessels  and  nerve;  by  its  deep  or  superior  surface, 
with  the  Genio-hyoid,  part  of  the  Hyo-glossus  and  Stylo-glossus  muscles,  the  hypo- 
glossal  and  lingual  nerves,  the  submaxillary  ganglion,  the  sublingual  gland,  the 
deep  portion  of  the  submaxillary  gland,  and  Wharton's  duct;  the  sublingual  and 
ranine  vessels,  and  the  buccal  mucous  membrane. 

Dissection. — The  Mylo-hyoid  should  now  be  removed,  in  order  to  expose  the  muscles  which 
lie  beneath;  this  is  effected  by  reflecting  it  from  its  attachments  to  the  hyoid  bone  and  jaw,  and 
separating  it  by  a  vertical  incision  from  its  fellow  of  the  opposite  side. 

The  Genio-hyoid  (m.  geniohyoideus)  (Fig.  272)  is  a  narrow,  slender  muscle, 
situated  immediately  beneath1  the  inner  border  of  the  preceding.  It  arises  from 
the  inferior  genial  tubercle  on  the  inner  side  of  the  symphysis  of  the  jaw,  and 


1  This  refers  to  the  depth  of  the  muscles  from  the  skin  in  the  order  of  dissection, 
the  body  the  Genio-hyoid  is  above  the  Mylo-hyoid. 


In  the  erect  position  of 


398 


THE  MUSCLES  AND  FASCIAE 


passes  downward  and  backward,  to  be  inserted  into  the  anterior  surface  of  the 
body  of  the  hyoid  bone.  This  muscle  lies  in  close  contact  with  its  fellow  of  the 
opposite  side,  and  increases  slightly  in  breadth  as  it  descends. 

Relations. — It  is  covered  by  the  Mylo-hyoid  and  lies  along  the  lower  border 
of  the  Genio-hyo-glossus. 

Nerves. — The  anterior  belly  of  the  Digastric  is  supplied  by  the  mylo-hyoi<i 
branch  of  the  inferior  dental;  its  posterior  belly,  by  the  facial;  the  Stylo-hyoid 
is  supplied  by  the  facial;  the  Mylo-hyoid,  by  the  mylo-hyoid  branch  of  the 
inferior  dental;  the  Genio-hyoid,  by  the  hypoglossal. 

Actions. — This  group  of  muscles  performs  two  very  important  actions.  *They 
raise  the  hyoid  bone,  and  with  it  the  base  of  the  tongue,  during  the  act  of  degluti- 
tion; or,  when  the  hyoid  bone  is  fixed  by  its  depressors  and  those  of  the  larynx, 
they  depress  the  lower  jaw.  During  the  first  act  of  deglutition,  when  the  mass 
is  being  driven  from  the  mouth  into  the  pharynx,  the  hyoid  bone,  and  with  it  the 
tongue,  is  carried  upward  and  forward  by  the  anterior  belly  of  the  Digastric,  the 
Mylo-hyoid,  and  Genio-hyoid  muscles.  In  the  second  act,  when  the  mass  is  pass- 


FIG.  272.— Muscles  of  the  tongue.     Left  side. 

ing  through  the  pharynx,  the  direct  elevation  of  the  hyoid  bone  takes  place  by  the 
combined  action  of  all  the  muscles;  and  after  the  food  has  passed,  the  hyoid  bone 
is  carried  upward  and  backward  by  the  posterior  belly  of  the  Digastric  and  Stylo- 
hyoid  muscles,  which  assist  in  preventing  the  return  of  the  morsel  into  the  mouth. 

4.  The  Lingual  Region  (Figs.  272,  273). 

Genio-hyo-glossus.  Stylo-glossus. 

Hyo-glossus.  Palato-glossus. 

Chondro-glossus. 


THE  LINGUAL  REGION  399 

Dissection. — After  completing  the  dissection  of  the  preceding  muscles,  saw  through  the 
lower  jaw  just  external  to  the  syraphysis.  Then  draw  the  tongue  forward,  and  attach  it,  by  a 
stitch,  to  the  nose;  when  its  muscles,  which  are  thus  put  on  a  stretch,  may  be  examined. 

The  Genio-hyo-glossus  (m.  genioglossus)  has  received  its  name  from  its  triple 
attachment  to  the  jaw,  hyoid  bone,  and  tongue,  but  it  is  better  to  name  it  the 
Genio-glossus,  since  its  attachment  to  the  hyoid  bone  is  very  slight  or  altogether 
absent.  It  is  a  flat,  triangular  muscle,  placed  vertically  on  either  side  of  the 
middle  line,  its  apex  corresponding  with  its  point  of  attachment  to  the  lower  jaw,  its 
base  with  its  insertion  into  the  tongue  and  hyoid  bone.  It  arises  by  a  short  tendon 
from  the  superior  genial  tubercle  on  the  inner  side  of  the  symphysis  of  the  jaw,  im- 
mediately above  the  Genio-hyoid ;  from  this  point  the  muscle  spreads  out  in  a  fan- 
like  form,  a  few  of  the  inferior  fibres  passing  downward,  to  be  attached  by  a  thin 
aponeurosis  into  the  upper  part  of  the  body  of  the  hyoid  bone,  a  few  fibres  passing 
between  the  Hyo-glossus  and  Chondro-glossus  to  blend  with  the  Constrictor  mus- 
cles of  the  pharynx;  the  middle  fibres  passing  backward,  and  the  superior  ones 
upward  and  forward,  to  enter  the  whole  length  of  the  under  surface  of  the  tongue, 
from  the  base  to  the  apex.  The  two  muscles  lie  on  either  side  of  the  median  plane; 
behind  they  are  quite  distinct  from  each  other,  and  are  separated  at  their  insertion 
into  the  under  surface  of  the  tongue  by  a  tendinous  raphe,  which  extends  through 
the  middle  of  the  organ;  in  front,  the  two  muscles  are  more  or  less  blended :  distinct 
fasciculi  are 'to  be  seen  passing  off  from  one  muscle,  crossing  the  middle  line,  and 
intersecting  with  bundles  of  fibres  derived  from  the  muscle  on  the  other  side. 

Relations. — By  its  internal  surface  it  is  in  contact  with  its  fellow  of  the  opposite 
side;  by  its  external  surface,  with  the  Inferior  lingualis,  the  Hyo-glossus,  the  lin- 
gual artery  and  hypoglossal  nerve,  the  lingual  nerve,  and  sublingual  gland;  by  its 
upper  border,  with  the  mucous  membrane  of  the  floor  of  the  mouth  (fraenum 
linguae);  by  its  lower  border  with  the  Genio-hyoid. 

The  Hyo-glossus  (m.  hyoglossus)  is  a  thin,  flat,  quadrilateral  muscle  which  arises 
from  the  side  of  the  body  and  whole  length  of  the  greater  cornu  of  the  hyoid  bone, 
and  passes  almost  vertically  upward  to  enter  the  side  of  the  tongue,  between  the 
Stylo-glossus  and  Lingualis.  Those  fibres  of  this  muscle  which  arise  from  the 
body  are  directed  upward  and  backward,  overlapping  those  arising  from  the 
greater  cornu,  which  are  directed  upward  and  forward. 

Relations. — By  its  external  surface,  with  the  Digastric,  the  Stylo-hyoid,  Stylo- 
glossus,  and  Mylo-hyoid  muscles,  the  submaxillary  ganglion,  the  lingual  and  hypo- 
glossal  nerves,  Wharton's  duct,  the  ranine  vein,  the  sublingual  gland  j  and  the  deep 
portion  of  the  submaxillary  gland.  By  its  deep  surface,  with  the  Stylo-hyoid  liga- 
ment, the  Genio-hyo-glossus,  Lingualis,  and  Middle  constrictor,  the  lingual  vessels 
and  the  glosso-pharyngeal  nerve. 

The  Chondro-glossus  (TO.  chondroglossus)  is  a  distinct  muscular  slip,  though  it  is 
sometimes  described  as  a  part  of  the  Hyo-glossus,  from  which,  however,  it  is  sepa- 
rated by  the  fibres  of  the  Genio-hyo-glossus,  which  pass  to  the  side  of  the  pharynx. 
It  is  about  three-quarters  to  an  inch  in  length,  and  arises  from  the  inner  side  and 
base  of  the  lesser  cornu  and  contiguous  portion  of  the  body  of  the  hyoid  bone, 
and  passes  directly  upward  to  blend  with  the  intrinsic  muscular  fibres  of  the  tongue, 
between  the  Hyo-glossus  and  Genio-hyo-glossus.  A  small  slip  of  muscular  fibre 
is  occasionally  found,  arising  from  the  cartilage  triticea  in  the  thyro-hyoid  ligament, 
and  passing  upward  and  forward  to  enter  the  tongue  with  the  hindermost  fibres  of 
the  Hyo-glossus. 

The  Stylo-glossus  (TO.  styloglossus) ,  the  shortest  and  smallest  of  the  three  styloid 
muscles,  arises  from  the  anterior  and  outer  side  of  the  styloid  process,  near  its  apex, 
and  from  the  stylo-mandibular  ligament,  to  which  its  fibres,  in  most  cases,  are 
attached  by  a  thin  aponeurosis.  Passing  downward  and  forward  between  the  inter- 
nal and  external  carotid  arteries,  and  becoming  nearly  horizontal  in  its  direction, 
it  divides  upon  the  side  of  the  tongue  into  two  portions :  one  longitudinal,  which 


400 


THE  MUSCLES  AND  FASCIAE 


enters  the  side  of  the  tongue  near  its  dorsal  surface,  blending  with  the  fibres  of  the 
Lingualis  in  front  of  the  Hyo-glossus;  the  other  oblique,  which  overlaps  the 
Hyo-glossus  muscle  and  decussates  with  its  fibres. 

Relations. — By  its  external  surface,  from  above  downward,  with  the  parotid 
gland,  the  Internal  pterygoid  muscle,  the  lingual  nerve,  and  the  mucous  membrane 
of  the  mouth;  by  its  internal  surface,  with  the  tonsil,  the  Superior  constrictor,  and 
the  Hyo-glossus  muscle. 

The  Palato-glossus  or  Constrictor  Isthmi  Faucium  (m.  glossopalatinus) , 
although  it  is  one  of  the  muscles  of  the  tongue,  serving  to  draw  its  base  upward 
during  the  act  of  deglutition,  is  more  nearly  associated  with  the  soft  palate,  both 
in  its  situation  and  function ;  it  will  consequently  be  described  with  that  group  of 
muscles. 

Nerves. — The  Palato-glossus  is  probably  innervated  by  the  accessory  nerve , 
through  the  pharyngeal  plexus;  the  remaining  muscles  of  this  group,  by  the  hypo- 
glossal  nerve. 

Muscular  Substance  of  the  Tongue  (Figs.  273  and  274). — The  muscular 
fibres  of  the  tongue  run  in  various  directions.  These  fibres  are  divided  into  two 
sets — Extrinsic  and  Intrinsic.  The  extrinsic  muscles  of  the  tongue  are  those 
which  have  their  origin  external,  and  only  their  terminal  fibres  contained  in  the 
substance  of  the  organ.  They  are :  the  Stylo-glossus,  the  Hyo-glossus,  the  Palato- 
glossus,  the  Genio-hyo-glossus,  and  part  of  the 
Superior  constrictor  of  the  pharynx  (Pharyngeo- 
glossus).  The  intrinsic  muscles  are  those  which 
are  contained  entirely  within  the  tongue,  and 
form  the  greater  part  of  its  muscular  struc- 
ture. 


CUT   EDGE    OF  SUPERIOR    LINGUALIS. 


FIG.  273.- 


-Muscles  on  the  dorsum  of  the 
tongue. 


FIG.  274.- — Coronal  section  of  tongue.  Showing  intrinsic 
muscles,  a,  lingual  artery;  b.  Inferior  lingualis,  cut  through; 
c,  fibres  of  Hyo-glossus;  d,  oblique  fibres  of  Stylo-glossus;  e,  in- 
sertion of  Transverse  lingualis;  /,  Superior  lingualis;  g,  papillae 
to  tongue;  h,  vertical  fibres  of  Genio-hyo-glossus  intersecting 
Transverse  lingualis;  i,  septum.  (Altered  from  Krause.) 


The  tongue  consists  of  symmetrical  halves  separated  from  each  other  in  the 
middle  line  by  a  fibrous  septum  (septum  linguae}.  Each  half  is  composed  of 
muscular  fibres  arranged  in  various  directions,  containing  much  interposed  fat, 
and  supplied  by  vessels  and  nerves. 

To  demonstrate  the  various  fibres  of  the  tongue,  the  organ  should  be  subjected  to 
prolonged  boiling,  in  order  to  soften  the  connective  tissue;  the  dissection  may  then 
be  commenced  from  the  dorsum  (Figs.  273  and  274).  Immediately  beneath  the 


THE  LINGUAL  REGION  401 

« 

mucous  membrane  is  a  submucous,  fibrous  layer,  into  which  the  muscular  fibres 
which  terminate  on  the  surface  of  the  tongue  are  inserted.  Upon  removing  this, 
with  the  mucous  membrane,  the  first  stratum  of  muscular  fibres  is  exposed. 
This  belongs  to  the  group  of  intrinsic  muscles,  and  has  been  named  the  Superior 
lingualis  (ra.  longitudinalis  superior).  It  consists  of  a  thin  layer  of  oblique  and 
longitudinal  fibres  which  arise  from  the  submucous  fibrous  layer,  close  to  the 
Epiglottis,  and  from  the  fibrous  septum,  and  pass  forward  and  outward  to  the 
edges  of  the  tongue.  Between  its  fibres  pass  some  vertical  fibres  derived  from 
the  Genio-hyo-glossus  and  from  the  vertical  intrinsic  muscle,  which  will  be  de- 
scribed later  on.  Beneath  this  layer  is  the  second  stratum  of  muscular  fibres, 
derived  principally  from  the  extrinsic  muscles.  In  front  it  is  formed  by  the  fibres 
derived  from  the  Stylo-glossus,  running  along  the  side  of  the  tongue,  and  sending 
one  set  of  fibres  over  the  dorsum  which  run  obliquely  forward  and  inward  to  the 
middle  line,  and  another  set  of  fibres  seen  at  a  later  period  of  the  dissection,  on  to 
the  under  surface  of  the  sides  of  the  anterior  part  of  the  tongue,  which  run  forward 
and  inward,  between  the  fibres  of  the  Hyo-glossus,  to  the  middle  line.  Behind  this 
layer  of  fibres,  derived  from  the  Stylo-glossus,  are  fibres  derived  from  the  Hyo- 
glossus,  assisted  by  some  few  fibres  of  the  Palato-glossus.  The  Hyo-glossus,  enter- 
ing the  side  of  the  under  surface  of  the  tongue,  between  the  Stylo-glossus  and 
Inferior  lingualis,  passes  round  its  margin  and  spreads  out  into  a  layer  on  the  dor- 
sum,  which  occupies  the  middle  third  of  the  organ,  and  runs  almost  transversely 
inward  to  the  septum.  It  is  reinforced  by  some  fibres  from  the  Palato-glossus; 
other  fibres  of  this  muscle  pass  more  deeply  and  intermingle  with  the  next  layer. 
The  posterior  part  of  the  second  layer  of  the  muscular  fibres  of  the  tongue  is 
derived  from  those  fibres  of  the  Hyo-glossus  which  arise  from  the  lesser  cornu  of 
thehyoid  bone,  and  are  here  described  as  a  separate  muscle — theChondro-glossus. 
The  fibres  of  this  muscle  are  arranged  in  a  fan-shaped  manner,  and  spread  out  over 
the  posterior  third  of.the  tongue.  Beneath  this  layer  is  the  great  mass  of  the  intrin- 
sic muscles  of  the  tongue,  intersected  at  right  angles  by  the  terminal  fibres  of  one  of 
the  extrinsic  muscles — the  Genio-hyo-glossus.  This  portion  of  the  tongue  is  paler 
in  color  and  softer  in  texture  than  that  already  described,  and  is  sometimes 
designated  the  medullary  portion  in  contradistinction  to  the  firmer  superficial  part, 
which  is  termed  the  cortical  portion.  It  consists  largely  of  transverse  fibres,  the 
Transverse  lingualis  (m.  transversus  linguae),  and  of  vertical  fibres,  the  Vertical 
lingualis  (m.  verticalis  linguae).  The  Transverse  lingualis  forms  the  largest  portion 
of  the  third  layer  of  muscular  fibres  of  the  tongue.  The  fibres  arise  from  the 
median  septum,  and  pass  outward  to  be  inserted  into  the  submucous  fibrous  layer 
at  the  sides  of  the  tongue.  Intermingled  with  these  transverse  intrinsic  fibres  are 
transverse  extrinsic  fibres  derived  from  the  Palato-glossus  and  the  Superior  con- 
strictor of  the  pharynx.  These  transverse  extrinsic  fibres,  however,  run  in  the 
opposite  direction,  passing  inward  toward  the  septum.  Intersecting  the  transverse 
fibres  are  a  large  number  of  vertical  fibres  derived  partly  from  the  Genio-hyo- 
glossus  and  partly  from  intrinsic  fibres,  the  Vertical  lingualis.  The  fibres  derived 
from  the  Genio-hyo-glossus  enter  the  under  surface  of  the  tongue  on  each  side  of 
the  median  septum  from  base  to  apex.  They  ascend  in  a  radiating  manner  to  the 
dorsum,  being  inserted  into  the  submucous  fibrous  layer  covering  the  tongue  on 
each  side  of  the  middle  line.  The  Vertical  lingualis  is  found  only  at  the  borders 
of  the  forepart  of  the  tongue,  external  to  the  fibres  of  the  Genio-hyo-glossus. 
Its  fibres  extend  from  the  upper  to  the  under  surface  of  the  organ,  decussating 
writh  the  fibres  of  the  other  muscles,  and  especially  with  the  Transverse  lingualis. 
The  fourth  layer  of  muscular  fibres  of  the  tongue  consists  partly  of  extrinsic  fibres 
derived  from  the  Stylo-glossus,  and  partly  of  intrinsic  fibres,  the  Inferior  lingualis 
(m.  longitudinalis  inferior).  At  the  sides  of  the  under  surface  of  the  organ  are 
some  fibres  derived  from  the  Stylo-glossus,  which,  as  it  runs  forward  at  the  side  of 

26 


402  THE  MUSCLES  AND  FASCIAE 

the  tongue,  gives  off  fibres  which,  passing  forward  and  inward  between  the  fibres 
of  the  Hyo-glossus,  form  an  inferior  oblique  stratum  which  joins  in  front  with  the 
anterior  fibres  of  the  Inferior  lingualis.  The  Inferior  lingualis  is  a  longitudinal 
band,  situated  on  the  under  surface  of  the  tongue,  and  extending  from  the  base  to 
the  apex  of  the  organ.  Behind,  some  of  its  fibres  are  connected  with  the  body  of 
the  hyoid  bone.  It  lies  between  the  Hyo-glossus  and  the  Genio-hyo-glossus,  and 
in  front  of  the  Hyo-glossus  it  enters  into  relation  with  the  Stylo-glossus,  with  the 
fibres  of  which  it  blends.  It  is  in  relation  by  its  under  surface  with  the  ranine 
artery. 

Surgical  Anatomy. — The  fibrous  septum  which  exists  between  the  two  halves  of  the  tongue 
is  very  complete,  so  that  the  anastomosis  between  the  two  lingual  arteries  is  not  very  free, 
a  fact  often  illustrated  by  injecting  one-half  of  the  tongue  with  colored  size,  while  the  other 
half  is  left  uninjected  or  is  injected  with  size  of  a  different  color. 

This  is  a  point  of  considerable  importance  in  connection  with  removal  of  one-half  of  the 
tongue  for  cancer,  an  operation  which  is  now  frequently  resorted  to  when  the  disease  is  strictly 
confined  to  one  side  of  the  anterior  portion  of  the  tongue.  If  the  mucous  membrane  is  divided 
longitudinally  exactly  in  the  middle  line,  the  tongue  can  be  split  into  halves  along  the  median 
raph£  without  any  appreciable  hemorrhage,  and  the  diseased  half  can  then  be  removed. 

Actions. — The  movements  of  the  tongue,  although  numerous  and  complicated, 
may  be  understood  by  carefully  considering  the  direction  of  the  fibres  of  its 
muscles.  The  Genio-hyo-glossi  muscles,  by  means  of  their  posterior  fibres,  draw 
the  base  of  the  tongue  forward,  so  as  to  protrude  the  apex  from  the  mouth.  The 
anterior  fibres  draw  the  tongue  back  into  the  mouth.  The  whole  length  of  these 
two  muscles,  acting  along  the  middle  line  of  the  tongue,  draw  it  downward,  so  as  to 
make  it  concave  from  side  to  side,  forming  a  channel  along  which  fluids  may  pass 
toward  the  pharynx,  as  in  sucking.  The  Hyo-glossi  muscles  depress  the  tongue 
and  draw  down  its  sides,  so  as  to  render  it  convex  from  side  to  side.  The  Stylo- 
glossi  muscles  draw  the  tongue  upward  and  backward.  The  Palato-glossi  muscles 
draw  the  base  of  the  tongue  upward.  With  regard  to  the  intrinsic  muscles,  both 
the  Superior  and  Inferior  linguales  tend  to  shorten  the  tongue,  but  the  former,  in 
addition,  turn  the  tip  and  sides  upward  so  as  to  render  the  dorsum  concave,  while 
the  latter  pull  the  tip  downward  and  cause  the  dorsum  to  become  convex.  The 
Transverse  lingualis  narrows  and  elongates  the  tongue,  and  the  Vertical  lingualis 
flattens  and  broadens  it.  The  complex  arrangement  of  the  muscular  fibres  of 
the  tongue,  and  the  various  directions  in  which  they  run,  give  to  this  organ  the 
power  of  assuming  the  various  forms  necessary  for  the  enunciation  of  the  different 
consonantal  sounds;  and  Dr.  Macalister  states  that  "there  is  reason  to  believe 
that  the  musculature  of  the  tongue  varies  in  different  races  owing  to  the  hereditary 
practice  and  habitual  use  of  certain  motions  required  for  enunciating  the  several 
vernacular  languages." 

5.  The  Pharyngeal  Region  (Figs.  275,  276,  277). 

Inferior  constrictor.  Superior  constrictor. 

Middle  constrictor.  Stylo-pharyngeus. 

Palato-pharyngeus.      ) 

Salpingo-pharyngeus.  / 

Dissection  (Fig.  275). — In  order  to  examine  the  muscles  of  the  pharynx,  cut  through  the 
trachea  and  oesophagus  just  above  the  sternum,  and  draw  them  upward  by  dividing  the  loose 
areolar  tissue  connecting  the  pharynx  with  the  front  of  the  vertebral  column.  The  parts  being 
drawn  well  forward,  apply  the  edge  of  the  saw  immediately  behind  the  styloid  processes,  and 
saw  the  base  of  the  skull  through  from  below  upward.  The  pharynx  and  mouth  should  then 
be  stuffed  with  tow,  in  order  to  distend  its  cavity  and  render  the  muscles  tense  and  easier  of 
dissection. 

The  Inferior  Constrictor  (m.  constrictor  pharyngis  inferior) ,  the  most  superficial 
and  thickest  of  the  three  constrictors,  arises  from  the  sides  of  the  cricoid  and 


THE  PHARYNGEAL  REGION 


403 


thyroid  cartilages.  To  the  cricoid  cartilage  it  is  attached  in  the  interval  between 
the  Crico-thyroid  muscle  in  front  and  the  articular  facet  for  the  thyroid  cartilage 
behind.  To  the  thyroid  cartilage  it  is  attached  to  the  oblique  line  on  the  side  of 
the  great  ala,  the  cartilaginous  surface  behind  it,  nearly  as  far  as  its  posterior  border, 
and  to  the  inferior  cornu.  From  these  attachments  the  fibres  spread  backward  and 
inward,  to  be  inserted  into  the  fibrous  raphe*  in  the  posterior  median  line  of  the 
pharynx.  The  inferior  fibres  are  horizontal,  and  continuous  with  the  fibres  of  the 
oesophagus:  the  rest  ascend,  increasing  in  obliquity,  and  overlap  the  Middle  con^ 
stricter. 

Relations. — It  is  covered  bv  a  thin  membrane  which  surrounds  the  entire 
pharynx,  bucco-pharyngeal  fascia  (fascia  buccopharyngea) .  Behind,  it  is  in 
relation  with  the  vertebral  column 
and  the  prevertebral  fascia  and  mus- 
cles; laterally,  with  the  thyroid  gland, 
the  common  carotid  artery,  and  the 
Sterno-thyroid  muscle;  by  its  internal 
surface,  with  the  Middle  constrictor, 
the  Stylo-pharyngeus,  Palato-pharyn- 
geus,  the  fibrous  coat  and  mucous 
membrane  of  the  pharynx.  The  in- 
ternal laryngeal  nerve  and  the  laryn- 
geal  branch  of  the  Superior  Thyroid 
artery  pass  near  the  upper  border,  and 
the  inferior,  or  recurrent  laryngeal 
nerve,  and  the  laryngeal  branch  of  the 
Inferior  Thyroid  artery,  beneath  the 
lower  border  of  this  muscle,  previous  to 
their  entering  the  larynx. 

The  Middle  Constrictor  (m.  constric- 
tor pharyngis  medius)  is  a  flattened, 
fan-shaped  muscle,  smaller  than  the 
preceding.  It  arises  from  the  whole 
length  of  the  upper  border  of  the 
greater  cornu  of  the  hyoid  bone,  from 
the  lesser  cornu,  and  from  the  stylo- 
hyoid  ligament.  The  fibres  diverge 
from  their  origin,  the  lower  ones  de- 
scending beneath  the  Inferior  con- 
strictor, the  middle  fibres  passing 
transversely,  and  the  upper  fibres  ascending  and  overlapping  the  Superior  con- 
strictor. The  muscle  is  inserted  into  the  posterior  median  fibrous  raphe",  blending 
in  the  middle  line  with  the  one  of  the  opposite  side. 

Relations. — Between  this  muscle  and  the  Superior  constrictor  are  the  glosso- 
pharyngeal  nerve,  the  Stylo-pharyngeus  muscle  and  the  stylo-hyoid  ligament; 
and  between  it  and  the  Inferior  constrictor  is  the  superior  laryngeal  nerve. 
Behind,  it  lies  on  the  vertebral  column,  the  Longus  colli,  and  the  Rectus  capitis 
anticus  major.  On  each  side  it  is  in  relation  with  the  carotid  vessels,  the  pharyn- 
geal  plexus,  and  some  lymphatic  glands.  Near  its  origin  it  is  covered  by  the 
Hyo-glossus,  the  lingual  vessels  being  placed  between  the  two  muscles.  It  lies 
upon  the  Superior  constrictor,  the  Stylo-pharyngeus,  the  Palato-pharyngeus,  the 
fibrous  coat,  and  the  mucous  membrane  of  the  larynx. 

The  Superior  Constrictor  (m.  constrictor  pharyngis  superior)  is  a  quadrilateral 
muscle,  thinner  and  paler  than  the  other  constrictors,  and  situated  at  the  upper 
part  of  the  pharynx.  It  arises  from  the  lower  third  of  the  posterior  margin  of  the 


FIG.  275. — Muscles  of  the  pharynx.     External  view. 


404 


THE  MUSCLES  AND  FASCIA 


internal  pterygoid  plate  and  its  hamular  process  from  the  contiguous  portion  of  the 
palate  bone  and  the  reflected  tendon  of  the  Tensor  palati  muscle,  from  the  pterygo- 
maxillary  ligament,  from  the  alveolar  process  above  the  posterior  extremity  of  the 
mylo-hyoid  ridge,  and  by  a  few  fibres  from  the  side  of  the  tongue.  From  these 
points  the  fibres  curve  backward,  to  be  inserted  into  the  median  raphe",  being  also 
prolonged  by  means  of  a  fibrous  aponeurosis  to  the  pharyngeal  spine  on  the  basilar 
process  of  the  occipital  bone.  The  superior  fibres  arch  beneath  the  Levator  palati 
and  the  Eustachian  tube,  the  interval  between  the  upper  border  of  the  muscle  and 
the  basilar  process  being  deficient  in  muscular  fibres  and  closed  by  a  portion 
of  the  pharyngeai  aponeurosis  (fascia  pharyngobasilaris) .  This  interval  is  known  as 
the  sinus  of  Morgagni. 


ACCESSORY  BUNDLE 
FROM  PETROSAL  PO 
TION  OF  TEMPORAL 


8TYLOID  PROCESS 


EXPANSION  OF 
STYLO-PHARYNGEUS 


EXPANSION   OF 
PALATO-PHARYNGEUS 


FIG.  276. — The  muscles  of  the  pharynx.     On  the  right  side  most  of  the  inferior  constrictor  has  been  removed, 
on  the  left  side  the  Digastric  and  Stylo-hyoid  have  been  removed.     (Spalteholz.) 

Relations. — By  its  outer  surface,  with  the  prevertebral  fascia  and  muscles, 
the  vertebral  column,  the  internal  carotid  and  ascending  pharyngeal  arteries,  the 
internal  jugular  vein  and  pharyngeal  venous  plexus,  the  glosso-pharyngeal,  vagus, 
accessory,  hypoglossal,  lingual,  and  sympathetic  nerves,  the  Middle  constrictor 


THE  PALATAL  REGION  405 

and  Internal  pterygoid  muscles,  the  Styloid  process,  the  Stylo-hyoid  ligament, 
and  the  Stylo-pharyngeus.  By  its  internal  surface,  with  the  Palato-pharyngeus, 
the  tonsil,  the  fibrous  coat  and  mucous  membrane  of  the  pharynx. 

The  Stylo-pharyngeus  (m.  stylopharyngeus)  is  a  long,  slender  muscle,  round 
above,  broad  and  thin  below.  It  arises  from  the  inner  side  of  the  base  of  the 
styloid  process  of  the  temporal  bone,  passes  down  ward,  along  the  side  of  the 
pharynx  between  the  Superior  and  Middle  constrictors,  and  spreads  out  beneath 
the  mucous  membrane,  where  some  of  its  fibres  are  lost  in  the  Constrictor  muscles; 
and  others,  joining  with  the  Palato-pharyngeus,  are  inserted  into  the  posterior 
border  of  the  thyroid  cartilage.  The  glosso-pharyngeal  nerve  runs  on  the  outer 
side  of  this  muscle,  and  crosses  over  it  in  passing  forward  to  the  tongue. 

Relations. — Externally,  with  the  Stylo-glossus  muscle,  the  parotid  gland,  the 
external  carotid  artery,  and  the  Middle  constrictor;  internally,  with  the  internal 
carotid,  the  internal  jugular  vein,  the  Superior  constrictor,  Palato-pharyngeus, 
and  mucous  membrane. 

Nerves. — The  Constrictors  are  supplied  by  branches  from  the  pharyngeal 
plexus.  The  Inferior  constrictor  also  receives  an  additional"  branch  from  the 
external  laryngeal  nerve  and  one  from  the  recurrent  laryngeal.  The  Stylo- 
pharyngeus  is  supplied  by  the  glosso-pharyngeal  nerve. 

Actions. — When  deglutition  is  about  to  be  performed,  the  pharynx  is  drawn 
upward  and  dilated  in  different  directions,  to  receive  the  morsel  propelled  into  it 
from  the  mouth.  The  Stylo-pharyngei,  which  are  much  farther  removed  from 
one  another  at  their  origin  than  at  their  insertion,  draw  the  sides  of  the  pharynx 
upward  and  outward,  and  so  increase  its  transverse  diameter,  its  breadth  in  the 
antero-posterior  direction  being  increased  by  the  larynx  and  tongue  being  carried 
forward  in  their  ascent.  As  soon  as  the  morsel  is  received  in  the  pharynx,  the 
Elevator  muscles  relax,  the  bag  descends,  and  the  Constrictors  contract  upon 
the  morsel,  and  convey  it  gradually  downward  into  the  oesophagus.  Besides  its 
action  in  deglutition,  the  pharynx  also  exerts  an  important  influence  in  the  modu- 
lation of  the  voice,  especially  in  the  production  of  the  higher  tones. 

6.  The  Palatal  Region  (Fig.  277). 

Levator  palati.  Palato-glossus. 

Tensor  palati.  Palato-pharyngeus. 

Azygos  uvulae.  Salpingo-pharyngeus. 

Dissection  (Fig.  277). — Lay  open  the  pharynx  from  behind  by  a  vertical  incision  extending 
from  its  upper  to  its  lower  part,  and  partially  divide  the  occipital  attachment  by  a  transverse 
incision  on  each  side  of  the  vertical  one;  the  posterior  surface  of  the  soft  palate  is  then  exposed. 
Having  fixed  the  uvula  so  as  to  make  it  tense,  the  mucous  membrane  and  glands  should  be 
carefully  removed  from  the  posterior  surface  of  the  soft  palate,  and  the  muscles  of  this  part 
are  at  once  exposed. 

The  Levator  Palati  (m.  levator  veli  palatini)  is  a  long,  thick,  rounded  muscle, 
placed  on  the  outer  side  of  the  posterior  nares.  It  arises  from  the  under  surface  of 
the  apex  of  the  petrous  portion  of  the  temporal  bone,  and  from  the  inner  surface 
of  the  cartilaginous  portion  of  the  Eustachian  tube;  after  passing  into  the  pharynx, 
above  the  upper  concave  margin  of  the  Superior  constrictor,  it  passes  obliquely 
downward  and  inward,  its  fibres  spreading  out  in  the  soft  palate  as  far  as  the 
middle  line,  where  they  blend  with  those  of  the  opposite  side. 

Relations. — Externally,  with  the  Tensor  palati  and  Superior  constrictor  and 
Eustachian  tube;  internally,  with  the  mucous  membrane  of  the  pharynx;  pos- 
teriorly, with  the  posterior  fasciculus  of  the  Palato-pharyngeus,  the  Azygos  uvulae, 
and  the  mucous  lining  of  the  soft  palate. 


406 


THE  MUSCLES  AND   FASCIAE 


The  Circumflexus  or  Tensor  Palati  (m.  tensor  veli  palatini)  is  a  broad,  thin, 
ribbon-like  muscle,  placed  on  the  outer  side  of  the  Levator  palati,  and  consisting  of 
a  vertical  and  a  horizontal  portion.  The  vertical  portion  arises  by  a  flat  lamella 
from  the  scaphoid  fossa  at  the  base  of  the  internal  pterygoid  plate;  from  the  spine 
of  the  sphenoid  and  the  outer  side  of  the  cartilaginous  portion  of  the  Eustachian 
tube:  descending  vertically  between  the  internal  pterygoid  plate  and  the  inner  sur- 
face of  the  Internal  pterygoid  muscle,  it  terminates  in  a  tendon,  which  winds  round 
the  hamular  process,  being  retained  in  this  situation  by  some  of  the  fibres  of  origin 
of  the  Internal  pterygoid  muscle.  Between  the  hamular  process  and  the  tendon  is 
a  small  bursa  (bursa  m.  tensoris  veli  palati) .  The  tendon  or  horizontal  portion  then 


FIG.  277. — Muscles  of  the  soft  palate,  the  pharynx  being  laid  open  from  behind. 

passes  horizontally  inward,  and  is  inserted  into  a  broad  aponeurosis,  the  palatine 
aponeurosis,  and  into  the  transverse  ridge  on  the  horizontal  portion  of  the  palate 
bone. 

Relations. — Externally,  with  the  Internal  pterygoid;  internally,  with  the  Levator 
palati,  from  which  it  is  separated  by  the  Eustachian  tube  and  Superior  constrictor 
and  with  the  internal  pterygoid  plate.  In  the  soft  palate  its  tendon  and  the  pala- 
tine aponeurosis  are  anterior  to  those  of  the  Levator  palati,  being  covered  by  the 
Palato-glossus  and  the  mucous  membrane. 

Palatine  Aponeurosis.— Attached  to  the  posterior  border  of  the  hard  palate  is 
a  thin,  firm,  fibrous  lamella  which  supports  the  muscles  and  gives  strength  to  the 
soft  palate.  It  is  thicker  above  than  below,  where  it  becomes  very  thin  and 
difficult  to  define.  Laterally,  it  is  continuous  with  the  pharyngeal  aponeurosis. 


THE  PALATAL   REGION  407 

The  Azygos  Uvulae  (m.  uvulae)  is  not  a  single  muscle,  as  would  be  inferred  from 
its  name,  but  a  pair  of  narrow  cylindrical  fleshy  fasciculi  placed  on  either  side  of  the 
median  line  of  the  soft  palate.  Each  muscle  arises  from  the  posterior  nasal  spine 
of  the  palate  bone  and  from  the  contiguous  tendinous  aponeurosis  of  the  soft  palate, 
and  descends  to  be  inserted  into  the  uvula. 

Relations. — Anteriorly,  with  the  tendinous  expansion  of  the  Levatores  palati; 
behind,  with  the  posterior  fasciculus  of  the  Palato-pharyngeus  and  the  mucous 
membrane. 

The  next  two  muscles  are  exposed  by  removing  the  mucous  membrane  from  the  pillars  of 
the  fauces  throughout  nearly  their  whole  extent. 

The  Palato-glossus  or  the  Constrictor  Isthmi  Faucium  (m.  glossopalatinus) 
is  a  small  fleshy  fasciculus,  narrower  in  the  middle  than  at  either  extremity, 
forming,  with  the  mucous  membrane  covering  its  surface,  the  anterior  pillar  of 
the  soft  palate.  It  arises  from  the  anterior  surface  of  the  soft  palate  on  each 
side  of  the  uvula,  and,  passing  downward,  forward,  and  outward  in  front  of  the 
tonsil,  is  inserted  into  the  side  of  the  tongue,  some  of  its  fibres  spreading  over 
the  dorsum,  and  others  passing  deeply  into  the  substance  of  the  organ  to  inter- 
mingle with  the  Transverse  lingualis.  In  the  soft  palate  the  fibres  of  this  muscle 
are  continuous  with  those  of  the  muscle  of  the  opposite  side. 

The  Palato-pharyngeus  (m.  pharyngopalatinus)  is  a  long,  fleshy  fasciculus, 
narrower  in  the  middle  than  at  either  extremity,  forming,  with  the  mucous 
membrane  covering  its  surface,  the  posterior  pillar  of  the  soft  palate.  It  is  sepa- 
rated from  the  Palato-glossus  by  an  angular  interval,  in  which  the  tonsil  is 
lodged.  It  arises  from  the  soft  palate  by  an  expanded  fasciculus,  which  is 
divided  into  two  parts  by  the  Levator  palati  and  Azygos  uvulae.  The  posterior 
fasciculus  lies  in  contact  with  the  mucous  membrane,  and  also  joins  with  the 
corresponding  muscle  in  the  middle  line;  the  anterior  fasciculus,  the  thicker,  lies 
in  the  soft  palate  between  the  Levator  and  Tensor,  and  joins  in  the  middle  line 
the  corresponding  part  of  the  opposite  muscle.  Passing  outward  and  downward 
behind  the  tonsil,  the  Palato-pharyngeus  joins  the  Stylo-pharyngeus,  and  is 
inserted  with  that  muscle  into  the  posterior  border  of  the  thyroid  cartilage,  some 
of  its  fibres  being  lost  on  the  side  of  the  pharynx,  and  others  passing  across  the 
middle  line  posteriorly  to  decussate  with  the  muscle  of  the  opposite  side. 

Relations. — In  the  soft  palate  its  posterior  surface  is  covered  by  mucous  mem- 
brane, from  which  it  is  separated  by  a  layer  of  palatine  glands.  By  its  anterior 
surface  it  is  in  relation  with  the  Tensor  palati.  Where  it  forms  the  posterior  pillar 
of  the  fauces  it  is  covered  by  mucous  membrane,  excepting  on  its  outer  surface.  In 
the  pharynx  it  lies  between  the  mucous  membrane  and  the  Constrictor  muscles. 

The  Salpingo-pharyngeus  arises  from  the  inferior  part  of  the  Eustachian  tube 
near  its  orifice;  it  passes  downward  and  blends  with  the  posterior  fasciculus  of 
the  Palato-pharyngeus. 

In  a  dissection  of  the  soft  palate  from  its  posterior  or  nasal  surface  to  its  ante- 
rior or  oral  surface,  the  muscles  would  be  exposed  in  the  following  order — viz.,  the 
posterior  fasciculus  of  the  Palato-pharyngeus,  covered  over  by  the  mucous  mem- 
brane reflected  from  the  floor  of  the  nasal  fossae;  the  Azygos  uvulae;  the  Levator 
palati;  the  anterior  fasciculus  of  the  Palato-pharyngeus;  the  aponeurosis  of  the 
Tensor  palati,  and  the  Palato-glossus,  covered  over  by  a  reflection  from  the  oral 
mucous  membrane. 

Nerves. — The  Tensor  palati  is  supplied  by  a  branch  from  the  otic  ganglion; 
the  remaining  muscles  of  this  group  are  in  all  probability  supplied  by  the  internal 
branch  of  the  accessory,  whose  fibres  are  distributed  along  with  certain  branches 
of  the  vagus  through  the  pharyngeal  plexus.1  It  is  possible,  however,  that  the 

1  Journal  of  Anatomy  and  Physiology,  vol.  xxiii,  p.  523. 


408  THE  MUSCLES  AND  FASCIA 

Levator  palati  may  be  supplied  by  the  facial  through  the  Petrosal  branch  of  the 
Vidian. 

Actions. — During  the  first  stage  of  deglutition  the  morsel  of  food  is  driven 
back  into  the  fauces  by  the  pressure  of  the  tongue  against  the  hard  palate,  the 
base  of  the  tongue  being,  at  the  same  time,  retracted,  and  the  larynx  raised  with 
the  pharynx,  and  carried  forward  under  it.  During  the  second  stage  the  entrance 
to  the  larynx  is  closed,  not,  as  was  formerly  supposed,  by  the  folding  backward 
of  the  epiglottis  over  it,  but,  as  Anderson  Stuart  has  shown,  by  the  drawing 
forward  of  the  arytenoid  cartilages  toward  the  cushion  of  the  epiglottis — a  move- 
ment produced  by  the  contraction  of  the  External  thyro-arytenoid,  the  Arytenoid, 
and  Aryteno-epiglottidean  muscles. 

The  morsel  of  food  after  leaving  the  tongue  passes  on  to  the  posterior  or  laryn- 
geal  surface  of  the  epiglottis,  and  glides  along  this  for  a  certain  distance;1  then 
the  Palato-glossi  muscles,  the  constrictors  of  the  fauces,  contract  behind  the  food; 
the  soft  palate  is  slightly  raised  by  the  Levator  palati,  and  made  tense  by  the 
Tensor  palati;  and  the  Palato-pharyngei,  by  their  contraction,  pull  the  pharynx 
upward  over  the  morsel  of  food,  and  at  the  same  time  come  nearly  together,  the 
uvula  filling  up  the  slight  interval  between  them.  By  these  means  the  food  is 
prevented  passing  into  the  upper  part  of  the  larynx  or  the  posterior  nares;  at 
the  same  time  the  latter  muscles  form  an  inclined  plane,  directed  obliquely  down- 
ward and  backward,  along  the  under  surface  of  which  the  morsel  descends  into 
the  lower  part  of  the  pharynx.  The  Salpingo-pharyngeus  raises  the  upper  and 
lateral  part  of  the  pharynx — i.  e.,  that  part  which  is  above  the  point  where  the 
Stylo-pharyngeus  is  attached  to  the  pharynx. 

Surgical  Anatomy. — The  muscles  of  the  soft  palate  should  be  carefully  dissected,  the  rela- 
tions they  bear  to  the  surrounding  parts  especially  examined,  and  their  action  attentively  studied 
upon  the  dead  subject,  as  the  surgeon  is  required  to  divide  orie  or  more  of  these  muscles  in  the 
operation  of  staphylorraphy.  Sir  W.  Fergusson  was  the  first  to  show  that  in  the  congenital 
deficiency  called  deft  palate  the  edges  of  the  fissure  are  forcibly  separated  by  the  action  of  the 
Levatores  palati  and  Palato-pharyngei  muscles,  producing  very  considerable  impediment  to  the 
healing  process  after  the  performance  of  the  operation  for  uniting  their  margins  by  adhesion ;  he 
consequently  recommended  the  division  of  these  muscles  as  one  of  the  most  important  steps  in 
the  operation.  This  he  effected  by  an  incision  made  with  a  curved  knife  introduced  behind  the 
soft  palate.  The  incision  is  to  be  half-way  between  the  hamular  process  and  Eustachian  tube 
and  perpendicular  to  a  line  drawn  between  them.  This  incision  perfectly  accomplishes  the 
division  of  the  Levator  palati.  The  Palato-pharyngeus  may  be  divided  by  cutting  across  the 
posterior  pillar  of  the  soft  palate,  just  below  the  tonsil,  with  a  pair  of  blunt-pointed  curved 
scissors;  and  the  anterior  pillar  may  be  divided  also.  To  divide  the  Levator  palati  the  plan 
recommended  by  Mr.  Pollock  is  to  be  greatly  preferred.  The  soft  palate  being  put  upon  the 
stretch,  a  double-edged  knife  is  passed  through  it  just  on  the  inner  side  of  the  hamular  process 
and  above  the  line  of  the  Levator  palati.  The  handle  being  now  alternately  raised  and  depressed, 
a  sweeping  cut  is  made  along  the  posterior  surface  of  the  soft  palate,  and  the  knife  withdrawn, 
leaving  only  a  small  opening  in  the  mucous  membrane  on  the  anterior  surface.  If  this  operation 
is  performed  on  the  dead  body  and  the  parts  afterward  dissected,  the  Levator  palati  will  be 
found  completely  divided.  In  the  present  day,  however,  this  division  of  the  muscles,  as  part 
of  the  operation  of  staphylorraphy,  is  not  so  much  insisted  upon.  All  tension  is  prevented  by 
making  longitudinal  incisions  on  either  side,  parallel  to  the  cleft  and  just  internal  to  the  hamular 
process,  in  such  a  position  as  to  avoid  the  posterior  palatine  artery. 

7.  The  Anterior  Vertebral  Region  (Fig.  278). 

Rectus  capitis  anticus  major.  Rectus  capitis  lateralis. 

Rectus  capitis  anticus  minor.  Longus  colli. 

The  Eectus  Capitis  Anticus  Major  or  the  Longus  Capitis,  broad  and 
thick  above,  narrow  below,  appears  like  a  continuation  upward  of  the  Sca- 

1  We  now  know  that  normal  deglutition  can  be  carried  out  when  the  epiglottis  is  so  small  that  it  cannot  coyer 
the  opening  into  the  larynx,  or  when  it  has  been  removed  surgically.  In  such  cases  the  sphincter  muscles  which 
surround  the  laryngeal  aperture  contract  during  swallowing  and  prevent  the  entrance  of  foreign  bodies  into  the 
larynx. — ED. 


THE  ANTERIOR    VERTEBRAL   REGION 


409 


lenus>  anticus.  It  arises  by  four  tendinous  slips  from  the  anterior  tubercles  of 
the  transverse  processes  of  the  third,  fourth,  fifth,  and  sixth  cervical  vertebrae,  and 
ascends,  converging  toward  its  fellow  of  the  opposite  side,  to  be  inserted  into  the 
basilar  process  of  the  occipital  bone. 

Relations. — By  its  anterior  surface,  with  the  pharynx,  the  sympathetic  nerve, 
and  the  sheath  enclosing  the  internal  and  common  carotid  artery,  internal  jugular 
vein,  and  vagus  nerve;  by  its  posterior  surface,  with  the  Longus  colli,  the  Rectus 
capitis  anticus  minor,  and  the  upper  cervical  vertebrae. 


FIG.  278. — The  prevertebral  muscles. 

The  Rectus  Capitis  Anticus  Minor  is  a  short,  flat  muscle,  situated  imme- 
diately behind  the  upper  part  of  the  preceding.  It  arises  from  the  anterior 
surface  of  the  lateral  mass  of  the  atlas  and  from  the  root  of  its  transverse  process, 
and,  passing  obliquely  upward  and  inward,  is  inserted  into  the  basilar  process 
immediately  behind  the  preceding  muscle. 

Relations. — By  its  anterior  surface,  with  the  Rectus  capitis  anticus  major;  by 
its  posterior  surface,  with  the  front  of  the  occipito-atlantal  articulation. 

The  Rectus  Capitis  Lateralis  is  a  short,  flat  muscle,  which  arises  from  the 
upper  surface  of  the  transverse  process  of  the  atlas,  and  is  inserted  into  the  under 
surface  of  the  jugular  process  of  the  occipital  bone. 

Relations. — By  its  anterior  surface,  with  the  internal  jugular  vein;  by  its  pos- 
terior surface,  with  the  vertebral  artery.  On  its  outer  side  lies  the  occipital  artery; 
on  its  inner  side,  the  suboccipital  nerve. 

The  Longus  Colli  is  a  long,  flat  muscle,  situated  on  the  anterior  surface  of  the 
spine,  between  the  atlas  and  the  third  thoracic  vertebra.  It  is  broad  in  the  middle, 


410 


THE  MUSCLES  AND    FASCIAE 


narrow  and  pointed  at  each  extremity,  and  consists  of  three  portions:  a  superior 
oblique,  an  inferior  oblique,  and  a  vertical  portion.  The  superior  oblique  portion 
arises  from  the  anterior  tubercles  of  the  transverse  processes  of  the  third,  fourth, 
and  fifth  cervical  vertebra?,  and,  ascending  obliquely  inward,  is  inserted  by  a  nar- 
row tendon  into  the  tubercle  on  the  anterior  arch  of  the  atlas.  The  inferior  oblique 
portion,  the  smallest  part  of  the  muscle,  arises  from  the  front  of  the  bodies  of  the 
first  two  or  three  thoracic  vertebrae,  and,  ascending  obliquely  outward,  is  inserted 
into  the  anterior  tubercles  of  the  transverse  processes  of  the  fifth  and  sixth  cervi- 
cal vertebrae.  The  vertical  portion  lies  directly  on  the  front  of  the  spine;  it  arises, 
below,  from  the  front  of  the  bodies  of  the  upper  three  thoracic  and  lower  three  cer- 
vical vertebrae,  and  is  inserted  above  into  the  front  of  the  bodies  of  the  second, 
third,  and  fourth  cervical  vertebrae. 

Relations. — By  its  anterior  surface,  with  the  prevertebral  fascia,  the  pharynx,, 
the  ossophagus,  sympathetic  nerve,  the  sheath  of  the  great  vessels  of  the  neck, 
the  inferior  thyroid  artery,  and  recurrent  laryngeal  nerve;  by  its  posterior  surface, 
with  the  cervical  and  thoracic  portions  of  the  spine.  Its  inner  border  is  separated 
from  the  opposite  muscle  by  a  considerable  interval  below,  but  they  approach 
each  other  above. 

8.  The  Lateral  Vertebral  Region  (Figs.  278, 279). 


Scalenus  anticus. 


Scalenus  medius. 


Scalenus  posticus. 

The   Scalenus  Anticus   (TO.  scalenus  anterior)  is  a   conical-shaped    muscle, 
situated   deeply    at   the    side   of    the    neck,    behind    the    Sterno-mastoid.      It 

arises  from  the  anterior  tubercles  of 
the  transverse  processes  of  the  third, 
fourth,  fifth,  and  sixth  cervical  verte- 
bras, and,  descending  almost  vertically, 
is  inserted  by  a  narrow,  flat  tendon 
into  the  Scalene  tubercle  on  the  inner 
border  and  upper  surface  of  the  first 
rib.  The  lower  part  of  this  muscle  sep- 
arates the  subclavian  artery  and  vein, 
the  latter  being  in  front,  and  the  former, 
with  the  brachial  plexus,  behind. 

Relations. — In  front,  with  the  clav- 
icle, the  Subclavius,  Sterno-mastoid, 
and  Omo-hyoid  muscles,  the  Trans- 
versalis  colli,  the  suprascapular  and 
ascending  cervical  arteries,  the  subcla- 
vian vein,  and  the  phrenic  nerve;  by 
its  posterior  surface,  with  the  Scalenus 
medius,  pleura,  subclavian  artery,  and 
brachial  plexus  of  nerves.  It  is  sep- 
arated from  the  Longus  colli,  on  the 
inner  side,  by  the  vertebral  artery. 
On  the  anterior  tubercles  of  the  trans- 
verse processes  of  the  cervical  vertebrae, 
between  the  attachments  of  the  Scale- 
nus anticus  and  Longus  colli,  lies  the 

FIG.  279.— Scaleni  muscles.     (Poirier  and  Charpy.)          ascending    Cervical  branch  of    the  infe' 

rior  thyroid  artery. 

The  Scalenus  Medius,  the  largest  and  longest  of  the  three  Scaleni,  arises  from 
the  posterior  tubercles  of  the  transverse  processes  of  the  lower  six  cervical  vertebrae, 


THE  LATERAL    VERTEBRAL    REGION  41 1 

and,  descending  along  the  side  of  the  vertebral  column,  is  inserted  by  a  broad 
attachment  into  the  upper  surface  of  the  first  rib,  behind  the  groove  for  the  sub- 
clavian  artery,  as  far  back  as  the  tubercle.  It  is  separated  from  the  Scalenus 
anticus  by  the  subclavian  artery  below  and  the  cervical  nerves  above.  The  pos- 
terior thoracic,  or  nerve  of  Bell,  is  formed  in  the  substance  of  the  Scalenus  medius 
and  emerges  from  it.  The  nerve  to  the  Rhomboids  also  pierces  it. 

Relations. — By  its  anterior  surface,  with  the  Sterno-mastoid ;  it  is  crossed  by 
the  clavicle,  the  Omo-hyoid  muscle,  subclavian  artery,  and  cervical  nerves.  To 
its  outer  side  is  the  Levator  anguli  scapulae  and  the  Scalenus  posticus  muscle. 

The  Scalenus  Posticus  (m.  scalenus  posterior),  the  smallest  of  the  three  Scaleni, 
arises,  by  two  or  three  separate  tendons,  from  the  posterior  tubercles  of  the  trans- 
verse processes  of  the  lower  two  or  three  cervical  vertebras,  and,  diminishing  as  it 
descends,  is  inserted  by  a  thin  tendon  into  the  outer  surface  of  the  second  rib, 
behind  the  attachment  of  the  Serratus  magnus.  This  is  the  most  deeply  placed  of 
the  three  Scaleni,  and  is  occasionally  blended  with  the  Scalenus  medius. 

Nerves. — The  Rectus  capitis  anticus  major  and  minor  and  the  Rectus  lateralis 
are  supplied  by  the  first  cervical  nerve,  and  from  the  loop  formed  between  it  and 
the  second;  the  Longus  colli  and  Scaleni,  by  branches  from  the  anterior  divisions 
of  the  lower  cervical  nerves  (fifth,  sixth,  seventh,  and  eighth)  before  they  form  the 
brachial  plexus.  The  Scalenus  medius  also  receives  a  filament  from  the  deep 
external  branches  of  the  cervical  plexus. 

Actions. — The  Rectus  anticus  major  and  minor  are  the  direct  antagonists  of  the 
muscles  at  the  back  of  the  neck,  serving  to  restore  the  head  to  its  natural  position 
after  it  has  been  drawn  backward.  These  muscles  also  serve  to  flex  the  head,  and, 
from  their  obliquity,  rotate  it,  so  as  to  turn  the  face  to  one  or  the  other  side.  The 
Longus  colli  flexes  and  slightly  rotates  the  cervical  portion  of  the  spine.  The 
Scaleni  muscles,  when  they  take  their  fixed  point  from  above,  elevate  the  first  and 
second  ribs,  and  are,  therefore,  inspiratory  muscles.  When  they  take  their  fixed 
point  from  below,  they  bend  the  spinal  column  to  one  or  the  other  side.  If  the 
muscles  of  both  sides  act,  lateral  movement  is  prevented,  but  the  spine  is  slightly 
flexed.  The  Rectus  lateralis,  acting  on  one  side,  bends  the  head  laterally. 

Surface  Form. — The  muscles  in  the  neck,  with  the  exception  of  the  Platysma  myoides,  are 
invested  by  the  deep  cervical  fascia,  which  softens  down  their  form,  and  is  of  considerable 
importance  in  connection  with  deep  cervical  abscesses  and  tumors,  modifying  the  direction  of 
the  growth  of  tumors  and  of  the  enlargement  of  abscesses,  and  causing  them  to  extend 
laterally  instead  of  toward  the  surface.  The  Platysma  myoides  does  not  influence  surface 
form  except  when  in  action,  when  it  produces  wrinkling  of  the  skin  of  the  neck,  which  is 
thrown  into  oblique  ridges  parallel  with  the  fasciculi  of  the  muscle.  Sometimes  this  con- 
traction takes  place  suddenly  and  repeatedly  as  a  sort  of  spasmodic  twitching,  the  result  of 
a  nervous  habit.  The  Slerno-deido-mastoid  is  the  most  important  muscle  of  the  neck  as 
regards  its  surface  form.  If  the  muscle  is  put  into  action  by  drawing  the  chin  downward  and 
to  the  opposite  shoulder,  its  surface  form  will  be  plainly  outlined.  The  sternal  origin  will 
stand  out  as  a  sharply-defined  ridge,  while  the  clavicular  origin  will  present  a  flatter  and  not  so 
prominent  an  outline.  The  fleshy  middle  portion  will  appear  as  an  oblique  roll  or  elevation, 
with  a  thick  rounded  anterior  border  gradually  becoming  less  marked  above.  On  the  opposite 
side — i.  e.,  on  the  side  to  which  the  head  is  turned — the  outline  is  lost,  its  place  being  occupied 
by  an  oblique  groove  in  the  integument.  When  the  muscle  is  at  rest  its  anterior  border  is  still 
visible,  forming  an  oblique  rounded  ridge,  terminating  below  in  the  sharp  outline  of  the  sternal 
head.  The  posterior  border  of  the  muscle  does  not  show  above  the  clavicular  head.  The 
anterior  border  is  defined  by  drawing  a  line  from  the  tip  of  the  mastoid  process  to  the  sterno- 
clavicular  joint.  It  is  an  important  surface-marking  in  the  operation  of  ligature  of  the  common 
carotid  artery  and  in  some  other  operations.  Between  the  sternal  and  clavicular  heads  is  a  slight 
depression,  most  marked  when  the  muscle  is  in  action.  This  is  bounded  below  by  the  prominent 
sternal  extremity  of  the  clavicle.  Between  the  sternal  origins  of  the  two  muscles  is  a  V-shaped 
space,  the  suprasternal  notch,  more  pronounced  below,  and  becoming  toned  down  above,  where 
the  Sterno-hyoid  and  Sterno-thyroid  muscles,  lying  upon  the  trachea,  become  more  prominent. 
Above  the  hyoid  bone,  in  the  middle  line,  the  anterior  belly  of  the  Digastric  to  a  certain  extent 
influences  surface  form.  It  corresponds  to  a  line  drawn  from  the  symphysis  of  the  lower  jaw  to 


412 


THE  MUSCLES  AND    FASCIA 


the  side  of  the  body  of  the  hyoid  bone,  and  renders  this  part  of  the  hyo-mental  region  convex. 
In  the  posterior  triangle  of  the  neck,  the  posterior  belly  of  the  Omo-hyoid,  when  in  action,  forms 
a  conspicuous  object,  especially  in  thin  necks,  presenting  a  cord-like  form  running  across  this 
region,  almost  parallel  with,  and  a  little  above,  the  clavicle. 


MUSCLES  AND  FASCLffi  OF  THE  TRUNK. 

The  muscles  of  the  Trunk  may  be  arranged  in  four  groups,  corresponding 
with  the  region  in  which  they  are  situated. 


I.  The  Back. 
II.  The  Thorax. 


III.  The  Abdomen. 

IV.  The  Perinseum. 


I.  MUSCLES  OF  THE  BACK. 

The  muscles  of  the  Back  are  very  numerous,  and  may  be  subdivided  into  five 
layers : 

FIRST  LAYER. 


Trapezius. 
Latissimus  dorsi. 

SECOND  LAYER. 

Levator  anguli  scapulae. 
Rhomboideus  minor. 
Rhomboideus  major. 

THIRD  LAYER. 

Serratus  posticus  superior. 
Serratus  posticus  inferior. 
Splenius  capitis. 
Splenius  colli. 

FOURTH  LAYER. 
Sacral  and  Lumbar  Regions. 
Erector  spinse. 

Dorsal  Region. 

Ilio-costalis. 

Musculus  accessorius  ad  ilio-costalem. 


Longissimus  dorsi. 
Spinalis  dorsi. 

Cervical  Region. 

Cervicalis  ascendens. 
Transversalis  cervicis. 
Trachelo-mastoid. 
Complexus. 
Biventer  cervicis. 
Spinalis  colli. 

FIFTH  LAYER. 

Semispinalis  dorsi. 
Semispinalis  colli. 
Multifidus  spinse. 
Rotatores  spinse. 
Supraspinales. 
Interspinales. 
Extensor  coccygis. 
Intertransversalis. 
Rectus  capitis  posticus  major. 
Rectus  capitis  posticus  minor. 
Obliquus  capitis  inferior. 
Obliquus  capitis  superior. 


The  First  Layer  (Fig.  281). 
Trapezius.  Latissimus  dorsi. 

Dissection  (Fig.  280).— Place  the  body  in  a  prone  position,  with  the  arms  extended  over 
the  sides  of  the  table,  and  the  chest  and  abdomen  supported  by  several  blocks,  so  as  to  render 
the  muscles  tense.  Then  make  an  incision  along  the  middle  line  of  the  back  from  the  occipital 
protuberance  to  the  coccyx.  Make  a  transverse  incision  from  the  upper  end  of  this  to  the  mas- 
toid  process,  and  a  third  incision  from  its  lower  end,  along  the  crest  of  the  ilium  to  about  its 
middle.  This  large  intervening  space  should,  for  convenience  of  dissection,  be  subdivided  by 
a  fourth  incision,  extending  obliquely  from  the  spinous  process  of  the  last  thoracic  vertebra, 
upward  and  outward,  to  the  acromion  process.  This  incision  corresponds  with  the  lower  border 
of  the  Trapezius  muscle.  The  flaps  of  integument  are  then  to  be  removed  in  the  direction  shown 
in  the  figure. 


OF    THE   BACK 


413 


Superficial  Fascia. — The  superficial  fascia  is  exposed  upon  removing  the  skin 
from  the  back.  It  forms  a  layer  of  considerable  thickness  and  strength,  in  which 
a  quantity  of  granular  pinkish  fat  is  contained.  It  is  continuous  with  the  super- 
ficial fascia  in  other  parts  of  the  body. 

Deep  Fascia. — The  deep  fascia  is  a  dense  fibrous  layer  attached  to  the 
occipital  bone,  the  spines  of  the  vertebrae,  the  crest  of  the  ilium,  and  the  spine 
of  the  scapula.  It  covers  over  the  superficial 
muscles,  forming  sheaths  for  them,  and  in  the 
neck  forms  the  posterior  part  of  the  deep  cer- 
vical fascia;  in  the  thorax  it  is  continuous  with 
the  deep  fascia  of  the  axilla  and  chest,  and  in 
the  abdomen  with  that  covering  the  abdominal 
muscles.  In  the  back  of  the  thoracic  region 
the  deep  fascia  is  called  the  vertebral  aponeurosis 
or  the  aponeurosis  of  the  latissimus  dorsi  muscle. 
It  covers  the  erector  spinse  muscles,  and  is  the 
posterior  layer  of  the  lumbar  fascia. 

The  Trapezius  is  a  broad,  flat,  triangular 
muscle,  placed  immediately  beneath  the  skin 
and  fascia,  and  covering  the  upper  and  back 
part  of  the  neck  and  shoulders.  It  arises  from 
the  external  occipital  protuberance  and  the 
inner  third  of  the  superior  curved  line  of  the 
occipital  bone;  from  the  ligamentum  nuchse,  the 
spinous  process  of  the  seventh  cervical,  and  the 
spinous  processes  of  all  the  thoracic  vertebrae; 
and  from  the  corresponding  portion  of  the 
supraspinous  ligament.  From  this  origin  the 
superior  fibres  proceed  downward  and  outward, 
the  inferior  ones  upward  and  outward,  and 
the  middle  fibres  horizontally,  and  are  in- 
serted, the  superior  ones  into  the  outer  third  of 
the  posterior  border  of  the  clavicle ;  the  middle 
fibres  into  the  inner  margin  of  the  acromion 

process,  and  into  the  superior  lip  of  the  posterior  border  or  crest  of  the  spine 
of  the  scapula;  the  inferior  fibres  converge  near  the  scapula,  and  terminate  in  a 
triangular  aponeurosis,  which  glides  over  a  smooth  surface  at  the  inner  extremity 
of  the  spine,  to  be  inserted  into  a  tubercle  at  the  outer  part  of  this  smooth  surface. 
The  Trapezius  is  fleshy  in  the  greater  part  of  its  extent,  but  tendinous  at  its  origin 
and  insertion.  At  its  occipital  origin  it  is  connected  to  the  bone  by  a  thin  fibrous 
lamina,  firmly  adherent  to  the  skin,  and  wanting  the  lustrous,  shining  appearance 
of  aponeuroses.  At  its  origin  from  the  spines  of  the  vertebrae  it  is  connected  to 
the  bones  by  means  of  a  broad  semi-elliptical  aponeurosis,  which  occupies  the 
space  between  the  sixth  cervical  and  the  third  thoracic  vertebrae,  and  forms,  with 
the  aponeurosis  of  the  opposite  muscle,  a  tendinous  ellipse.  The  rest  of  the  muscle 
arises  by  numerous  short  tendinous  fibres.  If  the  Trapezius  is  dissected  on  both 
sides,  the  two  muscles  resemble  a  trapezium  or  diamond-shaped  quadrangle; 
two  angles  corresponding  to  the  shoulders;  a  third  to  the  occipital  protuberance; 
and  the  fourth  to  the  spinous  process  of  the  last  thoracic  vertebra.  The 
clavicular  insertion  of  this  muscle  varies  as  to  the  extent  of  its  attachment;  it 
sometimes  advances  as  far  as  the  middle  of  the  clavicle,  and  may  even  become 
blended  with  the  posterior  edge  of  the  Sterno-mastoid  or  overlap  it.  This  should 
be  borne  in  mind  in  the  operation  for  tying  the  third  part  of  the  subclavian 
artery. 


FIG.  280. — Dissection  of  the  muscles  of 
the  back. 


414 


THE   MUSCLES   AND    FASCIA 


FIG.  281.— Muscles  of  the  back.     On  the  left  side  is  exposed  the  first  layer;  on  the  right  side,  the  second  layet 

and  part  of  the  third. 


OF   THE  BACK  415 

Relations. — By  its  superficial  surface,  with  the  integument;  by  its  deep  sur- 
jace,  in  the  neck,  with  the  Complexus,  Splenius,  Levator  anguli  scapula?,  and 
Rhomboideus  minor;  in  the  back,  with  the  Rhomboideus  major,  Supraspinatus, 
Infraspinatus,  and  Vertebral  aponeurosis  (which  separates  it  from  the  prolonga- 
tions of  the  Erector  spinae),  and  the  Latissimus  dorsi.  The  accessory  nerve  and 
the  superficial  cervical  artery  and  branches  from  the  third  and  fourth  cervical 
nerves  pass  beneath  the  anterior  border  of  this  muscle.  The  anterior  margin  of  its 
cervical  portion  forms  the  posterior  boundary  of  the  posterior  triangle  of  the  neck, 
the  other  boundaries  being  the  Sterno-mastoid  in  front  and  the  clavicle  below. 

The  Ligamentum  nuchae  (Fig.  281)  is  a  fibrous  membrane,  which,  in  the  neck, 
represents  the  supraspinous  and  interspinous  ligaments  of  the  lower  vertebrae. 
It  extends  from  the  external  occipital  protuberance  to  the  spinbus  process  of  the 
seventh  cervical  vertebra.  From  its  anterior  border  a  fibrous  lamina  (fascia 
nuchae)  is  given  off,  which  is  attached  to  the  external  occipital  crest,  the  posterior 
tubercle  of  the  atlas,  and  the  spinous  process  of  each  of  the  cervical  vertebrae,  so 
as  to  form  a  septum  between  the  muscles  on  each  side  of  the  neck.  In  man  it  is 
merely  the  rudiment  of  an  important  elastic  ligament,  which,  in  some  of  .the  lower 
animals,  serves  to  sustain  the  weight  of  the  head. 

The  Latissimus  Dorsi  is  a  broad  flat  muscle,  which  covers  the  lumbar  and  the 
lower  half  of  the  thoracic  regions,  and  is  gradually  contracted  into  a  narrow  fascic- 
ulus at  its  insertion  into  the  humerus.  It  arises  by  tendinous  fibres  from  the 
spinous  processes  of  the  six  inferior  thoracic  vertebras  and  from  the  posterior  layer 
of  the  lumbar  fascia  (see  page  418),  by  which  it  is  attached  to  the  spines  of  the 
lumbar  and  sacral  vertebme  and  to  the  supraspinous  ligament.  It  also  arises 
from  the  external  lip  of  the  crest  of  the  ilium,  behind  the  origin  of  the  External 
oblique,  and  by  fleshy  digitations  from  the  three  or  four  lower  ribs,  which  are 
interposed  between  similar  processes  of  the  External  oblique  muscle  (Fig.  288, 
page  436).  From  this  extensive  origin  the  fibres  pass  in  different  directions,  the 
upper  ones  horizontally,  the  middle  obliquely  upward,  and  the  lower  vertically 
upward,  so  as  to  converge  and  form  a  thick  fasciculus,  which  crosses  the  inferior 
angle  of  the  scapula,  and  occasionally  receives  a  few  fibres  of  origin  from  it.  The 
muscle  then  curves  around  the  lower  border  of  the  Teres  major,  and  is  twisted 
upon  itself  so  that  the  superior  fibres  become  at  first  posterior  and  then  inferior, 
and  the  vertical  fibres  at  first  anterior  and  then  superior.  It  then  terminates  in  a 
short  quadrilateral  tendon,  about  three  inches  in  length,  which,  passing  in  front  of 
the  tendon  of  the  Teres  major,  is  inserted  into  the  bottom  of  the  bicipital  groove 
of  the  humerus,  its  insertion  extending  higher  on  the  humerus  than  that  of  the 
tendon  of  the  Pectoralis  major.  The  lower  border  of  the  tendon  of  this  muscle  is 
united  with  that  of  the  Teres  major,  the  surfaces  of  the  two  being  separated  by  a 
bursa;  another  bursa  is  sometimes  interposed  between  the  muscle  and  the  inferior 
angle  of  the  scapula.  This  muscle  at  its  insertion  gives  off  an  expansion  to  the 
deep  fascia  of  the  arm. 

A  muscular  slip,  the  axillary  arch,  varying  from  3  to  4  inches  in  length,  and  from  J  to  f  of  an 
inch  in  breadth,  occasionally  arises  from  the  upper  edge  of  the  Latissimus  dorsi  about  the  mid- 
dle of  the  posterior  fold  of  the  axilla,  and  crosses  the  axilla  in  front  of  the  axillary  vessels  and 
nerves,  to  join  the  under  surface  of  the  tendon  of  the  Pectoralis  major,  the  Coraco-brachialis, 
or  the  fascia  over  the  Biceps.  The  position  of  this  abnormal  slip  is  a  point  of  interest  in  its 
relation  to  the  axillary  artery,  as  it  crosses  the  vessel  just  above  the  spot  usually  selected  for  the 
application  of  a  ligature,  and  may  mislead  the  surgeon  during  the  operation.  It  may  be  easily 
recognized  by  the  transverse  direction  of  its  fibres.  Dr.  Struther  found  it,  in  8  out  of  105  sub- 
jects, occurring  seven  times  on  both  sides.  In  most  subjects  there  is  a. fibrous  axillary  arch, 
in  only  a  few  is  the  arch  muscular. 

There  is  usually  a  fibrous  slip  which  passes  from  the  lower  border  of  the  tendon  of  the  Latis- 
simus dorsi,  near  its  insertion,  to  the  long  head  of  the  Triceps.  This  is  occasionally  muscular, 
and  is  the  representative  of  the  Dorso-epitrochlearis  muscle  of  apes. 


416  THE  MUSCLES   AND    FASCIA 

Relations. — Its  superficial  surface  is  subcutaneous,  excepting  at  its  upper  part, 
where  it  is  covered  by  the  Trapezius,  and  at  its  insertion,  where  its  tendon  is 
crossed  by  the  axillary  vessels  and  the  brachial  plexus  of  nerves.  By  its  deep 
surface  it  is  in  relation  with  the  lumbar  fascia,  the  Serratus  posticus  inferior, 
the  lower  External  intercostal  muscles  and  ribs,  inferior  angle  of  the  scapula, 
Rhomboideus  major,  Infraspinatus,  and  Teres  major.  Its  outer  margin  is  sepa- 
rated below  from  the  External  oblique  by  a  small  triangular  interval,  the  triangle 
of  Petit  (trigonum  lumbale  [Petiti]) ;  and  another  triangular  interval  exists  between 
its  upper  border  and  the  margin  of  the  Trapezius,  in  which  the  Rhomboideus 
major  muscle  is  exposed. 

Nerves. — The  Trapezius  is  supplied  by  the  accessory,  and  by  branches  from 
the  anterior  divisions  of  the  third  and  fourth  cervical  nerves:  the  Latissimus 
dorsi,  by  the  middle  or  long  subscapular  nerve. 

The  Second  Layer  (Fig.  281). 

Levator  anguli  scapulae.  Rhomboideus  minor. 

Rhomboideus  major. 

Dissection. — The  Trapezius  must  be  removed,  in  order  to  expose  the  next  layer;  to  effect 
this,  detach  the  muscle  from  its  attachment  to  the  clavicle  and  spine  of  the  scapula,  and  turn 
it  back  toward  the  spine. 

The  Levator  Anguli  Scapulae  (m.  levator  scapulae)  is  situated  at  the  back  part 
and  side  of  the  neck.  It  arises  by  tendinous  slips  from  the  transverse  process  of 
the  atlas,  and  from  the  posterior  tubercles  of  the  transverse  processes  of  the  second, 
third,  and  fourth  cervical  vertebra?;  these,  becoming  fleshy,  are  united  so  as  to 
form  a  flat  muscle,  which,  passing  downward  and  backward,  is  inserted  into  the 
posterior  border  of  the  scapula,  between  the  superior  angle  and  the  triangular 
smooth  surface  at  the  root  of  the  spine. 

Relations. — By  its  superficial  surface,  with  the  integument,  Trapezius,  and 
Sterno-mastoid ;  by  its  deep  surface,  with  the  Splenius  colli,  Transversalis  cervicis, 
Cervicalis  ascendens,  and  Serratus  posticus  superior  muscles,  and  with  the  pos- 
terior scapular  artery  and  the  nerve  to  the  Rhomboids. 

The  Rhomboideus  Minor  arises  from  the  ligamentum  nuchae  and  spinous 
processes  of  the  seventh  cervical  and  first  thoracic  vertebrae.  Passing  downward 
and  outward,  it  is  inserted  into  the  margin  of  the  triangular  smooth  surface  at  the 
root  of  the  spine  of  the  scapula.  This  small  muscle  is  usually  separated  from  the 
Rhomboideus  major  by  a  slight  cellular  interval. 

Relations. — By  its  superficial  (posterior)  surface,  with  the  Trapezius;  by  its  deep 
(anterior)  surface,  with  the  same  structures  as  the  Rhomboideus  major. 

The  Rhomboideus  Major  is  situated  immediately  below  the  preceding,  the 
adjacent  margins  of  the  two  being  occasionally  united.  It  arises  by  tendinous 
fibres  from  the  spinous  processes  of  the  four  or  five  upper  thoracic  vertebrae  and 
the  supraspinous  ligament,  and  is  inserted  into  a  narrow  tendinous  arch  attached 
above  to  the  lower  part  of  the  triangular  surface  at  the  root  of  the  spine;  below, 
to  the  inferior  angle,  the  arch  being  connected  to  the  border  of  the  scapula  by  a 
thin  membrane.  When  the  arch  extends,  as  it  occasionally  does,  but  a  short 
distance,  the  muscular  fibres  are  inserted  into  the  scapula  itself. 

Relations. — By  its  superficial  (posterior)  surface,  with  the  Trapezius  and  Latis- 
simus dorsi;  by  its  deep  (anterior)  surface,  with  the  Serratus  posticus  superior, 
posterior  scapular  artery,  the  vertebral  aponeurosis  which  separates  it  from  the 
prolongations  from  the  Erector  spinae,  the  Intercostal  muscles,  and  ribs. 

Nerves. — The  Rhomboid  muscles  are  supplied  by  branches  from  the  anterior 
division  of  the  fifth  cervical  nerve;  the  Levator  anguli  scapulae,  by  the  anterior 


OF   THE  BACK  417 

divisions  of  the  third  and  fourth  cervical  nerves,  and  frequently  by  a  branch  from 
the  nerve  to  the  Rhomboids. 

Actions.  —  The  movements  effected  by  the  preceding  muscles  are  numerous,  as 
may  be  conceived  from  their  extensive  attachment.  The  whole  of  the  Trapezius 
when  in  action  retracts  the  scapula  and  braces  back  the  shoulder;  if  the  head  is 
fixed,  the  upper  part  of  the  Trapezius  will  elevate  the  point  of  the  shoulder,  as  in 
supporting  weights;  when  the  lower  fibres  are  brought  into  action,  they  assist 
in  depressing  the  bone.  The  middle  and  lower  fibres  of  the  muscle  rotate  the 
scapula,  causing  elevation  of  the  acromion  process.  If  the  shoulders  are  fixed,  both 
Trapezii,  acting  together,  will  draw  the  head  directly  backward;  or  if  only  one 
acts  the  head  is  drawn  to  the  corresponding  side.  The  Latissimus  dorsi,  when  it 
acts  upon  the  humerus,  depresses  it,  draws  it  backward,  adducts,  and  at  the  same 
time  rotates  it  inward.  It  is  the  muscle  which  is  principally  employed  in  giving  a 
downward  blow,  as  in  felling  a  tree  or  in  sabre  practice.  If  the  arm  is  fixed,  the 
muscle  may  act  in  various  ways  upon  the  trunk;  thus,  it  may  raise  the  lower  ribs 
and  assist  in  forcible  inspiration;  or,  if  both  arms  are  fixed,  the  two  muscles  may 
assist  the  Abdominal  and  great  Pectoral  muscles  in  suspending  and  drawing  the 
whole  trunk  forward,  as  in  climbing  or  walking  on  crutches.  The  Levator  anguli 
scapulae  raises  the  superior  angle  of  the  scapula,  and  by  so  doing  depresses  the 
point  of  the  shoulder.  It  assists  the  Trapezius  in  bearing  weights  and  in  shrugging 
the  shoulders.  If  the  shoulder  be  fixed,  the  Levator  anguli  scapulae  inclines  the 
neck  to  the  corresponding  side  and  rotates  it  in  the  same  direction.  The  Rhom- 
boid muscles  carry  the  inferior  angle  backward  and  upward,  thus  producing  a 
slight  rotation  of  the  scapula  upon  the  side  of  the  chest,  the  Rhomboideus  major 
acting  especially  on  the  lower  angle  of  the  scapula  through  the  tendinous  arch  by 
which  it  is  inserted.  The  Rhomboid  muscles,  acting  together  with  the  middle  and 
inferior  fibres  of  the  Trapezius,  will  draw  the  scapula  directly  backward  toward 
the  spine. 

The  Third  Layer. 

Serratus  posticus  superior.  Serratus  posticus  inferior. 

f  Splenius  capitis. 
Splemus       slenius  collL 


Dissection.  —  To  bring  into  view  the  third  layer  of  muscles,  remove  the  whole  of  the  second, 
together  with  the  Latissimus  dorsi,  by  cutting  through  the  Levator  anguli  scapulae  and  Rhom- 
boid muscles  near  their  origin,  and  reflecting  them  downward,  and  by  dividing  the  Latissimus 
dorsi  in  the  middle  by  a  vertical  incision  carried  from  its  upper  to  its  lower  part,  and  reflecting 
the  two  halves  of  the  muscle. 

The  Serratus  Posticus  Superior  (m.  serratus  posterior  superior)  is  a  thin,  flat, 
quadrilateral  muscle  situated  at  the  upper  and  back  part  of  the  thorax.  It  arises 
by  a  thin  and  broad  aponeurosis  from  the  ligamentum  nuchae,  and  from  the 
spinous  processes  of  the  last  cervical  and  two  or  three  upper  thoracic  vertebrae  and 
from  the  supraspinous  ligament.  Inclining  downward  and  outward,  it  becomes 
muscular,  and  is  inserted,  by  four  fleshy  digitations,  into  the  upper  borders  of  the 
second,  third,  fourth,  and  fifth  ribs,  a  little  beyond  their  angles. 

Relations.  —  By  its  superficial  surface,  with  the  Trapezius,  Rhomboidei,  and 
Levator  anguli  scapulae;  by  its  deep  surface,  with  the  Splenius  and  the  vertebral 
aponeurosis,  which  separates  it  from  the  prolongations  of  the  Erector  spinae,  and 
with  the  Intercostal  muscles  and  ribs. 

The  Serratus  Posticus  Inferior  (m.  serratus  posterior  inferior]  (Fig.  281)  is 
situated  at  the  junction  of  the  thoracic  and  lumbar  regions;  it  is  of  an  irregularly 
quadrilateral  form,  broader  than  the  preceding,  and  separated  from  it  by  a  consid- 
erable interval.  It  arises  by  a  thin  aponeurosis  from  the  spinous  processes  of  the 
last  two  thoracic  and  two  or  three  upper  lumbar  vertebrae,  and  from  the  supra- 

27 


418  THE   MUSCLES    AND    FASCIAE 

spinous  ligaments.  Passing  obliquely  upward  and  outward,  it  becomes  fleshy, 
and  divides  into  four  flat  digitations,  which  are  inserted  into  the  lower  borders  of 
the  four  lower  ribs,  a  little  beyond  their  angles.  The  thin  aponeurosis  of  origin 
is  intimately  blended  with  the  lumbar  fascia. 

Relations. — By  its  superficial  surface,  with  the  Latissimus  dorsi.  By  its  deep 
surface,  with  the  Erector  spinse,  ribs,  and  Intercostal  muscles.  Its  upper  margin 
is  continuous  with  the  vertebral  aponeurosis. 

The  vertebral  aponeurosis  is  a  thin,  fibrous  lamina,  extending  along  the  whole 
length  of  the  back  part  of  the  thoracic  region,  serving  to  bind  down  the  long 
Extensor  muscles  of  the  back  which  support  the  spine  and  head,  and  separate  them 
from  those  muscles  which  connect  the  spine  to  the  upper  extremity.  It  consists  of 
longitudinal  and  transverse  fibres  blended  together,  forming  a  thin  lamella,  which 
is  attached  in  the  median  line  to  the  spinous  processes  of  the  thoracic  vertebrae; 
externally,  to  the  angles  "of  the  ribs ;  and  below,  to  the  upper  border  of  the  Serratus 
posticus  inferior  and  a  portion  of  the  lumbar  fascia,  which  gives  origin  to  the  Latis- 
simus dorsi;  above,  it  passes  beneath  the  Serratus  posticus  superior  and  the 
Splenius,  and  blends  with  the  deep  fascia  of  the  neck. 

The  lumbar  fascia  or  aponeurosis  (Figs.  281  and  294),  which  may  be  regarded 
as  the  posterior  aponeurosis  of  the  Transversalis  abdominis  muscle,  consists 
of  three  laminae,  which  are  attached  as  follows:  the  posterior  layer,  to  the 
spines  of  the  lumbar  and  sacral  vertebras  and  their  supraspinous  ligaments;  the 
middle  layer,  to  the  tips  of  the  transverse  processes  of  the  lumbar  vertebrae  and 
their  intertrans verse  ligaments;  the  anterior  layer,  to  the  roots  of  the  lumbar 
transverse  processes.  The  posterior  layer  is  continued  above  as  the  vertebral 
aponeurosis,  while  inferiorly  it  is  fixed  to  the  outer  lip  of  the  iliac  crest.  With  this 
layer  are  blended  the  aponeurotic  origin  of  the  Serratus  posticus  inferior  and  part 
of  that  of  the  Latissimus  dorsi.  The  middle  layer  is  attached  above  to  the  last 
rib,  and  below  to  the  iliac  crest;  the  anterior  layer  is  fixed  below  to  the  ilio-lumbar 
ligament  and  iliac  crest;  while  above  it  is  thickened  to  form  the  external  arcuate 
ligament  of  the  Diaphragm,  and  stretches  from  the  tip  of  the  last  rib  to  the  trans- 
verse process  of  the  first  or  second  lumbar  vertebra.  These  three  layers,  together 
with  the  vertebral  column,  enclose  two  spaces,  the  posterior  of  which  is  occupied 
by  the  Erector  spinas  muscle,  and  the  anterior  by  the  Quadratus  lumborum. 

Now  detach  the  Serratus  posticus  superior  from  its  origin,  and  turn  it  outward,  when  the 
Splenius  muscle  will  be  brought  into  view. 

The  Splenius  (Fig.  281)  is  situated  at  the  back  of  the  neck  and  upper  part 
of  the  thoracic  region.  At  its  origin  it  is  a  single  muscle,  which  soon  after  its 
origin  becomes  broad,  and  divides  into  two  portions,  which  have  separate  inser- 
tions. It  arises,  by  tendinous  fibres,  from  the  lower  half  of  the  ligamentum 
nuchae,  from  the  spinous  processes  of  the  last  cervical  and  of  the  six  upper  tho- 
racic vertebrae,  and  from  the  supraspinous  ligament.  From  this  origin  the  fleshy 
fibres  proceed  obliquely  upward  and  outward,  forming  a  broad  flat  muscle,  which 
divides  as  it  ascends  into  two  portions,  the  Splenius  capitis  and  Splenius  colli. 

The  Splenius  capitis  (TO.  splenius  capitis)  is  inserted  into  the  mastoid  process  of 
the  temporal  bone,  and  into  the  rough  surface  on  the  occipital  bone  just  beneath 
the  superior  curved  line. 

The  Splenius  colli  (TO.  splenius  cervicis)  is  inserted,  by  tendinous  fasciculi,  into  the 
posterior  tubercles  of  the  transverse  processes  of  the  two  or  three  upper  cervical 
vertebrae. 

The  Splenius  is  separated  from  its  fellow  of  the  opposite  side  by  a  triangular 
interval,  in  which  is  seen  the  Complexus. 

Relations. — By  its  superficial  surface,  with  the  Trapezius,  from  which  it  is  sepa- 
rated below  by  the  Rhomboidei  and  the  Serratus  posticus  superior.  It  is  covered 


OF    THE  BACK  419 

at  its  insertion  by  the  Sterno-mastoid,  and  at  the  lower  and  back  part  of  the  neck 
by  the  Levator  anguli  scapulae;  by  its  deep  surface,  with  the  Spinalis  dorsi,  Longis- 
simus  dorsi,  Semispinalis  colli,  Complexus,  Trachelo-mastoid,  and  Transversalis 
cervicis. 

Nerves. — The  Splenius  is  supplied  from  the  external  branches  of  the  posterior 
divisions  of  the  cervical  nerves;  the  Serratus  posticus  superior  is  supplied  by  the 
external  branches  of  the  posterior  divisions  of  the  upper  thoracic  nerves;  the 
Serratus  posticus  inferior  by  the  external  branches  of  the  posterior  divisions  of 
the  lower  thoracic  nerves. 

Actions. — The  Serrati  are  respiratory  muscles.  The  Serratus  posticus  supe- 
rior elevates  the  ribs;  it  is  therefore  an  inspiratory  muscle;  while  the  Serratus 
inferior  draws  the  lower  ribs  downward  and  backward,  and  thus  elongates  the 
thorax.  It  also  fixes  the  lower  ribs,  thus  aiding  the  downward  action  of  the 
diaphragm  and  resisting  the  tendency  which  it  has  to  draw  the  lower  ribs  upward 
and  forward.  It  must  therefore  be  regarded  as  a  muscle  of  inspiration.  This 
muscle  is  also  probably  a  tensor  of  the  vertebral  aponeurosis.  The  Splenii  muscles 
of  the  two  sides,  acting  together,  draw  the  head  directly  backward,  assisting  the 
Trapezius  and  Complexus;  acting  separately,  they  draw  the  head  to  one  or  the 
other  side,  and  slightly  rotate  it,  turning  the  face  to  the  same  side.  They  also 
assist  in  supporting  the  head  in  the  erect  position. 

The  Fourth  Layer  (Fig.  282). 

I.  Erector  spinse. 

a.  Outer  Column.  b.  Middle  Column. 

Ilio-costalis.  Longissirnus  dorsi. 

Musculus  accessorius.  Transversalis  cervicis. 

Cervicalis  ascendens.  Trachelo-mastoid. 

c.  Inner  Column. 
Spinalis  dorsi.  Spinalis  colli. 

II.  Complexus. 

Dissection. — To  expose  the  muscles  of  the  fourth  layer,  remove  entirely  the  Serrati  and  the 
vertebral  and  lumbar  fascise.  Then  detach  the  Splenius  by  separating  its  attachment  to  the 
spinous  processes  and  reflecting  it  outward. 

The  Erector  Spinae  (m.  sacrospinalis]  and  its  prolongations  in  the  thoracic 
and  cervical  regions  fill  up  the  vertebral  groove  on  each  side  of  the  spine.  It 
is  covered  in  the  lumbar  region  by  the  lumbar  fascia;  in  the  thoracic  region,  by 
the  Serrati  muscles  and  the  vertebral  aponeurosis;  and  in  the  cervical  region,  by 
a  layer  of  cervical  fascia  continued  beneath  the  Trapezius  and  the  Splenius.  This 
large  muscular  and  tendinous  mass  varies  in  size  and  structure  at  different  parts 
of  the  spine.  In  the  sacral  region  the  Erector  spinae  is  narrow  and  pointed,  and 
its  origin  chiefly  tendinous  in  structure.  In  the  lumbar  region  the  muscle  becomes 
enlarged,  and  forms  a  large,  fleshy  mass.  In  the  thoracic  region  it  subdivides  into 
two  parts,  which  gradually  diminish  in  size  as  they  ascend  to  be  inserted  into  the 
vertebrae  and  ribs. 

The  Erector  spinae  arises  from  the  anterior  surface  of  a  very  broad  and  thick 
tendon,  which  is  attached,  internally,  to  the  spines  of  the  sacrum,  to  the  spinous 
processes  of  the  lumbar  and  the  eleventh  and  twelfth  thoracic  vertebrae,  and  the 
supraspinous  ligament;  externally,  to  the  back  part  of  the  inner  lip  of  the  crest  of 
the  ilium,  and  to  the  series  of  eminences  on  the  posterior  part  of  the  sacrum,  which 
represents  the  transverse  processes,  where  it  blends  with  the  great  sacro-sciatic  and 
posterior  sacro-iliac  ligaments.  Some  of  its  fibres  are  continuous  with  the  fibres 


420 


THE   MUSCLES    AND    FASCIA 


Occipital  bone. 


MULTIFIDUS   SPIN>E. 


First  dorsal  vertebra. 


First  lumbar  vertebra. 


First  sacral  vertebra. 


FIG.  282. — Muscles  of  the  back.     Deep  layers. 


OF   THE   BACK  421 

of  origin  of  the  Gluteus  maximus.  The  muscular  fibres  form  a  single  large  fleshy 
mass,  bounded  in  front  by  the  transverse  processes  of  the  lumbar  vertebrae  and  by 
the  middle  lamella  of  the  lumbar  fascia.  Opposite  the  last  rib  it  divides  into  two 
parts,  the  Ilio-costalis  and  the  Longissimus  dorsi;  the  Spinalis  dorsi  is  given  off 
from  the  latter  in  the  upper  thoracic  region. 

The  Hio-costalis  or  Sacro-lumbalis  (m.  iliocostalis  lumborum),  the  external  por- 
tion of  the  Erector  spinae,  is  inserted,  generally,  by  six  or  seven  flattened  tendons  into 
the  inferior  borders  of  the  angles  of  the  six  or  seven  lower  ribs.  The  number  of  the 
tendons  of  this  muscle  is,  however,  very  variable,  and  therefore  the  number  of  ribs 
into  which  it  is  inserted  vary.  Frequently  it  is  found  to  possess  nine  or  ten 
tendons,  and  sometimes  as  many  tendons  as  there  are  ribs,  and  is  then  inserted 
into  the  angles  of  all  the  ribs.  If  this  muscle  is  reflected  outward,  it  will  be 
seen  to  be  reinforced  by  a  series  of  muscular  slips  which  arise  from  the  angles 
of  the  ribs;  by  means  of  these  the  Ilio-costalis  is  continued  upward  to  the  upper 
ribs  and  cervical  portion  of  the  spine.  The  accessory  portions  form  two  additional 
muscles,  the  Musculus  accessorius  and  the  Cervicalis  ascendens. 

The  Musculus  accessorius  ad  ilio-costalem  (m.  iliocostalis  dorsi)  arises,  by  separate 
flattened  tendons,  from  the  upper  borders  of  the  angles  of  the  six  lower  ribs:  these 
become  muscular,  and  are  finally  inserted,  by  separate  tendons,  into  the  upper 
borders  of  the  angles  of  the  six  upper  ribs  and  into  the  back  of  the  transverse 
processes  of  the  seventh  cervical  vertebra. 

The  Cervicalis  ascendens1  (m.  iliocostalis  cervicis)  is  the  continuation  of  the  Acces- 
sorius upward  into  the  neck;  it  is  situated  on  the  inner  *ide  of  the  tendons  of  the 
Accessorius,  arising  from  the  angles  of  the  four  or  five  upper  ribs,  and  is  inserted 
by  a  series  of  slender  tendons  into  the  posterior  tubercles  of  the  transverse  processes 
of  the  fourth,  fifth,  and  sixth  cervical  vertebra?. 

The  Longissimus  dorsi  is  the  middle  and  largest  portion  of  the  Erector  spinae. 
In  the  lumbar  region,  where  it  is  as  yet  blended  with  the  Ilio-costalis,  some  of  the 
fibres  are  attached  to  the  whole  length  of  the  posterior  surface  of  the  transverse 
processes  and  the  accessory  processes  of  the  lumbar  vertebrae,  and  to  the  middle 
layer  of  the  lumbar  fascia.  In  the  thoracic  region  the  Longissimus  dorsi  is  inserted, 
by  long,  thin  tendons,  into  the  tips  of  the  transverse  processes  of  all  the  thoracic 
vertebras,  and  into  from  seven  to  eleven  of  the  lower  ribs  between  their  tubercles 
and  angles.  This  muscle  is  continued  upward  to  the  cranium  and  cervical  portion 
of  the  spine  by  means  of  two  additional  muscles,  the  Transversalis  cervicis  and 
Trachelo-mastoid. 

The  Transversalis  cervicis  or  Transversalis  colli  (m.  longissimus  cervicis},  placed 
on  the  inner  side  of  the  Longissimus  dorsi,  arises  by  long,  thin  tendons  from  the 
summits  of  the  transverse  processes  of  the  six  upper  thoracic  vertebrae,  and  is 
inserted  by  similar  tendons  into  the  posterior  tubercles  of  the  transverse  processes 
of  the  cervical  vertebras,  from  the  second  to  the  sixth  inclusive. 

The  Trachelo-mastoid  (m.  longissimus  capitis)  lies  on  the  inner  side  of  the  preced- 
ing, between  it  and  the  Complexus  muscle.  It  arises,  by  tendons,  from  the  trans- 
verse processes  of  the  five  or  six  upper  thoracic  vertebrae,  and  the  articular  processes 
of  the  three  or  four  lower  cervical.  The  fibres  form  a  small  muscle,  which  ascends 
to  be  inserted  into  the  posterior  margin  of  the  mastoid  process,  beneath  the  Splenius 
and  Sterno-mastoid  muscles.  This  small  muscle  is  almost  always  crossed  by  a 
tendinous  intersection  near  its  insertion  into  the  mastoid  process.2 

The  Spinalis  dorsi  connects  the  spinous  processes  of  the  upper  lumbar  and  the 
thoracic  vertebrae  together  by  a  series  of  muscular  and  tendinous  slips  which  are 

This  muscle  is  sometimes  called  "Cervicalis  descendens."  The  student  should  remember  that  these  long 
muscles  take  their  fixed  point  from  above  or  from  below,  according  to  circumstances. — ED.  of  15th  English 
edition. 

2  These  two  muscles  (Transversalis  cervicis  and  Trachelo-mastoid)  are  sometimes  described  as  one,  having  a 
common  origin,  but  dividing  above  at  their  insertion.  The  Trachelo-mastoid  is  then  termed  the  Transversalis 
capiti*. — ED.  of  15th  English  edition. 


422  THE  MUSCLES  AND  FASCIA 

intimately  blended  with  the  Longissimus  dorsi.  It  is  situated  at  the  inner  side 
of  the  Longissimus  dorsi,  arising,  by  three  or  four  tendons,  from  the  spinous 
processes  of  the  first  two  lumbar  and  the  last  two  thoracic  vertebrae:  these,  uniting, 
form  a  small  muscle,  which  is  inserted,  by  separate  tendons,  into  spinous  processes 
of  the  thoracic  vertebrae,  the  number  varying  from  four  to  eight.  It  is  intimately 
united  with  the  Semispinalis  dorsi,  which  lies  beneath  it. 

The  Spinalis  colli  (TO.  spinalis  cervicis)  is  a  small  muscle,  connecting  together  the 
spinous  processes  of  the  cervical  vertebrae,  and  analogous  to  the  Spinalis  dorsi  in 
the  thoracic  region.  It  varies  considerably  in  its  size  and  in  its  extent  of  attachment 
to  the.  vertebras,  not  only  in  different  bodies,  but  on  the  two  sides  of  the  same  body. 
It  usually  arises  by  fleshy  or  tendinous  slips,  varying  from  two  to  four  in  number, 
from  the  spinous  processes  of  the  fifth,  sixth,  and  seventh  cervical  vertebras,  and 
occasionally  from  the  first  and  second  thoracic,  and  is  inserted  into  the  spinous 
process  of  the  axis,  and  occasionally  into  the  spinous  processes  of  the  two  vertebrae 
below  it.  This  muscle  was  found  absent  in  five  cases  out  of  twenty-four. 

Relations. — The  Erector  spinae  and  its  prolongations  are  bound  down  to  the 
vertebrae  and  ribs  in  the  lumbar  and  thoracic  regions  by  the  lumbar  fascia  and 
the  vertebral  aponeurosis.  The  inner  part  of  these  muscles  covers  the  muscles 
of  the  fifth  layer.  In  the  neck  they  are  in  relation,  by  their  superficial  surface,  with 
the  Trapezius  and  Splenius;  by  their  deep  surface,  with  the  Semispinalis  dorsi  et 
colli  and  the  Recti  and  Obliqui. 

The  Complexus  (m.  Semispinalis  capitis}  is  a  broad  thick  muscle,  situated  at  the 
upper  and  back  part  of  tFie  neck,  beneath  the  Splenius,  and  internal  to  the  Trans- 
versalis  cervicis  and  Trachelo-mastoid.  It  arises,  by  a  series  of  tendons,  from 
the  tips  of  the  transverse  processes  of  the  upper  six  or  seven  thoracic  and  the  last 
cervical  vertebrae,  and  from  the  articular  processes  of  the  three  cervical  above 
this.  The  tendons,  uniting,  form  a  broad  muscle,  which  passes  obliquely  upward 
and  inward,  and  is  inserted  into  the  innermost  depression  between  the  two  curved 
lines  of  the  occipital  bone.  This  muscle,  about  its  middle,  is  traversed  by  a  trans- 
verse tendinous  intersection.  The  biventor  cervicis  is  a  small  fasciculus,  situated 
on  the  inner  side  of  the  preceding,  and  in  the  majority  of  cases  blended  with  it; 
it  has  received  its  name  from  having  a  tendon  intervening  between  two  fleshy 
bellies.  It  is  sometimes  described  as  a  part  of  the  Complexus.  It  arises,  by  from 
two  to  four  tendinous  slips,  from  the  transverse  processes  of  as  many  of  the  upper 
thoracic  vertebrae,  and  is  inserted,  on  the  inner  side  of  the  Complexus,  into  the  supe- 
rior curved  line  of  the  occipital  bone. 

Relations. — The  Complexus  is  covered  by  the  Splenius  and  the  Trapezius.  It 
lies  on  the  Rectus  capitis  posticus  major  and  minor,  the  Obliquus  capitis  superior 
and  inferior,  and  on  the  Semispinalis  colli,  from  which  it  is  separated  by  the  pro- 
funda  cervicis  artery,  the  princeps  cervicis  artery,  and  branches  of  the  posterior 
primary  divisions  of  the  cervical  nerves.  The  Biventer  cervicis  is  separated  from 
its  fellow  of  the  opposite  side  by  the  ligamentum  nuchae. 

The  Fifth  Layer  (Fig.  282). 

Semispinalis  dorsi.  Extensor  coccygis. 

Semispinalis  colli.  Intertransversales. 

Multifidus  spinae.  Rectus  capitis  posticus  major. 

Rotatores  spinae.  Rectus  capitis  posticus  minor. 

Supraspinales.  Obliquus  capitis  inferior. 

Interspinales.  Obliquus  capitis  superior. 

Dissection. — Remove  the  muscles  of  the  preceding  layer  by  dividing  and  turning  aside  the 
Complexus;  then  detach  the  Spinalis  and  Longissimus  dorsi  from  their  attachments,  divide  the 
Erector  spinse  at  its  connection  below  to  the  sacral  and  lumbar  spines  and  turn  it  outward.  The 
muscles  filling  up  the  interval  between  the  spinous  and  transverse  processes  are  then  exposed. 


OF  THE  BACK  423 

The  Semispinalis  Dorsi  consists  of  thin,  narrow,  fleshy  fasciculi  interposed 
between  tendons  of  considerable  length.  It  arises  by  a  series  of  small  tendons 
from  the  transverse  processes  of  the  lower  thoracic  vertebra?,  from  the  tenth  or 
eleventh  to  the  fifth  or  sixth;  and  is  inserted,  by  five  or  six  tendons,  into  the 
spinous  processes  of  the  upper  four  thoracic  and  lower  two  cervical  vertebrae. 

The  Semispinalis  Colli  (m.  semispinalis  cervicis},  thicker  than  the  preceding, 
arises  by  a  series  of  tendinous  and  fleshy  fibres  from  the  transverse  processes  of 
the  upper  five  or  six  thoracic  vertebrae,  and  is  inserted  into  the  spinous  processes  of 
four  cervical  vertebrae,  from  the  axis  to  the  fifth  cervical.  The  fasciculus  con- 
nected with  the  axis  is  the  largest,  and  chiefly  muscular  in  structure. 

Relations. — By  their  superficial  surface,  from  below  upward,  with  the  Spinalis 
dorsi,  Longissimus  dorsi,  Splenius,  Complexus,  the  profunda  cervicis  artery,  the 
princeps  cervicis  artery,  and  the  internal  branches  of  the  posterior  divisions  of 
the  first,  second,  and  third  cervical  nerves;  by  their  deep  surface,  with  the  Mul- 
tifidus  spinae. 

The  Multifidus  Spinae  (m.  multifidus)  consists  of  a  number  of  fleshy  and  ten- 
dinous fasciculi  which  fill  up  the  groove  on  either  side  of  the  spinous  processes  of  the 
vertebrae,  from  the  sacrum  to  the  axis.  In  the  sacral  region  these  fasciculi  arise  from 
the  back  of  the  sacrum,  as  low  as  the  fourth  sacral  foramen,  and  from  the  aponeu- 
rosis  of  origin  of  the  Erector  spinae;  from  the  inner  surface  of  the  posterior  superior 
spine  of  the  ilium  and  posterior  sacro-iliac  ligaments;  in  the  lumbar  regions,  from 
the  articular  processes;  in  the  thoracic  region,  from  the  transverse  processes;  and 
in  the  cervical  region,  from  the  articular  processes  of  the  three  or  four  lower  verte- 
brae. Each  fasciculus,  passing  obliquely  upward  and  inward,  is  inserted  into  the 
whole  length  of  the  spinous  process  of  one  of  the  vertebrae  above.  These  fasciculi 
vary  in  length :  the  most  superficial,  the  longest,  pass  from  one  vertebra  to  the  third 
or  fourth  above;  those  next  in  order  pass  from  one  vertebra  to  the  second  or  third 
above ;  whilst  the  deepest  connect  two  contiguous  vertebrae. 

Relations. — By  its  superficial  surface,  with  the  Longissimus  dorsi,  Spinalis  dorsi, 
Semispinalis  dorsi,  and  Semispinalis  colli;  by  its  deep  surface,  with  the  laminae 
and  spinous  processes  of  the  vertebrae,  and  with  the  Rotatores  spinae  in  the  thoracic 
region. 

The  Rotatpres  Spinse  (mm.  rotatores]  are  found  only  in  the  thoracic  region  of  the 
spine,  beneath  the  Multifidus  spinae;  they  are  eleven  in  number  on  each  side.  Each 
muscle  is  small  and  somewhat  quadrilateral  in  form;  it  arises  from  the  upper  and 
back  part  of  the  transverse  process,  and  is  inserted  into  the  lower  border  and  outer 
surface  of  the  lamina  of  the  vertebra  above,  the  fibres  extending  as  far  inward  as 
the  root  of  the  spinous  process.  The  first  is  found  between  the  first  and  second 
thoracic;  the  last,  between  the  eleventh  and  twelfth.  Sometimes  the  number  of  these 
muscles  is  diminished  by  the  absence  of  one  or  more  from  the  upper  or  lower  end. 

The  Supraspinales  consist  of  a  series  of  fleshy  bands  which  lie  on  the  spinous 
processes  in  the  cervical  region  of  the  spine. 

The  Interspinales  are  short  muscular  fasciculi,  placed  in  pairs  between  the 
spinous  processes  of  the  contiguous  vertebrae,  one  on  each  side  of  the  interspinous 
ligament.  In  the  cervical  region  they  are  most  distinct,  and  consist  of  six  pairs, 
the  first  being  situated  between  the  axis  and  third  vertebra,  and  the  last  between 
the  last  cervical  and  the  first  thoracic.  They  are  small  narrow  bundles,  attached, 
above  and  below,  to  the  apices  of  the  spinous  processes.  In  the  thoracic  region 
they  are  found  between  the  first  and  second  vertebrae,  and  occasionally  between 
the  second  and  third;  and  below,  between  the  eleventh  and  twelfth.  In  the 
lumbar  region  there  are  four  pairs  of  these  muscles  in  the  intervals  between  the 
five  lumbar  vertebrae.  There  is  also  occasionally  one  in  the  interspinous  space 
between  the  last  thoracic  and  first  lumbar,  and  between  the  fifth  lumbar  and  the 
sacrum. 


424  THE  MUSCLES   AND    FASCIA 

The  Extensor  Coccygis  is  a  slender  muscular  fasciculus,  occasionally  present, 
which  extends  over  the  lower  part  of  the  posterior  surface  of  the  sacrum  and 
coccyx.  It  arises  by  tendinous  fibres  from  the  last  bone  of  the  sacrum  or  first 
piece  of  the  coccyx,  and  passes  downward  to  be  inserted  into  the  lower  part  of 
the  coccyx.  It  is  a  rudiment  of  the  Extensor  muscle  of  the  caudal  vertebrae  of 
the  lower  animals. 

The  Intertransversales  (mm.  intertransversarii)  are  small  muscles  placed 
between  the  transverse  processes  of  the  vertebrae.  In  the  cervical  region  they  are 
most  developed,  consisting  of  rounded  muscular  and  tendinous  fasciculi,  which  are 
placed  in  pairs,  passing  between  the  anterior  and  the  posterior  tubercles  of  the 
transverse  processes  of  two  contiguous  vertebrae,  separated  from  one  another  by 
the  anterior  division  of  the  cervical  nerve,  which  lies  in  the  groove  between  them. 
In  this  region  there  are  seven  pairs  of  these  muscles,  the  first  pair  being  between 
the  atlaS  and  axis,  and  the  last  pair  between  the  seventh  cervical  and  first  thoracic 
vertebrae.  In  the  thoracic  region  they  are  least  developed,  consisting  chiefly  of 
rounded  tendinous  cords  in  the  intertransverse  spaces  of  the  upper  thoracic  verte- 
brae; but  between  the  transverse  processes  of  the  lower  three  thoracic  vertebrae,  and 
between  the  transverse  processes  of  the  last  thoracic  and  the  first  lumbar,  they  are 
muscular  in  structure.  In  the  lumbar  region  they  are  arranged  in  pairs,  on  either 
side  of  the  spine,  one  set  occupying  the  entire  interspace  between  the  transverse 
processes  of  the  lumbar  vertebrae,  the  intertransversales  laterales  (mm.  intertrans- 
versarii laterales} ;  the  other  set,  intertransversales  mediales  (mm.  intertransversarii 
mediales},  passing  from  the  accessory  process  of  one  vertebra  to  the  mammillary 
process  of  the  next. 

The  Rectus  Capitis  Posticus  Major  (m.  rectus  capitis  posterior  major}  arises  by 
a  pointed  tendinous  origin  from  the  spinous  process  of  the  axis,  and,  becoming 
broader  as  it  ascends,  is  inserted  into  the  inferior  curved  line  of  the  occipital  bone 
and  the  surface  of  bone  immediately  below  it.  As  the  muscles  of  the  two  sides  pass 
upward  and  outward,  they  leave  between  them  a  triangular  space,  in  which  are 
seen  the  Recti  capitis  postici  minores  muscles. 

Relations. — By  its  superficial  surface,  with  the  Complexus,  and,  at  its  insertion, 
with  the  Superior  oblique;  by  its  deep  surface,  with  part  of  the  Rectus  capitis 
posticus  minor,  the  posterior  arch  of  the  atlas,  the  posterior  occipito-atlantal  liga- 
ment, and  part  of  the  occipital  bone. 

The  Rectus  Capitis  Posticus  Minor  (m.  rectus  capitis  posterior  minor],  the  small- 
est of  the  four  muscles  in  this  region,  is  of  a  triangular  shape;  it  arises  by  a  narrow 
pointed  tendon  from  the  tubercle  on  the  posterior  arch  of  the  atlas,  and,  becom- 
ing broader  as  it  ascends,  is  inserted  into  the  rough  surface  beneath  the  inferior 
curved  line,  nearly  as  far  as  the  foramen  magnum,  nearer  to  the  middle  line  than 
the  preceding. 

Relations.— By  its  superficial  surface,  with  the  Complexus  and  the  Rectus  capitis 
posticus  major;  by  its  deep  surface,  with  the  posterior  occipito-atlantal  ligament. 

The  Obliquus  Capitis  Inferior,  the  larger  of  the  two  Oblique  muscles,  arises 
from  the  apex  of  the  spinous  process  of  the  axis,  and  passes  outward  and  slightly 
upward,  to  be  inserted  into  the  lower  and  back  part  of  the  transverse  process  of 
the  atlas. 

Relations. — By  its  superficial  surface,  with  the  Complexus  and  with  the  pos- 
terior division  of  the  second  cervical  nerve,  which  crosses  it;  by  its  deep  surface, 
with  the  vertebral  artery  and  posterior  atlanto-axial  ligament. 

The  Obliquus  Capitis  Superior,  narrow  below,  wide  and  expanded  above, 
arises  by  tendinous  fibres  from  the  upper  surface  of  the  transverse  process  of  the 
atlas,  joining  with  the  insertion  of  the  preceding,  and,  passing  obliquely  upward 
and  inward,  is  inserted  into  the  occipital  bone,  between  the  two  curved  lines, 
external  to  the  Complexus. 


OF    THE  BACK  425 

Relations. — By  its  superficial  surface,  with  the  Complexus  and  Trachelo-mastoid 
and  occipital  artery.  By  its  deep  surf  ace, with  the  posterior  occipito-atlantal  ligament. 

Between  the  two  oblique  muscles  and  the  Rectus  capitis  posticus  major  a  trian- 
gular interval  exists,  the  suboccipital  triangle.  This  triangle  is-  bounded,  above 
and  internally,  by  the  Rectus  capitis  posticus  major;  above  and  externally,  by  the 
Obliquus  capitis  superior;  below  and  externally,  by  the  Obliquus  capitis  inferior. 
It  is  covered  in  by  a  layer  of  dense  fibro-fatty  tissue,  situated  beneath  the  Com- 
plexus muscle.  The  floor  is  formed  by  the  posterior  occipito-atlantal  ligament 
and  the  posterior  arch  of  the  atlas.  It  contains  the  vertebral  artery,  as  it  runs  in 
a  deep  groove  on  the  upper  surface  of  the  posterior  arch  of  the  atlas,  and  the  pos- 
terior division  of  the  suboccipital  nerve. 

Nerves.— The  third,  fourth,  and  fifth  layers  of  the  muscles  of  the  back  are 
supplied  by  the  posterior  primary  divisions  of  the  spinal  nerves. 

Actions. — When  both  the  Spinales  dorsi  contract,  they  extend  the  thoracic  region 
of  the  spine;  when  only  one  muscle  contracts,  it  helps  to  bend  the  thoracic  por- 
tion of  the  spine  to  one  side.  The  Erector  spinse,  comprising  the  Ilio-costalis  and 
the  Ixmgissimus  dorsi  with  their  accessory  muscles,  serves,  as  its  name  implies, 
to  maintain  the  spine  in  the  erect  posture;  it  also  serves  to  bend  the  trunk  back- 
ward when  it  is  required  to  counterbalance  the  influence  of  any  weight  at  the 
front  of  the  body,  as,  for  instance,  when  a  heavy  weight  is  suspended  from  the 
neck,  or  when  there  is  any  great  abdominal  distention,  as  in  pregnancy  or  dropsy; 
the  peculiar  gait  under  such  circumstances  depends  upon  the  spine  being  drawn 
backward  by  the  counterbalancing  action  of  the  Erector  spinse  muscles.  The 
muscles  which  form  the  continuation  of  the  Erector  spinse  upward  steady  the 
head  and  neck,  and  fix  them  in  the  upright  position.  If  the  Ilio-costalis  and 
Longissimus  dorsi  of  one  side  act,  they  serve  to  draw  down  the  chest  and  spine  to 
the  corresponding  side.  The  Cervicales  ascendens,  taking  their  fixed  points  from 
the  cervical  vertebrse,  elevate  those  ribs  to  which  they  are  attached;  taking  their 
fixed  points  from  the  ribs,  both  muscles  help  to  extend  the  neck;  while  one  muscle 
bends  the  neck  to  its  own  side.  The  Transversalis  cervicis,  when  both  muscles  act, 
taking  their  fixed  point  from  below,  bend  the  neck  backward.  The  Trachelo- 
mastoid,  when  both  muscles  act,  taking  their  fixed  point  from  below,  bend  the  head 
backward;  while,  if  only  one  muscle  acts,  the  face  is  turned  to  the  side  on  which 
the  muscle  is  acting,  and  then  the  head  is  bent  to  the  shoulder.  The  two  Recti 
muscles  draw  the  head  backward.  The  Rectus  capitis  posticus  major,  owing  to 
its  obliquity,  rotates  the  cranium,  with  the  atlas,  round  the  odontoid  process, 
turning  the  face  to  the  same  side.  The  Multifidus  spinse  acts  successively  upon  the 
different  parts  of  the  spine;  thus,  the  sacrum  furnishes  a  fixed  point  from  which 
the  fasciculi  of  this  muscle  act  upon  the  lumbar  region;  these  then  become  the 
fixed  points  for  the  fasciculi  moving  the  thoracic  region,  and  so  on  throughout  the 
entire  length  of  the  spine;  it  is  by  the  successive  contraction  and  relaxation  of 
the  separate  fasciculi  of  this  and  other  muscles  that  the  spine  preserves  the  erect 
posture  without  the  fatigue  that  would  necessarily  have  been  produced  had  this 
position  been  maintained  by  the  action  of  a  single  muscle.  The  Multifidus  spinae, 
besides  preserving  the  erect  position  of  the  spine,  serves  to  rotate  it,  so  that  the 
front  of  the  trunk  is  turned  to  the  side  opposite  to  that  from  which  the  muscle 
acts,  this  muscle  being  assisted  in  its  action  by  the  Obliquus  externus  abdominis. 
The  Complexi  draw  the  head  directly  backward:  if  one  muscle  acts,  it  draws 
the  head  to  one  side,  and  rotates  it  so  that  the  face  is  turned  to  the  opposite 
side.  The  Superior  oblique  draws  the  head  backward,  and,  from  the  obliquity 
in  the  direction  of  its  fibres,  will  slightly  rotate  the  cranium,  turning  the  face  to 
the  opposite  side.  The  Obliquus  capitis  inferior  rotates  the  atlas,  and  with  it  the 
cranium,  round  the  odontoid  process,  turning  the  face  to  the  same  side.  The 
Semispinales,  when  the  muscles  of  the  two  sides  act  together,  help  to  extend  the 


426  THE  MUSCLES  AND  FASCIA 

spine;  when  the  muscles  of  one  side  only  act,  they  rotate  the  thoracic  and  cervical 
parts  of  the  spine,  turning  the  body  to  the  opposite  side.  The  Supraspinales  and 
Interspinales  by  approximating  the  spinous  processes  help  to  extend  the  spine. 
The  Intertransversales  approximate  the  transverse  processes,  and  help  to  bend  the 
spine  to  one  side.  The  Rotatores  spinse  assist  the  Multifidus  spinse  to  rotate  the 
spine,  so  that  the  front  of  the  trunk  is  turned  to  the  side  opposite  to  that  from 
which  the  muscle  acts. 

Surface  Forms. — The  surface  forms  produced  by  the  muscles  of  the  back  are  numerous  and 
difficult  to  analyze  unless  they  are  considered  in  systematic  order.  The  most  superficial  layer, 
consisting  of  large  strata  of  muscular  substance,  influences  to  a  certain  extent  the  surface  form, 
and  at  the  same  time  reveals  the  forms  of  the  layers  beneath.  The  Trapezius  at  the  upper  part 
of  the  back,  and  in  the  neck,  covers  over  and  softens  down  the  outline  of  the  underlying  muscles. 
Its  anterior  border  forms  the  posterior  boundary  of  the  posterior  triangle  of  the  neck.  It  forms 
a  slight  undulating  ridge  which  passes  downward  and  forward  from  the  occiput  to  the  junction 
of  the  middle  and  outer  third  of  the  clavicle.  The  tendinous  ellipse  formed  by  a  part  of  the 
origin  of  the  two  muscles  at  the  back  of  the  neck  is  always  to  be  seen  as  an  oval  depression, 
more  marked  when  the  muscle  is  in  action.  A  slight  dimple  on  the  skin  opposite  the  interval 
between  the  spinous  processes  of  the  third  and  fourth  thoracic  vertebrae  marks  the  triangular 
aponeurosis  by  which  the  inferior  fibres  are  inserted  into  the  root  of  the  spine  of  the  scapula. 
From  this  point  the  inferior  border  of  the  muscle  may  be  traced  as  an  undulating  ridge  to  the 
spinous  process  of  the  twelfth  thoracic  vertebra.  In  like  manner  the  Latissimus  dorsi  softens 
down  and  modulates  the  underlying  structures  at  the  lower  part  of  the  back  and  lower  part  of 
the  side  of  the  chest.  In  this  way  it  modulates  the  outline  of  the  Erector  spinse;  of  the  Serratus 
posticus  inferior,  which  is  sometimes  to  be  discerned  through  it,  and  is  sometimes  entirely 
obscured  by  it;  of  part  of  the  Serratus  magnus  and  Superior  oblique,  which  it  covers;  and  of 
the  convex  oblique  ridges  formed  by  the  ribs  with  the  intervening  intercostal  spaces.  The 
anterior  border  of  the  muscle  is  the  only  part  which  gives  a  distinct  surface  form.  This  border 
may  be  traced,  when  the  muscle  is  in  action,  as  a  rounded  edge,  starting  from  the  crest  of  the 
ilium,  and  passing  obliquely  forward  and  upward  to  the  posterior  border  of  the  axilla,  where  it 
combines  with  the  Teres  major  in  forming  a  thick  rounded  fold,  the  posterior  boundary  of  the 
axillary  space.  The  muscles  in  the  second  layer  influence  to  a  very  considerable  extent  the  sur- 
face form  of  the  back  of  the  neck  and  upper  part  of  the  trunk.  The  Levator  anguli  scapulae 
reveals  itself  as  a  prominent  divergent  line,  running  downward  and  outward,  from  the  trans- 
verse processes  of  the  upper  cervical  vertebrae  to  the  angle  of  the  scapula,  covered  over  and 
toned  down  by  the  overlying  Trapezius.  The  Rhomboidei  produce,  when  in  action,  a  vertical 
eminence  between  the  vertebral  border  of  the  scapula  and  the  spinal  furrow,  varying  in  intensity 
according  to  the  condition  of  contraction  or  relaxation  of  the  Trapezius  muscle,  by  which  they 
are  for  the  most  part  covered.  The  lowermost  part  of  the  Rhomboideus  major  is  uncovered 
by  the  Trapezius,  and  forms  on  the  surface  an  oblique  ridge  running  upward  and  inward  from 
the 'inferior  angle  of  the  scapula.  Of  the  muscles  of  the  third  layer  of  the  back,  the  Serratus 
posticus  superior  does  not  in  any  way  influence  surface  form.  The  Serratus  posticus  inferior, 
when  in  strong  action,  may  occasionally  be  revealed  as  an  elevation  beneath  the  Latissimus 
dorsi.  The  Splenii  by  their  divergence  serve  to  broaden  out  the  upper  part  of  the  back  of  the 
neck  and  produce  a  local  fulness  in  this  situation,  but  do  not  otherwise  influence  surface  form. 
Beneath  all  these  muscles  those  of  the  fourth  layer — the  Erector  spinae  and  its  continuations — 
influence  the  surface  form  in  a  decided  manner.  In  the  loins,  the  Erector  spinae,  bound  down 
by  the  lumbar  fascia,  forms  a  rounded  vertical  eminence,  which  determines  the  depth  of  the 
spinal  furrow,  and  which  below  tapers  to  a  point  on  the  posterior  surface  of  the  sacrum  and 
becomes  lost  there.  In  the  back  it  forms  a  flattened  plane1  which  gradually  becomes  lost.  In 
the  neck  the  only  part  of  this  group  of  muscles  which  influences  surface  form  is  the  Trachelo- 
mastoid,  which  produces  a  short  convergent  line  across  the  upper  part  of  the  posterior  triangle 
of  the  neck,  appearing  from  under  cover  of  the  posterior  border  of  the  Sterno-mastoid  and 
being  lost  below  beneath  the  Trapezius. 

II.  MUSCLES  AND  FASCIA  OF  THE  THORAX. 

The  muscles  belonging  exclusively  to  this  region  are  few  in  number.  They  are  the 

Intercostales  externi.  Triangularis  sterni. 

Intercostales  interni.  Levatores  costarum. 

Infracostales.  Diaphragm. 

Intercostal  Fascia. — A  thin  but  firm  layer  of  fascia  covers  the  outer  surface  of 
the  External  intercostal  and  the  inner  surface  of  the  Internal  intercostal  muscles; 


OF    THE    THORAX  427 

and  a  third  layer,  more  delicate,  is  interposed  between  the  two  planes  of  muscular 
fibres.  These  are  the  intercostal  fasciae,  external,  middle,  and  internal;  they  are  best 
marked  in  those  situations  where  the  muscular  fibres  are  deficient,  as  between  the 
External  intercostal  muscles  and  sternum,  in  front,  and  between  the  Internal 
intercostals  and  spine,  behind. 

The  Intercostal  Muscles  (Figs.  290  and  314)  are  two  thin  planes  of  muscular 
and  tendinous  fibres,  placed  one  over  the  other,  filling  up  the  intercostal  spaces, 
and  being  directed  obliquely  between  the  margins  of  the  adjacent  ribs.  They 
have  received  the  name  external  and  internal  from  the  position  they  bear  to  one 
another.  The  tendinous  fibres  are  longer  and  more  numerous  than  the  muscular; 
hence  the  walls  of  the  intercostal  spaces  possess  very  considerable  strength,  to 
which  the  crossing  of  the  muscular  fibres  materially  contributes. 

The  External  Intercostals  (mm.  intercostales  externi)  are  eleven  in  number  on 
each  side.  They  extend  from  the  tubercles  of  the  ribs,  behind,  to  the  commence- 
ment of  the  cartilages  of  the  ribs,  in  front,  where  they  terminate  in  a  thin  mem- 
brane, the  anterior  intercostal  membrane,  which  is  continued  forward  to  the  sternum. 
They  arise  from  the  lower  border  of  the  rib  above,  and  are  inserted  into  the  upper 
border  of  the  rib  below7.  In  the  two  lowest  spaces  they  extend  to  the  ends  of  the 
cartilages,  and  in  the  upper  two  or  three  spaces  they  do  not  quite  extend  to  the  ends 
of  the  ribs.  Their  fibres  are  directed  obliquely  downward  and  forward,  in  a 
similar  direction  with  those  of  the  External  oblique  muscle  of  the  abdomen. 
They  are  thicker  than  the  Internal  intercostals. 

Relations. — By  their  outer  surface,  with  the  muscles  which  immediately  invest 
the  chest — viz.,  the  Pectoralis  major  and  minor,  Serratus  magnus,  and  Rhom- 
boideus  major,  Serratus  posticus  superior  and  inferior,  Scalenus  posticus,  Ilio- 
costalis,  Longissimus  dorsi,  Cervicalis  ascendens,  Transversalis  cervicis,  Leva- 
tores  costarum,  Obliquus  externus  abdominis,  and  the  Latissimus  dorsi;  by  their 
internal  surface,  with  the  middle  intercostal  fascia,  which  separates  them  from  the 
intercostal  vessels  and  nerve  and  the  Internal  intercostal  muscles,  and,  behind, 
from  the  pleura. 

The  Internal  Intercostals  (mm.  intercostales  interni)  are  also  eleven  in  number  on 
each  side.  They  commence  anteriorly  at  the  sternum  in  the  interspaces  between 
the  cartilages  of  the  true  ribs,  and  from  the  anterior  extremities  of  the  cartilages 
of  the  false  ribs,  and  extend  backward  as  far  as  the  angles  of  the  ribs,  whence  they 
are  continued  to  the  vertebral  column  by  a  thin  aponeurosis,  the  posterior  inter- 
costal membrane.  They  arise  from  the  ridge  on  the  inner  surface  of  the  rib  above, 
as  well  as  from  the  corresponding  costal  cartilage,  and  are  inserted  into  the  upper 
border  of  the  rib  below.  Their  fibres  are  directed  obliquely  downward  and  back- 
ward, passing  in  the  opposite  direction  to  the  fibres  of  the  External  intercostal 
muscle. 

Relations. — By  their  external  surface,  with  the  intercostal  vessels  and  nerves 
and  the  External  intercostal  muscles;  near  the  sternum,  with  the  anterior  inter- 
costal membrane  and  the  Pectoralis  major.  By  their  internal  surface,  with  the 
pleura  costalis,  Triangularis  sterni,  and  Diaphragm. 

The  Infracostales  (mm.  subcostales]  consist  of  muscular  and  aponeurotic  fas- 
ciculi, which  vary  in  number  and  length;  they  are  placed  on  the  inner  surface  of  the 
ribs,  where  the  Internal  intercostal  muscles  cease;  they  arise  from  the  inner  sur- 
face of  one  rib,  and  are  inserted  into  the  inner  surface  of  the  first,  second,  or  third 
rib  below.  Their  direction  is  most  usually  oblique,  like  the  Internal  intercostals. 
They  are  most  frequent  between  the  lower  ribs. 

The  Triangularis  Sterni  (m.  transversus  thoracis}  (Fig.  283)  is  a  thin  plane  of 
muscular  and  tendinous  fibres,  situated  upon  the  inner  wall  of  the  front  of  the  chest. 
It  arises  from  the  lower  third  of  the  posterior  surface  of  the  sternum,  from  the 
posterior  surface  of  the  ensiform  cartilage,  and  from  the  sternal  ends  of  the  costal 


428 


cartilages  of  the  three  or  four  lower  true  ribs.  Its  fibres  diverge  upward  and  out- 
ward, to  be  inserted  by  digitations  into  the  lower  borders  and  inner  surfaces  of  the 
costal  cartilages  of  the  second,  third,  fourth,  fifth,  and  sixth  ribs.  The  lowest 
fibres  of  this  muscle  are  horizontal  in  their  direction,  and  are  continuous  with 
those  of  the  Transversalis ;  those  which  succeed  are  oblique,  whilst  the  superior 
fibres  are  almost  vertical.  This  muscle  varies  much  in  its  attachment,  not  only  in 
different  bodies,  but  on  opposite  sides  of  the  same  body. 

Relations. — In  front,  with  the  sternum,  ensiform  cartilage,  costal  cartilages, 
Internal  intercostal  muscles,  and  internal  mammary  vessels;  behind,  with  the 
pleura,  pericardium,  and  anterior  mediastinum. 


STERNO-MASTOID. 


SUBCLAVIUS. 


SUBCLAVIUS. 


Internal  mam- 
mary artery. 


,TRIANGULARIS 
STERNI. 


TRANSVERSALIS    ABDOMINIS. 


FIG.  283. — Posterior  surface  of  sternum  and  costal  cartilages,  showing  Triangularis  sterni  muscle.     (From  a 
preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 

The  Levatores  Costarum  (Fig.  282),  twelve  in  number  on  each  side,  are  small 
tendinous  and  fleshy  bundles  which  arise  from  the  extremities  of  the  transverse 
processes  of  the  seventh  cervical  and  eleven  upper  thoracic  vertebrae,  and,  passing 
obliquely  downward  and  outward,  are  inserted  into  the  upper  border  of  the  rib 
below  them,  between  the  tubercle  and  the  angle.  The  Inferior  levatores  divide 
into  two  fasciculi,  one  of  which  is  inserted  as  above  described;  the  other  fasciculus 
passes  down  to  the  second  rib  below  its  origin;  thus,  each  of  the  lower  ribs  receives 
fibres  from  the  transverse  processes  of  two  vertebrae. 

Nerves. — The  muscles  of  this  group  are  supplied  by  the  intercostal  nerves. 


OF  THE  THORAX  429 

The  Diaphragm  (diaphragma,  from  did<ppa?fjta,  a  partition  wall)  (Figs.  284, 285, 
and  286)  is  a  thin,  musculo-fibrous  septum,  consisting  of  muscular  fibres  externally, 
which  arise  from  the  circumference  of  the  thoracic  cavity  and  pass  upward  and 
inward  to  converge  to  a  central  tendon.  It  is  placed  obliquely  at  the  junction  of 
the  upper  with  the  middle  third  of  the  trunk,  and  separates  the  thorax  from  the 
abdomen,  forming  the  floor  of  the  former  cavity  and  the  roof  of  the  latter.  It  is 
elliptical,  its  longest  diameter  being  from  side  to  side;  is  somewhat  fan-shaped,  the 
broad  elliptical  portion  being  horizontal,  the  narrow  part,  the  crura,  which  repre- 
sents the  handle  of  the  fan,  vertical,  and  joined  at  right  angles  to  the  former.  It 
is  from  this  circumstance  that  some  anatomists  describe  it  as  consisting  of  two 
portions,  the  upper  or  great  muscle  of  the  Diaphragm,  and  the  lower  or  lesser 
muscle.  It  arises  from  the  whole  of  the  internal  circumference  of  the  thorax, 
being  attached,  in  front,  by  fleshy  fibres  to  the  ensiform  cartilage,  sternal  portion 
of  the  Diaphragm  (pars  sternalis};  on  either  side,  to  the  inner  surface  of  the 
cartilages  and  bony  portions  of  the  six  or  seven  inferior  ribs,  costal  portion  (pars 
costalis),  interdigitating  with  the  Transversalis;  and  behind,  to  two  aponeurotic 
arches,  named  the  ligamentum  arcuatum  externum  and  the  ligamentum  arcuatum 
internum,  and  by  the  crura,  to  the  lumbar  vertebrae,  lumbar  portion  (pars  lumbalis). 
The  fibres  from  these  sources  vary  in  length:  those  arising  from  the  ensiform 
appendix  are  very  short  and  occasionally  aponeurotic;  those  from  the  ligamenta 
arcuata,  and  more  especially  those  from  the  cartilages  of  the  ribs  at  the  side 
of  the  chest,  are  longer,  describe  well-marked  curves  as  they  ascend,  and  finally 
converge  to  be  inserted  into  the  circumference  of  the  central  tendon.  Between 
the  sides  of  the  muscular  slip  from  the  ensiform  appendix  and  the  cartilages  of 
the  adjoining  ribs  the  fibres  of  the  Diaphragm  are  deficient,  the  interval  being 
filled  by  areolar  tissue,  covered  on  the  thoracic  side  by  the  pleurae;  on  the  abdom- 
inal, by  the  peritoneum.  This  is,  consequently,  a  weak  point,  and  a  portion  of 
the  contents  of  the  abdomen  may  protrude  through  it  into  the  chest,  forming  a 
phrenic  or  diaphragmatic  hernia,  or  a  collection  of  pus  in  the  mediastinum  may 
descend  through  it,  so  as  to  point  at  the  epigastrium.  A  triangular  gap  is  some- 
times seen  between  the  fibres  springing  from  the  internal  and  those  arising  from 
the  external  arcuate  ligament.  When  it  exists,  the  kidney  is  separated  from  the 
pleura  only  by  fatty  and  areolar  tissue. 

A  congenital  deficiency  in  the  Diaphragm  may  produce  diaphragmatic  hernia; 
in  deficiency  of  the  central  tendon  the  hernia  passes  into  the  pericardial  sac;  in 
deficiency  of  one  of  the  lateral  portions  the  hernia  passes  into  the  pleural  sac. 

There  are  five  arcuate  ligaments,  two  internal,  two  external,  and  one  middle. 

The  Ligamentum  Arcuatum  Internum  (arcus  lumbocostalis  medialis)  is  a  tendinous 
arch,  thrown  across  the  upper  part  of  the  Psoas  magnus  muscle,  on  each  side  of 
the  spine.  It  is  connected,  by  one  end,  to  the  outer  side  of  the  body  of  the  first  or 
second  lumbar  vertebra,  being  continuous  with  the  outer  side  of  the  tendon  of 
the  corresponding  crus;  and,  by  the  other  end,  to  the  front  of  the  transverse  process 
of  the  first,  and  sometimes  also  to  that  of  the  second,  lumbar  vertebra. 

The  Ligamentum  Arcuatum  Externum  (arcus  lumbocostalis  lateralis)  is  the  thick- 
ened upper  margin  of  the  anterior  lamella  of  the  lumbar  fascia;  it  arches  across 
the  upper  part  of  the  Quadratus  lumborum,  being  attached,  by  one  extremity,  to 
the  front  of  the  transverse  process  of  the  first  lumbar  vertebra,  and,  by  the  other, 
to  the  apex  and  lower  margin  of  the^last  rib. 

The  arch  of  fibrous  tissue  which  connects  the  crura  of  the  diaphragm  in  front 
of  the  aorta  is  sometimes  called  the  middle  arcuate  ligament.  The  Diaphragm  is 
connected  to  the  spine' by  two  crura  or  pillars,  which  are  situated  on  the  bodies  of 
lumbar  vertebrae,  on  each  side  of  the  aorta.  The  crura,  at  their  origin,  are  ten- 
dinous in  structure;  the  right  crus,  larger  and  .longer  than  the  left,  arising  from 
the  anterior  common  ligament  and  intervertebral  substances  of  the  three  or  four 


430 

upper  lumbar  vertebrae;  the  left,  from  the  two  upper  lumbar  vertebrae.     These 
tendinous  portions  of  the  crura  pass  forward  and  inward,  and  gradually  con- 


CESOPHAGUS 


FORAMEN    QUADRATUM 
FOR  VCNA  CAVA 


CENTRAL   TENDON, 
LEFT  SIDE 

AORTA  CENTRAL  TENDON. 

RIGHT  SIDE 

FIG.  284. — The  Diaphragm,  seen  from  above.     (Poirier  and  Charpy.) 


FIG.  285.— The  Diaphragm,  viewed  from  in  front.     (Testut.) 


verge  to  meet  in  the  middle  line,  forming  an  arch,  beneath  which  passes  the 
aorta,  vena  azygos  major,  and  thoracic  duct.  From  this  tendinous  arch  muscular 
fibres  arise,  which  diverge,  the  outermost  portion  being  directed  upward  and 


OF   THE    THORAX 


431 


outward  to  the  central  tendon;  the  innermost  decussating  in  front  of  the  aorta 
and  then  diverging,  so  as  to  surround  the  oesophagus  before  ending  in  the  central 
tendon.  The  fibres  derived  from  the  right  crus  are  the  most  numerous  and  pass 
in  front  of  those  derived  from  the  left.  His  and  Spalteholz  teach  that  three  crura 
exist  on  each  side — viz.,  the  crus  mediale,  arising  from  the  third  and  fourth  lumbar 
vertebrae;  the  crus  intermedium,  from  the  second  and  third  lumbar  vertebrae;  and 
the  crus  laterale,  from  the  second  or  first  lumbar  vertebrae,  and  from  the  band  of 
fascia  which  is  stretched  between  the  lateral  part  of  the  body  of  the  first  lumbar 
vertebra  and  the  transverse  process  of  the  second  lumbar  vertebra  in  front  of  the 
Psoas  muscle. 

The  Central  or  Cordiform  Tendon  of  the  Diaphragm  (centrum  tendineum)  is  a  thin 
but  strong  tendinous  aponeurosis,  situated  at  the  centre  of  the  vault  formed  by 
the  muscle,  immediately  below  the  pericardium,  with  which  it  is  partly  blended. 
It  is  shaped  somewhat  like  a  trefoil  leaf,  consisting  of  three  divisions,  or  leaflets, 


FIG.  286. — The  Diaphragm,  viewed  from  below.    (Testut.) 

separated  from  one  another  by  slight  indentations.  The  right  leaflet  is  the  largest; 
the  middle  one,  directed  toward  the  ensiform  cartilage,  the  next  in  size;  and  the 
left,  the  smallest.  In  structure,  the  tendon  is  composed  of  several  planes  of  fibres 
which  intersect  one  another  at  various  angles,  and  unite  into  straight  or  curved 
bundles — an  arrangement  which  affords  it  additional  strength. 

The  Openings. — The  openings  connected  with  the  Diaphragm  are  three  large 
and  several  smaller  apertures.  The  former  are  the  aortic,  the  oesophageal,  and  the 
opening  for  the  vena  cava. 

The  Aortic  Opening  (hiatus  aorticus}  is  the  lowest  and  the  most  posterior  of  the 
three  large  apertures  connected  with  this  muscle,  being  at  the  level  of  the  first 
lumbar  vertebra.  It  is  situated  slightly  to  the  left  of  the  middle  line,  immediately 
in  front  of  the  bodies  of  the  vertebrae;  and  is,  therefore,  behind  the  Diaphragm,  not 
in  it.  It  is  an  osseo-aponeurotic  aperture,  formed  by  a  tendinous  arch  thrown 
across  the  front  of  the  bodies  of  the  vertebrae,  from  the  crus  on  one  side  to  that 
on  the  other,  and  transmits  the  aorta,  vena  azygos  major,  and  thoracic  duct. 
Sometimes  the  vena  azygos  major  is  transmitted  upward  through  the  right  crus. 


432  THE  MUSCLES  AND  FASCIAE 

Occasionally  some  tendinous  fibres  are  prolonged  across  the  bodies  of  the  ver- 
tebrae from  the  inner  part  of  the  lower  end  of  the  crura,  passing  behind  the  aorta, 
and  thus  converting  the  opening  into  a  fibrous  ring. 

The  (Esophageal  Opening  (hiatus  oesophageus)  is  situated  at  the  level  of  the  tenth 
thoracic  vertebrae;  it  is  elliptical  in  form,  oblique  in  direction,  muscular  in  structure, 
and,  formed  by  the  decussating  fibres  of  the  two  crura,  is  placed  above,  and,  at 
the  same  time,  anterior,  and  a  little  to  the  left  of  the  preceding.  It  transmits  the 
oesophagus  and  vagus  nerves  and  some  small  cesophageal  arteries.  The  anterior 
margin  of  this  aperture  is  occasionally  tendinous,  being  formed  by  the  margin 
of  the  central  tendon.  The  posterior  and  lateral  margins  are  thick  and  the  gullet 
is  in  contact  with  them  for  about  half  an  inch.  The  right  margin  of  the  cesophageal 
opening  is  particularly  prominent  and  lies  in  the  oesophageal  groove  on  the  posterior 
surface  of  the  left  lobe  of  the  liver. 

The  Opening  for  the  Vena  Cava  or  the  Foramen  Quadratum  (foramen  venae  cavae) 
is  the  highest  opening,  being  about  on  the  level  of  the  disk  between  the  eighth 
and  ninth  thoracic  vertebrae;  it  is  quadrilateral  in  form,  tendinous  in  structure,  and 
placed  at  the  junction  of  the  right  and  middle  leaflets  of  the  central  tendon,  its 
margins  being  adherent  to  the  wall  of  the  inferior  vena  cava  (postcava). 

The  right  cms  transmits  the  greater  and  lesser  splanchnic  nerves  of  the  right 
side;  the  left  crus  transmits  the  greater  and  lesser  splanchnic  nerves  of  the  left 
side,  and  the  vena  azygos  minor.  The  gangliated  cords  of  the  sympathetic 
usually  enter  the  abdominal  cavity  by  passing  behind  the  internal  arcuate  liga- 
ments. 

Serous  Membranes. — The  serous  membranes  in  relation  with  the  Diaphragm  are 
four  in  number:  three  lining  its  upper  or  thoracic  surface;  one,  its  abdominal.  The 
three  serous  membranes  on  its  upper  surface  are  the  pleura  on  either  side  and  the 
pericardium,  which  covers  the  middle  portion  of  the  tendinous  centre.  The 
serous  membrane  covering  the  under  surface  of  the  Diaphragm  is  a  portion  of 
the  general  peritoneal  membrane  of  the  abdominal  cavity. 

The  Diaphragm  is  arched,  being  convex  toward  the  chest  and  concave  toward  the 
abdomen.  The  right  portion  forms  a  complete  arch  from  before  backward,  being 
accurately  moulded  over  the  convex  surface  of  the  liver,  and  having  resting  upon 
it  the  concave  base  of  the  right  lung.  The  left  portion  is  arched  from  before  back- 
ward in  a  similar  manner;  but  the  arch  is  narrower  in  front,  being  encroached  upon 
by  the  pericardium,  and  lower  than  the  right,  at  its  summit,  by  about  three-quarters 
of  an  inch.  It  supports  the  base  of  the  left  lung,  and  covers  the  great  end  of  the 
stomach,  the  spleen,  and  left  kidney.  At  its  circumference  the  Diaphragm  is 
higher  in  the  medial  line  of  the  body  than  at  either  side;  but  in  the  middle  of  the 
thorax  the  central  portion,  which  supports  the  heart,  is  on  a  lower  level  than  the 
two  lateral  portions. 

Nerves. — The  Diaphragm  is  supplied  by  the  phrenic  nerves,  the  lower  inter- 
costal nerves  and  the  phrenic  plexus  of  the  sympathetic. 

Actions. — The  Intercostals  are  the  chief  agents  in  the  movement  of  the  ribs 
in  ordinary  respiration.  When  the  first  rib  is  elevated  and  fixed  by  the  Scaleni,  the 
External  intercostals  raise  the  other  ribs,  especially  their  forepart,  and  so  increase 
the  capacity  of  the  chest  from  before  backward ;  at  the  same  time  they  evert  their 
lower  borders,  and  so  enlarge  the  thoracic  cavity  transversely.  The  Internal 
intercostals,  at  the  side  of  the  thorax,  depress  the  ribs  and  invert  their  lower 
borders,  and  so  diminish  the  thoracic  cavity;  but  at  the  forepart  of  the  chest  these 
muscles  assist  the  External  intercostals  in  raising  the  cartilages.1  The  Levatores 

1  The  view  of  the  action  of  the  Intercostal  muscles  given  in  the  text  is  that  which  is  taught  by  Hutchinson 
(Cycl.  of  Anat.  and  Phys.,  art.  Thorax),  and  is  usually  adopted  in  our  schools.  It  is,  however,  much  dis- 
puted. Hamberger  believed  that  the  External  intercostals  act  as  elevators  of  the  ribs,  or  muscles  of  inspira- 
tion, while  the  internal  act  in  expiration.  Haller  taught  that  both  sets  of  muscles  act  in  common — viz.,  as  muscles 
of  inspiration — and  this  view  is  adopted  by  many  of  the  best  anatomists  of  the  Continent,  and  appears  sup- 


OF    THE    THORAX  433 

costarum  assist  the  External  intercostals  in  raising  the  ribs.  The  Triangularis 
sterni  draws  down  the  costal  cartilages;  it  is  therefore  an  expiratory  muscle. 

The  Diaphragm  is  the  principal  muscle  of  inspiration.  When  in  a  condition 
of  rest  the  muscle  presents  a  domed  surface,  concave  toward  the  abdomen;  and 
consists  of  a  circumferential  muscular  and  a  central  tendinous  part.  When 
the  muscular  fibres  contract,  they  become  less  arched,  or  nearly  straight,  and 
thus  cause  the  central  tendon  to  descend,  and  in  consequence  the  level  of  the 
chest-wall  is  lowered,  the  vertical  diameter  of  the  chest  being  proportionally 
increased.  In  this  descent  the  different  parts  of  the  tendon  move  unequally. 
The  left  leaflet  descends  to  the  greatest  extent;  the  right  to  a  less  extent,  on 
account  of  the  liver;  and  the  central  leaflet  the  least,  because  of  its  connection  to 
the  pericardium.  In  descending  the  Diaphragm  presses  on  the  abdominal  viscera, 
and  so  to  a  certain  extent  causes  a  projection  of  the  abdominal  wall;  but  in  conse- 
quence of  these  viscera  not  yielding  completely,  the  central  tendon  becomes  a  fixed 
point,  and  enables  the  circumferential  muscular  fibres  to  act  from  it,  and  so  elevate 
the  lower  ribs  and  expand  the  lower  part  of  the  thoracic  cavity;  and  Duchenne 
has  shown  that  the  Diaphragm  has  the  power  of  elevating  the  ribs,  to  which  it 
is  attached,  by  its  contraction,  if  the  abdominal  viscera  are  in  situ,  but  that  if  these 
organs  are  removed,  this  power  is  lost.  When  at  the  end  of  inspiration  the  Dia- 
phragm relaxes,  the  thoracic  walls  return  to  their  natural  position  in  consequence 
of  their  elastic  reaction  and  of  the  elasticity  and  weight  of  the  displaced  viscera.1 

In  all  expulsive  acts  the  Diaphragm  is  called  into  action,  to  give  additional 
power  to  each  expulsive  effort.  Thus,  before  sneezing,  coughing,  laughing,  and 
crying,  before  vomiting,  previous  to  the  expulsion  of  the  urine  and  faeces,  or  of 
the  foetus  from  the  womb,  a  deep  inspiration  takes  place. 

The  height  of  the  Diaphragm  is  constantly  varying  during  respiration,  the 
muscle  being  carried  upward  or  downward  from  the  average  level ;  its  height  also 
varies  according  to  the  degree  of  distention  of  the  stomach  and  intestines,  and  the 
size  of  the  liver.  After  a  forced  expiration,  the  right  arch  is  on  a  level,  in  front, 
with  the  fourth  costal  cartilage;  at  the  side,  with  the  fifth,  sixth,  and  seventh 
ribs;  and  behind,  with  the  eighth  rib,  the  left  arch  being  usually  from  one  to  two 
ribs'  breadth  below'the  level  of  the  right  one.  In  a  forced  inspiration,  it  descends 
from  one  to  two  inches;  its  slope  would  then  be  represented  by  a  line  drawn 
from  the  ensiform  cartilage  toward  the  tenth  rib.  Prof.  Wm.  S.  Forbes2  is  of  the 
opinion  that  the  Diaphragm  is  an  appendage  of  the  circulatory  apparatus  rather 
than  the  chief  agent  in  respiration.  He  maintains  that  the  opening  in  the 
vena  cava  is  stationary  and  holds  a  constant  relation  to  the  ninth  thoracic  verte- 
bra. He  emphasizes  the  fact  that  the  base  of  the  pericardium  is  attached  to  the 
central  tendon  of  the  Diaphragm,  and  on  the  anterior  and  left  side.  The  muscular 
fibres  of  the  Diaphragm  ascend  upon  and  are  attached  to  the  pericardium.  Pro- 
longations of  the  fibrous  pericardium  pass  upward  as  the  pericardial  ligaments. 
These  ligaments  form  fibrous  planes  reaching  from  each  side  of  the  central 
tendon  of  the  Diaphragm  to  the  "  bony  apex  of  the  thoracic  line  "  and  to  the 
fascia  stretched  across  the  thoracic  apex,  and  they  may  be  called  the  "  superior 
tendinous  crura."  It  is  thus  evident  that  the  deep  cervical  fascia  is  connected 
to  the  lateral  and  superior  parts  of  the  pericardium.  At  birth  the  muscular 

ported  by  many  observations  made  on  the  human  subject  under  various  conditions  of  disease,  and  on  living 
animals  after  the  muscles  have  been  exposed  under  chloroform.  The  reader  may  consult  an  interesting  paper 
by  Dr.  Cleland  in  the  Journal  of  Anat.  and  Phys.,  No.  II.,  May,  1867,  p.  209,  On  the  Hutchinsonian  Theory 
of  the  Action  of  the  Intercostal  Muscles,  who  refers  also  to  Henle,  Luschka,  Budge,  and  Baumler,  Observa- 
tions on  the  Action  of  the  Intercostal  Muscles,  Erlangen,  1860.  (In  New  Syd.  Soc.'s  Year-book  for  1861,  p.  69.) 
Dr.  W.  W.  Keen  has  come  to  the  conclusion,  from  experiments  made  upon  a  criminal  executed  by  hanging, 
that  the  External  intercostals  are  muscles  of  expiration,  as  they  pulled  the  ribs  down,  while  the  Internal  inter- 
costals pulled  the  ribs  up  and  are  muscles  of  inspiration  (Trans.  Coll.  Phys.,  Philadelphia,  Third  Series,  vol.  i., 
1875,  p.  97).— ED.  of  loth  English  edition. 

1  For  a  detailed  description  of  the  general  relations  of  the  Diaphragm,  and  its  action,  refer  to  Dr.  Sibson's 
Medical  Anatomy. — ED.  of  15th  English  edition. 

J  American  Journal  of  the  Medical  Sciences,  July,  1880. — ED.  of  15th  English  edition. 

28 


434  THE  MUSCLES   AND   FASCIAE 

i 

fibres  of  the  Diaphragm  contract  at  the  first  inspiration.  The  ductus  arteriosus 
is  lodged  in  an  elliptical  opening  of  a  tendinous  scaffolding.  The  contractions 
of  the  Diaphragm  cause  the  tendinous  scaffolding  to  compress  the  ductus  arteri- 
osus "  and  eventually  close  it."  The  chief  agents  in  the  compression  are  the 
muscular  fibres  which  pass  from  the  Diaphragm  to  the  pericardium.  When  the 
lateral  wings  of  the  Diaphragm  descend  they  tend  to  form  a  vacuum  in  the  thorax 
and  thus  assist  the  venous  circulation. 

"  The  descent  of  the  Diaphragm  is  not  necessary  to  respiration,"  but  it  "  is 
necessary  in  order  to  protect  the  heart  from  the  movement  of  surrounding 
viscera,  and  in  order  to  promote  the  free  circulation  of  the  blood  through  the 
vessels  forming  the  cardiac  roots." 

Muscles  of  Inspiration  and  Expiration. — The  muscles  which  assist  the  action 
of  the  Diaphragm  in  ordinary  tranquil  inspiration  are  the  Intercostals  and  the 
Levatores  costarum,  as  above  stated,  and  the  Scaleni.  When  the  need  for  more 
forcible  action  exists,  the  shoulders  and  the  base  of  the  scapula  are  fixed,  and  then 
the  powerful  muscles  of  forced  inspiration  come  into  play;  the  chief  of  these  are 
the  Trapezius,  the  Pectoralis  minor,  the  Serratus  posticus  superior  and  inferior, 
and  the  Rhomboidei.  The  lower  fibres  of  the  Serratus  magnus  may  possibly  assist 
slightly  in  dilating  the  chest  by  raising  and  everting  the  ribs.  The  Sterno-mastoid 
also,  when  the  head  is  fixed,  assists  in  forced  inspiration  by  drawing  up  the  sternum 
and  by  fixing  the  clavicle,  and  thus  affording  a  fixed  point  for  the  action  of  the 
muscles  of  the  chest.  The  Ilio-costalis  and  Quadratus  lumborum  assist  in  forced 
inspiration  by  fixing  the  last  rib. 

The  ordinary  action  of  expiration  is  hardly  effected  by  muscular  force,  but 
results  from  a  return  of  the  walls  of  the  thorax  to  a  condition  of  rest,  owing  to 
their  own  elasticity  and  to  that  of  the  lungs.  Forced  expiratory  actions  are  per- 
formed mainly  by  the  flat  muscles  (Obliqui  and  Transversalis)  of  the  abdomen, 
assisted  by  the  Rectus.  Other  muscles  of  forced  expiration  are  the  Internal 
intercostals  and  Triangularis  sterni  (as  above  mentioned). 

III.  MUSCLES  OF  THE  ABDOMEN.    . 

The  muscles  of  the  abdomen  may  be  divided  into  two  groups:  1.  The  super- 
ficial muscles  of  the  abdomen.  2.  The  deep  muscles  of  the  abdomen. 

1.  The  Superficial  Muscles  of  the  Abdomen. 

The  Muscles  in  this  region  are,  the 

External  Oblique.  Transversalis. 

Internal  Oblique.  Rectus. 

Pyramidalis. 

Dissection  (Fig.  287). — To  dissect  the  abdominal  muscles,  make  a  vertical  incision  from  the 
ensiform  cartilage  to  the  symphysis  pubis;  a  second  incision  from  the  umbilicus  obliquely  upward 
and  outward  to  the  outer  surface  of  the  chest,  as  high  as  the  lower  border  of  the  fifth  or  sixth 
rib;  and  a  third,  commencing  midway  between  the  umbilicus  and  pubes,  transversely  outward 
to  the  anterior  superior  iliac  spine,  and  along  the  crest  of  the  ilium  as  far  as  its  posterior  third. 
Then  reflect  the  three  flaps  included  between  these  incisions  from  within  outward,  in  the  lines 
of  direction  of  the  muscular  fibres.  If  necessary,  the  abdominal  muscles  may  be  made  tense 
by  inflating  the  peritoneal  cavity  through  the  umbilicus. 

Superficial  Fascia. — The  superficial  fascia  of  the  abdomen  consists,  over  the 
greater  part  of  the  abdominal  wall,  of  a  single  layer  of  fascia,  which  contains  a 
variable  amount  of  fat ;  but  as  this  layer  approaches  the  groin  it  is  easily  divisible 
into  two  layers,  between  which  are  found  the  superficial  vessels  and  nerves  and 
the  superficial  inguinal  lymphatic  glands.  The  superficial  layer  of  the  superficial 


OF  THE  ABDOMi:X 


435 


sory    ligament  of 
superficial    layer 
superficial    fascia    over    the 
below,    it    blends    with    the 


inguinal 
hernia. 


FIG.  287. — Dissection  of  abdomen. 


fascia,  or  the  fascia  of  Camper,  is  thick,  areolar  in  texture,  containing  adipose  tissue 
in  its  meshes,  the  quantity  of  which  varies  in  different  subjects.  Below  it  passes 
over  Poupart's  ligament,  and  is  continuous  with  the  outer  layer  of  the  superficial 
fascia  of  the  thigh.  In  the  male  this  fascia  is  continued  over  the  penis  and  outer  sur- 
face of  the  cord  to  the  scrotum,  where  it  helps  to 
form  the  dartos.  As  it  passes  to  the  scrotum  it 
changes  its  character,  becoming  thin,  destitute  of 
adipose  tissue,  and  of  a  pale  hue,  it  has  a  reddish 
color,  and  in  the  scrotum  it  acquires  some  invol- 
untary muscular  fibres.  From  the  scrotum  it  may 
be  traced  backward  to  be  continuous  with  the 
superficial  fascia  of  the  perinseum.  In  the  female 
this  fascia  is  continued  into  the  labia  majora. 
The  deep  layer  of  the  superficial  fascia  or  the  fascia 
of  Scarpa,  is  thinner  and  more  membranous  in 
character  than  the  superficial  layer.  In  the  mid- 
dle line  it  is  intimately  adherent  to  the  linea  alba 
and  to  the  symphysis  pubis,  and  is  prolonged  on  section  of\ 
to  the  dorsum  of  the  penis,  forming  the  suspen- 
the  penis;  above,  it  joins  the 
and  is  continuous  with  the 
rest  of  the  trunk; 
fascia  lata  of  the 

thigh  a  little  below  Poupart's  ligament;  and 
below  and  internally  it  is  continued  over  the 
penis  and  spermatic  cord  to  the  scrotum,  where 
it  helps  to  form  the  dartos.  From  the  scrotum 
it  may  be  traced  backward  to  be  continuous  with  the  deep  layer  of  the  super- 
ficial fascia  of  the  perinaeum.  In  the  female  it  is  continued  into  the  labia 
majora. 

Deep  Fascia. — The  deep  fascia  invests  the  external  oblique  muscle,  but  is  so 
thin  over  the  aponeurosis  of  the  muscle  as  to  be  scarcely  recognizable. 

The  External  or  Descending  Oblique  Muscle  (m.  obliquus  externus  abdominis) 
(Fig.  288)  is  situated  on  the  side  and  forepart  of  the  abdomen ;  being  the  largest 
and  the  most  superficial  of  the  three  flat  muscles  in  this  region.  It  is  broad,  thin, 
and  irregularly  quadrilateral,  its  muscular  portion  occupying  the  side,  its  aponeu- 
rosis the  anterior  wall,  of  the  abdomen.  It  arises,  by  eight  fleshy  digitations, 
from  the  external  surface  and  lower  borders  of  the  eight  inferior  ribs;  these 
digitations  are  arranged  in  an  oblique  line  running  downward  and  backward; 
the  upper  ones  being  attached  close  to  the  cartilages  of  the  corresponding  ribs; 
the  lowest,  to  the  apex  of  the  cartilage  of  the  last  rib;  the  intermediate  ones,  to 
the  ribs  at  some  distance  from  their  cartilages.  The  five  superior  serrations 
increase  in  size  from  above  downward,  and-  are  received  between  corresponding 
processes  of  the  Serratus  magnus;  the  three  lower  ones  diminish  in  size  from 
above  downward,  receiving  between  them  corresponding  processes  from  the  Latis- 
simus  dorsi.  From  these  attachments",  the  fleshy  fibres  proceed  in  various  direc- 
tions. Those  from  the  lowest  ribs  pass  nearly  vertically  downward,  to  be  inserted 
into  the  anterior  half  of  the  outer  lip  of  the  crest  of  the  ilium ;  the  middle  and 
upper  fibres,  directed  downward  and  forward,  terminate  in  an  aponeurosis,  oppo- 
site a  line  drawn  from  the  prominence  of  the  ninth  costal  cartilage  to  the  anterior 
superior  spinous  process  of  the  ilium. 

Aponeurosis  of  External  Oblique. — The  aponeurosis  of  the  external  oblique  is  a 
thin,  but  strong  membranous  aponeurosis,  the  fibres  of  which  are  directed 


436 


THE  MUSCLES  AND  FASCIA 


obliquely  downward  and  inward.  It  is  joined  with  that  of  the  opposite  muscle 
along  the  median  line,  covers  the  whole  of  the  front  of  the  abdomen;  above,  it  is 
connected  with  the  lower  border  of  the  Pectoralis  major;  below,  its  fibres  are  closely 


External  abdo- 
minal ring. 
Gimbernafs—, 
ligament.      I 


fPubes. 
FIG.  288. — The  External  oblique  muscle. 


aggregated  together,  and  extend  obliquely  across  from  the  anterior  superior  spine 
of  the  ilium  to  the  spine  of  the  os  pubis  and  the  linea  ilio-pectinea.  In  the  median 
line  it  interlaces  with  the  aponeurosis  of  the  opposite  muscle,  forming  the  linea 
alba,  which  extends  from  the  ensiform  cartilage  to  the  symphysis  pubis. 

That  portion  of  the  aponeurosis  which  extends  between  the  anterior  superior 
spine  of  the  ilium  and  the  spine  of  the  os  pubis  is  a  broad  band,  folded  inward, 
and  continuous  below  with  the  fascia  lata;  it  is  called  Poupart's  ligament  or  the 
ligament  of  Fallopius.  The  portion  which  is  reflected  from  Poupart's  ligament 
at  the  spine  of  the  os  pubis  along  the  pectineal  line  is  called  Gimbernat's  ligament. 
From  the  point  of  attachment  of  the  latter  to  the  pectineal  line,  a  few  fibres 


OF  THE  ABDOMEN 


437 


pass  upward  and  inward,  behind  the  inner  pillar  of  the  ring,  to  the  linea  alba. 
They  diverge  as  they  ascend,  and  form  a  thin,  triangular,  fibrous  layer,  which  is 
called  the  triangular  fascia  of  the  abdomen  or  Colles's  ligament  (ligamentum 
inguinale  reflexum).  The  point  of  the  triangle  is  at  the  origin  of  Colles's  ligament ; 
the  base  is  at  the  linea  alba.  Colles's  ligament  is  in  front  of  the  conjoined  tendon, 
the  Rectus  muscle,  and  the  Pyramidalis  muscle. 

In  the  aponeurosis  of  the  External  oblique,  immediately  above  the  crest  of  the 
os  pubis,  is  a  triangular  opening,  the  external  abdominal  ring,  formed  by  a  separa- 
tion of  the  fibres  of  the  aponeurosis  in  this  situation. 


POUPART'S 
LIGAMENT 


INTERCOLUMNAR 
FIBRES 


GIMBEflNAT'S 
LIGAMENT 

SAPHENOUS 

OPENING 

FEMORAL 

VEIN 

LONG 

SAPHENOUS 
VEIN 


EXTERNAL 

ABDOMINAL 
RING 


CRUS 
SUPERIOR 


FIG.  289. — Right  external  abdominal  ring  and  saphenous  opening  in  the  male.     (Spalteholz.) 

Relations. — By  its  external  surface,  with  the  superficial  fascia,  superficial  epi- 
gastric and  circumflex  iliac  vessels,  and  some  cutaneous  nerves;  by  its  internal 
surface,  with  the  Internal  oblique,  the  lower  part  of  the  eight  inferior  ribs,  and 
Intercostal  muscles,  the  Cremaster,  the  spermatic  cord  in  the  male,  and  round  liga- 
ment in  the  female.  Its  posterior  border,  extending  from  the  last  rib  to  the  crest 
of  the  ilium,  is  fleshy  throughout  and  free;  it  is  occasionally  overlapped  by  the 
Latissimus  dorsi,  though  generally  a  triangular  interval  exists  between  the  two 
muscles  near  the  crest  of  the  ilium,  in  which  is  seen  a  portion  of  the  internal 
oblique.  This  triangle,  Petit's  triangle  (trigonum  lumbale),  is  therefore  bounded 
in  front  by  the  External  oblique,  behind  by  the  Latissimus  dorsi,  below  by  the 
crest  of  the  ilium,  while  its  floor  is  formed  by  the  Internal  oblique  (Fig.  288). 

The  following  parts  of  the  aponeurosis  of  the  External  oblique  muscle  require 
to  be  further  described — viz.,  the  external  abdominal  ring,  the  intercoiumnar  fibres 
and  fascia,  Poupart's  ligament,  Gimbernat's  ligament,  and  the  triangular  fascia  of 
the  abdomen. 

The  External  Abdominal  Ring  (annulus  inguinalis  subcutaneous)  (Figs.  289  and 
292). — Just  above  and  to  the  outer  side  of  the  crest  of  the  os  pubis  an  interval  is  seen 


438  THE  MUSCLES  AND  FASCIA 

in  the  aponeurosis  of  the  External  oblique,  called  the  external  abdominal  ring.  The 
aperture  is  oblique  in  direction,  somewhat  triangular  in  form,  and  corresponds  with 
the  course  of  the  fibres  of  the  aponeurosis.  It  usually  measures  from  base  to  apex 
about  an  inch,  and  transversely  about  half  an  inch.  It  is  bounded  below  by  the 
crest  of  the  os  pubis;  above,  by  a  series  of  curved  fibres,  the  external  spermatic  or 
the  intercolumnar  fibres  which  pass  across  the  upper  angle  of  the  ring,  so  as  to 
increase  its  strength;  and  on  each  side,  by  the  margins  of  the  opening  in  the 
aponeurosis,  which  are  called  the  columns  or  pillars  of  the  ring. 

The  External  Pillar  or  inferior  crus  (crus  inferius)  is  inferior  from  the  obliquity 
of  its  direction.  It  is  stronger  than  the  internal  pillar;  it  is  formed  by  that 
portion  of  Poupart's  ligament  which  is  inserted  into  the  spine  of  the  os  pubis;  it  is 
curved  so  as  to  form  a  kind  of  groove,  upon  which  the  spermatic  cord  rests. 

The  Internal  Pillar  or  superior  crus  (crus  superius)  is  a  broad,  thin,  flat  band, 
which  is  attached  to  the  front  of  the  symphysis  pubis,  interlacing  with  its  'fellow 
of  the  opposite  side. 

The  external  abdominal  ring  gives  passage  to  the  spermatic  cord  in  the  male 
(funiculus  spermaticus)  and  round  ligament  in  the  female  (ligamentum  teres  uteri) : 
it  is  much  larger  in  men  than  in  women,  on  account  of  the  large  size  of  the  sper- 
matic cord,  and  hence  the  greater  frequency  of  inguinal  hernia  in  men. 

Intercolumnar  Fibres  (fibrae  intercrurales)  (Fig.  289). — The  intercolumnar  fibres 
are  a  series  of  curved  tendinous  fibres,  which  arch  across  the  lower  part  of 
the  aponeurosis  of  the  External  oblique.  They  have  received  their  name  from 
stretching  across  between  the  two  pillars  of  the  external  ring,  describing  a  curve 
with  the  convexity  downward.  They  are  much  thicker  and  stronger  at  the  outer 
margin  of  the  external  ring,  where  they  are  connected  to  the  outer  third  of  Pou- 
part's ligament,  than  internally,  where  they  are  inserted  into  the  linea  alba.  They 
are  more  strongly  developed  in  the  male  than  in  the  female.  The  inter- 
columnar fibres  increase  the  strength  of  the  lower  part  of  the  aponeurosis, 
and  prevent  the  divergence  of  the  pillars  from  one  another. 

These  intercolumnar  fibres  as  they  pass  across  the  external  abdominal  ring 
are  themselves  connected  together  by  delicate  fibrous  tissue,  thus  forming  a  fascia, 
which  as  it  is  attached  to  the  pillars  of  the  ring  covers  it  in,  and  is  called  the 
intercolumnar  fascia  or  the  external  spermatic  fascia.  This  intercolumnar  fascia 
is  continued  down  as  a  tubular  prolongation  around  the  outer  surface  of  the 
cord  and  testis  or  of  the  round  ligament,  and  encloses  them  in  a  distinct  sheath. 

The  sac  of  an  inguinal  hernia,  in  passing  through  the  external  abdominal  ring,  receives  an 
investment  from  the  intercolumnar  fascia. 

If  the  finger  is  introduced  a  short  distance  into  the  external  abdominal  ring 
and  the  limb  is  then  extended  and  rotated  outward,  the  aponeurosis  of  the  External 
oblique,  together  with  the  iliac  portion  of  the  fascia  lata,  will  be  felt  to  become 
tense,  and  the  external  ring  much  contracted;  if  the  limb  is,  on  the  contrary,  flexed 
upon  the  pelvis  and  rotated  inward,  this  aponeurosis  will  become  lax  and  the 
external  abdominal  ring  sufficiently  enlarged  to  admit  the  finger  with  compara- 
tive ease;  hence  the  patient  should  always  be  put  in  the  latter  position  when  the 
taxis  is  applied  for  the  reduction  of  an  inguinal  hernia  in  order  that  the  abdominal 
walls  may  be  relaxed  as  much  as  possible. 

Poupart's  Ligament  (ligamentum  inguinale). — The  portion  of  Poupart's  ligament 
in  front  of  the  crural  ring  is  called  the  superficial  crural  arch.  Poupart's  ligament 
is  the  lower  border  of  the  aponeurosis  of  the  External  oblique  muscle,  and  extends 
from  the  anterior  superior  spine  of  the  ilium  to  the  pubic  spine.  From  this 
latter  point  it  is  reflected  outward  to  be  attached  to  the  pectineal  line  for  about 
half  an  inch,  forming  Gimbernat's  Ligament.  Its  general  direction  is  curved  down- 


OF  THE  ABDOMEN 

ward  toward  the  thigh,  where  it  is  continuous  with  the  fascia  lata.  Its  outer  half 
is  rounded  and  oblique  in  direction.  Its  inner  half  gradually  widens  at  its  attach- 
ment to  the  os  pubis,  is  more  horizontal  in  direction,  and  lies  beneath  the  spermatic 
cord.  Nearly  the  whole  of  the  space  included  between  the  crural  arch  and  the 
innominate  bone  is  filled  in  by  the  parts  which  descend  from  the  abdomen  into 
the  thigh  (Fig.  297).  These  will  be  referred  to  again  on  a  subsequent  page. 

Gimbernat's  t  Ligament  (ligamentum  lacunare)  (Figs.  289  and  297). — Gimbernat's 
ligament  is  that  part  of  the  aponeurosis  of  the  External  oblique  muscle  which  is 
reflected  upward  and  outward  from  the  spine  of  the  os  pubis  to  be  inserted  into  the 
pectineal  line.  It  is  about  half  an  inch  in  length,  larger  in  the  male  than  in  the 
female,  almost  horizontal  in  direction  in  the  erect  posture,  and  of  a  triangular  form 
with  the  base  directed  outward.  Its  base,  or  outer  margin,  is  concave,  thin,  and 
sharp,  and  lies  in  contact  with  the  crural  sheath,  forming  the  inner  boundary  of 
the  femoral  or  crural  ring  (annulus  femoralis).  Its  apex  corresponds  to  the  spine 
of  the  os  pubis.  Its  posterior  margin  is  attached  to  the  pectineal  line,  and  is  con- 
tinuous with  the  pubic  portion  of  the  fascia  lata.  Its  anterior  margin  is  continuous 
with  Poupart's  ligament.  Its  surfaces  are  directed  upward  and  downward. 

Triangular  Fascia  or  Colles's  Ligament  (ligamentum  inguinal  reflexum). — The 
triangular  fascia  of  the  abdomen  is  a  layer  of  tendinous  fibres  of  a  triangular 
shape,  which  is  attached  by  its  apex  to  the  pectineal  line,  where  it  is  continuous 
with  Gimbernat's  ligament.  It  passes  inward  beneath  the  spermatic  cord,  and 
expands  into  a  somewhat  fan-shaped  fascia,  lying  behind  the  inner  pillar  of  the 
external  abdominal  ring,  and  in  front  of  the  conjoined  tendon,  and  interlaces  with 
the  ligament  of  the  other  side  at  the  linea  alba. 

Ligament  of  Cooper  (Fig.  297). — This  is  a  strong  ligamentous  band,  which  was 
first  described  by  Sir  Astley  Cooper.  It  extends  upward  and  backward  from  the 
base  of  Gimbernat's  ligament  along  the  ilio-pectineal  line,  to  which  it  is  attached. 
It  is  strengthened  by  the  fascia  transversalis,  by  the  pectineal  aponeurosis,  and 
by  a  lateral  expansion  from  the  lower  attachment  of  the  linea  alba  (adminiculum 
linecp  albce). 

Suspensory  Ligament  of  the  Penis  (ligamentum  fundiforme  penis). — The  suspen- 
sory ligament  of  the  penis  arises  from  the  linea  alba,  the  anterior  portion  of 
the  sheath  of  the  Rectus  muscle,  and  the  superficial  fascia.  It  splits  into  two 
portions,  blends  with  the  inserting  fascia  of  the  penis,  and  passes  into  the  scrotum. 

Suspensory  Ligament  of  the  Clitoris  (ligamentum  fundiforme  clitoridis). — The 
suspensory  ligament  of  the  clitoris  corresponds  in  the  female  to  the  suspen- 
sory ligament  of  the  penis  in  the  male. 

Dissection — Detach  the  External  oblique  by  dividing  it  across,  just  in  front  of  its  attach- 
ment to  the  ribs,  as  far  as  its  posterior  border,  and  separate  it  below  from  the  crest  of  the  ilium 
as  far  as  the  anterior  superior  spine;  then  separate  the  muscle  carefully  from  the  Internal  oblique, 
which  lies  beneath,  and  turn  it  toward  the  opposite  side. 

The  Internal  or  Ascending  Oblique  Muscle  (m.  obliqum  internus  abdominis) 
(Fig.  290),  thinner  and  smaller  than  the  preceding,  beneath  which  it  lies,  is  of 
an  irregularly  quadrilateral  form,  and  is  situated  at  the  side  and  forepart  of  the 
abdomen.  It  arises,  by  fleshy  fibres,  from  the  outer  half  of  Poupart's  ligament, 
being  attached  to  the  groove  on  its  upper  surface;  from  the  anterior  two-thirds 
of  the  middle  lip  of  the  crest  of  the  ilium,  and  from  the  posterior  lamella  of  the 
lumbar  fascia  (Fig.  294).  From  this  origin  the  fibres  diverge :  those  from  Poupart's 
ligament,  few  in  number  and  paler  in  color  than  the  rest,  arch  downward  and 
inward  across  the  spermatic  cord  in  the  male  and  the  round  ligament  in  the 
female,  and,  becoming  tendinous,  are  inserted,  conjointly  with  those  of  the  Trans- 
versalis, into  the  crest  of  the  os  pubis  and  pectineal  line,  to  the  extent  of  half  an  inch 
or  more,  forming  what  is  known  as  the  conjoined  tendon  of  the  Internal  oblique  and 


440 


THE   MUSCLES    AND    FASCIAE 


Transversalis ;  those  from  the  anterior  third  of  the  iliac  origin  are  horizontal  in 
their  direction,  and,  becoming  tendinous  along  the  lower  fourth  of  the  linea 
semilunaris,  pass  in  front  of  the  Rectus  muscle  to  be  inserted  into  the  linea  alba; 
those  which  arise  from  the  middle  third  of  the  origin  from  the  crest  of  the 
ilium  pass  obliquely  upward  and  inward,  and  terminate  in  an  aponeurosis  which 
divides  at  the  outer  border  of  the  Rectus  muscle  into  two  lamellae  (Fig.  295), 
which  are  continued  forward,  in  front  and  behind  this  muscle,  to  the  linea  alba, 
the  posterior  lamella  being  also  connected  to  the  cartilages  of  the  seventh,  eighth, 
and  ninth  ribs;  the  most  posterior  fibres  pass  almost  vertically  upward,  to  be 
inserted  into  the  lower  borders  of  the  cartilages  of  the  three  lower  ribs,  being  con- 
tinuous with  the  Internal  intercostal  muscles. 


Conjoined  tendon. 


CREMASTER. 


FIG.  290. — The  Internal  oblique  muscle. 

The  conjoined  tendon  of  the  Internal  oblique  and  Transversalis  is  inserted  into 
the  crest  of  the  os  pubis  and  pectineal  line,  immediately  behind  the  external 
abdominal  ring,  serving  to  protect  what  would  otherwise  be  a  weak  point  in  the 
abdominal  wall.  Sometimes  this  tendon  is  insufficient  to  resist  the  pressure  from 
within,  and  is  carried  forward  in  front  of  a  protrusion  through  the  external  ring, 
forming  one  of  the  coverings  of  direct  inguinal  hernia;  or  the  hernia  forces  its  way 
through  the  fibres  of  the  conjoined  tendon.  The  conjoined  tendon  is  sometimes 
divided  into  an  outer  and  an  inner  portion — the  former  being  termed  the  liga- 
ment of  Hesselbach;  the  latter,  the  ligament  of  Henle  (Fig.  291).  See  pages  444 
and  446. 


OF   THE  ABDOMEN 


441 


Aponeurosis  of  Internal  Oblique.— The  aponeurosis  of  the  Internal  oblique  is 
continued  forward  to  the  middle  line  of  the  abdomen,  where  it  joins  with  the 
aponeurosis  of  the  opposite  muscle  at  the  linea  alba,  and  extends  from  the  margin 
of  the  thorax  to  the  os  pubis.  At  the  outer  margin  of  the  Rectus  muscle  this 
aponeurosis,  for  the  upper  three-fourths  of  its  extent,  divides  into  two  lamellae, 
which  pass,  one  in  front  and  the  other  behind  the  muscle,  enclosing  it  in  a  kind  of 
sheath,  and  reuniting  on  its  inner  border  of  the  linea  alba;  the  anterior  layer  is 
blended  with  the  aponeurosis  of  the  External  oblique  muscle ;  the  posterior  layer 
with  that  of  the  Transversalis.  Along  the  lower  fourth  the  aponeurosis  passes 
altogether  in  front  of  the  Rectus  without  any  separation.  Where  the  aponeurosis 


SEMILUNAR   FOLD 
OF  DOUGLAS 


TRANSVERSALIS 


RECTUS 
ABDOMINIS 


DEEP  EPI- 
GASTRIC ARTERY 
AND  VEIN 


INTERNAL 
OBLIQUE 


LiGAMENT  OF  HENLC 


LIGAMENT  OF  HESSELBACH 


FIG.  291. — The  deep  epigastric  artery  and  veins,  ligament  of  Henle  and  ligament  of  Hesselbach,  seen 
from  in  front.     (Modified  from  Braune.) 

ceases  to  split,  and  passes  altogether  in  front  of  the  Rectus  muscle,  a  deficiency  is 
left  in  the  sheath  of  the  muscle  behind;  this  is  marked  above  by  a  sharp  lunated 
margin  having  its  concavity  downward.  This  is  known  as  the  semilunar  fold  of 
Douglas  (linea  semicircularis)  (Fig.  292). 

Relations. — By  its  external  surface,  with  the  External  oblique,  Latissimus  dorsi, 
spermatic  cord,  and  external  ring;  by  its  internal  surface,  with  the  Transversalis 
muscle,  the  lower  intercostal  vessels  and  nerves,  the  ilio-hypogastric  and  the  ilio- 
inguinal  nerves.  Near  Poupart's  ligament  it  lies  on  the  fascia  transversalis, 
internal  ring,  and  spermatic  cord.  Its  lower  border  forms  the  upper  boundary 
of  the  inguinal  canal. 

The  Cremaster  muscle  (Fig.  290)  is  a  thin,  muscular  layer,  composed  of  a  num- 
ber of  fasciculi  which  arise  from  the  "inner  part  of  Poupart's  ligament,  where  its 
fibres  are  continuous  with  those  of  the  Internal  oblique  and  also  occasionally  with 
the  Transversalis.  It  passes  along  the  outer  side  of  the  spermatic  cord,  descends 
with  it  through  the  external  abdominal  ring  upon  the  front  and  sides  of  the  cord, 
and  forms  a  series  of  loops  which  differ  in  thickness  and  length  in  different  sub- 
jects. Those  at  the  upper  part  of  the  cord  are  exceedingly  short,  but  they  become 
in  succession  longer  and  longer,  the  longest  reaching  down  as  low  as  the  testicle, 
where  a  few  are  inserted  into  the  tunica  vaginalis.  These  loops  are  united  together 
by  areolar  tissue,  and  form  a  thin  covering  over  the  cord  and  testis,  the  middle 


442 


THE  MUSCLES   AND    FASCIAE 


spermatic  fascia  (fascia  cremastericd).  The  fibres  ascend  along  the  inner  side  of 
the  cord,  and  are  inserted  by  a  small  pointed  tendon  into  the  crest  of  the  os 
pubis  and  front  of  the  sheath  of  the  Rectus  muscle. 


LINEA  ALBA 


POSTERIOR    LEAF 
OF  SHEATH   OF 
RECTUS  ABDOMINIS 


LINEA  SEMILUNARIS 


TRANSVERSALIS 


SEMILUNAR  FOLD 
OF  DOUGLAS 


RECTUS  ABDOMINIS 

(cut  through) 


ANTERIOR  LEAF 

F  SHEATH   OF 
RECTUS  ABDOMINIS 


FIG.  292. — The  muscles  of  the  abdomen,  showing  the  semilunar  fold  of  Douglas.     Viewed  from  in  front. 

(Spalteholz.) 

It  will  be  observed  that  the  origin  and  insertion  of  the  Cremaster  is  precisely 
similar  to  that  of  the  lower  fibres  of  the  Internal  oblique.  This  fact  affords  an  easy 
explanation  of  the  manner  in  which  the  testicle  and  cord  are  invested  by  this 
muscle.  At  an  early  period  of  foetal  life  the  testis  is  placed  at  the  lower  and  back 
part  of  the  abdominal  cavity,  but  during  its  descent  toward  the  scrotum,  which 
takes  place  before  birth,  it  passes  beneath  the  arched  fibres  of  the  Internal  oblique. 
In  its  passage  beneath  this  muscle  some  fibres  are  derived  from  its  lower  part 
which  accompany  the  testicle  and  cord  into  the  scrotum.  It  occasionally  happens 


OF    THE   ABDOMEN 


443 


that  the  loops  of  the  Cremaster  surround  the  cord,  some  lying  behind  as  well  as  in 
front.  It  is  probable  that  under  these  circumstances  the  testis,  in  its  descent, 
passed  through  instead  of  beneath  the  fibres  of  the  Internal  oblique. 

In  the  descent  of  an  oblique  inguinal  hernia,  which  takes  the  same  course  as 
the  spermatic  cord,  the  Cremaster  muscle  forms  one  of  its  coverings.  This  muscle 
becomes  largely  developed  in  cases  of  hydrocele  and  large  old  scrotal  hernia.  The 
Cremaster  muscle  is  found  only  in  the  male,  but  almost  constantly  in  the  female 


Linea  alba. 


FIG.  293. — The  Transversalis,  Rectus,  and  Pyramidalis  muscles. 

a  few  muscular  fibres  may  be  seen  on  the  surface  of  the  round  ligament,  which 
correspond  to  this  muscle,  and  in  cases  of  oblique  inguinal  hernia  in  the  female  a 
considerable  amount  of  muscular  fibre  may  be  found  covering  the  sac. 

Dissection. — Detach  the  Internal  oblique  in  order  to  expose  the  Transversalis  beneath.  This 
may  be  effected  by  dividing  the  muscle,  above,  at  its  attachment  to  the  ribs;  below,  at  its  con- 
nection with  Poupart's  ligament  and  the  crest  of  the  ilium;  and  behind,  by  a  vertical  incision 


444  THE    MUSCLES   AND    FASCIA 

extending  from  the  last  rib  to  the  crest  of  the  ilium.  The  muscle  should  previously  be  made 
tense  by  drawing  upon  it  with  the  fingers  of  the  left  hand,  and  if  its  division  is  carefully  effected, 
the  cellular  interval  between  it  and  the  Transversalis,  as  well  as  the  direction  of  the  fibres  of  the 
latter  muscle,  will  afford  a. clear  guide  to  their  separation;  along  the  crest  of  the  ilium  the  cir- 
cumflex iliac  vessels  are  interposed  between  them,  and  form  an  important  guide  in  separating 
them.  The  muscle  should  then  be  thrown  inward  toward  the  linea  alba. 

The  Transversalis  Muscle  (m.  transversus  abdominis)  (Fig.  293),  so  called 
from  the  direction  of  its  fibres,  is  the  most  internal  flat  muscle  of  the  abdomen, 
being  placed  immediately  beneath  the  Internal  oblique.  It  arises  by  fleshy  fibres 
from  the  outer  third  of  Poupart's  ligament;  from  the  inner  lip  of  the  crest  of  the 
ilium  for  its  anterior  three-fourths;  from  the  inner  surface  of  the  cartilages  of  the 
six  lower  ribs,  interdigitating  with  the  Diaphragm;  and  from  the  lumbar  fascia 
(Fig.  294),  which  may  be  regarded  as  the  posterior  aponeurosis  of  the  muscle. 
The  muscle  terminates  in  front  in  a  broad  aponeurosis,  the  lower  fibres  of 
which  curve  downward  and  inward,  and  are  inserted,  together  with  those  of  the 
Internal  oblique,  into  the  lower  part  of  the  linea  alba,  the  crest  of  the  os  pubis 
and  pectineal  line  forming  what  is  known  as  the  conjoined  tendon  of  the  Internal 
oblique  and  Transversalis.  The  lowermost  fibres  help  to  form  the  posterior  wall 
of  the  inguinal  canal.  Throughout  the  rest  of  its  extent  the  aponeurosis  passes 
horizontally  inward,  and  is  inserted  into  the  linea  alba,  its  upper  three-fourths 
passing  behind  the  Rectus  muscle,  blending  with  the  posterior  lamella  of  the 
Internal  oblique;  its  lower  fourth  passing  in  front  of  the  Rectus.  The  external 
portion  of  the  lower  fibres  of  the  conjoined  tendon  is  known  as  the  ligament  of 
Hesselbach  (Fig.  291)  (ligamentum  interfoveolare};  the  internal  portion  as  the  liga- 
ment of  Henle  (Fig.  291)  (falx  inguinalis}. 

Relations. — By  its  external  surface,  with  the  Internal  oblique,  the  lower  inter- 
costal nerves,  and  the  inner  surface  of  the  cartilages  of  the  lower  ribs;  by  its 
internal  surface,  "with  the  fascia  transversalis,  which  separates  it  from  the  periton- 
eum. Its  lower  border  forms  the  upper  boundary  of  the  inguinal  canal. 

Dissection. — To  expose  the  Rectus  muscle,  open  its  sheath  by  a  vertical  incision  extending 
from  the  margin  of  the  thorax  to  the  os  pubis,  and  then  reflect  the  two  portions  from  the  surface 
of  the  muscle,  which  is  easily  done,  excepting  at  the  linese  transversse,  where  so  close  an  adhesion 
exists  that  the  greatest  care  is  requisite  in  separating  them.  Now  raise  the  outer  edge  of  the 
muscle,  in  order  to  examine  the  posterior  layer  of  the  sheath.  By  dividing  the  muscle  in  the 
centre,  and  turning  its  lower  part  downward,  the  point  where  the  posterior  wall  of  the  sheath 
terminates  in  a  thin  curved  margin  will  be  seen. 

The  Rectus  Abdominis  (Figs.  291,  293  and  295)  is  a  long  flat  muscle,  which 
extends  along  the  whole  length  of  the  front  of  the  abdomen,  being  separated  from 
its  fellow  of  the  opposite  side  by  the  linea  alba.  It  is  much  broader,  but  thinner, 
above  than  below,  and  arises  by  two  tendons,  the  external  or  larger  being  attached 
to  the  crest  of  the  os  pubis,  the  internal,  smaller  portion  interlacing  with  its  fellow  of 
the  opposite  side,  and  being  connected  with  the  ligaments  covering  the  front  of  the 
symphysis  pubis.  The  fibres  as'cend,  and  the  muscle  is  inserted  by  three  portions  of 
unequal  size  into  the  cartilages  of  the  fifth,  sixth,  and  seventh  ribs.  The  upper  por- 
tion, attached  principally  to  the  cartilage  of  the  fifth  rib,  usually  has  some  fibres  of 
insertion  into  the  anterior  extremity  of  the  rib  itself.  Some  fibres  are  occasionally 
connected  with  the  costo-xiphoid  ligaments  and  side  of  the  ensiform  cartilage. 

The  Rectus  muscle  is  traversed  by  tendinous  intersections,  three  in  number, 
which  have  received  the  name  of  linese  transversae.  One  of  these  is  usually 
situated  opposite  the  umbilicus,  and  two  above  that  point;  of  the  latter,  one 
corresponds  to  the  extremity  of  the  ensiform  cartilage,  and  the  other  to  the  inter- 
val between  the  ensiform  cartilage  and  the  umbilicus.  These  intersections  pass 
transversely  or  obliquely  across  the  muscle  in  a  zigzag  course;  they  rarely  extend 
completely  through  its  substance,  sometimes  they  pass  only  half-way  across  it,  and 
are  intimately  adherent  in  front  to  the  sheath  in  which  the  muscle  is  enclosed. 


OF    THE   ABDOMEN 


445 


Sometimes  one  or  two  additional  lines  may  be  seen,  one  usually  below  the 
umbilicus;  the  position  of  the  other,  when  it  exists,  is  variable.  These  addi- 
tional lines  are  for  the  most  part  incomplete. 


FIG.  294. — A  transverse  section  of  the  abdomen  in  the  lumbar  region. 

The  Rectus  is  enclosed  in  a  sheath,  the  rectus  sheath  (vagina  m.  recti  abdominis) 
(Figs.  294  and  295),  formed  by  the  aponeurosis  of  the  Oblique  and  Transversalis 


SHEATH    OF 
RECTUS  ABOOMINIS 

(anterior  leaf) 


Posterior  leaf       Anterior  leaf 


SHEATH  OF  RECTUS  ABDOMINIS 

FIG.  295. — Transition  of  the  tendon  of  the  right  internal  oblique  into  the  sheath  of  the  rectus.     (Spalteholz.) 

muscles,  which  are  arranged  in  the  following  manner.    When  the  aponeurosis  of  the 
Internal  oblique  arrives  at  the  outer  margin  of  the  Rectus  it  divides  into  two  lamellae, 


446  THE  MUSCLES  AND   FASCIAE 

one  of  which  passes  in  front  of  the  Rectus,  blending  with  the  aponeurosis  of  the 
External  oblique ;  the  other,  behind  it,  blending  with  the  aponeurosis  of  the  Trans- 
versalis;  and  these,  joining  again  at  its  inner  border,  are  inserted  into  the  linea  alba. 
This  arrangement  of  the  aponeuroses  exists  along  the  upper  three-fourths  of  the 
muscle :  at  the  commencement  of  the  lower  fourth,  the  posterior  wall  of  the  sheath 
terminates  in  a  thin  curved  margin,  the  semilunar  fold  of  Douglas  (linea  semicir- 
cularis)  (Fig.  292),  the  concavity  of  which  looks  downward  toward  the  pubes;  the 
aponeuroses  of  all  three  muscles  passing  in  front  of  the  Rectus  without  any  sepa- 
ration. A  very  thin  aponeurotic  layer  does  pass  behind  the  lower  one-fourth  of 
the  muscle,  but  it  is  trivial  as  compared  with  the  thickness  of  the  layer  behind  the 
upper  three-fourths  of  the  muscle.  This  sudden  thinning  causes  the  semilunar 
fold  of  Douglas.  The  extremities  of  the  fold  of  Douglas  descend  as  pillars  to  the 
os  pubis.  The  inner  pillar  is  attached  to  the  symphysis  pubis;  the  outer  pillar 
passes  downward  as  a  distinct  band  on  the  inner  side  of  the  internal  abdominal 
ring  to  join  with  the  outer  fibres  of  the  conjoined  tendon,  and  assist  to  form 
the  ligament  of  Hesselbach  (ligamentum  inter  foveolare)  (Fig.  291).  There  its  fibres 
divide  into  two  sets,  internal  and  external;  the  internal  fibres  are  attached  to  the 
ascending  ramus  of  the  os  pubis  and  the  pectineal  fascia;  the  external  ones  pass  to 
the  Psoas  fascia,  to  the  deep  surface  of  Poupart's  ligament,  and  to  the  tendon  of 
the  Transversalis  on  the  outer  side  of  the  ring.  The  Rectus  muscle,  in  the  situation 
where  its  sheath  is  deficient,  is  separated  from  the  peritoneum  by  the  transversalis 
fascia.  The  convex  outer  border  of  the  Rectus  muscle  corresponds  to  the  linea 
semilunaris. 

The  Pyramidalis  is  a  small  muscle,  triangular  in  shape,  placed  at  the  lower 
part  of  the  abdomen,  in  front  of  the  Rectus,  and  contained  in  the  same  sheath 
with  that  muscle.  It  arises  by  tendinous  fibres  from  the  front  of  the  os  pubis 
and  the  anterior  pubic  ligament ;  the  fleshy  portion  of  the  muscle  passes  upward, 
diminishing  in  size  as  it  ascends,  and  terminates  by  a  pointed  extremity,  which  is 
inserted  into  the  linea  alba,  midway  between  the  umbilicus  and  the  os  pubis.  This 
muscle  is  sometimes  found  wanting  on  one  or  both  sides;  the  lower  end  of  the 
Rectus  then  becomes  proportionately  increased  in  size.  Occasionally  it  has  been 
found  double  on  one  side,  or  the  muscles  of  the  two  sides  are  of  unequal  size. 
Sometimes  its  length  exceeds  what  is  stated  above. 

Besides  the  Rectus  and  Pyramidalis  muscles,  the  sheath  of  the  Rectus  contains 
the  superior  and  deep  epigastric  arteries,  the  terminations  of  the  lumbar  arteries 
and  of  the  lower  intercostal  arteries  and  nerves. 

Nerves. — The  abdominal  muscles  are  supplied  by  the  lower  intercostal  nerves. 
The  Transversalis  and  Internal  oblique  also  receive  filaments  from  the  hypogastric 
branch  of  the  ilio-hypogastric  and  sometimes  from  the  ilio-inguinal.  The  Cremas- 
ter  is  supplied  by  the  genital  branch  of  the  genito-femoral. 

In  the  description  of  the  abdominal  muscles  mention  has  frequently  been  made 
of  the  linea  alba,  lineae  semilunares,  and  lineae  transversae;  when  the  dissection  of 
the  muscles  is  completed  these  structures  should  be  examined. 

The  Linea  Alba  (Figs.  292,  293,  and  294). — The  linea  alba  is  a  tendinous  raphe 
seen  along  the  middle  line  of  the  abdomen,  extending  from  the  ensiform  cartilage  to 
the  symphysis  pubis,  to  the  superior  pubic  ligament  of  which  it  is  attached.  It 
is  placed  between  the  inner  borders  of  the  Recti  muscles,  and  is  formed  by  the 
blending  of  the  aponeuroses  of  the  Obliqui  and  Transversales  muscles.  It  is 
narrow  below,  corresponding  to  the  narrow  interval  existing  between,  the  Recti; 
but  broader  above,  as  these  muscles  diverge  from  one  another  in  their  ascent, 
becoming  of  considerable  breadth  when  there  is  great  distention  of  the  abdomen 
from  pregnancy  or  ascites.  It  presents  numerous  apertures  for  the  passage  of 
vessels  and  nerves:  the  largest  of  these  is  the  umbilicus  (Fig.  296).  The  umbilicus 
is  a  fibrous  ring  formed  by  the  fibres  of  the  aponeurosis  of  the  linea  alba,  is  filled 
with  scar  tissue;  in  the  fcetus  transmits  the  umbilical  vein,  the  two  hypogas- 


OF  THE  ABDOMEN 


447 


UMBILICAL 
VEIN 


LINEA   ALBA 


NTERVASCULAR 
FOSSA 


YPOGASTRIC 
RTERY 


FIG.  296. — The  umbilicus  of  the  foetus 
seen  from  within  the  abdomen.  (Poirier 
and  Charpy.) 


trie  arteries,  the  allantoic  duct,  and  the  vitello-intestinal  duct;  but  in  the 
adult  is  obliterated,  the  cicatrix  being  stronger  than  the  neighboring  parts;  hence 
umbilical  hernia  occurs  in  the  adult  near  the  umbilicus,  whilst  in  the  foetus  it  occurs 
at  the  umbilicus.  The  remains  of  the  foetal  structures  are  cord-like  in  character, 
and  they  diverge  from  the  umbilicus  within  the 
abdomen.  The  remains  of  the  umbilical  vein  con- 
stitute the  round  ligament  of  the  liver,  and  this 
cord  passes  upward  (Fig.  296).  The  remains  of 
the  hypogastric  arteries  pass  downward  (Fig.  296). 
The  remains  of  the  allantois  become  the  urachus, 
which  passes  to  the  summit  of  the  bladder  (Fig. 
296).  The  depression  of  the  umbilicus  was 
created  by  the  urachus.  The  linea  alba  is  in  re- 
lation, in  front,  with  the  integument,  to  which  it 
is  adherent,  especially  at  the  umbilicus;  behind, 
it  is  separated  from  the  peritoneum  by  the  trans- 
versalis  fascia;  and  below,  by  the  urachus,  and 
the  bladder  when  that  organ  is  distended. 

The  Lineae  Semilunares  (Figs.  288  and  292).— 
The  linese  semilunares  are  two  curved  tendinous 
lines  placed  one  on  each  side  of  the  linea  alba. 
Each  corresponds  with  the  outer  border  of  the 
Rectus  muscle,  extends  from  the  cartilage  of  the 
ninth  rib  to  the  pubic  spine,  and  is  formed  by  the 
aponeurosis  of  the  Internal  oblique  at  its  point  of  division  to  enclose  the  Rectus, 
where  it  is  reinforced  in  front  by  the  External  oblique  and  behind  by  the  Trans- 
versalis. 

The  Lineae  Transversse  (inscriptiones  tendineae)  (Fig.  288). — The  linese  trans- 
verses  are  narrow  transverse  lines  which  intersect  the  Recti  muscles,  as  already 
mentioned;  they  connect  the  linese  semilunares  with  the  linea  alba. 

Actions. — The  abdominal  muscles  perform  a  threefold  action: 

When  the  pelvis  and  thorax  are  fixed,  they  compress  the  abdominal  viscera,  by 
constricting  the  cavity  of  the  abdomen,  in  which  action  they  are  materially  assisted 
by  the  descent  of  the  Diaphragm.  By  these  means  the  foetus  is  expelled  from  the 
uterus,  the  faeces  from  the  rectum,  the  urine  from  the  bladder,  and  the  contents  of 
the  stomach  in  vomiting. 

If  the  pelvis  and  spine  are  fixed,  these  muscles  compress  the  lower  part  of  the 
thorax,  materially  assisting  expiration.  If  the  pelvis  alone  is  fixed,  the  thorax  is 
bent  directly  forward  when  the  muscles  of  both  sides  act,  or  to  either  side  when 
those  of  the  two  sides  act  alternately,  rotation  of  the  trunk  at  the  same  time  taking 
place  to  the  opposite  side. 

If  the  thorax  is  fixed,  these  muscles,  acting  together,  draw  the  pelvis  upward, 
as  in  climbing;  or,  acting  singly,  they  draw  the  pelvis  upward,  and  bend  the 
vertebral  column  to  one  side  or  the  other.  The  Recti  muscles,  acting  from  below, 
depress  the  thorax,  and  consequently  flex  the  vertebral  column ;  when  acting  from 
above,  they  flex  the  pelvis  upon  the  vertebral  column.  The  Pyramidalis  are 
tensors  of  the  linea  alba. 

The  Transversalis  Fascia  (fascia  transversalis}. — The  fascia  transversalis  is  a 
thin  aponeurotic  membrane  which  lies  between  the  inner  surf  ace  of  the  Transversalis 
muscle  and  the  extra-peritoneal  fat.  It  forms  part  of  the  general  layer  of  fascia 
which  lines  the  interior  of  the  abdominal  and  pelvis  cavities,  and  is  directly  continu- 
ous with  the  iliac  and  pelvic  fasciae.  In  the  inguinal  region  the  transversalis  fascia  is 
thick  and  dense  in  structure,  and  joined  by  fibres  from  the  aponeurosis  of  the  Trans- 
versalis muscle,  but  it  becomes  thin  and  cellular  as  it  ascends  to  the  Diaphragm, 
and  blends  with  the  fascia  covering  this  muscle.  In  front,  it  unites  across  the 


44S 


THE  MUSCLES  AND  FASCIA 


middle  line  with  the  fascia  on  the  opposite  side  of  the  body,  and  behind  it  becomes 
lost  in  the  fat  which  covers  the  posterior  surfaces  of  the  kidneys.  Below,  it  has 
the  following  attachments:  posteriorly,  it  is  connected  to  the  whole  length  of  the 
crest  of  the  iiium,  between  the  attachments  of  the  Transversalis  and  Iliacus 
muscles;  between  the  anterior  superior  spine  of  the  ilium  and  the  femoral  vessels 
it  is  connected  to  the  posterior  margin  of  Poupart's  ligament,  and-  is  there  con- 
tinuous with  the  iliac  fascia.  Internal  to  the  femoral  vessels  it  is  thin  and  attached 
to  the  os  pubis  and  pectineal  line,  behind  the  conjoined  tendon,  with  which  it  is 
united;  and,  corresponding  to  the  point  where  the  femoral  vessels  pass  into  the 
thigh,  this  fascia  descends  in  front  of  them,  forming  the  anterior  wall  of  the  crural 
sheath.  Beneath  Poupart's  ligament  it  is  strengthened  by  a  band  of  fibrous  tissue, 
which  is  only  loosely  connected  to  Poupart's  ligament,  and  is  specialized  as  the 
deep  crural  arch.  The  spermatic  cord  in  the  male  and  the  round  ligament  in  the 
female  pass  through  this  fascia;  the  point  where  they  pass  through  is  called  the 
internal  abdominal  ring.  This  opening  is  not  visible  externally,  owing  to  a  pro- 
longation of  the  transversalis  fascia  on  these  structures,  forming  the  infundibuliform 
fascia. 

The  internal  or  deep  abdominal  ring  (annulus  inguinalis  abdominis}  (Figs.  291 
and  297)   is   situated  in  the  transversalis  fascia,  midway  between  the  anterior 


TRANSVERSALIS 
FASCIA 


INTERNAL 

ABDOMINAL 

RING 


CRURAL  NERVE 


FEMORAL  ARTERY. 


ILIAC  FASCIA 


GIMBERNAT'S 
LIGAMENT 


CRURAL 
SEPTUM 
COOPER'S 
LIGAMENT 


FIG.  297.-  The  relation  of  the  femoral  and  internal  abdominal  rings,  seen  from  within  the  abdomen  after 
removal  of  the  peritoneum.      (Poirier  and  Charpy.) 

superior  spine  of  the  ilium  and  the  symphysis  pubis,  and  about  half  an  inch  above 
Poupart's  ligament.  It  is  of  an  oval  form,  the  extremities  of  the  oval  directed 
upward  and  downward,  varies  in  size  in  different  subjects,  and  is  much  larger  in 
the  male  than  in  the  female.  Its  lower  border  is  strengthened  by  the  collection  of 
fibres  called  Hesselbach's  ligament,  lying  directly  in  front  of  the  deep  epigastric 
artery.  It  is  the  outer  portion  of  the  conjoined  tendon  fused  with  the  outer 
pillar  of  the  semilunar  fold  of  Douglas.  The  internal  ring  is  bounded,  above 
and  externally,  by  the  arched  fibres  of  the  Transversalis;  below  and  internally, 
by  the  deep  epigastric  vessels.  It  transmits  the  spermatic  cord  in  the  male 
and  the  round  ligament  in  the  female.  From  its  circumference  a  thin  funnel- 
shaped  membrane,  the  infundibuliform  or  internal  spermatic  fascia,  is  continued 
round  the  cord  and  testis.  enclosing  them  in  a  distinct  pouch. 


OF    THE    ABDOMEN 


449 


EXTERNAL  OBLIQUE 

(reflected  inward; 


POSTERIOR  WALL  OF 
INGUINAL  CANAL 


INTERNAL   ORIGIN 
OF  CRENASTER 


FIG.  298. — The  right  inguinal  canal  in  the  male,  second  layer,  viewed  from  in  front, 
is  shown  in  Fig.  289.)     (Spalteholz.) 


(The  first  layer 


INTERNAL  OBLIQUE 

(reflected  inward) 


EXTERNAL  OBLIQUE 

(reflected  inward) 


OBLIQUE 

(reflected 
downward) 


FIG.  299. — The  right  inguinal  canal  in  the  male,  third  layer,  viewed  from  in  front. 

29 


(Spalteholz.> 


450  THE   MUSCLES  AND    FASCIA 

When  the  sac  of  an  oblique  inguinal  hernia  passes  through  the  internal  or  deep  abdominal 
ring,  the  infundibuliform  process  of  the  transversalis  fascia  forms  one  of  its  coverings. 

The  Inguinal  or  Spermatic  Canal  (canalis  inguinalis}  (Figs.  298  and  299) . — The 
inguinal  or  spermatic  canal  contains  the  spermatic  cord  (funiculus  spermaticus)  in 
the  male  and  the  round  ligament  (ligamentum  teres  uteri]  in  the  female.  It  is  an 
oblique  canal  about  an  inch  and  a  half  in  length,  directed  downward  and  inward, 
and  placed  parallel  to  and  a  little  above  Poupart's  ligament.  It  commences  above 
at  the  internal  or  deep  abdominal  ring,  which  is  the  point  where  the  cord  enters 
the  spermatic  canal,  and  terminates  below  at  the  external  ring.  It  is  bounded 
in  front  by  the  integument  and  superficial  fascia,  by  the  aponeurosis  of  the 
External  oblique  throughout  its  whole  length,  and  by  the  Internal  oblique  for 
its  outer  third;  behind,  by  the  triangular  fascia,  the  conjoined  tendon  of  the 
Internal  oblique  and  Transversalis,  transversalis  fascia,  and  the  subperitoneal 
fat  and  peritoneum ;  above,  by  the  arched  fibres  of  the  Internal  oblique  and  Trans- 
versalis; below,  by  Gimbernat's  ligament,  and  by  the  union  of  the  fascia  trans- 
versalis with  Poupart's  ligament.  The  median  aspect  of  the  floor  of  the  canal  is 
strengthened  by  dense  fibres  which  are  attached  to  the  pubis  and  to  the  Rectus 
muscle.  These  fibres  constitute  the  falx  inguinalis,  or  ligament  of  Henle.  The  deep 
epigastric  artery  passes  upward  and  inward  behind  the  canal  lying  close  to  the 
inner  side  of  the  internal  abdominal  ring  (Fig.  291).  The  interval  between  this 
artery  and  the  outer  edge  of  the  Rectus  is  named  Hesse Ibach's  triangle,  the  base  of 
which  is  formed  by  Poupart's  ligament. 

That  form  of  protrusion  in  which  the  intestine  follows  the  course  of  the  spermatic  cord  along 
the  spermatic  canal  is  called  oblique  inguinal  hernia. 

The  Deep  Crural  Arch. — Curving  over  the  vessels,  just  at  the  point  where  they 
become  femoral,  on  the  abdominal  side  of  Poupart's  ligament  and  loosely  con- 
nected with  it,  is  a  thickened  band  of  fibres  called  the  deep  crural  arch.  It  is 
apparently  a  thickening  of  the  fascia  transversalis,  joining  externally  to  the  centre 
of  Poupart's  ligament,  and  arching  across  the  front  of  the  crural  sheath  to  be 
inserted  by  a  broad  attachment  into  the  spine  of  the  os  pubis  and  ilio-pectineal 
line,  behind  the  conjoined  tendon.  In  some  subjects  this  structure  is  not  very 
prominently  marked,  and  not  infrequently  it  is  altogether  wanting. 

Cooper's  Ligament  or  the  Reflected  Tendon  of  Cooper  (Fig.  297)  is  a  small  reflection 
from  the  tendon  of  the  Transversalis  which  passes  downward  and  outward  behind 
Gimbernat's  ligament. 

The  External  Abdominal  Ring  (annulus  abdominalis  subcutaneus). — See  p.  437. 

Surface  Form. — The  only  two  muscles  of  this  group  which  have  any  considerable  influ- 
ence on  surface  form  are  the  External  oblique  and  Rectus  muscles  of  the  abdomen.  With 
regard  to  the  External  oblique,  the  upper  digitations  of  its  origin  from  the  ribs  are  well  marked, 
intermingled  with  the  serrations  of  the  Serratus  magnus;  the  lower  digitations  are  not  visible, 
being  covered  by  the  thick  border  of  the  Latissimus  dorsi.  Its  attachment  to  the  crest  of  the 
ilium,  in  conjunction  with  the  Internal  oblique,  forms  a  thick  oblique  roll,  which  determines  the 
iliac  furrow.  Sometimes  on  the  front  of  the  lateral  region  of  the  abdomen  an  undulating  out- 
line marks  the  spot  where  the  muscular  fibres  terminate  and  the  aponeurosis  commences.  The 
outer  border  of  the  Rectus  is  defined  by  the  linea  semilunaris,  which  may  be  exactly  defined  by 
putting  the  muscle  into  action.  It  corresponds  with  a  curved  line,  with  its  convexity  outward, 
drawn  from  the  end  of  the  cartilage  of  the  ninth  rib  to  the  spine  of  the  os  pubis,  so  that  the 
centre  of  the  line,  at  or  near  the  umbilicus,  is  three  inches  from  the  median  line.  The  inner 
border  of  the  Rectus  corresponds  to  the  linea  alba,  marked  on  the  surface  of  the  body  by  a 
groove,  the  abdominal  furrow,  which  extends  from  the  infrasternal  fossa  to,  or  to  a  little  below, 
the  umbilicus,  where  it  gradually  becomes  lost.  The  surface  of  the  Rectus  presents  three  trans- 
verse furrows,  the  linese  transversae.  The  upper  two  of  these,  one  opposite  or  a  little  below  the 
tip  of  the  ensiform  cartilage,  and  another,  midway  between  this  point  and  the  umbilicus,  are 
usually  well  marked;  the  third,  opposite  the  umbilicus,  is  not  so  distinct.  The  umbilicus,  situ- 
ated in  the  linea  alba,  varies  very  much  in  position  as  regards  its  level.  It  is  always  situated 
above  a  zone  drawn  round  the  body  opposite  the  highest  point  of  the  crest  of  the  ilium,  gen- 
erally being  about  three-quarters  of  an  inch  to  an  inch  above  this  line.  It  usually  corresponds, 
therefore,  to  the  fibro-cartilage  between  the  third  and  fourth  lumbar  vertebrae. 


OF   THE  1SCHIO- RECTAL   REGION  451 

2.  The  Deep  Muscles  of  the  Abdomen. 

Psoas  magnus.  Iliacus. 

Psoas  parvus.  Quadratus  lumborum. 

The  Psoas  magnus,  the  Psoas  parvus,  and  the  Iliacus  muscles,  with  the  fascia 
covering  them,  will  be  described  with  the  Muscles  of  the  Lower  Extremity. 

The  Fascia  Covering  the  Quadratus  Lumborum  (Fig.  294).— This  is  the  most 
anterior  of  the  three  layers  of  the  lumbar  fascia.  It  is  a  thin  layer  of  fascia,  which, 
passing  over  the  anterior  surface  of  the  Quadratus  lumborum,  is  attached,  inter- 
nally, to  the  bases  of  the  transverse  processes  of  the  lumbar  vertebrae;  below,  to 
the  ilio-lumbar  ligament;  and  above,  to  the  apex  and  lower  border  of  the  last  rib. 

The  portion  of  this  fascia  which  extends  from  the  transverse  process  of  the 
first  lumbar  vertebra  to  the  apex  and  lower  border  of  the  last  rib  constitutes  the 
ligamentum  arcuatum  externum. 

The  Quadratus  Lumborum  (Fig.  282)  is  situated  in  the  lumbar  region.  It  is 
irregularly  quadrilateral  in  shape,  and  broader  below  than  above.  It  arises  by 
aponeurotic  fibres  from  the  ilio-lumbar  ligament  and  the  adjacent  portion  of  the 
crest  of  the  ilium  for  about  two  inches,  and  is  inserted  into  the  lower  border  of 
the  last  rib  for  about  half  its  length,  and  by  four  small  tendons,  into  the  apices 
of  the  transverse  processes  of  the  four  upper  lumbar  vertebrae.  Occasionally  a 
second  portion  of  this  muscle  is  found  situated  in  front  of  the  preceding.  This 
arises  from  the  upper  borders  of  the  transverse  processes  of  three  or  four  of  the 
lower  lumbar  vertebras,  and  is  inserted  into  the  lower  margin  of  the  last  rib.  The 
Quadratus  lumborum  is  contained  in  a  sheath  formed  by  the  anterior  and  middle 
lamellae  of  the  lumbar  fasciae. 

Relations. — Its  anterior  surface  (or  rather  the  fascia  which  covers  its  anterior 
surface)  is  in  relation  with  the  colon,  the  kidney,  the  Psoas  muscle,  and  the 
Diaphragm.  Between  the  fascia  and  the  muscle  are  the  last  thoracic,  ilio-hypogas- 
tric,  and  ilio-inguinal  nerves.  Its  posterior  surface  is  in  relation  with  the  middle 
lamella  of  the  lumbar  fascia,  which  separates  it  from  the  Erector  spinae.  The 
Quadratus  lumborum  extends,  however,  beyond  the  outer  border  of  the  Erector 
spinae. 

Nerve-supply. — The  anterior  branches  of  the  last  thoracic  and  first  lumbar 
nerves ;  sometimes  also  a  branch  from  the  second  lumbar  nerve. 

Actions. — The  Quadratus  lumborum  draws  down  the  last  rib.  It  acts  as  a 
muscle  of  inspiration  by  helping  to  fix  the  origin  of  the  Diaphragm.  If  the  thorax 
and  spine  are  fixed,  it  may  act  upon  the  pelvis,  raising  it  toward  its  own  side 
when  only  one  muscle  is  put  in  action ;  and  when  both  muscles  act  together,  either 
from  below  or  above,  they  flex  the  trunk. 

IV.  MUSCLES  OF  THE  PELVIC  OUTLET. 

The  muscles  of  this  region  are  situated  at  the  pelvic  outlet  in  the  ischio-rectal 
region  and  the  perinaeum.  They  include^  the  following: 

1.  Muscles  of  the  ischio-rectal  region. 

2.  Muscles  of  the  perinaeum  in  the  male. 

3.  Muscles  of  the  perinaeum  in  the  female. 

1.  The  Muscles  of  the  Ischio-rectal  Region. 

Corrugator  cutis  ani.  Internal  sphincter  ani. 

External  sphincter  ani.  Levator  ani. 

Coccygeus. 

The  Corrugator  Cutis  Ani. — Around  the  anus  is  a  thin  stratum  of  involuntary 
muscular  fibre,  which  radiates  from  the  orifice.  Internally,  the  fibres  fade  off 


452 


THE   MUSCLES   AND    FASCIA 


into  the  submucous  tissue,  while  externally  they  blend  with  the  true  skin.     By 
its  contraction  it  raises  the  skin  into  ridges  around  the  margin  of  the  anus. 

The  External  Sphincter  Ani  (m.  sphincter  ani  externus)  (Figs.  300,  305,  306,  and 
307)  is  a  thin,  flat  plane  of  muscular  fibres,  elliptical  in  shape  and  intimately  adher- 


FR/ENUM   OF 
PREPUCE 


EXTERNAL 
ABDOMINAL  RING 


FASCIA  OF 
PENIS 


INFERIOR 

RAMUS   OF 
ISCHIUM 


rUBEROSITY 
OF  ISCHIUM 


:;  INFERIOR 

|i LAYER   OF 

:N      TRIANGULAR 
Sl|     LIGAMENT 
sJM"      TRANSVERSUS 

^||: PERINEI 

^|      SUPERFICIALIS 


OBTURATOR 
'FASCIA 


ISCHIO-RECTAU 
'FOSSA 


ANO-COCCYGEAL  LIGAMENT 

FIG.  300. — The  muscles  of  the  male  perinseum,  viewed  from  below.     (Spalteholz.) 

ent  to  the  integument  surrounding  the  margin  of  the  anus.  It  measures  about 
three  or  four  inches  in  length  from  its  anterior  to  its  posterior  extremity,  being 
about  an  inch  in  breadth  opposite  the  anus.  It  arises  from  the  tip  and  back  of 
the  coccyx  by  a  narrow  tendinous  band,  and  from  the  superficial  fascia  in  front 


OF   THE  I8CHIO- RECTAL    REGION 


453 


of  that  bone;  and  is  inserted  into  the  raphe  of  the  Accelerator  urinae  muscle  and 
into  the  central  tendinous  point  of  the  perinaeum,  joining  with  the  two  Superficial 
transverse  perineal,  the  I^evator  ani,  and  the  Accelerator  urinae  muscles.  Many 
of  the  fibres  are  continuous  with  the  Accelerator  urinje  in  the  male  and  with  the 
Sphincter  vaginae  in  the  female.  Often  some  of  the  fibres  are  continuous  with  the 
Transverse  perineal  muscles.  It  is  continuous  above  with  the  Levator  ani.  Like 
other  sphincter  muscles,  it  consists  of  two  planes  of  muscular  fibre,  which  sur- 
round the  margin  of  the  anus  and  join  in  a  commissure  in  front  and  behind, 
some  fibres  crossing  from  side  to  side  in  front  and  behind  the  anus. 

Nerve-supply. — A  branch  from  the  anterior  division  of  the  fourth  sacral  and 
the  inferior  hsemorrhoidal  branch  of  the  internal  pudic. 

Actions. — The  action  of  this  muscle  is  peculiar:  1.  It  is,  like  other  sphincter 
muscles,  always  in  a  state  of  tonic  contraction,  and  having  no  antagonistic  muscle, 
it  keeps  the  anal  orifice  closed.  2.  It  can  be  put  into  a  condition  of  greater  con- 


PECTINEUS 
ADDUCTOR 
UONGUS. 
GRACILIS. 


Epididymis. 


Ampulla. 


Ampulla  of  vasa 
deferens. 


Testicle. 

Ascending  ramus  of 
ISCHIUM. 

Internal  pudic 
vessels  and  nerve 


OBTURATOR    INTERNUS. 


FIG.  301. --Side  view  of  pelvis,  showing  Levator  ani.     (From  a  preparation  in  the  Museum  of  the  Royal 

College  of  Surgeons.) 

. 

traction  under  the  influence  of  the  will,  so  as  to  occlude  more  firmly  the  anal 
aperture  in  expiratory  efforts  unconnected  with  defecation.  3.  Taking  its  fixed 
point  at  the  coccyx,  it  helps  to  fix  the  central  point  of  the  perinseum,  so  that  the 
Accelerator  urinse  may  act  from  this  fixed  point. 

The  Internal  Sphincter  Ani  (TO.  sphincter  ani  internus)  is  a  muscular  ring 
which  surrounds  the  lower  extremity  of  the  rectum  for  about  an  inch,  its  inferior 
border  being  contiguous  to,  but  quite  separate  from,  the  External  sphincter. 
This  muscle  is  about  two  lines  in  thickness,  and  is  formed  by  an  aggregation 
of  the  involuntary  circular  fibres  of  the  intestine.  It  is  paler  in  color  and  less 
coarse  in  texture  than  the  External  sphincter. 

Actions. — Its  action  is  entirely  involuntary.  It  helps  the  External  sphincter 
to  occlude  the  anal  aperture. 

The  Levator  Ani  (Figs.  301,  302,  303,  and  304)  is  a  broad,  thin  muscle, 
situated  on  each  side  of  the  pelvis.  It  is  attached  to  the  inner  surface  of  the 


454 


THE  MUSCLES  AND    FASCIA 


sides  of  the  true  pelvis,  and,  descending,  unites  with  its  fellow  of  the  opposite  side 
to  form  the  floor  of  the  pelvic  cavity.  It  supports  the  viscera  in  this  cavity  and 
surrounds  the  various  structures  which  pass  through  it.  It  is  usually  possible  to 
detect  an  interval  between  the  fibres  rising  from  the  pubis  and  those  rising  from 
the  pelvic  fascia,  and  this  interval  marks  the  fact  that  the  muscle  described  as  one 
is  really  two.  The  pubic  fibres  constitute  the  Pubococcygeus  muscle  and  the 
other  fibres  the  Iliococcygeus  muscle.1 

The  Pubococcygeus  muscle  takes  origin  from  the  posterior  aspect  of  the  ramus 
of  the  pubis  and  from  the  most  anterior  portion  of  the  tendinous  arch  of  the 
Levator  ani  muscle.  The  fibres  of  origin  from  the  pubis  surround  anteriorly  the 
origin  of  the  Internal  obturator  muscle.  The  muscle  is  a  band,  about  one  inch  in 
width,  thickest  at  its  outer  border,  where  it  overlaps  the  Iliococcygeus.  It  passes 
backward,  downward,  and  inward,  "near  the  prostate  in  the  male,  the  urethra 
and  vagina  in  the  female,"2  and  near  to  the  rectum.  Most  of  the  fibres  pass  back 


ANTERIOR  SACRO- 
COCCYGEAL    LIGAMENT 


GREAT  SACRO- 
SCIATIC   LIGAMENT 


OBTURATOR 
CANAL 


SUPERIOR    LAYER 
OF  TRIANGULAR 
LIGAMENT 


FIG.  302. — The  Levator  ani  of  the  male,  viewed  from  above.     (Spalteholz.) 

of  the  rectum,  where  they  meet  and  join  with  the  corresponding  fibres  of  the 
opposite  side.  These  united  fibres  form  a  thick,  tendinous  aponeurosis.  "This 
is  continued  upward  in  front  of  the  coccyx  for  some  distance,  and  finally  divides 
into  two  lateral  portions,  which  have  been  named  the  ligamenta  sacro-coccygea 
anterior.  They  are  situated  on  either  side  of  the  middle  sacral  artery,  and  are 
finally  inserted  into  the  last  one  or  two  pieces  of  the  sacrum  and  the  first  piece 
of  the  coccyx."3  A  few  of  the  fibres  of  the  Pubococcygeus  muscle  pass  to  the 

1  Peter  Thompson.     The  Myology  of  the  Pelvic  Floor. 

2  Spalteholz's  Atlas.     Translated  and  edited  by  Barker. 
8  Peter  Thompson.     The  Myology  of  the  Pelvic  Floor. 


OF   THE   ISCHIO- RECTAL    REGION 


455 


central  tendon  of  the  perinseum,  come  in  contact  with  but  do  not  terminate  in  the 
rectal  wall,  descend  in  front  of  and  close  to  the  anterior  rectal  wall,  and  terminate 
in  the  anterior  portion  of  the  sphincter  ani  and  in  the  skin  of  the  anus  (Peter 
Thompson). 

Luschka  and  others  believe  that  these  anterior  fibres  descend  among  the  longi- 
tudinal fibres  of  the  rectum.     It  is  certain  that  the  most  anterior  fibres  of  the 


•""•-"•'V  inaniiufliiiiiIIL 


COWPER'S      SUPERFICIAL  TRANS- 
GLANDS          VERSUS   PEP.INEI 


FIG.  303. — The  right  Levator  ani  in  the  male,  viewed  from  the  left.     (Spalteholz.) 

Pubococcygeus  muscle  pass  to  the  central  point  of  the  perineum.  They  pass 
"backward  and  downward  on  the  side  of  the  prostate,  and  in  some  cases  on  the 
side  of  the  urethra  immediately  it  emerges  from  the  prostate."1  These  anterior 
fibres  in  the  female  descend  upon  the  side  of  the  vagina.  The  anterior  fibres 
are  the  preanal  fibres  of  the  Levator  ani.  They  constitute  what  Santorini  named 

1  Peter  Thompson.     The  Myology  of  the  Pelvic  Floor. 


456 


THE  MUSCLES   AND    FASCIAE 


the  levator  prostatse,  because  he  regarded  them  as  constituting  a  distinct 
muscle,  which  surrounds  the  prostate  as  a  sling.  Krause  calls  these  fibres 
the  levator  urethrae;  Testut,  the  fibres  pre"-rectales,  and  Prout,  the  Recto-urethralis 
muscle. 

The  Iliococcygeus  muscle  arises  from  the  tendinous  arch  of  the  Levator  ani  muscle 
(arcus  tendineus  m.  levatoris  ani).  This  arch  is  concave  upward.  The  anterior 
end  of  the  arch  begins  on  the  posterior  surface  of  the  superior  ramus  of  the 
pubis.  "The  posterior  end  can  be  followed  as  far  as  the  linea  arcuata  of  the 
ilium,  between  these  two  points  it  descends  for  a  variable  distance,  but  always 
leaves  the  canalis  obturatorius  free."1  The  fibres,  coursing  internally  and  down- 
ward, pass  below  the  posterior  portion  of  the  Pubococcygeus.  The  anterior 
fibres  join  the  fibres  of  the  other  side,  between  the  anus  and  the  tip  of  the  coccyx 
in  a  median  raphe. 

The  posterior  fibres  are  inserted  into  the  sides  of  the  last  two  pieces  and  into 
the  tip  of  the  coccyx.  Peter  Thompson  points  out  that  the  Iliococcygeus  muscle 
is  liable  to  variations.  It  is  strongly  developed  in  but  few,  is  usually  thin,  the 
muscular  bundles  being  separated  by  membranous  intervals;  it  may  be  replaced 
by  fibrous  tissue  and  may  even  be  absent.2 


ANTERIOR- 
SUPERIOR 
SPINES 


POU 
LIGAMENT 


OBTURATOR 
ARTERY 


"^f —  WHITE   LINE 


EATER 

SACRO-SCIATIC 
LIGAMENT 


FASCIA  OF 

LEVATOR   ANI 

MUSCLE 


TUBEHOSITY 
OF  ISCHIUM 


FIG.  304. — Pelvic  fascia  (semi-diagrammatic). 

Relations  of  the  Levator  Ani. — By  its  inner  or  pelvic  surface,  with  the  recto- 
vesical  fascia,  which  separates  it  from  the  viscera  of  the  pelvis  and  from  the 
peritoneum.  By  its  outer  or  perineal  surface,  it  forms  the  inner  boundary 
of  the  ischio-rectal  fossa,  and  is  covered  by  a  thin  layer  of  fascia,  the  ischio- 
rectal  or  anal  fascia,  given  off  from  the  obturator  fascia.  Its  posterior  border  is 
free  and  separated  from  the  Coccygeus  muscle  by  a  cellular  interspace.  Its 
anterior  border  is  separated  from  the  muscle  of  the  opposite  side  by  a  triangular 
space,  through  which  the  urethra,  and  in  the  female  the  vagina,  passes  from  the 
pelvis. 

Nerve-supply. — A  branch  from  the  anterior  division  of  the  fourth  sacral  nerve 
and  a  branch  from  the  pudic  nerve,  which  is  sometimes  derived  from  the  perineal 
and  sometimes  from  the  inferior  hemorrhoidal  division. 

Actions. — The  entire  Levator  ani  muscle  enters  into  the  formation  of  the 
diaphragm  of  the  pelvis  and  aids  in  supporting  the  rectum,  vagina,  and  bladder. 


1  Spalteholz's  Atlas.     Translated  and  edited  by  Barker. 


2  Myology  of  Muscles. 


OF    THE  PERINEUM  IN    THE   MALE  457 

The  two  parts  of  the  muscle  have  different  functions.  The  Iliococcygei  have 
no  other  function  than  that  of  supporting  the  viscera.  In  early  life  they  flex  the 
vertebrae  of  the  coccyx  on  one  another  and  flex  the  coccyx  on  the  sacrum,  but  do 
not  act  directly  at  any  age  on  the  rectum  or  pelvic  viscera  (Peter  Thompson). 
The  Pubococcygei,  especially  in  the  female,  have  most  important  functions. 
They  are  the  most  influential  supports  of  the  pelvic  floor  and  restore  the  pelvic 
floor  to  its  proper  position  after  the  depression  induced  by  parturition,  defecation, 
and  efforts  at  urination.1  Normally,  they  pull  the  perinaeum  upward  after  the 
descending  head  has  pulled  it  down.  In  some  cases  the  contraction  of  the  muscles 
actually  obstructs  the  descent  of  the  head  (Peter  Thompson).  The  muscles  are 
strongly  developed  in  females,  and,  acting  with  the  Sphincter  vaginae,  they  aid 
in  contracting  the  vaginal  canal.  The  muscles  constrict  the  rectum  and  also  lift 
the  rectum  with  the  pelvic  floor.  During  defecation  the  position  of  the  rectal 
contents  is  maintained  by  intra-abdominal  pressure,  the  muscles  lift  the  perinseum 
over  the  fecal  matter  (Goffe).  The  Levator  ani  is  also  a  muscle  of  forced 
expiration. 

The  Coccygeus  is  a  flat,  triangular  muscle  situated  behind  and  parallel  with 
the  preceding.  It  is  a  triangular  plane  of  muscular  and  tendinous  fibres,  arising, 
by  its  apex,  from  the  spine  of  the  ischium,  the  obturator  fascia,  the  edge  of  the 
great  sacro-sciatic  notch,  and  from  the  lesser  sacro-sciatic  ligament,  and  inserted, 
by  its  base,  into  the  side  of  the  lower  two  vertebras  of  the  sacrum  and  the  upper 
two  vertebrae  of  the  coccyx.  It  assists  the  Levator  ani  and  Pyriformis  in  closing 
in  the  back  part  of  the  outlet  of  the  pelvis. 

Relations. — By  its  inner  or  pelvic  surface,  with  the  rectum.  By  its  external 
surface,  with  the  lesser  sacro-sciatic  ligament.  The  lower  border  is  in  relation 
with  the  posterior  border  of  the  Levator  ani,  but  separated  from  it  by  a 
cellular  interval:  its  upper  border  is  in  relation  with  the  lower  border  of  the 
Pyriformis,  but  separated  from  it  by  the  sciatic  and  internal  pudic  vessels  and 
nerve. 

Nerve-supply. — A  branch  from  the  fourth  and  fifth  sacral  nerves. 

Action. — The  Coccygei  muscles  raise  and  support  the  coccyx,  after  it  has  been 
pressed  backward  during  defecation  or  parturition. 


2.  The  Muscles  and  Fasciae  of  the  Perinaeum  in  the  Male 
(Figs.  300,  305,  306,  307). 

Transversus  perinei  superficialis.  Erector  penis. 

Accelerator  urinse.  Compressor  urethrae. 

Superficial  Fascia  (fascia  superficialis  perinei). — The  superficial  fascia  of  the 
perinaeum  consists  of  two  layers,  superficial  and  deep,  as  in  other  regions  of  the 
body.  The  superficial  fascia  over  the  posterior  portion  of  the  perinaeum  is 
arranged  in  fatty  layers  which  fill  the  ischio-rectal  fossa  on  each  side  of  the 
rectum  and  anus.  The  superficial  fascia  over  the  anterior  portion  of  the  peri- 
naeum (urethra!  region)  requires  fuller  consideration. 

The  Superficial  Layer  is  thick,  loose,  areolar  in  texture,  and,  except  toward  the 
scrotum,  contains  much  adipose  tissue  in  its  meshes,  the  amount  of  which  varies 
in  different  subjects.  In  front,  it  is  continuous  with  the  dartos  of  the  scrotum; 
behind,  it  is  continuous  with  the  subcutaneous  areolar  tissue  surrounding  the 
anus;  and,  on  either  side,  with  the  same  fascia  on  the  inner  side  of  the  thighs.  In 
the  middle  line  it  is  adherent  to  the  skin  of  the  raphe*  and  to  the  deep  layer  of 

1  Peter  Thompson.     The  Myology  of  the  Pelvic  Floor. 


458 


THE   MUSCLES   AND    FASCIA 


the  superficial  fascia.    This  layer  should  be  carefully  removed  after  it  has  been 
examined,  when  the  deep  layer  will  be  exposed. 

The  Deep  Layer  of  Superficial  Fascia  or  the  Fascia  of  Golles  is  thin,  aponeurotic 
in  structure,  and  of  considerable  strength,  serving  to  bind  down  the  muscles  of  the 
root  of  the  penis.  It  is  continuous,  in  front,  with  the  deep  fascia  of  the  penis, 
and  the  dartos  of  the  scrotum,  the  fascia  of  the  spermatic  cord,  and  Scarpa's 
fascia  upon  the  anterior  portion  of  the  abdomen;  on  either  side  it  is  firmly 
attached  to  the  margins  of  the  rami  of  the  os  pubis  and  ischium,  external  to 
the  crus  penis,  and  as  far  back  as  the  tuberosity  of  the  ischium;  posteriorly, 
it  curves  down  behind  the  Superficial  transverse  perineal  muscles  (reflected 
portion  of  fascia)  to  join  the  lower  margin  of  the*  triangular  ligament,  which 
structure  is  a  prolongation  of  the  deep  layer  of  the  superficial  fascia.  The 
deep  layer  is  attached  to  the  superficial  layer  in  the  median  line  and  to  the 


FIG.  305. — The  perinseum.     The  integument  and  superficial  layer  of  superficial  fascia  reflected. 

median  septum  of  the  Accelerator  urinae  muscle.  At  the  central  tendon  of  the 
perinseum  the  reflected  portion  of  the  fascia  becomes  blended  with  the  inser- 
tions of  the  External  anal  sphincter,  the  two  Superficial  transverse  perineal 
muscles,  and  the  Accelerator  urinse.  This  fascia  not  only  covers  the  muscles 
in  this  region,  but  sends  upward  a  vertical  septum  from  its  deep  surface,  which 
separates  the  back  part  of  the  subjacent  space  into  two,  the  septum  being 
incomplete  in  front. 

The  Central  Tendinous  Point  of  the  Perinaeum. — This  is  a  fibrous  point  in  the 
middle  line  of  the  perinseum,  between  the  urethra  and  the  rectum,  being  about 
half  an  inch  in  front  of  the  anus.  At  this  point  four  muscles  converge  and  are 
attached — viz.,  the  External  sphincter  ani,  the  Accelerator  urinse,  and  the  two 
Superficial  transverse  perineal ;  so  that  by  the  contraction  of  these  muscles,  which 
extend  in  opposite  directions,  it  serves  as  a  fixed  point  of  support. 


OF   THE  PERINEUM  IN   THE  MALE 


459 


The  Transversus  Perinei  Superficialis  is  a  narrow  muscular  slip,  which  passes 
more  or  less  transversely  across  the  back  part  of  the  perineal  space.  It  arises 
by  a  small  tendon  from  the  inner  and  forepart  of  the  tuberosity  of  the  ischium, 
and,  passing  inward,  is  inserted  into  the  central  tendinous  point  of  the  perineum, 
joining  in  this  situation  with  the  muscle  of  the  opposite  side,  the  External 
sphincter  ani  behind,  and  the  Accelerator  urinse  in  front.  The  base  of  the  tri- 
angular ligament  lies  just  beneath  this  muscle. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — By  their  contraction  they  serve  to  fix  the  central  tendinous  point  of 
the  perinfeum. 

The  Accelerator  Urinae,  called  also  the  Ejaculator  seminis  and  the  Ejaculator 
urinae  (m.  bulbocavernosus) ,  is  placed  in  the  middle  line  of  the  perineeum,  imme- 
diately in  front  of  the  anus.  It  consists  of  two  symmetrical  halves,  united 
along  the  median  line  by  a  tendinous  raphe".  It  arises  from  the  central  tendon 


Transrersus  perinei 
superficialis. 


GREAT  SACRO- 
SCIATIC   LIGAMENT 


Superficial  perineal  artery. 
Superficial  perineal  nerve. 
Internal  pudic  nerve. 
Internal  pudic  artery. 


FIG.  306. — The  superficial  muscles  and  vessels  of  the  perinseum. 

of  the  perinseum,  and  from  the  median  raphe"  in  front.  From  this  point  its  fibres 
diverge  like  the  plumes  of  a  pen;  the  most  posterior  form  a  thin  layer,  which  is 
lost  on  the  anterior  surface  of  the  triangular  ligament;  the  middle  fibres  encircle 
the  bulb  and  adjacent  parts  of  the  corpus  spongiosum,  and  join  with  the  fibres 
of  the  opposite  side,  on  the  upper  part  of  the  corpus  spongiosum,  in  a  strong 
aponeurosis;  the  anterior  fibres,  the  longest  and  most  distinct,  spread  out  over 
the  sides  of  the  corpus  cavernosum,  to  be  inserted  partly  into  that  body,  anterior 
to  the  Erector  penis,  occasionally  extending  to  the  os  pubis;  partly  terminating 
in  a  tendinous  expansion,  which  covers  the  dorsal  vessels  of  the  penis.  The  latter 
fibres  are  best  seen  by  dividing  the  muscle  longitudinally,  and  dissecting  it  out- 
ward from  the  surface  of  the  urethra.  Many  fibres  of  the  External  sphincter 
ani  and  of  the  Superficial  transverse  perineal  muscles  pass  into  this  muscle. 

Action. — This  muscle  serves    to  empty  the  canal  of    the  urethra,  after  the 
bladder  has  expelled  its  contents ;  during  the  greater  part  of  the  act  of  micturition 


460 


THE  MUSCLES   AND    FASCIAE 


its  fibres  are  relaxed,  and  it  only  comes  into  action  at  the  end  of  the  process. 
The  middle  fibres  are  supposed,  by  Krause,  to  assist  in  the  erection  of  the  corpus 
spongiosum,  by  compressing  the  erectile  tissue  of  the  bulb.  The  anterior  fibres, 
on  each  side,  which  are  known  as  Houston's  muscles,  according  to  Tyrrel,  also 
contribute  to  the  erection  of  the  penis,  as  they  are  inserted  into,  and  continuous 
with,  the  fascia  of  the  penis,  compressing  the  dorsal  vein  during  the  contraction 
of  the  muscle. 

The  Erector  Penis  (TO.  ischiocavernosus)  covers  part  of  the  crus  penis.  It  is  an 
elongated  muscle,  broader  in  the  middle  than  at  either  extremity,  and  situated  on 
either  side  of  the  lateral  boundary  of  the  perinaeum.  It  arises  by  tendinous  and 
fleshy  fibres  from  the  inner  surface  of  the  tuberosity  of  the  ischium,  behind  the 
crus  penis,  from  the  surface  of  the  crus,  and  from  the  adjacent  portion  of  the 
ramus  of  the  ischium.  From  these  points  fleshy  fibres  succeed,  which  end 
in  an  aponeurosis  which  is  inserted  into  the  sides  and  under  surface  of  the 
crus  penis. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 


Anterior  layer  of 

deep  perineal  fascia  removed, 

showing 

COMPRESSOR    URETHRJE. 

rnternal  pudic  artery. 
•Artery  of  the  bulb. 
Cowper's  gland. 


FIG.  307. — Triangular  ligament  or  deep  perineal  fascia.     On  the  left  side  the  anterior  layer  has  been  removed. 

Actions. — It  compresses  the  crus  penis  and  retards  the  return  of  the  blood 
through  the  veins,  and  thus  serves  to  maintain  the  organ  erect. 

Between  the  muscles  just  examined  a  triangular  space  exists,  bounded  inter- 
nally by  the  Accelerator  urinse,  externally  by  the  Erector  penis,  and  behind  by 
the  Trans  versus  perinei  superficialis.  The  floor  of  this  space  is  formed  by  the 
triangular  ligament  of  the  urethra  (deep  perineal  fascia),  and  running  from  behind 
forward  in  it  are  the  superficial  perineal  vessels  and  nerves,  the  long  pudendal 
nerve,  and  the  transverse  perineal  artery  coursing  along  the  posterior  boundary 
of  the  space  on  the  Trans  versus  perinei  superficialis. 

The  Triangular  Ligament  or  the  Deep  Perineal  Fascia  (trigonum  or  diaphragma 
urogenitale)  (Figs.  304,  308,  and  309)  is  stretched  almost  horizontally  across  the 
pubic  arch,  so  as  to  close  in  the  front  part  of  the  outlet  of  the  pelvis.  It  con- 


OF    THE   PERINEUM  IN    THE   MALE 


461 


sists  of  two  dense  musculo-membranous  laminae,  which  are  united  along  their 
posterior  borders,  but  are  separated  in  front  by  intervening  structures.  The 
superficial  of  these  two  layers,  the  superficial,  anterior,  or  inferior  layer  of  the 
triangular  ligament  (fascia  trigoni  urogenitalis  inferior),  is  triangular  in  shape 
and  about  an  inch  and  a  half  in  depth.  Its  apex  is  directed  forward,  and  is 
separated  from  the  subpubic  ligament  by  an  oval  opening  for  the  transmission 
of  the  dorsal  vein  of  the  penis.  The  apex  of  the  triangular  ligament  is  called  the 


PERITONEUM 


PRO-STATIC 
FASCIA 


DEEP  LAYER  OF 
SUPERFICIAL   FASCIA 


DEEP    LAYER 
OF  TRIANGULAR 
LIGAMENT 


COMPRESSOR 
URETHR« 
MUSCLE 
SUPERFICIAL  LAYER  OF 
TRIANGULAR   LIGAMENT 


FIG.  308. — The  aponeurosis  of  the  perinseum.    (Denonvilliers.) 

transverse  perineal  or  transverse  pelvic  ligament  (ligamentum  transversum  pelvis). 
The  lateral  margins  of  the  inferior  layer  of  the  triangular  ligament  are  attached 
on  each  side  to  the  rami  of  the  ischium  and  os  pubis,  above  the  crura  penis. 
The  fusion  of  the  two  leaves  posteriorly  takes  place  beneath  the  Superficial 
transverse  perineal  muscles.  The  region  of  fusion  of  the  two  leaflets  posteriorly 
is  called  the  base.  The  base  is  directed  toward  the  rectum,  and  connected  to 


URETHRA-j- 


DORSAL  VEIN 

OF    PENIS 

DORSAL  NERVE 

OF    PENIS 

DORSAL  ARTERY 

OF  PENIS 


ARTERY  TO 
BULB 

COMPRESSOR 
URETHR/E 


CORPUS 
SPONGIOSUM 


CORPUS 
CAVERNOSUM 
TRIANGULAR 
LIGAMENT 

upper  margin) 


•^  ^ii. 

FIG.  309. — The  superficial  layer  of  the  triangular  ligament.     The  Compressor  urethra;  muscle  lies  behind  the 
superficial  layer  of  the  triangular  ligament  and  is  shown  in  the  figure  for  convenience.    (Poirier  and  Charpy.) 


the  central  tendinous  point  of  the  perinaeum.  It  is  continuous  with  the  deep 
layer  of  the  superficial  fascia  behind  the  Superficial  transverse  perineal  muscles, 
and  with  a  thin  fascia  which  covers  the  cutaneous  surface  of  the  Levator  ani 
muscle,  the  anal  or  ischio-rectal  fascia. 

This  layer  of  the  triangular  ligament  is  perforated,  about  an  inch  below  the 
symphysis  pubis,  by  the  urethra,  the  aperture  for  which  is  circular  in  form  and 


462  THE  MUSCLES  AND   FASCIAE 

about  three  or  four  lines  in  diameter;  by  the  arteries  to  the  bulb  and  the  ducts  of 
Cowper's  glands  close  to  the  urethral  orifice;  by  the  arteries  to  the  corpora  caver- 
.nosa — one  on  each  side,  close  to  the  pubic  arch  and  about  half-way  along  the 
attached  margin  of  the  ligament;  by  the  dorsal  arteries  and  nerves  of  the  penis  near 
the  apex  of  the  ligament.  Its  base  is  also  perforated  by  the  superficial  perineal 
vessels  and  nerves,  while  between  its  apex  and  the  subpubic  ligament  the  dorsal 
nerve  of  the  penis  and  the  dorsal  vein  of  the  penis  passes  upward  into  the 
pelvis. 

If  this  superficial  or  inferior  layer  of  the  triangular  ligament  is  detached  on 
either  side,  the  following  structures  will  be  seen  between  it  and  the  deeper 
layer:  the  dorsal  vein  of  the  penis;  the  membranous  portion  of  the  urethra, 
and  the  Compressor  urethra?  muscle;  Cowper's  glands  and  their  ducts;  the 
pudic  vessels  and  dorsal  nerve  of  the  penis;  the  artery  and  nerve  of  the  bulb, 
and  a  plexus  of  veins.  The  two  layers  join  the  urethral  wall  and  vagina 
median  ward. 

The  deep,  posterior,  or  superior  layer  (fascia  trigoni  urogenitalis  superior)  of  the 
triangular  ligament  is  derived  from  the  obturator  fascia  and  stretches  across 
the  pubic  arch.  If  the  obturator  fascia  is  traced  inward  after  covering  the 
Obturator  internus  muscle,  it  will  be  found  to  be  attached  by  some  of  its 
deeper  or  anterior  fibres  to  the  inner  margin  of  the  ischio-pubic  ramus,  while  its 
superficial  or  posterior  fibres  pass  over  this  attachment  to  become  the  superior 
layer  of  the  triangular  ligament.  Behind,  this  layer  of  the  fascia  is  continuous 
with  the  inferior  layer  and  with  the  fascia  of  Colles,  and  in  front  it  is  separated 
from  the  apex  of  the  prostate  gland  through  the  intervention  of  a  prolongation  of 
the  recto-vesical  fascia.  It  is  pierced  by  the  urethra,  or  rather  consists  of  two 
halves  which  are  separated  in  the  middle  line  by  the  urethra  passing  between 
them. 

The  Compressor  or  Constrictor  Urethra  (m.  constrictor  urethrae)  in  the  male 
surrounds  the  whole  length  of  the  membranous  portion  of  the  urethra,  and  is 
contained  between  the  two  layers  of  the  triangular  ligament.  It  arises,  by  apon- 
eurotic  fibres,  from  the  junction  of  the  rami  of  the  os  pubis  and  ischium,  to  the 
extent  of  half  or  three-quarters  of  an  inch:  the  point  where  the  crura  penis  joins 
the  transverse  ligament  of  the  perineum  and  the  layers  of  the  triangular  liga- 
ment; each  segment  of  the  muscle  passes  inward,  and  divides  into  two  fasciculi, 
which  surround  the  membranous  urethra  and  unite,  at  the  upper  and  lower 
surfaces  of  this  tube,  with  the  muscle  of  the  opposite  side  by  means  of  a  tendinous 
raphe.  The  Compressor  urethrae  is  continuous  posteriorly  with  the  m.  prostaticus 
and  is  continuous  anteriorly  with  the  circular  fibres  of  the  cavernous  portion  of 
the  urethra.  This  muscle  is  frequently  in  two  portions,  an  anterior  and  a 
posterior,  separated  by  a  distinct  interval.  In  such  cases  the  posterior  fibres  are 
called  the  transversus  perinei  profundus,  and  the  anterior  fibres  are  called  the 
sphincter  urethrae  membranaceae. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — The  muscles  of  both  sides  act  together  as  a  sphincter,  compressing 
the  membranous  portion  of  the  urethra.  During  the  transmission  of  fluids  they, 
like  the  Acceleratores  urinse,  are  relaxed,  and  come  into  action  only  at  the  end  of 
the  process,  to  eject  the  last  drops  of  the  fluid. 

3.  The  Muscles  of  the  Perinseum  in  the  Female  (Fig.  310). 

Transversus  perinei  superficialis.  Erector  clitoridis. 

Sphincter  vaginae.  Compressor  urethras. 

The  Transversus  Perinei  Superficialis  in  the  female  is  a  narrow  muscular  slip, 
which  passes  more  or  less  transversely  across  the  back  part  of  the  perineal  space. 


OF   THE   PERINEUM  IN    THE   FEMALE 


463 


It  arises  by  a  small  tendon  from  the  inner  and  forepart  of  the  tuberosity  of  the 
ischium,  and,  passing  inward,  is  inserted  into  the  central  point  of  the  perinseum, 
joining  in  this  situation  with  the  muscle  of  the  opposite  side,  the  External  sphinc- 
ter ani  behind,  and  the  Sphincter  vaginae  in  front. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — By  their  contraction  they  serve  to  fix  the  central  tendinous  point  of 
the  perinseum. 

The  Sphincter  Vaginae  (m.  'bulbocavernosus)  surrounds  the  orifice  of  the 
vagina,  and  is  analogous  to  the  Accelerator  urinse  in  the  male.  It  is  attached 
posteriorly  to  the  central  tendinous  point  of  the  perinseum,  where  it  blends  with 


FIG.  310. — Muscles  of  the  female  perinaeum. 

the  External  sphincter  ani.  Its  fibres  pass  forward  on  each  side  of  the  vagina,  to 
be  inserted  into  the  corpora  cavernosa  of  the  clitoris,  a  fasciculus  crossing  over 
the  body  of  the  organ  so  as  to  compress  the  dorsal  vein. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — It  diminishes  the  orifice  of  the  vagina.  The  anterior  fibres  contribute 
to  the  erection  of  the  clitoris,  as  they  are  inserted  into  and  are  continuous  with  the 
fascia  of  the  clitoris;  compressing  the  dorsal  vein  during  the  contraction  of  the 
muscle. 

The  Erector  Glitoridis  (m.  ischiocavernosus)  resembles  the  Erector  penis  in  the 
male,  but  is  smaller  than  it.  It  covers  the  unattached  part  of  the  crus  clitoridis. 
It  is  an  elongated  muscle,  broader  at  the  middle  than  at  either  extremity,  and 
situated  on  either  side  of  the  lateral  boundary  of  the  perinseum.  It  arises  by 
tendinous  and  fleshy  fibres  from  the  inner  surface  of  the  tuberosity  of  the  ischium, 
behind  the  crus  clitoridis  from  the  surface  of  the  crus,  and  from  the  adjacent 
portion  of  the  ramus  of  the  ischium.  From  these  points  fleshy  fibres  succeed, 


464 


THE   MUSCLES   AND    FASCIA 


which  end  in  an  aponeurosis,  which  is  inserted  into  the  sides  and  under  surface 
of  the  crus  clitoridis. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — It  compresses  the  crus  clitoridis  and  retards  the  return  of  blood 
through  the  veins,  and  thus  serves  to  maintain  the  organ  erect. 

The  Triangular  Ligament  (trigonum  urogenitale)  in  the  female  is  not  so  strong 
as  in  the  male.  It  is  divided  in  the  middle  line  by  the  aperture  of  the  vagina, 
with  the  external  coat  of  which  it  becomes  blended,  and  in  front  of  this  is 
perforated  by  the  urethra.  Its  posterior  border  is  continuous,  as  in  the  male, 
with  the  deep  layer  of  the  superficial  fascia  around  the  Transversus  perinei 
muscle. 

Like  the  triangular  ligament  in  the  male,  it  consists  of  two  layers,  between 
which  are  to  be  found  the  following  structures:  the  dorsal  vein  of  the  clitoris, 
a  portion  of  the  urethra  and  the  Compressor  urethrse  muscle,  the  glands  of  Bar- 
tholin  and  their  ducts;  the  pudic  vessels  and  the  dorsal  nerve  of  the  clitoris;  the 
arteries  of  the  bulbi  vestibuli,  and  a  plexus  of  veins. 

The  Compressor  Urethrae  (m.  constrictor  urethrae)  arises  on  each  side  from  the 
margin  of  the  descending  ramus  of  the  os  pubis.  The  fibres,  passing  inward, 
divide  into  two  sets:  those  of  the  forepart  of  the  muscle  are  directed  across  the 
subpubic  arch  in  front  of  the  urethra  to  blend  with  the  muscular  fibres  of  the 
opposite  side;  while  those  of  the  hinder  and  larger  part  pass  inward  to  blend  with 
the  wall  of  the  vagina  behind  the  urethra. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 


MUSCLES  AND  FASCIAE  OF  THE  UPPER  EXTREMITY. 

The  'muscles  of  the  Upper  Extremity  are  divisible  into  groups,  corresponding 
with  the  different  regions  of  the  limb. 


I.  OF  THE  THORACIC  REGION. 

1.  Anterior  Thoracic  Region. 

Pectoralis  major.     Pectoralis  minor. 
Subclavius. 

2.  Lateral  Thoracic  Region. 

Serratus  magnus. 

II.  OF  THE  SHOULDER  AND  ARM. 

3.  Acromial  Region. 

Deltoid. 

4.  Anterior  Scapular  Region. 

Subscapularis. 

5.  Posterior  Scapular  Region. 

Supraspinatus.  Teres  minor. 

Infraspinatus.  Teres  major. 


6.  Anterior  Humeral  Region. 

Coraco-brachialis.  Biceps. 

Brachialis  anticus. 

7.  Posterior  Humeral  Region. 
Triceps.  Subanconeus. 

III.  OF  THE  FOREARM. 

8.  Anterior  Radio-ulnar  Region. 

Pronator  radii  teres. 
Flexor  carpi  radialis. 
Palmaris  longus. 
Flexor  carpi  ulnaris. 
[Flexor  sublimis  digitorum. 
gi  £   f  Flexor  profundus  digitorum. 
Q  £3*  |  Flexor  longus  pollicis. 
"   [  Pronator  quadratus. 

9.  Radial   Region. 

Supinator   longus. 

Extensor  carpi  radialis  longior. 

Extensor  carpi  radialis  brevior. 


|J 


§%3 

c/3 


ANTERIOR    THORACIC  REGION  465 

10.  Posterior   Radio-Ulnar   Region.  Flexor  brevis  pollicis. 

Extensor  communis  digitorum.  Adductor  obliquus  pollicis. 

Extensor  minimi  digiti.  Adductor  transversus  pollicis. 
Extensor  carpi  ulnaris. 
Anconeus.  12.  Ulnar  Region. 

Supinator  brevis.  Palmaris  brevis. 

Extensor  ossis  metacarpi  polhci.    Abductor  minimi  digiti. 

Extensor  brevis  polhcis.  Flexor  breyis  minimi  digiti 

Extensor  longus  pollicis.  Flexor  ossig  metacarpi   minimi  digiti 

Extensor  mdi  (Opponens  minimi  digiti). 

IV.  OF  THE  HAND. 

11.  Radial  Region.  13'  Middle  P-almar  Re^n' 

Abductor  pollicis.  Lumbricales. 

Flexor  ossis  metacarpi  pollicis  Interossei  palmares. 

(Opponens  pollicis).  Interossei  dorsales. 

Dissection  of  Pectoral  Region  and  Axilla  (Fig.  311).— The  arm  being  drawn  away  from 
the  side  nearly  at  right  angles  with  the  trunk  and  rotated  outward,  make  a  vertical  incision 
through  the  integument  in  the  median  line  of  the  chest,  from  the  upper  to  the  lower  part  of  the 
sternum;  a  second  incision  along  the  lower  border  of  the  Pectoral  muscle,  from  the  ensiform 
cartilage  to  the  inner  side  of  the  axilla;  a  third,  from  the  sternum  along  the  clavicle,  as  far  as  its 
centre;  and  a  fourth,  from  the  middle  of  the  clavicle  obliquely  downward,  along  the  interspace 
between  the  Pectoral  and  Deltoid  muscles,  as  low  as  the  fold  of  the  armpit.  The  flap  of  integu- 
ment is  then  to  be  dissected  off  in  the  direction  indicated  in  the  figure,  but  not  entirely  removed, 
as  it  should  be  replaced  on  completing  the  dissection.  If  a  transverse  incision  is  now  made 
from  the  lower  end  of  the  sternum  to  the  side  of  the  chest,  as  far  as  the  posterior  fold  of  the 
armpit,  and  the  integument  reflected  outward,  the  axillary  space  will  be  more  completely  exposed. 

I.  THE  MUSCLES  AND  FASCIAE  OF  THE  THORACIC  REGION. 
1.  The  Anterior  Thoracic  Region. 

Pectoralis  major.  Pectoralis  minor. 

Subclavius. 

Superficial  Fascia. — The  superficial  fascia  of.  the  thoracic  region  is  a  loose 
cellulo-fibrous  layer  enclosing  masses  of  fat  in  its  spaces.  It  is  continuous  with 
the  superficial  fascia  of  the  neck  and  upper  extremity  above,  and  of  the  abdomen 
below.  Opposite  the  mamma  it  divides  into  two  layers,  one  of  which  passes  in 
front,  the  other  behind,  that  gland ;  and  from  both  of  these  layers  numerous  septa 
pass  into  its  substance,  supporting  its  various  lobes :  from  the  anterior  layer  fibrous 
processes  pass  forward  to  the  integument  and  nipple.  These  processes  were  called 
by  Sir  A.  Cooper  the  suspensory  ligaments  (ligamenta  suspensoria) ,  from  the  sup- 
port they  afford  to  the  gland  in  this  situation. 

Deep  Fascia. — The  deep  thoracic  fascia  is  a  thin  aponeurotic  lamina,  cover- 
ing the  surface  of  the  great  Pectoral  muscle,  and  sending  numerous  prolongations 
between  its  fasciculi:  it  is  attached,  in  the  middle  line,  to  the  front  of  the  sternum, 
and  above  to  the  clavicle;  externally  and  below  it  becomes  continuous  with  the 
fascia  over  the  shoulder,  axilla,  and  thorax.  It  is  very  thin  over  the  upper  part 
of  the  muscle,  thicker  in  the  interval  between  the  Pectoralis  major  and  Latissimus 
dorsi,  where  it  closes  in  the  axillary  space,  and  is  known  as  the  axillary  fascia  (fascia 
axillaris).  It  passes  behind  into  the  fascia  of  the  Latissimus  dorsi  and  Teres 
major,  in  front  into  the  fascia  of  the  deltoid  and  outward  into  the  brachial 
fascia.  The  fascia  of  the  Latissimus  dorsi  divides  at  the  outer  margin  of  the 
muscle  into  two  layers,  one  of  which  passes  in  front  and  the  other  behind  it;  these 
proceed  as  far  as  the  spinous  processes  of  the  thoracic  vertebrae,  to  which  they  are 

30 


466 


THE   MUSCLES   AND    FASCIAE 


attached.  As  the  axillary  fascia  leaves  the  lower  edge  of  the  Pectoralis  major  to 
pass  across  the  floor  of  the  axilla  it  sends  a  layer  upward  under  cover  of  the 
muscle,  deep  pectoral  fascia:  this  lamina  splits  to  envelop  the  Pectoralis  minor,  at 
the  upper  edge  of  which  it  becomes  continuous  with  the  costo-coracoid  membrane, 
or  the  clavi-pectoral  fascia.  The  hollow  of  the  armpit,  seen  when  the  arm  is 
abducted,  is  mainly  produced  by  the  traction  of  this  fascia  on  the  axillary  floor, 
the  axillary  fascia  (fascia  axillaris),  and  hence  it  is  sometimes  named  the 
suspensory  ligament  of  the  axilla.  The  axillary  fascia  (Fig.  312)  is  not  a  dis- 
tinct and  complete  rigid  floor  of  the  axillary  space.  Like  all  other  fascia?,  it 
follows  muscular  planes,  and  splits  to  encompass  vessels,  nerves,  and  muscles. 
In  it  are  numerous  perforations.  In  this  fascia  is  a  curved  arch  which  often 
contains  muscular  fibres  and  which  passes  from  the  tendon  of  the  great  Pectoral, 


3.  Dissection  of 
Shoulder  and  Arm. 


1.  Dissection  of 
Pectoral  Region 
and  Axilla. 


2.  Bend  of  Elbow. 


4:  Forearm. 


Palm  of  Hand. 


FIG.  311. — Dissection  of  the  upper  extremity. 

the  Coraco-brachialis  or  the  fascia  over  the  biceps  to  the  tendon  of  the  Latissimus 
dorsi.  This  is  called  the  axillary  arch  (arcus  axillaris}.  Langer  showed  many  years 
ago  that  there  is  an  opening  in  the  centre  of  the  dense  axillary  fascia,  the  foramen 
of  Langer.  Through  this  opening  axillary  glands  not  unusually  protrude.  The 
axillary  arch  is  the  inner  margin  of  the  foramen  of  Langer.  At  the  lower  part  of 
the  thoracic  region  the  deep  thoracic  fascia  is  well  developed,  and  is  continuous 
with  the  fibrous  sheath  of  the  Recti  muscles. 

The  Pectoralis  Major  (Fig.  313)  is  a  broad,  thick,  triangular  muscle,  situated 
at  the  upper  and  forepart  of  the  chest,  in  front  of  the  axilla.  It  arises  from  the 
anterior  surface  of  the  sternal  half  of  the  clavicle;  from  half  the  breadth  of  the 
anterior  surface  of  the  sternum,  as  low  down  as  the  attachment  of  the  cartilage 
of  the  sixth  or  seventh  rib;  this  portion  of  its  origin  consists  of  aponeurotic  fibres, 
which  intersect  with  those  of  the  opposite  muscle;  it  also  arises  from  the  carti- 


THE   ANTERIOR    THORACIC  REGION 


467 


lages  of  all  true  ribs,  with  the  exception,  frequently,  of  the  first  or  of  the  seventh, 
or  both;  and  from  the  aponeurosis  of  the  External  oblique  muscle  of  the  abdo- 
men. The  fibres  from  this  extensive  origin  converge  toward  its  insertion,  giving 
to  the  muscle  a  radiated  appearance.  Those  fibres  which  arise  from  the  clavicle 
pass  obliquely  outward  and  downward  and  are  usually  separated  from  the  rest 
by  a  cellular  interval:  those  from  the  lower  part  of  the  sternum,  and  the  cartilages 
of  the  lower  true  ribs,  pass  upward  and  outward,  whilst  the  middle  fibres  pass 
horizontally.  They  all  terminate  in  a  flat  tendon,  about  two  inches  broad,  which 
is  inserted  into  the  outer  bicipital  ridge  of  the  humerus.  This  tendon  consists  of 
two  laminge,  placed  one  in  front  of  the  other,  and  usually  blended  together  below. 
The  anterior,  the  thicker,  receives  the  clavicular  and  upper  half  of  the  sternal 
portion  of  the  muscle;  and  its  fibres  are  inserted  in  the  same  order  as  that  in 
which  they  arise;  that  is  to  say,  the  outermost  fibres  of  origin  from  the  clavicle  are 


SUBSCAPULAR 
ARTERY  AND  VEIN 


FIG.  312. — The  fascia  of  the  right  axilla,  viewed  from  below.      (Spalteholz.) 

inserted  at  the  uppermost  part  of  the  tendon;  the  upper  fibres  of  origin  from  the 
sternum  pass  down  to  the  lowermost  part  of  this  anterior  lamina  of  the  tendon 
and  extend  as  low  as  the  tendon  of  the  Deltoid  and  join  with  it.  The  posterior 
lamina  of  the  tendon  receives  the  attachment  of  the  lower  half  of  the  sternal  por- 
tion and  the  deeper  part  of  the  muscle  from  the  costal  cartilages.  These  deep 
fibres,  and  particularly  those  from  the  lower  costal  cartilages,  ascend,  the  higher, 
turning  backward  successively  behind  the  superficial  and  upper  ones,  so  that  the 
tendon  appears  to  be  twisted.  The  posterior  lamina  reaches  higher  on  the  humerus 
than  does  the  anterior  one,  and  from  it  an  expansion  is  given  off  which  covers 
the  bicipital  groove  and  blends  with  the  capsule  of  the  shoulder-joint.  From  the 
deepest  fibres  of  this  lamina  at  its  insertion  an  expansion  is  given  off  which  lines 
the  bicipital  groove  of  the  humerus,  while  from  the  lower  border  of  the  tendon  a 
third  expansion  passes  downward  to  the  fascia  of  the  arm.  Between  the  poste- 


468 


THE   MUSCLES   AND    FASCIA 


rior  surface  of  the  tendon  of  the  great   pectoral  and  the  anterior  surface  of  the 
long  head  of  the  biceps  there  is  usually  a  bursa  (bursa  m.  pectoralis  majoris), 

Relations. — By  its  anterior  surface,  with  the  integument,  the  superficial  fascia, 
the  Platysma,  some  of  the  branches  of  the  descending  cervical  nerves,  the  mam- 
mary gland,  and  the  deep  fascia;  by  its  posterior  surface:  its  thoracic  portion,  with 
the  sternum,  the  ribs  and  costal  cartilages,  the  costo-coracoid  membrane,  the  Sub- 
clavius,  Pectoralis  minor,  Serratus  magnus,  and  the  Intercostals ;  its  axillary  por- 


FIG.  313. — Muscles  of  the  chest  and  front  of  the  arm.     Superficial  view. 

tion  forms  the  anterior  wall  of  the  axillary  space,  and  covers  the  axillary  vessels  and 
nerves,  the  Biceps  and  Coraco-brachialis  muscles.  Its  upper  border  lies  parallel 
with  the  Deltoid,  from  which  it  is  separated  by  a  slight  interspace  in  which  lie  the 
cephalic  vein  and  humeral  branch  of  the  acromial  thoracic  artery.  Its  lower  border 
forms  the  anterior  margin  of  the  axilla,  being  at  first  separated  from  the  Latissimus 
dorsi  by  a  considerable  interval;  but  both  muscles  gradually  converge  toward  the 
outer  part  of  the  space. 


TI1K   ANTERIOR    THORACIC   REGION 


469 


Dissection. — Detach  the  Pectoralis  major  by  dividing  the  muscle  along  its  attachment  to 
the  clavicle,  and  by  making  a  vertical  incision  through  its  substance  a  little  external  to  its  line  of 
attachment  to  the  sternum  and  costal  cartilages.  The  muscle  should  then  be  reflected  outward, 
and  its  tendon  carefully  examined.  The  Pectoralis  minor  is  now  exposed,  and  immediately 
above  it,  in  the  interval  between  its  upper  border  and  the  clavicle,  a  strong  fascia,  the  costo- 
coracoid  membrane. 

The  Costo-coracoid  Membrane  or  the  Clavipectoral  Fascia  is  a  strong  fascia, 
situated  under  cover  of  the  clavicular  portion  of  the  Pectoralis  major  muscle.  It 
occupies  the  interval  between  the  Pectoralis  minor  and  Subclavius  muscle,  and  pro- 
tects the  axillary  vessels  and  nerves.  Traced  upward,  it  splits  to  enclose  the  Sub- 
clavius muscle,  and  its  two  layers  are  attached  to  the  clavicle,  one  in  front  of  and 
the  other  behind  the  muscle;  the  latter  layer  fuses  with  the  deep  cervical  fascia  and 


FIG.  314. — Muscles  of  the  chest  and  front  of  the  arm,  showing  some  of  the  boundaries  of  the  axilla. 

with  the  sheath  of  the  axillary  vessels.  Internally,  it  blends  with  the  fascia  covering 
the  first  two  intercostal  spaces,  and  is  attached  also  to  the  first  rib  internal  to  the 
origin  of  the  Subclavius  muscle.  Externally  it  is  very  thick  and  dense,  and  is 
attached  to  the  coracoid  process.  The  portion  extending  from  its  attachment  to 
the  first  rib  to  the  coracoid  process  is  often  whiter  and  denser  than  the  rest;  this 
is  sometimes  called  the  costo-coracoid  ligament.  Below,  it  is  thin,  and  at  the  upper 
border  of  the  Pectoralis  minor  it  splits  into  two  layers  to  invest  the  muscle;  from 
the  lower  border  of  the  Pectoralis  minor  it  is  continued  downward  to  join  the  axil- 
lary fascia,  and  outward  to  join  the  fascia  over  the  short  head  of  the  Biceps.  The 
costo-coracoid  membrane  is  pierced  by  the  cephalic  vein,  the  acromial  thoracic 
artery  and  vein,  superior  thoracic  artery,  and  anterior  thoracic  nerves. 


470  THE  MUSCLES  AND    FASCIAE 

The  Pectoralis  Minor  (Fig.  314)  is  a  thin,  flat,  triangular  muscle,  situated  at 
the  upper  part  of  the  thorax,  beneath  the  Pectoralis  major.  It  arises  by  three 
tendinous  digitations  from  the  upper  margin  and  outer  surface  of  the  third,  fourth, 
and  fifth  ribs,  near  their  cartilages,  and  from  the  aponeurosis  covering  the  Inter- 
costal muscles;  the  fibres  pass  upward  and  outward,  and  converge  to  form  a  flat 
tendon,  which  is  inserted  into  the  inner  border  and  upper  surface  of  the  coracoid 
process  of  the  scapula. 

Relations. — By  its  anterior  surface,  with  the  Pectoralis  major  and  the  thoracic 
branches  of  the  acromial  thoracic  artery.  By  its  posterior  surface,  with  the 
ribs,  Intercostal  muscles,  Serratus  magnus,  the  axillary  space,  and  the  axillary 
vessels  and  brachial  plexus  of  nerves.  Its  upper  border  is  separated  from  the 
clavicle  by  a  triangular  interval,  broad  internally,  narrow  externally,  which  is 
occupied  by  the  costo-coracoid  membrane.  This  space  contains  the  first  part  of 
the  axillary  vessels  and  the  axillary  nerves.  Running  parallel  to  the  lower  border 
of  the  muscle  is  the  long  thoracic  artery. 

The  costo-coracoid  membrane  should  now  be  removed,  when  the  Subclavius  muscle  will 
be  seen. 

The  Subclavius  is  a  small  triangular  muscle,  placed  in  the  interval  between  the 
clavicle  and  the  first  rib.  It  arises  by  a  short,  thick  tendon  from  the  first  rib  and 
its  cartilage  at  their  junction,  in  front  of  the  rhomboid  ligament;  the  fleshy  fibres 
proceed  obliquely  upward  and  outward,  to  be  inserted  into  a  deep  groove  on  the 
under  surface  of  the  clavicle.  An  extension  from  the  aponeurosis  of  this  muscle 
lies  upon  the  subclavian  vein. 

Relations. — By  its  upper  surface,  with  the  clavicle.  By  its  deep  surface  it  is 
separated  from  the  first  rib  by  the  subclavian  vessels  and  brachial  plexus  of  nerves. 
Its  anterior  surface  is  separated  from  the  Pectoralis  major  by  the  costo-coracoid 
membrane,  which,  with  the  clavicle,  forms  an  osseo-fibrous  sheath  in  which  the 
muscle  is  enclosed. 

If  the  costal  attachment  of  the  Pectoralis  minor  is  divided  across,  and  the  muscle  reflected 
outward,  the  axillary  vessels  and  nerves  are  brought  fully  into  view,  and  should  be  examined. 

Nerves. — The  Pectoral  muscles  are  supplied  by  the  anterior  thoracic  nerves; 
the  Pectoralis  major  through  these  nerves  receives  filaments  from  all  the  spinal 
nerves  entering  into  the  formation  of  the  brachial  plexus;  the  Pectoralis  minor 
receives  its  fibres  from  the  eighth  cervical  and  first  thoracic  nerves.  The  Sub- 
clavius is  supplied  by  a  filament  from  the  fifth  cervical  nerve. 

Actions. — If  the  arm  has  been  raised  by  the  Deltoid,  the  Pectoralis  major  will, 
conjointly  with  the  Latissimus  dorsi  and  Teres  major,  depress  it  to  the  side  of  the 
chest.  If  acting  alone,  it  adducts  and  draws  forward  the  arm,  bringing  it  across 
the  front  of  the  chest,  and  at  the  same  time  rotates  it  inward.  The  Pectoralis  minor 
depresses  the  point  of  the  shoulder,  drawing  the  scapula  downward  and  inward 
to  the  thorax,  and  throwing  the  inferior  angle  backward.  The  Subclavius  de- 
presses the  shoulder,  drawing  the  clavicle  downward  and  forward.  When  the 
arms  are  fixed,  all  three  muscles  act  upon  the  ribs,  drawing  them  upward  and 
expanding  the  chest,  and  thus  becoming  very  important  agents  in  forced  inspira- 
tion. Asthmatic  patients  always  assume  an  attitude  which  fixes  the  shoulders,  so 
that  all  these  muscles  may  be  brought  into  action  to  assist  in  dilating  the  cavity 
of  the  chest. 


THE  LATERAL  THORACIC -REGION  471 

2.  The  Lateral  Thoracic  Region. 

Serratus  magnus. 

The  Serratus  Magnus  (m.  serratus  anterior}  (Fig.  314)  is  a  thin,  irregularly 
quadrilateral  muscle,  situated  between  the  ribs  and  the  scapula  at  the  upper 
and  lateral  part  of  the  chest.  It  arises  by  nine  digitations  or  slips  from  the  outer 
surface  and  upper  border  of  the  eight  upper  ribs  (the  second  rib  giving  origin  to 
two  slips),  and  from  the  aponeurosis  covering  the  corresponding  intercostal 
muscles.  From  this  extensive  attachment  the  fibres  pass  backward,  closely  applied 
to  the  chest-wall,  and  reach  the  vertebral  border  of  the  scapula,  and  are  inserted 
into  its  ventral  aspect  in  the  following  manner.  The  upper  two'  digitations — i.  e., 
the  one  from  the  first  rib  and  the  higher  of  the  two  from  the  second  rib — converge 
to  be  inserted  into  a  triangular  area  on  the  ventral  aspect  of  the  superior  angle. 
The  next  two  digitations  spread  out  to  form  a  thin  triangular  sheet,  the  base  of 
which  is  directed  backward  and  is  inserted  into  nearly  the  whole  length  of  the 
ventral  aspect  of  the  vertebral  border.  The  lower  five  digitations  converge,  as  they 
pass  backward  from  the  ribs,  to  form  a  fan-shaped  structure,  the  apex  of  which 
is  inserted,  partly  by  muscular  and  partly  by  tendinous  fibres,  into  a  triangular 
impression  on  the  ventral  aspect  of  the  inferior  angle.  The  lower  four  slips  inter- 
digitate  at  their  origin  with  the  upper  five  slips  of  the  External  oblique  muscle 
of  the  abdomen. 

Relations. — This  muscle  is  partly  covered,  in  front,  by  the  Pectoral  muscles; 
behind,  by  the  Subscapularis.  The  axillary  vessels  and  nerves  lie  upon  its  upper 
part,  while  its  deep  surface  rests  upon  the  ribs  and  intercostal  muscles. 

Nerve. — The  Serratus  magnus  is  supplied  by  the  posterior  thoracic  nerve, 
which  is  derived  from  the  fifth,  sixth,  and  generally  the  seventh  cervical  nerves. 

Actions. — The  Serratus  magnus,  as  a  whole,  carries  the  scapula  forward,  and  at 
the  same  time  raises  the  vertebral  border  of  the  bone.  It  is  therefore  concerned 
in  the  action  of  pushing.  Its  lower  and  stronger  fibres  move  forward  the  lower 
angle  and  assist  the  Trapezius  in  rotating  the  bone  round  an  axis  through  its 
centre,  and  thus  assists  this  muscle  in  raising  the  acromion  and  supporting  weights 
upon  the  shoulder.  It  is  also  an  assistant  to  the  Deltoid  in  raising  the  arm,  inas- 
much as  during  the  action  of  this  latter  muscle  it  fixes  the  scapula  and  so  steadies 
the  glenoid  cavity  on  which  the  head  of  the  humerus  rotates.  After  the  Deltoid 
has  raised  the  arm  to  a  right  angle  with  the  trunk,  the  Serratus  magnus  and  the 
Trapezius,  by  rotating  the  scapula,  raise  the  arm  into  an  almost  vertical  position. 
It  is  possible  that  when  the  shoulders  are  fixed  the  lower  fibres  of  the  Serratus 
magnus  may  assist  in  raising  and  everting  the  ribs;  but  it  is  not  the  important 
inspiratory  muscle  which  it  was  formerly  believed  to  be. 

Surgical  Anatomy. — When  the  muscle  is  paralyzed,  the  vertebral  border,  and  especially  the 
lower  angle  of  the  scapula,  leaves  the  ribs  and  stands  out  prominently  on  the  surface,  giving 
a  peculiar  "winged"  appearance  to  the  back.  The  patient  is  unable  to  raise  the  arm,  and  an 
attempt  to  do  so  is  followed  by  a  further  projection  of  the  lower  angle  of  the  scapula  from  the 
back  of  the  thorax. 

Dissection. — After  completing  the  dissection  of  the  axilla,  if  the  muscles  of  the  back  have 
been  dissected,  the  upper  extremity  should  be  separated  from  the  trunk.  Saw  through  the 
clavicle  at  its  centre,  and  then  cut  through  the  muscles  which  connect  the  scapula  and  arm  with 
the  trunk — viz.,  the  Pectoralis  minor  in  front,  Serratus  magnus  at  the  side,  and  the  Levator 
anguli  scapulae,  the  Rhomboids,  Trapezius,  and  Latissimus  dorsi  behind.  These  muscles  should 
be  cleaned  and  traced  to  their  respective  insertions.  Then  make  an  incision  through  the  integu- 
ment, commencing  at  the  outer  third  of  the  clavicle,  and  extending  along  the  margin  of  that 
bone,  the  acromion  process,  and  spine  of  the  scapula;  the  integument  should  be  dissected  from 
above  downward  and  outward,  when  the  fascia  covering  the  Deltoid  is  exposed  (Fig.  311,  No.  3). 


472  THE  MUSCLES  AND  FASCIAE 


II.  MUSCLES  AND  FASCIA  OF  THE  SHOULDER  AND  ARM. 

Superficial  Fascia. — The  superficial  fascia  of  the  upper  extremity  is  a  thin 
cellulo-fibrous  layer,  containing  the  superficial  veins  and  lymphatics,  and  the 
cutaneous  nerves.  It  is  most  distinct  in  front  of  the  elbow,  and  contains  very  large 
superficial  veins  and  nerves ;  in  the  hand  it  is  hardly  demonstrable,  the  integument 
being  closely  adherent  to  the  deep  fascia  by  dense  fibrous  bands.  Small  sub- 
cutaneous bursse  are  found  in  this  fascia  over  the  acromion,  the  olecranon,  and 
the  knuckles. 

Deep  Fascia. — The  deep  fascia  of  the  upper  extremity  comprises  the  aponeurosis 
of  the  shoulder,  arm,  and  forearm,  the  anterior  and  posterior  annular  ligaments  of 
the  carpus,  and  the  palmar  fascia.  These  will  be  considered  in  the  description 
of  the  muscles  of  the  several  regions. 

3.  The  Acromial  Region. 
Deltoid. 

Deep  Fascia. — The  deep  fascia  covering  the  Deltoid,  and  known  as  the  deltoid 
aponeurosis,  is  a  fibrous  layer  which  covers  the  outer  surface  of  the  muscle,  thick 
and  strong  behind,  where  it  is  continuous  with  the  infraspinatus  fascia,  thinner 
over  the  rest  of  its  extent.  It  sends  down  numerous  prolongations  between  the 
fasciculi  of  the  muscle.  In  front,  it  is  continuous  with  the  fascia  covering  the 
great  Pectoral  muscle;  behind,  with  that  covering  the  Infraspinatus;  above,  it 
is  attached  to  the  clavicle,  the  acromion,  and  spine  of  the  scapula;  below,  it  is 
continuous  with  the  deep  fascia  of  the  arm. 

The  Deltoid  (m.  deltoideus)  (Fig.  313)  is  a  large,  thick,  triangular  muscle,  which 
gives  the  rounded  outline  to  the  shoulder,  and  has  received  its  name  from  its  resem- 
blance to  the  Greek  letter  A  reversed.  It  surrounds  the  shoulder-joint  in  the  greater 
part  of  its  extent,  covering  it  on  its  outer  side,  and  in  front  and  behind.  It  arises 
from  the  outer  third  of  the  anterior  border  and  upper  surface  of  the  clavicle;  from 
the  outer  margin  and  upper  surface  of  the  acromion  process,  and  from  the  lower  lip 
of  the  posterior  border  of  the  spine  of  the  scapula,  as  far  back  as  the  triangular  sur- 
face at  its  inner  end.  From  this  extensive  origin  the  fibres  converge  toward  their 
insertion,  the  middle  passing  vertically,  the  anterior  obliquely  backward,  the  pos- 
terior obliquely  forward;  they  unite  to  form  a  thick  tendon,  which  is  inserted  into 
a  rough  triangular  prominence  on  the  middle  of  the  outer  side  of  the  shaft  of  the 
humerus.  At  its  insertion  the  muscle  gives  off  an  expansion  to  the  deep  fascia  of 
the  arm.  This  muscle  is  remarkably  coarse  in  texture,  and  the  arrangement  of 
its  muscular  fibres  is  somewhat  peculiar;  the  central  portion  of  the  muscle — that 
is  to  say,  the  part  arising  from  the  acromion  process— consists  of  oblique  fibres, 
which  arise  in  a  bipenniform  manner  from  the  sides  of  tendinous  intersections, 
generally  four  in  number,  which  are  attached  above  to  the  acromion  process  and 
pass  downward  parallel  to  one  another  in  the  substance  of  the  muscle.  The 
oblique  muscular  fibres  thus  formed  are  inserted  into  similar  tendinous  intersec- 
tions, generally  three  in  number,  which  pass  upward  from  the  insertion  of  the 
muscle  into  the  humerus  and  alternate  with  the  descending  septa.  The  portions 
of  the  muscle  which  arise  from  the  clavicle  and  spine  of  the  scapula  are  not 
arranged  in  this  manner,  but  pass  from  their  origin  above,  to  be  inserted  into  the 
margins  of  the  inferior  tendon. 

Relations.— By  its  superficial  surface,  with  the  integument,  the  superficial  and 
deep  fasciae,  Platysma,  and  supra-acromial  nerves.  Its  deep  surface  is  separated 


THE  ANTERIOR  SCAPULAR  REGION  473 

• 

from  the  head  of  the  humerus  by  a  large  sacculated  synovial  bursa,  the  subdeltoid 
bursa  (bursa  subdeltoid  ea).  It  often  communicates  with  the  subacromial  bursa 
(bursa  subacromialis),  which  is  between  the  acromial  process  and  the  coraco- 
acromial  ligament  above  and  the  capsule  of  the  shoulder-joint  and  the  Supra- 
spinatus  muscle  below.  The  deep  surface  of  the  deltoid  covers  the  coracoid 
process,  coraco-acromial  ligament,  Pectoralis  minor,  Coraco-brachialis,  both  heads 
of  the  Biceps,  the  tendon  of  the  Pectoralis  major,  the  insertions  of  the  Supra- 
spinatus,  Infraspinatus,  and  Teres  minor,  the  scapular  and  external  heads  of  the 
Triceps,  the  circumflex  vessels  and  nerve,  and  the  humerus.  Its  anterior  border 
is  separated  at  its  upper  part  from  the  Pectoralis  major  by  a  cellular  interspace, 
which  lodges  the  cephalic  vein  and  humeral  branch  of  the  acromial  thoracic  artery : 
lower  down  the  two  muscles  are  in  close  contact.  Its  posterior  border  rests  on  the 
Infraspinatus  and  Triceps  muscles. 

Nerves. — The  Deltoid  is  supplied  by  the  fifth  and  sixth  cervical  through  the 
circumflex  nerve. 

Actions. — The  Deltoid  raises  the  arm  directly  from  the  side,  so  as  to  bring  it 
at  right  angles  with  the  trunk,  but  this  act  cannot  be  performed  without  the  aid 
of  the  Serratus  magnus,  which  muscle  steadies  the  lower  angle  of  the  scapula. 
Its  anterior  fibres,  assisted  by  the  Pectoralis  major,  draw  the  arm  forward;  and  its 
posterior  fibres,  aided  by  the  Teres  major  and  Latissimus  dorsi,  draw  it  backward. 

Surgical  Anatomy. — The  Deltoid  is  very  liable  to  atrophy,  and  when  in  this  condition 
simulates  dislocation  of  the  shoulder-joint,  as  there  is  flattening  of  the  shoulder  and  apparent 
prominence  of  the  acromion  process;  upon  examination,  however,  it  will  be  found  that  the 
relative  position  of  the  great  tuberosity  of  the  humerus  to  the  acromion  and  coracoid  process  is 
unchanged.  Atrophy  of  the  Deltoid  may  be  due  to  disuse  or  loss  of  trophic  influence,  either 
from  injury  to  the  circumflex  nerve  or  cord  lesions,  as  in  infantile  paralysis. 

4.  The  Anterior  Scapular  Region. 

Subscapularis. 

Dissection. —  Divide  the  Deltoid  across,  near  its  upper  part,  by  an  incision  carried  along  the 
margin  of  the  clavicle,  the  acromion  process  and  spine  of  the  scapula,  and  reflect  it  downward, 
when  the  structures  under  cover  of  it  will  be  seen. 

The  Subscapular  Fascia  (fascia  subscapularis} . — The  subscapular  fascia  is  a 
thin  membrane  attached  to  the  entire  circumference  of  the  subscapular  fossa,  and 
affording  attachment  by  its  inner  surface  to  some  of  the  fibres  of  the  Subscapu- 
laris muscle:  when  this  is  removed,  the  Subscapularis  muscle  is  exposed. 

The  Subscapularis  (Fig.  314)  is  a  large  triangular  muscle  which  fills  up  the 
subscapular  fossa,  arising  from  its  internal  two-thirds,  with  the  exception  of  a 
narrow  margin  along  the  posterior  border,  and  the  surfaces  at  the  superior  and 
inferior  angles  which  afford  attachment  to  the  Serratus  magnus :  it  also  arises  from 
the  lower  two-thirds  of  the  groove  on  the  axillary  border  of  the  bone.  Some  fibres 
arise  from  tendinous  laminae,  which  intersect  the  muscle,  and  are  attached  to  ridges 
on  the  bone;  and  others  from  an  aponeurosis,  which  separates  the  muscles  from  the 
Teres  major  and  the  long  head  of  the  Triceps.  The  fibres  pass  outward,  and, 
gradually  converging,  terminate  in  a  tendon,  which  is  inserted  into  the  lesser 
tuberosity  of  the  humerus.  Those  fibres  which  arise  from  the  axillary  border  of 
the  scapula  are  inserted  into  the  neck  of  the  humerus  to  the  extent  of  an  inch  below 
the  tuberosity.  The  tendon  of  the  muscle  is  in  close  contact  with  the  anterior  part 
of  the  capsular  ligament  of  the  shoulder-joint,  and  glides  over  a  large  bursa,  the 
bursa  of  the  subscapularis  muscle  (bursa  m.  subscapular  is),  which  separates  it  from 
the  base  of  the  coracoid  process.  This  bursa  communicates  with  the  cavity  of  the 
joint  by  an  aperture  in  the  capsular  ligament. 


474  THE  MUSCLES  AND  FASCIJS 

Relations. — Its  anterior  surface  forms  a  considerable  part  of  the  posterior  wall 
of  the  axilla,  and  is  in  relation  with  the  Serratus  magnus,  Coraco-brachialis,  and 
Biceps,  the  axillary  vessels  and  brachial  plexus  of  nerves,  and  the  subscapular 
vessels  and  nerves.  By  its  posterior  surface,  with  the  scapula  and  the  capsular 
ligament  of  the  shoulder-joint.  Its  lower  border  is  contiguous  with  the  Teres  major 
and  Latissimus  dorsi. 

Nerves. — It  is  supplied  by  the  fifth  and  sixth  cervical  nerves  through  the  upper 
and  lower  subscapular  nerves. 

Actions. — The  Subscapularis  rotates  the  head  of  the  humerus  inward;  when 
the  arm  is  raised,  it  draws  the  humerus  forward  and  downward.  It  is  a  powerful 
defence  to  the  front  of  the  shoulder-joint,  preventing  displacement  of  the  head  of 
the  bone. 

5.  The  Posterior  Scapular  Region  (Fig.  315). 

Supraspinatus.  Teres  minor. 

Infraspinatus.  Teres  major. 

Dissection. — To  expose  these  muscles,  and  to  examine  their  mode  of  insertion  into  the 
humerus,  detach  the  deltoid  and  Trapezius  from  their  attachment  to  the  spine  of  the  scapula 
and  acromion  process.  Remove  the  clavicle  by  dividing  the  ligaments  connecting  it  with  the 
coracoid  process,  and  separate  it  at  its  articulation  with  the  scapula:  divide  the  acromion  process 
near  its  root  with  a  saw.  The  fragments  being  removed,  the  tendons  of  the  posterior  Scapular 
muscles  will  be  fully  exposed,  and  can  be  examined.  A  block  should  be  placed  beneath  the 
shoulder-joint,  so  as  to  make  the  muscles  tense. 

The  Supraspinatus  Fascia  (fascia  supraspinata) . — The  supraspinatus  fascia  is 
a  thick  and  dense  membranous  layer,  which  completes  the  osseo-fibrous  case 
in  which  the  Supraspinatus  muscle  is  contained,  affording  attachment,  by  its 
inner  surface,  to  some  of  the  fibres  of  the  muscle.  It  is  thick  internally,  but 
thinner  externally  under  the  coraco-acromial  ligament.  When  this  fascia  is 
removed,  the  Supraspinatus  muscle  is  exposed. 

The  Supraspinatus  Muscle  occupies  the  whole  of  the  supraspinatus  fossa, 
arising  from  its  internal  two-thirds  and  from  the  strong  fascia  which  covers  its  sur- 
face. The  muscular  fibres  converge  to  a  tendon  which  passes  across  the  upper 
part  of  the  capsular  ligament  of  the  shoulder-joint,  to  which  it  is  intimately  adher- 
ent, and  is  inserted  into  the  highest  of  the  three  facets  on  the  great  tuberosity  of 
the  humerus. 

Relations. — By  its  upper  surface,  with  the  Trapezius,  the  clavicle,  the  acromion, 
the  coraco-acromial  ligament,  and  the  Deltoid;  by  its  under  surface,  with  the 
scapula,  the  suprascapular  vessels  and  nerve,  and  upper  part  of  the  shoulder-joint. 

The  Infraspinatus  Fascia  (fascia  infraspinata). — The  infraspinatus  fascia  is 
a  dense  fibrous  membrane,  covering  in  the  Infraspinatus  muscle  and  attached 
to  the  circumference  of  the  infraspinatus  fossa;  it  affords  attachment,  by  its  inner 
surface,  to  some  fibres  of  that  muscle.  At  the  point  where  the  Infraspinatus 
commences  to  be  covered  by  the  Deltoid,  this  fascia  divides  into  two  layers:  one 
layer  passes  over  the  Deltoid  muscle,  helping  to  form  the  Deltoid  fascia  already 
described ;  the  other  passes  beneath  the  Deltoid  to  the  capsule  of  the  shoulder-joint. 

The  Infraspinatus  is  a  thick,  triangular  muscle,  which  occupies  the  chief  part 
of  the  infraspinatus  fossa,  arising  by  fleshy  fibres  from  its  internal  two-thirds,  and 
by  tendinous  fibres  from  the  ridges  on  its  surfaces:  it  also  arises  from  a  strong 
fascia  which  covers  it  externally,  and  separates  it  from  the  Teres  major  and  minor. 
The  fibres  converge  to  a  tendon  which  glides  over  the  external  border  of  the 
spine  of  the  scapula,  and,  passing  across  the  posterior  part  of  the  capsular  ligament 
of  the  shoulder-joint,  is  inserted  into  the  middle  facet  on  the  great  tuberosity  of 
the  humerus.  The  tendon  of  this  muscle  has  interposed  between  it  and  the  joint 


THE  POSTERIOR  SCAPULAR  REGION 


475 


capsule  a  synovial  bursa,  the  bursa  of  the  Infraspinatus  muscle  (bursa  m.  infra- 
xpinati),  which  communicates  with  the  synovial  cavity  of  the  shoulder-joint. 

Relations. — By  its  posterior  surface,  with  the  Deltoid,  the  Trapezius,  Latissimus 
dorsi,  and  the  integument;  by  its  anterior  surface,  with  the  scapula,  from  which 
it  is  separated  by  the  suprascapular  and  dorsalis  scapulae  vessels,  and  with  the 


FIG.  315. — Muscles  on  the  dorsum  of  the  Scapula  and  the  Triceps. 

capsular  ligament  of  the  shoulder-joint.  Its  lower  border  is  in  contact  with  the 
Teres  minor,  occasionally  united  with  it,  and  with  the  Teres  major. 

The  Teres  Minor  is  a  narrow,  elongated  muscle,  which  arises  from  the  dorsal 
surface  of  the  axillary  border  of  the  scapula  for  the  upper  two-thirds  of  its  extent, 
and  from  two  aponeurotic  laminae,  one  of  which  separates  this  muscle  from  the 
Infraspinatus,  the  other  from  the  Teres  major;  its  fibres  pass  obliquely  upward 
and  outward,  and  terminate  in  a  tendon  which  is  inserted  into  the  lowest  of  the 
three  facets  on  the  great  tuberosity  of  the  humerus,  and,  by  fleshy  fibres,  into  the 
humerus  immediately  below  it.  The  tendon  of  this  muscle  passes  across  the 
posterior  part  of  the  capsular  ligament  of  the  shoulder-joint. 

Relations. — By  its  posterior  surface,  with  the  Deltoid  and  the  integument; 
by  its  anterior  surface,  with  the  scapula  and  dorsal  branch  of  the  subscapular 
artery,  the  long  head  of  the  Triceps,  and  the  shoulder-joint;  by  its  upper  border, 
with  the  Infraspinatus;  by  its  lower  border,  with  the  Teres  major,  from  which  it 
is  separated  anteriorly  by  the  long  head  of  the  Triceps. 

The  Teres  Major  is  a  thick  but  somewhat  flattened  muscle,  which  arises  from 
the  oval  surface  on  the  dorsal  aspect  of  the  inferior  angle  of  the  scapula,  and  from 
the  fibrous  septa  interposed  between  it  and  the  Teres  minor  and  Infraspinatus;  the 


476 

fibres  are  directed  upward  and  outward,  and  terminate  in  a  flat  tendon,  about  two 
inches  in  length,  which  is  inserted  into  the  inner  bicipital  ridge  of  the  humerus. 
The  tendon  of  this  muscle,  at  its  insertion  into  the  humerus,  lies  behind  that  of  the 
Latissimus  dorsi,  from  which  it  is  separated  by  a  synovial  bursa,  the  bursa  of  the 
Latissimus  dorsi  muscle  (bursa  m.  latissimi  dorsi),  the  two  tendons  being,  however, 
united  along  their  lower  borders  for  a  short  distance.  Between  the  tendon  of 
the  Teres  major  and  the  bone  is  the  bursa  m.  teretis  majoris. 

Relations. — By  its  posterior  surface,  with  the  Latissimus  dorsi  below,  and  the 
long  head  of  the  Triceps  above.  By  its  anterior  surface,  with  the  Subscapularis, 
Latissimus  dorsi,  Coraco-brachialis,  short  head  of  the  Biceps,  the  axillary  vessels, 
and  brachial  plexus  of  nerves.  Its  upper  border  is  at  first  in  relation  with  the 
Teres  minor,  from  which  it  is  afterward  separated  by  the  long  head  of  the  Triceps. 
Its  lower  border  forms,  in  conjunction  with  the  Latissimus  dorsi,  part  of  the  pos- 
terior boundary  of  the  axilla.  The  Latissimus  dorsi  at  first  covers  the  origin  of 
the  Teres  major,  then  wraps  itself  obliquely  round  its  lower  border,  so  that  its 
tendon  ultimately  comes  to  lie  in  front  of  that  of  the  Teres  major. 

Nerves. — The  Supra-  and  Infraspinatus  muscles  are  supplied  by  the  fifth  and 
sixth  cervical  nerves  through  the  suprascapular  nerve;  the  Teres  minor,  by  the 
fifth  cervical,  through  the  circumflex;  and  the  Teres  major,  by  the  fifth  and  sixth 
cervical,  through  the  lower  subscapular. 

Actions. — -The  Supraspinatus  assists  the  Deltoid  in  raising  the  arm  from  the 
side,  and  fixes  the  head  of  the  humerus  in  the  glenoid  cavity.  The  Infraspinatus 
and  Teres  minor  rotate  the  head  of  the  humerus  outward :  when  the  arm  is  raised, 
they  assist  in  retaining  it  in  that  position  and  carrying  it  backward.  One  of  the 
most  important  uses  of  these  three  muscles  is  the  great  protection  they  afford  to 
the  shoulder-joint,  the  Supraspinatus  supporting  it  above,  and  preventing  displace- 
ment of  the  head  of  the  humerus  upward,  while  the  Infraspinatus  and  Teres  minor 
protect  it  behind,  and  prevent  dislocation  backward.  The  Teres  major  assists  the 
Latissimus  dorsi  in  drawing  the  humerus  downward  and  backward,  when  pre- 
viously raised,  and  rotating  it  inward;  when  the  arm  is  fixed,  it  may  assist  the 
Pectoral  and  Latissimus  dorsi  muscles  in  drawing  the  trunk  forward. 

THE  MUSCLES  AND  FASCIA  OF  THE  ARM. 

6.  The  Anterior  Humeral  Region  (Fig.  314). 
Coraco-brachialis.  Biceps.  Brachialis  anticus. 

Dissection. — The  arm  being  placed  on  the  table,  with  the  front  surface  uppermost,  make 
a  vertical  incision  through  the  integument  along  the  middle  line,  from  the  clavicle  to  about 
two  inches  below  the  elbow-joint,  where  it  should  be  joined  by  a  transverse  incision,  extending 
from  the  inner  to  the  outer  side  of  the  forearm;  the  two  flaps  being  reflected  on  either  side, 
the  fascia  should  be  examined  (Fig.  311). 

Deep  Fascia  (fascia  brachii). — The  deep  fascia  of  the  arm  is  continuous  with 
that  covering  the  Deltoid  and  the  great  Pectoral  muscles,  by  means  of  which  it  is 
attached,  above,  to  the  clavicle,  acromion,  and  spine  of  the  scapula,  and  is  also 
continuous  with  the  axillary  fascia.  It  forms  a  thin,  loose,  membranous  sheath 
investing  the  muscles  of  the  arm,  sending  down  septa  between  them,  and  com- 
posed of  fibres  disposed  in  a  circular  or  spiral  direction,  and  connected  together 
by  vertical  and  oblique  fibres.  It  differs  in  thickness  at  different  parts,  being 
thin  over  the  Biceps,  but  thicker  where  it  covers  the  Triceps,  and  over  the 
condyles  of  the  humerus;  it  is  strengthened  by  fibrous  aponeuroses,  derived 
from  the  Pectoralis  major  and  Latissimus  dorsi  on  the  inner  side,  and  from  the 
Deltoid  externally.  On  either  side  it  gives  off  a  strong  intermuscular  septum, 


THE  ANTERIOR  HUMERAL  REGION  477 

which  is  attached  to  the  supracondylar  ridge  and  condyle  of  the  humerus.  These 
septa  serve  to  separate  the  muscles  of  the  anterior  from  those  of  the  posterior 
brachial  region.  The  external  intermuscular  septum  (septum  intermusculare 
laterale)  extends  from  the  lower  part  of  the  anterior  bicipital  ridge,  along  the 
external  supracondylar  ridge,  to  the  outer  condyle;  it  is  blended  with  the  tendon 
of  the  Deltoid,  gives  attachment  to  the  Triceps  behind,  to  the  Brachialis  anticus, 
Supinator  longus,  and  Extensor  carpi  radialis  longior,  in  front,  and  is  perforated 
by  the  musculo-spiral  nerve  and  superior  profunda  artery.  The  internal  inter- 
muscular  septum  (septum  intermusculare  mediate),  thicker  than  the  preceding, 
extends  from  the  lower  part  of  the  posterior  lip  of  the  bicipital  groove  below  the 
Teres  major,  along  the  internal  supracondylar  ridge  to  the  inner  condyle;  it  is 
blended  with  the  tendon  of  the  Coraco-brachialis,  and  affords  attachment  to  the 
Triceps  behind,  and  the  Brachialis  anticus  in  front.  It  is  perforated  by  the  ulnar 
nerve  and  the  inferior  profunda  and  anastomotic  arteries.  At  the  elbow  the  deep 
fascia  is  attached  to  all  the  prominent  points  round  the  joint — viz.,  the  condyles  of 
the  humerus  and  the  olecranon  process  of  the  ulna — and  is  continuous  with  the 
deep  fascia  of  the  forearm.  Just  below  the  middle  of  the  arm,  on  its  inner  side,  in 
front  of  the  intermuscular  septum,  is  an  oval  opening  in  the  deep  fascia  which 
transmits  the  basilic  vein  and  some  lymphatic  vessels.  On  the  removal  of  this 
fascia  the  muscles,  vessels,  and  nerves  of  the  anterior  humeral  region  are  exposed. 

The  Coraco-brachialis,  the  smallest  of  the  three  muscles  in  this  region,  is 
situated  at  the  upper  and  inner  part  of  the  arm.  It  arises  by  fleshy  fibres  from 
the  apex  of  the  coracoid  process,  in  common  with  the  short  head  of  the  Biceps, 
and  from  the  intermuscular  septum  between  the  two  muscles;  the  fibres  pass 
downward,  backward,  and  a  little  outward,  to  be  inserted  by  means  of  a  flat 
tendon  into  an  impression  at  the  middle  of  the  inner  surface  and  internal  border 
of  the  shaft  of  the  humerus  between  the  origins  of  the  Triceps  and  Brachialis 
anticus.  It  is  perforated  by  the  musculo-cutaneous  nerve.  The  inner  border  of 
the  muscle  forms  a  guide  to  the  position  of  the  brachial  artery  in  tying  the  vessel 
in  the  upper  part  of  its  course.  Between  the  tendon  of  the  subscapularis, 
the  coracoid  process  and  the  tendon  of  the  Coraco-brachialis,  is  the  bursa  of  the 
Coraco-brachialis  muscle  (bursa  m.  coracobrachialis). 

Relations. — By  its  anterior  surface,  with  the  Pectoralis  major  above,  and  at 
its  insertion  with  the  brachial  vessels  and  median  nerve  which  cross  it;  by  its 
posterior  surface,  with  the  tendons  of  the  Subscapularis,  Latissimus  dorsi,  and 
Teres  major,  the  inner  head  of  the  Triceps,  the  humerus,  and  the  anterior  circum- 
flex vessels;  by  its  inner  border,  with  the  brachial  artery,  and  the  median  and 
musculo-cutaneous  nerves;  by  its  outer  border,  with  the  short  head  of  the  Biceps 
and  Brachialis  anticus. 

The  Biceps  or  the  Biceps  Flexor  Cubiti  (m.  biceps  brachii)  is  a  long  fusiform 
muscle,  occupying  the  whole  of  the  anterior  surface  of  the  arm,  and  divided  above 
into  two  portions  or  heads,  from  which  circumstance  it  has  received  its  name.  The 
short  head  (caput  breve)  arises^by  a  thick  flattened  tendon  from  the  apex  of  the  cora- 
coid process,  in  common  with  the  Coraco-brachialis.  The  long  head  (caput  longum) 
arises  from  the  upper  margin  of  the  glenoid  cavity,  and  is  continuous  with  the 
glenoid  ligament.  This  tendon  arches  over  the  head  of  the  humerus,  being  enclosed 
in  a  special  sheath  of  thesynovial  membrane  of  the  shoulder-joint;  it  then  passes 
through  an  opening  in  the  capsular  ligament  at  its  attachment  to  the  humerus, 
and  descends  in  the  bicipital  groove,  in  which  it  is  retained  by  a  fibrous  prolonga- 
tion from  the  tendon  of  the  Pectoralis  major.  Each  tendon  is  succeeded  by  an 
elongated  muscular  belly,  and  the  two  bellies,  although  closely  applied  to  each 
other,  can  readily  be  separated  until  within  about  three  inches  of  the  elbow-joint. 
Here  they  end  in  a  flattened  tendon,  which  is  inserted  into  the  back  part  of  the 
tuberosity  of  the  radius,  a  synovial  bursa  (bursa  bicipitoradialis) ,  being  interposed 


478  THE  MUSCLES  AND  FASCIA 

between  the  tendon  and  the  front  of  the  tuberosity,  and  another  bursa  (bursa 
cubitalis  interossea)  is  often  interposed  between  the  ulna  and  the  tendon.  As  the 
tendon  of  the  muscle  approaches  the  radius  it  becomes  twisted  upon  itself,  so  that 
its  anterior  surface  becomes  external  and  is  applied  to  the  tuberosity  of  the 
radius  at  its  insertion :  opposite  the  bend  of  the  elbow  the  tendon  gives  off,  from 
its  inner  side,  a  broad  aponeurosis,  the  bicipital  or  semilunar  fascia  (lacertus 
fibrosus),  which  passes  obliquely  downward  and  inward  across  the  brachial 
artery,  and  is  continuous  with  the  deep  fascia  of  the  forearm  (Fig.  313).  The 
inner  border  of  this  muscle  forms  a  guide  to  the  position  of  the  vessel  in  tying  the 
brachial  artery  in  the  middle  of  the  arm.1 

Relations. — Its  anterior  surface  is  overlapped  above  by  the  Pectoralis  major 
and  Deltoid;  in  the  rest  of  its  extent  it  is  covered  by  the  superficial  and  deep 
fasciae  and  the  integument.  Its  posterior  surface  rests  above  on  the  shoulder- 
joint  and  upper  part  of  the  humerus;  below  it  rests  on  the  Brachialis  anticus, 
with  the  musculo-cutaneous  nerve  intervening  between  the  two,  and  on  the 
Supinator  brevis.  Its  inner  border  is  in  relation  with  the  Coraco-brachialis,  and 
overlaps  the  brachial  vessels  and  median  nerve;  its  outer  border,  with  the  Deltoid 
and  Supinator  longus. 

The  Brachialis  Anticus  (ra.  brachialis)  is  a  broad  muscle,  which  covers  the  elbow- 
joint  and  the  lower  half  of  the  front  of  the  humerus.  It  is  somewhat  compressed 
from  before  backward,  and  is  broader  in  the  middle  than  at  either  extremity.  It 
urises  from  the  lower  half  of  the  outer  and  inner  surfaces  of  the  shaft  of  the  humerus, 
and  commences  above  at  the  insertion  of  the  Deltoid,  which  it  embraces  by  two 
angular  processes.  Its  origin  extends  below,  to  within  an  inch  of  the  margin  of 
the  articular  surface,  and  is  limited  on  each  side  by  the  external  and  internal 
borders  of  the  shaft  of  the  humerus.  It  also  arises  from  the  intermuscular  septa 
on  each  side,  but  more  extensively  from  the  inner  than  the  outer,  from  which  it  is 
separated  below  by  the  Supinator  longus  and  Extensor  carpi  radialis  longior.  Its 
fibres  converge  to  a  thick  tendon,  which  is  inserted  into  a  rough  depression  on 
the  anterior  surface  of  the  coronoid  process  of  the  ulna,  being  received  into  an 
interval  between  two  fleshy  slips  of  the  Flexor  profundus  digitorum. 

Relations. — By  its  anterior  surface,  with  the  Biceps,  the  brachial  vessels,  mus- 
culo-cutaneous, and  median  nerves;  by  its  posterior  surface,  with  the  humerus 
and  front  of  the  elbow-joint;  by  its  inner  border,  with  the  Triceps,  ulnar  nerve, 
and  Pronator  radii  teres,  from  which  it  is  separated  by  the  intermuscular  septum; 
by  its  outer  border,  with  the  musculo-spiral  nerve,  radial  recurrent  artery,  the 
Supinator  longus,  and  Extensor  carpi  radialis  longior. 

Nerves. — The  muscles  of  this  group  are  supplied  by  the  musculo-cutaneous 
nerve.  The  Brachialis  anticus  usually  receives  an  additional  filament  from  the 
musculo-spiral.  The  Coraco-brachialis  receives  its  supply  primarily  from  the 
seventh  cervical,  the  Biceps  and  Brachialis  anticus  from  the  fifth  and  sixth  cer- 
vical nerves. 

Actions. — The  Coraco-brachialis  draws  the  humerus  forward  and  inward,  and 
at  the  same  time  assists  in  elevating  it  toward  the  scapula.  The  Biceps  is  a  flexor 
of  the  forearm;  it  is  also  a  powerful  supinator,  and  serves  to  render  tense  the 
deep  fascia  of  the  forearm  by  means  of  the  broad  aponeurosis  given  off  from 
its  tendon.  The  Brachialis  anticus  is  a  flexor  of  the  forearm,  and  forms  an  impor- 
tant defence  to  the -elbow-joint.  When  the  forearm  is  fixed,  the  Biceps  and 
Brachialis  anticus  flex  the  arm  upon  the  forearm,  as  is  seen  in  efforts  at  climbing. 


THE  POSTERIOR  HUMERAL  REGION  479 

7.  The  Posterior  Humeral  Region. 
Triceps.  Subanconeus. 

The  Triceps  or  the  Triceps  Extensor  Cubiti  (m.  triceps  brachii)  (Fig.  315)  is 
situated  on  the  back  of  the  arm,  extending  the  entire  length  of  the  posterior  surface 
of  the  huraerus.  It  is  of  large  size,  and  divided  above  into  three  parts ;  hence  its 
name.  These  three  portions  have  been  named  (1)  the  middle,  scapular,  or  long  head ; 
(2)  the  external  or  long  humeral  head;  and  (3)  the  internal  or  short  humeral  head. 

The  Middle,  Long,  or  Scapular  Head  (caput  longum)  arises,  by  a  flattened  tendon, 
from  a  rough  triangular  depression  on  the  scapula,  immediately  below  the  glenoid 
cavity,  being  blended  at  its  upper  part  with  the  capsular  ligament;  the  muscular 
fibres  pass  downward  between  the  two  other  portions  of  the  muscle,  and  join  with 
them  in  the  common  tendon  of  insertion. 

The  External  Head  (caput  laterale)  arises  from  the  posterior  surface  of  the  shaft 
of  the  humerus,  between  the  insertion  of  the  Teres  minor  and  the  upper  part  of 
the  musculo-spiral  groove;  from  the  external  border  of  the  humerus  and  the 
external  intermuscular  septum:  the  fibres  from  this  origin  converge  toward  the 
common  tendon  of  insertion. 

The  Internal  Head  (caput  mediale)  arises  from  the  posterior  surface  of  the  shaft 
of  the  humerus,  below  the  groove  for  the  musculo-spiral  nerve;  commencing  above, 
narrow  and  pointed,  below  the  insertion  of  the  Teres  major,  and  extending  to 
within  an  inch  of  the  trochlear  surface:  it  also  arises  from  the  internal  border  of 
the  humerus,  and  from  the  back  of  the  whole  length  of  the  internal  and  lower  part 
of  the  external  intermuscular  septum.  The  fibres  of  this  portion  of  the  muscle  are 
directed,  some  downward  to  the  olecranon,  whilst  others  converge  to  the  common 
tendon  of  insertion. 

The  Common  Tendon  of  the  Triceps  commences  about  the  middle  of  the  back  part 
of  the  muscle :  it  consists  of  two  aponeurotic  laminae,  one  of  which  is  subcutaneous 
and  covers  the  posterior  surface  of  the  muscle  for  the  lower  half  of  its  extent;  the 
other  is  more  deeply  seated  in  the  substance  of  the  muscle:  after  receiving  the 
attachment  of  the  muscular  fibres,  they  join  together  above  the  elbow,  and  are 
inserted,  for  the  most  part,  into  the  back  part  of  the  upper  surface  of  the  olecranon 
process;  a  band  of  fibres  is,  however,  continued  downward,  on  the  outer  side, 
over  the  Anconeus,  to  blend  with  the  deep  fascia  of  the  forearm.  A  small  bursa 
(bursa  subtendinea  olecrani)  occasionally  multilocular,  is  situated  on  the  front  part 
of  this  surface,  beneath  the  tendon.  The  subcutaneous  olecranon  bursa  (bursa  sub- 
cutanea  olecrani)  is  situated  between  the  olecranon  process  and  the  skin.  Within 
the  tendon  of  the  triceps  is  often  found  the  bursa  intratendinea  olecrani. 

The  long  head  of  the  Triceps  descends  between  the  Teres  minor  and  Teres 
major,  dividing  the  triangular  space  between  these  two  muscles  and  the  humerus 
into  two  smaller  spaces,  one  triangular,  the  other  quadrangular  (Fig.  315).  The 
triangular  space  contains  the  dorsalis  scapulas  vessels;  it  is  bounded  by  the  Teres 
minor  above,  the  Teres  major  below,  and  the  scapular  head  of  the  Triceps  exter- 
nally: the  quadrangular  space  transmits  the  posterior  circumflex  vessels  and  the 
circumflex  nerve;  it  is  bounded  by  the  Teres  minor  above,  the  Teres  major  below, 
the  scapular  head  of  the  Triceps  internally,  and  the  humerus  externally. 

Relations. — By  its  posterior  surface,  with  the  Deltoid  above:  in  the  rest  of  its 
extent  it  is  subcutaneous;  by  its  anterior  surface,  with  the  humerus,  musculo- 
spiral  nerve,  superior  profunda  vessels,  and  back  part  of  the  elbow-joint.  Its 
middle  or  long  head  is  in  relation,  behind,  with  the  Deltoid  and  Teres  minor;  in 
front,  with  the  Subscapularis,  Latissimus  dorsi,  and  Teres  major. 


480  THE  MUSCLES  AND  FASCIA 

The  Subanconeus  (ra.  anconaeus)  is  a  name  given  to  a  few  fibres  from  the  under 
surface  of  the  lower  part  of  the  Triceps  muscle,  which  are  inserted  into  the  posterior 
ligament  of  the  elbow-joint.  By  some  authors  it  is  regarded  as  the  analogue  of 
the  Subcrureus  in  the  lower  limb,  but  it  is  not  a  separate  muscle. 

Nerves. — The  Triceps  is  supplied  by  the  seventh  and  eighth  cervical  nerves 
through  the  musculo-spiral  nerve. 

Actions. — The  Triceps  is  the  great  extensor  muscle  of  the  forearm,  serving, 
when  the  forearm  is  flexed,  to  extend  the  elbow-joint.  It  is  the  direct  antagonist 
of  the  Biceps  and  Brachialis  anticus.  When  the  arm  is  extended  the  long  head 
of  the  muscles  may  assist  the  Teres  major  and  Latissimus  dorsi  in  drawing  the 
humerus  backward  and  in  adducting  it  to  the  thorax.  The  long  head  of  the  Tri- 
ceps protects  the  under  part  of  the  shoulder-joint,  and  prevents  displacement  of 
the  head  of  the  humerus  downward  and  backward.  The  Subanconeus  draws 
up  the  posterior  ligament  during  extension  of  the  forearm. 

Surgical  Anatomy. — The  existence  of  the  band  of  fibres  from  the  Triceps  to  the  fascia  of 
the  forearm  is  of  importance  in  excision  of  the  elbow,  and  should  always  be  carefully  preserved 
from  injury  by  the  operator,  as  by  means  of  these  fibres  the  patient  is  enabled  to  extend  the 
forearm,  a  movement  which  would  otherwise  mainly  be  accomplished  by  gravity;  that  is  to  say, 
allowing  the  forearm  to  drop  from  its  own  weight. 

III.  MUSCLES  AND  FASCI-ffi  OF  THE  FOREARM. 

Dissection. — To  dissect  the  forearm,  place  the  limb  in  the  position  indicated  in  Fig.  311, 
make  a  vertical  incision  along  the  middle  line  from  the  elbow  to  the  wrist,  and  a  transverse 
incision  at  the  extremity  of  this;  the  superficial  structures  being  removed,  the  deep  fascia  of 
the  forearm  is  exposed. 

Deep  Fascia  (fascia  antibrachii). — The  deep  fascia  of  the  forearm,  continuous 
above  with  that  enclosing  the  arm,  is  a  dense,  highly  glistening  aponeurotic 
investment,  which  forms  a  general  sheath  enclosing  the  muscles  in  this  region; 
it  is  attached,  behind,  to  the  olecranon  and  posterior  border  of  the  ulna,  and  gives 
off  from  its  inner  surface  numerous  intermuscular  septa,  which  enclose  each  mus- 
cle separately.  Below,  it  is  continuous  in  front  with  the  anterior  annular  ligament 
(lig  amentum  carpi  volare) ,  and  forms  a  sheath  for  the  tendon  of  the  Palmaris  longus 
muscle,  which  passes  over  the  annular  ligament  to  be  inserted  into  the  palmar 
fascia.  Behind,  near  the  wrist-joint,  it  becomes  much  thickened  by  the  addition 
of  many  transverse  fibres,  and  forms  the  posterior  annular  ligament  (ligamentum 
carpi  dorsale).  It  consists  of  circular  and  oblique  fibres,  connected  together  by 
numerous  vertical  fibres.  It  is  much  thicker  on  the  dorsal  than  on  the  palmar  sur- 
face, and  at  the  lower  than  at  the  upper  part  of  the  forearm,  and  is  strengthened 
above  by  tendinous  fibres  derived  from  the  Brachialis  anticus  and  Biceps  in  front, 
and  from  the  Triceps  behind.  Its  deep  surface  gives  origin  to  muscular  fibres, 
especially  at  the  upper  part  of  the  inner  and  outer  sides  of  the  forearm,  and  forms 
the  boundaries  of  a  series  of  conical-shaped  cavities,  in  which  the  muscles  are 
contained.  Besidesjthe  vertical  septa  separating  each  muscle,  transverse  septa  are 
given  off  on  the  anterior  and  posterior  surfaces  of  the  forearm,  separating  the 
deep  from  the  superficial  layer  of  muscles.  Numerous  apertures  exist  in  the  fascia 
for  the  passage  of  vessels  and  nerves;  one  of  these,  of  large  size,  situated  at  the 
front  of  the  elbow,  serves  for  the  passage  of  a  communicating  branch  between 
the  superficial  and  deep  veins. 

The  muscles  of  the  forearm  may  be  subdivided  into  groups  corresponding  to 
the  region  they  occupy.  One  group  occupies  the  inner  and  anterior  aspect  of  the 
forearm,  and  comprises  the  Flexor  and  Pronator  muscles.  Another  group  occupies 
its  outer  side,  and  a  third  its  posterior  aspect.  The  two  latter  groups  include  all 
the  Extensor  and  Supinator  muscles. 


THE  ANTERIOR   RADIO -ULNAR   REGION  481 

8.  The  Anterior  Radio-ulnar  Region. 

The  muscles  in  this  region  are  divided  for  convenience  of  description  into  two 
groups  or  layers,  superficial  and  deep. 

The  Superficial  Layer. 

Pronator  radii  teres.  Palmaris  longus. 

Flexor  carpi  radialis.  Flexor  carpi  ulnaris. 

Flexor  sublimis  digitorum. 

These  muscles  take  origin  from  the  internal  condyle  of  the  humerus  by  a 
common  tendon. 

The  Pronator  Radii  Teres  (m.  pronator  teres)  arises  by  two  heads.  One,  the 
larger  and  more  superficial,  humeral  head  (caput  humerale),  arises  from  the  humerus, 
immediately  above  the  internal  condyle,  and  from  the  tendon  common  to  the 
origin  of  the  other  muscles ;  also  from  the  fascia  of  the  forearm  and  the  inter- 
muscular  septum  between  it  and  the  Flexor  carpi  radialis.  The  other  head,  the 
ulnar  head  (caput  idnare),  is  a  thin  fasciculus  which  arises  from  the  inner  side  of 
the  coronoid  process  of  the  ulna,  joining  the  preceding  at  an  acute  angle. 
Between  the  two  heads  the  median  nerve  enters  the  forearm.  The  muscle  passes 
obliquely  across  the  forearm  from  the  inner  to  the  outer  side,  and  terminates  in  a 
flat  tendon,  which  turns  over  the  outer  margin  of  the  radius,  and  is  inserted  into 
a  rough  impression  at  the  middle  of  the  outer  surface  of  the  shaft  of  that  bone. 

Relations. — By  its  anterior  surface,  throughout  the  greater  part  of  its  extent, 
with  the  deep  fascia;  at  its  insertion  it  is  crossed  by  the  radial  vessels  and  nerve, 
and  is  covered  by  the  Supinator  longus;  by  its  posterior  surface,  with  the  Brachialis 
anticus,  Flexor  sublimis  digitorum,  the  median  nerve,  and  ulnar  artery,  the  small 
or  deep  head  being  interposed  between  the  two  latter  structures.  Its  outer  border 
forms  the  inner  boundary  of  a  triangular  space  in  which  are  placed  the  brachial 
artery,  median  nerve,  and  tendon  of  the  Biceps  muscle.  Its  inner  border  is  in 
contact  with  the  Flexor  carpi  radialis. 

Surgical  Anatomy. — This  muscle,  when  suddenly  brought  into  very  active  use,  as  in  the 
game  of  lawn  tennis,  is  apt  to  be  strained,  producing  slight  swelling  and  tenderness,  and  pain 
on  putting  the  muscle  into  action.  This  is  known  as  lawn-tennis  arm. 

The  Flexor  Carpi  Radialis  lies  on  the  inner  side  of  the  preceding  muscle.  It 
arises  from  the  internal  condyle  by  the  common  tendon,  from  the  fascia  of  the  fore- 
arm, and  from  the  intermuscular  septa  between  it  and  the  Pronator  radii  teres,  on 
the  outside,  the  Palmaris  longus  internally,  and  the  Flexor  sublimis  digitorum 
beneath.  Slender  and  aponeurotic  in  structure  at  its  commencement,  it  increases 
in  size,  and  terminates  in  a  tendon  which  forms  rather  more  than  the  lower  half 
of  its  length.  This  tendon  passes  through  a  canal  on  the  outer  side  of  the  annular 
ligament,  runs  through  a  groove  in  the  os  trapezium  (which  is  converted  into  a 
canal  by  a  fibrous  sheath,  and  is  lined  by  a  synovial  membrane),  and  is  inserted 
into  the  base  of  the  metacarpal  bone  of  the  index  finger,  and  by  a  slip  into  the  base 
of  the  metacarpal  bone  of  the  middle  finger.  The  radial  artery  lies  between  the 
tendon  of  this  muscle  and  the  Supinator  longus,  and  may  easily  be  tied  in  this 
situation.  In  the  hand  a  bursa  (bursa  m.  flexoris  carpi  radialis)  lies  between  the 
base  of  the  second  metacarpal  bone  and  the  tendon  (Spalteholz) . 

Relations. — By  its  superficial  surface,  with  the  deep  fascia  and  the  integument; 
by  its  deep  surface,  with  the  Flexor  sublimis  digitorum,  Flexor  longus  pollicis, 
and  wrist-joint ;  by  its  outer  border,  with  the  Pronator  radii  teres  and  the  radial 
vessels;  by  its  inner  border,  with  the  Palmaris  longus  above  and  the  median 

nerve  below. 

31 


482 


THE    MUSCLES  AND    FASCIA 


The  Palmaris  Longus  (Fig.  316)  is  a  slender,  fusiform  muscle  lying  on  the  inner- 
side  of  the  preceding.  It  arises  from  the  inner  condyle  of  the  humerus  by  the  com- 
mon tendon,  from  the  deep  fascia,  and  the  inter- 
muscular  septa  between  it  and  the  adjacent  mus- 
cles. It  terminates  in  a  slender  flattened  tendon, 
which  passes  over  the  upper  part  of  the  annular 
ligament,  to  end  in  the  central  part  of  the  palmar 
fascia  and  lower  part  of  the  annular  ligament, 
frequently  sending  a  tendinous  slip  to  the  short 
muscles  of  the  thumb.  This  muscle  is  often 
absent,  and  is  subject  to  very  considerable  varia- 
tions; it  may  be  tendinous  above  and  muscular 
below;  or  it  may  be  muscular  in  the  centre,  with 
a  tendon  above  and  below;  or  it  may  present  two 
muscular  bundles  with  a  central  tendon;  or 
finally  it  may  consist  simply  of  a  mere  tendinous 
band. 

Relations. — By  its  superficial  surface,  with  the 
deep  fascia.  By  its  deep  surface,  with  the  Flexor 
sublimis  digitorum.  Internally,  with  the  Flexor 
carpi  ulnaris.  Externally,  with  the  Flexor  carpi 
radialis.  The  median  nerve  lies  close  to  the 
tendon,  just  above  the  wrist,  on  its  inner  and 
posterior  side. 

The  Flexor  Carpi  Ulnaris  (Fig.  316)  lies  along 
the  ulnar  side  of  the  forearm.  It  arises  by  two 
heads,  connected  by  a  tendinous  arch,  beneath 
which  pass  the  ulnar  nerve  and  posterior  ulnar 
recurrent  artery.  One  head  arises  from  the  inner 
condyle  of  the  humerus,  humeral  head  (caput 
humerale) ,  by  the  common  tendon ;  the  other  from 
the  inner  margin  of  the  olecranon  and  from  the 
upper  two-thirds  of  the  posterior  border  of  the 
ulna,  ulnar  head  (caput  ulnar  e],  by  an  aponeu- 
rosis,  common  to  it  and  the  Extensor  carpi 
ulnaris  and  Flexor  profundus  digitorum;  and  from 
the  intermuscular  septum  between  it  and  the 
Flexor  sublimis  digitorum.  The  fibres  terminate 
in  a  tendon  which  occupies  the  anterior  part  of 
the  lower  half  of  the  muscle,  and  is  inserted  into 
the  pisiform  bone,  and  is  prolonged  from  this  to 
the  fifth  metacarpal  and  unciform  bones,  by  the 
piso-metacarpal  and  piso-uncinate  ligaments:  it  is 
also  attached  by  a  few  fibres  to  the  annular  liga- 
ment. The  ulnar  artery  lies  on  the  outer  side  of 
the  tendon  of  this  muscle,  in  the  lower  two-thirds 
of  the  forearm,  the  tendon  forming  a  guide  in  tying  the  vessel  in  this  situation. 
A  bursa  (bursa  m.  flexoris  carpi  ulnaris)  is  placed  between  the  tendon  and  a 
part  of  the  pisiform  bone. 

Relations. — By  its  superficial  surface,  with  the  deep  fascia,  with  which  it  is 
intimately  connected  for  a  considerable  extent;  by  its  deep  surface,  with  the  Flexor 
sublimis  digitorum,  the  Flexor  profundus  digitorum,  the  Pronator  quadratus,  and 
the  ulnar  vessels  and  nerve;  by  its  outer  or  radial  border,  with  the  Palmaris  longus 
above  and  the  ulnar  vessels  and  nerve  below. 


FIG.  316.— Front  of  the  left  forearm. 
Superficial  muscles. 


THE  ANTERIOR    RADIO- ULNAR   REGION 


483 


The  Flexor  Sublimis  Digitorum  (m.  flexor  digitorum  sublimis)  (Fig.  316) 
is  placed  beneath  the  preceding  muscles,  which  therefore  must  be  removed 
in  order  to  bring  its  attachment  into  view.  It  is  the  largest  of  the  muscles  of  the 
superficial  layer,  and  arises  by  t.  iree  heads.  One  head,  the  humeral  head  (caput 
humerale) ,  arises  from  the  internal  condyle  of  the  humerus  by  the  common  ten- 
don, from  the  internal  lateral  ligament  of  the  elbow-joint,  and  from  the  intermus- 
cular  septum  common  to  it  and  the  preceding  muscles.  The  second  head,  ulnar 
head  (caput  ulnare),  arises  from  the  inner  side  of  the  coronoid  process  of  the  ulna, 
above  the  ulnar  origin  of  the  Pronator  radii  teres  (Fig.  134,  p.  187).  The  third 
head,  radial  head  (caput  radiate),  arises  from  the  oblique  line  of  the  radius,  extend- 
ing from  the  tuberosity  to  the  insertion  of  the  Pronator  radii  teres.  The  fibres  pass 
vertically  downward,  forming  a  broad  and  thick  muscle,  which  speedily  divides  into 
two  planes  of  muscular  fibres,  superficial  and  deep:  the  superficial  plane  divides 
into  two  parts  which  end  in  tendons  for  the  middle  and  ring  fingers;  the  deep 
plane  also  divides  into  two  parts,  which  end  in  tendons  for  the  index  and  little 
fingers,  but  previously  to  having  done  so  it  gives  off  a  muscular  slip,  which  joins 
that  part  of  the  superficial  plane  which  is  intended  for  the  ring  finger.  As  the 
four  tendons  thus  formed  pass  beneath  the  annular  ligament  into  the  palm  of  the 
hand,  they  are  arranged  in  pairs,  the  superficial  pair  corresponding  to  the  middle 
and  ring  fingers,  the  deep  pair  to  the  index  and  little  fingers.  The  tendons  diverge 
from  one  another  as  they  pass  onward.  Opposite  the  bases  of  the  first  phalanges 
each  tendon  divides  into  two  slips  (chiasma  tendinum)  to  allow  of  the  passage  of 
the  corresponding  tendon  of  the  Flexor  profundus  digitorum;  the  two  portions  of 
the  tendon  then  unite  and  form  a  grooved  channel  for  the  reception  of  the  accom- 
panying deep  flexor  tendon.  Finally  they  subdivide  a  second  time,  to  be  inserted 
into  the  sides  of  the  second  phalanges 
about  their  middle.  The  insertion  in  the 
index  finger  is  shown  in  Fig.  322.  After 
leaving  the  palm  the  tendons  of  the 
superficial  flexor,  accompanied  by  the  deep 
flexor  tendons,  lie  in  osseo-aponeurotic 
canals  (Fig.  318).  Each  canal  or  theca 
extends  from  the  metacarpo-phalangeal 
articulation  to  the  proximal  end  of  the 
distal  phalanx  (Fig.  232).  It  is  formed 
by  strong  fibrous  bands,  which  arch  across 
the  tendons,  and  are  attached  on  each  side 
to  the  margins  of  the  phalanges.  Oppo- 
site the  middle  of  the  proximal  and  second 
phalanges  the  sheath  is  very  strong,  and 
the  fibres  pass  transversely;  but  opposite  the  joints  it  is  much  thinner,  and  the 
fibres  pass  obliquely.  It  is  very  thin  over  the  metacarpo-phalangeal  articulation. 
It  is  absent  over  the  distal  phalanx.  Each  sheath  is  lined  by  a  synovial  mem- 
brane, which  is  reflected  on  the  contained  tendons. 

Relations. — In  the  forearm,  by  its  superficial  surface,  with  the  deep  fascia  and 
all  the  preceding  superficial  muscles;  by  its  deep  surface,  with  the  Flexor  profundus 
digitorum,  Flexor  longus  pollicis,  the  ulnar  vessels  and  nerve,  and  the  median 
nerve.  In  the  hand  its  tendons  are  in  relation,  in  front,  with  the  palmar  fascia, 
superficial  palmar  arch,  and  the  branches  of  the  median  nerve;  behind,  with  the 
tendons  of  the  deep  Flexor  and  the  Lumbricales. 


SHEATH  OF,, 
FLEXOR' 

TENDONS 


FLEXOR  PROFUNDUS 

DIGIT,ORUM 


/FLEXOR 
SUBLIMIS 
DIGITORUM 
DIGITAL 
ARTERIES 
AND  NERVES 


COMMON  TENDON  OF 
EXTENSOR   MUSCLE 
OF  FINGERS 


FIRST  PHALANX 


FIG.  317.  —  Section  passing  through  the  middle 
third  of  the  first  phalanx  of  the  middle  finger  (frozen 
section).  The  tendon  of  the  Flexor  sublimis  digi- 
torum is  divided  into  two  small  bands,  which  spread 
laterally  and  engage  themselves  between  the  osse- 
Flexor  profundus  digitorum. 


484  THE  MUSCLES  AND   FASCIAE 

The  Deep  Layer  (Fig.  318). 

Flexor  profundus  digitorum.  Flexor  longus  pollicis. 

Pronator  quadratus. 

Dissection. — Divide  each  of  the  superficial  muscles  at  its  centre,  and  turn  either  end  aside; 
the  deep  layer  of  muscles,  together  with  the  median  nerve  and  ulnar  vessels,  will  then  be  exposed. 

The  Flexor  Profundus  Digitorum  (TO.  flexor  digitorum  profundus)  (Fig.  318) 
is  situated  on  the  ulnar  side  of  the  forearm,  immediately  beneath  the  superficial 
Flexors.  It  arises  from  the  upper  three-fourths  of  the  anterior  and  inner 
surfaces  of  the  shaft  of  the  ulna,  embracing  the  insertion  of  the  Brachialis  anticus 
above,  and  extending,  below,  to  within  a  short  distance  of  the  Pronator  quadratus. 
It  also  arises  from  a  depression  on  the  inner  side  of  the  coronoid  process;  by  an  apo- 
neurosis  from  the  upper  three-fourths  of  the  posterior  border  of  the  ulna,  in  common 
with  the  Flexor  and  Extensor  carpi  ulnaris ;  and  from  the  ulnar  half  of  the  inter- 
osseous  membrane.  The  fibres  form  a  fleshy  belly  of  considerable  size,  which  divides 
into  four  tendons :  these  pass  under  the  annular  ligament  beneath  the  tendons  of  the 
Flexor  sublimis  digitorum.  Opposite  the  first  phalanges  the  tendons  pass  through 
the  openings  in  the  two  slips  of  the  tendons  of  the  Flexor  sublimis  digitorum,  and 
are  finally  inserted  into  the  bases  of  the  last  phalanges.  The  portion  of  the  muscle 
for  the  index  finger  (Fig.  322)  is  usually  distinct  throughout,  but  the  tendons  for 
the  three  inner  fingers  are  connected  together  by  cellular  tissue  and  tendinous  slips 
as  far  as  the  palm  of  the  hand.  The  tendons  of  this  muscle  and  those  of  the  Flexor 
sublimis  digitorum,  whilst  contained  in  the  osseo-aponeurotic  canals  of  the  fingers, 
are  invested  in  a  synovial  sheath,  and  are  connected  to  each  other  and  to  the 
phalanges  by  slender  tendinous  filaments,  called  vincula  accessoria  tendinum  (vin- 
culum  tendinum).  One  of  these  connects  the  deep  tendon  to  the  bone  before  it 
passes  through  the  superficial  tendon ;  a  second  connects  the  two  tendons  together, 
after  the  deep  tendons  have  passed  through;  and  a  third  connects  the  deep  ten- 
don to  the  head  of  the  second  phalanx.  This  last  consists  largely  of  yellow  elastic 
tissue,  and  may  assist  in  drawing  down  the  tendon  after  flexion  of  the  finger.1 

Four  small  muscles,  the  Lumbricales,  are  connected  with  the  tendons  of  the  Flexor 
profundus  in  the  palm.  They  will  be  described  with  the  muscles  in  that  region. 

Relations. — By  its  superficial  surface,  in  the  forearm,  with  the  Flexor  sublimis 
digitorum,  the  Flexor  carpi  ulnaris,  the  ulnar  vessels  and  nerve,  and  the  median 
nerve;  and  in  the  hand,  with  the  tendons  of  the  superficial  Flexor;  by  its  deep 
surface,  in  the  forearm,  with  the  ulna,  the  interosseous  membrane,  the  Pronator 
quadratus;  and  in  the  hand,  with  the  Interossei,  Adductor  pollicis,  and  deep 
palmar  arch;  by  its  ulnar  border,  with  the  Flexor  carpi  ulnaris;  by  its  radial  border, 
with  the  Flexor  longus  pollicis,  the  anterior  interosseous  vessels  and  nerve  being 
interposed. 

The  Flexor  Longus  Pollicis  (TO.  flexor  pollicis  longus}  (Fig.  318)  is  situated  on 
the  radial  side  of  the  forearm,  lying  on  the  same  plane  as  the  preceding.  It  arises 
from  the  grooved  anterior  surface  of  the  shaft  of  the  radius,  commencing  above, 
immediately  below  the  tuberosity  and  oblique  line,  and  extending  below  to  within 
a  short  distance  of  the  Pronator  quadratus.  It  also  arises  from  the  adjacent  part 
of  the  interosseous  membrane  and  generally  by  a  fleshy  slip  from  the  inner  border 
of  the  coronoid  process  or  from  the  internal  condyle  of  the  humerus.  The  fibres 
pass  downward,  and  terminate  in  a  flattened  tendon  which  passes  beneath  the 
annular  ligament,  is  then  lodged  in  the  interspace  between  the  outer  head  of  the 
Flexor  brevis  pollicis  and  the  Adductor  obliquus  pollicis,  and,  entering  an  osseo- 
aponeurotic  canal  similar  to  those  for  the  other  flexor  tendons,  is  inserted  into  the 
base  of  the  last  phalanx  of  the  thumb. 

1  Marshall,  Brit,  and  For.  Med  -Chir.  Rev.,  1853. 


THE  ANTERIOR   RADIO-  ULNAR   REGION 


485 


Relations. — By  its  superficial  sur- 
face, with  the  Flexor  sublimis  digi- 
torum,  Flexor  carpi  radialis,  Supi- 
nator  longus,  and  radial  vessels;  by 
its  deep  surface,  with  the  radius, 
interosseous  membrane,  and  Pro- 
nator  quadratus ;  by  its  ulnar  border, 
with  the  Flexor  profundus  digitorum, 
from  which  it  is  separated  by  the 
anterior  interosseous  vessels  and 
nerve. 

The  Pronator  Quadratus  (Figs. 
318  and  327)  is  a  small,  flat,  quadri- 
lateral muscle,  extending  transversely 
across  the  front  of  the  radius  and 
ulna,  above  their  carpal  extremities. 
It  arises  from  the  oblique  or  pronator 
ridge  on  the  lower  part  of  the  ante- 
rior surface  of  the  shaft  of  the  ulna; 
from  the  lower  fourth  of  the  anterior 
surface  and  the  anterior  border  of 
the  ulna;  and  from  a  strong  aponeu- 
rosis  which  covers  the  inner  third  of 
the  muscle.  The  fibres  pass  out- 
ward and  slightly  downward,  to  be 
inserted  into  the  lower  fourth  of  the 
anterior  surface  and  anterior  border 
of  the  shaft  of  the  radius. 

Relations. — By  its  superficial  sur- 
face, with  the  Flexor  profundus  digi- 
torum, the  Flexor  longus  pollicis, 
Flexor  carpi  radialis,  and  the  radial 
vessels;  by  its  deep  surface,  with  the 
radius,  ulna,  and  interosseous  mem- 
brane. 

Nerves.  —  All  the  muscles  of  the 
superficial  layer  are  supplied  by  the 
median  nerve,  excepting  the  Flexor 
carpi  ulnaris,  which  is  supplied  by  the 
ulnar  nerve.  The  Pronator  radii  teres 
and  the  Flexor  carpi  radialis  derive 
their  supply  primarily  from  the  sixth 
cervical;  the  Palmaris  longus  from 
the  eighth  cervical;  the  Flexor  sub- 
limis digitorum  from  the  seventh  and 
eighth  cervical  and  first  thoracic,  and 
the  Flexor  carpi  ulnaris  from  the 
eighth  cervical  and  first  thoracic 
nerves.  Of  the  deep  layer,  the  Flexor 
profundus  digitorum  is  supplied  by 
the  eighth  cervical  and  first  thoracic 
through  the  ulnar  and  anterior  in- 
terosseous branch  of  the  median. 
The  remaining  two  muscles,  the 


FIG.  318. — Front  of  the  left  forearm.     Deep  muscles. 


486  THE  MUSCLES  AND  FASCIJE 

Flexor  longus  pollicis  and  Pronator  quadratus,  are  also  supplied  by  the  eighth 
cervical  and  first  thoracic  through  the  anterior  interosseous  branch  of  the  median. 
Actions. — These  muscles  act  upon  the  forearm,  the  wrist,  and  hand.  The 
Pronator  radii  teres  helps  to  rotate  the  radius  upon  the  ulna,  rendering  the  hand 
prone:  when  the  radius  is  fixed  it  assists  the  other  muscles  in  flexing  the  forearm. 
The  Flexor  carpi  radialis  is  one  of  the  flexors  of  the  wrist;  when  acting  alone  it 
flexes  the  wrist,  inclining  it  to  the  radial  side.  It  can  also  assist  in  pronating  the 
forearm  and  hand,  and,  by  continuing  its  action,  in  bending  the  elbow.  The  Flexor 
carpi  ulnaris  is  one  of  the  flexors  of  the  wrist :  when  acting  alone  it  flexes  the  wrist, 
inclining  it  to  the  ulnar  side  (adducts  the  wrist),  and,  by  continuing  to  contract, 
it  bends  the  elbow.  The  Palmaris  longus  is  a  tensor  of  the  palmar  fascia,  and 
tension  of  this  fascia  protects  the  parts  beneath  it.  It  also  assists  in  flexing  the 
wrist  and  elbow.  The  Flexor  sublimis  digitorum  flexes  the  middle  phalanx  and 
then  assists  in  flexing  the  wrist  and  elbow.  The  Flexor  profundus  digitorum  is 
the  flexor  of  the  distal  phalanx.  After  the  Flexor  sublimis  has  bent  the  second 
phalanx,  the  Flexor  profundus  flexes  the  terminal  one,  but  it  cannot  do  so  until 
after  the  contraction  of  the  superficial  muscle.  After  flexing  the  distal  phalanx, 
it  assists  in  flexing  the  middle  phalanx,  the  proximal  phalanx,  and  the  wrist.  The 
Flexor  longus  pollicis  is  the  flexor  of  the  distal  phalanx  of  the  thumb.  When  the 
thumb  is  fixed  it  also  assists  in  flexing  the  wrist.  The  Pronator  quadratus  helps 
to  rotate  the  radius  upon  the  ulna,  rendering  the  hand  prone. 

Surgical  Anatomy. — When  a  finger  is  amputated  so  that  the  fibrous  sheath  of  the  flexor  ten- 
dons is  divided  in  a  region  in  which  it  is  firm  and  dense,  the  tendon  contracts  but  the  theca  does 
not,  and  the  rigid  theca  constitutes  a  permeable  passage  to  the  palm.  If  the  parts  should  be 
infected  the  theca  will  draw  pus  toward  the  palm.  Hence  it  is  best  to  close  the  theca  by  sutures. 
"Over  the  terminal  phalanx,  and  over  the  joint  between  the  middle  and  terminal  phalanges, 
there  is  no  fibrous  sheath.  In  front  of  the  metacarpo-phalangeal  joint  it  is  scarcely  evident. 
Over  the  first  and  second  (proximal  and  middle)  phalanges,  and  in  front  of  the  joint  between 
these  bones,  the  fibrous  sheath  is  well  marked,  and  appears  as  a  rigid  tube  when  cut  across. 
As  the  sheath  crosses  the  metacarpo-phalangeal  and  first  interphalangeal  joints,  it  is  adherent 
to  the  glenoid  ligament,  and  is  easily  closed  by  two  fine  catgut  sutures  passed  vertically — i.  e., 
from  the  dorsal  to  the  palmar  wall.  Opposite  the  shafts  of  the  first  and  second  phalanges, 
however,  there  is  much  difficulty  in  effecting  closure,  since  the  sheath  is  united  to  the  periosteum, 
and  that  membrane  is  very  thin.  In  these  situations  the  periosteum  should  be  stripped  up  a 
little  from  the  palmar  aspect  of  the  bone,  and  the  orifice  of  the  tube  secured  by  two  fine  sutures 
passed  either  vertically  or  transversely,  as  may  appear  the  more  convenient.  This  stripping 
off  of  periosteum  should  be  effected  before  the  bone  is  divided."1 

9.  The  Radial  Region  (Figs.  316,  319,  320). 

Supinator  longus.  Extensor  carpi  radialis  longior. 

Extensor  carpi  radialis  brevior. 

Dissection. — Divide  the  integument  in  the  same  manner  as  in  the  dissection  of  the  anterior 
brachial  region,  and,  after  having  examined  the  cutaneous  vessels  and  nerves  and  deep  fascia, 
remove  all  those  structures.  The  muscles  will  then  be  exposed.  The  removal  of  the  fascia 
will  be  considerably  facilitated  by  detaching  it  from  below  upward.  Great  care  should  be 
taken  to  avoid  cutting  across  the  tendons  of  the  muscles  of  the  thumb,  which  cross  obliquely 
the  larger  tendons  running  down  the  back  of  the  radius. 

The  Supinator  Longus  (m.  brachioradialis)  (Fig.  316)  is  the  most  superficial 
muscle  on  the  radial  side  of  the  forearm;  it  is  fleshy  for  the  upper  two-thirds  of 
its  extent,  tendinous  below.  It  arises  from  the  upper  two-thirds  of  the  external 
supracondylar  ridge  of  the  humerus,  and  from  the  external  intermuscular  septum, 
being  limited  above  by  the  musculo-spiral  groove.  The  fibres  terminate  above 
the  middle  of  the  forearm  in  a  flat  tendon,  which  is  inserted  into  the  outer  side 
of  the  base  of  the  styloid  process  of  the  radius. 

1  Operative  Surgery.     By  Sir  Frederick  Treves. 


THE   RADIAL    REGION 


Relations. — By  its  superficial  sur- 
face, with  the  integument  and  fascia 
for  the  greater  part  of  its  extent;  near 
its  insertion  it  is  crossed  by  the  Ex- 
tensor ossis  metacarpi  pollicis  and  the 
Extensor  brevis  pollicis;  by  its  deep 
surface,  with  the  humerus,  the  Ex- 
tensor carpi  radialis  longior  and  bre- 
vior,  the  insertion  of  the  Pronator 
radii  teres,  and  the  Supinator  brevis; 
by  its  inner  border,  above  the  elbow, 
with  the  Brachialis  anticus,  the  mus- 
culo-spiral  nerve,  and  the  radial  recur- 
rent artery;  and  in  the  forearm  with 
the  radial  vessels  and  nerve. 

The  Extensor  Carpi  Radialis 
Longior  (m.  extensor  carpi  radialis 
lonrfus]  (Fig.  319)  is  placed  partly 
beneath  the  preceding  muscle.  It 
arises  from  the  lower  third  of  the  ex- 
ternal supracondylar  ridge  of  the 
humerus,  and  from  the  external  in- 
termuscular  septum  by  a  few  fibres 
from  the  common  tendon  of  origin  of 
the  Extensor  muscles  of  the  forearm. 
The  fibres  terminate  at  the  upper  third 
of  the  forearm  in  a  flat  tendon,  which 
runs  along  the  outer  border  of  the 
radius,  beneath  the  extensor  tendons 
of  the  thumb;  it  then  passes  through 
a  groove  common  to  it  and  the  Ex- 
tensor carpi  radialis  brevior,  immedi- 
ately behind  the  styloid  process,  and 
is  inserted  into  the  base  of  the  meta- 
carpal  bone  of  the  index  finger,  on 
its  radial  side. 

Relations. — By  its  superficial  sur- 
face, with  the  Supinator  longus  and 
fascia  of  the  forearm;  its  outer  side 
is  crossed  obliquely  by  the  extensor 
tendons  of  the  thumb;  by  its  deep 
surface,  with  the  elbow-joint,  the 
Extensor  carpi  radialis  brevior,  and 
back  part  of  the  wrist. 

The  Extensor  Carpi  Radialis 
Brevior  (m.  extensor  carpi  radialis 
brevis}  (Fig.  319)  is  shorter,  as  its 
name  implies,  and  thicker  than  the 
preceding  muscle,  beneath  which  it  is 
placed.  It  arises  from  the  external 
condyle  of  the  humerus  by  a  tendon 
common  to  it  and  the  three  following 
muscles ;  from  the  external  lateral 
ligament  of  the  elbow-joint,  from  a 
strong  aponeurosis  which  covers  its 


FIG.  319. — Posterior  surface  of  the  forearm.     Superficial 
muscles. 


488  THE   MUSCLES  AND    FASCIA 

surface,  and  from  the  intermuscular  septa  between  it  and  the  adjacent  muscles. 
The  fibres  terminate  about  the  middle  of  the  forearm  in  a  flat  tendon  which  is 
closely  connected  with  that  of  the  preceding  muscle,  and  accompanies  it  to  the 
wrist,  lying  in  the  same  groove  on  the  posterior  surface  of  the  radius ;  it  passes 
beneath  the  extensor  tendons  of  the  thumb,  then  beneath  the  annular  ligament, 
and,  diverging  somewhat  from  its  fellow,  is  inserted  into  the  base  of  the  meta- 
carpal  bone  of  the  middle  finger,  on  its  radial  side.  There  is  often  a  bursa 
(bursa  m.  extensoris  carpi  radialis  brevis)  between  a  portion  of  the  base  of  the 
bone  and  the  tendon. 

The  tendons  of  the  two  preceding  muscles  pass  through  the  same  compartment 
of  the  annular  ligament,  and  are  lubricated  by  a  single  synovial  membrane,  but  are 
separated  from  each  other  by  a  small  vertical  ridge  of  bone  as  they  lie  in  the  groove 
at  the  back  of  the  radius. 

Relations. — By  its  superficial  surface,  with  the  Extensor  carpi  radialis  longior, 
and  with  the  Extensor  muscles  of  the  thumb  which  cross  it;  by  its  deep  surface, 
with  the  Supinator  brevis,  tendon  of  the  Pronator  radii  teres,  radius,  and  wrist- 
joint;  by  its  ulnar  border,  with  the  Extensor  cornmunis  digitorum. 

10.  The  Posterior  Radio-ulnar  Region  (Fig.  319). 

The  muscles  in  this  region  are  divided  for  purposes  of  description  into  two 
groups  or  layers,  superficial  and  deep. 

The  Superficial  Layer. 

Extensor  communes  digitorum.  Extensor  carpi  ulnaris. 

Extensor  minimi  digiti.  Anconeus. 

The  Extensor  Communis  Digitorum  (m.  extensor  digitorum  communis)  is 
situated  at  the  back  part  of  the  forearm.  It  arises  from  the  external  condyle  of 
the  humerus  by  the  common  tendon,  from  the  deep  fascia,  and  the  intermus- 
cular septa  between  it  and  the  adjacent  muscles.  Just  below  the  middle  of 
the  forearm  it  divides  into  three  fleshy  masses,  from  which  tendons  proceed; 
these  pass,  together  with  the  Extensor  indicis,  through  a  separate  compartment 
of  the  annular  ligament,  lubricated  by  a  synovial  membrane.  The  tendons 
then  diverge,  the  innermost  one  dividing  into  two;  and  all,  after  passing  across  the 
back  of  the  hand,  are  inserted  into  the  second  and  third  phalanges  of  the  fingers  in 
the  following  manner :  the  outermost  tendon,  accompanied  by  the  Extensor  indicis, 
goes  to  the  index  finger  (Figs.  319,  321,  and  322);  the  second  tendon  is  sometimes 
connected  to  the  first  by  a  thin  transverse  band,  and  receives  a  slip  from  the  third 
tendon  (Fig.  319);  it  goes  to  the  middle  finger;  the  third  tendon  gives  off  the  slip 
to  the  second  (Fig.  319),  and  receives  a  very  considerable  part  of  the  fourth  tendon; 
the  fourth,  or  innermost  tendon,  divides  into  two  parts:  one  goes  to  join  the  third 
tendon;  the  other,  reinforced  by  the  Extensor  minimi  digiti,  goes  to  the  little 
finger.  Each  tendon  opposite  the  metacarpo-phalangeal  articulation  becomes 
narrow  and  thickened,  and  gives  off  a  thin  fasciculus  upon  each  side  of  the  joint, 
which  blends  with  the  lateral  ligaments  and  serves  as  the  posterior  ligament; 
after  having  passed  the  joint  it  spreads  out  into  a  broad  aponeurosis,  which  covers 
the  whole  of  the  dorsal  surface  of  the  first  phalanx,  being  reinforced,  in  this 
situation,  by  the  tendons  of  the  Interossei  and  Lumbricales.  Opposite  the  first 
phalangeal  joint  this  aponeurosis  divides  into  three  slips,  a  middle  and  two 
lateral:  the  former  is  inserted  into  the  base  of  the  second  phalanx;  and  the  two 
lateral,  which  are  continued  onward  along  the  sides  of  the  second  phalanx,  unite 
by  their  contiguous  margins,  and  are  inserted  into  the  dorsal  surface  of  the  last 
phalanx.  As  the  tendons  cross  the  phalangeal  joints  they  furnish  them  with  pos- 
terior ligaments.  The  accessory  slips  or  lateral  vincula  which  join  the  tendon 


THE  POSTERIOR    RADIO- ULNAR   REGION  439 

of  the  ring  finger  to  the  tendon  of  the  little  finger  and  the  tendon  of  the  middle 
finger  are  constant.  If  the  middle  and  little  fingers  are  held  flexed  the  lateral 
vincula  greatly  limit  the  range  of  extension  possible  in  the  ring  finger — a  limi- 
tation which  interferes  with  a  piano-player  (Prof.  William  S.  Forbes). 

Relations. — By  its  superficial  surface,  with  the  fascia  of  the  forearm  and  hand, 
the  posterior  annular  ligament,  and  integument;  by  its  deep  surface,  with  the 
Supinator  brevis,  the  Extensor  muscles  of  the  thumb  and  index  finger,  the  pos- 
terior interosseous  vessels  and  nerve,  the  wrist-joint,  carpus,  metacarpus,  and 
phalanges;  by  its  radial  border,  with  the  Extensor  carpi  radialis  brevier;  by  its 
ulnar  border,  with  the  Extensor  minimi  digiti  and  Extensor  carpi  ulnaris. 

The  Extensor  Minimi  Digiti  (m.  extensor  digiti  quinti  proprius]  is  a  slender 
muscle  placed  on  the  inner  side  of  the  Extensor  communis,  with  which  it  is  gen- 
erally connected.  It  arises  from  the  common  tendon  by  a  thin,  tendinous  slip,  and 
from  the  intermuscular  septa  between  it  and  the  adjacent  muscles.  Its  tendon 
runs  through  a  separate  compartment  in  the  annular  ligament  behind  the  inferior 
radio-ulnar  joint,  then  divides  into  two  as  it  crosses  the  hand,  the  outermost 
division  being  joined  by  the  slip  from  the  innermost  tendon  of  the  common  exten- 
sor. The  two  slips  thus  formed  spread  into  a  broad  aponeurosis,  which  after 
receiving  a  slip  from  the  Abductor  minimi  digiti  is  inserted  into  the  second  and 
third  phalanges.  The  tendon  is  situated  on  the  ulnar  side  of,  and  somewhat  more 
superficial  than,  the  common  extensor. 

The  Extensor  Carpi  Ulnaris  is  the  most  superficial  muscle  on  the  ulnar  side  of 
the  forearm.  It  arises  from  the  external  condyle  of  the  humerus  by  the  common 
tendon;  by  an  aponeurosis  from  the  posterior  border  of  the  ulna  in  common 
with  the  Flexor  carpi  ulnaris  and  the  Flexor  prof undus  digitorum ;  and  from  the 
deep  fascia  of  the  forearm.  This  muscle  terminates  in  a  tendon  which  runs 
through  a  groove  behind  the  styloid  process  of  the  ulna,  passes  through  a  separate 
compartment  in  the  annular  ligament,  and  is  inserted  into  the  prominent  tubercle 
on  the  ulnar  side  of  the  base  of  the  metacarpal  bone  of  the  little  finger. 

Relations. — By  its  superficial  surface,  with  the  deep  fascia  of  the  forearm;  by 
its  deep  surface,  with  the  ulna  and  the  muscles  of  the  deep  layer. 

The  Anconeus  (m.  anconaeus)  is  a  small  triangular  muscle  placed  behind  and 
below  the  elbow-joint,  and  appears  to  be  a  continuation  of  the  external  portion  of 
the  Triceps.  It  arises  by  a  separate  tendon  from  the  back  part  of  the  outer  condyle 
of  the  humerus,  and  is  inserted  into  the  side  of  the  olecranon  and  upper  fourth  of 
the  posterior  surface  of  the  shaft  of  the  ulna;  its  fibres  diverge  from  their  origin, 
the  upper  ones  being  directed  transversely,  the  lower  obliquely  inward. 

Relations. — By  its  superficial  surface,  with  a  strong  fascia  derived  from  the 
Triceps;  by  its  deep  surface,  with  the  elbow-joint,  the  orbicular  ligament,  the 
ulna,  and  a  small  portion  of  the  Supinator  brevis. 

The  Deep  Layer  (Fig.  321). 

Supinator  radii  brevis.  Extensor  brevis  pollicis. 

Extensor  ossis  metacarpi  pollicis.  Extensor  longus  pollicis. 

Extensor  indicis. 

The  Supinator  Radii  Brevis  (m.  supinator]  (Figs.  320  and  321)  is  a  broad  muscle, 
of  hollow  cylindrical  form,  curved  round  the  upper  third  of  the  radius.  It  consists  of 
two  distinct  planes  of  muscular  fibres,  between  which  lies  the  posterior  interosseous 
nerve  (Fig.  320).  The  two  planes  arise  in  common:  the  superficial  one  by  tendin- 
ous, and  the  deeper  by  muscular,  fibres  from  the  external  condyle  of  the  humerus, 
from  the  external  lateral  ligament  of  the  elbow-joint  and  the  orbicular  ligament  of 
the  radius;  from  the  ridge  on  the  ulna,  which  runs  obliquely  downward  from  the 


490 


THE    MUSCLES    AND    FASCIAE 


posterior  extremity  of  the  lesser  sigmoid  cavity;  from  the  triangular  depression  in 
front  of  it;  and  from  a  tendinous  expansion  which  covers  the  surface  of  the  muscle. 


Int. 
Cvndyle. 


Coronoid 
proc. 

Head  of 
radius. 


Olecranon 


FIG.  320. — Supinator  brevis.  (From  a  prepa- 
ration in  the  Museum  of  the  Royal  College  of 
Surgeons  of  England.) 


EXTENSOR 
CARPI    ULNARIS 


The  superficial  fibres  surround  the 
upper  part  of  the  radius,  and  are  in- 
serted into  the  outer  edge  of  the  bicip- 
ital  tuberosity  and  into  the  oblique 
line  of  the  radius,  as  low  down  as  the 
insertion  of  the  Pronator  radii  teres. 
The  upper  fibres  of  the  deeper  plane 
form  a  sling-like  fasciculus,  which 
encircles  the  neck  of  the  radius 
above  the  tuberosity  and  is  at- 
tached to  the  back  part  of  its  inner 
surface :  the  greater  part  of  this  por- 
tion of  the  muscle  is  inserted  into 
the  posterior  and  external  surface 
of  the  shaft,  midway  between  the 
oblique  line  and  the  head  of  the  bone.  Between  the  insertion  of  the  two 
planes  the  posterior  interosseous  nerve  lies  on  the  shaft  of  the  bone  (Fig.  320). 


FIG.  321. — Posterior  surface  of  the  forearm.    Deep  muscles. 


THE  POSTERIOR   RADIO-  ULNAR   REGION 


491 


Relations. — By  its  superficial  surface,  with  the  superficial  Extensor  and  Supina- 
tor  muscles,  and  the  radial  vessels  and  nerve;  by  its  deep  surface,  with  the  elbow- 
joint,  the  interosseous  membrane,  and  the  radius. 

The  Extensor  Ossis  Metacarpi  Pollicis  (m.  abductor  pollicis  longus)  is  the  most 
external  and  the  largest  of  the  deep  extensor  muscles:  it  lies  immediately  below 
the  Supinator  brevis,  with  which  it  is  sometimes  united.  It  arises  from  the  outer 
part  of  the  posterior  surface  of  the  shaft  of  the  ulna  below  the  insertion  of  the 
Anconeus,  from  the  interosseous  membrane,  and  from  the  middle  third  of  the 
posterior  surface  of  the  shaft  of  the  radius.  Passing  obliquely  downward  and 
outward,  it  terminates  in  a  tendon  which  runs  through  a  groove  on  the  outer  side 
of  the  styloid  process  of  the  radius,  accompanied  by  the  tendon  of  the  Extensor 
brevis  pollicis,  and  is  inserted  into  the  base  of  the  metacarpal  bone  of  the  thumb. 
It  occasionally  gives  off  two  slips  near  its  insertion — one  to  the  Trapezium,  and  the 
other  to  blend  with  the  origin  of  the  Abductor  pollicis. 

Relations. — By  its  superficial  surface,  with  the  Extensor  communis  digitorum, 
Extensor  minimi  digiti,  and  fascia  of  the  forearm,  and  with  the  branches  of  the 
posterior  interosseous  artery  and  nerve  which  cross  it;  by  its  deep  surface,  with 
the  ulna,  interosseous  membrane,  radius,  the  tendons  of  the  Extensor  carpi  radialis 
longior  and  brevior,  which  it  crosses  obliquely,  and,  at  the  outer  side  of  the  wrist, 
with  the  radial  vessels;  by  its  upper  border,  with  the  Supinator  brevis;  by  its 
lower  border,  with  the  Extensor  brevis  pollicis. 

The  Extensor  Brevis  Pollicis,  often  called  the  extensor  primi  internodii  pollicis 
(m.  extensor  pollicis  brevis),  the  smallest  muscle  of  this  group,  lies  on  the  inner 
side  of  the  preceding.  It  arises  from  the  posterior  surface  of  the  shaft  of  the  radius, 
below  the  Extensor  ossis  metacarpi 
pollicis,  and  from  the  interosseous 
membrane.  Its  direction  is  similar  to 
that  of  the  Extensor  ossis  metacarpi 
pollicis,  its  tendon  passing  through  the 
same  groove  on  the  outer  side  of  the 
styloid  process,  to  be  inserted  into  the 
base  of  the  first  phalanx  of  the  thumb. 

Relations. — The  same  as  those  of 
the  Extensor  ossis  metacarpi  pollicis. 

The  Extensor  Longus  Poilicis, 
often  called  the  extensor  secundi  inter- 
nodii pollicis  (m.  extensor  pollicis  longus) 
is  much  larger  than  the  preceding 
muscle,  the  origin  of  which  it  partly 
covers  in.  It  arises  from  the  outer 
part  of  the  posterior  surface  of  the 
shaft  of  the  ulna,  below  the  origin  of 
the  Extensor  ossis  metacarpi  pollicis, 
and  from  the  interosseous  membrane. 
It  terminates  in  a  tendon  which  passes 
through  a  separate  compartment  in 
the  annular  ligament,  lying  in  a  nar- 
row, oblique  groove  at  the  back  part 

of  the  lower  end  of  the  radius.  It  then  crosses  obliquely  the  tendons  of  the 
Extensor  carpi  radialis  longior  and  brevior,  being  separated  from  the  other 
extensor  tendons  of  the  thumb  by  a  triangular  interval,  in  which  the  radial  artery 
is  found,  and  is  finally  inserted  into  the  base  of  the  last  phalanx  of  the  thumb. 

Relations. — By  its  superficial  surface,  with  the  same  parts  as  the  Extensor  ossis 
metacarpi  pollicis;  by  its  deep  surface,  with  the  ulna,  interosseous  membrane,  the 


LIGAMEN 

BREVIS 


LIGAMENTUM 
LONGUS 


LIGAMENTUM   BREVIS 

FLEXOR  SUBLIMIS 
DIGITORUM 
EXPANSION   OF 
EXTENSOR  TENDON 
FLEXOR    PROFUNDUS 
DIGITORUM 

FIRST  LUMBRICAL 
MUSCLE 

FIRST  DORSAL 

INTEROSSEOUS 

MUSCLE 

EXTENSOR   INDICIS 
TENDON 


EXTENSOR   COMMUNIS 
DIGITORUM  TENDON 


FIG.  322. — The  tendons  attached  to  the  index  finger. 
(Cunningham. ) 


492  THE  MUSCLES  AND  FASCIA 

posterior  interosseous  nerve,  radius,  the  wrist,  the  radial  vessels,  and  metacarpal 
bone  of  the  thumb. 

The  Extensor  Indicis  (m.  extensor  indicis  proprius)  (Figs.  319,  321,  and  322)  is 
a  narrow,  elongated  muscle  placed  on  the  inner  side  of,  and  parallel  with,  the 
preceding.  It  arises  from  the  posterior  surface  of  the  shaft  of  the  ulna,  below 
the  origin  of  the  Extensor  longus  pollicis  and  from  the  interosseous  membrane. 
Its  tendon  passes  with  the  Extensor  communis  digitorum  through  the  same  canal 
in  the  annular  ligament,  and  subsequently  joins  the  tendon  of  the  Extensor 
communis  which  belongs  to  the  index  finger,  opposite  the  lower  end  of  the 
corresponding  metacarpal  bone,  lying  to  the  ulnar  side  of  the  tendon  from  the 
common  extensor. 

Relations. — The  relations  are  similar  to  those  of  the  preceding  muscles. 

Nerves. — The  Supinator  longus  is  supplied  by  the  sixth,  the  Extensor  carpi 
radialis  longior  by  the  sixth  and  seventh,  and  the  Anconeus  by  the  seventh  and 
eighth  cervical  nerves,  all  through  the  musculo-spiral  nerve;  the  remaining  muscles 
of  the  radial  and  posterior  brachial  region  are  supplied  through  the  posterior 
interosseous  nerve,  the  Supinator  brevis  being  supplied  by  the  sixth  cervical,  the 
Extensor  carpi  radialis  brevier  by  the  sixth  and  seventh  cervical,  and  all  the  other 
muscles  by  the  seventh  cervical. 

Actions. — The  muscles  of  the  radial  and  posterior  brachial  regions,  which 
comprise  all  the  extensor  and  supinator  muscles,  act  upon  the  forearm,  wrist,  and 
hand;  they  are  the  direct  antagonists  of  the  pronator  and  flexor  muscles.  The 
Anconeus  assists  the  Triceps  in  extending  the  forearm.  The  chief  action  of  the 
Supinator  longus  is  that  of  a  flexor  of  the  elbow-joint,  but  in  addition  to  this  it 
may  act  both  as  a  supinator  or  a  pronator;  that  is  to  say,  if  the  forearm  is  forcibly 
pronated  it  will  act  as  a  supinator,  and  bring  the  bones  into  a  position  midway 
between  supination  and  pronation;  and  vice  versa,  if  the  arm  is  forcibly  supinated, 
it  will  act  as  a  pronator,  and  bring  the  bones  into  the  same  position,  midway 
between  supination  and  pronation.  The  action  of  the  muscle  is  therefore  to  throw 
the  forearm  and  hand  into  the  position  they  naturally  occcupy  when  placed  across 
the  chest.  The  Supinator  brevis  is  a  supinator;  that  is  to  say,  when  the  radius 
has  been  carried  across  the  ulna  in  pronation  and  the  back  of  the  hand  is  directed 
forward,  this  muscle  carries  the  radius  back  again  to  its  normal  position  on  the 
outer  side  of  the  ulna,  and  the  palm  of  the  hand  is  again  directed  forward.  The 
Extensor  carpi  radialis  longior  extends  the  wrist  and  abducts  the  hand.  It  may 
also  assist  in  bending  the  elbow-joint;  at  all  events,  it  serves  to  fix  or  steady  this 
articulation.  The  Extensor  carpi  radialis  brevior  assists  the  Extensor  carpi 
radialis  longior  in  extending  the  wrist,  and  may  also  act  slightly  as  an  abductor  of 
the  hand.  The  Extensor  carpi  ulnaris  helps  to  extend  the  hand,  but  when  acting 
alone  inclines  it  toward  the  ulnar  side;  by  its  continued  action  it  extends  the 
elbow-joint.  The  Extensor  communis  digitorum  extends  the  phalanges,  then  the 
wrist,  and  finally  the  elbow.  It  acts  principally  on  the  proximal  phalanges,  the 
middle  and  terminal  phalanges  being  extended  by  the  Interossei  and  Lumbri- 
cales.  It  has  also  a  tendency  to  separate  the  fingers  as  it  extends  them.  The 
Extensor  minimi  digiti  extends  similarly  the  little  finger,  and  by  its  continued 
action  it  assists  in  extending  the  wrist.  It  is  owing  to  this  muscle  that  the  little 
finger  can  be  extended  or  pointed  whilst  the  others  are  flexed.  The  chief  action  of 
the  Extensor  ossis  metacarpi  pollicis  is  to  carry  the  thumb  outward  and  backward 
from  the  palm  of  the  hand,  and  hence  it  has  been  called  the  abductor  pollicis  longus. 
By  its  continued  action  it  helps  to  extend  and  abduct  the  wrist.  The  Extensor 
brevis  pollicis  extends  the  proximal  phalanx  of  the  thumb.  By  its  continued 
action  it  helps  to  extend  and  abduct  the  wrist.  The  Extensor  longus  pollicis 
extends  the  terminal  phalanx  of  the  thumb.  By  its  continued  action  it  helps  to 
extend  and  abduct  the  wrist.  The  Extensor  indicis  extends  the  index  finger,  and 


OF    THE   HAND 


493 


by  its  continued  action  assists  in  extending  the  wrist.    It  is  owing  to  this  muscle 
that  the  index  finger  can  be  extended  or  pointed  while  the  others  are  flexed. 

Surgical  Anatomy.— The  tendons  of  the  extensor  muscles  of  the  thumb  are  liable  to  become 
strained  and  their  sheaths  inflamed  after  excessive  exercise,  producing  a  sausage-shaped  swell- 
ing along  the  course  of  the  tendon,  and  giving  a  peculiar  creaking  sensation  to  the  finger  when 
the  muscle  acts.  In  consequence  of  its  often  being  caused  by  such  movements  as  wringing 
clothes,  it  is  known  as  washerwoman's  sprain.  In  piano-players  the  slips  which  join  the  ten- 
dons of  the  Extensor  communis  digitorum  may  limit  freedom  of  motion  in  individual  fingers. 
"  When  the  middle  finger  and  little  finger  of  the  hand  are  brought  down  by  the  flexor  muscles, 
and  their  balls  are  held  down  firmly  against  the  keys  of  a  musical  instrument,  as  in  perform- 
ing on  a  piano  for  the  purpose  of  producing  continuous  sounds,  and  when  at  the  same  time  , 
it  is  necessary  to  extend  and  then  to  flex  the  ring-finger  in  order  to  produce  accompanying 
sounds,  it  will  be  found  that  in  the  still-flexed  position  of  the  middle  and  little  fingers,  the 
rim/  fitiyer  can  be  but  very  slightly  extended.  Its  complete  extension,  without  operative  inter- 
ference, can  only  be  brought  about  by  long-continued  exertion  in  practice,  when  elongation 
of  certain  accessory,  but  restricting,  tendons  is  made  by  nutritive  growth."1  If  there  is  much 
limitation  division  of  the  hindering  slips  is  proper.  This  was  suggested  by  Prof.  William  S. 
Forbes  in  1857. 

IV.  MUSCLES  AND  FASCI-ffi  OF  THE  HAND. 

The  muscles  of  the  hand  are  subdivided  into  three  groups:  1.  Those  of  the 
thumb,  which  occupy  the  radial  side  and  produce  the  thenar  eminence.  2.  Those 
of  the  little  finger,  which  occupy  the  ulnar  side  and  give  rise  to  the  hypothenar 
eminence.  3.  Those  in  the  middle  of  the  palm  and  within  the  interosseous  spaces. 

Dissection  (Fig.  311). — Make  a  transverse  incision  across  the  front  of  the  wrist,  and  a 
second  across  the  heads  of  the  metacarpal  bones:  connect  the  two  by  a  vertical  incision  in  the 
middle  line,  and  continue  it  through  the  centre  of  the  middle  finger.  The  anterior  and  poste- 
rior annular  ligaments  and  the  palmar  fascia  should  then  be  dissected. 


ANTERIOR 
ANNULAR 
LIGAMENT, 


FLEXOR    LONGUS    POLLICIS. 
FLEXOR    CARPI     RADIALIS. 
MUSCLES    OF   THUMB 


1st  Metacarpal 


EXT.    PRIM 

INTERNOD. 

POLL. 

EXT.    SEC. 

INTERNOO. 

POLL. 

Trapezium^ 

Radial  vessels. 

EXT.    CARP.    RAD.    LONG 

Trupezoid. 

EXTENSOR   CARPI    RADIALIS 
DREVIOR. 


,Median  nerve. 
JJlnar  vessels. 

ALMARIS    BREVIS. 

MUSCLES   OF 
LITTLE 
FINGER. 


EXT.    CARPI 
ULNARIS. 


XTENSOR 

INIMI 
DIGIT). 
EXTENSOR 
COMMUNIS 
DIGITORUM. 
EXTENSOR    INDICIS. 


On  magnum. 


FIG.  323. — Transverse  section  through  the  carpus,  showing  the  relative  positions  of  the  tendons,  vessels, 

and  nerves.     (Henle.) 

The  Ligamentum  Carpi  Volare  is  a  thickening  of  the  deep  fascia  of  the  forearm 
(fascia  antibrachii)  by  deep  fibres  just  above  the  wrist  (Fig.  328).  It  covers  the 
flexor  muscles  and  joins  the  anterior  annular  ligament. 

The  Anterior  Annular  Ligament  (ligamentum  carpi  transversum)  (Fig.  323)  is  a 
strong,  fibrous  band  which  arches  over  the  carpus,  converting  the  deep  groove 
on  the  front  of  the  carpal  bones  into  a  canal,  beneath  which  pass  the  flexor 
tendons  of  the  fingers.  It  is  attached,  internally,  to  the  pisiform  bone  and 


1  Prof.  William  S.  Forbes  in  the  Philadelphia  Medical  Journal,  January  15,  1898. 


494 


THE   MUSCLES   AND    FASCIAE 


the  hook  of  the  unciform  bone  (eminentia  carpi  ulnaris),  and  externally  to  the 
tuberosity  of  the  scaphoid  and  to  the  inner  part  of  the  anterior  surface  and 
the  ridge  of  the  trapezium  (eminentia  carpi  radialis).  It  is  continuous,  above, 
with  the  deep  fascia  of  the  forearm,  of  which  it  may  be  regarded  as  a  thickened 
portion,  and,  below,  with  the  palmar  fascia.  It  is  crossed  by  the  ulnar  vessels  and 
nerve  and  the  cutaneous  branches  of  the  median  and  ulnar  nerves.  At  its  outer 
extremity  is  the  tendon  of  the  Flexor  carpi  radialis,  which  lies  in  the  groove  on  the 

trapezium  between  the  attachments  of 
the  annular  ligaments  to  the  bone.  It 
has  inserted  into  its  anterior  surface  a 
part  of  the  tendon  of  the  Palmaris  longus 
and  part  of  the  tendon  of  the  Flexor 
carpi  ulnaris,  and  has  arising  from  it, 
below,  the  small  muscles  of  the  thumb 
and  little  finger.  Beneath  it  pass  the 
tendons  of  the  Flexor  sublimis  and  Pro- 
fundus  digitorum,  the  Flexor  longus 
pollicis,  and  the  median  nerve. 

The  Synovial  Membranes  of  the  Flexor 
Tendons  at  the  Wrist. — There  are  two 
vaginal  synovial  membranes  which  en- 
close all  the  tendons  as  they  pass  be- 
neath this  ligament — one  for  the  Flexor 
sublimis  and  Profundus  digitorum,  the 
other  for  the  Flexor  longus  pollicis. 
They  extend  up  into  the  forearm  for 
about  an  inch  above  the  annular  liga- 
ment, and  downward  about  half-way 
along  the  metacarpal  bone,  where  they 
terminate  in  a  blind  diverticulum  around 
each  pair  of  tendons,  with  the  exception 
of  that  of  the  thumb  and  those  of  the 
little  finger — in  each  of  these  two  digits  the  diverticulum  is  continued  on,  and 
communicates  with  the  synovial  sheath  of  the  tendons  in  the  fingers.  In  the  other 
three  fingers  the  synovial  sheath  of  the  tendons  begins  as  a  blind  pouch  without 
communication  with  the  large  synovial  sac  (Fig.  324). 

Surgical  Anatomy. — This  arrangement  of  the  synovial  sheaths  explains  the  fact  that  thecal 
abscess  in  the  thumb  and  little  finger  is  liable  to  be  followed  by  abscesses  in  the  forearm,  from 
extension  of  the  inflammation  along  the  continuous  synovial  sheaths.  Tuberculous  inflamma- 
tion is  apt  to  occur  in  this  situation,  constituting  compound  palmar  ganglion ;  it  presents  an  hour- 
glass outline,  with  a  swelling  in  front  of  the  wrist  and  in  the  palm  of  the  hand,  and  a  constriction 
corresponding  to  the  annular  ligament  between  the  two.  The  fluid  can  be  forced  from  the  one 
swelling  to  the  other  under  the  ligament. 

Bursae  about  the  Hand  and  Wrist. — Bursse  usually  exist  between  the  distal 
extremities  of  the  metacarpal  bones  (bursae  intermetacarpophalangeae),  and  a  sub- 
cutaneous bursa  often  exists  over  the  dorsal  surface  of  the  head  of  the  fifth 
metacarpal  bone.  Subcutaneous  digital  dorsal  bursae  occur  "almost  constantly 
in  the  first  finger-joints  (between  the  first  and  second  phalanx),  occasionally  in 
the  second  joint  of  the  second  and  fourth  fingers"1  (bursae  subcutaneae  digitorum 
dorsales).  A  bursa  exists  between  the  tendon  of  the  Extensor  carpi  radialis  brevior 
and  the  base  of  the  third  metacarpal  bone;  another  between  the  Flexor  carpi 
ulnaris  and  the  pisiform  bone ;  another  between  the  Flexor  carpi  radialis  and  the 
base  of  the  second  metacarpal  bone. 

1  Hand  Atlas  of  Human  Anatomy.     By  Werner  Spalteholz.     Translated  and  edited  by  Lewellys  F.  Barker. 


FIG.  324. — Diagram  showing  the  arrangement  of  the 
synovial  sheaths  of  the  palm  and  fingers. 


OF   THE  HAND  495 

The  Posterior  Annular  Ligament  (I ig amentum  carpi  dorsale)  is  a  strong  fibrous 
band  extending  obliquely  downward  and  inward  across  the  back  of  the  wrist,  and 
consisting  of  the  deep  fascia  of  the  back  of  the  forearm,  strengthened  by  the 
addition  of  some  transverse  fibres.  It  binds  down  the  extensor  tendons  in  their 
passage  to  the  fingers,  being  attached,  internally,  to  the  styloid  process  of  the  ulna, 
the  cuneiform  and  pisiform  bones;  externally,  to  the  margin  of  the  radius;  and,  in 
its  passage  across  the  wrist,  to  the  elevated  ridges  on  the  posterior  surface  of  the 
radius.  It  presents  six  compartments  for  the  passage  of  tendons,  each  of  which  is 
lined  by  a  separate  synovial  membrane 
(Fig.  325).  These  are,  from  without 
inward:  1.  On  the  outer  side  of  the 
styloid  process,  for  the  tendons  of  the 
Extensor  ossis  metacarpi  and  Extensor 
brevis  pollicis.  2.  Behind  the  styloid 
process,  for  the  tendons  of  the  Ex- 
tensor carpi  radialis  longior  and  bre- 
vior.  3.  About  the  middle  of  the 
posterior  surface  of  the  radius,  for  the 
tendon  of  the  Extensor  longus  pollicis. 
4.  To  the  inner  side  of  the  latter,  for 
the  tendons  of  the  Extensor  communis 

...  .     _  .      ,.    .  _          FIG.  325. — Transverse  section  through  the  wrist,  show- 

dlgltoriim    and     Extensor    mdlClS.       5.    ing  the  annular  ligaments  and  the  canals  for  the  passage 

Opposite   the    interval    between   the 

radius  and  ulna,  for  the  Extensor  minimi  digiti.     6.  Grooving  the  back  of  the 

ulna,  for  the  tendon  of  the  Extensor  carpi  ulnaris.     The  synovial   membranes 

lining  these  sheaths  are  usually  very  extensive,  reaching  from  above  the  annular 

ligament  down  upon  the  tendons  for  a  variable  distance  on  the  back  of  the 

hand. 

The  Deep  Palmar  Fascia  (aponeurosis  palmaris). — The  deep  palmar  fascia 
(Fig.  326)  forms  a  common  sheath  which  invests  the  muscles  of  the  hand. 
It  consists  of  a  central  and  two  lateral  portions. 

The  Central  Portion  occupies  the  middle  of  the  palm,  is  triangular  in  shape,  of 
great  strength  and  thickness,  and  binds  down  the  tendons  and  protects  the  vessels 
and  nerves  in  this  situation.  It  is  narrow  above,  where  it  is  attached  to  the  lower 
margin  of  the  annular  ligament,  and  receives  the  expanded  tendon  of  the  Pal- 
maris longus  muscle.  Below,  it  is  broad  and  expanded,  and  divides  into  four 
slips  for  the  four  fingers.  Each  slip  gives  off  superficial  fibres,  which  are  inserted 
into  the  skin  of  the  palm  and  finger,  those  to  the  palm  joining  the  skin  at  the 
furrow  corresponding  to  the  metacarpo-phalangeal  articulation,  and  those  to  the 
fingers  passing  into  the  skin  at  the  transverse  fold  at  the  base  of  the  fingers.  The 
deeper  part  of  each  slip  subdivides  into  two  processes,  which  are  inserted  into  the 
lateral  margins  of  the  anterior  (glenoid)  ligament  of  the  metacarpo-phalangeal 
joint.  From  the  sides  of  these  processes  offsets  are  sent  backward,  to  be  attached 
to  the  borders  of  the  lateral  surfaces  of  the  metacarpal  bones  at  their  distal  extrem- 
ities. By  this  arrangement  short  channels  are  formed  on  the  front  of  the  lower 
ends  of  the  metacarpal  bones,  through  which  the  flexor  tendons  pass.  Dr.  W.  W. 
Keen  describes  a  fifth  slip  as  frequently  found  passing  to  the  thumb.  The  inter- 
vals left  in  the  fascia  between  the  four  fibrous  slips  transmit  the  digital  vessels 
•and  nerves  and  the  tendons  of  the  Lumbricales.  At  the  points  of  division  of  the 
palmar  fascia  into  the  slips  above  mentioned  numerous  strong,  transverse  fibres 
bind  the  separate  processes  together.  The  palmar  fascia  is  intimately  adherent 
to  the  integument  by  dense  fibro-areolar  tissue,  forming  the  superficial  palmar 
fascia,  and  gives  origin  by  its  inner  margin  to  the  Palmaris  brevis:  it  covers  the 
superficial  palmar  arch,  the  tendons  of  the  flexor  muscles,  and  the  branches  of 


496 


THE  MUSCLES  AND    FASCIA 


the  median  and  ulnar  nerves,  and  on  each  side  it  gives  off  a  vertical  septum,  which 
is  continuous  with  the  interosseous  aponeurosis  and  separates  the  lateral  from 
the  middle  palmar  group  of  muscles. 

The  Lateral  Portions  of  the  Palmar  Fascia  are  thin,  fibrous  layers,  which  cover, 
on  the  radial  side,  the  muscles  of  the  ball  of  the  thumb,  and,  on  the  ulnar  side,  the 
muscles  of  the  little  finger;  they  are  continuous  with  the  dorsal  fascia,  and  in  the 
palm  with  the  central  portion  of  the  palmar  fascia. 


Digital  artery 
Digital  nerves. 


FIG.  326.  —Palmar  fascia.     (From  a  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 

The  Superficial  Transverse  Ligament  of  the  Fingers  is  a  thin,  fibrous  band  which 
stretches  across  the  roots  of  the  four  fingers,  and  is  closely  attached  to  the  skin 
of  the  clefts,  and  internally  to  the  fifth  metacarpal  bone,  forming  a  sort  of  rudi- 
mentary web.  Beneath  it  the  digital  vessels  and  nerves  pass  onward  to  their 
destination. 

Surgical  Anatomy. — The  palmar  fascia  is  liable  to  undergo  contraction,  producing  a  very 
inconvenient  deformity  known  as  Dupuytreris  contraction.  The  ring  and  little  fingers  are  most 
frequently  implicated,  but  the  middle,  index,  and  the  thumb  may  be  involved.  The  proximal 
phalanx  is  drawn  down  and  cannot  be  straightened,  and  the  two  distal  phalanges  become  simi- 
larly flexed  as  the  disease  advances. 


THE  RADIAL  REGION 
11.  The  Radial  Region  (Figs.  327,  328). 


497 


Abductor  pollicis. 
Opponens  pollicis. 


Adductor  transversus  pollicis. 


Flexor  brevis  pollicis. 
Adductor  obliquus  pollicis. 


The  Abductor  Pollicis  (m.  abductor  pollicis  brevis}  (Fig.  328)  is  a  thin,  flat 
muscle,  placed  immediately  beneath  the  integument.  It  arises  from  the  anterior 
annular  ligament,  the  tuberosity  of  the  scaphoid,  and  the  ridge  of  the  trapezium, 


FIG.  327. — Adductor  pollicis,  Opponens  pollicis,  and  Pronator  quadratus.      (Testut.) 

frequently  by  two  distinct  slips;  and,  passing  outward  and  downward,  is  inserted 
by  a  thin,  flat  tendon  into  the  radial  side  of  the  base  of  the  first  phalanx  of  the 
thumb,  sending  a  slip  to  join  the  tendon  of  the  Extensor  longus  pollicis. 

32 


498 


THE    MUSCLES  AND    FASCIAE 


Relations. — By  its  superficial  surface,  with  the  palmar  fascia  and  superficial 
volae  artery,  which  frequently  perforates  it.  By  its  deep  surface,  with  the  Opponens 
pollicis,  from  which  it  is  separated  by  a  thin  aponeurosis.  Its  inner  border  is 
separated  from  the  Flexor  brevis  pollicis  by  a  narrow  cellular  interval. 


FIG.  328. — Muscles  of  the  left  hand.     Palmar  surface. 

The  Opponens  Pollicis  (Figs.  327  and  328),  often  called  the  flexor  ossis  meta- 
carpi  pollicis,  is  a  small,  triangular  muscle,  placed  beneath  the  preceding.  It  arises 
from  the  palmar  surface  of  the  ridge  on  the  trapezium  and  from  the  annular 
ligament,  passes  downward  and  outward,  and  is  inserted  into  the  whole  length  of 
the  metacarpal  bone  of  the  thumb  on  its  radial  side. 


THE   RADIAL    REGION  499 

Relations. — By  its  superficial  surface,  with  the  Abductor  and  Flexor  brevis 
pollicis.     By  its  deep  surface,  with  the  trapezio-metacarpal  articulation.     By  its 
'inner  border,  with  the  Adductor  obliquus  pollicis. 

The  Flexor  Brevis  Pollicis  (m.  flexor  pollicis  brevis)  (Fig.  328)  consists  of  two 
portions,  outer  and  inner.  The  outer  and  more  superficial  portion  arises  from  the 
outer  two-thirds  of  the  lower  border  of  the  anterior  annular  ligament,  and  passes 
along  the  outer  side  of  the  tendon  of  the  Flexor  longus  pollicis;  and,  becoming 
tendinous,  has  a  sesamoid  bone  developed  in  its  tendon,  and  is  inserted  into- the 
outer  side  of  the  base  of  the  first  phalanx  of  the  thumb.  The  inner  and  deeper 
portion  of  the  muscle  is  very  small,  and  arises  from  the  ulnar  side  of  the  first 
metacarpal  bone  beneath  the  Adductor  obliquus  pollicis,  and  is  inserted  into  the 
inner  side  of  the  base  of  the  first  phalanx  with  this  muscle. 

Relations. — By  its  superficial  surface,  with  the  palmar  fascia.  By  its  deep  sur- 
face, with  the  tendon  of  the  Flexor  longus  pollicis.  By  its  external  surface,  with 
the  Opponens  pollicis.  Behind,  with  the  Adductor  obliquus  pollicis. 

The  Adductor  Obliquus  Pollicis  (m.  adductor  pollicis)  (Figs.  327  and  328) 
arises  by  several  slips  from  the  os  magnum,  the  bases  of  the  second  and  third 
metacarpal  bones,  the  anterior  carpal  ligaments,  and  the  sheath  of  the  tendon 
of  the  Flexor  carpi  radialis.  From  this  origin  the  greater  number  of  fibres 
pass  obliquely  downward  and  converge  to  a  tendon,  which,  uniting  with  the 
tendons  of  the  deeper  portion  of  the  Flexor  brevis  pollicis  and  the  Adductor 
transversus,  is  inserted  into  the  inner  side  of  the  base  of  the  first  phalanx  of  the 
thumb,  a  sesamoid  bone  being  developed  in  the  tendon  of  insertion.  A  consid- 
erable fasciculus,  however,  passes  more  obliquely  outward  beneath  the  tendon 
of  the  long  flexor  to  join  the  superficial  portion  of  the  short  flexor  and  the 
Abductor  pollicis.1 

Relations. — By  its  superficial  surface,  with  the  Flexor  longus  pollicis  and  the 
outer  head  of  the  Flexor  brevis  pollicis.  Its  deep  surface  is  in  relation  with  the 
deep  palmar  arch,  which  passes  between  the  two  adductors. 

The  Adductor  Transversus  Pollicis  (Figs.  327  and  328)  is  the  most  deeply 
seated  of  this  group  of  muscles.  It  is  of  a  triangular  form,  arising,  by  its  broad 
base,  from  the  lower  two-thirds  of  the  metacarpal  bone  of  the  middle  finger  on 
its  palmar  surface;  the  fibres,  proceeding  outward,  converge  to  be  inserted,  with 
the  inner  part  of  the  Flexor  brevis  pollicis,  and  the  Adductor  obliquus  pollicis, 
into  the  ulnar  side  of  the  base  of  the  first  phalanx  of  the  thumb.  From  the 
common  tendon  of  insertion  a  slip  is  prolonged  to  the  Extensor  longus  pollicis. 
The  name  adductor  pollicis  is  frequently  used  to  mean  both  of  the  adductors 
(Figs.  .327  and  328). 

Relations. — By  its  superficial  surface,  with  the  Adductor  obliquus  pollicis,  the 
tendons  of  the  Flexor  profundus,  and  the  Lumbricales.  Its  deep  surface  covers 
the  first  two  interosseous  spaces,  from  which  it  is  separated  by  a  strong  aponeu- 
rosis. 

Three  of  these  muscles  of  the  thumb,  the  Abductor,  the  Adductor  transversus, 
and  the  Flexor  brevis  pollicis,  at  their  insertions  give  off  fibrous  expansions  which 
join  the  tendon  of  the  Extensor  longus  pollicis.  This  permits  of  flexion  of  the 
proximal  phalanx  and  extension  of  the  terminal  phalanx  at  the  same  time.  These 
expansions,  originally  figured  by  Albinus,  have  been  more  recently  described  by 
M.  Duchenne.2 

Nerves. — The  Abductor,  Opponens,  and  outer  head  of  the  Flexor  brevis  pollicis 
are  supplied  by  the  sixth  cervical  through  the  median  nerve;  the  inner  head  of  the 
Flexor  brevis,  and  the  Adductors,  by  the  eighth  cervical  through  the  ulnar  nerve. 

1  This  muscle  is  described  by  some  as  the  deep  portion  of  the  Flexor  brevis  pollicis. 

2  Physiologic  des  Mouvements. 


500  THE  MUSCLES  AND   FASCIA 

Actions. — The  actions  of  the  muscles  of  the  thumb  are  almost  sufficiently  indi- 
cated by  their  names.  This  segment  of  the  hand  is  provided  with  three  extensors 
— an  extensor  of  the  metacarpal  bone,  an  extensor  of  the  first,  and  an  extensor  of 
the  second  phalanx;  these  occupy  the  dorsal  surface  of  the  forearm  and  hand. 
There  are  also  three  flexors  on  the  palmar  surface — a  flexor  of  the  metacarpal 
bone,  a  flexor  of  the  proximal,  and  a  flexor  of  the  terminal  phalanx;  there  is  also 
an  Abductor  and  two  Adductors.  The  Abductor  pollicis  moves  the  metacarpal 
bone  of  the  thumb  outward;  that  is,  away  from  the  index  finger.  The  Flexor 
ossis  metacarpi  pollicis  flexes  the  metacarpal  bone — that  is,  draws  it  inward  over 
the  palm — and  at  the  same  time  rotates  the  bone,  so  as  to  turn  the  ball  of  the 
thumb  toward  the  fingers,  thus  producing  the  movement  of  opposition.  The 
Flexor  brevis  pollicis  flexes  and  adducts  the  proximal  phalanx  of  the  thumb.  The 
Adductores  pollicis  move  the  metacarpal  bone  of  the  thumb  inward;  that  is, 
toward  the  index  finger.  These  muscles  give  to  the  thumb  its  extensive  range  of 
motion.  It  will  be  noticed,  however,  that  in  consequence  of  the  position  of  the 
first  metacarpal  bone,  these  movements  differ  from  the  corresponding  movements 
of  the  metacarpal  bones  of  the  other  fingers.  Thus  extension  of  the  thumb  more 
nearly  corresponds  to  the  motion  of  abduction  in  the  other  fingers,  and  flexion  to 
adduction. 

12.  The  Ulnar  Region  (Fig.  328). 

Palmaris  brevis.  Flexor  brevis  minimi  digiti. 

Abductor  minimi  digiti.  Opponens  minimi  digiti. 

The  Palmaris  Brevis  is  a  thin  quadrilateral  muscle  placed  beneath  the  integu- 
ment on  the  ulnar  side  of  the  hand.  It  arises  by  tendinous  fasciculi  from  the 
anterior  annular  ligament  and  palmar  fascia;  the  fleshy  fibres  pass  inward,  to  be 
inserted  into  the  skin  on  the  inner  border  of  the  palm  of  the  hand. 

Relations. — By  its  superficial  surface,  with  the  integument,  to  which  it  is  inti- 
mately adherent,  especially  by  its  inner  extremity;  by  its  deep  surface,  with  the 
inner  portion  of  the  palmar  fascia,  which  separates  it  from  the  ulnar  vessels  and 
nerve,  and  from  the  muscles  of  the  ulnar  side  of  the  hand. 

The  Abductor  Minimi  Digiti  (m.  abductor  digiti  quinti)  is  situated  on  the  ulnar 
border  of  the  palm  of  the  hand.  It  arises  from  the  pisiform  bone  and  from  the 
tendon  of  the  Flexor  carpi  ulnaris,  and  terminates  in  a  flat  tendon,  which  divides 
into  two  slips;  one  is  inserted  into  the  ulnar  side  of  the  base  of  the  first  phalanx 
of  the  little  finger.  The  other  slip  is  inserted  into  the  ulnar  border  of  the  aponeu- 
rosis  of  the  Extensor  minimi  digiti. 

Relations. — By  its  superficial  surface,  with  the  inner  portion  of  the  palmar  fascia 
and  the  Palmaris  brevis ;  by  its  deep  surface,  with  the  Opponens  minimi  digiti ; 
by  its  outer  border,  with  the  Flexor  brevis  minimi  digiti. 

The  Flexor  Brevis  Minimi  Digiti  (m.  fiexor  digiti  quinti  brevis)  lies  on  the  same 
plane  as  the  preceding  muscle,  on  its  radial  side.  It  arises  from  the  convex  aspect 
of  the  hook  of  the  unciform  bone  and  anterior  surface  of  the  annular  ligament, 
and  is  inserted  into  the  inner  side  of  the  base  of  the  first  phalanx  of  the  little  finger. 
It  is  separated  from  the  Abductor  at  its  origin  by  the  deep  branches  of  the  ulnar 
artery  and  nerve.  This  muscle  is  sometimes  wanting;  the  Abductor  is  then, 
usually,  of  large  size. 

Relations. — By  its  superficial  surface,  with  the  internal  portion  of  the  palmar 
fascia  and  the  Palmaris  brevis;  by  its  deep  surface,  with  the  Opponens.  The  deep 
branch  of  the  ulnar  artery  and  the  corresponding  branch  of  the  ulnar  nerve  pass 
between  the  Abductor  and  Flexor  brevis  minimi  digiti  muscles. 

The  Opponens  Minimi  Digiti  (m.  opponens  digiti  quinti). — This  muscle  is 
sometimes  called  the  flexor  ossis  metacarpi  (Fig.  318),  is  of  a  triangular  form,  and 
placed  immediately  beneath  the  preceding  muscles.  It  arises  from  the  convexity 


THE   MIDDLE   PALMAR    REGION 


501 


of  the  hook  of  the  unciform  bone  and  the  contiguous  portion  of  the  anterior 
annular  ligament;  its  fibres  pass  downward  and  inward,  to  be  inserted  into  the 
whole  length  of  the  metacarpal  bone  of  the  little  finger,  along  its  ulnar  margin. 

Relations. — By  its  superficial  surface,  with  the  Flexor  brevis  and  Abductor 
minimi  digiti;  by  its  deep  surface,  with  the  Interossei  muscles  in  the  fourth  meta- 
carpal space,  the  metacarpal  bone,  and  the  Flexor  tendons  of  the  little  finger. 

Nerves. — All  the  muscles  of  this  group  are  supplied  by  the  eighth  cervical  nerve 
through  the  ulnar  nerve. 

Actions. — The  Abductor  minimi  digiti  abducts  the  little  finger  from  the  middle 
line  of  the  hand.  It  corresponds  to  a  dorsal  interosseous  muscle.  It  also  assists 
in  flexing  the  proximal  phalanx  and  extending  the  second  and  third  phalanges. 
The  Flexor  brevis  minimi  digiti  abducts  the  little  finger  from  the  middle  line  of 
the  hand.  It  also  assists  in  flexing  the  proximal  phalanx.  The  Opponens  minimi 
digiti  draws  forward  the  fifth  metacarpal  bone,  so  as  to  deepen  the  hollow  of  the 
palm.  The  Palmaris  brevis  corrugates  the  skin  on  the  inner  side  of  the  palm  of 
the  hand  and  probably  serves  to  protect  the  ulnar  nerve  and  artery  from  damage 
by  the  pressure  of  grasping  a  hard  object. 

13.  The  Middle  Palmar  Region. 

Lumbricales.  Interossei  dorsales. 

Interossei  palmares. 

The  Lumbricales  (Fig.  328)  are  four  small  fleshy  fasciculi,  accessories  to  the 
deep  Flexor  muscle.  They  arise  from  the  tendons  of  the  deep  Flexor:  the  first  and 
second,  from  the  radial  side  and  palmar  surface  of  the  tendons  of  the  index  and 
middle  fingers  respectively;  the  third,  from  the  contiguous  sides  of  the  tendons  of 
the  middle  and  ring  fingers;  and  the  fourth,  from  the  contiguous  sides  of  the 
tendons  of  the  ring  and  little  fingers.  They  pass  to  the  radial  side  of  the  corre- 
sponding fingers  and  opposite  the  metacarpo-phalangeal  articulation  each  tendon 
is  inserted  into  the  tendinous  expansion  of  the  Extensor  communis  digitorum, 
covering  the  dorsal  aspect  of  each  finger. 

The  Interossei  Muscles  (Figs.  329  and  330)  are  so  named  from  occupying 
the  intervals  between  the  metacarpal  bones,  and  are  divided  into  two  sets,  dorsal 
and  palmar. 

The  Dorsal  interossei  (mm.  interossei  dorsales}  are  four  in  number,  larger  than  the 
palmar,  and  occupy  the  intervals  between  the  metacarpal  bones.  They  are  bipen- 
niform  muscles,  arising  by  two  heads  from  the  adjacent  sides  of  the  metacarpal 
bones,  but  more  extensively  from  the  metacarpal  bone  of  the  finger  into  which  the 
muscle  is  inserted.  They  are  inserted  into  the  bases  of  the  first  phalanges  and  into 
the  aponeurosis  of  the  common  Extensor  tendon.  Between  the  double  origin  of 
each  of  these  muscles  is  a  narrow  triangular  interval,  through  the  first  of  which 
passes  the  radial  artery;  through  each  of  the  other  three  passes  a  perforating 
branch  from  the  deep  palmar  arch. 

The  First  dorsal  interosseous  muscle  or  Abductor  indicis  is  larger  than  the 
others.  It  is  flat,  triangular  in  form,  and  arises  by  two  heads,  separated  by  a 
fibrous  arch,  for  the  passage  of  the  radial  artery  from  the  dorsum  to  the  palm  of 
the  hand.  The  outer  head  arises  from  the  upper  half  of  the  ulnar  border  of  the 
first  metacarpal  bone;  the  inner  head,  from  almost  the  entire  length  of  the  radial 
border  of  the  second  metacarpal  bone;  the  tendon  is  inserted  into  the  radial  side 
of  the  index  finger.  The  second  and  third  dorsal  interossei  are  inserted  into  the 
middle  finger,  the  former  into  its  radial,  the  latter  into  its  ulnar  side.  The  fourth 
is  inserted  into  the  ulnar  side  of  the  ring  finger. 

The  Palmar  interossei  (mm.  interossei  volares},  three  in  number,  are  smaller  than 
the  Dorsal,  and  placed  upon  the  palmar  surface  of  the  metacarpal  bones,  rather 


502 


THE   MUSCLES   AND    FASCIAE 


than  between  them.  Each  muscle  arises  from  the  entire  length  of  the  meta- 
carpal  bone  of  one  finger,  and  is  inserted  into  the  side  of  the  base  of  the  first 
phalanx  and  aponeurotic  expansion  of  the  common  extensor  tendon  of  the  same 
finger.  The  first  arises  from  the  ulnar  side  of  the  second  metacarpal  bone,  and 
is  inserted  into  the  same  side  of  the  first  phalanx  of  the  index  finger.  The  second 
arises  from  the  radial  side  of  the  fourth  metacarpal  bone,  and  is  inserted  into  the 


FIG.  329.— The  Dorsal  interossei  of  left  hand. 


FIG.  330. — The  Palmar  interossei  of  left  hand. 


same  side  of  the  ring  finger.  The  third  arises  from  the  radial  side  of  the  fifth 
metacarpal  bone,  and  is  inserted  into  the  same  side  of  the  little  finger.  From 
this  account  it  may  be  seen  that  each  finger  is  provided  with  two  Interosseous 
muscles,  with  the  exception  of  the  little  finger,  in  which  the  Abductor  muscle 
takes  the  place  of  one  of  the  pair. 

Nerves.— The  two  outer  Lumbricales  are  supplied  by  the  sixth  cervical  nerve, 
through  the  third  and  fourth  digital  branches  of  the  median  nerve:  the  two  inner 
Lumbricales  and  all  the  Interossei  are  supplied  by  the  eighth  cervical  nerve, 
through  the  deep  palmar  branch  of  the  ulnar  nerve.  Brooks  states  that  the  third 
lumbrical  received  a  twig  from  the  median  in  twelve  out  of  twenty-one  cases. 

Actions. — The  Palmar  interossei  muscles  adduct  the  fingers  to  an  imaginary 
line  drawn  longitudinally  through  the  centre  of  the  middle  finger;  and  the  Dorsal 
interossei  abduct  the  fingers  from  that  line.  In  addition  to  this,  the  Interossei,  in 
conjunction  with  the  Lumbricales,  flex  the  first  phalanges  at  the  metacarpo-phalan- 
geal  joints,  and  extend  the  second  and  third  phalanges  in  consequence  of  their 
insertion  into  the  expansion  of  .the  extensor  tendons.  The  Extensor  communis 
digitorum  is  believed  to  act  almost  entirely  on  the,  first  phalanges. 


SURFACE  FORM  OF  THE  UPPER  EXTREMITY. 

The  Pectoralis  major  muscle  largely  influences  surface  form  and  conceals  a  considerable  part 
oi  the  thoracic  wall  in  front.  Its  sternal  origin  presents  a  festooned  border  which  bounds  and 
determines  the  width  of  the  sternal  furrow.  Its  clavicular  origin  is  somewhat  depressed  and  flat- 
tened, and  between  the  two  portions  of  the  muscle  is  often  an  oblique  depression  which  differen- 
tiates the  one  from  the  other.  The  outer  margin  of  the  muscle  is  generally  well  marked  above, 
and  bounds  the  infradavicular  fossa,  a  triangular  interval  which  separates  the  Pectoralis  major 


SURFACE  FORM   OF  THE    UPPER   EXTREMITY  593 

from  the  Deltoid.  It  gradually  becomes  less  marked  as  it  approaches  the  tendon  of  insertion, 
and  becomes  more  closely  blended  with  the  Deltoid  muscle.  The  lower  border  of  the  Pectoralis 
m:i jor  forms  the  rounded  anterior  axillary  fold,  and  corresponds  with  the  direction  of  the  fifth  rib. 
The  Pectoralis  minor  muscle  influences  surface  form.  When  the  arm  is  raised  its  lowest  slip 
of  origin  produces  a  local  fulness  just  below  the  border  of  the  anterior  fold  of  the  axilla,  and  so 
serves  to  break  the  sharp  line  of  the  lower  border  of  the  Pectoralis  major  muscle,  which  is  pro- 
duced when  the  arm  is  in  this  position.  The  origin  of  the  Serratus  magnus  muscle  produces  a 
very  characteristic  surface  marking.  When  the  arm  is  raised  from  the  side  in  a  well-developed 
subject,  the  five  or  six  lower  serrations  are  plainly  discernible,  forming  a  zigzag  line,  caused  by 
the  series  of  digitations,  which  diminish  in  size  from  above  downward,  and  have  their  apices 
arranged  in  the  form  of  a  curve.  When  the  arm  is  lying  by  the  side,  the  first  serration  to 
appear,  at  the  lower  margin  of  the  Pectoralis  major,  is  the  one  attached  to  the  fifth  rib.  The 
Deltoid  muscle,  with  the  prominence  of  the  upper  extremity  of  the  humerus,  produces  the 
rounded  outline  of  the  shoulder.  It  is  rounder  and  fuller  in  front  than  behind,  where  it  presents 
a  somewhat  flattened  form.  Its  anterior  border,  above,  presents  a  rounded,  slightly  curved 
eminence,  which  bounds  externally  the  infraclavicular  fossa;  below,  it  is  closely  united  with  the 
Pectoralis  major.  Its  posterior  border  is  thin,  flattened,  and  scarcely  marked  above;  below,  it 
is  thicker  and  more  prominent.  When  the  muscle  is  in  action,  the  middle  portion  becomes 
irregular,  presenting  alternate  longitudinal  elevations  and  depressions,  the  elevations  correspond- 
ing to  the  fleshy  portions,  the  depressions  to  the  tendinous  intersections  of  the  muscle.  The 
insertion  of  the  Deltoid  is  marked  by  a  depression  on  the  outer  side  of  the  middle  of  the  arm. 
Of  the  scapular  muscles,  the  only  one  which  materially  influences  surface  form  is  the  Teres 
major,  which  assists  the  Latissimus  dorsi  in  forming  the  thick,  rounded  fold  of  the  posterior 
boundary  of  the  axilla.  When  the  arm  is  raised,  the  Coraco-brachialis  reveals  itself  as  a  long, 
narrow  elevation  which  emerges  'from  under  cover  of  the  anterior  fold  of  the  axilla  and  runs 
downward,  internal  to  the  shaft  of  the  humerus.  When  the  arm  is  hanging  by  the  side,  its 
front  and  inner  part  presents  the  prominence  of  the  Biceps,  bounded  on  either  side  by  an  inter- 
muscular  depression.  This  muscle  determines  the  contour  of  the  front  of  the  arm,  and  extends 
from  the  anterior  margin  of  the  axilla  to  the  bend  of  the  elbow.  Its  upper  tendons  are  con- 
cealed by  the  Pectoralis  major  and  the  Deltoid,  and  its  lower  tendon  sinks  into  the  space  at  the 
bend  of  the  elbow.  When  the  muscle  is  in  a  state  of  complete  contraction — that  is  to  say, 
when  the  forearm  has  been  flexed  and  supinated — it  presents  a  rounded  convex  form,  bulged 
out  laterally,  and  its  length  is  diminished.-  On  each  side  of  the  Biceps,  at  the  lower  part  of 
the  arm,  the  Brachialis  anticus  is  discernible.  On  the  outer  side  it  forms  a  narrow  eminence 
which  extends  some  distance  up  the  arm  along  the  border  of  the  Biceps.  On  the  inner  side  it 
shows  itself  only  as  a  little  fulness  just  above  the  elbow.  On  the  back  of  the  arm  the  long  head 
of  the  Triceps  may  be  seen  as  a  longitudinal  eminence  emerging  from  under  cover  of  the  Deltoid, 
and  gradually  merging  into  the  longitudinal  flattened  plane  of  the  tendon  of  the  muscle  on  the 
lower  part  of  the  back  of  the  arm.  The  tendon  of  insertion  of  the  muscle  extends  about  half- 
way up  the  back  of  the  arm,  where  it  forms  an  elongated  flattened  plane  when  the  muscle  is  in 
action.  Under  similar  conditions  the  surface  forms  produced  by  the  three  heads  of  the  muscle 
are  well  seen.  On  the  anterior  aspect  of  the  elbow  are  to  be  seen  two  muscular  elevations, 
one  on  each  side,  separated  above  and  converging  below  so  as  to  form  a  triangular  space. 
Of  these,  the  inner  elevation,  consisting  of  the  flexors  and  pronator,  forms  the  prominence 
along  the  inner  side  and  front  of  the  forearm.  It  is  a  fusiform  mass,  pointed  above  at  the 
internal  condyle  and  gradually  tapering  off  below.  The  Pronator  radii  teres,  the  innermost 
muscle  of  the  group,  forms  the  boundary  of  the  triangular  space  at  the  bend  of  the  elbow.  It 
is  shorter,  less  prominent,  and  more  oblique  than  the  outer  boundary.  The  most  prominent 
part  of  the  eminence  is  produced  by  the  Flexor  carpi  radialis,  the  muscle  next  in  order  on  the 
inner  side  of  the  preceding  one.  It  forms  a  rounded  prominence  above,  and  can  be  traced 
downward  to  its  tendon,  which  can  be  felt  lying  on  the  front  of  the  wrist,  nearer  to  the  radial 
than  to  the  ulnar  border,  and  to  the  inner  side  of  the  radial  artery.  The  Palmaris  longus  pre- 
sents no  surface  marking  above,  but  below  is  the  most  prominent  tendon  on  the  front  of  the 
wrist,  standing  out,  when  the  muscle  is  in  action,  as  a  sharp,  tense  cord  beneath  the  skin.  The 
Flexor  sublimis  digitorum  does  not  directly  influence  surface  form.  The  position  of  its  four 
tendons  on  the  front  of  the  lower  part  of  the  forearm  is  indicated  by  an  elongated  depression 
between  the  tendons  of  the  Palmaris  longus  and  the  Flexor  carpi  ulnaris.  The  Flexor  carpi 
ulnaris  occupies  a  small  part  of  the  posterior  surface  of  the  forearm,  and  is  separated  from  the 
extensor  and  supinator  group,  which  occupies  the  greater  part  of  this  surface,  by  the  ulnar 
furrow,  produced  by  the  subcutaneous  posterior  border  of  the  ulna.  Its  tendon  can  be  perceived 
along  the  ulnar  border  of  the  front  of  the  forearm,  and  is  most  marked  when  the  hand  is  flexed 
and  adducted.  The  deep  muscles  of  the  front  of  the  forearm  have  no  direct  influence  on  sur- 
face form.  The  external  group  of  muscles  of  the  forearm,  consisting  of  the  extensors  and  supi- 
nators,  occupy  the  outer  and  a  considerable  portion  of  the  posterior  surface  of  this  region.  It 
has  a  fusiform  outline,  which  is  altogether  on  a  higher  level  than  the  pronato-flexor  group.  Its 
apex  emerges  from  between  the  Triceps  and  Brachialis  anticus  muscles  some  distance  above  the 


504  THE  MUSCLES   AND    FASCIA 

elbow-joint,  and  acquires  its  greatest  breadth  opposite  the  external  condyle,  and  thence  gradually 
shades  off  into  a  flattened  surface.  About  the  middle  of  the  forearm  it  divides  into  two 
longitudinal  eminences  which  diverge  from  each  other,  leaving  a  triangular  interval  between 
them.  The  outer  of  these  two  groups  of  muscles  consists  of  the  Supinator  longus  and  the 
Extensor  carpi  radialis  longior  et  brevior,  which  form  a  longitudinal  eminence  descending  from 
the  external  condylar  ridge  in  the  direction  of  the  styloid  process  of  the  radius.  The  other  and 
more  posterior  group  consists  of  the  Extensor  communis  digitorum,  the  Extensor  minimi  digiti, 
and  the  Extensor  carpi  ulnaris.  It  commences  above  as  a  tapering  form  at  the  external  con- 
dyle of  the  humerus,  and  is  separated  behind  at  its  upper  part  from  the  Anconeus  by  a  well- 
marked  furrow,  and  below,  from  the  pronato-flexor  mass,  by  the  ulnar  furrow.  In  the  triangular 
interval  left  between  these  two  groups  the  extensors  of  the  thumb  and  index  finger  are  seen. 
The  only  two  muscles  of  this  region  which  require  special  mention  as  independently  influencing 
surface  form  are  the  Supinator  longus  and  the  Anconeus.  The  inner  border  of  the  Supinator 
longus  forms  the  outer  boundary  of  the  triangular  space  at  the  bend  of  the  elbow.  It  com- 
mences as  a  rounded  border  above  the  condyle,  and  is  longer,  less  oblique,  and  more  prominent 
than  the  inner  boundary.  Lower  down,  the  muscle  forms  a  full  fleshy  mass  on  the  outer  side  of 
the  upper  part  of  the  forearm,  and  below  tapers  into  a  tendon,  which  may  be  traced  down  to 
the  styloid  process  of  the  radius.  The  Anconeus  presents  a  well-marked  and  characteristic 
surface  form  in  the  shape  of  a  triangular,  slightly  elevated  surface,  immediately  external  to  the 
subcutaneous  posterior  surface  of  the  olecranon,  and  differentiated  from  the  common  extensor 
group  by  a  well-marked  oblique  longitudinal  depression.  The  upper  angle  of  the  triangle  corre- 
sponds to  the  external  condyle,  and  is  marked  by  a  depression  or  dimple  in  this  situation.  In 
the  interval  caused  by  the  divergence  from  each  other  of  the  two  groups  of  muscles  into  which 
the  extensor  and  supinator  group  is  divided  at  the  lower  part  of  the  forearm  an  oblique  elongated 
eminence  is  seen,  caused  by  the  emergence  of  two  of  the  extensors  of  the  thumb  from  their 
deep  origin  at  the  back  of  the  forearm.  This  eminence,  full  above  and  becoming  flattened 
out  and  partially  subdivided  below,  runs  downward  and  outward  over  the  back  and  outer  sur- 
face of  the  radius  to  the  outer  side  of  the  wrist-joint,  where  it  forms  a  ridge,  especially  marked 
when  the  thumb  is  extended,  which  passes  onward  to  the  posterior  aspect  of  the  thumb.  The 
tendons  of  most  of  the  extensor  muscles  are  to  be  seen  and  felt  at  the  level  of  the  wrist-joint. 
Most  externally  are  the  tendons  of  the  Extensor  ossis  metacarpi  pollicis  and  the  Extensor  brevis 
pollicis,  forming  a  vertical  ridge  over  the  outer  side  of  the  joint  from  the  styloid  process  of  the 
radius  to  the  thumb.  Internal  to  this  is  the  oblique-ridge  produced  by  the  tendon  of  the  Exten- 
sor longus  pollicis,  very  noticeable  when  the  muscle  is  in  action.  The  Extensor  carpi  radialis 
longior  is  scarcely  to  be  felt,  but  the  Extensor  carpi  radialis  brevior  can  be  distinctly  perceived 
as  a  vertical  ridge  emerging  from  under  the  inner  border  of  the  tendon  of  the  Extensor  longus 
pollicis,  when  the  hand  is  forcibly  extended  at  the  wrist.  Internal  to  this,  again,  can  be  felt 
the  tendons  of  the  Extensor  indicis,  Extensor  communis  digitorum,  and  Extensor  minimi  digiti; 
the  latter  tendon  being  separated  from  those  of  the  common  extensor  by  a  slight  furrow.  The 
muscles  of  the  hand  are  principally  concerned,  as  far  as  regards  surface-form,  in  producing 
the  thenar  and  hypothenar  eminences,  and  individually  are  not  to  be  distinguished,  on  the  sur- 
face, from  each  other.  The  Adductor  transversus  pollicis  is,  however,  an  exception  to  this; 
its  anterior  border  gives  rise  to  a  ridge  across  the  web  of  skin  connecting  the  thumb  to  the  rest 
of  the  hand.  The  thenar  eminence  is  much  larger  and  rounder  than  the  hypothenar  one,  which 
presents  a  longer  and  narrower  eminence  along  the  ulnar  side  of  the  hand.  When  the  Palmaris 
brevis  is  in  action  it  produces  a  wrinkling  of  the  skin  over  the  hypothenar  eminence,  and  a  deep 
dimple  on  the  ulnar  border  of  the  hand.  The  anterior  extremities  of  the  Lumbrical  muscles 
help  to  produce  the  soft  eminences  just  behind  the  clefts  of  the  fingers,  separated  from  each 
other  by  depressions  corresponding  to  the  flexor  tendons  in  their  sheaths.  Between  the  thenar 
and  hypothenar  eminences,  at  the  wrist-joint,  is  a  slight  groove  or  depression,  widening  out  as 
it  approaches  the  fingers;  beneath  this  we  have  the  strong  central  part  of  the  palmar  fascia. 
Here  we  have  some  furrows,  which  are  pretty  constant  in  their  arrangement,  and  bear  some 
resemblance  to  the  letter  M.  One  of  these  furrows  passes  obliquely  outward  from  the  groove 
between  the  thenar  and  hypothenar  regions  near  the  wrist  to  the  head  of  the  metacarpal  bone 
of  the  index  finger.  A  second  passes  inward,  with  a  slight  inclination  upward,  from  the  ter- 
mination of  the  first  to  the  ulnar  side  of  the  hand.  A  third  runs  nearly  parallel  with  the  second 
and  about  three-quarters  of  an  inch  below  it.  Lastly,  crossing  these  two  latter  furrows,  is  an 
oblique  furrow  parallel  with  the  first.  The  skin  of  the  palm  of  the  hand  differs  considerably 
from  that  of  the  forearm.  At  the  wrist  it  suddenly  becomes  hard  and  dense,  and  covered  with 
a  thick  layer  of  cuticle.  The  skin  in  the  thenar  region  presents  these  characteristics  less  than 
elsewhere.  In  spite  of  this  hardness  and  density,  the  skin  of  the  palm  is  exceedingly  sensitive 
and  very  vascular.  It  is  destitute  of  hair,  and  no  sebaceous  follicles  have  been  found  in  this 
region.  Over  the  fingers  the  skin  again  becomes  thinner,  especially  at  the  flexures  of  the  joints, 
and  over  the  terminal  phalanges  it  is  thrown  into  numerous  ridges  in  consequence  of  the  arrange- 
ment of  the  papilla?  in  it.  These  ridges  form,  in  different  individuals,  distinctive  and  permanent 
patterns,  which  may  be  used  for  purposes  of  identification.  The  superficial  fascia  in  the  palm 


SURGICAL   ANATOMY   OF    THE    UPPER    EXTREMITY        505 

is  made  up  of  dense  fibro-fatty  tissue.  This  tissue  binds  down  the  skin  so  firmly  to  the  deep 
palmar  fascia  that  verv  little  movement  is  permitted  between  the  two.  On  the  back  of  the  hand 
the  Dorsal  interossei  produce  elongated  swellings  between  the  metacarpal  bones.  The  first 
dorsal  interosseous  (Abductor  indicis),  when  the  thumb  is  closely  adducted  to  the  hand,  forms 
a  prominent  fusiform  bulging;  the  other  interossei  are  not  so  marked. 


SURGICAL  ANATOMY  OF  THE  UPPER  EXTREMITY. 

The  student,  having  completed  the  dissection  of  the  muscles  of  the  upper  extremity,  should 
consider  the  effects  likely  to  be  produced  by  the  action  of  the  various  muscles  in  fracture  of  the 
bones. 

In  considering  the  actions  of  the  various  muscles  upon  fractures  of  the  upper  extremity,  the 
most  common  forms  of  injury  have  been  selected  both  for  illustration  and  description. 

Fracture  of  the  middle  of  the  clavicle  (Fig.  331)  is  always  attended  with  considerable  dis- 
placement; the  inner  end  of  the  outer  fragment  is  displaced  inward  and  backward,  while  the 
outer  end  of  the  same  fragment  is  rotated  forward.  The  whole  outer  fragment  is  somewhat 
depressed.  The  deformity  is  described  by  saying  that  the  shoulder  goes  downward,  forward, 
and  inward. 

The  displacement  is  produced  as  follows:  inward,  by  the  muscles  passing  from  the  chest  to 
the  outer  fragment  of  the  clavicle,  to  the  scapula,  and  to  the-humerus — viz.,  the  Subclavius  and 
the  Pectoralis  minor,  and,  to  a  less  extent,  the  Pectoralis  major  and  the  Latissimus  dorsi;  back- 
ward, in  consequence  of  the  rotation  of  the  outer  fragment.  The  Serratus  magnus  causes  the 
scapula  to  rotate  on  the  wall  of  the  chest;  this  carries  the  acromion  and  outer  end  of  the  outer 
fragment  of  the  clavicle  forward  and  causes  the  piece  of  bone  to  rotate  round  a  vertical  axis 
through  its  centre,  and  so  carries  the  inner  end  of  the  outer  portion  backward.  The  depression 
of  the  whole  outer  fragment  is  produced  by  the  weight 
of  the  arm  and  by  the  contraction  of  the  Deltoid.  The 
outer  end  of  the  inner  fragment  appears  to  be  elevated, 
the  skin  being  drawn  tensely  over  it ;  this  is  owing  to 
the  depression  of  the  outer  fragment,  as  the  inner  frag- 
ment is  usually  kept  fixed  by  the  costo-clavicular  liga- 
ment and  by  the  antagonism  between  the  Sternomastoid 
and  Pectoralis  major  muscles.  But  it  may  be  raised  by 
an  unusually  strong  Sterno-mastoid,  or  by  the  inner  end 
of  the  outer  fragment  getting  below  and  behind  it.  The 
causes  of  displacement  having  been  ascertained,  it  is 
easy  to  apply  the  appropriate  treatment.  The  outer 
fragment  is  to  be  drawn  outward,  and,  together  with  the 
scapula,  raised  upward  to  a  level  with  the  inner  frag- 
ment, and  retained  in  that  position.  The  formula  for 
correcting  the  deformity  is  as  follows:  carry  the  shoulder 
upward,  outward,  and  backward. 

In  fracture  of  the  acromial  end  of  the  clavicle,  between 
the  conoid  and  trapezoid  ligaments,  only  slight  displace- 
ment occurs,  as  these  ligaments,  from  their  oblique  in- 
sertion, serve  to  hold  both  portions  of  the  bone  in  appo- 
sition. Fracture,  also,  of  the  sternal  end,  internal  to 
the  costoclavicular  ligament,  is  attended  with  only  slight 
displacement,  this  ligament  serving  to  retain  the  frag- 
ments in  close  apposition. 

Fracture  of  the  acromion  process  usually  arises  from 
violence  applied  to  the  upper  and  outer  part  of  the 
shoulder;  it  is  generally  known  by  the  rotundity  of  the 
shoulder  being  lost,  from  the  Deltoid  drawing  the  fractured  portion  downward  and  forward; 
and  .the  displacement  may  easily  be  discovered  by  tracing  the  margin  of  the  clavicle  outward, 
when  the  fragment  will  be  found  resting  on  the  front  and  upper  part  of  the  head  of  the 
humerus.  In  order  to  relax  the  anterior  and  outer  fibres  of  the  Deltoid  (the  opposing  muscle), 
the  arm  should  be  drawn  forward  across  the  chest  and  the  elbow  well  raised,  so  that  the  head 
of  the  bone  may  press  the  acromion  process  upward  and  retain  it  in  its  position. 

Fracture  of  the  coracoid  process  is  an  extremely  rare  accident,  and  is  usually  caused  by  a 
sharp  blow  on  the  point  of  the  shoulder.  Displacement  is  here  produced  by  the  combined 
actions  of  the  Pectoralis  minor,  short  head  of  the  Biceps,  and  Coraco-brachialis,  the  former 
muscle  drawing  the  fragment  inward,  and  the  latter  muscles  directly  downward,  the  amount  of 
displacement  being  limited  by  the  connection  of  this  process  to  the  acromion  by  means  of  the 
coraco-acromial  ligament.  In  many  cases  there  appears  to  have  been  little  or  no  displacement, 


FIG.  331. — Fracture  of  the  middle  of  the 
clavicle. 


506  THE   MUSCLES   AND    FASCIAE 

\ 

from  the  fact  that  the  coraco-clavicular  ligament  has  remained  intact,  and  has  kept  the  separated 
fragment  from  displacement.  In  order  to  relax  these  muscles  and  replace  the  fragments  in 
close  apposition,  the  forearm  should  be  flexed  so  as  to  relax  the  Biceps,  and  the  arm  drawn 
forward  and  inward  across  the  chest,  so  as  to  relax  the  Coraco-brachialis ;  the  humerus  should 
then  be  pushed  upward  against  the  coraco-acromial  ligament,  and  the  arm  retained  in  that 
position. 

Fracture  of  the  surgical  neck  of  the  humerus  (Fig.  332)  is  very  common,  is  attended  with 
considerable  displacement,  and  its  appearances  correspond  somewhat  with  those  of  dislocation 
of  the  head  of  the  humerus  into  the  axilla.  The  upper  fragment  is  slightly  elevated  under  the 
coraco-acromial  ligament  by  the  muscles  attached  to  the  greater  and  lesser  tuberosities ;  the 
lower  fragment  is  drawn  inward  by  the  Pectoralis  major,  Latissimus  dorsi,  and  Teres  major;  and 
the  humerus  is  thrown  obliquely  outward  from  the  side  by  the  Deltoid,  and  occasionally  elevated 

so  as  to  cause  the  upper  end  of  the  lower  fragment  to  project 
beneath  and  in  front  of  the  coracoid  process.  The  deformity 
is  reduced  by  fixing  the  shoulder,  and  drawing  the  arm  out- 
ward and  downward.  To  counteract  the  opposing  muscles, 
and  to  keep  the  fragments  in  position,  a  conical-shaped  pad 
should  be  placed  with  the  apex  in  the  axilla;  while  the  fore- 
arm is  flexed  to  an  angle  of  90  degrees  the  shoulder  is  padded 
with  cotton,  a  shoulder-cap  of  plaster-of-Paris  is  applied  to 
«over  the  shoulder,  a  portion  of  the  chest  and  back,  and  the 
arm  down  to  the  external  condyle  (Scudder).  The  arm,  with 
the  elbow  slightly  forward,  is  bandaged  to  the  side.  In  some 
cases  a  splint  is  placed  between  the  axillary  pad  and  the 
inner  side  of  the  arm. 

In  fracture  of  the  shaft  of  the  humerus  below  the  insertion 
of  the  Pectoralis  major,  Latissimus  dorsi,  and  Teres  major, 
and  above  the  insertion  of  the  Deltoid,  there  is  also  consider- 
able deformity,  the  upper  fragment  being  drawn  inward  by 
the  first-mentioned  muscles,  and  the  lower  fragment  upward 
and  outward  by  the  Deltoid,  producing  shortening  of  the  limb 
and  a  considerable  prominence  at  the  seat  of  fracture,  from 
4     FIG.  332. — Fracture  of  the  surgical      the  fractured  ends  of  the  bone  riding  over  one  another,  espe- 
neck  of  the  humerus.  cially  if  the  fracture  takes  place  in  an  oblique  direction.    The 

fragments  may  be  brought  into  apposition  by  extension  from 

the  elbow,  and  are  retained  in  that  position  by  adopting  the  same  means  as  in  the  preceding 
injury,  or  by  the  use  of  an  internal  angular  splint  with  three  short  humeral  splints. 

In  fractures  of  the  shaft  of  the  humerus  immediately  below  the  insertion  of  the  Deltoid,  the 
.amount  of  deformity  depends  greatly  upon  the  direction  of  the  fracture.  If  it  occurs  in  a  trans- 
verse direction,  only  slight  displacement  takes  place,  the  upper  fragment  being  drawn  a  little 
forward;  but  in  oblique  fracture  the  combined  actions  of  the  Biceps  and  Brachialis  anticus 
muscles  in  front  and  the  Triceps  behind  draw  upward  the  lower  fragment,  causing  it  to  glide 
over  the  upper  fragment,  either  backward  or  forward,  according  to  the  direction  of  the  fracture. 
Simple  extension  reduces  the  deformity,  and  the  application  of  an  internal  angular  splint  and 
three  short  humeral  splints  will  retain  the  fragments  in  apposition.  Care  should  be  taken  not 
to  raise  the  elbow,  but  the  forearm  and  hand  may  be  supported  in  a  sling. 

Fracture  of  the  humerus  (Fig.  333)  above  the  condyle  deserves  very  attentive  considera- 
tion, as  the  general  appearances  correspond  somewhat  with  those  produced  by  separation 
of  the  epiphysis  of  the  humerus,  and  with  those  of  dislocation  of  the  radius  and  ulna  back- 
ward. If  the  direction  of  the  fracture  is  oblique  from  above,  downward  and  forward,  the 
lower  fragment  is  drawn  upward  by  the  Brachialis  anticus  and  Biceps  in  front  and  the  Triceps 
behind;  and  at  the  same  time  is  drawn  backward  behind  the  upper  fragment  by  the  Triceps. 
This  injury  may  be  diagnosticated  from  dislocation  by  the  increased  mobility  in  fracture,  the 
existence  of  crepitus,  and  the  fact  of  the  deformity  being  remedied  by  extension,  on  the  discon- 
tinuance of  which  it  is  reproduced.  The  age  of  the  patient  is  of  importance  in  distinguishing 
this  form  of  injury  from  separation  of  the  epiphysis.  If  fracture  occurs  in  the  opposite  direc- 
tion to  that  shown  in  Fig.  333,  the  lower  fragment  is  drawn  upward  and  forward,  causing  a 
considerable  prominence  in  front,  and  the  upper  fragment  projects  backward  beneath  the 
tendon  of  the  Triceps  muscle. 

Fractures  of  the  lower  extremity  of  the  humerus  are  spoken  of  as  fractures  in  the  neighbor- 
hood of  the  elbow-joint.  The  term  includes  fracture  of  the  external  condyle,  of  the  internal  condyle, 
at  the  base  of  the  condyles,  and  T-  or  Y-shaped  fracture,  the  two  condyles  being  separated 
from  each  other  and  from  the  shaft  of  the  humerus.  Such  injuries  are  followed  by  great  and 
rapid  swelling.  Whenever  possible  the  a>rays  are  used  to  aid  in  diagnosis,  and  the  patient  is 
placed  under  ether,  to  set  and  dress  the  fracture. 

In  fracture  of  the  inner  condyle  the  fragment  with  the  ulna  passes  up  and  back,  and  when 


SURGICAL   ANATOMY   OF   THE    UPPER   EXTREMITY        507 

the  forearm  is  extended  the  ulna  projects  posteriorly.  The  "  carrying  function  "  of  the  arm  is 
lost,  because  the  forearm  deviates  to  the  ulnar  side. 

In  all  cases  of  fracture  of  the  lower  end  of  the  humerus,  except  fracture  at  the  base  of 
the  condyles,  effect  reduction  by  traction  upon  the  forearm,  and  supination,  extension,  and 
bending  the  forearm  slowly  into  acute  flexion.  In  transverse  fracture  above  the  condyles 
draw  the  forearm  and  the  lower  fragment  downward  and  forward  and  push  the  upper  frag- 
ment back.  A  case  can  be  treated  by  maintaining  a  position  of  acute  flexion  (Jones's  position) 
or  by  using  an  anterior  angular  splint.  Allis  and  others  treat  in  extension. 

Fracture  of  the  olecranon  process  (Fig.  334)  is  a  frequent  accident.  The  detached  fragment 
is  displaced  upward,  by  the  action  of  the  Triceps  muscle,  from  half  an  inch  to  two  inches;  the 
prominence  of  the  elbow  is  consequently  lost,  and  a  deep  hollow  is  felt  at  the  back  part  of  the 
joint,  which  is  much  increased  on  flexing  the  limb.  The  patient  at  the  same  time  loses,  more 
or  less,  the  power  of  extending  the  forearm.  The  treatment  consists  in  relaxing  the  Triceps  by 
extending  the  limb,  and  retaining  it  in  the  extended  position  by  means  of  a  long  straight  splint 
applied  to  the  front  of  the  arm ;  the  fragments  are  thus  brought  into  close  apposition,  and 
may  be  further  approximated  by  drawing  down  the  upper  fragment.  Union  is  generally 
ligamentous. 

Fracture  of  the  neck  of  the  radius  is  an  exceedingly  rare  accident,  and  is  generally  caused 
by  direct  violence.  Its  diagnosis  is  somewhat  obscure,  on  account  of  the  slight  deformity  visible, 
the  injured  part  being  surrounded  by  a  large  number  of  muscles;  but  the  movements  of  prona- 
tion  and  supination  are  entirely  lost.  The  upper  fragment  is  drawn  outward  by  the  Supinator 


FIG.  333. — Fracture  of  the  humerus  above  FIG.  334. — Fracture  of  the  olecranon. 

the  condyles. 

brevis,  the  extent  of  displacement  being  limited  by  the  attachment  of  the  orbicular  ligament. 
The  lower  fragment  is  drawn  forward  and  slightly  upward  by  the  Biceps,  and  inward  by  the 
Pronator  radii  teres,  its  displacement  forward  and  upward  being  counteracted  in  some  degree 
by  the  Supinator  brevis.  The  treatment  essentially  consists  in  relaxing  the  Biceps,  Supinator 
brevis,  and  Pronator  radii  teres  muscles  by  flexing  the  forearm,  and  placing  it  in  a  position  mid- 
way between  pronation  and  supination,  extension  having  been  previously  made  so  as  to  bring 
the  parts  i">.  apposition. 

In  fracture  of  the  radius  below  the  insertion  of  the  Biceps,  but  above  the  insertion  of  the 
Pronator  radii  teres,  the  upper  fragment  is  strongly  supinated  by  the  Biceps  and  Supinator 
brevis,  and  at  the  same  time  drawn  forward  and  flexed  by  the  Biceps;  the  lower  fragment  is 
pronated  and  drawn  inward  toward  the  ulna  by  the  pronators.  Thus  there  is  extreme  dis- 
placement with  very  little  deformity.  In  treating  such  a  fracture  the  arm  must  be  put  up  in 
a  position  of  supination,  otherwise  union  will  take  place  with  great  impairment  of  the  move- 
ments of  the  hand.  In  fractures  of  the  radius  below  the  insertion  of  the  Pronator  radii  teres 
(Fig.  335),  the  upper  fragment  is  drawn  upward  by  the  Biceps  and  inward  by  the  Pronator 
radii  teres,  holding  a  position  midway  between  pronation  and  supination,  and  a  degree  of  fulness 
in  the  upper  half  of  the  forearm  is  thus  produced ;  the  lower  fragment  is  drawn  downward  and 
inward  toward  the  ulna  by  the  Pronator  quadratus,  and  thrown  into  a  state  of  pronation  by  the 
same  muscle;  at  the  same  time,  the  Supinator  longus,  by  elevating  the  styloid  process,  into  which 


508 


THE   MUSCLES   AND    FASCIA 


it  is  inserted,  will  serve  to  depress  the  upper  end  of  the  lower  fragment  still  more  toward  the  ulna. 
In  order  to  relax  the  opposing  muscles  the  forearm  should  be  bent,  and  the  limb  placed  in  a 
position  midway  between  pronation  and  supination;  the  fracture  is  then  easily  reduced  by 
extension  from  the  wrist  and  elbow:  well-padded  splints  should  be  applied  on  both  sides  of 
the  forearm  from  the  elbow  to  the  wrist;  the  hand  being  allowed  to  fall,  will,  by  its  own  weight, 
counteract  the  action  of  the  Pronator  quadratus  and  Supinator  longus,  and  elevate  the-  lower 
fragment  to  the  level  of  the  upper  one. 

In  fracture  of  the  shaft  of  the  ulna  the  upper  fragment  retains  its  usual  position,  but  the 
lower  fragment  is  drawn  outward  toward  the  radius  by  the  Pronator  quadratus,  producing  a 
well-marked  depression  at  the  seat  of  fracture  and  some  fulness  on  the  dorsal  and  palmar  sur- 
faces of  the  forearm.  The  fracture  is  easily 
reduced  by  extension  from  the  wrist  and  fore- 
arm. The  forearm  should  be  flexed,  and 
placed  in  a  position  midway  between  pronation 
and  supination,  and  well-padded  splints  ap- 
plied from  the  elbow  to  the  ends  of  the  fingers. 
In  fracture  of  the  shafts  of  the  radius  and 
ulna  together  the  lower  fragments  are  drawn 
upward,  sometimes  forward,  sometimes  back- 
ward, according  to  the  direction  of  the  frac- 
ture, by  the  combined  actions  of  the  Flexor  and 
Extensor  muscles,  producing  a  degree  of  ful- 
ness on  the  dorsal  or  palmar  surface  of  the 

forearm;  at  the  same  time  the  two  fragments  are  drawn  into  contact  by  the  Pronator  quad- 
ratus, the  radius  being  in  a  state  of  pronation  :  the  upper  fragment  of  the  radius  is  drawn 
upward  and  inward  by  the  Biceps  and  Pronator  radii  teres  to  a  higher  level  than  the  ulna; 
the  upper  portion  of  the  ulna  is  slightly  elevated  by  the  Brachialis  anticus.  The  fracture  may 
be  reduced  by  extension  from  the  wrist  and  elbow,  and  the  forearm  should  be  placed  in  the 
same  position  as  in  fracture  of  the  ulna. 

In  fracture  of  the  lower  end  of  the  radius  (Colles's  fracture)  (Fig.  336)  the  displacement 
which  is  produced  is  very  considerable,  and  bears  some  resemblance  to  dislocation  of  the 
carpus  backward,  from  which  it  should  be  carefully  distinguished.  The  lower  fragment  is 
displaced  backward  and  upward,  but  this  displacement  is  probably  due  to  the  force  of  the 
blow  driving  the  portion  of  the  bone  into  this  position  and  not  to  any  muscular  influence. 
The  upper  fragment  projects  forward,  often  lacerating  the  substance  of  the  Pronator  quad- 
ratus, and  is  drawn  by  this  muscle  into  close  contact  with  the  lower  end  of  the  ulna,  causing  a 


FIG.  335. — Fracture  of  the  shaft  of  the  radius. 


FIG.  336. — Fracture  of  the  lower  end  of  the  radius. 

projection  on  the  anterior  surface  of  the  forearm,  immediately  above  the  carpus,  from  the  flexor 
tendons  being  thrust  forward.  This  fracture  may  be  distinguished  from  dislocation  by  the 
deformity  being  removed  on  making  sufficient  extension,  when  crepitus  may  be  occasionally 
detected;  at  the  same  time,  on  extension  being  discontinued,  the  parts  immediately  resume 
their  deformed  appearance.  The  age  of  the  patient  will  also  assist  in  determining  whether 
the  injury  is  fracture  or  separation  of  the  epiphysis.  Reduction  is  effected  by  hyperextension, 
longitudinal  traction,  and  forced  flexion.1  The  posterior  straight  splint  with  suitable  pads  is 
the  best  dressing. 


1  R.  J.  Levis. 


OF    THE   LOWER    EXTREMITY 


509 


MUSCLES  AND  FASCLffi  OF  THE  LOWER  EXTREMITY. 

The  Muscles  of  the  Lower  Extremity  are  subdivided  into  groups  corresponding 
with  the  different  regions  of  the  limb. 


I.  ILIAC  REGION. 

Psoas  magnus. 
Psoas  parvus. 
Iliacus. 

II.  THIGH. 

1.  Anterior  Femoral  Region. 

Tensor  fascise  Femoris. 
Sartorius. 
Rectus. 

Quadriceps     Vastus  externus. 
extensor.       Vastus  internus. 
'     Crureus. 
Subcrureus. 

2.  Internal  Femoral  Region. 

Gracilis. 
Pectineus. 
Adductor  longus. 
Adductor  brevis. 
Adductor  magnus. 

3.  Gluteal  Region. 
Gluteus  maximus. 
Gluteus  medius. 
Gluteus  minimus 
Pyriformis. 
Obturator  internus. 
Gemellus  superior. 
Gemellus  inferior. 
Quadratus  femoris. 
Obturator  externus. 

4.  Posterior  Femoral  Region. 

Biceps. 

Semitendinosus. 

Semimembranosus. 

III.  LEG. 

5.  Anterior  Tibio-fibular  Region. 

Tibialis  anticus. 
Extensor  proprius  hallucis. 
Extensor  longus  digitorum. 
Peroneus  tertius. 


6.  Posterior  Tibio-fibular  Region. 

Superficial  Layer. 

Gastrocnemius. 

Soleus. 

Plantaris. 

Deep  Layer. 

Popliteus. 

Flexor  longus  hallucis. 
Flexor  longus  digitorum. 
Tibialis  posticus. 

7.  Fibular  Region. 

Peroneus  longus. 
Peroneus  brevis. 

IV.  FOOT. 

8.  Dorsal  Region. 
Extensor  brevis  digitorum. 

9.  Plantar  Region. 

First  Layer. 

Abductor  hallucis. 
Flexor  brevis  digitorum. 
Abductor  minimi  digiti. 

Second  Layer. 

Flexor  accessorius. 
Lumbricales. 

Third  Layer. 

Flexor  brevis  hallucis. 
Adductor  obliquus  hallucis. 
Flexor  brevis  minimi  digiti. 
Adductor  transversus  hallucis, 

Fourth  Layer. 
The  Interossei- 


510 


THE   MUSCLES   AND    FASCIA 


I.  MUSCLES  AND  FASCI-ffl  OF  THE  ILIAC  REGION. 


Psoas  magnus. 


Psoas  parvus. 


Iliacus. 


Dissection. — No  detailed  description  is  required  for  the  dissection  of  these  muscles.  On 
the  removal  of  the  viscera  from  the  abdomen  they  are  exposed,  covered  by  the  peritoneum  and 
a  thin  layer  of  fascia,  the  iliac  fascia. 

Iliac  Fascia  (fascia  iliaca). — The  iliac  fascia1  is  the  aponeurotic  layer  which 
lines  the  back  part  of  the  abdominal  cavity,  and  covers  the  Psoas  and  Iliacus 
muscles  throughout  their  whole  extent.  It  is  thin  above,  and  becomes  gradually 
thicker  below  as  it  approaches  the  crural  arch. 

The  Portion  Covering  the  Psoas  is  attached,  above,  to  the  ligamentum  arcuatum 
internum;  internally,  by  a  series  of  arched  processes  to  the  intervertebral  sub- 
stances and  prominent  margins  of  the  bodies  of  the  vertebrae,  and  to  the  upper  part 
of  the  sacrum,  the  intervals  so  left,  opposite  the  constricted  portions  of  the  bodies, 


PROSTATIC 
VEINS 


PUDENDAL 
VEINS 


PUOENDAL 
VESSELS 


VISCERAL 
LAYER  OF 
PELVIC  FASCIA 


ANAL   FASCIA 

PARIETAL 
LAYER  OF 
PELVIC  FASCIA 


FIG.  337. — Horizontal  section  through  the  male  pelvis  at  the  level  of  the  middle  of  the  symphysis,  of 
the  tuberosity  of  the  ischial  bones  and  of  the  greater  trochanter. 

transmitting  the  lumbar  arteries  and  veins  and  filaments  of  the  sympathetic  cord. 
Externally,  above  the  crest  of  the  ilium,  this  portion  of  the  iliac  fascia  is  continu- 
ous with  the  anterior  lamella  of  the  lumbar  fascia,  but  below  the  crest  of  the 
ilium  it  is  continuous  with  the  fascia  covering  the  Iliacus. 

The  Portion  Investing  the  Iliacus  is  connected  externally  to  the  whole  length 
of  the  inner  border  of  the  crest  of  the  ilium,  and  internally  to  the  brim  of  the  true 
pelvis,  where  it  is  continuous  with  the  periosteum;  and  at  the  ilio-pectineal  emi- 
nence it  receives  the  tendon  of  insertion  of  the  Psoas  parvus,  when  that  muscle 
exists.  External  to  the  femoral  vessels,  this  fascia  is  intimately  connected  to  the 
posterior  margin  of  Poupart's  ligament,  and  is  continuous  with  the  fascia  transver- 
salis.  Immediately  to  the  outer  side  of  the  femoral  vessels  the  fascia  iliaca  is  pro- 
longed backward  and  inward  from  Poupart's  ligament  as  a  band,  the  ilio-pectineal 

1   The  student  must  not  confound  this  fascia  with  the  iliac  portion  of  the  fascia  lata  (see  p.  517). 


THE  ILIAC  REGION 


511 


ligament,  which  is  attached  to  the  ilio-pectineal  eminence.  The  ligament  divides 
the  space  between  Poupart's  ligament  and  the  innominate  bone  into  two  parts,  the 
inner  of  which  (lacuna  vasorum)  transmits  the  femoral  vessels,  and  contains  the 
margin  of  Gimbernat's  ligament  and  also  the  femoral  ring;  the  outer  (lacuna 
musculorum)  the  ilio-psoas  and  the  anterior  crural  nerve  (Fig.  338).  Internal  to 
the  vessels  the  iliac  fascia  is  attached  to  the  ilio-pectineal  line  behind  the  con- 
joined tendon,  where  it  is  again  continuous  with  the  transversalis  fascia;  and, 
corresponding  to  the  point  where  the  femoral  vessels  pass  into  the  thigh,  this 
fascia  descends  behind  them,  forming  the  posterior  wall  of-  the  femoral  sheath. 
This  portion  of  the  iliac  fascia  which  passes  behind  the  femoral  vessels  is  also 
attached  to  the  ilio-pectineal  line  beyond  the  limits  of  the  attachment  of  the  con- 
joined tendon;  at  this  part  it  is  continuous  with  the  pubic  portion  of  the  fascia  lata 
of  the  thigh.  The  external  iliac  vessels  lie  in  front  of  the  iliac  fascia,  but  all"  the 
branches  of  the  lumbar  plexus  behind  it ;  it  is  separated  from  the  peritoneum  by  a 
quantity  of  loose  areolar  tissue.  The  femoral  or  crural  sheath  (fascia  cruris)  is 


POUPART'S 
LIGAM  ENT 
ANTERIOR 
CRURAL   NERVE 
\-FEMORAL  ARTERY 


ILIAC  FASCIA 


FEMORAL  VEIN 


GIMBERNAT'S 
LIGAMENT 


PECTINEUS 


FIG.  338. — Poupart's  ligament  and  the  relation  of  the  parts  passing  beneath  it.     (Poirier  and  Charpy.) 


formed  by  the  transversalis  fascia  in  front  of  the  vessels  and  the  iliac  fascia  back 
of  them.  The  fasciae  join  to  the  inrier  side  of  the  femoral  vein,  a  space,  the  femoral 
canal,  intervening  between  the  vein  and  their  junction. 

Between  the  femoral  vein  and  the  edge  of  Gimbernat's  ligament  is  the  femoral  or 
crural  ring  (annulus  femoralis)  (Fig.  340).  The  crural  or  femoral  canal  (canalis 
femoralis}  is  the  interval  between  the  femoral  vein  and  the  inner  wall  of  the  femoral 
(crural)  sheath.  This  canal  extends  from  the  femoral  ring  to  the  saphenous  open- 
ing. The  femoral  ring  is  closed  by  the  septum  crurale  of  Cloquet  (septum  femorale 
\Cloqueti\),  which  is  a  process  of  transversalis  fascia. 


512  THE  MUSCLES  AND  FASCIAE 

The  Psoas  Magnus  (m.  psoas  major}  (Fig.  341)  is  a  long  fusiform  muscle  placed 
on  the  side  of  the  lumbar  region  of  the  spine  and  the  margin  of  the  pelvis.  It  arises 
from  the  front  of  the  bases  and  lower  borders  of  the  transverse  processes  of  the 
lumbar  vertebrae  by  five  fleshy  slips ;  also  from  the  sides  of  the  bodies  and  the  corre- 
sponding inter  vertebral  substances  of  the  last  thoracic  and  all  the  lumbar  vertebra. 
The  muscle  is  connected  to  the  bodies  of  the  vertebrae  by  five  slips;  each  slip  is 
attached  to  the  upper  and  lower  margins  of  two  vertebras,  and  to  the  intervertebral 
substance  between  them,  the  slips  themselves  being  connected  by  the  tendinous 
arches  which  extend  across  the  constricted  part  of  the  bodies,  and  beneath  which 
pass  the  lumbar  arteries  and  veins  and  filaments  of  the  sympathetic  cord.  These 
tendinous  arches  also  give  origin  to  muscular  fibres,  and  protect  the  blood-vessels 
and  nerves  from  pressure  during  the  action  of  the  muscle.  The  first  slip  is  attached 
to  the  contiguous  margins  of  the  last  thoracic  and  first  lumbar  vertebras;  the  last 
to  the  contiguous  margins  of  the  fourth  and  fifth  lumbar  vertebrae,  and  to  the 
intervertebral  substance.  From  these  points  the  muscle  descends  across  the 
brim  of  the  pelvis,  and,  diminishing  gradually  in  size,  passes  beneath  Pou- 
part's  ligament,  and  terminates  in  a  tendon  which,  after  receiving  nearly  the 
whole  of  the  fibres  of  the  Iliacus,  is  inserted  into  the  lesser  trochanter  of  the 
femur. 

Relations. — In  the  lumbar  region:  by  its  anterior  surface,  which  is  placed  behind 
the  peritoneum,  with  the  iliac  fascia,  the  ligamentumarcuatuminternum,  the  kidney, 
Psoas  parvus,  renal  vessels,  ureter,  spermatic  vessels,  genito-femoral  nerve,  and  the 
colon.  In  many  cases  the  vermiform  appendix  rests  upon  the  Psoas  muscle  (page 
513).  By  its  posterior  surface,  with  the  transverse  processes  of  the  lumbar  vertebrae 
and  the  Quadratus  lumborum  muscle,  from  which  it  is  separated  by  the  anterior 
lamella  of  the  lumbar  fascia.  The  lumbar  plexus  is  situated  in  the  posterior  part 
of  the  substance  of  the  muscle.  By  its  inner  side  the  muscle  is  in  relation  with  the 
bodies  of  the  lumbar  vertebrae,  the  lumbar  arteries,  the  ganglia  of  the  sympathetic 
nerve,  and  their  branches  of  communication  with  the  spinal  nerves;  the  lumbar 
glands ;  the  vena  cava  inferior  on  the  right  and  the  aorta  on  the  left  side,  and  along 
the  brim  of  the  pelvis  with  the  external  iliac  artery.  In  the  thigh  it  is  in  relation, 
in  front,  with  the  fascia  lata;  behind,  with  the  capsular  ligament  of  the  hip,  from 
which  it  is  separated  by  a  synovial  bursa  (bursa  iliopectinea) ,  which  frequently 
communicates  with  the  cavity  of  the  joint  through  an  opening  of  variable  size; 
between  the  tendon  and  part  of  the  lesser  trochanter  is  the  bursa  iliaca  sub- 
tendinea ;  by  its  inner  border,  with  the  Pectineus  and  internal  circumflex  artery, 
and  also  with  the  femoral  artery,  which  slightly  overlaps  it:  by  its  outer  border, 
with  the  anterior  crural  nerve  and  Iliacus  muscle. 

The  Psoas  Parvus  (m.  psoas  minor)  (Fig.  341)  is  a  long  slender  muscle  placed 
in  front  of  the  Psoas  magnus.  It  arises  from  the  sides  of  the  bodies  of  the  last 
thoracic  and  first  lumbar  vertebrae  and  from  the  intervertebral  substance  between 
them.  It  forms  a  small  flat  muscular  bundle,  which  terminates  in  a  long  flat 
tendon  inserted  into  the  ilio-pectineal  eminence,  and,  by  its  outer  border,  into 
the  iliac  fascia.  This  muscle  is  often  absent,  and,  according  to  Cruveilhier,  is 
sometimes  double. 

Relations. — It  is  covered  by  the  peritoneum,  and,  at  its  origin,  by  the  ligamentum 
arcuatum  internum;  it  rests  on  the  Psoas  magaus. 

The  Iliacus  (Fig.  341)  is  a  flat,  triangular  muscle  which  fills  up  the  whole  of  the 
iliac  fossa.  It  arises  from  the  upper  two-thirds  of  this  fossa  and  from  the  inner 
margin  of  the  crest  of  the  ilium ;  behind,  from  the  ilio-lumbar  ligament  and  base 
of  the  sacrum ;  in  front,  from  the  anterior  superior  and  anterior  inferior  spinous 
processes  of  the  ilium,  from  the  notch  between  them.  The  fibres  converge  to  be 
inserted  into  the  outer  side  of  the  tendon  of  the  Psoas,  some  of  them  being  pro- 
longed on  to  the  shaft  of  the  femur  for  about  an  inch  below  and  in  front  of  the 


THE  ILIAC  REGION  513 

lesser  trochanter.1  The  most  external  fibres  are  inserted  into  the  capsule  of  the 
hip-joint.  '  If  these  fibres  are  separate  they  constitute  the  Ilio-capsularis  muscle  or 
the  Iliacus  minor. 

Relations. — Within  the  abdomen:  by  its  anterior  surface,  with  the  iliac  fascia, 
which  separates  the  muscle  from  the  peritoneum,  and  with  the  external  cutaneous 
nerve;  on  the  right  side,  with  the  caecum;  on  the  left  side,  with  the  sigmoid  flexure 
of  the  colon;  by  its  posterior  surface,  with  the  iliac  fossa;  by  its  inner  border,  with 
the  Psoas  magnus  and  femoral  nerve.  In  the  thigh,  it  is  in  relation,  by  its  anterior 
surface,  with  the  fascia  lata,  the  Rectus  and  Sartorius  muscles,  and  the  profunda 
femoris  artery;  behind,  with  the  capsule  of  the  hip-joint,  a  synovial  bursa  common 
to  it  and  the  Psoas  magnus  being  interposed. 

Nerves. — The  Psoas  magnus  is  supplied  by  the  anterior  branches  of  the  second 
and  third  lumbar  nerves;  the  Psoas  parvus,  when  it  exists,  is  supplied  by  the 
anterior  branch  of  the  first  lumbar  nerve;  and  the  Iliacus  by  the  anterior  branches 
of  the  second  and  third  lumbar  nerves  through  the  femoral. 

Actions. — The  Psoas  and  Iliacus  muscles,  acting  from  above,  flex  the  thigh 
upon  the  pelvis.  Acting  from  below,  the  femur  being  fixed,  the  muscles  of 
both  sides  bend  the  lumbar  portion  of  the  spine  and  pelvis  forward.  They  also 
serve  to  maintain  the  erect  position,  by  supporting  the  spine  and  pelvis  upon 
the  femur,  and  assist  in  raising  the  trunk  when  the  body  is  in  the  recumbent 
posture. 

The  Psoas  parvus  is  a  tensor  of  the  iliac  fascia.  It  assists  in  flexing  the  lumbar 
spine  laterally,  the  pelvis  being  its  fixed  point. 

Surgical  Anatomy. — There  is  no  definite  septum  between  the  portions  of  the  iliac  fascia 
covering  the  Psoas  and  Iliacus  respectively,  and  the  fascia  is  only  connected  to  the  subjacent 
muscles  by  a  quantity  of  loose  connective  tissue.  When  an  abscess  forms  beneath  this  fascia, 
as  it  is  very  apt  to  do,  the  matter  is  contained  in  an  osseo-fibrous  cavity,  which  is  closed  on  all 
sides  within  the  abdomen,  and  is  open  only  at  its  lower  part,  where  the  fascia  is  prolonged  over 
the  muscle  into  the  thigh. 

Abscess  within  the  sheath  of  the  Psoas  muscle  (psoas  abscess}  is  generally  due  to  tuberculous 
caries  of  the  bodies  of  the  lower  thoracic  or  of  the  lumbar  vertebrae.  When  the  disease  is  in  the 
thoracic  region,  the  matter  tracts  down  the  posterior  mediastinum,  in  front  of  the  bodies  of  the 
vertebrae,  and,  passing  beneath  the  ligamentum  arcuatum  internum,  enters  the  sheath  of  the  Psoas 
muscle,  down  which  it  passes  as  far  as  the  pelvic  brim ;  it  then  gets  beneath  the  iliac  portion  of  the 
fascia  and  fills  up  the  iliac  fossa.  In  consequence  of  the  attachment  of  the  fascia  to  the  pelvic 
brim,  it  rarely  finds  its  way  into  the  pelvis,  but  passes  by  a  narrow  opening  under  Poupart's  liga- 
ment into  the  thigh,  to  the  outer  side  of  the  femoral  vessels.  It  thus  follows  that  a  Psoas  abscess 
may  be  described  as  consisting  of  four  parts:  (1)  a  somewhat  narrow  channel  at  its  upper  part,  in 
the  Psoas  sheath;  (2)  a  dilated  sac  in  the  iliac  fossa ;  (3)  a  constricted  neck  under  Poupart's  liga- 
ment; and  (4)  a  dilated  sac  in  the  upper  part  of  the  thigh.  When  the  lumbar  vertebrae  are  the  seat 
of  the  disease,  the  matter  finds  its  way  directly  into  the  substance  of  the  muscle.  If  a  Psoas  abscess 
forms  the  muscular  fibres  are  destroyed,  and  the  nervous  cords  contained  in  the  abscess  are  isolated 
and  exposed  in  its  interior;  the  femoral  vessels  which  lie  in  front  of  the  fascia  remain  intact,  and 
the  peritoneum  seldom  becomes  implicated.  All  Psoas  abscesses  do  not,  however,  pursue  this 
course:  the  matter  may  leave  the  muscle  above  the  crest  of  the  ilium,  and,  tracking  backward, 
may  point  in  the  loin  (lumbar  abscess) ;  or  it  may  point  above  Poupart's  ligament  in  the  inguinal 
region ;  or  it  may  follow  the  course  of  the  iliac  vessels  into  the  pelvis,  and,  passing  through  the 
great  sacro-sciatic  notch,  discharge  itself  on  the  back  of  the  thigh;  it  may  open  into  the  bladder 
or  find  its  way  into  the  perinaeum,  or  it  may  pass  down  the  thigh  to  the  popliteal  space  or  even 
lower.  Strain  of  the  Psoas  muscle  is  not  unusual,  and  induces  pain  which  may  be  mistaken 
for  appendicitis.  The  bursa  beneath  the  tendon  of  the  Psoas  and  Iliacus  and  the  hip-joint  or 
that  between  the  tendon  and  the  lesser  trochanter  may  greatly  enlarge  and  produce  pain  and 
disablement.  Byron  Robinson*  pointed  out  that  trauma  of  the  Psoas  muscle  may  be  an 
important  factor  in  the  etiology  of  appendicitis,  trauma  may  induce  periappendicular  adhe- 
sions and  adhesions  interfere  with  the  circulation  of  blood  and  faeces.  Robinson  says,  in  the 
previously  quoted  article,  that  in  46  per  cent,  of  men  and  in  20  per  cent,  of  women  the 
appendix  rests  on  the  Psoas  muscle. 

1  Th^-Ps0^  magnus,  Psoas  parvus,  and  Iliacus  are  regarded  by  His  and  others  as  a  single  muscle,  the  Ilio 
psoas  (Fig.  338).  2  Annals  of  Surgery,  April,  1901. 

33 


514 


THE   MUSCLES  AND   FASCIAE 


II.  MUSCLES  AND  FASCI-ffi  OF  THE  THIGH. 

1.  The  Anterior  Femoral  Region. 

[  Rectus. 

Tensor  fasciae  femoris.  Quadriceps  I  Vastus  externus. 

Sartorius.  extensor,     j  Vastus  internus. 

I  Crureus. 
Subcrureus. 

Dissection. — To  expose  the  muscles  and  fasciae  in  this  region,  make  an  incision  along 
Poupart's  ligament,  from  the  anterior  superior  spine  of  the  ilium  to  the  spine  of  the  os  pubis; 
a  vertical  incision  from  the  centre  of  this,  along  the  middle  of  the  thigh  to  below  the  knee-joint; 
and  a  transverse  incision  from  the  inner  to  the  outer  side  of  the  leg,  at  the  lower  end  of  the  ver- 
tical incision.  The  flaps  of  integument  having  been  removed,  the  superficial  and  deep  fasciae 
should  be  examined.  The  more  advanced  student  should  commence  the  study  of  this  region  by 
an  examination  of  the  anatomy  of  femoral  hernia  and  Scarpa's  triangle,  the  incisions  for  the 
dissection  of  which  are  marked  out  in  Fig.  339. 

Superficial  Fascia. — The  superficial  fascia  forms  a  continuous  layer  over  the 
whole  of  the  thigh.  It  consists  of  areolar  tissue,  containing  in  its  meshes  much  fat, 

and  is  capable  of  being  separated  into  two  or 
more  layers,  between  which  are  found  the  super- 
ficial vessels  and  nerves.  It  varies  in  thickness 
in  different  parts  of  the  limb:  in  the  groin  it 
is  thick,  and  the  two  layers  are  separated  from 
of  one  another  by  the  superficial  inguinal  lymphatic 
glands,  the  internal  saphenous  vein,  and  several 
smaller  vessels.  One  of  these  two  layers,  the 
superficial,  is  continuous  above  with  the  super- 
ficial fascia  of  the  abdomen  and  the  back.  In- 
ternally it  is  continuous  with  the  superficial 
fascia  of  the  perineum.  The  deep  layer  of  the 
superficial  fascia  is  a  very  thin  fibrous  layer, 
best  marked  on  the  inner  side  of  the  long 
saphenous  vein  and  below  Poupart's  ligament. 
It  is  placed  beneath  the  subcutaneous  vessels 
and  nerves  and  upon  the  surface  of  the  fascia 
lata.  It  is  intimately  adherent  to  the  fascia  lata 
a  little  below  Poupart's  ligament.  It  covers  the 
saphenous  opening  (Fig.  340)  in  the  fascia  lata, 
being  closely  united  to  the  margins  of  the  open- 
ing, and  is  connected  to  the  sheath  of  the  fem- 
3.  Front  of  leg.  oral  vessels  by  its  under  surface.  The  portion 
of  the  fascia  covering  this  aperture  is  perforated 
by  the  internal  saphenous  vein  and  by  numer- 
ous blood-  and  lymphatic  vessels;  hence  it  has 
been  termed  the  cribriform  fascia  (fascia  cribrosa), 
theopenings  for  these  vessels  having  been  likened 
to  the  holes  in  a  sieve.  .  The  cribriform  fascia 
adheres  closely  both  to  the  superficial  fascia  and 
to  the  fascia  lata,  so  that  it  is  described  by  some 
anatomists  as  part  of  the  fascia  lata,  but  is  usually 
considered  (as  in  this  work)  as  belonging  to  the 
superficial  fascia.  It  is  not  until  the  cribriform 

fascia  has  been  cleared  away  that  the  saphenous  opening  is  seen,  so  that  this  open- 
ing does  not  in  ordinary  cases  exist  naturally,  but  is  the  result  of  dissection.    Mr. 


1.  Dissection 
femoral  hernia, 

and     Scarpa's 

triangle. 


2.  Front  of  thigh. 


4-  Dorsum  of  foot. 


FIG.  339. — Dissection  of  lower  extremity. 
Front  view. 


THE   ANTERIOR    FEMORAL    REGION 


515 


Caliender,  however,  speaks  of  cases  in  which,  probably  as  the  result  of  pressure 
from  enlarged  inguinal  lymphatic  glands,  the  fascia  has  become  atrophied,  and  a 
saphenous  opening  exists  independent  of  dissection.  A  femoral  hernia  in  passing 
through  the  saphenous  opening  receives  the  cribriform  fascia  as  one  of  its  cover- 
ings. A  large  subcutaneous  bursa  (bur so.  praepatellaris  subcutanea)  is  found  in  the 
superficial  fascia  over  the  patella,  and  another  (bursa  trochanterica  subcutanea] 
in  the  superficial  fascia  over  the  great  trochanter. 

Deep  Fascia  or  Fascia  Lata  (Fig.  340) . — The  deep  fascia  of  the  thigh  is  exposed 
on  the  removal  of  the  superficial  fascia,  and  is  named,  from  its  great  extent,  the  fascia 
lata ;  it  forms  a  uniform  investment  for  the  whole  of  this  region  of  the  limb,  but  varies 
in  thickness  in  different  parts;  thus,  it  is  thicker  in  the  upper  and  outer  part  of 
the  thigh,  where  it  receives  a  fibrous  expansion  from  the  Gluteus  maximus  muscle, 
and  the  Tensor  fasciae  femoris  is  inserted  between  its  layers:  it  is  very  thin  behind, 
and  at  the  upper  and  inner  part  where  it  covers  the  Adductor  muscles,  and  again 


POUPART'S 
LIGAMENT 


INTERCOLUMNAR 
FIBRES 


M  BE  R  NAT'S 
LIGAMENT 

iAPHENOUS 

OPENING 

FEMORAL 

VEIN 

LONG 

iAPHENOUS 
VEIN 


EXTERNAL 
•ABDOMINAL 
RING 


FIG.  340.— Right  external  abdominal  ring  and  saphenous  opening  in  the  male.     (Spalteholz). 

becomes  stronger  around  the  knee,  receiving  fibrous  expansions  from  the  tendon  of 
the  Biceps  externally,  from  the  Sartorius  internally,  and  from  the  Quadriceps 
extensor  in  front.  The  fascia  lata  is  attached,  above  and  behind,  to  the  back  of 
the  sacrum  and  coccyx;  externally,  to  the  crest  of  the  ilium;  in  front,  to  Pou- 
part's  ligament  and  to  the  body  of  the  os  pubis;  and  internally,  to  the  descend- 
ing ramus  of  the  os  pubis,  to  the  ramus  and  tuberosity  of  the  ischium,  and  to  the 
lower  border  of  the  great  sacro-sciatic  ligament.  From  its  attachment  to  the  crest 
of  the  ilium  it  passes  down  over  the  Gluteus  medius  muscle  to  the  upper  border 
of  the  Gluteus  maximus,  where  it  splits  into  two  layers,  one  passing  superficial  to 
and  the  other  beneath  this  muscle.  At  the  lower  border  of  the  muscle  the  two  layers 
reunite.  Externally  the  fascia  lata  receives  the  greater  part  of  the  tendon  of  inser- 
tion of  the  Gluteus  maximus,  and  becomes  proportionately  thickened.  The 
portion  of  the  fascia  lata  arising  from  the  front  part  of  the  crest  of  the  ilium,  cor- 


516 


responding  to  the  origin  of  the  Tensor  fascia; 
femoris,  passes  down  the  outer  side  of  the  thigh 
as  two  layers,  one  superficial  to  and  the  other 
beneath  this  muscle.  The  deep  layer  is  a  con- 
tinuation of  the  tendinous  fibres  of  the  Gluteus 
maximus  muscle  and  the  superficial  layer  is 
chiefly  a  continuation  of  the  tendinous  fibres  of 
the  Tensor  fasciae  femoris,  but  receives  some 
fibres  from  the  fascia  covering  the  Gluteus 
medius  muscle.1  These  layers  at  the  lower 
end  of  the  muscle  become  blended  into  a  thick 
and  strong  band,  having  first  received  the  in- 
sertion of  the  muscle.  This  band  is  continued 
downward,  under  the  name  of  the  ilio-tibial  band 
(tract-us  iliotibialis  [Maissiati]),  to  be  inserted 
into  the  external  tuberosity  of  the  tibia.  A 
strengthening  band  of  transverse  fibres  is  placed 
in  the  gluteal  groove  or  s\ilc\is(sulcus glutaeus)and 
another  is  placed  across  the  roof  of  the  popliteal 
space.  Below,  the  fascia  lata  is  attached  to  all 
the  prominent  points  around  the  knee-joint — 
viz.,  the  condyles  of  the  femur,  tuberosities  of 
the  tibia,  and  head  of  the  fibula.  On  each  side 
of  the  patella  it  is  strengthened  by  transverse 
fibres  given  off  from  the  lower  part  of  the  Vasti 
muscles,  which  are  attached  to  and  support  this 
bone.  Of  these  the  outer  fibres  are  the  stronger, 
and  are  continuous  with  the  ilio-tibial  band. 
From  the  inner  surface  of  the  fascia  lata  are 
given  off  two  strong  intermuscular  septa,  which 
are  attached  to  the  whole  length  of  the  linea 
aspera  and  its  prolongations  above  and  below: 
the  external  intermuscular  septum  (septum  in- 
termusculare  laterale)  is  the  stronger.  It  extends 
from  the  insertion  of  the  Gluteus  maximus  to 
the  outer  condyle,  separates  the  Vastus  externus 
in  front  from  the  short  head  of  the  Biceps  be- 
hind, and  gives  partial  origin  to  these  muscles; 
the  internal  intermuscular  septum  (septum  inter- 
musculare  mediate),  the  thinner  of  the  two, 
separates  the  Vastus  internus  from  the  Adductor 
and  Pectineus  muscles.  Besides  these  there 
are  numerous  smaller  septa,  separating  the  in- 
dividual muscles  and  enclosing  each  in  a  dis- 
tinct sheath.  At  the  upper  and  inner  part  of 
the  thigh,  a  little  below  Poupart's  ligament,  a 
large  oval-shaped  aperture  is  observed  after 
the  superficial  fascia  has  been  cleared  off:  it 
transmits  the  internal  saphenous  vein  and  other 
smaller  vessels,  and  is  termed  the  saphenous 
opening  (fossa  ovalis)  (Fig.  340).  This  opening 
is  covered  by  a  portion  of  the  deep  layer  of  the 

FIG.  341. — Muscles  of  the  iliac  and  anterior         '  Werner  Spalteholz's  Hand  Atlas  of  Human  Anatomy.    Edited 
femoral  region.  and  translated  by  Lewellys  F.  Barker. 


m 


THE   ANTERIOR    FEMORAL    REGION  517 

superficial  fascia,  the  cribriform  fascia.  In  order  more  correctly  to  consider  the 
mode  of  formation  of  this  aperture,  the  fascia  lata  in  this  part  of  the  thigh  is 
described  as  consisting  of  two  portions — an  iliac  portion  and  a  pubic  portion. 

Iliac  Portion. — The  iliac  portion,  the  superficial  layer  of  the  fascia  lata  or  the 
Sartorial  portion  of  the  fascia  lata,  is  all  that  part  of  the  fascia  lata  on  the  outer 
side  of  the  saphenous  opening.  It  is  attached,  externally,  to  the  crest  of  the 
ilium  and  its  anterior  superior  spine,  to  the  whole  length  of  Poupart's  ligament  as 
far  internally  as  the  spine  of  the  os  pubis,  and  to  the  pectineal  line  in  conjunction 
with  Gimbernat's  ligament.  From  the  spine  of  the  os  pubis  it  is  reflected  down- 
ward and  outward,  forming  an  arched  margin,  the  falciform  process  or  the  falciform 
margin  of  Burns  (margo  falciformis),  or  the  superior  cornu  of  the  saphenous  opening 
(cornu  super  ius).  This  margin  overlies  and  is  adherent  to  the  anterior  layer  of 
the  sheath  of  the  femoral  vessels:  to  its  edge  is  attached  the  cribriform  fascia; 
and,  below,  it  is  continuous  with  the  pubic  portion  of  the  fascia  lata.  The 
femoral  ligament,  or  the  ligament  of  Hey,  is  the  point  at  which  the  falciform 
process  joins  the  base  of  Gimbernat's  ligament. 

Pubic  Portion. — The  pubic  portion,  or  the  pectineal  portion,  or  the  deep  layer  of 
the  fascia  lata,  is  situated  at  the  inner  side  of  the  saphenous  opening :  at  the  lower 
margin  of  this  aperture  it  is  continuous  with  the  iliac  portion.  The  lower  concave 
margin  of  the  saphenous  opening  where  the  two  layers  of  fascia  are  continuous  is 
called  the  inferior  cornu  (cornu  inferius).  Traced  upward,  the  pubic  portion  covers 
the  surface  of  the  Pectineus,  Adductor  longus,  and  Gracilis  muscles,  and,  passing 
behind  the  sheath  of  the  femoral  vessels,  to  which  it  is  closely  united,  is  continu- 
ous with  the  sheath  of  the  Psoas  and  Iliacus  muscles,  and  is  attached  above  to 
the  ilio-pectineal  line,  where  it  becomes  continuous  with  the  iliac  fascia.  From 
this  description  it  may  be  observed  that  the  iliac  portion  of  the  fascia  lata  passes 
in  front  of  the  femoral  vessels,  and  the  pubic  portion  behind  them,  so  that  an 
apparent  aperture  exists  between  the  two,  through  which  the  internal  saphenous 
joins  the  femoral  vein.1 

Surgical  Anatomy. — The  ilio-tibial  band  at  a  point  between  the  crest  of  the  ilium  and  the 
great  trochanter  is  so  tense  that  it  is  impossible  to  sink  the  fingers  in  deeply  in  this  region.  Dr. 
Allis  points  out  that  in  fracture  of  the  neck  of  the  femur  the  great  trochanter  mounts  toward 
the  iliac  crest,  the  ilio-tibial  band  relaxes,  and  the  fingers  can  be  sunk  deeply  into  the  space 
between  the  great  trochanter  and  the  iliac  crest — Allis's  sign.  Allis's  sign  indicates  shorten- 
ing. A  Psoas  abscess  usually  points  at  the  termination  of  the  Psoas  muscle,  but  the  tuberculous 
matter  may  be  directed  down  the  thigh  beneath  the  fascia  lata,  and  it  may  reach  the  popliteal 
space  or  even  lower. 

The  fascia  should  now  be  removed  from  the  surface  of  the  muscles.  This  may  be  effected  by 
pinching  it  up  between  the  forceps,  dividing  it,  and  separating  it  from  each  muscle  in  the  course 
of  its  fibres. 

The  Tensor  Fasciae  Femoris  (m.  tensor  fasciae  laiae,  m.  tensor  vaginae  femoris) 
(Fig.  341)  arises  from  the  anterior  part  of  the  outer  lip  of  the  crest  of  the  ilium, 
and  from  the  outer  surface  of  the  anterior  superior  spinous  process,  and  part  of 
the  outer  border  of  the  notch  below  it,  between  the  Gluteus  medius  and  Sartorius, 
and  from  the  surface  of  the  fascia  covering  the  Gluteus  medius.  It  is  inserted 
between  two  layers  of  the  fascia  lata,  about  one-fourth  down  the  outer  side  of 
the  thigh.  From  the  point  of  insertipn  the  fascia  is  continued  downward  to  the 
external  tuberosity  of  the  tibia  as  a  thickened  band,  the  ilio-tibial  band. 

Relations. — By  its  superficial  surface,  with  the  fascia  lata  and  the  integument; 
by  its  deep  surface,  with  the  Gluteus  medius,  Rectus  femoris,  and  Vastus  externus 
muscles,  and  the  ascending  branches  of  the  external  circumflex  artery;  by  its 
anterior  border,  with  the  Sartorius,  from  which  it  is  separated  below  by  a  triangular 

1  These  parts  will  be  again  more  particularly  described  with  the  anatomy  of  Hernia. 


518  THE  MUSCLES  AND  FASCIAE 

space,  in  which  is  seen  the  Rectus  femoris;  by  its  posterior  border,  with  the 
Gluteus  medius. 

The  Sartorius  (Fig.  341),  the  longest  muscle  in  the  body,  is  flat,  narrow,  and 
ribbon-like;  it  arises  by  tendinous  fibres  from  the  anterior  superior  spinous  process 
of  the  ilium  and  the  upper  half  of  the  notch  below  it,  passes  obliquely  across  the 
upper  and  anterior  part  of  the  thigh,  from  the  outer  to  the  inner  side  of  the  limb, 
then  descends  vertically,  as  far  as  the  inner  side  of  the  knee,  passing  behind  the 
inner  condyle  of  the  femur,  and  terminates  in  a  tendon  which,  curving  obliquely 
forward,  expands  into  a  broad  aponeurosis,  inserted  in  front  of  the  Gracilis  and 
Semitendinosus,  into  the  upper  part  of  the  inner  surface  of  the  shaft  of  the  tibia, 
nearly  as  far  forward  as  the  crest.  The  upper  part  of  the  tendon  is  curved  back- 
ward over  the  upper  edge  of  the  tendon  of  the  Gracilis  so  as  to  be  inserted  behind 
it.  An  offset  is  derived  from  the  upper  margin  of  this  aponeurosis,  which  blends 
with  the  fibrous  capsule  of  the  knee-joint,  and  another,  given  off  from  its  lower 
border,  blends  with  the  fascia  on  the  inner  side  of  the  leg. 

The  relations  of  this  muscle  to  the  femoral  artery  should  be  carefully  examined, 
as  it  constitutes  the  chief  guide  in  tying  the  vessel.  In  the  upper  third  of  the 
thigh  it  forms  the  outer  side  of  a  triangular  space,  Scarpa's  triangle  (trigonum 
femorale),  the  inner  side  of  which  is  formed  by  the  inner  border  of  the  Adductor 
longus,  and  the  base,  which  is  turned  upward,  by  Poupart's  ligament;  the  femoral 
artery  passes  perpendicularly  through  the  middle  of  this  space  from  its  base  to 
its  apex.  In  the  middle  third  of  the  thigh  the  femoral  artery  lies  first  along 
the  inner  border,  and  then  behind  the  Sartorius. 

Relations. — By  its  superficial  surface,  with  the  fascia  lata  and  integument;  by 
its  deep  surface,  with  the  Rectus,  Iliacus,  Vastus  internus,  femoral  nerve,  sheath 
of  the  femoral  vessels,  Adductor  longus,  Adductor  magnus,  Gracilis,  Semitendi- 
nosus, long  saphenous  nerve,  and  internal  lateral  ligament  of  the  knee-joint. 
Frequently  there  is  a  bursa  (bursa  m.  sartorii  propria)  between  the  tendon  of  the 
Sartorius  and  the  tendons  of  the  Gracilis  and  Semimembranosus.  It  may  be  in 
communication  with  the  bursa  anserina. 

The  Quadriceps  Extensor  (m.  quadriceps  femoris}  (Fig.  341)  includes  the  four 
remaining  muscles  on  the  front  of  the  thigh.  It  is  the  great  Extensor  muscle 
of  the  leg,  forming  a  large  fleshy  mass  which  covers  the  front  and  sides  of  the 
femur,  being  united  below  into  a  single  tendon,  attached  to  the  patella,  and 
above  subdivided  into  separate  portions,  which  have  received  distinct  names. 
Of  these,  one  occupying  the  middle  of  the  thigh,  connected  above  with  the  ilium, 
is  called  the  Rectus  femoris,  from  its  straight  course.  The  other  divisions  lie  in 
immediate  connection  with  the  shaft  of  the  femur,  which  they  cover  from  the 
trochanters  to  the  condyles.  The  portion  on  the  outer  side  of  the  femur  is 
termed  the  Vastus  externus;  that  covering  the  inner  side,  the  Vastus  internus; 
and  that  covering  the  front  of  the  femur,  the  Crureus. 

The  Rectus  Femoris  is  situated  in  the  middle  of  the  anterior  region  of  the  thigh; 
it  is  fusiform  in  shape,  and  its  superficial  fibres  are  arranged  in  a  bipenniform 
manner,  the  deep  fibres  running  straight  down  to  the  deep  aponeurosis.  It  arises 
by  two  tendons:  one,  the  anterior  or  straight,  from  the  anterior  inferior  spinous 
process  of  the  ilium;  the  other,  the  posterior  or  reflected  tendon,  from  a  groove 
above  the  brim  of  the  acetabulum;  the  two  unite  at  an  acute  angle  and  spread 
into  an  aponeurosis,  which  is  prolonged  downward  on  the  anterior  surface  of  the 
muscle  and  from  which  the  muscular  fibres  arise.1  The  muscle  terminates  in  a 
broad  and  thick  aponeurosis,  which  occupies  the  lower  two-thirds  of  its  posterior 
surface,  and,  gradually  becoming  narrowed  into  a  flattened  tendon,  is  inserted 

1  Mr.  W.  R.  Williams,  in  an  interesting  paper  in  the  Journ.  of  Anat.  and  Phya.,  vol.  xiii.  p.  204,  points 
out  that  the  reflected  tendon  is  the  real  origin  of  the  muscle,  and  is  alone  present  in  early  tetal  life.  The 
direct  tendon  is  merely  an  accessory  band  of  condensed  fascia.  The  paper  will  well  repay  perusal,  though  in 
some  particulars  I  think  the  description  in  the  text  more  generally  accurate. — ED.  of  15th  English  edition. 


THE  ANTERIOR  FEMORAL  REGION 


519 


FEMORAL  VEIN 
SAPHENOUS  VEIN 


FEMORAL  ARTERY    FEMORAL  NERVE 


PROFUNDA  ARTERY 


BRANCHES  OF 
OBTURATOR  NE 


EXTERNAL  CUTANEOUS 
NERVE 


FIG.  342. — Transverse  section  of  the  thigh  below  the  trochanter  minor.     (After  Braune.) 


POSTERIOR 

TIBIAL 
ARTERY. 


FIG.  343.— Transverse  section  at  the  middle  of  the  leg.  In  front  of  the  interosseous  membrane  are  the 
anterior  tibial  vessels  and  nerve;  in  front  of  the  soleus,  the  posterior  tibial  vessels  and  nerve;  and  close  to 
the  fibula,  the  peroneal  vessels.  (After  Braune.) 


520  THE  MUSCLES  AND  FASCIA 

into  the  patella  in  common  with  the  Vasti  and  Crureus.  Between  the  tendon  of 
origin  and  the  acetabulum  there  is  often  a  bursa  (bursa  m.  recti  femoris) . 

Relations. — By  its  superficial  surface,  with  the  anterior  fibres  of  the  Glutens 
minimus,  the  Tensor  fasciae  femoris,  the  Sartorius,  and  the  Iliacus;  by  its  lower 
three-fourths,  with  the  fascia  lata.  By  its  posterior  surface,  with  the  hip-joint, 
the  external  circumflex  vessels,  branches  of  the  femoral  nerve,  and  the  Crureus 
and  Vasti  muscles. 

The  Vastus  Externus  (m.  vastus  lateralis)  is  the  largest  part  of  the  Quadriceps 
extensor.  It  arises  by  a  broad  aponeurosis,  which  is  attached  to  the  upper  half 
of  the  anterior  intertrochanteric  line,  to  the  anterior  and  inferior  borders  of  the 
root  of  the  great  trochanter,  to  the  outer  lip  of  the  gluteal  ridge,  and  to  the  upper 
half  of  the  outer  lip  of  the  linea  aspera;  this  aponeurosis  covers  the  upper  three- 
fourths  of  the  muscle,  and  from  its  inner  surface  many  fibres  take  origin.  A  few 
additional  fibres  arise  from  the  tendon  of  the  Gluteus  maximus,  and  from  the 
external  intermuscular  septum  between  the  Vastus  externus  and  short  head  of  the 
Biceps.  The  fibres  form  a  large  fleshy  mass,  which  is  attached  to  a  strong  aponeu- 
rosis, placed  on  the  under  surface  of  the  muscle  at  its  lower  part:  this  becomes 
contracted  and  thickened  into  a  flat  tendon,  which  is  inserted  into  the  outer 
border  of  the  patella,  blending  with  the  great  Extensor  tendon,  and  giving  an 
expansion  to  the  capsule  of  the  knee-joint.  Some  of  the  fibres  run  down  by  the 
side  of  the  patella  to  the  condyle  of  the  tibia,  and  are  called  the  rptinacula  patellae 
later ale. 

Relations. — By  its  superficial  surface,  with  the  Rectus,  the  Tensor  fasciae  femoris, 
the  fascia  lata,  and  the  tendon  of  the  Gluteus  maximus,  from  which  it  is  separated 
by  a  synovial  bursa.  By  its  deep  surface,  with  the  Crureus,  some  large  branches 
of  the  external  circumflex  artery  and  femoral  nerve  being  interposed. 

The  Vastus  Internus  and  Crureus  appear  to  be  inseparably  united,  but  when 
the  Rectus  femoris  has  been  reflected,  a  narrow  interval  will  be  observed  extending 
upward  from  the  inner  border  of  the  patella  between  the  two  muscles.  Here  they 
can  be  separated,  and  the  separation  should  be  continued  upward  as  far  as  the 
lower  part  of  the  anterior  intertrochanteric  line,  where,  however,  the  two  muscles 
are  frequently  continuous. 

The  Vastus  Internus  (m.  vastus  medialis)  arises  from  the  lower  half  of  the 
anterior  intertrochanteric  line,  the  spiral  line,  the  inner  lip  of  the  linea  aspera, 
the  upper  part  of  the  internal  supra-condylar  line,  and  the  tendon  of  the  Adductor 
magnus  and  the  internal  intermuscular  septum.  Its  fibres  are  directed  downward 
and  forward,  and  are  chiefly  attached  to  an  aponeurosis  which  lies  on  the  deep 
surface  of  the  muscle  and  is  inserted  into  the  inner  border  of  the  patella  and 
the  Quadriceps  extensor  tendon,  an  expansion  being  sent  to  the  capsule  of  the 
knee-joint.  Some  of  the  fibres  run  down  by  the  side  of  the  patella  to  the  con- 
dyle of  the  tibia  and  are  called  the  retinacula  patellae  mediale. 

The  Crureus  (m.  vastus  intermedius)  arises  from  the  front  and  outer  aspect  of 
the  shaft  of  the  femur  in  its  upper  two-thirds  and  from  the  lower  part  of  the 
external  intermuscular  septum.  Its  fibres  end  in  a  superficial  aponeurosis,  which 
forms  the  deep  part  of  the  Quadriceps  extensor  tendon. 

Relations. — The  inner  edge  of  the  Crureus  is  in  contact  with  the  anterior  edge 
of  the  Vastus  internus,  but  when  separated  from  each  other,  as  directed  above,  the 
latter  muscle  is  seen  merely  to  overlap  the  inner  aspect  of  the  femoral  shaft  without 
taking  any  fibres  of  origin  from  it.  The  Vastus  internus  is  partly  covered  by  the 
Rectus  and  Sartorius,  but  where  these  separate  near  the  knee  it  becomes  superficial, 
and  produces  a  well-marked  prominence  above  the  inner  aspect  of  the  knee.  In 
the  middle  third  of  the  thigh  it  forms  the  outer  wall  of  Hunter's  canal  (canalis 
adductorius  [Hunteri]),  which  contains  the  femoral  vessels  and  the  long  saphenous 
nerve — the  roof  of  the  canal  being  formed  by  a  strong  fascia  which  extends  from 


THE  ANTERIOR  FEMORAL  REGION  521 

the  Vastus  interims  to  the  Adduc tores  longus  and  magnus.  The  Crureus  is  almost 
completely  hidden  by  the  Rectus  femoris  and  Vastus  externus.  The  deep  surface 
of  the  two  muscles  is  in  relation  with  the  femur  and  Subcrureus  muscles.  A 
synovial  bursa  (bursa  suprapatellaris)  is  situated  between  the  femur  and  the 
portion  of  the  Quadriceps  extensor  tendon  above  the  patella;  in  the  adult  it 
communicates  with  the  synovial  cavity  of  the  knee-joint. 

The  tendons  of  the  different  portions  of  the  Quadriceps  extensor  unite  at  the 
lower  part  of  the  thigh,  so  as  to  form  a  single  strong  tendon,  which  is  inserted  into 
the  upper  part  of  the  patella,  some  few  fibres  passing  over  it  to  blend  with  the 
Ligamentum  patellae.  More  properly,  the  patella  may  be  regarded  as  a  sesamoid 
bone,  developed  in  the  tendon  of  the  Quadriceps;  and  the  Ligamentum  patellae, 
which  is  continued  from  the  lower  part  of  the  patella  to  the  tuberosity  of  the  tibia, 
as  the  proper  tendon  of  insertion  of  the  muscle.  A  synovial  bursa,  the  deep  patel- 
lar  bursa  (bursa  infrapatellaris  prof  undo),  is  interposed  between  the  tendon  and 
the  upper  part  of  the  tuberosity  of  the  tibia;  and  another,  the  pre-patellar  bursa 
(bursa  praepatellaris  subcutanea),  is  placed  over  the  patella  itself.  This  latter 
bursa  often  becomes  enlarged,  constituting  "housemaid's  knee." 

The  Subcrureus  (m.  articularis  genu)  is  a  small  muscle,  usually  distinct  from 
the  Crureus,  but  occasionally  blended  with  it,  which  arises  from  the  anterior  sur- 
face of  the  lower  part  of  the  shaft  of  the  femur,  and  is  inserted  into  the  upper 
part  of  the  cul-de-sac  of  the  capsular  ligament  which  projects  upward  beneath 
the  Quadriceps  for  a  variable  distance.  It  sometimes  consists  of  several  separate 
muscular  bundles. 

Nerves. — The  Tensor  fasciae  femoris  is  supplied  by  the  fourth  and  fifth  lumbai 
and  first  sacral  nerves  through  the  superior  gluteal  nerve;  the  other  muscles  of 
this  region,  by  the  second,  third,  and  fourth  lumbar  nerves,  through  branches  of 
the  femoral. 

Actions. — The  Tensor  fasciae  femoris  is  a  tensor  of  the  fascia  lata;  continuing 
its  action,  the  oblique  direction  of  its  fibres  enables  it  to  abduct  and  to  rotate  the 
thigh  inward.  In  the  erect  posture,  acting  from  below,  it  will  serve  to  steady  the 
pelvis  upon  the  head  of  the  femur,  and  by  means  of  the  ilio-tibial  band  it  steadies 
the  condyles  of  the  femur  on  the  articular  surfaces  of  the  tibia,  and  assists  the 
Gluteus  maximus  in  supporting  the  knee  in  the  extended  position.  The  Sartorius 
flexes  the  leg  upon  the  thigh,  and,  continuing  to  act,  flexes  the  thigh  upon  the 
pelvis;  it  next  rotates  the  thigh  outward.  It  was  formerly  supposed  to  adduct  the 
thigh,  so  as  to  cross  one  leg  over  the  other,  and  hence  received  its  name  of  Sar- 
torius, or  tailor's  muscle  (sartor, a  tailor),  because  it  was  supposed  to  assist  in  cross- 
ing the  legs  in  the  squatting  position.  When  the  knee  is  bent  the  Sartorius  assists 
the  Semitendinosus,  Semimembranosus,  and  Popliteus  in  rotating  the  tibia  inward. 
Taking  its  fixed  point  from  the  leg,  it  flexes  the  pelvis  upon  the  thigh,  and,  if  one 
muscle  acts,  assists  in  rotating  the  pelvis.  The  Quadriceps  extensor  extends  the 
leg  upon  the  thigh.  The  Rectus  muscle  assists  the  Psoas  and  Iliacus  in  supporting 
the  pelvis  and  trunk  upon  the  femur.  It  also  assists  in  flexing  the  thigh  on  the 
pelvis,  or  if  the  thigh  is  fixed  it  will  flex  the  pelvis.  The  Vastus  internus  draws 
the  patella  inward  as  well  as  upward. 

Surgical  Anatomy. — A  few  fibres  of  the  Rectus  muscle  are  liable  to  be  ruptured  from- 
severe  strain.  This  accident  is  especially  liable  to  occur  during  the  games  of  football  and  cricket, 
and  is  sometimes  known  as  cricket  thigh.  The  patient  experiences  a  sudden  pain  in  the  part, 
as  if  he  had  been  struck,  and  the  Rectus  muscle  stands  out  and  is  felt  to  be  tense  and  rigid.  The 
accident  is  often  followed  by  considerable  swelling  from  inflammatory  effusion.  Occasionally  the 
Quadriceps  extensor  may  be  torn  away  from  its  insertion  into  the  patella,  or  the  tendon  of  the 
quadriceps  may  be  ruptured  about  an  inch  above  the  bone.  This  accident  is  caused  in  the  same 
manner  that  fracture  of  the  patella  by  muscular  action  is  produced — viz.,  by  a  violent  muscular 
effort  to  prevent  falling  whilst  the  knee  is  in  a  position  of  semiflexion.  A  distinct  gap  can  be 


522 

felt  above  the  patella,  and,  owing  to  the  retraction  of  the  muscular  fibres,  union  may  fail  to  take 
place.  Sudden  and  powerful  contraction  of  the  Quadriceps  extensor  femoris  is  the  cause  of 
transverse  fracture  of  the  patella. 

2.  The  Internal  Femoral  Region. 

Gracilis.  Adductor  longus. 

Pectineus.  Adductor  brevis. 

Adductor  magnus. 

Dissection. — These  muscles  are  at  once  exposed  by  removing  the  fascia  from  the  forepart 
and  inner  side  of  the  thigh.  The  limb  should  be  abducted,  so  as  to  render  the  muscles  tense 
and  easier  of  dissection. 

The  Gracilis  (Figs.  341,  346,  and  349)  is  the  most  superficial  muscle  on  the 
inner  side  of  the  thigh.  It  is  thin  and  flattened,  broad  above,  narrowing  and  taper- 
ing below.  It  arises  by  a  thin  aponeurosis  from  the  lower  half  of  the  margin  of  the 
symphysis  and  the  anterior  half  of  the  pubic  arch.  The  fibres  pass  vertically  down- 
ward, and  terminate  in  a  rounded  tendon  which  passes  behind  the  internal  condyle 
of  the  femur,  and,  curving  round  the  inner  tuberosity  of  the  tibia,  becomes  flattened, 
and  is  inserted  into  the  upper  part  of  the  inner  surface  of  the  shaft  of  the  tibia,  below 
the  tuberosity.  A  few  of  the  fibres  of  the  lower  part  of  the  tendon  are  prolonged 
into  the  deep  fascia  of  the  leg.  The  tendon  of  this  muscle  is  situated  immediately 
above  that  of  the  Semitendinosus,  and  its  upper  edge  is  overlapped  by  the  tendon 
of  the  Sartorius,  with  which  it  is  in  part  blended.  As  it  passes  across  the  internal 
lateral  ligament  of  the  knee-joint  it  is  separated  from  it  by  a  synovial  bursa 
(bursa  anserina)  common  to  it  and  the  Semitendinosus  muscle. 

Relations. — By  its  superficial  surf  ace,  with  the  fascia  lataand  the  Sartorius  below: 
the  internal  saphenous  vein  crosses  it  obliquely  near  its  lower  part,  lying  superficial 
to  the  fascia  lata;  the  internal  saphenous  nerve  emerges  between  its  tendon  and 
that  of  the  Sartorius ;  by  its  deep  surface,  with  the  Adductor  brevis  and  the  Adductor 
magnus  and  the  internal  lateral  ligament  of  the  knee-joint. 

The  Pectineus  (Fig.  341)  is  a  flat,  quadrangular  muscle,  situated  at  the  anterior 
part  of  the  upper  and  inner  aspect  of  the  thigh.  It  arises  from  the  linea  ilio-pec- 
tinea,  and  to  a  slight  extent  from  the  surface  of  the  bone  in  front  of  it  between  the 
pectineal  eminence  and  spine  of  the  os  pubis,  and  from  the  fascia  covering  the 
anterior  surface  of  the  muscle;  the  fibres  pass  downward,  backward,  and  outward, 
to  be  inserted  into  a  rough  line  leading  from  the  lesser  trbchanter  to  the  linea  aspera. 

Relations. — By  its  anterior  surface,  with  the  pubic  portion  of  the  fascia  lata, 
which  separates  it  from  the  femoral  vessels  and  internal  saphenous  vein;  by  its 
posterior  surface,  with  the  capsular  ligament  of  the  hip-joint,  the  Adductor  brevis 
and  Obturator  externus  muscles,  the  obturator  vessels  and  nerve  being  interposed; 
by  its  outer  border,  with  the  Psoas,  a  cellular  interval  separating  them,  through 
which  pass  the  internal  circumflex  vessels;  by  its  inner  border,  with  the  margin  of 
the  Adductor  longus.  There  is  usually  a  bursa  (bursa  m.  pectinei)  between  the 
pectineus  and  the  tendon  of  the  psoas  and  iliacus. 

The  Adductor  Longus  (Figs.  341  and  344),  the  most  superficial  of  the  three 
Adductors,  is  a  flat  triangular  muscle  lying  on  the  same  plane  as  the  Pectineus. 
It  arises,  by  a  flat  narrow  tendon,  from  the  front  of  the  os  pubis,  at  the  angle  of 
junction  of  the  crest  with  the  symphysis;  and  soon  expands  into  a  broad  fleshy 
belly,  which,  passing  downward,  backward,  and  outward,  is  inserted,  by  an 
aponeurosis,  into  the  linea  aspera,  between  the  Vastus  interims  and  the  Adductor 
magnus,  with  both  of  which  it  is  usually  blended. 

Relations. — By  its  anterior  surface,  with  the  fascia  lata,  the  Sartorius,  and,  near 
its  insertion,  with  the  femoral  artery  and  vein;  by  its  posterior  surface,  with  the 
Adductor  brevis  and  magnus,  the  anterior  branches  of  the  obturator  nerve,  and 


THE  INTERNAL  FEMORAL  REGION 


523 


with  the  profunda  artery  and  vein  near  its  insertion;  by  its  older  border,  with  the 
Pectineus;  by  its  inner  border,  with  the  Gracilis. 

The  Pectineus  and  Adductor  longus  should  now 
be  divided  near  their  origin,  and  turned  down- 
ward, when  the  Adductor  brevis  and  Obturator  ex- 
ternus  will  be  exposed. 

The  Adductor  Brevis  (Fig.  344)  is  situ- 
ated immediately  behind  the  two  preceding 
muscles.  It  is  somewhat  triangular  in 
form,  and  arises  by  a  narrow  origin  from 
the  outer  surface  of  the  body  and  descend- 
ing ramus  of  the  os  pubis,  between  the 
Gracilis  and  Obturator  externus.  Its  fibres 
passing  backward,  outward,  and  downward, 
are  inserted,  by  an  aponeurosis,  into  the 
lower  part  of  the  line  leading  from  the  lesser 
trochanter  to  the  linea  aspera  and  the  upper 
part  of  the  same  line,  immediately  behind 
the  Pectineus  and  upper  part  of  the  Ad- 
ductor longus. 

Relations. — By  its  anterior  surface,  with 
the  Pectineus,  Adductor  longus,  profunda 
femoris  artery,  and  anterior  branches  of  the 
obturator  nerve;  by  its  posterior  surface, 
with  the  Adductor  magnus  and  posterior 
branch  of  the  obturator  nerve ;  by  its  outer 
border,  with  the  internal  circumflex  artery, 
the  Obturator  externus,  and  conjoined  ten- 
don of  the  Psoas  and  Iliacus;  by  its  inner 
border,  with  the  Gracilis  and  Adductor 
magnus.  This  muscle  is  pierced,  near  its 
insertion,  by  the  second  or  by  the  first  and 
second  perforating  branches  of  the  pro- 
funda femoris  artery. 

The  Adductor  brevis  should  now  be  cut  away 
near  its  origin,  and  turned  outward,  when  the  en- 
tire extent  of  the  Adductor  magnus  will  be  exposed. 

The  Adductor  Magnus  (Fig.  344)  is  a 
large  triangular  muscle  forming  a  septum 
between  the  muscles  on  the  inner  and  those 
on  the  back  of  the  thigh.  It  arises  from  a 
small  part  of  the  descending  ramus  of  the 
os  pubis,  from  the  ramus  of  the  ischium, 
and  from  the  outer  margin  of  the  inferior 
part  of  the  tuberosity  of  the  ischium.  Those 
fibres  which  arise  from  the  ramus  of  the  os 
pubis  are  very  short,  horizontal  in  direction, 
and  are  inserted  into  the  rough  line  leading 
from  the  great  trochanter  to  the  linea  aspera, 
internal  to  the  Gluteus  maximus.  They  are 
considered  by  some  a  distinct  muscle  and  called  the  Adductor  minimus.  The  fibres 
taking  origin  from  the  ramus  of  the  ischium  are  directed  downward  and  outward 


FIG.  344.- 


-Deep  muscles  of  the  internal  femoral 
region. 


524  THE  MUSCLES  AND  FASCIA 

with  different  degrees  of  obliquity,  to  be  inserted,  by  means  of  a  broad  aponeurosisr 
into  the  linea  aspera  and  the  upper  part  of  its  internal  prolongation  below.  The 
internal  portion  of  the  muscle,  consisting  principally  of  those  fibres  which  arise  from 
the  tuberosity  of  the  ischium,  forms  a  thick  fleshy  mass  consisting  of  coarse  bundles 
which  descend  almost  vertically,  and  terminate  about  the  lower  third  of  the  thigh 
in  a  rounded  tendon,  which  is  inserted  into  the  Adductor  tubercle  on  the  inner 
condyle  of  the  femur,  being  connected  by  a  fibrous  expansion  to  the  line  leading 
upward  from  the  tubercle  to  the  linea  aspera.  Between  the  two  portions  of  the 
muscle  an  interval  is  left,  tendinous  in  front,  fleshy  behind,  for  the  passage  of  the 
femoral  vessels  from  Hunter's  canal  into  the  popliteal  space.  The  external  portion 
of  the  muscle  at  its  attachment  to  the  femur  presents  three  or  four  osseo-aponeurotic 
openings,  formed  by  tendinous  arches  attached  to  the  bone,  from  which  muscular 
fibres  arise.  The  three  superior  of  these  apertures  are  for  the  three  perforating 
arteries,  and  the  fourth,  when  it  exists,  is  for  the  terminal  branch  of  the  profunda. 

Relations. — By  its  anterior  surface,  with  the  Pectineus,  Adductor  brevis,  Ad- 
ductor longus,  and  the  femoral  and  profunda  vessels  and  obturator  nerve;  by  its 
posterior  surface,  with  the  great  sciatic  nerve,  the  Gluteus  maximus,  Biceps,  Semi- 
tendinosus,  and  Semimembranosus.  By  its  superior  or  shortest  border  it  lies 
parallel  with  the  Quadratus  femoris,  the  internal  circumflex  artery  passing  between 
them;  by  its  internal  or  longest  border,  with  the  Gracilis,  Sartorius,  and  fascia 
lata;  by  its  external  or  attached  border  it  is  inserted  into  the  femur  behind  the  Ad- 
ductor brevis  and  Adductor  longus,  which  separate  it  from  the  Vastus  internus, 
and  in  front  of  the  Gluteus  maximus  and  short  head  of  the  Biceps,  which  sep- 
arate it  from  the  Vastus  externus. 

Nerves.  The  three  Adductor  muscles  and  the  Gracilis  are  supplied  by  the 
third  and  fourth  lumbar  nerves  through  the  obturator  nerve;  the  Adductor  mag- 
nus  receiving  an  additional  branch  from  the  sacral  plexus  through  the  great  sciatic. 
The  Pectineus  is  supplied  by  the  second,  third,  and  fourth  lumbar  nerves  through 
the  femoral,  and  by  the  accessory  obturator,  from  the  third  lumbar,  when  it  exists. 
Occasionally  it  receives  a  branch  from  the  obturator  nerve.1 

Actions. — The  Pectineus  and  three  Adductors  adduct  the  thigh  powerfully; 
they  are  especially  used  in  horse  exercise,  the  flanks  of  the  horse  being  grasped 
between  the  knees  by  the  actions  of  these  muscles.  In  consequence  of  the  obliquity 
of  their  insertion  into  the  linea  aspera  they  rotate  the  thigh  outward,  assisting 
the  external  Rotators,  and  when  the  limb  has  been  abducted  they  draw  it  inward, 
carrying  the  thigh  across  that  of  the  opposite  side.  The  Pectineus  and  Adductor 
brevis  and  longus  assist  the  Psoas  and  Iliacus  in  flexing  the  thigh  upon  the  pelvis. 
In  progression,  also,  all  these  muscles  assist  in  drawing  forward  the  hinder  limb. 
The  Gracilis  assists  the  Sartorius  in  flexing  the  leg  and  rotating  it  inward;  it  is 
also  an  adductor  of  the  thigh.  If  the  lower  extremities  are  fixed,  these  muscles 
may  take  their  fixed  point  from  below  and  act  upon  the  pelvis,  serving  to  maintain 
the  body  in  an  erect  posture,  or,  if  their  action  is  continued,  to  flex  the  pelvis 
forward  upon  the  femur. 

Hunter's  Canal  (canalis  adductorius  [Hlinteri])  extends  from  the  apex  of  Scarpa's 
triangle  to  the  opening  in  the  Adductor  magnus  muscle.  The  antero-internal 
boundary  or  roof  of  Hunter's  canal  is  the  Sartorius  and  the  aponeurotic  expan- 
sion from  the  Adductors  to  the  Vastus  internus.  It  is  bounded  externally  by  the 
Vastus  internus.  The  Adductor  longus  and  Magnus  constitute  its  floor  or  the 
postero-internal  boundary.  The  canal  contains  the  femoral  artery,  femoral  vein, 
the  long  saphenous  nerve,  and  the  nerve  to  the  Vastus  internus.  The  anterior 
opening  of  Hunter's  canal  is  called  the  hiatus  tendinous . 

1  Professor  Paterson  describes  the  Pectineus  as  consisting  of  two  incompletely  separated  strata,  of  which 
the  outer  or  dorsal  stratum,  which  is  constant,  is  supplied  by  the  anterior  crural  nerve,  or  in  its  absence  by  the 
accessory  obturator,  with  which  it  is  intimately  related;  while  the  inner  or  ventral  stratum,  when  present,  is 
supplied  by  the  obturator  nerve. — Journ.  of  Anat.  and  Phys.,  vol.  xxvi.  p.  43. — ED.  of  15th  English  edition. 


THE  GLUTEAL  REGION 


525 


Surgical  Anatomy. — The  Adductor  longus  is  liable  to  be  severely  strained  in  those  who  ride 
much  on  horseback,  or  its  tendon  to  be  ruptured  by  suddenly  gripping  the  saddle.  Occasionally, 
especially  in  cowboys  and  cavalry  soldiers,  the  tendon  of  insertion  of  the  Adductor  magnus 
may  become  ossified,  constituting  the  rider's  bone. 


THE  MUSCLES  AND  FASCI-ffl  OF  THE  HIP. 

3.  The  Gluteal  Region  (Figs.  346,  347). 

Gluteus  maximus.  Obturator  internus. 

Gluteus  medius.  Gemellus  superior. 

Gluteus  minimus.  Gemellus  inferior. 

Pyriformis.  Quadratus  femoris. 

Obturator  externus. 

Dissection  (Fig.  345). — The  subject  should  be  turned  on  its  face,  a  block  placed  beneath 
the  pelvis  to  make  the  buttocks  tense,  and  the  limbs  allowed  to  hang  over  the  end  of  the  table, 
with  the  foot  inverted  and  the  thigh  abducted.    Make  an  incision  through  the  integument  along 
the  crest  of  the  ilium  to  the  middle  of  the  sacrum,  and 
thence  downward  to  the  tip  of  the  coccyx,  and  carry  a 
second  incision  from  that  point  obliquely  downward  and 
outward  to  the  outer  side  of  the  thigh,  four  inches  be- 
low the  great  trochanter.     The  portion  of  integument 
included  between  these  incisions  is  to  be  removed  in  im  x 

the  direction  shown  in  the  figure.  jl  /  \    L  Dussection  of 

Hi/      1      !\    gluteal  region. 

The  Gluteus  Maximus  (m.glutaeus maximus) 
(Fig.  346),  the  most  superficial  muscle  in  the 
gluteal  region,  is  a  very  broad  and  thick,  fleshy 
mass  of  a  quadrilateral  shape,  which  forms  the 
prominence  of  the  buttock.  Its  large  size  is  one 
of  the  most  characteristic  points  in  the  mus- 
cular system  of  man,  connected  as  it  is  with 
the  power  he  has  of  maintaining  the  trunk  in 
the  erect  posture.  In  structure  the  muscle  is 
remarkably  coarse,  being  made  up  of  muscular 
fasciculi  lying  parallel  with  one  another,  and 
collected  together  into  large  bundles,  separated 
by  deep  cellular  intervals.  It  arises  from  the 
superior  curved  line  of  the  ilium  and  the  por- 
tion of  bone,  including  the  crest,  immediately 
above  and  behind  it;  from  the  posterior  sur- 
face of  the  lower  part  of  the  sacrum,  the  side  of 
the  coccyx,  the  aponeurosis  of  the  Erector  spinse 
muscle,  the  great  sacro-sciatic  ligament,  and 
the  fascia  covering  the  Gluteus  medius.  The 
fibres  are  directed  obliquely  downward  and 
outward;  those  forming  the  upper  and  large 
portion  of  the  muscle,  together  with  the  super- 
ficial fibres  of  the  lower  portion,  terminate  in 
a  thick  tendinous  lamina,  which  passes  across 
the  great  trochanter  and  is  inserted  into  the 
fascia  lata  covering  the  outer  side  of  the  thigh ; 
the  deeper  fibres  of  the  lower  portion  of  the  muscles  are  inserted  into  the  rough 
line  leading  from  the  great  trochanter  to  the  linea  aspera  between  the  Vastus 
externus  and  Adductor  magnus. 


313.  Back  of  thigh. 


2.  Popliteal  space. 


•^•w  -  * 

4/4-  Back  of  leg. 


5.  Sole  of  foot. 


FIG.  345. — Dissection  of  lower  extremity. 
Posterior  view. 


526  THE  MUSCLES  AND  FASCIAE 

Several  synovial  bursae  are  found  in  relation  with  this  muscle.  One  of  these 
(bursa  trochanterica  m.  glutaei  maximi),  of  large  size,  and  generally  multilocular, 
separates  it  from  the  great  trochanter.  A  second  (bursa  ischiadica  m,  glutoei 
maximi),  often  wanting,  is  situated  on  the  tuberosity  of  the  ischium.  A  third 
bursa  is  found  between  the  tendon  of  this  muscle  and  the  Vastus  externus.  Two 
or  three  small  bursse  (bursae  glutaeofemorales)  are  placed  between  the  tendon  of 
the  muscle  and  the  gluteal  ridge. 

Relations. — By  its  superficial  surface,  with  a  thin  fascia,  which  separates  it  from 
the  subcutaneous  tissue;  by  its  deep  surface,  from  above  downward,  with  the  ilium, 
sacrum,  coccyx,  and  great  sacro-sciatic  ligament,  part  of  the  Gluteus  medius, 
Pyriformis,  Gemelli,  Obturator  internus,  Quadratus  femoris,  the  tuberosity  of 
the  ischium,  great  trochanter,  the  origin  of  the  Biceps,  Semitendinosus,  Semimem- 
branosus,  and  Adductor  magnus  muscles.  The  superficial  part  of  the  gluteal 
artery  reaches  the  deep  surface  of  the  muscle  by  passing  between  the  Pyriformis 
and  the  Gluteus  medius;  the  sciatic  and  internal  pudic  vessels  and  nerves  and 
muscular  branches  from  the  sacral  plexus  issue  from  the  pelvis  below  the  Pyri- 
formis. The  first  perforating  artery  and  the  terminal  branches  of  the  internal  cir- 
cumflex artery  are  also  found  under  cover  of  the  muscle.  Its  upper  border  is  thin, 
and  connected  with  the  Gluteus  medius  by  the  fascia  lata.  Its  lower  border  is  free 
and  prominent. 

Dissection. — Divide  the  Gluteus  maximus  near  its  origin  by  a  vertical  incision  carried  from 
its  upper  to  its  lower  border;  a  cellular  interval  will  be  exposed,  separating  it  from  the  Gluteus 
medius  and  External  rotator  muscles  beneath.  The  upper  portion  of  the  muscle  is  to  be  alto- 
gether detached,  and  the  lower  portion  turned  outward;  the  loose  areolar  tissue  filling  up  the 
interspace  between  the  trochanter  major  and  tuberosity  of  the  ischium  being  removed,  the  parts 
already  enumerated  as  exposed  by  the  removal  of  this  muscle  will  be  seen. 

The  Gluteus  Medius  (m.  glutceus  medius}  (Fig.  346)  is  a  broad,  thick,  radiated 
muscle,  situated  on  the  outer  surface  of  the  pelvis.  Its  posterior  third  is  covered  by 
the  Gluteus  maximus ;  its  anterior  two-thirds  by  the  fascia  lata,  which  separates 
it  from  the  integument.  It  arises  from  the  outer  surface  of  the  ilium,  between  the 
superior  and  middle  curved  lines,  and  from  the  outer  lip  of  that  portion  of  the 
crest  which  is  between  them ;  it  also  arises  from  the  dense  fascia,  the  gluteal  aponeu- 
rosis,  covering  its  outer  surface.  The  fibres  converge  to  a  strong  flattened  tendon 
which  is  inserted  into  the  oblique  line  which  traverses  the  outer  surface  of  the 
great  trochanter.  A  synovial  bursa  (bursa  trochanterica.  m.  glutaei  medii  anterior) 
separates  the  tendon  of  the  muscle  from  the  summit  of  the  great  trochanter. 
There  is  frequently  a  bursa  (bursa  trochanterica  m.  glutaei  medii  posterior)  between 
the  tendons  of  the  Gluteus  medius  and  Pyriformis. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  behind,  the 
Tensor  fasciae  femoris  and  deep  fascia  in  front;  by  its  deep  surface,  with  the  Glu- 
teus minimus  and  the  gluteal  vessels  and  superior  gluteal  nerve.  Its  anterior  border 
is  blended  with  the  Gluteus  minimus.  Its  posterior  border  lies  parallel  with  the 
Pyriformis,  the  gluteal  vessels  intervening. 

This  muscle  should  now  be  divided  near  its  insertion  and  turned  upward,  when  the  Gluteus 
minimus  will  be  exposed. 

The  Gluteus  Minimus  (m.  glutceus  minimus)  (Fig.  346),  the  smallest  of  the 
three  Glutei,  is  placed  immediately  beneath  the  preceding.  It  is  fan-shaped, 
arising  from  the  outer  surface  of  the  ilium,  between  the  middle  and  inferior 
curved  lines,  and  behind,  from  the  margin  of  the  great  sacro-sciatic  notch;  the 
.fibres  converge  to  the  deep  surface  of  a  radiated  aponeurosis,  which,  terminating 
in  a  tendon,  is  inserted  into  an  impression  on  the  anterior  border  of  the  great 
trochanter. 


THE  GLUTEAL  REGION 


527 


Relations. — By  its  superficial 
surf  ace, -with  the  Gluteus  medius 
and  the  gluteal  vessels  and  supe- 
rior gluteal  nerve;  by  its  deep 
surface,  with  the  ilium,  the  re- 
flected tendon  of  the  Rectus 
femoris,  and  the  capsular  liga- 
ment of  the  hip-joint.  Its  ante- 
rior margin  is  blended  with  the 
Gluteus  medius;  its  posterior 
margin  is  in  contact  and  some- 
times joined  with  the  tendon  of 
the  Pyriformis.  There  is  a 
synovial  bursa  (bursa  m.glutaei 
minimi)  between  the  tendon  of 
the  Gluteus  minimus  and  the 
great  trochanter. 

The  Pyriformis  (m.  pirifcr- 
mis]  (Figs.  346  and  347)  is 
a  flat  muscle,  pyramidal  in 
shape,  lying  almost  parallel 
with  the  posterior  margin  of  the 
Gluteus  medius.  It  is  situated 
partly  within  the  pelvis  at  its 
posterior  part  and  partly  at  the 
back  of  the  hip-joint.  It  arises 
from  the  front  of  the  sacrum 
by  three  fleshy  digitations  at- 
tached to  the  portions  of  bone 
between  the  first,  second,  third, 
and  fourth  anterior  sacral  fora- 
mina, and  also  from  the  groove 
leading  from  the  foramina:  a 
few  fibres  also  arise  from  the 
margin  of  the  great  sacro-sciatic 
foramen  and  from  the  anterior 
surface  of  the  great  sacro-sciatic 
ligament.  The  muscle  passes 
out  of  the  pelvis  through  the 
great  sacro-sciatic  foramen,  the 
upper  part  of  which  it  fills,  and 
is  inserted  by  a  rounded  tendon 
into  the  upper  border  of  the 
great  trochanter,  behind,  but 
often  partly  blended  with,  the 
tendon  of  the  Obturator  in- 
ternus  and  Gemelli  muscles. 

Relations.  —  By  its  anterior 
surface,  within  the  pelvis,  with 
the  Rectum  (especially  on  the 
left  side),  the  sacral  plexus  of 
nerves,  and  the  branches  of  the 
internal  iliac  vessels;  external 
to  the  pelvis,  with  the  posterior 


Inner  hamstring 
tendons. 

SARTORIUS. 

GRACILIS. 
SEMITENDINOSUS. 

SEMIMEMBRA- 
NOSUS. 


Outer 

hamstring 

tendon. 


Tibia. 
FIG.  346. — Muscles  of  the  hip  and  thigh. 


528  THE  MUSCLES  AND  FASCIA 

surface  of  the  ischium  and  the  capsular  ligament  of  the  hip-joint ;  by  its  posterior 
surface,  within  the  pelvis,  with  the  sacrum,  and  external  to  it,  with  the  Gluteus 
maximus;  by  its  upper  border,  with  the  Gluteus  medius,  from  which  it  is 
separated  by  the  gluteal  vessels  and  superior  gluteal  nerve;  by  its  lower  border, 
with  the  Gemellus  superior  and  Coccygeus,  the  sciatic  vessels  and  nerves,  the 
internal  pudic  vessels  and  nerve,  and  muscular  branches  from  the  sacral  plexus, 
passing  from  the  pelvis  in  the  interval  between  the  two  muscles.  There  is 
usually  a  bursa  (bursa  m.  piriformis)  between  the  tendon  of  the  pyriformis  and 
the  ilium. 

The  Obturator  Membrane  (membrana  obturatoria)  (Fig.  215)  is  a  thin  layer  of 
interlacing  fibres  which  closes  almost  completely  the  obturator  foramen.  It  is 
attached,  externally,  to  the  margin  of  the  foramen;  internally,  to  the  posterior 
surface  of  the  ischio-pubic  ramus,  below  and  internal  to  the  margin  of  the 
foramen.  It  presents  at  its  upper  and  outer  part  a  small  canal,  obturator  canal 
(canalis  obturatorius)  for  the  passage  of  the  obturator  vessels  and  nerve.  Both 
obturator  muscles  are  connected  with  this  membrane. 

Dissection. — The  next  muscle,  as  well  as  the  origin  of  the  Pyriformis,  can  only  be  seen  when 
the  pelvis  is  divided  and  the  viscera  removed. 

The  Obturator  Interims  (Figs.  346  and  347) ,  like  the  preceding  muscle,  is  situated 
partly  within  the  cavity  of  the  pelvis,  and  partly  at  the  back  of  the  hip-joint.  It  arises 
from  the  inner  surface  of  the  anterior  and  external  wall  of  the  pelvis,  where  it  sur- 
rounds the  greater  part  of  the  obturator  foramen,  being  attached  to  the  descending 
ramus  of  the  os  pubis  and  the  ramus  of  the  ischium,  and  at  the  side  to  the  inner  sur- 
face of  the  innominate  bone  below  and  behind  the  pelvic  brim,  reaching  from  the 
upper  part  of  the  great  sacro-sciatic  foramen  above  and  behind  to  the  obturator 
foramen  below  and  in  front.  It  also  arises  from  the  inner  surface  of  the  obturator 
membrane  except  at  its  posterior  part,  from  the  tendinous  arch  which  completes 
the  canal  for  the  passage  of  the  obturator  vessels  and  nerve  and  to  a  slight  extent 
from  the  obturator  layer  of  the  pelvic  fascia,  which  covers  it.  The  fibres  converge 
rapidly,  and  are  directed  backward  and  downward,  and  terminate  in  four  or  five 
tendinous  bands,  which  are  found  on  its  deep  surface;  these  bands  are  reflected  at 
a  right  angle  over  the  inner  surface  of  the  tuberosity  of  the  ischium,  which  is 
grooved  for  their  reception;  the  groove  is  covered  with  cartilage,  and  lined  by  a 
synovial  bursa  (bursa  m.  obturatoris  interni).  The  muscle  leaves  the  pelvis  by 
the  lesser  sacro-sciatic  foramen ;  and  the  tendinous  bands  unite  into  a  single  flat- 
tened tendon,  which  passes  horizontally  outward,  and,  after  receiving  the  attach- 
ment of  the  Gemelli,  is  inserted  into  the  forepart  of  the  inner  surface  of  the  great 
trochanter  in  front  of  the  Obturator  externus.  A  synovial  bursa,  narrow  and 
elongated  in  form,  is  usually  found  between  the  tendon  of  this  muscle  and  the 
capsular  ligament  of  the  hip:  it  occasionally  communicates  with  the  bursa 
between  the  tendon  and  the  tuberosity  of  the  ischium,  the  two  forming  a 
single  sac. 

In  order  to  display  the  peculiar  appearances  presented  by  the  tendon  of  this  muscle,  it  must 
be  divided  near  its  insertion  and  reflected  inward. 

Relations. — Within  the  pelvis  this  muscle  is  in  relation,  by  its  anterior  surface, 
with  the  obturator  membrane  and  inner  surface  of  the  anterior  wall  of  the  pelvis ; 
by  its  posterior  surface,  with  the  pelvic  and  obturator  fascise,  which  separate  it 
from  the  Levator  ani;  and  it  is  crossed  by  the  internal  pudic  vessels  and  nerve. 
This  surface  forms  the  outer  boundary  of  the  ischio-rectal  fossa  (Fig.  337). 
External  to  the  pelvis  it  is  covered  by  the  Gluteus  maximus,  is  crossed  by  the 
great  sciatic  nerve,  and  rests  on  the  back  part  of  the  hip-joint.  As  the  tendon 
of  the  Obturator  internus  emerges  from  the  lesser  sacro-sciatic  foramen  it  is  over- 


THE  GLUTEAL  REGION 


529 


lapped  by  the  two  Gemelli,  while  nearer  its  insertion  the  Gemelli  pass  in  front  of  it 
and  form  a  groove  in  which  the  tendon  lies. 

The  Gemelli  (Fig.  346)  are  two  small  muscular  fasciculi,  accessories  to  the 
tendon  of  the  Obturator  internus,  which  is  received  into  a  groove  between  them. 
They  are  called  superior  and  inferior. 

The  Gemellus  Superior,  the  smaller  of  the  two,  arises  from  the  outer  surface 
of  the  spine  of  the  ischium,  and,  passing  horizontally  outward,  becomes  blended 


SACRO-SPINAL 
LIGAMENT  WITH 

COCCYGEUS       Mfll! 
MUSCLE 


1-iG.  347. — Muscles  of  the  small  or  true  pelvis  on  the  right  side,  viewed  from  without  and  below.     (Spalteholz.) 


with  the  upper  part  of  the  tendon  of  the  Obturator  internus,  and  is  inserted  with 

it  into  the  inner  surface  of  the  great  trochanter.    This  muscle  is  sometimes  wanting. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  the  sciatic 

vessels  and  nerves;  by  its  deep  surface,  with  the  capsule  of  the  hip-joint;  by  its 

34 


530 


THE  MUSCLES  AND  FASCIAE 


upper  border,  with  the  lower  margin  of  the  Pyriformis;  by  its  lower  border,  with 
the  tendon  of  the  Obturator  internus. 

The  Gemellus  Inferior  arises  from  the  upper  part  of  the  tuberosity  of  the  ischium, 
where  it  forms  the  lower  edge  of  the  groove  for  the  Obturator  internus  tendon, 
and,  passing  horizontally  outward,  is  blended  with  the  lower  part  of  the  tendon 
of  the  Obturator  internus,  and  is  inserted  with  it  into  the  inner  surface  of  the  great 
trochanter. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  the  sciatic 
vessels  and  nerves;  by  its  deep  surface,  with  the  scapular  ligament  of  the  hip-joint; 
by  its  upper  border,  with  the  tendon  of  the  Obturator  internus ;  by  its  lower  border, 
with  the  tendon  of  the  Obturator  externus  and  Quadratus  femoris. 

The  Quadratus  Femoris  (Fig.  346)  is  a  short,  flat  muscle,  quadrilateral  in  shape 
(hence  its  name),  situated  between  the  Gemellus  inferior  and  the  upper  margin 
of  the  Adductor  magnus.  It  arises  from  the  upper  part  of  the  external  lip  of  the 
tuberosity  of  the  ischium,  and,  proceeding  horizontally  outward,  is  inserted  into 
the  upper  part  of  the  linea  quadrata;  that  is,  the  line  which  crosses  the  posterior 
intertrochanteric  line.  A  synovial  bursa  is  often  found  between  the  under  surface 
of  this  muscle  and  the  lesser  trochanter,  which  it  covers. 


Obturator 
artery. 


Anterior  division  of 
obturator  nerve. 


Anterior  inferior 
iliac  spine. 


Posterior  division 
of  obturator 
nerve. 

Internal  circum- 
flex artery. 


'apsular  liga- 
ment partly 
cut  away. 


FIG.  348. — Obturator  externus  muscle.     (From  a  preparation  in  the  Museum  of  the  Royal  College  of 

Surgeons  of  England.) 

Relations. — By  its  posterior  surface,  with  the  Gluteus  maximus  and  the  sciatic 
vessels  and  nerves ;  by  its  anterior  surface,  with  the  tendon  of  the  Obturator  exter- 
nus and  trochanter  minor  and  with  the  capsule  of  the  hip-joint;  by  its  upper 
border,  with  the  Gemellus  inferior.  Its  lower  border  is  separated  from  the  Adductor 
magnus  by  the  terminal  branches  of  the  internal  circumflex  vessels. 


Dissection. — In  order  to  expose  the  next  muscle  (the  Obturator  externus)  it  is  necessary 
to  remove  the  Psoas,  Iliacus,  Pectineus,  and  Adductor  brevis  and  longus  muscles  from  the  front 


THE  GLUTEAL  REGION  531 

and  inner  side  of  the  thigh,  and  the  Gluteus  maximus  and  Quadratus  femoris  from  the  back 
part.  Its  dissection  should,  consequently,  be  postponed  until  the  muscles  of  the  anterior  and 
internal  femoral  regions  have  been  explained. 

The  Obturator  Extermis  (Figs.  347  and  348)  is  a  flat,  triangular  muscle,  which 
covers  the  outer  surface  of  the  anterior  wall  of  the  pelvis.  It  arises  from  the  margin 
of  bone  immediately  around  the  inner  side  of  the  obturator  foramen — viz.,  from  the 
body  and  ramus  of  the  os  pubis  and  the  ramus  of  the  ischium ;  it  also  arises  from 
the  inner  two-thirds  of  the  outer  surface  of  the  obturator  membrane,  and  from 
the  tendinous  arch  which  completes  the  canal  for  the  passage  of  the  obturator 
vessels  and  nerves.  The  fibres  from  the  pubic  arch  extend  on  to  the  inner  sur- 
face of  the  bone,  from  which  they  obtain  a  narrow  origin  between  the  margin  of 
the  foramen  and  the  attachment  of  the  membrane.  The  fibres  converging 
pass  backward,  outward,  and  upward,  and  terminate  in  a  tendon  which  runs 
across  the  back  part  of  the  hip-joint,  and  is  inserted  into  the  digital  fossa  of  the 
femur. 

Relations. — By  its  anterior  surface,  with  the  Psoas,  Iliacus,  Pectineus,  Adductor 
magnus,  and  Adductor  brevis;  and  more  externally,  with  the  neck  of  the  femur 
and  capsule  of  the  hip-joint.  The  obturator  artery  and  vein  lie  between  this 
muscle  and  the  obturator  membrane;  the  superficial  part  of  the  obturator  nerve 
lies  above  the  muscle,  and  the  deep  branch  perforates  it;  by  its  posterior  surface, 
with  the  obturator  membrane  and  Quadratus  femoris. 

Nerves. — The  Gluteus  maximus  is  supplied  by  the  fifth  lumbar  and  first  and 
second  sacral  nerves  through  the  inferior  gluteal  nerve  from  the  sacral  plexus; 
the  Gluteus  medius  and  minimus,  by  the  fourth  and  fifth  lumbar  and  first  sacral 
nerves  through  the  superior  gluteal;  the  Pyriformis  is  supplied  by  the  first  and 
second  sacral  nerves;  the  Gemellus  inferior  and  Quadratus  femoris  by  the  last 
lumbar  and  first  sacral  nerve;  the  Gemellus  superior  and  Obturator  internus  by 
the  fifth  lumbar  and  first  and  second  sacral  nerves,  and  the  Obturator  externus 
by  the  second,  third,  and  fourth  lumbar  nerves  through  the  obturator. 

Actions. — The  Gluteus  maximus,  when  it  takes  its  fixed  point  from  the  pelvis, 
extends  the  femur  and  brings  the  bent  thigh  into  a  line  with  the  body.  Taking 
its  fixed  point  from  below,  it  acts  upon  the  pelvis,  supporting  it  and  the  whole 
trunk  upon  the  head  of  the  femur,  which  is  especially  obvious  in  standing  on  one 
leg.  Its  most  powerful  actions  are  to  hold  the  head  of  the  femur  in  close  approxi- 
mation to  the  acetabulum  in  walking  and  to  cause  the  body  to  regain  the  erect 
position  after  stooping  by  drawing  the  pelvis  backward,  being  assisted  in  this  action 
by  the  Biceps,  Semitendinosus,  and  Semimembranosus.  The  Gluteus  maximus 
is  a  tensor  of  the  fascia  lata,and  by  its  connection  with  the  ilio-tibial  band  it  steadies 
the  femur  on  the  articular  surface  of  the  tibia  during  standing,  when  the  Extensor 
muscles  are  relaxed.  The  lower  part  of  the  muscle  also  acts  as  an  adductor  and 
external  rotator  of  the  limb.  The  Gluteus  medius  and  minimus  abduct  the  thigh 
when  the  limb  is  extended,  and  are  principally  called  into  action  in  supporting 
the  body  on  one  limb,  in  conjunction  with  the  Tensor  fasciae  femoris.  Their 
anterior  fibres,  by  drawing  the  great  trochanter  forward,  rotate  the  thigh  inward, 
in  which  action  they  are  also  assisted  by  the  Tensor  fasciae  femoris.  The  remain- 
ing muscles  are  powerful  rotators  of  the  thigh  outward.  In  the  sitting  posture, 
when  the  thigh  is  flexed  upon  the  pelvis,  their  action  as  rotators  cease,  and  they 
become  abductors,  with  the  exception  of  the  Obturator  externus,  which  still 
rotates  the  femur  outward.  When  the  femur  is  fixed,  the  Pyriformis  and  Obturator 
muscles  serve  to  draw  the  pelvis  forward  if  it  has  been  inclined  backward,  and 
assist  in  steadying  it  upon  the  head  of  the  femur. 

Surgical  Anatomy. — The  fascia  over  the  gluteal  region  is  extremely  dense  and  an  abscess 
beneath  it  may  pass  far  down  into  the  thigh. 


532 


THE  MUSCLES  AND  FASCIA 


4.  The  Posterior  Femoral  Region. 

Biceps.  Semitendinosus.  Semimembranosus. 

(Hamstring  muscles.} 

Dissection  (Fig.  345). — Make  a  vertical  incision  along  the  middle  of  the  back  of  the  thigh,, 
from  the  lower  fold  of  the  buttock  to  about  three  inches  below  the  back  of  the  knee-joint,  and 
there  connect  it  with  a  transverse  incision,  carried  from  the  inner  to  the  outer  side  of  the  leg. 
Make  a  third  incision  transversely  at  the  junction  of  the  middle  with  the  lower  third  of  the 
thigh.  The  integument  having  been  removed  from  the  back  of  the  knee,  and  the  boundaries 
of  the  popliteal  space  having  been  examined,  the  removal  of  the  integument  from  the  remaining 
^>art  of  the  thigh  should  be  continued,  when  the  fascia  and  muscles  of  this  region  will  be  exposed- 


BURSA   OF 
SEMIMEMBRANOSUS 


GASTROCNEMIUS 

(inner  head) 

BURSA  OF  INNER 
HEAD  OF 
GASTROCNEMIUS 


BURSA  OF 

APONEUROTIC 

EXPANSION 

OF  SARTORIUS 


DEEP  FASCIA 
OF  LEG 


FIG.  349. — Region  of  the  knee,  seen  obliquely  from  behind  and  within.     Right  limb.     (Toldt.) 

The  Biceps  or  Biceps  Flexor  Cruris  (m.  biceps  femoris)  is  a  large  muscle,  of 
considerable  length,  situated  on  the  posterior  and  outer  aspect  of  the  thigh 
(Figs.  346  and  349).  It  arises  by  two  heads.  One,  the  long  head  (caput  longum), 
arises  horn  the  lower  and  inner  impression  on  the  back  part  of  the  tuberosity 


THE  POSTERIOR  FEMORAL  REGION  533 

of  the  ischinm,  by  a  tendon  common  to  it  and  the  Semitendinosus,  and  from 
the  lower  part  of  the  great  sacro-sciatic  ligament.  Between  this  tendon  of 
origin  and  the  Semimembranosus  there  is  often  a  bursa  (bursa  m.  bicipitis 
jemoris  superior).  The  femoral,  or  short  head  (caput  breve),  arises  from  the 
outer  lip  of  the  linea  aspera,  between  the  Adductor  magnus  and  Vastus  externus, 
extending  up  almost  as  high  as  the  insertion  of  the  Gluteus  maximus;  from 
the  outer  prolongation  of  the  linea  aspera  to  within  two  inches  of  the  outer  con- 
el  vie,  and  from  the  external  intermuscular  septum.  The  fibres  of  the  long  head 
form  a  fusiform  belly,  which,  passing  obliquely  downward  and  a  little  out- 
ward, terminates  in  an  aponeurosis  which  covers  the  posterior  surface  of  the 
muscle,  and  receives  the  fibres  of  the  short  head:  this  aponeurosis  becomes 
gradually  contracted  into  a  tendon,  which  is  inserted  into  the  outer  side  of  the 
head  of  the  fibula,  and  by  a  small  slip  into  the  lateral  surface  of  the  external 
tuberosity  of  the  tibia.  At  its  insertion  the  tendon  divides  into  two  portions,  which 
embrace  the  long  external  lateral  ligament  of  the  knee-joint.  From  the  posterior 
border  of  the  tendon  a  thin  expansion  is  given  off  to  the  fascia  of  the  leg.  The 
tendon  of  this  muscle  forms  the  outer  hamstring.  Sometimes  there  is  a  bursa 
(bursa  bicipitogastrocnemialis)  between  the  tendon  of  insertion  of  the  Biceps  and 
the  origin  of  the  Gastrocnemius,  and  there  is  a  bursa  (bursa  m.  bicipitis  femoris 
inferior)  between  the  tendon  of  the  biceps  and  the  external  lateral  ligament. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  the  small 
sciatic  nerve,  the  fascia  lata,  and  integument.  By  its  deep  surface,  with  the  Semi- 
membranosus, Adductor  magnus,  and  Vastus  externus,  the  great  sciatic  nerve, 
and,  near  its  insertion,  with  the  external  head  of  the  Gastrocnemius,  the  Plantaris, 
the  superior  external  articular  artery,  and  the  external  popliteal  nerve. 

The  Semitendinosus  (Figs.  346  and  349),  remarkable  for  the  great  length 
of  its  tendon,  is  situated  at  the  posterior  and  inner  aspect  of  the  thigh.  It 
arises  from  the  lower  and  inner  impression  on  the  tuberosity  of  the  ischium 
by  a  tendon  common  to  it  and  the  long  head  of  the  Biceps ;  it  also  arises  from 
an  aponeurosis  which  connects  the  adjacent  surfaces  of  the  two  muscles  to 
the  extent  of  about  three  inches  after  their  origin.  There  is  a  bursa  (bursa 
m.  bicipitis  femoris  superior)  between  the  tendons  of  origin  of  the  Biceps  and 
Semitendinosus  on  one  side  and  the  tendon  of  origin  of  the  Semimembranosus 
on  the  other.  The  Semitendinosus  is  a  fusiform  muscle,  which,  passing  down- 
ward and  inward,  terminates  a  little  below  the  middle  of  the  thigh  in  a  long 
round  tendon  which  lies  along  the  inner  side  of  the  popliteal  space,  then 
curves  around  the  inner  tuberosity  of  the  tibia,  and  is  inserted  into  the  upper 
part  of  the  inner  surface  of  the  shaft  of  that  bone  nearly  as  far  forward  as  its 
anterior  border.  At  its  insertion  it  gives  off  from  its  lower  border  a  prolongation 
to  the  deep  fascia  of  the  leg.  This  tendon  lies  behind  the  tendon  of  the  Sar- 
torius,  and  below  that  of  the  Gracilis,  to  which  it  is  united.  A  tendinous  inter- 
section is  usually  observed  about  the  middle  of  the  muscles.  The  bursa  anserina 
lies  between  the  tendon  of  the  Semitendinosus  and  the  tibia.  This  bursa  was 
referred  to  in  speaking  of  the  Gracilis,  p.  522. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  fascia  lata; 
by  its  deep  surface,  with  the  Semimembranosus,  Adductor  magnus,  inner  head  of 
the  Gastrocnemius,  and  internal  lateral  ligament  of  the  knee-joint. 

The  Semimembranosus  (Figs.  346  and  349),  so  called  from  its  membranous 
tendon  of  origin,  is  situated  at  the  back  part  and  inner  side  of  the  thigh.  It 
arises  by  a  thick  tendon  from  the  upper  and  outer  impression  on  the  back  part 
of  the  tuberosity  of  the  ischium,  above  and  to  the  outer  side  of  the  Biceps  and 
Semitendinosus,  and  is  inserted  into  the  groove  on  the  inner  and  back  part  of  the 
inner  tuberosity  of  the  tibia,  beneath  the  internal  lateral  ligament.  The  tendon  of 
the  muscle  at  its  origin  expands  into  an  aponeurosis  which  covers  the  upper  part 


534  THE  MUSCLES  AND  FASCIAE 

of  its  anterior  surface :  from  this  aponeurosis  muscular  fibres  arise,  and  converge 
to  another  aponeurosis,  which  covers  the  lower  part  of  its  posterior  surface  and 
contracts  into  the  tendon  of  insertion.  The  tendon  of  the  muscle  at  its  insertion 
gives  off  certain  fibrous  expansions;  one  of  these,  of  considerable  size,  passes 
upward  and  outward  to  be  inserted  into  the  back  part  of  the  outer  condyle  of 
the  femur,  forming  part  of  the  posterior  ligament  of  the  knee-joint;  a  second  is 
continued  downward  to  the  fascia  which  covers  the  Popliteus  muscle.  The 
tendon  also  sends  a  few  fibres  to  join  the  internal  lateral  ligament  of  the  joint. 

The  tendons  of  the  two  preceding  muscles,  with  that  of  the  Gracilis,  form 
the  inner  hamstrings. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus,  Semitendinosus, 
Biceps,  and  fascia  lata;  by  its  deep  surface,  with  the  origin  of  the  Quadratus 
femoris,  popliteal  vessels,  Adductor  magnus,  and  inner  head  of  the  Gastroc- 
nemius;  by  its  inner  border,  with  the  Gracilis;  by  its  outer  border,  with  the  great 
sciatic  nerve,  and  its  internal  popliteal  branch.  There  is  a  bursa  between  the 
Gastrocnemius  and  Semimembranosus  and  another  bursa  between  the  Semi- 
membranosus  and  the  inner  condyle  of  the  tibia.  The  first  bursa  usually  com- 
municates with  the  knee-joint.  These  two  bursae  are  in  communication  and  in 
reality  constitute  a  double  bursa  (bursa  m.  semimembranosi) . 

Nerves. — The  muscles  of  this  region  are  supplied  by  the  first,  second,  and 
third  sacral  nerves  through  the  great  sciatic  nerve. 

Actions. — The  hamstring  muscles  flex  the  leg  upon  the  thigh.  When  the  knee 
is  semiflexed,  the  Biceps,  in  consequence  of  its  oblique  direction  downward  and 
outward,  rotates  the  leg  slightly  outward;  and  the  Semitendinosus,  and  to  a 
slight  extent  the  Semimembranosus,  rotate  the  leg  inward,  assisting  the  Popliteus. 
Taking  their  fixed  point  from  below,  these  muscles,  especially  the  Semimem- 
branosus, serve  to  support  the  pelvis  upon  the  head  of  the  femur  and  to  draV 
the  trunk  directly  backward,  as  in  raising  it  from  the  stooping  position  or  in 
feats  of  strength,  when  the  body  is  thrown  backward  in  the  form  of  an  arch. 
When  the  leg  is  extended  on  the  thigh,  they  limit  the  amount  of  flexion  of  the 
trunk  on  the  lower  limbs. 

Surgical  Anatomy. — The  hamstring  tendons  are  occasionally  ruptured.  In  disease  of  the 
knee-joint  the  hamstrings  may  contract,  flexing  the  knee,  drawing  the  tibia  backward,  and  some- 
times causing  incomplete  dislocation.  The  tendons  of  these  muscles  occasionally  require  sub- 
cutaneous division  in  some  forms  of  spurious  ankylosis  of  the  knee-joint  dependent  upon 
permanent  contraction  and  rigidity  of  the  Flexor  muscles,  or  from  stiffening  of  the  ligamentous 
and  other  tissues  surrounding  the  joint,  the  result  of  disease.  Division  of  a  tendon  is  effected 
by  putting  the  tendon  upon  the  stretch,  and  inserting  a  narrow  sharp-pointed  knife  between 
it  and  the  skin:  the  cutting  edge  being  then  turned  toward  the  tendon,  it  should  be  divided, 
taking  great  care  that  the  wound  in  the  skin  is  not  at  the  same  time  enlarged.  The  relation  of  the 
external  popliteal  nerve  to  the  tendon  of  the  Biceps  must  always  be  borne  in  mind  in  dividing  this 
tendon. 

III.  MUSCLES  AND  FASCI-ffi  OF  THE  LEG. 

These  may  be  divided  into  three  groups:  those  on  the  anterior,  those  on  the 
posterior,  and  those  on  the  outer  side  of  the  leg. 

5.  The  Anterior  Tibio-fibular  Region  (Fig.  350). 

Tibialis  anticus.  Extensor  longus  digitorum. 

Extensor  proprius  hallucis.1  Peroneus  tertius. 

1  There  is  no  such  word  as  '  'Hallux,  -cis."  It  is  the  result  of  some  ignorant  blunder,  copied  until  it  has  become 
established  by  usage;  it  has  been  thought  better,  therefore,  to  retain  it.  According  to  Lewis  and  bhort,  the 
word  is  ALLEX,  masculine;  genitive,  ALLICIS,  the  great  toe,  and  the  correct  rendering  would  be  Extensor  pro- 
prius allicis.  It  is  a  rare  word,  and  is  sometimes  spelt,  but  not  so  correctly,  '  'Hallex.  It  is  used  by  Flautus, 
in  the  "Pcenulus,"  V.,  v.  31,  of  a  little  man,  as  we  might  say  "a  hop-o'-my-thumb.'  "Tune  hie  amator  audes 
esse,  allex  viri"  (To  think  of  you  daring  to  make  up  to  her,  you  hop-o'-my-thumb!).  The  word  alex,  some- 
times spelt  "allex,"  a  fish  sauce,  is  probably  a  different  word  altogether.  It  is  used  by  Horace  and  Fliny. 
— ED.  of  15th  English  edition. 


THE  ANTERIOR   TIBIO-FIBULAR  REGION  535 

Dissection  (Fig.  339). — The  knee  should  be  bent,  a  block  placed  beneath  it,  and  the  foot 
kept  in  an  extended  position ;  then  make  an  incision  through  the  integument  in  the  middle  line 
of  the  leg  to  the  ankle,  and  continue  it  along  the  dorsum  of  the  foot  to  the  toes.  Make  a  second 
incision  transversely  across  the  ankle,  and  a  third  in  the  same  direction  across  the  bases  of  the 
toes;  remove  the  flaps  of  integument  included  between  these  incisions  in  order  to  examine  the 
deep  fascia  of  the  leg. 

The  Deep  Fascia  of  the  Leg  (fascia  cruris)  forms  a  complete  investment  to 
the  muscles,  but  is  not  continuous  over  the  subcutaneous  surfaces  of  the  bones. 
It  is  continuous  above  with  the  fascia  lata,  receiving  an  expansion  from  the  tendon 
of  the  Biceps  on  the  outer  side,  and  from  the  tendons  of  the  Sartorius,  Gracilis, 
and  Semitendinosus  on  the  inner  side;  in  front  it  blends  with  the  periosteum 
covering  the  subcutaneous  surface  of  the  tibia,  and  with  that  covering  the  head 
and  external  malleolus  of  the  fibula;  below  it  is  continuous  with  the  annular  liga- 
ments of  the  ankle.  It  is  thick  and  dense  in  the  upper  and  anterior  part  of  the  leg, 
and  gives  attachment,  by  its  deep  surface,  to  the  Tibialis  anticus  and  Extensor 
longus  digitorum  muscles,  but  is  thinner  behind,  where  it  covers  the  Gastrocnemius 
and  Soleus  muscles.  Over  the  popliteal  space  it  is  much  strengthened  by  trans- 
verse fibres  which  stretch  across  from  the  inner  to  the  outer  hamstring  muscles, 
and  it  is  here  perforated  by  the  external  saphenous  vein.  Its  deep  surface  gives 
off,  on  the  outer  side  of  the  leg,  two  strong  intermuscular  septa  which  enclose  the 
Peronei  muscles,  and  separate  them  from  the  muscles  of  the  anterior  and  posterior 
tibial  regions.  It  also  gives  off  several  smaller  and  more  slender  processes 
which  enclose  the  individual  muscles  in  each  region;  at  the  same  time  a  broad 
transverse  intermuscular  septum,  called  the  deep  transverse  fascia  of  the  leg, 
intervenes  between  the  superficial  and  deep  muscles  in  the  posterior  tibio-fibular 
region. 

Remove  the  fascia  by  dividing  it  in  the  same  direction  as  the  integument,  excepting  opposite 
the  ankle,  where  it  should  be  left  entire.  Commence  the  removal  of  the  fascia  from  below, 
opposite  the  tendons,  and  detach  it  in  the  line  of  direction  of  the  muscular  fibres. 

The  Tibialis  Anticus  (m.  tibialis  anterior)  is  situated  on  the  outer  side  of  the 
tibia;  it  is  thick  and  fleshy  at  its  upper  part,  tendinous  below.  It  arises  from  the 
outer  tuberosity  and  upper  two-thirds  of  the  external  surface  of  the  shaft  of  the 
tibia;  from  the  adjoining  part  of  the  interosseous  membrane;  from  the  deep 
surface  of  the  fascia;  and  from  the  intermuscular  septum  between  it  and  the 
Extensor  longus  digitorum:  the  fibres  pass  vertically  downward,  and  terminate 
in  a  tendon  which  is  apparent  on  the  anterior  surface  of  the  muscle  at  the  lower 
third  of  the  leg.  After  passing  through  the  innermost  compartment  of  the  anterior 
annular  ligament,  it  is  inserted  into  the  inner  and  under  surface  of  the  internal 
cuneiform  bone  and  base  of  the  metatarsal  bone  of  the  great  toe.  There  is 
usually  a  bursa  (bursa  subtendinea  m.  tibialis  anterioris)  between  the  tendon  of 
the  tibialis  anticus  and  the  internal  cuneiform  bone. 

Relations. — By  its  anterior  surface,  with  the  fascia  and  with  the  annular  liga- 
ment; by  its  posterior  surface,  with  the  interosseous  membrane,  tibia,  ankle-joint, 
and  inner  side  of  the  tarsus :  .this  surface  also  overlaps  the  anterior  tibial  vessels 
and  nerve  in  the  upper  part  of  the  leg.  By  its  inner  surface,  with  the  tibia;  by 
its  outer  surface,  with  the  Extensor  longus  digitorum  and  Extensor  proprius 
hallucis,  and  the  anterior  tibial  vessels  and  nerve. 

The  Extensor  Proprius  Hallucis  (m.  extensor  hallucis  longus)  is  a  thin,  elon- 
gated, and  flattened  muscle  situated  between  the  Tibialis  anticus  and  Extensor 
longus  digitorum.  It  arises  from  the  anterior  surface  of  the  fibula  for  about  the 
middle  two-fourths  of  its  extent,  its  origin  being  internal  to  that  of  the  Extensor 
longus  digitorum;  it  also  arises  from  the  interosseous  membrane  to  a  similar 
extent.  The  fibres  pass  downward,  and  terminate  in  a  tendon  which  occupies 


536 


\TiAu 


'jtjainetit. 


THE  MUSCLES  AND  FASCIAE 

the  anterior  border  of  the  muscle,  passes  through  a 
distinct  compartment  in  the  lower  portion  of  the 
annular  ligament,  crosses  the  anterior  tibial  vessels 
near  the  bend  of  the  ankle,  and  is  inserted  into  the 
base  of  the  last  phalanx  of  the  great  toe.  Opposite 
the  metatarso-phalangeal  articulation  the  tendon 
gives  off  a  thin  prolongation  on  each  side,  which 
covers  the  surface  of  the  joint.  It  usually  sends  an 
expansion  from  the  inner  side  of  the  tendon,  to  be 
inserted  into  the  base  of  the  first  phalanx. 

Relations. — By  its  anterior  surface,  with  the  fascia 
and  the  anterior  annular  ligament;  by  its  posterior 
surface,  with  the  interosseous  membrane,  fibula, 
tibia,  and  ankle-joint;  by  its  outer  side,  with  the 
Extensor  longus  digitorum  above,  the  dorsalis  pedis 
vessels,  anterior  tibial  nerve,  and  Extensor  brevis 
digitorum  below;  by  its  inner  side,  with  the  Tibialis 
anticus  and  the  anterior  tibial  vessels  above.  The 
muscle  is  external  to  the  anterior  tibial  vessels  in 
the  upper  part  of  the  leg;  but  in  the  lower  third  its 
tendon  crosses  over  them,  so  that  it  lies  internal  to 
them  on  the  dorsum  of  the  foot. 

The  Extensor  Longus  Digitorum  (m.  extensor 
digitorum  longus}  is  an  elongated,  flattened,  penni- 
form  muscle  situated  the  most  externally  of  all  the 
muscles  on  the  forepart  of  the  leg.  It  arises  from 
the  outer  tuberosity  of  the  tibia;  from  the  upper 
three-fourths  of  the  anterior  surface  of  the  shaft  of 
the  fibula;  from  the  interosseous  membrane;  from 
th*1  d^ep  surface  of  the  fascia;  and  from  the  inter- 
muscular  septa  between  it  and  the  Tibialis  anticus 
on  the  inner  and  the  Peronei  on  the  outer  side. 
The  tendon  enters  a  canal  in  the  annular  ligament 
with  the  Peroneus  tertius,  and  divides  into  four 
slips,  which  run  across  the  dorsum  of  the  foot  ancl 
are  inserted  into  the  second  and  third  phalanges  of 
the  four  lesser  toes.  The  mode  in  which  the  tendons 
are  inserted  is  the  following:  Each  of  the  three 
tendons  opposite  the  metatarso-phalangeal 


inner 


FIG.  350. — Muscles  of  the  front  of 
the  leg. 


articulation  is  joined,  on  its  outer  side,  by  a  ten- 
don from  the  Extensor  brevis  digitorum.  The  outer 
tendon  does  not  receive  such  a  tendinous  slip.  They 
all  receive  a  fibrous  expansion  from  the  Interossei 
and  Lumbricales,  and  then  spread  out  into  a  broad 
aponeurosis,  which  covers  the  dorsal  surface  of  the 
first  phalanx:  this  aponeurosis,  at  the  articulation  of 
the  first  with  the  second  phalanx,  divides  into  three 
slips — a  middle  one,  which  is  inserted  into  the  base 
of  the  second  phalanx,  and  two  lateral  slips,  which, 
after  uniting  on  the  dorsal  surface  of  the  second 
phalanx,  are  continued  onward,  to  be  inserted  into 
the  base  of  the  third. 

Relations. — By  its  anterior  surface,  with  the  fascia 
and  the  annular  ligament;   by  its   posterior  surface, 


THE  POSTERIOR  TIBIO-FIBULAR  REGION  537 

with  the  fibula,  interosseous  membrane,  ankle-joint,  and  Extensor  brevis  digi- 
torum;  by  its  inner  side,  with  the  Tibialis  anticus,  Extensor  proprius  hallucis, 
and  anterior  tibial  vessels  and  nerve;  by  its  outer  side,  with  the  Peroneus  longus 
and  brevis. 

The  Peroneus  Tertius  (m.  peronceus  tertius)  is  a  part  of  the  Extensor  longus 
digitorum,  and  might  be  described  as  its  fifth  tendon.  The  fibres  belonging  to 
this  tendon  arise  from  the  lower  fourth  of  the  anterior  surface  of  the  fibula,  from 
the  lower  part  of  the  interosseous  membrane,  and  from  an  intermuscular  septum 
between  it  and  the  Peroneus  brevis.  The  tendon,  after  passing  through  the  same 
canal  in  the  annular  ligament  as  the  Extensor  longus  digitorum,  is  inserted  into 
the  dorsal  surface  of  the  base  of  the  metatarsal  bone  of  the  little  toe.  This 
muscle  is  sometimes  wanting. 

Nerves. — These  muscles  are  supplied  by  the  fourth  and  fifth  lumbar  and  first 
sacral  nerves  through  the  anterior  tibial  nerve. 

Actions. — The  Tibialis  anticus  and  Peroneus  tertius  are  the  direct  flexors  of  the 
foot  at  the  ankle-joint;  the  former  muscle,  when  acting  in  conjunction  with  the 
Tibialis  posticus,  raises  the  inner  border  of  the  foot  (i.e.,  inverts  the  foot);  and 
the  latter,  acting  with  the  Peroneus  brevis  and  longus,  draws  the  outer  border  of 
the  foot  upward  and  the  sole  outward  (i.  e.,  everts  the  foot).  The  Extensor  longus 
digitorum  and  Extensor  proprius  hallucis  extend  the  phalanges  of  the  toes,  and, 
continuing  their  action,  flex  the  foot  upon  the  leg.  Talcing  their  fixed  point  from 
below,  in  the  erect  posture,  all  these  muscles  serve  to  fix  the  bones  of  the  leg  in  the 
perpendicular  position,  and  give  increased  strength  to  the  ankle-joint. 

6.  The  Posterior  Tibio-fibular  Region  (Figs.  349,  352). 

Dissection  (Fig.  345). — Make  a  vertical  incision  along  the  middle  line  of  the  back  of  the 
leg,  from  the  lower  part  of  the  popliteal  space  to  the  heel,  connecting  it  below  by  a  transverse 
incision  extending  between  the  two  malleoli;  the  flaps  of  integument  being  removed,  the  fascia 
and  muscles  should  be  examined. 

The  muscles  in  this  region  of  the  leg  are  subdivided  into  two  layers — superficial 
and  deep.  The  superficial  layer  constitutes  a  powerful  muscular  mass,  forming 
the  calf  of  the  leg.  Their  large  size  is  one  of  the  most  characteristic  features  of 
the  muscular  apparatus  in  man,  and  bears  a  direct  connection  with  his  ordinary 
attitude  and  mode  of  progression. 

The  Superficial  Layer. 
Gastrocnemius.  Soleus.  Plantaris. 

The  Gastrocnemius  is  the  most  superficial  muscle,  and  forms  the  greater  part 
of  the  calf.  It  arises  by  two  heads,  which  are  connected  to  the  condyles  of  the  femur 
by  two  strong  flat  tendons.  The  inner  and  larger  head  (caput  mediate)  arises  from 
a  depression  at  the  upper  and  back  part  of  the  inner  condyle  and  from  the 
adjacent  part  of  the  femur.  There  is  a  bursa  (bursa  m.  gastrocnemii  medialis) 
between  the  tendon  of  origin  and  the  inner  condyle.  The  outer  head  (caput 
laterale)  arises  from  an  impression  on  the  outer  side  of  the  external  condyle  and 
from  the  posterior  surface  of  the  femur  immediately  above  the  condyle.  There 
is  a  bursa  (bursa  m.  gastrocnemii  lateralis)  between  the  tendon  of  origin  and  the 
outer  condyle.  Both  heads,  also,  arise  by  a  few  tendinous  and  fleshy  fibres 
from  the  ridges  which  are  continued  upward  from  the  condyles  to  the  linea  aspera. 
Each  tendon  spreads  out  into  an  aponeurosis,  which  covers  the  posterior  surface 
of  that  portion  of  the  muscle  to  which  it  belongs;  the  muscular  fibres  of  the 
inner  head  being  thicker  and  extending  lower  than  those  of  the  outer.  From 
the  anterior  surface  of  these  tendinous  expansions  muscular  fibres  are  given  off. 


538 


THE  MUSCLES  AND  FASCIAE 


The  fibres  in  the  median  line,  which  correspond  to  the  accessory  portions  of  the 
muscle  derived  from  the  bifurcations  of  the  linea  aspera,  unite  at  an  angle 
upon  a  median  tendinous  raphe  below:  the  remaining  fibres  converge  to  an 
aponeurosis  which  covers  the  anterior  surface  of  the  muscle,  and  this,  gradually 
contracting,  unites  with  the  tendon  of  the  Soleus,  and  forms  with  it  the  tendo 
Achillis. 

Relations. — By  its  superficial  surface,  with  the  fascia  of  the  leg,  which  separates 
it  from  the  external  saphenous  vein  and  nerve;  by  its  deep  surface,  with  the  pos- 
terior ligament  of  the  knee-joint,  the  Popliteus,  Soleus,  Plantaris,  popliteal  vessels, 
and  internal  popliteal  nerve.  The  tendon  of  the  inner  head  corresponds  with  the 
back  part  of  the  inner  condyle,  from  which  it  is  separated  by  a  synovial  bursa, 
which,  in  some  cases,  communicates  with  the  cavity  of  the  knee-joint.  The 
tendon  of  the  outer  head  contains  a  sesamoid  fibro-cartilage  '(rarely  osseous) 
where  it  plays  over  the  corresponding  outer  condyle;  and  one  is  occasionally 
found  in  the  tendon  of  the  inner  head. 

The  Gastrocnemius  should  be  divided  across,  just  below  its  origin,  and  turned  downward, 
in  order  to  expose  the  next  two  muscles. 

The  Soleus  is  a  broad  flat  muscle  situated  immediately  beneath  the  Gastroc- 
nemius. It  has  received  its  name  from  its  resemblance  in  shape  to  a  sole-fish.  It 
arises  by  tendinous  fibres  from  the  back  part  of  the  head  of  the  fibula  and  from 

the  upper  third  of  the  posterior  surface  of  its  shaft; 
from  the  oblique  line  of  the  tibia  and  from  the  mid- 
dle third  of  its  internal  border;  some  fibres  also  arise 
from  a  tendinous  arch  placed  between  the  tibial  and 
fibular  origins  of  the  muscle,  beneath  which  the 
popliteal  vessels  and  internal  popliteal  nerve  pass. 
The  fibres  pass  backward  to  an  aponeurosis  which 
covers  the  posterior  surface  of  the  muscle,  and  this, 
gradually  becoming  thicker  and  narrower,  joins  with 
the  tendon  of  the  Gastrocnemius,  and  forrhs  with  it 
the  tendo  Achillis. 

The  triceps  surce  is  the  designation  in  the  new 
nomenclature  of  the  Gastrocnemius  and  Soleus. 

Relations.  —  By  its  superficial  surface,  with  the 
Ga.strocnemius  and  Plantaris;  by  its  deep  surface, 
with  the  Flexor  longus  digitorum,  Flexor  longus 
hallucis,  Tibialis  posticus,  and  posterior  tibial 
vessels  and  nerve,  from  which  it  is  separated  by 
the  transverse  intermuscular  septum  or  deep  transverse  fascia  of  the  leg. 

The  Tendo  Achillis  (tendo  cakaneus],  the  common  tendon  of  the  Gastrocnemius 
and  Soleus,1  is  the  thickest  and  strongest  tendon  in  the  body.  It  is  about  six 
inches  in  length,  and  commences  about  the  middle  of  the  leg,  but  receives  fleshy 
fibres  on  its  anterior  surface  nearly  to  its  lower  end.  Gradually  becoming  con- 
tracted below,  it  is  inserted  into  the  lower  part  of  the  posterior  surface  of  the 
os  calcis,  a  synovial  bursa,  the  retro-calcaneal  bursa  (bursa  tendinis  calcanei 
[Achillis])  (Fig.  351),  being  interposed  between  the  tendon  and  the  upper  part 
of  this  surface.  The  tendon  spreads  out  somewhat  at  its  lower  end,  so  that  its 
narrowest  part  is  usually  about  an  inch  and  a  half  above  its  insertion.  The  tendon 
is  covered  by  the  fascia  and  the  integument,  a  bursa  (bursa  subcutanea  calcanea) 
(Fig.  351)  being  often  interposed  between  the  tendon  and  the  fascia.  The  tendon 


BURSA  BETWEEN 
FASCIA  AND 
TENDON 


BURSA  BETWEEN 

TENDON    AND 
OS  CALCIS 


FIG.  351. — Bursse  of  the  tendo 
Achillis.    (Poirier  and  Charpy.) 


1  These  two  muscles  with  a  common  tendon  are  by  some  anatomists  classed  together  as  one  muscle,  the 
Triceps  sura,  the  two  heads  of  origin  of  the  Gastrocnemius  and  the  Soleus  constituting  the  three  heads  of  the 
Triceps,  and  the  tendo  Achillis  the  single  tendon  of  insertion. — ED.  of  15th  English  edition. 


THE  POSTERIOR   TIBIO-FIBULAR  REGION 


539 


is  separated  from  the  deep  muscles  and  vessels  by  a  considerable  interval  filled 
up  with  areolar  and  adipose  tissue.  Along  its  outer  side,  but  superficial  to  it,  is 
the  external  saphenous  vein. 


'  Femur. \ 


Tendons  of 

fpERONEUS    LONGUS 

and  BREVIS. 


FIG.  352. — Muscles  of  the  back  of  the  leg. 
Superficial  layer. 


FIG.  353. — Muscles  of  the  back 
of  the  leg.     Deep  layer. 


The  Plantaris  is  an  extremely  diminutive  muscle  placed  between  the  Gas- 
trocnemius  and  Soleus,  and  remarkable  fof  its  long  and  delicate  tendon.    It  arises 


540  THE  MUSCLES  AND  FASCIAE 

from  the  lower  part  of  the  outer  prolongation  of  the  linea  aspera  and  from  the  pos- 
terior ligament  of  the  knee-joint.  It  forms  a  small  fusiform  belly,  about  three  or 
four  inches  in  length,  terminating  in  a  long  slender  tendon  which  crosses  obliquely 
between  the  two  muscles  of  the  calf,  and,  running  along  the  inner  border  of  the 
tendo  Achillis,  is  inserted  with  it  into  the  posterior  part  of  the  os  calcis.  This 
muscle  is  occasionally  double,  and  is  sometimes  wanting.  Occasionally  its  tendon 
is  lost  in  the  internal  annular  ligament  or  in  the  fascia  of  the  leg. 

Nerves. — The  Gastrocnemius  is  supplied  by  the  first  and  second  sacral  nerves, 
and  the  Plantaris  by  the  fourth  and  fifth  lumbar  and  first  sacral  nerves  through  the 
internal  popliteal.  The  Soleus  is  supplied  by  the  fifth  lumbar  and  first  and  second 
sacral  nerves  through  the  internal  popliteal  and  posterior  tibial. 

Actions. — The  muscles  of  the  calf  are  the  chief  extensors  of  the  foot  at  the 
ankle-joint.  They  possess  considerable  power,  and  are  constantly  called  into  use 
in  standing,  walking,  dancing,  and  leaping;  hence  the  large  size  they  usually  pre- 
sent. In  walking  these  muscles  draw  powerfully  upon  the  os  calcis,  raising  the 
heel,  and  with  it  the  entire  body,  from  the  ground;  the  body  being  thus  supported 
on  the  raised  foot,  the  opposite  limb  can  be  carried  forward.  In  standing,  the 
Soleus,  taking  its  fixed  point  from  below,  steadies  the  leg  upon  the  foot,  and  pre- 
vents the  body  from  falling  forward,  to  which  there  is  a  constant  tendency  from  the 
.superincumbent  weight.  The  Gastrocnemius,  acting  from  below,  serves  to  flex  the 
femur  upon  the  tibia,  assisted  by  the  Popliteus.  The  Plantaris  is  the  rudiment  of 
a  large  muscle  which  exists  in  some  of  the  lower  animals  and  is  continued  over  the 
os  calcis  to  be  inserted  into  the  plantar  fascia.  In  man  it  is  an  accessory  to  the 
Gastrocnemius,  extending  the  ankle  if  the  foot  is  free,  or  bending  the  knee  if  the 
foot  is  fixed.  Possibly,  acting  from  below,  by  its  attachment  to  the  posterior  liga- 
ment of  the  knee-joint,  it  may  pull  that  ligament  backward  during  flexion,  and  so 
protect  it  from  being  compressed  between  the  two  articular  surfaces. 

The  Deep  Layer  (Fig.  353). 

Popliteus.  Flexor  longus  digitorum. 

Flexor  longus  hallucis.  Tibialis  posticus. 

> 

Dissection. — Detach  the  Soleus  from  its  attachment  to  the  fibula  and  tibia,  and  turn  it  down- 
ward, when  the  deep  layer  of  muscles  is  exposed,  covered  by  the  deep  transverse  fascia  of  the 
leg. 

Deep  Transverse  Fascia. — The  deep  transverse  fascia  of  the  leg  is  a  trans- 
versely placed,  intermuscular  septum,  between  the  superficial  and  deep  muscles 
in  the  posterior  tibio-fibular  region.  On  either  side  it  is  connected  to  the  margins 
of  the  tibia  and  fibula.  Above,  where  it  covers  the  Popliteus,  it  is  thick  and  dense, 
and  receives  an  expansion  from  the  tendon  of  the  Semimembranosus ;  it  is  thinner 
in  the  middle  of  the  leg,  but  below,  where  it  covers  the  tendons  passing  behind  the 
malleoli,  it  is  thickened  and  continuous  with  the  internal  annular  ligament. 

This  fascia  should  now  be  removed,  commencing  from  below  opposite  the  tendons,  and 
detaching  it  from  the  muscles  in  the  direction  of  their  fibres. 

The  Popliteus  (Fig.  349)  is  a  thin,  flat,  triangular  muscle,  which  forms  part  of 
the  floor  of  the  popliteal  space.  It  arises  by  a  strong  tendon,  about  an  inch  in 
length,  from  a  deep  depression  on  the  outer  side  of  the  external  condyle  of  the 
femur,  and  from  the  posterior  ligament  of  the  knee-joint.  A  bursa  (bursa  m. 
poplitei)  is  placed  between  the  condyle  and  the  muscle.  The  muscle  is  inserted 
into  the  inner  two-thirds  of  the  triangular  surface  above  the  oblique  line  on  the 
posterior  surface  of  the  shaft  of  the  tibia,  and  into  the  tendinous  expansion 
covering  the  surface  of  the  muscle.  The  tendon  of  the  muscle  is  covered  by 
that  of  the  Biceps  and  by  the  external  lateral  ligament  of  the  knee-joint;  it  grooves 


THE  POSTERIOR   TIBIO-FIB  ULAR  REGION  541 

the  posterior  border  of  the  external  semilunar  fibro-cartilage,  and  is  invested  by 
the  synovial  membrane  of  the  knee-joint. 

Relations. — By  its  superficial  surface,  with  the  fascia  covering  it,  which  separates 
it  from  the  Gastrocnemius,  Plantaris,  popliteal  vessels,  and  internal  popliteal  nerve; 
by  its  deep  surface,  with  the  knee-joint  and  back  of  the  tibia. 

The  Flexor  Longus  Hallucis  (m.  flexor  hallucis  longus)  is  situated  on  the  fibular 
side  of  the  leg,  and  is  the  most  superficial  and  largest  of  the  three  next  muscles. 
It  arises  from  the  lower  two-thirds  of  the  posterior  surface  of  the  shaft  of  the 
fibula,  with  the  exception  of  an  inch  at  its  lowest  part;  from  the  lower  part  of 
the  interosseous  membrane;  from  an  intermuscular  septum  between  it  and  the 
Peronei,  externally;  and  from  the  fascia  covering  the  Tibialis  posticus  internally. 
The  fibres  pass  obliquely  downward  and  backward,  and  terminate  in  a  tendon 
which  occupies  nearly  the  whole  length  of  the  posterior  surface  of  the  muscle. 
This  tendon  occupies  a  groove  on  the  posterior  surface  of  the  lower  end  of  the 
tibia;  it  then  lies  in  a  second  groove  on  the  posterior  surface  of  the  astragalus,  and 
finally  in  a  third  groove,  beneath  the  sustentaculum  tali  of  the  os  calcis,  and 
passes  into  the  sole  of  the  foot,  where  it  runs  forward  between  the  two  heads  of 
the  Flexor  brevis  hallucis,  and  is  inserted  into  the  base  of  the  last  phalanx  of  the 
great  toe  (Fig.  355).  The  grooves  in  the  astragalus  and  os  calcis,  which  contain 
the  tendon  of  the  muscle,  are  converted  by  tendinous  fibres  into  distinct  canals 
lined  by  synovial  membrane;  and  as  the  tendon  crosses  the  sole  of  the  foot,  it  is 
connected  to  the  common  flexor  by  a  tendinous  slip. 

Relations. — By  its  superficial  surface,  with  the  Soleus  and  tendo  Achillis,  from 
which  it  is  separated  by  the  deep  transverse  fascia;  by  its  deep  surface,  with  the 
fibula,  Tibialis  posticus,  the  peroneal  vessels,,  the  lower  part  of  the  interosseous 
membrane,  and  the  ankle-joint;  by  its  outer  border,  with  the  Peronei;  by  its  inner 
border,  with  the  Tibialis  posticus  and  posterior  tibial  vessels  and  nerve.  In  the 
sole  of  the  foot  it  lies  above  the  Abductor  hallucis  and  Flexor  longus  digitorum. 

The  Flexor  Longus  Digitorum  (m.  flexor  digitorum  longus)  is  situated  on 
the  tibial  side  of  the  leg.  At  its  origin  it  is  thin  and  pointed,  but  gradually 
.increases  in  size  as  it  descends.  It  arises  from  the  posterior  surface  of  the  shaft 
of  the  tibia,  immediately  below  the  oblique  line  to  within  three  inches  of  its 
extremity,  internal  to  the  tibial  origin  of  the  Tibialis  posticus;  some  fibres  also 
arise  from  the  fascia  covering  the  Tibialis  posticus.  The  fibres  terminate  in  a 
tendon  which  runs  nearly  the  whole  length  of  the  posterior  surface  of  the  muscle. 
This  tendon  passes  behind  the  internal  malleolus  in  a  groove,  common  to  it  and 
the  Tibialis  posticus,  but  separated  from  the  latter  by  a  fibrous  septum,  each 
tendon  being  contained  in  a  special  sheath  lined  by  a  separate  synovial  membrane. 
It  then  passes  obliquely  forward  and  outward,  superficial  to  the  internal  lateral 
ligament,  into  the  sole  of  the  foot  (Fig.  355),  where,  crossing  superficially  to  the 
tendon  of  the  Flexor  longus  hallucis,1  to  which  it  is  connected  by  a  strong 
tendinous  slip,  it  becomes  expanded,  is  joined  by  the  Flexor  accessorius,  and  finally 
divides  into  four  tendons  which  are  inserted  into  the  bases  of  the  last  phalanges 
of  the  four  lesser  toes,  each  tendon  passing  through  a  fissure  in  the  tendon  of  the 
Flexor  brevis  digitorum  opposite  the  base  of  the  first  phalanges  (Fig.  354). 

Relations. — In  the  leg:  by  its  superficial  surface,  with  the  posterior  tibial  vessels 
and  nerve,  and  the  deep  transverse  fascia,  which  separates  it  from  the  Soleus 
mliscle;  by  its  deep  surface,  with  the  Tibia  and  Tibialis  posticus.  In  the  foot  it  is 
covered  by  the  Abductor  hallucis  and  Flexor  brevis  digitorum,  and  crosses  super- 
ficial to  the  Flexor  longus  hallucis. 

The  Tibialis  Posticus  (m.  tibialis  posterior)  lies  between  the  two  preceding 
muscles,  and  is  the  most  deeply  seated  of  all  the  muscles  in  the  leg.  It  com- 

1  That  is,  in  the  order  of  dissection  of  the  sole  of  the  foot. 


542  THE  MUSCLES  AND  FASCIAE 

mences  above  by  two  pointed  processes,  separated  by  an  angular  interval, 
through  which  the  anterior  tibial  vessels  pass  forward  to  the  front  of  the  leg. 
It  arises  from  the  whole  of  the  posterior  surface  of  the  interosseous  membrane, 
excepting  its  lowest  part,  from  the  outer  portion  of  the  posterior  surface  of  the 
shaft  of  the  tibia,  between  the  commencement  of  the  oblique  line  above,  and  the 
junction  of  the  middle  and  lower  third  of  the  shaft  below;  and  from  the  upper 
two-thirds  of  the  internal  surface  of  the  fibula;  some  fibres  also  arise  from  the 
deep  transverse  fascia  and  from  the  intermuscular  septa,  separating  it  from  the 
adjacent  muscles  on  each  side.  This  muscle,  in  the  lower  fourth  of  the  leg, 
passes  in  front  of  the  Flexor  longus  digitorum,  and  terminates  in  a  tendon  which 
passes'  through  a  groove  behind  the  inner  malleolus  with  the  tendon  of  that 
muscle,  but  enclosed  in  a  separate  sheath;  it  then  passes  through  another  sheath, 
over  the  internal  lateral  ligament  into  the  foot,  and  then  beneath  the  inferior 
calcaneo-scaphoid  ligament,  and  is  inserted  into  the  tuberosity  of  the  scaphoid 
and  internal  cuneiform  bones  (Fig.  356).  The  tendon  of  this  muscle  contains  a 
sesamoid  fibro-cartilage  as  it  passes  over  the  scaphoid  bone,  and  gives  off  fibrous 
expansions,  one  of  which  passes  backward  to  the  sustentaculum  tali  of  the  os  calcis, 
others  outward  to  the  middle  and  external  cuneiform  and  cuboid,  and  some 
forward  to  the  base  of  the  second,  third,  and  fourth  metatarsal  bones  (Fig.  355). 

Relations. — By  its  superficial  surface,  with  the  Soleus,  from  which  it  is  separated 
by  the  deep  transverse  fascia,  the  Flexor  longus  digitorum,  the  posterior  tibial 
vessels  and  nerve,  and  the  peroneal  vessels;  by  its  deep  surface,  with  the  inter- 
osseous  ligament,  the  tibia,  fibula,  and  ankle-joint. 

Nerves. — The  Popliteus  is  supplied  by  the  fourth  and  fifth  lumbar  and  first  sacral 
nerves,  through  the  internal  popliteal;  the  Flexor  longus  digitorum  and  Tibialis 
posticus  by  the  fifth  lumbar  and  first  sacral;  and  the  Flexor  longus  hallucis  by  the 
fifth  lumbar  and  first  and  second  sacral  nerves  through  the  posterior  tibial. 

Actions. — The  Popliteus  assists  in  flexing  the  leg  upon  the  thigh;  when  the  leg 
is  flexed,  it  will  rotate  the  tibia  inward.  It  is  especially  called  into  action  at  the 
commencement  of  the  act  of  bending  the  knee,  inasmuch  as  it  produces  a  slight 
inward  rotation  of  the  tibia,  which  is  essential  in  the  early  stage  of  this  movement.. 
The  Tibialis  posticus  is  a  direct  extensor  of  the  foot  at  the  ankle-joint;  acting  in 
conjunction  with  the  Tibialis  anticus,  it  turns  the  sole  of  the  foot  inward  (i.  e., 
inverts  the  foot),  antagonizing  the  Peronei,  which  turn  it  outward  (evert  it).  In 
the  sole  of  the  foot  the  tendon  of  the  Tibialis  posticus  lies  directly  below  the  inferior 
calcaneo-scaphoid  ligament,  and  is  therefore  an  important  factor  in  maintaining 
the  arch  of  the  foot.  The  Flexor  longus  digitorum  and  Flexor  longus  hallucis  are 
the  direct  flexors  of  the  phalanges,  and,  continuing  their  action,  extend  the  foot 
upon  the  leg;  they  assist  the  Gastrocnemius  and  Soleus  in  extending  the  foot,  as  in 
the  act  of  walking  or  in  standing  on  tiptoe.  In  consequence  of  the  oblique  direction 
of  the  tendon  of  the  long  flexor  the  toes  would  be  drawn  inward  were  it  not  for  the 
Flexor  accessorius  muscle,  which  is  inserted  into  the  outer  side  of  its  tendon  and 
draws  it  to  the  middle  line  of  the  foot  during  its  action.  Taking  their  fixed  point 
from  the  foot,  these  muscles  serve  to  maintain  the  upright  posture  by  steadying 
the  tibia  and  fibula  perpendicularly  upon  the  ankle-joint.  They  also  serve  to  raise 
these  bones  from  the  oblique  position  they  assume  in  the  stooping  posture. 

7.  The  Fibular  Region  (Fig.  353). 
Peroneus  longus.  Peroneus  brevis. 

Dissection. — The  muscles  are  readily  exposed  by  removing  the  fascia  covering  their  surface, 
from  below  upward,  in  the  line  of  direction  of  their  fibres. 

The  Peroneus  Longus  (m.  peronceus  longus)  is  situated  at  the  upper  part  of 
the  outer  side  of  the  leg,  and  is  the  more  superficial  of  the  two  muscles.  It  arises 


THE  FIBULAR  REGION  543 

from  the  head  and  upper  two-thirds  of  the  outer  surface  of  the  shaft  of  the  fibula, 
from  the  deep  surface  of  the  fascia,  and  from  the  intermuscular  septa  between  it 
and  the  muscles  on  the  front,  and  those  on  the  back  of  the  leg,  occasionally  also 
by  a  few  fibres  from  the  outer  tuberosity  of  the  tibia.  Between  its  attachment 
to  the  head  and  to  the  shaft  of  the  fibula  there  is  a  small  interval  of  bone  from 
which  no  muscular  fibres  arise ;  through  this  gap  the  external  popliteal  nerve  passes 
beneath  the  muscle.  The  muscle  terminates  in  a  long  tendon,  which  passes  behind 
the  outer  malleolus,  in  a  groove  common  to  it  and  the  tendon  of  the  Peroneus 
brevis,  behind  which  it  lies,  the  groove  being  converted  into  a  canal  by  a  fibrous 
band,  and  the  tendons  being  invested  by  a  common  synovial  membrane;  it  is 
then  reflected  obliquely  forward  across  the  outer  side  of  the  os  calcis,  below  its 
peroneal  tubercle,  being  contained  in  a  separate  fibrous  sheath,  lined  by  a  pro- 
longation of  the  synovial  membrane  which  lines  the  groove  behind  the  malleolus. 
Having  reached  the  outer  side  of  the  cuboid  bone,  it  runs  in  a  groove  on  the 
under  surface  of  that  bone,  which  is  converted  into  a  canal  by  the  long  calcaneo- 
cuboid  ligament,  and  is  lined  by  a  synovial  membrane:  the  tendon  then  crosses 
the  sole  of  the  foot  obliquely,  and  is  inserted  into  the  outer  side  of  the  base  of  the 
metatarsal  bone  of  the  great  toe  and  the  internal  cuneiform  bone  (Figs.  355  and 
356).  Occasionally  it  sends  a  slip  to  the  base  of  the  second  metatarsal  bone.  The 
tendon  changes  its  direction  at  two  points:  first,  behind  the  external  malleolus; 
secondly,  on  the  outer  side  of  the  cuboid  bone;  in  both  of  these  situations  the 
tendon  is  thickened,  and  in  the  latter  a  sesamoid  fibre-cartilage,  or  sometimes  a 
bone,  is  usually  developed  in  its  substance. 

Relations. — By  its  superficial  surface,  with  the  fascia  and  integument;  by  its 
deep  surface,  with  the  fibula,  external  popliteal  nerve,  the  Peroneus  brevis,  os 
calcis,  and  cuboid  bone;  by  its  anterior  border,  with  an  intermuscular  septum,, 
which  intervenes  between  it  and  the  Extensor  longus  digitorum;  by  its  posterior 
border,  with  an  intermuscular  septum,  which  separates  it  from  the  Soleus  above 
and  the  Flexor  longus  hallucis  below. 

The  Peroneus  Brevis  (m.  peronaeus  brevis}  lies  beneath  the  Peroneus  longus, 
and  is  shorter  and  smaller  than  it.  It  arises  from  the  lower  two-thirds  of  the 
external  surface  of  the  shaft  of  the  fibula,  internal  to  the  Peroneus  longus,  and 
from  the  intermuscular  septa  separating  it  from  the  adjacent  muscles  on  the  front 
and  back  part  of  the  leg.  The  fibres  pass  vertically  downward,  and  terminate  in 
a  tendon  which  runs  in  front  of  that  of  the  preceding  muscle  through  the  same 
groove,  behind  the  external  malleolus,  being  contained  in  the  same  fibrous 
sheath  and  lubricated  by  the  same  synovial  membrane.  It  then  passes  through 
a  separate  sheath  on  the  outer  side  of  the  os  calcis,  above  that  for  the  tendon  of 
the  Peroneus  longus,  the  two  tendons  being  here  separated  by  the  peroneal 
tubercle,  and  is  finally  inserted  into  the  tuberosity  at  the  base  of  the  metatarsal 
bone  of  the  little  toe,  on  its  outer  side. 

Relations. — By  its  superficial  surface,  with  the  Peroneus  longus  and  the  fascia 
of  the  leg  and  foot;  by  its  deep  surface,  with  the  fibula  and  outer  side  of  the  os 
calcis. 

Nerves. — The  Peroneus  longus  and  brevis  are  supplied  by  the  fourth  and  fifth 
lumbar  and  first  sacral  nerves  through  the  musculo-cutaneous  branch  of  the 
external  popliteal  nerve. 

Actions. — The  Peroneus  longus  and  brevis  extend  the  foot  upon  the  leg,  in 
conjunction  with  the  Tibialis  posticus,  antagonizing  the  Tibialis  anticus  and 
Peroneus  tertius,  which  are  flexors  of  the  foot.  The  Peroneus  longus  also  everts 
the  sole  of  the  foot;  hence  the  extreme  eversion  occasionally  observed  in  fracture 
of  the  lower  end  of  the  fibula,  where  that  bone  offers  no  resistance  to  the  action 
of  this  muscle.  From  the  oblique  direction  of  the  Peroneus  longus  tendon  across 
the  sole  of  the  foot  it  is  an  important  agent  in  the  maintenance  of  the  transverse 


544  THE  MUSCLES  AND  FASCIAE 

arch  of  the  foot.  Taking  their  fixed  point  below,  the  Peronei  serve  to  steady  the 
leg  upon  the  foot.  This  is  especially  the  case  in  standing  upon  one  leg,  when 
the  tendency  of  the  superincumbent  weight  is  to  throw  the  leg  inward:  the 
Peroneus  longus  overcomes  this  tendency  by  drawing  on  the  outer  side  of  the 
leg,  and  thus  maintains  the  perpendicular  direction  of  the  limb. 

Surgical  Anatomy. — The  student  should  now  consider  the  position  of  the  tendons  of  the 
various  muscles  of  the  leg,  their  relation  with  the  ankle-joint  and  surrounding  blood-vessels,  and 
especially  their  action  upon  the  foot,  as  their  rigidity  and  contraction  give  rise  to  one  or  other  of 
the  kinds  of  deformity  known  as  club-foot.  The  most  simple  and  common  deformity,  and  one 
that  is  rarely,  if  ever,  congenital,  is  the  talipes  cquinus,  the  heel  being  raised  by  rigidity  and  con- 
traction of  the  Gastrocnemius  muscle,  and  the  patient  walking  upon  the  ball  of  the  foot.  In  the 
talipes  varus  the  foot  is  forcibly  adducted  and  the  inner  side  of  the  sole  raised,  sometimes  to  a 
right  angle  with  the  ground,  by  the  action  of  the  Tibialis  anticus  and  posticus.  In  the  talipes 
valgus  the  outer  edge  of  the  foot  is  raised  by  the  Peronei  muscles,  and  the  patient  walks  on  the 
inner  ankle.  In  the  talipes  calcaneus  the  toes  are  raised  by  the  Extensor  muscles,  the  heel  is 
depressed,  and  the  patient  walks  upon  it.  Other  varieties  of  deformity  are  met  with,  as  the 
talipes  equino-varus,  equino-valgus,  and  calcaneo-valgus,  whose  names  sufficiently  indicate  their 
nature.  Of  these,  the  talipes  equino-varus  is  the  most  common  congenital  form:  the  heel  is 
raised  by  the  tendo  Achillis,  the  inner  border  of  the  foot  drawn  upward  by  the  Tibialis  anticus, 
the  anterior  two-thirds  twisted  inward  by  the  Tibialis  posticus,  and  the  arch  increased  by  the 
contraction  of  the  plantar  fascia,  so  that  the  patient  walks  on  the  middle  of  the  outer  border  of 
the  foot.  Each  of  these  deformities  may  sometimes  be  successfully  relieved  by  division  of  the 
opposing  tendons  and  fascia;  by  this  means  the  foot  regains  its  proper  position,  and  the  tendons 
subsequently  heal.  The  operation  is  easily  performed  by  putting  the  contracted  tendon  upon 
the  stretch,  and  dividing  it  by  means  of  a  narrow,  sharp-pointed  knife  inserted  beneath  it. 
Pes  cavus  or  hollow  foot  is  accentuation  of  the  longitudinal  arch.  Pes  planus  or  flat-foot  has- 
been  discussed  elsewhere. 

Rupture  of  a  few  of  the  fibres  of  the  Gastrocnemius  may  take  place.  Rupture  of  the  Plantaris 
tendon  not  uncommonly  occurs,  especially  in  men  somewhat  advanced  in  life,  from  some  sudden 
exertion,  and  frequently  occurs  during  the  game  of  lawn  tennis,  and  is  hence  known  as  lawn- 
tennis  leg.  The  accident  is  accompanied  by  a  sudden  pain,  and  produces  a  sensation  as  if  the 
individual  had  been  struck  a  violent  blow  on  the  part.  The  tendo  Achillis  is  also  sometimes 
ruptured.  It  is  stated  that  John  Hunter  ruptured  his  tendo  Achillis  whilst  dancing  at  the 
age  of  forty.  The  retro-calcaneal  bursa  is  interposed  between  the  posterior  surface  of  the  os 
calcis  and  the  tendo  Achillis,  just  above  the  point  of  insertion  of  the  tendon.  If  it  inflames 
it  produces  disabling  pain  (achillodynia,  or  A Ibert's  disease,  retro-calcaneal  bursitis) .  This  bursa 
may  become  cartilaginous  or  osteophytes  may  form  on  the  surface  toward  the  os  calcis. 


IV.  MUSCLES  AND  FASCIA  OF  THE  FOOT. 

The  fibrous  bands,  or  thickened  portions  of  the  fascia  of  the  leg,  which  bind  down  the  tendons 
in  front  of  and  behind  the  ankle  in  their  passage  to  the  foot  should  now  be  examined;  they  are 
termed  the  annular  ligaments,  and  are  three  in  number — anterior,  internal,  and  external. 

The  Anterior  Annular  Ligament  (Fig.  350)  consists  of  a  superior  or  transverse  portion 
(ligamentum  transversum  cruris}  which  binds  down  the  Extensor  tendons  as  they 
descend  on  the  front  of  the  tibia  and  fibula;  and  an  inferior  or  Y-shaped  portion 
(ligamentum'  crudatum  cruris},  which  retains  them  in  connection  with  the  tarsus, 
the  two  portions  being  connected  by  a  thin  intervening  layer  of  fascia.  The 
transverse  portion  is  attached  externally  to  the  lower  end  of  the  fibula  and  inter- 
nally to  the  tibia;  above  it  is  continuous  with  the  fascia  of  the  leg;  it  contains 
only  one  synovial  sheath,  for  the  tendon  of  the  Tibialis  anticus;  the  other  tendons 
and  the  anterior  tibial  vessels  and  nerve  passing  beneath  it,  but  without  any  dis- 
tinct synovial  sheath.  The  Y-shaped  portion  is  placed  in  front  of  the  ankle-joint, 
the  stem  of  the  Y,  the  fundiform  ligament  of  Retzius,  being  attached  externally  to 
the  upper  surface  of  the  os  calcis,  in  front  of  the  depression  for  the  interosseous 
ligament;  it  is  directed  inward,  as  a  double  layer,  one  lamina  passing  in  front, 
and  the  other  behind,  the  tendons  of  the  Peroneus  tertius  and  Extensor  longus 
digitorum.  At  the  inner  border,  of  the  latter  tendon  these  two  layers  join 'together, 


OF  THE  FOOT  545 

forming  a  sort  of  loop  or  sheath  in  which  the  tendons  are  enclosed,  surrounded 
by  a  synovial  membrane.  From  the  inner  extremity  of  this  loop  the  two  limbs 
of  the  Y  diverge:  one  passes  upward  and  inward,  to  be  attached  to  the  internal 
malleolus,  passing  over  the  Extensor  proprius  hallucis  and  the  vessels  and  nerves, 
but  enclosing  the  Tibialis  anticus  and  its  synovial  sheath  by  a  splitting  of  its 
fibres.  The  other  limb  extends  downward  and  inward  to  be  attached  to  the 
inner  border  of  the  plantar  fascia,  and  passes  over  the  tendons  of  the  Extensor 
proprius  hallucis  and  Tibialis  anticus  and  also  the  vessels  and  nerves.  These 
two  tendons  are  contained  in  separate  synovial  sheaths  situated  beneath  the 
ligament. 

The  Internal  Annular  Ligament  (ligamentum  laciniatum}  is  a  strong  fibrous 
band  which  extends  from  the  inner  malleolus  above  to  the  internal  margin  of  the 
os  calcis  below,  converting  a  series  of  grooves  in  this  situation  into  canals  for  the 
passage  of  the  tendons  of  the  Flexor  muscles  and  vessels  into  the  sole  of  the  foot. 
It  is  continuous  by  its  upper  border  with  the  deep  fascia  of  the  leg,  and  by  its  lower 
border  with  the  plantar  fascia  and  the  fibres  of  origin  of  the  Abductor  hallucis 
muscle.  The  four  canals  which  the  ligament  completes  transmit,  counting  from 
before  backward,  first,  the  tendon  of  the  Tibialis  posticus;  second,  the  tendon  of  the 
Flexor  longus  digitorum;  third,  the  posterior  tibia!  vessels  and  nerve,  which  run 
through  a  broad  space  beneath  the  ligament;  lastly,  in  a  canal  formed  partly  by 
the  astragalus,  the  tendon  of  the  Flexor  longus  hallucis.  The  canals  for  the  tendons 
are  lined  by  a  separate  synovial  membrane. 

The  External  Annular  Ligament  is  divided  into  two  portions:  a  superior  por- 
tion (rctinaculum  mm.  peronaeorum  superius),  which  extends  from  the  extremity 
of  the  outer  malleolus  to  the  outer  surface  of  the  os  calcis:  it  binds  down  the 
tendons  of  the  Peroneus  longus  and  brevis  muscles  in  their  passage  behind  the 
external  malleolus.  The  two  tendons  are  enclosed  in  one  synovial  sac.  An 
inferior  portion  (retinaculum  mm.  peronaeorum  inferius),  which  bridges  the  Peronei 
on  the  side  of  the  os  calcis  and  is  attached  to  the  bone  above  and  below  them. 

Dissection  of  the  Sole  of  the  Foot.— The  foot  should  be  placed  on  a  high  block  with  the 
sole  uppermost,  and  firmly  secured  in  that  position.  Carry  an  incision  round  the  heel  and  along 
the  inner  and  outer  borders  of  the  foot  to  the  great  and  little  toes.  This  incision  should  divide 
the  integument  and  thick  layer  of  granular  fat  beneath  until  the  fascia  is  visible;  the  skin  and  fat 
should  then  be  removed  from  the  fascia  in  a  direction  from  behind  forward,  as  seen  in  Fig.  345. 

Plantar  Fascia  (aponeurosis  plantaris). — The  plantar  fascia,  the  densest  of  all 
the  fibrous  membranes,  is  of  great  strength,  and  consists  of  pearly-white  glisten- 
ing fibres,  disposed,  for  the  most  part,  longitudinally:  it  is  divided  into  a  central 
and  two  lateral  portions. 

Central  Portion. — The  central  portion,  the  thickest,  is  narrow  behind  and 
attached  to  the  inner  tubercle  of  the  os  calcis,  posterior  to  the  origin  of  the 
Flexor  brevis  digitorum,  and,  becoming  broader  and  thinner  in  front,  divides 
near  the  heads  of  the  metatarsal  bones  into  five  processes,  one  for  each  of  the  toes. 
Each  of  these  processes  divides  opposite  the  metatarso-phalangeal  articulation 
into  two  strata,  superficial  and  deep.  The  superficial  stratum  is  inserted  into 
the  skin  of  the  transverse  sulcus  which  divides  the  toes  from  the  sole.  The 
deeper  stratum  divides  into  two  slips  which  embrace  the  sides  of  the  flexor  tendons 
of  the  toes,  and  blend  with  the  sheaths  of  the  tendons,  and  laterally  with  the 
transverse  metatarsal  ligament,  thus  forming  a  series  of  arches  through  which 
the  tendons  of  the  short  and  long  flexors  pass  to  the  toes.  The  intervals  left 
between  the  five  processes  allow  the  digital  vessels  and  nerves  and  the'  tendons 
of  the  Lumbricales  muscles  to  become  superficial.  At  the  point  of  division  of  the 
fascia  into  processes  and  slips  numerous  transverse  fibres  are  superadded,  which 
serve  to  increase  the  strength  of  the  fascia  at  this  part  by  binding  the  processes 

35 


546  THE  MUSCLES  AND  FASCIAE 

together  and  connecting  them  with  the  integument.  The  central  portion  of  the 
plantar  fascia  is  continuous  with  the  lateral  portions  at  each  side,  and  sends 
upward  into  the  foot,  at  their  point  of  junction,  two  strong  vertical  intermuscular 
septa,  broader  in  front  than  behind,  which  separate  the  middle  from  the  external 
and  internal  plantar  group  of  muscles;  from  these,  again,  thinner  transverse 
septa  are  derived,  which  separate  the  various  layers  of  muscles  in  this  region. 
The  upper  surface  of  this  fascia  gives  attachment  behind  to  the  Flexor  brevis 
digitorum  muscle. 

Lateral  Portions. — The  lateral  portions  of  the  plantar  fascia  are  thinner  than 
the  central  piece,  and  cover  the  sides  of  the  foot.  The  outer  portion  covers  the 
under  surface  of  the  Abductor  minimi  digiti;  it  is  thick  behind,  thin  in  front,  and 
extends  from  the  os  calcis,  forward,  to  the  base  of  the  fifth  metatarsal  bone,  into 
the  outer  side  of  which  it  is  attached;  it  is  continuous  internally  with  the  middle 
portion  of  the  plantar  fascia,  and  externally  with  the  dorsal  fascia.  The  inner 
portion  is  very  thin,  and  covers  the  Abductor  hallucis  muscle;  it  is  attached 
behind  to  the  internal  annular  ligament,  and  is  continuous  around  the  side  of 
the  foot  with  the  dorsal  fascia,  and  externally  with  the  middle  portion  of  the 
plantar  fascia 

Bursse  about  the  Ankle  and  Foot. — (1)  A  subcutaneous  bursa  on  the  sole  of 
the  foot,  beneath  the  tuberosity  of  the  os  calcis.  (2)  A  subcutaneous  bursa 
over  the  tendo  Achillis  (bursa  subcutanea  calcanea).  (3)  The  retrocalcaneal 
bursa,  between  the  posterior  surface  of  the  os  calcis  and  the  insertion  of  the 
tcndo  Achillis  (bursa  tendinis  calcanei  [Achillis]).  (4)  A  bursa  between  the 
internal  cuneiform  bone  and  the  tendon  of  the  Tibialis  anticus  (bursa  subten- 
dinea  m.  tibialis  anterioris) .  (5)  Bursae  between  the  heads  of  the  metatarsal 
bones  (bursae  intermetatarsophalangeae).  (6)  A  subcutaneous  bursa  over  the 
internal  malleolus  (bursa  subcutanea  malleoli  medialis).  (7)  Bursse  between  the 
scaphoid  and  middle  cuneiform  bones  on  the  one  hand  and  the  tendon  of  the 
Tibialis  posticus  on  the  other  (bursa  subtendinea  m.  tibialis  posteriori*) .  (8)  Bursse 
between  the  Lumbricales  and  the  transverse  ligaments  (bursae  mm.  lumbricalium 
pedis) .  (9)  A  bursa  over  the  external  malleolus  (bursa  subcutanea  malleoli  lateralis). 
(10)  A  bursa  over  the  head  of  the  first  metatarsal  bone.  Various  muscles  have 
tendon-sheaths  lined  with  synovial  membrane  (vaginal  sheaths). 

Surgical  Anatomy. — The  dense  plantar  fascia  aids  powerfully  in  maintaining  the  arch  of  the 
foot.  When  this  fascia  stretches  or  gives  way  flat-foot  forms.  In  some  forms  of  club-foot 
the  plantar  fascia  is  contracted.  This  contraction  is  usually  a  secondary  change. 

When  inflammation  causes  tenderness  and  enlargement  of  the  bursa  over  the  metatarso- 
phalangeal  articulation  of  the  great  toe,  the  enlargement  is  called  a  bunion.  Enlargement  of 
the  retro-calcaneal  bursa  is  known  as  Albert's  disease,  or  achillodynia. 

8.  The  Dorsal  Region  (Fig.  350). 
Extensor  brevis  digitorum. 

Fascia  (fascia  dorsalis  pedis). — The  fascia  on  the  dorsum  of  the  foot  is  a  thin 
membranous  layer  continuous  above  with  the  anterior  margin  of  the  annular 
ligament;  it  becomes  gradually  lost  opposite  the  heads  of  the  metatarsal  bones, 
and  on  each  side  blends  with  the  lateral  portions  of  the  plantar  fascia ;  it  forms  a 
sheath  for  the  tendons  placed  o'n  the  dorsum  of  the  foot.  On  the  removal  of  this 
fascia  the  muscles  and  tendons  of  the  dorsal  region  of  the  foot  are  exposed. 

The  Extensor  Brevis  Digitorum  (m.  extensor  digitorum  brevis)  (Fig.  350) 
is  a  broad  thin  muscle  which  arises  from  the  forepart  of  the  upper  and 
outer  surfaces  of  the  os  calcis,  in  front  of  the  groove  for  the  Peroneus  brevis, 
from  the  external  calcaneo-astragaloid  ligament,  and  from  the  common  limb  of 
the  Y-shaped  portion  of  the  anterior  annular  ligament.  It  passes  obliquely 


THE  PLANTAR  REGION  547 

across  the  dorsum  of  the  foot,  and  terminates  in  four  tendons.  The  innermost, 
which  is  the  largest,  is  inserted  into  the  dorsal  surface  of  the  base  of  the  first 
phalanx  of  the  great  toe,  crossing  the  dorsalis  pedis  artery;  the  other  three,  into 
the  outer  sides  of  the  long  extensor  tendons  of  the  second,  third,  and  fourth  toes. 

Relations. — By  its  superficial  surface,  with  the  fascia  of  the  foot,  the  tendons 
of  the  Extensor  longus  digitorum  and  Peroneus  tertius;  by  its  deep  surface,  with 
the  tarsal  and  metatarsal  arteries  and  bones  and  the  Dorsal  interossei  muscles. 

Nerves. — It  is  supplied  by  the  anterior  tibial  nerve. 

Actions. — The  Extensor  brevis  digitorum  is  an  accessory  to  the  long  Extensor, 
extending  the  phalanges  of  the  four  inner  toes,  but  acting  only  on  the  first  phalanx 
of  the  great  toe.  The  obliquity  of  its  direction  counteracts  the  oblique  movement 
given  to  the  toes  by  the  long  Extensor,  so  that,  both  muscles  acting  together,  the 
toes  are  evenly  extended. 

9.  The  Plantar  Region  (Figs.  354,  355,  356,  357,  358). 

The  muscles  in  the  plantar  region  of  the  foot  may  be  divided  into  three  groups, 
in  a  similar  manner  to  those  in  the  hand.  Those  of  the  internal  plantar  region 
are  connected  with  the  great  toe,  and  correspond  with  those  of  the  thumb;  those 
of  the  external  plantar  region  are  connected  with  the  little  toe,  and  correspond 
with  those  of  the  little  finger;  and  those  of  the  middle  plantar  region  are  con- 
nected with  the  tendons  intervening  between  the  two  former  groups.  But  in  order 
to  facilitate  the  dissection  of  these  muscles  it  will  be  found  more  convenient  to 
divide  them  into  four  layers,  as  they  present  themselves,  in  the  order  in  which 
they  are  successively  exposed. 

The  First  Layer. 

Abductor  hallucis.  Flexor  brevis  digitorum. 

Abductor  minimi  digiti. 

Dissection. — Remove  the  fascia  on  the  inner  and  outer  sides  of  the  foot,  commencing  in 
front  over  the  tendons  and  proceeding  backward.  The  central  portion  should  be  divided 
transversely  in  the  middle  of  the  foot,  and  the  two  flaps  dissected  forward  and  backward. 

The  Abductor  Hallucis  lies  along  the  inner  border  of  the  foot.  It  arises  from 
the  inner  tubercle  on  the  under  surface  of  the  os  calcis;  from  the  internal  annular 
ligament ;  from  the  plantar  fascia ;  and  from  the  intermuscular  septum  between  it 
and  the  Flexor  brevis  digitorum.  The  fibres  terminate  in  a  tendon  which  is 
inserted,  together  with  the  innermost  tendon  of  the  Flexor  brevis  hallucis,  into 
the  inner  side  of  the  base  of  the  first  phalanx  of  the  great  toe. 

Relations. — By  its  superficial  surface,  with  the  plantar  fascia;  by  its  deep  sur- 
face, with  the  Flexor  brevis  hallucis,  the  Flexor  accessorius,  and  the  tendons  of 
the  Flexor  longus  digitorum  and  Flexor  longus  hallucis,  the  Tibialis  anticus  and 
posticus,  the  plantar  vessels  and  nerves.  Its  outer  border  is  in  relation  to  the 
Flexor  brevis  digitorum. 

The  Flexor  Brevis  Digitorum  (m.  flexor  digitorum  brevis}  lies  in  the 
middle  of  the  sole  of  the  foot,  immediately  beneath1  the  plantar  fascia,  with 
which  it  is  firmly  united.  It  arises  by  a  narrow  tendinous  process,  from  the 
inner  tubercle  of  the  os  calcis,  from  the  central  part  of  the  plantar  fascia,  and 
from  the  intermuscular  septa  between  it  and  the  adjacent  muscles.  It  passes 
forward,  and  divides  into  four  tendons,  one  for  each  of  the  four  outer  toes. 
Opposite  the  bases  of  the  first  phalanges  each  tendon  divides  into  two  slips,  to 
allow  of  the  passage  of  the  corresponding  tendon  of  the  Flexor  longus  digitorum; 

1  That  is,  in  order  of  dissection  of  the  sole  of  the  foot. 


548 


THE  MUSCLES  AND  FASCIA 


the  two  portions  of  the  tendon  then  unite  and  form  a  grooved  channel  for  the 
reception  of  the  accompanying  long  flexor  tendon.  Finally,  they  divide  a  second 
time,  to  be  inserted  into  the  sides  of  the  second  phalanges  about  their  middle.  The 
mode  of  division  of  the  tendons  of  the  Flexor  brevis  digitorum  and  their  insertion 

into  the  phalanges  is  analogous  to  the  division 
and  insertion  of  the  Flexor  sublimis  digitorum 
in  the  hand. 

Relations. — By  its  superficial  surface,  with 
the  plantar  fascia;  by  its  deep  surface,  with  the 
Flexor  accessorius,  the  Lumbricales,  the  ten- 
dons of  the  Flexor  longus  digitorum,  and  the 
lateral  plantar  vessels  and  nerve,  from  which 
it  is  separated  by  a  thin  layer  of  fascia.  The 
outer  and  inner  borders  are  separated  from  the 
adjacent  muscles  by  means  of  vertical  pro- 
longations of  the  plantar  fascia. 

Fibrous  Sheaths  of  the  Flexor  Tendons. — 
These  are  not  so  well  marked  as  in  the  fingers. 
The  flexor  tendons  of  the  toes  as  they  run 
along  the  phalanges  are  retained  against  the 
bones  by  a  fibrous  sheath,  forming  osseo- 
aponeurotic  canals.  These  sheaths  are  formed 
by  strong  fibrous  bands  which  arch  across  the 
tendons  and  are  attached  on  each  side  to  the 
margins  of  the  phalanges.  Opposite  the  mid- 
dle of  the  proximal  and  second  phalanges  the 
sheath  is  very  strong,  and  the  fibres  pass 
transversely,  but  opposite  the  joints  it  is 
much  thinner,  and  the  fibres  pass  obliquely. 
Each  sheath  is  lined  by  a  synovial  mem- 
brane which  is  reflected  on  the  contained 
tendon. 

The  Abductor  Minimi  Digiti  (m.  abductor 
digiti  quinti]  lies  along  the  outer  border  of  the 
foot.  It  arises,  by  a  very  broad  origin,  from 
the  outer  tubercle  of  the  os  calcis,  from  the 
under  surface  of  the  os  calcis  between  the  two 
tubercles,  from  the  forepart  of  the  inner 
tubercle,  from  the  plantar  fascia  and  the  in- 
termuscular  septum,  between  it  and  the  Flexor 
brevis  digitorum.  Its  tendon,  after  gliding 
over  a  smooth  facet  on  the  under  surface  of 
the  base  of  the  fifth  metatarsal  bone,  is  inserted 
with  the  short  Flexor  of  the  little  toe  into  the  outer  side  of  the  base  of  the  first 
phalanx  of  this  toe. 

Relations. — By  its  superficial  surface,  with  the  plantar  fascia;  by  its  deep  sur- 
face, with  the  Flexor  accessorius,  the  Flexor  brevis  minimi  digiti,  the  long  plantar 
ligament,  and  the  tendon  of  the  Peroneus  longus.  On  its  inner  side  are  the 
lateral  plantar  vessels  and  nerve,  and  it  is  separated  from  the  Flexor  brevis 
digitorum  by  a  vertical  septum  of  fascia. 

Dissection. — The  muscles  of  the  superficial  layer  should  be  divided  at  their  origin  by  insert- 
ing the  knife  beneath  each,  and  cutting  obliquely  backward,  so  as  to  detach  them  from  the 
bone;  they  should  then  be  drawn  forward,  in  order  to  expose  the  second  layer,  but  not  cut  away 
at  their  insertion.  The  two  layers  are  separated  by  a  thin  membrane,  the  deep  plantar  fascia, 


FIG.  3,54. — Muscles  of  the  sole  of  the  foot. 
First  layer. 


THE  PLANTAR  REGION  549 

on  the  removal  of  which  is  seen  the  tendon  of  the  Flexor  longus  digitorum,  the  Flexor  accessorius, 
the  tendon  of  the  Flexor  longus  hallucis,  and  the  Lumbricales.  The  long  flexor  tendons 
diverge  from  each  other  at  an  acute  angle;  the  Flexor  longus  hallucis  runs  along  the  inner  side 
of  the  foot,  on  a  plane  superior  to  that  of  the  Flexor  longus  digitorum,  the  direction  of  which  is 
obliquely  outward. 

The  Second  Layer. 
Flexor  accessorius.  Lumbricales. 

The  Flexor  Accessorius  (m.  quadratus  plantae]  arises  by  two  heads,  which  are 
separated  from  each  other  by  the  long  plantar  ligament:  the  inner  or  larger  head, 
which  is  muscular,  being  attached  to  the  inner  concave  surface  of  the  os  calcis 
below  the  groove  which  lodges  the  tendon  of  the  Flexor  longus  digitorum;  the 
outer  head,  flat  and  tendinous,  to  the  outer  surface  of  the  os  calcis,  in  front  of  its 
lesser  tubercle,  and  to  the  long  plantar  ligament;  the  two  portions  join  at  an 
acute  angle,  and  are  inserted  into  the  outer  margin  and  upper  and  under  sur- 
faces of  the  tendon  of  the  Flexor  longus  digitorum,  forming  a  kind  of  groove  in 
which  the  tendon  is  lodged.1 

Relations. — By  its  superficial  surface,  with  the  muscles  of  the  superficial  layer, 
from  which  it  is  separated  by  the  lateral  plantar  vessels  and  nerves;  by  its  deep 
surface,  with  the  os  calcis  and  long  calcaneo-cuboid  ligament. 

The  Lumbricales  are  four  small  muscles  accessory  to  the  tendons  of  the  Flexor 
longus  digitorum:  they  arise  from  the  tendons  of  the  long  Flexor,  as  far  back  as 
their  angle  of  division,  each  arising  from  two  tendons,  except  the  internal  one. 
Each  muscle  terminates  in  a  tendon,  which  passes  forward  on  the  inner  side  of 
the  four  lesser  toes  and  is  inserted  into  the  expansion  of  the  long  Extensor  tendon 
on  the  dorsum  of  the  first  phalanx  of  the  corresponding  toe. 

Dissection. — The  flexor  tendons  should  be  divided  at  the  back  part  of  the  foot,  and  the 
Flexor  accessorius  at  its  origin,  and  drawn  forward,  in  order  to  expose  the  third  layer. 

The  Third  Layer. 

Flexor  brevis  hallucis.  Flexor  brevis  minimi  digiti. 

Adductor  obliquus  hallucis.  Adductor  transversus  hallucis. 

The  Flexor  Brevis  Hallucis  (m.  flexor  hallucis  brevis)  arises,  by  a  pointed 
tendinous  process,  from  the  inner  part  of  the  under  surface  of  the  cuboid  bone, 
from  the  contiguous  portion  of  the  external  cuneiform,  and  from  the  prolongation 
of  the  tendon  of  the  Tibialis  posticus,  which  is  attached  to  that  bone.  The 
muscle  divides,  in  front,  into  two  portions,  which  are  inserted  into  the  inner 
and  outer  sides  of  the  base  of  the  first  phalanx  of  the  great  toe,  a  sesamoid  bone 
being  developed  in  each  tendon  at  its  insertion.  The  inner  portion  of  this 
muscle  is  blended  with  the  Abductor  hallucis  previous  to  its  insertion,  the  outer 
portion  with  the  Adductor  obliquus  hallucis,  and  the  tendon  of  the  Flexor 
longus  hallucis  lies  in  a  groove  between  them. 

Relations. — By  its  superficial  surface,  with  the  Abductor  hallucis  and  the  ten- 
don of  the  Flexor  longus  hallucis;  by  its  deep  surface,  with  the  tendon  of  the 
Peroneus  longus  and  metatarsal  bone  of  the  great  toe;  by  its  inner  border,  with 
the  Abductor  hallucis;  by  its  outer  border,  with  the  Adductor  obliquus  hallucis. 

The  Adductor  Obliquus  Hallucis  is  a  large,  thick,  fleshy  mass  passing  obliquely 
across  the  foot  and  occupying  the  hollow  space  between  the  four  inner  meta- 
tarsal bones.  It  arises  from  the  tarsal  extremities  of  the  second,  third,  and  fourth 
metatarsal  bones,  and  from  the  sheath  of  the  tendon  of  the  Peroneus  longus, 

1  According  to  Turner,  the  fibres  of  the  Flexor  accessorius  end  in  aponeurotic  bands,  which  contribute  slips 
to  the  second,  third,  and  fourth  digits. 


550 


THE  MUSCLES  AND  FASCIAE 


and  is  inserted,  together  with  the  outer  portion  of  the  Flexor  brevis  hallucis,  into 
the  outer  side  of  the  base  of  the  first  phalanx  of  the  great  toe. 

The  small  muscles  of  the  great  toe,  the  Abductor,  Flexor  brevis,  Adductor 
obliquus,  and  Adductor  transversus,  like  the  similar  muscles  of  the  thumb,  give 
aff  fibrous  expansions,  at  their  insertions,  to  blend  with  the  long  Extensor  tendon. 


FIG.  355. — Muscles  of  the  sole  of  the  foot. 
Second  layer. 


FIG.  356. — Muscles  of  the  sole  of  the  foot. 
Third  layer. 


The  Flexor  Brevis  Minimi  Digiti  (TO.  flexor  digiti  quinti  brevis)  lies  on  the  meta- 
tarsal  bone  of  the  little  toe,  and  much  resembles  one  of  the  Interossei.  It  arises 
from  the  base  of  the  metatarsal  bone  of  the  little  toe,  and  from  the  sheath  of  the 
Peroneus  longus;  its  tendon  is  inserted  into  the  base  of  the  first  phalanx  of 
the  little  toe  on  its  outer  side.  Occasionally  some  of  the  deeper  fibres  of  the 
muscle  are  inserted  into  the  outer  part  of  the  distal  half  of  the  fifth  metatarsal 
bone;  these  are  described  by  some  as  a  distinct  muscle,  the  Opponens  minimi 
digiti. 

Relations. — By  its  superficial  surface,  with  the  plantar  fascia  and  tendon  of 
the  Abductor  minimi  digiti;  by  its  deep  surface,  with  the  fifth  metatarsal  bone. 


THE  PLANTAR  REGION 


551 


The  Adductor  Transversus  Hallucis  (TO.  transversus  pedis)  is  a  narrow,  flat,  * 
muscular  fasciculus,  stretched  transversely  across  the  heads  of  the  metatarsal  bones, 
between  them  and  the  flexor  tendons.  It  arises  from  the  inferior  rnetatarso- 
phalangeal  ligaments  of  the  three  outer  toes,  sometimes  only  from  the  third  and 
fourth  and  from  the  transverse  ligament  of  the  metatarsus;  and  is  inserted  into 
the  outer  side  of  the  first  phalanx  of  the  great  toe,  its  fibres  being  blended  with 
the  tendon  of  insertion  of  the  Adductor  obliquus  hallucis. 

Relations. — By  its  superficial  surface,  with  the  tendons  of  the  long  and  short 
Flexors  and  Lumbricales ;  by  its  deep  surface,  with  the  Interossei. 

The  Fourth  Layer. 
The  Interossei. 

The  Interossei  Muscles  in  the  foot  are  similar  to  those  in  the  hand,  with  this 
exception,  that  they  are  grouped  around  the  middle  line  of  the*second  toe,  instead 
of  the  middle  line  of  the  third  finger,  as  in  the  hand.  They  are  seven  in  number, 
and  consist  of  two  groups,  Dorsal  and  Plantar. 


FIG.  357. — The  Dorsal  interossei.     Left  foot. 


FIG.  358.— The  Plantar  interossei.     Left  foot. 


The  Dorsal  Interossei  (TO.  interossei  dorsales)  ,four  in  number,  are  situated  between 
the  metatarsal  bones.  They  are  bipenniform  muscles,  arising  by  two  heads  from 
the  adjacent  sides  of  the  metatarsal  bones,  between  which  they  are  placed;  their 
tendons  are  inserted  into  the  bases  of  the  first  phalanges,  and  into  the  aponeurosis 
of  the  common  extensor  tendon.  In  the  angular  interval  left  between  the  heads 
of  each  muscle  at  its  posterior  extremity  the  perforating  arteries  pass  to  the 
dorsum  of  the  foot,  except  in  the  First  interosseous  muscle,  where  the  interval 
allows  the  passage  of  the  communicating  branch  of  the  dorsalis  pedis  artery.  The 
First  dorsal  interosseous  muscle  is  inserted  into  the  inner  side  of  the  second  toe; 
the  other  three  are  inserted  into  the  outer  sides  of  the  second,  third,  and  fourth  toes. 

The  Plantar  Interossei  (TO.  interossei  plantares],  three  in  number,  lie  beneath, 
rather  than  between,  the  metatarsal  bones.  They  are  single  muscles,  and  are 
each  connected  with  but  one  metatarsal  bone.  They  arise  from  the  base  and 


552  THE  MUSCLES  AND  FASCIA 

inner  sides  of  the  shaft  of  the  third,  fourth,  and  fifth  metatarsal  bones,  and  are 
inserted  into  the  inner  sides  of  the  bases  of  the  first  phalanges  of  the  same  toes, 
and  into  the  aponeurosis  of  the  common  extensor  tendon. 

Nerves. — The  Flexor  brevis  digitorum,  the  Flexor  brevis  and  Abductor  hallucis, 
and  the  innermost  Lumbrical1  are  supplied  by  the  medial  plantar  nerve.  All 
the  other  muscles  in  the  sole  of  the  foot  by  the  lateral  plantar.  The  first  dorsal 
interosseous  muscle  frequently  receives  an  extra  filament  from  the  internal 
branch  of  the  anterior  tibial  nerve  on  the  dorsum  of  the  foot,  and  the  second 
dorsal  interosseous  a  twig  from  the  external  branch  of  the  same  nerve. 

Actions. — All  the  muscles  of  the  foot  act  upon  the  toes,  and  for  purposes  of 
description  as  regard  their  action  may  be  grouped  as  Abductors,  Adductors, 
Flexors,  or  Extensors.  The  Abductors  are  the  Dorsal  interossei,  the  Abductor 
hallucis,  and  the  Abductor  minimi  digiti.  The  Dorsal  interossei  are  abductors 
from  an  imaginary  line  passing  through  the  axis  of  the  second  toe,  so  that  the 
first  muscle  draws  the  second  toe  inward,  toward  the  great  toe;  the  second  muscle 
draws  the  same  toe  outward;  the  third  draws  the  third  toe,  and  the  fourth  draws 
the  fourth  toe,  in  the  same  direction.  Like  the  interossei  in  the  hand,  they  also 
flex  the  proximal  phalanges  and  extend  the  two  terminal  phalanges.  The  Abduc- 
tor hallucis  abducts  the  great  toe  from  the  others,  and  also  flexes  the  proximal 
phalanx  of  this  toe.  And  in  the  same  way  the  action  of  the  Abductor  minimi 
digiti  is  twofold — as  an  abductor  of  this  toe  from  the  others,  and  also  as  a  flexor 
of  the  proximal  phalanx.  The  Adductors  are  the  Plantar  interossei,  the  Adductor 
obliquus  hallucis,  and  the  Adductor  transversus  hallucis.  The  Plantar  inter- 
osseous muscles  adduct  the  third,  fourth,  and  fifth  toes  toward  the  imaginary 
line  passing  through  the  second  toe,  and  by  means  of  their  insertion  into  the 
aponeurosis  of  the  extensor  tendon  they,  with  the  dorsal  interossei,  flex  the  prox- 
imal phalanges  and  extend  the  two  terminal  phalanges.  The  Adductor  obliquus 
hallucis  is  chiefly  concerned  in  adducting  the  great  toe  toward  the  second  one, 
but  also  assists  in  flexing  this  toe.  The  Adductor  transversus  hallucis  approxi- 
mates all  the  toes,  and  thus  increases  the  curve  of  the  transverse  arch  of  the 
metatarsus.  The  Flexors  are  the  Flexor  brevis  digitorum,  the  Flexor  accessorius, 
the  Flexor  brevis  hallucis,  the  Flexor  brevis  minimi  digiti,  and  the  Lumbricales. 
The  Flexor  brevis  digitorum  flexes  the  second  phalanges  upon  the  first,  and,  con- 
tinuing its  action,  may  flex  the  first  phalanges  also  and  bring  the  toes  together. 
The  Flexor  accessorius  assists  the  Long  flexor  of  the  toes,  and  converts  the 
oblique  pull  of  the  tendons  of  that  muscle  into  a  direct  backward  pull  upon  the 
toes.  The  Flexor  brevis  hallucis  flexes  and  slightly  adducts  the  first  phalanx  of 
the  great  toe.  The  Flexor  brevis  minimi  digiti  flexes  the  little  toe  and  draws  its 
metatarsal  bone  downward  and  inward.  The  Lumbricales,  like  the  correspond- 
ing muscles  in  the  hand,  assist  in  flexing  the  proximal  phalanx,  and  by  their 
insertion  into  the  long  Extensor  tendon  aid  in  straightening  the  two  terminal 
phalanges.  The  only  muscle  in  the  Extensor  group  is  the  Extensor  brevis  digi- 
torum. It  extends  the  first  phalanx  of  the  great  toe,  and  assists  the  long  Exten- 
sor in  extending  the  next  three  toes,  and  at  the  same  time  gives  to  the  toes  an 
outward  direction  when  they  are  extended. 


SURFACE  FORM  OF  THE  LOWER  EXTREMITY. 

Of  the  muscles  of  the  thigh,  those  of  the  iliac  region  have  no  influence  on  surface  form, 
while  those  of  the  anterior  femoral  region,  being  to  a  great  extent  superficial,  largely  con- 
tribute to  the  surface  form  of  this  part  of  the  body.  The  Tensor  fasciae  femoris  pro- 


1  Formerly  the  two  inner  Lumbricales  were  described  as  being  supplied  by  the  internal  plantar  nerve.  Brooks 
(Journal  of  Anatomy,  vol.  xxi.  p.  575)  in  ten  dissections  found  that  in  nine  of  them  only  the  inner  Lumbrical 
obtained  its  nerve  supply  from  this  source.  In  the  tenth  instance  the  first  and  second  Lumbricales  were 
supplied  by  both  external  and  internal  plantar. 


SURFACE  FORM  OF  THE  LOWER  EXTREMITY  553 

duces  a  broad  elevation  immediately  below  the  anterior  portion  of  the  crest  of  the  ilium  and 
behind  the  anterior  superior  spinous  process.  From  its  lower  border  a  longitudinal  groove, 
corresponding  to  the  ilio-tibial  band,  may  be  seen  running  down  the  outer  side  of  the  thigh  to 
the  outer  side  of  the  knee-joint.  The  Sartorius  muscle,  when  it  is  brought  into  action  by  flexing 
the  leg  on  the  thigh  and  the  thigh  on  the  pelvis,  and  rotating  the  thigh  outward,  presents  a 
well-marked  surface  form.  At  its  upper  part,  where  it  constitutes  the  outer  boundary  of 
Scarpa's  triangle,  it  forms  a  prominent  oblique  ridge,  which  becomes  changed  into  a  flattened 
plane  below,  and  this  gradually  merges  in  a  general  fulness  on  the  inner  side  of  the  knee-joint. 
When  the  Sartorius  is  not  in  action,  a  depression  exists  between  the  Quadriceps  extensor  and  the 
Adductor  muscles,  running  obliquely  downward  and  inward  from  the  apex  of  Scarpa's  triangle 
to  the  inner  side  of  the  knee,  which  depression  corresponds  to  this  muscle.  In  the  depressed  angle 
formed  by  the  divergence  of  the  Sartorius  and  Tensor  fasciae  femoris  muscles,  just  below  the 
anterior  superior  spinous  process  of  the  ilium,  the  Rectus  femoris  muscle  appears,  and,  below 
this,  determines  to  a  great  extent  the  convex  form  of  the  front  of  the  thigh.  In  a  well-developed 
subject  the  borders  of  the  muscle,  when  in  action,  are  clearly  to  be  defined.  The  VastUS  externus 
forms  a  long  flattened  plane  on  the  outer  side  of  the  thigh,  traversed  by  the  longitudinal  groove 
formed  by  the  ilio-tibial  band.  The  VastUS  internus,  on  the  inner  side  of  the  lower  half  of  the 
thigh,  gives  rise  to  a  considerable  prominence,  which  increases  toward  the  knee  and  terminates 
somewhat  abruptly  in  this  situation  with  a  full,  curved  outline.  The  Crureus  and  Subcrureus 
are  completely  hidden,  and  do  not  directly  influence  surface  form.  The  Adductor  muscles, 
constituting  the  internal  femoral  group,  are  not  to  be  individually  distinguished  from  each 
other,  with  the  exception  of  the  upper  tendon  of  the  Adductor  longus  and  the  lower  tendon  of 
the  Adductor  magnus.  The  upper  tendon  of  the  Adductor  longUS,  when  the  muscle  is  in  action, 
stands  out  as  a  prominent  ridge,  which  runs  obliquely  downward  and  outward  from  the  neigh- 
borhood of  the  pubic  spine,  and  forms  the  inner  boundary  of  a  flattened  triangular  space  on 
the  upper  part  of  the  front  of  the  thigh,  known  as  Scarpa's  triangle.  The  lower  tendon  of  the 
Adductor  magnus  can  be  distinctly  felt  as  a  short  ridge  extending  down  to  the  Adductor  tubercle 
on  the  internal  condyle,  between  the  Sartorius  and  Vastus  internus.  The  Adductor  group 
of  muscles  fills  in  the  triangular  space  at  the  upper  part  of  the  thigh,  formed  between  the  oblique 
femur  and  the  pelvic  wall,  and  to  them  is  due  the  contour  of  the  inner  border  of  the  thigh,  the 
Gracilis  largely  contributing  to  the  smoothness  of  the  outline.  These  muscles  are  not  marked 
off  on  the  surface  from  those  of  the  posterior  femoral  region  by  any  intermuscular  marking;  but 
on  the  outer  side  of  the  thigh  these  latter  muscles  are  defined  from  the  Vastus  externus  by  a 
distinct  marking,  corresponding  to  the  external  intermuscular  septum.  The  Gluteus  maximus 
and  a  part  of  the  Gluteus  medius  are  the  only  muscles  of  the  buttock  which  influence  surface 
form.  The  other  part  of  the  Gluteus  medius,  the  Gluteus  minimus,  and  the  External  rotators 
are  completely  hidden.  The  Gluteus  maximus  forms  the  full  rounded  outline  of  the  buttock; 
it  is  more  prominent  behind,  compressed  in  front,  and  terminates  at  its  tendinous  insertion  in 
a  depression  immediately  behind  the  great  trochanter.  Its  lower  border  does  not  correspond 
to  the  gluteal  fold,  but  is  much  more  oblique,  being  marked  by  a  line  drawn  from  the  side  of 
the  coccyx  to  the  junction  of  the  upper  with  the  lower  two-thirds  of  the  thigh  on  the  outer  side. 
From  beneath  the  lower  margin  of  this  muscle  the  Hamstring  muscles  appear,  at  first  narrow 
and  not  well  marked,  but  as  they  descend  becoming  more  prominent  and  widened  out,  and 
eventually  dividing  into  two  well-marked  ridges,  which  constitute  the  upper  boundaries  of  the 
popliteal  space,  and  are  formed  by  the  tendons  of  the  inner  and  outer  hamstring  muscles  respect- 
ively. In  the  upper  part  of  the  thigh  these  muscles  are  not  to  be  individually  distinguished 
from  each  other,  but  lower  down  the  separation  between  the  Semitendinosus  and  Semimem- 
branosusjs  denoted  by  a  slight  intermuscular  marking.  The  external  hamstring  tendon  formed 
by  the  Biceps  is  seen  as  a  thick  cord  running  down  to  the  head  of  the  fibula.  The  inner  ham- 
string tendons  comprise  the  Semitendinosus,  the  Semimembranosus,  and  the  Gracilis.  The 
Semitendinosus  is  the  most  internal  of  these,  and  can  be  felt,  in  certain  positions  of  the  limb, 
as  a  sharp  cord;  the  Semimembranosus  is  thick,  and  the  Gracilis  is  situated  a  little  farther 
forward  than  the  other  two.  All  the  muscles  on  the  front  of  the  leg  appear  to  a  certain  extent 
somewhere  on  the  surface,  but  the  form  of  this  region  is  mainly  dependent  upon  the  Tibialis 
anticus  and  the  Extensor  longus  digitorum.  The  Tibialis  anticus  is  well  marked,  and  presents 
a  fusiform  enlargement  at  the  outer  side  of  the  tibia,  and  projects  beyond  the  crest  of  the  shin- 
bone.  From  the  muscular  mass  its  tendons  may  be  traced  downward,  standing  out  boldly, 
when  the  muscle  is  in  action,  on  the  front  of  the  tibia  and  ankle-joint,  and  coursing  down  to  its 
insertion  along  the  inner  border  of  the  foot.  A  well-marked  groove  separates  this  muscle  exter- 
nally from  the  Extensor  longus  digitorum,  which  fills  up  the  rest  of  the  space  between  the  upper 
part  of  the  shaft  of  the  tibia  and  fibula.  It  does  not  present  so  bold  an  outline  as  the  Tibialis 
anticus,  and  its  tendon  below,  diverging  from  the  tendon  of  the  Tibialis  anticus,  forms  with  the 
latter  a  sort  of  plane,  in  which  may  be  seen  the  tendon  of  the  Extensor  proprius  hallucis.  A 
groove  on  the  outer  side  of  the  extensor  longus  digitorum,  seen  most  plainly  when  the  muscle 
is  in  action,  separates  the  tendon  from  a  slight  eminence  corresponding  to  the  Peroneus  tertius. 
The  fleshy  fibres  of  the  Peroneus  longus  are  strongly  marked  at  the  upper  part  of  the  outer 


554  THE  MUSCLES  AND  FASCIA 

side  of  the  leg,  especially  when  the  muscle  is  in  action.  It  forms  a  bold  swelling,  separated  by 
furrows  from  the  Extensor  longus  digitorum  in  front  and  the  Soleus  behind.  Below,  the  fleshy 
fibres  terminate  abruptly  in  a  tendon  which  overlaps  the  more  flattened  form  of  the  Peroneus 
brevis.  At  the  external  malleolus  the  tendon  of  the  Peroneus  brevis  is  more  marked  than  that 
of  the  Peroneus  longus.  On  the  dorsum  of  the  foot  the  tendons  of  the  Extensor  muscles, 
emerging  from  beneath  the  anterior  annular  ligament,  spread  out  and  can  be  distinguished 
in  the  following  order:  The  most  internal  and  largest  is  the  Tibialis  anticus.-then  the  Extensor 
proprillS  hallucis  J  next  comes  the  Extensor  longUS  digitorum,  dividing  into  four  tendons  to 
the  four  outer  toes;  and  lastly,  most  externally,  is  the  Peroneus  tertius.  The  flattened  form  of 
the  dorsum  of  the  foot  is  relieved  by  the  rounded  outline  of  the  fleshy  belly  of  the  Extensor 
brevis  digitorum,  which  forms  a  soft  fulness  on  the  outer  side  of  the  tarsus  in  front  of  the  external 
malleolus,  and  by  the  Dorsal  interossei,  which  bulge  between  the  metatarsal  bones.  At  the 
back  of  the  knee  is  the  popliteal  space,  bounded  above  by  the  tendons  of  the  hamstring  muscle; 
below,  by  the  two  heads  of  the  Gastrocnemius.  Below  this  space  is  the  prominent  fleshy  mass 
of  the  calf  of  the  leg,  produced  by  the  Gastrocnemius  and  Soleus.  When  these  muscles  are 
in  action,  as  in  standing  on  tiptoe,  the  borders  of  the  Gastrocnemius  are  well  defined,  presenting 
two  curved  lines,  which  converge  to  the  tendon  of  insertion.  Of  these  borders,  the  inner  is 
more  prominent  than  the  outer.  The  fleshy  mass  of  the  calf  terminates  somewhat  abruptly 
below  in  the  tendo  Achillis,  which  stands  out  prominently  on  the  lower  part  of  the  back  of  the 
leg.  It  presents  a  somewhat  tapering  form  in  the  upper  three-fourths  of  its  extent,  but  widens 
out  slightly  below.  When  the  muscles  of  the  calf  are  in  action,  the  lateral  portions  of  the  Soleus 
may  be  seen,  forming  curved  eminences,  of  which  the  outer  is  the  longer,  on  either  side  of  the 
Gastrocnemius.  Behind  the  inner  border  of  the  lower  part  of  the  shaft  of  the  tibia  a  well- 
marked  ridge,  produced  by  the  tendon  of  the  Tibialis  posticus,  is  visible  when  this  muscle  is  in 
a  state  of  contraction.  On  the  sole  of  the  foot  the  superficial  layer  of  muscles  influences  surface 
form;  the  Abductor  minimi  digiti  most  markedly.  This  muscle  forms  a  narrow  rounded 
elevation  along  the  outer  border  of  the  foot,  while  the  Abductor  hallucis  does  the  same,  though 
to  a  less  extent,  on  the  inner  side.  The  Flexor  brevis  digitorum,  bound  down  by  the  pldntar 
fascia,  is  not  very  apparent;  it  produces  a  flattened  form,  covered  by  the  thickened  skin  of  the 
sole,  which  is  here  thrown  into  numerous  wrinkles. 

SURGICAL  ANATOMY  OF  THE  LOWER  EXTREMITY. 

The  student  should  now  consider  the  effects  produced  by  the  action  of  the  various  muscles 
in  fractures  of  the  bones  of  the  lower  extremity.  The  more  common  forms  of  fractures  are 
selected  for  illustration  and  description. 


PYRIFORMIS. 
GEMELLUS    SUPERIOR. 
OBTURATOR     INTERNUS 
GEMELLUS    INFERIOR. 
OBTURATOR    EXTERNUS. 
QUADRATUS    FEMORIS. 


FIG.  359.- -Fracture  of  the  neck  of  the  femur  within  the  capsular  ligament. 


In  fracture  of  the  neck  of  the  femur  internal  to  the   capsular  ligament  (Fig.  359)  the  charac- 
teristic marks  are  slight  shortening  of  the  limb  and  eversion  of  the  foot,  neither  of  which  symp- 


SURGICAL  ANATOMY  OF  THE  LOWER  EXTREMITY         555 


toms  occurs,  however,  in  some  cases  until  some  time  after  the  injury.  The  eversion  is  caused 
l.v  the  weight  of  the  limb  rotating  it  outward.  The  shortening  is  produced  by  the  action  of  the 
Glutei,  and  by  the  Rectus  femoris  in  front  and  the  Biceps,  Semitendinosus,  and  Semimem- 
branosus  behind.  The  treatment  is  extension  by  means  of  adhesive  plaster  and  weights  and 
counter-extension  by  raising  the  foot  of  the  bed,  eversion  being  corrected  by  sand-bags.  In 
some  cases  Thomas's  splint  is  used. 

In  fracture  of  the  femur  just  below  the  trochanters  (Fig.  360)  the  upper  fragment,  the  por- 
tion chiefly  displaced,  is  tilted  forward  almost  at  right  angles  with  the  pelvis  by  the  combined 

action  of  the  Psoas  and  Iliacus,  and,  at  the  same  time,  everted 
and  drawn  outward  by  the  External  rotator  and  Glutei  muscles, 
causing  a  marked  prominence  at  the  upper  and  outer  side  of  the 
thigh,  and  much  pain  from  the  bruising  and  laceration  of  the 
muscles.  The  limb  is  shortened,  in  consequence  of  the  lower 
fragment  being  drawn  upward  by  the  rectus  in  front,  and  the 
Biceps,  Semimembranosus,  and  Semitendinosus  behind,  and  is 
at  the  same  time  everted.  This  fracture  may  be  reduced  by 
direct  relaxation  of  all  the  opposing  muscles,  to  effect  which  the 
limb  should  be  put  up  in  such  a  manner  that  the  thigh  is  flexed 
on  the  pelvis  and  the  leg  on  the  thigh,  the  extremity  being  placed 


SEMI- 
MEMBRANOSUS. 

SEMI- 
TENDINOSUS. 


FIG.  360. — Fracture  of   the  femur 
below  the  trochanters. 


FIG.  361. — Fracture  of  the  femur 
above  the  condyles. 


FIG.  362. — Fracture  of 
the  patella. 


upon  a  double  inclined  plane  and  extension  being  made  in  the  axis  of  the  partly  flexed 
thigh  by  means  of  adhesive  plaster  and  weights.  In  some  cases  it  is  necessary  to  incise  and 
wire  the  fragments  together. 

Oblique  fracture  of  the  femur  immediately  above  the  condyles  (Fig.  361)  is  a  formidable 
injury,  and  attended  with  considerable  displacement.  On  examination  of  the  limb  the  lower 
fragment  may  be  felt  deep  in  the  popliteal  space,  being  drawn  backward  by  the  Gastrocnemius 
and  Plantaris  muscles,  and  upward  by  the  Hamstring  and  Rectus  muscles.  The  pointed  end 
of  the  upper  fragment  is  drawn  inward  by  the  Pectineus  and  Adductor  muscles,  and  tilted  for- 
ward by  the  Psoas  and  Iliacus,  piercing  the  Rectus  muscle  and  occasionally  the  integument. 
Relaxation  of  these  muscles  and  direct  approximation  of  the  broken  fragments  are  effected  by 
placing  the  limb  on  a  double  inclined  plane.  The  greatest  care  is  requisite  in  keeping  the 
pointed  extremity  of  the  upper  fragment  in  proper  position;  otherwise,  after  union  of  the 
fracture,  the  power  of  extension  of  the  limb  is  partially  destroyed  from  the  Rectus  muscle  being 
held  down  by  the  fractured  end  of  the  bone,  and  from  the  patella,  when  elevated,  being  drawn 
upward  against  the  projecting  fragment. 

In  fracture  of  the  patella  (Fig.  362)  the  fragments  are  separated  by  the  effusion  which  takes 
place  into  the  joint,  and  by  the  action  of  the  Quadriceps  extensor;  the  extent  of  separation  of 
the  two  fragments  depending  upon  the  degree  of  laceration  of  the  ligamentous  structures 
around  the  bone.  Some  cases  may  be  treated  by  a  posterior  straight  splint,  the  fragments 
being  pulled  together  by  strips  of  adhesive  plaster.  In  many  cases  it  is  advisable  to  incise, 
remove  intervening  pieces  of  fibrous  tissue  and  wire  the  fragments  together. 


556 


THE  MUSCLES  AND  FASCIAE 


The  tibia  is  fractured  most  commonly  by  indirect  force  at  the  junction  of  the  middle  third 
with  the  lower  third  of  the  shaft.  Compound  fractures  are  more  common  in  the  leg  than 
in  any  other  region  of  the  body  because  the  tibia  is  such  a  superficial  bone  and  is  so  much 
exposed  to  injury.  Most  fractures  from  indirect  force  are  oblique. 

In  oblique  fracture  of  the  shaft  of  the  tibia  (Fig.  363),  if  the  fracture  has  taken  place  obliquely 
from  above,  downward  and  forward,  the  fragments  ride  over  one  another,  the  lower  fragments 
being  drawn  backward  and  upward  by  the  powerful  action  of  the  muscles  of  the  calf;  the 
pointed  extremity  of  the  upper  fragment  projects  forward  immediately  beneath  the  integu- 
ment, often  protruding  through  it  and  rendering  the  fracture  a  compound  one.  If  the  direc- 
tion of  the  fracture  is  the  reverse  of  that  shown  in  the  figure,  the  pointed  extremity  of  the  lower 
fragment  projects  forward,  riding  upon  the  lower  end  of  the  upper  one.  By  bending  the  knee, 


FIG.  363. — Oblique  fracture  of 
the  shaft  of  the  tibia. 


FIG.  364. — Fracture  of  the  fibula  with  dislocation  of 
the  foot  outward — "  Pott's  fracture." 


which  relaxes  the  opposing  muscles,  and  making  extension  from  the  ankle  and  counter- 
extension  at  the  knee,  the  fragments  may  be  brought  into  apposition.  It  is  often  necessary, 
however,  in  a  compound  fracture,  to  remove  a  portion  of  the  projecting  bone  with  the  saw 
before  complete  adaptation  can  be  effected. 

Fracture  of  the  fibula  with  dislocation  of  the  foot  outward  (Fig.  364),  commonly  known  as 
Pott's  fracture,  is  one  of  the  most  frequent  injuries  of  the  ankle-joint.  The  fibula  is  frac- 
tured about  three  inches  above  the  ankle;  in  addition  to  this  the  internal  malleolus  is  broken 
off,  or  the  deltoid  ligament  torn  through,  and  the  end  of  the  tibia  displaced  from  the  correspond- 
ing surface  of  the  astragalus.  The  foot  is  markedly  everted,  and  the  sharp  edge  of  the  upper 
end  of  the  fractured  malleolus  presses  strongly  against  the  skin ;  at  the  same  time,  the  heel  is 
drawn  up  by  the  muscles  of  the  calf.  This  injury  can  generally  be  reduced  by  flexing  the  leg  at 
right  angles  with  the  thigh,  which  relaxes  all  the  opposing  muscles,  and  by  making  extension 
from  the  ankle  and  counter-extension  at  the  knee. 


THE  BLOOD-VASCULAR  SYSTEM. 


A  NGIOLOGY  is  the  branch  of  anatomy  which  treats  of  the  blood-vessels. 
_L\_  The  blood-vascular  system  comprises  the  heart  and  blood-vessels  with 
their  contained  fluid,  the  blood. 

The  Heart  is  the  central  organ  of  the  entire  system,  and  is  a  hollow  muscle; 
by  its  contraction  the  blood  is  pumped  to  all  parts  of  the  body  through  a  com- 
plicated series  of  tubes,  termed  arteries.  The  arteries  undergo  almost  infinite 
ramification  in  their  course  throughout  the  body,  and  end  in  very  minute  vessels, 
called  arterioles,  which  in  their  turn  open  into  a  close-meshed  network  of  micro- 
scopic vessels,  termed  capillaries.  After  the  blood  has  passed  through  the  capil- 
laries it  enters  into  minute  vessels  called  venules  and  from  them  it  is  collected 
into  a  series  of  larger  vessels,  called  veins,  by  which  it  is  returned  to  the  heart. 
The  passage  of  the  blood  through  the  heart  and  blood-vessels  constitutes  what  is 
termed  the  circulation  of  the  blood,  of  which  the  following  is  an  outline. 

The  human  heart  is  divided  by  a  septum  into  two  halves,  right  and  left,  each 
half  being  further  constricted  into  two  cavities,  the  upper  of  the  two  being  termed 
the  auricle  and  the  lower  the  ventricle.  The  heart  therefore  consists  of  four 
chambers  or  cavities,  two  forming  the  right  half,  the  right  auricle  and  right 
ventricle;  and  two  the  left  half,  the  left  auricle  and  left  ventricle.  The  right 
half  of  the  heart  contains  venous  or  impure  blood ;  the  left,  arterial  or  pure  blood. 
From  the  cavity  of  the  left  ventricle  the  pure  blood  is  carried  into  a  large  artery, 
the  aorta,  through  the  numerous  branches  of  which  it  is  distributed  to  all  parts 
of  the  body,  with  the  exception  of  the  lungs.  In  its  passage  through  the  capil- 
laries of  the  body  the  blood  gives  up  to  the  tissues  the  materials  necessary  for 
their  growth  and  nourishment,  and  at  the  same  time  receives  from  the  tissues  the 
waste  products  resulting  from  their  metabolism,  and  in  doing  so  becomes  changed 
from  arterial  or  pure  blood  into  venous  or  impure  blood,  which  is  collected  by  the 
veins  and  through  them  returned  to  the  right  auricle  of  the  heart.  From  this 
cavity  the  impure  blood  passes  into  the  right  ventricle,  from  which  it  is  conveyed 
through  the  pulmonary  arteries  to  the  lungs.  In  the  capillaries  of  the  lungs  it 
again  becomes  arterialized,  and  is  then  carried  to  the  left  auricle  by  the  pulmonary 
veins.  From  this  cavity  it  passes  into  that  of  the  left  ventricle,  from  which  the 
cycle  once  more  begins. 

The  course  of  the  blood  from  the  left  ventricle  through  the  body  generally  to 
the  right  side  of  the  heart  constitutes  the  greater  or  systemic  circulation,  while  its 
passage  from  the  right  ventricle  through  the  lungs  to  the  left  side  of  the  heart  is 
termed  the  lesser  or  pulmonary  circulation. 

It  is  necessary,  however,  to  state  that  the  blood  which  circulates  through  the 
spleen,  pancreas,  stomach,  small  intestine,  and  the  greater  part  of  the  large  intes- 
tine is  not  returned  directly  from  these  organs  to  the  heart,  but  is  collected  into 
a  large  vein,  termed  the  portal  vein,  by  which  it  is  carried  to  the  liver.  In  the 
liver  this  vein  divides,  after  the  manner  of  an  artery,  and  ultimately  ends  in 
capillary  vessels,  from  which  the  rootlets  of  a  series  of  veins,  called  the  hepatic 
veins,  arise;  these  carry  the  blood  into  the  postcava  (inferior  vena  cava),  which 
conveys  it  to  the  right  auricle. 

(557) 


558 


THE   BLOOD -VASCULAR    SYSTEM 


Pulmonary  Capillaries 


From  this  it  will  be  seen  that  the  blood  contained  in  the  portal  vein  passes 
through  two  sets  of  capillary  vessels:  (1)  those  in  the  spleen,  pancreas,  stomach, 
etc.,  and  (2)  those  in  the  liver. 

Speaking  generally,  the  arteries  may  be  said  to  contain  pure,  and  the  veins 
impure,  blood.  This  is  true  of  the  systemic,  but  not  of  the  pulmonary,  vessels, 
since  it  has  been  seen  that  the  impure  blood  is  conveyed  from  the  heart  to  the 
lungs  by  the  pulmonary  arteries,  and  the  pure  blood  returned  from  the  lungs  to 

the  heart  by  the  pulmonary  veins.  Arteries, 
therefore,  must  be  defined  as  vessels  which 
convey  blood  from  the  heart,  and  veins  as 
vessels  which  return  blood  to  the  heart. 

The  heart  and  lungs  are  contained  within 
the  cavity  of  the  thorax,  the  walls  of  which 
afford  them  protection  (Fig.  366).  The  heart 
lies  between  the  two  lungs,  and  is  there 
enclosed  within  a  sero-membranous  bag,  the 
pericardium,  while  each  lung  is  invested  by  a 
serous  membrane,  the  pleura.  The  skeleton 
of  the  thorax  was  described  on  page  156. 

The  Cavity  of  the  Thorax  (cavum  tho- 
racis).— The  capacity  of  the  cavity  of  the 
thorax  does  not  correspond  with  its  apparent 
size  externally,  because  (1)  the  space  en- 
closed by  the  lower  ribs  is  occupied  by  some 
of  the  abdominal  viscera;  and  (2)  the  cavity 
extends  above  the  first  rib  into  the  neck. 
The  size  of  the  cavity  of  the  thorax  is  con- 
stantly varying  during  life,  with  the  move- 
ments of  the  ribs  and  diaphragm,  and  with 
the  degree  of  distention  of  the  abdominal 
viscera.  From  the  collapsed  state  of  the 
lungs,  as  seen  when  the  thorax  is  opened, 
in  the  dead  body,  it  would  appear  as  if  the 
viscera  only  partly  filled  the  cavity  of  the 
thorax,  but  during  life  there  is  no  vacant 
space,  that  which  is  seen  after  death  being 
filled  up  during  life  by  the  expanded  lungs. 
The  Upper  Opening  of  the  Thorax 
(apertura  thoracis  superior) .  —  The  parts 
which  pass  through  the  upper  opening  of 
the  thorax  are,  from  before  backward  in  or 
near  the  middle  line,  the  Sterno-hyoid  and 
Sterno-thyroid  muscles,  the  remains  of  the 

thymus  gland,  the  trachea,  oesophagus,  thoracic  duct,  the  inferior  thyroid  veins, 
and  the  Longus  colli  muscle  of  each  side;  at  the  sides,  the  innominate  artery, 
the  left  common  carotid,  and  left  subclavian  arteries,  the  internal  mammary 
and  superior  intercostal  arteries,  the  right  and  left  innominate  veins,  the  vagus, 
cardiac,  phrenic,  and  sympathetic  nerves,  the  anterior  branch  of  the  first  thoracic 
nerve,  and  the  recurrent  laryngeal  nerve  of  the  left  side.  The  apex  of  each  lung, 
covered  by  the  pleura,  also  projects  through  this  aperture,  a  little  above  the  margin 
of  the  first  rib. 

The  Lower  Opening  of  the  Thorax  (apertura  thoracis  inferior)  is  wider  trans- 
versely than  from  before  backward.  It  slopes  obliquely  downward  and  back- 
ward, so  that  the  cavity  of  the  thorax  is  much  deeper  behind  than  in  front.  The 


FIG.  365. — Diagram  to  show  the  course  of  the 
circulation  of  the  blood. 


THE   PERICARDIUM 


559 


Diaphragm  (see  page  429)  closes  in  the  opening,  forming  the  floor  of  the  thorax. 
The  floor  is  flatter  at  the  centre  than  at  the  sides,  and  is  higher  on  the  right  side 
than  on  the  left,  corresponding  in  the  dead  body  to  the  upper  border  of  the  fifth 


i' 

G.  366. — Front  view  of  the  thorax.  The  ribs  and  sternum  are  represented  in  relation  to  the  lungs,  heart, 
other  internal  organs.  1.  Pulmonary  orifice.  2.  Aortic  orifice.  3.  Left  auriculo- ventricular  orifice.  4. 
it  aiirinnlo-ventriciilar  orifine. 


FIG 
Right  auriculo-ventricular  orifice. 


costal  cartilage  on  the  former,  and  to  the  corresponding  part  of  the  sixth  costal 
cartilage  on  the  latter.  From  the  highest  point  on  each  side  the  floor  slopes  sud- 
denly downward  to  the  attachment  of  the  Diaphragm  to  the  ribs;  this  is  more 
marked  behind  than  in  front,  so  that  only  a  narrow  space  is  left  between  it  and 
the  wall  of  the  thorax. 

THE  PERICARDIUM. 

The  pericardium  (Figs.  367,  368,  369,  370,  371,  and  372)  is  a  conical  sero- 
membranous  sac,  placed  in  the  middle  mediastinum.  In  this  sac  the  heart  and 
the  commencement  of  the  great  vessels  are  contained.  It  is  placed  behind  the 
sternum  and  the  cartilages  of  the  third,  fourth,  fifth,  sixth,  and  seventh  ribs  of 
the  left  side,  in  the  interval  between  the  pleurae. 

Its  apex  is  directed  upward,  and  surrounds  the  great  vessels  about  two  inches 
above  their  origin  from  the  base  of  the  heart.  Its  base  is  attached  to  the  central 
tendon  and  to  the  left  part  of  the  adjoining  muscular  structure  of  the  Diaphragm. 
In  front  it  is  separated  from  the  sternum  by  the  remains  of  the  thymus  gland 


560 


THE    BLOOD -VASCULAR    SYSTEM 


above  and  a  little  loose  areolar  tissue  below,  and  is  covered  by  the  margins  of  the 
lungs,  especially  the  left.  Behind,  it  rests  upon  the  bronchi,  the  oesophagus,  and 
the  descending  aorta.  Laterally,  it  is  covered  by  the  pleurae,  and  is  in  relation  to 
the  inner  surface  of  the  lungs;  the  phrenic  nerve  with  its  accompanying  vessels 
descends  between  the  pericardium  and  pleura  on  either  side  (Fig.  371). 

Structure  of  the  Pericardium. — The  pericardium  is  a  fibre-serous  membrane, 
and  consists,  therefore,  of  two  layers,  an  external  fibrous  and  an  internal  serous. 


Right  common- 
carotid  artery. 
Inferior  thyroid  ^ 
vein. 
Left  innomi-^ 

nate  vein. 
Right  innomi-^ 
nate  vein. 
Precava  or 
Superior  vena 
cava. 


Bight  pulmo- 
nary veins. 


Right  sub- 
'clavian  art. 


Left  common 
carotid  art. 


Left  sub- 
clavian 
rtery. 


FIG.  367. — Pericardium  from  in  front.     The  sac  has  been  distended  with  plaster.      (From  a  preparation 
in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 

The  Fibrous  Layer  is  a  strong,  dense,  connective-tissue  membrane.  Above,  it 
surrounds  the  great  vessels  arising  from  the  base  of  the  heart,  on  which  it  is 
continued  in  the  form  of  tubular  prolongations  which  are  gradually  lost  upon 
their  external  coat,  the  strongest  being  that  which  encloses  the  aorta.  The  peri- 
cardium may  be  traced  over  these  vessels,  to  become  continuous  with  the  deep 
layer  of  the  cervical  fascia.  The  prolongations  to  the  cervical  fascia  constitute  the 
vertebro-pericardial  ligaments  (Fig.  370).  In  front  the  pericardium  is  connected  to 
the  posterior  surface  of  the  sternum  by  two  fibrous  bands,  the  superior  and  inferior 
sterno-pericardiac  ligaments  or  ligaments  of  Luschka  (ligamenta  sternopericardiaca) 
(Fig.  370).  The  superior  sterno-pericardial  ligament,  called  also  the  sternocosto- 


THE   PERICARDIUM 


561 


pericardial  ligament  (Fig.  370),  passes  to  the  manubrium.  The  inferior  sterno- 
pericardial  ligament,  called  also  the  xipho-pericardial  ligament  (Fig.  370),  passes  to 
the  ensiform  cartilage.  On  each  side  of  the  ascending  aorta  the  pericardium  sends 
upward  a  diverticulum :  the  one  on  the  left  side,  somewhat  conical  in  shape,  passes 
upward  and  outward,  between  the  arch  of  the  aorta  and  the  pulmonary  artery, 
as  far  as  the  ductus  arteriosus,  where  it  terminates  in  a  csecal  extremity,  which  is 
attached  by  loose  connective  tissue  to  the  obliterated  duct  (Fig.  367).  The  one  on 
the  right  side  passes  upward  and  to  the  right,  between  the  ascending  aorta  and 


Left  subclavian  artery. 
Right  pulmonary  artery 


Riqht  subclavian  artery. 
Left  com/Him 
ca rot i<l  artery. 


Eight  common 
carotid  artery. 


Right  pulmonary 
veins. 


FIG.  368. — Pericardium  from  behind.     (From  the  same  preparation  as  the  preceding  figure.) 


precava  (vena  cava  superior) ,  and  also  terminates  in  a  csecal  extremity.  Below, 
the  fibrous  layer  is  attached  to  the  central  tendon  of  the  Diaphragm,  and  on  the  left 
side  to  its  muscular  fibres.  The  pericardium  is  fixed  to  the  Diaphragm  by  the 
anterior  phreno-pericardial  ligament  and  by  the  lateral  phreno-pericardial  ligaments 
(Fig.  370). 

The  vessels  receiving  fibrous  prolongations  from  this  membrane  are  the  aorta, 
the  precava,  the  right  and  left  pulmonary  arteries,  and  the  four  pulmonary  veins. 
The  postcava  (inferior  vena  cava)  enters  the  pericardium  through  the  central 
tendon  of  the  Diaphragm,  and  consequently  it  receives  no  covering  from  the 
fibrous  layer  (Fig.  371). 

36 


562 


THE   BLOOD -VASCULAR    SYSTEM 


The  Serous  Pericardium  invests  the  heart,  and  is  then  reflected  on  the  inner  sur- 
face of  the  fibrous  pericardium.  It  consists,  therefore,  of  a  visceral  layer  (epicar- 
dium)  and  a  parietal  layer.  The  former  invests  the  surface  of  the  heart,  and  the 
commencement  of  the  great  vessels,  to  the  extent  of  an  inch  and  a  half  from 
their  origin ;  from  these  it  is  reflected  upon  the  inner  surface  of  the  fibrous  layer. 
The  serous  membrane  encloses  the  aorta  and  pulmonary  artery  in  a  single  tube, 
so  that  a  passage,  termed  the  great  transverse  sinus  of  the  pericardium  (sinus  trans- 
versus  pericardii) ,  exists  between  these  vessels  in  front  and  the  auricle  behind. 
This  sinus  is  closed  above  and  below  but  often  to  the  right  and  left.  The  mem- 


RIGHT 

PULMONARY. 
VEIN 


PAR  I  ETA 
PERICARDIUM 


FIG.  369. — The  line  of  reflection  of  the  serous  pericardium.     (Modified  from  Poirier  and  Charpy.) 

brane  only  partially  covers  the  precava  (superior  vena  cava)  and  the  four  pulmo- 
nary veins,  and  scarcely  covers  the  postcava  (inferior  vena  cava),  as  this  vessel 
enters  the  heart  almost  directly  after  it  has  passed  through  the  Diaphragm.  A  deep 
blind  recess  formed  by  the  serous  pericardium  is  found  behind  the  heart  when  that 
organ  is  raised  up.  This  recess  runs  backward  between  the  left  auricle  and  the 
posterior  portion  of  the  fibrous  pericardium,  and  forms  a  diverticulum  between  the 
heart  and  the  oesophagus.  This  recess  is  called  the  oblique  sinus.  It  passes  upward 
between  the  postcava  and  the  lower  left  pulmonary  vein  and  terminates  between  the 
right  and  left  pulmonary  veins.  The  inner  surface  of  the  pericardium  is  covered 
with  endothelium,  which  rests  upon  a  mixture  of  fibrous  and  elastic  tissue,  which  is 
smooth  and  glistening,  and  secretes  a  serous  fluid  (liquor  pericardii),  which  serves 


THE  PERICARDIUM 


563 


to  facilitate  the  movements  of  the  heart.  In  the  serous  layer  of  the  pericardium 
arc  many  blood-vessels,  lymph  vessels,  and  nerves. 

Arteries  of  the  Pericardium. — These  are  derived  from  the  internal  mammary  and 
its  musculo-phrenic  branch,  and  from  the  descending  thoracic  aorta. 

Nerves  of  the  Pericardium. — These  are  branches  from  the  vagus,  the  phrenic, 
and  the  sympathetic. 

The  Vestigial  Fold  of  the  Pericardium. — Between  the  left  pulmonary  artery  and 
subjacent  pulmonary  vein  and  behind  the  left  extremity  of  the  transverse  sinus  is 
a  triangular  fold  of  the  serous  pericardium;  it  is  known  as  the  vestigial  fold  of 


VERTEBRO- 

PERICAROIAL 

LIGAMENTS 


PRECAVA 

OR 

SUPERIOR 
VENA  CAVA 


POSTCAVA 

OR 

INFERIOR 
VENA  CAVA 

PHRENO- 

PERICAROIAL 

LIGAMENTS 


SUPERIOR  STERNO- 
PERICARDIAL  LIG- 
AMENTS 


ANTERIOR 
SURFACE    OF 
PERICARDIUM 


XIPHO- 

PERICARDIAL 

LIGAMENTS 


FIG.  370. — Ligaments  of  the  pericardium.  (Modified  from  Teutleben.)  Right  lateral  view,  showing  the  right 
vertebra — pericardial  ligaments,  the  right  phreno-pericardial,  and  the  superior  and*  inferior  sterno-pericardial 
ligaments.  (Poirier  and  Charpy.) 

Marshall  (ligamentum  v.  cavae  sinistrae).  It  is  formed  by  the  duplicature  of  the 
serous  layer  over  the  remnant  of  the  lower  part  of  the  left  precava  (superior  vena 
cava,  v.  cava  sinistra),  or  the  duct  of  Cuvier,  which,  after  birth,  becomes  obliterated, 
and  remains  as  a  fibrous  band  stretching  from  the  left  superior  intercostal  vein 
to  the  left  auricle,  where  it  is  continuous  with  a  small  vein,  the  oblique  vein  of 
Marshall  (v.  obliqua  atrii  sinistri  [Marshalli]),  which  opens  into  the  coronary  sinus 
and  is  a  remnant  of  the  fretal  left  precava. 

Surgical  Anatomy. — Aspiration  of  the  pericardium  (paracentesis  of  the  pericardium)  is  occa- 
sionally though  seldom  performed.  It  is  only  to  be  thought  of  when  pericardial  effusion  endangers 
life.  The  operation  is  very  dangerous,  because  the  effusion  lifts  the  heart  and  pushes  it  forward. 


564 


THE  BLOOD -VASCULAR   SYSTEM 


and  the  needle  is  apt  to  wound  the  heart  or  even  enter  one  of  the  cavities.  There  is  also  danger 
of  wounding  the  internal  mammary  artery.  The  operation  is  never  to  be  thought  of  in  puru- 
lent pericarditis.  The  safest  way  to  aspirate  is  to  introduce  the  needle  in  the  fifth  interspace 
two  inches  to  the  left  of  the  sternum  and  push  it  straight  backward. 

A  better  operation,  even  in  a  case  of  serous  effusion,  and  one  invariably  selected  in  purulent 
pericarditis,  is  incision  (pericardotomy).  A  portion  of  the  cartilage  of  the  fifth  rib.  of  the  left 
side  is  excised.  The  pericardium  is  exposed  and  is  punctured,  to  learn  the  nature  of  the 
contained  fluid,  and  is  then  incised.  By  this  method  the  surgeon  avoids  opening  the  pleural 
cavity,  and  can  obtain  free  drainage  if  pus  is  found. 

Porter  maintains  that  by  "reason  of  the  uncertain  and  varying  relations  of  the  pleura,  and 
also  of  the  anterior  position  of  the  heart,  whenever  the  pericardial  sac  is  distended  with  fluid, 
aspiration  of  the  pericardium  is  a  much  more  dangerous  procedure  than  open  incision  when 
done  by  skilled  hands." 


Line  of  reflection  of 
serous  pericardium 


Transverse  sinus 
of  pericardium 


Openings  of 
right  pulmo- 
nary veins 


Openings  of  left 
pulmonary  veins 


Left  phrenic 
nerve 


FIG.  371. — Posterior  wall  of  the  pericardial  sac,  showing  the  lines  of  reflection  of  the  serous 
pericardium  on  the  great  vessels. 


THE  HEART  (COE). 

The  heart  is  a* hollow  muscular  organ  of  a  conical  form,  placed  between  the 
lungs,  and  enclosed  in  the  cavity  of  the  pericardium. 

Position  (Fig.  372). — The  heart  is  placed  obliquely  in  the  chest:  the  broad 
attached  end,  or  base  (basis  cordis),  is  directed  upward,  backward,  and  to  the  right, 
and  corresponds  with  the  thoracic  vertebrae,  from  the  fifth  to  the  eighth  inclusive; 
the  apex  (apex  cordis)  is  directed  downward,  forward,  and  to  the  left,  and  corre- 
sponds to  the  space  between  the  cartilages  of  the  fifth  and  sixth  ribs,  three-quarters 


THE  HEART 


565 


of  an  inch  to  the  inner  side,  and  an  inch  and  a  half  below  the  left  nipple,  or  about 
three  and  a  half  inches  from  the  middle  line  of  the  sternum.  The  heart  is  placed 
behind  the  sternum,  and  projects  farther  into  the  left  than  into  the  right  half  of  the 
cavity  of  the  chest,  extending  from  the  median  line  about  three  inches  in  the  former 
direction,  and  only  one  and  a  half  in  the  latter;  about  one-third  of  the  heart  lies 
to  the  right  and  two-thirds  to  the  left  of  the  mesial  plane.  The  antero-superior 
surface  (fades  stemocosialis)  is  round  and  convex,  directed  upward  and  forward, 
is  formed  chiefly  by  the  right  auricle  and  ventricle,  together  with  a  small  part  of 
the  left  ventricle.  It  lies  behind  the  middle  portion  of  the  sternum  and  the  costal 
cartilages  of  the  third,  fourth,  fifth,  and  sixth  ribs  on  both  sides.  On  account  of 


FIG.  372. — Position  of  the  heart.     The  pericardium  laid  open.     Adult  male.     (Poirier  and  Charpy.) 

the  heart's  inclination  to  the  left  side,  only  a  small  part  of  it  lies  behind  the  carti- 
lages of  the  right  ribs.  Lying  in  front  of  the  heart,  between  it  and  the  anterior 
chest-wall,  is  the  thin  anterior  margin  of  the  lungs,  covered  by  the  pleura.  On 
the  left  side,  however,  owing  to  the  notch  in  the  anterior  margin  of  the  left 
lung  (incisura  cardiaca) ,  there  is  a  portion  of  the  pericardium  lying  in  contact 
with  the  Triangularis  sterni  muscle.  This  area  is  called  the  area  of  greatest  or 
of  absolute  cardiac  dulness  or  the  area  of  superficial  cardiac  dulness.  The  postero- 
inferior  surface  of  the  heart  (fades  diaphragmatica) ,  which  looks  downward  rather 


566 


THE   BLOOD -VASCULAR   SYSTEM 


than  backward,  is  flattened  and  rests  upon  the  Diaphragm,  and  is  formed  chiefly 
by  the  left  ventricle.  The  right  or  lower  border  is  long,  thin,  and  sharp;  the  left 
or  upper  border  short,  but  thick  and  round. 

Size  and  Weight. — The  heart,  in  the  adult,  measures  five  inches  in  length, 
three  inches  and  a  half  in  breadth  in  the  broadest  part,  and  two  inches  and  a  half 
in  thickness.  The  prevalent  weight,  in  the  male,  varies  from  ten  to  twelve  ounces; 
in  the  female,  from  eight  to  ten:  its  proportions  to  the  body  being  as  1  to  169  in 
males;  1  to  149  in  females.  The  heart  continues  increasing  in  weight,  and  also 
in  length,  breadth,  and  thickness,  up  to  an  advanced  period  of  life:  this  increase 
is  more  marked  in  men  than  in  women. 


AZVGOS 
VEIN 


H.EFT  APPENDIX 

AURICUUE 

LEFT  AURICULA 

VENTRICULA 

GROOVE 


CORONARY 
SINUS 


OESOPHAGUS 


FIG.  373. — Base  of  the  heart  in  place.     The  attachments  of  the  pericardium  are  outlined  in  red. 

(Poirier  and  Charpy.) 

Capacity  of  the  Cavities  of  the  Heart. — This  matter  is  in  dispute.  Professor 
'Cunningham  believes  that  during  life  the  capacity  of  the  ventricles  is  nearly  iden- 
tical, each  holding  about  four  ounces  of  blood.  Each  auricle  holds  a  little  less 
than  four  ounces.  Stewart  maintains  that  at  each  heart  beat  each  ventricle 
throws  out  only  eighty-seven  grams  of  blood.  Morrant  Baker1  says  that,  "taking 
the  mean  of  various  estimates,  it  may  be  inferred  that  each  ventricle  is  able  to 
contain  four  to  six  ounces  of  blood." 

Fat  upon  the  Heart. — Normally  there  is  a  certain  amount  of  fat  upon  the 
surface  of  the  heart.  This  begins  to  appear  in  the  early  weeks  of  life  and 
increases  in  amount  as  age  advances.  It  is  found  upon  the  surface  of  the 
muscles  and  along  the  course  of  the  vessels.  Poirier  is  of  the  opinion  that  the 
cardiac  fat  on  the  anterior  surface  of  the  heart  is  arranged  in  three  movable 

i  Kirkes'   Physiology,  10th  ed.,  p.  156. 


THE  HEART  507 

pads,  which  act  as  valves  and  fill  vacant  spaces  about  the  heart  created  during 
the-  cardiac  contractions.1 

Component  Parts. — The  heart  is  subdivided  by  a  muscular  septum  into  two 
lateral  halves,  which  are  named  respectively  the  right  or  pulmonary  heart  and  the 
left  or  systemic  heart;  and  a  transverse  constriction  subdivides  each  half  of  the 
organ  into  two  cavities,  the  upper  cavity  on  each  side  being  called  the  auricle, 
the  lower  the  ventricle.  The  course  of  the  blood  through  the  heart  cavities  and 
blood-vessels  has  already  been  described  (page  557). 

The  division  of  the  heart  into  four  cavities  is  indicated  by  grooves  upon  its  sur- 
face. The  groove  separating  the  auricles  from  the  ventricles  is  called  the  auriculo- 
ventricular  groove  (sulcus  coronarius).  It  is  deficient,  in  front,  where  it  is  crossed 
by  the  root  of  the  pulmonary  artery.  It  contains  the  trunks  of  the  nutrient  vessels 
of  the  heart.  The  auricular  portion  occupies  the  base  of  the  heart,  and  is  sub- 
divided into  two  cavities  by  a  median  septum.  The  two  ventricles  are  also  sepa- 
rated into  a  right  and  left  by  two  furrows,  the  interventricular  grooves  (sulci  longi- 
tudinales),  which  are  situated  one  on  the  anterior  (sulcus  longitudinalis  anterior), 
the  other  on  the  posterior  (sulcus  longitudinalis  posterior)  surface;  these  extend 
from  the  base  of  the  ventricular  portion  to  near  the  apex  of  the  organ ;  the  former 
being  situated  nearer  to  the  left  border  of  the  heart,  and  the  latter  to  the  right. 
It  follows,  therefore,  that  the  right  ventricle  forms  the  greater  portion  of  the 
anterior  surface  of  the  heart,  and  the  left  ventricle  more  of  its  posterior  surface. 
The  internal  surface  of  the  heart  is  lined  with  endocardium. 

The  auricular  portion  occupies  the  base  of  the  heart  and  is  subdivided  into  two 
cavities,  fore-chambers  or  auricles  (atria),  by  a  septum.  As  before  stated,  this  portion 
of  the  heart  corresponds  to  the  middle  segment  of  the  thoracic  spine.  Its  form  is 
quadrilateral  in  shape,  and  has  two  processes  extending  upward  from  its  two  upper 
angles,  called  the  auricular  appendices  (appendices  auriculae),  between  which  are 
found  the  aorta  and  the  pulmonary  artery.  The  greater  part  of  the  base  of  the 
heart  is  formed  by  the  left  auricle.  Its  boundaries  are,  above,  the  pulmonary 
artery;  below,  the  coronary  sinus;  on  the  left  it  is  bounded  by  the  left  superior 
and  inferior  pulmonary  veins,  while  on  the  right  side  it  is  limited  by  the  sulcus 
tenninalis.  The  latter  corresponds  to  a  ridge  in  the  interior  of  the  auricle,  called 
ttoe  crista  terminalis.  Running  vertically  on  this  surface,  just  to  the  left  of  the 
openings  of  the  two  venae  cavae,  is  the  interauricular  furrow,  which  exactly  indicates 
the  proportion  of  the  base  of  the  heart  formed  by  each  auricle. 

Each  of  the  cavities  should  now  be  separately  examined. 

The  Right  Fore-chamber  or  Auricle2  (atrium  dextrum)  is  a  little  larger  than  the  left, 
its  walls  somewhat  thinner,  measuring  about  one  line.  It  consists  of  two  parts:  a 
principal  cavity,  the  sinus  venosus,  situated  posteriorly,  and  an  anterior,  smaller 
portion,  the  auricular  appendix.  The  right  auricle  is  separated  from  the  left  auricle 
by  the  interauricular  septum  (septum  atriorum).  Part  of  this  septum  is  muscular; 
part  is  composed  of  connective  tissue. 

The  sinus  venosus  (sinus  venarum)  is  the  large  quadrangular  cavity,  placed 
between  the  two  venae  cavae;  its  walls  are  extremely  thin;  it  is  connected  below 
with  the  right  ventricle,  and  internally  with  the  left  auricle,  being  free  in  the 
rest  of  its  extent.  It  is  derived  from  a  portion  of  the  sinus  reuniens  of  the 
fcetal  heart. 

The  right  auricular  appendix  (auricula  dextra) ,  so-called  from  its  fancied  resem- 
blance to  a  dog's  ear,  is  a  small  conical  muscular  pouch,  the  margins  of  which 
present  a  dentated  edge.  It  projects  from  the  sinus  forward  and  to  the  left 
side,  overlapping  the  root  of  the  aorta. 

1  L'appariel  sero-graisseux.     La  Presse  MSdicale,  December  7,  1904. 

2  In  the  new  nomenclature  the  auricle  is  called  the  atrium,  and  auricular  appendix  is  called  the  auricle. 


568 


THE  BLOOD-VASCULAR  SYSTEM 


To  examine  the  interior  of  the  right  auricle,  an  incision  should  be  made  along  its  right  border, 
from  the  entrance  of  the  precava  to  that  of  the  postcava.  A  second  cut  is  to  be  made  from  the 
centre  of  the  first  incision  to  the  tip  of  the  auricular  appendix,  and  the  flaps  raised. 

The  internal  surface  of  the  right  auricle  is  smooth,  except  in  the  appendix 
and  adjacent  part  of  the  anterior  wall  of  the  sinus  venosus,  where  the  muscular 
wall  is  thrown  into  parallel  ridges  resembling  the  teeth  of  a  comb  and  hence 
named  the  musculi  pectinati.  These  end  behind  on  a  vertical  smooth  ridge,  the 


Bristle  passed  through 
Right  Auricula-  Ventricular  opening. 

FIG.  374.— The  right  auricle  and  ventricle  laid  open,  the  anterior  walls  of  both  being  removed. 

• 

crista  terminalis  of  His,  the  position  of  which  is  indicated  on  the  surface  of  the 
distended  auricle  by  a  furrow,  the  sulcus  terminalis  of  His.  The  sulcus  terminalis 
passes  from  in  front  of  the  precava  to  the  left  of  the  postcava.  It  represents  the 
line  of  fusion  of  the  sinus  venosus  of  the  embryo  with  the  primitive  auricle  proper. 
The  right  auricle  presents  the  following  parts  for  examination : 

(  Precava,  or  Superior  vena  cava. 
Postcava,  or  Inferior  vena  cava. 

Openings  \  Coronary  sinus.  Valves 

I  Foramini  Thebesii. 
I  Auriculo-  ventricular. 

Fossa  ovalis. 
Annulus  ovalis. 
Tuberculum  Loweri. 
Musculi  pectinati. 

The  precava  (superior  vena  cava)  returns  the  blood  from  the  upper  half  of  the 
body,  and  opens  into  the  upper  and  back  part  of  the  auricle,  the  direction  of  its 
orifice  being  downward  and  forward.  The  precava  does  not  possess  valves. 

The  postcava  (inferior  vena  cava),  larger  than  the  precava,  returns  the  blood  from 
the  lower  half  of  the  body,  and  opens  into  the  lowest  part  of  the  auricle  near  the 


Eustachian. 
Coronary. 


THE  HEART  569 

septum,  the  direction  of  its  orifice  being  upward  and  inward.  The  direction  of 
a  current  of  blood  through  the  precava  would  consequently  be  toward  the  auriculo- 
ventricular  orifice,  whilst  the  direction  of  the  blood  through  the  postcava  would  be 
toward  the  auricular  septum.  This  is  the  normal  direction  of  the  two  currents  in 
foetal  life.  The  postcava  does  not  possess  valves  until  its  termination  at  the  right 
auricle. 

The  coronary  sinus  (sinus  coronarius]  opens  into  the  auricle,  between  the  post- 
cava and  the  auriculo-ventricular  opening.  It  returns  the  blood  from  the  substance 
of  the  heart,  and  is  protected  by  a  semicircular  fold  of  the  lining  membrane  of 
the  auricle,  the  coronary  valve  or  valve  of  Thebesius.  The  sinus,  before  entering 
the  auricle,  is  considerably  dilated — nearly  to  the  size  of  the  end  of  the  little 
finger.  Its  wall  is  partly  muscular,  and  at  its  junction  with  the  great  coronary 
vein  it  is  somewhat  constricted  and  is  furnished  with  a  valve  consisting  of  two 
unequal  segments. 

The  foramini  Thebesii  (foramina  venarum  minimarum)  are  numerous  minute 
fossa3  or  apertures  on  various  parts  of  the  inner  surface  of  the  auricle.  Many  of 
these  foramina  have  at  their  points  the  minute  openings  of  small  veins  (venae 
minimfle  cordis).  They  return  the  blood  directly  from  the  muscular  substance 
of  the  heart.  Some  of  these  foramina  are  minute  depressions  in  the  walls  of  the 
heart,  presenting  a  closed  extremity. 

The  right  auriculo-ventricular  opening  or  the  tricuspid  orifice  (ostium  venosum 
dextrum)  is  the  large  oval  aperture  of  communication  between  the  right  auricle 
and  the  ventricle,  to  be  presently  described. 

The  Eustachian  valve  (valvula  venae  cavae  inferioris  [Eustachii])  is  situated 
between  the  anterior  margin  of  the  postcava  and  the  auriculo-ventricular  orifice. 
It  is  semilunar  in  form,  its  convex  margin  being  attached  to  the  wall  of  the  vein; 
its  concave  margin,  which  is  free,  terminating  in  two  cornua,  of  which  the  left  is 
attached  to  the  anterior  edge  of  the  annulus  ovalis,  the  right  being  lost  on  the  wall 
of  the  auricle.  The  valve  is  formed  by  a  duplicature  of  the  lining  membrane  of 
the  auricle  and  contains  a  few  muscular  fibres. 

In  the  foetus  this  valve  is  of  large  size,  and  serves  to  direct  the  blood  from  the 
postcava,  through  the  foramen  ovale,  into  the  left  auricle. 

In  the  adult  it  is  occasionally  large,  and  may  assist  in  preventing  the  reflux 
of  blood  into  the  postcava;  more  commonly  it  is  small,  and  its  free  margin  presents 
a  cribriform  or  filamentous  appearance;  occasionally  it  is  altogether  wanting. 

The  coronary  valve  or  valve  of  Thebesius  (valvulae  sinus  coronarii  [Thebesii]) 
is  a  semicircular  fold  of  the  lining  membrane  of  the  auricle,  protecting 
the  orifice  of  the  coronary  sinus.  It  prevents  the  regurgitation  of  blood 
into  the  sinus  during  the  contraction  of  the  auricle.  This  valve  is  occasionally 
double. 

The  fossa  ovalis  is  an  oval  depression  corresponding  to  the  situation  of  the 
foramen  ovale  in  the  fretus.  It  is  situated  at  the  lower  part  of  the  septum  atriorum, 
above  and  to  the  left  of  the  orifice  of  the  postcava.  In  foetal  life  an  opening, 
the  foramen  ovale,  exists  at  this  point  between  the  two  auricles;  almost  imme- 
diately after  birth  the  valve-like  edge  is  pressed  down  by  the  increased  pressure 
in  the  left  auricle,  and  by  the  tenth  day  it  passes  to  the  annulus  and  closes  the 
opening. 

The  annulus  ovalis  (limbus  fossae  ovalis  [Vieussenii])  is  a  prominent  oval  margin 
which  surrounds  anteriorly  and  superiorly  the  fossa  ovalis.  It  is  most  distinct 
above  and  at  the  sides;  below,  it  is  deficient.  A  small  slit-like  valvular  opening 
is  occasionally  found,  at  th^  upper  margin  of  the  fossa  ovalis,  which  leads  upward 
beneath  the  annulus  into  the  left  auricle,  and  is  the  remains  of  the  aperture  between 
the  two  auricles  in  the  foetus. 


570  THE  BLOOD-VASCULAR  SYSTEM 

The  tubercle  of  Lower  (tuberculum  intervenosum  [Loweri])  is  a  small  projection 
on  the  interauricular  septum  between  the  fossa  ovalis  and  the  opening  of  the 
precava.  It  is  most  distinct  in  the  hearts  of  quadrupeds;  in  man  it  is  scarcely 
visible.  It  was  supposed  by  Lower  to  direct  the  blood  from  the  precava  toward 
the  auriculo-ventricular  opening. 

The  Left  Fore-chamber  or  Auricle  (atrium  sinistrum)  is  rather  smaller  than  the 
right;  its  walls  are  thicker,  measuring  about  one  line  and  a  half;  and  it  consists, 
like  the  right,  of  two  parts,  a  principal  cavity,  or  sinus,  and  an  auricular  appendix. 

The  sinus  is  cuboidal  in  form,  and  concealed  in  front  by  the  pulmonary  artery 
and  aorta;  internally,  it  is  separated  from  the  right  auricle  by  the  auricular  septum 
(septum  atriorum);  behind,  it  receives  on  each  side  two  pulmonary  veins,  being 
free  in  the  rest  of  its  extent. 

The  left  auricular  appendix  (auricula  sinistra)  is  somewhat  constricted  at  its 
junction  with  the  auricle;  it  is  longer,  narrower,  and  more  curved  than  that  of 
the  right  side,  and  its  margins  are  more  deeply  indented,  presenting  a  kind  of 
foliated  appearance.  Its  direction  is  forward  and  toward  the  right  side,  over- 
lapping the  root  of  the  pulmonary  artery. 

Within  the  auricle  the  following  parts  present  themselves  for  examination: 

The  openings  of  the  four  pulmonary  veins. 
Auriculo-ventricular  opening. 
Musculi  pectinati. 
Foramina  Thebesii. 

The  pulmonary  veins,  four  in  number,  open,  two  into  the  right  and  two  into 
the  left  side  of  the  auricle.  The  two  left  veins  frequently  terminate  by  a  common 
opening.  They  are  not  provided  with  valves. 

The  auriculo-ventricular  opening  or  mitral  orifice  (ostium  venosum  ventriculi 
sinistri)  is  the  large  oval  aperture  of  communication  between  the  left  auricle 
and  the  left  ventricle.  It  is  rather  smaller  than  the  corresponding  opening  on 
the  opposite  side  (see  note,  page  571). 

The  musculi  pectinati  are  fewer  in  number  and  smaller  than  on  the  right  side; 
they  are  confined  to  the  inner  surface  of  the  auricular  appendix. 

On  the  inner  surface  of  the  auricular  septum  may  be  seen  a  lunated  impres- 
sion bounded  below  by  a  crescentic  ridge  the  concavity  of  which  is  turned  upward. 
The  depression  is  just  above  the  fossa  ovalis  in  the  right  auricle.  The  inner 
surface  of  the  auricle  shows  foramini  Thebesii  and  venae  minimis  cordis. 

To  examine  the  interior  of  the  left  ventricle,  make  an  incision  a  little  to  the  left  of  the  anterior 
interventricular  groove  from  the  base  to  the  apex  of  the  heart,  and  carry  it  up  from  thence, 
a  little  to  the  left  of  the  posterior  interventricular  groove,  nearly  as  far  as  the  auriculo-ventricular 
groove. 

The  ventricular  portion  of  the  heart  is  conical  in  shape  with  its  base  extending 
backward  and  upward  and  fitting  against  the  atrii  of  the  auricles.  Its  apex 
constitutes  the  apex  of  the  heart  (apex  cordis)  and  extends  to  the  fifth  intercostal 
space  three  and  a  quarter  inches  to  the  left  of  the  middle  line.  The  ventricles 
are  thick  and  muscular  and  have  an  antero -superior  surface  (fades  sternalis)  and 
'a  postero-inferior  surface  (fades  diaphragmatic 2)  and  two  borders,  a  right  and  a 
left  border.  The  antero-superior  surface  is  composed  mainly  of  the  right  ven- 
tricle; coursing  on  this  surface,  nearer  the  left  border  than  the  right  from  the 
auriculo-ventricular  groove  to  the  apex,  is  the  anterior  interventricular  groove 
(sulcus  longitudinalis  anterior).  The  inferior  surface  rests  on  the  diaphragm  and 
is  chiefly  made  by  the  left  ventricle ;  it  is  also  traversed  by  a  groove  called  the 
inferior  or  posterior  interventricular  groove  (sulcus  longitudinalis  posterior).  The 
two  grooves  meet  in  a  groove  (indsura  apids  cordis)  at  the  right  side  of  _  the 


THE  HEART  571 

apex  of  the  heart.  Of  the  two  borders  of  the  ventricular  portion  the  right  is 
sharp  and  thin  (margo  acuius)  and  is  a  continuation  of  the  sulcus  terminalis  of 
the  base  of  the  heart.  It  extends  from  right  to  left.  The  left  border  is  thick 
and  rounded  (margo  obtusus).  The  base  of  the  ventricles  is  perforated  by  four 
large  openings,  namely,  the  aorta,  the  pulmonary  artery,  the  right  and  left 
auriculo-ventricular  openings. 

The  Right  Ventricle  (ventriculus  dexter)  is  triangular  in  form,  and  extends 
from  the  right  auricle  to  near  the  apex  of  the  heart.  Its  antero-superior  surface 
is  rounded  and  convex,  and  forms  the  larger  part  of  the  front  of  the  heart.  Its 
inferior  surface  is  flattened,  rests  upon  the  Diaphragm,  and  forms  only  a  small 
part  of  the  back  of  the  heart.  Its  posterior  wall  is  formed  by  the  partition  between 
the  two  ventricles,  the  interventricular  septum  (septum  ventriculorum) ,  so  that  a 
transverse  section  of  the  cavity  presents  a  semilunar  outline.  The  surface  of 
the  septum  is  convex  and  bulges  into  the  cavity  of  the  right  ventricle.  The 
upper  and  inner  angle  of  the  ventricle  is  prolonged  into  a  conical  pouch,  the 
infundibulum  (conus  arteriosus},  from  which  the  pulmonary  artery  arises.  The 
balance  of  the  ventricle,  the  body,  is  the  portion  into  which  the  auriculo- 
ventricular  orifice  opens.  The  conus  arteriosus  is  marked  off  from  the  body  of 
the  ventricle  by  a  muscular  projection  (crista  supraventricularis) .  The  walls  of 
the  right  ventricle  are  thinner  than  those  of  the  left,  the  proportion  between  them 
being  as  1  to  3.  The  wall  is  thickest  at  the  base,  and  gradually  becomes  thinner 
toward  the  apex. 

To  examine  the  interior  of  the  right  ventricle,  its  anterior  wall  should  be  turned  downward 
and  to  the  right  in  the  form  of  a  triangular  flap.  This  is  accomplished  by  making  two  incisions: 
(1)  from  the  pulmonary  artery  to  the  apex  of  the  ventricle  parallel  to,  but  a  little  to  the  right 
of,  the  anterior  interventricular  furrow;  (2)  another,  starting  from  the  upper  extremity  of  the 
first  and  carried  outward  parallel  to,  but  a  little  below,  the  auriculo-ventricular  furrow,  care 
being  taken  not  to  injure  the  auriculo-ventricular  valve. 

The  following  parts  present  themselves  for  examination: 

^       .        f  Auriculo-ventricular. 

mgs  1  Opening  of  the  pulmonary  artery. 

( Tricuspid. 
Valves       ~\  o      -i 

I  Semilunar. 

And  a  muscular  and  tendinous  apparatus  connected  with  the  tricuspid  valve: 
Columnar  carnese.  Chorda?  tendineae. 

The  right  auriculo- ventricular  opening  or  the  tricuspid  orifice  (ostium  venosum  ven- 
triculi  dextri)  is  the  large  oval  aperture  of  communication  between  the  auricle  and 
ventricle.  It  is  situated  at  the  base  of  the  ventricle,  near  the  right  border  of 
the  heart.  It  is  about  an  inch  and  a  half  in  diameter,1  oval  from  side  to  side, 
surrounded  by  a  fibrous  ring  and  covered  by  the  lining  membrane  of  the  heart; 
it  is  considerably  larger  than  the  corresponding  aperture  on  the  left  side,  being 
sufficient  to  admit  the  ends  of  four  fingers.  It  is  guarded  by  the  tricuspid 
valve. 

The  opening  of  the  pulmonary  artery  (ostium  arteriosum)  is  circular  in  form, 
and  is  situated  at  the  summit  of  the  conus  arteriosus,  close  to  the  ventricular 
septum.  It  is  placed  above  and  on  the  left  side  of  the  auriculo-ventricular 

1  In  the  Pathological  Transactions,  vol.  vi.  p.  119,  Dr.  Peacock  has  given  some  careful  researches  upon  the 
weight  and  dimensions  of  the  heart  in  health  and  disease.  He  states,  as  a  result  of  his  investigations,  that 
in  the  healthy  adult  heart  the  right  auriculo-ventricular  aperture  has  a  mean  circumference  of  54.4  lines,  or 
420/24  inches;  the  left  auriculo-ventricular  aperture  a  mean  circumference  of  44.3  lines,  or  34/o4  inches;  the  pulmonic 
orifice  of  40  lines,  or  3':t/24  inches;  and  the  aortic  orifice  of  35.5  lines,  or  3--/24  inches;  but  the  dimensions  of  the 
orifices  varied  greatly  in  different  cases,  the  right  auriculo-ventricular  aperture  having  a  range  of  from  40  to  50 
line?,  and  the  others  in  the  same  proportion. — ED.  of  15th  English  edition. 


572  THE   BLOOD -VASCULAR    SYSTEM 

opening,  upon  the  anterior  aspect  of  the  heart.  Its  orifice  is  guarded  by  the 
pulmonary  semilunar  valves. 

The  tricuspid  valve  (vcdvida  tricuspidalis)  consists  of  three  segments  or  cusps 
(cuspides)  of  a  triangular  or  trapezoidal  shape,  each  formed  by  a  duplicature  of 
the  lining  membrane  of  the  heart,  strengthened  by  a  layer  of  fibrous  tissue,  which 
contains,  according  to  Kiirschner  and  Senac,  muscular  fibres.  These  segments 
are  connected  by  their  bases  to  the  oval  fibrous  ring  surrounding  the  auriculo- 
ventricular  orifice  (annulus  fibrosus  dexter),  and  by  their  sides  with  one  another, 
so  as  to  form  a  continuous  annular  membrane,  which  is  attached  round  the 
margin  of  the  auriculo-ventricular  opening,  their  free  margins  and  ventricular 
surfaces  affording  attachment  to  a  number  of  delicate  tendinous  cords,  the 
chordae  tendineae.  The  largest  and  most  movable  segment  is  placed  toward 
the  left  side  of  the  auriculo-ventricular  opening,  and  is  interposed  between  that 
opening  and  the  inf undibulum ;  hence  it  is  called  the  left  or  infundibular  cusp 
(cuspis  medialis).  Another  segment  corresponds  to  the  right  part  of  the  front 
of  the  ventricle,  the  right  or  marginal  cusp  (cuspis  anterior),  and  a  third  to  its 
posterior  wall,  the  posterior  or  septal  cusp  (cuspis  posterior).  The  central  part  of 
each  segment  is  thick  and  strong:  the  lateral  margins  are  thin  and  translucent. 
The  chordae  tendineae  are  connected  with  the  adjacent  margins  of  the  principal 
segments  of  the  valve,  and  are  further  attached  to  each  segment  in  the  following 
manner:  1.  Three  or  four  reach  the  attached  margin  of  each  segment,  where 
they  are  continuous  with  the  auriculo-ventricular  tendinous  ring.  2.  Others,  four 
to  six  in  number,  are  attached  to  the  central  thickened  part  of  each  segment.  3. 
The  most  numerous  and  finest  are  connected  with  the  marginal  portion  of  each 
segment. 

The  columnas  carneae  (trabeculae  carneae)  are  the  rounded  muscular  columns 
which  project  from  nearly  the  whole  of  the  inner  surface  of  the  ventricle,  except- 
ing near  the  opening  of  the  pulmonary  artery,  where  the  wall  is  smooth.  They 
may  be  classified,  according  to  their  mode  of  connection  with  the  ventricle,  into 
three  sets.  The  first  set  merely  forms  prominent  ridges  on  the  inner  surface  of 
the  ventricle,  being  attached  by  their  entire  length  on  one  side,  as  well  as  by 
their  extremities.  The  second  set  are  attached  by  their  two  extremities,  but  are 
free  in  the  rest  of  their  extent ;  while  the  third  set  (musculi  papillares)  are  attached 
by  one  extremity  to  the  wall  of  the  heart,  the  opposite  extremity  giving  attach- 
ment to  the  chordae  tendineae.  There  are  two  papillary  muscles,  the  anterior  and 
the  posterior:  of  these,  the  anterior  is  the  larger;  its  chordae  tendinae  are  connected 
with  the  right  and  left  segments  of  the  tricuspid  valve.  The  posterior  is  not 
always  single,  but  sometimes  consists  of  two  or  three  muscular  columns;  its 
chordae  tendineae  are  connected  with  the  posterior  and  the  right  segments  of  the 
tricuspid  valve.  In  addition  to  these,  some  few  chordae  may  be  seen  springing 
directly  from  the  ventricular  septum,  or  from  small  eminences  on  it,  and  passing 
to  the  left  and  posterior  segments.  A  fleshy  band,  well  marked  in  the  ox  and 
some  other  animals,  is  frequently  seen  passing  from  the  base  of  the  anterior 
papillary  muscle  to  the  interventricular  septum.  From  its  attachments  it  may 
assist  in  preventing  overdistention  of  the  auricle,  and  so  has  been  named  the 
moderator  band. 

The  right  auriculo-ventricular  orifice  allows  the  blood  to  pass  freely  from  the 
right  auricle  into  the  right  ventricle,  and  it  will  be  noted  that  the  surface  of  the 
tricuspid  valve  next  the  blood-current  is  quite  smooth.  When  the  right  ventricle 
contracts  to  force  the  blood  into  the  pulmonary  artery,  the  segments  of  the  tri- 
cuspid valve  come  together  and  close  the  auriculo-ventricular  opening,  and  so 
prevent  the  blood  from  passing  back  into  the  auricle.  The  papillary  muscles 
and  chordae  tendineae  moor  the  segments  of  the  valve  and  prevent  their  being 
forced  through  into  the  auricle  by  the  weight  of  blood  behind  them. 


THE  HEART  573 

The  semilunar  valves  (vahndae  semilunares  a.  pulmonalis) ,  three  in  number,1 
guard  the  orifice  of  the  pulmonary  artery.  They  consist  of  three  semicircular 
folds :  two  of  which  are  anterior  and  one  of  which  is  posterior.  They  are  formed 
by  duplicatures  of  the  lining  membrane  of  the  ventricle,  strengthened  by  fibrous 
tissue.  They  are  attached,  by  their  convex  margins,  to  the  wall  of  the  artery,  at  its 
junction  with  the  ventricle,  the  straight  border  being  free,  and  directed  upward  in 
the  lumen  of  the  vessel.  The  free  margin  of  each  is  somewhat  thicker  than  the  rest 
of  the  valve,  is  strengthened  by  a  bundle  of  tendinous  fibres,  and  presents,  at  its 
middle,  a  small  projecting  thickened  nodule,  consisting  of  bundles  of  interlacing 
connective-tissue  fibres  with  branched  connective-tissue  cells  and  some  few  elastic 
fibres.  Such  a  nodule  is  called  the  corpus  Arantii  or  body  of  Arangi  (noduli  valvu- 
larum  semilunarium  [Arantii]).  From  this  nodule  tendinous  fibres  radiate  through 
the  valve  to  its  attached  margin,  and  these  fibres  form  a  constituent  part  of  its 
substance  throughout  its  whole  extent,  excepting  two  narrow  lunated  portions,  the 
lunulae  (lunulae  valvularum  semilunarium),  placed  one  on  each  side  of  the  nodule 
immediately  adjoining  the  free  margin;  here  the  valve  is  thin,  and  formed  merely 
by  the  lining  membrane.  During  the  passage  of  the  blood  along  the  pulmonary 
artery  these  valves  are  opened,  and  the  course  of  the  blood  along  the  tube  is  unin- 
terrupted ;  but  during  the  ventricular  diastole,  when  the  current  of  blood  along  the 
pulmonary  artery  is  checked  and  partly  thrown  back  by  its  elastic  walls,  these 
valves  become  immediately  expanded,  and  effectually  close  the  entrance  of  the 
tube.  When  the  valves  are  closed,  the  lunated  portions  of  each  are  brought  into 
contact  with  one  another  by  their  opposed  surfaces,  the  three  corpora  Arantii 
filling  up  the  small  triangular  space  that  would  be  otherwise  left  by  the  approxi- 
mation of  the  three  semilunar  valves. 

Between  the  semilunar  valves  and  the  commencement  of  the  pulmonary  artery 
are  three  pouches  or  dilatations,  one  behind  each  valve.  These  are  the  pulmonary 
sinuses  of  Valsalva.  Similar  sinuses  exist  between  the  semilunar  valves  and  the 
commencement  of  the  aorta;  they  are  larger  than  the  pulmonary  sinuses.  The 
blood,  in  its  regurgitation  toward  the  heart,  finds  its  way  into  these  sinuses,  and 
so  shuts  down  the  valve-flaps. 

In  order  to  examine  the  interior  of  the  left  auricle,  make  an  incision  on  the  posterior  surface 
of  the  auricle  from  the  pulmonary  veins  on  one  side  to  those  on  the  other,  the  incision  being 
carried  a  little  way  into  the  vessels.  Make  another  incision  from  the  middle  of  the  horizontal 
one  to  the  appendix. 

The  Left  Ventricle  (ventriculus  sinister)  is  longer  and  more  conical  in  shape 
than  the  right  ventricle,  and  on  transverse  section  its  cavity  presents  an  oval  or 
nearly  circular  outline.  It  forms  a  small  part  of  the  anterior  surface  of  the  heart 
and  a  considerable  part  of  its  posterior  surface.  It  also  forms  the  apex  of  the 
heart  by  its  projection  beyond  the  right  ventricle.  Its  walls  are  much  thicker 
than  those  of  the  right  side,  the  proportion  being  as  3  to  1 .  They  are  thickest  oppo- 
site the  widest  part  of  the  ventricle,  becoming  gradually  thinner  toward  the  base, 
and  also  toward  the  apex,  which  is  the  thinnest  part. 

The  following  parts  present  themselves  for  examination : 

~       .        J  Auriculo- ventricular.  f  Mitral. 

Openings  \  Aortic  Valves  \  Semikmar< 

Chordae  tendinese.  Columnee  carneae. 

The  left  auriculo-ventricular  opening  or  the  mitral  orifice  (ostium  venosum  ven- 
triculi  sinistri)  is  placed  below  and  to  the  left  of  the  aortic  orifice.  It  is  a  little 


1  The  pulmonary  semilunar  valves  have  been  found  to  be  two  in  number  instead  of  three  (Dr.  Hand,  of  St. 

uli* 


me _|jumiuiiuiy  Memuuimr  vaive*  nave  ueeii  louiiu  MI  ue  iwo  in  iiuinoer  mtsieau  01  inree 

Paul,  Minn.,  in  North  Western  Med.  and  Surg.  Journ.,  July,  1873),  and  the  same  variety  is  more  frequently 
noticed  in  the  aortic  semilunar  valves. — ED.  of  15th  English  edition. 


574 


THE    BLOOD -VASCULAR    SYSTEM 


smaller  than  the  corresponding  aperture  of  the  opposite  side,  admitting  only  two 
fingers;  but,  like  it,  is  broader  in  the  transverse  than  in  the  antero-posterior 
diameter.  Its  right,  posterior,  and  left  sides  are  surrounded  by  a  dense  horseshoe- 
shaped  fibrous  ring  (annulus  fibrosus  sinister) .  The  orifice  is  guarded  by  the 
mitral  valves,  which  are  covered  with  endocardium. 

The  aortic  opening  (ostium  arteriosum)  is  a  circular  aperture,  in  front  and  to 
the  right  side  of  the  auriculo-ventricular  opening,  from  which  it  is  separated  by 
one  of  the  segments  of  the  mitral  valve.  Its  orifice  is  guarded  by  the  semilunar 
valves.  The  portion  of  the  ventricle  immediately  below  the  aortic  orifice  is  often 
termed  the  aortic  vestibule  of  Sibson.  It  possesses  fibrous  instead  of  muscular 
walls,  and  so  does  not  collapse  during  the  ventricular  diastole;  it  thus  gives  space 
for  the  segments  of  the  aortic  valve  during  its  closure. 


Bristle  passed  through  left 
auriculo-ventricular  opening. 


Passed  through  aortic  opening. 


FIG.  375. — The  left  auricle  and  ventricle  laid  open,  the  posterior  walls  of  both  being  removed. 

The  mitral  or  bicuspid  valve  (valvula  bicuspidalis)  is  attached  to  the  circumfer- 
ence of  the  auriculo-ventricular  orifice  in  the  same  way  that  the  tricuspid  valve  is 
on  the  opposite  side.  It  is  formed  by  a  duplicature  of  the  lining  membrane, 
strengthened  by  fibrous  tissue,  and  contains  a  few  muscular  fibres.  It  is  larger 
in  size,  thicker,  and  altogether  stronger  than  the  tricuspid,  and  consists  of  two 
segments  of  unequal  size.  The  larger  segment,  the  anterior  or  aortic  cusp  (cuspis 
anterior) ,  is  placed  in  front  and  to  the  right  between  the  auriculo-ventricular  and 
aortic  orifices,  the  smaller,  the  posterior  or  marginal  cusp  (cuspis  posterior),  is 
placed  to  the  left  and  behind  the  opening,  close  to  the  wall  of  the  ventricle.  Two 
smaller  segments  are  usually  found  at  the  angles  of  junction  of  the  larger.  The 
mitral  valve-flaps  are  furnished  with  chordae  tendinese,  the  mode  of  attachment 
of  which  is  precisely  similar  to  those  on  the  right  side;  but  they  are  thicker, 
stronger,  and  less  numerous. 

The  aortic  semilunar  valves  (valvulae  semilunares  aortae)  surround  the  orifice  of 
the  aorta;  one  is  posterior  (valvula  semilunaris  posterior);  one  right  (valvula 


THE   HEART 


575 


semilunarix  dc.rfra) ,  and  one  left  (valvula  semilunaris  sinistra) :  they  are  similar  in 
structure  and  in  their  mode  of  attachment  to  those  of  the  pulmonary  artery.  They 
are,  however,  larger,  thicker,  and  stronger  than  those  of  the  right  side ;  the  lunulae 
are  more  distinct  and  the  corpora  Arantii  larger  and  more  prominent.  Opposite 
each  segment  the  wall  of  the  aorta  presents  a  slight  dilatation  or  bulging,  the 
sinus  of  Valsalva, 

The  columns  carneae  admit  of  a  subdivision  into  three  sets,  like  those  upon 
the  right  side;  but  they  are  smaller,  more  numerous,  and  present  a  dense  inter- 
lacement, especially  at  the  apex,  and  upon  the  posterior  wall.  Those  attached  by 
one  extremity  only,  the  musculi  papillares,  are  two  in  number,  being  connected 


•ilmonary 
artery. 


FIG.  376. — Section  of  the  heart,  showing  the  interventricular  septum. 

one  to  the  anterior,  the  other  to  the  posterior  wall;   they  are  of  large  size,  and 
terminate  by  free  rounded  extremities,  from  which  the  chordae  tendineae  arise. 

The  septum  between  the  two  ventricles  (septum  ventriculorum)  is  thick  and 
muscular,  especially  below  (Fig.  376) .  At  its  upper  part  it  suddenly  tapers  off, 
becomes  destitute  of  muscular  fibres,  and  consists  only  of  fibrous  tissue,  covered 
by  two  layers  of  endocardium;  and  on  the  right  side  also  covered,  during  dias- 
tole, by  one  of  the  flaps  of  the  tricuspid  valve.  This  upper  portion  is  termed 
the  undefended  or  membranous  part  of  the  septum  (septum  membranaceum  ven- 
triculorum), and  is  continued  upward  and  forms  the  septum  between  the 
aortic  vestibule  and  the  right  auricle.  It  is  derived  from  the  lower  part  of 
the  aortic  septum  of  the  foetus,  and  an  abnormal  communication  may  exist  at 
this  part,  owing  to  defective  development  of  this  septum. 


57u 


THE  BLOOD- VASCULAR  SYSTEM 


Structure  of  the  Heart. — The  heart  is  a  hollow  muscular  organ,  and  its  walls 
are  divisible  into  three  layers:  the  endocardium,  myocardium,  and  epicardium  or 
visceral  layer  of  the  pericardium  (page  562). 

The  Endocardium  is  the  lining  membrane  of  the  cavities  of  the  heart.  It  is 
decidedly  thinner  than  the  epicardium.  It  is  composed  of  endothelial  cells  resting 
upon  a  connective-tissue  membrane  which  contains  unstriated  muscle  cells  and 
elastic  tissue.  This  connective-tissue  membrane  of  the  endocardium  is  attached 
to  the  myocardium  by  loose  elastic  tissue  which  contains  blood-vessels  and  nerves. 
The  endothelial  layer  of  the  endocardium  is  continuous  with  the  endothelial  coat 
of  the  blood-vessels  which  pass  to  and  emerge  from  the  heart.  The  endocar- 
dium is  more  opaque  on  the  left  than  on  the  right  side  of  the  heart,  thicker  in  the 
auricles  than  in  the  ventricles,  and  thickest  in  the  left  auricle.  It  is  thin  on  the 
musculi  pectinati  and  on  the  columnae  carnese,  but  thicker  on  the  smooth  parts  of 
the  auricular  and  ventricular  walls  and  on  the  tips  of  the  musculi  papillares. 

The  Fibrous  Rings  (annuli  fibrosi)  surround  the  auriculo-ventricular  and  arterial 
orifices;  they  are  stronger  upon  the  left  than  on  the  right  side  of  the  heart.  The 
auriculo-ventricular  rings  serve  for  the  attachment  of  the  muscular  fibres  of  the 
auricles  and  ventricles,  and  also  for  the  mitral  and  tricuspid  valves;  the  ring  on  the 


RIGHT  AURICULO- 
VENTRICULAR    ORIFICE 


PULMONA 
OR 


LEFT  AURICULO-  RIGHT 

VENTRICULAR    ORIFICE  NODULE 

FIG.  377. — Fibrous  bones  at  the  base  of  the  ventricles.     (Poirier  and  Charpy.) 

left  side  is  closely  connected  by  its  right  margin  with  the  aortic  arterial  ring.  Be- 
tween these  and  the  right  auriculo-ventricular  ring  is  a  mass  of  fibrous  tissue,  and  in 
some  of  the  larger  animals,  as  the  ox  and  elephant,  a  nodule  of  bone,  the  os  cordis. 

The  fibrous  rings  surrounding  the  arterial  orifices  serve  for  the  attachment  of 
the  great  vessels  and  semilunar  valves.  Each  ring  receives,  by  its  ventricular 
margin,  the  attachment  of  the  muscular  fibres  of  the  ventricles;  its  opposite  margin 
presents  three  deep  semicircular  notches,  within  which  the  middle  coat  of;  the 
artery  (which  presents  three  convex  semicircular  segments)  is  firmly  fixed,  the 
attachment  of  the  artery  to  its  fibrous  ring  being  strengthened  by  the  thin  cellular 
coat  and  serous  membrane  externally  and  by  the  endocardium  within.  It  is 
opposite  the  margins  of  these  semicircular  notches,  in  the  arterial  rings,  that  the 
endocardium  by  its  reduplication  forms  the  semilunar  valves,  the  fibrous  structure 
of  the  ring  being  continued  into  each  of  the  segments  of  the  valve  at  this  part. 
The  middle  coat  of  the  artery  in  this  situation  is  thin,  and  the  sides  of  the  vessel  are 
dilated  to  form  the  sinuses  of  Valsalva. 

The  Myocardium  is  composed  of  muscle  fibres.  The  muscle  fibres,  though  striated , 
are  involuntary  and  constitute  a  special  type  called  cardiac  fibres.  Cardiac  fibres 


THE  HEART  577 

are  shorter  than  ordinary  striated  muscle  fibres,  many  of  the  cells  are  oblong  and 
the  nuclei  are  centrally  placed.  During  the  first  year  of  life,  and  occasionally  even 
in  adult  life,  certain  peculiar  fibres  are  found  beneath  the  elastic  tissue  which 
attaches  the  endocardium  to  the  myocardium.  These  peculiar  fibres  are  called 
the  fibres  of  Purkinje.  The  striation  in  these  cells  is  peripheral  only.  Between 
individual  fibres  and  between  bundles  of  fibres  of  cardiac  muscle  is  connective 
tissue  carrying  capillaries. 

The  Muscular  Structure  of  the  heart  consists  of  bands  and  layers  of  fibres  which 
present  an  exceedingly  intricate  interlacement.  They  are  of  a  deep  red  color  and 
marked  with  transverse  striae.  The  arrangement  of  the  fasciculi  varies  in  different 
parts  of  the  heart.  It  requires  elaborate  care  to  demonstrate  the  layers,  and  it  is 
more  than  probable  that  some  of  those  described  are  really  artificially  produced. 

The  fasciculi  of  the  heart  admit  of  a  subdivision  into  two  groups,  those  of  the 
auricles  and  those  of  the  ventricles.  It  was  long  thought  that  auricular  fasciculi 
were  entirely  separate  from  the  ventricular  fasciculi.  It  is  now  known  that  there  is 
a  direct  connection  by  means  of  the  auriculo-ventricular  fasciculus  of  His  (see 
below). 


FIG.  378. — The  arrangement  of  the  muscles  of  the  auricles.     (Poirier  and  Charpy.) 

FIBRES  OF  THE  AURICLES  (Fig.  378). — These  are  disposed  in  two  layers — a 
superficial  layer  common  to  both  cavities,  and  a  deep  layer  proper  to  each.  The 
superficial  fibres  are  more  distinct  on  the  anterior  surface  of  the  auricles,  across 
the  bases  of  which  they  run  in  a  transverse  direction,  forming  a  thin  but  incomplete 
layer.  Some  of  these  fibres  pass  into  the  septum  atriorum.  The  internal  or  deep 
fibres  proper  to  each  auricle  consist  of  two  sets,  looped  and  annular  fibres.  The 
looped  fibres  pass  upward  over  each  auricle,  being  attached  by  two  extremities 
to  the  corresponding  auriculo-ventricular  rings  in  front  and  behind.  The  annular 
fibres  surround  the  whole  extent  of  the  auricular  appendices,  and  are  continued 
upon  the  walls  of  the  venae  cavse  and  coronary  sinus  on  the  right  side,  and  upon 
the  pulmonary  veins  on  the  left  side,  at  their  connection  with  the  heart.  In  the 
appendices  they  interlace  with  the  longitudinal  fibres. 

FIBRES  OF  THE  VENTRICLES. — These  are  arranged  in  an  exceedingly  complex 
manner,  and  the  accounts  given  by  various  anatomists  differ  considerably.  This 
is  probably  due  partly  to  the  fact  that  the  various  layers  of  muscular  fibres  of 
which  the  heart  is  said  to  be  composed  are  not  independent,  but  their  fibres  are 
interlaced  to  a  considerable  extent,  and  therefore  any  separation  into  layers  must 
be  to  a  great  extent  artificial;  and  also  partly  to  the  fact,  pointed  out  by  Henle, 
that  there  are  varieties  in  the  arrangement  due  to  individual  differences.  If  the 
epicardium  and  the  subjacent  fat  are  removed  from  a  heart  which  has  been  sub- 

37 


578 


THE  BLOOD-VASCULAR  SYSTEM 


jected  to  prolonged  boiling,  so  as  to  dissolve  the  connective  tissues,  the  superficial 
fibres  of  the  ventricles  will  be  exposed.  They  will  be  seen  to  commence  at  the  base 
of  the  heart,  where  they  are  attached  to  the  tendinous  rings  around  the  orifices, 
and  to  pass  obliquely  downward  toward  the  apex,  with  a  direction  from  right  to 
left.  At  the  apex  the  fibres  turn  suddenly  inward  into  the  interior  of  the  ventricle, 
forming  what  is  called  the  vortex  (Fig.  379).  On  the  back  of  the  heart  it  will  be 
seen  that  the  fibres  pass  continuously  from  one  ventricle  to.  the  other  over  the  inter- 
ventricular  groove;  and  the  same  thing  will  be  noticed  on  the  front  of  the  heart  at 
the  upper  and  lower  end  of  the  anterior  interventricular  groove,  but  in  the  middle 
portion  of  this  groove  the  fibres  passing  from  one  ventricle  to  the  other  are  inter- 
rupted by  fibres  emerging  from  the  septum  along  the  groove;  many  of  the  super- 
ficial fibres  pass  in  also  at  this  groove  to  the  septum.  The  vortex  is  produced, 

as  stated  above,  by  the  sudden  turning 
inward  of  the  superficial  fibres  in  a 
peculiar  spiral  manner  into  the  deepest 
portion  of  the  wall  of  the  ventricle. 
Those  fibres  which  descended  on  the 
posterior  surface  of  the  heart  enter  the 
left  ventricle  at  the  vortex,  and,  ascend- 
ing, form  the  posterior  part  of  the  inner 
layer  of  muscular  fibres  lining  this 
cavity  and  the  right  (posterior)  mus- 
culus  papillaris;  those  fibres  which 
descend  on  the  front  of  the  heart  to 
reach  the  apex  also  pass,  at  the  vortex, 
into  the  interior  of  the  ventricle,  where 
they  form  the  remainder  of  the  inner- 
most layer  of  the  ventricle  and  the  left 
(anterior)  musculus  papillaris.  The 

fibres  forming  the  inner  layer  of  the  wall  of  the  ventricle  ascend  to  be  attached 
to  the  fibrous  rings  around  the  orifices. 

By  dissection  these  superficial  fibres  may  be  removed  as  a  thin  stratum,  and  it 
will  then  be  found  that  the  ventricles  are  made  up  of  oblique  fibres  (Fig.  380),  super- 
imposed in  layers  one  on  the  top  of  another,  and  assuming  gradually  a  less  oblique 
direction  as  they  pass  to  the  middle  of  the  thickness  of  the  ventricular  wall,  so  that 
in  the  centre  of  the  wall  the  fibres  are  transverse.  Internal  to  this  central  transverse 
layer  the  fibres  become  oblique  again,  but  in  the  opposite  direction  to  the  external 
ones.  This  division  into  distinct  layers  is,  however,  to  a  great  extent  artificial,  as  the 
fibres  pass  across  from  one  layer  to  another,  and  have  therefore  to  be  divided  in 
the  dissection,  and  the  change  in  the  direction  of  the  fibres  is  very  gradual.  These 
oblique  fibres  commence  above  at  the  fibrous  rings  at  the  base  of  the  heart,  and, 
descending  toward  the  apex,  they  enter  the  septum  near  its  lower  end.  In  the 
septum  the  fibres  which  form  the  left  ventricle  may  be  traced  in  three  directions: 
1.  Some  pass  upward  to  be  attached  to  the  central  mass  of  fibrous  tissue.  2. 
Others  pass  through  the  septum  to  become  continuous  with  the  fibres  of  the  right 
ventricle.  3.  The  remainder  pass  through  the  septum  to  encircle  the  ventricle 
as  annular  fibres.  Of  the  fibres  of  the  right  ventricle,  some  on  entering  the  septum 
pass  upward  to  be  attached  to  the  central  mass  of  fibrous  tissue;  some,  entering 
the  septum  from  behind,  pass  forward  to  become  continuous  with  the  fibres  on 
the  anterior  surface  of  the  left  ventricle;  and  others,  entering  in  front,  pass  back- 
ward to  join  the  fibres  on  the  posterior  wall  of  the  left  ventricle.  The  septum 
therefore  consists  of  three  varieties  of  fibres — viz.,  annular  fibres,  special  to  the  left 
ventricle;  ascending  fibres,  derived  from  both  ventricles  and  ascending  through 
the  septum  to  the  central  fibro-cartilage ;  and  decussating  fibres,  derived  from  the 


FIG.  379.— -The  muscular  arrangement  of  the  apex 
of  the  heart.     (Poirier  and  Charpy.) 


THE  HEART 


579 


anterior  wall  of  one  ventricle  and  passing  to  the  posterior  wall  of  the  other  ven- 
tricle, or  from  the  posterior  wall  of  the  right  ventricle  and  passing  to  the  anterior 
wall  of  the  left.  In  addition  to  these  fibres  there  are  a  considerable  number 
which  appear  to  encircle  both  ventricles  and  which  pass  across  the  septum  without 
turning  into  it. 


FIG.  380. — The  muscular  arrangement  of  the  ventricle.     (Poirier  and  Charpy.) 

THE  AURICULO-VENTRICULAR  FASCICULUS,  OR  THE  BUNDLE  OF  His. — The  only 
direct  connection  between  the  muscle  of  the  auricles  and  the  muscle  of  the  ventri- 
cles is  the  muscular  bundle  described  by  His  and  known  as  the  auriculo-ventricular 
fasciculus.  It  takes  origin  from  the  posterior  wall  of  the  right  auricle  close  to  the 
auricular  septum.  This  bundle  descends  from  its  point  of  origin  and  reaches  the 
upper  margin  of  the  ventricular  septum.  At  a  portion  of  this  margin  which  is  dis- 
tinctly muscular  it  takes  a  turn  forward,  crosses  the  septum  between  the  mem- 
branous and  muscular  areas,  and  disappears  in  the  ventricular  muscle.  A  wave 
of  contraction  starts  in  the  auricles  and  is  transmitted  to  the  ventricles  by  the 
bundle  of  His.  If  this  bundle  is  cut  or  clamped,  heart  block  occurs,  because  the 
stimulus  is  no  longer  transmitted  from  the  auricle  to  the  ventricle. 

Erlanger  showed  that  all  degrees  of  heart  block  can  be  induced  by  compression 
of  the  bundle.  Erlanger  says  that,  "as  a  rule,  the  ventricles  take  on  a  constant  slow 
rate  at  the  moment  complete  heart  block  is  established."  The  auricles  beat  nor- 
mally or  more  rapidly  than  normally. 

Stokes-Adams  disease  is  a  condition  of  heart  block  produced  by  a  lesion  of  the 
auriculo-ventricular  bundle.  This  was  demonstrated  by  Erlanger. 

In  Stokes-Adams  disease  there  are  attacks  of  vertigo  or  syncope,  perhaps  with 
epileptiform  convulsions,  and  in  these  attacks  the  ventricles  beat  at  less  than  the 
normal  rate,  and  the  auricles  normally  or  more  frequently  than  normally. 


580  THE  BLOOD-VASCULAR  SYSTEM 

Vessels  and  Nerves. — The  arteries  supplying  the  heart  are  the  right  and  left 
coronary  from  the  aorta.  Branches  from  the  coronary  vessels  supply  the  mus- 
cular structure,  the  subendocardial,  and  the  subepicardial  tissue.  There  are  no 
vessels  in  the  endocardium.  The  valves  contain  no  vessels  unless  they  contain 
muscle,  in  which  case  minute  vessels  enter  them.  There  are  numerous  capillary 
networks  about  the  muscular  fibres. 

The  veins  accompany  the  arteries.  They  are:  the  anterior  or  great,  the  posterior, 
the  left,  and  the  anterior  cardiac  veins,  the  right  or  small,  and  the  left  or  great, 
coronary  sinuses.  The  coronary  sinus  receives  most  of  the  veins  of  the  heart  and 
empties  into  the  right  auricle.  Some  few  small  veins  open  directly  into  the  right 
and  left  auricles  and  into  the  ventricles.  They  are  the  venae  minimse  cordis.  The 
oblique  vein  of  the  left  auricle  is  known  as  the  oblique  vein  of  Marshall. 

The  lymphatics  are  arranged  in  two  networks:  one  in  the  muscle  beneath  the 
endocardium,  another  in  the  muscle  beneath  the  epicardium.  The  deep  empties 
into  the  superficial  network,  the  anterior  collecting  trunks  from  the  subepicardial 
network  pass  to  the  tracheo-bronchial  glands.  The  posterior  collecting  trunk 
terminates  in  the  same  group  of  glands.1 

The  nerves  are  derived  from  the  superficial  and  deep  cardiac  plexuses,  and  from 
these  plexuses  obtain  fibres  of  the  vagus,  accessory,  and  sympathetic.  The  super- 
ficial cardiac  plexus  lies  under  the  arch  of  the  aorta.  The  deep  cardiac  plexus 
is  in  front  of  the  tracheal  bifurcation.  The  nerves  from  the  plexuses  are  freely 
distributed  both  on  the  surface  and  in  the  substance  of  the  heart,  the  separate 
filaments  being  furnished  with  small  ganglia. 

Surface  Form. — In  order  to  show  the  extent  of  the  heart  in  relation  to  the  front  of  the  chest, 
draw  a  line  from  the  lower  border  of  the  second  left  costal  cartilage,  one  inch  from  the  sternum, 
to  the  upper  border  of  the  third  right  costal  cartilage,  half  an  inch  from  the  sternum.  This 
represents  the  base-line  or  upper  limit  of  the  organ.  Take  a  point  an  inch  and  a  half  below 
and  three-quarters  of  an  inch  internal  to  the  left  nipple — that  is,  about  three  and  a  half  inches 
to  the  left  of  the  median  line  of  the  body.  This  represents  the  apex  of  the  heart.  Draw  a  line 
from  this  apex-point,  with  a  slight  convexity  downward,  to  the  junction  of  the  seventh  right 
costal  cartilage  to  the  sternum.  This  represents  the  lower  limit  of  the  heart.  Join  the  right 
extremity  of  the  first  line — that  is,  the  base-line — with  the  right  extremity  of  this  line — that  is, 
to  the  seventh  right  chondro-sternal  joint — with  a  slight  curve  outward,  so  that  it  projects  about 
an  inch  and  a  half  from  the  middle  line  of  the  sternum.  Lastly,  join  the  left  extremity  of  the 
base-line  and  the  apex-point  by  a  line  curved  slightly  to  the  left. 

The  position  of  the  various  orifices  is  as  follows — viz.,  the  pulmonary  orifice  is  situated  in 
the  upper  angle  formed  by  the  articulation  of  the  third  left  costal  cartilage  with  the  sternum; 
the  aortic  orifice  is  a  little  below  and  internal  to  this,  behind  the  left  border  of  the  sternum, 
close  to  the  articulation  of  the  third  left  costal  cartilage  to  this  bone.  The  left  auriculo-ventric- 
ular  opening  is  behind  the  sternum,  rather  to  the  left  of  the  median  line,  and  opposite  the  fourth 
costal  cartilages.  The  right  auriculo-ventricular  opening  is  a  little  lower,  opposite  the  fourth 
interspace  and  in  the  middle  line  of  the  body  (Fig.  366). 

A  portion  of  the  area  of  the  heart  thus  mapped  out  is  uncovered  by  lung,  and  therefore 
gives  a  dull  note  on  percussion;  the  remainder,  being  overlapped  by  the  lung,  gives  a  more  or 
less  resonant  note.  The  former  is  known  as  the  area  of  superficial  cardiac  dulness;  the  latter 
as  the  area  of  deep  cardiac  dulness.  The  area  of  superficial  cardiac  dulness  is  included  between 
a  line  drawn  from  the  centre  of  the  sternum,  on  a  level  with  the  fourth  costal  cartilages,  to  the 
apex  of  the  heart  and  a  line  drawn  from  the  same  point  down  the  lower  third  of  the  middle  line 
of  the  sternum.  Below,  this  area  merges  into  the  dulness  which  corresponds  to  the  liver.  Dr. 
McClellan  states  that  the  area  of  superficial  cardiac  dulness  may  be  mapped  out  "  by  draw- 
ing a  line  from  the  middle  of  the  sternum  opposite  the  fourth  left  costal  cartilage  to  the  point 
of  junction  of  the  fifth  rib  and  its  cartilage,  and  from  this  point  horizontally  back  to  the  mid- 
sternal  line." 

Surgical  Anatomy.— Wounds  of  the  heart  are  often  immediately  fatal,  but  not  necessarily 
so.  They  may  be  non-penetrating,  when  death  may  occur  from  hemorrhage,  if  one  of  the  coro- 
nary vessels  has  been  wounded,  or  subsequently  from  pericarditis;  or,  on  the  other  hand,  the 
patient  may  recover.  Even  a  penetrating  wound  is  not  necessarily  fatal,  if  the  wound  is  a  small 
one.  An  attempt  should  be  made  to  save  the  patient  by  means  of  a  surgical  operation.  A 

1  The  Lymphatics.     By  Poirier,  Cuneo,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE  HEART  581 

trap-door  flip  comprising  the  whole  thickness  of  the  thoracic  wall  should  be  made.  The  hinges 
of  the  trap-door  are  the  rib  cartilages.  The  pericardium  is  exposed  and  opened  freely,  clots  are 
removed,  the  wound  in  the  heart  is  sought  for,  and  when  discovered  is  sutured.  In  a  pene- 
trating wound  the  sutures  include  the  whole  thickness  of  the  heart,  except  the  endocardium. 
Interrupted  sutures  should  be  used,  and  each  one  had  better  be  tied  during  diastole.  A  number 
of  successful  operations  of  this  character  have  been  performed. 

Peculiarities  in  the  Vascular  System  of  the  Foetus  (Fig.  382). 

The  chief  peculiarities  in  the  heart  of  the  foetus  are  the  direct  communication 
between  the  two  auricles  through  the  foramen  ovale,  and  the  large  size  of  the 
Eustachian  valve.  There  are  also  several  minor  peculiarities.  Thus,  the  position 
of  the  heart  is  vertical  until  the  fourth  month,  when  it  commences  to  assume  an 
oblique  direction.  Its  size  is  also  very  considerable  as  compared  with  the  body, 
the  proportion  at  the  second  month  being  1  to  50;  at  birth  it  is  as  1  to  120;  whilst 
in  the  adult  the  average  is  about  1  to  160.  At  an  early  period  of  foetal  life  the 
auricular  portion  of  the  heart  is  larger  than  the  ventricular,  the  right  auricle  being 
more  capacious  than  the  left;  but  toward  birth  the  ventricular  portion  becomes 
the  larger.  The  thickness  of  both  ventricles  is  at  first  about  equal,  but  toward 
birth  the  left  becomes  much  the  thicker  of  the  two. 


CONUS 
ARTERIOSUS 


VALVE  OF 
FORAMEN   OVALE 


VALVE  OF      AURICULO-VENTRICULAR 
CORONARY  SINUS      OPENING 


FIG.  381. — The  right  auricle  of  a  foetal  heart  (eighth  month).     Enlarged.     (Spalteholz.) 

The  foramen  ovale  (Fig.  381)  is  situated  at  the  lower  and  back  part  of  the  auric- 
ular septum,  forming  a  communication  between  the  auricles.  It  remains  as  a  free 
oval  opening  until  the  middle  period  of  foetal  life.  About  this  period  a  fold  grows 
up  from  the  posterior  wall  of  the  auricle  to  the  left  of  the  foramen  ovale,  and 
advances  over  the  opening  so  as  to  form  a  sort  of  valve,  which  allows  the  blood 
to  pass  only  from  the  right  to  the  left  auricle,  and  not  in  the  opposite  direction. 

The  Eustachian  valve  (Fig.  381)  is  directed  upward  on  the  left  side  of  the  open- 
ing of  the  postcava  (inferior  vena  cava),  and  serves  to  direct  the  blood  from  this 
vessel  through  the  foramen  ovale  into  the  left  auricle. 

The  peculiarities  in  the  arterial  system  of  the  foetus  are  the  communication 
between  the  pulmonary  artery  and  the  descending  aorta  by  means  of  the  ductus 
arteriosus,  and  the  communication  between  the  internal  iliac  arteries  and  the 
placenta  by  means  of  the  umbilical  arteries. 


582 


THE  BLOOD-VASCULAR  SYSTEM 


The  Ductus  Arteriosus  (Fig.  382). — The  ductus  arteriosus  is  a  short  tube,  about 
half  an  inch  in  length  at  birth,  and  of  the  diameter  of  a  goose-quill.  In  the  early 
condition  it  foros  the  continuation  of  the  pulmonary  artery,  and  opens  into  the 


Ductus  arteriosus. 


'Internal  iliac  artery. 


FIG.  382. — Plan  of  the  foetal  circulation.     In  this  plan  the  figured  arrows  represent  the  kind  of  blood,  as  well 

as  the  direction  which  it  takes  in  the  vessels.     Thus,  arterial  blood  is  figured  »— -->  ;  venous  blood, 

» >;  mixed  (arterial  and  venous)  blood,  »  ••  —  • >. 

descending  aorta  just  below  the  origin  of  the  left  subclavian  artery,  and  so  con- 
ducts the  chief  part  of  the  blood  from  the  right  ventricle  into  this  vessel.  When 
the  branches  of  the  pulmonary  artery  have  become  larger  relatively  to  the  ductus 
arteriosus,  the  latter  is  chiefly  connected  to  the  left  pulmonary  artery;  and  the 
fibrous  cord  (ligamentum  arteriosum),  which  is  all  that  remains  of  the  ductus 
arteriosus  in  later  life,  will  be  found  to  be  attached  to  the  root  of  that  vessel. 


THE  HEART  583 

The  Umbilical  Arteries. — The  umbilical  or  hypogastric  arteries  arise  from  the 
internal  iliacs,  in  addition  to  the  branches  given  off  from  those  vessels  in  the 
adult.  Ascending  along  the  sides  of  the  bladder  to  its  apex,  they  pass  out  of 
the  abdomen  at  the  umbilicus  and  are  continued  along  the  umbilical  cord  to 
the  placenta,  coiling  round  the  umbilical  vein.  They  carry  to  the  placenta  the 
blood  which  has  circulated  in  the  system  of  the  foetus. 

The  peculiarity  in  the  venous  system  of  the  foetus  is  the  communication  estab- 
lished between  the  placenta  and  the  liver  and  portal  vein  through  the  umbilical 
vein,  and  the  postcava  through  the  ductus  venosus. 

Foetal  Circulation. -*-The  blood  destined  for  the  nutrition  of  the  foetus  is 
returned  from  the  placenta  to  the  foetus  by  the  umbilical  vein.  This  vein  enters 
the  abdomen  at  the  umbilicus,  and  passes  upward  along  the  free  margin  of  the 
suspensory  ligament  of  the  liver  to  the  under  surface  of  that  organ,  where  it  gives 
off  two  or  three  branches  to  the  left  lobe,  one  of  which  is  of  large  size,  and  others 
to  the  lobus  quadratus  and  lobulus  Spigelii.  At  the  transverse  fissure  it  divides 
into  two  branches:  of  these,  the  larger  is  joined  by  the  portal  vein  and  enters  the 
right  lobe;  the  smaller  branch  continues  outward,  under  the  name  of  the  ductus 
venosus,  and  joins  the  left  hepatic  vein  at  the  point  of  junction  of  that  vessel  with 
the  postcava.  The  blood,  therefore,  which  traverses  the  umbilical  vein  reaches 
the  postcava  in  three  different  ways:  the  greater  quantity  circulates  through  the 
liver  with  the  portal  venous  blood  before  entering  the  postcava  by  the  hepatic 
veins;  some  enters  the  liver  directly,  and  is  also  returned  to  th'e  postcava  by  the 
hepatic  veins;  the  smaller  quantity  passes  directly  into  the  postcava  by  the  junction 
of  the  ductus  venosus  with  the  left  hepatic  vein. 

In  the  postcava  (inferior  vena  cava)  the  blood  carried  by  the  ductus  venosus  and 
hepatic  veins  becomes  mixed  with  that  returning  from  the  lower  extremities  and  wall 
of  the  abdomen.  It  enters  the  right  auricle,  and,  guided  by  the  Eustachian  valve, 
passes  through  the  foramen  ovale  into  the  left  auricle,  where  it  becomes  mixed  with 
a  small  quantity  of  blood  returned  from  the  lungs  by  the  pulmonary  veins.  From 
the  left  auricle  it  passes  into  the  left  ventricle,  and  from  the  left  ventricle  into 
the  aorta,  by  means  of  which  it  is  distributed  almost  entirely  to  the  head  and 
upper  extremities,  a  small  quantity  being  probably  carried  into  the  descending 
aorta.  From  the  head  and  upper  extremities  the  blood  is  returned  by  the  tributa- 
ries of  the  precava  (superior  vena  cava)  to  the  right  auricle,  where  it  becomes  mixed 
with  a  small  portion  of  the  blood  from  the  postcava  (inferior  vena  cava).  From 
the  right  auricle  it  descends  over  the  Eustachian  valve  into  the  right  ventricle,  and 
from  the  right  ventricle  passes  into  the  pulmonary  artery.  The  lungs  of  the  foetus 
being  inactive,  only  a  small  quantity  of  the  blood  of  the  pulmonary  artery  is  dis- 
tributed to  them  by  the  right  and  left  pulmonary  arteries,  and  is  returned  by  the 
pulmonary  veins  to  the  left  auricle;  the  greater  part  passes  through  the  ductus 
arteriosus  into  the  commencement  of  the  descending  aorta,  where  it  becomes 
mixed  with  a  small  quantity  of  blood  transmitted  by  the  left  ventricle  into  the 
aorta.  Through  this  vessel  it  descends  to  supply  the  lower  extremities  and  viscera 
of  the  abdomen  and  pelvis,  the  chief  portion  being,  however,  conveyed  by  the 
umbilical  arteries  to  the  placenta. 

From  the  preceding  account  of  the  circulation  of  the  blood  in  the  foetus  it  will 
be  seen — 

1.  That  the  placenta  serves  the  purposes  of  nutrition  and  excretion,  receiving 
the  impure  blood  from  the  foetus,  and  returning  it  charged  with  additional  nutri- 
tive material. 

2.  That  nearly  the  whole  of  the  blood  of  the  umbilical  vein  traverses  the  liver 
before  entering  the  postcava;  hence  the  large  size  of  this  organ,  especially  at  an 
«arly  period  of  foetal  life. 

3.  That  the  right  auricle  is  the  point  of  meeting  of  a  double  current,  the  blood 


584  THE  BLOOD-  VASCULAR  SYSTEM 

in  the  postcava  being  guided  by  the  Eustachian  valve  into  the  left  auricle,  whilst 
that  in  the  precava  descends  into  the  right  ventricle.  At  an  early  period  of  the 
foetal  life  it  is  highly  probable  that  the  two  streams  are  quite  distinct,  for  the 
postcava  opens  almost  directly  into  the  left  auricle,  and  the  Eustachian  valve 
would  exclude  the  current  along  the  vein  from  entering  the  right  ventricle.  At  a 
later  period,  as  the  separation  between  the  two  auricles  becomes  more  distinct, 
it  seems  probable  that  some  mixture  of  the  two  streams  must  take  place. 

4.  The  pure  blood  carried  from  the  placenta  to  the  fretus  by  the  umbilical  vein, 
mixed  with  the  blood  from  the  portal  vein  and  the  postcava,  passes  almost  directly 
to  the  arch  of  the  aorta,  and  is  distributed  by  the  branches  of  that  vessel  to  the 
head  and  upper  extremities;  hence  the  large  size  and  perfect  development  of 
those  parts  at  birth. 

5.  The  blood  contained  in  the  descending  aorta,  chiefly  derived  from  that 
which  has  already  circulated  through  the  head  and  upper  limbs,  together  with  a 
small  quantity  from  the  left  ventricle,  is  distributed  to  the  lower  extremities; 
hence  the  small  size  and  imperfect  development  of  these  parts  at  birth. 

Changes  in  the  Vascular  System  at  Birth. 

At  birth,  when  respiration  is  established,  an  increased  amount  of  blood  from 
the  pulmonary  artery  passes  through  the  lungs,  which  now  perform  their  office 
as  respiratory  organs,  and  at  the  same  time  the  placental  circulation  is  cut  off. 
Almost  immediately  after  birth  the  foramen  ovale  is  closed  by  the  valvular  edge 
being  pressed  against  the  annulus  ovalis,  the  pressure  being  due  to  respiration, 
which  increases  the  pressure  in  the  left  auricle.  The  structures  fuse,  and  closure 
is  complete  by  about  the  tenth  day  after  birth.  The  valvular  fold  above  men- 
tioned becomes  adherent  to  the  margins  of  the  foramen  for  the  greater  part  of  its 
circumference,  but  above  a  slit-like  opening  is  left  between  the  two  auricles  which 
sometimes  remains  persistent. 

The  ductus  arteriosus  begins  to  contract  immediately  after  respiration  is  estab- 
lished, becomes  completely  closed  from  the  fourth  to  the  tenth  day,  and  ultimately 
degenerates  into  an  impervious  cord  which  serves  to  connect  the  left  pulmonary 
artery  to  the  descending  aorta.  When  respiration  begins,  the  caval  opening  of 
the  diaphragm  being  fixed  and  the  balance  of  the  muscle  rising  and  falling,  the 
ductus  arteriosus  is  compressed  by  the  muscular  structures  which  pass  from  the 
diaphragm  to  the  pericardium,  is  narrowed,  and  is  finally  obliterated  (Forbes). 

Of  the  umbilical  or  hypogastric  arteries,  the  portion  continued  on  to  the  bladder 
from  the  trunk  of  the  corresponding  internal  iliac  remains  pervious  as  the  superior 
vesical  artery,  and  the  part  extending  from  the  side  of  the  bladder  to  the  umbilicus 
becomes  obliterated  between  the  second  and  fifth  days  after  birth,  and  projects 
as  a  fibrous  cord  toward  the  abdominal  cavity,  carrying  on  it  a  fold  of  peritoneum 
and  separating  two  of  the  fossae  of  the  peritoneum  spoken  of  in  the  section  on  the 
surgical  anatomy  of  direct  inguinal  hernia. 

The  umbilical  vein  and  the  ductus  venosus  become  completely  obliterated 
between  the  second  and  fifth  days  after  birth,  and  ultimately  dwindle  to  fibrous 
cords,  the  former  becoming  the  round  ligament  of  the  liver,  the  latter  the  fibrous 
cord,  which  in  the  adult  may  be  traced  along  the  fissure  of  the  ductus  venosus. 


THE  ARTERIES. 


THE  Arteries  are  cylindrical  tubular  vessels  which  serve  to  convey  blood  from 
both  ventricles  of  the  heart  to  every  part  of  the  body.  These  vessels  were  named 
arteries  (dyp,  air;  rypetv,  to  contain)  from  the  belief  entertained  by  the  ancients 
that  they  contained  air.  To  Galen  is  due  the  honor  of  refuting  this  opinion;  he 
showed  that  these  vessels,  though  for  the  most  part  empty  after  death,  contain 
blood  in  the  living  body. 

The  distribution  of  the  systemic  arteries  is  like  a  highly  ramified  tree,  the 
common  trunk  of  which,  formed  by  the  aorta,  commences  at  the  left  ventricle  of 
the  heart,  the  smallest  ramifications  corresponding  to  the  circumference  of  the 
body  and  the  contained  organs.  The  arteries  are  found  in  nearly  every  part  of 
the  body,  with  the  exception  of  the  hairs,  nails,  epidermis,  cartilages,  and  cornea; 
and  the  larger  trunks  usually  occupy  the  most  protected  situations,  running,  in 
a  limb,  along  the  flexor  side,  where  they  are  less  exposed  to  injury. 

There  is  considerable  variation  in  the  mode  of  division  of  the  arteries:  occa- 
sionally a  short  trunk  subdivides  into  several  branches  at  the  same  point,  as 
we  observe  in  the  coeliac  and  thyroid 

axes;  or  the  vessel  may  give  off  several  A  B 

branches  in  succession,  and  still  con- 
tinue as  the  main  trunk,  as  is  seen  in 
the  arteries  of  thefimbs;  but  the  usual 
division  is  dichotomous ;  as,  for  instance, 
the  aorta  dividing  into  the  two  common 
iliacs,  and  the  common  carotid  into  the 
external  and  internal  carotids. 

The  branches  of  arteries  arise  at  very 
variable  angles:  some,  as  the  superior 
intercostal  arteries  from  the  aorta,  arise 
at  an  obtuse  angle:  others,  as  the  lumbar 
arteries,  at  a  right  angle;  or,  as  the 
spermatic,  at  an  acute  angle.  An  artery 
from  below  the  point  at  which  a  branch 
is  given  off  is  smaller  in  size  than  be- 
fore. It  retains  a  uniform  diameter 
until  a  second  branch  is  derived  from 
it.  A  branch  of  an  artery  is  smaller 
than  the  trunk  from  which  it  arises ;  but 
if  an  artery  divides  into  two  branches, 
the  combined  area  of  the  two  vessels  is,  in  nearly  every  instance,  somewhat 
greater  than  that  of  the  trunk;  and  the  combined  area  of  all  the  arterial  branches 
greatly  exceeds  the  area  of  the  aorta;  so  that  the  arteries  collectively  may  be 
regarded  as  a  cone,  the  apex  of  which  corresponds  to  the  aorta,  the  base  to  the 
capillary  system. 

The  arteries,  in  their  -distribution,  communicate  with  one  another,  forming 
what  is  called  an  anastomosis  (dvd,  between;  ffropa,  mouth)  or  inosculation  (Fig. 
383) ;  and  this  communication  is  very  free  between  the  larger  as  well  as  between  the 

.  (585) 


FIG.  383. — Diagram  showing  the  anastomosis  of 
arteries.     (Poirier  and  Charpy.) 


586 


THE  BLOOD -VASCULAR    SYSTEM 


e, j 


smaller  branches.  An  anastomosis  between  trunks  of  equal  size  is  found  where 
great  activity  of  the  circulation  is  requisite,  as  at  the  base  of  the  brain ;  here  the 
two  vertebral  arteries  unite  to  form  the  basilar,  and  the  two  internal  carotid 
arteries  are  connected  by  a  short  communicating  trunk;  it  is  also  found  in  the 
abdomen,  the  intestinal  arteries  having  very  ample  anastomoses  between  their 
larger  branches.  In  the  limbs  the  anastomoses  are  most  numerous  and  of 
largest  size  around  the  joints,  the  branches  of  an  artery  above  inosculating 
with  branches  from  the  vessels  below;  these  anastomoses  are  of  considerable 
interest  to  the  surgeon,  as  it  is  by  their  enlargement  that  a  collateral  circula- 
tion is  established  after  the  application  of  a  ligature  to  an  artery  for  the  cure 
of  aneurism.  The  smaller  branches  of  arteries  anastomose  more  frequently 
than  the  larger,  and  between  the  smallest  twigs  these  inosculations  become  so 

numerous  as  to  constitute  a  close  network 
that  pervades  nearly  every  tissue  of  the  body. 
A  terminal  artery  is  one  which  forms  no 
anastomoses.  Such  vessels  are  found  in  the 
brain,  spleen,  kidneys,  lungs,  and  mesen- 
tery. 

Throughout  the  body  generally  the  larger 
arterial  branches  pursue  a  perfectly  straight 
course,  but  in  certain  situations  they  are  tor- 
tuous ;  thus  the  facial  arteries  in  their  course 
over  the  face,  and  the  arteries  of  the  lips, 
are  extremely  tortuous  in  their  course,  to 
accommodate  themselves  to  the  movements 
of  the  parts.  The  uterine  arteries  are  also 
tortuous,  to  accommodate  themselves  to  the 
increase  of  size  which  the  organ  undergoes 
during  pregnancy.  Afain,  the  internal 
carotid  and  vertebral  arteries,  previous  to 
their  entering  the  cavity  of  the  skull,  de- 
scribe a  series  of  curves,  which  are  evidently 
intended  to  diminish  the  velocity  of  the  cur- 
rent of  blood  by  increasing  the  extent  of 
surface  over  which  it  moves  and  adding  to 
the  resistance  which  is  produced  by  friction. 
The  arteries  are  dense  in  structure,  of 
considerable  strength,  highly  elastic,  and, 
when  divided,  they  preserve,  although  empty, 
their  cylindrical  form. 

Histology  of  the  Capillaries  and  Ar- 
teries. The  Capillaries  (Fig.  386). — The 
capillaries  are  very  small  endothelial  tubes 
which  connect  the  venous  system  with  the 
arterial  system.  In  diameter  they  vary  from  -g-^Vtr  t°  TOlFU"  °f  an  mcn>  in  length 
from  ^V  to  -gijj-  of  an  inch.  The  nucleated  endothelial  cells  which  constitute  the 
wall  of  a  capillary  are  flat,  irregular  in  outline,  and  are  united  by  a  cement 
material.  Small  openings  (stomata)  are  frequently  noted  between  these  cells, 
but  they  are  probably  artifacts  and  do  not  exist  during  life. 

The  capillaries  anastomose  and  form  vast  networks.  When  an  artery  is  about 
to  become  a  capillary  the  muscular  coat  disappears.  The  endothelial  coat  which 
constitutes  the  capillaries  extends  as  a  system  of  endothelial  tubes  throughout  the 
entire  blood-vascular  system.  The  heart  is  a  great  muscular  thickening  around 
a  portion  of  the  system  of  endothelial  tubes.  An  artery  consists  of  an  endothelial 


FIG.  384. — Transverse  section  through  a  small 
artery  and  vein  of  the  mucous  membrane  of  the 
epiglottis  of  a  child.  Magnified  about  350  diame- 
ters. A,  artery,  showing  the  nucleated  endothe- 
lium  e,  which  lines  it:  the  vessel  being  con- 
tracted, the  endothelial  cells  appear  very  thick. 
Underneath  the  endothelium  is  the  wavy  elastic 
intima.  The  chief  part  of  the  wall  of  the  vessel 
is  occupied  by  the  circular  muscle-coat  m;  the 
staff-shaped  nuclei  of  the  muscle-cells  are  well 
seen.  Outside  this  is  a,  part  of  the  adventitia. 
This  is  composed  of  bundles  of  connective-tissue 
fibres,  shown  in  section,  with  the  nuclei  of  the 
connective-tissue  corpuscles.  The  adventitia 
gradually  merges  into  the  surrounding  connective- 
tissue,  y,  vein  showing  a  thin  endothelial  mem- 
brane e,  raised  accidentally  from  the  intima, 
which  on  account  of  its  delicacy  is  seen  as  a  mere 
line  on  the  media  m.  This  latter  is  composed  of 
a  few  circular  unstriped  muscle-cells  ;  a,  the  ad- 
ventitia, similar  in  structure  to  that  of  an  artery. 
(Klein  and  Noble  Smith.) 


THE    ARTERIES 


587 


tube  covered  by  certain  accessory  coats.  The  wall  of  an  artery  diminishes 
greatly  in  thickness  (Fig.  387)  and  is  found  to  be  composed  of  endothelial  cells 
and  scattered  unstriated  muscle-fibres,  covered  merely  by  thin  connective  tissue 
or  elastic-tissue  sheath  (adventitia  capillaris).  Such  a  structure  is  known  as  an 
arteriole  or  a  precapillary  artery.  By  the  loss  of  its  thin  sheath  of  connective  or 
elastic  tissue  it  becomes  a  capillary.  A  capillary  takes  on  a  thin  sheath  and 
becomes  a  venule  or  precapillary  vein.  Nerves  do  not  terminate  in  capillaries, 
but  networks  of  nerve-filaments  often  encompass  these  small  vessels. 

An  artery  consists  of  an  internal  coat  or  tunica  intima,  a  middle  coat  or  tunica 
media,  and  an  external  coat  or  tunica  adventitia  (Figs.  384  and  385). 

The  Inner  Coat  (tunica  intima)  consists  of  endothelial  cells  and  yellow  elastic 
tissue.  In  some  cases  the  elastic  fibres  are  arranged  longitudinally,  but,  as  a  rule, 
they  form  a  distinct  fenestrated  membrane  known  as  the  fenestrated  membrane  of 

Endothelial   and   snb- 
endothelial  layer  of 
~     inner  coat. 
'Elastic  layer. 

Innermost  layers  of 
middle  coat. 


^ Outermost  Layers  of 

middle  coat. 


__  Innermost  part 
outer  coat. 


Outer  part  of  outer 
•  r       coat. 


FIG.  385. — Section  of  a  medium-sized  artery.     (After  Grtinstein.) 

Henle,  or  the  internal  elastic  coat.  In  medium-sized  vessels  the  elastic  layer  of  the 
intima  is  separated  from  the  endothelial  layer  by  a  layer  of  connective  tissue. 
In  the  large  arteries  the  interposed  layer  of  connective  tissue  is  thicker  and  con- 
tains elastic  fibres. 

The  Middle  Coat  (tunica  media)  consists  of  muscle,  elastic  tissue,  and  white 
fibrous  tissue,  and  it  is  often  called  the  elastomuscular  coat.  The  arterioles  con- 
tain scattered  unstriated  muscle  fibres.  In  the  small  arteries  they  constitute  a 
thin  but  definite  coat.  In  larger  arteries  the  muscular  coat  is  much  thicker.  The 
muscle  is  unstriated  and  the  fibres  are  arranged  circularly,  and  in  the  larger 
vessels  form  layers  which  are  separated  by  elastic  fibres.  Here  and  there  longi- 
tudinally-disposed muscle-fibres  exist.  The  larger  the  artery  the  greater  is  the 
amount  of  elastic  tissue  existing  in  the  middle  coat.  In  the  aorta  and  in  some 
of  the  very  large  arteries  the  amount  of  elastic  tissue  exceeds  the  amount  of 


588 


THE   BLOOD -VASCULAR    SYSTEM 


muscular  tissue.  "  In  the  first  part  of  the  aorta,  in  the  pulmonary  artery  and  in 
the  arteries  of  the  retina,  the  muscular  fibres  are  entirely  replaced  by  elastic 
tissue."1  The  arteries  within  the  skull  have  no  elastic  tissue  in  the  media, 
although  they  have  some  in  the  adventitia. 

The  External  Coat  (tunica  adventitia}  is  called  the  fibrous  coat.  It  contains 
fibrous  connective  tissue,  elastic  tissues,  and  in  some  arteries  fibres  of  unstriated 
muscle  arranged  longitudinally.  The  circular  elastic  membrane  which  sepa- 
rates the  outer  coat  from  the  middle  coat  is  known  as  the  external  elastic  mem- 
brane. 

Blood-vessels  of  the  Blood-vessel  Wall.— Many  small  blood-vessels  course  in  the 
external  and  middle  coats  of  arteries  of  large  and  of  moderate  size.  They  are 
mostly  in  the  adventitia.  They  may  arise  from  the  vessel  to  which  they  are  dis- 


FIG.  386. — Capillaries  from  the 
mesentery  of  a  guinea-pig  after  treat- 
ment with  solution  of  nitrate  of  silver, 
a,  cells;  b,  their  nuclei. 


FIG.  387. — Finest  vessels  on  the  arterial  side.  From  the  human 
brain.  Magnified  300  times.  1,  small  artery;  2,  transition  vessel; 
3,  coarser  capillaries;  4,  finer  capillaries;  a,  structureless  mem- 
brane still  with  some  nuclei,  representative  of  the  tunica  adven- 
titia; b,  nuclei  of  the  muscular  fibre-cells;  c,  nuclei  within  the 
small  artery,  perhaps  appertaining  to  an  endothelium;  d,  nuclei 
in  the  transition  vessels. 


tributed  or  take  origin  from  an  adjacent  vessel.  These  small  arteries  are  called 
the  vasa  vasorum.  The  blood  is  returned  from  the  walls  of  the  vessels  by  small 
veins. 

Lymphatics. — Distinct  lymphatic  vessels  may  exist  in  the  adventitia,  but  are 
not  found  in  either  of  the  other  coats.  Lymph-capillaries  often  surround  small 
blood-vessels  or  a  small  blood-vessel  may  lie  in  a  perivascular  lymph-space. 

Nerves. — Arteries  are  supplied  with  nerves,  myelinic  and  amyelinic.  A 
network  of  nerve-fibres  may  surround  a  vessel  and  usually  capillaries  are  so  sur- 
rounded. In  the  arteries  a  network  of  nerves  exists  in  the  media.  These  nerves 
supply  the  muscle-fibres  and  are  called  vasomotor  nerves. 

The  Arterial  Sheath  (vagina  vasis)  surrounds  the  artery.  It  is  composed  of  con- 
nective tissue,  and  is  attached  to  the  vessel  at  numerous  points  by  fibrous  tissue. 


1  D.  J.  Cunningham.     Text-book  of  Anatomy. 


THE  AORTA  589 

PULMONARY  ARTERY  (A.  PULMONALIS)  (Fig.  389,  393). 

In  the  description  of  the  arteries  we  shall  first  consider  the  efferent  trunk  of 
the  pulmonic  circulation,  the  pulmonary  artery,  and  then  the  efferent  trunk  of  the 
systemic  circulation,  the  aorta  and  its  branches. 

The  pulmonary  artery  conveys  the  venous  blo6d  from  the  right  side  of  the  heart 
to  the  lungs.  It  is  a  short,  wide  vessel,  about  2  inches  in  length  and  1^-  inches 
(30  mm.)  in  diameter,  arising  from  the  left  side  of  the  base  (conus  arteriosus} 
of  the  right  ventricle,  in  front  of  the  aorta.  It  extends  obliquely  upward  and 
backward,  passing  at  first  in  front  of  and  then  to  the  left  of  the  ascending 
aorta,  as  far  as  the  under  surface  of  the  arch,  where  it  divides,  about  on  a  level 
with  the  intervertebral  substance  between  the  fifth  and  sixth  thoracic  vertebrae, 
into  two  branches  of  nearly  equal  size,  the  right  and  left  pulmonary  arteries. 

The  Right  Pulmonary  Artery  (ramus  dexter  a.  pulmonalis},  longer  and 
larger  than  the  left,  runs  horizontally  outward  to  the  root  of  the  right  lung,  where 
it  divides  into  two  branches,  of  which  the  lower  and  larger  supplies  the  middle 
and  lower  lobes;  the  upper  and  smaller  is  distributed  to  the  upper  lobe.  It  has  in 
front  of  it  the  ascending  aorta,  the  precava,  and  the  right  phrenic  nerve.  It  has 
behind  it  the  right  bronchus.  Above  it  is  the  transverse  portion  of  the  arch  of  the 
aorta.  Below  it  is  the  right  auricle. 

The  Left  Pulmonary  Artery  (ramus  sinister  a.  pulmonalis) ,  shorter  and 
somewhat  smaller  than  the  right,  passes  horizontally  to  the  root  of  the  left  lung, 
where  it  divides  into  two  branches  for  the  two  lobes.  In  front  of  it  and  below  it 
are  the  pulmonary  veins  of  the  left  side.  Behind  are  the  descending  aorta  and  the 
left  bronchus.  Above  it  are  the  arch  of  the  aorta,  the  left  recurrent  laryngeal 
nerve,  and  the  ductus  arteriosus.  The  left  bronchus  in  a  portion  of  its  course  lies 
below  as  well  as  behind. 

Relations. — The  whole  of  the  vessel  is  contained,  together  with  the  ascending 
aorta,  in  the  pericardium.  It  is  enclosed  with  the  aorta  in  a  single  tube  of  the 
serous  pericardium,  which  is  continued  upward  upon  them  from  the  base  of  the 
heart  and  connects  them  together.  The  fibrous  layer  of  the  pericardium  becomes 
gradually  lost  upon  the  external  coats  of  its  two  branches.  In  front,  the  pulmonary 
artery  is  separated  from  the  anterior  extremity  of  the  second  left  intercostal  space 
by  the  pleura  and  left  lung,  in  addition  to  the  pericardium;  it  rests  at  first  upon 
the  ascending  aorta,  and  higher  up  lies  in  front  of  the  left  auricle  on  a  plane 
posterior  to  the  ascending  aorta.  On  each  side  of  its  origin  is  the  appendix  of 
the  corresponding  auricle  and  a  coronary  artery,  the  left  coronary  artery  passing, 
in  the  first  part  of  its  course,  behind  the  vessel. 

The  root  of  the  left  pulmonary  artery  is  connected  to  the  under  surface  of  the 
arch  of  the  aorta  by  a  short  fibrous  cord,  the  ligamentum  arteriosum;  this  is  the 
remains  of  a  vessel  peculiar  to  foetal  life,  the  ductus  arteriosus. 

The  terminal  branches  of  the  pulmonary  artery  will  be  described  with  the 
anatomy  of  the  lung. 

THE  AORTA  (Figs.  388,  389,  390,  393). 

The  aorta  or  arteria  magna  (dopnj)  is  the  main  trunk  of  a  series  of  vessels  which 
convey  the  oxygenated  blood  to  the  tissues  of  the  body  for  their  nutrition.  This 
vessel  commences  at  the  upper  part  of  the  left  ventricle,  where  it  is  about  one  and 
one-eighth  inches  in  diameter,  and,  after  ascending  for  a  short  distance,  arches 
backward  and  to  the  left  side,  over  the  root  of  the  left  lung,  then  descends  within 
the  thorax  on  the  left  side  of  the  vertebral  column,  passes  through  the  aortic  open- 
ing in  the  Diaphragm,  and,  entering  the  abdominal  cavity,  terminates,  consider- 


590 


THE   BLOOD -VASCULAR    SYSTEM 


ably  diminished  in  size  (about  seven-tenths  of  an  inch  in  diameter),  opposite  the 
lower  border  of  the  fourth  lumbar  vertebra,  where  it  divides  into  the  right  and  left 
common  iliac  arteries.  Hence  it  is  divided  into  the  ascending  aorta,  the  arch  of 
the  aorta,  and  the  descending  aorta,  which  last  is  again  divided  into  the  thoracic  aorta 
and  the  abdominal  aorta,  from  the  position  of  these  parts. 


THE  ASCENDING  AORTA  (AORTA  ASCENDENS). 

The  ascending  aorta  is  about  two  inches  in  length.  It  commences  at  the 
upper  part  of  the  left  ventricle.,  on  a  level  with  the  lower  border  of  the  third 
costal  cartilage,  behind  the  left  half  of  the  sternum  ;  it  passes  obliquely  upward, 
forward,  and  to  the  right,  in  the  direction  of  the  heart's  axis,  as  high  as  the 


VENA  AZYGOS 
MINOR 


SYMPATHETIC 
GANGLION 


SYMPATHETIC 
NERVE 


FIG.  388. — Arch  of  the  aorta  and  its  relations.     (Poirier  and  Charpy.) 

upper  border  of  the  second  right  costal  cartilage,  describing  a  slight  curve  in 
its  course,  and  being  situated,  when  distended,  about  a  quarter  of  an  inch  behind 
the  posterior  surface  of  the  sternum.  A  little  above  its  commencement  it  is  some- 
what enlarged  (bulbus  aortae),  and  presents  three  small  dilatations,  one  of  which  is 
anterior,  two  of  which  are  posterior,  which  are  called  the  sinuses  of  Valsalva  (sinus 
aortae).  Opposite  to  the  sinuses  are  attached  the  three  semilunar  valves  (Fig.  376), 


THE  ASCENDING    AORTA 


591 


which  serve  the  purpose  of  preventing  any  regurgitation  of  blood  into  the  cavity 
of  the  ventricle.  These  valves  are  placed  one  in  front  and  two  behind.  At  the 
union  of  the  ascending  with  the  transverse  part  of  the  aorta  the  calibre  of  the  vessel 
is  increased,  owing  to  a  bulging  outward  of  its  right  wall.  This  dilatation  is  termed 
the  great  sinus  of  the  aorta.  A  section  of  the  aorta  opposite  this  part  has  a  some- 
what oval  figure;  but  below  the  attachment  of  the  valves  it  is  circular.  This  por- 
tion of  the  aorta  is  contained  in  the  cavity  of  the  pericardium,  and,  together  with 
the  pulmonary  artery,  is  invested  in  a  tube  of  serous  membrane,  continued  on  to 
them  from  the  surface  of  the  heart. 


Right  vagus. 
Recurrent  laryngeal 


Left  vagus. 
Left  phrenic. 
Thoracic  duct. 


FIG.  390.— Plan  of 
branches. 


the 


Fia.  389. — The  arch  of  the  aorta  and  its  branches. 

Relations. — The  ascending  aorta  is  covered  at  its  commencement  by  the  trunk 
of  the  pulmonary  artery  and  the  right  auricular  appendix,  and,  higher  up,  is 
separated  from  the  sternum  by  the  pericardium,  the  right  pleura,  and  anterior 
margin  of  the  right  lung,  some  loose  areolar  tissue,  and  the  remains  of  the  thymus 
gland;  behind,  it  rests  upon  the  right  pulmonary  artery,  left  auricle,  and  the  right 
bronchus.  On  the  right  side  it  is  in  relation  with  the  precava  and  right  auricle; 
on  the  left  side,  with  the  pulmonary  artery. 


592 


THE   BLOOD -VASCULAR    SYSTEM 


PLAN  OF  THE  RELATIONS  OF  THE  ASCENDING  AORTA. 

In  front. 

Pulmonary  artery. 
Right  auricular  appendix. 
Pericardium. 
Right  pleura  and  lung. 
Remains  of  the  thymus  gland. 


Right  side. 
Precava. 
Right  auricle. 


Left  side. 
Pulmonary  artery. 


Behind. 

Right  pulmonary  artery. 
Left  auricle. 
Right  bronchus. 


VAGUS  NERVE 


RIGHT  AURICLE 


FIG.  391. — Horizontal  section  through  the  sixth  thoracic  vertebra — upper  surface  of  the  lower  segment — 
showing  the  ascending  portion  of  the  aortic  arch  and  the  thoracic  aorta. 

Branches — The  only  branches  of  the  ascending  aorta  are  the  coronary  arteries. 
They  supply  the  heart,  and  are  two  in  number,  right  and  left,  arising  near  the  com- 
mencement of  the  aorta,  immediately  above  the  free  margin  of  the  semilunar 
valves. 

The  Coronary  Arteries  (Fig.  389). 

The  Right  Coronary  Artery  (a.  coronaria  [cordis]  dextra),  about  the  size  of  a 
crow's  quill,  arises  from  the  anterior  sinus  of  Valsalva.  It  passes  forward  between 
the  pulmonary  artery  and  the  right  auricular  appendix,  then  runs  obliquely  to  the 
right  side,  in  the  groove  between  the  right  auricle  and  ventricle,  and,  curving 
around  the  right  border  of  the  heart,  runs  to  the  left  along  its  posterior  surface  as 
far  as  the  posterior  interventricular  groove,  where  it  divides  into  two  branches,  one 
of  which,  the  transverse,  continues  onward  in  the  groove  between  the  left  auricle 
and  ventricle,  and  anastomoses  with  the  left  coronary;  the  other,  the  descending 
(ramus  descendens  posterior  a.  coronariae  [cordis]  dextrae) ,  courses  along  the  posterior 
interventricular  furrow,  supplying  branches  to  both  ventricles  and  to  the  septum, 
and  anastomosing  at  the  apex  of  the  heart  with  the  descending  branches  of  the  left 
coronary.  This  vessel  sends  a  large  branch,  the  marginal,  along  the  thin  margin 
of  the  right  ventricle  to  the  apex,  which  in  its  course  gives  off  numerous  small 
branches  to  the  anterior  and  posterior  surfaces  of  the  ventricle.  It  also  gives  off 


THE  ARCH  OF  THE  AORTA 


593 


a  branch,  the  infundibular,  which  ramifies  over  the  front  part  of  the  conus  arte- 
riosus  of  the  right  ventricle. 

The  Left  Coronary  Artery  (a.  coronaria  [cordis]  sinistra),  larger  than  the 
former,  arises  from  the  left  posterior  sinus  of  Valsalva;  it  passes  forward  between 
the  pulmonary  artery  and  the  left  auricular  appendix,  and  divides  into  two 
branches.  Of  these,  one,  the  transverse,  passes  transversely  outward  in  the  left 
auriculo-ventricular  groove,  and  winds  around  the  left  border  of  the  heart  to  its 
posterior  surface,  where  it  anastomoses  with  the  transverse  branch  of  the  right 
coronary ;  the  other,  the  descending  (ramus  descendens  anterior  a.  coronariae  [cordis] 
sinistrae),  passes  along  the  anterior  interventricular  groove  to  the  apex  of  the  heart, 
where  it  anastomoses  with  the  descending  branches  of  the  right  coronary.  The  left 
coronary  supplies  the  left  auricle  and  its  appendix,  gives  branches  to  both  ventri- 
cles, and  numerous  small  branches  to  the  pulmonary  artery  and  commencement 
of  the  aorta.1 

Peculiarities. — These  vessels  occasionally  arise  by  a  common  trunk,  or  their  number  may 
be  increased  to  three,  the  additional  branch  being  of  small  size.  More  rarely  there  are  two 
additional  branches. 


THE  ARCH  OF  THE  AORTA  (ARCUS  AORTAE). 

The  arch,  or  transverse  aorta,  commences  at  the  upper  border  of  the  second 
chondro-sternal  articulation  of  the  right  side,  and  passes  at  first  upward  and  back- 
ward and  from  right  to  left,  and  then  from  before  backward,  to  the  left  side  of  the 
lower  border  of  the  fourth  thoracic  vertebra  behind.  Its  upper  border  is  usually 
about  an  inch  below  the  upper  margin  of  the  sternum. 


VENA  AZYGOS  MAJOR 
THORACIC  DUCT 

TRACHEA 
JUST  ABOVE  DIVISI 

PRECAVA 
RIGHT  PLEURA 

ASCENDING 
PORTION  OF  Al 


VAGUS  NERVE 


DESCENDING 
PORTION  OF  ARCH. 


LEFT  PLEURA 
PHRENIC  NERVE 


FIG.  392.— Horizontal  section  through  the  fourth  thoracic  vertebra — upper  surface  of  the  lower  segment. 
The  cut  is  made  at  the  lower  part  of  the  transverse  portion  of  the  aortic  arch. 

Between  the  origin  of  the  left  subclavian  artery  and  the  attachment  of  the 
ductus  arteriosus  the  lumen  of  the  foetal  aorta  is  considerably  narrowed,  forming 
what  is  termed  the  aortic  isthmus  (isthmus  aortae) ,  while  immediately  beyond  the 
ductus  arteriosus  the  vessel  presents  a  fusiform  dilatation  which  His  has  named 
the  aortic  spindle  (aortenspindel) — the  point  of  junction  of  the  two  parts  being 
marked  in  the  concavity  of  the  arch  by  an  indentation  or  angle.  These  con- 
ditions persist,  to  some  extent,  in  the  adult,  where  His  found  that  the  average 
diameter  of  the  spindle  exceeded  that  of  the  isthmus  by  3  mm.  (about  one-eighth 
of  an  inch). 

1  According  to  Dr.  Samuel  West,  there  is  a  very  free  and  complete  anastomosis  between  the  two  coronary 
arteries  (Lancet,  June  2,  1883,  p.  945).  This,  however,  is  not  the  view  generally  held  by  anatomists,  for,  with 
the  exception  of  the  anastomosis  mentioned  above  in  the  auriculo-ventricular  and  interventricular  grooves,  it 
is  believed  that  the  two  arteries  only  communicate  by  very  small  vessels  in  the  substance  of  the  heart. — ED.  of 
15th  English  edition. 

38 


594 


THE  BLOOD-VASCULAR  SYSTEM 


Relations. — Its  anterior  surface  is  covered  by  the  pleurae  and  lungs  (much 
more  by  the  left  lung  than  by  the  right)  and  the  remains  of  the  thy m us  gland, 
and  crossed  toward  the  left  side  by  the  left  vagus  and  phrenic  nerves  and 
superficial  cardiac  branches  of  the  left  sympathetic  and  vagus,  and  by  the  left 
superior  intercostal  vein.  Its  posterior  surface  lies  on  the  trachea,  just  above  its 
bifurcation,  on  the  great,  or  deep,  cardiac  plexus,  the  oesophagus,  thoracic  duct, 
and  left  recurrent  laryngeal  nerve.  Its  upper  border  is  in  relation  with  the  left 
innominate  vein,  and  from  its  upper  part  are  given  off  the  innominate,  left  com- 
mon carotid  and  left  subclavian  arteries.  Its  lower  border  is  in  relation  with  the 
bifurcation  of  the  pulmonary  artery,  the  remains  of  the  ductus  arteriosus,  which 
is  connected  with  the  left  division  of  that  vessel,  and  the  superficial  cardiac  plexus; 
the  left  recurrent  laryngeal  nerve  winds  round  it  from  before  backward,  whilst 
the  left  bronchus  passes  below  it. 

PLAN  OF  THE  RELATIONS  OF  THE  ARCH  OF  THE  AORTA. 

Above. 

Left  innominate  vein. 
Innominate  artery. 
Left  carotid. 
Left  subclavian. 


In  Front. 
Pleurae  and  lungs. 
Remains  of  thymus  gland. 
Left  vagus  nerve. 
Left  phrenic  nerve. 
Superficial  cardiac  nerves. 
Left  superior  intercostal  vein. 


Behind. 
Trachea. 

Deep  cardiac  plexus. 
(Esophagus. 
Thoracic  duct. 
Left  recurrent  nerve. 


Below. 


Bifurcation  of  pulmonary  artery. 
Remains  of  ductus  arteriosus. 
Superficial  cardiac  plexus. 
Left  recurrent  nerve. 
Left  bronchus. 

Peculiarities. — The  height  to  which  the  aorta  rises  in  the  chest  is  usually  about  an  inch  below 
the  upper  border  of  the  sternum ;  but  it  may  ascend  nearly  to  the  top  of  that  bone.  Occasionally 
it  is  found  an  inch  and  a  half,  more  rarely  two  or  even  three  inches,  below  this  point. 

IN  DIRECTION. — Sometimes  in  man,  as  is  normal  in  birds,  the  aorta  arches  over  the  root  of 
the  right  instead  of  the  left  lung,  and  passes  down  on  the  right  side  of  the  spine.  In  such  cases 
all  of  the  viscera  of  the  thoracic  and  abdominal  cavities  are  transposed.  Less  frequently,  the 
aorta,  after  arching  over  the  root  of  the  right  lung,  is  directed  to  its  usual  position  on  the  left 
side  of  the  spine,  this  peculiarity  not  being  accompanied  by  any  transposition  of  the  viscera. 

IN  CONFORMATION. — The  aorta  occasionally  divides,  as  in  some  quadrupeds,  into  an  ascend- 
ing and  descending  trunk,  the  former  of  which  is  directed  vertically  upward,  and  subdivides 
into  three  branches,  to  supply  the  head  and  upper  extremities.  Sometimes  the  aorta  subdivides 
soon  after  its  origin  into  two  branches,  which  soon  reunite.  In  one  of  these  cases  the  oesophagus 
and  trachea  were  found  to  pass  through  the  interval  left  by  the  division  of  the  aorta;  this  is 
the  normal  condition  of  the  vessel  in  the  reptilia. 

Surgical  Anatomy. — Of  all  the  vessels  of  the  arterial  system,  the  aorta,  and  more  especially 
its  arch,  is  most  frequently  the  seat  of  disease;  hence  it  is  important  to  consider  some  of  the 
consequences  that  may  ensue  from  aneurism  of  this  part. 

It  will  be  remembered  that  the  ascending  aorta  is  continued  in  the  pericardium,  just  behind 
the  sternum,  being  crossed  at  its  commencement  by  the  pulmonary  artery  and  right  auricular 
appendix,  and  having  the  right  pulmonary  artery  behind,  the  vena  cava  on  the  right  side,  and 
the  pulmonary  artery  and  left  auricle  on  the  left  side. 

Aneurism  of  the  ascending  aorta,  in  the  situation  of  the  sinuses  of  Valsalva,  in  the  great  major- 
ity of  cases,  affects  the  anterior  sinus;  this  is  mainly  owing  to  the  fact  that  the  regurgitation 
of  blood  upon  the  sinuses  takes  place  chiefly  on  the  anterior  aspect  of  the  vessel.  As  the  aneuris- 
mal  sac  enlarges  it  may  compress  any  or  all  of  the  structures  in  immediate  proximity  to  it, 
but  chiefly  projects  toward  the  right  anterior  side,  and,  consequently,  interferes  mainly  with 
those  structures  that  have  a  corresponding  relation  with  the  vessel.  In  the  majority  of  cases  it 


595 


hursts  into  the  cavity  of  the  pericardium,  the  patient  suddenly  drops  dead,  and,  upon  a  post- 
mortem examination,  the  pericardial  sac  is  found  full  of  blood;  or  it  may  compress  the  right 
auricle,  or  the  pulmonary  artery  and  adjoining  part  of  the  right  ventricle,  and  open  into  one  or 
the  other  of  these  parts,  or  may  press  upon  the  precava. 

Aneurism  of  the  ascending  aorta,  originating  above  the  sinuses,  most  frequently  implicates 
the  right  anterior  wall  of  the  vessel,  where,  as  has  been  explained,  there  exists  a  normal  dilata- 
tion, the  great  sinus  of  the  aorta;  this  is  probably  mainly  owing  to  the  blood  being  impelled 
a<rainst  this  part.  The  direction  of  the  aneurism  is  also  chiefly  toward  the  right  of  the  median 
line.  It  attains  a  large  size  and  projects  forward,  it  may  absorb  the  sternum  and  the  cartilages 
of  the  ribs,  usually  on  the  right  side,  and  appear  as  a  pulsating  tumor  on  the  front  of  the  chest, 
just  below  the  manubrium;  or  it  may  burst  into  the  pericardium,  or  may  compress  or  open  into 
the  right  lung,  the  trachea,  bronchi,  or  oesophagus. 


Right  pulmonary 
vein. 

Right  pulmonary 
vein. 


Vena  azyg< 
major 


Left  subclavian 
artery. 

Left  common 
carotid  artery. 


•Left  innomi- 
nate vein. 


Inferior  thyroid 
vein. 

^~ 

Right  innomi- 
nate vein. 

Right  subclavian  artery.     Right  common  carotid  artery. 

FIG.  393. — Relation  of  great  vessels  at  base  of  heart,  seen  from  above.     (From  a  preparation  in  the  Museum 
of  the  Royal  College  of  Surgeons  of  England.) 

Regarding  the  transverse  aorta,  the  student  is  reminded  that  the  vessel  lies  on  the  trachea, 
the  oesophagus,  and  thoracic  duct;  that  the  recurrent  laryngeal  nerve  winds  around  it;  and  that 
from  its  upper  part  are  given  off  three  large  trunks,  which  supply  the  head,  neck,  and  upper 
extremities.  An  aneurismal  tumor,  taking  origin  from  the  posterior  part  of  the  vessel,  its  most 
usual  site,  may  press  upon  the  tracheji,  impede  the  breathing,  or  produce  cough,  haemoptysis, 
or  stridulous  breathing,  or  it  may  ultimately  burst  into  that  tube,  producing  fatal  hemorrhage. 
Again,  its  pressure  on  the  laryngeal  nerves  may  give  rise  to  symptoms  which  so  accurately 
resemble  those  of  laryngitis  that  the  operation  of  tracheotomy  has  in  some  cases  been  resorted 
to,  from  the  supposition  that  disease  existed  in  the  larynx;  or  it  may  press  upon  the  thoracic 
duct  and  destroy  life  by  inanition;  or  it  may  involve  the  oesophagus,  producing  dysphagia;  or 
may  burst  into  the  oesophagus,  when  fatal  hemorrhage  will  occur.  Again,  the  innominate 
artery,  or  the  subclavian,  or  left  carotid,  may  be  so  obstructed  by  clots  as  to  produce  a  weakness, 
or  even  a  disappearance,  of  the  pulse  in  one  or  the  other  wrist  or  in  the  left  temporal  artery;  or 
the  tumor  may  present  itself  at  or  above  the  manubrium,  generally  either  in  the  median  line 
or  to  the  right  of  the  sternum,  and  may  simulate  an  aneurism  of  one  of  the  arteries  of  the  neck. 

Branches  (Figs.  389  and  390). — The  branches  given  off  from  the  arch  of  the 
aorta  are  three  in  number:  the  innominate,  the  left  common  carotid,  and  the  left 
subclavian  arteries. 

Peculiarities.  POSITION  OF  THE  BRANCHES. — The  branches,  instead  of  arising  from  the  high- 
est part  of  the  arch  (their  usual  position),  may  be  moved  more  to  the  right,  arising  from  the 
commencement  of  the  transverse  or  upper  part  of  the  ascending  portion;  or  the  distance  from 
one  another  at  their  origin  may  be  increased  or  diminished,  the  most  frequent  change  in  this 
respect  being  the  approximation  of  the  left  carotid  toward  the  innominate  artery. 


596  THE  BLOOD-VASCULAR  SYSTEM 

The  Number  of  the  primary  branches  may  be  reduced  to  a  single  vessel,  or  more  commonly 
two:  the  left  carotid  arising  from  the  innominate  artery,  or  (more  rarely)  the  carotid  and  sub- 
clavian  arteries  of  the  left  side  arising  from  the  innominate  artery.  But  the  number  may  be 
increased  to  four,  from  the  right  carotid  and  subclavian  arteries  arising  directly  from  the  aorta, 
the  innominate  being  absent.  In  most  of  these  latter  cases  the  right  subclavian  has  been  found 
to  arise  from  the  left  end  of  the  arch;  in  other  cases  it  was  the  second  or  third  branch  given  off 
instead  of  the  first.  Another  common  form  in  which  there  are  four  primary  branches  is  that 
in  which  the  left  vertebral  artery  arises  from  the  arch  of  the  aorta  between  the  left  carotid  and 
subclavian  arteries.  Lastly,  the  number  of  trunks  from  the  arch  may  be  increased  to  five  or 
six;  in  these  instances,  the  external  and  internal  carotids  arise  separately  from  the  arch,  the 
common  carotid  being  absent  on  one  or  both  sides.  In  some  cases,  where  six  branches  have 
been  found,  it  has  been  due  to  a  separate  origin  of  the  vertebral  on  both  sides. 

NUMBER  AS  USUAL,  ARRANGEMENT  DIFFERENT. — When  the  aorta  arches  over  to  the  right 
side,  the  three  branches  have  an  arrangement  the  reverse  of  what  is  usual,  the  innominate  sup- 
plying the  left  side,  and  the  carotid  and  subclavian  (which  arise  separately)  the  right  side.  In 
other  cases,  where  the  aorta  takes  its  usual  course,  the  tv/o  carotids  may  be  joined  in  a  common 
trunk,  and  the  subclavians  arise  separately  from  the  arch,  the  right  subclavian  generally  arising 
from  the  left  end  of  the  arch.1 

In  some  instances  other  arteries  are  found  to  arise  from  the  arch  of  the  aorta.  Of  these  the 
most  common  are  the  bronchial,  one  or  both,  and  the  thyroidea  ima;  but  the  internal  mammary 
and  the  inferior  thyroid  have  been  seen  to  arise  from  this  vessel. 

The  Innominate  Artery  (A.  Anonyma)  (Figs.  389  and  390). 

The  innominate  or  brachio-cephalic  artery  is  the  largest  branch  given  off 
from  the  arch  of  the  aorta.  It  arises,  on  a  level  with  the  upper  border  of 
the  second  right  costal  cartilage,  from  the  commencement  of  the  arch  of  the 
aorta  in  front  of  the  left  carotid,  and,  ascending  obliquely  to  the  upper  border  of 
the  right  sterno-clavicular  articulation,  divides  into  the  right  common  carotid  and 
right  subclavian  arteries.  This  vessel  varies  from  an  inch  and  a  half  to  two  inches 
in  length. 

Relations. — In  front,  it  is  separated  from  the  first  piece  of  the  sternum  by  the 
Sterno-hyoid  and  Sterno-thyroid  muscles,  the  remains  of  the  thymus  gland,  the 
left  innominate  and  right  inferior  thyroid  veins  which  cross  its  root,  and  some- 
times the  inferior  cervical  cardiac  branch  of  the  right  vagus.  Behind,  it  lies 
upon  the  trachea,  which  it  crosses  obliquely,  and  continuing  upward  it  lies  in  the 
right  pleura.  On  the  right  side  is  the  right  innominate  vein,  right  vagus  nerve, 
and  the  pleura;  and  on  the  left  side,  the  remains  of  the  thymus  gland,  the  origin 
of  the  left  carotid  artery,  the  left  inferior  thyroid  vein,  and  the  trachea 

Branches. — The  innominate  usually  gives  off  no  branches,  but  occasionally  a 
small  branch,  the  thyroidea  ima,  is  given  off  from  this  vessel.  It  also  sometimes 
gives  off  a  thymic  or  bronchial  branch. 

The  Thyroidea  Ima  (a.  thyroidea  ima),  which  is  occasionally  present,  ascends  in 
front  of  the  trachea  to  the  lower  part  of  the  thyroid  body,  which  it  supplies.  It 
varies  greatly  in  size,  and  appears  to  compensate  for  the  deficiency  or  absence  of 
one  of  the  other  thyroid  vessels.  It  occasionally  is  found  to  arise  from  the  right 
common  carotid  or  from  the  aorta,  the  subclavian,  or  internal  mammary  vessels. 

PLAN  OF  THE  RELATIONS  OF  THE  INNOMINATE  ARTERY. 

In  front. 
Sternum. 

Sterno-hyoid  and  Sterno-thyroid  muscles. 
Remains  of  the  thymus  gland. 
Left  innominate  and  right  inferior  thyroid  veins. 
Inferior  cervical  cardiac  branch  from  right  vagus  nerve.  « 

1  The  anomalies  of  the  aorta  and  its  branches  are  minutely  described  by  Krause  in  Henle's  Anatomy  (Bruns- 
wick, 1868),  vol.  iii.  p.  203  et  se<j. — ED.  of  15th  English  edition. 


THE  INNOMINATE  ARTERY  597 

Right  side.  f  >.  Left  side. 

Right  innominate  vein.  /  innominate  ]  Remains  of  thymus. 

Right  vagus  nerve.  I       A**1?-      \  Left  carotid. 

Pleura.  \  /  Left  inferior  thyroid  vein. 

^^_^^  Trachea. 

Behind. 

Trachea. 
Right  pleura. 

Peculiarities  in  Point  of  Division. — When  the  bifurcation  of  the  innominate  artery  varies 
from  the  point  above  mentioned  it  sometimes  ascends  a  considerable  distance  above  the  sternal 
end  of  the  clavicle;  less  frequently  it  divides  below  it.  In  the  former  class  of  cases  its  length 
may  exceed  two  inches,  and  in  the  latter  be  reduced  to  an  inch  or  less.  These  are  points  of  con- 
siderable interest  for  the  surgeon  to  remember  in  connection  with  the  operation  of  tying  this 
vessel. 

Position. — When  the  aorta  arches  over  to  the  right  side,  the  innominate  is  directed  to  the 
left  side  of  the  neck  instead  of  the  right. 

Collateral  Circulation. — Allan  Burns  demonstrated,  on  the  dead  subject,  the  possibility  of 
the  establishment  of  the  collateral  circulation  after  ligature  of  the  innominate  artery,  by  tying 
and  dividing  that  artery,  after  which,  he  says,  "Even  coarse  injection,  impelled  into  the  aorta, 
passing  freely  by  the  anastomosing  branches  into  the  arteries  of  the  right  arm,  filling  them  and 
all  the  vessels  of  the  head  completely."1  The  branches  by  which  this  circulation  would  be  car- 
ried on  are  very  numerous;  thus,  all  the  communications  across  the  middle  line  between  the 
branches  of  the  carotid  arteries  of  opposite  sides  would  be  available  for  the  supply  of  blood  to 
the  right  side  of  the  head  and  neck;  while  the  anastomosis  between  the  superior  intercostal  of 
the  subclavian  and  the  first  aortic  intercostal  (see  infra  on  the  collateral  circulation  after  oblitera- 
tion of  the  thoracic  aorta)  would  bring  the  blood,  by  a  free  and  direct  course,  into  the  right 
subclavian:  the  numerous  connections,  also,  between  the  intercostal  arteries  and  the  branches 
of  the  axillary  and  internal  mammary  arteries  would,  doubtless,  assist  in  the  supply  of  blood  to 
the  right  arm,  while  the  deep  epigastric,  from  the  external  iliac,  would,  by  means  of  its  anasto- 
mosis with  the  internal  mammary,  compensate  for  any  deficiency  in  the  vascularity  of  the  wall 
of  the  chest. 

Surgical  Anatomy.— The  innominate  artery  has  been  tied  at  least  thirty  times  and  in  six 
instances,  according  to  Mr.  Jacobson,  the  patient  survived.  Mott's  patient,  however,  on 
whom  the  operation  was  first  performed,  lived  nearly  four  weeks,  and  Graefe's  more  than 
two  months.  In  1895  Burrell,  of  Boston,  resected  the  right  sterno-clavicular  articulation  with 
the  upper  end  of  the  sternum  and  tied  the  innominate.  The  patient  lived  104  days.  The 
ligation  was  first  successfully  performed  by  A.  W.  Smyth,  of  New  Orleans,  in  1864,  for  sub- 
clavian aneurism.  The  patient  died  ten  years  later  of  the  original  aneurism,  which  was  reformed 
by  the  collaterals.  The  chief  danger  of  the  operation  appears  to  be  the  frequency  of  secondary 
hemorrhage;  but  in  the  present  day,  with  the  practice  of  aseptic  surgery  and  our  greater 
knowledge  of  the  use  of  the  ligature,  more  favorable  results  may  be  anticipated.  Other  causes 
of  death  after  operation  are  pleurisy,  pericarditis,  and  suppurative  cellulitis.  The  main 
obstacles  to  the  operation  are,  as  the  student  will  perceive  from  his  dissection  of  this  vessel, 
the  deep  situation  of  the  artery  behind  and  beneath  the  sternum,  and  the  number  of  important 
structures  which  surround  it  in  every  part. 

In  order  to  apply  a  ligature  to  this  vessel,  the  patient  is  to  be  placed  upon  his  back,  with  the 
thorax  slightly  raised,  the  head  bent  a  little  backward,  and  the  shoulder  on  the  side  of  the  aneu- 
rism strongly  depressed,  so  as  to  draw  out  the  artery  from  behind  the  sternum  into  the  neck. 
An  incision  three  or  more  inches  long  is  then  made  along  the  anterior  border  of  the  Sterno-mas- 
toid  muscle,  terminating  at  the  sternal  end  of  the  clavicle.  From  this  point  a  second  incision  is 
carried  about  the  same  length  along  the  upper  border  of  the  clavicle.  The  skin  is  then  dissected 
back,  and  the  Platysma  divided  on  a  director:  the  sternal  end  of  the  Sterno-mastoid  is  now 
brought  into  view,  and,  a  director  being  passed  beneath  it  and  close  to  its  under  surface,  so  as  to 
avoid  any  small  vessels,  it  is  to  be  divided;  in  like  manner  the  clavicular  origin  is  to  be  divided 
throughout  the  whole  or  greater  part  of  its  attachment.  By  pressing  aside  any  loose  cellular 
tissue  or  vessels  that  may  now  appear  the  Sterno-hyoid  and  Sterno-thyroid  muscles  will  be 
exposed,  and  must  be  divided,  a  director  being  previously  passed  beneath  them.  The  inferior 
thyroid  veins  may  come  into  view,  and  must  be  carefully  drawn,  either  upward  or  downward,  by 
means  of  a  blunt  hook,  or  tied  with  double  ligatures  and  divided.  After  tearing  through  a 
strong  fibro-cellular  lamina,  the  right  carotid  is  brought  into  view,  and,  being  traced  downward, 
the  arteria  innominata  is  arrived  at.  The  left  innominate  vein  should  now  be  depressed;  the 

1  Surgical  Anatomy  of  the  Head  and  Neck,  p.  62. 


598  THE  BLOOD-VASCULAR  SYSTEM 

right  innominate  vein,  the  internal  jugular  vein,  and  the  vagus  nerve  drawn  to  the  right  side; 
and  a  curved  aneurism  needle  may  then  be  passed  around  the  vessel,  close  to  its  surface, 
and  in  a  direction  from  below  upward  and  inward,  care  being  taken  to  avoid  the  right  pleural 
sac,  the  trachea,  and  cardiac  nerves.  The  ligature  should  be  applied  to  the  artery  as  high  as 
possible,  in  order  to  allow  room  between  it  and  the  aorta  for  the  formation  of  the  coagulum. 
The  importance  of  avoiding  the  thyroid  plexus  of  veins  during  the  primary  steps  of  the  opera- 
tion, and  the  pleural  sac  whilst  including  the  vessel  in  the  ligature,  should  be  most  carefully  borne 
in  mind.  After  the  artery  has  been  secured,  the  common  carotid  should  be  tied  about  half  an 
inch  above  its  origin,  and  also  the  thyroidea  ima  if  the  vessel  is  of  any  size.  The  several  muscles 
are  united  by  buried  sutures.  An  easier  and  safer  plan  than  the  above  is  that  employed  by 
Burrell — viz.,  resection  of  the  right  sterno-clavicular  articulation  and  of  the  upper  end  of  the 
.sternum. 

ARTERIES  OF  THE  HEAD  AND  NECK. 

The  chief  artery  which  supplies  the  head  and  neck  is  the  common  carotid:  it 
ascends  in  the  neck  and  divides  into  two  branches:  the  External  Carotid,  supply- 
ing the  superficial  parts  of  the  head  and  face  and  the  greater  part  of  the  neck; 
and  the  Internal  Carotid,  supplying  to  a  great  extent  the  parts  within  the  cranial 
cavity. 

THE  COMMON  CAROTID  ARTERY  (A.  CAROTIS  COMMUNIS)  (Figs.  388,  389, 

390,  394). 

The  common  carotid  arteries,  Although  occupying  a  nearly  similar  position  in 
the  neck,  differ  in  position,  and,  consequently,  in  their  relation  at  their  origin. 
The  right  common  carotid  (a.  carotis  communis  dextra)  arises  from  the  innom-- 
inate  artery,  behind  the  right  sterno-clavicular  articulation.  The  left  common 
carotid  (a.  carotis  communis  sinistra)  arises  from  the  highest  part  of  the  arch  of 
the  aorta,  and  is,  consequently,  longer,  and  at  its  origin  is  contained  within 
the  thorax.  The  course  and  relations  of  that  portion  of  the  left  carotid  which 
intervenes  between  the  arch  of  the  aorta  and  the  left  sterno-clavicular  articulation 
will  first  be  described.  (See  Figs.  388,  389,  and  390.) 

The  left  carotid  within  the  thorax  ascends  obliquely  outward  from  the  arch  of 
the  aorta  to  the  root  of  the  neck.  In  front,  it  is  separated  from  the  first  piece 
•of  the  sternum  by  the  Sterno-hyoid  and  Sterno-thyroid  muscles,  the  left  innomi- 
nate vein,  and  the  remains  of  the  thymus  gland;  behind,  it  lies  on  the  trachea, 
resophagus,  thoracic  duct,  and  the  left  recurrent  laryngeal  nerve.  Internally,  it 
is  in  relation  with  the  innominate  artery,  inferior  thyroid  veins,  and  remains  of  the 
thymus  gland;  externally,  with  the  left  vagus  nerve,  left  pleura,  and  left  lung. 
'The  left  subclavian  artery  is  posterior  and  slightly  external  to  it. 

PLAN  OF  THE  RELATIONS  OF  THE  LEFT  COMMON  CAROTID. 
THORACIC  PORTION. 

In  front. 
Sternum. 

Sterno-hyoid  and  Sterno-thyroid  muscles. 
Left  innominate  vein. 
Remains  of  the  thymus  gland. 

Internally.  /  \  Externally. 

I  Left  Common  \ 

Innominate  artery.  /       Carotid.      i  Left  vagus  nerve. 

Inferior  thyroid  veins.  I       portion.0     /  Left  pleura  and  lung. 

Remains  of  the  thymus  gland.  V  J  Left  subclavian  artery. 

Behind. 
Trachea. 
(Esophagus. 
Thoracic  duct. 
Left  recurrent  laryngeal  nerve. 


THK   COMMON  CAROTID   ARTERY 


599 


In  the  neck  the  two  common  carotids  resemble  each  other  so  closely  that  one 
description  will  apply  to  both.  Each  vessel  passes  obliquely  upward  from  behind 
the  sterno-clavicular  articulation  to  a  level  with  the  upper  border  of  the  thyroid 
cartilage,  opposite  the  fourth  cervical  vertebra,  where  it  divides  into  the  external 
and  internal  carotid;  these  names  being  derived  from  the  distribution  of  the  arteries 
to  the  external  parts  of  the  head  and  face  and  to  the  internal  parts  of  the  cranium 
and  orbit  respectively. 


FIG.  395.— Plan  of  the 
branches  of  the  external 
carotid. 


FIG.  394.  —  Surgical  anatomy  of  the  arteries  of  the  neck,  showing  the  carotid  and  subclavian  arteries 


At  the  lower  part  of  the  neck  the  two  common  carotid  arteries  are  separated 
from  each  other  by  a  small  interval,  which  contains  the  trachea;  but  at  the  upper 
part,  the  thyroid  body,  the  larynx  and  pharynx  project  forward  between  the 
two  vessels,  and  give  the  appearance  of  their  being  placed  farther  back  in  this 
situation.  The  common  carotid  artery  is  contained  in  a  sheath  derived  from  the 


600 


THE  BLOOD-VASCULAR  SYSTEM 


deep  cervical  fascia,  which  also  encloses  the  internal  jugular  vein  and  vagus  nerve, 
the  vein  lying  on  the  outer  side  of  the  artery,  and  the  nerve  between  the  artery 
and  vein,  on  a  plane  posterior  to  both.  On  opening  the  sheath  these  three  struc- 
tures are  seen  to  be  separated  from  one  another,  each  being  enclosed  in  a  separate 
fibrous  investment. 

Relations. — At  the  lower  part  of  the  neck  the  common  carotid  artery  is  very 
deeply  seated,  being  covered  by  the  integument,  superficial  fascia,  Platysma,  and 
deep  cervical  fascia,  the  Sterno-mastoid,  Sterno-hyoid,  an'd  Sterno-thyroid  muscles, 
and  by  the  Omo-hyoid,  opposite  the  cricoid  cartilage;  but  in  the  upper  part  of  its 
course,  near  its  termination,  it  is  more  superficial,  being  covered  merely  by  the 
integument,  the  superficial  fascia,  Platysma,  deep  cervical  fascia,  and  inner  margin 
of  the  Sterno-mastoid,  and,  when  the  latter  is  drawn  backward,  it  is  seen  to  be 
contained  in  a  triangular  space,  bounded  behind  by  the  Sterno-mastoid,  above  by 
the  posterior  belly  of  the  Digastric,  and  below  by  the  anterior  belly  of  the  Omo- 
hyoid.  This  part  of  the  artery  is  crossed  obliquely,  from  within  outward,  by  the 
sterno-mastoid  artery;  it  is  crossed  also  by  the  superior  and  middle  thyroid  veins, 
which  terminate  in  the  internal  jugular;  and,  descending  on  its-sheath  in  front,  is 
seen  the  descendens  hypoglossi  nerve,  this  filament  being  joined  by  one  or  two 
branches  from  the  cervical  nerves,  which  cross  the  vessel  from  without  inward. 
Sometimes  the  descendens  hypoglossi  is  contained  within  the  sheath.  The  middle 
thyroid  vein  crosses  the  artery  about  its  middle,  and  the  anterior  jugular  vein  below; 
the  latter,  however,  is  separated  from  the  artery  by  the  Sterno-hyoid  and  Sterno- 
thyroid  muscles.  Behind,  the  artery  is  separated  from  the  transverse  processes  of 
the  vertebrae  by  the  Longus  colli  and  Rectus  capitis  anticus  major  muscles,  the 
sympathetic  nerve  being  interposed  between  it  and  the  muscles.  The  recurrent 
laryngeal  nerve  and  inferior  thyroid  artery  cross  behind  the  vessel  at  its  lower  part. 
Internally,  it  is  in  relation  with  the  trachea  and  thyroid  gland,  the  latter  overlapping 
it,  the  inferior  thyroid  artery  and  recurrent  laryngeal  nerve  being  interposed: 
higher  up,  with  the  larynx  and  pharynx.  On  its  outer  side  are  placed  the 
internal  jugular  vein  and  vagus  nerve.  At  the  lower  part  of  the  neck  the  internal 
jugular  vein  on  the  right  side  diverges  from  the  artery,  but  on  the  left  side  it 
approaches  it,  and  often  overlaps  its  lower  part.  This  is  an  important  fact  to  bear 
in  mind  during  the  performance  of  any  operation  on  the  lower  part  of  the  left 
common  carotid  artery.  In  this  region  the  relation  which  the  right  and  left  recur- 
rent laryngeal  nerves  bear  to  the  arteries  is  not  identical.  The  left  recurrent  laryn- 
geal nerve  lies  behind  the  thoracic  portion  of  the  left  common  carotid  artery  and 
internal  to  the  cervical  portion  of  the  vessel.  The  right  nerve  passes  obliquely 
upward  and  inward  behind  the  right  common  carotid  to  reach  its  inner  side. 

PLAN  OF  THE  RELATIONS  OF  THE  COMMON  CAROTID  ARTERY. 


Integument  and  superficial  fascia. 

Deep  cervical  fascia. 

Platysma. 

Sterno-mastoid. 

Sterno-hyoid. 

Sterno-thyroid. 

Externally. 
Internal  jugular  vein. 
Vagus  nerve. 


In  front. 


Omo-hyoid. 

Descendens  and  Communicans  hypoglossi 

nerves. 

Sterno-mastoid  artery. 
Superior  and  middle  thyroid  veins. 
Anterior  jugular  vein. 


Internally. 
Trachea. 
Thyroid  gland. 
Recurrent  laryngeal  nerve. 
Inferior  thyroid  artery. 
Larynx. 
Pharynx. 


THE  COMMON  CAROTID  ARTERY  601 

Behind. 

Longus  colli.  Sympathetic  nerve. 

Rectus  capitis  anticus  major.  Inferior  thyroid  artery. 

Recurrent  laryngeal  nerve. 

Peculiarities  as  to  Origin. — The  right  common  carotid  may  arise  above  or  below  the  upper 
border  of  the  sterno-clavicular  articulation.  This  variation  occurs  in  one  out  of  about  eight 
cases  and  a  half,  and  the  origin  is  more  frequently  below  than  above;  or  the  artery  may  arise 
as  a  separate  branch  from  the  arch  of  the  aorta  or  in  conjunction  with  the  left  carotid.  The 
lc/f  common  carotid  varies  more  frequently  in  its  origin  than  the  right.  In  the  majority  of  abnor- 
mal cases  it  arises  with  the  innominate  artery,  or,  if  the  innominate  artery  is  absent,  the  two 
carotids  arise  usually  by  a  single  trunk.  It  rarely  joins  with  the  left  subclavian,  except  in  cases 
of  transposition  of  the  arch. 

Peculiarities  as  to  Point  of  Division.— The  most  important  peculiarities  of  this  vessel,  in 
a  surgical  point  of  view,  relate  to  its  place  of  division  in  the  neck.  In  the  majority  of  abnormal 
cases  this  occurs  higher  than  usual,  the  artery  dividing  into  two  branches  opposite  the  hyoid 
bone,  or  even  higher;  more  rarely  it  occurs  below,  opposite  the  middle  of  the  larynx  or  the  lower 
border  of  the  cricoid  cartilage;  and  one  case  is  related  by  Morgagni  where  the  common  carotid, 
only  an  inch  and  a  half  in  length,  divided  at  the  root  of  the  neck.  Very  rarely  the  common 
carotid  ascends  in  the  neck  without  any  subdivision,  the  internal  carotid  being  wanting;  and 
in  a  few  cases  the  common  carotid  has  been  found  to  be  absent,  the  external  and  internal  carotids 
arising  directly  from  the  arch  of  the  aorta.  This  peculiarity  existed  on  both  sides  in  some  instances, 
on  one  side  in  others. 

Occasional  Branches. — The  common  carotid  usually  gives  off  no  branch  previous  to  its 
bifurcation;  but  it  occasionally  gives  origin  to  the  superior  thyroid  or  its  laryngeal  branch,  the 
ascending  pharyngeal,  the  inferior  thyroid,  or,  more  rarely,  the  vertebral  artery. 

Surface  Marking. — The  carotid  arteries  are  covered  throughout  their  entire  extent  by  the 
Sterno-mastoid  muscle,  but  their  course  does  not  correspond  to  the  anterior  border  of  the  muscle, 
which  passes  in  a  somewhat  curved  direction  from  the  mastoid  process  to  the  sterno-clavicular 
joint.  The  course  of  the  artery  is  indicated  more  exactly  by  a  line  drawn  from  the  sternal  end 
of  the  clavicle  below,  to  a  point  midway  between  the  angle  of  the  jaw  and  the  mastoid  process 
above.  That  portion  of  the  line  below  the  level  of  the  upper  border  of  the  thyroid  cartilage 
would  represent  the  course  of  the  vessel. 

Surgical  Anatomy. — The  operation  of  tying  the  common  carotid  artery  may  be  necessary 
in  a  case  of  wound  of  that  vessel  or  its  branches,  in  aneurism,  or  in  a  case  of  pulsating  tumor  of 
the  orbit  or  skull.  If  the  wound  involves  the  trunk  of  the  common  carotid,  it  will  be  necessary 
to  tie  the  artery  through  the  wound  above  and  below  the  wounded  part.  If  the  wound  is  too  small 
to  admit  of  safe  and  rapid  work  it  must  be  enlarged.  In  cases  of  aneurism,  or  where  one  of 
the  branches  of  the  common  carotid  is  wounded  in  an  inaccessible  situation,  it  may  be  judged 
necessary  to  tie  the  trunk.  In  such  cases  the  whole  of  the  artery  is  accessible,  and  any  part  may 
be  tied  except  close  to  either  end.  When  the  case  is  such  as  to  allow  of  a  choice  being  made, 
the  lower  part  of  the  carotid  should  never  be  selected  as  the  spot  upon  which  to  place  a  ligature, 
for  not  only  is  the  artery  in  this  situation  placed  very  deeply  in  the  neck,  but  it  is  covered  by 
three  layers  of  muscles,  and,  on  the  left  side,  in  the  great  majority  of  cases,  the  internal  jugular 
vein  passes  obliquely  in  front  of  it.  Neither  should  the  upper  end  be  selected,  for  here  the 
superior  thyroid  vein  and  its  tributaries  would  give  rise  to  very  considerable  difficulty  in  the  appli- 
cation of  a  ligature.  The  point  most  favorable  for  the  operation  is  that  part  of  the  vessel  which 
is  at  the  level  of  the  cricoid  cartilage.  It  occasionally  happens  that  the  carotid  artery  bifurcates 
below  its  usual  position:  if  the  artery  be  exposed  at  its  point  of  bifurcation,  both  divisions  of 
the  vessel  should  be  tied  near  their  origin,  in  preference  to  tying  the  trunk  of  the  artery  near  its 
termination;  and  if,  in  consequence  of  the  entire  absence  of  the  common  carotid  or  from  its 
early  division,  two  arteries,  the  external  and  internal  carotids,  are  met  with,  the  ligature  should 
be  placed  on  that  vessel  which  is  found  on  compression  to  be  connected  with  the  disease. 

Ligation  of  the  Carotid  at  the  Level  of  the  Cricoid  Cartilage  (Ligation  in  the  Triangle  of 
Election). — The  triangle  of  election  is  bounded  posteriorly  by  the  anterior  edge  of  the  sterno- 
cleido-mastoid ;  is  bounded  above  by  the  posterior  belly  of  the  digastric;  is  bounded  below  by  the 
anterior  belly  of  the  omohyoid.  In  this  operation  the  direction  of  the  vessel  and  the  inner 
margin  of  the  Sterno-mastoid  are  the  chief  guides  to  its  performance.  The  patient  should  be 
placed  on  his  back  with  the  head  thrown  back  and  turned  slightly  to  the  opposite  side:  an 
incision  is  to  be  made,  three  inches  long,  in  the  direction  of  the  anterior  border  of  the  Sterno- 
mastoid,  so  that  the  centre  corresponds  to  the  level  of  the  cricoid  cartilage;  after  dividing  the 
integument,  superficial  fascia,  and  Platysma,  the  deep  fascia  must  be  cut  through  on  a  director, 
so  as  to  avoid  wounding  numerous  small  veins  that  are  usually  found  beneath.  The  head 
may  now  be  brought  forward  so  as  to  relax  the  parts  somewhat,  and  the  margins  of  the  wound 
are  held  asunder  by  retractors.  The  descendens  hypoglossi  nerve  may  now  be  exposed,  and  must 
be  avoided,  and,  the  sheath  of  the  vessel  having  been  raised  by  forceps,  is  to  be  opened  to  a  small 


602  THE  BLOOD-  VASCULAR  SYSTEM 

extent  over  the  artery  at  its  inner  side.  The  internal  jugular  vein  may  present  itself  alternately 
distended  and  relaxed;  this  should  be  compressed  both  above  and  below,  and  drawn  outward, 
in  order  to  facilitate  the  operation.  The  aneurism  needle  is  passed  from  the  outside,  care 
being  taken  to  keep  the  needle  in  close  contact  with  the  artery,  and  thus  avoid  the  risk  of 
injuring  the  internal  jugular  vein  or  including  the  vagus  nerve.  Before  the  ligature  is  tied  it 
should' be  ascertained  that  nothing  but  the  artery  is  included  in  it. 

Ligation  of  the  Common  Carotid  at  the  Lower  Part  of  the  Neck  (Ligation  in  the  Triangle 
of  Necessity}. — The  triangle  of  necessity  is  bounded  above  by  the  anterior  belly  of  the  omo- 
hyoid;  is  bounded  behind  by  the  anterior  margin  of  the  sterno-cleido-mastoid ;  is  bounded 
in  front  by  the  mid-line  of  the  neck.  This  operation  is  sometimes  required  in  cases  of 
aneurism  of  the  upper  part  of  the  carotid,  especially  if  the  sac  is  of  large  size.  It  is  best 
performed  by  dividing  the  sternal  origin  of  the  Sterno-mastoid  muscle,  but  may  be  done 
in  some  cases,  if  the  aneurism  is  not  of  very  large  size,  by  an  incision  along  the  anterior 
border  of  the  Sterno-mastoid,  extending  down  to  the  sterno-clavicular  articulation,  and  by 
then  retracting  the  muscle.  The  easiest  and  best  plan,  however,  is  to  make  an  incision  two 
or  three  inches  long  down  the  lower  part  of  the  anterior  border  of  the  Sterno-mastoid  muscle 
to  the  sterno-clavicular  joint,  and  a  second  incision,  starting  from  the  termination  of  the  first, 
along  the  upper  border  of  the  clavicle  for  about  two  inches.  This  incision  is  made  through  the 
superficial  and  deep  fascia,  and  the  sternal  origin  of  the  muscle  is  exposed.  This  is  to  be  divided 
on  a  director,  and  turned  up,  with  the  superficial  structures,  as  a  triangular  flap.  Some  loose 
connective  tissue  is  to  be  divided  or  torn  through,  and  the  outer  border  of  the  Sterno-hyoid 
muscle  exposed.  In  doing  this  care  must  be  taken  not  to  wound  the  anterior  jugular  vein,  which 
crosses  the  muscle  to  reach  the  external  jugular  or  subclavian  vein.  The  Sterno-hyoid,  and  with 
it  the  Sterno-thyroid,  are  to  be  drawn  inward  by  means  of  a  retractor,  and  the  sheath  of  the 
vessel  is  exposed.  This  must  be  opened  with  great  care  on  its  inner  or  tracheal  side,  so  as  to 
avoid  the  internal  jugular  vein.  This  is  especially  necessary  on  the  left  side,  where  the  artery 
is  commonly  overlapped  by  the  vein.  On  the  right  side  there  is  usually  an  interval  between  the 
artery  and  the  vein,  and  not  the  same  risk  of  wounding  the  latter. 

The  common  carotid  artery,  being  a  long  vessel  without  any  branches,  is  particularly  suitable 
for  the  performance  of  Brasdor's  operation  for  the  cure  of  an  aneurism  of  the  lower  part  of  the 
vessel.  Brasdor's  procedure  consists  in  ligaturing  the  artery  on  the  distal  side  of  the  aneurism, 
and  in  the  case  of  the  common  carotid  there  are  no  branches  given  off  from  the  vessel  between 
the  aneurism  and  the  site  of  the  ligature;  hence  the  flow  of  blood  through  the  sac  of  the  aneurism 
is  diminished  and  cure  takes  place  in  the  usual  way,  by  the  deposit  of  laminated  fibrin. 

Collateral  Circulation. — After  ligature  of  the  common  carotid  the  collateral  circulation 
can  be  perfectly  established,  by  the  free  communication  which  exists  between  the  carotid  arteries 
of  opposite  sides,  both  without  and  within  the  cranium,  and  by  enlargement  of  the  branches  of 
the  subclavian  artery  on  the  side  corresponding  to  that  on  which  the  vessel  has  been  tied — the 
chief  communication  outside  the  skull  taking  place  between  the  superior  thyroid  from  the 
external  carotid  and  the  inferior  thyroid  from  the  subclavian,  the  profunda  cervicis  from  the 
subclavian  and  the  superior  intercostal  with  the  arteria  princeps  cervicis  of  the  occipital; 
the  vertebral  taking  the  place  of  the  internal  carotid  within  the  cranium. 

Sir  A.  Cooper  had  an  opportunity  of  dissecting,  thirteen  years  after  the  operation,  the  case 
in  which  he  first  successfully  tied  the  common  carotid  (the  second  case  in  which  he  performed 
the  operation).1  The  injection,  however,  does  not  seem  to  have  been  a  successful  one.  It  showed 
merely  that  the  arteries  at  the  base  of  the  brain  (circle  of  Willis)  were  much  enlarged  on  the 
side  of  the  tied  artery,  and  that  the  anastomosis  between  the  branches  of  the  external  carotid  on 
the  affected  side  and  those  of  the  same  artery  on  the  sound  side  was  free,  so  that  the  external 
carotid  was  pervious  throughout. 

The  Intercarotid  Body  (carotid  gland,  retrocarotid  corpuscle)  (see  the  Ductless 
Glands).  < 

The  External  Carotid  Artery  (A.  Carotis  Externa)  (Figs.  392,  393,  394). 

The  external  carotid  artery  commences  opposite  the  upper  border  of  the  thyroid 
cartilage,  and,  taking  a  slightly  curved  course,  passes  upward  and  forward,  and 
then  inclines  backward  to  the  space  between  the  neck  of  the  condyle  of  the  lower 
jaw  and  the  external  meatus,  where  it  divides  into  the  superficial  temporal  and 
internal  maxillary  arteries.  It  rapidly  diminishes  in  size  in  its  course  up  the 
neck,  owing  to  the  number  and  large  size  of  the  branches  given  off  from  it.  In 
the  child  it  is  somewhat  smaller  than  the  internal  carotid,  but  in  the  adult  the 

1  Guy's  Hospital  Reports,  i.,  56. 


THE  EXTERNAL   CAROTID  ARTERY 


603 


two  vessels  are  of  nearly  equal  size.  At  its  commencement  this  artery  is  more 
superficial,  and  placed  nearer  the  middle  line  than  the  internal  carotid,  and  is 
contained  in  the  triangular  space  bounded  by  the  Sterno-mastoid  behind,  the 
anterior  belly  of  the  Omo-hyoid  below,  and  the  posterior  belly  of  the  Digastric 
and  the  Stylo-hyoid  above. 

Relations. — It  is  covered  by  the  skin,  superficial  fascia,  Platysma,  deep  fascia 
and  anterior  margin  of  the  Sterno-mastoid,  and  is  crossed  by  the  hypoglossal  nerve, 
and  by  the  lingual  and  facial  veins;  it  is  afterward  crossed  by  the  Digastric  and 
Stylo-hyoid  muscles,  and  higher  up  passes  deeply  into  the  substance  of  the  parotid 
gland,  where  it  lies  beneath  the  facial  nerve  and  the  junction  of  the  temporal  and 
internal  maxillary  veins.  Internally  is  the  hyoid  bone,  wall  of  the  pharynx,  the 
superior  laryngeal  nerve,  arid  the  ramus  of  the  jaw,  from  which  it  is  separated  by 
a  portion  of  the  parotid  gland.  Externally,  in  the  lower  part  of  its  course,  is  the 
internal  carotid  artery.  Behind  it,  near  its  origin,  is  the  superior  laryngeal  nerve; 
and  higher  up,  it  is  separated  from  the  internal  carotid  by  the  Stylo-glossus  and 
Stylo-pharyngeus  muscles,  the  glosso-pharyngeal  nerve,  and  part  of  the  parotid 
gland. 

PLAN  OF  THE  RELATIONS  OF  THE  EXTERNAL  CAROTID. 

In  front. 

Skin,  superficial  fascia. 
Platysma  and  deep  fascia. 
Anterior  border  of  Sterno-mastoid. 
Hypoglossal  nerve. 
Lingual  and  facial  veins. 
Digastric  and  Stylo-hyoid  muscles. 

Parotid  gland  with  facial  nerve  and    temporo-maxillary  vein 
in  its  substance. 


Externally. 
Internal  carotid  artery. 


Internally. 
Hyoid  bone. 
Pharynx. 

Superior  laryngeal  nerve. 
Parotid  gland. 
Ramus  of  jaw. 

Behind. 

Superior  laryngeal  nerve. 
Stylo-glossus. 
Stylo-pharyngeus. 
Glosso-pharyngeal  nerve. 
Parotid  gland. 

Surface  Marking. — The  position  of  the  external  carotid  artery  may  be  marked  out  with 
sufficient  accuracy  by  a  line  drawn  from  the  front  of  the  m6atus  of  the  external  ear  to  the  side 
of  the  cricoid  cartilage,  slightly  arching  the  line  forward.  • 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  external  carotid  may  be  required 
in  case  of  wounds  of  this  vessel,  or  of  its  branches  when  these  cannot  be  tied,  and  in  some  cases 
of  pulsating  tumor  of  the  scalp  or  face.  The  operation  has  not  received  the  attention  which  it 
deserves,  owing  to  the  fear  which  surgeons  have  entertained  of  secondary  hemorrhage,  on  account 
of  the  number  of  branches  given  off  from  the  vessel.  This  fear,  however,  has  been  shown  by 
Mr.  Cripps  not  to  be  well  founded.1  Ligation  is  often  very  useful  as  a  means  of  prevent- 
ing excessive  hemorrhage  in  operations  about  the  face,  jaws,  and  mouth.  It  is  sometimes 
employed  with  the  hope  of  lessening  the  growth  of  tumors  by  cutting  off  the  blood  supply,  but 
ligation  is  useless  for  this  purpose.  Ligation  of  one  external  carotid  artery  arrests  the  circu- 
lation for  only  a  brief  period,  and  within  a  very  few  days  the  circulation  is  practically  freely 
re-established.  This  result  is  seen  to  be  inevitable  when  we  recall  the  numerous  branches  of  the 
external  carotid,  their  free  anastomoses,  and  the  fact  that  a  very  great  number  of  extremely  minute 
vessels  in  the  middle  line  join  the  external  carotid  system  of  one  side  to  that  of  the  other  side. 
Robert  H.  M.  Dawbarn  points  out  that  ligation  of  both  external  carotids  produces  only  temporary 
anaemia,  for  "inside  of  a  week  or  ten  days  thereafter  the  pulse  can  again  be  felt  in  the  temporals  and 
facials  upon  both  sides."2  Dawbarn  points  out  that  even  after  excision  of  the  external  carotids, 
with  separate  ligation  of  each  of  the  eight  branches,  blood  can  still  reach  the  nose,  tongue,  etc., 


1  Med.-Chir  Trans.,  Ixi.,  229. 


*  The  Treatment  of  Certain  Malignant  Growths. 


604  THE  BLOOD-VASCULAR  SYSTEM 

from  outside  systems  by  twenty-nine  distinct  routes.  Whereas  ligation  of  even  both  carotids  will 
not  prevent  the  growth  of  a  malignant  tumor,  excision  of  each  external  carotid,  with  separate 
control  of  its  eight  branches,  will  sometimes  prove  of  great  value  in  retarding  the  progress  of  a 
growth.  It  "  starves  "  the  growth  and  may  cause  it  to  shrink  (Dawbarn's  operation).  To  tie  the 
external  carotid  near  its  origin,  below  the  point  where  it  is  crossed  by  the  Digastric,  an  incision 
about  three  inches  in  length  should  be  made  along  the  margin  of  the  Sterno-mastoid,  from  the 
angle  of  the  jaw  to  the  upper  border  of  the  thyroid  cartilage.  The  ligature  should  be  applied 
between  the  lingual  and  superior  thyroid  branches.  To  tie  the  vessel  above  the  Digastric, 
between  it  and  the  parotid  gland,  an  incision  should  be  made,  from  the  lobe  of  the  ear  to  the 
great  cornu  of  the  os  hyoides,  dividing  successfully  the  skin,  Platysma,  and  fascia.  By  drawing 
the  Sterno-mastoid  outward,  the  posterior  belly  of  the  Digastric  and  Stylo-hyoid  muscles  down- 
ward, and  separating  them  from  the  parotid  gland,  the  vessel  will  be  exposed,  and  a  ligature  may 
be  applied  to  it.  The  circulation  is  at  once  re-established  by  the  free  communication  between 
most  of  the  large  branches  of  the  artery  (facial,  lingual,  superior  thyroid,  occipital)  and  the  corre- 
sponding arteries  of  the  opposite  side  and  by  the  anastomosis  of  its  branches  with  those  of  the 
internal  carotid,  and  of  the  occipital  with  the  branches  of  the  subclavian,  etc. 

Branches. — The  external  carotid  artery  gives  off  eight  branches,  which,  for 
convenience  of  description,  may  be  divided  into  four  sets.  (See  Fig.  395,  Plan  of 
the  Branches.) 

Anterior.  Posterior.  Ascending.                         Terminal. 

Superior  Thyroid.  Occipital.  Ascending  Phar-  Superficial  Temporal. 

Lingual.  Posterior  Auric-  yngeal.  Internal  Maxillary. 

Facial.  ular. 

The  student  is  here  reminded  that  many  variations  are  met  with  in  the  number, 
origin,  and  course  of  these  branches  in  different  subjects;  but  the  above  arrange- 
ment is  that  which  is  found  in  the  great  majority  of  cases. 

The  Superior  Thyroid  Artery  (a.  thyreoidea  superior]  (Figs.  394,  395,  and  398) 
is  the  first  branch  given  off  from  the  external  carotid,  being  derived  from  that  vessel 
just  below  the  great  cornu  of  the  hyoid  bone.  At  its  commencement  it  is  quite 
superficial,  being  covered  by  the  integument,  fascia,  and  Platysma,  and  is  contained 
in  the  triangular  space  bounded  by  the  Sterno-mastoid,  Digastric,  and  Omo-hyoid 
muscles.  After  running  upward  and  inward  for  a  short  distance,  it  curves  down- 
ward and  forward,  in  an  arched  and  tortuous  manner,  to  the  upper  part  of  the 
thyroid  gland,  passing  beneath  the  Omo-hyoid,  Sterno-hyoid,  and  Sterno-thyroid 
muscles,  and  supplying  them.  It  distributes  numerous  branches  to  the  upper  part 
of  the  gland,  anastomosing  with  its  fellow  of  the  opposite  side  and  with  the 
inferior  thyroid  arteries.  The  terminal  branches  supplying  the  gland  are  generally 
two  in  number:  one,  the  largest,  the  anterior  branch  (ramus  anterior) ,  descends 
at  the  anterior  border  of  the  lateral  lobe  of  the  gland,  reaches  the  upper  border 
of  the  isthmus,  and  then  passes  in  the  substance  of  the  isthmus  to  the  middle 
line  of  the  neck,  where  it  anastomoses  with  the  corresponding  artery  of  the 
opposite  side :  the  posterior  branch  (ramus  posterior}  descends  along  the  posterior 
border  of  the  lateral  lobe  of  the  gland,  the  anterior  and  posterior  branches 
anastomose  with  each  other  and  with  branches  of  the  inferior  thyroid,  and  both 
of  them  send  branches  to  the  thyroid  gland  (rami  glandular  es) .  Besides  the 
arteries  distributed  to  the  muscles  by  which  it  is  covered  and  to  the  substance 
of  the  gland,  the  branches  of  the  superior,  thyroid  are  the  following: 

Hyoid.  Superior  Laryngeal. 

Superficial  Descending  Branch  (Sterno-mastoid).        Crico-thyroid. 

The  Hyoid  or  Infra-hyoid  (ramus  hyoideus)  is  a  small  branch  which  runs  along 
the  lower  border  of  the  os  hyoides  beneath  the  Thyro-hyoid  muscle;  after  sup- 
plying the  muscles  t  connected  to  that  bone,  it  forms  an  arch,  by  anastomosing 
with  the  vessel  of  the  opposite  side. 


THE  EXTERNAL  CAROTID  ARTERY  605 

The  Superficial  Descending  or  Sterno-mastoid  Branch  (ramus  sternoclcidomas- 
toideus]  runs  downward  and  outward  across  the  sheath  of  the  common  carotid 
artery,  and  supplies  the  Sterno-mastoid  and  neighboring  muscles  and  integument. 
There  is  frequently  a  separate  branch  from  the  external  carotid  distributed  to  the 
Sterno-mastoid  muscle. 

The  Superior  Laryngeal  (a.  laryngea  superior],  larger  than  either  of  the  preceding, 
accompanies  the  internal  laryngeal  nerve,  beneath  the  Thyro-hyoid  muscle:  it 
pierces  the  thyro-hyoid  membrane,  and  supplies  the  muscles,  mucous  membrane, 
and  glands  of  the  larynx,  anastomosing  with  the  branch  from  the  opposite 
side. 

The  Crico-thyroid  (ramus  cricothyreoideus]  is  a  small  branch  which  runs  trans- 
versely across  the  crico-thyroid  membrane,  communicating  with  the  artery  of  the 
opposite  side. 

Arteries  .of  the  Thyroid  Gland. — The*  thyroid  gland  is  supplied  by  the  two 
superior  thyroids  from  the  external  carotid ;  the  two  inferior  thyroids  from  the 
subclavian,  and  sometimes  also  by  the  thyreoidea  ima  from  the  innominate. 

The  superior  thyroid  joins  the  gland  at  the  summit  of  the  upper  horn,  passes 
down  the  posterior  surface  of  the  gland  toward  the  inner  surface  of  the  upper  horn, 
comes  forward  to  the  anterior  margin  of  the  inner  surface,  descends  to  the  isthmus, 
and  on  the  superior  border  of  the  isthmus  anastomoses  with  the  artery  from  the 
other  side.  The  superior  thyroid  artery  sends  numerous  branches  across  the 
anterior  surface  of  the  gland. 

The  inferior  thyroid  artery  is  larger  than  the  superior  artery.  It  passes  to 
the  posterior  surface  of  the  gland  and  divides  into  branches.  Some  of  the  branches 
enter  the  hilus ;  others  track  across  the  posterior  surface  of  the  gland.  The  inferior 
thyroid  artery  is  close  to  the  recurrent  laryngeal  nerve.  The  artery,  as  a  rule, 
passes  behind  the  nerve  before  it  divides  into  branches.  It  may  divide  first  and 
then  one  or  two  branches  may  be  in  front  of  the  nerve.  In  unusual  cases  the 
artery  before  division  is  in  front  of  the  nerve,  or  all  the  branches  are  in  front.1 

The  thyreoidea  ima  passes  to  the  lower  portion  of  the  gland.  Berry  points  out 
that  the  thyroid  arteries  communicate  very  freely  with  each  other;  only  the  small 
branches  pass  into  the  interior  of  the  gland;  the  larger  branches  "ramify  on  the 
surface  of  the  gland,  just  beneath  the  capsule."2 

Surgical  Anatomy. — The  superior  thyroid,  or  one 'of  its  branches,  is  often  divided  in  cases 
of  cut  throat,  giving  rise  to  considerable  hemorrhage.  In  such  cases  the  artery  should  be  secured, 
the  wound 'being  enlarged  for  that  purpose,  if  necessary.  The  operation  may  be  easily  per- 
formed, the  position  of  the  artery  being  very  superficial,  and  the  only  structures  of  importance 
covering  it  being  a  few  small  veins.  The  operation  of  tying  the  superior  thyroid  artery  to  lessen 
the  size  of  a  bronchocele  has  been  performed  in  numerous  instances  with  partial  or  temporary 
success.  When,  however,  the  collateral  circulation  between  this  vessel  and  the  artery  of  the 
opposite  side,  and  the  inferior  thyroid,  is  completely  re-established,  the  tumor  usually  regains 
its  former  size,  and  hence  the  operation  has  been  given '  up,  especially  as  better  results  are 
obtained  by  other  means.  Both  thyroid  arteries  on  the  same  side,  and  indeed  all  the  four 
thyroid  arteries,  have  been  tied  in  enlarged  thyroid.  The  superior  and  inferior  thyroid  arteries 
of  the  involved  side  are  ligated  before  extirpating  a  goitrous  lobe  of  the  thyroid. 

The  position  of  the  superficial  descending  branch  is  of  importance  in  connection  with  the 
operation  of  ligation  of  the  common  carotid  artery.  It  crosses  and  lies  on  the  sheath  of  this 
vessel,  and  may  chance  to  be  wounded  in  opening  the  sheath.  The  position  of  the  crico-thyroid 
branch  should  be  remembered,  as  it  may  prove  the  source  of  troublesome  hemorrhage  during 
the  operation  of  laryngotomy.  In  performing  the  operation  of  quick  laryngotomy  the  crico- 
thyroid  membrane  should  be  incised  transversely  in  order  to  avoid  this  vessel. 

The  Lingual  Artery  (a.  lingualis)  (Figs.  394  and  395)  arises  from  the  external 
carotid  between  the  superior  thyroid  and  facial;  it  first  runs  obliquely  upward 
and  inwrard  to  the  great  cornu  of  the  hyoid  bone;  it  then  curves  downward  and 
forward,  forming  a  loop  which  is  crossed  by  the  hypoglossal  nerve,  and,  passing 

1  Berry.     Diseases  of  the  Thyroid  Gland.  *  Ibid. 


006  THE  BLOOD-VASCULAR  SYSTEM 

beneath  the  Digastric  and  Stylo-hyoid  muscles,  it  runs  horizontally  forward, 
beneath  the  Hyo-glossus,  and  finally,  ascending  almost  perpendicularly  to  the 
tongue,  turns  forward  on  Its  under  surface  as  far  as  the  tip,  under  the  name  of 
the  ranine  artery. 

Relations. — Its  first,  or  oblique,  portion  is  superficial,  being  contained  in  the 
same  triangular  space  as  the  superior  thyroid  artery,  resting  upon  the  middle  con- 
strictor of  the  pharynx,  and  covered  by  the  Platysma  and  fascia  of  the  neck.  Its 
second,  or  curved,  portion  also  lies  upon  the  middle  constrictor,  being  covered  at 
first  by  the  tendon  of  the  Digastric  and  the  Stylo-hyoid  muscle,  and  afterward  by 
the  Hyo-glossus,  the  latter  muscle  separating  it  from  the  hypoglossal  nerve.  Its 
third,  or  horizontal,  portion  lies  between  the  Hyo-glossus  and  Genio-hyo-glossus 
muscles.  The  fourth,  or  terminal,  part,  under  the  name  of  the  ranine,  runs  along 
the  under  surface  of  the  tongue  to  its  tip:  it  is  very  superficial,  being  covered 
only  by  the  mucous  membrane,  and  rests  on  the  Lingualis  on  the  outer  side  of 
the  Genio-hyo-glossus.  The  hypoglossal  nerve  crosses  the  lingual  artery,  and  then 
becomes  separated  from  it,  in  the  second  part  of  its  course,  by  the  Hyo-glossus 
muscle. 

Branches. — The  branches  of  the  lingual  artery  are — the 

Hyoid.  Sublingual. 

Dorsalis  Linguae.  Ranine. 

The  Hyoid  or  Supra-hyoid  Branch  (ramus  hyoideus)  runs  along  the  upper  border 
of  the  hyoid  bone,  supplying  the  muscles  attached  to  it  and  anastomosing  with 
.its  fellow  of  the  opposite  side. 

The  Dorsalis  Linguae  (ramus  dorsalis  linguae]  (Fig.  445)  arises  from  the  lingual 
artery  beneath  the  Hyo-glossus  muscle  (which,  in  the  figure,  has  been  partly  cut 
away,  to  show  the  vessel) ;  it  ascends  to  the  dorsum  of  the  tongue,  and  supplies  the 
mucous  membrane,  the  tonsil,  soft  palate,  and  epiglottis,  anastomosing  with  its 
fellow  from  the  opposite  side.  This  artery  is  frequently  represented  by  two  or 
three  small  branches. 

The  Sublingual  (a.  sublingualis) ,  which  may  be  described  as  a  branch  of  bifur- 
cation of  the  lingual  artery,  arises  at  the  anterior  margin  of  the  Hyo-glossus  muscle, 
and  runs  forward  between  the  Genio-hyo-glossus  and  the  sublingual  gland.  It 
supplies  the  substance  of  the  gland,  giving  branches  to  the  Mylo-hyoid  and 
neighboring  muscles,  the  mucous  membrane  of  the  mouth  and  gums.  One 
branch  runs  behind  the  alveolar  process  of  the  lower  jaw  in  the  substance  of  the 
gum  to  anastomose  with  a  similar  artery  from  the  other  side. 

The  Ranine  or  Deep  Lingual  (a.  profunda  linguae)  may  be  regarded  as  the  other 
branch  of  bifurcation.  It  is  usually  described  as  the  continuatidn  of  the  lingual 
artery;  it  runs  along  the  under  surface  of  the  tongue,  resting  on  the  Inferior 
lingualis,  and  covered  by  the  mucous  membrane  of  the  mouth;  it  lies  on  the  outer 
side  of  the  Genio-hyo-glossus,  accompanied  by  the  lingual  nerve.  On  arriving 
at  the  tip  of  the  tongue  it  is  said  to  anastomose  with  the  artery  of  the  opposite 
side,  but  this  is  denied  by  Hyrtl.  These  vessels  in  the  mouth  are  placed  one  on 
each  side  of  the  frsenum. 

Surgical  Anatomy. — The  lingual  artery  may  be  divided  near  its  origin  in  cases  of  cut  throat, 
a  complication  that  not  unfrequently  happens  in  this  class  of  wounds;  or  severe  hemorrhage 
which  cannot  be  restrained  by  ordinary  means  may  ensue  from  a  wound  or  deep  ulcer  of  the 
tongue.  In  the  former  case  the  primary  wound  may  be  enlarged  if  necessary,  and  the  bleeding 
vessels  secured.  In  the  latter  case  it  has  been  suggested  that  the  lingual  artery  should  be  tied 
near  its  origin.  Ligature  of  the  lingual  artery  is  also  occasionally  practised,  as  a  palliative  measure, 
in  cases  of  cancer  of  the  tongue,  in  order  to  check  the  progress  of  the  disease  by  starving  the 
growth,  and  it  is  sometimes  tied  as  a  preliminary  measure  to  removal  of  the  tongue.  The  operation 
is  a  somewhat  difficult  one,  on  account  of  the  depth  of  the  artery,  the  number  of  important 
structures  by  which  it  is  surrounded,  the  loose  and  yielding  nature  of  the  parts  upon  which  it  is 
supported,  and  its  occasional  irregularity  of  origin.  An  incision  is  to  be  made  in  a  curved  direc- 


THE  EXTERNAL  CAROTID  ARTERY 


eo? 


tion  from  ;i  point  one  finder's  breadth  external  to  the  symphysis  of  the  jaw  downward  to  the 
cornu  of  the  hyoid  bone,  and  then  upward  to  near  the  angle  of  the  jaw.  Care  must  be  taken  not 
to  carry  this  ineision  too  far  backward,  for  fear  of  endangering  the  facial  vein.  In  the  first 
incision  the  skin,  superficial  fascia,  and  Platysma  will  be  divided,  and  the  deep  fascia  exposed. 
The  deep  fascia  is  then  to  be  incised  and  the  submaxillary  gland  exposed  and  pulled  upward  by 
ret  factors.  A  triangular  space  is  now  exposed,  Lesser  s  triangle,  bounded  internally  by  the  pos- 
terior border  of  the  Mylo-hyoid  muscle:  below  and  externally,  by  the  tendon  of  the  Digastric; 
and  above,  by  the  hypoglossal  nerve.  The  floor  of  the  space  is  formed  by  the  Hyo-glossus  muscle, 
beneath  which  the  artery  lies.  The  fibres  of  this  muscle  are  now  to  be  cut  through  horizontally 
and  the  vessel  exposed,  care  being  taken,  while  near  the  vessel,  not  to  open  the  pharynx. 

Troublesome  hemorrhage  may  occur  in  the  division  of  the  frcenum  in  children  if  the  ranine 
arteries,  which  lie  on  each  side  of  it,  are  wounded.  The  student  should  remember  that  the  opera- 
tion is  always  to  be  performed  with  a  pair  of  blunt-pointed  scissors,  and  the  mucous  membrane 
only  is  to  be  divided  by  a  very  superficial  cut,  which  cannot  endanger  any  vessel.  The  scissors, 
also,  should  be  directed  away  from  the  tongue.  Any  further  liberation  of  the  tongue  which  may 
be  necessary  can  be  effected  by  tearing. 

The  Facial  or  External  Maxillary  Artery  (a.  maxillaris  externa)  (Figs.  394, 
395,  396,  and  397)  arises  a  little  above  the  lingual,  and  passes  obliquely  upward, 
beneath  the  Digastric  and  Stylo-hyoid  muscles,  and  frequently  beneath  the  hypo- 
glossal  nerve;  it  now  runs  forward  under  cover  of  the  body  of  the  lower  jaw,  lodged 
in  a  groove  on  the  posterior  surface  of  the  submaxillary  gland ;  this  may  be  called 
the  cervical  part  of  the  artery.  It  then  curves  upward  over  the  body  of  the  jaw 
at  the  anterior  inferior  angle  of  the  Masseter  muscle;  passes  forward  and  upward 
across  the  cheek  to  the  angle  of  the  mouth,  then  upward  along  the  side  of  the  nose, 


ria  septi  nasi. 
erior  coronary. 


Inferior  coronary. 
Inferior  labial. 


FIG.  396. — The  arteries  of  the  face  and  scalp.1 


1  The  muscular  tissue  of  the  lips  must  be  supposed  to  have  been  cut  away,  in  order  to  show  the  courae  of  the 
coronary  arteries 


608  THE  BLOOD-  VASCULAR  SYSTEM 

and  terminates  at  the  inner  canthus  of  the  eye,  under  the  name  of  the  angular  artery. 
The  facial  artery,  both  in  the  neck  and  on  the  face,  is  remarkably  tortuous :  in 
the  former  situation  its  tortuosity  enables  it  to  accommodate  itself  to  the  move- 
ments of  the  pharynx  in  deglutition,  and  in  the  latter  to  the  movements  of  the  jaw 
and  the  lips  and  cheeks. 

Relations. — In  the  neck  its  origin  is  superficial,  being  covered  by  the  integu- 
ment, Platysma,  and  fascia;  it  then  passes  beneath  the  Digastric  and  Stylo-hyoid 
muscles  and  part  of  the  submaxillary  gland.  It  lies  upon  the  middle  constrictor 
of  the  pharynx,  and  is  separated  from  the  Stylo-glossus  and  Hyo-glossus  muscles 
by  a  portion  of  the  submaxillary  gland.  On  the  face,  where  it  passes  over  the 
body  of  the  lower  jaw,  it  is  comparatively  superficial,  lying  immediately  beneath 
the  Platysma.  In  this  situation  its  pulsation  may  be  distinctly  felt,  and  compres- 
sion of  the  vessel  against  the  bone  can  be  effectually  made.  In  its  course  over  the 
face  it  is  covered  by  the  integument,  the  fat  of  the  cheek,  and,  near  the  angle  of  the 
mouth,  by  the  Platysma,  Risorius,  and  Zygomatic  muscles.  It  rests  on  the  Bucci- 
nator, the  Levator  anguli  oris,  and  the  Levator  labii  superioris  (sometimes  piercing 
or  else  passing  under  this  last  muscle).  The  facial  vein  lies  to  the  outer  side  of 
the  artery,  and  takes  a  more  direct  course  across  the  face,  where  it  is  separated 
from  the  artery  by  a  considerable  interval.  In  the  neck  it  lies  superficial  to  the 
artery.  The  branches  of  the  facial  nerve  cross  the  artery,  and  branches  of  the 
infraorbital  nerve  lie  beneath  it. 

Branches. — The  branches  of  this  vessel  may  be  divided  into  two  sets:  those 
given  off  below  the  jaw  (cervical),  and  those  on  the  face  (facial). 

Cervical  Branches.  Facial  Branches. 

Inferior  or  Ascending  Palatine.  Muscular. 

Tonsillar.  Inferior  Labial. 

Submaxillary.  Inferior  Coronary. 

Submental.  Superior  Coronary. 

Muscular.  Lateral  Nasal. 

Angular. 

The  Inferior  or  Ascending  Palatine  (a.  palatine  ascendens)  passes  up  between 
the  Stylo-glossus  and  Stylo-pharyngeus  to  the  outer  side  of  the  pharynx,  along 
which  it  is  continued  between  the  Superior  constrictor  and  the  Internal  ptery- 
goid  to  near  the  base  of  the  skull.  It  supplies  the  neighboring  muscles,  the 
tonsil,  and  Eustachian  tube,  and  divides,  near  the  Levator  palati,  into  two 
branches:  one  follows  the  course  of  the  Levator  palati,  and,  winding  over  the 
upper  border  of  the  Superior  constrictor,  supplies  the  soft  palate  and  the  palatine 
glands,  anastomosing  with  its  fellow  of  the  opposite  side  and  with  the  posterior 
palatine  branch  of  the  internal  maxillary  artery;  the  other  pierces  the  Superior 
constrictor  and  supplies  the  tonsil,  anastomosing  with  the  tonsillar  and  ascending 
pharyngeal  arteries. 

The  Tonsillar  (ramus  tonsillaris)  passes  up  between  the  Internal  pterygoid 
and  Stylo-glossus,  and  then  ascends  along  the  side  of  the  pharynx,  perforating 
the  Superior  constrictor,  to  ramify  in  the  substance  of  the  tonsil  and  root  of  the 
tongue. 

The  Submaxillary  or  Glandular  Branches  (rami  glandulares]  consist  of  three  01 
four  large  vessels,  which  supply  the  submaxillary  gland,  some  being  prolonged  to 
the  neighboring  muscles,  lymphatic  glands,  and  integument. 

The  Submental  (a.  submentalis)  (Fig.  394),  the  largest  of  the  cervical  branches, 
is  given  off  from  the  facial  artery  just  as  that  vessel  quits  the  submaxillary  gland: 
it  runs  forward  upon  the  Mylo-hyoid  muscle,  just  below  the  body  of  the  jaw  and 
beneath  the  Digastric;  after  supplying  the  surrounding  muscles,  and  anastomosing 


THE  EXTERNAL  CAROTID  ARTERY  609 

with  the  sublingual  artery  by  branches  which  perforate  the  mylo-hyoid  muscle,  it 
arrives  at  the  symphysis  of  the  chin,  where  it  turns  over  the  border  of  the  jaw  and 
divides  into  a  superficial  and  a  deep  branch;  the  former  passes  between  the  integu- 
ment and  Depressor  labii  inferioris,  supplies  both,  and  anastomoses  with  the 
inferior  labial.  The  deep  branch  passes  between  the  latter  muscle  and  the  bone, 
supplies  the  lip,  and  anastomoses  with  the  inferior  labial  and  mental  arteries. 

The  Muscular  Branches  are  distributed  to  the  Internal  pterygoid  and  Stylo- 
hyoid  in  the  neck,  and  to  the  Masseter  and  Buccinator  on  the  face. 

The  Inferior  Labial  (a.  labialis  inferior)  (Fig.  396)  passes  beneath  the  Depressor 
anguli  oris,  to  supply  the  muscles  and  integument  of  the  chin  and  lower  lip,  anas- 
tomosing with  the  inferior  coronary  and  submental  branches  of  the  facial,  and  with 
the  mental  branch  of  the  inferior  dental  artery. 

The  Inferior  Coronary  (Figs.  396  and  397)  is  derived  from  the  facial  artery,  near 
the  angle  of  the  mouth :  it  passes  upward  and  inward  beneath  the  depressor  anguli 
oris,  and,  penetrating  the  Orbicularis  oris  muscle,  runs  in  a  tortuous  course  along 
the  edge  of  the  lower  lip  between  this  muscle  and  the  mucous  membrane,  inoscu- 
lating with  the  artery  of  the  opposite  side.  This  artery  supplies  the  labial  glands, 
the  mucous  membrane,  and  muscles  of  the  lower  lip,  and  anastomoses  with  the 
inferior  labial  from  the  facial  and  the  mental  branch  of  the  inferior  dental  artery. 


FIG.  397. — The  coronary  arteries,  the  glands  of  the  lips,  and  the  nerves  of  the  right  side  seen  from  the 
posterior  surface  after  removal  of  the  mucous  membrane.     (Poirier  and  Charpy.) 

The  Superior  Coronary  (a.  labialis  superior)  (Figs.  396  and  397)  is  larger  and  more 
tortuous  in  its  course  than  the  preceding.  It  follows  the  same  course  along,  the 
edge  of  the  upper  lip,  lying  between  the  mucous  membrane  and  the  Orbicularis 
oris,  and  anastomoses  with  the  artery  of  the  opposite  side.  It  supplies  the  textures 
of  the  upper  lip,  and  gives  off  in  its  course  two  or  three  vessels  which  ascend  to  the 
nose.  One,  named  the  inferior  artery  of  the  septum,  ramifies  on  the  septum  of  the 
nostrils  as  far  as  the  point  of  the  nose,  and  there  anastomoses  with  the  naso- 
palatine  artery;  another,  the  artery  of  the  ala,  supplies  the  ala  of  the  nose. 

The  Lateralis  Nasi  is  derived  from  the  facial,  as  that  vessel  is  ascending  along 
the  side  of  the  nose;  it  supplies  the  ala  and  dorsum  of  the  nose,  anastomosing 
with  its  fellow,  the  nasal  branch  of  the  ophthalmic,  the  inferior  artery  of  the  sep- 
tum, the  artery  of  the  ala,  and  the  infraorbital. 

The  Angular  Artery  (a.  angularis)  is  the  termination  of  the  trunk  of  the  facial; 
it  ascends  to  the  inner  angle  of  the  orbit,  embedded  in  the  fibres  of  the  Levator 
labii  superioris  alseque  nasi,  and  accompanied  by  a  large  vein,  the  angular  vein; 
it  distributes  some  branches  on  the  cheek  which  anastomose  with  the  infraorbital. 
After  supplying  the  lachrymal  sac  and  Orbicularis  palpebrarum  muscle,  the 
angular  artery  terminates  by  anastomosing  with  the  nasal  branch  of  the  oph- 
thalmic artery. 

The  anastomoses  of  the  facial  artery  are  very  numerous,  not  only  with  the 

39 


610 


THE  BLOOD-  VASCULAR  SYSTEM 


vessel  of  the  opposite  side,  but,  in  the  neck,  with  the  sublingual  branch  of  the 
lingual;  with  the  ascending  pharyngeal;  and  with  the  posterior  palatine,  a  branch  of 
the  internal  maxillary,  by  its  inferior  or  ascending  palatine  and  tonsillar  branches; 
on  the  face,  with  the  mental  branch  of  the  inferior  dental  as  it  emerges  from  the 
mental  foramen,  with  the  transverse  facial,  a  branch  of  the  temporal;  with  the 
infraorbital,  a  branch  of  the  internal  maxillary,  and  with  the  nasal  branch  of 
the  ophthalmic. 

Peculiarities. — The  facial  artery  not  unfrequently  arises  by  a  common  trunk  with  the  lingual. 
This  vessel  is  also  subject  to  some  variations  in  its  size  and  in  the  extent  to  which  it  supplies 
the  face.  It  occasionally  terminates  as  the  submental,  and  not  unfrequently  supplies  the  face 
only  as  high  as  the  angle  of  the  mouth  or  nose.  The  deficiency  is  then  supplied  by  enlargement 
of  one  of  the  neighboring  arteries. 

Surgical  Anatomy. — The  passage  of  the  facial  artery  over  the  body  of  the  jaw  would  appear 
to  afford  a  favorable  position  for  the  application  of  pressure  in  case  of  hemorrhage  from  the 
lips,  the  result  either  of  an  accidental  wound  or  during  an  operation;  but  its  application  is  useless, 
except  for  a  very  short  time,  on  account  of  the  free  communication  of  this  vessel  with  its  fellow 
and  with  numerous  branches  from  different  sources.  In  a  wound  involving  the  lip  it  is  better 
to  seize  the  part  between  the  fingers,  and  evert  it,  when  the  bleeding  vessel  may  be  at  once  secured 
with  pressure-forceps.  In  order  to  prevent  hemorrhage  in  cases  of  removal  of  diseased  growths 
from  the  part,  the  lip  should  be  compressed  on  each  side  between  the  fingers  and  thumb  or  by 
a  pair  of  specially  devised  clamp-forceps,  whilst  the  surgeon  excises  the  diseased  part.  In  order 
to  stop  hemorrhage  where  the  lip  has  been  divided  in  an  operation,  it  is  necessary,  in  uniting 
the  edges  of  the  wound,  to  pass  the  sutures  through  the  cut  edges  from  the  skin  almost  as  deep 
as  the  mucous  surface;  by  these  means  not  only  are  the  cut  surfaces  more  neatly  and  securely 
adapted  to  each  other,  but  the  possibility  of  hemorrhage  is  prevented  by  including  in  the  suture 

the  divided  artery.  If  the  suture  is,  on  the  contrary,  passed 
through  merely  the  cutaneous  portion  of  the  wound,  hemor- 
rhage occurs  into  the  cavity  of  the  mouth.  The  student 
should,  lastly,  observe  the  relation  of  the  angular  artery  to 
the  lachrymal  sac,  and  it  will  be  seen  that,  as  the  vessel 
passes  up  along  the  inner  margin  of  the  orbit,  it  ascends  on 
its  nasal  side.  In  operating  for  fistula  lacrimalis  the  sac 
should  always  be  opened  on  its  outer  side,  in  order  that  this 
vessel  may  be  avoided. 

The  Occipital  Artery  (a.  occipitalis)  (Figs.  394, 
395,  396,  and  398)  arises  from  the  posterior  part  of 
the  external  carotid,  opposite  the  facial,  near  the 
lower  margin  of  the  Digastric  muscle.  At  its  origin 
it  is  covered  by  the  posterior  belly  of  the  Digastric 
muscle  and  the  Stylo-hyoid  muscle,  and  the  hypo- 
glossal  nerve  winds  around  it  from  behind  forward ; 
higher  up,  it  passes  across  the  internal  carotid  artery, 
the  internal  jugular  vein,  and  the  vagus  and  accessory 
nerves;  it  then  ascends  to  the  interval  between  the 
transverse  process  of  the  atlas  and  the  mastoid  pro- 
cess of  the  temporal  bone,  and  passes  horizontally 
backward,  grooving  the  surface  of  the  latter  bone, 
being  covered  by  the  Sterno-mastoid,  Splenius, 
Trachelo-mastoid,  and  Digastric  muscles,  and  rest- 
ing upon  the  Rectus  lateralis,  the  Superior  oblique, 
and  Complexus  muscles ;  it  then  changes  its  course 

and  passes  vertically  upward,  pierces  the  fascia  which  connects  the  cranial  attach- 
ment of  the  Trapezius  with  the  Sterno-mastoid,  and  ascends  in  a  tortuous  course 
over  the  occiput,  as  high  as  the  vertex,  where  it  divides  into  numerous  branches. 
It  is  accompanied  in  the  latter  part  of  its  course  by  the  great  occipital  nerve,  and 
occasionally  by  a  cutaneous  filament  from  the  suboccipital  nerve. 


DESCENDING 

BRANCH   OF 

HYPOGLOSSAL 

NERVE 


FIG.  398. — The  loop  of  the  hypo- 
glossal  nerve  and  the  branches  of  the 
external  carotid  artery. 


611 

Branches. — The  branches  given  off  from  this  vessel  are — 

Muscular.  Dural  or  Meningeal. 

Sterno-mastoid.  Mastoid. 

Auricular.  Arteria  Princeps  Cervicis. 

The  Muscular  Branches  (rami  musculares)  supply  the  Digastric,  Stylo-hyoid, 
Splenius,  and  Trachelo-mastoid  muscles. 

The  Sterno-mastoid  (a.  sternocleidomastoided)  is  a  large  and  constant  branch, 
generally  arising  from  the  artery  close  to  its  commencement,  but  sometimes 
springing  directly  from  the  external  carotid.  It  first  passes  downward  and  back- 
ward over  the  hypoglossal  nerve,  and  enters  the  substance  of  the  muscle  in  com- 
pany with  the  accessory  nerve. 

The  Auricular  Branch  (ramus  auricularis]  supplies  the  back  part  of  the  concha* 
It  frequently  gives  off  a  branch,  which  enters  the  skull  through  the  mastoid 
foramen  and  supplies  the  dura,  the  diploe,  and  the  mastoid  cells. 

The  Dural  or  Meningeal  Branch  (ramus  meningeus]  ascends  with  the  internal 
jugular  vein,  and  enters  the  skull  through  the  foramen  lacerum  posterius,  or 
through  the  anterior  condyloid  foramen,  to  supply  the  dura  in  the  posterior  fossa. 

The  Mastoid  Branch  (ramus  mastoideus)  is  a  small  vessel,  by  no  means  constant. 
It  passes  into  the  skull  through  the  mastoid  foramen  and  is  distributed  upon  the 
dura  of  the  posterior  fossa. 

The  Arteria  Princeps  Cervicis  (ramus  descendens),  the  largest  branch  of  the 
occipital,  descends  along  the  back  part  of  the  neck  and  divides  into  a  super- 
ficial and  a  deep  portion.  The  former  runs  beneath  the  Splenius,  giving  off 
branches  which  perforate  that  muscle  to  supply  the  Trapezius,  which  anastomose 
with  the  superficial  cervical  artery,  a  branch  of  the  Transversalis  colli :  the  latter 
passes  beneath  the  Complexus  between  it  and  the  Semispinalis  colli,  and  anasto- 
moses with  branches  from  the  vertebral  and  with  the  deep  cervical  artery,  a 
branch  of  either  the  superior  intercostal  or  the  subclavian.  The  anastomosis 
between  these  vessels  serves  mainly  to  establish  the  collateral  circulation  after 
ligation  of  the  carotid  or  subclavian  artery. 

The  cranial  branches  (rami  occipitales)  of  the  occipital  artery  are  distributed 
upon  the  occiput;  they  are  very  tortuous,  and  lie  between  the  integument  and 
Occipito-frontalis,  anastomosing  with  the  artery  of  the  opposite  side,  the  pos- 
terior auricular  and  temporal  arteries.  They  supply  the  back  part  of  the 
Occipito-frontalis  muscle,  the  integument,  and  pericranium. 

The  Posterior  Auricular  Artery  (a.  auricularis  posterior}  (Figs.  394,  395,  and 
396)  is  a  small  vessel  which  arises  from  the  external  carotid,  above  the  Digastric 
and  Stylo-hyoid  muscles,  opposite  the  apex  of  the  styloid  process.  It  ascends, 
under  cover  of  the  parotid  gland,  on  the  styloid  process  of  the  temporal  bone,  to 
the  groove  between  the  cartilage  of  the  ear  and  the  mastoid  process,  immediately 
above  which  it  divides  into  its  two  terminal  branches,  the  auricular  and  mastoid. 
Just  before  arriving  at  the  mastoid  process,  this  artery  is  crossed  by  the  facial 
nerve,  and  has  beneath  it  the  accessory  nerve. 

Branches. — Besides  several  small  branches  to  the  Digastric,  Stylo-hyoid,  and 
Sterno-mastoid  muscles  and  to  the  parotid  gland,  this  vessel  gives  off  three 
branches : 

Stylo-mastoid.  Auricular.  Mastoid. 

The  Stylo-mastoid  Branch  (a.  stylomastoidea)  enters  the  stylo-mastoid  foramen, 
and  supplies  the  tympanum,  mastoid  cells,  and  semicircular  canals.  In  the 
young  subject  a  branch  from  this  vessel  forms,  with  the  tympanic  branch  from 
the  internal  maxillary,  a  vascular  circle,  which  surrounds  the  membrana  tympani, 
and  from  which  delicate  vessels  ramify  on  that  membrane.  It  anastomoses  with 


612  THE  BLOOD-VASCULAR  SYSTEM 

the  petrosal  branch  of  the  medidural  artery  by  a  twig,  which  enters  the  hiatus 
Fallopii. 

The  Auricular  Branch  (ramus  auricularis),  one  of  the  terminal  branches,  ascends 
behind  the  ear,  beneath  the  Retrahens  auriculam  muscle,  and  is  distributed  to 
the  back  part  of  the  cartilage  of  the  ear,  upon  which  it  ramifies  minutely,  some 
branches  curving  round  the  margin  of  the  fibro-cartilage,  others  perforating  it, 
to  supply  its  anterior  surface.  It  anastomoses  with  the  posterior  branch  of  the 
superficial  temporal  and  also  with  the  anterior  auricular  branches. 

The  Mastoid  Branch  (ramus  mastoideus)  passes  backward,  over  the  Sterno- 
mastoid  muscle,  to  the  scalp  above  and  behind  the  ear.  It  supplies  the  posterior 
belly  of  the  Occipito-frontalis  muscles  and  the  scalp  in  this  situation.  It  anasto- 
moses with  the  occipital  artery. 

The  Ascending  Pharyngeal  Artery  (a.  pharyngea  ascendens]  (Figs.  394  and 
395),  the  smallest  branch  of  the  external  carotid,  is  a  long,  slender  vessel,  deeply 
seated  in  the  neck,  beneath  the  other  branches  of  the  external  carotid  and  the 
Stylopharyngeus  muscle.  It  arises  from  the  back  part  of  the  external  carotid,  near 
the  commencement  of  that  vessel,  and  ascends  vertically  between  the  internal 
carotid  and  the  side  of  the  pharynx,  to  the  under  surface  of  the  base  of  the  skull, 
lying  on  the  Rectus  capitis  anticus  major  muscle. 

Branches. — Its  branches  may  be  subdivided  into  four  sets: 

Prevertebral.         Pharyngeal.         Tympanic.         Dural  or  Meningeal. 

The  Prevertebral  Branches  are  numerous  small  vessels  which  supply  the  Recti 
capitis  antici  and  Longus  colli  muscles,  the  sympathetic,  hypoglossal,  and  vagus 
nerves,  and  the  lymphatic  glands.  They  anastomose  with  the  ascending  cervical 
artery. 

The  Pharyngeal  Branches  (rami  pharyngei)  are  three  or  four  in  number.  Two 
of  these  descend  to  supply  the  middle  and  inferior  Constrictors  and  the  Stylo- 
pharyngeus, ramifying  in  the  substance  of  the  muscles  and  in  the  submucous 
tissue  of  the  mucous  membrane  lining  them.  The  largest  of  the  pharyngeal 
branches  passes  inward,  running  upon  the  Superior  constrictor,  and  sends  rami- 
fications to  the  soft  palate  and  tonsil,  which  take  the  place  of  the  ascending 
palatine  branch  of  the  facial  artery  when  that  vessel  is  of  small  size.  A  twig 
from  this  branch  supplies  the  Eustachian  tube. 

The  Tympanic  Branch  (a.  tympanica  inferior)  is  a  small  artery  which  passes 
through  a  minute  foramen  in  the  petrous  portion  of  the  temporal  bone,  in  com- 
pany with  the  tympanic  branch  of  the  Glosso-pharyngeal  nerve  to  supply  the 
inner  wall  of  the  tympanum  and  anastomose  with  the  other  tympanic  arteries. 

The  Dural  or  Meningeal  Branches  consist  of  several  small  vessels,  which  pass 
through  foramina  in  the  base  of  the  skull,  to  supply  the  dura.  One,  the  postdural 
or  posterior  meningeal  (a.  meningea  posterior),  enters  the  cranium  through  the 
foramen  lacerumposterius;  a  second  passes  through  the  foramen  lacerum  medium; 
and  occasionally  a  third  through  the  anterior  condyloid  foramen.  They  are  all 
distributed  to  the  dura. 

Surgical  Anatomy. — The  ascending  pharyngeal  artery  has  been  wounded  from  the  throat, 
as  in  the  case  in  which  the  stem  of  a  tobacco-pipe  was  driven  into  the  vessel,  causing  fatal  hemor- 
rhage. After  removal  of  the  tonsil  there  is  sometimes  severe  bleeding.  This  is  almost  never 
due  to  wounding  of  the  internal  carotid  artery,  as  the  latter  vessel,  if  normally  placed,  is  too 
far  away  to  be  damaged.  The  bleeding  comes  from  branches  of  the  ascending  pharyngeal, 
tonsillar,  or  ascending  palatine  arteries. 

The  Superficial  Temporal  Artery  (a.  temporalis  superficialis)  (Fig.  394, 395,  and 
396),  the  smaller  of  the  two  terminal  branches  of  the  external  carotid,  appears,  from 
its  direction,  to  be  the  continuation  of  that  vessel.  It  commences  in  the  substance 
of  the  parotid  gland,  in  the  interspace  between  the  neck  of  the  lower  jaw  and  the 


THE  EXTERNAL  CAROTID  ARTERY  613 

external  auditory  meatus,  crosses  over  the  posterior  root  of  the  zygoma,  passes 
beneath  the  Attrahens  auriculam  muscle,  lying  on  the  temporal  fascia,  and 
divides,  about  two  inches  above  the  zygomatic  arch,  into  two  branches,  an  anterior 
and  a  posterior.  This  vessel  is  accompanied  by  the  auriculo-temporal  nerve. 

The  Anterior  Temporal  runs  tortuously  upward  and  forward  to  the  forehead, 
supplying  the  muscles,  integument,  and  pericranium  in  this  region,  and  anasto- 
moses with  the  supra-orbital  and  frontal  arteries.  The  terminal  portion  of  the 
anterior  branch  is  called  the  frontal  artery  (ramus  frontalis) . 

The  Posterior  Temporal,  larger  than  the  anterior,  curves  upward  and  backward 
along  the  side  of  the  head,  lying  superficial  to  the  temporal  fascia,  and  inosculates 
with  its  fellow  of  the  opposite  side,  and  with  the  posterior  auricular  and  occipital 
arteries.  The  terminal  portion  of  the  posterior  branch  is  named  the  parietal 
artery  (ramus  parietalis). 

The  superficial  temporal  artery,  as  it  crosses  the  zygoma,  is  covered  by  the 
Attrahens  auriculam  muscle,  and  by  a  dense  fascia  given  off  from  the  parotid 
gland:  it  is  crossed  by  the  tempo  ro-facial  division  of  the  facial  nerve  and  one  or 
two  veins,  and  is  accompanied  by  the  auriculo-temporal  nerve,  which  lies  behind 
it.  Besides  some  twigs  to  the  parotid  gland,  the  articulation  of  the  jaw,  and  the 
Masseter  muscle. 

Branches. — The  branches  of  the  superficial  temporal  artery  are  the — 

Transverse  Facial.  Orbital. 

Middle  Temporal.  Anterior  Auricular. 

The  Transverse  Facial  Branch  (a.  transversa  faciei)  is  given  off  from  the  tem- 
poral before  that  vessel  quits  the  parotid  gland;  running  forward  through  its 
substance,  it  passes  transversely  across  the  face,  between  Stenson's  duct  and 
the  lower  border  of  the  zygoma,  and  divides  on  the  side  of  the  face  into  numerous 
branches,  which  supply  the  parotid  gland,  the  Masseter  muscle,  and  the  integu- 
ment, anastomosing  with  the  facial,  masseteric,  and  infra-orbital  arteries.  This 
vessel  rests  on  the  Masseter,  and  is  accompanied  by  one  or  two  branches  of  the 
facial  nerve.  It  is  sometimes  a  branch  of  the  external  carotid. 

The  Middle  Temporal  Artery  (a.  temporalis  media)  arises  immediately  above 
the  zygomatic  arch,  and,  perforating  the  temporal  fascia,  gives  branches  to  the 
Temporal  muscle,  anastomosing  with  the  deep  temporal  branches  of  the  internal 
maxillary.  It  occasionally  gives  off  an  orbital  branch,  which  runs  along  the  upper 
border  of  the  zygoma,  between  the  two  layers  of  the  temporal  fascia,  to  the  outer 
angle  of  the  orbit.  This  branch,  which  may  arise  directly  from  the  superficial 
temporal  artery,  supplies  the  Orbicularis  palpebrarum,  and  anastomoses  with 
the  lachrymal  and  palpebral  branches  of  the  ophthalmic  artery. 

The  Orbital  Artery  (a.  zygomaticoorbitalis)  comes  off  from  the  temporal  just 
above  the  zygoma  and  is  distributed  to  the  upper  orbital  margin. 

The  Anterior  Auricular  Branches  (rami  auriculares  anteriores)  are  distributed 
to  the  anterior  portion  of  the  pinna,  the  lobule,  and  part  of  the  external  meatus, 
anastomosing  with  branches  of  the  posterior  auricular. 

Surgical  Anatomy. — Formerly  the  operation  of  arteriotomy  was  performed  upon  this  vessel 
in  cases  of  inflammation  of  the  eye  or  brain,  but  at  the  present  time  the  operation  is  obsolete. 
If  the  student  will  consider  the  relations  of  the  trunk  of  the  vessels  as  it  crosses  the  zygomatic 
arch,  with  the  surrounding  structures,  he  will  observe  that  it  is  covered  by  a  thick  and  dense 
fascia,  crossed  by  one  of  the  main  divisions  of  the  facial  nerve  and  one  or  two  veins,  and  accom- 
panied by  the  auriculo-temporal  nerve.  'The  anterior  branch,  on  the  contrary,  is  subcutaneous, 
and  is  a  large  vessel. 

The  Internal  Maxillary  Artery  (a.  maxillaris  internet)  (Figs.  399  and  400),  the 
larger  of  the  two  terminal  branches  of  the  external  carotid,  arises  from  that  vessel 
opposite  the  neck  of  the  condyle  of  the  lower  jaw,  and  is  at  first  imbedded  in  the 


614 


THE  BLOOD-VASCULAR  SYSTEM 


substance  of  the  parotid  gland ;  it  passes  inward  between  the  ramus  of  the  jaw 
and  the  internal  lateral  ligament,  and  then  upon  the  outer  surface  of  the  External 
pterygoid  muscle  to 'the  spheno-maxillary  fossa,  to  supply  the  deep  structures 
of  the  face.  For  convenience  of  description  it  is  divided  into  three  portions :  a 
maxillary,  a  pterygoid,  and  spheno-maxillary. 

In  the  first  part  of  its  course,  the  maxillary  portion,  the  artery  passes  horizontally 
forward  and  inward,  between  the  ramus  of  the  jaw  and  the  internal  lateral  liga- 
ment. The  artery  here  lies  parallel  to  and  a  little  below  the  auriculo-temporal 
nerve;  it  crosses  the  inferior  dental  nerve,  and  lies  along  the  lower  border  of  the 
External  pterygoid  muscle. 


Ant.  Temporal  A. 
Post.  Temporal  A. 


FIG.  399. — The  internal  maxillary  artery  and  its  branches. 


Pterjfffo-palati, 


Parvidu 
Small  M<n 
JUedidural 
Middle  Mem 
Tympanic 


FIG.  400.— Plan  of  the  branches. 

In  the  second  part  of  its  course,  the  pterygoid  portion,  it  runs  obliquely  forward, 
and  upward  upon  the  outer  surface  of  the  External  pterygoid  muscle,  being 
covered  by  the  ramus  of  the  lower  jaw  and  lower  part  of  the  Temporal  muscle; 
or  it  may  pass  on  the  inner  surface  of  the  External  pterygoid  muscle  to  reach  the 
interval  between  its  two  heads,  between  which  it  passes  to  reach  the  spheno- 
maxillary  fossa. 

In  the  third  part  of  its  course,  the  spheno-maxillary  portion,  it  approaches  the 
superior  maxillary  bone,  and  enters  the  spheno-maxillary  fossa  in  the  interval 
between  the  two  heads  of  the  External  pterygoid  muscle,  where  it  lies  in  relation 
with  Meckel's  ganglion,  and  gives  off  its  terminal  branches. 

The  branches  of  this  vessel  may  be  divided  into  three  groups,  corresponding 
with  its  three  divisions. 


THE  EXTERNAL  CAROTID  ARTERY  615 

Branches  of  the  First  or  Maxillary  Portion  (Fig.  400) : 

Anterior  Tympanic.  Parvidural  or  Small  Meningeal. 

Deep  Auricular.  Inferior  Dental. 

Medidural  or  Middle  Meningeal. 

The  Anterior  Tympanic  Branch  (a.  tympanica  anterior]  passes  upward  behind 
the  articulation  of  the  lower  jaw,  enters  the  tympanum  through  the  Glaserian 
fissure,  and  ramifies  upon  the  membrana  tympani,  forming  a  vascular  circle 
around  the  membrane  with  the  stylo-mastoid  artery,  and  anastomosing  with 
the  Vidian  and  the  tympanic  branch  from  the  internal  carotid. 

The  Deep  Auricular  Branch  (a.  auricidaris  profunda)  often  arises  in  common 
with  the  preceding.  It  passes  upward  in  the  substance  of  the  parotid  gland, 
behind  the  temporo-maxillary  articulation,  pierces  the  cartilaginous  or  bony  wall 
of  the  external  auditory  meatus,  and  supplies  its  cuticular  lining  and  the  outer 
surface  of  the  membrana  tympani. 

The  Medidural  or  Middle  Meningeal  Branch  (a.  mediduralis,  a.  meningea  media)  is 
the  largest  of  the  branches  which  supply  the  dura.  It  arises  from  the  internal  max- 
illary, between  the  internal  lateral  ligament  and  the  neck  of  the  jaw,  and  passes 
vertically  upward  between  the  two  roots  of  the  auriculo-temporal  nerve  to  the  fora- 
men spinosum  of  the  sphenoid  bone.  On  entering  the  cranium  it  divides  into  two 
branches,  anterior  and  posterior.  The  anterior  branch,  the  larger,  crosses  the  great 
ala  of  the  sphenoid,  and  reaches  the  groove,  or  canal,  in  the  anterior  inferior  angle 
of  the  parietal  bone;  it  then  divides  into  two  branches  which  spread  out  between  the 
dura  and  internal  surface  of  the  cranium,  one  passing  upward  over  the  parietal  bone 
as  far  as  the  vertex,  and  sending  rami  backward  to  the  occipital  bone,  the  other 
passing  front  to  the  inner  surface  of  the  frontal  bone.  The  posterior  branch 
crosses  the  squamous  portion  of  the  temporal,  and  on  the  inner  surface  of  the 
parietal  bone  divides  into  branches  which  supply  the  posterior  part  of  the  dura 
and  cranium.  The  branches  of  this  vessel  are  distributed  partly  to  the  dura, 
but  chiefly  to  the  bones;  they  anastomose  with  the  arteries  of  the  opposite  side, 
and  with  the  predural  and  postdural  arteries. 

The  medidural  on  entering  the  cranium  gives  off  the  following  collateral 
branches:  1.  Numerous  small  vessels  to  the  Gasserian  ganglion,  and  to  the  dura 
in  this  situation.  2.  A  branch,  the  petrosal  branch  (ramus  petrosus  super ficialis) , 
which  enters  the  hiatus  Fallopii,  supplies  the  facial  nerve,  and  anastomoses  with 
the  stylo-mastoid  branch  of  the  posterior  auricular  artery.  3.  A  minute  superior 
tympanic  branch  (a.  tympanica  superior),  which  runs  in  the  canal  for  the  Tensor 
tympani  muscle,  and  supplies  this  muscle  and  the  lining  membrane  of  the  canal. 
4.  Orbital  branches,  which  pass  through  the  sphenoidal  fissure,  or  through  separate 
canals  in  the  great  wing  of  the  sphenoid  to  anastomose  with  the  lachrymal  or 
other  branches  of  the  ophthalmic  artery.  5.  Temporal  or  anastomotic  branches, 
which  pass  through  the  foramina  in  the  great  wing  of  the  sphenoid  bone  and 
anastomose  in  the  temporal  fossa  with  the  deep  temporal  arteries. 

Surgical  Anatomy. — The  medidural  is  an  artery  of  considerable  surgical  importance,  as 
it  may  be  injured  in  fractures  of  the  temporal  region  of  the  skull.  The  vessel  may  be  ruptured 
by  traumatism,  even  though  the  skull  escapes  fracture.  Rupture  of  the  medidural  artery  will 
be  followed  by  considerable  hemorrhage  between  the  bone  and  dura,  which  may  cause 
compression  of  the  brain  and  require  the  operation  of  trephining  for  its  relief.  This  artery 
crosses  the  anterior  inferior  angle  of  the  parietal  bone  at  a  point  1  \  inches  behind  the  external 
angular  process  of  the  frontal  bone,  and  1 J  inches  above  the  zygoma.  From  this  point  the  ante- 
rior branch  passes  upward  and  slightly  backward  to  the  sagittal  suture,  lying  about  \  inch  to 
J  inch  behind  the  coronal  suture.  The  posterior  branch  passes  upward  and  backward  over  the 
squamous  portion  of  the  temporal  bone.  In  order  to  expose  the  artery  as  it  lies  in  the  groove  in 
the  parietal  bone,  a  semilunar  incision,  with  its  convexity  upward,  should  be  made,  commencing 
an  inch  behind  the  external  angular  process,  and  carried  backward  for  two  inches.  The  struc- 


616  THE  BLOOD- VASCULAR  SYSTEM 

tures  cut  through  are:  (1)  skin;  (2)  superficial  fascia,  with  branches  of  the  superficial  temporal 
vessels  and  nerves;  (3)  the  fascia  continued  down  from  the  aponeurosis  of  the  Occipito-frontalis; 
(4)  the  two  layers  of  the  temporal  fascia;  (5)  the  temporal  muscle;  (6)  the  deep  temporal  vessels; 
(7)  the  pericranium.  The  bone  is  trephined,  the  clot  removed,  and  the  vessel  secured  by 
ligatures,  suture  ligatures,  or  gauze  packing. 

The  Parvidural  or  Small  Meningeal  Branch  (parviduralis,  ramus  meningeus  acces- 
sorius)  is  sometimes  derived  from  the  preceding,  usually  from  the  internal  maxil- 
lary. It  enters  the  skull  through  the  foramen  ovale,  and  supplies  the  Gasserian 
ganglion  and  dura. 

The  Mandibular,  Inferior  Alveolar  or  Inferior  Dental  Branch  (a.  alveolaris  inferior} 
descends  with  the  inferior  dental  nerve  to  the  foramen  on  the  inner  side  of  the 
ramus  of  the  jaw.  It  runs  along  the  dental  canal  in  the  substance  of  the  bone, 
accompanied  by  the  nerve,  and  opposite  the  first  bicuspid  tooth  divides  into  two 
branches,  the  incisor  and  mental ;  the  incisor  branch  is  continued  forward  beneath 
the  incisor  teeth  as  far  as  the  symphysis,  where  it  anastomoses  with  the  artery 
of  the  opposite  side;  the  mental  branch  (a.  mentalis)  escapes  with  the  nerve  at  the 
mental  foramen,  supplies  the  structures  composing  the  chin,  and  anastomoses 
with  the  submental,  inferior  labial  and  inferior  coronary  arteries.  Near  its  origin 
the  inferior  dental  artery  gives  off  a  lingual  branch,  which  descends  with  the  lingual 
(gustatory)  nerve  and  supplies  the  mucous  membrane  of  the  mouth.  As  the 
inferior  dental  artery  enters  the  foramen  it  gives  off  a  mylo-hyoid  branch  (ramus 
mylohyoideus) ,  which  runs  in  the  mylo-hyoid  groove,  and  ramifies  on  the  under 
surface  of  the  Mylo-hyoid  muscle.  The  dental  and  incisor  arteries  during  their 
course  through  the  substance  of  the  bone  give  off  a  few  twigs  which  are  lost  in 
the  cancellous  tissue,  and  a  series  of  branches  which  correspond  in  number  to 
the  roots  of  the  teeth:  these  enter  the  minute  apertures  at  the  extremities  of  the 
fangs  and  supply  the  pulp  of  the  teeth. 

Branches  of  the  Second  or  Pterygoid  Portion  (Fig.  400) : 

Deep  Temporal.  Masseteric. 

Pterygoid.  Buccal. 

These  branches  are  distributed,  as  their  names  imply,  to  the  muscles  in  the 
maxillary  region. 

The  Deep  Temporal  Branches,  two  in  number,  anterior  (a.  temporalis  profunda 
anterior)  and  posterior  (a.  temporalis  profunda  posterior),  each  occupy  that  part 
of  the  temporal  fossa  indicated  by  its  name.  Ascending  between  the  Temporal 
muscle  and  pericranium,  they  supply  that  muscle  and  anastomose  with  the  middle 
temporal  artery.  The  anterior  branch  communicates  with  the  lachrymal  artery 
through  small  branches  which  perforate  the  malar  bone  and  great  wing  of  the 
sphenoid. 

The  Pterygoid  Branches  (rami  pterygoidei),  irregular  in  their  number  and 
origin,  supply  the  Pterygoid  muscles. 

The  Masseteric  (a.  masseterica)  is  a  small  branch  which  passes  outward,  above 
the  sigmoid  notch  of  the  lower  jaw,  to  the  deep  surface  of  the  Masseter  muscle. 
It  supplies  that  muscle,  and  anastomoses  with  the  masseteric  branches  of  the 
facial  and  with  the  transverse  facial  artery. 

The  Buccal  (a.  buccinatoria)  is  a  small  branch  which  runs  obliquely  forward 
between  the  Internal  pterygoid  and  the  ramus  of  the  jaw,  to  the  outer  surface  of 
the  Buccinator,  to  which  it  is  distributed,  anastomosing  with  branches  of  the 
facial  artery. 

Branches  of  the  Third  or  Spheno -maxillary  Portion  (Fig.  400) : 

Superior  Alveolar  or  Alveolar.  Vidian. 

Infraorbital.  Ptery  go-palatine. 

Descending  or  Posterior  Palatine.  Naso-  or  Spheno-palatine. 


THE  EXTERNAL  CAROTID  ARTERY  617 

The  Superior  Alveolar,  Alveolar  or  Posterior  Dental  Branch  (a.  alveolaris  superior 
posterior]  is  given  off  from  the  internal  maxillary  by  a  common  branch  with  the 
infraorbital,  and  just  as  the  trunk  of  the  vessel  is  passing  into  the  spheno-maxillary 
fossa.  Descending  upon  the  tuberosity  of  the  superior  maxillary  bone,  it  divides 
into  numerous  branches,  some  of  which  enter  the  posterior  dental  canals,  to  supply 
the  upper  molar  and  bicuspid  teeth  and  the  lining  of  the  antrum,  and  others  are 
continued  forward  on  the  alveolar  process  to  supply  the  gums  of  the  upper  jaw. 

The  Infraorbital  (a.  infraorbitalis)  appears,  from  its  direction,  to  be  the  con- 
tinuation of  the  trunk  of  the  internal  maxillary.  It  arises  from  that  vessel  by  a 
common  trunk  with  the  preceding  branch,  and  runs  along  the  infra-orbital 
canal  with  the  superior  maxillary  nerve,  emerging  upon  the  face  at  the  infra- 
orbital  foramen,  beneath  the  Levator  labii  superioris  muscle.  Whilst  contained 
in  the  canal,  it  gives  off  branches  which  ascend  into  the  orbit,  and  assist 
in  supplying  the  Inferior  rectus  and  Inferior  oblique  muscles  and  the  lachrymal 
gland.  Other  branches,  anterior  dental  (aa.  alveolar es  superiores  anteriores),  descend 
through  the  anterior  dental  canals  in  the  bone,  to  supply  the  mucous  membrane  of 
the  antrum  and  the  front  teeth  of  the  upper  jaw.  On  the  face,  some  branches  pass 
upward  t6  the  inner  angle  of  the  orbit  and  the  lachrymal  sac,  anastomosing  with 
the  angular  branch  of  the  facial  artery;  other  branches  pass  inward  toward  the 
nose,  anastomosing  with  the  nasal  branch  of  the  ophthalmic;  and  other  branches 
descend  beneath  the  Levator  labii  superioris  muscle,  and  anastomose  with  the 
transverse  facial  and  buccal  arteries. 

The  four  remaining  branches  arise  from  that  portion  of  the  internal  maxillary 
which  is  contained  in  the  spheno-maxillary  fossa. 

The  Descending  or  Posterior  Palatine  (a.  palatina  descendens)  descends  through 
the  posterior  palatine  canal  with  the  anterior  palatine  branch  of  Meckel's  ganglion, 
and,  emerging  from  the  posterior  palatine  foramen,  runs  forward  in  a  groove  on 
the  inner  side  of  the  alveolar  border  of  the  hard  palate  to  the  anterior  palatine 
canal,  where  the  terminal  branch  of  the  artery  passes  upward  through  the  fora- 
men of  Stenson  to  anastomose  with  the  naso-palatine  artery.  Its  branches  are 
distributed  to  the  gums,  the  mucous  membrane  of  the  hard  palate,  and  the 
palatine  glands.  Whilst  it  is  contained  in  the  palatine  canal  it  gives  off  branches 
which  descend  in  the  accessory  palatine  canals  to  supply  the  soft  palate  and 
tonsil,  anastomosing  with  the  ascending  palatine  artery. 

Surgical  Anatomy. — The  position  of  the  descending  palatine  artery  on  the  hard  palate 
should  be  borne  in  mind  in  performing  an  operation  for  the  closure  of  a  cleft  in  the  hard 
palate,  as  the  vessel  is  in  danger  of  being  wounded,  and  may  give  rise  to  formidable  hemor- 
rhage. In  case  it  should  be  wounded  it  may  be  necessary  to  plug  the  posterior  palatine 
canal  in  order  to  arrest  the  bleeding.  This  artery  may  bleed  furiously  in  the  operation  of 
resection  of  the  upper  jaw. 

The  Vidian  Branch  (a.  canalis  pterygoidei)  passes  backward  along  the  Vidian 
canal  with  the  Vidian  nerve.  It  is  distributed  to  the  upper  part  of  the  pharynx 
and  Eustachian  tube,  sending  a  small  branch  into  the  tympanum,  which  anasto- 
moses with  the  other  tympanic  arteries. 

The  Pterygo -palatine  is  a  very  small  branch,  which  passes  backward  through 
the  pterygo-palatine  canal  with  the  pharyngeal  nerve,  and  is  distributed  to  the 
upper  part  of  the  pharynx  and  Eustachian  tube. 

The  Naso-  or  Spheno -palatine  (a.  spheno  palatina)  passes  through  the  spheno- 
palatine  foramen  into  the  cavity  of  the  nose,  at  the  back  part  of  the  superior 
meatus,  and  divides  into  two  branches:  one  internal,  the  naso-palatine  or  artery  of 
the  septum,  passes  obliquely  downward  and  forward  along  the  septum  nasi,  supplies 
the  mucous  membrane,  and  anastomoses  in  front  with  the  terminal  branch  of  the 
descending  palatine  and  the  inferior  artery  of  the  septum,  which  is  a  branch 
of  the  superior  coronary.  The  external  branches,  two  or  three  in  number,  supply 


618  THE  BLOOD-VASCULAR  SYSTEM 

the  mucous  membrane  covering  the  lateral  wall  of  the  nose,  the  antrum,  and 
the  ethmoid  and  sphenoid  cells. 

SURGICAL  ANATOMY  OF  THE  TRIANGLES  OF  THE  NECK 

(Fig.  269). 

The  student  having  considered  the  relative  anatomy  of  the  large  arteries  of  the 
neck  and  their  branches,  and  the  relations  they  bear  to  the  veins  and  nerves,  should 
now  examine  these  structures  collectively,  as  they  present  themselves  in  certain 
regions  of  the  neck,  in  each  of  which  important  operations  are  constantly  being 
performed. 

The  side  of  the  neck  presents  a  somewhat  quadrilateral  outline,  limited,  above, 
by  the  lower  border  of  the  body  of  the  jaw,  and  an  imaginary  line  extending  from 
the  angle  of  the  jaw  to  the  mastoid  process;  below,  by  the  prominent  upper  border 
of  the  clavicle;  in  front,  by  the  median  line  of  the  neck;  behind,  by  the  anterior 
margin  of  the  Trapezius  muscle.  This  space  is  subdivided  into  two  large  triangles 
by  the  Sterno-mastoid  muscle,  which  passes  obliquely  across  the  neck,  from  the 
sternum  and  clavicle  below  to  the  mastoid  process  above.  The  triangular  space 
in  front  of  this  muscle  is  called  the  anterior  triangle;  and  that  behind  it,  me  poste- 
rior triangle. 

Anterior  Triangle  of  the  Neck. — The  anterior  triangle  is  bounded  in  front, 
by  an  imaginary  line  extending  from  the  chin  to  the  sternum;  behind,  by  the 
anterior  margin  of  the  Sterno-mastoid;  its  base,  directed  upward,  is  formed  by 
the  lower  border  of  the  body  of  the  jaw  and  an  imaginary  line  extending  from 
the  angle  of  the  jaw  to  the  mastoid  process;  its  apex  is  below,  at  the  sternum. 
This  space  is  subdivided  into  three  smaller  triangles  by  the  Digastric  muscle 
above  and  the  anterior  belly  of  the  Omo-hyoid  below.  These  smaller  triangles 
are  named,  from  below  upward,  the  inferior  carotid,  the  superior  carotid,  and  the 
submaxillary  triangle. 

The  Inferior  Carotid  Triangle  or  the  Triangle  of  Necessity  is  bounded,  in  front, 
by  the  median  line  of  the  neck;  behind,  by  the  anterior  margin  of  the  Sterno- 
mastoid  ;  above,  by  the  anterior  belly  of  the  Omo-hyoid ;  and  is  covered  by  the 
integument,  superficial  fascia,  Platysma,  and  deep  fascia,  ramifying  between 
which  are  some  of  the  descending  branches  of  the  superficial  cervical  plexus. 
Beneath  these  superficial  structures  are  the  Sterno-hyoid  and  Sterno-thyroid 
muscles,  which,  together  with  the  anterior  margin  of  the  Sterno-mastoid,  conceal 
the  lower  part  of  the  common  carotid  artery.1  The  floor  of  this  triangle  is  formed 
by  the  Longus  colli  muscle  below  and  by  the  Scalenus  anticus  muscle  above,  between 
which  muscles  the  vertebral  artery  and  vein  will  be  found  passing  into  the  foramen 
of  the  transverse  process  of  the  sixth  cervical  vertebra.  A  small  portion  of  the  origin 
of  the  Rectus  capitis  anticus  major  may  also  be  seen  on  the  floor  of  the  space. 

The  common  carotid  artery  is  enclosed  within  its  sheath,  together  with  the 
internal  jugular  vein  and  vagus  nerve;  the  vein  lying  on  the  outer  side  of  the 
artery  on  the  right  side  of  the  neck,  but  overlapping  it  below  on  the  left  side; 
the  nerve  lying  between  the  artery  and  vein,  on  a  plane  posterior  to  both.  In 
front  of  the  sheath  are  a  few  filaments  descending  from  the  loop  of  communica- 
tion between  the  Descendens  and  communicans  hypoglossi;  behind  the  sheath 
are  seen  the  inferior  thyroid  artery,  the  recurrent  laryngeal  nerve,  and  the  sym- 
pathetic nerve;  and  on  its  inner  side,  the  trachea,  the  thyroid  gland — much  more 
prominent  in  the  female  than  in  the  male — and  the  lower  part  of  the  larynx.  By 
cutting  into  the  upper  part  of  this  space  and  slightly  displacing  the  Sterno-mastoid 
muscle  the  common  carotid  artery  may  be  tied  below  the  Omo-hyoid  muscle. 

1  Therefore  the  common  carotid  artery  and  internal  jugular  vein  are  not,  strictly  speaking,  contained  in  this 
triangle,  since  they  are  covered  by  the  Sterno-mastoid  muscle;  that  is  to  say,  lie  behind  the  anterior  border  of 
that  muscle,  which  forms  the  posterior  border  of  the  triangle.  But,  as  they  lie  very  close  to  the  structures 
which  are  really  contained  in  the  triangle,  and  whose  position  it  is  essential  to  remember  in  operating  on  this 
part  of  the  artery,  it  has  seemed  expedient  to  study  the  relations  of  all  these  parts  together. — ED.  of  15th 
English  edition. 


SURGICAL  ANATOMY  OF  THE  TRIANGLES  OF  THE  NECK   619 

The  Superior  Carotid  Triangle  or  the  Triangle  of  Election  is  bounded,  behind, 
by  the  Sterno-mastoid ;  below,  by  the  anterior  belly  of  the  Omo-hyoid;  and 
above,  by  the  posterior  belly  of  the  Digastric  muscle.  It  is  covered  by  the 
integument,  superficial  fascia,  Platysma,  and  deep  fascia,  ramifying  between 
which  are  branches  of  the  facial  and  superficial  cervical  nerves.  Its  floor  is 
formed  by  parts  of  the  Thyro-hyoid  and  Hyo-glossus  muscles,  and  the  Inferior 
and  Middle  constrictor  muscles  of  the  pharynx.  This  space,  when  dissected, 
is  seen  to  contain  the  upper  part  of  the  common  carotid  artery,  which  bifur- 
cates opposite  the  upper  border  of  the  thyroid  cartilage  into  the  external  and 
internal  carotid.  These  vessels  are  occasionally  somewhat  concealed  from  view 
by  the  anterior  margin  of  the  Sterno-mastoid  muscle,  which  overlaps  them. 
The  external  and  internal  carotid  lie  side  by  side,  the  external  being  the  more 
anterior  of  the  two.  The  following  branches  of  the  external  carotid  are  also 
met  with  in  this  space:  the  superior  thyroid,  running  forward  and  downward;  the 
lingual,  directly  forward;  the  facial,  forward  and  upward;  the  occipital,  back- 
ward; and  the  ascending  pharyngeal  directly  upward  on  the  inner  side  of  the 
internal  carotid.  The  veins  met  with  are:  the  internal  jugular,  which  lies  on  the 
outer  side  of  the  common  and  internal  carotid  arteries,  and  veins  corresponding  to 
the  above-mentioned  branches  of  the  external  carotid — viz.,  the  superior  thyroid, 
the  lingual,  facial,  ascending  pharyngeal,  and  sometimes  the  occipital,  all  of 
which  accompany  their  corresponding  arteries  and  terminate  in  the  internal  jugular. 
The  nerves  in  this  space  are  the  following:  In  front  of  the  sheath  of  the  common 
carotid  is  the  descendens  hypoglossi.  The  hypoglossal  nerve  crosses  both  the 
internal  and  external  carotids  above,  curving  round  the  occipital  artery  at  its 
origin.  Within  the  sheath,  between  the  artery  and  vein,  and  behind  both,  is  the 
vagus  nerve;  behind  the  sheath,  the  sympathetic.  On  the  outer  side  of  the  vessels 
the  accessory  nerve  runs  for  a  short  distance  before  it  pierces  the  Sterno-mastoid 
muscle;  and  on  the  inner  side  of  the  external  carotid,  just  below  the  hyoid  bone, 
may  be  seen  the  internal  laryngeal  nerve;  and,  still  more  inferiorly,  the  external 
laryngeal  nerve.  The  upper  part  of  the  larynx  and  lower  part  of  the  pharynx 
are  also  found  in  the  front  part  of  this  space. 

The  Submaxillary  Triangle  corresponds  to  the  part  of  the  neck  immediately 
beneath  the  body  of  the  jaw.  It  is  bounded,  above,  by  the  lower  border  of  the 
body  of  the  jaw  and  a  line  drawn  from  its  angle  to  the  mastoid  process;  below,  by 
the  posterior  belly  of  the  Digastric  muscle  and  the  Stylo-hyoid  muscle;  in  front, 
by  the  anterior  belly  of  the  Digastric.  It  is  covered  by  the  integument,  superficial 
fascia,  Platysma,  and  deep  fascia,  ramifying  between  which  are  branches  of  the 
facial  and  ascending  filaments  of  the  superficial  cervical  nerves.  Its  floor  is  formed 
by  the  Mylo-hyoid  and  Hyo-glossus  muscles.  This  space  contains,  in  front,  the  sub- 
maxillary  gland,  superficial  to  which  is  the  facial  vein,  while  imbedded  in  it  are  the 
facial  artery  and  its  glandular  branches;  beneath  this  gland,  on  the  surface  of  the 
Mylo-hyoid  muscle,  are  the  submental  artery  and  the  mylo-hyoid  artery  and  nerve. 
The  posterior  part  of  this  triangle  is  separated  from  the  anterior  part  by  the  stylo- 
maxillary  ligament:  it  contains  the  external  carotid  artery,  ascending  deeply  in 
the  substance  of  the  parotid  gland :  this  vessel  here  lies  in  front  of,  and  superficial 
to,  the  internal  carotid,  being  crossed  by  the  facial  nerve,  and  gives  off  in  its 
course  the  posterior  auricular,  temporal,  and  internal  maxillary  branches:  more 
deeply  are  the  internal  carotid  artery,  the  internal  jugular  vein,  and  the  vagus 

I  nerve,  separated  from  the  external  carotid  by  the  Stylo-glossus  and  Stylo-pharyn- 
geus  muscles  and  the  glosso-pharyngeal  nerve.1 
1  The  same  remark  will  apply  to  this  triangle  as  was  made  about  the  inferior  carotid  triangle.    The  structures 
enumerated  as  contained  in  the  back  part  of  the  space  lie,  strictly  speaking,  beneath  the  muscles  which  form 
the  posterior  boundary  of  the  triangle;  but  as  it  is  very  important  to  bear  in  mind  their  close  relation  to  the 
parotid  gland  and  its  boundaries  (on  account  of  the  frequency  of  surgical  operations  on  this  gland),  all  these 
parts  are  spoken  of  together. — ED.  of  15th  English  edition. 
' 


620  THE  BLOOD-VASCULAR  SYSTEM 

Posterior  Triangle  of  the  Neck. — The  posterior  triangle  is  bounded,  in  front, 
by  the  Sterno-mastoid  muscle;  behind,  by  the  anterior  margin  of  the  Trapezius; 
its  base  corresponds  to  the  middle  third  of  the  clavicle;  its  apex,  to  the  occiput. 
The  space  is  crossed,  about  an  inch  above  the  clavicle,  by  the  posterior  belly  of 
the  Omo-hyoid,  which  divides  it  unequally  into  two,  an  upper  or  occipital  and  a 
lower  or  subclavian  triangle. 

The  Occipital  Triangle,  the  larger  division  of  the  posterior  triangle,  is  bounded, 
in  front,  by  the  Sterno-mastoid;  behind,  by  the  Trapezius;  below,  by  the  Omo- 
hyoid.  Its  floor  is  formed  from  above  downward  by  the  Splenius,  Levator 
anguli  scapulas,  and  the  Middle  and  Posterior  scaleni  muscles.  It  is  covered 
by  the  integument,  the  Platysma  below,  the  superficial  and  deep  fasciae;  the 
accessory  nerve  is  directed  obliquely  across  the  space  from  the  Sterno-mastoid, 
which  it  pierces,  to  the  under  surface  of  the  Trapezius;  below,  the  descending 
branches  of  the  cervical  plexus  and  the  transversalis  colli  artery  and  vein  cross  the 
space.  A  chain  of  lymphatic  glands  is  also  found  running  along  the  posterior 
border  of  the  Sterno-mastoid,  from  the  mastoid  process  to  the  root  of  the  neck. 

The  Subclavian  Triangle,  the  smaller  of  the  two  posterior  triangles,  is  bounded, 
above,  by  the  posterior  belly  of  the  Omo-hyoid;  below,  by  the  clavicle,  its  base, 
directed  forward,  being  formed  by  the  Sterno-mastoid.  The  size  of  the  subclavian 
triangle  varies  according  to  the  extent  of  attachment  of  the  clavicular  portion  of  the 
Sterno-mastoid  and  Trapezius  muscles,  and  also  according  to  the  height  at  which 
the  Omo-hyoid  crosses  the  neck  above  the  clavicle.  Its  height  also  varies  much 
according  to  the  position  of  the  arm,  being  much  diminished  by  raising  the  limb, 
on  account  of  the  ascent  of  the  clavicle,  and  increased  by  drawing  the  arm  down- 
ward, when  that  bone  is  depressed.  This  space  is  covered  by  the  integument, 
the  Platysma,  the  superficial  and  deep  fasciae,  and  crossed  by  the  descending 
branches  of  the  cervical  plexus.  Just  above  the  level  of  the  clavicle  the  third 
portion  of  the  subclavian  artery  curves  outward  and  downward  from  the  outer 
margin  of  the  Scalenus  anticus,  across  the  first  rib,  to  the  axilla.  Sometimes  this 
vessel  rises  as  high  as  an  inch  and  a  half  above  the  clavicle,  or  to  any  point  inter- 
mediate between  this  and  its  usual  level.  Occasionally  it  passes  in  front  of  the 
Scalenus  anticus  or  pierces  the  fibres  of  that  muscle.  The  subclavian  vein  lies 
behind  the  clavicle,  and  is  usually  not  seen  in  this  space;  but  it  occasionally  rises 
as  high  up  as  the  artery,  and  has  even  been  seen  to  pass  with  that  vessel  behind 
the  Scalenus  anticus.  The  brachial  plexus  of  nerves  lies  above  the  artery,  and 
in  close  contact  with  it.  Passing  transversely  behind  the  clavicle  are  the  supra- 
scapular  vessels,  and  traversing  its  upper  angle  in  the  same  direction,  the  trans- 
versalis colli  artery  and  vein.  The  external  jugular  vein  runs  vertically  downward 
behind  the  posterior  border  of  the  Sterno-mastoid  muscle,  to  terminate  in  the 
subclavian  vein;  it  receives  the  transverse  cervical  and  suprascapular  veins,  which 
occasionally  form  a  plexus  in  front  of  the  artery,  and  a  small  vein  which  crosses 
the  clavicle  from  the  cephalic.  The  small  nerve  to  the  Subclavius  muscle  also 
crosses  this  triangle  about  its  middle.  A  lymphatic  gland  is  also  found  in  the  space. 
Its  floor  is  formed  by  the  first  rib  with  the  first  digitation  of  the  Serratus  magnus. 

The  Internal  Carotid  Artery  (A.  Carotis  Interna). 

The  internal  carotid  artery  supplies  the  anterior  part  of  the  brain,  the  eye, 
and  its  appendages,  and  sends  branches  to  the  forehead  and  nose.  Its  size 
in  the  adult  is  equal  to  that  of  the  external  carotid,  though  in  the  child  it  is 
larger  than  that  vessel.  It  is  remarkable  for  the  number  of  curvatures  that  it 
presents  in  different  parts  of  its  course.  It  occasionally  has  one  or  two  flexures 
near  the  base  of  the  skull,  whilst  in  its  passage  through  the  carotid  canal  and 
along  the  side  of  the  body  of  the  sphenoid  bone  it  describes  a  double  curve 
which  resembles  somewhat  the  letter  S  placed  horizontally.  These  curvatures  most 


THE  INTERNAL  CAROTID  ARTERY 


621 


probably  diminish  the  velocity  of  the  current  of  blood,  by  increasing  the  extent  of 
surface  over  which  it  moves  and  adding  to  the  impediment  produced  from  friction. 

In  considering  the  course  and  relations  of  this  vessel  it  may  be  conveniently 
divided  into  four  portions:  the  cervical,  petrous,  cavernous,  and  cerebral  portions. 

Cervical  Portion. — This  portion  of  the  internal  carotid  commences  at  the 
bifurcation  of  the  common  carotid,  opposite  the  upper  border  of  the  thyroid 


M  Aortic 


FIG.  401. — The  internal  carotid  and  vertebral  arteries.     Right  side. 


cartilage,  and  runs  perpendicularly  upward,  in  front  of  the  transverse  processes 
of  the  three  upper  cervical  vertebrae,  to  the  carotid  canal  in  the  petrous  portion 
of  the  temporal  bone.  It  is  superficial  at  its  commencement,  being  contained  in  the 
superior  carotid  triangle,  and  lying  on  the  same  level  as  the  external  carotid,  but 
behind  that  artery  overlapped  by  the  Sterno-mastoid  and  covered  by  the  deep 


622  THE  BLOOD-VASCULAR  SYSTEM 

fascia,  Platysma,  and  integument:  it  then  passes  beneath  the  parotid  gland,  being 
crossed  by  the  hypoglossal  nerve,  the  Digastric  and  Stylo-hyoid  muscles,  and 
the  occipital  and  posterior  auricular  arteries.  Higher  up,  it  is  separated  from  the 
external  carotid  by  the  Stylo-glossus  and  Stylo-pharyngeus  muscles,  the  glosso- 
pharyngeal  nerve,  and  pharyngeal  branch  of  the  vagus. 

Relations. — It  is  in  relation,  behind,  with  the  Rectus  capitis  anticus  major,  the 
superior  cervical  ganglion  of  the  sympathetic,  and  superior  laryngeal  nerve;  exter- 
nally, with  the  internal  jugular  vein  and  vagus  nerve,  the  nerve  lying  on  a  plane 
posterior  to  the  artery;  internally,  with  the  pharynx,  tonsil,  the  superior  laryngeal 
nerve,  and  ascending  pharyngeal  artery.  At  the  base  of  the  skull  the  glosso- 
pharyngeal,  vagus,  accessory,  and  hypoglossal  nerves  lie  between  the  artery  and 
the  internal  jugular  vein. 

PLAN  OF  THE  RELATIONS  OF  THE  INTERNAL  CAROTID  ARTERY  IN  THE  NECK. 

In  front. 

Skin,  superficial  and  deep  fasciae. 
Platysma. 
Sterno-mastoid. 

Occipital  and  posterior  auricular  arteries. 
Hypoglossal  nerve. 
Parotid  gland. 

Stylo-glossus  and  Stylo-pharyngeus  muscles. 
Glosso-pharyngeal  nerve. 
Pharyngeal  branch  of  the  vagus. 

Externally.  /  \  Internally. 

Internal  jugular  vein.  /      Carotid1      )  Pharynx. 

Vagus  nerve.  \       Artery.       1  Superior  laryngeal  nerve. 

V  /  Ascending  pharyngeal  artery. 

Tonsil. 
Behind. 

Rectus  capitis  anticus  major. 
Sympathetic. 
Superior  laryngeal  nerve. 

Petrous  Portion. — When  the  internal  carotid  artery  enters  the  canal  in  the 
petrous  portion  of  the  temporal  bone,  it  first  ascends  a  short  distance,  then  curves 
forward  and  inward,  and  again  ascends  as  it  leaves  the  canal  to  enter  the  cavity  of 
the  skull  between  the  lingula  and  petrosal  process.  In  this  canal  the  artery  lies 
at  first  in  front  of  the  cochlea  and  tympanum ;  from  the  latter  cavity  it  is  separated 
by  a  thin,  bony  lamella,  which  is  cribriform  in  the  young  subject,  and  is  often 
absorbed  in  old  age.  Farther  forward  it  is  separated  from  the  Gasserian  ganglion 
by  a  thin  plate  of  bone,  which  forms  the  floor  of  the  fossa  for  the  ganglion  and  the 
roof  of  the  horizontal  portion  of  the  canal.  Frequently  this  bony  plate  is  more 
or  less  deficient,  and  then  the  ganglion  is  separated  from  the  artery  by  a  fibrous 
membrane.  The  artery  is  separated  from  the  bony  wall  of  the  carotid  canal  by  a 
prolongation  of  the  dura,  and  is  surrounded  by  a  number  of  small  veins  and 
by  filaments  of  the  carotid  plexus,  derived  from  the  ascending  branch  of  the 
superior  cervical  ganglion  of  the  sympathetic. 

Cavernous  Portion. — The  internal  carotid  artery  in  this  part  of  its  course  is 
situated  between  the  layers  of  the  dura  forming  the  cavernous  sinus,  but  is  covered 
by  the  lining  membrane  of  the  sinus.  It  at  first  ascends  to  the  posterior  clinoid 
process,  then  passes  forward  by  the  side  of  the  body  of  the  sphenoid  bone,  and 
again  curves  upward  on  the  inner  side  of  the  anterior  clinoid  process,  and  per- 
forates the  dura,  forming  the  roof  of  the  sinus.  In  this  part  of  its  course  it  is 
surrounded  by  filaments  of  the  sympathetic  nerve,  and  has  in  relation  with  it 
externally  the  abducent  nerve. 


THE  INTERNAL  CAROTID  ARTERY  623 

Cerebral  Portion. — Having  perforated  the  dura,  on  the  inner  side  of  the  anterior 
clinoid  process,  the  internal  carotid  passes  between  the  optic  and  oculomotor 
nerves  to  the  preperforatum  at  the  inner  extremity  of  the  fissure  of  Sylvius,  where 
it  gives  off  its  terminal  or  cerebral  branches.  This  portion  of  the  artery  has  the 
optic  nerve  on  its  inner  side,  and  the  oculomotor  nerve  externally. 

Peculiarities. — The  length  of  the  internal  carotid  varies  according  to  the  length  of  the  neck, 
and  also  according  to  the  point  of  bifurcation  of  the  common  carotid.  Its  origin  sometimes 
takes  place  from  the  arch  of  the  aorta;  in  such  rare  instances  this  vessel  has  been  found  to  be 
placed  nearer  the  middle  line  of  the  neck  than  the  external  carotid,  as  far  upward  as  the  larynx, 
when  the  latter  vessel  crossed  the  internal  carotid.  The  course  of  the  vessel,  instead  of  being 
straight,  may  be  very  tortuous.  A  few  instances  are  recorded  in  which  this  vessel  was  altogether 
absent:  in  one  of  these  the  common  carotid  passed  up  the  neck,  and  gave  off  the  usual  branches 
of  the  external  carotid,  the  cranial  portion  of  the  internal  carotid  being  replaced  by  two  branches 
of  the  internal  maxillary,  which  entered  the  skull  through  the  foramen  rotundum  and  the  foramen 
ovale  and  joined  to  form  a  single  vessel. 

Surgical  Anatomy. — The  cervical  part  of  the  internal  carotid  is  very  rarely  wounded.  Mr. 
Cripps,  in  an  interesting  paper  in  the  Medico-Chirurgical  Transactions,  compares  the  rareness 
of  a  wound  of  the  internal  carotid  with  one  of  the  external  carotid  or  its  branches.  It  is,  however, 
sometimes  injured  by  a  stab  or  gunshot  wound  in  the  neck,  or  even  occasionally  by  a  stab  from 
within  the  mouth,  as  when  a  person  receives  a  thrust  from  the  end  of  a  parasol  or  falls  down 
with  a  tobacco-pipe  in  his  mouth.  It  used  to  be  believed  that  the  internal  carotid  was  occa- 
sionally wounded  in  the  removal  of  the  tonsil.  Such  an  accident  cannot  happen  if  the  artery  is 
normally  placed.  The  severe  and  sometimes  fatal  hemorrhage  which  has  followed  this  opera- 
tion in  a  few  instances  probably  had  as  its  source  enlarged  branches  of  the  ascending  pharyn- 
geal,  tonsillar,  or  ascending  palatine  arteries.  Recently,  however,  Dr.  Gwilym  G.  Davis,  of 
Philadelphia,  demonstrated  a  specimen  in  which  the  internal  carotid  could  have  been  wounded 
by  incision  of  the  tonsil.  The  indications  for  ligature  are  wounds,  when  the  vessel  should  be 
exposed  by  a  careful  dissection  and  tied  above  and  below  the  bleeding  point;  and  aneurism, 
which  if  non-traumatic  may  be  treated  by  ligature  of  the  common  carotid,  but  if  traumatic  in 
origin  by  exposing  the  sac  and  tying  the  vessel  above  and  below.  The  incision  for  ligature  of 
the  cervical  portion  of  the  internal  carotid  should  be  made  along  the  anterior  border  of  the 
Sterno-mastoid,  from  the  angle  of  the  jaw  to  the  upper  border  of  the  thyroid  cartilage.  The 
superficial  structures  being  divided  and  the  SteAo-mastoid  defined  and  drawn  outward,  the 
cellular  tissue  must  be  carefully  separated  and  the  posterior  belly  of  the  Digastric  muscle  and 
the  hypoglossal  nerve  sought  for  as  guides  to  the  vessel.  When  the  artery  is  found  the  external 
carotid  should  be  drawn  inward  and  the  Digastric  muscles  upward,  and  the  aneurism  needle 
passed  from  without  inward. 

Branches. — The  branches  given  off  from  the  internal  carotid  artery  are — 

From  the  Petrous  portion     .     Tympanic  (internal  or  deep). 

(  Arterise  Receptaculi. 
From  the  Cavernous  portion  <  Predural,  or  Anterior  Meningeal. 

(^  Ophthalmic. 

rPrecerebral,  or  Anterior  Cerebral. 

Medicerebral,  or  Middle  Cerebral. 
From  the  Cerebral  portion  .  j  Postcommunicantj  or  Posterior  Communicating. 

(^Prechoroid,  or  Anterior  Choroid. 

The  cervical  portion  of  the  internal  carotid  gives  off  no  branches. 

The  Tympanic  (ramus  caroticotympanicus]  is  a  small  branch  from  the  petrous 
portion,  which  enters  the  cavity  of  the  tympanum  through  a  minute  foramen  in 
the  carotid  canal,  and  anastomoses  with  the  tympanic  branch  of  the  internal 
maxillary,  and  with  the  stylo-mastoid  artery. 

The  Arteriae  Receptaculi  are  numerous  small  vessels,  derived  from  the  inter- 
nal carotid  in  the  cavernous  sinus;  they  supply  the  pituitary  body,  the  Gasserian 
ganglion,  and  the  walls  of  the  cavernous  and  inferior  petrosal  sinuses.  Some  of 
these  branches  anastomose  with  branches  of  the  medidural. 

The  Predural  or  Anterior  Meningeal  (a.  praeduralis,  a.  meningea  anterior}  is  a 
small  branch  which  passes  over  the  lesser  wing  of  the  sphenoid  to  supply  the  dura 
of  the  anterior  fossa;  it  anastomoses  with  the  dural  branch  from  the  posterior 
ethmoid al  artery. 


624 


THE  BLOOD-VASCULAR  SYSTEM 


The  Ophthalmic  Artery  (a.  ophthalmica)  arises  from  the  internal  carotid, 
just  as  that  vessel  is  emerging  from  the  cavernous  sinus,  on  the  inner  side  of  the 
anterior  clinoid  process,  and  enters  the  orbit  through  the  optic  foramen,  below  and 


Nasal.        Palpebral. 


Supra-orbital. 


Anterior  ethmoidal. 


Posterior  ethmoidal. 


Muscular. 


Temporal  branches 

Arterial  J        of 
centralis  retinse. 


Ophthalmic- 


Internal  carotid. 


FIG.  402. — The  ophthalmic  artery  and  its  branches,  the  roof  of  the  orbit  having  been  removed. 

on  the  outer  side  of  the  optic  nerve.  It  then  passes  over  the  nerve  to  the  inner  wall 
of  the  orbit,  and  thence  horizontally  forward,  beneath  the  lower  border  of  the 
Superior  oblique  muscle,  to  a  point  behind  the  internal  angular  process  of  the 
frontal  bone,  where  it  divides  into  two  terminal  branches,  the  frontal  and  nasal 
branches.  As  the  artery  crosses  the  optic  nerve  it  is  accompanied  by  the  nasal 
nerve,  and  is  separated  from  the  frontal  nerve  by  the  Rectus  superior  and 
Levator  palpebrse  superioris  muscles. 

Branches. — The  branches  of  this  vessel  may  be  divided  into  an  orbital  group, 
which  are  distributed  to  the  orbit  and  surrounding  parts,  and  an  ocular  group, 
which  supply  the  muscles  and  globe  of  the  eye: 


Orbital  Group. 
Lachrymal. 
Supraorbital. 
Posterior  Ethmoidal. 
Anterior  Ethmoidal. 
Internal  Palpebral. 
Frontal. 
Nasal. 


Ocular  Group.- 
Short  Ciliary. 
Long  Ciliary. 
Anterior  Ciliary. 
Arteria  Centralis  Retinae. 
Muscular. 


The  Lachrymal  (a.  lachrimalis)  is  one  of  the  largest  branches  derived  from  the 
ophthalmic,  arising  close  to  the  optic  foramen;  not  infrequently  it  is  given  off  from 
the  ophthalmic  artery  before  it  enters  the  orbit.  It  accompanies  the  lachrymal  nerve 
along  the  upper  border  of  the  External  rectus  muscle,  and  is  distributed  to  the 


THE  INTKItXAL   CAROTID  ARTERY  625 

lachrymal  gland.  Its  terminal  branches,  escaping  from  the  gland,  are  distributed  to 
the  eyelids  and  conjunctiva :  of  those  supplying  the  eyelids,  two  are  of  considerable 
size  and  are  named  the  external  palpebral ;  they  run  inward  in  the  upper  and  lower 
lids  respectively,  and  anastomose  with  the  internal  palpebral  arteries,  forming  an 
arterial  circle  in  this  situation.  The  lachrymal  artery  gives  off  one  or  two  malax 
branches,  one  of  which  passes  through  a  foramen  in  the  malar  bone,  to  reach  the 
temporal  fossa,  and  anastomoses  with  the  deep  temporal  arteries;  the  other  appears 
on  the  cheek  through  the  malar  foramen,  and  anastomoses  with  the  transverse  facial. 
A  branch,  the  recurrent,  is  also  sent  backward  through  the  sphenoidal  fissure  to  the 
dura,  which  anastomoses  with  a  branch  of  the  medidural  artery. 

Peculiarities. — The  lachrymal  artery  is  sometimes  derived  from  one  of  the  anterior  branches 
of  the  medidural  artery. 

The  Supraorbital  Artery  (a.  supraorbitalis)  arises  from  the  ophthalmic  as  that 
vessel  is  crossing  over  the  optic  nerve.  Ascending  so  as  to  arise  above  all  the  muscles 
of  the  orbit,  it  passes  forward,  with  the  supraorbital  nerve,  between  the  periosteum 
and  Levator  palpebne  muscle;  and,  passing  through  the  supraorbital  foramen, 
divides  into  a  superficial  and  deep  branch,  which  supply  the  integument,  the 
muscles,  and  the  pericranium  of  the  forehead,  anastomosing  with  the  frontal,  the 
anterior  branch  of  the  temporal,  and  the  supraorbital  artery  of  the  opposite  side. 
This  artery  in  the  orbit  supplies  the  Superior  rectus  and  the  Levator  palpebne 
muscles,  and  sends  a  branch  inward,  across  the  pulley  of  the  Superior  oblique 
muscle,  to  supply  the  parts  at  the  inner  canthus.  At  the  supraorbital  foramen 
it  frequently  transmits  a  branch  to  the  diploe. 

The  Ethmoidal  Branches  are  two  in  number— posterior  (a.  ethmoidalis  posterior) 
and  anterior  (a.  ethmoidalis  anterior).  The  former,  which  is  the  smaller,  passes 
through  the  posterior  ethmoidal  foramen,  supplies  the  posterior  ethmoidal  cells, 
and,  entering  the  cranium,  gives  off  a  dural  or  meningeal  branch,  which  supplies  the 
adjacent  dura;  and  nasal  branches  which  descend  into  the  nose  through  aper- 
tures in  the  cribriform  plate,  anastomosing  with  branches  of  the  spheno-palatine. 
The  anterior  ethmoidal  artery  accompanies  the  nasal  nerve  through  the  anterior 
ethmoidal  foramen,  supplies  the  anterior  ethmoidal  cells  and  frontal  sinuses,  and, 
entering  the  cranium, gives  off  a  dural  branch  which  supplies  the  adjacent  dura; 
and  nasal  branches,  which  descend  into  the  nose,  through  the  slit  by  the  side  of 
the  crista  galli,  and,  running  along  the  groove  on  the  under  surface  of  the  nasal 
bone,  supply  the  skin  of  the  nose. 

The  Internal  Palpebral  Arteries  (aa.  palpebrales  mediates),  two  in  number,  supe- 
rior and  inferior,  arise  from  the  ophthalmic,  opposite  the  pulley  of  the  Superior 
oblique  muscle;  they  leave  the  orbit  to  encircle  the  eyelids  near  their  free  margin, 
forming  a  superior  tarsal  arch  (arcus  tarseus  superior}  and  an  inferior  tarsal  arch  (arcus 
tarseus  inferior),  which  lie  between  the  Orbicularis  muscle  and  the  tarsal  plates; 
the  superior  palpebral  inosculating  at  the  outer  angle  of  the  orbit  with  the  orbital 
branch  of  the  temporal  artery,  and  with  the  upper  of  the  two  external  palpebral 
branches  from  the  lachrymal  artery — the  inferior  palpebral  inosculating,  at  the 
outer  angle  of  the  orbit,  with  the  lower  of  the  two  external  palpebral  branches 
from  the  lachrymal  and  with  the  transverse  facial  artery,  and  at  the  inner  side 
of  the  lid  with  a  branch  from  the  angular  artery.  From  this  last  anastomosis  a 
branch  passes  to  the  nasal  duct,  ramifying  in  its  mucous  membrane,  as  far  as  the 
inferior  meatus. 

The  Frontal  Artery  (a.  frontalis),  one  of  the  terminal  branches  of  the  ophthalmic, 
passes  from  the  orbit  at  its  inner  angle,  and,  ascending  on  the  forehead,  supplies 
the  integument,  muscles,  and  pericranium,  anastomosing  with  the  supraorbital 
artery  and  with  the  frontal  artery  of  the  opposite  side. 

40 


626 


THE  BLOOD-VASCULAR  SYSTEM 


The  Nasal  Artery  (a.  dorsalis  nasi),  the  other  terminal  branch  of.  the  ophthalmic,, 
emerges  from  the  orbit  above  the  tendo  oculi,  and,  after  giving  a  branch  to  the 
upper  part  of  the  lachrymal  sac,  divides  into  two  branches,  one  of  which  crosses 
the  root  of  the  nose,  the  transverse  nasal,  and  anastomoses  with  the  angular  artery; 
the  other,  the  dorsalis  nasi,  runs  along  the  dorsum  of  the  nose,  supplies  its  outer 
surface,  and  anastomoses  with  the  artery  of  the  opposite  side  and  with  the  lateral 
nasal  branch  of  the  facial. 


FIG.  403. — The  arteries  of  the  base  of  the  brain.  The  right  half  of  the  cerebellum  and  pons  have  been  re- 
moved. N.  B. — It  will  be  noticed  that  the  two  precerebral  arteries  have  been  drawn  at  a  considerable  distance 
from  each  other:  this  makes  the  precommunicant  artery  appear  very  much  longer  than  it  really  is. 


THE  INTERNAL  CARO1ID  ARTERY 


627 


The  Ciliary  Arteries  (a.  ciliares)  are  divisible  into  three  groups,  the  short,  long, 
and  anterior.  The  short  ciliary  arteries  (aa.  ciliaris  posteriores  breves),  from  six 
to  twelve  in  number,  arise  from  the  ophthalmic  or  some  of  its  branches;  they  sur- 
round the  optic  nerve  as  they  pass  forward  to  the  posterior  part  of  the  eyeball, 
pierce  the  sclerotic  coat  around  the  entrance  of  the  nerve,  and  supply  the  choroid 
coat  and  ciliary  processes.  The  long  ciliary  arteries  (aa.  ciliares  posteriores  longae) , 
two  in  number,  pierce  the  posterior  part  of  the  sclerotic  at  some  little  distance  from 
the  optic  nerve,  and  run  forward,  along  each  side  of  the  eyeball,  between  the 
sclerotic  and  choroid,  to  the  ciliary  muscle,  where  they  divide  into  two  branches; 
these  form  an  arterial  circle,  the  circulus  major,  around  the  circumference  of  the 
iris,  from  which  numerous  radiating  branches  pass  forward,  in  its  substance,  to 
its  free  margin,  where  they  form  a  second  arterial  circle,  the  circulus  minor,  around 
its  pupillary  margin.  The  anterior  ciliary  arteries  (aa.  ciliares  anteriores)  are 


Fro.  404. — Vascular  area 'of  the  upper  surface  of  the  cerebrum.  I.  The  part  supplied  by  the  external  and 
inferior  frontal  artery.  II.  The  part  supplied  by  the  ascending  frontal.  III.  The  part  supplied  by  the 
ascending  parietal.  IV.  The  part  supplied  by  the  sphenoparietal  artery.  (After  Duret.) 

derived  from  the  muscular  branches;  they  pass  to  the  front  of  the  eyeball  in  com- 
pany with  the  tendons  of  the  Recti  muscles,  form  a  vascular  zone  beneath  the 
conjunctiva,  and  then  pierces  the  sclerotic  a  short  distance  from  the  cornea  and 
terminate  in  the  circulus  major  of  the  iris. 

The  Arteria  Centralis  Retinae  is  the  first  and  one  of  the  smallest  branches  of  the 
ophthalmic  artery.  It  runs  for  a  short  distance  within  the  dural  sheath  of  the 
optic  nerve,  but  about  half  an  inch  behind  the  eyeball  it  pierces  the  optic  nerve 
obliquely,  and  runs  forward  in  the  centre  of  its  substance,  and  enters  the  globe 
of  the  eye  through  the  porus  opticus.  Its  mode  of  distribution  will  be  described 
in  the  account  of  the  anatomy  of  the  eye. 

The  Muscular  Branches  (rami  musculares) ,  two  in  number,  superior  and  inferior, 
frequently  spring  from  a  common  trunk.  The  superior,  the  smaller,  often  wanting, 


628 


THE  BLOOD-VASCULAR  SYSTEM 


supplies  the  Levator  palpebrse,  Superior  rectus,  and  Superior  oblique.  The  infe- 
rior, more  constant  in  its  existence,  passes  forward  between  the  optic  nerve  and 
the  Inferior  rectus  muscle,  and  is  distributed  to  the  External,  Internal,  and 
Inferior  recti,  and  Inferior  oblique.  This  vessel  gives  off  most  of  the  anterior 
ciliary  arteries.  Additional  muscular  branches  are  given  off  from  the  lachrymal 
and  supraorbital  arteries  or  from  the  ophthalmic  itself. 

(For  the  Circulus  or  Circle  of  Willis,  the  postcerebral  artery,  and  the  blood- 
vessels of  the  cerebellum,  see  page  642.) 

The  Precerebral  or  Anterior  Cerebral  (a.  praecerebralis,  a.  cerebri  anterior) 
arises  from  the  internal  carotid  at  the  inner  extremity  of  the  fissure  of  Sylvius.  It 
passes  forward  and  inward  across  the  preperforatum,  above  the  optic  nerve,  to  the 
commencement  of  the  intercerebral  fissure.  Here  it  comes  into  close  relationship 
with  the  precerebral  artery  of  the  opposite  side,  and  the  two  vessels  are  connected 
together  by  a  short  anastomosing  trunk,  about  two  lines  in  length,  the  precommuni- 
cant  or  anterior  communicating  artery.  From  this  point  the  two  vessels  run  side  by 


Central  Fissure 


Occipital 
'Fissure 


FIG.  405. — Vascular  area  of  the  internal  surface  of  the  cerebrum.  I.  The  part  supplied  by  the  anterior 

internal  frontal.     II.  The  part  supplied  by  the  middle  internal  frontal.  III.  The  part  supplied  by  the  posterior 

internal  frontal.  IV.  The  part  supplied  by  the  posterior  temporal.  V.  The  part  supplied  by  the  occipital,  both 
terminal  branches  of  the  posterior  cerebral.  (After  Duret.) 

side  in  the  intercerebral  fissure,  curve  round  thegenu  of  the  callosum,and,  turning 
backward,  continue  along  its  upper  surface  to  its  posterior  part,  where  they  ter- 
minate by  anastomosing  with  the  postcerebral  arteries. 

Branches. — In  their  course  the  precerebral  arteries  give  off  the  following 
branches : 

Antero-median  ganglionic.  Anterior  internal  frontal. 

Inferior  internal  frontal.  Middle  internal  frontal. 

Posterior  internal  frontal. 

The  Antero-median  Ganglionic  is  a  group  of  small  arteries  which  arise  at  the 
commencement  of  the  precerebral  artery;  they  pierce  the  preperforatum  and 
terma,  and  supply  the  head  of  the  caudatum. 

The  Inferior  Internal  Frontal  Branches  or  the  Internal  Orbital  Arteries,  two  or 
three  in  number,  are  distributed  to  the  orbital  surface  of  the  frontal  lobe,  where 
they  supply  the  olfactory  lobe,  gyrus  rectus,  and  internal  orbital  convolution. 

The  Anterior  Internal  Frontal  supplies  a  part  of  the  marginal  convolution,  and 
sends  branches  over  the  edge  of  the  hemisphere  to  the  superfrontal  and  medifrontal 
gyre  and  upper  part  of  the  precentral  gyre. 


THE  INTERNAL  CAROTID  ARTERY 


629 


The  Middle  Internal  Frontal  supplies  the  callosum,  the  callosal  gyre,  the  inesal 
surface  of  the  superfrontal  convolution,  and  the  dorsal  part  of  the  precentral  gyre. 

The  Posterior  Internal  Frontal  supplies  the  quadrate  lobe  and  adjacent  outer 
surface  of  the  hemisphere. 

The  Precommunicant  or  Anterior  Communicating  Artery  (a.  praecommunicans,  a. 
communicans  anterior]  is  a  short  branch,  about  two  lines  in  length,  but  of  moderate 
diameter,  connecting  together  the  two  precerebral  arteries  across  the  intercerebral 
fissure.  Sometimes  this  vessel  is  wanting,  the  two  arteries  joining  together  to  form 
a  single  trunk,  which  afterward  divides.  Or  the  vessel  may  be  wholly  or  partially 
divided  into  two;  frequently  it  is  longer  and  smaller  than  usual.  It  gives  off  some 
of  the  antero-median  ganglionic  group  of  vessels,  which  are,  however,  principally 
derived  from  the  precerebral. 


FIG.  406. — Vascular  area  of  the  inferior  surface  of  the  cerebrum.  I.  The  part  supplied  by  the  anterior 
temporal  from  the  postcerebral  artery.  II.  The  part  supplied  by  the  posterior  temporal  from  the  postcere- 
bral  artery.  III.  The  part  supplied  by  the  occipital  from  the  postcerebral  artery.  (After  Duret.) 

The  Medicerebral  or  Middle  Cerebral  Artery  (a.  medicerebralis,  a.  cerebri 
media)  (Fig.  407),  the  largest  branch  of  the  internal  carotid,  passes  obliquely 
outward  along  the  fissure  of  Sylvius,  and  opposite  the  island  of  Reil  divides  into 
temporal  and  parieto-temporal  terminal  branches. 

Branches.— The  branches  of  the  medicerebral  artery  are — 


Antero-lateral  ganglionic. 
Inferior  external  frontal. 


Parieto-temporal. 


Ascending  frontal. 
Ascending  parietal. 


The  Antero-lateral  Ganglionic  Branches  are  a  group  of  small  arteries  which  arise 
at  the  commencement  of  the  medicerebral  artery;  they  pierce  the  preperforatum 
and  supply  the  greater  part  of  the  caudatum,  the  lenticular  nucleus,  the  internal 


630  THE  BLOOD-VASCULAR  SYSTEM 

capsule,  and  a  part  of  the  optic  thalamus.  One  artery  of  this  group  (one  of  the 
lenticulo-striate  arteries)  is  of  larger  size  than  the  rest,  and  is  of  special  importance, 
as  being  the  artery  in  the  brain  most  frequently  ruptured;  it  has  been  termed  by 
Charcot  the  artery  of  cerebral  hemorrhage.  It  passes  up  between  the  lenticular 
nucleus  and  the  external  capsule,  and  ultimately  ends  in  the  caudatum. 

The  Inferior  External  Frontal  supplies  the  third  or  subfrontal  convolution 
(Broca's  convolution)  and  the  outer  part  of  the  orbital  surface  of  the  frontal  lobe. 

The  Ascending  Frontal  supplies  the  precentral  gyre. 

The  Ascending  Parietal  supplies  the  ascending  parietal  convolution  and  the 
lower  part  of  the  superior  parietal  convolution. 

The  Parieto-temporal  or  Parieto-sphenoidal  supplies  the  supramarginal,  the 
supertemporal,  and  part  of  the  meditemporal  gyre,  and  the  angular  gyrus. 


ANTERO-IATERAL 
6ANSLIONIC  OR  PER- 
FORATING BRANCH[$ 

MEDICCREBRAL  ARTERY 


FIG.  407. — The  distribution  of  the  medicerebral  artery.     (After  Charcot.) 

The  Postcommunicant  or  Posterior  Communicating  Artery  (a.  postcommuni- 
cans,  a.  communicans  posterior]  arises  from  the  back  part  of  the  internal  carotid ,  runs 
directly  backward,  and  anastomoses  with  the  postcerebral,  a  branch  of  the  basilar. 
This  artery  varies  considerably  in  size,  being  sometimes  small,  and  occasionally 
so  large  that  the  postcerebral  may  be  considered  as  arising  from  the  internal 
carotid  rather  than  from  the  basilar.  It  is  frequently  larger  on  one  side  than  on  the 
other  side.  From  the  posterior  half  of  this  vessel  are  given  off  a  number  of  small 
branches,  the  postero-median  ganglionic  branches,  which,  with  similar  vessels  from 
the  postcerebral,  pierce  the  postperforatum  and  supply  the  internal  surfaces  of  the 
optic  thalami  and  the  walls  of  the  third  ventricle. 

The  Prechoroid  or  Anterior  Choroid  (a.  praechoroidea,  a.  chorioidea]  is  a  small 
but  constant  branch  which  arises  from  the  back  part  of  the  internal  carotid,  near 
the  postcommunicant  artery.  Passing  backward  and  outward  between  the  tem- 
poral lobe  and  the  crus,  it  enters  the  medicornu  of  the  lateral  ventricle  through 
the  choroid  fissure  and  ends  in  the  paraplexus.  It  is  distributed  to  the  hippo- 
campus, fimbria,  velum,  and  paraplexus. 


THE  BLOOD-VESSELS  OF  THE  BRAIN. 

Recent  investigations  have  tended  to  show  that  the  mode  of  distribution  of 
the  vessels  of  the  brain  has  an  important  bearing  upon  a  considerable  number  of 


THE  BLOOD-VESSELS  OF  THE  BMAIN 


631 


the  anatomical  lesions  of  which  this  part  of  the  nervous  system  may  be  the  seat; 
it  therefore  becomes  important  to  consider  a  little  more  in  detail  the  way  in  which 
the  cerebral  vessels  are  distributed. 

The  cerebral  arteries  are  derived  from  the  internal  carotid  and  the  vertebral, 
which  at  the  base  of  the  brain  form  a  remarkable  anastomosis  known  as  the  cir- 
culus  or  circle  of  Willis  (see  page  642).  The  tortuosity  of  the  constituent  vessels 
of  the  anastomosis  lessens  the  impact  of  the  circulation  and  saves  the  brain  from 
damage.  The  outline  of  the  vessels  forming  the  so-called  circle  is  said  by  Sappey 
to  be  hexagonal,  and  by  Testut  to  be  heptagonal.  The  circulus  is  formed  in  front 
bv  the  precerebral  arteries,  branches  of  the  internal  carotid,  which  are  connected 
together 'by  the  precommunicant;  behind  by  the  two  postcerebrals,  branches  of  the 
bjisilar,  which  are  connected  on  each  side  to  the  internal  carotid  by  the  postcom- 
municant  (Fig.  403).  The  parts  of  the  brain  included  within  this  arterial  circle 
are  the  terma,  the  chiasm  or  commissure  of  the  optic  nerves,  the  tuber,  the  albi- 


~^<  Precerebral  artery. 

/Internarcarotid  artery. 
\ 

Medicerebral  artery. 


FIG.  408. — Diagram  of  the  arterial  circulation  at  the  base  of  the  brain.  I.  Antero-median  group  of  ganglionic 
branches.  II.  Postero-median  group.  III.  Right  and  left  anterq-lateral  group.  IV.  Right  and  left  postero- 
lateral  group.  The  dotted  line  shows  the  limit  of  the  ganglionic  circle.  (After  Charcot.) 

cantia,  and  the  postperforatum.  This  arrangement  of  the  vessels  of  the  circulus  is 
not  invariable;  according  to  Windle  it  is  maintained  in  little  more  than  half  the 
recorded  cases.  In  the  other  cases  there  are  various  anomalies. 

From  the  circulus  arise  the  three  trunks  which  together  supply  each  cerebral 
hemisphere.  From  its  anterior  part  proceed  the  two  precerebrals,  from  its  antero- 
lateral  part  the  medicerebrals,  and  from  its  posterior  part  the  postcerebrals. 
Each  of  these  principal  arteries  gives  origin  to  two  very  different  systems  of 
secondary  vessels.  One  of  these  systems  has  been  named  the  central  ganglionic 
system,  and  the  vessels  belonging  to  it  supply  the  central  ganglia  of  the  brain;  the 
other  has  been  named  the  cortical  arterial  system,  and  its  vessels  ramify  in  the 
pia  and  supply  the  cortex  and  subjacent  medullary  matter.  These  two  systems, 
although  they  have  a  common  origin,  do  not  communicate  at  any  point  of  their 
peripheral  distribution,  and  are  entirely  independent  of  each  other.  Though  some 
of  the  arteries  of  the  cortical  system  approach,  at  their  terminations,  the  regions 


632 


THE  BLOOD-VASCULAR  SYSTEM 


supplied  by  the  central  ganglionic  system,  no  communication  between  the  two 
sets  of  vessels  takes  place,  and  there  is  between  the  parts  supplied  by  the  two 
systems  a  borderland  of  diminished  nutritive  activity.  In  the  brains  of  old  people 
softening  is  especially  apt  to  occur  in  this  ill-nourished  territory. 

The  Central  Ganglionic  System. — All  the  vessels  belonging  to  this  system 
are  given  off  from  the  circulus  or  from  the  vessels  immediately  after  their  origin 
from  it,  so  that  if  a  circle  is  drawn  at  a  distance  of  about  an  inch  from  the  circulus, 
it  will  include  the  origin  of  all  the  arteries  belonging  to  this  system  (Fig.  408). 
The  vessels  of  this  system  form  six  principal  groups:  (I.)  the  antero-median  group, 
derived  from  the  precerebrals  and  precommunicans ;  (II.)  the  postero-median  group, 
from  the  postcerebrals  and  postcommunicans ;  (III.)  the  right  and  left  antero- 
lateral  group,  from  the  medicerebrals;  and  (IV.)  the  right  and  left  postero-lateral 
group,  from  the  postcerebrals,  after  they  have  wound  round  the  crura.  The  vessels 
belonging  to  this  system  are  larger  than  those  of  the  cortical  system,  and  are  what 


FIG.  409. — Distribution  of  the  cortical  arteries.  1.  Medullary  arteries.  1'.  Group  of  medullary  arteries  in 
the  sulcus  between  two  adjacent  convolutions.  1".  Arteries  situated  among  the  short  association  fibres.  2,  2. 
Cortical  arteries,  a.  Capillary  network  with  fairly  wide  meshes,  situated  beneath  the  pia.  6.  Network  with 
more  compact,  polygonal  meshes,  situated  in  the  cortex,  c.  Transitional  network  with  wider  meshes,  d. 
Capillary  network  in  the  white  matter.  (After  Charcot.) 

Cohnheim  has  termed  terminal  arteries;  that  is  to  say,  vessels  which  from  their 
origin  to  their  termination  neither  supply  nor  receive  any  anastomotic  branches, 
so  that  by  one  of  the  small  vessels  only  a  limited  area  of  the  central  ganglia  can 
be  injected ;  and  the  injection  cannot  be  driven  beyond  the  area  of  the  part  sup- 
plied by  the  particular  vessel  which  is  the  subject  of  the  experiment. 

The  Cortical  Arterial  System. — The  vessels  forming  this  system  are  the  ter- 
minal branches  of  the  pre-,  medi-,  and  postcerebral  arteries,  described  above. 
These  vessels  divide  and  ramify  in  the  substance  of  the  pia,  and  give  off  nutrient 
arteries  which  penetrate  the  cortex  perpendicularly.  These  nutrient  vessels  are 
divisible  into  two  classes — the  long  and  short.  The  long — or,  as  they  are  some- 
times called,  the  medullary — arteries  pass  through  the  gray  matter  to  penetrate 
the  centrum  ovale  to  the  depth  of  about  an  inch  and  a  half,  without  intercom- 
municating otherwise  than  by  very  fine  capillaries,  and  thus  constitute  so  many 


THE  8UBCLA  VIAN  ARTERY  C33 

independent  small  systems.  The  short  vessels  are  confined  to  the  cortex,  where 
ihrv  form  with  the  long  vessels  a  compact  network  in  the  middle  zone  of  the  gray 
matter,  the  outer  and  inner  zones  being  sparingly  supplied  with  blood  (Fig.  409). 
The  vessels  of  the  cortical  arterial  system  are  not  so  strictly  terminal  as  those  of  the 
central  ganglionic  system,  but  they  approach  this  type  very  closely,  so  that  injec- 
tion of  one  area  from  the  vessel  of  another  area,  though  it  may  be  possible,  is  fre- 
quently very  difficult,  and  is  only  effected  through  vessels  of  small  calibre.  As  a 
result  of  this,  obstruction  of  one  of  the  main  branches  or  its  divisions  may  have 
the  effect  of  producing  softening  in  a  very  limited  area  of  the  cortex.1 

ARTERIES  OF  THE  UPPER  EXTREMITY. 

The  artery  which  supplies  the  upper  extremity  continues  as  a  single  trunk 
from  its  commencement  down  to  the  elbow,  but  different  portions  of  it  have 
received  different  names  according  to  the  region  through  which  it  passes.  That 
part  of  the  vessel  which  extends  from  its  origin  to  the  outer  border  of  the  first 
rib  is  termed  the  subclavian  artery ;  beyond  this  point  to  the  lower  border  of  the 
axilla-it  is  termed  the  axillary  artery;  and  from  the  lower  margin  of  the  axillary  space 
to  the  bend  of  the  elbow  it  is  termed  the  brachial  artery;  here  the  single  trunk 
terminates  by  dividing  into  two  branches,  the  radial  and  ulnar — an  arrangement 
precisely  similar  to  what  occurs  in  the  lower  limb. 

THE  SUBCLAVIAN  ARTERY  (A.  SUBCLAVIA)  (Fig.  410). 

The  subclavian  artery  on  the  right  side  arises  from  the  innominate  artery 
opposite  the  right  sterno-clavicular  articulation;  on  the  left  side  it  arises  from 
the  arch  of  the  aorta.  It  follows,  therefore,  that  these  two  vessels  must,  in  the  first 
part  of  their  course,  differ  in  their  length,  their  direction,  and  their  relation  with 
neighboring  parts. 

In  order  to  facilitate  the  description  of  these  vessels,  more  especially  from  a 
surgical  point  of  view,  each  subclavian  artery  has  been  divided  into  three  parts. 
The  first  portion,  on  the  right  side,  passes  upward  and  outward  from  the  origin 
of  the  vessel  to  the  inner  border  of  the  Scalenus  anticus.  On  the  left  side  it  ascends 
nearly  vertically,  to  gain  the  inner  border  of  that  muscle.  The  second  part  passes 
outward,  behind  the  Scalenus  anticus;  and  the  third  part  passes  from  the  outer 
margin  of  that  muscle,  beneath  the  clavicle,  to  the  outer  border  of  the  first  rib, 
where  it  becomes  the  axillary  artery.  The  first  portion  of  these  two  vessels  differs 
so  much  in  its  course  and  in  its  relations  with  neighboring  parts  that  it  will  be 
described  separately.  The  second  and  third  parts  are  alike  on  the  two  sides. 

First  Part  of  the  Right  Subclavian  Artery  (Figs.  389,  390,  394,  410). 

On  the  right  side  the  subclavian  artery  arises  from  the  arteria  innominata,  oppo- 
site the  upper  part  of  the  right  sterno-clavicular  articulation,  and  passes  upward 
and  outward  to  the  inner  margin  of  the  Scalenus  anticus  muscle  (Figs.  389,  390, 
and  410).  In  this  part  of  its  course  it  ascends  a  little  above  the  clavicle,  the  extent 
to  which  it  does  so  varying  in  different  cases. 

Relations. — It  is  covered,  in  front,  by  the  integument,  superficial  fascia,  Platysma, 
deep  fascia,  the  clavicular  origin  of  the  Sterno-mastoid,  the  Stern o-hyoid,  and 
the  Sterno-thyroid  muscles,  and  a  second  layer  of  deep  fascia.  It  is  crossed 
by  the  internal  jugular  and  vertebral  veins,  and  by  the  vagus  nerve  and  the 

1  The  student  who  desires  further  information  on  this  subject  is  referred  to  Charcot's  Localization  of  Cerebral 
and  Spinal  Diseases,  p.  42  et  seg.,  whence  the  facts  above  given  have  been  principally  derived. — ED.  of  15th 
English  edition. 


034 


THE  BLOOD-VASCULAR  SYSTEM 


cardiac  branches  of  the  sympathetic  nerve.  A  loop  of  the  sympathetic  nerve 
itself  also  crosses  the  artery,  forming  a  ring  around  the  vessels.  The  anterior 
jugular  vein  passes  outward  in  front  of  the  artery  but  is  not  in  contact  with  it, 
being  separated  from  it  by  the  Sterno-hyoid  and  Sterno-thyroid  muscles.  Below 
and  behind  the  artery  is  the  pleura,  which  separates  it  from  the  apex  of  the  lung; 
behind  is  the  cord  of  the  sympathetic  nerve;  the  recurrent  laryngeal  nerve  winds 
round  the  lower  and  back  part  of  the  vessel. 


Phrenic  nerve. 

I 


Vertebral  artery. 

'erior  thyroid  artery. 


Supra-scapular 

artery. 
Supra- 
scapular 
nerve. 


Vagus  nerve. 


Subclaman 

artery. 

External  jugu- 
lar vein. 
.Right  innmili- 

nate  vein. 
Innomi- 
nate artery. 

«&\ 


'  Profunda  artery. 
-Muscido-spiral  nerve. 

FIG.  410. — The  subclavian  artery,  showing  its  relations.     (From  a  preparation  in  the  Museum  of  the  Royal 

College  of  Surgeons  of  England.) 

PLAN  OF  THE  RELATIONS  OF  FIRST  PORTION  OF  THE  RIGHT  SUBCLAVIAN  ARTERY. 

In  front. 

Skin,  superficial  fascia. 
Platysma,  deep  fascia. 
Clavicular  origin  of  Sterno-mastoid. 
Sterno-hyoid  and  Sterno-thyroid. 

Anterior  jugular,  Internal  jugular,  and  vertebral  veins. 
Vagus  and  cardiac  nerves. 
Loop  from  the  sympathetic. 


Beneath. 
Pleura. 
Recurrent  laryngeal  nerve. 


THE  SUBCLAVIAN  ARTERY  635 

Behind. 

Recurrent  laryngeal  nerve. 
Sympathetic. 
Pleura  and  apex  of  lung. 

First  Part  of  the  Left  Subclavian  Artery  (Figs.  388,  389). 

The  left  subclavian  artery  arises  from  the  end  of  the  arch  of  the  aorta,  opposite 
the  fourth  thoracic  vertebra,  and  ascends  nearly  vertically  to  the  inner  margin  of 
the  Scalenus  anticus  muscle.  This  part  of  the  vessel  is,  therefore,  longer  than  the 
right,  is  situated  deeply  in  the  cavity  of  the  chest,  and  is  directed  nearly  vertically 
upward,  instead  of  arching  outward  like  the  vessel  of  the  opposite  side. 

Relations. — It  is  in  relation,  in  front,  with  the  vagus,  cardiac,  and  phrenic 
nerves,  which  lie  parallel  with  it,  the  left  carotid  artery,  left  internal  jugular 
and  vertebral  veins,  and  the  commencement  of  the  left  innominate  vein  and  is 
covered  by  the  Sterno-thyroid,  Sterno-hyoid,  and  Sterno-mastoid  muscles;  behind, 
it  is  in  relation  with  the  oesophagus,  thoracic  duct,  inferior  cervical  ganglion  of  the 
sympathetic,  and  Longus  colli  muscle;  higher  up,  however,  the  oesophagus  and 
tlioracic  duct  lie  to  its  right  side;  the  latter  ultimately  arching  over  the  vessel  to 
join  the  angle  of  union  between  the  subclavian  and  internal  jugular  veins.  To 
its  inner  side  are  the  oesophagus,  trachea,  and  thoracic  duct;  to  its  outer  side,  the 
left  pleura  and  lung. 

PLAN  OF  THE  RELATIONS  OF  FIRST  PORTION  OF  THE  LEFT  SUBCLAVIAN  ARTERY. 

In  front. 

Vagus,  cardiac,  and  phrenic  nerves. 
Left  carotid  artery. 
Thoracic  duct. 

Left  internal  jugular,  vertebral,  and  in-nominate  veins. 
Sterno-thyroid,  Sterno-hyoid,  and  Sterno-mastoid  muscles. 

Inner  side.  /  ^  Outer  side. 

Trachea.  [   &n^l.an   \  Pleura  and  left  lung. 

(Esophagus. 
Thoracic  duct. 

Behind. 

(Esophagus  and  thoracic  duct. 
Inferior  cervical  ganglion  of  sympathetic. 
Longus  colli. 

Second  and  Third  Parts  of  the  Subclavian  Artery  (Figs.  392,  410). 

The  Second  Portion  of  the  Subclavian  Artery  lies  behind  the  Scalenus  anticus 
muscle;  it  is  very  short,  and  forms  the  highest  part  of  the  arch  described  by  that 
vessel. 

Relations. — It  is  covered,  in  front,  by  the  skin,  superficial  fascia,  Platysma, 
deep  cervical  fascia,  the  Sterno-mastoid  and  the  Scalenus  anticus  muscles.  On 
the  right  side  the  phrenic  nerve  is  separated  from  the  second  part  of  the  artery  by 
the  Scalenus  anticus  muscle,  while  on  the  left  side  the  nerve  crosses  the  first  part 
of  the  artery  immediately  to  the  inner  edge  of  the  muscle.  Behind,  it  is  in  rela- 
tion with  the  pleura  and  the  Scalenus  medius  muscle.  Above,  with  the  br'achial 
plexus  of  nerves.  Below,  with  the  pleura.  The  subclavian  vein  lies  below  and 
in  front  of  the  artery,  separated  from  it  by  the  Scalenus  anticus  muscle. 


636  THE  BLOOD-  VASCULAR  SYSTEM 

PLAN  OF  THE  RELATIONS  OF  SECOND  PORTION  OF  SUBCLAVIAN  ARTERY. 

In  front. 

Skin  and  superficial  fascia. 
Platysma  and  deep  cervical  fascia. 
Sterno-mastoid . 
Phrenic  nerve. 
Scalenus  anticus. 
Subclavian  vein. 


A  7  /    Subclavian    \  »>  7 

Above.  I        Artery.         ]  BelOW. 

Brachial  plexus.  (      *™»*      j  Pleura. 


Behind. 
Pleura  and  Middle  Scalenus. 

The  Third  Portion  of  the  Subclavian  Artery  passes  downward  and  outward 
from  the  outer  margin  of  the  Scalenus  anticus  muscle  to  the  outer  border  of  the 
first  rib,  where  it  becomes  the  axillary  artery.  This  portion  of  the  vessel  is  the 
most  superficial,  and  is  contained  in  the  subclavian  triangle  (see  page  620). 

Relations. — It  is  covered,  in  front,  by  the  skin,  the  superficial  fascia,  the  Platysma 
the  descending  clavicular  branches  of  the  cervical  plexus,  and  the  deep  cervical 
fascia;  by  the  clavicle,  the  Subclavius  muscle,  the  suprascapular  artery  and 
vein,  and  the  transverse  cervical  vein;  the  nerve  to  the  Subclavius  muscle  passes 
vertically  downward  in  front  of  the  artery.  The  external  jugular  vein  crosses 
the  artery  at  its  inner  side,  and  receives  the  suprascapular  and  transverse  cervical 
veins,  which  frequently  form  a  plexus  in  front  of  it.  The  subclavian  vein  is 
below  and  in  front  of  the  artery,  lying  close  behind  the  clavicle.  Behind,  it  lies  on 
the  Middle  scalenus  muscle  and  the  lowest  cord  of  the  brachial  plexus,  formed 
by  the  union  of  the  last  cervical  and  first  thoracic  nerves.  Above  it,  and  to  its 
outer  side,  is  the  brachial  plexus  and  Omo-hyoid  muscle.  Beloiv,  it  rests  on  the 
upper  surface  of  the  first  rib. 

PLAN  OF  THE  RELATIONS  OF  THIRD  PORTION  OF  SUBCLAVIAN  ARTERY. 

In  front. 

Skin  and  superficial  fascia. 
Platysma  and  deep  cervical  fascia. 

Descending  branches  of  cervical  plexus.     Nerve  to  Subclavius  muscle. 
Subclavius  muscle,  suprascapular  artery,  and  vein. 
The  external  jugular  and  transverse  cervical  veins. 
The  clavicle. 

/   Subclavian    \ 
Above.  I         Artery.         1  BelOW. 

Brachial  plexus.  I      portion.     /  First  rib. 

Omo-hyoid.  \.  y 

Behind. 

Scalenus  medius. 
Lower  cord  of  brachial  plexus. 

Peculiarities. — The  subclavian  arteries  vary  in  their  origin,  their  course,  and  the  height  to 
which  they  rise  in  the  neck. 

The  origin  of  the  right  subclavian  from  the  innominate  takes  place,  in  some  cases,  above  the 
sterno-clavicular  articulation,  and  occasionally,  but  less  frequently,  in  the  cavity  of  the  thorax, 
below  that  point.  Or  the  artery  may  arise  as  a  separate  trunk  from  the  arch  of  the  aorta.  In 
such  cases  it  may  be  either  the  first,  second,  third,  or  even  the  last  branch  derived  from  that 
vessel;  in  the  majority  of  cases  it  is  the  first  or  last,  rarely  the  second  or  third.  When  it  is  the  first 
branch,  it  occupies  the  ordinary  position  of  the  innominate  artery;  when  the  second  or  third,  it 
gains  its  usual  position  by  passing  behind  the  right  carotid;  and  when  the  last  branch,  it  arises 
from  the  left  extremity  of  the  arch,  at  its  upper  or  back  part,  and  passes  obliquely  toward  the 


THE  SUBCLA  VI AN  ARTERY  637 

right  side,  usually  behind  the  trachea,  oesophagus,  and  right  carotid,  sometimes  between  the 
•oesophagus  t>nd  trachea  to  the  upper  border  of  the  first  rib,  whence  it  follows  its  ordinary  course. 
In  very  rare  instances  this  vessel  arises  from  the  thoracic  aorta,  as  low  down  as  the  fourth 
thoracic  vertebra.  Occasionally  it  perforates  the  Scalenus  anticus  muscle;  more  rarely  it  passes 
in  front  of  that  muscle.  Sometimes  the  subclavian  vein  passes  with  the  artery  behind  the 
Scalenus  anticus  muscle.  The  artery  may  ascend  as  high  as  an  inch  and  a  half  above  the 
clavicle  or  any  intermediate  point  between  this  and  the  upper  border  of  the  bone,  the  right 
subclavian  usually  ascending  higher  than  the  left. 

The  left  subclavian  is  occasionally  joined  at  its  origin  with  the  left  carotid. 

Surface  Marking. — The  course  of  the  subclavian  artery  in  the  neck  may  be  mapped  out 
by  describing  a  curve,  with  its  convexity  upward  at  the  base  of  the  posterior  triangle.  The  inner 
end  of  this  curve  corresponds  to  the  sterno-clavicular  joint,  the  outer  end  of  the  centre  of  the 
lower  border  of  the  clavicle.  The  curve  is  to  be  drawn  with  such  an  amount  of  convexity  that 
its  mid-point  reaches  half  an  inch  above  the  upper  border  of  the  clavicle.  The  left  subclavian 
artery  is  more  deeply  placed  than  the  right  in  the  first  part  of  its  course,  and,  as  a  rule,  does  not 
reach  quite  as  high  a  level  in  the  neck.  It  should  be  borne  in  mind  that  the  posterior  border  of 
the  Sterno-mastoid  muscle  corresponds  to  the  outer  border  of  the  Scalenus  anticus  muscle,  so 
that  the  third  portion  of  the  artery,  that  part  most  accessible  for  operation,  lies  immediately 
external  to  the  posterior  border  of  the  Sterno-mastoid  muscle. 

Surgical  Anatomy. — The  relations  of  the  subclavian  arteries  of  the  two  sides  having  been 
examined,  the  student  should  direct  his  attention  to  a  consideration  of  the  best  position  in  which 
compression  of  the  vessel  may  be  effected,  or  in  what  situation  a  ligature  may  be  best  applied  in 
cases  of  aneurism  or  wound. 

Compression  of  the  .subclavian  artery  is  required  in  cases  of  operations  about  the  shoulder, 
in  the  axilla,  or  at  the  upper  part  of  the  arm;  and  the  student  will  observe  that  there  is  only 
one  situation  in  which  it  can  be  effectually  applied — viz.,  where  the  artery  passes  across  the 
upper  surface  of  the  first  rib.  In  order  to  compress  the  vessel  in  this  situation,  the  shoulder 
should  be  depressed,  and  the  surgeon,  grasping  the  side  of  the  neck,  should  press  with  his  thumb 
in  the  angle  formed  by  the  posterior  border  of  the  Sterno-mastoid  with  the  upper  border  of 
the  clavicle,  downward,  backward,  and  inward  against  the  rib;  if  from  any  cause  the  shoulder 
cannot  be  sufficiently  depressed,  pressure  may  be  made  from  before  backward,  so  as  to  compress 
the  artery  against  the  Scalenus  medius  muscle  and  the  transverse  process  of  the  seventh  cervical 
vertebra.  In  appropriate  cases,  a  preliminary  incision  may  be  made  through  the  cervical 
fascia,  and  the  finger  may  be  pressed  down  directly  upon  the  artery. 

Ligature  of  the  subclavian  artery  may  be  required  in  cases  of  wounds  or  of  aneurism  in 
the  axilla,  or  in  cases  of  aneurism  on  the  cardiac  side  of  the  point  of  ligature;  and  the  third  part 
of  the  artery  is  that  which  is  most  favorable  for  an  operation,  on  account  of  its  being  compara- 
tively superficial  and  most  remote  from  the  origin  of  the  large  branches.  In  those  cases  where 
the  clavicle  is  not  displaced,  this  operation  may  be  performed  with  comparative  facility;  but 
where  the  clavicle  is  pushed  up  by  a  large  aneurismal  tumor  in  the  axilla  the  artery  is  placed  at 
a  great  depth  from  the  surface,  which  materially  increases  the  difficulty  of  the  operation.  Under 
these  circumstances  it  becomes  a  matter  of  importance  to  consider  the  height  to  which  this 
vessel  reaches  above  the  bone.  In  ordinary  cases  its  arch  is  about  half  an  inch  above  the  clavicle, 
occasionally  it  is  as  high  as  an  inch  and  a  half,  and  sometimes  so  low  as  to  be  on  a  level  with 
the  upper  border  of  the  clavicle.  If  the  clavicle  is  displaced,  these  variations  will  necessarily 
make  the  operation  more  or  less  difficult  according  as  the  vessel  is  more  or  less  accessible. 

The  chief  points  in  the  operation  of  tying  the  third  portion  of  the  subclavian  artery  are  as 
follows:  The  patient  being  placed  on  a  table  in  the  supine  position,  with  the  head  drawn  over  to 
the  opposite  side  and  the  shoulder  depressed  as  much  as  possible,  the  integument  should  be 
drawn  downward  over  the  clavicle,  and  an  incision  made  through  it,  upon  that  bone,  from  the 
anterior  border  of  the  Trapezius  to  the  posterior  border  of  the  Sterno-mastoid,  to  which  may  be 
added  a  short  vertical  incision  meeting  the  inner  end  of  the  preceding.  The  object  in  drawing 
the  skin  downward  is  to  avoid  any  risk  of  wounding  the  external  jugular  vein,  for  as  it  perforates 
the  deep  fascia  above  the  clavicle,  it  cannot  be  drawn  downward  with  the  skin.  The  soft  parts 
should  now  be  allowed  to  glide  up,  and  the  cervical  fascia  should  be  divided  upon  a  director, 
and  if  the  interval  between  the  Trapezius  and  Sterno-mastoid  muscles  be  insufficient  for  the  per- 
formance of  the  operation,  a  portion  of  one  or  both  may  be  divided.  The  external  jugular  vein 
will  now  be  seen  toward  the  inner  side  of  the  wound:  this  and  the  suprascapular  and  transverse 
cervical  veins,  which  terminate  in  it,  should  be  held  aside.  If  the  external  jugular  vein  is  at  all 
in  the  way  and  exposed  to  injury,  it  should  be  tied  in  two  places  and  divided.  The  suprascapu- 
lar artery  should  be  avoided,  and  the  Omo-hyoid  muscle  held  aside  if  necessary.  In  the  space 
beneath  this  muscle  careful  search  must  be  made  for  the  vessel :  a  deep  layer  of  fascia  and  some 
connective  tissue  having  been  divided  carefully,  the  outer  margin  of  the  Scalenus  anticus  muscle 
must  be  felt  for,  and,  the  finger  being  guided  by  it  to  the  first  rib,  the  pulsation  of  the  subcla- 
vian artery  will  be  felt  as  it  passes  over  the  rib.  The  sheath  of  the  vessels  having  been  opened, 
the  aneurism  needle  may  then  be  passed  around  the  artery  from  above  downward  and  inward,  so 
as  to  avoid  including  any  of  the  branches  of  the  brachial  plexus.  If  the  clavicle  is  so  raised  by 


638  THE  BLOOD-VASCULAR  SYSTEM 

the  tumor  that  the  application  of  the  ligature  cannot  be  effected  in  this  situation,  the  artery  may 
be  tied  above  the  first  rib,  or  even  behind  the  Scalenus  anticus  muscle;  the  difficulties  of  the  < 
operation  in  such  a  case  will  be  materially  increased,  on  account  of  the  greater  depth  of  the  artery 
and  the  alteration  in  position  of  the  surrounding  parts. 

The  second  part  of  the  subclavian  artery,  from  being  that  portion  which  rises  highest  in 
the  neck,  has  been  considered  favorable  for  the  application  of  the  ligature  when  it  is  difficult  to 
tie  the  artery  in  the  third  part  of  its  course.  There  are,  however,  many  objections  to  the  opera- 
tion in  this  situation.  It  is  necessary  to  divide  the  Scalenus  anticus  muscle,  upon  which  lies 
the  phrenic  nerve,  and  at  the  inner  side  of  which  is  situated  the  internal  jugular  vein;  and  a 
wound  of  either  of  these  structures  might  lead  to  the  most  dangerous  consequences.  Again, 
the  artery  is  in  contact,  below,  with  the  pleura,  which  must  also  be  avoided;  and,  lastly,  .the 
proximity  of  so  many  of  its  large  branches  arising  internal  to  this  point  must  be  a  still  further 
objection  to  the  operation.  In  cases,  however,  where  the  sac  of  an  axillary  aneurism  encroaches 
on  the  neck,  it  may  be  necessary  to  divide  the  outer  half  or  two-thirds  of  the  Scalenus  anticus 
muscle,  so  as  to  place  the  ligature  on  the  vessel  at  a  greater  distance  from  the  sac.  The  opera- 
tion is  performed  exactly  in  the  same  way  as  a  ligature  of  the  third  portion,  until  the  Scalenus 
anticus  is  exposed,  when  it  is  to  be  divided  on  a  director  (never  to  a  greater  extent  than  its  outer 
two-thirds),  and  it  immediately  retracts.  The  operation  is  therefore  merely  an  extension  of 
ligature  of  the  third  portion  of  the  vessel. 

In  those  cases  of  aneurism  of  the  axillary  or  subclavian  artery  in  which  the  aneurism 
encroaches  upon  the  outer  portion  of  the  Scalenus  muscle  to  such  an  extent  that  a  ligature 
cannot  be  applied  in  that  situation,  it  may  be  deemed  advisable,  as  a  last  resource,  to  tie  the 
first  portion  of  the  subclavian  artery.  On  the  left  side  this  operation  has  been  regarded  as 
almost  impracticable;  the  great  depth  of  the  artery  from  the  surface,  its  intimate  relation 
with  the  pleura,  and  its  close  proximity  to  the  thoracic  duct  and  to  so  many  important  veins 
and  nerves,  present  a  series  of  difficulties  which  it  is  very  difficult  to  overcome.  Nevertheless, 
Professor  Halsted  and  Schumpert  have  each  tied  successfully  the  first  portion  of  the  left  sub- 
clavian for  aneurism.  J.  K.  Rodgers,  of  New  York,  also  did  it  successfully.  On  the  right 
side  the  operation  is  practicable,  and  has  been  performed.  Dr.  Nassau,  of  Philadelphia,  suc- 
cessfully ligated  the  first  part  of  the  right  subclavian.  The  main  objection  to  the  operation 
in  this  situation  is  the  smallness  of  the  interval  which  usually  exists  between  the  com- 
mencement of  the  vessel  and  the  origin  of  the  nearest  branch.  The  operation  may  be  per- 
formed in  the  following  manner:  The  patient  being  placed  on  the  table  in  the  supine  position 
with  the  neck  extended,  an  incision  should  be  made  along  the  upper  border  of  the  inner  part 
of  the  clavicle,  and  a  second  along  the  inner  border  of  the  Sterno-mastoid,  meeting  the 
former  at  an  angle.  The  attachment  of  both  heads  of  the  Sterno-mastoid  must  be  divided 
on  a  director  and  turned  outward;  a  few  small  arteries  and  veins,  and  occasionally  the 
anterior  jugular  vein,  must  be  avoided,  or,  if  necessary,  ligatured  in  two  places  and  divided, 
and  the  Sterno-hyoid  and  Sterno-thyroid  muscles  are  to  be  divided  in  the  same  manner  as  the 
preceding  muscle.  After  tearing  through  the  deep  fascia  with  the  finger-nail,  the  internal  jugul'ar 
vein  will  be  seen  crossing  the  subclavian  artery;  this  should  be  pressed  aside  and  the  artery 
secured  by  passing  the  needle  from  below  upward,  by  which  the  pleura  is  more  effectually 
avoided.  The  exact  position  of  the  vagus,  the  recurrent  laryngeal,  the  phrenic  and  sympa- 
thetic nerves  should  be  remembered,  and  the  ligature  should  be  applied  near  the  origin  of  the 
vertebral,  in  order  to  afford  as  much  room  as  possible  for  the  formation  of  a  coagulum 
between  the  ligature  and  the  orgin  of  the  vessel.  It  should  be  remembered  that  the  right  sub- 
clavian artery  is  occasionally  deeply  placed  in  the  first  part  of  its  course  when  it  arises  from 
the  left  side  of  the  aortic  arch,  and  passes  in  such  cases  behind  the  oesophagus  or  between  it 
and  the  trachea. 

Collateral  Circulation. — After  ligature  of  the  third  part  of  the  subclavian  artery  the  col- 
lateral circulation  is  mainly  established  by  three  sets  of  vessels,  thus  described  in  a  dissection: 

"1.  A  posterior  set,  consisting  of  the  suprascapular  and  posterior  scapular  branches  of  the 
subclavian,  anastomosing  with  the  subscapular  from  the  axillary. 

"  2.  An  internal  set  produced  by  the  connection  of  the  internal  mammary  on  the  one  hand, 
with  the  superior  and  long  thoracic  arteries,  and  the  branches  from  the  subscapular  on  the  other. 

"  3.  A  middle  or  axillary  set,  which  consisted  of  a  number  of  small  vessels  derived  from  branches 
of  the  subclavian,  above,  and,  passing  through  the  axilla,  terminated  either  in  the  main  trunk 
or  some  of  the  branches  of  the  axillary  below.  This  last  set  presented  most  conspicuously  the 
peculiar  character  of  the  newly  formed  or,  rather,  dilated  arteries,  being  excessively  tortuous, 
and  forming  a  complete  plexus. 

"The  chief  agent  in  the  restoration  of  the  axillary  artery  below  the  tumor  was  the  subscapular 
artery,  which  communicated  most  freely  with  the  internal  mammary,  suprascapular,  and  pos- 
terior scapular  branches  of  the  subclavian,  from  all  of  which  is  received  so  great  an  influx  of 
blood  as  to  dilate  it  to  three  times  its  natural  size."1 

1  Guy's  Hospital  Reports,  vol.  i.,  1836;  case  of  axillary  aneurism,  in  which  Mr.  Aston  Key  had  tied  the  sub- 
clavian artery  on  the  outer  edge  of  the  Scalenus  muscle  twelve  years  previously. — ED.  of  15th  English  edition. 


THE  SUBCLA  VIAN  ARTERY  639 

Wlicn  a  ligatuiv  is  applied  to  the  first  part  of  the  sulx-Iavian  artery,  the  collateral  circulation 
is  carried  on  by — 1,  the  anastomosis  between  the  superior  and  inferior  thyroid;  2,  the  anasto- 
mosis of  the  two  vertebrals;  3,  the  anastomosis  of  the  internal  mammary  with  the  deep  epi- 
gastric and  the  aortic  intercostals ;  4,  the  superior  intercostal  anastomosing  with  the  aortic  inter- 
costals;  5,  the  profunda  cervicis  anastomosing  with  the  princeps  cervicis;  6,  the  scapular  branches 
of  the  thyroid  axis  anastomosing  with  the  branches  of  the  axillary;  and  7,  the  thoracic  branches 
of  the  axillary  anastomosing  with  the  aortic  intercostals. 

Branches. — The  branches  given  off  from  the  subclavian  artery  are: 

Vertebral.  Internal  mammary. 

Thyroid  axis.  Superior  intercostal. 

On  the  left  side  all  four  branches  generally  arise  from  the  first  portion  of  the 
vessel;  but  on  the  right  side,  the  superior  intercostal  usually  arises  from  the  second 
portion  of  the  vessel.  On  both  sides  of  the  body  the  first  three  branches  arise  close 
together  at  the  inner  margin  of  the  Scalenus  anticus;  in  the  majority  of  cases  a 
free  interval  of  from  half  an  inch  to  an  inch  exists  between  the  commencement  of 
the  artery  and  the  origin  of  the  nearest  branch;  in  a  smaller  number  of  cases  an 
interval  of  more  than  an  inch  exists,  but  it  never  exceeds  an  inch  and  three-quarters. 
In  a  very  few  instances  the  interval  has  been  found  to  be  less  than  half  an  inch. 
The  vertebral  artery  arises  from  the  upper  and  posterior  part  of  the  subclavian 
artery,  the  internal  mammary  from  the  lower  part  of  the  artery;  the  thyroid  axis 
from  in  front  and  the  superior  intercostal  from  behind. 

The  Vertebral  Artery  (a.  vertebralis)  (Figs.  401  and  411).  is  generally  the  first  and 
largest  branch  of  the  subclavian;  it  arises  from  the  upper  and  back  part  of  the 
first  portion  of  the  vessel,  and,  passing  up- 
ward, enters  the  foramen  in  the  transverse 
process  of  the  sixth  cervical  vertebra,1  and 
ascends  through  the  foramina  in  the  trans- 
verse processes  of  all  the  vertebrae  above  this. 
Above  the  tipper  border  of  the  axis  it  inclines 
outward  ami  upward  to  the  foramen  in  the 
transverse  process  of  the  atlas,  through  which 
it  passes;  it  then  winds  backward  behind  its 
articular  process,  runs  in  a  deep  groove  on 
the  upper  surface  of  the  posterior  arch  of 
this  bone  (Fig.  16),  and,  passing  beneath  the 
posterior  occipito-atlantal  ligament  (Figs.  199 
and  202),  pierces  the  dura  and  arachnoid, 

and  enters  the  skull  through  the   foramen          FlG-  41  ^'SbML^eJ'y68  °f  th6 
magnum.      It  then  passes  forward  and  up- 
ward, inclining  from  the  lateral  aspect  to  the  front  of  the  oblongata.     It  unites  in 
the  middle  line  with  the  vessel  of  the  opposite  side  at  the  lower  border  of  the  pons 
to  form  the  basilar  artery  (Fig.  403). 

Relations. — At  its  origin  it  is  situated  behind  the  internal  jugular  and  vertebral 
veins,  and  is  crossed  by  the  inferior  thyroid  artery:  it  lies  between  the  Longus 
colli  and  Scalenus  anticus  muscles,  having  the  thoracic  duct  in  front  of  it  on  the 
left  side.  It  rests  on  the  transverse  process  of  the  seventh  cervical  vertebra  and 
the  sympathetic  nerve.  Within  the  foramina  formed  by  the  transverse  processes 
of  the  vertebra?  it  is  accompanied  by  a  plexus  of  nerves  from  the  inferior  cervical 
ganglion  of  the  sympathetic,  and  is  surrounded  by  a  dense  plexus  of  veins  which 
unite  to  form  the  vertebral  vein  at  the  lower  part  of  the  neck.  It  is  situated  in 
front  of  the  cervical  nerves,  as  they  issue  from  the  intervertebral  foramina.  While 


1  The  vertebral  artery  sometimes  enters  the  foramen  in  the  transverse  process  of  the  fifth  vertebra.     Dr. 
myth,  who  tied  this  artery  in  the  living  subject,  founj  "' 
in  the  seventh  vertebra. — ED.  of  15th  English  edition. 


640  THE  BLOOD-VASCULAR  SYSTEM 

winding  round  the  articular  process  of  the  atlas,  it  is  contained  in  a  triangular 
space,  the  suboccipital  triangle,  formed  by  the  Rectus  capitis  posticus  major,  the 
Superior  oblique  and  the  Inferior  oblique  muscles;  and  at  this  point  is  covered 
by  the  Complexus  muscle  (Fig.  282).  The  suboccipital  nerve  here  lies  between 
the  artery  and  the  bone.  Within  the  skull,  as  the  artery  winds  round  the  oblon- 
gata,  it  is  placed  between  the  hypoglossal  nerve  and  the  anterior  root  of  the 
suboccipital  nerve,  beneath  the  first  digitation  of  the  ligamentum  denticulatum, 
and  finally  ascends  between  the  basilar  process  of  the  occipital  bone  and  the 
anterior  surface  of  the  oblongata. 

Branches. — These  may  be  divided  into  two  sets — those  given  off  in  the  neck 
and  those  within  the  cranium. 

Cervical  Branches.  Cranial  Branches. 

Spinal  Kami,  or  Lateral  Spinal.      Meningeal  Ramus,  or  Posterior  Meningeal. 
Muscular.  Ventral  Spinal,  or  Anterior  Spinal. 

Dorsal  Spinal,  or  Posterior  Spinal. 
Postcerebellar,  or  Posterior  Inferior  Cere- 

bellar. 
Bulbar. 

The  Spinal  Kami,  or  Lateral  Spinal  Branches  (rami  spinales],  enter  the  spinal  canal 
through  the  intervertebral  foramina  and  divide  into  two  branches.  Of  these,  one 
passes  along  the  roots  of  the  nerves  to  supply  the  spinal  cord  and  its  membranes, 
anastomosing  with  the  other  arteries  of  the  spinal  cord;  the  other  divides  into  an 
ascending  and  a  descending  branch,  which  unite  with  similar  branches  from  the 
artery  above  and  below,  so  that  two  lateral  anastomotic  chains  are  formed  on  the 
posterior  surface  of  the  bodies  of  the  vertebrae  near  the  attachment  of  the  pedicles. 
From  these  anastomotic  chains  branches  are  given  off  to  supply  the  periosteum  and 
the  bodies  of  the  vertebra?,  and  to  communicate  with  similar  branches  from  the 
opposite  side;  from  these  communicating  branches  small  branches  are  given  off 
which  join  similar  branches  above  and  below,  so  that  a  central  anastomotic  chain 
is  formed  on  the  posterior  surface  of  the  bodies  of  the  vertebrae. 

Muscular  Branches  are  given  off  to  the  deep  muscles  of  the  neck,  where  the 
vertebral  artery  curves  round  the  articular  process  of  the  atlas.  They  anastomose 
with  the  occipital  and  with  the  ascending  and  deep  cervical  arteries. 

The  Meningeal  Ramus  or  Posterior  Meningeal  (ramus  meningeus)  is  a  small 
branch  given  off  from  the  vertebral  opposite  the  foramen  magnum.  It  ramifies 
between  the  bone  and  dura  in  the  cerebellar  fossa?,  and  supplies  the  falcula. 

The  Ventral  or  Anterior  Spinal  (a.  spinalis  ventralis,  a.  spinalis  anterior)  is  a 
small  branch  which  arises  near  the  termination  of  the  vertebral,  and,  descending 
in  front  of  the  oblongata,  unites  with  its  fellow  on  the  opposite  side  at  about  the 
level  of  the  foramen  magnum.  One  of  these  vessels  is  usually  larger  than  the 
other,  but  occasionally  they  are  about  equal  in  size.  The  single  trunk  thus  formed 
descends  on  the  front  of  the  spinal  cord,  and  is  reinforced  by  a  succession  of  small 
branches  which  enter  the  spinal  canal  through  the  intervertebral  foramina;  these 
branches  are  derived  from  the  vertebral  artery  and  the  ascending  cervical  branch 
of  the  inferior  thyroid  artery  in  the  neck;  from  the  intercostal  in  the  thoracic  region ; 
and  from  the  lumbar,  ilio-lumbar,  and  lateral  sacral  arteries  in  the  lower  part  of 
the  spine.  They  unite,  by  means  of  ascending  and  descending  branches,  to  form 
a  single  termatic  artery,  which  extends  as  far  as  the  lower  part  of  the  spinal  cord. 
This  vessel  is  placed  in  the  pia  along  the  anterior  median  fissure;  it  supplies  that 
membrane  and  the  substance  of  the  cord,  and  sends  off  branches  at  its  lower  part 
to  be  distributed  to  the  cauda,  and  ends  on  the  central  fibrous  prolongation  of 
the  cord. 


THE  S  UB  CLA  VI AN  AR  TER  Y  p4 1 

The  Dorsal  or  Posterior  Spinal  (a.  spinalis  dor  sails,  a.  spinalis  posterior]  arises 
from  the  vertebral  at  the  side  of  the  oblongata:  passing  backward  to  the  posterior 
aspect  of  the  spinal  cord,  it  descends  on  each  side,  lying  behind  the  posterior  roots 
of  the  spinal  nerves,  and  is  reinforced  by  a  succession  of  small  branches  which 
enter  the  spinal  canal  through  the  intervertebral  foramina,  and  by  which  it  is  con- 
tinued to  the  lower  part  of  the  cord  and  to  the  cauda.  Branches  from  these  vessels 
form  a  free  anastomosis  round  the  posterior  roots  of  the  spinal  nerves,  and  com- 
municate, by  means  of  very  tortuous  transverse  branches,  with  the  vessel  of  the 
opposite  side.  At  its  commencement  it  gives  off  an  ascending  branch,  which 
terminates  on  the  side  of  the  fourth  ventricle. 

The  Postcerebellar  or  Posterior  Inferior  Cerebellar  Artery  (a.  postcerebellaris , 
a.  cerebelli  inferior  posterior)  (Fig.  403),  the  largest  branch  of  the  vertebral,  winds 
backward  round  the  upper  part  of  the  oblongata,  passing  between  the  origin  of 
the  vagus  and  accessory  nerves,  over  the  restis  to  the  under  surface  of  the  cere- 
bellum, where  it  divides  into  two  branches — an  internal,  which  is  continued  back- 
ward to  the  notch  between  the  two  hemispheres  of  the  cerebellum;  and  an  external, 
which  supplies  the  under  surface  of  the  cerebellum  as  far  as  its  outer  border, 
where  it  anastomoses  with  the  medicerebellar  and  the  precerebellar  branches 
of  the  basilar  artery.  Branches  from  this  artery  supply  the  paraplexus  of  the 
fourth  ventricle. 

The  Bulbar  Arteries  comprise  several  minute  vessels  which  spring  from  the 
vertebral  and  its  branches  and  are  distributed  to  the  oblongata. 

Surgical  Anatomy. — The  vertebral  artery  has  been  tied  in  several  instances :  1 ,  for  wounds 
or  traumatic  aneurism;  2,  after  ligation  of  the  innominate,  either  immediately  to  prevent  hem- 
orrhage, or  later  on  to  arrest  bleeding  where  it  has  occurred  at  the  seat  of  ligation;  and  3, 
in  epilepsy.  In  these  latter  cases  the  treatment  has  been  recommended  by  Dr.  Alexander,  of 
Liverpool,  in  the  hope  that  by  diminishing  the  supply  of  blood  to  the  posterior  part  of  the  brain 
and  the  spinal  cord-a  diminution  or  cessation  of  the  epileptic  fits  would  result.  But,  on  account 
of  the  uncertainty  as  to  what  cases,  if  any,  derived  benefit  from  the  operation,  it  has  now  been 
abandoned  as  a  treatment  for  epilepsy.  The  operation  of  ligation  of  the  vertebral  is  performed 
by  making  an  incision  along  the  posterior  border  of  the  Sterno-mastoid  muscle,  just  above  the 
clavicle.  The  muscle  is  pulled  to  the  inner  side,  and  the  anterior  tubercle  of  the  transverse 
process  of  the  sixth  cervical  vertebra  is  sought  for.  A  deep  layer  of  fascia  being  now  divided, 
the  interval  between  the  Scalenus  anticus  and  the  Longus  colli  muscles  just  below  their  attach- 
ment to  the  tubercle  is  defined,  and  the  artery  and  vein  are  found  in  the  interspace.  The  vein 
is  to  be  drawn  to  the  outer  side,  and  the  aneurism  needle  is  passed  from  without  inward.  Drs. 
Ramskill  and  Bright  have  pointed  out  that  severe  pain  at  the  back  of  the  head  may  be  symp- 
tomatic of  disease  of  the  vertebral  artery  just  before  it  enters  the  skull.  This  is  explained  by 
the  close  connection  of  the  artery  with  the  suboccipital  nerve  in  the  groove  on  the  posterior 
arch  of  the  atlas.  Disease  of  the  same  artery  has  been  also  said  to  affect  speech,  from  pressure 
on  the  hypoglossal  nerve  where  it  is  in  relation  with  the  vessel,  leading  to  paralysis  of  the  muscles 
of  the  tongue. 

The  Basilar  Artery  (a.  basilaris)  (Fig.  403),  so  named  from  its  position  at  the 
base  of  the  skull,  is  a  single  trunk  formed  by  the  junction  of  the  two  vertebral 
arteries;  it  extends  from  the  posterior  to  the  anterior  border  of  the  pons,  lying  in 
the  median  pontine  groove,  under  cover  of  the  arachnoid.  It  ends  by  dividing  into 
the  two  postcerebral  arteries. 

Branches. — Its  branches  are,  on  each  side,  the  following: 

Transverse.  Medicerebellar,  or  Anterior  Inferior  Cerebellar. 

Internal  Auditory.  Precerebellar,  or  Superior  Cerebellar. 

Postcerebral,  or  Posterior  Cerebral, 

The  Transverse  or  Pontal  Branches  (rami  ad  pontem)  supply  the  substance  of 
the  pons. 

The  Internal  Auditory  (a.  auditiva  interna)  accompanies  the  auditory  nerve 
into  the  internal  auditory  meatus.  It  supplies  the  internal  ear. 

41 


642  THE  BLOOD-VASCULAR  SYSTEM 

The  Medicerebellar  or  Anterior  Inferior  Cerebellar  Artery  (a.  medicerebellaris,  a. 
cerebelli  inferior  anterior)  passes  backward  across  the  peduncle,  to  be  distributed 
to  the  anterior  border  of  the  under  surface  of  the  cerebellum,  anastomosing  with 
the  postcerebellar  branch  of  the  vertebral. 

The  Precerebellar  or  Superior  Cerebellar  Artery  (a.  praecerebellaris,  a.  cerebelli 
superior)  on  each  side  arises  near  the  termination  of  the  basilar.  It  passes  outward, 
immediately  behind  the  oculomotor  nerve,  which  separates  it  from  the  postcere- 
bral,  winds  round  the  cms,  close  to  the  trochlear  nerve,  and,  arriving  at  the  upper 
surface  of  the  cerebellum,  divides  into  branches  which  ramify  in  the  pia  and, 
reaching  the  circumference  of  the  cerebellum,  anastomose  with  the  branches  of  the 
medicerebellar  arteries.  Several  branches  are  given  to  the  pineal  gland,  the  valve 
of  Vieussens,  and  the  velum. 

The  Postcerebral  or  Posterior  Cerebral  Artery  (a.  postccrebralis,  a.  cerebri  posterior) 
(Figs.  403,  405,  406,  and  408),  on  each  side,  is  the  terminal  branch  of  the  basilar. 
It  is  larger  than  the  preceding,  from  which  it  is  separated  near  its  origin  by  the 
oculomotor  nerve.  Passing  outward,  parallel  to  the  precerebellar  artery,  and 
receiving  the  postcommunicant  from  the  internal  carotid,  it  winds  round  the  crus, 
and  passes  to  the  under  surface  of  the  occipital  lobes  of  the  cerebrum,  and  break 
up  into  branches  for  the  supply  of  the  temporal  and  occipital  lobes.  The  branches 
of  the  postcerebral  artery  are: 

Postero-median  ganglionic.  (  Anterior  temporal. 

Postchoroid  or  Posterior  choroid.         Three  terminal  <  Posterior  temporal. 
Postero-lateral  ganglionic.  (  Occipital. 

The  postero-median  ganglionic  branches  (Fig.  408)  are  a  group  of  small  arteries 
which  arise  at  the  commencement  of  the  postcerebral  artery;  these,  with  simi- 
lar branches  from  the  postcommunicant,  pierce  the  postperforatum,  and  supply 
the  internal  surfaces  of  the  thalamus  and  the  walls  of  the  third  ventricle.  The 
postchoroid  enters  the  interior  of  the  brain  beneath  the  splenium  of  the  callosum, 
and  supplies  the  velum  and  the  paraplexus.  The  postero-lateral  ganglionic  branches 
are  a  group  of  small  arteries  which  arise  from  the  postcerebral  artery,  after  it  has 
turned  round  the  crus;  they  supply  a  considerable  portion  of  the  thalamus.  The 
terminal  branches  are  distributed  as  follows:  the  first,  or  the  anterior  temporal 
branches,  to  the  basal  surface  of  the  anterior  portion  of  the  temporal  lobe;  the 
second,  or  the  posterior  temporal  branches,  to  the  external  surface  of  the  occipital 
lobe  and  the  subtemporal  convolution;  and  the  third,  or  the  occipital  branches, 
to  the  mesal  and  lateral  surfaces  of  the  occipital  lobe. 

Circulus  or  Circle  of  Willis  (circulus  arteriosus[Willisi]). — The  remarkable  anas- 
tomosis which  exists  between  the  branches  of  the  internal  carotid  and  vertebral 
arteries  at  the  base  of  the  brain  constitutes  the  circulus.  It  is  formed  in  front,  by  the 
precerebral  arteries,  branches  of  the  internal  carotid,  which  are  connected  together 
by  the  precommunicant;  behind,  by  the  two  postcerebrals,  branches  of  the  basilar, 
which  are  connected  on  each  side  with  the  internal  carotid  by  the  postcommunicant 
arteries  (Fig.  403).  It  is  by  this  anastomosis  that  the  cerebral  circulation  is  equal- 
ized, and  provision  made  for  effectually  carrying  it  on  if  one  or  more  of  the  branches 
are  obliterated.  The  parts  of  the  brain  included  within  this  arterial  circle  are — the 
terma,  the  chiasm,  the  tuber,  the  tuber  cinereum,  the  albicans,  and  the  post- 
perforatum. 

The  Thyroid  Axis  (truncus  thyreocermcalis)  (Figs.  394  and  413)  is  a  short  thick 
trunk  which  arises  from  the  forepart  of  the  first  portion  of  the  subclavian  artery, 
close  to  the  inner  border  of  the  Scalenus  anticus  muscle,  and  divides,  almost 
immediately  after  its  origin,  into  three  branches — the  inferior  thyroid,  supra- 
scapular,  and  transversalis  colli. 


THE    SUBCLAVIAN  ARTERY 


643 


The  Inferior  Thyroid  Artery  (a.  thyreoidea  inferior)  (Fig.  394)  passes  upward,  in 
front  of  the  vertebral  artery  and  Longus  colli  muscle;  then  turns  inward  behind  the 
sheath  of  the  common  carotid  artery  and  internal  jugular  vein,  and  also  behind 
the  sympathetic  nerve,  the  middle  cervical  ganglion  resting  upon  the  vessel,  and 
reaching  the  lower  border  of  the  lateral  lobe  of  the  thyroid  gland  it  divides  into 
two  branches,  which  supply  the  posterior  and  under  part  of  the  organ,  and  anasto- 
mose in  its  substance  with  the  superior  thyroid  and  with  the  corresponding  artery 
of  the  opposite  side.  (See  page  605.)  The  recurrent  laryngeal  nerve  passes  upward, 
generally  behind  but  occasionally  in  front  of  the  artery.  Its  branches  are: 

Inferior  Laryngeal.  (Esophageal. 

Tracheal.  Ascending  Cervical. 

Muscular. 

The  inferior  laryngeal  branch  (a.  laryngea  inferior]  ascends  upon  the  trachea 
to  the  back  part  of  the  larynx,  in  company  with  the  recurrent  laryngeal  nerve, 
and  supplies  the  muscles  and  mucous  membrane  of  this  part,  anastomosing  with 
the  laryngeal  branch  from  the  superior  thyroid  artery  and  with  the  inferior  laryn- 
geal branch  from  the  opposite  side.  The  tracheal  branches  (rami  tracheales)  are 
distributed  upon  the  trachea,  anastomosing  below  with  the  bronchial  arteries. 
The  oesophageal  branches  (rami  oesophagei)  are  distributed  to  the  oesophagus, 
and  anastomose  with  the  rcsophageal  branches  of  the  aorta.  The  ascending 
cervical  (a.  cervicalis  ascendens)  is  a  small  branch  which  arises  from  the  inferior 
thyroid  just  where  that  vessel  is  passing  behind  the  common  carotid  artery,  and 
runs  up  on  the  anterior  tubercles  of  the  transverse  processes  of  the  cervical 
vertebrae  in  the  interval  between  the  Scalenus  anticus  and  Rectus  capitis  anticus 
major  muscles.  It  gives  muscular  branches  (rami  musculares)  to  the  muscles  of 
the  neck,  which  anastomose  with  branches  of  the  vertebral,  and  sends  one  or  two 
branches  (rami  spinales)  into  the  spinal  canal  through  the  intervertebral  foramina 
to  be  distributed  to  the  spinal  cord  and  its  membranes,  and  to  the  bodies  of  the 
vertebrae  in  the  same  manner  as  the  lateral  spinal  branches  from  the  vertebral. 
It  anastomoses  with  the  ascending  pharyngeal  and  occipital  arteries.  The  mus- 
cular branches  supply  the  depressors  of  the  hyoid  bone,  the  Longus  colli,  the 
Scalenus  anticus,  and  the  Inferior  constrictor  of  the  pharynx.  One  of  the  mus- 
cular branches  passes  between  the  transverse  processes  of  the  fourth  and  fifth 
cervical  vertebrae  and  reaches  the  deep  muscles  of  the  neck.  It  is  called  the 
ramus  profundus. 

Surgical  Anatomy. — The  inferior  thyroid  artery  has  been  tied,  in  conjunction  with  the 
superior  thyroid,  in  cases  of  bronchocele.  An  incision  is  made  along  the  anterior  border  of  the 
Sterno-mastoid  down  to  the  clavicle.  After  the  deep  fascia  has  been  divided,  the  Sterno-mas- 
toid  and  carotid  vessels  are  drawn  outward  and  the  carotid  tubercle  (Chassaignac's  tubercle) 
sought  for.  The  vessel  will  be  found  just  below  this  tubercle,  between  the  carotid  sheath  on  the 
outer  side  of  the  trachea  and  oesophagus  on  the  inner  side.  In  passing  the  ligature  great  care 
must  be  exercised  to  avoid  including  the  recurrent  laryngeal  nerve,  which  is  occasionally  found 
crossing  in  front  of  the  vessel.  Before  extirpating  a  goitrous  lobe  of  the  thyroid  the  superior 
and  inferior  thyroid  arteries  of  the  diseased  side  are  to  be  ligated. 

The  Suprascapular  or  Transversalis  Humeri  Artery  (a.  transversa  scapula}  (Figs.  394 
and  412),  smaller  than  the  tranversalis  colli,  passes  obliquely  from  within  outward, 
across  the  root  of  the  neck.  It  at  first  passes  downward  and  outward  across  the 
Scalenus  anticus  muscle  and  phrenic  nerve,  being  covered  by  the  Sterno-mastoid; 
it  then  crosses  the  subclavian  artery  and  the  cords  of  the  brachial  plexus,  and  runs 
outward,  behind  and  parallel  with  the  clavicle  and  Subclavius  muscle,  and  beneath 
the  posterior  belly  of  the  Omo-hyoid,  to  the  superior  border  of  the  scapula,  where 
it  passes  over  the  transverse  ligament  of  the  scapula,  which  separates  it  from  the 
suprascapular  nerve,  and  reaches  the  supraspinous  fossa.  In  this  situation  it  lies 
close  to  the  bone,  and  ramifies  between  it  and  the  Supraspinatus  muscle,  to  which  it 


644  THE    BLOOD -VASCULAR    SYSTEM 

supplies  branches.  It  then  passes  downward  behind  the  neck  of  the  scapula,  to 
reach  the  infraspinous  fossa,  where  it  anastomoses  with  the  dorsalis  scapulse  branch 
of  the  subscapular  artery  and  branches  of  the  posterior  scapular  arteries.  Besides 
distributing  branches  to  the  Sterno-mastoid,  Subclavius,  and  neighboring  muscles, 
it  gives  off  a  suprasternal  branch,  which  crosses  over  the  sternal  end  of  the  clavicle  to 
the  skin  of  the  upper  part  of  the  chest;  and  a  supra-acromial  branch  (ramus  acro- 
mialis),  which,  piercing  the  Trapezius  muscle,  supplies  the  skin  over  the  acromion, 
anastomosing  with  the  acromial  thoracic  artery.  As  the  artery  passes  over  the  trans- 
verse ligament  of  the  scapula,  a  branch  descends  into  the  subscapular  fossa, 
ramifies  beneath  the  subscapular  muscle,  and  anastomoses  with  the  posterior  and 
subscapular  arteries.  The  suprascapular  artery  also  sends  branches  to  the 
acromio-clavicular  and  shoulder  joints,  and  a  nutrient  artery  to  the  clavicle. 

Posterior  scapular. 

Suprascapular.  Acromiai  branch 

o/  Thoracico-acromialis. 

Anterior 
circumflex. 


ermination  of 
subscapular. 

FIG.  412. — The  scapular  and  circumflex  arteries. 

The  Transverse  Cervical  or  Transversalis  Colli  Artery  (a.  transversa  colli)  (Fig.  394) 
passes  transversely  outward,  across  the  upper  part  of  the  subclavian  triangle,  to 
the  anterior  margin  of  the  Trapezius  muscle,  beneath  which  it  divides  into  two 
branches,  the  superficial  cervical  and  the  posterior  scapular.  In  its  passage  across 
the  neck  it  crosses  in  front  of  the  phrenic  nerve,  Scaleni  muscles,  and  the  brachial 
plexus,  between  the  divisions  of  which  it  sometimes  passes,  and  is  covered  by  the 
Platysma,  Sterno-mastoid,  Omo-hyoid,  and  Trapezius  muscles.  The  superficial 
cervical  (ramus  ascendens)  ascends  beneath  the  anterior  margin  of  the  Trapezius, 
distributing  branches  to  it  and  to  the  neighboring  muscles  and  glands  in  the  neck, 
and  anastomosing  with  the  superficial  branch  of  the  arteria  princeps  cervicis.  The 
posterior  scapular  (ramus  descendens)  (Fig.  412)  passes  beneath  the  Levator  anguli 
scapulae  muscle  to  the  superior  angle  of  the  scapula,  and  then  descends  along  the 
posterior  border  of  that  bone  as  far  as  the  inferior  angle.  In  its  course  it  is 
covered  by  the  Rhomboid  muscles,  supplying  them  and  the  Latissimus  dorsi  and 
Trapezius,  and  anastomosing  with  the  suprascapular  and  subscapular  arteries, 
and  with  the  posterior  branches  of  some  of  the  intercostal  arteries. 

Peculiarities. — The  superficial  cervical  frequently  arises  as  a  separate  branch  from  the  thyroid 
axis;  and  the  posterior  scapular,  from  the  third,  more  rarely  from  the  second,  part  of  the  sub- 
clavian. 


THE   SUBCLAV1AN  ARTERY 


645 


The  Internal  Mammary  (a.  mammaria  interna)   (Fig.  413)  arises  from  the 
under  surface  of  the  first  portion  of  the  subclavian  artery,  opposite  the  thyroid 


Scalenus 

mil  it-nit.  _ 


Anterior  intercostal 
branches. 


Musculo- 
phrenic 


Thyroid  axis. 

Common  carotid. 
Innominate. 


^-Internal  mam- 
mary. 


Perforating 
branches. 


-Superior  epi- 
gastric. 


—Deep  epi- 
gastric. 


•External 
iliac. 


FIG.  413. — The  internal  mammary  artery  and  its  branches. 

axis.  It  passes  downward  and  inward  behind  the  costal  cartilage  of  the  first  rib 
to  the  inner  surface  of  the  anterior  wall  of  the  chest,  resting  against  the  costal 
cartilages  about  half  an  inch  from  the  margin  of  the  sternum ;  and,  at  the  interval 


646  THE   BLOOD -VASCULAR   SYSTEM 

between  the  sixth  and  seventh  cartilages,  divides  into  two  branches,  the  musculo- 
phrenic  and  superior  epigastric. 

Relations.— At  its  origin  it  is  covered  by  the  internal  jugular  and  subclavian 
veins,  and  as  it  enters  the  thorax  is  crossed  from  without  inward  by  the  phrenic 
nerve,  and  then  passes  forward  close  to  the  outer  side  of  the  innominate  vein.  In 
the  upper  part  of  the  thorax  it  lies  behind  the  costal  cartilages  and  Internal  inter- 
costal muscles,  and  is  crossed  by  the  terminations  of  the  upper  six  intercostal 
nerves.  At  first  it  lies  upon  the  pleura,  but  at  the  lower  part  of  the  thorax  the 
Triangularis  sterni  separates  the  artery  from  this  membrane.  It  has  two  venae 
comites;  these  unite  into  a  single  vein,  which  joins  the  innominate  vein  of  its  own 
side. 

Branches. — The  branches  of  the  internal  mammary  are — 

Comes  Nervi  Phrenici  (Superior  Phrenic).  Anterior  Intercostal. 

Mediastinal.  Perforating. 

Pericardiac.  Musculo-phrenic. 

Sternal.  Superior  Epigastric. 

The  Comes  Nervi  Phrenici  or  Superior  Phrenic  (a.  pericardiacophrenica}  is  a  long 
slender  branch  which  accompanies  the  phrenic  nerve,  between  the  pleura  and 
pericardium,  to  the  Diaphragm.  It  gives  branches  to  the  pericardium  and  is 
distributed  upon  the  Diaphragm,  anastomosing  with  the  other  phrenic  branches 
from  the  internal  mammary  and  with  phrenic  branches  of  the  abdominal  aorta. 

The  Mediastinal  Branches  (aa.  mediastinales  anteriores)  are  small  vessels 
which  are  distributed  to  the  areolar  tissue  and  lymphatic  glands  in  the  anterior 
mediastinum  and  to  the  remains  of  the  thymus  gland. 

The  Pericardiac  Branches  supply  the  upper  part  of  the  anterior  surface  of  the 
pericardium,  the  lower  part  receiving  branches  from  the  musculo-phrenic  artery. 

The  Sternal  Branches  (rami  sternales)  are  distributed  to  the  Triangularis  sterni 
and  to  the  posterior  surface  of  the  sternum. 

The  inediastinal,  pericardiac,  and  sternal  branches,  together  with  some  twigs 
from  the  comes  nervi  phrenici,  anastomose  with  branches  from  the  intercostal  and 
bronchial  arteries,  and  form  a  minute  plexus  beneath  the  pleura,  which  has  been 
named  by  Turner  the  subpleural  mediastinal  plexus. 

The  Anterior  Intercostal  Arteries  (rami  intercostales]  supply  the  five  or  six  upper 
intercostal  spaces.  The  branch  corresponding  to  each  space  soon  divides  into 
two,  or  the  two  branches  may  come  off  separately  from  the  parent  trunk.  The 
small  vessels  pass  outward  in  the  intercostal  spaces,  one,  the  larger,  lying  near 
the  lower  margin  of  the  rib  above,  and  the  other,  the  smaller,  near  the  upper 
margin  of  the  rib  below,  and  anastomose  with  the  intercostal  arteries  from  the 
aorta.  They  are  at  first  situated  between  the  pleura  and  the  Internal  intercostal 
muscles,  and  then  between  the  Internal  and  External  intercostal  muscles.  They 
supply  the  Intercostal  muscles,  and,  by  branches  which  perforate  the  External 
intercostal  muscle,  reach  the  Pectoral  muscles  and  the  mammary  gland. 

The  Perforating  or  Anterior  Perforating  Arteries  (rami  perforantes)  correspond 
to  the  five  or  six  upper  intercostal  spaces.  They  arise  trom  the  internal  mam- 
mary, pass  forward  through  the  intercostal  spaces,  and,  curving  outward,  supply 
the  Pectoralis  major  and  the  integument.  Those  which  correspond  to  the  second, 
third,  and  fourth  spaces  are  distributed  to  the  mammary  gland.  In  females, 
during  lactation,  these  branches  are  of  large  size. 

The  Musculo-phrenic  Artery  (a.  musculophrenica)  is  directed  obliquely  down- 
ward and  outward,  behind  the  cartilages  of  the  false  ribs,  perforating  the  Dia- 
phragm at  the  eighth  or  ninth  rib,  and  terminating,  considerably  reduced  in  size, 
opposite  the  last  intercostal  space.  It  gives  off  anterior  intercostal  arteries  to 
each  of  the  intercostal  spaces  across  which  it  passes;  these  diminish  in  size  as  the 


SURGICAL   ANATOMY   OF   THE  AXILLA  647 

spaces  decrease  in  length,  and  are  distributed  in  a  manner  precisely  similar  to 
the  anterior  intercostals  from  the  internal  mammary.  The  musculo-phrenic  also 
gives  branches  to  the  lower  part  of  the  pericardium,  and  others  which  run  back- 
ward to  the  Diaphragm  and  downward  to  the  abdominal  muscles. 

The  Superior  Epigastric  (a.  epigastrica  superior)  continues  in  the  original  direc- 
tion of  the  internal  mammary;  it  descends  through  the  cellular  interval  between 
the  costal  and  sternal  attachments  of  the  Diaphragm,  and  enters  the  sheath  of  the 
Rectus  abdominis  muscle,  at  first  lying  behind  the  muscle,  and  then  perforating 
it  and  supplying  it,  and  anastomosing  with  the  deep  epigastric  artery  from  the 
external  iliac.  Some  branches  perforate  the  sheath  of  the  Rectus,  and  supply  the 
muscles  of  the  abdomen  and  the  integument,  and  a  small  branch,  which  passes 
inward  upon  the  side  of  the  ensiform  appendix,  anastomoses  in  front  of  that 
cartilage  with  the  superior  epigastric  artery  of  the  opposite  side.  It  also  gives 
some  twigs  to  the  Diaphragm,  while  from  the  artery  of  the  right  side  small 
branches  extend  into  the  falciform  ligament  of  the  liver  and  anastomose  with 
the  hepatic  artery. 

Surgical  Anatomy. — The  course  of  the  internal  mammary  artery  may  be  defined  by  draw- 
ing a  line  across  the  six  upper  intercostal  spaces  half  an  inch  from  and  parallel  with  the  sternum. 
The  position  of  the  vessel  must  be  remembered,  as  it  is  liable  to  be  wounded  in  stabs  of  the 
chest-wall.  It  is  most  easily  reached  by  a  transverse  incision  in  the  second  intercostal  space. 

The  Superior  Intercostal  (truncus  costocervicalis)(¥igs.  401  and  419)  arises  from 
the  upper  and  back  part  of  the  siibclavian  artery,  behind  the  Scalenus  anticus  mus- 
cle on  the  right  side  and  to  the  inner  side  of  that  muscle  on  the  left  side.  Passing 
backward,  it  gives  off  the  deep  cervical  branch,  and  then  descends  behind  the 
pleura  in  front  of  the  necks  of  the  first  two  ribs,  and  inosculates  with  the  first 
aortic  intercostal.  As  it  crosses  the  neck  of  the  first  rib  it  lies  to  the  inner  side 
of  the  anterior  division  of  the  first  thoracic  nerve  and  to  the  outer  side  of  the  first 
thoracic  ganglion  of  the  sympathetic.  In  the  first  intercostal  space  it  gives  off  a 
branch  which  is  distributed  in  a  manner  similar  to  the  distribution  of  the  aortic 
intercostals.  The  branch  for  the  second  intercostal  space  usually  joins  with  one 
from  the  highest  aortic  intercostal.  Each  intercostal  gives  off  a  branch  to  the 
posterior  spinal  muscles,  and  a  small  branch  which  passes  through  the  corre- 
sponding intervertebral  foramen  to  the  spinal  cord  and  its  membranes. 

The  Deep  Cervical  Branch  (a.  cervicalis  profunda)  arises,  in  most  cases,  from 
the  superior  intercostal,  and  is  analogous  to  the  posterior  branch  of  an  aortic 
intercostal  artery;  occasionally  it  arises  as  a  separate  branch  from  the  sub- 
clavian  artery.  Passing  backward,  above  the  eighth  cervical  nerve  and  between 
the  transverse  process  of  the  seventh  cervical  vertebra  and  the  first  rib,  it  runs 
up  the  back  part  of  the  neck,  between  the  Complexus  and  Semispinalis  colli 
muscles,  as  high  as  the  axis  vertebra,  supplying  these  and  adjacent  muscles,  and 
anastomosing  with  the  deep  branch  of  the  arteria  princeps  cervicis  of  the  occipital, 
and  with  branches  which  pass  outward  from  the  vertebral.  It  gives  off  a  special 
branch  which  enters  the  spinal  canal  through  the  intervertebral  foramen  between 
the  seventh  cervical  and  first  thoracic  vertebrae. 


SURGICAL  ANATOMY  OF  THE  AXILLA. 

The  axilla  is  a  pyramidal  space,  situated  between  the  upper  and  lateral  part 
of  the  chest  and  the  inner  side  of  the  arm. 

Boundaries. — Its  apex,  which  is  directed  upward  toward  the  root  of  the  neck, 
corresponds  to  the  interval  between  the  first  rib,  the  upper  edge  of  the  scapula, 
and  the  clavicle,  through  which  the  axillary  vessels,  the  brachial  plexus  of  nerves, 
and  the  long  thoracic  nerve  pass.  This  interval  is  the  cervico -axillary  passage. 


648  THE    BLOOD -VASCULAR    SYSTEM 

The  base,  directed  downward,  is  formed  by  the  integument  and  a  thick  layer  of 
fascia,  the  axillary  fascia  (fascia  axillaris)  (Fig.  312),  extending  between  the  lower 
border  of  the  Pectoralis  major  in  front  and  the  lower  border  of  the  Latissimus 
dorsi  behind  (page  465).  The  axillary  fascia  is  perforated  at  several  points. 
The  large  central  opening  is  called  the  foramen  of  Langer.  The  inner  margin  of 
the  foramen  of  Langer  is  dense  and  constitutes  a  part  of  the  axillary  arch, 
which  is  a  fibro-muscular  slip  derived  from  the  latissimus  dorsi.  The  axilla 
is  broad  internally  at  the  chest,  but  narrow  and  pointed  externally  at  the 
arm.  The  anterior  boundary  is  formed  by  the  Pectoralis  major  and  minor  mus- 
cles, the  former  covering  the  whole  of  the  anterior  wall  of  the  axilla,  the  latter 
covering  only  its  central  part,  the  costo-coracoid  membrane,  the  clavicle,  and  the 
Subclavius  muscle.  The  posterior  boundary,  which  extends  somewhat  lower 
than  the  anterior,  is  formed  by  the  Subscapularis  above,  the  Teres  major  and 
Latissimus  dorsi  below.  On  the  inner  side  are  the  first  four  ribs  with  their 
corresponding  Intercostal  muscles,  and  part  of  the  Serratus  rnagnus.  On 
the  outer  side,  where  the  anterior  and  posterior  boundaries  converge,  the  space 
is  narrow,  and  bounded  by  the  humerus,  the  Coraco-brachialis  and  Biceps 
muscles. 

Contents. — This  space  contains  the  axillary  vessels  and  brachial  plexus  of 
nerves,  with  their  branches,  some  branches  of  the  intercostal  nerves,  and  a  large 
number  of  lymphatic  glands,  all  connected  together  by  a  quantity  of  fat  and  loose 
areolar  tissue. 

Position  of  the  Contents. — The  axillary  artery  and  vein,  with  the  brachial  plexus 
of  nerves,  extend  obliquely  along  the  outer  boundary  of  the  axillary  space,  from 
its  apex  to  its  base,  and  are  placed  much  nearer  the  anterior  than  the  posterior  wall, 
the  vein  lying  to  the  inner  or  thoracic  side  of  the  artery  and  partially  concealing 
it.  At  the  forepart  of  the  axillary  space,  in  contact  with  the  Pectoral  muscles,  and 
along  the  anterior  margin  are  the  thoracic  branches  of  the  axillary  artery,  and 
along  the  lower  margin  of  the  Pectoralis  minor  the  long  thoracic  artery  extends 
to  the  side  of  the  chest.  At  the  back  part,  in  contact  with  the  lower  margin  of 
the  Subscapularis  muscle,  are  the  subscapular  vessels  and  nerves;  winding  around 
the  outer  border  of  this  muscle  is  the  dorsalis  scapulae  artery  and  veins;  and,  close 
to  the  neck  of  the  humerus,  the  posterior  circumflex  vessels  and  the  circumflex 
nerve  are  seen  curving  backward  to  the  shoulder. 

Along  the  inner  or  thoracic  side  no  vessel  of  any  importance  exists,  the  upper 
part  of  the  space  being  crossed  merely  by  a  few  small  branches  from  the  superior 
thoracic  artery.  There  are  some  important  nerves,  however,  in  this  situation — 
viz.,  the  long  thoracic  or  external  respiratory  nerve,  descending  on  the  surface 
of  the  Serratus  magnus,  to  which  it  is  distributed;  and  perforating  the  upper 
and  anterior  part  of  this  wall,  the  intercosto-humeral  nerve  or  nerves,  passing 
across  the  axilla  to  the  inner  side  of  the  arm. 

The  cavity  of  the  axilla  is  filled  by  a  quantity  of  loose  areolar  tissue  and  a  large 
number  of  small  arteries  and  veins,  all  of  which  are,  however,  of  inconsiderable 
size,  and  numerous  lymphatic  glands,  the  position  and  arrangement  of  which  are 
described  on  a  subsequent  page. 

Surgical  Anatomy. — The  axilla  is  a  space  of  considerable  surgical  importance.  It  trans- 
mits the  large  vessels  and  nerves  to  the  upper  extremity,  and  these  may  be  the  seat  of  injury  or 
disease:  it  contains  numerous  lymphatic  glands  which  may  require  removal  when  diseased;  in  it 
is  'a  quantity  of  loose  connective  and  adipose  tissue  which  may  be  readily  infiltrated  with  blood 
or  pus.  The  axilla  may  be  the  seat  of  rapidly  growing  tumors.  Moreover,  it  is  covered  at  its 
base  by  thin  skin,  largely  supplied  with  sebaceous  and  sweat  glands,  which  is  frequently  the 
seat  of  small  cutaneous  abscesses  and  boils,  and  of  eruptions  due  to  irritation. 

In  suppuration  in  the  axilla  the  arrangement  of  the  fasciae  plays  a  very  important  part  in  the 
direction  which  the  pus  takes.  As  described  on  page  466,  the  costo-coracoid  membrane,  after 
covering  in  the  space  between  the  clavicle  and  the  upper  border  of  the  Pectoralis  minor,  splits 


THE   AXILLARY   ARTERY 


649 


to  enclose  this  muscle,  and,  reblending  at  its  lower  border,  becomes  incorporated  with  the  axillary 
fascia  at  the  anterior  fold  of  the  axilla.  This  is  known  as  the  dam-pectoral  fascia.  Suppura- 
tion may  take  place  either  superficial  to  or  beneath  this  layer  of  fascia;  that  is,  either  between 
the  Pectorals  or  below  the  Pectoralis  minor:  in  the  former  case,  the  pus  would  point  either  at  the 
anterior  border  of  the  axillary  fold  or  in  the  groove  between  the  Deltoid  and  the  Pectoralis  major; 
in  the  latter,  the  pus  would  have  a  tendency  to  surround  the  vessels  and  nerves  and  ascend  into 
the  neck,  that  being  the  direction  in  which  there  is  least  resistance.  Its  progress  toward  the 
skin  is  prevented  by  the  axillary  fascia;  its  progress  backward,  by  the  Serratus  magnus;  forward, 
by  the  clavi-pectoral  fascia;  inward,  by  the  wall  of  the  thorax;  and  outward,  by  the  upper  limb. 
The  pus  in  these  cases,  after  extending  into  the  neck,  has  been  known  to  spread  through  the 
superior  opening  of  the  thorax  into  the  mediastinum. 

In  opening  an  axillary  abscess  the  knife  should  be  entered  in  the  floor  of  the  axilla,  midway 
between  the  anterior  and  posterior  margins  and  near  the  thoracic  side  of  the  space.  It  is  well 
to  use  a  director  and  dressing  forceps  after  an  incision  has  been  made  through  the  skin  and  fascia 
in  the  manner  directed  by  the  late  Mr.  Hilton. 

The  student  should  attentively  consider  the  relation  of  the  vessels  and  nerves  in  the  several 
parts  of  the  axilla,  for  it  is  the  universal  plan,  at  the  present  day,  to  remove  the  glands  from 
the  axilla  in  operating  for  cancer  of  the  breast.  In  performing  such  an  operation  it  will  be 
necessary  to  proceed  with  much  caution  in  the  direction  of  the  outer  wall  and  apex  of  the  space, 


Anterior 
circumflex. 


FIG.  414. — The  axillary  artery  and  its  branches. 


as  here  the  axillary  vessels  will  be  in  danger  of  being  wounded.  Toward  the  posterior  wall  it 
will  be  necessary  to  avoid  the  subscapular,  dorsalis  scapulae,  and  posterior  circumflex  vessels. 
Along  the  anterior  wall  it  will  be  necessary  to  avoid  the  thoracic  branches.  In  clearing  out  the 
axilla  the  axillary  vein  should  be  first  defined  and  cleared  up  to  the  apex  of  the  axilla. 
When  the  apex  of  the  space  is  reached,  all  fat  and  glands  must  be  carefully  removed  and  the 
whole  axilla  cleared  by  separating  the  tissues  along  the  inner  and  posterior  walls,  so  that  when 
the  proceeding  is  completed,  the  axilla  is  cleared  of  all  its  contents  except  the  main  vessels  and 
nerves. 

THE  AXILLARY  ARTERY  (A.  AXILLARIS)  (Fig.  414). 

The  axillary  artery,  the  continuation  of   the  subclavian,  commences  at  the 
outer  border  of  the  first  rib,  and  terminates  at  the  lower  border  of  the  tendon 


650  THE   BLOOD -VASCULAR    SYSTEM 

of  the  Teres  major  muscle,  where  it  takes  the  name  of  brachial.  Its  direction 
varies  with  the  position  of  the  limb:  when  the  arm  lies  by  the  side  of  the 
chest,  the  vessel  forms  a  gentle  curve,  the  convexity  being  upward  and  outward ; 
when  the  arm  is  directed  at  right  angles  with  the  trunk,  the  vessel  is  nearly 
straight;  and  when  the  arm  is  elevated  still  higher,  the  arteries  describe  a  curve 
the  concavity  of  which  is  directed  upward.  At  its  commencement  the  artery  is 
very  deeply  situated,  but  near  its  termination  it  is  superficial,  being  covered  only 
by  the  skin  and  fascia.  The  description  of  the  relations  of  this  vessel  is  facili- 
tated by  its  division  into  three  portions,  the  first  portion  being  above  the 
Pectoralis  minor;  the  second  portion  behind;  and  the  third  below  that  muscle. 

Relations. — The  first  portion  of  the  axillary  artery  is  in  relation,  in  front,  with 
the  clavicular  portion  of  the  Pectoralis  major,  the  costo-coracoid  membrane,  the 
external  anterior  thoracic  nerve,  and  the  acromio-thoracic  and  cephalic  veins; 
behind,  with  the  first  intercostal  space,  the  corresponding  Intercostal  muscle, 
the  second  and  a  portion  of  the  third  digitation  of  the  Serratus  magnus,  and  the 
long  thoracic  and  internal  anterior  thoracic  nerves;  on  its  outer  side,  with  the 
brachial  plexus,  from  which  it  is  separated  by  a  little  cellular  interval;  on  its  inner 
or  thoracic  side,  with  the  axillary  vein,  which  overlaps  the  artery. 

RELATIONS  OF  THE  FIRST  PORTION  OF  THE  AXILLARY  ARTERY. 

In  front. 
Pectoralis  major. 
Costo-coracoid  membrane. 
External  anterior  thoracic  nerve. 
Acromio-thoracic  and  cephalic  veins. 


Outer  side.  I      Axillary     \  Inner  side. 

Arterv 

Brachial  plexus.  I  First  portion.  I  Axillary  vein. 

Behind. 

First  Intercostal  space  and  Intercostal  muscle. 
Second  and  third  digitations  of  Serratus  magnus. 
Long  thoracic  and  Internal  anterior  thoracic  nerves. 

The  second  portion  of  the  axillary  artery  lies  beyond  the  Pectoralis  minor.  It 
is  covered,  in  front,  by  the  Pectoralis  major  and  minor  muscles;  behind,  it  is 
separated  from  the  Subscapularis  by  a  cellular  interval;  on  the  inner  side  is  the 
axillary  vein,  separated  from  the  artery  by  the  inner  cord  of  the  plexus  and  the 
internal  anterior  thoracic  nerve.  The  brachial  plexus  of  nerves  surrounds  the 
artery  on  three  sides,  and  separates  it  from  direct  contact  with  the  vein  and 
adjacent  muscles. 

RELATIONS  OF  THE  SECOND  PORTION  OF  THE  AXILLARY  ARTERY. 

In  front. 
Pectoralis  major  and  minor. 

Outer  side.  /  \  Inner  side. 

...  f       Axillary      \ 

Outer  cord  or  plexus.  [       Artery.       |  Axillary  vein. 

Inner  cord  of  plexus. 

Internal  anterior  thoracic  nerve. 

/- 

Behind. 
Subscapularis. 
Posterior  cord  of  plexus. 


THE   AXILLARY  ARTERY  651 

The  third  portion  of  the  axillary  artery  lies  below  the  Pectoralis  minor.  It  is 
in  relation,  in  front,  with  the  lower  part  of  the  Pectoralis  major  above,  being 
covnrd  only  by  the  integument  and  fascia  below,  where  it  is  crossed  by  the  inner 
head  of  the  median  nerve;  behind,  with  the  lower  part  of  the  Subscapularis  and 
the  tendons  of  the  Latissimus  dorsi  and  Teres  major;  on  its  outer  side,  with  the 
( loraco-brachialis;  on  its  inner  or  thoracic  side,  with  the  axillary  vein.  The  nerves 
of  the  brachial  plexus  bear  the  following  relation  to  the  artery  in  this  part  of  its 
course:  on  the  outer  side  is  the  median  nerve,  and  the  musculo-cutaneous  for  a 
short  distance;  on  the  inner  side,  the  ulnar  nerve  (between  the  vein  and  artery) 
and  the  lesser  internal  cutaneous  nerve  (to  the  inner  side  of  the  vein);  in  front 
is  the  internal  cutaneous  nerve,  and  behind,  the  musculo-spiral  and  circumflex,  the 
latter  extending  only  to  the  lower  border  of  the  Subscapularis  muscle. 

RELATIONS  OF  THE  THIRD  PORTION  OF  THE  AXILLARY  ARTERY. 

In  front. 

Integument  and  fascia. 
Pectoralis  major. 
Inner  head  of  median  nerve. 
Internal  cutaneous  nerve. 


Outer  side.  f  \  Inner  side. 

Coraco-brachialis.  i       ^Lery.      \  Ulnar  nerve. 

Median  nerve.  I  Third  portion,  y  Axillary  vein. 

Musculo-cutaneous  nerve.  V  /  Lesser  internal  cutaneous  nerve. 

Behind. 
Subscapularis. 

Tendons  of  Latissimus  dorsi  and  Teres  major. 
Musculo-spiral  and  circumflex  nerves. 

Peculiarities. — The  axillary  artery,  in  about  one  case  out  of  every  ten,  gives  off  a  large 
branch,  which  forms  either  one  of  the  arteries  of  the  forearm  or  a  large  muscular  trunk.  In  the 
first  set  of  cases  this  artery  is  most  frequently  the  radial  (1  in  33),  sometimes  the  ulnar  (1  in  72), 
and,  very  rarely,  the  interosseous  (1  in  506).  In  the  second  set  of  cases  the  trunk  has  been 
found  to  give  origin  to  the  subscapular,  circumflex,  and  profunda  arteries  of  the  arm.  Some- 
times only  one  of  the  circumflex,  or  one  of  the  profunda  arteries,  arose  from  the  trunk.  In 
these  cases  the  brachial  plexus  surrounded  the  trunk  of  the  branches  and  not  the  main  vessel. 

Surface  Marking. — The  course  of  the  axillary  artery  may  be  marked  out  by  raising  the 
arm  to  a  right  angle  with  the  body  and  drawing  a  line  from  the  middle  of  the  clavicle  to  the 
point  where  the  tendon  of  the  Pectoralis  major  crosses  the  prominence  caused  by  the  Coraco- 
brachialis  as  it  emerges  from  under  cover  of  the  anterior  fold  of  the  axilla.  The  third  portion 
of  the  artery  can  be  felt  pulsating  beneath  the  skin  and  fascia,  at  the  junction  of  the  anterior 
with  the  middle  third  of  the  space  between  the  anterior  and  posterior  folds  of  the  axilla,  close  to 
the  inner  border  of  the  Coraco-brachialis  muscle. 

Surgical  Anatomy. — The  student,  having  carefully  examined  the  relations  of  the  axillary 
artery  in  its  various  parts,  should  now  consider  in  what  situation  compression  of  this  vessel 
may  be  most  easily  effected,  and  the  best  position  for  the  application  of  a  ligature  to  it  when 
necessary. 

Compression  of  the  vessel  may  be  required  in  the  removal  of  tumors  or  in  amputation  of 
the  upper  part  of  the  arm;  and  the  only  situation  in  which  this  can  be  effectually  made  is  in  the 
lower  part  of  its  course;  by  pressing  on  it  in  this  situation  from  within  outward  against  the 
humerus  the  circulation  may  be  effectually  arrested. 

The  axillary  artery  is  perhaps  more  frequently  lacerated  than  any  other  artery  in  the  body, 
with  the  exception  of  the  popliteal,  by  violent  movements  of  the  extremity,  especially  in  those 
cases  where  its  coats  are  diseased.  It  has  occasionally  been  ruptured  in  attempts  to  reduce  old 
dislocations  of  the  shoulder-joint.  This  accident  is  most  likely  to  occur  during  the  preliminary 
breaking  down  of  adhesions,  in  consequence  of  the  artery  having  become  fixed  to  the  capsule 
of  the  joint.  Aneurism  of  the  axillary  artery  is  of  frequent  occurrence,  a  large  percentage  of 
the  cases  being  traumatic  in  their  origin,  due  to  the  violence  to  which  the  vessel  is  exposed  in 
the  varied,  extensive,  and  often  violent  movements  of  the  limb. 

The  (tpi>hration  of  a  ligature  to  the  axillary  artery  may  be  required  in  cases  of 
aneurism  of  the  upper  part  of  the  brachial  or  as  a  distal  operation  for  aneurism  of  the  sub- 


652  THE   BLOOD -VASCULAR    SYSTEM 

clavian;  and  there  are  only  two  situations  in  which  the  vessel  can  be  secured — viz.,  in  the  first 
and  in  the  third  parts  of  its  course;  for  the  axillary  artery  at  its  central  part  is  so  deeply  seated, 
and,  at  the  same  time,  so  closely  surrounded  with  large  nerve  trunks,  that  the  application  of  a 
ligature  to  it  in  that  situation  would  be  almost  impracticable. 

In  the  third  part  of  its  course  the  operation  is  most  simple,  and  may  be  performed  in  the 
following  manner:  The  patient  being  placed  on  a  bed  and  the  arm  separated  from  the  side,  with 
the  hand  supinated,  an  incision  about  two  inches  in  length  is  made  through  the  integument 
forming  the  floor  of  the  axilla,  the  cut  being  a  little  nearer  to  the  anterior  than  the  posterior 
fold  of  the  axilla.  After  carefully  dissecting  through  the  areolar  tissue  and  fascia,  the  median 
nerve  and  axillary  vein  are  exposed;  the  former  having  been  displaced  to  the  outer  and  the 
latter  to  the  inner  side  of  the  arm,  the  elbow  being  at  the  same  time  bent,  so  as  to  relax  the 
structures  and  facilitate  their  separation,  the  ligature  may  be  passed  round  the  artery  from  the 
ulnar  to  the  radial  side. 

This  portion  of  the  artery  is  occasionally  crossed  by  a  muscular  slip,  the  axillary  arch,  derived 
from  the  Latissimus  dorsi,  which  may  mislead  the  surgeon  during  an  operation.  The  occasional 
existence  of  this  muscular  fasciculus  was  spoken  of  in  the  description  of  the  muscles.  It  may 
easily  be  recognized  by  the  transverse  direction  of  its  fibres. 

The  first  portion  of  the  axillary  artery  may  be  tied  in  cases  of  aneurism  encroaching  so  far 
upward  that  a  ligature  cannot  be  applied  in  the  lower  part  of  its  course.  Notwithstanding  that 
this  operation  has  been  performed  in  some  few  cases,  and  with  success,  its  performance  is  at- 
tended with  much  difficulty  and  danger.  The  student  will  remark  that  in  this  situation  it  would 
be  necessary  to  divide  a  thick  muscle,  and,  after  incising  the  costo-coracoid  membrane,  the 
artery  would  be  exposed  at  the  bottom  of  a  more  or  less  deep  space,  with  the  cephalic  and  axil- 
lary veins  in  such  relation  with  it  as  must  render  the  application  of  a  ligature  to  this  part  of 
the  vessel  particularly  hazardous.  Under  such  circumstances  it  is  an  easier,  and  at  the  same 
time  more  advisable,  operation  to  tie  the  subclavian  artery  in  the  third  part  of  its  course. 

The  vessel  in  the  first  part  of  its  course  can  best  be  secured  through  a  curved  incision  the 
convexity  of  which  is  downward.  This  incision  passes  from  a  point  half  an  inch  external  to 
the  sterno-clavicular  joint  to  a  point  half  an  inch  internal  to  the  coracoid  process.  The  limb 
is  to  be  well  abducted  and  the  head  inclined  to  the  opposite  side,  and  this  incision  is  carried 
through  the  superficial  structures,  care  being  taken  to  avoid  the  cephalic  vein  at  the  outer  angle 
of  the  incision.  The  clavicular  origin  of  the  Pectoralis  major  is  then  divided  in  the  whole 
extent  of  the  wound.  The  arm  is  now  to  be  brought  to  the  side,  and  the  upper  edge  of  the 
Pectoralis  minor  defined  and  drawn  downward.  The  costo-coracoid  membrane  is  to  be  care- 
fully divided  close  to  the  coracoid  process,  and  the  axillary  sheath  exposed ;  this  is  to  be  opened 
with  especial  care  on  account  of  the  vein  overlapping  the  artery.  The  needle  should  be  passed 
from  below,  so  as  to  avoid  wounding  the  vein. 

In  a  case  of  wound  of  the  vessel  the  general  practice  of  cutting  down  upon  and  tying  it  above 
and  below  the  wounded  point  should  be  adopted  in  all  cases. 

Collateral  Circulation  after  Ligature  of  the  Axillary  Artery.— If  the  artery  be  tied 
above  the  origin  of  the  acromial  thoracic,  the  collateral  circulation  will  be  carried  on  bv  the  same 
branches  as  after  the  ligature  of  the  subclavian;  if  at  a  lower  point,  between  the  acromial  thoracic 
and  subscapular  arteries,  the  latter  vessel,  by  its  free  anastomoses  with  the  other  scapular  arteries, 
branches  of  the  subclavian,  will  become  the  chief  agent  in  carrying  on  the  circulation,  to  which 
the  long  thoracic,  if  it  be  below  the  ligature,  will  materially  contribute  by  its  anastomoses  with 
the  intercostal  and  internal  mammary  arteries.  If  the  point  included  in  the  ligature  be  below 
the  origin  of  the  subscapular  artery,  it  will  most  probably  also  be  below  the  origins  of  the  cir- 
cumflex arteries.  The  chief  agents  in  restoring  the  circulation  will  then  be  the  subscapular  and 
the  two  circumflex  arteries  anastomosing  with  the  superior  profunda  from  the  brachial,  which 
will  be  afterward  referred  to  as  performing  the  same  office  after  ligation  of  the  brachial.  The 
cases  in  which  the  operation  has  been  performed  are  few  in  number,  and  no  published  account 
of  dissections  of  the  collateral  circulation  appears  to  exist. 

Branches. — The  branches  of  the  axillary  artery  are — 

p          *  ,  f Superior  Thoracic.  ^  ,         ,  f  Long  Thoracic. 

r  rom  first  part  <    .   '       .  ,  —,,  f  rom  second  part  \   A ,    &  r™ 

(  Acromial   1  horacic.  (  Alar   1  horacic. 

C  Subscapular. 

From  third  part  <  Posterior  Circumflex. 
'  Anterior  Circumflex. 

The  Superior  Thoracic  (a.  thoracalis  supremo)  is  a  small  artery  which  arises 
from  the  axillary  separately  or  by  a  common  trunk  with  the  acromial  thoracic. 
Running  forward  and  inward  along  the  upper  border  of  the  Pectoralis  minor,  it 


THE   AXILLARY  ARTERY  653 

passes  between  it  and  the  Pectoralis  major  to  the  side  of  the  chest.  It  supplies 
thrse  muscles  and  the  parietes  of  the  thorax,  anastomosing  with  the  internal  mam- 
mary and  intercostal  arteries. 

The  Acromial  Thoracic  or  the  Thoracic  Axis  (a.  thoracoacromialis)  is  a 
short  trunk  which  arises  from  the  forepart  of  the  axillary  artery,  its  origin  being 
generally  overlapped  by  the  upper  edge  of  the  Pectoralis  minor.  Projecting 
forward  to  the  upper  border  of  the  Pectoralis  minor,  it  divides  into  four  sets  of 
branches — thoracic,  acromial,  descending,  and  clavicular. 

The  Thoracic  Branches  (rami  pectorales),  two  or  three  in  number,  are  distributed 
to  the  Serratus  magnus  and  Pectoral  muscles,  anastomosing  with  the  intercostal 
branches  of  the  internal  mammary. 

The  Acromial  Branch  (ramus  acromialis)  is  directed  outward  toward  the  acro- 
mion,  supplying  the  Deltoid  muscle,  and  anastomosing,  on  the  surface  of  the 
acromion,  with  the  suprascapular  and  posterior  circumflex  arteries. 

The  Descending  or  Humeral  Branch  (ramus  deltoideus)  passes  in  the  space  between 
the  Pectoralis  major  and  Deltoid,  in  the  same  groove  as  the  cephalic  vein,  and 
supplies  both  muscles. 

The  Clavicular  Branch  (ramus  clavicularis) ,  which  is  very  small,  passes  upward 
to  the  Subclavius  muscle. 

The  Long  Thoracic  or  the  External  Mammary  (a.  thoracalis  lateralis)  passes 
downward  and  inward  along  the  lower  border  of  the  Pectoralis  minor  to  the  side 
of  the  chest,  supplying  the  Serratus  magnus,  the  Pectoral  muscles,  and  mammary 
gland,  and  sending  branches  across  the  axilla  to  the  axillary  glands  and  Sub- 
scapularis;  it  anastomoses  with  the  internal  mammary  and  intercostal  arteries. 

The  Alar  Thoracic  is  a  small  branch  which  supplies  the  glands  and  areolar 
tissue  of  the  axilla.  Its  place  is  frequently  supplied  by  branches  from  some  of  the 
other  thoracic  arteries. 

The  Subscapular  (a.  subscapularis),  the  largest  branch  of  the  axillary  artery, 
arises  opposite  the  lower  border  of  the  Subscapularis  muscle,  and  passes  downward 
and  backward  along  its  lower  margin  to  the  inferior  angle  of  the  scapula,  where  it 
anastomoses  with  the  long  thoracic  and  intercostal  arteries  and  with  the  posterior 
scapular,  a  branch  of  the  transversalis  colli,  from  the  thyroid  axis  of  the  sub- 
clavian.  About  an  inch  and  a  half  from  its  origin  it  gives  off  a  large  branch,  the 
dorsalis  scapulae,  and  terminates  by  supplying  branches  to  the  muscles  in  the 
neighborhood. 

The  Dorsalis  Scapulae  (a.  circumflexa  scapulae)  is  given  off  from  the  subscapular 
about  an  inch  and  a  half  from  its  origin,  and  is  generally  larger  than  the  continua- 
tion of  the  vessel.  It  curves  round  the  axillary  border  of  the  scapula,  leaving  the 
axilla  through  the  space  between  the  Teres  minor  above,  the  Teres  major  below, 
and  the  long  head  of  the  Triceps  externally  (Fig.  412),  and  enters  the  infraspinous 
fossa  by  passing  under  cover  of  the  Teres  minor,  where  it  anastomoses  with  the 
posterior  scapular  and  suprascapular  arteries.  In  its  course  it  gives  off  two  sets 
of  branches:  one  enters  the  subscapular  fossa  beneath  the  Subscapularis,  which  it 
supplies,  anastomosing  with  the  posterior  scapular  and  suprascapular  arteries; 
the  other  is  continued  along  the  axillary  border  of  the  scapula,  between  the  Teres 
major  and  minor,  and,  at  the  dorsal  surface  of  the  inferior  angle  of  the  bone,  anas- 
tomoses with  the  posterior  scapular.  In  addition  to  these,  small  branches  are 
distributed  to  the  back  part  of  the  Deltoid  muscle  and  the  long  head  of  the 
Triceps,  anastomosing  with  an  ascending  branch  of  the  superior  profunda  of  the 
brachial. 

The  Circumflex  Arteries  wind  round  the  surgical  neck  of  the  humerus.  The 
posterior  circumflex  (a.  circumflexa  humeri  posterior)  (Fig.  412),  the  larger  of  the 
two,  arises  from  the  back  part  of  the  axillary  opposite  the  lower  border  of  the 
Subscapularis  muscle,  and,  passing  backward  with  the  circumflex  veins  and  nerve 


654 


THE   BLOOD -VASCULAR    SYSTEM 


through  the  quadrangular  space  bounded  by  the  Te'res  major  and  minor,  the 
scapular  head  of  the  Triceps  and  the  humerus,  winds  round  the  neck  of  that  bone 
and  is  distributed  to  the  Deltoid  muscle  and  shoulder-joint,  anastomosing  with  the 
anterior  circumflex  and  acromial  thoracic  arteries,  and  with  the  superior  profunda 
branch  of  the  brachial  artery.  The  anterior  circumflex  (a.  circumflexa  humeri  ante- 
rior) (Figs.  412  and  414),  considerably  smaller  than  the  preceding,  arises  nearly 
opposite  that  vessel  from  the  outer  side  of  the  axillary  artery.  It  passes  horizon- 
tally outward  beneath  the  Coraco-brachialis  and  short  head  of  the  Biceps,  lying 

upon  the  forepart  of  the  neck  of  the 
humerus,  and,  on  reaching  the  bicipital 
groove,  gives  off  an  ascending  branch 
which  passes  upward  along  the  groove 
to  supply  the  head  of  the  bone  and  the 
shoulder-joint.  The  trunk  of  the  vessel 
is  then  continued  outward  beneath  the 
Deltoid,  which  it  supplies,  and  anasto- 
moses with  the  posterior  circumflex 
artery. 


THE    BRACHIAL    ARTERY    (A.    BRA- 
CHIALIS)  (Fig.  415). 

The  brachial  artery  (a.  brachialis) 
commences  at  the  lower  margin  of  the 
tendon  of  the  Teres  major,  and,  passing 
down  the  inner  and  anterior  aspect  of 
the  arm,  terminates  about  half  an  inch 
below  the  bend  of  the  elbow,  where  it 
divides  into  the  radial  and  ulnar  arteries. 
At  first  the  brachial  artery  lies  internal 
to  the  humerus ;  but  as  it  passes  down 
the  arm  it  gradually  gets  in  front  of 
the  bone,  and  at  the  bend  of  the  elbow 
it  lies  midway  between  the  two  condyles. 
Relations. — This  artery  is  superficial 
throughout  its  entire  extent,  being  cov- 
ered, in  front,  by  the  integument,  the 
superficial  and  deep  fasciae;  the  bicipital 
fascia  separates  it  opposite  the  elbow 
from  the  median  basilic  vein ;  the  median 
nerve  crosses  it  at  its  middle;  behind,  it 
is  separated  from  the  long  head  of  the 
Triceps  by  the  musculo-spiral  nerve  and 
superior  profunda  artery.  It  then  lies 
upon  the  inner  head  of  the  Triceps,  next 
upon  the  insertion  of  the  Coraco-bra- 
chialis, and  lastly  on  the  Brachialis  an- 
ticus;  by  its  outer  side,  it  is  in  relation  with  the  commencement  of  the  median 
nerve  and  the  Coraco-brachialis  and  Biceps  muscles,  which  overlap  the  artery 
to  a  considerable  extent;  by  its  inner  side,  its  upper  half  is  in  relation  with  the 
internal  cutaneous  and  ulnar  nerves,  its  lower  half  with  the  median  nerve.  The 
basilic  vein  lies  on  the  inner  side  of  the  artery,  but  is  separated  from  it  in  the 
lower  part  of  the  arm  by  the  deep  fascia.  The  brachial  artery  is  accompanied  by 


FIG.  415. — The  brachial  artery. 


SURGICAL   ANATOMY   OF    THE  BEND    OF    THE   ELBOW    655 

two  venae  comites,  which  lie  in  close  contact  with  the  artery,  being  connected 
together  at  intervals  by  short  transverse  communicating  branches. 

PLAN  OF  THE  RELATIONS  OF  THE  BRACHIAL  ARTERY. 

In  front. 

Integument  and  fasciae. 

Bicipital  fascia,  median  basilic  vein. 

Median  nerve. 

Overlapped  by  Coraco-brachialis  and  Biceps. 

Outer  side.  /  \  Inner  side. 

Median  nerve  (above).  /      Brachial      j  Internal  cutaneous  and  Ulnar  nerves. 

Coraco-brachialis.  I      Artei7-       I  Median  nerve  (below). 

Biceps.  V  J  Basilic  vein. 

Behind. 

Triceps  (long  and  inner  heads). 
Musculo-spiral  nerve. 
Superior  profunda  artery. 
Coraco-brachialis. 
Brachialis  anticus. 

SURGICAL  ANATOMY  OF  THE  BEND  OF  THE  ELBOW. 

At  the  bend  of  the  elbow  the  brachial  artery  sinks  deeply  into  a  triangular  inter- 
val, the  antecubital  space,  the  base  of  which  is  directed  upward,  and  may  be  repre- 
sented by  a  line  connecting  the  two  condyles  of  the  humerus;  the  sides  are  bounded, 
externally,  by  the  inner  edge  of  the  Supinator  longus ;  internally,  by  the  outer  mar- 
gin of  the  Pronator  radii  teres;  its  floor  is  formed  by  the  Brachialis  anticus  and 
Supinator  brevis.  This  space  contains  the  brachial  artery  with  its  accompanying 
veins,  the  radial  and  ulnar  arteries,  the  median  and  musculo-spiral  nerves,  and  the 
tendon  of  the  Biceps.  The  brachial  artery  occupies  the  middle  line  of  this  space,  and 
divides  opposite  the  neck  of  the  radius  into  the  radial  and  ulnar  arteries;  it  is 
covered,  in  front,  by  the  integument,  the  superficial  fascia,  and  the  median  basilic 
vein,  the  vein  being  separated  from  direct  contact  with  the  artery  by  the  bicipital 
fascia.  Behind,  it  lies  on  the  Brachialis  anticus,  which  separates  it  from  the 
elbow-joint.  The  median  nerve  lies  on  the  inner  side  of  the  artery,  close  to  it 
above,  but  separated  from  it  below  by  the  coronoid  origin  of  the  Pronator  radii 
teres.  The  tendon  of  the  Biceps  lies  to  the  outer  side  of  the  space,  and  the  mus- 
culo-spiral nerve  still  more  externally,  situated  upon  the  Supinator  brevis  and 
partly  concealed  by  the  Supinator  longus. 

Peculiarities  of  the  Brachial  Artery  as  Regards  its  Course.— The  brachial  artery,  accom- 
panied by  the  median  nerve,  may  leave  the  inner  border  of  the  Biceps  and  descend  toward  the 
inner  condyle  of  the  humerus,  where  it  usually  curves  round  a  prominence  of  bone,  the  supra- 
condylar  process.  From  this  process,  in  most  subjects,  a  fibrous  arch  is  thrown  over  the 
artery.  The  vessel  then  inclines  outward,  beneath  or  through  the  substance  of  the  Pronator 
radii  teres  muscle,  to  the  bend  of  the  elbow.  The  variation  bears  considerable  analogy  to  the 
normal  condition  of  the  artery  in  some  of  the  carnivora:  it  has  been  referred  to  in  the  descrip- 
tion of  the  humerus  (page  181). 

As  Regards  its  Division. — Occasionally,  the  artery  is  divided  for  a  short  distance  at  its  upper 
part  into  two  trunks,  which  are  united  above  and  below.  A  similar  peculiarity  occurs  in  the  main 
vessel  of  the  lower  limb. 

The  point  of  bifurcation  may  be  above  or  below  the  usual  point,  the  former  condition  being 
by  far  the  more  frequent.  Out  of  481  examinations  recorded  by  Mr.  Quain,  some  made  on  the 
right  and  some  on  the  left  side  of  the  body,  in  386  the  artery  bifurcated  in  its  normal  position. 
In  one  case  only  was  the  place  of  division  lower  than  usual,  being  two  or  three  inches  below  the 
elbow-joint.  "In  94  cases  out  of  481,  or  about  1  in  5^,  there  were  two  arteries  instead  of  one 
in  some  part  or  in  the  whole  of  the  arm." 


656  THE   BLOOD -VASCULAR    SYSTEM 

There  appears,  however,  to  be  no  correspondence  between  the  arteries  of  the  two  arms  with 
respect  to  their  irregular  division;  for  in  61  bodies  it  occurred  on  one  side  only  in  43;  on  both 
sides,  in  different  positions,  in  13;  on  both  sides,  in  the  same  position,  in  5. 

The  point  of  bifurcation  takes  place  at  different  parts  of  the  arm,  being  most  frequent  in 
the  upper  part,  less  so  in  the  lower  part,  and  least  so  in  the  middle,  the  most  usual  point  for 
the  application  of  a  ligature ;  under  any  of  these  circumstances  two  large  arteries  would  be  found 
in  the  arm  instead  of  one.  The  most  frequent  (in  three  out  of  four)  of  these  peculiarities  is 
the  high  origin  of  the  radial.  That  artery  often  arises  from  the  inner  side  of  the  brachial, 
and  runs  parallel  with  the  main  trunk  to  the  elbow,  where  it  crosses  it,  lying  beneath  the  fascia; 
or  it  may  perforate  the  fascia  and  pass  over  the  artery  immediately  beneath  the  integument. 

The  ulnar  sometimes  arises  from  the  brachial  high  up,  and  accompanies  that  vessel  to  the 
lower  part  of  the  arm,  and  descends  toward  the  inner  condyle.  In  the  forearm  it  generally  lies 
beneath  the  deep  fascia,  superficial  to  the  flexor  muscles;  occasionally  between  the  integument 
and  deep  fascia,  and  very  rarely  beneath  the  flexor  muscles. 

The  interosseous  artery  sometimes  arises  from  the  upper  part  of  the  brachial  or  axillary;  as 
it  passes  down  the  arm  it  lies  behind  the  main  trunk,  and  at  the  bend  of  the  elbow  regains  its 
usual  position. 

In  some  cases  of  high  origin  of  the  radial  the  remaining  trunk  (ulnar  interosseous)  occa- 
sionally passes,  together  with  the  median  nerve,  along  the  inner  margin  of  the  arm  to  the  inner 
condyle,  and  then  passing  from  within  outward,  beneath  or  through  the  Pronator  radii  teres, 
regains  its  usual  position  at  the  bend  of  the  elbow. 

Occasionally  the  two  arteries  representing  the  brachial  are  connected  at  the  bend  of  the  elbow 
by  a  short  transverse  branch,  and  are  even  sometimes  reunited. 

Sometimes,  long  slender  vessels,  vasa  aberrantia,  connect  the  brachial  or  axillary  arteries 
with  one  of  the  arteries  of  the  forearm  or  a  branch  from  them.  These  vessels  usually  join  the 
radial. 

Varieties  in  Muscular  Relations.1 — The  brachial  artery  is  occasionally  concealed  in  some 
part  of  its  course  by  muscular  or  tendinous  slips  derived  from  the  Coraco-brachialis,  Biceps, 
Brachialis  anticus,  and  Pronator  radii  teres  muscles. 

Surface  Marking. — The  direction  of  the  brachial  artery  is  marked  by  a  line  drawn  along 
the  inner  edge  of  the  Biceps  from  the  junction  of  the  anterior  and  middle  thirds  of  the  axillary 
outlet  to  the  middle  of  the  front  of  the  elbow-joint. 

Surgical  Anatomy. — Compression  of  the  brachial  artery  is  required  in  cases  of  amputation 
and  some  other  operations  in  the  arm  and  forearm;  and  it  will  be  observed  that  it  may  be  effected 
in  almost  any  part  of  the  course  of  the  artery.  If  pressure  is  made  in  the  upper  part  of  the 
limb,  it  should  be  directed  from  within  outward ;  and  if  in  the  lower  part,  from  before  backward, 
as  the  artery  lies  on  the  inner  side  of  the  humerus  above  and  in  front  of  the  humerus  below. 
The  most  favorable  situation  is  about  the  middle  of  the  arm,  where  it  lies  on  the  tendon  of  the 
Coraco-brachialis  on  the  inner  flat  side  of  the  humerus. 

The  application  of  a  ligature  to  the  brachial  artery  may  be  required  in  case  of  wound  of 
the  vessel  and  in  some  cases  of  wound  of  the  palmar  arch.  It  is  also  sometimes  necessary  in 
cases  of  aneurism  of  the  brachial,  the  radial,  ulnar,  or  interosseous  arteries.  The  artery  may 
be  secured  in  any  part  of  its  course.  The  chief  guides  in  determining  its  position  are  the  sur- 
face markings  produced  by  the  inner  margin  of  the  Coraco-brachialis  and  Biceps,  the  known 
course  of  the  vessel,  and  its  pulsation,  which  should  be  carefully  felt  for  before  any  operation  is 
performed,  as  the  vessel  occasionally  deviates  from  its  usual  position  in  the  arm.  In  whatever 
situation  the  operation  is  performed,  great  care  is  necessary,  on  account  of  the  extreme  thinness 
of  the  parts  covering  the  artery  and  the  intimate  connection  which  the  vessel  has  throughout  its 
whole  course  with  important  nerves  and  veins.  Sometimes  a  thin  layer  of  muscular  fibre  is 
met  with  concealing  the  artery;  if  such  is  the  case,  it  must  be  cut  across  in  order  to  expose  the 
vessel. 

In  the  upper  third  of  the  arm  the  artery  may  be  exposed  in  the  following  manner:  The 
patient  being  placed  supine  upon  a  table,  the  affected  limb  should  be  raised  from  the  side  and 
the  hand  supinated.  An  incision  about  two  inches  in  length  should  be  made  on  the  inner 
side  of  the  Coraco-brachialis  muscle,  and  the  subjacent  fascia  cautiously  divided,  so  as  to  avoid 
wounding  the  internal  cutaneous  nerve  or  basilic  vein,  which  sometimes  runs  on  the  surface  of 
the  artery  as  high  as  the  axillary.  The  fascia  having  been  divided,  it  should  be  remembered  that 
the  ulnar  and  internal  cutaneous  nerves  lie  on  the  inner  side  of  the  artery,  the  median  on  the 
outer  side,  the  latter  nerve  being  occasionally  superficial  to  the  artery  in  this  situation,  and  that 
the  vense  comites  are  also  in  relation  with  the  vessel,  one  on  either  side.  These  being  carefully 
separated,  the  aneurism  needle  should  be  passed  round  the  artery  from  the  inner  to  the  outer 
side. 

If  two  arteries  are  present  in  the  arm  in  consequence  of  a  high  division,  they  are  usually 
placed  side  by  side:  and  if  they  are  exposed  in  an  operation,  the  surgeon  should  endeavor  to 

1  See  Struther's  Anatomical  and  Physiological  Observations. 


BRANCHES    OF    THE   BRACHIAL    ARTERY  657 

ascertain,  by  alternately  pressing  on  each  vessel,  which  of  the  two  communicates  with  the  wound 
or  aneurism,  when  a  ligature  may  be  applied  accordingly;  or  if  pulsation  or  hemorrhage  ceases 
only  when  both  vessels  are  compressed,  both  vessels  may  be  tied,  as  it  may  be  concluded  that 
the  two  communicate  above  the  seat  of  disease  or  are  reunited. 

It  should  also  be  remembered  that  two  arteries  may  be  present  in  the  arm  in  a  case  of  high 
division,  and  that  one  of  these  may  be  found  along  the  inner  intermuscular  septum,  in  a  line 
toward  the  inner  condyle  of  the  humerus,  or  in  the  usual  position  of  the  brachial,  but  deeply 
placed  beneath  the  common  trunk:  a  knowledge  of  these  facts  will  suggest  the  precautions 
necessary  in  every  case,  and  indicate  the  measures  to  be  adopted  when  anomalies  are  met  with. 

In  the  middle  of  the  arm  the  brachial  artery  may  be  exposed  by  making  an  incision  along 
the  inner  margin  of  the  Biceps  muscle.  The  forearm  being  bent  so  as  to  relax  the  muscle,  it 
should  be  drawn  slightly  aside,  and,  the  fascia  being  carefully  divided,  the  median  nerve  will  be 
exposed  lying  upon  the  artery  (sometimes  beneath);  this  being  drawn  inward  and  the  muscle 
outward,  the  artery  should  be  separated  from  its  accompanying  veins  and  secured.  In  this 
situation  the  inferior  profunda  may  be  mistaken  for  the  main  trunk,  especially  if  enlarged,  from 
the  collateral  circulation  having  become  established;  this  may  be  avoided  by  directing  the 
incision  externally  toward  the  Biceps,  rather  than  inward  or  backward  toward  the  Triceps. 

The  lower  part  of  the  brachial  artery  is  of  interest  in  a  surgical  point  of  view,  on  account 
of  the  relation  which  it  bears  to  the  veins  most  commonly  opened  in  venesection.  Of  these 
vessels,  the  median  basilic  is  the  largest  and  most  prominent,  and,  consequently,  the  one  usually 
selected  for  the  operation.  It  should  be  remembered  that  this  vein  runs  parallel  with  the 
brachial  artery,  from  which  it  is  separated  by  the  bicipital  fascia,  and  that  care  should  be  taken 
in  opening  the  vein  not  to  carry  the  incision  too  deeply,  so  as  to  endanger  the  artery. 

Collateral  Circulation. — After  the  application  of  a  ligature  to  the  brachial  artery  in  the 
upper  third  of  the  arm,  the  circulation  is  carried  on  by  branches  from  the  circumflex  and  sub- 
scapular  arteries,  anastomosing  with  ascending  branches  from  the  superior  profunda.  If  the 
brachial  is  tied  below  the  origin  of  the  profunda  arteries,  the  circulation  is  maintained  by  the 
branches  of  the  profundse,  anastomosing  with  the  recurrent  radial,  ulnar,  and  interosseous 
arteries.  In  two  cases  described  by  Mr.  South,1  in  which  the  brachial  artery  had  been  tied  some 
time  previously,  in  one  "a  long  portion  of  the  artery  had  been  obliterated,  and  sets  of  vessels 
are  descending  on  either  side  from  above  the  obliteration,  to  be  received  into  others  which  ascend 
in  a  similar  manner  from  below  it.  In  the  other  the  obliteration  is  less  extensive,  and  a  single 
curved  artery  about  as  big  as  a  crow-quill  passes  from  the  upper  to  the  lower  open  part  of  the 
artery." 

Branches. — The  branches  of  the  brachial  artery  are — the 

Superior  Profunda.  Inferior  Profunda. 

Nutrient.  Anastomotica  Magna. 

Muscular. 

The  Superior  Profunda  Artery  (a.  profunda  brachii)  arises  from  the  inner  and 
back  part  of  the  brachial,  just  below  the  lower  border  of  the  Teres  major,  and 
passes  backward  to  the  interval  between  the  outer  and  inner  heads  of  the  Triceps 
muscle;  accompanied  by  the  musculo-spiral  nerve  it  winds  around  the  back  part  of 
the  shaft  of  the  humerus  in  the  spiral  groove,  between  the  outer  head  of  the  Triceps 
and  the  bone,  to  the  outer  side  of  the  humerus,  where  it  reaches  the  external  inter- 
muscular  septum  and  divides  into  two  terminal  branches.  One  of  these  pierces 
the  external  intermuscular  septum,  and  descends,  in  company  with  the  musculo- 
spiral  nerve,  to  the  space  between  the  Brachialis  anticus  and  Supinator  longus, 
where  it  anastomoses  with  the  recurrent  branch  of  the  radial  artery;  while  the 
other,  much  the  larger  of  the  two,  descends  along  the  back  of  the  external  inter- 
muscular septum  to  the  back  of  the  elbow-joint,  where  it  anastomoses  with  the 
posterior  interosseous  recurrent,  and  across  the  back  of  the  humerus  with  the  pos- 
terior ulnar  recurrent,  the  anastomotica  magna,  and  inferior  profunda  (Fig.  418). 
The  superior  profunda  supplies  the  Triceps  muscle  and  gives  off  a  nutrient  artery 
which  enters  the  bone  at  the  upper  end  of  the  musculo-spiral  groove.  Near  its 
commencement  it  sends  off  a  branch  which  passes  upward  between  the  external 
and  long  heads  of  the  Triceps  muscle  to  anastomose  with  the  posterior  circumflex 

1  Chelius's  Surgery,  vol.  ii.  p.  254.  See  also  White's  engravings,  referred  to  by  Mr.  South,  of  the  anastomos- 
ing branches  after  ligature  of  the  brachial,  in  White's  Cases  in  Surgery.  Porta  also  gives  a  case  (with  drawings) 
of  the  circulation  after  ligature  of  both  brachial  and  radial  (Alterazioni  Patoligiche  delle  Arterie). — ED.  of  15th 
English  edition. 

42 


658 


THE   BLOOD -VASCULAR    SYSTEM 


Sadial  recurrent. 


artery,  and,  while  in  the  groove,  a  small  branch  which  accompanies  a  branch  of 
the  musculo-spiral  nerve  through  the  substance  of  the  Triceps  muscle  and  ends 

in    the  Anconeus   below  the   outer 
condyle  of  the  humerus. 

The  Nutrient  Artery  (a.  nutricia 
humeri)  of  the  shaft  of  the  hurnerus 
arises  from  the  brachial,  about  the 
middle  of  the  arm.  Passing  down- 
ward it  enters  the  nutrient  canal  of 
that  bone  near  the  insertion  of  the 
Coraco-brachialis  muscle. 

The  Inferior  Profunda  (a.  col- 
lateralis  ulnaris  superior),  of  small 
size,  arises  from  the  brachial,  a  little 
below  the  middle  of  the  arm ;  pierc- 
ing the  internal  intermuscular  sep- 
tum, it  descends  on  the  surface  of 
the  inner  head  of  the  Triceps  mus- 
cle to  the  space  between  the  inner 
condyle  and  olecranon,  accompanied 
by  the  ulnar  nerve,  and  terminates 
by  anastomosing  with  the  posterior 
ulnar  recurrent  and  anastomotica 
magna.  It  sometimes  supplies  a 
branch  to  the  front  of  the  internal 
condyle,  which  anastomoses  with 
the  anterior  ulnar  recurrent. 

The  Anastomotica  Magna  (a. 
collateralis  ulnaris  inferior)  arises 
from  the  brachial  about  two  inches 
above  the  elbow-joint.  It  passes 
transversely  inward  upon  the  Bra- 
chialis  anticus,  and,  piercing  the 
internal  intermuscular  septum/winds 
round  the  back  of  the  humerus  be- 
tween the  Triceps  and  the  bone, 
forming  an  arch  above  the  olecranon 
fossa  by  its  junction  with  the  poste- 
rior articular  branch  of  the  superior 
profunda.  As  this  vessel  lies  on  the 
Brachialis  anticus,  branches  ascend 
to  join  the  inferior  profunda,  and 
others  descend  in  front  of  the  inner 
condyle  to  anastomose  with  the  an- 
terior ulnar  recurrent.  Behind  the 
internal  condyle  an  offset  is  given 
off  which  anastomoses  with  the  infe- 
rior profunda  and  posterior  ulnar 
recurrent  arteries  and  supplies  the 
Triceps. 

The  Muscular  (rami  musculares) 

FIG.  416.— The  radial  and  ulnar  arteries.  are    ^hrCC    or    four    large     branches, 

which  are  distributed  to  the  muscles  in  the  course  of  the  artery.    They  supply 
the  Coraco-brachialis,  Biceps,  and  Brachialis  anticus  muscles. 


Deep  branch 
of  ulnar. 


Superficial™  volse. 


THE  RADIAL    ARTERY  659 

The  Anastomosis  around  the  Elbow- joint  (Fig.  418). — The  vessels  engaged 
in  this  anastomosis  may  be  conveniently  divided  into  those  situated  in  front  and 
behind  the  internal  and  external  condyles.  The  branches  anastomosing  in  front 
of  the  internal  condyle  are  the  anastomotica  magna,  the  anterior  ulnar  recurrent, 
and  the  anterior  terminal  branch  of  the  inferior  profunda.  Those  behind  the  in- 
ternal condyle  are  the  anastomotica  magna,  the  posterior  ulnar  recurrent,  and  the 
posterior  terminal  branch  of  the  inferior  profunda.  The  branches  anastomosing 
in  front  of  the  external  condyle  are  the  radial  recurrent  and  the  anterior  terminal 
branch  of  the  superior  profunda.  Those  behind  the  external  condyle  (perhaps 
more  properly  described  as  being  situated  between  the  external  condyle  and  the 
olecranon)are  the  anastomotica  magna,  the  interosseous  recurrent, and  the  posterior 
terminal  branch  of  the  superior  profunda.  There  is  also  a  large  arch  of  anasto- 
mosis above  the  olecranon,  formed  by  the  interosseous  recurrent,  joining  with  the 
anastomotica  magna  and  posterior  ulnar  recurrent. 

From  this  description  it  will  be  observed  that  the  anastomotica  magna  is  the 
vessel  most  engaged,  the  only  part  of  the  anastomosis  in  which  it  is  not  employed 
being  that  in  front  of  the  external  condyle. 

The  Radial  Artery  (A.  Radialis)  (Figs.  416,  417). 

The  radial  artery  appears,  from  its  direction,  to  be  the  continuation  of  the 
brachial,  but  in  size  it  is  smaller  than  the  ulnar.  It  commences  at  the  bifurcation  of 
the  brachial,  just  below  the  bend  of  the  elbow,  and  passes  along  the  radial  side  of 
the  forearm  to  the  wrist;  it  then  winds  backward,  round  the  outer  side  of  the  carpus, 
beneath  the  extensor  tendons  of  the  thumb,  to  the  upper  end  of  the  space  between 
the  metacarpal  bones  of  the  thumb  and  index  ringer,  and  finally  passes  forward, 
between  the  two  heads  of  the  First  dorsal  interosseous  muscle,  into  the  palm  of  the 
hand,  where  it  crosses  the  metacarpal  bones  to  the  ulnar  border  of  the  hand,  to  form 
the  deep  palmar  arch.  At  its  termination  it  inosculates  with  the  deep  branch  of  the 
ulnar  artery.  The  relations  of  this  vessel  may  thus  be  conveniently  divided  into 
three  parts — viz.,  in  the  forearm,  at  the  back  of  the  wrist,  and  in  the  hand. 

Relations. — In  the  forearm  this  vessel  extends  from  opposite  the  neck  of  the 
radius  to  the  forepart  of  the  styloid  process,  being  placed  to  the  inner  side  of  the 
shaft  of  the  bone  above  and  in  front  of  it  below.  It  is  overlapped  in  the  upper 
part  of  its  course  by  the  fleshy  belly  of  the  Supinator  longus  muscle;  throughout 
the  rest  of  its  course  it  is  superficial,  being  covered  by  the  integument,  the  super- 
ficial and  deep  fasciae.  In  its  course  downward  it  lies  upon  the  tendon  of  the 
Biceps,  the  Supinator  brevis,  the  Pronator  radii  teres,  the  radial  origin  of  the 
Flexor  sublimis  digitorum,  the  Flexor  longus  pollicis,  the  Pronator  quadratus,  and 
the  lower  extremity  of  the  radius.  In  the  upper  third  of  its  course  it  lies  between 
the  Supinator  longus  and  the  Pronator  radii  teres;  in  the  lower  two-thirds,  between 
the  tendons  of  the  Supinator  longus  and  the  Flexor  carpi  radialis.  The  radial 
nerve  lies  close  to  the  outer  side  of  the  artery  in  the  middle  third  of  its  course, 
and  some  filaments  of  the  musculo-cutaneous  nerve,  after  piercing  the  deep  fascia, 
run  along  the  lower  part  of  the  artery  as  it  winds  round  the  wrist.  The  vessel  is 
accompanied  by  venre  comites  throughout  its  whole  course. 

PLAN  OF  THE  RELATIONS  OF  THE  RADIAL  ARTERY  IN  THE  FOREARM. 

In  front. 

Skin,  superficial  and  deep  fasciae. 
Supinator  longus. 

Inner  side.  f      Radial     \  Outer  side. 

Pronator  radii  teres.  Forearm"1     /  Supinator  longus. 

Flexor  carpi  radialis.  V  J  Radial  nerve  (middle  third). 


660  THE   BLOOD -VASCULAR   SYSTEM 

Behind. 

Tendon  of  Biceps. 
Supinator  brevis. 
Pronator  radii  teres. 
Flexor  sublimis  digitorum. 
Flexor  longus  pollicis. 
Pronator  quadratus. 
Radius. 

At  the  wrist,  as  it  winds  round  the  outer  side  of  the  carpus  from  the  styloid 
process  to  the  first  interosseous  space,  it  lies  upon  the  external  lateral  ligament, 
and  then  upon  the  scaphoid  bone  and  trapezium,  being  covered  by  the  extensor 
tendons  of  the  thumb,  subcutaneous  veins,  some  filaments  of  the  radial  nerve,  and 
the  integument.  It  is  accompanied  by  two  veins  and  a  filament  of  the  musculo- 
cutaneous  nerve. 

In  the  hand  it  passes  from  the  upper  end  of  the  first  interosseous  space, 
between  the  heads  of  the  Abductor  indicis  or  First  dorsal  interosseous  muscle, 
transversely  across  the  palm,  to  the  base  of  the  metacarpal  bone  of  the  little 
finger,  where  it  inosculates  with  the  communicating  branch  from  the  ulnar  artery, 
forming  the  deep  palmar  arch. 

The  Deep  Palmar  Arch  (arcus  volaris  profundus)  (Fig.  417). — It  lies  upon  the 
carpal  extremities  of  the  metacarpal  bones  and  the  Interossei  muscles,  being 
covered  by  the  Adductor  obliquus  pollicis,  the  flexor  tendons  of  the  fingers,  the 
Lumbricales,  the  Opponens,  and  Flexor  brevis  minimi  digiti.  Alongside  of  it  is 
the  deep  branch  of  the  ulnar  nerve,  but  running  in  the  opposite  direction;  that 
is  to  say,  from  within  outward.  The  branches  of  the  deep  palmar  arch  are  the 
palmar  interosseous,  perforating  and  palmar  recurrent  vessels  (page  662). 

Peculiarities. — The  origin  of  the  radial  artery,  according  to  Quain,  is,  in  nearly  one  case 
in  eight,  higher  than  usual;  more  frequently  arising  from  the  axillary  or  upper  part  of  the  brachial 
than  from  the  lower  part  of  this  vessel.  The  variations  in  the  position  of  this  vessel  in  the  arm 
and  at  the  bend  of  the  elbow  have  been  already  mentioned.  In  the  forearm  it  deviates  less  fre- 
quently from  its  position  than  the  ulnar.  It  has  been  found  lying  over  the  fascia  instead  of 
beneath  it.  It  has  also  been  observed  on  the  surface  of  the  Supinator  longus,  instead  of  under 
its  inner  border;  and  in  turning  round  the  wrist  it  has  been  seen  lying  over,  instead  of  beneath, 
the  extensor  tendons  of  the  thumb. 

Surface  Marking. — The  position  of  the  radial  artery  in  the  forearm  is  represented  by  a  line 
drawn  from  the  outer  border  of  the  tendon  of  the  Biceps  in  the  centre  of  the  hollow  in  front 
of  the  elbow-joint  with  a  straight  course  to  the  inner  side  of  the  forepart  of  the  styloid  process 
of  the  radius. 

Surgical  Anatomy.— The  radial  artery  is  much  exposed  to  injury  in  its  lower  third,  and  is 
frequently  wounded  by  the  hand  being  driven  through  a  pane  of  glass,  by  the  slipping  of  a 
knife  or  chisel  held  in  the  other  hand,  and  similar  accidents.  The  injury  is  often  followed  by 
a  traumatic  aneurism,  for  which  the  operation  of  extirpating  or  laying  open  the  sac  after  securing 
the  vessel  above  and  below  is  required. 

The  operation  of  tying  the  radial  artery  is  required  in  cases  of  wounds  either  of  its  trunk  or 
of  some  of  its  branches,  or  for  aneurism;  and  it  will  be  observed  that  the  vessel  may  be  exposed 
in  any  part  of  its  course  through  the  forearm  without  the  division  of  any  muscular  fibres.  The 
operation  in  the  middle  or  inferior  third  of  the  forearm  is  easily  performed,  but  in  the  upper 
third,  near  the  elbow,  it  is  attended  with  some  difficulty,  from  the  greater  depth  of  tlje  vessel 
and  from  its  being  overlapped  by  the  Supinator  longus  muscle. 

To  tie  the  artery  in  the  upper  third  an  incision  three  inches  in  length  should  be  made  through 
the  integument,  in  a  line  drawn  from  the  centre  of  the  bend  of  the  elbow  to  the  front  of  the 
styloid  process  of  the  radius,  avoiding  the  branches  of  the  median  vein;  the  fascia  of  the  arm 
being  divided  and  the  Supinator  longus  drawn  a  little  outward,  the  artery  will  be  exposed.  The 
venae  comites  should  be  carefully  separated  from  the  vessel,  and  the  ligature  passed  from  the 
radial  to  the  ulnar  side. 

In  the  middle  third  of  the  forearm  the  artery  may  be  exposed  by  making  an  incision  of  similar 
length  on  the  inner  margin  of  the  Supinator  longus.  In  this  situation  the  radial  nerve  lies  in  close 
relation  with  the  outer  side  of  the  artery,  and  should,  as  well  as  the  veins,  be  carefully  avoided. 

In  the  lower  third  the  artery  is  easily  secured  by  dividing  the  integument  and  fascia  in  the 
interval  between  the  tendons  of  the  Supinator  longus  and  Flexor  carpi  radialis  muscles. 


THE   RADIAL    ARTERY 


661 


Branches  (Figs.  416,  417,  and  418).— The  branches  of  the  radial  artery  may 
be  divided  into  three  groups,  corresponding  with  the  three  regions  in  which  the 
vessel  is  situated. 


In  the 
Forearm 


Wrist 


Radial  Recurrent. 

Muscular. 

Anterior  Radial  Carpal. 

Superficialis  Volre. 

Princeps  Pollicis. 

Radialis  Indicis. 


Posterior  Radial  Carpal. 

Metacarpal. 

1  )orsales  Pollicis. 

Dorsalis  Indicis. 


Hand 


Perforating. 

Palmar  Interosseous. 

Palmar  Recurrent. 


The  Radial  Recurrent  (a.  recurrens  radialis)  (Fig.  417)  is  given  off  imme- 
diately below  the  elbow.  It  ascends  between  the  branches  of  the  musculo-spiral 
nerve  lying  on  the  Supinator  brevis,  and  then  between  the  Supinator  longus  and 
Brachialis  anticus,  supplying  these  muscles  and  the  elbow-joint,  and  anastomosing 
with  the  terminal  branches  of  the  superior  profunda. 

The  Muscular  Branches  (rami  musculares)  are  distributed  to  the  muscles  on 
the  radial  side  of  the  forearm. 

The  Anterior  Radial  Carpal  (ramus  carpeus  volaris)  (Fig.  417)  is  a  small 
vessel  which  arises  from  the  radial  artery  near  the  lower  border  of  the  Pronator 
quadratus,  and,  running  inward  in  front  of  the  radius,  anastomoses  with  the  ante- 
rior carpal  branch  of  the  ulnar  artery.  In  this  way  an  arterial  anastomosis,  the 
anterior  carpal  arch  (rete  carpi  volare),  is  formed  in  front  of  the  wrist;  it  is  joined 
by  branches  from  the  anterior  interosseous  above,  and  by  recurrent  branches  from 
the  deep  palmar  arch  below,  and  gives  off  branches  which  descend  to  supply  the 
articulations  of  the  wrist  and  carpus. 

The  Superficialis  Volse  (ramus  volaris  superficialis)  (Fig.  417)  arises  from  the 
radial  artery,  just  where  this  vessel  is  about  to  wind  round  the  wrist.  Running 
forward,  it  passes  between,  occasionally  over,  the  muscles  of  the  thumb,  which  it 
supplies,  and  sometimes  anastomoses  with  the  palmar  portion  of  the  ulnar  artery, 
completing  the  superficial  palmar  arch.  This  vessel  varies  considerably  in  size: 
usually  it  is  very  small,  and  terminates  in  the  muscles  of  the  thumb ;  sometimes 
it  is  as  large  as  the  continuation  of  the  radial. 

The  Posterior  Radial  Carpal  (ramus  carpeus  dorsalis)  (Fig.  418)  is  a  small 
vessel  which  arises  from  the  radial  artery  beneath  the  extensor  tendons  of  the 
thumb;  crossing  the  carpus  transversely  to  the  inner  border  of  the  hand,  it 
anastomoses  with  the  posterior  carpal  branch  of  the  ulnar,  forming  the  posterior 
carpal  arch  (rete  carpi  dorsale) ,  which  is  joined  by  the  termination  of  the  anterior 
interosseous  artery.  From  this  arch  are  given  off  descending  branches,  the 
dorsal  interosseous  arteries  (aa.  metacarpeae  dor  sales)  for  the  second,  third,  and 
fourth  interosseous  spaces,  which  run  forward  on  the  Second,  Third,  and 
Fourth  dorsal  interossei  muscles,  and  divide  into  dorsal  digital  branches  (aa. 
digitales  dorsales),  which  supply  the  adjacent  sides  of  the  index,  middle,  ring, 
and  little  fingers  respectively,  communicating  with  the  digital  arteries  of  the 
superficial  palmar  arch.  The  dorsal  interosseous  arteries  anastomose  with  the 
perforating  branches  from  the  deep  palmar  arch. 

The  Dorsales  Pollicis  (Fig.  418)  are  two  vessels  which  run  along  the  sides  of 
the  dorsal  aspect  of  the  thumb.  They  arise  separately,  or  occasionally  by  a 
common  trunk,  near  the  base  of  the  first  metacarpal  bone. 

The  Dorsalis  Indicis  (Fig.  418),  also  a  small  branch,  runs  along  the  radial  side 
of  the  back  of  the  index  finger,  sending  a  few  branches  to  the  Abductor  indicis. 


662 


THE  BLOOD -VASCULAR    SYSTEM 


Anastomotica, 
magna. 


Radial 
recurrent. 


Posterior 
•inter  osseous. 


Anterior  ulnar 
recurrent. 

Posterior  ulnar 
recurrent. 


The  Princeps  Pollicis  (a.  princeps  pollicis)  (Fig.  4l7)arises  from  the  radial  just  as 
it  turns  inward  to  the  deep  part  of  the  hand ;  it  descends  between  the  Abductor  indicis 

and  Adductor  obliquus  pollicis,  then 
between  the  Adductor  transversus 
pollicis  and  Adductor  obliquus 
pollicis,  along  the  ulnar  side  of  the 
metacarpal  bone  of  the  thumb,  to 
the  base  of  the  first  phalanx,  where 
it  divides  into  two  branches,  which 
run  along  the  sides  of  the  palmar 
aspect  of  the  thumb,  and  form  an 
arch  on  the  palmar  surface  of  the 
last  phalanx,  from  which  branches 
are  distributed  to  the  integument 
and  pulp  of  the  thumb. 

The  Radialis  Indicis  (a.  volaris 
indicis  radialis)  (Fig.  417)  arises 
close  to  the  preceding,  descends 
between  the  Abductor  indicis  and 
Adductor  transversus  pollicis,  and 
runs  along  the  radial  side  of  the 
index  finger  to  its  extremity,  where 
it  anastomoses  with  the  collateral 
digital  artery  from  the  superficial 
palmar  arch.  At  the  lower  border 
of  the  Adductor  transversus  pollicis 
this  vessel  anastomoses  with  the 
princeps  pollicis,  and  gives  a  com- 
municating branch  to  the  super- 
ficial palmar  arch. 

The  Perforating  Arteries  (rami 


Muscular. 


Anterior  ca: 
Superficial  volse 


in 


perforantes)  (Fig.  417),  three 
number,  pass  backward  from  the 
deep  palmar  arch  between  the 
heads  of  the  last  three  Dorsal  inter- 
ossei  muscles,  to  inosculate  with 
the  dorsal  interosseous  arteries. 

The  Palmar  Interosseous  (aa. 
metacarpeaevolares)  (Fig.  417),  three 
or  four  in  number,  arise  from  the 
convexity  of  the  deep  palmar  arch ; 
they  run  forward  upon  the  Inter- 
ossei  muscles,and  anastomose  at  the 
clefts  of  the  fingers  with  the  digital 
branches  of  the  superficial  arch. 
The  Palmar  Recurrent  Branches  arise  from  the  concavity  of  the  deep  palmar 

arch.    They  pass  upward  in  front  of  the  wrist,  supplying  the  carpal  articulations 

and  anastomosing  with  the  anterior  carpal  arch. 


FIG.  417. — Ulnar  and  radial  arteries.     Deep  view. 


The  Ulnar  Artery  (A.  Ulnaris)  (Figs.  416,  417). 

The  ulnar  artery,  the  larger  of  the   two   terminal   branches  of  the  brachial, 
commences  a  little   below  the  bend  of  the  elbow,  and  crosses  obliquely  the 


THE    ULNAR    ARTERY  663 

inner  side  of  the  forearm  to  the  commencement  of  its  lower  half;  it  then 
runs  along  its  ulnar  border  to  the  wrist,  crosses  the  annular  ligament  on  the 
radial  side  of  the  pisiform  bone,  and  immediately  beyond  this  bone  divides  into 
two  branches  which  enter  into  the  formation  of  the  superficial  and  deep  palmar 
arches. 

Relations.  In  the  Forearm. — In  its  upper  half  it  is  deeply  seated,  being  cov- 
ered by  all  the  superficial  Flexor  muscles,  excepting  the  Flexor  carpi  ulnaris;  the 
median  nerve  is  in  relation  with  the  inner  side  of  the  artery  for  about  an  inch  and 
then  crosses  the  vessel,  being  separated  from  it  by  the  deep  head  of  the  Pronator 
radii  teres;  it  lies  upon  the  Brachialis  anticus  and  Flexor  profundus  digitorum 
muscles.  In  the  lower  half  of  the  forearm  it  lies  upon  the  Flexor  profundus,  being 
covered  by  the  integument,  the  superficial  and  deep  fasciae,  and  is  placed  between 
the  Flexor  carpi  ulnaris  and  Flexor  sublimis  digitorum  muscles.  It  is  accompanied 
by  two  venae  comites;  the  ulnar  nerve  lies  on  its  inner  side  for  the  lower  two- 
thirds  of  its  extent,  and  a  small  branch  from  the  nerve  descends  on  the  lower  part 
of  the  vessel  to  the  palm  of  the  hand. 

PLAN  OF  RELATIONS  OF  THE  ULNAR  ARTERY  IN  THE  FOREARM. 

In  front. 

Superficial  layer  of  flexor  muscles.  ]  TT 
Median  nerve.  I  UPPer  half" 

Superficial  and  deep  fasciae.  Lower  half. 

Inner  side.  (       Ulnar       \  Outer  side. 

Artery  in 

Flexor  carpi  ulnaris.  \     Forearm.     )  Flexor  sublimis  digitorum. 

Ulnar  nerve  (lower  two-thirds).       V^  / 

Behind. 

Brachialis  anticus. 
Flexor  profundus  digitorum. 

At  the  wrist  (Fig.  416)  the  ulnar  artery  is  covered  by  the  integument  and  fascia, 
and  lies  upon  the  anterior  annular  ligament.  On  its  inner  side  is  the  pisiform  bone. 
The  ulnar  nerve  lies  at  the  inner  side,  and  somewhat  behind  the  artery;  here  the 
nerve  and  artery  are  crossed  by  a  band  of  fibres,  which  extends  from  the  pisiform 
bone  to  the  anterior  annular  ligament. 

Peculiarities. — The  ulnar  artery  has  been  found  to  vary  in  its  origin  nearly  in  the  propor- 
tion of  one  in  thirteen  cases,  in  one  case  arising  lower  than  usual,  about  two  or  three  inches 
below  the  elbow,  and  in  all  other  cases  much  higher,  the  brachial  being  a  more  frequent  source 
or  origin  than  the  axillary. 

Variations  in  the  position  of  this  vessel  are  more  frequent  than  in  the  radial.  When  its  origin 
is  normal  the  course  of  the  vessel  is  rarely  changed.  When  it  arises  high  up  it  is  almost  invaria- 
bly superficial  to  the  Flexor  muscles  in  the  forearm,  lying  commonly  beneath  the  fascia,  more 
rarely  between  the  fascia  and  integument.  In  a  few  cases  its  position  was  subcutaneous  in  the 
upper  part  of  the  forearm,  subaponeurotic  in  the  lower  part. 

Surface  Marking. — On  account  of  the  curved  direction  of  the  ulnar  artery  the  line  on  the 
surface  of  the  body  which  indicates  its  course  is  somewhat  complicated.  First,  draw  a  line  from 
the  front  of  the  internal  condyle  of  the  humerus  to  the  radial  side  of  the  pisiform  bone;  the 
lower  two-thirds  of  this  line  represents  the  course  of  the  middle  and  lower  third  of  the  ulnar 
artery.  Secondly,  draw  a  line  from  the  centre  of  the  antecubital  space  to  the  junction  of  the 
upper  and  middle  third  of  the  first  line;  this  represents  the  course  of  the  upper  third  of  the 
artery. 

Surgical  Anatomy. — The  application  of  a  ligature  to  this  vessel  is  required  in  cases  of  wound 
of  the  artery  or  of  its  branches,  or  in  consequence  of  aneurism.  In  the  upper  half  of  the  fore- 
arm the  artery  is  deeply  seated  beneath  the  superficial  flexor  muscles,  and  the  application  of  a 
ligature  in  this  situation  is  attended  with  some  difficulty.  An  incision  is  to  be  made  in  the 
course  of  a  line  drawn  from  the  front  of  the  internal  condyle  of  the  humerus  to  the  outer  side 


664  THE   BLOOD    VASCULAR    SYSTEM 

of  the  pisiform  bone,  so  that  the  centre  of  the  incision  is  three  fingers'  breadth  below  the  internal 
condyle.  The  skin  and  superficial  fascia  having  been  divided  and  the  deep  fascia  exposed, 
the  white  line  which  separates  the  Flexor  carpi  ulnaris  from  the  other  flexor  muscles  is  to  be 
sought  for,  and  the  fascia  incised  in  this  line.  The  Flexor  carpi  ulnaris  is  now  to  be  carefully 
separated  from  the  other  muscles,  when  the  ulnar  nerve  will  be  exposed,  and  must  be  drawn 
aside.  Some  little  distance  below  the  nerve  the  artery  will  be  found  accompanied  by  its  vense 
comites,  and  it  may  be  ligatured  by  passing  the  needle  from  within  outward.  In  the  middle  and 
lower  third  of  the  forearm  this  vessel  may  be  easily  secured  by  making  an  incision  on  the  radial 
side  of  the  tendon  of  the  Flexor  carpi  ulnaris:  the  deep  fascia  being  divided,  and  the  Flexor 
carpi  ulnaris  and  its  companion  muscle,  the  Flexor  sublimis,  being  separated  from  each  other, 
the  vessel  will  be  exposed,  accompanied  by  its  vense  comites,  the  ulnar  nerve  lying  on  its  inner 
side.  The  veins  being  separated  from  the  artery,  the  ligature  should  be  passed  from  the  ulnar 
to  the  radial  side,  taking  care  to  avoid  the  ulnar  nerve. 

Branches  (Figs.  416,  417,  and  418). — The  branches  of  the  ulnar  artery  may 
be  arranged  in  the  following  groups: 


Forearm 


Wrist 


Anterior  Ulnar  Recurrent. 
Posterior  Ulnar  Recurrent. 

,  -Anterior  Interosseous. 
Interosseous       •{  r>         •      T  j 

Posterior  Interosseous. 


Muscular. 
Anterior  Carpal. 
Posterior  Carpal. 

,      f  Deep  Palmar  or  Communicating. 
Hand      [Superficial  Palmar  Arch. 


The  Anterior  Ulnar  Recurrent  (a.  recurrences  ulnaris  anterior)  (Fig.  417) 
arises  immediately  below  the  elbow-joint,  passes  upward  and  inward  between  the 
Brachialis  anticus  and  Pronator  radii  teres,  supplies  twigs  to  those  muscles,  and, 
in  front,  of  the  inner  condyle  anastomoses  with  the  anastomotica  magna  and 
inferior  profunda. 

The  Posterior  Ulnar  Recurrent  (a.  recurrentes  ulnaris  posterior)  (Figs.  417  and 
418)  is  much  larger,  and  arises  somewhat  lower  than  the  preceding.  It  passes 
backward  and  inward,  beneath  the  Flexor  sublimis,  and  ascends  behind  the  inner 
condyle  of  the  humerus.  In  the  interval  between  this  process  and  the  olecranon 
it  lies  beneath  the  Flexor  carpi  ulnaris,  and  ascending  between  the  heads  of  thai 
muscle,  in  relation  with  the  ulnar  nerve ;  it  supplies  the  neighboring  muscles  and 
joint,  and  anastomoses  with  the  inferior  profunda,  anastomotica  magna,  and 
interosseous  recurrent  arteries. 

The  Interosseous  Artery  (a.  interossea  communis)  (Fig.  417)  is  a  short  trunk 
about  half  an  inch  in  length,  and  of  considerable  size,  which  arises  immediately, 
below  the  tuberosity  of  the  radius,  'and,  passing  backward  to  the  upper  border  oi 
the  interosseous  membrane,  divides  into  two  branches,  the  anterior  and  posterior 
interosseous. 

The  Anterior  Interosseous  (a.  interossea  volaris]  (Fig.  417)  passes  down  the  fore- 
arm on  the  anterior  surface  of  the  interosseous  membrane,  to  which  it  is  connected 
by  a  thin  aponeurotic  arch.  It  is  accompanied  by  the  interosseous  branch  of  the 
median  nerve,  and  overlapped  by  the  contiguous  margins  of  the  Flexor  profundus 
digitorum  and  Flexor  longus  pollicis  muscles,  giving  off  in  this  situation  muscular 
branches  and  the  nutrient  arteries  of  the  radius  and  ulna.  At  the  upper  border 
of  the  Pronator  quadratus  a  branch,  anterior  communicating  artery,  descends 
beneath  the  muscle  to  anastomose  in  front  of  the  carpus  with  the  anterior  carpal 
arch.  The  continuation  of  the  artery  passes  behind  the  Pronator  quadratus,  and, 
piercing  the  interosseous  membrane,  reaches  the  back  of  the  forearm,  and  anasto- 
moses with  the  posterior  interosseous  artery  (Fig.  418).  It  then  descends  to  the 
back  of  the  wrist  to  join  the  posterior  carpal  arch.  The  anterior  interosseous  gives 


THE    ULNAR   ARTERY 


665 


recurrent. 


—Posterior  interosseous. 


off  a  long,  slender  branch,  the  median  artery  or  artery  comes  nervi  mediana 
(a.  mediana),  which  accompanies  the  median  nerve  and  gives  offsets  to  its  sub- 
stance. This  artery  is  some- 

iii  /  m  .Descending  branch  from 

times  much  enlarged,  and  ac-  /     ^fj      superior  profunda. 

companies  the  nerve  into  the 
palm  of  the  hand. 

The  Posterior  Interosseous 
Artery  (a.  interossea  dorsalis)  Anastomotica 
(Figs.  417  and  418)  passes  magna. 
backward  through  the  inter- 
val between  the  oblique  liga-  Posterior  uinar^ 
ment  and  the  upper  border  of 
the  interosseous  membrane. 
It  appears  between  the  con- 
tiguous borders  of  the  Supina- 
tor  brevis  and  the  Extensor 
ossis  metacarpi  pollicis,  and 
runs  down  the  back  part  of 
the  forearm,  between  the  su- 
perficial and  deep  layer  of 
muscles,  to  both  of  which  it 
distributes  branches.  At  the 
lower  part  of  the  forearm  it 
anastomoses  with  the  termina- 
tion of  the  anterior  interosse- 
ous artery.  Then,  continuing 
its  course  over  the  head  of 
the  ulna,  it  joins  the  posterior 
carpal  branch  of  the  ulnar 
artery.  This  artery  gives  off, 
near  its  origin,  the  interosseous 
recurrent  branch. 

The  interosseous  recurrent 
artery  (a.  interossea  recurrens) 
(Fig.418)  is  a  large  vessel  which 
ascends  to  the  interval  between 
the  external  condyle  and  olec- 
ranon,  on  or  through  the  fibres 
of  the  Supinator  brevis,  but 
beneath  the  Anconeus,  anas- 
tomosing with  a  branch  from 
the  superior  profunda,  and 
with  the  posterior  ulnar  recur- 
rent and  anastomotica  magna. 

The  Muscular  Branches 
(rami  muscidares)  are  distri- 
buted to  the  muscles  along 
the  ulnar  side  of  the  forearm. 

The  Anterior  Carpal  (ramus  carpeus  volaris)  (Fig.  417)  is  a  small  vessel 
which  crosses  the  front  of  the  carpus  beneath  the  tendons  of  the  Flexor  pro- 
fundus,  and  inosculates  with  a  corresponding  branch  of  the  radial  artery. 

The  Posterior  Carpal  (rarmis  carpeus  dorsalis)  (Fig.  418)  arises  immediately 
above  the  pisiform  bone,  and  winds  backward  beneath  the  tendon  of  the  Flexor 
carpi  ulnaris :  it  passes  across  the  dorsal  surface  of  the  carpus  beneath  the  extensor 


Termination  of  an- 
terior interosseous. 


Posterior  carpal 
(ulnar). 


Posterior  carpal 
(radial). 

Radial. 

vsalis  pollicis. 
Dorsalis  indicia. 


FIG.  418. — Arteries  of  the  back  of  the  forearm  and.hand. 


666  THE   BLOOD -VASCULAR   SYSTEM 

tendons,  anastomosing  with  a  corresponding  branch  of  the  radial  artery,  and 
forming  the  posterior  carpal  arch  (rete  carpi  dorsale)  (Fig.  418).  Immediately  after 
its  origin  it  gives  off  a  small  branch  which  runs  along  the  ulnar  side  of  the  meta- 
carpal  bone  of  the  little  finger,  forming  one  of  the  metacarpal  arteries,  and  supplies 
the  ulnar  side  of  the  dorsal  surface  of  the  little  finger. 

The  Deep  or  Communicating  Branch  to  the  Deep  Palmar  Arch  (ramus 
volaris  profundus)  (Fig.  417)  passes  deeply  inward  between  the  Abductor  minimi 
digiti  and  Flexor  brevis  minimi  digiti,  near  their  origins;  it  anastomoses  with  the 
termination  of  the  radial  artery,  completing  the  deep  palmar  arch. 

The  continuation  of  the  trunk  of  the  ulnar  artery  in  the  hand  forms  the  greater 
part  of  the  superficial  palmar  arch. 

The  Superficial  Palmar  Arch  (arcus  volaris  superficial™)  (Fig.  416)  is  formed 
by  the  ulnar  artery  in  the  hand,  and  is  completed  on  the  outer  side  by  this  vessel 
anastomosing  with  a  branch  from  the  radialis  indicis,  though  sometimes  the  arch 
is  completed  by  the  ulnar  anastomosing  with  the  superficialis  volse  or  the  princeps 
pollicis  of  the  radial  artery.  The  arch  passes  across  the  palm,  describing  a  curve, 
with  its  convexity  forward,  to  the  space  between  the  ball  of  the  thumb  and  the 
index  finger,  where  the  above-mentioned  anastomosis  takes  place. 

Relations. — The  superficial  palmar  arch  is  covered  by  the  skin,  the  Palmaris 
brevis,  and  the  palmar  fascia.  It  lies  upon  the  annular  ligament,  the  Flexor 
brevis  of  the  little  finger,  the  tendons  of  the  superficial  flexor  of  the  fingers,  and 
the  divisions  of  the  median  and  ulnar  nerves. 

PLAN  OF  THE  RELATIONS  OF  THE  SUPERFICIAL  PALMAR  ARCH. 

In  front. 
Skin. 

Palmaris  brevis. 
Palmar  fascia. 


Behind. 

Annular  ligament. 
Flexor  brevis  of  little  finger. 
Superficial  flexor  tendons. 
Divisions  of  median  and  ulnar  nerves. 

Branches. — The  branches  of  the  Superficial  Palmar  Arch  are  the 

Digital. 

The  Digital  Branches  (aa.  digitales  volares  communes)  (Fig.  416),  four  in  number, 
are  given  off  from  the  convexity  of  the  superficial  palmar  arch.  They  supply  the 
ulnar  side  of  the  little  finger  and  the  adjoining  sides  of  the  little,  ring,  middle,  and 
index  fingers,  the  radial  side  of  the  index  finger  and  thumb  being  supplied  from 
the  radial  artery.  The  digital  arteries  at  first  lie  superficial  to  the  flexor  tendons, 
but  as  they  pass  forward  with  the  digital  nerves  to  the  clefts  between  the  fingers 
they  lie  between  them,  and  are  there  joined  by  the  interosseous  branches  from  the 
deep  palmar  arch.  The  digital  arteries  on  the  sides  of  the  fingers  lie  beneath  the 
digital  nerves;  and  about  the  middle  of  the  last  phalanx  the  two  branches  for  each 
finger  form  an  arch,  from  the  convexity  of  which  branches  pass  to  supply  the 
pulp  of  the  finger. 


THE    THORACIC  AORTA  667 

Surface  Marking. — The  superficial  palmar  arch  is  represented  by  a  curved  line,  starting 
from  the  outer  side  of  the  pisiform  bone  and  carried  downward  as  far  as  the  middle  third  of 
the  palm,  and  then  curved  outward  on  a  level  with  the  upper  end  of  the  cleft  between  the  thumb 
and  index  finger.  The  deep  palmar  arch  is  situated  about  half  an  inch  nearer  to  the  carpus. 

Surgical  Anatomy. — Wounds  of  the  palmar  arches  are  of  special  interest,  and  are  always 
difficult  to  deal  with.  When  the  superficial  arch  is  wounded  it  is  generally  possible,  by  enlarging 
the  wound  if  necessary,  to  secure  the  vessel  and  tie  it;  or  in  cases  where  it  is  found  impossible  to 
encircle  the  vessel  with  a  ligature,  a  pair  of  haemostatic  forceps  may  be  applied  and  left  on  for 
twenty-four  or  forty-eight  hours.  Wounds  of  the  deep  arch  are  not  so  easily  dealt  with.  It  may 
be  possible  to  secure  the  vessel  by  ligature  or  by  forcipressure  forceps,  which  may  be  left  on; 
or,  failing  in  this,  the  wound  may  be  carefully  plugged  with  gauze  and  an  outside  dressing  care- 
fully bandaged  on.  The  plug  should  be  allowed  to  remain  untouched  for  three  or  four  days. 
In  wounds  of  the  deep  palmar  arch  a  ligature  may  be  applied  to  the  bleeding  points  from  the 
dorsum  of  the  hand  by  resection  of  the  upper  part  of  the  third  metacarpal  bone.  It  is  -useless 
in  these  cases  to  ligate  one  of  the  arteries  of  the  forearm  alone,  and  indeed  simultaneous  Hga- 
tion  of  both  radial  and  ulnar  arteries  above  the  wrist  is  often  unsuccessful,  on  account  of  the 
anastomosis  carried  on  by  the  carpal  arches.  Therefore,  if  unable  to  ligate  the  divided  ends 
of  the  arch,  upon  the  failure  of  pressure  to  arrest  hemorrhage,  it  is  expedient  to  apply  a  ligature 
to  the  brachial  artery. 

ARTERIES  OF  THE  TRUNK. 
THE  DESCENDING  AORTA  (Figs.  419,  420). 

The  descending  aorta  is  divided  into  two  portions,  the  thoracic  and  abdominal, 
in  correspondence  with  the  two  great  cavities  of  the  trunk  in  which  it  is  situated. 

The  Thoracic  Aorta  (Aorta  Thoracalis)  (Fig.  419). 

The  thoracic  aorta  commences  at  the  lower  border  of  the  fourth  thoracic 
vertebra,  on  the  left  side,  and  terminates  at  the  aortic  opening  in  the  Diaphragm, 
in  front  of  the  lower  border  of  the  last  thoracic  vertebra.  At  its  commencement 
it  is  situated  on  the  left  side  of  the  spine;  it  approaches  the  median  line  as  it 
descends,  and  at  its  termination  lies  directly  in  front  of  the  spinal  column.  The 
direction  of  this  vessel  being  influenced  by  the  spine,  upon  which  it  rests,  it 
describes  a  curve  which  is  concave  forward  in  the  thoracic  region.  As  the  branches 
given  off  from  it  are  small,  the  diminution  in  the  size  of  the  vessel  is  inconsider- 
able. It  is  contained  in  the  back  part  of  the  posterior  mediastinum. 

Relations. — It  is  in  relation,  in  front,  from  above  downward,  with  the  root  of 
the  left  lung,  the  pericardium,  the  oesophagus,  and  the  Diaphragm:  behind,  with 
the  vertebral  column  and  the  vena?  azygos  minor;  on  the  right  side,  with  the  vena 
azygos  major  and  thoracic  duct;  on  the  left  side,  with  the  left  pleura  and  lung. 
The  oesophagus,  with  its  accompanying  nerves,  lies  on  the  right  side  of  the  aorta 
above;  but  at  the  lower  part  of  the  thorax  it  gets  in  front  of  the  aorta,  and  close 
to  the  Diaphragm  is  situated  to  its  left  side. 

PLAN  OF  THE  RELATIONS  OF  THE  THORACIC  AORTA. 

In  front. 
Root  of  left  lung. 
Pericardium. 
(Esophagus. 
Diaphragm. 

Right  side.  y  >>  Left  side. 

(Esophagus  (above).  [  Thoracic      \  Pleura. 

Vena  azygos  major.  l  Aorta.        I  Left  lung. 

Thoracic  duct.  J  (Esophagus  (below). 

Behind. 

Vertebral  column. 
Superior  and  inferior  azygos  minor  veins. 


THE   BLOOD -VASCULAR    SYSTEM 

The  aorta  is  occasionally  found  to  be  obliterated  at  a  particular  spot— viz.,  at  the  junction  of 
the  arch  with  the  thoracic  aorta  just  below  the  ductus  arteriosus.  Whether  this  is  the  result  of 
disease  or  of  congenital  malformation  is  immaterial  to  our  present  purpose;  it  affords  an  interest- 
ing opportunity  of  observing  the  resources  of  the  collateral  circulation.  The  course  of  the  anas- 
tomosing vessels,  by  which  the  blood  is  brought  from  the  upper  to  the  lower  part  of  the  artery, 
will  be  found  well  described  in  an  account  of  two  cases  in  the  Pathological  Transactions,  vols.  viii. 
and  x.  In  the  former  (p.  162)  Mr.  Sydney  Jones  thus  sums  up  the  detailed  description  of  the 
anastomosing  vessels:  "The  principal  communications  by  which  the  circulation  was  carried  on, 
were— Firstly,  the  internal  mammary,  anastomosing  with  the  intercostal  arteries,  with  the  phrenic 
of  the  abdominal  aorta  by  means  of  the  musculo-phrenic  and  comes  nervi  phrenici,  and  largely 
with  the  deep  epigastric.  Secondly,  the  superior  intercostal,  anastomosing  anteriorly  by  means 
of  a  large  branch  with  the  first  aortic  intercostal,  and  posteriorly  with  the  posterior  branch  of  the 
same  artery.  Thirdly,  the  inferior  thyroid,  by  means  of  a  branch  about  the  size  of  an  ordinary 
radial,  formed  a  communication  with  the  first  aortic  intercostal.  Fourthly,  the  transversalis  colli, 
by  means  of  very  large  communications  with  the  posterior  branches  of  the  intercostals.  Fifthly, 
the  branches  (of  the  subclavian  and  axillary)  going  to  the  side  of  the  chest  were  large,  and  anas- 
tomosed freely  with  the  lateral  branches  of  the  intercostals."  In  the  second  case  also  (vol.  x. 
p.  97)  Mr.  Wood  describes  the  anastomoses  in  a  somewhat  similar  manner,  adding  the  remark 
that  "the  blood  which  was  brought  into  the  aorta  through  the  anastomoses  of  the  intercostal 
arteries  appeared  to  be  expended  principally  in  supplying  the  abdomen  and  pelvis,  while  the 
supply  to  the  lower  extremities  had  passed  through  the  internal  mammary  and  epigastrics." 

Surgical  Anatomy. — The  student  should  now  consider  the  effects  likely  to  be  produced  by 
aneurism  of  the  thoracic  aorta,  a  disease  of  common  occurrence.  When  we  consider  the  great 
depth  of  the  vessel  from  the  surface  and  the  number  of  important  structures  which  surround  it 
on  every  side,  it  may  easily  be  conceived  what  a  variety  of  obscure  symptoms  may  arise  from  dis- 
ease of  this  part  of  the  arterial  system,  and  how  they  may  be  liable  to  be  mistaken  for  those  of 
other  affections.  Aneurism  of  the  thoracic  aorta  most  usually  extends  backward  along  the  left 
side  of  the  spine,  producing  absorption  of  the  bodies  of  the  vertebrae,  with  curvature  of  the  spine; 
whilst  the  irritation  or  pressure  on  the  cord  will  give  rise  to  pain,  either  in  the  chest,  back,  or 
loins,  with  radiating  pain  in  the  left  upper  intercostal  spaces,  from  pressure  on  the  intercostal 
nerves ;  at  the  same  time  the  tumor  may  project  backward  on  each  side  of  the  spine,  beneath  the 
integument,  as  a  pulsating  swelling,  simulating  abscess  connected  with  diseased  bone,  or  it  may 
displace  the  oesophagus  and  compress  the  lung  on  one  or  the  other  side.  If  the  tumor  extend 
forward,  it  may  press  upon  and  displace  the  heart,  giving  rise  to  palpitation  and  other  symptoms 
of  disease  of  that  organ;  or  it  may  displace,  or  even  compress,  the  resophagus,  causing  pain  and 
difficulty  of  swallowing,  as  in  stricture  of  that  tube;  and  ultimately  even  open  into  it  by  ulcera- 
tion,  producing  fatal  hemorrhage.  If  the  disease  extends  to  the  right  side,  it  may  press  upon 
the  thoracic  duct;  or  it  may  burst  into  the  pleural  cavity  or  into  the  trachea  or  lung;  and,  lastly, 
it  may  open  into  the  posterior  mediastinum. 

Branches. — Branches  of  the  thoracic  aorta  supply  the  thoracic  viscera. 
They  are  known  as  rami  viscerales.  The  rarai  viscerales  are  the  bronchial,  cesoph- 
ageal,  pericardial,  and  mediastinal  arteries.  Other  branches  of  the  thoracic  aorta 
supply  the  walls  of  the  chest*  They  are  known  as  rami  parietales  or  intercostal  arteries. 

The  Bronchial  Arteries  (aa.  bronchiales)  are  the  nutrient  vessels  of  the  lungs, 
and  vary  in  number,  size,  and  origin.  That  of  the  right  side  arises  from  the  first 
aortic  intercostal,  or  by  a  common  trunk  with  the  left  bronchial  from  the  front  of 
the  thoracic  aorta.  Those  of  the  left  side,  usually  two  in  number,  arise  from  the 
thoracic  aorta,  one  a  little  lower  than  the  other.  Each  vessel  is  directed  to  the 
back  part  of  the  corresponding  bronchus  along  which  it  runs,  dividing  and  sub- 
dividing along  the  bronchial  tube,  supplying  them,  the  cellular  tissue  of  the  lungs, 
the  bronchial  glands,  and  the  oesophagus. 

The  (Esophageal  Arteries  (aa.  oesophageae),  usually  four  or  five  in  number, 
arise  from  the  front  of  the  aorta,  and  pass  obliquely  downward  to  the  oesophagus, 
forming  a  chain  of  anastomoses  along  that  tube,  anastomosing  with  the  oesoph- 
ageal  branches  of  the  inferior  thyroid  arteries  above,  and  with  ascending  branches 
from  the  phrenic  and  gastric  arteries  below. 

The  Pericardiac  (rami  pericardiaci)  are  a  few  small  vessels,  irregular  in  their 
origin,  distributed  to  the  pericardium. 

The  Posterior  Mediastinal  Arteries  (rami  mediastinales]  are  numerous 
small  vessels  which  supply  the  glands  and  loose  areolar  tissue  in  the  mediastinum. 


THE    THORACIC  AORTA 


669 


The  lower  mediastinal  branches  are  known  as  the  superior  phrenic  arteries  (aa. 
phren  leaf  super  lores),  and  are  distributed  to  the  posterior  portion  of  the  Diaphragm. 
The  Intercostal  Arteries  (aa.  intercostales]  (Fig.  419)  arise  from  the  back  of  the 
aorta.     The  aortic  intercostals  are  usually  nine  in  number  on  each  side,  the  two 
superior  intercostal  spaces  being  supplied 
by  the  superior  intercostal,  a  branch  of  the 
subclavian.     The   second  space    usually 
receives  a  considerable  branch  from  the 
first  aortic  intercostal,  which  joins  with 
the  branch  from  the  superior  intercostal 
of  the  subclavian.   The  branch  which  runs 
along  the  lower  border  of  the  last  rib  is 
named    the   subcostal  artery.    The   right 
intercostals    are  longer  than  the   left,  on 
account  of  the  position  of  the  aorta  on  the 
left  side  of  the  spine:  they  pass  outward, 
across  the  bodies  of  the  vertebra,  to  the 
intercostal  spaces,  being  covered  by  the 
pleura,    the    oesophagus,    thoracic    duct, 
sympathetic  nerve,  and  the  vena  azygos 
major;    the    left,   passing   outward,    are 
crossed  by  the  sympathetic ;  the  upper  two 
are  also  crossed   by  the  superior  inter- 
costal vein,  the  lower  by  the  azygos  minor 
veins.    In  each  intercostal  space  the  artery 
passes  outward,  the  External  intercostal 
muscle  being  behind,  the  pleura  and  a  thin 
fascia  being  in  front.    It  then  passes  be- 
tween the  two  layers  of  Intercostal  mus- 
cles, and,  having  ascended   obliquely  to 
the  lower  border  of  the  rib  above  it,  is 
continued  forward  in  the  groove  on  its 
lower  border  and  anastomoses  with  the 
anterior  intercostal  branches  of   the  in- 
ternal mammary.     The  first  aortic  inter- 
costal anastomoses  with  the  superior  in- 
tercostal branch  of  the  subclavian,  and 
the   last  three  intercostals  pass  between 
the  abdominal  muscles,  inosculating  with  the  epigastric  in  front  and  with  the 
phrenic  and  lumbar  arteries.  Each  intercostal  artery  is  accompanied  by  a  vein  and 
nerve,  the  former  being  above,  and  the  latter  below,  except  in  the  upper  inter- 
costal spaces,  where  the  nerve  is  at  first  above  the  artery.    The  arteries  are  pro- 
tected from  pressure  during  the  action  of  the  Intercostal  muscles  by  fibrous  arches 
thrown  across,  and  attached  by  each  extremity  to  the  bone.    The  lower  intercostal 
arteries  are  continued  anteriorly  from  the  intercostal  spaces  into  the  abdominal 
wall,  except  the  subcostal,  which  lies  throughout  its  whole  course  in  the  abdominal 
wall,  since  it  is  placed  below  the  last  rib.    They  pass  behind  the  costal  cartilages 
between  the  Internal  oblique  and  Transversalis  muscle  to  the  sheath  of  the  Rectus, 
where  they  anastomose  with  the  internal  mammary  and  the  deep  epigastric 
arteries.     Behind,  the  subcostal  artery  anastomoses  with  the  first  lumbar  artery. 
Branches. — Each  intercostal  artery  gives  off  numerous  muscular  branches  (rami 
musculares). 

Lateral  cutaneous.  Muscular. 

Posterior  or  dorsal  branch.  Collateral  intercostal. 


FIG.  419. — Thoracic  aorta.     (Testut.) 


670  THE  BLOOD -VASCULAR    SYSTEM 

Lateral  Cutaneous  Branches  (rami  cutanei  laterales)  come  off  from  each  intercostal 
and  take  a  similar  course  to  that  of  the  lateral  cutaneous  branch  of  the  intercostal 
nerve.  These  arteries  are  distributed  to  the  walls  of  the  chest  and  to  the  mammary 
gland  (rami  mammarii  laterales). 

Small  branches  pass  to  the  mammary  gland  through  the  fourth,  fifth,  and  sixth 
interspaces  (rami  mammarii  medialis),  and  to  the  skin  to  the  inner  side  of  the 
nipple  (rami  cutanei  anteriores). 

The  portion  of  the  artery  considered  here  as  the  prolongation  of  the  main  trunk 
is  called  by  Spalteholz  and  others  the  anterior  branch  (ramus  anterior). 

The  Posterior  or  Dorsal  Branch  (ramus  posterior)  of  each  intercostal  artery  passes 
backward  to  the  inner  side  of  the  anterior  costo-transverse  ligament,  and  divides 
into  an  external  branch  (ramus  cutaneus  lateralis),  and  an  internal  branch  (ramus 
cutaneus  medialis),  which  are  distributed  to  the  muscles  and  integument  of  the 
back.  Muscular  branches  (rami  musculares)  are  given  off  by  the  dorsal  branch  soon 
after  its  origin.  A  spinal  branch  (ramus  spinalis)  comes  off  from  the  dorsal 
branch  of  the  intercostal.  It  traverses  the  vertebral  arches  and  enters  the  spinal 
canal  through  the  intervertebral  foramen,  is  distributed  to  the  spinal  cord  and 
its  membranes,  and  td  the  bodies  of  the  vertebrae  in  the  same  manner  as  the 
lateral  spinal  branches  from  the  vertebral.  It  gives  off  three  branches,  the 
neural,  which  accompanies  the  spinal  nerve-roots,  and  is  distributed  to  the  mem- 
branes of  the  spinal  cord.  The  post-central  branch  divides  into  ascending  and 
descending  branches,  which,  anastomosing  with  similar  branches  above  and 
below,  form  a  series  of  vertical  arches  in  the  back  of  the  bodies  of  the  verte- 
brae.1 The  prelaminar  branch  is  distributed  to  "the  posterior  wall  of  the  spinal 
canal."2 

The  Collateral  Intercostal  Branch  comes  off  from  the  intercostal  artery  near  the 
angle  of  the  rib,  and  descends  to  the  upper  border  of  the  rib  below,  along  which 
it  courses  to  anastomose  with  the  anterior  intercostal  branch  of  the  internal 
mammary  or  its  branch,  the  musculo-phrenic. 

The  two  lower  intercostals  on  each  side  have  not  constant  collateral  branches. 
Even  when  present  they  are  of  small  size  and  end  in  the  wall  of  the  abdomen. 
Each  collateral  intercostal  branch  gives  off  muscular  branches. 

Surgical  Anatomy. — The  position  of  the  intercostal  vessels  should  be  borne  in  mind  in 
performing  the  operation  of  paracentesis  thoracis.  The  puncture  should  never  be  made  nearer 
the  middle  line  posteriorly  than  the  angle  of  the  rib,  as  the  artery  crosses  the  space  internal  to 
this  .point.  In  the  lateral  portion  of  the  chest,  where  the  puncture  is  usually  made,  the  artery 
lies  at  the  upper  part  of  the  intercostal  space,  and  therefore  the  puncture  should  be  made  just 
above  the  upper  border  of  the  rib  forming  the  lower  boundary  of  the  space. 

The  Abdominal  Aorta  (Aorta  Abdominalis)  (Fig.  420). 

The  abdominal  aorta  commences  at  the  aortic  opening  of  the  Diaphragm,  in 
front  of  the  lower  border  of  the  body  of  the  last  thoracic  vertebra,  and,  descending 
a  little  to  the  left  side  of  the  vertebral  column,  terminates  on  the  body  of  the  fourth 
lumbar  vertebra,  commonly  a  little  to  the  left  of  the  middle  line,3  where  it 
divides  into  the  two  common  iliac  arteries.  It  diminishes  rapidly  in  size,  in 
consequence  of  the  many  large  branches  which  it  gives  off.  As  it  lies  upon  the 
bodies  of  the  vertebrae,  the  curve  which  it  describes  is  convex  forward,  the 
greatest  convexity  corresponding  to  the  third  lumbar  vertebra,  which  is  a  little 
above  and  to  the  left  side  of  the  umbilicus. 

1  Cunningham's  Text-book  of  Anatomy.  2  Ibid. 

8  Lord  Lister,  having  accurately  examined  30  bodies  in  order  to  ascertain  the  exact  point  of  termination  of 
this  vessel,  found  it  "  either  absolutely,  or  almost  absolutely,  mesial  in  15,  while  in  13  it  deviated  more  or  less 
to  the  left,  and  in  2  was  slightly  to  the  right"  (System  of  Surgery,  edited  by  T.  Holmes,  2d  ed.,  vol.  v.  p.  652). 
— ED.  of  15th  English  edition. 


THE   ABDOMINAL    AORTA 


671 


Relations. — It  is  covered,  in  front,  by  the  lesser  omentum  and  stomach,  behind 
which  are  the  branches  of  the  cocliac  axis  and  the  solar  plexus;  below  these,  by 
the  splenic  vein,  the  pancreas,  the  left  renal  vein,  the  transverse  portion  of  the 
duodenum,  the  mesentery,  and  aortic  plexus.  Behind,  it  is  separated  from  the 
lumbar  vertebrae  and  intervening  disks  by  the  anterior  common  ligament  and  left 


\ 


FIG.  420. — The  abdominal  aorta  and  its  branches. 

lumbar  veins.     On  the  right  side  it  is  in  relation  with  the  postcava  (the  right  crus 
of   he  Diaphragm  being  interposed  above),  the  vena  azygos  major,  thoracic  duct 
and  right  sermlunar  ganglion;  on  the  left  side,  with  the  sympathetic  nerve  and 
lett  semilunar  ganglion. 


672  THE    BLOOD -VASCULAR    SYSTEM 

PLAN  OF  THE  RELATIONS  OF  THE  ABDOMINAL  AORTA,, 

In  front. 

Lesser  omentum  and  stomach. 
Branches  of  the  coeliac  axis  and  solar  plexus. 
Splenic  vein. 
Pancreas. 
Left  renal  vein. 
Transverse  duodenum. 
Mesentery. 
Aortic  plexus. 

Right  side.  ^     ^^ 

Right  crus  of  Diaphragm.  /  \  Left  side. 

Postcava.  ^rt^*1  Sympathetic  nerve. 

Vena  azygos  major.  \  I  Left  sernilunar  ganglion. 

Thoracic  duct.  \.  ./ 

Right  semilunar  ganglion. 

Behind. 

Left  lumbar  .veins. 
Vertebral  column. 

Surface  Marking. — In  order  to  map  out  the  abdominal  aorta  on  the  surface  of  the  abdomen, 
a  line  must  be  drawn  from  the  middle  line  of  the  body,  on  a  level  with  the  distal  extremity  of 
the  seventh  costal  cartilage,  downward  and  slightly  to  the  left,  so  that  it  just  skirts  the  umbilicus, 
to  a  zone  drawn  round  the  body  opposite  the  highest  point  of  the  crest  of  the  ilium.  This 
point  is  generally  half  an  inch  below  and  to  the  left  of  the  umbilicus,  but  as  the  position  of  this 
structure  varies  with  the  obesity  of  the  individual,  it  is  not  a  reliable  landmark  as  to  the  situation 
of  the  bifurcation  of  the  aorta. 

Surgical  Anatomy. — Aneurisms  of  the  abdominal  aorta  near  the  cceliac  axis  communicate 
in  nearly  equal  proportion  with  the  anterior  and  posterior  parts  of  the  artery. 

When  an  aneurismal  sac  is  connected  with  the  back  part  of  the  abdominal  aorta,  it  usually 
produces  absorption  of  the  bodies  of  the  vertebrae,  and  forms  a  pulsating  tumor  that  presents 
itself  in  the  left  hypochondriac  or  epigastric  regions,  and  is  accompanied  by  symptoms  of  dis- 
turbance in  the  alimentary  canal.  Pain  is  invariably  present,  and  is  usually  of  two  kinds — a 
fixed  and  constant  pain  in  the  back,  caused  by  the  tumor  pressing  on  or  displacing  the  branches 
of  the  solar  plexus  and  splanchnic  nerves;  and  a  sharp  lancinating  pain,  radiating  along  those 
branches  of  the  lumbar  nerves  which  are  pressed  on  by  the  tumor;  hence  the  pain  in  the  loins, 
the  testes,  the  hypogastrium,  and  in  the  lower  limb  (usually  of  the  left  side).  This  form  of 
aneurism  usually  bursts  into  the  peritoneal  cavity  or  behind  the  peritoneum  in  the  left  hypo- 
chondriac region;  or  it  may  form  a  large  aneurismal  sac,  extending  down  as  low  as  Poupart's 
ligament;  hemorrhage  in  these  cases  being  generally  very  extensive,  but  slowly  produced,  and 
not  rapidly  fatal. 

When  an  aneurismal  sac  is  connected  with  the  front  of  the  aorta  near  the  coeliac  axis  it 
forms  a  pulsating  tumor  in  the  left  hypochondriac  or  epigastric  regions,  usually  attended  with 
symptoms  of  disturbance  of  the  alimentary  canal,  as  sickness,  dyspepsia,  or  constipation,  and 
is  accompanied  by  pain,  which  is  constant,  but  nearly  always  fixed  in  the  loins,  epigastrium,  or 
some  part  of  the  abdomen;  the  radiating  pain  being  rare,  as  the  lumbar  nerves  are  seldom 
implicated.  This  form  of  aneurism  may  burst  into  the  peritoneal  cavity  or  behind  the  peri- 
toneum, between  the  layers  of  the  mesentery,  or,  more  rarely,  into  the  duodenum;  it  seldom 
extends  backward  so  as  to  affect  the  spine. 

The  abdominal  aorta  has  been  tied  1 5  times,  and  although  none  of  the  patients  permanently 
recovered,  still,  as  Prof.  Keen's  lived  48  days,  the  possibility  of  the  re-establishment  of  the 
circulation  is  proved.  In  the  lower  animals  this  artery  has  been  often  successfully  tied.  The 
vessel  may  be  reached  in  several  ways.  In  the  original  operation,  performed  by  Sir  A.  Cooper, 
in  1817,  an  incision  was  made  in  the  linea  alba,  the  peritoneum  opened  in  front,  the  finger 
carried  down  amongst  the  intestines  toward  the  spine,  the  peritoneum  again  opened  behind  by 
scratching  through  the  mesentery,  and  the  vessel  thus  readied.  Or  either  of  the  operations 
described  below  for  securing  the  common  iliac  artery  may,  by  extending  the  dissection  a  suf- 
ficient distance  upward,  be  made  use  of  to  expose  the  aorta.  The  chief  difficulty  in  the 
dead  subject  consists  in  isolating  the  artery  in  consequence  of  its  great  depth;  but  in  the 
living  subject  the  embarrassment  resulting  from  the  proximity  of  the  aneurismal  tumor,  and 
the  great  probability  of  disease  in  the  vessel  itself,  add  to  the  dangers  and  difficulties  of  this 
formidable  operation  so  greatly  that  it  is  very  doubtful  whether  it  ought  ever  to  be  performed. 

The  collateral  circulation  would  be  carried  on  by  the  anastomosis  between  the  internal  mam- 


THE  ABDOMINAL    AORTA  673 

mary  and  the  deep  epigastric;  by  the  free  communication  between  the  superior  and  inferior 
mesenteries  if  the  ligature  were  placed  above  the  latter  vessel;  or  by  the  anastomosis  between 
the  inferior  mesenteric  and  the  internal  pudic  when  (as  is  more  common)  the  point  of  ligature  is 
below  the  origin  of  the  inferior  mesenteric;  and  possibly  by  the  anastomoses  of  the  lumbar 
arteries  with  the  branches  of  the  internal  iliac. 

During  an  amputation  at  the  hip  the  circulation  through  the  abdominal  aorta  may  be  com- 
manded by  an  assistant,  who  throws  the  entire  weight  of  his  body  upon  his  rigidly  extended 
forearm,  the  fist  of  which  lies  directly  upon  the  patient's  aorta  (Macewen's  method).  The 
abdominal  tourniquet  is  no  longer  used,  as  modern  methods  enable  the  surgeon  to  do  a  prac- 
tically bloodless  hip-joint  amputation  (Wyeth's  method,  Senn's  method,  McBurney's  method). 


Branches  (Fig.  420).  —  The  branches  of  the  abdominal  aorta  are  —  the 

pi        •  C  Gastric.  Superior  Mesenteric.          Ovarian  in  female. 

r™      .  \v'^\  Hepatic.  Suprarenal.  Inferior  Mesenteric. 

V>Oclld,C    .rLXlb   I  c<    1       •  -r>  i  T  i 

(^  Splenic.  Renal.  Lumbar. 

Spermatic  in  male.  Sacra  Media. 

Branches.  —  The  branches  of  the  abdominal  aorta  may  be  divided  into  two 
sets:  1.  Those  supplying  the  viscera  (rami  vicerales).  2.  Those  distributed  to 
the  walls  of  the  abdomen  (rami  parietales). 

Visceral  Branches.  Parietal  Branches. 

(  Gastric. 
Coeliac  Axis<  Hepatic.  Inferior  Phrenic. 

I  Splenic.  Lumbar. 

Superior  Mesenteric.  Sacra  Media. 

Inferior  Mesenteric. 
Suprarenal. 
Renal. 
Spermatic  or  Ovarian. 

To  expose  the  cceliac  axis  raise  the  liver,  draw  down  the  stomach,  and  then  tear  through  the 
layers  of  the  lesser  omen  turn. 

The  Cceliac  Axis  or  Artery  (a.  coeliaca)  (Figs.  420,  421,  and  422).  —  The  coeliac 
axis  is  a  short  thick  trunk,  about  half  an  inch  in  length,  which  arises  from  the 
aorta,  close  to  the  margin  of  the  opening  in  the  Diaphragm,  behind  the  posterior 
parietal  peritoneum,  above  the  pancreas,  and  below  the  twelfth  thoracic  vertebra, 
and,  passing  nearly  horizontally  forward  (in  the  erect  posture),  divides  into  three 
large  branches,  the  gastric,  hepatic,  and  splenic,  occasionally  giving  off  one  of  the 
phrenic  arteries. 

Relations.  —  It  is  covered  by  the  lesser  omentum.  On  the  right  side  it  is  in 
relation  with  the  right  semilunar  ganglion  and  the  lobus  Spigelii;  on  the  left  side, 
with  the  left  semilunar  ganglion  and  cardiac  end  of  the  stomach.  Below,  it  rests 
upon  the  upper  border  of  the  pancreas. 

The  Gastric  or  Coronary  Artery  (a.  gastrica  sinistra)  (Figs.  421  and  422),  the  small- 
est of  the  three  branches  of  the  coeliac  axis,  passes  upward  and  to  the  left  side, 
behind  the  peritoneum  of  the  lesser  peritoneal  cavity,  raising  this  portion  of  the 
peritoneum  into  a  fold,  known  as  the  left  or  secondary  pancreatico  -gastric  fold.  It 
continues  this  course  until  it  nearly  reaches  the  lesser  curvature  of  the  stomach  just 
below  the  cardia.  It  then  turns  to  the  front  and  curves  forward  to  the  cardiac 
orifice  of  the  stomach,  distributing  branches  to  the  oesophagus  which  anastomose 
with  the  aortic  oesophageal  arteries;  others  supply  the  cardiac  end  of  the  stomach, 
inosculating  with  branches  of  the  splenic  artery;  it  then  passes  from  left  to 
right,  along  and  upon  the  lesser  curvature  of  the  stomach  and  beneath  the 
peritoneum  to  the  pylorus,  lying  in  its  course  between  the  layers  of  the  lesser 
omentum,  and  sometimes  dividing  into  two  vessels,  which  run  along  each  side 

43 


674 


THE  BLOOD-VASCULAR  SYSTEM 


of  the  lesser  curvature.  One  vascular  arch  gives  branches  to  the  anterior 
wall  of  the  stomach  and  the  other  to  the  posterior  wall,  and  both  give  them 
to  the  lesser  omentum  or  the  single  artery  gives  branches  to  both  surfaces 
of  the  organ  and  to  the  lesser  omentum :  at  its  termination  it  anastomoses  with 
the  pyloric  branch  or  the  two  pyloric  branches  of  the  hepatic.  It  gives  off 
gastric  branches  to  both  the  anterior  and  posterior  surfaces  of  the  stomach, 
branches  to  the  lesser  omentum,  a  small  hepatic  branch,  to  the  left  lobe  of  the  liver 
and  oesophageal  branches  (rami  oesophagei)  which  anastomose  with  cesophageal 
branches  from  the  thoracic  aorta  and  the  inferior  phrenic. 


Oystic  artery. 


e  af 
FIG.  421. — The  cceliac  axis  and  its  branches,  the  liver  having  been  raised  and  the  lesser  omentum  removed. 


The  Hepatic  Artery  (a.  hepatica)  (Figs.  421  and  422)  in  the  adult  is  intermediate 
in  size  between  the  gastric  and  splenic;  in  the  foetus  it  is  the  largest  of  the  three 
branches  of  the  cceliac  axis.  It  is  first  directed  forward  and  to  the  right,  in  the 
right  pancreatico-gastric  fold,  to  the  upper  margin  of  the  pyloric  end  of  the 
stomach,  forming  the  lower  boundary  of  the  foramen  of  Winslow.  It  then  passes 
upward  between  the  layers  of  the  lesser  omentum,  and  in  front  of  the  foramen  of 
Winslow,  to  the  transverse  fissure  of  the  liver,  where  it  divides  into  two  branches, 
right  and  left,  which  supply  the  corresponding  lobes  of  that  organ,  accompanying 
the  ramifications  of  the  vena  portae  and  hepatic  duct.  The  hepatic  artery,  in 
its  course  along  the  right  border  of  the  lesser  omentum,  is  in  relation  with  the 
ductus  communis  choledochus  and  portal  veins,  the  duct  lying  to  the  right  of 
the  artery  and  the  vena  portse  behind. 


THE   ABDOMINAL    AORTA 


675 


Its  branches  (Figs.  421  and  422)  are — the 


Pyloric. 

Gastro-duodenalis 

Cystic. 


j  Gastro-epiploica  Dextra. 

|  Pancreatico-duodenalis  Superior 


The  pyloric  or  superior  pyloric  branch  (a.  gastrica  dextra)  arises  from  the 
hepatic,  above  the  pylorus,  descends  between  the  layers  of  the  lesser  omentum 
to  the  pyloric  end  of  the  stomach,  and  passes  from  right  to  left  along  its  lesser  cur- 
vature, supplying  it  with  branches  and  inosculating  with  the  gastric  branches  of 
the  coronary  artery.  The  vessel  often  divides  into  two  vascular  arches  to  anas- 
tomose with  two  vascular  arches  from  the  gastric. 


FIG.  422. — The  coeliac  axis  and  its  branches,  the  stomach  having  been  raised  and  the  transverse  mesocolon 
removed  (semi-diagrammatic). 

The  gastro-duodenalis  (Fig.  422)  is  a  short  but  large  branch,  which  descends 
near  the  pylorus,  behind  the  first  portion  of  the  duodenum,  and  divides  at  the 
lower  border  of  this  viscus  into  two  branches,  the  gastro-epiploica  dextra  and  the 
pancreatico-duodenalis  superior.  Previous  to  its  division,  it  gives  off  two  or  three 
small  inferior  pyloric  branches,  to  the  pyloric  end  of  the  stomach  and  pancreas. 

The  gastro-epiploica  dextra  runs  from  right  to  left  along  but  distinctly  below 
the  greater  curvature  of  the  stomach,  between  the  layers  of  the  great  omentum, 
anastomosing  about  the  middle  of  the  lower  border  of  the  stomach  with  the  gastro- 
epiploica  sinfstra  from  the  splenic  artery.  This  vessel  gives  off  numerous  branches, 


676  THE    BLOOD -VASCULAR   SYSTEM 

some  of  which  ascend  to  supply  both  surfaces  of  the  stomach,  whilst  others 
descend  to  supply  the  great  omentum  (rami  epiploici). 

The  pancreatico-duodenalis  superior  descends  between  the  contiguous  margins 
of  the  duodenum  and  pancreas.  It  supplies  the  head  of  the  pancreas  by  means 
of  the  rami  pancreatica,  and  the  duodenuni  by  means  of  the  rami  duodenalis, 
and  anastomoses  with  the  inferior  pancreatico-duodenal  branch  of  the  superior 
mesenteric  artery  and  with  the  pancreatic  branches  of  the  splenic. 

The  cystic  artery  (a.  cystica)  (Fig.  421),  usually  a  branch  of  the  right  hepatic, 
passes  downward  and  forward  along  the  cystic  duct  to  the  gall-bladder,  and 
divides  into  two  branches,  one  of  which  ramifies  on  its  free  surface  beneath 
the  peritoneum,  the  other  between  the  gall-bladder  and  the  substance  of  the 
liver. 

The  Splenic  Artery  (a.  lienalis}  (Figs.  421  and  422),  in  the  adult,  is  the  largest  of 
the  three  branches  of  the  creliac  axis,  and  is  remarkable  for  the  extreme  tortuosity 
of  its  course.  It  passes  horizontally  to  the  left  side,  behind  the  peritoneum  and 
along  the  upper  border  of  the  pancreas,  accompanied  by  the  splenic  vein,  which  lies 
below  it,  and  on  arriving  near  the  spleen  divides  into  branches,  some  of  which 
enter  the  hilum  of  that  organ  to  be  distributed  to  its  structure,  whilst  others  are 
distributed  to  the  pancreas  and  great  end  of  the  stomach.  Its  branches  are — the 

Pancreaticae  Parvce.  Gastric  (Vasa  Brevia). 

Pancreatica  Magna.  Gastro-epiploica  Sinistra. 

Rami  Lienalis. 

The  pancreatic  branches  (rami  pancreatici)  are  numerous  small  branches 
derived  from  the  splenic  as  it  runs  behind  the  upper  border  of  the  pancreas, 
supplying  its  middle  and  left  parts.  One  of  these,  larger  than  the  rest,  is  given 
off  from  the  splenic  near  the  left  extremity  of  the  pancreas;  it  runs  from  left 
to  right  near  the  posterior  surface  of  the  gland,  following  the  course  of  the  pan- 
creatic duct,  and  is  called  the  pancreatica  magna.  The  others  are  called  the 
pancreaticae  parvae.  These  vessels  anastomose  with  the  pancreatic  branches  of 
the  pancreatico-duodenal  arteries,  derived  from  the  hepatic  on  the  one  hand  and 
superior  mesenteric  on  the  other. 

The  gastric  branches  or  vasa  brevia  (aa.  gastricae  breves)  consists  of  from  five  to 
seven  small  branches,  which  arise  either  from  the  termination  of  the  splenic 
artery  or  from  its  terminal  branches,  and,  passing  from  left  to  right,  between 
the  layers  of  the  gastro-splenic  omentum,  are  distributed  to  the  great  curvature 
of  the  stomach,  anastomosing  with  branches  of  the  gastric  and  gastro-epiploica 
sinistra  arteries. 

The  gastro-epiploica  sinistra,  the  largest  branch  of  the  splenic,  runs  from  left 
to  right  along  but  distinctly  below  the  great  curvature  of  the  stomach,  between 
the  layers  of  the  great  omentum,  and  anastomoses  with  the  gastro-epiploica 
dextra.  In  its  course  it  distributes  several  branches  to  the  stomach,  which 
ascend  upon  both  surfaces;  others  descend  to  supply  the  omentum. 

The  rami  lienales  leave  the  splenic  artery  in  the  hilum  and  pass  into  the  spleen. 

Surgical  Anatomy. — The  operation  of  pylorectomy  can  be  made  an  almost  bloodless  pro- 
cedure by  tying  the  gastric,  the  pyloric,  and  the  right  and  left  gastro-epiploic  arteries.  "The 
gastric  is  doubly  tied  about  one  inch  below  the  cardiac  orifice  at  a  point  where  it  joins  the  lesser 
curvature  and  is  divided  between  the  ligatures.  The  superior  pyloric  is  doubly  tied  and  divided. 
The  fingers  are  passed  beneath  the  pylorus,  raising  the  gastro-colic  omentum  from  the  trans- 
verse mesocolon,  and  in  this  way  safe  ligation  behind  the  pylorus  of  the  right  gastro-epiploic 
artery,  or  in  most  cases  its  parent  vessel,  the  gastro-duodenal,  is  secured.  The  left  gastro- 
epiploic  is  now  tied  at  an  appropriate  point,  and  the  necessary  amount  of  gastro-colic  omentum 
doubly  tied  and  cut."1 

1  William  J.  Mayo.    Annals  of  Surgery,  March,  1904. 


THE   ABDOMINAL   AORTA  677 

The  Superior  Mesenteric  Artery  (a.  mesenterica  superior]  (Figs.  420  and  423). 
— The  superior  mesenteric  artery  supplies  the  whole  length  of  the  small  intestine, 
except  the  first  part  of  the  duodenum ;  it  also  supplies  the  cuecum  and  the  ascending 
and  transverse  colon ;  it  is  a  vessel  of  large  size,  arising  from  the  forepart  of  the 
aorta  about  a  quarter  of  an  inch  below  the  cosliac  axis;  being  covered  at  its  origin 
by  the  splenic  vein  and  pancreas.  It  passes  forward,  between  the  pancreas  and  the 
transverse  portion  of  the  duodenum,  crosses  in  front  of  this  portion  of  the  intes- 
tine, and  descends  between  the  layers  of  the  mesentery  to  the  right  iliac  fossa, 
where,  considerably  diminished  in  size,  it  anastomoses  with  one  of  its  own  branches 
— viz.,  the  ileo-colic.  In  its  course  it  forms  an  arch,  the  convexity  of  which  is 
directed  forward  and  downward  to  the  left  side,  the  concavity  backward  and 
upward  to  the  right.  It  is  accompanied  by  the  superior  mesenteric  vein,  and  is 
surrounded  by  the  superior  mesenteric  plexus  of  nerves. 

In  order  to  expose  the  superior  mesenteric  artery  raise  the  great  omentum  and  transverse 
colon,  draw  down  the  small  intestines,  and  cut  through  the  peritoneum  where  the  transverse 
mesocolon  and  mesentery  join;  the  artery  will  then  be  exposed  just  as  it  issues  from  beneath 
the  lower  border  of  the  pancreas 

Branches. — Its  branches  are — the 

Inferior  Pancreatico-duodenal.  Ileo-colic. 

Vasa  Intestini  Tenuis.  Right  Colic. 

Middle  Colic. 

The  Inferior  Pancreatico-duodenal  (a.  pancreaticoduodenalis  inferior]  is  given 
off  from  the  superior  mesenteric,  or  from  its  first  intestinal  branch  behind  the 
pancreas.  It  courses  to  the  right  between  the  head  of  the  pancreas  and  duodenum, 
and  then  ascends  to  anastomose  with  the  superior  pancreatico-duodenal  artery. 
It  distributes  branches  to  the  head  of  the  pancreas  and  to  the  transverse  and 
descending  portions  of  the  duodenum. 

The  Vasa  Intestini  Tenuis  (aa.  intestinales]  arise  from  the  convex  side  of  the 
superior  mesenteric  artery.  They  are  usually  from  twelve  to  fifteen  in  number, 
and  are  distributed  to  the  jejunum  (aa.  jcjunales]  and  ileum  (aa.ileae].  They 
run  parallel  with  one  another  between  the  layers  of  the  mesentery,  each  vessel 
dividing  into  two  branches,  which  unite  with  similar  branches  on  each  side, 
forming  a  series  of  arches  the  convexities  of  which  are  directed  toward  the 
intestine.  From  this  first  set  of  arches  branches  arise,  which  again  unite  with 
similar  branches  from  either  side,  and  thus  a  second  series  of  arches  is  formed; 
and  from  these  latter,  a  third  and  a  fourth,  or  even  a  fifth,  series  of  arches  is 
constituted,  diminishing  in  size  the  nearer  they  approach  the  intestine.  From 
the  terminal  arches  numerous  small  straight  vessels  arise  which  encircle  the 
intestine,  upon  which  they  are  distributed,  ramifying  between  its  coats.  Through- 
out their  course  small  branches  are  given  off  to  the  glands  and  other  structures 
between  the  layers  of  the  mesentery.  (See  the  description  of  the  vascular  loops 
in  the  section  upon  the  Intestines.  The  form  and  arrangement  of  the  loops 
have  been  studied  by  Monks,  of  Boston.) 

The  Ileo-colic  Artery  (a.  ileocolica]  is  the  lowest  branch  given  off  from  the 
concavity  of  the  superior  mesenteric  artery.  It  descends  between  the  layers  of 
the  mesentery  to  the  right  iliac  fossa,  where  it  divides  into  two  branches.  Of 
these,  the  inferior  division  inosculates  with  the  termination  of  the  superior  mesen- 
teric artery,  forming  with  it  an  arch,  from  the  convexity  of  which  branches 
proceed  to  supply*  the  termination  of  the  ileum,  the  caecum,  the  vermiform 
appendix,  and  the  ileo-csecal  valve.  The  superior  division  inosculates  with 
the  colica  dextra  and  supplies  the  commencement  of  the  colon. 

The  Right  Colic  Artery  (a.  colica  dextra]  arises  from  about  the  middle  of  the 
concavity  of  the  superior  mesenteric  artery,  and,  passing  behind  the  peritoneum 


678 


THE  BLOOD -VASCULAR    SYSTEM 


to  the  middle  of  the  ascending  colon,  divides  into  two  branches — a  descending 
branch,  which  inosculates  with  the  ileo-colic,  and  an  ascending  branch,  which 
anastomoses  with  the  colica  media.  These  branches  form  arches,  from  the 
convexity  of"  which  vessels  are  distributed  to  the  ascending  colon.  The  branches 
of  this  vessel  are  covered  with  peritoneum  only  on  their  anterior  aspect. 

The  Middle  Colic  Artery  (a.  colica  media)  arises  from  the  upper  part  of  the 
concavity  of  the  superior  mesenteric,  and,  passing  forward  between  the  layers 
of  the  transverse  mesocolon,  divides  into  two  branches,  the  one  on  the  right 
side  inosculating  with  the  colica  dextra;  that  on  the  left  side,  with  the  colica 
sinistra,  a  branch  of  the  inferior  mesenteric.  From  the  arches  formed  by  their 
inosculation  branches  are  distributed  to  the  transverse  colon.  The  branches 
of  this  vessel  lie  between  the  two  layers  of  the  transverse  mesocolon. 


FIG.  423. — The  superior  mesenteric  artery  and  its  branches. 

Blood-supply  of  the  Right  Iliac  Fossa.— The  descending  branch  of  the  right  colic  artery  by 
anastomosing  with  the  ascending  branch  of  the  ileo-colic  artery  forms  a  vascular  loop.  The 
union  of  the  descending  branch  of  the  ileo-colic  artery  with  the  terminal  vessel  of  the  superior 
mesenteric  artery  forms  another  vascular  loop.  These  two  loops  give  off  secondary  loops,  and 
from  the  secondary  loops  come  the  vessels  which  supply  the  appendix,  the  caecum,  and  the 
lower  end  of  the  ileum.  The  branch  which  goes  to  the  appendix  is  called  the  appendicular 
artery  (a.  appendicularis).  If  there  is  a  distinct  meso-appendix  the  artery  passes  along  its 
unattached  edge.  If  there  is  a  rudimentary  meso-appendix  or  no  meso-appendix  the  artery 


THE   ABDOMINAL    AORTA 


679 


usually  lies  upon  the  appendix  from  base  to  tip  beneath  the  peritoneal  covering.  In  females 
the  appendix  may  receive  an  additional  vessel  from  the  ovarian,  which  vessel  lies  in  the 
appendiculo-ovarian  ligament. 

The  Inferior  Mesenteric  Artery  (a.  mesenterica  inferior]  (Figs.  420  and  424).— 
The  inferior  mesenteric  artery  supplies  the  descending  colon,  the  sigmoid  flexure 
of  the  colon  and  the  greater  part  of  the  rectum.  It  is  smaller  than  the  superior 
mesenteric,  and  arises  from  the  left  side  of  the  aorta,  between  one  and  two  inches 
above  the  division  of  that  vessel  into  the  common  iliacs.  It  passes  downward 
to  the  left  iliac  fossa,  and  then  descends  between  the  layers  of  the  mesorectum, 


Middle  hsemorrhoidal, 
Inferior  haemorrhoidal. 


FIG.  424. — The  inferior  mesenteric  and  its  branches. 

into  the  pelvis,  under  the  name  of  the  superior  hsemorrhoidal  artery.  It  lies  at  first 
in  close  relation  with  the  left  side  of  the  aorta,  and  then  passes  as  the  superior 
hsemorrhoidal  in  front  of  the  left  common  iliac  artery. 

In  order  to  expose  the  inferior  mesenteric  artery  draw  the  small  intestines  and  mesentery  over 
to  the  right  side  of  the  abdomen,  raise  the  transverse  colon  toward  the  thorax,  and  divide  the 
peritoneum  covering  the  front  of  the  aorta. 


Branches. — Its  branches  are — the 

Left  Colic. 

Superior  Hsemorrhoidal. 


Sigmoid. 


680  THE    BLOOD -VASCULAR    SYSTEM 

The  Left  Colic  Artery  (a.  colica  sinistra)  passes  behind  the  peritoneum,  in 
front  of  the  left  kidney,  to  reach  the  descending  colon,  and  divides  into  two 
branches — an  ascending  branch,  which  inosculates  with  the  colica  media;  and 
a  descending  branch,  which  anastomoses  with  the  sigmoid  artery.  From  the 
arches  formed  by  these  inosculations  branches  are  distributed  to  the  descending 
colon. 

The  Sigmoid  Arteries  (aa.  sigmoideae). — As  a  rule  there  are  two  of  these  vessels, 
but  may  be  three.  They  run  obliquely  downward  across  the  Psoas  muscle  to  the 
sigmoid  flexure  of  the  colon,  and  divide  into  branches  which  supply  that  part  of 
the  intestine,  anastomosing  above  with  the  left  colic,  and  below  with  the  superior 
hsemorrhoidal  artery. 

The  Superior  Hemorrhoidal  Artery  (a.  hcemorrhoidalis  superior)  (Figs.  424  and 
427),  the  continuation  of  the  inferior  mesenteric,  descends  into  the  pelvis  between 
the  layers  of  the  mesorectum,  crossing,  in  its  course,  the  ureter  and  left  common 
.iliac  vessels.  Opposite  the  middle  of  the  sacrum  it  divides  into  two  branches, 
which  descend  one  on  each  side  of  the  rectum,  and  about  five  inches  from  the 
arms  break  up  into  several  small  branches,  which  pierce  the  muscular  coat  of  the 
bowel  and  run  downward,  as  straight  vessels,  placed  at  regular  intervals  from 
each  other  in  the  wall  of  the. gut  between  its  muscular  and  mucous  coat,  to  the 
level  of  the  internal  sphincter;  here  they  form  a  series  of  loops  around  the  lower 
end  of  the  rectum,  and  communicate  with  the  middle  hsemorrhoidal  arteries  which 
are  branches  of  the  internal  iliac  and  with  the  inferior  hsemorrhoidal  branches 
of  the  internal  pudic. 

The  Suprarenal  Artery  (a.  suprarenalis  media)  (Fig.  420). — A  suprarenal  or 
•capsular  artery  arises,  one  on  each  side  of  the  aorta,  opposite  the  superior  mesenteric 
artery.  It  is  a  small  vessel  which  passes  obliquely  upward  and  outward,  over 
the  crura  of  the  Diaphragm,  to  the  under  surface  of  the  suprarenal  capsule,  to 
which  it  is  distributed,  anastomosing  with  capsular  branches  from  the  phrenic 
and  renal  arteries.  In  the  adult  these  arteries  are  of  small  size;  in  the  fretus 
they  are  as  large  as  the  renal  arteries. 

The  Renal  Arteries  (aa.  renales)  (Fig.  420). — The  renal  arteries  are  two 
large  trunks  which  arise  from  the  sides  of  the  aorta  immediately  below  the  superior 
mesenteric  artery.  Each  is  directed  outward  across  the  crus  of  the  Diaphragm, 
so  as  to  form  nearly  a  right  angle  with  the  aorta.  The  right  is  longer  than  the 
left,  on  account  of  the  position  of  the  aorta;  it  passes  behind  the  postcava. 
The  left  is  somewhat  higher  than  the  right.  Before  reaching  the  hilum  of 
the  kidney,  each  artery  usually  divides  into  four  branches.  Two  of  these  vessels 
•enter  the  anterior  portion  and  two  the  posterior  portion  of  the  kidney.  There 
may  be  but  one  renal  artery;  there  may  be  two,  three,  four,  or  five  branches.  The 
greater  number  of  the  branches  generally  lie  between  the  renal  vein  and  ureter,  the 
vein  being  in  front  of  the  arteries,  the  ureter  behind.  The  anterior  branches  supply 
three-fourths  of  the  kidney,  the  posterior  supply  one-fourth.  Each  vessel  gives 
off  a  small  branch  to  the  suprarenal  capsule  (a.  suprarenalis  inferior)  and  branches 
to  the  ureter,  ureteral  branches,  and  to  the  surrounding  cellular  tissue  and  muscles, 
perirenal  branches.  Hyrtl,  in  1870,  pointed  out  that  the  renal  artery  gives  off  a 
branch  which  divides  and  supplies  the  dorsal  or  posterior  portion  of  the  kidney  and 
its  pelvis,  and  a  branch  which  divides  and  supplies  the  ventral  or  anterior  portion 
of  the  kidney  and  its  pelvis.  The  two  circulations  are  distinct  and  do  not  anas- 
tomose even  at  the  periphery.  Between  these  two  sets  of  vessels  is  a  bloodless  zone, 
the  exsanguinated  renal  zone  of  Hyrtl,  which  does  not  correspond  to  the  median 
line,  but  is  one-half  inch  dorsal  to  the  lateral  longitudinal  renal  border.  The 
ventral  or  anterior  segment  is  much  the  larger.  In  very  rare  instances  the  blood- 
less zone  corresponds  to  the  median  line  (Kummel).  An  incision  of  the  middle 
third  of  the  kidney  exactly  at  the  junction  of  the  two  segments  does  not  divide 


THE  ABDOMINAL  AORTA 


681 


vessels.  As  the  incision  approaches  either  pole  there  is  danger  of  cutting  a  branch 
(Schecle).  Frequently  there  is  a  second  renal  artery,  which  is  given  off  from  the 
alxlominal  aorta  either  above  or  below  the  renal  artery  proper,  the  former  being 
the  more  common  position.  Instead  of  entering  the  kidney  at  the  hilum,  an 
accessory  renal  artery  usually  pierces  the  upper  or  the  lower  part  of  the  gland. 

The  Spermatic  Arteries  (aa.  spermaticae  internae)  (Fig.  420). — The  internal 
spermatic  arteries  are  distributed  to  the  testes.  They  are  two  slender  vessels  of 
considerable  length,  which  arise  from  the  front  of  the  aorta  a  little  below  the  renal 
arteries.  Each  artery  passes  obliquely  outward  and  downward  behind  the  peri- 
toneum, resting  on  the  Psoas  muscle,  the  right  spermatic  lying  in  front  of  the 


IB 


FIG.  425. — The  renal  artery  and  the  distribution  FIG.  426. — A,  A,  "Brodei's  white  line;"    B,  B, 

of  its  branches :  A,  A,  correct  incision;  B,B,  incor-         line   of    best    incision    for    splitting   the    kidney, 
rect  incision.     (Campbell.)  (Campbell.) 

postcava,  the  left  behind  the  sigmoid  flexure  of  the  colon.  It  then  crosses  obliquely 
over  the  ureter  (to  which  it  sends  a  few  branches)  and  the  lower  part  of  the  external 
iliac  artery  to  reach  the  internal  abdominal  ring,  through  which  it  passes,  afnd 
accompanies  the  other  constituents  of  the  spermatic  cord  along  the  inguinal  canal 
to  the  scrotum,  where  it  becomes  tortuous  and  is  prolonged  as  the  testicular  artery 
(a.  testicularis) ,  which  accompanies  the  vas  deferens,  anastomosing  with  the 
artery  of  the  vas  deferens  and  is  distributed  to  the  epididymis,  the  back  part  of 
the  tunica  albuginea,  and  the  substance  of  the  testes.  The  spermatic  artery  in  the 
inguinal  canal  gives  off  cremasteric  branches  to  supply  the  Cremaster  muscle. 
In  the  canal  and  scrotum  the  artery  lies  behind  the  pampiniform  plexus  and  in 
front  of  the  vas  deferens. 

The  Ovarian  Arteries  (aa.  ovaricae). — The  ovarian  arteries  (Fig.  428)  are  the 
corresponding  arteries  in  the  female  to  the  spermatic  in  the  male.  They  supply  the 
ovaries,  are  shorter  than  the  spermatic,  and  do  not  pass  out  of  the  abdominal 
cavity.  The  origin  and  course  of  the  first  part  of  the  artery  are  the  same  as  the 
spermatic  in  the  male,  but  on  arriving  at  the  margin  of  the  pelvis  the  ovarian 
irtery  passes  inward,  between  the  two  layers  of  the  broad  ligament  of  the  uterus, 


682  THE  BLOOD-VASCULAR  SYSTEM 

to  be  distributed  to  the  ovary,  ovarian  branches.  Branches  go  to  the  Fallopian 
tube,tubal  branches,  the  ureter,  ureteral  branches,  and  the  broad  ligament,  ligamentous 
branches.  A  branch  passes  on  to  the  side  of  the  uterus  and  anastomoses  with  the 
uterine  arteries,  uterine  branch.  Other  offsets  are  continued  along  the  round 
ligament  through  the  inguinal  canal,  to  the  integument  of  the  labiurn  and  groin. 

At  an  early  period  of  foetal  life,  when  the  testes  or  ovaries  lie  by  the  side  of 
the  spine  below  the  kidneys,  the  spermatic  or  ovarian  arteries  are  short;  but  as 
these  organs  descend  from  the  abdomen  into  the  scrotum  or  pelvis,  the  arteries 
become  gradually  lengthened. 

The  Inferior  Phrenic  Arteries  (aa.  phrenicae  inferiores)  (Fig.  420). — The  inferior 
phrenic  arteries  are  two  small  vessels  which  present  much  variety  in  their  origin. 
They  may  arise  separately  from  the  front  of  the  aorta,  immediately  above  the 
cceliac  axis,  or  by  a  common  trunk,  which  may  spring  either  from  the  aorta  or 
from  the  creliac  axis.  Sometimes  one  is  derived  from  the  aorta,  and  the  other 
from  one  of  the  renal  arteries.  In  only  one  out  of  thirty-six  cases  examined  did 
these  arteries  arise  as  two  separate  vessels  from  the  aorta.  They  diverge  from 
one  another  across  the  crura  of  the  Diaphragm,  and  then  pass  obliquely  upward 
and  outward  upon  the  under  surface  of  the  Diaphragm.  The  left  phrenic  passes 
behind  the  oesophagus  and  runs  forward  on  the  left  side  of  the  cesophageal 
opening.  The  right  phrenic  passes  behind  the  postcava,  and  ascends  along  the 
right  side  of  the  aperture  for  transmitting  that  vein.  Near  the  back  part  of  the 
central  tendon  each  vessel  divides  into  two  branches.  The  internal  branch  runs 
forward  to  the  front  of  the  thorax,  supplying  the  Diaphragm  and  anastomosing 
with  its  fellow  of  the  opposite  side,  and  with  the  musculo-phrenic  and  comes  nervi 
phrenici  branches  of  the  internal  mammary.  The  external  branch  passes  toward 
the  side  of  the  thorax  and  inosculates  with  the  intercostal  arteries.  The  internal 
branch  of  the  right  phrenic  gives  off  a  few  vessels  to  the  postcava,  and  the  left 
one  some  branches  to  the  oesophagus.  Each  vessel  also  sends  capsular  branches 
(rami  suprarenales  superior]  to  the  suprarenal  capsule  of  its  own  side.  The  spleen 
on  the  left  side  and  the  liver  on  the  right  also  receive  a  few  branches  from  these 
vessels. 

The  Lumbar  Arteries  (aa.  lumbales). — The  lumbar  arteries  are  analogous  to 
the  intercostals.  They  are  usually  four  in  number  on  each  side,  and  arise  from 
the  back  part  of  the  aorta,  nearly  at  right  angles  with  that  vessel.  They  pass 
outward  and  backward,  around  the  sides  of  the  bodies  of  the  lumbar  vertebrae, 
behind  the  sympathetic  nerve  and  the  Psoas  magnus  muscle,  those  on  the  right 
side  being  covered  by  the  postcava,  and  the  two  upper  ones  on  each  side  by  the 
crura  of  the  Diaphragm.  In  the  interval  between  the  transverse  processes  of  the 
vertebrae  each  artery  gives  off  a  dorsal  branch. 

After  the  formation  of  the  dorsal  branch  the  artery  passes  outward,  having 
a  variable  relation  to  the  Quadratus  lumborum  muscle.  Most  frequently  the 
first  lumbar  passes  in  front  of  the  muscle  and  the  others  behind  it;  sometimes 
the  order  is  reversed  and  the  lowest  lumbar  passes  in  front  of  the  muscle.  At 
the  outer  border  of  the  Quadratus  they  are  continued  between  the  abdominal 
muscles,  anastomose  with  branches  of  the  epigastric  and  internal  mammary 
in  front,  the  intercostals  above,  and  branches  of  the  ilio-lumbar  and  circumflex 
iliac  below.  The  lumbar  arteries  are  also  distributed  to  the  skin  of  the  sides  of 
the  abdomen. 

The  Dorsal  Branch  (ramus  dorsalis]  gives  off,  immediately  after  its  origin,  a 
spinal  branch,  which  enters  the  spinal  canal.  The  dorsal  branch  then  continues 
its  course  backward  between  the  transverse  processes,  and  is  distributed  to  the 
muscles  and  integument  of  the  back,  anastomosing  with  similar  branches  of  the 
adjacent  lumbar  arteries  and  with  the  posterior  branches  of  the  intercostal 
arteries. 


THE  COMMON  ILIAC  ARTERIES 


683 


The  Spinal  Branch  (ramus  spinalis)  enters  the  vertebral  canal  through  the  inter- 
vertebral  foramen,  to  be  distributed  to  the  spinal  cord  and  its  membranes  and 
to  the  bodies  of  the  vertebrae  in  the  same  manner  as  the  lateral  spinal  branches 
from  the  vertebral  (see  page  640). 

The  Middle  Sacral  Artery  (a.  sacralis  media]  (Fig.  427).— The  middle  sacral 
artery  is  a  small  vessel,  which  arises  from  the  back  part  of  the  aorta  just  at  its  bifur- 
cation. It  descends  upon  the  last  lumbar  vertebra,  and  along  the  middle  line  of  the 
front  of  the  sacrum,  to  the  upper  part  of  the  coccyx,  where  it  anastomoses  with  the 
lateral  sacral  arteries,  and  terminates  in  a  minute  branch,  which  runs  down  to 
the  situation  of  the  body  described  as  Luschka's  gland.  It  gives  off  on  each 
side  opposite  the  body  of  the  fifth  lumbar  vertebra  a  branch  known  as  the 
a.  lumbalis  ima.  From  the  middle  sacral  artery  branches  arise  which  run  through 
the  mesorectum  to  supply  the  posterior  surface  of  the  rectum.  Other  branches 
are  given  off  on  each  side,  which  anastomose  with  the  lateral  sacral  arteries,  and 
send  off  small  offsets  which  enter  the  anterior  sacral  foramina. 

The  artery  is  the  representative  of  the  caudal  prolongation  of  the  aorta  of 
animals,  and  its  lateral  branches  correspond  to  the  intercostal  and  lumbar  arteries 
in  the  thoracic  and  lumbar  regions. 


THE  COMMON  ILIAC  ARTERIES  (AA.  ILIACAE  COMMUTES)  (Figs.  420,  427). 

The  abdominal  aorta  divides  into  the  two  common  iliac  arteries.  The  bifurca- 
tion usually  takes  place  on  the  left  side  of  the  body  of  the  fourth  lumbar  ver- 
tebra. The  common  iliac  arteries  are  about  two  inches  in  length;  diverging 
from  the  termination  of  the  aorta,  they  pass  downward  and  outward  to  the  margin 
of  the  pelvis,  each  divides  opposite  the  intervertebral  substance,  between  the  last 
lumbar  vertebra  and  the  sacrum,  into  two  branches,  the  internal  and  external 
iliac  arteries,  the  latter  supplying  the  lower  extremity;  the  former,  the  viscera  and 
parietes  of  the  pelvis. 

The  right  common  iliac  is  somewhat  longer  than  the  left,  and  passes  more 
obliquely  across  the  body  of  the  last  lumbar  vertebra.  In  front  of  it  are  the 
peritoneum,  the  small  intestines,  branches  of  the  sympathetic  nerve,  and,  at  its 
point  of  division,  the  ureter.  Behind,  it  is  separated  from  the  fourth  and  fifth 
lumbar  vertebrae,  with  the  intervening  intervertebral  disk,  by  the  two  common 
iliac  veins.  On  its  outer  side,  it  is  in  relation  with  the  postcava  and  the  right 
common  iliac  vein,  above,  and  the  Psoas  magnus  muscle  below. 

The  left  common  iliac  is  in  relation,  in  front,  with  the  peritoneum,  branches 
of  the  sympathetic  nerve,  and  the  superior  hiemorrhoidal  artery;  and  is  crossed 
at  its  point  of  bifurcation  by  the  ureter.  It  rests  on  the  bodies  of  the  fourth  and 
fifth  lumbar  vertebrae,  with  the  intervening  intervertebral  disk.  The  left  common 
iliac  vein  lies  partly  on  the  inner  side,  and  partly  beneath  the  artery;  on  its  outer 
side,  the  artery  is  in  relation  with  the  Psoas  magnus  muscle. 

PLAN  OF  THE  RELATIONS  OF  THE  COMMON  ILIAC  ARTERIES. 


In  front. 
Peritoneum. 
Small  intestines. 
Sympathetic  nerves. 
Ureter. 


Outer  side. 
Vena  cava. 
Right  common 

iliac  vein. 
Psoas  muscle. 


Inner  side. 

Left  common 

iliac  vein. 


In  front. 
Peritoneum. 
Sympathetic  nerves. 
Superior  hsemorrhoidal  artery. 
Ureter. 


Outer  side. 
Psoas  magnus 
muscle. 


684  THE  BLOOD-VASCULAR  SYSTEM 

Behind.  Behind. 

Fourth  and  fifth  lumbar  vertebrae.  Fourth  and  fifth   lumbar  vertebrae. 

Right  and  left  common  iliac  veins.  Left  common  iliac  vein. 

Branches. — The  common  iliac  arteries  give  off  small  branches  to  the  perito- 
neum, Psoas  magnus,  ureters,  and  the  surrounding  cellular  tissue,  and  occasionally 
give  origin  to  the  ilio-lumbar  or  renal  arteries. 

Peculiarities. — The  point  of  origin  varies  according  to  the  bifurcation  of  the  aorta.  In 
three-fourths  of  a  large  number  of  cases  the  aorta  bifurcated  either  upon  the  fourth  lumbar 
vertebra  or  upon  the  intervertebral  disk  between  it  and  the  fifth,  the  bifurcation  being,  in  one 
case  out  of  nine  below,  and  in  one  out  of  eleven  above,  this  point.  In  ten  out  of  every  thirteen 
cases  the  vessel  bifurcated  within  half  an  inch  above  or  below  the  level  of  the  crest  of  the  ilium, 
more  frequently  below  than  above. 

The  point  of  division  is  subject  to  great  variety.  In  two-thirds  of  a  large  number  of  cases 
it  was  between  the  last  lumbar  vertebra  and  the  upper  border  of  the  sacrum,  being  above  that 
point  in  one  case  out  of  eight  and  below  it  in  one  case  out  of  six.  The  left  common  iliac  artery 
divides  lower  down  more  frequently  than  the  right. 

The  relative  length,  also,  of  the  two  common  iliac  arteries  varies.  The  right  common  iliac 
was  the  longer  in  sixty-three  cases,  the  left  in  fifty-two,  whilst  they  were  both  equal  in  fifty- 
three.  The  length  of  the  arteries  varied  in  five-sevenths  of  the  cases  examined  from  an  inch 
and  a  half  to  three  inches;  in  about  half  of  the  remaining  cases  the  artery  was  longer  and  in 
the  other  half  shorter,  the  minimum  length  being  less  than  half  an  inch,  the  maximum  four 
and  a  half  inches.  In  two  instances  the  right  common  iliac  has  been  found  wanting,  the  external 
and  internal  iliacs  arising  directly  from  the  aorta. 

Surface  Marking.— Draw  a  zone  around  the  body  opposite  the  highest  part  of  the  crest  of 
the  ilium;  in  this  line  take  a  point  half  an  inch  to  the  left  of  the  middle  line.  From  this  draw 
two  lines  to  points  midway  between  the  anterior  superior  spines  of  the  ilium  and  the  symphysis 
pubis.  These  two  diverging  lines  will  represent  the  course  of  the  common  and  external  iliac 
arteries.  Draw  a  second  zone  round  the  body  corresponding  to  the  level  of  the  anterior  superior 
spines  of  the  ilium:  the  portion  of  the  diverging  lines  between  the  two  zones  will  represent  the 
course  of  the  common  iliac  artery;  the  portion  below  the  lower  zone,  that  of  the  external  iliac 
artery. 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  common  iliac  artery  may  be 
required  on  account  of  aneurism  or  hemorrhage  implicating  the  external  or  internal  iliacs. 
Now  that  the  surgeon  no  longer  dreads  opening  the  peritoneal  cavity,  there  can  be  no  question 
that  the  easiest  and  best  method  of  tying  the  artery  is  by  a  transperitoneal  route.  The  abdomen 
is  opened  by  an  incision  in  either  the  semilunar  line  or  the  linea  alba;  the  intestines  are  drawn 
to  one  side  and  the  peritoneum  covering  the  artery  divided.  The  sheath  is  then  opened,  and 
the  needle  passed  from  within  outward.  On  the  right  side  great  care  must  be  exercised  in 
passing  the  needle,  since  both  the  common  iliac  veins  lie  behind  the  artery.  After  the  vessel 
has  been  tied  the  incision  in  the  peritoneum  over  the  artery  should  be  sutured.  Formerly  there 
were  two  different  methods  by  which  the  common  iliac  artery  was  tied  without  opening  the 
peritoneal  cavity:  1,  an  anterior  or  iliac  incision,  by  which  the  vessel  is  approached  more  directly 
from  the  front;  and  2,  a  posterior  abdominal  or  lumbar  incision,  by  which  the  vessel  is  reached 
from  behind.  If  the  surgeon  select  the  iliac  region,  a  curved  incision,  from  five  to  eight  inches 
in  length,  according  to  the  amount  of  fat,  is  made,  commencing  just  outside  the  middle  of 
Poupart's  ligament  and  a  finger's  breadth  above  it,  and  carried  outward  toward  the  anterior 
superior  iliac  spine,  then  upward  toward  the  ribs,  and  finally  curving  inward  toward  the  umbili- 
cus. The  abdominal  muscles  and  transversalis  fascia  are  divided,  and  the  peritoneum  raised 
upward  and  inward  until  the  Psoas  is  reached.  The  artery  will  be  found  on  the  inner  side  of 
this  muscle,  and  is  to  be  cleared  with  a  director,  especial  care  being  taken  on  the  right  side,  as 
here  the  common  iliac  veins  lie  behind  the  artery.  The  aneurism  needle  is  to  be  passed  from 
within  outward.  But  if  the  aneurismal  tumor  should  extend  high  up  in  the  abdomen,  along 
the  external  iliac,  it  is  better  to  select  the  posterior  or  lumbar  route,  making  an  incision  partly  in 
the  abdomen,  partly  in  the  loin.  The  incision  is  commenced  at  the  anterior  extremity  of  the 
last  rib,  proceeding  directly  downward  to  the  ilium ;  it  is  then  curved  forward  along  the  crest  of 
the  ilium  and  a  little  above  it  to  the  anterior  superior  spine  of  that  bone.  The  abdominal  mus- 
cles having  been  cautiously  divided  in  succession,  the  transversalis  fascia  must  be  carefully  cut 
through,  and  the  peritoneum,  together  with  the  ureter,  separated  from  the  artery  and  pushed 
aside;  the  sacro-iliac  articulation  must  then  be  felt  for,  and  upon  it  the  vessel  will  be  felt  pulsat- 
ing, and  may  be  fully  exposed  in  close  connection  with  the  accompanying  vein.  On  the  right 
side  both  common  iliac  veins,  as  well  as  the  postcava,  are  in  close  connection  with  the  artery, 
and  must  be  carefully  avoided.  On  the  left  side  the  vein  usually  lies  on  the  inner  side  and 
behind  the  artery;  but  it  occasionally  happens  that  the  two  common  iliac  veins  are  joined  on 


'/'///;  IXTKRNAL  ILIAC  ARTERY  685 

the  left  instead  of  the  right  side,  which  would  add  much  to  the  difficulty  of  an  operation  in 
such  a  case.  The  common  iliac  artery  may  be  so  short  that  danger  may  be  apprehended  from 
secondary  hemorrhage  it'  a  ligature  is  applied  to  it.  It  would  be  preferable,  in  such  a  case,  to 
tie  both  the  external  and  internal  iliacs  near  their  origin. 

Collateral  Circulation. — The  principal  agents  in  carrying  on  the  collateral  circulation  after 
the  application  of  a  ligature  to  the  common  iliac  are — the  anastomoses  of  the  hsemorrhoidal 
1) ranches  of  the  internal  iliac  with  the  superior  hsemorrhoidal  from  the  inferior  mesenteric;  the 
anastomoses  of  the  uterine  and  ovarian  arteries  and  of  the  vesical  arteries  of  opposite  sides;  of 
the  lateral  sacral  with  the  middle  sacral  artery;  of  the  epigastric  with  the  internal  mammary, 
inferior  intercostal,  and  lumbar  arteries;  of  the  circumflex  iliac  with  the  lumbar  arteries;  of  the 
ilio-lumbar  with  the  last  lumbar  artery;  of  the  obturator  artery,  by  means  of  its  pubic  branch, 
with  the  vessel  of  the  opposite  side  and  with  the  deep  epigastric. 

Compression  of  the  Common  Iliac  Arteries. — The  common  iliac  arteries  may  be  com- 
pressed by  Davy's  lever.  The  instrument  consists  of  a  gum-elastic  tube  about  two  feet  long, 
in  which  fits  a  round  wrooden  "lever"  considerably  longer  than  the  tube.  A  small  quantity 
of  olive  oil  having  been  injected  into  the  rectum,  the  gum-elastic  tube,  softened  in  hot  w^ater, 
is  passed  into  the  bowel  sufficiently  far  to  permit  its  pressing  upon  the  common  iliac  artery 
as  it  lies  in  the  groove  between  the  last  lumbar  vertebra  and  the  Psoas  muscle.  The  wooden 
lever  is  then  inserted  into  the  tube,  and  the  projecting  end  carried  toward  the  opposite  thigh 
and  raised,  when  it  acts  as  a  lever  of  the  first  order,  the  anus  being  the  fulcrum.  In  cases  where 
the  niesorectum  is  abnormally  short  it  may  be  impossible,  without  unjustifiable  force,  to  com- 
press the  artery  on  the  right  side.  In  amputation  of  the  hip-joint  the  common  iliac  can  be 
compressed  most  certainly  and  safely  by  opening  the  abdomen  and  compressing  the  vessel  by 
means  of  the  fingers  against  the  Psoas  muscle  (McBurney's  method). 

The  Internal  Iliac  Artery  (Figs.  420,  427). 

The  internal  iliac  or  hypogastric  artery  (a.  hypogastrica)  supplies  the  walls  and 
viscera  of  the  pelvis,  the  generative  organs,  and  inner  side  of  the  thigh.  It  is 
a  short  thick  vessel,  smaller  in  the  adult  than  the  external  iliac,  and  about  an 
inch  and  a  half  in  length.  It  arises  at  the  point  of  bifurcation  of  the  common 
iliac,  and,  passing  downward  to  the  upper  margin  of  the  great  sacro-sciatic 
foramen,  divides  into  two  large  trunks,  an  anterior,  and  posterior;  from  its  anterior 
division  a  partially  obliterated  cord,  a  part  of  the  fcetal  hypogastric  artery,  extends 
forward  to  the  bladder. 

Relations. — In  front,  with  the  ureter,  which  is  between  the  artery  and  the 
peritoneum.  Behind,  with  the  internal  iliac  vein,  the  lumbo-sacral  cord,  and 
Pyriformis  muscle.  By  its  outer  side,  near  its  origin,  with  the  Psoas  magnus  muscle. 

PLAN  OF  THE  RELATIONS  OF  THE  INTERNAL  ILIAC  ARTERY. 

In  front. 
Peritoneum. 
Ureter. 


Outer  side. 
Psoas  magnus. 

Behind. 

Internal  iliac  vein. 
Lumbo-sacral  cord. 
Pyriformis  muscle. 

In  the  foetus  the  hypogastric  artery  is  twice  as  large  as  the  external  iliac,  and 
appears  to  be  the  continuation  of  the  common  iliac.  Instead  of  dipping  into 
the  pelvis,  it  passes  forward  to  the  bladder,  and  ascends  along  the  sides  of  that 
viscus  to  its  summit,  to  which  it  gives  branches;  it  then  passes  upward  along  the 
"  >ack  part  of  the  anterior  wall  of  the  abdomen  to  the  umbilicus,  converging 
toward  its  fellow  of  the  opposite  side.  Having  passed  through  the  umbilical 


686 


THE  BLOOD-VASCULAR  SYSTEM 


opening,  the  two  arteries  twine  round  the  umbilical  vein  in  the  umbilical  cord, 
and  ultimately  ramify  in  the  placenta.  The  portion  of  the  vessel  within  the 
abdomen  is  called  the  hypogastric  artery;  the  portion  external  to  that  cavity,  the 
umbilical  artery. 

At  birth,  when  the  placental  circulation  ceases,  the  upper  portion  of  the  hypo- 
gastric  artery,  extending  from  the  summit  of  the  bladder  to  the  umbilicus,  con- 
tracts, and  ultimately  dwindles  to  a  solid  fibrous  cord;  but  the  lower  portion, 
extending  from  its  origin  (in  what  is  now  the  internal  iliac  artery)  for  about  an 
inch  and  a  half  to  the  wall  of  the  bladder,  arid  thence  to  the  summit  of  that  organ, 
is  not  totally  impervious,  though  it  becomes  considerably  reduced  in  size,  and 
serves  to  convey  blood  to  the  bladder  under  the  name  of  the  superior  vesical 
artery. 


Ileo-lumbar. 


-Gluteal. 


FIG.  427. — Arteries  of  the  pelvis. 

Peculiarities  as  Regards  Length. — In  two-thirds  of  a  large  number  of  cases  the  length  of 
the  internal  iliac  varied  between  an  inch  and  an  inch  and  a  half;  in  the  remaining  third  it  was 
more  frequently  longer  than  shorter,  the  maximum  length  being  three  inches,  the  minimum 
half  an  inch. 

The  lengths  of  the  common  and  internal  iliac  arteries  bear  an  inverse  proportion  to  each 
other,  the  internal  iliac  artery  being  long  when  the  common  iliac  is  short,  and  vice  versa. 

As'  Regards  its  Place  of  Division. — The  place  of  division  of  the  internal  iliac  varies 
between  the  upper  margin  of  the  sacrum  and  the  upper  border  of  the  sacro-sciatic  foramen. 

The  arteries  of  the  two  sides  in  a  series  of  cases  often  differed  in  length,  but  neither  seemed 
constantly  to  exceed  the  other. 


THE  INTERNAL  ILIAC  ARTERY  087 

Surgical  Anatomy.— The  application  of  a  ligature  to  the  internal  iliac  artery  may  be 
required  in  cases  of  aneurism  or  hemorrhage  affecting  one  of  its  branches.  The  vessel  may  be 
secured  by  making  an  incision  through  the  abdominal  parietes  in  the  iliac  region  in  a  direction 
and  to  an  extent  similar  to  that  for  securing  the  common  iliac;  the  transversalis  fascia  having 
been  cautiously  divided,  and  the  peritoneum  pushed  inward  from  the  iliac  fossa  toward  the 
pelvis,  the  finger  may  feel  the  pulsation  of  the  external  iliac  at  the  bottom  of  the  wound,  and  by 
tracing  this  vessel  upward  the  internal  iliac  is  arrived  at,  opposite  the  sacro-iliac  articulation.  It 
should  be  remembered  that  the  vein  lies  behind  and  on  the  right  side,  a  little  external  to  the 
artery,  and  in  close  contact  with  it;  the  ureter  and  peritoneum,  which  lie  in  front,  must  also  be 
avoided.  The  degree  of  facility  in  applying  a  ligature  to  this  vessel  will  mainly  depend  upon 
the  length  of  the  vessel.  It  has  been  seen  that  in  the  great  majority  of  the  cases  examined  the 
artery  was  short,  varying  from  an  inch  to  an  inch  and  a  half;  in  these  cases  the  artery  is  deeply 
seated  in  the  pelvis;  when,  on  the  contrary,  the  vessel  is  longer,  it  is  found  partly  above  that 
cavity.  If  the  artery  is  very  short,  as  occasionally  happens,  it  would  be  preferable  to  apply  a 
ligature  to  the  common  iliac  or  to  both  the  external  and  internal  iliacs  at  their  origin. 

A  better  method  of  tying  the  internal  iliac  artery  is  by  an  abdominal  section  in  the  median 
line  and  reaching  the  vessel  through  the  peritoneal  cavity.  This  plan  has  been  advocated  by 
Dennis,  of  Xew  York,  on  the  following  grounds:  (1)  It  in  no  way  increases  the  danger  of  the 
operation;  (2)  it  prevents  a  series  of  accidents  which  have  occurred  during  ligature  of  the  artery 
by  the  older  methods;  (3)  it  enables  the  surgeon  to  ascertain  the  exact  extent  of  disease  in  the 
main  arterial  trunk,  and  select  his  spot  for  the  application  of  the  ligature;  and  (4)  it  occupies 
much  less  time. 

Collateral  Circulation. — In  Professor  Owen's  dissection  of  a  case  in  which  the  internal 
iliac  artery  had  been  tied  by  Stevens  ten  years  before  death  for  aneurism  of  the  sciatic  artery, 
the  internal  iliac  was  found  impervious  for  about  an  inch  above  the  point  where  the  ligature  had 
been  applied,  but  the  obliteration  did  not  extend  to  the  origin  of  the  external  iliac,  as  the  ilio- 
lumbar  artery  arose  just  above  this  point.  Below  the  point  of  obliteration  the  artery  resumed 
its  natural  diameter,  and  continued  so  for  half  an  inch,  the  obturator,  lateral  sacral,  and  gluteal 
arising  in  succession  from  the  latter  portion.  The  obturator  artery  was  entirely  obliterated. 
The  lateral  sacral  artery  was  as  large  as  a  crow's  quill,  and  had  a  very  free  anastomosis  with  the 
artery  of  the  opposite  side  and  with  the  middle  sacral  artery.  The  sciatic  artery  was  entirely 
obliterated  as  far  as  its  point  of  connection  with  the  aneurismal  tumor,  but  on  the  distal  side  of 
the  sac  it  was  continued  down  along  the  back  of  the  thigh  nearly  as  large  in  size  as  the  femoral, 
being  pervious  about  an  inch  below  the  sac  by  receiving  an  anastomosing  vessel  from  the  pro- 
funda.1  The  circulation  was  carried  on  by  the  anastomoses  of  the  uterine  and  ovarian  arteries; 
of  the  opposite  vesical  arteries;  of  the  hemorrhoidal  branches  of  the  internal  iliac  with  those 
from  the  inferior  mesenteric;  of  the  obturator  artery,  by  means  of  its  pubic  branch,  with  the 
vessel  of  the  opposite  side  and  with  the  epigastric  and  internal  circumflex;  of  the  circumflex 
and  perforating  branches  of  the  profunda  femoris  with  the  sciatic;  of  the  gluteal  with  the  poste- 
rior branches  of  the  sacral  arteries;  of  the  ilio-lumbar  with  the  last  lumbar;  of  the  lateral  sacral 
with  the  middle  sacral;  and  of  the  circumflex  iliac  with  the  ilio-lumbar  and  gluteal. 

Branches  (Fig.  427). — The  branches  of  the  internal  iliac  are: 

From  the  Anterior  Trunk.  From  the  Posterior  Trunk, 

Superior  Vesical.  Ilio-lumbar. 

Middle  Vesical.  Lateral  Sacral. 

Inferior  Vesical.  Gluteal. 

Middle  Hsemorrhoidal. 
Obturator. 
Internal  Pudic. 
Sciatic. 
Uterine. 
Vaginal. 

The  Superior  Vesical  (a.  vesicalis  superior]  (Fig. 427), is  that  part  of  the  foetal 
hypogastric  artery,  which  remains  pervious  after  birth.  It  extends  to  the  side  of 
the  bladder,  distributing  numerous  branches  to  the  apex  and  body  of  the  organ. 
From  one  of  these  a  slender  vessel  is  derived  which  accompanies  the  vas  deferens 
in  its  course  to  the  testis,  where  it  anastomoses  with  the  spermatic  artery.  This  is 
the  artery  of  the  vas  deferens.  Other  branches  supply  the  ureter. 

1  Medico-Chirurgical  Transactions,  vol.  xvi. 


688  THE  BLOOD-  VASCULAR  SYSTEM 

The  Middle  Vesical  (a.  vesicalis  medialis)  (Fig.  427),  usually  a  branch  of  the 
superior,  is  distributed  to  the  base  of  the  bladder  and  under  surface  of  the  vesiculse 
seminales. 

The  Inferior  Vesical  (a.  vesicalis  inferior}  (Fig.  427)  arises  from  the  anterior 
division  of  the  internal  iliac,  frequently  in  common  with  the  middle  hemorrhoidal, 
and  is  distributed  to  the  base  of  the  bladder,  the  prostate  gland,  and  vesiculse 
seminales.  The  branches  distributed  to  the  prostate  communicate  with  the 
corresponding  vessel  of  the  opposite  side. 

The  Middle  Hsemorrhoidal  Artery  (a.  hcemorrhoidalis  media)  (Fig.  427) 
usually  arises  together  with  the  preceding  vessel.  It  supplies  the  anus  and 
parts  outside  the  rectum,  anastomosing  with  the  other  hemorrhoidal  arteries. 

The  Uterine  Artery  (a.  uterina)  (Fig.  428)  passes  inward  from  the  anterior 
trunk  of  the  internal  iliac  to  the  neck  of  the  uterus.  Ascending  in  a  tortuous  course 
on  the  side  of  this  viscus,  between  the  layers  of  the  broad  ligament,  it  distributes 
branches  to  its  substance  and  to  the  round  ligament  and  the  Fallopian  tube  (ramus 
tubarius),  anastomosing,  near  its  termination,  with  the  ovarian  artery.  It  gives  a 
branch  to  the  ovary  (ramus  ovarii),  which  anastomoses  with  a  branch  from  the 
ovarian  branches  to  the  cervix  uteri  (cervico-uteri) ,  and  a  branch  which  descends 


Branches  to  tube. 


Branches  to  fnndus. 


Ovarian  artery. 
Branch  to  round  ligament. 


ROUND    LIGAMENT. 

Uterine  artery. 
Arteries  of  cervix. 


Vaginal  arteries. 
FIG.  428. — The  arteries  of  the  internal  organs  of  generation  of  the  female,  seen  from  behind.     (After  Hyrtl.) 

on  the  vagina  (cervico-vaginal) ,  and,  joining  with  branches  from  the  vaginal 
arteries,  form  a  median  longitudinal  vessel  both  in  front  and  behind;  these  descend 
on  the  anterior  and  posterior  surfaces  of  the  vagina,  and  are  named  the  azygos 
arteries  of  the  vagina. 

The  Vaginal  Artery  (a.  vaginalis]  is  analogous  to  the  inferior  vesical  in  the 
male;  it  descends  upon  the  vagina,  supplying  its  mucous  membrane,  and  sending 
branches  to  the  neck  of  the  bladder  and  contiguous  part  of  the  rectum.  There 
may  be  several  vaginal  arteries.  The  vaginal  artery  assists  in  forming  the  azygos 
arteries  of  the  vagina,  which  are  anterior  and  posterior  vessels,  running  longi- 
tudinally, and  due  to  anastomoses  of  the  branches  of  the  vaginal  from  each  side 
and  the  cervico-vaginal  artery. 


THE  INTERNAL  ILIAC  ARTERY  689 

Luschka,  Hyrtl,  Waldeyer,  Robinson,  and  others,  instead  of  describing  the 
ovarian  and  uterine  arteries  as  two  distinct  vessels,  regard  them  as  constituting 
the  chief  parts  of  one  vessel,  the  arteria  uterina  ovarica.  What  has  been  called  "  the 
circle  of  Robinson"  is  composed  of  a  spiral  segment  (the  arteria  uterina  ovarica), 
with  a  portion  of  the  abdominal  aorta,  common  iliacs,  and  internal  iliacs. 

Robinson1  has  made  a  careful  study  of  this  vascular  circle;  he  shows  that 
it  is  of  great  importance  in  certain  surgical  procedures,  and  that  its  remark- 
able "capacity  for  extension"  saves  it  from  damage  when  the  uterus  is  enormously 
distended  by  pregnancy,  or  when  it  is  "drawn  through  the  pudendum  with  trac- 
tion forceps  for  palpation,  inspection,  or  repair." 

The  author  just  quoted  says  further  that  the  utero-ovarian  artery  has  three 
origins,  because  it  develops  from  the  Wolffian  body:  The  ovarian  segment  arises 
from  the  abdominal  aorta.  The  uterine  segment  arises  from  the  anterior  branch 
of  the  internal  iliac  artery.  The  artery  of  the  round  ligament  arises  from  the  deep 
epigastric.  The  arteria  uterina  ovarica  artery  secures  nutrition  to  the  uterus  by 
bringing  blood  from  three  sources.  It  is  spiral  throughout  its  entire  course,  in 
certain  parts  is  convoluted  or  looped,  and  it  is  accompanied  by  the  pampiniform 
plexus  of  veins. 

The  three  origins  of  this  vessel  are  freely  united  by  anastomoses,  and  rami 
laterales  are  given  off,  which  unite  the  bilateral  vessels  in  the  median  line.  Robin- 
son describes  three  bifurcations  of  the  utero-ovarian  artery.  The  distal  bifurcation, 
which  is  "about  midway  between  the  uterus  and  the  pelvic  wall,"  and  forms  an 
acute  angle  with  the  main  vessel.  This  bifurcation  indicates  the  point  of  division 
of  the  external  from  the  internal  genitals.  The  cervico-vaginal  artery  supplies  the 
external  genitals.  The  proximal  bifurcation  marks  the  situation  of  the  ovary.  The 
artery  bifurcates  at  an  acute  angle  into  two  branches  to  supply  the  ovary  and 
Fallopian  tube.  The  middle  bifurcation  consists  of  (1)  the  division  of  the  uterine 
segment  at  the  angle  formed  by  the  uterus  and  oviduct  ("forming  the  ramus  ovi- 
ductus  and  ramus  ovarii")  and  (2)  "the  bifurcation  of  the  ramus  oviductus  form- 
ing the  ramus  oviductus  and  the  ramus  ligamenti  teretis,  or  the  segment  of  the 
round  ligament.'''2 

Surgical  Anatomy. — As  pointed  out  by  Robinson,  the  source  of  bleeding  after  vaginal  hys- 
terectomy is  usually  the  torn  and  undamped  cervico-vaginal  artery. 

As  previously  pointed  out,  the  spiral  and  convoluted  shape  of  the  utero-ovarian  artery  allows 
the  uterus,  ovary,  and  tube  to  be  drawn  into  the  vagina  without  injury  to  the  vessels.  Robinson 
points  out  that  in  vaginal  hysterectomy  the  genital  circle  is  not  divided  and  only  the  rami  later- 
ales  which  go  to  the  uterus  are  cut,  the  ovaries  retaining  a  normal  blood-supply  and  continuing 
to  functionate. 

The  Obturator  Artery  (a.  obturatoria)  (Fig.  427)  usually  arises  from  the  anterior 
trunk  of  the  internal  iliac;  frequently  from  the  posterior.  It  passes  forward,  below 
the  brim  of  the  pelvis,  to  the  upper  part  of  the  obturator  foramen,  accompanied  by 
the  obturator  nerve  and  vein,  and,  escaping  from  the  pelvic  cavity  through  a  short 
canal  formed  by  a  groove  on  the  under  surface  of  the  ascending  ramus  of  the  os 
pubis  and  the  arched  border  of  the  obturator  membrane,  it  divides  into  an  internal 
and  external  branch.  In  the  pelvic  cavity  this  vessel  lies  upon  the  pelvic  fascia, 
beneath  the  peritoneum,  and  a  little  below  the  obturator  nerve. 

Branches. — Within  the  pelvis,  the  obturator  artery  gives  off  an  iliac  branch 
(ramus  iliacus)  to  the  iliac  fossa,  which  supplies  the  bone  and  the  Iliacus  muscle, 
and  anastomoses  with  the  ilio-lumbar  artery;  a  vesical  branch  (ramus  vesicalis), 
which  runs  backward  to  supply  the  bladder;  and  a  pubic  branch  (ramus  pubicus), 
which  is  given  off  from  the  vessel  just  before  it  leaves  the  pelvic  cavity.  This 
branch  ascends  upon  the  back  of  the  os  pubis,  communicating  with  offsets  from 

1  Robinson.     The  Utero-ovarian  Artery.  2  Ibid. 

44 


690  THE  BLOOD-VASCULAR  SYSTEM 

the  deep  epigastric  artery  and  with  the  corresponding  vessel  of  the  opposite 
side.  It  is  placed  on  the  inner  side  of  the  femoral  ring.  External  to  the  pelvis, 
the  obturator  artery  divides  into  an  internal  and  an  external  branch,  which  are 
deeply  situated  beneath  the  Obturator  externus  muscle. 

The  Internal  Branch  (ramus  anterior]  curves  downward  along  the  inner  margin 
of  the  obturator  foramen,  lying  beneath  the  Obturator  externus  muscle;  it  dis- 
tributes branches  to  the  Obturator  externus,  Pectineus,  Adductors,  and  Gracilis, 
and  anastomoses  with  the  external  branch  and  with  the  internal  circumflex  artery. 

The  External  Branch  (ramus  posterior)  curves  round  the  outer  margin  of  the 
obturator  foramen,  also  lying  beneath  the  Obturator  externus  muscle,  to  the  space 
between  the  Gemellus  inferior  and  Quadratus  femoris,  where  it  divides  into  two 
branches:  one,  smaller,  courses  inward  around  the  lower  margin  of  the  foramen 
and  anastomoses  with  the  internal  branch  and  with  the  internal  circumflex;  the 
other  inclines  outward  in  the  groove  below  the  acetabulum  (a.  acetabulis) ,  and 
supplies  the  muscles  attached  to  the  tuberosity  of  the  ischium  and  anastomoses 
with  the  sciatic  artery.  It  sends  a  branch  to  the  hip-joint  through  the  cotyloid 
notch,  which  ramifies  on  the  round  ligament  as  far  as  the  head  of  the  femur. 

Peculiarities  (Fig.  429).— In  two  out  of  every  three  cases  the  obturator  arises  from  the 
internal  iliac ;  in  one  case  in  three  and  a  half  from  the  epigastric ;  and  in  about  one  in  seventy- 
two  cases  by  two  roots  from  both  vessels.  It  arises  in  about  the  same  proportion  from  the 
external  iliac  artery.  The  origin  of  the  obturator  from  the  epigastric  is  not  commonly  found 
on  both  sides  of  the  same  body. 


FIG.  429. — Variations  in  origin  and  course  of  the  obturator  artery. 

When  the  obturator  artery  arises  at  the  front  of  the  pelvis  from  the  epigastric,  it  descends 
almost  vertically  to  the  upper  part  of  the  obturator  foramen.  The  artery  in  this  course  usually 
lies  in  contact  with  the  external  iliac  vein  and  on  the  outer  side  of  the  femoral  ring  (Fig.  429,  A); 
in  such  cases  it  would  not  be  endangered  in  the  operation  for  femoral  hernia.  Occasionally, 
however,  it  curves  inward  along  the  free  margin  of  Gimbernat's  ligament  (Fig.  429,  B),  and 
under  such  circumstances  would  almost  completely  encircle  the  neck  of  a  hernial  sac  (supposing 
a  hernia  to  exist  in  such  a  case),  and  would  be  in  great  danger  of  being  wounded  if  an  operation 
was  performed. 

The  Internal  Pudic  Artery  (a.  pudenda  interna)  (Figs.  427,  430,  and  431)  is  the 
smaller  of  the  two  terminal  branches  of  the  anterior  trunk  of  the  internal  iliac, 
and  supplies  the  external  organs  of  generation.  Though  the  course  of  the  artery 
is  the  same  in  the  two  sexes,  the  vessel  is  much  smaller  in  the  female  than  in  the 
male,  and  the  distribution  of  its  branches  somewhat  different.  The  description  of 
its  arrangement  in  the  male  will  first  be  given,  and  subsequently  the  differences 
which  it  presents  in  the  female  will  be  mentioned. 

The  Internal  Pudic  Artery  in  the  Male  passes  downward  and  outward  to  the 
lower  border  of  the  great  sacro-sciatic  foramen,  and  emerges  from  the  pelvis 
between  the  Pyriformis  and  Coccygeus  muscles:  it  then  crosses  the  spine  of  the 
ischium  and  re-enters  the  pelvis  through  the  lesser  sacro-sciatic  foramen.  The 
artery  now  crosses  the  Obturator  internus  muscle  along  the  outer  wall  of  the  ischio- 
rectal  fossa,  being  situated  about  an  inch  and  a  half  above  the  lower  margin  of  the 
ischial  tuberosity.  It  is  here  contained  in  a  sheath  of  the  obturator  fascia,  and 


THE  INTERNAL  ILIAC  ARTERY  691 

gradually  approaches  the  margin  of  the  ramus  of  the  ischium,  along  which  it  passes 
forward  and  upward,  pierces  the  base  of  the  superficial  layer  of  the  triangular 
ligament  of  the  urethra,  and  runs  forward  along  the  inner  margin  of  the  ramus  of 
the  os  pubis,  and  divides  into  its  two  terminal  branches,  the  dorsal  artery  of  the 
penis  and  the  artery  of  the  corpus  cavernosum. 

Relations. — In  the  first  part  of  its  course,  within  the  pelvis,  it  lies  in  front  of 
the  Pyriformis  muscle  and  sacral  plexus  of  nerves,  and  the  sciatic  artery,  and 
on  the  outer  side  of  the  rectum  (on  the  left  side).  As  it.  crosses  the  spine  of  the 
ischium  it  is  covered  by  the  Gluteus  maximus  and  overlapped  by  the  great  sacro- 
sciatic  ligament.  Here  the  obturator  nerve  lies  to  the  inner  side  and  the  nerve 
to  the  Obturator  internus  to  the  outer  side  of  the  vessel.  In  the  pelvis  it  lies  on 
the  outer  side  of  the  ischio-rectal  fossa,  upon  the  surface  of  the  Obturator  internus 
muscle,  contained  in  a  fibrous  canal,  the  canal  of  Alcock,  formed  by  the  splitting  of 
the  obturator  fascia.  It  is  accompanied  by  the  pudic  veins  and  the  pudic  nerve. 

Peculiarities.— The  internal  pudic  is  sometimes  smaller  than  usual,  or  fails  to  give  off  one 
or  two  of  its  usual  branches;  in  such  cases  the  deficiency  is  supplied  by  branches  derived  from 
an  additional  vessel,  the  accessory  pudic,  which  generally  arises  from  the  internal  pudic  artery 
before  its  exit  from  the  great  sacro-sciatic  foramen.  It  passes  forward  along  the  lower  part  of 
the  bladder  and  across  the  side  of  the  prosta*'1  gland  to  the  root  of  the  penis,  where  it  perforates 
the  triangular  ligament  and  gives  off  the  branches  usually  derived  from  the  pudic  artery.  The 
deficiency  most  frequently,  met  with  is  that  in  which  the  internal  pudic  ends  as  the  artery  of  the 
bulb,  the  artery  of  the  corpus  cavernosum  and  arteria  dorsalis  penis  being  derived  from  the 
accessory  pudic.  Or  the  pudic  may  terminate  as  the  superficial  perineal,  the  artery  of  the  bulb 
being  derived,  with  the  other  two  branches,  from  the  accessory  vessel.  Occasionally  the  acces- 
sory pudic  artery  is  derived  from  one  of  the  other  branches  of  the  internal  iliac,  most  frequently 
the  inferior  vesical  or  the  obturator. 

Surgical  Anatomy. — The  relation  of  the  accessory  pudic  to  the  prostate  gland  and  urethra 
is  of  the  greatest  interest  in  a  surgical  point  of  view,  as  this  vessel  is  in  danger  of  being  wounded 
in  the  operation  of  lateral  lithotomy.  The  student  should  also  study  the  position  of  the  internal 
pudic  artery  and  its  branches,  when  running  a  normal  course  with  regard  to  the  same  operation. 
The  superficial  and  the  transverse  perineal  arteries  are,  of  necessity,  divided  in  this  operation, 
but  the  hemorrhage  from  these  vessels  is  seldom  excessive;  should  a  ligature  be  required,  it 
can  readily  be  applied  on  account  of  their  superficial  position.  The  artery  of  the  bulb  may 
be  divided  if  the  incision  be  carried  too  far  forward,  and  injury  of  this  vessel  may  be  attended 
with  serious  or  even  fatal  consequences.  The  main  trunk  of  the  internal  pudic  artery  may  be 
wounded  if  the  incision  be  carried  too  far  outward;  but,  being  bound  down  by  the  strong  obtura- 
tor fascia  and  under  cover  of  the  ramus  of  the  ischium,  the  accident  is  not  very  likely  to  occur 
unless  the  vessel  runs  an  anomalous  course. 

Branches. — The  branches  of  the  internal  pudic  artery  are — the 

Muscular.  Transverse  Perineal. 

Inferior  FLemorrhoidal.  Artery  of  the  Bulb. 

Superficial  Perineal.  Artery  of  the  Corpus  Cavernosum. 

Dorsal  Artery  of  the  Penis. 

The  Muscular  Branches  consist  of  two  sets — one  given  off  in  the  pelvis,  the 
other  as  the  vessel  crosses  the  ischial  spine.  The  former  are  several  small  offsets 
which  supply  the  Levator  ani,  the  Obturator  internus,  the  Pyriformis,  and  the 
Coccygeus  muscles.  The  branches  given  off  outside  the  pelvis  are  distributed  to 
the  adjacent  part  of  the  Gluteus  maximus  and  External  rotator  muscles.  They 
anastomose  with  branches  of  the  sciatic  artery. 

The  Inferior  Haemorrhoidal  Artery  (a.  hcemorrhoidalis  inferior}  arises  from 
the  internal  pudic  as  it  passes  above  the  tuberosity  of  the  ischium.  Crossing  the 
ischio-rectal  fossa  it  is  distributed  by  two  or  three  terminal  branches  to  the 
muscles  and  integument  of  the  anal  region.  Instead  of  one  inferior  hemor- 
rhoidal  artery  two  or  three  small  vessels  may  arise  from  the  internal  pudic. 

The  Superficial  Perineal  Artery  (a.  perinei)(¥\g.  430)  supplies  the  scrotum  and  the 
muscles  and  integument  of  the  perinseum.  It  arises  from  the  internal  pudic  in  front 


692 


THE  BLOOD-  VASCULAR  SYSTEM 


of  the  preceding  branches,  and  turns  upward,  crossing  either  over  or  under  the 
Transversus  perinei  superficialis  muscle,  and  runs  forward,  parallel  to  the  pubic 
arch,  in  the  interspace  between  the  Accelerator  urinse  and  Erector  penis  muscles, 
both  of  which  it  supplies,  and  is  finally  distributed  to  the  skin  and  dartos  of  the 
scrotum.  In  its  passage  through  the  perinseum  it  lies  beneath  the  superficial 
perineal  fascia. 

The  Transverse  Perineal  Artery  is  a  small  branch  which  arises  either  from  the 
internal  pudic  or  from  the  superficial  perineal  artery  as  it  crosses  the  Transversus 
perinsei  muscle.  It  runs  transversely  inward  along  the  cutaneous  surface  of  the 
Transversus  perinei  superficialis  muscle,  which  it  supplies,  as  well  as  the  structures 
between  the  anus  and  bulb  of  the  urethra,  and  anastomoses  with  the  like  vessel 
of  the  opposite  side. 


Transversuit  perinei 
superficialis. 


GREAT  SACRO- 
SCIATIC    LIGAMENT 


Superficial  perineal  artery. 
Superficial  perineal  nerve* 
Internal  pudic  nerve. 
Internal  pudic  artery. 


Fio.  430. — The  superficial  muscles  and  vessels  of  the  perinseum. 

The  Artery  of  the  Bulb  (a.  bulbi  urethrae)  is  a  large  but  very  short  vessel  which 
arises  from  the  internal  pudic  between  the  two  layers  of  the  triangular  ligament, 
and,  passing  nearly  transversely  inward,  between  the  fibres  of  the  Compressor 
urethrse  muscle,  it  pierces  the  bulb  of  the  urethra,  which  it  supplies,  and  con- 
tinues anteriorly  in  the  corpus  spongiosum  to  the  glans  and  anastomoses  with  its 
fellow  of  the  opposite  side.  It  gives  off  a  small  branch  which  descends  to  supply 
Cowper's  gland. 

Surgical  Anatomy. — This  artery  is  of  considerable  importance  in  a  surgical  point  of  view, 
as  it  is  in  danger  of  being  wounded  in  the  median  or  the  lateral  operation  of  lithotomy— an 
accident  usually  attended  in  the  adult  with  alarming  hemorrhage.  The  vessel  is  sometimes 
very  small,  occasionally  wanting,  or  even  double.  It  sometimes  arises  from  the  internal  pudic 
earlier  than  usual,  and  crosses  the  perinseum  to  reach  the  back  part  of  the  bulb.  In  such  a  case 
the  vessel  could  hardly  fail  to  be  wounded  in  the  performance  of  the  lateral  operation  of  lith- 
otomy. If,  on  the  contrary,  it  should  arise  from  an  accessory  pudic,  it  lies  more  forward  than 
usual  and  is  out  of  danger  in  the  operation. 

The  Artery  of  the  Corpus  Cavernosum  (a.  profunda  penis'),  one  of  the  terminal 
branches  of  the  internal  pudic,  arises  from  that  vessel  while  it  is  situated  between 


THE  INTERNAL  ILIAC  ARTERY 


693 


the  two  layers  of  the  triangular  ligament;  it  pierces  the  superficial  layer,  and, 
entering  the  crus  penis  obliquely,  it  runs  forward  in  the  centre  of  the  corpus 
cavernosum,  to  which  its  branches  are  distributed. 

The  Dorsal  Artery  of  the  Penis  (a.  dorsalis  penis)  ascends  between  the  crus  and 
pubic  symphysis,  and,  piercing  the  triangular  ligament,  passes  between  the  two 
layers  of  the  suspensory  ligament 
of  the  penis,  and  runs  forward 
on  the  dorsum  of  the  penis  to  the 
glans,  where  it  divides  into  iwo 
branches  which  supply  the  glans 
and  prepuce.  On  the  dorsum 
of  the  penis  it  lies  immediately 
beneath  the  integument,  parallel 
with  the  dorsal  vein  and  the 
corresponding  artery  of  the  op- 
posite side.  It  supplies  the  in- 
tegument and  fibrous  sheath  of 
the  corpus  cavernosum,  sending 
branches  through  the  sheath  to 
anastomose  with  the  preceding 
vessel. 

The  Internal  Pudic  Artery  in 
the  Female  is  smaller  than  in  the 
male.  Its  origin  and  course  are 
similar,  and  there  is  consider- 
able analogy  in  the  distribution 
of  its  branches.  The  superficial 
perineal  artery  supplies  the  labia 
pudendi;  the  artery  of  the  bulb 
supplies  the  bulbi  vestibuli  and 
the  erectile  tissue  of  the  vagina; 
the  artery  of  the  corpus  cav- 
ernosum (a.  profunda  clitoridis) 
supplies  the  cavernous  body  of 
the  clitoris;  and  the  arteria 
dorsalis  clitoridis  supplies  the 
dorsum  of  that  organ,  and  ter- 
minates in  the  glans  and  in  the 
membranous  fold  corresponding 
to  the  prepuce  of  the  male. 

The  Sciatic  Artery  (a.  glutaea 
inferior)  (Fig.  431),  the  larger  of 
the  two  terminal  branches  of  the 
anterior  trunk  of  the  internal 
iliac,  is  distributed  to  the  mus- 
cles at  the  back  of  the  pelvis. 
It  passes  down  to  the  lower  part 
of  the  great  sacro-sciatic  fora- 
men behind  the  internal  pudic  artery,  resting  on  the  sacral  plexus  of  nerves  and 
Pyriformis  muscle,  and  escapes  from  the  pelvis  through  this  foramen  between  the 
Pyriformis  and  Coccygeus.  It  then  descends  in  the  interval  between  the  tro- 
chanter  major  and  tuberosity  of  the  ischium,  accompanied  by  the  sciatic  nerves, 
and  covered  by  the  Gluteus  maximus,  and  is  continued  down  the  back  of  the  thigh 
supplying  the  skin,  and  anastomosing  with  branches  of  the  perforating  arteries. 


Termination 
of  internal 
circumflex. 


Superior 
perforating. 


Middle 
perforating. 

Inferior 
perforating. 


Termination  of 
profunda. 


.Superior  muscular. 


Superior  external 
articular. 


Inferior  muscular. 


FIG.  431. —  The  arteries  of  the  gluteal  and  posterior  femoral 
regions. 


Superior  internal 
articular. 


694  THE  BLOOD-  VASCULAR  SYSTEM 

Within  the  pelvis  it  distributes  branches  to  the  Pyriformis,  Coccygeus,  and 
Levator  ani  muscles;  some  hemorrhoidal  branches,  which  supply  the  rectum,  and 
occasionally  take  the  place  of  the  middle  hemorrhoidal  artery;  and  vesical 
branches  to  the  base  and  neck  of  the  bladder,  vesiculse  seminales,  and  prostate 
gland.  External  to  the  pelvis  it  gives  off  the  following  branches: 

Coccygeal.  Muscular. 

Inferior  Gluteal.  Anastomotic. 

Comes  Nervi  Ischiadici.  Articular. 

The  Coccygeal  Branch  runs  inward,  pierces  the  great  sacro-sciatic  ligament,  and 
supplies  the  Glutetis  maximus,  the  integument,  and  other  structures  on  the  back 
of  the  coccyx. 

The  Inferior  Gluteal  Branches,  three  or  four  in  number,  supply  the  Gluteus 
maximus  muscle,  anastomosing  with  the  gluteal  artery  in  the  substance  of  the 
muscle. 

The  Comes  Nervi  Ischiadici  (a.  comitans  n,  ischiadici}  is  a  long,  slender  vessel 
which  accompanies  the  great  sciatic  nerve  for  a  short  distance;  it  then  penetrates 
it  and  runs  in  its  substance  to  the  lower  part  of  the  thigh. 

The  Muscular  Branches  supply  the  Gluteus  maximus,  anastomosing  with  the 
gluteal  artery  in  the  substance  of  the  muscle;  the  external  rotators,  anastomosing 
with  the  internal  pudic  artery;  and  the  muscles  attached  to  the  tuberosity  of  the 
ischium,  anastomosing  with  the  external  branch  of  the  obturator  and  the  internal 
circumflex  arteries. 

The  Anastomotic  Artery  is  directed  downward  across  the  external  rotators  and 
assists  in  forming  the  so-called  crucial  anastomosis  by  anastomosing  with  the 
superior  perforating  and  the  internal  and  external  circumflex  arteries. 

The  Articular  Branch,  generally  derived  from  the  anastomotic,  is  distributed  to 
the  capsule  of  the  hip-joint. 

The  Ilio-lumbar  Artery  (a.  ilio  lumbalis),  given  off  from  the  posterior  trunk 
of  the  internal  iliac,  turns  upward  and  outward  between  the  obturator  nerve  and 
lumbo-sacral  cord,  to  the  inner  margin  of  the  Psoas  muscle,  behind  which  it  divides 
into  a  lumbar  and  an  iliac  branch. 

The  Lumbar  Branch  (ramus  lumbalis)  supplies  the  Psoas  and  Quadratus  lum- 
borum  muscles,  anastomosing  with  the  last  lumbar  artery,  and  sends  a  small 
spinal  branch  (ramus  spinalis)  through  the  intervertebral  foramen,  between  the  last 
lumbar  vertebra  and  the  sacrum,  into  the  spinal  canal,  to  supply  the  cauda  equina. 

The  Iliac  Branch  (ramus  iliacus}  descends  to  supply  the  Iliacus  muscle;  some 
offsets,  running  between  the  muscle  and  the  bone,  anastomose  with  the  iliac  branch 
of  the  obturator;  one  of  these  enters  an  oblique  canal  to  supply  the  diploe,  whilst 
others  run  along  the  crest  of  the  ilium,  distributing  branches  to  the  Gluteal  and 
Abdominal  muscles,  and  anastomose  in  their  course  with  the  gluteal,  circumflex 
iliac,  and  external  circumflex  arteries. 

The  Lateral  Sacral  Artery  (a.  sacralis  lateralis)  (Fig.  427)  runs  downward. 
It  may  be  single,  but  usually  there  are  two  on  each  side,  the  superior  and  inferior 
divisions. 

The  Superior  Division,  which  is  of  large  size,  passes  inward,  and,  after  anastomos- 
ing with  branches  from  the  middle  sacral,  enters  the  first  or  second  anterior  sacral 
foramen,  gives  spinal  branches  (rami  spinalis)  to  the  contents  of  the  sacral  canal, 
and,  escaping  by  the  corresponding  posterior  sacral  foramen,  supplies  the  skin 
and  muscles  on  the  dorsum  of  the  sacrum,  anastomosing  with  the  gluteal. 

The  Inferior  Division  passes  obliquely  across  the  front  of  the  Pyriformis  muscle 
and  sacral  nerves  to  the  inner  side  of  the  anterior  sacral  foramina,  descends  on  the 
front  of  the  sacrum,  and  anastomoses  over  the  coccyx  with  the  middle  sacral  and 
opposite  lateral  sacral  arteries.  In  its  course  it  gives  off  spinal  branches  which 


THE  INTERNAL  ILIAC  ARTERY  695 

enter  the  anterior  sacral  foramina  (rand  spinales) ;  these,  after  supplying  the  con- 
tents of  the  sacral  canal,  escape  by  the  posterior  sacral  foramina,  and  are  dis- 
tributed to  the  muscles  and  skin  on  the  dorsal  surface  of  the  sacrum,  anastomosing 
with  the  gluteal. 

The  Gluteal  Artery  (a.  glutaea  superior)  (Fig.  431)  is  the  largest  branch  of 
the  internal  iliac,  and  appears  to  be  the  continuation  of  the  posterior  division  of 
that  vessel.  It  is  a  short  thick  trunk,  which  passes  out  of  the  pelvis  above  the 
upper  border  of  the  Pyriformis  muscle,  and  immediately  divides  into  a  superficial 
and  deep  branch.  Within  the  pelvis  it  gives  off  a  few  muscular  branches  to  the 
Iliacus,  Pyriformis,  and  Obturator  internus,  and,  just  previous  to  emerging  from 
that  cavity,  a  nutrient  artery,  which  enters  the  ilium. 

The  Superficial  Branch  passes  beneath  the  Gluteus  maximus  and  divides  into 
numerous  branches,  some  of  which  supply  that  muscle,  whilst  others  perforate  its 
tendinous  origin,  and  supply  the  integument  covering  the  posterior  surface  of  the. 
sacrum,  anastomosing  with  the  posterior  branches  of  the  sacral  arteries. 

The  Deep  Branch  runs  between  the  Gluteus  medius  and  minimus,  and  sub- 
divides into  two.  Of  these,  the  superior  division  (ramus  superior),  continuing  the 
original  course  of  the  vessel,  passes  along  the  upper  border  of  the  Gluteus  minimus 
to  the  anterior  superior  spine  of  the  ilium,  anastomosing  with  the  circumflex  iliac 
and  ascending  branches  of  the  external  circumflex  artery.  The  inferior  division 
(ramus  inferior)  crosses  the  Gluteus  minimus  obliquely  to  the  trochanter  major, 
distributing  branches  to  the  Glutei  muscles,  and  inosculates  with  the  external 
circumflex  artery.  Some  branches  piece  the  Gluteus  minimus  to  supply  the  hip- 
joint. 

Surface  Marking. — The  position  of  the  three  main  branches  of  the  internal  iliac,  the 
sciatic,  internal  pudic,  and  gluteal,  which  may  occasionally  be  the  object  of  surgical  interference, 
is  indicated  on  the  surface  in  the  following  way:  A  line  is  to  be  drawn  from  the  posterior  supe- 
rior iliac  spine  to  the  posterior  superior  angle  of  the  great  trochanter,  with  the  limb  slightly 
flexed  and  rotated  inward:  the  point  of  emergence  of  the  gluteai  artery  from  the  upper  part  of 
the  sciatic  notch  will  correspond  with  the  junction  of  the  upper  with  the  middle  third  of  this 
line.  A  second  line  is  to  be  drawn  from  the  same  point  to  the  outer  part  of  the  tuberosity  of 
the  ischium;  the  junction  of  the  lower  with  the  middle  third  marks  the  point  of  emergence  of 
the  sciatic  and  pudic  arteries  from  the  great  sciatic  notch. 

Surgical  Anatomy. — Any  of  these  three  vessels  may  require  ligating  for  a  wound  or  for 
aneurism,  which  is  generally  traumatic.  The  gluteal  artery  is  ligated  by  turning  the  patient 
two-thirds  over  on  his  face  and  making  an  incision  from  the  posterior  superior  spine  of  the  ilium 
to  the  upper  and  posterior  angle  of  the  great  trochanter.  This  must  expose  the  Gluteus  maxi- 
mus muscle,  and  its  fibres  are  to  be  separated  through  the  whole  thickness  of  the  muscle  and 
pulled  apart  with  retractors.  The  contiguous  margins  of  the  gluteus  medius  and  Pyriformis 
are  now  to  be  separated  from  each  other,  and  the  artery  will  be  exposed  emerging  from  the 
sciatic  notch.  In  ligation  of  the  sciatic  artery,  the  incision  should  be  made  parallel  with  that 
for  ligation  of  the  gluteal,  but  one  inch  and  a  half  lower  down.  After  the  fibres  of  the  Gluteus 
maximus  have  been  separated,  the  vessel  is  to  be  sought  for  at  the  lower  border  of  the  Pyri- 
formis; the  great  sciatic  nerve,  which  lies  just  above  it,  forming  the  chief  guide  to  the  artery. 
The  internal  pudic  can  be  reached  through  the  incision  used  to  reach  the  sciatic. 

The  External  Iliac  Artery  (A.  Hiaca  Externa)  (Fig.  427). 

The  external  iliac  artery  is  larger  in  the  adult  than  is  the  internal  iliac.  It 
passes  obliquely  downward  and  outward  along  the  inner  border  of  the  Psoas 
muscle,  from  the  bifurcation  of  the  common  iliac  to  Poupart's  ligament,  where 
it  enters  the  thigh  and  becomes  the  femoral  artery. 

Relations. — In  front,  with  the  peritoneum,  subperitoneal  areolar  tissue  or  Aber- 
nethy's  fascia,  the  termination  of  the  ileum  on  the  right  side,  and  the  sigmoid  flexure 
on  the  left,  and  a  thin  layer  of  fascia  derived  from  the  iliac  fascia,  which  surrounds 
the  artery  and  vein.  At  its  origin  it  is  occasionally  crossed  by  the  ureter.  The 
spermatic  vessels  descend  for  some  distance  upon  it  near  its  termination,  and  it  is 


696  THE  BLOOD-VASCULAR  SYSTEM 

crossed  in  this  situation  by  the  genital  branch  of  the  genito-femoral  nerve  and  the 
deep  circumflex  iliac  vein;  the  vas  deferens  curves  down  along  its  inner  side.  Be- 
hind, it  is  in  relation  with  the  external  iliac  vein,  which,  at  Poupart's  ligament,  lies  at 
its  inner  side;  on  the  left  side  the  vein  is  altogether  internal  to  the  artery.  Exter- 
nally, it  rests  against  the  Psoas  muscle,  from  which  it  is  separated  by  the  iliac 
fascia.  The  artery  rests  upon  this  muscle,  near  Poupart's  ligament.  Numerous 
lymphatic  vessels  and  glands  are  found  lying  on  the  front  and  inner  side  of  the 
vessel. 

PLAN  OF  THE  RELATIONS  OF  THE  EXTERNAL  ILIAC  ARTERY. 


Near 
Poupart's 
Ligament. 


In  front. 

Peritoneum,  intestines,  and  fascia. 
Lymphatic  vessels  and  glands. 
Spermatic  vessels. 

Genito-femoral  nerve  (genital  branch). 
Deep  circumflex  iliac  vein. 


Outer  side.  /  \  Inner  side. 

Psoas  magnus.  Eiifacnal  External  iliac  vein  and  vas  deferens 

Iliac  fascia.  V  J  near  Poupart's  ligament. 

Behind. 

External  iliac  vein. 
Psoas  magnus. 

Surface  Marking. — The  surface  line  indicating  the  course  of  the  external  iliac  artery  has 
been  already  given  (see  page  684). 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  external  iliac  may  be  required  in 
cases  of  aneurism  of  the  femoral  artery  or  for  a  wound  of  the  artery.  This  vessel  may  be 
secured  in  any  part  of  its  course,  excepting  near  its  upper  end,  which  is  to  be  avoided  on  account 
of  the  proximity  of  the  great  stream  of  blood  in  the  internal  iliac,  and  near  its  lower  end,  which 
should  also  be  avoided,  on  account  of  the  proximity  of  the  deep  epigastric  and  circumflex  iliac 
vessels.  The  patient  having  been  placed  in  the  supine  position,  an  incision  should  be  made, 
commencing  below  at  a  point  about  three-quarters  of  an  inch  above  Poupart's  ligament,  and 
a  little  external  to  its  middle,  and  running  upward  and  outward,  parallel  to  Poupart's  ligament, 
to  a  point  one  inch  internal  and  one  inch  above  the  anterior  superior  spine  of  the  ilium.  When 
the  artery  is  deeply  seated  more  room  will  be  required,  and  may  be  obtained  by  curving  the 
incision  from  the  point  last  named  inward  toward  the  umbilicus  for  a  short  distance.  Another 
mode  of  ligating  the  vessel  is  the  plan  advocated  by  Sir  Astley  Cooper,  by  making  an  incision 
close  to  Poupart's  ligament  from  about  half  an  inch  outside  of  the  external  abdominal  ring  to 
one  inch  internal  to  the  anterior  superior  spine  of  the  ilium.  This  incision,  being  made  in  the 
course  of  the  fibres  of  the  aponeurosis  of  the  external  oblique,  is  less  likely  to  be  followed  by  a 
ventral  hernia,  but  there  is  danger  of  wounding  the  epigastric  artery,  and  only  the  lower  end 
of  the  vessel  can'  be  ligated.  Abernethy,  who  first  tied  this  artery,  made  his  incision  in  the 
course  of  the  vessel.  The  abdominal  muscles  and  transversalis  fascia  having  been  cautiously 
divided,  the  peritoneum  should  be  separated  from  the  iliac  fossa  and  raised  toward  the  pelvis; 
and  on  introducing  the  finger  to  the  bottom  of  the  wound,  the  artery  may  be  felt  pulsating  along 
the  inner  border  of  the  Psoas  muscle.  The  external  iliac  vein  is  generally  found  on  the  inner 
side  of  the  artery,  and  must  be  cautiously  separated  from  it  by  the  finger-nail  or  handle  of  the 
knife,  and  the  aneurism  needle  should  be  introduced  on  the  inner  side,  between  the  artery  and 
the  vein. 

Ligation  of  the  external  iliac  artery  has  recently  been  performed  by  a  transperitoneal  method. 
An  incision  four  inches  in  length  is  made  in  the  semilunar  line,  commencing  about  an  inch 
below  the  umbilicus  and  carried  through  tne  abdominal  wall  into  the  peritoneal  cavity.  The 
intestines  are  then  pushed  upward  and  held  out  of  the  way  by  a  broad  abdominal  retractor,  and 
an  incision  is  made  through  the  peritoneum  at  the  margin  of  the  pelvis  in  the  course  of  the  artery, 
and  the  vessel  is  secured  in  any  part  of  its  course  which  may  seem  desirable  to  the  operator.  The 
advantages  of  this  operation  appear  to  be  that  if  it  is  found  necessary,  the  common  iliac  artery 
can  be  ligated  instead  of  the  external  iliac  without  extension  or  modification  of  the  incision; 
and  secondly,  that  the  vessel  can  be  ligated  without  in  any  way  interfering  with  the  coverings 
of  the  sac  of  an  aneurism.  Possibly  a  disadvantage  may  exist  in  the  greater  risk  of  hernia  after 
this  method. 


THE  EXTERNAL  ILIAC  ARTERY  697 

Collateral  Circulation. — The  principal  anastomoses  in  carrying  on  the  collateral  circulation, 
after  the  application  of  a  ligature  to  the  external  iliac,  are — the  ilio-lumbar  with  the  circumflex 
iliac;  the  gluteal  with  the  external  circumflex;  the  obturator  with  the  internal  circumflex;  the 
sciatic  with  the  superior  perforating  and  circumflex  branches  of  the  profunda  artery;  and  the 
internal  pudic  with  the  external  pudic.  When  the  obturator  arises  from  the  epigastric  it  is 
supplied  with  blood  by  branches,  either  from  the  internal  iliac,  the  lateral  sacral,  or  the  internal 
pudic.  The  epigastric  receives  its  supply  from  the  internal  mammary  and  inferior  intercostal 
arteries,  and  from  the  internal  iliac  by  the  anastomoses  of  its  branches  with  the  obturator. 

In  the  dissection  of  a  limb  eighteen  years  after  the  successful  ligature  of  the  external  iliac 
artery  by  Sir  A.  Cooper,  the  report  of  which  is  to  be  found  in  Guy's  Hospital  Reports,  vol. 
i.  p.  50,  the  anastomosing  branches  are  described  in  three  sets:  An  anterior  set. — 1,  a  very 
large  branch  from  the  ilio-lumbar  artery  to  the  circumflex  iliac;  2,  another  branch  from  the 
ilio-lumbar,  joined  by  one  from  the  obturator,  and  breaking  up  into  numerous  tortuous  branches 
to  anastomose  with  the  external  circumflex;  3,  two  other  branches  from  the  obturator,  which 
passed  over  the  brim  of  the  pelvis,  communicated  with  the  epigastric,  and  then  broke  up  into  a 
plexus  to  anastomose  with  the  internal  circumflex.  An  internal  set. — Branches  given  off  from 
the  obturator,  after  quitting  the  pelvis,  which  ramified  among  the  adductor  muscles  on  the 
inner  side  of  the  hip-joint,  and  joined  most  freely  with  branches  of  the  internal  circumflex. 
A  posterior  set. — 1,  three  large  branches  from  the  gluteal  to  the  external  circumflex;  2,  several 
branches  from  the  sciatic  around  the  great  sciatic  notch  to  the  internal  and  external  circumflex, 
and  the  perforating  branches  of  the  profunda. 

Branches. — Besides  several  small  branches  to  the  Psoas  muscle  and  the  neigh- 
boring lymphatic  glands,  the  external  iliac  gives  off  two  branches  of  considerable 
size — the  deep  epigastric  and  deep  circumflex  iliac  arteries. 

The  Internal  or  Deep  Epigastric  Artery  (a.  cpigastrica  inferior)  (Fig.  427) 
arises  from  the  external  iliac  a  few  lines  above  Poupart's  ligament.  It  at  first 
descends  to  reach  this  ligament,  and  then  ascends  obliquely  along  the  inner  margin 
of  the  internal  abdominal  ring,  lying  between  the  transversalis  fascia  and  peri- 
toneum, and,  continuing  its  course  upward,  it  pierces  the  transversalis  fascia,  and 
passing  over  the  semilunar  fold  of  Douglas,  enters  the  sheath  of  the  Rectus  muscle. 
It  then  ascends  on  the  posterior  surface  of  the  muscle,  and  finally  divides  into 
numerous  branches  which  anastomose,  above  the  umbilicus,  with  the  superior 
epigastric  branch  of  the  internal  mammary  and  with  the  inferior  intercostal  arteries 
(Fig.  413).  The  deep  epigastric  artery  bears  a  very  important  relation  to  the 
internal  abdominal  ring  as  it  passes  obliquely  upward  and  inward  from  its  origin 
from  the  external  iliac.  In  this  part  of  its  course  it  lies  along  the  lower  and  inner 
margin  of  the  ring  and  beneath  the  commencement  of  the  spermatic  cord.  As 
it  passes  to  the  inner  side  of  the  internal  abdominal  ring  it  is  crossed  by  the  vas 
deferens  in  the  male  and  the  round  ligament  in  the  female. 

Branches. — The  branches  of  this  vessel  are  the  following:  The  cremasteric 
(a.  spermatica  externa  in  the  male,  a.  ligamenti  teretis  uteri  in  the  jemale),  which 
accompanies  the  spermatic  cord,  and  supplies  the  Cremaster  muscle  and  other 
coverings  of  the  cord,  anastomosing  with  the  spermatic  artery  in  the  male, 
and  which  accompanies  the  round  ligament  in  the  female;  a  pubic  branch 
(ramus  pubicus),  which  runs  along  Poupart's  ligament,  and  then  descends  behind 
the  os  pubis  to  the  inner  side  of  the  femoral  ring,  and  anastomoses  with  offsets 
from  the  obturator  artery;  muscular  branches,  some  of  which  are  distributed  to  the 
abdominal  muscles  and  peritoneum,  anastomosing* with  the  lumbar  and  circum- 
flex iliac  arteries ;  cutaneous  branches  perforate  the  tendon  of  the  External  oblique, 
and  supply  the  integument,  anastomosing  with  branches  of  the  superficial  epi- 
gastric. 

Peculiarities. — The  origin  of  the  deep  epigastric  may  take  place  from  any  part  of  the 
external  iliac  between  Poupart's  ligament  and  two  inches  and  a  half  above  it,  or  it  may  arise 
below  this  ligament,  from  the  common  femoral  or  from  the  deep  femoral. 

Union  with  Branches. — It  frequently  arises  from  the  external  iliac  by  a  common  trunk 
with  the  obturator.  Sometimes  the  epigastric  arises  from  the  obturator,  the  latter  vessel  being 
furnished  by  the  internal  iliac,  or  the  epigastric .  may  be  formed  by  two  branches,  one  derived 

3m  the  external  iliac,  the  other  from  the  internal  iliac. 


698  THE  BLOOD-VASCULAR  SYSTEM 

Surgical  Anatomy. — The  deep  epigastric  artery  follows  a  line  drawn  from  the  middle  of 
Poupart's  ligament  toward  the  umbilicus;  but  shortly  after  this  line  crosses  the  linea  semilunaris 
the  direction  changes,  and  the  course  of  the  vessel  is  directly  upward  in  the  line  of  junction  of 
the  inner  third  with  the  outer  two-thirds  of  the  Rectus  muscle.  It  has  important  surgical  rela- 
tions, in  addition  to  the  fact  that  it  is  one  of  the  principal  means,  through  its  anastomosis  with 
the  internal  mammary,  in  establishing  the  collateral  circulation  after  ligature  of  either  the  com- 
mon or  external  iliac  arteries.  It  lies  close  to  the  internal  abdominal  ring,  and  is  therefore 
internal  to  an  oblique  inguinal  hernia,  but  external  to  a  direct  inguinal  hernia,  as  the  hernia 
emerges  from  the  abdomen.  It  forms  the  outer  boundary  of  Hesselbach's  triangle.  It  is  in 
close  relationship  with  the  spermatic  cord,  which  lies  in  front  of  it  in  the  inguinal  canal, 
separated  only  by  the  transversalis  fascia.  The  vas  deferens  hooks  round  its  outer  side. 

The  Deep  Circumflex  Iliac  Artery  (a.  circwnflexa  ilium  profunda}  (Fig.  427) 
arises  from  the  outer  side  of  the  external  iliac  nearly  opposite  the  epigastric  artery. 
It  ascends  obliquely  outward  behind  Poupart's  ligament,  contained  in  a  fibrous 
sheath  formed  by  the  junction  of  the  transversalis  and  iliac  fasciae,  to  the  anterior 
superior  spinous  process  of  the  ilium.  It  then  runs  along  the  inner  surface  of  the 
crest  of  the  ilium  to  about  its  middle,  where  it  pierces  the  Transversalis,  and 
runs  backward  between  that  muscle  and  the  Internal  oblique,  to  anastomose  with 
the  ilio-lumbar  and  gluteal  arteries.  Opposite  the  anterior  superior  spine  of  the 
ilium  it  gives  off  a  large  branch  which  ascends  between  the  Internal  oblique  and 
Transversalis  muscles,  supplying  them,  and  anastomosing  with  the  lumbar  and 
epigastric  arteries.  It  also  gives  off  cutaneous  branches. 


ARTERIES  OF  THE  LOWER  EXTREMITY. 

The  artery  which  supplies  the  greater  part  of  the  lower  extremity  is  the  direct 
continuation  of  the  external  iliac.  It  continues  as  a  single  trunk  from  Poupart's 
ligament  to  the  lower  border  of  the  Popliteus  muscle,  and  here  divides  into  two 
branches,  the  anterior  and  posterior  tibial,  an  arrangement  exactly  similar  to  what 
occurs  in  the  upper  limb.  For  convenience  of  description,  the  upper  part  of  the 
main  trunk  is  named  femoral,  the  lower  part,  popliteal. 


THE  FEMORAL  ARTERY  (A.  FEMORALIS)  (Figs.  432  and  433). 

The  femoral  artery  commences  immediately  behind  Poupart's  ligament, 
midway  between  the  anterior  superior  spine  of  the  ilium  and  the  symphysis 
pubis,  and,  passing  down  the  forepart  and  inner  side  of  the  thigh,  terminates 
at  the  opening  in  the  Adductor  magnus,  at  the  junction  of  the  middle  with  the 
lower  third  of  the  thigh,  where  it  becomes  the  popliteal  artery.  The  vessel,  at 
the  upper  part  of  the  thigh,  lies  in  front  of  the  hip-joint,  just  on  a  line  with  the 
innermost  part  of  the  head  of  the  femur;  in  the  lower  part  of  its  course  it  is  in  close 
relation  with  the  inner  side  of  the  shaft  of  the  bone,  and  between  these  two  parts 
the  vessel  is  some  distance  from  the  bone.  In  the  upper  third  of  the  thigh  it  is 
contained  in  a  triangular  space  called  Scarpa's  triangle.  In  the  middle  third  of  the 
thigh  it  is  contained  in  an  aponeurotic  canal  called  Hunter's  canal. 

Scarpa's  Triangle  (trigonum  femorale}.—  Scarpa's  triangle  corresponds  to  the 
depression  seen  immediately  below  the  fold  of  the  groin.  It  is  a  triangular  space, 
the  apex  of  which  is  directed  downward,  and  the  sides  formed  externally  by  the 
Sartorius,  internally  by  the  inner  margin  of  the  Adductor  longus,  and  above  by 
Poupart's  ligament.  The  floor  of  the  space  is  formed  from  without  inward  by  the 
Iliacus,  Psoas,  Pectineus  (in  some  cases  a  small  part  of  the  Adductor  brevis),  and 
the  Adductor  longus  muscles;  and  it  is  divided  into  two  nearly  equal  parts  by  the 
femoral  vessels,  which  extend  from  the  middle  of  its  base  to  its  apex,  the  artery 


THE  FEMORAL  ARTERY 


699 


giving  off  in  this  situation  its  superficial  and  profunda  branches,  the  vein  receiving 
the  deep  femoral  and  internal  saphenous.  On  the  outer  side  of  the  femoral  artery 
is  the  femoral  nerve  dividing  into  its  branches.  In  the  outer  corner  of  the  space 
is  the  external  cutaneous  nerve.  Within  the  sheath  of  the  artery,  and  lying  upon 
the  outer  side  of  the  vessel,  is  the  crural  branch  of  the  genito-femoral  nerve.  At 
the  base  of  the  triangle  the  vein  is  to  the  inner  side  of  the  artery;  at  the  apex 
of  the  triangle  it  is  passing  behind  the  artery.  Besides  the  vessels  and  nerves, 
this  space  contains  some  fat  and  lymphatics. 


SUPERFICIAL 
EPIGASTRIC 

SUPERFICIAL  CIR. 
CUMFLEX  ILIAC 

COMMON 
FEMORAL 


EXTERNAL 
CIRCUMFLEX 

DESCENDING 
RAMUS  OF 
EXTERNAL 

CIRCUMFLEX 


SUPERIOR  EXTER- 
NAL ARTICULAR 
BRANCH   OF 
POPLITEAL 


SUPERFICIAL 

EXTERNAL 

PUDIC 

DEEP 

EXTERNAL 

PUDIC 


ANASTOMOTICA 
MAGNA 


SUPERIOR   INTERNAL 
ARTICULAR 
BRANCH  OF 
POPLITEAL 


FIG.  432. — Scheme  of  the  femoral  artery.     (Poirier  and  Charpy.) 


Hunter's  Canal  or  the  Adductor  Canal  (canalis  adductorius  [Hunteri]).— 
This  is  the  aponeurotic  space  in  the  middle  third  of  the  thigh,  extending  from 
the  apex  of  Scarpa's  triangle  to  the  femoral  opening  in  the  Adductor  magnus 
muscle.  It  is  bounded,  externally,  by  the  Vastus  internus;  internally  by  the 
Adductors  tongus  and  magnus  muscles;  and  is  covered  in  by  a  strong  apon- 
eurosis  which  extends  transversely  from  the  Vastus  internus  across  the  femoral 


700 


THE  BLOOD-  VASCULAR  SYSTEM 


'rotum. 


vessels  to  the  Adductor  longus  and  magnus;  lying  on  which  aponeurosis  is  the 
Sartorius  muscle.  It  contains  the  femoral  artery  and  vein  enclosed  in  their  own 
sheath  of  areolar  tissue,  the  vein  being  behind  and  on  the  outer  side  of  the  artery, 

and  the  internal  or  long  saphenous 
nerve  lying  at  first  on  the  outer  side 
and  then  in  front  of  the  vessels. 

For  convenience  of  description, 
and  also  in  reference  to  its  surgi- 
cal anatomy,  the  femoral  artery  is 
divided  into  a  short  trunk,  about 
an  inch  and  a  half  or  two  inches 
long,  which  is  known  as  the  com- 
mon femoral  artery,  while  the  re- 
mainder of  the  vessel  is  termed 
the  superficial  femoral  artery,  to 
distinguish  it  from  the  deep  femoral 
(profunda  femoris),  a  large  branch 
given  off  from  the  common  femoral 
at  its  termination,  and  which, 
by  its  derivation,  from  the  parent 
trunk,  marks  the  commencement 
of  the  superficial  femoral  artery. 

The  Common  Femoral  Artery 

(Figs.  432  and  433). 

The  common  femoral  artery  is 
very  superficial,  being  covered  by 
the  skin  and  superficial  fascia, 
superficial  inguinal  lymphatic 
glands,  the  iliac  portion  of  the 
fascia  lata,  and  the  prolongation 
downward  of  the  transversalis 
fascia,  which  forms  the  anterior 
part  of  the  sheath  of  the  vessels. 
It  has  in  front  of  it  filaments  from 
the  crural  branch  of  the  geni  to- 
femoral  nerve,  the  superficial  cir- 
cumflex iliac  vein,  and  occasionally 
the  superficial  epigastric  vein.  It 
rests  on  the  inner  margin  of  the 
Psoas  muscle,  which  separates  it 
from  the  capsular  ligament  of  the 
hip-joint,  and  a  little  lower  on  the 
Pectineus  muscle  ;  and  crossing 
behind  it  is  the  branch  to  the 
Pectineus  from  the  femoral  nerve. 
Separating  the  artery  from  the 
Pectineus  muscles  is  the  pubic  portion  of  the  fascia  lata  and  the  prolongation 
from  the  fascia  covering  the  Iliacus  muscle,  which  forms  the  posterior  layer  of  the 
sheath  of  the  vessels.  The  femoral  nerve  lies  about  half  an  inch  to  the  outer 
side  of  the  common  femoral  artery,  being  separated  from  the  artery  by  a  small 
part  of  the  Psoas  muscle.  To  the  inner  side  of  the  artery  is  the  femoral  vein, 
between  the  margins  of  the  Pectineus  and  Psoas  muscles.  The-  two  vessels  are 


Long  saphenous 
nerve. 


Superior  external 
articular. 


Inferior  internal 
articular. 


Anastomotica 

magna. 
Superior  internal 

articular. 


Inferior  internal 
articular. 


Anterior  tibial 
recurrent. 


FIQ.  433. — The  femoral  artery. 


THE  SUPERFICIAL  FEMORAL  ARTERY 


701 


enclosed  in  a  strong  fibrous  sheath  formed  by  the  proper  sheath  of  the  vessels, 
strengthened  by  fascia  (see  page  511) ;  the  artery  and  vein  are  separated,  however, 
from  one  another  by  a  thin  fibrous  partition. 

PLAN  OF  THE  RELATIONS  OF  THE  COMMON  FEMORAL  ARTERY. 

In  front. 

Skin  and  superficial  fascia. 
Superficial  inguinal  glands. 
Iliac  portion  of  fascia  lata. 
Prolongation  of  transversalis  fascia. 
Crural  branch  of  genito-femoral  nerve. 
Superficial  circumflex  iliac  vein. 
Superficial  epigastric  vein. 


Inner  side. 
Femoral  vein. 


Outer  side. 

Small  part  of  Psoas  muscle, 
separating  the  artery  from  the 
femoral  nerve. 


Behind. 

Prolongation  of  fascia  covering  the  Iliacus  muscle. 
Pubic  portion  of  fascia  lata. 
Nerve  to  Pectineus. 
Psoas  muscle. 
Pectineus  muscle. 
Capsule  of  hip-joint. 

The  Superficial  Femoral  Artery  (Figs.  432  and  433). 

The  superficial  femoral  artery  is  only  superficial  where  it  lies  in  Scarpa's 
triangle.  Here  it  is  covered  by  the  skin,  superficial  and  deep  fascia,  and 
crossed  by  the  internal  cutaneous  branch  of  the  femoral  nerve.  In  Hunter's  canal 
it  is  more  deeply  seated,  being  covered  by  the  integument,  the  superficial  and 
deep  fascia,  the  Sartorius  and  the  aponeurotic  covering  of  Hunter's  canal.  The 
internal  saphenous  nerve  crosses  the  artery  from  without  inward.  Behind,  the 
artery  lies  at  its  upper  part  on  the  femoral  vein  and  the  profunda  artery  and 
vein,  which  separate  it  from  the  Pectineus  muscle,  and  lower  down  on  the  Adduc- 
tor longus  and  Adductor  magnus  muscles.  To  the  outer  side  is  the  long  saphenous 
nerve  and  the  nerve  to  the  Vastus  internus,  the  Vastus  internus  muscle,  and, 
at  its  lower  part,  the  femoral  vein.  To  the  inner  side  is  the  Adductor  longus 
above  and  the  Adductor  magnus  and  Sartorius  below. 

PLAN  OF  THE  RELATIONS  OF  THE  SUPERFICIAL  FEMORAL  ARTERY. 

In  front. 

Skin,  superficial  and  deep  fasciae. 
Internal  cutaneous  nerve. 
Sartorius. 

Aponeurotic  covering  of  Hunter's  canal. 
Internal  saphenous  nerve. 

Outer  side. 

Long  saphenous  nerve. 

Nerve  to  vastus  internus. 

Vastus  internus. 

Femoral  vein  (below). 

Behind. 
Femoral  vein. 
Profunda  artery  and  vein. 
Pectineus  muscle. 
Adductor  longus. 
Adductor  magnus. 


Inner  side. 
Adductor  longus. 
Adductor  magnus. 
Sartorius. 


702  THE  BLOOD-VASCULAR  SYSTEM 

The  femoral  vein,  at  Poupart's  ligament,  lies  close  to  the  inner  side  of  the  artery, 
separated  from  it  by  a  thin  fibrous  partition;  but  lower  down  it  is  behind  it,  and 
then  to  its  outer  side. 

The  internal  saphenous  nerve  is  situated  on  the  outer  side  of  the  artery,  in  the 
middle  third  of  the  thigh,  beneath  the  aponeurotic  covering  of  Hunter's  canal,  but 
not  usually  within  the  sheath  of  the  vessels.  The  internal  cutaneous  nerve  passes 
obliquely  across  the  upper  part  of  the  sheath  of  the  femoral  artery. 

Peculiarities.  Double  Femoral  Reunited.— Several  cases  are  recorded  in  which  the  femoral 
artery  divided  into  two  trunks  below  the  origin  of  the  profunda,  and  became  reunited  near  the 
opening  of  the  Adductor  magnus  so  as  to  form  a  single  popliteal  artery.  One  of  them  occurred 
in  a  patient  operated  upon  for  popliteal  aneurism. 

Change  of  Position. — A  few  cases  have  been  recorded  in  which  the  femoral  artery  was 
situated  at  the  back  of  the  thigh,  the  vessel  being  continuous  above  with  the  internal  iliac,  escap- 
ing from  the  pelvis  through  the  great  sacro-sciatic  foramen,  and  accompanying  the  great  sciatic 
nerve  to  the  popliteal  space,  where  its  division  occurred  in  the  usual  manner.  The  external 
iliac  in  these  cases  was  small,  and  terminated  in  the  profunda. 

Position  of  the  Vein. — The  femoral  vein  is  occasionally  placed  along  the  inner  side  of  the 
artery,  throughout  the  entire  extent  of  Scarpa's  triangle,  or  it  may  be  slit  so  that  a  large  vein  is 
placed  on  each  side  of  the  artery  for  a  greater  or  less  extent. 

Origin  of  the  Profunda. — This  vessel  occasionally  arises  from  the  inner  side,  and,  more 
rarely,  from  the  back  of  the  common  trunk;  but  the  more  important  peculiarity,  in  a  surgical 
point  of  view,  is  that  which  relates  to  the  height  at  which  the  vessel  arises  from  the  femoral.  In 
three-fourths  of  a  large  number  of  cases  it  arose  between  one  or  two  inches  below  Poupart's 
ligament;  in  a  few  cases  the  distance  was  less  than  an  inch;  more  rarely,  opposite  the  ligament; 
and  in  one  case,  above  Poupart's  ligament,  from  the  external  iliac.  Occasionally,  the  distance 
between  the  origin  of  the  vessel  and  Poupart's  ligament  exceeds  two  inches,  and  in  one  case  it 
was  found  to  be  as  much  as  four  inches. 

Surface  Marking. — The  upper  two-thirds  of  a  line  drawn  from  a  point  midway  between 
the  anterior  superior  spine  of  the  ilium  and  the  symphysis  pubis  to  the  adductor  tubercle  on 
the  inner  condyle  of  the  femur,  with  the  thigh  abducted  and  rotated  outward,  will  indicate  the 
course  of  the  femoral  artery. 

Surgical  Anatomy. — Compression  of  the  femoral  artery,  which  is  constantly  requisite  in 
amputations  and  other  operations  on  the  lower  limbs,  and  also  for  the  cure  of  popliteal  aneurisms, 
is  most  effectually  made  immediately  below  Poupart's  ligament.  In  this  situation  the  artery  is 
very  superficial,  and  is  merely  separated  from  the  ascending  ramus  of  the  os  pubis  by  the  Psoas 
muscle;  so  that  the  surgeon,  by  means  of  his  thumb  or  a  compressor,  may  effectually  control  the 
circulation  through  it.  This  vessel  may  also  be  compressed  in  the  middle  third  of  the  thigh  by 
placing  a  compress  over  the  artery,  beneath  the  tourniquet,  and  directing  the  pressure  from 
within  outward,  so  as  to  compress  the  vessel  against  the  inner  side  of  the  shaft  of  the  femur. 

The  application  of  a  ligature  to  the  femoral  artery  may  be  required  in  the  cases  of  wound 
or  aneurism  of  the  arteries  of  the  leg,  of  the  popliteal  or  femoral;1  and  the  vessel  may  be  exposed 
and  tied  in  any  part  of  its  course.  The  great  depth  of  this  vessel  at  its  lower  part,  its  close  con- 
nection with  important  structures,  and  the  density  of  its  sheath  render  the  operation  in  this 
situation  one  of  much  greater  difficulty  than  the  application  of  a  ligature  at  its  upper  part, 
where  it  is  more  superficial. 

Ligature  of  the  common  femoral  artery  is  usually  considered  unsafe,  on  account  of  the  con- 
nection of  large  branches  with  it — viz.,  the  deep  epigastric  and  the  deep  circumflex  iliac  arising 
just  above  Poupart's  ligament;  on  account  of  the  number  of  small  branches  which  arise  from 
it  in  its  short  course;  and  on  account  of  the  uncertainty  of  the  origin  of  the  profunda  femoris, 
which,  if  it  arise  high  up,  would  be  too  close  to  the  ligature  for  the  formation  of  a  firm  coagu- 
lum.  The  profunda  sometimes  arises  higher  than  the  point  above  mentioned,  and  rarely  between 
two  or  three  inches  (in  one  case  four)  below  Poupart's  ligament.  It  would  appear,  then,  that 
the  most  favorable  situation  for  the  application  of  a  ligature  to  the  femoral  is  on  the  superficial 
femoral  at  the  apex  of  Scarpa's  triangle.  In  order  to  expose  the  artery  in  this  situation,  an  inci- 
sion between  three  and  four  inches  long  should  be  made  in  the  course  of  the  vessel,  the  patient 
lying  in  the  recumbent  position,  with  the  limb  slightly  flexed  and  abducted,  and  rotated  outward. 
A  large  vein  is  frequently  met  with,  passing  in  the  course  of  the  artery  to  join  the  internal  saphe- 
nous vein;  this  must  be  avoided,  and  the  fascia  lata  having  been  cautiously  divided  and  the 
Sartorius  exposed,  that  muscle  must  be  drawn  outward  in  order  to  expose  fully  the  sheath  of 
the  vessels.  The  finger  being  introduced  into  the  wound  and  the  pulsation  of  the  artery  felt, 
the  sheath  should  be  opened  on  the  outer  side  of  the  vessel  to  a  sufficient  extent  to  allow  of  the 

1  Ligation  of  the  femoral  artery  has  been  also  recommended  and  performed  for  elephantiasis  of  the  leg  and 
acute  inflammation  of  the  knee-joint  (Maunder,  Clin.  Soc.  Trans.,  vol.  ii.  p.  37). — ED.  of  15th  English  edition. 


THE  SUPERFICIAL  FEMORAL  ARTERY  703 

introduction  of  the  ligature,  but  no  farther;  otherwise  the  nutrition  of  the  coats  of  the  vessel 
may  be  interfered  with,  or  muscular  branches  which  arise  from  the  vessel  at  irregular  intervals 
may  be  divided.  In  this  part  of  the  operation  the  long  saphenous  nerve  and  the  nerve  to  the 
Vastus  internus,  which  is  in  close  relation  with  the  sheath,  should  be  avoided.  The  aneurism 
needle  must  be  carefully  introduced  and  kept  close  to  the  artery,  to  avoid  the  femoral  vein,  which 
lies  behind  the  vessel  in  this  part  of  its  course. 

To  expose  the  artery  in  Hunter's  canal,  an  incision  should  be  made  between  three  and  four 
inches  in  length,  a  finger's  breadth  internal  to  the  line  of  the  artery,  in  the  middle  of  the  thigh 
— i,  e.,  midway  between  the  groin  and  the  knee.  The  integument  is  first  divided.  The  fascia 
lata  having  been  divided,  and  the  outer  border  of  the  Sartorius  muscle  exposed,  it  should  be 
drawn  inward,  when  the  strong  fascia  which  is  stretched  across  from  the  Adductors  to  the  Vastus 
internus  will  be  exposed,  and  must  be  freely  divided;  the  sheath  of  the  vessels  is  now  seen, 
and  must  be  opened,  and  the  artery  secured  by  passing  the  aneurism  needle  between  the  vein 
and  artery  in  the  direction  from  without  inward.  The  femoral  vein  in  this  situation  lies  on  the 
outer  side  of  the  artery  and  the  long  saphenous  nerve  on  the  anterior  and  outer  side  of  the 
artery. 

It  has  been  seen  that  the  femoral  artery  occasionally  divides  into  two  trunks  below  the  origin 
of  the  profunda.  If  in  the  operation  for  tying  the  femoral  two  vessels  are  met  with,  the  surgeon 
should  alternately  compress  each,  in  order  to  ascertain  which  vessel  is  connected  with  the 
aneurismal  tumor  or  with  the  bleeding  from  the  wound,  and  that  one  only  should  be  tied  which 
controls  the  pulsation  or  hemorrhage.  If,  however,  it  is  necessary  to  compress  both  vessels 
before  the  circulation  in  the  tumor  is  controlled,  both  should  be  tied,  as  it  would  be  probable  that 
they  became  reunited,  as  in  the  instances  referred  to  above. 

In  wounds  of  the  femoral  artery  the  question  of  the  mode  of  treatment  is  of  considerable 
importance.  If  the  wound  in  the  superficial  structures  is  a  large  one,  the  injured  vessel  must 
be  exposed  and  tied;  but  if  the  wound  is  a  punctured  one  and  the  bleeding  has  ceased,  the  ques- 
tion will  arise  whether  to  cut  down  upon  the  artery  or  to  trust  to  pressure.  Mr.  Cripps1  advises 
that  if  the  wound  is  in  the  "upper  part  of  the  thigh — that  is  to  say,  in  a  position  where  the 
femoral  artery  is  comparatively  superficial — the  surgeon  may  enlarge  the  opening  with  a  good 
prospect  of  finding  the  wounded  vessel  without  an  extensive  or  prolonged  operation.  If  the 
wound  be  in  the  lower  half  of  the  thigh,  owing  to  the  greater  depth  of  the  artery  and  the  possi- 
bility of  its  being  the  popliteal  that  is  wounded,  the  search  is  rendered  a  far  more  severe  and 
hazardous  operation,  and  it  should  not  be  undertaken  until  a  thorough  trial  of  pressure  has 
proved  ineffectual." 

Great  care  and  attention  are  necessary  for  the  successful  application  of  pressure.  The  limb 
should  be  carefully  bandaged  from  the  foot  upward  to  the  wound,  which  is  not  covered,  and  then 
onward  to  the  groin.  The  wound  is  then  dusted  with  iodoform  or  boracic  powder  and  a  conical 
pad  applied  over  the  wound.  Rollers  the  thickness  of  the  index  finger  are  then  placed  along 
the  course  of  the  vessel  above  and  below  the  wound,  and  the  whole  carefully  bandaged  to  a  back 
splint  with  a  foot-piece. 

Collateral  Circulation. — When  the  common  femoral  is  tied  the  main  channels  for  carrying 
on  the  circulation  are  the  anastomoses  of  the  gluteal  and  circumflex  iliac  arteries  above  with  the 
external  circumflex  below;  of  the  obturator  and  sciatic  above  with  the  internal  circumflex  below; 
and  of  the  comes  nervi  ischiadici  with  the  arteries  in  the  ham. 

The  principal  agents  in  carrying  on  the  collateral  circulation  after  ligature  of  the  superficial 
femoral  artery  are,  according  to  Sir  A.  Cooper,  as  follows: 

"The  arteria  profunda  formed  the  new  channel  for  the  blood.  The  first  artery  sent  off 
passed  down  close  to  the  back  of  the  thigh-bone,  and  entered  the  two  superior  articular  branches 
of  the  popliteal  artery. 

"The  second  new  large  vessel,  arising  from  the  profunda  at  the  same  part  with  the  former, 
passed  down  by  the  inner  side  of  the  Biceps  muscle  to  a  branch  of  the  popliteal  which  was  dis- 
tributed to  the  Gastrocnemius  muscle;  whilst  a  third  artery,  dividing  into  several  branches, 
passed  down  with  the  sciatic  nerve  behind  the  knee-joint,  and  some  of  its  branches  united  them- 
selves with  the  inferior  articular  arteries  of  the  popliteal,  with  some  recurrent  branches  of  those 
arteries,  with  arteries  passing  to  the  Gastrocnemii,  and,  lastly,  with  the  origin  of  the  anterior 
and  posterior  tibial  arteries. 

"  It  appears,  then,  that  it  is  those  branches  of  the  profunda  which  accompany  the  sciatic 
nerve  that  are  the  principal  supporters  of  the  new  circulation."2 

In  Porta's  work3  (tab.  xii.,  xiii.)  is  a  good  representation  of  the  collateral  circulation  after 
the  ligature  of  the  femoral  artery.  The  patient  had  survived  the  operation  three  years.  The 
lower  part  of  the  artery  is  at  least  as  large  as  the  upper;  about  two  inches  of  the  vessel  appear 
to  have  been  obliterated.  The  external  and  internal  circumflex  arteries  are  seen  anastomosing 
by  a  great  number  of  branches  with  the  lower  branches  of  the  femoral  (muscular  and  anasto- 

1  Heath's  Dictionary  of  Practical  Surgery,  vol.  i.  p.  525.  2  Med.-Chir.  Trans.,  vol.  ii.,  1811. 

3  Alterazioni  patologiche  delle  Arterie. 


704  THE  BLOOD-  VASCULAR  SYSTEM 

motica  magna)  and  with  the  articular  branches  of  the  popliteal.  The  branches  from  the  external 
circumflex  are  extremely  large  and  numerous.  One  very  distinct  anastomosis  can  be  traced 
between  this  artery  on  the  outside  and  the  anastomotica  magna  on  the  inside  through  the  inter- 
vention of  the  superior  external  articular  artery,  with  which  they  both  anastomose;  and  blood 
reaches  even  the  anterior  tibial  recurrent  from  the  external  circumflex  by  means  of  anastomosis 
with  the  same  external  articular  artery.  The  perforating  branches  of  the  profunda  are  also 
seen  bringing  blood  round  the  obliterated  portion  of  the  artery  into  long  branches  (muscular) 
which  have  been  ^iven  off  just  below  that  portion.  The  termination  of  the  profunda  itself 
anastomoses  most  freely  with  the  superior  external  articular.  A  long  branch  of  anastomosis 
is  also  traced  down  from  the  internal  iliac  by  means  of  the  comes  nervi  ischiadici  of  the  sciatic, 
which  anastomoses  on  the  popliteal  nerves  with  branches  from  the  popliteal  and  posterior  tibial 
arteries.  In  this  case  the  anastomosis  had  been  too  free,  since  the  pulsation  and  growth  of  the 
aneurism  recurred,  and  the  patient  died  after  ligature  of  the  external  iliac. 

There  is  an  interesting  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  a 
limb  on  which  John  Hunter  had  tied  the  femoral  artery  fifty  years  before  the  patient's  death. 
The  whole  of  the  superficial  femoral  and  popliteal  artery  seems  to  have  been  obliterated.  The 
anastomosis  by  means  of  the  comes  nervi  ischiadici,  which  is  shown  in  Porta's  plate,  is  distinctly 
seen:  the  external  circumflex  and  the  termination  of  the  profunda  artery  seem  to  have  been  the 
chief  channels  of  anastomoses;  but  the  injection  has  not  been  a  very  successful  one. 

Branches  (Figs.  432  and  433). — The  branches  of  the  femoral  artery  are — the 

Superficial  Epigastric.  (  External  Circumflex. 

Superficial  Circumflex  Iliac.  Profunda  Femoris  -\  Internal  Circumflex. 

Superficial  External  Pudic.  (  Three  Perforating. 

Deep  External  Pudic.  Muscular. 

Anastomotica  Magna. 

The  Superficial  Epigastric  (a.  epigastrica  superficialis)  arises  from  the  fem- 
oral about  half  an  inch  below  Poupart's  ligament,  and,  passing  through  the 
saphenous  opening  in  the  fascia  lata,  ascends  on  the  abdomen,  in  the  superficial 
fascia  covering  the  External  oblique  muscle,  nearly  as  high  as  the  umbilicus.  It 
distributes  branches  to  the  superficial  inguinal  glands,  the  superficial  fascia,  and 
the  integument,  anastomosing  with  branches  of  the  deep  epigastric. 

The  Superficial  Circumflex  Iliac  (a.  circumflexa  ilium  superficialis) ,  the 
smallest  of  the  cutaneous  branches,  arises  close  to  the  preceding,  and,  piercing  the 
fascia  lata,  runs  outward,  parallel  with  Poupart's  ligament,  as  far  as  the  crest  of 
the  ilium,  dividing  into  branches  which  supply  the  integument  of  the  groin,  the 
superficial  fascia,  and  the  superficial  inguinal  lymphatic  glands,  anastomosing 
with  the  deep  circumflex  iliac  and  with  the  gluteal  and  external  circumflex 
arteries. 

The  Superficial  External  Pudic  or  the  Superior  Superficial  External  Pudic 
(a.  pudenda  externa  superficialis)  arises  from  the  inner  side  of  the  femoral  artery, 
close  to  the  preceding  vessels,  and,  after  passing  through  the  saphenous  opening, 
courses  inward,  across  the  spermatic  cord  or  round  ligament,  to  be  distributed  to 
the  integument  on  the  lower  part  of  the  abdomen,  the  penis  and  scrotum  in  the 
male,  and  the  labium  in  the  female,  anastomosing  with  branches  of  the  internal 
pudic. 

The  Deep  External  Pudic  or  the  Deep  Superficial  External  Pudic  (a.  pudenda 
externa  profunda},  more  deeply  seated  than  the  preceding,  passes  inward  across 
the  Pectineus  and  Adductor  longus  muscles,  covered  by  the  fascia  lata,  which  it 
pierces  at  the  inner  border  of  the  thigh,  its  branches  being  distributed,  in  the  male, 
to  the  integument  of  the  scrotum  and  perinaeum;  and  in  the  female  to  the  labium, 
anastomosing  with  branches  of  the  superficial  perineal  artery. 

The  Deep  Femoral  or  the  Profunda  Femoris  (a.  profunda  femoris)  (Figs.  432 
and  433)  nearly  equals  the  size  of  the  superficial  femoral.  It  arises  from  the 
outer  and  back  part  of  the  femoral  artery,  from  one  to  two  inches  below  Poupart's 


THE  SUPERFICIAL  FEMORAL  ARTERY  705 

ligament.  It  at  first  lies  on  the  outer  side  of  the  superficial  femoral,  arid  then 
passes  behind  it  and  the  femoral  vein  to  the  inner  side  of  the  femur,  and,  passing 
downward  beneath  the  Adductor  longus,  terminates  at  the  lower  third  of  the  thigh 
in  a  small  branch  which  pierces  the  Adductor  magnus  (and  from  this  circum- 
stance is  sometimes  called  the  fourth  perforating  artery),  and  is  distributed  to  the 
flexor  muscles  on  the  back  of  the  thigh,  anastomosing  with  branches  of  the 
popliteal  and  inferior  perforating  arteries. 

Relations. — Behind,  it  lies  first  upon  the  Iliacus,  and  then  on  the  Pectineus, 
Adductor  brevis,  and  Adductor  magnus  muscles.  In  front,  it  is  separated  from 
the  superficial  femoral  artery,  above  by  the  femoral  and  profunda  veins,  and 
below  by  the  Adductor  longus.  On  its  outer  side  the  origin  of  the  Vastus  interims 
separates  it  from  the  femur. 

PLAN  OF  THE  RELATIONS  OF  THE  PROFUNDA  ARTERY. 

In  front. 

Superficial  femoral  artery. 
Femoral  and  profunda  veins. 
Adductor  longus. 

Outer  side. 
Vastus  internus. 


Behind. 
Iliacus. 
Pectineus. 
Adductor  brevis. 
Adductor  magnus. 

Branches. — The  profunda  gives  off  the  following  named  branches: 

Muscular.  Internal  circumflex. 

External  circumflex.  Four  perforating. 

Muscular  Branches  are  given  off  in  Scarpa's  triangle,  and  also  from  the  vessel  as 
it  lies  between  the  Adductor  muscles. 

The  External  Circumflex  Artery  (a.  circumflexa  femoris  lateralis)  supplies  the 
muscles  on  the  front  of  the  thigh.  It  arises  from  the  outer  side  of  the  profunda, 
passes  horizontally  outward,  between  the  divisions  of  the  femoral  nerve  and 
behind  the  Sartorius  and  Rectus  muscles,  and  divides  into  three  sets  of  branches — 
ascending,  transverse,  and  descending. 

The  ascending  branch  (ramus  asceiidens)  passes  upward,  beneath  the  Tensor 
fascine  femoris  muscle,  to  the  outer  side  of  the  hip,  anastomosing  with  the  terminal 
branches  of  the  gluteal  arid  deep  circumflex  iliac  arteries.  It  sends  out  muscular 
branches.  The  descending  branch  (ramus  descendens)  passes  downward,  behind 
the  Rectus,  upon  the  Vasti  muscles,  to  which  its  branches  are  distributed,  one 
or  two  passing  beneath  the  Vastus  externus  as  far  as  the  knee,  anastomosing  with 
the  superior  articular  branches  of  the  popliteal  artery.  These  are  accompanied  by 
the  branch  of  the  femoral  nerve  to  the  Vastus  externus.  The  transverse  branch, 
the  smallest,  passes  outward  over  the  Crureus,  pierces  the  Vastus  externus,  and 
winds  round  the  ferpur  to  its  back  part,  just  below  the  great  trochanter,  anasto- 
mosing at  the  back  of  the  thigh  with  the  internal  circumflex,  sciatic,  and  superior 
perforating  arteries. 

The  Internal  Circumflex  Artery  (a.  circumflexa  femoris  medialis],  smaller  than 
the  external,  arises  from  the  inner  and  back  part  of  the  profunda,  and  winds 
round  the  inner  side  of  the  femur,  between  the  Pectineus  and  Psoas  muscles.  On 

45 


706  THE  BLOOD-VASCULAR  SYSTEM 

reaching  the  upper  border  of  the  Adductor  brevis  it  gives  off  two  muscular  branches, 
one  of  which  passes  inward  to  be  distributed  to  the  Adductor  muscles,  the  Gracilis, 
and  Obturator  externus,  anastomosing  with  the  obturator  artery;  the  other 
descends,  and  passes  beneath  the  Adductor  brevis,  to  supply  it  and  the  great 
Adductor;  while  the  continuation  of  the  vessel  passes  backward  and  divides  into 
an  ascending  and  a  transverse  branch  (Fig.  348).  The  ascending  branch  (ramus 
profundus)  passes  obliquely  upward  upon  the  tendon  of  the  Obturator  externus 
and  under  cover  of  the  Quadratus  femoris  toward  the  digital  fossa,  where  it 
anastomoses  with  twigs  from  the  gluteal  and  sciatic  arteries.  The  transverse 
branch  (ramus  superficialis) ,  larger  than  the  ascending,  appears  between  the 
Quadratus  femoris  and  upper  border  of  the  Adductor  magnus,  anastomosing  with 
the  sciatic,  external  circumflex,  and  superior  perforating  arteries,  the  crucial  anas- 
tomosis. Opposite  the  hip-joint  the  artery  gives  off  an  articular  vessel  (ramus 
acetabuli),  which  enters  the  joint  beneath  the  transverse  ligament;  and,  after  sup- 
plying the  adipose  tissue,  passes  along  the  round  ligament  to  the  head  of  the  bone. 

The  Perforating  Arteries  (Figs.  431,  432,  and  433),  usually  three  in  number,  are 
so  called  from  their  perforating  the  tendon  of  the  Adductor  magnus  muscle  to 
reach  the  back  of  the  thigh.  They  pass  backward  close  to  the  linea  aspera  of  the 
femur,  under  cover  of  small  tendinous  arches  in  the  Adductor  magnus.  The 
first  is  given  off  above  the  Adductor  brevis,  the  second  in  front  of  that  muscle, 
and  the  third  immediately  below  it. 

The  first  perforating  artery  (a.  perforans  primd)  passes  backward  between  the 
Pectineus  and  Adductor  brevis  (sometimes  perforates  the  latter) ;  it  then  pierces 
the  Adductor  magnus  close  to  the  linea  aspera.  It  gives  off  branches  which  supply 
the  Adductor  brevis,  the  Adductor  magnus,  the  Biceps,  and  Gluteus  maximus 
muscles,  and  anastomoses  with  the  sciatic,  internal  and  external  circumflex,  and 
middle  perforating  arteries.  The  second  perforating  artery  (a.  perforans  secunda], 
larger  than  the  first,  pierces  the  tendons  of  the  Adductor  brevis  and  Adductor 
magnus  muscles,  and  divides  into  ascending  and  descending  branches,  which 
supply  the  flexor  muscles  of  the  thigh,  anastomosing  with  the  first  and  third 
perforating  arteries.  The  second  artery  frequently  arises  in  common  with  the  first. 
The  nutrient  artery  of  the  femur  is  usually  given  off  from  this  branch.  The  third 
perforating  artery  (a.  perforans  tertia)  is  given  off  below  the  Adductor  brevis;  it 
pierces  the  Adductor  magnus,  and  divides  into  branches  which  supply  the  flexor 
muscles  of  the  thigh ;  anastomosing  above  with  the  higher  perforating  arteries,  and 
below  with  the  terminal  branches  of  the  profunda  and  the  muscular  branches  of 
the  popliteal.  A  fourth  perforating  artery  is  represented  by  the  termination  of  the 
profunda  femoris  artery. 

The  nutritive  artery  of  the  femur  (a.  nutricia  femoris),  if  single,  comes  from  the 
second  perforating  artery;  if  double,  from  the  first  and  third  perforating  arteries. 
If  double,  one  vessel  is  called  superior  and  the  other  inferior. 

Muscular  Branches  (rami  musculares)  are  given  off  from  the  superficial  femoral 
throughout  its  entire  course.  They  vary  from  two  to  seven  in  number,  and  supply 
chiefly  the  Sartorius  and  Vastus  internus. 

The  Anastomotica  Magna  (a.  genii  supremo)  (Figs.  432  and  433)  arises  from 
the  femoral  artery  just  before  it  passes  through  the  tendinous  opening  in  the 
Adductor  magnus  muscle,  and  immediately  divides  into  a  superficial  and  deep  branch. 

The  Superficial  Branch  (ramus  saphenous)  pierces  the  aponeurotic  covering  of 
Hunter's  canal,  and  accompanies  the  long  saphenous  nerve  to  the  inner  side  of  the 
thigh.  It  passes  between  the  Sartorius  and  Gracilis  muscles,  aid,  piercing  the  fascia 
lata,  is  distributed  to  the  integument  of  the  upper  and  inner  part  of  the  leg,  anasto- 
mosing with  the  inferior  internal  articular  artery. 

The  Deep  Branch  (ramus  musculoarticularis)  descends  in  the  substance  of  the 
Vastus  internus,  lying  in  front  of  the  tendon  of  the  Adductor  magnus,  to  the  inner 
side  of  the  knee,  where  it  anastomoses  with  the  superior  internal  articular  artery 


THE  POPLITEAL  SPACE 


707 


-Sural  arteries. 


and  the  anterior  recurrent  branch  of  the 
anterior  tibial.  A  branch  from  this  vessel 
crosses  outward  above  the  articular  surface 
of  the  femur,  forming  an  anastomotic  arch 
with  the  superior  external  articular  artery, 
and  supplies  branches  to  the  knee-joint. 

THE  POPLITEAL  ARTERY  (A.  POPLITEA) 

(Figs.  431  and  432). 

The  popliteal  artery  commences  at  the  ter- 
mination of  the  femoral  at  the  opening  in  the 
Adductor  magnus,  and,  passing  obliquely 
downward  and  outward  behind  the  knee-joint 
to  the  lower  border  of  the  Popliteus  muscle 
divides  into  the  anterior  and  posterior  tibial 
arteries.  A  portion  of  the  artery  lies  in  the 
popliteal  space;  but  above  and  below,  to 
a  considerable  extent,  it  is  covered  by  the 
muscles  which  form  the  boundaries  of  the 
space,  and  is  therefore  beyond  the  confines 
of  the  hollow. 

The  Popliteal  Space  (Fig.  434). 

Dissection.— A  vertical  incision  about  eight  inches 
in  length  should  be  made  along  the  back  part  of  the 
knee-joint,  connected  above  and  below  by  a  trans- 
verse incision  from  the  inner  to  the  outer  side  of  the 
limb.  The  flaps  of  integument  included  between 
these  incisions  should  be  reflected  in  the  direction 
shown  in  Fig.  345,  page  525. 

Boundaries. — The  popliteal  space,  or  the 
ham,  is  a  lozenge-shaped  space,  widest  at  the 
back  part  of  the  knee-joint,  and  deepest  above 
the  articular  end  of  the  femur.  It  is  bounded 
externally,  above  the  joint,  by  the  Biceps,  and 
below  the  joint  by  the  Plantaris  and  external 
head  of  the  Gastrocnemius.  Internally,  above 
the  joint,  by  the  Semimembranosus,  Semiten- 
dinosus,  Gracilis,  and  Sartorius;  below  the 
joint,  by  the  inner  head  of  the  Gastrocnemius. 

Above,  it  is  limited  by  the  apposition  of  the 
inner  and  outer  hamstring  muscles ;  below,  by 
the  junction  of  the  two  heads  of  the  Gastroc- 
nemius. The  floor  is  formed  by  the  lower 
part  of  the  posterior  surface  of  the  shaft 
of  the  femur,  the  posterior  ligament  of  the 
knee-joint,  the  upper  end  of  the  tibia,  and 
the  fascia  covering  the  Popliteus  muscle,  and 
the  space  is  covered  in  by  the  fascia  lata. 

Contents. — It  contains  the  popliteal  vessels 
and  their  branches,  together  with  the  termination  of  the  external  saphenous  vein, 
the  internal  and  external  popliteal  nerves  and  some  of  their  branches,  the  lower 
extremity  of  the  small  sciatic  nerve,  the  articular  bra*nch  from  the  obturator  nerve, 
a  few  small  lymphatic  glands,  and  a  considerable  quantity  of  loose  adipose  tissue. 


-Anterior  peroneal. 


FIG.  434. — The  popliteal,  posterior  tibial,  and 
peroneal  arteries. 


708  THE  BLOOD-VASCULAR  SYSTEM 

Position  of  Contained  Parts. — The  internal  popliteal  nerve  descends  in  the 
middle  line  of  the  space  lying  superficial  and  crossing  the  artery  from  without 
inward.  The  external  popliteal  nerve  descends  on  the  outer  side  of  the  upper  part 
of  the  space,  lying  close  to  the  tendon  of  the  Biceps  muscle.  More  deeply  at  the 
bottom  of  the  space  are  the  popliteal  vessels,  the  vein  lying  superficial  to  the  artery, 
to  which  it  is  closely  united  by  dense  areolar  tissue;  it  is  a  thick-walled  vessel,  and 
lies  at  first  to  the  outer  side  of  the  artery,  and  then  crosses  it  to  gain  the  inner  side 
below;  sometimes  the  vein  is  double,  the  artery  lying  between  the  two  venae  comites, 
which  are  usually  connected  by  short  transverse  branches.  More  deeply  and,  at 
its  upper  part,  close  to  the  surface  of  the  bone  is  the  popliteal  artery,  and  passing 
off  from  it  at  right  angles  are  its  articular  branches.  The  articular  branch  from 
the  obturator  nerve  descends  upon  the  popliteal  artery  to  supply  the  knee,  and 
occasionally  there  is  found  deep  in  the  space  an  articular  filament  from  the  great 
sciatic  nerve. 

The  popliteal  lymphatic  glands,  four  or  five  in  number,  are  found  surrounding 
the  artery;  one  usually  lies  superficial  to  the  vessel;  another  is  situated  between 
it  and  the  bone,  and  the  rest  are  placed  on  either  side  of  it. 

The  Popliteal  Artery,  in  its  course  downward  from  the  aperture  in  the  Adductor 
magnus  to  the  lower  border  of  the  Popliteus  muscle,  rests  first  on  the  inner  surface 
of  the  femur,  and  is  then  separated  by  a  little  fat  from  the  hollowed  popliteal 
surface  of  the  bone;  in  the  middle  of  its  course  it  rests  on  the  posterior  ligament 
of  the  knee-joint,  and  below  on  the  fascia  covering  the  Popliteus  muscle.  Super- 
ficially, it  is  covered  above  by  the  Semimembranosus ;  in  the  middle  of  its  course, 
by  a  quantity  of  fat,  which  separates  it  from  the  deep  fascia  and  integument;  and 
below  it  is  overlapped  by  the  Gastrocnemius,  Plantaris,  and  Soleus  muscles,  the 
popliteal  vein,  and  the  internal  popliteal  nerve.  The  popliteal  vein,  which  is 
intimately  attached  to  the  artery,  lies  superficial  and  external  to  it  above;  it  then 
crosses  it  and  lies  to  its  inner  side.  The  internal  popliteal  nerve  is  still  more 
superficial  and  external  above,  but  below  the  joint  it  crosses  the  artery  and  lies 
on  its  inner  side.  Laterally,  the  artery  is  bounded  by  the  muscles  which  are 
situated  on  either  side  of  the  popliteal  space. 

PLAN  OF  THE  RELATIONS  or  THE  POPLITEAL  ARTERY. 

In  front. 
Femur. 

Ligamentum  posticum. 
Popliteus. 
Inner  side  /**     ~"~\  Outer  side. 

Semimembranosus.  /  \ 

Internal   oondvle  I  p°Pliteal      1  Outer  condyle. 

,       ,,  I  Artery-      }  Gastrocnemius  (outer  head). 

Gastrocnemius  (inner  head).  \  /  p.          . 

Behind. 

Semimembranosus. 
Fascia. 

Popliteal  vein. 
Internal  popliteal  nerve. 
Gastrocnemius. 
Plantaris. 
Soleus. 

Peculiarities  in  Point  of  Division.— Occasionally  the  popliteal  artery  divides  prematurely 
into  its  terminal  branches;  this  unusual  division  occurs  most  frequently  opposite  the  knee-joint- 
The  anterior  tibial  under  these  circumstances  may  pass  in  front  of  the  Popliteus  muscle. 

Unusual  Branches.— The  artery  sometimes  divides  into  the  anterior  tibial  and  peroneal,  the 
posterior  tibial  being  wanting  or  very  small.  Occasionally  the  popliteal  is  found  to  divide  into 
three  branches,  the  anterior  and  posterior  tibial  and  peroneal. 


THE  POPLITEAL  SPACE  709 

Surface  Marking. — The  course  of  the  upper  part  of  the  popliteal  artery  is  indicated  by 
a  line  drawn  from  the  outer  border  of  the  Semimembranosus  muscle  at  the  junction  of  the 
middle  and  lower'  third  of  the  thigh  obliquely  downward  to  the  middle  of  the  popliteal  space, 
exactly  behind  the  knee-joint.  From  this  point  it  passes  vertically  downward  to  the  level  of  a 
line  drawn  through  the  lower  part  of  the  tubercle  of  the  tibia. 

Surgical  Anatomy. — The  popliteal  artery  is  not  infrequently  the  seat  of  injury.  It  may  be 
torn  by  direct  violence,  as  by  the  passage  of  a  cart-wheel  over  the  knee  or  by  hyper-extension  of 
the  knee;  and  in  the  dead  body,  at  all  events,  the  middle  and  internal  coats  may  be  ruptured  by 
extreme  flexion.  It  may  also  be  lacerated  by  fracture  of  the  lower  part  of  the  shaft  of  the 
femur  or  by  antero-posterior  dislocation  of  the  knee-joint.  It  has  been  torn  in  breaking  down 
adhesions  in  cases  of  fibrous  ankylosis  of  the  knee,  and  is  in  danger  of  being  wounded,  and  in 
fact  has  been  wounded,  in  performing  Macewen's  operation  of  osteotomy  of  the  lower  end  of  the 
femur  for  genu  valgum.  In  addition,  Spencer  records  a  case  in  which  the  popliteal  artery  was 
wounded  from  in  front  by  a  stab  just  below  the  knee,  the  knife  passing  through  the  interosseous 
space.  The  popliteal  artery  is  more  frequently  the  seat  of  aneurism  than  is  any  other  artery 
in  the  body,  with  the  exception  of  the  thoracic  aorta/  This  is  due  no  doubt,  in  a  great  measure, 
to  the  amount  of  movement  to  which  it  is  subjected,  and  to  the  fact  that  it  is  supported  by  loose 
and  lax  tissue  only,  and  not  by  muscles,  as  is  the  case  with  most  arteries. 

Ligature  of  the  popliteal  artery  is  required  in  cases  of  wound  of  that  vessel,  but  for  aneurism 
of  the  posterior  tibial  it  is  preferable  to  tie  the  superficial  femoral.  The  popliteal  may  be  tied 
in  the  upper  or  lower  part  of  its  course;  but  in  the  middle  of  the  ham  the  operation  is  attended 
with  considerable  difficulty,  from  the  great  depth  of  the  artery  and  from,  the  extreme  degree  of 
tension  of  the  lateral  boundaries  of  the  space. 

In  order  to  expose  the  vessel  in  the  upper  part  of  its  course,  the  patient  should  be  placed 
in  the  supine  position,  with  the  knee  flexed  and  the  thigh  rotated  outward,  so  that  it  rests  on 
its  outer  surface;  an  incision  three  inches  in  length,  beginning  at  the  junction  of  the  middle 
and  lower  third  of  the  thigh,  is  to  be  made  parallel  to  and  immediately  behind  the  tendon  of 
the  Adductor  magnus,  and  the  skin,  superficial  and  deep  fascia  divided.  The  tendon  of  the 
muscle  is  thus  exposed,  and  is  to  be  drawn  forward  and  the  hamstring  tendons  backward.  A 
quantity  of  fatty  tissue  will  now  be  opened  up,  in  which  the  artery  will  be  felt  pulsating.  This 
is  to  be  separated  with  the  point  of  a  director  until  the  artery  is  exposed.  The  vein  and  nerve 
will  not  be  seen,  as  they  lie  to  the  outer  side  of  the  artery.  The  sheath  is  to  be  opened  and 
the  aneurism  needle  passed  from  before  backward,  keeping  its  point  close  to  the  artery  for  fear 
of  injuring  the  vein.  The  only  structure  to  avoid  is  the  long  saphenous  vein  in  the  superficial 
incision.  The  upper  part  of  the  popliteal  artery  may  also  be  tied  by  an  incision  on  the  back  of 
the  limb,  along  the  outer  margin  of  the  Semimembranosus,  but  the  operation  is  a  more  difficult 
one,  as  the  internal  popliteal  nerve  and  the  popliteal  vein  are  first  exposed,  and  great  care  has 
to  be  exercised  in  separating  them  from  the  artery. 

To  expose  the  vessel  in  the  lower  part  of  its  course,  where  the  artery  lies  between  the  two 
heads  of  the  Gastrocnemius,  the  patient  should  be  placed  in  the  prone  position  with  the  limb 
extended.  An  incision  should  then  be  made  through  the  integument  in  the  middle  line,  com- 
mencing opposite  the  bend  of  the  knee-joint,  care  being  taken  to  avoid  the  external  saphenous 
vein  and  nerve.  After  dividing  the  deep  fascia  and  separating  some  dense  cellular  membrane, 
the  artery,  vein,  and  nerve  will  be  exposed,  descending  between  the  two  heads  of  the  Gastrocne- 
mius. Some  muscular  branches  of  the  popliteal  should  be  avoided  if  possible,  or,  if  divided, 
tied  immediately.  The  leg  being  now  flexed,  in  order  the  more  effectually  to  separate  the  two 
heads  of  the  Gastrocnemius,  the  nerve  should  be  drawn  inward  and  the  vein  outward,  and  the 
aneurism  needle  passed  between  the  artery  and  vein  from  without  inward. 

Branches. — The  branches  of  the  popliteal  artery  are — the 

Muscular  {  Superior.  Superior  External  Articular. 

\  Inferior  or  Sural.  Azygos  Articular. 

Cutaneous.    ,  Inferior  Internal  Articular. 

Superior  Internal  Articular.  Inferior  External  Articular. 

The  Superior  Muscular  Branches,  two  or  three  in  number,  arise  from  the 
upper  part  of  the  popliteal  artery,  and  are  distributed  to  the  lower  part  of  the 
Adductor  magnus  and  flexor  muscles  of  the  thigh,  anastomosing  with  the  fourth 
perforating  branch  of  the  profunda. 

The  Inferior  Muscular  (aa.  surales)  are  two  large  branches  which  are  dis- 
tributed to  the  two  heads  of  the  Gastrocnemius  and  to  the  Plantaris  muscle.  They 
arise  from  the  popliteal  artery  opposite  the  knee-joint. 


710  THE  BLOOD-VASCULAR  SYSTEM 

The  Cutaneous  Branches  arise  separately  from  the  popliteal  artery  or  from 
some  of  its  branches ;  they  descend  between  the  two  heads  of  the.  Gastrocnemius 
muscle,  and,  piercing  the  deep  fascia,  are  distributed  to  the  integument  of  the 
calf.  One  branch  usually  accompanies  the  short,  or  external,  saphenous  vein, 
the  superficial  sural  artery. 

The  Superior  Articular  Arteries,  two  in  number,  arise  one  on  each  side  of  the 
popliteal,  and  wind  round  the  femur  immediately  above  its  condyles  to  the  front 
of  the  knee-joint.  The  internal  branch  (a.  genu  superior  medialis]  winds  inward 
beneath  the  hamstring  muscles,  to  which  it  supplies  branches,  above  the  inner 
head  of  the  Gastrocnemius,  and,  passing  beneath  the  tendon  of  the  Adductor 
magnus,  divides  into  two  branches,  one  of  which  supplies  the  Vastus  internus, 
inosculating  with  the  anastomotica  magna  and  inferior  internal  articular;  the  other 
ramifies  close  to  the  surface  of  the  femur,  supplying  it  and  the  knee-joint,  and  an- 
astomosing with  the  superior  external  articular  artery.  This  branch  is  frequently 
of  small  size,  a  condition  which  is  associated  with  an  increase  in  the  size  of  the  an- 
astomotica magna.  The  external  branch  (a.  genu  superior  lateralis)  passes  above 
the  outer  condyle,  beneath  the  tendon  of  the  Biceps,  and  divides  into  a  superficial 
and  deep  branch:  the  superficial  branch  supplies  the  Vastus  externus,  and  anasto- 
moses with  the  descending  branch  of  the  external  circumflex  and  the  inferior  exter- 
nal articular  arteries;  the  deep  branch  supplies  the  lower  part  of  the  femur  and 
knee-joint,  and  forms  an  anastomotic  arch  across  the  bone  with  the  anastomotica 
magna  and  the  inferior  internal  articular  arteries. 

The  Azygos  Articular  (a.  genu  media)  is  a  small  branch  arising  from  the  pop- 
liteal artery  opposite  the  bend  of  the  knee-joint.  It  pierces  the  posterior  ligament, 
and  supplies  the  ligaments  and  synovial  membrane  in  the  interior  of  the  articu- 
lation. 

The  Inferior  Articular  Arteries,  two  in  number,  arise  from  the  popliteal 
beneath  the  Gastrocnemius,  and  wind  round  the  head  of  the  tibia  below  the  joint. 
The  internal  branch  (a.  genu  inferior  medialis)  first  descends  along  the  upper  mar- 
gin of  the  Popliteus  muscle,  to  which  it  gives  branches;  it  then  passes  below  the 
inner  tuberosity,  beneath  the  internal  lateral  ligament,  at  the  anterior  border  of 
which  it  ascends  to  the  front  and  inner  side  of  the  joint,  to  supply  the  head  of  the 
tibia  and  the  articulation  of  the  knee,  anastomosing  with  the  inferior  external 
articular  and  superior  internal  articular  arteries.  The  external  branch  (a.  genu 
inferior  lateralis]  passes  outward  above  the  head  of  the  fibula,  to  the  front  of  the 
knee-joint,  passing  in  its  course  beneath  the  outer  head  of  the  Gastrocnemius,  the 
external  lateral  ligament,  and  the  tendon  of  the  Biceps  muscle,  and  divides  into 
branches  which  anastomose  with  the  inferior  internal  articular  artery,  the  superior 
external  articular  artery,  and  the  anterior  recurrent  branch  of  the  anterior  tibial. 

Gircumpatellar  Anastomosis. — Around  and  above  the  patella,  and  on  the  con- 
tiguous ends  of  the  femur  and  tibia,  is  a  large  network  of  vessels,  forming  a  super- 
ficial and  a  deep  plexus.  The  superficial  plexus  is  situated  between  the  fascia  and 
skin  round  about  the  patella;  the  deep  plexus,  which  forms  a  close  network  of 
vessels,  lies  on  the  surface  of  the  lower  end  of  the  femur  and  upper  end  of  the 
tibia  around  their  articular  surfaces,  and  sends  numerous  offsets  into  the  interior 
of  the  joint.  The  arteries  from  which  this  plexus  is  formed  are  the  two  internal  and 
two  external  articular  branches  of  the  popliteal,  the  anastomotica  magna,  the  ter- 
minal branch  of  the  profunda,  the  descending  branch  from  the  external  circumflex 
and  the  anterior  recurrent  branch  of  the  anterior  tibial. 

The  Anterior  Tibial  Artery  (A.  Tibialis  Anterior)   (Fig.  435). 

The  anterior  tibial  artery  commences  at  the  bifurcation  of  the  popliteal  at 
the  lower  border  of  the  Popliteus  muscle,  passes  forward  between  the  two 


THE  ANTERIOR  TIBIAL  ARTERY  711 

heads  of  the  Tibialis  posticus,  and  through  the  large  oval  aperture  above  the 
upper  border  of  the  interosseous  membrane  to  the  deep  part  of  the  front  of  the 
leg;  it  here  lies  close  to  the  inner  side  of  the  neck  of  the  fibula;  it  then  descends  on 
the  anterior  surface  of  the  interosseous  membrane,  gradually  approaching  the 
tibia;  and  at  the  lower  part  of  the  leg  lies  on  this  bone,  and  then  on  the  anterior 
ligament  of  the  ankle  to  the  bend  of  the  ankle-joint,  where  it  lies  more  superficially, 
and  becomes  the  dorsalis  pedis. 

Relations. — In  the  upper  two-thirds  of  its  extent  it  rests  upon  the  interosseous 
membrane,  to  which  it  is  connected  by  delicate  fibrous  arches  thrown  across  it; 
in  the  lower  third,  upon  the  front  of  the  tibia  and  the  anterior  ligament  of  the 
ankle-joint.  In  the  upper  third  of  its  course  it  lies  between  the  Tibialis  anticus 
and  Extensor  longus  digitorum;  in  the  middle  third,  between  the  Tibialis  anticus 
and  Extensor  proprius  hallucis.  At  the  bend  of  the  ankle  it  is  crossed  by  the 
tendon  of  the  Extensor  proprius  hallucis,  and  lies  between  it  and  the  innermost 
tendon  of  the  Extensor  longus  digitorum.  It  is  covered,  in  the  upper  two- 
thirds  of  its  course,  by  the  muscles  which  lie  on  either  side  of  it  and  by  the 
deep  fascia  ;  in  the  lower  third,  by  the  integument,  anterior  annular  ligament, 
and  fascia. 

The  anterior  tibial  artery  is  accompanied  by  two  veins,  venae  comites,  which 
lie  one  on  each  side  of  the  artery;  the  anterior  tibial  nerve,  coursing  round  the 
outer  side  of  the  neck  of  the  fibula,  comes  into  relation  with  the  outer  side  of  the 
artery  shortly  after  it  has  passed  through  the  opening  in  the  interosseous  mem- 
brane; about  the  middle  of  the  leg  it  is  placed  superficial  to  it;  at  the  lower  part 
of  the  artery  the  nerve  is  generally  again  on  the  outer  side. 

PLAN  OF  THE  RELATIONS  OF  THE  ANTERIOR  TIBIAL  ARTERY. 

In  front. 

Integument,  superficial  and  deep  fasciae. 

Anterior  tibial  nerve. 

Tibialis  anticus  (overlaps  it  in  the  upper  part  of  the  leg). 

Extensor  longus  digitorum  I     ,        ,       .,    ,.  ,,,  . 

Extensor  proprius  hallucis  }    (overlap  it  slightly). 

Anterior  annular  ligament. 

Inner  side.  f  \                           Outer  side. 

Tibialis  anticus.  /  Anterior     \           Anterior  tibial  nerve. 

Extensor  proprius  hallucis  I  Tibial.       1           Extensor  longus  digitorum. 

(crosses  it  at  its   lower  V  J           Extensor  proprius  hallucis. 

part). 

Behind. 

Interosseous  membrane. 

Tibia. 

Anterior  ligament  of  ankle-joint. 

Peculiarities  in  Size. — This  vessel  may  be  very  small,  may  be  deficient  to  a  greater  or  less 
extent,  or  may  be  entirely  wanting,  its  place  being  supplied  by  perforating  branches  from  the 
posterior  tibial  or  by  the  anterior  division  of  the  peroneal  artery. 

Course. — The  artery  occasionally  deviates  in  its  course  toward  the  fibular  side  of  the  leg, 
regaining  its  usual  position  beneath  the  annular  ligament  at  the  front  of  the  ankle.  In  two 
instances  the  vessel  has  been  found  to  approach  the  surface  in  the  middle  of  the  leg,  being  covered 
merely  by  the  integument  and  fascia  below  that  point. 

Surface  Marking. — Draw  a  line  from  the  inner  side  of  the  head  of  the  fibula  to  midway 
between  the  two  malleoli.  In  this  line  take  a  point  one  inch  and  a  quarter  below  the  head  of 
the  fibula,  and  the  portion  of  the  line  below  this  point  will  mark  the  course  of  the  artery. 

Surgical  Anatomy. — The  anterior  tibial  artery  may  be  tied  in  the  upper  or  lower  part  of 
the  leg.  In  the  upper  part  the  operation  is  attentled  with  great  difficulty,  on  account  of  the 
depth  of  the  vessel  from  the  surface.  An  incision,  about  four  inches  in  length,  should  be  made 


712 


THE  BLOOD-VASCULAR  SYSTEM 


Inferior 
external  — ' 
articular. 


Inferior  internal 
articular. 


through  the  integument,  midway  between  the 
spine  of  the  tibia  and  the  outer  margin  of  the 
fibula,  and  the  deep  fascia  exposed.  The 
wound  must  now  be  carefully  dried,  its  edges 
retracted,  and  the  white  line  separating  the 
Tibialis  anticus  from  the  Extensor  longus 
digitorum  sought  for.  When  this  has  been 
clearly  defined,  the  deep  fascia  is  to  be 
divided  in  this  line,  and  the  Tibialis  anticus 
separated  from  adjacent  muscles  with  the 
handle  of  the  scalpel  or  a  director  until  the 
interosseous  membrane  is  reached.  The  foot 
is  to  be  flexed  in  order  to  relax  the  muscles, 
and  upon  drawing  them  apart  the  artery  will 
be  found  lying  on  the  interosseous  membrane 
with  the  nerve  on  its  outer  side  or  on  the  top 
of  the  artery.  The  nerve  should  be  drawn 
outward,  and  the  venae  comites  separated 
from  the  artery  and  the  needle  passed 
round  it. 

To  tie  the  vessel  in  the  lower  third  of  the 
leg  above  the  ankle-joint  an  incision  about 
three  inches  in  length  should  be  made  through 
the  integument  between  the  tendons  of  the 
Tibialis  anticus  and  Extensor  proprius  hal- 
lucis  muscles,  the  deep  fascia  being  divided 
to  the  same  extent.  The  tendon  on  either 
side  should  be  held  aside,  when  the  vessel 
will  be  seen  lying  upon  the  tibia,  with  the 
nerve  on  the  outer  side  and  one  of  the  vense 
comites  on  either  side. 

Branches. — The  branches  of  the 
anterior  tibial  artery  are — the 

Posterior  Recurrent  Tibial. 
Superior  Fibular. 
Anterior  Recurrent  Tibial. 
Muscular. 
Internal  Malleolar. 
External  Malleolar. 


The   Posterior  Recurrent  Tibial 

(a.  recurrens  tibialis  posterior)  is  not 
a  constant  branch,  and  is  given  off 
from  the  anterior  tibial  before  that 
vessel  passes  through  the-  interosse- 
ous space.  It  ascends  beneath  the 
Popliteus  muscle,  which  it  supplies, 
and  anastomoses  with  the  lower 
articular  branches  of  the  popliteal 
artery,  giving  off  an  offset  to  the 
superior  tibio-fibular  joint. 

The  Superior  Fibular  is  some- 
times given  off  from  the  anterior 
tibial,  sometimes  from  the  posterior 
tibial.  It  passes  outward,  round 

the  neck  of  the  fibula,  through  the  Soleus,  which  it  supplies,  and  ends  in  the 

substance  of  the  Peroneus  longus  muscle. 


Communicating. 


FIG.  435. — Surgical  anatomy  of  the  anterior  tibial 
and  dorsalis  pedls  arteries. 


THE  ANTERIOR  TIBIAL  ARTERY  713 

The  Anterior  Recurrent  Tibial  (a.  recurrens  tibialis  anterior)  arises  from  the 
anterior  tibial  as  soon  as  that  vessel  has  passed  through  the  interosseous  space; 
it  ascends  in  the  Tibialis  anticus  muscle,  and  ramifies  on  the  front  and  sides 
of  the  knee-joint,  anastomosing  with  the  articular  branches  of  the  popliteal,  with 
the  anastomotica  magna,  and  the  external  articular  branches  of  the  popliteal, 
assisting  in  the  formation  of  the  circumpatellar  plexus. 

The  Muscular  Branches  are  numerous;  they  are  distributed  to  the  muscles 
which  lie  on  each  side  of  the  vessel,  some  cutaneous  branches  piercing  the  deep 
fascia  to  supply  the  integument,  others  passing  through  the  interosseous  membrane, 
and  anastomosing  with  branches  of  the  posterior  tibial  and  peroneal  arteries. 

The  Malleolar  Arteries  supply  the  ankle-joint.  The  internal  branch  (a.  mal- 
leolaris  anterior  medialis)  arises  about  two  inches  above  the  articulation,  and 
passes  beneath  the  tendons  of  the  Extensor  proprius  hallucis  and  Tibialis  anticus 
to  the  inner  ankle,  upon  which  it  ramifies,  anastomosing  with  branches  of  the 
posterior  tibial  and  internal  plantar  arteries  and  with  the  internal  calcanean 
from  the  posterior  tibial.  The  external  branch  (a.  malleolaris  anterior  lateralis) 
passes  beneath  the  tendons  of  the  Extensor  longus  digitorum  and  Peroneous 
tertius,  and  supplies  the  outer  ankle,  anastomosing  with  the  anterior  peroneal 
artery  and  with  ascending  branches  from  the  tarsal  branch  of  the  dorsalis 
pedis.  * 

The  Dorsalis  Pedis  Artery  (A.  Dorsalis  Pedis)  (Figs.  435,  436). 

The  dorsalis  pedis,  the  continuation  of  the  anterior  tibial,  passes  forward  from 
the  bend  of  the  ankle  along  the  tibial  side  of  the  foot  to  the  back  part  of  the  first 
intermetatarsal  space,  where  it  divides  into  two  branches,  the  dorsalis  hallucis  and 
communicating. 

Relations. — This  vessel,  in  its  course  forward,  rests  upon  the  astragalus,  navic- 
ular,  and  middle  cuneiform  bones  and  the  ligaments  connecting  them,  being  cov- 
ered by  the  integument  and  fascia,  anterior  annular  ligament,  and  crossed  near 
its  termination  by  the  innermost  tendon  of  the  Extensor  brevis  digitorum.  On 
its  tibial  side  is  the  tendon  of  the  Extensor  proprius  hallucis;  on  its  fibular  side, 
the  innermost  tendon  of  the  Extensor  longus  digitorum,  and  the  termination  of 
the  anterior  tibial  nerve.  It  is  accompanied  by  two  veins. 

PLAN  OF  THE  RELATIONS  OF  THE  DORSALIS  PEDIS  ARTERY. 

In  front. 

Integument  and  fascia. 

Anterior  annular  ligament. 

Innermost  tendon  of  Extensor  brevis  digitorum. 


Tibial  side.  f  Fibular  side. 


Extensor  proprius  hallucis.  [        Pedis.       I  Extensor  longus  digitorum. 

J  Anterior  tibial  nerve. 

Behind. 
Astragalus. 
Navicular. 
Middle  cuneiform. 
And  their  ligaments. 

Peculiarities  in  Size. — The  dorsal  artery  of  the  foot  may  be  larger  than  usual,  to  compen- 
sate for  a  deficient  plantar  artery;  or  it  may  be  deficient  in  its  terminal  branches,  to  the  toes, 
which  are  then  derived  from  the  internal  plantar;  or  its  place  may  be  supplied  altogether  by  a 
large  anterior  peroneal  artery. 


714 


THE  BLOOD-VASCULAR  SYSTEM 


Position. — This  artery  frequently  curves  outward,  lying  external  to  the  line  between  the 
middle  of  the  ankle  and  the  back  part  of  the  first  interosseous  space. 

Surface  Marking. — The  dorsalis  pedis  artery  is  indicated  on  the  surface  of  the  dorsum  of 
the  foot  by  a  line  drawn  from  the  centre  of  the  space  between  the  two  malleoli  to  the  back  of  the 
first  intermetatarsal  space. 

Surgical  Anatomy. — This  artery  may  be  tied,  by  making  an  incision  through  the  integu- 
ment between  two  and  three  inches  in  length,  on  the  fibular  side  of  the  tendon  of  the  Extensor 
proprius  hallucis,  in  the  interval  between  it  and  the  inner  border  of  the  short  Extensor  muscle. 
The  incision  should  not  extend  farther  forward  than  the  back  part  of  the  first  intermetatarsal 
space,  as  the  artery  divides  in  that  situation.  The  deep  fascia  being  divided  to  the  same  extent, 
the  artery  will  be  exposed,  the  nerve  lying  upon  its  outer  side. 


ANTERIOR 

PERONEAL 

ARTERY 


EXTERNAL 

MALLEOLAR 

ARTERY 


METATARSAL 
ARTERY 


DORSAL 
INTEROSSCOUS 


INTERNAL 

MALLEOLAR 

ARTERY 


DORSALIS  PEDIS 
ARTERY 


COMMUNICATING 
ARTERY 

DORSALIS 
HALLUCIS 
ARTERY 


FIG.  436.— Diagram  of  the  arteries  of  the  dorsal  surface  of  the  foot.     (Poirier  and  Charpy.) 

Branches. — The  branches  of  the  dorsalis  pedis  are — the 


Cutaneous. 
Tarsal. 


Metatarsal — Interosseous. 
Dorsalis  Hallucis. 
Communicating. 


Cutaneous  Branches  go  to  the  skin  of  the  dorsum  and  inner  surface  of  the 
foot. 

The  Tarsal  Artery  (a.  tarsea  lateralis)  arises  from  the  dorsalis  pedis,  as  that 
vessel  crosses  the  navicular  bone;  it  passes  in  an  arched  direction  outward,  lying 
upon  the  tarsal  bones,  and  covered  by  the  Extensor  brevis  digitorum;  it  supplies 
that  muscle  and  the  articulations  of  the  tarsus,  and  anastomoses  with  branches 
from  the  metatarsal,  external  malleolar,  peroneal,  and  external  plantar  arteries. 


THE  POSTERIOR  TIBIAL  ARTERY  715 

The  Metatarsal  (a.  arcuata)  arises  a  little  anterior  to  the  preceding;  it  passes 
outward  to  the  outer  part  of  the  foot,  over  the  bases  of  the  metatarsal  bones, 
beneath  the  tendons  of  the  short  Extensor,  its  direction  being  influenced  by  its 
point  of  origin;  and  it  anastomoses  with  the  tarsal  and  external  plantar  arteries. 
This  vessel  gives  off  three  branches,  the  dorsal  interosseous  arteries  (aa.  meta- 
far^raedorsales),-whic\\  pass  forward  upon  the  three  outer  Dorsal  interossei  mus- 
cles, and,  in  the  clefts  between  the  toes,  divide  into  two  dorsal  collateral  branches 
for  the  adjoining  toes  (aa.  digitales  dor  sales}.  At  the  back  part  of  each  inter- 
osseous  space  these  vessels  receive  the  posterior  perforating  branches  from  the 
plantar  arch,  and  at  the  forepart  of  each  interosseous  space  they  are  joined  by 
the  anterior  perforating  branches  from  the  digital  arteries.  The  outermost 
interosseous  artery  gives  off  a  branch  which  supplies  the  outer  side  of  the  little 
toe. 

The  Dorsalis  Hallucis  or  the  First  Dorsal  Interosseous  (a.  dorsalis  hallucis)  is  one 
of  the  terminal  branches  of  the  dorsalis  pedis.  It  runs  forward  along  the  outer 
border  of  the  first  metatarsal  bone,  and  at  the  cleft  between  the  first  and  second 
toes  divides  into  two  branches,  one  of  which  passes  inward,  beneath  the  tendon  of 
the  Extensor  proprius  hallucis,  and  is  distributed  to  the  inner  border  of  the  great 
toe;  the  outer  branch  bifurcates,  to  supply  the  adjoining  sides  of  the  great  and 
second  toes. 

The  Communicating  Artery  (ramus  plantaris  profundus),  the  other  terminal 
branch  of  the  dorsalis  pedis,  dips  down  into  the  sole  of  the  foot,  between  the  two 
heads  of  the  First  dorsal  interosseous  muscle,  and  inosculates  with  the  termina- 
tion of  the  external  plantar  artery,  to  complete  the  plantar  arch.  It  here  gives 
off  its  plantar  digital  branch,  which  is  named  the  arteria  magna  hallucis,  or  the 
princeps  hallucis.  This  artery  passes  forward  along  the  first  interosseous  space, 
and,  after  sending  a  branch  along  the  inner  side  of  the  great  toe,  bifurcates  for 
the  supply  of  the  adjacent  sides  of  the  great  and  second  toes. 

The  Posterior  Tibial  Artery  (A.  Tibialis  Posterior)  (Fig.  434). 

The  posterior  tibial  is  an  artery  of  large  size,  which  extends  obliquely  down- 
ward from  the  lower  border  of  the  Popliteus  muscle,  along  the  tibial  side  of  the 
leg,  to  the  fossa  between  the  inner  ankle  and  the  heel,  where  it  divides  beneath 
the  origin  of  the  Abductor  hallucis,  on  a  level  with  a  line  drawn  from  the  point 
of  the  internal  malleolus  to  the  centre  of  the  convexity  of  the  heel,  into  the 
internal  and  external  plantar  arteries!,  At  its  origin  it  lies  opposite  the  interval 
between  the  tibia  and  fibula;  as  it  descends,  it  approaches  the  inner  side  of 
the  leg,  lying  behind  the  tibia,  and,  in  the  lower  part  of  its  course,  is  situated 
midway  between  the  inner  malleolus  and  the  tuberosity  of  the  os  calcis. 

Relations. — It  lies  successively  upon  the  Tibialis  posticus,  the  Flexor  longus 
digitorum,  the  tibia,  and  the  back  part  of  the  ankle-joint.  It  is  covered  by  the 
deep  transverse  fascia,  which  separates  it  above  from  the  Gastrocnemius  and 
Soleus  muscles:  at  its  termination  it  is  covered  by  the  Abductor  hallucis  muscle. 
In  the  lower  third,  where  it  is  more  superficial,  it  is  covered  only  by  the  integu- 
ment and  fascia,  and  runs  parallel  with  the  inner  border  of  the  tendo  Achillis. 
It  is  accompanied  by  two  veins  and  by  the  posterior  tibial  nerve,  which  lies  at 
first  to  the  inner  side  of  the  artery,  but  soon  crosses  it,  and  is,  in  the  greater  part 
of  its  course,  on  its  outer  side. 

PLAN  OF  THE  RELATIONS  OF  THE  POSTERIOR  TIBIAL  ARTERY. 

In  front. 
Tibialis  posticus. 
Flexor  longus  digitorum. 
Tibia. 
Ankle-joint. 


716  THE  BLOOD-VASCULAR  SYSTEM 

Inner  side.  Outer  side. 

Posterior  tibial  nerve,  Posterior  tibial  nerve, 

upper  third.  lower  two-thirds. 

Behind. 

Integument  and  fascia. 
Gastrocnemius. 
Soleus. 

Deep  transverse  fascia. 
Posterior  tibial  nerve. 
Abductor  hallucis. 

Behind  the  inner  ankle  the  tendons  and  blood-vessels  are  arranged,  under 
cover  of  the  internal  annular  ligament,  in  the  following  order,  from  within  out- 
ward: First,  the  tendons  of  the  Tibialis  posticus  and  Flexor  longus  digitorum, 
lying  in  the  same  groove,  behind  the  inner  malleolus,  the  former  being  the  most 
internal.  External  to  these  is  the  posterior  tibial  artery,  having  a  vein  on  either 
side:  and,  still  more  externally,  the  posterior  tibial  nerve.  About  half  an  inch 
nearer  the  heel  is  the  tendon  of  the  Flexor  longus  hallucis. 

Peculiarities  in  Size. — The  posterior  tibial  is  not  unfrequently  smaller  than  usual,  or  absent, 
its  place  being  supplied  by  a  large  peroneal  artery  which  passes  inward  at  the  lower  end  of  the 
tibia,  and  either  joins  the  small  tibial  artery  or  continues  alone  to  the  sole  of  the  foot. 

Surface  Marking. — The  course  of  the  posterior  tibial  artery  is  indicated  by  a  line  drawn  from 
a  point  one  inch  below  the  centre  of  the  popliteal  space  to  midway  between  the  tip  of  the 
internal  malleolus  and  the  centre  of  the  convexity  of  the  heel. 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  posterior  tibial  may  be  required 
in  cases  of  wound  of  the  sole  of  the  foot  attended  with  great  hemorrhage,  when  the  vessel 
should  be  tied  at  the  inner  ankle.  In  cases  of  wound  of  the  posterior  tibial  it  will  be  necessary 
to  enlarge  the  opening  so  as  to  expose  the  vessel  at  the  wounded  point,  excepting  where  the 
vessel  is  injured  by  a  punctured  wound  from  the  front  of  the  leg.  In  cases  of  aneurism  from 
wound  of  the  artery  low  down,  the  vessel  should  be  tied  in  the  middle  of  the  leg.  But  in  aneurism 
of  the  posterior  tibial  high  up  it  would  be  better  to  tie  the  femoral  artery. 

To  tie  the  posterior  tibial  artery  at  the  ankle,  a  semilunar  incision,  convex  backward,  should 
be  made  through  the  integument,  about  two  inches  and  a  half  in  length,  midway  between  the 
heel  and  the  inner  ankle  or  a  little  nearer  the  latter.  The  subcutaneous  cellular  tissue  having  been 
divided,  a  strong  and  dense  fascia,  the  internal  annular  ligament,  is  exposed.  This  ligament  is 
continuous  above  with  the  deep  fascia  of  the  leg,  covers  the  vessels  and  nerves,  and  is  intimately 
adherent  to  the  sheaths  of  the  tendons.  This  having  been  cautiously  divided  upon  a  director, 
the  sheath  of  the  vessels  is  exposed,  and,  being  opened,  the  artery  is  seen  with  one  of  the  venae 
comites  on  each  side.  The  aneurism  needle  should  be  passed  round  the  vessel  from  the  heel 
toward  the  ankle,  in  order  to  avoid  the  posterior  tibial  nerve,  care  being  at  the  same  time  taken 
not  to  include  the  vense  comites. 

The  vessel  may  also  be  tied  in  the  lower  third  of  the  leg  by  making  an  incision,  about  three 
inches  in  length,  parallel  with  the  inner  margin  of  the  tendo  Achillis.  The  internal  saphenous 
vein  being  carefully  avoided,  the  Iwo  layers  of  fascia  must  be  divided  upon  a  director,  when  the 
artery  is  exposed  along  the  outer  margin  of  the  Flexor  longus  digitorum,  with  one  of  its  vense 
comites  on  either  side  and  the  nerve  lying  external  to  it. 

To  tie  the  posterior  tibial  in  the  middle  of  the  leg  is  a  very  difficult  operation,  on  account  of 
the  great  depth  of  the  vessel  from  the  surface.  The  patient  being  placed  in  the  recumbent  posi- 
tion, the  injured  limb  should  rest  on  its  outer  side,  the  knee  being  partially  bent  and  the  foot 
extended,  sO  as  to  relax  the  muscles  of  the  calf.  An  incision  about  four  inches  in  length  should 
then  be  made  through  the  integument  a  finger's  breadth  behind  the  inner  margin  of  the  tibia, 
taking  care  to  avoid  the  internal  saphenous  vein:  The  deep  fascia  having  been  divided,  the 
margin  of  the  Gastrocnemius  is  exposed,  and  must  be  drawn  aside,  and  the  tibial  attachment  of 
the  Soleus  divided,  a  director  being  previously  passed  beneath  it.  The  artery  may  now  be 
felt  pulsating  beneath  the  deep  fascia  about  an  inch  from  the  margin  of  the  tibia.  The  fascia 
having  been  divided,  and  the  limb  placed  in  such  a  position  as  to  relax  the  muscles  of  the  calf 
as  much  as  possible,  the  veins  should  be  separated  from  the  artery,  and  the  aneurism  needle 
passed  round  the  vessel  from  without  inward,  so  as  to  avoid  wounding  the  posterior  tibial  nerve. 

Branches. — The  branches  of  the  posterior  tibial  artery  are — the 

Peroneal.  Cutaneous. 

Nutrient.  Communicating. 

Muscular.  Internal  Calcanean. 

Malleolar  cutaneous. 


THE  POSTERIOR  TIBIA L  ARTERY  717 

The  Peroneal  Artery  (a.  peronaea)  (Fig.  434)  lies,  deeply  seated,  along  the  back 
part  of  the  fibular  side  of  the  leg.  It  arises  from  the  posterior  tibial  about  an  inch 
below  the  lower  border  of  the  Popliteus  muscle,  passes  obliquely  outward  to  the 
fibula,  and  then  descends  along  the  inner  border  of  that  bone,  contained  in  a 
fibrous  canal  between  the  Tibialis  posticus  and  the  Flexor  longus  hallucis,  or  in 
the  substance  of  the  latter  muscle  to  the  lower  third  of  the  leg,  where  it  gives  off 
the  anterior  peroneal.  It  then  passes  across  the  articulation  between  the  tibia  and 
fibula  to  the  outer  side  of  the  os  calcis,  where  it  gives  off  its  terminal  branches,  the 
external  calcanean. 

Relations. — This  vessel  rests  at  first  upon  the  Tibialis  posticus,  and  then,  for 
the  greater  part  of  its  course,  in  a  fibrous  canal  between  the  origins  of  the  Flexor 
longus  hallucis  and  Tibialis  posticus,  covered  or  surrounded  by  the  fibres  of  the 
Flexor  longus  hallucis.  It  is  covered,  in  the  upper  part  of  its  course,  by  the  Soleus 
and  deep  transverse  fascia;  below,  by  the  Flexor  longus  hallucis. 

PLAN  OF  THE  RELATIONS  OF  THE  PERONEAL  ARTERY. 

In  front. 

Tibialis  posticus. 
Flexor  longus  hallucis. 

Outer  side.  /  \  Inner  side. 

Fibula.  [     ^f™,^1     I  Flexor  longus  hallucis. 

Flexor  longus  hallucis. 


Behind. 
Soleus. 

Deep  transverse  fascia. 
Flexor  longus  hallucis. 

Peculiarities  in  Origin. — The  peroneal  artery  may  arise  three  inches  below  the  Popliteus, 
or  from  the  posterior  tibial  high  up,  or  even  from  the  popliteal, 

Its  size  is  more  frequently  increased  than  diminished ;  and  then  it  either  reinforces  the  poste- 
rior tibial  by  its  junction  with  it,  or  altogether  takes  the  place  of  the  posterior  tibial  in  the  lower 
part  of  the  leg  and  foot,  the  latter  vessel  only  existing  as  a  short  muscular  branch.  In  those 
rare  cases  where  the  peroneal  artery  is  smaller  than  usual  a  branch  from  the  posterior  tibial 
supplies  its  place,  and  a  branch  from  the  anterior  tibial  compensates  for  the  diminished  anterior 
peroneal  artery.  In  one  case  the  peroneal  artery  has  been  found  entirely  wanting. 

The  anterior  peroneal  is  sometimes  enlarged,  and  takes  the  place  of  the  dorsal  artery  of  the 
foot. 

Branches. — The  branches  of  the  peroneal  are — the 

Muscular.  Communicating. 

Nutrient.  Posterior  Peroneal. 

Anterior  Peroneal.  External  Calcanean. 

Muscular  Branches. — The  peroneal  artery  in  its  course  gives  off  branches  to  the 
Soleus,  Tibialis  posticus,  Flexor  longus  hallucis,  and  Peronei  muscles. 

The  Nutrient  Artery  (a.  nutritia  fibulae)  supplies  the  fibula. 

The  Anterior  Peroneal  (ramus  perforans)  (Fig.  436)  pierces  the  interosseous 
membrane,  about  two  inches  above  the  outer  malleolus,  to  reach  the  forepart  of 
the  leg,  and,  passing  down  beneath  the  Peroneus  tertius  to  the  outer  ankle,  ramifies 
on  the  front  and  outer  side  of  the  tarsus,  anastomosing  with  the  external  malleolar 
and  tarsal  arteries. 

The  Communicating  (ramus  communicans)  is  given  off  from  the  peroneal  about 
an  inch  from  its  lower  end,  and,  passing  inward,  joins  the  communicating  branch 
of  the  posterior  tibial. 


718 


THE  BLOOD-VASCULAR  SYSTEM 


The  Posterior  Peroneal  passes  down  behind  the  outer  ankle  to  the  back  of  the 
external  malleolus,  to  terminate  in  branches  which  ramify  on  the  outer  surface 
and  back  of  the  os  calcis. 

External  Calcanean  (ramus  calcaneus  later  alls)  are  the  terminal  branches  of  the 
peroneal  artery;  they  pass  to  the  outer  side  of  the  heel,  and  communicate  with  the 
external  malleolar,  and,  on  the  back  of  the  heel,  with  the  internal  calcanean 
arteries. 

Cutaneous  Branches  come  from  the  posterior  tibial  and  supply  the  skin  of 
the  inner  side  and  back  of  the  leg. 

The  Nutrient  Artery  of  the  tibia  (a.  nutricia  tibiae)  arises  from  the  posterior 
tibial  near  its  origin,  and,  after  supplying  a  few  muscular  branches,  enters  the 
nutrient  canal  of  that  bone,  which  it  traverses  obliquely  from  above  downward. 
This  is  the  largest  nutrient  artery  of  bone  in  the  body. 

The  Muscular  Branches  of  the  posterior  tibial  are  distributed  to  the  Soleus  and 
deep  muscles  along  the  back  of  the  leg. 

The  Communicating  Branch  (ramus  communicans) ,  to  join  a  similar  branch 
of  the  peroneal,  runs  transversely  across  the  back  of  the  tibia,  about  two  inches 
above  its  lower  end,  passing  beneath  the  Flexor  longus  hallucis. 

The  Malleolar  or  Internal  Malleolar  (a.  malleolaris  posterior  medialis)  lies 
upon  the  tibia,  sends  branches  over  the  inner  ankle,  and  anastomoses  with  the 
inner  malleolar  branch  of  the  anterior  tibial. 

The  Internal  Calcanean  (rami  calcanei  mediales)  are  several  large  arteries 
which  arise  from  the  posterior  tibial  just  before  its  division:  they  are  distributed 


Communicating 

branch  of 
dorsalis  pedis. 
Its  digital 
branches. 


FIG.  437. — The  plantar  arteries.     Superficial  view. 


FIG.  438. — The  plantar  arteries.     Deep  view. 


to  the  fat  and  integument  behind  the  tendo  Achillis  and  about  the  heel,  and  to  the 
muscles  on  the  inner  side  of  the  sole,  anastomosing  with  the  peroneal  and  internal 
malleolar,  and,  on  the  back  of  the  heel,  with  the  external  calcanean  arteries. 

The  Internal  Plantar  Artery  (a.  plantaris  medialis)  (Figs.  437  and  438),  much 
smaller  than  the  external,  passes  forward  along  the  inner  side  of  the  foot.     It  is 


THE  POSTERIOR   TIBIAL  ARTERY  719 

at  first  situated  above1  the  Abductor  hallucis,  and  then  between  it  and  the  Flexor 
brevis  digitorum,  both  of  which  it  supplies.  At  the  base  of  the  first  metatarsal 
bone,  where  it  has  become  much  diminished  in  size,  it  passes  along  the  inner  border 
of  the  great  toe,  inosculating  with  its  digital  branch.  Small  superficial  digital 
branches  (ramus  superficialis}  accompany  the  digital  branches  of  the  medial 
plantar  nerve  and  join  the  plantar  digital  arteries  of  the  three  inner  spaces.  In 
addition,  this  vessel  gives  off  numerous  cutaneous  branches. 

The  External  Plantar  Artery  (a.  plantaris  lateralis)  (Figs.  437  and  438),  much 
larger  than  the  internal,  passes  obliquely  outward  and  forward  to  the  base  of  the 

»  fifth  metatarsal  bone.  It  then  turns  obliquely  inward  to  the  interval  between 
the  bases  of  the  first  and  second  metatarsal  bones,  where  it  anastomoses  with 
the  communicating  branch  from  the  dorsalis  pedis  artery,  thus  completing  the 
plantar  arch  (arcm  plantaris}  (Fig.  438).  As  this  artery  passes  outward,  it  is  first 
placed  between  the  os  calcis  and  Abductor  hallucis,  and  then  between  the  Flexor 
brevis  digitorum  and  Flexor  accessorius,  and  as  it  passes  forward  to  the  base  of 
the  little  toe  it  lies  more  superficially  between  the  Flexor  brevis  digitorum  and 
Abductor  minimi  digiti,  covered  by  the  deep  fascia  and  integument.  The  remain- 
ing portion  of  the  vessel  is  deeply  situated :  it  extends  from  the  base  of  the  meta- 
tarsal bone  of  the  little  toe  to  the  back  part  of  the  first  interosseous  space,  and 
forms  the  plantar  arch;  it  is  convex  forward,  lies  upon  the  Interossei  muscles 
opposite  the  tarsal  ends  of  the  metatarsal  bones,  and  is  covered  by  the  Adductor 
obliquus  hallucis,  the  flexor  tendons  of  the  toes,  and  the  Lumbricales. 

Surface  Marking. — The  course  of  the  internal  plantar  artery  is  represented  by  a  line 
drawn  from  the  mid-point  between  the  tip  of  the  internal  malleolus  and  the  centre  of  the  con- 
vexity of  the  heel  to  the  middle  of  the  under  surface  of  the  great  toe;  the  external  plantar  by 
a  line  from  the  same  point  to  within  a  finger's  breadth  of  the  tuberosity  of  the  fifth  metatarsal 
bone.  The  plantar  arch  is  indicated  by  a  line  drawn  from  this  point — i.  e.,  a  finger's  breadth 
internal  to  the  tuberosity  of  the  fifth  metatarsal  bone  transversely  across  the  foot  to  the  back  of 
the  first  interosseous  space. 

Surgical  Anatomy. — Wounds  of  the  plantar  arch  are  always  serious,  on  account  of  the 
depth  of  the  vessel  and  the  important  structures  which  must  be  interfered  with  in  an  attempt 
to  ligate  it.  They  must  be  treated  on  similar  lines  to  those  of  wounds  of  the  palmar  arches 
(see  page  667).  Delorme  has  shown  that  the  plantar  arch  may  be  ligated  from  the  dorsum  of  the 
foot  in  almost  any  part  of  its  course  by  removing  a  portion  of  one  of  the  three  middle  metatarsal 
bones. 

Branches. — The  plantar  arch,  besides  distributing  numerous  branches  to  the 
muscles,  integument,  and  fasciae  in  the  sole,  gives  off  the  following  branches: 

Posterior  Perforating.  Digital. 

The  Posterior  Perforating  (rami  perforantes  posteriores)  are  three  small  branches 
which  ascend  through  the  back  part  of  the  three  outer  interosseous  spaces,  between 
the  heads  of  the  Dorsal  interossei  muscles,  and  anastomoses  with  the  interosseous 
branches  from  the  metatarsal  artery. 

The  Digital  Branches  (aa.  metatarseae  plantares)  are  four  in  number,  and  supply 
the  three  outer  toes  and  half  the  second  toe.  It  will  be  remembered  that  the 
irteria  princeps  hallucis  is  the  plantar  digital  branch  of  the  communicating 
irms  in  the  first  interosseous  space  and  supplies  the  adjacent  sides  of  the  great 
and  little  toes.  The  first  digital  branch  of  the  plantar  arch  passes  outward 
from  the  outer  side  of  the  plantar  arch,  and  is  distributed  to  the  outer  side  of  the 
little  toe,  passing  in  its  course  beneath  the  Abductor  and  short  Flexor  muscles, 
e  second,  third,  and  fourth  run  forward  along  the  interosseous  spaces,  and  on 
arriving  at  the  clefts  between  the  toes  divides  into  collateral  digital  branches  (aa/ 
digitales  plantares),  which  supply  the  adjacent  sides  of  the  three  outer  toes  and 

1  This  refers  to  the  erect  position  of  the  body.  In  the  ordinary  position  for  dissection  the  artery  is  deeper 
than  the  muscle. 


720  THE  BLOOD-VASCULAR  SYSTEM 

the  outer  side  of  the  second.  At  the  bifurcation  of  the  toes  each  digital  artery 
sends  upward,  through  the  forepart  of  the  corresponding  interosseous  space,  a 
small  branch  which  inosculates  with  the  interosseous  branches  of  the  metatarsal 
artery.  These  are  the  anterior  perforating  branches  (rami  perforantes  anterior  es). 
From  the  arrangement  already  described  of  the  distribution  of  the  vessels  to 
the  toes  it  will  be  seen  that  both  sides  of  the  three  outer  toes  and  the  outer  side 
of  the  second  toe  are  supplied  by  branches  from  the  plantar  arch;  both  sides  of 
the  great  toe  and  the  inner  side  of  the  second  are  supplied  by  the  communicating 
branch  of  the  dorsalis  pedis. 


THE  VEINS. 


THE  Veins  are  the  vessels  which  serve  to  return  the  blood  from  the  capillaries 
of  the  different  parts  of  the  body  to  the  heart.  They  consist  of  two  distinct  sets 
of  vessels,  the  pulmonary  and  systemic  veins,  and  an  appendage  to  the  systemic, 
the  portal  system. 

The  Pulmonary  Veins  are  concerned  in  the  circulation  in  the  lungs.  Unlike 
other  vessels  of  this  kind,  they  contain  arterial  blood,  which  they  return  from  the 
lungs  to  the  left  auricle  of  the  heart.  The  pulmonary  veins  are  four  in  number. 


A 


A 


FIG.  439. — Valves  of  a  vein.  In  the  lower  part 
of  the  figure  is  seen  the  parietal  valves;  the  upper 
part  shows  the  mouth  of  a  vein  guarded  by  a  valve. 
(Poirier  and  Charpy.) 


FIG.  440. — Collateral  anastomosis  of  veins.  The  arrows 
indicate  the  direction  of  the  flow  of  blood  (schematic). 
(Poirier  and  Charpy.) 


The  Systemic  Veins  are  concerned  in  the  general  circulation;  they  return  the 
venous  blood  from  the  body  generally  to  the  right  auricle  of  the  heart.  The  sys- 
temic veins  are  the  precava  or  superior  vena  cava,  the  postcava  or  inferior  vena  cava, 
and  the  coronary  sinus. 

The  Portal  Vein  and  its  radicles  constitute  the  portal  system.  The  portal  system 
is  in  reality  an  appendage  to  the  systemic  venous  system.  It  is  confined  to  the 
abdominal  cavity,  returning  the  venous  blood  from  the  viscera  of  digestion,  and 
carrying  it  to  the  liver  by  a  single  trunk  of  large  size,  the  portal  vein  or  vena  portae. 
This  vessel  ramifies  in  the  substance  of  the  liver  and  breaks  up  into  a  minute 

46  (  721  ) 


722 


THE  BLOOD-VASCULAR  SYSTEM 


fif—- j-^^i 


network  of  capillaries.    These  capillaries  then  re-collect  to  form  the  hepatic  veins, 
by  which  the  blood  is  conveyed  to  the  postcava. 

The  veins,  like  the  arteries,  are  found  in  nearly  every  tissue  of  the  body.  They 
commence  by  minute  plexuses  which  receive  the  blood  from  the  capillaries.  The 
branches  which  have  their  commencement  in  these  plexuses  unite  together 
into  trunks,  and  these,  in  their  passage  toward  the  heart,  constantly  increase  in 
size  as  they  receive  tributaries  or  join  other  veins.  The  veins  are  larger  and 
altogether  more  numerous  than  the  arteries;  hence  the  entire  capacity  of  the 
venous  system  is  much  greater  than  that  of  the  arterial,  the  pulmonary  veins 
excepted,  which  only  slightly  exceed  in  capacity  the  pulmonary  arteries.  From 
the  combined  area  of  the  smaller  venous  branches  being  greater  than  the  main 
trunks,  it  results  that  the  venous  system  represents  a  cone,  the  summit  of  which 
corresponds  to  the  heart,  its  base  to  the  circumference  of  the  body.  In  form  the 
veins  are  perfectly  cylindrical,  like  the  arteries,  their  walls  being  collapsed  when 
empty,  and  the  uniformity  of  their  surface  being  interrupted  at  intervals  by  slight 
constrictions,  which  indicate  the  existence  of  valves  in  their  interior  (Fig.  439)  . 
They  usually  retain,  however,  about  the  same  calibre  as  long  as  they  receive  no 
branches,  but  not  so  uniformly  as  do  the  arteries. 

The  veins  communicate  very  freely  with  one  another  (Fig.  441),  especially  in 
certain  regions  of  the  body,  and  this  communication  exists  between  the  larger 

trunks  as  well  as  between  the  smaller 
branches.  Thus,  in  tha  cavity  of  the 
cranium  and  between  the  veins  of  the 
neck,  where  obstruction  would  be  at- 
tended with  imminent  danger  to  the 
cerebral  -venous  system,  we  find  that 
the  sinuses  and  larger  veins  have  large 
and  very  frequent  anastomoses  (Fig. 

U\\  ^^^^^^^^^^^     f    A    1     440).    The  same  free  communication 
I  ^^S,        ^^^  IT      if     exists  between  the  veins  throughout 

the  whole  extent  of  the  spinal  canal, 
and  between  the  veins  composing  the 
various  venous  plexuses  in  the  abdo- 
men and  pelvis,  as  the  spermatic, 
uterine,  vesical,  and  prostatic. 

Veins  have  thinner  walls  than 
arteries,  the  difference  in  thickness 
being  due  to  the  small  amount  of 
elastic  and  muscular  tissues  which 
the  veins  contain.  The  superficial  veins  usually  have  thicker  coats  than  the  deep 
veins,  and  the  veins  of  the  lower  limb  are  thicker  than  those  of  the  upper. 

Histology  of  the  Veins.  —  As  previously  stated,  capillaries  enter  into  venules 
or  precapillary  veins.  The  venules  empty  into  larger  veins.  Vein  walls  are  much 
thinner  than  arterial  walls.  A  vein  has  a  much  thinner  media  and  much  less 
elastic  tissue  than  an  artery,  and  a  very  strongly  developed  adventitia.  The 
intima  is  a  connective-tissue  layer  containing  a  small  number  of  elastic  fibres 
and  lined  with  endothelium.  The  media  contains  some  circular  muscle  fibres 
and  some  fine  elastic  fibres.  In  some  veins  the  media  is  thoroughly  well  devel- 
oped (veins  of  the  lower  extremities),  in  others  it  is  practically  absent  (veins  of 
the  retina,  of  the  pia,  of  bone,  the  precava).  The  adventitia  is  dense  and  strong, 
and  is  composed  of  connective-tissue  elastic  fibres  and  non-striated  muscle  fibres 
placed  longitudinally.  Fig.  442  shows  a  transverse  section  of  part  of  the  wall  of  a 
vein.  The  vein  valves  (Fig.  439)  are  composed  of  intima  and  contain  elastic  fibres. 
The  large  veins  and  the  veins  of  medium  size  possess  vasa  vasorum,  in  the  adven- 


FIG.  44i.—  The  venous  circle  of  Braune  (schematic), 
°ethe  ^^'^  of  the  blood  current- 


THE  PULMONARY  VEINS 


723 


titia  and  to  some  extent  in  the  media.  The  walls  of  veins  contain  vasomotor  nerves. 
"Small  blood-vessels  are  often  surrounded  by  lymph  capillaries  and  sometimes  by 
endothelium-lined  spaces  which  are  in  communication  with  the  lymphatic  system. 
These  are  called  perivascular  lymph  spaces."1 

The  systemic  veins  are  subdivided  into  three  sets:  superficial,  deep,  and  sinuses. 

The  Superficial  or  Cutaneous  Veins  are  found  between  the  layers  of  the  super- 
ficial fascia,  immediately  beneath  the  integument;  they  return  the  blood  from 
these  structures,  and  communicate  with  the  deep  veins  by  perforating  the  deep 
fascia. 


Endothdial  and 
S  subendothelial 

'layers. 
Elastic  layer. 


— Middle  coat. 


•—Outer  coat. 


FIG.  442. — Transverse  section  of  part  of  the  wall  of  one  of  the  posterior  tibial  veins.     (After  Schiifer.) 

The  Deep  Veins  accompany  the  arteries,  and  are  usually  enclosed  in  the  same 
sheath  with  those  vessels.  With  the  smaller  arteries — as  the  radial,  ulnar,  brachial, 
tibial,  and  peroneal — they  exist  generally  in  pairs,  one  lying  on  each  side  of  the 
vessel,  and  are  called  venae  comites.  The  larger  arteries — as  the  axillary,  sub- 
clavian,  popliteal,  and  femoral — have  usually  only  one  accompanying  vein.  In 
certain  organs  of  the  body,  however,  the  deep  veins  do  not  accompany  the 
arteries;  for  instance,  the  veins  in  the  skull  and  spinal  canal,  the  hepatic  veins  in 
the  liver,  and  the  larger  veins  returning  blood  from  the  osseous  tissue. 

Sinuses  are  venous  channels  which,  in  their  structure  and  mode  of  distribution, 
differ  altogether  from  the  veins.  They  are  found  only  in  the  interior  of  the  skull, 
and  consist  of  channels  formed  by  a  separation  of  the  two  layers  of  the  dura, 
their  outer  coat  consisting  of  fibrous  tissue,  their  inner  of  an  endothelial  layer 
continuous  with  the  lining  membrane  of  the  veins. 


THE  PULMONARY  VEINS  (V.  PULMONALES)  (Fig.  443). 

The  pulmonary  veins  return  the  arterial  blood  from  the  lungs  to  the  left  auricle 
of  the  heart.  They  are  four  in  number,  two  for  each  lung.  The  pulmonary  veins 
differ  from  other  veins  in  several  respects:  1.  They  carry  arterial  instead  of 
venous  blood.  2.  They  are  destitute  of  valves.  3.  They  are  only  slightly  larger 
than  the  arteries  they  accompany.  4.  They  accompany  those  vessels  singly. 
They  commence  in  a  capillary  network  upon  the  walls  of  the  air-cells,  where  they 
are  continuous  with  the  capillary  ramifications  of  the  pulmonary  artery,  and, 
uniting  together,  form  one  vessel  for  each  lobule.  These  vessels,  uniting  suc- 
cessively, form  a  single  trunk  for  each  lobe,  three  for  the  right  and  two  for  the 
left  lung.  The  vein  from  the  middle  lobe  of  the  right  lung  generally  unites  with 
that  from  the  upper  lobe,  forming  two  trunks  on  each  side,  which  open  separately 
into  the  left  auricle.  Occasionally  they  remain  separate;  there  are  then  three 


Histology  and  Microscopic  Anatomy.    By  Szymonowicz  and  MacCallum. 


724 


THE   BLOOD -VASCULAR   SYSTEM 


veins  on  the  right  side.  Not  unfrequently  the  two  left  pulmonary  veins  terminate 
by  a  common  opening. 

Within  the  lung,  the  branches  of  the  pulmonary  artery  are  in  front,  the  veins 
behind,  and  the  bronchi  between  the  two. 

At  the  root  of  the  lung,  the  veins  are  in  front,  the  artery  in  the  middle,  and  the 
bronchus  behind. 


ENTRANCE   OF 

t VENA     AZYGOS 

BRANCH    OF   PUL- 
MONARY  ARTERY 


FIG.  443. — Pulmonary  veins,  seen  in  a  dorsal  view  of  the  heart  and  lungs.  The  left  lung  is  pulled  to  the 
left,  and  the  right  lung  has  been  partly  cut  away  to  show  the  ramifications  of  the  air-tubes  and  blood-vessels. 
(Testut.) 

Within  the  pericardium,  their  anterior  surface  is  invested  by  the  serous  layer 
of  this  membrane.  The  right  pulmonary  veins  pass  behind  the  right  auricle  and 
ascending  aorta  and  precava;  the  left  pass  in  front  of  the  thoracic  aorta  with  the 
left  pulmonary  artery. 


THE  SYSTEMIC  VEINS. 

The  systemic  veins  may  be  arranged  into  three  groups:  1.  Those  of  the  head 
and  neck,  upper  extremity,  and  thorax,  which  terminate  in  the  precava.  2.  Those 
of  the  lower  extremity,  abdomen,  and  pelvis,  which  terminate  in  the  postcava.  3. 
The  cardiac  veins,  which  open  directly  into  the  right  auricle  of  the  heart. 


VEINS  OF  THE  HEAD  AND  NECK. 

The  veins  of  the  head  and  neck  may  be  subdivided  into  three  groups:  1.  The 
veins  of  the  exterior  of  the  head  and  face.  2.  The  veins  of  the  neck.  3.  The  veins 
of  the  diploe  and  interior  of  the  cranium. 


VEIXS    OF    THE  EXTERIOR    OF    THE    HEAD    AND    FACE     725 


Veins  of  the  Exterior  of  the  Head  and  Face  (Fig.  444). 
The  veins  of  the  exterior  of  the  head  and  face  are — the 


Frontal. 
Supraorbital. 
Angular. 
Facial. 


Temporal. 
Internal  Maxillary. 
Temporo-m  axillary. 
Posterior  Auricular. 


Occipital. 


The  Frontal  Vein  (v.  frontalis)  commences  on  the  anterior  part  of  the  skull  by 
a  venous  plexus  which  communicates  with  the  anterior  tributaries  of  the  temporal 
vein.  The  veins  converge  to  form  a  single  trunk,  which  runs  downward  near  the 


Frontal 
Communicating 

branch  with 
ophthalmic  vein. 
Angular. 


Anterior  division 

of  the  temporo- 

maxillary. 


Anterior 
'facial. 


Common 
•facial 
Lingual. 
LaryngeaL 


FIG.  444. — Veins  of  the  head  and  neck. 


middle  line  of  the  forehead  parallel  with  the  vein  of  the  opposite  side,  and  unites 
with  it  at  the  root  of  the  nose  by  a  transverse  branch  called  the  nasal  arch  (v.  naso- 
frontalis).  Occasionally  the  frontal  veins  join  to  form  a  single  trunk,  which 


726  THE   BLOOD -VASCULAR    SYSTEM 

bifurcates  at  the  root  of  the  nose  into  the  two  angular  veins.  At  the  root  of 
the  nose  the  veins  diverge  and  join  the  supraorbital  vein,  at  the  inner  angle  of 
the  orbit,  to  form  the  angular  vein. 

The  Supraorbital  Vein  (v.  supraorbitalis)  commences  on  the  forehead,  com- 
municating with  the  anterior  temporal  vein,  and  runs  downward  and  inward, 
superficial  to  the  Occipito-frontalis  muscle,  receiving  tributaries  from  the  neigh- 
boring structures,  and  from  the  frontal  vein  of  the  diploe,  and  joins  the  frontal 
vein  at  the  inner  angle  of  the  orbit  to  form  the  angular  vein. 

The  Angular  Vein  (v.  angularis),  formed  by  the  junction  of  the  frontal  and 
supraorbital  veins,  runs  obliquely  downward  and  outward  on  the  side  of  the  root 
of  the  nose,  and  receives  the  veins  of  the  ala  nasi  on  its  inner  side  and  the  superior 
palpebral  veins  on  its  outer  side;  it  moreover  communicates  with  the  ophthalmic 
vein,  thus  establishing  an  important  anastomosis  between  this  vessel  and  the 
cavernous  sinus.  Some  small  veins  from  the  dorsum  of  the  nose  terminate  in  the 
nasal  arch. 

The  Anterior  Facial  Vein  (v.  facialis  anterior)  commences  at  the  side  of  the 
root  of  the  nose,  being  a  direct  continuation  of  the  angular  vein,  which  is  itself 
formed  by  the  union  of  the  frontal  vein  and  the  supraorbital  vein.  It  lies  behind 
and  follows  a  less  tortuous  course  than  the  facial  artery.  It  passes  obliquely 
downward  and  outward,  beneath  the  Zygomaticus  major  and  minor  muscles, 
descends  along  the  anterior  border  of  the  Masseter,  crosses  over  the  body  of  the 
lower  jaw,  with  the  facial  artery  to  beneath  the  angle,  and  unites  with  the  anterior 
division  of  the  temporo-maxillary  vein  (v.  facialis  posterior)  to  form  the  common 
facial  vein. 

The  Common  Facial  Vein  (v.  facialis  communis)  is  formed  by  the  union  of  the 
anterior  facial  and  the  anterior  division  of  the  temporo-maxillary  vein,  just  beneath 
the  angle  of  the  niandible.  The  vein  is  covered  by  the  Platysma  myoid  muscle, 
runs  downward  and  backward  beneath  the  Sterno-cleido-mastoid  muscle,  crosses 
the  external  carotid  artery,  and  empties  into  the  internal  jugular  vein  at  the  level 
of  the  hyoid  line.  It  receives  a  large  branch  at  the  anterior  border  of  the  Sterno- 
cleido-mastoid  muscle,  which  comes  from  the  anterior  jugular  vein  in  the  supra- 
sternal  fossa. 

Tributaries  of  the  Anterior  and  Common  Facial  Veins. — The  anterior  facial  vein 
receives,  near  the  angle  of  the  mouth,  communicating  tributaries  of  considerable 
size,  the  deep  facial  or  anterior  internal  maxillary  vein,  from  the  pterygoid 
plexus.  It  is  also  joined  by  the  inferior  palpebral,  the  superior  and  inferior 
labial  veins,  the  buccal  veins  from  the  cheek,  and  the  masseteric  veins.  The 
common  facial  vein  receives  the  submental;  the  inferior  palatine,  which  returns 
the  blood  from  the  plexus  round  the  tonsil  and  soft  palate;  the  submaxillary 
vein,  which  commences  in  the  submaxillary  gland;  and,  generally,  the  ranine 
vein. 

Surgical  Anatomy. — There  are  some  points  about  the  facial  vein  which  render  it  of  great 
importance  in  surgery.  It  is  not  so  flaccid  as  are  most  superficial  veins,  and,  in  consequence  of 
this,  remains  more  patent  when  divided.  It  has,  moreover,  no  valves.  It  communicates  freely 
with  the  intracranial  circulation,  not  only  at  its  commencement  by  its  tributaries,  the  angular 
and  supraorbital  veins,  communicating  with  the  ophthalmic  vein,  a  tributary  of  the  cavernous 
sinus,  but  also  by  its  deep  branch,  which  communicates  through  the  pterygoid  plexus  with  the 
cavernous  sinus  by  branches  which  pass  through  the  foramen  ovale  and  foramen  lacerum 
medium.  These  facts  have  an  important  bearing  upon  the  surgery  of  some  diseases  of  the 
face,  for  on  account  of  its  patency  the  facial  vein  favors  septic  absorption,  and  therefore  any 
phlegmonous  inflammation  of  the  face  following  a  poisoned  wound  is  liable  to  set  up  thrombosis 
in  the  facial  vein,  and  detached  portions  of  the  clot  may  give  rise  to  purulent  foci  in  other 
parts  of  the  body.  And  on  account  of  its  communications  with  the  cerebral  sinuses  these 
thrombi  are  apt  to  extend  upward  into  them  and  so  induce  a  fatal  issue. 


VEINS    OF    THE  EXTERIOR    OF    THE    HEAD    AND    FACE     727 

The  Superficial  Temporal  Vein  (vv.  temporales  super  fi  dales)  commences  by  a 
minute  plexus  on  the  side  and  vertex  of  the  skull,  which  communicates  with  the 
frontal  and  supraorbital  veins  in  front,  the  corresponding  vein  of  the  opposite 
side,  and  the  posterior  auricular  and  occipital  veins  behind.  From  this  network 
anterior  and  posterior  branches  are  formed  which  unite  above  the  zygoma,  form- 
ing the  trunk  of  the  vein.  The  trunk  is  joined  in  this  situation  by  a  large  vein, 
the  middle  temporal  (v.  temporalis  media),  which  receives  blood  from  the  sub- 
stance of  the  Temporal  muscle  and  pierces  the  fascia  at  the  upper  border  of 
the  zygoma.  The  junction  of  the  superficial  temporal  and  the  middle  temporal 
veins  forms  the  common  temporal  vein  (v.  temporalis  communis),  which  descends 
between  the  external  auditory  meatus  and  the  -condyle  of  the  jaw,  enters  the 
substance  of  the  parotid  gland,  and  unites  with  the  internal  maxillary  vein  to  form 
the  temporo-maxillary  vein. 

Tributaries. — The  common  temporal  vein  receives  in  its  course  some  parotid 
veins,  an  articular  branch  from  the  articulation  of  the  jaw,  anterior  auricular  veins 
from  the  external  ear,  and  a  vein  of  large  size,  the  transverse  facial  (v.  transversa 
faciei),  from  the  side  of  the  face.  The  middle  temporal  vein,  previous  to  its  junc- 
tion with  the  temporal  vein,  receives  a  branch,  the  orbital  vein  (v.  crbitalis),  which 
is  formed  by  some  external  palpebral  branches,  and  passes  backward  between 
the  layers  of  the  temporal  fascia. 

The  Pterygoid  Plexus  (plexus  pterygoideus)  and  the  Internal  Maxillary 
Vein. — The  internal  maxillary  vein  is  a  vessel  of  considerable  size,  receiving 
branches  which  correspond  with  those  of  the  internal  maxillary  artery.  Thus  it 
receives  the  two  medidural  or  middle  meningeal  veins,  the  deep  temporal,  the 
pterygoid,  masseteric,  buccal,  and  alveolar  veins,  some  palatine  veins,  the  spheno- 
palatine  and  the  inferior  dental  veins.  The  deep  temporal  veins  (vv.  temporales 
profundae)  come  to  the  pterygoid  plexus  from  the  temporal  muscle.  These  branches 
form  a  large  plexus,  the  pterygoid  plexus,  which  is  placed  between  the  Temporal 
and  External  pterygoid  and  partly  between  the  Pterygoid  muscles.  This  plexus  is 
a  tributary  of  the  internal  maxillary  vein,  and  communicates  very  freely  with  the 
facial  vein  and  with  the  cavernous  sinus  by  branches  through  the  foramen  Vesalii, 
foramen  ovale,  and  foramen  lacerum  medium,  at  the  base  of  the  skull.  The  trunk 
of  the  internal  maxillary  vein  comes  from  the  plexus,  then  passes  backward  behind 
the  neck  of  the  lower  jaw,  and  unites  with  the  temporal  vein,  forming  the  temporo- 
maxillary  vein. 

The  Temporo-maxillary  Vein  (v.  facialis  posterior),  formed  by  the  union  of 
the  superficial  temporal  and  internal  maxillary  veins,  descends  in  the  substance  of 
the  parotid  gland  on  the  outer  surface  of  the  external  carotid  artery,  between  the 
ramus  of  the  jaw  and  the  Sterno-mastoid  muscle,  and  divides  into  two  branches, 
an  anterior,  which  passes  inward  to  join  the  facial  vein,  and  a  posterior,  which 
is  joined  by  the  posterior  auricular  vein  and  becomes  the  external  jugular. 

The  Posterior  Auricular  Vein  (v.  auricularis  posterior)  commences  upon  the 
side  of  the  head  by  a  plexus  which  communicates  with  the  tributaries  of  the  tem- 
poral and  occipital  veins.  The  vein  descends  behind  the  external  ear  and  joins 
the  posterior  division  of  the  temporo-maxillary  vein,  forming  the  external  jugular. 
This  vessel  receives  the  stylo-mastoid  vein  and  some  tributaries  from  the  back 
part  of  the  external  ear. 

The  Occipital  Vein  (v.  occipitalis)  commences  at  the  back  part  of  tiie  vertex 
of  the  skull  by  a  plexus  in  a  similar  manner  to  the  other  veins.  From  the  plexus 
comes  one  or  two  veins,  which  follow  the  course  of  the  occipital  artery,  passing 
deeply  beneath  the  muscles  of  the  back  part  of  the  neck,  and  terminating  in  the 
suboccipital  triangle  by  becoming  continuous  with  the  posterior  vertebral  vein. 
Sometimes  they  are  more  superficial,  and  in  this  case  they  are  tributaries  of  the 


728  THE  BLOOD -VASCULAR   SYSTEM 

external  jugular  vein.  As  the  outermost  occipital  vein  passes  across  the  mastoid 
portion  of  the  temporal  bone,  it  receives  the  mastoid  vein,  which  thus  establishes 
a  communication  with  the  lateral  sinus. 


The  Veins  of  the  Neck  (Fig.  444). 

The  veins  of  the  neck,  which  return  the  blood  from  the  head  and  face,  are — the 

External  Jugular.  Anterior  Jugular. 

Posterior  External  Jugular.  Internal  Jugular. 

Vertebral. 

The  External  Jugular  Vein  (v.  jugularis  externa)  receives  the  greater  part 
of  the  blood  from  the  exterior  of  the  cranium  and  deep  parts  of  the  face,  being 
formed  by  the  junction  of  the  posterior  division  of  the  temporo-maxillary  and 
the  posterior  auricular  veins.  It  commences  in  the  substance  of  the  parotid  gland, 
on  a  level  with  the  angle  of  the  lower  jaw,  and  runs  perpendicularly  down  the  neck 
in  the  direction  of  a  line  drawn  from  the  angle  of  the  jaw  to  the  middle  of  the 
clavicle.  In  its  course  it  crosses  the  Sterno-mastoid  muscle,  and  runs  parallel  with 
its  posterior  border  as  far  as  its  attachment  to  the  clavicle,  where  it  perforates  the 
deep  fascia,  and  terminates  in  the  subclavian  vein,  on  the  outer  side  of,  or  in  front 
of,  the  Scalenus  anticus  muscle.  In  the  neck  it  is  separated  from  the  Sterno- 
mastoid  by  the  investing  layer  of  the  deep  cervical  fascia,  and  is  covered  by  the 
Platysma,  the  superficial  fascia,  and  the  integument.  This  vein  is  crossed  about 
its  middle  by  the  superficialis  colli  nerve,  and  throughout  the  upper  half  of  its 
course  is  accompanied  by  the  auricularis  magnus  nerve.  The  external  jugular  vein 
varies  in  size,  bearing  an  inverse  proportion  to  that  of  the  other  veins  of  the  neck; 
it  is  occasionally  double.  It  is  provided  with  two  pairs  of  valves,  the  lower  pair 
being  placed  at  its  entrance  into  the  subclavian  vein,  the  upper  pair  in  most  cases 
about  an  inch  and  a  half  above  the  clavicle.  The  portion  of  vein  between  the  two 
sets  of  valves  is  often  dilated,  and  is  termed  the  sinus.  These  valves  do  not  prevent 
the  regurgitation  of  the  blood  or  the  passage  of  injection  from  below  upward.1 

Tributaries. — This  vein  receives  the  occipital  occasionally,  the  posterior  external 
jugular,  and,  near  its  termination,  the  suprascapular  and  transverse  cervical  veins. 
It  communicates  with  the  anterior  jugular,  and,  in  the  substance  of  the  parotid, 
receives  a  large  branch  of  communication  from  the  internal  jugular. 

The  Posterior  External  Jugular  Vein  (v.  jugularis  posterior]  commences  in 
the  occipital  region,  and  returns  the  blood  from  the  integument  and  superficial 
muscles  in  the  upper  and  back  part  of  the  neck,  lying  between  the  Splenius  and 
Trapezius  muscles.  It  runs  down  the  back  part  of  the  neck,  and  opens  into  the 
external  jugular  just  below  the  middle  of  its  course. 

The  Anterior  Jugular  Vein  (v.  jugularis  anterior)  commences  near  the 
hyoid  bone  from  the  convergence  of  the  inferior  coronary,  the  submental  and  the 
mental  veins,  and  communicating  branches.  It  passes  down  between  the  median 
line  and  the  anterior  border  of  the  Sterno-mastoid,  and  at  the  lower  part  of  the 
neck  passes  beneath  that  muscle  to  open  into  the  termination  of  the  external 
jugular  or  into  the  subclavian  vein  (Fig.  465).  This  vein  varies  considerably  in 
size,  bearing  almost  always  an  inverse  proportion  to  the  external  jugular.  Most 
frequently  there  are  two  anterior  jugulars,  a  right  and  left,  but  occasionally  only 
one.  This  vein  receives  some  laryngeal  veins,  and  occasionally  a  small  thyroid 
vein.  Just  above  the  sternum  the  two  anterior  jugular  veins  communicate  by  a 

1  The  student  may  refer  to  an  interesting   paper  by  Dr.  Struthers,   "  On  Jugular  Venesection  in  Asphyxia. 
Anatomically  and  Experimentally  Considered,  including  the  Demonstration  of  Valves  in  the  Veins  of  the  Neck, 
in  the  Edinburgh  Medical  Journal  for  November,  1856. — ED.  of  15th  English  edition. 


THE    VEINS    OF   THE  NECK 


729 


transverse  trunk,  which  receives  tributaries  from  the  inferior  thyroid  veins.  It 
also  communicates  with  the  internal  jugular.  There  are  no  valves  in  this  vein. 
The  Internal  Jugular  Vein  (v.  jugularis  interna)  collects  the  blood  from 
the  interior  of  the  cranium,  from  the  superficial  parts  of  the  face,  and  from  the 
neck.  It  commences  just  external  to  the  jugular  foramen,  at  the  base  of  the  skull, 
being  formed  by  the  coalescence  of  the  lateral  and  inferior  petrosal  sinuses  (Fig. 
458).  At  its  origin  it  is  somewhat  dilated,  and  this  dilatation  is  called  the  sinus 
or  gulf  of  the  internal  jugular  vein  (bulbus  v.  jugularis  superior).  It  runs  down  the 
side  of  the  neck  in  a  vertical  direction,  lying  at  first  on  the  outer  side  of  the  internal 
carotid  artery,  and  then  on  the  outer  side  of  the  common  carotid  artery,  and  at 
the  root  of  the  neck  unites  with  the  subclavian  vein  to  form  the  innominate  vein. 
Just  before  its  termination  it  is  distinctly  dilated  (bulbus  v.  jugularis  inferior).  The 


HYPOGLOSSAL 

FIG.  445. — Veins  of  the  tongue.     (Testut,  modified  from  Hirschfeld.) 


internal  jugular  vein,  at  its  commencement,  lies  upon  the  Rectus  capitis  lateralis, 
and  behind  the  internal  carotid  artery  and  the  nerves  passing  through  the  jugular 
foramen;  lower  down,  the  vein  and  artery  lie  upon  the  same  plane,  the  glosso- 
pharyngeal  and  hypoglossal  nerves  passing  forward  between  them;  the  vagus 
descends  between  and  behind  them  in  the  same  sheath,  and  the  accessory  passes 
obliquely  outward,  behind  or  in  front  of  the  vein.  At  the  root  of  the  neck  the  vein 
of  the  right  side  is  placed  at  a  little  distance  from  the  artery;  on  the  left  side  it 
usually  lies  over  the  artery  at  its  lower  part.  The  right  internal  jugular  vein  crosses 
the  first  part  of  the  subclavian  artery.  The  internal  jugular  vein  is  of  considerable 
size,  but  varies  in  different  individuals,  the  left  one  being  usually  the  smaller. 
It  is  provided  with  a  pair  of  valves,  which  are  placed  at  its  point  of  termination 
or  from  one-half  to  three-quarters  of  an  inch  above  it. 

Tributaries. — This  vein  receives  in  its  course  the  facial,  lingual,  pharyngeal, 
superior,  and  middle  thyroid  veins.  A  branch  from  the  cochlea  opens  into  the 
sinus  of  the  internal  jugular  vein.  A  venous  plexus  from  the  lateral  sinus  (plexus 
venosus  caroticus  internus)  surrounds  the  internal  carotid  artery  in  the  carotid 
canal  and  empties  into  the  internal  jugular  vein.  At  its  point  of  junction  with  the 
common  facial  vein  it  becomes  increased  in  size.  (See  Facial  Veins,  p.  726.) 

The  Lingual  Veins  (vv.  linguale)  (Fig.  445)  commence  on  the  dorsum,  sides,  and 
under  surface  of  the  tongue,  and,  passing  backward,  following  the  course  of  the 
lingual  artery  and  its  branches,  terminate  in  the  internal  jugular.  Sometimes  the 
ranine  vein,  which  is  a  branch  of  considerable  size  commencing  below  the  tip  of  the 


730 


THE   BLOOD -VASCULAR   SYSTEM 


tongue,  joins  the  lingual.  Generally,  however,  it  passes  backward,  crosses  the 
Hyo-glossus  muscle  in  company  with  the  hypoglossal  nerve,  and  joins  the  internal 
jugular.  The  lingual  vein  receives  the  sublingual  vein  and  the  dorsalis  linguae  veins. 
The  Pharyngeal  Veins  (vv.  pharync/eae)  vary  in  number.  They  commence  in  a 
minute  plexus,  the  pharyngeal  plexus  (plexus  pharyngeus),  at  the  back  part  and 
sides  of  the  pharynx,  and,  after  receiving  meningeal  tributaries,  the  dural  or 
meningeal  veins  (vv.  meningea),  the  Vidian  veins  (vv.  canalis  pierygoidei  [Vidii]), 
and  the  spheno-palatine  veins,  terminate  in  the  internal  jugular.  They  occasion- 
ally open  into  the  facial,  lingual,  or  superior  thyroid  vein. 


SUBMENTAL 


INFERIOR 
PALAT 


STERNO-CLEIDO- 
MASTOID  MUSCLE 


SUPERIOR 
THYROID' 


TEMPORO- 
M  AXILLARY 


TRANSVERSE 
VICAL 


SUBCLAVIAN 

FIG.  446. — The  veins  of  the  neck,  viewed  from  in  front.     (Spalteholz.) 


The  Superior  Thyroid  Vein  (v.  thyreoidea  superioris)  (Fig.  446)  commences  in  the 
substance  and  on  the  surface  of  the  thyroid  gland  by  tributaries  corresponding 
with  the  branches  of  the  superior  thyroid  artery,  and  terminates  in  the  upper 
part  of  the  internal  jugular  vein.  It  receives  the  superior  laryngeal  and  crico- 
thyroid  veins.  Some  anatomists  teach  that  there  are  two  superior  thyroid  veins 
on  each  side,  the  upper  vein  being  the  one  just  considered,  the  lower  vein  being 
the  one  usually  pointed  out  as  the  middle  thyroid. 

The  Middle  Thyroid  Vein  (Fig.  448)  collects  the  blood  from  the  lower  part  of  the 
lateral  lobe  of  the  thyroid  gland,  and,  being  joined  by  some  veins  from  the  larynx 
and  trachea,  terminates  in  the  lower  part  of  the  internal  jugular  vein. 


Often  in 


731 


place  of  the  middle  thyroid  vein  there  are  two  veins,  the  superior  and  inferior 
accessory  thyroid.    These  veins  pass  into  the  internal  jugular. 


FIG.  447. — Diagram  showing  common  arrangement  of  thyroid  veins.     (Kocher.) 


INFERIOR 

THYROID 
VEIN 


INFERIOR 
THYROID 
VEIN 


FIG.  448. — The  fascia  and  middle  thyroid  veins.     The  veins  here  designated  the  inferior  thyroid  are  called  by 
Kocher  the  thyreoidea  ima.     (Poirier  and  Charpy.) 

Veins  of  the  Thyroid  Gland1  (Fig.  447) . — On  the  surface  of  the  thyroid  glands 
the  veins  form  a  plexus  between  the  capsule  and  the  gland.     A  number  of  veins 


1  See  Kocher's  description  in  Langenbeck's  Arch.  f.  klin.  Chir.,  vol.  xxix.,  and  James  Berry's  description  in  his 
treatise  on  Diseases  of  the  Thyroid  Gland. 


732  THE   BLOOD -VASCULAR    SYSTEM 

penetrate  the  capsule  and  pass  into  adjacent  trunks.  The  most  important  veins 
coming  from  the  gland  are  the  superior,  middle,  and  inferior  thyroids  (or  instead 
of  the  middle  thyroid  the  superior  and  inferior  accessory  thyroid)  and  the 
thyreoidea  ima. 

The  superior  thyroid  vein  emerges  from  the  summit  of  the  superior  horn  of  the 
gland,  runs  along  by  the  superior  thyroid  artery,  and  terminates  in  the  internal 
jugular  vein.  A  large  branch  which  passes  along  the  inner  margin  of  the  upper 
horn  and  across  the  upper  surface  of  the  isthmus  joins  the  superior  thyroid  veins 
of  each  side.  The  middle  thyroid  vein  when  present  emerges  from  the  side  of  the 
gland  and  empties  into  the  internal  jugular.  This  single  vein  may  be  replaced  by 
two  veins,  the  superior  and  inferior  accessory  thyroid  veins.  The  superior  vein 
emerges  from  the  outer  surface  of  the  upper  horn  somewhat  below  the  apex.  The 
inferior  vein  comes  from  the  posterior  and  inferior  portion  of  the  gland.  Both 
empty  into  the  internal  jugular.  The  lower  surface  of  the  isthmus  and  the  inner 
side  of  each  inferior  horn  is  drained  by  two  veins.  Each  vein  is  called  the  thy- 
reoidea ima  (Kocher).  The  left  vein  empties  into  the  left  innominate  vein.  The 
right  vein  empties  into  either  the  right  or  left  innominate  vein.  These  veins  may 
be  very  small,  may  be  absent,  or  may  join  and  form  one  vein  which  empties  into 
the  left  innominate.  An  inferior  thyroid  is  often  also  present.  It  comes  from  the 
outer  portion  of  the  inferior  horn  of  the  gland  and  empties  into  the  innominate  vein, 

The  facial  and  occipital  veins  have  been  described  on  pages  726  and  727. 

Surgical  Anatomy. — The  internal  jugular  vein  occasionally  requires  ligature  in  cases  of  septic 
thrombosis  of  the  lateral  sinus  from  suppuration  in  the  middle  ear.  This  is  done  in  order  to 
prevent  septic  emboli  being  carried  into  the  general  circulation.  This  operation  has  been 
performed  in  a  number  of  cases,  with  satisfactory  results.  The  cases  are  generally  those  of 
chronic  disease  of  the  middle  ear,  with  discharge  of  pus  which  perhaps  has  existed  for  many 
years.  The  patient  is  seized  with  acute  septic  inflammation,  spreading  to  the  mastoid  cells, 
and,  consequent  on  this,  septic  thrombosis  of  the  lateral  sinus  extending  to  the  internal  jugular 
vein.  Such  cases  are  always  extremely  grave,  for  there  is  danger  that  a  portion  of  the  septic 
clot  will  be  detached  and  cause  septic  embolism  in  the  thoracic  viscera.  If  th^ombo-phlebitis 
of  the  sinus  is  suspected  the  mastoid  should  be  opened  and  cleansed  and  the  sinus  should  be  at 
once  exposed  and  explored.  If  the  sinus  is  found  to  be  thrombosed  the  surgeon  should  at 
once  proceed  to  ligate  the  internal  jugular  vein,  by  an  incision  along  the  anterior  border  of  the 
sterno-mastoid,  the  centre  of  which  is  on  a  level  with  the  greater  cornu  of  the  hyoid  bone.  The 
vein  should  be  ligated  in  two  places  and  divided  between.  After  the  vessel  has  been  secured 
and  divided  the  lateral  sinus  is  to  be  thoroughly  cleared  out,  and,  by  removing  the  ligature  from 
the  upper  end  of  the  divided  vein,  all  septic  clots  may  be  removed  by  syringing  from  the  sinus 
through  the  vein.  If  hemorrhage  occurs  from  the  distal  end  of  the  sinus,  it  can  be  arrested  by 
careful  plugging  with  antiseptic  gauze. 

The  thyroid  veins  are  small  vessels  when  the  gland  is  of  normal  size,  but  become  enormous 
when  the  gland  is  much  enlarged. 

In  the  operation  of  thyroidectomy  the  veins  as  well  as  the  arteries  are  ligated  before  the  gland, 
or  rather  before  one  lobe  of  it  is  extirpated. 

The  Vertebral  Vein  (v.  vertebralis]  (Fig.  449)  commences  by  numerous  small 
veins  from  the  intraspinal  venous  plexuses  (plexus  venosi  vertebrates');  these  pass 
outward  and  enter  the  foramen  in  the  transverse  process  of  the  atlas,  and  descend, 
forming  a  dense  plexus  around  the  vertebral  artery  in  the  canal  formed  by  the 
foramina  in  the  transverse  processes  of  the  cervical  vertebrse.  The  vessels  of  this 
plexus  unite  at  the  lower  part  of  the  neck  into  two  main  trunks,  one  of  which 
emerges  from  the  foramen  in  the  transverse  process  of  the  sixth  cervical  vertebra, 
and  the  other  through  that  of  the  seventh.  Uniting,  these  two  trunks  form  a 
single  vessel  which  terminates  at  the  root  of  the  neck  in  the  back  part  of  the 
innominate  vein  near  its  origin,  its  mouth  being  guarded  by  a  pair  of  valves. 
On  the  right  side  it  crosses  the  first  part  of  the  subclavian  artery. 

Tributaries. — The  vertebral  vein  receives  in  its  course  a  vein  from  the  inside 
of  the  skull  through  the  posterior  condyloid  foramen.  It  anastomoses  with  the 


THE    VEINS    OF   THE   DIPLOE 


733 


occipital  vein  and  receives  muscular  veins  from  the  muscles  in  the  prevertebral 
region;  dorsi-spinal  veins,  from  the  back  part  of  the  cervical  portion  of  the  spine; 
meningo-rachidian  veins,  from  the  interior  of  the  spinal  canal;  the  anterior  and 
posterior  vertebral  veins;  and  close  to  its  termination  it  is  joined  by  a  small  vein 
from  the  first  intercostal  space  which  accompanies  the  superior  intercostal  artery. 
The  Anterior  Vertebral  or  Anterior  Deep  Cervical  Vein  commences  in  a  plexus 
around  the  transverse  processes  of  the  upper  cervical  vertebrae,  descends  in  com- 
pany with  the  ascending  cervical  artery  between  the  Scalenus  anticus  and  Rectus 
capitis  anticus  major  muscles,  and  opens  into  the  vertebral  vein  just  before  its 
termination. 


VERTEBRAL 


POSTERIOR 

DEEP 

CERVICAL 


POSTERIOR 

EXTERNAL 

JUGULAR 


VERTEBRAL 


ASCENDING 
CERVICAL 


FIG.  449. — The  vertebral  vein.     (Poirier  and  Charpy.) 

The  Posterior  Vertebral  or  Posterior  Deep  Cervical  Vein  (v.  cervicalis  profunda) 
(Fig.  449)  accompanies  the  profunda  cervicis  artery,  lying  between  the  Corn- 
plexus  and  Semispinalis  colli.  It  commences  in  the  suboccipital  region  by  com- 
municating branches  from  the  occipital  vein  and  tributaries  from  the  deep  muscles 
at  the  back  of  the  neck.  It  receives  tributaries  from  the  plexuses  around  the  spinous 
processes  of  the  cervical  vertebrae,  and  terminates  in  the  lower  end  of  the  vertebral 


vein. 


The  Veins  of  the  Diploe  (Venae  Diploicae)  (Fig.  450). 


The  diploe  of  the  cranial  bones  is  channelled  in  the  adult  by  a  number  of 
tortuous  canals,  the  diploic  canals  or  canals  of  Breschet  (canales  diploici  [Brescheti]) , 
which  are  lined  by  a  more  or  less  complete  layer  of  compact  tissue.  The  veins 
they  contain  are  large  and  capacious,  their  walls  being  thin,  and  formed  only  of 
endothelium  resting  upon  a  layer  of  elastic  tissue,  and  they  present  at  irregular 
intervals  pouch -like  dilatations,  or  culs-de-sac,  which  serve  as  reservoirs  for  the 
blood.  These  are  the  veins  of  the  diploe ;  they  can  only  be  displayed  by  removing 
the  outer  table  of  the  skull. 

In  adult  life,  as  long  as  the  cranial  bones  are  distinct  and  separable,  these 
veins  are  confined  to  the  particular  bones;  but  in  old  age,  when  the  sutures  are 


734  THE  BLOOD-VASCULAR  SYSTEM 

united,  they  communicate  with  each  other  and  increase  in  size.  These  vessels 
communicate,  in  the  interior  of  the  cranium,  with  the  dural  veins  and  with 
the  sinuses  of  the  dura,  and  on  the  exterior  of  the  skull  with  the  veins  of 
the  pericranium.  They  are  divided  into  the  frontal  diploic  vein  (v.  diploica  fron- 
talis),  which  opens  into  the  supraorbital  vein  by  an  aperture  in  the  supraorbital 
notch  and  into  the  superior  longitudinal  sinus;  the  anterior  temporal  diploic  vein 
(v.  diploica  temporalis  anterior),  which  is  confined  chiefly  to  the  frontal  bone, 
communicates  with  the  spheno-parietal  sinus  and,  after  escaping  by  an  aperture 
in  the  great  wing  of  the  sphenoid,  opens  into  one  of  the  deep  temporal  veins;  the 
posterior  temporal,  or  external  parietal  diploic  vein  (v.  diploica  temporalis  posterior), 
is  between  the  emissarium  parietale  and  the  emissarium  mastoideum;  and  the 
occipital  diploic  vein  (v.  diploica  occipitalis) ,  the  largest  of  the  four,  which  is 
confined  to  the  occipital  bone,  and  opens  into  the  emissarium  occipitale. 


FIG.  450. — Veins  of  the  diploe  as  displayed  by  the  removal  of  the  outer  table  of  the  skull. 

The  Emissary  Veins  are  considered  on  page  743. 

The  Dural  or  Meningeal  Veins  (w.  meningeae). — They  are  numerous  in  the 
dura,  are  without  valves,  anastomose  freely  with  each  other,  do  not  increase  in  size 
as  they  reach  the  sinus  which  receives  them,  and  bear  no  regular  relation  to  the 
dural  arteries.  The  medidural  artery  has  two  vena?  comites.  The  other  dural 
arteries  usually  have  two  apiece,  but  may  have  but  one.  The  medidural  or  middle 
meningeal  veins  (w.  mediduralis,  vv.  meningeae  mediae)  accompany  the  medidural 
artery,  are  united  to  the  sphenoparietal  sinus,  pass  through  the  foramen  spino- 
sum,  and  join  the  pterygoid  plexus.  The  other  dural  veins  empty  into  the  longi- 
tudinal sinus  and  communicate  with  the  plexus  of  the  foramen  ovale. 

The  Cerebral  Veins  (Venae  Cerebri). 

The  cerebral  veins  are  remarkable  for  the  absence  of  valves  and  for  the  extreme 
thinness  of  their  coats.  The  coats  are  thin  because  they  contain  no  muscular 
tissue.  The  cerebral  veins  may  be  divided  into  two  sets :  the  superficial  veins, 
which  are  placed  on  the  surface,  and  the  deep  veins,  which  occupy  the  interior  of 
the  organ.  The  veins  of  the  brain  do  not  accompany  associated  arteries. 


THE  CEREBRAL    VEINS  735 

The  Superficial  or  Cortical  Cerebral  Veins  (venae  cerebri  externae)  ramify  upon 
the  surface  of  the  brain,  being  lodged  in  the  fissures  between  the  convolutions, 
a  few  running  across  the  convolutions.  They  receive  branches  from  the  sub- 
stiiuce  of  the  brain  and  terminate  in  the  sinuses.  They  are  named,  from  the 
position  they  occupy,  supercerebral  or  superior,  medicerebral  or  median,  and 
subcerebral  or  inferior  cerebral  veins. 

The  Supercerebral  or  Superior  Cerebral  Veins  (vv.  superccrebrales,  vv.  cerebri 
superiores],  eight  to  twelve  in  number  on  each  side,  return  the  blood  from  the 
convolutions  on  the  superior  surface  of  the  hemisphere;  they  pass  forward  and 
inward  toward  the  intercerebral  fissure,  where  they  receive  the  medicerebral 
veins;  near  their  termination  they  become  invested  with  a  tubular  sheath  of  the 
arachnoid,  and  open  into  the  longitudinal  sinus  in  the  opposite  direction  to  the 
course  of  the  current  of  the  blood. 

The  Medicerebral  or  Median  Cerebral  Veins  (v.  medicerebrales,  v.  cerebri  media) 
return  the  blood  from  the  convolutions  of  the  mesal  surface  of  the  corresponding 
hemisphere;  they  open  into  the  supercerebral  veins,  or  occasionally  into  the  falcial 
sinus. 

The  Subcerebral  or  Inferior  Cerebral  Veins  (vv.  subcerebrales,  vv.  cerebri  inferiores) 
ramify  on  the  lower  part  of  the  outer  surface  and  on  the  under  surface  of  the  cere- 
bral hemisphere.  Some,  collecting  tributaries  from  the  under  surface  of  the  frontal 
lobes  of  the  brain,  terminate  in  the  cavernous  sinus.  One  vein  of  large  size,  the 
medicerebral  or  superficial  sylvian  vein,  commences  on  the  under  surface  of  the 
temporal  lobe,  and,  running  along  a  portion  of  the  sylvian  fissure,  opens  into  the 
cavernous  sinus.  The  great  anastomotic  vein  of  Trolard  or  the  superficial  communi- 
cating vein  establishes  a  union  between  the  sinuses  of  the  vertex  and  those  of  the 
base  of  the  brain.  It  comes  from  one  of  the  supercerebral  veins,  passes  down- 
ward into  the  sylvian  fissure,  and,  by  means  of  the  medicerebral  vein,  effects  a 
communication  with  the  cavernous  sinus.  The  posterior  anastomotic  vein  connects 
the  medicerebral  vein  with  the  lateral  sinus.  Other  veins  commence  on  the  under 
surface  of  the  base  of  the  brain,  and  unite  to  form  'from  three  to  five  veins,  which 
open  into  the  superpetrosal  and  lateral  sinuses  from  before  backward. 

The  Velar,  Deep  Cerebral,  Central,  or  Ventricular  Veins,  Veins  of  Galen  (vv. 
velares,  venae  Galeni,  vv.  cerebri  internae)  (Fig.  647),  are  two  in  number.  Each  is 
formed  by  the  unton  of  two  veins,  the  vena  corporis  striati,  and  the  choroid  vein,  on 
either  side.  The  velar  veins  run  backward,  parallel  with  one  another,  between 
the  layers  of  the  velum,  and  in  the  region  of  the  epiphysis  unite  to  form  one 
vein,  the  vena  magna  Galeni  (v.  cerebri  magna),  which  passes  out  of  the  brain  at 
the  great  transverse  fissure,  between  the  posterior  extremity,  or  splenium,  of  the 
callosum  and  the  quadrigemina,  to  enter  the  tentorial  sinus.  The  two  velar  veins 
receive  tributaries  from  the  callosal  region,  from  a  portion  of  the  occipital  lobe,  and 
just  before  their  union  each  vein  receives  the  basilar  vein.  The  vena  magna 
Galeni  receives  the  vermian  vein  from  the  superficial  cerebellar  veins. 

The  Vena  Corporis  Striati  on  each  side  commences  in  the  groove  between  the 
corpus  striatum  and  optic  thalamus,  receives  numerous  veins  from  both  of  these 
parts,  and  unites  behind  the  fornicolumn  with  the  choroid  vein  to  form  one  of  the 
velar  veins. 

The  Choroid  Vein  (v.  choroidea)  originates  in  the  extreme  end  of  the  medi- 
cornu  of  the  lateral  ventricle  and  runs  along  the  whole  length  of  the  outer  border  of 
the  paraplexus,  receiving  veins  from  the  hippocampus,  the  fornix,  and  callosum, 
and  unites,  at  the  anterior  extremity  of  the  paraplexus,  with  the  vein  of  the  corpus 
striatum  to  form  the  velar  vein  of  that  side. 

The  Basilar  Vein  (v.  basalis)  commences  at  the  preperforatum  at  the  base  of 
the  brain  by  the  union  of  a  small  precerebral  vein,  which  courses  backward 
between  the  frontal  lobes  of  the  cerebrum,  with  the  deep  sylvian  vein,  which 


736  THE  BLOOD-VASCULAR  8Y8TEM 

descends  through  the  lower  part  of  the  sylvian  fissure  and  receives  veins  from 
the  insula.  It  passes  backward  over  the  crus,  receiving  the  inferior  striate  vein 
from  the  corpus  striatum,  intercrural  veins  from  the  intercrural  space,  ventricular 
veins  from  the  medicornu  of  the  lateral  ventricles,  and  tributaries  from  the  uncinate 
gyre,  and  enters  the  vein  of  Galen  just  before  its  junction  with  the  vein  of  the 
opposite  side.  » 

The  Superficial  Cerebellar  Veins  (Fig.  645)  occupy  the  surface  of  the  cerebellum, 
and  are  disposed  in  two  sets,  supercerebellar  or  superior,  and  subcerebellar  or  inferior. 

The  Supercerebellar  or  Superior  Superficial  Cerebellar  Veins  (w.  supercerebellares, 
vv.  cerebelli  superiores]  pass  partly  forward  and  inward ,  across  the  superior  vermis 
(prevermis) ,  to  terminate  in  lateral  branches  which  pass  partly  to  the  tentorial 
sinus  and  partly  outward  to  the  lateral  and  superpetrosal  sinuses. 

The  Subcerebellar  or  Inferior  Superficial  Cerebellar  Veins  (w.  subcerebellares,  vv. 
cerebelli  inferiores) ,  of  large  size,  terminate  in  the  lateral,  subpetrosal,  and  occipital 
sinuses. 

The  Deep  Cerebellar  Veins  bring  blood  from  the  interior  of  the  cerebellum  to 
the  superficial  veins. 

Veins  of  the  Pons. — Veins  come  from  the  depth  of  the  pons,  the  deep  veins, 
and  empty  into  a  plexus  of  superficial  veins.  From  this  superficial  venous  plexus 
a  superior  vein  passes  to  the  basilar  vein,  and  an  inferior  vein  either  into  a  cerebellar 
vein  or  into  the  superpetrosal  sinus. 

Veins  of  the  Oblongata. — Veins  pass  from  the  depth  of  the  oblongata  and  end 
in  a  plexus  on  the  surface.  From  this  plexus  comes  a  ventro-median  vein,  which 
is  a  prolongation  of  a  like  vein  of  the  spinal  cord — a  dorso-median  vein  corre- 
sponding to  a  like  vein  of  the  cord — and  small  branches  which  pass  with  the  roots 
of  the  glosso-pharyngeal,  vagus,  accessory,  and  hypoglossal  nerves,  and  empty 
into  the  occipital  and  the  subpetrosal  sinuses. 

The  peri  vascular  lymph-spaces  are  especially  found  in  connection  with  the  vessels  of  the  brain. 
These  vessels  are  enclosed  in  a  sheath,  which  acts  as  a  lymphatic  channel,  through  which  the 
lymph  is  carried  to  the  subarachnoid  and  subdural  spaces,  from  which  it  is  returned  into  the 
general  circulation. 

The  Sinuses  of  the  Dura  (Sinus  Durae  Matris)  (Figs.  451,  452,  453,  456,  457) 
Ophthalmic  Veins  and  Emissary  Veins. 

The  sinuses  of  the  dura  are  venous  channels  formed  by  a  separation  of  the  two 
layers  of  this  membrane,  the  outer  coat  consisting  of  fibrous  tissue,  the  inner  coat 
of  an  endothelial  layer  continuous  with  the  lining  membrane  of  the  veins.  The 
thick  walls  of  a  sinus  resist  intracranial  pressure.1  They  are  divided  into  two 
sets:  (1)  those  situated  at  the  upper  and  back  part  of  the  skull;  (2)  those  at  the 
base  of  the  skull.  The  former  are — the 

Longitudinal  or  Superior  Longitudinal  Sinus.  Tentorial  or  Straight  Sinus. 

Falcial  or  Inferior  Longitudinal  Sinus.  Lateral  Sinuses. 

Occipital  Sinus. 

The  Longitudinal  or  Superior  Longitudinal  Sinus  (sinus  longitudinalis,  sinus 
sagiUalis  superior)  (Figs.  451,  452,  and  453)  occupies  the  attached  margin  of  the 
falx.  Commencing  at  the  foramen  caecum,  through  which,  in  the  child,  it  constantly 
communicates  by  a  small  branch  with  the  veins  of  the  nasal  fossae,  it  runs  from 
before  backward,  grooving  the  inner  surface  of  the  frontal,  the  adjacent  margins 
of  the  two  parietal,  and  the  superior  division  of  the  crucial  ridge  of  the  occipital 
bone,  and  terminates  by  opening  into  the  torcular.  The  sinus  is  triangular  on 
transverse  section,  is  narrow  in  front,  and  gradually  increases  in  size  as  it  passes 
backward.  On  examining  its  inner  surface  it  presents  the  internal  openings  of  the 
supercerebral  veins,  which  run,  for  the  most  part,  from  behind  forward,  and  open 

i  A.  W.  Hughes. 


THE  SINUSES  OF  THE  DURA 


737 


chiefly  at  the  back  part  of  the  sinus,  their  orifices  being  concealed  by  fibrous 
folds;  numerous  fibrous  bands,  chordae  Willisii  (Fig.  453),  are  also  seen  extend- 
ing transversely  across  the  inferior  angle  of  the  sinus;  and  some  small,  white, 
projecting  bodies,  the  glandulae  Pacchioni  (granulationes  arachnoidales) .  This 
sinus  communicates  by  numerous  small  apertures  with  spaces  in  the  dura 


LONGITUDINAL 
SINUS 


ORIAL 
SINUS 


FIG.  451. — Coronal  section  of  the  skull  to  show  the  situations  and  shapes  of  the  chief  sinuses. 

(Poirier  and  Charpy.). 

known  as  lacunae  laterales  or  parasinoidal  spaces  (Fig.  453).  The  arachnoid  villi 
project  into  these  spaces.  This  sinus  receives  the  supercerebral  veins,  numerous 
veins  from  the  diploe  and  dura,  the  outlets  of  the  parasinoidal  spaces,  and,  at  the 
posterior  extremity  of  the  sagittal  suture,  veins  from  the  pericranium,  which  pass 
through  the  parietal  foramina.  In  children  the  longitudinal  sinus  receives  a  twig 
from  the  nose  which  passes  through  the  foramen  caecum. 


Torcular. 


Foramen  caecum. 


FIG.  452.— Sagittal  section  of  skull,  showing  the  sinuses  of  the  dura. 

The  Torcular  or  the  Confluence  of  the  Sinuses  (Figs.  452  and  456)  is  the  dilated 
ctremity  of  the  longitudinal  sinus.    It  is  of  irregular  form,  and  is  lodged  on  one 

47 


738 


THE  BLOOD-VASCULAR  SYSTEM 


side  (generally  the  right)  of  the  internal  occipital  protuberance.  From  it  the 
lateral  sinus  of  the  side  to  which  it  is  deflected  is  derived.  It  receives  also  the 
blood  from  the  occipital  sinus. 

The  Falcial  or  Inferior  Longitudinal  Sinus  (sinus  falcialis,  sinus  sagittalis 
inferior)  (Fig.  452),  more  correctly  described  as  the  inferior  longitudinal  vein,  is 
contained  in  the  posterior  part  of  the  free  margin  of  thefalx.  It  is  of  a  cylindrical 
form,  increases  in  size  as  it  passes  backward,  and  terminates  in  the  tentorial 
sinus.  It  receives  several  veins  from  the  falx,  and  occasionally  a  few  from  the 
mesal  surface  of  the  hemispheres. 

The  Tentorial  or  Straight  Sinus  (sinus  tentorii,  sinus  rectus)  (Figs.  451  and  452) 
is  situated  at  the  line  of  junction  of  the  falx  with  the  tentorium.  It  is  triangular  in 
form,  increases  in  size  as  it  proceeds  backward,  and  runs  obliquely  downward  and 


LONGITUDINAL 
SINUS 


PARASINOIDAL 
SINUS 


FIG.  453. — Longitudinal  sinus  seen  from  above  after  removal  of  the  skull-cap.  The  chordae  Willisii  are 
clearly  visible.  The  parasinoidal  sinuses  are  also  well  shown.  Probes  passing  from  the  latter  to  the  longi- 
tudinal sinus  show  that  they  communicate.  (Poirier  and  Charpy.) 


backward  from  the  termination  of  the  falcial  sinus  to  the  lateral  sinus  of  the  oppo- 
site side  to  that  into  which  the  longitudinal  sinus  is  prolonged.  It  communicates 
by  a  cross-branch  with  the  torcular.  Besides  the  falcial  sinus,  it  receives  the  vena 
magna  Galeni  and  the  supercerebellar  veins.  A  few  transverse  bands  cross  its 
interior.  This  sinus  is  usually  considered  to  be  formed  by  the  union  of  the  great 
vein  of  Galen  and  the  falcial  sinus. 

The  Lateral  Sinus  (sinus  lateralis,  sinus  transversus)  (Figs.  451,  452,  456,  and 
457)  is  of  large  size.  There  are  two  lateral  sinuses  situated  in  the  attached  margin 
of  the  tentorium  throughout  most  of  its  extent.  They  commence  at  the  internal 
occipital  protuberance,  one,  generally  the  right,  being  the  direct  continuation  of  the 


THE  SINUSES  OF  THE  DURA  739 

longitudinal  sinus,  the  other  of  the  tentorial  sinus.  Each  passes  outward  and 
forward,  describing  a  slight  curve  with  its  convexity  upward,  to  the  base  of  the 
petrous  portion  of  the  temporal  bone,  then,  leaving  the  tentorium,  curves  down- 
ward and  inward  to  reach  the  jugular  foramen,  where  it  terminates  in  the  internal 
jugular  vein.  It  rests,  in  its  course,  upon  the  inner  surface  of  the  occipital,  the 
posterior  inferior  angle  of  the  parietal,  and  the  mastoid  portion  of  the  temporal 
bone,  and  on  the  occipital  again,  at  the  jugular  process,  just  before  its  termination. 
The  portion  of  the  sinus  resting  on  the  mastoid  process  of  the  temporal  and  the 
jugular  process  of  the  occipital  bone  is  not  covered  by  the  tentorium  and  is  often 
called  the  sigmoid  sinus  because  of  its  shape,  which  resembles  the  letter  S.  These 
sinuses  are  frequently  of  unequal  size,  that  formed  by  the  longitudinal  sinus  being 
the  larger,  and  they  increase  in  size  as  they  proceed  from  behind  forward.  The 
horizontal  portion  is  of  a  triangular  form,  the  curved  portion  semicylindrical. 
Their  inner  surface  is  smooth,  and  not  crossed  by  the  fibrous  bands  found  in  the 
other  sinuses.  The  lateral  sinuses  receive  the  blood  from  the  superpetrosal  sinuses 
at  the  base  of  the  petrous  portion  of  the  temporal  bone,  and  they  unite  with  the 
subpetrosal  sinus,  just  external  to  the  jugular  foramen,  to  form  the  internal  jugular 
vein  (Fig.  457).  They  communicate  with  the  veins  of  the  pericranium  by  means 
of  the  mastoid  and  posterior  condyloid  veins,  and  they  receive  some  of  the  subcere- 
bral  and  subcerebellar  veins,  some  veins  from  the  diploe,  and  often  veins  from 
the  internal  ear  (w.  auditivae  internae),  which  come  out  of  the  internal  auditory 
meatus.  The  petro-squamous  sinus,  when  present,  runs  backward  along  the  junc- 
tion of  the  petrous  and  squamous  portions  of  the  temporal  bone,  and  opens  into  the 
lateral  sinus. 

Surgical  Anatomy. — The  lateral  sinus  may,  as  a  result  of  middle-ear  disease,  be  attacked  by 
suppurative  inflammation,  which  leads  to  blocking  (septic  thrombophlebitis).  In  such  a  case 
the  surgeon  will  be  obliged  to  open  the  sinus  to  remove  infected  clot  and  tie  the  internal  jugular 
vein  to  intercept  thrombi.  The  line  overlying  the  sinus  is  as  follows:  Draw  a  line  horizontally 
outward  from  the  occipital  protuberance  to  a  point  one  inch  posterior  to  a  vertical  line  drawn 
through  the  external  auditory  meatus  and  from  this  point  drop  a  second  line  to  the  mastoid 
process. 

The  Occipital  Sinus  (sinus  occipitalis)  (Fig.  452)  is  the  smallest  of  the  cranial 
sinuses.  There  is  often  but  a  single  occipital  sinus,  but  occasionally  there  are 
two.  It  is  situated  in  the  attached  margin  of  the  falcula.  It  commences  by  several 
small  veins  around  the  margin  of  the  foramen  magnum,  one  of  which  joins  the 
termination  of  the  lateral  sinus;  it  communicates  with  the  posterior  spinal  veins 
and  terminates  in  the  torcular. 

The  sinuses  at  the  base  of  the  skull  are — the 

Cavernous  Sinuses.  Superpetrosal  Sinuses  or  Superior  Petrosal  Sinuses. 

Sphenoparietal  Sinuses.  Subpetrosal  Sinuses  or  Inferior  Petrosal  Sinuses. 

Circular  Sinus.  Transverse  Sinus. 

The  Cavernous  Sinus  (sinus  cavernosus)  (Figs.  456  and  457)  is  named  from 
presenting  a  reticulated  structure,  due  to  being  traversed  by  numerous  interlacing 
filaments  (Fig.  454).  There  are  two  cavernous  sinuses,  of  irregular  form,  larger 
behind  than  in  front,  and  placed  one  on  each  side  of  the  sella  turcica,  extending 
from  the  sphenoidal  fissure  to  the  apex  of  the  petrous  portion  of  the  temporal  bone. 
Each  receives  anteriorly  the  ophthalmic  vein  through  the  sphenoidal  fissure,  and 
opens  behind  into  the  petrosal  sinuses.  On  the  inner  wall  of  each  sinus  is  found 
the  internal  carotid  artery,  accompanied  by  filaments  of  the  carotid  plexus  and 
by  the  abducent  nerve;  and  on  its  outer  wall,  the  oculomotor,  trochlear,  and 
ophthalmic  division  of  the  trigeminal  nerve  (Fig.  454).  These  parts  are  separated 


740 


THE  BLOOD-VASCULAR  SYSTEM 


from  the  blood  flowing  along  the  sinus  by  the  lining  membrane,  which  is  continuous 
with  the  inner  coat  of  the  veins.  The  cavernous  sinuses  receive  some  of  the  cerebral 
veins,  and  also  the  sphenoparietal  sinuses.  They  communicate  with  the  lateral 
sinuses  by  means  of  the  super-  and  subpetrosal  sinuses,  and  with  the  facial  veins 
through  the  ophthalmic  veins.  They  also  communicate  with  each  other  by  means 
of  the  circular  sinus. 


CAVERNOUS 


TRANSVERSE 
SINUS 


OCULOMOTOR 
NERVE 

.TROCHLEAR 
NERVE 

ABDUCENT 
NERVE 

OPHTHALMIC 
DIVISION  OF 
TRIGEMINAL  NERVE 

SUPERIOR  MAXIL- 
LARY DIVISION  OF 
TRIGEMINAL  NERVE 


FIG.  454. — Frontal  section  through  the  right  cavernous  sinus.     (Spalteholz.) 

Surgical  Anatomy.— An  arterio-venous  communication  may  be  established  between  the 
cavernous  sinus  and  the  carotid  artery,  as  it  lies  in  it,  giving  rise  to  a  pulsating  tumor  in  the 
orbit.  Such  a  communication  may  be  the  result  of  injury,  such  as  a  bullet  wound,  a  stab,  or 
a  blow  or  fall  sufficiently  severe  to  cause  a  fracture  of  the  base  of  the  skull  in  this  situation, 
or  it  may  occur  from  the  rupture  of  an  aneurism  or  a  diseased  condition  of  the  internal 
carotid  artery.  The  disease  begins  with  sudden  noise  and  pain  in  the  head,  followed  by 
exophthalmos,  swelling  and  "congestion  of  the  lids  and  conjunctive.  A  pulsating  tumor 
develops  at  the  margin  of  the  orbit,  with  thrill  and  the  characteristic  bruit;  accompanying 
these  symptoms  there  may  be  impairment  of  sight,  paralysis  of  the  iris  and  orbital  muscles, 
and  pain  of  varying  intensity.  In  some  cases  the  opposite  orbit  becomes  affected  by  the  passage 
of  the  arterial  blood  into  the  opposite  sinus  by  means  of  the  circular  sinus.  Or  the  arterial 
blood  may  find  its  way  through  the  emissary  veins  into  the  pterygoid  plexus,  and  thence  into  the 
veins  of  the  face.  Pulsating  tumors  of  the  orbit  may  also  be  due  to  traumatic  aneurism  of 
one  of  the  orbital  arteries,  and  symptoms  resembling  those  of  pulsating  tumor  may  be  produced 
by  pressure  on  the  ophthalmic  vein,  as  it  enters  the  sinus,  by  an  aneurism  of  the  internal 
carotid  artery. 

The  Sphenoparietal  Sinus  or  Sinus  Alae  Parvae  (sinus  sphenoparietalis}.— 
Each  of  these  sinuses  is  lodged  in  the  dura  on  the  under  surface  of  the  lesser  wing  of 
the  sphenoid  bone.  It  takes  origin  from  one  of  the  medidural  veins,  usually 
receives  blood  from  the  diploe  of  the  skull,  passes  inward,  and  ends  in  the  anterior 
part  of  the  cavernous  sinus. 

The  Ophthalmic  Veins  are  two  in  number,  superior  and  inferior. 

The  superior  ophthalmic  vein  (v.  ophthalmica  superior}  (Fig.  455)  begins  as  the 
naso-frontal  vein  (v.  nasofrontalis) ,  at  the  inner  angle  of  the  orbit,  which  communi- 
cates with  the  angular  vein.  It  joins  the  angular  vein  with  the  cavernous  sinus; 
it  pursues  the  same  course  as  the  ophthalmic  artery,  and  receives  tributaries  corre- 
sponding to  the  branches  derived  from  that  vessel.  Forming  a  short  single  trunk, 
it  passes  through  the  inner  extremity  of  the  sphenoidal  fissure,  and  terminates  in 
the  cavernous  sinus.  It  anastomoses  with  the  inferior  ophthalmic  vein  and  receives 
lachrymal,  anterior,  and  posterior  ethmoidal  and  muscular  branches,  and  veins 
of  the  eyelids  and  of  the  bulbus  oculi. 


THE  SINUSES  OF  THE  DURA 


741 


The  inferior  ophthalmic  vein  (v.  ophthalmica  inferior)  (Fig.  455)  arises  in  the  veins 
of  the  eyelids  and  lachrymal  sac,  receives  the  veins  from  the  floor  of  the  orbit,  and 


CAVERNOUS. 
SINUS 


INFERIOR 
OPHTHALMIC 


FIG.  455  — Veins  of  the  orbit.     (Poirier  and  Charpy.) 


from  the  portion  of  the  nasal  fossa  supplied  by  the  anterior  and  posterior  ethmoidal 
arteries.  It  either  passes  out  of  the  orbit  through  the  spheno-m axillary  fissure  to 
join  the  pterygoid  plexus  of  veins,  or  else,  passing  backward  through  the  sphenoidal 


Opening  of  mastoid 
vein. 


-  Torculur 
FIG.  456. — The  sinuses  at  the  base  of  the  skull. 


fissure,  it  enters  the  cavernous  sinus,  either  by  a  separate  opening,  or,  more  fre- 
quently, in  common  with  the  superior  ophthalmic  vein.     It  receives  muscular 


742 


THE  BLOOD-  VASCULAR  SYSTEM 


tributaries  and  veins  of   the  bulbus  oculi,  and    anastomoses  with   the  superior 
ophthalmic  vein. 

The  Circular  Sinus  (sinus  circularis)  (Figs.  454  and  456)  is  formed  by  two  trans- 
verse vessels,  the  anterior  and  posterior  intercavernous  sinuses  (sinus  intercavernous 
anterior  and  sinus  intercavernous  posterior),  which  connect  together  the  two 
cavernous  sinuses;  the  one  passing  in  front  and  the  other  behind  the  hypophysis, 
and  thus  forming  with  the  cavernous  sinuses  a  venous  circle  around  that  body. 
The  anterior  one  is  usually  the  larger  of  the  two,  and  one  or  other  is  occasionally 
found  to  be  absent. 

Falx 


Optic  nerve 
Int.  carotid  artery 


Oculomotor  nerve 


— Dorsum  sellse 


Glosso-pharyngeal, 
vagus,  and  acces- 
sory nerves 


Lateral  sinus 
FIG.  457. — Relation  of  nerves  to  sinuses  in  jugular  foramen.     (Henle.) 

The  Superpetrosal  or  Superior  Petrosal  Sinus  (sinus  super petrosus,  sinus  petro- 
sus  superior)  (Figs.  452  and  456)  is  situated  along  the  superior  border  of  the  petrous 
portion  of  the  temporal  bone,  in  the  front  part  of  the  attached  margin  of  the 
tentorium.  It  is  small  and  narrow,  and  connects  together  the  cavernous  and 
lateral  sinuses  at  each  side.  It  receives  some  cerebellar  and  subcerebral  veins,  and 
usually  veins  from  the  tympanic  cavity. 

The  Subpetrosal  or  Inferior  Petrosal  Sinus  (sinus  subpetrosus,  sinus  petrosus 
inferior)  (Figs.  452  and  456)  is  situated  in  the  groove  formed  by  the  junction  of  the 
posterior  border  of  the  petrous  portion  of  the  temporal  with  the  basilar  process  of 
the  occipital  bone.  It  commences  in  front  at  the  termination  of  the  cavernous 
sinus,  and  behind  joins  the  lateral  sinus  after  it  has  passed  through  the  jugular 
foramen;  the  junction  of  these  two  sinuses  forming  the  commencement  of  the 
internal  jugular  vein.  The  subpetrosal  sinus  receives  a  vein  from  the  internal 
ear  and  also  veins  from  the  medulla,  pons,  and  under  surface  of  the  cerebellum. 

The  junction  of  the  two  sinuses  takes  place  at  the  lower  border  of,  or  just  external 
to,  the  jugular  foramen.  The  exact  relation  of  the  parts  to  one  another  in  the 


THE  SINUSES  OF  THE  DURA  743 

foramen  is  as  follows:  The  subpetrosal  sinus  is  in  front,  with  the  dural  branch  of 
the  ascending  pharyngeal  artery,  and  is  directed  obliquely  downward  and  back- 
ward; the  lateral  sinus  is  situated  at  the  back  part  of  the  foramen  with  a  dural 
branch  of  the  occipital  artery,  and  between  the  two  are  the  glosso-pharyngeal, 
vagus,  and  accessory  nerves  (Fig.  457).  These  three  sets  of  structures  are  divided 
from  each  other  by  two  processes  of  fibrous  tissue.  The  junction  of  the  sinuses 
takes  place  superficial  to  the  nerves,  so  that  these  latter  lie  a  little  internal  to  the 
venous  channels  in  the  foramen  (Fig.  457).  These  sinuses  are  semicylindrical 
in  form. 

The  Transverse  or  Basilar  Sinus  (plexus  basilaris}  (Figs.  456  and  457)  con- 
sists of  several  interlacing  veins  between  the  layers  of  the  dura  over  the  basilar 
process  of  the  occipital  bone,  which  serve  to  connect  the  two  subpetrosal  sinuses. 
With  them  the  anterior  spinal  veins  communicate. 

Emissary  Veins  (emissaria). — The  emissary  veins  are  vessels  which  pass 
through  apertures  in  the  cranial  wall  and  establish  communications  between  the 
sinuses  inside  the  skull  and  the  diploic  veins  in  the  diploe,  and  the  veins  external 
to  the  skull.  Some  of  these  are  always  present,  others  only  occasionally  so. 
They  vary  much  in  size  in  different  individuals.  The  principal  emissary  veins 
are  the  following:  1.  A  vein,  almost  always  present,  which  passes  through  the 
mastoid  foramen  (emissarium  mastoideum}  and  connects  the  lateral  sinus  with 
the  posterior  auricular  or  with  an  occipital  vein.  2.  A  constant  vein  which 
passes  through  the  parietal  foramen  (emissarium  parietale)  and  connects  the 
longitudinal  sinus  with  the  veins  of  the  scalp.  3.  A  plexus  of  minute  veins  which 
pass  through  the  anterior  condyloid  foramen  (emissarium  condyloideum)  and 
connect  the  occipital  sinus  with  the  vertebral  vein  and  deep  veins  of  the  neck. 
4.  An  inconstant  vein  which  passes  through  the  posterior  condyloid  foramen  and 
connects  the  lateral  sinus  with  the  deep  veins  of  the  neck.  5.  One  or  two  veins 
of  considerable  size  which  pass  through  the  foramen  ovale  and  connect  the  cav- 
ernous sinus  with  the  pterygoid  and  pharyngeal  plexuses.  6.  Two  or  three  small 
veins  which  pass  through  the  foramen  lacerum  medium  and  connect  the  cavernous 
sinus  with  the  pterygoid  and  pharyngeal  plexuses.  7.  There  is  sometimes  a  small 
vein  connecting  the  same  parts  and  passing  through  the  inconstant  foramen  of 
Vesalius  at  the  root  of  the  pterygoid  process  of  the  sphenoid  bone.  8.  A  plexus  of 
veins  passing  through  the  carotid  canal  and  connecting  the  cavernous  sinus  with 
the  internal  jugular  vein.  9.  A  small  vein  (emissarivm  occipitale)  usually  con- 
nects the  occipital  vein  with  the  lateral  sinus  or  the  torcular  and  the  occipital 
diploic  vein. 

Surgical  Anatomy. — These  emissary  veins  are  of  great  importance  in  surgery.  In  addition 
to  them  there  are,  however,  other  communications  between  the  intra-  and  extra-cranial  circula- 
tion, as,  for  instance,  the  communication  of  the  angular  and  supra-orbital  veins  with  the  ophthal- 
mic vein  at  the  inner  angle  of  the  orbit,  and  the  communication  of  the  veins  of  the  scalp  with 
the  diploic  veins.  Through  these  communications  inflammatory  processes  commencing  on  the 
outside  of  the  skull  may  travel  inward,  leading  to  osteo-phlebitis  of  the  diploe  and  inflammation 
of  the  membranes  of  the  brain.  To  this  in  former  days  was  to  be  attributed  one  of  the  principal 
dangers  of  scalp  wounds  and  other  injuries  of  the  scalp. 

By  means  of  these  emissary  veins  blood  may  be  abstracted  almost  directly  from  the  intra- 
cranial  circulation.  For  instance,  leeches  applied  behind  the  ear  abstract  blood  almost  directly 
from  the  lateral  sinus  by  means  of  the  vein  passing  through  the  mastoid  foramen.  Again, 
epistaxis  in  children  will  frequently  relieve  severe  headache,  the  blood  which  flows  from  the  nose 
being  derived  from  the  longitudinal  sinus  by  means  of  the  vein  which  passes  through  the  foramen 
caecum,  which  is  another  communication  between  the  intracranial  and  extracranial  circulation 
constantly  found  in  children. 


744 


THE   BLOOD -VASCULAR    SYSTEM 


VEINS  OF  THE  UPPER  EXTREMITY  AND  THORAX. 

The  veins  of  the  Upper  Extremity  are  divided  into  two  sets,  superficial  and 
deep. 

The  Superficial  Veins  are  placed  immediately  beneath  the  integument  between 
the  layers  of  superficial  fascia. 


POSTERIOR 
ULNAR' 


SUPERFICIAL 
RADIAL 


DORSAL 
VENOUS  ARCH 


FIG.  458.— The  veins  on  the  dorsum  of  the  hand.     (Bourgery.) 

The  Deep  Veins  accompany  the  arteries,  and  constitute  the  venae  comites  of 
those  vessels. 

Both  sets  of  vessels  are  provided  with  valves,  which  are  more  numerous  in  the 
deep  than  in  the  superficial  veins. 


THE  SUPERFICIAL     VEINS    OF    THE    UPPER    EXTREMITY    745 

The  Superficial  Veins  of  the  Upper  Extremity  (Fig.  459). 
The  superficial  veins  of  the  upper  extremity  are — the 

Superficial  Veins  of  the  Hand.  Median. 

Anterior  Ulnar.  Median  Cephalic. 

Posterior  Ulnar.  Median  Basilic. 

Common  Ulnar.  Basilic. 

Radial.  Cephalic. 

The  Superficial  Veins  of  the  Hand  and  Fingers  (Figs.  458  and  459)  are 
principally  situated  on  the  dorsal  surface.  These  dorsal  veins  begin  in  each  finger 
as  a  venous  plexus,  in  which  are  distinct  veins  running  in  a  longitudinal  direction, 
and  called  dorsal  digital  veins  (w.  digitales  dorsales  propriae) .  The  dorsal  digital 
veins  terminate  over  the  first  phalanges,  in  the  venous  arches  of  the  fingers  (arcus 
venosi  digitales}.  From  these  arches  take  origin  the  four  dorsal  interosseous  or 
the  interdigital  veins  (vv.  metacarpeae  dorsales).  These  veins  form  the  dorsal  venous 
plexus  of  the  hand  (rete  venosum  dor  sale  manus).  This  plexus  lies  in  a  line  with  the 
lower  ends  of  the  shafts  of  the  metacarpal  bones.  It  receives  the  dorsal  inter- 
osseous  veins,  the  radial  digital  vein  of  the  index  finger,  and  numerous  superficial 
veins  from  the  back  of  the  hand.  It  gives  origin  to  the  superficial  radial  vein  and 
the  posterior  ulnar  vein.  The  superficial  veins  of  the  palmar  surface  are  of  less 
diameter  than  the  dorsal  veins.  They  arise  from  each  of  the  phalanges  by  a 
plexus  (vv.  digitales  volares  propriae).  Vessels  at  the  edges  of  the  fingers  take  most 
of  the  blood  to  the  dorsal  veins.  There  are  also  veins  in  the  finger  webs  (w.  inter- 
capitulares) ,  which  take  blood  from  the  palm  to  the  dorsum.  A  superficial  plexus, 
the  palmar  plexus,  lies  upon  the  palmar  fascia,  the  fascia  of  the  thenar  eminence, 
and  the  fascia  of  the  hypo  thenar  eminence. 

The  Anterior  Ulnar  Vein  (v.  ulnaris  anterior)  (Fig.  459)  commences  on  the 
anterior  surface  of  the  ulnar  side  of  the  hand  and  wrist,  and  ascends  along  the 
anterior  surface  of  the  ulnar  side  of  the  forearm  to  the  bend  of  the  elbow,  where 
it  joins  with  the  posterior  ulnar  vein  to  form  the  common  ulnar.  Occasionally  it 
opens  separately  into  the  median  basilic  vein.  It  communicates  with  branches 
of  the  median  vein  in  front  and  with  the  posterior  ulnar  behind. 

The  Posterior  or  Dorsal  Ulnar  Vein  (v.  ulnaris  posterior)  (Fig.  458)  commences 
on  the  posterior  surface  of  the  ulnar  side  of  the  wrist.  It  runs  on  the  posterior 
surface  of  the  ulnar  side  of  the  forearm,  and  just  below  the  elbow  unites  with 
the  anterior  ulnar  vein  to  form  the  common  ulnar,  or  else  joins  the  median 
basilic  and  helps  to  form  the  basilic.  It  communicates  with  the  deep  veins 
of  the  palm  by  a  branch  which  emerges  from  beneath  the  Abductor  minimi  digiti 
muscle. 

The  Common  Ulnar  Vein  (v.  ulnaris  communis)  (Fig.  459)  is  a  short  trunk 
which  is  not  constant.  When  it  exists  it  is  formed  by  the  junction  of  the  two 
preceding  veins,  and,  passing  upward  and  outward,  joins  the  median  basilic  to 
form  the  basilic  vein.  When  it  does  not  exist  the  anterior  and  posterior  ulnar 
veins  open  separately  into  the  median  basilic  vein. 

The  Radial  Vein  '(v.  radialis)  (Figs.  459  and  460)  commences  upon  the  dorsal 
surface  of  the  wrist,  communicating  with  the  deep  veins  of  the  palm  by  a  branch 
which  passes  through  the  first  interosseous  space.  The  radial  vein  soon  forms  a 
large  vessel,  which  ascends  along  the  radial  side  of  the  forearm  and  receives 
numerous  veins  from  both  its  surfaces.  At  the  bend  of  the  elbow  it  unites  with 
the  median  cephalic  to  form  the  cephalic  vein.  Spalteholz  considers  the  ulnar 
vein  as  a  portion  of  the  basilic  and  the  radial  vein  a  portion  of  the  cephalic. 

The  Median  Vein  (v.  mediana  cubiti)  (Fig.  459)  ascends  on  the  front  of  the 
forearm,  and  communicates  with  the  anterior  ulnar  and  radial  veins.  At  the  bend 


746 


THE   BLOOD -VASCULAR    SYSTEM 


Median  cephalic. 

External 
cutaneous  nerve. 


FIG.  459. — The  superficial  veins  of  the  flexor  aspect 
of  the  upper  extremity. 


of  the  elbow  it  receives  a  branch  of 
communication  from  the  deep  veins, 
the  deep  median  vein,  and  divides  into 
two  branches,  the  median  cephalic  and 
median  basilic,  which  diverge  from  each 
other  as  they  ascend. 

The  Median  Cephalic  (v.  mediana 
cephalica)(F'ig.  459),  usually  the  smaller 
of  the  two,  passes  outward  in  the  groove 
between  the  Supinator  longus  and  Bi- 
ceps muscles,  and  joins  with  the  radial 
to  form  the  cephalic  vein.  The  branches 
of  the  external  cutaneous  nerve  pass 
beneath  this  vessel. 

The  Median  Basilic  Vein  (v.  mediana 
basilica)  (Fig.  459)  passes  obliquely  in- 
ward, in  the  groove  between  the  Biceps 
and  Pronator  radii  teres  muscles,  and 
joins  the  common  ulnar  to  form  the 
basilic.  This  vein  passes  in  front  of 
the  brachial  artery,  from  which  it  is 
separated  by  a  fibrous  expansion,  the 
bicipital  fascia,  which  is  given  off  from 
the  tendon  of  the  Biceps  to  the  fascia 
covering  the  Flexor  muscles  of  the  fore- 
arm. Filaments  of  the  internal  cuta- 
neous nerve  pass  in  front  as  well  as 
behind  this  vessel.1 

Venesection  is  usually  performed  at  the 
bend  of  the  elbow,  and  as  a  matter  of  practice 
the  largest  vein  in  this  situation  is  commonly 
selected.  This  is  usually  the  median  basilic, 
and  there  are  anatomical  advantages  and  dis- 
advantages in  selecting  this  vein.  The  advan- 
tages are,  that  in  addition  to  its  being  the 
largest,  and  therefore  yielding  a  greater  supply 
of  blood,  it  is  the  least  movable  and  can  be 
easily  steadied  on  the  bicipital  fascia  on  which 
it  rests.  The  disadvantages  are,  that  it  is  in 
close  relationship  with  the  brachial  artery, 
separated  only  by  the  bicipital  fascia;  and 
formerly,  when  venesection  was  frequently 
practised,  arterio- venous  aneurism  was  no 
uncommon  result  of  this  practice.  Another 
disadvantage  is.  that  the  median  basilic  is 
crossed  by  some  of  the  branches  of  the  internal 
cutaneous  nerve,  and  these  may  be  divided 
in  the  operation,  giving  rise  to  "  traumatic 
neuralgia  of  extreme  intensity"  (Tillaux). 

The  Basilic  Vein  (v.  basilica)  (Figs. 
460  and  462)  is  of  considerable  size  and 
is  formed  by  the  coalescence  of  the 
common  ulnar  vein  with  the  median 


1  Cruveilhier  says:  "Numerous  varieties  are  observed  in  the  disposition  of  the  veins  of  the  elbow;  some- 
times the  common  median  vein  is  wanting;  but  in  those  cases  its  two  branches  are  furnished  by  the  radial  vein, 
and  the  cephalic  is  almost  always  in  a  rudimentary  condition.  In  other  cases  only  two  veins  are  found  at  the 
bend  of  the  elbow,  the  radial  and  ulnar,  which  are  continuous,  without  any  demarcation,  with  the  cephalic  and 
basilic." — ED.  of  15th  English  edition. 


THE   DEEP    VEINS    OF    THE    UPPER   EXTREMITY  747 

basilic.  It  passes  upward  along  the  inner  side  of  the  Biceps  muscle  and  pierces 
the  deep  fascia  a  little  below  the  middle  of  the  arm.  The  opening  in  the  fascia 
is  known  as  the  semilunar  hiatus  (hiatus  semilunaris) .  The  vein  ascends  in  the 
course  of  the  brachial  artery  to  the  lower  border  of  the  tendons  of  the  Latissimus 
dorsi  and  Teres  major  muscles,  and  is  continued  onward  as  the  axillary  vein. 

The  Cephalic  Vein  (v.  cephalica)  (Fig.  459)  is  formed  by  the  union  of  the 
median  cephalic  and  the  radial  veins.  It  courses  along  the  outer  border  of  the 
Biceps  muscle,  lying  in  the  same  groove  with  the  upper  external  cutaneous  branch 
of  the  musculo-spiral  nerve,  to  the  upper  third  of  the  arm;  it  then  passes  in  the 
interval  between  the  Pectoralis  major  and  Deltoid  muscles,  lying  in  the  same 
groove  with  the  descending  or  humeral  branch  of  the  acromial-thoracic  artery. 
It  pierces  the  costo-coracoid  membrane,  and,  crossing  the  axillary  artery,  ter- 
minates in  the  axillary  vein  just  below  the  clavicle.  This  vein  is  occasionally 
connected  with  the  external  jugular  or  subclavian  by  a  branch  which  passes 
from  it  upward  in  front  of  the  clavicle. 

The  Deep  Veins  of  the  Upper  Extremity  (Fig.  460). 

The  deep  veins  of  the  upper  extremity  follow  the  course  of  the  arteries,  forming 
their  venae  comites  or  companion  veins.  Usually  there  is  one  vein  lying  on  each 
side  of  the  corresponding  artery,  and  they  are  connected  at  intervals  by  short 
transverse  branches. 

There  are  two  digital  veins  accompanying  each  artery  along  the  sides  of  the 
fingers:  these,  uniting  at  their  base,  pass  along  the  interosseous  spaces  in  the 
palm,  and  terminate  in  the  two  venae  comites  which  accompany  the  superficial 
palmar  arch.  Branches  from  these  vessels  on  the  radial  side  of  the  hand  accom- 
pany the  superficialis  volae,  and  on  the  ulnar  side  terminate  in  the  deep  ulnar 
veins  (Fig.  460).  The  deep  ulnar  veins,  as  they  pass  in  front  of  the  wrist,  com- 
municate with  the  interosseous  and  superficial  veins,  and  at  the  elbow  unite  with 
the  deep  radial  veins  to  form  the  venae  comites  of  the  brachial  artery.  The  vense 
comites  of  the  brachial  communicate  by  numerous  transverse  branches,  which 
cross  over  or  under  the  artery. 

The  Interosseous  Veins  (Fig.  460)  accompany  the  anterior  and  posterior 
interosseous  arteries.  The  anterior  interosseous  veins  commence  in  front  of  the 
wrist,  where  they  communicate  with  the  deep  radial  and  ulnar  veins;  at  the  upper 
part  of  the  forearm  they  receive  the  posterior  interosseous  veins,  and  terminate  in 
the  venae  comites  of  the  ulnar  artery. 

The  Deep  Palmar  Veins  accompany  the  deep  palmar  arch,  being  formed  by 
tributaries  which  accompany  the  ramifications  of  that  vessel.  At«the  wrist  they 
receive  a  dorsal  and  a  palmar  tributary  from  the  thumb.  The  deep  palmar  veins 
communicate  with  the  deep  ulnar  veins  at  the  inner  side  of  the  hand,  and  on  the 
outer  side  terminate  in  the  deep  radial  veins  (Fig.  460),  which  are  the  venae 
comites  of  the  radial  artery.  Accompanying  the  radial  artery  the  deep  radial 
veins  terminate  in  the  venae  comites  of  the  brachial  artery. 

The  Brachial  Veins  (vv.  brachiales)  (Fig.  460)  are  placed  one  on  each  side  of 
the  brachial  artery,  receiving  tributaries  corresponding  with  the  branches  given  off 
from  that  vessel;  at  the  lower  margin  of  the  Subscapularis  muscle  they  join  the 
axillary  vein. 

These  deep  veins  have  numerous  anastomoses,  not  only  with  each  other,  but 
also  with  the  superficial  veins.  'One  of  the  brachial  veins  empties  into  the 
axillary,  the  other,  usually  the  smaller,  generally  unites  with  the  basilic. 

The  Axillary  Vein  (v.  axillaris)  (Fig.  461)  is  of  large  she,  and  may  be  regarded 
as  the  continuation  upward  of  the  basilic  vein,  or  as  formed  by  the  fusion  of  a 
brachial  vein  with  the  basilic  vein.  If  the  first  view  is  accepted  a.  brachial  vein 
is  described  as  one  of  the  tributaries  of  the  axillary  vein.  The  axillary  vein  com- 


748 


THE   BLOOD-VASCULAR   SYSTEM 


mences  at  the  lower  border  of  the  tendons  of  the  Teres  major  and  Latissimus  dorsi 
muscles,  increases  in  size  as  it  ascends,  by  receiving  tributaries  corresponding  with 
the  branches  of  the  axillary  artery,  and  terminates  immediately  beneath  the  clavicle 
at  the  outer  border  of  the  first  rib,  where  it  becomes  the  subclavian  vein.  This 
vessel  is  covered  in  front  by  the  Pectoral  muscles  and  costocoracoid  membrane, 
and  lies  on  the  thoracic  side  of  the  axillary  artery,  which  it  partially  overlaps.  It 
receives  the  brachial  veins,  the  venae  comites  of  the  axillary  artery  except  the  cir- 
cumflex veins;  and  near  its  termination  the  cephalic  vein.  This  vein  is  provided 
with  a  pair  of  valves  opposite  the  lower  border  of  the  Subscapularis  muscle;  valves 
are  also  found  at  the  termination  of  the  cephalic  and  subscapular  veins.  The 
circumflex  veins  end  in  the  subscapular  or  one  of  the  brachial  veins. 

The  Long  Thoracic  Branch  (v.  thoracalis  lateralis)  (Fig.  462)  receives  the  thoracico- 
epigastric  vein  (v.  thoracoepigastrica),  which  comes  all  the  way  from  the  superficial 
epigastric  or  from  the  femoral  vein. 

The  Costo-axillary  Veins  (w.  costoaxillares)  (Fig.  462)  come  from  the  first  six 
intercostal  spaces  and  bring  blood  from  the  intercostal  veins  to  the  axillary. 


INTEROSSEOUS 
VEINS 


ULNAR  DEEP 
VEINS 


VENJE   COMITES 
'OF    BRACHIAL 
AR/TERV 


ANASTOMOSIS 
OF  RADIAL 
AND  ULNAR 


RADIAL  DEEP 
VEINS 


FIG.  460. — The  deep  veins  of  the  upper  extremity.     (Bourgery.) 


Surgical  Anatomy. — There  are  several  points  of  surgical  interest  in  connection  with  the 
axillary  vein.  Being  more  superficial,  larger,  and  slightly  overlapping  the  axillary  artery,  it  is 
more  liable  to  be  wounded  in  the  operation  of  extirpation  of  the  axillary  glands,  especially  as 
these  glands,  when  diseased,  are  apt  to  become  adherent  to  the  vessel.  When  wounded  there 
is  always  danger  of  air  being  drawn  into  its  interior,  and  death  resulting.  This  is  due  not  only 
to  the  fact  that  it  is  near  the  thorax,  and  therefore  liable  to  be  influenced  by  the  respiratory 
movements,  but  also  because  it  is  adherent  by  its  anterior  surface  to  the  costo-coracoid  membrane, 
and  therefore  if  wounded  is  likely  to  remain  patulous  and  favor  the  chance  of  air  being  sucked 
in.  This  adhesion  of  the  vein  to  the  fascia  prevents  its  collapsing,  and  therefore  favors  the 
furious  bleeding  which  takes  place  in  these  cases. 


THE   DEEP     VEINS    OF    THE    UPPER    EXTREMITY 


749 


To  avoid  wounding  the  axillary  vein  in  the  extirpation  of  glands  from  the  axilla  no  undue 
force  should  be  used  in  isolating  the  glands.  If  the  vein  is  found  to  be  so  embedded  in  the 
malignant  deposit  that  the  latter  cannot  be  removed  without  taking  away  a  part  of  the  vein, 
this  must  be  done,  the  vessel  having  been  first  ligated  above  and  below. 


AXILLARY 
ARTERY 
MUSCULO- 
CUTANEUS  NERVC 


-AXILLARY 


PECTORALIS 

MAJOR 

MUSCLE 


SUBCLAVIUS 
MUSCLE 


COSTO-AXILLARY 
LONG  THORACIC 

FIG.  461.— The  veins  of  the  right  axilla,  viewed  from  in  front.     (Spalteholz.) 

•  The  Subclavian  Vein  (v.  subclavia)  (Figs.  424  and  446),  the  continuation  of  the 
axillary,  extends  from  the  outer  border  of  the  first  rib  to  the  inner  end  of  the  clavicle, 
where  it  unites  with  the  internal  jugular  to  form  the  innominate  vein.  It  is  in 
relation,  in  front,  with  the  clavicle  and  Subclavius  muscle;  behind  and  above,  with 
the  subclavian  artery,  from  which  it 
is  separated  internally  by  the  Scal- 
enus  anticus  muscle  and  phrenic 
nerve.  Below,  it  rests  in  a  depres- 
sion on  the  first  rib  and  upon  the 
pleura.  Above,  it  is  covered  by  the 
cervical  fascia  and  integument. 

An  expansion  of  the  aponeurosis 
of  the  Subclavius  muscle  lies  upon 
the  vein  (Fig.  462). 

The  subclavian  vein  occasionally 
rises  in  the  neck  to  a  level  with  the 
third  part  of  the  subclavian  artery,  and  in  two  instances  has  been  seen  passing 
with  this  vessel  behind  the  Scalenus  anticus.  This  vessel  is  usually  provided 
with  valves  about  an  inch  from  its  termination  in  the  innominate,  just  external 
to  the  entrance  of  the  external  jugular  vein. 

Tributaries. — It  receives  the  external  and  anterior  jugular  veins  and  a  small 
branch  from  the  cephalic,  outside  the  Scalenus,  and  on  the  inner  side  of  that 
muscle  the  internal  jugular  vein.  At  the  angle  of  junction  with  the  internal 


The  aponeurotic  expansion  of  the  Subclavius 
(Poirier  and  Charpy.) 


FIG.  462 
muscle  over  the  subclavian  vein. 


750 


THE  BLOOD-  VASCULAR  SYSTEM 


jugular  the  left  subclavian  vein  receives  the  thoracic  duct  (Fig.  463),  while  the 
right  subclavian  vein  receives  the  right  lymphatic  duct. 

The  Innominate  or  Brachio-cephalic  Veins  (w.  anonymae]  (Fig.  464)  are 
two  large  trunks,  placed  one  on  each  side  of  the  root  of  the  neck,  and  formed  by 
the  union  of  the  internal  jugular  and  subclavian  veins  of  the  corresponding  side. 

The  Right  Innominate  Vein  (v.  anonyma  dextra)  is  a  short  vessel,  an  inch 
in  length,  which  commences  at  the  inner  end  of  the  clavicle,  and,  passing  almost 
vertically  downward,  joins  with  the  left  innominate  vein  just  below  the  cartilage 
of  the  first  rib,  close  to  the  right  border  of  the  sternum,  to  form  the  precava,  or 
superior  vena  cava.  It  lies  superficial  and  external  to  the  innominate  artery;  on  its 
right  side  is  the  phrenic  nerve,  and  the  pleura  is  here  interposed  between  it  and  the 
apex  of  the  lung.  This  vein,  at  the  angle  of  junction  of  the  internal  jugular  with 
the  subclavian,  receives  the  right  vertebral  vein,  and,  lower  down,  the  right  internal 
mammary,  right  inferior  thyroid,  and  sometimes  the  right  thyroid ea  ima  and  the 
right  superior  intercostal  veins. 

The  Left  Innominate  Vein  (v.  anonyma  sinistra),  about  two  and  a  half  inches 
in  length,  and  larger  than  the  right,  passes  from  left  to  right  across  the  upper  and 
front  part  of  the  chest,  at  the  same  time  inclining  downward,  and  unites  with 


LONGUS   COLLI    MUSCLE 

COMMON   CAROTID 

ARTERY 

LEFT  VAGUS 

NERVE 

VERTEBRAL  ARTERY 

VERTEBRAL  VEIN 
THORACIC  DUCT 

INTERNAL  JUGULAR 

VEIN 

EXTERNAL  JUGULAR 

VEIN 

ANTERIOR  JUGULAR 

VEIN 

SUBCLAVIAN 

VEIN 


FIG.  463. — The  bend  of  the  thoracic  duct  at  its  termination  in  the  subclavian  vein.     (Poirier  and  Charpy.) 


the  right  innominate  vein  to  form  the  precava.  It  is  in  relation,  in  front,  with  the 
first  piece  of  the  sternum,  from  which  it  is  separated  by  the  Sterno-hyoid  and 
Sterno-thyroid  muscles,  the  thymus  gland  or  its  remains,  and  some  loose  areolar 
tissue.  Behind,  it  lies  across  the  roots  of  the  three  large  arteries  arising  from  the 
arch  of  the  aorta.  This  vessel  is  joined  by  the  left  vertebral,  left  internal  mammary, 
left  inferior  thyroid,  left  thyroid  ea  ima,  and  the  left  superior  intercostal  veins,  and 
occasionally  some  thymic  and  pericardiac  veins,  and  the  right  thyroidea  ima. 
There  are  no  valves  in  the  innominate  veins. 

Peculiarities. — Sometimes  the  innominate  veins  open  separately  into  the  right  auricle;  in 
such  cases  the  right  vein  takes  the  ordinary  course  of  the  precava;  but  the  left  vein — the  left 
precava,  or  left  superior  vena  cava,  as  it  is  termed — after  communicating  by  a  small  branch  with 
the  right  one,  passes  in  front  of  the  root  of  the  left  lung,  and,  turning  to  the  back  of  the  heart, 
receives  the  cardiac  veins,  and  terminates  in  the  back  of  the  right  auricle.  This  occasional 
condition  in  the  adult  is  due  to  the  persistence  of  the  early  foetal  condition,  and  is  the  normal 
state  of  things  in  birds  and  some  mammalia. 

The  Internal  Mammary  Vein  (v.  mammaria  internet)  corresponds  to  the  internal 
mammary  artery,  follows  the  course  of  that  vessel,  and  receives  branches  corre- 
sponding with  those  derived  from  it.  There  are  two  internal  mammary  veins  in  the 
region  of  the  Triangularis  sterni  muscle,  but  above  this  point  the  vein  is  single.  The 
double  vein  is  formed  by  the  union  of  the  vense  comites  of  the  superior  epigastric 


THE   DEEP     VEINS    OF    THE    UPPER    EXTREMITY 


751 


..Anterior  jugular. 


Superior  thyroid. 


External  jugular. 


Mediastinal 

and 
pericardiac. 


artery  (vv.  epigastricae  superiores)  and  the  venae  comites  of  the  musculo-phrenic 

artery  (vv.musculophrenicae).  It  receives  the  twelve  anterior  intercostal  veins  from 

the  upper  six  intercostal  spaces  of  the  corresponding  side — six  anterior  perforating 

veins    (rami    perforantes) — 

veins  from  the  surface  of  the 

sternum   (rami  sternales)  — 

muscular  veins,  and  vessels 

from  the  mediastinum  and 

pleura.     The  two  veins   of  Middle  thyroid. A 

each  side  unite  into  a  single 

trunk,  at  the  upper  margin 

of    the    triangularis    sterni 

muscle,  which  terminates  in 

the  innominate  vein. 

The  Vertebral  Vein  (see 
p.  732). 

Thelnf  erior  Thyroid  Veins 
(vv.  thyreoideae  inferiores) 
(Fig.  464),  two,  frequently 
three  or  four,  in  number, 
arise  in  the  venous  plexus 
on  the  thyroid  body  (plexus 
thyreoideus  impar),  commu- 
nicating with  the  middle 
and  superior  thyroid  veins. 
(See  Kocher's  views,  pages 
731  and  732.)  Kocher  states 
that  two  thyroidea  ima  veins 
are  present,  and  that  inferior 
thyroid  veins  may  also  be 
present.  The  veins  from  the 
lower  portion  of  the  gland 
form  a  plexus  in  front  of  the 
trachea,  behind  the  Sterno- 
thyroid  muscles.  From  this 
plexus  a  left  vein  descends 
and  joins  the  left  innomi- 
nate trunk,  and  a  right  vein 
passes  obliquely  downward 
and  outward  across  the  in- 
nominate artery  to  open  into 
the  right  innominate  vein, 
just  at  its  junction  with  the 
precava.  The  thyroidea  ima 
vein  (v.  thyreoidea  ima) 
passes  downward  in  front  of 
the  trachea  and  terminates 
in  the  left  innominate  vein. 
These  veins  receive  tribu- 
taries from  the  tracheal  veins 
(vv.  tracheales),  from  the 
ffisophageal  veins  (vv.  oesopha- 
geae),  from  the  inferior  laryn- 

Vein(l?  lartinoea  inferior]        ^IG'  ^4' — ^^  venae  cavse  and  azygos  veins,  with  their  formative 
y    u  J  /  branches. 


752 


THE   BLOOD -VASCULAR   SYSTEM 


The  Intercostal  Veins  (vv.  intercostales)  are  divided  into  anterior  and  posterior 
intercostals. 

The  Anterior  Intercostal  Veins  are  tributaries  of  the  internal  mammary  or  the 
musculo-phrenic  veins  (p.  750). 

The  Posterior  Intercostal  Veins  (Fig.  464)  number  eleven  on  each  side,  there 
being  one  vein  in  each  intercostal  space.  Each  vein  lies  in  the  groove  at  the 
lower  margin  of  the  rib  above  the  corresponding  intercostal  artery.  On  the  right 
side  the  first  posterior  intercostal  vein  crosses  the  neck  of  the  first  rib  anteriorly 
and  opens  into  the  vertebral  vein  or  the  innominate  vein.  The  first  posterior 
intercostal  of  the  left  side  follows  a  like  course,  and  empties  into  the  vertebral 
or  innominate  vein.  The  posterior  intercostals  of  the  right  side,  from  the  fifth 
to  the  eleventh,  inclusive,  open  individually  into  the  vena  azygos  major.  The 
left  upper  azygos  vein  receives  the  fifth,  sixth,  seventh,  and  eighth  posterior 
intercostals  of  the  left  side.  The  left  lower  azygos  vein  receives  the  ninth,  tenth, 
and  eleventh  left  posterior  intercostals. 

The  Right  Superior  Intercostal  Vein  (v.  intercostalis  suprema  dextra)  is  formed 
by  the  union  of  the  second,  third,  and  fourth  right  posterior  intercostals.  It 
passes  downward  and  inward  and  opens  into  the  vena  azygos  major. 

The  Left  Superior  Intercostal  Vein  (v.  intercostalis  suprema  sinister)  runs  across 
the  transverse  aorta  and  opens  into  the  left  innominate  vein.  It  usually  receives 
the  left  bronchial  and  left  superior  phrenic  vein,  and  communicates  below  with 
the  vena  azygos  minor  superior.  Each  posterior  intercostal  vein  obtains  branches 
from  the  ribs  and  muscles  and  also  a  dorsal  branch,  which  receives  blood  from  the 
muscles  of  the  back,  from  in  front  of  the  vertebral  bodies,  from  back  of  the  ver- 
tebral arches,  and  from  the  spinal  canal  by  way  of  a  vein  which  passes  through 
the  intervertebral  foramen. 

The  Precava  or  Superior  Vena  Cava  (v.  cava  superior)  (Fig.  464)  receives  the 
blood  which  is  conveyed  to  the  heart  from  the  whole  of  the  upper  half  of  the  body. 
It  is  a  short  trunk,  varying  from  two  inches  and  a  half  to  three  inches  in  length, 
formed  by  the  junction  of  the  two  innominate  veins.  It  commences  immediately 
below  the  cartilage  of  the  first  rib  close  to  the  sternum  on  the  right  side,  and, 
descending  vertically,  enters  the  pericardium  about  an  inch  arid  a  half  above  the 
heart,  and  terminates  in  the  upper  part  of  the  right  auricle  opposite  the  upper 
border  of  the  third  right  costal  cartilage.  In  its  course  it  describes  a  slight  curve, 
the  convexity  of  which  is  turned  to  the  right  side. 

Relations. — In  front,  with  the  pericardium  and  process  of  cervical  fascia  which 
is  continuous  with  it:  this  separates  it  from  the  thymus  gland  and  from  the  ster- 
num; behind,  with  the  root  of  the  right  lung;  on  its  right  side,  with  the  phrenic 
nerve  and  right  pleura ;  on  its  left  side,  with  the  commencement  of  the  innominate 
artery  and  ascending  part  of  the  aorta.  The  portion  contained  within  the  peri- 
cardium is  covered  by  the  serous  layer  of  that  membrane  in  its  anterior  three- 
fourths.  It  receives  the  vena  azygos  major  just  before  it  enters  the  pericardium, 
and  several  small  veins  from  the  pericardium  and  parts  in  the  mediastinum.  The 
precava  has  no  valves. 

The  Azygos  Veins  connect  together  the  precava  and  postcava,  taking  the 
place  of  those  vessels  in  that  part  of  the  chest  occupied  by  the  heart. 

The  Larger  or  Right  Azygos  Vein  or  the  Vena  Azygos  Major  (v.  azygos)  (Fig.  464) 
commences  opposite  the  first  or  second  lumbar  vertebra  by  a  branch  from  the  right 
lumbar  veins,  called  the  right  ascending  lumbar  vein  (v.  lumbalis  ascendens  dextra) ; 
sometimes  by  a  branch  from  the  right  renal  vein  or  from  the  postcava.  It  enters 
the  thorax  through  the  aortic  opening  in  the  Diaphragm,  and  passes  along  the 
right  side  of  the  vertebral  column  to  the  fourth  thoracic  vertebra,  where  it  arches 
forward  over  the  root  of  the  right  lung,  and  terminates  in  the  precava  just  before 
that  vessel  enters  the  pericardium.  Whilst  passing  through  the  aortic  opening 


THE  SPINAL   VEINS  753 

of  the  Diaphragm  it  lies  with  the  thoracic  duct  on  the  right  side  of  the  aorta, 
and  in  the  thorax  it  lies  upon  the  intercostal  arteries  on  the  right  side  of  the  aorta 
and  thoracic  duct,  and  is  partly  covered  by  pleura. 

Tributaries. — It  receives  the  lower  ten  posterior  intercostal  veins  of  the  right  side, 
the  upper  two  or  three  of  these  opening,  first  of  all,  into  the  right  superior  inter- 
costal vein.  It  receives  the  azygos  minor  veins,  several  oesophageal,  mediastinal, 
and  pericardial  veins;  near  its  termination,  the  right  bronchial  vein;  and  generally 
the  right  superior  intercostal  vein.  A  few  imperfect  valves  are  found  in  this  vein; 
but  its  tributaries  are  provided  with  complete  valves. 

The  intercostal  veins  on  the  left  side,  below  the  three  upper  intercostal  spaces, 
usually  form  two  trunks,  named  the  left  lower  and  the  left  upper  azygos  veins. 

The  Left  Lower  or  Smaller  Azygos  Vein  or  the  Vena  Azygos  Minor  (v.  hemiazygos} 
(Fig.  464)  commences  in  the  lumbar  region  by  a  branch  from  one  of  the  lumbar 
veins,  ascending  lumbar  (v.  lumbalis  ascendens),  or  from  the  left  renal.  It  passes 
into  the  thorax  through  the  left  crus  of  the  Diaphragm,  and,  ascending  on  the 
left  side  of  the  spine  as  high  as  the  ninth  thoracic  vertebra,  passes  across  the 
column,  behind  the  aorta  and  thoracic  duct,  to  terminate  in  the  right  azygos  vein. 
It  receives  the  four  or  five  lower  intercostal  veins  of  the  left  side,  and  some 
oesophageal  and  mediastinal  veins. 

The  Left  Upper  Azygos  Vein  (v.  hemiazygos  accessorial)  varies  inversely  with  the 
size  of  the  left  superior  intercostal.  It  receives  veins  from  the  intercostal  spaces 
between  the  left  superior  intercostal  vein  and  highest  tributary  of  the  left  lower 
azygos.  They  are  usually  three  or  four  in  number,  usually  the  fourth,  fifth,  sixth, 
and  seventh  left  posterior  intercostal  veins.  They  join  to  form  a  trunk  which  ends 
in  the  right  azygos  vein  or  in  the  left  lower  azygos.  It  sometimes  receives  the  left 
bronchial  vein.  When  this  vein  is  small  or  altogether  wanting,  the  left  superior 
intercostal  vein  will  extend  as  low  as  the  fifth  or  sixth  intercostal  space. 

Surgical  Anatomy.—  In  obstruction  of  the  postcava  the  azygos  veins  are  one  of  the  prin- 
cipal means  by  which  the  venous  circulation  is  carried  on,  connecting  as  they  do  the  precava 
and  postcava,  and  communicating  with  the  common  iliac  veins  by  the  ascending  lumbar  veins, 
and  with  many  of  the  tributaries  of  the  postcava. 

The  Bronchial  Veins  (vv.  bronchioles)  return  the  blood  from  the  substance  of 
the  lungs,  except  from  the  smaller  bronchial  tubes  and  alveola.  The  blood  from 
them  is  received  by  the  pulmonary  veins.  The  bronchial  vein  of  the  right  side 
opens  into  the  vena  azygos  major  near  its  termination.  The  bronchial  vein  of 
the  left  side  opens  into  the  left  superior  intercostal  vein  or  the  left  upper  azygos 
vein.  The  bronchial  veins  are  joined  by  veins  from  the  trachea  and  medias- 
tinum. 

The  Spinal  Veins. 

The  numerous  venous  plexuses  placed  upon  and  within  the  spine  may  be 
arranged  into  four  sets: 

1.  Those  placed  on  the  exterior  of  the  spinal  column,  the  dorsi-spinal  veins. 

2.  Those  situated  in  the  interior  of  the  spinal  canal,  between  the  vertebrae  and 
the  theca  vertebralis,  meningo-rachidian  veins. 

3.  The  veins  of  the  bodies  of  the  vertebra*,  venae  basis  vertebrarum. 

4.  The  veins  of  the  spinal  cord,  medulli-spinal  veins. 

1.  The  Dorsi-spinal  Veins  (plexus  venosi  vertebrates  externi)  commence  by 
small  branches  which  receive  their  blood  from  the  integument  of  the  back  of  the 
spine  and  from  the  muscles  in  the  vertebral  grooves.  They  constitute  two  plexuses : 
an  anterior  plexus  (plexus  venosi  vertebrates  anteriores)  upon  the  vertebral  bodies 
and  a  posterior  plexus  (plexus  venosi  vertebrates  posteriores) ,  which  surrounds  the 
spinous  processes,  the  laminae,  and  the  transverse  and  articular  processes  of 

48 


754 


THE    BLOOD -VASCULAR   SYSTEM 


all  the  vertebrae.  At  the  bases  of  the  transverse  processes  they  communicate,  by 
means  of  ascending  and  descending  branches,  with  the  veins  surrounding  the 
contiguous  vertebrae,  and  they  join  with  the  veins  in  the  spinal  canal  by  branches 
which  perforate  the  ligamenta  subflava.  Other  branches  pass  obliquely  forward, 
between  the  transverse  processes,  and  communicate  with  the  intraspinal  veins 
through  the  intervertebral  foramina  (w.  intervertebrales).  The  dorsi-spinal  veins 
terminate  by  joining  the  vertebral  veins  in  the  neck,  the  intercostal  veins  in  the 
thorax,  and  the  lumbar  and  sacral  veins  in  the  loins  and  pelvis. 


The  dorsi-spinal  veins. 


FIG.  465. — Transverse  section  of  a  thoracic  vertebra,  showing  the  spinal  veins. 

2.  The  Meningo-rachidian  Veins  (plexus  venosi  vertebrates  interni). — The 
principal  veins  contained  in  the  spinal  canal  are  situated  between  the  theca  verte- 
bralis  and  the  vertebrae.  They  consist  of  two  longitudinal  plexuses,  one  of  which 
runs  along  the  posterior  surface  of  the  bodies  of  the  vertebrae,  anterior  longitudinal 
spinal  veins.  The  other  plexus,  posterior  longitudinal  spinal  veins,  is  placed  on  the 
inner  or  anterior  surface  of  the  laminae  of  the  vertebrae. 


FIG.  466. — Vertical  section  of  two  thoracic  vertebra?,  showing  the  spinal  veins. 


The  Anterior  Longitudinal  Spinal  Veins  (sinus  vertebrales  longitudinales]  consist 
of  two  large,  tortuous  veins  which  extend  along  the  whole  length  of  the  vertebral 
column,  from  the  foramen  magnum,  where  they  communicate  by  a  venous  ring 
around  that  opening,  to  the  base  of  the  coccyx,  being  placed  one  on  each  side  of 
the  posterior  surface  of  the  bodies  of  the  vertebrae  along  the  margin  of  the  posterior 
common  ligament.  These  veins  communicate  together  opposite  each  vertebra  by 


VEIN8    OF  LOWER    EXTREMITY,    ABDOMEN   AND    PELVIS     755 

transverse  trunks  which  pass  beneath  the  ligament.  Each  transverse  trunk 
receives  the  large  vena  basis  vertebrae  (v.  basivertebralis)  from  the  interior  of  the 
body  of  the  vertebra.  The  anterior  longitudinal  spinal  veins  are  least  developed 
in  the  cervical  and  sacral  regions.  They  are  not  of  uniform  size  throughout, 
being  alternately  enlarged  and  constricted.  At  the  intervertebral  foramina  they 
communicate  with  the  dorsi-spinal  veins,  and  with  the  vertebral  veins  in  the  neck, 
with  the  intercostal  veins  in  the  thoracic  region,  and  with  the  lumbar  and  sacral 
veins  in  the  corresponding  regions. 

The  Posterior  Longitudinal  Spinal  Veins,  smaller  than  the  anterior,  are  situated 
one  on  each  side,  between  the  inner  surface  of  the  laminae  and  the  theca  verte- 
bralis.  They  communicate  (like  the  anterior)  opposite  each  vertebra  by  trans- 
verse trunks,  and  with  the  anterior  longitudinal  veins  by  lateral  transverse  branches 
which  pass  from  behind  forward.  The  posterior  longitudinal  veins,  by  branches 
which  perforate  the  ligamenta  subflava,  join  with  the  dorsi-spinal  veins.  From 
them  branches  are  given  off  which  pass  through  the  intervertebral  foramina  and 
join  the  vertebral,  intercostal,  lumbar,  and  sacral  veins.  The  anterior  and  pos- 
terior longitudinal  spinal  veins  join  by  numerous  branches  and  really  constitute 
one  plexus,  the  plexus  venosi  vertebrales  interni. 

The  Intervertebral  Veins  (w.  intervertebrales)  accompany  the  spinal  nerves 
in  the  intervertebral  foramina,  receive  veins  from  the  spinal  cord,  and  join  the 
meningo-rachidian  and  the  dorsi-spinal  veins. 

3.  The  Veins  of  the  Bodies  of  the  Vertebrae  or  the  Venae  Basis  Vertebrarum 
(w.  basivertebrales)  emerge  from  the  foramen  on  the  posterior  surface  of  each 
vertebra  and  join  the  transverse  trunk  connecting  the  anterior  longitudinal  spinal 
veins.    They  are  contained  in  large,  tortuous  channels  in  the  substance  of  the 
bones,  similar  in  every  respect  to  those  found  in  the  diploe  of  the  cranial  bones. 
These  canals  lie  parallel  to  the  upper  and  lower  surface  of  the  bones.    They  com- 
mence by  small  openings  on  the  front  and  sides  of  the  bodies  of  the  vertebrae, 
through  which  communicating  branches  from  the  veins  external  to  the  bone  pass 
into  its  substance,  and  converge  to  the  principal  canal,  which  is  sometimes  double 
toward  its  posterior  part.  They  open  into  the  corresponding  transverse  branch  unit- 
ing the  anterior  longitudinal  veins.    They  become  greatly  developed  in  advanced  age. 

4.  The  Veins  of  the  Spinal  Cord  or  the  Medulli-spinal  Veins  (w.  spinales] 
emerge  from  the  cord  substance  and  enter  the  pia  plexus.    The  pia  plexus  is  a 
minute,  tortuous,  venous  plexus  which  covers  the  entire  surface  of  the  cord,  being 
situated  between  the  pia  and  arachnoid.    "In  this  plexus  there  are  six  longitudinal 
channels — one   antero-median,    along   the   anterior    fissure — two    antero-lateral, 
immediately  behind  the  anterior  nerve  roots — two  postero-lateral,  immediately 
behind   the  posterior  nerve  roots — and   one  postero-median,  over  the  postero- 
septum"  (Cunningham).    These  vessels  are  largest  in  the  lumbar  region.    Near 
the  base  of  the  skull  they  unite  and  form  two  or  three  small  trunks,  which  com- 
municate with  the  vertebral  veins,  and  terminate  in  the  subcerebellar  veins  or  in 
the  subpetrosal  sinuses.     Each  of  the  spinal  nerves  is  accompanied  by  a  branch 
as  far  as  the  intervertebral  foramina,  where  it  joins  the  other  veins  from  the  spinal 
canal. 

There  are  no  valves  in  the  spinal  veins. 


VEINS  OF  THE  LOWER  EXTREMITY,  ABDOMEN,  AND  PELVIS 

(Figs.  467,  468). 

The  Veins  of  the  Lower  Extremity  are  subdivided,  like  those  of  the  upper, 
into  two  sets,  superficial  and  deep,  the  superficial  veins  being  placed  beneath  the 


756  THE   BLOOD -VASCULAR    SYSTEM 

integument,  between  the  two  layers  of  superficial  fascia,  the  deep  veins  accom- 
panying the  arteries,  and  forming  the  venae  comites  of  those  vessels.  Both  sets 
of  veins  are  provided  with  valves,  which  are  more  numerous  in  the  deep  than  in 
the  superficial  set.  These  valves  are  also  more  numerous  in  the  lower  than  in 
the  upper  limb. 

The  Superficial  Veins  of  the  Lower  Extremity. 

The  Superficial  Veins  of  the  Foot. — On  the  sole  of  the  foot  there  is  a  sub- 
cutaneous venous  plexus  (rete  venosum  plantar e  cutaneum},  from  which  some 
branches  go  to  the  deep  veins,  but  most  of  the  branches  pass  around  the  margins 
to  the  dorsum  of  the  foot.  There  is  a  transverse  venous  arch  at  the  root  of  the 
toes  which  receives  plantar  vessels  from  the  toes  and  sends  branches  between  the 
toes  (w.  intercapitulares)  to  the  venous  arch  of  the  dorsum.  On  the  dorsum  of  each 
toe  the  veins  gather  into  two  vessels,  known  as  the  dorsal  digital  veins  (vv.  digitales 
pedis  dorsales).  The  dorsal  digital  veins  from  the  opposed  margins  of  two  toes 
unite  to  form  a  dorsal  interdigital  vein.  There  are  four  dorsal  interdigital  veins 
(vv.  digitales  communes  pedis),  and  they  pass  into  the  venous  arch  of  the  dorsum. 
The  dorsal  digital  vein,  from  the  inner  surface  of  the  great  toe,  passes  directly 
into  the  internal  saphenous  vein,  and  the  dorsal  digital  vein,  from  the  outer 
surface  of  the  little  toe,  passes  directly  into  the  external  saphenous  vein. 

On  the  dorsum  of  the  foot  is  a  venous  arch  (arcus  venosus  dorsalis  pedis 
[cutaneus]),  situated  in  the  superficial  structures  over  the  anterior  extremities  of 
the  metatarsal  bones.  It  has  its  convexity  directed  forward,  and  receives  digital 
tributaries  from  the  upper  surface  of  the  toes;  at  its  concavity  it  is  joined  by 
numerous  small  veins  which  form  a  plexus  on  the  dorsum  of  the  foot  (rete 
venosum  dorsale  pedis  cutaneum).  The  arch  terminates  internally  in  the  long 
saphenous,  externally  in  the  short  saphenous  vein. 

The  chief  superficial  veins  of  the  lower  extremity  are  the  internal  or  long  saphenous 
and  the  external  or  short  saphenous. 

The  Internal  or  Long  Saphenous  Vein  (v.  saphena  magna)  (Figs.  467  and  470) 
commences  at  the  inner  side  of  the  arch  on  the  dorsum  of  the  foot;  it  ascends  in  front 
of  the  inner  malleolus  and  along  the  inner  side  of  the  leg,  behind  the  inner  margin 
of  the  tibia,  accompanied  by  the  internal  saphenous  nerve.  At  the  knee  it  passes 
backward  behind  the  inner  condyle  of  the  femur,  ascends  along  the  inside  of  the 
thigh,  and,  passing  through  the  saphenous  opening  in  the  fascia  lata,  terminates 
in  the  femoral  vein  about  an  inch  and  a  half  below  Poupart's  ligament.  This  vein 
receives  in  its  course  cutaneous  tributaries  from  the  leg  and  thigh,  and  at  the 
saphenous  opening  receives  the  superficial  epigastric,  superficial  circumflex  iliac, 
and  external  pudic  veins.  The  veins  from  the  inner  and  back  part  of  the  thigh 
frequently  unite  to  form  a  large  vessel,  which  enters  the  main  trunk  near  the 
saphenous  opening;  and  sometimes  those  on  the  outer  side  of  the  thigh  join  to  form 
another  large  vessel;  so  that  occasionally  three  large  veins  are  seen  converging  from 
different  parts  of  the  thigh  toward  the  saphenous  opening.  The  internal  saphenous 
vein  communicates  in  the  foot  with  the  internal  plantar  vein;  in  the  leg,  with  the 
posterior  tibial  veins  by  branches  which  perforate  the  tibial  origin  of  the  Soleus 
muscle,  and  also  with  the  anterior  tibial  veins;  at  the  knee,  with  the  articular 
veins;  in  the  thigh,  with  the  femoral  vein  by  one  or  more  branches.  The  valves 
in  this  vein  vary  from  two  to  six  in  number;  they  are  more  numerous  in  the  thigh 
than  in  the  leg. 

The  External  or  Short  Saphenous  Vein  (v.  saphena  parva)  (Fig.  468)  com- 
mences at  the  outer  side  of  the  arch  on  the  dorsum  of  the  foot;  it  ascends  behind  the 
outer  malleolus,  and  along  the  outer  border  of  the  tendo  Achillis,  across  which  it 
passes  at  an  acute  angle  to  reach  the  middle  line  of  the  posterior  aspect  of  the  leg. 


THE   SUPERFICIAL    VEINS    OF    THE  LOWER    EXTREMITY    757 

Passing-  directly  upward,  it  perforates  the  deep  fascia  in  the  lower  part  of  the 
popliteal  space,  a'nd  terminates  in  the  popliteal  vein,  between  the  heads  of  the 


I 


andTtsbranchS8 


FIG.  468.  —  External  or  short  saphenous  vein. 

Gastrocnemius  muscle.1  It  receives  numerous  large 
tributaries  from  the  back  part  of  the  leg,  and  com- 
municates with  the  deep  veins  on  the  dorsum  of  the 
foot  and  behind  the  outer  malleolus.  Before  it  per- 
forates the  deep  fascia  it  gives  off  a  communicating 
branch,  which  passes  upward  and  inward  to  join  the 
internal  saphenous  vein.  This  vein  has  a  variable 
number  of  valves,  from  three  to  nine  (Gay),  one  of 
which  is  always  found  near  its  termination  in  the 
popliteal  vein.  The  external  saphenous  nerve  lies 
close  beside  this  vein. 

Surgical  Anatomy.  —  The  saphenous  veins  are  of  consider- 
able surgical  importance,  since  a  varicose  condition  of  these 
vessels  is  more  frequently  met  with  than  of  those  in  other  parts 


1  Mr.  Gay  calls  attention  to  the  fact  that  the  external  saphenous  vein  often  (he  says  invariably)  penetrates 
the  fascia  at  or  about  the  point  where  the  tendon  of  the  Gastrocnemius  commences,  and  runs^below  the  fascia 
in  the  rest  of  its  course,  or  sometimes  among  the  muscular  fibres,  to  join  the  popliteal  vein.  (See  Gay  on  Vari- 
cose Disease  of  the  Lower  Extremities,  p.  24,  where  there  is  also  a  careful  and  elaborate  description  of  the 
branches  of  the  saphena  veins.)  —  ED.  of  15th  English  edition. 


758 


THE   BLOOD -VASCULAR    SYSTEM 


of  the  body,  except  perhaps  the  spermatic  and  hemorrhoidal  veins.  The  course  of  the  internal 
saphenous  is  in  front  of  the  tip  of  the  inner  malleolus,  over  the  subcutaneous  surface  of  the  lower 
end  of  the  tibia,  and  then  along  the  internal  border  of  this  bone  to  the  back  part  of  the  internal 
condyle  of  the  femur,  whence  it  follows  the  course  of  the  Sartorius  muscle,  and  is  represented  on 
the  surface  by  a  line  drawn  from  the  posterior  border  of  the  Sartorius  on  a  level  with  the  internal 
condyle  to  the  saphenous  opening.  The  external  saphenous  lies  behind  the  external  malleolus, 
and  from  this  follows  the  middle  line  of  the  calf  to  just  below  the  ham.  It  is  not  generally  so 
apparent  beneath  the  skin  as  the  internal  saphenous.  Both  these  veins  in  the  leg  are  accom- 
panied 
level 
fact. 


UI.VU*     •^»V/lAV^l*V/AX       IfUflrf      LjiVAAi      C*0       IrllVs       AllbV/l  UG*1      OCfcl^Ai^AiV^lAO*  A^XSfeU       CllA^O^        VJ^lllO       111       tllC      ICii      <*  *  ^      CHJULJl  J.1™ 

sd   by  nerves,  the  internal  saphenous  being  joined  by  its  companion  nerve  just  below  the 
of  the  knee-joint.     No  doubt  much  of  the  pain  of  varicose  veins  in  the  leg  is  due  to  this 


The  Deep  Veins  of  the  Lower  Extremity. 

The  deep  veins  of  the  lower  extremity  accompany  the  arteries  and  their  branches 
and  are  called  the  venae  comites  of  those  vessels.    The  vense  comites  in  the  lower 

extremity  pass  into  one  trunk,  the  popliteal  vein, 
whereas  in  the  upper  extremity  the  vense  comites  con- 
tinue with  the  artery  to  the  axilla. 

The  Deep  Veins  of  the. Foot. — The  plantar  digital 
veins  (w.  digitales  plantar  es)  form  the  plantar  metatarsal 
veins  (w.  metaiarseae  plantares),  which  communicate 
with  the  veins  of  the  dorsum  of  the  foot  by  perfor- 
ating veins  and  also  communicate  with  the  deep  venous 
arch  of  the  sole  of  the  foot  (arcus  venosus  plantaris  pro- 
fundus).  The  plantar  arch  gives  off  lateral  or  external 
plantar  veins,  which  unite  with  median  or  internal  plantar 
veins  to  form  the  posterior  tibial  veins.  On  the  dorsum 
of  the  foot  the  deep  veins  begin  as  the  dorsal  metatarsal 
veins  (vv.  metatarseae  dorsales  pedis},  wrhich  form  the 
vense  comites  of  the  dorsalis  pedis  artery. 

The  Posterior  Tibial  Veins  (vv.  tibiales  posteriores) 
accompany  the  posterior  tibial  artery  and  are  joined 
by  the  peroneal  veins. 

The  Anterior  Tibial  Veins  (w.  tibiales  anterior  es) 
are  formed  by  a  continuation  upward  of  the  vense 
comites  of  the  dorsalis  pedis  artery.  They  pass  be- 
tween the  tibia  and  fibula,  through  the  large  oval  aper- 
ture above  the  interosseous  membrane,  and  form,  by 
their  junction  with  the  posterior  tibial,  the  popliteal 
vein. 

The  valves  in  the  deep  veins  are  very  numerous. 
The  Popliteal  Vein  (v.  poplitea)  (Fig.  469)  is  formed 
by  the  junction  of  the  anterior  and  posterior  tibial 
veins;  it  ascends  through  the  popliteal  space  to  the 
aperture  in  the  Adductor  magnus,  where  it  becomes  the  femoral  vein.  In  the 
lower  part  of  its  course  it  is  placed  internal  to  the  artery;  between  the  heads  of 
the  Gastrocnemius  it  is  superficial  to  that  vessel;  but  above  the  knee-joint  it  is 
close  to  the  outer  side  of  the  artery.  It  receives  the  sural  veins  from  the  Gastroc- 
nemius muscle,  the  articular  veins,  and  the  external  saphenous  vein.  The  valves 
in  this  vein  are  usually  four  in  number. 

The  Femoral  Vein  (v.  femoralis)  (Figs.  470  and  471)  accompanies  the  femoral 
artery  through  the  upper  two-thirds  of  the  thigh.  In  the  lower  part  of  its  course 
it  lies  external  to  the  artery;  higher  up  it  is  behind  it;  and  at  Poupart's  ligament 
it  lies  to  its  inner  side  and  on  the  same  plane.  It  receives  numerous  muscular 
tributaries,  and  about  an  inch  and  a  half  below  Poupart's  ligament  it  is  joined  by 


FIG.  469. — The  popliteal  vein. 
(Poirier  and  Charpy.) 


THE    DEEP     VEINS    OF    THE    LOWER    EXTREMITY 


759 


the  profunda  femoris  (v.  profunda  femoris);  near  its  termination  it  is  joined  by 
the  internal  saphenous  vein.  The  valves  in  this  vein  are  four  or  five  in  number. 
The  External  Iliac  Vein  (v.  iliaca  externa)  (Figs.  464,  471 ,  and  473)  commences 
at  the  termination  of  the  femoral,  beneath  the  crural  arch,  and,  passing  upward 
along  the  brim  of  the  pelvis,  terminates  opposite  the  sacro-iliac  synchondrosis  by 
uniting  with  the  internal  iliac  to  form  the  common  iliac  vein.  On  the  right  side  it 
lies  at  first  along  the  inner  side  of  the  external  iliac  artery,  but  as  it  passes  upward 
gradually  inclines  behind  it.  On  the  left  side  it  lies  altogether  on  the  inner  side 
of  the  artery.  It  receives,  immediately  above  Poupart's  ligament,  the  deep  epi- 


SUPERFICIAL 
EPIGASTRIC 


SUPERFICIAL 

INTERNAL 

CIRCUMFLEX 


SUPERFICIAL 

EXTERNAL 

PUDIC 


SUPERFICIAL 

EXTERNAL 

CIRCUMFLEX 


FIG.  470. — The  femoral  vein  and  its  tributaries.     (Poirier  and  Charpy.) 

gastric  and  deep  circumflex  iliac  veins  and  a  small  pubic  vein,  corresponding  to 
the  pubic  branch  of  the  obturator  artery.  According  to  Friedreich,  it  frequently 
contains  one  and  sometimes  two  valves. 

The  Deep  Epigastric  Vein  (v.  epigastrica  inferior)  (Fig.  471). — Two  veins 
accompany  the  deep  epigastric  artery;  they  usually  unite  into  a  single  trunk 
before  their  termination  in  the  external  iliac  vein. 

The  Deep  Circumflex  Iliac  Vein  (v.  circumflexa  ilium  profunda)  (Fig.  471).— 
Two  veins  accompany  the  deep  circumflex  iliac  artery.  These  unite  into  a  single 
trunk  which  crosses  the  external  iliac  artery  just  above  Poupart's  ligament  and 
terminates  in  the  external  iliac  vein. 


760 


THE  BLOOD -VASCULAR    SYSTEM 


The  Hypogastric  or  Internal  Iliac  Vein  (v.  iliaca  interna  or  v.  hypogastrica) 
(Figs.  464, 471,  and  473)  is  formed  by  the  veins  corresponding  to  all  the  branches 
of  the  internal  iliac  artery  except  the  umbilical  branch.  It  receives  the  blood 
from  the  exterior  of  the  pelvis  by  the  gluteal,  sciatic,  internal  pudic,  and  obturator 
veins,  and  from  the  organs  in  the  cavity  of  the  pelvis  by  the  middle  hemor- 
rhoidal  veins,  the  superior  vesical  plexus  and  the  prostatico-vesical  plexus  in  the 
male,  and  the  superior  vesical,  inferior  vesical,  uterine  and  vaginal  plexuses  in 
the  female.  The  vessels  forming  these  plexuses  are  remarkable  for  their  large  size, 
their  frequent  anastomoses,  and  the  number  of  valves  which  they  contain.  The 
internal  iliac  vein  lies  at  first  on  the  inner  side,  and  then  behind  the  internal  iliac 
artery,  and  terminates  opposite  the  sacro-iliac  articulation  by  uniting  with  the 
external  iliac  to  form  the  common  iliac  vein.  This  vessel  has  no  valves. 

The  Internal  Pudic  Veins  (vv.  pudendoe  internw)  (Fig.  471)  have  the  same  course  as 
the  internal  pudic  artery.  They  receive  tributaries  corresponding  to  the  branches 
of  the  artery,  except  the  tributary  corresponding  to  the  dorsal  artery  of  the 
penis;  that  is,  the  deep  dorsal  vein  of  the  penis,  which  opens  into  the  prostatico- 
vesical  plexus. 


CIRCUMFLEX 
ILIAC 


DEEP 
EPIGASTRIC 


LATERAL 
SACRAL 


MIDDLE 
SACRAL 


FIG.  471. — The  iliac  veins.     (Poirier  and  Charpy.) 

The  Inferior  or  External  Hemorrhoidal  Veins  (vv.  hemorrhoidalis  inferiores) 
(Figs  472  and  473)  collect  blood  from  the  anus.  Tljey  pass  outward  over  the 
External  sphincter  muscle,  unite  with  numerous  subcutaneous  veins,  and  form 
larger  vessels  which  join  the  internal  pudic  veins. 

The  Middle  Hemorrhoidal  Veins  (w.  hemorrhoidalis  media)  (Figs.  472  and  473) 
help  to  form  the  hemorrhoidal  plexus,  perforate  the  rectal  wall,  and  empty  into  the 
internal  iliac  vein.  These  veins,  by  their  anastomoses  in  the  hemorrhoidal  plexus, 
establish  a  communication  between  the  portal  and  systemic  venous  systems. 

The  Lateral  Sacral  Veins  (vv.  sacrales  laterales]  (Fig.  471)  accompany  the  lateral 
sacral  arteries  and  terminate  in  the  internal  iliac  vein. 


THE   DEEP    VEINS    OF    THE   LOWER    EXTREMITY 


701 


Surgical  Anatomy. — The  veins  of  the  hemorrhoidal  plexus  are  apt  to  become  dilated  and 
varicose,  and  form  piles,  hemorrhoids.  This  is  due  to  several  anatomical  reasons:  the  vessels  are 
contained  in  very  loose,  or  connective  tissue,  so  that  they  obtain  less  support  from  surrounding 
structures  than  most  other  veins,  and  are  less  capable  of  resisting  increased  blood  pressure: 
the  condition  is  favored  by  gravitation,  being  influenced  by  the  erect  posture,  either  sitting  or 
standing,  and  by  the  fact  that  the  superior  hemorrhoidal  and  portal  veins  have  no  valves.  The 
veins  pass  through  muscular  tissue  and  are  liable  to  be  compressed  by  its  contraction,  especially 
during  the  act  of  defecation,  and  they  are  affected  by  every  form  of  portal  obstruction. 

The  Obturator  Vein  (v.  obturatoriae)  (Figs.  471  and  473)  follows  the  course  of 
the  obturator  artery,  lying  below  the  artery  as  it  passes  over  the  side  of  the 
pelvis;  this  vein  empties  into  the  front  part  of  the  internal  iliac  vein. 

The  Sciatic  Veins  are  two  in  number;  they  accompany  the  sciatic  artery  in 
the  upper  part  of  the  back  of  the  thigh,  and  just  before  their  termination  in  the 
internal  iliac  the  two  veins  unite. 

« The  Gluteal  Veins  (vv.  glutea)  are  usually  two  in  number,  and  return  to  the 
internal  iliac  vein  the  blood  that  has  been  distributed  by  the  gluteal  artery  and 
its  branches. 


SUPERIOR 
HEMORRHOIDAL 


MIDDLE 
HCMORRHOiDAL' 


INFERIOR, 

HEMORRHOIDAL 


FIG.  472. — Scheme  of  the  anastomosis  of  the  veins  of  the  rectum.     (Poirier  and  Charpy.) 


The  Superior  Vesical  Plexus  (Fig.  473)  is  placed  upon  the  fundus  and 
lateral  aspects  of  the  bladder  on  the  external  aspect  of  the  muscular  coat.  It 
receives  vessels  from  the  mucous  membrane  and  from  the  muscular  walls.  It 
empties  into  the  internal  pudic  vein:  in  the  male  it  communicates  with  the 
prostatico-vesical  plexus,  and  in  the  female  with  the  inferior  vesical  plexus. 

The  Prostatic  or  the  Prostatico-vesical  Plexus  "(Fig.  473)  surrounds  the 
prostate  gland  and  the  neck  of  the  bladder.  It  is  contained  between  the  recto- 
vesical  fascia  which  surrounds  the  base  and  sides  of  the  gland  and  the  true  capsule 
of  the  gland.  It  communicates  with  the  superior  vesical  plexus  behind  and 
above,  and  receives  the  deep  dorsal  vein  of  the  penis,  which  enters  the  pelvis 
between  the  subpubic  and  triangular  ligaments.  This  plexus  receives  veins  from 
the  seminal  vesicles  and  vasa  deferentia.  On  each  side  one  or  more  vessels  pass 


762 


THE   BLOOD -VASCULAR    SYSTEM 


from  the  prostatico-vesical  plexus  to  the  internal  iliac  vein.  The  veins  composing 
the  prostatic  plexus  are  very  liable  to  become  varicose,  and  often  contain  hard, 
earthy  concretions  called  phleboliths. 

The  Inferior  Vesical  Plexus  exists  only  in  the  female,  and  corresponds  to  the 
prostatico-vesical  plexus  in  the  male,  and  surrounds  the  neck  of  the  bladder  and 
the  upper  portion  of  the  urethra.  It  receives  the  dorsal  vein  of  the  clitoris  and 
sends  efferents  to  the  internal  iliac  vein. 


THIRD  LUMBAR 


SUPERIOR 

HEMORRHOIDAL 


DEEP 

CIRCUMFLEX 
ILIAC 


OBTURATOR 


PROSTATIC 
PLEXUS 


HEMORRHOIDAL 
PLEXUS 


MIDDLE 
HEMORRHOIDAL 


INFERIOR 
HEMORRHOIDAL 


DORSAL  VEIN 
OF  PENIS 


VESICAL   PLEXUS 


INTERNAL  PUDIC 

FIG.  473. — The  veins  of  the  male  pelvis,  right  half,  viewed  from  the  left.     The  psoas  muscle  has  been  removed 
and  the  rectum  drawn  down  somewhat  to  the  side.      (Spalteholz.) 

Surgical  Anatomy. — The  prostatico-vesical  plexus  is  wounded  in  the  lateral  operation  of 
lithotomy,  and  it  is  through  it  that  septic  matter  finds  its  way  into  the  general  circulation  after 
this  operation.  In  enucleating  the  prostate  the  gland  is  shelled  out  from  its  capsule  of  recto- 
vesical  fascia.  The  veins  of  the  plexus  remain  attached  to  the  sheath. 

The  Dorsal  Veins  of  the  Penis. — The  Superficial  Dorsal  Vein  of  the  Penis  (Fig. 
474)  receives  blood  from  the  prepuce  and  runs  backward  beneath  the  skin,  and 
divides  into  two  branches  which  terminate  in  the  superficial  external  pudic  vein. 

The  Deep  Dorsal  Vein  of  the  Penis  (v.  dorsalis  penis)  (Figs.  473  and  474)  is  a  vessel 
of  large  size  which  returns  the  blood  from  the  body  of  that  organ.  At  first  it  con- 


THE   DEEP     VEINS    OF    Till-:    LOWER    EXTREMITY 


7(33 


SUPERFICIAL    DOR- 
SAL  VEIN 

DORSAL  ARTERY  j  .DEEP  DORSAL  VEIN 
CORPUS  CAVERNOSUNT. 


CAVERNOUS..  (. 
ARTERY 


sists  of  two  branches,  which  are  contained  in  the  groove  on  the  dorsum  of  the  penis, 
and  it  receives  numerous  superficial  veins  and  veins  from  the  glans  penis  and  the 
corpus  spongiosum.  These  vessels  unite  into  a  single  trunk,  which  passes  between 
the  two  parts  of  the  suspensory  ligament  of  the  penis,  and  through  an  aperture 
between  the  subpubic  ligament  and 
the  apex  of  the  triangular  ligament, 
and  divides  into  two  branches,  which 
enter  the  prostatico-vesical  plexus. 
The  dorsal  vein  of  the  clitoris  corre- 
sponds in  woman  to  the  dorsal  vein 
of  the  penis  in  man,  and  runs  into 
the  inferior  vesical  plexus. 

The  Vaginal  Plexuses  and  Veins 
(Fig.  475). — The  vaginal  plexuses  are 
placed  at  the  sides  of  the  vagina,  being 
especially  developed  at  the  orifice  of 
the  canal.  They  receive  vessels  from 
the  vaginal  walls.  The  plexuses 
communicate  with  the  uterine  plexus  above,  with  the  bulbar  veins  below,  with 
the  inferior  vesical  plexus  in  front  and  with  the  hemorrhoidal  plexus  behind. 
From  the  upper  part  of  each  vaginal  plexus  comes  a  vaginal  vein  which  passes 
to  the  internal  iliac. 

The  Uterine  Plexuses  (Fig.  475)  are  situated  along  the  sides  and  superior  angles 
of  the  uterus,  between  the  layers  of  the  broad  ligament.  They  receive  the  veins 
from  the  uterus,  which  veins  are  without  valves.  During  pregnancy  these  veins 


DEEP 
FASCIA 


BULBO-CAVERNOUS    ARTERY/ 
-ANTERIOR    BRANCH 

CORPUS 
SPONGIOSUM 

FIG.  474. — The  penis  in  transverse  section,  showing  the 
blood-vessels.     (Testut.) 


URETHRA 


TUBAL   VESSELS 


NASTOMOSIS  OF 

UTERINE    AND 

OVARIAN  ARTERIES 


UTERINE 
VEINS 


VAGINAL   VENOUS    PLEXUS 


TERINE    ARTEHY 


"-SUPERIOR    VAGINAL 
ARTERIES 


os  UTERI'     VAGINA  CUT  OPEN  BEHIND 
FIG.  475. — Vessels  of  the  uterus  and  its  appendages,  rear  view.     (Testut.) 

become  large  venous  canals  known  as  the  uterine  sinuses,  and  bring  blood  from  the 
substance  of  the  placenta.  These  veins  join  the  ovarian  above  and  the  vaginal 
below,  and  anastomose  with  each  other.  They  are  not  tortuous  like  the  artery. 

The  Uterine  Veins  (vv.  uterinae)  (Fig.  475)  arise  from  the  lower  part  of  the 
plexus,  and  there  are  usually  two  veins  on  each  side  and  they  are  without  valves. 
These  veins  for  the  first  portion  of  their  course  are  placed  in  the  base  and  inner 
portion  of  the  broad  ligament;  they  then  pass  back  with  the  uterine  artery  in  a 
peritoneal  fold  between  the  back  of  the  broad  ligament  and  the  recto-uterine 
fold  (Cunningham) ;  they  then  pass  upward  and  enter  the  internal  iliac  vein. 


764  THE   BLOOD -VASCULAR    SYSTEM 

The  Common  Iliac  Vein  (v.  iliaca  communis)  (Figs.  464,  471,  and  473)  on 
each  side  is  formed  by  the  union  of  the  external  and  internal  iliac  veins  in 
front  of  the  sacro-iliac  articulation:  passing  obliquely  upward  teward  the  right 
side,  each  vein  terminates  upon  the  intervertebral  substance  between  the  fourth 
and  fifth  lumbar  vertebrae,  where  the  veins  of  the  two  sides  unite  at  an  acute 
angle  to  form  the  postcava  or  inferior  vena  cava.  The  right  common  iliac  (v.  iliaca 
communis  dextra)  is  shorter  than  the  left,  nearly  vertical  in  its  direction,  and  ascends 
behind  and  then  to  the  outer  side  of  its  corresponding  artery.  The  left  common 
iliac  (v.  iliaca  communis  sinistra),  longer  and  more  oblique  in  its  course,  is  at  first 
situated  on  the  inner  side  of  the  corresponding  artery,  and  then  behind  the  right 
common  iliac.  Each  common  iliac  receives  the  ilio-lumbar,  and  sometimes  the 
lateral  sacral,  veins.  The  left  receives,  in  addition,  the  middle  sacral  vein.  No 
valves  are  found  in  these  veins. 

The  Middle  Sacral  Veins  (Figs.  471  and  472)  accompany  the  corresponding 
artery  along  the  front  of  the  sacrum,  and  join  to  form  a  single  vein  (v.  sacralis 
media),  which  terminates  in  the  left  common  iliac  vein;  occasionally  in  the  angle 
of  junction  of  the  two  iliac  veins.  The  middle  sacral  veins  communicate  with 
the  inferior  hemorrhoidal. 

The  Ilio-lumbar  Veins  (vv.  iliolumbales)  receive  branches  from  the  iliac  fossae, 
spinal  muscles,  and  spinal  canal.  One  vein  on  each  side  runs  with  the  artery, 
passes  posterior  to  the  psoas  muscle,  and  joins  the  common  iliac  vein. 

Peculiarities. — The  left  common  iliac  vein,  instead  of  joining  with  the  right  in  its  usual 
position,  occasionally  ascends  on  the  left  side  of  the  aorta  as  high  as  the  kidney,  where,  after 
receiving  the  left  renal  vein,  it  crosses  over  the  aorta,  and  then  joins  with  the  right  vein  to  form 
the  postcava.  In  these  cases  the  two  common  iliacs  are  connected  by  a  small  communicating 
branch  at  the  spot  where  they  are  usually  united.1 

The  Postcava,  Ascending,  or  Inferior  Vena  Cava  (v.  cava  inferior)  (Figs.  464 
and  471)  returns  to  the  heart  the  blood  from  all  the  parts  below  the  Diaphragm.  It 
is  formed  by  the  junction  of  the  two  common  iliac  veins  on  the  right  side  of  the 
intervertebral  substance  between  the  fourth  and  fifth  lumbar  vertebrae.  It  passes 
upward  along  the  front  of  the  spine  on  the  right  side  of  the  aorta,  and,  having 
reached  the  under  surface  of  the  liver,  is  contained  in  a  groove  on  its  posterior  sur- 
face. It  then  perforates  the  central  tendon  of  the  Diaphragm,  enters  the  peri- 
cardium, where  it  is  covered  for  a  very  short  distance  by  the  serous  layer  of  the 
pericardium,  and  terminates  in  the  lower  and  back  part  of  the  right  auricle.  At 
its  termination  in  the  auricle  it  is  provided  with  a  valve,  the  Eustachian  valve 
(valvula  v.  cavae  inferioris  [Eustachii]),  which  is  of  large  size  during  total  life. 

Relations. — In  front,  from  below  upward,  with  the  mesentery,  right  spermatic 
artery,  transverse  portion  of  the  duodenum,  the  pancreas,  portal  vein,  and  the 
posterior  surface  of  the  liver,  which,  in  most  cases,  partly  and  occasionally  com- 
pletely surrounds  it;  behind,  with  the  vertebral  column,  the  right  crus  of  the 
Diaphragm,  the  right  renal  and  lumbar  arteries,  and  the  right  semilunar  ganglion; 
on  the  left  side,  with  the  aorta. 

Peculiarities.  In  Position. — This  vessel  is  sometimes  placed  on  the  left  side  of  the  aorta, 
as  high  as  the  left  renal  veins,  after  receiving  which  it  crosses  over  to  its  usual  position  on  the 
right  side;  or  it  may  be  placed  altogether  on  the  left  side  of  the  aorta,  as  far  upward  as  its  ter- 
mination in  the  heart:  in  such  cases  the  abdominal  and  thoracic  viscera,  together  with  the  great 
vessels,  are  all  transposed. 

Point  of  Termination.— Occasionally  the  postcava  joins  the  right  azygos  vein,  which  is  then 
of  large  size.  In  such  cases  the  precava  receives  the  whole  of  the  blood  from  the  body  before 
transmitting  it  to  the  right  auricle,  except  the  blood  from  the  hepatic  veins,  which  passes 
directly  into  the  right  auricle. 

i  See  two  cases  which  have  been  described  by  Mr.  Walsham  in  St.  Bartholomew's  Hospital  Reports,  vols. 
xvi.  and  xvii. — ED.  of  15th  English  edition. 


THE   DEEP    VEINS    OF    THE   LOWER    EXTREMITY          765 

Tributaries. — It  receives  in  its  course  the  following  veins: 

Lumbar.  Suprarenal. 

Right  Spermatic.  Phrenic. 

Renal.  Hepatic. 

The  Lumbar  Veins  (w.  lumbales),  four  in  number  on  each  side,  collect  the 
blood  by  dorsal  tributaries  from  the  muscles  and  integument  of  the  loins  and  by 
abdominal  tributaries  from  the  walls  of  the  abdomen,  where  they  communicate 
with  the  epigastric  veins.  At  the  spine  they  receive  veins  from  the  spinal  plexuses, 
and  then  pass  forward,  round  the  sides  of  the  bodies  of  the  vertebrae  beneath  the 


FIG.  476. — Spermatic  veins.     (Testut.) 

Psoas  magnus  muscle,  and  terminate  at  the  back  part  of  the  postcava.  The 
left  lumbar  veins  are  longer  than  the  right,  and  pass  behind  the  aorta.  The  lumbar 
veins  of  a  side  are  connected  together  by  a  longitudinal  vein  which  passes  in  front 
of  the  transverse  processes  of  the  lumbar  vertebras,  and  is  called  the  ascending 
lumbar  vein  (v.  lumbalis  ascendens)  (Fig.  464).  It  forms  the  most  frequent  origin 
of  the  corresponding  vena  azygos,  and  serves  to  connect  the  common  iliac,  ilio- 
lumbar,  lumbar,  and  azygos  veins  of  the  corresponding  side  of  the  body. 

The  Spermatic  Veins  (vv.spermaticae)(F'\g.  476)  emerge  from  the  back  of  the  testis, 
and  receive  tributaries  from  the  epididymis;  they  unite  and  form  a  convoluted 
plexus  called  the  spermatic  plexus  (plexus  pampiniformis) ,  which  forms  the  chief 


760 


THE   BLOOD -VASCULAR   SYSTEM 


mass  of  the  cord :  the  vessels  composing  this  plexus  are  very  numerous,  and  ascend 
along  the  cord  in  front  of  the  vas  deferens;  below  the  external  abdominal  ring  they 
unite  to  form  three  or  four  veins,  which  pass  along  the  inguinal  canal,  and,  enter- 
ing the  abdomen  through  the  internal  abdominal  ring,  coalesce  to  form  two  veins, 
which  ascend  on  the  Psoas  muscle  behind  the  peritoneum,  lying  one  on  each  side 
of  the  spermatic  artery,  and  unite  to  form  a  single  vein,  which  opens  on  the  right 


SPERMATIC  VEIN- 
LEFT   SIDE 


SPERMATIC   VEIN — __ 
RIGHT  SIDE 


FIG.  477. — Terminations  of  the  right  and  left  spermatic  veins.     (Poirier  and  Charpy.) 

side  into  the  postcava  at  an  acute  angle;  on  the  left  side  into  the  left  renal  vein 
at  a  right  angle  (Fig.  477).  The  termination  of  the  left  spermatic  vein  is  called 
the  emulgent  vein.  Professor  John  H.  Brinton  pointed  out  that  a  valve  is  usually 
absent  in  the  emulgent  vein  (Fig.  478),  but  regularly  present  in  the  right  spermatic 
vein.1  The  left  spermatic  vein  passes  behind  the  sigmoid  flexure  of  the  colon, 
and  is  thus  exposed  to  pressure  from  the  contents  of  that  bowel. 

Surgical  Anatomy. — The  spermatic  veins  are  very  frequently  varicose,  constituting  the  dis- 
ease known  as  varicocele.  Though  it  is  quite  possible  that  the  originating  cause  of  this  affection 
may  be  a  congenital  abnormality  either  in  the  size  or  number  of  the  veins  of  the  pampiniform 
plexus,  still  it  must  be  admitted  that  there  are  many  anatomical  reasons  why  these  veins  should 
become  varicose — viz.,  the  imperfect  support  afforded  to  them  by  the  loose  tissue  of  the  scrotum; 
their  great  length;  their  vertical  course;  their  dependent  position;  their  plexiform  arrangement 
in  the  scrotum,  with  their  termination  in  one  small  vein  in  the  abdomen;  their  few  and  imperfect 
valves ;  and  the  fact  that  they  may  be  subjected  to  pressure  in  their  passage  through  the  abdominal 
wall.  The  left  veins  more  often  become  varicose  than  the  right  veins,  probably,  as  Brinton  sug- 
gests, because  the  right  spermatic  vein  practically  always  has  a  valve  and  opens  into  the  post- 
cava at  an  acute  angle,  whereas  the  left  spermatic  vein  is  not  unusually  destitute  of  a  valve  at 
its  opening  and  passes  into  the  left  renal  vein  at  a  right  angle. 

The  Ovarian  Veins  (vv.  ovaricae)  (Fig.  475)  are  analogous  to  the  spermatic  in  the 
male;  they  form  a  plexus  near  the  ovary  in  the  broad  ligament  and  about  the  Fallo- 
pian tube,  communicating  with  the  uterine  plexus.  They  terminate  in  the  same  way 
as  the  spermatic  veins  in  the  male.  Valves  are  occasionally  found  in  these  veins. 
These  vessels,  like  the  uterine  veins,  become  much  enlarged  during  pregnancy. 

1  See  John  H.  Brinton  in  the  American  Journal  of  the  Medical  Sciences,  and  also  Handbuch  der  Topographi- 
schen  Anatomie.von  Joseph  Hyrtl.  Rivington  maintains  that  a  valve  is  usually  found  at  the  orifices  of  both  the 
right  and  left  spermatic  veins.  When  no  valves  exist  at  the  opening  of  the  left  spermatic  vein  into  the  left  renal 
vein,  valves  are  generally  present  in  the  left  renal  vein  within  a  quarter  of  an  inch  from  the  orifice  of  the 
spermatic  vein.  (Journal  of  Anatomy  and  Physiology,  vol.  vii.  p.  163). — ED.  of  15th  English  edition. 


THE  DEEP   VrEINS  OF  THE  LOWER  EXTREMITY 


767 


The  Renal  Veins  (vv.  renales)  (Fig.  465)  are  of  large  size,  and  are  placed  in  front 
of  the  renal  arteries.1  The  left  is  longer  than  the  right,  and  passes  in  front  of  the 
aorta,  just  below  the  origin  of  the  superior  mesenteric  artery.  It  receives  the  left 
spermatic,  the  left  inferior,  and,  generally,  the  left  suprarenal  veins.  It  opens  into 
the  postcava  a  little  higher  than  the  right.  The  utero-venous  triangle  of  Robinson 
is  formed  by  the  ureter,  the  renal  veins,  and  the  ovarian  veins. 

The  Suprarenal  Veins  (vv.  suprarenales)  (Fig.  464)  are  two  in  number:  that  on 
the  right  side  terminates  in  the  postcava;  that  on  the  left  side,  in  the  left  renal 
or  in  the  left  phrenic  vein. 

The  Phrenic  Veins  (vv.  phrenicae}  follow  the  course  of  the  phrenic  arteries. 
The  two  superior  phrenic  veins  (vv.  phrenicae  superiores),  of  small  size,  accom- 
pany the  phrenic  nerve  and  comes  nervi  phrenici  artery,  and  join  the  internal 


in  the  left  renal  vein.     (John  H.  Brinton.) 


mammary  vein.  The  two  inferior  phrenic  veins  (w.  phrenicae  inferiores)  follow 
the  course  of  the  phrenic  arteries,  and  terminate,  the  right  in  the  postcava,  the 
left  in  the  left  renal  vein. 

The  Hepatic  Veins  (vv.  hepaticae)  commence  in  the  substance  of  the  liver,  in 
the  capillary  terminations  of  the  portal  vein  and  hepatic  artery,  intralobular  veins: 
these  tributaries,  gradually  uniting  into  sublobular  veins;  usually  form  three  large 
hepatic  veins,  which  converge  toward  the  posterior  surface  of  the  liver  and  open 
into  the  postcava,  whilst  that  vessel  is  situated  in  the  groove  at  the  back  part  of 
this  organ.  Of  these  three  veins,  one  from  the  right  and  another  from  the  left 

1  The  student  may  observe  that  all  veins  above  the  Diaphragm,  which  do  not  lie  on  the  same  plane  as  the 
arteries  which  they  accompany,  lie  in  front  of  them,  and  that  all  veins  below  the  Diaphragm,  which  do  Tiot 
lie  on  the  same  plane  as  the  arteries  which  they  accompany,  lie  behind  them,  except  the  renal  and  profunda 
femoris  vein. — ED.  of  15th  English  edition. 


768  THE  BLOOD-VASCULAR  SYSTEM 

lobe  open  obliquely  into  the  postcava,  that  from  the  middle  of  the  organ  and 
lobulus  Spigelii  having  a  straight  course.  The  hepatic  veins  run  singly,  and  are 
in  direct  contact  with  the  hepatic  tissue.  They  are  destitute  of  valves. 

The  Portal  System  of  Veins  (Fig.  479). 

The  portal  venous  system  is  composed  of  four  large  veins  which  collect  the 
venous  blood  from  the  viscera  of  digestion  (stomach,  intestine,  and  pancreas)  and 
from  the  spleen.  The  trunk  formed  by  their  union,  the  portal  vein,  enters  the  liver 
and  ramifies  throughout  its  substance  after  the  manner  of  an  artery  and  ends 
in  capillaries,  from  which  the  blood  is  collected  into  the  hepatic  veins,  which 
terminate  in  the  postcava.  The  branches  of  this  vein  are  in  all  cases  single,  and 
destitute  of  valves. 

The  veins  forming  the  portal  system  are — -the 

Superior  Mesenteric.  Inferior  Mesenteric. 

Splenic.  Gastric. 

Cystic. 

The  Superior  Mesenteric  Vein  (v.  mesenterica  superior}  (Fig.  479)  returns  the 
blood  from  the  small  intestines  and  from  the  caecum  and  ascending  and  transverse 
portions  of  the  colon,  corresponding  with  the  distribution  of  the  branches  of  the 
superior  mesenteric  artery.  The  large  trunk  formed  by  the  union  of  these  branches 
ascends  along  the  right  side  and  in  front  of  the  corresponding  artery,  passes  in  front 
of  the  transverse  portion  of  the  duodenum,  and  unites,  behind  the  upper  border 
of  the  pancreas,  with  the  splenic  vein  to  form  the  portal  vein.  It  receives  the 
right  gastro-epiploic  vein.  The  appendicular  vein  is  a  tributary  of  the  superior 
mesenteric  vein. 

The  Splenic  Vein  (v.  lienalis)  (Fig.  479)  commences  by  five  or  six  large  branches 
which  return  the  blood  from  the  substance  of  the  spleen.  These,  uniting,  form  a 
single  vessel,  which  passes  from  left  to  right,  grooving  the  upper  and  back  part  of 
the  pancreas  below  the  artery,  and  terminates  at  its  greater  end  by  uniting  at  a 
right  angle  with  the  superior  mesenteric  to  form  the  portal  vein.  The  splenic  vein 
is  of  large  size,  and  not  tortuous  like  the  artery.  It  receives  the  vasa  brevia  from 
the  left  extremity  of  the  stomach,  the  left  gastro-epiploic  vein,  pancreatic  branches 
from  the  pancreas,  the  pancreatico-duodenal  vein,  and  the  inferior  mesenteric  vein. 

The  Inferior  Mesenteric  Vein  (v.  mesenterica  inferior}  (Fig.  479)  returns  the 
blood  from  the  rectum,  sigmoid  flexure,  and  descending  colon,  corresponding  with 
the  ramifications  of  the  branches  of  the  inferior  mesenteric  artery.  It  lies  to  the  left 
of  the  artery,  and  ascends  beneath  the  peritoneum  in  the  lumbar  region;  it  passes 
behind  the  transverse  portion  of  the  duodenum  and  pancreas,  and  terminates  in 
the  splenic  vein.  Its  hemorrhoidal  branches,  the  superior  hemorrhoidal  veins  (w. 
hemorrhoidalis  superior),  inosculate  with  the  middle  hemorrhoidal  branches  of  the 
internal  iliac,  and  thus  establish  a  communication  between  the  portal  and  the 
general  venous  system.1 

The  Gastric  Veins  (w.  gastricae)  (Fig.  479)  are  two  in  number :  one,  a  small  vein, 
corresponds  to  the  pyloric  branch  of  the  hepatic  artery;  the  other,  considerably 
larger,  corresponds  to  the  gastric  artery.  The  former,  the  pyloric  vein  (v.  pylorica), 
runs  along  the  lesser  curvature  of  the  stomach  toward  the  pyloric  end,  receives 
branches  from  the  pylorus  and  duodenum,  and  ends  in  the  portal  vein.  The 
latter,  the  gastric  or  coronary  vein  (v.  coronaria  ventriculi),  begins  near  the  pylorus, 


THE  PORTAL  SYSTEM  OF  VEINS 


769 


runs  along  the  lesser  curvature  of  the  stomach  toward  the  oesophageal  opening 
in  the  diaphragm,  and  then  passes  across  the  front  of  the  spine  from  left  to  right 
to  end  in  the  portal  vein,  at  a  point  a  little  above  the  junction  of  the  pyloric  vein. 
The  Cystic  Vein  (y.  cystica)  (Fig.  479). — The  portal  vein  generally  receives  the 
cystic  vein,  although  that  vessel  sometimes  terminates  in  the  right  branch  of  the 
portal  vein. 


FIG.  479. — Portal  vein  and  its  branches. 

NOTE. — In  this  diagram  the  right  gastro-epiploic  vein  opens  into  the  splenic  vein;  generally 
it  empties  itself  into  the  superior  mesenteric,  close  to  its  termination. 

The  Portal  Vein  (vena  portae)(F\g.  479)  is  formed  by  the  junction  of  the  superior 
mesenteric  and  splenic  veins,  their  union  taking  place  in  front  of  the  vena  cava  and 
behind  the  upper  border  of  the  head  of  the  pancreas.  Passing  upward  through 
the  right  border  of  the  lesser  omentum  to  the  under  surface  of  the  liver,  it  enters 
the  transverse  fissure,  where  it  is  somewhat  enlarged,  forming  the  sinus  of  the 
portal  vein,  and  divides  into  two  branches  which  accompany  the  ramifications  of 
the  hepatic  artery  and  hepatic  duct  throughout  the  substance  of  the  liver.  Of 

49 


770 


THE   BLOOD -VASCULAR    SYSTEM 


these  two  branches,  the  right  is  the  larger,  but  the  shorter,  of  the  two.  The  portal 
vein  is  about  three  or  four  inches  in  length,  and,  whilst  contained  in  the  lesser 
omentum,  lies  behind  and  between  the  common  bile-duct  and  the  hepatic  artery, 
the  former  being  to  the  right,  the  latter  to  the  left.  These  structures  are  accom- 
panied by  filaments  of  the  hepatic  plexus  of  nerves  and  numerous  lymphatics, 
and  are  surrounded  by  a  quantity  of  loose  areolar  tissue,  the  capsule  of  Glisson. 

The  portal  vein  divides,  in  the  substance  of  the  liver,  like  an  artery,  and  its 
minute  ramifications  end  in  capillaries,  from  which  the  blood  is  carried  to  the 
postcava  by  the  hepatic  veins;  these  veins  also  collect  the  blood  which  has  been 
brought  to  the  liver  by  the  hepatic  artery.  It  will  therefore  be  seen  that  the  blood 
which  is  carried  to  the  liver  by  the  portal  vein  passes  through  two  sets  of  capillary 
vessels— vi z. :  (1)  the  capillaries  in  the  stomach,  intestine,  pancreas,  and  spleen, 
and  (2)  the  capillaries  of  the  portal  vein  in  the  liver. 


THE  CARDIAC  VEINS  (Fig.  480). 
The  veins  which  return  the  blood  from  the  substance  of  the  heart  are — the 


Great  Cardiac  Vein. 
Posterior  Cardiac  Vein. 
Left  Cardiac  Veins. 


Anterior  Cardiac  Veins. 
Right  or  Small  Coronary  Vein. 
Coronary  Sinus. 
Venae  Thebesii. 


The  Great  Cardiac  or  Left  Coronary  Vein  (v.  cordis  magna)  is  a  vessel  of 
considerable  size,  which  commences  at  the  apex  of  the  heart,  and  ascends  along 
the  anterior  interventricular  groove  to  the  base  of  the  ventricles.  It  then  curves 


PULMONARY 

VEINS 

LEFT    AURICULAR, 
APPENDIX 


RIGHT  CORONARY   ARTERY 

AURICULAR- VENTRICULAR 

GROOVE 

CORONARY.. 
SINUS 


LEFT 
VENTRICLE' 


•VENA    AZYGOS 
MAJOR 


.PULMONARY 

VEINS 
LEFT 

AURICLE 


POSTERIOR  CARDIAC1 
VEIN 

POSTERIOR 


RIGHT  CORONARY 

iRTERY DESCEND" 

INQ  BRANCH 


ULAR  GROOVE     VENTRICLE 

FIG.  480. — Cardiac  veins,  dorsal  view.      (Testut.) 


to  the  left  side,  around  the  auriculo-ventricular  groove,  between  the  left  auricle 
and  ventricle,  to  the  back  part  of  the  heart,  and  opens  into  the  left  extremity 
of  the  coronary  sinus,  its  aperture  being  guarded  by  two  valves.  It  receives,  in 


THE    CARDIAC    VEINS  771 

its  course,  tributaries  from  both  ventricles,  but  especially  from  the  left,  and  also 
from  the  left  auricle;  one  of  these  ascending  along  the  thick  margin  of  the  left 
ventricle  is  of  considerable  size,  and  is  called  the  left  marginal  vein.  The  vessels 
joining  the  great  cardiac  vein  are  provided  with  valves. 

The  Posterior  or  Middle  Cardiac  Vein  (v.  cordis  media)  commences  by  small 
tributaries,  at  the  apex  of  the  heart,  communicating  with  those  of  the  preceding. 
It  ascends  along  the  posterior  interventricular  groove  to  the  base  of  the  heart, 
and  terminates  in  the  coronary  sinus,  its  orifice  being  guarded  by  a  valve.  It 
receives  veins  from  the  posterior  surface  of  both  ventricles. 

The  Left  Cardiac  Vein  (v.  posterior  ventriculi  sinistri)  receives  three  or  four 
small  vessels,  which  collect  the  blood  from  the  posterior  surface  of  the  left  ven- 
tricle. It  opens  into  the  lower  border  of  the  coronary  sinus. 

The  Anterior  Cardiac  Veins  (vv.  cordis  anteriores)  are  three  or  four  small 
vessels,  which  collect  the  blood  from  the  anterior  surface  of  the  right  ventricle. 
One  of  these,  the  vein  of  Galen,  larger  than  the  rest,  runs  along  the  right  border 
of  the  heart.  They  open  separately  into  the  lower  part  of  the  right  auricle. 

The  Right  Cardiac  or  Small  Coronary  Vein  (v.  cordis  parva)  runs  along  the 
groove  between  the  right  auricle  and  ventricle,  to  open  into  the  right  extremity  of 
the  coronary  sinus.  It  receives  blood  from  the  back  part  of  the  right  auricle  and 
ventricle. 

The  Coronary  Sinus  (sinus  coronarius)  is  that  portion  of  the  anterior  or  great 
cardiac  vein  which  is  situated  in  the  posterior  part  of  the  left  auriculo-ventricular 
groove.  It  is  about  an  inch  in  length,  presents  a  considerable  dilatation,  and  is 
covered  by  the  muscular  fibres  of  the  left  auricle.  It  receives  most  of  the  veins  of 
the  heart.  Besides  those  mentioned  it  receives  the  oblique  vein  of  Marshall  (v.  obliqua 
atrii  sinistri)  from  the  back  part  of  the  left  auricle,  the  remnant  of  the  obliterated 
left  Cuvierian  duct  of  the  foetus,  described  by  Mr.  Marshall.  The  great  coronary 
sinus  terminates  in  the  right  auricle,  between  the  postcava  and  the  auriculo- 
ventricular  aperture,  its  orifice  being  guarded  by  a  semilunar  fold  of  the  lining 
membrane  of  the  heart,  the  Thebesian  valve.  All  the  veins  joining  this  vessel, 
excepting  the  oblique  vein  above  mentioned,  are  provided  with  valves. 

The  Venae  Thebesii  (venae  cordis  minimae)  are  numerous  minute  veins,  which 
return  the  blood  directly  from  the  muscular  substance,  without  entering  the  venous 
current.  They  open  by  minute  orifices,  foramina  Thebesii  (foramina  venarum 
minamarum),  chiefly  on  the  inner  surface  of  the  right  auricle. 


THE  LYMPHATIC  SYSTEM. 


LYMPH  is  obtained  from  the  blood-plasma.  From  lymph  the  body  cells  obtain 
food,  into  lymph  they  discharge  their  waste  materials,  and  there  is  a  distinct 
lymphatic  circulation,  the  constituents  of  the  plasma  passing  into  the  perivascular 
lymph-spaces  and  returning  to  the  heart  by  way  of  the  lymphatics  and  certain 
veins. 

The  lymphatic  system  consists  of  lymphatic  glands — large  lymph- vessels,  small 
lymph- vessels  (lymphatic  capillaries],  the  perivascular  lymph-spaces,  the  lymph 
canalicular  system,  and  the  body  cavities.  To  this  system  also  belong  the  lacteal  or 
chyliferous  vessels.  The  lacteals  are  the  lymphatic  vessels  of  the  small  intestine, 
and  differ  in  no  respect  from  the  lymphatics  generally,  excepting  that  during  the 
process  of  digestion  they  contain  a  milk-white  fluid,  the  chyle,  which  passes  into 
the  blood  through  the  thoracic  duct. 

The  lymph  canalicular  system  is  the  system  of  spaces  in  areolar  connective 
tissue.  The  spaces  are  called  lymph-spaces,  and  are  found  practically  in  every 
region  of  the  body.  In  these  spaces  lie  the  cells  of  the  tissue.  The  larger  spaces 
are  lined  with  endothelium,  the  smaller  spaces  are  not  lined  with  endothelium; 
they  form  connections  with  each  other  by  anastomotic  channels  and  constitute  a 
system  of  spaces  and  channels  which  many  observers  believe  join  the  lymphatic 
capillaries.  Others  maintain  that  lymph-spaces  are  not  direct  continuations  or 
expansions  of  lymph-capillaries,  but  that  networks  of  lymphatic  capillaries  exist 
in  the  tissue  immediately  around  each  space,  an  arrangement  which  permits  of 
interchange  between  the  contents  of  a  space  and  the  contents  of  the  surrounding 
capillaries.  Mall  seems  to  have  proved  this  by  his  experimental  injections  into 
the  portal  vein.  He  showed  that  colored  fluid  injected  into  the  portal  vein  passes 
through  the  walls  of  the  venous  capillaries,  enters  the  lymph-spaces,  and  finally  gets 
into  the  lymph-capillaries  of  the  liver. 

The  perivascular  lymph-spaces  are  found  around  certain  blood-vessels.  Each 
space  is  lined  with  endothelium,  and  is  joined  to  other  spaces  by  trabeculse  of  con- 
nective tissue.  The  spaces  form  a  system,  and  the  fluid  in  these  spaces  reaches  the 
lymphatic  capillaries.  Perivascular  lymph-spaces  have  been  demonstrated  in  the 
Haversian  canals  and  in  the  subdural  space  of  the  pia. 

The  pleural,  pericardial,  peritoneal,  and  synovial  cavities  are  lined  by  endothelial 
cells.  Beneath  the  layer  of  lining  cells  are  lymph-spaces  or  lymph -vessels.  It  was 
long  thought  that  these  lymph-vessels  communicate  directly  with  the  body  cavity 
by  means  of  numerous  openings  in  the  lining  membrane.  This  view  is  probably 
incorrect.  The  subarachnoid  space/the  subdural  space,  the  cavity  for  the  aqueous 
humor  of  the  eye,  the  cavity  for  the  vitreous  humor,  and  the  space  of  Tenon  are 
probably  lymph-spaces. 

Lymph-capillaries  are  arranged  in  networks,  are  larger  than  blood-capillaries, 
but  the  diameter  of  a  lymph -capillary  is  different  at  different  points,  at  some  places 
being  much  larger  than  at  others.  Lymph-capillaries  are  formed  of  flattened 
endothelial  cells.  In  some  situations  networks  of  lymphatic  capillaries  surround 
the  blood-vessels.  The  lymph-vessels  are  called  the  lymphatics. 

The  lymphatics  have  derived  their  name  from  the  appearance  of  the  fluid  con- 
tained in  their  interior  (lympha,  water).  They  are  also  called  absorbents,  from  the 
(772) 


THE  LYMPHATIC  SYSTEM  773 

property  they  possess  of  absorbing  certain  materials  from  the  tissues  and  con- 
veying them  into  the  circulation.  Larger  lymphatics  are  called  trunks  and  the 
largest  are  called  ducts. 

The  lymphatics  are  exceedingly  delicate  vessels,  the  coats  of  which  are  so 
transparent  that  the  fluid  they  contain  is  readily  seen  through  them,  and  they 
appear  milky-white;  hence  the  name  Asellius  gave  them  of  lacteal  veins.  They 
retain  a  nearly  uniform  size,  and  may  be  cylindrical  in  shape,  but  usually  are  inter- 
rupted at  intervals  by  constrictions  which  give  them  a  knotted,  beaded,  or  sac- 
like  appearance.  These  constrictions  are  due  to  the  presence  of  valves  in  the 
interior  of  the  vessel.  Lymphatic  vessels  do  not  invariably  contain  valves.  Valves 
are  absent  at  the  starting  points  of  lymphatics,  are  absent  in  lymphatic  capillaries, 
are  not  numerous  in  the  largest  ducts  (thoracic  duct),  and  are  seldom  found  in  vis- 
ceral lymphatics.  The  valves  are  not  found  in  fixed  situations  and  vary  in  number. 
Between  the  ends  of  the  fingers  and  the  axillary  glands  Sappey  counted  from  sixty 
to  eighty.  "They  are  arranged  in  pairs  and  resemble  the  aortic  semilunar  valves."1 
The  lymphatic  capillaries  are  composed  purely  of  endothelium,  but  the  collecting 
trunks  possess  not  only  an  endothelial  inner  coat,  but  an  investing  elasto-muscular 
coat.  Vessels  in  the  subcutaneous  connective  tissue  are  devoid  of  muscle.  Lymph- 
atics have  been  found  in  nearly  every  texture  and  organ  of  the  body  which  contains 
blood-vessels.  Such  non-vascular  structures  as  cartilage,  the  nails,  cuticle,  and 
hair  have  none,  but  with  these  exceptions  it  is  probable  that  eventually  all  parts 
will  be  found  to  be  permeated  by  these  vessels. 

A  larger  lymphatic  vessel  is  composed  of  three  coats.  The  inner  coat  is 
composed  of  elastic  tissue  lined  with  endothelium.  The  middle  coat  is  com- 
posed of  elastic  and  muscular  fibres.  The  external  coat  is  composed  of  connec- 
tive tissue  intermixed  with  smooth  muscular  fibres  longitudinally  or  obliquely 
placed. 

The  thoracic  duct  possesses  a  subendothelial  layer  of  connective  tissue  like  that 
found  in  the  arteries,  and  in  the  middle  coat  there  is  a  longitudinal  layer  of 
connective  tissue.  The  wall  of  a  smaller  lymphatic  contains  no  elastic  and  no 
muscular  tissue,  and  consists  merely  of  connective  tissue  lined  with  endothelium. 

The  lymphatics  are  arranged  in  superficial  and  deep  sets.  The  superficial  lym- 
phatics, on  the  surface  of  the  body,  are  placed  immediately  beneath  the  integument, 
accompanying  the  superficial  veins;  they  join  the  deep  lymphatics  in  certain  situa- 
tions by  perforating  the  deep  fascia.  In  the  interior  of  the  body  the  lymphatics 
lie  in  the  submucous  areolar  tissue  throughout  the  whole  length  of  the  gastro- 
pulmonary  and  genito-urinary  tracts,  and  in  the  subserous  tissue  of  the  thoracic 
and  abdominal  cavities.  In  the  cranial  cavity  the  perivascular  sheaths  are  lymph- 
spaces.  A  plexiform  network  of  minute,  closed,  capillary  lymphatics  may  be  found 
interspersed  among  the  proper  elements  and  blood-vessels  of  the  several  tissues,  the 
vessels  composing  which,  as  well  as  the  meshes  between  them,  are  much  larger  than 
those  of  the  capillary  blood-vessel  plexus.  From  these  networks  small  collecting 
vessels  emerge,  pass  to  a  neighboring  gland,  and  divide  into  a  capillary  network 
in  the  gland.  Numerous  small  vessels  emerge  from  the  gland,  which  unite  into 
one  lymphatic  vessel,  which  joins  a  larger  lymphatic  trunk,  which  empties  into 
a  branch  of  the  precava.  The  deep  lymphatics,  fewer  in  number  and  larger  than 
the  superficial,  accompany  the  deep  blood-vessels.  Their  mode  of  origin  is  prob- 
ably similar  to  that  of  the  superficial  vessels.  The  lymphatics  of  any  part  or  organ 
exceed  the  veins  in  number  and  in  capacity,  but  in  size  they  are  much  smaller. 
Their  anastomoses  also,  especially  those  of  the  large  trunks,  are  more  frequent, 
and  are  effected  by  vessels  equal  in  diameter  to  those  which  they  connect.  The 
continuous  trunks  retain  the  same  diameter  throughout.  As  the  lymphatic  vessels 

1  A  Treatise  on  Anatomy.  By  P.  Poirier  and  A.  Charpy.  Article  on  the  Lymphatics.  By  G.  Delamare, 
P.  Poirier,  and  B.  Cune"o. 


774 


THE  LYMPHATIC  SYSTEM 


approach  their  point  of  discharge  their  number  diminishes,  but  the  calibre  of  the 
remainder  does  not  increase  in  proportion. 

The  gaps  in  the  connective  tissue,  the  larger  of  which  are  lined  with  endothelium, 
the  smaller  of  which  are  devoid  of  endothelial  lining,  are  known  as  lymphatic 
spaces.  (See  page  772.) 

The  lymphatic  or  absorbent  glands  (lymphoglandulae) ,  named  also  conglobate 
glands  and  lymph-nodes,  are  small,  solid,  glandular  bodies  situated  in  the  course  of 
the  lymphatic  and  lacteal  vessels.  They  vary  from  microscopic  dimensions  to  the 
size  of  an  olive,  and  their  color,  on  section,  is  of  a  pinkish-gray  tint,  excepting  the 
bronchial  glands,  which  in  the  adult  are  mottled  with  black,  the  hepatic  glands, 
which  are  yellow,  and  the  splenic  glands,  which  are  brown.  Each  gland  has 
a  layer  or  capsule  of  cellular  tissue  investing  it,  from  which  prolongations  dip 
into  its  substance,  forming  partitions.  The  lymphatic  and  lacteal  vessels  pass 

through  these  glands  in  their  passage  to  the  lymph- 
atic ducts.  A  lymphatic  or  lacteal  vessel,  previous  to 
entering  a  gland,  divides  into  several  small  branches, 
which  are  named  afferent  vessels  (vasa  afferentia}. 
As  they  enter  the  gland,  the  external  coat  of  each 
becomes  continuous  with  the  capsule  of  the  gland, 
and  the  vessels  becoming  much  thinned,  and  consist- 
ing only  of  their  internal  or  endothelial  coat,  pass 
into  the  gland,  and  branch  out  upon  and  in  the  tissue 
of  the  capsule,  these  branches  opening  into  the  lymph- 
sinuses  of  the  gland.  There  is  an  extensive  sinus 
beneath  the  capsule;  from  this  subcapsular  sinus 
numerous  branches  run  inward  to  a  central  sinus. 
From  both  sinuses  fine  branches  proceed  to  form  a 
plexus,  the  vessels  of  which  unite  to  form  a  single 
efferent  vessel  (vas  efferens),  which,  on  emerging 
from  the  gland,  is  again  invested  with  an  external 
coat  from  the  gland  capsule.  The  lymph-glands  are 
filters  through  which  lymph  and  chyle  flow.  Car- 
cinoma cells  are  caught  in  them,  and  the  dissemina- 
tion of  the  disease  is  retarded.  In  the  glands  are 
masses  of  newly  formed  leukocytes  which  attack  any 
bacteria  in  the  lymph  or  chyle. 

The  size  of  the  lymphatic  glands  decreases  as  age 
advances,  and  in  very  old  individuals  many  glands 
actually  disappear.  It  is  impossible  to  estimate  the 

number  of  macroscopic  glands.  Sappey  estimated  the  number  to  be  from  600  to 
700.  Glands  are  embedded  in  fat  and  are  distinctly  movable.  Some  of  them  are 
superficial  (above  the  deep  fascia);  others  are  deep  (below  the  deep  fascia). 
Occasionally  a  gland  exists  alone,  but,  as  a  rule,  they  are  assembled  in  com- 
munities or  chains  of  from  eight  to  twelve,  or  even  more.  They  are  usually 
arranged  around  vessels,  and  often  are  upon  vessels.  The  glands  have  a  plen- 
tiful blood-supply,  and  contain  not  only  vascular  nerves,  but  definite  nerve- 
plexuses.  Besides  the  glands,  the  body  contains  numerous  lymphoid  areas, 
which,  in  structure  and  function,  are  allied  to  lymph-glands  (tonsils,  Peyer's 
patches,  etc.). 

Hemolymph  nodes  exist  in  various  regions,  but  are  most  common  in  the  abdomen 
in  front  of  the  vertebras.  They  are  like  ordinary  lymph-nodes  in  form  and  also  in 
size,  but  differ  from  them  in  being  deep  red  instead  of  light  pink.  Some  regard 
hemolymph  nodes  as  structures  like  the  spleen;  others  regard  them  as  very  vas- 
cular but  otherwise  ordinary  nodes. 


FIG.  481. — A  lymph-node  with  its 
afferent  and  efferent  vessels.  (Tes- 
tut.)  • 


THE  THORACIC  AND  RIGHT  LYMPHATIC  DUCT 


775 


Surgical  Anatomy. — In  an  operation  for  cancer  it  is  not  sufficient  to  cut  wide  of  the  growth 
and  remove  it;  it  is  imperatively  necessary  to  remove  the  lymphatic  glands  which  receive  lymph 
from  the  diseased  area,  and  also,  when  possible,  the  lymphatic  vessels  between  the  cancer  and 
the  glands.  Glands  are  diseased  very  early  in  cancer,  long  before  they  are  palpably  enlarged, 
and  are  usually  infected  by  emboli  of  can- 
cer cells.  The  rule  is  in  any  cancer,  how- 
ever recent,  to  regard  the  associated  glands 
as  diseased,  whether  enlarged  or  not,  and 
to  thoroughly  remove  them,  if  possible,  in 
one  piece,  with  the  intervening  lymph-ves- 
sels and  the  area  of  primary  malignant 
growth. 


Bight 

lymphatic 
duct. 


THE    THORACIC    DUCT    AND 

THE  RIGHT  LYMPHATIC 

DUCT. 

The  thoracic  duct  or  the  left 
lymphatic  duct  (ductus  thoracicus) 
(Fig.  482)  conveys  the  great  mass 
of  lymph  and  chyle  into  the  blood. 
It  is  the  common  trunk  of  all  the 
lymphatic  vessels  of  the  body  below 
the  Diaphragm,  and  usually,  but  not 
always,  also  receives  the  lymph  from 
the  left  side  of  the  body  above  the 
Diaphragm.  It  does  not  drain  the 
right  side  of  the  head  and  neck, 
the  right  upper  extremity,  the  right 
lung,  right  side  of  the 'heart,  and  the 
convex  surface  of  the  liver.  It  partly 
drains  the  right  chest  wall.  It  varies 
in  length  from  fifteen  to  eighteen 
inches  in  the  adult,  and  extends  from 
the  second  lumbar  vertebra  to  the 
root  of  the  neck.  The  duct  is  formed 
by  the  union  of  the  right  and  left 
lumbar  trunks  (trunci  lumbales), 
from  the  lumbar  lymph-nodes.  The 
left  lumbar  trunk  also  obtains  lymph 
from  the  creliac  and  mesenteric 
nodes.  A  little  distance  above  its 
origin  the  thoracic  duct  usually  pre- 
sents a  triangular  dilatation,  the 
receptaculum  chyli  or  the  reservoir 
or  cistern  of  Pecquet  (cisterna  chyli}, 
which  is  situated  upon  the  front  of 
the  bodies  of  the  first  and  of  the  sec- 
ond lumbar  vertebra?,  to  the  right 
side  and  behind  the  aorta,  by  the 
side  of  the  right  crus  of  the  Dia- 
phragm. The  receptaculum  is 
absent  in  some  individuals.  The  thoracic  duct  ascends  into  the  thorax  through 
the  aortic  opening  in  the  Diaphragm,  lying  to  the  right  of  the  aorta,  and  is  placed 
in  the  posterior  mediastinum  in  front  of  the  vertebral  column,  lying  between  the 
aorta  and  vena  azygos  major.  Opposite  the  fourth  thoracic  vertebra  it  inclines 


FIG.  482. — The  thoracic  and  rirfit  lymphatic  ducts. 


776 


THE  LYMPHATIC  SYSTEM 


toward  the  left  side,  and  ascends  behind  the  arch  of  the  aorta  on  the  left  side  of 
the  oesophagus,  and  behind  the  first  portion  of  the  left  subclavian  artery,  to  the 
upper  orifice  of  the  thorax.  Opposite  the  seventh  cervical  vertebra  it  turns  out- 
ward and  then  curves  downward  over  the  subclavian  artery  and  in  front  of  the 
Scalenus  anticus  muscle,  so  as  to  form  an  arch,  and  terminates  in  the  left  sub- 
clavian vein  at  its  angle  of  junction  with  the  left  internal  jugular  vein.  It  usually 
opens  at  the  apex  of  the  angle  in  the  superior  and  outer  surface,  but  may  open 
on  the  posterior  surface.  Sometimes  it  terminates  by  two  branches.  Figs.  482 
and  484  show  the  termination  of  the  thoracic  duct.  The  thoracic  duct,  at 
its  commencement,  is  about  equal  in  diameter  to  that  of  a  goose-quill,  dimin- 
ishes considerably  in  its  calibre  in  the  middle  of  the  thorax,  and  is  again 
dilated  just  before  its  termination,  the  ampulla.  It  is  generally  flexuous  in  its 
course,  the  older  the  person  the  greater  the  flexuosity,  and  it  is  constricted  at  inter- 
vals so  as  to  present  a  varicose  appearance.  The  thoracic  duct  not  infrequently 
divides  in  the  middle  of  its  course  into  two  branches  of  unequal  size,  which 
soon  reunite,  or  divides  into  several  branches,  which  form  a  plexiform  interlace- 
ment. It  occasionally  divides,  at  its  upper  part,  into  two  branches,  of  which  the 
one  on  the  left  side  terminates  in  the  usual  manner,  while  that  on  the  right  opens 
into  the  right  subclavian  vein,  in  connection  with  the  right  lymphatic  duct.  The 
thoracic  duct  has  several  valves  throughout  its  whole  course,  but  they  are  more 
numerous  in  the  upper  than  in  the  lower  part,  and  the  lower  valves  are  not  com- 
petent; at  its  termination  it  is  provided  with  a  pair  of  competent  valves,  the  free 
borders  of  which  are  turned  toward  the  vein,  so  as  to  prevent  the  passage  of 
venous  blood  into  the  duct. 

The  common  intestinal  trunk  (truncus  intestinalis)  (Figs.  482,  483,  and  509) 
empties  into  the  receptaculum  and  brings  lymph  from  the  small  intestine  (lacteals), 
the  stomach,  the  pancreas,  and  the  spleen. 

Radicals  of  Origin  and  Tributaries. — In  most  individuals  the  juxta-aortic 
glands  which  are  placed  on  each  side  of  the  aorta  send  a  vessel  upward  and 
inward,  which  unite  to  form  the  thoracic  duct.  The  right  vessel  is  known  as 
the  truncus  lymphaticus  lumbalis  dextra.  The  left  vessel  is  known  as  the  truncus 
lymphaticus  lumbalis  sinistra.  A  vessel  from  the  glands  in  front  of  (pre-aortic) 
and  back  (retro-aortic)  of  the  aorta  empties  into  each  of  the  above-named  vessels. 
In  some  cases  a  large  vessel  forms  from  the  glands  in  front  of  the  aorta  and  helps 
form  the  duct.  The  receptaculum  chyli  receives  the  common  intestinal  lymphatic 
trunk,  which  conveys  lymph  from  the  small  intestine,  stomach,  spleen,  pancreas, 
and  a  portion  of  the  liver. 


FIG.  483. — Modes  of  origin  of  the  thoracic  duct,      o,   -    -   .      .          . 

trunk  of  the  efferents  of  the  right  juxta-aortic  glands;   c,  common  trunk  of  the  efferent s 


the  downward  course.      (Poirier  and  Charpy.) 


THE  RIGHT  LYMPHATIC  DUCT 


777 


The  branches  of  the  left  lymphatic  duct  are:  1.  A  descending  trunk,  which 
collects  lymph  from  the  posterior  intercostal  glands  of  the  seven  lower  inter- 
costal spaces.  2.  A  trunk  is  formed  by  vessels  coming  from  the  superior  juxta- 
aortic  glands  beneath  the  Diaphragm.  3.  The  lymphatic  vessels  form  the  upper 
five  intercostal  spaces.  4.  The  lymphatic  vessels  form  the  posterior  mediastinal 
glands  and  retrosternal  glands.  5.  The  left  jugular  trunk  (truncus  jugularis), 
although  this  may  open  directly  into  the  junction  of  the  subclavian  and  internal 
jugular  veins.  6.  In  rare  cases  the  thoracic  duct  receives  near  its  termination 
the  left  subclavian  trunk  (truncus  subclavius)  and  a  broncho-mediastinal  trunk. 
As  a  rule,  however,  the  two  last-mentioned  trunks  empty  into  the  jugulo-subclavian 
junction  separately  or  as  one  duct. 

The  thoracic  duct  receives  the  lymph  from  the  extremities,  the  deep  portion 
of  the  abdominal  wall  and  of  the  pelvic  wall,  the  pelvic  viscera,  the  kidneys  and 
suprarenal  capsules,  the  large  intestine,  the  small  intestine,  the  walls  of  the 
thoracic  cavity,  the  under  surface  and  anterior  portion  of  the  liver,  the  stomach, 
the  spleen,  the  pancreas,  the  sternal  and  intercostal  glands,  the  left  lung,  left 
side  of  the  heart,  trachea,  and  oesophagus,  and  often,  just  before  its  termination, 
the  lymphatics  of  the  left  side  of  the  head  and  neck,  and  of  the  left  upper 
extremity. 

Structure. — The  thoracic  duct  is  composed  of  three  coats,  which  differ  in  some 
respects  from  those  of  the  lymphatic  vessels.  The  internal  coat  consists  of  a  single 
layer  of  flattened  endothelial  cells;  of  a  subendothelial  layer,  similar  to  that  found 
in  the  arteries;  and  an  elastic  fibrous  coat,  the  fibres  of  which  run  in  a  longitudinal 
direction.  Each  endothelial  cell  is  shaped  like  a  lance-head  and  has  serrated 


LONGUS  COLLI   MUSCLE 

COMMON  CAROTID 

ARTERY 

LEFT  VAGUS 

NERVE 

VERTEBRAL  ARTERV 

VERTEBRAL  VEIN 
THORACIC  DUCT 

INTERNAL  JUGULAR 

VEIN 

EXTERNAL  JUGULAR 

VEIN 

ANTERIOR  JUGULAR 

VEIN 

SUBCLAVIAN 

VEIN 


FIG.  484. — The  bend  of  the  thoracic  duct  at  its  termination  in  the  subclavian  vein.      (Poirier  and  Charpy.) 

borders.  The  middle  coat  consists  of  a  longitudinal  layer  of  white  connective 
tissue  with  elastic  fibres,  external  to  which  are  several  laminse  of  muscular 
tissue,  the  fibres  of  which  are  for  the  most  part  disposed  transversely,  but  some 
are  oblique  or  longitudinal.  The  muscular  fibres  are  intermixed  with  elastic 
fibres.  The  external  coat  is  composed  of  areolar  tissue,  with  elastic  fibres  and 
isolated  fasciculi  of  muscular  fibres. 

The  Right  Lymphatic  Duct  (Ductus  Lymphaticus  Dexter) 

(Figs.  482,  485,  486,  509). 

A  right  lymphatic  duct  is  frequently  present.  It  is  a  short  trunk,  about  half  an 
inch  in  length  and  a  line  or  a  line  and  a  half  in  diameter.  It  is  formed  by  the  union 
of  the  right  jugular,  right  broncho-mediastinal,  and  right  subclavian  trunks. 
Often  on  the  right  side  the  jugular,  subclavian,  and  broncho-mediastinal  trunks 


778 


THE  LYMPHATIC  SYSTEM 


are  double.  Usually  they  open  into  the  junction  of  the  internal  jugular  and 
subclavian  veins  separately.  Sometimes  they  unite  and  open  by  one  duct,  and 
that  is  the  right  lymphatic  duct.  The  orifice  of  the  right  lymphatic  duct  is 
guarded  by  two  semilunar  valves,  which  prevent  the  passage  of  venous  blood 
into  the  duct. 

Tributaries. — The  right  lymphatic  duct,  if  present,  receives  lymph  from  the 
right  side  of  the  head  and  neck,  the  right  upper  extremity,  the  right  side  of 
the  thorax,  the  right  lung,  and  the  right  side  of  the  heart,  and  from  part  of  the 
convex  surface  of  the  liver. 


FIG.  485. — Terminal  collecting  trunks  of  the  right  half  of  the  supra-diaphragmatic  portion  of  the  body.  a. 
jugular  trunk;  b,  subclavian  trunk;  c,  broncho-mediastinal  trunk;  d,  right  lymphatic  trunk;  e,  gland  of  the 
internal  mammary  chain;  /,  gland  of  the  deep  cervical  chain.  (Poirier  and  Charpy.) 

LYMPHATICS  OF  THE  CRANIAL  REGION,  FACE,  AND  NECK. 

It  is  customary  to  divide  the  lymphatics  of  this  region  into  intracranial  and 
extracranial  lymphatics.  The  statement  is  made  by  Poirier  and  Cuneo1  that  the 
brain  and  its  membranes  are  without  lymphatics.  They  state  that  there  are 
spaces  in  the  nervous  centres  comparable  to  lymphatic  channels,  but  which  are 
not  truly  lymphatic  vessels  and  which  are  regarded  by  most  as  independent  of  the 
lymphatic  system.  Other  writers  believe  that  there  are  cerebral  and  meningeal 
lymphatic  vessels.  It  is  highly  probable  that  the  perivascular  spaces  around  the 
cerebral  arteries  are  the  beginning  of  a  cerebral  lymph  system,  and  that  these  peri- 
vascular  lymph-channels  pass  out  of  the  cranium  with  the  arteries  and  the  internal 
jugular  vein  and  terminate  in  the  superior  deep  cervical  glands.  It  is  also  probable 
that  lymph-spaces  surround  the  dural  blood-vessels  and  terminate  in  the  superior 
deep  cervical  and  the  internal  maxillary  glands. 

The  extracranial  lymphatics  are  divided  into  superficial  and  deep,  and  the  two 
systems  freely  communicate.  All  of  these  vessels  run  into  glands  about  the 
head  and  neck.  The  superficial  lymphatics  take  origin  in  the  subcutaneous 
tissue  and  superficial  muscles.  The  deep  vessels  arise  in  the  orbit,  mouth,  nose, 
pharynx,  oesophagus,  tongue,  larynx,  and  the  muscular,  ligamentous,  and  osseous 
structures. 

The  Lymphatic  Glands  of  the  Head  and  Face. 

The  lymphatic  glands  of  the  head  and  face  are  as  follows: 

1.  The  Occipital. 

2.  The  Posterior  Auricular. 

3.  The  Parotid  and  Subparotid. 

4.  The  Internal  Maxillary. 

5.  The  Facial. 

1  Article  on  the  Lymphatics  in  the  Treatise  on  Human  Anatomy.     By  Poirier  and  Charpy. 


THE  LYMPHATIC  GLANDS  OF  THE  HEAD  AND  FACE 


779 


The  Occipital  or  Sub  occipital  Glands  (lymphoglandulae  occipitales)  (Figs. 
486  and  487). — There  are  only  two  or  three  of  these  glands  on  each  side.  They 
arc  situated  beneath  the  deep  fascia,  a  little  in  front  of  the  anterior  edge  of  the 


FIG.  486. — The  lymphatics  of  the  head  and  neck.     (Sappey.) 

Trapezius  muscle,  near  to  but  seldom  upon  the  insertion  of  the  Complexus 
muscle.  They  receive  lymph  from  the  occipital  region  of  the  scalp  and  from 
them  it  is  sent  to  the  upper  deep  cervical  glands. 

The  Posterior  Auricular  Retro-auricular  or  Mastoid  Glands  (lymphoglandulae 
auricular es  posterior  es)  (Figs.  486,  487,  and  491). — There  are  two  of  these  on  each 
side.  They  are  situated  just  beneath  the  lower  margin  of  the  Retrahens  aurem 
muscle.  They  receive  lymph  from  the  parietal  lymph -vessels,  "from  the  internal 
surface  of  the  auricle,  with  the  exception  of  the  lobule,  and  from  the  posterior 
surface  of  the  external  auditory  meatus."1  The  lymph-vessels  from  these  glands 
empty  into  the  upper  deep  cervical  glands. 

The  Parotid  Lymph-glands  (lymphoglandulae  auriculares  anteriores)  (Figs. 
486,  487,  and  488)  are  divided  into  two  groups,  the  superficial  and  the  deep. 

The  Superficial  Parotid  or  Pre-auricular  Lymph-glands. — The  superficial  parotid 
lymph-glands  are  not  the  subcutaneous  lymph-glands  occasionally  but  very  rarely 
found  in  this  region,  and  which  have  been  described  by  Richet,  but  are  lymph- 
nodes  situated  between  the  parotid  fascia  and  the  parotid  salivary  gland.  There 
may  be  three  glands,  two  glands,  or  only  one  gland. 

1  The  Lymphatics.  By  G.  Delamare,  P.  Poirier,  and  B.  Cuneb.  English  edition,  translated  and  edited  by 
Cecil  H.  Leaf. 


780 


THE   LYMPHATIC  SYSTEM 


The  Deep  Parotid  Lymph-glands. — The  deep  parotid  lymph-glands  are  situated 
within  the  parotid  salivary  gland.  There  are  from  fifteen  to  twenty  of  the  deep  glands. 
The  parotid  glands  receive  lymph  from  the  eyelids,  eyebrows,  the  root  of  the  nose, 
upper  portion  of  the  cheek,  frontal  portion  of  the  scalp,  temporal  portion  of  the 


FACIAL 

SUBMAXILLARY 
SUBMENTAL 


FIG.  487. — General  arrangement  of  the  lymphatic  gland  groups  of  the  head  and  neck.     (Poirier  and  Charpy.) 


GLANDS   OF 

EXTERNAL  JUGULAR 

CHAIN 


SUBMAXILLARY 


GLAND  OF 
INTERNAL  JUGULAR 
CHAIN 


FIG.  488.— The  lymphatics  of  the  neck.     (Kiittner.) 


scalp,  from  the  outer  surface  of  the  pinna,  from  the  external  auditory  meatus, 
from  the  tympanum,  and  possibly  from  the  mucous  membrane  of  the  nose,  the 


THE  LYMPHATIC  GLANDS  OF  THE  HEAD  AND  FACE       781 

posterior  alveolar  region  of  the  superior  maxillary  bone,  and  the  soft  palate. 
Lymphatics  pass  from  the  superficial  parotid  glands  into  the  superficial  cervical 
and  the  upper  deep  cervical  glands.  Lymphatics  pass  from  the  deep  parotid 
glands  into  the  upper  deep  cervical  glands. 

The  Subparotid  Glands  (lymphoglandulae  parotidae). — The  subparotid  glands 
lie  between  the  parotid  salivary  gland  and  the  pharyntf ,  and  they  are  close  to  the 
internal  carotid  artery  and  the  internal  jugular  vein.  They  receive  lymph  from 
the  nasal  fossae,  naso-pharynx,  and  Eustachian  tube,  and  send  vessels  to  the  upper 
deep  cervical  glands. 


SUBORBITAL 
GLAND  OF  NASO- 
GCNIAL  GROOVE 
BUCCINATOR 

(posterior  mass) 

BUCCINATOR 

(middle  mass) 


SUPRAMAXILLARY 
INFRAMAXILLARV 


FIG.  489. — Facial  glands.     (Poirier  and  Charpy.) 

The  Internal  Maxillary  or  Zygomatic  Glands  (lymphoglandulae  faciales  pro- 
fundae)  (Fig.  486). — The  internal  maxillary  glands  lie  in  the  course  of  the  internal 
maxillary  artery  in  the  anterior  pharyngeal  wall.  They  receive  vessels  from  the 
naso-pharynx,  palate,  zygomatic  fossa,  temporal  fossa,  and  orbit.  From  them 
vessels  go  to  the  upper  deep  cervical  glands. 

The  Facial  Glands  or  Genial  Glands  (lymphoglandulae  faciales)  (Figs.  487, 
488,  and  489). — The  facial  glands  lie  in  three  groups  in  the  course  of  the  lymphatic 
vessels  which  are  passing  to  the  submaxillary  glands.  According  to  Poirier  and 
Cuneo  the  supramaxillary  or  inferior  group  (Fig.  489)  lies  upon  the  outer  surface 
of  the  mandible,  at  the  anterior  margin  of  the  Masseter  muscle,  and  beneath  the 
Platysma  myoides.  There  may  be  only  one  or  two  glands  in  this  group,  but  often 
there  are  ten  or  twelve.  These  glands  lie  about  the  facial  artery  and  vein  and 
are  not  constantly  present.  In  many  cases  a  salivary  gland,  the  inframaxillary 
(Fig.  489),  is  interposed  between  the  supramaxillary  and  submaxillary  glands. 
The  buccinator,  buccal,  or  middle  group  (Figs.  486  and  489)  is  present  in  about 
one-third  of  the  subjects  and  lies  upon  the  outer  surface  of  the  Buccinator  muscle 
external  to  the  buccal  fascia.  Some  of  these  glands  are  situated  in  the  region 
where  Steno's  duct  perforates  the  Buccinator  muscle.  Others  are  beneath  the 
posterior  fibres  of  the  Zygomaticus  major  muscle. 

The  superior  group  of  facial  glands  (Fig.  489)  includes  a  malar  gland,  a  suborbital 
gland,  and  a  gland  in  the  naso-genial  groove.1  An  anterior  gland  is  sometimes 
found,  subcutaneous,  on  the  outer  surface  of  the  Orbicularis  oris  muscle,  the 
commissural  gland. 

The  Lymphatic  Vessels  of  the  Cranial  Region  (Fig.  486). 

The  lymphatic  vessels  of  the  cranial  subcutaneous  tissues  are  divided  into 
anterior,  lateral,  and  posterior.  The  anterior  or  frontal  terminate  in  the  parotid 

»  Article  on  the  Lymphatics  in  the  Treatise  on  Human  Anatomy.     By  P.  Poirier  and  B.  Cune"o. 


782 


THE  LYMPHATIC  SYSTEM 


lymph-glands.  The  lateral  or  parietal  terminate  in  the  parotid  and  mastoid  lymph- 
glands.  The  posterior  or  occipital  terminate  in  the  sterno-mastoid  and  occipital 
glands. 

The  Lymphatic  Vessels  of  the  Face,  the  Interior  of  the  Nose,  Tongue, 
Floor  of  the  Mouth,  Pharynx,  Larynx,  and  Thyroid  Gland 

(Figs.  486,  488,  489,  490,  491,  492). 

The  lymphatic  vessels  of  the  face  are  more  numerous  than  those  of  the  cranial 
region,  and  commence  over  its  entire  surface.  Those  from  the  frontal  region 
accompany  the  frontal  vessels;  they  then  pass  obliquely  across  the  face,  running 
with  the  facial  vein,  pass  through  the  glands  on  the  buccal  surface  of  the  Buccina- 
tor muscle,  and  join  the  submaxillary  lymphatic  glands.  The  submaxillary  lymph 
glands  receive  the  lymphatic  vessels  from  the  lips,  and  are  often  found  enlarged 
in  cases  of  malignant  disease  of  those  parts. 

The  lymphatics  of  the  orbit  and  of  the  temporal  and  zygomatic  fossae  run  with 
the  branches  of  the  internal  maxillary  artery  to  the  maxillary  glands,  and  after- 
ward to  the  deep  cervical  glands. 


VESSELS   FROM 
BASE  OF  TONGUE 


MARGINAL  COL- 
LECTING TRUNKS 

TRUNKS  OF 


PRINCIPAL 
GLAND 


W-SUBMENTAL 
(TRUNKS  OF 

j  MARGIN 


FIG.  490. — The  lymphatics  of 'the  tongue;  anterior  view.     (Poirier  and  Charpy.) 


The  lymphatics  of  the  nose  can  be  injected  from  the  subdural  and  subarachnoid 
spaces.  They  terminate  in  the  retro-pharyngeal  and  suprahyoid  glands.  The 
lymphatics  of  the  tongue  (Fig.  490)  chiefly  accompany  the  ranine  vein  first  to  the 


THE  LYMPHATIC  GLANDS  OF  THE  NECK 


783 


lingual  glands  and  from  these  to  the  deep  cervical  glands.  The  lymphatics  from 
the  anterior  part  of  the  tongue  and  floor  of  the  mouth  pierce  the  Mylo-hyoid 
muscles  and  so  reach  the  submaxillary  lymph-glands.  From  the  upper  part  of 
the  pharynx  the  lymphatics  pass  to  the  retro-pharyngeal  glands;  from  the  lower 
part  of  the  pharynx  to  the  deep  cervical  glands.  From  the  larynx  two  sets  of  vessels 
arise:  an  upper,  piercing  the  thyro-hyoid  membrane  and  joining  the  upper  set 
of  deep  cervical  glands;  and  a  lower,  perforating  the  crico-thyroid  membrane  to 
join  the  lower  set  of  deep  cervical  glands.  The  lymphatics  of  the  thyroid  gland 
accompany  the  superior  and  inferior  thyroid  arteries,  and  open  partly  into  the 
upper  and  partly  into  the  lower  set  of  deep  cervical  glands. 


The  Lymphatic  Glands  of  the  Neck. 

The  lymphatic  glands  of  the  neck  are: 

1.  The  Superficial  Cervical,  including  the  external  jugular  and  the  superficial 
anterior  cervical. 

2.  The  Submaxillary. 

3.  The  Submental. 

4.  The  Retro-pharyngeal. 

5.  The  Deep  Cervical,  including  the  anterior  deep  cervical. 

The  Superficial  Cervical  Glands  (lymphoglandulae  cervicales  superficiales) 
(Figs  486  and  491). — The  superficial  cervical  glands  are  composed  of  two  groups, 
the  external  jugular  and  the  superficial  anterior  cervical  glands. 

The  External  Jugular  Glands  (Figs.  488  and  491). — The  external  jugular  glands 
are  superficial  to  the  Sterno-cleido-mastoid  muscle.  They  are  four  to  six  in 


LYMPHATIC   VESSELS 
OF  AURICLE 


MASTOID  GLANDS 


STCRNO-MASTOIO 

T~ GLAND  (external 
group) 

GLAND  OF 
EXTERNAL  JUGULAR 
CHAIN 


STERNO-MASTOID 

GLAND  (internal 
group)    . 

SUBHYOID   GLAND 


FIG.  491.— Deep  cervical  chain.     (Poirier  and  Charpy.) 

number  and  lie  along  the  external  jugular  vein  upon  the  outer  surface  of  the  deep 
cervical  fascia,  each  gland  occupying  a  depression  in  the  fascia.  The  sterno- 
cleido-mastoid  muscle  is  beneath  them.  They  are  usually  gathered  in  a  group 
a  little  below  the  parotid  gland,  but  sometimes  extend  to  the  middle  of  the  vein. 
They  receive  vessels  from  the  occipital,  the  posterior  auricular,  the  parotid,  and 
the  submaxillary  lymph-glands,  from  the  auricle,  and  from  the  skin  and  subcu- 
taneous structures  of  the  neck.  From  them  lymphatic  vessels  pass  to  the  upper 
deep  cervical  and  to  the  lower  deep  cervical  glands. 


784 


THE  LYMPHATIC  SYSTEM 


The  Superficial  Anterior  Cervical  Glands. — The  superficial  anterior  cervical  glands 
lie  along  the  anterior  jugular  vein  and  from  them  vessels  pass  to  the  deep  cervical 
glands. 

The  Submaxillary  or  Lateral  Suprahyoid  Glands  (lymphoglandulae  submaxil- 
lares)  (Figs.  486,  487,  and  488). — The  submaxillary  glands  are  in  the  submaxil- 
lary  triangle  beneath  the  deep  fascia.  They  number  three  to  six;  are  embedded 
in  the  superficial  surface  of  the  sheath  of  the  submaxillary  gland,  but  are  not  found 
within  the  sheath.  Occasionally  one  or  two  are  found  in  the  deep  portion  of  the 
sheath  toward  the  floor  of  the  mouth.  The  middle  gland  of  Stahr  is  situated  at 
the  point  where  the  submaxillary  group  is  crossed  by  the  facial  artery.  This  is 
the  largest  gland  of  the  group.  The  submaxillary  glands  receive  vessels  from  the 
"nose,  the  cheek,  the  upper  lip,  and  the  external  part  of  the  lower  lip,  almost 
the  whole  of  the  gums,  and  the  anterior  third  of  the  lateral  border  of  the  tongue."1 
They  also  obtain  lymph  from  the  floor  of  the  mouth  and  from  the  sublingual  and 
submaxillary  salivary  glands.  They  send  vessels  to  the  jugular  and  to  the  upper 
deep  cervical  glands. 

The  Submental  or  Median  Suprahyoid  Glands  (Figs.  486,  487,  and  490).— 
There  are  usually  two  glands  situated  between  the  anterior  bellies  of  the  two 
digastric  muscles  and  upon  the  Mylo-hyoid  muscle.  They  receive  lymph  from  the 
cutaneous  surface  of  the  chin,  from  the  cutaneous  and  mucous  surfaces  of  the 
central  portion  of  the  lower  lip,  from  the  central  portion  of  the  gums,  from  the 
floor  of  the  mouth,  and  from  the  tip  of  the  tongue.  They  send  some  vessels  to 
the  submaxillary  lymph-glands,  and  frequently  a  gland  is  interposed  on  the  anterior 
belly  of  the  Digastric  muscle.  They  send  other  vessels  to  the  upper  deep  cervical 
glands. 

The  Retro-pharyngeal  or  Post-pharyngeal  Glands  (Fig.  492). — The  retro- 
pharyngeal  glands  are  placed  between  the  upper  lateral  portion  of  the  posterior 
part  of  the  pharynx  and  the  first  two  cervical  vertebrae.  Leaf  tells  us  that,  as  a 


LYMPHATICS 
OF  PHARYNX 


INTERRUPTING 
GLANDULAR 
NODULE 
GLAND  OF 
DEEP  CERVICAL 
CHAIN 
.EFFERENT 
VESSEL  OF 
RETRO-PHARYNGEAL 
GLANDS 


FIG.  492. — The  retro-pharyngeal  glands.     (Poirier  and  Charpy.) 

rule,  there  is  but  one  gland  on  each  side,  though  two  may  be  present.  The  retro- 
pharyngeal  glands  lie  upon  the  Rectus  capitis  anticus  major  muscle,  which  sepa- 
rates them  from  the  vertebra.  They  receive  vessels  from  the  muscles  and  fascia 
in  front  of  the  vertebrae,  from  the  nasal  fossae  and  accessory  cavities,  from  the  naso- 


i  The  Lymphatics.     By  G.  Delamare,  P.  Poirier,  and  B.  Cunte.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE  LYMPHATIC  GLANDS  OF  THE  NECK  7Sf> 

pharynx  and  Eustachian  tube,  and  possibly  from  the  cavity  of  the  tympanum. 
They  send  vessels  to  the  upper  deep  cervical  glands. 

The  Deep  Cervical,  Carotid,  or  Sterno-mastoid  Glands  (lymphoglandulae 
cervicales  profundae)  (Figs.  486,  487,  488,  490,  491,  and  492).— The  deep  cervical 
glands  are  divided  into  the  upper  deep  cervical  and  the  lower  deep  cervical,  and  are 
associated  with  certain  accessory  glands,  including  the  jugular  and  superficial  anterior 
cervical,  which  have  been  discussed  under  the  head  of  superficial  cervical  glands; 
and  the  anterior  deep  cervical  and  the  recurrent  glands,  which  have  not  yet  been 
studied.  The  deep  cervical  chain  extends  from  the  apex  of  the  mastoid  process 
of  the  temporal  bone  to  the  junction  of  the  internal  jugular  and  subclavian  veins. 

The  Upper  Deep  Cervical  or  Substemo -mastoid  Glands  (lymphoglandulae  cervi- 
cales profundae  superiores). — The  upper  deep  cervical  glands  extend  from  the 
tip  of  the  mastoid  process  of  the  temporal  bone  to  about  the  region  where  the 
common  carotid  artery  is  crossed  by  the  Omo-hyoid  muscle.  One  group, 
the  external  group,  is  placed  external  and  posterior  to  the  internal  jugular  vein. 
The  glands  are  small  and  numerous,  are  embedded  in  the  fatty  tissue  about  the 
nerves  from  the  deep  cervical  plexus,  and  at  the  posterior  margin  of  the  Sterno- 
cleido-mastoid  muscle  constitute  a  continuous  mass  passing  to  join  the  subclavian 
glands.  Another  group,  known  as  the  internal  group  or  the  internal  jugular 
glands,  lie  directly  upon  or  close  by  the  outer  border  of  the  internal  jugular  vein. 
This  group  forms  a  chain  along  the  internal  jugular  vein,  and  the  glands  are 
of  larger  size  than  those  of  the  external  group.  Some  glands  of  this  group 
are  beneath  the  vein.  The  glands  of  the  internal  jugular  group  communicate 
freely  with  each  other  and  with  the  external  group.  The  external  group  receives 
lymph-vessels  from  the  posterior  auricular,  occipital,  and  external  jugular  glands, 
from  the  occipital  region  of  the  scalp,  from  the  auricle,  and  from  the  skin,  sub- 
cutaneous tissue,  and  muscles  of  the  upper  portion  of  the  neck.1  The  internal 
group  receives  lymph-vessels  from  the  retro-pharyngeal,  parotid,  subparotid,  sub- 
maxillary,  and  submental  glands,  the  anterior  cervical  glands  (superficial  and 
deep),  and  the  recurrent  glands,  and  from  the  tongue,  naso-pharynx,  larynx,  soft 
palate,  roof  of  the  mouth,  oesophagus  (cervical  portion),  nasal  fossse,  trachea 
(cervical  portion),  and  the  thyroid  gland.2  The  external  group  terminates  in 
the  supraclavicular  glands.  The  internal  jugular  group  terminates  in  the 
jugular  trunk,  which,  on  the  right  side,  helps  to  form  the  right  lymphatic  duct 
or  empties  directly  into  the  junction  of  the  internal  jugular  and  subclavian  veins, 
and  on  the  left  side  empties  directly  into  the  venous  junction  or  into  the  thoracic 
duct. 

The  Lower  Deep  Cervical  or  Supraclavicular  Glands  (lymphoglandulae  cervicales 
profundae  inferior  es). — The  lower  deep  cervical  glands  lie  along  the  internal 
jugular  vein  in  the  lower  part  of  its  course.  They  receive  lymph- vessels 
from  the  superficial  cervical  glands,  the  upper  deep  cervical  glands,  the 
axillary  glands,  the  accessory  chain,  the  occipital  region  of  the  scalp,  the  skin  of 
the  neck,  the  lower  prevertebral  muscles,  the  skin  of  the  pectoral  and  mammary 
regions,  and  the  skin  of  the  arm.  The  supraclavicular  glands  send  vessels  which 
unite  with  the  vessels  of  the  upper  deep  glands  to  form  the  jugular  lymphatic 
trunk.  The  jugular  trunk  on  the  right  side  may  empty  directly  into  the  junc- 
tion of  the  internal  jugular  and  subclavian  veins  or  may  unite  with  the  subclavian 
trunk  to  form  the  right  lymphatic  duct.  On  the  left  side  it  may  empty  into  the 
thoracic  duct  or  directly  into  the  venous  junction. 

Accessory  Chains  to  the  Deep  Cervical  Glands. — The  accessory  chains  to  the  deep 
cervical  glands  are :  1.  The  external  jugular  glands  (p.  783).  2.  The  superficial 
anterior  cervical  (p.  784).  3.  The  prelaryngeal  or  infralaryngeal  glands  (Fig.  486) 

1  The  Lymphatics.     By  G.  Delamare,  P.  Poirier,  and  B.  Cun6o.     Translated  and  edited  by  Cecil  H.  Leaf. 

2  Ibid. 

50 


786  THE  LYMPHATIC  SYSTEM 

between  the  Crico-thyroid  muscles.  They  receive  lymph  from  the  trachea,  larynx, 
and  thyroid  gland,  and  send  vessels  to  the  pretracheal  glands  and  to  the  upper 
deep  cervical  glands.  4.  The  trachea!  or  pretracheal  glands  (Fig.  486)  lie  upon  the 
front  of  the  trachea,  receive  vessels  from  the  trachea,  thyroid  body,  and  prelaryngeal 
glands,  and  send  vessels  to  the  lower  deep  cervical  glands.  Some  anatomists  speak 
of  the  prelaryngeal  and  the  pretracheal  glands  as  the  anterior  deep  cervical  glands. 
5.  The  recurrent  glands  lie  on  the  sides  of  the  oesophagus  and  trachea,  by  the  recur- 
rent laryngeal  nerves.  They  receive  vessels  from  the  larynx,  trachea,  resophagus, 
and  thyroid  gland,  and  send  vessels  to  the  upper  and  lower  deep  cervical  glands. 

The  Lymphatic  Vessels  of  the  Neck  (Figs.  486,490,491). 

The  superficial  and  deep  cervical  lymphatic  vessels  are  continuations  of  those 
already  described  on  the  cranium  and  face.  After  traversing  the  glands  in  those 
regions,  they  pass  through  the  chain  of  glands  which  lie  along  the  sheath  of  the 
carotid  vessels,  being  joined  by  the  lymphatics  from  the  pharynx,  resophagus, 
larynx,  trachea,  and  thyroid  gland.  At  the  lower  part  of  the  neck,  after  receiving 
some  lymphatics  from  the  thorax,  they  unite  to  form  the  jugular  trunk  (Fig.  485), 
which  often  terminates,  on  the  left  side,  in  the  thoracic  duct,  and  on  the  right  side, 
in  the  right  lymphatic  duct,  but  which  may  on  either  side  open  directly  into  the  vein. 

Surgical  Anatomy. — In  secondary  syphilis  there  is  general  enlargement  of  the  lymphatic 
glands,  and  in  the  posterior  triangle  of  the  neck  the  enlarged  glands  are  distinctly  palpable.  The 
occipital  glands  may  enlarge  because  of  inflammation  or  suppuration  about  the  occipital  region 
of  the  scalp,  and  the  posterior-auricular  glands  enlarge  from  inflammation  or  suppuration  of  the 
temporal  portion  of  the  scalp,  the  external  ear  (except  the  lobule),  and  the  external  auditory  meatus. 
Otorrhcea  sometimes  causes  them  to  enlarge. 

The  cervical  glands  are  very  frequently  the  seat  of  tuberculous  disease.  This  condition  is 
usually  preceded  by  a  lesion  in  those  parts  from  which  they  receive  their  lymph.  The  lesion  may 
be  tuberculous  or  inflammatory.  If  tuberculous  it  furnishes  bacilli  directly  to  the  lymph.  If 
inflammatory  it  lessens  tissue  resistance  and  opens  the  portals  to  infection.  The  glands  receive 
the  lymph  from  the  seat  of  primary  disease  and  become  tuberculous.  It  is  very  desirable,  there- 
fore, for  the  surgeon,  in  dealing  with  these  cases,  to  possess  a  knowledge  of  the  relation  of  the 
respective  groups  of  glands  to  the  periphery.  Some  years  ago  Sir  Frederick  Treves  prepared  a 
table  to  show  to  what  glandular  group  lymph  from  each  region  is  sent.  The  table  is  practically 
as  follows: 

Scalp. — Posterior  part  =  suboccipital  and  mastoid  glands.  Frontal  and  parietal  portions  = 
parotid  glands. 

Lymphatic  vessels  from  the  scalp  also  enter  the  superficial  cervical  set  of  glands. 

Skin  of  face  and  neck  —  submaxillary,  parotid,  and  superficial  cervical  glands. 

External  ear  =  superficial  cervical  glands. 

Lower  lip  =  submaxillary  and  suprahyoid  glands. 

Buccal  cavity  —-  submaxillary  and  upper  set  of  deep  cervical  glands. 

Gums  of  lower  jaw  =  submaxillary  glands. 

Tongue. — Anterior  portion  =  suprahyoid  and  submaxillary  glands.  Posterior  portion  = 
upper  set  of  deep  cervical  glands. 

Tonsils  and  palate  =  upper  set  of  deep  cervical  glands. 

Pharynx. — Upper  part  =  parotid  and  retro-pharyngeal  glands.  Lower  part  =  upper  set  of 
deep  cervical  glands. 

Larynx,  orbit,  and  roof  of  mouth  =  upper  set  of  deep  cervical  glands. 

Nasal  fossv  =  retropharyngeal  glands,  upper  set  of  deep  cervical  glands.  Some  'lymphatic 
vessels  from  posterior  part  of  the  fossse  enter  the  parotid  glands. 

'  Treves's  table  indicates  the  glands  usually  involved,  but  the  seat  of  primary  disease  cannot  in- 
variably be  affirmed  from  a  knowledge  of  the  seat  of  glandular  involvement,  because  the  course 
of  the  lymphatic  vessels  is  sometimes  varied  from  that  which  usually  maintains ;  for  instance,  in 
some  cases  lymphatics  from  the  right  side  of  the  tongue  pass  to  glands  in  the  left  side  of  the 
neck. 

Glands  may  enlarge  directly  because  of  primary  inflammation,  injury,  or  tumor,  but  usually 
a  glandular  enlargement  is  secondary  to  a  bacterial  disease  or  to  cancer  involving  the  lymph- 
vessels  which  come  to  the  gland.  The  seat  of  disease  may  be  distant.  Disease  of  the  nasal 
fossae  may  cause  retropharyngeal  abscess  or  enlargement  of  the  submaxillary  glands.  Cancer 
of  the  breast,  stomach,  or  oesophagus  may  be  followed  by  disease  of  the  cervical  glands.  Dis- 


THE  LYMPHATIC  GLANDS  OF  THE  UPPER  EXTREMITY     787 

ease  of  the  teeth,  tongue,  gums,  floor  of  the  mouth,  and  alveolar  processes  may  cause  enlarge- 
ment of  the  submaxillary  and  other  glands,  and  disease  of  the  tonsil  may  lead  to  enlargement 
of  the  glands  at  the  angle  of  the  jaw. 

The  modern  radical  surgery  of  cancer  depends  on  a  knowledge  of  these  glandular  relations, 
and  consists  in  thoroughly  removing  the  growth  and  also  the  associated  lymphatic  glands,  and, 
when  possible,  the  lymph-vessels  running  from  the  tumor  to  the  glands.  The  lower  deep  cer- 
vical glands  occasionally  enlarge  secondarily  to  malignant  growths  of  the  abdomen  or  medias- 
tinum, but  this  is  not  due  to  a  direct  flow  of  lymph,  as  the  mediastinal  glands  do  not  send  ves- 
sels to  the  supraclavicular  glands.  It  is  due  to  blocking  of  lymphatic  vessels  and  reversal  of 
the  lymph-stream,  so  that  lymph  containing  cancerous  cells  regurgitates. 

A  retropharyngeal  abscess  begins  to  the  side  of  the  pharynx.  It  enlarges  toward  the  centre 
rather  than  from  it,  because  the  constrictions  of  the  pharynx  limit  the  outward  progress  of  the 
pus. 

The  glands  within  the  parotid  salivary  gland  not  unusually  become  tuberculous,  and  the 
•  surgeon  may  be  led  to  believe  that  the  salivary  gland  is  the  seat  of  primary  disease. 

Sometimes,  though  seldom,  after  the  extensive  removal  of  lymph-glands  the  region  drained 
by  their  tributaries  becomes  the  seat  of  persistent  hard  cedema  (lymph  oedema).  It  used  to  be 
thought  that  wounds  of  the  thoracic  duct  were  of  necessity  fatal,  but  it  is  now  known  that,  unless 
close  to  the  vein,  they  are  seldom  even  very  dangerous.  It  may  be  possible  to  suture  a  partly 
divided  duct.1  In  an  unsutured  wound  of  the  duct  recovery  follows  if  a  collateral  lymphatic 
circulation  is  established.2 

THE  LYMPHATICS  OF  THE  UPPER  EXTREMITY. 

The  Lymphatic  Glands  of  the  Upper  Extremity. 

The  lymphatic  glands  of  the  upper  extremity  are  divided  into  two  sets,  super- 
ficial and  deep. 

Superficial  Lymphatic  Glands  (Figs.  493  and  501). — The  superficial  lymphatic 
glands  of  the  upper  extremity  are  few  in  number  and  small  in  size.  They  lie  in  the 
subcutaneous  tissue.  They  are  not  receiving  depots  of  great  areas,  but  interrupt 
lymphatic  vessels  here  and  there.  The  glands  in  the  axilla  receive  all  of  the 
lymphatic  vessels,  superficial  and  deep.  There  may  be  three  sets  of  superficial 
glands. 

One  set,  the  ante-cubital  glands,  lies  in  front  of  the  elbow.  These  glands  are 
often  absent.  When  these  glands  are  present  they  receive  vessels  from  the  anterior 
portion  of  the  forearm  and  the  middle  of  the  palm.  The  vessels  from  them  pass 
upward  along  the  front  and  inner  aspect  of  the  arm. 

Another  superficial  gland  lies  above  the  internal  condyle.  It  is  the  supratrochlear 
or  supraepitrochlear  gland  or  group  of  glands.  There  is  usually  but  one  gland,  but 
there  may  be  two  or  more.  It  receives  vessels  from  the  inner  portion  of  the  hand, 
the  three  inner  fingers-,  and  the  inner  portion  of  the  forearm,  but,  because  of  free 
anastomoses,  also  may  receive  lymph  from  any  portion  of  the  hand  and  forearm. 
Lymph-vessels  from  the  supratrochlear  gland  pass  up  along  the  basilic  vein  to 
the  axillary  glands. 

There  are  sometimes  several  small  glands  by  the  cephalic  vein  in  the  groove 
between  the  Deltoid  and  great  Pectoral  muscles.  These  are  called  infraclavicular 
glands.  The  lymph-tract  from  the  infraclavicular  glands  does  not  terminate  in 
the  axillary  glands,  but  ends  in  the  subclavian  glands. 

The  Deep  Lymphatic  Glands  of  the  Upper  Extremity  or  the  Axillary  Glands 
(lymphoglandulae  axillares]  (Figs.  493,  494,  495,  496,  and  501). — The  chief  deep 
glands  are  situated  adjacent  to  the  axillary  vessels.  There  are  also  a  few  small 
glands  along  the  radial,  ulnar,  and  brachial  arteries  which  receive  deep  lymphatics 
from  bones,  muscles,  and  ligaments,  and  send  lymphatics  to  the  axillary  glands. 
The  axillary  glands  number  from  fifteen  to  thirty-five  in  each  axilla.  They  are 
embedded  in  the  axillary  fat  and  receive  the  lymphatic  vessels  from  the  upper 

1  Dudley  P.  Allen's  case.     See  Allen  arid  Brings,  in  American  Medicine,  September  21,  1901. 

2  Harvey  Gushing,  Annals  of  Surgery,  June,  1898. 


788 


THE  LYMPHATIC  SYSTEM 


extremity,  from  the  skin  of  the  upper  portion  of  the  chest,  from  the  Pectoral 
muscles,  and  from  the  mammary  gland.  The  following  division  of  the  axillary 
glands  is  made  by  Poirier,  Cuneo,  and  Delamare:1  1.  An  external  group,  the 


Axillary  glands. 


FIG.  493. — The  superficial  lymphatics  and  glands  of  the  upper  extremity. 

humeral  chain,  lying  on  the  inner  surface  of  the  vessels  and  nerves,  particularly  the 
axillary  vein,  to  the  sheath  of  which  they  are  adherent.  Occasionally  one  or  several 
of  these  glands  are  found  beneath  the  vein.  Some  of  the  vessels  from  these  glands 
pass  into  the  central  group  of  lymph-nodes;  others  enter  the  subclavian  glands; 
others  pass  above  the  clavicle  and  terminate  in  glands  situated  in  that  region.  2. 
An  anterior  group,  the  thoracic  chain,  called  also  the  pectoral  glands  (lymphoglandulae 
pectorales) .  One  mass  of  this  chain,  the  supero-internal,  is  situated  in  the  second  or 
third  intercostal  space  in  front  of  the  long  thoracic  artery  and  beneath  the  lower 
edge  of  the  great  Pectoral  muscle.  Another  mass,  the  infero-external,  is  situated  in 
the  fourth  and  fifth  intercostal  spaces  along  the  course  of  the  long  thoracic  artery. 
The  vessels  from  this  chain  end  in  the  central  group,  and  some  few  of  them  in  the 
subclavian  glands.  3.  A  posterior  group,  the  scapular  chain,  lying  along  the  dorsali? 

1  The  Lymphatics.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE  LYMPHATIC  GLANDS  OF  THE   UPPER  EXTREMITY    789 


scapulae  artery  in  the  groove  between  the  Teres  major  and  the  Subscapularis 
muscles.     They  send  vessels  to  the  humeral  and  central  chains.     4.  A  central 


DELTA-PECTORAL      HUMERAL  CHAIN 

HUMERAL 


CENTRAL- 
GROUP 
SCAPULAR 
CHAIN 


MAMMARY   LYMPHATIC 
ENDING  IN  SUB- 
CLAVIAN  GLANDS 


THORACIC 
CHAIN 

MAMMARY  COL- 
LECTING TRUNKS 


3 SUBAREOLAR 

PLEXUS 


THORACIC 

CHAIN 


CUTANEOUS  COLLECTING 

TRUNK  FROM  THE 

THORACIC  WALL 


CUTANEOUS  COL-  "\  -\V_ COLLECT!  NG  TRUN  KS 

LECTING  TRUNKS  PASSI  NG  TO  I  NTE RNAL 

MAMMARY  GLANDS 

i-io.  494.— Axillary  glands  and  lymphatics  of  the  breast.     (Poirier  and  Charpy.) 


FIG.  495.— Lymphatics  of  the  antero-lateral  portion  of  the  thorax.     (Sappey.) 


790  THE  LYMPHATIC  SYSTEM 

group,  the  intermediate  glands,  placed  near  the  base  of  the  axilla,  between  the  pre- 
viously described  chains.  Their  efferent  vessels  end  in  the  subclavian  glands.  The 
glands  of  the  central  group  in  many  individuals  protrude  through  the  opening  in  the 
axillary  fascia  known  as  the  foramen  of  Langer  (Fig.  312).  5.  A  subclavian  group, 
situated  above  the  upper  margin  of  the  lesser  Pectoral  muscle.  Most  of  them  are 
internal  to  the  axillary  vein,  "between  this  vein  and  the  first  digitation  of  the 
Serratus  magnus."1  The  humeral  chain  and  the  thoracic  chain  come  together  and 
form  the  subclavian  group  of  glands  situated  at  the  apex  of  the  axilla.  From  the 
axillary  glands  come  many  vessels  which,  by  anastomosing,  form  the  infraclavic- 
ular  plexus,  they  then  unite  into  a  trunk,  the  subclavian  trunk,  which  courses 
between  the  subclavian  vein  and  Subclavius  muscle.  On  the  right  side  it  empties 
into  the  junction  of  the  internal  jugular  and  subclavian  vein  or  unites  with  the 
jugular  trunk  to  form  the  right  lymphatic  duct.  On  the  left  side  it  may  empty  into 
the  venous  junction  or  into  the  thoracic  duct. 


SUPRA 
CLAVICULAR 


LINE  OFTHE 
CLAVICLE 


SUBCLAVIAN 


-CENTRAL  GROUP 

HUMERAL- 


SCAPULAR 
CHAIN 


SUPEHO-INTERNAL 
PORTION  OF 
THORACIC  CHAIN 


INFCRO-EXTEHNAL 
PORTION  OF 
THORACIC  CHAIN 

FIG.  496. — Scheme  of  the  axillary  glands.     The  dotted  line  indicates  the  position  of  the  clavicle. 

(Poirier  and  Charpy.) 

The  Lymphatic  Vessels  of  the  Upper  Extremity  (Figs.  493, 494, 495, 496, 497). 

The  lymphatic  vessels  of  the  upper  extremity  are  divided  into  the  superficial 
and  the  deep. 

The  Superficial  Lymphatic  Vessels  of  the  Upper  Extremity.— The  superficial 
vessels  begin  as  plexuses  in  the  skin  and  form  vessels  which  ascend  in  the  sub- 
cutaneous tissue.  These  plexuses  are  particularly  plentiful  in  the  palm  and 
palmar  surface  of  the  digits  (Fig.  497).  On  each  side  of  each  finger  two  lymph- 
vessels  are  formed;  they  ascend  toward  the  hand,  cross  the  dorsum,  and  anas- 
tomose frequently  with  each  other.  The  vessels  from  the  dorsum  of  the  hand 
join  the  lymph-vessels  of  the  forearm,  which  ascend  chiefly  along  the  superficial 
veins.  The  lymph-vessels  which  ascend  with  the  superficial  ulnar  vein  pass  into 
the  supratrochlear  gland.  The  vessels  which  accompany  the  median  veins  pass 
into  the  ante-cubital  or  supratrochlear  glands.  Some  of  the  lymph-vessels  on 
the  radial  side  of  the  forearm  run  up  along  the  cephalic  vein.  All  the  other 
lymph-vessels  of  the  upper  extremity  pass  direct  to  the  axillary  glands.  In  the 
forearm  there  are  about  thirty  vessels,  in  the  middle  of  the  arm  there  are  from 
fifteen  to  eighteen  (Sappey). 

The  Deep  Lymphatic  Vessels  of  the  Upper  Extremity.— The  deep  lymph- 
vessels  convey  the  lymph  from  bone,  periosteum,  muscle,  ligament,  etc.  They  pass 
up  the  limb  with  the  chief  vessels,  there  usually  being  two  trunks  to  each  artery. 

1  The  Lymphatics.     By  Poirier,  Cuneo,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE  LYMPHATIC  GLANDS  OF  THE  LOWER  EXTREMITY     791 


In  the  arm  there  are  two  or  three  vessels.  Some  few  vessels  terminate  in  the 
small  glands  along  the  radial,  ulnar,  and  brachial  arteries,  but  most  of  them  pass 
directly  to  the  axillary  glands. 


Surgical  Anatomy. — In  malignant  dis- 
eases, or  other  affections  implicating  the 
upper  part  of  the  back  and  shoulder,  the 
front  of  the  chest  and  mamma,  the  upper 
part  of  the  front  and  side  of  the  abdomen, 
or  the  hand,  forearm,  or  arm,  the  axillary 
glands  are  liable  to  be  found  enlarged. 

In  secondary  syphilis  the  supratrochlear 
gland  is  found  to  be  enlarged.  This  gland 
is  subcutaneous  and  readily  palpable  when 
enlarged.  Normal  axillary  glands  cannot 
be  palpated.  The  axilla  is  a  passage-way 
for  structures  between  the  neck  and  the 
upper  extremity,  and  purulent  collections 
or  tumors  may  extend  from  the  neck  into 
the  axilla  or  from  the  axilla  into  the  neck. 

The  axillary  glands  are  involved  early  in 
cases  of  cancer  of  the  mammary  gland,  and 
later  the  lower  deep  cervical  glands  are 
involved,  and,  as  Snow  has  pointed  out, 
regurgitation  of  lymph-containing  cancer 
cells  leads  to  retrosternal  involvement  and 
to  secondary  cancer  of  the  head  of  the 
humerus.  In  operating  for  cancer  of  the 
breast,  follow  the  principle  of  Halsted  and 
remove  the  breast,  the  skin  over  it,  the 
muscles  and  fascia,  the  lymph-vessels,  and 
the  axillary  glands  in  one  piece.  By  this 
plan  thorough  removal  is  possible,  and  as 
lymph-vessels  containing  carcinoma  cells 
are  not  cut  across,  the  wound  is  not  grafted 
with  malignant  epithelial  cells.  Diseased 
axillary  glands  are  apt  to  adhere  to  the 
sheath  of  the  vein.  In  removing  cancerous 
glands,  always  excise  the  sheath  of  the  vein. 


FIG.  497. — Lymphatic  vessels  of  the  dorsal  surface  of 
the  hand.     (Sappey.) 


THE  LYMPHATICS  OF  THE  LOWER  EXTREMITY. 
The  Lymphatic  Glands  of  the  Lower  Extremity. 

The  lymphatic  glands  of  the  lower  extremity  are  divided  into  two  sets,  super- 
ficial and  deep.  The  superficial  are  confined  to  the  inguinal  region,  forming  the 
superficial  inguinal  lymphatic  glands. 

The  Superficial  Inguinal  Lymphatic  Glands  (lymphoglandulae  inguinales 
superficiales)  (Figs.  498,  499,  500,  and  501). — The  superficial  inguinal  lymphatic- 
glands,  placed  immediately  beneath  the  integument  in  Scarpa's  triangle,  are  of 
large  size,  and  vary  in  number  from  ten  to  twenty.  It  is  customary  to  divide 
these  glands  into  groups  according  to  the  region  in  which  they  are  found.  The 
following  division  is  suggested  by  Poirier,  Cuneo,  and  Delamare:1  A  horizontal 
line  carried  through  the  saphenous  opening  divides  the  glands  into  two  groups, 
a  superior  group  and  an  inferior  group.  A  vertical  line  through  the  saphenous 
opening  divides  each  of  the  two  groups  into  two  secondary  groups,  an  external  and 
an  internal  group.  We  thus  have  an  external  and  superior  group,  and  internal  and 
superior  group,  an  external  and  inferior  group,  and  an  internal  and  inferior  group. 


1  The  Lymphatics.     Translated  and  edited  by  Cecil  H.  Leaf. 


792 


Directly  in  the  saphenous  opening  there  are  often  several  glands  constituting  a 
central  group. 


SUPERIOR 

EXTERNAL 

GROUP 


SUPERIOR 

INTERNAL 

GROUP 

INFERIOR 

INTERNAL 

GROUP 


INFERIOR 
EXTERNAL 
GROUP 


FIG.  498. — Superficial  inguinal  glands.     Cribriform  fascia  has  been  removed  so  as  to  expose  the  femoral 

vessels.     (Poirier  and  Charpy.) 


FIG.  499. — Glands  of  the  inguinal  region  with  the  afferent  and  efferent  lymphatics.      (Poirier  and  Charpy.) 

Leaf  points  out  that  a  gland  usually  exists  near  the  saphenous  opening,  which 
is  interposed  between  the  superficial  inguinal  and  deep  inguinal  glands.  The 
superior  group  of  glands,  sometimes  called  the  oblique  group,  is  so  placed  that  the 


////;  LYMPHATIC  GLANDS  OF  Til  H  LOWER  EXTREMITY    793 


Superficial 

iiitiniiial 
glands. 


glands  lie  with  a  certain  regularity  along 
and  below  Poupart's  ligament,  the  long 
axis  of  each  gland  corresponding  with 
the  direction  of  the  ligament.  It  is  now 
known  that  each  group  of  the  superficial 
glands  does  not  receive  with  regularity 
the  lymph  from  and  only  from  a  definite 
and  accurately  determined  area.  Hence, 
it  is  not  possible,  as  was  once  taught,  to 
determine  with  certainty  the  exact  situa- 
tion of  a  lesion  by  the  group  of  superficial 
glands  involved.  The  superficial  inguinal 


-* — «^~ 

FIG.  500. — The  superficial  lymphatics  and  glands 
of  the  lower  extremity. 


FIG.  501. — Superficial  lymphatic  vessels  of  the  lower 
extremity,  exterior  surfaee.     (Sappey.) 


794  THE  LYMPHATIC  SYSTEM 

glands  receive  vessels  from  the  skin  of  the  lower  extremity,  gluteal  region,  peri- 
neum, abdominal  wall,  scrotum,  anus,  and  from  the  prepuce  of  the  clitoris  and 
penis.  Occasionally,  though  not  normally,  they  receive  vessels  from  the  glans 
penis  and  glans  clitoris.  The  superficial  glands  send  vessels  to  the  deep  inguinal 
glands  and  to  the  external  iliac  glands,  and  these  vessels  penetrate  the  femoral 
sheath.  The  vessels  which  go  to  the  iliac  glands  ascend  with  the  femoral  vessels. 
Leaf  figures  some  of  the  efferent  vessels  from  these  glands  as  terminating  directlv 
in  the  veins  of  this  region. 

Surgical  Anatomy. — The  superficial  inguinal  glands  frequently  become  enlarged  in  diseases 
implicating  the  parts  from  which  their  lymphatics  originate.  Thus,  in  malignant  or  syphilitic 
affections  of  the  prepuce  and  penis,  or  of  the  labia  majora  in  the  female,  in  cancer  scroti,  in 
abscess  in  the  perineum,  and  in  other  diseases  affecting  the  integument  and  superficial  structures 
in  those  parts,  or  the  subumbilical  part  of  the  abdominal  wall  or  the  gluteal  region,  the  upper 
chain  of  glands  is  almost  invariably  enlarged,  the  lower  chain  being  implicated  in  diseases  affect- 
ing the  lower  limb. 

The  Deep  Lymphatic  Glands  of  the  Lower  Extremity.— The  deep  glands 
are  the  inguinal,  anterior  tibial,  popliteal,  gluteal,  and  ischiatic. 

The  Deep  Inguinal  or  Deep  Femoral  Lymphatic  Glands  (lymphoglandulae  ingui- 
nales  profundae). — The  deep  inguinal  lymphatic  glands  are  beneath  the  deep 
fascia.  There  are  only  two  or  three  of  them,  and  they  lie  to  the  inner  side  of 
the  femoral  vein,  the  upper  gland  being  in  the  crural  canal  and  projecting  into 
the  pelvis.  It  is  called  the  gland  of  Cloquet  or  the  gland  of  Rosenmiiller.  The 
deep  inguinal  glands  receive  vessels  from  the  superficial  inguinal  glands,  deep 
lymphatics  from  along  the  femoral  vessels,  and  vessels  from  the  glans  penis  or 
clitoris.  They  send  vessels  to  the  ilio-pelvic  glands. 

The  Anterior  Tibial  Gland  (lymphoglandula  tibialis  anierior). — The  anterior 
tibial  gland  is  not  constant  in  its  existence.  It  is  generally  found  by  the  side  of 
the  anterior  tibial  artery,  upon  the  interosseous  membrane  at  the  upper  part  of 
the  leg.  Occasionally  two  glands  are  found  in  this  situation.  It  receives  a  deep 
anterior  tibial  lymphatic  trunk  and  sends  off  a  vessel  to  the  popliteal  glands. 

The  Popliteal  Glands  (lymphoglandulae  popliteae). — The  popliteal  glands  are 
embedded  in  the  cellular  tissue  and  fat  of  the  popliteal  space  and  about  the  pero- 
neal  vessels.  The  juxta-articular  gland  receives  lymph-vessels  from  the  knee-joint. 
The  popliteal  glands  send  vessels  to  the  superficial  and  deep  inguinal  glands. 

The  popliteal  glands  are  divided  into  three  groups  :2  1.  A  gland  external  to  the 
termination  of  the  external  saphenous  vein,  the  external  saphenous  gland.  2.  A 
middle  group  of  three  or  four  glands  on  the  sides  of  the  popliteal  vessels.  The 
inferior  glands  of  this  group  are  the  intercondyloid  glands  of  Leaf.  The  superior 
glands  are  the  supracondyloid  glands  of  Leaf.  3.  A  gland  adherent  to  the  posterior 
ligament  of  the  knee-joint,  the  juxta-articular  gland  of  Poirier  and  Cuneo.  The  ex- 
ternal saphenous  gland  receives  vessels  which  ascend  along  the  external  saphenous 
vein.  The  middle  group  receives  vessels  from  the  anterior  tibial  glands  and  deep 
lymphatic  vessels  which  ascend  with  the  posterior  tibial. 

The  Gluteal  and  Ischiatic  Glands. — The  gluteal  and  ischiatic  glands  are  placed, 
the  former  above,  the  latter  below,  the  Pyriformis  muscle,  resting  on  their  corre- 
sponding blood-vessels  as  they  pass  through  the  great  sacro-sciatic  foramen. 

The  Lymphatic  Vessels  of  the  Lower  Extremity  (Figs.  500,  501). 

The  lymphatic  vessels  of  the  lower  extremity,  like  the  veins,  may  be  divided 
into  two  sets,  superficial  and  deep. 

•  The  Surgical  Anatomy  of  the  Lymphatic  Glands,  1898. 

2  The  Lymphatics.     By  Poirier,  Cuneo,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leat. 


THE  ILIAC  OR  ILIO-PELVIC  GLANDS  795 

The  Superficial  Lymphatic  Vessels  of  the  Lower  Extremity. — The  superficial 
lymphatic  vessels  are  placed  beneath  the  integument  in  the  superficial  fascia,  and 
are  divisible  into  three  sets:  trunks  which  follow  the  course  of  the  internal 
saphenous  vein,  trunks  which  accompany  the  external  saphenous  vein,  and 
trunks  from  the  gluteal  region.  1.  Trunks  which  follow  the  course  of  the 
internal  saphenous  vein  arise  from  a  plexus  on  the  dorsum  of  the  foot,  which 
plexus  obtains  lymphatics  from  all  the  toes,  the  sole,  and  both  borders  of  the  foot. 
The  internal  trunks,  three  or  four  in  number,  pass  to  the  superficial  inguinal 
glands.  Theexternal  trunks  run  upward  and  inward  and  end  in  the  internal  trunks. 
2.  The  trunks  which  follow  the  external  saphenous  vein  number  two  or  three,  and 
they  take  origin  from  the  heel  and  from  the  posterior  half  of  the  outer  edge  of 
the  foot.  They  empty  into  the  superficial  inguinal  glands.  3.  The  lymph-trunks 
from  the  gluteal  region  join  vessels  from  the  anus  and  enter  the  superficial 
inguinal  glands. 

The  Deep  Lymphatic  Vessels  of  the  Lower  Extremity. — The  deep  lymphatic 
vessels  of  the  lower  extremity  are  few  in  number  and  accompany  the  deep  blood- 
vessels. In  the  leg  they  consist  of  three  sets,  the  anterior  tibial,  peroneal,  and 
posterior  tibial,  which  accompany  the  corresponding  blood-vessels,  two  or  three 
to  each  artery;  they  ascend  with  the  blood-vessels  and  enter  the  lymphatic  glands 
in  the  popliteal  space;  the  efferent  vessels  from  these  glands  accompany  the  femoral 
vein  and  join  the  deep  inguinal  glands;  from  these  glands  vessels  pass  beneath  Pou- 
part's  ligament  and  communicate  with  the  chain  of  glands  surrounding  the  exter- 
nal iliac  vessels.  The  deep  lymphatic  vessels  of  the  gluteal  and  ischiatic  regions 
follow  the  course  of  the  blood-vessels,  and  join  the  gluteal  and  ischiatic  glands  at 
the  great  sacro-sciatic  foramen. 


THE  LYMPHATICS  OF  THE  PELVIS  AND  ABDOMEN. 

The  lymphatics  of  the  pelvis  and  abdomen  constitute  a  continuous  chain,  but 
for  convenience  of  study  it  is  customary  to  divide  them  into  two  groups,  which 
we  call,  with  Poirier  and  Cune'o,1  the  ilio-pelvic  glands  and  the  abdomino-aortic 
glands;  the  first  group  being  below  and  the  second  above  the  level  of  the  bifurca- 
tion of  the  aorta  into  the  two  common  iliac  arteries. 

The  Iliac  or  Ilio-pelvic  Glands  (Lymphoglandulae  Iliacae)  (Figs.  502,  503). 

The  ilio-pelvic  glands  are  at  the  level  of  the  inlet  of  or  in  the  cavity  of  the 
pelvis.  They  follow  the  course  of  the  blood-vessels  and  are  divisible  into  the 
external  iliac,  the  internal  iliac,  and  the  common  iliac  chains. 

The  External  Hiac  Glands. — The  external  iliac  glands  form  chains  around 
the  external  iliac  vessels.  There  are  three  chains  of  these  glands.  An  external 
chain  of  three  or  four  glands  lies  between  the  artery  and  the  Psoas  muscle. 
The  lowest  gland  of  the  external  chain  is  called  by  Poirier  and  Cune'o  the  external 
retro-crural  gland  (Fig.  502).  A  middle  chain  of  three  glands  lies  upon  the  front 
surface  of  the  external  iliac  vein.  The  lowest  gland  of  this  group  is  called  by 
Poirier  and  Cune'o  the  middle  retro-crural  gland.  An  internal  chain  of  three  or 
four  glands  is  placed  to  the  inner  side  of  the  external  iliac  vein.  The  lowest  gland 
of  this  chain  is  called  the  internal  retro-crural  gland,  and  is  close  to  the  upper  gland 
of  the  deep  inguinal  chain,  the  gland  of  Cloquet.  The  obturator  gland  belongs  to 
the  inner  chain  of  external  iliac  glands.  The  external  iliac  glands  receive  vessels 
from  the  superficial  and  deep  iliac  glands,  from  the  glans  penis  or  glans  clitoris, 
deep  lymphatics  from  the  umbilicus  and  lower  part  of  the  belly  wall,  vessels  from  the 
superior  portion  of  the  vagina,  the  uterine  neck,  the  prostate  gland,  the  bladder, 

1  Treatise  on  Human  Anatomy. 


796 


THE  LYMPHATIC  SYSTEM 


the  membranous  portion  of  the  urethra,  and  the  internal  iliac  glands,  and  the 
obturator  gland  receives  deep  lymph-vessels  from  along  the  course  of  the  obtu- 
rator vessels.  The  external  iliac  glands  send  vessels  direct  to  the  common  iliac 
glands  and  also  lymphatics  to  join  vessels  from  the  internal  iliac  glands  on  their 
way  to  the  common  iliac  group.  The  glands  along  the  deep  epigastric  artery 
and  those  along  the  deep  circumflex  iliac  artery  are  accessory  chains  to  the  main 
group  of  external  iliac  glands. 


RIGHT JUXTA 
AORTIC 


LEFT  JUXTA 
AORTIC 


COMMON 
ILIAC 


PROMONTORY  — 


COMMON   ILIAC 

(middle  group)  — 


EXTERNAL  ILIAC 

(external  chain) 


OBTURATOR 

ARTERY 


IIP 
FIG.  502. — Ilio-pelvic  glands.     (Poirier  and  Charpy.) 

The  Internal  Iliac  or  Hypogastric  Glands  (lymphoglandulae  hypogastricae).— 
The  internal  iliac  glands  are  placed  along  the  internal  iliac  artery  and  its  branches. 
The  gland  on  the  middle  hemorrhoidal  artery  is  called  the  middle  hemorrhoidal 
gland.  The  lateral  sacral  gland  is  on  the  lateral  sacral  artery.  The  internal  iliac 
glands  receive  lymph  from  the  pelvic  viscera,  perineum,  and  penile  portion  of  the 
urethra,  deep  tissues  of  the  posterior  portion  of  the  thigh,  and  from  the  buttocks. 
They  send  vessels  to  the  common  iliac  glands  and  also  to  the  external  iliac  glands. 

The  Common  Hiac  Glands, — The  common  iliac  glands  are  found  about  the 
common  iliac  artery  and  are  divided  into  an  external  group,  which  lies  upon  the 
inner  edge  of  the  Psoas  muscle;  a  middle  group,  behind  the  artery,  and  an  internal 
group,  which  lies  upon  the  front  of  the  body  of  the  fifth  lumbar  vertebra  or  upon 
the  sacro-vertebral  junction.  They  receive  vessels  from  the  external  and  internal 


THE  ABDOMINO-AORTIC  GLANDS 


797 


iliac  glands  and  from  the  pelvic  viscera,  the  vessels  from  the  pelvic  viscera  ascend- 
ing to  the  promontory  of  the  sacrum  and  containing  perhaps,  here  and  there, 
interrupting  glands,  known  as  sacral  glands  (lymphoglandulae  sacrales}  (Fig.  509). 
They  also  receive  lymph-vessels  from  the  lumbo-sacral  region.  They  send  vessels 
to  the  aortic  glands.  Some  anatomists  place  the  common  iliac  glands  and  the 
glands  about  the  lower  portion  of  the  aorta  and  vena  cava  in  a  group  called  the 
lumbar  glands  (lymphoglandulae  lumbales]  (Fig.  509). 


INTCRPCLVIC 
GLUTEAL 


PROMONTORY 


EXTERNAL  ILIAC 

(middle  chain) 


EXTERNAL  ILIAC 

(middle  chain) 


EXTERNAL  ILIAC 

(external  chain) 

RETROCRURAL 

EXTERNAL 

RETROCRURAL 

INTERNAL 

LYMPHATICS 

OF  BLADDER 

LYMPHATIC   FROM 

CLANS    PENIS 

LYMPHATICS 
OF  BLADDER 


LATERAL 
SACRAL 


HYPOGASTRIC 

HYPOGASTRIC 
SATELLITE  TRUNK 
OF   INTERNAL 
PUDIC  VESSELS 
TRUNK  OF 
MIDDLE  HEMOR- 
RHOIDAL  VESSELS 


PROSTATIC  COL- 
LECTING TRUNK 


URETHRAL  COL- 
LECTING TRUNKS 


LYMPHATIC  GLANDULAR  NODULE 
IN   FRONT  OF  SYMPHYSIS 


PROSTATIC  COL- 
LECTING TRUNK 


FIG.  503. — The  Ilio-pelvic  glands  (lateral  view).     (Poirier  and  Charpy.) 

The  Abdomino-aortic  Glands  (Figs.  483,  509). 

The  abdomino-aortic  glands  are  placed  about  the  abdominal  aorta.  There  are 
twenty-five  or  thirty  of  them.  They  are  divided  by  Poirier,  Cune'o,  and  Delamare1 
into  the  right  and  left  juxta-aortic  glands,  the  retro-aortic  glands,  and  the  pre-aortic 
glands. 

The  Right  Juxta-aortic  Glands. — The  right  juxta-aortic  glands  are  grouped 
in  front  of  and  behind  the  postcava,  the  posterior  glands  lying  upon  the  Psoas 
muscle  and  the  adjacent  pillar  of  the  Diaphragm.  They  receive  lymph-vessels 
from  the  right  common  iliac  glands,  from  the  right  testicle  or  the  right  half  of 
the  uterus,  and  the  right  tube,  ovary,  broad  ligament,  the  right  kidney  and  supra- 
renal capsule,  and  also  lymph-vessels  which  pass  along  the  lumbar  arteries. 
They  send  vessels  to  the  pre-aortic  and  the  retro-aortic  glands  and  the  receptaculum 
chyli. 


i  The  Lymphatics.     Translated  and  edited  by  Cecil  H.  Leaf. 


798  THE  L  YMPHA  TIC  SYSTEM 

The  Left  Juxta-aortic  Glands.— The  left  juxta-aortic  glands  lie  by  the  side  of 
the  abdominal  aorta,  upon  the  Psoas  muscle,  and  the  left  pillar  of  the  Diaphragm. 
They  receive  tributaries  from  the  left  side  corresponding  to  those  received  by 
the  glands  of  the  right  side,  and  also  send  out  corresponding  efferent  vessels,  and 
several  additional  vessels  which  pass  through  the  left  pillar  of  the  Diaphragm  and 
empty  into  the  thoracic  duct. 

The  Retro-aortic  Glands. — The  retro-aortic  glands  are  placed  beneath  the 
receptaculum  chyli  and  in  front  of  the  bodies  of  the  fourth  and  fifth  lumbar  ver- 
tebne.  They  receive  lymph-vessels  from  both  juxta-aortic  groups,  and  also  from 
the  pre-aortic  glands,  and  they  send  vessels  to  the  receptaculum  chyli. 

The  Pre-aortic  Glands. — The  pre-aortic  glands  lie  upon  the  front  of  the  aorta, 
and  in  most  subjects  are  divisible  into  three  groups :  an  inferior,  lying  at  the  origin 
of  the  inferior  mesenteric  artery;  a  middle,  at  the  origin  of  the  superior  mesenteric 
artery,  and  a  superior,  about  the  coeliac  axis,  the  coeliac  glands  (lymphoglandulae 
coeliacae).  Glands  which  are  found  along  the  course  of  all  the  branches  of  the 
abdominal  aorta  empty  into  and  belong  to  the  group  of  pre-aortic  glands.  The 
pre-aortic  glands  receive  vessels  from  the  juxta-aortic  glands  and  from  all  the 
glands  along  the  mesenteric  vessels  and  the  coeliac  axis  and  its  branches, 
and  receive  lymph  from  the  stomach,  intestines,  liver,  pancreas,  and  spleen. 
They  anastomose  with  each  other  and  send  vessels  to  the  retro-aortic  glands  and 
to  the  receptaculum  chyli.  Instead  of  the  glands  terminating  in  the  receptaculum 
by  separate  vessels,  the  vessels  may  unite  and  form  a  common  trunk,  the  intes- 
tinal trunk  (truncus  intestinalis] ,  which  runs  along  with  the  common  trunk  from 
the  juxta-aortic  glands,  and  empties  into  the  receptaculum  (Fig.  483). 

1.  The  Glands  along  the  Mesenteric  Arteries  (lymphoglandulae  mesentericae]  receive 
the    lymph  from  the  colon,  caecum,  appendix,  ileum,  jejunum,  duodenum,  and 
perhaps  also  some  from  the  stomach. 

2.  The  Glands  Connected  with  the  Cceliac  Axis  and  its  Branches. — There  are  three 
groups  of  these  glands:  the  gastric  or  coronary,  the  splenic,  and  the  hepatic  (in- 
cluding those  of  the  bile-ducts). 

The  Gastric  Glands  (lymphoglandulae  gastricae). — One  group  is  situated  in  the 
gastro-pancreatic  fold ;  another  group  is  connected  with  the  lesser  curvature  of  the 
stomach  (Fig.  506).  Some  of  them  are  in  the  lesser  omentum  close  to  insertion  of 
the  thicker  part  upon  the  stomach,  and  lie  near  the  ascending  branches  of  the  gastric 
artery,  that  is  to  say,  upon  the  vertical  portion  of  the  lesser  curvature.  Others  lie 
within  the  lesser  omentum  and  accompany  the  descending  branches  of  the  gas- 
tric artery,  and  particularly  gather  near  the  point  where  the  gastric  artery  comes 
toward  the  stomach  wall.  The  gastric  glands  receive  lymph  from  most  of  the 
stomach.  They  send  lymph  to  the  upper  group  of  pre-aortic  glands,  the  coeliac 
glands. 

The  Splenic  Glands  (lymphoglandulae  pancreaticolienales) . — The  splenic  glands 
accompany  the  splenic  artery  and  lie  upon  the  posterior  surface  of  the  spleen, 
between  the  spleen  and  pancreas.  They  receive  lymph  from  the  fundus  of  the 
stomach,  from  the  spleen,  and  from  the  pancreas,  and  send  it  to  the  coeliac  glands. 

The  Hepatic  Glands  (lymphoglandulae  hepaticae). — These  glands  lie  along  the 
hepatic  artery,  some  on  the  level  of  the  floor  of  the  foramen  of  Winslow,  others  by 
the  left  side  of  the  portal  vein.1  The  authors  previously  quoted  point  out  that  there 
is  a  secondary  chain  of  hepatic  glands  about  the  right  gastro-epiploic  artery,  the 
gastro-epiploic  chain,  and  that  this  comprises  a  subpyloric  group  and  a  retro-pyloric 
group.  The  subpyloric  group  (Fig.  506)  is  placed  in  the  great  omentum  below  the 
pylorus,  and  is  usually  distinctly  separated  from  it.  -The  retro-pyloric  group  is  not 
constant.  It  is  placed  along  the  gastro-duodenalis  artery  back  of  the  pylorus. 
There  is  also  a  group  of  glands,  secondary  to  the  hepatic  glands,  to  the  right  of 

1  The  Lymphatics.     By  Poirier,  Cuneo,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE  LYMPHATIC  VESSELS  OF  THE  ABDOMEN  AND  PELVIS    799 

or  posterior  to  the  cystic  duct  and  the  common  bile-ducts.  The  hepatic  glands 
proper  receive  lymph  from  the  liver  and  send  it  to  the  co?liac  glands.  The 
subpyloric  glands  receive  lymph  from  the  inferior  portion  of  the  stomach  and 
from  the  superior  portion  of  the  great  omentum.  They  send  lymph  to  the  hepatic 
glands  proper,  the  retro-pyloric  glands,  and  sometimes  also  to  the  glands  about 
the  superior  mesenteric  artery.  The  retro-pyloric  glands  receive  lymph  from  the 
subpyloric  glands,  from  the  upper  surface  and  from  the  posterior  surface  of 
the  pylorus,  and  from  the  duodenum.  They  send  lymph  to  the  hepatic  glands 
proper  and  sometimes  to  the  glands  along  the  superior  mesenteric  artery.  The 
glands  along  the  gall-ducts  empty  into  the  hepatic  glands  proper. 

The  Lymphatic  Vessels  of  the  Abdomen  and  Pelvis. 

The  lymphatic  vessels  of  the  abdomen  and  pelvis  may  be  divided  into  two  sets, 
superficial  and  deep. 

The  Superficial  Lymphatic  Vessels  of  the  Walls  of  the  Abdomen.— The 
superficial  lymphatic  vessels  of  the  walls  of  the  abdomen  follow  the  course  of  the 
superficial  blood-vessels.  The  superficial  lymphatics  are  derived  from  the  integu- 
ment. Those  of  the  lower  part  of  the  abdomen  below  the  umbilicus  follow  the  course 
of  the  superficial  epigastric  vessels  and  converge  to  the  superior  group  of  the  super- 
ficial inguinal  glands  (Figs.  499  and  501).  Those  from  the  costal  margins  of  the 
abdomen  terminate  in  the  axillary  glands  (Fig.  495).  The  superficial  lymphatics 
from  the  sides  of  the  lumbar  part  of  the  abdominal  wall  wind  around  the  crest  of 
the  ilium,  accompanying  the  superficial  circumflex  iliac  vessels,  to  join  the  super- 
ficial inguinal  glands  (Fig.  499). 

The  Superficial  Lymphatic  Vessels  of  the  Gluteal  Region. — The  superficial  lym- 
phatic vessels  of  the  gluteal  region  turn  horizontally  around  the  outer  side  of  the 
nates,  and  join  the  superficial  inguinal  glands. 

The  Superficial  Lymphatic  Vessels  of  the  Scrotum  and  Perinseum. — The  superficial 
lymphatic  vessels  of  the  scrotum  and  perinseum  terminate  in  the  superficial  inguinal 
glands. 

The  Superficial  Lymphatic  Vessels  of  the  Penis. — The  superficial  lymphatic  vessels 
of  the  penis  occupy  the  sides  and  dorsum  of  the  organ,  the  latter  receiving  the 
lymphatics  from  the  prepuce;  they  all  converge  to  the  superficial  inguinal  glands. 
Lymph  vessels  from  the  glans  penis  empty  into  the  deep  inguinal  and  the  external 
iliac  glands. 

In  the  female  the  lymphatic  vessels  of  the  vulva  and  prepuce  of  the  clitoris  pass 
to  the  superficial  inguinal  glands;  those  of  the  glans  of  the  clitoris  pass  to  the 
deep  inguinal  and  the  external  iliac  glands. 

The  Deep  Lymphatic  Vessels  of  the  Abdominal  Wall. — The  deep  lymphatic 
vessels  of  the  abdominal  wall  take  the  course  of  the  principal  blood-vessels,  and 
arise  from  muscular  or  aponeurotic  layers.  One  set  of  lymph-vessels  runs  along 
with  the  deep  epigastric  artery  and  terminates  in  the  external  iliac  glands.  Another 
accompanies  the  deep  circumflex  iliac  artery,  and  also  terminates  in  the  external 
iliac  glands.  Several  lymph-vessels  accompany  the  lumbar  arteries  and  empty 
into  the  juxta-aortic  glands.  A  vessel  accompanies  the  internal  mammary  artery 
and  empties  into  the  internal  mammary  glands.  Lymph-vessels  of  the  parietes  of 
the  pelvis,  which  accompany  the  gluteal,  ischiatic,  and  obturator  vessels,  follow 
the  course  of  the  internal  iliac  artery,  and  ultimately  join  the  external  iliac,  internal 
iliac,  and  common  iliac  glands,  and  the  glands  about  the  lower  portions  of  the  aorta 
and  vena  cava. 

The  Lymphatic  Vessels  of  the  Umbilicus. — The  lymphatics  of  the  umbilicus  are 
divided  into  three  groups:1  The  cutaneous  lymphatics,  which  are  very  superficial, 

1  The  Lymphatics.     By  Poirier,  CuneY>,  and  Deiamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


800  THE  LYMPHATIC  SYSTEM 

and  empty  into  the  superficial  inguinal  glands.  The  lymphatics  of  the  fibrous 
nucleus,  which  pass  through  the  rectus  sheath,  reach  the  deep  epigastric  artery 
and  join  the  deep  lymphatics  which  come  from  the  muscular  and  aponeurotic 
layers  of  the  belly  wall.  The  lymphatics  of  the  aponeurotic  margin  are  in  two  sets: 
An  anterior  set,  some  of  which  penetrate  the  rectus  sheath  and  join  the  lymphatics 
from  the  fibrous  nucleus;  others  of  which  pass  outward,  penetrate  the  external  and 
internal  oblique  muscles,  and  join  the  posterior  lymph-vessels  from  the  aponeu- 
rotic margin.  A  posterior  set,  which  forms  a  collection  of  vessels  on  the  posterior 
aspect  of  the  rectus  sheath,  from  which  several  trunks  emerge.  One  trunk  passes 
outward,  penetrates  the  Transversalis  muscle,  joins  the  anterior  trunk  from  the 
aponeurotic  margin,  and  empties  into  the  external  iliac  glands.1  Other  ducts  run 
along  with  the  deep  epigastric  artery  and  pass  into  the  external  iliac  glands. 
Glands  lie  along  the  lower  portion  of  these  lymph-ducts,  and  are  known  as 
the  superior  epigastric  glands,  and  a  gland  may  exist  in  the  subperitoneal  tissue 
beneath  the  umbilicus. 

The  Lymphatic  Vessels  of  the  Peritoneum. — It  seems  probable  that  the  peritoneal 
cavity  is  a  lymph-sac  and  that  lymphatics  take  origin  from  the  peritoneum  in 
several  ways.  Robinson2  points  out  three  modes  of  origin :  1.  By  stomata  between 
endothelial  cells.  These  stomata  are  in  direct  communication  with  lymph-vessels. 
2.  By  interstitial  spaces  in  the  subperitoneal  tissue.  3.  By  a  plexiform  origin 
similar  to  interstitial  spaces. 

Surgical  Anatomy. — The  fact  emphasized  by  Robinson  that  the  peritoneum  is  a  great 
lymph-sac  explains  the  quick  absorption  of  septic  material  and  the  rapid  spread  of  infectious  pro- 
cesses. If  the  exudate  clots  and  blocks  the  lymph-channels,  absorption  is  slew  and  life  may  be 
saved.  If  it  does  not  clot,  absorption  is  rapid  and  death  is  certain.  Whether  it  clots  or  not 
depends  on  the  nature  of  the  bacteria  present.3  Fowler,  impressed  by  the  fact  that  absorption 
takes  place  most  rapidly  from  the  diaphragmatic  region  and  least  rapidly  from  the  pelvic  region, 
advises  placing  the  victim  of  peritonitis  in  bed,  with  his  head  and  body  elevated.4 

The  Lymphatic  Vessels  of  the  Bladder. — No  lymphatics  exist  in  the  mucous  mem- 
brane of  the  bladder,  although  they  do  exist  in  the  mucous  membrane  of  the  pros- 
tate. There  are  some  lymphatics  in  the  bladder  muscle,  and  numerous  lymphatics 
in  the  subperitoneal  tissue.  The  network  of  lymph-vessels  in  the  muscles  is  con- 
nected with  the  network  beneath  the  peritoneum  and  prevesical  fascia,  and  collect- 
ing trunks  come  from  both  the  anterior  and  posterior  surfaces  of  the  bladder. 
The  anterior  collecting  trunks  are  divided  into  two  sets.  One  set  comes  from  the 
inferior  portion  of  the  anterior  surface  and  passes  outward  to  terminate  in  an 
external  iliac  gland  "between  the  external  iliac  vein  and  the  obturator  nerve."5 
The  other  set  comes  from  the  superior  and  anterior  vesical  surface,  runs  upward 
and  outward,  and  terminates  in  the  external  iliac  glands.  Each  set  of  vessels 
possesses  interrupting  lymph-nodes,  some  of  which  are  directly  in  front  of  the 
bladder. 

The  posterior  collecting  trunks  are  divided  into  four  sets.  The  first  set  comes 
from  the  superior  and  posterior  portion  and  passes  outward,  exhibiting  interrupting 
nodes  in  its  course.  These  trunks  terminate  in  the  external  iliac  glands.  The 
second  set  runs  directly  back  into  the  external  iliac  glands.  The  third  set  comes 
from  the  middle  of  the  posterior  portion  of  the  bladder  and  terminates  in  the 
hypogastric  glands.  The  fourth  set  comes  from  the  vesical  neck,  passes  back 
and  then  ascends  and  terminates  in  the  glands  in  front  of  the  sacral  promontory. 
This  fourth  set  joins  with  the  lymphatics  from  the  prostate  and  seminal  vesicles. 

The  Lymphatic  Vessels  of  the  Prostate  Gland. — These  vessels  form  a  peri-pros- 
tatic  plexus,  which  receives  its  afferents  from  the  gland  structure.  This  plexus  is 
drained  by  four  vessels,  three  of  which  commence  on  the  posterior  surface  of  the 

1  The  Lymphatics.     By  Poirier,  Cuneo,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 

2  The  Peritoneum.  8  Ibid. 
4  George  Ryerson  Fowler,  on  Diffuse  Septic  Peritonitis,  in  the  Medical  Record,  April  14,  1900. 

6  The  Lymphatics.     By  Poirier,  CuneY>,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE  LYMPHATIC  VESSEL8  OF  THE  ABDOMEN  AND  PELVIS    801 

gland .  Although  these  vessels  begin  on  the  posterior  surface  of  the  prostate,  their 
termination  in  each  case  is  different.  One  passes  on  the  under  surface  of  the 
bladder,  crosses  the  superior  vesical  artery,  runs  outward,  and  ends  in  the  middle 
chain  of  the  external  iliac  group.  Another  passes  upward,  outward,  and  back- 
ward, and  terminates  in  the  hypogastric  group.  A  third  passes  along  the 
floor  of  the  pelvis,  runs  by  the  side  of  the  rectum,  and  ascends  on  the  anterior 
surface  of  the  sacrum  to  terminate  in  the  lateral  sacral  glands  and  in  the  hypo- 
gastric  group.  Occasionally  a  fourth  trunk  is  found  on  the  anterior  surface  of 
the  prostate,  which  descends  and  joins  the  vessels  from  the  membranous  urethra 
and  ends  in  the  hypogastric  glands. 

The  Lymphatic  Vessels  of  the  Male  Urethra. — These  vessels  are  divided  into  two 
groups:  First,  those  of  the  penile  portion  of  the  urethra;  second,  those  of  the  bulb 
and  membranous  portion.  The  lymphatics  of  the  prostatic  urethra  belong  to  those 
of  the  prostate  gland.  The  lymph-vessels  of  the  penile  urethra  in  front  of  the 
sulcus  all  run  toward  the  freenum,  at  which  point  they  bend  backward  to  the  sul- 
cus;  here  they  run  to  the  dorsal  surface  of  the  penis  and  terminate  in  the  same  man- 
ner as  the  vessels  from  the  glans.  The  trunks  from  the  remainder  of  the  penile 
urethra  emerge  from  the  inferior  surface,  run  around  the  corpus  cavernosa,  and 
mostly  unite  with  the  vessels  from  the  glans  penis.  One  vessel,  though,  passes  over 
the  symphysis  and  enters  in  the  internal  retro-crural  gland,  whilst  another  passes 
beneath  the  symphysis  and  terminates  with  the  vessels  from  the  bulb  and  mem- 
branous portion  of  the  urethra.  The  lymphatics  of  the  bulb  and  membranous 
portions  end  in  three  trunks,  one  of  which  accompanies  first  the  artery  of  the  bulb 
and  then  the  internal  pudic  artery,  and  ends  in  the  hypogastric  gland  attached  to 
the  pelvic  portion  of  this  artery.  A  second  trunk  runs  behind  the  pubes,  to  end 
in  the  internal  retro-crural  gland.  A  third  trunk  runs  on  the  bladder,  where  it 
joins  with  vessels  from  this  organ,  to  end  in  the  internal  chain  of  external  iliac 
glands. 

The  Lymphatic  Vessels  of  the  Female  Urethra. — The  lymphatics  of  the  female 
urethra  terminate  in  the  same  manner  as  do  the  lymphatics  of  the  bulb  and  mem- 
branous portions  of  the  male  urethra 

The  Lymphatic  Vessels  of  the  Uterus. — These  consist  of  three  sets,  each  of  which 
arises  by  a  network  of  capillaries.  There  is  a  mucous  network,  a  muscular  network, 
and  a  peritoneal  network.  The  vessels  from  these  three  regions  of  origin  are  col- 
lected in  the  subperitoneal  tissue,  from  which  area  the  collecting  trunks  take  origin. 
From  the  cervix,  according  to  Poirier  and  Cune"o,  come  from  five  to  eight  collecting 
trunks,  which  pass  toward  the  sides  of  the  body  of  the  uterus,  forming  on  each 
side,  by  twisting  and  dilatation,  the  juxta-cervical  lymphatic  knot  of  Cune"o.  The 
cervical  connecting  trunks  are  divisible  into  three  groups  on  each  side.  One  group 
is  composed  of  two  vessels,  which  pass  to  the  middle  chain  of  the  external  iliac 
glands  (superior  and  middle  glands).  Another  group  is  composed  of  two  vessels, 
which  enter  the  hypogastric  glands.  A  third  group  is  composed  of  several  vessels, 
some  of  which  enter  the  lateral  sacral  glands,  and  the  balance  of  which  terminate 
in  the  glands  of  the  sacral  promontory.  From  the  body  of  the  uterus  come  three 
groups  on  each  side.  One  group  is  composed  of  four  or  five  vessels  which  emerge 
below  the  uterine  cornu,  pass  beneath  the  ovary,  where  they  receive  the  ovarian 
lymphatics,  and  terminate  in  the  juxta-aortic  glands  of  the  same  side.  One 
so-called  accessory  lymphatic  pedicle  terminates  in  the  external  iliac  glands,  the 
other  in  the  inguinal  glands. 

The  Lymphatic  Vessels  of  the  Fallopian  Tube. — The  lymphatics  of  the  Fallopian 
tube  join  with  those  of  the  uterus  and  ovary  and  terminate  in  the  lateral  aortic 
glands. 

The  Lymphatic  Vessels  of 'the  Ovary. — The  ovary  is  extremely  rich  in  lymphatics; 
they  form  a  plexus  which  is  superficial  to  the  veins.  The  vessels  leading  from  this 
plexus,  four  or  five  in  number,  pass  upward  in  company  with  the  ovarian  vessels 

51 


802  THE  LYMPHATIC  SYSTEM 

and  end  in  the  lateral  aortic  glands.  Above  the  firth  lumbar  vertebra  these  ves- 
sels anastomose  with  the  lymphatics  from  the  fundus  of  the  uterus  and  Fallopian 
tube.  Quite  often  there  is  a  lymph-vessel  which  emerges  from  the  ovary,  passes 
downward  and  outward  and  ends  in  the  middle  chain  of  the  internal  iliac  glands. 

The  Lymphatic  Vessels  of  the  Vagina. — The  lymphatics  of  the  vagina  are  divided 
into  those  of  the  mucous  coat  and  those  of  the  muscular  coat;  these  anastomose 
freely  with  each  other  and  terminate  in  a  peri-vaginal  network,  which  is  drained 
by  three  groups  of  trunks.  One  group  drains  the  upper  third  of  the  vagina  and 
passes  to  the  middle  chain  of  the  external  iliac  glands.  A  second  group  is  efferent 
to  the  middle  third  of  the  vagina  and  ends  in  the  hypogastric  glands.  A  third 
group  carries  the  lymph  from  the  lower  third  of  the  vagina  to  the  gland  of  the 
promontory. 

The  Lymphatic  Vessels  of  the  Testicle. — The  lymphatic  vessels  of  the  testicle 
consist  of  two  sets,  superficial  and  deep;  the  former  commence  on  the  visceral  sur- 
face of  the  tunica  vaginalis,  the  latter  in  the  epididymis  and  body  of  the  testis. 
They  form  several  large  trunks  which  ascend  with  the  spermatic  cord,  and,  accom- 
panying the  spermatic  vessels  into  the  abdomen,  terminate  in  the  juxta-aortic 
and  sometimes  also  in  the  pre-aortic  glands ;  hence  the  enlargement  of  these  glands 
in  malignant  disease  of  the  testis. 

The  Lymphatic  Vessels  of  the  Vas  Deferens. — These  lymphatics  empty  into  the 
external  iliac  glands. 

The  Lymphatic  Vessels  of  the  Seminal  Vesicles. — A  network  exists  on  the  surface 
of  each  vesicle,  formed  by  a  collection  of  lymph-vessels  from  the  mucous  lining  and 
from  the  muscular  structure  of  the  vesicle.  The  trunks  from  this  network  empty 
into  the  external  and  internal  iliac  glands. 

The  Lymphatic  Vessels  of  the  Kidney,  Ureter,  and  Suprarenal  Capsule. — Their 
courses  and  terminations  differ  on  the  two  sides.  They  take  origin  from  a  super- 
ficial network  just  beneath  the  capsule  of  the  kidney  and  a  deep  network  in  the  in- 
terior of  the  organ.  The  superficial  network  is  connected  to  the  collecting  vessels 
of  the  deep  network  at  the  hilum.  From  the  superficial  network  numerous  ves- 
sels penetrate  the  capsule  of  the  kidney  and  join  the  lymphatics  of  the  fatty  cap- 
sule. According  to  Poirier,  Cune"o,  and  Delamare,1  anterior  and  posterior  trunks 
come  off  from  the  deep  lymphatics  of  the  right  kidney.  The  anterior  trunk 
usually  terminates  in  the  right  juxta-aortic  glands  which  lie  upon  the  vena  cava. 
The  posterior  trunks  terminate  in  the  juxta-aortic  glands  which  lie  behind  the 
vena  cava.  On  the  left  side  all  the  collecting  trunks  terminate  in  the  juxta-aortic 
glands  of  the  left  side  of  the  aorta. 

The  lymphatics  of  the  fatty  capsule  of  the  kidney  communicate  with  the  lym- 
phatics of  the  kidney,  and  both  terminate  in  the  same  glands.  The  lymphatics  of 
the  suprarenal  capsule  terminate  in  the  juxta-aortic  glands  of  the  same  side.  From 
the  ureter  lymph-vessels  come  off  and  terminate  in  the  juxta-aortic  and  adjacent 
glands. 

The  Lymphatic  Vessels  of  the  Liver. — The  lymphatic  vessels  of  the  liver  are 
divisible  into  two  sets,  superficial  and  deep.  The  former  arise  in  the  lobules  at  the 
periphery  of  the  liver  and  pass  to  the  subperitoneal  connective  tissue  over  the 
entire  organ.  The  latter  arise  from  the  deeper  lobules,  and  emerge  from  the  liver 
along  the  portal  vein  or  the  hepatic  veins. 

According  to  Poirier,  Cune"o,  and  Delamare,2  three  groups  of  superficial  collect- 
ing trunks  arise  from  the  subperitoneal  network.  The  posterior  trunks  divide 
into  three  groups.  The  single  right  posterior  trunk  terminates  in  a  gland  about  the 
creliac  axis.  The  middle  posterior  trunks  (five  to  seven  in  number)  pass  through 
the  opening  in  the  Diaphragm.  The  left  posterior  trunks  pass  into  glands 

1  The  Lymphatics.     Translated  and  edited  by  Cecil  H.  Leaf.  2  Ibid. 


THE  LYMPHATIC   VESSELS  OF  THE  ABDOMEN  AND  PELVIS     803 

about  the  subdiaphragmatic  portion  of  the  oesophagus.  The  anterior  collecting 
trunks  terminate  in  the  lymph-glands  of  the  hilum  of  the  liver.  The  superior 
trunks  ascend.  One  of  these  trunks  or  a  posterior  trunk  passes  with  the  vena  cava 
through  the  Diaphragm  and  terminates  in  glands  about  the  vena  cava.  Another 
trunk,  an  anterior  one,  passes  over  the  anterior  border  of  the  liver,  runs  for  a  time 
with  the  round  ligament,  and  terminates  in  the  hepatic  glands.  Numerous  middle 
trunks  ascend  in  the  suspensory  ligament,  unite  beneath  the  Diaphragm  into  a 
short  trunk  of  large  size,  which  passes  through  the  Diaphragm  and  divides  into 
several  smaller  ducts,  which  terminate  in  the  glands  back  of  the  xiphoid  cartilage. 
Trunks  from  the  superficial  lymphatic  network  also  emerge  from  the  inferior 
surface  of  the  liver.  The  posterior  trunks  from  the  right  lobe  reach  the  vena  cava 
and  terminate  in  the  glands  about  the  intra-thoracic  end  of  that  vessel.  The 
middle  and  anterior  trunks  from  the  right  lobe  reach  the  glands  along  the  cystic 
duct.  The  trunks  from  the  left  lobe  terminate  in  the  glands  along  the  hepatic 
artery.  The  trunks  from  the  lobus  Spigelii  reach  the  glands  of  the  hilum  and  the 
glands  about  the  lower  intra-thoracic  portion  of  the  vena  cava.  The  trunks  from 
the  quadrate  lobe  terminate  in  the  glands  of  the  hilum.  The  deep  collecting  trunks 


LEFT   LATERAL 

LIGAMENT 


OBLITERATED 
UMBILICAL  VEIN 


FIG.  504. — Lymphatics  of  the  inferior  surface  of  the  liver.     (Sappey.) 

are  divisible  into  two  groups.  One  group  descends  along  the  portal  vein,  the  other 
ascends  along  the  hepatic  veins. 

Sappey  pointed  out  that  the  deep  descending  trunks  accompany  the  bile  pass- 
ages and  the  branches  of  the  portal  vein,  several  anastomosing  vessels  accom- 
panying each  branch  of  the  portal  vein.  The  same  authority  affirmed  that  from 
fifteen  to  eighteen  trunks  emerge  from  the  hilum  and  terminate  in  the  adjacent 
glands.  The  deep  ascending  trunks  surround  as  a  sheath  the  branches  of  the 
hepatic  vein  (Sappey).  As  they  approach  the  Diaphragm  they  diminish  in  num- 
ber to  five  or  six,  pass  through  the  opening  for  the  vena  cava,  and  terminate  in 
the  glands  about  the  lower  portion  of  the  intra-thoracic  cava. 

The  Lymphatic  Vessels  of  the  Bile-ducts. — The  lymphatics  of  the  bile-ducts  arise 
from  the  mucous  membrane  and  from  within  the  muscular  tissue,  and  terminate 
in  glands  along  the  cystic  and  common  ducts. 


804  THE  L  YMPHA  TIG  SYSTEM 

The  Lymphatic  Vessels  of  the  Stomach  (Figs.  505  and  506).— The  lymphatic 
vessels  of  the  stomach  consist  of  two  sets,  superficial  and  deep.  The  superficial 
arise  from  the  outer  (serous)  and  the  middle  (muscular)  coats.  The  deep  arise 
from  the  mucous  membrane  and  form  a  network  in  the  submucous  tissue.  Trunks 
from  the  submucous  network  pass  through  the  muscular  tunic  and  terminate  in 
the  trunks  coming  from  the  sero-muscular  layers.  These  latter,  the  musculo-serous 


CORONARY 
CURRENT 


RIGHT 

CASTRO-EPIPLOIC 
CURRENT 


FIG.  507. — Lymphatic  areas  of  the  stomach.     (Cuneo.) 

collecting  trunks,  are  divided  into  three  groups.  The  first  group  is  composed  of  six 
or  eight  vessels  which  pass  toward  the  lesser  curvature  (Sappey).  There  are  from 
three  to  ten  glands  upon  the  lesser  curvature  along  the  course  of  the  gastric  artery 
which  receive  these  superior  trunks.  Vessels  come  to  these  glands  from  the  cardia, 
from  the  body  of  the  stomach,  and  from  the  pyloric  end.  In  the  lesser  curvature 
the  lymphatic  vessels  lie  in  the  wall  of  the  stomach.  According  to  Cun^o,  two- 
thirds  of"  the  stomach  is  drained  by  the  lymph-vessels  of  group  I.  The  second 
group  comprises  the  trunks  from  the  greater  curvature  which  end  in  the  subpyloric 
glands.  The  glands  along  the  greater  curvature  are  some  distance  from  the 
stomach  wall  in  the  pyloric  region,  and  lymph-streams  flow  from  left  to  right,  that 
is,  toward  the  pylorus  and  not  from  it.  These  lymphatics  drain  one-third  of  the 
stomach.  The  first  and  second  groups  send  lymph  eventually  to  the  coeliac 
glands  and  juxta-aortic  glands.  The  third  group  comprises  trunks  which  come 
from  the  fundus  of  the  stomach  and  enter  the  lymphatic  glands  about  the  spleen. 

Surgical  Anatomy. — Mikulicz  pointed  out  the  early  infection  of  the  glands  of  the  lesser  curva- 
ture in  pyloric  cancer,  and  insisted  that  in  operation  for  pyloric  cancer  the  entire  lesser  curvature 
must  be  removed.  Cune*o  showed  us  that  in  pyloric  cancer  the  fundus  and  two-thirds  of  the 
greater  curvature1  usually  remain  free  from  disease,  because  the  lymph-current  is  toward  the 
pylorus  and  not  from  it.  Of  course,  if  the  lymphatics  become  blocked,  the  lymph-current  may 
be  reversed  (regurgitation),  and  then  infection  of  these  parts  can  occur.  William  J.  Mayo  has 
noted  the  ''lymphatic  isolation"  of  the  dome  of  the  stomach.  In  operating  for  cancer  of  the 
pylorus,  make  the  section  of  the  stomach  as  directed  by  Hartmann,  that  is,  a  section  which 
removes  all  of  the  lesser  curvature  and  cuts  the  greater  curvature  well  to  the  left  of  the  subpyloric 
glands. 

The  Lymphatic  Vessels  of  the  Pancreas. — The  lymphatics  of  the  pancreas  arise 
from  a  network  about  the  pancreatic  lobules.  The  collecting  trunks  anastomose 
freely  on  the  surface  of  the  pancreas.  Some  of  the  trunks  terminate  in  the 
splenic  glands,  which  send  vessels  to  the  coeliac  glands.  Others  terminate  directly 
in  the  coeliac  glands.  The  lymphatics  of  the  head  of  the  pancreas  communicate 
with  the  duodenal  lymphatics  and  the  lymphatics  of  the  lower  end  of  the  com- 
mon duct.  The  pancreatic  and  splenic  lymphatics  probably  communicate. 

The  Lymphatic  Vessels  of  the  Spleen. — The  lymphatics  of  the  spleen  consist  of 
two  sets,  superficial  and  deep;  the  former  are  placed  beneath  its  peritoneal  covering, 
the  latter  in  the  substance  of  the  organ;  they  accompany  the  blood-vessels,  passing 


THE  LYMPHATIC  SYSTEM  OF  THE  INTESTINES 


805 


through  a  series  of  small  glands,  and  pass  into  the  splenic  glands  which  are  placed 
in  the  omentum  between  the  spleen  and  pancreas.  The  gastro-splenic  omentum 
contains  no  glands. 


THE  LYMPHATIC  SYSTEM  OF  THE  INTESTINES. 

The  Lymphatic  Glands  of  the  Small  Intestine  (Fig.  507).— The  lymphatic 
glands  of  the  small  intestine  are  placed  between  the  layers  of  the  mesentery,  and  are 


LEFT    VAGUS. 
NERVE 


RIGHT  CASTRO 
EPIPLOIC  ARTERY 


SUBPYLORIC 
GLAND 


CORONARY 
VEIN 

GLANDS  OF  THE 
LESSER  CURVATURE 


RIGHT  GASTRO- 
CPIPLOIC  VEIN 


FIG.  506. — General  view  of  the  subperitoneal  lymphatic  plexus  of  the  stomach  prepared  by  the  method  of 

Gerota.     (Cune'o.) 

called  mesentery  glands  (lymphoglandulae  mesentericae) .  They  vary  in  number  from 
a  hundred  to  a  hundred  and  fifty,  and  in  size  from  that  of  a  pea  to  that  of  a  small 
almond.1  These  glands  are  most  numerous  and  largest  above,  the  glands  of  the 
jejunum  being  more  numerous  than  those  of  the  ileum.  This  latter  group  becomes 
enlarged  and  infiltrated  with  deposit  in  cases  of  fever  accompanied  with  ulceration 
of  the  intestines.  The  glands  diminish  in  number  as  we  descend  until  the  ileo- 
csecal  region  is  reached,  when  a  number  of  glands  appear  about  the  ileo-csecal 
artery.  The  mesenteric  glands  receive  the  lacteals  and  send  out  trunks  to  the 
receptaculum  chyli.  The  chyle  from  the  intestine  passes  through  the  glands  on 
its  way  to  the  thoracic  duct. 

The  glands  may  be  divided  into:  I.  A  group  of  glands  the  members  of  which 
are  chiefly  found  along  the  terminal  vessels  from  the  vascular  loops  of  the  intestinal 
branches  of  the  superior  mesenteric  artery.  Some  glands  of  this  group  are  placed 
upon  "the  anterior  surface  of  the  upper  end  of  the  jejunum."2  II.  A  group  of 

1  Leaf  (Surgical  Anatomy  of  the  Lymphatic  Glands)    says  it  is  very  common  to  find  not  more  than  forty  or 
fifty.  2  Ibid. 


806  THE  LYMPHATIC  SYSTEM 

glands  along  the  vascular  loops  of  the  superior  mesenteric  artery.  Most  of  them 
are  between  the  primary  loops.  Some  of  them  are  between  the  secondary  and 
tertiary  loops.  III.  A  group  of  glands  along  the  trunk  of  the  superior  mesenteric 
artery. 


FIG.  507. — Lymphatics  of  the  small  intestine..   (Poirier  and  Charpy.) 

The  Lymphatic  Vessels  of  the  Small  Intestine  (Fig.  507).— The  lymphatic 
vessels  of  the  small  intestine  are  called  lacteals,  from  the  milk-white  fluid  they 
usually  contain.  They  take  origin  in  the  intestinal  villi  and  in  lymphatic  sinuses 
around  the  bases  of  the  solitary  glands.  Lymphatic  plexuses  exist  in  the  submucous 
tissue,  the  muscular  coat,  and  the  subserous  tissue.  The  lymphatic  vessels  pass 
between  the  layers  of  the  mesentery,  enter  the  mesenteric  glands,  and  finally  unite 
to  form  two  or  three  large  trunks  which  terminate  separately  in  the  receptaculum 
chyli;  frequently,  however,  they  first  unite  to  form  a  single  large  trunk,  termed  the 
intestinal  lymphatic  trunk  (Figs.  483  and  509). 

The  Lymphatic  Glands  of  the  Large  Intestine. — The  lymphatic  glands  of 
the  large  intestine  are  divided  into  the  colic  glands  and  rectal  glands. , 

The  Colic  Glands  (lymphoglandulae  coliacae). — The  colic  glands  are  subdivided 
into:  1.  The  ileo-colic  or  ileo-csecal  glands  (Fig.  508),  which  lie  along  the  course 
of  the  ileo-colic  artery,  one  or  two  of  the  glands  being  placed  upon  the  anterior 
surface  of  the  caecum.  The  mesoappendix  also  contains  a  gland  which  com- 
municates with  glands  in  the  mesocolon,  and  receives  lymph  from  the  appendix 
and,  in  the  female,  from  the  ovary.  2.  Glands  in  the  mesocolon  along  the  right 
colic  artery,  which  receive  lymph  from  the  ascending  colon  and  the  hepatic  flexure. 
3.  Glands  in  the  mesocolon  along  the  middle  colic  artery,  which  receive  lymph 
from  the  hepatic  flexure  and  transverse  colon.  4.  Glands  in  the  mesocolon 
along  the  left  colic  artery,  which  receive  lymph  from  the  descending  colon  and 
sigmoid  flexure.  The  vessels  from  the  colic  glands  pass  to  the  pre-aortic 
glands. 

The  Rectal  Glands. — The  rectal  glands  lie  in  the  mesorectum;  they  receive  lymph 
from  the  anus  and  rectum  and  it  passes  from  them  to  the  lumbar  and  sacral  glands. 

The  Lymphatic  Vessels  of  the  Large  Intestine. — The  lymphatic  vessels  of  the 
large  intestine  consist  of  three  sets:  those  of  the  caecum,  ascending  and  transverse 
colon,  which,  after  passing  through  their  proper  glands,  enter  the  mesenteric 
glands;  those  of  the  descending  colon  and  sigmoid  flexure,  which  pass  to  the  lumbar 


THE  LYMPHATIC  GLANDS  OF  THE  THORACIC  WALL        807 

glands,  and  those  of  the  rectum  and  anus,  which  pass  to  the  sacral  and  superficial 
inguinal  glands. 

Lymphatics  of  the  Anus  and  Rectum. — These  vessels  take  origin  from  two 
networks,  one  from  the  skin  and  mucous  membrane  and  the  other  from  the  mus- 
cular coat.  The  lymph-vessels  from  the  skin  at  the  anal  margin  pass  to  the  super- 
ficial inguinal  glands.  Some  vessels  from  the  skin  of  the  anus  ascend  and  reach 
the  submucous  plexus  of  the  rectum,  from  which  region  lymph-vessels  pass  to 
the  rectal  glands,  to  the  glands  along  the  middle  hemorrhoidal  artery,  and  along 
the  inferior  hemorrhoidal  artery,  and  to  a  pelvic  gland  near  the  origin  of  the 
internal  pudic  artery.1  The  vessels  from  the  anal  mucous  membrane  and  from 
the  muscular  wall  of  the  rectum  penetrate  the  muscular  wall  of  the  rectum 
with  the  arteries  and  reach  the  rectal  glands. 


ANTERIOR 
LYMPHATICS 
OF  OECUM 


ANTERIOR 

C/ECAL 


GLAND  OF 
APPENDIX 


APPENDICULAR 

EFFERENT 

LYMPHATICS 


FIG.  508.— Anterior  view  of  the  lymphatics  of  the  ca-cum  and  appendix.    (Poirier  and  Charpy.) 

THE  LYMPHATICS  OF  THE  THORAX. 

The  thoracic  lymphatics  are  divided  into  the  deep  lymphatics  of  the  chest  wall, 
the  diaphragmatic  lymphatics,  and  the  visceral  lymphatics. 

The  Lymphatic  Glands  of  the  Thoracic  Wall  or  the  Parietal  Lymphatics. 

The  lymphatic  glands  of  the  thoracic  wall  include  the  internal  mammary  and 
intercostal  glands. 

The  Internal  Mammary  Glands. — The  internal  mammary,  retro-sternal,  or 
sternal  glands  (lymphoglandulae  sternales)  form  a  chain  of  five  or  six  glands  on  each 
side  of  the  sternum  along  the  course  of  the  corresponding  internal  mammary  artery, 
and  back  of  the  Internal  intercostal  muscles.  The  glands  are  separated  from  the 
pleura  by  cellular  tissue.  The  internal  mammary  glands  receive  vessels  from  the 
diaphragmatic  glands,  the  abdominal  muscles  above  the  umbilicus,  the  anterior 

'  The  Lymphatics.     By  Poirier,  Cun£o,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


808  THE  LYMPHATIC  SYSTEM 

ends  of  the  intercostal  spaces,  the  skin  over  the  sternum,  and  the  mammary  gland. 
The  vessels  given  off  by  each  chain  from  a  single  trunk.  On  the  right  side  this 
trunk  terminates  at  the  junction  of  the  internal  jugular  and  subclavian  veins, 
unites  with  the  subclavian  lymph-trunk  to  form  the  right  lymphatic  duct,  or 
empties  directly  into  the  subclavian  trunk  (Fig.  485).  On  the  left  side  it  empties 
either  at  the  junction  of  the  subclavian  and  internal  jugular  veins  or  into  the 
thoracic  duct. 

The  Intercostal  Glands  (lymphoglandulae  intercostales)  (Fig.  509).— The  inter- 
costal glands  are  small  glands  lying  in  the  intercostal  spaces  along  the  intercostal 
arteries.  In  the  posterior  end  of  each  space  they  are  constantly  found.  These  are 
called  the  posterior  glands,  and  there  are  one,  two,  or  three  in  each  space.  These 
glands  are  opposite  the  neck  of  the  rib  or  over  the  articulation  of  the  rib  with  the 
vertebra.  The  pleura  is  in  front  of  them,  and  they  lie  upon  the  external  inter- 
costal muscles.  In  the  middle  of  the  intercostal  spaces  are  inconstant  glands 
which  are  called  lateral  glands.  They  are  merely  interrupting  nodes  in  the 
trunks  from  the  intercostal  muscles.  The  intercostal  glands  receive  vessels  from 
the  intercostal  muscles  and  pleura.  They  send  vessels  back  toward  the  spine, 
which  unite  with  lymphatics  from  the  back  part  of  the  thorax  and  spinal  canal, 
and  which  pass  down  the  spine  and  terminate  in  the  thoracic  duct. 

The  Diaphragmatic  Lymphatics.— The  diaphragmatic  lymph-glands  are  dis- 
tinct and  numerous.  These  glands  are  on  the  convex  surface  of  the  Diaphragm 
and  are  divided  into  an  anterior,  a  middle,  and  a  posterior  group.  They  receive 
vessels  from  the  Diaphragm  and  liver  and  send  vessels  to  the  internal  mammary 
and  posterior  mediastinal  glands.  The  lymph-vessels  of  the  Diaphragm  take 
origin  from  a  capillary  network  contained  in  the  spaces  between  the  muscular 
and  tendinous  fasciculi  of  the  Diaphragm.  Numerous  lymph-vessels  descend 
until  they  reach  the  subperitoneal  tissues  and  then  ascend.  Others  immediately 
ascend  to  beneath  the  pleura.  The  collecting  trunks  are  all  on  the  convex  surface 
of  the  Diaphragm.  The  lymphatic  vessels  of  the  Diaphragm  anastomose  with 
the  lymphatic  vessels  of  the  pleura  and  the  peritoneum.  This  subperitoneal 
network  is  so  extensive  that  absorption  in  this  region  is  extremely  rapid. 
Hence,  after  an  abdominal  operation,  if  salt  solution  has  been  left  in  the  ab- 
domen, it  will  be  very  rapidly  absorbed  if  the  foot  of  the  bed  is  elevated. 
Influenced  by  the  knowledge  that  the  pelvic  peritoneum  absorbs  comparatively 
slowly  and  the  peritoneum  in  the  upper  abdomen  very  rapidly,  and  that  septic 
processes  in  the  upper  abdomen  are  more  rapidly  fatal  than  septic  processes  in 
the  pelvis,  Fowler  was  led  to  recommend  the  elevation  of  the  head  of  the  bed 
after  operations  for  abdominal  infections.  This  posture  causes  poisonous  fluids 
to  gravitate  away  from  the  Diaphragm. 

The  Visceral  Lymphatics. — The  visceral  lymphatics  include  the  anterior  medi- 
astinal glands,  the  posterior  mediastinal  glands,  and  the  peritracheo-bronchial  glands. 

The  Anterior  Mediastinal  Glands  (lymphoglandulae  mediastinales  anteriores) . — The 
anterior  mediastinal  glands  are  in  the  upper  portion  of  the  anterior  mediastinum, 
a  group  of  six  or  seven  glands  lying  above  and  upon  the  front  of  the  transverse 
portion  of  the  arch  of  the  aorta  and  sending  glandular  chains  toward  the  neck. 
On  the  right  side  these  glands  are  found  between  the  innominate  artery  and  vein 
and  in  front  of  the  vein.  On  the  left  side  they  are  in  front  of  and  behind  the  left 
common  carotid  and  left  subclavian  arteries.  They  receive  lymph  from  the  heart, 
pericardium,  thymus  gland,  and  anterior  mediastinum. 

The  Posterior  Mediastinal  Glands  (lymphoglandulae  mediastinales  posteriores) 
(Fig.  509). — The  posterior  mediastinal  glands  are  behind  the  pericardium  and 
in  front  of  the  oesophagus.  Occasionally  one  or  two  are  placed  back  of  the 
oesophagus.  They  receive  vessels  from  the  intercostal  glands,  aortic  glands, 
deep  cervical  glands,  and  pleura,  and  send  vessels  to  the  thoracic  duct. 


THE  LYMPHATIC  GLANDS  OF  THE  THORACIC   WALL 


809 


The  Peritracheo-bronchial  Glands. — The  peritracheo-bronchial  glands  are  divided 
by  Bare"ty  into  four  groups.  One  group  is  in  the  angle  formed  by  the  junction 
of  the  trachea  and  right  bronchus.  Another  group  is  in  a  corresponding  situation 
on  the  left  side.  Another  group  is  below  the  tracheal  bifurcation.  The  glands  of 
the  fourth  group  are  about  the  points  of  division  of  the  larger  bronchi.  The 
peritracheo-bronchial  glands  receive  lymph-vessels  from  the  lung,  heart,  peri- 
cardium, oesophagus,  trachea,  and  thymus. 


MEDIASTINAL 

GLANDS  AND 

VESSELS 


INTERCOSTAL 

GLANDS  AND 

VESSELS 


COMMON   INTES 
TINAL  TRUNK 

PRE-AORTIC 
GLANDS  AND 
VESSELS 


COMMON   INTES- 
TINAL TRUNK 


INTERNAL  ILIAC 
EXTERNAL  ILIAC 


FIG.  509; — Deep  lymphatic  glands  and  vessels  of  the  thorax  and  abdomen  (diagrammatic).     Afferent  vessels  are 
represented  by  continuous  lines,  and  efferent  and  interglandular  vessels  by  dotted  lines.      (Cunningham.) 

In  infancy  these  glands  present  the  same  appearance  as  the  lymphatic  glands  in  other  situa- 
tions. In  early  adult  life  they  assume  a  brownish  tinge,  and  in  old  age  become  deep  black, 
because  they  arrest  particles  of  carbon  brought  from  the  bronchi.  This  change  is  known  as 
anthracosis,  and  the  darkened  glands  are  usually  sclerotic.  In  fact,  in  old  age  these  glands  often 
lose  all  lymphatic  characters  and  become  fibrous  masses.  These  glands  enlarge  from  infection, 


8 1 0  THE  L  YMPHA  TIC  SYSTEM 

and  when  very  large  may  compress  the  bronchi,  the  pulmonary  artery,  etc.     They  are  often  the 
seat  of  tuberculous  deposits. 

The  Lymphatic  Vessels  of  the  Thoracic  Wall.— The  lymphatic  vessels  of  the 
thoracic  Wall  include  the  deep  lymphatic  vessels,  intercostal  and  internal  mammary, 
which  have  been  described,  the  cutaneous  lymphatics,  and  the  lymphatics  of  the 
mammary  gland. 

The  Cutaneous  Lymphatics  (Fig.  495).— The  area  drained  by  these  lymphatics 
is  very  extensive.  It  is  divided  by  Poirier,  Cune'o,  and  Delamare  into  three  regions. 
The  anterior  region  extends  from  over  the  middle  of  the  sternum  to  the  anterior  axil- 
lary line.  The  trunks  pass  to  the  axilla  and  terminate  in  the  thoracic  chain  of  the 
axillary  glands.  From  this  anterior  region  some  accessory  trunks  pass  above  the 
clavicle  and  reach  the  supra-clavicular  glands,  and  trunks  may  arise  to  one  side 
of  the  mid-sternal  line  and  pass  to  the  opposite  axilla.  From  the  lateral  region  the 
trunks  ascend  to  the  thoracic  chain  of  axillary  glands.  This  region  is  between 
the  anterior  and  posterior  axillary  lines.  The  posterior  region  is  back  of  the 
posterior  axillary  line,  and  includes  the  thorax  to  the  mid-line,  and  the  posterior 
portion  of  the  root  of  the  neck.  The  trunks  from  the  posterior  area  empty  into 
the  scapular  group  of  axillary  glands. 

Lymphatics  of  the  Mammary  Gland  (Figs.  494  and  510).— There  are  two  sets 
of  lymphatics  in  this  gland,  the  cutaneous  or  superficial  and  the  glandular  or  deep. 

The  Peripheral  Cutaneous  Lymphatics  of  the  Mammary  Gland. — The  peripheral 
cutaneous  lymphatics  do  not  arise  from  the  nipple.  Their  collecting  trunks  are 
arranged  as  are  other  collecting  trunks  of  the  anterior  portion  of  the  thorax,  and 
end  in  the  thoracic  group  of  axillary  glands  of  the  same  side.  Trunks  arising  from 
the  sternal  margin  of  the  skin  of  the  breast  may  run  to  the  glands  of  the  opposite 
axilla. 

The  Central  Deep  Lymphatics  of  the  Mammary  Gland. — The  central  lymphatics 
form  a  very  extensive  network  in  the  nipple  and  areola,  and  from  this  network 
numerous  vessels  pass  into  a  plexus  beneath  the  areola,  Sappey's  subareolar  plexus; 
most  of  the  trunks  coming  from  the  gland  also  enter  the  subareolar  plexus. 

The  Glandular  Lymphatics  of  the  Mammary  Gland. — The  glandular  lymphatics 
arise  from  spaces  about  the  lobules  and  from  networks  about  the  milk-ducts.  We 
can  distinguish  a  chief  lymphatic  channel  and  three  accessory  channels. 

The  chief  lymphatic  channel  takes  origin  from  collecting  trunks  which  begin 
in  the  spaces  about  the  lobules  and  in  the  lymph-capillaries  about  the  milk-ducts. 
These  collectors  pass  toward  the  nipple  and  terminate  in  the  subareolar  plexus, 
which  plexus  also  receives  the  vessels  from  the  areola  and  nipple.  Two  large 
trunks  take  origin  from  the  subareolar  plexus:  one  from  its  inner  side,  the  other 
from  its  outer  side.  "The  internal  trunk  runs  at  first  downward  and  then  out- 
ward, turning  round  the  inferior  border  of  the  subareolar  plexus.  It  is  thus 
directed  toward  the  axilla  and  runs  in  the  subcutaneous  cellular  tissue,  along  the 
lower  border  of  the  Pectoralis  major,  which  it  crosses  at  the  level  of  the  third 
rib  to  reach  the  base  of  the  axilla.  This  collecting  trunk  constantly  receives  as 
afferents  one  or  two  fair-sized  trunks  coining  directly  from  the  inferior  portion  of 
the  mammary  gland.  The  external  trunk,  which  is  usually  smaller  than  the  pre- 
ceding, runs  directly  outward  toward  the  axilla.  Before  it  reaches  the  latter  it 
is  augmented  by  a  vessel  coming  from  the  superior  part  of  the  gland.  At  the  base 
of  the  axilla  these  two  collecting  trunks  perforate  the  axillary  aponeurosis  and 
terminate  in  one  or  two  glands,  placed  on  the  inner  wall  of  the  axilla  on  the  third 
digitation  of  the  Serratus  magnus  muscle.  These  glands  (the  principal  regional 
glands  of  the  breast)  may  or  may  not  be  covered  by  the  lower  part  of  the  Pec- 
toralis major  muscle  according  to  the  muscular  development  of  the  subject  (Sur- 
gius)."1  These  glands  constitute  the  supero-internal  mass  of  the  anterior  axillary 

1  The  Lymphatics.     By  Poirier,  Cun6o,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE  LYMPHATIC  GLANDS  OF  THE  THORACIC  WALL        811 

chain.      An  interrupting  gland  is  sometimes  found  in  the  course  of    these  two 
trunks,  the  paramammary  gland. 

The  Accessory  Channels  from  the  Mammary  Gland. — The  accessory  channels  from 
the  mammary  gland,  according  to  Poirier,  Cune*o,  and  Delamare,  are  three.  They 
call  one  the  accessory  axillary  channel.  It  is  not  constant,  and  there  may  be  inter- 
rupting glands  on  its  collectors.  Its  collectors  come  off  from  the  inferior  portion 
of  the  mammary  gland  and  pass  directly  to  the  axillary  glands.  Another  channel 
is  the  subclavian  channel.  Neither  is  it  constant.  It  comes  off  from  the  posterior 
surface  of  the  mammary  gland,  pierces  the  great  Pectoral  muscle,  and  ascends 
between  the  greater  and  lesser  Pectorals  to  reach  the  subclavian  glands.  There 


FIG.  510. — The  vessels  and  lymphatics  of  the  anterior  face  of  the  mammary  glands.     (Sappey.) 

are  usually  interrupting  glands  along  this  channel,  the  retro-pectoral  glands.  The 
subclavian  channel  runs  along  the  superior  thoracic  artery.  They  call  the  third 
accessory  channel  the  internal  mammary  channel.  The  collecting  trunks  arise 
from  the  inner  portion  of  the  mammary  gland  and  pass  along  the  vessels  sent  off 
from  the  internal  mammary  artery  to  the  gland.  They  pierce  the  Pectoral  and 
Intercostal  muscles  and  reach  the  internal  mammary  glands.  This  channel  is 
constant  and  along  it  there  may  be  interrupting  glands. 

Lymphatics  of  the  Great  Pectoral  Muscle. — The  lymphatics  of  the  great  Pectoral 
muscle  end  in  the  subclavian  glands,  the  thoracic  group  of  axillary  glands,  and 
the  internal  mammary  glands. 

Surgical  Anatomy. — A  knowledge  of  the  lymphatics  of  the  breast  and  of  the  glands  into  which 
the  lymphatics  drain  is  of  the  first  importance  to  a  surgeon.  Certain  surgical  deductions  from 
the  anatomy  of  this  region  are  perfectly  obvious — viz. :  1 .  If  the  skin  of  the  mammary  gland  is 
involved  in  carcinoma,  the  thoracic  group  of  axillary  glands  of  the  same  side  is  involved.  If  the 
skin  over  the  sternal  margin  of  the  gland  is  involved,  the  glands  of  the  opposite  axilla  may  be  can- 
cerous, as  from  this  point  lymph-vessels  rise  and  pass  across  the  mid-line.  If  the  skin  of  the 
sternal  margin  is  involved  the  prognosis  is  worse  than  if  it  is  free,  the  opposite  axilla  may  be 
cancerous,  and  the  opposite  breast  may  become  diseased.  2.  When  lymphatic  ducts  become 
blocked  by  cancer  cells  the  lymph  backs  up,  flows  backward  instead  of  in  its  proper  direc- 


812  THE  L  YMPHA  TIC  SYSTEM 

tion,  and  may  cause  infection  in  the  most  unsuspected  situations.  For  instance,  a  block  in  the 
cutaneous  lymphatics  of  a  portion  of  the  breast  may  lead  to  infection  of  the  opposite  breast  and 
axilla,  though,  of  course,  it  is  not  so  likely  to  as  is  cancer  of  the  skin  of  the  sternal  margin.  By 
regurgitation  of  lymph  the  head  of  the  humerus  or  the  retro-sternal  structures  may  become  dis- 
eased in  mammary  cancer.  3.  If  the  nipple  or  areola  is  cancerous,  the  entire  gland  is  sure  to  be 
diseased,  as  the  lymphatic  network  of  this  region  empties  into  the  subareolar  plexus,  and  most 
of  the  trunks  coming  from  the  gland  also  enter  this  plexus.  4.  If  the  mammary  gland  is  cancer- 
ous, all  of  the  axillary  glands  are  regarded  as  diseased,  as  the  main  lymphatic  channel  from  the 
breast  reaches  the  glands  on  the  inner  wall  of  the  axilla  upon  the  third  digitation  of  the  Ser- 
ratus  magnus.  Furthermore,  in  many  cases  an  accessory  lymph-channel  comes  off  from  the 
lower  portion  of  the  mammary  gland  and  passes  directly  to  the  axilla.  5.  The  subclavian  glands 
are  to  be  regarded  as  diseased,  because  in  a  certain  proportion  of  cases  (the  exact  proportion 
being  uncertain)  an  accessory  lymph-channel  comes  off  from  the  posterior  surface  of  the  mam- 
mary gland,  passes  through  the  great  Pectoral  muscle  and  ascends  between  the  greater  and 
lesser  Pectorals  to  reach  the  subclavian  glands.  6.  The  element  which  greatly  interferes  with 
the  cure  of  mammary  carcinoma  is  the  existence  of  lymph-channels  which  arise  from  the  inner 
portion  of  the  mammary  gland,  pierce  the  greater  Pectoral  and  Internal  intercostal  muscles,  and 
reach  the  internal  mammary  glands.  Mediastinal  involvement  is  apt  to  be  earlier  in  carcinoma 
of  the  inner  portion  of  the  breast  than  in  carcinoma  of  other  portions,  and  the  prognosis  is  par- 
ticularly bad  in  cancer  of  the  inner  portion  of  the  breast.  What  is  known  as  the  sternal  symptom 
of  Snow  is  bulging  of  the  sternum  due  to  involvement  of  the  thymus  gland.  7.  The  sternal 
portion  of  the  great  Pectoral  and  the  tissue  between  it  and  the  lesser  Pectoral  muscle  are  to  be 
regarded  as  diseased,  because  in  some  cases  an  accessory  lymph-channel  from  the  breast  pene- 
trates the  greater  Pectoral  and  ascends  to  the  subclavian  glands.  This  trunk  has  several  inter- 
rupting or  satellite  glands,  the  retro-pectoral  glands,  in  the  tissue  back  of  the  great  Pectoral 
muscle.  8.  When  the  great  Pectoral  muscle  is  diseased,  cancer  cells  soon  spread  widely  through 
the  sternal  portion  of  the  muscle,  and  this  entire  portion  of  the  muscle  becomes  cancerous.  The 
clavicular  portion  does  not  suffer  early,  but  escapes  until  the  cancer  becomes  extensive,  as  it 
is  anatomically  distinct  from  the  sternal  portion.  If  the  fibres  of  the  great  Pectoral  are  exten- 
sively diseased,  the  thoracic  group  of  axillary  glands,  the  subclavian  glands,  and  possibly  the 
internal  mammary  glands  are  involved.  9.  The  only  operation  in  cancer  of  the  breast  which 
offers  any  real  hope  of  cure  is  one  which  is  done  early  and  is  radical.  10.  It  must  be  done 
early,  because  delay  permits  involvement  of  the  mediastinum,  and  if  the  disease  has  entered 
the  mediastinum  operation  is  hopeless.  If  the  sternum  is  bulged  operation  is  useless,  and 
nothing  short  of  amputation  at  the  shoulder-joint  could  be  of  help  if  the  head  of  the  humerus 
is  enlarged  by  the  disease.  Even  this  radical  procedure  is  of  no  avail,  because  the  mediastinum 
is  certainly  involved  if  the  head  of  the  humerus  is  diseased.  11.  If  the  lymph-glands  above 
the  clavicle  are  extensively  diseased  operation  is  useless,  as  in  such  cases  the  mediastinum  is 
sure  to  be  involved.  12.  A  radical  operation  means  the  removal  of  the  skin  of  the  breast  with 
the  nipple  and  areola,  the  subcutaneous  tissue  of  this  region,  the  entire  breast  the  sternal 
portion  of  the  great  Pectoral  with  its  fascia,  the  retro-pectoral  glands  and  tissue,  all  the  con- 
tents of  the  axilla  except  vessels  and  nerves,  the  glands  and  cellular  tissue  beneath  the  anterior 
margin  of  the  Latissimus  dorsi,  and  the  subclavian  glands.  It  is  probably  always  wisest  to 
open  above  the  clavicle  as  well  as  below  to  facilitate  the  removal  of  glands.  It  is  seldom  necessary 
to  remove  the  clavicular  portion  of  the  greater  Pectoral.  The  lesser  Pectoral  does  not  require 
removal,  but  it  should  be  taken  away,  because  of  the  added  safety  and  speed  thus  obtained 
in  cleaning  the  great  vessels  and  because  its  retention  does  not  improve  the  functional  result. 
The  surgeon  must  remember  that  the  breast  is  a  much  larger  organ  than  we  used  to  think,  and 
all  of  its  irregular  projections  and  outlying  lobules  must  be  removed  (p.  791).  Formerly, 
surgeons  did  not  completely  remove  the  breast,  but  only  got  rid  of  a  large  portion  of  it. 

The  Pulmonary  Lymphatics. — The  pulmonary  lymphatics  arise  from  net- 
works between  the  lobules,  around  the  bronchi  and  under  the  mucous  membrane. 
The  collecting  trunks  are  in  two  sets,  superficial  and  deep:  the  former  are  placed 
beneath  the  pleura,  forming  a  minute  plexus  which  covers  the  outer  surface  of 
the  lung;  the  latter  accompany  the  blood-vessels  and  run  along  the  bronchi;  they 
both  terminate  at  the  root  of  the  lungs  in  the  tracheo-bronchial  glands. 

The  Pleural  Lymphatics. — The  lymphatics  of  the  pulmonary  pleura  pass  into  the 
superficial  pulmonary  trunks;  those  from  the  costal  pleura  enter  the  intercostal 
trunks;  those  from  the  diaphragmatic  pleura  enter  the  diaphragmatic  trunks,  and 
those  from  the  mediastinal  pleura  enter  the  posterior  mediastinal  glands.1 

The  Cardiac  Lymphatic  Vessels. — The  cardiac  lymphatic  vessels  consist  of 
two  sets,  superficial  and  deep:  the  former  arise  in  the  subpericardial  areolar  tissue  of 

1  The  Lymphatics.     By  Poirier,  Cuneo,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE  LYMPHATIC  GLANDS  OF  THE  THORACIC  WALL        813 

the  surface,  and  the  latter  in  the  subendocardial  tissue.  From  the  network  of  deep 
lymphatics  trunks  pass  to  the  superficial  lymphatics.  The  superficial  lymphatics 
follow  the  course  of  the  coronary  vessels.  Two  trunks  are  formed:  an  anterior, 
which  lies  in  the  anterior  interventricular  furrow,  and  an  inferior,  which  lies  in 
the  inferior  interventricular  furrow.  These  two  trunks  collect  the  lymph  from  the 
ventricles  and  pass  to  the  base  of  the  heart,  where  they  receive  lymph  from  the 
auricles.  The  anterior  or  left  trunk  ascends  between  the  left  auricle  and  the  pul- 
monary artery  on  the  posterior  surface  of  the  artery,  perforates  the  pericardium,  and 
enters  the  glands  about  the  tracheal  bifurcation.  The  right,  posterior  or  inferior 
trunk  ascends  between  the  aorta  and  pulmonary  artery  and  terminates  in  the  same 
group  of  glands  as  the  left  trunk. 

The  Thymic  Lymphatic  Vessels. — The  thymic  lymphatic  vessels  arise  from 
the  under  surface  of  the  thymus  gland,  and  enter  the  anterior  mediastinal,  the 
internal  mammary,  and  the  peritracheo-bronchial  glands. 

The  Lymphatic  Vessels  of  the  (Esophagus. — The  lymphatics  of  the  thoracic 
oesophagus  arise  from  two  networks,  one  beneath  the  mucous  membrane  and  one 
beneath  the  muscular  fasciculi.  The  connecting  trunks  terminate  in  the  peri- 
cesophageal  glands. 

The  Lymphatic  Vessels  of  the  Thoracic  Trachea.— The  lymphatics  of  the 
thoracic  trachea  take  origin  from  a  network  in  the  submucous  tissue.  From  this 
a  number  of  collecting  trunks  pass  through  the  trachea  in  the  line  of  junction  of 
the  cartilaginous  with  the  membranous  portion.  They  terminate  the  peritracheo- 
bronchial  glands. 


THE  NEKVE  SYSTEM. 

THE  SPINAL  CORD  AND  BRAIN,  WITH  THEIR 

MENINGES. 

REVISED  AND  LARGELY  REWRITTEN,  WITH  NEW  ILLUSTRATIONS. 
BY  EDWARD  ANTHONY  SPITZKA,  M.D., 

PROFESSOR     OP     GENERAL     ANATOMY,     JEFFERSON    MEDICAL     COLLEGE,     PHILADELPHIA. 


THE  nerve  system  of  man  is  an  apparatus  by  means  of  which  he  appreciates 
and  becomes  influenced  by  impressions  from  the  outer  world,  reacts  on 
these  impressions,  and  hence  is  enabled  to  adapt  himself  to  his  environment. 
It  is  the  organic  substratum  for  those  manifestations  of  nerve  force  engaged  in  the 
characteristic  attributes  of  animal  life — sensation  and  motion.  Broadly  stated, 
the  nerve  system  connects  the  various  parts  of  the  body  with  each  other  and 
coordinates  them  into  one  harmonious  whole  in  order  to  carry  on  the  bodily 
functions  methodically  and  to  control  the  physiological  division  of  labor  through- 
out the  organism.  With  the  evolution  of  the  higher  forms  of  animal  life  through 
an  immense  phylogenetic  past  the  nerve  system  has  undergone  remarkable  differ- 
entiation and  specialization,  attaining  its  maximum  as  to  dominant  position  and 
complexity  of  structure  in  the  human  species. 

The  description  of  the  nerve  system  is  assisted  by  the  accommodation  of  physio- 
logical data  to  the  anatomical  basis  in  order  to  demonstrate  more  clearly  and 
to  render  more  practical  our  knowledge  of  the  mutual  relations  of  its  structure 
and  function.  The  cycle  of  events  which  accompanies  nerve  action  is  determined 
by  impressions  received  by  the  peripheral  end-organs,  apperception  and  reflexes 
of  these  impressions  in  the  lower  nerve-centres,  correlation  of  these  with  other 
impressions  in  higher  centres,  as  well  as  voluntary  reactions  or  inhibitions,  liber- 
ated in  compliance  with  the  organic  or  higher  needs  of  the  individual. 

Conventionally,  the  nerve  system  is  usually  considered  as  consisting  of  (1) 
the  cerebro-spinal  system,  comprising  (a)  the  central  nerve-axis  (brain  and  spinal 
cord)  and  (6)  the  peripheral  nerves  (cranial  and  spinal),  and  (2)  the  sympathetic 
nerve  system.  This  subdivision,  like  others  formulated  by  various  authors, 
is  an  arbitrary  one.  No  part  of  the  system  stands  isolated,  and  the  manifold 
groupings  and  chainings  of  the  units  of  the  system  intimately  connect  the  central 
nerve  organs  with  the  peripheral  nerve-endings,  the  organs  of  special  sense  and 
the  vegetative  organs.  The  distinction  between  the  central  and  the  sympathetic 
systems  has  been  too  absolute,  and  the  only  justification  for  adhering  to  the 
classification  given  above  is  based  upon  the  fact  that  the  sympathetic  system  is 
preponderatingly  related  to  the  interconnection  and  coordination  of  the  nutritive 
(digestive,  pulmonary,  and  vascular)  apparatus,  and,  therefore,  exercises  a  special 
control  over  its  activities. 

(815) 


816  THE  NERVE  SYSTEM 

Structurally  considered,  the  nerve  system  consists  of  cell-elements  peculiarly 
differentiated  from  all  other  tissue  cells  in  that  their  protoplasm  is  extended,  often 
to  great  distances  from  the  nuclear  region,  in  the  form  of  processes.  The  cell- 
elements  are  held  in  place  by  supporting  tissues,  partly  of  ectodermal  and  partly 
of  mesodermal  origin,  and  receive  an  abundant  blood-supply. 

The  cell-element  of  the  nerve  system  is  called  the  neurone.  The  neurone  is 
the  developmental,  structural,  and  functional  unit  of  the  nerve  system.  It 
is  in  reality  a  single  cell  presenting  unusual  structural  modifications.  It  com- 
prises not  only  the  nerve  cell-body  with  its  numerous  protoplasmic  processes  or 
dendrites,  but  also  the  axone,  which  may  vary  in  length  from  a  fraction  of  a  milli- 
metre to  fully  half  a  man's  stature;  so  that,  despite  the  delicacy  of  the  axone,  its 
bulk  may  be  almost  two  hundred  times  greater  than  that  of  the  cell-body  from 
which  it  proceeds.  The  long  axones  serve  to  make  a  connection  with  a  peripheral 
or  distant  nerve-cell,  muscle-cell,  or  gland -cell,  while  the  shorter  axones  of  certain 
neurones  divide  into  terminal  branches  in  the  immediate  vicinity  of  its  cell-body, 
presumably  to  come  into  relation  with  other  nerve-cells  in  the  same  or  adjacent 
groups. 

Neurones,  being  devoted  to  the  maintenance  of  functions  manifested  by  various 
phenomena  of  nerve-force,  are  differentiated  in  their  polarity,  both  structurally 
and  dynamically.  Receptive  neurones  are  so  arranged  as  to  receive  afferent  nerve- 
impulses  from  other  tissues;  emissive  or  excitatory  neurones  give  out  efferent 
nerve-impulses.  The  former  are  generally  termed  sensor  neurones,  the  latter 
motor  (excito-motor)  neurones  if  connected  with  muscle,  excito-glandular  if  connected 
with  gland-cells.  Were  the  nerve  system  made  up  solely  of  such  initial  and  ter- 
minal neurones  the  apparatus  would  be  merely  a  system  of  reflex  arcs.  Such  it 
is  in  low  forms  of  animal  life  which,  by  their  very  organization,  and  because 
of  the  close  juxtaposition  of  their  sensory  and  motor  elements,  are  compelled  to 
react  to  stimuli  from  without.  In  higher  forms,  with  more  profoundly  differ- 
entiated nerve  systems,  the  sensory  impression  must  pass  through  an  interposed 
medium  which  is  capable  of  either  transmitting  the  molecular  change  in  the  form 
of  an  excito-motor  impulse  or,  on  the  other  hand,  is  capable  of  reducing  or  check- 
ing the  impulse.  In  other  words,  reaction  is  not  imperative;  there  is  a  freedom 
of  choice  exercised  by  intermediate  neurones  endowed  with  inhibitory  function. 
The  simple  arc,  composed  of  an  afferent  sensory  neurone  and  an  efferent  motor 
neurone,  would  act  independently  of  all  other  arcs  were  it  not  for  the  interposition 
of  this  intermediate  neurone  and  of  other  association  neurones  which,  by  their  rela- 
tions toward  similar  arc-elements,  produce  harmony  of  action.  The  basis,  then, 
of  the  nerve  system  is  a  series  of  neurones,  with  projecting  and  association  pro- 
cesses, coordinated  for  the  purpose  of  performing  specific  actions  manifested 
either  by  motion,  by  trophic  changes,  or  by  the  apperception  of  stimuli  of  a  chemi- 
cal, mechanical  (tactile  and  auditory),  thermal,  or  photic  nature.  When  we  con- 
sider the  profoundly  complex  manifestations  of  nerve-phenomena  in  the  mental 
and  physical  life  of  man  it  is  not  surprising  to  learn  that  his  nerve  system  is 
made  up  of  an  immense  multitude  of  aggregations  of  neurones. 

Fundamental  Facts  Regarding  the  Development  of  the  Nerve  System.— 
The  nerve  system  is  formed  by  a  remarkable  metamorphosis  of  the  ectodermic 
layer  of  the  developing  ovum.  Along  the  mid-dorsal  line  of  the  embryonic  mass 
a  thickening  of  the  ectoderm  forms  a  well-defined  layer  of  cells,  the  neural  plate. 
The  proliferative  process  passes  rapidly  from  the  cephalic  toward  the  caudal 
end,  and  as  development  advances  it  is  seen  that  the  most  intense  growth-energy 
takes  place  at  the  cephalic  end,  indicative  of  the  higher  functional  potentiality 
of  what  is  to  become  the  brain.  The  neural  plate  undergoes  a  trough-like  for- 
mation as  its  edges  become  elevated  cephalad  and  laterally  to  form  the  neural 
groove  (Fig.  511).  The  edges  become  more  and  more  elevated  and  bend  toward 


DEVELOPMENT  OF  THE  NERVE  SYSTEM 


817 


the  median  line  until  the  margins  of  the  groove  coalesce  to  form  a  tube,  the  neural 
tube,  which  sinks  into  the  subjacent  mesodermal  tissues.  The  fusion  of  the  mar- 
gins of  the  neural  plate  occurs  first  in  the  cervical  region  and  rapidly  continues 
both  cephalad  and  caudad.  The  cephalic  portion,  destined  to  become  the  brain, 
expands  and  grows  considerably,  while  the  caudal  portion  is  chiefly  elongated 
to  form  the  spinal  cord. 


NEURAL     PLATES 


NEURAL    GROOVE 


SOMATOPLE 


PARAXIAL 
MESOOERM 


EIMTODERM 


FIG.  511. — Diagrams  showing  development  of  neural  tube  and  crest. 

Eventually  the  neural  tube,  as  it  sinks  into  the  subjacent  mesodermal  tissues, 
severs  all  connection  with  the  ectoderm  from  which  it  developed;  but  for  a  brief 
period  the  continuity  is  preserved  in  an  attenuated  septal  mass,  the  neural  crest 
(Fig.  51 1).  The  cell-elements  of  this  crest  subsequently  become  detached  from  the 
superficial  ectoderm,  the  continuity  of  which  is  again  restored  to  form  the  integu- 


NEURAL    TUBE 


L   GANGLION 


NOTOCHORD 


VENTRAL    ROOT 


RAMUS    COM- 
MUNICANS 


SPINAL     NERVE 


SYMPATHETIC 
GANGLION 


MESONEPHROS 


r 

MESENTERY 

FIG.  512. — Diagram  showing  development  of  a  spinal  nerve  and  its  components,  together 
with  the  spinal  and  sympathetic  ganglia. 

ment.  They  pass  ventrad  to  either  side  of  the  neural  tube,  proliferate  by  mitosis, 
and  accumulate  in  paired  masses,  corresponding  in  number  to  the  segments  of 
the  body,  to  become,  in  part  at  least,  the  cerebro-spinal  ganglion  cells  of  the  afferent 
system,  while  other  similarly  paired  masses  migrate  farther  ventrad  to  a  pre- 
vertebral  position  to  form  the  gangliated  cord  and  widely  spread  plexuses  of  the 
sympathetic  system.  From  the  tissues  of  the  wall  of  the  neural  tube  and  its  tem- 

52 


818 


THE  NERVE  SYSTEM 


porary  crest  the  entire  nerve  system  of  complex  and  intricate  structure  is  devel- 
oped. The  cavity  of  the  tube  shares  in  the  developmental  growth-changes  to 
become  the  ventricular  system  of  the  brain  and  central  canal  of  the  spinal  cord. 
The  major  details  of  the  development  of  the  principal  divisions  will  be  considered 
in  appropriate  chapters. 

Development  of  Nerve-tissue.  1.  In  the  Wall  of  the  Neural  Tube.— The 
single  layer  of  nucleated  epithelial  cells  of  ectodermal  origin  which  makes  up  the 
wall  of  the  neural  tube  early  becomes  modified  into  a  layer  of  tall  columnar  cells 
called  spongioblasts  (Fig.  513).  Their  protoplasmic  ends  undergo  differentiation 
in  that  the  central  ends  become  elongated  and  attenuated  or  collapsed  to  form  a 
series  of  striated  pillars  with  intervening  spaces.  The  free  ends  retain  their 
breadth,  however,  and  form  an  internal  limiting  membrane.  The  ectal  ends 
undergo  differentiation  to  form  a  spongy  felt-work  or  reticulum  (peripheral 
veil  of  His);  eventually  these  spongioblasts  become  (a)  ciliated  endymal  cells 
and  (6)  neuroglia. 


— Germinal  cell. 


-Myelospongium 
network. 


FIG.  513. — Transverse  section  of  the  spinal  cord  of  a  human  embryo  at  the  beginning  of  the  fpurth  week. 
Top  of  figure  corresponds  to  lining  of  central  canal.     (After  His.) 

In  the  intercellular  spaces  of  the  central  zone  there  appear  spherical  cells  of 
different  structure  and  destiny.  These  are  the  germinal  cells,  seen  in  very  early 
stages  and  proliferating  rapidly  by  karyokinesis.  They  soon  lose  their  spherical 
form,  becoming  pear-shaped  as  a  protoplasmic  process  extends  ectad.  These 
pear-shaped  cells  are  now  termed  neuroblasts  (Fig.  513),  the  protons  of  the  neu- 
rones, and  as  development  advances  they  leave  the  central  zone  and  migrate  into  the 
marginal  reticulum  to  the  positions  in  which  they  are  found  in  the  gray  substance 
of  the  brain  and  spinal  cord.  The  protoplasmic  process  is  at  first  slightly  bulbous 
and  elongates  to  form  the  axone  extending  toward  other  nerve-cells  or  to  the 
peripheral  tissue-elements  with  which  they  become  associated  by  the  contiguity 
of  the  terminal  arborizations  into  which  the  bulbous  extremity  develops.  The 
precision  with  which  the  axones  travel  toward  their  allotted  goal  is  one  of  the 
most  remarkable  manifestations  of  organic  development.  An  American  experi- 
menter, Ross  G.  Harrison,  has  devised  a  method  for  directly  observing  the  living, 


STRUCTURE  OF  THE  NERVE  SYSTEM 


819 


growing  nerve.  In  isolated  pieces  of  frog  embryos  the  differentiation  of  the  living 
nerve-elements  could  be  observed  from  day  to  day  during  several  weeks.  The 
bulbous  end  of  the  outflowing  protoplasmic  fibre,  showing  a  faint  fibrillation,  was 
seen  to  reveal  a  continuous  change  of  form  particularly  in  a  number  of  fine  simple 
and  branched  filaments  which  were  in  constant  amoeboid  movement.  Harrison's 
demonstration1  is  of  great  significance  in 
connection  with  the  "retraction  theory" 
and  other  ideas  related  to  the  neurone 
doctrine. 

2.  In  the  Neural-crest  Tissues. — The 
nerve-tissue  elements  of  the  sympathetic 
system  and  of  the  ganglia  of  the  cranial 
nerves  and  dorsal  roots  of  the  spinal  nerves 
are  derived  from  the  neural  crest.  Omit- 
ting, for  the  present,  the  development  of 
the  sympathetic  system,  it  is  found  that 
the  cells  of  the  paired  masses  which  event- 
ually become  the  cerebro-spinal  ganglia 
are  at  first  somewhat  spherical,  then  oval 
in  form,  sending  out  from  either  extremity 
or  pole  a  protoplasmic  process.  One  pro- 
cess migrates  centrad,  the  other  toward  the 
tissues  of  the  periphery.  The  central  pro- 
cess penetrates  the  tissues  of  the  neural 
tube  and,  assuming  the  typical  form  of 
an  axone  with  its  collaterals  and  end 
arborizations,  comes  into  contiguous  as- 
sociation with  certain  cells  of  the  cen- 
tral axis.  The  peripheral  process  is  in 
reality  an  unusually  long  dendrite,  for  it 
is  centripetal  in  function;  but  owing  to 
the  fact  that  it  is  usually  provided  with 
a  myelin  sheath  it  is  also  termed  the  per- 
ipheral axone  of  an  afferent  (or  sensor)  neu- 
rone. The  central  processes  of  the  cells  of 
a  single  spinal  nerve-ganglion  form  the 
dorsal  nerve-roots;  the  peripheral  pro- 
cesses constitute  the  afferent  portion  of 
a  spinal  nerve.  The  cells  themselves  are 
transformed  from  bipolar  into  appar- 
ently unipolar  cells  by  the  migration  of 
the  cell-body  to  one  side  and  the  conse- 
quent approximation  of  the  two  processes 
to  form  a  common  pedicle  in  a  T-shaped 
manner  (Fig.  535). 

Structure  of  the  Nerve  System.— 
The  whole  of  the  nerve  system  is  com- 
posed of  nerve-tissue  and  supporting  con- 
nective tissue.  The  neurones  constitute  the  nerve-tissue,  while  the  supportive 
tissue  is  composed  of  the  neuroglia  and  of  white  fibrous  tissue  derived  either 
from  the  investing  membrane  or  from  the  sheaths  of  its  numerous  vascular 
channels. 


FIG  514. — Scheme  of  central  motor  neurone.  (I. 
type  of  Golgi.)  The  motor  cell-body,  together  with 
all  its  protoplasmic  processes,  its  axis-cylinder  pro- 
cess, collaterals,  and  end  ramifications,  represent 
parts  of  a  single  cell  or  neurone,  a.h.,  axone-hillock 
devoid  of  Nissl  bodies,  and  showing  fibrillation; 
c.,  cytoplasm  showing  Nissl  bodies  and  lighter 
ground-substance;  n',  nucleolus.  (Barker.) 


'  American  Journal  of  Anatomy,  June  1.  1907,  vii.  1.     (Anatomical  Record,  p.  116.) 


820 


THE  NERVE  SYSTEM 


The  Neurone. — The  neurone  or  nerve  cell-element,  whose  individuality  has 
already  been  pointed  out,  exhibits  remarkable  variations  as  to  external  characters, 
dimensions,  and  form.  The  neurone  presents  a  concentrated  or  swollen  cell- 
mass  and  nucleus,  formerly  known  as  the  nerve-cell  (ganglion-cell)  and  still  retain- 
ing the  name.  From  this  cell- body  are  given  off  a  number  of  processes  of  two  dis- 
tinct kinds:  (1)  protoplasmic  processes  which  are  commonly  branched  and  gener- 
ally called  the  dendrites;  (2)  a  single,  thinner,  and  paler  process,  the  axone  (axis- 
cylinder  process;  Deiters'  process;  neuraxone;  neurite). 

Varied  Forms  of  Neurones. — Bearing  in  mind  that  each  neurone  includes  not 
only  the  cell-body  and  its  dendritic  processes,  but  also  the  axone  or  axis-cylinder 

process  with  all  its  ramifications,  we 
may  consider  each  of  these  divisions 
under  separate  heads. 

1.  Nerve  Cell-body.  External  Mor- 
phology.— The  bodies  of  nerve-cells 
vary  much  in  size,  measuring  from 
4  to  135  microns  or  more  in  diam- 
eter. The  largest  cells  are  found  in 
the  ventral  horns  of  the  spinal  cord, 
in  the  spinal  ganglia,  in  the  large 
pyramidal  cell-layer  of  the  cerebral 
cortex,  in  the  Purkinjean  cell-layer 
of  the  cerebellum,  and  in  the  column 
of  Clarke  (dorsal  nucleus)  of  the 
spinal  cord.  Very  small  cells  are 
found  in  the  olfactory  bulbs,  in  the 
granular  layers  of  the  cerebral  and 
the  cerebellar  cortex,  and  in  the 
gliosum  cornualis  of  the  cord. 

Although  all  nerve-cells  begin  in 
the  embryonic  ectoderm  as  spherical 
germinal  cells,  they  later  assume, 
in  different  regions,  very  different 
shapes.  These  external  morpholog- 
ical relations  have  been  best  revealed 
by  the  methods  of  Ehrlich  and' 
Golgi.  According  to  the  number  of 
processes  arising  from  the  cell-body, 
neurones  are  referred  to  as  (1)  uni- 
polar, (2)  bipolar,  and  (3)  multipolar 
nerve-cells. 

(1)  Unipolar  cells  are  met  with  fre- 
quently in  early  stages  of  embryonic 
development,  but  are  rare  in  the  adult, 
being  found  only  in  the  retina,  olfac- 
tory bulb,  and  within  the  baskets 
of  the  Purkinjean  cells  of  the  cerebellum.  They  are  called  amacrine  cells.  The 
cells  of  the  cerebro-spinal  ganglia  (excepting  the  cochlear  and  vestibular)  are  appar- 
ently unipolar,  but  they  are  developmentally  and  functionally  of  bipolar  nature. 

(2)  Bipolar  cells  are  found  almost  exclusively  in  the  peripheral  sensor  systems, 
as  in  the  olfactory  membrane,  in  the  retina,  in  the  cochlear  and  vestibular  ganglia, 
and  in  the  cerebro-spinal  ganglia  of  the  embryo. 

(3)  Multipolar  cells   are   the  most  numerous  and  form  the  principal  elements 
of  nerve-centres  throughout  the  system.     They  are  termed  multipolar  because 


FIG.  515. — Showing  some  varieties  of  cell-bodies  of  neu- 
rones (diagrammatic).  A,  unipolar  (amacrine)  cell  from 
the  retina;  B,  bipolar  cell  from  vestibular  ganglion;  C, 
multipolar  cell,  with  long  axone,  from  spinal  cord;  D, 
"Golgi  cell"  with  short  axone  breaking  up  into  numerous 
terminal  twigs;  E,  pyramidal  cell  from  cerebral  cortex. 
a,  axone;  clt,  collaterals;  t,  telodendria. 


STRUCTURE  OF  THE  NERVE  XYtiTEM 


821 


of  the  greater  or  lesser  number  of  dendrites  given  off  in  addition  to  the  single 
axone.1 

The  terms  "unipolar"  and  "multipolar"  must  be  restricted  to  the  morphological 
sense;  dynamically  all  nerve-cells  are  bipolar. 

According  to  the  relations  of  the  axone  we  distinguish,  after  Golgi,  two  kinds 
of  neurones. 

I.  Neurones  with  long  axones  which  become  the  axis-cylinder  of  a  central  or 
peripheral  nerve-fibre.     The  axones  give  off  several  collaterals  which,  like  the 
parent  stem,  break  into  finely  branched  terminals  or  telodendria. 

II.  Neurones  with  relatively  short  axones  which  do  not  go  into  the  formation 
of  a  nerve-fibre,  but  break  up  into  terminal  twigs  in  the  vicinity  of  the  cell-bodies 
from  which  they  arise. 

Type  II  is  generally  termed,  for  brevity's  sake,  the  Golgi  cell. 


FIG.  516. — Purkinjean  cell  from  human  cerebellum,     a,  axone;  clt,  collaterals.     (Golgi  method.) 

According  to  the  morphological  relations  of  the  dendrites,  neurones  are  classified 
as  follows: 

(a)  Stellate  cells,  the  dendrites  of  which  spring  at  intervals  from  the  whole  cir- 
cumference of  the  cell-body  and  pass  toward  all  directions  (motor  cells  in  ventral 
horn  and  tract-cells  of  the  cord). 

(6)  Cells  with  one  principal  stout  dendrite  (among  other  lesser  dendrites) 
which  gives  off  side  branches  and  ends  in  fine  terminal  twigs  (pyramidal  cells  of 
cerebral  cortex;  mitral  cells  of  olfactory  bulb). 

(c)  Arboriform  cells,  giving  off  branched  dendrites  from  both  base  and  apex, 
resembling  the  roots  and  the  branches  of  a  tree;  the  axone  often  springs  from 
the  base  of  one  of  the  root-like  dendrites  (pyramidal  cells  of  the  hippocampus). 

(d)  Cells  with  monopolar  dendrites.     Several  main  dendritic  stems  spring  from 
one  pole  of  the  cell  and,  undergoing  frequent  subdivision,  break  up  into  a  fine 
terminal  arborization.     The  axone  springs  from  the  opposite  pole  (Purkinjean 
cells  of  the  cerebellum;  granular  cells  of  the  fasciola). 


1  Exceptionally,  more  than  one  axone  has  been  observed  arising  from  a  single  cell,  as  in  the  Caial  cells  of 
the  cerebral  cortex. 


822 


THE  NERVE  SYSTEM 


2.  Nerve  Cell-body.  Internal  Morphology. — The  nucleus  of  the  nerve-cell  differs 
in  no  essential  from  the  typical  nuclear  structure.  Regarding  the  organization  of 
the  cytoplasm  several  conflicting  views  exist.  In  the  present  state  of  our  knowl- 
edge concerning  this  still  obscure  field  of  investigation  it  may  be  said  that  the 
nerve-cell  protoplasm  is  roughly  divided  into  a  peripheral  exoplasmic  portion  and  a 
central  endoplasmic  portion.  There  is  shown  throughout  the  cytoplasm  a  tendency 
to  fibrillary  structure,  more  pronounced  in  the  exoplasmic  portion.  Within  the 
meshes  of  a  more  or  less  homogeneous  ground-substance,  which  pervades  the 
whole,  are  deposited  larger  and  smaller  masses  of  a  granular  substance.  Nerve- 
cells  fixed  and  stained  by  the  methods  of  Nissl  and  Held  show  that  the  granule- 
masses  are  "stainable"  (chromatophiles ;  tigroid  bodies;  Nissl  bodies),  probably  of 
the  nature  of  a  nucleo-proteid  (MacCallum)  and  looked  upon  as  a  sort  of  nutritive 
reserve.  Many  of  the  larger  cells  possess  more  or  less  pigmented  material,  adja- 
cent to  the  nucleus.  The  cells  of  the  intercalatum  (substantia  nigra)  and  of  the 
locus  cceruleus  contain  an  abundance  of  such  pigment-granules. 


Axone. 


•ath  of 
cell  body. 

'Nucleus. 

Cell  protoplasm. 


FIG.  517. — Motor  nerve-cell  from  ventral  horn  of 
spinal  cord  of  rabbit.  The  angular  and  spindle- 
shaped  Nissl  bodies  are  well  shown.  (After  Nissl.) 


"  Axone. 
-Myelin  sheath. 


FIG.  518. — Bipolar  nerve-cell  from  the  spinal  gang- 
lion of  the  pike.       (After  Kolliker.) 


The  "  unstainable"  homogeneous  ground-substance  of  the  cytoplasm  is  probably 
the  more  important  functionally,  for  numerous  delicate  neuro-fibrils  have,  by  special 
methods,  been  shown  to  traverse  the  cell-body  and  its  processes,  crossing  and 
interlacing,  perhaps  anastomosing  with  each  other,  and  traceable  into  the  axone.1 
Nissl,  after  years  of  painstaking  investigation  has  classified  nerve-cells  into  a  great 
many  different  species  in  accordance  with  their  reaction  to  staining  agents. 

The  Dendrites. — The  dendrites  are  usually  numerous  attenuated  processes 
resembling  in  structure  and  staining  reactions  the  cytoplasm  and,  being  extensions 
thereof,  represent  an  increase  in  the  surface  of  the  cell-body.  Emerging  by  a 
broad  base  they  become  narrower  as  they  divide  into  many  branches  in  a  dichot- 
omous  or  arborescent  manner  to  end  free,  according  to  most  observers,  or  to  be 
joined  with  the  dendrites  of  other  neurones  by  means  of  minute  fibrillse  (as 
claimed  by  Apathy)  or  by  concrescence  (Held).  The  contour  of  the  dendrite  is 
usually  irregular  in  some  specimens,  revealing  varicosities  along  its  course ;  in  others, 
and  more  constantly,  being  seen  to  be  beset  with  numerous  lateral  buds  called 


1  That  the  neuro-fibrils  form  such  an  intracellular  network  and  that  the  axones  arise  therefrom  is  disputed 
by  Ramony  Cajal,  Bielschowsky,  and  others. 


STRUCTURE  OF  THE  NERVE  SYSTEM  823 

gemmules.  Various  hypotheses  have  been  advanced  in  explanation  of  these 
appearances,  it  being  held  by  some  investigators  that  they  are  related  to  conditions 
of  activity  as  contrasted  to  those  of  repose,  while  others  believe  them  to  be  arti- 
facts produced  by  the  fixing  and  staining  methods  at  present  employed.  How- 
ever, it  is  no  longer  disputed  that  the  function  of  the  dendrites  is  receptive  and 
conductive  (or  cellulipetal)  for  nerve-impulses,  although  they  probably  serve  the 
nutritional  requirements  of  the  cell-body  as  well. 

This  functional  distinction  gives  the  clue  to  the  correct  interpretation  of  the 
central  and  peripheral  prolongations  of  the  cerebro-spinal  ganglionic  neurones. 
The  cells  of  these  ganglia  are  at  first  bipolar  in  form,  but  gradually  undergo  trans- 
formation into  apparently  unipolar  cells  by  the  migration  of  the  cell-body  to  one 
side  and  the  consequent  approximation  of  the  two  processes  to  form  a  common 
pedicle  in  a  T-shaped  manner  so  typical  of  the  spinal  ganglion  cell  of  the  adult. 
The  central  branch  invariably  remains  cellulifugal,  the  peripheral  branch  invaria- 
bly remains  cellulipetal,  and  as  such  is  equivalent  to  the  dendrites  of  all  other  neu- 
rones. It  is  merely  a  modified  dendrite  in  that  it  courses  a  longer  distance  without 
branching  until  it  reaches  the  periphery  and  is  usually  myelinic.  Such  a  periph- 
eral prolongation  of  the  ganglion  cell  is  also  termed  a  centripetal  nerve-fibre  or 
medullated  (myelinic}  peripheral  axone  of  a  peripheral  centripetal  neurone. 

The  Axone. — The  axone  is  usually  much  longer  than  any  of  the  dendrites,  thin, 
pale,  smooth,  emerging  from  the  nerve-cell  as  a  direct  continuation  of  the  neuro- 
fibrillar  ground-substance  of  the  cell-body,  and  devoid,  so  far  as  at  present  known, 
of  chromatophile  granules.  Its  calibre  varies  for  the  different  cells,  corresponding 
in  general  to  the  length  of  its  course,  but  it  is  practically  of  uniform  diameter 
throughout  its  extent.  Axones  may  be  extremely  short  or  fully  a  metre  in  length. 
Most  cells  give  rise  to  only  one  axone  (monaxonic  neurones),  but  in  certain  localities 
diaxonic  (two  axones)  and  polyaxonic  (several  axones)  neurones  are  found.  In  a 
Golgi  preparation  axones  stand  out  like  pieces  of  black  thread,  taking  a  more 
direct  course  than  do  the  irregular  dendrites,  and  rarely  branching  before  reaching 
the  ultimate  termination,  although  giving  off  collaterals  along  their  course.  The 
central  axones  of  spinal  ganglion  (sensor)  neurones  are  the  principal  exception 
to  this  rule  in  that  they  bifurcate  in  a  Y-shaped  manner  after  their  entrance  into 
the  central  nervous  axis.  In  the  case  of  another  group  of  neurones,  Golgi's  Cell, 
Type  II,  the  axone  is  observed  to  break  up  into  numerous  branches  soon  after  its 
departure  from  the  cell;  such  axones  are  called  dendraxones.  The  axones  and 
their  collaterals  end  in  terminal  arborizations,  the  telodendria. 

The  axone  is  the  distributive  or  emissive  (cellulifugal)  conductor  of  nerve- 
impulses.  There  is,  therefore,  a  functional  opposition  attributable  to  the  two 
extremities  of  the  neurone,  based  upon  its  dynamic  polarity  and  upon  a  physio- 
logical principle  which  is  established  by  all  experiments  to  which  the  nerve 
system  is  submitted;  namely,  that  nerve-impulses  pass  through  the  neurone  in  a 
definite  direction  which  is  invariable  and  admitting  of  anatomical  localization. 

The  majority  of  the  peripheral  spinal  and  cerebral  axones  as  well  as  those 
constituting  the  white  matter  of  the  brain  and  cord  are  invested  by  a  myelinic 
sheath. 

The  Collaterals  (paraxones;  cylindro-dendrites ;  side  fibrils). — The  collaterals 
are  accessory  branchings  of  the  axones  which  are  more  numerous  in  the  cyto- 
proximal  portion  and  are  usually  directed  at  right  angles  to  the  parent  stem. 
Some  axones  possess  few  or  no  collaterals,  while  others  possess  many.  The  col- 
laterals, especially  those  in  the  gray  substance  of  the  central  axis,  are  frequently 
myelinic.  They  unquestionably  play  an  important  part  in  the  grouping  and 
chaining  of  neurones  within  the  system,  in  yielding  up  to  neighboring  neurones 
a  portion  of  the  impulse  that  the  cell  has  received  by  its  dendrites  and  transmits 
along  its  axone  to  a  distance. 


824 


THE  NERVE  SYSTEM 


Varieties  of  Axones. — Axones  are  divided  into  two  main  groups  depending  upon 
the  presence  or  absence  of  a  myelin  sheath — myelinic  axones  and  amyelinic  axones, 
or  medullated  and  non- medullated  axones. 

Myelinic  axones  or  medullated  axis-cylinder  processes  are  axones  enveloped  by  a 
relatively  thick  sheath  composed  of  semifluid  phosphorized  fat  which  gives  to 
the  bundles  of  these  structures  their  opaque,  white  appearance.  The  myelin 
sheath  is  in  turn  invested  by  a  delicate  membrane  (neurilemma)  in  one  group, 
while  another  group  is  devoid  of  such  covering,  giving  rise  to  the  further  subdivision 
into  (a)  myelinic  axones  with  a  neurilemma;  (6)  myelinic  axones  without  a  neuri- 
lemma. 

Myelinic  axones  with  a  neurilemma  constitute  the  bulk  of  the  cerebro-spinal 
nerves  and,  in  lesser  proportion,  of  the  sympathetic  nerves.  The  myelin  sheath 
(medullary  sheath  of  Schwami)  does  not  invest  the  axone  throughout  its  course  nor 


FIG. 

treated 


.  519. — A ,  myelinic  axones  in  fresh  state,  showing  a  few  internodes;   B,  portion  of  a  myelinic  axone 
d  with  boiling  ether  and  alcohol  to  remove  the  myelin  and  leaving  the  neurokeratin  network;  a,  axone. 


in  a  uniform  manner.  The  axone  after  its  emergence  from  the  cell-body  and 
likewise  in  its  preterminal  portion  is  naked;  and  the  delicate  external  membrane 
or  neurilemma  comes  in  contact  with  the  axone.  The  myelin  sheath  consists  of 
a  number  of  tubular  segments  demarcated  by  nodal  intersections  which  are  only 
0.08  mm.  apart  in  the  very  small  myelinic  axones,  while  for  larger  axones  the 
intervals  may  be  1  mm.  or  more.  At  the  internodes  (nodes  or  constrictions  of 
Ranvier)  the  neurilemma  dips  into  the  constriction  to  come  in  contact  with  the 
axone,  and  any  branches  of  the  axone  are  invariably  given  off  at  such  points. 
The  interruptions  in  the  continuity  of  the  myelin  sheath  have  been  assumed  to 
be  provisions  facilitating  nutritive  diffusion  between  the  axone  and  the  surrounding 
lymph.  Each  internodal  myelinic  segment  is  further  characterized  by  oblique 
clefts,  irregularly  distributed — the  incisures  of  Schmidt-Lautermann — seen  only 
in  fixed  specimens  and  probably  artifacts.  Extraction  of  the  fatty  substance  of 
the  myelin  sheath  by  boiling  alcohol  and  ether  brings  out  a  fine  network  which 


NER  VE-FIBRES  AND  NER  VES 


825 


IN 


INTERNODE 


AXONE    SHOWING 

FIBRILLAR 

STRUCTURE 


resists  trypsin  digestion,  and  termed  neurokeratin  on  account  of  its  resemblance 
to  the  keratin  of  epidermal  structures. 

The  neurilemma  (primitive  sheath  of  Schwann;  neurolemma),  a  delicate  struc- 
tureless membrane,  encloses  the  myelin  and  the  axone,  wherever  the  myelin  sheath 
is  wanting.  Against  the  inner  surface  of  the  neurilemma,  and  embedded  as  it  were 
in  the  myelin,  usually  midway  between 

two  nodes,  lies  the  oval-shaped  nucleus  A  B 

of  the  neurilemma. 

Myelinic  axones  are  usually  from  4 
to  10  microns  in  diameter;  the  extremes 
range  from  2  to  20  microns. 

Myelinic  axones  without  a  neurilemma 
constitute  the  white  substance  of  the  brain 
and  spinal  cord  as  well  as  the  optic 
nerves.  They  differ  from  the  axones 
just  described  in  two  particulars:  the 
neurilemma  is  absent  and  there  are  no 
internodes  interrupting  the  continuity  of 
the  myelin  sheath.  A  network  of  neu- 
roglia  replaces  the  neurilemma  as  a  sup- 
porting tissue. 

Amyelinic  axones  with  a  neurilemma 
(Remak's  fibres;  sympathetic  nerve-fibres) 
constitute  the  majority  of  the  sympathetic 
axones  and  the  axones  of  the  olfactory 
nerves.  The  myelin  sheath  is  absent  and 
the  axone  is  invested,  more  or  less  com- 
pletely, by  a  nucleated  cellular  sheath  or 
neurilemma. 

Amyelinic  axones  without  a  neurilemma 
are  naked  axones,  most  numerous  in 
the  central  ganglia.  Most  axones  of 
longer  course  are  devoid  of  any  sheath 
in  the  cytoproximal  and  preterminal  por- 
tions, whatever  investment  they  may  re- 
ceive in  the  intermediate  portion. 


1NCISURE  OF 
"SCHMIDT 


-NEURILEMMA 


NUCLEUS    OF 
-NEURILEMMA 


NERVE-FIBRES"  AND  NERVES. 


I  U 


Prior    tO    the    general    adoption    of    the  Fio.520.-A,  amyelinic  axones  with  a  neurilemma 

neurone    Concept     it     Was    CUStomary     tO  only  the  nuclei  of  which  can  be  seen;   B,  diagram 

.      '                                i          •             1                        e     i  showing  structure  of  amyelinic  axone  and  illustrating 

designate  the  Conducting   elements  Of  the  two  views  regarding  the  relations  of  the  sheaths  at  the 

,            ,                                       _,  internode  (compare  the  two  sides);  C,  trans-section  of 

nerve     System    by     the     term    nerve-fibres  a  group  of  myelinic  axones,  stained  with  osmic  acid, 

i.    ,.       ,•          f              ,i                       ...ii,.         A  showing:    NF,  axonic   neuro-fibrils;  M,  myelin;    F, 

in  distinction  from  the  nerve-cells.     As    endoneurium. 
has  been  pointed  out  above,  the  distinc- 
tion no  longer  holds,  but  the  designation  "nerve-fibre"  is  still  retained  in  anatom- 
ical vocabulary  and  recurs  so  frequently  in  common  parlance  that,  even  with  the 
new  conception  which  has  been  formed  of  the  architecture  of  the  nerve  system, 
the   term  cannot  yet  be  discarded  in  favor  of  ''axone,"  although  it  probably 
will  eventually. 

Nerves  are  round  or  flattened  bundles  of  axones  which  serve  to  bring  the  central 
axis  into  relation  with  the  periphery  and  other  tissues  of  the  body.  The  nerves  of 
the  botlv  are  subdivided  into  two  great  classes-^the  cerebro-spinal,  which  are 


826  THE  NER  VE  SYSTEM 

attached  to  the  cerebro-spinal  axis,  and  the  sympathetic  or  ganglionic  nerves,  which 
are  attached  to  the  ganglia  of  the  sympathetic.  The  cerebro-spinal  nerves  con- 
sist of  numerous  nerve-fibres  (myelinic  axones)  collected  together  into  small  or 
large  bundles  or  fasciculi  and  enclosed  in  a  membranous  sheath. 

In  structure  the  common  membranous  investment,  or  sheath  of  the  whole  nerve, 
which  is  called  the  epineurium,  as  well  as  the  septa  given  off  from  it,  and  which 
separate  the  fasciculi,  consists  of  connective  tissue,  composed  of  white  and  yellow 
elastic  fibres,  the  latter  existing  in  great  abundance.  The  tubular  sheath  of  the 
smaller  fasciculi  composing  the  nerve-trunk,  called  the  perineurium,  consists  of  a 
fine,  smooth,  transparent  membrane,  which  may  be  easily  separated,  in  the  form 
of  a  tube,  from  the  fibres  it  encloses;  in  structure  it  consists  of  connective  tissue 
which  has  a  distinctly  lamellar  arrangement,  being  composed  of  several  lamellae, 
separated  from  each  other  by  spaces  containing  lymph.  The  nerve-fibres  are 
held  together  and  supported  within  the  fasciculus  by  delicate  connective  tissue 
called  the  endoneurium  (sheath  of  Henle).  It  is  continuous  with  septa  which  pass 
inward  from  the  innermost  layer  of  the  perineurium,  and  consists  of  a  ground- 
substance  in  which  are  embedded  fine  bundles  of  fibrous  connective  tissue  which 
run  for  the  most  part  longitudinally.  It  serves  to  support  the  capillary  vessels, 
which  are  arranged  so  as  to  form  a  network  with  elongated  meshes.  The  cerebro- 
spinal  nerves  consist  almost  exclusively  of  myelinic  axones,  the  amyelinic  axones 
existing  in  very  small  proportions. 

The  blood-vessels  supplying  a  nerve  terminate  in  a  minute  capillary  plexus, 
the  vessels  composing  which  pierce  the  perineurium  and  run,  for  the  most  part, 
parallel  with  the  fibres;  they  are  connected  together  by  short,  transverse  vessels, 
forming  narrow,  oblong  meshes,  similar  to  the  capillary  system  of  muscle.  Fine 
amyelinic  axones  accompanying  these  capillary  vessels,  the  vasomotor  fibres, 
and  break  up  into  elementary  fibrils,  which  form  a  network  around  the  vessel. 
Horsley  has  also  demonstrated  certain  myelinic  fibres  as  running  in  the  epineu- 
rium and  terminating  in  small  bulboid  tactile  corpuscles  or  end-bulbs  of  Krause. 
These  nerve-fibres,  believed  to  be  sensor,  and  termed  nervi  nervomm,  are  con- 
sidered to  have  an  important  bearing  upon  certain  neuralgic  pains. 

Nerves,  in  their  course,  subdivide  into  branches,  and  these  frequently  commu- 
nicate with  branches  of  a  neighboring  nerve. 

The  axones,  as  far  as  is  at  present  known,  do  not  coalesce,  but  pursue  an  uninter- 
rupted course  from  the  centre  to  the  periphery.  In  separating  a  nerve,  however, 
into  its  component  fasciculi,  it  may  be  seen  that  they  do  not  pursue  a  perfectly 
insulated  course,  but  occasionally  join  at  a  very  acute  angle  with  other  fasciculi 
proceeding  in  the  same  direction;  from  this  branches  are  given  off,  to  join  again 
in  like  manner  with  other  fasciculi.  It  must  be  distinctly  understood,  however, 
that  in  these  communications  the  axones  do  not  coalesce,  but  merely  pass  into  the 
sheath  of  the  adjacent  nerve,  become  intermixed  with  its  axones,  and  again  pass 
on,  to  become  blended  with  the  axones  in  some  adjoining  fasciculus. 

The  communications  which  take  place  between  two  or  more  nerves  form  what 
is  called  a  plexus.  Sometimes  a  plexus  is  formed  by  the  primary  branches  of  the 
trunks  of  the  nerves — as  the  cervical,  brachial,  lumbar,  and  sacral  plexuses — and 
occasionally  by  the  terminal  fasciculi,  as  in  the  plexuses  formed  at  the  periphery 
of  the  body.  In  the  formation  of  a  plexus  the  component  nerves  divide,  then  join, 
and  again  subdivide  in  such  a  complex  manner  that  the  individual  fasciculi 
become  interlaced  most  intricately;  so  that  each  branch  leaving  a  plexus  may 
contain  filaments  from  each  of  the  primary  nerve-trunks  which  form  it.  In  the 
formation  also  of  smaller  plexuses  at  the  periphery  of  the  body  there  is  a  free 
interchange  of  the  fasciculi  and  primitive  fibres.  In  each  case,  however,  the 
individual  filaments  or  axones  remain  separate  and  distinct,  and  do  not  inosculate 
with  one  another. 


ORIGIN  AND  TERMINATION  OF  NER  VES  827 

It  is  probable  that  through  this  interchange  of  fibres  the  different  branches 
passing  off  from  a  plexus  have  a  more  extensive  connection  with  the  spinal  cord 
than  if  they  each  had  proceeded  to  be  distributed  without  such  connection  with 
other  nerves.  Consequently  the  parts  supplied  by  these  nerves  have  more  extended 
relations  with  the  nerve-centres;  by  this  means,  also,  groups  of  muscles  may  be 
associated  for  combined  action,  as  is  best  exemplified  in  the  formation  of  the 
limb-plexuses. 

The  sympathetic  nerves  are  constructed  in  the  same  manner  as  the  cerebro- 
spinal  nerves,  but  consist  mainly  of  amyelinic  axones,  collected  into  fasciculi  and 
enclosed  in  a  sheath  of  connective  tissue.  There  is,  however,  in  these  nerves 
a  certain  admixture  of  myelinic  axones,  and  the  amount  varies  in  different  nerves, 
and  may  be  known  by  their  color.  Those  branches  of  the  sympathetic  which 
present  a  well-marked  reddish-gray  color  are  composed  more  especially  of  amye- 
linic axones,  intermixed  with  a  few  myelinic  axones;  while  those  of  a  white  color 
contain  more  of  the  latter  and  a  few  of  the  former.  Occasionally,  the  gray  and 
white  cords  run  together  in  a  single  nerve,  without  any  intermixture,  as  in  the 
branches  of  communication  between  the  sympathetic  ganglia  and  the  spinal 
nerves,  or  in  the  communicating  cords  between  the  ganglia. 

The  nerves,  both  of  the  cerebro-spinal  and  sympathetic  systems,  convey  impres- 
sions of  a  twofold  kind.  The  afferent  or  centripetal  nerves,  generally  called  sensor, 
transmit  to  the  nerve-centres  impressions  made  upon  the  peripheral  ends  of  their 
components,  to  produce  reflexes  in  the  lower  centres  while  the  mind,  through  the 
medium  of  the  brain,  becomes  conscious  of  environmental  conditions  or  changes. 
The  efferent  or  centrifugal  (in  large  part  "motor")  nerves  transmit  impulses  from 
the  centres  to  the  parts  to  which  the  nerves  are  distributed ;  these  impulses  either 
excite  muscular  contraction  or  influence  the  processes  of  nutrition,  growth,  and 
secretion. 

The  Ganglia  may  be  regarded  as  separate  small  aggregations  of  nerve-cells, 
connected  with  each  other,  with  the  cerebro-spinal  axis,  and  with  the  nerves  in 
various  situations.  They  are  found  on  the  dorsal  root  of  each  of  the  spinal  nerves ; 
on  the  sensor  root  of  the  trigeminus;  on  the  facial  and  auditory  nerves;  and  on 
the  glosso-pharyngeal  and  vagus  nerves.  They  are  also  found  in  a  connected 
series  along  each  side  of  the  vertebral  column,  forming  the  gangliated  cord  or 
trunk  of  the  sympathetic;  and  on  the  branches  of  that  nerve,  generally  in  the 
plexuses  or  at  the  point  of  junction  of  two  or  more  nerves  with  each  other  or 
with  branches  of  the  cerebro-spinal  system.  On  section  they  are  seen  to  consist 
of  a  reddish-gray  substance,  traversed  by  numerous  white  nerve-fibres;  they  vary 
considerably  in  form  and  size;  the  largest  are  found  on  the  sensor  root  of  the 
trigeminus  and  in  the  cavity  of  the  abdomen;  the  smallest,  not  visible  to 
the  naked  eye,  exist  in  considerable  numbers  upon  the  nerves  distributed  to  the 
different  viscera.  The  ganglia  are  invested  by  a  smooth  and  firm,  closely  adhering 
membranous  envelope,  consisting  of  dense  areolar  tissue;  this  sheath  is  continu- 
ous with  the  perineurium  of  the  nerves,  and  sends  numerous  processes  into  the 
interior  of  the  ganglion,  which  support  the  blood-vessels  supplying  its  substance. 

Origin  and  Termination  of  Nerves. — To  the  central  and  the  peripheral 
ending  of  a  nerve  are  usually  given  the  names  of  "origin"  and  "termination." 
These  designations  have  been  rendered  inappropriate,  in  many  cases,  by  the  newer 
concept  of  neuronic  arrangement.  They  have  not  yet  become  obsolete,  however, 
particularly  in  dissecting-room  anatomy,  and  warrant  description  here  with  a 
certain  degree  of  reserve  alluded  to  above. 

Origin. — The  origin  in  some  cases  is  single — that  is  to  say,  the  whole  nerve 
emerges  from  the  nerve-centre  by  a  single  root;  in  other  instances  the  nerve 
arises  by  two  or  more  roots,  which  come  off  from  different  parts  of  the  nerve- 
centre,  sometimes  widely  apart  from  each  other;  and  it  often  happens,  when  a 


828 


THE  NER  VE  SYSTEM 


nerve  arises  in  this  way  by  two  roots,  that  the  functions  of  these  two  roots  are 
different;  as,  for  example,  in  the  spinal  nerves,  each  of  which  arises  by  two 
roots,  the  ventral  of  which  is  motor  and  the  dorsal  sensor.  The  point  where 
the  nerve-root  or  roots  emerge  from  the  nerve-centre  is  named  the  superficial  or 
apparent  origin,  but  the  axones  of  which  the  nerve  consists  can  be  traced  for 
a  certain  distance  into  the  nerve-centre  to  some  portion  of  the  gray  substance, 
which  constitutes  the  deep  or  real  origin  of  the  nerve. 

The  manner  in  which  these  fibres  arise  at  their  deep  origin  varies  with  their 
functions.  The  centrifugal  or  efferent  nerve-fibres  originate  in  the  nerve-cells 
of  the  gray  substance,  the  axones  of  these  cells  being  prolonged  to  form  the  fibres. 
In  the  case  of  the  centripetal  or  afferent  nerves  the  axones  grow  inward  either  from 
nerve-cells  in  the  organs  of  special  sense  (e.  g.,  the  retina)  or  from  nerve-cells 
in  the  ganglia.  Having  entered  the  nerve-centre,  they  branch  and  send  their 
ultimate  twigs  among  the  cells,  without,  however,  uniting  with  them. 


•  fill  '     -         ^ 

~:\:V. .'  •!'"'V^!*T  ••".."•  .'wt\> 


FIG.  521. — Diagrams  of  motor  nerve-endings  in  A,  striated  muscle;  B,  cardiac  muscle;  C,  unstriated  muscle 
a,  axone;  t,  telodendria.     (After  Huber,  Bohm  and  Davidoff,  and  others.) 

Termination. — Axones  terminate  peripherally  in  various  ways  and  may  be  most 
conveniently  studied  in  the  efferent  and  afferent  systems  respectively.  The 
so-called  peripheral  terminations  of  afferent  neurones  are  better  called  peripheral 
nerve-beginnings,  on  account  of  their  functional  relations;  the  impulse  is  excited 
in  the  peripheral  end  and  conducted  centrad  through  the  rest  of  the  neurone. 

Modes  of  Termination  of  Axones. — The  ultimate  terminals  of  the  axones  and  their 
collaterals  are  called  telodendrions  (or  telodendria).  As  far  as  can  be  determined 
by  present  methods  they  invariably  end  "free,"  commonly  by  exhaustion  through 
multiple  division.  This  manifold  branching  presumably  puts  the  neurone  in  a 
condition  to  influence  the  processes  of  many  other  neurones  ("avalanche  conduc- 
tion" of  Ramon  y  Cajal).  In  some  localities  the  formation  by  axonic  terminals 
of  pericellular  and  peridendritic  networks  has  been  observed.  Upon  muscle- 
fibres  the  axone  terminals  form  chains  of  flattened  disks,  the  motor  end-plates. 
Among  gland-cells  the  terminal  fibrils  form  more  or  less  intricate  plexuses. 

Peripheral  Nerve-beginnings  of  Centripetal  Neurones.— Nerve-beginnings  of  the 
centripetal  (sensor)  fibres  are  found  in  nearly  all  the  tissues  of  the  body.  They 


ORIGIN  AND  TERMINATION  OF  NERVES 


829 


are  peculiarly  differentiated  and  of  various  forms  in  different  localities  and  their 
function  is  apparently  the  conversion  of  mechanical,  thermal,  chemical,  and  other 
stimuli  into  nerve-impulses.  The  organs  of  vision,  hearing,  smell,  and  taste  possess 
variously  modified  nerve-beginnings  which  are  described  under  appropriate  titles 
in  the  chapter  on  the  Organs  of  Special  Sense.  The  end-organs  of  the  centripetal 
neurones  collecting  bodily  impressions  (tactile  sense,  muscular  sense)  and  con- 
nected with  the  central  axis  are  often  very  complicated  structures.  The  prin- 
cipal varieties  are: 

f  Terminal  fibrillae. 

Tactile  corpuscles  (Meissner's). 

"Ruffini's  endings." 
I.  \  Lamellated  corpuscles  (Pacini's). 

Bulboid  corpuscles  (Krause's). 

Genital  (nerve)  corpuscles. 

Articular  (nerve)  corpuscles. 


II. 


f  Neuro-muscular  spindles  (Ruffini). 
(  Neuro-tendinous  spindles  (Golgi). 


D 


FIG.  522. — Showing  some  var 
beginnings"):     A,  terminal   fibr 

Dogiel);    C,    bulboid  corpuscle   (Krause's,   after    Dogiel);    D,   lamellated    corpuscle    (Pacini's,   after    Dogiel, 
Sala,  and  others);    E,  genital  nerve  corpuscle  from  human  glans  penis  (after  Dogiel);   a,  axone;    t,  telodendria. 


830 


THE  NERVE  SYSTEM 


Terminal  Fibrillse  are  best  demonstrable  in  the  epithelium  of  the  skin,  mucous 
membranes,  and  cornea.  The  axone  is  seen  to  break  up  into  its  constituent 
fibrilhe,  which  often  present  regular  varicosities  and  anastomose  with  each  other 
in  a  plexiform  manner. 

Tactile  Corpuscles  (corpuscula  tactus;  touch  corpuscles  of  Meissner  and  Wagner] 
consist  of  elongated  oval  lobules  of  delicate  epithelioid  tissue  invaded  by  one  or 
more  axones  which  divide  into  their  primitive  fibrils,  each  terminal  branch  ending 
free  usually  as  a  somewhat  flattened,  disk-like  plate  in  among  the  wedge-shaped 
cells  of  the  corpuscle.  Tactile  corpuscles  occur  in  large  numbers  in  the  cutaneous 
papillne  of  the  finger-tips,  in  the  conjunctiva,  and,  less  abundantly,  in  the  rest  of 
the  skin ;  they  appear  to  be  concerned  with  the  finer  tactile  sensations. 

Ruffini  has  described  a  special  variety  of  sensor  nerve-beginning  in  the  sub- 
cutaneous tissue  of  the  human  finger  (Fig.  523).  They  are  principally  situated  at 
the  junction  of  the  corium  with  the  subcutaneous  tissue;  they  are  of  oval  shape, 
and  consist  of  a  strong  connective-tissue  sheath  within  which  the  axone  divides 
into  numerous  varicose  fibrils  ending  in  small,  free  knobs. 

Lamellated  Corpuscles  (corpuscula  lamellosa;  Pacinian  corpuscles;  Vater's 
corpuscles;  Herbst's  corpuscles)  are  among  the  largest  of  the  tactile  end-organs 
and  are  found  chiefly  in  the  palmar  surface  of  the  hand,  the  sole  of  the  foot,  the 
genital  organs,  the  serous  membranes,  and  many  other  structures.  Each  corpuscle 


Axones. 


Terminal  ramifications 
of  axones. 


FIG.  523. — Nerve-ending  of  Ruffini.      (After  A.  Ruffirii,  Aich.  ital.  de  Biol.,  Turin,  1894,  t.  xxi.) 

consists  of  a  number  of  capsular  connective-tissue  lamellae  arranged  more  or  less 
concentrically  around  a  central  granular  protoplasmic  core,  pierced  by  a  single 
axone  which  usually  divides  into  two  or  more  branches  giving  off  collaterals  of 
beaded  appearance  and  terminating  in  rounded  knobs. 

Bulboid  Corpuscles  (corpuscula  bulboidea;  Krause's  end-bulbs)  are  minute  cylin- 
drical or  oval  bodies,  consisting  of  a  capsule  continuous  with  the  perineurium 
enclosing  a  core  (inner  bulb)  of  semifluid,  finely  granular  protoplasm  in  which  an 
axone  runs  out  to  end  quite  free  at  the  distal  end,  usually  terminates  in  a  bulbous 
extremity,  or,  as  is  frequently  observed,  the  axone  divides  into  a  number  of 
branches  of  which  each  one  terminates  in  an  end-bulb. 

The  genital  corpuscles  (corpuscula  nervorum  genitalia)  and  the  articular  corpuscles 
(corpuscula  nervorum  articularia)  very  much  resemble  the  bulboid  corpuscles 
just  described. 

The  genital  corpuscles  form  aggregations  of  from  two  to  six  knob-like  masses 
in  the  penis  and  clitoris.  The  articular  corpuscles  are  found  in  the  synovial 
membranes  of  the  joints. 

Neuro-muscular  Spindles  (muscle-spindle  of  Kuhne) . — These  are  found  in  nearly 
all  the  skeletal  muscles  and  are  most  numerous  in  the  extrinsic  muscles  of  the 
tongue,  in  the  small  muscles  of  the  hand  and  foot,  and  in  the  intercostal  muscles. 
Most  elaborate  investigations  upon  these  spindles  have  been  conducted  recently 
by  Ruffini  in  Italy,  Sihler,  Huber,  and  De  Witt  in  America.  Neuro-muscular 


ORIGIN  AND  TERMINATION  OF  NERVES 


831 


spindles  are  usually  found  in  the  fibrous  septa  of  the  perimysium  and  consist  of 
the  flattened  nerve-fibrils  of  centripetal  axones  arranged  in  one  or  all  of  three 
ways:  (1)  annular,  where  the  fibrils  surround  the  muscle-fibres  in  rings;  (2) 
spiral,  and  (3)  dendritic  or  branched  (Fig.  524).  They  are  doubtlessly  concerned 
with  the  so-called  muscle-sense. 


Dendritic  branchings 


Rings. 


Spirals./ 
FIG.  524. — Middle  third  of  a  terminal  plaque  in  the  muscle-spindle  of  an  adult  cat.      (After  Ruffini.) 

Neuro-tendinous  Spindles  (Organ  of  Golgi). — The  nerves  conveying  sensory 
impulses  from  the  tendons  have  a  special  modification  of  the  terminal  fibres,  in 
the  form  of  numerous  fibrils  with  branching  end-plates  or  of  an  annular  and  spiral 
arrangement  resembling  the  neuro-muscular  spindles.  They  usually  occur  at 
the  junction  of  the  tendon  bundles  with  the  muscle-fibres  (Fig.  525). 


Organ  of  Golgi,  showing 
ramification  of  nerve-fibrils. 
Muscular  fibres. 
FIG.  525. — Neuro-tendinous  spindle  organ  of  Golgi  from  the  human  tendo  calcaneus  (Achillis). 


Tendon  bundles. 


(After  Ciaccio.) 


The  Neurone  Doctrine. — The  results  of  the  investigations  of  Golgi,  Cajal,  Forel, 
and  others  prompted  Waldeyer  to  enunciate  a  theory  with  regard  to  the  nerve 
mechanism  of  the  neurone.  This  hypothesis  is  generally  known  as  the  neurone 
theory  and  assumes  that  (1)  each  neurone  is  a  distinct  and  separate  entity;  (2) 
the  collaterals  and  other  terminals  of  the  neurone  form  no  connections  among 
themselves;  (3)  neurones  are  associated,  and  impulses  conveyed,  by  contact  or 
contiguity  of  the  axonic  terminals  of  one  axone  with  the  cell-bod  v  or  dendrites  of 


832 


THE  NERVE  SYSTEM 


another  neurone.  The  theory  postulates  a  nerve-cell  amrebism  analogous  to  the 
extension  and  retraction  of  the  pseudopodia  of  an  amoeba,  and  the  "retraction 
theory"  has  been  propounded  in  explanation  of  certain  functional  dissociation 
phenomena  attending  nerve-force  manifestations. 

Opposed  to  the  "neurone  theory"  or  "contact  theory"  is  the  more  recent 
continuity  theory  which  is  being  earnestly  advocated  by  Apathy,  Bethe,  and  Nissl. 
In  behalf  of  this  theory  it  is  claimed  that  the  neurofibrils  are  continuous  not  only 
within  the  cell  and  its  processes,  but  through  an  extracellular  network  as  well. 
The  dispute  now  being  waged  does  not,  however,  affect  our  fundamental  ideas 
regarding  the  individuality  of  neurones  with  regard  to  their  dynamic  condition. 

The  Supporting  Tissue  Elements  of  the  Nerve  System.— A  fine  meshwork 
of  non-nerve  tissue,  more  or  less  dense  in  different  localities,  but  apparently 
restricted  to  the  central  axis,  serves  to  support  the  neurones.  This  sustentacular 
tissue  is  of  two  kinds:  (1)  the  neuroglia;  (2)  connective-tissue  trabeculae  derived 
from  (a)  the  pia  or  (6)  vascular  channels. 


FIG.  526. — Neuroglia-cells  of  brain  shown  by  Golgi's  method:     A,  cell  with  branched  processes;     B,  spider- 
cell  with  unbranched  processes.      (After  Andriezen.)     (From  Schiifer's  Essentials  of  Histology.) 

The  Neuroglia. — The  neuroglia  consists  of  glia-cells  of  varied  forms  and  glia- 
fibres.  Glia-cells  are  divisible  into  two  species:  endymal  cells  and  astrocytes  of 
long-rayed  and  short-rayed  type. 

Endymal  cells  are  the  columnar  epithelial  cells  which  line  the  neural  canal 
throughout.  In  the  embryonic  condition  each  cell  is  seen  to  project  a  long  multi- 
branched  filament  toward  the  periphery  of  the  neural  tube,  while  the  free  end 
carries  a  tuft  of  cilia.  In  adult  life  both  the  cilia  and  the  radial  filament  are 
apparently  lost  or  very  much  reduced. 

Regarding  the  structure  of  the  glia-cells  proper  as  well  as  of  the  glia-fibres  there 
is  a  variance  of  opinion  among  different  investigators.  The  astrocytes,  as  they 
are  commonly  revealed  in  Golgi  preparations,  may,  as  pointed  out  by  Weigert 
and  others,  be  due  to  an  extension  of  the  silver  deposit  upon  glia-cell  nuclei  as 
well  as  upon  adjacent  filaments.  Huber,1  Hardesty,2  and  others  regard  neuroglia 
tissue  as  a  syncitium  resulting  from  an  early  fusion  of  the  protoplasm  of  the  cells 
of  the  neural  tube  which  at  first  were  individual  and  definitely  bounded.  The 
filamentous  reticulum  of  glia-fibres  ordinarily  seen  in  adult  tissues  seems  to  result 


1  American  Journal  of  Anatomy,  1901,  pp.  45-61. 


2  Ibid.,  1904,  pp.  229-268. 


THE  CENTRAL  NERVE  SYSTEM  833 

from  an  increase  of  the  fine  threads  of  the  spongio-plasmic  network  of  the  original 
cell-protoplasm.  Neuroglia  occurs  in  both  gray  and  white  substance  as  an 
all-pervading  supporting  tissue.  In  certain  localities,  as  upon  the  surface  of  the 
brain  and  cord,  the  neuroglia  tissue  is  disposed  in  the  form  of  a  thin  layer. 

Besides  the  neuroglia,  the  central  nerve  system  contains  as  supporting  tissues 
numerous  fine  and  coarse  septa  or  trabeculse  derived  from  the  investing  pia,  or 
from  the  sheaths  of  blood-vessels. 

Chemical  Composition. — The  amount  of  water  in  nerve-tissue  varies  with  the 
situation.  Thus  in  the  gray  substance  of  the  cerebrum  it  constitutes  about  83  per 
cent.,  in  the  white  substance  from  the  same  region  about  70  per  cent.,  while  in 
the  peripheral  nerves,  such  as  the  sciatic,  it  may  fall  to  60  per  cent. 

The  solids  consist  of  neuro-albumins,  neuro-globulins,  nucleo-proteins,  neuro- 
keratin  (in  the  gray  substance  proteins  constitute  about  one-third  of  the  total 
solids),  lecithins,  cerebrosides  (chiefly  phrenosin),  cholesterin,  unidentified  organic 
sulpho-compounds,  amino-fatty  substances,  nitrogenous  extractives  and  inorganic 
salts,  with  some  collagen,  fat,  etc.,  in  the  adherent  connective  tissue  (W.  J.  Gies). 


THE  CENTRAL  NERVE  SYSTEM. 

The  central  nerve  system,  as  it  is  conventionally  distinguished  from  the  sympa- 
thetic system,  is  composed  of  a  central  axial  aggregation  of  ganglia  forming  the 
brain  and  spinal  cord,  which  are  connected  with  the  other  tissues  of  the  body 
by  43  pairs  of  nerves,  of  which  12  pairs  are  attached  to  the  brain  and  31  pairs 
to  the  spinal  cord.  The  functional  relations  of  the  central  mechanisms  with  the 
periphery  are  maintained  by  the  essential  cell-elements  of  the  nerve-tissues,  the 
neurones.  The  chief  task  in  the  study  and  analysis  of  the  structure  of  the  nerve 
system  lies  in  the  dovetailing  of  features  visible  to  the  naked  eye  with  those 
visible  only  under  high  magnifying  powers.  By  the  combination  of  macroscopic 
with  microscopic  features  the  attentive  student  is  enabled  to  resolve  or  recon- 
struct, in  the  three  dimensions  of  space,  and  see  with  his  mental  eye  the  opaque 
interior  transparently  resolved  into  intricate  yet  well-defined  projecting  and  asso- 
ciating mechanisms.  Assistance  in  such  study  may  be  derived  from  illustrations 
depicting  hidden  structures  in  accordance  with  this  principle. 

Preliminary  Considerations.  Gray  Substance  and  White  Substance. — The  cen- 
tral axis  of  the  nerve  system  contains  two  categories  of  substance,  their  difference 
to  the  eye  being  one  of  color.  They  are  conventionally  designated  the  gray  and 
white  substance.  The  white  substance  (alba),  which  forms  about  two-thirds  of  the 
neuraxis,  is  the  conducting  substance  and  its  characteristic  appearance  is  due  to 
the  myelin  sheaths  which  invest  the  axones  in  it.  The  gray  substance  (cinerea; 
grisea)  is  the  sentient  and  reacting  mass  containing  the  cell-bodies  of  neurones. 
Its  color  is  due  to  its  translucency,  its  greater  vascularity,  and  to  a  certain 
amount  of  pigmented  material  in  the  cell-elements.  The  white  and  the  gray 
substance  is  not  sharply  demarcated  everywhere,  for  although  the  white  substance 
is  exclusively  conducting  substance,  the  gray  is  not  exclusively  ganglionic,  for 
the  former  encroaches  on  the  latter;  in  some  localities,  as  in  the  ventral  horns  of 
the  spinal  gray,  in  parts  of  the  cerebral  cortex,  in  the  reticular  formation  of  the 
pons  and  oblongata,  and  in  the  column  of  Clarke  (dorsal  nucleus),  the  admixture 
of  myelinic  fibres  is  considerable.  Both  white  and  gray  substance  is  pervaded 
by  the  neuroglia. 

The  specific  gravity  of  the  cortical  gray  is  1.021,  of  the  great  ganglia  1.034, 
of  the  gray  substance  in  the  cerebellum  and  mesencephalon  1.050,  and  of  the 
white  substance  1.028. 

For  convenience  of  study,  and  somewhat  in  correspondence  with  phyletic 

53 


THE  NERVE  XY8TEM 


development,  the  central  axis  of  the  nerve  system  is  divided  into  (1)  the  spinal 
cord  and  (2)  the  brain,  grossly  sub-divided  into  (a)  oblongata,  pons,  and  cerebellum; 
(6)  mid-brain  and  (c)  fore-brain.  This  gross  subdivision  is  arbitrary  and  the  inter- 
relations of  the  parts  would  be  obscured  were  too  much  stress  laid  upon  any  mode 
of  separation. 


THE  SPINAL  CORD  (MYELON;  MEDULLA  SPINALIS). 

The  spinal  cord  is  the  attenuated,  nearly  cylindrical  part  of  the  cerebro-spinal 
axis  which  lies  in  the  vertebral  canal,  occupying  its  upper  two-thirds  in  the  adult. 

It  extends  from  about  the  level  of  the 
atlo-occipital  articulation  (or  lower 
border  of  the  pyramid  decussation)  to 
the  level  of  the  lower  border  of  the 
body  of  the  first  lumbar  vertebra, 
where  it  terminates  in  a  slender  fila- 
ment of  gray  substance  enveloped  by 
pia,  and,  further  caudad,  by  a  sheath 


N.CERV.  I. 


LIGAMENTUM 
DENTICULATUM 


FIG.  528. — Ventral   view   of   nblongata  and   upper 
part  of  spinal  cord.     Dura  and  arachnoid    cut  along 

FIG.  527. — Showing  the  relation  of  the  spinal  cord  to  median  line  and  folded  aside.  A  and  K  are  fairly 
the  dorsal  surface  of  the  trunk.  The  vertebra  are  constant  velar  folds  of  the  arachnoid.  (After  Key 
.shown  in  red  outlines.  and  Retzius.) 


of  dura  which  is  attached  to  the  dorsum  of  the  coccyx.  The  spinal  cord  is 
continuous  cephalad  with  the  oblongata.  Its  length  is  45  cm.  (44  to  50  cm.) 
in  the  male  and  43.5  cm.  (39.5  to  47  cm.)  in  the  female.  In  the  course  of 
foetal  development,  the  spinal  cord  occupies  the  entire  length  of  the  vertebral 
canal  up  to  the  third  month,  but  after  this  period  it  gradually  recedes  cephalad 
owing  to  the  more  rapid  growth  of  the  vertebral  column,  so  that  at  birth  the 
caudal  end  of  the  spinal  cord  has  risen  to  the  level  of  the  third  lumbar  vertebra. 
The  spinal  cord  does  not  entirely  fill  the  vertebral  canal.  A  wide  space,  or 
rather  a  concentric  series  of  spaces  intervene  between  its  surface  and  the  walls 


THE  SPINAL   CORD 


835 


of  the  canal,  affording  a  marked  freedom  of  movement  of  the  vertebral  column 
without  exerting  undue  tension  upon  the  spinal  cord.  These  spaces,  three  in 
.number,  which  concentrically  surround  the  cord,  are  demarcated  by  the  three 
protective  membranes:  (1)  pia,  (2)  arachnoid,  and  (3)  dura,  which  are  continuous 
with  the  like  meninges  of  the  brain.  The  arrangement  of  the  spaces  and  the 
membranes  may  be  shown  thus: 


t . 


— 

c  ~ 

-t-i    -• 
i   it 

1 


Epidural 
space. 


Subdural 
space. 


Subarachnoid 

space 

and 

subarachnoid 
reticulum. 


•2     PH 


The  pia  closely  invests  the  entire  surface  of  the  spinal  cord  and  sends  septal 
ingrowths  into  its  substance  as  well  as  a  fold  occupying  the  ventro-median 
fissure.  A  leaf-like,  serrated  fold  of  pia,  the  ligamentum  denticulatum,  passes 
from  each  lateral  border  to  the  inner  surface  of  the  dural  sheath  and  helps  to 
support  the  cord  within  the  subarachnoid  space.  The  arachnoid  and  the  pia 
are  not  separable  in  gross  dissection  as  they  merge  insensibly,  though  usually 
described  as  distinct  membranes.  The  arachnoid  is  in  reality  an  exceedingly 
delicate  and  transparent  web-like  reticulum  whose  meshes  constitute  a  relatively 
wide  cavity  filled  with  cerebro-spinal  fluid.  The  dura  constitutes  the  outermost 
and  thickest  sheath,  while  the  narrow  interval  between  the  dura  and  the  vertebral 
canal  is  filled  by  a  fine  venous  plexus,  together  with  soft,  areolo-fatty  tissue. 
Of  the  three  spaces  which  surround  the  cord,  only  the  two  innermost  contain 
fluid,  and  that  of  a  serous  character;  the  amount  in  the  sub-dural  space  is  very 
small,  just  sufficient  to  moisten  the  contiguous  endothelial  surfaces  of  the  dura 
and  arachnoid;  that  in  the  slib-arachnoid  space  is  considerable.  (For  detailed 
description  see  section  on  the  Meninges.) 

Weight. — The  weight  of  the  spinal  cord,  exclusive  of  all  nerve-roots,  averages 
2S  grams,  or  1  ounce  avoirdupois,  being  slightly  less  in  the  female.  Including  the 
nerve-roots  as  ordinarily  cut  in  postmortem  procedure,  the  weight  averages  45 
grams  in  the  male  and  40  grams  in  the  female.  The  ratio  of  weight  in  proportion 
to  that  of  the  brain  is1  lowest  in  the  human  species,  being  1  to  51  in  the  male  and 
1  to  49. S  in  the  female.  In  the  newborn  the  ratio  is  1  to  115.  Its  specific  gravity 
is  1.038. 

External  Morphology. — In  situ  the  spinal  cord  exhibits  slight  curvatures  in  the 
sagittal  plane,  being  convex  ventrad  in  the  transition  from  cervical  to  thoracic 
portion  and  slightly  concave  ventrad  to  the  lumbar  portion.  Its  position  varies 
also  according  to  the  degree  of  curvature  of  the  spinal  column,  being  raised 
slightly  (a  few  millimetres  only)  in  flexion  of  the  spine. 


836 


THE  NER  VE  SYSTEM 


The  intrinsically  segmental  nature  of  the  spinal  cord  is  expressed  by  the  asso- 
ciation of  each  definite  segment  with  the  somatic  segment  supplied  by  its  nerves. 
Thirty-one  pairs  of  spinal  nerves  are  commonly  enumerated,  although  two  addi- 
tional, rudimentary  pairs,  relics  of  a  tailed  vertebrate  ancestry,  are  demonstrable 
microscopically. 

The  first  pair  of  spinal  nerves  emerges 
between  the  occiput  and  atlas,  and  is 
designated  the  first  cervical;  the  other 
cervical  pairs  are  named  after  the  lower 
of  the  two  vertebra  which  form  the  in- 
tervertebral  foramen  through  which  the 
nerve  emerges.  Very  inconsistently  the 
pair  emerging  between  the  seventh  cervical 
and  first  thoracic  vertebra  is  called  the 
eighth  cervical  pair.  The  remaining 


XII.    THORACIC 


V.     LUMBAR 


I.    SACRAL- 


COCCYGEAL- 


FIG.  529. — Showing  the  relations  of  the  cord 
and  nerve  origins  to  the  levels  at  which  the  nerves 
emerge  through  the  intervertebral  foramina  (dia- 
grammatic). 


FIG.  530. — The  cauda  equina  exposed  within 
its  dural  sheath. 


spinal  nerves  are  named  after  the  upper  of  the  two  vertebra  forming  the  corre- 
sponding foramen.     In  all  there  are: 

Cervical  pairs 8 

Thoracic  pairs 12 

Lumbar  pairs 5 

Sacral  pairs 5 

Coccygeal  pairs 1 

31 


THE  ENLARGEMENTS  OF  THE  SPINAL  CORD 


837 


C.I. 


C.2. 


C5. 


All  spinal  nerves  are  made  up  of  two  roots  by  which  they  spring  from  the  lateral 
aspects  of  the  cord,  symmetrically  arranged,  and  these  nerve-root  attachments 
are  the  only  guides  to   the  demarcation  of  the 
various  segments  of  the  spinal  cord.     The  two 
roots  are  generally  termed  the  dorsal  (afferent  or 
sensor)    root,    which   enters   the   cord   along   the 
dorso-lateral   fissure  and  the  ventral    (efferent  or 
motor)  root  which  emerges  along  the  ventro-lateral 
fissure. 

Although  the  cervical  nerves  pass  outward 
through  the  intervertebral  foramina  at  nearly  a 
right  angle  to  the  long  axis  of  the  cord,  those  of 
the  lower  series  slope  more  and  more  downward, 
so  that  the  fifth  lumbar  pair  emerges  six  verte- 
bral bodies  lower  than  it  originates.  In  fact, 
the  lumbar  and  sacral  nerves  descend  as  parallel 
bundles  in  a  brush-like  manner  to  form  the  cauda 
equina,  enclosed  by  the  dural  sheath  as  far  as 
about  the  middle  of  the  sacral  canal.  The  topo- 
graphical relations  of  the  levels  of  origin  and 
exit  of  the  spinal  nerves  to  the  spinous  processes 
of  the  vertebra  is  shown  in  Fig.  529. 

Corresponding  with  the  degree  of  development 
of  the  periphery,  the  spinal  cord  is  more  mas- 
sive in  those  segments  which  are  associated  with 
the  limb.  Thus,  in  the  ground-mole,  the  cervical 
portion  is  very  much  enlarged  in  conformity  with 
the  powerfully  developed  fore-limbs,  while  in  the 
kangaroo  or  the  ostrich,  with  powerful  legs,  the 
lumbar  portion  of  the  spinal  cord  is  proportion- 
ately enlarged.  In  man,  both  the  cervical  and 
lumbar  portions  are  enlarged,  and  while  the  bulk 
of  the  lower  limbs  exceeds  that  of  the  upper,  the 
cervical  portion  of  the  spinal  cord  is  more  redun- 
dant because  it  innervates  a  limb  which  is  func- 
tionally more  differentiated,  capable  of  much  more 
skilful  and  complex  movements  and  endowed  with 
more  acutely  developed  tactile  sensibility. 

The  Enlargements  of  the  Spinal  Cord. — The 
spinal  cord  is  marked  by  two  spindle-shaped  en- 
largements in  its  cervical  and  lumbar  portions, 
while  the  intervening  thoracic  portion  is  nearly 
cylindrical,  being  slightly  reduced  in  its  dorso- 
ventral  diameter.  The  cervical  enlargement  (intu- 
mescentia  cervicalis)  extends  from  the  first  or 
second  cervical  segment  to  the  level  of  the  second 
thoracic  vertebra,  acquiring  a  maximum  breadth 
(13  to  14  mm.)  at  the  sixth  cervical  vertebra.  At 
its  junction  with  the  oblongata  its  breadth  is  about 
11  mm.  The  thoracic  portion  is  about  10  mm. 
in  breadth  (minimum  at  a  little  below  its  mid- 
dle) while  its  sagittal  diameter  is  8  mm.  The 
lumbar  enlargement  (inlumescentia  lumbalis)  be- 
gins at  the  level  of  the  tenth  thoracic  vertebra,  FlG- 


C.8. 


Th2. 


Th.8. 


Th.12. 


L.3. 


S.2. 


Coc. 


spinal 


838 


THE  NERVE  SYSTEM 


PYRAMIDAL 
DECUSSATION" 


VENTRO-LATERAL 
GROOVE 


DORSO-PARAMEDIAN 
"FISSURE 


^CERVICAL 
'ENLARGEMENT 


DORSAL 

"GROOVE 


DORSO-LATERAL 
"FISSURE 


acquires  its  maximum  breadth  (12  mm. ;  sagittal  diameter  =  9  mm.)  opposite  the 
twelfth  thoracic  vertebra  Below  the  lumbar  enlargement  the  cord  gradually 

tapers  to  form  a  cone  (conus), 
the  apex  of  which,  at  the  level 
of  the  lower  border  of  the  body 
of  the  first  lumbar  vertebra,  is 
continuous  with  the  attenuated 
filum. 

The  cervical  enlargement  is 
characterized  by  a  relatively 
greater  breadth  than  the  re- 
maining portions  of  the  cord 
which,  on  section,  appear  nearly 
circular. 

Conus  (conus  medullaris] . — 
The  conus  is  the  conical  ex- 
tremity of  the  cord.  The  Iow7er 
three  sacral  segments  and  the 
coccygeal  segment  are  usually 
included  under  this  term.  Its 
diameter  becomes  reduced  to 
2  mm.,  to  be  continued  below  as 
the  filum. 

Filum  (filum  terminate;  ner- 
vus  impar). — The  delicate  ter- 
minal thread  called  the  filum, 
continuous  with  the  tapered  end 
of  the  conus,  is  about  24  cm.  in 
length.  As  far  as  the  level  of 
the  second  sacral  vertebral  seg- 
ment it  is  enclosed,  together 
with  the  cauda  equina,  in  the 
tapering  sheath  of  the  dura. 
Within  the  dural  sac  it  is  called 
the  filum  internum,  in  contradis- 
tinction to  the  filum  externum, 
which  is  an  attenuated  process 
of  connective  and  nerve-tissue 
invested  by  a  prolongation  of 
the  dura,  which  finally  attaches 
to  the  periosteum  of  the  dorsum 
of  the  coccyx.  The  filum  ex- 
ternum occupies  one-third  of 
the  total  length  of  the  filum. 
Morphologically,  the  filum  is 
the  caudal  representative  of  the 
cord,  and  its  intradural  portion 
is  usually  accompanied  by  slen- 
der fascicles  of  nerve-fibres, 
which  are  rudimentary  second 
and  third  coccygeal  pairs  of 
spinal  nerves. 

Fissures  and  Grooves. — The 
FIQ.  532^;r:^^ZS  and  its  fissures.  spinal  cord  is  a  bilaterally  sym- 


.LUMBAR 
ENLARGEMENT 


or  rni-:  CORD 


839 


metrical  structure  and  exhibits  a  deep  ventral  fissure  and  a  slight  dorsal  groove 
partially  subdividing  the  cord  into  right  and  left  halves.  The  ventral  fissure 
extends  throughout  the  entire  length  of  the  eord,  being  shallower  in  the  cervical 
and  dorsal  portions  (less  than  one-third  of  the  sagittal  diameter)  than  in  the 
lumbar  portion.  It  is  lined  by  a  fold  of  pia  which  conveys  the  more  important 
nutritive  vessels  to  the  depths  of  the  cord  substance.  In  the  depth  of  this  fissure 
lies  the  white  ventral  commissure  of  the  cord.  The  dorsal  groove  has  been  re- 
garded, erroneously,  as  being  analogous  to  the  ventral  fissure.  Unlike  the  ventral 
fissure,  however,  the  pia  does  not  descend  into  its  depths,  but  passes  continuously 
over  it.  The  shallow  groove  marks  the  site  of  a  septum  made  up  of  neuroglial 
and  endymal  elements.  An  actual  groove  is  best  demonstrable  in  some  of  the 
lumbar  cord  and  in  the  oblongata,  where  it  constitutes  a  veritable  fissure  between 
the  clavse. 

Each  lateral  half  is  marked  by  the  lines  of  root-attachment  of  the  spinal  nerves. 
The  dorsal  nerve-root  fascicles  enter  the  cord  in  linear  series  and  in  a  depression 
or  true  sulcus  termed  the  dorso-lateral  fissure.  The  ventral  nerve-root  fascicles 


jSs. 
& 


Dorsal  nerve  root 
Central  canal. 


— Nuclei  of  spongio- 
blasts. 


euroblasts. 


C^Jv     Processes  of  neuroblasts 
^ —     growing  out  to  form 
anterior  nerve  root. 


-Ventral  column 


Fin.  533. — Section  of  spinal  cord  of  a  four  weeks'  embryo.     (His.) 

emerge,  irregularly  scattered,  out  of  a  greater  circumferential  area  and  no  true 
ventro-lateral  fissure  can  be  said  to  exist.  The  line  of  emergence  of  the  outermost 
fascicles  is  usually  taken  as  an  arbitrary  boundary  between  the  ventral  and  lateral 
districts  of  the  cord,  while  the  dorso-lateral  fissure  more  distinctly  maps  off  the 
lateral  from  the  dorsal  district.  An  additional  fissure,  observed  most  distinctly 
in  the  cervical  and  upper  thoracic  portions,  termed  the  dorso-paramedian  fissure, 
demarcates  the  two  principal  divisions  of  the  dorsal  columns,  the  dorso-median 
and  the  dorso-lateral  columns.  The  dorso-paramedian  fissure  is  an  exceedingly 
shallow  groove  and  is  best  denoted  in  sections  of  the  cord  by  its  continuance  as  a 
connective-tissue  (glia)  septum  into  the  substance  of  the  dorsal  column.  An  analo- 
gous ventro-paramedian  fissure  is  sometimes  observable  close  to  the  ventral  fissure, 
demarcating  the  ventral  (or  direct)  pyramidal  fasciculus. 

Columns  of  the  Cord  (funiculi  medullae  spinalis). — Each  half  of  the  spinal 
cord  is  thus  divided,  with  respect  to  its  white  substance,  into  three  chief  columns 
or  funiculi.  The  dorsal  column  occupies  the  area  between  the  dorsal  septum  and 
groove  and  the  line  of  attachment  of  the  dorsal  nerve-roots;  this  column  in  its 
turn  is  generally  subdivided  into  the  dorso-median  (funiculus  gracilis;  column  of 


840 


THE  NER  VE  SYSTEM 


Goll}  column  and  the  dorso-lateral  (funiculus  cuneatus;  column  of  Burdach)  by 
the  shallow  dorso-paramedian  groove  and  glia-septum  referred  to  above.  The 
ventral  column  (funiculus  anterior)  occupies  the  area  between  the  ventral  fissure 


DORSAL  ROOT 


SOMATIC  SENSOR 


VISCERAL  SENSOR 
VISCERAL  MOTOR 


SOMATIC  MOTOR 


FIG.  534. — A  diagram  of  the  component   elements  in  the  spinal  cord  and  the  nerve-roots  in  a  trunk-segment 
to  illustrate  the  four  functional  divisions  of  the  nervous  system.     (After  Johnston.)' 

and  the  outermost  fascicles  of  the  ventral  nerve-roots — an  arbitrary  boundary 
line.  The  lateral  column  (funiculus  lateralis]  constitutes  the  remainder  of  the 
cord,  between  the  dorsal  and  ventral  nerve-root  attachments.  Each  of  these 


PER    PHERAL 


SPONGIOBLAST 


GERMINAL    CELL 


NAL   QANGLION 


GERMINAL    CELL 


;>ERIPHERAL 
'ROCESSES 


NEUROBLAST- 


AXONES    OF    VENTRAL 
NERVE-ROOTS 


FIG.'  535. — Trans-section  through  neural  tube,  early  and  later  stages,  diagrammatical.  Earliest  stages 
shown  on  left  side.  On  the  right,  the  maturing  neuroblasts  are  seen  sending  their  axonic  processes  toward 
ths  periphery  or  to  other  regions  of  the  central  axis,  and  the  central  processes  of  the  spinal  ganghomc 
calls  are  seen  to  invade  the  dorso-lateral  region. 

columns  is  subdivided  into  its  component  bundles  or  fasciculi,  best  studied  in 
sections  of  the  cord. 

Development  of  the  Spinal  Cord. — The  elongated  postcranial  portion  of  the 
neural  tube  becomes  the  spinal  cord,  while  the  primitive  cavity  within  is  preserved 


841 


as  the  central  canal  of  the  cord.  The  metamorphosis  of  the  neuro-epithelial 
columnar  cells  has  been  described  (p.  818).  The  lateral  walls  thicken  considerably, 
the  central  slit-like  canal  widens  as  the  walls  bulge  outward  in  an  angular  manner, 
and  the  central  tubular  gray  becomes  a  fluted  column  with  dorsal  and  ventral 
ridges  (or  horns)  enveloped  by  a  rapidly  growing  mantle  of  axone  bundles  which 


LOCATION   OF  THE   SEGMENTS   FOR 

SENSIBILITY.  MOTILITY. 


Thoracic  and  abdominal 
viscera 
Occipital  region 

Front  of  neck 
Back  of 

Shoulder 

IXuiculo- 
spiral  n. 
Median  n. 
Ulnar  n. 


Navel 

Inferior  abdominal  refl< 


Sphincter  iridis 

Giliaris 

Rectus  int.,  levator  palpebr.  sup. 

Rectus  inf.  and  sup. 

Obi.  infer. 

—  Obi.  super. 

Masseter,  temporal,  pterygoids 

Rectus  extern. 

Occipitofront.,  orbicularis  oculi  (upper  facial' 

Muscles  of  expression  (lower  facial) 

Palatal  and  pharyngeal  muscles 

Muscles  of  the  larynx 

Muscles  of  the  tongue 

Sternocleidomastoid 
Deep  muscles  of  the  neck 
Scaleni 

Trapezius,  serratus  anticus 

Diaphragm 

Delt.,  biceps,  pectoral,  maj.  (clavic.  portion)  1  ^ 
Srachial.  antic.,  supinator  longus 
Triceps,  latis.  dorsi,pect.  maj.  (costal    "     ))» 
'  Extensores  carpi  et  digitorun 
Flexores  carpi  et  digitorum 
Interossei,  lumbricales  •> 

Thenar,  hypothenar     j 

Intercostal! 
Muscles  nf  the  back 
Abdominal  muscles 


*  Forearm 


— —  lliopsoas    -\ 

Sartorius    I 

—  Adductors  f 
— ••  Abductors  J 


ThigK 


Leg 


Scrotum,  penis,  etc 
Bladder,  rectum 


~  Quadriceps  f 
Flexors        >  Leg 
Extensors    ) 
Peronei 

Flexors,  extensors  of  the  foot  and  toes 
Glutei  (f) 
Perin 

Vesical    \  Musculature 
Rectal 


FIG.  536. — Explanation  of  abbreviations:  tr.  olf.,  olfactory  tract;  c.  g.  I.,  lateral  geniculate  body;  p,  r,  cr.  A, 
indicate  approximately  the  location  of  the  reflex  centres  for  the  pupillary  (p),  the  respiratory  (r),  cremas- 
teric  (cr),  patellar  (pat),  and  tendo-Achillis  (A)  reflexes.  The  vesical  centre  lies  in  the  third  and  fourth 
sacral  segments;  the  anal  centre  in  the  fourth  and  fifth  (represented  by  circles);  the  centres  for  erection, 
ejaculation,  Ijibor  pains  (?)  are  probably  also  situated  in  this  region.  In  reality,  the  divisions  between  the 
various  segments  are,  of  course,  not  so  sharp  as  they  are  shown  in  the  diagram,  so  that  a  given  muscle  or 
cutaneous  region  derives  some  of  its  controlling  nerve-roots  from  the  segments  lying  immediately  above 
and  below  ths  principal  segment.  The  sensor  segment  for  any  given  region  is  regularly  somewhat  higher 
than  the  corresponding  motor  segment.  (Jakob.) 

become  myelinic  in  successive  stages.  The  bulging  of  the  thickening  walls  in  the 
dorsal  and  ventral  as  wrell  as  lateral  directions  produces  the  ventral  fissure  and  the 
post-septum. 

The  segmental  nature  of  the  spinal  cord  has  been  alluded  to  before  with  regard 
to  the  segmental  derivation  of  the  cerebro-spinal  ganglia  and  the  disposition  of  the 
out-growing  nerve-bundles.  There  is  a  further  mode  of  division  into  longitudinal 


842 


THE  NERVE  SYSTEM 


systems  based  upon  functional  relationships.  Two  main  categories  of  activity 
characterize  the  mechanism  of  the  nervous  system  and  find  somatic  expression  in 
its  architectural  plan:  First,  actions  in  relation  to  the  external  world  (somatic — 
involving  skin,  muscle,  skeleton,  etc.);  second,  internal  activities  concerned  with 
the  processes  of  nutrition  and  reproduction  (visceral — involving  the  alimentary 
tract,  circulatory,  excretory,  and  reproductive  systems).  In  each  there  is  a  twofold 
activity  on  the  part  of  the  nerve  system:  reception  of  stimuli  and  motor  responses. 
In  the  cord  (and  to  some  extent  in  the  brain  as  well)  the  following  functional 
divisions  may  be  distinguished  and  located  anatomically  (Fig.  534) : 


Ventral   aspect.  Dorsal  aspect. 

FIG.  537. — Distribution  of  cutaneous  nerves. 

Somatic  sensor  elements. 

Somatic  motor  elements. 

Visceral  sensor  elements. 

Visceral  motor  elements. 

This  functional  differentiation  of  the  neural  axis  into  sensor  and  motor  divi- 
sions apparently  finds  organic  expression  in  an  important  modification  of  the 
developing  neural  tube  Each  lateral  wall  of  the  neural  tube  is  early  demarcated 


INTERNAL  STRUCTURE  OF  THE  SPINAL   C<H;i> 


into  a  dorsal  and  a  ventral  strip  or  lamina  and  the  slit-like  central  canal  becomes 
more  or  less  lozenge-shaped  on  trans-section,  owing  to  the  formation  of  a  lateral 
longitudinal  furrow  within.  The  dorsal  lamina  or  zone  is  preponderatingly 
sensor  in  function,  while  the  ventral  zone  is  principally  motor  in  function.  This 
fundamental  fact  has  been  of  the  greatest  aid  in  the  correct  interpretation  of  many 
hitherto  obscure  facts  regarding  the  mechanism  of  the  nerve  system,  and  will 
be  found  to  underlie  our  method  of  description  throughout. 

Muscular  Supply  from  Motor  Segments  of  the  Cord. — This  is  shown  in 
Fig.  r>36. 

Internal  Structure  of  the  Spinal  Cord. — If  a  transverse  section  of  the  spinal 
cord  be  made,  it  will  be  seen  to  consist  of  white  and  gray  nerve  substance. 
The  white  substance  is  made  up  of  myelinated  axones;  the  gray  contains  the  cell- 
bodies  of  neurones  and  non-myelinated  axones.  The  color  of  the  gray  substance, 
so  called,  varies  according  to  the  degree  of  capillary  injection  and  the  age  of  the 
individual.  It  is  usually  of  a  faint  reddish-gray  tinge,  the  gray  preponderating  in 
older  persons,  but  various  shades  of  red,  yellow,  and  light-slate  color  may  be  noted. 


DORSAL  GROOVE 


DORSAL  SEPTUM 


DORSAL   ROOT 


DORSO-LATERAL 
FISSURE 


RETICULAR 
FORMATION 


LATERAL    HORN 


VENTRAL    HORN 


FIG.  538. — Trans-section  of  the  spinal  cord  at  the  mid-thoracic  region. 


Nor  is  the  color  uniform  even  in  the  same  section.  Around  the  central  canal  and 
at  the  periphery  of  the  dorsal  horn  the  gray  substance  is  very  translucent  and 
is  termed,  according  to  its  situation,  the  gliosa  centralis  (gelatinosa  centralis) 
and  gliosa  cornualis  (gelatinosa  Rolandi  or  caput  gliosum}.  The  white  substance 
surrounds  the  gray  column  as  a  variously  thickened  tunic,  closely  invested  by  the 
pia,  which  sends  numerous  delicate,  vessel-bearing  ingrowths  into  the  substance  of 
the  cord.  The  relative  area  of  the  white  substance,  as  seen  on  section,  increases 
cephalad ;  the  absolute  area  of  both  white  and  gray  is  largest  in  the  region  of  the 
enlargements  (Fig.  539). 

Gray  Substance  of  the  Cord  (nitocinerea;  substantia  grisea  centralis). — A 
plastic  conception  of  the  gray  substance  of  the  cord  is  essential  to  an  understand- 
ing of  the  internal  architecture.  The  gray  core  must  be  imagined  not  alone  in  the 
relations  in  which  it  is  conventionally  studied,  as  exposed  in  trans-sections,  but 
also  as  a  fluted  column  having  a  continuous  extent  throughout  the  cord.  This 
gray  column,  is  drawn  into  ventral  and  dorsal  ridges,  connected  respectively 
with  the  ventral  and  dorsal  nerve-roots,  while  the  white  substance  fills  out  the 


844 


THE  NERVE  SYSTEM 


irregularities   and  completes  the  nearly  cylindrical  outline  of  the  cprd  (Ficrs 
540  and  541). 

On  viewing  a  trans-section,  it  is  seen  that  the  gray  substance  is  so  arranged  as  to 
present,  in  each  lateral  half  of  the  cord,  a  crescentic  or  comma-shaped  mass,  the 
concavity  of  which  is  directed  laterad.  The  two  lateral  masses  are  connected 
by  a  transverse  bar  or  band  of  gray  substance,  termed  the  gray  commissure  (com- 
missura  cinerea  [grisea]),  and  containing  the  central  canal,  which  extends  the 
entire  length  of  the  cord.  The  dorsal  septum  of  the  cord  reaches  quite  to  the 
gray  commissure,  there  being  but  a  few  white  commissural  fibres  in  the  dorsal 

zone.  Ventrad,  however,  a  lamina  of 
white  substance,  the  commissura  ventralis 
alba,  separates  the  gray  commissure 
from  the  ventral  fissure  (Fig.  538) . 

In  trans-sections  of  the  cord  it  is 
seen  that  the  lateral  crescentic  gray 
masses,  united  across  the  middle  line 
by  a  gray  commissure,  have  the  aggre- 
gate appearance  of  the  letter  H.  Each 
crescentic  mass  presents  projections 
which  are  more  or  less  pronounced 
according  to  the  segment  of  the  cord 


FIG.  539. — Projection  upon  a  plane  of  the  absolute 
and.  relative  extent  of  the  gray  and  white  substance 
of  the  cord  as  determined  by  successive  sectional 
areas.  Gray  substance  shown  in  black.  (Adapted 
from  the  measurements  of  Stilling.) 


FIG.  540. — Formation  of  a  spinal  nerve. 
(Testut.) 


under  consideration.  Broadly  stated  and  without  reference  to  special  levels,  the 
most  marked  projections  are  the  dorsal  and  ventral  horns  or  cornua. 

The  Dorsal  Horn,  directed  dorso-laterad ,  is  elongated  and  narrow,  and  its  apex 
is  composed  of  a  translucent  V-shaped  mass  termed  the  gliosa  cornualis  (caput 
gelatinosa  Rolandi  [caput  gliosum  would  be  a  better  term]). 

The  attenuated  apex  of  the  dorsal  cornu  approaches  the  surface  of  the  cord 
along  the  line  of  entrance  of  the  dorsal  nerve-roots.  The  apex  of  the  dorsal  horn 
is  wider  in  the  regions  of  the  enlargements  and  the  gliosa  is  most  marked  in 
the  higher  cervical  segments.  The  base  or  cervix  of  the  dorsal  horn  is  constricted 
somewhat  except  in  the  thoracic  portion,  where  its  greater  breadth  is  due  to  the 
presence  of  the  nucleus  dorsalis  (Clarke's  column}. 

The  Ventral  Horn  is  shorter,  thicker,  and  more  blunt,  and  is  separated  from  the 
ventral  and  lateral  surfaces  of  the  cord  by  a  tolerably  thick  lamina  of  white 


INTERNAL  STRUCTURE  OF  THE  SPINAL  CORD  845 

substance.  Its  margin,  in  trans-sections,  presents  a  dentate  or  stellate  appearance 
due  to  the  emergence  of  fascicles  of  efferent  or  ventral  root-axones  on  their  way  to 
the  ventral  surface  of  the  cord. 

\Vhat  is  known  as  the  lateral  horn  projects  as  a  lateral  peninsular  extension  of 
the  central  gray  nearly  on  the  line  of  the  gray  commissure.  It  is  best  marked  as 
a  triangular  projection  in  the  upper  thoracic  segments.  In  the  cervical  enlarge- 
ment it  is  merged  with  the  greatly  expanded  ventral  horn,  but  it  again  becomes 
prominent  in  the  upper  cervical  segments. 

The  gray  substance  of  the  cord  is  not  everywhere  sharply  demarcated  from  the 
white  owing  to  the  invasion  of  myelinic  and  amyelinic  nerve-fibres.  Facing  the 
lateral  column,  in  the  angle  between  the  dorsal  and  ventral  horns,  small  fascicles 
of  white  fibres  are  embedded  in  the  gray  so  that  it  is  broken  up  in  a  peculiar  basket- 
work  pattern  termed  the  reticula  or  reticular  formation.  This  gray  network  is 
best  marked  in  the  cervical  region  and  becomes  more  abundant  in  the  oblongata. 

The  mode  of  arrangement  of  the  gray  substance  and  its  amount  in  proportion  to 
the  white  vary  in  different  parts  of  the  cord.  Thus,  the  posterior  horns  are  long 
and  narrow  in  the  cervical  region ;  short  and  narrower  in  the  thoracic ;  short  but 
wider  in  the  lumbar  region.  In  the  cervical  region  the  crescentic  portions  are 


DORSAL    RO 


VENTRAL    FISSURE 

FIG.  541. — Showing  origin  of  two  pairs  of  spinal  nerves  (schematic). 

small,  and  the  white  substance  more  abundant  than  in  any  other  region  of  the 
cord.  In  the  thoracic  region  the  gray  substance  is  least  developed,  the  white 
substance  being  also  small  in  quantity.  In  the  lumbar  region  the  gray  substance 
is  more  abundant  than  in  any  other  region  of  the  cord.  Toward  the  lower  end  of 
the  cord  the  white  substance  gradually  ceases.  The  crescentic  portions  of  the 
gray  substance  soon  blend  into  a  single  mass,  which  forms  the  only  constituent 
of  the  extreme  point  of  the  cord. 

The  Gray  Commissure  which  connects  the  two  crescentic  masses  of  gray  substance 
consists  of  myelinic  and  amyelinic  nerve-fibres  and  neuroglia.  The  fibres  pass 
transversely,  spreading  out  at  various  angles,  into  the  lateral  gray  masses.  In 
the  gray  commissure,  and  extending  the  whole  length  of  the  cord,  is  a  minute 
channel,  the  central  canal  (myelocele;  canalis  centralis),  which  is  barely  visible  to 
the  naked  eye,  but  is  proportionately  larger  in  some  of  the  lower  vertebrates. 
Cephalad,  in  the  oblongata,  it  opens  out  into  the  fourth  ventricle;  caudad  it  is 
continued  for  a  short  distance  into  the  filum,  in  which  it  ends  blindly.  The  canal 
is  very  minute,  less  than  0.1  mm.,  except  in  the  terminal  part  of  the  conus,  where 
it  expands  into  a  fusiform  dilatation,  the  sinus  terminalis  (rhombocaele;  veutriculus 
terminalis  [Krause]).  The  central  canal  is  lined  by  a  layer  of  columnar  cells  which 


THE  NERVE  SYSTEM 


are  seen  to  be  ciliated  in  the  embryo  and  are  in  all  respects  identical  with  the 
endymal  cells  lining  the  ventricles  of  the  brain.     Surrounding  the  endymal  lining 


DOHSO-LATERAL. 
GROUP 


INTERMEDIATE 
CROUP 


VENTRO-LATEHA 
GROUP 


DORSO-MEDIAL 
"GROUP 


VENTRO-MEDIAL 
"GROUP 


DORSAL  NUCLEUS 
(.CLARKE) 


INTERMEDIATE 
GROUP 


DO  RSO- LATERAL- 
GROUP 


VENTRO-LATERAL 
GROUPS 


VENTRO-MEDIAL 
"GROUP 


INTERMEDIATE 
GROUP 


F-ic..  542. — Trans-sections  of  the  spinal  cord  at  different  levels   to  show  the  topographical  arrangement 

of  the    principal   cell-groups. 

of  the  central  canal  and  gradually  merging  into  the  spongy  substance  which  con- 
stitutes the  remainder  of  the  gray  commissure  is  a  finely  granular  and  reticulated 


INTERNAL  STRUCTURE  OF  THE  SPINAL  CORD  847 

substance,  the  gliosa  or  gelatinosa  centralis,  almost  entirely  composed  of  neuroglia, 
with  a  few  fine  fibrils  apparently  proceeding  from  the  endymal  cells,  and  having  a 
translucent,  gelatinous  appearance. 

The  gray  substance  of  the  cord  is  composed  of  (1)  the  gliosa,  which  envelops 
the  head  of  the  dorsal  horn  and  which  encircles  the  central  canal  of  the  cord ;  (2) 
the  spongiosa,  which  forms  the  crescentic  horns  (except  the  heads  of  the  posterior 
horns  and  the  envelope  of  the  central  canal).  Further,  it  may  be  stated  that  the 
gray  substance  consists  of  nerve-fibres  of  variable  but  smaller  average  diameter 
than  those  of  the  white  column ;  (3)  nerve-cells  of  various  shapes  and  sizes,  with  few 
or  many  processes;  (4)  blood-vessels,  lymphatic  channels,  and  connective  tissue. 

The  nerve-fibres  of  the  gray  substance  of  the  posterior  horn  are  for  the  most  part 
composed  of  a  dense  interlacement  of  minute  fibrils,  intermingled  with  nerves 
of  a  larger  size.  This  interlacement  is  formed  partly  by  the  axones  and  dendrites 
of  the  cells  of  the  gray  substance,  and  partly  by  fibres  which  enter  the  gray  substance 
and  which  come  from  various  sources. 

The  nerve-cells  of  the  gray  substance  are  collected  into  groups  as  seen  on  trans- 
verse section,  but  they  really  form  columns  of  cells  placed  longitudinally;  or  else 
they  are  found  scattered  throughout  the  whole  of  the  gray  substance  (Fig.  542). 

In  the  ventral  horn  four  main  groups  of  cells  may  be  distinguished  which  are 
not  wholly  represented,  however,  in  all  regions  of  the  cord:  (1)  A  ventral  group 
of  cells,  separable  in  the  cervical  and  lumbar  regions  into  ventro-medial  and  ventro- 
lateral  sub-groups;  (2)  a  dorso-medial  group,  situated  in  the  cervix  of  the  ventral 
horn,  usually  demonstrable  in  the  thoracic  portion  as  well  as  a  few  contiguous 
cervical  and  lumbar  segments;  (3)  a  lateral  group,  separable  in  the  lower  cervical 
and  lumbar  regions  into  ventro-lateral  and  dorso-lateral  sub-groups,  and  supplying 
the  muscles  of  the  extremities;  (4)  a  central  group  of  cells  in  the  lumbar  and  sacral 
regions. 

In  the  lateral  horn,  which  is  most  prominent  in  the  thoracic  and  upper  cervical 
segments,  lies  an  intermediate  group  of  cells,  a  long,  slender  column  which  is 
nearly  restricted  to  the  thoracic  portion  of  the  cord,  but  is  seen  to  reappear  in  the 
upper  three  cervical  and  in  the  third  and  fourth  sacral  segments.  The  axones 
from  these  cells  probably  do  not  pass  out  with  the  ventral  nerve-roots,  but  rather 
course  within  the  cord  to  terminate  at  various  levels  on  the  same  as  well  as  on 
the  opposite  side.  A  close  connection  with  the  sympathetic  nerve  system,  and 
with  vasomotor  and  sweat-gland  nerves,  has  been  suggested. 

In  the  dorsal  horn  the  most  conspicuous  group  of  cells  is  a  columniform  nucleus 
commonly  termed  Clarke's  column  (nucleus  dorsalis),  which  extends  between  the 
seventh  cervical  and  second  (or  third)  lumbar  segments  of  the  cord.  The  cells 
are  large  and  the  group  presents  an  oval  outline  in  trans-sections,  lying  in  the  medial 
part  of  the  cervix  of  the  dorsal  horn.  The  axones  of  these  cells  pass  out  of  the 
gray  into  the  lateral  column  of  the  cord  to  form  the  spino-cerebellar  tract,  and 
convey  tactile  impulses  to  the  cerebellum. 

Just  ventrad  of  Clarke's  nucleus,  and  extending  through  a  greater  length  of 
the  cord,  scattered  cells  constitute  the  nucleus  of  Stilling,  represented  in  the 
oblongata  by  the  accessory  cuneate  nucleus.  Aside  from  these  nuclear  columns, 
the  cells  of  the  dorsal  horn  are  not  grouped  very  definitely,  and  for  the  purposes 
of  description  they  are  sub-divided  according  to  their  location.  The  cells  vary 
much  in  form  and  size  and  their  branched  axones  pass  toward  other  regions 
within  the  gray  substance  at  various  levels  on  the  same  or  on  opposite  sides,  or  via 
the  ground-bundles.  Many  fibres  of  the  dorsal  nerve-roots  are  in  relation  with 
the  dorsal-horn  cells. 

The  various  groups  of  cells  enumerated  above  are  frequently  demarcated  from 
neighboring  groups  by  nerve-fibre  intervals  which  may  be  straight,  curved,  inter- 
laced, or  loop-shaped. 


848 


THE  NERVE  SYSTEM 


\ 


CERVICAL 
NUCLEUS 


DIRECT 

SPINO-CEREBELLAR 
TRACT 


Through  the  gliosa  cornualis  pass  numerous  fine  fibrils,  chiefly  the  afferent 
dorsal  nerve-root  fibres,  but  in  addition  this  peculiar,  gelatinous,  a-nd  semitrans- 
lucent  substance  contains  numerous  small  stellate  cells;  the  region  is  so  densely 
filled  with  axones  and  collaterals,  as  well  as  neuroglia-cells  that  until  stain  ing- 
methods  became  sufficiently  developed  the  importance  of  this  substance  remained 
in  dispute.  In  man  the  gliosa  cornualis  shows  convolutions  feebly  imitating 
those  of  the  olive,  and  its  structure  is  analogous.  Dorsad  of  the  gliosa  lies  the 
ultimate  zone  of  the  dorsal  horn ;  this  gray  substance  resembles  the  spongiosa  in  its 
essential  characters. 

The  White  Substance  of  the  Cord  (substantia  alba). — The  white  substance  of  the 
cord,  consisting  chiefly  of  longitudinally  disposed  myelinic  fibres,  with  blood-vessels, 

neuroglia,  and  connective-tissue  septa,  forms 
a  thick  mantle  which  invests  the  central 
gray  column.  When  stained  with  carmine, 
a  transverse  section  of  the  white  substance  is 
seen  to  be  studded  all  over  with  minute 
dots  surrounded  by  unstained  circular  areas. 
The  dots  are  the  transversely  cut  axones ; 
the  lighter  areas  are  the  myelin  sheaths.  The 
mass  of  white  substance  is  closely  invested 
by  a  sheath  of  neuroglia  immediately  be- 
neath the  pia.  Numerous  septa,  derived  from 
the  pia,  but  always  coated  by  a  thin  layer 
of  neuroglia,  pass  into  the  white  substance 
to  separate  the  respective  bundles  of  fibres 
and  are  often  interwoven  between  individual 
nerve-fibres,  acting  as  a  supporting  frame- 
work in  which  they  are  embedded.  In  ad- 
dition to  the  longitudinal  fibres  there  are 
shorter  and  less  numerous  transverse  fibres 
collected  into  the  so-called  ccmmissural  bundle 
or  white  commissure. 

Longitudinal  Fibres. —  The  longitudinal 
fibres  constitute  the  conducting  tracts.  Al- 
though a  purely  anatomical  examination 
fails  to  reveal  the  functional  relations  of 
these  fibre-bundles,  the  structural  alterations 
which  ensue  (in  accordance  with  the  laws 
of  Waller)  in  the  distal  portion  of  a. neurone 
whose  proximal  portion  has  been  destroyed, 
the  progressive  myelinization  of  separate 
tracts  in  the  embryo  and  infant  (as  proved 
by  the  researches  of  Meynert  and  Flechsig), 
the  comparative  anatomy  method  and  electro-physiological  experimentation  have 
rendered  possible  the  demonstration  of  the  origin  and  destination  of  the  various 
conducting  systems  or  tracts  with  almost  mathematic  accuracy.  While  some  fibres 
pursue  a  lengthy  course,  serving  as  conduction  paths  between  the  brain-centres  and 
the  various  spinal  centres,  others  are  shorter  and  serve  to  associate  different  spinal 
levels — in  juxtaposition  or  relatively  not  far  distant.  It  must  be  borne  in  mind 
that  the  gray  substance,  intercalated  as  it  is  in  the  course  of  the  impulses  which  pass 
to  and  fro  in  the  cord,  contains  the  neural  elements  which  are  either  (a)  the  source 
or  (6)  the  destination  of  these  impulses,  and  thus  complete  the  nerve-cycle 
requisite  for  the  organization  of  the  functions  belonging  to  the  cord.  The  motor 
and  sensor  phenomena,  though  interacting,  depend  upon  distinct  nerve  elements 


DORSAL   NUCLEUS 
"(CLARKE'S  COLUMN) 


j  /    SACRAL 
[T~NUCLEUS 


FIG.  543. — Showing  the  dorsal  nucleus  (of 
Clarke),  and  its  cervical  and  sacral  extensions 
on  one  side,  and  the  direct  spino-cerebellar  tract 
on  the  other.  The  fibres  of  the  tract  ascend  on 
the  same  side  as  the  nucleus  in  which  they  arise. 


INTERNAL  STRUCTURE  OF  THE  SPINAL  CORD  849 

which,  because  of  their  functional  relationship,  or  because  of  the  direction  in 
which  they  convey  impulses,  are  generally  referred  to  as  motor  or  sensor,  efferent 
or  afferent  neurones;  and  in  the  spinal  cord  usage  has  sanctioned  the  employ- 
ment of  the  terms  descending  and  ascending  for  tracts  conveying  motor  and  sensor 
impulses,  respectively.  Anatomically  speaking,  however,  it  is  preferable  to- de- 
scribe the  tracts  with  reference  to  their  origins  and  termini  (as  cerebro-spinal, 
spino-thalamic,  etc.),  when  known,  or  to  their  topographical  relations  as  studied 
in  trans-sections  of  the  cord. 

For  the  purposes  of  description  it  is  convenient  to  classify  the  longitudinal 
fibres  into  three  general  systems:  (1)  The  cerebro-spinal  system  of  axones 
forming  conduction  paths  for  efferent  impulses  from  the  cerebrum  to  the 
spinal  centres  for  peripheral  organs,  and  axones  for  afferent  impulses  received 
in  the  spinal  centres  from  the  periphery  and  conveyed  in  turn  to  the  cerebrum. 
(2)  The  spino-cerebellar  system,  consisting  of  conduction  paths,  afferent  and 
efferent,  between  the  cerebellum  and  the  spinal  centres.  (3)  Numberless  asso- 
ciation systems  strictly  confined  within  the  cord  (or  only  extending  into  the 
oblongata),  composed  of  shorter  or  longer  axones  which  serve  to  associate  not  only 
different  levels  of  the  same  spinal  segment,  but  also  the  different  segments,  that 
are  in  juxtaposition  or  more  remotely  situated.  These  spinal  association  axones 
form  bundles  in  close  contact  with  the  central  gray  column  and  are  termed  the 
fasciculi  proprii  or  ground-bundles. 

The  columns  of  white  substance  have  already  been  enumerated  (p.  839)  as  the 
dorsal,  lateral,  and  ventral  columns  or  funiculi. 

In  the  dorsal  column  there  are  described  the  following  tracts : 

Ascending: 

(1)  Fasciculus  gracilis  (Golli) . 

(2)  Fasciculus  cuneatus  (Burdachi) . 
Descending: 

(1)  Comma  tract  (Schultze) . 

(2)  Median  oval  tract  (Flechsig). 
Associating: 

(1)  Fasciculus  dorsalis  proprius. 

(2)  Dorsal  cornu-commissural  tract. 

(3)  Septo-marginal  tract  (Bruce). 

Another  tract,  usually  described  as  belonging  to  the  lateral  column,  but  func- 
tionally more  intimately  related  to  the  sensor  neurone-system  of  the  dorsal 
column  is  the  fasciculus  marginalis  (of  Spitzka  and  Lissauer). 

The  great  majority  of  the  axones  constituting  the  dorsal  column  are  the  afferent 
(sensor)  axones  arising  from  the  spinal  ganglion  cells,  entering  the  cord  by  the 
dorsal  roots.  These  dorsal  root-axones  bifurcate  in  the  region  of  the  dorsal 
horn,  one  branch  ascending  a  little  obliquely  at  first,  then  vertical,  while  the  other 
branch  takes  a  similar  downward  course  for  a  shorter  distance  (Fig.  544). 
As  additional  groups  of  fibres  are  contributed  by  each  successive  dorsal  nerve- 
root  the  mass  of  white  substance  in  the  dorsal  column  accumulates  as  the  cord  is 
ascended,  though  it  must  be  noted  that  not  all  of  these  afferent  fibres  traverse  the 
whole  of  the  cord  above,  but  end  in  relation  with  cells  in  the  gray  substance  at  various 
levels.  The  successive  accessions  of  afferent  fibres  are  disposed  in  a  laminated 
manner  so  that  the  lumbar  fibres  come  to  lie  laterad  of  the  sacral  bundle,  the 
thoracic  laterad  of  the  lumbar,  and  so  on  as  the  cord  is  ascended.  A  section 
of  the  cord  at  its  highest  level  would  therefore  traverse  a  collection  of  bundles 
derived  from  all  of  the  dorsal-nerve  roots  of  the  cord,  arranged  as  shown  in  Fig.  544. 

In  the  upper  segments  of  the  cord  it  is  possible  to  distinguish  a  division  of  the 
dorsal  column  into  two  principal  fasciculi  owing  to  the  presence  of  a  distinct 
connective-tissue  septum  which  passes  into  the  substance  of  the  dorsal  column 

54 


850 


THE  NERVE  SYSTEM 


along  the  dorso-paramedian  groove.     These  fasciculi  are  termed,  according  to 
their  position,  the  dorso-median  and  dorso-lateral  fasciculi  or  Goll's  column  and 


SULCO-MARGINAL  TRACT 
FOR    PREGEMINUM 


VENTRO-MARGINAL   TRACT 
FROM    FASTIGIUM   (LoWCntlial's) 


SIXTH 
THORACIC 


THIRD 
LUMBAR 


WHITE    VENTRAL    COMMISSURE 

FIG.  544. — Sections  of  the  spinal  cord  at  the  level  of  the  sixth  cervical,  sixth  thoracic,  and  third  lumbar 
segments,  the  conducting  tracts  being  indicated  on  the  right  side  of  each  section:  C,  comma  tract  of  Schultze; 
H,  spino-olivary  tract  of  Helweg;  M,  marginal  tract  of  Spitzka-Lissauer;  O,  oval  field  of  Flechsig. 

Burdach's  column;  in  the  consideration  of  the  external  morphology  of  the  cord, 
these  have  already  been  referred  to  as  the  funiculus  gracilis  and  funiculus  cune- 
atus,  respectively. 


INTERNAL  STRUCTURE  OF  THE  SPINAL  CORD 


851 


It  has  been  noted  that  even  in  the  fresh  cord,  when  sectioned,  the  gracile  bundle 
has  a  different  tinge  and  stains  more  deeply  with  carmine  than  does  the  cuneate 
bundle. 

The  caudad  or  descending  branches  of  the  bifurcate  dorsal-root  axones  are 
considerably  shorter  than  the  ascending  branches.  They  terminate  in  the  gray 
substance  in  relation  with  its  cells  and,  by  numerous  collaterals  which  are  shorter  or 
larger  and  given  off  at  various  intervals,  serve  to  associate  different  levels  of  the 
cord.  Some  of  these  collaterals  cross  the  median  line  in  the  dorsal  commissure 
to  come  into  relation  with  neurones  of  the  opposite  side.  Certain  of  the  longer 


D.R 


D.R 


D.R" 


D.R; 


FIG.  545. — Ramifications  of  the  central  processes  (axones)  of  afferent  neurones  entering  the  spinal  cord  as 
seen  in  longitudinal  section  (schematic) :  D.  R.,  axones  of  dorsal  roots;  6,  their  bifurcation;  clt,  collaterals; 
t,  telodendria  ending  in  proximity  of  cells  in  the  gray  matter;  F,  C.,  axones  of  gracile  and  cuneate  fasciculi. 


descending  branches  show  a  tendency  to  collect  into  a  feebly  marked  bundle  along 
the  mesal  border  of  the  dorso-lateral  fasciculus,  called  because  of  its  outline  in 
trans-sections — as  seen  in  cases  of  descending  degeneration  from  injury  at  a  higher 
level — the  comma  tract  of  Schultze.  A  similar  bundle,  situated  along  the  dorsal 
septum,  best  demonstrable  in  the  lumbar  cord,  and  with  its  fellow  of  the  opposite 
side  of  oval  outline  as  seen  on  section,  is  called  the  oval  bundle  of  Flechsig  (tractus 
cervicolurribalis  [Edinger];  dorsomediales  Sakralfeld  [Obersteiner] ). 

Marginal  Tract. — Not  all  the  axones  of  the  dorsal-nerve  root  enter  the  dorsal 
column.     Another  group  elsewhere  described  passes  into  the  dorsal  horn   as 


852  THE  NERVE  SYSTEM 

well  as  toward  Clarke's  column,  while  a  third  group  of  fibres  forms  the  so-called 
marginal  tract,1  situated  close  to  or  among  the  entering  fibres  of  the  dorsal  roots, 
but  frequently  described  as  lying  in  the  lateral  column.  The  tract  is  demonstrable 
in  all  levels  and  is  made  up  of  successive  increments  of  relatively  short  axones 
(traversing  not  more  than  three  or  four  segments)  to  end  in  relation  with  the  cells 
of  the  gliosa  cornualis.  It  has  been  assumed  that  the  tract  is  concerned  with 
the  transmission  of  pain-sense. 

Ground-bundle  of  the  Dorsal  Column. — A  zone  of  fibres  contiguous  with  the 
dorsal  face  of  the  gray  column,  and  termed  the  fasciculus  dorsalis  proprius  or  dorsal 
ground-bundle,  is  composed  of  axones  arising  from  the  smaller  cells  of  the  dorsal 
horn,  which,  after  entering  the  white  substance  and  bifurcating  into  ascending 
and  descending  branches,  come  into  relation  with  other  levels  of  the  gray  column 
by  means  of  collaterals  and  terminating  in  it  after  a  comparatively  short  course. 
They  are  therefore  to  be  regarded  purely  as  association  or  "longitudinal  com- 
missural"  fibres.  The  dorsal  cornu-commissural  tract  (ventrales  hinterstrangs- 
biindel  [Striimpell];  zone  cornucommissurale  [Marie] ),  occupying  a  triangular 
interval  at  the  apex  of  the  trans-sected  dorsal  column,  and  the  septo-marginal 
tract  [of  Bruce],  in  apposition  with  the  post-septum,  belong  to  this  category  of 
association  bundles.  Both  tracts  are  most  evident  in  the  lumbar  portion  of  the 
cord. 

In  the  lateral  column  the  following  tracts  may  be  enumerated : 

Ascending: 

(1)  Dorso-lateral  spino-cerebellar  tract   (Flechsig). 

(2)  Superficial  ventro-lateral  spino-cerebellar  tract  (Gowers) . 

(3)  Spino-thalamic  tract. 

(4)  Spino-mesencephalic  tract. 

(5)  Spino-olivary  tract  (Hellweg). 
Descending: 

(1)  Crossed  pyramidal  tract. 

(2)  Rubro-spinal  tract. 

(3)  Cerebello-spinal  tract  (Marchi  and  Lowenthal). 

(4)  Vestibulo-spinal  tract. 

(5)  Olivo-spinal  tract. 
Associating: 

(1)  Fasciculus  lateralis  proprius. 

The  dorso-lateral  spino-cerebellax  or  direct  cerebellar  tract  (of  Gratiolet  and 
Flechsig)  lies  at  the  periphery,  laterad  of  the  crossed  pyramidal  tract.  Its 
axones  arise  from  the  cells  of  Clarke's  column  and  ascend  uninterruptedly  to 
the  oblongata.  and  thence  to  the  vermis  of  the  cerebellum  in  its  post-peduncle. 
The  tract  becomes  more  massive  as  the  cord  is  ascended  (Fig.  543). 

The  superficial  ventro-lateral  spino-cerebellar  tract  also  courses  along  the  per- 
iphery, but  farther  ventrad.  The  origin  of  its  axones  is  yet  in  dispute;  they  prob- 
ably arise  frorn  cells  in  the  gray  column  of  both  sides,  in  the  zone  between  the 
dorsal  and  ventral  horns  as  well  as  from  some  of  the  ventral-horn  cells.  The 
destination  of  the  axones  of  this  tract  is  equally  uncertain,  but  most  of  the  fibres 
have  been  traced  through  the  dorso-lateral  region  of  the  oblongata  and  the  pontile 
reticula,  whence  it  turns  dorsi-mesad,  to  enter  the  cerebellum  through  the  valvula 
and  ending  in  the  dorsal  vermis.  A  lesser  portion  of  the  tract  has  been  traced  to 
the  quadrigemina,  while  other  groups  of  axones  end  in  various  levels  of  the 
gray  column. 

The  spino-thalamic  and  spino-mesencephalic  (iractus  spinotectalis)  tracts  are 
not  gathered  into  compact  bundles,  but  are  rather  scattered  among  the  fibres  of 

1  First  described  by  E.  C.  Spitzka  (in  1885)  and  Lissauer  (1886)  and  usually  bearing  the  name  of  the  latter. 


INTERNAL  STRUCTURE  OF  THE  SPINAL  CORD  853 

the  lateral  column  just  mesad  of  the  superficial  ventro-lateral  spino-cerebellar 
tract  (Gowers).  The  axones  of  both  systems  arise  from  cells  in  the  dorsal  horn 
and  its  cervix  of  the  opposite  side,  coursing  through  the  white  ventral  commissure 
and  ascending  the  cord,  the  spino-thalmic  fibres  ending  in  the  thalamus,  the 
spino-mesencephalic  fibres  ending  in  the  region  of  the  quadrigemina.  The  two 
tracts  are  collectively  called  tractus  spino-tectalis  et  thalamicus. 

The  spino-olivary  tract  (Helweg's  Dreikantenbahn;  Bechterew's  Olivenbiindel) 
is  found  only  in  the  higher  segments  of  the  cord,  at  its  periphery  and  just  laterad 
of  the  emergence  of  the  ventral  nerve-roots. 

Its  connections  and  functional  direction  are  uncertain;  some  investigators  have 
traced  its  fibres  between  the  olive  and  certain  ventral-horn  cells;  Obersteiner 
suggests  a  relationship  with  the  pyramidal  tract.  The  coincidence,  in  point  of 
time,  of  the  myelinization  of  both  tracts  is  significant  in  this  connection. 

The  crossed  pyramidal  tract  (lateral  cerebro-spinal  fasciculus)  occupies  an 
approximately  triangular  or  oval  area  in  the  dorsal  portion  of  the  lateral  column, 
just  mesad  of  the  direct  cerebellar  tract,  except  in  the  lumbar  cord,  where  it  lies 
at  the  surface.  The  axones  of  this  tract  arise  from  the  pyramidal  cells  of  the 
cerebral  cortex  (motor  area)  of  the  opposite  side.  After  having  descended 
through  the  internal  capsule,  crusta,  pons,  to  the  pyramis  of  the  oblongata,  the 
major  portion  of  the  fibres  derived  from  one-half  of  the  brain  decussate  with  those 
of  the  other  half,  crossing  the  median  line  to  descend  in  the  lateral  column  of  the 
cord.  The  fibres  which  do  not  decussate  constitute  the  direct  pyramidal  tract 
in  the  ventral  column.  As  the  crossed  pyramidal  tract  descends  it  diminishes  in 
size  as  its  axones  become  distributed  to  the  ventral  horn,  where  they  terminate  in 
contiguity  with  the  ventral  motor  cells  which  give  rise  to  the  fibres  of  the  ventral- 
(motor)  nerve  roots.  The  bundle  becomes  exhausted  as  a  distinct  strand  at  the 
level  of  the  fourth  sacral  segment. 

The  rubro-spinal,  cerebello-spinal,  lateral  vestibule-spinal,  and  olivo-spinal  tracts 
consist  of  descending  axones  which  are  intermingled  so  that  their  mutual  topo- 
graphical relations  cannot  at  present  be  described.  Collectively  they  constitute 
the  fasciculus  intermedius  of  Lowenthal  and  Bechterew  (intei -media-lateral  tract 
of  Bruce  and  Campbell)  and  they  lie  ventrad  of  the  crossed  pyramidal  tract  and 
mesad  of  the  combined  spino-thalamic  and  spino-mesencephalic  tracts. 

The  rubro-spinal  tract  (Monakow's  tract;  prepyramidal  tract)  originates  in  the 
rubrum  (red  nucleus  in  the  tegmentum  of  the  mid-brain)  of  the  opposite  side  and 
its  axones  terminate  in  relation  with  ventral-horn  cells.  In  their  course  these 
fibres  are  seen  to  invade  the  area  of  the  crossed  pyramidal  tract. 

The  cerebello-spinal  tract  (Marchi's  tract)  is  supposed  to  arise  in  the  cortex  of 
the  cerebellar  hemispheres,  to  become  distributed  to  the  motor  centres  in  the 
ventral  horn. 

The  lateral  vestibulo-spinal  tract  arises  in  the  lateral  nucleus  of  the  vestibular 
nerve  (Deiters'  nucleus)  and  by  its  relations  with  spinal  centres  establishes  a 
connection  with  the  equilibratory  apparatus. 

The  olivo-spinal  tract,  according  to  Kolliker,  is  a  crossed  tract  whose  axones 
arise  in  the  olive  and  terminate  in  relation  with  the  motor  cells  of  the  ventral 
horn. 

Several  other  descending  tracts  ending  in  the  spinal  cord  and  arising  in  higher 
centres  like  the  quadrigemina,  central  gray  of  the  mesencephalon,  and  the  cere- 
bellum have  been  recently  described  by  Held,  Boyce,  and  Bechterew. 

Ground-bundle  of  the  Lateral  Column  (fasciculus  lateralis  proprius). — This  lies 
in  the  concavity  of  the  lateral  aspect  of  the  gray  column  and  consists  of  axones 
having  a  purely  commissural  function.  In  the  regions  where  the  reticula  is  best 
marked  it  is  subdivided  into  a  group  of  smaller  bundles  by  numerous  glial 
septa. 


854  THE  NER  VE  SYSTEM 

In  the  ventral  column  are  described  the  following  tracts : 
Descending: 

(1)  Direct  pyramidal  tract. 

(2)  Sulco-marginal  tract. 

(3)  Ventral  vestibulo-spinal  tract. 
Associating: 

(1)  Association-axones  between  spinal  centres   and   several   cranial  nerve 

nuclei. 

(2)  Fasciculus  ventralis  proprius. 

The  direct  pyramidal  tract  (fasciculus  cerebrospinalis  ventralis;  fasciculus  of 
Tiirck)  is  the  uncrossed  portion  of  the  pyramidal  tract  below  the  decussation  in 
the  oblongata,  and  constituting  only  10  to  15  per  cent,  of  the  fibre  system  arising 
in  the  motor  cortex  of  the  same  side.  It  is  a  small,  oblong  bundle,  as  seen  on 
trans-section,  lying  parallel  with  the  ventral  fissure,  from  which  it  is  separated 
in  the  higher  segments  by  the  relatively  narrow  sulco-marginal  tract.  The  tract 
diminishes  in  bulk  as  the  cord  is  descended,  to  disappear  in  the  thoracic  portion 
of  the  cord ;  though,  in  rare  instances,  it  has  been  observed  to  extend  throughout 
the  lumbar  portion  as  well.  This  diminution  and  eventual  disappearance  of 
the  tract  is  due  to  the  successive  decussations  of  its  fibres  throughout  its  course, 
for,  with  a  few  exceptions,  these  cross  in  the  ventral  white  commissure  to  come 
into  relation  with  the  ventral-horn  cells  (motor  cells)  of  the  opposite  side.  This 
partial  longitudinal  extension  of  the  pyramidal  decussation  and  consequent 
formation  of  an  uncrossed,  ventrally  situated  pyramidal  tract  is  peculiar  to  the 
primate  order  of  vertebrates. 

The  sulco-marginal  tract  (tractus  tectospinalis)  is  a  thin  bundle  whose  axones 
arise  in  the  quadrigemina  of  the  opposite  side,  immediately  decussating  and 
descending  through  the  oblongata,  to  be  distributed  to  various  spinal  centres  in 
a  manner  not  yet  accurately  ascertained.  The  system  is  assumed  to  be  concerned 
in  the  coordination  of  movements  of  the  head,  with  optic  and  acoustic  reflexes. 

The  ventral  vestibulo-spinal  tract  (Lowenthal's  tract;  anterior  marginal  fascic- 
ulus; ventral  cerebello-spinal  tract}  lies  at  the  periphery  of  the  ventral  column, 
extending,  as  seen  on  trans-section,  from  the  ventral-root  zone  to  the  ventral  fissure. 
Its  axones  arise  from  (1)  the  lateral  (I)eiters')  and  (2)  superior  (Bechterew's) 
nuclei  of  the  vestibular  nerve;  (3)  from  the  fastigatum  of  the  cerebellum.  Their 
termination  about  the  ventral-horn  cells  has  been  traced  as  far  as  the  sacral  region 
of  the  cord. 

As  in  the  lateral  column,  and  continuous  with  the  like  formation,  there  is  in  the 
ventral  column  an  intermediate  zone  of  mixed  systems  of  axones  which  serve  to 
associate  various  levels  of  the  cord  with  ganglionic  masses  in  the  oblongata  as 
well  as  with  the  cerebellum  and  quadrigemina.  The  nuclei  of  the  trigeminus, 
facial,  auditory,  glosso-pharyngeal,  and  vagus  nerves,  together  with  the  olive 
and  the  cerebellum,  seem  most  intimately  associated  with  the  spinal  centres  for 
movements  of  the  head  and  neck. 

Ground-bundle  of  the  Ventral  Column. — The  white  substance  of  the  ventral  column 
contiguous  with  the  central  gray  is  made  up  of  intersegmental  axones  of  associa- 
tion connecting  different  levels  of  the  cord. 

The  ventral  white  commissure  (commissura  ventralis  alba]  is  composed  of  mye- 
linic  fibres  which  decussate  with  or  cross  each  other  and,  on  trans-section,  are 
seen  to  form  a  narrow  band  connecting  the  ventral  columns  of  the  two  sides.  The 
axones  composing  it  are  chiefly  (1)  those  arising  from  ventral-horn  cells,  which 
after  crossing  the  mid-line,  course  horizontally  or  cephalad  and  caudad  to  come 
into  relation  with  neurones  at  the  same  or  at  different  levels  of  the  gray  substance; 
(2)  the  decussating  axones  of  the  direct  pyramidal  tract;  (3)  numerous  collaterals 
from  the  ventral  and  lateral  column  axones.  The  white  commissure  is  most 


INTERNAL  STRUCTURE  OF  THE  SPINAL   CORD 


855 


massive  in  the  enlargements  where  the  associations  of  the  limb-centres  are  neces- 
sarily greater  in  number. 

Myelinization  of  the  Axones  of  the  Cord. — The  acquisition  of  the  myelin  sheath 
is  not  contemporary  for  all  axones  in  the  cord,  but  is  characterized  by  a  regular 
progression  in  the  myelinization  of  separate  fasciculi.  As  a  rule,  those  axone 
systems  which  are  concerned  with  simpler  or  intrinsically  spinal  reflexes  become 
myelinic  or  "mature"  at  an  earlier  stage  of  fetal  development  than  do  those  con- 
cerned in  the  more  elaborate  connections  of  the  cord  with  the  brain.  Thus,  the 
efferent  and  afferent  axones,  and  those  of  associating  neurones,  become  myelin- 
ated  in  the  fifth  and  sixth  months  of  foetal  life,  while  the  pyramidal  tracts  and  the 
spinp-olivary  tract  (of  Helweg)  are  observed  to  be  the  last  to  mature  at  the  time 
of  birth,  in  correspondence,  apparently,  with  the  inception  of  the  functional  use 
of  these  tracts.  The  order  of  myelinization  of  the  separate  fasciculi  is  indicated 
in  Fig.  546. 


FIG.  546. — Diagram  showing  the  order  of  myelinization  of  the  various  tracts  in  the  spinal  cord  (cervical 
level).  The  tracts  are  named  on  the  right  side;  the  Roman  numerals  on  the  left  side  correspond  with  the 
enumeration  given  in  the  text.  H,  Helweg's  tract;  M ,  marginal  tract. 

Summary.  The  Gray  Substance. — The  gray  substance  consists,  aside  from  its 
supporting  tissues,  of  sentient  and  reacting  nerve-cells,  with  their  dendrites  and 
axones,  and  of  the  terminals  of  axones  entering  from  without.  These  nerve- 
cells  may  be  classified  as  follows: 

(a)  Nerve-cells  whose  axones  pass  directly  out  of  the  cord.  These  lie  in  the 
ventral  horn,  are  "motor"  in  function,  and  their  axones  form  the  ventral-nerve 
roots. 

(6)  Nerve-cells  whose  axones  pass  into  the  white  substance,  usually  bifurcating 
into  a  shorter  descending  and  a  longer  ascending  branch.  Two  kinds  of  cells 
are  distinguished : 

1.  Strand-  or  tract-cells  whose  axones  (ascending  branches)  traverse  the  cord, 
to  come  into  relation  with  higher  centres  in  the  brain. 

2.  Association-cells  whose  axones,  after  a   comparatively  brief  course  in  the 
white  substance,  reenter  the  gray  substance  and  serve  to  coordinate  different 
levels  of  the  cord. 

The  tract-cells  may  be  further  divided  into  two  categories :  homo-lateral  and 
contra-lateral  tract-cells.  Homo-lateral  cells  are  those  whose  axones  enter  the  white 


856  THE  NERVE  SYSTEM 

columns  of  the  same  side ;  contra-lateral  cells  are  those  whose  axones  traverse  the 
white  ventral  commissure  to  the  other  side.  Tract-cells  exist  in  all  parts  of  the 
gray  substance  and  are  termed,  according  to  their  situation:  ventral-,  lateral-,  and 
dorsal-horn  cells.  The  contra-lateral  tract-cells  preponderate  in  the  dorsal  horn, 
its  cervix,  and  in  the  intermediate  zone,  and,  on  account  of  their  course,  are  also 
called  commissural  cells. 

(c)  Nerve-cells  of  Golgi's  type  II,  or  cells  with  short,  multi-branched  axones. 

The  motor  ventral-horn  cells  differ,  therefore,  from  the  other  categories  in  that 
they  alone  send  their  axones  out  of  the  central  axis  to  the  periphery.  The  tract- 
cells,  commissural  cells,  and  the  Golgi  type  II  cells  are  strictly  confined  to  the 
central  axis;  the  tract-cells  serve  to  coordinate  the  separate  units  of  the  spinal 
neurone  system  with  higher  centres;  the  association-cells  maintain  the  paths  of 
conduction  between  higher  and  lower  cell-complexes;  while  the  cells  of  Golgi's 
type  II  are  limited  to  a  narrower  field  of  nerve-activity  as  nerve  links  in  the 
chaining  together  of  neurones. 

White  Substance. — The  white  substance  consists  essentially  of  axones  the  great 
majority  of  which  are  disposed  longitudinally.  These  axones  comprise: 

(a)  Axones  arising  in  the  cerebral  cortex,  the  gray  ganglionic  masses  in  the 
mid-brain,  pons,  and  cerebellum,  and  descending  to  their  terminations  in  different 
levels  of  the  cord. 

(6)  Axones  which,  conversely,  arise  in  the  gray  substance  of  the  cord  (tract-cell 
axones),  to  terminate  in  the  higher  brain-centres. 

(c)  Axones  which  coordinate  different  levels  of  the  cord  with  each  other  (associa- 
tion-cell axones.) 

(d)  Axones  which,  arising  from  the  spinal-ganglion  cells  of  the  dorsal-nerve 
roots,  enter  the  cord  and  ascend  in  the  dorsal  columns. 

Dissection. — To  dissect  the  cord  and  its  membranes  it  will  be  necessary  to  lay  open  the 
whole  length  of  the  vertebral  canal.  For  this  purpose  the  muscles  must  be  separated  from  the 
vertebral  grooves,  so  as  to  expose  the  spinous  processes  and  laminae  of  the  vertebrae;  and  the 
latter  must  be  sawed  through  on  each  side,  close  to  the  roots  of  the  transverse  processes,  from 
the  third  or  fourth  cervical  vertebra  above  to  the  sacrum  below.  The  vertebral  arches  having 
been  displaced  by  means  of  a  chisel  and  the  separate  fragments  removed,  the  dura  will  be 
exposed,  covered  by  a  plexus  of  veins  and  a  quantity  of  loose  areolar  tissue,  often  infiltrated 
with  serous  fluid.  The  arches  of  the  upper  vertebrae  are  best  divided  by  means  of  a  strong 
pair  of  cutting  bone-forceps  or  by  a  rachitome. 


MEMBRANES   OF   THE    CORD. 

The  membranes  which  envelop  the  spinal  cord  are  three  in  number.  The  most 
external  is  the  dura,  a  strong  fibrous  membrane  which  forms  a  loose  sheath  around 
the  cord.  The  most  internal  is  the  pia,  a  cellulo-vascular  membrane  which  closely 
invests  the  entire  surface  of  the  cord.  Between  the  two  is  the  arachnoid,  a  non- 
vascular  membrane  which  envelops  the  cord  and  is  connected  to  the  pia  by 
slender  filaments  of  connective  tissue. 

The  Spinal  Dura  (Dura  Spinalis)  (Figs.  528,  530,  547,  549). 

The  spinal  dura  represents  only  the  meningeal  or  supporting  layer  of  the  cranial 
dura.  The  endocranial  or  endosteal  layer  ceases  at  the  foramen  magnum  dor- 
sally,  but  reaches  as  low  as  the  third  cervical  vertebra  ventrad;  below  these 
levels  its  place  is  taken  by  the  periosteum.  The  dura  forms  a  loose  sheath  which 
surrounds  the  cord  and  the  cauda  equina,  and  is  loosely  connected  with  the 
vertebral  periosteum  and  the  ligaments  by  a  quantity  of  lax  areolar  tissue  and  a 
plexus  of  veins,  the  meningo-rachidian  veins  (plexus  venosi  vertebrales  interni).  The 


MEMBRANES  OF  THE  CORD 


857 


space  containing  the  fat  and  veins  is  called  the  epidural  space  (cavum  epidurale}. 
The  situation  of  the  veins  between  the  dura  and  the  periosteum  of  the  vertebrae 
corresponds  therefore  to  that  of  the  cranial  sinuses  between  the  endocranial  and 
supporting  layers.  The  dura  is  attached  to  the  circumference  of  the  foramen 
magnum  and  to  the  axis  and  third  cervical  vertebra ;  it  is  also  fixed  to  the  posterior 
common  ligament,  especially  near  the  lower  end  of  the  spinal  canal,  by  fibrous 
slips;  it  extends  below  as  far  as  the  second  or  third  piece  of  the  sacrum;  here  it 
becomes  impervious,  and,  ensheathing  the  filum  terminale,  constitutes  the  filum 
durae  spinalis  (Fig.  530),  and  descends  to  the  dorsum  of  the  coccyx,  to  blend  with 
the.  periosteum.  This  part  of  the  dura 
is  called  the  coccygeal  ligament  (Fig. 
549).  The  dura  is  much  larger  than  is 
necessary  for  its  contents,  and  its  size  is 
greater  in  the  cervical  and  lumbar  re- 
gions  than  in  the  thoracic.  Its  inner 
surface  is  smooth.  On  each  side  may 


VENTRAL 
NERVE  ROOT 


FIG.  547. — The  spinal  cord  and  its  membranes. 


FIG.  548.— The  dentate 
opened  and  turned  back. 
(Hirschfeld.) 


ligament.     The  dura  has  been 
The  ventral  surface  is  seen. 


be  seen  the  double  openings,  which  transmit  the  two  roots  of  the  corresponding 
spinal  nerve,  the  fibrous  layer  of  the  dura  being  continued  in  the  form  of  a  tubu- 
lar prolongation  on  them  as  they  pass  through  these  apertures.  These  prolonga- 
tions of  the  dura  are  short  in  the  upper  part  of  the  spine,  but  become  gradually 
longer  below,  forming  a  number  of  tubes  of  fibrous  membrane,  which  enclose  the 
sacral  nerves,  and  are  contained  in  the  vertebral  canal. 

The  chief  peculiarities  of  the  dura  of  the  cord,  as  compared  with  that  investing 
the  brain,  are  the  following: 

The  dura  of  the  cord  is  not  closely  adherent  to  the  bones  of  the  vertebral  canal, 
and  is  not,  as  is  the  cranial  dura,  the  internal  periosteum  of  the  vertebrae.  The 
vertebrae  have  an  independent  periosteum. 

It  does  not  send  partitions  into  the  fissures  of  the  cord,  as  the  cranial  dura 
sends  partitions  into  certain  fissures  of  the  brain. 

Its  fibrous  laminae  do  not  separate  to  form  venous  sinuses,  as  in  the  cranium. 

It  contains  no  Pacchionian  bodies. 


858 


THE  NERVE  SYSTEM 


Structure. — The  dura  consists  of  white  fibrous  and  elastic  tissue  arranged  in 
bands  or  lamellae,  which,  for  the  most  part,  are  parallel  with  one  another  and 
have  a  longitudinal  arrangement.  Each  surface  is  covered  by  a  layer  of  endothelial 
cells.  It  is  sparingly  supplied  with  vessels,  and  some  few  nerves  have  been  traced 
into  it. 


FILUM 
TERMINALE 


COCCYGEAt 
LIGAMENT 


FIG.  549. — The  filum  terminate  (schematic).      (Poirier  and  Charpy.) 


The  Arachnoid  (Arachnoidea  Spinalis)  (Figs.  528,  547). 

The  arachnoid  is  exposed  by  slitting  the  dura  and  reflecting  that  mem- 
brane to  either  side.  It  is  a  thin,  delicate,  tubular  membrane  which  invests 
the  surface  of  the  cord,  and  is  connected  to  the  pia  by  slender  filaments  of  con- 
nective tissue.  Above,  it  is  continuous  writh  the  cranial  arachnoid;  on  each  side 
it  is  continued  on  the  various  nerves,  so  as  to  form  a  sheath  for  them  as  they 
pass  outward  to  the  intervertebral  foramina.  The  outer  surface  of  the  arachnoid 
is  in  contact  with  the  inner  surface  of  the  dura,  and  the  two  are,  here  and  there, 
joined  together  by  isolated  connective-tissue  trabeculse.  These  trabeculse  are 
especially  numerous  on  the  posterior  surface  of  the  cord.  For  the  most  part, 
however,  the  membranes  are  not  connected  together,  and  the  interval  between 
them  is  named  the  subdural  space  (cavum  subdurale).  The  subdural  space  con- 
tains a  very  small  amount  of  lymph-like  fluid.  There  is  no  communication 
between  the  subdural  and  the  subarachnoid  spaces.  The  subdural  space  is  pro- 
longed outward  for  a  short  distance  on  each  emerging  nerve  and  communicates 
with  the  lymph  tract  of  the  nerve.  The  inner  surface  of  the  arachnoid  is  separated 


THE  PI  A    OF  THE  CORD 


859 


from  the  pia  by  a  considerable  interval,  which  is  called  the  subarachnoid  space 
(cavum  subarachnoideale).  The  space  is  largest  at  the  lower  part  of  the  spinal 
canal,  and  encloses  the  mass  of  nerves  which  forms  the  cauda  equina.  Cephalad 
ft  is  continuous  with  the  cranial  subarachnoid  space,  and  communicates  with  the 
general  ventricular  cavity  of  the  brain  by  means  of  openings  in  the  pia,  in  the 
roof  of  the  fourth  ventricle,  the  metapore  or  foramen  of  Majendie  and  foramina 
of  Key  and  Retzius.  It  contains  an  abundant  serous  secretion,  the  cerebro- 
spinal  fluid  (liquor  cerebrospinalis).  This  secretion  is  sufficient  in  amount  to 
expand  the  arachnoid,  and  thus  to  distend  completely  the  whole  of  the  space  in- 
cluded in  the  dura.  The  subarachnoid  space  is  occupied  by  trabeculse  of  delicate 
endothelial  covered  connective  tissue,  connecting  the  pia  on  the  one  hand  with 
the  arachnoid  on  the  other.  This  is  named  subarachnoid  tissue. 

In  addition  to  this  the  space  is  partially  subdivided  by  a  longitudinal  mem- 
branous partition,  the  septum  posticum  or  the  posterior  fenestrated  septum  (septum 
subarachnoideale),  which  serves  to  connect  the  arachnoid  with  the  pia,  opposite 
the  dorso-median  fissure  of  the  spinal  cord.  It  is  a  partition,  but  an  incomplete 
and  cribriform  partition,  consists  of  bundles  of  white  fibrous  tissue  interlacing 
with  each  other,  and  is  coated  with  endothelium.  The  dentate  ligament  (liga- 
menia  denticulate),  which  run  from  the  pia  to  the  dura  on  either  side  of  the 
cord,  divide  the  subarachnoid  space  into  an  anterior  and  a  posterior  space  (cavum 
subarachnoideale  anterius  et  posterius),  which  join  like  spaces  in  the  cavity  of  the 
cranium.  The  external  spinal  veins  (venae  spinales  externae)  lie  in  the  subarach- 
noid space. 

Structure. — The  arachnoid  is  a  delicate  membrane  made  up  of  closely  arranged 
interlacing  bundles  of  connective  tissue  in  several  layers.  It  contains  many  elastic 
fibres,  and  is  covered  on  each  side  by  endothelial  cells.  The  arachnoid  contains 
neither  vessels  nor  nerves. 


Dura 


Arachnoid 
Dorsal  root 
Ventral  root 


The  Pia  of  the  Cord  (Pia  Spinalis). 

The  pia  of  the  cord  is  exposed  on  the  removal  of  the  arachnoid  (Figs.  547 
and  548).  It  covers  the  entire  surface  of  the  cord,  to  which  it  is  very  intimately 
adherent,  forming  its  neurilemma,  and  send- 
ing a  process  downward  into  its  ventral  fis- 
sure. It  also  forms  a  sheath  for  each  of  the 
filaments  of  the  spinal  nerves,  and  invests  the 
nerves  themselves.  A  longitudinal  fibrous 
band  extends  along  the  middle  line  on  its 
ventral  surface,  called  by  Haller  the  linea 
splendens;  and  a  somewhat  similar  band, 
the  ligamentum  denticulatum,  is  situated  on 
each  side.  At  the  point  where  the  cord 
terminates  the  pia  becomes  contracted,  and 
is  continued  caudad  as  a  long,  slender  fila- 
ment, the  filum  terminate  (Fig.  549),  which 
descends  within  the  sheath  of  the  dura  and 
the  arachnoid  and  through  the  centre  of 
the  mass  of  nerves  forming  the  cauda  equina. 
It  unites  with  the  dura  and  arachnoid  about  the  level  of  the  third  sacral  vertebra, 
and  as  the  central  ligament  of  the  spinal  cord,  the  coccygeal  ligament,  or  the  filum 
durae  spinalis  the  fused  membranes  extend  caudad  as  far  as  the  base  of  the  coccyx, 
where  they  blend  with  the  periosteum.  It  assists  in  maintaining  the  cord  in  its 
position  during  the  movements  of  the  trunk.  It  contains  a  little  gray  nerve 
substance,  which  may  be  traced  for  some  distance  into  its  upper  part,  and  is 


Dura 

Plexus  venosvs 


Vasa  vertebralia 


FIG.  550. — Transverse  section  of  the  spinal 
cord  and  its  membranes.    (Gegenbauer.) 


860  THE  NERVE  SYSTEM 

accompanied  by  a  small  artery  and  vein.  At  the  upper  part  of  the  cord  the 
pia  presents  a  grayish,  mottled  tint,  which  is  owing  to  yellow  or  brown  pigment- 
cells  scattered  among  the  elastic  fibres. 

Structure. — The  pia  of  the  cord  is  less  vascular  in  structure,  but  thicker  and 
denser,  than  the  pia  of  the  brain,  with  which  it  is  continuous.  It  consists  of  two 
layers:  an  outer,  resembling  the  arachnoid,  composed  of  bundles  of  connective- 
tissue  fibres,  arranged  for  the  most  part  longitudinally;  and  an  inner  (intima  pia), 
consisting  of  stiff  circular  bundles  of  the  same  tissue,  which  present  peculiar 
angular  bends.  It  is  covered  on  both  surfaces  by  a  layer  of  endothelium.  Be- 
tween the  two  layers  are  a  number  of  cleft-like  lymphatic  spaces  which  com- 
municate with  the  subarachnoid  cavity,  and  a  number  of  blood-vessels  which  are 
enclosed  in  a  perivascular  sheath,  derived  from  the  inner  layer  of  the  pia, 
into  which  the  lymphatic  spaces  open.  The  pia  contains  the  anterior  spinal 
artery  and  its  branches,  the  two  posterior  spinal  arteries,  and  numerous  veins 
which  pass  to  the  external  spinal  veins.  It  is  also  supplied  with  nerves,  which  are 
derived  in  part  from  the  sympathetic  and  in  part  from  the  cerebro-spinal  nerves. 
These  nerves  supply  the  walls  of  the  blood-vessels  and  enter  the  cord  with  the 
vessels. 

The  Dentate  Ligament  (ligamentum  denticuLatum}  (Figs.  528  and  548)  is  a  narrow, 
fibrous  band,  situated  on  each  side  of  the  spinal  cord,  throughout  its  entire  length, 
running  from  the  pia  to  the  dura,  and  separating  the  ventral  from  the  dorsal 
roots  of  the  spinal  nerves.  It  has  received  its  name  from  the  serrated  appearance 
which  it  presents.  Its  inner  border  is  continuous  with  the  pia  at  the  side  of  the 
cord.  Its  outer  border  presents  a  series  of  triangular,  dentated  serrations,  the 
points  of  which  are  fixed  at  intervals  to  the  dura.  These  serrations  are  twenty- 
one  in  number  on  each  si4e,  the  first  being  attached  to  the  dura  opposite  the 
margin  of  the  foramen  magnum  between  the  vertebral  artery  and  the  hypoglossal 
nerve,  and  the  last  near  the  lower  end  of  the  cord.  Its  use  is  to  support  the  cord. 

Surgical  Anatomy. — Evidence  of  value  in  the  diagnosis  of  meningitis  may  be  obtained  by 
the  operation  of  lumbar  puncture,  that  is,  by  puncturing  the  theca  of  the  cord  and  withdrawing 
some  of  the  cerebro-spinal  fluid,  and  the  operation  is  regarded  by  some  as  curative,  under  the 
supposition  that  the  draining  away  of  the  cerebro-spinal  fluid  relieves  the  patient  by  diminish- 
ing the  intracranial  pressure.  Lumbar  puncture  may  give  important  diagnostic  aid  after  a 
head  injury  by  disclosing  bloody  cerebro-spinal  fluid.  The  operation  is  performed  by  inserting 
a  trocar,  of  the  smallest  size,  below  the  level  of  the  fourth  lumbar  vertebra.  In  an  adult  the 
cord  terminates  at  the  lower  border  of  the  first  lumbar  vertebra,  and  in  a  child  opposite  the 
body  of  the  third  lumbar  vertebra.  The  canal  may  be  punctured  below  the  fourth  vertebra 
without  any  risk  of  injuring  its  contents.  The  point  of  puncture  is  indicated  by  laying  the 
child  on  its  side  and  dropping  a  perpendicular  line  from  the  highest  point  of  the  crest  of  the 
ilium;  this  will  cross  the  upper  border  of  the  spine  of  the  fourth  lumbar  vertebra.  In  a  child 
the  puncture  is  made  just  below  the  vertebral  spine.  In  adults  one-half  an  inch  to  one  side  of 
the  end  of  the  vertebral  spine.  However  the  preliminary  puncture  is  made,  the  needle  pene- 
trates the  dura  in  the  middle  line.  In  entering  the  needle  it  should  be  directed  upward  and 
forward  in  a  child;  upward,  forward,  and  slightly  inward  in  an  adult. 


THE    BRAIN  OR   ENCEPHALON, 

The  brain  is  that  greatly  modified  and  enlarged  portion  of  the  cerebro-spinal 
axis  which,  with  its  membranes,  almost  completely  fills  the  cavity  of  the  cranium. 
It  is  a  complex  organ  in  which  reside  the  highest  functions — consciousness,  idea- 
tion, judgment,  volition,  and  intellect — together  with  the  centres  of  special  sense 
and  for  the  mechanism  of  life  (respiration  and  circulation),  and  it  is  the  agent  of 
the  will. 

1    General  Appearance  and  Topography  of  the  Brain.    Corresponding  to  the 
varieties  of  cranial  form,  the  shape  of  the  fresh  or  the  successfully  preserved  brain 


THE  BRAIN  OR  ENCEPHALON  861 

varies  from  the  ovoid  to  the  nearly  spherical  form,  as  viewed  dorsally.  The 
frontal  pole  is  usually  narrower,  though  more  squarely  formed ;  while  the  parieto- 
occipital  portion  is  more  massive,  but  more  sharply  pointed  in  each  half.  The 
outline  is  often  rather  that  of  an  irregular  pentagon  with  its  angles  rounded  off. 
A  dorsal  view  shows  only  the  extensive  convex  surface  of  the  two  great  convoluted 
hemicerebra  (cerebral  hemispheres]  separated  by  a  median  cleft,  the  intercerebral 
fissure  (jissura  longitudinalis  cerebri).  On  divaricating  the  cerebral  halves  it  is 
seen  that  the  separation  is  not  a  total  one,  for  in  the  depths  of  the  fissure  a  broad 
commissural  mass  of  white  fibres — the  callosum — joins  the  hemicerebra.  Frontad 
the  intercerebral  fissure  is  continued  to  the  ventral  or  basal  aspect  of  the  brain; 
caudad  it  passes  into  the  tentorial  hiatus  (jissura  transversa  cerebri}  or  interval, 
separating  the  cerebrum  from  the  cerebellum. 

In  a  lateral  view  the  continuity  of  the  spinal  cord  with  the  oblongata,  then  the 
pons  and  cerebellum  are  seen  in  part,  overlapped  by  the  cerebrum.  Prominent 
is  the  temporal  lobe  with  its  rounded  pole,  separated  from  the  frontal  and  parietal 
lobes  by  a  deep  cleft,  the  sylvian  fissure,  in  whose  depths — overlapped  by  the 
opercula  of  the  adjacent  lobes — lies  the  insula. 

A  ventral  view  presents  many  of  the  subdivisions  of  the  brain.  Here  is  seen 
the  continuity  of  the  spinal  cord,  with  the  short  and  slightly  expanding  oblongata 
lying  ventrad  of  the  cerebellum  and  somewhat  buried  in  its  vallecula  or  depression 
between  the  lateral  hemispheres,  which  alone  are  visible.  The  cerebellum  is  a 
grayish-colored  mass  of  considerable  size  and  easily  recognized  by  its  foliated 
appearance,  due  to  the  numerous  parallel  and  closely-set  curved  fissures.  A  mass 
of  white  fibres,  the  pons,  passes  transversely  from  one  cerebellar  hemisphere  to 
the  other,  ventrad  of  the  upper  portion  of  the  oblongata.  Above  the  pons  are 
seen  two  large  bundles,  the  crura,  one  on  either  side,  diverging  to  pass  into  the 
cerebral  halves.  The  interval  between  the  divergent  crura  and  temporal  poles 
laterad  and  the  orbital  portions  of  the  cerebrum  frontad  contains  a  number  of 
important  structures.  Encircling  the  crura  and  meeting  in  the  fore-part  of  the 
fossa  are  the  optic  tracts,  decussating  in  the  median  plane  to  form  the  chiasm  and 
continuing  frontad  as  the  optic  nerves.  The  arch  of  the  optic  tracts  and  chiasm 
and  the  crura  enclose  the  intercrural  space,  in  which  may  be  seen  (1)  the  postper- 
foratum  (substantia  perforata  posterior);  (2)  the  albicantia  (corpora  albicantia; 
c.  mammillaria;c.  candicantia) ;  (3)  the  tuber  (tuber  cinereum),  and  the  stalk  of  the 
hypophysis.  A  groove  marking  the  lateral  boundary  of  the  fossa  along  each  crus 
is  termed  the  oculomotor  sulcus,  as  the  root-fibres  of  the  oculomotor  nerve  have 
their  superficial  origin  therein.  The  postperforatum  is  a  gray  area  with  numerous 
minute  apertures  for  the  entrance  of  postperforant  branches  of  the  post-cerebral 
artery.  The  albicantia  are  two  small,  pea-like,  white  eminences  closely  set  side 
by  side.  The  tuber  is  a  conical  projection  between  the  albicantia  and  the  chiasm, 
to  which  the  hypophysis  (pituitary  body),  resting  in  the  sella  of  the  sphenoid,  is 
attached.  In  the  removal  of  the  brain  from  the  skull  the  stalk  of  the  hypophysis 
is  usually  torn  through  and  an  orifice,  the  lura,  leading  to  the  infundibular  recess 
of  the  third  ventricle,  is  thus  exposed. 

In  the  interval  between  the  optic  tract  and  the  orbital  surface  of  each  hemi- 
cerebrum  a  small,  depressed,  triangular  area  of  gray  substance  leading  laterad  into 
the  basisylvian  fissure  and  dotted  with  numerous  apertures  for  the  minute  basal 
branches  of  the  medicerebral  artery  and  called  the  preperforatum. 

If  the  chiasm  be  drawn  somewhat  ventrad,  a  delicate  gray  lamina,  the  terma 
(lamina  terminalis;  lamina  cinerea)  is  seen  attached  to  the  dorsal  surface  of  the 
chiasm  and  passing  dorsad  into  the  intercerebral  cleft  to  the  region  of  the  precom- 
missure. 

Parallel  to  the  mesal  border  of  the  orbital  surface  of  each  hemicerebrum  lie 
the  olfactory  tract  and  bulb,  torn  away  from  the  fila  olfactoria  as  these  pass  through 


862 


THE  NERVE  SYSTEM 


the  cribrosa  of  the  ethmoid.     The  olfactory  tract  may  be  traced  to  its  root-area, 
the  olfactory  trigone,  just  frontad  of  the  preperforatum. 

The  superficial  origin  of  nearly  all  of  the  cranial  nerves  may  be  seen  upon  the 
basal  aspect  of  the  brain  (Fig.  551).  These  nerves,  their  superficial  attachments 
to  the  brain,  and  the  foramina  of  exit  in  the  skull  are  enumerated  in  the  following 
table : 


TABULATION  OF  THE  CRANIAL  NERVES,  THEIR  SUPERFICIAL  ATTACHMENTS  TO 
THE  BRAIN,  AND  THE  FORAMINA  OF  EXIT  IN  THE  SKULL. 


NERVE. 


SUPERFICIAL   "ORIGIN"  OR  AT- 
TACHMENT TO  THE  BRAIN. 


FORAMEN  OF  EXIT  FROM  THE 
SKULL. 


I.  Olfactory  fila. 
II.  Optic  nerve. 

III.  Oculomotor  nerve 

IV.  Trochlear  nerve.    . 
V.  Trigeminal  nerve. 


VI.  Abducent  nerve. 
VII.  Facial  nerve. 

VIII.  Acoustic  nerve. 

IX.  Glosso-pharyngeal 
nerve. 

X.  Vagus  nerve. 
XI.  Accessory  nerve. 


XII.  Hypoglossal  nerve, 


Olfactory  bulb  and  tract. 
Chiasm. 

Oculomotor  groove  along  medial 
border  of  crus. 

Valvula,  laterad  of  frenulum. 
Prelateral  part  of  pons. 


Postpontile  groove  (prepyram- 
idal  part). 

Postpontile  groove  (laterad  of 
abducent  nerve  in  preolivary 
part) . 

Postpontile  groove  (laterad  of 
facial  nerve). 

Dorso-lateral  groove  of  oblongata. 


Dorso-lateral  groove  of  oblongata. 

(a)  Encephalic  part :  Dorso-lateral 
groove  of  oblongata. 

(6)  Spinal  part:  Lateral  column 
of  spinal  cord,  between  ven- 
tral and  dorsal  roots  of  cer- 
vical nerves  as  far  as  the  fifth 
and  sixth  cervical  nerves. 

Pyramido-olivary  groove. 


Ethmoidal  cribrosa. 
Optic  foramen. 
Superior  orbital  fissure. 

Superior  orbital  fissure. 

(a)  Ophthalmic    ramus,    superior 

orbital  fissure. 

(b)  Maxillary      ramus,      foramen 

rotundum. 

(c)  Mandibular    ramus,    foramen 

ovale. 

Superior  orbital  fissure. 


Porus  acusticus  internus ;  meatus 
acusticus  internus;  facial  canal; 
stylomastoid  foramen. 

Porus  acusticus  internus. 


Jugular  foramen. 

Jugular  foramen. 
Jugular  foramen. 


Canalis      hypoglossi      ("  anterior 
condyloid  foramen"). 


The  olfactory,  optic,  and  acoustic  nerves  are  afferent  or  sensory  nerves. 
The  trigeminal,  glosso-pharyngeal,  and  vagus  nerves  are  mixed  nerves. 

The  oculomotor,  trochlear,  abducent,  facial,  accessory,  and  hypoglossal  nerves  are  efferent  or 
motor  nerves. 

Dimensions. — The  sagittal  or  fronto-occipital  diameter  of  the  white  male 
adult  brain  averages  16  to  17  cm.;  the  maximum  width  in  the  parietal  region 
averages  13  to  14  cm.,  while  the  maximum  height  is  about  12.5  cm.  The  dimen- 
sions of  the  female  brain  are  usually  somewhat  less.  The  brains  of  dolichocephalic 


THE  BRAIN  OR  ENCEPHALON 


863 


individuals  are  naturally  longer  and  narrower  than  those  of  brachycephalic,  and 
other  differences  in  size  and  shape  are  found  in  conformity  with  the  cranial  con- 
figuration and  other  factors. 

The  Development  of  the  Brain  and  the  Usual  Classifications  of  its  Sub- 
divisions.— The  cephalic  region  of  the  embryonic  neural  plate  is  characterized, 
as  already  pointed  out  (p.  816),  by  a  rapid  process  of  expansion  and  intensity  of 
growth-energy  which  seems  to  indicate  the  higher  functional  potentiality  of  what 
is  to  become  the  brain.  The  fusion  of  the  margins  of  the  neural  plate,  proceeding 
rapidly  cephalad  and  caudad  from  about  the  cervical  region,  soon  effects  the 


FIG.  551. — Basal  aspect  of  the  brain  showing  the  superficial  origin  of  the  cranial  nerves. 

numerals  indicate  the  nerves. 


The  Roman 


complete  closing  in  of  the  brain  portion  of  the  neural  tube  and  its  complete  separa- 
tion from  the  overlying  ectoderm.  For  a  brief  period  prior  to  the  completion  of 
the  tube-formation  there  exists  a  minute  opening  affording  communication  be- 
twreen  the  interior  of  the  neural  tube  and  the  surrounding  amniotic  cavity;  this 
temporary  passage  is  called  the  neuropore  (Fig.  542),  and  is  morphologically 
the  cephalic  end  of  the  tube.  Its  adult  position  is  probably  in  the  hypophysial 
region. 

The   simple  Jgrab  bend~pt  expands  very  early   in    intra-uterine   life    in   a   sac- 
like  mannFproxjmaj  ^rTdigmfierfon    of  three    dilatations  or  pouches — the  primary 


864 


THE  NERVE  SYSTEM 


brain-vesicles — demarcated  by  two   constrictions.1     The   vesicles  are  designated 
respectively  the 

Fore-brain   (Prosencephalon) 

Mid-brain   (Mesencephalon) 

Hind-brain  (Rhombencephalon  or  Metencephalon) 


ECTODERM 


NEUROPORE 


FORE-BRAJN 


MID-BRAIN 


HIND-BRAIN 


PROTOVERTEBRAl. 


FIG.  553. — Brain-tube  of  chick 
hours)     showing     partly 
closed    brain-tube     with     eleven 
folds  or  neuromeres.     (After   C. 
Hill.) 


/  :..f->Mid-brain 
Prepeduncle 


Oblongata 
FIG.  554. — Scheme  showing  the  connections  of  the  several  parts  of  the  brain. 

This  classification  has  been  found  acceptable  from  every  comparative  standpoint 
in  brain  morphology,  but  attempts  have  been  made  to  establish  a  further  seg- 
mentation into  definite  anatomical  divisions  regarding  which  opinions  and  usages 
differ  widely  and  have  proven  to  be  a  hindrance  rather  than  an  aid  to  the  homo- 
logization  of  brain-structures  in  the  vertebrate  series.  The  difficulties  in  formula- 

1  The  constriction  between  mid-  and  hind-brain  has  been  called  the  isthmus  rhombencephali  by  Prof.  His,  and 
he  regards  it  as  coordinate  with  the  other  segments  recognized  by  him;  the  region,  however,  no  more  deserves 
a  definitive  segmental  value  than  would  the  cephalic  constriction  even  if  it  were  dignified  by  the  term 
isthmus  prosencephali. 


THE  BRAIN  OR  ENCEPHALON  865 

ting  a  satisfactory  schema  of  the  segmental  divisions  of  the  brain  will  be  overcome, 
perhaps,  only  by  distinguishing  the  neuromeres  or  neural  segments  conforming  to 
the  general  segmental  plan  of  the  vertebrate  body.  The  existence  of  a  neuro- 
merism  that  is  akin  to  the  metamerism  or  serial  segmentation  of  the  body,  or  to 
the  branchiomerism  characterizing  the  arrangement  of  the  branchial  arches, 
is  indicated  in  several  ways,  but  thus  far  only  the  earliest  embryonic  stages  and 
the  disposition  of  certain  of  the  cranial  nerves  afford  a  clue  to  the  definitive  seg- 
mentation of  the  brain.  According  to  the  most  recent  researches,  as  many  as 
eleven,  sixteen,  and  even  more  neuromeres  have  been  established  in  various  verte- 
brate brains.  The  hind-brain  alone  shows  from  six  to  eight  such  neural  segments 
(Figs.  552  and  553).  The  whole  matter  is  yet  so  obscure  that  confusion  will  be 
avoided  by  restricting  our  description  to  the  three  primary  divisions  and  their  deriva- 
tives without  insisting  upon  the  recognition  of  further  definitive  segments  proposed 
by  various  authors  in  consequence  of  preconceived  ideas  obtained  from  the  com- 
plicated adult  structure  of  the  brain.  At  this  transitional  period  the  student  is, 
however,  obliged  to  be  familiar  with  the  commonly  accepted — yet  provisional — 
schemes  of  segmentation  and  a  comparative  view  is  given  in  the  following  table : 


TABLE  SHOWING  COMPARISON  OF  THE  SEGMENTAL  SCHEMAS  ADOPTED  BY 

The  Anatomische  Gesellschaft  The  Association  of  American 

in  1895.  Anatomists  in  1897. 

f  I.  RHINENCEPHALON. 

Paries  ventrales.  Paries  dorsales.  Rulbi   olfactorii   with   their    tractg> 

VI.  TELENCEPHALON. 

,•      i         ,11      •         f  Corpus  striatum  ;  rhinen-  - 
Parsopticahypothalami.       {     cepfaalon;  pallium.  II.  PROSENCEPHALON. 

Palliums,  connected  by  part  of  the 
aula  and  part  of  the  precommis- 
[      sure. 

V.  DlENCEPHALON.  -          III.  DlENCEPHALON. 


IV.  MESENCEPHALON.  1 

Pedunculi  cerebri.  Corpora  quadrigemina. 

IV.  MESENCEPHALON. 

III.  ISTHMUS  RHOMBENCEPHALI.  '  Crura  and  quadrigeminum. 

,    •  f  Brar.hia  conjunctiva;  vel- 

Pedunculi  cerebn.  j      um  meduiare  anterius 

II.  METENCEPHALON.  )  V.  EPENCEPHALON. 

Pons.  Cerebellum.  j  Cerebellum;  pons;  pre-oblohgata. 

I.  MVELENCEPHALON.  ]         VI.  METENCEPHALON. 

Medulla  oblongata.  j  Post-oblongata. 

Brief  Consideration  of  the  Phases  of  Development  of  the  Brain-tube.— 
I.  Fore-brain.  —  The  cephalic  or  fore-brain  vesicle  widens  and  expands  most 
rapidly  and  attains  to  a  comparatively  large  size  even  before  the  mid-  and  hind- 
brain  vesicles  become  markedly  defined.  A  series  of  remarkable  developmental 
changes  ensue  in  the  following  order  :  (a)  Optic  vesicles  appear  as  two  diverticula, 
each  budding  from  either  side  of  the  primary  fore-brain  vesicle,  their  distal  ends 
growing  considerably  and  coming  into  contact  with  the  overlying  epidermis, 
while  the  proximal  or  attached  ends  assume  a  stalk-like  shape.  The  distal 

55 


866 


THE  NERVE  SYSTEM 


sac-like  end  becomes  invaginated  and  forms  the  retina  of  the  eye,  while  the 
stalk  upon  obliteration  of  its  cavity  forms  the  optic  nerve.  It  is  necessary  to 
state  here  that  as  development  proceeds  the  optic  stalks  become  relatively  shifted 
caudad  and  form  more  intimate  connections  with  the  thalamus  and  mid-brain. 


Head  fold  of  amnion. 

i Forebraiit. 

-  -  Optic  reside. 


Midbrain.—*F\ 
Hindbrain 


Auditory  reside. 


:z± 


Neural  ridge.  — 


I- — '•»—  -Heart. 


CjiA---Omphalo-mesenteric  vein. 


Protovertebrse  or 
mesoblastic  somites. 


jR-4-9-  -  -Sinus  rhomboidalis. 


Remains  of  primitive— 
streak. 


FIG.  555. — Chick  embryo  of  thirty-three  hours'  incubation,  viewed  from  the  dorsal  aspect. 
(From  Duval's  Atlas  d'Embryologie.) 


X  30. 


(&)  A  second  pair  of  budding  vesicles  arises  cephalad  in  the  dorsal  portion  of 
the  fore-brain  vesicle  and  are  destined  to  develop  into  the  ponderous  hemicerebra 
with  their  great  ganglia,  growing  with  great  rapidity  and  exceeding  in  this  respect 
all  other  parts  of  the  brain.  The  growth  of  these  secondary  fore-brain  vesicles  is 
principally  in  the  distal  parts,  and  in  this  manner  each  forms  a  great  pouch  whose 
interior  communicates  with  the  primary  neural  cavity  through  a  small  opening, 
the  porta  or  foramen  of  Monro.  It  must  be  remembered  that  in  these  initial 


THE  BRAIN  OR  ENCEPHALON 


867 


stages  the  vesicles  are  all  extremely  thin-walled,  but  later  the  walls  thicken  or 
hypertrophy  to  a  marked  degree,  so  that  the  neural  cavity  becomes  relatively 
small. 

(c)  Meanwhile  (in  the  fourth  week)  the  most  cephalic  portion  of  the  fore-brain 
also  becomes  differentiated.  As  the  enlarging  hemicerebral  vesicles  crowd  upon 
the  median,  slower-growing  portion,  there  is  observed,  on  either  side,  the  develop- 
ment of  a  groove  or  furrow,  the  primary  arcuate  fissure,  which  demarcates  the 

Neural  canal 

Neural  crest 


Romatopleure 


Pleuroperi- 
toneal  cavity 


Splanchnopleure 


Omphalo- 
meseiiteric  vein 


FIG.  556. — Transverse  section  of  a  portion  of  a  chick  embryo  of  twenty-nine  hours   incubation. 
(From  Duval'a  Atlas  d'Embryologie.) 

olfactory  region  (rliinencephalon}  into  a  cephalic  and  a  caudal  portion.  The 
cephalic  portion  develops  into  a  blind  tubular  diverticulum,  which  grows  cephalad 
to  form  the  olfactory  bulb  and  tract,  its  central  cavity  becoming  obliterated  (per- 
sistent in  certain  other  mammals),  while  the  caudal  portion  forms  the  roots  of  the 
olfactory  nerve,  the  preperforatum  and  the  subcallosal  gyre. 

(d)  At  the  ventral  margin  of  the  hemicerebral  or  secondary  fore-brain  vesicle 
an  excessive  proliferation  of  cells  results  in  the  production  of  several  ganglionic 
masses — the  basal  ganglia,  of  which  the  largest  are  the  lenticula  and  caudatum 


Forebrain 


Imagination  of  Ectoderm 
to  form  the  lens  rudiment' 


Pigmented  layer 
'  >f  retina. 


--Nervous  part 

of  retina. 
—  Optic  stalk. 


FIG.  557. — Trans-section  of  head  of  chick  embryo  of  forty-eight  hours'  incubation.     X  55. 
(From  Dmal's  Atlas  d'Kmbryologie.) 

(e)  The  median-cephalic  terminal  wall  intervening  between  the  large  hemi- 
cerebral vesicles  persists  as  a  thin  and  relatively  undeveloped  lamina,  the  terma. 

(/)  The  remainder  of  the  fore-brain  undergoes  great  hypertrophy  in  its  lateral 
walls  to  form  the  thalami,  while  the  ventral  portion  develops  moderately  to  form 
the  hypothalamus,  tuber,  post-hypophysis,  and  albicantia.  The  dorsal  wall  fails  to 
develop  and  remains  epithelial  except  at  a  point  immediately  adjacent  to  the 
quadrigeminal  lamina  of  the  mid-brain;  here  a  diverticulum  grows  out  to  form  the 
epiphysis  (a  rudimentary  structure  in  man,  but  undoubtedly  of  functional  use  in 
ancestral  vertebrates). 


868 


THE  NER  VE  SYSTEM 


(g)  The  cavity  of  the  primary  fore-brain  vesicle  undergoes  alterations  in  form 
as  the  secondary  metamorphoses  of  its  walls  proceed  in  the  course  of  development. 


OLFACTORY    FOLD 


FIG.  558. — Profile  views  of  the  brain  of  human  embryos  at  three  several  stages,  reconstructed  from  sections: 
A ,  brain  of  an  embryo  of  about  fifteen  days;  B,  brain  of  an  embryo  about  three  and  a  half  weeks  old; 
C,  brain  of  an  embryo  about  seven  and  a  half  weeks  old.  (After  His.) 

The  hollow  cerebral  buds  so  rapidly  outstrip  all  other  parts  of  the  brain  that  their 
internal  cavities,  the  lateral  ventricles,  become  the  most  spacious  of  the  ventricular 


THE  BRAIN  OR  ENCEPHALON 


869 


system.  The  great  hypertrophy  of  the  thalarnic  ganglia  in  the  lateral  walls  of  the 
primary  fore-brain  determine  the  sagittally  placed,  slit-like  form  of  the  so-called 
third  ventricle.  The  cavities  of  the  optic  and  olfactory  buds  become  obliterated. 

II.  Mid-brain. — The  second  primary  vesicle  becomes  somewhat  later  differen- 
tiated and  takes  a  less  prominent  part  in  the  adult  brain.     Its  dorsal  wall  goes 
into  the  formation  of  four  eminences,  the  quadrigemina,  while  the  lateral  and 
ventral  sections  grow  considerably  to  form  the  crura.     The  neural  cavity  within 
the  mid-brain  persists  as  the  narrow  aqueduct  joining  the  third  and  fourth  ventricles. 

III.  Hind-brain. — The  third  primary  brain-vesicle  is  demarcated  from  the  mid- 
brain  by  a  marked  constriction  to  which  has  been  given  the  term  isthmus  rhomb- 
encephali.      The  hind-brain    is  specially  characterized  by  the  great  expansion  of 
its  thinned-out,  membranous  dorsal  wall  caudad,  while  cephalad  the  dorsal  wall 
becomes  very  much  thickened  as  the  proton  or  fundament  of  the  cerebellum. 

The  ventral  and  lateral  parts  undergo  thickening  to  form  the  pons  and  oblongata. 

Pontcommissure. 
I  Epiphysis. 

Cms  cerebri. 
Aqueduct 

Quadrigemina. 
i  Cerebellum. 


^  '-IV.  Ventricle. 


Cerebral  hemisphere.     Olfactory  lobe  or 
rhmencephalon. 
Terma. 


Pons.  OMmiftata. 
Albicans. 


Spinal  cord. 


Optic  nerve.  \ 

Chiasm:       j     j 

Hypophysis.  < 

Tuber. 

FIG.  559. — Median  section  of  brain  of  human  foetus  during  the  third  month.     (After  His.) 


Flexures  of  the  Brain-tube. — The  difference  in  growth-rate  of  the  differ- 
ent parts  of  the  brain-tube  and  the  marked  disproportion  between  the  rapid 
brain-growth  and  slower  head-growth  causes  the  encephalic  neural  tube  to  become 
sharply  bent  upon  itself  at  certain  points.  The  first  flexure  to  occur  is  involved 
in  a  bending  of  the  entire  head  and  takes  place  in  the  -region  of  the  mid-brain ; 
this  flexure  is  termed  the  cephalic  flexure.  A  second  bending  of  the  tube  occurs 
at  the  junction  of  the  spinal  cord  and  hind-brain;  this  is  termed  the  cervical  flexure 
and  is  so  pronounced  in  the  fifth  week  of  intra-uterine  life  that  the  brain-tube  and 
spinal  cord  form  a  right  angle  with  each  other.  A  third  flexure  is  produced,  in 
consequence  of  the  other  two,  in  the  region  of  the  future  pons,  and  is  therefore  called 
the  pontile  flexure.  Subsequently  the  cervical  and  pontile  flexures  are  obliterated 
by  a  gradual  straightening  of  this  portion  of  the  brain  axis. 


870 


THE  NERVE  SYSTEM 


Dorsal  and  Ventral  Laminae  or  Longitudinal  Zones  of  the  Brain. — Quite 
like  the  longitudinal  division  of  the  developing  spinal  cord,  there  is  a  differ- 
entiation of  the  brain-tube  into  dorsal  and  ventral  zones,  though  much  less  clearly 
shown.  The  limiting  furrow  between  the  two  is  not  demonstrable  in  the  fore- 
brain;  at  least  it  is  disputed,  on  good  grounds,  that  it  exists  there.  It  Is  claimed, 
even,  that  three  such  longitudinal  divisions  exist  on  each  side  (Kupffer)  and  the 
formation  of  the  cranial  nerves  is  not  quite  comparable  to  the  spinal  nerves, 
although  there  is  a  fair  homology  with  their  dorsal-sensor  and  ventral-motor  func- 
tional differentiation,  despite  their  frequent  admixture  in  some  cranial  nerves  or  the 


DORSAL 
LAMINA 


FASC. 
SOUTARIUS 


VAGUS 
GANGLION 


itxn, 


B 


RHOMBOIDAL 
SECONDARY  f  Ll  P 


FASC 
SOLITARIU8 


OMBOIDAL  LIP 

(FUSED) 


FASC.   SOLITARIUS 


FIG.  560. — Three  stages  in  the  development  of  the  oblongata,  showing  the  metamorphosis  of  the 
rhomboidal  lip.     (Modified  after  His.) 

total  absence  of  the  one  category  in  others.  Thus  the  motor  elements  do  not 
extend  higher  than  the  mid-brain  and  the  dorsal  division  preponderates  in  the 
more  highly  organized  parts  of  the  brain,  becoming  predominant  in  the  higher 
vertebrate  species — particularly  in  man. 

In  its  simplest  expression  the  brain  is  a  tube  like  the  rest  of  the  central  nerve- 
axis,  but  a  remarkably  modified  one.  There  is  the  same  primitive  endymal 
lining  throughout  its  interior;  there  is  likewise  a  central  tubular  gray  mass  of 
ganglionic  tissue  which,  however,  undergoes  nuclear  differentiation  in  some 
portions,  atrophies  in  others,  while  in  certain  localities  it  is  crowded  away  from 


871 

the  central  cavity  by  the  intrusion  of  white-fibre  masses  which  are  chiefly  com- 
missural.  A  total  atrophy  occurs  in  a  part  of  the  dorsal  wall  of  both  fore-brain 
and  hind-brain;  partial  atrophy  is  observable  in  the  floor  of  the  third  ventricle, 
near  the  chiasm,  once  perhaps  the  optic  centre  in  the  earliest  of  the  ancestral 
vertebrates,  but  atrophied  in  higher  forms  as  the  visual  tract  became  secondarily 
projected  in  the  mid-brain.  Great  hypertrophy  characterizes  the  growth  of  the 
gangh'onic  gray  in  the  floor  of  the  lateral  ventricle  (cerebral  vesicle),  resulting 
in  the  formation  of  nugget-like  masses,  the  caudatum,  lenticula,  and  amygdala. 
The  central  gray  of  the  primary  fore-brain  also  undergoes  great  hypertrophy,  but 
in  the  lateral  walls  only,  to  form  the  large,  compact  thalami. 


BASAL    GANGLIA 
Of    FORE-BRAIN 


QUADRIGEMINA 


RETICULAR    GANGLIONIC 
MASS    WITH    CRANIA 
NERVE    NUCLEI 


CENTRAL  GRAY (FLOOR  OF 
FOURTH  VENTRICLE  AND 
AROUND  AQUEDUCT) 


CENTRAL   GRAY   OF 
SPINAL    CORD 


\«B  \ 

FIG.  561. — Schematic  representation  of  the  chief  ganglionic  categories.     Accurate  topographical  relations  and 

interconnections  are  shown  in  other  figures. 


As  in  the  cord,  fibre  masses  develop  ectad  of  the  central  tubular  gray  in  some 
localities,  while  in  other  regions  the  ganglionic  gray  remains  at  the  surface  and 
the  white  conducting  substance  is  developed  on  its  inner  aspect.  Thus  we  have, 
secondarily,  the  formation  of  superficial  gray  matter  as  the  cortex  (or  rind)  of  the 
cerebrum  and  cerebellum.  The  isolation  of  ganglionic  gray  masses  from  the 
primitive  central  tubular  gray  and  their  differentiation  into  cell-nests  (nidi  or 
nuclei)  is  also  observable  in  the  reticular  ganglionic  formation  of  the  oblongata 
and  pons  as  well  as  in  the  roof  of  the  mid-brain.  Certain  aggregations  of  gray 
ganglionic  tissue  are  intercalated  in  the  course  of  fibre  strands,  receive  an  ad- 
mixture of  these,  and  are  regarded  as  terminal,  interrupting,  or  as  condensing 


872  THE  NERVE  SYSTEM 

station^  not  unlike  some  very  complex  relay  telegraph  system.  The  olive,  den- 
tatum,  rubnun,  the  nuclei  of  the  gracile  and  cuneate  funiculi,  the  basketwork 
intercalations  of  the  reticular  and  lemniscus  fields  belong  to  this  intrafascicular 
type  of  ganglionic  structures. 

The  plan  of  structure  of  the  brain  differs,  therefore,  from  the  comparatively 
simple  arrangement  of  the  gray  and  white  substance  in  the  spinal  cord.  In  the  brain 
the  gray  substance  is  not  centrally  situated  throughout,  and  there  is  a  tendency  to 
nuclear  differentiation  of  great  and  small  ganglionic  masses  These  are  connected 
with  each  other  and  with  the  centres  in  the  cord  by  longitudinal  strands  of  fibres 
of  greater  and  lesser  length,  as  well  as  by  transverse  associating  fibres  uniting  the 
bilateral  nuclei  of  the  same  ganglionic  category;  with  the  periphery  they  gain 
connection  through  the  cranial  nerves  and  (via  the  spinal  cord)  the  spinal  nerves. 

In  tracing  the  various  structures  of  the  brain  from  the  oblongata  to  the  cere- 
bral cortex  we  follow  anatomically  what  nature  has  done  in  the  evolution  of  the 
highest  type  of  brain  from  that  of  the  simplest  and  most  ancient  vertebrate.  In 
the  oblongata  lie  the  centres  which  exert  a  very  direct  influence  over  those  of  the 
entire  cord.  The  striate  bodies  and  the  thalami  form  a  connecting  link  between 


Medipeduncle 
Postpeduncle 

.-     //-Oblongata 
FIG.  562. — Scheme  showing  the  connections  of  the  several  parts  of  the  brain. 

the  higher  cerebral  cortex  and  the  oblongata  and  cord  below.  The  extensive 
cerebral  cortex,  an  aggregation  of  psychic  centres  and  therefore  the  seat  of  the 
will,  controls  the  activities  of  the  fore-brain  ganglia  (striatum,  thalamus)  and 
the  cerebellar  cortex,  and  these  in  turn  preside  over  the  functions  of  lower  centres, 
as  in  the  way  of  motor  responses  to  external  impressions;  such  reactions  may  be 
delayed  or  immediate  according  to  the  exercise  of  the  will-power  residing  in  the 
cerebral  cortex. 

This  control  by  the  will  is  intensified  the  higher  we  ascend  the  animal  scale; 
the  pyramidal  tract,  which  originates  in  the  cerebral  cortex  and  threads  its  way 
to  the  motor  centres  of  the  spinal  cord  without  interruption  along  the  brain-axis, 
is  better  developed  in  man  than  in  any  other  animal.  In  the  course  of  evolution 
the  lower  or  more  automatic  ganglia  and  tracts  remain  relatively  about  the  same 
in  mass  as  in  other  mammalia,  but  the  higher,  more  intellectual  ganglia  surpass 
these  in  growth  so  that  there  is  an  apparent  but  not  real  diminution  of  the  auto- 
matic systems  observed  in  the  human  brain. 

It  has  been  seen  from  the  foregoing  brief  accounts  of  the  development  of  the 
nervous  system  that  the  most  prominent  feature  is  the  redundant  growth  of  the 


DESCRIPTIVE  ANATOMY  OF  THE  ADULT  HUMAN  BRAIN    873 

cephalic  or  brain  end  of  the  neural  tube.  Comparative  neuro-anatomic  re- 
searches have  thrown  much  light  upon  the  probable  genesis  of  this  remarkable 
characteristic.  The  ancestral  vertebrate,  built  upon  the  segmental  type,  was  a 
swimming  animal,  and  its  locomotion  took  place  in  the  direction  of  its  long  axis. 
In  its  progress  through  the  water  the  cephalic  (or  anterior)  segments  were  those 
which  first  encountered  the  foreign  objects  floating  in  the  same  medium.  It  was 
for  these  segments  to  determine  the  quality  of  the  objects  encountered — whether 
they  were  inimical  or  indifferent  or  beneficial  to  its  individual  ends.  The  sensory 
periphery,  in  consequence  of  the  demands  of  evolution,  underwent  specialization 
in  the  development  of  olfactory  and  gustatory  end-organs  for  testing  the  quality 
of  the  food  and  of  the  surrounding  medium;  optical  organs  for  perceiving  rays  of 
light;  auditory  organs  for  the  appreciation  of  certain  oscillations  of  the  surround- 
ings; while  others,  strictly  tactile  in  nature,  underwent  elaboration  as  such  in  the 
development  of  sensitive  antennae  or  tentacles.  Motor  contrivances,  useful  in 
the  quest  for  food  or  in  encounters  with  the  enemy,  were  developed  in  the  way 
of  powerful  jaws  and  masticatory  muscles.  In  brief,  a  remarkable  specialization 
and  differentiation  of  structure  attended  the  development  of  the  head-end  and  with 
it  the  central  organ  of  control  kept  pace.  In  the  human  species  we  find  certain 
of  these  structural  characteristics  in  a  highly  developed  condition,  while  others 
have  dwindled  or  disappeared  in  the  course  of  evolution.  Thus  in  the  myxinoid 
fishes  and  the  lamprey  the  cerebral  hemispheres  themselves  are  mere  appendages 
of  the  olfactory  lobes;  the  sense  of  smell  was  probably  the  most  important  in  lower 
animals.  In  the  brain  of  man  conditions  are  reversed  and  the  olfactory  system 
is  seen  to  have  dwindled  to  an  extreme  degree  as  compared  with  the  immense  size 
of  the  cerebrum;  this  in  conformity  with  the  relatively  slight  use  made  of  the  smell- 
sense  in  the  mental  life  of  man.  Other  organs  of  special  sense,  however,  became 
augmented  and  these,  together  with  the  nerve-mechanisms  controlling  the  vital 
functions  (respiration,  circulation),  required  a  more  and  more  elaborate  central 
nervous  organ  for  the  harmonious  interaction  of  the  several  elements.  This 
central  organ  or  brain  developed,  in  bulk  and  complexity,  hand  in  hand  with  the 
increase  of  the  intellectual  faculties.  Man's  most  manifest  distinction  from  other 
animals  has  resulted  from  a  remarkable  evolutionary  growth  in  brain-size  and 
brain-power;  and  as  the  brain  is  the  material  organ  of  mental  and  moral  mani- 
festations, we  find  in  mankind  the  highest  degree  of  superiority  and  culture — 
not  only  as  compared  with  the  nearest  related  apes,  but  of  the  civilized  and  pro- 
gressive races  as  compared  with  the  primitive  and  unprogressive  races. 


DESCRIPTIVE  ANATOMY  OF  THE  ADULT  HUMAN  BRAIN. 

Morphologically  considered,  the  brain  consists  of  a  common  trunk  (or  brain-axis) 
from  which  the  two  cerebral  hemispheres  crop  out  like  swollen  terminal  buds, 
while  the  cerebellum  is  an  excrescence  of  the  trunk  itself.  The  axially  situated 
brain-axis  or  "brain-stem"1  comprises,  roughly  speaking,  the  axial  parts  of  all 
three  primary  divisions  of  the  brain-tube:  (a)  oblongata,  (6)  pens,  (e)  mid-brain, 
(d)  thalamic  division  of  fore-brain.  In  this  brain-stem  lie  the  majority  of  the  gan- 
glionic  masses  enumerated  above,  together  with  the  nerve-tracts  uniting  the  vari- 
ous cell-nests  in  (presumable)  automatic  coordination  as  well  as  the  great  nerve- 
tracts  connecting  the  spinal  gray  with  the  cerebral  hemispheres,  the  thalami, 

1  Also  "  brain-isthmus,"  a  loosely  used  term.  It  may  here  be  remarked  that  most  extant  accounts  of  the 
anatomy  of  the  brain  over-emphasize  the  distinction  of  brain-parts  from  each  other.  Some  authors  follow 
one  or  another  system  based  upon  the  theories  of  the  segmentation  of  the  brain-tube;  others  divide  the  brain 
into  (a)  rhombencephalon  or  hind-brain  and  (6)  cerebrum,  comprising  mid-  and  fore-brain.  None  of  the 
classifications  proposed  are,  as  already  pointed  out,  quite  satisfactory.  The  continuity  of  the  parts  can  only 
be  interrupted  arbitrarily,  and  such  procedure  leads  to  a  too  narrow  conception  of  brain-structures  single  and 
apart  rather  than  serial  and  connected. 


874 


THE  NER  VE  SYSTEM 


cerebellum,  and  the  ganglia  of  the  oblongata  (including  the  cranial-nerve  nuclei), 
and  still  other  tracts  connecting  the  oblongata  with  the  cerebral  hemispheres,  the 
cerebellum,  and  the  special  ganglia  of  the  pons  and  mid-brain. 


Parts  Derived  from  the  Hind-brain  (Rhombencephalon).    External 

Morphology. 

The  Oblongata  (Medulla  Oblongata;  Spinal  Bulb;  Post-oblongata  of  Wilder; 

Myelencephalon). 

The  oblongata  is  the  continuation  cephalad  of  the  spinal  cord,  the  transition 
lying  at  the  level  of  the  foramen  magnum  and  marked  by  the  decussation  of  the 
pyramids.  Its  cephalic  limit  is  sharply  defined  ventrad  by  the  rounded  margin 
of  the  pons,  while  its  dorsal  surface  is  sunk  into  the  cerebellar  vallecula.  The 
length  of  the  oblongata  along  its  ventral  surface  is  20  to  25  mm.;  its  maximum 
width  at  the  pontile  end  is  17  to  18  mm.,  and  half  as  much  at  its  transition  into 


SEMILUNAR    GANGLION 
OF  TRIGEMINAL   NERVE 


FACIAL    NERVE 


N.    INTERMEDIUS 
ACOUSTIC    NERVE 


GLOSSOPHARYNGEAL    NERVE 
VAGUS    NERVE 


ACCESSORY    NERVE 
HYPOGLOSSAL    NERVE 


I.    CERVICAL    NERVE 


BASILAR    GROOVE 


POST-PONTILE    RECESS 


PYRAMID 
OLIVE 


DECUSSATION 
OF    PYRAMIDS 


VENTRAL    FISSURE 


FIG.  563. — Ventral  view  of  pons  and  oblongata  showing  the  attachments  of  certain  cranial  nerves  on  one  side. 
*  The  inter-radicular  pons  tract  or  corpus  ponto-bulbare,  described  in  the  text. 

the  spinal  cord;  its  maximum  thickness  is  about  15  mm.  Its  expansion  as  it 
approaches  the  pons  gives  it  the  form  of  a  truncated  cone.  The  ventral  surface 
rests  upon  the  basilar  groove  of  the  occipital. 

Fissures. — The  ventral  and  dorsal  fissures  of  the  cord  are  continued  upon 
the  oblongata,  making  it  a  bilaterally  symmetrical  structure.  The  ventral  or 
ventro-median  fissure  (fissura  mediana  anterior) ,  at  the  level  of  the  foramen  mag- 
num is  interrupted  by  a  number  of  obliquely  intercrossing  fibres,  called  the 
decussation  of  the  pyramids.  Beyond  this  interruption  the  ventral  fissure  passes 
cephalad  to  end  at  the  ventro-caudal  border  of  the  pons  in  a  recess  called  the 
postpontile  recess  or  foramen  caecum. 


THE  OBLONG  AT  A  875 

The  dorsal  or  dorso-median  fissure  (jissura  mediana  posterior)  is  of  short  extent 
upon  the  oblongata,  for  the  neural  cavity  is  here  expanded  into  a  rhomboidal 
fossa  whose  dorsal  wall,  profoundly  atrophied,  is  represented  only  by  a  delicate 
membranous  lamina;  the  dorsal  fissure  rapidly  becomes  shallower  as  it  ascends 
to  cease  at  the  caudal  apex  of  the  " fourth  ventricle." 

Like  the  spinal  cord,  the  surface  of  each  half  of  the  oblongata  is  divided  into 
three  longitudinal  districts  by  fissures  called  the  ventro-lateral  and  dorso-lateral 
fissures.  Of  these  the  latter  only  is  a  continuation  of  the  fissure  of  the  same 
name  in  the  spinal  cord. 

The  ventro-lateral  fissure  (sulcus  lateralis  anterior]  of  the  oblongata  demarcates 
the  ventral  column  (pyramid)  from  the  lateral  column  as  well  as  the  olive,  and  the 
roots  of  the  hypoglossal  nerve,  arranged  in  linear  order,  emerge  from  this  fissure. 
(The  ventro-lateral  fissure  of  the  spinal  cord  becomes  obscured  as  it  ascends  into 
the  oblongatal  region,  for  cephalad  of  the  emergence  of  the  ventral  roots  of  the  first 
cervical  nerve  a  band  of  superficial  arcuate  fibres  usually  obliterates  all  traces  of  the 
furrow.) 

The  dorso-lateral  fissure  (sulcus  lateralis  posterior)  of  the  oblongata  is  directly 
continuous  with  the  same-named  fissure  of  the  spinal  cord,  and  the  root-bundles 
of  the  accessory,  vagus,  and  glosso-pharyngeal  nerves  are  attached  along  the  bot- 
tom of  this  fissure.  Unlike  the  dorsal  roots  of  the  spinal  nerves,  the  root-bundles 
of  these  three  cranial  nerves  are  not  all  composed  of  afferent  fibres  arising  in 
extraneous  ganglionic  cells  and  entering  the  oblongata,  for  the  accessory  nerve 
is  purely  efferent  and  the  vagus  contains  both  afferent  and  efferent  fibres. 

Areas. — The  ventro-lateral  and  dorso-lateral  fissures  with  their  rows  of  nerve- 
fascicles  divide  the  surface  of  the  oblongata  on  each  side  into  three  districts  which 
appear  to  be  continuous  with  the  three  columns  of  the  spinal  cord ;  they  are  not  so 
in  reality,  however,  owing  to  the  rearrangement  of  the  fibre-tracts  and  the  central 
ganglionic  mass  in  the  myel-oblongatal  transition.  This  portion  of  the  brain- 
axis  is  sculptured  into  several  eminences  and  depressions;  of  the  eminences,  some, 
like  the  olives,  the  tubercula  cinerea,  and  the  clavse  are  due  to  the  accumulation 
of  gray  substance  beneath  the  surface  at  that  point;  others,  like  the  pyramids 
and  restes,  are  due  to  the  prominence  at  certain  points  of  the  surface  of  the  great 
nerve-tracts. 

AREAS  OF  THE  OBLONGATA. 
I.  Ventral  Area: 

Pyramid. 
II.  Lateral  Area: 

(a)  Lateral  Tract. 
(6)  Olive. 

III.  Dorsal  Area,  marked  by  slight  furrows  dividing  it  into: 
(a)  Funiculus  gracilis. 
(6)  Funiculus  cuneatus. 

(c)  Funiculus  lateralis  and  tuberculum  cinereum. 

The  last  three  structures  mentioned  appear  to  become  fused  cephalad  to  con- 
tinue as  the  restis;  in  reality  the  restis  is  formed  in  a  different  manner. 

I.  The  Pyramids  (pyramis  medullae  oblongatae). — The  pyramids  constitute  the 
oblongatal  portion  of  the  direct  cerebro-spinal  efferent  tracts  conveying  (voluntary) 
motor  impulses  from  the  precentral  cortex,  through  the  internal  capsule,  crusta, 
and  ventral  pons  to  descend  in  the  crossed  and  direct  pyramidal  tracts  to  the 
efferent  (motor)  cell-groups  in  the  ventral  horns  of  the  spinal  gray.  In  their 
external  appearance  in  the  oblongata  they  are  moderately  constricted  at  their 
pontile  ends,  appear  to  become  somewhat  expanded,  to  again  taper  as  they  pass, 
partly  into  the  ventral  columns  of  the  cord,  partly,  by  decussation,  into  the  lateral 


876  THE  NERVE  SYSTEM 

columns.  The  pyramids  are  separated  from  each  other  by  the  ventral  (or  ventro- 
median)  fissure  except  where  this  is  more  or  less  completely  obliterated  by  the 
decussating  bundles.  Each  pyramid  is  bounded  laterally  by  a  slight  furrow,  the 
ventro-lateral  or  pyramido-olivary  groove,  in  which  arise  the  hypoglossal  nerve- 
roots  and  which  separates  the  pyramid  from  the  olive.  The  pontile  end  of  each 
pyramid  is  frequently  traversed  by  a  band  of  arched  fibres  (fibrae  arcuatae  ectales; 
ponticulus  of  Arnold  (not  the  ponticulus  of  Henle),  the  ectal  arcuate  fibres. 

The  De cassation  of  the  Pyramids  (decussatio  pyramidum)  is  a  term  given  to  the 
obliquely  intercrossing  bundles  seen  at  the  oblongata-myelon  transition.  The 
extent  to  which  this  decussation  occurs  and  the  degree  of  its  visibility  varies  in 
different  individuals.  While  in  most  cases  the  majority  (90  per  cent.)  of  the  fibres 
cross  the  median  line  in  this  decussation  to  continue  as  the  crossed  or  lateral 
pyramidal  tract,  it  is  sometimes  observed  that  a  larger  share  of  the  fibres  pass 
into  the  direct  or  uncrossed  pyramidal  tract  with  a  corresponding  reduction  of  the 
crossed  tract.  Occasionally  the  decussating  bundles  are  so  deeply  situated  in  the 
ventral  fissure  as  not  to  be  visible. 

II.  Lateral  Area. — The  lateral  area  of  the  oblongata  is  continuous  with  that  of 
the  spinal  cord  and  is  bounded  by  the  dorso-lateral  and  ventro-lateral  fissures. 
It  is  composed  of  the  ventro-lateral  spino-cerebellar  tract  (fasciculus  anterolateralis 
super ficialis),  the  ventro-lateral  ground-bundle  (fasciculus  proprius  anterolateralis), 
and  the  direct  spino-cerebellar  tract  (fasciculus  cerebellospinahs  [Flechsig]),  while  it 
is  invaded  from  above  by  the  crossed  pyramidal  tract.     The  olive  is  interpolated 
in  the  cephalic  part  of  this  area. 

The  Olive  (oliva;  olivary  body)  is  a  prominent,  elongated  oval  mass  bulging  from 
the  cephalic  part  of  the  lateral  area  of  the  oblongata,  bounded  by  shallow  grooves, 
of  which  one,  for  the  hypoglossal  nerve-roots  (ventro-lateral  fissure)  separates  it 
from  the  pyramid,  while  the  other,  containing  the  nerve-fascicles  of  the  vagus, 
glosso-pharyngeal  and  accessory  nerves,  separates  the  olive  from  the  restis.  From 
the  pons  it  is  separated  by  a  shallow  groove  in  which  a  band  of  arched  fibres  is 
sometimes  seen.  Numerous  white  fibres  (ectal  arcuate  fibres)  emerging  from  the 
ventral  fissure  and  traversing  the  pyramid  loop  across  the  lower  parts  of  the  olive 
to  enter  the  restis.  The  olive  is  formed  by  the  olivary  nucleus,  embedded  in  a  thin 
layer  of  white  matter. 

The  olive  is  about  12  mm.  in  length  and  5  mm.  in  breadth. 

III.  Dorsal  Area,     (a)  Funiculus  Gracilis. — The  funiculus  gracilis  is  the  direct 
continuation  of  the  tract  of  the  same  name  in  the  spinal  cord.     It  is  a  narrow 
white  band  placed  along  the   dorso-median  fissure,   and    separated    from   the 
funiculus  cuneatus  by  the  dorso-paramedian  furrow  (sulcus  intermedius  posterior). 
At  the  apex  of  the  rhomboidal  fossa    (fourth  ventricle)  each  funiculus  gracilis 
diverges  from  the  median  plane,  presenting  at  this  point  a  club-like  enlargement, 
the  clava.     The  prominence  of  the  funiculus  gracilis  (and  clava)  is  due  to  the 
gray  nucleus  funiculi  gracilis  beneath. 

(b)  Funiculus  Cuneatus. — The  funiculus  cuneatus  is  the  direct  continuation  of 
the  tract  of  the  same  name  in  the  spinal  cord.     It  enlarges  as  it  ascends,  exhibiting 
a  slight   eminence  or  enlargement,  the  cuneate  tubercle  (tuberculum  einereum), 
which  is  marked  only  in  the  oblongata  of  young  individuals,  and  is  due  to  the 
nucleus  funiculi  cuneati  beneath. 

(c)  Funiculus  Lateralis  and  Tuberculum  Cinereum. — The  funiculus  lateralis  is  a 
longitudinal  prominence  which  gradually  enlarges  cephalad  into  a  slight  tubercle, 
the  tuberculum  cinereum   (hiberculum   Rolandi),  marking   the  approach  of   the 
gliosa  to  the  surface  so  as  to  form  a  prominence  at  a  level  with  the  lower  border 
of  the  olive. 

The  Restis  (corpus  restiforme)  occupies  the  upper  dorso-lateral  area  of  the  oblon- 
gata on  each  side,  lying  between  the  floor  of  the  fourth  ventricle  and  the  roots 


THE  PONS  AND  PRE-OBLONGATA 


877 


of  the  vagus  and  glosso-pharyngeal  nerves.  This  structure  might  at  first  glance 
appear  to  be  the  continuation  of  the  three  funiculi  just  described.  But  as  a  matter 
of  fact  it  is  made  up  of  the  direct  spino-cerebellar  tract,  a  set  of  ectal  arcuate  fibres 
(fibrae  arcuatea  externae)  and  a  set  of  ental  arcuate  fibres  (fibrae  arcuatae  internae). 
Each  restis  assists  in  forming  the  lower  part  of  the  lateral  boundaries  of  the 
fourth  ventricle  and  then  enters  the  cerebellum  as  the  postpeduncle  of  that  body. 

The  Pons  and  Pre-oblongata  (Pons  Varolii;  Protuberantia  Annularis). 

The  pons  is  a  prominent  white  mass  on  the  ventral  aspect  of  the  brain-stem 
which  is  interposed  between  the  oblongata  and  the  crura.  It  is  convex  from  side 
to  side  and  its  fibres,  running  chiefly  in  a  transverse  arched  direction,  are  gathered 
into  rounded,  compact  strands  on  either  side,  to  continue  as  the  medipeduncles 
into  the  white  substance  of  the  corresponding  cerebellar  hemisphere.  The  fibre- 
bundles  of  the  pyramidal  tracts  thread  their  way  through  the  pons  on  either  side 


Superficial 

and  middle 

fibres  of  pons 


FIG.  564. — Superficial  dissection  of  the  oblongata  and  pons.     (Ellis.) 

of  the  median  plane  and  small  aggregations  of  gray  sijbstance  (nuclei  pontis)  are 
packed  in  the  intervals  between  the  transverse  pontile  and  longitudinal  pyramidal 
fibre-bundles. 

The  Ventral  Surface  (pars  basilaris  pontis). — The  ventral  surface  of  the 
pons  is  in  relation  with  the  basilar  process  of  the  occipital  and  the  dorsum 
sellfle  of  the  sphenoid.  A  shallow  mesal  groove  lies  between  the  eminences  por- 
duced  by  the  pyramidal  tracts  in  their  course  through  the  pons.  The  groove  is 
called  the  basilar  groove  (sulcus  basilaris},  as  the  basilar  artery  is  usually  accom- 
modated in  it;  the  artery  is  not,  however,  a  factor  in  the  production  of  the  groove. 
The  large  sensor  and  small  motor-root  bundles  of  the  trigeminal  nerve  pierce  the 
mass  of  the  poris  near  the  prepontile  border,  and  a  line  drawn  from  this  nerve- 


878 


THE  NERVE  SYSTEM 


root  to  that  of  the  facial  nerve  is  usually  employed  as  an  arbitrary  boundary 
between  the  pons  proper  and  the  medipeduncle  of  the  cerebellum.  The  abducent 
nerve  emerges  from  the  postpontile  border  (prepyramidal  part);  the  facial  and 
acoustic  nerves  are  attached  farther  laterad. 

While  most  of  the  superficial  fibre-bundles  of  the  pons  are  seen  to  arch  trans- 
versely, certain  small  compact  bundles1  are  seen  to  extend  in  an  obliquely  longitu- 
dinal direction  from  the  region  of  the  trigeminal  nerve-root  to  and  among  the 
roots  of  the  facial  and  acoustic  nerves. 

The  Pre-oblongata  (pars  dorsalis  pontis;  pars  metencephalica  medullae  oblon- 
gatae). — The  pre-oblongata  is  not  sharply  demarcated  from  the  oblongata  or  the 

tegmentum  and  crusta  of  the  mid-brain  and 
the  margins  of  the  pons  on  the  ventral  surface 
afford  only  arbitrary  boundary  lines;  for  in  the 
vertebrate  series  the  pons  varies  greatly  in  width 
and  its  margins  can  hardly  be  accepted  as  the 
boundaries  of  a  definitive  brain-segment.  The 
dorsal  surface  of  the  pre-oblongata  is  continuous 
with  that  of  the  oblongatal  ventricular  surface, 
and  its  description  more  properly  belongs  to 
a  consideration  of  the  anatomy-  of  the  fossa 
rhomboidalis  or  "floor  of  the  fourth  ventricle." 

Fourth  Ventricle  of  the  Brain  (Ventriculus 
Quartus). 

In  a  previous  section  on  brain-development 
it  has  been  pointed  out  how  the  growth-changes 
and  differentiations  in  the  hind-brain  differ  from 
those  of  the  rest  of  the  neural  tube  in  that  there 
is  a  marked  disproportion  in  the  degree  of  growth 
in  the  dorsal  and  ventral  walls.  While  the 
ventral  wall  thickens  greatly  throughout  to  form 
the  pons-oblongata,  the  dorsal  wrall  hypertrophies 
in  its  cephalic  portion  to  form  the  cerebellum, 
while  caudad  thereof  the  roof  atrophies  and 
expands  and  becomes  so  attenuated  as  to  be 
represented  merely  by  a  thin  epithelial  mem- 
brane. The  outwrard  folding  of  the  walls  of  the 
neural  tube  in  this  region  creates  an  expansion 
of  the  central  cavity  in  the  form  of  a  rhomboidal 
fossa  roofed  in  by  the  cerebellum  and  a  thin 
epithelial  layer.  A  time-honored  custom  enu- 
merates this  as  the  fourth  of  a  system  of  ven- 
tricles of  which  the  other  three  lie  in  the  fore- 
brain. 

A  cast  of  the  cavity  (Fig.  565)  shows  it  to  be 
irregularly  pyramidal,  with  a  lozenge-shaped 
base  and  ridge-like  apex  extending  from  side  to  side,  corresponding  to  the 
acute-angled  recessus  tecti  in  the  fastigium  ("gable  roof")  formed  by  the 
valvula  and  velum.  Such  a  cast  also  indicates  the  ventral  extension  of  the  cavity 
from  the  lateral  angles  of  the  rhomboidal  base  in  the  form  of  the  lateral  recesses. 
It  is  customary  to  describe  for  the  fourth  ventricle  a  roof  and  a  floor,  although  an 


V 

FIG.  565. — Plan  showing  the  mode  of 
formation  of  the  ventricles  of  the  brain 
and  the  central  canal  of  the  spinal  cord: 
A,  prosencephalon;  B,  thalamencephalon; 
C,  mesencephalon;  D,  metencephalon;  E, 
myelencephalon;  F,  central  canal  of  cord; 
G,  lateral  ventricle;  H ,  porta  or  foramen 
of  Monro.  (After  Gerrish.) 


i  Called  the  inter-radicular  pons  tract  by  E.  C.  Spitzka  (1884)  and  more  recently  described  as  part  of  the 
corpus  ponto-bulbare  by  Essick  (American  Journal  of  Anatomy,  vii,  1). 


FOURTH  VENTRICLE  OF  THE  BRAIN 


879 


examination  of  a  sagittal  section  of  a  brain  hardened  in  situ  shows  the  floor  to  be 
in  a  vertical  plane  in  the  erect  attitude.  Caudad  the  cavity  is  continuous  with 
the  minute  central  canal  of  the  spinal  cord  and  postoblongata  (in  part);  cephalad 
it  passes  into  the  aqueduct  or  mesocele.  The  dorsal  wall  or  "roof"  is  formed 
by  the  valvula,  the  pre peduncles,  metatela,  and  fastigium  of  the  cerebellum.  The 
ventral  wall  or  "floor"  is  the  rhomboidal  fossa  occupied  by  the  expanded  central 
gray  of  the  pre-  and  postoblongatal  portions  of  the  hind-brain. 

''Floor"  of  the  Fourth  Ventricle  (fossa  rhomboidea).—The  "floor"  of  the 
fourth  ventricle  is  lozenge-shaped  and  exhibits  regional  elevations,  depressions, 
and  color  differences  which  are  in  relation  with  the  deep  anatomy  of  the  oblongata 
and  tegmentum  (of  pre-oblongata).  It  is  divided  longitudinally  into  symmetrical 
halves  by  a  median  groove  and  each  lateral  half  is  subdivided  into  a  larger  cephalic 
and  a  smaller  caudal  triangle  by  white,  transverse  striae,  composed  of  bundles  of 
myelinic  fibres  connected  with  the  acoustic  tract  and  appearing  to  sink  beneath 
the  surface  near  the  median  groove.  The  portion  occupied  by  these  striae  acus- 
ticae  (striae  medullares;  striae  transversales)  is  termed  by  His  the  pars  intermedia 
as  distinguished  from  the  pars  superior  and  pars  inferior  or  frontal  and  caudal 
triangles  respectively.  Much  variation  is  met  with  in  regard  to  the  course  and 


FIG.  566. — Varieties  of  fourth  ventricle. 

degree  of  prominence  of  the  striae  acusticse  (Fig.  566).  There  may  be  none  visible 
or  as  many  as  twelve  distinct  bundles;  bilateral  symmetry  is  the  exception  and 
not  infrequently  one  or  more  bundles  run  obliquely  cephalo-laterad — the  striae 
obliquae  (conductor  sonorus).  This  irregularity  of  the  acoustic  striae  has  led  to 
another  mode  of  division  of  the  "floor"  for  descriptive  purposes — each  side  to  be 
divided  into  a  median  and  a  lateral  area,  indicated  by  a  more  or  less  well-marked 
groove,  the  lateral  furrow  (sidcus  limitans),  connecting  the  superior  and  inferior 
(a/a  cinerea]  fovea?.  This  groove  probably  corresponds  to  one  of  the  interzonal 
sulci  of  the  embryonic  tube  and  in  a  gross  way  it  separates  the  motor  and  sensor 
fields  of  the  "floor."  The  median  area  is  usually  a  continuous  ridge  which  is 
quite  accentuated  in  the  cephalic  division  as  the  eminentia  abducentis,  while  caudad 
it  becomes  narrowed  as  it  approaches  the  closed  part  of  the  oblongata.  The  con- 
vergence of  the  median  and  lateral  furrows  at  the  caudal  apex  of  the  rhomboidal 
fossa  gives  the  appearance  of  the  point  of  an  ancient  writing  reed-  or  quill-pen ; 
hence  the  term  calamus  scriptorius. 

In  the  caudal  quarter-triangle  a  middle  area  is  occupied  by  an  elongated  tri- 
angular field  whose  depressed  apex  is  directed  frontad.  A  slight  oblique  ridge, 
the  funiculus  separans,  composed  chiefly  of  neuroglia,  separates  the  area  postrema 


880 


THE  NER  VE  SYSTEM 


caudad  from  the  ala  cinerea  or  trigonum  vagi  of  a  pronounced  grayish  color.  The 
apical  depression  has  been  termed  the  fovea  inferior.  Mesally  lies  a  narrow 

triangular  field  with  its  apex  directed  caudad  and  with  slightly  raised  surface 

the  trigonum  hypoglossi.  This  area  is  resolved  into  two  fields  by  a  single  or  double 
formation  of  oblique  rugae  affording  a  "feathered"  appearance  to  the  lateral  field, 
area  plumiformis.  Laterad  of  the  trigonum  vagi  lies  the  caudal  portion  of  the 
lateral  area  of  the  "floor,"  also  called  (in  part)  the  area  vestibularis  (area  acustica) 
and  crossed  over  its  middle  by  the  striae  acusticae  when  these  are  present.  The 
area  vestibularis  is  an  irregularly  triangular  raised  surface  with  its  convex  base 
toward  the  median  line,  and  extending  laterally  to  the  attachment  of  the  meta- 
tela  and  into  the  lateral  recess.  In  the  foetus  and  in  certain  lower  vertebrates 
the  area  is  more  prominent  and  is  designated  the  tuberculum  acusticum  s.  vestibu- 
laris. 


POST-GEMINUM 

N.IV 

STRIA    PONTIS 

N.  V 

LOCUS    CCERULEUS- 
FOVEA    MEOIANA 


FOVEA    TR 


I  / 

(GEMINI •/- — 


EMINENTIA 
ABDUCENTIS 


AREA  VESTIBULARIS 


STRI/E    ACUSTIOE 


N.   VIM 
N.    IX    AND    X 
EMINENTIA    HYPOGLOSSI 

NUCL.    INTERCALATUS  — 

FOVEA    VAGI 

LIGULA 

AREA    POSTREMA 

NUCL.   CUNEATUS 

OBEX 

NUCL.    GRACILIS 


AREA  NUCL. 
INCERTI 

AREA   N. 
TRIGEMINI 

AREA  N.   FACIALIS 
ET   ABDUCENTIS 
AREA   N. 

'VESTIBULARIS 
AREA  NUCL. 
FUNIC.  TERET. 

ARE*   N.    INTERCALATI 


AREA    N.   VAGI     ET 
GLOSSOPHARVNGEI 


TRACTUS    SOLITARIUS 


AREA    N.    HVPOGLOSSI 


FIG.  567.— Surface  markings  and  topography  of  the  principal  nuclei  of  the  floor  of  the  fourth  ventricle. 

(Modified  from  Streeter.) 

The  "frontal"  division  of  the  floor  or  triangular  quarter-field  is  marked  by  a 
depression  at  about  its  middle,  the  superior  fovea,  from  which  the  slight  "lateral 
furrow"  runs  caudad,  and  but  for  the  intervention  of  the  striae  would  reach  the 
inferior  fovea.  Cephalad  of  the  superior  fovea,  and  continuing  some  distance 
along  the  aqueduct,  is  the  locus  cceruleus,  which  owes  its  color  to  the  refraction 
of  the  pigmented  cells,  the  substantia  ferruginea,  by  the  milky-white  endyma.  At 
this  altitude,  the  medial  elevation  between  the  superior  fovea  and  the  median 
sulcus  is  accentuated  into  a  fairly  pronounced  eminence,  the  eminentia  abducentis 
(eminentia  teres},  overlying  the  nucleus  of  the  abducent  nerve  and  the  genu  of 
the  root  of  the  facial  nerve.  The  portion  of  the  median  sulcus  intervening  between 
the  eminentia  abducentia  is  correspondingly  depressed  to  form  the  fovea  mediana. 

The  ventricular  features  enumerated  above  correspond  in  a  crude  way  to  the 
deep  structures  of  the  pons-oblongata,  and  most  of  the  cranial  nerve  nuclei  are 
held  in  a  rhomboidal  frame  formed  by  the  pre-  and  postpeduncles.  The  surface- 
markings  are  only  imperfect  replicas  of  the  subjacent  structures :  the  various  cell- 


FOURTH  VENTRICLE  OF  THE  BRAIN  881 

nests  overlap  each  other  more  or  less  and  their  relations  can  best  be  studied  in 
the  projection  drawing  in  Fig.  567. 

Membranous  Portion  of  the  "  Roof  "  of  the  Fourth  Ventricle. — The  caudal 
extension  of  the  hypertrophied  cerebellum  hides  from  view  the  whole  of  the  rhom- 
boidal  fossa,  but  this  structure,  as  before  stated,  forms  but  a  part  of  the  actual  dorsal 
wall  or  "roof."  This  includes  the  converging  prepeduncles,  the  valvula  intervening 
between  these,  the  fastigium  of  the  cerebellum,  the  velum,  and  the  metatela. 

The  Velum  (velum  medidlareposterius}. — The  velum  is  a  thin  and  narrow  lamina 
of  white  substance,  continued  laterad  as  the  flocculi  of  the  cerebellum.  At  its  caudal 
edge,  i.  e.,  where  nerve-tissue  ceases,  the  endyma  or  ventricular  lining  epithelium 
and  the  pia  over  this  portion  coalesce  to  form  a  delicate  membrane — the  metatela 
— attached  along  the  caudo-lateral  boundary-line  of  the  rhomboidal  fossa.  Along 
this  attachment  there  is  another  intrusion  of  nerve  matter  between  the  endymal 
and  pial  layers;  this  reenforced  lamina  is  usually  termed  the  ligula  and  may  be 
traced  on  the  clava  and  cuneate  tubercle,  thence  laterad  over  the  restis  to  bound 
the  lateral  recess.  The  structure  is  probably  a  vestige  of  the  secondary  rhom- 
boidal lip  and  has  actually  been  found  to  be  a  part  of  the  ponto-bulbar  body 
referred  to  above.  Another  small  semilunar  lamina  of  nerve  tissue  bridges  the 
the  caudal  apex  of  the  fourth  ventricle  and  is  called  the  obex.  This  structure  is 
often  devoid  of  nerve  tissue  and  is  then  a  mere  membranous  lamina. 

Except  in  rare  instances,  the  metatela  is  perforated  a  short  distance  from  the 
calamus  region.  The  opening  is  of  variable  shape  and  size;  it  permits  of  com- 
munication between  the  ventricular  cavity  and  the  subarachnoid  space  and  is 
termed  the  metapore  (apertura  medialis  ventriculi  quarti}  or  foramen  of  Majendie. 

Similar  apertures  at  the  extremities  of  the  lateral  recesses,  and  called  the 
foramina  Luschkae  (apertura  lateralis  ventriculi  quarti}  also  permit  of  a  tidal  flow 
of  the  cerebro-spinal  fluid. 

The  metaplexuses  or  choroid  plexuses  of  the  fourth  ventricle  are  highly  vascular 
infoldings  of  the  metatela,  one  on  either  side  of  the,  median  plane,  from  each  of 
which  offshoots  extend  laterad  into  the  lateral  recesses.  As  the  choroid  plexuses 
of  the  brain  are  always  formed  by  infoldings  or  invaginations  of  the  membranous 
portions  of  the  brain-tube,  the  endymal  continuity  is  nowhere  interrupted. 

Internal  Structure  of  the  Postoblongata. — While  the  spinal  cord  remains  a 
closed  tube  with  centrally  situated  gray,  the  oblongata  opens  out  on  the  dorsal 
aspect  so  as  to  uncover  its  part  of  the  neural  canal  as  the  "floor"  of  the  fourth 
ventricle.  This  involves  a  tilting  of  the  functionally  differentiated  gray  segments 
and,  after  a  gradual  transition  in  the  post-oblongata,  the  motor  gray  is  to  be  sought 
nearest  the  middle  line,  the  mixed  gray  just  ectad,  while  the  sensor  is  the  outermost 
of  all.  Instead  of  the  ventral,  lateral,  and  dorsal  horns  of  each  half  of  the  spinal 
cord,  we  have  an  ental,  middle,  and  ectal  cornu  in  each  half  of  the  oblongata.  The 
positions  alone  have  changed ;  the  functional  relations  to  nerve-roots  having  corre- 
sponding functions  are  homologous.  Thus  the  motor  hypoglossal  nucleus  is 
placed  in  the  mesal  part  of  the  ventricular  floor,  while  the  terminal  nuclei  of  the 
afferent  vagus,  glosso-pharyngeal,  and  auditory  nerves  lie  in  the  lateral  part. 

Another  cardinal  change  in  the  internal  structure  of  the  oblongata,  accompany- 
ing the  preponderating  development  of  the  cerebrum  and  great  basal  ganglia, 
is  caused  by  interrupting  and  decussating  fibre  systems  which  seek  passage 
through  the  brain-stem  and  encroach  more  or  less  on  its  primitive  architecture. 
While  in  the  spinal  cord  there  is  a  perfect  continuity  of  the  central  tubular  gray, 
we  find  in  the  oblongata  more  pronounced  peninsular  and  isolated  insular  nuclei 
or  ganglionic  gray  masses. 

Pyramidal  Decussation  (decussatio  pyramidum). — An  important  change  in  the 
internal  structure  is  caused  by  the  passage  of  the  fibres  of  the  pyramidal  tract  as 
these  pass  to  the  same  and  opposite  sides  of  the  cord,  the  latter  category  forming 

56 


882 


THE  NER  VE  SYSTEM 


the  pyramidal  decussation.  In  consequence  of  this  passage  of  white  (crossed 
pyramidal)  fibres  through  its  substance  the  ventral  gray  horn  is  broken  up  into  a 
coarse  network,  while  one  portion  of  it,  the  caput  cornu,  is  entirely  separated  from 

the  rest;  only  a  small  portion  of 
the  base  of  the  cornu  remains 
intact  close  to  the  ventro-lateral 
aspect  of  the  central  canal.  The 
caput  cornu,  thus  separated,  is 
displaced  laterally,  and  comes  to 
lie  close  to  the  caput  cornu  dor- 
salis,  which  has  also  shifted  its 
position.  In  consequence  of  this 
breaking  up  of  the  greater  part 
of  the  ventral  gray  cornu  by  white 
fibres  a  coarse  network  is  formed 
in  the  anterior  and  lateral  areas 
of  the  medulla,  which  is  named 
the  formatio  reticularis. 

The  gliosa  (gelatinosa  Rolandi) 
of  the  dorsal  horn  is  continued 
into  the  oblongata,  but  becomes 
insignificant,  relatively,  in  the 
pre-oblongata.  The  spinal  root 
of  the  trigeminal  nerve  is  in  ectal 
relation  with  the  gliosa;  at  higher 
levels  the  spinal  root  of  the  ves- 
tibular  nerve  intervenes. 

Decussation  of  the  Lemnisci. — 
A  similar  change,  dorsad  and 
caphalad  of  the  pyramidal  de- 


PYRAMIDAL 
DECUSSATION 


CROSSED  PYRAMIDAL 
TRACT 


DIRECT  PYRAMIDAL 
TRACT 


FIG.  568. — Schema  of  the  pyramidal  decussation. 


cussation,  is  caused  by  the  decus- 
sation of  axone  bundles  arising  in  the  nuclei  of  the  gracile  and  cuneate  fasciculi 
(Goll  and  Burdach).  At  this  level  the  base  of  the  dorsal  gray  cornu  undergoes 
change  in  the  form  of  two  thick  dorsal  peninsular  outgrowths  which  form  the 


DORSO-MEDIAN 
FISSURE 


DORSO-MEDIAN 


DORSO- LATERAL 
COLUMN 


.CROSSED    PYRAM- 
IDAL TRACT 


VENTRAL. 
HORN 


VENTRALX 

VENTRO-MEDIAN 
FISSURE 

FIG.  569. — Transverse  section  of  the  oblongata  at  its 
lower  end.     (Testut.) 


NUCLEUS    GRACILIS 

SOR 
ROOTS 


HEAD  OF 
DORSAL 
HORN 
BASE  OF 
•VENTRAL 
HORN 
HEAD  OF 
VENTRAL 
HORN 


MOTOR 
ROOTS 


VENTRO-MEDIAN 
FISSURE 

FIG.  570. — Transverse  section  of  the  oblon- 
gata at  the  decussation  of  the  pyramids. 
(Testut,  after  Duval.) 


nuclei  of  termination  of  theaxones  in  the  gracile  and  cuneate  fasciculi;  externally 
these  gray  masses  produce  the  eminences  of  the  clava  and  cuneate  tubercle. 
The  axones  from  these  nuclei  stream  mesad  and  cephalad  in  a  series  of  con- 


FOURTH  VENTRICLE  OF  THE  BRAIN 


883 


centric  arches,  decussating  in  the  raphe*  with  the  bundles  of  the  opposite  side  to 
form  the  decussation  of  the  lemnisci1  or  sensor  decussation.  Cephalad  of  this 
decussation  the  lemnisci  are  two  bundles  of  fibres  coursing  on  either  side  of 


LATERAL 
LEMNISCUS 


TRAPEZIUM 


MEDIAL 
LEMNISCUS 


DECUSSATION 
OF    LEMNISCI' 


POSTGEMINUM 


NUCLEUS    OF 
LATERAL    LCMNISCUS 


VENTRAL 

COCHLEAR    NUCLEUS 

TERMINAL    NUCLEI 
OF    AFFERENT 
CRANIAL    NERVES 


NUCLEUS    OF 
F.    GRACILIS 


NUCLEUS    OF 
F.  CUNEATUS 


FIG.  571. — Diagram  showing  the  course  of  the  lemnisci  and  their  decussation, 


oftEVrUS  :        DOHSOMEDIAN    - 

&      ^ h^^r— s.ix- — ^^ J% 


•HEAD  OF  DORSAL  HORN 
BASE  OF  VENTRAL  HORN 
HEAD  OF  VENTRAL  HORN 


FIG.  572. — Transverse  section  of  the  oblongata  at  the  crossing  of  the  fillets.     (Testut.) 


the  raph^  between  the  olives,  and  just  dorsad  of  the  pyramids;  their  further  course 
toward  the  cerebrum  will  be  described  farther  on. 


1  Also  called  "  mesal  lemnisci  "  in  contradistinction  to  the  "  lateral  lemnisci  " — of  different  origin. 


884 


THE  NERVE  SYSTEM 


With  the  extension  of  the  central  gray  to  form  the  floor  of  the  fourth  ventricle, 
the  caput  cornu  dorsale  is  displaced  ectad  so  as  to  almost  reach  the  surface,  where 
it  forms  a  projection,  the  funiculus  lateralis  (Rolandi),  which  enlarges  caphalad 
into  a  distinct  prominence,  the  tuberculum  cinereum.  At  a  higher  level  the 
caput  is  separated  from  the  surface  by  the  spinal  root  of  the  trigeminal  nerve  and 
by  the  ectal  arcuate  fibres  (Fig.  575).  The  cervix  of  the  cornu  becomes  broken 


FLOOR    OF    FOURTH    VENTRICLE 


NUCLEUS    GRACIUS 
NUCLEUS    CUNEATUS 

BASE    OF   VENTRAL   HORN 
ROOT   OF  TRIFACIAL   CAPPING 
HEAD    OF    DORSAL    HORN       - 

VAGUS    NERVE 

HEAD  OF  VENTRAL  HORN 


HYPOGLOSSAL  NERVE 


LEMNISCUS     VENTRAL  PYRAMID 


FIG.  573. — Transverse  section  of  the  oblongata  at  the  lower  end  of  the  olives.     The  roof  of  the  fourth 
ventricle  is  not  represented.     (Testut,  after  Duval.) 

up  into  a  reticular  formation  by  the  decussating  fibres.  A  portion  of  the  base 
is  placed  ectad  of  the  nucleus  funiculi  cuneati  and  is  called  the  accessory  cuneate 
nucleus,  supposed  to  be  a  continuation  of  Clarke's  column. 

The  Formatio  Reticularis  (Fig.  575). — The  formatio  reticularis  consists  of  dif- 
fusely scattered  gray  substance  in  a.  meshwork  of  white  fibres.  It  is  far  more 
abundant  in  the  pre-  and  postoblongata  than  in  the  cord.  In  trans-sections  of  the 
postoblongata  it  is  seen  to  be  divided  by  the  hypoglossal  nerve-root  fascicles  into  a 


HYPOGLOSSAL 
NUCLEUS 


SENSORY  NUCLEUS 


NUCLEUS  CUNEATUS 

HEAD  OF  DORSAL  HORN 
ROOT  OF  TRIFACIAL  NERVE 

MOTOR  NUCLEUS  OF  MIXED 

NERVES 

ACCESSORY    HYPOGLOSSAL 
NUCLEUS 

OLIVE 


jHYPOGLOSSAL    NERVE 
VENTRAL 

LEMNISCUS'    VENTROMEOIAN    ARCIFORM 

FISSURE  NUCLEUS 

FIG.  574. — Transverse  section  of  the  oblongata  at  the  middle  of  the  olives.     The  roof  of  the  fourth 
ventricle  is  not  represented.      (Testut,  after  Duval.) 

mesal  and  a  lateral  field.  In  the  mesal  field  the  gray  substance  is  scanty  and  white 
fibres — principally  longitudinal  ones — preponderate;  this  is  called  the  formatio 
reticularis  alba  in  contradistinction  to  the  lateral  grayer  reticulated  field,  the  formatio 
reticularis  grisea.  Its  numerous  nerve-cells  mostly  possess  short  axones  and  for 
the  most  part  exercise  associative  functions  for  the  constantly  active  centres  of 
respiration  (nuclei  of  the  vagus,  phrenic,  facial,  etc.).  Certain  axones  of  longer 
course  are  collected  into  a  small  compact  bundle  just  ventrad  of  the  ventricular 


FOURTH  VENTRICLE  OF  THE  BRAIN 


885 


floor  and  central  canal  (and  aqueduct  in  the  mid-brain),  and  known  as  the  medial 
longitudinal  fasciculus  (posterior  longitudinal  bundle).  This  tract  is  in  intimate 
association  with  the  cranial  nerve  nuclei.  The  formatio  alba  is  principally  made 
up  of  this  tract  and  the  lemniscus  (interolivary  stratum). 

The  Raphe  (Fig.  575). — The  raphd  is  situated  in  the  middle  line  of  the  oblongata 
above  the  decussation  of  the  pyramids.  It  consists  of  nerve-fibres  intermingled 
with  nerve-cells.  The  fibres  have  different  directions,  which  can  only  be  seen  in 
suitable  microscopic  sections,  thus:  (1)  Some  run  dorso-ventrad ;  these  are  con- 
tinuous with  the  superficial  arciform  fibres.  (2)  Some  are  longitudinal;  these 
are  derived  from  the  arciform  fibres,  which  on  entering  the  raphe*  change  their 
direction  and  become  longitudinal.  (3)  Some  are  oblique;  these  are  continuous 
with  the  deep  arciform  fibres  which  pass  from  the  raphe. 

The  nerve-cells  of  the  raph^  are  multipolar;  some  are  connected  with  the  dorso- 
ventral  fibres,  others  with  the  superficial  arcuate  fibres. 

FOURTH  VENTRICLE.       NUCLEUS    INTERCALATU8         FASCICULUS    SOLITARIUS 

/AND    ITS    NUCLEUS 
DESCENDING    ROOT   VIII 


SUBST. 
GELATINOSA 


SPINAL    ROOT   OF 
TRIGEMINUS 


VAGUS    NERVE 

DORSAL)    ACCESSORY 

f  OLIVE 

MESAL     ' 


XT.  ARCUATE    FIBERS 


HYPOGLOSSAL    NERVE 


HILUM    OLIV/C 
ARCUATE    NUCLEUS 

FIG.  575. — Trans-section  of  the  postoblongata  at  about  the  middle  of  the  olive. 

The  Restis. — The  restis  succeeds  the  gracile  and  cuneate  nuclei  in  the  dorso- 
lateral  part  of  the  postoblongata.  Its  fibres  converge  from  various  sources  and 
ultimately  enter  the  cerebellum  as  its  postpeduncle.  For  a  description  of  these 
fibre  systems  see  the  section  on  the  "peduncles  of  the  cerebellum." 

The  Nucleus  of  the  Olive  or  Inferior  Olivary  Nucleus  (nucleus  olivarius  inferior) 
is  a  corrugated  lamina  of  gray  substance  whose  extent  nearly  corresponds  to  that 
of  the  external  elevation  called  the  olive.  It  can  be  compared  to  a  hollow  oval 
sac  or  purse,  slit  on  its  mesal  aspect  and  the  edges  of  the  slit  everted.  The  opening 
is  called  the  hilum.  Numerous  fibres  stream  into  the  interior  through  the  hilum, 
while  others  cut  through  the  lamina  to  join  the  fibre-arches  of  the  reticular  field  and 
there  passing  toward  the  restis. 

What  are  known  as  accessory  olivary  nuclei  (nucleii  olivarii  accessorii)  are  smaller 
detached  or  semidetached  portions  of  the  olivary  nucleus  named,  according  to 
their  position,  the  dorsal  and  medial  accessory  olivary  nuclei  (nucleus  olivarius 
accessorius  dorsalis  et  medialis).  The  root  fascicles  of  the  hypoglossal  nerve  pass 
between  the  medial  accessory  nucleus  and  the  chief  olivary  nucleus. 


886  THE  NER  VE  SYSTEM 

The  olivary  nuclei  play  an  important  part  as  relay  stations  in  cerebellar  connec- 
tions. A  considerable  mass  of  fibres,  the  olivo-cerebellar  fibres  (fibrae  cerebello- 
olivares),  originate  in  the  olivary  nucleus  of  one  side  to  enter  the  cerebellum 
along  the  restis  of  the  opposite  side.  A  much  lesser  number  of  fibres,  running 
contrariwise,  reach  the  olivary  nuclei  from  the  opposite  cerebellar  hemispheres — 
the  cerebello-olivary  (vestibulo-olivary  tract)  fibres.  The  olivary  nuclei  are  also 
the  termini  of  two  important  tracts:  (1)  the  spino-olivary  tract  or  Helweg's  bundle 
and  (2)  the  thalamo-olivary  tract. 

The  Arcuate  Fibre  Systems. — The  arcuate  fibre  systems  comprise  two  sets  of 
fibres  according  as  they  course  dorsad  or  ventrad  of  the  olivary  nuclei: 

1.  The  Ental  Arcuate  Fibres  comprise  the  olivo-cerebellar  fibres,  just  described, 
and  a  number  of  commissural  systems  for  the  association  of  the  tegmental  retic- 
ular  gray  ganglia  and  cranial-nerve  nuclei.     Others  pass  cerebralward,  others 
to  the  cerebellum. 

2.  The  FiCtal  Arcuate  Fibres  take  origin  (a)  from  the  gracile  and  cuneate  nuclei 
and  enter  the  restis  of  the  same  side;  (6)  from  the  same  nuclei  of  the  opposite  side, 
decussating  in  the  raphe  and  sweeping  ventrad  over  the  pyramid  and  olive,  form- 
ing a  thin  layer  over  them  and  ultimately  reaching  the  restis.     Many  of  these 
fibres  are  interrupted,  on   each   side,  in   the   nucleus   arcuatus,  a  thin,  isolated 
lamina  of  gray  matter  lying  on  the  ventral  aspect  of  the  pyramid. 

The  nucleus  lateralis  is  seen  in  the  lateral  column  (lower  part  of  oblongata)  as 
a  diffuse  gray  mass  lying  between  the  gliosa  and  the  olive;  it  gradually  disappears 
cephalad. 

The  nucleus  intercalatus  (of  Staderini  and  Van  Gehuchteri)  forms  the  elongated, 
wedge-shaped  elevation  in  the  medial  triangle  of  the  caudal  portion  of  the  ventric- 
ular floor  called  the  area  plumiformis  (p.  880) ;  the  nucleus  derives  its  name  from 
its  (intercalated)  position  between  the  hypoglossal  and  dorso-vagal  nuclei.  Its 
functional  connections  are  not  yet  precisely  known. 

A  nucleus  postremus  has  been  described  (J.  T.  Wilson)  as  lying  subjacent  to 
the  area  postrema. 

The  nucleus  funiculi  teretis  lies  close  to  the  median  sulcus  in  the  altitude  of  the 
acoustic  striae,  and  seems  to  bear  an  intimate  relation  to  these. 

Summary  of  the  Gray  Masses  in  the  Postoblongata: 

*  Central  tubular  gray  (in  "closed"  part). 

*  Gray  floor  of  fourth  ventricle  (in  "open"  part). 

*  Gliosa  (or  gelatinosa  Rolandi). 

*  Nucleus  funiculi  gracilis. 

*  Nucleus  funiculi  cuneatus. 

*  Nucleus  funiculi  cuneati  accessorius. 

*  Nucleus  lateralis. 

*  Nucleus  olivaris  inferior. 

*  Nucleus  olivaris  accessorius  dorsalis. 

*  Nucleus  olivaris  accessorius  medialis. 

*  Nucleus  arcuatus. 
Nucleus  nervi  hypoglossi. 

*  Nucleus  intercalatus. 

*  Nucleus  postremus. 
Nucleus  vagi  (alse  cinerese). 
Nucleus  vestibularis  (spinal  division). 

*  Nucleus  funiculi  teretis. 
Nucleus  ambiguus. 
Nucleus  tractus  solitarii. 

Nucleus  tractus  spinalis  n.  trigemini. 

*  Formatio  reticularis. 


INTERNAL  STRUCTURE  OF  THE  PONS  AND  PRE-OBLONGATA  887 

In  the  foregoing  enumeration  of  the  gray  masses  of  the  postoblongata,  those 
marked  with  an  asterisk  have  been  described  above;  the  remaining  structures 
relate  to  the  deep  connections  of  the  cranial  nerves  and  will  be  discussed  in  detail 
under  that  head. 

Internal  Structure  of  the  Pons  and  Pre-oblongata. — Trans-sections  of  the 
pons  also  pass  through  the  pre-oblongata  (or  tegmental  part  of  the  pons).  To 
consider  first  the  internal  structure  of  the  pons  proper  (or  pars  basilaris  pontis) : 
The  pons  is  composed  chiefly  of  (1)  transverse  fibres  arranged  in  coarse  bundles, 
(2)  longitudinal  fibres  gathered  in  compact  bundles,  and  (3)  diffusely  scattered 
masses  of  gray  substance  among  the  fibre  bundles,  the  nuclei  pontis. 

The  Transverse  Fibres. — The  transverse  fibres,  corresponding  to  the  large  size 
of  the  cerebellum,  are  more  abundant  in  man,  relatively,  than  in  any  other  animal. 
They  form  a  massive  series  of  bundles  coursing  ventrad  of  the  brain  axis  from  one 
cerebellar  hemisphere  to  the  other.  At  the  caudal  border  of  the  pons  they  embrace 
the  pyramidal  tracts  as  well,  but  farther  cephalad  the  transverse  pontile  fibres 
are  seen  to  intersect  the  pyramidal  tracts,  breaking  these  up  into  pyramidal 
fasciculi;  still  farther  cephalad  the  pyramidal  tracts  are  wholly  embedded  in 
the  mass  of  transverse  pontile  fibres  so  that  these  in  turn,  with  reference  to 
the  location  of  the  pyramidal  tracts,  may  be  divided  into  a  superficial  and  a  deep 
set.  Laterad  they  are  gathered  together  to  form  the  medipeduncles  (described 
on  p.  901). 

The  Longitudinal  Fibres. — The  longitudinal  fibres  consist  chiefly  of  the  pyramidal 
tracts,  which  are  solid  strands  at  their  entrance  to  and  exit  from  the  pons,  but  are 
broken  up  into  lesser  bundles  at  its  middle.  A  certain  number  of  the  pyramidal 
fibres,  as  well  as  other  cerebro-pontile  fibre-tracts,  terminate  in  relation  with  the 
cells  of  the  nuclei  pontis,  as  well  as  certain  of  the  efferent  cranial-nerve  nuclei. 
This  fact  accounts  for  the  demonstrable  diminution  in  bulk  of  the  pyramidal 
tract  in  its  course  through  the  pons. 

The  Nuclei  Pontis. — The  nuclei  pontis  are  small  aggregations  of  gray  substance 
(which  in  serial  sections  show  them  to  be  continuations  of  the  arcuate  nuclei) 
diffusely  scattered  among  the  fibre-systems  of  the  pons  proper.  They  are 
intercalated  in  the  course  (1)  of  tracts  passing  from  one  cerebellar  hemisphere 
to  the  other  and  (2)  of  descending  cerebro-pontile  tracts.  The  cells  of  the  pontile 
nuclei  send  their  axones  chiefly  to  the  opposite  cerebellar  hemisphere  and  plav 
an  important  part  as  links  in  the  complex  chain  of  the  neurone  systems  which 
make  the  cerebellum  such  an  important  organ  of  senso-motor  coordination. 

In  the  contact-zone  of  pons  proper  and  the  pre-oblongata  (or  pontile  tegmentum) 
lies  a  group  of  transversely  decussating  fibres  with  interspersed  gray  masses  with 
large  cells  called  the  trapezium.  This  body  will  be  more  fully  described  in  con- 
nection with  the  central  auditory  paths. 

The  Pre-oblongata. — The  pre-oblongata  (or  tegmental  part  of  the  pons)  is  of  much 
smaller  bulk  than  the  pons  proper,  as  seen  on  trans-sections.  On  the  dorsal  sur- 
face is  spread  a  layer  of  gray  substance,  covered  by  endyma,  which  forms  the  floor 
of  the  cephalic  part  of  the  fourth  ventricle.  Beneath  this  gray  substance  lies  the 
formatio  reticularis  divided  into  symmetrical  halves  by  the  raphe" — continued  from 
the  postoblongata.  Embedded  in  the  formatio  reticularis  are  various  isolated 
masses  of  gray  substance  and  various  more  or  less  compact  fibre-tracts.  Among 
the  gray  masses  are  several  of  the  cranial-nerve  nuclei,  to  be  described  in  a  separate 
section,  and  the  following: 

The  Superior  Olivary  Nucleus  (nucleus  olivarius  superior]  is  a  small  gray  mass 
or  aggregation  of  several  smaller  masses  situated  laterad  of  the  trapezium,  inter- 
calated in  the  path  of  the  trapezial  fibres  and  forming  a  link  in  the  central  acoustic 
chain  (Fig.  579). 


888  THE  NERVE  SYSTEM 

The  Nucleus  Incertus  (Streeter)  is  an  aggregation  of  gray  substance  in  the  floor  of 
the  fourth  ventricle  near  the  median  sulcus  and  forming  a  slight,  rounded  elevation 
which  extends  to  the  aqueduct.  Its  functional  relations  are  unknown. 

Fibre-tracts  in  the  Pre-oblongata. — Among  the  fibre-tracts  in  the  pre-oblon- 
gata  the  chief  ones  are  (1)  the  medial  lemnisci,  (2)  the  lateral  lemnisci,  (3)  the 
medial  longitudinal  bundle,  and  (4)  the  prepeduncles  of  the  cerebellum. 

The  Medial  Lemniscus. — Each  medial  lemniscus,  in  its  passage  through  the 
pre-oblongata,  is  gathered  into  a  compact,  ribbon-like  bundle  along  the  contact- 
zone  of  the  tegmentum  and  pons  proper,  latero-ventrad  of  the  trapezium,  some 
fibres  of  which  traverse  it  on  their  way  toward  the  raphe".  The  medial  lemniscus 
has  been  described  in  the  postoblongata  as  occupying  the  field  between  raphe  and 
inferior  olivary  nucleus  (the  interolivary  stratum) ;  in  its  ascent  the  medial  lemniscus 
gradually  trends  laterad  so  that  it  almost  reaches  the  surface  (Figs.  571  and  573). 

The  Lateral  Lemniscus. — The  lateral  lemniscus  is  a  constituent  of  the  central 
auditory  path  and  will  be  described  more  fully  in  the  sequel.  In  trans-sections 
above  the  level  of  the  trigeminal  nuclei  the  lateral  lemniscus  is  seen  as  a  flattened 
band  spreading  over  the  surface  (externally  the  trigonum  lemnisci)  ectad  of  the 
prepeduncle.  Its  fibres  are  interrupted  by  an  intercalated  nucleus  of  the  lateral 
lemniscus. 

The  Medial  Longitudinal  Bundle  (posterior  longitudinal  bundle). — The  medial 
longitudinal  bundle  maintains  its  position  just  ventrad  of  the  central  gray,  close 
to  the  raphe. 

The  Cerebellar  Prepeduncle. — The  cerebellar  prepeduncle,  in  trans-sections,  is 
seen  to  be  a  very  compact  bundle  of  crescentic  outline  with  the  concavity  turned 
toward  the  ventricular  cavity.  Its  dorsi-mesal  edge  is  joined  to  the  valvula; 
its  ventral  border  is  sunk  into  the  tegmentum  and  in  its  ascent  it  becomes  sub- 
merged laterally  beneath  the  lateral  lemniscus,  dorsally  beneath  the  quadrigeminal 
plate  of  the  mid-brain. 

Summary  of  the  Gray  Masses  in  the  Pre-oblongata: 
Nucleus  of  Abducent  Nerve. 
Nucleus  of  Facial  Nerve. 

Afferent  and  Efferent  Nucleus  of  Trigeminal  Nerve. 
Nucleus  of  Spinal  Root  of  Trigeminal  Nerve. 

f  Dorsal  Nucleus. 
fCochlear  Division    {  Ventral  Nucieus. 

Nuclei  of  Acoustic  Nerve  "j  (  Medial  Nucleus. 

^Vestibular  Division^  Lateral  Nucleus. 
(  Superior  Nucleus. 

*  Superior  Olivary  Nucleus. 
Nucleus  of  Trapezium. 

*  Reticular  Ganglionic  Formation. 

*  Nucleus  Incertus. 

*  Nucleus  of  Lateral  Lemniscus. 

Those  marked  with  an  asterisk  have  already  been  described;  the  remaining 
structures  relate  to  the  deep  connections  of  several  cranial  nerves  to  be  described 
in  the  succeeding  section. 

Central  Connections  of  the  Cranial  Nerves  attached  to  the  Hind-brain.— 
Eight  of  the  twelve  pairs  of  cranial  nerves  are  attached  to  the  hind-brain  portion 
of  the  central  axis.  Their  superficial  or  apparent  origin  and  the  cranial  fora- 
mina of  exit  are  enumerated  in  the  table  on  page  889.  In  coordination  with 
the  internal  descriptive  anatomy  of  the  hind-brain  the  central  connections  of 
these  eight  cranial  nerves  must  now  be  considered.  They  comprise : 


CENTRAL   CONNECTIONS  OF  THE  CRANIAL  NERVES 


Purely  efferent  or  motor 
nerves. 


Mixed  nerves. 


Purely  afferent  or  sensor 
nerve. 


[     XII.  Hypoglossal  nerve. 
XI.  Accessory  nerve. 


VII.  Facial  nerve  (proper). 

VI.  Abducent  nerve. 

X.  Vagus  nerve. 

IX.  Glosso-pharyngeal  nerve. 

V.  Trigeminal  nerve. 

VIII.  Acoustic  nerve. 


Motor  to  muscles  of  tongue. 

(a)  Motor    accessory     to     vagus 

nerve; 

(b)  Motor  to  trapezius  and  sterno- 

mastoid  muscles. 
Motor  to   muscles   of   scalp   and 

face. 
Motor   to  external  rectus  muscle 

of  eyeball. 

Senso-motor  to  respiratory  tract 
and  upper  part  of  alimentary 
tract. 

Sensor  to  tongue  (and  motor  ?) 
to  Stylo-pharyngeus  muscle. 

Sensor  to  face,  tongue,  teeth; 
motor  to  muscles  of  mastica- 
tion. 

(a)  Cochlear  division  for  hearing 
(6)  Vestibular    division  for  equi- 
librium 


Another  nerve  which  pursues  a  remarkably  aberrant  course,  becoming  asso- 
ciated with  three  of  the  above-mentioned  cranial  nerves,  is  the  nervus  intermedius, 
known  peripherally  as  the  chorda  tympani.  It  is  chiefly  sensor  (taste)  in  function, 
but  also  contains  efferent  fibres  which  are  excito-glandular  for  the  submaxillary 
and  sublingual  salivary  glands. 

In  the  hind-brain  axis  lie  certain  gray  masses  which  are  functionally  homol- 
ogous with  the  nuclear  masses  in  the  different  parts  of  the  spinal  central  gray. 
These  defined  nests  of  nerve-elements,  from  their  relations  to  the  cranial-nerve 
roots,  are  called  the  cranial-nerve  nuclei  or  nidi.  Their  analogy  to  the  origins  of 
the  spinal  nerves  extends  to  the  shape  and  character  of  their  cell-elements  and 
their  differentiation  into  (a)  nuclei  of  origin  and  (6)  nuclei  of  termination  or  recipient 
nuclei. 

The  Nuclei  of  Origin. — Nuclei  of  origin  or  motor  nuclei  are  cell-clusters  from 
which  arise  the  axones  of  efferent  nerves  or  the  efferent  components  of  the  mixed 
nerves.  Some  of  these  nuclei  are  in  line  with  the  basal  portion  of  the  ventral 
gray  horn  in  the  cord  below  and  are  termed,  owing  to  their  situation  near  the  mesal 
plane,  the  medial  nuclei  of  origin.  Other  nuclei  are  isolated  cell-columns  in  the 
line  of  the  caput  cornu  ventrale  detached  by  the  decussation  of  the  pyramids, 
termed,  from  their  position  in  the  tegmental  substance,  the  lateral  nuclei  of  origin. 
The  different  nuclei  of  origin  of  the  efferent  cranial  nerves  are  under  the  domi- 
nance of  the  cerebral  cortex  by  way  of  the  cortico-tegmental  (or  cortico-bulbar) 
path — usually  included  in  the  pyramidal  tract. 

The  Nuclei  of  Termination. — The  nuclei  of  termination  or  sensor  cranial-nerve 
nidi  are  likewise  repetitions  in  structure  of  the  dorsal  horn  of  the  spinal  gray,  but 
with  less  regularity  and  definiteness  of  position.  Thus,  while  the  caput  gliosum 
of  the  cord  is  continuous  with  the  nucleus  of  the  spinal  root  of  the  trigeminal 
nerve,  other  recipient  or  afferent  nuclei  are  more  or  less  isolated  in  the  tegmental 
substance,  while  the  two  (lateral  and  ventral)  nuclei  of  the  cochlear  nerve  actually 
lie  on  the  surface  of  the  brain-stem. 

The  afferent  impulses  carried  in  by  the  sensor  cranial  nerves  excite  impulses 
in  the  neurones  of  the  nuclei  of  termination;  their  axones  enter  the  tegmental 
substance  as  arcuate  fibres,  cross  the  mesal  plane  to  join  the  lemnisci  to  connect 
with  the  thalamus  and  postgeminum  and  via  thalamus  and  postgeminum  with 
the  cerebral  cortex. 

The  location  of  the  various  cranial  nerve  nuclei  in  the  brain-stem  may  be  under- 
stood by  a  reference  to  the  diagrams  in  Figs.  567,  576,  577,  and  578. 

Hypoglossal  Nerve. — The  nucleus  of  origin  of  the  hypoglossal  nerve  is  a  rod- 
like  cell-column  close  to  the  mesal  plane,  extending  for  about  7  mm.  in  the  caudal 


890 


THE  NERVE  SYSTEM 


portion  of  the  fourth  ventricle,  while  its  extraventricular  portion  extends  about 
5  mm.  caudad  of  the  tip  of  the  calamus.  Its  efferent  axones  course  ventrad 
between  the  formatio  reticularis  alba  and  grisea,  thence  between  the  olivary  and 
medial  accessory  olivary  nuclei,  to  emerge  between  pyramid  and  olive.  None 
of  the  fibres  decussate  across  the  middle  line,  but  the  nuclei  are  coordinated  by 

commissural  fibres.  Axones  from 
cortical  cells  (ventral  third  of  pre- 
central  gyre)  terminate  in  relation 
with  the  cells  of  the  hypoglossal 
nucleus. 

The  hypoglossal  nucleus  permits 
of  subdivision  into  groups:  (a)  a 
medial  and  (6)  a  lateral  sub-group. 
The  lateral  group  innervates  the 
palatoglossus  and  pharyngoglossus, 
while  the  medial  nuclear  group  in- 
nervates the  remainder  of  the  tongue 
muscles  (lingualis  transversus  and  in- 
ferior, genioglossus  and  hyoglossus) . 
The  Accessory  Nerve. — The  acces- 
sory nerve  is  also  a  purely  motor 
or  efferent  nerve  whose  axones  arise 
from  an  attenuated  nucleus,  with 
large  multipolar  cells,  in  direct  con- 
tinuation with  the  nucleus  ambiguus 
cephalad,  and  with  the  dorso-lateral 
cell-column  of  the  ventral  horn  of 
the  upper  five  or  six  segments  of  the 
cord.  The  oblongatal  portion  of  the 
nucleus,  giving  rise  to  the  enceph- 
alic root  of  the  accessory  nerve,  may 
also  be  termed  the  nidus  laryngei,  for 
its  axones  join  the  vagus  Jierve  to 
innervate  the  laryngeal  muscles  (in 
contradistinction  to  the  nidus  pharyn- 
gei  or  nucleus  ambiguus,  whose  axones 
join  the  vagus  and  glosso-pharyngeal 
to  be  distributed  to  the  pharynx). 
The  axones  from  the  spinal  nucleus 
are  distributed  to  the  Trapezius  and 
Stern o-mastoid  muscles. 

The  nucleus  of  the  accessory  nerve 
is  likewise  under  the  dominion  of  the 
cerebral  cortex  by  way  of  the  pyra- 
midal tract,  and  a  reflex  arc  is  completed  by  afferent  axones  from  the  dorsal 
roots  of  the  spinal  nerves. 

The  Vagus  and  Glosso-pharyngeal  Nuclei  are  usually  considered  in  their  aggregate, 
justified  not  only  by  their  similarity  in  origin  and  central  connections,  but  also 
by  the  uncertainty  which  prevails  regarding  their  peripheral  interlacement  and 
complex  terminations.  Both  nerves  are  in  greater  part  afferent,  but  also  contain 
efferent  axones. 

1.  Afferent  Portions. — The  afferent  axones  of  the  vagus  arise  from  the  cells  in  the 
jugular  ganglion  and  ganglion  nodosum  (ganglion  of  the  trunk) ;  the  afferent  axones 
of  the  glosso-pharyngeal  arise  from  the  cells  in  its  ganglion  superius  and  ganglion 


NUCLEUS  AMBIGUUS 


FIG.  576. — The  cranial  nerve  nuclei  schematically  rep- 
resented in  a  supposedly  transparent  brain-stem,  dorsal 
view.  Motor  nuclei  in  red;  primary  terminal  nuclei  of 
afferent  (sensor)  nerves  in  blue.  (Optic  and  olfactory 
centres  are  omitted.) 


CENTRAL  CONNECTIONS  OF  THE  CRANIAL  NERVES 


891 


petrosum.  The  root-fascicles  of  both  nerves  enter  the  oblongata  along  its  dorso- 
lateral  groove  and  the  axones  then  undergo  bifurcation  into  ascending  and  de- 
scending rami,  similar  to  those  of  the  dorsal  roots  of  the  spinal  nerves.  The 
ascending  rami  end  in  the  nucleus  alae  cinerese  (nucleus  vagi  et  glossopharyngei] ; 
the  descending  rami  collect  to  form  a  compact  bundle  called  the  tractus  solitarius 
or  trineural  fasciculus,1  and  terminating  in  a  gray  cell-column  called  the  nucleus 
of  the  solitary  tract2 — a  caudal  prolongation  of  the  nucleus  alse  cinerese.  Both  tract 
and  nucleus  become  attenuated  caudad,  to  disappear  in  the  fourth  cervical  seg- 
ment (relation  with  phrenic  nerve  nucleus),  while  cephalad  it  has  been  traced  as 
far  as  the  region  of  the  locus  cceruleus  (relation  with  trigeminal  nerve  nuclei?). 


CERVICAL  NERVES 


FIG.  577. — Nuclei  of  origin  of  the  cranial  motor' nerves  schematically  represented  in  a  supposedly 
transparent  brain-stem,  lateral  view. 

From  the  cells  of  the  nucleus  alse  cinerese  and  nucleus  tractus  solitarii  axones 
pass  across  the  raph^  to  the  contralateral  interolivary  stratum  to  join  the  medial 
lemniscus,  establishing  connections  with  the  thalamus  and  cortex;  other  axones 
join  the  tractus  nucleo-cerebellaris. 

2.  Efferent  Portions. — The  efferent  components  of  the  vagus  and  glosso-pharyn- 
geal  nerves  come  from  two  sources:  (a)  the  dorsal  efferent  (vagal)  nucleus  and 
(6)  the  nucleus  ambiguus. 

The  dorsal  efferent  nucleus  lies  ventro-mesad  of  the  principal  nucleus  alse  cinerese 
and  laterad  of  the  hypoglossal  nucleus.  The  axones  from  its  cells  pass  obliquely 
ventro-laterad  to  enter  the  root-fascicles  of  the  vagus  and  to  become  distributed  to 

'There  are  other  "solitary"  fasciculi  in  the  nervous  system,  and  the  name  "trineural  fasciculus"  aptly 
characterizes  a  tract  which  has  for  its  object  that  mutual  interchange  of  functions  among  the  central  nuclei 
of  the  accessory,  vagus,  and  glosso-pharyngeal  nerves. 

2  The  nucleus  of  the  solitary  tract  lies  to  the  mesal  side  of  the  tract.  Another  nucleus  has  been  described 
by  Mellus,  lying  laterad  of  the  tract. 


892 


THE  NERVE  SYSTEM 


the  oesophagus,  stomach,  trachea,  and  bronchi.  Whether  the  glosso-pharyngea) 
nerve  receives  efferent  axones  or  not  is  still  in  debate. 

The  nucleus  ambiguus  (nidus  pharyngei)  is  a  rod-like  mass  of  large,  multipolai 
cells  seen,  in  trans-sections,  lying  in  the  gray,  reticular  formation  midway  between 
olive  and  trineural  fasciculus.  The  axones  arising  from  its  qells  run  dorsi- 
mesad  at  first,  then  turn  abruptly  ectad  to  join  the  vagus  (and  glosso-pharyngeal  ?) 
nerve-root  fascicles,  becoming  distributed  to  the  pharyngeal  muscles,  oesophagus, 
crico-thyroid  and  laryngeal  muscles. 

The  Acoustic  Nerve. — The  acoustic  nerve  consists  of  a  cochlear  and  a  vestibular 
division;  the  former  is  concerned  with  the  sense  of  hearing,  the  latter  with  the 
sense  of  equilibrium. 


FIG.  578. — Primary  terminal  nuclei  of  the  afferent  (sensor)  cranial    nerves  schematically  represented  in  a 
supposedly  transparent  brain-stem,  lateral  view.     The  optic  and  olfactory  centres  are  omitted. 

1.  The  Cochlear  or  true  auditory  nerve  arises  in  the  bipolar  cells  of  the  cochlear 
spiral  ganglion;  its  axones  terminate  in  (a) the  dorsal  nucleus  (tuberculum  acusticum), 
a  pyriform  mass  on  the  dorso-lateral  aspect  of  the  restis,  and  (b)  the  ventral  nucleus, 
somewhat  detached  from  the  former. 

From  the  dorsal  nucleus  cells  arise  the  axones  which  compose  the  striae  acusticae, 
myelinic  fibre-bundles  traversing  the  ventricular  surface  to  near  the  median 
sulcus,  dipping  into  the  tegmental  substance,  crossing  to  the  opposite  side  in  the 
raphe,  and  eventually  joining  the  lateral  lemniscus  to  end  in  the  postgeminum 
and  postgeniculum. 

From  the  ventral  nucleus  cells  arise  the  axones  which  course  transversely  to  form 
the  trapezium  at  the  contact-zone  of  the  pons  proper  and  tegmentum.  Additional 
axones  from  cells  in  the  superior  olives  of  both  sides  and  in  the  trapezium  itself 
increase  the  bulk  of  this  tract;  some  of  the  primary  axones  end  in  relation  with 


CENTRAL  CONNECTIONS  OF  THE  CRANIAL  NERVES 


893 


these  cells.  These  axone-groups  form  the  contralateral  lemniscus  lateralis,  which 
contains  the  intercalated  nucleus  of  the  lateral  lemniscus  as  a  relay  station,  to  be 
continued  to  the  postgeminum  and  postgeniculum  and  thence  to  the  cortical 
auditory  "centre"  in  the  supertemporal  gyre. 

2.  The  Vestibular  Nerve  axones  arise  in  the  bipolar  vestibular  ganglion  cells 
(G.  of  Scarpa),  enter  the  brain-stem,  and  bifurcate  into  ascending  and  descending 
rami,  which  terminate  as  follows:  The  ascending  rami  end  in  the  medial  nucleus 
(Schwalbe's) ;  the  descending  rami  end  in  the  spinal  vestibular  nucleus,  which  extends 
down  to  the  gracile  and  cuneate  nuclear  level;  another  group  of  axones  ends  in 
the  lateral  nucleus  (nucleus  magnocellularis)  (Deiters5);  while  a  fourth  and  last 
group  ends  in  the  superior  nucleus  (Bechterew's).  From  the  cells  of  all  these  nuclei 
of  termination  axones  proceed  toward  the  cortex,  dentatum,  and  fastigatum  of  the 
cerebellum,  as  part  of  the  nucleo-cerebellar  tract,  to  the  nuclei  of  the  abducent, 
trochlear,  trigeminal,  and  oculomotor  nerves  by  collaterals  from  axones  in  the 


PREGCMINUM 


LATERAL 
LEMNISCUS 


CORTEX 
CORTICAL  TRACT 


POST-GEMINUM 


COCHLEAR, 
NERVE 


DORSA 
NUCLEUS 
S 


LATERAL 

LEMNISCUS 


RAPHE 

FIG.  579. — Diagram  of  the  central  auditory  tract  (system  of  the  second  order). 

medial  longitudinal  bundle,  to  the  thalamus,  and  to  the  ventral-horn  nuclei  of 
the  spinal  cord  along  the  tractus  vestibulospinalis.  The  far-reaching  and 
complex  connections  of  the  vestibular  nerve  with  the  cerebellum  and  the 
centres  for  eye-muscles  and  the  spinal  centres  for  bodily  movements  make  this 
cranial  nerve  a  most  interesting  subject  for  the  active  research  now  going  on. 

The  Facial  Nerve. — The  facial  nerve  proper  is  to  be  distinguished  from  its 
socalled  sensor  root,  or  pars  intermedia,  or  nervus  intermedius. 

The  axones  of  the  efferent  facial  nerve  arise  from  cells  forming  the  facial  nucleus 
in  the  ventro-lateral  region  of  the  reticular  formation,  in  line  with  the  nucleus 
ambiguus  or  nidus  pharyngei,  a  little  over  4  mm.  from  the  ventricular  floor.  These 
axones  converge  toward  the  ventricular  floor  to  form  a  compact  bundle  which 
curves  over  the  abducens  nucleus  from  behind  (caudad),  overlying  it  like  a  horse- 
shoe over  a  ball  (genu  facialis  internum);  not  as  a  straight  but  as  a  bent  horseshoe, 
bent  so  that  its  cephalic  branch  is  directed  more  laterad  than  its  caudal  branch. 


894  THE  NERVE  SYSTEM 

After  having  encircled  the  abducens  nucleus,  the  facial  root  passes  ventro-laterad, 
passing  its  own  nucleus  ectad,  and  emerging  in  the  postpontile  groove  (recessus 
facialis). 

Pyramidal  fibres  from  the  precentral  cortex  place  this  nucleus  under  the  in- 
fluence of  the  will;  it  also  receives  fibres  from  the  trigeminal  and  acoustic  central 
systems. 

The  nervus  intermedius  is  a  mixed  nerve,  containing  afferent  (taste)  fibres  and 
efferent  (excito-glandular  or  secretory)  fibres.  With  respect  to  its  afferent  com- 
ponent it  may  be  regarded  as  an  aberrant  portion  of  the  glosso-pharyngeal  nerve. 

1.  Afferent  Portion. — These  axones  arise,  from  the  cells  of  the  geniculate  ganglion, 
implanted  upon  the  genu  facialis  externum,  and  terminate  in  a  nuclear  extension 
cephalad  of  the  nucleus  tractus  solitaxii.     They  probably  convey  gustatory  sense 
impulses  from  the  tip  of  the  tongue  and  the  pillars  of  the  soft  palate. 

2.  Efferent  Portion. — A  nucleus  of  origin  for  the  excito-glandular  elements  has 
been  described  as  a  group  of  cells  extending  beneath  the  ventricular  floor  from 
the  level  of  the  facial  nucleus  to  that  of  the  motor  trigeminal  nerve,  close  to  the 
raphe",  and  called  the  nucleus  salivatorius. 

Peripherally  we  shall  study  this  nerve  as  the  chorda  tympani.  The  mixed  nature 
of  the  nervus  intermedius  and  of  the  geniculate  ganglion  makes  it  probable  that 
they  combine  the  elements  of  a  sympathetic  and  a  spinal  ganglion;  the  nerve,  at 
least,  contains  both  vegetative  and  sensorial  elements. 

The  Abducent  Nerve. — The  abducent  nerve  is  a  small  motor  nerve  supplying 
the  External  Rectus  muscle  of  the  eyeball.  Its  nucleus  of  origin,  with  large,  multi- 
polar  cells,  lies  close  to  the  median  plane  beneath  the  eminentia  abducentis.  The 
axones  from  these  cells  pass  ventrad  through  the  tegmentum  and  trapezium,  and 
laterad  of  the  pyramidal  tract,  to  emerge  in  the  postpontile  groove.  The  nuclei 
are  brought  under  the  dominion  of  the  cerebral  cortex  by  pyramidal  fibres  of 
the  opposite  side.  They  are  likewise  brought  into  intimate  relation  with  the 
trigeminal,  acoustic,  and  opposite  oculomotor  nerve  nuclei. 

The  Trigeminal  Nerve. — The  trigeminal  is  relatively  enormous  and  has  corre- 
spondingly extensive  central  connections,  including  nuclei  in  the  mid-brain, 
pre-  and  post-oblongata,  and  spinal  cord.  It  is  a  mixed  senso-motor  nerve  and 
the  afferent  and  efferent  divisions  must  be  considered  separately. 

1.  Afferent  Portion. — The  axones  of  the  afferent  or  sensor  root  arise  in  the  cells 
of  the  large  semiiunar  (Gasserian)  ganglion.     As  in  the  dorsal  roots  of  the  spinal 
nerves,  these  axones  bifurcate,  on  entering  the  brain-axis,  into  ascending  and 
descending  rami.     These  terminate  in  a  cephalic  nuclear  extension  of  the  caput 
gliosum  of  the  cord;  the  ascending  rami  terminate  in  the  so-called  sensor  nucleus 
of  the  trigeminus,  the  descending  rami  in  the  nucleus  of  the  spinal  tract  of  the 
trigeminus,  which  extends  as  far  as  the  second  cervical  segment  of  the  cord.     The 
sensor  nucleus,  at  the  level  of  the  entrance  of  the  nerve,  is  quite  massive,  becoming 
attenuated  cephalad.     The  spinal  tract,  in  its  descent,  likewise  decreases  rapidly 
as  it  gives  off  its  terminal  axones  to  the  nucleus  of  the  tract.     The  cells  of  these 
terminal  nuclei  send  out  axones  which  cross  the  median  plane,  giving  off  col- 
laterals to  the  facial  nucleus,  to  join  the  medial  lemniscus  to  reach  the  thalamus, 
and,  via  thalamus,  the  somsesthetic  cerebral  cortex.     Other  axones  are  distributed 
(a)  to  the  motor  or  efferent  nucleus  of  the  trigeminus  and  (6)  to  the  motor  or 
efferent  cranial-nerve  nuclei 

2.  Efferent  Portion. — The  efferent  or  motor  component  of  the  trigeminal  nerve 
consists  of  axones  arising  from  cells  in  two  nidi:  (a)  the  principal  nucleus  in  the 
dorso-lateral  part  of  the  pre-oblongatal  tegmentum,  dorso-mesad  of  the  sensor 
nucleus;  (6)  a  small,  slender,  so-called  mesencephalic  root-nucleus  (nucleus  radicis 
descendentis  nervi  trigemini)  extending  cephalad  of  the  region  of  the  locus  coeru- 
leus  to  lie  along  the  aqueduct  in  the  mid-brain.     The  fibres  from  the  principal 


THE  CEREBELLUM 


895 


nucleus  supply  the  muscles  of  mastication.  The  distribution  of  the  fibres  from 
the  mesencephalic  root  is  not  precisely  known.  Kolliker  suggests  that  they  may 
supply  the  Tensor  veli  palatini,  Tensor  tympani,  Mylo-hyoid  and  anterior  belly  of 
the  Digastric. 

Like  other  motor  nuclei,  these  efferent  divisions  of  the  trigeminus  are  under  the 
dominion  of  the  cerebral  cortex  via  pyramidal  fibres. 

The  Cerebellum. — The  cerebellum  occupies  the  greater  part  of  the  posterior 
or  cerebellar  part  of  the  skull  and  is  the  largest  portion  of  the  hind-brain.  It  is 
overlapped  by  the  occipital  lobes  of  the  cerebrum,  being  separated  from  these  by 
the  tentorium.  It  lies  dorsad  of  the  pons-oblongata  and  partly  embraces  this 
portion  of  the  brain-stem.  It  is  composed  of  a  white  central  core  with  scattered 
gray  masses,  and  a  surface  layer  of  gray  substance  that  is  of  darker  hue  than  the 
cerebral  cortex. 

The  cerebellum  is  convoluted  on  a  plan  entirely  different  from  that  of  the  cere- 
brum. Each  primary  fold  is  folded  by  secondary  and  these  in  turn  by  tertiary 
folds,  so  that  on  sagittal  section  a  cypress-leaf  appearance  is  noted,  the  arbor 
vitae  cerebelli.  The  interior  or  medullary  white  substance  follows  all  these 
branchings  and  sub-branchings,  forming  a  skeleton  of  the  minute  folds  which  are 
called  folia.  These  folia  are  demarcated  on  the  surface  by  numerous  curved 
and  more  or  less  parallel  fissures  of  various  depths. 


Ala  lobuli  centralis.     Post-central        Pre-clival  fissure. 
Lobulus  centralis. 


Great 

horizontal 

Jissure. 


-clival  Jissure. 


FIG.  580. — Upper  surface  of  the  cerebellum.     (Schiifer.) 

The  cerebellum  is  connected  to  the  brain-stem  by  three  pairs  of  peduncles  and 
by  vestigial  portions  of  the  primitive  dorsal  wall  of  the  brain-tube.  Among  the 
latter  the  medullary  vela  or  laminae  are  most  important;  they  are  the  valvula 
(superior  medullary  velum)  and  the  velum  (inferior  medullary  velum),  which  enter 
into  the  formation  of  the  "roof"  of  the  fourth  ventricle. 

The  rounded  margin  of  the  cerebellum  demarcates  two  surfaces  looking 
respectively  "upward"  and  "downward,"  or  cephalic  and  caudal  surfaces.  Both 
are  convex,  the  inferior  or  caudal  surface  more  so  than  the  upper  or  cephalic. 
The  inferior  surface  shows  a  deep  median  depression,  the  vallecula,  into  which 
the  oblongata  is  sunk.  The  ventral  margin  is  widely  notched  to  partly  embrace 
the  brain-stem  (pre-oblongata  and  quadrigemina) ;  a  dorsal  notch  (incisura  cerebelli 
posterior),  which  is  smaller  and  narrower  and  lodges  the  falcula,  separates  the 
hemispheres  as  these  project  beyond  the  postvermis. 

The  cerebellum  is  arbitrarily  sub-divided  into  a  medial  segment,  the  vermis  or 
worm,  from  its  annulated  appearance,  and  two  lateral  portions,  commonly  called 


896 


THE  NERVE  SYSTEM 


the  cerebellar  "hemispheres"  or  pileums.  The  vermis  may,  according  to  the  aspect 
in  which  it  is  viewed,  be  divided  into  the  prevermis  on  the  upper  or  cephalic  sur- 
face, and  the  postvermis  on  the  inferior  or  caudal  aspect.  The  prevermis  is  hardly 
distinguished  from  the  adjacent  sloping  surfaces  of  the  hemispheres;  occasionally 
a  slight  furrow  exists  on  either  side.  Ordinarily  the  term  is  to  be  restricted  to 
the  high  median  elevation  usually  called  the  monticulus  cerebelli.  The  postvermis 
is  more  distinctly  bounded  by  a  deep  fissure,  the  sulcus  valleculse,  on  each  side, 
separating  it  from  the  corresponding  lateral  hemisphere. 

Among  the  many  fissures  which  traverse  the  surface  of  the  cerebellum,  one  is 
particularly  conspicuous  as  a  deep  cleft  which  may  be  traced  along  -the  dorso- 
lateral  margin  from  the  dorsal  notch  to  the  point  of  entrance  of  the  cerebellar 
peduncles.  This  is  the  peduncular  sulcus  or  great  horizontal  sulcus  (sulcus  horizon- 
tails  cerebelli),  and  it  divides  the  cerebellum  into  a  cephalic  and  caudal  or  upper 
and  lower  part.  The  sulcus  is  usually  quite  deep  in  the  hemispheral  portion,  but 
it  frequently  fails  to  traverse  the  vermis.  Other  deep  fissures  demarcate  the  lobes 
or  major  sub-divisions  of  the  intricately  convoluted  surface  of  the  cerebellum. 


Post-  nodular  fissure. 


Flocculus. 


Pre- 

pyramidal 
fissur.e. 


ho 


Great 
risontal 
fissure. 


Post 

pyramidal 
fissure. 


FIG.  581.- — Under  surface  of  the  cerebellum.     (Schafer.) 


Conventionally  the  lobes  and  fissures  or  sulci  are  described  upon  the  "  upper  and 
"lower"  surfaces  respectively,  and  this  mode  of  description  is  briefly  adhered  to 
here.  A  better  idea  of  the  topographical  relations  of  the  lobes  and  sulci  in  the 
vermis  and  the  hemispheres  may  be  gained  from  a  study  of  the  divisions  of  the 
cerebellum  as  if  extended  in  one  plane  as  well  as  on  sagittal  sections  through 
the  mesal  and  lateral  planes. 

Lobes  and  Fissures  of  the  Cerebellum.- — The  surface  of  the  cerebellum  is  traversed 
by  eight  more  or  less  curved  and  deep  fissures  demarcating  nine  lobar  sub-divisions. 
Distinctive  names  are  given  to  the  portions  of  each  lobe  in  the  hemispheres  as 
contrasted  with  that  in  the  vermis,  although  often  without  warrant,  as  the  two  are 
quite  continuous  and  merit  no  such  distinction.  This  burdensome  nomenclature 
seems  so  firmly  rooted  in  descriptive  anatomy  that  the  various  terms  must  be 
repeated  here.  The  arrangement  of  the  fissures  and  lobes  will  be  understood  by 
reference  to  the  following  schema,  in  which  the  structures  are  named  from  "before 
backward,"  or  cephalo-caudad : 


THE  CEREBELLUM 


897 


VERMIS. 
p  Lingula. 

<- 

Lobulis  centralis. 

<- 
Culmen  monticuli. 

<- 
Clivus  monticuli 

Folium  cacuminis. 
<- 

Tuber  vermis. 


.a 


Pyramis. 


Uvula 

[  Nodulus 


HEMISPHERE. 
Vincula  lingulae. 
Precentral  Fissure. 

Ala  lobuli  centralis. 

Postcentral  Fissure. 

Anterior  crescentic  lobe.1 

Preclival  Fissure.  > 

Posterior  crescentic  lobe. 

Postclival  Fissure.         > 

Superior  semilunar  lobe. 
Peduncular  Fissure.       > 

j"  Inferior  semilunar  lobe. 

•<  <: Postgracile  fissure. 

(  Gracile  lobe. 

Postpyramidal  Fissure.  > 

Biventral  lobe. 
Prepyramidal  Fissure.    > 

Tonsilla. 

Postnodular  Fissure.       > 

Flocculus. 


FIG.  582. — Diagram  showing  fissures  on  under  surface  of  the  cerebellum:  F,  flocculus;  N,  nodule; 
U,  uvula;  Py,  pyramid;  Am,  amygdala;  Bivent.,  biventral  lobe. 

The  Lingula  (lingula  cerebelli)  is  a  tongue-shaped  process  of  the  vermis  lying  in 
the  ventral  cerebellar  notch,  ventrad  of  the  central  lobe,  and  is  partially  or  com- 
pletely concealed  by  it.  It  consists  of  5,  6,  or  7  lamellae  lying  upon  and  connected 
with  the  dorsum  of  the  valvula.  At  either  side  the  lingula  gradually  shades  off, 
being  prolonged  only  for  a  short  distance  toward  the  region  of  the  peduncles  as  the 
vincula  lingulae. 

The  Central  Lobe  (lobulus  centralis}  is  a  small  median  mass  situated  in  the 
ventral  notch,  dorsad  of  and  overlapping  the  lingula.  Its  lateral,  wing-like  pro- 
longation is  called  the  ala  lobuli  centralis. 

The  Culminal  Lobe  is  much  larger  than  the  two  lobes  just  described  and  con- 
stitutes, with  the  succeeding  lobe  (the  clival  lobe),  the  bulk  of  the  prevermis  and 
"upper"  surface  of  the  cerebellum.  It  partly  overlaps  the  central  lobe.  Its 
lateral  extensions  are  also  termed  the  anterior  crescentic  lobes. 

i  The  anterior  and  posterior  crescentic  lobes  are  often  called  the  pars  anterior  and  pars  posterior  respectively 
of  the  "  lobulus  quadrangularis." 

57 


898 


THE  NERVE  SYSTEM 


The  Clival  Lobe  is  of  considerable  size,  separated  from  the  culminal  lobe  by 
the  preclival  fissure  and  from  the  cacuminal  lobe  by  the  postclival  fissure.  Its 
lateral  extensions  are  also  termed  the  posterior  crescentic  lobes. 

The  anterior  and  posterior  crescentic  lobes  of  either  side  have  been  described 
by  some  writers  as  the  pars  anterior  and  pars  posterior  of  the  quadrate  lobe  or  lobulus 
quadrangular  is. 

The  Cacuminal  Lobe  (folium  vermis;  superior  semilunar  lobe)  is  a  short,  narrow 
band  at  the  dorsal  margin  of  the  vermis,  which  expands  in  either  hemisphere 
into  a  lobe  of  considerable  size,  of  semilunar  shape,  and  bounded  caudad  by  the 
peduncular  fissure. 

The  Tuberal  Lobe  is  of  small  size  in  the  region  of  the  postvermis,  but  laterally 
spreads  out  into  the  large  inferior  semilunar  (lobulus  semilunaris  inferior]  and 
gracile  lobes  demarcated  by  the  intervening  postgracile  fissure.  These  lobes  com- 
prise at  least  two-thirds  of  the  "inferior"  surface  of  the  cerebellar  hemispheres. 


Anterior 
crescentic  lobe. 


Ala  Jobidi  centralis. 


Lingula. 


Superior  peduncles 
of  cerebellum. 


Great, 

horizontal 

fissure. 


Slender  lobe. 


A  mygdala. 


Module.    Fourth  ventricle. 


FIG.  583. — Sagittal  section  of  the  cerebellum,  near  the  junction  of  the  vermis  with  the  hemisphere. 

(Schafer.) 

The  Gracile  Lobe  is  often  divided  by  an  intragracile  fissure  into  pre-  and  post- 
gracile lobes. 

The  Pyramidal  Lobe  is  a  conical  projection,  forming  the  largest  prominence 
of  the  postvermis.  It  is  continued  laterad  into  the  hemisphere  as  the  biventral 
lobe  (lobulus  biventer] ;  the  demarcation  between  the  latter  and  the  pyramis  proper 
is  accentuated  by  the  deep  sulcus  valleculae. 

The  Uvular  Lobe  (uvula  vermis}  occupies  a  considerable  portion  of  the  post- 
vermis as  the  uvula,  while  its  lateral  extension  in  either  hemisphere,  the  tonsilla 
or  amygdala  (tonsilla  cerebelli],  is  a  rounded  mass  lying  in  a  deep  fossa  between 
the  uvula  and  biventral  lobe.  (This  fossa  was  termed,  by  the  older  anatomists, 
the  nidus  avis  or  "bird's  nest"  [Reil  and  Vicq  d'Azyr].)  The  junction  of  uvula 
and  tonsilla  is  an  attenuated  isthmus  marked  by  a  few  shallow  furrows  and 
termed  the  furrowed  band. 

The  Nodular  Lobe  comprises  the  nodulus  (nodulus  vermis)  (in  the  postvermis) 
and  the  flocculus  (floccuh  secondarii)  of  each  side,  connected  by  a  delicate  lamina 
of  white  matter,  the  velum.  Each  flocculus  lies  adjacent  to  the  ventro-lateral  sur- 
face of  the  peduncular  mass,  extending  into  the  ventral  extremity  of  the  pedun- 


THE  CEREBELLUM 


899 


cular  fissure.  The  flocculi  of  the  two  sides  are  connected  with  each  other  by  a 
hand  of  white  matter,  termed  the  velum  (posterior  medullary  velum]  in  its  medial 
portion,  while  its  lateral  expansions  toward  the  flocculi  are  termed  the  peduncles 
of  the  flocculi. 

The  Internal  Structure  of  the  Cerebellum. — In  any  section  of  the  cerebellum  we 
may  recognize  the  interior  white  substance,  corpus  medullare  (medullary  body],  and 
the  peripheral  gray  cortex.  The  white  substance  in  each  lateral  hemisphere  is  more 
bulky  than  in  the  median  vermis,  while  the  cortex  is  of  more  uniform  thickness 
throughout.  In  a  sagittal  section  in  the  mesal  plane  the  central  white  core  is  seen 
to  divide  into  two  main  branches,  preramus  and  postramus;  these  main  branches 


Med.sp 


FIG.  584. — Diagram  showing  the  origin  and  course  of  the  fibres  of  the  peduncles  of  the  cerebellum. 

(Edinger.) 

divide  and  subdivide  into  a  series  of  medullary  laminae  surmounted  by  the  foliated 
cortex,  and  presenting  the  characteristic  appearance  known  as  the  arbor  vitae 
cerebelli. 

Isolated  Gray  Masses  or  Nuclei  of    the  Cerebellum. — Embedded  in  the  white 
matter  of  the  cerebellum  are  several  gray  masses.     They  are  four  in  number  on 

1          .j  tS        J  J 

each  side: 

1.  Dentatum  or  dentate  nucleus. 

2.  Embolus  or  nucleus  emboliformis. 

3.  Globulus  or  nucleus  globosus. 

4.  Fastigatum  or  nucleus  fastigii. 


9CO 


THE  NER  VE  SYSTEM 


The  dentatum  is  the  largest  and  best  studied  of  the  cerebellar  nuclei.  It  is 
located  in  the  mesal  part  of  the  corresponding  cerebellar  hemisphere,  in  the  direct 
prolongation  of  the  prepedunculus,  which  appears  to  enter  it.  It  consists  of  a 
folded  lamina  of  gray  matter  convoluted  like  the  similar  nucleus  of  the  olive,  and 
opens  cephalo-mesad  where  its  hilum  (hilus  nuclei  dentati)  permits  of  the  entrance 
and  exit  of  fibres  from  various  sources. 

The  embolus  is  a  small  mass  of  gray  substance,  elongated  cephalo-caudad,  and 
placed  entad  of  the  dentatum,  partly  covering  its  hilum. 

The  globulus  consists  of  several  small  round  or  oval  masses  connected  with  each 
other  and  lying  entad  of  the  preceding. 

The  fastigatum  (nucleus  of  the  "roof")  is  second  in  size  to  the  dentatum,  situated 
close  to  the  mesal  plane  directly  dorsad  of  the  fourth  ventricle,  or  in  the  fastigium 
of  the  cerebellum,  and  within  the  postvermis.  The  nuclei  of  opposite  sides 
approach  each  other  so  nearly  as  almost  to  fuse. 


FIG.  585. — The  peduncles  of  the  cerebellum.  On  the  left  the  three  peduncles  have  been  cut  at  their 
entrance  into  the  cerebellum;  on  the  right  side  they  are  shown  penetrating  the  cerebellar  hemisphere. 
(Poirier  and  Charpy.) 

The  Cerebellar  Peduncles. — Three  pairs  of  peduncles  constitute  the  chief  avenues 
for  the  entrance  and  emergence  of  the  fibres  composing  the  white  substance  of 
the  cerebellum  and  connecting  adjacent  parts  of  the  brain-stem  therewith.  The 
peduncles  are,  on  each  side,  the  prepeduncle,  medipeduncle,  and  postpeduncle. 

The  Postpeduncle  (corpus  restiforme)  is  the  continuation  of  the  restis  of  the 
oblorigata.  It  contains  both  afferent  and  efferent  fibres,  connecting  the  cerebellar 
cortex  with  structures  situated  ca"udad:  (1)  The  dorsal  or  direct  spino-cerebellar 
tract,  composed  of  axones  arising  in  Clarke's  column  (spinal  cord)  and  terminating 
in  the  cortex  of  the  prevermis  on  both  sides  of  the  median  line,  but  chiefly  on  the 
opposite  side.  (2)  The  olivo-cerebellar  tract,  composed  of  axones  arising  in  the 
(inferior)  olivary  nuclei — principally  from  the  contralateral  or  opposite  olive,  and 
terminating  in  the  cortex  of  the  prevermis  and  adjacent  hemispheral  portions,  as 
well  as  in  the  dentatum.  (3)  External  arcuate  fibres  from  the  homo-lateral  and 
contralateral  nuclei  of  the  gracile  and  cuneate  funiculi.  (4)  The  nucleo-cerebellar 


THE  CEREBELLUM  901 

tract,  composed  of  axones  from  the  recioient  nuclei  of  certain  cranial  nerves 
(vestibular,  trigeminal).  (5)  The  cerebello-spinal  (descending)  tract,  terminating 
in  relation  with  the  ventral-horn  cells  at  various  levels  of  the  spinal  cord. 

The  Medipeduncles  (brachia  pontis)  are  the  largest  of  the  three  pairs.  They 
consist  of  a  mass  of  curved  fibres  comprising  the  pons  and  entering  either  cerebellar 
hemisphere  between  the  parted  lips  of  the  ventral  end  of  the  peduncular  fissure, 
just  ectad  of  the  postpeduncle.  Each  peduncle  contains  axones  coursing  in  oppo- 
site directions  and  in  large  part  may  be  considered  as  purely  commissural  fibres. 
Some  of  the  axones  terminate,  however,  in  the  nuclei  pontis  to  convey  impulses 
so  the  cells  therein;  these  in  turn  send  their  axones  (tractus  pontocerebellares) 
into  the  opposite  medipeduncle,  and  therefore  constitute  interrupted  commissural 
systems.  A  few  fibre-systems  in  the  medipeduncles  establish  relations  with 
certain  other  structures  in  the  brain-stem,  notably  the  nuclei  of  the  oculomotor, 
trochlear,  and  abducent  cranial  nerves. 

The  Prepeduncles  (brachia  conjunctiva)  emerge  cephalad  from  the  cerebellum 
entad  of  the  medipeduncles.     As  they  extend  cephalad  they  converge  to  form  the 
lateral  boundaries  of  the  fourth  ventricle  and  partly  roofing  it  in.     On  trans-section 
they  appear  of   oval  outline,  somewhat 
concave  toward  the  cavity  of  the  ventricle. 
The  valvula,  a  thin  lamina  of  white  sub- 
stance, spans  the  interval  between  the  con- 
verging prepeduncles,  and  thus  completes 
the  roofing-in  of  the  cephalic  portion  of 
the  fourth  ventricle. 

The  prepeduncles  consist  almost  wholly 
of  axones  arising  from  the  cells  of  the 
dentatum,  the  ectal  part  of  the  fastigatum 
of  the  same  side,  and  mesal  part  of  the 
fastigatum  of  the  opposite  side.  In  their 
course,  converging  cephalad,  these  bun- 
dles pass  into  the  tegmentum  of  the  mid- 
brain  ventrad  of  the  quadrigemina,  and 
decussate  almost  wholly.  The  fibres  of 
each  peduncle  terminate  in  the  rubrum 
(red  nucleus-)  of  the  opposite  side,  although  FlG-  58&--s™l£*%eT  ^S"0  cerebellar 
a  few  continue  to  enter  the  thalamus. 

This  system  of  fibres  is  also  called  the  tractus  cerebello-tegmentalis,  and  axones 
of  inverse  functional  direction  have  been  included  therein. 

The  Ventral  spino-cerebellar  tract  (Gowers'  tract)  is  in  relation  with  the  prepeduncle 
and  valvula.  Unlike  the  dorsal  or  direct  spino-cerebellar  tract,  it  does  not  enter  the 
cerebellum  along  the  postpeduncle.  Its  fibres  pass  farther  cephalad,  through  the 
reticular  formation  of  the  pre-  and  postoblongata,  to  become  reflected  dorso- 
caudad  at  the  level  of  the  isthmus  of  the  hind-brain,  and  entering  the  valvula, 
proceed  with  the  prepeduncle  into  the  cerebellum. 

The  Medullary  Vela. — These  are  two  thin,  relatively  undeveloped  laminae  of 
white  substance,  representatives  of  the  mid-dorsal  wall  of  the  brain-tube  adjacent 
to  the  cerebellar  proton,  and  in  the  adult  brain  appear  as  prolongations  of  the 
white  central  core  of  the  cerebellum.  They  are  the  valvula  (anterior  or  superior 
medullary  velum;  valve  of  Vieussens)  and  the  velum  (posterior  or  inferior  medul- 
lary velum). 

The  Valvula  is  a  thin  lamina  of  white  substance  spanning  the  interval  between  the 
converging  prepeduncles,  and  with  these  assisting  in  the  formation  of  the  "roof" 
of  the  fourth  ventricle.  Caudad  it  is  continuous  with  the  white  substance  of  the 
cerebellum,  while  on  its  dorsal  surface  lie  the  five  to  seven  folia  of  the  lingula. 


902  THE  NERVE  SYSTEM 

Cephalad  it  narrows  as  the  quadrigemina  are  approached,  and  a  slight  median 
ridge,  the  frenulum,  descends  upon  the  dorsal  surface  of  its  apical  portion  from 
between  the  postgemina;  on  either  side  of  the  frenulum  may  be  seen  the  super- 
ficial root  of  the  trochlear  nerve.  The  majority  of  the  fibres  in  the  valvula  are 
longitudinal;  as  already  described  (p.  901),  the  ventral  spino-cerebellar  tract 
reaches  the  cerebellum  along  the  valvula. 

The  Velum  is  a  still  thinner  lamina  of  white  substance  which  bears  the  same  rela- 
tions to  the  nodulus  that  the  valvula  presents  to  the  lingula.  Laterad  it  extends 
to  the  flocculus  of  either  side.  The  velum  ends  in  a  free  crescentic  edge  and  its 
endymal  and  pial  coverings  continue  as  a  fused,  delicate  membrane,  the  metatela. 

The  valvula  and  velum  enter  the  cerebellum  at  an  acute  angle,  forming  the 
peaked  roof  (fastigium),  while  the  tent-like  recess  is  called  the  recessus  tecti. 

The  Fibres  Proper  of  the  Cerebellum.— The  fibrae  propriae  of  the  cerebellum  are 
of  two  kinds:  (1)  commissural  fibres,  which  cross  the  middle  line  to  connect  the 
opposite  halves  of  the  cerebellum,  some  at  the  anterior  part  and  others  at  the 
posterior  part  of  the  vermis;  (2)  association  fibres,  which  are  homo-lateral  fibres 
connecting  adjacent  laminae  with  each  other. 

Microscopic  Appearance  of  the  Cerebellar  Cortex. — The  cerebellar  cortex,  on 
section,  presents  two  marked  layers:  an  outer,  of  a  pale-gray  color,  the  molecular 
layer,  and  an  inner,  of  a  rusty-brown  tint,  the  granular  layer.  At  the  contact  line 
of  these  two  layers,  but  more  within  the  molecular  than  the  granular,  are  found 
the  characteristic  nerve-elements  of  the  cerebellum,  the  flask-shaped  Purkinjean 
nerve-cells. 

The  Molecular  or  Ectal  Layer  consists  of  cells  and  delicate  fibrillse  embedded  in  a 
neuroglial  network.  The  cells  are  small  and  are  characterized  by  the  course  of 
their  branching  axones  which  run  parallel  with  the  surface  of  the  folium,  give 
off  numerous  collaterals  which  pass  in  a  vertical  direction  toward  the  cell-bodies 
of  the  Purkinjean  elements  and  embrace  these  in  a  basket-like  network.  Hence 
these  cells  are  called  basket-cells  (Fig.  587). 

The  Purkinjean  Cells  are  flask-shaped,  and  form  a  stratum  at  the  junction  of 
the  molecular  and  granular  layers,  their  bases  directed  toward  the  latter.  Each 
cell  gives  off  an  axone  entad,  while  ectad  it  gives  off  numerous  dichotomously 
branching  dendrites  covering  a  very  large  field  of  the  molecula'r  layer.  The  axone, 
after  giving  off  several  collaterals  which  pass  toward  different  parts  of  the  granular 
layer,  becomes  myelinic  not  far  from  the  cell-body  and  passes  into  the  white  sub- 
stance to  establish  connections  with  other  folia  within  the  cerebellum  or  with 
more  distant  brain-structures. 

The  Granular  or  Ental  Layer  is  characterized  by  containing  numerous  small  nerve- 
cells  or  granules  of  a  reddish-brown  color,  together  with  many  nerve-fibrils.  Most 
of  the  cells  are  nearly  spherical  and  provided  with  short  dendrites,  which  spread 
out  in  a  spider-like  manner  in  the  granular  layer.  Their  axones  pass  outward 
into  the  molecular  layer,  and,  bifurcating  at  right  angles,  run  horizontally  for 
some  distance.  In  the  outer  part  of  the  granular  layer  are  also  to  be  observed 
some  larger  cells,  of  the  type  termed  Golgi  cells  (Fig.  587).  Their  axones  undergo 
frequent  division  as  soon  as  they  leave  the  nerve-cells,  and  pass  into  the  granular 
layer,  while  their  dendrites  ramify  chiefly  in  the  molecular  layer. 

Finally,  in  the  gray  substance  of  the  cerebellar  cortex  fibres  are  to  be  seen  which 
come  from  the  white  centre  and  penetrate  the  cortex.  The  cell  origin  of  these 
fibres  is  unknown,  though  it  is  believed  that  it  is  probably  in  the  gray  substance  of 
the  spinal  cord.  Some  of  these  fibres  end  in  the  granular  layer,  by  dividing  into 
numerous  branches,  on  which  are  to  be  seen  peculiar  moss-like  appendages;  hence 
they  have  been  termed  by  Ramon  y.  Cajal  the  moss-fibres  (Fig.  587) ;  they  form 
an  arborescence  around  the  cells  of  the  granular  layer.  Other  fibres  derived 
from  the  medullary  centre  can  be  traced  into  the  molecular  layer,  where  their 


THE  CEREBELLUM 


903 


branches  cling  around  the  dendrites  of  Purkinje's  cells,  and  hence  they  have  been 
named  the  clinging  or  tendril  fibres  (Fig.  587). 

The  cerebellum  is  an  important  senso-motor  organ,  transmuting  sensor 
impressions  into  motor  impulses  under  the  dominance  of  the  cerebral  centres. 
Its  connections  with  other  brain  portions  and  the  spinal  cord  are  established  by 
the  peduncular  fibres.  It  is  essentially  an  apparatus  for  the  coordination  of 
movements  and  the  orientation  of  the  body  and  its  parts  in  space.  These  func- 
tions depend  principally  upon  the  reception  of  sensor  impulses  from  (1)  the 


PURKI NJEAN  CELL 


AXONC  OF 
GRANULE  CELL, 
CUT  TRANS- 
VERSELY 


SMALL  CELL 

OF  MOLECULAR 

LAYER 


BASKET  CELL 


^MOLECULAR 
LAYER 


GOLGI    CELL 


GRANULAR 
LAYER 


!  AXONE  OF 
'PURKINJEAN 
CELL 

'TENDRIL  FIBRE 
'MOSSY  FIBRE 
FIG.  587. — Trans-section  of  a  eerebellar  folium.     (Diagrammatic  after  Cajal  and  Kolliker.) 


NEUROGLIA 
CELL 


vestibular  nerve  and  (2)  the  spino-cerebellar  (ascending)  tracts.  Motor  impulses 
pass  along  (1)  the  cerebello-spinal  (descending)  tracts  to  the  ventral-horn  nuclei 
of  the  cervical  cord;  (2)  the  tractus  rubro-spinalis,  which  arises  in  the  rubrum 
(red  nucleus) — an  intercalated  ganglionic  mass  connected  with  the  eerebellar 
cortex  by  the  prepeduncles,  or  tractus  cerebello-tegmentales.  The  tractus 
rubro-spinalis  is  a  tract  for  voluntary  motor  impulses  next  in  importance  to  the 
pyramidal  tract. 

Weight  of  the  Cerebellum. — Its  average  weight  in  the  male  is  165  grams  and 
155  grams  in  the  female.     It  attains  its  maximum  between  the  twenty-fifth  and 


904 


THE  NERVE  SYSTEM 


thirty-fifth  years,  its  increase  in  weight  after  the  fourteenth  year  being  relatively 
greater  in  the  female  than  in  the  male.  The  proportion  between  the  cerebellum 
and  the  cerebrum  is  as  1  to  7.5;  among  eminent  men  it  is  1  to  8.5.  In  the  new- 
born the  ratio  is  as  1  to  20. 


The  Mid-brain  (Mesencephalon) . 

The  mid-brain  is  the  short  and  constricted  portion  of  the  brain  which  lies  in 
the  opening  of  the  tentorium  cerebelli  (incisura  tentorii)  and  which  connects  the 
pons  with  the  inter-brain  and  hemispheres,  and  hence  it  is  frequently  called 
the  isthmus  cerebri.  It  is  developed  from  the  second  brain-vesicle,  the  cavity  of 
which  becomes  the  aqueduct.  It  comprises  the  crura  cerebri,  the  quadagemina, 


FRENULUM 
TROCHLEAR    NERVE 


VALVULA (CUT) 


CUNEATE    TUBERCLE 
TUBERCULUM    CINERE       .' 


T/EINIA    PONTIS 
TRIGEMINAL    NERVE 


FACIAL    NERVE 
ACOUSTIC    NERVE 
GL03SOPHARYNGEAL 
AND    VAGUS    NERVES 
HYPOGLOSSAL    NERVE 


ACCESSORY    NERVE 


FIG.  588. — The  brain-stem,  showing  oblongata,  pons,  mid-brain,  and  part  of  the  thalami. 

the  geniculate  bodies,  and  the  aqueduct.  Its  two  surfaces  are  ventral  and  dorsal. 
They  are  free,  but  concealed :  the  ventral  surface  by  the  apices  of  the  temporal  lobes 
which  overlap  it ;  the  dorsal,  by  the  overhanging  cerebral  hemispheres.  The  ventral 
surface,  when  exposed  by  drawing  aside  the  temporal  lobes,  is  seen  to  consist  of 
two  cylindrical  bundles  of  white  substance,  which  emerge  from  the  pons  and  diverge 
as  they  pass  forward  and  outward  to  enter  the  inner  and  under  part  of  either  hemi- 
sphere. They  are  the  crura  cerebri,  and  between  them  is  a  triangular  area,  the 
intercmral  space;  near  the  point  of  divergence  of  the  crura  the  roots  of  the  third 
nerve  are  seen  to  emerge  in  several  bundles  from  a  groove,  the  sulcus  oculomotorius 
(sulcus  nervi  oculomotorii)  (Fig.  551).  The  dorsal  surface  is  not  visible  until  a 
considerable  portion  of  the  cerebral  hemispheres  and  other  overlying  structures 
have  been  removed.  It  then  presents  four  rounded  eminences  placed  in  pairs, 
two  cephalad  and  two  caudad,  and  separated  from  one  another  by  a  crucial 


THE  MID-BRAIN  905 

depression.  These  are  termed  the  quadrigemina  (tubercula  quadrigemina')  (Fig. 
,">ss).  The  ventral  and  dorsal  surfaces  meet  on  the  side  of  the  mid-brain,  and  are 
separated  from  each  other  by  a  furrow,  the  lateral  groove  (sulcus  lateralis  mesen- 
cephali},  which  runs  caudo-cephalad  (Fig.  588). 

External  Morphology. — Dorsal  Surface. — The  quadrigemina  are  four  rounded 
eminences  placed  in  pairs  separated  by  a  flat  median  groove  and  a  more  sharply 
cut  transverse  furrow.  The  cephalic  pair,  the  pregemina  (superior  colliculi;  the 
nates  of  older  authors),  are  the  larger  and  the  epiphysis  rests  in  the  flattened 
depression  between  them.  The  pregemina  are  oval,  their  long  diameter  being 
directed  cephalo-laterad,  and  are  of  a  yellowish-gray  color.  The  postgemina 
(colliculi  inferiores;  the  testes  of  older  authors)  are  hemispherical  in  form,  and 
lighter  in  color  than  the  preceding.  The  lamina  quadrigemina,  comprising  the 
whole  of  the  dorsal  wall  of  the  mid-brain,  extends  from  the  root-region  (post- 
commissure)  of  the  epiphysis  to  the  cephalic  end  of  the  valvula. 

Each  pre-  and  postgeminum  is  continued  latero-ventrad  in  prominent  white 
bands,  the  brachia.  The  band  from  the  pregeminum  is  termed  the  prebrachium ; 
that  from  the  postgeminum  is  called  the  postbrachium. 

The  Prebrachium  (brachium  quadrigeminum  superius)  proceeds  cephalo-ventrad 
between  the  overhanging  pulvinar  and  a  light-gray  eminence,  the  postgeniculum. 
In  reality  it  is  a  continuation  of  a  part  of  the  optic  tract.  The  Postbrachium 
(brachium  quadrigeminum  inferius)  proceeds  in  a  similar  direction  to  disappear 
beneath  the  postgeniculum. 

Of  the  two  geniculate  bodies,  on  either  side,  the  pregeniculum  belongs  rather 
to  the  thalamus,  while  the  postgeniculum  may  properly  be  considered  here  among 
the  structures  of  the  mid-brain. 

The  Postgeniculum  (corpus  geniculatum  mediale  s.  internale]  is  a  small  oval 
eminence  on  the  lateral  surface  of  the  mid-brain  in  which  the  mesal  root  of  the 
optic  tract  appears  to  terminate.  The  postbrachium  likewise  appears  to  run  into 
this  body;  as  a  matter  of  fact,  so  far  as  is  known,  the  postgeniculum  is  (1)  a  way- 
station  for  auditory  impulses  in  their  course  toward  the  cerebrum;  (2)  the  origin 
and  terminus  for  the  arched  commissure  of  Gudden  (infracommissure;  commissura 
inferior  [Guddeni]),  by  means  of  which  circuitous  path,  through  the  chiasm,  and 
along  the  mesal  root  of  optic  tract,  the  postgenicula  of  the  two  sides  are  con- 
nected. 

The  quadrigeminal  lamina  is  continuous  caudad  with  the  cerebellar  pre- 
peduncles  and  the  intervening  valvula.  A  slight,  median,  ridge-like  projection, 
the  frenulum  valvulae,  descends  from  between  the  postgemina  onto  the  valvula; 
on  either  side  of  the  frenulum  emerge  the  slender  trochlear  nerves. 

The  Crura  constitute  the  bulk  of  this  portion  of  the  brain-stem.  Upon  the 
ventral  aspect  of  the  brain  they  appear  as  two  large,  white,  rope-like  strands  emerg- 
ing from  the  pons  and  diverging  to  either  cerebral  hemisphere,  becoming  embraced 
by  the  optic  tracts.  Each  crus  is  composed  of  a  dorsal  tegmental  part — a  continua- 
tion of  the  tegmentum  of  the  hind-brain — and  a  ventral  crusta  or  pes.  These  parts 
are  demarcated  from  each  other  on  the  external  surface  by  the  oculomotor  sulcus 
ventrad  (which  looks  into  the  intercrural  space)  and  the  sulcus  lateralis  mesen- 
cephali  on  the  lateral  aspect.  The  lateral  surface  shows  dorsally  the  cerebellar 
prepeduncle  dipping  into  the  substance  of  the  mid-brain,  while  between  it  and  the 
crusta  is  a  small  triangular  field  of  oblique  fibre-strands,  not  always  well  defined, 
called  the  trigonum  lemnisci  because  the  lateral  lemniscus  tends  to  reach  the  sur- 
face of  the  brain-stem  at  this  situation  (Fig.  588). 

The  surface  of  the  crura  shows  a  rope-like  twist  in  the  course  of  its  fibre-bundles. 
Oblique  or  transverse  fasciculi  are  sometimes  seen  upon  the  surface,  two  of 
which  are  fairly  constant.  They  are  (1)  the  taenia  pontis,  and  (2)  Gudden's 
tractus  peduncularis  transversas  (cimbia). 


906 


THE  NERVE  SYSTEM 


The  Taenia  Pontis,  as  Horsley  has  shown,  takes  origin  contralaterally  in  the 
gray  substance  continuous  with  the  "interpeduncular  ganglion,"  but  ventral  to  it. 
The  ta?nia  then  passes  over  the  lateral  lemniscus  and  cerebellar  prepeduncle  to 
the  dentatum  and  fastigatum. 

The  Cimbia1  or  Tractus  Peduncularis  Trans  versus  may  he  traced  from  the  pre- 
geminum  and  postgeniculum  over  the  surface  of  the  crus  to  near  the  ventro-meson, 
disappearing  from  view  in  the  oculomotor  sulcus. 


AQUEDUCT 


NUCLEUS  OF 

OCULOMOTOR 

NERVE 


POSTBRACHIUM 

MEDIAL  LONGI- 
TUDINAL FASCIC- 
ULUS 


OCULOMOTOR 
NERVE 


FIG.  589. — Trans-section  of  the  mid-brain  through  the  level  of  the  pregeminum. 

Internal  Structures  of  the  Mid-brain. — If  a  cross-section  be  made  through 
the  mesencephalon  it  will  be  seen  that  each  lateral  half  is  divided  into  two  unequal 
portions  by  a  lamina  of  deeply  pigmented  gray  substance,  named  the  substantia 
nigra  (intercalation;  ganglion  of  Soemmering).  The  postero-superior  portion  of 
the  crus  is  named  the  tegmentum,  and  the  antero-inferior  the  crusta  or  pes.  The 
substantia  nigra  is  curved  on  section  with  its  concavity  upward,  and  extends  from 


MESENCCPHALIC  ROOT 
OFTRIGEMINAL  NERVE 

NUCLEUS  OF 
TROCHLEAR    NERVE 
LATERAL   LEMNISCUS 
MEDIAL  LONGITUD- 
INAL FASCICULUS 

DECUSSATION  OF 
CEREBELLAR  PED- 
UNCLES 

MEDIAL 
LEMNISCUS 


FIG.  590. — Trans-section  of  the  mid-brain  through  the  level  of  the  postgeminum. 

the  lateral  groove  externally  to  the  oculomotor  sulcus  internally.  The  two 
crustse  are  in  contact  in  front  of  the  pons,  from  which  point  they  diverge  from  each 
other,  but  the  two  halves  of  the  tegmentum  are  joined  to  each  other  in  the  mesal 

1  In  architecture — a  band  or  fillet  about  a  column.     Also  called  fasciculus  arciformis  pedis. 


THE  MID-BRAIN  907 

plane  by  a  forward  prolongation  of  the  raphe  or  median  septum  of  the  pons. 
Laterally  the  tegmenta  are  free,  but  dorsally  they  blend  with  the  quadrigemina. 

Traversing  the  mid-brain  in  the  median  plane  and  nearer  the  dorsal  surface  is 
the  aqueduct,  surrounded  by  the  central  tubular  gray,  which  in  this  brain-segment 
has  retained  the  comparatively  primitive  arrangement  of  the  embryonic  brain-tube. 

The  Aqueduct  (Mexoccle)  and  Central  Gray  Aqueduct. — The  aqueduct  is  a  nar- 
row canal  connecting  the  third  with  the  fourth  ventricle,  and  demarcating  the 
lamina  quadrigemina  dorsad  from  the  tegmental  zone.  Its  shape  on  trans-section 
varies  at  different  levels,  being  T-shaped  caudad,  oval  or  quadrangular  along  its 
middle,  and  triangular  cephalad.  It  is  lined  by  the  endyma  (columnar  ciliated 
epithelium)  and  surrounded  by  the  central  aqueduct  gray.  The  central  gray  is 
separated  dorsally  from  the  quadrigemina  by  the  stratum  lemnisci;  ventrad  near 
the  median  plane  lie  the  medial  longitudinal  bundles.  Within  the  gray  substance 
lie  certain  well-defined  cell-clusters,  the  nuclei  of  origin  of  the  oculomotor  and 
trochlear  nerves  and  the  mesencephalic  root  of  the  trigeminal  nerve.  These 
will  be  described  in  detail  later. 

The  Substantia  Nigra  or  Intercalatum. — The  substantia  nigra  is  a  crescentic 
layer  of  deeply  pigmented  gray  substance  interpolated  between  the  crusta  and 
the  tegmentum.  Mesad  it  nearly  touches  its  fellow  of  the  opposite  side,  being 
separated  by  the  rudimentary  ganglionic  gray  (the  postperforatum)  in  the  inter- 
crural  space.  Its  ventral  face  sends  numerous  ramifying  prolongations  among 
the  fasciculi  of  the  crusta.  It  extends  from  the  cephalic  border  of  the  pons  to 
the  subthalamic  region,  while  its  lateral  edge  reaches  the  surface  along  the  lateral 
sulcus.  Its  cells  are  medium-sized,  multipolar,  their  bodies  approaching  the 
fusiform,  or  angular  in  outline.  The  cells  are  characterized  by  a  pigment  (marked 
only  in  man)  which  varies  from  a  pale  brown  in  the  young  to  an  absolute  blackness 
in  the  very  aged.  The  axones  arising  from  the  cells  proceed  in  various  directions 
toward  the  tegmentum  and  cruita,  but  their  exact  course  is  not  known.  Experi- 
mental excitation  of  this  ganglionic  mass  elicits  movements  of  deglutition  accom- 
panied by  respiratory  changes.  Mellus  has  found  in  the  monkey  that  a  portion 
of  the  pyramidal  tracts  is  interrupted  in  the  substantia  nigra. 

The  Quadrigemina. — The  quadrigemina  are  largely  composed  of  gray  substance, 
but  the  pre-  and  postgemina  differ  distinctly  in  structure. 

The  Pregeminum  presents  a  true  cortical  type,  which  is  more  evident  in  the  optic 
lobes  of  lower  vertebrates.  In  man  the  thin,  outermost  white  layer — the  stratum 
zonale — is  an  expansion  of  the  optic  tract.  Beneath  this  lies  a  gray  nucleus,  with 
numerous  small  cells — the  stratum  cinereum — a  cup-like  layer  of  crescentic  outline 
on  trans-section.  The  succeeding  ental  layer  is  a  white  stratum,  also  derived 
from  the  optic  tract — the  stratum  opticum.  Between  this  and  the  underlying 
stratum  lemnisci  is  a  second  gray  layer,  less  defined  because  of  the  diffuse  inter- 
lacing of  white  fibres. 

Each  pregeminum  is  one  of  a  series  of  primary  centres  of  vision  related  more 
to  eye-muscle  reflexes  resulting  from  optic  and  auditory  stimuli  than  to  actual 
light  and  color  perception.  Fibres  from  the  retina,  for  the  most  part,  form  the 
stratum  zonale  and  end  in  the  ganglionic  gray;  others  enter  into  the  formation 
of  the  stratum  opticum.  Return  fibres  from  the  occipital  cortex  also  enter  the 
stratum  opticum.  The  retinal  and  occipital  fibres  determine  the  formation  of  the 
prebrachium.  Other  fibres  reach  the  pregeminum  through  the  lateral  and 
medial  lemnisci — from  both  sides — to  end  in  relation  with  the  deeper  cells  of  the 
stratum  cinereum.  The  connections  of  the  pregeminum  with  the  cochlear  centres 
afforded  by  the  lateral  lemniscus  establishes  the  so-called  optic-acoustic  reflex  path. 

The  Postgemina  are  more  homogeneous  in  texture,  comprising  a  pair  of  compact 
ganglia  which  on  trans-section  have  the  shape  of  biconvex  lenses,  encapsulated  by 
white  substance.  The  cells  are  small,  multipolar,  and  very  numerous,  embedded 


90S  THE  NER  VE  SYSTEM 

in  a  fine  molecular  groundwork.  The  white  stratum  zonale  is  principally  derived 
from  the  fibres  of  the  lateral  lemniscus,  which  terminate  in  the  central  gray  of  the 
postgeminum  as  well  as  in  the  postgeniculum.  The  axones  of  the  cells  in  the 
postgeminum  course  cephalad  in  the  postbrachium,  dip  beneath  the  postgenicu- 
lum into  the  tegmentum  and  proceed  to  the  thalamus.  The  postgemina  are  im- 
portant links  in  the  chain  of  the  auditory  neurone  system,  and  are  special  localities 
for  the  reflexion  of  auditory  impulses. 

The  Tegmentum. — The  tegmentum  of  the  mid-brain  is  continuous  with  the 
like  formations  in  the  hind-brain  stem  and  consists  of  longitudinal  fibre-bundles 
intersected  by  transverse  arched  fibre-systems  with  gray  substance  irregularly 
scattered  in  the  interstices,  composing  the  formatio  reticularis.  In  its  ventral  por- 
tion, on  either  side,  and  at  the  level  of  the  pregeminum,  lies  a  gray  ganglionic 
mass,  the  rubrum  or  red  nucleus,  (nucleus  tegmenti;  nucleus  ruber}. 

The  Rubrum  or  Red  Nucleus,  so  termed  from  its  reddish  tinge  in  the  fresh  brain, 
which  it  owes  to  the  pigmentation  of  its  cells  as  well  as  to  its  great  vascularity,  is 
found  subjacent  to  the  pregemina  in  those  section-levels  where  the  substantia  nigra 
has  its  greatest  expansion.  In  trans-sections  its  outline  is  irregularly  circular;  in 
sagittal  sections  an  elongated  oval.  The  rubrum  is  the  end-station  for  the  majority 
of  the  decussated  cerebellar  prepeduncle  fibres,  for  fibres  from  the  cerebral  cortex, 
and  from  the  striatum.  These  fibre-bundles  form  for  the  nucleus  a'  capsule 
which  is  thicker  on  its  ectal  surface.  From'the  cells  of  each  rubrum  arise  axones 
which  pass  (1)  to  thalamus  and  cerebral  cortex  (links  in  the  cerebello-cortical 
neurone-chain),  and  (2)  axones  which  descend  into  the  spinal  cord  to  form  the 
tractus  rubrospinalis  (Monakow's) — a  continuation  of  an  indirect  motor  path  from 
the  cerebral  cortex  to  peripheral  motor  nerve.  The  tracts  arising  from  the  red 
nuclei  of  the  two  sides  decussate  with  each  other  and  descend  in  the  tegmentum. 

In  the  intercrural  space  lies  a  primitive  gray  ganglionic  mass,  the  postperfo- 
ratum.  Cephalad  of  the  pons,  in  the  median  line,  lies  a  cluster  of  cells,  the  inter- 
peduncular  ganglion  (Gudden).  The  fasciculus  retroflexus  (Meynert),  whose  fibres 
arise  in  the  habenal  ganglion,  descends  to  end  in  the  interpeduncular  ganglion. 

The  principal  longitudinal  fibre-tracts  in  the  tegmentum  of  the  mid-brain  are 
(1)  the  medial  longitudinal  fasciculus,  (2)  lateral  lemniscus,  (3)  medial  lemniscus, 
(4)  the  decussating  cerebellar  prepeduncles,  (5)  the  decussating  rubro-spinal  tracts, 
and  (6)  the  central  tegmental  tracts. 

The  Medial  Longitudinal  Bundle  lies  on  each  side  of  the  median  plane,  lying 
ventrad  of  the  central  aqueduct  gray  in  the  mid-brain  and  continuous  throughout 
the  brain-stem  in  its  formatio  reticularis.  It  is  the  continuation  and  the  equiva- 
lent, but  in  a  more  differentiated  form,  of  the  ventral  basis  bundle  of  the  spinal 
cord.  It  is  formed  by  association  neurones  and  acts  as  an  associating  agent  with 
regard  to  many  cranial  and  spinal-nerve  centres  for  the  performance  of  certain 
definite  functions.  Its  neurones  receive  impulses  from  afferent  elements  and 
transmit  them  to  motor  or  efferent  elements.  It  particularly  brings  into  relation 
the  sensor  cranial-nerve  nuclei  and  the  quadrigemina  with  the  motor  nerves  of 
the  eye  (III,  IV,  and  VI),  of  the  face  (VII),  and  of  the  trunk.  A  special  nucleus 
for  the  bundle  is  described  as  being  situated  in  the  gray  floor  of  the  third  ventricle, 
at  its  junction  with  aqueduct.  The  axones  from  the  cells  of  this  nucleus  cross 
to  the  opposite  side  through  the  postcommissure  (Fig.  591). 

The  Lateral  Lemniscus,  we  have  learned,  is  a  continuation  of  the  auditory  path 
in  its  course  to  the  cerebral  cortex.  Its  formation  is  described  on  p.  888.  In  the 
mid-brain  the  fibres  of  the  lateral  lemniscus  course  through  the  lateral  part  of 
the  tegmentum,  near  the  surface,  and  most  of  them  end  in  the  postgeminal  gray 
nucleus  and  in  the  postgeniculum.  A  few  fibres  are.carried  into  the  pregeminum. 

The  Medial  Lemniscus,  or  principal  conduction  path  for  sensor  impulses  from 
the  trunk  and  extremities,  and  already  discussed  in  the  preceding  (p.  888),  ascends 


THE  MID-BRAIN 


909 


in  the  tegmentum  of  the  mid-brain  in  the  contact-zone  with  the  crusta.  In  its 
ascent  it  is  deflected  slightly  dorso-laterad  by  the  red  nucleus.  The  lateral  border 
of  the  ribbon-like  bundle  is  in  contact  with  the  lateral  lemniscus,  and  forms  an 
angle  with  it,  as  seen  on  trans-sections  (Figs.  589  and  590) . 

Many  of  the  fibres  of  the  medial  lemniscus  terminate  in  the  pregeminum;  the 
remainder  proceed  to  the  thalamus. 


POSTCOMMISSURE 


SPECIAL    NUCLEUS 
OF  THE  MEDIAL 
LONGITUDINAL 
BUNDLE 


FOUNTAIN 
DECUSSATION 


PREGEMINUM 


FIG.  591. — The  medial  longitudinal  bundle. 

The  Prepeduncles  of  the  Cerebellum  sink  into  the  mid-brain  tegmentum  in  a 
cephalo-ventral  direction,  the  two  prepeduncles  converging  and  their  fibres  under- 
going a  complete  decussation  (Wernekinck's  commissure)  subjacent  to  the  post- 
gemina.  The  crossed  fibres  end,  for  the  most  part,  in  the  rubrum  of  each  side; 
others  circumvent  the  nucleus,  forming  a  white  capsule  for  it  which  is  thicker 
on  its  ental  surface,  and  proceed  to  the  thalamus. 

The  Tractus  Rubrospinalis  (Monakow's)  is  composed  of  axones  arising  in  the 
red  nucleus,  decussating  with  those  of  the  opposite  tract,  and  descending  in 


9 10  THE  NER  VE  S  YSTEM 

the  tegmentum  to  the  lateral  intermedial  fasciculus  of  the  cord,  to  terminate 
in  relation  with  ventral-horn  cells. 

The  Central  Tegmental  Tract  (olivary  fasciculus]  probably  arises  in  the  inferior 
olivary  nucleus  and  ascends  in  the  tegmentum.  In  the  pre-oblongata  it  is  best 
seen  in  trans-sections  as  a  compact  longitudinal  bundle  along  the  dorsi-mesal 
aspect  of  the  superior  olive.  Cephalad  it  is  said  to  end  in  the  lenticula. 

Fountain  Decussation.1 — A  dense  decussation  may  be  found  in  the  space  between 
the  two  red  nuclei.  The  fibres  composing  the  decussating  bundles  arise  from 
cells  in  the  pregemina  and  central  aqueduct  gray.  After  having  crossed  the 
middle  line  they  descend,  join  the  medial  longitudinal  fasciculus,  and  give  off 
collaterals  to,  or  terminate  in  the  nuclei  of  the  eye-muscle  nerves. 

The  Crusta  or  Pes. — The  crusta  or  pes  is  somewhat  crescentic  in  outline 
on  section  and  is  composed  of  longitudinal  fibre-bundles — the  continuation  of 
the  internal  capsule — divisible  into  three  sectors.  The  middle  sector  comprises 
three-fifths  of  the  cross-section  area  of  the  crusta,  and  comprises  the  pyramidal 
tract  on  its  way  from  the  cerebral  cortex  (motor  area)  to  cranial  and  spinal 
centres  below.  The  ectal  sector,  or  lateral  one-fifth,  comprises  the  temporo- 
pontile  tract;2  its  axones  arise  from  cortical  cells  in  the  temporal  lobe  and  end 
in  fine  terminal  arborizations  in  relation  with  cells  of  the  nuclei  pontis.  The 
ental  sector,  or  mesal  one-fifth  of  the  crusta,  comprises  the  fronto-pontile  tract; 
its  axones  arise  from  cells  in  the  cortex  of  the  frontal  lobe  and  terminate  in 
the  nuclei  pontis. 

The  Pyramidal  Tract  is  a  direct  "voluntary"  motor  tract;  the  two  cortico-pontile 
tracts  enumerated  above  are  links  in  a  chain  of  neurones  which  constitute  an 
indirect  motor  tract.  The  series  may  be  shown  in  the  following  order:  Cortico- 
pontile  tract;  nuclei  pontis;  cerebello-cortex;  dentatum;  pre peduncle;  rubrum;  tractus 
rubrospinalis;  spinal  gray;  spinal  nerve;  muscle. 

Summary  of  the  Gray  Masses  in  the  Mid-brain. 

*  Central  aqueduct  gray 

(a)  Oculomotor  n.  nucleus 
(6)  Trochlear  n.  nucleus 
Nucleus  radicis  descendentis  nervi  trigemini 

*  Nucleus  of  medial  longitudinal  bundle  and  postcommissure 

*  Formatio  reticularis 

*  Substantia  nigra  (intercalatum) 

*  Rubrum  (red  nucleus) 

*  Stratum  cinereum  pregemini     • 

*  Nucleus  postgemini 

*  "  Interpeduncular"  ganglion. 

Structures  marked  with  an  asterisk  have  been  considered  in  the  preceding 
description.  The  central  connections  of  the  oculomotor,  trochlear,  and  trige- 
minal  nerves  may  now  be  described. 

Deep  Origin  of  Cranial  Nerves  Arising  in  the  Mid-brain. — The  mesen- 
cephalic  root  of  the  trigeminal  nerve  has  been  described  on  p.  894. 

The  Trochlear-nerve  Nucleus. — The  trochlear-nerve  nucleus  is  situated  in  the 
level  of  the  cephalic  half  of  the  postgeminum.  It  is  a  small  oval  mass  of  gray 
substance  in  the  ventral  part  of  the  central  aqueduct  gray.  The  cells  are  large, 
sometimes  stellate  in  appearance.  The  root  fibres  pursue  a  peculiar  course; 
they  accumulate  in  the  latero- ventral  angle  of  the  aqueduct  gray,  run  caudad, 
gradually  rising  dorsad,  and  suddenly  turn  mesad  to  undergo  a  complete  decus- 

1  Decussaiio  fontinalis,  so   called  because  of  the   resemblance  of  the  scattering  strands   to  the  jets  of   a 
fountain. 

2  Turck's  bundle;  not  to  be  confused  with  Tiirck  s  column  m  the  cord. 


PARTS  DERIVED  FROM  THE  FORE-BRAIN  9H 

sation  with  the  root  of  the  opposite  side  in  the  valvula,  emerging  laterad  of  the 
frenulum,  or  at  the  inner  border  of  the  prepeduncle. 

The  nucleus  is  placed  under  the  dominion  of  the  cerebral  cortex  by  pyramidal 
fibres,  and  it  is  associated  with  other  nuclei  in  the  brain-stem  by  the  medial 
longitudinal  bundle. 

The  Oculomotor-nerve  Nucleus.— The  oculomotor-nerve  nucleus  is  a  group  of 
cell-clusters  in  the  ventral  portion  of  the  aqueduct  gray,  subjacent  to  the  pregemi- 
num,  and  extending  cephalad  to  become  lost  in  the  gray  wall  of  the  third  ventricle 
at  the  slope  formed  by  the  opening  out  of  the  aqueduct.  Its  nerve-elements  are 
arranged  in  definite  groups.  The  most  cephalic  of  these  is  composed  of  smaller 
elements,  closely  crowded  and  embedded  in  deeply  staining  molecular  ground- 
substance.  In  a  flat-wise  section  of  the  brain-stem  the  outline  of  this  nucleus 
resembles  an  inverted  L  or  the  tip  of  a  boat-hook;  the  axones  from  the  cells  of 
this  nucleus  £of  Edinger  and  Westphal)  supply  the  ciliary  muscle  and  sphincter 
iridis  (pupillary  motion).  The  main  nucleus,  composed  of  several  sub-groups,  lies 
caudo-laterad  of  the  preceding,  and  is  composed  of  larger  cell-elements. 

The  root-fibre  bundles  from  this  nuclear  group  pass  ventrad,  breaking  through 
the  medial  longitudinal  fasciculus,  separating  like  the  strands  of  a  horse's  tail  by 
the  interference  of  the  red  nucleus,  to  become  gathered  into  more  compact  bundles 
between  the  mesal  edge  of  the  substantia  nigra  and  intercrural  region,  and  emerg- 
ing by  eight  to  twelve  fascicles  which  compose  the  trunk  of  the  oculomotor  nerve. 

The  origin  of  each  nerve  is  not  limited  to  the  nuclei  of  its  side;  a  part  is  decussated 
and  the  decussated  origin  is  related  to  the  innervation  of  the  Internal  Rectus.  By 
means  of  association  neurones  in  the  medial  longitudinal  fasciculus  the  oculo- 
motor and  abducens  nuclei  of  one  side  are  brought  into  relation,  affording  an 
organic  basis  for  the  synergism  existing  between  the  Internal  and  External  Recti 
muscles  in  the  conjugated  lateral  eye-movements. 

The  paradox  of  the  facial  nerve  supplying  muscles  under  the  reflex  dominion  of 
the  retina  (orbicularis  oculi)  instead  of  the  oculomotor  may  be  explained  by  the 
assumed  existence  of  fibres  emerging  from  the  oculomotor  nucleus,  entering  the 
medial  longitudinal  fasciculus  and  joining  the  root  of  the  facial. 


Parts  Derived  from  the  Fore-brain. 

The  Fore-brain  or  Prosencephalon  includes  those  portions  of  the  brain  which  are 
derived  from  the  cephalic  one  of  the  three  primary  brain-vesicles.  It  includes, 
according  to  prevailing  schemas,  a  thalamic  portion  (the  thalamencephalon  or 
diencephalon)  and  the  telencephalon.  The  two  divisions  constitute  a  structural 
continuity  and  exhibit  a  mutual  dependency  so  close  that  the  arbitrary  distinction 
now  in  vogue  tends  to  mislead.  The  relations  of  "diencephalon"  and  "telen- 
cephalon" are  further  complicated  by  the  intimate  fusion  of  the  sides  of  the  former 
(thalami)  with  the  floors  of  the  latter  (caudatums) ;  this  caudatothalamic  fusion, 
in  the  adult  brain,  gives  rise  to  some  difficulty  in  distinguishing  the  two  segments. 
The  internal  capsule  which  intervenes  between  thalamus  and  lenticula  also  inter- 
venes between  lenticula  and  caudatum,  both  telencephalic  parts. 

External  Morphology. — The  diencephalon  or  thalamencephalon  comprises  the 
thalami,  the  epiphysis  and  habenae,  the  pregeniculums,  and  the  pars  mammillaris 
hypothalami.  (Other  classifications  include  also  the  pars  optica,  with  tuber,  chiasm, 
and  hypophysis.  It  is  also  defined  as  so  much  of  the  fore-brain  as  does  not  enter 
into  the  formation  of  the  cerebral  hemispheres.)  Caudad  it  is  continuous  with 
the  mid-brain,  cephalad  with  the  cerebral  hemispheres.  Its  primitive  cavity 
becomes  metamorphosed  in  the  adult  into  the  third  ventricle  or  diacele  as  the 
lateral  walls  hypertrophy  to  form  the  thalami.  Its  ventral  surface  is  the  relatively 


912 


THE  NERVE  SYSTEM 


insignificant  gray  lamina  in  the  intercrural  space.  Its  dorsal  surface  is  concealed 
from  view  by  the  massive  hemispheres  and  their  great  commissure,  the  callosum, 
and  by  the  fornix.  Its  actual  roof,  separating  it  from  the  overlapping  cerebral 
parts,  is  a  delicate  membranous  fold,  the  diatela  or  velum  interpositum. 

The  Thalami.1 — The  thalami  constitute  the  bulk  of  this  portion  of  the  brain. 
They  are  large  ovoid  masses  of  gray  substance  so  named  by  the  ancients  after  their 
resemblance  to  a  pair  of  couches.  Each  thalamus  is  smaller  frontad  than  caudad 
and  the  caudal  ends  are  more  widely  separated  from  each  other.  The  mesal  or 
ventricular  surface  is  largely  free,  except  for  an  area,  of  variable  size,  by  which 
the  two  thalami  are  fused  in  90  per  cent,  of  brains.  This  thalamic  fusion  is  also 
called  the  medicommissure.  This  surface  is  covered  by  endyma  and  of  smooth 
contour.  Its  dorsal  limit  is  marked  by  an  endymal  ridge,  usually  torn  through 
in  dissection,  the  ripa2  or  tsenia  thalami,  fortified  by  a  subjacent  narrow  band  of 


MEDICOMMISSURE 

CHOROID   PLEXUS  OF 
THIRD  VENTRICLE 

TENIA  THALAMI 


COMMISSURE 


POSTCOMMISSURE 


ROSTRUM 

COPULA 
PRECOM- 
MISSURE 

TERMA 

CHIASM 

O  PT I C 

NERVE 

HYPOPHYs'lS 


FIG.  592. — Mesal  aspect  of  a  brain  sectioned  in  the  median  sagittal  plane. 


fibres  called  the  stria  medullaris,  which  may  be  traced  to  the  habenal  nucleus 
and  habenal  commissure  (or  "stalk"  of  the  epiphysis).  Caudad  lies  a  depressed 
triangular  area — the  trigonum  habenae,  situated  cephalad  of  the  pregeminum. 

The  dorsal  surface  is  usually  described  as  being  free,  but  only  a  narrow  ectal 
portion  can  be  so  described,  the  endyma  of  the  lateral  ventricle  being  slightly 
reflected  upon  it  (the  lamina  affixa]  before  entering  into  the  formation  of  the  para- 
plexus.  The  rest  of  the  dorsal  surface  is  not  lined  by  endyma,  but  is  in  contact 
with  the  pial  fold  called  the  velum  interpositum.  This  surface  is  of  a  whitish 
color  owing  to  a  thin  layer  of  white  fibres,  the  stratum  zonale.  A  faint  oblique 
groove  crosses  this  surface  in  a  caudo-lateral  direction,  corresponding  to  the  ectal 


1  Thalamos,  bed  or  couch;  bed-chamber. 

2  The  name  ripa  was  proposed  by  Wilder  for  the  line  formed  by  the  rupture  of  the  endyma  along  the  lines 
of  its  reflection  from  entocoelian  (ventricular)  surfaces. 


PARTS  DERIVED  FROM  THE  FORE-BRAIN 


913 


edge  of  the  fornix.  Laterad  it  is  demarcated  from  the  caudatum  by  a  groove 
which  is  occupied  by  a  slender  band  of  fibres  and  the  striatal  vein,  called  the  taenia 
semicircularis  or  stria  terminalis.  The  surface  is  not  of  even  contour  throughout, 
usually  showing  three  eminences  (in  addition  to  the  pulvinar)  corresponding  to 
the  main  nuclear  aggregations  within  the  thalamus,  viz. : 

Tuberculum  anterius. 

Tuberculum  medialis. 

Tuberculum  lateral  is. 


PSEUDOCELE 
HEM  (SEPTUM 


PRECOMMISSURC 
TENIA   THALAMI 
TENIA   SEMI- 
CIRCULARIS 
GROOVE  CORRE- 

PONDING  TO 
FORNIX 

TRIGONUM 

HABEN/E 

POSTCOM  MISSURE 

PREGEMINUM 
POSTGEMINUM 
TROCHLEAR 
NERVE 

FRENULUM 


•VALVULA  (CUt) 

FIG.  593. — Dissection  showing  the  two  thalami,  the  two  caudatums,  and  adjacent  parts. 

The  Tuberculum  Anterius. — The  tuberculum  anterius  forms  a  marked  bulging 
frontal  extremity,  which  helps  to  form  the  boundary  of  the  porta  (foramen  of 
Monro)  or  aperture  of  communication  between  lateral  and  third  ventricles. 

The  caudal  extremity  of  the  thalamus  is  a  prominent,  bolster-like  projection 
which  overhangs  the  brachia  of  the  quadrigemina  and  'is  called  the  pulvinar. 
A  smaller  oval  prominence,  situated  ventro-laterad  of  the  pulvinar,  is  termed  the 
pregeniculum  (corpus  geniculatum  externum) — a  partial  end-station  for  the  optic 
tract. 

58 


914  THE  NERVE  SYSTEM 

The  lateral  surface  of  the  thalamus  is  in  contact  with  the  internal  capsule — that 
great  concentration  of  fibre-tracts  coursing  to  and  from  cerebral  centres  and 
forming  the  crusta  below.  To  this  white  stratum  the  thalamus  itself  contributes 
fibres  destined  to  reach  the  cortex,  and  in  turn  it  receives  fibres  from  the  cortex. 
These  thalamo-cortical  and  cortico-thalamic  sets  of  fibres  constitute  the  thalamic 
radiation,  forming  a  more  or  less  distinct  reticulated  capsular  zone  (external 
medullary  lamina;  stratum  reticulatum)  for  the  thalamus. 

The  ventral  surface  is  in  contact  with  the  sub-thalamic  tegmental  substance 
and  continuous  with  the  central  gray  of  the  third  ventricle  lining  its  sides  and  floor. 

Internal  Structure  of  the  Thalamus  and  its  Connections. — The  thalamus  is  com- 
posed of  gray  substance,  with  large  multipolar  cells,  which  is  sub-divided  into  a 
number  of  distinct  nuclei;  twenty  such  have  been  described;  three  are  universally 
recognized.  They  are  separated  from  each  other  by  a  white  layer  (lamina  medul- 
laris  interna]  which  runs  parallel  to  the  wall  of  the  third  ventricle  for  its  greater 
length;  caudally  it  runs  mesad,  overlapped  by  the  ectal  nucleus,  and  numerous 
sub-laminae  run  into  it.  Frontad  the  internal  medullary  lamina  sub-divides  into 
two  branches,  thus  permitting  the  intrusion  of  the  nucleus  anterius  between  the 
two  main  nuclei  (medial  and  lateral}. 

The  nucleus  anterior  lies  fronto-dorsad ;  in  it  terminate  the  axones  of  the  fasciculus 
thalamomammillaris  (fasciculus  albicantiothalami — bundle  of  Vicq  d'Azyr}.  The 
nucleus  medialis  is  lined  mesad  by  the  central  gray  of  the  third  ventricle  and  is 
usually  fused  with  its  fellow  of  the  opposite  side  (medicommissure).  A  special 
spheroidal  cell-cluster  in  this  nucleus  is  called  the  centrum  medianum  (Luys). 
The  nucleus  lateralis  is  the  largest  of  the  three,  extending  the  entire  length  of  the 
thalamus  and  including  the  pulvinar.  A  special  semilunar  cluster  of  cells  in  the 
ventral  portion  of  this  nucleus  is  called  the  nucleus  semilunaris  (Flechsig). 

The  Connections  of  the  Thalamus. — The  thalamus  is  a  ganglion  interposed 
between  the  sensor  tracts  in  the  tegmentum  and  the  cerebral  cortex,  as  well  as 
an  important  link  in  the  optic  path.  It  also  gives  rise  to  motor  tracts  con- 
cerned with  instinctive  movements  of  an  emotional  nature.  It  is  a  relay  station 
for  the  various  tracts  which  convey  sensations  of  touch,  temperature,  and  pain 
from  the  body,  extremities,  head,  and  neck,  of  muscle-sense,  and  of  the  special 
senses.  It  transmits  these  impulses  to,  and,  reciprocally,  receives  impulses  from 
the  cerebral  cortex.  As  an  "emotional"  centre  it  is  also  under  the  inhibitory 
influence  of  the  cerebral  cortex,  which,  if  the  emotion  be  not  too  strong,  prevents 
its  external  manifestation. 

The  thalamo-cortical  and  cortico-thalamic  fibres,  with  the  internal  capsule,  enter 
into  the  corona  radiata  or  fan-like  formation  of  the  white  substance  of  the  cerebral 
hemisphere.  Although  there  is  no  anatomic  sub-division  into  distinct  groups  of 
these  fibres  as  they  stream  to  and  from  the  thalamus,  it  is  customary  to  distinguish 
a  frontal,  a  parietal,  an  occipital,  and  a  ventral  stalk.  The  frontal  and  parietal 
stalks,  as  their  names  indicate,  pass  between  thalamus  and  fronto-parietal  cortex, 
as  well  as  to  the  lenticula  and  caudatum.  The  occipital  stalk  is  composed  of 
fibres  passing  in  both  directions  between  the  pulvinar  and  occipital  cortex,  con- 
stituting the  so-called  optic  radiation.  The  ventral  stalk  comprises  the  ansa 
lenticularis  (thalamolenticular}  and  the  ansa  peduncularis  (thalamotemporal  and 
thalamoinsular}.  They  will  be  described  in  detail  farther  on. 

The  Pregeniculum  is  an  intercalar  ganglion  proper  to  the  optic  nerve,  derived 
from  the  thalamus.  On  section  it  is  seen  to  be  characterized  by  the  regular 
alternation  of  deeply  gray  and  white  laminae.  The  latter  are  thicker  and  com- 
posed of  fibres  which  enter  the  pregeniculum  from  the  optic  tract  and  optic  radia- 
tion. The  nerve-cells  in  the  gray  substance  are  large,  multipolar,  and  pigmented. 

[NoTE. — The  pregeniculum  and  the  more  isolated  postgeniculum  are  gener- 
ally included  under  the  head  of  metathalamus.} 


PARTS  DERIVED  FROM  THE  FORE-BRAIN  915 

The  Hypothalamic  Tegmental  Substance,  continuous  with  the  mid-brain  tegmen- 
tum,  is  interpolated  between  the  ventral  face  of  the  thalamus,  the  red  nucleus, 
and  a  continuation  of  the  substantia  nigra  known  as  the  corpus  hypothalamicus 
or  body  of  Luys.  Through  the  hypothalamic  tegmentum  stream  the  fibres  of 
the  medial  lemniscus,  of  the  cerebellar  pre peduncle,  and  from  the  red  nucleus,  to 
end  in  relation  with  thalamic  cells.  The  corpus  hypothalamicus  is  a  grayish- 
brown,  lentiform  mass  which  lies  in  the  ideal  continuation  frontad  of  the  lateral 
part  of  the  substantia  nigra,  and,  like  it,  situated  between  pes  and  tegmentum.  It 
is  made  up  of  fine  myelinated  fibres  crowded  in  great  profusion  and  confusion, 
with  numerous  delicate,  coiled  capillaries  and  sparse,  multipolar,  more  or  less 
pigmented,  nerve  elements  of  moderate  size.  The  outline  of  the  body  is  defined 
by  a  white  capsule,  some  of  the  fibres  of  which  are  seen  to  decussate  in  the  floor 
of  the  third  ventricle,  with  those  of  the  opposite  side  dorso-caudad  of  the  albicantia. 

The  Epiphysis  (corpus  piiieale)  (Figs.  592,  593). — The  epiphysis  (pineal  body, 
from  its  shape  resembling  a  fir-cone — pinus)  is  a  small,  reddish-gray  body  placed 
between  the  caudal  ends  of  the  thalami  and  occupying  the  depression  between 
the  two  pregemina.  It  is  covered  by  the  velum  interpositum,  which  intervenes 
between  it  and  the  splehium  of  the  callosum.  It  is  an  outgrowth  which  is  not 
regarded  as  an  important  neural  ingredient  of  the  human  brain  and  is  generally 
believed  to  be  a  rudimentary  relic,  representing  a  cyclopean  eye1  of  some  extinct 
ancestral  vertebrate,  homologous  with  the  parietal  organ,  resembling  a  molluscan 
eye  of  a  living  species  of  lizard  (the  Hatteria  of  Australia).  Its  attached  base  is 
a  hollow  peduncle  divisible  into  a  dorsal  and  ventral  part  by  the  intrusion  of  the 
epiphyseal  recess  (recessus  pinealis]  of  the  third  ventricle.  The  dorsal  stalk  con- 
tinues on  either  side  and  upon  each  thalamus  as  the  stria  medullaris;  it  is  reen- 
forced  by  commissural  fibres  joining  the  habenee  of  the  two  sides;  hence  another 
name  for  the  dorsal  stalk  is  the  habenal  commissure  (supracommissure  of  Osborn). 
The  ventral  stalk  is  folded  over  another  commissural  band — the  postcommissure. 

Structure. — The  epiphysis,  or  pineal  gland,  consists  of  a  number  of  follicles, 
lined  by  epithelium,  and  connected  together  by  ingrowths  of  connective  tissue. 
The  follicles  contain  a  transparent,  viscid  fluid,  and  a  quantity  of  sabulous  matter 
named  brain  sand  (acervus  cerebri),  composed  of  phosphate  and  carbonate  of 
lime,  phosphate  of  magnesia  and  ammonia,  with  a  little  animal  matter.  These 
concretions  are  almost  constant  in  their  existence,  and  are  present  at  all  periods 
of  life. 

In  the  interval  between  the  epiphysis  and  the  caudal  end  of  the  thalamus  lies 
a  small  triangular  depression  (sometimes  an  elevation)  known  as  the  trigonum 
habenae,  marking  the  position  of  the  nidus  or  ganglion  habenae,  a  group  of  small 
angular  cells.  The  axones  from  these  cells  are  collected  ventrad  into  the  fasciculus 
retroflexus  (Meynert),  which  courses  through  the  tegmentum  mesad  of  the  red 
nucleus  to  end  in  the  interpeduncular  ganglion  (Gudden)  in  the  postperforatum 
In  addition  to  this  fasciculus,  the  habena  is  the  reunion  point  for  two  other  sets 
of  fibres:  (1)  the  stria  medullaris  and  (2)  the  habena  proper  or  habenal  commissure. 
The  stria  medullaris  (p.  912)  is  made  up  of  axones  arising  from  two  sources: 
(1)  cells  in  the  hippocampus  (via  fornix)  and  (2)  cells  in  the  ganglion  opticum 
basale.  These  join  near  the  fornicolumn  (anterior  pillar  of  fornix)  and  run 
caudad  on  the  mesal  thalamic  surface,  to  end  in  the  habenal  ganglion  of  the  same 
side  and,  by  crossing  in  the  dorsal  stalk  of  the  epiphysis  form  the  habenal  com- 
missure, ending  in  the  corresponding  nidus  habenae  of  the  opposite  side. 

Postcommissure. — The  postcommissure  is  a  round  band  of  white  fibres  crossing 
from  side  to  side  in  the  ventral  stalk  of  the  epiphysis  bridging  the  aqueduct  at 

i  Although  most  vertebrates  show  a  single  epiphysis  or  parietal  organ,  it  is  double  in  the  lamprey  and  cer- 
tain reptiles;  the  two  epiphyses  lie  one  in  front  of  the  other — not  side  by  side  (although  probably  paired 
organs  originally).  The  frontal  organ  sends  its  fibres  into  the  habenal  nucleus;  the  caudal  organ  to  the 
region  of  the  postcommissure  (tectum  opticum). 


916  THE  NERVE  SYSTEM 

its  continuation  into  the  third  ventricle.  The  postcommissure  shares  relation 
with  both  fore-  and  mid-brain  structures  and  is  formed  of  decussating  fibres 
which  may  be  enumerated  in  the  following  systems:  (a)  fibres  arising  in  the  special 
nucleus  (described  on  p.  908)  for  the  medial  longitudinal  bundle;  (6)  fibres  connecting 
the  two  thalami;  (c)  fibres  connecting  the  habenal  nidi;  (d)  fibres  connecting  the 
pregemina. 

[NOTE. — The  habense,  epiphysis,  and  postcommissure  are  generally  included 
under  the  head  of  epithalamus.] 

The  Postperforatum  (locus  perforate  posticus). — The  postperforatum  has  been 
described  on  p.  861.  It  marks  the  situation  of  the  "  interpeduncular  ganglion," 
small  in  man,  but  very  large  in  rodent  brains.  From  the  cells  in  this  primitive 
gray  lamina  arise  the  fibre-tracts  already  described  as  the  taenia  pontis  (p.  906), 
and  often  visible  at  the  point  of  emergence  from  the  gray  substance  of  the  inter- 
crural  space. 

The  Albicantia  (Fig.  592). — The  albicantia  or  mammillaria  are  two  symmetrical, 
small,  round,  white  protuberances  situated  side  by  side  in  the  intercrural  space 
cephalad  of  the  postperforatum,  at  a  point  where  the  floor  of  the  third  ventricle 
rapidly  decreases  in  thickness  to  form  the  tuber.  The  color  of  each  albicans  is 
white,  owing  to  a  superficial  stratum  of  fibres  derived  from  the  fornix.  Within  lie 
three  nuclear  masses:  two  medial,  constituting  the  main  mass,  and  a  smaller 
lateral  nucleus  applied  against  the  former,  so  as  to  represent  a  crescent  on  cross- 
section. 

The  fibres  of  the  fornix  terminate  in  the  albicans.  From  its  cells  arise  two 
fasciculi  which  have  a  common  neurone  origin.  Cajal  discovered,  and  Kolliker 
confirmed  the  fact,  that  the  axones  from  the  medial  nucleus  cells  bifurcate;  one 
set  of  limbs  passes  fronto-dorsad  to  form  the  fasciculus  thalamomammillaris 
(bundle  of  Vicq  d'Azyr),  which  ends  in  the  nucleus  anterius  of  the  thalamus,  while 
the  other  set  of  limbs  of  the  primary  axones  passes  caudad  to  form  the  fasciculus 
pedunculomammillaris  in  the  mid-brain  tegmentum;  its  destination  is  doubtful. 
The  axones  from  the  lateral  nucleus  join  the  latter  bundle. 

[NOTE. — The  postperforatum  and  the  albicantia  are  generally  included  under 
the  head  of  the  Pars  Mammillaris  Hypothalami.] 

Third  Ventricle  (ventriculus  tertius)  (Fig.  592).— The  third  ventricle  is  the  adult 
representative  of  the  cavity  of  the  primary  fore-brain  vesicle,  but  only  so  much  of  it 
as  is  not  carried  laterad,  on  either  side,  in  the  rapidly  growing,  eventually  huge 
cerebral  hemisphere  buds  to  form  the  lateral  ventricles.  It  is  a  narrow,  cleft-like 
interval  between  the  two  thalami  and  hypothalamic  gray,  limited  frontad  by  the 
terma,  continuous  caudad  with  the  aqueduct  and  laterad,  through  the  portse, 
with  the  lateral  ventricles.  Its  roof  is  destitute  of  nerve  tissue  and  is  formed 
by  a  delicate,  fused  endymal  and  pial  layer,  invaginated  on  either  side  of  the 
median  plane  by  paraplexuses.  The  pial  layer  is  one  of  the  constituents  of 
the  fold  known  as  the  velum.  The  floor  of  the  ventricle  is  formed  by  structures 
already  described  on  the  basal  aspect  in  the  intercrural  space,  viz.,  the  tuber, 
albicantia,  and  postperforatum,  as  well  as  the  chiasm  and  a  portion  of  the  teg- 
mentum of  the  crura.  Much  of  the  floor,  it  may  be  noted,  is  formed  by  the 
primitive,  undifferentiated  central  gray;  and  although  the  optic  vesicle  developed 
from  its  ventro-cephalic  portion,  the  caudal  shifting  of  central  optic  connections 
to  thalamus  and  mid-brain  has  made  this  portion  of  the  neural  tube  wall  com- 
paratively insignificant.  The  lateral  walls  are  formed,  in  part  by  the  thalami,  in 
part  by  the  hypothalamic  gray  ventral  extension.  The  fornix  may  be  seen,  shining 
through  a  thin  lamina  of  gray  substance  and  the  endyma,  coursing  caudo-ventrad 
to  the  albicans.  A  slight  furrow,  the  aulix  or  sulcus  of  Monro,  may  sometimes  be 
traced  from  the  aqueduct  to  the  porta,  curving  ventrad  of  a  bridge-like  fusion  of 
the  two  thalami — the  medicommissure.  (The  latter  term  is  inappropriate,  as  no 


PARTS  DERIVED  FROM  THE  FORE-BRAIN  917 

commissural  fibres  appear  to  pass  from  one  thalamus  to  the  other  in  this  "thalamic 
fusion;"  it  is  absent  in  about  10  per  cent,  of  brains  examined.) 

The  cephalic  wall  is  formed  by  the  terma,  the  rudimentary  median-cephalic 
wall  of  the  neural  tube.  The  terma  is  attached  to  the  dorsum  of  the  chiasm; 
dorsally  it  is  reenforced  by  the  precommissure. 

As  seen  in  mesal  section  or  as  shown  by  a  cast  of  the  ventricle  (Fig.  592) 
it  is  seen  to  be  of  irregular  outline.  Frontad  is  the  optic  recess,  dorsad  of  the 
chiasm;  caudad  thereof  is  the  infundibular  recess  in  the  tuber.  The  epiphyseal 
recess  is  seen  between  the  habenal  commissure  and  the  postcommissure.  Dorsad 
of  the  epiphysis  is  a  diverticular  recess  of  variable  extent  (recessus  suprapinealis). 

If  the  segmentation  of  the  fore-brain  into  two  divisions  be  adopted  ultimately, 
it  will  be  necessary  to  allot  one  portion  of  the  third  ventricle  (between  the  thalami) 
to  the  diencephalon  (hence  diacele),  and  the  rest  to  the  telencephalon  (the  medial 
cavity  of  which  is  termed  the  aula  by  Wilder). 

In  anticipation  of  the  description  of  the  cerebral  hemispheres  we  may  consider 
here  the  remaining  structures  in  the  floor  of  the  third  ventricle,  usually  included 
under  the  head  of  the  pars  optica  hypothalami  of  the  telencephalon,  in  order  to  lead 
up  to  a  description  of  the  cerebral  connections  of  the  optic  tract. 

External  Morphology  of  the  Optic  Portion  of  the  Hypothalamus. — This 
includes  the  tuber  and  hypophysis,  the  terma,  the  chiasm,  and  the  optic  tracts. 

The  Tuber  (tuber  cinereum)  (Fig.  592). — The  tuber  is  a  thin-walled  conical  pro- 
jection in  the  intercrural  space  cephalad  of  the  albicantia.  Its  apical  portion  is 
attenuated  to  form  the  stalk  of  the  hypophysis ;  this  is  generally  termed  the  infundib- 
ulum,  while  the  cavity  of  the  funnel-shaped  diverticulum  is  called  the  infundibular 
recess  of  the  third  ventricle.  The  gray  lamina  composing  the  tuber  is  continuous 
with  the  central  ventricular  gray,  and  therefore  with  the  terma. 

The  Hypophysis. — The  hypophysis  is  a  structure  of  two-fold  origin,  giving  rise 
to  a  division  into  a  prehypophysis  and  a  posthypophysis.  The  posthypophysis 
alone  is  of  neural  origin,  developing  as  a  ventral  diverticulum  from  the  primitive 
neural  tube.  The  prehypophysis  develops  from  the  stomodseum,  or  primitive 
buccal  cavity,  as  a  tubular  diverticulum  (Rathke's),  which  eventually  loses  its 
connection1  with  the  oral  tissues  to  become  included  within  the  cranial  cavity 
and  intimately  attached  to  the  neural  bud.  Both  pre-  and  posthypophysis  are 
therefore  of  ectodermal  origin  and  have  developed  from  a  conjunction  of  surface 
tissues  which  have  migrated  from  opposed  (ventral  and  dorsal)  parts  through  the 
head!  The  prehypophysis  is  much  the  larger  and  somewhat  embraces  the  post- 
hypophysis;  the  two  are  inseparable,  however,  and  together  occupy  the  fossa 
hypophyseos  of  the  sphenoid. 

The  two  parts  of  the  hypophysis  are  as  distinct  in  structure  as  they  are  in  em- 
bryonic origin.  The  posthypophysis  consists  of  a  mass  of  neuroglia,  connective 
tissue,  and  bloodvessels;  the  structure  of  the  prehypophysis  is  distinctly  glandu- 
lar, resembling  that  of  the  parathyroid  bodies.  It  is  surmised  that  the  latter  is 
the  functional  part  of  the  hypophysis — concerned  with  the  internal  secretions, 
and  usually  involved  in  the  pathological  form  of  giantism  called  acromegaly. 

The  Terma  (lamina  terminalis  s.  cinerea]  (Fig.  592). — The  terma  is  a  thin,  easily 
torn  lamina  between  the  chiasm  and  the  precommissure,  limited  laterally  by  the 
closely  approximated  hemicerebra,  and  constituting  the  primitive,  undifferentiated 
cephalic  boundary  of  the  original  neural  tube. 

The  Optic  Tract  and  its  Central  Connections. — In  the  section  on  the  develop- 
ment of  the  brain  it  was  learned  that  the  optic  nerve  is  not  a  peripheral  nerve ;  it  is 
rather  a  central  brain  tract  extruded  from  the  neural  tube.  Evidence  is  at  hand 
that  in  ancestral  vertebrates  the  general  cutaneous  sensor  system  was  also  capable 

1  Occasionally  the  channel  persists  as  the  cranio-pharyngeal  canal. 


918 


THE  NERVE  SYSTEM 


of  light  perception.  With  the  recession  of  the  neural  tube  from  the  surface  and 
in  company  with  the  morphological  differentiation  of  the  head-end,  a  light-perceiv- 
ing pair  of  organs  arose  as  a  special  development.  The  distal  end  of  the  optic 
brain-vesicle  becomes  the  retina,  in  structure  like  the  brain-wall,  whose  cell- 
axones  carry  afferent  impulses  to  the  brain.  Although  the  optic  fibres  enter  the 
ventral  wall  of  the  brain,  the  retina  is  originally  derived  from  the  dorso-lateral 
(sensor)  wall  of  the  second  neuromere  (Fig.  558).  The  parietal  organs,  also 
light-perceiving,  likewise  developed  as  paired  dorsal  buds  farther  caudad,  eventu- 
ally to  atrophy,  as  the  more  frontal  optic  organs  better  subserved  the  purposes 
of  the  organism. 

The  remarkable  and  as  yet  unexplained  fact  regarding  the  optic  apparatus 
is  that  the  afferent  fibres  from  the  retinal  cells  pass  into  the  ventral  wall  to  cross 


UNCROSSED    FIBRES    FROM     LEFT    HALF 
OF    LEFT    RETINA    TO     LEFT    CENTRES 


CROSSED  FIBRES  FROM  LEFT  HALF 
OF  RIGHT  RETINA  TO  LEFT  CEN- 
TRES 


CONNECTING    LEFT   SIDE    OF    BRAIN   I 
WITH   LEFT    HALF    OF    RETINA  AND  1. 
CONSEQUENTLY     RIGHT     HALF   OF 
FIELD    OF    VISION 


MACULA    LUTEA 


INTERNAL  GENICULATE  BODY 
AND  ITS  NERVE  CELLS 

EXTERNAL  GENICULATE  BODY 
AND  ITS  NERVE  CELLS 


OPTIC    RADIATION 


FIG.  594. — Diagram  of  the  course  of  the  optic  fibres.     (W.  Keiller  in  Gerrish's  Anatomy.) 


to  the  opposite  side,  forming  a  decussation  which  is  total,  or  nearly  so,  in  vertebrates 
below  the  mammals;  the  more  laterally  placed  the  eyes  are  the  more  nearly  total 
is  the  decussation.1 

Although  the  optic  vesicle  is  a  diverticulum  of  the  fore-brain  in  its  cephalic 
portion,  the  optic  tract  in  its  central  connections  becomes  intimately  related  with 
the  pregeniculum  and  pulvinar,  with  the  pregeminum  of  the  mid-brain,  and  with 
the  occipital  cortex  of  the  cerebrum.  Some  of  these  central  structures  are  way- 
stations  in  reflex-paths;  the  occipital  cortex  alone  is  the  actual  visual  centre, 
though  visual  perceptions  are  here  brought  into  association  with  tactile,  auditory, 
and  other  impulses. 

1  Possibly  the  reflex  contraction  of  the  muscles  on  one  side  of  the  body  in  the  ancestral  vertebrate  followed 
the  perception  of  a  menacing  object  by  the  eye  of  the  opposite  side;   hence  the  advantage  of  a  decussation. 


THE  CEREBRAL  HEMISPHERES  919 

Chiasm. — From  the  retina  of  each  eye  the  so-called  optic  nerves  converge  to  par- 
tially decussate  at  the  base  of  the  brain  to  form  the  chiasm,  a  white  quadrangular 
plate  which  presses  in  the  primitive  central  gray  floor  of  the  third  ventricle,  as  pre- 
viously described.  Approximately  one-third  of  the  fibres  of  each  optic  nerve  do  not 
cross  to  the  opposite  side.  The  chiasm  is  further  reenforced  by  the  infracommis- 
sure  (of  Gudden)  and  other  lesser  fibre-tracts  (commissura  superior  [Meynerti]  and 
commissura  ansata  [Koliiker]).  The  fibres  in  the  chiasm  are  so  complexly  inter- 
woven that  only  through  exhaustive  experimental,  developmental,  and  pathologic 
studies  has  it  been  possible  to  understand  its  structure.  Broadly  stated,  the 
fibres  from  the  medial  (or  nasal)  halves  of  the  retinae  decussate  in  toto,  while  those 
from  the  lateral  (or  temporal)  halves  do  not  cross.  Leaving  the  chiasm,  the 
crossed  medial  and  uncrossed  lateral  fibres  form  the  slightly  flattened  optic  tracts 
coursing  caudo-laterad,  embracing  the  crura  cerebri  and  dividing  in  the  neighbor- 
hood of  the  pregeniculum  into  two  "roots,"  a  mesal  and  a  lateral  root.  The 
mesal  root  is  in  reality  not  a  part  of  the  true  optic  path;  it  is  a  separate  fascicular 
representation  of  the  infracommissure  of  Gudden,  composed  of  fibres  forming  a 
reciprocal  bond  of  union  (commissural)  between  the  postgeniculums  of  the  two 
sides  and  coursing  through  the  chiasm  i^Fig.  594).  The  lateral  root  of  the  optic 
tract  is  the  true  visual  path,  composed  of  (a)  the  uncrossed  fibres  from  the  lateral 
half  of  the  retina  of  the  same  side  and  (6)  the  crossed  fibres  from  the  mesal  half  of 
the  retina  of  the  opposite  side.  The  fibres  of  the  lateral  root  are  distributed  to 
the  primary  or  lower  optic  centres  as  follows:  (1)  Most  fibres  end  in  the  pregenicu- 
lum; (2)  a  lesser  number  end  in  the  pulvinar;  (3)  the  remainder  end  in  the  nucleus 
of  the  pregeminum. 

The  pregeniculum  and  pulvinar  are  ganglionic  way-stations  or  internodes  in 
which  visual  impulses  are  reflected,  in  large  part,  to  the  visual  cortex  in  the  occip- 
ital lobe;  the  pregeminum,  on  the  other  hand,  plays  no  part  in  the  conduction  of 
impulses  perceived  as  light  or  color;  it  presides  rather  over  the  eye-muscle  reflexes 
to  visual1  stimuli,  and  in  its  turn  is  under  the  dominion  of  the  higher  cortical 
centre.  Reflex  impulses  are  sent  to  oblongatal  and  spinal  centres  along  axones 
entering  into  the  formation  of  the  medial  longitudinal  bundle.  The  axones  of 
corticifugal  neurones  proceed  to  the  nucleus  of  the  pregeminum  along  the  optic 
radiation.2 

The  connections  of  the  pregeniculum  and  pulvinar  with  the  higher  cortical 
centre  of  vision  are  established  by  neurones,  the  cells  of  wrhich  lie  in  the  two  gan- 
glia just  mentioned,  and  whose  axones  stream  in  an  arched,  more  or  less  compact 
bundle  in  the  white  matter  of  the  hemicerebrum  toward  the  occipital  cortex. 
Another  system  of  neurones,  whose  cells  lie  in  the  cortex,  sends  its  axones  in 
the  reverse  direction  (corticifugal)  to  the  two  lower  centres.  The  cerebral  tract 
thus  formed  between  primary  and  secondary  (cortical)  centres  is  called  the  optic 
radiation,  to  be  studied  more  fully  in  the  sequel.  The  components  of  the  optic 
path  are  delineated  schematically  in  Fig.  594. 


The  Cerebral  Hemispheres. 

External  Morphology. — Of  all  the  component  parts  of  the  brain,  the  cerebral 
hemispheres  form  the  largest  part,  and  their  preponderance  and  remarkable 
specialization  underlie  the  extraordinary  manifestations  of  the  intellect  so  highly 
amplified  in  man. 

The  term  cerebrum,  often  employed  loosely  as  embracing  several  brain-parts, 


1  And  auditory  stimuli  as  well  (see  p.  907). 

2  Centrifugal  fibres,  ending  in  the  retina  and  probably  arising  from  cells  in  the  pr 
discovered  in  the  optic  tracts. 


egeminum.  have  been 


920 


THE  NERVE  SYSTEM 


is  here  intended  to  include  the  brain-mantle  and  the  olfactory  lobe — equivalent  to 
the  telencephalon  of  His,  with  the  exception  of  the  pars  optica  hypothalami.  As 
already  indicated  in  the  section  on  brain-development,  there  has  occurred,  in  the 
evolutionary  history  of  man's  vertebrate  ancestry,  a  progressive  increase  of  the 
secondary  fore-brain,  with  concomitant  reduction  of  the  rhinencephalon,  or  smell- 
brain — the  most  archaic  portion  because  of  the  important  relations  of  the  smell- 
sense  to  the  life  history  of  the  earliest  vertebrates.1 

In  a  mesal  view  of  a  hemisected  brain  (Fig.  595)  may  be  seen  the  various  parts 
of  the  brain-stem  and  the  cerebellum  overlapped  by  the  preponderatingly  greater 
cerebrum.  Among  the  many  notable  features  exposed  to  view  in  this  brain- 
section  are  certain  fibre-masses,  commissures,  extending  across  the  meson,  and 
therefore  divided  by  the  knife  in  this  preparation.  Of  the  commissures  pertaining 
to  the  cerebrum  one  is  conspicuous  for  its  size  and  firm  consistency.  This  great 


DICOMMISSURE 
CHOROID    PLEXUS  OF 
HIRD  VENTRICLE 

TENIA  THALAMI 


HABENAL 
COMMISSURE 


POSTCOMMISSURE 


ROSTRUM 

COPULA 
PRECOM- 
MISSURE 

TERMA 

CHIASM 
O 

NERVE 
HYPOPHYSIS 


VEN 

FIG.  595. — Mesal  aspect  of  a  brain  sectioned  in  the  median  sagittal  plane. 


fore-brain  commissure  is  the  callosum  already  mentioned  as  being  demonstrable 
in  the  depths  of  the  intercerebral  cleft  on  divaricating  the  lips  of  this  fissure.  The 
callosum  constitutes  a  massive  system  of  association  fibres  for  the  bilateral  coordi- 
nation of  corresponding  cortical  parts.  It  is  thickened  caudally,  forming  the 
splenium  of  the  callosum ;  f rontad  it  bends  on  itself  ventro-caudad  to  form  the  germ 
("knee"),  including  an  interval,  between  the  two  limbs,  which  is  flanked  on  both 
sides  by  a  thin  lamina  (hemiseptum)  and  bounded  ventrad  by  the  fornix,  constitu- 
ting a  closed  cavity,  the  pseudocele  (or  "fifth  ventricle").  The  recurved  ventral 
part  of  the  genu  tapers  into  a  thinner,  beak-shaped  part,  the  rostrum.  The  rostrum 
is  joined  to  the  terma,  frontad  of  the  precommissure,  by  a  thin  lamina,  the  copula 
(lamina  rostralis;  lamina  baseos  alba). 


1  For  a  more  thorough  discussion  on  the  natural  subdivision  of  the  fore-brain,  based  upon  comparative 
morphology,  see  the  paper  by  G.   Elliott  Smith,  Journal  of  Anatomy  and  Physiology,   1901. 


THE  CEREBRAL  HEMISPHERES 


921 


An  arched  structure  composed  of  longitudinal  fibre-bundles  comes  to  view 
ventrad  of  the  junction  of  the  splenium  with  the  body  of  the  callosum,  proceeds 
fronto-ventrad  with  its  convexity  frontad,  to  sink  from  view  in  the  substance  of 
the  hypothalamic  gray  at  a  point  just  caudad  of  the  precommissure.  This  white 
arched  bundle  is  the  fornix.  Between  it  and  the  callosum,  rostrum,  and  copula 
stretches  a  thin,  translucent  lamina  of  nerve-tissue — the  hemiseptum.  The  hemi- 
septa  of  the  two  sides  together  have  usually  been  termed  the  septum  pellucidum, 
while  the  enclosed  narrow  cavity  is  called  the  pseudocele  or  fifth  ventricle.  The 
subjacent  parts  revealed  in  this  section  have  already  been  described;  the  mor- 
phology and  internal  relations  of  the  callosum,  fornix,  and  hemiseptum  will  be 
described  at  a  later  stage. 


OCCIPITAL 
PO 


INTCRCEREBRAL 
ISSURE 


FRONTAL          INTERCEREBRAL 
POLE          FISSURE 

FIG.  596. — The  cerebral  hemispheres  viewed  from  above.     (Spalteholz.) 

The  cerebral  hemispheres  together,  as  viewed  from  above  or  dorsally,  appear 
as  two  symmetrical  masses  in  close  apposition,  conforming  in  outline  to  that  of 
the  cranial  cavity,  which  they  so  nearly  fill.  The  frontal  extremities  or  poles  are 
massive  and  rounded,  preponderatingly  so  in  comparison  with  the  brains  of  any 
related  primate  species.  The  occipital  poles  are  each  more  pointed,  but  expand 
frontad  into  the  widest  part  of  the  cerebrum — the  parietal  lobes.  The  cerebral 
hemispheres  or,  briefly,  the  hemicerebra  are  partially  separated  from  each  other 
by  the  intercerebral  cleft  or  fissure  (fissura  longitudinalis  cerebri),  into  which  fits 


922 


THE  NERVE  SYSTEM 


a  fold  of  the  dura— the  falx.  By  means  of  a  large  commissural  band  of  white  fibres 
—the  callosum — the  cerebral  halves  are  joined  together  in  the  depths  of  the  inter- 
cerebral  cleft.  All  adjacent  parts  of  the  brain  are  overlapped  by  the  ponderous 
cerebrum  so  as  to  entirely  conceal  the  thalamic  portion  and  the  mid-brain,  while 
the  occipital  lobes  overlap  the  cerebellum  with  the  intervening  tentorium— another 
fold  of  the  dura.  Further  description  will  be  restricted  to  each  hemicerebrum. 

Configuration  of  Each  Hemicerebrum.— Each  hemicerebrum  presents  an 
outer  convex  surface  (fades  convexa  cerebri),  applied  to  the  corresponding  half  of 
the  cranial  vault;  a  mesal  flattened  surface  (fades  medialis  cerebri),  which  lies  in 
a  sagittal  plane,  applied  to  the  corresponding  surface  of  the  opposite  hemicerebrum, 
with  the  intercerebral  cleft  intervening,  and  for  the  most  part  in  contact  with  the 
falx;  and  a  basal  or  ventral  surface,  of  irregular  form,  resting  frontad  upon  the  floors 
of  the  anterior  and  middle  cranial  fossae,  and  caudad  upon  the  tentorium. 


OCCIPITAL  F. 


FIG.  597. — Principal  fissures  and  lobes  of  the  cerebrum  viewed  laterally. 

Prominent  in  the  lateral  and  ventral  views  is  the  blunt  projection  of  the  temporal 
pole,  while  at  the  ventro-lateral  border,  nearer  the  occipital  pole,  is  a  slightly 
marked  indentation  usually  called  the  pre-occipital  notch.  The  deep  valleculai1 
depression  between  the  orbital  surface  and  the  temporal  pole  accommodates  the 
great  wing  of  the  sphenoid. 

More  or  less  distinct  borders  demarcate  the  surfaces.  The  arched  dorsi-mesal 
border  intervenes  between  the  mesal  and  the  convex  surfaces;  a  straight  mesorbital 
border  intervenes  between  the  orbital  and  mesal  surfaces  of  the  frontal  lobe;  a 
ventro-lateral  border  separates  the  tentorial  surface  from  the  lateral,  convex 
surface  of  the  occipital  and  temporal  lobes ;  while  an  obtuse  border — the  meso- 
ventral  or  internal  occipital  border  separates  the  tentorial  from  the  mesal  surfaces. 

Cerebral  Fissures  and  Gyres. — The  surface  of  each  hemicerebrum  presents 
alternating  depressions  or  fissures  which  demarcate  gyral  elevations — the  convolu- 
tions or  gyres.1  The  fissures  vary  in  depth  from  that  of  a  mere  shallow  groove 
to  as  much  as  30  mm.,  and  may  attain  a  length  of  15  cm.  They  are  more  or  less 

:  Consistent  with  the  use  of  the  English  lobe  and  lobes  (for  lobus  and  lobi),  the  English  (lyre  and  gyres  are 
preferable  to  ayrus  and  gyri.  The  term  fissure  is  here  uniformly  employed  for  all  anfraetuosities  of  the  sur- 
face, though  sulcus  (pi.  sulci)  is  quite  as  generally  used;  sometimes  both  terms  are  indiscriminately  mixed. 


THE  CEREBRAL  HEMISPHERES  923 

sinuous  and  ramified.  They  mark  the  surface  with  fairly  approximate  uniformity, 
that  is,  one  rarely  finds  an  unfissured  surface  more  than  15  to  20  mm.  in  width. 
Numerous  functional  and  mechanical  influences  must  be  credited  with  bringing 
about  the  complex  foldings  of  the  cerebral  surface,  principally  (a)  resistance  of 
the  cranium  to  the  expanding  brain  or  "mechanical  packing;"  (6)  differences  of 
growth-rate  in  different  parts  of  the  cortical  surface;  (c)  differences  of  growth- 
rate  of  different  fibre-bundles  retarding  cortical  expansion  along  the  fissure-lines 
and  elongating  to  help  in  the  formation  of  the  gyres.  The  obvious  result,  whatever 
the  influences  may  be,  is  an  expansion  of  the  cerebral  cortex  to  an  enormous 
degree,  so  that,  instead  of  having  a  surface-area  of  only  60,000  sq.  mm.  (if  un- 
convoluted),  the  average  adult  cerebrum  has  a  cortical  area  of  200,000  sq.  mm. 
or  more.  Furthermore,  the  vascular  pia,  closely  investing  the  surface  and  dipping 
into  every  fissure,  is  expanded  in  a  like  manner,  affording  an  ample  and  uniform 
supply  of  blood  for  the  entire  cerebral  cortex. 

The  cerebral  vesicle  of  the  fcetal  brain  presents  a  smooth  surface  during  the  first 
half  of  intrauterine  life,1  except  for  the  depressed  fossa  at  the  site  of  the  future 
insula — destined  to  become  buried  in  the  depths  of  the  sylvian  cleft  formed  by  the 
apposition  of  the  more  energetically  growing  contiguous  parts  of  the  cerebral 
mantle.  Some  of  the  cerebral  fissures  develop  early  as  infoldings  of  the  com- 
paratively thin  wall  of  the  vesicle,  and  hence  produce  corresponding  projections 
into  the  cerebral  cavity;  these  are  termed  the  total  or  complete  fissures.  The 
remaining  fissures  are  only  linear  depressions  of  the  surface  not  involving  the  entire 
thickness  of  the  wall — the  partial  or  incomplete  fissures.  The  complete  fissures  and 
their  correlative  projections  into  the  cerebral  cavity  (lateral  ventricle)  are: 

Fissure.  Internal  Eminence. 

Hippocampal  fissure.  Hippocampus. 

Calcarine  fissure.  Calcar. 

Collateral  fissure.  Collateral  eminence. 

Occipital  fissure.  Occipital  eminence. 

Among  the  remaining  cerebral  fissures,  of  which  over  fifty  have  been  recognized 
and  named,  some  are  constant  in  representation  in  all  normal  brains,  while  others 
are  of  variable  occurrence  in  different  individual  specimens.  The  constant 
fissures  are  those  which  regularly  exist  as  interlobar  and  intergyral  boundary 
lines  forming  a  common  pattern  for  all  normal  brains,  but  these,  like  all  cerebral 
fissures,  are  subject  to  many  individual  variations  as  to  course,  depth,  length, 
mode  of  branching,  and  anastomosis  with  neighboring  fissures  or  manner  of 
interruption  by  gyral  isthmuses.  The  range  of  individual  variations  is  so  great 
that  no  two  brains  can  be  said  to  be  exactly  alike ;  in  fact,  one  may  find  numberless 
stages  of  complexity  in  the  cerebral  surface  configuration  from  the  simply  fissured 
brains  of  mentally  inferior  individuals  and  races  to  the  complexly  fissured  and 
more  highly  organized  brains  of  vigorous  thinkers  and  talented  geniuses  among 
the  highly  intellectual  races  of  man. 

Cerebral  Lobes  and  Fissures. — The  cerebral  surface  is  divided  into  five  prin- 
cipal areas  called  lobes,  demarcated  by  certain  constant  fissures  which  are  more 
or  less  conspicuous,  and  were  therefore  selected  by  the  older  anatomists  as  arbi- 
trary boundary  lines;  these  are  termed  the  interlobar  fissures. 

The  lobes  are:  (1)  the  frontal;  (2)  the  parietal;  (3)  the  temporal;  (4)  the  occipital; 
(5)  the  insula.  The  inter-lobar  fissures  are :  (1)  the  sylvian;  (2)  the  central;  (3)  the 
occipital;  (4)  the  calcarine;  (5)  the  circuminsular.  A  series  of  fissures  demarcating 

1  The  so-called  transitory  fissures  of  older  descriptions  may  be  neglected,  since  the  researches  of  Retzius, 
Hochstetter,  and  Mall  have  shown  these  to  be  in  reality  artifacts  due  to  postmortem  swelling. 


924 


THE  NERVE  SYSTEM 


the  rhinencephalon  from  the  pallium  or  cerebral  mantle  proper  will  be  considered 
at  a  later  stage. 

The  Interlobar  Fissures.  The  Sylvian  Fissure  and  its  Kami  (fissura  cerebri 
lateralis  [Sylvii]). — This  fissure  is  a  well-marked  cleft  on  the  base  and  side  of  the 
hemicerebrum.  Traced  laterad  from  the  region  of  the  preperforatum,  it  begins 
as  a  deep  depression  between  the  orbital  surface  of  the  frontal  lobe  and  the  tem- 
poral pole,  corresponding  to  the  bony  ridge  formed  by  the  lesser  wing  of  the  sphe- 
noid and  extending  to  the  convex  surface.  This  portion  of  the  fissure  is  termed 
the  basisylvian  fissure  or  vallecula  sylvii,  as  far  as  the  sylvian  point.1  The  sylvian 
point  marks  the  conjunction  of  the  main  portion  of  the  sylvian  fissure  with  its 
basisylvian  part  as  well  as  one  or  two  rami.  These  rami  are:  (1)  the  presylvian 
ramus;  (2)  the  subsylvian  ramus. 


INTERCEREBRAL  F. 


F.=FISSURE 
G.=  GYRE 


FIG.  598. — Cerebral  fissures  and  gyres  viewed  dorsally. 

The  Presylvian  Ramus2  usually  proceeds  dorsad,  slightly  inclined  frontad,  for 
a  distance  of  2  to  3  cm.  into  the  subfrontal  gyre. 

The  Subsylvian  Ramus  (anterior  horizontal  limb]  extends  frontad  for  a  distance 
of  1.5  to  2.  cm.,  parallel  to  the  orbito-f rental  (superciliary)  margin. 

These  two  rami  often  spring  as  shorter  branches  from  a  common  stem  and  both 
may  be  replaced  by  a  single  unbranched  limb. 

The  sylvian  fissure  proper  is  the  most  conspicuous  part.  It  extends  from  the 
sylvian  point  in  a  caudal  direction,  inclined  slightly  dorsad,3  on  the  lateral  surface 
of  the  cerebrum  for  a  distance  averaging  6  cm.  It  separates  the  temporal  lobe 

1  So  called  in  cranial  topography. 

2  Also   called  the  anterior  ascending  limb.     In  B.  N.  A.  terms  the  name  for  this  fissural   branch  is  Kamua 
anterior  asc.endens  fissurie  cerebri  lateralis. 

3  Its  inclination  to  the  horizontal  plane  is  called  the  syh^n  angle,  approximately  15  degrees. 


THE  CEREBRAL  HEMISPHERES 


925 


wholly  from  the  frontal  and  partly  from  the  parietal  lobe.  It  usually  ends  in  an 
upturned  manner,  in  the  parietal  lobe,  the  change  of  direction  being  oftener 
abrupt  than  gradual;  this  terminal  piece  receives  the  name  of  episylvian  ramus. 
Occasionally  a  short  ramus  is  sent  ventrad  into  the  supertemporal  gyre  and  is 
called  the  hyposylvian  ramus. 

The  sylvian  fissure  ranges  in  depth  from  15  mm.  or  less  at  the  presylvian  point 
to  25  or  30  mm.  at  the  postsylvian  point,  correlative  with  the  contour  of  the  insula, 
which  lies  in  its  depths.  If  the  lips  of  the  sylvian  fissure  be  divaricated  the 
insula  is  revealed  as  a  cortical  district,  of  tetrahedral  form,  which  is  normally 
completely  concealed  by  overlapping  portions  of  the  hemicerebrum  called  the 
opercula.  These  are  four  in  number:  (1)  the  operculum  proper,  (2)  the  preoper- 
culum,  (3)  the  suboperculum,  and  (4)  the  postoperculum. 

The  operculum  (frontoparietal  operculum)  is  composed  of  the  adjacent  portions 
of  the  ventral  border  of  the  frontal  and  parietal  lobes,  the  sylvian  fissure  interven- 
ing between  it  and  the  postoperculum,  which  is  the  overlapping  part  of  the  temporal 
lobe.  The  pre-operculum  is  a  small  triangular  portion  embraced  by  the  presylvian 


INTERLOCKING 
GYRES 


PRECENTRAL 
GYRE 


POSTCENTRAL 
GYRE 


FIG.  599. — Central  fissure  fully  opened  up,  so  as  to  exhibit  the  interlocking  gyres. 


and  subsylvian  rami,  and  is  also  called  the  pars  triangularis  or  Broca's  cap.  The 
suboperculum  (orbital  operculum)  is  small,  demarcated  by  the  subsylvian  ramus, 
and  for  the  most  part  on  the  orbital  face  of  the  frontal  lobe,  projecting  slightly 
over  the  frontal  part  of  the  insula,  with  its  margin  separated  from  the  temporal 
pole  by  the  basisylvian  cleft. 

The  overlapping  opercula  are  demarcated  from  the  insula  by  the  circuminsular 
fissure  (sulcus  circular  is  Reilii). 

Development  of  the  Insula  and  the  Sylvian  Cleft. — The  insular  cortical  district 
is  topographically  correlative  with  the  great  gray  ganglia  of  the  cerebral  hemi- 
sphere, particularly  the  lenticula,  from  whose  ectal  surface  the  insular  cortex  is 
but  little  removed.  As  will  be  learned  at  a  later  stage,  few  if  any  projection  fibres 
pass  to  and  from  the  insula ;  its  function  is  almost  wholly  associative  for  adjacent 
parts  of  the  cerebral  mantle.  The  insula  therefore  becomes  buried  beneath  the 
more  energetically  growing  and  bulging  parts  immediately  around  it.  There  is  at 
first  a  slight  fossa  (observable  in  the  tenth  to  twelfth  week)  which,  as  develop- 
ment proceeds,  and  as  the  overhanging  opercula  encroach  upon  the  insula,  becomes 
more  deeply  situated  as  a  cleft-like  depression  until  at  birth  the  fossa  has  become 
a  fissure,  with  the  insula  perhaps  slightly  exposed  near  its  cephalic  extremity, 
where  the  incomplete  apposition  of  the  opercula  leaves  a  triangular  space.  This 


926  THE  NERVE  SYSTEM 

space  is  usually  obliterated  in  childhood,  but  is  commonly  met  with  in  certain 
races  (negro,  Australian)  and  in  brains  showing  developmental  defects  or  arrest. 
The  mechanics  of  the  formation  of  the  surface  outline  of  the  sylvian  fissure  by 
the  apposition  of  the  growing  and  plastic  opercula  may  be  understood  by  a  refer- 
ence to  Fig.  604. 

The  Central  Fissure  (fissure  of  R,olando  [sulcus  centralis]). — The  central  fissure  is 
situated  at  about  the  middle  of  the  convex  surface,  and,  coursing  obliquely  latero- 
frontad,  divides  this  surface  into  approximately  equal  parts,  intervening  between  the 
frontal  and  parietal  lobes.  It  may  be  traced  from  a  point  at  or  near  the  dorsi-mesal 
border,  about  1  cm.  caudad  of  the  mid-point  of  the  occipito-f  rontal  arc.  It  then  runs 
sinuously  latero-frontad  to  within  a  short  distance  of  the  sylvian  fissure,  about  2  cm. 
caudad  of  the  sylvian  point;  its  line  of  general  direction  makes  an  angle  of  about 
70  degrees  with  the  median  line  (Rolandic  angle).  If  measured  along  its  sinuosities, 
its  length  averages  10.5  cm.  Its  curved  course  may  be  analyzed  into  five  alternate 
curves  (sometimes  more  or  less),  of  which  three  are  convex  frontad  and  two  caudad. 
It  is  rarely  very  much  branched  and  does  not  often  anastomose  with  neighboring 
fissures.  Its  dorsal  end  bears  a  constant  relation  to  the  caudal  limb  of  the  para- 
central,  frontad  of  which  it  can  be  found  as  a  hook-like  curve.  If  the  lips  of  the 
central  fissure  be  divaricated,  interdigitating  sub-gyres  are  commonly  seen  in  its 
depths.  These  interlocking  gyres  are  often  fused  to  a  greater  or  lesser  degree, 
and  a  total  interruption  of  the  fissure  has,  in  rare  instances,  been  observed.  The 
central  fissure  develops  at  about  the  end  of  the  fifth  month  of  intrauterine  life,  not 
as  a  single  integer,  but  as  the  result  of  the  union  of  two  segments:  a  short  dorsal  and 
a  longer  ventral  segment.  As  development  proceeds  these  segments  eventually 
unite  end  to  end,  and  at  the  site  of  this  union  a  vadum  (or  shallow  uprising  of  the 
floor  of  the  fissure)  or  even  a  complete  isthmus  may  be  demonstrated  in  the  adult 
brain.  Only  three  cases  of  bilateral  interruption  are  on  record. 

The  Occipital  Fissure  (fissura  occipitalis). — The  occipital  fissure  is  a  deep 
cleft  across  the  dorsi-mesal  border  trans-secting  the  occipito-frontal  arc  at  about 
5  cm.  from  the  occipital  pole,  and  extending  upon  both  the  mesal  and  the  convex 
surfaces.  On  the  meson  it  attains  a  length  of  3  to  3.5  cm.  (to  its  junction  with  the 
calcarine  fissure)  while  its  lateral  extent  is  shorter  (2  to  2.5  cm.).  It  is  quite 
deep  throughout  and  usually  shows  a  number  of  interdigitating  sub-gyres. 

The  Calcarine  Fissure  ( fissura  calcarind). — The  calcarine  fissure  is  a  slightly  arched 
fissure  which  is  usually  joined  with  the  occipital  fissure  at  the  apex  of  the  cuneus 
and  extends  caudad  to  the  occipital  pole,  ending  in  a  bifurcation.  The  fissure  is 
composed  of  two  integers  which  may  be  partially  or  completely  separated  (by  a 
vadum  or  an  isthmus);  the  caudal  segment  may  then  be  distinguished  as  the  post- 
calcarine  fissure. 

The  occipital  and  calcarine  fissures  join  to  form  a  Y-shaped  junction ;  the  two 
limbs  of  the  Y  embrace  the  cuneus,  while  the  stem  is  continued  as  the  occipito- 
calcarine  stem  for  a  distance  of  about  3  cm.  This  fissural  stem  is  allotted  to  the 
occipital  fissure  by  some  and  to  the  calcarine  fissure  by  other  authors.  As  there 
is  no  greater  frequency  of  confluence  with  one  as  against  the  other,  so  far  as  present 
statistics  go,  it  is  preferable  to  assign  no  special  relationship  for  this  stem  to  one 
cr  the  other  principal  fissure. 

I.  Frontal  Lobe.  Fissures  of  the  Frontal  Lobe.  1.  LATERAL  SURFACE. — 
The  lateral  surface  is  bounded  by  the  dorsi-mesal  arched  border,  by  the  fronto- 
orbital  (or  superciliary)  border,  by  the  sylvian  fissure  (in  part),  and  by  the  central 
fissure.  The  principal  fissures  making  this  surface  demarcate  four  gyres:  (1)  the 
precentral,  (2)  superfrontal,  (3)  me dif rontal,  and  (4)  subfrontal  gyres.  The  fissures 
are:  (1)  the  precentral,  (2)  superfrontal,  and  (3)  subfrontal  fissures.  In  addition 
must  be  described  certain  fissures  which  are  intragyral  and  of  more  or  less  con- 
stant occurrence. 


THE  CEREBRAL  HEMISPHERES 


927 


The  Precentral  Fissural  Complex  (milcus  prccentralis) . — Two  fissural  integers 
which  are  sometimes  joined  extend  more  or  less  parallel  with  the  central  fissure. 
The  mesally  situated  piece  is  usually  of  zygal  (yoke-shaped)  shape  or  triradiate,  and 
usually  anastomoses  with  the  superfrontal  fissure.  From  its  position  it  is  termed 
the  supercen|ral  or  superior  precentral  fissure  (sulcus  precentralis  superior).  The 
laterally  situated  piece  is  of  longer  extent,  sometimes  straight  or  slightly  sinuous, 
sometimes  arched  like  an  inverted  L,  or  T-shaped.  It  usually  anastomoses  with  the 
subfrontal  fissure.  The  t\vo  precentral  segments  demarcate  the  precentral  gyre 
from  the  remaining  three  gyres  of  the  lateral  surface  of  the  frontal  lobe. 

The  Superfrontal  Fissure  (sulcus  frontalis  superior)  usually  springs  from  the 
supercentral  and  pursues  a  sinuous  course  frontad,  to  become  lost,  as  a  rule,  in 
the  zigzag  or  transverse  ramifications  of  the  prefrontal  region.  It  is  usually  quite 
ramified  and  often  anastomoses  with  other  fissures.  It  demarcates  the  superfrontal 
from  the  medifrontal  gyre. 


GYRE 
•RAMUS 
FIG.  600. — Fissures  and  gyres  of  the  lateral  surface  of  the  left  hemi cerebrum. 

The  Subfrontal  Fissure  (sulcus  frontalis  inferior)  is  most  often  confluent  with  the 
precentral,  less  often  with  the  supercentral  fissure.  It  proceeds  frontad  in  an  arched 
course,  to  end  either  in  a  bifurcation  or  by  anastomosing  with  other  fissures  (radiate 
fissures,  orbito-frontal  fissures,  or  medifrontal  fissures).  The  subfrontal  fissure 
demarcates  the  medifrontal  from  the  subfrontal  gyre. 

Both  the  superfrontal  and  medifrontal  gyres  are  characterized  by  a  more  or 
less  pronounced  longitudinal  subdivision  by  less  constant  fissural  segments.  They 
are:  (1)  the  paramesal  fissure  (sulcus  paramedialis)  occupying  an  intermediate  posi- 
tion between  the  superfrontal  fissure  and  the  dorsi-mesal  border,  in  the  super- 
frontal  gyre,  more  often  composed  of  a  series  of  short  segments  which  become  lost  in 
the  more  complex  configuration  of  the  prefrontal  region;  (2)  the  medifrontal  fissure 
(sulcus  frontalis  medius)  situated  in  the  prefrontal  part  of  the  medifrontal  gyre, 
rarely  extending  throughout,  and  usually  ending  cephalad  in  a  widely  spread 
bifurcation  which  constitutes  the  orbito-frontal  fissure  when  independent.  The 
medifrontal  fissure  is  usually  very  much  ramified  and  frequently  anastomoses 
with  neighboring  fissures.  The  fissure  is  a  characteristic  of  human  and  anthro- 
poid brains  only. 


928 


THE  NERVE  SYSTEM 


By  the  occurrence  of  either  or  both  paramesal  and  medifrontal  fissures,  the 
ordinary  three-tier  type  of  frontal  lobe  is  converted  into  a  four-tier  and  five-tier 
type;  the  latter  more  often  in  the  brains  of  the  more  highly  intellectual— a  feature 
which  is  concomitant  with  the  comparatively  late  phyletic  and  embryonic  develop- 
ment of  the  two  secondary  fissures  described. 

Other,  less  important,  fissures  are:  (1)  the  inflected  fissure  (fissura  inflexa) ,  incis- 
ing the  dorsi-mesal  border  between  the  central  fissure  and  the  cephalic  limb  of  the 
paracentral;  (2)  the  radiate  fissure,  near  the  lateral  orbito-f rental  border;  (3)  the 
trans-precentral,  a  short  oblique  piece  ventrad  of  the  central  and  usually  dipping  into 
the  sylvian  cleft,  and  (4)  the  diagonal  fissure  between  the  presylvian  ramus  and 
the  ventral  end  of  the  central,  and  often  confluent  with  the  precentral  (Fig.  600) 

2.  MESAL  SURFACE.— The  mesal  surface  of  the  frontal  surface  lobe  is  bounded 
by  the  dorsi-mesal  border,  the  mesorbital  border,  and  the  callosal  fissure.  An 
arcuate  fissure  or  system  of  fissures  intermediate  between  the  dorsi-mesal  margin 
and  the  callosal  fissure  divides  this  surface  into  the  superfrontal  gyre,  mesal 
aspect,  and  the  callosal  gyre.  The  name  " calloso-marginal"  was  usually  applied 


G.  =  GYRE 
F.=  FISSURE 


FIG.  601. — Fissures  and  gyres  of  the  mesal  surface  of  the  left  hemicerebrum. 


to  this  fissure,  but  an  examination  of  many  brains  reveals  a  certain  integrality 
of  fissural  parts  which  are  not  always  connected.  One  constant  segment  from 
its  relations  with  the  central  fissure  is  called  the  paracentral  fissure,  composed 
of  a  main  stem  with  a  cephalic  and  a  caudal  limb,  embracing  the  paracentral 
gyre.  Frontad  thereof  extends  the  supercallosal  fissure,  often  in  two  segments, 
running  a  concentric  course  between  the  arched  dorsi-mesal  border  and  the  genii 
of  the  callosum.  The  supercallosal  may  be  confluent  with  the  paracentral.  The 
supercallosal  is,  as  a  rule,  quite  ramified,  its  branches  transcribing  the  super- 
frontal  gyre.  In  the  prefrontal  region  and  ventrad  of  the  genu  of  the  callosum 
lie  one  or  two  fissures,  more  or  less  parallel  to  the  mesorbital  border,  and  called, 
respectively,  the  rostral  and  subrostral  fissures  (sulci  rostrales). 

3.  ORBITAL  SURFACE. — The  orbital  surface  of  the  frontal  lobe  is  constantly 
marked  by  a  straight  fissure,  the  olfactory  fissure  (sulci  olfactorius) ,  which  runs 
parallel  to  the  mesorbital  border  and  is  occupied  by  the  olfactory  bulb  and  tract. 
It  is  about  5  cm.  in  length  and  demarcates  the  mesorbital  gyre  from  the  remaining 
orbital  gyres.  This  orbital  surface  is  marked  by  a  fissural  system  (sulci  orbitales) 


THE  CEREBRAL  HEMISPHERES 


929 


that  is  usually  of  zygal  type,  H-shaped  or  K-shaped,  quadriradiate,  or,  rarely, 
triradiate.  When  the  transverse  element  is  sufficiently  pronounced  it  merits 
the  name  of  transorbital  fissure,  demarcating  the  preorbital  from  the  postorbital 
gyral  field. 

Gyres  of  the  Frontal  Lobe  (lobus  frontalis}.  1.  LATERAL  SURFACE. — The  pre- 
central  gyre  (gyrus  centralis  anterior] ,  one  of  the  chief  motor  areas  of  the  cerebral 
cortex,  is  a  moderately  sinuous  gyre  extending  from  the  dorsi-mesal  border  to 
the  sylvian  fissure  and  demarcated  by  the  central  and  the  precentral  fissures 
(supercentral  +  precentral). 

The  superfrontal  gyre  is  limited  laterally  by  the  superfrontal  fissure,  while  it 
is  continuous  over  the  dorsi-mesal  border  with  its  mesal  surface.1  It  merges 
insensibly  with  the  medifrontal  gyre  in  the  prefrontal  region,  while  it  may  be 
partially  subdivided  by  the  paramesal  fissure. 


INTERCEREBRAL  F. 


R=  FISSURE  ' 
G.  =  GYRE 


FIG.  602. — Fissures  and  gyres  of  the  basal  surface  of  the  cerebrum. 

The  medifrontal  gyre  (gyrus  frontalis  medius)  is  broader  than  the  preceding, 
demarcated  by  the  superfrontal  and  subf rental  fissures,  and  often  marked  by  the 
medifrontal  fissure  in  its  prefrontal  portion. 

The  subfrontal  gyre  (gyrus  frontalis  inferior]  is  limited  by  the  subfrontal  fissure 
and  the  basisylvian  +  sylvian  proper.  It  is  traversed  by  the  presylvian  and  sub- 
sylvian  rami,  embracing  the  pre-operculum  or  pars  trianglaris.  The  gyre  is  of 
historic  importance  since  Broca,  in  1861,  declared  it  to  be  the  seat  of  speech  con- 
trol. (See  Cerebral  Localization.) 

1  There  being  no  fissure  at  this  border,  it  is  improper  to  give  the  mesal  surface  of  this  gyre  a  different  name 
(i.  e.,  "  marginal  gyrus"  of  the  authors). 

59 


930  THE  NERVE  SYSTEM 

2.  MESAL  SURFACE. — On  the  mesal  surface  of  the  frontal  lobe  and  embracing 
the  dorsal  end  of  the  central  fissure  lies  an  oval  lobule  or  gyre  called  the  par;: 
central   gyre   (lobulus  paracentralis) ,  limited  by  the  paracentral  fissure  with  its 
caudal  and  cephalic  limbs.      Frontad   thereof  extends  the  large  arched  mesal 
surface  of  the  superfrontal  gyre  (gyrus  frontalis  superior),  limited  by  the  super- 
callosal  fissure.     Between  the  latter  fissure  and  the  callosal  fissure,  concentrically 
situated  with  respect  to  the  superfrontal,  lies  the  callosal  gyre  (the  "gyrus  form- 
catus"  of  the  authors). 

Frontad  these  two  gyres  arch  around  the  genu  of  the  callosum,  to  become  merged 
through  the  disappearance  of  the  intervening  supercallosal  fissure,  and  the  rostral 
fissures  alone  mark  this  surface. 

3.  ORBITAL  SURFACE. — The  olfactory  fissure  and  the  mesorbital  border  bound 
the  mesorbital  gyre  (gyrus  rectus}.     The  remaining  orbital  surface  is  not  regularly 
divisible  on  account  of  the  great   variability  of  the  orbital  fissures;  when  the 
transorbital  fissure  is  pronounced,  a  pre-  and  postorbital  gyre  may  be  distin- 
guished. 

The  postorbital  limbus  is  a  formation  occasionally  met  with  on  the  orbital  sur- 
face. It  consists  of  a  curved,  welt-shaped  eminence  demarcated  by  an  incisure 
created  by  the  lesser  wing  of  the  sphenoid,  and  due,  apparently,  to  the  intrusion 
of  the  postorbital  portion  into  the  middle  fossa. 

II.  Parietal  Lobe  (lobus  parietalis).  Fissures  of  the  Parietal  Lobe.  1.  LATERAL 
SURFACE. — The  lateral  surface  is  bounded  by  the  dorsi-mesal  border,  by  the  central 
fissure,  and  by  a  part  of  the  sylvian  fissure;  it  is  only  partially  demarcated  from 
the  occipital  lobe  by  the  occipital  fissure,  and  merges  gradually  into  the  temporal 
lobe. 

The  principal  fissures  marking  its  surface  consist  of  a  group  of  integral  segments 
showing  various  degrees  of  confluence  in  different  individuals  and  formerly 
known  in  the  aggregate  as  the  intraparietal  sulcus  of  Turner  (sulcus  intraparietalis). 
Two  of  the  fissural  segments  present  much  the  same  parallelism  to  the  central 
fissure  which  was  noted  for  the  precentral  group,  and  hence  these  are  termed 
the  postcentral  fissural  complex. 

The  postcentral  fissural  complex  (sulcus  postcentralis)  comprises  a  longer  mesal 
and  a  shorter  lateral  (and  ventral)  segment,  which  are  confluent  in  about  75  per 
cent,  of  brains  and  then  very  much  resemble  in  length,  continuity,  and  course 
the  central  fissure.  This  appearance  has  given  rise  to  reports  of  alleged  duplica- 
tion of  the  central;  an  analysis  of  the  relations  of  the  dorsal  ends  of  the  fissures 
in  question  with  the  caudal  limb  of  the  paracentral  removes  all  doubt. 

The  postcentral  fissure  (proper)  is  the  longer  mesal  (and  dorsal)  segment.  Its 
dorsal  end  is  frequently  bifurcated  and  sometimes  embraces  the  dorsal  extension 
of  the  caudal  limb  of  the  paracentral.  The  subcentral  fissure  constitutes  the  shorter 
latero-ventral  segment. 

The  parietal  fissure  is  usually  a  slightly  arched  fissure  inclining  meso-caudad, 
sometimes  independent  but  more  often  confluent,  with  one  or  both  of  the  post- 
central  segments  just  described.  It  demarcates  the  parietal  gyre  from  the  sub- 
parietal  district. 

The  paroccipital  fissure,  in  whole  or  in  part,  probably  represents  a  part  of  the 
simian  exoccipital  or  "  Affenspalte,"  isolated  by  the  upgrowth  of  gyral  protons 
which  are  totally  submerged  in  the  ape  brain,  but  rose  to  the  surface  concomitant 
with  the  rise  in  functional  dignity  of  cortical  areas  so  important  in  the  human 
brain.  The  fissure  is  almost  invariably  of  zygal  shape,  its  stem  directed  sagittally, 
its  ends  bifurcated.  Its  confluence  with  the  parietal  fissure  seems  to  be  subject  to 
some  morphologic  law;  continuity  is  the  rule  on  the  left  side  (77  per  cent.),  and 
occurs  less  often  on  the  right.  The  combination  of  continuity  on  the  right  and 
separation  on  the  left  is  a  rare  one  (6  per  cent.). 


THE  CEREBRAL  HEMISPHERES  931 

Less  constant  fissures  are  the  transparietal,  in  the  parietal  lobe  and  the  inter- 
medial  (Fig.  600).  In  the  subparietal  district  terminate  the  upturned  ends  of 
the  sylvian  (i.  e.,  episylvian  ramus]  of  the  supertemporal  and  the  meditemporal 
fissures. 

2.  MESAL  SURFACE. — The  mesal  surface  of  the  parietal  lobe  is  equivalent  to 
the  quadrangular  precuneus,  limited  by  the  paracentral  and  occipital  fissures, 
while  ventrad  it  is  imperfectly  separated  from  the  callosal  gyre  by  the  precuneal 
fissure  (posilimbic  sulcus),  usually  of  zygal  or  triradiate  form  and  occasionally 
confluent  with  the  paracentral. 

Gyres  of  the  Parietal  Lobe.  1.  LATERAL  SURFACE. — The  postcentral  gyre  (gyms 
centralis  posterior)  is  one  of  the  chief  somsesthetic  areas  of  the  cortex.  It  is  a  long, 
more  or  less  sinuous  convolution  extending  obliquely  from  the  dorsi-mesal  border 
to  the  sylvian  fissure  and  demarcated  by  the  central  and  the  postcentral  +  sub- 
central  fissures. 

The  parietal  gyre  (gyrus  parietalis)  lies  between  the  dorsi-mesal  border  and  the 
parietal  fissure,  bounded  cephalad  by  the  postcentral,  caudad  partly  by  the 
occipital  fissure,  the  transition  to  occipital  lobe  being  maintained  by  the  arched 
paroccipital  gyre. 

The  subparietal  district  or  lobule  (lobulus  parietalis  inferior]  is  divided  into 
three  convolutions  which  arch  around  the  upturned  ends  of  the  sylvian,  super- 
temporal,  and  meditemporal,  and  merge  insensibly  with  the  adjacent  temporo- 
occipital  gyres.  The  marginal  (supramarginal)  gyre  arches  over  the  extremity  of 
the  episylvian  ramus  and  is  connected  frontad  with  the  postcentral  gyre,  ventrad 
with  the  supertemporal  gyre.  The  angular  gyre  (gyrus  angularis)  arches  over  the 
upturned  extremity  of  the  supertemporal  fissure,  and  its  limbs  fuse  with  the  super- 
temporal  and  meditemporal  gyres.  The  postparietal  gyre  is  not  always  clearly 
defined ;  it  arches  around  the  upturned  end  of  the  meditemporal  or  its  representa- 
tive segment;  mesally  it  is  bounded  by  the  paroccipital  fissure.  Variable  inter- 
medial  fissures  sometimes  help  to  define  the  angular  gyre  from  its  two  neighbors. 

2.  MESAL  SURFACE. — The  mesal  surface  of  the  parietal  lobe  has  already 
been  described  as  equivalent  to  the  precuneus,  from  its  position  in  "front"  of  the 
cuneus  or  quadrate  lobe  from  its  general  shape.  It  is  sometimes  marked  by  a 
mesal  extension  of  the  transparietal  fissure  or  by  intraprecuneal  fissures. 

III.  Occipital  Lobe  (lobusoccipitalis).     Fissures  of  the  Occipital  Lobe.     1.  LAT- 
ERAL SURFACE. — The  lateral  surface  of  the  occipital  lobe  is  imperfectly  demarcated 
from  the  adjacent  parietal  and  temporal  lobes  in  most  brains.   The  sharply  defined 
exoccipital  fissure  or  "  Affenspalte"  of  other  primates  has,  in  the  ancestry  of  man, 
been  reduced  to  a  series  of  fissural  segments  by  the  upgrowth  of  submerged  cortical 
parts.      The  paroccipital  fissure,  we  have  already  learned,  probably  represents 
one  of  the  gaps  in  the  series;  another  may  be  the  sulcus  lunatus  (Elliott  Smith), 
usually  termed  the  lateral  occipital  by  the  authors;  lastly,  a  fissure  sometimes  called 
the  inferior  occipital  (suboccipital),  and  usually  embraced,  on  the  occipital  pole, 
by  the  bifurcate  limbs  of  the  postcalcarine,  may  complete  the  series.     Further 
researches  are  necessary  to  elucidate  the  morphology  of  this  region. 

2.  MESAL  SURFACE. — The  mesal  surface  is  equivalent  to  the  wedge-shaped 
region  embraced  by  the  occipital  and  calcarine  fissures,  and  called  the  cuneus. 
A  fairly  constant  cuneal  fissure  traverses  its  surface  parallel  to  the  calcarine. 

If  it  is  ever  determined  that  the  morphological  boundary  of  the  occipital  lobe  is 
as  outlined  above,  the  lobe  is  practically  excluded  from  the  basal  surface  of  the 
hemicerebrum. 

IV.  Temporal  Lobe  (lobus  temporalis).     Fissures  of   the  Temporal   Lobe.     1. 
LATERAL  SURFACE. — The  lateral  surface  of  the  temporal  lobe  is  bounded  by  the 
basisylvian  and   sylvian  fissures  and   by  the  ventro-lateral  border;  caudally  it 
merges  into  the  adjacent  parietal  and  occipital  lobes. 


932  THE  NERVE  SYSTEM 

The  supertemporal  fissure  (sulcus  temporalis  superior)  is  a  deep,  long  (10  to  12 
cm.),  and  usually  continuous  fissure  which  begins  near  the  temporal  pole,  proceeds 
ventrad  of  but  parallel  with  the  sylvian,  to  become  upturned  in  the  parietal  lobe 
and  embraced  by  the  arched  angular  gyre. 

The  meditemporal  fissure  (sulcus  temporalis  medius)  is  rarely  continuous;  more 
often  it  is  represented  by  a  series  of  segments,  two,  three,  or  four  in  number,  the 
caudal  segment  running  more  vertically  into  the  parietal  lobe  to  be  embraced  by 
the  postparietal  gyre.  The  meditemporal  fissural  segments  run  nearly  parallel 
with  the  supertemporal  and  demarcate  the  meditemporal  from  the  subtemporal  gyre. 

2.  TENTORIAL  OR  VENTRAL  SURFACE. — Close  to  the  ventro-lateral  margin  and 
more  or  less  parallel  with  it  runs  the  subtemporal  fissure  (sulcus  temporalis  inferior], 
extending  from  near  the  temporal  to  near  the  occipital  pole.  It  is  rarely  continuous, 
being  usually  broken  up  into  two  or  more  segments.  It  demarcates  the  subtem- 
poral from  the  subcollateral  gyre. 

The  collateral  fissure  (fissura  collateralis)  is  a  well-marked  long  (8  to  12  cm.)  and 
deep  fissure  extending  from  near  the  occipital  to  near  the  temporal  pole.  Caudally 
it  demarcates  the  subcalcarine  gyre  from  the  subcollateral;  frontad  it  intervenes 
between  the  latter  gyre  and  the  hippocampal  gyre.  Its  middle  part  is  correlative 
with  the  collateral  eminence.  On  the  ventro-mesal  aspect  of  the  temporal  lobe 
and  near  its  pole,  cephalad  of  the  uncus  is  a  moderately  marked  fissure  or  groove 
called,  because  of  its  topographic  relation  to  the  amygdala — a  gray,  ganglionic  mass 
— the  amygdaline  fissure  (fissura  ectorhinalis  s.  postrhinalis)  or  incisura  temporalis. 


OLFACTORY 

CEREBELLUM.— liMiaiBiiP  "  <,  LOBE. 


FIG.  604.- — Cerebrum  of  an  eight-months'  human 
FIG.  603. — Brain  of  a  six-months'  human  embryo,  embryo,  left  side.     The  insula  is  nearly  covered  in. 

natural  size,  right  side.      (Kolliker.)  (Testut.) 

3.  DORSAL  OR  OPERCULAR  SURFACE. — The  dorsal  or  opercular  surface  of  the 
temporal  lobe  enters  into  the  formation  of  the  sylvian  cleft.  It  is  but  slightly 
marked  by  a  few  oblique  or  transverse  furrows  (transtemporal  fissures)  demar- 
cating slightly  elevated  transtemporal  gyres. 

Gyres  of  the  Temporal  Lobe. — The  five  principal  fissures  named  subdivide  the 
lobe  into  five  gyres.  On  the  lateral  surface  lie  the  supertemporal,  meditemporal, 
and  subtemporal  gyres  (gg.  temporalis  superior,  medius  et  inferior) ;  on  the  ten- 
torial  surface  are  the  subcalcarine  (gyrus  lingualis),  subcollateral  (gyrus  fusiformis; 
g.  occipitotemporalis)  and  part  of  the  subtemporal. 

The  hippocampal  gyre  (gyrus  hippocampi),  formerly  included  in  the  "limbic 
lobe,"  but  morphologically  belonging  to  the  neopallium,  occupies  the  dorsi-mesal 
part  of  the  ventral  surface  of  the  temporal  lobe.  The  longer  or  shorter  extension 
of  the  occipito-calcarine  stem  partially  (forming  the  isthmus  gyri  hippocampi) 
interrupts  its  continuity  with  the  callosal  gyre.  It  is  demarcated  by  the  collateral 
fissure  (in  part)  and  the  hippocampal  fissure,  broadens  out  toward  the  temporal 
pole,  and  appears  to  become  bent  upon  itself  dorsally  to  form  the  uncinate  gyre 
(uncus).  As  will  be  learned  in  the  sequel,  the  hippocampal  gyre  is  demarcated 


THE  CEREBRAL  HEMISPHERIC 


933 


from  the  uncus  proper  by  the  intervention  of  the  frenulum  Giacomini — an  exten- 
sion of  the  narrow,  gray,  dentate  gyre. 

Near  the  temporal  pole  it  is  demarcated  from  the  subcollateral  gyre  by  the 
fissura  rhinica,1  or  postrhinal  fissure;  this  fissure  is  not  infrequently  confluent  with 
the  collateral.  . 

The  surface  of  the  hippocampal  gyre,  particularly  in  the  zone  along  the  hippo- 
campal  fissure,  is  of  a  more  whitish  color  than  is  characteristic  of  other  cerebral 
gyres;  this  is  due  to  a  white  reticular  stratum  of  fibres,  the  substantia  reticularis  alba 
(Arnold).  The  convex,  broader  part  of  the  gyre  is  marked  by  numerous  small, 
wart-like  eminences,  resembling  the  skin  of  an  amphibian,  and  called  by  Retzius 
the  verrucas  gyri  hippocampi.  Just  ventrad  of  the  uncinate  portion,  or  the  ter- 
minus of  the  hippocampal  fissure,  lies  a  groove  marking  the  impression  of  the 
free  edge  of  the  tentorium. 


Fio.  605. — The  left  insula  schematically  represented  in  a  supposedly  transparent  hemi cerebrum,  showing  how 

it  is  concealed  from  view  by  the  opercula. 


The  Insula  (Central  Lobe  or  Island  of  Reil)  (Figs.  603,  604,  605).— The  insula 
lies  deeply  in  the  sylvian  cleft  and  can  only  be  seen  when  the  lips  of  that  cleft  are 
widely  separated,  since  it  is  overlapped  by  .the  opercula  already  described.  With 
the  opercula  removed,  the  insula  presents  a  tetrahedral  shape  with  its  apex  or 
pole  directed  ventro-cephalad.  Its  borders  are  sharply  outlined  by  the  circum- 
insular  fissure  except  in  the  depths  of  the  basisylvian  cleft,  where  the  insular  cortex 
is  continuous  with  the  gray  substance  of  the  preperforatum — the  threshold  or  limen 
insulae  (belonging  to  the  rhinencephalon).  An  oblique  transinsular  or  central  insular 
fissure  divides  this  district  into  a  larger  preinsula  and  a  smaller  postinsula.  The 
postinsula  is  usually  a  single  long  gyre  (gyrus  longus  insulae),  while  the  preinsula 
is  subdivided  by  shallow  fissures  into  three,  four,  or  five  shorter  preinsular  gyres 
built  upon  a  radiate  plan,  converging  in  the  region  of  the  insular  pole.  As  already 
hinted,  the  insula  represents  an  area  of  the  brain-mantle  whose  growth  did  not 


1  Called  by  Wilder,  on  account  of  its  correlation  with  the  amygdala,  the  amyadaline  fissure. 
palls   it    (in  part)   the  incisura  temporalis. 


Schwalbe 


934  THE  NERVE  SYSTEM 

keep  pace  with  that  of  the  surrounding  parts;  hence  its  submergence  by  them. 
The  close  apposition  of  the  insular  region  to  the  subjacent  basal  ganglia,  and  the 
failure  of  development  of  great  masses  of  projection  fibres  so  prominent  elsewhere, 
were  doubtlessly  factors  therein.  The  insular  cortex  is  uninterruptedly  continuous 
with  the  rest  of  the  cortex,  but  it  has  become  specialized  into  the  purest  association 
centre  in  the  cerebrum,  and  we  shall  learn  of  its  intimate  relations  to  the  faculty 
of  speech  at  a  later  stage. 

The  Rhinencephalon  or  Olfactory  Lobe  (lobus  olfactorius}  (Figs.  606,  607, 
609). — The  grouping  of  the  parts  constituting  the  central  olfactory  structures 
under  the  term  "rhinencephalon"  as  distinguished  from  the  rest  of  the  fore- 
brain  (pallium)  was  first  clearly  made  by  Turner  and  proved  by  His  to  be 
embryologically  well  founded  and  by  Edinger  to  agree  with  phylogenetic  develop- 
ment. More  light  has  been  thrown  upon  the  subject  recently  by  Retzius  and 
Elliott  Smith.  The  sense  of  smell,  while  highly  useful  in  the  quest  for  food  in 
earlier  and  lower  forms  of  vertebrates,  is  relatively  little  used  in  the  mental  life 
of  man.  The  enormous  preponderance  of  the  cerebral  mantle  and  the  concomi- 
tant atrophy  of  the  rhinencephalon  in  the  human  brain  afford  one  of  the  most 
striking  contrasts  in  brain  morphology.  This  relatively  feeble  development  in 
bulk  of  the  olfactory  apparatus  in  the  human  brain  by  no  means  renders  its 
description  simple.  In  fact,  not  until  its  development  in  lower  macrosmatic  animals 
was  studied  could  anatomists  form  even  an  approximately  clear  conception  of  the 
seemingly  disjointed  remnants  in  the  human  brain  of  an  olfactory  apparatus  so 
relatively  huge  in  lower  animals.  The  great  expansion  of  the  cerebral  hemispheres 
and  of  the  great  commissure  which  connects  them  (the  callosum)  has  been  an 
important  factor  in  widely  displacing  primitively  connected  parts.  The  devel- 
opmental history  must  be  sought  for  in  the  writings  of  Edinger,  Retzius,  and 
Elliott  Smith. 

The  Rhinencephalon  comprises: 

1.  Peripheral  parts 

2.  Central  or  Cortical  parts. 

A  comprehensive  term  for  the  peripheral  part  is  lobus  olfactcrius,  divisible  into 
pre-  and  postolfactory  parts. 

1.  Bulbus  olfactorius. 

2.  Tractus  olfactorius. 

3.  Tuberculum  olfactorium  and  trigonum. 
Preolfactory  lobe  ^  4.  Area  parolfactoria  (Broca). 

I  5.  Stria  (gurus)  olfactorius  medialis. 

6.  Stria  (gyrus)  olfactorius  intermedialis. 

[^7.  Stria  (gyrus)  olfactorius  lateralis. 

,t  ,  ,     f  8.  Preperforatum. 

01>y  [     e\  9.  Gyrus  sulcallosus  and  Broca' s  diagonal  band. 

The  Preolfactory  Division. — :The  olfactory  bulb  and  tract  form  a  long  and 
slender  band  with  a  bulbous  extremity  situated  on  the  basal  aspect  of  the  frontal 
lobe  and  constituting  a  rudimentary  remnant  of  a  relatively  large  diverticulum, 
developed  from  the  sensor  ectoderm  close  to  the  border  of  the  neural  plate  before 
it  becomes  converted  into  the  neural  tube  and  situated  on  either  side  of  the  neu- 
ropore  at  the  extreme  frontal  end.  Although  hollow  at  first,  the  cavity  (rhinocele) 
soon  becomes  obliterated. 

The  olfactory  bulb  (bidbus  olfactorius)  is  an  oval  mass  of  reddish-gray  color, 
which  rests  on  the  cribriform  plate  of  the  ethmoid  and  is  received  in  the  olfac- 
tory fissure  on  the  orbital  surface  of  the  frontal  lobe.  It  receives  the  numerous 
olfactory  nerves  (fila  olfactoria)  from  the  nasal  mucous  membrane.  The  olfactory 


THE  CEREBRAL  HEMISPHERES 


935 


tract  (tractus  olfactorius]  is  a  bum!  of  white  substance,  of  prismatic  outline  on 
section,  its  apical  ridge  fitting  into  the  olfactory  fissure.  Toward  its  root-region  it  is 
somewhat  narrowed. 

The  medial  and  lateral  olfactory  gyres  are  also  termed  the  medial  and  lateral 
roots  of  the  tract,  and  diverge  in  the  region  of  the  trigonum.  The  olfactory 
tubercle  (tuberculum  olf actor ium)  is  best  seen  if  the  bulb  and  tract  be  lifted 
away  from  the  olfactory  fissure;  the  tubercle  appears  as  a  small  pyramidal 
elevation,  its  apex  buried  in  the  olfactory  fissure,  its  irregularly  triangular  base 
forming  the  trigonum  olfactorium,  a  small  gray  area  frontad  of  the  preperforatum. 
This  area  is  marked  by  ridge-like  elevations  which  appear  like  radiating  roots  of 
the  tract,  and  named,  according  to  their  position,  the  medial,  intermediate,  and. 
lateral  roots,  striae  or  gyres.  The  lateral  olfactory  stria  or  gyre  is  continuous  with 
the  limen  insulse  in  the  depths  of  the  basisylvian  cleft,  and  thence  passes  to  the 


BULB 
TRACT 

TRICONE 

G.    OLFACTORIO- 
ORBITALIS 

LATERAL  STRIA 
ANGULUS   LATCRALIS 

INTERMEDIATE  STRIA 

PREPERFORATUM 

GVRUS  AMBIENS 

GYRUS  SCMILUNARIS 

FRCNULUM    GIACOMINI 

uncut 


CYRUS  SUBCALLOSUS 
AREA    PAROLFACTORIA 


GYRUS  OLFACTORIUS 
MEDIALIS 


LIMEN   INSURE 


BROCA'S    DIAGONAL 
BAND 


SULCUS  SEMI- 
ANNULARIS 


FIG.  606. — Schematic  representation  of  the  rhinencephalon,  basal  aspect. 

uncus  to  end  in  the  gyms  ambiens  and  gyrus  semilunaris.  The  sharp  turn  made 
at  the  limen  insulae  is  called  the  angulus  lateralis.  The  medial  olfactory  stria  or 
gyre,  a  narrow  gyral  band,  proceeds  mesad  and  merges  with  the  adjacent  cerebral 
surface;  its  extension  on  the  mesal  surface  is  known  as  the  parolfactory  area 
(Broca)  limited  frontad  by  the  anterior  parolfactory  sulcus  (sulcus  parolfactorius 
anterior}  and  separated  from  the  subcallosal  gyre  by  the  posterior  parolfactory 
sulcus  (sulcus  parolfactorius  posterior). 

The  intermediate  stria  is  not  always  very  distinct ;  when  present  it  may  be  traced 
from  the  proximal  end  of  the  olfactory  tract  for  a  short  distance  over  the  gray 
field  of  the  trigonum,  to  plunge  into  the  gray  of  the  preperforatum. 

Postolfactory  Division. — The  preperforatum  (anterior  perforated  substance] 
occupies  an  irregular  quadrate  field  between  the  olfactory  trigone  and  the  optic 
chiasm  and  tract.  A  more  or  less  marked  groove  (sulcus  parolfactorius  posterior}, 
which  is  identical  with  the  fissura  prima  (His)  of  the  embryo,  separates  the  tri- 
gonum from  the  preperforatum.  Its  frontal  part,  much  perforated,  is  of  a  darker 


936 


THE  NERVE  SYSTEM 


color  than  the  hind  portion;  the  latter  is  distinguished  by  the  name  of  Broca's 
diagonal  band.  This  courses  obliquely  laterad  along  the  optic  tract  toward  the 
uncus;  mesally  the  bands  of  the  two  sides  converge,  frontad  of  the  terma,  and 
proceed  toward  the  rostrum  of  the  callosum  as  narrow  fields  which  taper  to  curve 
ajound  the  genu  and  continue  in  the  indusium  of  the  callosum  as  the  striae  longi- 
tudinales.  The  narrow  field  seen  on  the  mesal  aspect  frontad  of  the  terma  and 
precommissure  is  known  as  the  gyrus  subcallosus  (formerly  peduncle  of  the  corpus 
callosum).  The  continuity  of  the  various  parts  may  be  understood  by  reference 
to  Figs.  606,  607,  and  609. 


INDUSIUM    AND    STRI/E 


FUSION    OF    FASCIOLA 
AND    DENTATE    GYRE 


GYRI    ANDRE/ 
RETZII 


DENTATE    GYRE 


HIPPOCAMPAL    FISSURE 


•UNCUS 

FRENULUM    GIACOMINI 
I  GYRUS   SEMILUNARI8 
GYRUS     AMBIENS 


FIG.  607. — Schematic  representation  of  the  rhinencephalon,  mesal  aspect. 

The  cortical  and  central  parts  of  the  rhinencephalon  comprise; 

C   1.  The  hippocampus.1 

2.  The  uncus. 

3.  Gyrus  dentatus. 
Cortical  \    4.  Fasciola. 

5.  Indusium,  medial  and  lateral  longitudinal  striae  upon  the  callosum. 

6.  Gyri  Andrese  Retzii. 

7.  Gyri  subcallosi. 

8.  Fornix  and  fimbria. 

9.  Albicans  and  albicantio-thalamic  tract. 
10.  Part  of  precommissure. 

.11.  Part  of  hemiseptums. 

Central  or  Cortical  Parts  of  the  Rhinencephalon. — Following  the  suggestion  made 
by  Broca  in  1878,  it  has  been  customary  to  designate  these  various  parts  by  the 
comprehensive  term:  limbic  lobe.  Broca's  notion  of  the  limbic  lobe  in  man 
was  founded  upon  attempts  to  homologize  the  human  cerebral  configurations 
with  those  found  in  lower  animals.  More  recent  researches  have  proved  that 
Broca's  "limbic  lobe"  included  parts  belonging  to  the  neopallium  and  not  to  the 
rhinencephalon.  The  term  is  therefore  inappropriate  in  a  morphologic  sense. 

The  hippocampus  is  the  submerged,  peculiarly  folded  margin  of  the  cerebral 


Central  \ 


I 


1  Not  to  be  confounded  with  the  hippocampal  (tyre  of  the  pallium. 


THE  CEREBRAL  HEMISPHERES 


937 


hemisphere  produced  by  the  hippocampal  fissure.  Its  architecture  can  best 
be  understood  by  referring  to  a  frontal  section  (Fig.  608).  It  is  seen  that  the 
whole  cerebral  marginal  wall  is  pushed  into  the  ventricular  cavity  (medicornu) 
as  a  fold  caused  by  the  intrusion  of  the  hippocampal  fissure.  A  secondary  fold — 
not  produced  by  a  fissure,  however — constitutes  the  gyms  dentatus.  Super- 
imposed lies  a  prominent  white  band — the  fimbria — composed  of  axones  from 
the  hippocampal  cells,  assisting  in  the  formation  of  a  white  lamina,  subjacent 
to  the  endyma  of  the  ventricle,  and  called  the  alveus.  The  whole  formation 
is  characteristic  of  this  region  and  from  its  fancied  resemblance  to  a  ram's  horn — 
a  symbol  used  on  the  temple  of  Jupiter  Ammon — the  name  of  cornu  ammonis1 


FIG.  608. — Trans-section  of  the  hippocampal  gyrus.     (Edinger.) 

has  been  given;  the  name  hippocampus  was  applied  because  of  a  fancied  re- 
semblance to  the  marine  animal  of  the  same  name.  The  ventricular  relations 
and  internal  structure  of  the  hippocampus  will  be  given  farther  on  (p.  947). 

The  uncus,  with  the  atrophied  lateral  olfactory  stria,  is  all  that  remains  in  the 
human  brain  of  the  relatively  large  pyriform  lobe  of  lower  forms.  It  appears 
to  be  a  hook-like  retroflexion  of  the  hippocampal  gyre  which  is  partially  encircled 
by  the  gyrus  dentatus.  Morphologically  speaking,  it  is  only  the  apical  portion, 
or  that  which  lies  caudad  of  the  dentate  gyre  which  is  the  true  uncus  (the  gyrus 
intralimbicus  of  Retzius);  the  remainder  is  neopallial  and  a  part  of  the  hippo- 
campal gyre.  The  uncinate  or  intralimbic  gyre  may  be  traced  caudad  in  the 
depths  of  the  fimbrio-dentate  fissure,  along  the  dentate  gyre,  the  dentato-fascicolar 

i  Frequently,  but  incorrectly,  given  as  Amman's  Horn. 


938  THE  NERVE  SYSTEM 

groove  intervening,  to  be  continued  as  the  fasciola  (gyrus  fasciolaris  of  Retzius) 
over  the  splenium  of  the  callosum. 

If  the  hippocampal  gyre  be  depressed  for  the  purpose  of  examining  the  depths 
of  the  hippocampal  fissure,  there  is  revealed  a  narrow,  gray  band  whose  surface 
is  scored  by  numerous  incisures  and  whose  edge  is  notched  at  frequent  intervals. 
This  corrugated  band  is  the  dentate  gyre  or  fascia  dentata.  Partly  overlapping  it, 
but  farther  laterad,  lies  a  white  band — the  fimbria — extending  caudad  from  the 
uncus  to  become  continued  as  the  fornix. 

The  dentate  gyre  is  demarcated  from  the  hippocampal  gyre  by  the  hippocampal 
fissure,  from  the  fimbria  by  the  fimbriodentate  fissure,  in  whose  depths  lies  the 
narrow  continuation  of  the  uncus  or  gyrus  intralimbicus — the  fasciola.  Extending 
caudad,  and  for  the  most  part  parallel  -with  the  fimbria,  it  loses  its  corrugated 
appearance  on  approaching  the  splenium,  then  fuses  with  the  fasciola,  parting 
company  with  the  fimbria  (which  now  becomes  fornix),  to  be  continued  upon  the 
callosum  as  a  thin,  broad  plate  of  gray  matter — the  indusium  or  gyrus  epicallosus. 
At  the  uncus  the  dentate  gyre  makes  an  abrupt  turn  to  appear  upon  the  mesal 
surface,  out  of  the  depths  of  the  hippocampal  fissure,  and  encircles  the  neck  of 
the  uncus,  forming  the  frenulum  Giacomini.  Beyond  this  point  it  can  be  traced, 
in  rare  instances,  to  the  gyrus  semilunaris. 

The  gyri  Andre  se  Retzii  are  rudimentary  gyral  formations  consisting  of  small, 
rounded,  oval  or  spirally  corrugated  eminences  situated  ventrad  of  the  splenium 
in  the  angular  interval  between  the  dentate  and  the  hippocampal  gyres.  Struc- 
turally they  have  been  shown  to  belong  to  the  hippocampal  formation. 

The  indusium  (gyrus  epicallosus  s.  supracallosus},  considered  to  be  a  vestige 
of  the  hippocampus,  is  a  thin  strip  of  gray  substance  superimposed  upon  the  callosum 
and  raised  into  two  paired  ridges  by  longitudinal  fibre-bundles  which  constitute 
the  mesal  and  lateral  longitudinal  striae.1  The  indusium  and  its  striae  are  continued 
cephalad  into  the  gyrus  subcallosus;  perhaps,  also,  into  the  parolfactory  area 
(Fig.  607). 

The  central  connections  of  the  rhinencephalon  will  be  considered  in  the  de- 
scription of  the  internal  configuration  of  the  hemisphere.  (See  Fornix,  Precom- 
missure,  etc.) 

Internal  Configuration. — Each  hemicerebrum  contains  a  cavity,  the  lateral 
ventricle  or  paracele,  an  extension  of  the  primitive  neural  cavity  carried  outward, 
its  contours  modified  by  the  developmental  changes  in  the  growth-history  of  the 
secondary  fore-brain  vesicle.  This  central  cavity  is  surrounded  by  the  thick, 
convoluted  walls  of  nerve-tissue  which  make  up  the  bulky  cerebral  hemi- 
spheres. The  cerebral  tissue,  as  elsewhere  in  the  central  axis,  is  made  up  of  gray 
and  white  substance. '  Two  well-marked  types  of  gray  substance  are  recognizable: 
(a)  the  cortical,  so  named  because  its  situation  upon  an  interior  white  centre, 
invites  comparison  with  the  rind  (cortex)  of  a  fruit;  (6)  the  massive  ganglionic 
or  nugget-like  masses  not  dissimilar  from  the  thalamus  already  described, 
comprising,  in  this  division  of  the  brain,  the  caudatum,  lenticula,  and  amygdala. 
The  white  substance  fills  out  the  entire  space  intervening  between  the  cortex, 
the  cavity  of  the  lateral  ventricle  and  the  great  basal  ganglia,  and  is  composed 
of  myelinic  axones  which  connect  the  elements  of  the  cortex  with  other  parts  of 
the  nerve  system,  or  with  other  regions  of  the  cortex  of  the  same  or  the  oppo- 
site hemicerebrum. 

If  a  brain,  resting  upon  its  basal  surface,  be  sliced  by  successive  horizontal 
sections  from  above,  the  peripheral  gray  and  internal  white  are  brought  into  view. 
The  more  superficial  sections  reveal  relatively  more  gray  than  white  substance; 
deeper  sections  show  a  reverse  condition  and  a  section  immediately  dorsad  of  the 

1  The  mesal  striae  are  also  called  Striae  Lancisii;  the  lateral  strias,  Teniae  tecti. 


THE  CEREBRAL  HEMISPHERES 


939 


callosum  reveals,  in  each  hemicerebrum,  a  very  extensive  semioval  field  of  white 
substance,  the  centrum  semiovale,  surrounded  on  all  sides  by  a  narrow,  convoluted 
margin  of  gray  substance,  the  cortex.  A  close  examination  of  the  cut  surface,  in  a 
fresh  and  normal  brain,  shows  it  to  be  studded  with  numerous  minute  red  dots 
(pumta  vasculosa)  produced  by  the  escape  of  blood  from  divided  blood-vessels. 
The  Cortex. — The  cortex,  as  revealed  in  such  a  section,  is  not  of  uniform  thickness 
throughout;  different  regions  show  different  cortical  thicknesses.  In  general,  the 
cortex  is  somewhat  thicker  at  the  summit  of  a  gyre  than  in  the  depths  of  an  ad- 
joining fissure,  and  it  is  thicker  upon  the  convex  than  upon  the  mesal  or  basal  sur- 
faces. The  maximum  thickness  is  observed  in  the  cortex  of  the  central  gyres  and 
the  insula ;  the  minimum  at  the  frontal  and  occipital  poles,  notably  the  latter.  Not 
only  is  the  cortex  not  of  uniform  thickness,  but  it  is  not  of  homogeneous  structure 
as  seen  with  the  naked  eye.  An  alternation  of  gray  and  white  stripes  is  discernible, 
particularly  in  the  occipital  cortex,  where  a  white  band  runs  parallel  with  the  corti- 
cal surface  between  two  gray  strata;  this  white  stripe,  first  described  by  Gennari 
and  usually  bearing  his  name,  is  also  called  the  band  of  Vicq  d'Azyr. 


GYRUS 
SEMILUNARIS 


FRENULUM 
GIACOMINI 


FIG.  609. — Mesal  view  of  a  partly  dissected  hemicerebrum,  to  show  the  relations  of  fimbria,  fasciola, 

dentate  gyre,  and  uncus. 

The  preponderance  of  white  substance  over  gray  substance  in  the  cerebrum  is  a  human  charac- 
teristic concomitant  with  the  relative  increase  of  the  association  cortex,  in  turn  demanding  a  more 
intricate  interconnection  of  the  many  nerve-cells  by  a  multitude  of  association  neurones.  These 
coordinating  fibre-systems  are  as  truly  representative  of  the  complexity  of  man's  thought  appa- 
ratus as  the  number  of  interconnecting  wires  within  a  telephone  "central"  station  is  indica- 
tive of  the  amplitude  of  connections  possible  in  that  system.  The  proportions  of  gray  and 
white  substance  are  expressed  in  the  following  tabulation: 

Gray  substance  {£ortef.   '     -     : 33  per  cent. 

I  Ganglia 6  per  cent. 

White  substance 61  per  cent. 

The  removal,  by  successive  slices,  of  the  dorsal  parts  of  the  cerebrum  soon 
brings  into  view  the  large  expanse  of  transverse  myelinic  fibres,  the  callosum, 
which  connects  the  two  hemispheres. 

The  Callosum  (corpus  callosum;  trabs  cerebri;  commissura  maxima}. — The 
callosum  is  a  thick  stratum  of  transversely  directed  nerve-fibres,  by  which 


940 


THE  NERVE  SYSTEM 


almost  every  part  of  one  hemicerebrum  is  connected  with  the  corresponding  part 
of  the  other  hemicerebrum  (Figs.  610  and  611).  The  axones  composing  it  arise 
from  the  small  pyramidal  or  the  polymorphous  cells  of  the  cerebral  cortex,  or 
they  may  be  collaterals  from  the  long  association  or  even  the  projection  neurones. 
They  pass  in  both  directions  and  within  the  centrum  semiovale  radiate  in  various 
directions  (radiatio  callosi)  between  the  fibres  of  the  corona  radiata  to  terminate  in 
the  layer  of  small  pyramidal  cells  of  the  cortex,  thus  forming  a  great  transverse 
commissural  system,  and  at  the  same  time  roofing  in  the  greater  part  of  the  lateral 
ventricle  in  each  half.  A  portion  of  the  dorsal  surface  is  free  for  a  width  of 
about  1  cm.  on  either  side  of  the  mesal  plane,  partly  covered  by  the  indusium  and 
overlapped  by  the  callosal  gyres  of  the  two  sides,  a  fold  of  pia  intervening. 

The  radiating  mass  of  fibres  may,  for  convenience  of  description,  be  sub- 
divided into  a  pars  frontalis,  a  pars  parietalis,  and  a  pars  occipitotemporalis.  The 
frontal  and  occipito-temporal  portions  are  compressed  or  thickened  mesally 
because  the  fibres  cannot  pass  directly  across,  but  curve,  respectively,  frontad 
and  caudad  in  each  hemicerebrum  to  form  two  tong-like  bundles,  the  preforceps 
(forceps  anterior  s.  minor)  and  postf creeps  (forceps  posterior  s.  major).  The  pars 
parietalis  constitutes  the  greater  part  of  the  "body"  of  the  callosum.  The  fibres 


FIG.  610. — Diagram  of  coronal  section  of  cerebrum 
to  show  course  of  fibres  of  callosum.      (Testut.) 


FIG.  611. — Diagram  of  horizontal  section  of  cerebrum 
to  show  course  of  fibres  of  callosum.     (Testut.) 


traversing  the  body  (truncus  corporis  callosi)  and  the  adjacent  part  of  the 
splenium  curve  round  the  postcornu  and  trigonum  ventriculi  of  the  lateral 
ventricle,  to  form  a  thin  but  definite  white  stratum,  the  tapetum,  in  the  roof 
and  ectal  wall  of  these  parts  of  the  cavity. 

The  transverse  direction  of  the  fibres  is  rendered  apparent  in  a  dorsal  view 
of  the  exposed  callosum  in  the  form  of  the  striae  transversae.  These  are  but  little 
obscured  by  a  thin,  gray  lamina — the  indusium — which  is  thickened  longitudinally 
by  two  symmetrically  situated  fibre-strands,  the  mesal  (striae  lancisii)  and  lateral 
longitudinal  striae  (teniae  tectae),  already  mentioned  as  rudiments  of  the  rhinen- 
cephalon. 

The  best  conception  of  the  size  and  form  of  the  callosum  is  obtained  from  a 
view  of  a  mesal  section.  It  is  then  seen  to  be  a  long,  thick,  somewhat  flattened 
arch  which  bends  sharply  upon  itself  frontad  to  form  the  genu  (genu  corporis 
callosi)  while  its  caudal  end  is  rounded  and  somewhat  folded  closely  upon  itself 
to  form  the  splenium.  The  callosum  ranges  in  length  from  7  to  10  cm.,  its  cross- 
section  area  from  5  to  10  sq.  cm.,  being  longer  and  larger  in  heavier  brains  and 
in  those  of  the  highly  intellectual  as  compared  with  smaller  and  less  highly  efficient 
brains.  It  extends  to  within  4  cm.  of  the  frontal  pole  and  to  within  6  cm.  of 
the  occipital  pole.  The  thickness  of  the  "body"  averages  5  mm.,  of  the  splenium 


THE  CEREBRAL  HEMISPHERES 


941 


9  mm.  or  more,  while  the  maximum  thickness  of  the  genu  is  about  13  to  15  mm. 
The  reflected  portion  or  rostrum  (rostrum  corporis  callosi)  gradually  tapers  into 
a  very  thin  lamina,  the  copula  (lamina  baseos  alba),  which  in  turn  joins  the  terma 
frontad  of  the  precommissure. 

The  splenium  (splenium  corporis  callosi)  projects  as  a  rounded  welt  over  the 
mid-brain,  but  is  separated  from  it  by  a  pial  fold — the  velum  interpositum. 
Further  frontad  the  fornix  becomes  fused  to  the  ventral  surface  of  the  callosum 
for  a  short  distance,  to  again  leave  it  in  its  more  arched  course  toward  the  albicans. 
Two  thin  laminae,  one  on  either  side  of  the  median  plane,  but  closely  applied  to 
each  other  and  frequently  partially  fused,  occupy  the  interval  between  callosum 
and  the  fornix  of  each  side.  The  laminae  together  are  termed  the  septum  lucidum 
of  the  authors,  each  one  being  called  a  hemiseptum;  the  enclosed  cavity  is  called 
the  pseudocele  or  fifth  ventricle,  though  not  derived  from  the  original  neural 
cavity. 


FORNICOMMISSURE 
CALLOSUM 


CALLOSUM 


PRECOMMISSURE 
PRCCOMMISSURAL 
REGION 


PRECOMMISSURE 


C.  SUBCALLOSU8 

PRECOMMISSURE 


C 


FIG.  612. — Schemata  showing  the  development  of  the  callosum  and  its  relations  to  hippocampus,  fornix,  and 
precommissure.  Lamina  terminalis  (terma)  in  heavy  black,  callosum  dotted.  *  Represents  the  attenuated 
indusium  and  longitudinal  strise  already  described. 

Development. — The  callosum  develops  as  a  mass  of  commissural  fibres  which  grow  from 
side  to  side  in  the  terma  (lamina  terminalis).  The  terma  serves  as  a  matrix  for  several  com- 
missural systems,  viz.,  the  hippocampal  or  fornicommissure  and  the  precommissure,  in  addition 
to  the  callosum.  The  last  develops  rapidly  in  higher  mammalian  brains,  thrusts  aside  the  hippo- 
campal margin  of  the  pallium  so  that  it  atrophies  in  large  part,  and  stretches  out  within  its  sharply 
bent  arch  a  portion  of  the  preeommissural  wall  of  each  cerebral  vesicle.  It  thus  withdraws 
a  part  of  the  intercerebral  cleft,  eventually  enclosing  it  entirely  as  the  pseudocele.  The  stages 
of  development  are  shown  schematically  in  Fig.  612  and  its  development  in  the  human  embryo 
is  shown  in  Fig.  613.  The  callosum  is  most  fully  developed  in  man  and  does  not  appear  below 
the  marsupials.  Its  growth  kept  pace  with  the  preponderatingly  greater  development  of  the 
neopallium  in  higher  forms,  and  it  may  be  looked  upon  as  an  index  of  the  elaboration  of  at  least 
one  division  of  the  association  systems — those  concerned  with  bilateral  coordinations. 

The  Lateral  Ventricles. — An  incision  through  the  callosum,  on  either  side  of  the 
median  plane,  will  expose  two  large,  irregular,  symmetrically  situated  cavities, 
the  lateral  ventricles  (paraceles),  extending  through  a  great  part  of  each  hemi- 
cerebrum.  Each  lateral  ventricle  communicates  with  the  third  ventricle  through 
a  small  opening,  the  porta  or  foramen  of  Monro,  situated  between  the  fornicolumn 
(anterior  pillar  of  fornix)  and  frontal  end  of  thalamus.  The  cavity  is  lined  through- 
out by  endyma;  it  is  narrow  in  some  and  wide  in  other  localities,  and  contains 
cerebro-spinal  fluid. 

The  shape  of  the  ventricle  is  best  understood  by  reference  to  a  cast  of  its 
interior  and  its  location  within  the  cerebrum  may  be  appreciated  by  a  study  of 
Figs.  614  and  615.  Conventionally  the  paracele  or  lateral  ventricle  is  described  as 
being  composed  of  a  body  or  cella  and  three  horn-like  extensions  or  cornua. 
Viewed  laterally  its  contour  corresponds  to  that  of  the  cerebral  hemisphere  and 
its  cornua  project  toward  the  three  poles,  viz.,  frontal,  occipital,  and  temporal. 


942 


THE  NERVE  SYSTEM 


FIG.  613. — Brains  of  human  embryos;  mesal  aspects  of  median  sagittal  section  show  the  development  of  the 
callosum:     A,  fourth  month;  B,  fifth  month;  C,  sixth  month;  D,  seventh  month. 


THE  CEREBRAL  HEMISPHERES 


943 


The  body  (pars  ccntralis  ventriculi  lateralis]  or  cella  of  the  lateral  ventricle  is 
defined  as  that  portion  which  extends  from  the  porta  to  the  region  of  the  splenium. 
Its  frontal  prolongation  is  called  the  precornu.  Near  the  splenium  the  cavity 
may  be  traced  ventro-laterad  into  a  capacious  part  (trigonum  ventriculi),  from 
which  the  postcornu  and  medicornu  are  prolonged,  respectively,  toward  the 
occipital  and  temporal  poles. 

The  Precornu  (cornu  anterius)  passes  frontad,  inclined  slightly  ventro-laterad. 
Its  floor  is  the  head  (caput)  of  the  caudatum,  forming  a  rounded  incline  sloping 
inesad  toward  a  trench-like  recess  floored  by  the  rostrum  of  the  callosum.  Its 
roof  is  the  preforceps  of  the  callosum.  Its  mesal  wall  is  formed  by  a  portion  of 
the  hemiseptum.  Laterally  it  is  limited  by  the  apposition,  at  an  acute  angle,  of 
callosum  and  caudatum.  Its  apex  reaches  the  ventricular  surface  of  the  genu 
of  the  callosum.  The  general  outline  of  the  ventricle,  in  a  frontal  section,  is 
triangular  (Fig.  625). 


FIG.  614. — Showing  the  ventricular  system  of  the  brain  as  a  solid  cast  as  if  seen  through  a  transparent  brain. 

The  body  of  the  cavity  is  curved  with  its  convexity  dorsad;  its  outline  in  trans- 
sections  varies  from  the  triangular  to  a  mere  slit  which  slopes  slightly  meso- 
ventrad.  It  is  wholly  roofed  in  by  the  callosum  (pars  frontoparietalis').  Its 
floor  is  formed  by  the  following  structures  named  in  order  from  its  ectal  toward 
its  ental  limit:  (1)  caudatum;  (2)  a  groove  which  marks  the  line  of  coalescence  of 
caudatum  and  thalamus  and  lodges  the  tcenial  vein  and  a  narrow  fibre-strand— 
the  tsenia  semicircularis,  beneath  the  endyma;  (3)  a  reflexion  of  the  endyma  onto 
a  narrow  area  of  the  thalamus;  (4)  the  paraplexus  or  choroid  plexus  of  the  lateral 
ventricle;  (5)  the  thin,  sharp  (fimbriated)  edge  of  the  fornix.  The  caudatum 
narrows  rapidly  as  it  passes  caudad.  The  tsenia  semicircularis,  lying  along  the 
ental  border  of  the  ventricular  surface  of  the  caudatum,  is  a  small  band  of  white 
fibres  arching  from  the  amygdala  (near  the  temporal  pole)  to  the  preperforatum. 
The  entrance  of  a  part  of  the  thalamus  into  the  formation  of  the  floor  of  the  para- 
cele  is  apparent  enough,  but  morphologically  it  should  be  strictly  excluded  there- 


944 


THE  NERVE  SYSTEM 


from.  The  thalamus  is  in  no  way  formed  from  the  parietes  of  the  secondary 
fore-brain  vesicle  (telencephalon),  for  it  is,  in  fact,  excluded  by  a  layer  of  endyma 
(lamina  affixa)  reflected  onto,  and  often  separable  from,  the  surface  of  the  thala- 
mus, so  that  it  appears  as  a  constituent  of  the  floor  because  of  the  transparency  of 
the  endymal  sheet.  The  paraplexus  is  a  richly  vascular  invagination  over  which 
the  endyma  is  continuous  to  again  become  reflected  onto  the  fornix  along  its 


HIPPOCAMPAL 
DIGITATIONS 


COLLATERAL 
EMINENCE 


^--—^^ 

FIG.  615. — Dissection  showing  the  left  lateral  ventricle  (paracele)  exposed. 


sharp  edge.     A  reference  to  Fig.  608,  showing  the  topographical  relations  of  these 
structures  in  a  frontal  section,  may  be  of  assistance. 

The  cavity  is  thence  continued  ventro-laterad  in  a  bold  sweep  to  become 
expanded  as  an  obliquely  pyramidal  space  of  a  somewhat  triangular  outline  on 
section,  and  placed  subjacent  to  the  parietal  lobe — the  trigonum  ventriculi.  A 
conspicuous  feature  in  its  floor  is  the  collateral  eminence,  correlated  with  the 


THE  CEREBRAL  HEMISPHERES 


945 


collateral  fissure.     From  the  trigonum,  the  most  capacious  part  of  the  paracele, 
the  cavity  is  prolonged  in  opposite  directions  as  the  medicornu  and  postcornu. 

The  Medicornu  (cornu  inferius)  is  a  prolongation  of  the  ventricular  cavity, 
from  its  trigone  toward  the  temporal  pole,  which  pursues  a  curved  course  with  its 
convexity  directed  ventro-laterad  (Figs.  614  and  615),  corresponding  to  the  curved 
contour  of  the  temporal  lobe,  and  situated  at  a  depth  of  about  3  cm.  from  its 
lateral  surface  as  well  as  from  the  temporal  pole.  The  roof  is  formed  by  (a)  the 
tapetum  of  the  callosum;  (6)  the  cauda  (tail)  of  the  caudatum;  (c)  the  taenia  semi- 
circularis.  The  medial  wall  is  principally  composed  of  the  hippocampus,  a  promi- 
nent welt-like  eminence  bulging  into  the  cavity,  largely  filling  it,  and  produced 
by  the  hippocampal  fissure.  The  hippocampus  nearly  conceals  from  view  the 
actual  floor,  which  is  of  variable  extent  in  different  brains  and  usually  marked  by 
an  extension  of  the  collateral  eminence  previously  described.  Surmounting  the 


FIG.  616. — Diagram  showing  the  topography  of  the  lateral  ventricle,  medidural  artery,  and 
cerebrum  within  the  cranium. 

corrugated  hippocampal  formation  and  projecting  slightly  into  the  cavity,  is  the 
fimbria,  and  from  its  sharp  edge  the  ventricular  endyma  is  reflected  upon  the 
invaginated  paraplexus.  The  paraplexus  of  the  medicornu  is  more  voluminous 
than  that  of  the  body  of  the  ventricle,  and  must  be  lifted  in  order  to  expose  the 
whole  of  the  ventricular  aspect  of  the  hippocampus. 

At  the  apex  of  the  medicornu  the  roof  presents  a  more  or  less  pronounced 
bulging,  the  amygdaloid  tubercle,  due  to  the  presence  of  the  amygdala,  a  small 
mass  of  ganglionic  gray  from  which  the  tsenia  semicircularis  arises  and  in  which 
the  caudatum  apparently  ends. 

The  Postcornu  is  a  shorter  diverticulum  which  passes  toward  the  occipital 
pole  in  a  gently  curved  course,  with  its  convexity  directed  laterad.  It  is  not  very 
capacious,  usually  slit-like  on  section,  and  tapers  to  a  point  within  2  or  3  cm.  of 
the  occipital  pole.  Its  roof,  slanting  latero-ventrad,  is  formed  by  the  tapetum  of  the 

60 


946  THE  NERVE  SYSTEM 

callosum.  On  the  inner  or  mesal  wall  two  elongated  bulgings  may  be  observed. 
The  upper  or  dorsal  elevation,  called  the  occipital  bulb  or  bulb  of  the  cornu 
(bulbus  cornu  posterioris;  callosal  eminence  [Wilder]),  is  formed  by  the  compact 
arched  postforceps  of  the  callosum  as  it  curves  around  the  very  deep  occipital 
fissure.  The  occipital  bulb  is  not  always  well  marked.  Ventrad  of  it  lies  a 
more  constant  limbus  or  welt-like  elevation,  the  calcar  (calcar  avis;  hippocampus 
minor},  a  projection  produced  by  the  infolding  of  the  cerebral  wall  along  the 
calcarine  fissure.  The  paraplexus  does  not  enter  the  postcornu. 

The  Choroid  Fissure  or  Rima  (rima  transversa  cerebri  magna;  fissure  of 
Bichat}  is  not  a  true  fissure,  and  only  becomes  one  when  the  (paraplexus)  choroid 
plexus  of  the  lateral  ventricle  is  torn  from  its  connections.  The  rima  is  never- 
theless a  gap  between  the  diencephalic  part  and  the  overlapping  and  recurved 
telencephalon  produced  by  the  extension  of  the  secondary  fore-brain  vesicle  in 
an  arcuate  manner  which  Hill  described  by  the  phrase  "  rotation  of  the  great 
fore-brain."  It  is  along  this  arcuate  and  fissure-like  gap  that  the  richly  vascular 
(pial)  paraplexus  invaginates  the  atrophied  parietes  of  the  secondary  fore-brain 
to  form  the  paraplexus  which  is  everywhere  covered  by  endyma.  The  rima 


Fie.  617. — Diagram  showing  the  choroid  fissure. 

extends  from  the  porta  to  near  the  tip  of  the  medicornu  in  an  arcuate  course  and 
endymal  reflections  everywhere  close  in  this  gap  except  at  the  porta  (Fig.  617). 
The  manner  in  which  this  is  accomplished  may  best  be  understood  by  a  study  of 
trans-section  showing  the  endymal  reflections  from  the  ventricular  wall  onto  the 
invaginated  paraplexus.  The  caudato-thalamic  fusion  and  the  intrusion  of  the 
great  fibre-masses  constituting  the  cerebral  crura  play  their  parts  in  complicating 
the  relations  in  brains  of  higher  type. 

The  Paraplexus  and  Velum.— The  paraplexus  is  a  highly  vascular,  fringe-like 
structure  composed  of  pia  which  is  invaginated  into  the  paracele  along  the 
rima,  or  gap  between  hemicerebrum  and  diencephalon.  The  portion  of  the 
paraplexus  protruding  into  the  "body"  of  the  paracele  is  the  fringed  vascular 
border — a  triangular  fold  of  pia — the  velum  interpositum  (tela  chorioidea  superior}, 
which,  as  its  name  implies,  is  interposed  between  the  relatively  small  primary 
fore-brain  and  the  enormous  overlapping  secondary  fore-brain,  and  is  produced  by 
the  overgrowth  of  the  latter  onto . the  former.  Inasmuch  as  the  nerve-tissue  in 
the  roof  of  the  third  ventricle  atrophies  totally,  the  ventral  fold  of  the  pia  comes 
into  contact  with  the  endyma  of  that  ventricle  and  here  permits  a  similar  vascular 
invagination  in  the  form  of  two  parallel  fringes  hanging  into  the  cavity  (diaplexus 


THE  CEREBRAL  HEMISPHERES 


947 


or  choroid  plexuses  of  the  third  ventricle).  The  dorsal  leaf  of  the  pial  fold  is 
in  contact  with  the  ventral  face  of  the  body  of  the  fornix.  Frontad,  the  velum 
tapers  toward  the  region  of  the  two  portse,  where  the  paraplexuses  of  the  two 
sides  are  continuous  with  each  other.  The  ventricular  surface  of  the  choroid 
plexuses  is  everywhere  covered  by  endyma  which  is  reflected  from  it  to  the  fim- 
briated  edge  of  the  fornix  on  the  one  hand  and  to  the  line  of  the  tsenia  semicircu- 
laris  (over  the  thalamus  by  the  lamina  affixa)  on  the  other.  Its  vascular  com- 
ponents, in  addition  to  undefined  lymphatic  channels,  are:  the  prechoroid  (anterior 
choroid}  artery,  a  branch  of  the  internal  carotid,  entering  the  paraplexus  of  the 
medicornu;  the  postchoroid  (posterior  choroid}  artery  from  the  postcerebral  artery 
reaching  the  paraplexus  in  the  neighborhood  of  the  splenium.  The  venules  of  the 
plexus  join  to  form  a  tortuous  medicornual  vein  which  terminates  frontad  by 
joining  one  of  the  velar  veins. 


Fornix 

Thalamus 
Quadrigemina 


Fie.  618. — Diagram  showing  the  mode  of  formation  of  the  velum. 

The  velar  veins  (veins  of  Galen},  one  on  each  side  close  to  the  median  line, 
running  in  the  fold  of  the  velum,  are  formed  by  the  union  of  the  tsenial,  striatal, 
and  medicornual  veins.  The  two  velar  veins  unite  to  form  a  common  trunk 
which  empties  into  the  straight  sinus. 

The  Hippocampus  and  Fornix. — The  hippocampus  and  the  fornix  merit  special 
description.  The  hippocampus,  as  seen  in  the  medicornu,  is  a  white  eminence 
about  5  cm.  in  length,  of  a  curved  elongated  form,  enlarging  cephalad  and  tapering 
caudad  as  the  hippocampal  fissure  decreases  in  depth.  The  enlarged  extremity 
is  marked  by  alternate  elevations  and  depressions,  usually  three  in  number,  the 
hippocampal  digitations;  because  of  its  resemblance  to  a  lion's  paw  it  is  sometimes 
called  the  pes  leonis  or  pes  hippocampi.  The  white  appearance  of  the  ventricular 
aspect  of  the  hippocampus  is  due  to  a  stratum  of  white  substance,  the  alveus,  made 
up  of  myelinic  axones  from  hippocampal  cells  and  continued  into  the  fimbria. 
The  fimbria  is  folded  so  that  its  sharp  margin  is  directed  toward  the  cavity  of 
the  medicornu;  eventually  its  fibres  will  be  seen  to  enter  into  the  formation  of  the 
fornix.  The  formation  of  the  hippocampus  is  best  observed  in  a  coronal  section 
(Fig.  008).  In  this  view  it  is  seen  to  be  a  peculiarly  folded  margin  of  the  cere- 
bral cortex,  corrugated  by  the  intrusion  of  the  hippocampal  and  fimbriodentate 


948 


THE  NERVE  SYSTEM 


fissures.    Morphologically  it  is  a  vestigial  submerged  portion  of  the  rhinencephalon, 
as  a  part  of  which  it  has  already  been  described. 


FIG.  619. — The  fornix,  velum,  and  medicornu  of  the  lateral  ventricle. 


Eminentia 
collateralis. 


Hippocampus 

Gray  substance  ) 

of  the        > 

hippocampus.  J 


f  Fascia 

(  (I I'll  III /H. 

f  Hippocampal 

(gyre 
Uncinate 
process  or 
uncus. 


FIG.  620.— Transverse  section  of  the  middle  horn  of  the  lateral  ventricle. 


THE  CEREBRAL  HEMISPHERES 


949 


The  fornix  (Figs.  615, 621, 622)  is  really  a  paired  structure  consisting  of  bilaterally 
symmetrical  halves  composed  of  longitudinally  directed  fibres  which  arch  on  each 
side  from  the  region  of  the  uncus  to  the  albicans.  The  two  lateral  parts  join  each 


FRENULUM 
GIACOMINI 


FORN  (COM- 
MISSURE 


FIG.  621. — The  fornix,  fornicommissure,  splenium,  and  dentate  gyre  seen  from  the  basal  aspect. 


FIG.  622. — Diagram  of  the  fornix. 


other  in  the  mesal  plane  along  the  summit  of  the  arch  to  form  the  body  of  the  fornix 
(corpus  fornicis).  Frontad  they  diverge  slightly  as  they  proceed  toward  the  albi- 
cantia ;  caudad  they  diverge  more  widely.  The  paired  diverging  portions  are  called 


950 


THE  NERVE  SYSTEM 


respectively  the  anterior  and  posterior  pillars  of  the  fornix.     The  fibres  of  each  half- 
fornix  arise  from  the  pyramidal  cells  in  the  hippocampus  and  their  course  will 


CALLOSUM 

CAUDATUM 

(CAPUT) 

PRECORNU  OFLATERAL 
VENTRICLE 


CALLOSUM 
(ROSTRUM) 

PSEUDOCELE 
FIG.  623. — A  frontal  section  of  the  brain  slightly  caudad  of  the  genu  of  the  callosum. 

be  traced  from  this  source  to  the  ending  in  the  albicans.     Beginning  at  first  as  a 
stratum  of  white  substance  (alveus)  constituting  the  ectal  surface  of  the  ventricular 


CALLOSUM 

PRECORNU  OF  LATERAL' 
VENTRICLE 

CALLOSUM 
(ROSTRUM) 

CLAUSTRUM 


FIG.  624.— A  frontal  section  through  the  brain  in  the  plane  of  the  junction  of  caudatum  and  lenticula. 

bulge  of  the  hippocampus,  the  fibres  become  collected  along  its  medial  border 
in  a  narrow  but  distinct  folded  band,  the  fimbria.     This  increases  in  calibre 


THE  CEREBRAL  HEMISPHERES 


951 


as  increments  are  added  to  it  along  its  course,  until,  at  the  apical  region  of  the 
trigonum  ventriculi,  it  leaves  the  dwindling  hippocampus  to  ascend  in  a  curved 
course  (dorsi-mesad)  toward  the  subsplenial  callosal  surface  as  a  thick,  flattened 
band.  Once  free  from  the  hippocampus  on  each  side,  the  two  converging  bands 
of  opposite  sides  are  called  the  posterior  pillars  or  crura  fornicis.  The  majority 
of  the  fibres  continue  frontad  in  each  half-fornix,  but  a  number  course 
transversely  to  enter  the  crus  fornicis  of  the  opposite  side  to  end  in  the  hippo- 
campal  formation.  These  fibres,  of  transverse  course,  form  a  thin  lamina  filling 
in  the  small  triangular  space  in  the  subsplenial  region  between  the  converging 
crura  fornicis  and  constituting  the  fornicommissure  (Lyra;  psalterium;  hippocampal 
commissure).  Occasionally  a  small  recess  called  Verga's  ventricle  is  formed 
between  callosum  and  fornicommissure. 

The  two  half-fornices  now  become  joined  in  the  mesal  plane  and,  leaving  the 
subsplenial  surface  of  the  callosum,  dip  fronto-ventrad  in  dn  arch — the  body  of  the 
fornix.  Its  caudal  part  is  broad  and  each  half  is  of  triangular  outline  (on  section) 
with  a  sharp  edge  directed  laterad.  Where  it  is  not  in  contact  with  the  callosum 


LATERAL  VENTRICLE 


INTERNAL  CAPSULE 


FORNICOLUMN 


CLAUSTRUM 


PRECOMMISSURE 


AMYGDALA 


FIG.  625. — A  frontal  section  of  the  brain  in  the  plane  of  the  precommissure. 


it  affords  attachment,  on  each  side  of  the  mesal  plane,  to  the  hemiseptum. 
Laterad  of  these  lines  of  attachment  the  dorsal  surface  of  each  fornix  enters  into 
the  formation  of  the  floor  of  the  lateral  ventricle  and  is  covered  by  endyma  (Fig. 
615).  The  ventral  surface  rests  upon  the  velum,  which  separates  it  from  the 
third  ventricle  and  the  dorsal  surface  of  the  thalamus. 

Near  the  region  of  the  precommissure  the  fornix  again  divides  into  its  con- 
stituent lateral  halves,  separating  as  rounded  strands  called  the  fornicolumns  or 
anterior  pillars.  These  curve  ventrad  to  form  the  frontal  boundary  of  the  porta 
and  thence  plunge  into  the  hypothalamic  gray,  inclined  slightly  caudad,  to  end 
in  the  albicans.  The  terminals  of  the  fornix  fibres  come  into  relation  with  the 
cells  of  the  nucleus  of  the  albicans,  which  in  turn  give  off  the  bifurcating  Y-shaped 
axone-bundles  already  described  (p.  920). 

In  rare  instances  each  fornicolumn  has  been  seen. to  divide  on, approaching  the 
precommissure,  a  part  passing  frontad  thereof  as  an  anomalous  precommissural 


952  THE  NERVE  SYSTEM 

fornicolumn.  The  fornix,  in  its  course  from  hippocampus  to  albicans,  gives  off, 
in  addition  to  those  described  as  hippocampal  commissural  fibres,  axones  (a)  to 
the  opposite  half-fornix,  decussating  in  the  fused  portion  (body),  (6)  to  the 
hemiseptum,  and  (c)  to  the  gray  tissues  of  the  preperforatum  (Fig.  607).  It 
constitutes  an  inner  olfactory  arc  as  distinguished  from  the  epicallosal  or  outer 
arc,  represented  by  the  atrophied  indusium  and  its  longitudinal  strise. 

The  Septum  Lucidum  (septum  pellucidum). — The  so-called  septum  lucidum 
really  consists  of  two  vertically  placed  laminae  or  hemisepta.  Between  them  lies 
a  narrow,  enclosed  space,  the  pseudocele  or  fifth  ventricle  (cavum  septi  pellucida), 
roofed  in  by  the  calfosum,  while  the  floor  consists  of  the  fused  fornices  and  the 
rostrum.  Each  hemiseptum  bounds  a  part  of  the  precornu  and  body  of  the 
paracele  in  its  mesal  wall  and  in  a  lateral  view  is  of  triangular  outline.  The 
hemisepta  represent  the  thin,  undeveloped  parts  of  the  mesal  walls  of  the  cerebral 
vesicles,  which  were  enclosed  within  the  rapidly  developing  arch  of  the  callosum. 
The  pseudocele  is  therefore  a  closed-off  part  of  the  original  intercerebral  cleft  and 
not  a  part  of  the  neural  cavity  as  its  older  name  "fifth  ventricle"  seems  to  imply. 

The  Precommissure. — The  precommissure  is  a  bundle  of  white  fibres,  of  oval 
outline  in  a  sagittal  section,  which  crosses  the  mid-line  as  a  localized  reenforce- 
ment  of  the  terma,  slightly  bulging  into  the  frontal  part  (aula)  of  the  third  ventricle 
and  clothed  by  its  endyma.  It  is  a  comparatively  insignificant  intercerebral 
commissure  in  the  human  brain,  having  become  diminished  as  the  callosum 
increased  in  mammalian  development.  It  courses  from  side  to  side  frontad  of  the 
fornicolumns,  ventrad  of  the  head  of  the  caudatum,  and  passes,  in  part,  through 
the  frontal  end  of  the  lenticula.  Its  fibres  radiate  chiefly  to  the  cortex  of  the 
temporal  lobe  and  to  certain  parts  of  the  rhinencephalon. 

The  bundle  is  slightly  twisted  in  each  lateral,  buried  part.  Two  divisions  are 
distinguishable:  1.  The  pars  anterior  or  frontal  part  (in  the  median  plane)  con- 
tains two  groups  of  fibres  belonging  to  the  olfactory  apparatus:  (a)  fibres  arising 
from  the  mitral  cells  in  the  olfactory  bulb  of  one  side  to  the  same  layer  in  the 
opposite  bulb;  (6)  fibres  which  associate  the  uncus  of  one  side  with  that  of  the 
other.  2.  The  pars  posterior  contains  the  fibres  passing  between  the  cortices  of 
the  two  temporal  lobes. 

Gray  Masses  in  the  Hemicerebrum. — Aside  from  the  cortex,  the  hemicerebrum 
contains  certain  gray  ganglionic  masses  in  its  interior,  more  or  less  embedded  in 
the  white  centrum  and  called,  because  of  their  proximity  to  the  base  of  the  cere- 
brum, the  basal  ganglia.  These  comprise  the  caudatum,  the  lenticula,  and  the 
amygdala.  It  is  usual  to  include  the  claustrum  among  the  basal  ganglia,  but 
morphologically  this  structure  belongs  rather  to  the  insular  cortex. 

Conventionally  the  caudatum  and  lenticula  together  are  described  as  the 
striatum  (corpus  striatum) — a  ganglionic  mass  which  in  earlier  vertebrate  brains 
bore  intimate  relations  with  the  olfactory  apparatus,  but  later,  with  the  rise  in 
functional  dignity  and  growth  of  the  neopallium,  underwent  specialization  and 
differentiation  concomitant  with  the  reduction  of  the  rhinencephalon.  The 
intrusion  of  great  projection  fibre-masses,  thrusting  the  cortical  gray  outward, 
has  not  been  everywhere  uniform,  and  we  still  find,  in  the  human  brain,  a  common 
ground  in  which  the  neopallial  cortical  gray,  the  striatum,  rhinencephalon,  and 
amygdala  meet — the  site  of  fusion  being  in  the  gray  substance  of  the  preperforatum. 
To  the  cortical  mantle  they  are  regarded  as  bearing  the  relation  of  subordinate 
(subcortical)  centres.  In  the  human  brain  the  striatum — so-called  because  of  its 
striated  appearance  in  sections — is  composed  of  two  masses,  the  caudatum  and 
lenticula,  directly  continuous  with  each  other  at  their  frontal  ends  (Fig.  627). 
The  connecting  gray  bridge  becomes  broken  up  into  numerous  small  bands  of 
gray  substance  as  the  fibre-masses  of  the  internal  capsule  insinuate  themselves 
between  the  two"  nuclei  (Fig.  624). 


THE  CEREBRAL  HEMISPHERES  953 

The  Caudatum  (nucleus  caudatus]  (Figs.  623,  626,  627)  presents  a  ventricular 
and  a  capsular  surface;  the  ventricular  surface,  covered  by  endyma,  forms  part 
of  the  floor  of  the  body  and  precornu,  while  in  the  medicornu  it  is  a  constituent  of 
its  roof,  owing  to  its  arched  contour  in  correspondence  with  the  sweeping  curve 
of  the  ventricle  itself.  It  is  of  a  pyriform  shape  with  a  very  much  attenuated  tail. 
The  large,  thick  head  projects  into  the  precornu  whilst  its  thinner  tail  is  pro- 
longed caudo-laterad,  separated  from  the  thalamus  by  the  narrow  taenia  semi- 
circularis.  Following  the  curved  contour  of  -the  ventricle  it  is  prolonged  as  a 


FIG.  626. — The  basal  ganglia  and  thalamus  schematically  represented  in    a   supposedly  transparent  brain 
(right  side);  on  the  left  is  shown  the  outline  of  the  paracele  (lateral  ventricle). 

narrow  gray  band  in  the  roof  of  the  medicornu.  where  it  joins  the  amygdala.  The 
non-ventricular  or  capsular  surface  is  embedded  in  the  white  substance  of  the 
hemi-cerebrum,  and  is  chiefly  related  to  the  internal  capsule. 

The  ventricular  surface  shows,  in  microscopic  sections,  a  dense  endymal 
lining.  The  capsular  face  is  not  sharply  outlined,  numerous  strands  of  fibres, 
to  and  from  the  internal  capsule,  entering  it  obliquely  so  as  to  appear  as  streaks 


954 


THE  NERVE  SYSTEM 


AMYGDALA 


which  extend  to  about  the  middle  of   the  ganglion,  there   separating  into  finer 
and  finer  strands  which  become  lost  to  the  naked  eye. 

The  Lenticula  (Figs.  624,  626,  628)  is  wholly  embedded  in  the  white  substance 
and  must  be  studied  in  sections.  In  its  shape  it  resembles  an  irregular  trian- 
gular pyramid  with  its  convex  base  directed  laterad  and  parallel  with  and  near 
to  the  cortical  expanse  of  the  insula  and  of  about  the  same  extent.  Its  ental, 
apical  portion  is  directed  toward  the  interval  between  caudattim  (head)  and 
thalamus.  The  contour  and  slope  of  the  surfaces  of  the  ental  pyramidal  face 
may  be  judged  from  the  model  pictured  in  Fig.  627.  Its  outline,  as  revealed  in 
sections  passing  in  different  planes,  is  shown  in  Figs.  625  and  628. 

Sections  of  the  lenticula  show  it  to  be  composed  of  three1  concentric  segments 
separated  by  two  white  medullary  laminae.  The  segments  are  known  as  articuli; 
the  ectal  one  is  designated  the  putamen;  the  two  ental  zones  constitute  the  palli- 

dum  (globus  pallidus).  The  putamen  is 
the  larger  and  of  a  deeper  reddish-gray 
tint;  the  two  mesal  divisions  are  lighter 
in  color  owing  to  a  greater  proportion  of 
radiating  streaks  of  white  fibres  passing 
to  and  from  the  internal  capsule.  The 
ectal  outline  of  the  putamen  is  sharply 
defined  against  a  white  lamina,  the  external 
capsule. 

The  Amygdala  is  usually  regarded  as  an 
hypertrophied  aggregation  of  the  tem- 
poral cortex  which  has  become  nearly 
isolated  from  its  cortical  connection  by 
intruding  white  substance.  It  is  a 
rounded,  gray,  striated  mass  situated  in 
the  forepart  of  the  temporal  lobe  in  the 
roof  of  the  medicornu  at  its  apex,  where 
it  produces  the  bulging  called  the  amygda- 
loid tubercle.  Caudad  it  is  joined  by  the 
tail  of  the  caudatum;  frontad  it  is  contin- 
uous with  the  putamen.  Except  for  the 
marked  streaking  shown  in  sections,  its 
structure  is  like  that  of  the  cortex.  Its 
cells  apparently  give  rise  to  the  narrow 
band  of  fibres — the  tsenia  semicircularis — 
which  courses  along  the  mesal  margin  of 
the  ventricular  surface  of  the  caudatum 

throughout  its  arched  course  and  ends  in  the  preperforatal  gray  so  that  it  nearly 
completes  a  circle. 

The  Claustrum  is  a  thin  plate  of  gray  substance  embedded  in  the  white  sub- 
stance which  intervenes  between  the  putamen  and  the  insular  cortex,  and  corre- 
sponding in  extent  to  these.  Its  dorsal  edge  is  very  much  attenuated;  traced 
ventrad  it  thickens  considerably  and  becomes  continuous  with  the  surface  gray  at 
the  preperforatum.  Its  ectal  surface  presents  alternate  ridges  and  depressions 
which  correspond  to  the  corrugations  of  the  insular  cortex.  The  "external 
capsule"  intervenes  between  its  ental  face  and  the  putamen  of  the  lenticula.  From 
the  insular  cortex  proper  it  is  separated  by  a  white  lamina  which  may  be  termed 
the  periclaustral  lamina  or  capsula  extrema.  Apparently  the  claustrum  is  the 
thickened  and  isolated  spindle-cell  stratum  of  the  insular  cortex,  a  feature  which 


B 


AMYGDALA 


FIG.  627. — Two  views  of  a  model  of  the  striatum 
A,  lateral  view  aspect;  B,  mesal  view  aspect. 


1  Four  and  even  five  have  been  observed. 


THE  CEREBRAL  HEMISPHERES 


955 


may  be  of  significance  in  relation  to  the  preponderatingly  associative  function  of 
the  insular  region. 

Internal  Capsule  (Fig.  628). — Between  the  lenticula  on  the  one  hand  and  the  cau- 
latum  and  thalamus  on  the  other  lies  the  internal  capsule,  a  broad  band  of  white 
fibres  which,  as  seen  on  horizontal  section,  appears  bent,  very  much  as  a  leg  is  bent 
on  the  thigh,  with  the  knee  (genu)  directed  mesad.  The  frontal  or  caudatp-len- 
ticular  division  or  limb  is  confined  between  the  opposed  faces  of  the  caudatum  and 
lenticula.  The  genu  receives  the  mesal  apex  of  the  lenticula  in  its  hollow,  while 


PRECORNU  OF 
LAT.    VENTR. 

PSEUDOCELE 

CORTEX    OF    INSULA 

FORNIX 

CLAUSTRUM 

EXTERNAL    CAPSULE — 

ALBICANTIO- 
THALAMIC    TR. 
PARACLAUSTRA 
WHITE    LAMINA 


EPIPHYSIS 

TAIL   OF  CAUDATUM 
HIPPOCAMPUS 

CHOROID    PLEXUS 

OPTIC    RADIATION 

TAPETUM 

CALCARINE 
FISSURE 


WHITE    STRIPE    OF 
VICQ      D'AZYR 


FIG.  628. — Horizontal  section  through  the  cerebrum.     The  various  structures  are  shown  in  their   natural 
appearance  on  the  right  side  and  are  named  on  the  left  side. 

the  caudal  or  thalamo-lenticular  limb  lies  between  the  opposed  faces  of  lenticula 
and  thalamus.  The  frontal  limb  constitutes  about  one-third,  the  caudal  limb 
two-thirds  of  the  internal  capsule  mass. 

The  term  "internal  capsule"  is  often  loosely  employed  and  is  variously  stated 
to  include  fibre-tracts  which  do  not  course  between  the  cerebral  cortex  and  the 
"lower"  brain  centres.  In  a  strict  sense  it  is  a  mass  of  fibres  which  converge, 
like  the  sticks  of  a  fan,  toward  the  cerebral  base  and  into  the  crusta.  Dorsad 
of  the  basal  ganglia  the  fibres  radiate  in  various  directions,  streaming  among 
the  radiating  callosal  fibres  and  forming  the  so-called  corona  radiata.  Yet  other 


THE  NER  VE  SYSTEM 


TH  A  LA  MO- 
FRONTAL 
TRACT 


GENICULATE 

PORTION  OF 

MOTOR  TRACT 

(FOR  MUSCLES'" 

OF  FACE  AND 

TONGUE) 


fibre-tracts  leave  and  enter  the  great  ganglia  at  various  altitudes  along  the  internal 
capsule,  and  we  must  therefore  distinguish  the  following  cerebral  fibre-systems . 

Projecting  systems,  ascending  and  descending  (in  the  functional  sense),  of 
longer  and  shorter  course,  connecting  the  cerebral  cortex  with  (a)  spinal  gray 
centres;  (6)  mid-brain  and  pontile  nuclei;  (c)  basal  ganglia  and  thalamus.  The 
last-mentioned  system  traverses  the  internal  capsule  to  a  greater  or  lesser  extent, 

but  does  not  continue  into  the 
crusta.  These  various  systems 
are  summarized  on  page  963.  It 
may  here  be  mentioned  that  the 
internal  capsule,  topograpically, 
exhibits  a  functional  dissociation 
in  that  its  frontal  or  lenticulo- 
caudate  limb  is  composed  of  pre- 
ponderatingly  corticipetal  fibres, 
while  corticifugal  fibres  form  the 
major  portion  of  the  thalamo- 
lenticular  limb  (Fig.  629).  In 
the  frontal  limb  are  the  thalamo- 
frontal  and  thalamo-striate  fibres; 
the  former  ending  in  the  cortex 
of  the  frontal  lobe,  the  latter  in 
the  caudatum  and  lenticula.  The 
chief  corticifugal  components  are 
the  fronto-pontile  tract,  and  fewer 
fronto-thalamic  and  striato-thala- 
mic  fibres.  The  fronto-pontile 
tract  arises  in  the  cortex  of  the 
pref rental  region,  traverses  the 
frontal  limb  of  the  internal  cap- 
sule, forms  the  ental  sector  (one- 
fifth)  of  the  crusta,  and  ends  in 
the  nuclei  pontis. 

In  the  genu  and  the  thalamo- 
lenticular  limb  of  the  internal 
capsule  course  several  important 
fibre-tracts  which  are  chiefly  cor- 
ticifugal. 

The  Pyramidal  (Motor)  Tract, 
in  its  course  from  the  precentral 
cortex  to  the  lower  motor  centres 
occupies  the  frontal  half  of  this 
limb.  The  portion  in  the  genu, 
often  designated  the  geniculate 
tract,  comprises  the  pyramidal 
fibres  which  are  destined  to  go 
to  the  facial  and  hypoglossal 
nerve  nuclei;  further  caudad  lie,  in  succession,  the  fibres  going  to  the  motor 
centres  for  the  upper  and  the  lower  extremity.  The  most  caudal  segment  (also 
called  the  retrolenticular  part)  of  the  internal  capsule  contains  (a)  the  optic  radia- 
tion, composed  of  fibres  coursing  in  both  directions  between  the  occipital  cortex 
and  the  pulvinar,  pregeniculum  and  pregeminum;  (6)  the  auditory  radiation,  com- 
posed of  fibres  passing  in  both  directions  between  the  cortex  of  the  temporal 
lobe  (auditory  centre)  and  the  postgeminum  and  postgeniculum ;  (c)  the  occipito- 


OPTIC 
RADIATION 


FIG.  629. — Diagram  of  the  tracts  in  the  internal  capsule. 
Motor  tract  red.  The  sensor  tract  (blue)  is  not  direct  but 
formed  of  neurones  receiving  impulses  irom  below  in  the 
thalamus  and  transmitting  them  to  the  cortex.  The  optic 
radiation  (occipito-thalamic)  is  shown  in  violet. 


THE  CEREBRAL  HEMISPHERES 


957 


pontile  and  temporo-pontile  tracts  from  the  occipital  and  part  of  the  temporal 
cortex,  coursing  through  the  caudal  segment  of  the  internal  capsule,  constituting 
the  ectal  (one-fifth)  sector  of  the  crusta  and  ending  in  the  nuclei  pontis.  In  ad- 
dition there  are  scattered  fibre-bundles  which  arise  from  the  ventral  portion  of 


FIG.  630.— Diagram  of  motor  path  from  right  brain.  The  upper  segment  is  black,  the  lower  red.  The  nuclei 
of  the  motor  cerebral  nerves  are  shown  on  the  left  side:  on  the  right  side  the  craniaj  nerves  of  that  side  are 
indicated.  A  lesion  at  1  would  cause  upper  segment  paralysis  in  the  arm  of  the  opposite  side — cerebral  mono- 
plegia;  at  2,  upper  segment  paralysis  of  the  whole  opposite  side  of  the  body — hemiplegia;  at  3,  upper  segment 
paralysis  of  the  opposite  face,  arm,  and  leg,  and  lower  segment  paralysis  of  the  eye  muscles  on  the  same  side — 
crossed  paralysis;  at  4,  upper  segment  paralysis  of  opposite  arm  and  leg,  and  lower  segment  paralysis  of 
the  face  and  the  external  rectus  on  the  same  side — crossed  paralysis;  at  5,  upper  segment  paralysis  of  all  mus- 
cles below  lesion,  and  lower  segment  paralysis  of  muscles  represented  at  level  of  lesion-^spinal  paraplegia;  at 
6,  lower  segment  paralysis  of  muscles  localized  at  seat  of  lesion — anterior  poliomyelitis.  (Van  Gehuchten, 
modified.) 

the  thalamus,  enter  the  internal  capsule  to  pass  toward  the  cortex,  in  part  through 
the  lenticula,  in  part  in  the  sublenticular  zone,  to  form  the  ansa  lenticularis.  The 
reenforcement  of  this  sublenticular  white-fibre  tract  by  cortico-thalamic  fibres  from 
the  temporal  lobe  to  thalamus  forms  the  ansa  peduncularis.  The  topographic  rela- 
tions of  the  various  tract-masses  as  seen  in  a  flat-wise  section  is  schematically 


958 


THE  NERVE  SYS1EM 


\ 


MOLECULAR    LAYER 


ECTAL  POLYMOR- 
PHOUS CELL  LAYER 


a 


ft 


LAYER  OF  SMALL 
>  PYRAMIDAL  CELLS 


shown  in  Fig.  630;  on  the  whole  they  correspond  to  the  cortical  areas  with 
which  they  are  connected. 

The  External  Capsule  (Fig.  628).— The  external  capsule  is  a  thin  lamina  of  white 
substance  interposed  between  the  ectal  face  of  the  lenticula  and  the  claustrum 
Dprsally,  frontad  and  caudad,  at  the  corresponding  borders  of  the  lenticula  it 
joins  the  internal  capsule  mass,  while  ventrally  it  is  continuous  with  the  white 

centrum  of  the  temporal  lobe.  Its  compara- 
tively few  projection  fibres  course  to  and 
from  the  ventral  parts  of  the  thalamus;  its 
chief  constituents  are  association  axones  for 
the  circuminsular  cortical  areas. 

Intimate  Structure  of  the  Cerebral  Cortex  and 
its  Special  Types  in  Different  Regions  (Fig. 
631). — A  section  of  the  cerebral  cortex  re- 
veals a  tendency  on  the  part  of  its  constituent 
cells  to  arrange  themselves  in  layers  which 
alternate  with  zones  less  rich  in  cellular  ele- 
ments. Among  the  cells  course  the  axones 
arising  from  them  or  terminating  in  their 
neighborhood.  The  axones  are  chiefly  amye- 
linic,  though  some  are  myelinic  for  a  part 
of  their  intracortical  course.  The  cells,  of 
various  sizes  and  shapes,  together  with  their 
dendrites  and  axones  are  embedded  in  a 
matrix  of  neuroglia. 

The  nerve-cells  in  a  typical  section  of  the 
cortex  are  arranged  in  five  tangential  layers, 
as  follows:  (1)  the  molecular  layer;  (2)  the 
ectal  polymorphous  cell  layer;  (3)  the  layer  of 
small  pyramidal  cells;  (4)  the  layer  of  large 
pyramidal  cells;  (5)  the  ental  polymorphous 
cell  layer. 

The  molecular  layer  (neuroglia  layer]  lies 
immediately  subjacent  to  the  pia  and  is 
chiefly  made  up  of  glia  cells  and  fibres 
amongst  which  the  dendrites  of  the  subjacent 
layer  of  cells  intrude. 

The  ectal  polymorphous  layer  cells  are  poly- 
gonal, triangular  and  fusiform  in  shape  and 
tend  to  gather  in  groups  in  certain  cortical 
regions.  The  fusiform  cells  are  placed  with 
their  long  axes  parallel  (i.  e.,  tangential)  to 
the  gyral  surface  and  are  presumably  associa- 
tive in  function. 

The  Layer  of  Small  and  the  Layer  of  Large 
Pyramidal  Cells. — The  cells  in  the  second 
and  third  layers  may  be  studied  together, 
since,  with  the  exception  of  the  difference 
in  size  and  the  more  superficial  position  of  the 
smaller  cells,  they  resemble  each  other.  The  body  of  each  cell  is  pyramidal  in 
shape,  its  base  being  directed  to  the  deeper  parts  and  its  apex  toward  the  sur- 
face. It  contains  granular  pigment,  and  stains  deeply  with  ordinary  reagents. 
The  nucleus  is  nucleolated,  of  large  size,  and  round  or  oval  in  shape.  The  base 
of  the  cell  gives  off  the  axone,  and  this  passes  into  the  central  white  substance, 


LAYER  OF  LARGE 
PYRAMIDAL  CELLS 


ENTAL  POLYMOR- 
PHOUS CELL  LAYER 


FIG.  631. — Typical  arrangement  of  the  cell 
layers  in  the  cerebral  cortex. 


THE  CEREBRAL  HEMISPHERES  959 

giving  off  collaterals  in  its  course  to  be  distributed  as  a  projection,  commissural, 
or  association  fibres.  Both  the  apical  and  basal  parts  of  the  cell  give  off  dendrites. 
The  apical  dendrite  is  directed  toward  the  surface,  and  ends  in  the  molecular 
layer  by  dividing  into  numerous  branches,  all  of  which  may  be  seen  to  be  studded 
with  projecting  bristle-like  processes  when  prepared  by  the  silver  or  methylene- 
blue  method.  The  larger  pyramidal  cells,  especially  in  the  precentral  gyre, 
may  exceed  50  fj.  in  length  and  40  /*  in  breadth,  and  are  termed  giant  cells.  The 
chief  function  of  the  small  pyramidal  cells  is  commissural  and  associative. 
The  chief  function  of  the  large  pyramids  is  motor,  but  they  have  also  commissural 
and  associative  functions. 

Layer  of  Ental  Polymorphous  Cells. — The  cells  in  this  layer,  as  their  name 
implies,  vary  greatly  in  contour,  the  commonest  varieties  being  of  a  spindle, 
star,  oval,  or  triangular  shape.  Their  dendrites  are  directed  outward,  toward, 
but  do  not  reach,  the  molecular  layer;  their  axones  pass  into  the  subjacent  white 
substance.  From  this  layer  come  commissural  fibres,  long  association  fibres,  and 
some  projection  fibres. 

There  are  two  other  kinds  of  cells  in  the  cerebral  cortex,  but  their  axones  pass 
in  a  direction  opposite  to  that  of  the  pyramidal  and  polymorphous  cells,  among 
which  they  lie.  They  are:  (a)  the  cells  of  Golgi,  the  axones  of  which  do  not 
become  myelinated,  but  divide  immediately  after  their  origin  into  a  large  number 
of  branches,  which  are  directed  toward  the  surface  of  the  cortex;  (6)  the  cells  of 
Martinotti,  which  are  chiefly  found  in  the  polymorphous  layer.  Their  dendrites 
are  short,  and  may  have  an  ascending  or  descending  course,  while  their  axones 
pass  out  into  the  molecular  layer  and  form  an  extensive  horizontal  arborization. 

Nerve-fibres  in  the  Cortex. — These  fill  up  a  large  part  of  the  intervals  between 
the  cells.  Some  of  these  fibres  form  fasciculi;  some  are  isolated,  and  others  are 
arranged  in  plexuses.  They  may  be  myelinic  or  amyelinic,  the  latter  comprising 
the  axones  of  the  smallest  pyramidal  cells  and  the  cells  of  Golgi.  In  their  direction 
the  fibres  may  be  either  transverse,  the  transverse  tangential  or  horizontal  fibres, 
or  vertical,  the  vertical  or  radial  fibres.  The  transverse  fibres  run  parallel  to  the 
surface  of  the  hemisphere,  intersecting  the  vertical  fibres  at  a  right  angle.  They 
consist  of  several  strata,  of  which  the  following  are  the  most  important:  (1)  a 
stratum  of  white  fibres  covering  the  superficial  aspect  of  the  molecular  layer;  (2) 
the  band  of  Bechterew,  found  in  certain  parts  of  the  superficial  portion  of  the 
layer  of  the  smaller  pyramidal  cells;  (3)  the  external  or  outer  band  of  Baillarger 
or  the  band  of  Gennari,  which  runs  through  the  layer  of  large  pyramidal  cells; 
(4)  the  internal  band  of  Baillarger,  which  intervenes  between  the  layer  of  large 
pyramidal  cells  and  the  polymorphous  layer.  According  to  Cajal,  the  transverse 
fibres  consist  of  (a)  the  collaterals  of  the  pyramidal  and  polymorphous  cells  and 
of  the  cells  of  Martinotti;  (6)  the  arborizations  of  the  axones  of  Golgi 's  cells;  (c) 
the  collaterals  and  terminal  arborizations  of  the  projection,  commissural,  or 
association  fibres.  The  vertical  fibres:  Some  of  these,  viz.,  the  axones  of  the 
pyramidal  and  polymorphous  cells,  are  directed  toward  the  central  white  sub- 
stance, while  others,  the  terminations  of  the  commissural,  projection,  or  association 
fibres,  pass  outward  to  end  in  the  cortex.  The  axones  of  the  cells  of  Martinotti 
are  also  ascending  fibres. 

In  certain  parts  of  the  cortex  this  typical  structure  is  departed  from.  The  chief 
of  these  regions  are:  (1)  the  occipital  lobe,  (2)  the  transtemporal  gyres,  (3)  the  hippo- 
campus, (4)  the  dentate,  and  (5)  the  olfactory  bulb. 

Special  Types  of  Gray  Substance.  1.  The  Occipital  Lobe. — In  -the  cuneus  and 
the  calcarine  fissure  of  the  occipital  lobe,  Cajal  has  recently  described  as  many  as 
nine  layers.  Here  the  inner  band  of  Baillarger  is  absent;  the  outer  band  of  Bail- 
larger  or  band  of  Gennari  is,  on  the  other  hand,  of  considerable  thickness.  If  a 
section  be  examined  microscopically,  an  additional  layer  is  seen  to  be  interpolated 


960  THE  NER  VE  SYSTEM 

between  the  molecular  layer  and  the  layer  of  small  pyramidal  cells.  This  extra 
layer  consists  of  two  or  three  strata  of  fusiform  cells,  the  long  axes  of  which  are  at 
right  angles  to  the  surface.  Each  cell  gives  off  two  dendrites,  external  and  internal, 
from  thS  latter  of  which  the  axone  arises  and  passes  into  the  white  central  sub- 
stance. In  the  layer  of  small  pyramidal  cells,  fusiform  cells,  identical  with  the 
above,  are  seen,  as  well  as  ovoid  or  star-like  elements  with  ascending  axones,  the 
cells  of  Martinotti.  This  area  of  the  cortex  forms  the  visual  centre,  and  it  has 
been  shown  by  Dr.  J.  S.  Bolton1  that  in  old-standing  cases  of  optic  atrophy  the 
thickness  of  Gennari's  band  is  reduced  by  nearly  50  per  cent. 

2.  The  Transtemporal  Gyres. — The  transtemporal  gyres  are  distinguished  by  a 
reduction  of  thickness  of  the  pyramidal  cell  layer  with  closer  approximation  of 
the  giant-cells  to  each  other,  while  the  fusiform  cell  layer  is  more  deeply  situated 
than   elsewhere.     This   cortical  formation  is  the  end-station  for  cochlear  nerve 
projections. 

3.  The  Hippocampus. — In  the  hippocampus  the  molecular  layer  is  very  thick 
and  contains  a  large  number  of  Golgi  cells.     It  has  been  divided  into  three 
strata:  (a)  S.  convolutum  or  S.  granulosum,  containing  many  tangential  fibres;  (6) 
S.  lacunosum,  presenting  numerous  lymphatic  or  vascular  spaces;  (c)  S.  radiatum, 
exhibiting  a  rich  plexus  of  fibrils.     The  two  layers  of  pyramidal  cells  are  con- 
densed into  one,  and  these  are  mostly  of  large  size.     The  axones  of  the  cells  in 
the  polymorphous  layer  may  run    in   an   ascending,  descending,  or  horizontal 
direction.     Between  the  polymorphous  layer  and  the  ventricular  ependyma  is 
the  white  substance  of  the  alveus  (Fig.  608). 

4.  The   Dentate   Gyre. — In  the  rudimentary  dentate  convolution  the  molec- 
ular layer  contains  some  pyramidal  cells,  while  the  pyramidal   layer  is  almost 
entirely  represented  by  small  ovoid  elements. 

5.  The  Olfactory  Bulb. — In  many  of  the  lower  animals  this  contains  a  cavity 
which  communicates  through  the  hollow  olfactory  stalk  with  the  cavity  of  the 
lateral  ventricle.     In  man  the  original  cavity  is  filled  by  neuroglia  and  its  wall 
becomes  thickened,  but  much  more  so  on  its  ventral  than  on  its  dorsal  aspect. 
Its  dorsal  part  contains  a  small  amount  of  gray  and  white  substance,  but  this  is 
scanty  and  ill  defined.     A  section  through  the  ventral  part  shows  it  to  consist  of  the 
following  layers  from  without  inward.     (1)  A  layer  of  olfactory-nerve  fibres,  which 
are  the  myelinated  axones  prolonged  from  the  olfactory  cells  of  the  nose,  and 
which  reach  the  bulb  by  passing  through  the  cribriform  plate  of  the  ethmoid  bone. 
At  first  they  cover  the  bulb,  and  then  penetrate  it  to  end  by  forming  synapses 
with  the  dendrites  of  the  mitral  cells,  presently  to  be  described.     (2)  Glomerular 
layer   (stratum  glomerulosum) :     This  contains  numerous  spheroidal  reticulated 
enlargements,  termed  glomeruli,  which  are  produced  by  the  branching  and  arbor- 
ization of  the  processes  of  the  olfactory  nerve-fibres  with  the  descending  dendrites 
of  the  mitral  cells.     (3)  Molecular  layer:     This  layer  is  formed  of  a  matrix  of 
neuroglia,  embedded  in  which  are  the  mitral  cells.     These  cells  are  pyramidal  in 
shape,  and  the  basal  part  of  each  gives  off  a  thick  dendrite  which  descends  into 
the    glomerular   layer,  where    it    arborizes    as    above,  or,    on    the   other   hand, 
interlaces  with  similar  dendrites  of  neighboring  mitral  cells.     The  axones  pass 
through  the  next  layer  into  the  white  substance  of  the  bulb,  from  which,  after  becom- 
ing bent  on  themselves  at  a  right  angle,  they  are  continued  into  the  olfactory  tract. 
(4)  Nerve-fibre  layer:     This  lies  next  the  central  core  of  neuroglia,  and  its  fibres 
consist  of  the  axones  or  afferent  processes  of  the  mitral  cells  which  are  passing  on 
their  way  to  the   brain;   some   efferent   fibres   are,   however,   also   present,   and 
terminate  in  the  molecular  layer  and  presumably  come  via  the  precommissure 
from  the  mitral  cells  of  the  opposite  bulb. 

1  Phil.  Trans,  of  Royal  Society,  Series  B,  vol.  cxciii,  p.  165. 


'"' 


EMERSON 


THE  CEREBRAL  HEMISPHERES 


961 


The  claustnim,  although  usually  enumerated  among  the  basal  ganglia,  is 
probably  the  thickened  and  isolated  deepest  layer  of  fusiform  cells  belonging  to 
the  cortex  of  the  insula.  The  white  lamina1  intervening  between  it  and  the  cortex 
proper  consists  of  association  axones  of  longer  and  shorter  course. 

Summary  of  the  Cerebral  Fibre  Systems. — The  white  substance  of  the  cerebrum 
consists  of  myelinic  fibres  intricately  interwoven  but  permitting  of  classification 
into  three  systems  arranged  according  to  the  course  they  take.  These  systems 
comprise:  (1)  association  fibres,  which  connect  neighboring  or  distant  parts 
within  the  same  hemicerebrum ;  (2)  commissural  fibres,  which  unite  allied  parts  in 
the  two  cerebral  halves  and  come  transversely  across  the  mid-line  to  form  the 
commissures;  (3)  projection  fibres,  which  connect  the  cerebral  cortex  with  lower 
centres  in  the  brain  and  spinal  cord,  and,  conversely,  those  fibres  which  connect 
lower  centres  with  the  cerebral  cortex. 

1.  The  Association  Fibres  (Fig.  632)  connect  different  structures  in  the 
same  hemispheres,  and  are  in  or  near  to  the  cortex.  They  take  origin  from  the 
small  pyramidal  and  polymorphous  cells  of  the  deep  layer  of  the  cortex.  Their 


FIG.  632. — Diagram  showing  the  principal  systems  of  associating  fibres  in  the  cerebrum. 

direction  is  parallel  to  the  surface  of  the  hemisphere,  and  in  their  course  they 
cross  the  projection  and  commissural  fibres.  They  are  of  two  kinds:  (1)  those 
which  unite  adjacent  convolutions,  short  association  fibres;  (2)  those  which  pass 
between  more  distant  parts  in  the  same  hemisphere,  long  association  fibres. 

The  short  association  fibres  are  situated  immediately  beneath  the  gray  cortex  of 
the  hemispheres,  and  connect  together  adjacent  convolutions.  They  constitute 
subcortical  tracts  and  are  divided  into  arcuate  fibres  and  tangential  fibres.  Some 
of  these  fibres  connect  the  "visual  sensor  area  with  the  visual  memory  area,  and 
the  auditory  sensor  with  the  auditory  memory  area." 

The  long  association  fibres  associate  cerebral  centres  which  are  far  apart.  They 
are  gathered  into  bundles  and  dip  down  deep  into  the  centrum  ovale.  They 
include  the  following:  (a)  the  uncinate  fasciculus;  (6)  the  superior  longitudinal 
fasciculus;  (c)  the  inferior  longitudinal  fasciculus  (doubtful);  (d]  the  cingulum;  and 
(e),the  fasciculus  rectus. 

1  Previously  described  as  the  periclaustral  lamina  or  capsula  extrema. 
61 


962 


THE  NER  VE  SYSTEM 


(a)  The  UNCINATE  FASCICULUS   (/.  uncinatus)  passes   between  the  uncinate 
gyre  and  the  orbital  portion  of  the  frontal  lobe;  in  its  course  it  curves  beneath  the 
depths  of  the  basisylvian  fissure  (Fig.  632). 

(b)  The  SUPERIOR  LONGITUDINAL  FASCICULUS  (fasciculus  longitudinalis  supe- 
rior}  (Fig.   632). — The  superior  longitudinal  fasciculus  is  beneath  the  convex 
surface  of  the  hemisphere.     It  joins  the  frontal  cortex  with  the  parietal  and  tem- 
poral cortex  and  brings  into  relation  the  motor  speech  centres  and  the  centres  of 
auditory  and  visual  memories. 

(c)  The  INFERIOR  LONGITUDINAL  FASCICULUS  is  usually  described  as  a  tract 
associating  the  centres  of  auditory  and  visual  memory.     Such  association  fibres 
undoubtedly  exist,  but  it  is  doubtful  whether  they  are  collected  into  a  distinct 


FIG.  633. — The  projection  tracts  joining  the  cortex  with  lower  nerve  centres.  Sagittal  section  showing  the 
arrangements  of  tracts  in  the  internal  capsule:  A,  tract  from  the  frontal  lobe  to  the  frontal  half  of  the 
capsule,  thence  in  part  to  the  optic  thalamus,  A2,  and  in  part  to  the  pons,  and  thus  to  the  cerebellar  hemi- 
sphere of  the  opposite  side;  B,  motor  tract  from  the  central  convolutions  to  the  fascial  nucleus  in  the  pons  and 
to  the  spinal  cord;  C,  sensor  tract  from  dorsal  columns  of  the  cord,  through  the  dorsal  or  caudal  part  of  the 
oblongata,  pons,  crus,  and  capsule  to  the  parietal  lobe;  D,  visual  tract  from  the  optic  thalamus  (OT)  to  the 
occipital  lobe;  E,  auditory  tract  from  the  internal  geniculate  body  (to  which  a  tract  passes  from  the  VIII  N. 
nucleus)  to  the  temporal  lobe;  F,  prepeduncle;  G,  jnedi peduncle;  H,  postpeduncle;  CN,  caudate  nucleus; 
CQ,  quadrigemina.  The  numerals  refer  to  the  cranial  nerves.  (Starr.) 


fasciculus.  The  bundle  which  is  usually  designated  by  this  term  has  been  proved 
to  be  in  part  the  projection  system  between  the  occipital  cortex  and  the  thalamus 
and  pregeniculum  (E.  Redlich)  and  in  part  also  the  fibres  from  the  temporal 
cortex  (meditemporal  and  subtemporal  gyre)  to  the  crusta. 

(d)  The  CINGULUM,  also  called  the  fornix  periphericus,  is  a  band  of  white 
fibres  that  course  in  the  white  substance  of  the  callosal  gyre  and  runs  excentrically 
to  the  callosum.     Its  fibres  may  be  traced  frontad  into  the  mesal  olfactory  stria 
and  the  preperforatum,  while  caudad    they  radiate    into  the  hippocampus.     It 
may  be  regarded  as  an  association  tract  of  the  rhinencephalon  akin  to  the  fornix. 

(e)  The    FASCICULUS  RECTUS  or  PERPENDICULAR  FASCICULUS   runs  dorso- 
ventrad  in  the  occipito-parietal   transition  and  associates  the  subparietal  gyres 


THE  CEREBRAL  HEMISPHERES  963 

with  the  medi-  and  subtemporal  gyres;  a  part  of  the  fasciculus  associates  the  dorsal 
occipital  region  with  its  ventral  part  and  with  the  subcollateral  gyre  (Fig.  632). 

The  FORNIX,  previously  described,  may  be  enumerated  among  the  long  associa- 
tion tracts;  it  belongs  exclusively  to  the  olfactory  apparatus. 

'2.  The  Commissural  Fibres  are  grouped  under  the  following  heads:  (a)  the 
callosum,  described  on  p.  939;  (6)  the  precommissure,  described  on  p.  952;  and  (c) 
the  fornicommissure,  described  on  p.  951. 

3.  The  Projection  Fibres  connect  the  cerebral  cortex  with  lower  brain  centres 
(caudatum  and  lenticula,  thalamus,  hypothalamic  region,  quadrigemina,  pons, 
oblongata),  and  with  the  spinal  cord  centres.  They  either  project  impulses  from 
the  cortex  to  the  periphery  or  bring  in  impressions  from  without.  Their  radiations 
to  and  from  the  cortex,  together  with  the  radiations  of  the  ca"llosal  fibres,  give 
rise  to  the  characteristic  appearance  of  the  corona  radiata.  We  may  distinguish 
the  projection  tracts  of  long  course  from  those  of  short  course  and,  in  the  func- 
tional sense,  those  that  are  centrifugal,  descending  or  motor,  from  those  that  are 
centripetal,  ascending,  or  sensor.  The  latter  mode  of  classification  is  more 
desirable. 

1.  DESCENDING  (corticifugal)  TRACTS  are  composed  of  axones  arising  from 
the  cortical  pyramidal  cells. 

(a)  The  pyramidal  or  motor  tract  from  the  "motor  area,"  comprising  the  pre- 
central  gyre  and  paracentral  gyre,  courses  through  the  genu  and  frontal  two-thirds  of 
the  thalamo-lenticular  limb  of  the  internal  capsule,  forms  the  middle  (three-fifths) 
sector  of  the  crusta,  passes  through  the  pons  into  the  postoblongata  and  spinal 
cord.  The  tract  may  be  subdivided  into  a  cortico-bulbar  and  a  cortico-spinal  division. 

The  cortico-bulbar  division  is  the  pyramidal  tract  to  the  efferent  cranial-nerve 
nuclei.  Only  those  fibres  which  are  destined  to  go  to  the  facial  and  hypoglossal 
can  be  traced  throughout.  They  originate  in  the  ventral  part  of  the  precentral 
gyre  (face  and  tongue  centre),  course  through  the  genu  of  the  internal  capsule  and 
end,  contralaterally,  in  relation  with  the  facial  and  hypoglossal-nerve  nuclei  (also 
called  the  emissary  speech  tract). 

The  cortico-spinal  division  arises  from  the  remainder  of  the  motor  area,  courses 
through  the  frontal  two-thirds  of  the  internal  capsule,  through  crusta,  pons,  and 
postoblongata,  to  form  the  pyramids,  and  undergoing  partial  decussation,  forms 
the  direct  and  the  crossed  pyramidal  tracts  described  in  the  spinal  cord. 

(6)  The  fronto-pontile  tract  (Arnold's  bundle)  arises  in  the  midfrontal  cortex, 
courses  through  the  internal  capsule  (caudal  part  of  frontal  limb),  forms  the  mesal 
sector  (one-fifth)  of  the  crusta,  and  ends  in  the  nuclei  pontis. 

(c)  The  temporo-pontile  tract  (Tiirck's  bundle)  arises  in  the  cortex  of  the  tem- 
poral lobe,  descends  through  the  internal  capsule  (caudal  segment),  forms  the  ectal 
(one-fifth)  sector  of  the  crusta,  and  ends  in  the  nuclei  pontis.     The  existence  of 
occipito-pontile  fibres  is  denied  by  Archambault  in  a  recent  contribution  (1906). 

(d)  The   occipito-mesencephalic   tract   arises   in   the   visual   area    (cuneus   and 
calcarine   formation),  courses  through    the  retrolenticular  part  of   the  internal 
capsule,  to  end  in  the  pregeminum  and  in  relation  with  the  nuclei  for  movements 
of  the  eyeball. 

(e)  Part  of  the  fibres  composing  the  optic  radiation  are  corticipetal,  arising  in 
the  occipital  cortex  and  ending  in  the  pulvinar  of  the  thalamus  and  the  pregenic- 
ulum. 

2.  ASCENDING  (corticipetal)  TRACTS  arise  mostly  from  the  nuclei  of  the  thalamus 
and  hypothalamus,  mid-brain,  and  cerebellum. 

(a)  The  terminal  or  cerebral  part  of  the  general  sensor  pathway  of  the  body 
comprises  the  axones  arising  in  the  cells  of  the  lateral  nucleus  of  the  thalamus 
and  the  hypothalamic  nucleus — interposed  way-stations  which  transfer  the  im- 
pressions carried  along  the  medial  lemniscus  from  the  nuclei  of  the  gracile  and 


964 


THE  NERVE  SYSTEM 


cuneate  fasciculi  in  the  myeloblongata  transition.  They  convey  sensor  impres- 
sions from  the  body  periphery  to  the  somsesthetic  area  of  the  cortex — chiefly  the 
postcentral  and  parietal  gyres. 

(6)  The  terminal  or  cerebral  part  of  the  general  sensor  pathway  of  the  head  and 
neck  comprises  the  axones  which  arise  from  the  afferent  cranial-nerve  nuclei 
(excepting  the  auditory)  and  course  along  the  medial  lemniscus  to  the  thalamus  and 
hypothalamic  nucleus,  to  be  thence  projected  to  the  somsesthetic  cerebral  cortex. 

(c)  The  terminal  or  cerebral  part  of  the  auditory  pathway  from  the  postgeminum, 
postgeniculum,  and  the  interposed  nucleus  of  the  lateral  lemniscus,  ending  in  the 
auditory  sphere  of  the  cerebral  cortex. 

(d)  The  terminal  part  of  the  visual  pathway,  described  on  pages  919. 

(e)  The  terminal  (ascending]  cerebello-cortical  pathway,  arising  as  the  fibres  of 
the  cerebellar  prepeduncles,  decussating  and  ending  in  the  rubrum  (red  nucleus) 
and  lateral  nucleus  of  thalamus,  is  thence  directly  projected  by  new  axones  to  the 
sonuesthetic  cortical  area,  or  indirectly  projected  via  thalamus  (lateral  nucleus). 

Connections  of  the  Striatum. — The  connections  of  the  caudatum  and  lenticula 
with  each  other  and  with  the  cortex  may  be  summarized  as  follows : 

(a)  Fibres  from  the  cortex  to  caudatum  and  lenticula,  entering  into  the  forma- 
tion of  the  corona  radiata. 


CENTRIFUGAL  FIBRE 
TERMINATING  IN   BULB 


OLFACTORY 

GLOMEHULI 


OLFACTORY 
MUCOSA 


FIG.  634. — Schema  of  the  olfactory  bulb  and  tract  neurones. 

(6)  Fibres  from  the  caudatum  and  putamen  of  lenticula  coursing  to  the  thalamus 
and  hypothalamic  region.  Those  from  the  caudatum  pass  through  the  internal 
capsule  to  traverse  the  pallidum,  are  joined  by  the  fibres  from  the  putamen  to 
again  traverse  the  internal  capsule  and  end  in  the  thalamus,  forming  the  striato- 
thalamic  radiation. 

(c)  Fibres  coursing  ventrad  in  the  medullary  laminse  of  the  lenticula,  and  re- 
enforced  by  additional  fibres  from  the  pallidum,  course  mesad  to  the  hypothalamic 
region  to  form  the  subthalamic  radiation  or  ansa  lenticularis  (described  on  p.  957). 
This  radiation  is  further  reenforced  by  the  ventral  stalk  of  the  thalamo-cortical 
radiation  to  form  the  ansa  peduncularis  (described  on  p.  957). 

The  Olfactory  Pathways.  1.  Peripheral  Pathway. — Impressions  from  the 
upper  portion  of  the  Schneiderian  mucous  membrane  pass  along  the  olfactory  fila 
(central  processes  of  the  intra-epithelial  bipolar  olfactory  cells)  to  the  glomeruli 
olfactorii  in  the  olfactory  bulb  (Fig.  634). 

2.  Central  Pathway. — In  the  glomeruli  the  impression  is  transmitted  to  the 
brush-like,  dendritic  endings  of  the  mitral  cells  and  brush-cells;  the  axones  of 
these  cells  carry  the  impression  centrad  to  the  gray  masses  of  the  olfactory  tract, 
trigonum  olfactorium,  preperforatum,  and  adjacent  parts  (Fig.  630).  These 
constitute  the  primary  centres. 


THE  CEREBRAL  HEMISPHERES  965 

The  primary  centres  are  connected  with  secondary  or  cortical  centres  (hippo- 
campus, gyrus  dentatus,  uncus)  by  the  following  tracts : 

1.  Lateral  olfactory  striae,  from  the  olfactory  trigone  to  the  uncus,  ending  in 
the  gyrus  ambiens  and  gyrus  semilunaris  (p.  935). 

2.  Axones  from  cells  in  the  olfactory  trigonal  gray  through  the  fornix  to  hippo- 
campus. 

3.  Striae  medialis  (Lancisii)  from  the  trigone  into  gyrus  subcallosus  around  the 
callosum  to  gyrus  dentatus  and  hippocampus. 

The  amygdala  is  by  some  regarded  a  cortical  centre  to  which  impressions  are 
carried  by  the  taenia  semicircularis. 

The  fornix  fibres  arise  from  the  pyramidal  cells  in  the  hippocampus  and  the 
polymorphous  cells  of  the  dentate  gyre.  Some  fibres  traverse  the  median  plane 
as  the  fornicommissure  to  the  opposite  hippocampus;  the  remainder  end  in  the 
albicans  gray  nucleus  or,  in  small  part,  are  retroflexed  as  the  stria  medullaris 
thalami  to  the  habenal  ganglion. 

In  the  albicans  impressions  are  transmitted  to  the  cells  of  two  nuclear  masses; 
from  the  medial  nucleus  arise  axones  constituting  the  fasciculus  albicantis  princeps, 
each  axone  bifurcating  and  the  diverging  bundles  forming,  respectively,  the 
albicantiothalamic  and  the  albicantiotegmental  fasciculi  (p.  916). 

The  stria  medullaris  thalami  consists  of  the  following  bundles  ending  in  the 
habenal  ganglion: 

(a)  Axones  from  hippocampus  via  fornix — the  cortico-habenal  tract ;  (6)  axones 
from  the  hemiseptum  and  olfactory  gray — the  olfacto-habenal  tract;  (c)  axones 
from  the  thalamus  to  the  habenal  ganglion — the  thalamo-habenal  tract. 

In  the  habenal  ganglion  axones  arise  which  pass  as  a  distinct  bundle  ventrad 
through  the  tegmentum  to  the  gray  of  the  postperforatum  (ganglion  interpedun- 
culare  [intercrurale]  of  Gudden) — the  fasciculus  retroflexus  of  Meynert. 

The  primary  olfactory  centres  of  the  two  sides  are  connected  by  the  pars 
olfactoria  of  the  precommissure ,  a  bundle  of  fibres  passing  from  side  to  side  to 
end  in  the  tract,  granular  stratum,  and  glomerular  layer  of  the  bulb. 

Further  connections  are  established  with  the  tuber,  mid-brain,  and  even  spinal 
centres;  one  division  has-been  named  the  olfacto-mesencephalic tract  (Wallenberg). 

The  cingulum  or  fornix  periphericus  is  an  arcuate  association  bundle,  or 
rather  an  arcuate  series  of  short  bundles  which  establishes  the  connections  of  the 
rhinencephalon  with  the  adjacent  cortical  areas.  (See  p.  962.) 

Weight  of  the  Brain. — The  average  jveight  of  the  brain  in  the  adult  male  is  1400 
grams;  that  of  the  female  1250  grams.  Among  1500  brains  of  males  the  brain- 
weights  ranged  from  960  grams  to  over  1900  grams;  the  great  majority  of  this 
series  ranged  from  1250  grams  to  1500  grams.  The  average  weight  in  the  new- 
born is  400  grams  in  the  male  and  380  grams  in  the  female.  The  weight  is  doubled 
at  the  end  of  the  first  and  trebled  at  the  end  of  the  fourth  or  fifth  year,  the  female 
brain  growing  less  rapidly  than  the  male  brain.  Brain-growth  generally  ceases 
in  the  eighteenth  or  twentieth  year,  earlier  in  the  female  than  the  male.  After  the 
sixtieth  year  the  brain  loses  weight,  at  first  slowly,  but  more  rapidly  in  advanced 
senescence.  Other  factors,  besides  age  and  sex,  which  influence  brain-weight  are 
stature,  body-weight,  cranial  form,  and  race.  Persons  of  large  stature  average 
heavier  brains  than  those  of  short  stature  in  absolute  figures,  but  not  relatively. 
Brachycephalic  persons  average  heavier  brains  than  the  dolichocephalic.  A 
most  profound  influence  upon  brain-weight  appears  to  be  exerted  by  racial  differ- 
ences. Representatives  of  the  white  race  have  heavier  brains  than  those  of  the 
other  races,  although  data  are  not  sufficient  to  make  a  positive  statement.  Thus 
the  few  Eskimo  brains  that  have  been  secured  so  far  are  notable  for  their  size 
and  weight.  The  following  table  gives  approximately  accurate  averages  based 
upon  greater  or  lesser  numbers  of  brain-weights: 


966 


THE  NER  VE  SYSTEM 


Males. 

Females. 

White  race   • 

Japanese 
Chinese    . 

Germans      
Bohemians  . 

1425 
1420 
1420 
1415 
1395 
1380 
1375 
1360 

1365 
1360 
1390-1200 
1330 
1250 
1185 

1260 
1290 
1260 
1260 
1260 
1255 
1240 
1250 

1215 

Scots       

Swedes              ,      
Russians      

English  

Italians  

French  

Negroes,  vari 
Hawaiians 
Papuans  . 

ous  races  

Australians 

The  intellectual  status  is  in  some  way  reflected  in  the  mass  and  weight  of  the 
brain.  The  average  brain-weight  of  100  men  eminent  in  the  professions,  arts,  and 
sciences,  with  an  average  age  of  62  years,  was  1470  grams,  exceeding  the  average 
weight  of  the  ordinary  population  of  about  the  same  age  by  more  than  100  grams. 
A  further  analysis  shows  that  the  brains  of  men  devoted  to  the  higher  intellectual 
occupations,  such  as  the  mathematical  sciences,  involving  the  most  complex 
mechanisms  of  the  mind,  those  of  men  who  have  devised  original  lines  of  research 
and  those  of  forceful  character  are  among  the  heaviest  of  all. 

The  brains  of  microcephalic  idiots  are  far  under  the  minimal  size  necessary  for 
mental  integrity,  which  is  about  1000  grams  in  the  male  and  900  grams  in  the 
female.  Certain  idiotic  individuals  possess  brains  of  normal  size  or  even  abnormally 
large  brains,  but  structural  defects  underlie  these  forms  of  idiocy 

The  whale,  porpoise,  dolphin,  and  elephant  possess  larger  brains  than  man, 
but  relative  to  the  size  and  weight  of  the  body  the  human  brain  is  proportionately 
larger. 

CORTICAL  LOCALIZATION  OF  FUNCTION. 

Patient  researches  conducted  along  clinico-pathologic,  experimental,  physiologic,  and  de- 
velopmental lines  have  furnished  us  with  a  topographic  map  of  the  somsesthetic  and  sense 
areas  and,  inferentially,  of  the  association  areas  of  the  cerebral  cortex.  The  somsesthetic  and 
sense  areas  constitute  less  than  one-third  of  the  cortical  area,  while  the  remainder  is  presumed 
to  be  devoted  to  the  elaboration  of  the  higher  mental  activities  manifested  by  abstract  thought, 
ideation,  reasoning,  and  language.  The  acquisition  of  these  specifically  human  mental  attri- 
butes has  been  the  chief  factor  in  bringing  about  the  superior  structure  of  the  human  brain,  and 
those  cortical  regions  which  were  subjected  to  increased  associations  rose  in  functional  dignity 
and  increased  in  size.  With  over  nine  billion  functional  nerve-cells  in  the  human  cerebral 
cortex  devoted  to  the  mental  processes  and  less  than  one-third  of  these  concerned  with  emissary 
and  receptive  functions,  the  intricacy  and  capacity  of  the  human  brain  for  the  manifold  registra- 
tion of  sensations  and  the  numerous  transformations  that  characterize  man's  mental  process 
far  exceed  that  of  any  other  animal. 

The  delineation  of  areas  called  motor,  visual,  auditory,  etc.,  is  not  to  be  deemed  as  mathe- 
matically accurate  or  sharply  defined  as  the  boundaries  of  a  State,  county,  or  township.  The  areas 
rather  shade  off  in  a  diffuse  manner  and  the  arbitrary  demarcations  employed  in  the  appended 
figures  merely  show  the  maximum  concentration  of  those  cortical  parts  which  most  distinctly 
appertain  to  the  function  alleged  for  them. 

The  principal  areas  that  are  known  to  be  functionally  differentiated  are  the  following: 

1 .  Motor  Area. — The  motor  area  comprises  the  precentral  gyre  and  parts  of  the  frontal  gyres 
adjacent  thereto,  together  with  the  paracentral  gyre  and  the  adjacent  portion  of  the  superfrontal 
gyre  on  its  mesal  face.  Stimulation  of  various  parts  of  this  area  causes  movement,  while  their 
destruction  impairs  or  abolishes  voluntary  movements.  Within  this  motor  area  may  be  defined 
districts  which  are  cortical  projections  of  the  muscular  systems  of  the  body.  Thus,  movements 
of  the  lower  limb  seem  to  be  controlled  by  the  dorsal  part  of  the  precentral  and  the  paracentral 


967 

gvro:  the  trunk  musculature  by  the  area  lying  frontad  both  on  the  mesal  aspect  and  in  the  dorsal 
sujHTtVoiital;  the  upper  limb  seems  to  be  controlled  by  the  mid-portion  of  the  precentral;  while 
the  facial  musculature  is  projected  in  the  ventral  part.  The  motor  regions  for  the  tongue, 


FIG.  635. — Mesal  view  of  left  hemi cerebrum,  showing  localization  of  functions.     The  schema 
of  the  fissures  and  gyres  is  the  same  as  in  Fig.  601. 

larynx,  muscles  of  mastication,  and  pharynx  lie  in  the  frontal  opercular  part;  and  the  movement 
of  the  head  and  eye  are  dominated  by  the  medifrontal  gyre,  adjacent  to  the  precentral.  Re- 
calling the  fact  that  the  pyramidal  (motor)  tract  decussates  in  its  course  to  the  primary  motor 


FIG.  636. — Lateral  view  of  left  hemicerebrum,  showing  localization  of  functions.     The  schema 
of  the  fissures  and  gyres  is  the  same  as  in  Fig.  600. 

centres,  it  follows  that  the  motor  centres  in  one  hemicerebrum  control  the  movements  of  the 
opposite  side  of  the  body.  As  elsewhere  in  the  cortex,  these  motor  areas  gradually  pass  one  into 
the  other  and  the  boundaries  are  indeterminate.  The  localization  of  motor  function  is  rather 


968 


THE  NER  VE  SYSTEM 


for  coordinated  groups  of  muscles  than  for  individual  muscles;  as  a  rule  the  most  powerful 
articulation,  as  the  thigh  and  the  shoulder,  is  localizable  frontad  in  the  respective  limb  centres, 
while  the  smaller  articulations  and  those  more  differentiated  as  regards  motility  (digits,  etc.) 
are  localizable  more  posteriorly. 

2.  Sensor  Areas. — (a)  The  area  for  tactile  and  temperature  impressions  is  more 
intensely  localized  in  the  postcentral  gyre  and  in  corresponding  order  with  its  neighboring  pre- 
central  motor  areas;  that  is  to  say,  there  is  the  most  intimate  intercommunication  between  the 
sensor  and  the  motor  regions  which  preside  over  corresponding  parts  of  the  body.  So  closely 
coupled  are  the  related  sensor  and  motor  cells  in  the  highest  category  of  the  reflex  arc  system 
represented  in  the  cerebral  cortex  that  both  sensor  and  motor  areas  are  included  under  the 
term  of  somaesthetic  or  senso-motor  area,  devoted  to  the  registration  of  cutaneous  impressions, 
impressions  from  the  muscles,  tendons,  and  joints;  in  short,  the  sense  of  movement.  The  cortical 
area  embraced  by  the  parietal  gyre,  together  with  its  extension  in  the  precuneus  on  the  mesal 
aspect,  appears  to  be  devoted  to  the  concrete  perception  of  the  form  and  solidity  of  objects  and 
is  therefore  termed  the  stereognostic  sense  area. 

(6)  The  auditory  area  is  localized  in  the  middle  third  of  the  supertemporal  gyre  and  in  the 
adjacent  transtemporal  gyres  in  the  sylvian  cleft. 


FIG.  637. — Diagram  showing  the  language  zone.     The  opercula  are  divaricated  to  expose  the  insula. 

(c)  The  visual  area  is  most  intensely  localizable  in  the  region  of  the  calcarine  fissure  as  well 
as  in  the  cuneus  as  a  whole.     There  seems  to  be  an  interrelation  between  the  visual  function  and 
the  special  type  of  cortex  already  described,  and  chiefly  characterized  by  the  stripe  of  Gennari. 

(d)  The  olfactory  area  comprises  the  uncus,  frontal  part  of  hippocampus,  indusium,  sub- 
callosal  gyre,  parolfactory  area,  and  preperforatum. 

(e)  The  gustatory  area  has  not  yet  been  accurately  localized;  presumably  it  lies  in  the  neigh- 
borhood of  the  olfactory  area  in  the  temporal  lobe  (uncinate  and  hippocampal  gyre?). 

3.  The  Language  Areas. — The  cortical  zone  of  language  comprises  certain  specialized  areas 
which  take  part  in  the  intimate  relations  of  speech  to  thought-expression,  to  memory,  in  its 
reading  form  to  sight,  in  writing  to  manual  muscular  innervation,  and  in  "word-understanding" 
to  hearing. 

(a)  The  emissive  (articular]  centre  for  speech  is  localized  in  the  region  of  the  junction  of  the 
subfrontal  gyre  with  the  precentral  gyre — a  region  known  to  be  intimately  related  to  the  control 
of  the  muscles  used  in  speech  (larynx,  tongue,  jaw  muscles).  Destruction  of  this  region  at  least 
causes  a  loss  or  disturbance  of  articulation  of  words. 

(6)  The  auditory  receptive  centre,  clinically  known  as  the  centre  of  "word-deafness,"  is 
localized  in  the  marginal  gyre  and  adjacent  part  of  supertemporal  gyre.  A  patient  suffering  with 
a  lesion  of  this  area  may  clearly  hear  but  not  understand  the  spoken  word.  The  centre  might 
also  be  called  the  lalognostic  (word-understanding)  centre. 

(c)  The  visual  receptive  centre,  clinically  known  as  the  centre  of  "word-blindness,"  is 


CORTICAL  LOCALIZATION  OF  FUNCTION 


969 


localized  in  rlu-  angular  gyre.-  Lesions  of  this  area  renders  the  patient  incapable  of  understand- 
ing the  significance  of  the  words  and  objects  which  he  sees. 

(d)  An  emissive  "writing"  centre,  not  positively  proven  to  exist,  has  been  localized  in  the 
medifrontal  gyre,  frontad  of  the  motor  area  for  the  upper  limb. 

(e)  Of  not  a  little  importance  with  reference  to  the  intellectual  control  of  the  faculty  of  language 
is  the  insula,  purely  an  association  centre,  serving  to  connect  the  various  receptive  sense-areas 
relating  to  the  understanding  of  the  written  and  spoken  word  with  the  somgesthetic  emissary 
centres  related  to  articulate  speech  and  writing. 

The  union  of  the  various  centres  enumerated  above  forms  the  cortical  zone  of  language 
and  is  most  intensely,  if  not  exclusively,  localized  in  the  left  hemicerebrum  in  right-handed 
persons,  and  vice  versa  in  left-handed  persons. 


FIG.  638. — Drawing  to  illustrate  cranio-cerebral  topography.    (Taken  from  a  cast  in  the  Museum  of  the  Royal 
College  of  Surgeons  of  England,  prepared  by  Professor  Cunningham.) 


4.  The  Association  Areas. — The  remaining  area  of  the  cerebral  cortex  is  presumably  the 
organic  substratum  for  the  higher  psychic  activities.  At  the  present  time  not  much  is  known  about 
them,  but  broadly  stated  the  frontal  association  area  is  concerned  rather  with  the  powers  of 
thought  in  the  abstract;  creative,  constructive,  and  philosophic.  The  parieto-occipito-temporal 
association  area,  on  the  other  hand,  seems  to  be  concerned  more  with  the  powers  of  conception 
of  the  concrete,  for  the  comprehension  of  analogies,  comparing,  generalizing,  and  systematizing 
things  heard,  observed,  and  felt. 

The  great  extent  of  the  association  areas  in  the  human  brain  is  a  somatic  expression  of  man's 
possession  of  an  associative  memory  or  ability  to  register  and  compare  sensations  far  greater  than 
that  of  the  highest  ape.  The  pattern  of  the  fissures  and  gyres  in  the  brains  of  the  higher  anthro- 
poids and  man  present  the  same  general  features  in  all  these  types.  In  the  course  of  evolution, 
however,  the  regions  known  as  association  areas  assumed  a  greater  energy  of  growth  and  ex- 
panded in  proportion  to  the  rise  in  functional  dignity  of  these  areas.  They  are  regions  of  "un- 
stable equilibrium"  which  afford  greater  and  more  complex  associations  as  mental  development 


970 


THE  NER  VE  SYSTEM 


goes  on  in  the  species,  and  concomitant  with  this  great  cortical  •  expansion  the  associating  or 
coordinating  fibre  systems  became  more  elaborate,  complex,  and  far-reaching. 

With  the  aid  of  the  microscope  the  maturing  of  the  brain-elements  can  be  followed  from  the 
earliest  stages  of  embryonic  life  to  the  adult  period.  The  Flechsig  method  has  shown  how  the 
function  of  nerve-fibres  within  the  brain  is  only  established  when  the  myelin-sheath  has  developed. 
But  this  development  of  mature  nerve-fibres  does  not  occur  simultaneously  throughout  the  brain] 
but  step  by  step  in  a  definite  order  of  succession:  equally  important  bundles  are  myelinated' 
simultaneously,  but  those  of  dissimilar  importance  develop  one  after  another  in  accordance 
with  Flechsig's  law.  The  successive  myelinization  of  fibre-bundles  to  and  from  the  cerebral 
cortex  corresponds  to  the  successive  awakenings  of  mental  activities  and  faculties  in  the  growing 
child.  Flechsig's  method  of  investigation  has  been  of  great  service  in  the  elucidation  of  the 
problems  of  cerebral  localization. 

Cranio-cerebral  Topography.— The  position  of  the  principal  fissures  and  convolution  of  the 
cerebrum  and  their  relation  to  the  outer  surface  of  the  scalp  (Fig.  638)  have  been  the  subject  of 
much  investigation,  and  many  systems  have  been  devised  by  which  one  may  localize  these  parts 
from  an  explanation  of  the  external  surface  of  the  head. 


FIG.  639. — Relations  of  the  principal  fissures  and  convolutions  of  the  cerebrum  to  the  outer  surface  of 

the  scalp.     (Reid.) 

These  plans  can  only  be  regarded  as  approximately  correct  for  several  reasons;  in  the  first 
place,  because  the  relations  of  the  convolutions  and  fissures  to  the  surface  are  found  to  be  quite 
variable  in  different  individuals;  secondly,  because  the  surface  area  of  the  scalp  is  greater  than 
the  surface  area  of  the  brain,  so  that  lines  drawn  on  the  one  cannot  correspond  exactly  to  fissures 
or  convolutions  on  the  other;  thirdly,  because  the  fissures  and  convolutions  in  two  individuals 
are  never  precisely  alike.  Nevertheless,  the  principal  fissures  and  convolutions  can  be  mapped 
out  with  sufficient  accuracy  for  all  practical  purposes,  so  that  any  particular  convolution  can  be 
generally  exposed  by  removing  with  the  trephine  a  certain  portion  of  the  skull's  area.  An 
excellent  method  is  given  by  Chipault  in  his  Chirurgie  operatoire  du  syst^me  nerveux,  1894,  vol.  i. 
The  following  systems  have  been  the  longest  in  vogue. 

The  various  landmarks  on  the  outside  of  the  skull,  which  can  be  easily  felt,  and  which  serve 
as  indications  of  the  position  of  the  parts  beneath,  have  been  already  referred  to,  and  the  rela- 
tion of  the  fissures  and  convolutions  to  these  landmarks  is  as  follows : 

Intercerebral  or  Longitudinal  Fissure  (Fig.  639). — This  corresponds  to  a  line  drawn  from 
the  glabella  at  the  root  of  the  nose  to  the  external  occipital  protuberance. 

The  Sylvian  Fissure  (Fig.  639). — The  position  of  the  sylvian  fissure  is  marked  by  a  line  starting 
from  a  point  3  cm.  horizontally  behind  the  external  angular  process  of  the  frontal  bone  to  a  point 
2  cm.  below  the  most  prominent  point  of  the  parietal  eminence.  The  first  2  cm.  will  represent  the 
basisylvian  fissure,  the  remainder  the  sylvian  fissure  proper.  The  sylvian  point  is  therefore 


971 

5  cm.  behind  and  about  1  cm.  above  the  level  of  the  external  angular  process.  The  presylvian 
nunus  of  the  fissure  passes  upward  from  this  point  parallel  to,  and  immediately  behind,  the 
coronal  suture. 

The  Tentorial  Hiatus  or  Transverse  Fissure.— This  is  between  the  cerebrum  and  cerebellum 
and  corresponds  to  a  line  drawn  from  the  inion  to  the  external  auditory  meatus  (the  line  B  C  in 
Fig.  639). 

Central  Fissure. — To  find  the  dorsal  end  of  the  central  fissure,  a  measurement  should  be  taken 
from  the  glabella  to  the  external  occipital  protuberance.  The  position  of  the  top  of  the  fissure 
will  be,  measuring  from  in  front,  55.6  per  cent,  of  the  whole  distance  from  the  glabella  to  the 
external  occipital  protuberance.  Professor  Thane  adopts  a  somewhat  simpler  method.  He 
divides  the  distance  from  the  glabella  to  the  external  occipital  protuberance  over  the  top  of  the 


Supra  orbital  line            /** 
(Superior  Horizontal}  K/^a 

B 

S 
K' 

Orbital-auricular  line 
(Baseline) 

z 

FIG.  640. — Kronlein's  method  for  determining  the  portions  of  certain  fissures  of  the  brain. 

head  into  two  equal  parts,  and,  having  thus  defined  the  middle  point  of  the  vertex,  he  takes  a  point 
half  an  inch  behind  it  as  the  top  of  the  sulcus.  This  is  not  quite  so  accurate  as  the  former  method ; 
but  it  is  sufficiently  so  for  all  practical  purposes,  and  on  account  of  its  simplicity  is  very  generally 
adopted.  From  this  point  the  fissure  runs  downward  and  forward  for  9  to  10  cm.,  its  axis  making 
an  angle  of  67  degrees  with  the  middle  line.  Cunningham  states  that  this  angle  more  nearly  averages 
71 .5  degrees.  In  order  to  mark  this  groove,  two  strips  of  metal  may  be  employed — one,  the  shorter, 
being  fixed  to  the  middle  of  the  other  at  the  angle  mentioned.  If  the  longer  strip  is  now  placed 
along  the  sagittal  suture  so  that  the  junction  of  the  two  strips  is  over  the  point  corresponding  to 
the  top  of  the  furrow,  the  shorter,  oblique  strip  will  indicate  the  direction  and  9  to  10  cm.  will 
mark  the  length  of  the  furrow.  Dr.  Wilson  has  devised  an  instrument,  called  a  cyrtometer, 
which  combines  the  scale  of  measurements  for  localizing  the  fissure  with  data  for  representing 


972  THE  NERVE  SYSTEM 

its  length  and  direction.1  Professor  Thane  gives  the  lower  end  of  the  furrow  as  close  to  the 
sylvian  fissure,  and  about  1.5  cm.  behind  the  sylvian  point.  So  that,  according  to  this  anatomist, 
a  line  drawn  from  a  point  1.5  cm.  behind  the  mid-point  between  the  glabella  and  external  occipital 
protuberance  to  this  spot  would  mark  out  the  central  fissure.  Dr.  Reid  adopts  a  different  method 
(Fig.  639).  He  first  indicates  on  the  surface  the  longitudinal  fissure  and  the  sylvian  fissure 
(as  above).  He  then  draws  two  perpendicular  lines  from  his  "base-line"  (that  is,  a  line  from 
the  lowest  part  of  the  infraorbital  margin  through  the  middle  of  the  external  auditory  meatus 
to  the  back  of  the  head)  to  the  top  of  the  cranium,  one  (D  E,  Fig.  639)  from  the  depression  in 
front  of  the  external  auditory  meatus,  and  the  other  (F  G,  Fig.  639)  from  the  posterior  border 
of  the  mastoid  process  at  its  root.  He  has  thus  described  on  the  surface  of  the  head  a  four-sided 
figure  (F  D  GE,  Fig.  639),  and  a  diagonal  line  from  the  posterior  superior  angle  to  the  anterior 
perpendicular  line  where  it  is  crossed  by  the  sylvian  fissure  will  represent  the  furrow. 

The  Occipital  Fissure  on  the  dorsal  surface  of  the  cerebrum  runs  outward  at  right  angles  to  the 
great  longitudinal  fissure  for  about  2  to  3  cm.,  from  a  point  0.5  cm.  in  front  of  the  lambda  (poste- 
rior fontanelle).  Reid  states  that  if  the  sylvian  fissure  be  continued  onward  to  the  sagittal 
suture,  the  last  2  to  3  cm.  of  this  line  will  indicate  the  position  of  the  fissure  (Fig.  639). 

The  Precentral  SulcilS  begins  2  cm.  in  front  of  the  middle  of  the  central  fissure  and  extends 
nearly,  but  not  quite,  to  the  sylvian  fissure. 

The  Superfrontal  Fissure  runs  backward  from  the  supraorbital  notch,  parallel  with  the  line 
of  the  longitudinal  fissure  to  1  cm.  in  front  of  the  line  indicating  the  position  of  the  central  fissure. 

The  Subfrontal  Fissure  follows  the  course  of  the  supertemporal  ridge  on  the  frontal  bone. 

The  Intraparietal  Fissure,  comprising  the  parietal,  subcentral  and  paroccipital  fissures,  begins 
on  a  level  with  the  junction  of  the  middle  and  lower  third  of  the  central  fissure,  on  a  line  carried 
across  the  head  from  the  back  of  the  root  of  one  auricle  to  that  of  the  other.  After  passing  upward 
it  curves  backward,  lying  parallel  to  the  longitudinal  fissure,  midway  between  it  and  the  parietal 
eminence;  then  curves  downward  to  end  midway  between  the  posterior  fontanelle  and  the 
parietal  eminence. 

Kronlein's  method  for  determining  the  portions  of  certain  fissures  of  the  brain  is  very  useful 
and  easy  of  application  (Fig.  640).  It  is  as  follows:  (1)  The  base  line,  Z  M ,  is  a  horizontal 
line  running  at  the  level  of  the  lower  border  of  the  orbit  and  the  upper  border  of  the  external 
auditory  meatus.  (2)  Another  horizontal  line,  K  K',  is  drawn  parallel  to  Z  M.  The  second 
horizontal  line  is  on  a  level  with  the  supraorbital  ridge.  (3)  A  vertical  line,  Z  K,  is  erected 
from  Z  M  at  the  middle  of  the  zygoma  and  is  carried  to  the  line,  K  Kf.  (4)  Another  vertical  line, 
A  R,  is  erected  from  the  base-line  at  the  level  of  the  articulation  of  the  mandible  and  is  carried 
to  R.  (5)  A  third  vertical  line,  M  P,  is  erected  from  the  base-line  at  the  posterior  border  of  the 
mastoid  process  and  is  carried  to  the  middle  line  of  the  skull,  which  is  marked  P.  (6)  A  line  is 
drawn  from  K  to  P.  The  portion  of  this  line  between  R  and  P'  corresponds  to  the  central 
fissure.  (7)  The  angle  P  K  K'  is  bisected  by  the  line  K  S.  K  S  corresponds  to  the  sylvian 
fissure,  and  K  is  directly  over  the  sylvian  point.  To  reach  the  anterior  branch  of  the  middle 
meningeal,  apply  the  trephine  at  K ;  to  reach  the  posterior  branch,  apply  it  at  K'.  In  abscess 
of  the  temporal  lobe  the  trephine  should  be  applied,  according  to  von  Bergmann,  in  the  region 
Aa  K  M. 


THE  MENINGES  OR  MENINGEAL  MEMBRANES  OF  THE  BRAIN 
(MENINGES  ENCEPHALI). 

Dissection. — To  examine  the  brain  with  its  membranes,  the  skull-cap  must  be  removed. 
In  order  to  effect  this,  saw  through  the  external  table,  the  section  commencing,  in  front,  about 
2  cm.  (1  in.)  above  the  margin  of  the  orbit,  and  extending,  behind,  to  a  little  above  the  level  with 
the  occipital  protuberance.  Then  break  the  internal  table  with  the  chisel  and  hammer,  to  a  void 
injuring  the  investing  membranes  or  brain;  loosen  and  forcibly  detach  the  skull-cap,  and  dura 
will  be  exposed.  The  adhesion  between  the  bone  and  the  dura  is  very  intimate,  and  much  more 
so  in  the  young  subject  than  in  the  adult. 

The  membranes  of  the  brain  are  from  without  inward :  the  dura,  arachnoid,  and 
the  pia. 

The  Dura  of  the  Brain  (Dura  Mater  Encephali)  (Figs.  641,  642,  643,  644). 

The  dura  of  the  brain  is  a  thick  and  dense,  inelastic,  fibrous  membrane  which 
lines  the  interior  of  the  skull.  It  is  a  covering  for  the  brain  and  is  also  the  internal 

1  Lancet,  1888,  vol.  i,  p    408. 


THE  DURA   OF  THE  BRAIN  973 

periosteum.  Its  outer  surface  is  rough  and  fibrillated,  and  adheres  closely  to  the 
inner  surface  of  the  bones  by  fibrous  processes  and  blood-vessels.  The  adhesion  is 
most  marked  on  bony  projections,  opposite  the  sutures,  and  at  the  base  of  the  skull. 
Except  at  the  sutures  the  adhesions  are  not  dense,  and  between  the  fibrous  pro- 
cesses which  pass  to  the  bone  are  spaces  which  are  thought  to  be  lymph-spaces,  and 
are  called  epidural  spaces.  At  these  points  the  outer  surface  of  the  dura  is  covered 
with  endothelium.  Fibrous  tissue  passes  through  the  open  sutures  and  joins  the 
outer  layer  of  the  dura  to  the  external  periosteum.  It  is  known  as  the  sutural  mem- 
brane. The  inner  surface  of  the  dura  limits  the  subdural  space.  It  is  smooth  and 
lined  by  a  layer  of  endothelium.  The  dura  sends  four  processes  inward,  into  the 
cavity  of  the  skull,  for  the  support  and  protection  of  the  different  parts  of  the  brain, 
and  is  prolonged  to  the  outer  surface  of  the  skull  through  the  various  foramina 
which  exist  at  the  base,  and  thus  becomes  continuous  with  the  pericranium;  its 
fibrous  layer  forms  sheaths  for  the  nerves  which  pass  through  these  apertures.  At 
the  base  of  the  skull  it  sends  a  fibrous  prolongation  into  the  foramen  csecum;  it 
sends  a  series  of  tubular  prolongations  around  the  filaments  of  the  olfactory  nerves 
as  they  pass  through  the  cribriform  plate,  and  also  around  the  nasal  nerve  as  it 
passes  through  the  nasal  slit;  a  prolongation  is  also  continued  through  the  sphe- 
noidal  fissure  into  the  orbit,  and  another  is  continued  into  the  same  cavity  through 
the  optic  foramen,  forming  a  sheath  for  the  optic  nerve,  where  it  is  continued  as  far 
as  the  eyeball.  In  the  posterior  fossa  it  sends  a  process  into  the  internal  auditory 


ENDOSTCAL 
LAYER 
MENINGEAL 
LAYER 

ENDOTHELIAL 
LINING 


FIG.  641. — The  structure  of  the  dura.     Section  through  the  cranial  vault  of  a  child,  slightly  enlarged. 

(Poirier  and  Charpy.) 

meatus,  ensheathing  the  facial  and  auditory  nerves;  another  through  the  jugular 
foramen,  forming  a  sheath  for  the  structures  which  pass  through  this  opening;  and 
a  third  through  the  anterior  condyloid  foramen.  Around  the  margin  of  the  foramen 
magnum  it  is  closely  adherent  to  the  bone,  and  is  continuous  with  the  dura  lining 
the  spinal  canal.  The  cavity  or  cave  of  Meckel  (cavum  Meckeli]  (Fig.  641)  is  an 
osteo-fibrous  recess  near  the  apex  of  the  petrous  portion  of  the  temporal  bone, 
formed  by  folding  of  the  dura  in  a  bony  depression.  It  contains  the  Gasserian 
ganglion.  In  certain  situations,  as  already  mentioned  (p.  736),  the  fibrous  layers 
of-this  membrane  separate  to  form  sinuses  for  the  passage  of  venous  blood.  Upon 
the  outer  surface  of  the  dura,  in  the  situation  of  the  longitudinal  sinus,  may  be  seen 
numerous  small,  whitish  bodies,  the  arachnoid  villi  (p.  979). 

Structure  (Fig.  641). — The  dura  consists  of  white  fibrous  tissue  with  connective- 
tissue  cells  and  elastic  fibres  arranged  in  flattened  laminse,  which  are  imperfectly 
separated  by  lacunar  spaces  and  blood-vessels  into  two  layers,  endosteal  and 
meningeal.  The  endosteal  layer  is  the  internal  periosteum  for  the  cranial  bones  and 
contains  the  bloodvessels  for  their  supply.  At  the  margin  of  the  foramen  magnum 
it  becomes  continuous  with  the  periosteum  lining  the  spinal  canal.  The  meningeal 
or  supporting  layer  is  lined  on  its  inner  surface  by  a  layer  of  nucleated  endothelium, 
similar  to  that  found  on  serous  membranes.  By  its  reduplication  the  meningeal 
layer  forms  the  falx,  the  tentorium  and  falcula,  and  the  diaphragma  sellae.  The  two 
layers  are  connected  by  fibers  which  intersect  each  other  obliquely. 


974 


THE  NER  VE  SYSTEM 


The  Arteries  of  the  Dura  (see  section  on  Arteries). — The  arteries  of  the  dura 
are  very  numerous,  but  are  chiefly  distributed  to  the  bones.  Those  found  in  the 
anterior  fossa  are  the  predural  branches  of  the  anterior  and  posterior  ethmoidal  and 
internal  carotid,  and  a  branch  from  the  medidural  or  middle  meningeal.  In  the  middle 
fossa  are  the  medi-  and  parvidural  branches  of  the  internal  maxillary,  a  branch  from 
the  ascending  pharyngeal,  which  enters  the  skull  through  the  foramen  lacerum 
medium  basis  cranii,  branches  from  the  internal  carotid,  and  a  recurrent  branch 
from  the  lacrimal.  In  the  posterior  fossa  are  dural  branches  from  the  occipital,  one 
of  which  enters  the  skull  through  the  jugular  foramen,  and  the  other  through  the 
mastoid  foramen;  the  postdural  or  posterior  meningeal,  from  the  vertebral;  occa- 
sionally dural  branches  from  the  ascending  pharyngeal,  which  enter  the  skull,  one  at 
the  jugular  foramen,  the  other  at  the  anterior  condyloid  foramen,  and  a  branch 
from  the  medidural. 

The  Veins  of  the  Dura. — The  veins  which  return  the  blood  from  the  dura  (see 
p.  734),  and  partly  from  the  bones,  anastomose  with  the  diploic  veins  (see  p.  733). 
These  vessels  terminate  in  the  various  sinuses,  with  the  exception  of  two  which 
accompany  the  medidural  artery,  and  pass  out  of  the  skull  at  the  foramen  spinosum 


SUPERIOR  LONGI- 
TUDINAL SINUS 


TENTORIUM 


FIG.  642. — Crucial  prolongation  of  the  dura.     Frontal  section  passing  through  the  tentorium.     The  torcular 
is  seen  in  the  centre.     (Poirier  and  Charpy.) 


to  join  the  internal  maxillary  vein ;  above,  the  dural  veins  communicate  with  the 
superior  longitudinal  sinus.  The  sinuses  are  considered  on  pages  736  to  743 
inclusive.  On  either  side  of  the  superior  longitudinal  sinus,  especially  near  its 
middle,  and  also  near  the  lateral  and  straight  sinuses,  are  numerous  spaces  in  the 
dura  which  communicate  with  the  sinus,  either  by  a  small  opening  or  a  distinct 
venous  channel.  These  spaces  are  the  parasinoidal  sinuses  (lacunce  laterales)  (Fig. 
642).  Many  of  the  dural  veins  do  not  open  directly  into  the  sinuses,  but  indirectly 
through  the  parasinoidal  sinuses.  These  venous  lacunae  are  often  invaginated  by 
arachnoid  villi,  and  they  communicate  with  the  underlying  cerebral  veins,  and 
also  with  the  diploic  and  emissary  veins. 

The  Lymphatics  of  the  Dura. — The  existence  of  lymphatic  vessels  is  not  proved. 
Some  anatomists  claim  to  have  injected  such  vessels  along  the  middle  meningeal 
arteries  (Mascagni,  Arnold).  Perivascular  lymph-spaces  do  exist. 

The  Nerves  of  the  Dura. — The  nerves  of  the  dura  are  filaments  from  the  trochlear, 
the  ophthalmic  division  of  the  trigeminal,  the  semilunar  or  Gasserian  ganglion,  the 
vagus,  the  hypoglossal,  and  the  sympathetic. 


THE  DURA   OF  THE  BRAIN 


975 


Processes  of  the  Dura  (processus  durae  matris). — The  processes  of  the  dura 
sent  inward  into  the  cavity  of  the  skull,  are  four  in  number:  the  falx,  the  tento- 
rium,  the  falcula,  and  the  diaphragma  sellse. 

The  Falx  (Figs.  642  and  644). — The  falx  or  falx  cerebri,  so  named  from  its 
sickle-like  form,  is  a  strong  arched  process  of  the  dura,  which  descends  vertically 
in  the  intercerebral  fissure  between  the  two  hemispheres  of  the  brain.  It  is  narrow 
in  front,  where  it  is  attached  to  the  crista  galli  of  the  ethmoid  bone,  and  broad 
behind,  where  it  is  connected  with  the  upper  surface  of  the  tentorium.  Its  upper 
margin  is  convex,  and  attached  to  the  inner  surface  of  the  skull,  in  the  middle  line, 
as  far  back  as  the  internal  occipital  protuberance;  it  contains  the  superior  or  great 
longitudinal  sinus  (sinus  sagittalis  superior}.  Its  lower  margin  is  free,  concave,  and 
presents  a  sharp,  curved  edge,  which  contains  the  falcial  or  inferior  longitudinal  sinus 


DIAPHRAGMA  SCLLAE 


ANTERIOR 

CLINOID 
PROCESS 


TENTORIUM 


TORCULAR 


FIG.  643. — The  tentorium.     (Poirier  and  Charpy.) 

(sinus  sagittalis  inferior).     The  tentorial  or  straight  sinus  (sinus  rectus)  is  formed 
by  the  attachment  of  the  falx  to  the  tentorium. 

The  Tentorium  (Figs.  642,  643,  and  644). — The  tentorium  is  an  arched  lamina 
of  dura,  elevated  in  the  middle  and  slightly  inclined  toward  the  circumference. 
It  intervenes  between  the  upper  surface  of  the  cerebellum  and  the  occipital  lobes  of 
the  cerebrum.  It  is  attached,  behind,  by  its  convex  border  to  the  transverse  ridges 
upon  the  inner  surface  of  the  occipital  bone,  and  there  encloses  on  each  side  the 
transverse  or  lateral  sinus  (sinus  transversus) ;  frontad,  to  the  superior  margin  of 
the  petrous  portion  of  the  temporal  bone  on  either  side,  there  enclosing  the  super- 
petrosal  sinus  (sinus  petrosus  superior) ;  and  at  the  apex  of  this  bone  the  free  or 
internal  border  and  the  attached  or  external  border  meet,  and,  crossing  one  another, 
are  continued  forward,  to  be  attached  to  the  anterior  and  posterior  clinoid  processes 
respectively.  Along  the  middle  line  of  its  upper  surface  the  posterior  border  of  the 


976 


THE  NER  VE  SYSTEM 


falx  is  attached,  the  tentorial  or  straight  sinus  being  placed  at  their  point  of  junction. 
Its  frontal  border  is  free  and  concave,  and  with  the  dorsum  sella?  forms  a  large 
oval  opening.  This  opening  is  called  the  incisura  tentorii  and  transmits  the  mes- 
encephalon. 

The  Falcula  (Fig.  642). — The  falcula  is  a  small  triangular  process  of  dura 
received  into  the  indentation  between  the  two  lateral  lobes  of  the  cerebellum 
behind.  Its  base  is  attached,  above,  to  the  under  and  back  part  of  the  tentorium; 
its  posterior  margin,  to  the  lower  division  of  the  vertical  crest  on  the  inner  surface 
of  the  occipital  bone.  As  it  descends  it  sometimes  divides  into  two  smaller  folds, 
which  are  lost  on  the  sides  of  the  foramen  magnum. 


.INTERNAL  JUGULAR 
VEIN 

FIG.  644. — Falx  and  tentorium,  left  lateral  view.     (Testut.) 

The  Diaphragma  Sell®  (Fig.  643). — The  diaphragma  sellse  is  a  horizontal  pro- 
cess formed  by  a  reduplication  of  the  meningeal  layer  of  the  dura.  It  forms  a  small 
circular  fold,  which  constitutes  a  roof  for  the  sella  turcica.  This  almost  completely 
covers  the  hypophysis,  presenting  merely  a  small  central  opening  (foramen 
diaphragmatis  sellae)  for  the  passage  of  the  infundibulum. 


The  Arachnoid  (Arachnoidea  Encephali)  (Fig.  645). 

The  term  arachnoid  is  from  the  Greek  apdyvir]  elooc,  like  a  spider's  web, 
so  named  for  its  extreme  thinness.  The  cranial  arachnoid  is  a  delicate  mem- 
brane which  envelops  the  brain,  lying  between  the  pia  internally  and  the  dura 
externally;  from  this  latter  membrane  it  is  separated  by  a  very  fine  slit  or  space, 
the  subdural  space  (cavum  subdurale).  The  subdural  space  contains  a  very  minute 
quantity  of  fluid  of  the  nature  of  lymph.  This  fluid  obtains  exit  by  way  of  the 


THE  ARACHNOID 


977 


parasinoidal  sinuses.  The  sulxlural  space  is  prolonged  upon  emerging  nerves  and 
joins  the  lymph  spaces  of  the  nerves.  The  subdural  space  does  not  communicate 
with  the  subarachnoid  space. 

The  arachnoid  invests  the  brain  loosely,  being  separated  from  direct  contact 
with  the  cerebral  substance  by  the  pia,  and  a  quantity  of  loose  areolar  tissue,  the 
subarachnoidean  areolar  tissue.  On  the  upper  surface  of  the  cerebrum  the  arachnoid 
is  thin  and  transparent,  and  may  be  easily  demonstrated  by  injecting  a  stream  of 
air  beneath  it  by  means  of  a  blowpipe;  it  passes  over  the  convolutions  without 
dipping  down  into  the  fissures  between  them,  but  does  pass  into  the  sylvian  and  inter- 
cerebral  fissures  and  is  prolonged  upon  the  nerves  as  a  sheath.  At  the  base  of  the 


OLFACTORY 
NERVE 


VERTEBRAL 
ARTERY 


SPINAL 
ARACHNOID 

FIG.  645. — The  arachnoid  upon  the  base  of  the  brain.     On  the  right  the  arachnoid  has  been  partly  removed 
to  show  the  cerebrum  and  cerebellum  with  their  superficial  veins.     (Poirier  and  Charpy.) 

brain  the  arachnoid  is  thicker,  and  slightly  opaque  toward  the  central  part;  it 
covers  the  orbital  surface  of  the  anterior  lobes,  and  extends  across  between  the 
two  temporal  lobes  so  as  to  leave  a  considerable  interval  between  it  and  the  brain, 
the  cisterna  basalis. 

The  Subarachnoid  Space  (cavum  subarachnoideale]  (Fig.  646). — The  subarach- 
noid space  is  the  interval  between  the  arachnoid  and  pia.  It  is  not  only  on  the 
surface,  but  dips  between  the  convolutions.  It  is  not,  properly  speaking,  a 
space,  for  it  is  occupied  everywhere  by  a  spongy  tissue  consisting  of  trabeculae 
of  delicate  connective  tissue  covered  with  endothelium,  which  pass  from  the  pia 
to  the  arachnoid,  and  in  the  meshes  of  which  the  subarachnoid  fluid  is  contained. 

62 


978  THE  NERVE  SYSTEM 

This  so-called  space  is  small  on  the  surface  of  the  cerebrum;  but  at  the  base  of 
the  brain  the  subarachnoid  tissue  is  less  abundant  and  its  meshes  larger. 

In  certain  regions  the  arachnoid  and  pia  are  farther  apart  than  was  previously 
indicated,  and  these  spaces  are  called  subarachnoid  cisternae  (cisternae  subarach- 
noidalis).  The  largest  space  is  the  continuation  of  the  posterior  part  of  the  sub- 
arachnoid  space  of  the  spinal  cord.  It  is  called  the  postcisterna  (cisterna  cere- 
bellomedullaris}.  It  is  a  space  formed  by  the  arachnoid  passing  across  the  back 
and  under  portions  of  the  oblongata  and  cerebellum.  It  communicates  with  the 
fourth  ventricle  by  three  foramina.  The  largest  opening  is  the  metapore  or 
foramen  of  Majendie  (apertura  medialis  ventriculi  quarti).  It  is  in  the  middle  line 
of  the  metatela.  At  the  end  of  each  recessus  lateralis  of  the  fourth  ventricle 
there  is  also  an  opening,  and  each  opening  is  called  the  foramen  of  Luschka  or 
of  Key  and  Retzius  (apertura  lateralis  ventriculi  quarti).  The  cisterna  pontis  is 
the  continuation  upward  of  the  anterior  part  of  the  subarachnoid  space  of  the 
cord.  About  the  oblongata  it  is  continuous  with  the  postcisterna,  so  this  important 
nerve-centre  is  surrounded  by  a  large  subarachnoid  space.  The  crural  cisterna  or 
cisterna  basalis  (cisterna  interpeduncularis)  is  formed  by  the  arachnoid  extending 
between  the  two  temporal  lobes,  and  contains  the  arteries  forming  the  circulus. 


ARACHNOID 
PIA 


CONVOLUTION 
OF  CEREBRUM 


FIG.  646. — The  subarachnoid  space.     (Schematic.)       (Poirier  and  Charpy.) 

The  anterior  subarachnoid  space  (cisterna  pontis,  inter  peduncular  is  et  chiasmatis) 
includes  the  cisterna  pontis,  the  cisterna  basalis,  and  the  cisterna  of  the  chiasm. 
There  is  a  cisterna  between  the  inferior  edge  of  the  falx  and  the  superior  surface 
of  the  callosum  which  contains  the  precerebral  arteries,  a  cisterna  in  the  sylvian 
fissure  (cisterna  sylviana)  which  contains  the  precerebral  artery,  and  a  cisterna 
between  the  quadrigemina  which  contains  the  vena  magna  Galeni. 

The  cerebro-spinal  fluid  (coeliolympha;  liquor  cerebrospinalis)  fills  the  sub- 
arachnoid  space.  It  is  a  clear,  limpid  fluid,  having  a  saltish  taste  and  a  slightly 
alkaline  reaction.  According  to  Lassaigne,  it  consists  of  98.5  parts  of  water, 
the  remaining  1.5  per  cent,  being  solid  matters,  animal  and  saline.  It  varies  in. 
quantity,  being  most  abundant  in  old  persons,  and  is  quickly  reproduced.  Its 
chief  use  is  probably  to  afford  mechanical  protection  to  the  nervous  centres,  and 
to  prevent  the  effects  of  concussions  communicated  from  without. 

Structure. — The  arachnoid  consists  of  bundles  of  connective  tissue,  the  fine 
fibres  of  which  form  one  layer  and  cross  each  other  in  every  direction.  At  the 
level  of  the  large  fissures,  and  especially  around  the  circulus,  it  is  reenforced 
by  thick  fibrous  tissue.  Both  surfaces  are  covered  with  endothelium.  There 
are  no  blood-vessels  in  the  arachnoid;  the  vessels  which  appear  to  be  in  it  are 
really  in  the  pia.  There  is  no  positive  proof  that  nerves  are  present  in  the 


THE  ARACHNOID   VILLI  OR  PAGGHIONIAN  BODIES         979 

arachnoid.     It  is  true  that  Bochdalek  and  Luschka  long  ago  described  arachnoid 
nerves,  but  these  observations  have  never  been  corroborated. 


The  Arachnoid  Villi  or  Pacchionian  Bodies  (Granulationes  Arachnoideales). 

The  arachnoid  villi,  erroneously  called  glandulse  Pacchioni,  are  numerous 
small  whitish  or  purplish  projections,  usually  collected  into  clusters  of  variable 
size,  which  are  found  in  the  following  situations:  (1)  Upon  the  outer  surface  of  the 
dura,  in  the  vicinity  of  the  superior  longitudinal  sinus,  being  received  into  little 
depressions  on  the  inner  surface  of  the  calvarium.  (2)  On  the  inner  surface  of  the 
dura.  (3)  In  the  superior  longitudinal  sinus  and  the  other  sinuses. 

A  hasty  examination  would  lead  us  to  suppose  that  these  bodies  spring  from 
the  dura,  but,  as  a  matter  of  fact,  they  originate  from  the  arachnoid.  They  are 
not  glandular  in  structure,  but  are  simply  enlarged  normal  villi  of  the  arachnoid. 
In  their  growth  they  appear  to  perforate  the  dura,  and  when  a  group  of  villi  is  of 


JAUOATUM 

it  ::-i;"/mm^Jmm^r'    ~  ~  M\ 

FORNICOLUMNS 


VENA 

OALENI 


FIG.  647. — Velum.     (Poirier  and  Charpy.) 

large  size  it  causes  absorption  of  the  bone,  and  comes  to  be  lodged  in  a  pit  or 
depression  (foveola  granularis  [Pacchioni]}  on  the  inner  table  of  the  skull. 
Their  manner  of  growth  is  as  follows :  At  an  early  period  they  project  through 
minute  holes  in  the  inner  layer  of  the  dura,  which  open  into  large  venous  spaces 
situated  in  the  tissues  of  the  membrane,  on  either  side  of  the  longitudinal  sinus 
and  communicating  with  it.  In  their  onward  growth  the  villi  push  the  outer 
layer  of  the  dura  before  them,  and  this  forms  over  them  a  delicate  membran- 
ous sheath.  In  structure  they  consist  of  spongy  trabecular  tissue,  covered  over 
by  a  membrane,  which  is  continuous  with  the  arachnoid.  The  space  between 
these  two  coverings,  derived  from  the  dura  and  arachnoid  respectively,  corre- 
sponds to  and  is  continuous  with  the  subdural  space.  The  spongy  tissue  of  which 
they  are  composed  is  continuous  with  the  trabecular  tissue  of  the  subarachnoid 
space;  so  that  fluid  injected  into  the  subarachnoid  space  finds  its  way  into 
the  Pacchionian  bodies,  and  through  their  coverings  filters  into  the  superior 
longitudinal  sinus.  They  are  supposed  to  be  a  means  of  getting  rid  of  an 
excess  of  cerebro-spinal  fluid,  when  its  quantity  is  increased  above  normal  or 


980 


THE  NERVE  SYSTEM 


for  replenishing  the  cerebro-spinal  fluid  from  the  blood  plasma  when  needed. 
Another  means  of  getting  rid  of  cerebro-spinal  fluid  is  absorption  by  the  lymph- 
spaces  of  the  cranial  nerves,  which  possess  sheaths  of  arachnoid  up  to  the  'points 
at  which  they  emerge  from  the  skull. 

These  bodies  are  not  found  in  infancy,  and  very  rarely  until  the  third  year. 
They  are  usually  found  after  the  tenth  year;  and  from  this  period  they  increase 
in  number  as  age  advances.  Occasionally  they  are  wanting. 


FRONTAL 
LOBE 


MEDICERCBRAL 
ARTERY 


PRECHORO 

ARTERY 


PREGENICULUM 
POSTGENICULUM 


MEOICORNU 
OF    LATCRA 
VENTRICLE 


PRECCREBRAL 
ARTERY 


PRE- 

COMMUNICANT 

ARTERY 

INTERNAL 

CAROTID 

POST- 
COMMUNICANT 
ARTERY 

BASILAR 
ARTERY 

POST- 
CEREBRAL 
ARTERY 


UADRIGEMINA 


OCCIPITAL 
•     LOBE 


FIG.  648. — The  precerebral  and  choroid  arteries.     (Spalteholz.) 


The  Pia  of  the  Brain  (Pia  Mater  Encephali)  (Figs.  646  and  647). 

The  pia  of  the  brain  is  a  vascular  membrane,  and  derives  its  blood  from  the 
internal  carotid  and  vertebral  arteries.  It  consists  of  a  minute  plexus  of  blood- 
vessels, held  together  by  an  extremely  fine  areolar  tissue.  It  invests  the  entire 
surface  of  the  brain,  dipping  down  between  the  convolutions  and  laminse,  and 
is  prolonged  into  the  interior,  forming  the  velum  and  the  choroid  plexuses  of  the 
lateral  and  fourth  ventricles. 


THE  PIA   OF  THE  BRAIN 


981 


The  Velum  or  the  Tela  Chorioidea  Superior  (tela  chorioidca  ventriculi  tertii) 
(Fig.  047). — The  velum  is  the  prolongation  of  the  pia  into  the  interior  of  the  brain 
through  the  medium  of  the  transverse  fissure.  It  is  a  double  triangular  vascular 
fold,  that  lies  between  the  body  of  the  fornix  above  and  the  optic  thalami  and  the 
epithelial  roof  of  the  third  ventricle  below,  and  passes  forward  to  the  porta.  At 
each  edge  of  the  velum  is  the  paraplexus  or  choroid  plexus  (plexus  chorioideus 
rentricnli  lateral  is)  of  the  corresponding  lateral  ventricle.  In  front  the  two 
plexuses  join  behind  the  porta,  and  at  the  point  of  junction  two  lesser  choroid 
plexuses  pass  back  along  the  under  surface  of  the  velum  to  the  third  ventricle, 
the  diaplexus  or  median  plexus  (plexus  chorioideus  ventriculi  tertii).  The  velar 
veins  or  veins  of  Galen  (p.  947)  are  two  veins  which  lie  on  either  side  of  the  middle 
of  the  velum  and  pass  back.  Each  velar  vein  is  formed  by  the  union  of  the  vein 
from  the  striatum  and  the  choroid  vein  from  the  choroid  plexuses.  The  two  velar 
veins  unite  and  form  the  vena  magna  (Galeni),  which  empties  into  the  straight 
sinus. 


SUPERCALLOSAL 
FISSURE 


OCCIPITAL 


PRECCREBRAL 
ARTERY 

OPTIC 
NERVE 


CALCARINE 
FISSURE 


PRECOMMUNI- 
CANT.   ARTERY 

INTERNAL    POSTCOMMUNI-      POST- 
CAROTID      CANT    ARTERY       CEREBRAL 
ARTERY  ARTERY 

FIG.  649. — The  arteries  of  the  medial  surface  of  the  right  hemicerebrum.     (Spalteholz.) 

The  pia  of  the  surfaces  of  the  hemispheres,  where  it  covers  the  gray  matter 
of  the  convolutions,  is  very  vascular,  and  gives  off  from  its  inner  surface  a  multi- 
tude of  minute  vessels,  which  extend  perpendicularly  for  some  distance  into  the 
cerebral  substance.  At  the  base  of  the  brain,  in  the  situation  of  the  pre-  and  post- 
perforatum,  a  number  of  long,  straight  vessels  are  given  off,  which  pass  through 
the  white  substance  to  reach  the  gray  substance  in  the  interior.  On  the  cerebellum 
the  membrane  is  more  delicate,  and  the  vessels  from  its  inner  surface  are  shorter. 
The  pia  of  the  spinal  cord  is  thicker,  firmer,  and  less  vascular  than  that  of  the 
brain,  and  as  it  is  traced  upward  over  the  oblongata  it  is  seen  to  preserve  these 
characters.  At  the  upper  border  of  the  oblongata  it  is  prolonged  over  the  lower 
half  of  the  fourth  ventricle,  forming,  before  it  is  reflected  on  to  the  under  surface 
of  the  cerebellum,  a  covering  for  the  fourth  ventricle  called  the  metatela  or  tela 
chorioidea  inferior  (tela  chorioidea  ventriculi  quarti) ;  this  carries  the  choroid  plexus 
of  the  fourth  ventricle  (plexus  chorioideus  ventriculi  quarti). 


982  THE  NERVE  SYSTEM 

The  arteries  of  the  pia  (see  pp.  628,  629,  and  630)  (Figs.  648  and  649)  are  the 
precerebrals,  medicerebrals,  postcerebrals,  prechoroids,  postchoroids,  the  precere- 
bellars,  medicerebellars,  and  postcerebellars.  (The  vessels  of  the  cerebral  ganglionic 
system  and  of  the  cortical  arterial  system  are  considered  on  p.  632.) 

The  veins  of  the  pia  (see  pp.  734,  735,  and  736)  are  the  basilar  vein,  the  velar  veins 
(Fig.  647),  the  veins  constituting  the  choroid  plexuses  of  the  third  ventricle,  the 
lateral  ventricles,  and  the  fourth  ventricle;  the  cerebral  veins  (Fig.  645)  and  the 
cerebellar  veins  (Fig.  645). 

The  nerves  of  the  pia  accompany  the  branches  of  the  arteries  and  are  derived 
chiefly  from  the  sympathetic.  A  few  fibres  are  derived  from  certain  cranial 
nerves,  all  of  which  are  probably  of  the  afferent  variety. 


THE   SPINAL  NERVES    (NERVI  SPINALES). 

The  spinal  nerves  are  so  called  because  they  apparently  originate  from  the  spinal 
cord,  and  are  transmitted  through  the  intervertebral  foramina  on  either  side  of  the 
spinal  column.  There  are  thirty-one  pairs  of  spinal  nerves,  which  are  arranged 
into  the  following  groups,  corresponding  to  the  region  of  the  spine  through  which 
they  pass: 

Cervical 8  pairs. 

Thoracic .  12      " 

Lumbar 5      " 

;  Sacral 5      •' 

Coccygeal 1  pair. 

It  will  be  observed  that  each  group  of  nerves  corresponds  in  number  with  the 
vertebrae  in  that  region,  except  the  cervical  and  coccygeal.  Sometimes  there  is  no 
thirty-first  pair.  Occasionally  below  the  thirty-first  pair  there  may  be  one  or  even 
two  filamentous  pairs  which  do  not  pass  out  of  the  vertebral  canal. 

Each  spinal  nerve  arises  by  two  roots,  a  ventral  or  motor  root  and  a  dorsal  or 
sensor  root,  the  latter  being  distinguished  by  a  ganglion  termed  the  spinal  ganglion. 


The  Roots  of  the  Spinal  Nerves  (Figs.  540,  541,  650,  651,  652). 

The  Ventral  Root  (radix  anterior}. — The  superficial  origin  is  from  the  ventro- 
lateral  columns  of  the  corcl,  corresponding  to  the  situation  of  the  ventral  cornu  of 
gray  matter.  Each  root  is  composed  of  from  four  to  eight  filaments. 

The  deep  origin  can  be  traced  from  cells  in  the  gray  substance  of  the  ventral 
cornu  of  the  same  as  well  as  of  the  opposite  side.  The  majority  of  the  axones 
arise  from  the  various  groups  of  cells  in  the  ventral  cornu  of  the  same  side, 
while  others  arise  from  the  large  cells  of  the  ventral  cornu  of  the  opposite  side, 
the  axones  passing  across  the  median  plane  in  the  ventral  white  commissure. 
The  axone  bundles,  after  leaving  the  gray  substance,  penetrate  horizontally 
through  the  longitudinal  bundles  of  the  ventro-lateral  column  to  emerge  as 
described  above. 

The  Dorsal  Root  (radix  posterior}. — The  superficial  origin  is  by  filaments  (fila 
radicularia} ,  from  the  dorso-lateral  fissure  of  the  cord.  The  real  origin  of  these 
fibres  is  from  the  nerve-cells  in  the  dorsal-root  ganglion,  from  which  they  can  be 
traced  into  the  cord  in  two  main  bundles,  the  course  of  which  has  already  been 
studied  (p.  849). 

The  ventral  roots  are  smaller  than  the  dorsal,  devoid  of  ganglionic  enlargement, 


THE  GANGLIA   OF  THE  SPINAL  NERVES 


983 


and  their  component  fibrils  are  collected  into  two  bundles  near  the  intervertebr;:! 
foramina. 

The  dorsal  roots  of  the  nerves  are  larger,  but  the  individual  filaments  are  finer  and 
more  delicate  than  those  of  the  ventral.  The  cells  of  the  ganglion  upon  each 
dorsal  root  give  rise  to  central  and  peripheral  processes;  the  central  processes 
constitute  the  dorsal  roots,  the  peripheral  processes  are  modified  dendrites 
(p.  827)  which  join  the  ventral  efferent  axones  and  form  the  spinal  nerve  trunk 
ensheathed  by  a  tubular  process  of  the  dura  and  pia. 

The  dorsal  root  of  the  first  cervical  nerve  forms  an  exception  to  these  characters. 
It  is  smaller  than  the  ventral,  has  occasionally  no  ganglion  developed  upon  it,  and 
when  the  ganglion  exists  it  is  often  situated  within  the  dura.  The  first  cervical 
may  have  a  rudimentary  dorsal  root  or  no  dorsal  root. 

Within  the  vertebral  canal  the  nerve-roots  are  separated  from  each  other  by  the 
ligamentum  denticulatum  (Fig.  651).  In  the  cervical  region  the  spinal  portion  of 
the  accessory  nerve  separates  the  roots. 
Each  root  obtains  a  covering  of  pia, 
which  becomes  continuous  with  the  neuri- 
lemma;  "the  arachnoid  invests  each  root 
as  far  as  the  point  where  it  meets  with  the 
dura;  the  two  roots,  after  piercing  the 
dura  separately,  are  enclosed  by  it  in  a 
single  tubular  sheath,  in  which  is  included 
the  spinal  ganglion  of  the  dorsal  root." 
(Cunningham.) 


DORSAL 
NERVE      ' 
ROOTS     ) 


DORSAL 
ROOTS 


I  VENTRAL 
•\      NERVE 
(.    ROOTS 


LIGAMENTUM 
,DENTICULATUM 
DURA 


..VENTRAL 
ROOTS 


SPINAL  NERVE 
IN  ITS  RIAL 
SHEATH 


LIGAMENTUM 
DENTICULATUM 
VENTRAL  ROOTS 


The  Ganglia  of  the  Spinal  Nerves  (Gan- 
glia Spinales)  (Figs.  650,  651,  652). 

A  ganglion  is  developed  upon  the  dorsal 
root  of  each  of  the  spinal  nerves.  The 
ganglion  upon  the  dorsal  root  of  the  first 
cervical  nerve  may  be  rudimentary  or 
absent.  These  ganglia  are  of  an  oval  form 
and  of  a  reddish  color;  they  bear  a  pro- 
portion in  size  to  the  nerves  upon  which 
they  are  formed,  and  are  placed  in  the 
intervertebral  foramina,  ectad  of  the  point 
where  the  nerves  perforate  the  dura. 
Each  ganglion  is  bifid  internally,  where  it 
is  joined  by  the  two  bundles  of  the  dorsal 
root,  the  two  portions  being  united  into  a 
single  mass  externally.  The  ganglia  upon 
the  first  and  second  cervical  nerves  form 
an  exception  to  these  characters,  being  placed  on  the  arches  of  the  vertebra  over 
t  which  the  nerves  pass.  The  ganglia  of  the  sacral  nerves  are  placed  within  the  verte- 
bral canal;  and  that  on  the  coceygeal  nerve,  also  in  the  canal,  is  situated  at  some 
distance  from  the  origin  of  the  dorsal  root. 

The  ganglion  in  an  embryo  is  composed  of  bipolar  nerve-cells.  In  an  adult  the 
bipolar  nerve-cells  by  fusion  of  their  two  poles  form  unipolar  elements.  The 
process  of  each  unipolar  cell  divides  into  two  a  short  distance  from  the  cell.  One 
of  the  processes  from  each  cell  passes  to  the  spinal  cord,  and  the  other  passes  into 
the  spinal  nerve.  On  the  dorsal  roots  of  the  lumbar  and  sacral  nerves,  between 
the  spinal  ganglia  and  the  cord,  small  cellular  masses  occasionally  exist.  They  are 
called  accessory  or  aberrant  ganglia  (ganglia  aberrantia}. 


SPINAL    NERVE 
IN   ITS    SHEATH 


FIG.  650. 


portion  of  the  spinal  cord,  showing 
its  right  lateral  surface.  The  dura  is  opened  and 
arranged  to  show  the  nerve-roots.  (Testut.) 


984 


THE  NERVE  SYSTEM 


Distribution  of  the  Spinal  Nerves. 

Immediately  beyond  the  ganglion  the  two  roots  coalesce,  their  fibres  inter- 
mingle, and  the  trunk  thus  formed  constitutes  the  spinal  nerve;  it  passes  out  of  the 
intervertebral  foramen,  and  divides  into  a  dorsal  primary  division  for  the  supply  of 
the  dorsal  part  of  the  body,  and  a  ventral  primary  division  for  the  supply  of  the 
ventral  part  of  the  body  (Fig.  651).  Each  division  contains  fibres  from  both  roots. 


NAL  BRANCH 
:XTERNALBriANCH 


RSAL    PRIMARY 
DIVISION 


S  COMMUNICANS 


FIG.  651. — Plan  of  the  constitution  of  a  spinal  nerve.     (W.  Keiller,  in  Gerrish's  Text-book  of  Anatomy.) 

Before  dividing,  each  spinal  nerve  gives  off  a  small  recurrent  or  meningeal 
branch  (ramus  meningeus)  (Fig.  651),  which  is  joined  by  a  filament  from  the  com- 
municating branch  of  the  sympathetic  (ramus  communiccms)  (Fig.  651),  which  con- 
nects the  ganglion  with  the  ventral  division.  The  meningeal  branches  unite  and 
form  one  nerve,  which  passes  inward  through  the  intervertebral  foramen  and 
supplies  the  dura,  sending  branches  to  the  vertebra?  and  vertebral  ligaments. 


Neuraxis  of  Peripheral 

Sensor  Neurone 


Nerve  Trunk  ! 


Spinal  Ganglion 


Dendrite  of 
Peripheral  Sensor 
Neurone 


Neuraxis  of 
Sympathetic  Neurone 


'Neuraxis  of  Peripheral  Motor  Neurone 
jt 

:f Sympathetic  Ganglion 


-    FIG.  652. — Diagram  to  show  the  composition  of  a  peripheral  nerve-trunk.     (Bohm  and  Davidoff.) 

The  Dorsal  Primary  Divisions  (rami  posteriores)  (Fig.  631). — The  dorsal  primary 
divisions  of  the  spinal  nerves  are  generally  smaller  than  the  ventral;  they  arise 
from  the  trunk  resulting  from  the  union  of  the  roots,  in  the  intervertebral  foramina; 
and,  passing  dorsad,  divide  into  internal  and  external  branches,  which  are  dis- 
tributed to  the  muscles  and  integument  behind  the  spine.  The  dorsal  primary 
divisions  of  the  spinal  nerves  form  two  small  plexuses,  the  dorsal  cervical  plexus 
and  the  dorsal  sacral  plexus.  The  first  cervical,  the  fourth  and  fifth  sacral,  and  the 
coccygeal  nerves  do  not  divide  into  external  and  internal  branches. 


POINTS  OF  EMERGENCE  OF  THE  SPINAL  NERVES 


985 


The  Ventral  Primary  Divisions  (rami  anteriores)  (Fig.  651). — The  ventral  primary 
divisions  of  the  spinal  nerves  supply  the  parts  of  the  body  ventrad  of  the  spine, 
including  the  limbs.  They  are  for  the  most  part  larger  than  the  dorsal  primary 
divisions.  Each  division,  soon  after  its  origin,  receives  a  slender  filament  from  the 
.sympathetic,  which  is  called  the  gray  ramus  communicans.  In  the  thoracic  region 
the  ventral  primary  divisions  of  the  spinal  nerves  are  quite  separate  from  each 
other,  and  are  uniform  in  their  distribution;  but  in  thetervical,  lumbar,  and  sacral 
regions  they  form  intricate  plexuses  previous  to  their  distribution.  The  ventral 
primary  divisions  of  certain  thoracic,  lumbar,  and  sacral  nerves  give  off  a  delicate 
collection  of  nerve-filaments  to  the  sympathetic  cord.  These  are  called  the  white 
rami  communicants s  or  the  visceral  branches  of  the  spinal  nerves. 


Ventral  aspect. 


FIG.  653. — Distribution  of  cutaneous  nerves. 


Points  of  Emergence  of  the  Spinal  Nerves. 

The  roots  of  the  spinal  nerves  from  their  origin  in  the  cord  run  obliquely  caudad 
to  their  point  of  exit  from  the  intervertebral  foramina,  the  amount  of  obliquity 
varying  in  different  regions  of  the  spine,  and  being  greater  in  the  lower  than  the 


986  THE  NER  VE  SYSTEM 

upper  part.  The  level  of  their  emergence  from  the  cord  is  within  certain  limits 
variable,  and  of  course  does  not  correspond  to  the  point  of  emergence  of  the  nerve 
from  the  intervertebral  foramina  (Fig.  653). 

THE  CERVICAL  NERVES  (NN.  CERVICALES). 
The  Roots  of  the  Cervical  Nerves. 

The  roots  of  the  cervical  nerves  increase  in  size  from  the  first  to  the  fifth,  and  then 
remain  the  same  size  to  the  eighth.  The  dorsal  roots  bear  a  proportion  to  the 
ventral  as  3  to  1,  which  is  much  greater  than  in  any  other  region,  the  individual 
filaments  being  also  much  larger  than  those  of  the  ventral  roots.  The  dorsal  root 
of  the  first  cervical  is  an  exception  to  this  rule;  it  is  smaller  than  the  ventral  root. 
In  direction  the  roots  of  the  cervical  are  less  oblique  than  those  of  the  other  spinal 
nerves.  The  first  cervical  nerve  is  directed  a  little  cephalad  and  ectad;  the 
second  is  horizontal;  the  others  are  directed  obliquely  caudad  and  ectad,  the 
lowest  being  the  most  oblique,  and  consequently  longer  than  the  upper,  the  distance 
between  their  place  of  origin  and  their  point  of  exit  from  the  vertebral  canal  never 
exceeding  the  depth  of  one  vertebra. 

The  First  Cervical  or  Suboccipital  Nerve  (n.  suboccipitalis]  (Fig.  654).— The 
dorsal  root  may  be  rudimentary  or  absent.  The  trunk  of  the  first  cervical  nerve 
leaves  the  vertebral  canal  between  the  occipital  bone  and  the  dorsal  arch  of  the  atlas 
(Figs.  16  and  202). 

The  Trunk  of  the  Second  Cervical  Nerve  leaves  the  vertebral  canal  between  the 
dorsal  arch  of  the  atlas  and  the  lamina  of  the  axis;  and  the  eighth  (the  last) 
between  the  last  cervical  and  first  thoracic  vertebrae. 

Each  nerve,  at  its  exit  from  the  intervertebral  foramen,  divides  into  a  dorsal  and 
a  ventral  division.  The  ventral  divisions  of  the  four  upper  cervical  nerves  form  the 
cervical  plexus.  The  ventral  divisions  of  the  four  lower  cervical  nerves,  together 
with  the  first  thoracic,  form  the  brachial  plexus. 

The  Dorsal  Divisions  of  the  Cervical  Nerves  (Kami  Posteriores). 

The  Dorsal  Division  of  the  First  Cervical  Nerve  (Fig.  654)  differs  from  the  dorsal 
divisions  of  the  other  cervical  nerves  in  not  dividing  into  an  internal  and  external 
branch.  It  is  larger  than  the  ventral  division,  and  escapes  from  the  vertebral 
canal  between  the  occipital  bone  and  the  dorsal  arch  of  the  atlas,  lying  beneath  the 
vertebral  artery.  It  enters  the  suboccipital  triangle  formed  by  the  Rectus  capitis 
posticus  major,  the  Obliquus  superior  and  Obliquus  inferior,  and,  by  muscular 
branches,  supplies  the  Recti  and  Obliqui  muscles,  and  the  Complexus.  From  the 
branch  which  supplies  the  Inferior  oblique  a  communicating  filament  is  given  off 
which  joins  the  second  cervical  nerve.  This  nerve  also  occasionally  gives  off  a 
cutaneous  filament,  which  accompanies  the  occipital  artery  and  communicates- 
with  the  occipitalis  major  and  minor  nerves. 

The  Dorsal  Division  of  the  Second  Cervical  Nerve  is  three  or  four  times  greater 
in  diameter  than  the  ventral  division,  and  the  largest  of  all  the  dorsal  cervical 
divisions.  It  emerges  from  the  vertebral  canal  between  the  dorsal  arch  of  the  atlas 
and  lamina  of  the  axis,  below  the  Inferior  oblique.  It  supplies  a  twig  to  this 
muscle,  and  receives  a  communicating  filament  from  the  first  cervical.  It  then 
divides  into  an  internal  and  an  external  branch. 

The  internal  branch  called,  from  its  size  and  distribution,  the  great  occipital  nerve 
(occipitalis  major]  (Fig.  654),  ascends  obliquely  inward  between  the  Obliquus- 


THE  DORSAL  DIVISIONS  OF  THE  CERVICAL  NERVES 


987 


inferior  and  Complexus,  and  pierces  the  latter  muscle  and  the  Trapezius  near 
their  attachments  to  the  cranium.  It  is  now  joined  by  a  filament  from  the  dorsal 
division  of  the  third  cervical  nerve,  the  anastomotic,  and,  ascending  on  the 
back  part  of  the  head  with  the  occipital  artery,  divides  into  two  branches,  which 
supply  the  integument  of  the  scalp  as  far  forward  as  the  vertex,  communicating 
with  the  occipitalis  minor.  It  gives  off  an  auricular  branch  to  the  back  part  of  the 
ear  and  muscular  branches  to  the  Complexus. 

The  external  branch  is  often  joined  by  the  external  branch  of  the  dorsal  division 
of  the  third  cervical  nerve,  and  supplies  the  Splenius,  Trachelo-mastoid,  and 
Complexus. 

The  Dorsal  Division  of  the  Third  Cervical  Nerve  (Fig.  654)  is  smaller  than  the 
preceding,  but  larger  than  the  fourth;  it  differs  from  the  dorsal  divisions  of  the 
remaining  cervical  nerves  in  its  supplying  an  additional  filament,  the  third  occipital 
nerve,  to  the  integument  of  the  occiput.  The  dorsal  division  of  the  third  nerve,  like 
the  others,  divides  into  an  internal  and  external  branch. 


GREAT    OCCIPI- 
TAL   NERVE 


RECTUS    CAPITIS 

LATERALIS 
VENTRAL    PRIMARY    DIVI- 
SION OF  FIRST  CERVICAL 


OBLIQUUS 
SUPERIOR 


DORSAL    PRIMARY    DIVI- 
SION OF  FIRST  CERVICALl 


ICH   TO   COMPLEXUS — OUT 

VERTEBRAL    ARTERV 

ORSAL  PRIMARY  DIVISION 
OF  FIRST  CERVICAL 
ANASTOMOTIC  BRANCH 

ANASTOMOTIC 
THIRD    CERVICAL 


OBLIQUUS 
INFERIOR 


RECTUS 
MAJOR 

FIG.  654. — Dorsal  primary  divisions  of  the  upper  three  cervical  nerves.      (Testut.) 

The  internal  or  cutaneous  branch  passes  between  the  Complexus  and  Semispinalis, 
and,  piercing  the  Splenius  and  Trapezius,  supplies  the  skin  over  the  latter  muscle. 

The  external  branch  joins  with  that  of  the  dorsal  division  of  the  second  to  supply 
the  Splenius,  Trachelo-mastoid,  and  Complexus. 

The  third  or  least  occipital  nerve  (n.  occipitalis  minimus  or  n.  occipitalis  tertius) 
(Fig.  654)  arises  from  the  internal  or  cutaneous  branch  of  the  dorsal  division  of 
the  third  cervical  nerve,  beneath  the  Trapezius;  it  then  pierces  that  muscle,  and 
supplies  the  skin  on  the  lower  and  back  part  of  the  head.  It  lies  to  the  inner  side 
of  the  occipitalis  major,  with  which  it  is  connected. 

The  dorsal  division  of  the  suboccipital  nerve  and  the  internal  branches  of  the 
dorsal  divisions  of  the  second  and  third  cervical  nerves  are  occasionally  joined 
beneath  the  Complexus  by  communicating  branches.  This  communication  is 
described  by  Cruveilhier  as  the  dorsal  cervical  plexus. 

The  Dorsal  Divisions  of  the  Fourth,  Fifth,  Sixth,  Seventh,  and  Eighth  Cervical 
Nerves  pass  dorsad,  and  divide,  behind  the  Intertransversales  muscles,  into  internal 
and  external  branches. 

The  internal  branches,  the  larger,  are  distributed  differently  in  the  upper  and 
lower  part  of  the  neck.  Those  derived  from  the  fourth  and  fifth  nerves  pass 
between  the  Complexus  and  Semispinalis  muscles,  and,  having  reached  the  spinous 


988  THE  NERVE  SYSTEM 

processes,  perforate  the  aponeurosis  of  the  Splenius  and  Trapezius,  and  are  con- 
tinued outward  to  the  integument  over  the  Trapezius,  whilst  those  derived  from 
the  three  lowest  cervical  nerves  are  the  smallest,  and  are  placed  beneath  the  Semi- 
spinalis  colli,  which  they  supply,  and  then  pass  into  the  Interspinalis,  Multifidus 
spinse,  and  Complexus,  and  send  twigs  through  this  latter  muscle  to  supply  the 
integument  near  the  spinous  processes  (Hirschfeld). 

The  external  branches  supply  the  muscles  at  the  side  of  the  neck — viz.,  the 
Cervicalis  ascendens,  Transversalis  colli,  and  Trachelo-mastoid. 


The  Ventral  Divisions  of  the  Cervical  Nerves  (Kami  Anteriores). 

The  Ventral  Division  of  the  First  Cervical  Nerve  (Fig.  656)  is  of  small  size.  It 
escapes  from  the  vertebral  canal  through  a  groove  upon  the  dorsal  arch  of  the  atlas. 
In  this  groove  it  lies  beneath  the  vertebral  artery,  to  the  inner  side  of  the  Rectus 
capitis  lateralis.  As  it  crosses  the  foramen  in  the  transverse  process  of  the  atlas  it  re 
ceives  a  filament  from  the  sympathetic.  It  then  descends  ventrad  of  the  transverse 
process,  to  communicate  with  an  ascending  branch  from  the  second  cervical  nerve. 

Communicating  filaments  from  the  loop  between  this  nerve  and  the  second  cervi- 
cal nerve  join  the  vagus,  the  hypoglossal,  and  sympathetic,  and  some  branches  are 
distributed  to  the  Rectus  lateralis  and  the  two  Anterior  recti.  The  fibres  which 
communicate  with  the  hypoglossal  simply  pass  through  the  latter  nerve  to  become 
for  the  most  part  the  descendens  hypoglossi.  According  to  Valentin,  the  ventral 
division  of  the  suboccipital  nerve  distributes  filaments  to  the  occipito-atlantal 
articulation  and  to  the  mastoid  process  of  the  temporal  bone. 

The  Ventral  Division  of  the  Second  Cervical  Nerve  (Fig.  656)  escapes  from  the 
vertebral  canal,  between  the  dorsal  arch  of  the  atlas  and  the  lamina  of  the  axis,  and, 
passing  forward  on  the  outer  side  of  the  vertebral  artery,  divides  ventrad  of  the 
Intertransverse  muscle  into  an  ascending  branch,  which  joins  the  first  cervical;  and 
one  or  two  descending  branches,  which  join  the  third  cervical.  It  gives  off  the  small 
occipital;  a  branch  to  assist  in  forming  the  great  auricular;  another  to  assist  in 
forming  the  superficial  cervical;  one  of  the  communicantes  hypoglossi,  and  a  filament 
to  the  Stern o-mastoid,  which  communicates  in  the  substance  of  the  muscle  with 
the  spinal  accessory. 

The  Ventral  Division  of  the  Third  Cervical  Nerve  (Fig.  656)  is  double  the  size  of 
the  preceding.  At  its  exit  from  the  intervertebral  foramen  it  passes  caudad  and 
outward  beneath  the  Sterno-mastoid  muscle,  and  divides  into  two  branches.  The 
ascending  branch  joins  the  ventral  division  of  the  second  cervical;  the  descending 
branch  passes  down  ventrad  of  the  Scalenus  anticus  muscle  and  communicates  with 
the  fourth  cervical.  It  gives  off  the  larger  part  of  the  great  auricular  and  superficial 
cervical  nerves;  one  of  the  communicantes  hypoglossi;  a  branch  to  the  supraclavic- 
ular  nerves;  a  filament  to  assist  in  forming  the  phrenic;  and  muscular  branches 
to  the  Levator  anguli  scapulae  and  Trapezius;  this  latter  nerve  communicates 
beneath  the  muscle  with  the  accessory  nerve.  Sometimes  the  nerve  to  the  Scalenus 
medius  is  derived  from  this  source. 

The  Ventral  Division  of  the  Fourth  Cervical  Nerve  (Fig.  656)  is  of  the  same  size  as 
the  preceding.  It  receives  a  branch  from  the  third,  sends  a  communicating  branch 
to  the  fifth  cervical,  and,  passing  caudad  and  outward,  divides  into  numerous 
filaments,  which  cross  the  dorsal  triangle  of  the  neck,  forming  the  supraclavicular 
nerves.  It  gives  a  branch  to  the  phrenic  nerve,  while  it  is  contained  in  the  inter- 
transverse  space,  and  sometimes  a  branch  to  the  Scalenus  medius  muscle.  It  also 
gives  a  branch  to  the  I^evator  anguli  scapula?  and  to  the  Trapezius,  which  unites 
with  the  branch  given  off  from  the  third  nerve,  and  communicates  beneath  the 
muscle  with  the  accessory  nerve. 


THE  CERVICAL  PLEXUS  989 

The  Ventral  Divisions  of  the  Fifth,  Sixth,  Seventh,  and  Eighth  Cervical  Nerves  are 
remarkable  for  their  size.  They  are  much  larger  than  the  preceding  nerves,  and 
are  all  of  equal  dimensions.  They  assist  in  the  formation  of  the  brachial  plexus. 

The  Cervical  Plexus  (Plexus  Cervicalis)  (Figs.  655  and  656). 

The  cervical  plexus  is  formed  by  the  ventral  divisions  of  the  four  upper  cervical 
nerves.  It  is  situated  opposite  the  four  upper  cervical  vertebrae,  resting  upon  the 
Levator  anguli  scapulae  and  Scalenus  medius  muscles,  and  covered  in  by  the 
Sterno-mastoid. 

Its  branches  may  be  divided  into  two  groups,  superficial  and  deep,  which  may 
be  thus  arranged: 

(  Occipitalis  minor. 
C  Ascending    .       .     <   Auricularis  magnus. 

:Superficialis  colli. 
Superficial 

C  Suprasternal. 

Descending   .      .         Supraclavicular  <  Supraclavicular. 

(  Supra-acromial. 
C  Communicating. 
/•  T  *        i  )  Muscular. 

j  Communicantes  hypoglossi. 
Deep         .    1  [^  Phrenic. 

Fxternal  J  Communicating. 

'     1  Muscular. 

The  Superficial  Branches  of  the  Cervical  Plexus.  The  Small  Occipital  Nerve 
(n.  occipitalis  minor)  (Fig.  655). — The  small  occipital  nerve  arises  from  the  second 
cervical  nerve,  sometimes  also  from  the  third;  it  curves  round  the  dorsal  border 
of  the  Sterno-mastoid,  and  ascends,  running  parallel  to  the  dorsal  border  of  the 
muscle,  to  the  back  part  of  the  side  of  the  head.  Near  the  cranium  it  perforates 
the  deep  fascia,  and  is  continued  cephalad  along  the  side  of  the  head  behind  the 
ear,  supplying  the  integument,  and  communicating  with  the  occipitalis  major, 
auricularis  magnus,  and  with  the  dorsal  auricular  branch  of  the  facial. 

This  nerve  gives  off  an  auricular  branch,  which  supplies  the  integument  of  the 
upper  and  back  part  of  the  auricle,  communicating  with  the  mastoid  branch 
of  the  auricularis  magnus.  The  auricular  branch  is  occasionally  derived  from 
the  great  occipital  nerve.  The  occipitalis  minor  varies  in  size;  it  is  occasionally 
double. 

The  Great  Auricular  Nerve  (n.  auricularis  magnus}  (Fig.  655). — The  great 
auricular  nerve  is  the  largest  of  the  ascending  branches.  It  arises  from  the 
second  and  third  cervical  nerves,  winds  around  the  dorsal  border  of  the  Sterno- 
mastoid,  and,  after  perforating  the  deep  fascia,  ascends  upon  that  muscle  beneath 
the  Platysma  to  the  parotid  gland,  where  it  divides  into  facial,  auricular,  and 
mastoid  branches. 

The  Facial  Branches  pass  across  the  parotid,  and  are  distributed  to  the  integ- 
ument of  the  face  over  the  parotid  gland;  others  penetrate  the  substance  of  the 
gland  and  communicate  with  the  facial  nerve. 

The  Auricular  Branches  ascend  to  supply  the  integument  of  the  back  of  the 
pinna,  except  at  its  upper  part,  communicating  with  the  auricular  branches  of 
the  facial  and  vagus  nerves.  A  filament  pierces  the  pinna  to  reach  its  outer 
surface,  where  it  is  distributed  to  the  lobule  and  lower  part  of  the  concha. 


990 


THE  NERVE  SYSTEM 


The  Mastoid  Branch  communicates  with  the  occipitalis  minor  and  the  dorsal 
auricular  branch  of  the  facial,  and  is  distributed  to  the  integument  behind  the 
ear. 

The  Superficial  Cervical  Nerve  or  the  Superficialis  Colli  (n.  cutaneus  colli}  (Fig. 
655). — The  superficial  cervical  nerve  or  the  superficialis  colli  arises  from  the 
second  and  third  cervical  nerves,  turns  around  the  dorsal  border  of  the  Sterno- 
mastoid  about  its  middle,  and,  passing  obliquely  forward  beneath  the  external 
jugular  vein  to  the  ventral  border  of  the  muscle,  perforates  the  deep  cervical 
fascia,  and  divides  beneath  the  Platysma  into  two  branches,  which  are  distributed 
to  the  ventro-lateral  parts  of  the  neck. 


DORSAL 
AURICULAR 
NERVE 


GREAT 
OCCIPITAL 

GREAT 
AURICULAR 

(dorsal  branch) 

SMALL 

OCCIPITAL 

THIRD 

OCCIPITAL 

GREAT 

AURICULAR 

(ventral  branches) 


BRANCHES  TO 

TRAPEZIUS 

SUPRACLAVICULAR 

NERVES 

(acromial 
branches) 


INFRAMANDIBULAR 
BRANCH  OF 
FACIAL 

SUPERFICIAL 

CERVICAL 

NERVES 


BRANCHES 
OF  FACIAL 
NERVE 


SUPRACLAVICULAR 


NERVES  (sternal 
branches) 


SUPRACLAVICULAR 

NERVES  (clavicular 
branches) 

FIG.  655.— The  cutaneous  branches  of  the  right  cervical  plexus,  viewed  from  the  right.     The  Platysma 
has  been  partly  removed.      (Spalteholz.) 

The  Ascending  Branch  or  Branches  (rami  superiores}  gives  a  filament  which 
accompanies  the  external  jugular  vein;  it  then  passes  cephalad  to  the  submaxillary 
region,  and  divides  into  branches,  some  of  which  form  a  plexus  with  the  cervical 
branches  of  the  facial  nerve  beneath  the  Platysma;  others  pierce  that  muscle 
and  are  distributed  to  the  integument  of  the  upper  half  of  the  neck,  at  its  forepart, 
as  high  as  the  chin. 


THE  CERVICAL  PLEXUS 


991 


The  Descending  Branches  (rami  inferior -es),  usually  represented  by  two  or  more 
filaments,  pierce  the  Platysma,  and  are  distributed  to  the  integument  of  the  side 
and  front  of  the  neck,  as  low  as  the  sternum. 

The  Descending  or  Supraclavicular  Branches  (mi.  supraclaviculares}  (Fig.  655). — 
The  descending  or  supraclavicular  branches  arise  from  the  third  and  fourth 
cervical  nerves;  emerging  beneath  the  dorsal  border  of  the  Stern o-mastoid,  they 
descend  in  the  dorsal  triangle  of  the  neck  beneath  the  Platysma  and  deep 
cervical  fascia.  Near  the  clavicle  they  perforate  the  fascia  and  Platysma  to 
become  cutaneous,  and  are  arranged,  according  to  their  position,  into  three 
groups. 


COMMUNICATING  TO 
HYPOGLOSSAL 


SYMPATHETIC 


LONGUS  COLL.  A 
RECTUS  ANT.  MAJOR 


TO  GENIOHYOID 
H^ 
TOTHYROHYOID 

SUBMANDIBULAR 
BR.   OF  FACIAL 


LEVATOR    ANGULI    SCAP. 

ASCALENUS  MEDIUS 


FROM  SYMPATHETIC 


FIG.  656. — Plan  of  the  cervical  plexus.     (Gerrish.) 


The  Internal  or  Suprasternal  Branches  (nn.  supraclaviculares  anteriores]  cross 
obliquely  over  the  external  jugular  vein  and  the  clavicular  and  sternal  attach- 
ments of  the  Sterno-mastoid  muscle,  and  supply  the  integument  as  far  as  the 
median  line.  They  furnish  one  or  two  filaments  to  the  sterno-clavicular  joint. 

The  Middle  or  Supraclavicular  Branches  (nn.  supraclaviculares  medii)  cross  the 
clavicle,  and  supply  the  integument  over  the  Pectoral  and  Deltoid  muscles,  com- 
municating with  the  cutaneous  branches  of  the  upper  intercostal  nerves. 


992  THE  NERVE  SYSTEM 

The  External  or  Supra-acromial  Branches  (nn.  supraclaviculares  posteriores]  pass 
obliquely  across  the  outer  surface  of  the  Trapezius  and  the  acromion,  and  supply 
the  integument  of  the  upper  and  back  part  of  the  shoulder. 

The  Deep  Branches  of  the  Cervical  Plexus  (Fig.  656).  Internal  Series. 
The  Communicating  Branches. — The  communicating  branches  consist  of  several 
filaments  which  pass  from  the  loop  between  the  first  and  second  cervical  nerves 
ventrad  of  the  atlas  to  the  vagus,  hypoglossal,  and  sympathetic;  of  branches 
from  all  four  cervical  nerves  to  the  superior  cervical  ganglion  of  the  sympathetic, 
together  with  a  branch  from  the  fourth  to  the  fifth  cervical. 

Muscular  Branches. — Muscular  branches  supply  the  Anterior  recti  and  Rectus 
lateralis  muscles;  they  proceed  from  the  first  cervical  nerve,  and  from  the  loop 
formed  between  it  and  the  second. 

The  Communicantes  Hypoglossi  (Fig.  656). — The  communicantes  hypoglossi 
consist  usually  of  two  filaments,  one  being  derived  from  the  second  and  the  other 
from  the  third  cervical.  These  filaments  pass  caudad  on  the  outer  side  of  the 
internal  jugular  vein,  cross  ventrad  of  the  vein  a  little  below  the  middle  of  the 
neck,  and  form  a  loop  with  the  descendens  hypoglossi  ventrad  of  the  sheath  of 
the  carotid  vessels.  Occasionally,  the  junction  of  these  nerves  takes  place  within 
the  sheath. 

The  Phrenic  or  the  Internal  Respiratory  Nerve  of  Bell  (n.  phrenicus]  (Figs.  656  and 
657). — The  phrenic  nerve  arises  chiefly  from  the  fourth  cervical  nerve,  with  a  few 
filaments  from  the  third  and  a  communicating  branch  from  the  fifth.  It  descends 
to  the  root  of  the  neck,  running  obliquely  across  the  front  of  the  Scalenus  anticus 
muscle,  and  beneath  the  Sterno-mastoid  muscle,  the  posterior  belly  of  the  Omo- 
hyoid  muscle,  and  the  Transversalis  colli  and  suprascapular  vessels.  It  next 
passes  over  the  first  part  of  the  subclavian  artery,  between  it  and  the  subclavian 
vein,  and,  as  it  enters  the  chest,  crosses  the  internal  mammary  artery  near  its 
origin.  Within  the  chest  it  descends  nearly  vertically  ventrad  of  the  root  of  the 
lung  and  by  the  side  of  the  pericardium,  between  it  and  the  mediastinal  portion 
of  the  pleura,  to  the  Diaphragm,  where  it  divides  into  branches,  some  few  of 
which  are  distributed  to  its  thoracic  surface,  but  most  of  which  separately  pierce 
that  muscle  and  are  distributed  to  its  under  surface  (rami  phrenicoabdominales). 
A  ramus  pericardiacus  is  distributed  to  the  pericardium.  The  two  phrenic  nerves 
differ  in  their  length,  and  also  in  their  relations  at  the  upper  part  of  the  thorax. 

The  right  phrenic  nervo  is  situated  more  deeply,  and  is  shorter  and  more  vertical 
in  direction  than  the  left;  it  lies  on  the  outer  side  of  the  right  vena  innominata 
and  precava. 

The  left  phrenic  nerve  is  r  ther  longer  than  the  right,  from  the  inclination  of 
the  heart  to  the  left  side,  and  f  om  the  Diaphragm  being  lower  on  this  than  on  the 
opposite  side.  It  enters  the  thorax  behind  the  left  innominate  vein,  and  crosses 
ventrad  of  the  vagus  and  the  arch  of  the  aorta  and  the  root  of  the  lung.  In  the 
thorax  each  phrenic  nerve  is  accompanied  by  a  branch  of  the  internal  mammary 
artery,  the  comes  nervi  phrenici. 

Each  nerve  supplies  filaments  to  the  Diaphragm,  pericardium,  and  pleura, 
and  near  the  chest  is  joined  by  a  filament  from  the  sympathetic,  and,  occasion- 
ally, by  one  from  the  union  of  the  descendens  hypoglossi  with  the  spinal  nerves; 
this  filament  is  found,  according  to  Swan,  only  on  the  left  side.  The  phrenic  fre- 
quently receives  a  filament  from  the  nerve  to  the  Subclavius  muscle.  Branches 
have  been  described  as  passing  to  the  peritoneum. 

From  the  right  nerve  one  or  two  filaments  pass  to  join  in  a  small  ganglion  with 
phrenic  branches  of  the  solar  plexus;  and  branches  from  this  ganglion  are  dis- 
tributed to  the  hepatic  plexus,  the  adrenal  gland,  and  postcava. 

From  the  left  nerve  filaments  pass  to  join  the  phrenic  plexus  of  the  sympathetic, 
but  without  any  ganglionic  enlargement. 


THE  CERVICAL  PLEXUS 


993 


Surgical  Anatomy. — Irritation  of  the  phrenic  nerve  causes  hiccough  and  persistent  cough. 
Bilateral  paralysis  of  the  phrenic  causes  death  from  paralysis  of  the  Diaphragm.  This  form  of 
death  is  seen  by  the  surgeon  in  fracture-dislocation  of  the  third  cervical  vertebra.  Division  of 
the  phrenic  on  one  side  is  not  fatal,  and  is  occasionally  practised  by  the  surgeon  in  removing 
a  tumor  of  the  neck.  In  Hearn's  and  Franklin's  cases  of  removal  of  the  vagus,  the  phrenic 
was  also  divided.  Unilateral  division  of  the  phrenic  nerve  causes  paralysis  of  the  corre- 
sponding half  of  the  Diaphragm,  which  is  difficult  of  recognition,  because,  as  Gowers  points  out, 
the  patient  can  still  take  deep  inspirations,  the  thoracic  muscles  not  being  paralyzed. 


VENTRAL  PHIMARY 

DIVISION   OF 

FOURTH  CERVICAL 


3RACHIAL 
PLEXUS 


PERICARDIAL 
BRANCH 


PHRENIC 

INFERIOR 
CERVICAL 
GANGLION 

INFERIOR 

LARYNGEAL 

NERVE  TO 

SUBCLAVIUS 

MUSCLE 

COMMUNICATING 
BRANCH    FROM 
BRACHIAL  PLEXUS 

THORACIC  CARDIAC 
BRANCH  OF 
VAGUS 
INFERIOR 
LARYNGEAL 

VENTRAL 
PULMONARY 

VENTRAL 

PULMONARY 

PLEXUS 


RAMIFICATIONS 
OF  PHRENIC 


Fin.  657. — The  phrenic  nerve  and  its  relations  with  the  vagus  nerve.     (Toldt.) 

The  Deep  Branches  of  the  Cervical  Plexus.  External  Series.  Communi- 
cating Branches. — The  deep  branches  of  the  external  series  of  the  cervical  plexus 
communicate  with  the  accessory  nerve,  in  the  substance  of  the  Stern o-mastoid 
muscle,  in  the  dorsal  triangle,  and  beneath  the  Trapezius. 

Muscular  Branches. — Muscular  branches  are  distributed  to  the  Sterno-mastoid, 
Trapezius,  Levator  anguli  scapulae,  and  Scalenus  medius. 

The  branch  for  the  Sterno-mastoid  is  derived  from  the  second  cervical;  the 
Trapezius  and  Levator  anguli  scapulae  receive  branches  from  the  third  and  fourth. 

63 


994 


THE  NER  VE  SYSTEM 


The  Scalenus  medius  is  derived  sometimes  from  the  third,  sometimes  the  fourth, 
and  occasionally  from  both  nerves. 

Surgical  Anatomy.— The  cervical  plexus  may  be  damaged  by  wounds  or  contusions,  which 
may  or  may  not  be  associated  with  fracture  of  the  clavicle.  Paralysis  ensues,  the  extent  depend- 
ing on  the  degree  of  damage.  After  a  contusion  the  paralysis  is  apt  to  be  temporary  and  to 
be  followed  by  pain  and  muscular  spasm  in  the  arm.  Paralysis  of  the  arm  due  to  plexus  injury 
may  be  partial  or  complete.  In  some  cases  there  is  complete  motor  palsy  and  partial  sensor 
palsy,  the  sensor  impulses  passing  along  undamaged  collaterals.  In  certain  spasmodic  diffi- 
culties the  surgeon  occasionally  stretches  the  cervical  plexus.  It  is  reached  by  an  incision  at  the 
dorsal  margin  of  the  Sternocleidomastoid  muscle.  This  incision  begins  two  inches  below 
the  level  of  the  tip  of  the  mastoid  and  is  carried  downward  for  three  inches. 


VENTRAL 

DIVISION  OF 
FOURTH  CERVICAL" 


SUPRASCAPULAR 


DESCENDING 
BRANCH  OF 
HYPOGLOSSAL 

ANSA 
HYPOGLOSSI 


THYROID 

AXIS 

INTERNAL 

MAMMARY 

ARTERY 

SUBCLAVIAN 


BRANCH  TO 
PHRENIC 


VENTRAL 
THORACIC 


FIG.  658. — The  right  brachial  plexus  with  its  short  branches,  viewed  from  in  front.  The  Sternocleido- 
mastoid and  trapezius  muscles  have  been  completely,  the  omohyoid  and  subclavius  have  been  partially, 
removed;  a  piece  has  been  sawed  out  of  the  clavicle;  the  pectoralis  muscles  have  been  incised  and  reflected. 
(Spalteholz.) 

The  Brachial  Plexus  (Plexus  Brachialis)  (Figs.  658,  659,  660). 

The  brachial  plexus  is  formed  by  the  union  of  the  ventral  divisions  of  the 
four  lower  cervical  and  the  greater  part  of  the  first  thoracic  nerves,  receiving  usually 
a  fasciculus  from  the  fourth  cervical  nerve,  and  frequently  one  from  the  second 
thoracic  nerve.  It  extends  from  the  lower  part  of  the  side  of  the  neck  to  the  axilla. 
It  is  ve*y  broad,  and  presents  little  of  a  plexiform  arrangement  at  its  commence- 
ment. It  is  narrow  opposite  the  clavicle,  becomes  broad  and  forms  a  more  dense 
interlacement  in  the  axilla,  and  divides  opposite  the  coracoid  process  into  numer- 
ous branches  for  the  supply  of  the  upper  limb.  The  nerves  which  form  the  plexus 
are  all  similar  in  size,  and  their  mode  of  communication  is  subject  to  considerable 
variation,  so  that  no  one  plan  can  be  given  as  applying  to  every  case.1  The  follow- 

1  Kerr,  Bardeen,  and  Elting,  from  a  study  of  175  brachial  plexuses,  recognized  seven  types.  In  58  per 
cent,  the  outer  cord  was  formed  from  the  fourth  to  the  seventh,  the  inner  cord  from  the  eighth  to  the  ninth 
spinal  nerves,  and  the  dorsal  or  posterior  cord  from  the  fourth  to  the  ninth.  In  30  per  cent,  the  outer  cord 
was  formed  from  the  fifth  to  the  seventh,  the  inner  cord  from  the  eighth  to  the  ninth,  and  the  dorsal  cord  from 
the  fifth  to  the  ninth. 


THE  BRACHIAL  PLEXUS 


995 


ing  appears,  however,  to  be  the  most  constant  arrangement:  above  the  clavicle 
(pars  supraclavicidaris)  the  fifth  and  sixth  cervical  unite  soon  after  their  exit 


MUSCULOCUTANCOUS 
NERVE 


INTERCOSTC-HUMERAL 
NERVES 


LESSER  INTERNAL 
CUTANEOUS  NERVES 


LONG  SUBSCAPULAR 
NERVE 


SUBSCAPULAR 
NERVES 


,y    LATERAL  CUTA- 
NEOUS BRANCH 
OF  FOURTH 
INTERCOSTAL 


LATERAL  CUTANEOUS 

BRANCH  OF 

THIRD  INTERCOSTAL 


LONG  THORACIC 
NERVE 


Fir,.  659. — The  right  brachial  plexus  (infraclavicular  portion)  in  the  axillary  fossa,  viewed  from  below  and 
in  front.  The  pectoralis  major  and  minor  muscles  have  been  in  large  part  removed;  their  attachments  have 
been  reflected.  (Spalteholz.) 


-FROM  FOURTH  CERVICAL 


LEVEL  OF  THE 
CLAVICLE 


TO  SCALENI  A. 
LONGUS  COLL1 


UPPER  TRUN 

NERVE'TO  SUBCLAVIUS 


POSTERIOR 
THORACIC 


Fia.  660.— Plan  of  the  brachial  plexus.      (Gerrish.) 


996 


THE  NERVE  SYSTEM 


from  the  intervertebral  foramina  to  form  a  common  trunk.  The  eighth  cervical 
and  first  thoracic  also  unite  to  form  one  trunk.  So  that  the  nerves  forming  the 
plexus,  as  they  lie  on  the  Scalenus  medius  ectad  to  the  outer  border  of  the 
Scalenus  anticus  muscle,  are  blended  into  three  trunks — an  upper  one,  formed 


FIG.  661. — Cutaneous  nerves  of  right  upper 
extremity.     Ventral  view. 


FIG.  662.— Cutaneous  nerves  of  right  upper 
extremity.     Dorsal  view. 


by  the  junction  of  the  fifth  and  sixth  cervical  nerves;  a  middle  one,  consisting 
of  the  seventh  cervical  nerve;  and  a  lower  one,  formed  by  the  junction  of  the 
eighth  cervical  and  first  thoracic  nerves.  As  they  pass  beneath  the  clavicle,  to 
compose  the  infraclavicular  part  of  the  plexus  (pars  infraclavicularis},  each  of 


THE  BRACHIAL  PLEXUS 


997 


these  three  trunks  divides  into  two  branches,  a  ventral  and  a  dorsal.1  The  ventral 
divisions  of  the  upper  and  middle  trunks  then  unite  to  form  a  common  cord, 
which  is  situated  on  the  outer 
side  of  the  middle  part  of  the 
axillary  artery,  and  is  called 
the  outer  cord  of  the  brachial 
plexus  (fasciculus  later  alls). 
The  ventral  division  of  the 
lower  trunk  passes  caudad  on 
the  inner  side  of  the  axillary 
artery  in  the  middle  of  the 
axilla,  and  forms  the  inner  cord 
of  the  brachial  plexus  (fasciculus 
medialis).  The  dorsal  divi- 
sions of  all  three  trunks  unite 
to  form  the  dorsal  cord  of  the 
brachial  plexus  (fasciculus  pos- 
terior), which  is  situated  be- 
hind the  second  portion  of  the 
axillary  artery.  From  this 
dorsal  cord  are  given  off  the 
two  lower  subscapular  nerves, 
the  upper  subscapular  nerve 
being  given  off  from  the  dorsal 
division  of  the  upper  trunk 
prior  to  its  junction  with  the 
dorsal  division  of  the  lower 
and  middle  trunks.  The  dor- 
sal cord  divides  into  the  cir- 
cumflex and  musculospiral 
nerves. 

The  brachial  plexus  com- 
municates with  the  cervical 
plexus  by  a  branch  from  the 
fourth  to  the  fifth  cervical 
nerve,  and  with  the  phrenic 
nerve  by  a  branch  from  the 
fifth  cervical,  which  joins  that 
nerve  on  the  Anterior  scalenus 
muscle ;  the  fifth  and  sixth  cer- 
vical nerves  are  joined  by 
filaments  to  the  middle  cer- 
vical ganglion  of  the  sympa- 
thetic, the  seventh  and  eighth 
cervical  to  its  inferior  ganglion, 
and  the  first  thoracic  nerve  to 
its  first  thoracic  ganglion. 
Close  to  their  exit  from  the 
intervertebral  foramina  the 
nerves  give  off  the  filaments 

ir\  +Vi£>     ranrrlia  FIG.  663. — Cutaneous  nerves  of  the  upper  limb,  ventral  aspect, 

tne  ganglia.  (W   Keiller,  in  Gerrish's  Text-book  of  Anatomy.) 


1  The  dorsal  division  of  the  lower  trunk  is  verv  much  smaller  than  the  others,  and  is  frequently  derived 
entirely  from  the  eighth  cervical  nerve. — ED.  of  15th  English  edition. 


998 


THE  NER  VE  SYSTEM 


Relations. — In  the  neck,  the  brachial  plexus  lies  in  the  posterior  triangle,  being 
covered  by  the  skin,  Platysma,  and  deep  fascia;  it  is  crossed  by  the  posterior  belly 
of  the  Omo-hyoid  muscle  and  by  the  transversalis  colli  artery.  When  the  dorsal 
scapular  artery  arises  from  the  third  part  of  the  subclavian  it  usually  passes  between 
the  roots  of  the  plexus.  The  plexus  lies  at  first  between  the  Anterior  and  Middle 

scaleni  muscles,  and  then 
above  and  to  the  outer  side 
of  the  subclavian  artery;  it 
next  passes  behind  the  clavicle 
and  Subclavius  muscle,  lying 
upon  the  first  serration  of  the 
Serratus  magnus,  and  the 
Subscapularis  muscles.  It  is 
in  close  relation  with  the  apex 
of  the  lung  (Luschka).  In  the 
axilla  it  is  placed  on  the  outer 
side  of  the  first  portion  of  the 
axillary  artery;  it  surrounds 
the  artery  in  the  second  part 
of  its  course,  one  cord  lying 
upon  the  outer  side  of  that 
vessel,  one  on  the  inner  side, 
and  one  behind  it,  and  at  the 
lower  part  of  the  axillary  space 
gives  off  its  terminal  branches 
to  the  upper  extremity. 

Branches.— The  branches 
of  the  brachial  plexus  are 
arranged  in  two  groups — viz., 
those  given  off  above  the 
clavicle,  and  those  below  the 
clavicle. 

Branches  above  the  Clavicle 
(Figs.  658  and  660).— The 
branches  above  the  clavicle, 
from  the  pars  supraclavicu- 
laris,  are — the 

Communicating. 
Muscular. 
Long  thoracic. 
Suprascapular. 

The  Communicating  Branch 
(Figs.  657  and  660).— The 
communicating  branch  with 
the  phrenic  is  derived  from  the 
fifth  cervical  nerve  or  from 
the  loop  between  the  fifth  and 
sixth;  it  joins  the  phrenic  on 
the  Anterior  scalenus  muscle. 
The  communications  with  the 

FIG.  664.— Cutaneous  nerve  of  the  upper  limb,  dorsal  aspect.  c\rmr>atVip>tir»  lin\>p>  nlrp>nrl  v  K<^>n 

(W.  Keiller,  in  Gerrish's  Text-book  of  Anatomy.)  Sympatnet      na\  6  already  DCCH 

referred  to. 

The  Muscular  Branches  (rami  muscular  es}. — The  muscular  branches  supply  the 
Longus  colli,  Scaleni,  Rhomboidei,  and  Subclavius  muscles.  Those  for  the 


THE  BRACHIAL  PLEXUS 


999 


Longus  colli  and  Scaleni  arise  from  the  four  lower  cervical  nerves  at  their  exit 
from  the  intervertebral    foramina.       The  Rhomboid    branch,  called  the  dorsal 


External  anterior  thoracic. 


Internal  anterior  thoracic. 


Muscnlo-cutaneous. 


Median. 


Musculo-spiral. 
—Dorsal 

interosseons. 


Radial. 


Volar 

interosseous. 


New  terms 


Old  terms. 

Intercosto-humeral  =  Intercosto-brachial. 

Posterior  thoracic     =  Long  thoracic. 

Xerve  of  Wrisberg  =  Medial  cutaneous  nerve  of  upper  arm 

(N.  cutaneus  brachii  medialis  ) 
Internal  cutaneous  =  Medial  nerve  of  forearm. 

(N.  cutaneus  antibrachii  medialis.) 


FIG.  665. — Nerves  of  the  left  upper  extremity. 


1000  THE  NERVE  SYSTEM 

scapular  nerve  (n.  dor  sails  scapulae]  (Figs.  658  and  660),  arises  from  the  fifth 
cervical,  pierces  the  Scalenus  medius,  and  passes  beneath  the  Levator  anguli 
scapula?,  which  it  occasionally  supplies,  to  the  Rhomboid  muscles.  The  nerve  to 
the  Subclavius  (n.  subclamus)  is  a  small  filament  which  arises  from  the  fifth  cervical 
at  its  point  of  junction  with  the  sixth  nerve;  it  descends  in  front  of  the  third  part 
of  the  subclavian  artery  to  the  Subclavius  muscle,  and  is  usually  connected  by  a 
filament  with  the  phrenic  nerve. 

The  Long  Thoracic  or  the  External  Respiratory  Nerve  of  Bell  or  Posterior  Thoracic 
Nerve  (n.  thoracalis  longus)  (Figs.  658,  659,  660,  and  665). — The  long  thoracic 
supplies  the  Serratus  magnus  muscle,  and  is  remarkable  for  the  length  of  its  course. 
It  sometimes  arises  by  two  roots  from  the  fifth  and  sixth  cervical  nerves  immediately 
after  their  exit  from  the  intervertebral  foramina,  but  generally  by  three  roots  from 
the  fifth,  sixth,  and  seventh  nerves.  These  unite  in  the  substance  of  the  Middle 
scalenus  muscle,  and,  after  emerging  from  it,  the  nerve  passes  caudad  behind  the 
brachial  plexus  and  the  axillary  vessels,  resting  on  the  outer  surface  of  the  Serratus 
magnus.  It  extends  along  the  side  of  the  chest  to  the  lower  border  of  that  muscle, 
supplying  filaments  to  each  of  the  muscular  digitations. 

The  Suprascapular  Nerve  (n.  suprascapularis}  (Figs.  658,  660,  and  665). — The 
suprascapular  nerve  arises  from  the  cord  formed  by  the  fifth  and  sixth  cervical 
nerves;  passing  obliquely  outward  beneath  the  Trapezius  and  the  Omo-hyoid,  it 
enters  the  supraspinous  fossa  below  the  transverse  or  suprascapular  ligament, 
and,  passing  beneath  the  Supraspinatus  muscle,  curves  around  the  external  border 
of  the  spine  of  the  scapula  to  the  infraspinous  fossa.  In  the  supraspinous  fossa 
it  gives  off  two  branches  to  the  Supraspinatus  muscle,  and  an  articular  filament 
to  the  shoulder-joint;  and  in  the  infraspinous  fossa  it  gives  off  two  branches  to 
the  Infraspinatus  muscle,  besides  some  filaments  to  the  shoulder-joint  and  scapula. 

Branches  below  the  Clavicle  (Figs.  659  and  660). — The  branches  below  the 
clavicle,  that  is,  the  branches  from  the  pars  subclavicularis  of  the  brachial  plexus, 
are  derived  from  the  three  cords  of  the  brachial  plexus,  in  the  following  manner: 

From  the  Outer  Cord. — From  the  outer  cord  arise  the  external  anterior  thoracic 
nerve,  the  musculo-cutaneous,  and  the  outer  head  of  the  median. 

From  the  Inner  Cord. — From  the  inner  cord  arise  the  internal  anterior  thoracic 
nerve,  the  medial  nerve  of  the  forearm  or  internal  cutaneous,  the  medial  nerve  of 
the  upper  arm  or  lesser  internal  cutaneous  (nerve  of  Wrisberg),  the  ulnar,  and 
inner  head  of  the  median. 

From  the  Dorsal  Cord. — From  the  dorsal  cord  arise  two  of  the  three  subscapular 
nerves,  the  third  taking  origin  from  the  dorsal  division  of  the  trunk  formed  by 
the  fifth  and  sixth  cervical  nerves;  the  cord  then  divides  into  the  musculo-spiral 
and  circumflex  nerves. 

These  branches  from  below  the  clavicle  may  be  arranged  according  to  the 
parts  they  supply: 

To  the  chest Anterior  thoracic. 

To  the  shoulder  .  {  Subscapular. 

(  Circumflex. 

(  Musculo-cutaneous. 
j   Internal  cutaneous  or  medial  nerve 
of  the  upper  arm. 

rr>    ^  £  Lesser  internal  cutaneous  or  medial 

To  the  arm,  forearm,  and  hand      .     <  , 

nerve  of  the  forearm. 

Median. 

Ulnar. 

Musculo-spiral. 


THE  BRACHIAL  PLEXUS  1001 

The  fasciculi  of  which  these  nerves  are  composed  may  be  traced  through  'the 
plexus  to  the  spinal  nerves  from  which  they  originate.  They  are  as  follows : 

External  anterior  thoracic  from  5th,  6th,  and  7th  cervical. 

Internal  anterior  thoracic  8th  cervical  and  1st  thoracic. 

Subscapular  5th,  6th,  7th,  and  8th  cervical. 

Circumflex  5th  and  6th  cervical. 

Musculo-cutaneous  "  5th  and  6th  cervical. 

Internal  cutaneous  8th  cervical  and  1st  thoracic. 

Lesser  internal  cutaneous      "  1st  thoracic. 

Median  6th,  7th,  and  8th  cervical,  and  1st  thoracic. 

Ulnar  8th  cervical  and  1st  thoracic. 

Musculo-spiral  "  6th,  7th,  and  8th  cervical,  sometimes  also 

from  the  5th. 

NOTE. — In  this  the  reconstructive  period  of  anatomic  nomenclature  the  terms 
"anterior"  and  "posterior"  are  yet  retained  in  the  description  of  the  relations  of 
structures  in  the  extremities,  for  "ventral"  and  "dorsal"  are  not  uniformly  applic- 
able in  the  same  strict  sense  as  in  the  trunk  and  neck  regions.  Further,  the  desig- 
nations "in  front  of"  and  "behind"  are  applied  only  to  the  position  of  structures 
when  the  body  is  standing  erect  and  with  the  volar  surface  of  the  hand  turned 
"forward."  The  employment  of  the  word  "dorsum"  for  the  back  of  the  hand  is 
already  quite  general. 

The  Anterior  Thoracic  Nerves  (mi.  thoracales  anteriores]  (Figs.  658,  659,  and  660). 
—The  anterior  thoracic  nerves,  two  in  number,  supply  the  Pectoral  muscles. 

The  External  or  Superficial  Anterior  Thoracic  Nerve  (Figs.  658  arid  665),  the  larger 
of  the  two,  arises  from  the  outer  cord  of  the  brachial  plexus,  through  which  its 
fibres  may  be  traced  to  the  fifth,  sixth,  and  seventh  cervical  nerves.  It  passes 
inward,  across  the  axillary  artery  and  vein,  pierces  the  costo-coracoid  membrane, 
and  is  distributed  to  the  under  surface  of  the  Pectoralis  major  muscle.  It  sends 
caudad  a  communicating  filament  to  join  the  internal  anterior  thoracic  nerve,  and 
this  communicating  filament  forms  a  loop  around  the  inner  side  of  the  axillary 
artery. 

The  Internal  or  Deep  Anterior  Thoracic  Nerve  arises  from  the  inner  cord  and 
through  it  from  the  eighth  cervical  and  first  thoracic  nerves.  It  passes  behind 
the  first  part  of  the  axillary  artery,  then  curves  forward  between  the  axillary 
artery  and  vein,  and  joins  with  the  filament  from  the  anterior  nerve.  It  then 
passes  to  the  under  surface  of  the  Pectoralis  minor  muscle,  where  it  divides  into 
a  number  of  branches,  which  supply  the  muscle  on  its  under  surface.  Some 
two  or  three  branches  pass  through  the  muscle  and  reach  the  Pectoralis  major. 

The  Subscapular  Nerves  (nn.  subscapidares}  (Figs.  659  and  660). — The  sub- 
scapular  nerves  arise  from  the  dorsal  cord  of  the  plexus.  There  are  three  sub- 
scapular  nerves,  and  they  supply  the  Subscapularis,  Teres  major,  and  Latissimus 
dorsi  muscles,  and  give  filaments  to  the  shoulder-joint.  The  fasciculi  of  which 
they  are  composed  may  be  traced  to  the  fifth,  sixth,  seventh,  and  eighth  cervical 
nerves. 

The  First,  Short,  or  Upper  Subscapular  Nerve,  the  smallest,  arises  from  the  dorsal 
division  of  the  upper  trunk  of  origin  of  the  brachial  plexus,  and  enters  the  upper 
part  of  the  Subscapularis  muscle ;  this  nerve  is  frequently  represented  by  two 
branches. 

The  Second  or  Lower  Subscapular  Nerve  arises  from  the  dorsal  cord  of  the  brachial 
plexus,  enters  the  axillary  border  of  the  Subscapularis  and  terminates  in  the 
Teres  major.  The  latter  muscle  is  sometimes  supplied  by  a  separate  branch. 


1002  THE  NER  VE  SYSTEM 

The  Third,  Middle  or  Long  Subscapular  Nerve  (n.  thoracodorsalis)  (Fig.  659),  the 
largest  of  the  three,  arises  from  the  dorsal  cord  of  the  brachial  plexus  and  follows 
the  course  of  the  subscapular  artery,  along  the  dorsal  wall  of  the  axilla  to  the 
Latissimus  dorsi  muscle,  through  which  it  may  be  traced  as  far  as  its  lower  border. 

The  Circumflex  Nerve  (n.  axillaris)  (Figs.  660  and  666).— The  circumflex  nerve 
supplies  some  of  the  muscles,  the  shoulder-joint,  and  the  integument  of  the  shoulder 
(Figs.  661  and  662).  It  arises  from  the  dorsal  cord  of  the  brachial  plexus,  in 
common  with  the  musculo-spiral  nerve,  and  its  fibres  may  be  traced  through  the 
dorsal  cord  to  the  fifth  and  sixth  cervical  nerves.  It  is  at  first  placed  behind  the 
axillary  artery,  between  it  and  the  Subscapularis  muscle,  and  passes  caudad 
and  outward  to  the  lower  border  of  that  muscle.  It  then  winds  dorsad  in  com- 
pany with  the  posterior  circumflex  artery,  through  a  quadrilateral  space  bounded 
above  by  the  Teres  minor  muscle,  below  by  the  Teres  major  muscle,  internally 
by  the  long  head  of  the  Triceps  muscle,  and  externally  by  the  neck  of  the  humerus. 
The  nerve  then  divides  into  two  branches. 

The  Upper  Branch  (Fig.  666)  winds  dorsad  around  the  surgical  neck  of  the 
humerus,  beneath  the  Deltoid,  with  the  posterior  circumflex  vessels,  as  far  as  the 
anterior  border  of  that  muscle,  supplying  it,  and  giving  off  cutaneous  branches, 
which  pierce  the  muscle  and  ramify  in  the  integument  covering  its  lower  part 
(Fig.  663). 

The  Lower  Branch  (Fig.  666),  at  its  origin,  distributes  filaments  to  the  Teres 
minor  and  back  part  of  the  Deltoid  muscles.  Upon  the  filaments  to  the  former 
muscle  an  oval  enlargement  usually  exists.  The  nerve  then  pierces  the  deep 
fascia,  and  supplies  the  integument  over  the  lower  two-thirds  of  the  posterior 
surface  of  the  Deltoid  (n.  cutaneus  brachii  lateralis),  as  well  as  that  covering 
the  long  head  of  the  Triceps  (caput  longum  n.  tricipitis  brachii)  (Fig.  664). 

The  circumflex  nerve,  before  its  division,  gives  off  an  articular  filament,  which 
enters  the  shoulder-joint  below  the  Subscapularis  muscle. 

The  Musculo-cutaneous  or  the  External  Cutaneous  Nerve  or  the  Perforating  Nerve 
of  Casserius1  (n.  musculocutaneus)  (Figs.  659,  660,  and  665). — The  musculo- 
cutaneous  or  the  external  cutaneous  nerve  supplies  some  of  the  muscles  of  the 
arm  and  the  integument  of  the  forearm.  It  arises  from  the  outer  cord  of  the 
brachial  plexus,  opposite  the  lower  border  of  the  Pectoralis  minor  muscle, 
receiving  filaments  from  the  fifth,  sixth,  and  seventh  cervical  nerves.  It  perfor- 
ates the  coraco-brachialis  muscle  (Fig.  665),  passes  obliquely  between  the  Biceps 
and  Brachialis  anticus  muscles  to  the  outer  side  of  the  arm,  and,  a  little  above 
the  elbow,  winds  around  the  outer  border  of  the  tendon  of  the  Biceps,  and,  per- 
forating the  deep  fascia,  becomes  cutaneous  (Fig.  661).  This  nerve,  in  its  course 
through  the  arm,  supplies  the  Coraco-brachialis,  Biceps,  and  the  greater  part 
of  the  Brachialis  anticus  muscles.  The  branch  to  the  Coraco-brachialis  is  given 
off  from  the  nerve  close  to  its  origin,  and  in  some  instances,  as  a  separate  fila- 
ment from  the  outer  cord  of  the  plexus.  The  branches  to  the  Biceps  and 
Brachialis  anticus  are  given  off  after  the  nerve  has  pierced  the  Coraco-brachialis. 
The  nerve  also  sends  a  small  branch  to  the  humerus,  which  enters  the  nutrient 
foramen  with  the  accompanying  artery,  and  a  filament  from  the  branch  supplying 
the  Brachialis  anticus,  goes  to  the  elbow-joint.  The  musculo-cutaneous  furnishes 
the  chief  nerve  supply  to  this  joint. 

The  Cutaneous  Portion  of  the  Musculo-cutaneous  Nerve  (n.  cutaneus  antibrachii 
lateralis)  passes  behind  the  median  cephalic  vein,  and  divides,  opposite  the  elbow- 
joint,  into  an  anterior  and  a  posterior  branch. 

The  anterior  branch  descends  along  the  radial  border  of  the  forearm  to  the 
wrist,  and  supplies  the  integument  over  the  outer  half  of  the  anterior  surface.  At 

1  See  foot-note,  page  1042. 


THE  BRACHIAL  PLEXUS  1003 

the  wrist-joint  it  is  placed  in  front  of  the  radial  artery,  and  some  filaments,  piercing 
the  deep  fascia,  accompany  that  vessel  to  the  dorsum  of  the  wrist,  supplying  the 
carpus.  The  nerve  then  passes  distad  to  the  ball  of  the  thumb,  where  it  termi- 
nates in  cutaneous  filaments.  It  communicates  with  a  branch  from  the  radial 
nerve  and  with  the  palmar  cutaneous  branch  of  the  median. 

The  posterior  branch  passes  distad  along  the  back  part  of  the  radial  side  of  the 
forearm  to  the  wrist.  It  supplies  the  integument  of  the  lower  third  of  the  forearm, 
communicating  with  the  radial  nerve  and  the  external  cutaneous  branch  of  the 
musculo-spiral.  The  cutaneous  areas  supplied  by  the  musculo-cutaneous  nerve 
are  indicated  in  Figs.  663  and  664. 

The  musculo-cutaneous  nerve  presents  frequent  irregularities.  It  may  adhere 
for  some  distance  to  the  median  and  then  pass  outward,  beneath  the  Biceps, 
instead  of  through  the  Coraco-brachialis.  Frequently  some  of  the  fibres  of  the 
median  run  for  some  distance  in  the  musculo-cutaneous  and  then  leave  it  to  join 
their  proper  trunk.  Less  frequently  the  reverse  is  the  case,  and  the  median  sends 
a  branch  to  joint  the  musculo-cutaneous.  Instead  of  piercing  the  Coraco-brachialis 
muscle  the  nerve  may  pass  under  it  or  through  the  Biceps.  Occasionally  it  gives  a 
filament  to  the  Pronator  radii  teres  muscle,  and  it  has  been  seen  to  supply  the 
back  of  the  thumb  when  the  radial  nerve  was  absent. 

The  Internal  Cutaneous  Nerve  (n.  cutaneus  antibrachii  medialis)  (Figs.  659,  660, 
and  665). — The  internal  cutaneous  nerve  or  medial  cutaneous  nerve  of  the  fore- 
arm is  one  of  the  smallest  branches  of  the  brachial  plexus.  It  arises  from  the 
inner  cord  in  common  with  the  ulnar  nerve  and  internal  head  of  the  median  nerve, 
and,  at  its  commencement,  is  placed  on  the  inner  side  of  the  axillary  artery,  and 
afterward  of  the  brachial  artery.  It  derives  its  fibres  from  the  eighth  cervical  and 
first  thoracic  nerves.  It  passes  down  the  inner  side  of  the  arm,  pierces  the  deep 
fascia  with  the  basilic  vein,  about  the  middle  of  the  limb,  and,  becoming  cutaneous, 
divides  into  two  branches,  anterior  and  posterior. 

This  nerve  gives  off,  near  the  axilla,  a  cutaneous  filament,  which  pierces  the 
fascia  and  supplies  the  integument  covering  the  Biceps  muscle  nearly  as  far  as 
the  elbow.  This  filament  lies  a  little  external  to  the  common  trunk,  from  which 
it  arises. 

The  anterior  branch,  the  larger  of  the  two,  passes  usually  in  front  of,  but  occa- 
sionally behind,  the  median  basilic  vein.  It  then  descends  on  the  anterior  surface 
of  the  ulnar  side  of  the  forearm,  distributing  filaments  to  the  integument  as  far 
as  the  wrist,  and  communicating  with  a  cutaneous  branch  of  the  ulnar  nerve 
(Fig.  661). 

The  posterior  branch  passes  obliquely  distad  on  the  inner  side  of  the  basilic 
vein,  passes  in  front  of,  or  over,  the  internal  condyle  of  the  humerus  to  the  back 
of  the  forearm,  and  descends  on  the  posterior  surface  of  its  ulnar  side  as  far  as 
the  wrist,  distributing  filaments  to  the  integument  (Fig.  662).  It  communicates, 
above  the  elbow,  with  the  lesser  internal  cutaneous  nerve,  and  above  the  wrist 
with  the  dorsal  cutaneous  branch  of  the  ulnar  nerve  (Swan).  The  cutaneous  areas 
supplied  by  the  internal  cutaneous  nerve  are  indicated  in  Figs.  663  and  664. 

The  Lesser  Internal  Cutaneous  Nerve  or  the  Nerve  of  Wrisberg  (n.  cutaneus  brachii 
medialis)  (Figs.  659,  660,  and  665). — The  lesser  internal  cutaneous  nerve  or  medial 
cutaneous  nerve  of  the  upper  arm  is  distributed  to  the  integument  on  the  inner 
side  of  the  arm.  It  is  the  smallest  of  the  branches  of  the  brachial  plexus,  and, 
arising  from  the  inner  cord,  receives  its  fibres  from  the  first  thoracic  nerve.  It 
passes  through  the  axillary  space,  at  first  lying  behind,  and  then  on  the  inner 
side  of,  the  axillary  vein,  and  communicates  with  the  intercosto-brachial  nerve. 
It  descends  along  the  inner  side  of  the  brachial  artery  to  the  middle  of  the  arm, 
where  it  pierces  the  deep  fascia,  and  is  distributed  to  the  integument  of  the  back 
of  the  lower  third  of  the  arm,  extending  as  far  as  the  elbow  (Figs.  661,  662,  and 


1004  THE  NER  VE  SYSTEM 

663),  where  some  filaments  are  lost  in  the  integument  ventrad  of  the  inner  condyle, 
and  others  over  the  olecranon.  It  communicates  with  the  posterior  branch  of 
the  internal  cutaneous  nerve. 

In  some  cases  the  nerve  of  Wrisberg  and  the  intercosto-brachial  or  intercosto- 
humeral  nerve  are  connected  by  two  or  three  filaments  which  form  a  plexus  at  the 
back  part  of  the  axilla.  In  other  cases  the  intercosto-brachial  is  of  large  size, 
and  takes  the  place  of  the  nerve  of  Wrisberg,  receiving  merely  a  filament  of  com- 
munication from  the  brachial  plexus,  which  filament  represents  the  latter  nerve. 
In  other  cases  this  filament  is  wanting,  the  place  of  the  nerve  of  Wrisberg  being 
supplied  entirely  by  the  intercosto-brachial. 

The  Median  Nerve  (n.  medianns)  (Figs.  659,  660,  and  665). — The  median  nerve 
has  received  its  name  from  the  course  it  takes  along  the  middle  of  the  arm  and  fore- 
arm to  the  hand,  lying  between  the  ulnar  and  musculo-spiral  nerves,  and  the  ulnar 
and  the  radial  nerves.  It  arises  by  two  roots,  one  from  the  outer  and  one  from 
the  inner  cord  of  the  brachial  plexus;  these  embrace  the  lower  part  of  the  axillary 
artery,  uniting  either  in  front  or  on  the  outer  side  of  that  vessel.  The  median  nerve 
receives  filaments  from  the  sixth,  seventh,  and  eighth  cervical  and  the  first  thoracic 
nerves  and  sometimes  from  the  fifth  cervical  as  well.  As  it  descends  through  the 
arm,  it  lies  at  first  on  the  outer  side  of  the  brachial  artery,  crosses  that  vessel  in 
the  middle  of  its  course,  usually  in  front,  but  occasionally  behind  it,  and  lies  on 
its  inner  side  to  the  bend  of  the  elbow,  where  it  is  placed  beneath  the  bicipital 
fascia,  and  is  separated  from  the  elbow-joint  by  the  Brachialis  anticus  muscle. 
In  the  forearm  it  passes  between  the  two  heads  of  the  Pronator  radii  teres  muscle, 
and  descends  beneath  the  Flexor  sublimis  muscle,  lying  on  the  Flexor  profundus 
muscle,  to  within  two  inches  (3  cm.)  above  the  annular  ligament,  where  it  becomes 
more  superficial,  lying  between  the  tendons  of  the  Flexor  sublimis  and  Flexor 
carpi  radialis  muscles,  beneath,  and  rather  to  the  radial  side  or  under  the  tendon 
of  the  Palmaris  longus,  covered  by  the  integument  and  fascia.  It  then  passes 
through  the  carpal  canal  (canalis  carpi)  beneath  the  annular  ligament  into  the 
hand.  In  its  course  through  the  forearm  it  is  accompanied  by  the  arteria  comes 
nervi  mediani,  a  branch  of  the  anterior  interosseous  artery. 

Branches.— With  the  exception  of  the  nerve  to  the  Pronator  radii  teres  muscle, 
which  sometimes  arises  above  the  elbow-joint,  and  filaments  to  the  elbow-joint, 
the  median  nerve  gives  off  no  branches  in  the  arm.  In  the  forearm  its  branches 
are  muscular,  anterior  interosseous,  and  palmar  cutaneous,  and  two  articular  twigs 
to  the  elbow-joint. 

The  Muscular  Branches  (rami  musculares)  supply  all  the  superficial  muscles  on 
the  front  of  the  forearm  except  the  Flexor  carpi  ulnaris.  These  branches  are 
derived  from  the  nerve  near  the  elbow. 

The  Volar  Interosseous  or  Anterior  Interosseous  (n.  interosseus  [antibrachii] 
volaris)  (Fig.  665)  supplies  the  deep  muscles  on  the  front  of  the  forearm,  except 
the  inner  half  of  the  Flexor  profundus  digitorum.  It  accompanies  the  volar 
interosseous  artery  along  the  interosseous  membrane,  in  the  interval  between 
the  Flexor  longus  pollicis  and  Flexor  profundus  digitorum  muscles,  both  of  which 
it  supplies,  and  terminates  below  in  the  Pronator  quadratus  muscle,  sending  fila- 
ments to  the  inferior  radio-ulnar  articulation  and  the  wrist-joint. 

The  Palmar  Cutaneous  Branch  (ramus  cutaneus  palmaris  n.  mediani)  arises  from 
the  median  nerve  at  the  lower  part  of  the  forearm.  It  pierces  the  fascia  above 
the  annular  ligament,  and,  descending  over  that  ligament,  divides  into  two 
branches;  of  which  the  outer  branch  supplies  the  skin  over  the  ball  of  the  thumb, 
and  communicates  with  the  anterior  cutaneous  branch  of  the  musculo-cutaneous 
nerve;  and  the  inner  branch  supplies  the  integument  of  the  palm  of  the  hand, 
communicating  with  the  cutaneous  branch  of  the  ulnar. 

In  the  palm  of  the  hand  the  median  nerve  is  covered  by  the  integument  and 
palmar  fascia  and  is  crossed  by  the  superficial  palmar  arch.  It  rests  upon  the 


THE  BRACHIAL  PLEXUS  1005 

tendons  of  the  flexor  muscles.  In  this  situation  it  becomes  enlarged,  somewhat 
flattened,  of  a  reddish  color,  and  divides  into  two  branches.  Of  these,  the  external 
branch  supplies  a  muscular  branch  to  some  of  the  muscles  of  the  thumb  and 
digital  branches  to  the  thumb  and  index  finger;  the  internal  branch  supplies  digital 
branches  to  the  contiguous  sides  of  the  index  and  middle  and  of  the  middle  and 
ring  fingers.  The  digital  branches,  before  they  subdivide,  are  called  common 
palmar  digital  branches  of  the  median  nerve  (nn.  digitales  volares  communes). 

The  branch  to  the  muscles  of  the  thumb  (ramus  muscularis)  is  a  short  nerve  which 
divides  to  supply  the  Abductor,  Opponens,  and  the  superficial  head  of  the  Flexor 
brevis  pollicis  muscles,  the  remaining  muscles  of  this  group  being  supplied  by 
the  ulnar  nerve. 

The  Collateral  Palmar  Digital  or  the  Digital  Branches  (nn.  digitales  volares  proprii) 
are  five  in  number.  The  first  and  second  pass  along  the  borders  of  the  thumb, 
the  external  branch  communicating  with  branches  of  the  radial  nerve.  The  third 
passes  along  the  radial  side  of  the  index  finger,  and  supplies  the  First  lumbricalis 
muscle.  The  fourth  subdivides  to  supply  the  adjacent  sides  of  the  index  and 
middle  fingers,  and  sends  a  branch  to  the  Second  lumbricalis  muscle.  The  fifth 
supplies  the  adjacent  sides  of  the  middle  and  ring  fingers,  and  communicates  with 
a  branch  from  the  ulnar  nerve. 

Each  digital  nerve,  opposite  the  base  of  the  first  phalanx,  gives  off  a  dorsal 
branch,  which  joins  the  dorsal  digital  nerve  from  the  radial  nerve  and  runs  along 
the  side  of  the  dorsum  of  the  finger,  to  end- in  the  integument  over  the  last  phalanx. 
At  the  end  of  the  finger  the  digital  nerve  divides  into  a  palmar  and  a  dorsal  branch, 
the  former  of  which  supplies  the  extremity  of  the  finger,  and  the  latter  ramifies 
around  and  beneath  the  nail.  The  digital  nerves,  as  they  run  along  the  fingers,  are 
placed  superficial  to  the  digital  arteries.  The  cutaneous  areas  supplied  by  the 
median  nerve  are  shown  in  Figs.  663  and  664. 

The  Ulnar  Nerve  (n.  ulnaris)  (Figs.  659,  660,  and  665). — The  ulnar  nerve  is 
placed  along  the  inner  or  ulnar  side  of  the  upper  limb,  and  is  distributed  to  the 
muscles  and  integument  of  the  forearm  and  hand.  It  is  smaller  than  the  median, 
behind  which  it  is  placed,  diverging  from  it  in  its  course  down  the  arm.  It  arises 
from  the  inner  cord  of  the  brachial  plexus,  in  common  with  the  inner  head  of  the 
median  and  the  internal  cutaneous  nerve,  and  derives  its  fibres  from  the  eighth 
cervical  and  first  thoracic  nerves.  At  its  commencement  it  lies  to  the  inner  side 
of  the  axillary  artery,  and  holds  the  same  relation  with  the  brachial  artery  to  the 
middle  of  the  arm.  From  this  point  it  runs  obliquely  across  the  internal  head 
of  the  Triceps,  pierces  the  internal  intermuscular  septum,  and  descends  to  the 
groove  between  the  'internal  condyle  and  the  olecranon,  accompanied  by  the  in- 
ferior profunda  artery.  At  the  elbow  it  rests  upon  the  back  of  the  inner  condyle, 
and  passes  into  the  forearm  between  the  two  heads  of  the  Flexor  carpi  ulnaris 
muscle.  In  the  forearm  it  descends  in  a  perfectly  straight  course  along  the  ulnar 
side  of  the  extremity,  lying  upon  the  Flexor  profundus  digitorum  muscle,  its 
upper  half  being  covered  by  the  Flexor  carpi  ulnaris  muscle,  its  lower  half  lying 
on  the  outer  side  of  the  muscle,  being  covered  by  the  integument  and  fascia. 
The  ulnar  artery,  in  the  upper  third  of  its  course,  is  separated  from  the  ulnar 
nerve  by  a  considerable  interval,  but  in  the  rest  of  its  extent  the  nerve  lies  to 
its  inner  side.  At  the  wrist  the  ulnar  nerve  crosses  the  annular  ligament  on  the 
outer  side  of  the  pisiform  bone,  to  the  inner  side  of  and  a  little  behind  the  ulnar 
artery,  and  immediately  beyond  this  bone  divides  into  two  branches,  the 
superficial  and  the  deep  palmar. 

Branches. — The  branches  of  the  ulnar  nerve  are — 
Articular. 


In  the  forearm 


Muscular.  T      ,      ,       ,    [Superficial  palmar. 

^   ,  In  the  hand  -<  ^  t 
Cutaneous.  I  Deep  palmar. 

.  Dorsal  cutaneous. 


1006  THE  NERVE  SYSTEM 

The  Articular  Branches  distributed  to  the  elbow-joint  consist  of  several  small 
filaments.  They  arise  from  the  nerve  as  it  lies  in  the  groove  between  the  inner 
condyle  of  the  humerus  and  the  olecranon  process  of  the  ulnar. 

The  Muscular  Branches  (rami  musculares)  are  two  in  number — one  supplying 
the  Flexor  carpi  ulnaris;  the  other,  the  inner  half  of  the  Flexor  profundus  digi- 
torum.  They  arise  from  the  trunk  of  the  nerve  near  the  elbow. 

The  Cutaneous  Branch  arises  from  the  ulnar  nerve  about  the  middle  of  the  fore- 
arm, and  divides  into  two  branches. 

One  branch  (frequently  absent)  pierces  the  deep  fascia  near  the  wrist,  and  is 
distributed  to  the  integument,  communicating  with  a  branch  of  the  internal 
cutaneous  nerve. 

The  second  branch,  the  palmar  cutaneous  (ramus  cutaneus  palmaris)  lies  on  the 
ulnar  artery,  which  it  accompanies  to  the  hand,  some  filaments  entwining  around 
the  vessel;  it  ends  in  the  integument  of  the  palm,  communicating  with  branches 
of  the  median  nerve. 

The  Dorsal  Cutaneous  Branch  (ramus  dorsalis  manus)  arises  about  two  inches 
above  the  wrist;  it  passes  dorsad  beneath  the  Flexor  carpi  ulnaris  muscle, 
perforates  the  deep  fascia,  and,  running  along  the  ulnar  side  of  the  back  of  the 
wrist  and  hand,  divides  into  branches  (nn.  digitales  dorsales)',  one  of  these  sup- 
plies the  inner  side  of  the  little  finger;  a  second  supplies  the  adjacent  sides  of 
the  little  and  ring  fingers;  a  third  joins  the  branch  of  the  radial  nerve  which 
supplies  the  adjoining  sides  of  the  middle  and  ring  fingers,  and  assists  in  sup- 
plying these  parts;  a  fourth  is  distributed  to  the  metacarpal  region  of  the  hand, 
communicating  with  a  branch  of  the  radial  nerve. 

On  the  little  finger  the  dorsal  digital  branches  extend  only  as  far  as  the  base 
of  the  terminal  phalanx,  and  on  the  ring  finger  as  far  as  the  base  of  the  second 
phalanx;  the  more  distal  parts  of  these  digits  are  supplied  by  dorsal  branches 
derived  from  the  palmar  digital  branches  of  the  ulnar. 

The  Superficial  Palmar  Branch  (ramus  superficialis  n.  ulnaris}  supplies  the 
Palmaris  brevis  and  the  integument  on  the  inner  side  of  the  hand,  and  terminates 
in  two  digital  branches,  which  are  distributed,  one  to  the  ulnar  side  of  the  little 
finger,  the  other  to  the  adjoining  sides  of  the  little  and  ring  fingers,  the  latter 
communicating  with  a  branch  from  the  median.  The  digital  branches  are  dis- 
tributed to  the  fingers  in  the  same  manner  as  the  digital  branches  of  the  median. 

The  Deep  Palmar  Branch  (ramus  profundus  n.  ulnaris),  accompanied  by  the 
deep  branch  of  the  ulnar  artery,  passes  between  the  Abductor  and  Flexor  brevis 
minimi  digiti  muscles;  it  then  perforates  the  Opponens  minimi  digiti  and  follows 
the  course  of  the  deep  palmar  arch  beneath  the  flexor  tendons.  At  its  origin  it 
supplies  the  muscles  of  the  little  finger.  As  it  crosses  the  deep  part  of  the  hand 
it  sends  two  branches  to  each  interosseous  space,  one  for  the  Dorsal  and  one  for 
the  Palmar  interosseous  muscle,  the  branches  to  the  Second  and  Third  palmar 
interossei  supplying  filaments  to  the  two  inner  Lumbrical  muscles.  At  its  ter- 
mination between  the  thumb  and  index  finger,  it  supplies  the  Adductores  trans- 
versus  et  obliquus  pollicis  and  the  inner  head  of  the  Flexor  brevis  pollicis.  It  also 
sends  articular  filaments  to  the  wrist-joint,  and  to  the  bones  and  joints  of  the  hand. 

It  will  be  remembered  that  the  inner  part  of  the  Flexor  profundus  digitorum 
muscle  is  supplied  by  the  ulnar  nerve;  the  two  inner  Lumbricales,  which  are 
connected  with  the  tendons  of  this  part  of  the  muscle,  are  therefore  supplied  by 
the  same  nerve.  The  outer  part  of  the  Flexor  profundus  is  supplied  by  the 
median  nerve;  the  two  outer  Lumbricales,  which  are  connected  with  the  tendons 
of  this  part  of  the  muscles,  are  therefore  supplied  by  the  same  nerve.  Brooks 
states  that  in  twelve  instances  out  of  twenty-one  he  found  that  the  third  lum- 
brical  received  a  twig  from  the  median  nerve,  in  addition  to  its  branch  from  the 
ulnar.  The  palmar  branches  of  the  ulnar  which  go  to  the  fingers  are  called  by 


THE  BRACHIAL  PLEXUS 


1007 


Circumflex. 


Toldt  before  division  common  Suprascapuia 
palmar  digital  branches,  and 
after  division  collateral  palmar 
digital  branches.  The  cutane- 
ous areas  supplied  by  the  ulnar 
nerve  are  shown  in  Figs.  663 
and  664. 

The  Musculo-spiral  Nerve 
(n.  radiolis)  (Figs.  660,  665, 
and  666). — The  musculospiral 
nerve,  the  largest  branch  of  the 
brachial  plexus,  supplies  the 
muscles  of  the  back  part  of  the 
arm  and  forearm,  and  the  in- 
tegument of  the  same  parts,  as 
well  as  that  of  the  back  of  the 
hand  (Figs.  663  and  664).  It 
arises  from  the  posterior  cord 
of  the  brachial  plexus,  of  which 
it  may  be  regarded  as  the  con- 
tinuation. It  receives  filaments 
from  the  sixth,  seventh,  and 
eighth,  and  sometimes  also 
from  the  fifth  cervical  and  first 
thoracic  nerves.  At  its  com- 
mencement it  is  placed  behind 
the  axillary  artery  and  the 
upper  part  of  the  brachial 
artery,  passing  down  in  front 
of  the  tendons  of  the  Latissi- 
mus  dorsi  and  Teres  major 
muscles.  It  winds  around  the 
humerus  in  the  musculo-spiral 
groove  with  the  superior  pro- 
funda  artery,  passing  from  the 
inner  to  the  outer  side  of  the 
bone,  between  the  internal  and 
external  heads  of  the  Triceps 
muscle  (Fig.  666).  It  pierces 
the  external  intermuscular  sep- 
tum, and  descends  between  the 
Brachialis  anticus  and  Supina- 
tor  longus  muscles  to  the  front 
of  the  external  condyle  of  the 
humerus,  where  it  sends  filaments  to  the  elbow-joint  and  divides  into  the  radial 
and  posterior  interosseous  nerves. 

Branches. — The  branches  of  the  musculo-spiral  nerve  are — 

Muscular.  Radial. 

Cutaneous.  Posterior  interosseous. 

The  Muscular  Branches  (rami  musculares  n.  radialis}  are  divided  into  internal, 
posterior,  and  external;  they  supply  the  Triceps,  Anconeus,  Supinator  longus, 
Extensor  carpi  radialis  longior,  and  Brachialis  anticus  muscles.  These  branches 
are  derived  from  the  nerve  at  the  inner  side,  back  part,  and  outer  side  of  the  arm. 


FIG.  666. — The  suprascapular,  circumflex,  and  musculo-spiral 
nerves. 


1008  THE  NERVE  SYSTEM 

The  internal  muscular  branches  supply  the  inner  and  middle  heads  of  the  Tri- 
ceps muscle.  That  to  the  inner  head  of  the  Triceps  is  a  long,  slender  filament 
which  lies  close  to  the  ulnar  nerve,  as  far  as  the  lower  third  of  the  arm,  and  is 
therefore  frequently  spoken  of  as  the  ulnar  collateral  branch. 

The  posterior  muscular  branch,  of  large  size,  arises  from  the  nerve  in  the  groove 
between  the  Triceps  muscle  and  the  humerus.  It  divides  into  branches  which 
supply  the  outer  and  inner  heads  of  the  Triceps  and  the  Anconeus  muscles.  The 
branch  for  the  latter  muscle  is  a  long,  slender  filament  which  descends  in  the 
substance  of  the  Triceps  to  the  Anconeus. 

The  external  muscular  branches  supply  the  Supinator  longus,  Extensor  carpi 
radialis  longior,  and  (usually)  the  outer  part  of  the  Brachialis  anticus  muscles. 

The  Cutaneous  Branches  are  three  in  number,  one  internal  and  two  external. 

The  internal  cutaneous  branch  (n.  cutaneus  brachii  posterior)  arises  in  the  axil- 
lary space  with  the  inner  muscular  branch.  It  is  of  small  size,  and  passes  through 
the  axilla  to  the  inner  side  of  the  arm,  supplying  the  integument  on  its  posterior 
aspect  nearly  as  far  as  the  olecranon.  In  its  course  it  crosses  beneath  the  inter- 
costo-brachial  nerve,  with  which  it  communicates. 

The  external  cutaneous  branch  (n.  cutaneus  antibrachii  dorsalis)  divides  into  two 
branches,  and  each  one  perforates  the  outer  head  of  the  Triceps  muscle  at  its 
attachment  to  the  humerus.  The  upper  and  smaller  one  passes  to  the  front  of  the 
elbow,  lying  close  to  the  cephalic  vein,  and  supplies  the  integument  of  the  lower  half 
of  the  arm  on  its  anterior  aspect.  The  lower  branch  pierces  the  deep  fascia  below 
the  insertion  of  the  Deltoid  muscle,  and  passes  down  along  the  outer  side  of  the 
arm  and  elbow,  and  then  along  the  back  part  of  the  radial  side  of  the  forearm  to 
the  wrist,  supplying  the  integument  in  its  course,  and  joining,  near  its  termination, 
with  the  posterior  cutaneous  branch  of  the  musculo-cutaneous  nerve. 

The  Radial  Nerve  (ramus  superficial^  n.  radialis)  (Fig.  665),  passes  along  the  front 
of  the  radial  side  of  the  forearm  to  the  commencement  of  its  lower  third.  It  lies  at 
first  a  little  to  the  outer  side  of  the  radial  artery,  concealed  beneath  the  Supinator 
longus  muscle.  In  the  middle  third  of  the  forearm  it  lies  beneath  the  same 
muscle,  in  close  relation  with  the  outer  side  of  the  artery.  It  leaves  the  artery 
about  three  inches  above  the  wrist,  passes  beneath  the  tendon  of  the  Supinator 
longus  muscle,  and,  piercing  the  deep  fascia  at  the  outer  border  of  the  forearm, 
divides  into  two  branches. 

The  external  branch,  the  smaller  of  the  two,  supplies  the  integument  of  the 
radial  side  and  ball  of  the  thumb,  joining  with  the  anterior  branch  of  the  musculo- 
cutaneous  nerve. 

The  internal  branch  communicates,  above  the  wrist,  with  the  posterior  cuta- 
neous branch  from  the  musculo-cutaneous,  and  on  the  back  of  the  hand  forms  an 
arch  with  the  dorsal  cutaneous  branch  of  the  ulnar  nerve.  It  then  divides  into 
four  digital  nerves  (nn.  digitales  dorsales),  which  are  distributed  as  follows:  The 
first  supplies  the  ulnar  side  of  the  thumb;  the  second,  the  radial  side  of  the  index 
finger;  the  third,  the  adjoining  sides  of  the  index  and  middle  fingers;  and  the 
fourth,  the  adjacent  borders  of  the  middle  and  ring  fingers.1  The  latter  nerve 
communicates  with  a  filament  from  the  dorsal  branch  of  the  ulnar  nerve. 

The  Dorsal  or  Posterior  Interosseous  Nerve  (n.  interosseus  [antibrachii]  dorsalis) 
(Figs.  665  and  666). — The  dorsal  interosseous  nerve  winds  to  the  back  of  the 
forearm  around  the  outer  side  of  the  radius,  passes  between  the  two  planes  of 
fibres  of  the  Supinator  brevis  muscle,  and  is  prolonged  distad  between  the  super- 
ficial and  deep  layer  of  muscles,  to  the  middle  of  the  forearm.  Considerably 
diminished  in  size,  it  descends  on  the  interosseous  membrane,  beneath  the  Extensor 
longus  pollicis  muscle,  to  the  back  of  the  carpus,  where  it  presents  a  gangliform 

1  According  to  Hutchinson,  the  digital  nerve  to  the  thumb  reaches  only  as  high  as  the  root  of  the  nail;  the 
one  to  the  forefinger  as  high  as  the  middle  of  the  second  phalanx,  and  the  one  to  the  middle  and  ring  fingers  not 
higher  than  the  first  phalangeal  joint  (London  Hospital  Gazette,  vol.  iii,  p.  319).— ED.  15th  English  edition. 


THE  BRACHIAL  PLEXUS  1009 

enlargement  from  which  filaments  are  distributed  to  the  inferior  radio-ulnar 
articulation,  to  the  wrist-joint,  and  to  the  ligaments  and  articulations  of  the  carpus. 
It  supplies  all  the  muscles  of  the  radial  and  posterior  brachial  regions,  excepting 
the  Anconeus,  Supinator  longus,  and  Extensor  carpi  radialis  longior. 

Surgical  Anatomy. — The  brachial  plexus  may  be  ruptured  by  traction  on  the  limb,  leading 
to  complete  paralysis.  Bristow1  has  reported  three  cases  of  avulsion  of  the  plexus  and  has 
described  twenty-four  cases.  In  these  cases  it  is  generally  believed  that  the  lesion  is  rather  a 
tearing  away  of  the  nerves  from  the  spinal  cord  than  a  solution  of  continuity  of  the  nerve-fibres 
themselves.  In  a  case  operated  upon  by  Bristow  it  was  found  that  the  plexus  had  given  way 
where  the  four  cervical  nerves  and  the  first  thoracic  nerve  unite  to  form  three  trunks.  In  supracla- 
vicular  division  of  the  brachial  plexus,  not  only  will  there  be  motor  and  sensor  paralysis  in  the 
limb,  but  the  Serratus  magnus  muscle  will  probably  be  paralyzed,  because  of  injury  to  the  dorsal 
thoracic  nerves.  In  the  axilla  any  of  the  nerves  forming  the  brachial  plexus  may  be  injured  by  a 
wound  of  this  part,  the  median  being  the  one  which  is  most  frequently  damaged  from  its  exposed 
position.  The  musculo-spiral,  on  account  of  its  sheltered  and  deep  position,  is  least  often 
wounded.  The  brachial  plexus  in  the  axilla  is  often  damaged  from  the  pressure  of  a  crutch,  pro- 
ducing the  condition  known  as  crutch  paralysis.  In  these  cases  the  musculo-spiral  is  the  nerve  most 
frequently  implicated;  the  ulnar  nerve  being  the  one  that  appears  to  suffer  next  in  frequency. 

The  circumflex  nerve  is  of  particular  surgical  interest.  On  account  of  its  course  around  the 
surgical  neck  of  the  humerus,  it  is  liable  to  be  torn  in  fractures  of  this  part  of  the  bone,  and 
in  dislocations  of  the  shoulder-foint,  leading  to  paralysis  of  the  deltoid,  and,  according  to  Erb, 
inflammation  of  the  shoulder-joint  is  liable  to  be  followed  by  a  neuritis  of  this  nerve  from  extension 
of  the  inflammation  to  it. 

Mr.  Hilton  takes  the  circumflex  nerve  as  an  illustration  of  a  law  which  he  lays  down,  that 
"the  same  trunks  of  nerves  whose  branches  supply  the  groups  of  muscles  moving  a  joint  furnish 
also  a  distribution  of  nerves  to  the  skin  over  the  insertions  of  the  same  muscles,  and  the  interior 
of  the  joint  receives  its  nerves  from  the  same  source"  In  this  way  he  explains  the  fact  that  an 
inflamed  joint  becomes  rigid,  because  the  same  nerves  which  supply  the  interior  of  the  joint 
supply  the  muscles  which  move  that  joint. 

The  median  nerve  is  liable  to  injury  in  wounds  of  the  forearm.  When  paralyzed,  there  is 
loss  of  flexion  of  the  second  phalanges  of  all  the  fingers  and  of  the  terminal  phalanges  of  the 
index  and  middle  fingers.  Flexion  of  the  terminal  phalanges  of  the  ring  and  middle  fingers  can 
still  be  effected  by  that  portion  of  the  Flexor  profundus  digitorum  which  is  supplied  by  the  ulnar 
nerve.  There  is  power  to  flex  the  proximal  phalanges  through  the  Interossei.  The  thumb 
cannot  be  flexed  or  opposed,  and  is  maintained  in  a  position  of  extension  and  adduction.  All 
power  of  pronation  is  lost.  The  wrist  can  be  flexed,  if  the  hand  is  first  adducted,  by  the  action 
of  the  Flexor  carpi  ulnaris.  There  is  loss  or  impairment  of  sensation  on  the  palmar  surface 
of  the  thumb,  index,  middle,  and  outer  half  of  the  ring  fingers,  and  on  the  dorsal  surface  of  the 
same  fingers  over  the  last  two  phalanges;  except  in  the  thumb,  where  the  loss  of  sensation  is 
limited  to  the  back  of  the  last  phalanx.  In  order  to  expose  the  median  nerve  for  the  purpose 
of  stretching  it  an  incision  should  be  made  along  the  radial  side  of  the  tendon  of  the  Palmaris 
longus  muscle,  which  serves  as  a  guide  to  the  nerve. 

The  ulnar  nerve  is  liable  to  be  injured  in  wounds  of  the  forearm.  When  paralyzed,  there 
is  loss  of  power  of  flexion  in  the  ring  and  little  fingers;  there  is  impaired  power  of  ulnar 
flexion  and  adduction  of  the  hand;  there  is  inability  to  spread  out  the  fingers  from  paralysis  of 
the  Interossei;  and  there  is  inability  to  adduct  the  thumb.  The  fingers  cannot  be  flexed  at  the 
first  joints,  and  cannot  be  extended  at  the  other  joints.  A  claw-hand  develops,  the  first  pha- 
langes being  overextended  and  the  others  flexed.  Sensation  is  lost  or  impaired  in  the  skin  of  the 
ulnar  side  of  the  hand  anteriorly  and  posteriorly,  involving  the  little  finger,  the  ring  finger,  and 
the  ulnar  half  of  the  middle  finger  posteriorly,  and  anteriorly  involving  the  little  finger  and  the 
ulnar  half  of  the  ring  finger.  In  order  to  expose  the  nerve  in  the  lower  part  of  the  forearm, 
an  incision  should  be  made  along  the  outer  border  of  the  tendon  of  the  Flexor  carpi  ulnaris,  and 
the  nerve  will  be  found  lying  on  the  ulnar  side  of  the  ulnar  artery. 

The  musculo-spiral  nerve  is  probably  more  frequently  injured  than  any  other  nerve  of  the 
upper  extremity.  In  consequence  of  its  close  relationship  to  the  humerus  as  it  lies  in  the 
musculo-spiral  groove,  it  is  frequently  torn  or  injured  in  fractures  of  this  bone,  or  subsequently 
involved  in  the  callus  that  may  be  thrown  out  around  a  fracture,  and  thus  pressed  upon  and  its 
funetions  interfered  with.  It  is  also  liable  to  be  squeezed  against  the  bone  by  kicks  or  blows  and 
it  may  be  divided  by  wounds  of  the  arm.  When  paralyzed,  the  hand  is  flexed  at  the  wrist 
and  lies  flaccid.  This  condition  is  known  as  drop-wrist.  The  fingers  are  also  flexed,  and  on 
an  attempt  being  made  to  extend  them  the  last  two  phalanges  only  will  be  extended  through  the 
action  of  the  Interossei,  the  first  phalanges  remaining  flexed.  There  is  no  power  of  extending 
the  wrist.  Supination  is  completely  lost  when  the  forearm  is  extended  on  the  arm,  but  is 

1  Annals  of  Surgery,  September,  1902. 
64 


1010  THE  NERVE  SYSTEM 

possible  to  a  certain  extent  if  the  forearm  is  flexed  so  as  to  allow  of  the  action  of  the  Biceps. 
The  power  of  extension  of  the  forearm  is  lost  on  account  of  paralysis  of  the  Triceps.  Loss  of 
sensation  may  be  considerable  or  slight.  Its  area  is  shown  in  Fig.  664.  The  best  position  in 
which  to  expose  the  nerve  for  the  purpose  of  stretching  is  to  make  an  incision  along  the  inner  border 
of  the  Supinator  longus  muscle,  just  above  the  level  of  the  elbow-joint.  The  skin  and  superficial 
structures  are  to  be  divided  and  the  deep  fascia  exposed.  The  white  line  in  this  structure  indicat- 
ing the  border  of  the  muscle  is  to  be  defined,  and  the  deep  fascia  divided  in  this  line.  By  now  raising 
the  Supinator  longus  the  nerve  will  be  found  lying  beneath  it,  on  the  Brachialis  anticus  muscle. 

Post-anaesthetic  paralysis.  When  a  person  emerges  from  the  influence  of  a  general  anaesthetic 
palsy  of  the  arm  may  be  found  to  exist.  The  brachial  plexus  may  have  been  compressed  during 
the  operation  by  drawing  the  arm  strongly  from  the  body  or  elevating  it  by  the  side  of  the 
head.  In  such  a  case  the  plexus  was  compressed  by  the  head  of  the  humerus  (Braun). 

The  median  nerve  is  stretched  when  the  arm  is  rotated  externally  and  drawn  backward  and 
outward.  The  ulnar  nerve  is  stretched  when  the  forearm  is  flexed  and  supinated  (Braun). 
Garrigues  believes  that  in  most  cases  of  post-anaesthetic  paralysis  the  brachial  plexus  was  squeezed 
between  the  collar  bone  and  the  first  rib  by  the  head  of  the  patient  being  drawn  to  the  opposite 
side  or  being  allowed  to  fall  back. 

THE  THORACIC  NERVES  (NN.  THORACALES). 

The  thoracic  nerves  are  twelve  in  number  on  each  side.  The  first  appears 
between  the  first  and  second  thoracic  vertebrae,  and  the  last  between  the  last 
thoracic  and  first  lumbar. 

The  Roots  of  the  Thoracic  Nerves. 

The  roots  of  the  thoracic  nerves  are  of  small  size,  and  vary  but  slightly  from 
the  second  to  the  last.  Both  roots  are  very  slender,  the  dorsal  roots  slightly 
exceeding  the  ventral  in  thickness.  They  gradually  increase  in  length  from 
above  downward,  and  in  the  lower  part  of  the  thoracic  region  pass  down  in  con- 
tact with  the  spinal  cord  for  a  distance  equal  to  the  height  of  at  least  two  vertebrae, 
before  they  emerge  from  the  vertebral  canal.  They  then  join  in  the  intervertebral 
foramen,  and  at  their  exit  divide  into  two  primary  divisions,  a  dorsal  (posterior) 
and  a  ventral  (intercostal). 

The  Dorsal  Divisions  of  the  Thoracic  Nerves  (Kami  Posteriores). 

The  dorsal  divisions  of  the  thoracic  nerves  are  smaller  than  the  ventral,  pass 
dorsad  between  the  transverse  processes,  and  divide  into  medial  or  internal  and 
lateral  or  external  branches. 

The  Medial  Branches. — The  medial  branches  of  the  six  upper  nerves  pass 
inward  between  the  Semispinalis  dorsi  and  Multifidus  spinse  muscles,  which  they 
supply,  and  then,  piercing  the  origins  of  the  Rhomboidei  and  Trapezius  muscles, 
become  cutaneous  by  the  side  of  the  spinous  processes  and  ramify  in  the  integu-. 
ment.  The  medial  branches  of  the  six  lower  nerves  are  distributed  to  the 
Multifidus  spinse,  without  giving  off  any  cutaneous  filaments. 

The  Lateral  Branches. — The  lateral  branches  increase  in  size  from  above 
caudad.  They  pass  through  the  Longissimus  dorsi  muscle  to  the  cellular  inter- 
val between  it  and  the  Iliocostalis  muscle,  and  supply  those  muscles,  as  well 
as  their  continuations  cephalad  to  the  head,  and  also  the  Levatores  costarum 
muscles;  the  five  or  six  lower  nerves  also  give  off  cutaneous  filaments,  which  pierce 
the  Serratus  posticus  inferior  and  Latissimus  dorsi  muscles  in  a  line  -with  the 
angles  of  the  ribs,  and  then  ramify  in  the  integument. 

The  Cutaneous  Branches. — The  cutaneous  branches  of  the  dorsal  primary 
divisions  of  the  thoracic  nerves  are  twelve  in  number.  From  each  ramus  medialis 
of  the  upper  six  nerves  comes  a  ramus  cutaneus  medialis,  and  from  each  ramus 


VENTRAL  DIVISIONS  OF  THE  THORACIC  NERVES          1011 

lateralis  of  the  lower  six  nerves  comes  a  ramus  cutaneus  lateralis.  The  six  upper 
cutaneous  nerves  are  derived  from  the  medial  branches  of  the  dorsal  divisions 
of  the  thoracic  nerves.  They  pierce  the  origins  of  the  Rhomboidei  and  Trapezius 
muscles,  and  become  cutaneous  by  the  side  of  the  spinous  processes,  and  then 
ramify  in  the  integument.  They  are  frequently  furnished  with  gangliform  enlarge- 
ments. The  six  lower  cutaneous  nerves  are  derived  from  the  lateral  branches 
of  the  dorsal  divisions  of  the  thoracic  nerves.  They  pierce  the  Serratus  posticus 
inferior  and  Latissimus  dorsi  muscles  in  a  line  with  the  angles  of  the  ribs,  and 
then  ramify  in  the  integument. 

The  Ventral  Divisions  of  the  Thoracic  Nerves  or  the  Intercostal  Nerves 

(Rami  Anteriores). 

The  ventral  divisions  of  the  thoracic  nerves  or  the  intercostal  nerves  (nn.  inter- 
costales)  are  twelve  in  number  on  each  side.  They  are,  for  the  most  part, 
distributed  to  the  parietes  of  the  thorax  and  abdomen,  separately  from  each 
other,  without  being  joined  in  a  plexus;  in  which  respect  they  differ  from  the 
other  spinal  nerves.  Each  nerve  is  connected  with  the  adjoining  ganglion  of  the 
sympathetic  by  one  or  two  filaments  (ramus  communicans).  The  intercostal  nerves 
may  be  divided  into  two  sets,  from  the  difference  they  present  in  their  distribution. 
The  six  upper,  with  the  exception  of  the  first  and  the  intercosto-brachial  branch 
of  the  second,  are  limited  in  their  distribution  to  the  parietes  of  the  chest.  The 
six  lower  supply  the  parietes  of  the  chest  and  abdomen,  the  last  one  sending  a 
cutaneous  filament  to  the  buttock. 

The  Ventral  Division  of  the  First  Thoracic  Nerve.— The  ventral  division 
of  the  first  thoracic  nerve  divides  into  two  branches:  one,  the  larger,  leaves  the 
thorax  ventrad  of  the  neck  of  the  first  rib,  and  enters  into  the  formation  of  the 
brachial  plexus ;  the  other  and  smaller  branch  runs  along  the  first  intercostal  space, 
forming  the  first  intercostal  nerve  (n.  intercostalis  7),  giving  off  muscular  branches, 
and  terminates  on  ventral  part  of  the  chest  by  forming  the  first  ventral  cutaneous 
nerve  (ramus  cutaneus  anterior  n.  intercostalis  1}  of  the  thorax.  Occasionally 
this  ventral  cutaneous  branch  is  wanting.  The  first  intercostal  nerve,  as  a  rule, 
gives  off  no  lateral  cutaneous  branch,  but  sometimes  a  small  branch  is  given  off 
which  communicates  with  the  intercosto-brachial.  It  frequently  receives  a  con- 
necting twig  from  the  second  thoracic  nerve,  which  passes  upward  over  the  neck 
of  the  second  rib. 

The  Ventral  Divisions  of  the  Upper  Thoracic  Nerves  (nn.  intercostales). 
—The  ventral  divisions  of  the  second,  third,  fourth,  fifth,  and  sixth  thoracic 
nerves  and  the  small  branch  from  the  first  thoracic  are  confined  to  the  parietes 
of  the  thorax,  and  are  named  upper  or  pectoral  intercostal  nerves.  They  pass 
forward  in  the  intercostal  spaces  with  the  intercostal  vessels,  being  situated  below 
them.  At  the  back  of  the  chest  they  lie  between  the  pleura  and  the  External 
intercostal  muscle,  but  are  soon  placed  between  the  two  planes  of  Intercostal 
muscles  as  far  as  the  middle  of  the  rib.  They  then  enter  the  substance  of  the 
Internal  intercostal  muscles,  and,  running  amidst  their  fibres  as  far  as  the  costal 
cartilages,  they  gain  the  inner  surface  of  the  muscles  and  lie  between  them  and 
the  pleura.  Near  the  sternum,  they  cross  ventrad  of  the  internal  mammary  artery 
and  Triangularis  sterni  muscle,  pierce  the  Internal  intercostal  muscles,  the  anterior 
intercostal  membrane,  and  Pectoralis  major  muscle,  and  supply  the  integument 
of  ventral  wall  of  the  chest  and  over  the  mammary  gland,  forming  the  ventral 
cutaneous  nerves  of  the  thorax;  the  branch  from  the  second  nerve  is  joined  with 
the  supraclavicular  nerves  of  the  cervical  plexus. 

Branches. — Numerous  slender  muscular  filaments  (rami  musculares)  supply  the 
Intercostals,  the  Infracostales,  the  Levatores  costarum,  Serratus  posticus  superior, 


1012 


THE  NERVE  SYSTEM 


and  Triangularis  sterni  muscles.  Some  of  these  branches,  in  the  ventral  wall 
of  the  chest,  cross  the  costal  cartilages  from  one  to  another  intercostal  space. 

Lateral  Cutaneous  Nerves  of  the  Thorax  (rami  cutanei  laterales  [pectorales])  (Fig. 
659). — These  are  derived  from  the  intercostal  nerves,  midway  between  the  vertebrae 
and  sternum;  they  pierce  the  External  intercostal  and  Serratus  magnus  muscles, 
and  divide  into  two  branches,  ventral  and  dorsal. 

The  Ventral  Branches  (rami  anteriores)  are  reflected  forward  to  the  side  and  the 
forepart  of  the  chest,  supplying  the  integument  of  the  chest  and  mamma;  those 
of  the  fifth  and  sixth  nerves  supply  the  upper  digitations  of  the  External  oblique 
muscle. 


Ventral  aspect. 

FIG.  667. — Distribution  of  cutaneous  nerves. 


The  Dorsal  Branches  (rami  posteriores)  are  reflected  dorsad  to  supply  the  integu- 
ment over  the  scapula  and  over  the  Latissimus  dorsi  muscle. 

The  Lateral  Cutaneous  Branch  of  the  Second  Intercostal  Nerve  (n.  intercosto- 
brachialis)  is  of  large  size,  and  does  not  divide,  like  the  other  nerves,  into  a 
ventral  and  dorsal  branch.  It  may  unite  with  a  branch  of  the  third  intercostal. 
The  single  nerve  or  the  united  nerve  is  named,  from  its  origin  and  distribution,  the 


VENTRAL  DIVISIONS  OF  THE  THORACIC  NERVES 


1013 


intercosto-brachial  or  intercosto-humeral  nerve  (Figs.  659  and  665).  It  pierces  the 
External  intercostal  muscle,  crosses  the  axilla  to  the  inner  side  of  the  arm,  and 
joins  with  a  filament  from  the  medial  cutaneous  nerve  of  the  upper  arm  (nerve 
of  Wrisberg}.  It  then  pierces  the  fascia,  and  supplies  the  skin  of  the  upper 
half  of  the  inner  and  back  part  of  the  arm  (Figs.  663  and  664),  communicating 
with  the  internal  cutaneous  branch  (n.  cutaneus  antibrachii  medialis]  of  the 
musculo-spiral  nerve.  The  size  of  this  nerve  is  in  inverse  proportion  to  the  size 
of  the  other  cutaneous  nerves,  especially  the  nerve  of  Wrisberg.  A  second  inter- 
costo-brachial nerve  is  frequently  given  off  from  the  third  intercostal.  It  supplies 
filaments  to  the  armpit  and  inner  side  of  the  arm.  It  may  or  may  not  send  a 
branch  to  the  intercosto-brachial. 


/INTERNAL  BRANCH 
(CUTANEOUS) 


EXTERNAL  BRANCH 
(MUSCULAR) 


DORSAL 
PRIMARY  DIVISION 


VENTRAL  CUTANEOUS 

FIG.  668. — Plan  of  a  typic  intercostal  nerve.  (W.  Keiller.) 

The  Ventral  Divisions  of  the  Lower  Thoracic  Nerves. — The  ventral  divisions 
of  the  seventh,  eighth,  ninth,  tenth,  and  eleventh  thoracic  nerves  are  continued 
ventrad  from  the  intercostal  spaces  into  the  abdominal  wall,  and  the  twelfth 
thoracic  is  continued  throughout  its  whole  course  in  the  abdominal  wall,  since 
it  is  placed  below  the  last  rib;  hence  these  nerves  are  named  lower  or  abdom- 
inal intercostal  nerves.  They  have  (with  the  exception  of  the  last)  the  same  arrange- 
ment as  the  upper  ones  as  far  as  the  anterior  extremities  of  the  intercostal  spaces, 
where  they  pass  behind  the  costal  cartilages,  and  between  the  Internal  oblique  and 
Transversalis  muscles,  to  the  sheath  of  the  Rectus,  which  they  perforate.  They 
supply  the  Rectus  muscle,  and  terminate  in  branches  which  become  subcutaneous 
near  the  linea  alba.  These  branches  are  named  the  ventral  or  anterior  cutaneous 
nerves  of  the  abdomen.  They  are  directed  outward  as  far  as  the  lateral  cutaneous 
nerves,  supplying  the  integument  of  the  front  of  the  belly.  The  lower  intercostal 
nerves  supply  the  Intercostals,  Serratus  posticus  inferior,  and  Abdominal  muscles, 
and,  about  the  middle  of  their  course,  give  off  lateral  cutaneous  branches  which 


1014  THE  NERVE  SYTSEM 

pierce  the  External  intercostal  and  External  oblique  muscles,  in  the  same  line  as 
the  lateral  cutaneous  nerves  of  the  thorax,  and  divide  into  ventral  and  dorsal 
branches,  which  are  distributed  to  the  integument  of  the  abdomen  and  back;  the 
ventral  branches  supply  the  digitations  of  the  External  oblique  muscle  and  extend 
caudad  and  forward  nearly  as  far  as  the  margin  of  the  Rectus  muscle;  the  dorsal 
branches  pass  dorsad  to  supply  the  skin  over  the  Latissimus  dorsi  muscle. 

The  Last  Thoracic  Nerve.— The  last  thoracic  is  larger  than  the  other  thoracic 
nerves.  Its  ventral  division  runs  along  the  lower  border  of  the  last  rib,  and  passes 
under  the  external  arcuate  ligament  of  the  Diaphragm.  It  then  runs  ventrad  of 
the  Quadratus  lumborum  muscle,  perforates  the  Transversalis  muscle,  and  passes 
distad  between  it  and  the  Internal  oblique  muscle,  to  be  distributed  in  the 
same  manner  as  the  lower  intercostal  nerves.  It  communicates  with  the  ilio- 
hypogastric  branch  of  the  lumbar  plexus,  and  is  frequently  connected  with  the 
first  lumbar  nerve  by  a  slender  branch,  the  thoracico-lumbar  nerve,  which  descends 
in  the  substance  of  the  Quadratus  lumborum  muscle.  It  gives  a  branch  to  the 
Pyramidalis  muscle. 

The  Cutaneous  Branches. — There  are  two  cutaneous  branches,  a  ventral  and  a 
lateral. 

The  Ventral  Cutaneous  Branch  is  a  terminal  branch  and  is  a  direct  prolongation 
of  the  intercostal.  It  supplies  an  area  of  skin  of  the  abdominal  wall  between 
the  umbilicus  and  pubis. 

The  Lateral  Cutaneous  Branch  (ramus  cutaneus  lateralis  [abdominalis]  inter- 
costalis  XII)  is  remarkable  for  its  large  size;  it  perforates  the  Internal  and  Exter- 
nal oblique  muscles,  passes  over  the  crest  of  the  ilium  ventrad  of  the  iliac  branch 
of  the  ilio-hypogastric,  and  is  distributed  to  the  integument  of  the  front  part  of 
the  gluteal  region,  some  of  its  filaments  extending  as  low  down  as  the  trochanter 
major.  It  does  ijot  divide  into  a  ventral  and  a  dorsal  branch,  like  the  other 
lateral  cutaneous  branches  of  the  intercostal  nerves. 

Surgical  Anatomy. — The  lower  seven  intercostal  nerves  and  the  ilio-hypogastric  from  the 
first  lumbar  nerve  supply  the  skin  of  the  abdominal  wall.  They  run  caudad  and  inward 
fairly  equidistant  from  each  other.  The  sixth  and  seventh  supply  the  skin  over  the  "pit  of  the 
stomach;"  the  eighth  corresponds  to  about  the  position  of  the  middle  linea  transversa;  the 
tenth  to  the  umbilicus;  and  the  ilio-hypogastric  supplies  the  skin  over  the  pubes  and  external 
abdominal  ring.  There  are  several  points  of  surgical  significance  about  the  distribution  of  these 
nerves,  and  it  is  important  to  remember  their  origin  and  course,  for  in  many  diseases  affecting 
the  nerve-trunks  at  or  near  their  origin  the  pain  is  referred  to  their  peripheral  origins.  Thus 
in  Pott's  disease  of  the  spine  children  will  often  be  brought  to  the  surgeon  suffering  from  pain 
in  the  belly.  This  is  due  to  the  fact  that  the  nerves  are  irritated  at  the  seat  of  disease  as  they 
issue  from  the  spinal  canal.  When  the  irritation  is  confined  to  a  single  pair  of  nerves,  the  sen- 
sation complained  of  is  often  a  feeling  of  constriction,  as  if  a  cord  were  tied  around  the  abdomen; 
and  in  these  cases  the  situation  of  the  sense  of  constriction  may  serve  to  localize  the  disease  in 
the  spinal  column.  In  other  cases,  where  the  bone  disease  is  more  extensive  and  two  or  more 
nerves  are  involved,  a  more  diffused  pain  in  the  abdomen  is  complained  of.  A  similar  conditon 
is  sometimes  present  in  affections  of  the  cord  itself,  as  in  tabes  dorsalis. 

Again,  it  must  be  borne  in  mind  that  the  same  nerves  which  supply  the  skin  of  the  abdomen 
supply  also  the  muscles  which  constitute  the  greater  part  of  the  abdominal  wall.  Hence,  it  follows 
that  any  irritation  applied  to  the  peripheral  terminations  of  the  cutaneous  branches  in  the 
skin  of  the  abdomen  is  immediately  followed  by  reflex  contraction  of  the  abdominal  muscles. 
A  good  practical  illustration  of  this  may  sometimes  be  seen  in  watching  two  surgeons  examine 
the  abdomen  of  the  same  patient.  One,  whose  hand  is  cold,  causes  the  muscles  of  the  abdom- 
inal wall  to  at  once  contract  and  the  belly  to  become  rigid,  and  thus  not  nearly  so  suitable 
for  examination;  the  other,  who  has  taken  the  precaution  to  warm  his  hand,  examines  the 
abdomen  without  exciting  any  reflex  contraction.  The  supply  of  both  muscles  and  skin  from 
the  same  source  is  of  importance  in  protecting  the  abdominal  viscera  from  injury.  A  blow 
on  the  abdomen,  even  of  a  severe  character,  will  do  no  injury  to  the  viscera  if  the  muscles  are 
in  a  condition  of  firm  contraction;  whereas  in  cases  where  the  muscles  have  been  taken  unawares, 
and  the  blow  has  been  struck  while  they  were  in  a  state  of  rest,  an  injury  insufficient  to  produce 
any  lesion  of  the  abdominal  wall  has  been  attended  with  rupture  of  some  of  the  abdominal  con- 
tents. The  importance,  therefore,  of  immediate  reflex  contraction  upon  the  receipt  of  an  injury 


THE  VENTRAL  DIVISIONS  OF  THE  LUMBAR  NERVES     1015 

c-innot  be  overestimated,  and  the  intimate  association  of  the  cutaneous  and  muscular  fibres  in 
the  same  nerve  produces  a  much  more  immediate  response  on  the  part  of  the  muscles  to  any 
peripheral  stimulation  of  the  cutaneous  filaments  than  would  be  the  case  if  the  two  sets  of  fibres 
were  derived  from  independent  sources. 

Again,  the  nerves  supplying  the  abdominal  muscles  and  skin  are  derived  from  the  lower  inter- 
costal nerves  and  are  intimately  connected  with  the  sympathetic  supplying  the  abdominal  viscera 
through  the  lower  thoracic  ganglia  from  which  the  splanchnic  nerves  are  derived.  In  conse- 
quence of  this,  in  rupture  of  the  abdominal  viscera  and  in  acute  peritonitis  the  muscles  of  the 
belly-wall  become  firmly  contracted,  and  thus  as  far  as  possible  preserve  the  abdominal  contents 
in  a  condition  of  rest. 

THE  LUMBAR  NERVES  (NN.  LUMBALES). 

The  lumbar  nerves  are  five  in  number  on  each  side.  The  first  lumbar  nerve 
appears  between  the  first  and  second  lumbar  vertebrae,  and  the  last  between  the 
last  lumbar  vertebra  and  the  base  of  the  sacrum. 

The  Roots  of  the  Lumbar  Nerves. 

The  roots  of  the  lumbar  nerves  are  the  largest,  and  their  filaments  the  most 
numerous,  of  all  the  spinal  nerves,  and  they  are  closely  aggregated  together  upon 
the  lower  end  of  the  cord.  The  ventral  roots  are  the  smaller,  but  there  is  not  the 
same  disproportion  between  them  and  the  dorsal  roots  as  in  the  cervical  nerves. 
The  roots  of  these  nerves  have  a  vertical  direction,  and  are  of  considerable  length, 
more  especially  the  lower  ones,  since  the  spinal  cord  does  not  extend  beyond  the 
first  lumbar  vertebra.  The  roots  become  joined  in  the  intervertebral  foramina, 
and  the  nerves  so  formed  divide  at  their  exit  into  two  divisions,  dorsal  and  ventral. 

The  Dorsal  Divisions  of  the  Lumbar  Nerves  (Kami  Posteriores). 

The  dorsal  divisions  of  the  lumbar  nerves  diminish  in  size  from  above  down- 
ward; they  pass  dorso-laterad  between  the  transverse  processes,  and  divide  into 
medial  and  lateral  branches. 

The  Medial  Branches  (rami  mediales). — The  medial  branches,  the  smaller, 
pass  inward  close  to  the  articular  processes  of  the  vertebrae,  and  supply  the  Multi- 
fidus  spinse  and  Interspinales  muscles. 

The  Lateral  Branches  (rami  later  ales). — The  lateral  branches  supply  the 
Erector  spinse  and  Intertransverse  muscles.  From  the  three  upper  branches 
cutaneous  nerves  are  derived  which  pierce  the  aponeurosis  of  the  Latissimus  dorsi 
muscle  and  descend  over  the  dorsum  of  the  crest  of  the  ilium,  to  be  distributed 
to  the  integument  of  the  gluteal  region,  some  of  the  filaments  passing  as  far  as  the 
trochanter  major  (Fig.  672). 

The  dorsal  division  of  the  fifth  lumbar  nerve  usually  sends  a  branch  which 
forms  a  loop  with  the  dorsal  division  of  the  first  sacral  nerve. 

The  Ventral  Divisions  of  the  Lumbar  Nerves  (Rami  Anteriores). 

The  ventral  divisions  of  the  lumbar  nerves  increase  in  size  from  above  cau- 
dad.  At  their  origin  they  communicate  with  the  lumbar  ganglia  of  the  sym- 
pathetic by  long,  slender  filaments,  which  accompany  the  lumbar  arteries  around 
the  sides  of  the  bodies  of  the  vertebrae,  beneath  the  Psoas  muscle.  The  nerves  pass 
obliquely  outward  behind  the  Psoas  magnus  or  between  its  fasciculi,  distributing 
filaments  to  it  and  the  Quadratus  lumborum.  The  ventral  divisions  of  the  five 
lumbar,  five  sacral,  and  first  coccygeal  nerve  constitute  the  lumbo-sacral  plexus 
(plexus  lumbosacralis).  This  is  subdivided  into  the  lumbar  plexus,  the  sacral 
plexus,  and  the  pudendal  plexus.  The  ventral  divisions  of  the  four  upper  nerves 


1016 


THE  NER  VE  SYSTEM 


are  connected  together  in  this  situation  by  anastomotic  loops,  and  form  the  lumbar 
plexus.  The  ventral  division  of  the  fifth  lumbar,  joined  with  a  branch  from  the 
fourth,  descends  across  the  base  of  the  sacrum  to  join  the  ventral  division-  of  the 
first  sacral  nerve  and  assists  in  the  formation  of  the  sacral  plexus.  The  cord  result- 
ing from  the  union  of  the  fifth  lumbar  and  the  branch  from  the  fourth  is  called 
the  lumbo-sacral  cord  (truncus  lumbosacralis)  (Figs.  670  and  675). 

The  Lumbar  Plexus  (Plexus  Lumbalis)  (Figs.  669,  670). 

The  lumbar  plexus  is  formed  by  the  loops  of  communication  between  the 
ventral  divisions  of  the  four  upper  lumbar  nerves.  The  plexus  is  narrow  above, 
and  often  connected  with  the  last  thoracic  nerve  by  a  slender  branch,  the  dorsi- 
lumbar  nerve.  The  plexus  is  broad  below,  where  it  is  joined  to  the  sacral  plexus 
by  the  lumbo-sacral  cord.  The  lumbar  plexus  is  situated  in  the  substance  of 
the  Psoas  muscle  near  its  dorsal  part,  in  front  of  the  transverse  processes  of 
the  lumbar  vertebrae. 

The  mode  in  which  the  plexus  is  arranged  varies  in  different  subjects.1  It 
differs  from  the  brachial  plexus  in  not  forming  an  intricate  interlacement,  but  the 

several  nerves  of  distribution 

-  ^u  ,  XI I 

arise  from  one  or  more  of 
the  spinal  nerves  in  the  fol- 
lowing manner:  The  first 
lumbar  nerve  receives  a 
branch  from  the  last  tho- 
racic, gives  off  a  larger 
branch,  which  subdivides 
into  the  ilio-hypogastric  and 
ilio-inguinal  nerves;  the  first 
lumbar  also  gives  off  a  com- 
municating branch  which 
IV  passes  down  to  the  second 
tumbar  nerve,  and  a  third 
branch  which  unites  with 
,  a  branch  of  the  second 
lumbar,  to  form  the  genito- 
femoral  nerve.  The  second, 
third,  and  fourth  lumbar 
nerves  divide  into  ventral 
and  dorsal  divisions.  The 
ventral  division  of  the  second 
divides  into  two  branches,  one  of  which  joins  with  the  above-mentioned  branch 
of  the  first  nerve  to  form  the  genito-femoral ;  the  other  unites  with  the  ventral 
division  of  the  third  nerve,  and  a  part  of  the  ventral  division  of  the  fourth  nerve 
to  form  the  obturator  nerve.  The  remainder  of  the  ventral  division  of  the  fourth 
nerve  passes  down  to  communicate  with  the  fifth  lumbar  nerve.  The  dorsal 
divisions  of  the  second  and  third  nerves  divide  into  two  branches,  a  smaller 
branch  from  each  uniting  to  form  the  lateral  or  external  cutaneous  nerve,  and  a  larger 
branch  from  each,  which  join  the  whole  of  the  dorsal  division  of  the  fourth 
lumbar  nerve  to  form  the  femoral  or  anterior  crural  nerve.  The  accessory  obturator, 
when  it  exists,  is  formed  by  the  union  of  two  small  branches  given  off  from  the 
third  and  fourth  nerves. 

From  this  arrangement  it  follows  that  the  ilio-hypogastric  and  ilio-inguinal 
are  derived  entirely  from  the  first  lumbar  nerve;  the  genito-femoral  from  the  first 


ILIO-HYPOGASTRIC 
ILIO-INGUINAL 


GENITO-FEMORAL 


LATERAL 
CUTANEOUS 


TO  PSOAS   AND 
ILIACUS 


FEMORAL  (ANTFRIOR 
CRURAL) 


OBTURATOR  l(- 
OBTURATOR^, 


FIG.  669. — Diagram  of  the  lumbar  plexus. 


1  For  statistical  studies  of  the  variations  encountered  in  different  individuals,  see  the  article  by  Bardeen 
in  the  American  Journal  of  Anatomy. 


THE  LUMBAR  PLEXUS 


1017 


and  second  nerves;  the  lateral  cutaneous  from  the  second  and  third;  the  femoral 
and  obturator  by  fibres  derived  from  the  second,  third,  and  fourth;  and  the 
accessory  obturator,  when  it  exists,  from  the  third  and  fourth. 
Branches  (Figs.  669  and  670). — The  branches  of  the  lumbar  plexus  are — the 


Ilio-hypogastric. 
Ilio-inguinal. 
Genito-femoral. 
Lateral  cutaneous. 


Obturator. 
Accessory  obturator. 
Femoral  (Anterior  crural). 


The  Ilio-hypogastric  Nerve  (n.  iliohypogastricus)  (Figs.  669  and  670). — The 
ilio-hypogastric  nerve  arises  from  the  first  lumbar  nerve.  It  emerges  from  the 
outer  border  of  the  Psoas  muscle  at  its  upper  part,  and  crosses  obliquely  ventrad 
of  the  Quadratus  lumborum  to  the  crest  of  the  ilium.  It  then  perforates  the 
Transversalis  muscle  dorsally  near  the  crest  of  the  ilium.  It  gives  off  muscular 
branches  (rami  muscuiares}  to  the  abdominal  wall,  and  divides  between  the  Trans- 
versalis and  the  Internal  oblique  into  two  cutaneous  branches,  iliac  and  hypogastric. 


FIG.  670. — The  lumbar  plexus  and  its  branches. 


The  Iliac  Branch  (ramus  cutaneus  lateralis)  pierces  the  Internal  and  External 
oblique  muscles  immediately  above  the  crest  of  the  ilium,  and  is  distributed  to  the 
integument  of  the  gluteal  region,  behind  the  lateral  cutaneous  branch  of  the  last 
thoracic  nerve  (Fig.  676).  The  size  of  this  nerve  bears  an.  in  verse  proportion  to 
that  of  the  cutaneous  branch  of  the  last  thoracic  nerve. 


1018  THE  NERVE  SYSTEM 

The  Hypogastric  Branch  (ramus  cutaneus  anterior)  (Fig.  671)  continues  onward  be- 
tween the  Internal  oblique  and  Transversalis  muscles.  It  then  pierces  the  Internal 
oblique,  and  becomes  cutaneous  by  perforating  the  aponeurosis  of  the  External 
oblique,  about  an  inch  (2  cm.)  above  and  a  little  laterad  of  the  external  abdominal 
ring,  and  is  distributed  to  the  integument  of  the  hypogastric  region.  The  ilio- 
hypogastric  nerve  communicates  with  the  last  thoracic  and  ilio-inguinal  nerves. 

The  Ilio-inguinal  Nerve  (n.  ilioinguinalis)  (Figs.  669,  670,  and  671). — The  ilio- 
inguinal  nerve,  smaller  than  the  preceding,  arises  with  it  from  the  first  lumbar 
nerve.  It  emerges  from  the  outer  border  of  the  Psoas  muscle  just  below  the  ilio- 
hypogastric  nerve,  and,  passing  obliquely  across  the  Quadratus  lumborum  and 
Iliacus  muscles,  perforates  the  Transversalis  near  the  forepart  of  the  crest  of  the 
ilium,  and  communicates  with  the  ilio-hypogastric  nerve  between  that  muscle  and 
the  Internal  oblique.  The  nerve  then  pierces  the  Internal  oblique,  distributing 
muscular  branches  (rami  muscidares)  to  it,  and,  accompanying  the  spermatic 
cord  through  the  external  abdominal  ring,  is  distributed  to  the  integument  of  the 
upper  and  inner  part  of  the  thigh,  and  to  the  scrotum  in  the  male  (nn.  scrotales 
anteriores)  and  to  the  labium  majus  in  the  female  (nn.  labiales  anteriores).  The 
size  of  this  nerve  is  in  inverse  proportion  to  that  of  the  ilio-hypogastric.  Occa- 
sionally it  is  very  small,  and  ends  by  joining  the  ilio-hypogastric;  in  such  cases  a 
branch  from  the  ilio-hypogastric  takes  the  place  of  the  ilio-inguinal,  or  the  ilio- 
inguinal  nerve  may  be  altogether  absent. 

The  Genito-femoral  or  Genito-crural  Nerve  (n.  genitofemoralis)  (Figs.  669  and 
670)  arises  from  the  first  and  second  lumbar  nerves.  It  passes  obliquely  through 
the  substance  of  the  Psoas  muscle,  and  emerges  from  its  inner  border  at  a  level 
corresponding  to  the  intervertebral  substance  between  the  third  and  fourth 
lumbar  vertebrae;  it  then  descends  on  the  surface  of  the  Psoas  muscle,  under  cover 
of  the  peritoneum,  and  divides  into  a  genital  and  a  femoral  branch. 

The  Genital  Branch  or  External  Spermatic  Nerve  (n.  spermaticus  externus)  passes 
outward  on  the  Psoas  magnus,  and  pierces  the  fascia  transversalis,  or  passes 
through  the  internal  abdominal  ring;  in  the  male  it  then  descends  along  the  back 
part  of  the  spermatic  cord  to  the  scrotum,  and  supplies  the  Cremaster  muscle. 
In  the  female  it  accompanies  the  round  ligament,  and  is  lost  upon  it. 

The  Femoral  Branch  or  Lumbo-inguinal  Nerve  (n.  lumboinguinalis)  (Fig.  671) 
descends  on  the  external  iliac  artery,  sending  a  few  filaments  around  it,  and, 
passing  beneath  Poupart's  ligament  to  the  thigh,  enters  the  sheath  of  the  femoral 
vessels,  lying  superficial  and  a  little  external  to  the  femoral  artery.  It  pierces  the 
anterior  layer  of  the  sheath  of  the  vessels,  and,  becoming  superficial  by  passing 
through  the  fascia  lata,  it  supplies  the  skin  of  the  anterior  aspect  of  the  thigh  as 
far  as  midway  between  the  pelvis  and  knee.  On  the  front  of  the  thigh  it  com- 
municates with  the  outer  branch  of  the  middle  cutaneous  nerve,  derived  from  the 
femoral  nerve.  A  few  filaments  from  this  nerve  may  be  traced  on  to  the  femoral 
artery;  they  are  derived  from  the  nerve  as  it  passes  beneath  Poupart's  ligament. 

The  Lateral  Cutaneous  Nerve,  (n.  cutaneus  femoris  lateralis)  (Figs.  669,  670, 
671,  and  672). — The  lateral  cutaneous  nerve  arises  from  the  second  and  third 
lumbar  nerves.  It  emerges  from  the  outer  border  of  the  Psoas  muscle  about  its 
middle,  and  crosses  the  Iliacus  muscle  obliquely,  toward  the  anterior1  superior 
spine  of  the  ilium.  It  then  passes  under  Poupart's  ligament  and  over  the  Sartorius 
muscle  into  the  thigh,  where  it  divides  into  two  branches,  anterior  and  posterior. 

The  Anterior  Branch  descends  in  an  aponeurotic  canal  formed  in  the  fascia  lata, 
becomes  superficial  about  four  inches  below  Poupart's  ligament,  and  divides  into 
branches  which  are  distributed  to  the  integument  along  the  anterior  and  outer 
part  of  the  thigh,  as  far  down  as  the  knee.  This  nerve  occasionally  communicates 
with  a  branch  of  the  long  saphenous  nerve  in  front  of  the  knee-joint. 


1  Cf.  note  on  p.  1005. 


THE    LUMBAR    PLEXUS 


1019 


Rural  or 
external  f 
sapfienous. 


Femoral  or 
anterior  crural. 


-Anterior  tibial. 


—  Anterior  division 

of  obturator. 
Internal 
cutaneous. 


Saphenous. 


FIG.  671. — Cutaneous  nerves  of  lower 
extremity.     Front  view. 


FIG.  672. — Nerves  of  the  lower  extremity. 
Front  view. 


1020  THE  NERVE  SYSTEM 

The  Posterior  Branch  pierces  the  fascia  lata,  and  subdivides  into  branches  which 
pass  dorsad  across  the  outer  and  posterior  surface  of  the  thigh,  supplying  the 
integument  from  the  crest  of  the  ilium  as  far  as  the  knee. 

The  Obturator  Nerve  (n.  obturatorius)  (Figs.  669,  670,  and  672). — The  obturator 
nerve  supplies  the  Obturator  externus  and  Adductor  muscles  of  the  thigh,  the 
articulations  of  the  hip  and  knee,  and  occasionally  the  integument  of  the  thigh 
and  leg.  It  arises  by  three  branches — from  the  second,  the  third,  and  the  fourth 
lumbar  nerves.  Of  these,  the  branch  from  the  third  is  the  largest,  while  that 
from  the  second  is  often  very  small.  It  descends  through  the  inner  fibres  of  the 
Psoas  muscle,  and  emerges  from  its  inner  border  near  the  brim  of  the  pelvis;  it  then 
runs  along  the  lateral  wall  of  the  pelvis,  above  the  obturator  vessels,  to  the  upper 
part  of  the  obturator  foramen,  where  it  enters  the  thigh,  and  divides  into  an 
anterior  and  a  posterior  branch,  separated  by  some  of  the  fibres  of  the  Obturator 
externus  muscle,  and  lower  down  by  the  Adductor  brevis  muscle. 

The  Anterior  Branch  (ramus  anterior}  (Fig.  672)  passes  down  in  front  of  the 
Adductor  brevis,  being  covered  by  the  Pectineus  and  Adductor  longus,  and  at  the 
lower  border  of  the  latter  muscle  communicates  with  the  internal  cutaneous  and 
saphenous  nerves,  forming  a  kind  of  plexus.  It  then  descends  upon  the  femoral 
artery,  upon  which  it  is  finally  distributed.  The  nerve,  near  the  obturator 
foramen,  gives  off  an  articular  branch  to  the  hip-joint.  Behind  the  Pectineus  it 
distributes  muscular  branches  to  the  Adductor  longus  and  Gracilis,  and  usually 
to  the  Adductor  brevis,  and  in  rare  cases  to  the  Pectineus,  and  receives  a  com- 
municating branch  from  the  accessory  obturator  nerve. 

Occasionally  the  communicating  branch  to  the  internal  cutaneous  and  saphe- 
nous nerves  is  continued  down,  as  a  cutaneous  branch  (ramus  cutaneus],  to  the 
thigh  and  leg.  When  this  is  so,  this  occasional  cutaneous  branch  emerges  from 
beneath  the  lower  border  of  the  Adductor  longus,  descends  along  the  posterior 
margin  of  the  Sartorius  to  the  inner  side  of  the  knee,  where  it  pierces  the  deep 
fascia,  communicates  with  the  long  saphenous  nerve,  and  is  distributed  to  the 
integument  of  the  inner  side  of  the  leg  as  low  down  as  its  middle.  When  this 
communicating  branch  is  small  its  place  is  supplied  by  the  internal  cutaneous 
nerve. 

The  Posterior  Branch  (ramus  posterior)  pierces  the  Obturator  externus,  sending 
branches  to  supply  it,  and  passes  behind  the  Adductor  brevis  on  the  front  of  the 
Adductor  magnus,  where  it  divides  into  numerous  muscular  branches,  which 
supply  the  Adductor  magnus,  and  the  Adductor  brevis  when  the  latter  does  not 
receive  a  branch  from  the  anterior  division  of  the  nerve.  One  of  the  branches 
gives  off  a  filament  to  the  knee-joint. 

The  Articular  Branch  for  the  Knee-joint  is  sometimes  absent;  it  perforates  the 
lower  part  of  the  Adductor  magnus,  and  enters  the  popliteal  space;  it  then 
descends  upon  the  popliteal  artery,  as  far  as  the  back  part  of  the  knee-joint, 
where  it  perforates  the  posterior  ligament,  and  is  distributed  to  the  synovial 
membrane.  It  gives  filaments  to  the  popliteal  artery  in  its  course. 

The  Accessory  Obturator  Nerve  or  the  Accessory  Anterior  Femoral  Nerve  of  Winslow 
(n.  obturatorius  accessorius  (Fig.  675). — The  accessory  obturator  nerve  is  not  con- 
stantly present.  It  is  of  small  size,  and  arises  by  separate  filaments  from  the 
third  and  fourth  lumbar  nerves.  It  descends  along  the  inner  border  of  the  Psoas 
muscle,  crosses  the  ascending  ramus  of  the  os  pubis,  and  passes  under  the  outer 
border  of  the  Pectineus  muscle,  where  it  divides  into  numerous  branches.  One 
of  these  supplies  the  Pectineus,  penetrating  its  under  surface;  another  is  dis- 
tributed to  the  hip-joint;  while  a  third  communicates  with  the  anterior  branch  of 
the  obturator  nerve.  When  this  nerve  is  absent  the  hip-joint  receives  two  branches 
from  the  obturator  nerve.  Occasionally  the  articular  branch  is  very  small,  and 
becomes  lost  in  the  capsule  of  the  hip-joint. 


THE  LUMBAR  PLEXUS  1021 

The  Femoral  or  Anterior  Crural  Nerve  (n.  femoralis)  (Figs.  669,  670,  and  672). — 
The  femoral  nerve  is  the  largest  branch  of  the  lumbar  plexus.  It  supplies 
muscular  branches  to  the  Iliacus,  Pectineus,  and  all  the  muscles  on  the  front 
of  the  thigh,  excepting  the  Tensor  fasciae  femoris;  cutaneous  filaments  to  the 
front  and  inner  side  of  the  thigh,  and  to  the  leg  and  foot  (Fig.  667);  and 
articular  branches  to  the  hip  and  knee.  It  arises  from  the  second,  third,  and 
fourth  lumbar  nerves,  sometimes  from  the  first  or  fifth  as  well.  It  descends 
through  the  fibres  of  the  Psoas  muscle,  emerging  from  this  muscle  at  the  lower 
part  of  its  outer  border,  and  passes  caudad  between  it  and  the  Iliacus  muscle,  and 
beneath  Poupart's  ligament,  into  the  thigh,  where  it  becomes  somewhat  flattened, 
and  divides  into  an  anterior  and  a  posterior  part.  Under  Poupart's  ligament  it 
is  separated  from  the  femoral  artery  by  a  portion  of  the  Psoas  muscle,  and  lies 
beneath  the  iliac  fascia. 

Within  the  abdomen  the  femoral  nerve  gives  off  from  its  outer  side  some  small 
muscular  branches  to  the  Iliacus,  and  a  branch  to  the  femoral  artery  which  is 
distributed  upon  the  upper  part  of  that  vessel.  The  origin  of  this  branch  varies; 
it  occasionally  arises  higher  than  usual,  or  it  may  arise  lower  down  in  the  thigh. 

External  to  the  pelvis  the  following  branches  are  given  off : 

From  the  Anterior  Division.  From  the  Posterior  Division. 
Middle  cutaneous.  Long  saphenous. 

Internal  cutaneous.  Muscular. 

Muscular.  Articular. 

The  middle  and  internal  cutaneous  branches  of  the  femoral  nerve  are  the 
rami  cutanei  anteriores  n.  femoralis  of  the  new  nomenclature. 

The  Middle  Cutaneous  Nerve  (Figs.  671  and  672)  pierces  the  fascia  lata  (generally 
the  Sartorius  muscle  also)  about  three  inches  (8  cm.)  below  Poupart's  ligament,  and 
divides  into  two  branches  (Fig.  671),  which  descends  in  immediate  proximity  along 
the  forepart  of  the  thigh,  to  supply  the  integument  as  low  as  the  front  of  the  knee, 
where  it  communicates  with  the  internal  cutaneous  nerve  and  the  patellar  branch 
of  the  saphenous  nerve,  to  form  the  patellar  plexus.  In  the  upper  part  of  the  thigh 
the  outer  division  of  the  middle  cutaneous  nerve  communicates  with  the  femoral 
branch  of  the  genito-femoral  nerve. 

The  Internal  Cutaneous  Nerve  (Fig.  671)  passes  obliquely  across  the  upper  part 
of  the  sheath  of  the  femoral  artery,  and  divides  in  front  or  at  the  inner  side  of  that 
vessel  into  two  branches,  anterior  and  posterior  or  internal. 

The  anterior  branch  runs  caudad  on  the  Sartorius,  perforates  the  fascia  lata 
at  the  lower  third  of  the  thigh,  and  divides  into  two  branches,  one  of  which  sup- 
plies the  integument  as  low  down  as  the  inner  side  of  the  knee;  the  other  crosses 
to  the  outer  side  of  the  patella,  communicating  in  its  course  with  the  nervus 
cutaneus  patellae,  a  branch  of  the  saphenous  nerve. 

The  posterior  or  internal  branch  descends  along  the  inner  border  of  the  Sartorius 
muscle  to  the  knee,  where  it  pierces  the  fascia  lata,  communicates  with  the  long 
saphenous  nerve,  and  gives  off  several  cutaneous  branches.  The  nerve  then 
passes  down  the  inner  side  of  the  leg,  to  the  integument  of  which  it  is  distributed. 
This  nerve,  beneath  the  fascia  lata,  at  the  lower  border  of  the  Adductor  longus, 
joins  in  a  plexiform  network  by  uniting  with  branches  of  the  saphenous  and 
obturator  nerves  (Fig.  672).  When  the  communicating  branch  from  the  obturator 
nerve  is  large  and  continued  to  the  integument  of  the  leg,  the  inner  branch  of  the 
internal  cutaneous  is  small  and  terminates  at  the  plexus,  occasionally  giving  off 
a  few  cutaneous  filaments. 

The  internal  cutaneous  nerve,  before  dividing,  gives  off  a  few  filaments,  which 
pierce  the  fascia  lata,  to  supply  the  integument  of  the  inner  side  of  the  thigh. 


1022  THE  NERVE  SYSTEM 

One  of  these  filaments  passes  through  the  saphenous  opening;  a  second  becomes 
subcutaneous  about  the  middle  of  the  thigh  (Fig.  671);  and  a  third  pierces  the 
fascia  at  its  lower  third  (Fig.  671). 

The  Muscular  Branches  of  the  Anterior  Division  (rami  musculares). — The  nerve 
to  the  Pectineus  is  often  duplicated;  it  arises  from  the  femoral  nerve  immediately 
below  Poupart's  ligament,  and  passes  inward  behind  the  femoral  sheath  to  enter 
the  anterior  surface  of  the  muscle.  The  nerve  to  the  Sartorius  arises  in  common 
with  the  middle  cutaneous. 

The  Saphenous,  Long  Saphenous  or  Internal  Saphenous  Nerve  (n.  saphenus] 
(Figs.  671  and  672)  is  the  largest  of  the  cutaneous  branches  of  the  femoral  nerve. 
It  approaches  the  femoral  artery  where  this  vessel  passes  beneath  the  Sartorius, 
and  lies  ventrad  of  it,  beneath  the  aponeurotic  covering  of  Hunter's  canal,  as  far 
as  the  opening  in  the  lower  part  of  the  Adductor  magnus.  It  then  leaves  the 
artery,  and  proceeds  distally  along  the  inner  side  of  the  knee,  beneath  the  Sartorius 
muscle,  pierces  the  fascia  lata  opposite  the  interval  between  the  tendons  of  the 
Sartorius  and  Gracilis  muscles,  and  becomes  subcutaneous.  The  nerve  then 
passes  along  the  inner  side  of  the  leg  (Fig.  671),  accompanied  by  the  internal 
saphenous  vein,  descends  behind  the  internal  border  of  the  tibia,  and,  at  the 
lower  third  of  the  leg,  divides  into  two  branches :  one  continues  its  course  along  the 
margin  of  the  tibia,  terminating  at  the  inner  ankle;  the  other  passes  in  front  of 
the  ankle,  and  is  distributed  to  the  integument  along  the  inner  side  of  the  foot,  as 
far  as  the  great  toe,  communicating  with  the  internal  branch  of  the  musculo- 
cutaneous  nerve. 

The  saphenous  nerve  about  the  middle  of  the  thigh  gives  off  a  communicating 
branch  which  joins  the  plexus  formed  by  the  obturator  and  internal  cutaneous 
nerves. 

At  the  inner  side  of  the  knee  it  gives  off  a  large  patellar  branch,  the  nervus 
cutaneus  patellae  (ramus  infrapatellaris] ,  which  pierces  the  Sartorius  and  fascia 
lata,  and  is  distributed  to  the  integument  in  front  of  the  patella.  This  nerve  com- 
municates above  the  knee  with  the  anterior  branch  of  the  internal  cutaneous  and 
with  the  middle  cutaneous;  below  the  knee,  with  other  branches  of  the  saphenous; 
and  on  the  outer  side  of  the  joint,  with  branches  of  the  external  cutaneous  nerve, 
forming  a  plexiform  network,  the  patella  plexus  (plexus  patellae).  The  cutaneous 
nerve  of  the  patella  is  occasionally  small,  and  terminates  by  joining  the  internal 
cutaneous,  which  supplies  its  place  in  front  of  the  knee. 

Below  the  knee  the  branches  of  the  saphenous  nerves  are  distributed  to  the 
integument  of  the  front  and  inner  side  of  the  leg,  communicating  with  the  cuta- 
neous branches  from  the  internal  cutaneous  or  from  the  obturator  nerve.  The 
nerve  also  sends  filaments  to  the  ankle-joint. 

The  Muscular  Branches  of  the  Posterior  Division. — The  muscular  branches  of  the 
posterior  division  supply  the  four  parts  of  the  Quadriceps  extensor  muscle. 

The  branch  to  the  Rectus  muscle  enters  its  under  surface  high  up,  sending  off  a 
small  filament  to  the  hip-joint. 

The  branch  to  the  Vastus  externus  muscle,  of  large  size,  follows  the  course  of 
the  descending  branch  of  the  external  circumflex  artery  to  the  lower  part  of  the 
muscle.  It  gives  off  an  articular  filament  to  the  knee-joint. 

The  branch  to  the  Vastus  internus  muscle  is  a  long  branch  which  runs  down 
on  the  outer  side  of  the  femoral  vessels  in  company  with  the  saphenous  nerve 
for  its  upper  part.  It  enters  the  muscle  about  its  middle,  and  gives  off  a  fila- 
ment which  can  usually  be  traced  caudad  on  the  surface  of  the  muscle  to  the 
knee-joint. 

The  branch  to  the  Crureus  muscle  enters  the  muscle  on  its  anterior  surface 
about  the  middle  of  the  thigh,  and  sends  a  filament  through  the  muscle  to  the 
Subcrureus  and  the  knee-joint. 


THE  DORSAL  DIVISIONS  OF  THE  SACRAL  NERVES        1Q23 

The  articular  branch  to  the  hip-joint  is  derived  from  the  nerve  to  the  Rectus 
muscle. 

The  articular  branches  to  the  knee-joint  are  three  in  number.  One,  a  long,  slender 
filament,  is  derived  from  the  nerve  to  the  Vastus  extern  us  muscle;  it  penetrates  the 
capsular  ligament  of  the  joint  on  its  anterior  aspect.  Another  is  derived  from 
the  nerve  to  the  Vastus  internus  muscle.  It  can  usually  be  traced  downward 
on  the  surface  of  this  muscle  to  near  the  joint;  it  then  penetrates  the  muscle 
and  accompanies  the  deep  branch  of  the  ariastomotica  magna  artery,  pierces  the 
capsular  ligament  of  the  joint  on  its  inner  side,  and  supplies  the  synovial 
membrane.  The  third  branch  is  derived  from  the  nerve  to  the  Crureus. 


THE  SACRAL  AND  COCCYGEAL  NERVES  (NN.  SACRALES  ET  COGGYGEUS). 

The  sacral  nerves  are  five  in  number  on  each  side.  The  four  upper  ones  pass 
from  the  sacral  canal  through  the  sacral  foramina;  the  fifth  through  the  foramen 
between  the  sacrum  and  coccyx. 

The  Roots  of  the  Upper  Sacral  Nerves. 

The  roots  of  the  upper  sacral  nerves  are  the  largest  of  all  the  spinal  nerves; 
while  those  of  the  lower  sacral  and  the  coccygeal  nerve  are  the  smallest.  They  are 
longer  than  those  of  any  of  the  other  spinal  nerves,  on  account  of  the  spinal  cord 
'  not  extending  beyond  the  first  lumbar  vertebra.  From  their  great  length,  and  the 
appearance  they  present  in  connection  with  their  attachment  to  the  spinal  cord, 
the  roots  of  origin  of  these  nerves  are  called  collectively  the  cauda  equina. 

Each  sacral  and  coccygeal  nerve  separates  into  two  divisions,  dorsal  and 
ventral. 

The  Dorsal  Divisions  of  the  Sacral  Nerves  (Rami  Posteriores)    (Fig.  673). 

The  dorsal  divisions  of  the  sacral  nerves  are  small,  diminish  in  size  from  above 
caudad,  and  emerge,  except  the  last,  from  the  sacral  canal  by  the  dorsal  sacral 
foramina. 

The  Upper  Sacral  Nerves. — Each  of  the  three  upper  ones  is  covered,  at  its 
exit  from  the  sacral  canal,  by  the  Multifidus  spinse  muscle,  and  divides  into  a 
medial  branch  and  a  lateral  branch. 

The  Medial  Branches  (ramus  medialis). — The  medial  branches  are  small,  and 
supply  the  Multifidus  spinse  muscle. 

The  Lateral  Branches  (ramus  later  alls'). — The  lateral  branches  join  with  one 
another,  and  with  the  last  lumbar  and  fourth  sacral  nerves,  in  the  form  of  loops  on 
the  dorsal  surface  of  the  sacrum,  constituting  the  dorsal  sacral  plexus.  From  these 
loops  branches  pass  to  the  outer  surface  of  the  great  sacro-ischiatic  ligament,  where 
they  form  a  second  series  of  loops  beneath  the  Gluteus  maximus  muscle.  Cuta- 
neous branches  from  this  second  series  of  loops,  usually  two  or  three  in  number, 
pierce  the  Gluteus  maximus  muscle  along  a  line  drawn  from  the  posterior  superior 
spine  of  the  ilium  to  the  tip  of  the  coccyx.  They  supply  the  integument  over  the 
dorsal  part  of  the  gluteal  region. 

The  Lower  Sacral  Nerves. — The  dorsal  divisions  of  the  two  lower  sacral 
nerves  are  situated  below  the  Multifidus  spinae  muscle.  They  are  of  small  size, 
and  do  not  divide  into  medial  and  lateral  branches,  but  join  with  each  other, 
and  with  the  dorsal  division  of  the  coccygeal  nerve  to  form  the  dorsal  sacro- 
coccygeal  nerve,  which  passes  through  the  sacro-sciatic  ligament,  and  forms  loops 
on  the  back  of  the  sacrum,  filaments  from  which  supply  the  Extensor  coccygeus 
and  the  integument  over  the  coccyx. 


1024 


THE  NERVE  SYSTEM 


FIG.  673. — The  posterior  sacral  nerves. 


Femoral  artery. 


Coccygeal. 
'Br.  to'  Br.  to 

LEVATOH   ANI.    SPHINCTER   ANI 

FIG.  674. — Side  view  of  pelvis,  showing  sacral  nerves. 


Br.  to 

COCCYGEUS. 


THE   VENTRAL  DIVISION  OF  THE  COCCYGEAL  NERVE     1Q25 

The  Ventral  Divisions  of  the  Sacral  Nerves  (Rami  Anteriores)  (Fig.  675). 

The  ventral  divisions  of  the  sacral  nerves  diminish  in  size  from  above  down- 
ward. The  four  upper  ones  emerge  from  the  anterior  sacral  foramina;  the  ventral 
division  of  the  fifth,  after  emerging  from  the  vertebral  canal  through  its  terminal 
opening,  curves  forward  between  the  sacrum  and  the  coccyx.  All  the  ventral 
sacral  nerves  at  their  exit  from  the  sacral  foramina  communicate  with  the  sacral 
ganglia  of  the  sympathetic.  The  first  nerve  (Fig.  674),  of  large  size,  unites  with 
the  lumbo-sacral  cord  (truncus  lumbosacralis),  formed  by  the  fifth  lumbar,  and  a 
branch  from  the  fourth  lumbar  (n.  furcalis).  The  second  (Fig.  674),  equal  in 
size  to  the  preceding,  and  the  third  (n.  bigeminus)  (Fig.  674),  about  one-fourth 
the  size  of  the  second,  unite  with  this  trunk,  and  form,  with  a  small  fasciculus 
from  the  fourth,  the  sacral  plexus,  a  visceral  branch  being  given  off  from  the  third 
nerve  to  the  bladder  (Fig.  675). 

The  Fourth  Ventral  Sacral  Nerve  sends  a  branch  to  join  the  sacral  plexus.  The 
remaining  portion  of  the  nerve  divides  into  visceral  and  muscular  branches,  and  a 
communicating  filament  descends  to  join  the  fifth  sacral  nerve. 

The  visceral  branches  are  distributed  to  the  viscera  of  the  pelvis,  communicating 
with  the  sympathetic  nerve.  These  branches  ascend  upon  the  rectum  and  bladder, 
and  in  the  female  upon  the  vagina,  communicating  with  branches  of  the  sym- 
pathetic from  the  pelvic  plexus.  The  visceral  branches  of  the  third  and  fourth 
sacral  do  not  join  the  gangliated  cord. 

The  muscular  branches  are  distributed  to  the  Levator  ani,  Coccygeus,  and 
Sphincter  ani.  The  branch  to  the  Sphincter  ani  pierces  the  Levator  ani,  so  as  to 
reach  the  ischio-rectal  fossa,  where  it  is  found  lying  in  front  of  the  coccyx.  Cuta- 
neous filaments  arise  from  the  latter  branch,  which  supply  the  integument  between 
the  anus  and  coccyx.  Another  cutaneous  branch  is  frequently  given  off  from  this 
nerve,  though  sometimes  from  the  pudic  (Schwalbe).  It  perforates  the  great 
sacro-sciatic  ligament,  and,  winding  around  the  lower  border  of  the  Gluteus 
maximus,  supplies  the  skin  over  the  lower  and  inner  part  of  this  muscle. 

The  Fifth  Ventral  Sacral  Nerve,  after  passing  from  the  lower  end  of  the  sacral 
canal,  curves  forward  through  the  fifth  sacral  foramen,  formed  between  the  lower 
part  of  the  sacrum  and  the  transverse  process  of  the  first  piece  of  the  coccyx.  It 
pierces  the  Coccygeus  muscle,  and  descends  upon  its  anterior  surface  to  near  the 
tip  of  the  coccyx,  where  it  again  perforates  the  muscle,  to  be  distributed  to  the 
integument  over  the  back  part  and  side  of  the  coccyx.  This  nerve  communicates 
above  with  the  fourth  sacral  and  below  with  the  coccygeal  nerve,  and  supplies  the 
Coccygeus  muscle. 

The  Dorsal  Division  of  the  Coccygeal  Nerve. 

The  coccygeal  nerve  divides  into  its  ventral  and  dorsal  divisions  in  the  vertebral 
canal.  The  dorsal  division  is  the  smaller.  It  does  not  divide,  but  receives,  as 
already  mentioned,  a  communicating  branch  from  the  last  sacral,  and  is  lost 
in  the  integument  over  the  back  of  the  coccyx. 

The  Ventral  Division  of  the  Coccygeal  Nerve. 

The  ventral  division  of  the  coccygeal  nerve  is  a  delicate  filament  which  escapes 
at  the  termination  of  the  sacral  canal;  it  passes  caudad  behind  the  rudimentary 
transverse  process  of  the  first  piece  of  the  coccyx,  and  curves  ventrad  through 
the  notch  between  the  first  and  second  pieces,  piercing  the  Coccygeus  muscle  and 
descending  on  its  ventral  surface  to  near  the  tip  of  the  coccyx,  wrhere  it  again 

65 


1026 


THE  NERVE  SYSTEM 


pierces  the  muscle,  to  be  distributed  to  the  integument  over  the  back  part  and  side 
of  the  coccyx.  It  is  joined  by  a  branch  from  the  fifth  ventral  sacral  as  it  descends 
on  the  surface  of  the  Coccygeus  muscle. 

The  Pudendal  Plexus  (plexus  pudendus).  —  The  pudendal  plexus  is  formed  by 
fibres  obtained  from  the  ventral  divisions  of  the  first  three  sacral  nerves  and  by 
the  ventral  divisions  of  the  two  lower  sacral  nerves  and  the  coccygeal  nerve.  It 
is,  so  to  speak,  interpolated  in  the  sacral  plexus  and  is  considered  as  a  portion  of  it. 

The  Sacral  or  Sciatic  Plexus  (Plexus  Sacralis)  and  the  Pudic  or  Pudendal 
Plexus  (Plexus  Pudendalis)  (Fig.  675). 

The  sacral  plexus  is  formed  by  the  lumbo-sacral  cord,  the  ventral  divisions 
of  the  three  upper  sacral  nerves,  and  a  branch  from  the  fourth.  The  pudic  or 
pudendal  plexus  is  considered  with  the  sacral  plexus.  It  is  usually  composed 


FOURTH  LUMBAR 


FIFTH  LUMBAR 


FIRST  SACRAL 


SECOND  SACRAL 


THIRD  SACRAL 


FOURTH  SACRAL 


PERINEAL  BR.  TO  SPHINCTER 
LEVATOR  ANI 

,',  FIFTH  SACRAL 

N.TOCOCCYGEUS 


,y-— ^COCCYGEAL 
/? 


SCIATICA 


FIG.  675. — Plan  of  sacral  plexus  with  the  pudendal  plexus.     (Gerrish.) 

of  the  ventral  divisions  of  the  second,  third,  fourth  and  fifth  sacral  nerves  and 
the  coccygeal  nerve.  It  is  irregular  in  composition.  Prof.  Cunningham  says: 
"There  is  no  distinct  point  of  separation  between  the  two  plexuses.  On  the  con- 
trary, there  is  considerable  overlapping,  so  that  two  and  sometimes  three  of  the 
principal  nerves  derived  from  the  pudendal  plexus  have  their  origin  in  common 
with  nerves  of  the  sacral  plexus."  The  nerves  of  these  two  plexuses  proceed  in 
different  directions:  the  upper  ones  obliquely  caudad  and  outward,  the  lower 
ones  nearly  horizontally  outward,  and  they  all  unite  into  two  cords;  an  upper  and 
larger  cord,  which  is  formed  by  the  lumbo-sacral  cord  with  the  first,  second,  and 
the  greater  part  of  the  third  sacral  nerves;  and  a  lower  and  smaller  cord,  formed 
by  the  remainder  of  the  third,  with  a  portion  of  the  fourth  sacral  nerve.  The 
upper  cord  is  prolonged  into  the  great  sciatic  nerve  and  the  lower  into  the  pudic. 
Frequently  a  small  filament  is  given  off  from  the  second  sacral  nerve  to  join  the 
lower  cord. 


THE  SACRAL  OR  SCIATIC  PLEXUS  1027 

Each  of  the  nerves  which  form  the  plexus  joins  the  sympathetic  by  gray  rami 
communicantes.  White  rami  communicantes  join  the  third  sacral  and  sometimes 
also  the  second  and  fourth  sacrals  to  the  sympathetic. 

The  sacro-pudendal  plexus  is  triangular  in  form,  its  base  corresponding  with 
the  exit  of  the  nerves  from  the  sacrum,  its  apex  with  the  lower  part  of  the  great 
sacro-sciatic  foramen.  It  rests  upon  the  anterior  or  ventral  surface  of  the  Pyri- 
formis,  and  is  covered  ventrad  by  the  pelvic  fascia,  which  separates  it  from  the 
sciatic  and  pudic  branches  of  the  internal  iliac  artery  and  from  the  viscera  of  the 
pelvis.  The  sacral  plexus  proper  sends  branches  to  the  lower  extremity;  the 
pudendal  plexus  proper  is  largely  limited  to  supplying  the  perineum. 

Branches. — The  branches  of  the  sacro-pudendal  plexus  are  divided  into  col- 
lateral and  terminal  branches. 

Muscular. 
Superior  gluteal. 
Collateral  branches  •{  Inferior  gluteal. 

I  Small  sciatic. 
I  Perforating  cutaneous. 

Terminal  branches  { 

The  Muscular  Branches  (rami  musculares). — The  muscular  branches  supply  the . 
Pyriformis,  Obturator  internus,  the  two  Gemelli  and  the  Quadratus  femoris. 
The  branch  to  the  Pyriformis  muscle  arises  from  the  upper  two  sacral  nerves 
before  they  enter  the  plexus;  the  branch  to  the  Obturator  internus  muscle  arises 
at  the  junction  of  the  lumbo-sacral  and  first  sacral  nerves;  it  passes  out  of  the  pelvis 
through  the  great  sacro-sciatic  foramen  below  the  Pyriformis,  crosses  the  spine 
of  the  ischium,  and  re-enters  the  pelvis  through  the  lesser  sacro-sciatic  foramen 
to  enter  the  inner  surface  of  the  Obturator  internus;  the  branch  to  the  Gemellus 
superior  muscle  arises  in  common  with  the  nerve  to  the  Obturator  internus 
muscle;  it  enters  the  muscle  at  the  upper  part  of  its  dorsal  surface;  the  small 
branch  to  the  Gemellus  inferior  and  Quadratus  femoris  muscles  also  arises  from 
the  upper  part  of  the  plexus;  it  passes  through  the  great  sacro-sciatic  foramen 
below  the  Pyriformis,  and  courses  down  beneath  the  great  sciatic  nerve,  the  Gemelli 
and  tendon  of  the  Obturator  internus,  supplies  the  muscles  on  their  deep  or 
ventral  surface,  and  gives  off  an  articular  branch  to  the  hip-joint.  A  second 
articular  branch  is  occasionally  derived  from  the  upper  part  of  the  sacral  plexus. 

The  Superior  Gluteal  Nerve  (n.  glutaeus  superior)  (Figs.  675  and  677). — The 
superior  gluteal  nerve  arises  from  the  back  part  of  the  lumbo-sacral  cord,  with 
some  filaments  from  the  first  sacral  nerve;  it  passes  from  the  pelvis  through  the 
great  sacro-sciatic  foramen  above  the  Pyriformis  muscle,  accompanied  by  the 
gluteal  vessels,  and  divides  into  a  superior  and  an  inferior  branch. 

The  Superior  Branch  follows  the  line  of  origin  of  the  Gluteus  minimus,  and 
supplies  the  Gluteus  medius  muscle. 

The  Inferior  Branch  crosses  obliquely  between  the  Gluteus  minimus  and  medius, 
distributing  filaments  to  both  these  muscles,  and  terminates  in  the  Tensor  fasciae 
femoris  muscle,  extending  nearly  to  its  lower  end. 

The  Inferior  Gluteal  Nerve  (n.  glutaeus  inferior)  (Fig.  675).— The  inferior  gluteal 
nerve  arises  from  the  lumbo-sacral  cord  and  first  and  second  sacral  nerves,  and  is 
intimately  connected  with  the  small  sciatic  at  its  origin.  It  passes  out  of  the  pelvis 
through  the  great  sciatic  notch,  beneath  the  Pyriformis  muscle,  and,  dividing  into 
a  number  of  branches,  enters  the  Gluteus  maximus  muscle  on  its  under  surface. 

The  Small  Sciatic  Nerve  (n.  cutaneus  femoris  posterior]  (Figs.  675,  676,  and  677). 

—The  small  sciatic  or  postfemoral  cutaneous  nerve  supplies  the  integument  of  the 

perineum  and  back  part  of  the  thigh  and  leg.    It  is  usually  formed  by  the  union  of 


1028  THE  NERVE  SYSTEM 

two  branches,  which  arise  from  the  second  and  third  nerves  of  the  sacral  plexus. 
It  issues  from  the  pelvis  through  the  great  sacro-sciatic  foramen  below  the  Pyrifor- 
mis  muscle,  descends  beneath  the  Gluteus  maximus  with  the  sciatic  artery,  and  at 
the  lower  border  of  that  muscle  passes  along  the  back  part  of  the  thigh,  beneath  the 
fascia  lata  and  over  the  long  head  of  the  Biceps,  to  the  lower  part  of  the  popliteal 
region,  where  it  pierces  the  fascia  and  becomes  cutaneous.  It  then  accompanies 
the  external  saphenous  vein  (v.  saphena  parva)  to  about  the  middle  of  the  leg,  its 
terminal  filaments  communicating  with  the  sural  or  external  saphenous  nerve. 

The  Branches  of  the  small  sciatic  nerve  are  all  cutaneous,  and  are  grouped  as 
follows :  gluteal,  perineal,  and  femoral. 

The  Gluteal  Cutaneous  Branches  (nn.  clunium  inferiores  [laterales])  consist  of  two 
or  three  ascending  filaments,  which  turn  upward  around  the  lower  border  of  the 
Gluteus  maximus  to  supply  the  integument  covering  the  lower  and  outer  part  of 
that  muscle. 

The  Perineal  Cutaneous  Branches  (rami  perineales]  are  distributed  to  the  skin  at 
the  upper  and  inner  side  of  the  thigh,  on  its  posterior  aspect.  One  branch,  longer 
than  the  rest,  the  inferior  pudendal  or  long  scrotal  nerve  (Fig.  677),  curves  forward 
below  the  tuber  ischii,  pierces  the  fascia  lata,  and  passes  forward  beneath  the 
superficial  fascia  of  the  perineum  to  be  distributed  to  the  integument  of  the  scrotum 
in  the  male  and  the  labium  in  the  female,  communicating  with  the  superficial 
perineal  and  inferior  hemorrhoidal  nerves. 

The  Femoral  Cutaneous  Branches  are  numerous  descending  filaments,  derived 
from  both  sides  of  the  nerves,  which  are  distributed  to  the  back,  inner,  and  outer 
sides  of  the  thigh,  to  the  skin  covering  the  popliteal  space,  and  to  the  upper  part 
of  the  leg. 

The  Perforating  Cutaneous  Nerve  (n.  clunium  inferior  medialis)  (Fig.  675). — The 
perforating  cutaneous  nerve  usually  arises  from  the  second  and  third  sacral  nerves, 
and  is  of  small  size.  It  is  continued  dorsad  through  the  great  sacro-sciatic  ligament, 
and,  winding  around  the  lower  border  of  the  Gluteus  maximus,  supplies  the  integu- 
ment covering  the  inner  and  lower  part  of  that  muscle. 

The  Pudic  Nerve  (n.  pudendus}  (Figs.  675  and  677). — The  pudic  nerve  is  the 
direct  continuation  of  the  lower  cord  of  the  sacral  plexus,  and  derives  its  fibres 
from  the  third  and  fourth  sacral  nerves,  and  frequently  from  the  second  also.  It 
leaves  the  pelvis  through  the  great  sacro-sciatic  foramen,  below  the  Pyriformis. 
It  then  crosses  the  spine  of  the  ischium,  and  re-enters  the  pelvis  through  the  lesser 
sacro-sciatic  foramen.  It  accompanies  the  pudic  vessels  upward  and  forward 
along  the  outer  wall  of  the  ischio-rectal  fossa,  being  contained  in  a  sheath  of  the 
obturator  fascia,  termed  Alcock's  canal,  and  divides  into  two  terminal  branches, 
the  perineal  nerve  and  the  dorsal  nerve  of  the  penis  or  clitoris.  Before  its  division  it 
gives  off  the  inferior  hemorrhoidal  nerve. 

The  Inferior  Hemorrhoidal  Nerve  (n.  hcemorrhoidalis  inferior}  is  occasionally 
derived  separately  from  the  sacral  plexus.  It  passes  across  the  ischio-rectal  fossa, 
with  its  accompanying  vessels,  toward  the  lower  end  of  the  rectum,  and  is  dis- 
tributed to  the  Sphincter  ani  externus  and  to  the  integument  around  the  anus. 
Branches  of  this  nerve  communicate  with  the  inferior  pudendal  and  superficial 
perineal  nerves  at  the  forepart  of  the  perineum. 

The  Perineal  Nerve  (n.  perinei],  the  inferior  and  larger  of  the  two  terminal 
branches  of  the  pudic,  is  situated  below  the  pudic  artery.  It  accompanies  the 
superficial  perineal  artery  in  the  perineum,  dividing  into  cutaneous  and  muscular 
branches. 

The  cutaneous  branches  (superficial  perineal)  are  two  in  number,  posterior  and 
anterior.  The  posterior  or  external  branch  pierces  the  base  of  the  triangular  liga- 
ment of  the  urethra,  and  passes  forward  along  the  outer  side  of  the  urethral 
triangle  in  company  with  the  superficial  perineal  artery;  it  is  distributed  to  the 


THE  SACRAL  OR  SCIATIC  PLEXUS 


1029 


A 

\ 


Superior 
gluteal. 

PuiUc.r 
Nerve  to 
obturator  ihternus. 


Small  sciatic.  • 


Inferior  _5tf 
pudendal. 


Descending 
cutaneous. 


Internal 
popliteal* 


External 
-popliteal,  or 
common 
peroneaL 


Sural  or 
external  . 
saphenous. 
Posterior 
tibial. 


Plantar, 
cutaneous. 


Communicant 
peronei. 


FIG.  676. — Cutaneous  nerves  of  lower 
extremity.     Posterior  view. 


FIG.  677. — Nerves  of  the  lower  extremity.1 
Posterior  view. 


1  N.  B. — In  this  diagram  the  external  saphenous  (or  sural  nerve)  and  eommunicans  peronei  are  not  in  their 
normal  position.     They  have  been  displaced  by  the  removal  of  the  superficial  muscles. 


1030  THE  NERVE  SYSTEM 

skin  of  the  scrotum  (nn.  scrotales  posteriores).  It  communicates  with  the  inferior 
hemorrhoidal,  the  inferior  pudenda!,  and  the  other  superficial  perineal  nerve. 
The  anterior  or  internal  branch  also  pierces  the  base  of  the  triangular  ligament,  and 
passes  forward  nearer  to  the  middle  line,  to  be  distributed  to  the  inner  and  back 
part  of  the  scrotum.  Both  these  nerves  supply  the  labia  majora  in  the  female. 

The  muscular  branches  are  distributed  to  the  Transversus  perinaei,  Accelerator 
urinae,  Erector  penis,  and  Compressor  urethrae.  A  distant  branch  is  given  off 
from  the  nerve  to  the  Accelerator  urinae,  which  pierces  this  muscle,  and  supplies 
the  corpus  spongiosum,  ending  in  the  mucous  membrane  of  the  urethra.  This 
is  the  nerve  to  the  bulb. 

The  Dorsal  Nerve  of  the  Penis  (n.  dorsalis  penis')  is  the  deepest  division  of  the 
pudic  nerve;  it  accompanies  the  pudic  artery  along  the  ramus  of  the  ischium;  it 
then  runs  forward  along  the  inner  margin  of  the  ramus  of  the  os  pubis,  between 
the  superficial  and  deep  layers  of  the  triangular  ligament.  Piercing  the  superficial 
layer  it  gives  a  branch  to  the  corpus  cavernosum,  and  passes  forward,  in  company 
with  the  dorsal  artery  of  the  penis,  between  the  layers  of  the  suspensory  ligament, 
on  to  the  dorsum  of  the  penis,  along  which  it  is  carried  as  far  as  the  glans,  to  which 
it  is  distributed. 

In  the  female  the  dorsal  nerve  is  very  small,  and  supplies  the  clitoris  (n.  dorsalis 
clitoridis}. 

The  Great  Sciatic  Nerve  (n.  iscliiadicus)  (Figs.  675  and  677) . — The  great  sciatic 
nerve  supplies  nearly  the  whole  of  the  integument  of  the  leg,  the  muscles  of  the 
back  of  the  thigh,  and  those  of  the  leg  and  foot.  It  is  the  largest  nerve  cord  in  the 
body,  measuring  three-quarters  of  an  inch  in  breadth,  and  is  the  direct  continuation 
of  the  upper  division  of  the  sacral  plexus.  It  passes  out  of  the  pelvis  through  the 
great  sacro-sciatic  foramen,  below  the  Pyriformis  muscle.  It  descends  between 
the  trochanter  major  and  tuberosity  of  the  ischium,  along  the  back  part  of  the 
thigh,  to  about  its  lower  third,  where  it  divides  into  two  large  branches,  the  internal 
or  tibial  and  external  popliteal  or  peroneal  nerves  (Fig.  677). 

This  division  may  take  place  at  any  point  between  the  sacral  plexus  and  the 
lower  third  of  the  thigh.  When  the  division  occurs  at  the  plexus  (in  10  per  cent,  of 
cases)  the  two  nerves  descend  together  side  by  side;  or  they  may  be  separated,  at 
their  commencement,  by  the  interposition  of  part  or  the  whole  of  the  Pyriformis 
muscle.  As  the  nerve  descends  along  the  back  of  the  thigh,  it  rests  upon  the 
dorsal  surface  of  the  ischium,  the  nerve  of  the  Quadratus  femoris,  and  the  External 
rotator  muscles,  in  company  with  the  small  sciatic  nerve  and  artery,  being  covered 
by  the  Gluteus  maximus;  lower  down,  it  lies  upon  the  Adductor  magnus,  and  is 
covered  by  the  long  head  of  the  Biceps.  The  great  sciatic,  even  when  apparently 
a  single  nerve,  is  really  two  nerves  appearing  as  one. 

Branches. — The  branches  of  the  nerve,  before  its  division,  are  articular  and 
muscular. 

The  Articular  Branches  (mini  articulares]  arise  from  the  upper  part  of  the  nerve; 
they  supply  the  hip-joint,  perforating  the  posterior  part  of  its  fibrous  capsule. 
These  branches  are  sometimes  derived  from  the  sacral  plexus. 

The  Muscular  Branches  (rami  musculares)  are  distributed  to  the  flexors  of  the  leg 
— viz.,  the  Biceps,  Semitendinosus,  and  Semimembranosus,  and  a  branch  goes  to 
the  Adductor  magnus.  These  branches  are  given  off  beneath  the  Biceps  muscle. 

The  Internal  Popliteal  or  Tibial  Nerve  (n.tibialis)  (Figs.  675  and  677),  in  reality, 
arises  from  the  fourth  and  fifth  lumbar  nerves  and  the  first  three  sacral  nerves,  and 
becomes  a  part  of  the  trunk  of  the  great  sciatic  in  the  buttock,  to  emerge  from  it 
again  at  the  bifurcation  of  the  sciatic.  It  is  the  larger  of  the  two  terminal  branches 
of  the  great  sciatic,  descends  along  the  back  part  of  the  thigh,  through  the  middle  of 
the  popliteal  space,  to  the  lower  part  of  the  Popliteus  muscle,  where  it  passes  with 
the  arterv  beneath  the  arch  of  the  Soleus  and  becomes  the  posttibial.  It  is  over- 


THE  SACRAL  OR  SCIATIC  PLEXUS  1031 

lapped  by  the  hamstring  muscles  above,  and  then  becomes  more  superficial,  and 
lies  to  the  outer  side  of,  and  some  distance  from,  the  popliteal  vessels;  opposite 
the  knee-joint  it  is  in  close  relation  with  the  vessels,  and  crosses  to  the  inner  side  of 
the  artery.  Below,  it  is  overlapped  by  the  Gastrocnemius  muscle. 

The  branches  of  this  nerve  are — articular,  muscular,  and  a  cutaneous  branch,  the 
communicating  tibial  nerve. 

The  articular  branches  (rami  articulares),  usually  three  in  number,  supply  the 
knee-joint;  two  of  these  branches  accompany  the  superior  and  inferior  internal 
articular  arteries,  and  a  third,  the  azygos  articular  artery. 

The  muscular  branches  (rami  m,usculares),  four  or  five  in  number,  arise  from  the 
nerve  as  it  lies  between  the  two  heads  of  the  Gastrocnemius  muscle;  they  supply 
that  muscle,  and  the  Plantaris,  Soleus,  and  Popliteus.  The  filaments  which 
supply  the  Popliteus  turn  around  its  lower  border  and  are  distributed  to  its  deep 
surface. 

The  tibial  communicating  nerve  (n.  cutaneus  surae  medialis)  is  the  cutaneous 
branch.  It  descends  between  the  two  heads  of  the  Gastrocnemius  muscle,  and 
about  the  middle  of  the  back  of  the  leg  pierces  the  deep  fascia,  and  joins  the 
peroneal  or  fibular  communicating  nerve  (ramus  anastomoticus  peronaeus)  from  the 
external  popliteal  nerve  to  form  the  sural  nerve  (external  or  short  saphenous)  (Fig. 
677).  The  sural  nerve,  formed  by  the  communicating  branches  of  the  internal  and 
external  popliteal  nerves,  passes  downward  and  outward  near  the  outer  margin  of 
the  tendo  Achillis,  lying  close  to  the  small  saphenous  vein,  to  the  interval  between 
the  external  malleolus  and  the  os  calcis.  It  divides  in  two  branches,  the  posterior 
of  which  breaks  up  into  lateral  calcaneal  branches  (rami  calcanei  laterales).  The 
anterior  branch  (n.  cutaneus  dorsalis  lateralis)  winds  around  the  outer  malleolus, 
and  is  distributed  to  the  integument  along  the  outer  side  of  the  foot  and  little  toe, 
communicating  on  the  dorsum  of  the  foot  with  the  musculo-cutaneous  nerve.  In 
the  leg  its  branches  communicate  with  those  of  the  small  sciatic.  The  cutaneous 
area  supplied  by  the  sural  nerve  is  indicated  in  Fig.  679. 

The  Posttibial  Nerve  (Fig.  677)  is  the  terminal  portion  of  the  internal  pop- 
liteal nerve.  It  commences  at  the  lower  border  of  the  Popliteus  muscle,  and 
passes  along  the  back  part  of  the  leg  with  the  posterior  tibial  vessels  to  the  interval 
between  the  inner  malleolus  and  the  heel,  where  it  divides  into  the  external  and 
internal  plantar  nerves.  It  lies  upon  the  deep  muscles  of  the  leg,  and  is  covered  in 
the  upper  part  by  the  muscles  of  the  calf,  lower  down  by  the  skin  and  fascia.  In 
the  upper  part  of  its  course  it  lies  to  the  inner  side  of  the  posterior  tibial  artery,  but 
it  soon  crosses  that  vessel,  and  lies  to  its  outer  side  as  far  as  the  ankle.  In  the  lower 
third  of  the  leg  it  is  placed  parallel  with  the  inner  margin  of  the  tendo  Achillis. 

The  branches  of  the  posttibial  nerve  are  muscular,  medial  or  internal  calcaneal  or 
calcaneo-plantar,  and  articular. 

The  muscular  branches  (rami  musculares)  arise  either  separately  or  by  a  common 
trunk  from  the  upper  part  of  the  nerve.  They  supply  the  Soleus,  Tibialis  posticus, 
Flexor  longus  digitorum,  and  Flexor  longus  hallucis  muscles;  the  branch  to  the 
latter  muscle  accompanying  the  peroneal  artery.  The  branch  to  the  Soleus  enters 
its  deep  surface,  while  the  branch  which  this  muscle  receives  from  the  internal 
popliteal  enters  its  superficial  aspect. 

The  medial  or  internal  calcaneal  or  calcaneo-plantar  branches  (rami  calcanei 
mediates)  perforate  the  internal  annular  ligament,  and  supply  the  integument  of 
the  heel  and  inner  side  of  the  foot  (Fig.  679). 

The  articular  branch  (ramus  articularis  ad  articulation  em  talocruralem)  is  given 
off  just  above  the  bifurcation  of  the  nerve  and  supplies  the  ankle-joint. 

The  Medial  or  Internal  Plantar  Nerve  (n.  plantaris  medialis}  (Fig.  678),  the  larger 
of  the  two  terminal  branches  of  the  posttibial,  accompanies  the  medial  plantar 
artery  along  the  inner  side  of  the  foot.  From  its  origin  at  the  inner  ankle  it  passes 


1032 


THE  NERVE  SYSTEM 


beneath  the  Abductor  hallucis,  and  divides  into  the  common  plantar  digital  nerves 
(nn.  digitales  plantares  communes),  which  pass  distad  between  the  Abductor 
hallucis  and  the  Flexor  brevis  digitorum,  dividing  opposite  the  bases  of  the  metatar- 
sal  bones  into  four  collateral  plantar  digital  branches,  and  communicating  with  the 
lateral  plantar  nerve. 

In  its  course  the  medial  plantar  nerve  gives  off  cutaneous  branches,  which  pierce 
the  plantar  fascia  and  supply  the  integument  of  the  sole  of  the  foot  (Fig.  679); 
muscular  branches,  which  supply  the  Abductor  hallucis  and  Flexor  brevis  digitorum; 
articular  branches,  to  the  articulations  of  the  tarsus  and  metatarsus;  and  four  col- 
lateral plantar  digital  branches  (nn.  digitales  plantares  proprii).  The  three  outer 
branches  pass  between  the  divisions  of  the  plantar  fascia  in  the  clefts  between  the 

toes;  the  first  (innermost)  branch  becomes 
cutaneous  more  proximally  between  the  Ad- 
ductor hallucis  and  Flexor  brevis  digitorum. 
They  are  distributed  in  the  following  man- 
ner: The  first  supplies  the  inner  border  of 
the  great  toe,  and  sends  a  filament  to  the 
Flexor  brevis  hallucis  muscle;  the  second 
bifurcates,  to  supply  the  adjacent  sides  of 


Medial 

or 

Internal 
plantar 


Lateral 

or 

External 
plantar 


Deep 

branch. 


FIG.  678. — The  plantar  nerves. 


FIG.  679. — Areas  of  distribution  of  the  cutaneous  nerves  of 
the  sole.      (W.  Keiller,  in  Gerrish's  Text-book  of  Anatomy.) 


the  great  and  second  toes,  sending  a  filament  to  the  First  lumbrical  muscle;  the 
third  supplies  the  adjacent  sides  of  the  second  and  third  toes;  the  fourth  supplies 
the  corresponding  sides  of  the  third  and  fourth  toes,  and  receives  a  communicating 
branch  from  the  external  plantar  nerve  (Fig.  679).  Each  digital  nerve  gives  off 
cutaneous  and  articular  filaments;  and  opposite  the  last  phalanx  sends  a  dorsal 
branch,  which  supplies  the  structures  around  the  nail,  the  continuation  of  the  nerve 
being  distributed  to  the  ball  of  the  toe.  It  will  be  observed  that  the  distribution 
of  these  branches  is  precisely  similar  to  that  of  the  median  nerve  in  the  hand. 

The  Lateral  or  External  Plantar  Nerve  (n.  plantar  is  lateralis)  (Fig.  678),  the  smaller 
of  the  two,  completes  the  nerve  supply  to  the  structures  of  the  sole  of  the  foot 
(Fig.  679),  being  distributed  to  the  little  toe,  and  one-half  of  the  fourth,  as  well  as 
to  most  of  the  deep  muscles,  its  distribution  being  similar  to  that  of  the  ulnar  in  the 
hand.  It  passes  obliquely  distad  with  the  lateral  plantar  artery  to  the  outer  side  of 
the  foot,  lying  between  the  Flexor  brevis  digitorum  and  Flexor  accessorius,  and  in 
the  interval  between  the  former  muscle  and  Abductor  minimi  digiti  divides  into  a 


THE  SACRAL  OR  WIA'IIC  PLEXUS  1033 

superficial  and  a  deep  branch.    Before  its  division  it  supplies  the  Flexor  accessorius 
and  Abductor  minimi  digiti. 

The  superficial  branch  (minus  superficialis)  separates  into  two  digital  nerves. 
Before  division  they  are  called  common  plantar  digital  nerves  (nn.  digitales  plantares 
communes),  after  division  the  collateral  plantar  digital  nerves  (nn.  digitales  plantares 
proprii):  one,  the  external  branch,  the  smaller  of  the  two,  supplies  the  outer  side  of 
the  little  toe,  the  Flexor  brevis  minimi  digiti,  and  the  two  Interosseous  muscles  of 
the  fourth  metatarsal  space;  the  other  and  larger  digital  branch  supplies  the 
adjoining  sides  of  the  fourth  and  fifth  toes,  and  communicates  with  the  medial 
plantar  nerve. 

The  deep  or  muscular  branch  (ramus  profundus)  accompanies  the  lateral  plantar 
artery  into  the  deep  part  of  the  sole  of  the  foot,  beneath  the  tendons  of  the  Flexor 
muscles  and  Adductor  obliquus  hallucis,  and  supplies  all  the  Interossei  (except 
those  in  the  fourth  metatarsal  space),  the  three  outer  Lumbricales,  the  Adductor 
obliquus  hallucis,  and  the  Adductor  transversus  hallucis. 

The  External  Popliteal  or  Common  Peroneal  Nerve  (n.  peronaeus  communis)  (Figs. 
675  and  677)  in  reality  arises  from  the  fourth  and  fifth  lumbar  and  the  first  and 
second  sacral  nerves.  It  is  about  one-half  the  size  of  the  internal  popliteal,  descends 
obliquely  along  the  outer  sides  of  the  popliteal  space  to  the  head  of  the  fibula,  close 
to  the  inner  margin  of  the  Biceps  muscle.  It  is  easily  felt  beneath  the  skin  behind 
the  head  of  the  fibula  at  the  inner  side  of  the  tendon  of  the  Biceps.  It  passes 
between  the  tendon  of  the  Biceps  and  outer  head  of  the  Gastrocnemius  muscle, 
winds  around  the  neck  of  the  fibula,  between  the  Peroneus  longus  and  the  bone, 
and  divides  beneath  the  muscle  into  the  deep  peroneal  (anterior  tibial)  and  musculo- 
cutaneous  nerves. 

The  branches  of  the  peroneal  nerve,  previous  to  its  division,  are  articular  and 
cutaneous. 

The  articular  branches  (rami  articulares)  are  three  in  number:  two  of  these  accom- 
pany the  superior  and  inferior  lateral  articular  arteries  to  the  outer  side  of  the  knee. 
The  upper  one  occasionally  arises  from  the  great  sciatic  nerve  before  its  bifurcation. 
The  third  (recurrent}  articular  nerve  is  given  off  at  the  point  of  division  of  the 
peroneal  nerve;  it  ascends  with  the  anterior  recurrent  tibial  artery  through  the 
Tibialis  anticus  muscle  to  the  front  of  the  knee,  which  it  supplies. 

The  Sural  or  Lateral  Cutaneous  Branch  (n.  cutaneus  surae  lateralis). — There  may 
be  two  or  three  of  these  branches.  They  supply  the  integument  along  the  back 
part  and  outer  side  of  the  leg.  The  largest  cutaneous  branch  of  the  peroneal  is  the 
peroneal  communicating  (ramus  anastomoticus  peronaeus  or  communicans  fibularis), 
arises  near  the  head  of  the  fibula,  crosses  the  external  head  of  the  Gastrocnemius 
to  the  middle  of  the  leg,  and  joins  with  the  communicans  tibialis  to  form  the 
external  saphenous.  This  nerve  occasionally  exists  as  a  separate  branch,  which  is 
continued  as  far  down  as  the  heel. 

The  Deep  Peroneal  or  Anterior  Tibial  Nerve  (n.  peronaeus  profundus)  (Fig.  672) 
commences  at  the  bifurcation  of  the  peroneal  nerve,  between  the  fibula  and  upper 
part  of  the  Peroneus  longus  muscle,  passes  obliquely  distad  beneath  the  Extensor 
longus  digitorum  muscle  to  the  forepart  of  the  interosseous  membrane,  and 
gets  into  relation  with  the  anterior  tibial  artery  above  the  middle  of  the  leg; 
it  then  descends  with  the  artery  to  the  front  of  the  ankle-joint,  where  it  divides 
into  an  external  and  an  internal  branch.  This  nerve  lies  at  first  on  the  outer  side 
of  the  anterior  tibial  artery,  then  in  front  of  it,  and  again  at  its  outer  side  at  the 
ankle-joint. 

The  branches  of  the  anterior  tibial  nerve  in  its  course  through  the  leg  are  the 
muscular  branches  (rami  musculares)  to  the  Tibialis  anticus,  Extensor  longus  digi- 
torum, Peroneus  tertius,  and  Extensor  proprius  hallucis  muscles,  and  an  articular 
branch  to  the  ankle-joint. 


1034  THE  NERVE  SYSTEM 

The  external  or  tarsal  branch  of  the  anterior  tibial  passes  outward  across  the 
tarsus,  beneath  the  Extensor  brevis  digitorum,  and,  having  become  enlarged,  like 
the  posterior  interosseous  nerve  at  the  wrist,  supplies  the  Extensor  brevis  digitorum 
muscle.  From  the  enlargement  three  minute  interosseous  branches  are  given  off 
which  supply  the  tarsal  joints  and  the  metatarso-phalangeal  joints  of  the  second, 
third,  and  fourth  toes.  The  first  of  these  sends  a  filament  to  the  second  dorsal 
interosseous  muscle. 

The  internal  branch,  the  continuation  of  the  nerve,  accompanies  the  dorsalis 
pedis  artery  along  the  inner  side  of  the  dorsum  of  the  foot,  and  at  the  first  inter- 
osseous space  divides  into  two  dorsal  digital  branches  (nn.  digitales  dorsales  hallucis 
later  alls  et  digiti  secundi  medialis),  which  supply  the  adjacent  sides  of  the  great 
and  second  toes,  communicating  with  the  internal  branch  of  the  musculo-cutaneous 
nerve.  Before  it  divides  it  gives  off  an  interosseous  branch  to  the  first  space, 
which  supplies  the  metatarso-phalangeal  joint  of  the  great  toe  and  sends  a  fila- 
ment to  the  First  dorsal  interosseous  muscle. 

The  Musculo-cutaneous  Nerve  (n.  peronaeus  superficialis)  (Fig.  672)  supplies  the 
muscles  on  the  fibular  side  of  the  leg  and  the  integument  of  the  dorsum  of  the  foot. 
It  passes  forward  between  the  Peronei  muscles  and  the  Extensor  longus  digitorum, 
pierces  the  deep  fascia  at  the  lower  third  of  the  leg  on  its  front  and  outer  side,  and 
divides  into  two  branches.  This  nerve  in  its  course  between  the  muscles  gives  off 
muscular  branches  (rami  musculares)  to  the  Peroneus  longus  and  brevis,  and  cutane- 
ous filaments  to  the  integument  of  the  lower  part  of  the  leg. 

The  medial  dorsal  cutaneous  branch  (n.  cutaneus  dorsalis  medians')  of  the  musculo- 
cutaneous  nerve  passes  in  front  of  the  ankle-joint,  and  divides  into  two  dorsal 
digital  branches  (nn.  digitales  dorsales  pedis),  one  of  which  supplies  the  inner  side  of 
the  great  toe,  the  other  the  adjacent  sides  of  the  second  and  third  toes.  It  also 
supplies  the  integument  of  the  inner  ankle  and  inner  side  of  the  foot,  communicating 
with  the  saphenous  nerve,  and  joining  with  the  anterior  tibial  nerve,  between  the 
great  and  second  toes. 

The  intermediate  dorsal  cutaneous  branch  (n.  cutaneus  dorsalis  intermedius] ,  the 
smaller,  passes  along  the  outer  side  of  the  dorsum  of  the  foot,  and  divides  into  two 
dorsal  digital  branches,  the  inner  being  distributed  to  the  contiguous  sides  of  the 
third  and  fourth  toes,  the  outer  to  the  opposed  sides  of  the  fourth  and  fifth  toes. 
It  also  supplies  the  integument  of  the  outer  ankle  and  outer  side  of  the  foot,  com- 
municating with  the  short  saphenous  nerve. 

The  branches  of  the  musculo-cutaneous  nerve  supply  all  the  toes  excepting  the 
outer  side  of  the  little  toe,  which  is  supplied  by  the  small  saphenous  nerve.  The 
adjoining  sides  of  the  great  toe  or  second  toe  are  also  supplied  by  the  internal 
branch  of  the  anterior  tibial.  It  frequently  happens  that  some  of  the  outer  branches 
of  the  musculo-cutaneous  are  absent,  their  place  being  then  taken  by  branches  of 
the  small  saphenous  nerve. 

The  Coccygeal  Plexus. 

The  coccygeal  plexus  is  a  subdivision  of  the  pudendal  plexus,  formed  chiefly  by 
the  anterior  division  of  the  fifth  sacral  nerve,  sometimes  the  fourth  also,  and  the 
coccygeal  nerve.  From  this  plexus  arise  the  anococcygeal  nerves  which  pierce  the 
great  sacrosciatic  ligament  and  supply  the  integument  over  the  coccyx. 

Surgical  Anatomy. — The  lumbar  plexus  passes  through  the  Psoas  muscle,  and,  therefore, 
in  psoas  abscess  any  or  all  of  its  branches  may  be  irritated,  causing  severe  pain  in  the  parts  to 
which  the  irritated  nerves  are  distributed.  The  genito-femoral  nerve  is  the  one  which  is  most 
frequently  implicated.  This  nerve  is  also  of  importance,  as  it  is  concerned  in  one  of  the  reflexes 
employed  in  the  investigation  of  diseases  of  the  spine.  If  the  skin  over  the  inner  side  of  the 
thigh  just  below  Poupart's  ligament,  the  part  supplied  by  the  femoral  branch  of  the  genito- 


THE  COCCYGEAL  PLEXUS  1035 

femoral  nerve,  be  gently  tickled  in  a  male  child,  the  testicle  will  be  noticed  to  be  drawn  upward 
through  the  action  of  the  Cremaster  muscle,  which  is  supplied  by  the  genital  branch  of  the 
same  nerve.  The  same  result  may  sometimes  be  noticed  in  adults,  and  can  almost  always  be 
produced  by  severe  stimulation.  This  reflex,  when  present,  shows  that  the  portion  of  the  cord 
from  which  the  first  and  second  lumbar  nerves  are  derived  is  in  a  normal  condition. 

The  femoral  or  anterior  crural  nerve  is  in  danger  of  being  injured  in  fractures  of  the  true  pelvis, 
since  the  fracture  most  commonly  takes  place  through  the  ascending  ramus  of  the  os  pubis,  at  or 
near  the  point  where  this  nerve  crosses  the  bone.  It  is  also  liable  to  be  injured  in  fractures  and 
(I i. Plications  of  the  femur,  and  is  likely  to  be  pressed  upon,  and  its  functions  impaired,  in  some 
tumor*  growing  in  the  pelvis.  Moreover,  on  account  of  its  superficial  position,  it  is  exposed  to 
injury  in  wounds  and  stabs  in  the  groin.  When  this  nerve  is  paralyzed,  the  patient  is  unable  to  flex 
his  hip  completely,  on  account  of  the  loss  of  motion  in  the  Iliacus;  or  to  extend  the  knee  on  the 
thigh,  on  account  of  paralysis  of  the  Quadriceps  extensor  cruris;  there  are  complete  paralysis  of 
the  Sartorius  and  partial  paralysis  of  the  Pectineus.  There  is  loss  of  sensation  down  the  front  and 
inner  side  of  the  thigh,  except  in  that  part  supplied  by  the  femoral  branch  of  the  genito-femoral 
nerve,  and  by  the  ilio-inguinal  nerve.  There  is  also  loss  of  sensation  down  the  inner  side  of  the 
leg  and  foot  as  far  as  the  ball  of  the  great  toe. 

The  obturator  nerve  is  of  special  surgical  interest.  It  is  rarely  paralyzed  alone,  but  occa- 
sionally is  paralyzed  in  association  with  the  femoral.  The  principal  interest  attached  to  it  is  in 
connection  with  its  supply  to  the  knee;  pain  in  the  knee  being  symptomatic  of  many  diseases 
in  which  the  trunk  of  this  nerve,  or  one  of  its  branches,  is  irritated.  Thus  it  is  well  known  that 
in  the  earlier  stages  of  hip-joint  disease  the  patient  does  not  complain  of  pain  in  that  articulation, 
but  on  the  inner  side  of  the  knee,  or  in  the  knee-joint  itself,  both  these  articulations  being  sup- 
plied by  the  obturator  nerve,  the  final  distribution  of  the  nerve  being  to  the  knee-joint.  Again, 
the  same  thing  occurs  in  sacro-iliac  disease:  pain  is  complained  of  in  the  knee-joint  or  on  its 
inner  side.  The  obturator  nerve  is  in  close  relationship  with  the  sacro-iliac  articulation,  passing 
over  it,  and,  according  to  some  anatomists,  distributing  filaments  to  it.  Again,  in  cancer  of 
the  rigmoid  flexure,  and  even  in  cases  where  masses  of  hardened  faeces  are  impacted  in  this 
portion  of  the  gut,  pain  is  complained  of  in  the  knee.  The  left  obturator  nerve  lies  beneath  the 
sigmoid  flexure,  and  is  readily  pressed  upon  and  irritated  when  disease  exists  in  this  part  of  the 
intestine.  Finally,  pain  in  the  knee  forms  an  important  diagnostic  sign  in  obturator  hernia. 
The  hernial  protrusion  as  it  passes  out  through  the  opening  in  the  obturator  membrane  presses 
upon  the  nerve  and  causes  pain  in  the  parts  supplied  by  its  peripheral  filaments.  When  the 
obturator  nerve  is  paralyzed,  the  patient  is  unable  to  press  his  knees  together  or  to  cross  one 
leg  over  the  other,  on  account  of  paralysis  of  the  Adductor  muscles.  Rotation  outward  of  the 
thigh  is  impaired  from  paralysis  of  the  Obturator  externus.  Sometimes  there  is  loss  of  sensation 
in  the  upper  half  of  the  inner  side  of  the  thigh. 

The  great  sciatic  nerve  is  liable  to  be  pressed  upon  by  various  pelvic  tumors,  giving  rise  to 
pain  along  its  trunk,  to  which  the  term  sciatica  is  applied.  Tumors  growing  from  the  pelvic 
viscera,  or  bones,  aneurisms  of  some  of  the  branches  of  the  internal  iliac  artery,  calculus  in  the 
bladder  when  of  large  size,  accumulation  of  faeces  in  the  rectum,  may  all  cause  pressure  on  the 
nerve  inside  the  pelvis,  and  give  rise  to  sciatica.  -Outside  the  pelvis  exposure  to  cold,  violent 
movements  of  the  hip-joint,  exostoses  or  other  tumors  growing  from  the  margin  of  the  sacro- 
sciatic  foramen,  may  also  give  rise  to  the  same  condition.  When  paralyzed  there  is  loss  of 
motion  in  all  the  muscles  below  the  knee,  and  loss  of  sensation  in  the  same  situation,  except  the 
upper  half  of  the  back  of  the  leg,  supplied  by  the  small  sciatic  and  the  upper  half  of  the  inner 
side  of  the  leg,  when  the  communicating  branch  of  the  obturator  is  large. 

The  sciatic  nerve  has  been  frequently  cut  down  upon  and  stretched,  or  has  been  acupunctured 
for  the  relief  of  sciatica.  The  nerve  has  also  been  stretched  in  cases  of  locomotor  ataxia,  the 
anaesthesia  of  leprosy,  etc.  In  order  to  define  it  on  the  surface,  a  point  is  taken  at  the  junction 
of  the  middle  and  lower  third  of  a  line  stretching  from  the  posterior  superior  spine  of  the  ilium 
to  the  outer  part  of  the  tuber  ischii,  and  a  line  is  drawn  from  this  point  to  the  middle  of  the  upper 
part  of  the  popliteal  space.  The  line  must  be  slightly  curved  with  its  convexity  outward,  and  as 
it  passes  downward  to  the  lower  border  of  the  Gluteus  maximus  is  slightly  nearer  the  tuberosity 
of  the  ischium  than  to  the  great  trochanter,  as  it  crosses  a  line  drawn  between  these  two  points. 
The  operation  of  stretching  the  sciatic  nerve  is  performed  by  making  an  incision  over  the  course 
of  the  nerve  about  the  centre  of  the  thigh.  The  skin,  superficial  structures,  and  deep  fascia 
having  been  divided,  the  interval  between  the  inner  and  outer  hamstrings  is  to  be  defined,  and 
these  muscles  respectively  pulled  inward  and  outward  with  retractors.  The  nerve  will  be  found  a 
little  to  the  inner  side  of  the  Biceps.  It  is  to  be  separated  from  the  surrounding  structures,  hooked 
up  with  the  finger,  and  stretched  by  steady  and  continuous  traction  for  two  or  three  minutes. 
The  sciatic  nerve  may  also  be  stretched  by  what  is  known  as  the  "dry"  plan.  The  patient  is 
laid  on  his  back,  the  foot  is  extended,  the  leg  flexed  on  the  thigh,  and  the  thigh  strongly  flexed 
on  the  abdomen.  While  the  thigh  is  maintained  in  this  position  the  leg  is  forcibly  extended  to 
its  full  extent,  and  the  foot  as  fully  flexed  on  the  leg.  This  last-named  method  is  uncertain. 

The  position  of  the  external  popliteal  nerve,  close  behind  the  tendon  of  the  Biceps  on  the  outer 
side  of  the  ham,  should  be  remembered  in  subcutaneous  division  of  the  tendon.  After  it  is  divided, 


1036 


THE  NERVE  SYSTEM 


a  cord  often  rises  up  close  beside  it,  which  might  be  mistaken  for  a  small  undivided  portion  of  the 
tendon,  and  the  surgeon  might  be  tempted  to  reintroduce  his  knife  and  divide  it.  This  must 
never  be  done,  as  the  cord  is  the  external  popliteal  nerve,  which  becomes  prominent  as  soon  as 
the  tendon  is  divided. 

THE  CRANIAL  NERVES  (NERVI  CEREBRALES). 

The  irregularities  of  origin  and  distribution  of  the  cranial  nerves,  as  compared 
with  the  relatively  simple  spinal  nerves,  is  so  great  and  their  functions  were  for- 
merly so  little  known  that  the  older  anatomists  contented  themselves  with  number- 
ing them  in  order,  beginning  at  the  cephalic  end  of  the  brain,  and  named 
them  with  reference  to  their  anatomical  connections.  The  enumeration  of  the 
cranial  nerves  was  as  variously  given,  almost,  as  there  were  writers  upon  the 
subject ;  the  systems  of  Willis  and  of  Sommering  were  most  in  vogue  for  a  time, 
but  the  latter  prevails  to-day.  In  Sommering's  arrangement  twelve  pairs  of  cranial 
nerves  are  recognized,  but,  on  morphological  and  functional  grounds,  the  nerves  of 
the  seventh  and  eighth  pairs  should  each  be  considered  as  being  composed  of  two 
nerves,  the  eleventh  pair  should  be  included  with  the  nerves  of  the  tenth,  and  the 
optic  "nerve"  is  rather  a  diverticulum  of  the  brain  itself  than  a  nerve  in  the  strict 
sense.  Furthermore,  while  some  of  the  nerves  are  sensor  or  motor  in  a  sense 
strictly  comparable  with  the  spinal  nerves,  others  are  "mixed"  in  function,  and 
yet  others  constitute  nerves  of  special  sense,  lacking  general  sensibility.  The 
numerical  names,  based  upon  the  order  in  which  they  pass  through  the  foramina 
in  the  base  of  the  cranium,  are  being  abandoned  gradually  for  the  more  appro- 
priate functional  names,  »but  not  yet  entirely  so.  Thus  glossopharyngeal  has 
not  yet  given  way  to  "gustatory;"  "vagus"  is  shorter  than  " pneumogastric"- 
a  term  which  is  misleading  for  a  nerve  which  is  distributed  not  only  to  lungs 
and  stomach,  but  also  to  the  meninges,  the  pharynx  and  oesophagus,  larynx  and 
trachea,  heart  and  pericardium,  liver  and  spleen. 

The  cranial  nerves,  as  usually  enumerated,  together  with  their  superficial 
"origin"  or  attachment  to  the  brain  and  their  foramina  of  exit  from  the  skull,  are 
tabulated  on  p.  866.  The  central  olfactory  pathway  is  described  on  p.  938,  and 
the  central  connections  of  the  optic  tracts  are  given  on  p.  921.  The  central  con- 
nections of  the  remaining  cranial  nerves  are  described  on  pp.  892  to  914. 

The  following  is  a  brief  summary  of  the  twelve  pairs  of  cranial  nerves,  indicating 
their  functional  nature: 


No. 

Name. 

Functional   nature. 

I. 

Olfactory  (fila.) 

Smell-sense. 

II. 

Optic. 

Visual  -sense. 

III. 

Oculomotor. 

Motor  to  muscles  of  eyeball  and  orbit. 

IV. 

Trochlear. 

Motor  to  Superior  oblique  muscles  of  eyeball. 

V. 

Trigeminal. 

Mixed:    Sensor  to   face,   tongue,  and   teeth; 

motor   to 

muscles  of  mastication. 

VI 

Abducent. 

Motor  to  External  rectus  muscle  of  eyeball. 

VII. 

Facial. 

Motor  to  muscles  of  scalp  and  face. 

Nervus  intermedius. 

Mixed:   Sensor  (gustatory)  to  tongue;  excito-glandular 

to  submaxillary  and  sublingual  salivary  glan 

ds. 

VIII. 

Acoustic: 

I.  Cochlearis. 

Hearing-sense. 

II.   Vestibularis. 

Equilibratory-sense. 

IX. 

Glossopharyngeal. 

•  Mixed:    Sensor  (and  gustatory)  to  tongue  and 

pharynx  ; 

motor  (?)  to  Stylopharyngeus  muscle. 

X. 

Vagus. 

Mixed:  Sensori-motor  to  respiratory  tract  and  part  of 

alimentary  tract. 

XI. 

Accessory. 

I.  Accessory  to  vagus. 

Motor  to  muscles  of  palate,  pharynx,  etc.;  respiratory 

organs;  inhibitory  to  heart. 

II.  Spinal  part. 

Motor  to  Trapezius  and  Sternomastoid  muscles 

XII.   i  Hypoglossal.                          Motor  to  muscles  of  tongue. 

THE  FIRST  OR  OLFACTORY  NERVE 


1037 


THE   FIRST   OR   OLFACTORY   NERVE    (N.   OLFACTORIUS). 


The  olfactory  nerves  or  fila  are  the  special  nerves  of  the  sense  of  smell,  and  are 
about  twenty  in  number  on  each  side.  These  filaments  constitute  the  first  or 
olfactory  nerves  and  are  the  axones  of  the  olfactory  cells,  lying  in  the  small  olfac- 
tory region  in  the  upper  part  of  the  superior  concha  and  corresponding  portion 
of  the  septum  and  are  macroscopically  differentiated  from  the  respiratory  region 
in  being  of  a  more  brownish  hue  (Fig.  680).  The  olfactory  fila  are  amyelinic  and 


FIG.  680. — Extent  of  true  olfactory  mucous  membrane,     (v.  Brunn.) 

exhibit  a  plexiform  arrangement  in  the  deeper  layers.  After  piercing  the  cribrosa 
(cribriform  plate)  of  the  ethmoid  they  become  attached  to  the  under  surface  of  the 
olfactory  bulb,  an  oval  mass  of  a  grayish  color,  which  rests  on  the  cribriform 
plate  of  the  ethmoid  bone  and  forms  the  anterior  expanded  extremity  or  a  slender 
process  of  brain-substance,  named  the  olfactory  tract.  The  olfactory  tract  and 
bulb  have  already  been  described  (p.  935).  The  olfactory  tubercle  (trigonum 
olf actor  ium)  is  a  small  triangular  mass  of  gray  substance  between  the  diverging 
roots  of  the  optic  tract  (p.  935). 

Each  nerve  is  surrounded  by  tubular  prolongations  from  the  dura  and  pia, 
the  former  being  lost  on  the  periosteum  lining  the  nose,  the  latter  in  the  neuri- 
lemma  of  the  nerve.  The  nerves,  as  they  enter  the  nares,  are  divisible  into  two 
groups:  an  inner  group,  larger  than  those  on  the  outer  wall,  spread  out  over  the 
upper  third  of  the  septum;  and  an  outer  set,  which  is  distributed  over  the  superior 
turbinated  bone,  and  the  surface  of  the  ethmoid  in  front  of  it.  As  the  filaments 
descend,  they  unite  in  a  plexiform  network,  and  are  believed  by  most  observers 
to  terminate  by  becoming  continuous  with  the  deep  .extremities  of  the  olfactory  cells. 

The  olfactory  nerves  differ  in  structure  from  other  nerves  in  being  composed 
exclusively  of  non-medullated  (amyelinic  fibres).  They  are  deficient  in  the  white 
substance  of  Schwann,  and  consist  of  axones  with  a  distinct  nucleated  sheath, 
in  which  there  are,  however,  fewer  nuclei  than  in  ordinary  amyelinic  fibres. 

The  central  olfactory  pathways  are  described  on  p.  964. 


1038 


THE  NERVE  SYSTEM 


Surgical  Anatomy. — Destruction  of  the  olfactory  tract  of  one  side  causes  loss  of  smell  (anos- 
mia) on  the  side  of  the  injury,  because  the  olfactory  tract  is  practically  uncrossed.  In  severe 
injuries  to  the  head  the  olfactory  bulb  may  become  separated  from  the  olfactory  nerves,  thus 
producing  loss  of  the  sense  of  smell,  and  with  this  a  considerable  loss  in  the  sense.of  taste,  as  much 
of  the  perfection  of  the  sense  of  taste  is  due  to  the  sapid  substances,  being  also  odorous  and 
simultaneously  exciting  the  sense  of  smell.  When  the  sense  of  smell  is  lost,  an  individual  cannot 
distinguish  the  flavor  of  food,  but  he  can  distinguish  that  a  substance  is  salt,  or  sweet,  or  bitter, 
or  acid.  The  most  usual  cause  of  injury  to  the  olfactory  nerve  is  fracture  of  the  base  of  the  skull 
the  line  of  fracture  passing  through  the  cribriform  plate  of  the  ethmoid  bone,  but  a  blow  upon  the 
face,  forehead,  or  back  of  the  head,  which  does  not  produce  fracture  may  injure  the  nerve. 

THE  SECOND  OR  OPTIC  NERVE  (N.  OPTICUS). 

The  fibres  of  the  optic  nerve,  the  special  nerve  of  the  sense  of  sight,  are  the  central 
processes  of  the  retinal  ganglion  cells  which,  after  converging  to  the  optic  papilla, 
leave  the  eyeball  by  piercing  its  fibrous  and  vascular  tunics  as  a  rounded  cord. 
The  point  of  emergence  is  situated  a  little  mesad  (3  to  4  mm.)  of  the  central  axis  of 
the  globe.  Behind  the  eyeball  the  nerve  passes  backward  and  inward  through 
the  orbital  fat  and  optic  foramen  to  enter  the  middle  fossa  of  the  cranium.  The 
total  length  of  the  nerve  averages  45  to  50  mm.  The  two  nerves  converge  to 
decussate  partially,  forming  the  chiasm. 

The  Chiasm  (chiasma  opticum)  (Figs.  681  and  682  and  p.  919). — The  chiasm 
is  somewhat  quadrilateral  in  form,  rests  upon  the  olivary  eminence  and  on  the 
anterior  part  of  the  diaphragma  sellse,  being  bounded  above  by  the  terma;  behind 
by  the  tuber;  on  either  side  by  the  preperforatum.  Within  the  commissure,  the 
optic  nerves  of  the  two  sides  undergo  a  partial  decussation  (Figs.  594  and  682) 
described  in  detail  on  pp.  918  and  919. 


FIG.  681.— The  left  optic  nerve  and  optic  tracts. 


From  half-retina 
of  same  side. 
Of  opposite 
side. 

FIG.  682. — Course  of  the  fibres  in  the  optic  commissure. 

From  the  chiasm  the  optic  tracts  wind  as 
flattened  bands  obliquely  caudo-laterad 
around  the  crura  to  subdivide,  each  into 
two  bands,  one  (mesial  root)  passing  to  the 
postgeniculum  and  not  a  true  continuation 
of  the  optic  path  (see  Gudden's  commissure, 
p.  919),  the  other  (lateral  root)  passing  to 
the  pregeniculum,  the  pulvinar,  and  the 
pregeminum  (p.  919). 

The  optic  path  has  been  described  on  p. 
917. 


Surgical  Anatomy.— The  optic  nerve  is  peculiarly  liable-  to  become  the  seat  of  neuritis  or 
undergo  atrophy  in  affections  of  the  central  nerve  system,  and,  as  a  rule,  the  pathologic 
relationship  between  the  two  affections  is  exceedingly  difficult  to  trace.  There  are,  however, 
certain  points  in  connection  with  the  anatomy  of  this  nerve  which  tend  to  throw  light  upon  the 
frequent  association  of  these  affections  with  intracranial  disease:  (1)  From  its  mode  of  develop- 
ment and  from  its  structure  the  optic  nerve  must  be  regarded  as  a  prolongation  of  the  brain- 
substance,  rather  than  as  an  ordinary  eerebro-spinal  nerve.  (2)  As  it  passes  from  the  brain  it 
receives  sheaths  from  the  three  cerebral  membranes — a  perineural  sheath  from  the  pia,  an 
intermediate  sheath  from  the  arachnoid,  and  an  outer  sheath  from  the  dura,  which  is  also 
connected  with  the  periosteum  as  it  passes  through  the  optic  foramen.  These  sheaths  are 


1039 

separated  from  each  other  by  spaces  which  communicate  with  the  subdural  and  subarachnoid 
spiico  respectively.  The  innermost  or  perineural  sheath  sends  a  process  around  the  arteria  cen- 
tralis  retinre  into  the  interior  of  the  nerve,  and  enters  intimately  into  its  structure.  Thus  inflam- 
matory infections  of  the  meninges  or  of  the  brain  may  readily  extend  themselves  along  these 
spaces  or  along  the  interstitial  connective  tissue  in  the  nerve. 

The  course  of  the  fibres  in  the  optic  commissure  has  an  important  pathologic  bearing,  and 
his  been  the  subject  of  much  controversy.  Microscopic  examination,  experiments,  and  pathology 
all  seem  to  point  to  the  fact  that  there  is  a  partial  decussation  of  the  fibres,  each  tract  supplying 
the  corresponding  half  of  each  eye,  so  that  the  right  tract  supplies  the  right  half  of  each  eye,  and 
the  left  tract  the  left  half  of  each  eye.  At  the  same  time,  Charcot  believes — and  his  view  has 
met  with  general  acceptation — that  the  fibres  which  do  not  decussate  at  the  optic  commissure 
will  decussate  in  the  corpora  quadrigemina,  so  that  lesion  of  the  cerebral  centre  of  one  side 
causes  complete  blindness  of  the  opposite  eye,  because  both  sets  of  decussating  fibres  are  de- 
stroyed. Whereas  should  one  tract — say  the  right — be  destroyed  by  disease,  there  will  be 
blindness  of  the  right  half  of  both  retinae. 

A  .sagittal  section  through  the  commissure  would  divide  the  decussating  fibres,  and  would 
therefore  produce  blindness  of  the  inner  half  of  each  eye;  while  a  section  at  the  margin  of  the 
side  of  the  optic  commissure  would  produce  blindness  of  the  external  half  of  the  retina  of  the 
same  side. 

The  optic  nerve  may  also  be  affected  in  injuries  or  diseases  involving  the  orbit,  in  fractures 
of  the  anterior  fossa  of  the  base  of  the  skull,  in  tumors  of  the  orbit  itself,  or  those  invading  this 
cavity  from  neighboring  parts. 

THE  THIRD  OR  OCULOMOTOR  NERVE  (N.  OCULOMOTORIUS) 

(Figs.  683,  684,  687). 

The  third  or  oculomotor  nerve  supplies  all  the  muscles  of  the  orbit  except  the 
Superior  oblique  and  External  rectus;  it  also  supplies,  through  its  connection 
with  the  ciliary  ganglion,  the  Sphincter  muscle  of  the  iris  and  the  Ciliary  muscle. 
It  is  rather  a  large  nerve,  of  rounded  form  and  firm  texture. 

Its  apparent  origin  is  from  the  oculomotor  groove  along  the  ventro-mesal  bor- 
der of  the  crus.  The  deep  origin  may  be  traced  through  the  substantia  nigra  and 
tegmentum  of  the  crus  to  a  nucleus  situated  on  either  side  of  the  median  line  beneath 
the  floor  of  the  aqueduct.  The  nucleus  of  the  oculomotor  nerve  also  receives 
fibres  from  the  abducent  nerve  of  the  opposite  side.  The  nucleus  of  the  oculo- 
motor nerve,  considered  from  a  physiological  standpoint,  can  be  subdivided  into 
several  smaller  groups  of  cells,  each  group  controlling  a  particular  muscle  (see  p. 
911).  The  nerves  to  the  different  muscles  appear  to  take  their  origin  from  before 
backward,  as  follows:  Inferior  oblique,  Inferior  rectus,  Superior  rectus  and 
Levator  palpebrse,  Internal  rectus;  while  from  the  cephalic  end  of  the  nucleus 
the  fibres  for  accommodation  and  for  the  Sphincter  pupillse  take  their  origin. 

On  emerging  from  the  brain,  the  nerve  is  invested  with  a  sheath  of  pia,  and 
enclosed  in  a  prolongation  from  the  arachnoid.  It  passes  between  precerebellar 
and  postcerebral  arteries,  and  then  pierces  the  dura  in  front  of  and  external  to 
the  posterior  clinoid  process,  passing  between  the  two  processes  from  the  free  and 
attached  borders  of  the  tentorium,  which  are  prolonged  forward  to  be  connected 
with  the  anterior  and  posterior  clinoid  processes  of  the  sphenoid  bone.  It  passes 
along  the  outer  wall  of  the  cavernous  sinus  (Figs.  454  and  455) ;  above  the  other 
orbital  nerves,  receiving  in  its  course  one  or  two  filaments  from  the  cavernous 
plexus  of  the  sympathetic,  and  a  communicating  branch  from  the  first  division 
of  the  trigeminal  nerve.  It  then  divides  into  two  branches,  which  enter  the  orbit 
through  the  sphenoidal  fissure,  between  the  two  heads  of  the  External  rectus 
muscle  (Fig.  683).  On  passing  through  the  fissure,  the  nerve  is  placed  below 
the  trochlear  nerve  and  the  frontal  and  lacrimal  branches  of  the  ophthalmic  nerve, 
and  has  passing  between  its  two  divisions  the  nasal  nerve  (Fig.  692). 

The  Superior  Division  (ramus  superior]  (Fig.  684). — The  superior  division,  the 
smaller,  passes  inward  over  the  optic  nerve,  and  supplies  the  Superior  rectus  and 
Levator  palpebras. 


1040 


THE  NER  VE  SYSTEM 


Infratrochlear 

nerve. 


The  Inferior  Division  (ramus  inferior)   (Fig.  684).— The  inferior  division,  the 
larger,  divides  into  three  branches.     One  passes  beneath  the  optic  nerve  to  the  • 
Internal  rectus;  another,  to  the  Inferior  rectus;  and  the  third,  the  longest  of  the 

three,  passes  forward  between  the 
Inferior  and  External  recti  to  the 
Inferior  oblique.  From  this  latter 
a  short,  thick  branch,  radix  brevis 
ganglii  ciliaris,  is  given  off  to  the  lower 
part  of  the  ciliary  or  lenticular  ganglion 
and  forms  its  short  or  motor  root 
(Figs.  684  and  687).  It  also  gives  off 
one  or  two  filaments  to  the  Inferior 
rectus.  All  these  branches  enter  the 
muscles  on  their  ocular  surface,  ex- 
cept that  to  the  Inferior  oblique, 
which  enters  its  posterior  border. 

Surgical  Anatomy.— Paralysis  of  the 
oculomotor  nerve  may  be  the  result  of 
many  causes:  as  cerebral  disease;  condi- 
tions causing  pressure  on  the  cavernous 
sinus;  periostitis  of  the  bone  entering  into 
the  formation  of  the  sphenoidal  fissure; 
fracture  of  the  orbit.  It  results,  when  com- 
plete, in  (1)  ptosis,  or  drooping  of  the  upper 
eyelid,  in  consequence  of  the  Levator  pal- 
pebrse  being  paralyzed;  (2)  external  stra- 
bismus, on  account  of  the  unopposed  action 
of  the  External  rectus  muscle,  which  is  not 
supplied  by  the  oculomotor  nerve,  and  is 
not  therefore  paralyzed;  (3)  dilatation  of 
the  pupil,  because  the  sphincter  fibres  of 
the  iris  are  paralyzed ;  (4)  loss  of  power  of 
accommodation,  as  the  Sphincter  pupillee, 

Motor  root.  /    ^—Recurrent  filament  the  Ciliary  muscle,  and  the  Internal  rectus 
Sensor  root.  are  paralyzed;   (5)  slight   prominence   of 

FIG.  683,-Nerves  of  the  orbit,  seen  from  above.  tjje  eyeball,  owing  to  most   of  its  muscles 

being  relaxed.    Occasionally  paralysis  may 

affect  only  a  part  of  the  nerve;  that  is  to  say,  there  may  be,  for  example,  a  dilated  and  fixed 
pupil,  with  ptosis,  but  no  other  signs.     Irritation  of  the  nerve  causes  spasm  of  one  or  other  of 


^Oculomoter    'Nerve 


From  Cavernous  Plexus 


__  OWiguus 
Inferior 


FIG.  684. — Plan  of  the  oculomotor  nerve. 


the  muscles  supplied  by  it;  thus,  there  may  be  internal  strabismus  from  spasm  of  the  Internal 
rectus;  accommodation  for  near  objects  only  from  spasm  of  the  Ciliary  muscle,  or  contraction 
of  the  pupil  (myosis),  from  irritation  of  the  sphincter  of  the  pupil. 


THE  FIFTH,   TRIGEMINAL  OR  TRIFACIAL  NERVE         1Q41 


THE  FOURTH  OR  TROCHLEAR  NERVE  (N.  TROCHLEARIS)  (Figs.  683  and  687). 

The  fourth  or  trochlear  nerve  or  patheticus,  with  the  exception  of  the  n.  inter- 
medius,  the  smallest  of  the  cranial  nerves,  supplies  the  Superior  oblique  muscle. 

The  apparent  origin,  at  the  base  of  the  brain,  is  on  the  outer  side  of  the  crus 
cerebri,  just  in  front  of  the  pons,  but  the  fibres  can  be  traced  backward  behind 
the  quadrigemina  to  the  valvula,  on  the  upper  surface  of  which  the  two  nerves 
decussate,  decussatio  nervorum  trochlearium.  Its  deep  origin  may  be  traced  to  a 
nucleus  in  the  floor  of  the  aqueduct  immediately  below  that  of  the  oculomotor 
nerve,  with  which  it  is  continuous  (Fig.  578). 

Emerging  from  the  valvula,  the  nerve  is  directed  outward  across  the  prepe- 
(1  uncle  of  the  cerebellum,  and  then  winds  forward  around  the  outer  side  of  the 
cms  cerebri,  immediately  above  the  pons,  pierces  the  dura  in  the  free  border  of  the 
tentorium,  just  behind,  and  external  to,  the  posterior  clinoid  process,  and  passes 
forward  in  the  outer  wall  of  the  cavernous  sinus,  between  the  oculomotor  nerve 
and  the  ophthalmic  division  of  the  trigeminal  nerve  (Figs.  454  and  455).  It  crosses 
the  oculomotor  nerve  and  enters  the  orbit  through  the  sphenoidal  fissure  (Fig. 
692).  It  now  becomes  the  highest  of  all  the  nerves,  lying  at  the  inner  extremity 
of  the  fissure  internal  to  the  frontal  nerve.  In  the  orbit  it  passes  inward,  above 
the  origin  of  the  Levator  palpebrse,  and  finally  enters  the  orbital  surface  of  the 
Superior  oblique  muscle.  In  the  outer  wall  of  the  cavernous  sinus  this  nerve  is 
not  infrequently  blended  with  the  ophthalmic  division  of  the  trigeminal  nerve. 

Branches  of  Communication. — In  the  outer  wall  of  the  cavernous  sinus  it 
receives  some  filaments  from  the  cavernous  plexus  of  the  sympathetic.  In  the 
sphenoidal  fissure  it  occasionally  gives  off  a  branch  to  assist  in  the  formation  of 
the  lacrimal  nerve. 

Branches  of  Distribution. — It  gives  off  a  recurrent  branch,  which  passes 
backward  between  the  layers  of  the  tentorium,  dividing  into  two  or  three  filaments 
which  may  be  traced  as  far  back  as  the  wall  of  the  lateral  sinus. 

Surgical  Anatomy. — The  trochlear  nerve  when  paralyzed  causes  loss  of  function  in  the  Superior 
oblique,  so  that  the  patient  is  unable  to  turn  his  eye  downward  and  outward.  Should  the  patient 
attempt  to  do  this,  the  eye  on  the  affected  side  is  twisted  inward,  producing  diplopia  or  double 
vision.  Accordingly,  it  is  said  that  the  first  symptom  of  this  disease  which  presents  itself  is  giddi- 
ness when  going  down  hill  or  in  descending  stairs,  owing  to  the  double  vision  induced  by  the 
patient  looking  at  his  steps  while  descending. 


THE  FIFTH,  TRIGEMINAL  OR  TRIFACIAL  NERVE  (N.  TRIGE MINUS) 

Figs.  683,  685,  686,  687,  688,  689,  690,  691). 

The  fifth  or  trigeminal  or  trifacial  nerve  is  the  largest  cranial  nerve.  It  resembles 
a  spinal  nerve  (1)  in  having  two  roots;  (2)  in  having  a  ganglion  developed  on 
its  dorsal  root;  and  (3)  in  its  function,  since  it  is  a  compound  nerve.  It  is  the 
great  sensor  nerve  of  the  head  and  face  and  the  motor  nerve  of  the  muscles 
of  mastication.  Its  upper  two  divisions,  portio  major,  are  entirely  sensor,  the 
third  division,  portio  minor,  is  partly  sensor  and  partly  motor.  It  arises  by  two 
roots :  of  these  the  ventral  is  the  smaller,  and  is  the  motor  root  (Fig.  578) ;  the 
dorsal,  the  larger  and  sensor  root.  Its  superficial  origin  is  from  the  side  of 
the  pons  nearer  to  the  upper  than  the  lower  border  (Fig.  578).  The  smaller 
root  consists  of  three  or  four  bundles ;  the  larger  root  consists  of  numerous  bundles 
of  fibres,  varying  in  number  from  seventy  to  a  hundred.  The  two  roots  are 
separated  from  one  another  by  a  few  of  the  transverse  fibres  of  the  pons.  The 

66 


1042  THE  NERVE  SYSTEM 

deep  termination  of  the  larger  or  sensor  root  is  chiefly  in  a  long  tract  in  the 
oblongata,  the  lower  sensor  nucleus,  which  is  continuous  below  with  the  gliosa 
or  substantia  gelatinosa  of  Rolando.  The  fibres  from  this  nucleus  form  the 
so-called  ascending  root  of  the  fifth  nerve ;  they  pass  upward  through  the  pons 
and  join  with  fibres  from  the  locus  coeruleus  or  upper  sensor  nucleus  (Fig.  578), 
which  is  situated  to  the  outer  side  of  the  nucleus,  from  which  the  lower  part  of  the 
motor  root  takes  origin.  The  deep  origin  of  the  smaller  or  motor  root  is  derived 
partly  from  a  nucleus  embedded  in  the  gray  substance  of  the  upper  part  of  the  floor 
of  the  fourth  ventricle  and  partly  from  a  collection  of  nerve-cells  situated  at  the 
side  of  the  aqueduct  from  which  the  fibres  pass  caudad  under  the  name  of  the 
descending  root  of  the  fifth  nerve  (Fig.  578). 

The  two  roots  of  the  nerve  pass  forward  below  the  tentorium  as  it  bridges  over 
the  notch  on  the  inner  part  of  the  superior  border  of  the  petrous  portion  of  the 
temporal  bone  (Fig.  686);  they  then  run  between  the  bone  and  the  dura  to  the 
apex  of  the  petrous  portion  of  the  temporal  bone,  where  the  fibres  of  the  sensor 
root  appear  to  enter  into  the  formation  of  the  large  semilunar  or  Gasserian  ganglion 
(Figs.  685  and  686),  while  the  motor  root  passes  beneath  the  ganglion  without 
having  any  connection  with  it,  and  joins  outside  the  cranium  with  one  of  the  trunks 
derived  from  it  (Figs.  685  and  686). 


OCULOMOTOR  TROCHLEAR  ABOUCENS 
NERVE       NERVE  NERVE 


MOTOR  PORTION 
OF  FIFTH  NERVE 


SENSOR  PORTION 
OFTRIGEMINAL  NERVE 


SEMILUNAR  NERVE 

(Gasserian  ganglion) 


MAXILLARY 
NERVE 


MANDIBULAR 
NERVE 


FIQ.  685. — The  right  semilunar  or  Gasserian  ganglion,  viewed  from  the  medial  side.     (Spalteholz.) 

The  Gasserian  or  Semilunar  Ganglion1  (ganglion  semilunare)  (Figs.  685,  686, 
687,  688,  689,  and  690). — The  Gasserian  or  semilunar  ganglion  is  lodged  in  an 
osteo-fibrous  space,  the  cavum  Meckelii  (Figs.  644  and  686),  near  the  apex  of  the 
petrous  portion  of  the  temporal  bone.  The  ganglion  is  of  somewhat  crescentic 
form,  with  its  convexity  turned  forward.  Its  upper  surface  is  intimately  adherent 
to  the  dura.  Besides  the  small  or  motor  root,  the  large  superficial  petrosal  nerve 
lies  underneath  the  ganglion. 

Branches  of  Communication. — This  ganglion  receives  on  its  inner  side  filaments 
from  the  carotid  plexus  of  the  sympathetic. 

Branches  of  Distribution. — It  gives  off  minute  branches  to  the  tentorium  and  the 
dura  in  the  middle  fossa  of  the  cranium.  From  its  anterior  border,  which  is 

1  A  Viennese  anatomist,  Raimund  Balthasar  Hirsch  (1765),  was  the  first  who  recognized  the  ganglionic 
nature  of  the  swelling  on  the  sensory  root  of  the  fifth  nerve,  and  called  it,  in  honor  of  his  otherwise  unknown 
teucher,  Jon.  Laur.  Gasser,  the  "  Ganglion  Gasseri."  Julius  Casserius,  whose  name  is  given  to  the  musculo- 
cutaneous  nerve  of  the  arm,  was  professor  at  Padua,  1545-1605.  (See  Hyrtl,  Lehrbuch  der  Anatomic,  p.  895 
and  p.  55.) — ED.  of  15th  English  edition. 


THE  FIFTH,    TRIGEM I  .\.\L   OR  TRIFACIAL  NERVE 


1043 


directed  forward  and  outward,  three  large  branches  proceed — the  ophthalmic, 
superior  maxillary,  and  inferior  maxillary.  The  ophthalmic  and  superior  maxillary 
consist  exclusively  of  fibres  derived  from  the  larger  root  and  ganglion,  and  are  solely 
nerves  of  common  sensation.  The  third  division,  or  inferior  maxillary,  is  joined 
outside  the  cranium  by  the  motor  root.  This,  therefore,  strictly  speaking,  is  the 
only  portion  of  the  trigeminal  nerve  which  can  be  said  to  resemble  a  spinal  nerve. 

Ophthalmic  Nerve  (»i.  ophthalmicus)  (Figs.  683,  685,  686,  687,  688,  689,  and 
690). — The  ophthalmic  or  first  division  of  the  trigeminal  is  a  sensor  nerve.  It 
supplies  the  eyeball,  the  lacrimal 
gland,  the  mucous  lining  of  the  eye 
and  nasal  fossa?,  and  the  integument 
of  the  eyebrow,  forehead,  and  nose 
(Fig.  691).  It  is  the  smallest  of  the 
three  divisions  of  the  fifth,  arising  from 
the  upper  part  of  the  Gasserian  gan- 
glion. It  is  a  short,  flattened  band, 
about  2  cm.  in  length,  which  passes 
forward  along  the  outer  wall  of  the 
cavernous  sinus  (Figs.  454  and  455), 
below  the  other  nerves  (Fig.  685),  and 
just  before  entering  the  orbit,  through 
the  sphenoidal  fissure,  divides  into 
three  branches — lacrimal,  frontal,  and 
nasal  (Figs.  683,  687,  and  688). 

Branches  of  Communication. — The 
ophthalmic  nerve  gives  off  in  the 
cavernous  sinus  a  branch  to  the  dura 
(ji.  tentorii),  is  joined  by  filaments 
from  the  cavernous  plexus  of  the  sym- 
pathetic, and  gives  off  minute  branches  to  communicate  with  the  oculomotor  and 
abducent  nerves,  and  not  infrequently  with  the  trochlear. 

Branches  of  Distribution. — It  gives  off  recurrent  filaments  which  pass  between 
the  layers  of  the  tentorium,  and  then  divide  into — 

Lacrimal.  Frontal.  Nasal. 

The  Lacrimal  Nerve  (n.  lacrimalis)  (Figs.  683,  687,  and  688). — The  lacrimal 
is  the  smallest  of  the  three  branches  of  the  ophthalmic.  It  sometimes  receives 
a  filament  from  the  trochlear  nerve,  but  this  is  possibly  derived  from  the  branch 
of  communication  which  passes  from  the  ophthalmic  to  the  trochlear.  It  passes 
forward  in  a  separate  tube  of  dura,  and  enters  the  orbit  through  the  nar- 
rowest part  of  the  sphenoidal  fissure  (Fig.  692).  In  the  orbit  it  runs  along  the 
upper  border  of  the  External  rectus  muscle,  with  the  lacrimal  artery,  and  com- 
municates with  the  temporomalar  branch  of  the  superior  maxillary  nerve.  It 
enters  the  lacrimal  gland  and  gives  off  several  filaments,  which  supply  the 
gland  and  the  conjunctiva.  Finally,  it  pierces  the  superior  palpebral  ligament, 
and  terminates  in  the  integument  of  the  upper  eyelid,  joining  with  filaments  of 
the  facial  nerve.  The  lacrimal  nerve  is  occasionally  absent,  when  its  place  is 
taken  by  the  temporal  branch  of  the  superior  maxillary.  Sometimes  the  latter 
branch  is  absent,  and  a  continuation  of  the  lacrimal  is  substituted  for  it. 

The  Frontal  Nerve  (n.  frontalis)  (Figs.  683  and  687). — The  frontal  is  the  largest 
division  of  the  ophthalmic,  and  may  be  regarded,  both  from  its  size  and  direc- 
tion, as  the  continuation  of  the  nerve.  It  enters  the  orbit  above  the  muscles, 
through  the  sphenoidal  fissure  (Fig.  692),  and  runs  forward  along  the  middle  line, 
between  the  Levator  palpebrae  and  the  periosteum.  Midway  between  the  apex  and 
the  base  of  the  orbit  it  divides  into  two  branches,  supratrochlear  and  supraorbital. 


SENSOR    ROOT. 
DIVIDED 


SUPERIOR 
PETROSAL  SINUS 


FACIAL   AND 
ACOUSTIC    NERVES 


FIG.  686. — The  course  of  the  motor  root  of  the  trigem- 
inal nerve.     (Poirier  and  Charpy.) 


1044 


THE  NERVE  SYSTEM 


The  Supratrochlear  Branch  (n.  supratrochlearis)  (Fig.  683),  the  smaller  of  the 
two,  passes  inward,  above  the  pulley  of  the  superior  oblique  muscle,  and  gives 
off  a  descending  filament,  which  joins  with  the  infratrochlear  branch  of  the  nasal 
nerve.  It  then  escapes  from  the  orbit  between  the  pulley  of  the  Superior  oblique  and 
the  supraorbital  foramen,  curves  up  on  to  the  forehead  close  to  the  bone,  ascends 
beneath  the  Corrugator  supercilii  and  Occipito-frontalis  muscles,  and,  dividing 
into  branches  which  pierce  these  muscles,  it  supplies  the  integument  of  the  lower 
part  of  the  forehead  on  either  side  of  the  middle  line  and  sends  filaments  to  the 
conjunctiva  and  skin  of  the  upper  lid. 

The  Supraorbital  Branch  (n.  supraorbitalis]  (Fig.  692)  passes  forward  through 
the  supraorbital  foramen,  and  gives  off,  in  this  situation,  palpebral  filaments  to 
the  upper  eyelid.  It  then  ascends  upon  the  forehead,  and  terminates  in  cutaneous 
and  pericranial  branches. 

The  cutaneous  branches,  two  in  number,  an  inner  and  an  outer,  supply  the  integ- 
ument of  the  cranium  as  far  back  as  the  vertex.  They  are  at  first  situated  beneath 
the  Occipito-frontalis,  the  inner  branch  perforating  the  frontal  portion  of  the 
muscle,  the  outer  branch  its  tendinous  aponeurosis. 

The  pericranial  branches  are  distributed  to  the  pericranium  over  the  frontal  and 
parietal  bones. 


Internal  carotid  artery 
and  carotid  plexus. 


FIG.  687. — Nerves  of  the  orbit  and  ophthalmic  ganglion,  side  view. 

The  Nasal  Nerve  (n.  nasociliaris)  (Figs.  683  and  687). — The  nasal  nerve  is 
intermediate  in  size  between  the  frontal  and  lacrimal,  and  more  deeply  placed 
than  the  other  branches  of  the  ophthalmic.  It  enters  the  orbit  by  way  of  the 
sphenoidal  fissure  (Fig.  692)  between  the  two  heads  of  the  External  rectus, 
and  passes  obliquely  inward  across  the  optic  nerve,  beneath  the  Superior  rectus 
and  Superior  oblique  muscles,  to  the  inner  wall  of  the  orbit,  where  it  passes  through 
the  anterior  ethmoidal  foramen,  and,  entering  the  cavity  of  the  cranium,  tra- 
verses a  shallow  groove  on  the  front  of  the  cribriform  plate  of  the  ethmoid 
bone,  and  passes  down,  through  the  slit  by  the  side  of  the  crista  galli,  into  the 
nose  (Fig.  689),  where  it  divides  into  two  branches,  an  internal  and  an  external 
branch.  The  internal  branch  (rami  nasales  mediales)  supplies  the  mucous  mem- 
brane near  the  forepart  of  the  septum  of  the  nose.  The  external  branch  (rami 
nasales  laterales]  descends  in  a  groove  on  the  inner  surface  of  the  nasal  bone,  and 
supplies  a  few  filaments  to  the  mucous  membrane  covering  the  forepart  of  the 
outer  wall  of  the  nares  as  far  as  the  inferior  turbinate  bone;  it  then  leaves  the  cavity 


THE  FIFTH,   TRIGEMINAL  OR  TRIFACIAL  NERVE          1045 

of  the  nose,  between  the  lower  border  of  the  nasal  bone  and  the  upper  lateral 
cartilage  of  the  nose,  and,  passing  down  beneath  the  Compressor  nasi,  supplies 
the  integument  of  the  ala  and  the  tip  of  the  nose,  joining  with  the  facial  nerve. 

Branches. — The  branches  of  the  nasal  nerve  are  the  ganglionic,  ciliary,  and  infra- 
trochlear. 

The  Ganglionic  Branch  or  the  long  root  of  the  ciliary  ganglion  (radix  longa  ganglii 
cilia  rix)  (Figs.  684  and  687)  is  a  slender  branch,  about  1  to  2  cm.  in  length, 
which  usually  arises  from  the  nasal  nerve,  between  the  two  heads  of  the  External 
rectus  muscle.  It  passes  forward  on  the  outer  side  of  the  optic  nerve,  and  enters 
the  postero-superior  angle  of  the  ciliary  ganglion,  forming  its  long  root.  It  is 
sometimes  joined  by  a  filament  from  the  cavernous  plexus  of  the  sympathetic  or 
from  the  superior  division  of  the  third  nerve. 

The  Long  Ciliary  Nerves  (/m.  ciliares  longi),  two  or  three  in  number,  are  given 
off  from  the  nasal  as  it  crosses  the  optic  nerve.  They  join  the  short  ciliary  nerves 
(Figs.  684  and  687)  from  the  ciliary  ganglion,  pierce  the  posterior  part  of  the  sclera, 
and,  running  forward  between  it  and  the  choroid,  are  distributed  to  the  ciliary 
muscle,  iris,  and  cornea. 

The  Infratrochlear  Branch  (n.  infratrochlearis)  (Fig.  683)  is  given  off  just  before 
the  nasal  nerve  passes  through  the  anterior  ethmoidal  foramen.  It  runs  for- 
ward along  the  upper  border  of  the  Internal  rectus  muscle,  and  is  joined,  beneath 
the  pulley  of  the  Superior  oblique,  by  a  filament  from  the  supratrochlear  nerve. 
It  then  passes  to  the  inner  angle  of  the  eye,  and  supplies  the  integument  of  the 
evelids  and  side  of  the  nose,  the  conjunctiva,  the  lacrimal  sac,  and  the  caruncula 
lacrimalis. 

Connected  with  the  three  divisions  of  the  trigeminal  nerve  are  four  small  ganglia. 
With  the  first  division  is  connected  the  ophthalmic  ganglion;  with  the  second 
division,  the  sphenopalatine  or  Meckel's  ganglion ;  and  with  the  third,  the  otic  and 
submaxillary  ganglia.  All  the  four  receive  sensor  filaments  from  the  trigeminal 
nerve,  and  motor  and  sympathetic  filaments  from  various  sources;  these  filaments 
are  called  the  roots  of  the  ganglia. 

The  Ophthalmic,  Lenticular  or  Ciliary  Ganglion  (ganglion  ciliare)  (Figs.  684  and 
687)  is  a  small,  quadrangular,  flattened  ganglion,  of  a  reddish-gray  color,  and 
about  the  size  of  a  pin's  head,  situated  at  the  back  part  of  the  orbit  between  the 
optic  nerve  and  the  External  rectus  muscle,  lying  generally  on  the  outer  side  of 
the  ophthalmic  artery.  It  is  enclosed  in  a  quantity  of  loose  fat,  which  makes  its 
exposure  by  dissection  somewhat  difficult. 

Its  branches  of  communication  or  roots  are  three,  all  of  which  enter  its  posterior 
border.  One,  the  long  or  sensor  root  (radix  longa  ganglii  ciliaris],  is  derived 
from  the  nasal  branch  of  the  ophthalmic  and  joins  the  superior  angle  of  the 
ganglion.  The  second,  the  short  or  motor  root  (radix  brevis  ganglii  ciliaris),  is  a 
short,  thick  nerve,  occasionally  divided  into  two  parts,  which  is  derived  from  the 
branch  of  the  oculomotor  to  the  Inferior  oblique  muscle,  and  is  connected  with 
the  inferior  angle  of  the  ganglion.  The  third,  the  sympathetic  root  (radix  sympa- 
thetica  ganglii  ciliaris),  is  a  slender  filament  from  the  cavernous  plexus  of  the 
sympathetic.  This  is  frequently  blended  with  the  long  root,  although  it  some- 
times passes  to  the  ganglion  separately.  The  ganglion  occasionally  receives  a 
filament  of  communication  from  the  sphenopalatine  ganglion. 

Its  branches  of  distribution  are  the  short  ciliary  nerves  (nn.  ciliares  breves]  (Figs. 
684  and  687).  These  are  delicate  filaments,  from  six  to  ten  in  number,  which 
arise  from  the  forepart  of  the  ganglion  in  two  bundles,  connected  with  its  superior 
and  inferior  angles;  the  lower  bundle  is  the  larger.  They  run  forward  with  the 
ciliary  arteries  in  a  wavy  course,  one  set  above  and  the  other  below  the  optic 
nerve,  and  are  accompanied  by  the  long  ciliary  branches  of  the  nasal  nerve. 
They  pierce  the  sclera  at  the  back  part  of  the  globe,  pass  forward  in  delicate 


1046  THE  NERVE  SYSTEM 

grooves  on  its  inner  surface,  and  are  distributed  to  the  Ciliary  muscle,  iris,  and 
cornea.  One  small  branch  is  said  to  penetrate  the  optic  nerve  with  the  arteria 
centralis  retinte. 

The  circular  fibres  of  the  iris  are  innervated  by  the  oculomotor  nerve;  the 
radiating  fibres  are  innervated  by  the  sympathetic. 

The  Superior  Maxillary  Nerve  (n.  maxillaris)  (Figs.  685,  686,  687,  and  688). 
—The  superior  maxillary  or  second  division  of  the  trigeminal  is  a  sensor  nerve. 
It  is  intermediate,  both  in  position  and  size,  between  the  ophthalmic  and  inferior 
maxillary.  It  commences  at  the  middle  of  the  Gasserian  ganglion  as  a  flat- 
tened plexiform  band  (Fig.  685),  and,  passing  horizontally  forward,  it  leaves  the 
skull  through  the  foramen  rotundum  (Fig.  686),  where  it  becomes  more  cylindrical 
in  form  and  firmer  in  texture.  It  then  crosses  the  spheno-maxillary  fossa  (Fig.  67) 
enters  the  orbit  through  the  spheno-maxillary  fissure,  traverses  the  infraorbital 
canal  in  the  floor  of  the  orbit,  and  appears  upon  the  face  at  the  infraorbital  fora- 
men. After  it  enters  the  infraorbital  canal  the  nerve  is  usually  called  the  infra- 
orbital  (n.  infraorbitalis),  and  is,  therefore,  the  terminal  branch  of  the  superior 
maxillary  nerve  (Fig.  G88).  At  its  termination  the  nerve  lies  beneath  the  Levator 
labii  superioris  muscle,  and  divides  into  a  leash  of  branches,  which  spread  out 
upon  the  side  of  the  nose,  the  lower  eyelid,  and  upper  lip,  joining  with  filaments 
of  the  facial  nerve. 

Branches  of  Distribution. — The  branches  of  this  nerve  may  be  divided  into  four 
groups:  1.  Those  given  off  in  the  cranium.  2.  Those  given  off  in  the  spheno- 
maxillary  fossa.  3.  Those  in  the  infraorbital  canal.  4.  Those  on  the  face. 

In  the  cranium       .      .      .        Dural. 

(  Orbital  or  temporo-malar. 
Spheno-maxillary  fossa      .    <  Spheno-palatine. 

(  Posterior  superior  dental. 
Infraorbital  canal  f  Middle  superior  dental. 

J-IJIlttUl  Ulldl    (  <l  1 1<1 1      .          .          .       ^i      A  •  •  i         j.     i 

[  Anterior  superior  dental. 
(  Palpebral. 

On  the  face  .    <  Nasal. 

t  Labial. 

The  Dural  Branch  (n.  meningeus  medius). — The  dural  branch  is  given  off  by 
the  superior  maxillary  nerve  directly  after  its  orgin  from  the  Gasserian  ganglion; 
it  accompanies  the  medidural  artery  and  supplies  the  dura  of  the  middle  fossa 
of  the  base  of  the  skull. 

The  Orbital  or  Temporo-malar  Branch  (n.  zygomaticus]  (Figs.  687  and  688).— 
The  orbital  or  temporo-malar  branch  arises  in  the  spheno-maxillary  fossa,  enters 
the  orbit  by  the  spheno-maxillary  fissure,  and  divides  at  the  back  of  that  cavity 
into  two  branches,  temporal  and  malar. 

The  Temporal  Branch  (ramus  zygomaticotemporalis)  runs  in  a  groove  along  the 
outer  wall  of  the  orbit  (in  the  malar  bone,),  receives  a  branch  of  communication 
from  the  lacrimal,  and,  passing  through  a  foramen  in  the  malar  bone,  enters  the 
temporal  fossa.  It  ascends  between  the  bone  and  the  substance  of  the  Temporal 
muscle,  pierces  this  muscle  and  the  temporal  fascia  about  an  inch  above  the 
zygoma,  and  is  distributed  to  the  integument  covering  the  temple  and  side  of 
the  forehead,  communicating  with  the  facial  and  the  auriculo-temporal  branch  of 
the  inferior  maxillary  nerve.  As  it  pierces  the  temporal  fascia  it  gives  off  a  slender 
twig,  which  runs  between  the  two  layers  of  the  fascia  to  the  outer  angle  of  the 
orbit. 

The  Malar  Branch  (ramus  zygomaticofacialis)  passes  along  the  external  inferior 
angle  of  the  orbit,  emerges  upon  the  face  through  a  foramen  in  the  malar  bone, 
and,  perforating  the  Orbicularis  palpebrarum  muscle,  supplies  the  skin  on  the 


THE  FIFTH,    TRIGEMINAL   OR  TRIFACIAL  NERVE         1047 

prominence  of  the  cheek,  where  it  is  named  the  subcutaneus  malae.  It  joins  with 
the  facial  and  the  palpebral  branches  of  the  superior  maxillary. 

The  Spheno-palatine  Branches  (nn.  sphenopalatini)  (Fig.  688).— The  spheno- 
palutine  branches,  two  in  number,  descend  to  the  spheno-palatine  ganglion,  of 
which  ganglion  they  are  the  sensor  or  short  roots. 

The  Posterior  Superior  Dental  Branches  (rami  alveolares  superiores  posteriores] 
(Fig.  688). — The  posterior  superior  dental  branches  arise  from  the  trunk  of  the 
nerve  just  as  it  is  about  to  enter  the  infraorbital  canal;  they  are  generally  two 
in  number,  but  sometimes  arise  by  a  single  trunk,  and  immediately  divide  and 
pass  downward  on  the  tuberosity  of  the  superior  maxillary  bone.  They  give 
off  several  twigs  to  the  gums  and  neighboring  parts  of  the  mucous  membrane  of 
the  cheek,  superior  gingival  branches  (rami  gingivales  superiores}.  They  then 
enter  the  posterior  dental  canals  on  the  zygomatic  surface  of  the  superior  maxil- 


Auriculo-temporal/ 
nerve. 


FIG.  688. — Distribution  of  the  second  and  third  divisions  of  the  fifth  nerve  and  submaxillayy  ganglion. 

lary  bone,  and,  passing  from  behind  forward  in  the  substance  of  the  bone,  com- 
municate with  the  middle  dental  nerve  by  a  plexus  formation,  and  give  off  branches 
to  the  lining  membrane  of  the  antrum  and  three  twigs  to  each  of  the  molar  teeth. 
These  twigs  enter  the  foramina  at  the  apices  of  the  fangs  and  supply  the  pulp. 

The  Middle  Superior  Dental  Branch  (ramus  alveolaris  superior  medius}. — The 
middle  superior  dental  branch  is  given  off  from  the  superior  maxillary  nerve  in  the 
back  part  of  the  infraorbital  canal,  and  runs  downward  and  forward  in  a  special 
canal  in  the  outer  wall  of  the  antrum  to  supply  the  two  bicuspid  teeth.  It  com- 
municates with  the  posterior  and  anterior  dental  branches  by  a  plexus  formation. 
At  its  point  of  communication  with  the  posterior  branch,  above  the  root  of  the 
second  bicuspid  tooth,  is  a  slight  thickening  which  is  the  so-called  ganglion  of 
Valentin;  and  at  its  point  of  communication  with  the  anterior  branch  is  a  second 


1048  THE  NER  VE  SYSTEM 

enlargement,  which  is  called  the  ganglion  of  Bochdalek.  Neither  of  these  is  a  true 
ganglion. 

The  Anterior  Superior  Dental  Branch  (ramus  alveolaris  superior  anterior  es}. — The 
anterior  superior  dental  branch,  of  large  size,  is  given  off  from  the  superior  maxil- 
lary nerve  just  before  its  exit  from  the  infraorbital  foramen;  it  enters  a  special 
canal  in  the  anterior  wall  of  the  antrum,  and  divides  into  a  series  of  branches 
which  supply  the  incisor  and  canine  teeth.  It  communicates  with  the  middle 
dental  nerve  by  a  plexus,  and  gives  off  a  nasal  branch,  which  passes  through  a 
minute  canal  into  the  nasal  fossa,  and  supplies  the  mucous  membrane  of  the 
forepart  of  the  inferior  meatus  and  the  floor  of  the  cavity,  communicating  with 
the  nasal  branches  from  the  spheno-palatine  ganglion. 

The  superior  dental  plexus  (plexus  dentalis  superior)  is  formed  by  twigs  of  the 
three  superior  dental  nerves.  From  the  plexus  come  the  nerves  which  supply  the 
teeth  of  the  upper  jaw  (rami  dentales  superior  es}  and  the  gums  (rami  gingivales 
super  lores}. 

The  branches  upon  the  face  are  known  as  the  rami  n.  infraorbitalis  (Fig.  688). 
There  are  three  sets  of  them. 

The  Palpebral  Branches  (rami  palpebrales  inferiores). — The  palpebral  branches 
pass  upward  beneath  the  Orbicularis  palpebrarum  muscle.  They  supply  the 
integument  and  conjunctiva  of  the  lower  eyelid  with  sensation,  joining  at 
the  outer  angle  of  the  orbit  with  the  facial  nerve  and  the  malar  branch  of  the 
orbital. 

The  Nasal  Branches  (rami  nasales  interni}. — The  nasal  branches  pass  inward: 
they  supply  the  integument  of  the  side  of  the  nose  and  join  with  the  nasal  branch 
of  the  ophthalmic. 

The  Labial  Branches  (rami  labiales  superior  es]. — The  labial  branches,  the 
largest  and  most  numerous,  descend  beneath  the  Levator  labii  superioris  muscle, 
and  are  distributed  to  the  integument  of  the  upper  lip,  the  mucous  membrane 
of  the  mouth,  and  the  labial  glands. 

All  these  branches  are  joined,  immediately  beneath  the  orbit,  by  filaments  from 
the  facial  nerve,  forming  an  intricate  plexus,  the  infraorbital  plexus. 

The  Spheno-palatine  or  Meckel's  Ganglion  (ganglion  sphenopalatinum}  (Fig. 
689). — The  spheno-palatine  ganglion,  the  largest  of  the  cranial  ganglia,  is  deeply 
placed  in  the  spheno-maxillary  fossa,  close  to  the  spheno-palatine  foramen.  It 
is  triangular  or  heart-shaped,  of  a  reddish-gray  color,  and  is  situated  just  below 
the  superior  maxillary  nerve  as  it  crosses  the  fossa. 

Branches  of  Communication. — Like  the  other  ganglia  of  the  trigeminal  nerve,  it 
possesses  a  motor,  a  sensor,  and  a  sympathetic  root.  Its  sensor  root  is  derived 
from  the  superior  maxillary  nerve  through  its  two  spheno-palatine  branches 
(p.  1047).  These  branches  of  the  nerve  are  given  off  in  the  spheno-maxillary  fossa 
and  descend  to  the  ganglion.  Their  fibres,  for  the  most  part,  pass  in  front  of  the 
ganglion,  as  they  proceed  to  their  destination,  in  the  palate  and  nasal  fossa,  and 
are  not  incorporated  in  the  ganglionic  mass;  some  few  of  the  fibres,  however,  enter 
the  ganglion,  constituting  its  sensor  root.  Its  motor  root  is  derived  from  the  facial 
nerve  through  the  large  superficial  petrosal  nerve,  and  its  sympathetic  root  from 
the  carotid  plexus,  through  the  large  deep  petrosal  nerve.  These  two  nerves  join 
together  before  their  entrance  into  the  ganglion  to  form  a  single  nerve,  the  Vidian. 

The  Large  or  Great  Superficial  Petrosal  Branch  (n.  petrosus  super ficialis  major} 
(Fig.  693)  is  given  off  from  the  geniculate  ganglion  of  the  facial  nerve  in  the 
aquaeductus  Fallopii;  it  passes  through  the  hiatus  Fallopii;  enterS  the  cranial 
cavity,  and  runs  forward,  being  contained  in  a  groove  on  the  anterior  surface 
of  the  petrous  portion  of  the  temporal  bone  and  lies  beneath  the  dura.  It  then 
enters  the  cartilaginous  substance  which  fills  in  the  foramen  lacerum  medium  basis 
cranii,  and,  joining  with  the  large  deep  petrosal  branch,  forms  the  Vidian  nerve. 


THE  FIFTH,    TRIGEMINAL  OR   TRIFACIAL  NERVE 


1049 


The  Large  or  Great  Deep  Petrosal  Branch  (n.  petrosus  prof  undies')  (Fig.  694)  is 
given  off  from  the  carotid  plexus  of  the  sympathetic  upon  the  internal  carotid 
artery,  and  runs  through  the  carotid  canal  on  the  outer  side  of  the  internal  carotid 
artery.  It  then  enters  the  cartilaginous  substance  which  fills  in  the  foramen 
laecTiim  medium  basis  cranii,  and  joins  with  the  large  superficial  petrosal  nerve 
to  form  the  Vidian. 

The  Vidian  Nerve  (n.  canalis  pterygoidei)  (Fig.  689),  formed  in  the  cartilagi- 
nous substance  which  fills  in  the  middle  lacerated  foramen  by  the  junction  of 
the  two  preceding  nerves,  passes  forward,  through  the  Vidian  canal,  with  the 
artery  of  the  same  name,  and  is  joined  by  a  small  ascending  nervous  branch,  the 
sphenoidal  branch,  from  the  otic  ganglion.  Finally,  it  enters  the  spheno-maxillary 
fossa,  and  joins  the  posterior  angle  of  the  spheno-palatine  ganglion. 

Branches  of  Distribution  of  the  Spheno-palatine  Ganglion. — Its  branches  of  distri- 
bution are  divisible  into  four  groups:  ascending,  which  pass  to  the  orbit;  descend- 
ing, to  the  palate;  internal,  to  the  nose;  and  posterior  branches,  to  the  pharynx  and 
nasal  fossae. 


Termination  of 

naso-palatine 

nerve. 


FIG.  689. — The  spheno-palatine  or  Meckel's  ganglion  and  its  branches. 

The  Ascending  Branches  (rami  orbitales}  are  two  or  three  delicate  filaments  which 
enter  the  orbit  by  the  spheno-maxillary  fissure,  and  supply  the  periosteum.  Accord- 
ing to  Luschka,  some  filaments  pass  through  foramina  in  the  suture  between  the 
os  planum  of  the  ethmoid  and  frontal  bones  to  supply  the  mucous  membrane  of 
the  posterior  ethmoidal  and  sphenoidal  sinuses. 

The  Descending  or  Palatine  Branches  (nn.  palatini)  (Fig.  689)  are  distributed 
to  the  roof  of  the  mouth,  the  soft  palate,  tonsil,  and  lining  membrane  of  the  nose. 
They  are  almost  a  direct  continuation  of  the  spheno-palatine  branches  of  the 
superior  maxillary  nerve,  and  are  three  in  number — anterior,  middle,  and  posterior. 

The  anterior  or  large  palatine  nerve  (n.  palatinus  anterior}  descends  through 
the  large  posterior  palatine  canal,  emerges  upon  the  hard  palate  at  the  posterior 
palatine  foramen,  and  passes  forward  through  a  groove  in  the  hard  palate  nearly 


1050  THE  NER  VE  SYSTEM 

as  far  as  the  incisor  teeth.  It  supplies  the  gums,  the  mucous  membrane  and  glands 
of  the  hard  palate,  and  communicates  in  front  with  the  termination  of  the  naso- 
palatine  nerve  (see  below).  While  in  the  posterior  palatine  canal  it  gives  oft'  inferior 
nasal  branches  (rami  nasales  posteriores  inferiores),  which  enter  the  nose  through 
openings  in  the  palate  bone,  and  ramify  over  the  inferior  turbinated  bone,  the 
middle  and  the  inferior  meatus;  and  at  its  exit  from  the  canal  a  palatine  branch 
is  distributed  to  both  surfaces  of  the  soft  palate. 

The  middle  or  external  palatine  nerve  (n.  palatinus  medius)  descends  through 
one  of  the  accessory  palatine  canals,  distributing  branches  to  the  uvula,  tonsil, 
and  soft  palate.  It  is  occasionally  wanting. 

The  posterior  or  small  palatine  nerve  (n.  palatinus  posterior}  descends  with  a 
minute  artery  through  the  small  posterior  palatine  canal,  emerging  by  a  separate 
opening  behind  the  posterior  palatine  foramen.  It  supplies  the  Levator  palati 
and  Azygos  uvulae  muscles,1  the  soft  palate,  tonsil,  and  uvula.  The  middle  and 
posterior  palatine  join  with  the  tonsillar  branches  of  the  glosso-pharyngeal  to  form 
the  plexus  around  the  tonsil,  the  circulus  tonsillaris. 

The  Internal  Branches  are  distributed  to  the  septum  and  outer  wall  of  the  nasal 
fossae.  They  are  the  posterior  superior  nasal  and  the  naso-palatine. 

The  posterior  superior  nasal  branches  (rami  nasales  posteriores  superiores),  three 
in  number,  enter  the  back  part  of  the  nasal  fossa  by  the  spheno-palatine  foramen. 
They  supply  the  mucous  membrane  covering  the  superior  and  middle  spongy 
bones,  and  that  lining  the  posterior  ethmoidal  cells,  a  few  being  prolonged  to  the 
upper  and  back  part  of  the  septum. 

The  naso-palatine  nerve  (n.  nasopalatinus}  has  been  called  the  nerve  of  Scarpa 
and  also  the  nerve  of  Cotunnius.  It  enters  the  nasal  fossa  through  the  spheno- 
palatine  foramen,  and  passes  inward  across  the  roof  of  the  nose,  below  the  orifice 
of  the  sphenoidal  sinus,  to  reach  the  septum;  it  then  runs  obliquely  downward  and 
forward  along  the  lower  part  of  the  septum,  to  the  anterior  palatine  foramen, 
lying  between  the  periosteum  and  mucous  membrane.  It  descends  to  the  roof  of 
the  mouth  through  the  anterior  palatine  canal  (Fig.  689).  The  two  nerves  are  here 
contained  in  separate  and  distinct  canals,  situated  in  the  intermaxillary  suture,  and 
termed  the  foramina  of  Scarpa,  the  left  nerve  being  usually  anterior  to  the  right 
one.  In  the  mouth  they  become  united,  supply  the  mucous  membrane  behind 
the  incisor  teeth,  and  join  with  the  anterior  palatine  nerve.  The  naso-palatine 
nerve  furnishes  a  few  small  filaments  to  the  mucous  membrane  of  the  septum. 

The  Posterior  Branches  are  the  pharyngeal  or  pterygo-palatine  and  the  upper 
posterior  nasal  branches. 

The  pharyngeal  or  pterygo-palatine  nerve  (Fig.  689)  is  a  small  branch  arising 
from  the  back  part  of  the  spheno-palatine  ganglion,  being  generally  blended  with 
the  Vidian  nerve.  It  passes  through  the  pterygo-palatine  canal  with  the  pterygo- 
palatine  artery,  and  is  distributed  to  the  mucous  membrane  of  the  upper  part 
of  the  pharynx,  behind  the  Eustachian  tube. 

The  upper  posterior  nasal  branches  are  a  few  twigs  given  off  from  the  posterior 
part  of  the  spheno-palatine  ganglion,  which  run  backward  in  the  sheath  of  the 
Vidian  nerve  to  the  mucous  membrane  at  the  back  part  of  the  roof,  septum,  and 
superior  meatus  of  the  nose  and  that  covering  the  end  of  the  Eustachian  tube. 

The  Mandibular  or  Inferior  Maxillary  Nerve  (n.  mandibularis)  (Figs.  685, 
687,  and  688). — The  inferior  maxillary  or  third  division  of  the  trigeminal  nerve  dis- 
tributes branches  to  the  teeth  and  gums  of  the  lower  jaw,  the  integument  of  the 
temple  and  external  ear,  the  lower  part  of  the  face  and  lower  lip,  and  the  muscles 
of  mastication ;  it  also  supplies  the  tongue  with  a  large  branch.  It  is  the  largest  of 
the  three  divisions  of  the  trigeminal,  and  is  made  up  of  two  roots:  a  large  or  sensor 

1  It  is  probable  that  this  is  not  the  true  motor  supply  to  these  muscles,  but  that  they  are  supplied  by  the 
accessory  nerve  through  the  pharyngeal  plexus. — ED.  of  15th  English  edition. 


THE  FIFTH,   TRIGEMINAL  OR  TRIFACIAL  NERVE          1051 

root,  proceeding  from  the  inferior  angle  of  the  Gasserian  ganglion;  and  a  small  or 
motor  root,  which  passes  beneath  the  ganglion  and  unites  with  the  sensor  root  just 
after  its  exit  from  the  skull  through  the  foramen  ovale  (Figs.  685,  686,  and  688). 
Immediately  beneath  the  base  of  the  skull  this  nerve  divides  into  two  trunks, 
anterior  and  posterior.  Previous  to  its  division  the  primary  trunk  gives  off  from 
its  inner  side  a  recurrent  branch  and  the  nerve  to  the  Internal  pterygoid  muscle. 

The  Recurrent  or  Meningeal  Branch  (n.  spinosus). — The  recurrent  or  meningeal 
branch  is  given  off  directly  after  the  exit  of  the  mandibular  nerve  from  the  foramen 
ovale.  It  passes  backward  into  the  skull  through  the  foramen  spinosum  with 
the  medidural  artery.  It  divides  into  two  branches,  anterior  and  posterior, 
which  accompany  the  main  divisions  of  the  artery  and  supply  the  dura.  The  pos- 
terior branch  also  supplies  the  mucous  lining  of  the  mastoid  cells.  The  anterior 
branch  communicates  with  the  dural  branch  of  the  superior  maxillary  nerve. 

The  Internal  Pterygoid  Nerve  (n.  pterygoideus  internus). — Tht  internal  ptery- 
goid nerve,  given  off  from  the  inferior  maxillary  previous  to  its  division,  is  inti- 
mately connected  at  its  origin  with  the  otic  ganglion.  It  is  a  long  and  slender 
branch,  which  passes  inward  to  enter  the  deep  surface  of  the  Internal  pterygoid 
muscle. 

The  anterior  and  smaller  division  of  the  inferior  maxillary  nerve,  which  receives 
nearly  the  whole  of  the  motor  root  of  the  trigeminal  nerve,  divides  into  branches 
which  supply  the  muscles  of  mastication.  They  are  the  masseteric,  deep  temporal, 
buccal,  and  external  pterygoid  branches  (Fig.  688). 

The  Masseteric  Branch  (n.  massetericus)  passes  outward,  above  the  External 
pterygoid  muscle,  in  front  of  the  temporo-mandibular  articulation  and  behind  the 
tendon  of  the  temporal  muscle;  it  crosses  the  sigmoid  notch  with  the  masseteric 
artery,  to  the  deep  surface  of  the  Masseter  muscle,  in  which  it  ramifies  nearly  as 
far  as  its  anterior  border.  It  occasionally  gives  a  branch  to  the  Temporal  muscle, 
and  a  filament  to  the  articulation  of  the  jaw. 

The  Deep  Temporal  Branches  (nn.  temporales  profundi),  two  in  number,  anterior 
and  posterior,  supply  the  deep  surface  of  the  Temporal  muscle.  The  posterior 
branch  (n.  temporalis  profundus  posterior),  of  small  size,  is  placed  at  the  back  of 
the  temporal  fossa.  It  is  sometimes  joined  with  the  masseteric  branch.  The 
anterior  branch  (n.  temporalis  profundus  anterior)  is  frequently  given  off  from  the 
buccal  nerve;  it  is  reflected  upward,  at  the  pterygoid  ridge  of  the  sphenoid,  to  the 
front  of  the  temporal  fossa.  Sometimes  there  are  three  deep  temporal  branches, 
and  if  this  maintains  the  third  branch,  the  middle  deep  temporal,  passes  outward 
above  the  External  pterygoid  muscle,  and  runs  upward  on  the  bone  to  enter  the 
deep  surface  of  the  Temporal  muscle. 

The  Buccal  or  Buccinator  Branch  (n.  buccinatorius)  passes  forward  between  the 
two  heads  of  the  External  pterygoid,  and  downward  beneath  the  inner  surface  of 
the  coronoid  processes  of  the  lower  jaw,  or  through  the  fibres  of  the  Temporal 
muscle,  to  reach  the  surface  of  the  Buccinator  muscle,  upon  which  it  divides  into 
a  superior  and  an  inferior  branch.  It  gives  a  branch  to  the  External  pterygoid 
during  its  passage  through  that  muscle,  and  a  few  ascending  filaments  to  the 
Temporal  muscle,  one  of  which  occasionally  joins  with  the  anterior  branch  of  the 
deep  temporal  nerve.  The  superior  or  upper  branch  supplies  the  integument  and 
upper  part  of  the  Buccinator  muscle,  joining  with  the  facial  nerve  around  the 
facial  vein.  The  inferior  or  lower  branch  passes  forward  to  the  angle  of  the  mouth; 
it  supplies  the  integument  and  Buccinator  muscle,  as  well  as  the  mucous  membrane 
lining  the  inner  surface  of  that  muscle,  and  joins  the  facial  nerve.1 

The  External  Pterygoid  Nerve  (n.  pterygoideus  externus)  is  most  frequently 
derived  from  the  buccal,  but  it  may  be  given  off  separately  from  the  anterior 
trunk  of  the  mandibular  nerve.  It  enters  the  muscle  on  its  inner  surface. 

1  There  seems  to  be  no  reason  to  doubt  that  the  branch  supplying  the  Buccinator  muscle  is  entirely  a  nerve  of 
ordinary  sensation,  and  that  the  true  motor  supply  of  this  muscle  is  from  the  facial. — ED.  of  15th  English  edition. 


1052  THE  NER  VE  SYSTEM 

The  posterior  and  larger  division  of  the  inferior  maxillary  nerve  is  for  the  most  part 
sensor,  but  receives  a  few  filaments  from  the  motor  root.  It  divides  into  three 
branches:  auriculo-temporal,  lingual  (gustatory),  and  inferior  dental  (Fig.  688). 

The  Auriculo-temporal  Nerve  (n.  auriculotemporalis)  (Fig.  690)  generally  arises 
by  two  roots,  between  which  the  medidural  artery  passes.  It  runs  backward 
beneath  the  External  pterygoid  muscle  to  the  inner  side  of  the  neck  of  the  lower 
jaw.  It  then  turns  upward  with  the  temporal  artery,  between  the  external  ear 
and  the  condyle  of  the  jaw,  under  cover  of  the  parotid  gland,  and,  escaping  from 
beneath  this  structure,  ascends  over  the  zygoma  and  divides  into  two  temporal 
branches. 

The  branches  of  communication  are  with  the  facial  and  with  the  otic  ganglion. 
The  branches  of  communication  with  the  facial  (rami  anastomotici  cum  n.  faciali], 
usually  two  in  number,  pass  forward  from  behind  the  neck  of  the  condyle  of  the 
jaw,  to  join  this  nerve  at  the  posterior  border  of  the  Masseter  muscle.  They 
form  one  of  the  principal  branches  of  communication  between  the  facial  and  the 
trigeminal  nerve.  The  filaments  of  communication  with  the  otic  ganglion  are 
derived  from  the  commencement  of  the  auriculotemporal  nerve. 

The  branches  of  distribution  are — 

Anterior  auricular.  Articular. 

Branches  to  the  meatus  auditorius.  Parotid. 

Superficial  temporal. 

The  anterior  auricular  branches  (nn.  auriculares  anteriores)  are  usually  two  in 
number.  They  supply  the  front  of  the  upper  part  of  the  pinna,  being  distributed 
principally  to  the  skin  covering  the  front  of  the  helix  and  tragus. 

A  branch  to  the  external  auditory  meatus  (n.  meatus  auditorii  externi)  divides  into 
two.  The  two  nerves  enter  the  canal  between  the  bony  and  cartilaginous  portion 
of  the  meatus.  They  supply  the  skin  lining  the  meatus;  the  upper  one  sending 
a  filament  to  the  membrana  tympani  (ramus  membranae  tympani). 

A  branch  to  the  temporo-mandibular  articulation,  the  articular  branch,  is  usually 
derived  from  the  auriculo-temporal  nerve. 

The  parotid  branches  (rami  parotidei)  supply  the  parotid  gland. 

The  superficial  temporal  branches  (rami  temporales  superficiales)  accompany  the 
temporal  artery  to  the  vertex  of  the  skull,  and  supply  the  integument  of  the  tem- 
poral region,  communicating  with  the  facial  nerve,  and  with  the  temporal  branch 
of  the  temporo-malar  from  the  superior  maxillary. 

The  Lingual  Nerve  (n.  lingualis)  (Fig.  688). — The  lingual  nerve  supplies  the 
papillae  and  mucous  membrane  of  the  anterior  two-thirds  of  the  tongue.  It  is 
deeply  placed  throughout  the  whole  of  its  course.  It  lies  at  first  beneath  the 
External  pterygoid  muscle,  together  with  the  inferior  dental  nerve,  being  placed 
to  the  inner  side  of  this  nerve,  and  is  occasionally  joined  to  it  by  a  branch  which 
may  cross  the  internal  maxillary  artery.  The  chorda  tympani  nerve  also  joins  it 
at  an  acute  angle  in  this  situation.  The  nerve  then  passes  between  the  Internal 
pterygoid  muscle  and  the  inner  side  of  the  ramus  of  the  jaw,  and  crosses  obliquely 
to  the  side  of  the  tongue  over  the  Superior  constrictor  of  the  pharynx  and  the 
Stylo-glossus  muscles,  and  then  between  the  Hyo-glossus  muscle  and  the  deep 
part  of  the  submaxillary  r;land;  the  nerve  finally  runs  across  Wharton's  duct,  and 
along  the  side  of  the  tongue  to  its  apex,  lying  immediately  beneath  the  mucous 
membrane. 

The  branches  of  communication  are  with  the  inferior  dental  and  hypoglossal 
nerves,  and  the  submaxillary  ganglion,  and,  apparently  only,  with  the  facial  through 
the  chorda.  The  chorda  tympani  branch  of  the  facial  joins  the  lingual  nerve  under 
the  external  pterygoid  muscle  and  is  distributed  with  the  lingual  to  the  tongue. 


THE  FIFTH,   TRIGEMINAL  OR  TRIP  ACT AL  NERVE         1Q53 

The  hypoglossal  nerve  and  the  lingual  nerve  lie  near  together,  over  the  Hyo- 
glossus  muscle,  and  the  two  nerves  are  joined  by  loops  (rami  anastomotici  cum 
it.  hypoglosso).  The  branches  to  the  submaxillary  ganglion  are  two  or  three  in 
number;  those  connected  with  the  hypoglossal  nerve  form  a  plexus  at  the  anterior 
margin  of  the  Hyo-glossus  muscle. 

The  branches  of  distribution  supply  the  mucous  membrane  of  the  mouth,  the 
gums,  the  sublingual  gland,  the  filiform  and  fungiform  papillae  and  mucous  mem- 
brane of  the  tongue ;  the  terminal  filaments  communicate,  at  the  tip  of  the  tongue, 
with  the  hypoglossaf  nerve.  The  lingual  fibres  are  fibres  of  common  sensation. 
The  chorda  tympani  fibres  which  join  the  lingual  nerve  are  probably  taste- 
fibres  and  excito-glandular  for  the  submaxillary  and  sublingual  salivary  glands. 

The  Inferior  Dental  Nerve  (n.  alveolaris  inferior)  (Fig.  688). — The  inferior 
dental  is  the  largest  of  the  branches  of  the  inferior  maxillary  nerve.  It  passes 
downward  with  the  inferior  dental  artery,  at  first  beneath  the  External  pterygoid 
muscle,  and  then  between  the  internal  lateral  ligament  and  the  ramus  of  the  jaw 
to  the  dental  foramen.  It  then  passes  forward  in  the  dental  canal  of  the  inferior 
maxillary  bone,  lying  beneath  the  teeth,  as  far  as  the  mental  foramen,  where  it 
divides  into  two  terminal  branches,  incisor  and  mental. 

The  Branches  of  the  inferior  dental  are:  the  mylo-hyoid,  dental,  incisor,  and 
mental. 

The  Mylo-hyoid  (n.  mylohyoideus]  is  derived  from  the  inferior  dental  just  as  that 
nerve  is  about  to  enter  the  dental  foramen.  It  descends  in  a  groove  on  the  inner 
surface  of  the  ramus  of  the  jaw,  in  which  it  is  retained  by  a  process  of  fibrous  mem- 
brane. It  reaches  the  under  surface  of  the  Mylo-hyoid  muscle,  and  supplies  it  and 
the  anterior  belly  of  the  Digastric. 

The  Dental  Branches  supply  the  molar  and  bicuspid  teeth.  They  correspond 
in  number  to  the  fangs  of  those  teeth :  each  nerve  entering  the  orifice  at  the  point 
of  the  fang  and  supplying  the  pulp  of  the  tooth. 

The  Incisor  Branch  is  continued  onward  within  the  bone  to  the  middle  line,  and 
supplies  the  canine  and  incisor  teeth. 

The  dental  branches  and  the  incisor  branch  form  a  plexus  (plexus  dentalis  infe- 
rior}, and  from  this  plexus  come  the  branches  to  the  teeth  (rami  dentales  inferior  es] 
and  to  the  gums  (rami  gingivales  inferiores). 

The  Mental  Branch  (n.  mentalis)  emerges  from  the  bone  at  the  mental  foramen, 
and  divides  beneatWthe  Depressor  anguli  oris  muscle  into  two  or  three  branches; 
one  descends  to  suAply  the  skin  of  the  chin,  and  another  (sometimes  two)  ascends 
to  supply  the  skin  and  mucous  membrane  of  the  lower  lip.  These  branches  com- 
municate freely  with  the  facial  nerve. 

Two  small  ganglia  are  connected  with  the  inferior  maxillary  nerve — the  otic 
with  the  trunk  of  the  nerve,  and  the  submaxillary  with  its  lingual  branch. 

Otic  or  Arnold's  Ganglion  (ganglion  oticum)  (Fig.  690). — The  otic  or  Arnold's 
ganglion  is  a  small,  oval-shaped,  flattened  ganglion  of  a  reddish-gray  color,  situ- 
ated immediately  below  the  foramen  ovale,  on  the  inner  surface  of  the  inferior 
maxillary  nerve,  and  round  the  origin  of  the  internal  pterygoid  nerve.  It  is  in 
relation,  externally,  with  the  trunk  of  the  inferior  maxillary  nerve,  at  the  point 
where  the  motor  root  joins  the  sensor  portion;  internally,  with  the  cartilaginous 
part  of  the  Eustachian  tube,  and  the  origin  of  the  Tensor  palati  muscle;  behind, 
it  lies  in  relation  with  the  medidural  artery. 

Branches  of  Communication. — This  ganglion  is  connected  with  the  internal 
pterygoid  branch  of  the  inferior  maxillary  nerve  by  two  or  three  short  delicate 
filaments.  From  this  nerve  the  ganglion  may  obtain  a  motor  root,  and  possibly 
also  a  sensor  root,  as  these  filaments  from  the  nerve  to  the  Internal  pterygoid 
perhaps  contain  sensor  fibres.  The  otic  ganglion  communicates  with  the  glosso- 
pharyngeal  and  facial  nerves  through  the  small  superficial  petrosal  nerve  (Figs.  690 


1054 


THE  NERVE  SYSTEM 


and  693)  continued  from  the  tympanic  plexus,  and  through  this  communication 
it  probably  receives  its  sensor  root  from  the  glosso-pharyngeal  and  its  motor 
root  from  the  facial;  its  communication  with  the  sympathetic  is  effected  by  a  fila- 
ment from  the  plexus  surrounding  the  medidural  artery.  The  ganglion  also 
communicates  with  the  auriculo-temporal  nerve  (ramus  anastomoticus  cum  n. 
auriculotemporali).  This  communicating  filament  is  probably  a  branch  from  the 
glosso-pharyngeal  which  passes  to  the  ganglion,  and  through  it  and  the  auriculo- 
temporal  nerve  to  the  parotid  gland.  A  slender  filament,  the  sphenoidal,  ascends 
from  it  to  the  Vidian  nerve. 

Branches  of  Distribution. — Its  branches  of  distribution  are  a  filament  to  the 
Tensor  tympani  (n.  tensoris  tympani}  and  one  to  the  Tensor  palati  (n.  tensoris  veli 
palatini).  The  former  passes  backward  on  the  outer  side  of  the  Eustachian  tube; 
the  latter  arises  from  the  ganglion,  near  the  origin  of  the  internal  pterygoid  nerve, 
and  passes  forward.  The  fibres  of  these  nerves  are,  however,  mainly  derived 
from  the  nerve  to  the  Internal  pterygoid  muscle.  It  also  gives  off  a  small  com- 
municating branch  to  the  chorda  tympani  (ramus  anastomoticus  cum  n.  chorda 
tympani). 


FIG.  690. — The  otic  ganglion  and  its  branches. 

The  Submaxillary  Ganglion  (ganglion  submaxillare)  (Fig.  688). — The  submaxil- 
lary  ganglion  is  of  small  size,  fusiform  in  shape,  and  situated  above  the  deep 
portion  of  the  submaxillary  gland,  near  the  posterior  border  of  the  Mylo-hyoid 
muscle,  being  connected  by  filaments  with  the  lower  border  of  the  lingual  nerve. 

Branches  of  Communication. — This  ganglion  is  connected  with  the  lingual  nerve 
by  a  few  filaments  (rami  communicantes  cum  n.  linguaK),  which  join  it  separately 
at  its  fore  and  back  part.  It  also  receives  a  branch  from  the  chorda  tympani,  by 
which  it  communicates  with  the  facial,  and  communicates  with  the  sympathetic 
by  filaments  from  the  sympathetic  plexus  around  the  facial  artery. 

Branches  of  Distribution. — These  are  five  or  six  in  number;  they  arise  from  the 
lower  part  of  the  ganglion,  and  supply  the  mucous  membrane  of  the  mouth  and 
Wharton's  duct,  some  being  lost  in  the  submaxillary  gland  (rami  submaxillares). 
The  branch  of  communication  from  the  lingual  nerve  to  the  forepart  of  the  gan- 
glion is  by  some  regarded  as  a  branch  of  distribution,  by  which  filaments  of  the 
chorda  tympani  pass  from  the  ganglion  to  the  lingual  nerve,  and  by  it  are  con- 
veyed to  the  sublingual  gland  and  the  tongue. 


THE  FIFTH,    TRIGEMINAL  OR   TRIFAGIAL  NERVE 


1055 


Summary  of  the  Distribution  and  Connections  of  the  Trigeminal  Nerve. — It  is  the 
chief  sensor  nerve  of  the  face,  the  anterior  half  of  the  scalp,  the  mouth,  nasal  cavity, 
lips,  teeth,  anterior  two-thirds  of  the  tongue,  orbit,  and  eyeball.  The  clearly 
defined  cutaneous  distributions  of  the  branches  are  shown  in  Fig.  691.  The 
motor  portion  of  the  nerve  supplies  the  muscles  of  mastication,  the  mylo-hyoid, 
and  the  anterior  belly  of  the  digastric.  By  way  of  branches  from  the  otic 
ganglion  it  supplies  the  Tensor  tympani  and  Tensor  palati  muscles,  and  by 
way  of  branches  from  the  spheno-palatine  ganglion  perhaps  supplies  the  Levator 
palati  and  Azygos  uvulae  muscles,  although  it  is  more  probable  that  these  muscles 
receive  their  motor  influence  by  the  accessory  nerves  through  the  pharyngeal 
plexus.  The  ganglia  associated  with  the  nerve  create  communications  with  the 
sympathetic,  the  motor  oculi,  the  facial,  and  the  glosso-pharyngeal,  and  through 
these  ganglia,  as  Prof.  Cunningham  says,  "important  organs,  areas,  and  muscles" 
are  innervated.  The  trigeminal  communicates  many  times  with  the  facial,  and 
thus  gives  sensor  fibres  to  the  "muscles  of  expression  supplied  by  the  facial 
nerve."1 


SUPRATROCHLEAR  N. 

SUPRAORBITAL  N. 


1NFRATROCHLEAR 


NASAL  NERVE 


MENTAL  NERVE 


TEMPORAL  BH. 
OF  TEMPORO-MALAR 


MALAR  BR.   OF 
TEMPORO-MALAR 


AURICULO-TEMPORAL 
NERVE 


FIG.  691. — Sensor  areas  of  the  head,  showing  the  general  distribution  of  the  three  divisions  of  the  fifth 
nerve.     Gerrish's  Anatomy.     (Modified  from  Testut.) 

Surface  Marking. — It  will  be  seen  from  the  above  description  that  the  three  terminal  branches 
of  the  three  divisions  of  the  trigeminal  nerve  emerge  from  foramina  in  the  bones  of  the  skull  and 
pass  on  to  the  face:  the  terminal  branch  of  the  first  division  emerging  through  the  supraorbital 
foramen;  that  of  the  second  through  the  infraorbital  foramen;  and  the  third  through  the  mental 
foramen.  The  supraorbital  foramen  is  situated  at  the  junction  of  the  internal  and  middle 
third  of  the  supraorbital  arch.  If  a  straight  line  is  drawn  from  this  point  to  the  lower  border 
of  the  inferior  maxillary  bone,  so  that  it  passes  between  the  two  bicuspid  teeth  of  the  lower  jaw, 
it  will  pass  over  the  infraorbital  and  mental  foramina,  the  former  being  situated  about  one 
centimetre  (two-fifths  of  an  inch)  below  the  margin  of  the  orbit,  and  the  latter  varying  in  posi- 
tion according  to  the  age  of  the  individual.  In  the  adult  it  is  midway  between  the  upper  and 
lower  borders  of  the  inferior  maxillary  bone ;  in  the  child  it  is  nearer  the  lower  border ;  and  in  the 
edentulous  jaw  of  old  age  it  is  close  to  the  upper  margin. 

Surgical  Anatomy. — In  fracture  of  the  base  of  the  skull  the  trigeminal  nerve  or  one  of  its 
branches  may  be  injured.  It  seems  certain  that  occasionally,  though  seldom,  the  trigeminal 
nerve  may  be  actually  divided  by  such  an  injury.  The  trigeminal  nerve  may  be  affected  in  its 
entirety,  or  its  sensor  or  motor  root  may  be  affected,  or  one  of  its  primary  main  divisions. 


1  Cunningham's  Text-book  of  Anatomy. 


1056  THE  NER  VE  SYSTEM 

In  injury  to  the  sensor  root  there  is  anaesthesia  of  the  half  of  the  face  on  the  side  of  the  lesion, 
with  the  exception  of  the  skin  over  the  parotid  gland;  insensibility  of  the  conjunctiva,  fol- 
lowed, if  the  eye  is  not  temporarily  protected  with  a  watch-glass,  by  destructive  inflammation 
of  the  cornea,  partly,  it  is  held,  from  loss  of  trophic  influence,  and  partly,  it  is  certain,  from  the 
irritation  produced  by  the  presence  of  foreign  bodies  on  it,  which  are  not  perceived  by  the 
patient,  and  therefore  not  expelled  by  the  act  of  winking;  dryness  of  the  nose,  loss  to  a  consider- 
able extent  of  the  sense  of  taste,  and  diminished  secretion  of  the  lacrimal  and  salivary  glands. 
In  injury  to  the  motor  root  there  is  impaired  action  of  the  lower  jaw  from  paralysis  of  the  muscles 
of  mastication  on  the  affected  side. 

The  trigeminal  nerve  is  often  the  seat  of  neuralgia,  and  each  of  the  three  divisions  has  been 
divided  or  a  portion  of  the  nerve  excised  for  this  affection.  The  supraorbital  nerve  may  be  ex- 
posed by  making  an  incision  an  inch  and  a  half  in  length  along  the  supraorbital  margin  below  the 
eyebrow,  which  is  to  be  drawn  upward,  the  centre  of  the  incision  corresponding  to  the  supra- 
orbital  notch.  The  skin  and  Orbicularis  palpebrarum  having  been  divided,  the  nerve  can  be 
easily  found  emerging  from  the  notch  and  lying  in  some  loose  cellular  tissue.  It  should  be  drawn 
up  by  a  blunt  hook  and  divided,  or,  what  is  better,  a  portion  of  it  should  be  removed.  The 
infraorbital  nerve  has  been  divided  at  its  exit  by  an  incision  on  the  cheek;  or  the  floor  of  the 
orbit  has  been  exposed,  the  infraorbital  canal  opened  up,  and  the  anterior  part  of  the  nerve 
resected;  or  the  whole  nerve,  together  with  Meckel's  ganglion  as  far  back  as  the  foramen  rotun- 
dum,  has  been  removed.  This  latter  operation,  though  undoubtedly  a  severe  proceeding,  appears 
to  have  been  followed  by  better  results  than  has  nerve  resection.  The  operation  is  performed 
as  follows:  The  superior  maxillary  bone  is  first  exposed  by  a  T-shaped  incision,  one  limb  of 
the  incision  passing  along  the  lower  margin  of  the  orbit,  the  other  from  the  centre  of  the  first 
cut  vertically  down  the  cheek  toward  the  angle  of  the  mouth.  The  nerve  is  then  found,  is  divided, 
and  a  piece  of  silk  is  tied  to  it  as  a  guide.  A  small  trephine  (one-half  inch)  is  then  applied 
to  the  bone  below,  but  including  the  infraorbital  foramen,  and  the  antrum  opened.  The 
trephine  is  now  applied  to  the  posterior  wall  of  the  antrum,  and  the  spheno-maxillary  fossa 
exposed.  The  infraorbital  canal  is  now  opened  up  from  below  by  fine  cutting-pliers  or  a 
chisel,  and  the  nerve  drawn  down  into  the  trephine  hole,  it  being  held  on  the  stretch  by 
means  of  the  piece  of  silk;  it  is  severed  with  fine  curved  scissors  as  near  the  foramen  rotundum 
as  possible,  any  branches  coming  off  from  the  ganglion  being  also  divided.1  The  mental 
branch  of  the  inferior  .dental  nerve  may  be  divided  at  its  exit  from  the  foramen  through  an 
incision  made  through  the  mucous  membrane  where  it  is  reflected  from  the  alveolar  process  on 
to  the  lower  lip ;  or  a  portion  of  the  trunk  of  the  inferior  dental  nerve  may  be  resected  through 
an  incision  on  the  cheek  through  the  Masseter  muscle,  exposing  the  outer  surface  of  the  ramus  of 
the  jaw.  A  trephine  is  then  applied  over  the  position  of  the  inferior  dental  foramen  and  the 
outer  table  removed,  so  as  to  expose  the  inferior  dental  canal.  The  nerve  is  dissected  out  of 
the  portion  of  the  canal  exposed,  and,  having  been  divided  after  its  exit  from  the  mental  foramen, 
it  is  by  traction  on  the  end  exposed  in  the  trephine-hole,  drawn  out  entire,  and  cut  off  as  high  up 
as  possible.2  The  inferior  dental  nerve  has  also  been  divided  through  an  incision  within  the  mouth, 
the  bony  point  guarding  the  inferior  dental  foramen  forming  the  guide  to  the  nerve.  The  buccal 
nerve  may  be  divided  by  an  incision  through  the  mucous  membrane  of  the  mouth  and  the  Buc- 
cinator muscle  just  in  front  of  the  anterior  border  of  the  ramus  of  the  lower  jaw  (Stimson). 

In  inveterate  neuralgia  of  one  or  two  of  the  branches  of  the  trigeminal  nerve  a  peripheral  opera- 
tion may  cure  the  case,  but  seldom  does.  It  often  gives  relief,  perhaps  for  months.  In  neuralgia 
of  the  second  division  or  third  division,  or  of  the  second  division  and  third  division,  Abbe,  of 
New  York,  opens  the  skull  and  divides  the  nerve  or  nerves  by  an  intracranial  operation, 
removes  a  piece  of  nerve  so  as  the  foramen  of  exit  is  empty,  and  covers  the  foramen  with  rubber 
tissue,  to  hinder  regrowth  of  the  nervel  Other  operators,  after  removing  a  piece  from  each 
nerve,  have  plugged  the  foramina  of  the  exit  with  dentists'  cement  or  silver-foil. 

Rose's  method  of  neurectomy  is  very  valuable  for  neuralgia  of  the  second  division.  It  is  a 
modification  of  the  Braun-Lossen  method.  The  infraorbital  nerve  is  exposed,  a  ligature  is 
tied  about  it,  the  roof  of  the  infraorbital  canal  is  chiselled  open,  and  the  nerve  is  freed  as  far 
back  as  possible.  An  incision  is  made  from  below  the  external  angular  process  outward  along 
the  zygoma  to  in  front  of  the  lobule  of  the  ear,  downward  to  just  above  the  angle  of  the  jaw, 
and  forward  for  two  inches.  The  flap  is  raised  and  the  zygoma  is  exposed.  The  root  of  the 
zygoma  is  drilled  at  two  points,  and  the  zygomatic  process  of  the  temporal  bone  is  drilled  at  two 
points.  The  bone  is  sawed  in  two  places  between  the  drill-holes.  The  freed  arch  is  lifted  down 
and  back,  the  tendon  of  the  temporal  muscle  is  drawn  backward,  and  the  pterygo-maxillary 
fossa  is  thus  exposed.  The  internal  maxillary  artery  is  divided  between  two  ligatures.  The 
External  pterygoid  muscle  is  separated  from  the  greater  wing  of  the  sphenoid  and  from  the  root 
of  the  external  pterygoid  process.  The  superior  maxillary  nerve  is  grasped  and  twisted  off  as 
near  the  ganglion  as  possible.  The  entire  nerve  is  then  drawn  back  from  the  infraorbital  foramen 
and  removed.  The  wound  is  then  closed.  If  the  third  division  is  also  haunted  by  neuralgia, 
it  too  should  be  removed  a  few  weeks  after  the  performance  of  Rose's  operation. 

1  Carnochan,  American  Journal  of  the  Medical  Sciences,  1858,  p.  136. 

2  Mears,  Transactions  of  the  American  Surgical  Association,  vol.  ii,  p.  469. 


THE  SIXTH  OR  ABDUCENT  NERVE  1057 

If  a  peripheral  operation  fails,  or  if  all  the  branches  of  the  trigeminal  are  involved,  the  Gasserian 
ganglion  must  be  removed  or  the  sensor  root  of  the  trigeminal  must  be  divided,  as  suggested  by 
Fru/ier  and  Spiller. 

Removal  of  the  Gasserian  ganglion  was  suggested  by  J.  Ewing  Hears  in  1884,  and  was  first 
carried  out  by  Rose  in  1890. 

The  method  chiefly  in  vogue  was  devised  by  Hartley,  and  was  first  performed  by  him  in  1891. 
An  osteoplastic  flap  is  made  in  front  of  the  ear,  the  dura  is  exposed  and  lifted.  Following  Krause's 
advice,  the  third  division  is  exposed  and  clamped.  The  second  division  is  exposed  and  clamped. 
The  nerves  are  loosened  from  their  beds  and  then  are  rolled  about  the  clamps.  This  twisting 
pulls  out  the  ganglion  intact  along  with  the  motor  root,  and  also  the  sensor  root  from  the  pons. 

A  difficulty  in  the  Hartley  operation  is  the  danger  of  division  of  the  dural  artery.  If  this 
happens,  the  surgeon  may  be  able  to  arrest  bleeding  and  proceed  with  the  operation.  If  the 
vessel  is  torn  off  at  the  foramen  spinosum,  it  will  be  necessary  to  pack  the  wound  and  postpone 
any  further  operative  manipulation  for  forty-eight  hours. 

Dr.  Harvey  Gushing  has  modified  Hartley's  operation  by  trephining  the  wall  of  the  temporal 
fossa  very  low  down.  He  opens  the  skull  below  the  arch  of  the  dural  vessels,  and  thus  avoids  the 
medidural  at  the  foramen  spinosum,  and  also  the  sulcus  arteriosus  of  the  parietal  bone. 

After  the  removal  of  the  ganglion,  Professor  Keen,  in  order  to  prevent  undue  inflammation  of 
the  eye,  sews  the  eyelids  of  the  affected  side  together,  leaving  a  space  open  at  each  angle,  and 
covers  the  eye  with  a  watch-crystal.  Boric  acid  solution  is  flushed  into  the  opening  at  the  external 
angle  at  frequent  intervals.  The  stitches  are  removed  from  the  lid  in  from  eight  to  ten  days. 

The  lingual  nerve  is  occasionally  divided  with  the  view  of  relieving  the  pain  in  cancerous 
disease  of  the  tongue.  This  may  be  done  in  that  part  of  its  course  where  it  lies  below  and  behind 
the  last  molar  tooth.  If  a  line  is  drawn  from  the  middle  of  the  crown  of  the  last  molar  tooth  to 
the  angle  of  the  jaw,  it  will  cross  the  nerve,  which  lies  about  half  an  inch  behind  the  tooth,  par- 
allel to  the  bulging  alveolar  ridge  on  the  inner  side  of  the  body  of  the  bone.  If  the  knife  is 
entered  three-quarters  of  an  inch  behind  and  below  the  last  molar  tooth  and  carried  down  to  the 
bone,  the  nerve  will  be  divided.  Hilton  divided  it  opposite  the  second  molar  tooth,  where 
it  is  covered  only  by  the  mucous  membrane,  and  Lucas  pulls  the  tongue  forward  and  over  to  the 
opposite  side,  when  the  nerve  can  be  seen  standing  out  as  a  firm  cord  under  the  mucous  mem- 
brane by  the  side  of  the  tongue  and  can  be  easily  seized  with  a  sharp  hook  and  divided  or  a 
portion  excised.  This  is  a  simple  enough  operation  on  the  cadaver,  but  when  the  disease  is  exten- 
sive and  has  extended  to  the  floor  of  the  mouth,  as  is  generally  the  case  when  division  of  the  nerve 
is  thought  of,  the  operation  is  not  practicable. 


THE  SIXTH  OR  ABDUCENT  NERVE  (N.  ABDUCENS)  (Fig.  687). 

The  sixth  or  abducent  nerve  supplies  the  External  rectus  muscle.  Its  super- 
ficial origin  is  by  several  filaments  from  the  postpontile  groove,  between  pons  and 
pyramid.  Its  deep  origin  is  from  the  upper  part  of  the  floor  of  the  fourth  ven- 
tricle, close  to  the  median  line,  beneath  the  eminentia  abducentis  (Fig.  578). 

From  the  nucleus  of  the  abducent  nerve  some  fibres  are  supposed  to  pass 
through  the  medial  longitudinal  bundle  to  the  oculomotor  nucleus  of  the  opposite 
side  and  into  the  oculomotor  nerve,  along  which  they  are  carried  to  the  Internal 
rectus  muscle.  The  External  rectus  of  one  eye  and  the  Internal  rectus  of  the 
other  may  therefore  be  said  to  receive  their  nerves  from  the  same  nucleus — a 
factor  of  great  importance  in  connection  with  the  conjugate  movements  of  the 
eyeball,  and  one  that  may  explain  certain  paralytic  phenomena  of  the  Recti 
muscles,  which  are  often  associated  with  lesions  in  the  pons. 

The  nerve  pierces  the  dura  on  the  basilar  surface  of  the  sphenoid  bone,  runs 
through  a  notch  immediately  below  the  posterior  clinoid  process,  and  enters  the 
cavernous  sinus.  It  passes  forward  through  the  sinus,  lying  on  the  outer  side 
of  the  internal  carotid  artery  (Fig.  454).  It  enters  the  orbit  through  the  sphenoid 
fissure,  and  lies  above  the  ophthalmic  vein,  from  which  it  is  separated  by  a  lamina 
of  dura  (Fig.  692).  It  then  passes  between  the  two  heads  of  the  External  rectus 
muscle,  and  is  distributed  to  that  muscle  on  its  ocular  surface. 

Branches  of  Communication. — It  is  joined  by  several  filaments  from  the 
carotid  and  cavernous  plexuses,  and  by  one  from  the  ophthalmic  nerve. 

67 


1058 


THE  NERVE  SYSTEM 


Frontal. 


Relations  to  Each  Other  of  the  Oculomotor,  Trochlear,  Ophthalmic  Division  of  the 
Trigeminal  and  Abducent  Nerves  as  they  Pass  to  the  Orbit. — The  oculomotor, 
trochlear,  the  ophthalmic  division  of  the  trigeminal,  and  the  abducent  nerves, 
as  they  pass  to  the  orbit,  bear  a  certain  relation  to  one  another  in  the  cavernous 
sinus,  at  the  sphenoidal  fissure,  and  in  the  cavity  of  the  orbit,  which  will  now  be 
described. 

In  the  Cavernous  Sinus  (Figs.  454  and  455)  the  oculomotor,  trochlear,  and 
ophthalmic  division  of  the  trigeminal  are  placed  on  the  outer  wall  of  the  sinus, 
in  their  numerical  order,  both  from  above  downward  and  from  within  outward. 
The  abducent  nerve  lies  at  the  outer  side  of  the  internal  carotid  artery.  As  these 
nerves  pass  forward  to  the  sphenoidal  fissure,  the  oculomotor  and  trigeminal 
nerves  become  divided  into  branches,  and  the  abducent  nerve  approaches  the  rest, 
so  that  their  relative  position  becomes  considerably  changed. 

In  the  Sphenoidal  Fissure  (Fig.  692)  the  trochlear  nerve  and  the  frontal  and 
lacrimal  branches  of  the  ophthalmic  division  of  the  trigeminal  lie  upon  the  same 
plane,  the  former  being  most  internal,  the  latter  external,  and  they  enter  the  cavity 

of  the  orbit  above  the  muscles. 
The  remaining  nerves  enter 
the  orbit  between  the  two  heads 
of  the  External  rectus  muscle. 
The  superior  division  of  the 
oculomotor  nerve  is  the  highest 
of  these;  beneath  this  lies  the 
nasal  branch  of  the  ophthalmic 
nerve;  then  the  inferior  division 
of  the  oculomotor  nerve;  and 
the  abducent  nerve  lowest  of 
all. 

In  the  Orbit  (Figs.  683  and 
687)  the '  trochlear  nerve  and 
the  frontal  and  lacrimal  divi- 
sions of  the  ophthalmic  nerve  lie  on  the  same  plane  immediately  beneath  the  peri- 
osteum, the  trochlear  nerve  being  internal  and  resting  on  the  Superior  oblique 
muscle,  the  frontal  nerve  resting  on  the  Levator  palpebrae  muscle,  and  the  lacrimal 
nerve  on  the  External  rectus  muscle.  Next  in  order  comes  the  superior  division 
of  the  oculomotor  nerve,  lying  immediately  beneath  the  Superior  rectus  muscle, 
and  then  the  nasal  branch  of  the  ophthalmic  nerve,  crossing  the  optic  nerve 
from  the  outer  to  the  inner  side  of  the  orbit.  Beneath  these  is  found  the 
optic  nerve,  surrounded  in  front  by  the  ciliary  nerves,  and  having  the  ciliary 
ganglion  on  its  outer  side,  between  it  and  the  External  rectus  muscle.  Below  the 
optic  nerve  is  the  inferior  division  of  the  oculomotor  nerve  and  the  abducent 
nerve,  which  lies  on  the  outer  side  of  the  orbit. 

Surgical  Anatomy. — It  is  often  stated  that  the  abducent  nerve  is  more  frequently  involved  in 
fractures  of  the  base  of  the  skull  than  any  other  of  the  cranial  nerves.  As  a  matter  of  fact,  however, 
it  is  injured  in  only  about  2  per  cent,  of  cases  of  fracture  of  the  skull  (Putscher).  Cases  have  been 
reported  in  which  the  nerve  was  actually  ruptured.  The  nerve  may  be  injured  by  traction, 
pressure  of  a  blood  clot,  of  a  tumor,  or  of  an  arterio-venous  aneurism.  The  result  of  paralysis  of 
this  nerve  is  internal  or  convergent  squint.  When  injured  so  that  its  function  is  destroyed,  there 
is,  in  addition  to  the  paralysis  of  the  External  rectus  muscle,  often  a  certain  amount  of  contrac- 
tion of  the  pupil,  because  some  of  the  sympathetic  fibres  to  the  radiating  muscle  of  the  iris  pass 
along  with  this  nerve. 


Superior  division  of  oculo-motor. 
'/Nasal. 

'Inferior  division  of  oculo-motor. 
^Abducent. 
"Ophthalmic  vein. 


FIG.  692. — Relations  of  structures  passing  through 
the  sphenoidal  fissure. 


THE  SEVENTH  OR  FACIAL  NERVE  1059 

THE  SEVENTH  OR  FACIAL  NERVE  (N.  FACIALIS)  (Figs.  693,  694,  695). 

The  seventh  or  facial  nerve  is  the  motor  nerve  of  all  the  muscles  of  expression 
in  the  face,  and  of  the  Platysma  and  Buccinator;  the  muscles  of  the  External  ear; 
the  posterior  belly  of  the  Digastric,  and  the  Stylo-hyoid.  The  chorda  tympani 
(or  nervus  intermedius)  is  referred  to  as  the  sensor  portion  of  the  facial. 

Its  superficial  origin  is  from  the  upper  end  of  the  oblongata,  in  the  groove 
between  the  olive  and  restis.  Its  deep  origin  is  from  a  nucleus  situated  in  the 
floor  of  the  fourth  ventricle,  beneath  the  superior  fovea  (Fig.  578).  The  facial 
nucleus  is  deeply  placed  in  the 
reticular  formation  of  the  lower 
part  of  the  preoblongata,  a  little  External  petrot 

external  and  ventral  to  the  nucleus        |™^  Jgggg  ffiroTai- 

of  the  abducent  nerve.       From  this      Intumescentia  ganglioformis. 

origin  the  fibres  pursue  a  curved 
course  in  the  substance  of  the  pre- 
oblongata.    They  first  pass  back- 
ward and  inward,  and  then  turn        FlG-  693--The  co^r^iea^mc^rnaf  £°nneof  the  facial  nerve 
upward  and  forward,  forming  the 

fasciculus  teres,  which  with  the  nucleus  abducentis  produces  an  eminence,  the 
eminentia  abducentis,  on  the  floor  of  the  fourth  ventricle,  and  finally  bend  sharply 
downward  and  outward  around  the  upper  end  of  the  nucleus  of  origin  of  the 
abducent  nerve,  to  reach  their  superficial  origin  between  the  olive  and  rectis. 
From  the  nucleus  of  the  oculomotor  nerve  some  fibres  arise  which  descend  in 
the  medial  longitudinal  bundle  and  join  the  facial  just  before  it  leaves  the  pre- 
oblongata; these  fibres  are  said  to  supply  the  anterior  belly  of  the  Occipito- 
frontalis,  the  Orbicularis  palpebrarum,  and  the  Corrugator  supercilii,  as  these 
muscles  have  been  observed  to  escape  paralysis  in  lesions  of  the  nucleus  of  the 
facial  nerve. 

The  acoustic  or  auditory  nerve  lies  to  the  outer  side  of  the  facial  nerve ;  and  between 
the  two  is  a  small  fasciculus,  the  nervus  intermedius  or  pars  intermedia  of  Wrisberg, 
which  apparently  arises  from  the  oblongata  and  joins  the  facial  nerve  in  the  internal 
auditory  meatus.  The  central  processes  of  the  ganglion  cells,  known  as  the  nervus 
intermedius,  end  in  the  upper  end  of  the  nucleus  of  the  glosso-pharyngeal  nerve. 

The  nervus  intermedius  may  be  regarded  as  the  sensor  root  of  the  facial  nerve, 
analogous  to  the  sensor  root  of  the  trigeminal,  and  its  real  nucleus  of  origin 
consists  of  the  geniculate  ganglion  (see  p.  894). 

The  facial  nerve,  firmer,  rounder,  and  smaller  than  the  auditory,  passes  forward 
and  outward  upon  the  medipeduncle  of  the  cerebellum,  and  enters  the  internal 
auditory  meatus  with  the,  auditory  nerve.  Within  the  meatus  the  facial  nerve 
lies  in  a  groove  along  the  upper  and  anterior  part  of  the  auditory  nerve,  and  the 
nervus  intermedius  is  placed  between  the  two  and  joins  the  inner  angle  of  the 
geniculate  ganglion.  Beyond  the  ganglion  its  fibres  are  generally  regarded  as 
forming  the  chorda  tympani  (see  p.  894). 

At  the  bottom  of  the  meatus  the  facial  nerve  enters  the  aquaeductus  Fallopii 
and  follows  the  course  of  that  canal  through  the  petrous  portion  of  the  temporal 
bone,  from  its  commencement  at  the  internal  meatus  to  its  termination  at  the  stylo- 
mastoid  foramen  (Figs.  49  and  693).  It  is  at  first  directed  outward  between  the 
cochlea  and  vestibule  toward  the  inner  wall  of  the  tympanum ;  it  then  bends  sud- 
denly backward  and  arches  downward  behind  the  tympanum  to  the  stylo-mastoid 
foramen.  At  the  point  in  the  aqueduct  of  Fallopius  where  the  nerve  changes  its 
direction  (geniculum  n.  facialis),  it  presents  a  reddish,  gangliform  swelling,  the 
geniculate  ganglion  (ganglion  geniculi),  which  is  also  called  the  intumescentia  ganglio- 


1000 


THE  NERVE  SYSTEM 


In  the  internal  auditory  meatus    . 


formis  (Fig.  693).  The  geniculate  ganglion  receives  a  branch  from  the  vestibular 
division  of  the  auditory  nerve.  On  emerging  from  the  stylo-mastoid  foramen 
the  facial  nerve  runs  forward  in  the  substance  of  the  parotid  gland,  crosses  the 
external  carotid  artery,  and  divides  behind  the  ramus  of  the  lower  jaw  into  two 
primary  branches,  temporo-facial  and  cervico-facial,  from  which  numerous  offsets 
are  distributed  over  the  side  of  the  head,  face,  and  upper  part  of  the  neck, 
supplying 'the  superficial  muscles  in  these  regions.  As  the  primary  branches  and 
their  offsets  diverge  from  each  other,  they  present  somewhat  the  appearance  of  a 
bird's  claw;  hence  the  name  of  pes  anserinus  is  given  to  the  divisions  of  the  facial 
nerve  in  and  near  the  parotid  gland. 

Branches  of  Communication   (Fig.  694). — The  communications  of  the  facial 
nerve  may  be  thus  arranged: 

With  the  acoustic  nerve.  The  nervus 
intermedius,  which  is  between  the 
facial  and  acoustic,  is  supposed  to  give 
branches  to  both.  The  branch  given 
to  the  acoustic  accompanies  it  for  a 
certain  distance,  and  then  departs 
from  it  to  join  the  geniculate  ganglion. 

With  the  acoustic  as  explained  above. 

With  the  spheno-palatine  ganglion  by 
the  large  superficial  petrosal  nerve. 

With  the  otic  ganglion  by  the  small 
superficial  petrosal  nerve. 

With  the  sympathetic  on  the  medi- 
dural  artery  by  the  external  super- 
ficial petrosal  nerve. 

With  the  auricular  branch  of  the  vagus. 

With  the  glosso-pharyngeal. 

With  the  vagus. 

With  the  auricularis  magnus. 

With  the  auriculotemporal. 

With  the  small  occipital. 

With  three  divisions  of  the  trigeminal. 

With  the  superficial  cervical. 


From  the  geniculate  ganglion  . 


In  the  Fallopian  aqueduct 

At  its  exit  from  the    stylomastoid 
foramen 


Behind  the  ear    . 
On  the  face  . 
In  the  neck  . 


In  the  internal  auditory  meatus  some  minute  filaments  pass  between  the  facial 
and  acoustic  nerves. 

Opposite  the  hiatus  Fallopii  the  gangliform  enlargement  on  the  facial  nerve 
communicates  with  the  spheno-palatine  ganglion  by  means  of  the  large  superficial 
petrosal  nerve,  which  forms  its  motor  root;  with  the  o^ic  ganglion,  by  the  small 
superficial  petrosal  nerve;  and  with  the  sympathetic  filaments  accompanying  the 
medidural  artery,  by  the  external  petrosal  nerve  (Bidder).  From  the  gangliform 
enlargement,  according  to  Arnold,  a  twig  is  sent  back  to  the  acoustic  nerve.  Just 
before  the  facial  nerve  emerges  from  the  stylo-mastoid  foramen  it  generally  receives 
a  twig  of  communication  from  the  auricular  branch  of  the  vagus. 

After  its  exit  from  the  stylo-mastoid  foramen,  it  sends  a  twig  to  the  glosso- 
pharyngeal,  another  to  the  vagus  nerve,  and  communicates  with  the  great  auric- 
ular branch  of  the  cervical  plexus,  with  the  auriculo-temporal  branch  of  the 
inferior^  maxillary  nerve  in  the  parotid  gland,  with  the  small  occipital  nerve 
behind  the  ear,  on  the  face  with  the  terminal  branches  of  the  three  divisions  of 
the  trigeminal,  and  in  the  neck  with  the  transverse  cervical. 

Branches  of  Distribution  (Fig.  694). — The  branches  of  distribution  of  the 
facial  nerves  may  be  thus  arranged: 


THE  SEVENTH  OR  FACIAL  NERVE 


1061 


f  Tvmpanic,   to   the   Stapedius   muscle. 
\\ithm  the  aquaeductus  Fallopn    .     j  ^^  tympani. 


(  Posterior  Auricular. 
At  its  exit  from  the  stylo-mastoid     I   j)jffas^rjc 

foramen       •"   •'•  '     \Stylo-hyoid. 

(  Temporal. 
(  Temporo-facial  .    <  Malar. 

(  Infraorbital. 
On  the  face 1 


L  Cervico-facial 


(  Buccal. 
Supramaxillary. 
Inframaxillary. 


The  branches  of  the  two  terminal  divisions  form  the  paxotid  plexus  (plexus 
parotideus). 

The  Tympanic  Branch  (n.  stapedius)  (Fig.  694). — The  tympanic  branch  arises 
from  the  nerve  opposite  the  pyramid ;  it  passes  through  a  small ,  canal  in  the 
pyramid  and  supplies  the  Stapedius  muscle. 


Nucleus  Salivatortua 


Superior  Maxillary  X 
Vidian  N. 


To  Auricular 
Branch  of  I'ayus  .V. 


Post 
Auricular  Br. 


To  Digastric 
To  Stylo-hyoid 


Infraorbital 
Buccal 

Supramaxillary 
Imframaxillary 


Afferent  (taste)  fiben 


Efferent  (excito^landular) 

fibers  to  submaxillary  and 

sublingual  ganglia  and  glands 

FIG.  694. — Plan  of  the  facial  and  intermediate  nerves  and  their  communication  with  other  nerves. 

The  Chorda  Tympani  (Figs.  688,  693,  and  694). — The  chorda  tympani  is  appar- 
ently given  off  from  the  facial  as  it  passes  vertically  downward  at  the  back  of  the 
tympanum,  about  5  mm.  before  its  exit  from  the  stylo-mastoid  foramen.  It 
passes  from  below  upward  and  forward  in  a  distinct  canal,  and  enters  the  cavity 
of  the  tympanum  through  an  aperture  (Her  chordae  posierius]  on  its  posterior  wall 
between  the  opening  of  the  mastoid  cells  and  the  attachment  of  the  membrana 
tympani,  and  becomes  invested  with  mucous  membrane.  It  passes  forward  through 
the  cavity  of  the  tympanum,  between  the  fibrous  and  mucous  layers  of  the  mem- 
brana tympani,  and  over  the  handle  of  the  malleus,  emerging  from  that  cavity 


1062  THE  NERVE  SYSTEM 

through  a  foramen  at  the  inner  end  of  the  Glaserian  fissure,  which  is  called  the 
canal  of  Huguier  (iter  chordae  anterius).  It  then  descends  between  the  two 
Pterygoid  muscles,  meets  the  lingual  nerve  at  an  acute  angle,  and  accompanies 
it  to  the  submaxillary  gland;  part  of  it  then  joins  the  submaxillary  ganglion;  the 
rest  is  continued  onward  through  the  muscular  substance  of  the  tongue  to  the 
mucous  membrane  covering  its  anterior  two-thirds.  A  few  of  its  fibres  probably 
pass  through  the  submaxillary  ganglion  to  the  sublingual  gland.  Before  joining 
the  lingual  nerve  it  receives  a  small  communicating  branch  from  the  otic  ganglion. 
As  already  stated,  the  chorda  tympani  nerve  is  regarded  as  the  peripheral  con- 
tinuation of  the  nervus  intermedius  (see  p.  894). 

The  Posterior  Auricular  Nerve  (n.  auricularis  posterior)  (Figs.  655,  694,  and 
695). — The  posterior  auricular  nerve  arises  close  to  the  stylo-mastoid  foramen, 
and  passes  upward  in  front  of  the  mastoid  process  and  between  the  mastoid  pro- 
cess and  the  external  ear,  where  it  is  joined  by  a  filament  from  the  auricular 
branch  of  the  vagus,  and  communicates  with  the  mastoid  branch  of  the  great 
auricular  and  with  the  small  occipital.  As  it  ascends  between  the  external  auditory 
meatus  and  the  mastoid  process  it  divides  into  two  branches,  the  auricular  and 
the  occipital  branches. 

The  Auricular  Branch  supplies  the  Retrahens  auriculam  and  the  small  muscles 
on  the  cranial  surface  of  the  pinna. 

The  Occipital  Branch  (ramus  occipitalis] ,  the  larger,  passes  backward  along  the 
superior  curved  line  of  the  occipital  bone,  and  supplies  the  occipital  portion  of  the 
Occipito-frontalis. 

The  Digastric  Branch  of  the  Facial  Nerve  (ramus  digastricus). — The  digastric 
branch  usually  arises  by  a  common  trunk  with  the  Stylo-hyoid  branch;  it  divides 
into  several  filaments,  which  supply  the  posterior  belly  of  the  Digastric;  one  of 
these  perforates  that  muscle  to  join  the  glosso-pharyngeal  nerve  (ramus  anasto- 
moticus  cum  n.  glossopharyngeo) . 

The  Stylo-hyoid  Branch  (ramus  stylohyoideus}. — The  stylo-hyoid  branch  is  a 
long,  slender  branch,  which  passes  inward,  entering  the  Stylo-hyoid  muscle  about 
its  middle. 

The  Temporo-facial  Division  (Figs.  694  and  695). — The  tempo ro-facial,  the  larger 
of  the  two  terminal  branches  of  the  facial,  passes  upward  and  forward  through 
the  parotid  gland,  crosses  the  external  carotid  artery  and  temporo-maxillary  vein, 
and  passes  over  the  neck  of  the  condyle  of  the  jaw,  being  connected  in  this  situation 
with  the  auriculo-temporal  branch  of  the  inferior  maxillary  nerve,  and  divides 
into  branches  which  are  distributed  over  the  temple  and  upper  part  of  the  face; 
these  are  divided  into  three  sets — temporal,  malar,  and  infraorbital. 

The  Temporal  Branches  (rami  temporales]  cross  the  zygoma  to  the  temporal 
region,  supplying  the  Attrahens  and  Attollens  auriculam  muscles,  and  join  \vith 
the  temporal  branch  of  the  temporo-malar  division  of  the  superior  maxillary, 
and  \vith  the  auriculo-temporal  branch  of  the  inferior  maxillary.  The  more  ante- 
rior branches  supply  the  frontal  portion  of  the  Occipito-frontalis,  the  Orbicularis 
palpebrarum,  and  Corrugator  supercilii  muscles,  joining  with  the  supraorbital 
and  lacrimal  branches  of  the  ophthalmic. 

The  Malar  Branches  (rami  zygomatici)  pass  across  the  malar  bone  to  the  outer 
angle  of  the  orbit,  where  they  supply  the  Orbicularis  palpebrarum  muscle,  join- 
ing with  filaments  from  the  lacrimal  nerve;  others  supply  the  lower  eyelid, 
joining  with  filaments  of  the  malar  branch  (subcutaneus  malae)  of  the  superior 
maxillary  nerve. 

The  Infraorbital  Branches  (rami  buccales),  of  larger  size  than  the  rest  of  the  malar 
branches,  pass  horizontally  forward  to  be  distributed  between  the  lower  margin  of 
the  orbit  and  the  mouth.  The  superficial  branches  run  beneath  the  skin  and 
above  the  superficial  muscles  of  the  face,  which  they  supply;  some  branches  are 


THE  SEVENTH  OR  FACIAL  NERVE 


1063 


distributed  to  the  Pyramidalis  nasi,  joining  at  the  inner  angle  of  the  orbit  with  the 
infratrochlear  and  nasal  branches  of  the  ophthalmic.  The  deep  branches  pass 
beneath  the  Zygomatici  and  the  Levator  labii  superioris,  supplying  the  Levator 
anguli  oris,  the  Levator  labii  superioris  alaeque  nasi  and  the  small  muscles  of  the 
nose,  and  form  a  plexus,  infraorbital  plexus,  by  joining  with  the  branches  of  the 
infraorbital  branch  of  the  superior  maxillary  nerve  and  the  buccal  branches  of 
the  cervico-facial. 


Terminations 
of  supratrochlear. 

)f  infratrochlear 
of  nasal. 


FIG.  695. — The  nerves  of  the  scalp,  face,  and  side  of  the  neck. 


The  Cervico-facial  Division. — The  cervi'co-facial  division  of  the  facial  nerve 
passes  obliquely  downward  and  forward  through  the  parotid  gland,  crossing  the 
external  carotid  artery.  In  this  situation  it  is  joined  by  branches  from  the  great 
auricular  nerve.  Opposite  the  angle  of  the  lower  jaw  it  divides  into  branches 
which  are  distributed  on  the  lower  half  of  the  face  and  upper  part  of  the  neck. 
These  may  be  divided  into  three  sets — buccal,  supramaxillary,  and  inframaxillary. 

The  Buccal  Branches  (rami  buccales)  cross  the  Masseter  muscle.  They  supply 
the  Buccinator  and  Orbicularis  oris,  and  join  with  the  infraorbital  branches  of 
the  temporo-facial  division  of  the  nerve,  and  with  filaments  of  the  buccal  branch 
of  the  inferior  maxillary  nerve. 

The  Supramaxillary  or  Supramandibular  Branch  (ramus  marginalis  mandibulae) 
passes  forward  beneath  the  Platysma  and  Depressor  anguli  oris,  supplying  the 


1064  THE  NERVE  SYSTEM 

muscles  of  the  lower  lip  and  chin,  and  communicating  with  the  mental  branch  of 
the  inferior  dental  nerve. 

The  Inframaxillary,  Inframandibular  or  Cervical  Branch  (ramus  colli)  runs  for- 
ward beneath  the  Platysma,  and  forms  a  series  of  arches  across  the  side  of  the 
neck  over  the  suprahyoid  region.  A  branch  descends  vertically  to  join  with  the 
superficial  cervical  nerve  from  the  cervical  plexus;  others  supply  the  Platysma. 

Surgical  Anatomy. — The  facial  nerve  is  more  frequently  paralyzed  than  any  of  the  other 
of  the  cranial  nerves.  The  paralysis  may  depend  either  upon  (1)  central  causes — i.  e.,  blood-clots 
or  intracranial  tumors  pressing  on  the  nerve  before  its  entrance  into  the  internal  auditory  meatus. 
It  is  also  one  of  the  nerves  involved  in  bulbar  paralysis.  Or  (2)  it  may  be  paralyzed  in  its  pass- 
age through  the  petrous  bone  by  damage  due  to  middle-ear  disease  or  by  fractures  of  the  base. 
Or  (3)  it  may  be  affected  at  or  after  its  exit  from  the  stylo-mastoid  foramen.  This  is  commonly 
known  as  Bell's  paralysis.  It  may  be  due  to  exposure  to  cold  or  to  injury  of  the  nerve,  either 
from  accidental  wounds  of  the  face  or  during  some  surgical  operation,  as  removal  of  parotid 
tumors,  opening  of  abscesses,  or  operations  on  the  lower  jaw. 

When  the  cause  is  central,  the  abducent  nerve  is  usually  paralyzed  as  well, and  there  is  also  hemi- 
plegia  on  the  opposite  side.  In  these  cases  the  electric  reactions  are  the  same  as  in  health; 
whereas,  when  the  paralysis  is  due  to  a  lesion  in  the  course  of  the  nerve,  the  reactions  of  degenera- 
tion develop.  When  the  nerve  is  paralyzed  in  the  petrous  bone,  in  addition  to  the  paralysis  of  the 
muscles  of  expression,  there  is  loss  of  taste  in  the  anterior  part  of  the  tongue,  and  the  patient  is 
unable  to  recognize  the  difference  between  bitters  and  sweets,  acids  and  salines,  from  involvement 
of  the  chorda  tympani.  The  mouth  is  dry,  because  the  salivary  glands  are  not  secreting;  the  sense 
of  hearing  is  affected  from  paralysis  of  the  Stapedius,  but  there  is  no  hemiplegia.  When  the 
cause  of  the  paralysis  is  from  fracture  of  the  base  of  the  skull,  the  acoustic  nerve  and  the  petrosal 
nerves,  which  are  connected  with  the  intumescentia  ganglioformis,  are  also  involved.  When 
the  injury  to  the  nerve  is  after  its  exit  from  the  stylo-mastoid  foramen,  all  the  muscles  of-expression 
except  the  Levator  palpebrse,  tpgether  with  the  posterior  belly  of  the  Digastric  and  Stylo-hyoid, 
are  paralyzed.  There  is  smoothness  of  the  forehead,  and  the  patient  is  unable  to  frown;  the 
eyelids  cannot  be  closed,  and  the  lower  lid  droops,  so  that  the  punctum  is  no  longer  in  contact 
with  the  globe,  and  the  tears  run  down  the  cheek;  there  is  smoothness  of  the  cheek  and  loss  of 
the  nasolabial  furrow;  the  nostril  of  the  paralyzed  side  cannot  be  dilated;  the  mouth  is  drawn 
to  the  sound  side,  and  there  is  inability  to  whistle;  food  collects  between  the  cheek  and  gum 
from  paralysis  of  the  Buccinator. 

The  facial  nerve  is  at  fault  in  cases  of  so-called  histrionic  spasm,  which  consists  in  an  almost 
constant  and  uncontrollable  twitching  of  the  muscles  of  the  face.  This  twitching  is  sometimes 
so  severe  as  to  cause  great  discomfort  and  annoyance  to  the  patient  and  to  interfere  with  sleep, 
and  for  its  relief  the  facial  nerve  has  been  stretched.  The  operation  is  performed  by  making  an 
incision  behind  the  ear  from  the  root  of  the  mastoid  process  to  the  angle  of  the  jaw.  The 
parotid  is  turned  forward,  and  the  dissection  carried  along  the  anterior  border  of  the  Sterno- 
mastoid  muscle  and  mastoid  process  until  the  upper  border  of  the  posterior  belly  of  the  Digas- 
tric is  found.  The  nerve  is  parallel  to  this  on  about  a  level  with  the  middle  of  the  mastoid  process. 
When  found,  the  nerve  may  be  stretched  by  passing  a  blunt  hook  beneath  it  and  pulling  it  for- 
ward and  outward.  Too  great  force  must  not  be  used,  for  fear  of  permanent  injury  to  the  nerve. 
In  facial  palsy  of  extracerebral  origin  it  may  be  advisable  to  expose  the  nerve,  cut  it  across,  and 
anastomose  the  distal  end  of  the  paralyzed  nerve  to  the  accessory  nerve  or,  better,  to  the  hypo- 
glossal  nerve  (facio-accessory  anastomosis  or  facio-hypoglossal  anastomosis).  The  idea  was  first 
proposed  by  Ballance,  and  has  been  put  in  practice  by  Ballance  and  Stewart,  Keen,  Gushing, 
Faure,  Kennedy,  and  others. 

THE  EIGHTH  OR  ACOUSTIC  NERVE   (N.  ACUSTICUS)   (Fig.  696). 

The  eighth  or  acoustic  or  auditory  nerve  comprises  two  distinct  sets  of  fibres 
which,  although  both  are  devoted  to  the  transmission  of  afferent  impulses,  differ 
in  their  peripheral  distribution  and  in  their  central  connections.  The  two  divisions 
appear  blended  in  the  interval  between  the  oblongata  and  the  internal  auditory 
meatus,  running  oblique  latero-frontad  in  company  with  the  facial  nerve  and 
internal  auditory  artery.  At  the  internal  auditory  meatus  the  two  divisions  of 
the  nerve  are  separable,  the  vestibular  division  above,  the  cochlear  below. 

The  Cochlear  Nerve  (radix  cochlearis) . — The  cochlear  nerve  is  the  true  nerve  of 
hearing,  lacking  general  sensibility,  however,  and  therefore  a  nerve  of  special  sense. 


THE  EIGHTH  OR  ACOUSTIC  NERVE 


1065 


The  fibres  of  this  division  arise  from  the  cells  of  the  spiral  ganglion  of  the  cochlear 
as  axones  of  bipolar  cells  whose  dendrites  or  peripheral  processes  terminate  about 
the  (auditory)  hair-cells  of  the  organ  of  Corti.  The  central  connections  of  the 
cochlear  division  are  described  on  p.  892. 

The  Vestibular  Nerve  (radix  vestibularis}. — The  vestibular  nerve  conducts 
impulses  of  equilibratory-sense  from  the  semicircular  canals,  utricle,  and  saccule  to 
the  vestibular  nuclei.  The  ganglion  of  origin  of  this  nerve  differs  from  ordinary 
sensor  ganglia  in  that  its  cells  are  of  bipolar  structure,  having  retained  this 
embryonic  characteristic  of  the  ganglion-cells  throughout  life.  The  central 
processes  of  the  cells  of  the  vestibular  ganglion  (or  ganglion  of  Scarpa)  enter  the 
oblongata  with  the  trunk  of  the  cochlear  nerve  in  the  postpontile  groove,  laterad 
of  the  facial  nerve,  to  establish  central  connections  already  described  on  p.  893. 
The  peripheral  processes  constitute  the  two  main  branches  of  the  nerve,  viz., 
(a)  the  utricujb-ampullar  and  (6)  the  sacculo-ampullar. 


FIG.  696. — Distribution  of  the  acoustic  nerve.     (Semidiagrammatic.)     (Testut.) 

The  upper  or  utriculo-ampullar  branch  divides  into: 

(a)  The  Utricular  Branch,  passing  through  the  superior  macula  cribrosa  of  the 
vestibule  to  end  in  the  macula  acustica  of  the  utricle. 

(b)  The  Superior  Ampullar  Branch,  accompanying  the  utricular  branch,  to  end 
in  the  crista  acustica  of  the  ampulla  of  the  superior  semicircular  canal. 

(c)  The  Lateral  Ampullar,  to  the  ampulla  of  the  lateral  semicircular  canal. 
The  lower  or  sacculo-ampullar  branch  is  somewhat  longer  and  divides  into: 

(a)  The  Posterior  Ampullar,  passing  through  the  foramen  singulare  and  the 
inferior  macula  cribrosa  to  end  in  the  ampulla  of  the  posterior  semicircular  canal. 

(6)  The  Saccular  Branch,  passing  through  the  middle  macula  cribrosa  to  end  in 
the  macula  acustica  of  the  sacculus. 

Surgical  Anatomy. — The  acoustic  nerve  is  frequently  injured,  together  with  the  facial  nerve, 
in  fractures  of  the  middle  fossa  of  the  base  of  the  skull  implicating  the  internal  auditory  meatus. 
The  nerve  may  be  either  torn  across,  producing  permanent  deafness,  it  may  be  bruised  or  it  may 
be  pressed  upon  by  extra vasated  blood  or  inflammatory  exudation,  when  the  deafness  will  in  all 
probability  be  temporary.  The  nerve  may  also  be  injured  by  violent  blows  on  the  head  without 


1066  THE  NER  VE  SYSTEM 

fracture,  and  deafness  may  follow  loud  explosions  of  dynamite,  etc.,  probably  from  some  lesion 
of  this  nerve,  which  is  more  liable  to  be  injured  than  the  other  cranial  nerves  on  account  of 
its  structure.  The  test  that  the  nerve  is  destroyed  and  that  the  deafness  is  not  due  to  some 
lesion  of  the  auditory  apparatus  is  obtained  by  placing  a  vibrating  tuning-fork  on  the  head. 
The  vibrations  will  be  heard  in  cases  where  the  auditory  apparatus  is  at  fault,  but  not  in  cases 
of  destruction  of  the  auditory  nerve. 

THE  NINTH  OR  GLOSSO-PHARYNGEAL   NERVE    (N.   GLOSSOPHARYNGEUS) 

(Figs.  697  and  698). 

'  The  ninth  or  glosso-pharyngeal  nerve  is  distributed,  as  its  name  implies,  to 
the  tongue  and  pharynx,  being  the  nerve  of  ordinary  sensation  to  the  mucous 
membrane  of  the  pharynx,  fauces,  and  tonsil ;  and  the  nerve  of  taste  to  all  parts  of 
the  tongue  to  which  it  is  distributed. 

Its  (apparent)  superficial  origin  is  by  three  or  four  filaments,  closely  connected 

together,  from  the  upper  part  of  the  oblongata,  in  the  dorso-lateral  groove  (Fig.  697) . 

The  central  connections  are  described  on  p.  890.     The  small  motor  component 

arises  from  cells  in  the  nucleus  ambiguus.     The  real  origin  of  the  sensor  fibres 

of  the  glosso-pharyngeal  must  be  looked  for  in  the 
"^     L  jugular  and  petrosal  ganglia  which  are  developed 

from  the  neural  crest. 

From  its  superficial  origin  it  passes  outward  across 
the  flocculus,  and  leaves  the  skull  at  the  central  part 
of  the  jugular  foramen,  in  a  separate  sheath  of  the 
dura  external  to  and  in  front  of  the  vagus  and  ac- 
cessory nerves  (Fig.  698).      In  its  passage  through 
the  jugular  foramen  it  grooves  the  lower  border  of 
the  petrous  portion  of  the  temporal  bone,  and  at  its 
.         ^  from.the  sku11  Pass.es  forward  between  the  jugular 
eleventh  cranial  nerves.  vein  and  internal  carotid  artery,  and  descends  ventrad 

of  the  latter  vessel,  and  beneath  the  styloid  process 

of  the  temporal  bone  and  the  muscles  connected  with  it,  to  the  lower  border  of  the 
Stylo-pharyngeus  muscle.  The  nerve  now  curves  inward,  forming  an  arch  on  the 
side  of  the  neck,  and  lying  upon  the  Stylo-pharyngeus  muscle  and  the  Middle 
constrictor  of  the  pharynx.  It  then  passes  beneath  the  Hyo-glossus  muscle,  and 
is  finally  distributed  to  the  mucous  membrane  of  the  fauces  and  base  of  the 
tongue,  and  the  mucous  glands  of  the  mouth  and  tonsil. 

In  passing  through  the  jugular  foramen  the  nerve  presents,  in  succession,  two 
gangliform  enlargements.  The  superior  and  smaller  is  called  the  jugular  ganglion; 
the  inferior  and  larger,  the  petrous  ganglion  or  the  ganglion  of  Andersch. 

The  Superior  or  Jugular  Ganglion  (Ganglion  Superius  n.  Glossopharyngei). 

The  superior  or  jugular  ganglion  is  situated  in  the  upper  part  of  the  groove  in 
which  the  nerve  is  lodged  during  its  passage  through  the  jugular  foramen.  It  is 
of  very  small  size,  and  involves  only  the  lower  part  of  the  trunk  of  the  nerve.  It 
is  usually  regarded  as  a  segmentation  from  the  lower  ganglion. 

The  Inferior  or  Petrous  Ganglion  (Ganglion  Petrosum  n.  Glossopharyngei) 

(Fig.  697). 

The  inferior  or  petrous  ganglion  is  situated  in  a  depression  in  the  lower  border  of 
the  petrous  portion  of  the  temporal  bone;  it  is  larger  than  the  superior  ganglion  and 
involves  the  whole  of  the  fibres  of  the  nerve.  From  this  ganglion  arise  those  fila- 
ments which  connect  the  glosso-pharyngeal  with  the  vagus  and  sympathetic  nerves. 


THE  NINTH  OR  GLOSSO-PHARYNGEAL  NERVE  1Q67 

Branches  of  Communication. — The  branches  of  communication  are  with  the 
va^us,  sympathetic,  and  facial. 

The  branches  to  the  vagus  are  two  filaments,  arising  from  the  petrous  ganglion, 
one  of  which  passes  to  the  auricular  branch  of  the  vagus,  and  one  to  the  upper 
ganglion  of  the  vagus. 

The  branch  to  the  sympathetic,  also  arising  from  the  petrous  ganglion,  is  con- 
nected with*  the  superior  cervical  ganglion. 

The  branch  of  communication  with  the  facial  perforates  the  posterior  belly  of 
the  Digastric  muscle.  It  arises  from  the  trunk  of  the  nerve  below  the  petrous 
ganglion,  and  joins  the  facial  just  after  its  exit  from  the  stylo-mastoid  foramen. 

Branches  of  Distribution. — The  branches  of  distribution  are  the  tympanic, 
carotid,  pharyngeal,  muscular,  tonsillar,  and  lingual. 

The  Tympanic  Branch  or  Jacobson's  Nerve  (n.  tympanicus). — The  tympanic  branch 
or  Jacobson's  nerve  arises  from  the  petrous  ganglion,  and  enters  a  small  bony 
canal  in  the  lower  surface  of  the  petrous  portion  of  the  temporal  bone,  the  lower 
opening  of  which  is  situated  on  the  bony  ridge  which  separates  the  carotid  canal 
from  the  jugular  fossa.  It  ascends  to  the  tympanum,  enters  that  cavity  by  an 
aperture  in  its  floor  close  to  the  inner  wall,  and  divides  into  branches  which  are 
contained  in  grooves  upon  the  surface  of  the  promontory.  These  branches  form 
a  tympanic  plexus  (plexus  tympanicus).  This  plexus  gives  off  (1)  the  greater 
part  of  the  small  superficial  petrosal  nerve  (Fig.  694);  (2)  a  branch  to  join  the 
great  superficial  petrosal  nerve;  and  (3)  branches  to  the  tympanic  cavity,  all  of 
which  will  be.  described  in  connection  with  the  anatomy  of  the  ear. 

The  Carotid  Branches  (n,  caroticotympanicus  superior  and  n.  caroticotympanicus 
inferior). — The  carotid  branches  descend  along  the  trunk  of  the  internal  carotid 
artery  as  far  as  its  commencement,  communicating  with  the  pharyngeal  branch 
of  the  vagus  and  with  branches  of  the  sympathetic. 

The  Pharyngeal  Branches  (rami  pharyngei). — The  pharyngeal  branches  are  three 
or  four  filaments  which  unite  opposite  the  Middle  constrictor  of  the  pharynx  with 
the  pharyngeal  branches  of  the  vagus  and  sympathetic  nerves  to  form  the  pharyn- 
geal plexus,  branches  from  which  perforate  the  muscular  coat  of  the  pharynx  to 
supply  the  muscles  and  mucous  membrane. 

The  Muscular  Branch  (ramus  stylopharyngeus). — The  muscular  branch  is  dis- 
tributed to  the  Stylo-pharyngeus  muscle. 

The  Tonsillar  Branches  (rami  tonsillares). — The  tonsillar  branches  supply  the 
tonsil,  forming  a  plexus   (circulus  tonsillaris)   around  this  body,  from  which  . 
branches  are  distributed  to  the  soft  palate  and  fauces,  where  they  communicate 
with  the  palatine  nerves. 

The  Lingual  Branches  (rami  linguales). — The  lingual  branches  are  two  in  num- 
ber :  one  supplies  the  circumvallate  papillae  and  the  mucous  membrane  covering 
the  surface  of  the  base  of  the  tongue;  the  other  perforates  its  substance,  and 
supplies  the  mucous  membrane  and  follicular  glands  of  the  posterior  one-third 
of  the  tongue  and  communicates  with  the  lingual  nerve. 

The  Gustatory  Path. — The  impressions  of  taste  reach  the  glosso-pharyngeal 
nucleus  in  the  oblongata  in  two  ways.  From  the  posterior  one-third  of  the  tongue 
and  from  the  palate  they  reach  the  nucleus  by  the  glosso-pharyngeal  nerve.  From 
the  anterior  two-thirds  of  the  tongue  impulses  of  taste  are  conveyed  by  the  chorda 
tympani  and  nervus  intermedius.  From  the  glosso-pharyngeal  nucleus  gustatory 
impressions  pass  by  way  of  the  medial  fillet  to  the  thalamus  of  the  opposite  side, 
and  from  the  thalamus  through  ventral  thalamo-cortical  radiation  to  the  gyrus 
hippocampi,  where  the  cortical  gustatory  centre  is  situated. 

Surgical  Anatomy. — Injury  may  produce  hemorrhage  about  the  roots  of  the  nerve.  Berg- 
mann  reported  such  a  case.  The  patient  died  from  o?dema  of  the  glottis  after  presenting 
evidences  of  disorder  of  speech  and  difficulty  in  swallowing. 


1068 


THE  NERVE  SYSTEM 


Glosso-pharyngeal. 

Vagus. 
Accessory. 


THE  TENTH,  VAGUS  OR  PNEUMOGASTRIC  NERVE  (N.  VAGUS). 

(Figs.  697  and  698). 

The  tenth,  vagus  or  pneumogastric   nerve  has  a  more  extensive   distribution 
than  any  of  the  other  cranial  nerves,  passing  through  the  neck  and  thorax  to  the 

upper  part  of  the  abdomen.  It 
is  composed  of  both  motor  and 
sensor  fibres.  It  supplies  the 
organs  of  voice  and  respiration 
with  motor  and  sensor  fibres,  and 
the  pharynx,  oesophagus,  stom- 
ach, and  heart  with  motor  fibres. 
Its  superficial  origin  (Fig.  697) 
is  by  eight  or  ten  filaments  from 
the  groove  between  the  olive  and 
the  restis  below  the  glosso-phar- 
yngeal;  its  central  connections 
are  described  on  p.  890. 

The  real  origin  of  the  sensor 
fibres  of  the  vagus  is  to  be  found 
in  the  cells  of  the  ganglia  on  the 
nerve — viz.,  the  ganglion  of  the 
root  and  the  ganglion  of  the 
trunk.  The  filaments  become 
united  and  form  a  flat  cord, 
which  passes  outward  beneath 
the  flocculus  to  the  jugular  fora- 
men, through  which  it  emerges 
from  the  cranium  (Fig.  698).  In 
passing  through  this  opening  the 
vagus  accompanies  the  accessory 
nerve,  being  contained  in  the 
same  sheath  of  dura  with  it,  a 
membranous  septum  separating 
them  from  the  glosso-pharyngeal, 
which  lies  in  front  (Fig.  698). 
The  nerve  in  this  situation  pre- 
sents a  well-marked  ganglionic 
enlargement,  which  is  called  the 
superior  ganglion,  or  jugular  gan- 
glion; to  it  the  vagal  accessory 
part  of  the  accessory  nerve  is 
connected  by  one  or  two  fila- 
ments. After  the  exit  of  the 
nerve  from  the  jugular  foramen 
the  nerve  is  joined  by  the  acces- 
sory portion  of  the  accessory 
nerve  and  enlarges  into  a  second 
gangliform  swelling,  called  the 
inferior  ganglion  or  the  ganglion 
of  the  trunk  of  the  nerve,  through 
which  the  fibres  of  the  accessory 

FIG.  698.— Course  and  distribution  of  the  glosso-pharyngeal,        nprVP      nass     Unchanged       being 
vagus,  and  accessory  nerves. 


THE  TENTH  OR   VAGUS  NERVE  1069 

principally  distributed  to  the  pharyngeal  and  superior  laryngeal  branches  of  the 
vagus;  but  some  of  the  filaments  from  it  are  continued  into  the  trunk  of  the 
vagus  below  the  ganglion  to  be  distributed  with  the  recurrent  laryngeal  nerve, 
and  probably  also  with  the  cardiac  nerves.  The  vagus  nerve  passes  vertically 
down  the  neck  within  the  sheath  of  the  carotid  vessels  lying  between  the  inter- 
nal carotid  artery  and  the  internal  jugular  vein  as  far  as  the  thyroid  cartilage, 
and  then  between  the  same  vein  and  the  common  carotid  to  the  root  of  the  neck 
(Fig.  698).  From  here  the  course  of  the  nerve  differs  on  the  two  sides  of  the 
body. 

On  the  right  side  (Fig.  698)  the  nerve  passes  across  the  subclavian  artery  between 
it  and  the  right  innominate  vein,  and  descends  by  the  side  of  the  trachea  to  the  back 
part  of  the  root  of  the  lung,  where  it  spreads  out  in  a  plexiform  network,  the 
dorsal  pulmonary  plexus  (plexus  pidmonalis  posterior),  from  the  lower  part  of  which 
two  cords  descend  upon  the  oesophagus,  on  which  tube  they  divide,  forming,  with 
branches  from  the  opposite  nerve,  the  oesophageal  plexus  (plexus  gulae) ;  below,  these 
branches  are  collected  into  a  single  cord,  which  runs  along  the  back  part  of  the 
oesophagus,  enters  the  abdomen,  and  is  distributed  to  the  dorsal  surface  of 
the  stomach,  joining  the  left  side  of  the  solar  plexus,  and  sending  filaments  to  the 
splenic  plexus  and  a  considerable  branch  to  the  coeliac  plexus. 

On  the  left  side  the  vagus  nerve  enters  the  chest  between  the  left  carotid  and 
subclavian  arteries,  behind  the  left  innominate  vein.  It  crosses  the  arch  of 
the  aorta  and  descends  behind  the  root  of  the  left  lung,  forming  the  ventral  pul- 
monary plexus  (plexus  pidmonalis  anterior),  and  along  the  ventral  surface  of  the 
oesophagus,  where  it  unites  with  the  nerve  of  the  right  side  in  forming  the  oesopha- 
geal plexus.  It  passes  to  the  stomach,  distributing  branches  over  the  ventral 
surface  of  that  viscus,  some  extending  over  the  great  cul-de-sac,  and  others  along 
the  lesser  curvature.  Filaments  from  these  branches  enter  the  gastro-hepatic 
omentum  and  join  the  hepatic  plexus. 

The  Ganglion  of  the  Eoot  of  the  Vagus  Nerve  (Ganglion  Jugulare). 

The  ganglion  of  the  root  or  the  jugular  ganglion  is  of  a  grayish  color,  circular 
in  form,  about  two  lines  in  diameter,  and  resembles  the  ganglion  on  the  larger 
root  of  the  fifth  nerve. 

Connecting  Branches. — To  this  ganglion  the  accessory  portion  of  the  ac- 
cessory nerve  is  connected  by  several  delicate  filaments;  it  also  has  a  com- 
municating twig  with  the  petrous  ganglion  of  the  glosso-pharyngeal,  with  the 
facial  nerve  by  means  of  its  (the  ganglion's)  auricular  branch,  and  with  the 
sympathetic  by  means  of  an  ascending  filament  from  the  superior  cervical 
ganglion. 

The  Ganglion  of  the  Trunk  of  the  Vagus  Nerve  (Ganglion  Nodosum). 

The  ganglion  of  the  trunk  or  the  inferior  ganglion  is  a  plexiform  cord,  cylin- 
drical in  form,  of  a  reddish  color,  and  about  an  inch  (2  cm.)  in  length;  it  involves 
the  whole  of  the  fibres  of  the  nerve,  and  passing  through  it  is  the  accessory 
portion  of  the  accessory  nerve,  which  blends  with  the  vagus  below  the  ganglion, 
to  be  then  continued  principally  into  its  pharyngeal  and  superior  laryngeal 
branches. 

Connecting  Branches. — This  ganglion  is  connected  with  the  hypoglossal,  the 
superior  cervical  ganglion  of  the  sympathetic,  and  the  loop  between  the  first  and 
second  cervical  nerves. 


1070  THE  NERVE  SYSTEM 

The  branches  of  the  vagus  are — 


In  the  jugular  fossa 
In  the  neck  ... 

In  the  thorax 
In  the  abdomen 


f  Dural. 
\  Auricular. 
f  Pharyngeal. 
I  Superior  laryngeal. 
I   Recurrent  laryngeal. 
L  Cervical  cardiac, 
f  Thoracic  cardiac. 
I   Ventral  pulmonary. 
I   Dorsal  pulmonary. 
I  (Esophageal. 
Gastric. 


The  Dural  Branch  (ramus  meningeus). — The  dural  branch  is  a  recurrent  fila- 
ment given  off  from  the  ganglion  of  the  root  in  the  jugular  foramen.  It  passes 
backward^  and  is  distributed  to  the  dura  lining  the  posterior  fossa  of  the  base  of 
the  skull. 

The  Auricular  Branch  or  Arnold's  Nerve  (ramus  auricularis)  (Fig.  699). — The 
auricular  branch  or  Arnold's  nerve  arises  from  the  ganglion  of  the  root,  and  is 
joined  soon  after  its  origin  by  a  filament  from  the  petrous  ganglion  of  the  glosso- 
pharyngeal;  it  passes  outward  behind  the  jugular  vein,  and  enters  a  small  canal 
on  the  outer  wall  of  the  jugular  fossa.  Traversing  the  substance  of  the  tem- 
poral bone,  it  crosses  the  aquaeductus  Fallopii  about  two  lines  above  its  termina- 
tion at  the  stylo-mastoid  foramen;  here  it  gives  off  an  ascending  branch,  which 
joins  the  facial;  the  continuation  of  the  nerve  reaches  the  surface  by  passing 
through  the  auricular  fissure  between  the  mastoid  process  and  the  external  audi- 
tory meatus,  and  divides  into  two  branches,  one  of  which  communicates  with  the 
posterior  auricular  nerve,  while  the  other  supplies  the  integument  at  the  back 
part  of  the  pinna  and  the  dorsal  part  of  the  external  auditory  meatus. 


TO  EXTERNAL  AUDITORY 

US  AND 
\(OF 


TO  POSTERIOR 

AURICULAR  OF 

FACIAL 


FROM  GLOSSOPHARYNGEAL 


AURICULAR  BRANCH 
OF  VAGUS 


1° 

ARTERIOSUS         X  • 

FIG.  700. — Relations  of  vagus  and  recurrent 


FIG.  699.— Plan  of  Arnold's  nerve.     (W.  Keiller.) 

The  Pharyngeal  Branch  (ramus  pharyngeus). 

—The     pharyngeal    branch,    the    principal 

motor  nerve  of  the  pharynx,  arises  from  the 

upper  part  of  the  ganglion  of  the  trunk  of  the 

VagUS.        It    Consists    principally    of    filaments     laryngeal    nerves    to   the   great   vessels.       (W. 

from  the  accessory  portion  of  the  accessory   Keiller>) 

nerve;  it  passes  across  the  internal  carotid  artery  to  the  upper  border  of  the 
Middle  constrictor  of  the  pharynx,  where  it  divides  into  numerous  filaments  which 
join  with  those  from  the  glosso-pharyngeal,  the  superior  laryngeal  (its  external 
branch),  and  sympathetic,  to  form  the  pharyngeal  plexus  (plexus  pharyngeus}, 


THE  TENTH  OR   VAGUS  NERVE  1071 

from  which  branches  are  distributed  to  the  muscles  and  mucous  membrane  of 
the  pharynx  and  the  muscles  of  the  soft  palate.  From  the  pharyngeal  plexus  a 
minute  filament  is  given  off,  which  descends  and  joins  the  hypoglossal  nerve  as 
it  winds  around  the  occipital  artery. 

The  Superior  Laryngeal  Nerve  (n.  laryngeus  superior]  (Figs.  697  and  698). — It  is 
larger  than  the  preceding,  and  arises  partly  from  the  middle  of  the  ganglion  of  the 
trunk  of  the  vagus.  It  consists  principally  of  filaments  from  the  accessory  nerve. 
In  its  course  it  receives  a  branch  from  the  superior  cervical  ganglion  of  the  sympa- 
thetic. It  descends  by  the  side  of  the  pharynx  behind  the  internal  carotid  artery, 
where  it  divides  into  two  branches,  the  external  and  internal  laryngeal.  This  nerve 
is  the  nerve  of  sensation  of  the  larynx,  and  also  supplies  the  crico-thyroid  muscle. 
Exner  has  pointed  out  that  the  superior  laryngeal  nerve  innervates  to  some  ex- 
tent the  muscles  supplied  by  the  inferior  laryngeal,  and  this  fact  explains  why 
division  of  the  inferior  laryngeal  nerve  is  not  of  necessity  followed  by  complete 
paralysis  of  the  muscles  it  supplies. 

The  External  Laryngeal  Branch  of  the  Superior  Laryngeal  (ramus  externus)  (Fig. 
698),  the  smaller,  descends  by  the  side  of  the  larynx,  beneath  the  Sterno-thyroid, 
to  supply  the  Crico-thyroid  muscle.  It  gives  branches  to  the  pharyngeal  plexus 
and  the  Inferior  constrictor,  and  communicates  with  the  superior  cardiac  nerve, 
behind  the  common  carotid. 

The  Internal  Laryngeal  Branch  of  the  Superior  Laryngeal  (ramus  internus) 
descends  to  the  opening  in  the  thyro-hyoid  membrane,  through  which  it  passes 
with  the  superior  laryngeal  artery,  and  is  distributed  to  the  mucous  membrane  of 
the  larynx.  A  small  branch  communicates  with  the  recurrent  laryngeal  nerve. 
The  branches  to  the  mucous  membrane  are  distributed,  some  in  front  to  the 
epiglottis,  the  base  of  the  tongue,  and  the  epiglottidean  glands;  while  others 
pass  backward,  in  the  aryteno-epiglottidean  fold,  to  supply  the  mucous  mem- 
brane surrounding  the  superior  orifice  of  the  larynx,  as  well  as  the  membrane 
which  lines  the  cavity  of  the  larynx  as  low  down  as  the  vocal  cord.  The  fila- 
ment which  joins  with  the  recurrent  laryngeal  descends  beneath  the  mucous 
membrane  on  the  inner  surface  of  the  thyroid  cartilage,  where  the  two  nerves 
become  united. 

The  Inferior  or  Recurrent  Laryngeal  Branch  of  the  Vagus  (n.  laryngeus  inferior] 
(Figs.  698  and  700). — The  inferior  or  recurrent  laryngeal  branch,  so  called  from 
its  reflected  course,  is  the  motor  nerve  of  the  larynx.  It  arises  on  the  right  side, 
in  front  of  the  subclavian  artery;  winds  from  before  backward  around  that  vessel, 
and  ascends  obliquely  to  the  side  of  the  trachea,  behind  the  common  carotid  artery 
and  behind  or  in  front  of  the  inferior  thyroid  artery.  On  the  left  side  it  arises  in 
front  of  the  arch  of  the  aorta,  and  winds  from  before  backward  around  the  aorta 
at  the  point  where  the  remains  of  the  ductus  arteriosus  are  connected  with  it,  and 
then  ascends  to  the  side  of  the  trachea.  The  nerve  on  each  side  ascends  in  the 
groove  between  the  trachea  and  oesophagus,  and,  passing  under  the  lower  border 
of  the  Inferior  constrictor  muscle,  enters  the  larynx  behind  the  articulation  of 
the  inferior  cornu  of  the  thyroid  cartilage  with  the  cricoid,  being  distributed  to  all 
the  muscles  of  the  larynx  except  the  Crico-thyroid.  It  communicates  with  the 
superior  laryngeal  nerve  and  gives  off  a  few  filaments  to  the  mucous  membrane 
of  the  lower  part  of  the  larynx. 

The  recurrent  laryngeal,  as  it  winds  around  the  subclavian  artery  and  aorta, 
gives  off  several  cardiac  filaments,  which  unite  with  the  cardiac  branches  from 
the  vagus  and  sympathetic.  As  it  ascends  in  the  neck  it  gives  off  oesophageal 
branches,  more  numerous  on  the  left  than  on  the  right  side,  which  supply  the 
mucous  membrane  and  muscular  coat  of  the  oesophagus;  tracheal  branches  to 
the  mucous  membrane  and  muscular  fibres  of  the  trachea;  and  some  pharyngeal 
filaments  to  the  Inferior  constrictor  of  the  pharynx. 


1072  THE  NERVE  SYSTEM 

The  Cervical  Cardiac  Branches  (rami  cardiaci  superiores). — The  cervical  cardiac 
branches,  two  or  three  in  number,  arise  from  the  vagus,  at  the  upper  and  lower 
part  of  the  neck. 

The  Superior  Branches  are  small,  and  communicate  with  the  cardiac  branches 
of  the  sympathetic.  They  can  be  traced  to  the  great  or  deep  cardiac  plexus. 

The  Inferior  Branches,  one  on  each  side,  arise  at  the  lower  part  of  the  neck, 
just  above  the  first  rib.  On  the  right  side  this  branch  passes  ventrad  or  by  the 
side  of  the  arteria  innominata,  and  communicates  with  one  of  the  cardiac  nerves 
proceeding  to  the  great  or  deep  cardiac  plexus.  On  the  left  side  it  passes  ventrad 
of  the  arch  of  the  aorta  and  joins  the  superficial  cardiac  plexus. 

The  Thoracic  Cardiac  Branches  (rami  cardiaci  inferiores). — The  thoracic  cardiac 
branches,  on  the  right  side,  arise  from  the  trunk  of  the  vagus  as  it  lies  by  the  side 
of  the  trachea,  and  from  its  recurrent  laryngeal  branch,  but  on  the  left  side  from 
the  recurrent  nerve  only;  passing  inward,  they  terminate  in  the  deep  cardiac  plexus. 

The  Ventral  Pulmonary  Branches. — The  ventral  pulmonary  branches,  two  or  three 
in  number,  and  of  small  size,  are  distributed  on  the  ventral 'aspect  of  the  root  of 
the  lungs.  They  join  with  filaments  from  the  sympathetic,  and  form  the  ventral 
pulmonary  plexus  (plexus  pulmonalis  anterior). 

The  Dorsal  Pulmonary  Branches. — The  dorsal  pulmonary  branches,  more  numer- 
ous and  larger  than  the  ventral,  are  distributed  on  the  dorsal  aspect  of  the 
root  of  the  lung;  they  are  joined  by  filaments  from  the  third  and  fourth  (some- 
times also  from  the  first  and  second)  thoracic  ganglia  of  the  sympathetic, 
and  form  the  dorsal  pulmonary  plexus  (plexus  pulmonalis  posterior).  Branches 
from  both  plexuses  accompany  the  ramification  of  the  air-tubes  through  the  sub- 
stance of  the  lungs  (rami  bronchioles  anteriores  and  rami  bronchioles  posterior  es}. 

The  (Esophageal  Branches  (rami  oesophagei). — The  cesophageal  branches  are 
given  off  from  the  vagus  both  above  and  below  the  pulmonary  branches.  The 
lower  are  more  numerous  and  larger  than  the  upper.  They  form,  together 
with  branches  from  the  opposite  nerve,  the  oesophageal  plexus.  From  this  plexus 
branches  are  distributed  to  the  back  of  the  pericardium. 

The  Gastric  Branches  (rami  gastrici)  (Fig.  698). — The  gastric  branches  are  the 
terminal  filaments  of  the  vagus  nerve.  The  nerve  on  the  right  side  is  distri- 
buted to  the  posterior  surface  of  the  stomach.  The  right  vagus  sends  branches 
to  the  cceliac  plexus  (rami  coeliaci),  to  the  splenic  plexus  (rami  lienales),  and  to 
the  renal  plexus  (rami  renales).  The  nerve  on  the  left  side  is  distributed  over  the 
anterior  surface  of  the  stomach,  some  filaments  (rami  hepatica)  passing  across  the 
great  cul-de-sac,  and  others  along  the  lesser  curvature.  They  unite  with  branches 
of  the  right  nerve  and  with  the  sympathetic,  some  filaments  passing  through  the 
lesser  omentum  to  the  hepatic  plexus. 

Surgical  Anatomy. — The  laryngeal  nerves  are  of  considerable  importance  in  considering 
some  of  the  morbid  conditions  of  the  larynx.  When  the  peripheral  terminations  of  the  superior 
laryngeal  nerve  are  irritated  by  some  foreign  body  passing  over  them,  reflex  spasm  of  the  glottis 
is  the  result.  When  the  trunk  of  the  same  nerve  is  pressed  upon  by,  for  instance,  a  goitre  or 
an  aneurism  of  the  upper  part  of  the  carotid,  we  have  a  peculiar  dry,  brassy  cough.  When  the 
nerve  is  paralyzed,  we  have  anaesthesia  of  the  mucous  membrane  of  the  larynx,  so  that  foreign 
bodies  can  readily  enter  the  cavity,  and,  in  consequence  of  its  supplying  the  crico-thyroid  muscle, 
the  vocal  cords  cannot  be  made  tense,  and  the  voice  is  deep  and  hoarse.  Paralysis  of  the  supe- 
rior laryngeal  nerves  may  be  the  result  of  bulbar  paralysis,  may  be  a  sequel  to  diphtheria,  when 
both  nerves  are  usually  involved,  or  it  may,  though  less  commonly,  be  caused  by  the  pressure 
of  tumors  or  aneurisms,  when  the  paralysis  is  generally  unilateral.  Irritation  of  the  inferior 
laryngeal  nerves  produces  spasm  of  the  muscles  of  the  larynx.  When  both  the  recurrent 
nerves  are  paralyzed,  the  vocal  cords  are  motionless  in  the  so-called  cadaveric  position — that 
is  to  say,  in  the  position  in  which  they  are  found  in  ordinary  tranquil  respiration — neither  closed 
as  in  phonation,  nor  open  as  in  deep  inspiratory  effort.  When  one  recurrent  nerve  is  paralyzed, 
the  cord  of  the  same  side  is  motionless,  while  the  opposite  cord  crosses  the  middle  line  to  accom- 
modate itself  to  the  affected  one;  hence  phonation  is  present,  but  the  voice  is  altered  and  weak 
in  timbre.  The  recurrent  laryngeal  nerves  may  be  paralyzed  in  bulbar  paralysis  or  after  diph- 


THE  ELEVENTH  OR  ACCESSORY  NERVE  1073 

tlieria,  when  the  paralysis  usually  affects  both  sides;  or  they  may  be  affected  by  the  pressure 
of  aneurisms  of  the  aorta,  innominate  or  subclavian  arteries;  by  mediastinal  tumors;  by  bron- 
chocele;  or  by  cancer  of  the  upper  part  of  the  oesophagus,  when  the  paralysis  is  often  unilat- 
eral. The  nerve  may  be  accidentally  divided  during  the  operation  for  goitre. 

It  is  a  well-recognized  fact  that  disease  or  injury  of  the  vagus  may  induce  serious  symptoms. 
Bruising  may  cause  such  symptoms;  so  may  injury  of  the  nerve  by  a  stab,  a  bullet,  or  during 
surgical  operations.  Either  accidental  ligation  or  crushing  with  clamp  forceps  is  particularly 
dangerous.  Michaux  accidentally  ligated  the  vagus,  and  the  patient  became  comatose  and 
ceased  to  breathe,  but  was  restored  on  removing  the  ligature.  Tillmanns,  while  removing  a 
cancer,  accidentally  caught  and  crushed  a  portion  of  the  nerve  in  a  clamp,  and  both  pulse  and 
respiration  ceased.  The  clamp  was  removed,  the  patient  was  restored  with  difficulty,  and  the 
nerve  was  sutured.  Recovery  followed.  It  thus  becomes  evident  that  division  of  the  vagus  on 
one  side  is  not,  as  was  so  long  taught,  a  necessarily  fatal  accident;  in  fact,  it  is  sometimes  under- 
taken deliberately  in  removing  tumors  adherent  to  the  nerve.  Division  of  a  nerve  which  has 
been  long  compressed  is  probably  not  so  dangerous  as  division  of  a  healthy  nerve,  as  in  the  former 
case  the  opposite  vagus  has  probably  assumed  some  of  its  colleague's  duties.  A  number  of  cases 
of  deliberate  division  have  been  reported.  Twenty-three  cases  are  referred  to  in  the  system  df 
surgery  by  von  Bergmann  and  Mikulicz,  and  twelve  of  them  died,  but  in  none  of  the  deaths  was 
the  removal  of  the  vagus  the  apparent  cause  of  the  fatality.  The  editor  of  this  American  edition 
of  "Gray"  has  seen  three  cases:  One  was  operated  upon  by  Dr.  W.  Joseph  Hearn,  one  by  Dr. 
Melvin  Franklin,  and  one  by  the  editor.  All  three  recovered,  and  not  one  presented  any 
serious  disturbance,  although  each  had  hoarseness  and  weakness  of  voice. 

One  would  assume  that  after  division  of  the  vagus  below  the  superior  laryngeal  nerve  and 
above  the  recurrent  laryngeal  nerve  (the  region  usually  attacked)  that  there  would  be  paralysis 
of  all  the  muscles  of  one  side  of  the  larynx,  except  the  crico-thyroid,  and  widespread  aberration 
evinced  by  disturbances  of  the  heart,  stomach,  and  lungs.  As  a  matter  of  fact,  this  has  not  been 
the  case.  It  might  be  and  probably  would  be  the  case,  were  a  healthy  nerve  divided;  but  the 
surgeon  who  deliberately  divides  the  nerve  does  so  during  the  removal  of  a  tumor  which  has  long 
made  pressure.  In  most  cases  there  is  no  change  in  the  pulse  or  respiration.  In  some  cases 
dysphagia  and  pneumonia  arise,  but  they  may  be  due  to  other  causes  than  vagus-nerve  injury 
(the  formidable  nature  and  the  duration  of  the  operation — the  ligation  of  vessels  of  large  size — 
the  age  of  the  subject) 

Laryngeal  symptoms,  to  a  greater  or  less  degree,  are  always  noted.  The  difference  in  the 
degree  of  the  palsy  is  explainable  when  we  recall  Exner's  statement  that  the  muscles  supplied 
by  the  recurrent  laryngeal  also  receive  some  innervation  from  the  superior  laryngeal.  In  fact, 
Mills  points  out  that  a  portion  of  the  recurrent  laryngeal  has  been  resected  without  completely 
paralyzing  the  muscles  supposed  to  be  supplied  solely  by  the  recurrent  laryngeal.  The  laryngeal 
symptoms  result  from  unilateral  laryngeal  paralysis,  in  which  there  is  paralysis  of  the  muscles 
which  open  the  glottis.  The  voice  may  be  lost  or  may  be  hoarse.  Usually,  after  a  time,  this  is, 
to  a  great  extent,  compensated  for  by  the  opposite  vocal  cord,  although  the  voice  may  always 
remain  weak,  and  the  patient  will  tire  easily  on  talking.  If  both  vagi  were  to  be  divided  death 
would  ensue. 


THE  ELEVENTH  OR  ACCESSORY  NERVE  (N.  ACCESSORIUS) 

(Figs.  697  and  698). 

The  eleventh,  accessory,  or  spinal  accessory  nerve  consists  of  two  parts:  one  the 
accessory  part  to  the  vagus,  and  the  other  the  spinal  portion. 


The  Bulbar  or  Vagal  Accessory  Part  of  the  Accessory  Nerve  (Ramus 

Interims). 

The  bulbar  or  vagal  accessory  part  is  the  smaller  of  the  two.  It  is  accessory  to 
the  vagus.  Its  superficial  origin  (Fig.  697)  is  by  four  or  five  delicate  filaments 
from  the  side  of  the  oblongata,  below  the  roots  of  the  vagus.  Its  deep  origin  is 
described  in  detail  on  page  890.  It  passes  outward  to  the  jugular  foramen,  where 
it  interchanges  fibres  with  the  spinal  portion  or  becomes  united  to  it  for  a  short 
distance;  it  is  also  connected,  in  the  foramen,  with  the  upper  ganglion  of  the  vagus 
by  one  or  two  filaments.  It  then  passes  through  the  foramen  (Fig.  698),  and 
becoming  again  separated  from  the  spinal  portion  it  is  continued  over  the  surface 

68 


1074  THE  NERVE  SYSTEM 

of  the  ganglion  of  the  trunk  of  the  vagus,  being  adherent  to  its  surface,  and  is 
distributed  principally  to  the  pharyngeal  and  superior  laryngeal  branches  of  the 
vagus.  Through  the  pharyngeal  branch  it  probably  supplies  the  muscles  of  the  soft 
palate.  Some  few  filaments  from  it  are  continued  into  the  trunk  of  the  vagus  below 
the  ganglion,  to  be  distributed  with  the  recurrent  laryngeal  nerve  to  supply  most 
of  the  laryngeal  muscle,  and  probably  also  with  the  cardiac  nerves. 

The  Spinal  Portion  of  the  Accessory  Nerve  (Ramus  Externus). 

The  spinal  portion  is  firm  in  texture.  Its  superficial  origin  (Fig.  697)  is  by 
several  filaments  or  rootlets  from  the  lateral  tract  of  the  cord,  as  low  down  as 
the  sixth  cervical  nerve.  Its  deep  origin  (Fig  578)  may  be  traced  to  the  inter- 
medio-lateral  tract  of  the  gray  substance  of  the  cord.  The  rootlets  of  origin  join  and 
form  a  trunk  which  ascends  in  the  subdural  space  between  the  ligamentum  den- 
ticulatum  and  the  ventral  roots  of  the  spinal  nerves,  enters  the  skull  through  the 
foramen  magnum,  and  is  then  directed  outward  to  the  jugular  foramen,  through 
which  it  passes,  lying  in  the  same  sheath  as  the  vagus,  but  separated  from  it  by  a 
fold  of  the  arachnoid.  In  the  jugular  foramen  it  receives  one  or  two  filaments 
from  the  vagal  accessory  portion.  At  its  exit  from  the  jugular  foramen  it  passes 
into  the  neck  and  becomes  the  external  branch  (Figs.  655  and  698).  It  passes 
backward,  either  in  front  of  or  behind  the  internal  jugular  vein,  and  descends 
obliquely  behind  the  Digastric  and  Stylo-hyoid  muscles  to  the  upper  part  of  the 
Sterno-mastoid  muscle.  It  pierces  that  muscle,  and  passes  obliquely  across  the 
posterior  triangle,  to  terminate  in  the  deep  surface  of  the  Trapezius  muscle. 
This  nerve  gives  several  branches  to  the  Sterno-mastoid  muscle  during  its  passage 
through  it,  and  joins  in  its  substance  with  branches  from  the  second  cervical,  which 
supply  the  muscle.  In  the  posterior  triangle  it  joins  with  the  second  and 
third  cervical  nerves,  while  beneath  the  Trapezius  it  forms  a  sort  of  plexus  with 
the  third  and  fourth  cervical  nerves,  and  from  this  plexus  fibres  are  distributed 
to  the  muscle. 

Surgical  Anatomy. — Division  of  the  external  branch  of  the  accessory  nerve  causes  paralysis 
of  the  Sterno-cleido-mastoid  and  Trapezius  muscles;  not  absolute  paralysis,  for  these  muscles 
also  receive  nerves  from  the  cervical  plexus.  In  cases  of  spasmodic  torticollis  in  which  all 
palliative  treatment  has  failed  division  or  excision  of  a  portion  of  the  external  branch  of  the 
accessory  nerve  has  been  suggested  by  Keen.  This  may  be  done  either  along  the  anterior  or 
posterior  border  of  the  Sterno-mastoid  muscle.  The  former  operation  is  performed  by  making 
an  incision  from  the  apex  of  the  mastoid  process,  three  inches  in  length,  along  the  anterior  border 
of  the  Sterno-mastoid  muscle.  The  anterior  border  of  the  muscle  is  defined  and  pulled  back- 
ward, so  as  to  stretch  the  nerve,  which  is  then  to  be  sought  for  beneath  the  Digastric  muscle, 
about  two  inches  below  the  apex  of  the  mastoid  process.  The  other  operation  consists  in 
making  an  incision  along  the  posterior  border  of  the  muscle,  so  that  the  centre  of  the  incision 
corresponds  to  the  middle  of  this  border  of  the  muscle.  The  superficial  structures  having  been 
divided  and  the  border  of  the  muscle  defined,  the  nerve  is  to  be  sought  for  as  it  emerges  from 
the  muscle  to  cross  the  occipital  triangle.  When  found,  it  is  to  be  traced  upward  through  the 
muscle,  and  a  portion  of  it  is  excised  above  the  point  where  it  gives  off  its  branches  to  the  Sterno- 
mastoid.  In  this  operation  one  of  the  descending  branches  of  the  superficial  cervical  plexus  is 
liable  to  be  mistaken  for  the  nerve. 

THE  TWELFTH  OR  HYPOGLOSSAL  NERVE  (N.  HYPOGLOSSUS) 

(Figs.  701  and  702). 

The  twelfth  or  hypoglossal  nerve  is  the  motor  nerve  of  the  tongue.  Its  super- 
ficial origin  is  by  several  filaments,  from  ten  to  fifteen  in  number,  from  the  groove 
between  the  pyramidal  and  olivary  bodies  of  the  oblongata,  in  a  continuous  line 
with  the  ventral  roots  of  the  spinal  nerves.  Its  deep  origin  can  be  traced  to  a 


THE  TWELFTH  OR  HYPOGLOSSAL  NERVE 


1075 


nucleus  of  gray  substance  (nucleus  hypoglossi)  in  the  floor  of  the  fourth  ventricle 
described  on  p.  890. 

The  filaments  of  this  nerve  are  collected  into  two  bundles,  which  perforate  the 
dura  separately,  opposite  the  anterior  condyloid  foramen,  and  unite  together 
after  their  passage  through  it.  In  those  cases  in  which  the  anterior  condyloid 


To  Lingual  Nerve 
To  Qenio-hyoid 

To  Thyro-hyoid 
'o  Anterior  Belly  of  Omo-hj/oid 


'  To  Stemo-hyoid 
'To  Sterna-thyroid 
To  Posterior  Belly  of  Omo-hyoid 

FIG.  701. — Plan  of  the  hypoglossal  nerve. 

or  hypoglossal  foramen  in  the  occipital  bone  is  double,  these  two  portions  of  the 
nerve  are  separated  by  the  small  piece  of  bone  which  divides  the  foramen.  The 
nerve  descends  almost  vertically  to  a  point  corresponding  with  the  angle  of  the 
jaw.  It  is  at  first  deeply  seated  beneath  the  internal  carotid  artery  and  internal 
jugular  vein,  and  is  intimately  connected  with  the  vagus  nerve  (Fig.  702);  it  then 
passes  forward  between  the  vein  and  artery,  and  lower  down  in  the  neck  becomes 
superficial  below  the  Digastric  muscle.  The  nerve  then  loops  around  the  occipital 
artery,  and  crosses  the  external  carotid  and  its  lingual  branch  below  the  tendon 
of  the  Digastric  muscle.  It  passes  beneath  the  tendon  of  the  Digastric,  the  Stylo- 
hyoid,  and  the  Mylo-hyoid  muscles,  lying  between  the  last-named  muscle  and  the 
Hyo-glossus  (Fig.  702),  and  communicates  at  the  anterior  border  of  the  Hyo- 
glossus  with  the  lingual  nerve  (Fig.  701);  it  is  then  continued  forward  in  the  fibres 
of  the  Genio-hyoglossus  muscle  as  far  as  the  tip  of  the  tongue,  distributing  branches 
to  its  muscular  substance. 

Branches   of  Communication  (Fig.  701). — The  branches  of  communication 
are  with  the 


Vagus. 
Sympathetic. 


First  and  Second  Cervical  Nerves. 
Lingual  (gustatory). 


1076 


THE  NERVE  SYSTEM 


The  first  mentioned  takes  place  close  to  the  exit  of  the  nerve  from  the  skull, 
numerous  filaments  passing  between  the  hypoglossal  and  the  ganglion  of  the  trunk 
of  the  vagus  through  the  mass  of  connective  tissue  which  here  unites  the  two 
nerves.  It  also  communicates  with  the  pharyngeal  plexus  by  a  minute  filament 
as  it  winds  around  the  occipital  artery. 

The  communication  with  the  sympathetic  takes  place  opposite  the  atlas  vertebra 
by  branches  derived  from  the  superior  cervical  ganglion,  and  in  the  same  situa- 
tion the  nerve  is  joined  by  filaments  derived  from  the  loop  connecting  the  first 
two  cervical  nerves. 

The  communication  with  the  lingual  nerve  takes  place  near  the  anterior  border 
of  the  Hyo-glossus  muscle  by  numerous  filaments  which  ascend  upon  it. 


Hypoglossal  nerve. 
Vagus  nerve. 
Gloksopharyngeal  nerve 


FIG.  702. — Hypoglossal  nerve,  cervical  plexus,  and  their  branches. 


Branches  of  Distribution  (Fig.  701). — The  branches  of  distribution  are — the 

Dural.  Thyro-hyoid. 

Descendens  hypoglossi.  Muscular. 

Dural  Branches  (Fig.  701). — As  the  hypoglossal  nerve  passes  through  the 
anterior  condyloid  foramen  it  gives  off,  according  to  Luschka,  several  filaments  to 
the  dura  in  the  posterior  fossa  of  the  base  of  the  skull;  these  filaments  are  probably 
derived  from  a  branch  which  passes  from  the  first  cervical  nerve  to  the  hypo-glossal 


nerve. 


The   Descendens   Hypoglossi   (ramus  descendens)    (Figs.   701    and   702).— The 
descendens  hypoglossi,  long  called  the  descendens  noni,  is  a  long  slender  branch, 


THE  SYMPA  THETIC  NER  VE  SYSTEM  1077 

which  quits  the  hypo-glossal  where  it  turns  around  the  occipital  artery.  It  con- 
sists mainly  of  fibres  which  pass  to  the  hypo-glossal  from  the  first  and  'second 
cervical  nerves  in  the  above-mentioned  communication.  It  descends  in  front  of 
or  within  the  sheath  of  the  common  carotid  artery,  giving  off  a  branch  to  the 
anterior  belly  of  the  Omo-hyoid,  and  then  joins  the  communicating  branches 
from  the  second  and  third  cervical  nerves,  just  below  the  middle  of  the  neck,  to 
form  a  loop,  the  ansa  hypo-glossi.  From  the  convexity  of  this  loop  branches  pass 
to  supply  the  Sterno-hyoid,  Sterno-thyroid,  and  the  posterior  belly  of  the  Omo- 
hyoid.  According  to  Arnold,  another  filament  descends  in  front  of  the  vessels  into 
the  chest,  and  joins  the  cardiac  and  phrenic  nerves. 

The  Thyro-hyoid  Branch  (ramus  thyreohyoideus)  (Fig.  701). — The  thyro-hyoid 
is  a  small  branch  arising  from  the  hypoglossal  near  the  posterior  border  of  the 
Hyo-glossus;  it  passes  obliquely  across  the  great  cornu  of  the  hyoid  bone  and 
supplies  the  Thyro-hyoid  muscle. 

The  Muscular  Branches  (Fig.  701). — The  muscular  branches  are  distributed  to 
the  Stylo-glossus,  Hyo-glossus,  Genio-hyoid,  and  Genio-hyo-glossus  muscles.  At 
the  under  surface  of  the  tongue  numerous  slender  branches  (rami  linguales)  pass 
upward  into  the  substance  of  the  organ  to  supply  its  intrinsic  muscles. 

Surgical  Anatomy. — A  wound  in  the  submaxillary  region  may  injure  the  hypoglossal  nerve 
and  result  in  motor  paralysis  of  the  corresponding  half  of  the  tongue.  The  hypo-glossal  nerve  is 
an  important  guide  in  the  operation  of  ligation  of  the  lingual  artery  (see  page  606).  It  runs  for- 
ward on  the  Hyo-glossus  muscle  just  above  the  great  cornu  of  the  hyoid  bone,  and  forms  the 
upper  boundary  of  the  triangular  space  in  which  the  artery  is  to  be  sought  for  by  cutting  through 
the  fibres  of  the  Hyo-glossus  muscle. 


THE  SYMPATHETIC  NERVE  SYSTEM  (SYMPATHICUS)  (Fig.  703). 

The  sympathetic  nerve  system  consists  of  (1)  a  series  of  ganglia  (ganglia  trunci 
sympathici)  connected  together  by  a  great  ganglionic  cord,  the  gangliated  cord 
(truncus  sympathicus] ,  extending  from  the  base  of  the  skull  to  the  coccyx,  one 
gangliated  cord  on  each  side  of  the  middle  line  of  the  body,  partly  in  front  and 
partly  on  each  side  of  the  vertebral  column ;  (2)  of  three  great  gangliated  plexuses 
(plexus  sympathici)  or  aggregations  of  nerves  and  ganglia,  situated  in  front  of 
the  spine  in  the  thoracic,  abdominal,  and  pelvic  cavities  respectively;  (3)  of  smaller 
or  terminal  ganglia,  situated  in  relation  with  the  abdominal  viscera;  and  (4)  of 
numerous  nerve-fibres.  These  latter  are  of  two  kinds:  communicating,  by  which 
the  ganglia  communicate  with  each  other  and  with  the  cerebro-spinal  nerves;  and 
distributory,  supplying  the  internal  viscera  and  the  coats  of  the  blood-vessels. 

Each  gangliated  cord  may  be  traced  upward  from  the  base  of  the  skull  into  the 
cranial  cavity  by  an  ascending  branch,  which  passes  through. the  carotid  canal, 
forms  a  plexus  on  the  internal  carotid  artery  and  in  the  cavernous  sinus  (Fig.  707), 
and  communicates  with  certain  cranial  nerves  (p.  1084).  According  to  some 
anatomists,  the  two  cords  are  joined,  at  their  cephalic  extremities,  by  these  ascend- 
ing branches  communicating  in  a  small  ganglion,  the  ganglion  of  Ribes,  situated 
upon  the  anterior  communicating  artery.  Upon  the  gangliated  cord  are  ganglia 
distinguished  as  cervical,  thoracic,  lumbar,  and  sacral,  and  except  in  the  neck  they 
correspond  pretty  nearly  in  number  to  the  vertebrae  against  which  they  lie.  They 
may  be  thus  arranged: 

Cervical  portion 3  pairs  of  ganglia. 

Thoracic     " 12     " 

Lumbar       " 4     " 

Sacral          "      .  .    4  or  5     " 


1078 


THE  NER  VE  SYSTEM 


ACCESSORY 


CERVICAL 
PLEXUS 


SUPERIOR  CERVICAL 
GANGLION  OF  SYM- 
PATHETIC 


MIDDLE  CERVI- 
CAL  GANGLION 


INFERIOR  CERVI- 
CAL GANGLION 


In  the  neck  they  are  situated  in  front  of  the  transverse  processes  of  the  vertebrae; 
in  the  thoracic  region,  in  front  of  the  heads  of  the  ribs;  in  the  lumbar  region,  on  the 
sides  of  the  bodies  of  the  vertebra?;  and  in  the  sacral  region,  in  front  of  the  sacrum. 

As  the  two  cords  pass  into  the 
pelvis  they  converge  and  unite 
together  in  a  single  ganglion,  the 
coccygeal  ganglion  or  ganglion 
impar  (ganglion  coccygeum  im- 
par)  placed  in  front  of  the  coccyx. 
Each  ganglion  may  be  regarded 
as  a  distinct  centre,  and,  in  ad- 
dition to  its  branches  of  distri- 
bution, possesses  also  branches 
of  communication  which  com- 
municate with  other  ganglia  and 
with  the  cerebro-spinal  nerves. 

The  branches  of  communication 
between  the  ganglia  (Figs.  704 
and  705)  are  composed  of  gray 
nerve-fibres  (gray  rami  commu- 
nicantes)  and  white  nerve-fibres 
(white  rami  communicantes) ,  the 
latter  being  continuous  with 
those  fibres  of  the  spinal  nerves 
which  pass  to  the  ganglia. 

The  three  great  gangliated 
plexuses  (collateral  ganglia)  are 
situated  in  front  of  the  spine  in 
the  thoracic,  abdominal,  and 
pelvic  regions,  and  are  named, 
respectively,  the  cardiac,  the  solar 
or  epigastric,  and  the  hypogastric 
plexus.  They  consist  of  collec- 
tions of  nerves  and  ganglia,  the 
nerves  being  derived  from  the 
gangliated  cords  and  from  the 
cerebro-spinal  nerves.  They  dis- 
tribute branches  to  the  viscera. 

Smaller  or  Terminal  ganglia  are 
also  found  lying  amidst  the 
nerves,  some  of  them  of  micro- 
scopic size,  in  certain  viscera — 
as,  for  instance,  in  the  heart,  the 
stomach,  and  the  uterus.  They 
serve  as  additional  centres  for 
the  origin  of  nerve-fibres.  There 
are  numerous  special  ganglia 
connected  with  the  cranial  nerves. 

FIG.  703. — Anterior   surface  of  the  spinal  cord,  showing  the  These    ganglia    have   been  de- 

spinal  nerves  and  their  connections  with  the  sympathetic  trunk  .,       ,  .  .  ,.          / 

on  one  side.    (Testut.)  scribed  in  a  previous  section  (see 

ophthalmic  ganglion,  otic  gan- 
glion, spheno-palatine  ganglion,  and  submaxillary  ganglion). 

The  branches  of  distribution  derived  from  the  gangliated  cords,  from  the  pre- 
vertebral  plexuses,  and  also  from  the  smaller  ganglia,  are  principally  destined 


LUMBAR    GANGLIA 


COCCYGEAL 
PLEXUS 


THE  S  YMPA  THETIC  NER  VE  S  YSTEM  \  079 

for  the  blood-vessels  and  thoracic  and  abdominal  viscera,  supplying  the  involun- 
tary muscular  fibre  of  the  coats  of  the  vessels  and  the  hollow  viscera,  and  the 
secreting  cells,  as  well  as  the  muscular  coats  of  the  vessels  in  the  glandular  viscera. 
Structure  of  the  Sympathetic  System. — The  sympathetic  system  is  not,  as  was 
so  long  taught,  an  independent  system.  It  receives  fibres  from  the  cerebro-spinal 
svstem  and  arranges  them  for  distribution  to  the  splanchnic  blood-vessels  and 
the  viscera.  It  receives  fibres  from  the  viscera  and  transmits  them  to  the  cerebro- 
spinal  system,  and  it  transmits  fibres  by  way  of  the  spinal  nerves  to  unstriped 
muscles,  to  vessels,  and  to  glands.  It  is  simply  an  arrangement  of  spinal 
nerves  to  permit  of  the  re-arrangement  and  transmission  of  impulses.  In  order 
to  effect  this,  the  spinal  nerves  are  connected  with  a  series  of  ganglia,  which  possess 
a  certain  power  of  government  or  automatic  action.  In  the  sympathetic  system 
amyelinic  fibres  predominate.  The  individual  nerve-fibres  are  smaller  in  diam- 
eter than  those  of  the  cerebro-spinal  system,  and  the  fibres  are  interrupted  by 
nerve-cells  contained  in  a  ganglia  chain,  known  as  the  gangliated  cord,  and  are 
also  sometimes  interrupted  in  gangliated  plexuses  and  in  terminal  ganglia.  The 
sympathetic  nerves  have  a  notable  disposition  to  form  plexuses.  It  is  important 
to  note  that  not  all  of  the  visceral  branches  of  the  spinal  nerves  join  the  gangli- 
ated cord — for  instance,  the  visceral  branches  of  the  third  and  fourth  sacral  do 
not.  The  majority,  but  not  all,  of  the  sympathetic  fibres  are  amyelinic  (fibres  of 
Remak},  but  in  the  adult  true  amyelinic  fibres  are  found  only  in  the  sympathetic 
system.  These  fibres  are  of  smaller  diameter  than  spinal  nerve-fibres,  and  are 
prolongations  of  axones  of  sympathetic  ganglia  cells.  Each  fibre  is  surrounded 
by  connective-tissue  structure  which  resembles  the  neurilemma,  which  contains 
numerous  nuclei,  and  which  is  a  prolongation  of  the  capsule  of  a  sympathetic  cell 
capsule. 

A  sympathetic  nerve  consists  of  numerous  amyelinic  and  some  myelinic  fibres. 
The  connective  tissue  which  separates  the  nerve-bundles  carries  blood-vessels  and 
nervi  nervorum,  but  no  lymph  vessels. 

The  sympathetic  ganglia  contain  multipolar  cells  which  are  smaller.  4han  those 
of  the  spinal  ganglia.  Each  cell  contains  two  nuclei,  and  is  surrounded  by  a 
delicate  capsule  of  connective  tissue.  The  cell  gives  off  one  axone  and  several 
short  dendrites.  The  axone  is  amyelinic  when  it  begins  and  may  remain  so  or 
may  become  myelinic.  Fibres  which  take  origin  from  sympathetic  axones, 
the  commissural  fibre,  may  pass  to  an  adjacent  ganglion  cell,  may  pass  toward  the 
centre,  central  fibre  or  gray  ramus  communicans,  or  may  pass  toward  the  periphery, 
peripheral  fibre,  and  reach  certain  glands,  or  to  unstriped  muscle  of  blood-vessels, 
intestines,  iris,  etc.  The  fibres  passing  to  glands  are  called  secretor  fibres. 

The  dendrites  of  a  sympathetic  ganglion  cell  form  arborizations  about  other 
ganglion  cells.  The  sympathetic  ganglia  contains  fibres  as  well  as  cells.  Some 
of  the  fibres  are  myelinic  and  some  are  amyelinic,  the  latter  taking  origin  from  the 
sympathetic  ganglion  cells,  the  former  being  motor  and  sensor  cerebro-spinal 
fibres  which  have  reached  the  sympathetic  by  the  rami  communicantes.1 

The  myelinic  fibres,  the  white  rami  communicantes  or  the  visceral  branches  of  the 
spinal  nerves  (Figs.  704  and  705),  originate  from  the  ventral  divisions  of  certain 
accessory  nerves.  Two  groups  of  them  can  be  recognized,  one  group  coming  from 
the  nerves  from  the  first  or  second  thoracic  to  the  second  or  third  lumbar  nerves; 
another  group  from  the  second  or  third  lumbar  to  the  third  or  fourth  sacral.  The 
visceral  branches  of  the  third  and  fourth  sacral  do  not  join  the  gangliated  cord; 
the  other  visceral  branches  do  join  it.  The  fibres  of  the  visceral  branches  of  the 
spinal  nerves  are  derived  from  both  the  ventral  and  the  dorsal  nerve-roots,  but 
more  largely  from  the  ventral  than  from  the  dorsal.  The  visceral  fibres  of  the 
ventral  roots  are  axones  of  nerve-cells  of  the  spinal  cord,  and  by  way  of  the  white 

1  Histology  and  Microscopic  Anatomy,  by  Szymonowicz.     Translated  and  edited  by  John  Bruce  MacCallum. 


1080 


THE  NERVE  SYSTEM 


rami  enter  into  the  sympathetic  ganglia.  Some  of  them  end  and  form  networks 
about  the  ganglia  cells.  Others  pass  up  or  down  and  end  in  an  adjacent  ganglion. 
Others  pass  through  a  ganglion  of  the  gangliated  cord  and  end  in  a  peripheral 
ganglion  with  amyelinic  fibres,  which  take  origin  from  ganglia  of  the  gangliated 
cord.  The  fibres  of  the  white  ramus  which  pass  through  the  ganglion  and  go  to 
the  periphery  are  known  as  the  splanchnic  efferent  fibres,  and  constitute  the  secretor 
fibres  of  the  splanchnic  glands  and  the  motor  fibres  of  the  muscular  tissue  of 
splanchnic  blood-vessels  and  viscera.  The  visceral  fibres  of  the  dorsal  nerve- 
roots  aid  in  the  formation  of  the  white  rami  and  arise  as  axones  of  nerve-cells  in 
the  spinal  ganglia  on  the  dorsal  roots;  they  then  pass  through  the  ganglia  of  the 
sympathetic  cord,  but  do  not  terminate  in  them,  and  leave  the  ganglion  directly  to 
pass  through  a  peripheral  ganglion  to  be  distributed  to  the  periphery,  or  ascend, 
or  descend  to  an  adjacent  ganglion  and  pass  through  this  to  a  collateral  ganglion, 
and  thence  to  the  periphery.  They  constitute  the  splanchnic  afferent  fibres,  the 
sensor  fibres  of  the  viscera. 


ACCOMPANYING    DORSAL 

ROOT  TO  DURA       ^  DORSAL    SPINAL 
NERVE  ROOT 


/ERTEBR/t     LIGAMENTS, 
INAL  VESSELS  A  DURA 


SOMATIC  VASOMOTOR, 
PILOMOTOR,  SECRETORY 


FROM  RAMUS' COMMUN. 
TO  VERTEBR/E  AND 
INTERCOSTAL  AND 
LUMBAR  VESSELS. 


.YMPATHETIC  TRUNK 


RAMI  EFFERENTES 


-SYMPATHETIC  GANGLION 


MEDufLATEO  FIBRES  PASSING  THROUGH  THE 

GANGLION  TO  PREVERTEBRAL  PLEXUSES 

OR  DIRECTLY  TO  VISCERA. 

^SYMPATHETIC  TRUNK 

[•FROM  LOWER  GANGLIA 


fTO  LOWER  GANGLIA 


FIG.  704.— Plan  of  a  vertebral  ganglion  of  the  sympathetic  cord  and  its  connections.  Myelinic  fibres  consti- 
tuting white  ramus  communicans,  represented  by  continuous  lines,  amyelinic  fibres,  constituting  gray  ramus 
communicans,  by  interrupted  lines.  For  references  to  letters  see  text.  (W.  Keiller.) 

The  amyelinic  fibres  take  origin  from  the  cells  of  the  sympathetic  ganglia  and 
are  axones  of  these  cells.  Some  help  to  form  the  commissure,  which  joins  a 
ganglion  to  adjacent  ganglia  and  end  as  networks  about  the  cells  of  an  adjacent 
ganglion.  Others  run  to  the  periphery  and  help  to  form  the  splanchnic  efferent 
branches.  Some  pass  from  the  ganglia  to  the  spinal  nerve-roots  and  to  the 
ventral  and  dorsal  divisions  of  the  nerves.  The  latter  are  the  gray  rami  communi- 
cantes  (Fig.  705),  largely  composed  of  amyelinic  but  containing  some  myelinic 
fibres.  They  give  branches  to  the  somatic  part  of  the  nerves  but  not  the  visceral, 
and  furnish  secretor  fibres  and  fibres  to  unstriated  muscle  and  minute  branches 
to  the  membranes  which  enwrap  the  nerve-roots.  The  commissures  of  the 
gangliated  cord  are  composed  of  white  and  gray  fibres.  The  former  consist  of 
both  splanchnic  efferent  and  splanchnic  afferent  fibres.  The  latter  are  axones 
from  sympathetic  ganglion  cells,  and  some  of  these  are  truly  commissural,  but 


THE  CERVICAL  PORTION  OF  THE  GANGLIA  TED  CORD     1081 

others  pass  up  or  down  the  cord  and  through  a  ganglion  and  become  branches 
which  go  to  the  periphery. 

From  the  above  it  becomes  evident  that  the  peripheral  branches  of  the  sym- 
pathetic contain  white  fibres,  which  are  composed  of  splanchnic  efferent  and 
splanchnic  afferent  branches  and  also  contain  splanchnic  efferent  gray  fibres. 

These  connections  will  be  better  understood  by  examining  the  plan  drawn  out 
in  Fig.  704.  There  a  represents  a  myelinic  nerve-fibre  from  a  ventral  nerve- 
root,  passing  by  a  white  ramus  communicans  through  the  ganglion  directly  con- 
nected with  that  spinal  nerve  to  a  ganglion  higher  up,  where  it  will  form  an 
arborization  round  a  nerve-cell,  like  e;  b,  a  myelinic  nerve-fibre  forming  an 
arborization  round  a  cell  of  the  ganglion  of  its  own  segment;  c,  a  fibre  passing 
through  the  ganglion  without  interruption  and  leaving  it  by  one  of  its  efferent 
branches  to  a  prevertebral  plexus  or  directly  to  some  viscus;  d,  a  fibre  passing 
through  the  ganglion  to  some  lower  ganglion,  there  to  end  round  some  nerve-cell, 
or  pass  out  through  an  efferent  ramus;  e,  a  myelinic  nerve  from  a  lower  ganglion, 
behaving  as  a. 

The  dotted  lines  are  amyelinic  nerves.  The  fibre,  /,  arises  as  the  axis-cylinder 
process  of  a  ganglion  cell,  and  passes  by  a  gray  ramus  communicans  along  the 
sheath  of  the  posterior  nerve-root  to  the  spinal  meninges;  g  passes  by  the  posterior 
division  to  supply  sympathetic  fibres  to  its  area  of  distribution;  h  enters  the 
anterior  division  and  is  similarly  distributed;  k  joins  the  spinal  recurrent  branch 
to  supply  the  interior  of  the  vertebral  canal,  and  /  passes  for  a  little  way  along  the 
gray  ramus  communicans,  but  leaves  it  to  be  distributed  to  the  sides  of  the  verte- 
brae and  intercostal  or  lumbar  vessels.  Gray  fibres  to  the  prevertebral  plexuses, 
vessels,  or  viscera,  are  represented  by  m,  m;  and  n,  n  are  amyelinic  fibres  joining 
neighboring  ganglia.  In  addition  to  these,  sensor  fibres  from  the  ganglia  of  the 
posterior  spinal  nerve-roots  pass  through  the  sympathetic  ganglia  to  viscera  without 
interruption. 

THE  GANGLIATED  CORD   (TRUNCUS  SYMPATHICUS). 
The  Cervical  Portion  (Pars  Cervicalis)  of  the  Gangliated  Cord. 

The  cervical  portion  of  the  gangliated  cord  is  to  be  regarded  as  a  prolongation 
upward  of  the  primitive  sympathetic  along  the  great  vessels  of  the  neck 
(Cunningham).  It  is  not  connected  to  the  cervical  spinal  nerves  by  white  rami 
communicantes.  It  obtains  its  spinal  fibres  from  the  upper  thoracic  nerves.  These 
fibres  ascend  in  the  commissure  of  the  gangliated  cord  and  join  the  cells  of  the 
cervical  ganglia.  From  the  cervical  ganglia  come  fibres  to  the  unstriped  muscle 
(veins  and  arteries  of  the  head,  neck,  and  limbs,  and  to  the  skin  of  the  head  and 
neck,  secretor  fibres  to  the  salivary  glands  and  fibres  to  the  heart).  The  fibres 
to  the  vessels  are  called  vasomotor  nerves,  and  the  fibres  to  the  heart  are  called 
cardio-motor  nerves.  In  the  neck  the  gangliated  cord  is  situated  behind  the  carotid 
vessels  and  upon  the  muscles  in  front  of  the  vertebrae,  and  runs  from  the  root 
of  the  neck  to  the  base  of  the  skull,  being  continuous  below  with  the  thoracic 
gangliated  cord  and  ending  above  in  the  carotid  plexus.  There  are  usually  three 
ganglia  on  each  side,  each  of  which  is  distinguished,  according  to  its  position,  as  the 
superior,  middle,  and  inferior  cervical  ganglion. 

The  Superior  Cervical  Ganglion  (ganglion  cervicale  superius)  (Figs.  705  and 
706). — The  superior  cervical  ganglion,  the  largest  of  the  three,  is  about  three- 
quarters  of  an  inch  in  length.  It  is  placed  opposite  the  second  and  third  cervical 
vertebne.  It  is  of  a  reddish-gray  color,  is  usually  fusiform  in  shape,  is  sometimes 
broad  and  flattened,  and  is  occasionally  constricted  at  intervals,  so  as  to  give  rise  to 


1082 


THE  NERVE  SYSTEM 


the  opinion  that  it  consists  of  the  coalescence  of  several  smaller  ganglia ;  and  it  is 
usually  believed  that  it  is  formed  by  the  coalescence  of  the  four  ganglia  correspond- 


Superior  cervical  ganglion. 


Middle  cervical  ganglion. 


Inferior  cervical  ganglion. 


Pharyngeal  branches. 


Cardiac  branches. 


Deep  cardiac  plexus. 

Superficial  cardiac  plexus. 


Solar  plexus. 


Aortic  plexus. 


Hypogastric  plexus. 


Sacral  ganglia. 


Ganglion  impar. 


FIG.  705. — The  sympathetic  nerve  system. 


THE  CERVICAL  PORTION  OF  THE  GANGLIATED  CORD     1Q83 

ing  to  the  four  upper  cervical  nerves.  It  is  in  relation,  in  front,  with  the  sheath 
of  the  internal  carotid  artery  and  internal  jugular  vein;  behind,  it  lies  on  the 
Ilectus  capitis  anticus  major  muscle.  It  is  connected  to  the  middle  cervical  gan- 
glion by  the  commissure  of  the  gangliated  cord. 

Branches. — The  branches  of  the  superior  cervical  ganglion  are  central  and 
peripheral. 

Central  or  Communicating  Branches. — 1.  Gray  rami  communicantes  arise  in  the 
ganglion  and  pass  to  the  first,  second,  third,  and  fourth  cervical  nerves.  2. 
Branches  are  given  oi¥  to  certain  cranial  nerves  in  the  neck  (Fig.  706).  What  is 
known  as  the  jugular  nerve  (n.  jugularis)  passes  to  the  ganglion  on  the  trunk 
of  the  vagus,  a  branch  from  the  ganglion  passes  to  the  ganglia  on  the  root  of 
the  vagus  and  to  the  petrosal  ganglion  of  the  glosso-pharyngeal,  and  a  branch 
goes  to  the  hypo-glossal. 

Peripheral  Branches. — These  branches  may  be  divided  into  superior,  internal, 
and  anterior. 

The  Superior  Branch  of  the  Superior  Cervical  Ganglion  or  the  Internal  Carotid 
Branch  (n.  caroticus  internus)  (Fig.  706)  appears  to  be  a  direct  prolongation  of  the 
ganglion.  It  is  soft  in  texture  and  of  a  reddish  color.  It  ascends  by  the  side  of 
the  internal  carotid  artery,  and,  entering  the  carotid  canal  in  the  temporal  bone, 
divides  into  two  branches,  which  lie,  one  on  the  outer,  and  the  other  on  the  inner, 
side  of  that  vessel. 

The  outer  branch,  the  larger  of  the  two,  distributes  filaments  to  the  internal 
carotid  artery  and  forms  the  internal  carotid  plexus. 

The  inner  branch  also  distributes  filaments  to  the  internal  carotid,  and,  continu- 
ing onward,  forms  the  cavernous  plexus. 

THE  INTERNAL  CAROTID  PLEXUS  (plexus  caroticus  internus}  (Figs.  705  and 
706). — The  carotid  plexus  is  situated  on  the  outer  side  of  the  internal  carotid 
artery.  Filaments  from  this  plexus  occasionally  form  a  small  gangliform  swelling 
on  the  under  surface  of  the  artery,  which  is  called  the  carotid  ganglion.  The  internal 
carotid  plexus  communicates  with  the  Gasserian  ganglion,  with  the  abducent  nerve, 
and  the  spheno-palatine  ganglion,  and  distributes  filaments  to  the  wall  of  the 
carotid  artery  and  to  the  dura  (Valentin),  while  in  the  carotid  canal  it  com- 
municates with  Jacobson's  nerve,  which  is  the  tympanic  branch  of  the  glosso- 
pharyngeal. 

The  communicating  branches  to  the  abducent  nerve  consist  of  one  or  two 
filaments  which  join  that  nerve  as  it  lies  upon  the  outer  side  of  the  internal 
carotid.  Other  filaments  are  also  connected  with  the  Gasserian  ganglion.  The 
communication  with  the  spheno-palatine  ganglion  is  effected  by  a  branch,  the 
large  deep  petrosal  nerve  (Fig.  694),  which  is  given  off  from  the  plexus  on  the 
outer  side  of  the  artery,  and  which  passes  through  the  cartilage  filling  up  the 
foramen  lacerum  medium,  and  joins  the  large  superficial  petrosal  from  the  facial 
to  form  the  Vidian  nerve  (Figs.  689  and  694).  The  Vidian  nerve  then  proceeds 
along  the  pterygoid  or  Vidian  canal  to  the  spheno-palatine  ganglion.  The  com- 
munication with  Jacobson's  nerve  is  effected  by  two  branches,  one  of  which 
is  called  the  deep  petrosal  nerve,  and  the  other  the  carotico-tympanic  nerve;  the 
latter  may  consist  of  two  or  three  delicate  filaments. 

THE  CAVERNOUS  PLEXUS  (plexus  cavernosus)  (Fig.  706). — The  cavernous 
plexus  is  situated  below  and  internal  to  that  part  of  the  internal  carotid  wrhich 
is  placed  by  the  side  of  the  sella  cavernous  sinus,  and  is  formed  chiefly  by  the 
internal  division  of  the  ascending  branch  from  the  superior  cervical  ganglion. 
It  communicates  with  the  oculomotor,  the  trochlear,  the  ophthalmic  division  of 
the  trigeminal,  and  the  abducent  nerves,  and  with  the  ophthalmic  ganglion,  and 
distributes  filaments  to  the  wall  of  the  internal  carotid  and  to  the  hypophysis. 
The  branch  of  communication  with  the  oculomotor  nerve  joins  it  at  its  point  of 


1084 


THE  NER  VE  SYSTEM 


division;  the  branch  to  the  trochlear  nerve  joins  it  as  it  lies  on  the  outer  wall  of 
the  cavernous  sinus ;  other  filaments  are  connected  with  the  under  surface  of  the 
trunk  of  the  ophthalmic  nerve;  and  a  second  filament  of  communication  joins  the 
abducent  nerve. 

The  filament  of  connection  with  the  ophthalmic  ganglion  (Fig.  684)  arises  from 
the  anterior  part  of  the  cavernous  plexus;  it  accompanies  the  nasal  nerve  or  con- 
tinues forward  as  a  separate  branch. 

Terminal  Branches  of  the  Carotid  and  Cavernous  Plexuses.— The  terminal 
filaments  from  the  carotid  and  cavernous  plexuses  are  prolonged  along  the  internal 
carotid,  forming  plexuses  which  entwine  around  the  cerebral  and  ophthalmic 
arteries;  along  the  former  vessels  they  may  be  traced  on  to  the  pia;  along  the 
latter,  into  the  orbit,  where  they  accompany  each  of  the  subdivisions  of  the  vessel, 
a  separate  plexus  passing,  with  the  arteria  centralis  retinae,  into  the  interior  of 


EXTERNAL 
RECTUS 
MUSCLE 


OPHTHALMIC 
GANGLION 

SENSOR  ROOT 

OF  OPHTHALMIC 

GANGLION 


OPHTHALMIC 

GASSERIAN 
GANGLION 

(turned  forward) 

GREAT  DEEP 
PETROSAL 

TEMPORO- 

MAXILLARY 

ARTICULATION 


SMALL   DEEP 
PETROSAL 


MOTOR  ROOT  OF 

OPHTHALMIC  GANGLION 

UPPER  BRANCH 

OF   OCULO-MOTOR 

LOWER    BRANCH 

OF   OCULO-MOTOR 

SYMPATHETIC  ROOT  OF 
OPHTHALMIC  GANGLION 
OCULO-MOTOR    NERVE 

OPHTHALMIC 
ARTERY 


HYPOPHYSIS 


CAVERNOUS 
PLEXUS 

ABDUCENT   NERVE 


COMMUNICATING 

BRANCH  TO    ABDUCENT    NERVE 


INTERNAL 
CAROTID   PLEXUS 
INTERNAL 
.CAROTID   BRANCH 
OF   SUPERIOR 
CERVICAL  GANGLION 

INFERIOR       INTERNAL^  jS||f— ^SUPERIOR 
COROTICOTYMPANIC          CAROTID    »  CERVICAL 

ARTERY  GANGLION 

FIG.  706.— The  cephalic  portion  of  the  sympathetic  nerve  system,  seen  obliquely  from 
above  and  behind.      (Toldt.) 

the  eyeball.  The  filaments  prolonged  on  to  the  anterior  communicating  artery 
form  a  small  ganglion,  the  ganglion  of  Ribes,1  which  serves,  as  mentioned  above, 
to  connect  the  sympathetic  nerves  of  the  right  and  left  sides. 

The  so-called  Inferior  or  Descending  Branch  of  the  Superior  Cervical  Ganglion 
communicates  with  the  middle  cervical  ganglion.  It  is  the  commissure  of  the 
gangliated  cord. 

The  Internal  Branches  of  the  Superior  Cervical  Ganglion  are  three  in  number — the 
pharyngeal,  laryngeal,  and  superior  cardiac  nerve. 

The  pharyngeal  branches  (rami  pkaryngei)  (Fig.  705)  pass  inward  to  the  side  of 
the  pharynx,  where  they  join  with  branches  from  the  glosso-pharyngeal,  vagus, 
and  external  laryngeal  nerves  to  form  the  pharyngeal  plexus. 

i  The  existence  of  this  ganglion  is  doubted  by  some  observers.— ED.  of  15th  English  edition. 


THE  CERVICAL  PORTION  OF  THE  GANGLIATED  CORD     1085 


CAVERNOUS    PLEXUS 


SUP.    MAXILLARY  NERVE 


FIRST 

Cf  RVICAL 

NERVE 


The  laryngeal  branches  unite  with  the  superior  laryngeal  nerve  and  its  branches. 

The  superior  cardiac  nerve  or  the  nervus  superficialis  cordis  (n.  cardiacus  supe- 
rior) (Fig.  705)  arises  by  two  or  more  branches  from  the  superior  cervical  gan- 
glion, and  occasionally  receives  a  filament  from  the  cord  of  communication 
between  the  first  and  second  cervical  ganglia.  It  runs  down  the  neck  behind  the 
common  carotid  artery,  lying  upon  the  Longus  colli  muscle,  and  crosses  in  front  of 
the  inferior  thyroid  artery  and  recurrent  laryngeal  nerve.  The  right  superior  cardiac 
nerve,  at  the  root  of  the  neck,  passes  either  in  front  of  or  behind  the  subclavian 
artery,  and  along  the  arteria  innominata,  to  the  back  part  of  the  arch  of  the  aorta, 
where  it  joins  the  deep  cardiac  plexus.  This  nerve,  in  its  course,  is  connected  with 
other  branches  of  the  sympathetic;  about  the  middle  of  the  neck  it  receives  fila- 
ments from  the  external  laryngeal  nerve;  lower  down  it  obtains  one  or  two  twigs 
from  the  vagus,  and  as  it  enters 
the  thorax  it  is  joined  by  a  fila- 
ment from  the  recurrent  laryn- 
geal. Filaments  from  this  nerve 
communicate  with  the  thyroid 
branches  from  the  middle  cer- 
vical ganglion.  The  left  superior 
cardiac  nerve,  in  the  chest,  runs 
by  the  side  of  the  left  common, 
carotid  artery  and  in  front  of  the 
arch  of  the  aorta  to  the  superficial 
cardiac  plexus,  but  occasionally 
it  passes  behind  the  aorta  and 
terminates  in  the  deep  cardiac 
plexus. 

The  Anterior  Branches  of  the 
Superior  Cervical  Ganglion  (nn. 
carotid  externi)  (Fig.  707)  ramify 
upon  the  external  carotid  artery 
and  its  branches,  forming  around 
each  a  delicate  plexus,  on  the 
nerves  composing  which  small 
ganglia  are  occasionally  found. 
The  plexuses  accompanying 
some  of  these  arteries  have 
important  communications  with 
other  nerves.  That  surrounding 
the  external  carotid  artery  (plexus 
caroticus  externus]  is  connected 
with  the  branch  of  the  facial 
nerve  to  the  Stylohyoid  muscle;  ^  Nl 

J      .  *  '    JIG.  707. — Diagram  of  the  cervical  sympathetic  cord.     (Testut.) 

that  surrounding  the  facial  artery 

communicates  with  the  submaxillary  ganglion  by  one  or  two  filaments;  and  that 
accompanying  the  medidural  artery  sends  offsets  which  pass  to  the  otic  ganglion 
and  to  the  geniculate  ganglion  of  the  facial  nerve  and  constitute  the  external  super- 
ficial petrosal  nerve  (Fig.  694). 

The  Middle  Cervical  or  Thyroid  Ganglion  (ganglion  cervical  medium)  (Figs. 
705  and  707). — The  middle  cervical  or  thyroid  ganglion  is  the  smallest  of  the  three 
cervical  ganglia,  and  is  occasionally  altogether  wanting.  It  varies  somewhat  in 
position,  but  in  most  individuals  is  placed  opposite  the  sixth  cervical  vertebra, 
usually  upon,  or  close  to,  the  inferior  thyroid  artery;  hence  the  name,  thyroid 
ganglion,  assigned  to  it  by  Haller.  It  is  probably  formed  by  the  coalescence  of 
two  ganglia  corresponding  to  the  fifth  and  sixth  cervical  nerves. 


LOWER    CERVICAL 

GANGLION 


INFERIOR  CER 
GANGLIO 


1086  THE  NERVE  SYSTEM 

It  communicates  above  with  the  superior  cervical  ganglion  and  below  with 
the  inferior  cervical  ganglion  by  means  of  the  commissure  of  the  gangliated  cord. 
The  Central  Communicating  Branches. — The  central  communicating  branches 
are:  1.  Gray  rami  communicantes  passing  from  the  ganglion  to  the  anterior 
divisions  of  the  fifth  and  sixth  cervical  nerves.  2.  The  subclavian  loop  or  the 
ansa  of  Vieussens  (ansa  subclavia)  (Fig.  708)  arises  from  the  ganglion,  passes  down 
over  the  front  and  under  the  subclavian  artery  and  runs  back  to  join  the  inferior 
cervical  ganglion.  It  gives  branches  to  the  artery.  In  some  cases  this  nerve  takes 
origin  from  the  sympathetic  trunk  below  the  ganglion. 

The  Peripheral  Branches. — The  peripheral  branches  are  the  thyroid  and  the 
middle  cardiac  nerve. 

The  Thyroid  Branches  are  small  filaments  which  accompany  the  inferior  thyroid 

artery  to  the  thyroid  gland,  forming  the  inferior  thyroid  plexus  (plexus  thyreoideus 

inferior) ;  they  communicate,  on  the  artery,  with  the  superior  cardiac  nerve,  and, 

in  the  gland,  with  branches  from  the  recurrent  and  external  laryngeal  nerves. 

The  Middle  or  Great  Cardiac  Nerve  (n.  cardiacus  medius)  (Fig.  705),  the  largest 

of  the  three  cardiac  nerves,  arises  from  the 
middle  cervical  ganglion  or  from  the  cord 
between  the  middle  and  inferior  ganglia.  On 
the  right  side  it  descends  behind  the  common 
carotid  artery,  and  at  the  root  of  the  neck 
passes  either  in  front  of  or  behind  the  sub- 
clavian artery;  it  then  descends  on  the 
trachea,  receives  a  few  filaments  from  the 
recurrent  laryngeal  nerve,  and  joins  the  right 
side  of  the  deep  cardiac  plexus.  In  the  neck 
it  communicates  with  the  superior  cardiac 

FIG.  708. — The  subclavian  loop  passing  from  the    „„,]   rpmrrpnt  larvno-pnl  nprvps        On  thp  Ipff 
middle  to  the  inferior  cervical  ganglia.  nl  l^ryngea         .rVCS. 

side  the  middle  cardiac  nerve  enters  the  chest 

between  the  left  carotid  and  subclavian  arteries,  and  joins  the  left  side  of  the  deep 
cardiac  plexus.  If  the  middle  cervical  ganglion  is  absent,  the  above-named 
branches  arise  from  the  gangliated  cord. 

The  Inferior  Cervical  Ganglion  (ganglion  cervicale  inferius)  (Figs.  705  and  707) . 
—The  inferior  cervical  ganglion  is  situated  between  the  base  of  the  transverse 
process  of  the  last  cervical  vertebra  and  the  neck  of  the  first  rib  on  the  inner  side 
of  the  superior  intercostal  artery.  Its  form  is  irregular;  it  is  larger  in  size  than  the 
preceding,  and  is  frequently  joined  to  the  first  thoracic  ganglion.  It  is  prob- 
ably formed  by  the  coalescence  of  two  ganglia  which  correspond  to  the  two  last 
cervical  nerves.  It  joins  the  middle  ganglion  above  and  the  first  thoracic  ganglion 
below  by  means  of  the  commissural  cord,  and  is  usually  also  joined  to  the  middle 
ganglion  by  the  subclavian  loop. 

The  Central  Communicating  Branches. — Its  central  communicating  branches  are: 
1.  Gray  rami  communicantes  passing  to  the  anterior  divisions  of  the  seventh  and 
eighth  cervical  nerves  (Fig.  707).  2.  The  subclavian  loop  (Fig.  708),  which  has 
been  previously  described  and  which  passes  under  and  in  front  of  the  subclavian 
artery  to  reach  the  middle  cervical  ganglion  or  the  commissural  cord. 

The  Peripheral  Branches. — The  peripheral  branches  are:  1.  Vascular.  The 
vertebral  plexus  (plexus  vertebralis)  lies  upon  the  vertebral  artery  and  its  branches 
in  the  neck  and  in  the  cranial  cavity,  The  subclavian  plexus  (plexus  subclavius) 
arises  from  the  subclavian  loop,  which  may  be  regarded  as  a  branch  of  the  inferior 
or  of  the  middle  ganglion.  2.  Cardiac.  The  inferior  or  minor  cardiac  nerve  (n. 
cardiacus  inferior)  arises  from  the  inferior  cervical  or  first  thoracic  ganglion.  It 
passes  down  behind  the  subclavian  artery  and  along  the  front  of  the  trachea  to 
join  the  deep  cardiac  plexus.  It  communicates  freely  behind  the  subclavian 
artery  with  the  recurrent  laryngeal  and  middle  cardiac  nerves. 


THE  THORACIC  PORTION  OF  THE  GANGLIATED  CORD     1Q87 

Surgical  Anatomy. — The  situation  of  the  cervical  sympathetic  makes  wounds  of  it  rare. 
Thirteen  cases  of  sympathetic  traumatic  injury  were  collected  by  Seeligmiiller.  In  ten  cases 
paralysis  existed;  in  three,  irritation.  Tumors  of  the  neck  may  cause  irritation  or  paralysis.  In 
irritation  of  the  sympathetic  the  corresponding  side  of  the  face  becomes  pale,  the  pupil  dilates, 
the  palpebral  fissure  widens,  and  the  eyeball  protrudes.  In  many  cases  there  is  acceleration 
of  the  heart  beats.  In  paraly.ns  of  the  sympathetic  the  pupil  contracts,  the  palpebral  fissure  is 
narrowed  by  partial  ptosis,  the  corresponding  side  of  the  face  reddens,  there  is  an  increase  in 
the  flow  of  tears,  and  recession  of  the  eyeball. 

The  surgeon  occasionally  resects  the  sympathetic.  Jonnesco  recommends  bilateral  removal 
of  the  superior  cervical  ganglia  for  glaucoma,  and  bilateral  removal  of  all  the  cervical  sympa- 
thetic ganglia  for  epilepsy  and  for  exophthalmic  goitre. 

The  Thoracic  Portion  (Pars  Thoracalis)  of  the  Gangliated  Cord  (Fig.  709). 

The  thoracic  portion  of  the  gangliated  cord  consists  of  a  series  of  ganglia 
which  usually  correspond  in  number  to  that  of  the  vertebrae,  but,  from  the  occa- 
sional coalescence  of  two,  their  number  is  uncertain.  These  ganglia  are  placed 
on  each  side  of  the  spine,  resting  against  the  heads  of  the  ribs,  and  are  covered  by 
the  pleura  costalis;  the  last  two  ganglia  are,  however,  ventral  to  the  rest,  being 
placed  on  the  side  of  the  bodies  of  the  eleventh  and  twelfth  thoracic  vertebrae.  The 
ganglia  are  small  in  size  and  of  a  grayish  color.  The  first  ganglion,  larger  than 
the  rest,  is  of  an  elongated  form  and  is  frequently  blended  with  the  last  cervical 
ganglion.  They  are  connected  together  by  cord-like  prolongations  from  their 
substance.  In  the  thorax  each  thoracic  spinal  nerve,  with  occasionally  the 
exception  of  the  first,  sends  a  visceral  branch  or  white  ramus  communicans  to 
the  thoracic  gangliated  cord  (Fig.  709).  As  Prof.  Cunningham  points  out,  the 
white  rami  "separate  into  two  main  streams  in  relation  to  the  sympathetic  cord. 
Those  of  the  upper  five  nerves  are,  for  the  most  part,  directed  upward  in  the 
gangliated  cord  to  be  distributed  through  the  cervical  part  of  the  sympathetic 
in  the  manner  already  described.  The  white  rami  of  the  lower  thoracic  nerves 
are,  for  the  most  part,  directed  downward  in  the  lower  part  of  the  sympathetic 
cord  and  its  branches,  to  be  distributed  to  the  abdomen;  at  the  same  time  some 
of  their  fibres  are  directly  associated  with  the  supply  of  certain  thoracic  viscera — 
lungs,  aorta,  oesophagus."  The  white  rami  are  composed  of  splanchnic  afferent 
fibres  and  somatic  and  splanchnic  efferent  fibres. 

Central  Communicating  Branches. — 1.  White  rami  communicantes  (see  above). 
2.  Gray  rami  communicantes  arise  from  each  one  of  the  thoracic  ganglia,  pass  back- 
ward with  the  white  rami,  and  enter  into  the  ventral  divisions  of  the  thoracic  nerves. 

Peripheral  Branches. — 1.  Aortic  Branches  come  off  from  the  first  five  or  six 
upper  ganglia.  They  send  filaments  to  the  aorta  and  its  branches,  to  the  vertebral 
bodies,  and  to  the  vertebral  ligaments.  The  aortic  branches  help  to  form  the 
thoracic  aortic  plexus  (plexus  aorticus  thoracalis).  This  plexus  is  completed  by 
branches  from  the  cardiac  plexus. 

2.  Pulmonary  Branches  come  off  from  the  third  and  fourth  and  sometimes  from 
the  first  and  second  ganglia. 

3.  The  Splanchnic  Nerves  (Figs.  705  and  709). — From  the  six  or  seven  lower 
ganglia  and  from  the  commissural  cord  a  number  of  large  white  branches  arise. 
They  give  filaments  to  the  aorta  and  unite  to  form  the  three  splanchnic  nerves  on 
each  side.  These  are  named  the  great,  the  lesser, and  the  smallest  or  renal  splanchnic. 

The  superior  or  great  splanchnic  nerve  (»..  splanchnicus  major)  is  of  a  white 
color,  firm  in  texture,  and  presents  a  marked  contrast  to  the  ganglionic  nerves. 
It  is  formed  by  branches  from  the  thoracic  ganglia  between  the  fifth  or  sixth 
and  the  ninth  or  tenth,  but  the  fibres  in  the  higher  roots  may  be  traced  upward 
in  the  sympathetic  cord  as  far  as  the  first  or  second  thoracic  ganglion.  These 
roots  unite  to  form  a  large  round  cord  of  considerable  size.  It  descends  obliquely 


1088 


THE  NER  VE  SYSTEM 


inward  in  front  of  the  bodies  of  the  vertebrae  along  the  posterior  mediastinum, 
perforates  the  crus  of  the  Diaphragm,  and  terminates  in  the  semilunar  ganglion  of 
the  solar  plexus  (Fig.  709),  distributing  filaments  to  the  renal  and  adrenal  plexuses. 
The  middle,  lesser,  or  small  splanchnic  nerve  (n.  splanchnicus  minor)  is  formed 
by  filaments  from  the  tenth  and  eleventh  ganglia,  and  from  the  cord  between  them. 
It  pierces  the  Diaphragm  with  the  preceding  nerve,  and  joins  the  solar  plexus 
(Fig.  709).  It  communicates  in  the  chest  with  the  great  splanchnic  nerve,  and 
occasionally  sends  filaments  to  the  renal  plexus. 


THORACI 
RAMI   COMMU 


INFERIOR    CER- 
VICAL   GANGLION 


VISCERAL 
BRANCHES 


SPLANCHNIC 
GANGLION 

GREAT 
SPLANCHNIC 


SMALL 
SPLANCHNIC 


RIGHT   VAGUS 


SMALL 
SPLANCHNIC 


BRANCH  OF  VAGUS 
TO  SEMILUNAR  GANGLION 
CELIAC    AXIS 


SEMILUNAR  GANGLION 
SUPERIOR  MESENTERIO 
ARTERY  AND  PLEXUS 

SOLAR     PLEXUS 


QUADRATUS 
LUMBORUM 

RENAL    PLEXUS 

FIG.  709. — Plan  of  the  right  sympathetic  cord  and  splanchnic  nerves.     (Testut.) 

The  inferior,  smallest,  least,  or  renal  splanchnic  nerve  (n.  splanchnicus  imus)  arises 
from  the  last  thoracic  ganglion,  and,  piercing  the  Diaphragm,  terminates  in  the 
renal  plexus  and  lower  part  of  the  solar  plexus.  It  occasionally  communicates  with 
the  preceding  nerve. 

A  striking  analogy  appears  to  exist  between  the  splanchnic  and  the  cardiac 
nerves.  The  cardiac  nerves  are  three  in  number;  they  arise  from  the  three  cer- 
vical ganglia,  and  are  distributed  to  a  large  and  important  organ  in  the  thoracic 


PELVIC  OR  SACRAL  PORTION  OF  GANGLIA  TED  CORD     1089 

cavity.  The  splanchnic  nerves,  also  three  in  number,  are  connected  probably 
with  all  the  thoracic  ganglia,  and  are  distributed  to  important  organs  in  the 
abdominal  cavity 

The  Lumbar  Portion  (Pars  Lumbalis)  of  the  Gangliated  Cord  (Fig.  705). 

The  lumbar  portion  of  the  gangliated  cord  is  situated  in  front  of  the  vertebral 
column  along  the  inner  margin  of  the  Psoas  muscle.  It  consists  usually  of  four 
ganglia,  but  there  may  be  as  many  as  eight,  connected  together  by  interganglionic 
cords.  The  ganglia  are  of  small  size,  of  a  grayish  color,  shaped  like  a  barleycorn, 
and  placed  much  nearer  the  median  line  than  the  thoracic  ganglia.  Sometimes 
several  ganglia  are  fused  together. 

It  is  connected  with  the  thoracic  portion  by  a  thin  commissure,  which  passes 
back  of  or  through  the  Diaphragm.  It  is  connected  with  the  sacral  portion  by 
a  commissure  which  is  under  the  common  iliac  artery. 

The  upper  lumbar  ganglia  or  the  upper  portion  of  the  gangliated  cord  receives 
white  rami  communicantes  from  the  first  two  or  three  lumbar  spinal  nerves. 

Central  Communicating  Branches. — Gray  rami  communicantes  pass  irregularly  from 
the  gangliated  cord  to  the  ventral  divisions  of  the  lumbar  spinal  nerves,  the  gray 
rami  accompanying  the  white  rami. 

From  the  situation  of  the  lumbar  ganglia  these  branches  are  longer  than  in  the 
other  regions.  They  are  -usually  two  in  number  from  each  ganglion,  but  their 
connection  with  the  spinal  nerves  is  not  so  uniform  as  in  other  regions.  They 
accompany  the  lumbar  arteries  around  the  sides  of  the  bodies  of  the  vertebrae, 
passing  beneath  the  fibrous  arches  from  which  some  of  the  fibres  of  the  Psoas 
muscle  arise. 

Peripheral  Branches. — Some  branches  pass  inward,  in  front  of  the  aorta,  and 
help  to  form  the  abdominal  aortic  plexus  (plexus  aorticus  abdominalis)  (Fig.  705) 
which  plexus  is,  however,  developed  chiefly  by  filaments  from  the  cceliac  plexus. 
Other  branches  descend  in  front  of  the  common  iliac  arteries,  and  join  over  the 
promontory  of  the  sacrum,  helping  to  form  the  hypogastric  plexus  (plexus  hypo- 
gastricus)  (Fig.  705).  Numerous  delicate  filaments  are  also  distributed  to  the 
bodies  of  the  vertebrae  and  the  ligaments  connecting  them. 

Pelvic  or  Sacral  Portion  (Pars  Sacralis)  of  the  Gangliated  Cord  (Fig.  705). 

The  pelvic  portion  of  the  gangliated  cord  is  situated  in  front  of  the  sacrum 
along  the  inner  side  of  the  ventral  sacral  foramina.  It  consists  of  four  or  five 
small  ganglia  on  each  side,  connected  together  by  interganglionic  cords.  Below 
these  cords  converge  and  unite  on  the  front  of  the  coccyx  by  means  of  a  small 
ganglion,  the  coccygeal  ganglion  or  ganglion  impar  (ganglion  coccygeum  impar 
(Fig.  705).  The  commissural  cord  joins  the  pelvic  portion  to  the  lumbar  portion 
of  the  gangliated  cord.  Like  the  cervical  and  the  lower  lumbar  divisions  the 
sacral  portion  receives  no  white  rami  communicantes. 

The  visceral  branches  of  the  third  sacral,  and  usually  of  the  second  and  fourth 
sacral  spinal  nerves,  are  not  connected  with  the  ganglionic  cord. 

Central  Communicating  Branches. — Gray  rami  communicantes,  which  arise  in  the 
sacral  ganglia  and  pass  to  the  anterior  divisions  of  the  sacral  and  coccygeal  nerves. 

Peripheral  Branches. — 1.  Visceral  branches  arise  from  the  upper  portion  of  the 
gangliated  cord  and  pass  to  the  pelvic  plexus. 

2.  Parietal  branches  communicate,  on  the  front  of  the  sacrum,  with  the  corre- 
sponding branches  from  the  opposite  side;  some,  from  the  first  two  ganglia,  pass  to 

69 


1090  THE  NERVE  SYSTEM 

join  the  pelvic  plexus,  and  others  form  a  plexus  which  accompanies  the  middle 
sacral  artery  and  sends  filaments  to  the  coccygeal  gland. 

THE  GREAT  PLEXUSES  OF  THE  SYMPATHETIC  SYSTEM. 

The  great  plexuses  of  the  sympathetic  are  the  large  aggregations  of  nerves 
and  ganglia,  previously  alluded  to,  situated  in  the  thoracic,  abdominal,  and  pelvic 
cavities  respectively.  From  them  are  derived  the  branches  which  supply  the 
viscera. 

The  Cardiac  Plexus  (Plexus  Cardiacus)  (Fig.  705). 

The  cardiac  plexus  is  situated  at  the  base  of  the  heart,  and  is  divided  into  a 
superficial  part,  which  lies  in  the  concavity  of  the  arch  of  the  aorta,  and  a  deep 
part,  which  lies  between  the  trachea  and  aorta.  The  two  plexuses  are,  however, 
closely  connected. 

The  Great  or  Deep  Cardiac  Plexus.— The  great  or  deep  cardiac  plexus, 
the  plexus  magnus  profundus  of  Scarpa,  is  situated  in  front  of  the  trachea  at  its 
bifurcation,  above  the  point  of  division  of  the  pulmonary  artery  and  behind  the 
arch  of  the  aorta.  It  is  formed  by  the  cardiac  nerves  derived  from  the  cervical 
ganglia  of  the  sympathetic  and  the  cardiac  branches  of  the  recurrent  laryngeal 
and  vagus.  The  only  cardiac  nerves  which  do  not  enter  into  the  formation  of 
this  plexus  are  the  left  superior  cardiac  nerve  and  the  inferior  cervical  cardiac 
branch  from  the  left  vagus. 

The  branches  from  the  right  side  of  this  plexus  pass,  some  in  front  of,  and 
others  behind,  the  right  pulmonary  artery;  the  former,  the  more  numerous,  trans- 
mit a  few  filaments  to  the  ventral  pulmonary  plexus,  and  are  then  continued 
onward  to  form  part  of  the  left  or  ventral  coronary  plexus;  those  behind  the  pul- 
monary artery  distribute  a  few  filaments  to  the  right  auricle,  and  are  then  con- 
tinued onward  to  form  a  part  of  the  right  or  dorsal  coronary  plexus. 

The  branches  from  the  left  side  of  the  deep  cardiac  plexus  distribute  a  few 
filaments  to  the  superficial  cardiac  plexus,  to  the  left  auricle  of  the  heart,  and  to 
the  ventral  pulmonary  plexus,  and  then  pass  on  to  form  the  greater  part  of  the 
dorsal  coronary  plexus. 

The  Ventral  or  Left  Coronary  Plexus  (plexus  coronarius  cordis  anterior}. — The 
ventral  or  left  coronary  plexus  is  formed  chiefly  from  the  superficial  cardiac 
plexus,  but  receives  filaments  from  the  deep  cardiac  plexus.  Passing  forward 
between  the  aorta  and  pulmonary  artery,  it  accompanies  the  left  coronary  artery 
on  the  ventral  surface  of  the  heart. 

The  Dorsal  or  Right  Coronary  Plexus  (plexus  coronarius  cordis  posterior}. — 
The  dorsal  or  right  coronary  plexus  is  chiefly  formed  by  filaments  prolonged 
from  the  left  side  of  the  deep  cardiac  plexus,  and  by  a  few  from  the  right  side. 
It  surrounds  the  branches  of  the  coronary  artery  at  the  back  of  the  heart,  and 
its  filaments  are  distributed  with  those  vessels  to  the  muscular  substance  of  the 
ventricles. 

The  Superficial  or  Ventral  Cardiac  Plexus. — The  superficial  or  ventral  cardiac 
plexus  lies  beneath  the  arch  of  the  aorta,  in  front  of  the  right  pulmonary  artery. 
It  is  formed  by  the  left  superior  cardiac  nerve,  the  left  (and  occasionally  also  the 
right)  inferior  cervical  cardiac  branches  of  the  vagus,  and  filaments  from  the 
deep  cardiac  plexus.  A  small  ganglion,  the  cardiac  ganglion  of  Wrisberg  (ganglion 
cardiacum  [  Wrisbergi])  is  occasionally  found  connected  with  these  nerves  at  their 
point  of  junction.  This  ganglion,  when  present,  is  situated  immediately  beneath 
the  arch  of  the  aorta,  on  the  right  side  of  the  ductus  arteriosus.  The  superficial 


THE  EPIGASTRIC  OR  SOLAR  PLEXUS  1091 

cardiac  plexus  forms  the  chief  part  of  the  ventral  coronary  plexus,  and  several 
filaments  pass  along  the  pulmonary  artery  to  the  left  ventral  pulmonary  plexus. 
Valentin  has  described  nerve  filaments  ramifying  under  the  endocardium; 
and  Remak  has  found,  in  several  mammalia,  numerous  small  ganglia  on  the  car- 
diac nerves,  both  on  the  surface  of  the  heart  and  in  its  muscular  substance. 

The  Pulmonary  Plexus  (Plexus  Pulmonalis). 

The  larger  dorsal  pulmonary  plexus  is  situated  back  of  the  root  of  the  lung. 
It  is  formed  by  the  vagus  nerve  and  branches  from  the  second,  third,  and  fourth 
thoracic  sympathetic  ganglia.  It  sends  branches  along  the  bronchi  and  blood- 
vessels into  the  lung  and  some  fibres  pass  to  the  front  of  the  root  of  the  lung  to 
form  the  ventral  pulmonary  plexus.  The  smaller  ventral  pulmonary  plexus  is 
in  front  of  and  above  the  root  of  the  lung.  It  is  formed  on  each  side  by  the  fibres 
from  the  dorsal  pulmonary  plexus.  The  left  plexus  receives  branches  from  the 
superficial  cardiac  plexus.  The  ventral  plexus  supplies  the  structures  of  the  root 
of  the  lung. 

The  (Esophageal  Plexus  (Plexus  Oesophageus). 

The  cesophageal  plexus  is  in  the  dorsal  mediastinum  and  surrounds  the 
oesophagus.  It  is  formed  by  the  vagus  nerves  which  have  come  from  the  dorsal 
pulmonary  plexuses,  and  by  fibres  from  the  great  splanchnic  nerve  and  ganglion. 
The  cesophageal  plexus  is  usually  considered  as  a  portion  of  the  vagus  nerve 
(p.  1072). 

The  Epigastric  or  Solar  Plexus  (Plexus  Coeliacum)  (Figs.  705,  710,  711). 

The  epigastric  or  solar  plexus  supplies  all  the  viscera  in  the  abdominal  cavity. 
It  consists  of  a  great  network  of  nerves  and  ganglia,  situated  behind  the  pancreas 
and  the  lesser  peritoneal  cavity  and  in  front  of  the  aorta  and  crura  of  the  Dia- 
phragm. It  surrounds  the  cceliac  axis  and  root  of  the  superior  mesenteric  artery, 
extending  downward  as  low  as  the  pancreas  and  outward  to  the  suprarenal  cap- 
sules. This  plexus,  and  the  ganglia  connected  with  it,  receive  the  great,  the  small, 
and  the  least  splanchnic  nerves  of  both  sides,  and  some  filaments  from  the  right 
vagus  nerve.  It  distributes  filaments  which  accompany,  under  the  name  of  plexuses, 
all  the  branches  from  the  front  of  the  abdominal  aorta. 

Of  the  ganglia  of  which  the  solar  plexus  is  partly  composed  the  principal 
are  the  two  semilunar  ganglia  (ganglia  coeliaca]  (Figs.  710  and  711),  which  are 
situated  one  on  each  side  of  the  plexus,  and  are  the  largest  ganglia  in  the  body. 
They  are  large,  irregular,  gangliform  masses  formed  by  the  aggregation  of  smaller 
ganglia,  having  interspaces  between  them.  They  are  situated  in  front  of  the 
crura  of  the  diaphragm,  close  to  the  suprarenal  capsules:  the  one  on  the  right 
side  lies  beneath  the  postcava;  the  upper  part  of  each  ganglion  is  joined  by  the 
greater  splanchnic  nerve,  and  to  the  inner  side  of  each  the  branches  of  the  solar 
plexus  are  connected. 

From  the  epigastric  or  solar  plexus  are  derived  the  following : 

Phrenic  or  Diaphragmatic  plexus.  (  Gastric  plexus. 

Adrenal  plexus.  Cceliac  plexus     <  Splenic  plexus. 

Renal  plexus.  (  Hepatic  plexus. 

Spermatic  plexus.  Superior  mesenteric  plexus. 

Aortic  plexus. 


1092 


THE  NERVE  SYSTEM 


The  Phrenic  Plexus  (plexus  phrenicus)  (Fig.  710). — The  phrenic  plexus  accom- 
panies the  phrenic  artery  to  the  Diaphragm,  which  it  supplies,  some  filaments 
passing  to  the  adrenal.  It  arises  from  the  upper  part  of  the  semilunar  gan- 
glion, and  is  larger  on  the  right  than  on  the  left  side.  It  receives  one  or  two 
branches  from  the  phrenic  nerve.  In  connection  with  this  plexus,  on  the  right 
side,  at  its  point  of  junction  with  the  phrenic  nerve,  is  a  small  ganglion,  the 
diaphragmatic  or  phrenic  ganglion  (ganglion  phrenicum)  (Fig.  711).  This  gan- 
glion is  placed  on  the  under  surface  of  the  Diaphragm,  near  the  right  adrenal. 


SOLAR      LEFT 

PHRENIC  PLEXUS     VAGUS 

PLEXUS 


RIGHT 
VAGUS 


HEPATIC 
PLEXUS 


COMMON 

BILE-DUCT 


SUPERIOR 

MESENTERIC 

PLEXUS 

ABDOMINAL 

AORTIC 

PLEXUS 


GREAT 
SPLANCHNIC 


SEMILUNAR 
GANGLION 


SUPERIOR 

MESENTERIC 

GANGLION 


SPERMATIC 
PLEXUS 


LUMBAR 
GANGLIA 


NFERIOR 
MESENTERIC 
PLEXUS 


FIG.  710. — The  semilunar  ganglia  with  the  sympathetic  plexuses  of  the  abdominal  viscera  radiating  from 

the  ganglia.      (Toldt.) 

Its  branches  are  distributed  to  the  postcava,  adrenal,  and  hepatic  plexus.     There 
is  no  ganglion  on  the  left  side. 

The  Adrenal  Plexus  (plexus  suprarenalis}  (Fig.  710). — The  adrenal  plexus 
is  formed  by  branches  from  the  solar  plexus,  from  the  semilunar  ganglion,  and 
from  the  phrenic  and  great  splanchnic  nerves,  a  ganglion  being  formed  at  the 
point  of  junction  of  the  latter  nerve.  It  supplies  the  adrenal.  The  branches 
of  this  plexus  are  remarkable  for  their  large  size  in  comparison  with  the  size  of 
the  organ  they  supply. 


1093 


The  Renal  Plexus  (plexus  renalis)  (Figs.  710  and  711). — The  renal  plexus  is 
formed  by  filaments  from  the  solar  plexus,  the  outer  part  of  the  semilunar  ganglion, 
and  the  aortic  plexus.  It  is  also  joined  by  filaments  from  the  lesser  and  smallest 
splanchnic  nerves.  The  nerves  from  these  sources,  fifteen  or  twenty  in  number, 


Diaphragmatic  ganglion 
Adrenal. 

Great 
splanchni 

no-re. 

Right 
semilunar 
ganglion. 

Renal  ganglion 
Small  splanchnic  nerve. 


Hepatic 

(i)'ti'ri/. 


Left  semilunar  ganglion. 
Superior  mesenteric  artery. 

Great  splanchnic  nerve. 

.Small  splanchnic  nerve. 

Renal  ganglion. 


Renal  artery. 


Superior  mesenteric  ganglion. 


Branch  to  aortic  plexus. 


Gangliated  cord  of 
sympathetic. 


Inferior  mesenteric  artery. 


Inferior  mesenteric  ganglion. 


Sacro-vertebral  angle. 
Common  iliac  vein. 
Common  iliac  artery. 


FIG.  711. — Lumbar  portion  of  the  gangliated  cord,  with  the  solar  and  hypogastric  plexuses.     (After  Henle.) 


1094  THE  NER  VE  SYSTEM 

have  numerous  ganglia  developed  upon  them.  They  accompany  the  branches 
of  the  renal  artery  into  the  kidney,  some  filaments  on  the  right  side  being  distrib- 
uted to  the  postcava,  and  others,  on  both  sides,  to  the  spermatic  plexuses. 

The  Spermatic  Plexus  (plexus  spermaticus)  (Fig.  710). — The  spermatic  plexus 
is  derived  from  the  renal  plexus,  receiving  branches  from  the  aortic  plexus.  It 
accompanies  the  spermatic  vessels  to  the  testes. 

The  Ovarian  Plexus  (plexus  arteriae  ovaricae). — In  the  female  the  ovarian  plexus 
is  distributed  to  the  ovaries  and  fundus  of  the  uterus. 

The  Cceliac  Plexus  (plexus  coeliacus). — The  cceliac  plexus,  of  large  size,  is  a 
direct  continuation  from  the  solar  plexus;  it  surrounds  the  cceliac  axis  and  sub- 
divides into  the  gastric,  hepatic,  and  splenic  plexuses.  It  receives  branches  from 
the  lesser  splanchnic  nerves,  and,  on  the  left  side,  a  filament  from  the  right  vagus. 

The  Gastric  or  Coronary  Plexus  (plexus  gastricus  superior}  (Fig.  710)  accompanies 
the  gastric  artery  along  the  lesser  curvature  of  the  stomach,  and  joins  with  branches 
from  the  left  vagus  nerve.  It  is  distributed  to  the  stomach. 

The  Splenic  Plexus  (plexus  lienalis)  (Fig.  710)  is  formed  by  branches  from  the 
cceliac  plexus,  the  left  semilunar  ganglion,  and  from  the  right  vagus  nerve.  It 
accompanies  the  splenic  artery  and  its  branches  to  the  substance  of  the  spleen, 
giving  off,  in  its  course,  filaments  to  the  pancreas,  the  pancreatic  plexus,  and  the 
left  gastro-epiploic  plexus,  which  accompanies  the  gastro-epiploica  sinistra  artery 
along  the  convex  border  of  the  stomach. 

The  Hepatic  Plexus  (plexus  hepaticus)  (Fig.  710),  the  largest  offset  from  the 
cceliac  plexus,  receives  filaments  from  the  left  vagus  and  right  phrenic  nerves. 
It  accompanies  the  hepatic  artery,  ramifying  in  the  substance  of  the  liver  upon 
its  branches  and  upon  those  of  the  vena  portse. 

Branches  from  this  plexus  accompany  all  the  divisions  of  the  hepatic  artery. 
Thus  there  is  a  pyloric  plexus  accompanying  the  pyloric  branch  of  the  hepatic, 
which  joins  with  the  gastric  plexus  and  vagus  nerves.  There  is  also  a  gastro- 
duodenal  plexus,  which  subdivides  into  the  pancreatico-duodendal  plexus,  which 
accompanies  the  pancreatico-duodenal  artery,  to  supply  the  pancreas  and  duo- 
denum, joining  with  branches  from  the  mesenteric  plexus.  The  gastro-epiploic 
plexus,  which  accompanies  the  right  gastro-epiploic  artery  along  the  greater 
curvature  of  the  stomach,  and  which  is  said  to  anastomose  with  branches  from 
the  splenic  plexus,  is  in  reality  derived  from  the  splenic  plexus.  A  cystic  plexus, 
which  supplies  the  gall-bladder,  also  arises  from  the  hepatic  plexus  near  the  liver. 

The  Superior  Mesenteric  Plexus  (plexus  mesentericus  superior)  (Fig.  710).— The 
superior  mesenteric  plexus  is  a  continuation  of  the  lower  part  of  the  great  solar 
plexus,  receiving  a  branch  from  the  junction  of  the  right  vagus  nerve  with  the 
cceliac  plexus.  It  surrounds  the  superior  mesenteric  artery,  which  it  accom- 
panies into  the  mesentery,  and  divides  into  a  number  of  secondary  plexuses,  which 
are  distributed  to  all  the  parts  supplied  by  the  artery — viz.,  pancreatic  branches  to 
the  pancreas;  intestinal  branches,  which  supply  the  whole  of  the  small  intestine; 
and  ileo-colic,  right  colic,  and  middle  colic  branches,  which  supply  the  corresponding 
parts  of  the  large  intestine.  The  nerves  composing  this  plexus  are  white  in  color  and 
firm  in  texture,  and  have  numerous  ganglia  developed  upon  them  near  their  origin. 

The  Abdominal  Aortic  Plexus  (plexus  aorticus  abdominalis)  (Figs.  705,  710,  and 
711). — The  abdominal  aortic  plexus  is  formed  by  branches  derived,  on  each  side, 
from  the  solar  plexus  and  the  semilunar  ganglia,  receiving  filaments  from  some 
of  the  lumbar  ganglia.  It  is  situated  upon  the  sides  and  front  of  the  aorta, 
between  the  origins  of  the  superior  and  inferior  mesenteric  arteries.  From  this 
plexus  arise  part  of  the  spermatic,  the  inferior  mesenteric,  and  the  hypogastric 
plexuses;  and  it  distributes  filaments  to  the  postcava. 

The  Inferior  Mesenteric  Plexus  (plexus  mesentericus  inferior)  (Fig.  710)  is  derived 
chiefly  from  the  left  side  of  the  aortic  plexus.  It  surrounds  the  inferior  mesenteric 


THE  PELVIC  OR  SACRAL  PLEXUS  1095 

artery,  and  divides  into  a  number  of  secondary  plexuses,  which  are  distributed  to 
all  the  parts  supplied  by  the  artery — viz.,  the  left  colic  and  sigmoid  plexuses,  which 
supply  the  descending  and  sigmoid  flexure  of  the  colon;  and  the  superior  hem- 
orrhoidal  plexus  (plexus  haemorrhoidalis  superior),  which  supplies  the  upper  part 
of  the  rectum  and  joins  in  the  pelvis  with  branches  from  the  pelvic  plexus. 

The  Hypogastric  Plexus  (Plexus  Hypogastricus)  (Figs.  705  and  711). 

The  hypogastric  plexus  supplies  the  viscera  of  the  pelvic  cavity.  It  is  situated 
in  front  of  the  promontory  of  the  sacrum,  between  the  two  common  iliac  arteries, 
and  is  formed  by  the  union  of  numerous  filaments,  which  descend  on  each  side 
from  the  abdominal  aortic  plexus  and  from  the  lumbar  ganglia.  This  plexus  con- 
tains no  evident  ganglia;  it  bifurcates,  below,  into  two  lateral  portions,  right  and 
left,  which  form  the  pelvic  plexuses. 

The  Pelvic  or  Sacral  Plexus  (Plexus  Sacralis). 

Each  pelvic  plexus,  sometimes  called  the  inferior  hypogastric,  supplies  the  viscera 
of  the  pelvic  cavity,  is  situated  at  the  side  of  the  rectum  in  the  male,  while  in  the 
female  it  lies  in  the  base  of  the  broad  ligament  near  the  ureters.  It  is  formed  by 
a  continuation  of  the  hypogastric  plexus,  by  branches  from  the  second,  third, 
and  fourth  sacral  nerves,  and  by  a  few  filaments  from  the  first  two  sacral  ganglia. 
At  the  points  of  junction  of  these  nerves  small  ganglia  are  found.  From  this  plexus 
numerous  branches  are  distributed  to  the  rectum  and  bladder  in  the  male  and 
to  the  rectum,  bladder,  uterus,  and  vagina  in  the  female.  They  accompany  the 
branches  of  the  internal  iliac  artery.  These  secondary  plexuses  are  (1)  the  interior 
hemorrhoidal,  (2)  vesical,  (3)  prostatic,  (4)  vaginal,  and  (5)  uterine  plexus. 

The  Inferior  Hemorrhoidal  Plexus  (plexus  haemorrhoidalis  inferior). — The  infe- 
rior hemorrhoidal  plexus  arises  from  the  back  part  of  the  pelvic  plexus.  It 
supplies  the  rectum,  joining  with  branches  of  the  superior  hemorrhoidal  plexus. 

The  Vesical  Plexus  (plexus  vesicalis). — The  vesical  plexus  arises  from  the  fore- 
part of  the  pelvic  plexus.  The  nerves  composing  it  are  numerous,  and  contain 
a  large  proportion  of  spinal  nerve-fibres.  They  accompany  the  vesical  arteries, 
and  are  distributed  at  the  side  and  base  of  the  bladder.  Numerous  filaments  also 
pass  to  the  vesiculse  seminales  and  vasa  deferentia;  those  accompanying  the  vas 
deferens  join,  on  the  spermatic  cord,  with  branches  from  the  spermatic  plexus. 

The  Prostatic  Plexus  (plexus  prostaticus). — The  prostatic  plexus  is  continued 
from  the  lower  part  of  the  pelvic  plexus.  The  nerves  composing  it  are  of  large 
size.  They  are  distributed  to  the  prostate  gland,  vesiculse  seminales,  and  erectile 
structure  of  the  penis.  The  nerves  supplying  the  erectile  structure  of  the  penis 
consist  of  two  sets,  the  small  and  large  cavernous  nerves.  They  are  slender  fila- 
ments, which  arise  from  the  forepart  of  the  prostatic  plexus,  and,  after  joining 
with  branches  from  the  internal  pubic  nerve,  pass  forward  beneath  the  pubic 
arch. 

The  Small  Cavernous  Nerve  (n.  cavernosus  penis  minor)  perforates  the  fibrous 
covering  of  the  penis  near  its  roots. 

The  Large  Cavernous  Nerve  (n.  cavernosus  penis  major)  passes  forward  along  the 
dorsum  of  the  penis,  joins  with  the  dorsal  branch  of  the  pudic  nerve,  and  is  dis- 
tributed to  the  corpora  cavernosa  and  corpus  spongiosum. 

The  uterine  and  vaginal  plexuses  in  reality  constitute  one  plexus,  the  utero- 
vaginal  plexus  (plexus  uterovaginalis). 

The  Vaginal  Plexus  arises  from  the  lower  part  of  the  pelvic  plexus.  It  is  lost 
on  the  walls  of  the  vagina,  being  distributed  to  the  erectile  tissue  at  its  ventral 


1096  THE  NERVE  SYSTEM 

part  and  to  the  mucous  membrane.  The  nerves  composing  this  plexus  contain, 
like  the  vesical  nerves,  a  large  proportion  of  spinal  nerve-fibres. 

The  Uterine  Plexus  arises  from  the  upper  part  of  the  pelvic  plexus  above  the 
point  where  the  branches  from  the  sacral  nerves  join  the  plexus.  Its  branches 
accompany  the  uterine  arteries  to  the  sides  of  the  organ  between  the  layers  of  the 
broad  ligaments,  and  are  distributed  to  the  cervix  and  lower  part  of  the  body  of 
the  uterus,  penetrating  its  substance. 

Other  filaments  pass  separately  to  the  body  of  the  uterus  and  the  oviduct. 

Branches  from  the  plexus  accompany  the  uterine  arteries  into  the  substance 
of  the  uterus.  Upon  these  filaments  ganglionic  enlargements  are  found. 


THE  OKGANS  OF  SPECIAL  SENSE. 


Organs  of  the  Senses  are  five  in  number— viz.,  those  of  Taste,  of  Smell, 
of  Sight,  of  Hearing,  and  of  Touch. 


THE  TONGUE  (LINGUA)  (Fig.  712). 

The  tongue  is  a  very  mobile  muscular  organ,  undergoing  changes  in  length  and 
width  at  every  contraction  of  its  muscle.  It  is  the  organ  of  the  special  sense  of 
taste,  and  is  also  an  organ  of  speech,  mastication,  and  deglutition.  It  is  situated 
in  the  floor  of  the  mouth,  in  the  interval  between  the  two  lateral  portions  of  the 
body  of  the  lower  jaw,  and  when  at  rest  is  about  three  and  one-half  inches  in 
length.  We  describe  the  body,  base,  apex,  dorsum,  margin,  and  inferior  surface. 

The  Body  (corpus  linguae}. — The  body  forms  the  great  bulk  of  the  organ 
and  is  composed  of  striated  muscle. 

The  Base  or  Root  (radix  linguae). — The  base  or  root  is  directed  backward,  and 
connected  with  the  os  hyoideum  by  the  Hyo-glossi  and  Genio-hyo-glossi  muscles 
and  the  hyo-glossal  membrane ;  with  the  epiglottis  by  three  folds  of  mucous  mem- 
brane, the  glosso-epiglottic  folds ;  with  the  soft  palate  by  means  of  the  anterior 
pillars  of  the  fauces;  and  with  the  pharynx  by  the  Superior  constrictors  and  the 
mucous  membrane. 

The  Apex  or  Tip  (apex  linguae). — The  apex  or  tip  is  thin  and  narrow,  and  is 
directed  forward  against  the  inner  surface  of  the  lower  incisor  teeth. 

The  Dorsum  of  the  Tongue  (dorsum  linguae). — The  dorsum  when  the  tongue 
of  a  living  person  is  at  rest  is  markedly  arched  from  before  backward.  On  the 
dorsum  is  a  median  longitudinal  raph6  (sulcus  medianus  linguae).  This  slight 
depression  terminates  posteriorly  in  the  depression  known  as  the  foramen  caecum 
(foramen  caecum  linguae  [Morgagnii\),  from  which  a  shallow-shaped  groove,  the 
sulcus  terminalis  of  His,  runs  outward  and  forward  on  each  side  to  the  lateral 
margin  of  the  tongue.  The  part  of  the  dorsum  of  the  tongue  in  front  of  this 
groove,  known  as  the  anterior  or  oral  part,  forming  about  two-thirds  of  its  upper 
surface,  is  rough  and  covered  with  papillae;  the  posterior  third  of  the  dorsum 
is  back  of  the  sulcus  terminalis,  is  known  as  the  posterior  or  pharyngeal  portion,  is 
smoother,  and  contains  numerous  muciparous  glands  and  lymphoid  follicles. 

The  Margin  of  the  Tongue  (margo  lateralis  linguae). — The  margin  of  the 
tongue  is  free  in  front  of  the  anterior  arch  of  the  palate.  Just  in  front  of  the 
arch  are  several  vertical  folds,  the  folia  linguae. 

The  Under  or  Inferior  Surface  (fades  inferior  linguae). — The  under  or 
inferior  surface  of  the  tongue  is  connected  with  the  lower  jaw  by  the  Genio-hyo- 
glossi  muscles,  from  its  sides  the  mucous  membrane  is  reflected  to  the  inner  sur- 
face of  the  gums;  and  from  its  under  surface'on  to  the  floor  of  the  mouth,  where, 
in  the  middle  line,  it  is  elevated  into  a  distinct  vertical  fold,  the  fraenum  linguae 
(frenulum  linguae).  To  each  side  of  the  fraenum  is  a  slight  fold  of  the  mucous 
membrane,  the  plica  fimbriata,  the  free  edge  of  which  exhibits  a  series  of  fringe- 
like  processes. 

The  tip  of  the  tongue,  part  of  the  under  surface,  its  sides,  and  dorsum  are  free. 

( 1097 ) 


1098 


THE   ORGANS   OF  SPECIAL   SENSE 


Structure  of  the  Tongue. — The  tongue  is  partly  invested  by  mucous  mem- 
brane and  a  submucous  fibrous  layer.  It  consists  of  symmetrical  halves,  sepa- 
rated from  each  other,  in  the  middle  line,  by  a  fibrous  septum.  Each  half  is  com-, 
posed  of  muscular  fibres  arranged  in  various  directions  (page  400),  containing 
much  interposed  fat,  and  supplied  by  vessels  and  nerves. 

The  Mucous  Membrane  (tunica  mucosa  linguae). — The  mucous  membrane 
invests  the  entire  extent  of  the  free  surface  of  the  tongue.  On  the  dorsum  it  is 
thicker  behind  than  in  front,  and  is  continuous  with  the  sheath  of  the  muscles 
attached  to  it,  through  the  submucous  fibrous  layer.  On  the  under  surface  of  the 
organ,  where  it  is  thin  and  smooth,  it  can  be  traced  on  each  side  of  the  fraenum 


NSIL. 


-EPIGLOTTIS. 


CIRCUM- 
VALLATC 

PAPILL/E. 


FIG.  712. — Upper  surface  of  the  tongue. 

through  the  ducts  of  the  submaxillary  and  the  sublingual  glands.    As  it  passes 
over  the  borders  of  the  organ  it  gradually  assumes  a  papillary  character. 

Structure. — The  structure  of  the  mucous  membrane  of  the  tongue  differs  in 
different  parts.  That  covering  the  under  surface  of  the  organ  is  thin,  smooth, 
and  identical  in  structure  with  that  lining  the  rest  of  the  oral  cavity.  The  mucous 
membrane  covering  the  tongue  behind  the  foramen  caecum  and  sulcus  terminalis 
is  thick  and  freely  movable  over  the  subjacent  parts.  It  contains  a  large  number 
of  lymphoid  follicles  (folliculi  linguales},  which  together  constitute  what  is  some- 
times termed  the  lingual  tonsil  (tonsilla  lingualis).  Each  follicle  forms  a  rounded 
eminence,  the  centre  of  which  is  perforated  by  a  minute  orifice  leading  into  a 


THE    TONGUE 


1099 


funnel-shaped  cavity  or  recess;  around  this  recess  are  grouped  numerous  oval  or 
rounded  nodules  of  lymphoid  tissue,  each  enveloped  by  a  capsule  derived  from 
the  submucosa,  while  opening  into  the  bottom  of  the  recesses  are  also  seen  the 
ducts  of  mucous  glands  (glandulae  linguales).  The  mucous  membrane  on  the 
anterior  part  of  the  dorsum  of  the  tongue  is  thin  and  intimately  adherent  to  the 
muscular  tissue,  and  covered  with  minute  eminences,  the  papillae  of  the  tongue. 
It  consists  of  a  layer  of  connective  tissue,  the  corium  or  mucosa,  supporting  numer- 
ous papillae,  and  covered,  as  well  as  the  papillae,  with  epithelium. 

The  epithelium  is  of  the  scaly  variety,  like  that  of  the  epidermis.  It  covers  the 
free  surface  of  the  tongue,  as  maybe  readily  demonstrated  by  maceration  or  boiling, 
when  it  can  be  easily  detached  entire;  it  is  much  thinner  than  that  of  the  skin;  the 
intervals  between  the  large  papillae  are  not  filled  up  by  it,  but  each  papilla  has 
a  separate  investment  from  root  to  summit.  The  deepest  cells  may  sometimes  be 
detached  as  a  separate  layer,  corresponding  to  the  rete  mucosum,  but  they  never 
contain  coloring  matter. 

The  Corium. — The  corium  consists  of  a  dense  feltwork  of  fibrous  connective 
tissue,  with  numerous  elastic  fibres,  firmly  connected  with  the  fibrous  tissue  form- 
ing the  septa  between  the  muscular  bundles  of  the  tongue.  It  contains  the  ramifi- 
cations of  the  numerous  vessels  (Fig.  713)  and  nerves  from  which  the  papillae  are 
supplied,  large  plexuses  of  lymphatic  vessels,  and  the  glands  of  the  tongue. 


Filiform, 


Fungiform. 


Secondary 


Circumvallate. 


Artery. 


Vein. 


Artery.1 
Vein. 


FIG.  713. — Three  kinds  of  papillae,  magnified. 


The  Papillae  of  the  Tongue  (papillae  linguales)  (Figs.  712,  713,  714,  and  715).— 
These  are  papillary  projections  of  the  corium.  They  are  thickly  distributed  over 
the  anterior  two-thirds  of  the  upper  surface  of  the  tongue,  giving  to  it  its  char- 
acteristic roughness.  The  varieties  of  papillae  met  with  are — the  papillae  maximae 
or  circumvallate  papillae,  papillae  mediae  or  fungiforme  papillae,  papillae  minimae, 
conical  or  filiform e  papillae,  and  papillae  simplices  or  simple  papillae. 

The  Papillae  Maximae  or  Circumvallate  Papillae  (papillae  vallatae  (Figs.  712,  713, 
and  714)  are  of  large  size,  and  vary  from  eight  to  twelve  in  number.  They  are 
situated  at  the  back  part  of  the  dorsum  of  the  tongue,  near  its  base,  in  front  of 
the  foramen  caecum  and  sulcus  terminalis,  forming  a  row  on  each  side,  which, 
running  backward  and  inward,  meet  in  the  middle  line,  like  the  two  lines  of  the 
letter  V  inverted  A..  Each  papilla  consists  of  a  projection  of  mucous  membrane 
from  -j1^  to  YJ  °f  an  inch  wide,  attached  to  the  bottom  of  a  cup-shaped  depression  of 
the  mucous  membrane;  the  papilla  is  in  shape  like  a  truncated  cone,  the  smaller 
end  being  directed  downward  and  attached  to  the  tongue,  the  broader  part  or 
base  projecting  on  the  surface  and  being  studded  with  numerous  small  secondary 
papillae  (Fig.  713),  which,  however,  are  covered  by  a  smooth  layer  of  the  epithe- 
lium. The  cup-shaped  depression  forms  a  kind  of  fossa  around  the  papilla, 
having  a  circular  margin  of  about  the  same  elevation  covered  with  smaller  papillae. 


1100 


Immediately  behind  the  apex  of  the  V  is  the  foramen  caecum,  mentioned  above. 
This  foramen,  according  to  His,  represents  the  remains  of  the  invagination  which 
forms  the  median  rudiment  of  the  thyroid  body,  and  which  for  a  time  opens  by 
a  duct,  the  thyroglossal  duct  (ductus  thyreoglossus] ,  on  to  the  dorsum  of  the  tongue. 
It  may  extend  downward  toward  the  hyoid  bone.  Kanthack,  however,  disputes 
.  this  view.1 

The  Fungiforme  Papillae  or  Papillae  Mediae  (papillae  fungiformes  el  papillae  len- 
ticulares)  (Fig.  713), -more  numerous  than  the  preceding,  are  scattered  irregularly 
and  sparingly  over  the  dorsum  of  the  tongue,  but  are  found  chiefly  at  its  sides 
and  apex.  They  are  easily  recognized  among  the  other  papillae,  by  their  large 
size,  rounded  eminences,  and  deep-red  color.  They  are  narrow  at  their  attach- 
ment to  the  tongue,  but  broad  and  rounded  at  their  free  extremities,  and  are 
covered  with  secondary  papillae.  Their  epithelial  investment  is  very  thin. 

The  Conical  or  Filiform  Papillae  or  Papillae  Minimae  (papillae  conicae  et  papillae 
filiformes)  (Fig.  713)  cover  the  anterior  two-thirds  of  the  dorsum  of  the  tongue. 
They  are  very  minute,  more  or  less  conical  or  filiform  in  shape,  and  arranged  in  lines 
corresponding  in  direction  with  the  two  rows  of  the  papillae  circumvallatae,  except- 
ing at  the  apex  of  the  organ,  where  their  direction  is  transverse.  Projecting  from  their 
apices  are  numerous  filiform  processes  or  secondary  papillae;  these  are  of  a  whitish 
tint,  owing  to  the  thickness  and  density  of  the  epithelium  of  which  they  are  com- 
posed, and  which  has  here  undergone  a 
peculiar  modification,  the  cells  having  be- 
come cornified  and  elongated  into  dense, 
imbricated,  brush-like  processes.  They 
contain  also  a  number  of  elastic  fibres,  which 
render  them  firmer  and  more  elastic  than 
the  papillae  of  mucous  membrane  generally. 
Simple  Papillae,  similar  to  those  of  the  skin, 
cover  the  whole  of  the  mucous  membrane  of 
the  tongue,  as  well  as  the  larger  papillae. 
They  consist  of  closely  set,  microscopic  ele- 
vations of  the  corium,  containing  a  capillary 
loop,  covered  by  a  layer  of  epithelium. 

Structure  of  the  Papillae  (Figs.  713and  714). 
— The  papillae  apparently  resemble  in  struc- 
ture the  papillae  of  the  cutis,  consisting  of  a 
cone-shaped  projection  of  connective  tissue, 

FIG.  714. — Circumvallate  papillae  of  tongue  of  i-,iji*ii  p  • 

rabbit,  showing  position  of  taste-goblets.  a.  COVCred  With  a  thick  layer  OI  SquaniOUS  epl- 
Duct  of  gland,  a.  Serous  gland,  g.  Taste-buds.  .1  i-  j  '11 

i.  Primary  septa,  and  i',  secondary  sepia,  of  thelium,  and  contain  one  or  more  capillary 
fibresae'(Stncihr]V)edullated  nerve-  Muscular  loops,  amongst  which  nerves  are  distributed 

in  great  abundance.      If  the  epithelium  is 

removed,  it  will  be  found,  however,  that  they  are  not  simple  elevations  like  the 
papillae  of  the  skin,  for  the  surface  of  each  is  studded  with  minute  conical  pro- 
cesses of  the  mucous  membrane,  which  form  secondary  papillae  (Todd  and  Bow- 
man). In  the  papillae  circumvallatae  the  nerves  are  numerous  and  of  large  size;  in 
the  papillae  fungiformes  they  are  also  numerous,  and  terminate  in  a  plexiform  net- 
work, from  which  brush-like  branches  proceed;  in  the  papillae  filiformes  their  mode 
of  termination  is  uncertain.  Buried  in  the  epidermis  of  the  papillae  circumvallatae, 
and  in  some  of  the  fungiformes,  are  certain  peculiar  bodies,  called  taste-buds2  (Fig. 
715).  Each  is  flask-like  in  shape,  the  broad  base  resting  on  the  corium,  and  the 
neck  opening  by  an  orifice,  the  gustatory  pore,  between  the  cells  of  the  epithelium. 


1  Journal  of  Anatomy  and  Physiology,  1891. 

2  These  bodies  are  also  found  in  considerable  numbers  at  the  side  of  the  base  of  the  tongue,  just  in  front  of  the 
anterior  pillars  of  the  fauces,  and  also  on  the  posterior  surface  of  the  epiglottis  and  anterior  surface  of  the  soft 
palate. — ED.  of  15th  English  edition. 


THE    TONGUE  HOI 

They  are  formed  by  two  kinds  of  cells,  supporting  cells  and  gustatory  cells.  The 
supporting  cells  are  mostly  arranged  like  the  staves  of  a  cask,  and  form  an  outer 
envelope  for  the  bud.  Some,  however,  are  found  in  the  interior  of  the  bud  between 
the  gustatory  cells.  The  gustatory  cells  occupy  the  central  portion  of  the  bud; 
they  are  spindle-shaped,  and  each  possesses  a  large  spherical  nucleus  near  the 
middle  of  the  cell.  Until  recently  the  teaching  was  as  follows :  The  peripheral 
end  of  the  cell  terminates  as  the  gustatory  pore  in  a  fine,  hair-like  filament,  the 
gustatory  hair.  The  central  process  passes  toward  the  deep  extremity  of  the  bud, 
and  there  ends  in  a  single  or  bifurcated  varicose  filament,  which  was  formerly 
supposed  to  be  continuous  with  the  terminal  fibril  of  a  nerve;  the  investigations 
of  Lenhosse"k  and  others  would  seem  to  prove,  however,  that  this  is  not  so,  but 
that  the  nerve-fibrils  after  losing  their  medullary  sheaths  enter  the  taste-bud,  and 


Gustatory  hairs 


Epithelium 


Taste  bud 


Tunica  propria- 
FIG.  715. — Taste-buds  from  the  papilla  foliata  of  a  rabbit.     X  850.     (Szymonowicz.) 

terminate  in  a  fine  extremity  between  the  gustatory  cells.  Other  nerve-fibrils 
may  be  seen  ramifying  between  the  cortical  cells  and  terminating  in  fine  extrem- 
ities; these,  however,  are  believed  to  be  nerves  of  ordinary  sensation,  and  not 
gustatory.  It  is  now  not  believed  that  the  epithelia  of  the  taste-buds  are  directly 
connected  with  the  nerve-fibres  by  long  processes.  "The  latest  researches  have 
shown  that  dendrites  of  sensor  neurones  (sensor  nerves)  enter  the  taste-buds 
and  end  free  in  telodendria.  The  latter  surround  the  neuro-epithelial,  and,  to 
some  extent,  the  sustentacular  cells,  their  relations  depending  on  contact."1 

Glands  of  the  Tongue. — The  tongue  is  provided  with  mucous  and  serous  glands. 
The  mucous  glands  are  similar  in  structure  to  the  labial  and  buccal  glands.  They 
are  found  especially  at  the  back  part,  behind  the  circumvallate  papillae,  but  are 
also  present  at  the  apex  and  marginal  parts.  In  connection  with  these  glands 
special  ones  have  been  described  by  Blandin  and  Nuhn.  They  are  known  as  the 
glands  of  Nuhn  and  Blandin  or  apical  glands  (glandulae  linguales  anteriores  of  Nuhn 
and  Blandin)  (Fig.  716).  They  are  situated  near  the  apex  of  the  tongue  on  either 
side  of  the  fraenum,  and  each  is  covered  over  by  a  fasciculus  of  muscular  fibre 
derived  from  the  Stylo-glossus  and  Inferior  lingualis  muscles.  Each  gland  is  from 
half  an  inch  to  nearly  an  inch  long  and  about  the  third  of  an  inch  broad.  It  has 
from  four  to  six  ducts,  which  open  on  the  under  surface  of  the  apex. 

The  Serous  Glands  or  Glands  of  v.  Ebner  occur  only  at  the  back  of  the  tongue  in 
the  neighborhood  of  the  taste-buds,  their  ducts  opening  for  the  most  part  into  the 

1  Text-book  of  Histology.     By  A.  A.  Bohm  and  M.  von  Davidoff.     Edited  by  G.  Carl  Huber. 


1102 


THE    ORGANS    OF  SPECIAL    SENSE 


fossae  of  the  papillae  circumvallatae.  These  glands  are  racemose,  the  duct  branch- 
ing into  several  minute  ducts,  which  terminate  in  alveoli  lined  by  a  single  layer 
of  more  or  less  columnar  epithelium.  Their  secretion  is  of  a  watery  nature,  and 
probably  assists  in  the  distribution  of  the  substance  to  be  tasted  over  the  taste- 
area  (Ebner). 

The  Hyo-glossal  membrane  is  a  strong  fibrous  lamina  which  is  derived  from  the 
septum  of  the  tongue  and  which  connects  the  under  surface  of  the  base  of  the 
tongue  to  the  body  of  the  hyoid  bone.  This  membrane  receives,  in  front,  some 
of  the  posterior  fibres  of  the  Genio-hyo-glossi  muscles. 

The  Vessels  of  the  Tongue. — The  arteries  of  the  tongue  are  derived  from  the 
lingual,  the  facial,  and  ascending  pharyngeal.  The  veins  of  the  tongue  open  into 
the  internal  jugular. 

The  lingual  artery  (Fig.  718)  on  each  side  passes  forward  beneath  the  Hyo- 
glossus  muscle  and  courses  to  the  apex  of  the  tongue,  between  the  Genio-glossus 
and  the  Inferior  lingual  muscles,  about  one-eighth  of  an  inch  from  the  surface. 
It  divides  into  the  ranine  (Fig.  716)  and  sublingual  (Fig.  718).  Near  the  apex  a 
branch  is  given  off  from  the  ranine  artery,  which  penetrates  the  septum  and  joins 
a  like  branch  from  the  other  side.  The  dorsalis  linguae  is  a  branch  of  the  lingual 


Bristles 
in  ducts 
of  glands. 

Glands  of 
\     Blandin 
or  Nuhn. 


Lingual  nerve.         Ranine  artery. 

FIG.  716. — Under  surface  of  tongue,  showing  position  and  relations  of  gland  of  Blandin  or  Nuhn. 
a  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 


(from 


supplying  the  posterior  part  of  the  tongue,  and  rami  from  the  tonsillar  branch 
of  the  facial  go  to  the  same  region.  A  network  of  capillary  vessels  is  placed 
beneath  the  epithelium. 

The  ranine  veins  lie  to  the  sides  of  the  fraenum  underneath  the  mucous  mem- 
brane. Each  ranine  vein  runs  backward,  superficial  to  and  upon  the  Hyo-glossus 
muscle  and  near  to  the  hypo-glossal  nerve.  The  venae  comites  of  the  lingual  artery 
usually  join  the  ranine  vein,  and  the  trunk  opens  into  the  internal  jugular  vein, 
but  the  vessels  may  open  separately  into  the  jugular  (Fig.  445). 

The  Muscles  of  the  Tongue. — The  muscular  fibres  of  the  tongue  run  in  various 
directions.  These  fibres  are  divided  into  two  sets,  Extrinsic  and  Intrinsic,  which 
have  already  been  described  (pp.  398,  399,  400,  401,  and  4Q2). 


THE    TONGUE 


1103 


The  Extrinsic  come  from  the  Stylo-glossus,  Hyo-glossus,  Genio-glossus, 
Palato-glossus,  and  Chondro-glossus.  The  Intrinsic  muscles  are  the  Superior 
lingualis  (m.  longitudinalis  superior),  the  Inferior  lingualis  (m.  longitudinalis 
inferior],  the  Transverse  lingual  (m.  transversus  linguae),  and  the  Vertical  lingual 
(m.  verticalis  linguae).  The  outer  or  cortical  portion  of  the  tongue  is  composed 
chiefly  of  longitudinal  fibres.  The  central  or  medullary  portion  is  composed  chiefly 
of  vertical  and  transverse  fibres  and  is  divided  into  two  parts  by  a  vertical  sep- 
tum (septum  linguae),  which  is  a  fibrous  structure,  beginning  at  the  apex  and 
passing  back.  As  it  approaches  the  back  it  becomes  narrower  vertically  and 
broadens  out  transversely  to  form  the  hyo-glossal  membrane.  The  fibrous  septum 
is  well  displayed  by  making  a  vertical  section  of  the  tongue. 

The  Lymphatic  Vessels  of  the  Tongue  (Fig.  490). — The  lymphatic  vessels  from 
the  anterior  half  of  the  tongue  pass  to  the  submaxillary  lymph  glands. 

Lymph  vessels  from  the  posterior  half  of  the  tongue  are  connected  with  satellite 
glands  on  the  Hyo-glossus  muscle  and  terminate  in  the  deep  cervical  glands.  The 
last-named  lymph- vessel  accompanies  the  ranine  vein.  The  lingual  lymphatics 
arise  from  a  network  beneath  the  epithelium.  Across  the  anterior  two-thirds 
of  the  tongue  there  is  little  or  no  lymphatic  connection  between  the  two  sides; 
in  the  posterior  one-third  there  is  free  connection. 


SUPERIOR 

LONGITUDINALIS 

MUSCLE 

VERTICALIS, 
LINGUAE  MUSCLE 

TRANSVERSUS 
LINGUAE   MUSCLE 

INFERIOR 

LONGITUDINALIS 

MUSCLE 


STYLOGL06SUS 
MUSCLE 


DEEP  LINGUAL 
ARTERY 


SUBLINGUAL 
GLAND 

GENIOGLOSSUS 
MUSCLE 


FIG.  717. — Frontal  section  through  the  body  of  the  tongue  of  a  new-born  babe.     X  3.     (Spalteholz.) 

The  Nerves  of  the  Tongue  (Fig.  718). — The  nerves  of  the  tongue  are  five  in  number 
in  each  half:  the  lingual  branch  of  the  inferior  maxillary  division  of  the  trigeminal, 
which  is  distributed  to  the  papillae  at  the  forepart  and  sides  of  the  tongue,  and  forms 
the  nerve  of  ordinary  sensibility  for  its  anterior  two-thirds;  the  chorda  tympani, 
which  runs  in  the  sheath  of  the  lingual,  is  generally  regarded  as  the  nerve  of 
taste  for  the  same  area  (p.  898) ;  the  lingual  branch  of  the  glosso-pharyngeal,  which 
is  distributed  to  the  mucous  membrane  at  the  base  and  sides  of  the  tongue,  and 
to  the  papillae  circumvallatae,  and  which  supplies  both  sensory  and  gustatory 
filaments  to  this  region;  the  hypo-glossal  nerve,  which  is  the  motor  nerve  to  the 
muscular  substance  of  the  tongue ;  and  the  internal  laryngeal  branch  of  the  superior 
laryngeal,  which  sends  some  fine  branches  to  the  root  near  to  the  epiglottis. 
Sympathetic  filaments  also  pass  to  the  tongue  from  the  nervi  molles  on  the 
lingual  and  other  arteries  supplying  it.  Some  of  the  nerves  end  free  between  the 
cells  of  epithelium;  others  terminate  as  end  organs  (Meissner's  corpuscles  and 
the  end-bulbs  of  Krause),  and  in  taste-buds  as  sensory  dendrites  (p.  833). 

Surgical  Anatomy. — The  diseases  to  which  the  tongue  is  liable  are  numerous,  and  its  sur- 
gical anatomy  is  of  importance,  since  any  or  all  the  structures  of  which  it  is  composed — muscles, 
connective  tissue,  mucous  membrane,  glands,  vessels,  nerves,  and  lymphatics — may  be  the  seat 
of  morbid  changes.  It  is  not  often  the  seat  of  congenital  defects,  though  a  few  cases  of  vertical 


1104 


THE    ORGANS    OF  SPECIAL    SENSE 


cleft  have  been  recorded,  and  it  is  occasionally,  though  much  more  rarely  than  is  commonly  sup- 
posed, the  seat  of  tongue-tie,  from  shortness  of  the  fraenum. 

There  is,  however,  one  condition  which  must  be  regarded  as  congenital,  though  not  uncom 
monly  it  does  not  exhibit  the  significant  changes  until  a  year  or  two  after  birth.  This  is  an 
enlargement  of  the  tongue  which  is  due  primarily  to  a  dilatation  of  the  lymph-channels  and  a 
greatly  increased  development  of  the  lymphatic  tissue  throughout  the  tongue  (macroglossia).  This 
is  often  aggravated  by  inflammatory  changes  induced  by  injury  or  exposure,  and  the  tongue  may 
assume  enormous  dimensions  and  hang  out  of  the  mouth,  giving  the  child  an  imbecile  expression. 
The  treatment  consists  in  excising  a  V-shaped  portion  and  bringing  the  cut  surfaces  together 
with  deeply  placed  silver  sutures.  Compression  has  been  resorted  to  in  some  cases  with  occa- 
sional success,  but  it  is  difficult  to  apply.  Acute  inflammation  of  the  tongue  (acute  glossitis), 
which  may  be  caused  by  injury  or  the  introduction  of  some  septic  or  irritating  matter,  and  it 
is  attended  by  great  swelling  from  infiltration  of  the  connective  tissue  of  the  tongue;  this  con- 
nective tissue  is  present  in  considerable  quantity.  The  great  swelling  renders  the  patient 
incapable  of  swallowing  or  speaking,  and  may  seriously  impede  respiration.  The  condition  may 
eventuate  in  suppuration  and  the  formation  of  an  acute  abscess.  Chronic  abscess,  which  has 
been  mistaken  for  cancer,  may  also  occur  in  the  substance  of  the  tongue. 

Sublingual 
\    artery. 


Glosso-pharyn- 
geal  nerve. 


Internal  laryngeal 

branch  of  the 

superior  laryngeal 

nerve. 


FIG.  718. — Under  surface  of  tongue,  showing  the  distribution  of  nerves  to  this  organ.     (From  a  preparation 
in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 

The  mucous  membrane  of  the  tongue  may  become  chronically  inflamed,  and  presents  different 
appearances  in  different  stages  of  the  disease,  to  which  the  terms  leucoplakia,  psorias,  and 
ichthyosis  have  been  given. 

The  tongue,  being  very  vascular,  is  often  the  seat  of  naevoid  growths,  and  these  have  a  tendency- 
to  grow  rapidly. 

The  tongue  is  frequently  the  seat  of  ulceration,  which  may  arise  from  many  causes,  as  from 
the  irritation  of  jagged  teeth,  dyspepsia,  tuberculosis,  syphilis,  and  cancer.  Of  these  the  cancerous 
ulcer  is  the  most  important,  and  probably  also  the  most  common.  The  variety  is  the  squamous 
epithelioma,  which  soon  develops  into  an  ulcer  with  an  indurated  base.  It  produces  great  pain 
which  speedily  extends  to  all  parts  supplied  with  sensation  by  the  trigeminal  nerve,  especially  to  the 


THE  NOSE  H05 

region  of  the  ear.  The  pain  in  these  cases  is  conducted  to  the  ear  and  temporal  region  by  the 
lingual  nerve,  and  from  this  nerve  pain  radiates  to  the  other  branches  of  the  inferior  maxillary 
nerve,  especially  the  auriculo-temporal.  Possibly  pain  in  the  ear  itself  may  be  due  to  implication 
of  the  fibres  of  the  glosso-pharyngeal  nerve,  which  by  its  tympanic  branch  reaches  the  tympanic 
plexus.  Cancer  of  the  tongue  spreads  through  the  organ  very  rapidly  because  of  the  almost 
constant  muscular  movements. 

Cancer  of  the  tongue  may  necessitate  removal  of  a  part  or  the  whole  of  the  organ,  and  many 
different  methods  have  been  adopted  for  its  excision.  It  may  be  removed  from  the  mouth  by 
the  e"craseur  or  the  scissors.  The  better  method  is  by  the  scissors,  usually  known  as  Whitehead's 
method.  The  mouth  is  widely  opened  with  a  gag  the  tongue  is  transfixed  with  a  stout  silk  liga- 
ture, by  which  to  hold  and  make  traction  on  it  and  the  reflection  of  mucous  membrane  from 
the  tongue  to  the  jaw,  and  the  insertion  of  the  Genio-hyo-glossi  first  divided  with  a  pair  of 
curved  blunt  scissors.  The  Palato-glossi  are  aiso  divided.  The  tongue  can  now  be  pulled  well 
out  of  the  mouth.  The  base  of  the  tongue  is  cut  through  by  a  series  of  short  snips,  each  bleed- 
ing vessel  being  dealt  with  as  soon  as  divided,  until  the  situation  of  the  ranine  artery  is  reached. 
The  remaining  undivided  portion  of  tissue  is  to  be  seized  with  a  pair  of  Wells's  forceps,  the  tongue 
removed,  and  the  vessel  secured.  In  the  event  of  the  ranine  artery  being  accidentally  injured 
early  in  the  operation,  hemorrhage  can  be  at  once  controlled  by  passing  two  fingers  over  the 
dorsum  of  the  tongue  as  far  as  the  epiglottis  and  dragging  the  root  of  the  tongue  forcibly  forward. 

In  cases  where  the  disease  is  confined  to  one  side  of  the  anterior  portion  of  the  tongue  this 
operation  may  be  modified  by  splitting  the  tongue  down  the  centre  and  removing  only  the  affected 
half.  If  the  posterior  portion  of  the  tongue  is  attacked  by  cancer  the  entire  tongue  must  be 
removed,  even  if  but  one  side  of  the  organ  is  apparently  involved.  The  exchange  of  lymph 
between  the  halves  of  the  posterior  portion  of  the  tongue  makes  it  certain  that  the  opposite  half 
becomes  involved  soon  after  the  origin  of  the  disease.  Whatever  operation  is  performed  for 
cancer  of  the  tongue,  the  glands  must  be  removed  ^rom  both  sides  of  the  neck.  This  is  to  be 
done,  even  if  but  one  side  of  the  tongue  is  removed.  Kocher;  after  performing  a  preliminary  trache- 
otomy, removes  the  tongue  from  the  neck;  by  an  incision  taken  from  near  the  lobule  of  the  ear, 
down  the  anterior  border  of  the  Sterno-mastoid  to  the  level  of  the  great  cornu  of  the  hyoid  bone, 
then  forward  to  the  body  of  the  hyoid  bone,  and  upward  to  near  the  symphysis  of  the  jaw.  The 
lingual  artery  is  now  secured  and  by  a  careful  dissection  the  submaxillary  lymphatic  glands 
and  the  tongue  removed.  Regnoli  advocated  the  removal  of  the  tongue  by  a  semilunar  incision 
in  the  submaxillary  triangle  along  the  line  of  the  lower  jaw.  and  a  vertical  incision  from  the 
centre  of  the  semilunar  one  backward  to  the  hyoid  bone.  Care  must  be  taken  not  to  carry  the 
first  incision  too  far  backward,  so  as  to  wound  the  facial  arteries.  The  tongue  is  thus  reached 
through  the  floor  of  the  mouth  pulled  out  through  the  external  incision,  and  removed  with  the 
knife.  The  great  objection  to  this  operation  is  that  all  the  muscles  which  raise  the  hyoid 
bone  and  larynx  are  divided,  and  that  therefore  the  movements  of  deglutition  and  respiration  are 
interfered  with. 

Finally,  where  both  sides  of  the  floor  of  the  mouth  are  involved  in  the  disease,  or  where  very 
free  access  is  required  on  account  of  the  extension  backward  of  the  disease  to  the  pillars  of  the 
fauces  and  the  tonsil,  or  where  the  lower  jaw  is  involved,  the  operation  recommended  by  Syme 
must  be  performed.  This  is  done  by  an  incision  through  the  central  line  of  the  lip-  across  the 
chin,  and  down  as  far  as  the  hyoid  bone.  The  lower  jaw  is  sawed  through  at  the  symphysis,  and 
the  two  halves  of  the  bone  forcibly  separated  from  each  other.  The  mucous  membrane  is  sepa- 
rated from  the  bone,  and  the  Genio-hyo-glossi  detached  from  the  bone,  and  the  Hyo-glossi 
divided.  The  tongue  is  then  drawn  forward  and  removed  close  to  its  attachment  to  the  hyoid 
bone.  Adjacent  lymph  glands  can  be  removed  and  if  the  bone  is  implicated  in  the  dis- 
ease, it  can  also  be  removed  by  freeing  it  from  the  soft  parts  externally  and  internally,  and 
making  a  second  section  with  the  saw  beyond  the  diseased  part. 

Formerly  many  surgeons  before  removing  the  tongue  performed  a  preliminary  tracheotomy: 
(1)  to  prevent  blood  entering  the  air-passages;  and  (2)  to  allow  the  patient  to  breathe  through 
the  tube  and  not  inspire  air  which  had  passed  over  a  sloughy  wound,  and  which  was  loaded  with 
septic  organisms  and  likely  to  induce  septic  pneumonia.  By  operating  with  the  patient  in  the 
Trendelenburg  position,  the  blood  is  caused  to  flow  away  from  the  air-passages.  By  the  judicious 
use  of  iodoform  the  evil  mentioned  secondly  may  be  obviated,  and  the  preliminary  tracheotomy  is 
now  usually  dispensed  with. 

THE  NOSE. 

The  nose  is  the  peripheral  portion  of  the  organ  of  smell  (organon  olfactus) :  by 
means  of  the  peculiar  properties  of  its  nerves  it  protects  the  lungs  from  the  inhala- 
tion of  deleterious  gases  and  assists  the  organ  of  taste  in  discriminating  the  prop- 
erties of  food.  The  organ  of  smell  consists  of  two  parts;  one  external,  the  outer 
nose;  the  other  internal,  the  nasal  fossae 

70 


1106 


THE    ORGANS    OF  SPECIAL    SENSE 


THE  OUTER  NOSE   (NASUS  EXTERNUS). 

The  outer  nose  is  the  more  anterior  and  prominent  part  of  the  organ  of  smell. 
Of  a  triangular  form,  it  is  directed  downward,  and  projects  from  the  centre  of 
the  face,  immediately  above  the  upper  lip.  Its  summit  or  root  (radix  nasi)  is 
connected  directly  with  the  forehead.  Its  inferior  part  or  base  (basis  nasi)  pre- 
sents two  elliptical  orifices,  the  nostrils  or  anterior  nares  (nares),  separated  from 
each  other  by  an  antero-posterior  septum,  the  mobile  septum  or  columna  nasi 
(septum  mobile  nasi).  The  margins  of  the  nostrils  are  provided  with  a  number 
of  stiff  hairs  or  vibrissae,  which  arrest  the  passage  of  foreign  substances  carried 
with  the  current  of  air  intended  for  respiration.  The  point  (apex  nasi)  is  the  free 
extremity  of  the  nose.  The  lateral  surfaces  of  the  nose  form,  by  their  union  in 
the  middle  line,  the  dorsum  (dorsum  nasi),  the  direction  of  which  varies  considerably 
in  different  individuals.  The  portion  of  the  dorsum  over  the  nasal  bones  is  the 
bridge.  Each  lateral  surface  terminates  below  in  a  rounded  eminence,  the  wing 
or  ala  nasi,  which,  by  its  lower  margin  (margo  nasi),  forms  the  outer  boundary 
of  the  corresponding  nostril.  Above  the  ala  is  a  depression,  the  alar  sulcus. 


Seen  from  below. 


Side  view. 


Lower  lateral  cartilage. 


Sesamoid  cartilages, 


FIGS.  719  and  720. — Cartilages  of  the  nose. 

Structure. — The  nose  is  composed  of  a  framework  of  bones  and  cartilages,  the 
latter  being  slightly  acted  upon  by  certain  muscles.  It  is  covered  externally  by  the 
integument,  internally  by  mucous  membrane,  and  is  supplied  with  vessels  and  nerves. 

The  Bony  Framework. — The  bony  framework  occupies  the  upper  part  of  the 
organ;  it  consists  of  the  nasal  bones  and  the  nasal  processes  of  the  superior  maxillary 
bones  (pp.  104  and  109). 

The  Cartilaginous  Framework  (cartilagines  nasi)  (Figs.  719  and  720). — The  car- 
tilaginous framework  consists  of  five  pieces,  the  two  upper  and  the  two  lower 
lateral  cartilages  and  the  cartilage  of  the  septum. 

The  Upper  Lateral  Cartilage  (cartilago  nasi  lateralis)  of  each  side  is  situated  below 
the  free  margin  of  the  nasal  bone.  It  is  flattened  and  triangular  in  shape.  Its  ante- 
rior margin  is  thicker  than  the  posterior,  and  continuous  with  the  cartilage  of  the 
septum.  Its  posterior  margin  is  attached  to  the  nasal  process  of  the  superior 
maxillary  and  nasal  bones.  Its  inferior  margin  is  connected  by  fibrous  tissue  with 
the  lower  lateral  cartilage;  one  surface  is  turned  outward,  the  other  inward  toward 
the  nasal  cavity. 


THE    OUTER    NOSE 


1107 


The  Lower  Lateral  Cartilage,  the  Cartilage  of  the  Aperture  or  the  Greater  Alar  Car- 
tilage ( cartilago  alaris  major)  of  each  side  consists  of  two  thin,  flexible  plates  situated 
immediately  below  the  preceding,  and  bent  upon  themselves  in  such  a  manner  as 
to  form  the  inner  and  outer  walls  of  the  orifice  of  the  nostril.  The  portion  which 
forms  the  inner  wall  (crus  mediale),  thicker  than  the  rest,  is  loosely  connected  with 
the  corresponding  portion  of  the  opposite  cartilage,  and  forms  a  small  part  of  the 
columna.  Its  inferior  border,  free,  rounded,  and  projecting,  forms,  with  the  thick- 
ened integument  and  subjacent  tissue  and  the  corresponding  parts  of  the  opposite 
side,  the  mobile  septum.  The  part  of  the  cartilage  which  forms  the  outer  wall  (crus 
latcrale)  is  curved  to  correspond  with  the  ala  of  the  nose;  it  is  oval  and  flattened, 
narrow  behind,  where  it  is  connected  with  the  nasal  process  of  the  superior  maxilla 
by  a  tough  fibrous  membrane,  in  which  are  found  three  or  four  small  cartilaginous 
plates,  the  sesamoid,  accessory  quadrate  or  lesser  alar  cartilages  (cartilagines  alares 
minores}.  Above,  it  is  connected  by  fibrous  tissue  to  the  upper  lateral  cartilage 
and  front  part  of  the  cartilage  of  the  septum;  below,  it  falls  short  of  the  margin 
of  the  nostril;  the  ala  being  formed  by  dense  cellular  tissue  covered  by  skin.  In 
front  the  lower  lateral  cartilages  are  separated  by  a  notch  which  corresponds 
with  the  point  of  the  nose. 

The  Triangular  Cartilage  of  the  Septum  (cartilago  septi  nasi)  (Figs.  719  and  721) 
is  somewhat  quadrilateral  in  form,  thicker  at  its  margins  than  at  its  centre,  and 
completes  the  separation  between  the 
nasal  fossae  in  front.  Its  anterior 
margin,  thickest  above,  is  connected 
with  the  nasal  bones,  and  is  continuous 
with  the  anterior  margins  of  the  two 
upper  lateral  cartilages.  Below,  it  is 
connected  to  the  inner  portions  of  the 
lower  lateral  cartilages  by  fibrous 
tissue.  Its  posterior  margin  is  con- 
nected with  the  perpendicular  lamella 
of  the  ethmoid ;  its  inferior  margin  with 
the  vomer  and  the  palate  processes  of 
the  superior  maxillary  bones  (Fig.  103). 

It  may  be  prolonged  backward 
(especially  in  children)  for  some  dis- 
tance between  the  vomer  and  perpen- 
dicular plate  of  the  ethmoid,  forming 
what  is  termed  the  sphenoidal  process 
(processus  sphenoidalis  septi  cartilaginei).  The  septal  cartilage  does  not  reach 
as  far  as  the  lowest  part  of  the  nasal  septum.  This  is  formed  by  the  inner 
portions  of  the  lower  lateral  cartilages  and  by  the  skin ;  it  is  freely  movable,  and 
hence  is  termed  the  mobile  septum. 

Along  the  lower  margin  of  the  anterior  half  of  the  cartilage  of  the  septum  is 
another  cartilage  which  is  attached  to  the  vomer  and  is  known  as  the  vomerine 
cartilage  or  cartilage  of  Jacobson  (cartilago  vomeronasalis) . 

These  various  cartilages  are  connected  to  each  other  and  to  the  bones  by  a  tough 
fibrous  membrane,  which  allows  the  utmost  facility  of  movement  between  them. 

The  Muscles  of  the  Nose. — The  muscles  of  the  nose  are  situated  beneath  the 
integument;  they  are  (on  each  side)  the  Pyramidalis  nasi,  the  Levator  labii  supe- 
riores  alaeque  nasi,  the  Dilatator  naris,  anterior  and  posterior,  the  Compressor 
nasi,  the  Compressor  narium  minor,  and  the  Depressor  alae  nasi.  They  have  been 
previously  described  (p.  378). 

The  Integument  covering  the  dorsum  and  sides  of  the  nose  is  thin,  and  loosely 
connected  with  the  subjacent  parts;  but  the  integument  of  the  tip  and  the  alae  of 


FIG.  721. — Bones  and  cartilages  of  septum  of  the  nose. 
Right  side. 


1108 


THE    ORGANS    OF   SPECIAL   SENSE 


the  nose  is  thicker  and  more  firmly  adherent,  and  is  furnished  with  a  large  number 
of  sebaceous  follicles,  the  orifices  of  which  are  usually  very  distinct. 

The  Mucous  Membrane  lining  the  interior  of  the  nose  is  continuous  with  the 
skin  externally  and  with  the  mucous  membrane  which  lines  the  nasal  fossae  within. 

The  Arteries  of  the  Outer  Nose. — The  arteries  of  the  nose  are  the  lateralis  nasi  from 
the  facial,  and  the  inferior  artery  of  the  septum  from  the  superior  coronary,  which 
supply  the  alae  and  septum,  the  sides  and  dorsum  being  supplied  from  the  nasal 
branch  of  the  ophthalmic  and  the  infraorbital. 

The  Veins  of  the  Outer  Nose. — The  veins  of  the  nose  terminate  in  the  facial  and 
ophthalmic. 

The  Lymphatics  of  the  Outer  Nose. — These  vessels  are  shown  in  Figs.  486,  488, 
and  489.  They  empty  chiefly  into  the  submaxillary  lymph  glands. 

The  Nerves  of  the  Outer  Nose.— The  nerves  for  the  muscles  of  the  nose  are  derived 
from  the  facial,  while  the  skin  receives  its  branches  from  the  infraorbital,  infra- 
trochlear,  and  nasal  branches  of  the  ophthalmic. 


THE  NASAL  FOSSAE   (CAVUM  NASI). 

The  nasal  fossae  are  two  irregular  cavities  situated  in  the  middle  of  the  face, 
one  on  each  side  of  the  middle  line,  and  extending  from  before  backward.  They 
open  in  front,  when  the  soft  parts  are  in  place,  by  the  two  nostrils  or  anterior  nares, 
and  terminate,  behind,  in  the  naso-pharynx  by  the  posterior  nares. 


FIG.  722. — External  wall  of  right  nasal  fossa,  parts  of  the  turbinates  having  been  cut  away  to  show  the 
orifices  of  the  sinuses  which  open  into  the  meatuses.     (Testut.) 

The  Anterior  Nares  (nares). — The  anterior  nares  are  somewhat  pear-shaped 
apertures,  each  measuring  about  one  inch  antero-posteriorly  and  half  an  inch 
transversely  at  their  widest  part.  The  nasal  fossae  in  the  dry  skull  open  in  front 
by  the  anterior  nasal  aperture  (apertura  pyriformis). 

The  Posterior  Nares  (choanae). — The  posterior  nares  are  two  oval  openings, 
which  are  smaller  in  the  living  or  recent  subject  than  in  the  skeleton,  because  they 


THE    NASAL    FOSSAE 


1109 


are  narrowed  by  the  mucous  membrane.  Each  measures  an  inch  in  the  vertical 
and  half  an  inch  in  the  transverse  direction  in  a  well-developed  adult  skull. 

For  the  description  of  the  bony  boundaries  of  the  nasal  fossae  see  section  on 
.Osteology  (p.  143). 

Inside  the  aperture  of  the  nostril  is  a  slight  dilatation,  the  vestibule  (vestibulum 
iiaxi),  which  extends  as  a  small  pouch,  the  ventricle,  toward  the  point  of  the  nose. 
Above  and  behind  the  vestibule  is  surrounded  by  a  prominence  (limen  nasi}. 
Below  the  prominence  the  vestibule  is  lined  with  skin;  above  and  behind  it  the 
fossa  is  lined  with  mucous  membrane.  The  fossa,  above  and  behind  the  vestibule, 
has  been  divided  into  two  parts:  an  olfactory  portion  (regio  olfactoria),  a  slit-like 
cavity,  comprising  the  upper  and  central  part  of  the  septum  and  probably  the 
superior  turbinated  bone,  and  a  respiratory  portion  (regio  respiratoria) ,  which  com- 
prises the  rest  of  the  fossa. 


Eye-ball 


Groove  (hiatus  semilunaris) 
leading  to  infundibulum 
Middle  turbinated  bone 

Middle  meatus 
Antrum  of  Highmore 
Inferior  meatus 

Inferior  turbinated  bone 


f  Buccal  cavity 

\  Space  between  cheek  and  gum 
Molar  tooth,  upper  jaw 


of  molar  tooth 


Inferior  dental  nerve 


FIG.  723. — Transverse  vertical  section  of  the  nasal  fossae.     The  section  is  made  anterior  to  the  superior 

turbinated  bones.     (Cryer.) 

Outer  Wall  (Figs.  722  and  723). — The  superior,  middle,  and  inferior  meatus 
(meatus  nasi  superior,  medius,  and  inferior]  are  described  on  pages  144  and  145. 
The  sphenoidal  air  sinus  opens  into  the  spheno-ethmoidal  recess  (recessus  spheno- 
ethmoidalis),  a  narrow  recess  above  the  superior  turbinated  bone  (Fig.  722).  The 
posterior  ethmoidal  cells  (cellula  ethmoidalis  posterior)  open  into  the  front  and  upper 
part  of  the  superior  meatus  (Fig.  722).  On  raising  or  cutting  away  the  middle  tur- 
binated bone  the  outer  wall  of  the  middle  meatus  is  fully  exposed  (Figs.  722  and 
723)  and  presents  (1)  a  rounded  elevation,  termed  the  bulla  ethmoidalis,  opening 
on  or  immediately  above  which  are  the  orifices  of  the  middle  ethmoidal  cells;  (2)  a 


1110  THE  ORGANS  OF  SPECIAL  SENSE 

deep,  narrow,  curved  groove,  in  front  of  the  bulla  ethmoidalis,  termed  the  hiatus 
semilunaris,  into  which  the  anterior  ethmoidal  cells  (cellula  ethmoidalis  anterior} 
and  the  antrum  of  Highmore  (sinus  maxillaris]  open,  the  orifice  of  the  latter  being 
placed  near  the  level  of  its  roof.  The  middle  meatus  is  prolonged,  above  and  in 
front,  into  the  infundibulum  (infundibulum  ethmoidale),  which  leads  into  the  frontal 
sinus  (sinus  frontal  is).  The  anterior  extremity  of  the  meatus  is  continued  into  a 
depressed  area  which  lies  above  the  vestibule  and  is  named  the  atrium  (atrium 
meatus  medii  mm").  The  nasal  duct  (ductus  nasalis)  opens  into  the  anterior  part 
of  the  inferior  meatus,  the  opening  being  frequently  overlapped  by  a  fold  of 
mucous  membrane,  and  from  the  orifice  of  the  duct  a  groove  leads  downward 
and  forward. 

The  Inner  Wall  (Fig.  723). — The  inner  wall  or  septum  is  frequently  more  or  less 
deflected  from  the  mesal  plane  (Figs.  101  and  723),  thus  limiting  the  size  of  one 
fossa  and  increasing  that  of  the  other.  Ridges  or  spurs  of  bone  growing  outward 
from  the  septum  are  also  sometimes  present.  Immediately  over  the  incisive 
foramen  at  the  lower  edge  of  the  cartilage  of  the  septum  a  depression,  the  naso- 
palatine  recess  (recessus  nasopalatinus} ,  may  be  seen.  In  the  septum  close  to  this 
recess  a  minute  orifice  may  be  discerned ;  it  leads  into  a  blind  pouch,  the  rudi- 
mentary organ  of  Jacobson  (organon  vomeronasale) ,  which  is  well  developed  in 
some  of  the  lower  animals,  but  is  rudimentary  in  man.  The  organ  is  supported 
by  a  plate  of  cartilage,  distinct  from  the  cartilage  of  the  septum,  the  cartilage  of 
Jacobson  (p.  1107).  The  cartilage  of  Jacobson  is  to  the  outer  side  of  the  lower 
edge  of  the  cartilage  of  the  septum.  The  diverticulum  opens  anteriorly  near  the 
floor  of  the  nose  and  close  by  Stenson's  foramen.  Just  below  the  opening  of 
the  blind  pouch  is  an  elevation,  the  eminence  of  Jacobson. 

The  Mucous  Membrane  (membrana  mucosa  nasi). — The  mucous  membrane  lining 
the  nasal  fossae  is  called  the  pituitary,  from  the  nature  of  its  secretion ;  or  Schneide- 
rian,  from  Schneider,  the  first  anatomist  who  showed  that  the  secretion  proceeded 
from  the  mucous  membrane,  and  not,  as  was  formerly  imagined,  from  the  brain. 
It  is  intimately  adherent  to  the  periosteum  or  perichondrium,  over  which  it  lies. 
It  is  continuous  externally  with  the  skin  through  the  anterior  nares,  and  with  the 
mucous  membrane  of  the  naso-pharynx  through  the  posterior  nares.  From  the 
nasal  fossae  its  continuity  may  be  traced  with  the  conjunctiva  through  the  nasal 
duct  and  lachrymal  canals ;  with  the  lining  membrane  of  the  tympanum  and  mas- 
toid  cells  through  the  Eustachian  tube;  and  with  the  frontal,  ethmoidal,  and 
sphenoidal  sinuses,  and  the  antrum  of  Highmore  through  the  several  openings  in 
the  meatuses.  The  mucous  membrane  is  thickest  and  most  vascular  over  the 
turbinated  bones.  It  is  also  thick  over  the  septum,  but  in  the  intervals  between 
the  spongy  bones  and  on  the  floor  of  the  nasal  fossae  it  is  very  thin.  Where  it 
lines  the  various  sinuses  and  the  antrum  of  Highmore  it  is  thin  and  pale. 

Owing  to  the  great  thickness  of  this  membrane,  the  nasal  fossae  are  much 
narrower,  and  the  turbinated  bones,  especially  the  lower  ones,  appear  larger  and 
more  prominent  than  in  the  skeleton.  From  the  same  circumstances  also  the 
various  apertures  communicating  with  the  meatuses  are  considerably  narrowed 
or  completely  closed.  The  vestibule  is  lined  by  modified  skin,  and  contains  hairs 
(vibrissae)  which  guard  the  entrance  of  the  nostril. 

Structure  of  the  Mucous  Membrane  (Fig.  724). — The  epithelium  covering  the 
mucous  membrane  differs  in  its  character  according  to  the  functions  of  the  part  of 
the  nose  in  which  it  is  found.  In  the  respiratory  portion  of  the  nasal  cavity  the 
epithelium  is  columnar  and  ciliated.  Interspersed  among  the  columnar  ciliated 
cells  are  goblet  or  mucin  cells,  while  between  their  bases  are  found  smaller  pyra- 
midal cells.  In  this  region,  beneath  the  epithelium  and  its  basement  membrane, 
is  a  fibrous  layer  infiltrated  with  lymph-corpuscles,  so  as  to  form  in  many  parts 


mi 


a  diffuse  adenoid  tissue,  which  is  particularly  plentiful  in  children,  and  beneath 
this  a  nearly  continuous  layer  of  smaller  and  larger  glands,  some  mucous  and  some 
serous,  the  ducts  of  which  open  upon  the  surface.  In  the  respiratory  portion  of 
the  mucous  membrane  there  is  an  extensive  anastomosing  plexus  of  veins,  which 
in  some  regions  forms  a  distinct  cavernous  tissue  (plexus  cavernosus  concharum). 
The  cavernous  tissue  is  particularly  distinct  over  the  inferior  turbinated  bones. 
In  the  olfactory  region  the  mucous  membrane  is  yellowish  in  color  and  the  epi- 
thelial cells  are  columnar  and  non-ciliated;  they  are  of  two  kinds,  supporting  cells 
and  olfactory  cells. 

The  Supporting  Cells  contain  oval  nuclei,  situated  in  the  deeper  parts  of  the  cells ; 
the  free  surface  of  each  cell  presents  a  sharp,  outline,  and  its  deep  extremity  is 
prolonged  into  a  process  which  runs  inward,  branching  to  communicate  with 
similar  processes  from  neighboring  cells,  so  as  to  form  a  network  in  the  deep  part 
of  the  mucous  membrane.  Lying  between  these  central  processes  of  the  support- 
ing cells  are  a  large  number  of  spindle-shaped  cells,  the  olfactory  cells,  which  con- 
sist of  a  large  spherical  nucleus  surrounded  by  a  small  amount  of  granular  proto- 
plasm, and  possessing  two  processes,  of  which  one  runs  outward  between  the 
columnar  epithelial  cells,  and  projects  on  the  surface  of  the  mucous  membrane 
as  a  fine,  hair-like  process,  the  olfactory  hair;  the  other  or  deep  process  runs  inward, 
is  frequently  beaded  like  a  nerve-fibre,  and  is  believed  by  most  observers  to  be  in 
connection  with  one  of  the  terminal  filaments  of  the  olfactory  nerve.  Beneath  the 


EPITHELIUM 


NERVE 
BUNDLESV         _— 


GLANDS    OF 
BOWMAN 


NERVE 
BUNDLES 


FIG.  724. — Section  of  the  olfactory  mucous  membrane.     (Cadiat.) 

epithelium,  extending  through  the  thickness  of  the  mucous  membrane,  is  a  layer 
of  tubular,,  often  branched,  glands,  the  glands  of  Bowman  (glandulae  olfactoriae) , 
identical  in  structure  with  serous  glands. 

The  Arteries  of  the  Nasal  Fossae. — The  arteries  of  the  nasal  fossae  are  the  anterior 
and  posterior  ethmoidal,  from  the  ophthalmic,  which  supply  the  ethmoidal  cells, 
frontal  sinuses,  and  roof  of  the  nose;  the  spheno -palatine,  from  the  internal  maxil- 
lary, which  supplies  the  mucous  membrane  covering  the  spongy  bones,  the 
meatuses,  and  septum;  the  inferior  artery  of  the  septum,  from  the  superior 
coronary  of  the  facial;  and  the  infraorbital  and  alveolar  branches  of  the  internal 
maxillary,  which  supply  the  lining  membrane  of  the  antrum.  The  ramifications 
of  these  vessels  form  a  close,  plexiform  network,  beneath  and  in  the  substance  of 
the  mucous  membrane. 

The  Veins  of  the  Nasal  Fossae. — The  veins  of  the  nasal  fossae  form  a  close,  cav- 
ernous-like  network  beneath  the  mucous  membrane.  This  cavernous  appearance 


1112  THE  ORGANS  OF  SPECIAL  SENSE 

is  especially  well  marked  over  the  lower  part  of  the  septum  and  over  the  middle 
and  inferior  turbinated  bones.  Some  of  the  veins  pass,  with  those  accompanying 
the  spheno-palatine  artery,  through  the  spheno-palatine  foramen;  and  others, 
through  the  alveolar  branch,  to  join  the  facial  vein;  some  accompany  the  eth- 
moidal  arteries,  and  terminate  in  the  ophthalmic  vein;  and,  lastly,  a  few  com- 
municate with  the  veins  in  the  interior  of  the  skull,  through  the  foramina  in  the 
cribriform  plate  of  the  ethmoid  bone,  and  the  foramen  caecum. 

The  Lymphatics  of  the  Nasal  Fossae. — The  lymphatics  can  be  injected  from  the 
subdural  and  subarachnoid  spaces,  and  form  a  plexus  in  the  superficial  portion  of 
the  mucous  membrane.  The  lymph  is  drained  partly  into  one  or  two  glands  which 
lie  near  the  great  cornu  of  the  hyoid  bone  and  partly  into  a  gland  situated  in  front 
of  the  axis. 

The  Nerves  of  the  Nasal  Fossae. — The  nerves  are:  the  olfactory,  the  nasal  branch 
of  the  ophthalmic,  filaments  from  the  anterior  dental  branch  of  the  superior  maxillary, 
the  Vidian,  the  naso-pala'tine,  descending  anterior  palatine,  and  nasal  branches 
of  Meckel's  ganglion.  The  olfactory,  the  special  nerve  of  the  sense  of  smell,  is 
distributed  to  the  olfactory  region,  and  has  been  already  referred  to  (p.  1019). 
The  nasal  branch  of  the  ophthalmic  division  of  the  trigeminal  nerve  distributes 
filaments  to  the  forepart  of  the  septum  and  outer  wall  of  the  nasal  fossae. 
Filaments  from  the  anterior  dental  branch  of  the  superior  maxillary  supply  the 
inferior  meatus  and  inferior  turbinated  bone.  The  Vidian  nerve  supplies  the 
upper  and  back  part  of  the  septum  and  superior  spongy  bone,  and  the  upper 
anterior  nasal  branches  from  the  spheno-palatine  ganglion  have  a  similar  distribution. 
The  naso-palatine  nerve  supplies  the  middle  of  the  septum.  The  larger  or 
anterior  palatine  nerve  supplies  the  lower  nasal  branches  to  the  middle  and  lower 
spongy  bones. 

Surgical  Anatomy. — Instances  of  congenital  deformity  of  the  nose  are  occasionally  met  with, 
such  as  complete  absence  of  the  nose,  an  aperture  only  being  present;  or  perfect  development 
on  one  side,  and  suppression  or  malformation  on  the  other;  or  there  may  be  imperfect  apposi- 
tion of  the  nasal  bones,  so  that  the  nose  presents  a  median  cleft  or  furrow.  Deformities  which 
have  been  acquired  are  much  more  common,  such  as  flattening  of  the  nose  (saddle  nose),  the  result 
of  syphilitic  necrosis,  imperfect  development  of  the  nasal  bones  in  cases  of  congenital  syphilis,  or 
a  lateral  deviation  of  the  nose  the  result  of  fracture. 

The  skin  over  the  alae  and  tip  of  the  nose  is  thick  and  closely  adherent  to  subjacent  parts. 
Inflammation  of  this  part  is  therefore  very  painful,  on  account  of  the  tension.  The  skin  is  largely 
supplied  with  blood,  and,  the  circulation  here  being  terminal,  vascular  engorgement  is  liable  to 
occur,  especially  in  women  at  the  menopause  and  in  both  sexes  from  disorders  of  digestion,  exposure 
to  cold,  etc.  The  skin  of  the  nose  also  contains  a  large  number  of  sebaceous  follicles,  and  these,  as 
a  result  of  intemperance,  are  apt  to  become  affected,  and  the  nose  becomes  reddened,  congested, 
and  irregularly  swollen.  To  this  condition  the  term  grog-blossom  is  popularly  applied.  In  some 
of  these  cases  there  is  enormous  hypertrophy  of  the  skin  and  subcutaneous  tissues,  producing 
pendulous  masses,  termed  lipomata  nasi.  Ordinary  epithelioma  and  rodent  ulcer  may  attack 
the  nose,  the  latter  being  the  more  common  of  the  two.  Lupus  and  syphilitic  ulceration  fre- 
quently attack  the  nose,  and  may  destroy  the  whole  of  the  cartilaginous  portion.  In  fact,  lupus 
vulgaris  begins  more  frequently  on  the  ala  of  the  nose  than  in  any  other  situation. 

Cases  of  congenital  occlusion  of  one  or  both  nostrils,  or  adhesion  between  the  ala  and  septum 
may  occur,  and  may  require  immediate  operation,  since  the  obstruction  much  interferes  with 
sucking.  Bony  closure  of  the  posterior  nares  may  also  occur. 

To  examine  the  nasal  cavities,  the  head  should  be  thrown  back  and  the  nose  drawn  upward, 
the  parts  being  dilated  by  some  form  of  speculum.  They  can  also  be  examined  with  the  little  finger 
or  a  probe,  and  in  this  way  foreign  bodies  detected.  A  still  more  extensive  examination  can  be 
made  by  Roux's  operation,  which  was  introduced  for  the  cure  of  ozcena.  This  operation  enables 
the  surgeon  to  remove  any  dead  bone  which  may  be  present  in  this  disease.  The  cartilaginous 
framework  of  the  nose  is  lifted  up  by  an  incision  made  inside  the  mouth,  through  the  junction 
of  the  upper  lip  with  the  bone;  the  septum  nasi  and  the  lateral  cartilages  are  divided  with  strong 
scissors  till  the  anterior  nares  are  completely  exposed.  The  posterior  nares  can  be  explored  by 
the  aid  of  reflected  light  from  the  mouth,  by  which  the  posterior  nares  can  be  illuminated.  The 
examination  is  very  difficult  to  carry  out,  and,  as  a  rule,  sufficient  information  regarding  the 


THE  EYE  1113 

presence  of  foreign  bodies  or  tumors  in  the  naso-pharynx  can  be  obtained  by  the  introduction 
of  the  finger  behind  the  soft  palate  through  the  mouth.  The  septum  of  the  nose  may  be  dis- 
placed or  deviate  from  the  middle  line:  this  may  be  the  result  of  an  injury  or  from  some  con- 
genital defect  in  its  development;  in  the  latter  case  the  deviation  usually  occurs  along  the  line 
of  union  of  the  vomer  and  mesethmoid,  and  rarely  occurs  before  the  seventh  year.  Sometimes 
the  deviation  may  be  so  great  that  the  septum  may  come  in  contact  with  the  outer  wall  of  the 
nasal  fossa,  and  may  even  become  adherent  to  it,  thus  producing  complete  obstruction.  Per- 
foration of  the  septum  is  not  an  uncommon  affection  and  may  arise  from  several  causes:  syphilitic 
or  tuberculous  ulceration,  blood-tumor  or  abscess  of  the  septum,  and  especially  in  workmen 
exposed  to  the  vapor  of  bichromate  of  potash,  from  the  irritating  and  corrosive  action  of  fumes. 
\\hen  small,  the  perforation  may  cause  a  peculiar  whistling  sound  during  respiration.  When 
large,  it  may  lead  to  the  falling  in  of  the  bridge  of  the  nose. 

Epistaxis  is  a  very  common  affection  in  children.  It  is  rarely  of  much  consequence,  and  will 
almost  always  subside,  but  in  the  more  violent  hemorrhages  of  later  life  it  may  be  necessary 
to  plug  the  posterior  nares.  In  performing  this  operation  it  is  desirable  to  remember  the  size 
of  the  posterior  nares.  A  ready  method  of  regulating  the  size  of  the  plug  to  fit  the  opening 
is  to  make  it  of  the  same  size  as  the  terminal  phalanx  of  the  thumb  of  the  patient  to  be  oper- 
ated on. 

.VrtA-o/  polypus  is  a  very  common  disease,  and  presents  itself  in  three  forms:  the  gelatinous, 
the  fibrous,  and  the  malignant.  The  first  is  by  far  the  most  common.  It  grows  from  the  mucous 
membrane  of  the  outer  wall  of  the  nasal  fossa,  where  there  is  an  abundant  layer  of  highly  vas- 
cular submucous  tissue;  rarely  from  the  septum,  where  the  mucous  membrane  is  closely  adher- 
ent to  the  cartilage  and  bone,  without  the  intervention  of  much,  if  any,  submucous  tissue.  The 
most  common  seat  of  gelatinous  polyps  is  probably  the  middle  turbinated  bone.  The  fibrous 
polypus  generally  grows  from  the  base  of  the  skull  behind  the  posterior  nares  or  from  the  roof 
of  the  nasal  fossae.  The  malignant  polypi,  both  sarcomatous  and  carcinomatous,  may  arise 
in  the  nasal  cavities  and  the  naso-pharynx;  or  they  may  originate  in  the  antrum,  and  protrude 
through  its  inner  wall  into  the  nasal  fossa. 

Rhinoliths  or  nose-stones  may  sometimes  be  found  in  the  nasal  cavities.  They  arise  from 
the  deposition  of  phosphate  of  lime  upon  either  a  foreign  body  or  a  piece  of  inspissated  secretion. 

The  nasal  passages  furnish  a  secretion  of  their  own  and  receive  secretion  from  other  parts 
(tears  and  secretions  of  the  accessory  sinuses).  The  nasal  cavities  contain  the  ethmoidal  laby- 
rinths, the  lateral  masses  of  the  ethmoid  (which  form  the  superior  and  middle  turbinated  bones), 
and  the  inferior  turbinated  bones.  The  nasal  cavity  is  surrounded  by  three  pairs  of  pneumatic 
spaces,  the  accessory  sinuses.  These  are  the  maxillary  sinuses,  the  frontal  sinuses,  and  the 
cells  of  the  ethmoidal  labyrinth.  The  lachrymal  duct  opens  into  the  inferior  meatus.  Inflam- 
mation of  the  air-cells  may  follow  inflammation  of  the  nasal  mucous  membrane  or  bone  disease. 
One  set  of  cells  or  many  may  suffer.  Suppuration  may  occur.  Pus  may  be  blocked  up  and 
retained.  Dead  bone  may  form.  The  most  serious  conditions  may  follow  (abscess  of  brain, 
sinus  thrombosis,  septicaemia),  and  an  operation  is  necessary  to  obtain  relief. 


THE  EYE. 

The  eyeball  or  globe  (hulbus  oculi)  (Figs.  725  and  729)  is  contained  in  the  ante- 
rior part  of  the  cavity  of  the  orbit.  In  this  situation  it  is  securely  protected  from 
injury,  whilst  its  position  is  such  as  to  ensure  the  most  extensive  range  of  sight. 
It  is  acted  upon  by  numerous  muscles,  by  which  it  is  capable  of  being  directed 
to  different  parts;  it  is  supplied  by  vessels  and  nerves,  and  is  additionally  pro- 
tected in  front  by  the  orbital  margins,  eyelids,  etc. 

The  eyeball  is  embedded  in  the  fat  of  the  orbit,  but  is  partly  surrounded  by 
a  thin  membranous  sac,  the  capsule  of  Te'non,  which  isolates  it,  so  as  to  allow 
of  free  movement. 

The  Fascia  or  Capsule  of  Te'non  (fascia  bulbi  [Tenoni\)  (Figs.  725  and 
726). — The  fascia  or  capsule  of  Tenon  consists  of  a  thin  membrane  which 
envelops  the  eyeball  from  the  optic  nerve  to  the  ciliary  region,  separating  it  from 
the  orbital  fat  and  forming  a  socket  in  which  it  plays.  Its  inner  surface  is  smooth, 
and  is  in  contact  with  the  outer  surface  of  the  sclerotic,  the  perisclerotic  or  supra- 
scleral  lymph-space  only  intervening.  This  lymph-space  is  continuous  with  the 
subdural  and  subarachnoid  spaces,  and  is  traversed  by  delicate  bands  of  con- 


1114 


THE  ORGANS  OF  SPECIAL  SENSE 


OPTIC   NERVE- 


CAPSULE 
OF  TENON 


FIG.  725. — The  right  eye  in  sagittal  section,  showing  the  capsule  of  Tenon  (semidiagrammatic).    (Testut.) 

nective  tissue  which  extend  between 
the  capsule  and  the  sclerotic.  This 
lymph-space  forms  a  flexible  pocket, 
in  which  the  globe  rotates.  The  cap- 
sule of  Tenon,  with  the  globe,  forms 
a  ball-and-socket  joint  (Deaver). 
The  capsule  is  perforated  behind  by 
d  the  ciliaxy  vessels  and  nerves  and  by 
the  optic  nerve,  being  continuous  with 
the  sheath  of  the  latter.  In  front  it 
blends  with  the  ocular  conjunctiva, 
and  with  it  is  attached  to  the  ciliary 
region  of  the  eyeball.  It  is  perforated 
by  the  muscles  which  move  the  eye- 
ball and  on  to  each  muscle  it  sends 
a  tubular  sheath.  The  sheath  of  the 
Superior  oblique  is  carried  as  far  as 

FIG.  726-— The  capsule  of  T<5non.     The  aponeurosis  is  the  fibroUS  pulley  of  that  muscle:  that 

seen  from  behind  forward  on  the  posterior  hemisphere  of  i        •     <•      •            i  i«                                          f 

theglobe:a,cellulo-nbrousintermuscular  laminae;  b,  deep  On  the  interior  ObllOUe   reaches  as  tar 

leaf  of  the  sheath  incised  at  the  point  where  it  leaves  the  ,  i         n               t    ,  i             i  • ,                  i  •    i     • , 

muscle  to  fold  itself  on  the   posterior   hemisphere  when  as   the    IlOOr    Ot    the  Orbit,    tO   WhlCll   it 

it  forms  the  posterior  capsule;  d,  partly  incised;  c,  serous  •„„      ^flp   „      !•           T*U^   ^U^+l™        ,    +U« 

membrane.     (Poirier  and  Charpy.)  glVCS  On   a   Slip.       1  he  Sheaths  On    the 

recti  are  gradually  lost  in   the  peri- 

mysium,  but  they  give  off  important  expansions.  The  expansion  from  the 
Superior  rectus  blends  with  the  tendon  of  the  Levator  palpebrae;  that  of  the 
Inferior  rectus  is  attached  to  the  inferior  tarsal  plate.  These  two  recti,  therefore, 
will  exercise  some  influence  on  the  movements  of  the  eyelids.  The  expansions 


THE  EYE 


1115 


from  the  sheaths  of  the  Internal  and  External  recti  are  strong,  especially  the  one 
from  the  latter  muscle,  and  are  attached  to  the  lachrymal  and  malar  bones  respec- 
tively. As  they  probably  check  the  action  of  these  two  recti,  they  have  been 
named  the  internal  and  external  check  ligaments. 

Lockwood  has  also  described  a  thickening  of  the  lower  part  of  the  capsule  of 
Tenon,  which  he  has  named  the  suspensory  ligament  of  the  eye.  It  is  slung  like  a 
hammock  below  the  eyeball,  being  expanded  in  the  centre  and  narrow  at  its 
extremities,  which  are  attached  to  the  malar  and  lachrymal  bones  respectively.1 

The  anterior  one-third  of  the  globe  is  covered  by  the  conjunctiva,  or  mucous 
membrane,  reflected  from  the  inner  surfaces  of  the  lids  (Fig.  728).  A  lateral  view 


POSTERIOR  CHAMBER 
OF  EYE 


CILIARY 
PROCESS 


PARS  CILIARIS 
RETINAE 


ORA  SERRATA 


PARS  OPTIC  A 
RETINJE 


SCLEROTIC 


YELLOW 
SPOT 


OPTIC 
EXCAVATION 


FIG.  727. — The  right  eye  iix  horizontal  section.     (Toldt.) 

of  the  globe  shows  that  it  is  composed  of  segments  of  two  spheres  of  different  sizes 
(Figs.  725,  727,  728,  and  729).  The  anterior  segment  is  one  of  a  small  sphere,  and 
forms  about  one-sixth  of  the  eyeball.  It  is  more  prominent  than  the  posterior  seg- 
ment, which  is  one  of  a  much  larger  sphere,  and  forms  about  five-sixths  of  the  globe. 
The  segment  of  the  larger  sphere  is  opaque,  and  formed  by  the  sclerotic,  the  tunic 
of  protection  to  the  eyeball ;  the  smaller  sphere  is  transparent,  and  formed  by  the 
cornea.  Between  the  small,  anterior  or  corneal  segment,  and  the  large,  posterior 
or  scleral  segment,  is  a  shallow  and  narrow  groove,  the  scleral  sulcus  (sulcus  sclerae). 
The  anterior  pole  is  the  centre  of  the  anterior  portion  of  the  cornea.  The  posterior 
pole  is  the  centre  of  the  posterior  portion  of  the  sclerotic.  A  straight  line  joining 
these  two  poles  is  the  sagittal  or  optic  axis  (axis  optica)  (Fig.  727).  A  line  drawn 
around  the  eyeball  equally  distant  at  all  points  from  the  two  poles  is  called  the 


1  See  a  paper  by  C.  B.  Lockwood,  Journal  of  Anatomy  and  Physiology,  vol.  xx.,  part  i.,  p.  1. — ED   of  15th 
English  edition. 


1116 


THE  ORGANS  OF  SPECIAL  SENSE 


equatorial  diameter  or  the  equator  (Fig.  727).  The  plane  of  the  equator  divides 
the  globe  in  an  anterior  and  a  posterior  hemisphere.  Meridians  may  be  drawn  from 
one  pole  to  the  other  at  right  angles  to  the  equator.  The  visual  axis  (linea  visus) 
(Fig.  727)  passes  in  a  straight  line  from  the  first  nodal  point  on  the  cornea  to  the 
fovea  centralis  of  the  yellow  spot  on  the  retina.  A  nodal  point  is  the  point  of  inter- 
section of  convergent  rays  with  the  visual  axis.  The  first  nodal  point  is  6.9685  mm. 


FIG.  728. — Diagram  of  a  horizontal  section  of  the  right  eye,  showing  the  upper  surface  of  the  lower 

segment.      (Testut.) 


behind  the  summit  of  the  cornea.  The  axes  of  the  eyeballs  are  nearly  parallel, 
and  therefore  do  not  correspond  to  the  axes  of  the  orbits,  which  are  directed 
outward.  The  optic  nerves  follow  the  direction  of  the  axes  of  the  orbits,  and 
are  therefore  not  parallel;  each  nerve  enters  its  eyeball  about  1  mm.  below  and 
3  mm.  to  the  inner  or  nasal  side  of  the  posterior  pole  (Fig.  727).  The  eyeball 
measures  rather  more  in  its  transverse  and  antero-posteror  diameters  than  in  its 
vertical  diameter,  the  former  amounting  to  nearly  an  inch,  the  latter  to  about 
nine-tenths  of  an  inch.  The  diameters  in  the  female  are  somewhat  less  than 
in  the  male. 

The  eyeball  is  composed  of  three  investing  tunics  and  of  three  refracting  media. 


THE    SCLERA 


1117 


THE  TUNICS  OF  THE  EYE. 

From  without  inward  the  three  tunics  are: 

I.  Sclerotic  Coat  and  Cornea. 
II.  Choroid,  Ciliary  Body,  and  Iris. 
III.  Retina. 

I.  The  Fibrous  or  External  Coat:  The  Sclerotic  and  Cornea 
(Tunica  Fibrosa  Oculi). 

The  sclerotic  and  cornea  (Figs.  727,  728,  and  729)  form  the  external  tunic  of 
the  eyeball;  they  are  essentially  fibrous  in  structure,  the  sclerotic  being  opaque, 
and  forming  the  posterior  five-sixths  of  the  globe;  the  cornea,  which  forms  the 
remaining  sixth,  being  transparent. 

The  Sclera  or  Sclerotic  Coat  (axXypbs,  hard).— The  sclera  or  sclerotic  coat 
has  received  its  name  from  its  extreme  density  and  hardness;  it  is  a  firm,  unyield- 
ing, opaque,  fibrous  membrane,  forming  the  posterior  five-sixths  of  the  outer  coat 


Canal  of  Schlemm. 


Posterior 
chamber. 
Ciliary 


Cavity  occupied 
by  vitreous  humor 


Retina. 


Choroid 
coat. 


Sclerotic  coat. 

Nerve  sheath. 


Canal  for 
"central  artery. 


Optic  nerve. 


FIG.  729. — A  horizontal  section  of  the  eyeball.     (Allen.) 

and  serving  to  maintain  the  form  of  the  globe.  It  is  much  thicker  behind  than  in 
front.  Its  external  surface  is  of  a  white  color,  and  is  in  contact  with  the  inner 
surface  of  the  capsule  of  Tenon,  a  lymph-space  intervening;  it  is  quite  smooth, 
except  one-quarter  of  an  inch  back  of  the  sclero-corneal  junction,  at  the  points 
where  the  Recti  and  Obliqui  muscles  are  inserted  into  it,  and  its  anterior  part  is 
covered  by  the  conjunctival  membrane  (Fig.  757);  hence  the  whiteness  and  bril- 
liancy of  the  front  of  the  eyeball.  Its  inner  surface  is  stained  a  brown  color,  marked 
by  grooves,  in  which  are  lodged  the  ciliary  nerves  and  vessels  (Figs.  732,  737,  and 
738) ;  the  inner  surface  of  the  sclera  is  loosely  connected  by  three  layers  of  exceed- 


1118  THE  ORGANS  OF  SPECIAL  SENSE 

ingly  fine  cellular  pigmented  tissue  (lamina  fusca)  with  the  outer  surface  of  the 
choroicl,  an  extensive  lymph-space,  the  perichoroidal  space  (spatium  perichorioideale) 
(Figs.  740  and  757)  intervening  between  the  sclerotic  and  choroid.  Behind,  the 
sclera  is  pierced  by  the  optic  nevre  (n.  opticus),  and  is  continuous  with  the  fibrous 
sheath  of  the  nerve,  which  is  derived  from  the  dura  (Fig.  734).  At  the  point  where 
the  optic  nerve  passes  through  the  sclerotic,  the  lamina  fusca  is  represented  by  an 
arrangement  of  the  fibrous  tissue  which  forms  a  thin  network,  the  cribriform  lamina 
(lamina  cribrosa  sclerae)  (Fig.  744) ;  the  minute  orifices  in  this  network  serve  for  the 
transmission  of  separate  bundles  of  nervous  filaments,  and  the  fibrous  septa  divid- 
ing them  from  one  another  are  continuous  with  the  membranous  processes  which 
separate  the  bundles  of  nerve-fibres.  One  of  these  openings  (porus  opticus),  larger 
than  the  rest,  occupies  the  centre  of  the  lamella;  it  transmits  the  arteria  centralis 
retinae  to  the  interior  of  the  eyeball  (Fig.  744).  Around  the  cribriform  lamella  are 
numerous  small  apertures  for  the  transmission  of  the  ciliary  nerves  and  the  short 
ciliary  arteries,  and  about  midway  between  the  margin  of  the  cornea  and  the 
entrance  of  the  optic  nerve  are  four  or  five  large  apertures,  for  the  transmission  of 
veins  (venae  vorticosae)  (Fig.  757).  In  front,  the  fibrous  tissue  of  the  sclerotic  is  con- 
tinuous with  the  substantia  propria  of  the  cornea  by  direct  continuity  of  tissue  (Fig. 
757),  but  the  opaque  sclerotic  slightly  overlaps  the  outer  surface  of  the  transparent 
cornea.  In  the  depths  of  the  line  of  junction  between  the  cornea  and  the  sclera 
there  is  a  circular  canal,  the  canal  of  Schlemm  (sinus  venosus  sclerae)  (Figs.  729, 736, 
740,  and  757).  This  canal  receives  the  sclera  veins  (Fig.  736)  and  communicates 
internally  by  numerous  minute  openings  in  the  pectineal  ligament  of  the  iris  (Fig. 
757)  with  the  anterior  chamber  of  the  eyeball.  These  openings  are  the  spaces  of 
Fontana  (Fig.  740). 

Structure. — The  sclerotic  is  formed  of  white  fibrous  tissue  intermixed  with  fine 
elastic  fibres,  and  of  flattened  connective-tissue  corpuscles,  some  of  which  are  pig- 
mented, contained  in  cell-spaces  between  the  fibres  (Figs.  733  and  744).  These 
fibres  are  aggregated  into  bundles,  some  of  which  are  arranged  in  layers  having  an 
equatorial  direction,  but  most  of  which  are  arranged  in  layers  lying  in  meridian 
lines.  The  sclera  is  joined  to  the  choroid  by  three  thin  layers  of  loose  connective 
tissue  containing  pigment  cells,  the  lamina  fusca  (lamina  fasciae  sclerae)  (Fig.  737). 
Where  the  optic  nerve  passes  through  the  sclera  there  is  very  thin  network  to  repre- 
sent the  lamina  fusca.  This  network  is  the  lamina  cribrosa  (Fig.  744).  The  muscles 
of  the  eyeball  are  attached  to  the  sclera  (Figs.  728,  729,  and  757),  and  their  tendons 
enter  among  the  bundles  of  fibrous  connective  tissue.  The  conjunctiva  covers  the 
anterior  portion  of  the  sclera  and  is  attached  to  it  by  submucous  tissue  (Figs.  728 
and  740).  The  sclera  yields  gelatin  on  boiling.  Its  vessels  (Figs.  734  and  736)  are 
not  numerous,  the  capillaries  being  of  small  size  and  uniting  at  long  and  wide  inter- 
vals. It  obtains  arterial  blood  from  the  short  posterior  ciliary  and  the  anterior  ciliary 
arteries.  The  venous  blood  is  removed  by  the  venae  vorticosae  and  the  anterior  ciliary 
veins.  There  are  lymph-spaces  between  the  cells  which  empty  into  the  periscleral 
(Fig.  725  and  p.  1114)  and  perichoroidal  lymph-spaces  (Fig.  740).  Its  nerves  are 
derived  from  the  ciliary  nerves  (Fig.  732).  They  lose  their  medullary  sheaths  and 
enter  among  the  bundles  of  fibrous  tissue,  but  it  is  not  known  how  they  terminate. 

The  Cornea  (Figs.  725, 728,  and  734). — The  cornea  is  the  projecting  transparent 
part  of  the  external  tunic  of  the  eyeball,  and  forms  the  anterior  sixth  of  the  globe.  It 
is  almost,  but  not  quite,  circular  in  shape,  occasionally  a  little  broader  in  the  trans- 
verse than  in  the  vertical  direction.  It  is  convex  anteriorly,  and  projects  forward 
from  the  sclerotic  in  the  same  manner  that  a  watch-glass  does  from  the  case.  Its 
degree  of  curvature  varies  in  different  individuals,  and  in  the  same  individual  at  dif- 
ferent periods  of  life,  it  being  more  prominent  in  youth  than  in  advanced  life,  when 
it  becomes  flattened.  Usually  the  curvature  is  slightly  greater  in  the  vertical  plane 
than  in  the  horizontal  plane;  at  its  centre  than  at  its  periphery,  and  at  its  temporal 
than  at  its  nasal  side.  The  cornea  is  dense  and  of  uniform  thickness  throughout; 


THE    CORNEA 


1119 


its  posterior  surface  is  perfectly  circular  in  outline,  and  exceeds  the  anterior  sur- 
face slightly  in  extent,  from  the  latter  being  overlapped  by  the  sclerotic.  The 
anterior  surface  is  covered  with  conjunctiva  (Fig.  740). 

Structure  (Fig.  730). — The  cornea  consists  of  five  layers — namely:  (1)  the  anterior 
or  epithelial  layer;  (2)  the  anterior  elastic  layer;  (3)  the  substantia  propria;  (4) 
the  posterior  elastic  layer;  (5)  the  posterior  or  endothelial  layer. 


Anterior 
epithelium 


^Substantia 
'  propria 


-Posterior 
epithelium 
FIG  730. — Vertical  section  through  the  cornea  of  a  newborn  child.     X  200.     (Szymonowicz.) 

(1)  The  Anterior  Layer  (epithelium  corneae]  is  composed  of  stratified  epithelium 
and  is  continuous  with  the  cells  of  the  conjunctiva  at  the  borders  of  the  cornea. 
There  are  from  five  to  eight  strata  of  nucleated  cells  in  the  anterior  layer.     The 
deepest  cells  are  columnar.     Above  the  columnar  cells  are  several  layers  of 
polygonal  cells,  most  of  which  have  finger-like  processes  and  are  called  prickle 
cells.     At  the  surface  the  cells  and  nuclei  become  flat.    The  anterior  epithelial 
layer  prevents  the  absorption  of  the  fluid  of  the  tears. 

(2)  The  Anterior  Elastic  or  Anterior  Limiting  Layer  or  Bowman's  Membrane  (lamina 
elastica  anterior)  is  less  than  half  the  thickness  of  the  layer  of  stratified  epithelium. 


1120 


THE   ORGANS    OF  SPECIAL   SENSE 


It  differs  in  some  essential  respects  from  true  elastic  tissue.  It  shows  evidences 
of  fibrillary  structure,  and  does  not  have  a  tendency  to  curl  inward  or  to  undergo 
fracture  when  detached  from  the  other  layers  of  the  cornea.  It  consists  of  ex- 
tremely close  interwoven  fibrils,  similar  to  those  found  in  the  rest  of  the  cornea 
proper,  but  contains  no  corneal  corpuscles.  It  ought,  therefore,  to  be  regarded 
as  a  part  of  the  proper  tissue  of  the  cornea* 

(3)  The  Substantia  Propria  or  proper  substance  of  the  cornea  forms  the  main 
thickness  of  that  structure.  It  is  fibrous,  tough,  unyielding,  perfectly  transparent, 
and  continuous  with  the  sclerotic.  It  is  composed  of  about  sixty  flattened  lamellae, 
superimposed  one  on  another.  These  lamellae  are  made  up  of  bundles  of  modified 
connective  tissue,  the  fibres  of  which  are  directly  continuous  with  the  fibres  of  the 
sclerotic.  The  fibres  of  each  lamella  are  for  the  most  part  parallel  with  each 
other;  those  of  alternating  lamellae  at  right  angles  to  each  other.  Fibres,  however, 
frequently  pass  obliquely  from  one  lamella  to  the  next  (fibrae  arcuatae). 

The  lamellae  are  connected  with  each  other  by  an  interstitial  cement-substance, 
in  which  are  spaces,  the  corneal  spaces,  cell  spaces  or  lacunae  (Fig.  731).  The 
spaces  are  stellate  in  shape,  and  have  numerous  offsets  or  canaliculi  (Fig.  731), 
by  which  they  communicate  with  each  other.  Each  space  contains  a  cell,  the 
corneal  corpuscle  (Fig.  731),  which  resembles  in  form  the  space  in  which  it  is 


Lymph  canaliculi 


Corneal  cell  in 
lymph  space 


FIG.  731. — From  a  horizontal  section  of  an  ox's  cornea.     Positive  picture  of  the  canal  system  demonstrated 
by  the  gold  chloride  method.     X  450.     (Szymonowicz.) 


lodged,  but  it  does  not  entirely  fill  it,  the  remainder  of  the  space  containing 
lymph.  In  the  aged  the  margin  of  the  cornea  becomes  opaque  gray.  This  rim 
is  called  the  arcus  senilis,  and  is  due  to  fat  deposit  in  the  lamellae  and  corneal 
corpuscles. 

(4)  The  Posterior  Elastic  Lamina,  the  Membrane  of  Descemet,  or  the  Membrane 
of  Demours  (lamina  elastica  posterior],  which  covers  the  proper  structure  of  the 
cornea  behind,  presents  no  structure  recognizable  under  the  microscope.  It 
consists  of  an  elastic,  and  perfectly  transparent  homogeneous  membrane,  of 
extreme  thinness,  which  is  not  rendered  opaque  by  either  water,  alcohol,  or  acids. 
It  is  very  brittle,  but  its  most  remarkable  property  is  its  extreme  elasticity,  and 
the  tendency  which  it  presents  to  curl  up,  or  roll  upon  itself,  with  the  attached 
surface  innermost,  when  separated  from  the  proper  substance  of  the  cornea.  Its 
use  appears  to  be  (as  suggested  by  Dr.  Jacob)  "to  preserve  the  requisite  perma- 
nent correct  curvature  of  the  flaccid  cornea  proper." 

At  the  margin  of  the  cornea  this  posterior  elastic  membrane  breaks  up  into  fibres 
to  form  a  reticular  structure  at  the  outer  angle  of  the  anterior  chamber,  the  intervals 
between  the  fibres  forming  small  cavernous  spaces,  the  spaces  of  Fontana  (spatia 


THE  CHOROID  1121 

anguli  iridis)  (Fig.  740).  These  little  recesses  communicate  with  a  circular  canal 
in  the  deeper  parts  of  the  corneo-scleral  junction.  This  is  the  canal  of  Schlemm 
(Figs.  729,  736,  and  740);  it  communicates  internally  with  the  anterior  chamber 
through  the  spaces  of  Fontana,  and  externally  with  the  scleral  veins.  Some  of  the 
fibres  of  this  reticulated  structure  are  continued  into  the  front  of  the  iris,  forming 
the  ligamentum  pectinatum  iridis;  while  others  are  connected  with  the  forepart  of 
the  sclerotic  and  choroid. 

(5)  The  Posterior  Layer  or  the  Cornea!  Endothelium  (endothelium  camerae  ante- 
riorift)  lines  the  aqueous  chamber  and  prevents  the  absorption  of  the  aqueous 
humor.  It  covers  the  posterior  surface  of  the  elastic  lamina,  is  reflected  on  to 
the  front  of  the  iris,  and  also  lines  the  spaces  of  Fontana.  It  consists  of  a  single 
layer  of  polygonal  flattened  transparent  nucleated  cells,  similar  to  those  lining 
other  serous  cavities. 

Arteries  and  Nerves. — The  foetal  cornea  contains  blood-vessels  which  pass  from 
the  margin  almost  to  the  centre.  The  adult  cornea  contains  no  blood-vessels, 
except  at  its  margin.  The  capillaries  from  the 'solera  and  conjunctiva  form  loops 
at  the  corneal  margin,  and  many  of  these  loops  enter  the  cornea  for  a  distance  of 
1  mm.  (Fig.  736).  The  balance  of  the  cornea  is  non-vascular  and  obtains  its 
nourishment  from  the  lymph  in  the  lacunae  and  canaliculi.  Lymphatic  vessels 
have  not  as  yet  been  demonstrated  in  it,  but  are  represented  by  the  channels  in 
which  the  bundles  of  nerves  run;  these  channels  are  lined  by  endothelium  and  are 
continuous  with  the  cell-spaces.  The  nerves  are  numerous,  twenty-four  to  thirty- 
six  in  number  (Kolliker),  forty  to  forty-five  (Waldeyer  and  Siimisch);  they  are 
derived  from  the  ciliary  nerves;  they  form  the  annular  plexus  (plexus  annularis), 
at  the  corneal  margin,  and  enter  the  laminated  tissue  of  the  cornea,  lose  their 
medullary  sheaths,  and  ramify  throughout  the  substantia  propria  as  the  funda- 
mental plexus  or  the  plexus  of  the  stroma.  From  this  deep  plexus  come  perforating 
fibres  (fibrae  perforantes) ,  which  pass  through  the  anterior  elastic  lamina  and  form 
the  subepithelial  plexus,  and  from  it  fibrils  are  given  off  which  ramify  between 
the  epithelial  cells,  forming  a  network  which  is  termed  the  intra-epithelial  plexus. 
Nerve-fibres  from  the  annular  plexus  and  from  the  plexus  of  the  stroma  come 
into  close  relation  with  the  corneal  corpuscles. 

Dissection. — In  order  to  separate  the  sclerotic  and  cornea,  so  as  to  expose  the  second  tunic, 
the  eyeball  should  be  immersed  in  a  small  vessel  of  water  and  held  between  the  finger  and  thumb. 
The  sclerotic  is  then  carefully  incised,  in  the  equator  of  the  globe,  till  the  choroid  is  exposed. 
One  blade  of  a  pair  of  probe-pointed  scissors  is  now  introduced  through  the  opening  thus  made, 
and  the  sclerotic  divided  around  its  entire  circumference,  and  removed  in  separate  portions. 
The  front  segment  being  then  drawn  forward,  the  handle  of  the  scalpel  should  be  pressed  gently 
against  it  at  its  connection  with  the  iris,  and,  these  being  separated,  a  quantity  of  perfectly  trans- 
parent fluid  will  escape;  this  is  the  aqueous  humor.  In  the  course  of  the  dissection  the  ciliary 
nerves  (Fig.  732)  may  be  seen  lying  in  the  loose  cellular  tissue  between  the  choroid  and  sclerotic 
or  continued  in  delicate  grooves  on  the  inner  surface  of  the  latter  membrane. 

II.  The  Choroid,  Ciliary  Body,  and  Iris,  the  Tunica  Media,  the  Uveal  Tract 
(Tunica  Vasculosa  Oculi)  (Figs.  727,  729,  732,  737,  757). 

The  second  or  middle  tunic  of  the  eye  is  formed  from  behind  forward  by  the 
choroid,  the  ciliary  body,  and  the  iris. 

The  choroid  is  the  vascular  and  pigmentary  tunic  of  the  eyeball,  investing  the 
posterior  five-sixths  of  the  globe,  and  extending  as  far  forward  as  the  ora  serrata 
of  the  retina;  the  ciliary  body  connects  the  choroid  to  the  circumference  of  the 
iris.  The  iris  is  the  circular  muscular  septum,  which  hangs  vertically  behind  the 
cornea,  presenting  in  its  centre  a  large  rounded  aperture,  the  pupil. 

The  Choroid  (chorioidea). — The  choroid  is  a  thin,  highly  vascular  membrane, 
of  a  dark-brown  or  chocolate  color,  which  invests  the  posterior  five-sixths  of  the 

71 


1122 


THE    ORGANS    OF   SPECIAL    SENSE 


globe,  and  is  pierced  behind  by  the  optic  nerve,  and  in  this  situation  is  firmly 
adherent  to  the  sclerotic.     It  is  thicker  behind  than  in  front.     Externally,  it  is 

loosely  connected  by  the  lamina 
fusca  with  the  inner  surface  of  the 
sclerotic  (p.  1118).  Its  inner  sur- 
face is  attached  to  the  retina. 

Structure  (Fig.  733) .— The  choroid 
consists  of  a  dense  capillary  plexus 
and  of  small  arteries  and  veins, 
carrying  the  blood  to  and  returning 
it  from  this  plexus  (Fig.  736),  and  of 
branched  and  pigmented  cells  which 
lie  in  connective  tissue.  There  are 
three  layers  in  the  choroid.  Named 
from  without  inward,  they  are  the 
lamina  suprachorioidea,  the  choroid 
proper,  and  lamina  basalis  (Fig.  733) . 
(1)  The  Lamina  Suprachorioidea 
is  on  the  external  surface,  that  is, 
the  surface  next  to  the  sclerotic. 

It  resembles  the  lamina  fusca  of 
the  sclerotic.  It  is  composed  of 
delicate  non-vascular  lamellae,  each 
lamella  consisting  of  a  network  of 
fine  elastic  fibres,  among  which  are 
branched  pigment-cells.  The  spaces 
between  the  lamellae  are  lined  by 
endothelium,  and  open  freely  into  the  perichoroidal  lymph-space,  which,  in  its 
turn,  communicates  with  the  periscleral  space  by  the  perforations  in  the  sclerotic 
through  which  the  vessels  and  nerves  are  transmitted. 

(2)  The  Choroid  Proper  is  internal  to  the  lamina  suprachorioidea.  In  consequence 
of  the  small  arteries  and  veins  of  the  choroid  proper  being  arranged  on  the  outer 
surface  of  the  capillary  network,  it  is  customary  to  describe  this  as  consisting  of 
two  layers:  the  outermost  (lamina  vasculosa),  composed  of  small  arteries  and 


FIG.  732.— The  choroid  and  iris.     (Enlarged.) 


Pigment  layer 
of  retina 

Lamina 
basalts' 

Lamina 

chorio- 

capillaris 

Lamina 
vasculosa 


Lamina  supra- 

chorioidea 


Part  of  the 
sdera 


FIG.  733.— Vertical  section  through  the  chorioidea  and  a  part  of  the  sclera  of  an  ape.     X  440.     (Szymonowicz.) 


veins,  with  pigment-cells  interspersed  between  them,  and  the  inner  (lamina 
choriocapillaris) ,  consisting  of  a  capillary  plexus.  The  external  layer  of  the  choroid 
proper  or  the  lamina  vasculosa  consists,  in  part,  of  the  larger  branches  of  the  short 


THE    CHOROID 


1123 


posterior  ciliary  arteries  (Figs.  734,  736,  and  738).  which  run  forward  between  the 
veins,  before  they  bend  inward  to  terminate  in  the  capillaries;  but  this  layer  is 


VENA 
VORTICOSA 


ANTERIOR 
•S     CILIARY 
I     ARTERY 


-SCLEROTIC 


SHORT 

POSTERIOR 

CILIARY 

ARTERIES 


LONG    POSTERIOR 
CILIARY    ARTERY 


FIG.  734. — Vessels  and  nerves  of  the  choroid  and  iris,  seen  from  above.     The  sclerotic  and  cornea  have 
been  largely  removed.     (Testut.) 

formed  principally  of  veins,  which  have  a  whirl-like  arrangement  and  empty  into 
four  or  five  large  equidistant  trunks,  the  venae  vorticosae  (Figs.  734,  735,  and  736), 
which  pierce  the  sclerotic  midway 
between  the  margin  of  the  cornea 
and  the  entrance  of  the  optic 
nerve.  Around  the  veins  are 
lymph-spaces.  Interspersed  be- 
tween the  vessels  are  dark  star- 
shaped  pigment-cells,  the  offsets 
from  which,  communicating  with 
similar  branchings  from  neigh- 
boring cells,  form  a  delicate  net- 
work or  stroma,  which  toward 
the  inner  surface  of  the  choroid 
loses  its  pigmentary  chraacter. 
The  internal  layer  of  the  choroid 
proper  consists  of  an  exceedingly 
fine  capillary  plexus,  formed  by 
the  short  ciliary  vessels  (Fig.  736), 

and    is    known    as    the    tunic     Of  FIG.  735.— The  veins  of  the  choroid.     (Enlarged.) 

Ruysch  (lamina  choriocapillaris) . 

The  network  is  close,  and  finer  at  the  hinder  part  of  the  choroid  than  in  front. 

About  half  an  inch  behind  the  cornea  its  meshes  become  larger,  and  are  continuous 


1124 


THE    ORGANS   OF  SPECIAL    SENSE 


with  those  of  the  ciliary  processes.  These  two  laminae  are  connected  by  an  interme- 
diate stratum,  which  is  destitute  of  pigment-cells  and  consists  of  fine  elastic  fibres. 
On  the  inner  surface  of  the  lamina  choriocapillaris  is  a  very  thin,  structureless, 
or,  according  to  Kolliker,  faintly  fibrous  membrane,  called  the  lamina  basalis 
or  membrane  of  Bruch;  it  is  closely  connected  with  the  stroma  of  the  choroid,  and 
separates  it  from  the  pigmentary  layer  of  the  retina. 


Oornea-U 


Iris 


Lens 


FIG.  736.  —  Diagram  of  the  blood-vessels  of  the  eye,  as  seen  in  a  horizontal  section.     (Leber,  after  Stohr.) 


,  .  . 

Course  of  vasa  centralia  retinae:  a,  arteria,  ai  vena  centralis  retinae;  /?,  anastomosis  with  vessels  of  outer 
coats;  7,  anastomosis  with  branches  of  short  posterior  ciliary  arteries;  (J,  anastomosis  with  chorioideal  vessels. 

Course  of  vasa  ciliar.  postic.  brev.  :  I,  arteriae,  and  Ij,  venae  ciliar.  postic.  brev.;  II,  episcleral  artery; 
III,  episcleral  vein;  III,  capillaries  of  lamina  choriocapillaris. 

Course  of  vasa  ciliar.  postic.  long.:  1,  a.  ciliar.  post,  longa;  2,  circulus  iridis  major  cut  across;  3,  branches  to 
ciliarv  bodv:  4.  branches  to  iris. 


Tapetum  (lucidum). — This  name  is  applied  to  the  iridescent  appearance  which 
is  seen  in  the  outer  and  posterior  parts  of  the  choroid  of  many  animals,  but  not 
in  man. 

The  ciliary  body  should  now  be  examined.  It  may  be  exposed,  either  by  detaching  the  iris 
from  its  connection  with  the  Ciliary  muscle,  or  by  making  a  transverse  section  of  the  globe,  and 
examining  it  from  behind. 


THE  CILIARY  BODY 


1125 


ANNULUS 

ILIARIS 


ORBICULUS 
CILIARIS 


POSTERIOR 
SMOOTH 
PORTION 
OF  CHOROID 


INNER 

SURFACE 

OF  SCLERA 


The  Ciliary  Body  (corpus  ciliare)  (Fig.  729). — The  ciliary  body  or  cyclon  joins 
the  choroid  to  the  margin  of  the  iris.  It  is  in  reality  a  process  of  the  choroid 
or  uveal  tract  and  comprises  the  orbiculus  ciliaris,  the  ciliary  processes,  and  the 
Ciliary  muscle. 

•The  Orbiculus  Ciliaris  or  Annulus  Ciliaris  (Figs.  737,  739,  and  755). — The 
orbiculus  ciliaris  is  a  zone  of  about  one-sixth  of  an  inch  in  width,  directly  con- 
tinuous with  the  anterior  part  of  the  choroid.  The  lamina  basalis  presents  numer- 
ous ridges  arranged  in  a  radial  manner.  The  depressions  between  the  ridges 
are  filled  with  retinal  pigment  epithelium  (Szymonowicz).  The  orbiculus  contains 
no  lamina  choriocapillaris. 

The  Ciliary  Processes  (processus  ciliares)  (Figs.  727,  729,  739,  and  757). — The 
ciliary  processes  are  formed  by  the  plaiting  and  folding  inward  of  the  various 
layers  of  the  choroid — i.  e.,  the  choroid  proper  and  the  lamina  basalis — at  its 
anterior  margin,  and  are  received  between  corresponding  foldings  of  the  suspen- 
sory ligament  of  the  lens,  thus  establishing  a  connection  between  the  choroid  and 
inner  tunic  of  the  eye.  They  are  arranged  in  a  circle,  and  form  a  sort  of  plaited 
frill,  the  corona  ciliaris,  behind  the  iris, 
round  the  margin  of  the  lens  (Figs.  739 
and  757).  They  vary  between  sixty  and 
eighty  in  number,  lie  side  by  side,  and 
may  be  divided  into  large  and  small; 
the  latter,  consisting  of  about  one-third 
of  the  entire  number,  are  situated  in  the 
spaces  between  the  former,  but  without 
regular  alternation.  The  larger  processes 
are  each  about  one-tenth  of  an  inch  in 
length,  and  are  attached  by  their  per- 
iphery to  three  or  four  of  the  ridges  of 
the  orbiculus  ciliaris,  and  are  continu- 
ous with  the  layers  of  the  choroid;  the 
opposite  margin  is  free,  and  rests  upon 
the  circumference  of  the  lens.  Their 
anterior  surface  is  turned  toward  the 

back  of  the  iris,  with  the  circumference  of  which  they  are  continuous, 
posterior  surface  is  connected  with  the  suspensory  ligament  of  the  lens. 

Structure. — The  ciliary  processes  are  similar  in  structure  to  the  choroid,  but  the 
vessels  are  larger,  and  have  chiefly  a  longitudinal  direction.  They  are  the  most 
vascular  portion  of  the  eyeball.  The  processes  are  covered  on  their  inner  surface 
by  two  strata  of  black  pigment-cells,  which  are  continued  forward  from  the  retina, 
and  are  named  the  pars  ciliaris  retinae  (Figs.  733  and  740).  In  the  stroma  of  the 
ciliary  processes  there  are  also  stellate  pigment-cells,  which,  however,  are  not  so 
numerous  as  in  the  choroid  itself. 

The  Ciliary  Muscle  or  Bowman's  Muscle  (m.  ciliaris}  (Figs.  732,  734,  738, 
740,  741,  and  742). — The  ciliary  muscle  consists  of  unstriped  fibres;  it  forms 
a  grayish,  semitransparent,  circular  band,  about  one-eighth  of  an  inch  broad, 
on  the  outer  surface  of  the  forepart  of  the  choroid,  between  the  choroid  and 
the  iris  and  back  of  the  sclero-corneal  junction.  It  is  thickest  in  front  and 
gradually  becomes  thinner  behind.  It  consists  of  two  sets  of  fibres,  radiating  and 
circular. 

The  Radiating  Fibres  (fibrae  meridianales  [Bruckei])  (Figs.  740  and  757),  much 
the  more  numerous,  arise  at  the  point  of  junction  of  the  cornea  and  sclerotic,  and 
partly  also  from  the  ligamentum  pectinatum  iridis,  and,  passing  backward,  are 
attached  to  the  choroid  opposite  to  the  ciliary  processes.  One  bundle,  according 
to  Waldeyer,  is  continued  backward  to  be  inserted  into  the  sclerotic. 


CORNEA  (POS 

tenor  surface) 


FIG.  737. — The  middle  or  vascular  coat  of  the  eyeball 
exposed  from  without.  Left  eye,  seen  obliquely  from 
above  and  before.  (Toldt.) 


The 


1126 


THE    ORGANS    OF   SPECIAL    SENSE 


The  Circular  Fibres  (fibrae  circulares  [Mulleri]}  (Figs.  740  and  757)  are  internal  to 
the  radiating  ones  and  to  some  extent  unconnected  with  them,  and  have  a  circular 
course  around  the  attachment  of  the  iris.  They  are  sometimes  called  the  "ring 
muscle"  of  Muller,  and  were  formerly  described  as  the  ciliary  ligament.  They  are 
well  developed  in  hypermetropic,  but  are  rudimentary  or  absent  in  myopic  eyes. 


Anterior  ciliary  artery. 


Short  ciliary  arteries. 


interior  ciliary  artery. 


FIG.  738. — The  arteries  of  the  choroid  and  iris.     The  sclerotic  has  been  mostly  removed.     (Enlarged.) 


The  Ciliary  muscle  is  admitted  to  be  the  chief  agent  in  accommodation — i.  e.,  in 
adjusting  the  eye  to  the  vision  of  near  objects.  Bowman  believed  that  this  was 
effected  by  its  compressing  the  vitreous  body,  and  so  causing  the  lens  to  advance. 
At  the  present  time  all  agree  that  the  chief  element  in  accommodation  is  altered 
curvature  of  the  lens,  but  there  is  diversity  of  opinion  as  to  the  manner  in  which 


ORBICULARIS 

CILIARIS 


CILIARY 
PROCESSES 


RIS  (poste- 
ior  surface) 


EQUATOR 
OF  LENS 


LENS 

W:-- ^^-.-,. 

FIG.  739. — A  portion  of  the  corona  ciliaris  magnified.     The  ciliary  processes  and  the  ciliary  folds.     (Toldt.) 

this  is  accomplished.  The  view  which  now  prevails  is  that  of  Helmholtz.  He 
maintained  that  in  an  unaccommodated  eye  the  capsule  and  suspensory  ligament 
of  the  lens  are  tense,  and  their  pressure  flattens  the  anterior  surface  of  the  lens, 
and  parallel  rays  (and  rays  from  objects  far  off  are  practically  parallel)  "are 
focused  on  the  retina  without  any  sense  of  effort."1 

"  In  accommodation  for  a  near  object  the  meridional  or  antero-posterior  fibres 

1  Stewart,  Manual  of  Physiology. 


THE  IRIS 


1127 


of  the  ciliary  muscle  by  their  contraction  pull  forward  the  choroid  and  relax  the 
suspensory  ligament.  The  elasticity  of  the  lens  at  once  causes  it  to  bulge  forward 
till  it  is  again  checked  by  the  tension  of  the  capsule."1  The  pupil  is  at  the  same 
time  slightly  contracted. 

The  Iris  (iris,  a  rainbow)  (Figs  729,  732,  734,  736,  737,  740,  741,  742,  743,  and 
757). — The  iris  has  received  its  name  from  its  various  colors  in  different  individ- 
uals. It  is  a  thin,  circular-shaped,  contractile  curtain,  suspended  in  the  aqueous 
humor  behind  the  cornea,  and  in  front  of  the  lens,  being  perforated  a  little  to  the 
nasal  side  of  its  centre  by  a  circular  aperture,  the  pupil  (pupilla)  (Fig.  743),  for 
the  transmission  of  light.  The  pupil  of  a  living  person  varies  in  size  under  the 
influence  of  light  and  in  efforts  at  accommodation.  In  looking  at  a  near  object  the 
pupil  is  small ;  in  looking  at  a  distant  object  it  is  large.  In  light  the  pupil  contracts, 
in  darkness  it  dilates;  hence  the  pupil  is  a  window  which  permits  light  to  pass  into 
the  interior  of  the  eye.  The  size  of  this  window  depends  on  the  contraction  or 
relaxation  of  the  iris.  The  iris  divides  the  aqueous  chamber  (the  space  between 


Circ.  fibres 
of  sclerotic. 


Circ.  fibres  / 
of  Ciliary  muscle. 


Radiating 

fibres  of 

Ciliary  muscle. 


( Pars  ciliaris 
\     retinas. 


•^^S' 

PIG.  740. — Section  of  the  eye,  showing  the  relations  of  the  cornea,  sclerotic,  and  iris,  together  with  the  Ciliary 
muscle  and  the  cavernous  spaces  near  the  angle  of  the  anterior  chamber.     (Waldeyer.) 


the  cornea  and  lens)  into  an  anterior  chamber  and  a  posterior  chamber  which  com- 
municate through  the  pupil  (Figs.  727  and  729).  By  its  circumference  or  ciliary  mar- 
gin (margo  ciliaris)  (Figs.  740  and  741)  the  iris  is  continuous  with  the  ciliary  body, 
and  it  is  also  connected  with  the  posterior  elastic  lamina  of  the  cornea  by  means  of 
the  pectinate  ligament  (ligamentum  pectinatum  iridis]  (Fig.  757).  The  pectinate 
ligament  of  the  iris  is  derived  from  the  posterior  elastic  layer  of  the  cornea.  This 
layer  divides  into  numerous  fibrillae,  and  some  of  them  reach  the  iris  and  bridge 
the  angle  between  the  cornea  and  base  of  the  iris  (Deaver).  The  fibrillae  which 
reach  the  iris  constitute  the  ligament.  In  this  ligament  are  numerous  lymph- 
spaces,  the  spaces  of  Fontana  (spatia  anguli  iridis  [Fontanae])  (Fig.  740),  and 
they  join  the  canal  of  Schlemm  to  the  anterior  chamber  of  the  eye.  The  inner  or 
free  edge  of  the  iris  forms  the  margin  of  the  pupil,  and  is  called  the  pupillary 
margin  (margo  pupillaris)  (Fig.  741).  The  surfaces  of  the  iris  are  flattened,  and 

1  Stewart,  Manual  of  Physiology. 


1128 


THE  ORGANS  OF  SPECIAL  SENSE 


look  forward  and  backward,  the  anterior  toward  the  cornea,  the  posterior  toward 
the  ciliary  processes  and  lens.  The  iris  is  pigmented  and  the  color  of  an  individual's 
eyes  depends  upon  this  pigment.  The  anterior  surface  (fades  anterior}  (Figs.  741 
and  757)  of  the  iris  is  variously  colored  in  different  individuals,  and  is  marked  by 
lines  which  converge  toward  the  pupil.  The  posterior  surface  (fades  posterior)  (Figs. 
739  and  757)  is  of  a  deep-purple  tint,  from  being  covered  by  two  layers  of  pig- 
mented, columnar  epithelium,  which  layers  are  continuous  posteriorly  with  the 
pars  ciliaris  retinae.  This  pigmented  epithelium  is  termed  the  pars  iridica  retinae, 
though  it  is  sometimes  named  uvea,  from  its  resemblance  in  color  to  a  ripe  grape. 
Structure. — The  iris  is  composed  of  the  following  structures: 

1.  In  front  is  a  layer  of  flattened  endothelial  cells  placed  on  a  delicate  hyaline 
basement-membrane.    This  layer  is  continuous  with  the  endothelial  layer  covering 
the  membrane  of  Descemet,  and  in  men  with  dark-colored  irides  the  cells  contain 
pigment-granules. 

2.  Stroma  (stroma  iridis). — The  stroma  consists  of  fibres  and  cells.    The  former 
are  made  of  fine,  delicate  bundles  of  fibrous  tissue,  of  which  some  few  fibres  have 


CILIARY  GANGLIATEO 
PLEXUS 


CILIARY  MARGIN 
OF   IRIS 


CILIARY 

iPirMuscLE 

ATTACHED 
REMNANT  OF 
CORNEAL 
MARGIN 

STROMA 
OF  IRIS 


CILIARY  ZONE 
OF 


TRACTINGS 
LDS  OF  IRIS 

VASCULAR 
NENCES 


GMENT-CELL 


PUPILLARY 
OF 


FREE   BORDER 
'OF  PIGMENTARY 
LAYER 

FIG    741. — Section  of  the  iris.     Anterior  surface  magnified.     (Toldt.) 


PUPILLARY 
MARGIN 


a  circular  direction  at  the  circumference  of  the  iris,  but  the  chief  mass  consists  of 
fibres  radiating  toward  the  pupil.  They  form,  by  their  interlacement,  a  delicate 
mesh,  in  which  the  vessels  and  nerves  are  contained.  Interspersed  between  the 
bundles  of  connective  tissue  are  numerous  branched  cells  with  fine  processes. 
Many  of  them  in  dark  eyes  contain  pigment-granules,  but  in  blue  eyes  and  the 
pink  eyes  of  albinos  they  are  unpigmented. 

3.  The  Muscular  Fibre  is  involuntary  and  consists  of  circular  and  radiating 
fibres.  The  circular  fibres  (m.  sphincter  pupillae)  surround  the  margin  of  the  pupil 
on  the  posterior  surface  of  the  iris,  like  a  sphincter,  forming  a  narrow  band  about 
one-thirtieth  of  an  inch  in  width,  those  near  the  free  margin  being  closely  aggre- 
gated ;  those  more  external  somewhat  separated,  and  forming  less  complete  circles. 
The  radiating  fibres  (TO.  dilator  pupillae)  converge  from  the  circumference  toward 
the  centre,  and  blend  with  the  circular  fibres  near  the  margin  of  the  pupil.  These 
fibres  are  regarded  by  some  as  elastic,  not  muscular,  but  Grunnert  positively 
demonstrated  them.1  The  fibres  are  very  small  and  are  placed  between  the 
stroma  and  the  posterior  layer  of  endothelium. 

i  Von  Graefe's  Arch.  f.  Ophthal.,  Bd.  xlvii. 


THE   IRIS 


1129 


4.  Pigment. — The  situation  of  the  pigment-cells  differs  in  different  irides.  In 
the  various  shades  of  blue  eyes  the  only  pigment-cells  are  several  layers  of  small 
round  or  polyhedral  cells  filled  with  dark  pigment,  situated  on  the  posterior  surface 


CILIARY 
MUSCLE 


CILIARY 

GANGLIATCD 

PLEXUS 


POSTER 
LONG  CILI, 

ARTERY 


ANTERIOR  RADICLES 
'OF  ONE  OF  THE 
VORTICOSE  VEINS 


II    •IIIIBIIillBfc      

FIG.  742. — The  ciliary  gangliated  plexus  and   the  ciliary  nerves  entering  the  plexus.     Outer  surface  of  the 
middle  or  vascular  coat  of  the  eyeball.    (Toldt.) 

of  the  iris  and  continuous  with  the  pigmentary  lining  of  the  ciliary  processes.  The 
color  of  the  eye  in  these  individuals  is  due  to  this  coloring-matter  showing  more 
or  less  through  the  texture  of  the  iris.  'In  the  albino  even  this  pigment  is  absent. 


ANTERIOR    CILIARY    ARTERIES 


LONG   CILIARY 
ARTERY 


ANTERIOR  CILIARY   ARTERIES 

FIG.  743.— Iris,  front  view.     (Testut.) 


In  the  gray,  brown,  and  black  eye  there  are,  as  mentioned  above,  pigment-granules 
to  be  found  in  the  cells  of  the  stroma  and  in  the  endothelial  layers  on  the  front  of 
the  iris;  to  these  the  dark  color  of  the  eve  is  due. 


1130  THE  ORGANS  OF  SPECIAL  SENSE 

The  Arteries  of  the  Iris  (Figs.  736,  738,  740,  and  743).— The  arteries  of  the  iris  are 
derived  from  the  long  posterior  ciliary  and  anterior  ciliary  and  from  the  vessels  of  the 
ciliary  processes  (see  p.  1125).  The  long  posterior  ciliary  arteries  (Figs.  734  and  736), 
two  in  number,  pass  through  the  sclera,  one  on  the  inner  and  one  on  the  outer  side 
of  the  optic  nerve,  and  pass  forward  between  the  sclera  and  choroid,  and,  having 
reached  the  attached  margin  of  the  iris  (Figs.  734  and  743),  divide  into  an  upper  and 
a  lower  branch,  and,  encircling  the  iris,  anastomose  with  corresponding  branches 
from  the  opposite  side;  into  this  vascular  zone  (circulus  arteriosus major)  (Fig.  757) 
the  anterior  ciliary  arteries  (Fig.  757),  from  the  lachrymal  and  anterior  ciliary  from  the 
muscular  branches  of  the  ophthalmic,  pour  their  blood.  From  this  zone  vessels  con-J 
verge  to  the  free  margin  of  the  iris,  and  these  communicate  by  branches  from  one 
to  another  and  thus  form  a  second  zone  (circulus  arteriosus  minor)  in  this  situation. 
The  veins  pass  toward  the  ciliary  margin  and  communicate  with  the  veins  of  the 
ciliary  processes  and  of  the  canal  of  Schlemm  (Figs.  734  and  736). 

The  Nerves  of  the  Choroid  and  Iris  (Fig.  732). — The  nerves  of  the  choroid  and 
iris  are  the  short  ciliary,  the  ciliary  branches  of  the  lenticular  ganglion,  and  the  long 
ciliary  from  the  nasal  branch  of  the  ophthalmic  division  of  the  trigeminal.  They 
pierce  the  sclerotic  around  the  entrance  of  the  optic  nerve,  and  run  forward  in  the 
perichoroidal  lymph-space  in  which  they  form  a  plexus,  from  which  plexus  fila- 
ments pass  to  supply  the  blood-vessels  of  the  choroid.  After  reaching  the  iris  they 
form  a  plexus  around  its  attached  margin;  from  this  are  derived  amyelinic  fibres 
which  terminate  in  the  circular  and  radiating  muscular  fibres.  Their  exact  mode 
of  termination  has  not  been  ascertained.  Other  fibres  from  the  plexus  terminate 
in  a  network  on  the  anterior  surface  of  the  iris.  The  fibres  derived  from  the  motor 
root  of  the  lenticular  ganglion  (oculomotor  nerve)  supply  the  circular  fibres,  while 
those  derived  from  the  sympathetic  supply  the  radiating  fibres. 

Membrana  Pupillaris. — In  the  foetus  the  pupil  is  closed  by  a  delicate  transparent 
vascular  membrane,  the  membrana  pupillaris,  which  divides  the  space  into  which 
the  iris  is  suspended  into  two  distinct  chambers.  This  membrane  contains  numer- 
ous minute  vessels,  continued  from  the  margin  of  the  iris  to  those  on  the  front  part 
of  the  capsule  of  the  lens.  These  vessels  have  a  looped  arrangement,  and  converge 
toward  each  other  without  anastomosing.  Between  the  seventh  and  eighth  months 
the  membrane  begins  to  disappear,  by  gradual  absorption  from  the  centre  toward 
the  circumference,  and  at  birth  only  a  few  fragments  remain.  It  is  said  some- 
times to  remain  permanent  and  produce  blindness. 

III.  The  Tunica  Interna  or  Retina  (Figs.  736,  744,  746). 

The  retina  is  a  delicate  nerve  membrane,  in  which  the  fibres  of  the  optic  nerve 
are  spread  out  and  upon  the  surface  of  which  the  images  of  external  objects  are 
received.  Its  outer  surface  is  in  contact  with  the  choroid ;  its  inner  with  the  vitreous 
body.  Behind,  it  is  continuous  with  the  optic  nerve;  it  gradually  diminishes  in 
thickness  from  behind  forward;  and, in  front,  extends  nearly  as  far  as  the  ciliary 
body,  where  it  appears  to  terminate  in  a  jagged  margin,  the  ora  serrata  (Figs.  736, 
745,  and  757).  Here  the  nerve  tissues  of  the  retina  end,  but  a  thin  prolongation 
of  the  membrane  extends  forward  over  the  back  of  the  ciliary  processes  and  iris, 
forming  the  pars  ciliaris  retinae  and  pars  iridica  retinae,  already  referred  to  (Figs.  740 
and  757).  This  forward  prolongation  consists  of  the  pigmentary  layer  of  the  retina, 
together  with  a  stratum  of  columnar  epithelium.  The  portion  back  of  the  ora 
serrata  is  called  the  physiological  retina  (pars  optica  retinae)  (Fig.  757).  The  retina 
is  soft,  semi  transparent,  and  of  a  purple  tint  in  the  fresh  state,  owing  to  the  presence 
of  a  coloring-material  named  rhodopsin  or  visual  purple;  but  it  soon  becomes 
clouded,  opaque,  and  bleached  when  exposed  to  sunlight.  Exactly  in  the  centre 
of  the  front  surface  of  the  posterior  part  of  the  retina,  corresponding  to  the  visual 
axis,  and  at  a  point  in  which  the  sense  of  vision  is  most  perfect,  is  an  oval  yellowish 


THE   TUNICA    INTERNA    OR   RETINA 


1131 


spot,  called,  after  its  discoverer,  the  yellow  spot  of  Sb'mmerring  (macula  luiea]  (Figs. 
727  and  746),  having  a  central  depression,  the  fovea  centralis.  The  retina  in  the 
situation  of  the  fovea  centralis  is  exceedingly  thin,  and  the  dark  color  of  the  choroid 
is  distinctly  seen  through  it;  so  that  it  presents  more  the  appearance  of  a  foramen, 
and  hence  the  name  foramen  of  Sdmmerring  at  first  given  to  it.  It  exists  only  in 
man,  the  quadrumana,  and  some  saurian  reptiles.  About  one-eighth  of  an  inch  (3 
mm.)  to  the  nasal  side  of  the  yellow  spot  and  one-twenty-fourth  of  an  inch  below 
it,  is  the  point  of  entrance  of  the  optic  nerve,  the  optic  disk  (porus  opticus}  (Figs. 
744  and  746).  The  circumference  of  the  optic  disk  is  slightly  raised  so  as  to  form 
an  eminence,  the  optic  papilla  (colliculus  nervi  optici);  the  central  portion  is 
depressed  and  is  called  the  optic  cup  (excavatio  papillae  nervi  optici).  The  arteria 
centralis  retinae  pierces  its  centre.  This  is  the  only  part  of  the  surface  of  the  retina 
from  which  the  power  of  vision  is  absent,  and  is  termed  the  blind  spot. 


OPTIC 

LAMINA  CRIBROSR      PAPILLA 
OF  SCLERA 

OPTIC 


CHOROID    — . 


POSTERIOR 

SHORT  CILIARY 

ARTERY  AND 

VEIN 


INTERVAGINAL 
SPACES 


BUNDLES  OF 
OPTIC  NERVE 


CENTRAL  ARTERY 
VEIN  OF  RETINA 


FIG.  744. — The  terminal  portion  of  the  optic  nerve  and  its  entrance  into  the  eyeball,  in  horizontal  section.    (Toldt.) 

Structure. — The  optical  portion  of  the  retina  is  an  exceedingly  complex  structure, 
and,  when  examined  microscopically  by  means  of  sections  made  perpendicularly 
to  its  surface,  is  found  to  consist  of  many  layers  of  nerve  structure.  These  nerve 
structures  are  bound  together  and  supported  by  the  sustentacular  fibres.  There 
are  three  layers:  a  middle  or  neuro-epithelial  layer,  an  inner  layer,  and  an  outer 
or  pigmentary  layer.  The  neuro-epithelial  layer  is  subdivided  into  four,  and  the 
middle  layer  into  six  layers;  hence  the  retina  consists  of  eleven  layers.  The  layers 
from  within  outward  are  as  follows  (Figs.  745,  747,  748,  and  749) : 

1.  Membrana  limitans  interna. 

2.  Layer  of  nerve-fibres  (stratum  opticum). 

3.  Ganglionic  layer,  consisting  of  nerve-cells. 

4.  Inner  molecular,  or  plexiform,  layer. 

5.  Inner  nuclear  layer,  or  layer  of  inner  granules. 

6.  Outer  molecular,  or  plexiform,  layer. 

7.  Henle's  fibre-layer. 

8.  Outer  nuclear  layer,  or  layer  of  outer  granules. 

9.  Membrana  limitans  externa. 

10.  Jacob's  membrane  (layer  of  rods  and  cones). 
3.  Outer  layer   ....    11.  Pigmentary  layer  (tapetum  nigrum). 


1.  Inner  layer 


2.  Neuro-epithelial  layer 


1132 


THE    ORGANS    OF   SPECIAL    SENSE 


1.  The  Membrana  Limitans  Interna  (Figs.  745,  747,  and  748),  is  the  most  internal 
layer  of  the  retina,  and  is  in  contact  with  the  hyaloid  membrane  of  the  vitreous 

Pigmentary  layer. 
Jacob's  membrane. 
Membrana  limitans  externa. 

Outer  nuclear  layer. 
Outer  molecular  layer. 

Inner  nuclear  layer. 
Fibre  of  Mutter. 


Inner  molecular  layer. 

Ganglionic  layer. 
Layer  of  nerve-fibres. 

Membrana  limitans  interna. 
FIG.  745. — The  layers  of  the  retina  with  the  exception  of  Henle's  fibre-layer.    (Diagrammatic.)  (After  Schultze.) 

humor.  It  is  derived  from  the  sup- 
porting framework  of  the  retina,  with 
which  tissue  it  will  be  described. 

2.  The  Layer  of  Nerve-fibres  (Figs. 
745,  747,  and  748)  is  formed  by 
the  expansion  of  the  optic  nerve. 
This  nerve  passes  through  all  the 
other  layers  of  the  retina,  except 
the  membrana  limitans  interna,  to 
reach  its  destination.  As  the  nerve 
passes  through  the  lamina  cribrosa  of 
the  sclerotic  coat,  the  fibres  of  which 
it  is  composed  lose  their  myelin 
sheaths  and  are  continued  onward, 
through  the  choroid  and  retina,  as 
simple  axones.  When  these  amye- 
linic  axones  reach  the  internal  surface 
of  the  retina,  they  radiate  from  their 
point  of  entrance  over  the  surface  of  the  retina,  become  grouped  in  bundles,  and 
in  many  places,  according  to  Michel,  arranged  in  plexuses.  Most  of  the  axones 
in  this  layer  are  centripetal,  and  are  the  direct  continuations  of  the  axones  of  the 


FIG. 746. — The  arteria  centralis  retinae,  yellow  spot, etc., the 
anterior  half  of  the  eyeball  being  removed.  (Enlarged.) 


THE  TUNICA  INTERNA  OR  RETINA 


1133 


cells  of  the  next  layer.  A  few  of  the  axones  are  centrifugal,  which  are  axones  of 
ganglion-cells  within  the  brain.  The  centrifugal  fibres  in  the  layer  of  nerve-fibres 
pass  through  it  and  the  next  succeeding  layer  to  ramify  in  the  inner  molecular 
and  inner  nuclear  layers,  where  they  terminate  in  enlarged  extremities.  The 
layer  is  thickest  at  the  optic  nerve  entrance,  and  gradually  diminishes  in  thickness 
toward  the  ora  serrata. 

3.  The  Ganglionic  Layer  or  the  Inner  Ganglionic  Layer  (Figs.  745,  747,  and  748) 
consists  of  a  single  layer  of  large  ganglion-cells;  except  in  the  macula  lutea, 
where  there  are  several  strata.  The  cells  are  somewhat  flask-shaped,  the  rounded 
internal  margin  of  each  cell  resting  on  the  preceding  layer  and  sending  off  an  axone 
which  is  prolonged  as  a  nerve-fibre  into  the  fibrous  layer.  From  the  opposite 
extremity  numerous  thicker  processes  (dendrites)  extend  into  the  inner  molecular 
layer,  where  they  branch  out  into  flattened  arborizations  at  different  levels.  The 
ganglion-cells  vary  much  in  size,  and  the  dendrites  of  the  smaller  ones,  as  a  rule, 


FIGS.  747  and  748. — Vertical  sections  of  the  human  retina.  Fig.  747,  half  an  inch  from  the  entrance  of  the 
optic  nerve.  Fig.  748,  close  to  the  latter.  1.  Layer  of  rods  and  cones,  Jacob's  membrane,  bounded  underneath 
by  the  membrana  limitans  externa.  2.  Outer  nuclear  layer.  3.  Outer  molecular  layer.  4.  Inner  nuclear  layer. 
5.  Inner  molecular  layer.  6.  Ganglionic  layer.  7.  Layer  of  nerve  fibres.  8.  Sustentacular  fibres  of  Miiller. 
9.  Their  attachment  to  the  membrana  limitans  interns. 

arborize  in  the  inner  molecular  layer  as  soon  as  they  enter  it;  while  the  processes 
of  the  larger  cells  ramify  close  to  the  inner  nuclear  layer. 

4.  The  Inner  Molecular,  the  Plexiform  or  the  Inner  Reticular  Layer  (Figs.  745, 747, 
and  748)  is  made  up  of  a  dense  reticulum  of  minute  fibrils,  formed  by  the  inter- 
lacement of  the  dendrites  of  the  ganglion-cells  with  those  of  the  cells  contained  in 
the  next  layer,  immediately  to  be  described.     Within  the  reticulum  formed  by 
these  fibrils  a  few  branched  spongioblasts  are  sometimes  embedded. 

5.  The  Inner  Nuclear  or  Inner  Granular  Layer  (Figs.  745, 747,  and  748)  is  made  up 
of  a  number  of  closely  packed  cells,  of  which  there  are  three  different  kinds.    (1)  A 
large  number  of  oval  cells,  which  are  commonly  regarded  as  bipolar  nerve-cells,  and 
are  much  more  numerous  than  either  of  the  other  kind.    They  each  consist  of  a 
large  oval  body  placed  vertically  to  the  surface,  and  containing  a  distinct  nucleus. 
The  protoplasm  is  prolonged  into  two  processes;  one  of  these  passes  inward  into  the 
inner  molecular  layer,  is  varicose  in  appearance,  and  ends  in  a  terminal  ramification, 
which  is  often  in  close  proximity  to  the  ganglion-cells  (Fig.  749,  I,  c).    The  outer 
process  passes  outward  into  the  outer  molecular  layer,  and  there  breaks  up  into  a 


THE    ORGANS   OF  SPECIAL    SENSE 


THE  TUNICA  INTERN  A   OR  RETINA  1135 

number  of  branches.  According  to  Cajal,  there  are  two  varieties  of  these  bipolar 
cells:  one  in  which  the  outer  process  arborizes  around  the  knobbed  ends  of  the 
rod-fibres,  and  the  inner  around  the  cells  of  the  ganglionic  layer;  these  he  calls 
rod-bipolars  (Fig.  749,  i) ;  the  others  are  those  in  which  the  outer  process  breaks  up 
in  a  horizontal  ramification,  in  contact  with  the  end  of  a  cone-fibre;  these  are  the 
cone-bipolars,  and  their  inner  process  breaks  up  into  its  terminal  ramifications  in 
the  inner  molecular  layer  (Fig.  749,  i).  (2)  At  the  innermost  part  of  this  inner 
nuclear  layer  is  a  stratum  of  cells,  which  are  named  amacrine  cells  of  Cajal,  from  the 
fact  that  they  have  no  axis-cylinder  process,  but  they  give  a  number  of  short  proto- 
plasmic processes  which  extend  into  the  inner  molecular  layer  and  there  ramify 
(Fig.  749,  i).  There  are  also  at  the  outermost  part  of  this  layer  some  cells-,  the 
processes  of  which  extend  into  and  ramify  in  the  outer  molecular  layer.  These 
are  the  horizontal  cells  of  Cajal.  (3)  Some  few  cells  are  also  found  in  this  layer, 
connected  with  the  fibres  of  Miiller,  and  will  be  described  with  those  structures. 

6.  The  Outer  Molecular  or  Outer  Reticular  Layer  or  the  Plexiform  Layer  (Figs. 
745,  747,  and  748)  is  much  thinner  than  the  inner  molecular  layer;  but,  like  it, 
consists  of  a  dense  network  of  minute  fibrils,  derived  from  the  processes  of  the 
horizontal  cells  of  the  preceding  layer  and  the  outer  processes  of  the  bipolar  cells, 
which  ramify  in  it,  forming  arborizations  around  the  ends  of  the  rod-fibres  and 
with  the  branched  foot-plates  of  the  cone-fibres. 

7.  Henle's  Fibre  Layer  is  a  non-granular  layer  in  the  neighborhood  of  the  macula 
lutea,  and  is  produced  by  elongations  from  the  inner  segments  of  rod-fibres  and 
cone-fibres. 

8.  The  Outer  Nuclear  or  Outer  Granular  Layer  (Figs.  745,  747,  and  748),  like  the 
inner  nuclear  layer,  contains  several  strata  of  clear  oval  nuclear  bodies;  they  are 
of  two  kinds,  and  on  account  of  their  being  respectively  connected  with  the  rods 
and  cones  of  Jacob's  membrane   (rod-fibres  and  cone-fibres)  are  named  rod- 
granules  and  cone-granules. 

The  rod-granules  are  much  the  more  numerous,  and  are  placed  at  different  levels 
throughout  the  layer.  Their  nuclei  present  a  peculiar  cross-striped  appearance, 
and  prolonged  from  either  extremity  of  the  granule  is  a  fine  process;  the  outer 
process  is  continuous  with  a  single  rod  of  Jacob's  membrane;  the  inner  passes 
inward  toward  the  outer  molecular  layer  and  terminates  in  an  enlarged  extremity, 


DESCRIPTION  OF  FIG.  749. 

I.  Section  of  the  dog's  retina,  a.  Cone-fibre.  6.  Rod-fibre  and  nucleus,  e,  d.  Bipolar  cells  (inner  granules) 
with  vertical  ramification  of  outer  processes  destined  to  receive  the  enlarged  ends  of  rod-fibres. 
e.  Bipolars  with  flattened  ramification  for  ends  of  cone-fibres.  /.  Giant  bipolar  with  flattened  ramifica- 
tion, fir.  Cell  sending  a  neurone  or  nerve-fibre  process  to  the  outer  molecular  layer,  h.  Amacrine  cell 
with  diffuse  arborization  in  inner  molecular  layer,  i.  Nerve-fibrils  passing  to  outer  molecular  layer. 
j.  Centrifugal  fibres  passing  from  nerve-fibre  layer  to  inner  molecular  layer,  m.  Nervo-fibril  passing 
into  inner  molecular  layer,  n.  Ganglionic  cells. 

II.  Horizontal  or  basal  cells  of  the  outer  molecular  layer  of  the  dog's  retina.  A.  Small  cell  with  dense  arbori- 
zation. R.  Large  cell,  lying  in  inner  nuclear  layer,  but  with  its  processes  branching  in  the  outer 
molecular,  a.  Its  horizontal  neurone.  C.  Medium-sized  cell  of  the  same  character. 

III.  Cells  from  the  retina  of  the  ox.     a.  Rod-bipolars  with  vertical  arborizations.     6,  c,  d,  e.  Cone-bipolars  with 

horizontal  ramification  of  outer  process,  h.  Cell  lying  on  the  outer  surface  of  the  outer  molecular 
layer,  and  ramifying  within  it.  i,j,m.  Amacrine  cells  within  the  substance  of  the  inner  molecular 
layer. 

IV.  Neurones  or  axis-cylinder  processes  belonging  to  horizontal  cells  of  the  outer  molecular  layer,  one  of  them, 

b,  ending  in  a  close  ramification  at  a. 

V.  Nervous  elements  connected  with  the  inner  molecular  layer  of  the  ox's  retina.  A.  Amacrine  cell,  with 
Jong  processes  ramifying  in  the  outermost  stratum.  B.  Large  amacrine  with  thick  processes  ramifying 
in  second  stratum,  c.  Flattened  amacrine  with  long  and  fine  processes  ramifying  mainly  in  the  first 
and  fifth  strata.  D.  Amacrine  with  radiating  tuft  of  fibrils  destined  for  third  stratum.  E.  Large 
amacrine,  with  processes  ramifying  in  fifth  stratum.  v.  Small  amacrine,  branching  into  second 
stratum.  G,  H.  Other  amacrines  destined  for  fourth  stratum,  a.  Small  ganglion-/;ell  sending  its  pro- 
cesses to  fourth  stratum,  b.  A  small  ganglion-ceU  with  ramifications  in  three  strata.  C.  A  small  cell 
ramifying  ultimately  in  first  stratum,  d.  A  medium-sized  ganglion-cell  ramifying  in  fourth  stratum. 
e.  Giant-cell,  branching  in  third  stratum.  /.  A  bistratified  cell  ramifying  in  second  and  fourth  strata. 
VI.  Amacrines  and  ganglion-cells  from  the  dog.  A.  Amacrine  with  radiating  tuft.  B.  Large  amacrine  passing 
to  third  stratum.  C  and  Q.  Small  amacrines  with  radiations  in  second  stratum.  F.  Small  amacrine 
passing  to  third  stratum.  D.  Amacrine  with  diffuse  arborization.  E.  Amacrine  belonging  to  fourth 
stratum,  a,  d,  e,  ff.  Small  ganglion-cells  ramifying  in  various  strata.  b,/.  Large  ganglion-cells  show- 
ing two  different  characters  of  arborization,  i.  Bistratified  cell. 

VII.  Amacrines  and  ganglion-cells  from  the  dog.  A,  B,  c.  Small  amacrines  ramifying  in  middle  of  molecular 
layer.  6,  d,  g,  h,  i.  Small  ganglion-cells  showing  various  kinds  of  arborization.  /.  A  larger  cell,  similar 
in  character  to  fir,  but  with  longer  branch,  a,  f.  e.  Giant-cells  with  thick  branches  ramifying  in  the 
first,  second,  and  third  layers.  L,  L.  Ends  of  bipolars  branching  over  ganglion-cells. 


1136 


THE    ORGANS    OF  SPECIAL    SENSE 


and  is  embedded  in  the  tuft  into  which  the  outer  process  of  the  rod-bipolars  break 
up.    In  its  course  it  presents  numerous  varicosities. 

The  cone-granules,  fewer  in  number  than  the  rod-granules,  are  placed  close  to  the 
membrana  limitans  externa,  through  which  they  are  continuous  with  the  cones  of 
Jacob's  membrane.  They  do  not  present  any  cross-striping,  but  contain  a  pyri- 
form  nucleus  which  almost  completely  fills  the  cell.  From  their  inner  extremity  a 
thick  process  passes  inward  to  the  outer  molecular  layer,  upon  which  it  rests  by  a 
somewhat  pyramidal  enlargement,  from  which  are  given  off  numerous  fine  fibrils, 

A     B 


External 
segment 


Intermediary 

disc" 
Elliptoid-- 


Nucleus 


FIG.  750.— The  cells  of  the  rods  of  the 
retina  in  the  frog.  A,  red  rod;  B,  green 
rod.  (Poirier  and  Charpy.) 

which  enter  the  outer  molecular 
layer,  where  they  come  in  con- 
tact with  the  outer  processes  of 
the  cone-bipolars. 

9.  The    Membrana    Limitans 
Externa(Figs.  745, 747, and 748), 
like  the  membrana  limitans  in- 
terna,  is  derived  from  the  fibres 
of  Miiller,  with  which  structures 
it  will  be  described. 

10.  Jacob's  Membrane  or  the 
Layer  of  Rods  and  Cones  (Figs. 
745,  747,  and  748)     consists  of 

visual  Cells,  and  the  elements  FIG.  751. — Cones  in  the  different  regions  of  the  retina.  7,  near 
,  .  .  .  „  the  ora  serrata;  //,  at  3  mm.  from  the  ora  serrata;  ///,  at  an 

Which  COinpOSe  it  are  OI  tWO  equal  distance  from  the  ora  serrata  and  the  papilla;  IV,  at  the 

periphery  of  the  fovea  centralis;  V,  in  the  fovea  centralis;  VI,  at 
the  centre  of  the  fovea  centralis;  E,  length  of  the  external  seg- 
ment; /,  length  9f  internal  segment;  D,  diameter  of  the  internal 
segment.  (Poirier  and  Charpy.) 


kinds,  rod-cells  and  cone-cells, 
the  former  being  much  more 
numerous  than  the  latter. 

The  rod-cells  (Fig.  750)  are  of  nearly  uniform  size,  and  arranged  perpen- 
dicularly to  the  surface.  A  rod-cell  consists  of  a  rod  and  a  rod-fibre,  and  the 
fibre  contains  the  nucleus.  The  rods  are  cylindrical  and  each  consists  of  two  por- 
tions, an  outer  segment  and  an  inner  segment,  which  are  of  about  equal  length. 
The  segments  differ  from  each  other  as  regards  refraction  and  in  their  behavior 
with  coloring  reagents,  the  inner  portion  becoming  stained  by  carmine,  iodine,  etc., 
the  outer  portion  remaining  unstained  with  these  reagents,  but  staining  yellowish- 
brown  with  osmic  acid .  The  outer  portion  of  each  rod  is  marked  by  transverse  striae, 
and  is  made  up  of  a  number  of  thin  disks  superimposed  on  one  another.  It  also 


THE    TUNICA    INTERN  A    OR   RETINA  1137 

exhibits  faint  longitudinal  markings.  The  inner  portion  of  each  rod,  at  its  deeper 
part  where  it  is  joined  to  the  outer  process  of  the  rod-granule,  is  indistinctly  gran- 
ular; its  more  superficial  part  presents  a  longitudinal  striation,  being  composed  of 
fine,  bright,  highly  refracting  fibres.  In  most  vertebrates  the  outer  portion  of  the 
inner  segment  contains  a  fibrous  body,  the  ellipsoid  of  Krause.  The  visual  purple,  or 
rhodopsin ,  is  found  only  in  the  outer  segments  of  the  rods.  At  its  inner  end  each  rod 
is  prolonged  into  a  very  fine  fibre,  the  rod-fibre,  which  contains  a  nucleus,  and  which 
terminates  in  the  outer  nuclear  layer,  being  somewhat  enlarged  at  its  termination. 

The  cone-cells  (Fig.  751)  are  conical  or  flask-shaped,  their  broad  ends  resting 
upon  the  membrana  limitans  externa,  the  narrow  pointed  extremity  being  turned 
to  the  choroid.  Each  cone-cell  consists  of  two  parts,  the  cone  and  the  cone-fibre. 

The  cones  are  shorter  than  the  rods  and  exhibit  an  outer  and  an  inner  segment. 

The  outer  segment  is  a  short  conical  process,  which,  like  the  outer  segment  of  a 
rod,  presents  transverse  striae.  The  inner  segment  resembles  the  inner  portion 
of  the  rods  in  structure,  presenting  a  superficial  striated  and  deeper  granular  part; 
but  differs  from  it  in  size,  being  bulged  out  laterally  and  presenting  a  flask  shape. 

The  inner  segment  of  the  cone,  as  does  the  rod,  contains  an  ellipsoid  of  Krause. 
Each  cone  is  prolonged  into  a  cone-fibre,  and  at  the  junction  of  the  cone  with  the 
fibre  is  the  nucleus  of  the  cone-cell.  The  cone-fibre  passes  to  the  outer  nuclear 
layer,  and  terminates  as  an  expansion  from  which  very  minute  fibrils  are  given  off. 
The  chemical  and  optical  characters  of  the  rod -cells  and  cone-cells  are  identical. 

11.  The  Pigmentary  Layer  or  Tapetum  Nigrum(Fig.  745). — The  most  external  layer 
of  the  retina,  formerly  regarded  as  a  part  of  the  choroid,  consists  of  a  single  layer 
of  hexagonal  epithelial  cells,  loaded  with  pigment-granules.  Each  cell  contains  a 
flattened  nucleus  in  the  outer  portion  of  the  cell  which  is  free  from  pigment  at  this 
point.  These  cells  are  smooth  externally,  where  they  are  in  contact  with  the 
choroid,  but  internally  they  are  prolonged  into  fine,  straight  processes,  which 
extend  between  the  rods,  this  being  especially  the  case  when  the  eye  is  exposed  to 
light.  The  pigment  changes  its  position  under  the  influence  of  light,  and  is  dis- 
tributed through  the  entire  cell.  In  the  eyes  of  albinos,  the  cells  of  the  pigmentary 
layer  are  present,  but  they  contain  no  coloring-matter.  In  the  eyes  of  many 
mammals  also,  as  in  the  horse,  and  many  of  the  carnivora,  there  is  no  pigment 
in  the  cells  of  this  layer,  and  the  choroid  possesses  a  beautiful  iridescent  lustre, 
which  is  termed  the  tapetum  lucidum. 

Supporting  Framework  of  the  Retina. — Almost  all  these  layers  of  the  retina  are 
connected  together  by  a  supporting  framework,  formed  by  the  supporting  cells  or 
supporting  fibres  of  Miiller  or  radiating  fibres,  from  which  the  membrana  limitans 
interna  et  externa  are  derived.  These  fibres  are  found  stretched  between  the  two 
limiting  layers  (Fig.  745),  "like  columns  between  a  floor  and  a  roof,"  and  they 
pass  through  all  the  nervous  layers  except  Jacob's  membrane.  Each  commences 
on  the  inner  surface  of  the  retina  by  a  conical  hollow  base,  which  sometimes 
contains  a  spheroidal  body  which  stains  deeply  with  haematoxylin,  the  edges  of 
the  bases  of  adjoining  fibres  being  united  and  thus  forming  a  boundary  line,  which 
is  the  membrana  limitans  interna.  As  they  pass  through  the  nerve-fibre  and  gan- 
glionic  layers  they  give  off  few  lateral  branches ;  in  the  inner  nuclear  layer  they  give 
off  numerous  lateral  processes  for  the  support  of  the  inner  granules,  while  in  the 
outer  nuclear  layer  they  form  a  network,  the  fibre-baskets,  around  the  rod  and 
cone-fibrils,  and  unite  to  form  the  external  limiting  membrane  at  the  bases  of 
the  rods  and  cones.  In  the  inner  nuclear  layer  each  fibre  of  Miiller  presents  a  clear 
oval  nucleus,  which  is  sometimes  situated  at  the  side  of,  sometimes  altogether 
within,  the  fibre.  The  supporting  framework  of  the  retina  contains  neuroglia  cells. 

The  Path  of  Light  Stimuli. — The  stimulus  is  first  received  by  the  rod  and  cone- 
cells  (the  visual  cells),  and  is  transmitted  to  the  bipolar  cells  of  the  inner  nuclear 
layer  and  then  to  the  cells  of  the  ganglionic  layer,  which  send  fibres  by  way  of  the 
optic  nerve  to  the  brain.  79 


1138  THE    ORGANS    OF  SPECIAL   SENSE 

Macula  Lutea  and  Fovea  Centralis.  —  The  structure  of  the  retina  at  the  yellow 
spot  presents  some  modifications.  In  the  macula  lutea  (1)  the  nerve-fibres  are 
wanting  as  a  continuous  layer;  (2)  the  ganglionic  layer  consists  of  several  strata 
of  cells,  instead  of  a  single  layer;  (3)  in  Jacob's  membrane  there  are  no  rods,  but 
only  cones,  and  these  are  longer  and  narrower  than  in  other  parts;  and  (4)  in  the 
outer  nuclear  layer  there  are  only  cone-fibres,  which  are  very  long  and  arranged 
in  curved  lines.  At  the  fovea  centralis  the  only  parts  which  exist  are  the  cones 
of  Jacob's  membrane,  the  outer  nuclear  layer,  the  cone-fibres  of  which  are  almost 
horizontal  in  direction,  and  an  exceedingly  thin  inner  granular  layer,  the  pigment- 
ary layer,  which  is  thicker  and  its  pigment  more  pronounced  than  elsewhere.  The 
color  of  the  macula  seems  to  imbue  all  the  layers  except  Jacob's  membrane;  it  is 
of  a  rich  yellow,  deepest  toward  the  centre,  and  does  not  appear  to  consist  of 
pigment-cells,  but  simply  a  staining  of  the  constituent  parts. 

At  the  Ora  Serrata  (Fig.  736)  the  nerve  layers  of  the  retina  terminate  abruptly, 
and  the  retina  is  continued  onward  as  a  single  layer  of  elongated  columnar  cells 
covered  by  the  pigmentary  layer.  This  prolongation  is  known  as  the  pars  ciliaris 
retinae  (Fig.  740),  and  can  be  traced  forward  from  the  ciliary  processes  on  to  the 
back  of  the  iris,  where  it  is  termed  the  pars  iridica  retinae  or  uvea. 

From  the  description  given  of  the  nerve  elements  of  the  retina  it  will  be  seen 
that  there  is  no  direct  continuity  between  the  structures  which  form  its  differ- 
ent layers  except  between  the  ganglionic  and  nerve-fibre  layers,  the  majority 
of  the  nerve-fibres  being  formed  of  the  axones  of  the  ganglionic  cells.  In  the 
inner  molecular  layer  the  dendrites  of  the  ganglionic  layer  interlace  with  those 

of  the  cells  of  the  inner  nuclear  layer,  while  in  the 
outer  molecular  layer  a  like  synapsis  occurs  between 
the  processes  of  the  inner  granules  and  the  rod  and 
FOSSA    i  IKM      cone  elements. 

PATELLAR.S-,  Centralis  Retinae  (Figs.  736  and  744) 


and  its  accompanying  vein,  vena  centralis  retinae, 
pierce  the  optic  nerve,  and  enter  the  globe  of  the  eye 
through  the  porus  opticus.  It  immediately  bifurcates 
into  an  upper  and  a  lower  branch,  and  each  of  these 

,     ftgain  dlvideS  illtO  an  inneF  °F  naSft1'  alld  an  °Uter  OT 

with  the  saucer-shaped  hollow  in  which  temporal,  branch,  which  at  first  run  between  the 

the  lens  lies.      Seen  obliquely  from  the     ,        -T  .  ,  ,  ,      ,  ,  i  .1 

side  and  before.   (Toidt.)  hyaloid  membrane  and  the  nerve  layer;  but  they 

soon  enter  the  latter,  and  pass  forward,  dividing 

dichotomously.  From  these  branches  a  minute  capillary  plexus  is  given  off,  which 
does  not  extend  beyond  the  inner  nuclear  layer.  The  macula  receives  small  twigs 
from  the  temporal  branches  and  others  directly  from  the  central  artery;  these  do 
not,  however,  reach  as  far  as  the  fovea  centralis,  which  has  no  blood-vessels.  The 
branches  of  the  arteria  centralis  retinae  do  not  anastomose  with  each  other  —  in  other 
words,  they  are  "terminal  arteries."  In  the  foetus,  a  small  vessel  passes  forward, 
through  the  hyaloid  canal  in  the  vitreous  body,  to  the  posterior  surface  of  the  cap- 
sule of  the  lens  (Fig.  728). 

THE   REFRACTING  MEDIA. 

The  Refracting  media  are  three,  viz.: 

Aqueous  humor.  Vitreous  body.  Crystalline  lens. 

I.  The  Aqueous  Humor  (Humor  Aqueus). 

The  aqueous  humor  completely  fills  the  lymph  space  known  as  the  aqueous 
chamber,  the  space  which  is  bounded  in  front  by  the  cornea  and  behind  by  the  lens 
and  its  suspensory  ligament  and  the  ciliary  body  (Fig.  757)  .  The  aqueous  chamber 


THE    VITREOUS  BODY  1139 

is  partly  divided  by  the  iris  into  two  communicating  parts,  the  anterior  and  posterior 
chambers  (Figs.  727,  728,  and  757).  The  posterior  chamber  (cumera  oculi  posterior) 
is  only  a  narrow  chink  between  the  peripheral  part  of  the  iris,  the  suspensory 
ligament  of  the  lens,  and  the  ciliary  processes.  The  anterior  chamber  (cumera  oculi 
anterior  is  bounded  in  front  by  the  cornea  and  behind  by  the  iris.  The  external 
angle  of  the  anterior  chamber  is  bounded  by  the  periphery  of  the  cornea  and  of 
the  iris.  It  is  called  the  angle  or  sinus  of  the  anterior  chamber  or  the  nitration  angle 
(angulus  iridis) .  It  is  by  way  of  the  filtration  angle  that  any  excess  of  aqueous 
humor  passes  by  way  of  the  spaces  of  Fontana  and  the  canal  of  Schlemm  (Fig. 
740)  to  the  anterior  ciliary  veins  and  relieves  tension.  The  aqueous  humor  is 
small  in  quantity  (scarcely  exceeding,  according  to  Petit,  four  or  five  grains  in 
weight),  has  an  alkaline  reaction,  in  composition  is  little  more  than  water,  less 
than  one-fiftieth  of  its  weight  being  solid  matter,  chiefly  chloride  of  sodium. 

In  the  adult,  these  two  chambers  communicate  through  the  pupil;  but  in  the 
foetus  of  the  seventh  month,  when  the  pupil  is  closed  by  the  membrana  pupillaris, 
the  two  chambers  are  quite  separate. 

II.  The  Vitreous  Body  (Corpus  Vitreum)  (Figs.  725,  728,  752). 

The  vitreous  body  forms  about  four-fifths  of  the  entire  globe.  It  is  composed  of 
a  jelly-like  tissue  containing  98  per  .cent,  water,  some  salts,  and  a  little  albumin, 
and  called  the  vitreous  humor  (humor  vitreus),  connective-tissue  fibres,  and 
connective-tissue  cells.  It  fills  the  concavity  of  the  retina,  and  is  hollowed  in 
front,  forming  a  deep  concavity,  the  fossa  patellaris  (fossa  hyaloidea)  (Fig.  752), 
for  the  reception  of  the  lens.  It  is  perfectly  transparent,  of  the  corsistence 
of  thin  jelly,  and  is  composed  of  an  albuminous  fluid  enclosed  in  a  delicate 
transparent  membrane,  the  hyaloid  membrane  (membrana  hyaloidea),  the  outside 
of  which  is  in  contact  with  the  membrana  limitans  interna  of  the  retina.  It 
has  been  supposed  by  Hannover,  that  from  its  inner  surface  numerous  thin 
lamellae  (stroma  vitreum)  are  prolonged  inward  in  a  radiating  manner,  forming 
spaces  in  which  the  fluid  is  contained.  In  the  adult,  these  lamellae  cannot  be 
detected  even  after  careful  microscopic  examination  in  the  fresh  state,  but  in  prep- 
arations hardened  in  weak  chromic  acid  it  is  possible  to  make  out  a  distinct 
lamellation  at  the  periphery  of  the  body;  and  in  the  foetus  a  peculiar  fibrous 
texture  pervades  the  mass,  the  fibres  joining  at  the  numerous  points,  and  pre- 
senting minute  nuclear  granules  at  their  point  of  junction.  In  the  centre  of 
the  vitreous  humor,  running  from  the  entrance  of  the  optic  nerve  to  the  posterior 
surface  of  the  lens,  is  a  canal,  filled  with  fluid  and  lined  by  a  prolongation  of  the 
hyaloid  membrane.  This  is  the  canal  of  Stilling,  the  hyaloid  canal,  or  the  canal  of 
Cloquet  (canalis  hyaloideus]  (Fig.  728),  which  in  the  embryonic  vitreous  humor 
conveyed  the  minute  vessel  from  the  central  artery  of  the  retina  to  the  back  of 
the  lens. 

The  hyaloid  membrane  encloses  the  whole  of  the  vitreous  humor.  In  front  of 
the  ora  serrata  it  is  thickened  by  the  accession  of  radial  fibres  and  is  termed  the 
zonule  of  Zinn  (zonula  ciliaris)  (Figs.  755  and  757).  It  presents  a  series  of  radially 
arranged  furrows,  in  which  the  ciliary  processes  are  accommodated  and  to  which 
they  are  adherent,  as  evidenced  by  the  fact  that  when  removed  some  of  their  pig- 
ment remains  attached  to  the  zonule.  The  zonule  of  Zinn  splits  into  two  layers,  one 
of  which  is  thin  and  lines  the  fossa  patellaris;  the  other  is  named  the  suspensory 
ligament  of  the  lens;  it  is  thicker,  and  passes  over  the  ciliary  body  to  be  attached 
to  the  capsule  of  the  lens  a  short  distance  in  front  of  its  equator.  Scattered  and 
delicate  fibres  are  also  attached  to  the  region  of  the  equator  itself.  This  ligament 
retains  the  lens  in  position,  and  is  relaxed  by  the  contraction  of  the  radial  fibres 
of  the  Ciliary  muscle,  so  that  the  lens  is  allowed  to  become  more  convex.  Behind 


1140  THE    ORGANS    OF   SPECIAL    SENSE 

the  suspensory  ligament  there  is  a  sacculated  canal,  the  canal  of  Petit  (spatia 
zonularid);  which  encircles  the  margin  of  the  lens  and  which  can  be  easily  inflated 
through  a  fine  blow-pipe  inserted  through  the  suspensory  ligament.  It  is  bounded 
in  front  by  the  anterior  layer  of  the  suspensory  ligament,  of  the  lens,  behind  by  the 
hyaloidea  membrana,  and  internally  by  the  capsule  of  the  lens.  The  canal  of 
Petit  is  a  lymph-space.  All  the  spaces  of  the  canal  of  Petit  communicate  with  the 
posterior  chamber  of  the  eye. 

In  the  foetus,  the  centre  of  the  vitreous  humor  presents  the  hyaloid  canal  or 
canal  of  Stilling,  already  referred  to,  which  transmits  a  minute  artery,  the  hyaloid 
artery,  to  the  capsule  of  the  lens.  In  the  adult,  no  vessels  penetrate  its  substance, 
although  a  lymph  channel  remains;  so  that  its  nutrition  must  be  carried  on  by 
the  vessels  of  the  retina  and  ciliary  processes,  situated  upon  its  exterior. 

III.  The  Crystalline  Lens  (Lens  Crystallina)  (Figs.  729,  736,  753,  754, 

755,  756,  757). 

The  crystalline  lens,  enclosed  in  its  capsule,  is  situated  immediately  behind  the 
pupil,  in  front  of  the  vitreous  body,  and  is  encircled  by  the  ciliary  processes,  which 
slightly  overlap  its  margin. 

The  capsule  of  the  lens  (capsula  lentis}  (Fig.  757)  is  a  transparent,  highly  elastic, 
and  brittle  membrane,  which  closely  surrounds  the  lens,  and  is  composed  in  part  of 


POSTERIOR 
SURFACE 


\POSTERIOR 
POLE 


FIG.  753.— The  crystalline  lens,  hardened 

and  divided.    (Enlarged.)  FIG.  754. — The  terms  used  in  the  orientation  01  the  lens,  (loldt.) 


cuticular  and  in  part  of  connective  tissue.  It  is  not  white  fibrous  tissue,  and  is  not 
true  elastic  tissue  (Szymonowicz).  Its  outer  surface  is  composed  of  lamella  and 
possesses  transverse  striations.  It  rests,  behind,  in  the  fossa  patellaris  in  the  fore- 
part of  the  vitreous  body  (Fig.  752);  in  front,  it  is  in  contact  with  the  free  border 
of  the  iris,  this  latter  receding  from  it  at  the  circumference,  thus  forming  the 
posterior  chamber  of  the  eye  (Fig.  757);  and  it  is  retained  in  its  position  chiefly  by 
the  suspensory  ligament  of  the  lens,  already  described  (Fig.  757).  The  capsule^s 
much  thicker  in  front  than  behind,  and  when  ruptured  the  edges  roll  up  with  the 
outer  surface  innermost,  like  the  elastic  lamina  of  the  cornea. 

The  substance  of  the  lens  (substantia  lentis)  is  an  epithelial  structure  and  takes 
origin  from  the  ectoderm.  It  consists  early  in  development  of  transparent 
cylindrical  cells,  which  at  a  later  period  become  higher  at  the  posterior  surface 
of  the  lens.  Eventually  very  long  cells  form;  they  are  known  as  lens-fibres  (fibrae 
lentis},  and  are  joined  by  a  cement  substance.  The  adult  lens  consists  of  lens- 
fibres,  the  anterior  surface  being  covered  by  one  layer  of  cubical  epithelial  cells, 
known  as  lens  epithelium  (epithelium  lentis).  This  layer  extends  to  the  margin  of 
the  lens,  at  which  point  the  cells  gain  in  height  and  form  lens-fibres.  The  lens- 
fibres  at  the  margin  are  nucleated,  the  others  are  not.  The  lens-fibres  run  as 
meridians  from  the  anterior  surface  backward.  There  is  no  epithelium  on  the 
posterior  surface. 


THE    CRYSTALLINE    LENS 


1141 


In  the  foetus,  a  small  branch  from  the  arteria  centralis  retinae  runs  forward, 
as  already  mentioned,  through  the  vitreous  humor  to  the  posterior  part  of  the 
capsule  of  the  lens,  where  its  branches  radiate  and  form  a  plexiform  network, 
which  covers  its  surface,  and  they  are  continuous  around  the  margin  of  the  capsule 
with  the  vessels  of  the  pupillary  membrane  and  with  those  of  the  iris.  In  the  adult 
no  vessels  enter  its  substance. 

Structure. — The  lens  is  a  transparent,  biconvex  body,  the  convexity  being  greater 
on  the  posterior  than  on  the  anterior  surface  (Fig.  754).  The  central  points  of  its 


ORBICULARIS 

CILIARIS 


FIG.  755. — The  zonule  of  Zinn  or  the  suspensory  ligament  of  the  lens  viewed  from  behind  in  connection 
with  the  lens  and  the  ciliary  body.     (Toldt.) 

anterior  and  posterior  surfaces  are  known  as  its  anterior  and  posterior  poles  (polus 
anterior  lentis  et  polus  posterior  lentis)  (Fig.  754).  It  measures  from  9  to  10  mm. 
in  the  transverse  diameter,  and  about  4  mm.  in  the  antero-posterior.  It  consists 
of  concentric  layers  (Fig.  753),  of  which  the  external  in  the  fresh  state  are  soft  and 
easily  detached  (substantia  corticalis)  (Fig.  757) ;  those  beneath  are  firmer,  the  cen- 
tral ones  forming  a  hardened  nucleus  (nucleus  lentis)  (Fig.  753).  These  laminae 
are  best  demonstrated  by  boiling  or  immersion  in  alcohol,  and  consist  of  minute 
parallel  fibres,  which  are  hexagonal  prisms,  the  edges  being  dentated,  and  the 


FIG.  756.  —  Diagram  to  show  the  direction  and  arrangement  of  the  radiating  lines  on  the  front  and  back  of 
the  total  lens.     A,  from  the  front;  B,  from  the  back. 


dentations  fitting  accurately  into  each  other;  their  breadth  is  about  ^-gVfr  °f  an 
inch.  Faint  lines  radiate  from  the  anterior  and  posterior  poles  to  the  circumference 
of  the  lens.  In  the  adult  there  may  be  six  or  more  of  these,  but  in  the  foetus  they  are 
only  three  in  number  and  diverge  from  each  other  at  angles  of  1  20°  (Fig.  756).  On 
the  anterior  surface  one  line  ascends  vertically  and  the  other  two  diverge  down- 
ward and  outward.  On  the  posterior  surface  one  ray  descends  vertically  and 
the  other  two  diverge  upward.  They  correspond  with  the  free  edges  of  an  equal 
number  of  septa  in  the  lens,  along  which  the  ends  of  the  lens-fibres  come  into 


1142 


THE    ORGANS   OF  SPECIAL    SENSE 


apposition  and  are  joined  together  by  transparent  amorphous  substance.  The 
fibres  run  in  a  curved  manner  from  the  septa  on  the  anteror  surface  to  those  on 
the  posterior  surface.  No  fibres  pass  from  pole  to  pole,  but  they  are  arranged 
in  such  a  way  that  fibres  which  commence  near  the  pole  on  the  one  aspect  of 
the  lens  terminate  near  the  peripheral  extremity  of  the  plane  on  the  other,  and 
vice  versa.  Each  fibre  of  the  outer  layers  of  the  lens  contains  a  nucleus,  and 
these  nuclei  form  a  layer,  the  nuclear  layer  on  the  surface  of  the  lens.  The  nuclear 
layer  is  most  distinct  toward  the  circumference  of  the  lens. 


INSERTION  OF 
TENDON  OF  SUPERIOR. 
RECTUS  MUSCLE 


PARS  OPTICA 

RETIN/E 

ORA  SERRATA 

PARS  CILIARIS    RETINXE 


ANTERIOR  CILIARY 

ARTERIES  AND 

VCI 


CIRCULAR 
MAJOR 


PIGMENTARY   LAYER 
OF  RETINA 


CHOROID 
PERICHOROI  DAL  SPACE 


CIRCULAR 

FIBRES 
CILIARY 
PROCESS 

RADIATING    FIBRES 

OFZONULEOFZINN 

ZONUI  E    OF  ZINN 

ZONULAR   SPACES 

POSTERIOR  CHAMBER 


EPITHELIUM   OF 
LENS  CAPSULE 
CAPSULE 
OF  LENS 


ANT. CHAMBER 
OF    EYE 


ANGLE  OF 
ANTERIOR 

CHAMBER 
CANAL 
SCHLEMM 

CONJUNCTIVA 
EPISCLERAL 
CONNECTIVE- 
TISSUE 
LIGAMENTUM 
PECTINATUM 
IRIDIS 
RIMA 
CORNEALIS 

EDGE  OF 
CORNEA 

IRIS  (ante- 
rior surface) 


POSTERIOR 

SURFACE 

OF  CORNEA 

EPITHELIUM 

OF  CORNEA 

ANTERIOR 

ELASTIC 

LAMINA 


CORTICAL  SUBSTANCE 
'OF  LENS 


POSTERIOR  ELASTIC 
LAMINA 


TROMA   OF  IRIS 
SPHINCTER       PIGMENTARY 
OF  PUPIL      LAYERS  OF  IRIS 


FIG.  757. — The  upper  half  of  a  sagittal  section  through  the  front  of  the  eyeball.     (Toldt.) 

The  changes  produced  in  the  lens  by  age  are  the  following: 

In  the  foetus  its  form  is  nearly  spherical,  its  color  of  a  slightly  reddish  tint,  it 
is  not  perfectly  transparent,  and  is  so  soft  as  to  break  down  readily  on  the  slightest 
pressure. 

In  the  adult  the  posterior  surface  is  more  convex  than  the  anterior;  it  is  color- 
less, transparent,  and  firm  in  texture. 

In  old  age  it  becomes  flattened  on  both  surfaces,  slightly  opaque,  of  an  amber 
tint,  and  increases  in  density. 

Arteries  of  the  Globe  of  the  Eye. — The  arteries  of  the  globe  of  the  eye  are  the  short 
posterior  ciliary,  long  posterior  ciliary,  and  anterior  ciliary  arteries,  and  the  arteria 
centralis  retinae. 


THE  CRYSTALLINE  LENS  1143 

The  short  posterior  ciliary  arteries  (act.  ciliares  posteriores  breves)  (Figs.  734,  736, 
and  738)  are  from  eight  to  sixteen  in  number.  They  arise  from  the  ophthalmic 
branch  of  the  internal  carotid,  pass  through  the  sclerotic  coat  near  the  optic  nerve, 
and  are  distributed  to  the  choroid. 

There  are  two  long  posterior  ciliary  arteries  (aa.  ciliares  posteriores  longae)  (Figs. 
734,  736,  and  743),  one  on  each  side  of  the  optic  nerve.  They  are  branches  of  the 
ophthalmic.  They  pass  through  the  sclerotic  external  to  the  short  ciliary  arteries, 
and  extend  forward  in  the  choroid.  In  the  ciliary  body  they  form  an  anastomosis 
with  the  anterior  ciliary  arteries.  The  anastomosis  is  known  as  the  circulum  iridis 
major  (Figs.  736  and  757).  Branches  from  this  circle  pass  to  the  iris,  and  at  the 
periphery  of  the  sphincter  of  the  iris  form  the  circulum  iridis  minor.  The  muscular 
branches  and  the  lachrymal  branch  of  the  ophthalmic  give  off  the  anterior  ciliary 
arteries  (aa.  ciliares  anteriores},  six  or  eight  in  number.  They  pass  along  tendons 
of  the  muscles  of  the  eyeball,  reach  the  sclera,  and  pass  upon  the  sclera  to  the 
corneal  margin  (Fig.  743).  Branches  are  given  off  which  pass  backward  to  supply 
the  anterior  half  of  the  sclera,  and  which  are  known  as  episcleral  arteries  (aa. 
episclerales)  (Fig.  736).  Two  branches  are  given  off  which  pass  forward  to  the 
conjunctiva  bulbi,  which  are  known  as  the  anterior  conjunctival  arteries  (aa.  con- 
junctivales  anteriores},  which  anastomose  with  the  posterior  conjunctival  branches 
from  the  palpebral  arteries,  and  which  .give  branches  to  the  delicate  vascular  net- 
work of  the  corneal  margin  which  is  in  the  annulus  conjunctivae  (Spalteholz). 
Eight  or  even  more  branches  form  the  anterior  ciliary  arteries.  They  pass  through 
the  sclerotic  near  the  sclero-corneal  junction,  and  participate  in  the  formation  of  the 
circulum  iridis  major. 

The  Veins  of  the  Globe  of  the  Eye  (Figs.  734,  735,  and  736). — The  veins  are  seen 
on  the  outer  surface  of  the  choroid.  They  have  a  whorl-like  formation  and  empty 
into  four  or  five  large  veins,  the  venae  vorticosae.  These  four,  five,  or  six  equidistant 
venae  vorticosae  pierce  the  sclerotic  midway  between  the  margin  of  the  cornea 
and  the  entrance  of  the  optic  nerve,  and  empty  into  the  ophthalmic  vein.  Another 
set  of  veins  accompany  the  anterior  ciliary  arteries,  and  are  known  as  the  anterior 
ciliary  veins  (vv.  ciliares  anteriores).  They  are  derivatives  of  the  venous  sinus  of 
the  sclera  in  the  canal  of  Schlemm.  They  form  a  circular  plexus.  They  receive 
vessels,  the  ciliary  muscle,  and  pass  through  the  sclera  close  to  the  corneal  margin. 
Posterior  ciliary  veins  (w.  ciliares  posteriores)  receive  vessels  which  gather  venous 
blocd  from  the  outer  surface  of  the  sclera  near  the  optic  nerve.  The  posterior 
ciliary  veins  join  anteriorly  with  the  venae  vorticosae.  After  emerging  from  the 
sclera  they  receive  anterior  conjunctival  branches,  and  by  means  of  episcleral 
veins  communicate  with  the  venae  vorticosae. 

The  Lymphatic  Passages  of  the  Eyeball. — The  conjunctiva  contains  lymph- 
vessels.  The  eyeball  contains  lymph-spaces,  but  no  lymph- vessels 

There  are  two  sets  of  lymph-spaces  in  the  eyeball,  the  anterior  and  posterior. 

The  anterior  lymph-spaces  are  the  spaces  of  the  cornea,  of  the  iris,  of  the 
anterior  chamber,  and  of  the  posterior  chamber. 

The  lymph  from  the  intralamellar  lymph-spaces  of  the  cornea  enters  the  con- 
junctival lymphatics  at  the  margin  of  the  cornea. 

The  lymph-spaces  of  the  iris  open  into  the  anterior  chamber  by  the  crypts  of 
the  iris  and  at  the  margin  of  the  iris  join  the  spaces  of  Fontana. 

The  aqueous  humor  fills  the  anterior  and  posterior  chambers,  but  is  furnished 
by  the  vessels  in  the  posterior  chamber;  in  part  by  the  vessels  of  the  ciliary  body, 
and  in  part  by  the  vessels  of  the  posterior  surface  of  the  iris.  The  lymph  thus 
secreted  passes  by  way  of  the  pupil  into  the  anterior  chamber,  and  then  is  taken 
up  by  the  spaces  of  Fontana,  the  canal  of  Schlemm,  and  the  anterior  ciliary  veins.1 

1  Deaver's  Anatomy. 


1144  THE  ORGANS  OF  SPECIAL  SENSE 

The  posterior  lymph-spaces  are  the  hyaloid  canal,  the  perichoroklal  lymph- 
space,  the  space  of  Tenon,  the  intervaginal  space  of  the  optic  nerve,  and  the  supra- 
vaginal  space  (Deaver). 

The  hyaloid  canal  (Figs.  725  and  728)  passes  between  the  posterior  surface  of 
the  lens  and  the  optic  disk.  In  the  embryo  the  canal  holds  an  artery,1  the  hyaloid 
artery.  During  development  the  artery  disappears,  but  a  lymph  channel  remains. 
The  hyaloid  canal  opens  into  the  intervaginal  space  of  the  optic  nerve.  Between 
the  sclerotic  and  the  choroid  is  the  perichoroidal  lymph-space  (Fig.  757).  It  is 
around  the  choroid  vessels  and  the  venae  vorticosae,  and  empties  into  Tenon's 
space  by  means  of  openings  through  the  sclera  about  the  venae  vorticosae. 

Tenon's  space  (Figs.  725  and  726)  is  between  the  sclera  and  the  capsule  of  Tenon. 
It  receives  lymph  from  the  perichoroidal  space,  and  empties  into  the  supravaginal 
space. 

The  optic  nerve  (Fig.  744)  has  a  sheath  of  dura  and  a  sheath  of  pia,  and 
between  these  sheaths  is  the  intervaginal  lymph-space.  It  is  divided  by  a  pro- 
longation of  the  cerebral  arachnoid  into  a  subdural  space  and  a  subarachnoid 
space,  which  empty  into  the  corresponding  spaces  of  the  membranes  of  the  brain. 

The  supravaginal  space  is  between  the  dural  portion  of  the  sheath  of  the  optic 
nerve  and  a  posterior  prolongation  of  Tenon's  capsule.1 

The  Nerves  of  the  Globe  of  the  Eye. — The  long  ciliary  nerves  (nn.  ciliares  longi), 
two  in  number,  are  derived  from  the  nasal  branch  of  the  ophthalmic  and  the 
short  ciliary  nerves  (nn.  ciliares  breves],  twelve  to  fifteen  in  number,  are  derived 
from  the  ciliary  or  ophthalmic  ganglion.  Both  the  long  and  short  ciliary  nerves 
perforate  the  sclera  in  the  neighborhood  of  the  optic  nerve  (Fig.  734).  They  pass 
along  the  perichoroidal  lymph-space,  forming  a  plexus,  and  send  filaments  to  the 
choroid  vessels.  In  front  of  the  Ciliary  muscle  they  form  a  second  plexus,  and 
from  it  come  branches  which  go  to  the  Ciliary  muscle  and  the  muscular  fibres  and 
vessels  of  the  iris,  sclera,  choroid,  ciliary  body,  and  iris  (Fig.  742).  The  ciliary 
nerves  supply  the  cornea.  The  circular  fibers  of  the  iris  are  innervated  by  the 
oculomotor  nerve  and  the  radiating  fibres  by  the  sympathetic. 

Surgical  Anatomy. — From  a  surgical  point  of  view  the  cornea  may  be  regarded  as  consist- 
ing of  three  layers:  (1)  of  an  external  epithelial  layer,  developed  from  the  epiblast,  and  continu- 
ous with  the  external  epithelial  covering  of  the  rest  of  the  body,  and  therefore  in  its  lesions  resem- 
bling those  of  the  epidermis;  (2)  of  the  cornea  proper,  derived  from  the  mesoblast,  and  associated 
in  its  diseases  with  the  fibro- vascular  structures  of  the  body;  and  (3)  the  posterior  elastic  layer 
with  its  endothelium,  also  derived  from  the  mesoblast  and  having  the  characters  of  a  serous 
membrane,  so  that  inflammation  of  it  resembles  inflammation  of  the  other  serous  and  synovial 
membranes  of  the  body. 

The  cornea  contains  no  blood-vessels,  except  at  its  periphery,  where  numerous  delicate  loops, 
derived  from  the  anterior  ciliary  arteries,  may  be  demonstrated  on  the  anterior  surface  of  the 
cornea.  The  rest  of  the  cornea  is  nourished  by  lymph,  which  gains  access  to  the  proper  sub- 
stance of  the  cornea  and  the  posterior  layer  through  the  spaces  of  Fontana.  This  lack  of  a  direct 
blood-supply  renders  the  cornea  very  apt  to  inflame  in  the  cachectic  and  ill-nourished.  In  spite 
of  the  absence  of  blood-vessels,  wounds  of  the  cornea  usually  heal  rapidly.  A  wound  which  pene- 
trates the  cornea  opens  the  anterior  chamber,  and  aqueous  humor  escapes.  An  ulcer  may  also 
open  the  anterior  chamber.  Through  a  wound  or  a  perforated  ulcer  the  pupillary  margin  of  the 
iris  may  prolapse.  A  trivial  injury  of  the  cornea  is  repaired  by  transparent  tissue.  A  severe 
injury  is  repaired  by  fibrous  tissue,  and  opacity  results.  A  slight  opacity  resembling  a  cloud  of 
gray  smoke  is  called  nebula;  a  more  marked  white  opacity  is  called  leucoma. 

In  abscess  of  the  cornea  pus  gravitates  between  the  layers  to  the  lower  part  of  the  cornea  and 
the  purulent  collection  assumes  a  crescentic  shape  (onyx). 

The  arcus  senilis,  seen  in  the  aged,  is  a  condition  of  haziness  or  opacity  at  the  cornea!  margin 
due  to  fatty  degeneration  of  the  tissue  of  the  cornea.  It  signifies  interference  with  the  blood- 
supply,  because  of  senile  degeneration  of  adjacent  vessels.  In  cases  of  granular  lids  there  is  a 
peculiar  affection  of  the  cornea,  called  pannus,  in  which  the  anterior  layers  of  the  cornea  become 
vascularized,  and  a  rich  network  of  blood-vessels  may  be  seen  on  the  cornea;  and  in  interstitial 
keratitis  new  vessels  extend  into  the  cornea,  giving  it  a  pinkish  hue,  to  which  the  term  salmon 
patch  is  applied.  The  cornea  is  richly  supplied  with  nerves,  derived  from  the  ciliary  nerves,  which 

1  For  the  lymphatic  channels  of  the  eyeball  see  Beaver's  Surgical  Anatomy,  vol.  ii.  p.  392. 


THE    CRYSTALLINE   LENS  114.') 

enter  the  cornea  through  the  forepart  of  the  sclerotic  and  form  plexuses  in  the  stroma,  terminating 
between  the  epithelial  cells  by  free  ends  or  in  corpuscles.  In  cases  of  glaucoma  the  ciliary  nerves 
may  be  pressed  upon  as  they  course  between  the  choroid  and  sclerotic  (Fig.  732),  and  in  conse- 
quence of  the  pressure  upon  them,  the  cornea,  to  which  they  are  distributed,  becomes  anaes- 
thetic. When  a  scar  forms  on  the  cornea  and  the  iris  becomes  adherent,  the  scar  and  the  iris, 
and  sometimes  even  the  lens,  may  bulge  forward  from  intraocular  tension.  This  condition 
is  staphyloma  of  the  cornea.  In  conditions  of  impaired  nutrition  the  cornea  may  be  bulged  for- 
ward by  intraocular  pressure.  The  line  of  least  resistance  is  a  little  below  the  centre  of  the 
cornea,  and  it  is  bulged  forward  and  strongly  curved.  This  condition  is  known  as  conical  cornea. 
The  sclerotic  has  very  few  blood-vessels  and  nerves.  The  blood-vessels  are  derived  from  the 
anterior  ciliary,  and  form  an  open  plexus  in  its  substance.  As  they  approach  the  corneal  margin 
this  arrangement  is  peculiar.  Some  branches  pass  through  the  sclerotic  to  the  ciliary  body;  others 
become  superficial  and  lie  in  the  episcleral  tissue,  and  form  arches,  by  anastomosing  with  each 
other,  some  little  distance  behind  the  corneal  margin.  From  these  arches  numerous  straight 
vessels  are  given  off,  which  run  forward  to  the  cornea,  forming  its  marginal  plexus.  In  inflamma- 
tion of  the  sclerotic  and  episcleral  tissue  these  vessels  become  conspicuous,  and  form  a  pinkish 
zone  of  straight  vessels  radiating  from  the  corneal  margin,  commonly  known  as  the  zone  of  ciliary 
injection.  In  inflammation  of  the  iris  and  ciliary  body  this  zone  is  present,  since  the  sclerotic 
speedily  becomes  involved  when  these  structures  are  inflamed.  But  in  inflammation  of 'the  cornea 
the  sclerotic  is  seldom  much  affected,  though  the  cornea  and  sclerotic  are  structurally  continuous. 
This  would  appear  to  be  due  to  the  fact  that  the  nutrition  of  the  cornea  is  derived  from  a  different 
source  from  that  of  the  sclerotic.  The  sclerotic  may  be  ruptured  subcutaneously  without  any 
laceration  of  the  conjunctiva,  and  the  rupture  usually  occurs  near  the  corneal  margin,  where 
the  tunic  is  thinnest.  It  may  be  complicated  with  lesions  of  adjacent  parts — laceration  of  the 
choroid,  retina,  iris,  or  suspensory  ligament  of  the  lens — and  is  then  often  attended  with  hemor- 
rhage into  the  anterior  chamber,  which  masks  the  nature  of  the  injury.  In  some  cases  the  lens 
has  escaped  through  the  rent  in  the  sclerotic,  and  has  been  found  under  the  conjunctiva.  Wounds 
of  the  sclerotic,  if  they  do  not  perforate,  usually  heal  readily.  If  they  extend  through  the  sclerotic 
they  cause  diminished  tension,  are  always  dangerous,  and  are  often  followed  by  inflammation, 
suppuration,  and  by  sympathetic  ophthalmia.  The  sclerotic  may  be  weakened  by  injury,  inflam- 
mation, etc.,  and  the  weakened  portion  may  bulge  from  intraocular  pressure,  and  even  a  healthy 
sclera  may  bulge  from  excessive  intraocular  pressure.  According  to  its  situation  the  lesion  is 
known  as  ciliary  staphyloma,  equatorial  staphyloma,  or  posterior  staphyloma. 

One  of  the  functions  of  the  choroid  is  to  provide  nutrition  for  the  retina  and  to  convey  ves- 
sels and  nerves  to  the  ciliary  body  and  iris.  Inflammation  of  the  choroid  is  therefore  followed 
by  grave  disturbance  in  the  nutrition  of  the  retina,  and  is  attended  with  early  interference  with 
vision.  Purulent  choroiditis  is  not  confined  to  the  choroid;  the  retina,  the  vitreous,  and  the  entire 
uveal  tract  become  involved,  and  even  other  structures  may  suffer.  In  its  diseases  it  bears  a  con- 
siderable analogy  to  those  which  affect  the  skin,  and,  like  it,  is  one  of  the  places  from  which 
melanotic  sarcomata  may  grow.  These  tumors  contain  a  large  amount  of  pigment  in  their  cells, 
and  grow  only  from  those  parts  where  pigment  is  naturally  present.  The  choroid  may  be  ruptured 
without  injury  to  the  other  tunics,  as  well  as  participating  in  general  injuries  of  the  eyeball.  In 
cases  of  uncomplicated  rupture  the  injury  is  usually  at  its  posterior  part,  and  is  the  result  of  a 
blow  on  the  front  of  the  eye.  It  is  attended  by  considerable  hemorrhage,  which  for  a  time  may 
obscure  vision,  but  in  most  cases  this  is  restored  as  soon  as  the  blood  is  absorbed. 

The  iris  is  the  seat  of  a  malformation,  termed  coloboma,  which  consists  in  a  deficiency  or 
cleft,  which  in  a  great  number  of  cases  is  clearly  due  to  an  arrest  in  development.  In  these  cases 
it  is  found  at  the  lower  aspect,  extending  directly  downward  from  the  pupil,  and  the  gap  fre- 
quently extends  through  the  choroid  to  the  entrance  of  the  optic  nerve.  In  some  rarer  cases  the 
gap  is  found  in  other  parts  of  the  iris,  and  is  then  not  associated  with  any  deficiency  of  the  choroid. 
The  iris  is  abundantly  supplied  with  blood-vessels  and  nerves,  and  is  therefore  very  prone  to 
become  inflamed.  And  when  inflamed,  in  consequence  of  the  fact  that  the  iris  and  ciliary  body  are 
continuous,  and  that  their  vessels  communicate,  iritis  is  usually  associated  with  cyclitis,  the  dis- 
ease being  called  irido-cyclitis.  And,  in  addition,  inflammation  of  adjacent  structures,  the  cornea 
and  sclerotic,  is  apt  to  spread  into  the  iris.  The  iris  is  covered  with  endothelium,  and  partakes  of 
the  character  of  a  serous  membrane,  and,  like  these  structures,  is  liable  to  pour  out  a  plastic  exuda- 
tion when  inflamed,  and  contract  adhesions,  either  to  the  cornea  in  front  (synechia  anterior),  or 
to  the  capsule  of  the  lens  behind  (synechia  posterior).  In  iritis  the  lens  may  become  involved, 
and  the  condition  known  as  secondary  cataract  may  be  set  up.  Tumors  occasionally  commence  in 
the  iris;  of  these,  cysts,  which  are  usually  congenital  and  sarcomatous  tumors,  are  the  most  common 
and  require  removal.  Gummata  are  not  unfrequently  found  in  this  situation.  In  some  forms 
of  injury  of  the  eyeball,  as  the  impact  of  a  spent  shot, -the  rebound  of  a  twig,  or  a  blow  with  a 
whip,  the  iris  may  be  detached  from  the  Ciliary  muscle,  the  amount  of  detachment  varying  from 
the  slightest  degree  to  the  separation  of  the  whole  iris  from  its  ciliary  connection. 

The  Argyll-Robertson  pupil  shows  no  reaction  to  light,  but  retains  reaction  to  accommodation 
and  vision  remains  good. 


1146 


THE    ORGANS    OF  SPECIAL    SENSE 


The  retina,  with  the  exception  of  its  pigment-layer  and  its  vessels,  is-  perfectly  transparent, 
and  is  invisible  when  examined  by  the  ophthalmoscope,  so  that  its  diseased  conditions  are 
recognized  by  its  loss  of  transparency.  In  retinitis,  for  instance,  there  is  more  or  less  dense  and 
extensive  opacity  of  its  structure,  and  not  unfrequently  extravasations  of  blood  into  its  sub- 
stance. Hemorrhages  may  also  take  place  into  the  retina  from  rupture  of  a  blood-vessel  without 
inflammation. 

In  optic  neuritis,  papillitis,  or  choked  disk,  the  ophthalmoscope  shows  increase  in  vascularity, 
and  swelling  and  opacity  of  the  nerve,  which  extend  beyond  the  disk  margins.  Optic  atrophy 
is  apt  to  follow.  (Fig.  758  shows  a  normal  optic  disk.) 

The  retina  may  become  displaced  from  effusion  of  serum  between  it  and  the  choroid  or  by 
blows  on  the  eyeball,  or  may  occur  without  apparent  cause  in  progressive  myopia,  and  in  this 
case  the  ophthalmoscope  shows  an  opaque,  tremulous  cloud.  Glioma,  a  form  of  sarcoma,  and 
essentially  a  disease  of  early  life,  is  occasionally  met  with  in  connection  with  the  retina. 

The  lens  has  no  blood-vessels,  nerves,  or  connective  tissue  in  its  structure,  and  therefore  is 
not  subject  to  those  morbid  changes  to  which  tissues  containing  these  structures  are  liable.  It 
does,  however,  present  certain  morbid  or  abnormal  conditions  of  various  kinds.  Thus,  variations 
in  shape,  absence  of  the  whole  or  a  part  of  the  lens,  and  displacements  are  amongst  its  congenital 
defects.  Opacities  may  occur  from  injury,  senile  changes,  malnutrition,  or  errors  in  growth  or 
development.  An  opacity  of  the  capsule,  of  the  lens,  or  of  both,  is  known  as  a  cataract.  Senile 
changes  may  take  place  in  the  lens,  impairing  its  elasticity  and  rendering  it  harder  than  in  youth, 


FIG.  758. — Ophthalmoscopic  appearances  of  healthv  FIG.  759. — Ophthalmoscopic  appearance  of  severe 

fundus  in  a  person  of  very  fair  complexion.     Scleral  recent  papillitis.     Several  elongated  patches  of  blood 

ring  well  marked.    Left  eye,  inverted  image.    (Wecker  near  border  of  disk.      (After  Hughlings  Jackson.) 
and  Jaeger. ) 

so  that  its  curvature  can  only  be  altered  to  a  limited  extent  by  the  Ciliary  muscle.  And,  finally, 
the  lens  may  be  dislocated  or  displaced  by  blows  upon  the  eyeball,  and  its  relations  to  surround- 
ing structures  altered  by  adhesions  or  the  pressure  of  new  growths. 

There  are  two  particular  regions  of  the  eye  which  require  special  notice:  one  of  these  is  known 
as  the  "  filtratkm  area,"  and  the  other  as  the  "  dangerous  area."  The  filtration  area  is  the  circum- 
corneal  zone  immediately  in  front  of  the  iris.  Here  are  situated  the  cavernous  spaces  of 
Fontana,  which  communicate  with  the  canal  of  Schlemm,  through  which  the  chief  transudation 
of  fluid  from  the  eye  is  now  believed  to  take  place.  The  dangerous  area  of  the  eye  is  the  region 
in  the  neighborhood  of  the  ciliary  body,  and  wounds  or  injuries  in  this  situation  are  peculiarly 
dangerous;  for  inflammation  of  the  ciliary  body  is  liable  to  spread  to  many  of  the  other  structures 
of  the  eye,  especially  to  the  iris  and  choroid,  which  are  intimately  connected  by  nervous  and 
vascular  supplies.  Moreover,  wounds  which  involve  the  ciliary  region  are  especially  liable  to  be 
followed  by  sympathetic  ophthalmia,  in  which  destructive  inflammation  of  one  eye  is  excited  by 
some  irritation  in  the  other. 

Emmetropia  is  normal  vision.  In  normal  vision  the  practically  parallel  light  rays  from  distant 
objects  focus  on  the  retina  without  effort;  divergent  rays  from  near  objects  are  focused  on  the 
retina  by  an  effort  of  accommodation. 

Hyperopm  or  hypermetropia  is  far-sightedne,ss.  In  this  condition  the  retina  is  in  front  of  the 
principal  focus  when  the  eye  is  at  rest.  The  patient  endeavors  to  correct  the  failure  by  constant 
and  tiresome  efforts  at  accommodation.  The  condition  is  usually  due  to  inordinate  shortness  of 
the  axis  of  the  eye,  but  may  be  due  to  loss  of  the  lens,  decreased  convexity  of  the  refractive  sur- 
faces, or  lessened  refractive  power  in  the  refractive  media  of  the  eye.  It  is  corrected  by  the  use 
of  convex  glasses. 


THE   EYELID  1147 

Myopia  is  near-sightedness.  In  this  condition  the  rays  of  light  come  to  a  focus  in  front  of  the 
retina,  and  the  patient  is  subjected  to  continued  eye-strain.  It  is  usually  due  to  too  great  length 
of  the  axis  of  the  eye,  but  may  result  from  increase  in  refractive  power  of  refractive  media.  It  is 
corrected  by  concave  glasses.  Sometimes,  as  a  person  with  hyperopia  begins  to  age,  an  increased 
refractive  power  of  the  lens  causes  myopia.  The  occurrence  of  myopia  in  a  hyperopic  eye  is 
called  second  sight,  and  it  enables  the  individual  to  cease  wearing  convex  glasses. 

Excntrrafion  of  the  contents  of  the  orbit  means  removal  of  all  the  contents  except  those  at  the 
orbital  apex.  Even  the  periosteum  is  taken  away.  It  is  performed  for  malignant  disease. 

Kriwration  of  the  eyeball  is  performed  by  making  a  circular  incision  at  the  corneal  margin  and 
removing  the  internal  and  middle  coats  and  the  contents  of  the  globe.  The  sclera  is  not  removed. 
A  glass  ball  is  inserted  into  the  scleral  sheath,  and  the  sclera  is  closed  over  the  ball  by  vertical 
stitches,  and  the  conjunctiva  is  closed  over  it  by  transverse  stitches.  The  operation  is  performed 
for  leucoma  or  staphyloma  of  the  cornea.  An  artificial  eye  (a  shell)  is  placed  over  the  stump 
when  healing  is  complete. 

Enuclcation,  or  excision  of  the  eyeball,  differs  from  exenteration  of  the  orbital  contents  in  the 
fact  that  only  the  eyeball  is  removed.  A  circular  incision  through  the  ocular  conjunctiva 
is  carried  around  and  near  to  the  corneal  margin.  The  conjunctiva  and  capsule  of  T£non  are 
pushed  back  and  the  Rectus  muscles  are  clamped  and  divided  back  of  the  clamp.  Traction 
is  made  upon  the  globe  in  a  forward  and  inward  direction,  and  the  optic  nerve  and  adjacent 
structures  are  cut  with  scissors  from  the  outer  aspect  of  the  globe.  The  eye  is  then  pulled  out  of 
the  orbit,  and  all  structures  which  tend  to  retain  it  are  divided.  The  stumps  of  the  Recti  muscles 
are  sewed  together. 

THE  APPENDAGES  OF  THE  EYE  (TUTAMINA  OCULI). 

The  appendages  of  the  eye  include  the  eyebrows,  the  eyelids,  the  conjunctiva, 
and  the  lachrymal  apparatus — viz.,  the  lachrymal  gland,  the  lachrymal  sac,  and  the 
nasal  duct. 

The  Eyebrow  (Supercilium) . 

The  eyebrows  are  two  arched  eminences  of  integument  which  surmount  the 
upper  circumference  of  the  orbit  on  each  side,  and  support  numerous  short,  thick 
hairs,  directed  obliquely  on  the  surface.  The  hairs  may  entangle  foreign  bodies 
and  lessen  somewhat  the  force  of  blows.  In  structure  the  eyebrows  consist  of 
thickened  integument,  connected  beneath  with  the  Orbicularis  palpebrarum, 
Corrugator  supercilii,  and  Occipito-frontalis  muscles.  These  muscles  serve,  by 
their  action  on  this  part,  to  control  to  a  certain  extent  the  amount  of  light 
admitted  into  the  eye. 

The  Eyelid  (Palpebra)  (Figs.  760,  761). 

The  eyelids  are  two  thin,  movable  folds  placed  in  front  of  the  eye,  and  by  closure 
protecting  the  eye  from  injury.  The  eyelids  are  composed  of  skin,  superficial 
fascia,  and  areolar  tissue,  fibres  of  the  Orbicularis  palpebrarum  muscle,  palpebral 
and  orbito-tarsal  ligaments,  tarsal  cartilages,  and  conjunctiva.  The  upper  lid 
also  contains  the  Levator  palpebrae  superioris  muscle.  In  the  lids  are  blood-vessels, 
lymph-vessels,  nerves,  and  Meibomian  glands.  There  are  two  lids,  the  upper 
(palpebra  superior)  and  the  lower  (palpebra  inferior).  The  upper  lid  is  the  larger 
and  the  more  movable  of  the  two,  and  is  furnished  with  a  separate  elevator 
muscle,  the  Levator  palpebrae  superioris.  Each  lid  consists  of  two  portions.  The 
part  near  the  orbital  margin,  "whose  groundwork  is  formed  merely  by  the  thin 
palpebral  fascia  (septum  orbitale),"1  is  called  the  orbital  portion  (pars  orbitalis). 
The  part  in  which  the  tarsus  lies  is  called  the  tarsal  portion  ( pars  tarsalis).  Between 
the  two  portions  in  each  lid  is  a  sulcus,  called,  in  the  upper  lid,  the  superior  orbito- 
palpebral  sulcus  (sulcus  orbitopalpebralis  superior),  and,  in  the  lower  lid,  the  inferior 
orbito -palpebral  sulcus  (sulcus  orbitopalpebralis  inferior).  When  the  eyelids  are 

1  An  Atlas  of  Human  Anatomy.    By  Carl  Toldt,  assisted  by  A.  D.  Rosa.     Translated  by  M.  Eden  Paul. 


THE    ORGANS    OF  SPECIAL    SENSE 


opened  an  elliptical  space,  the  interpalpebral  slit  (fissura  palpebraruni),  is  left 
between  their  margins,  the  angles  of  which  correspond  to  the  junction  of  the  upper 
and  lower  lids,  and  are  called  canthi. 

The  Canthi. — The  outer  canthus  (angulus  oculi  lateralis)  is  more  acute  than  the 
inner,  and  the  lids  here  lie  in  close  contact  with  the  globe;  but  the  inner  canthus 
(angulus  oculi  medialis]  is  prolonged  for  a  short  distance  inward  toward  the  nose. 
The  two  lids  are  separated  at  the  inner  canthus  by  a  triangular  space,  the  lacus 
lacrimalis.  At  the  commencement  of  the  lacus  lacrimalis,  on  the  margin  of  each 
eyelid,  is  a  small  conical  elevation,  the  lachrymal  papilla,  the  apex  of  which  is 
pierced  by  a  small  orifice,  the  punctum  lacrimale  (Fig.  764),  the  commencement  of 
the  lachrymal  canal  (Fig.  763).  When  the  lids  are  closed  a  space  remains  between 
them  and  the  globe  to  permit  of  the  flow  of  tears  inward  (rivus  lacrimalis'). 

The  Eyelashes  (cilia)  (Fig.  761). — The  eyelashes  are  attached  to  the  free  edges  of 
the  eyelids;  they  are  short,  thick,  curved  hairs,  arranged  in  a  double  or  triple  row 
at  the  margin  of  the  lids;  those  of  the  upper  lid,  more  numerous  and  longer  than 
the  lower,  curve  upward;  those  of  the  lower  lid  curve  downward.  Because  of  this 
arrangement  the  two  sets  do  not  interlace  in  closing  the  lids.  Near  the  attachment 
of  the  eyelashes  are  the  openings  of  sebaceous  glands  (glandulae  sebaceae)  (Fig.  761) 
and  of  a  number  of  glands,  glands  of  Moll  (glandulae  ciliares  [Molli])  (Fig.  761), 
arranged  in  several  rows  close  to  the  free  margin  of  the  lid.  They  are  regarded  as 
enlarged  and  modified  sweat-glands.  On  the  inner  surface  are  the  Meibomian 
glands  (Fig.  763).  Internal  to  the  openings  of  the  lachrymal  canaliculi  there  are 
neither  lashes  nor  Meibomian  glands. 


LACHRYMAL  ARTERY. 
AND  NERVE 


EXTERNAL  LATERA 
LIGAMENT 


-SUPRAORBITAL  VES- 
SELS AND  NERVE 


LACHRYMAL   SAC 


INTERNAL  LATE- 
RAL LIGAMENT 


FIG.  760. — The  tarsi  and  their  ligaments.     Right  eye,  front  view.     (Testut.) 


Structure  of  the  Eyelids  (Fig.  761). — The  eyelids  are  composed  of  the  following 
structures,  taken  in  their  order  from  without  inward: 

Integument,  areolar  tissue,  fibres  of  the  Orbicularis  muscle,  tarsal  plate,  and 
its  ligament,  Meibomian  glands,  and  conjunctiva.  The  upper  lid  has,  in  addition, 
the  aponeurosis  of  the  Levator  palpebrse. 

The  integument  is  extremely  thin,  and  continuous  at  the  margin  of  the  lids  with 
the  conjunctiva. 

The  subcutaneous  areolar  tissue  is  very  lax  and  delicate,  seldom  contains  any 
fat,  and  is  extremely  liable  to  serous  infiltration. 

The  fibres  of  the  Orbicularis  muscle,  where  they  cover  the  palpebrae  (m.  ciliaris 
[Riolani]),  are  thin,  pale  in  color,  and  possess  an  involuntary  action. 


TIIK  EYELID 


1149 


The  tarsal  plates  are  two  thin  elongated  plates  of  dense  connective  tissue  about 
an  inch  in  length.  They  are  placed  one  in  each  lid,  contributing  to  their  form 
and  support. 

The  superior  tarsal  plate,  superior  tarsus  or  superior  tarsal  body  (tarsus  superior) 
(Fig.  760),  the  larger,  is  of  a  semilunar  form,  about  one-third  of  an  inch  in 
breadth  at  the  centre,  and  becoming  gradually  narrowed  at  each  extremity.  To 
the  anterior  surface  of  this  plate  the  aponeurosis  of  the  Levator  palpebrae  is 
attached. 

The  inferior  tarsal  plate,  inferior  tarsus  or  inferior  taxsal  body  (tarsus  inferior] 
(Fig.  760),  the  smaller  of  the  two,  is  thinner  and  of  an  elliptical  form. 

The  free  or  ciliary  margin  of  these  plates  is  thick,  and  presents  a  perfectly 
straight  edge.  The  attached  or  orbital  margin  is  connected  to  the  circumference  of 
the  orbit  by  the  fibrous  membrane  of  the 
lids,  with  which  it  is  continuous.  The 
outer  angle  of  each  plate  is  attached  to 
the  malar  bone  by  the  external  tarsal  or 
external  lateral  ligament,  or  the  external 
palpebral  ligament  or  raphe  (ligamentum 
palpebralis  later  alis)  (Fig.  760).  The  inner 
angles  of  the  two  plates  terminate  at  the 
commencement  of  the  lacus  lacrimalis; 
they  are  attached  to  the  nasal  process 
of  the  superior  maxilla  by  the  internal 
tarsal  or  internal  lateral  or  internal  palpe- 
bral ligament  or  the  tendo  oculi  (ligamen- 
fin/t  palpebrale  mediate)  (Fig.  760). 

The  fibrous  membrane  of  the  lids  con- 
stitutes the  orbito-tarsal  ligaments  or  the 
palpebral  fasciae.  In  reality  these  so-called 
ligaments  are  fascial  expansions  situated 
one  in  each  lid,  and  are  attached  margin- 
ally to  the  edge  of  the  orbit,  where  they 
are  continuous  with  the  periosteum.  The 
superior  ligament  blends  with  the  tendon 
of  the  Levator  palpebrae,  the  inferior  with 
the  inferior  tarsal  plate.  Externally  the 
superior  and  inferior  ligaments  fuse  to 
form  the  external  tarsal  ligament  or  raphe 
just  referred  to;  internally  they  are  much 
thinner,  and,  becoming  separated  from 
the  internal  tarsal  ligament,  are  fixed  to 
the  lachrymal  bone  immediately  behind 
the  lachrymal  sac.  Together  the  liga- 
ments form  an  incomplete  Septum,  the  . 
Orbital  SeptUin  (septum  Orbitale),  Which  is  ginal  'fasciculus  ofr  ort^ularis  (dliaryUIbundle)  &c 

perforated  by  the  vessels  and  nerves  which  tfB£S3&^*,?tiS^i£tt  ^ 
pass  from  the  orbital  cavity  to  the  face  jpS^^tt^^^SS^"1^  *' 
and  scalp. 

The  Meibomian  or  Tarsal  Glands  (glandulae  tarsales  [Meibomi])  (Figs.  761  and 
763). — The  Meibomian  or  tarsal  glands  are  situated  upon  the  inner  surface  of  the 
eyelids  between  the  tarsal  plates  and  conjunctiva,  and  may  be  distinctly  seen 
through  the  mucous  membrane  on  everting  the  eyelids,  presenting  the  appearance 
of  parallel  strings  of  pearls.  They  are  about  thirty  in  number  in  the  upper  eyelid, 
and  somewhat  fewer  in  the  lower.  They  are  embedded  in  grooves  in  the  inner 


b'.  f 

FIG.  761. — Vertical  section  through  the  upper  eye 


1150  THE    ORGANS   OF  SPECIAL   SENSE 

surface  of  the  tarsal  plates,  and  correspond  in  length  with  the  breadth  of  each  plate; 
they  are,  consequently,  longer  in  the  upper  than  in  the  lower  eyelid.  Their  ducts 
open  on  the  free  margin  of  the  lids  by  minute  foramina,  which  correspond  in  num- 
ber to  the  follicles.  The  use  of  their  secretion  is  to  prevent  adhesions  of  the  lids. 
Structure  of  the  Meibomian  Glands.— These  glands  are  a  variety  of  the  cutaneous 
sebaceous  glands,  each  consisting  of  a  single  straight  tube  or  follicle,  having  a 
caecal  termination,  and  with  numerous  small  secondary  follicles  opening  into  it. 
The  tubes  consist  of  basement-membrane,  lined  at  the  mouths  of  the  tubes  by 
stratified  epithelium;  the  deeper  parts  of  the  tubes  and  the  secondary  follicles  are 
lined  by  a  layer  of  polyhedral  cells.  They  are  thus  identical  in  structure  with  the 
sebaceous  glands. 

The  Conjunctiva  (Figs.  727,  728,  740,  762). 

The  conjunctiva  is  the  mucous  membrane  of  the  eye.  It  lines  the  inner  surface 
of  the  eyelids,  is  reflected  over  the  forepart  of  the  sclerotic  and  cornea,  and  joins 
the  lids  to  the  eyeball.  In  each  of  these  situations  its  structure  presents  some 
peculiarities. 

The  Palpebral  Portion  (tunica  conjunctiva  palpebrarum)  (Fig.  763). — The  palpe- 
bral  portion  of  the  conjunctiva  lines  the  posterior  surface  of  the  lids.  It  is  thick, 
opaque,  highly  vascular,  and  covered  with  numerous  papillae,  its  deeper  parts 
presenting  a  considerable  amount  of  lymphoid  tissue.  At  the  margin  of  the  lids 
it  becomes  continuous  with  the  lining  membrane  of  the  ducts  of  the  Meibomian 
glands,  and,  through  the  lachrymal  canals,  with  the  lining  membrane  of  the 
lachrymal  sac  and  nasal  duct.  At  the  outer  angle  of  the  upper  lid  the  lachrymal 
ducts  open  on  its  free  surface;  and  at  the  inner  angle  of  the  eye  it  forms  a  semi- 
lunar  fold,  the  plica  semilunaris  (plica  semilunaris  conjunctivae)  (Fig.  764).  The 
folds  formed  by  the  reflection  of  the  conjunctiva  from  the  lids  on  to  the  eye  are 
called  the  superior  and  inferior  palpebral  folds,  the  former  being  the  deeper  of  the 
two.  These  folds  form  the  superior  and  inferior  conjunctival  fornix  (Fig.  762). 

The  Bulbar  Portion  (tunica  conjunctiva  bulbi) . — Upon  the  sclerotic  the  conjunc- 
tiva is  loosely  connected  to  the  globe ;  it  becomes  thinner,  loses  its  papillary  struc- 
ture, is  transparent,  and  only  slightly  vascular  in  health.  Upon  the  cornea  the  con- 
junctiva consists  only  of  epithelium,  constituting  the  ante- 
rior layer  of  the  cornea  (conjunctival  epithelium)  already 
described  (p.  1119).  Lymphatics  arise  in  the  conjunc- 
tiva in  a  delicate  zone  around  the  cornea,  from  which  the 
vessels  run  to  the  ocular  conjunctiva. 

Fornix  of  Conjunctiva.  —  At  the  point  of  reflection  of 
each  fold  of  the  conjunctiva  from  the  lid  on  to  the  globe 
of  the  eye  a  pocket  or  arch  is  formed.  These  arches  are 

-INFERIOR  FORNIX  l     T  l  •  •  •  .•  /TV  TOON 

termed  the  fornix  conjunctivae  (Fig.  762). 
FIG.  762— Sagittal  section       Glands  of  Conjunctiva. — In  the  conjunctiva  there  are  a 

of  eye,   showing  superior  and  .  .    .  .  ,  . 

inferior  fomices  .of  the  con-  number  of  mucous  glands  which  are  much  convoluted. 

junctiva.     (Testut.)  mi  ,  .    n      f      °   ,    .       .,  i.  ,         y^,,  i         . 

They  are  chiefly  found  in  the  upper  lid.  Other  glands, 

analogous  to  lymphoid  follicles,  and  called  by  Henle  trachoma  glands,  are  found 
in  the  conjunctiva,  and,  according  to  Stromeyer,  are  chiefly  situated  near  the 
inner  canthus  of  the  eye.  They  were  first  described  by  Brush,  in  his  description 
of  Peyer's  patches  of  the  small  intestines,  as  "  identical  structures  existing  in  the 
under  eyelid  of  the  ox." 

The  Nerves  of  the  Conjunctiva. — The  nerves  in  the  conjunctiva  are  numerous  and 
form  rich  plexuses.  According  to  Krause,  they  terminate  in  a  peculiar  form  of 
tactile  corpuscle,  which  he  terms  the  terminal  bulb. 

The  Caruncula  Lacrimalis. — The  caruncula  lacrimalis  is  a  small,  reddish,  conical- 
shaped  body,  situated  at  the  inner  canthus  of  the  eye,  and  filling  up  the  small 


SUPERIOR  FORNIX 


THE    LACHRYMAL    APPARATUS 


1151 


triangular  space  in  this  situation,  the  lacus  lacrimalis.  It  consists  of  an  island 
of  skin  containing  sebaceous  and  sweat-glands,  and  is  the  source  of  the  whitish 
secretion  which  constantly  collects  at  the  inner  angle  of  the  eye.  A  few  slender 
hairs  are  attached  to  its  surface.  On  the  outer  side  of  the  caruncula  is  a  slight 
semilunar  fold  of  conjunctiva,  the  concavity  of  which  is  directed  toward  the 
cornea;  it  is  called  the  plica  semilunaris  (Fig.  764).  Miiller  found  smooth  mus- 
cular fibres  in  this  fold,  and  in  some  of  the  domesticated  animals  a  thin  plate  of 
cartilage  has  been  discovered.  This  structure  is  considered  to  be  the  rudiment 
of  the  third  eyelid  in  birds,  the  membrana  nictitans. 

The  Lachrymal  Apparatus  (Apparatus  Lacrimaiis)  (Figs.  763,  764). 

The  lachrymal  apparatus  consists  of  the  lachrymal  gland,  which  secretes  the 
tears,  and  its  excretory  ducts,  which  convey  the  fluid  to  the  surface  of  the  eye. 
This  fluid  is  carried  away  by  the  lachrymal  canals  into  the  lachrymal  sac,  and  along 
the  nasal  duct  into  the  cavity  of  the  nose. 

The  Lachrymal  Glands  (glandula  lacrimalis}. — The  lachrymal  gland  is  lodged 
in  a  depression  at  the  outer  angle  of  the  orbit,  on  the  inner  side  of  the  external 


Puncta  lachrymalia. 


FIG.  763. — The  Meibomian  glands,  etc.,  seen  from  the  inner  surface  of  the  eyelids. 

angular  process  of  the  frontal  bone.  It  is  of  an  oval  form,  about  the  size  and 
shape  of  an  almond.  Its  upper  convex  surface  is  in  contact  with  the. periosteum 
of  the  orbit,  to  which  it  is  connected  by  a  few  fibrous  bands.  Its  under  concave 
surface  rests  upon  the  convexity  of  the  eyeball  and  upon  the  Superior  and  External 
recti  muscles.  Its  vessels  and  nerves  enter  its  posterior  border,  whilst  its  anterior 
margin  is  closely  adherent  to  the  back  part  of  the  upper  eyelid,  where  it  is  covered 
to  a  slight  extent  by  the  reflection  of  the  conjunctiva.  The  forepart  of  the  gland 
is  separated  from  the  rest  by  a  fibrous  septum ;  hence  it  is  sometimes  described  as 
a  separate  lobe,  called  the  inferior  lachrymal  gland,  palpebral  portion  of  the  gland, 
or  the  accessory  gland  of  Rosenmuiler  (glandula  lacrimalis  inferior),  the  back  part 
of  the  gland  then  being  called  the  superior  lachrymal  gland  (glandula  lacrimalis 
superior).  The  ducts  of  the  lachrymal  gland,  from  six  to  twelve  in  number, 
run  obliquely  beneath  the  mucous  membrane  for  a  short  distance,  and,  separating 
from  each  other,  open  by  a  series  of  minute  orifices  on  the  upper  and  outer  half  of 
the  conjunctiva  near  its  reflection  on  to  the  globe.  These  orifices  are  arranged  in 
a  row,  so  as  to  disperse  the  secretion  over  the  surface  of  the  membrane. 

Structure  of  the  Lachrymal  Gland. — In  structure  and  general  appearance  the 
lachrymal  resembles  the  serous  salivary  glands.    In  the  recent  state  the  cells  are  so 


THE   ORGANS    OF  SPECIAL    SENSE 


FIG.  764.  —The  lachrymal  apparatus.     Right  side. 


crowded  with  granules  that  their  limits  can  hardly  be  defined.    Each  cell  contains 
an  oval  nucleus,  and  the  cell-protoplasm  is  finely  fibrillated. 

The  Lachrymal  Canaliculi  or  Canals  (Fig.  764)  commence  at  the  minute  orifices, 
puncta  lacrimalia,  on  the  summit  of  a  small  conical  elevation,  the  lachrymal  papilla 
or  caruncle  (carunculus  lacrimalis),  seen  on  the  margin  of  the  lids  at  the  outer  ex- 
tremity of  the  lacus  lacrimalis.  The  superior  canal  (ductus  lacrimalis  superior],  the 
smaller  and  shorter  of  the  two,  at  first  ascends,  and  then  bends  at  an  acute  angle, 
and  passes  inward  and  downward  to  the  ampulla.  The  inferior  canal  (ductus 

lacrimalis  inferior}  at  first  descends, 
and  then,  abruptly  changing  its  course, 
passes  almost  horizontally  inward  to 
the  ampulla.  These  canals  are  dense 
and  elastic  in  structure  and  somewhat 
dilated  at  their  angle.  The  mucous 
membrane  is  covered  with  scaly  epi- 
thelium. The  two  canals  join  in  a 
dilatation,  the  ampulla  (ampulla  ductus 
lacrimalis),  which  empties  into  the 
lachrymal  sac. 

The  Lachrymal  Sac  (saccus  lacri- 
malis} (Fig.  764)  .—The  lachrymal  sac  is 
the  upper  dilated  extremity  of  the  nasal 
duct,  and  is  lodged  in  a  deep  groove 
formed  by  the  lachrymal  bone  and  the 
nasal  process  of  the  superior  maxillary 
bone.  It  is  oval  in  form,  its  upper  ex- 
tremity being  closed  in  and  rounded, 
whilst  below  it  is  continued  into  the  nasal  duct.  It  is  covered  by  a  fibrous 
expansion  derived  from  the  tendo  oculi,  and  on  its  deep  surface  it  is  crossed  by 
the  Tensor  tarsi  muscle  (Horner's  muscle,  p.  373),  which  is  attached  to  the  ridge 
on  the  lachrymal  bone. 

Structure. — It  consists  of  a  fibrous  elastic  coat,  lined  internally  by  mucous  mem- 
brane, the  latter  being  continuous,  through  the  ampulla  and  lachrymal  canals, 
with  the  mucous  lining  of  the  conjunctiva,  and,  through  the  nasal  duct,  with  the 
pituitary  membrane  of  the  nose. 

The  Nasal  Duct  (ductus  nasolacrimalis)  (Fig.  764). — The  nasal  duct  is  a 
membranous  canal,  about  three-quarters  of  an  inch  in  length,  which  extends  from 
the  lower  part  of  the  lachrymal  sac  to  the  inferior  meatus  of  the  nose,  where  it 
terminates  by  a  somewhat  expanded  orifice,  provided  with  an  imperfect  valve,  the 
valve  of  Hasner  (plica  lacrimalis  [Hasneri]),  formed  by  the  mucous  membrane.  It 
is  contained  in  an  osseous  canal  formed  by  the  superior  maxillary,  the  lachrymal, 
and  the  inferior  turbinated  bones,  is  narrower  in  the  middle  than  at  each  extrem- 
ity, and  takes  a  direction  downward,  backward,  and  a  little  outward.  It  is  lined 
by  mucous  membrane,  which  is  continuous  below  with  the  pituitary  lining  of 
the  nose.  The  membrane  in  the  lachrymal  sac  and  nasal  duct  is  covered  with 
columnar  epithelium,  as  in  the  nose.  This  epithelium  is  in  places  ciliated. 

Surface  Form.— The  palpebrcd  fissure,  or  opening  between  the  eyelids,  is  elliptical  in  shape, 
and  differs  in  size  in  different  individuals  and  in  different  races  of  mankind.  In  the  Mongolian 
races,  for  instance,  the  opening  is  very  small,  merely  a  narrow  fissure,  and  this  makes  the  eye- 
ball appear  small  in  these  races,  whereas  the  size  of  the  eye  is  relatively  very  constant.  The 
normal  direction  of  the  fissure  is  slightly  oblique,  in  a  direction  upward  and  outward,  so  that  the 
outer  angle  is  on  a  slightly  higher  level  than  the  inner.  This  is  especially  noticeable  in  the  Mon- 
golian races,  in  whom,  owing  to  the  upward  projection  of  the  malar  bone  and  the  shortness  of 
the  external  angular  process  of  the  frontal  bone,  the  tarsal  plate  of  the  upper  lid  is  raised  at  its 
outer  part  and  gives  an  oblique  direction  to  the  palpebral  fissure. 


THE   LACHRYMAL   APPARATUS  1153 

When  the  eyes  are  directed  forward,  as  in  ordinary  vision,  the  upper  part  of  the  cornea  is 
covered  by  the  upper  lid,  and  the  lower  margin  of  the  cornea  corresponds  to  the  level  of  the 
lower  lid,  so  that  about  the  lower  three-fourths  of  the  cornea  is  exposed  under  ordinary  circum- 
stances. On  the  margins  of  the  lids,  about  a  quarter  of  an  inch  from  the  inner  canthus,  are  two 
small  openings,  the  punda  lacrimalia,  the  commencement  of  the  lachrymal  canals.  They  are 
best  seen  by  everting  the  eyelids.  In  the  natural  condition  they  are  in  contact  with  the  con- 
junctiva of  the  eyeball,  and  are  maintained  in  this  position  by  the  Tensor  tarsi  muscle,  so  that 
the  tears  running  over  the  surface  of  the  globe  easily  find  their  way  into  the  lachrymal  canals. 
The  position  of  the  lachrymal  sac  into  which  the  canals  open  is  indicated  by  a  little  tubercle, 
which  is  plainly  to  be  felt  on  the  lower  margin  of  the  orbit.  The  lachrymal  sac  lies  immediately 
above  and  to  the  inner  side  of  this  tubercle,  and  a  knife  passed  through  the  skin  in  this 
situation  would  open  the  cavity.  The  position  of  the  lachrymal  sac  may  also  be  indicated  by 
the  tendo  oculi  or  internal  tarsal  ligament.  If  both  lids  be  drawn  outward,  so  as  to  tense  the 
skin  at  the  inner  angle,  a  prominent  cord  will  be  seen  beneath  the  tightened  skin.  This  is  the 
truth  oculi,  which  lies  immediately  over  the  lachrymal  sac,  bisecting  it,  and  thus  forming  a  useful 
guide  to  its  situation.  A  knife  entered  immediately  beneath  the  tense  cord  would  open  the 
lower  part  of  the  sac.  A  probe  introduced  through  this  opening  can  be  readily  passed  down- 
ward through  the  duct  into  the  inferior  meatus  of  the  nose.  The  direction  of  the  duct  is  down- 
ward, outward,  and  backward,  and  this  course  should  be  borne  in  mind  in  passing  the  probe, 
otherwise  the  point  may  be  driven  through  the  thin  bony  walls  of  the  canal.  A  convenient 
plan  is  to  direct  the  probe  in  such  a  manner  that  if  it  were  pushed  onward  it  would  strike 
the  first  molar  tooth  of  the  lower  jaw  on  the  same  side  of  the  body.  In  other  words,  the 
surgeon  standing  in  front  of  his  patient  should  carry  in  his  mind  the  position  of  the  first 
molar  tooth,  and  should  push  his  probe  onward  in  such  a  way  as  if  he  desired  to  reach  this 
structure. 

Beneath  the  internal  angular  process  of  the  frontal  bone  the  pulley  of  the  Superior  oblique 
muscle  of  the  eye  can  be  plainly  felt  by  pushing  the  finger  backward  between  the  upper  and  inner 
angle  of  the  eye  and  the  roof  of  the  orbit;  passing  backward  and  outward  from  this  pulley,  the 
tendon  can  be  felt  for  a  short  distance. 

Surgical  Anatomy.— The  eyelids  are  composed  of  various  tissues,  and  consequently  are  liable 
to  a  variety  of  diseases.  The  skin  which  covers  them  is  exceedingly  thin  and  delicate,  and  is 
supported  on  a  quantity  of  loose  and  lax  subcutaneous  tissue  which  contains  no  fat.  In  conse- 
quence of  this  it  is  very  freely  movable,  and  is  liable  to  be  drawn  down  by  the  contraction  of 
neighboring  cicatrices.  Such  contractions  may  produce  an  eversion  of  the  lid  known  as  ectropion. 
Inversion  of  the  lids  (entropion)  from  spasm  of  the  Orbicularis  palpebrarum  or  from  chronic 
inflammation  of  the  palpebral  conjunctiva  may  also  occur.  In  some  individuals  there  is  an  extra 
row  of  eyelashes  on  the  inner  margin  of  the  lid,  directed  toward  the  cornea  (distichiasis).  Trich- 
iasis  is  a  condition  in  which  the  lashes  are  directed  toward  the  eye,  but  there  is  not  inversion  of 
the  lid.  The  eyelids  are  richly  supplied  with  blood,  and  are  often  the  seat  of  vascular  growths, 
such  as  ncrvi.  Rodent  ulcer  also  frequently  commences  in  this  situation.  The  loose  cellular  tissue 
beneath  the  skin  is  liable  to  become  extensively  infiltrated  either  with  blood  or  inflammatory 
products,  producing  very  great  swelling.  Even  from  very  slight  injuries  to  this  tissue  the  extrava- 
sation of  blood  may  be  so  great  as  to  produce  considerable  swelling  of  the  lids  and  complete 
closure  of  the  eye,  and  the  same  is  the  case  when  inflammatory  products  are  poured  out.  The 
follicles  are  liable  to  become  inflamed,  constituting  the  disease  known  as  marginal  blepharitis, 
blepharitis  ciliaris,  or  ''blear-eye."  Irregular  or  disorderly  growth  of  the  eyelashes  not  unfre- 
quently  occurs,  some  of  them  being  turned  toward  the  eyeball  and  producing  inflammation  and 
follicles  of  the  eyelashes  or  the  sebaceous  glands  associated  with  these  follicles  may  be  the  seat  of 
inflammation,  constituting  the  ordinary  hordeolum  or  "sty."  The  Meibomian  glands  are  affected 
in  the  so-called  ''  tarsal  tumor;"  the  tumor,  according  to  some,  being  caused  by  the  retained  secre- 
tion of  these  glands;  by  others  it  is  believed  to  be  a  neoplasm  connected  with  the  gland.  The  Orbic- 
ularis palpebrarum  may  be  the  seat  of  spasm  (blepharospasm),  either  in  the  form  of  slight  quiv- 
ering of  the  lids  or  repeated  twitchings,  most  commonly  due  to  errors  of  refraction  in  children, 
or  more  continuous  spasm,  due  to  some  irritation  of  the  fifth  or  seventh  cranial  nerves.  The 
Orbicularis  may  be  paralyzed,  generally  associated  with  paralysis  of  the  other  facial  muscles. 
Under  these  circumstances  the  patient  is  unable  to  close  the  lids,  and  if  he  attempts  to  do  so, 
rolls  the  eyeball  upward  under  the  upper  lid.  The  tears  overflow  from  displacement  of  the  lower 
lid,  and  the  conjunctiva  and  cornea,  being  constantly  exposed  and  the  patient  being  unable  to 
wink,  become  irritated  from  dust  and  foreign  bodies.  As  a  result  there  may  be  ulceration  of 
the  cornea,  and  possibly  eventually  complete  destruction  of  the  eye.  In  paralysis  of  the  Levator 
palpebrae  superioris  there  is  drooping  of  the  upper  eyelid  (ptosis)  and  other  symptoms  of  impli- 
cation of  the  third  nerve.  The  eyelids  may  be  the  seat  of  bruises,  wounds,  or  burns.  After 
wounds  or  burns  adhesions  of  the  margins  of  the  lids  to  each  other  or  adhesion  of  the  lids  to 
the  globe  may  take  place.  The  eyelids  are  sometimes  the  seat  of  emphysema  after  fracture  of 
some  of  the  thin  bones  forming  the  inner  wall  of  the  orbit.  If  shortly  after  such  an  injury  the 
patient  blows,  his  nose,  air  is  forced  from  the  nostrils  through  the  lacerated  structure  into  the 

73 


1154  THE    ORGANS    OF  SPECIAL   SENSE 

connective  tissue  of  the  eyelids,  which  suddenly  swell  up  and  present  the  peculiar  crackling  on 
pressure  which  is  characteristic  of  this  affection. 

Foreign  bodies  frequently  get  into  the  conjunctival  sac  and  cause  great  pain,  especially  if 
they  come  in  contact  with  the  corneal  surface,  during  the  movements  of  the  lid  and  the  eye  on 
each  other.  The  conjunctiva  is  frequently  involved  in  severe  injuries  of  the  eyeball,  but  is  seldom 
ruptured  alone;  the  most  common  form  of  injury  to  the  conjunctiva  alone  is  from  a  burn,  either 
from  fire,  strong  acids,  or  lime.  In  these  cases  union  is  liable  to  take  place  between  the  eyelid 
and  the  eyeball.  The  conjunctiva  is  often  the  seat  of  inflammation  arising  from  many  different 
causes,  and  the  arrangement  of  the  conjunctival  vessels  should  be  remembered  as  affording  a 
means  of  diagnosis  between  this  condition  and  injection  of  the  sclerotic,  which  is  present  in 
inflammation  of  the  deeper  structures  of  the  globe.  The  inflamed  conjunctiva  is  bright  red;  the 
vessels  are  large  and  tortuous,  and  greatest  at  the  circumference,  shading  off  toward  the  corneal 
margin;  they  anastomose  freely  and  form  a  dense  network,  and  they  can  be  emptied  by  gentle 
pressure. 

The  lachrymal  gland  is  occasionally,  though  rarely,  the  seat  of  inflammation  (dacryoadenitis) , 
either  acute  or  chronic;  it  is  also  sometimes  the  seat  of  tumors,  benign  or  malignant,  and  for  these 
may  require  removal.  This  may  be  done  by  an  incision  through  the  skin  just  below  the  eyebrow; 
and  the  gland,  being  invested  with  a  special  capsule  of  its  own,  may  be  isolated  and  removed 
without  opening  the  general  cavity  of  the  orbit.  The  canaliculi  may  be  obstructed,  either  as  a 
congenital  defect  or  by  some  foreign  body,  as  an  eyelash  or  a  dacryolith,  causing  the  tears  to  run 
over  the  cheek.  The  canaliculi  may  also  become  occluded  as  the  result  of  burns  or  injury;  over- 
flow of  tears  may  in  addition  result  from  deviation  of  the  puncta  or  from  chronic  inflammation 
of  the  lachrymal  sac.  When  there  is  failure  of  the  lachrymal  tubes  to  drain  off  the  tears  and 
the  fluid  gathers  beneath  and  flows  over  the  lids,  the  condition  is  known  as  epiphora  or  stilli- 
cidium.  This  latter  condition  is  set  up  by  some  obstruction  to  the  nasal  duct  frequently  occurring 
in  tuberculous  subjects.  In  consequence  of  this  the  tears  and  mucus  accumulate  in  the  lachrymal 
sac,  distending  it.  Suppuration  in  the  lachrymal  sac  (dacryocystitis)  is  sometimes  met  with; 
this  may  be  the  sequel  of  a  chronic  inflammation;  or  may  occur  after  some  of  the  eruptive  fevers 
in  cases  where  the  lachrymal  passages  were  previously  quite  healthy.  It  may  lead  to  lachrymal 
fistula. 

THE  EAR  (ORGANON  AUDITUS). 

The  organ  of  hearing  is  divisible  into  three  parts — the  external  ear,  the  middle 
ear  or  tympanum,  and  the  internal  ear  or  labyrinth. 

THE  EXTERNAL  EAR  (AURIS  EXTERNA). 

The  external  ear  consists  of  an  expanded  portion  named  pinna  or  auricle,  and 
the  auditory  canal  or  meatus.  The  former  serves  to  collect  the  vibrations  of  the  air 
by  which  sound  is  produced;  the  latter  conducts  those  vibrations  to  the  tympanum. 

The  Pinna  or  Auricle  (Auricula)  (Fig.  765). 

The  pinna  or  auricle  is  attached  to  the  side  of  the  head  midway  between  the 
forehead  and  occiput.  "Its  level  is  indicated  by  horizontal  lines  extending  back- 
ward from  the  eyebrows  above  and  from  the  tip  of  the  nose  below."  (Hensman.) 
It  is  of  an  ovoid  form,  with  its  larger  end  directed  upward.  Its  outer  surface  is  irreg- 
ularly concave,  directed  slightly  forward.  The  angle  which  it  bears  to  the  head  is 
called  the  cephalo- auricular  angle.  In  some  cases  this  angle  is  almost  absent.  In 
others  it  is  nearly  a  right  angle.  The  pinna  of  one  side  may  vary  in  size,  shape,  and 
angle  from  the  pinna  of  the  other  side.  The  pinna  of  a  woman  is  apt  to  be  smaller 
than  that  of  a  man,  and  is  less  often  deformed.  The  outer  surface  of  the  pinna 
presents  numerous  eminences  and  depressions  which  result  from  the  foldings  of  its 
fibro-cartilaginous  element.  To  each  of  these,  names  have  been  assigned.  Thus 
the  external  prominent  rim  of  the  auricle  is  called  the  helix .  Another  curved  prom- 
inence, parallel  with  and  in  front  of  the  helix,  is  called  the  antihelix;  this  bifurcates 
above  and  forms  the  crura  (crura  anthelicis),  which  encloses  a  triangular  depression, 
the  fossa  of  the  antihelix  (fossa  triangularis  [auriculae]).  The  narrow  curved  depres- 
sion between  the  helix  and  antihelix  is  called  the  fossa  of  the  helix  or  the  scaphoid 


THE  PINNA  OR  A  URICLE 


1155 


fossa  (scapha) ;  the  antihelix  describes  a  curve  around  a  deep,  capacious  cavity,  the 
concha  auriculae,  which  is  partially  divided  into  two  parts  by  the  crus  of  the  helix  (crus 
helicis),or  the  commencement  of  the  helix;  the  upper  part  is  termed  the  cymba- 


OARWINIAN 
TUBERCLE 


FOSSA 

TRIANGULARIS 


CRURA  OF 
ANTIHELIX 


SCAPHOID 
FOSSA 


INCISURA 
ANTERIOR 


TUBERCULUM 
SUPRATRAGICUM 


EXTERNAL 
AUDITORY 
MEATUS 


INCISURA 

INTEHTRAGICA 


POSTERIOR 
AURICULAR  • 

SULCUS 


CAVUM   CONCHAE 

FIG.  765. — The  right  pinna  or  auricle,  viewed  from  without. 


(Spalteholz.) 


INSERTION 

OF  SUPERIOR 

AURICULAR 

MUSCLE 

INSERTION 


AURICULAR 
MUSCLE 
OBLIQUE 

AURICULAR 
MUSCLE 


conchae,  the  lower  part  the  cavum 
conchae  In  front  of  the  concha, 
and  projecting  backward  over  the 
meatus,  is  a  small  pointed  emi- 
nence, the  tragus,  so  called  from 
its  being  generally  covered  on  its  OF  ANTERIOR 

,»  .  AURir.lll  AR 

under  surface  with  a  tuft  of  hair 
resembling  a  goat's  beard.  Oppo- 
site the  tragus,  and  separated  from 
it  by  a  deep  notch  (incisuria  inter- 
tragicd),  is  a  small  tubercle,  the 
antitragus.  Below  this  is  the  lobule 
(lobulus  auriculae),  composed  of 
tough  areolar  and  adipose  tissue, 
wanting  the  firmness  and  elasticity 
of  the  rest  of  the  pinna.  Some- 
times the  lobule  does  not  hang 
freely,  but  is  adherent.  Where 
the  helix  turns  downward  a  small  tubercle,  tubercle  of  Darwin  (tuberculum  auric- 
ulae [Darwini]),  is  frequently  seen.  This  tubercle  is  very  evident  about  the  sixth 
month  of  foetal  life;  at  this  stage  the  human  pinna  has  a  close  resemblance  to  that 
of  some  of  the  adult  monkeys. 


INSERTION  OF 

POSTERIOR 

AURICULAR 

MUSCLE 

TRANSVERSE 

AURICULAR 

MUSCLE 


CARTILAGE 

OF  EXTERNAL 

AUDITORY 

MEATUS 


FIG.  766. — The  cartilages  of  the  right  auricle,  isolated,  with, 
the  muscles,  viewed  trom  the  inside.     (Spalteholz.) 


1156 


THE    ORGANS    OF  SPECIAL  SENSE 


The  cranial  surface  of  the  pinna  presents  elevations  which  correspond  to  the 
depressions  on  its  outer  surface  and  after  which  they  are  named,  e.  g.,  eminentia 
conchae,  eminentia  fossae  triangularis,  etc. 

The  eminentia  conchae  and  the  fossae  triangularis  are  separated  by  a  furrow 
(sulcus  antihelicis  transversus) ,  which  corresponds  to  the  inferior  crus  of  the  anti- 
helix,  or  groove  (sulcus  cruris  helicis),  and  upon  the  eminence  there  is  a  vertical 
ridge,  the  ponticulus,  which  indicates  the  point  of  insertion  of  the  Retrahens 
auriculam  muscle. 

Structure  of  the  Pinna. — The  pinna  is  composed  of  a  thin  plate  of  yellow 
fibre-cartilage,  covered  with  integument,  and  connected  to  the  surrounding  parts 
by  the  extrinsic  ligaments  and  muscles,  and  to  the  commencement  of  the  external 
auditory  canal  by  fibrous  tissue. 

The  Integument. — The  integument  is  thin,  closely  adherent  to  the  cartilage,  and 
covered  with  hairs  furnished  with  sebaceous  glands,  which  are  most  numerous  in 
the  concha  and  scaphoid  fossa.  The  hairs  are  most  numerous  and  largest  on  the 
tragus  and  antitragus. 

The  Cartilage  of  the  Pinna  (cartilago  auriculae)  (Fig.  767) . — The  cartilage  of  the 
pinna  consists  of  one  single  piece;  it  gives  form  to  this  part  of  the  ear,  and  upon  its 

surface  are  found  all  the  eminences 
and  depressions  above  described. 
It  does  not  enter  into  the  construc- 
tion of  all  parts  of  the  auricle ;  thus 
it  does  not  form  a  constituent  part 
of  the  lobule;  it  is  deficient  also 
between  the  lamina  of  the  tragus 
and  beginning  of  the  crus  helix,  the 
notch  between  (incisura  terminalis 
auris)ihem  being  filled  up  by  dense 
fibrous  tissue.  At  the  front  part  of 
the  pinna,where  the  helix  bends  up- 
ward, is  a  small  projection  of  car- 
tilage, called  the  spine  of  the  helix 
(spina  helicis),  while  the  lower  part 
of  the  helix  is  prolonged  downward 
as  a  tail-like  process,  the  cauda 
helicis;  this  is  separated  from  the 
antihelix  by  a  fissure,  the  fissura  antitragohelicina.  The  fissures  of  Santorini  are 
usually  two  in  number:  one  in  the  substance  of  the  tragus,  which  partially  separates 
the  different  parts,  and  one  in  the  cartilage  of  the  meatus.  The  fissure  of  the  helix 
is  a  short  vertical  slit,  situated  at  the  forepart  of  the  pinna.  Another  fissure,  the 
fissure  of  the  tragus,  is  seen  upon  the  anterior  surface  of  the  tragus.  Anteriorly 
and  inferiorly  the  cartilage  of  the  pinna  is  continuous  with  the  cartilage  of  the 
external  auditory  meatus  by  a  cartilaginous  isthmus  (isthmus  cartilaginis  amis). 
Some  authors  regard  the  tragus  as  part  of  the  cartilage  of  the  meatus.  The 
cartilage  of  the  pinna  is  very  pliable,  elastic,  of  a  yellowish  color  and  belongs  to 
that  form  of  cartilage  which  is  known  under  the  name  of  yellow  fibro-cartilage. 
The  Ligaments  of  the  Pinna  (ligamenti  auricularia  [Valsalv'ae]). — The  ligaments 
of  the  pinna  consist  of  two  sets:  1.  The  extrinsic  set,  or  those  connecting  it  to  the 
side  of  the  head.  2.  The  intrinsic  set,  or  those  connecting  the  various  parts  of  its 
cartilage  together. 

The  Extrinsic  Ligaments,  the  most  important,  are  three  in  number:  superior, 
anterior,  and  posterior.  The  superior  ligament  (ligamentum  auriculare  superius) 
extends  from  the  suprameatal  spine  to  the  spine  of  the  helix.  The  anterior  ligament 
(ligamentum  auriculare  anterius)  extends  from  the  spina  helicis  and  tragus  to  the 


FISSURA 

ANTITRAGICO- 
HELICINA 


TRIANGULAR 
FOSSA 


SPINE   OF 
HELIX 

CRUS  OF 
HELIX 

LAMINA 

TRAGI 

INCISURA 

TERMINALIS 

AURIS 


INCISURA 
INTERTRAGICA 


ANTITRAGUS 


FIG.  767.— The  right  ear  cartilages,  isolated,  viewed  from 
without.     (Spalteholz.) 


THE   PINNA     OR   AURICLE 


1157 


root  of  the  zygoma.  The  posterior  ligament  (licjamentum  auriculare  posterius) 
passes  from  the  posterior  surface  of  the  concha  to  the  outer  surface  of  the  mastoid 
process  of  the  temporal  bone. 

The  chief  Intrinsic  Ligaments  are:  (1)  a'strong  fibrous  band,  stretching  across 
from  the  tragus  to  the  commencement  of  the  helix,  completing  the  meatus  in  front, 
and  partly  encircling  the  boundary  of  the  concha;  and  (2)  a  band  which  extends 
between  the  antihelix  and  the  cauda  helicis.  Other  less  important  bands  are 
found  on  the  cranial  surface  of  the  pinna. 

The  Muscles  of  the  Pinna  (Figs.  766  and  768) . — The  muscles  of  the  pinna  consist 
of  two  sets :  1 .  The  extrinsic,  which  connect  it  with  the  side  of  the  head,  moving  the 
pinna  as  a  whole — viz.,  the  Attollens,  Attrahens,  and  Retrahens  auriculam  (p.  372). 
2.  The  intrinsic,  which  extend  from  one  part  of  the  auricle  to  another,  viz. : 


Helicis  major. 
Helicis  minor. 
Tragicus. 


Antitragicus. 
Transversus  auriculae. 
Obliquus  auriculae. 


The  Helicis  Major  (m.  helicis  major}  is  a  narrow  vertical  band  of  muscular 
fibres,  situated  upon  the  anterior  margin  of  the  helix.    It  arises,  below,  from  the 
spina   helicis,   and   is  inserted    into 
the  anterior  border  of  the  helix,  just 
where  it  is  about  to  curve  backward. 
It  is  pretty  constant  in  its  existence. 

The  Helicis  Minor  (m.  helicis  minor) 
is  an  oblique  fasciculus  which  covers 
the  crus  helicis. 

The  Tragicus  (m.  tragicus)  is  a 
short,  flattened  band  of  muscular 
fibres  situated  upon  the  outer  surface 
of  the  tragus,  the  direction  of  its 
fibres  being  vertical. 

The  Antitragicus  (m.  antitragicus) 
arises  from  the  outer  part  of  the  anti- 
tragus;  its  fibres  are  inserted  into  the 
cauda  helicis  and  antihelix.  This 
muscle  is  usually  very  distinct. 

The  Transversus  Auriculae  (m. 
transversus  auriculae)  is  placed  on 
the  cranial  surface  of  the  pinna.  It 
consists  of  scattered  fibres,  partly 
tendinous  and  partly  muscular,  ex- 
tending from  the  convexity  of  the 
concha  to  the  prominence  corre- 
sponding with  the  groove  of  the  helix. 

The  Obliquus  Auriculae  (Tod)  (m. 
obliquus  auriculae)  consists  of  a  few 

fibres  extending  from  the  upper  and  back  part  of  the  concha  to  the  convexity 
immediately  above  it. 

The  Arteries  of  the  Pinna. — The  arteries  of  the  pinna  are  the  posterior  auricular 
from  the  external  carotid,  the  anterior  auricular  from  the  temporal  and  an  auric- 
ular branch  from  the  occipital  artery. 

The  Veins  of  the  Pinna. — The  veins  of  the  pinna  accompany  the  corresponding 
arteries. 

The  Lymphatics  of  the  Pinna. — The  lymphatics  enter  into  the  pre-auricular  glands 
and  the  glands  upon  the  Sterno-mastoid  muscle  at  its  insertion. 


FIG.  768. — The  muscles  of  the  pinna. 


1158  THE  ORGANS  OF  SPECIAL  SENSE 

The  Nerves  of  the  Pinna. — The  nerves  of  the  pinna  are:  the  great  auricular, 
from  the  cervical  plexus;  the  auricular  branch  of  the  vagus;  the  auriculo-temporal 
branch  of  the  inferior  maxillary  nerve;  the  small  occipital  from  the  cervical 
plexus,  and  the  great  occipital  or  internal  branch  of  the  dorsal  division  of  the 
second  cervical  nerve.  The  muscles  of  the  pinna  are  supplied  by  the  facial  nerve. 

The  External  Auditory  or  External  Acoustic  Canal  or  External  Auditory 

Meatus  (Meatus  Acusticus  Externus  or  Meatus 

Auditorius  Externus). 

The  external  auditory  or  acoustic  canal  or  meatus  extends  from  the  bottom 
of  the  concha  to  the  membrana  tympani  (Figs.  765,  769,  and  770).  It  is  about 
an  inch  and  a  half  in  length  if  measured  from  the  tragus;  from  the  bottom  of 
the  concha  its  length  is  about  an  inch.  It  forms  a  sort  of  S-shaped  curve,  and  is 
directed  at  first  inward,  forward,  and  slightly  upward  (pars  externa);  it  then 
passes  inward  and  backward  (pars  media],  and  lastly  is  carried  inward,  forward, 
and  slightly  downward  (pars  interna).  It  forms  an  oval  cylindrical  canal,  the 
greatest  diameter  being  in  the  vertical  direction  at  the  external  orifice,  but  in  the 


Cartilage  of 
the  pinna  ~ 


Promont. 


Int.  carat,  a. 

Membrana 
tympani 

Cartilage  of  'the  ext.    A  .'    :    ) 
auditory  meatus 

FIG.  769. — Transverse  section  of  external  auditory  meatus  and  tympanum.     Left  side.     (Gegenbaur.) 

transverse  direction  at  the  tympanic  end.  It  presents  two  constrictions,  one 
near  the  inner  end  of  the  cartilaginous  portion,  and  another,  the  isthmus,  in  the 
osseous  portion,  about  three-quarters  of  an  inch  from  the  bottom  of  the  concha. 
The  membrana  tympani  (Figs.  769  and  770),  which  occupies  the  termination  of  the 
meatus,  is  directed  obliquely,  in  consequence  of  which  the  floor  of  the  canal  is 
longer  than  the  roof,  and  the  anterior  wall  longer  than  the  posterior.  The  auditory 
canal  is  formed  partly  by  cartilage  and  membrane,  partly  by  bone,  and  is  lined  by 
perichoridrium  and  periosteum,  which  is  covered  with  skin. 

The  Cartilaginous  Portion  (meatus  acusticus  externus  cartilagineus}. — The  car- 
tilaginous portion  is  about  one-third  of  an  inch  (8  mm.)  in  length;  it  is  formed 
by  the  cartilage  of  the  pinna,  prolonged  inward,  and  firmly  attached  to  a  greater 
portion  of  the  circumference  of  the  auditory  process  of  the  temporal  bone.  The 
cartilage  is  deficient  at  its  upper  and  back  part,  its  place  being  supplied  by  fibrous 
membrane.  This  part  of  the  canal  is  rendered  extremely  movable  by  two  or 
three  deep  fissures,  the  fissures  of  Santorini  (incisurae  cartilaginis  meatus  acustici 
externi  [Santorini\) ,  which  extend  through  the  cartilage  in  a  vertical  direction. 
It  is  firmly  attached  at  its  lower  and  front  part  to  the  middle  root  of  the  zygoma 
and  to  the  lateral  edge  of  the  tympanic  portion  of  the  temporal  bone. 


THE   EXTERNAL   AUDITORY  MEATUS 


1159 


The  Osseous  Portion  (meatus  acusticus  externus  osseus). — The  osseous  por- 
tion is  about  two-thirds  of  an  inch  (16  mm.)  in  length,  and  narrower  than  the 
cartilaginous  portion.  It  is  directed  inward  and  a  little  forward,  forming  a  slight 
curve  in  its  course,  the  convexity  of  which  is  upward  and  backward.  Its  inner 
end,  which  communicates,  in  the  dry  bone,  with  the  cavity  of  the  tympanum,  is 
smaller  than  the  outer  and  sloped,  the  anterior  wall  projecting  beyond  the  poste- 
rior about  two  lines;  it  is  marked,  except  at  its  upper  part,  by  a  narrow  groove, 
the  tympanic  sulcus  (sidcus  tympanicus],  for  the  insertion  of  the  mernbrana  tym- 
pani.  Its  outer  edge  is  dilated  and  rough  in  the  greater  part  of  its  circumference, 
for  the  attachment  of  the  cartilage  of  the  pinna.  Its  vertical  transverse  section 
is  oval,  the  greatest  diameter  being  from  above  downward.  The  front  and  lower 
parts  of  this  canal  are  formed  by  a  curved  plate  of  bone,  which,  in  the  foetus, 
exists  as  a  separate  ring  (annulus  tympanicus),  incomplete  at  its  upper  part.  (See 
Section  on  Osteology.) 


FENESTRA  OVALIS 
CLOSED  BY  STAPES 


FIG.  770. — Vertical  section  through  the  external  auditory  meatus  and  tympanum,  passing  in  front  of  the 

fenestra  ovalis.     (Testut.) 

The  Skin  of  the  Meatus. — The  skin  lining  the  meatus  is  a  prolongation  of  the 
external  skin;  it  is  thin,  adheres  closely  to  the  cartilaginous  and  osseous  portions 
of  the  tube,  and  covers  the  surface  of  the  membrana  tympani,  forming  a  very 
thin  outer  layer.  After  maceration  the  thin  pouch  of  epidermis,  when  withdrawn, 
preserves  the  form  of  the  meatus.  In  the  thick  subcutaneous  tissue  of  the  cartil- 
aginous part  of  the  meatus  are  numerous  ceruminous  glands  (glandulae  ceruminosae) 
which  secrete  the  ear-wax.  They  resemble  in  structure  sweat-glands,  and  their 
ducts  open  on  the  surface  of  the  skin. 

Relations  of  the  Meatus. — In  front  of  the  osseous  part  is  the  glenoid  fossa,  which 
receives  the  condyle  of  the  mandible  (Fig.  762),  which,  however,  is  separated  from 
the  cartilaginous  part  by  the  retromandibular  part  of  the  parotid  gland.  The 
movements  of  the  jaw  influence  to  some  extent  the  lumen  of  the  cartilaginous 
portion.  Behind  the  osseous  part  are  the  mastoid  air-cells  (cellulae  mastoideae), 
separated  from  it  by  a  thin  layer  of  bone  (Fig.  46). 

The  Arteries  of  the  External  Meatus. — The  arteries  supplying  the  external  meatus 
are  branches  from  the  posterior  auricular,  internal  maxillary,  and  superficial 
temporal. 


s 

1160  THE    ORGANS    OFi  SPECIAL    SENSE 

The  Veins  of  the  External  Meatus. — Veins  accompany  the  corresponding  arteries 
and  pass  to  the  internal  maxillary,  temporal,  and  posterior  auricular  veins. 

The  Lymphatics  of  the  External  Meatus. — The  lymphatics  accompany  the  veins 
and  enter  the  parotid  and  posterior  auricular  lymph-glands. 

The  Nerves  of  the  External  Meatus. — The  nerves  are  derived  from  the  auriculo- 
temporal  branch  of  the  inferior  maxillary  nerve,  the  auricularis  magnus,  and  the 
auricular  branch  of  the  vagus. 

Surface  Form. — The  point  of  junction  of  the  osseous  and  cartilaginous  portions  of  the  tube 
is  an  obtuse  angle,  which  projects  into  the  canal  at  its  antero-inferior  wall.  This  produces  a 
sort  of  constriction  in  this  situation,  and  renders  it  the  narrowest  portion  of  the  canal — an  impor- 
tant point  to  be  borne  in  mind  in  connection  with  the  presence  of  foreign  bodies  in  the  ear. 
The  cartilaginous  is  connected  to  the  bony  part  by  fibrous  tissue,  which  renders  the  outer  part 
of  the  tube  very  movable,  and  therefore  by  drawing  the  pinna  upward  and  backward  the  canal 
is  rendered  almost  straight.  At  the  external  orifice  are  a  few  short,  crisp  hairs  which  serve  to 
prevent  the  entrance  of  small  particles  of  dust,  flies  or  other  insects.  In  the  external  auditory 
meatus  the  secretion  of  the  ceruminous  glands  serves  to  catch  any  small  particles  which  may 
find  their  way  into  the  canal,  and  prevent  their  reaching  the  membrana  tympani,  where  their 
presence  might  excite  irritation.  In  young  children  the  meatus  is  short,  the  osseous  part 
being  very  deficient,  and  consisting  merely  of  a  bony  ring  (annulus  tympanicus],  which  supports 
the  membrana  tympani.  In  the  fretus  the  osseous  part  is  entirely  absent.  The  shortness  of  the 
canal  in  children  should  be  borne  in  mind  in  introducing  the  aural  speculum,  so  that  it  shall  not 
be  pushed  in  too  far,  at  the  risk  of  injuring  the  membrawa  tympani;  indeed,  even  in  the  adult  the 
speculum  should  never  be  introduced  beyond  the  constriction  which  marks  the  junction  of  the 
osseous  and  cartilaginous  portions.  In  using  this  instrument  it  is  advisable  that  the  pinna 
should  be  drawn  upward,  backward,  and  a  little  outward,  so  as  to  render  the  canal  as  straight  as 
possible,  and  thus  assist  the  operator  in  obtaining,  by  the  aid  of  reflected  light,  a  good  view  of 
the  membrana  tympani.  Just  in  front  of  the  membrane  is  a  well-marked  depression,  situated 
on  the  floor  of  the  canal  and  bounded  by  a  somewhat  prominent  ridge;  in  this  foreign  bodies 
may  become  lodged.  By  aid  of  the  speculum,  combined  with  traction  of  the  auricle  upward 
and  backward,  the  whole  of  the  membrana  tympani  is  rendered  visible.  It  is  a  pearly-gray  mem- 
brane, slightly  glistening  in  the  adult,  placed  obliquely,  so  as  to  form  with  the  floor  of  the  meatus 
a  very  acute  angle  (about  55  degrees),  while  with  the  roof  it  forms  an  obtuse  angle.  At  birth  it 
is  more  horizontal — being  situated  in  almost  the  same  plane  as  the  base  of  the  skull.  About 
midway  between  the  anterior  and  posterior  margins  of  the  membrane,  and  extending  from  the 
centre  obliquely  upward,  is  a  reddish-yellow  streak;  this  is  the  handle  of  the  malleus,  which  is 
inserted  into  the  membrane  (Fig.  773).  At  the  upper  part  of  this  streak,  close  to  the  roof  of  the 
meatus,  a  little  white  rounded  prominence  is  plainly  to  be  seen;  this  is  the  processus  brevis  of 
the  malleus,  projecting  against  the  membrane.  The  membrana  tympani  does  not  present  a 
plane  surface;  on  the  contrary,  its  centre  is  drawn  inward,  on  account  of  its  connection  with  the 
handle  of  the  malleus,  and  thus  the  external  surface  is  rendered  concave. 

THE  MIDDLE  EAR,  DRUM  OR  TYMPANUM  (AURIS  MEDIA) 

(Figs.  769,  770,  771,  775). 

The  middle  ear  or  tympanum  is  an  irregular  cavity,  compressed  from  without 
inward,  and  is  situated  within  the  petrous  portion  of  the  temporal  bone.  It  is 
placed  above  the  jugular  fossa;  the  carotid  canal  lying  in  front,  the  mastoid  cells 
behind,  the  external  auditory  meatus  externally,  and  the  labyrinth  internally.  It  is 
lined  with  mucous  membrane,  is  filled  with  air,  and  communicates  with  the  mas- 
toid cells,  and  with  the  naso-pharynx  by  the  Eustachian  tube.  The  tympanum  is 
traversed  by  a  chain  of  movable  bones,  which  connect  the  membrana  tympani 
with  the  labyrinth,  and  serve  to  convey  the  vibrations  communicated  to  the  mem- 
brana tympani  across  the  cavity  of  the  tympanum  to  the  internal  ear.  In  shape 
it  is  roughly  biconcave,  the  concave  surfaces  being  placed  vertically  and  forming 
the  external  and  internal  walls.  The  cavity  forms  an  angle  of  45  degrees  with  the 
median  plane  (Spalteholz). 

The  Tympanic  Cavity  (cavum  tympani)  (Figs.  775  and  776).— The  tympanic 
cavity  consists  of  two  parts:  the  atrium  or  tympanic  cavity  proper  (Fig.  776), 
opposite  the  tympanic  membrane,  and  the  attic  or  epitympanic  recess  or  aditus 
ad  antrum  (recessus  epitympanicus)  (Figs.  774  and  775),  above  the  level  of  the 


THE  MIDDLE  EAR,    DRUM   OR    TYMPANUM 


1161 


upper  part  of  the  membrane;  the  latter  contains  the  upper  half  of  the  malleus 
and  the  greater  part  of  the  incus.  The  diameter  of  the  tympanic  cavity, 
including  the  attic,  measures  about  f-  inch  (15  mm.)  vertically  and  trans- 
versely. From  without  inward  it  measures  about  £  inch  (6  mm.)  above  and  £ 
inch  (4  mm.)  below;  opposite  the  centre  of  the  tympanic  membrane  it  is  only 
about  y1^-  inch  (2  mm.).  It  is  bounded  externally  by  the  membrana  tympani  and 
meatus;  internally,  by  the  outer  surface  of  the  internal  ear;  and  communicates 
behind  with  the  mastoid  antrum  and  through  it  with  the  mastoid  cells;  and  in 
front  with  the  Eustachian  tube  and  canal  for  the  Tensor  tympani.  Its  roof  and 
floor  are  formed  by  thin  osseous  laminae,  the  one  forming  the  roof  being  a  thin 
plate  situated  on  the  anterior  surface  of  the  petrous  portion  of  the  temporal  bone, 
close  to  its  angle  of  junction  with  the  squamous  portion  of  the  same  bone. 

The  Roof  of  the  Tympanum  (paries  tegmentalis). — The  roof  of  the  tympanum 
is  broad,  flattened,  and  formed  of  a  thin  plate  of  bone  (legmen  tympani}  (Fig. 
775),  which  separates  the  cranial  and  tympanic  cavities.  It  is  prolonged  back- 
ward so  as  to  roof  in  the  mastoid  antrum;  it  is  also  carried  forward  to  cover  in 
the  canal  for  the  Tensor  tympani  muscle. 

The  Floor  (paries  jugularis)  (Fig.  775). — The  floor  is  narrow,  and  is  separated 
by  a  thin  plate  of  bone  (jundus  tympani)  from  the  jugular  fossa.  It  frequently 


Chorda  tympani 


FIG.  771. — View  of  the  inner  wall  of  the  tympanum  (enlarged). 


presents  numerous  small  notches  in  the  bone  (cellulae  tympanicae).  There  is  one 
small  aperture  in  the  floor.  It  is  near  the  inner  wall  and  is  the  opening  of  the 
canaliculus  tympanicus,  for  the  transmission  of  Jacobson's  nerve  (n.  tympanicus). 
On  the  floor  near  the  posterior  wall  there  is  often  to  be  found  a  slight  bony 
projection  (prominentia  styloideae}. 

The  Outer  Wall  (Fig.  770). — The  outer  wall  is  formed  mainly  by  the  membrana 
tympani,  partly  by  the  ring  of  bone  into  which  this  membrane  is  inserted.  The 
part  formed  by  the  membrana  tympanum  is  called  the  paries  membranaceus.  This 
ring  of  bone  is  incomplete  at  its  upper  part,  forming  a  notch,  the  notch  of  Rivinus 
(incisura  tympanica  [Rivini])  (Fig.  773).  The  anterior  edge  of  the  notch  is 
known  as  the  spina  tympanica  major,  the  posterior  edge  as  the  spina  tympanica 
minor.  The  .groove  for  the  reception  of  the  membrana  tympani  is  the  sulcus 
tympanicus.  Close  to  the  notch  are  three  small  apertures:  the  iter  chordae  pos- 
terius,  the  Glaserian  fissure,  and  the  iter  chordae  anterius. 

The  iter  chordae  posterius  or  the  tympanic  aperture  (canalicutus  chordae  tympani) 
(Fig.  774)  is  in  the  angle  of  junction  between  the  posterior  and  external  walls  of 
the  tympanum,  immediately  behind  the  membrana  tympani  and  on  a  level  with  the 
upper  end  of  the  handle  of  the  malleus;  it  leads  into  a  minute  canal,  which  descends 


1162  THE  ORGANS  OF  SPECIAL  SENSE 

in  front  of  the  aquaeductus  Fallopii,  and  terminates  in  the  aqueduct  near  the 
stylomastoid  foramen.  Through  it  the  chorda  tympani  nerve  enters  the  tym- 
panum. 

The  Glaserian  or  petro-tympanic  fissure  (fissura  petrotympanica  [Glaseri]}  (Fig. 
774)  opens  just  above  and  in  front  of  the  ring  of  bone  into  which  the  membrana 
tympani  is  inserted;  in  this  situation  it  is  a  mere  slit  about  a  line  in  length.  It 
lodges  the  long  process  and  anterior  ligament  of  the  malleus,  and  gives  passage 
to  the  tympanic  branch  of  the  internal  maxillary  artery. 

The  iter  chordae  anterius  (Fig.  774)  is  seen  at  the  inner  end  of  the  preceding 
fissure;  it  leads  into  a  canal,  the  canal  of  Huguier,  which  runs  parallel  with  the 
Glaserian  fissure.  Through  it  the  chorda  tympani  nerve  leaves  the  tympanum. 

The  outer  wall  bounds  the  epitympanic  recess  externally. 

The  Internal  Wall  of  the  Tympanum  (paries  labyrinthica}  (Figs.  771  and  775). — 
The  internal  wall  of  the  tympanum  is  adjacent  to  the  labyrinth,  is  vertical  in  direc- 
tion, and  looks  directly  outward.    It  presents  for  examination  the  following  parts : 
Fenestra  ovalis.  Promontory. 

Fenestra  rotunda.  Ridge  of  the  aquaeductus  Fallopii. 

Prominence  of  the  external  semicircular  canal. 

The  Fenestra  Ovalis,  the  Oval  or  the  Vestibular  Window  (fenestra  vestibuli)  (Fig. 
771)  is  a  reniform  opening  leading  from  the  tympanum  into  the  vestibule.  It 
is  situated  in  the  depths  of  a  fossa  (fossula  fenestrae  vestibuli}.  Its  long  diameter 
is  directed  horizontally,  and  its  convex  border  is  upward.  The  opening  in  the 
recent  state  is  occupied  by  the  base  of  the  stapes  (Figs.  770  and  776),  which  is 
connected  to  the  margin  of  the  foramen  by  an  annular  ligament. 

The  Fenestra  Rotunda,  the  Round  or  Cochlear  Window  (fenestra  cochleae}  (Fig. 
771),  is  an  aperture  placed  at  the  bottom  of  a  funnel-shaped  depression  (fossula 
fenestrae  cochleae}  leading  into  the  cochlea.  It  is  situated  below  and  rather 
behind  the  fenestra  ovalis,  from  which  it  is  separated  by  a  rounded  elevation,  the 
promontory;  at  its  border  is  a  narrow  ridge  of  bone  (crista  fenestrae  cochleae}, 
which  is  closed  in  the  recent  state  by  a  membrane,  the  membrane  of  Scarpa  or  the 
secondary  ear-drum  membrane  (membrana  tympani  secundaria}.  This  membrane 
is  concave  toward  the  tympanum,  convex  toward  the  cochlea.  It  consists  of 
three  layers:  the  external  or  mucous,  derived  from  the  mucous  lining  of  the 
tympanum;  the  internal,  from  the  lining  membrane  of  the  cochlea;  and  an  inter- 
mediate or  fibrous  layer. 

The  Promontory  (promontorium)  (Fig.  775)  is  a  rounded  hollow  prominence, 
formed  by  the  projection  outward  of  the  first  turn  of  the  cochlea;  it  is  placed 
between  the  fenestrse,  and  is  furrowed  on  its  surface  (sulcus  promontorii}  for  the 
lodgement  of  the  tympanic  plexus.  A  minute  spicule  of  bone  frequently  connects 
the  promontory  to  the  pyramid. 

The  Rounded  Eminence  of  the  Aquaeductus  Fallopii  (prominentia  canalis  facialis} 
(Fig.  775),  the  prominence  of  the  bpny  canal  in  which  the  facial  nerve  is  contained, 
traverses  the  inner  wall  of  the  tympanum  above  the  fenestra  ovalis,  and  behind 
that  opening  curves  nearly  vertically  downward  along  the  posterior  wall. 

Just  above  the  eminence  of  the  aquaeductus  Fallopii  the  wall  is  bulged  by  the 
external  semicircular  canal  (prominentia  canalis  semicircularis  lateralis}. 

The  Posterior  Wall  of  the  Tympanum  (paries  mastoidea}  (Fig.  775). — The  pos- 
terior wall  of  the  tympanum  is  wider  above  than  below,  and  the  lower  portion  of/ 
the  posterior  wall  contains  many  tympanic  cells.  The  posterior  wall  presents  for 
examination  the — 

Opening  of  the  antrum.  Prominentia    styloideae. 

Fossa  incudis.  Pyramid. 

Apertura  tympanica  canaliculi  chordae. 


THE  MIDDLE  EAR,    DRUM   OR    TYMPANUM  1163 

The  Opening  of  the  Antrum  is  a  large  irregular  aperture,  which  extends  back- 
ward from  the  epityrapanic  recess  and  leads  into  a  considerable  air  space,  the* 
mastoid  antrum  (antrum  tympanicum) ,  which  is  the  entrance  to  the  mastoid  cells 
(p.  87).  The  antrum  communicates  with  large  irregular  cavities  contained 
in  the  interior  of  the  mastoid  process,  the  mastoid  air-cells.  These  cavities  vary 
considerably  in  number,  size,  and  form;  they  are  lined  by  mucous  membrane 
continuous  with  that  lining  the  cavity  of  the  tympanum. 

The  Fossa  Incudis  (Fig  775)  is  placed  in  the  posterior  and  inferior  part  of  the 
epitympanic  recess.  It  lodges  the  short  process  of  the  incus. 

The  Prominentia  Styloideae  is  sometimes  seen  below  the  apertura  tympanica 
canaliculi  chordae.  It  is  a  prominence  produced  by  a  prolongation  of  the  styloid 
process. 

The  Pyramid  (eminentia  pyramidalis)  (Fig.  771)  is  a  conical  eminence  situated 
immediately  behind  the  fenestra  ovalis,  and  in  front  of  the  vertical  portion  of  the 
eminence  above  described;  it  is  hollow  in  the  interior,  and  contains  the  Stapedius 
muscle;  its  summit  projects  forward  toward  the  fenestra  ovalis,  and  presents  a 
small  aperture  which  transmits  the  tendon  of  the  muscle.  The  cavity  in  the 
pyramid  is  prolonged  into  a  minute  canal,  which  communicates  with  the  aquae- 
ductus  Fallopii  and  transmits  the  nerve  which  supplies  the  Stapedius. 

The  Apertura  Tympanica  Canaliculi  Chordae  is  just  back  of  the  posterior  edge  of  the 
tympanic  membrane,  nearly  level  with  the  superior  end  of  the  manubrium  mallei. 

The  Anterior  Wall  of  the  Tympanum  (paries  carotica). — The  anterior  wall  of 
the  tympanum  is  bony  on  its  lower  portion.  Its  upper  part  is  the  tympanic 
opening  of  the  Eustachian  tube.  The  long  anterior  wall  contains  tympanic 
cells.  The  anterior  wall  is  wider  above  than  below;  it  corresponds  with  the 
carotid  canal,  from  which  it  is  separated  by  a  thin  plate  of  bone  (Fig.  775),  per- 
forated by  the  canaliculi  caroticotympanici,  which  transmit  the  tympanic  branch 
of  the  internal  carotid  artery  and  the  carotico-tympanic  nerves.  It  presents  for 
examination  the — 

Canal  for  the  Tensor  tympani.          Orifice    of    the    Eustachian    tube. 
The  processus  cochleariformis. 

The  orifice  of  the  canal  for  the  Tensor  tympani  and  the  orifice  of  the  Eustachian 
tube  are  situated  at  the  upper  part  of  the  anterior  wall,  being  incompletely  sepa- 
rated from  each  other  by  a  thin,  delicate,  horizontal  plate  of  bone,  the  processus 
cochleariformis  (septum  cancdis  musculotubarii)  (Figs.  49  and  771).  The  canalis 
musculotubarius  is  divided  by  this  long  process  into  the  canal  for  the  Tensor 
tympani  and  the  canal  for  the  Eustachian  tube.  These  canals  run  from  the 
tympanum  forward,  inward,  and  a  little  downward,  to  the  retiring  angle  between 
the  squamous  and  petrous  portions  of  the  temporal  bone. 

The  Canal  for  the  Tensor  Tympani  (semicanalis  m.  tensoris  tympani)  (Figs.  49, 
771,  and  775)  is  the  superior  and  the  smaller  of  the  two;  it  is  rounded  and  lies 
beneath  the  forward  prolongation  of  the  tegmen  tympani.  It  extends  on  to  the 
inner  wall  of  the  tympanum  and  ends  immediately  above  the  fenestra  ovalis.  The 
processus  cochleariformis  passes  backward  below  this  part  of  the  canal,  forming 
its  outer  wall  and  floor;  it  expands  above  the  anterior  extremity  of  the  fenestra 
ovalis  and  terminates  by  curving  outward  so  as  to  form  a  pulley  over  which  the 
tendon  passes.  The  bony  wall  of  this  canal  is  incomplete,  and  the  osseous  vacancy 
is  filled  by  tough  connective  tissue. 

The  Eustachian  Tube  or  Ear  Trumpet  (tuba  auditiva  [Eustachii])  (Figs.  49, 
771,  and  772)  is  the  channel  through  which  the  tympanum  communicates  with 
the  pharynx.  Its  length  is  an  inch  and  a  half  (36  mm.),  and  its  direction 
downward,  inward,  and  forward,  forming  an  angle  of  about  45  degrees  with 
the  sagittal  plane  and  one  of  from  30  to  40  degrees  with  the  horizontal  plane. 


1164 


THE    ORGANS    OF  SPECIAL   SENSE 


The  canal  for  the  Eustachian  tube  (semicanalis  tubae  auditivae)  (Fig.  772)  is  formed 
partly  of  bone,  partly  of  cartilage  and  fibrous  tissue. 

The  Osseous  Portion  (pars  ossea  tubae  auditivae  or  semicanalis  tubae  auditivae) 
is  about  half  an  inch  in  length.  It  is  the  outer  portion  of  the  tube.  It  commences 
in  the  anterior  wall  of  the  tympanum,  below  the  processus  cochleariformis  (ostium 
tympanicum  tubae  auditivae},  and,  gradually  narrowing,  terminates  at  the  angle 
of  junction  of  the  petrous  and  squamous  portions  of  the  temporal  bone,  its 
extremity  presenting  a  jagged  margin  which  serves  for  the  attachment  of  the 
cartilaginous  portion.  The  roof  of  the  osseous  portion  is  the  tegmen  tympani. 
The  inner  wall  is  formed  in  part  by  the  inner  wall  of  the  tympanum  and  in  part 
by  the  canal  for  the  Tensor  tympani  muscle.  The  outer  wall  is  the  tympanic 
portion  of  the  temporal  bone.  The  floor  is  a  groove  which  near  the  tympanum 
contains  the  openings  of  air-cells  (cellulae  pneumatici  tubarii). 


TENSOR   TYMPANI 


MEMBRANA 
TYMPAN 


.PHARYNGEAL   OPEN- 
ING   OF  TUBE 


FIG.  772. — Eustachian  tube,  laid  open  by  a  cut  in  its  long  axis.     (Testut.) 

The  Cartilaginous  Portion  (pars  cartilaginea  tubae  auditivae),  about  an  inch  in 
length,  is  formed  of  a  triangular  plate  of  elastic  fibre-cartilage  (cartilago  tubae 
auditivae),  the  apex  of  which  is  attached  to  the  margin  of  the  inner  extremity  of 
the  osseous  canal,  while  its  base  lies  directly  under  the  mucous  membrane  of 
the  naso-pharynx,  where  it  forms  an  elevation  or  cushion  above  and  behind  the 
pharyngeal  orifice  of  the  tube.  The  upper  edge  of  the  cartilage  is  curled  upon 
itself,  being  bent  outward  so  as  to  present  on  transverse  section  the  appearance  of 
a  hook  (lamina  lateralis);  a  groove  or  furrow  is  thus  produced,  which  opens  below 
and  externally,  and  this  part  of  the  canal  is  completed  by  fibrous  membrane.  On 
transverse  section  the  cartilage  exhibits  the  laminae  which  above  are  continuous 

o 

with  each  other:  the  hard,  thick  lamina  medialis  and  the  thin  and  hooked  lamina 
lateralis.  The  cartilage  of  the  Eustachian  tube,  with  a  hood  plate  of  cartilage, 
forms  the  posterior  portion  of  the  inner  wall  (the  lamina  medialis).  The  cartilage 
is  fixed  to  the  base  of  the  skull,  and  lies  in  a  groove  (sulcus  tubae  auditivae) 
between  the  petrous-temporal  and  the  greater  wing  of  the  sphenoid ;  this  groove 
ends  opposite  the  middle  of  the  internal  pterygoid  plate,  in  a  projection,  the 


THE  MIDDLE  EAR,    DRUM   OR    TYMPANUM 


1165 


processus  tubarius.  At  the  pharyngeal  orifice  the  entire  wall  of  the  tube  is  cartil- 
aginous, but  the  breadth  of  the  cartilage  progressively  lessens  as  the  isthmus  is 
approached.  Here  and  there  the  cartilage  is  deficient  or  pieces  lie  separate  from 
the  rest,  the  spaces  between  the  islands  being  occupied  by  fibrous  tissue.  The  Ten- 
sor palati  muscle  is  placed  to  the  outer  side  of  the  tube.  The  fibres  of  the  muscle 
which  take  origin  from  the  lamina  lateralis  are  known  as  the  dilator  tubae  muscle  of 
Rudinger.  The  Tensor  palati  muscle  and  the  mucous  membrane  of  the  pharynx  lie  to 
the  inner  side  of  the  tube.  The  under  and  outer  portion  of  the  canal  is  completed 
by  the  membranous  part  (lamina  membranaced},  which  is  a  strong  fibrous  mem- 
brane, passing  between  the  two  margins  of  the  cartilage.  It  is  thin  above,  but  thick 
below,  and  the  thick  portion  is  called  the  fascia  salpingopharyngea  of  Trbltsch, 
and  from  it  arise  some  fibres  of  the  Tensor  palati  (m.  salpingopharyngeus).  The 
cartilaginous  and  bony  portions  of  the  tube  are  not  in  the  same  plane,  the  former 


POSTERIOR    TYMPANO- 
MALLCOLAR   FOLD 


FLACCID  PORTION   OF 
MCMBRANA  TYMPANI 


POSTERIOR 

TYMPANIC 

SPINE 


MARGIN    OF 

MEMBRANA 

TYMPANI 

OR  LIMBUS 


MALLEOLAR 
PROMINENCE 


NOTCH  OF 
RIVINUS 


ANTERIOR 
TYMPANO- 
MALLEOLAR 
FOLD 

HANDLE    OF 
.MALLEOLUS 
SEEN  THROUGH 
MEMBRANE 


TENSE  PORTION 
OF  MEMBRANA 
TY  M  PA  N I 


FIG.  773. — The  right  membrana  tympani,  viewed  from  the  outside,  from  in  front,  and  from  below.    (Spalteholz.) 

inclining  downward  a  little  more  than  the  latter.  They  join  each  other  at  a  large 
obtuse  angle,  open  below.  The  diameter  of  the  canal  is  not  uniform  throughout, 
being  greatest  at  the  pharyngeal  orifice  and  least  at  the  junction  of  .the  bony  and 
cartilaginous  portions,  where  it  is  named  the  isthmus  (isthmus  tubae  auditivae) ; 
it  again  expands  somewhat  as  it  approaches  the  tympanic  cavity.  The 
position  and  relations  of  the  pharyngeal  orifice  (ostium  pharyngeum  tubae 
auditii'ae)  are  described  with  the  anatomy  of  the  naso-pharynx.  Through  this 
canal  the  mucous  membrane  of  the  pharynx  is  continuous  with  that  which  lines 
the  tympanum.  The  mucous  membrane  is  covered  with  ciliated  epithelium  and 
is  thin  in  the  osseous  portion,  while  in  the  cartilaginous  portion  it  contains  many 
mucous  glands  and  near  he  pharyngeal  orifice  a  considerable  amount  of  adenoid 
tissue,  which  has  been  named  by  Gerlach  the  tube-tonsil.  The  tube  is  opened 
during  deglutition  by  the  Salpingo-pharyngeus  and  Dilator  tubae  muscles. 

The  Drumhead  or  Membrana  Tympani  (Figs.  770,  772,  773,  and  774).— The 
membrana  tympani  or  drumhead  separates  the  cavity  of  the  tympanum  from 


1166 


THE    ORGANS    OF  SPECIAL  SENSE 


the  bottom  of  the  external  meatus.  It  is  a  thin,  semi-transparent  membrane, 
nearly  oval  in  form,  somewhat  broader  above  than  below,  and  directed  very 
obliquely  downward  and  inward,  so  as  to  form  an  angle  of  about  55  degrees 
with  the  floor  of  the  rneatus  (Fig.  770).  The  antero-inferior  portion  is,  there- 
fore, placed  at  the  greatest  distance  from  the  external  orifice  of  the  meatus.  It 
is  asserted  that  in  musicians  the  rnembrana  tympani  is  placed  more  nearly  per- 
pendicular, and  that  in  deaf-mutes  and  cretins  it  is  placed  more  obliquely  than 
the  usual  55  degrees.  In  a  newborn  child  the  membrana  tympani  is  almost  hori- 
zontal. The  greatest  diameter  of  the  membrana  tympani  is  from  9  to  10mm.; 


SUPERIOR  LIGAMENT 
OF    MALLEOLUS 


E  PITY  M  PA  NIC 
RECESS 


NCCK  OF 
MALLEUS\ 

ANTERIOR   LIGAMENT 

AND    ANTERIOR 

PROCESS   OF 

MALLEOLUS 

INSERTION 
OF  TENSOR 
TYMPANI 
MUSCL 


GLASERIAN 
FISSURE 


ARTICULAR    SURFACE 
FOR   BODY  OF  INCUS 


FLACCID   PORTION   OF 
MEMBRANA  TYMPANB 

POSTERIOR 

TYMPANIC 

SPINE 


TYMPANIC 
ORIFICE 
OF  CANAL 
FOR   CHORDA 
TYMPANI 
NERVE 


EUSTACHIAN 
TUBE 


TENSE   PORTION   OF 
MEMBRANA  TYMPANI 


FIG.  774. — The  right  membrana  tympani  with  the  hammer  and  the  chorda  tympani,  viewed  from  within, 
from  behind,  and  from  above.     (Spalteholz.) 

its  least  diameter  is  from  8  to  9  mm.  (Cunningham).  The  greater  part  of  its  cir- 
cumference (limbus  membranae  tympanae)  is  thickened  to  form  an  annular  ring 
(annulus  fibrocartilagineus] ,  which  is  fixed  in  a  groove,  the  sulcus  tympanicus,  at 
the  inner  extremity  of  the  external  meatus.  This  sulcus  is  deficient  superiorly  at 
the  incisure  or  notch  of  Rivinus  (incisura  tympanica  [Rivini])  (Fig.  773).  From  the 
extremities  of  the  notch  (spinae  tympanicae)  two  folds  pass  and  converge  to  the 
short  process  of  the  malleus  (Fig.  773).  One  is  known  as  the  anterior  tympano- 
malleolar  fold  or  ligament  (plica  membrana  tympani  anterior) .  The  other  is  known 
as  the  posterior  tympano-malleolar  fold  or  ligament  (plica  membrana  tympani  pos- 
terior). These  are  not  to  be  confused  with  the  anterior  and  posterior  malleolar 
folds  (p.  1172).  The  small,  somewhat  triangular  part  of  the  membrane  situated 
above  these  folds  is  lax  and  thin,  and  is  named  the  flaccid  portion  or  the  membrana 
flaccida  of  Shrapnell  (Figs.  773  and  774).  In  it  a  small  orifice  is  sometimes  seen, 
which  is  of  artificial  and  pathological  formation.  The  larger  lower  portion  of  the 
drum  membrane  is  stretched  tightly,  and  is  called  the  tense  portion  or  pars  tensa 
(Figs.  773  and  774). 


THE  MIDDLE  EAR,  DRUM  OR   TYMPANUM 


1167 


The  handle  of  the  malleus  is  firmly  attached  to  the  inner  aspect  of  the  mem- 
brana  tympani  as  far  as  its  centre  (Fig.  774).  It  draws  the  central  part  of  the 
membrane  inward  and  makes  its  outer  aspect  concave.  The  most  depressed  part 
of  the  concavity  is  called  the  umbo  or  navel  (umbo  membranae  tympanae)  (Fig.  773). 
The  walls  of  the  umbo  are  concave  outward. 

On  the  outer  surface  of  the  drum  membrane  a  light  stripe  (stria  mcdleolaris)  is 
seen.  It  runs  from  in  front  and  above  downward  and  backward,  and  is  produced 
by  the  handle  of  the  malleus,  showing  through  the  membrane  (Fig.  773). 

Structure. — This  membrane  is  composed  of  three  layers:  an  external  (cuticular)  t 
a  middle  (fibrous],  and  an  internal  (mucous).  The  cuticular  lining  (stratum  cuta- 
neum)  is  derived  from  the  integument  lining  the  meatus.  The  fibrous  or 
middle  layer  (membrana  propria)  consists  of  two  strata:  an  external,  of  radiating 
fibres  (stratum  radiatum),  which  diverge  from  the  handle  of  the  malleus,  and  an 


JUNCTION   BETWEEN   MAS- 
TOID  ANTRUM   AND 
EPITYMPANIC  RECESS 
I          TEGMEN 
*        TYMPANI 

I     EPITYMPANIC 
T    RECESS 

PROMINENCE  OF  EXTERNAL 
SEMICIRCULAR   CANAL 

PROMINENCE   OF  AQUEDUCT 
OF  FALLOPIUS 

TENDON   OF 
STAP.EDIUS   MUSCLE 

PLICA 
/  /  STAPEDIUS 

PROCESSUS 
COCHLEARIFORMIS 

TENSOR  TYMPANI 

MUSCLE  (cut  through) 

WALL  OF 
LABYRINTH 


POSTERIOR 
SINUS 

PYRAMIDAL 
EMINENCE 

TY  M  PA  N  I  C 
SINUS 


FOSSULA  OF  JUGULAR  TYMPANIC 

FENESTRA   ROTUNDA  WALL  PLEXUS 

FIG.  775. — The  medial  wall  and  part  of  the  posterior  and  anterior  walls  of  the  right  tympanic  cavity,  lateral 

view.     (Spalteholz.) 

internal,  of  circular  fibres  (stratum  circular -e),  which  are  plentiful  around  the  cir- 
cumference, but  sparse  and  scattered  near  the  centre  of  the  membrane.  Branched 
or  dendritic  fibres,  as  pointed  out  by  Griiber,  are  also  present,  especially  in  the 
posterior  half  of  the  membrane.  Both  muscular  layers  are  connected  to  the 
annulus  fibrocartilagineus,  and  both  are  absent  in  the  pars  flaccida.  The  inner 
or  epithelial  layer  is  mucous  membrane  (stratum  mucosum),  which  is  a  portion 
of  the  mucous  membrane  of  the  drum  cavity. 

The  Arteries  are  derived  from  the  deep  auricular  branch  of  the  internal  maxil- 
lary, which  ramifies  beneath  the  cuticular  layer  and  from  the  stylo-mastoid  branch 
of  the  posterior  auricular  and  tympanic  branch  of  the  internal  maxillary,  which 
are  distributed  on  the  mucous  surface.  The  arteries  of  the  cutaneous  set  anas- 
tomose with  the  arteries  of  the  mucous  set  by  minute  branches  which  penetrate 
the  drum  membrane  near  its  margin.  The  superficial  veins  open  into  the  external 
jugular;  those  on  the  mucous  surface  drain  themselves  partly  into  the  lateral 
sinus  and  veins  of  the  dura  and  partly  into  a  plexus  on  the  Eustachian  tube. 


1168 


THE  ORGANS  OF  SPECIAL  SENSE 


The  outer  surface  of  the  drum  membrane  receives  its  nerve  supply  from  the 
auriculo-temporal  branch  of  the  inferior  maxillary  and  the  auricular  branch  of 
the  vagus.  The  inner  surface  is  supplied  by  the  tympanic  branch  of  the  glosso- 
pharyngeal. 

There  are  two  sets  of  lymphatics,  the  cutaneous  and  mucous,  which  freely 
communicate.  The  spaces  between  the  dendritic  fibres  of  Griiber  are  lymph- 
spaces  (Kessel). 

The  Ossicles  of  the  Tympanum  (Ossicula  Auditus)  (Fig.  776). 

The  tympanum  contains  in  its  upper  part  a  chain  of  movable  bones,  three  in 
number,  the  malleus,  incus,  and  stapes.  The  first  is  attached  to  the  membrana 

tympani,  the  last  to  the  fenestra  ovalis.  The 
incus  is  placed  between  the  two,  and  is  con- 
nected to  both  by  delicate  articulations. 

The  Malleus  or  Hammer  (Fig.  777).— The 
malleus  or  hammer,  so  named  from  its  fancied 
resemblance  to  a  hammer,  is  placed  farthest  in 
front  and  outward.  It  consists  of  a  head,  neck, 
and  three  processes — the  handle  or  manubrium, 
the  processus  gracilis,  and  the  processus  brevis. 

The  Head  (capitulum  mallei}. — The  head  is 
the  large  upper  extremity  of  the  bone,  and  is 
situated  in  the  epitympanic  recess  (Fig.  774). 
It  is  oval  in  shape,  and  articulates  posteriorly 
with  the  incus,  being  free  in  the  rest  of  its  ex- 
tent. The  facet  for  articulation  with  the  incus 
is  covered  with  cartilage,  is  constricted  near 
the  middle,  and  is  divided  by  a  ridge  into  an 
upper,  larger,  and  a  lower,  lesser  part,  which 
form  nearly  a  right  angle  with  each  other.  Op- 
posite the  constriction  the  lower  margin  of  the 
facet  projects  in  the  form  of  a  process,  the 

FIG.  776. — Chain  of  ossicles  and  their  hga-  J  £ 

ments,  seen  from  the  front  in  a  vertical,  trans-  COg-tOOth  Or  SpUT  01  the  malleUS.  On  the  back 
verse  section  of  the  tympanum.  (Testut.)  »  ,1  i  i  i  i  •  ,  /  •  , 

oi  the  head  below  the  spur  is  a  crest  (crista 
mallei),  to  which  the  posterior  ligament  of  the  malleus  is  attached. 

The  Neck  (collum  mallei). — The  neck  is  the  narrow  contracted  part  just  beneath 
the  head;  and  below  this  is  a  prominence,  to  which  the  various  processes  are 
attached.  The  outer  surface  of  the  neck  faces  the  membrana  flaccida.  The 
chorda  tympani  nerve  crosses  the  inner  surface  (Fig.  774). 

The  Handle  or  Manubrium  (manubrium  mallei).— The  manubrium  is  a  vertical 
process  of  bone,  which  is  connected  by  its  outer  margin  with  the  fibrous  layer  of 
the  membrana  tympani,  its  entire  length  being  fastened  to  the  fibrous  layer  of 
the  drum  membrane  by  its  own  periosteum  and  by  a  layer  of  cartilage  (Griiber) 
(Figs.  774  and  776).  It  is  directed  downward,  inward,  and  backward;  it  decreases 
in  size  toward  its  extremity,  where  it  is  curved  slightly  forward,  and  is  flattened 
from  within  outward.  The  handle  forms  a  variable  angle  with  the  head  of  the 
hammer.  It  averages  about  130  degrees,  but  is  always  greater  in  the  right  ear 
than  in  the  left.  It  forms  an  angle  with  the  horizontal,  averaging  on  the  right 
side  50  degrees  and  on  the  left  side  45  degrees  (Spalteholz).  Internally  the 
handle  is  covered  by  the  mucous  membrane  of  the  tympanum.  On  the  inner 
side,  near  its  upper  end,  is  a  slight  projection,  into  which  the  tendon  of  the 
Tensor  tympani  is  inserted  (Fig.  774). 

The  Processus  Gracilis  or  Long  Process  (processus  anterior  [Folii\). — The  pro- 
cessus gracilis  is  a  long  and  very  delicate  process,  which  passes  from  the  front  of 


THE    OSSICLES   OF   THE    TYMPANUM 


1169 


the  neck  forward  and  outward  to  the  Glaserian  fissure,  to  which  it  is  connected 
by  ligamentous  fibres,  constituting  the  broad  ligament  of  Meckel.  In  the  foetus 
this  is  the  longest  process  of  the  malleus,  and  is  in  direct  continuity  with  the  car- 
tilage of  Meckel. 

The  Processus  Brevis  (processus  lateralis). — The  processus  brevis  is  a  slight 
conical  projection,  which  springs  from  the  root  of  the  manubrium;  it  is  directed 
outward,  and  is  attached  to  the  upper  part  of  the  tympanic  membrane  by  cartilage 
and  to  the  margins  of  the  notch  of  Rivinus  by  the  two  malleolar  folds. 


SHORT   ^H 
PROCESS       / 

LONG 
PROCESS 


INSERTION 

OF  TENSOR 

TYMPANI 

MUSCLE 


AURICULAR 
SURFACE 
FOR  BODY 
OF  INCUS 

INSERTION  OF 
EXTERNAL 
LIGAMENT 
OF  MALLEUS 


MANUBRIUM 


FIG.  777. — The  right  malleus:  a,  viewed  from  in  front;  b,  viewed  from  behind.     (Spalteholz.) 


The  Incus  or  Anvil  (Fig.  778). — The  incus  or  anvil  has  received  its  name  from 
its  supposed  resemblance  to  an  anvil,  but  it  is  more  like  a  bicuspid  tooth  with  two 
roots,  which  differ  in  length,  and  are  widely  separated  from  each  other.  It  con- 
sists of  a  body  and  two  processes.  The  body  and  the  short  process  are  placed  in 
the  epitympanic  recess  (Fig.  776). 

The  Body  (corpus  incudis). — The  body  is  somewhat  quadrilateral,  but  compressed 
laterally.  On  its  anterior  surface  is  a  deeply  concavo-convex  facet,  which  articu- 
lates with  the  head  of  the  malleus,  and  the  lower  part  is  hollowed  for  the  spur  of  the 
malleus.  In  the  fresh  state  the  articular  surface  is  covered  with  cartilage  and  the 
joint  is  lined  with  synovial  membrane. 


ARTICULAR  SURFACE 
FOR  HEAD  OF  MALLEUS 


ARTICULAR 
SURFACE  FOR 
HEAD  OF 
MALLEUS 


LONG 
PROCESS 


LENTICULAR 
PROCESS 


FIG.  778. — The  right  incus:  a,  lateral  view;  b,  medial  and  front  view.     (Spalteholz.) 


Processes. — The  two  processes  diverge  from  one  another  at  an  angle  of  from 
90  to  100  degrees. 

The  Short  Process  (crus  breve),  somewhat  conical  in  shape,  projects  nearly 
horizontally  backward,  and  articulates  with  a  depression,  the  incus  fossa  (fossa 
incudig),  in  the  lower  and  back  part  of  the  epitympanic  recess. 

The  Long  Process  (crus  longum),  longer  and  more  slender  than  the  preceding, 
descends  nearly  vertically  behind  and  parallel  to  the  handle  of  the  malleus,  and, 


1170  THE    ORGANS    OF  SPECIAL    SENSE 

bending  inward,  terminates  in  a  rounded  globular  projection,  the  os  orbiculaxe  or 
lenticular  process  (processus  lenticular -is) ,  which  is  tipped  with  cartilage,  and  articu- 
lates with  the  head  of  the  stapes.  In  the  fretus  the  os  orbiculare  exists  as  a  separate 
bone. 

The  Stapes  or  Stirrup  (Fig.  779). — The  stapes  or  stirrup,  so  called  from  its 
close  resemblance  to  a  stirrup,  consists  of  a  head,  neck,  two  crura,  and  a  base. 

The  Head  (capitulum  stapedis). — The  head  presents  a  depression,  tipped  with 
cartilage,  which  articulates  with  the  os  orbiculare. 

The  Neck. — The  neck,  the  constricted  part  of  the  bone  succeeding  the  head, 
receives  the  insertion  of  the  Stapedius  muscle. 

The  Crura. — The  two  crura  (crus  anterius  and  cms  posterius)  diverge  from  the 
neck  and  are  connected  at  their  extremities  by  a  flattened,  oval-shaped  plate,  the 
foot-plate  or  base  (basis  stapedis),  which  forms  the  foot-plate  of  the  stirrup  and 
is  fixed  to  the  margin  of  the  fei.estra  ovalis  by  ligamentous  fibres.  The  foot- 
plate almost  fills  the  oval  window  (Fig.  770).  Of  the  two  crura,  the  anterior  is 
shorter  and  less  curved  than  the  posterior.  In  a  recent  specimen  a  membrane  will 

be  observed  filling  the  space  between  the 
crura  and  the  foot-plate.  This  mem- 
brane is  connective  tissue  and  is  called 
the  membrana  obturatoria  stapedis.  The 


stirrup  lies  practically  horizontal. 


OBTURATOR 
•  MEMBRANE 

<TEcRus-jf         ^||_POSTERIOR    "sssi*Fm  Articulations  of  the  Ossicles  of  the  Tym- 

panum  (articulationes  ossiculorum  audi- 
tus)  (Fig.  776). — These  small  bones  are 
'*"  OF.8T*P"  connected  with  each  other  and  with  the 

FIG.  779. — The  right  stirrup :  a,  viewed  from  above;  11        j>    i  i 

b,  medial  vein.  (Spaitehoiz.)  walls  or  the  tympanum  by  ligaments,  and 

are  moved  by  small  muscles.  There  is  an 

articulation  between  the  head  of  the  hammer  and  the  body  of  the  anvil ;  one 
between  the  os  orbiculare  of  the  anvil  and  the  head  of  the  stirrup;  and  there  is  a 
syndesmosis  between  the  margins  of  the  oval  window  and  the  base  of  the  stirrup. 
The  bones  are  fastened  in  the  tympanum,  •  the  handle  of  the  hammer  being 
fastened  in  the  drum  membrane  and  the  base  of  the  stirrup  to  the  oval  window. 
The  articular  surfaces  of  the  malleus  and  incus  and  the  orbicular  process  of  the 
incus  and  head  of  the  stapes  are  covered  with  cartilage,  connected  together  by 
delicate  capsular  ligaments  and  lined  by  synovial  membrane. 

Ligaments  Connecting  the  Ossicula  with  the  Walls  of  the  Tympanum  (ligamenta 
ossiculorum  auditus). — The  malleus  is  fastened  to  the  wall  of  the  tympanum  by 
three  ligaments:  the  anterior,  superior,  and  external  ligaments. 

The  Anterior  Ligament  of  the  Malleus  (ligamentum  mallei  anterius)  consists  of 
two  parts,  the  band  of  Meckel  and  the  anterior  ligament  of  Helmholtz. 

The  band  of  Meckel  is  attached  to  the  base  of  the  processus  gracilis  and  passes 
through  the  Glaserian  fissure  to  reach  the  spine  of  the  sphenoid.  It  was  formerly 
described  by  Sommering  as  a  muscle,  and  it  was  called  the  laxator  tympani 
muscle.  It  is  now,  however,  believed  by  most  observers  to  consist  of  ligamentous 
fibres  only. 

The  anterior  ligament  of  Helmholtz  extends  from  the  anterior  margin  of  the 
notch  of  Rivinus  to  the  anterior  portion  of  the  malleus,  just  above  the  processus 
gracilis. 

The  Superior  Ligament  of  the  Malleus  (ligamentum  mallei  superius)  is  a  delicate 
round  bundle  of  fibres  which  descends  perpendicularly  from  the  roof  of  the  epi- 
tympanic  recess  to  the  head  of  the  malleus.  It  is  sometimes  called  the  suspensory 
ligament. 

The  External  Ligament  of  the  Malleus  (ligamentum  mallei  laterale)  is  a  triangular 
plane  of  fibres  passing  from  the  posterior  part  of  the  notch  in  the  tympanic  ring 


THE  OSSICLES  OF  THE  TYMPANUM  1171 

to  the  crest  of  the  malleus.  The  posterior  portion  of  the  external  ligament  is 
sometimes  called  the  posterior  ligament  of  Helmholtz  (ligamentum  mallei  posterius 
[Helmholtzi]).  The  malleus  rotates  around  an  axis  composed  of  the  external  and 
anterior  ligaments,  hence  these  two  ligaments  constitute  what  Helmholtz  called 
the  axis  ligament  of  the  malleus. 

The  incus  is  fastened  to  the  wall  of  the  tympanum  by  two  ligaments,  the  poste- 
rior and  the  superior. 

The  Posterior  Ligament  of  the  Incus  (ligamentum  incudis  posterius)  is  a  short, 
thick,  ligamentous  band  which  connects  the  extremity  of  the  short  process  of  the 
incus  to  the  posterior  and  lower  part  of  the  epitympanic  recess,  near  the  margin 
of  the  opening  of  the  mastoid  cells. 

A  Superior  Ligament  of  the  Incus  (ligamentum  incudis  superius)  has  been 
described  by  Arnold,  but  it  is  little  more  than  a  fold  of  mucous  membrane. 

The  inner  surface  and  the  circumference  of  the  base  of  the  stapes  are  covered  with 
hyaline  cartilage,  and  the  annular  ligament  of  the  stapes  (ligamentum  annulare  baseos 
stapedis)  connects  the  circumference  of  the  base  to  the  margin  of  the  fenestra  ovalis. 

The  Muscles  of  the  Tympanum  (m.  ossiculorum  auditus). — The  muscles  of  the 
tympanum  are  two: 

Tensor  tympani.  Stapedius. 

The  Tensor  Tympani  (m.  tensor  tympani}  (Fig.  775),  the  larger,  is  contained  in 
the  bony  canal  above  the  osseous  portion  of  the  Eustachian  tube,  from  which  it 
is  separated  by  the  processus  cochleariformis.  It  arises  from  the  under  surface  of 
the  petrous  bone,  from  the  cartilaginous  portion  of  the  Eustachian  tube,  and  from 
the  osseous  canal  in  which  it  is  contained.  Passing  backward  through  the  canal, 
it  terminates  in  a  slender  tendon  which  enters  the  tympanum  and  makes  a  sharp 
bend  outward  around  the  extremity  of  the  processus  cochleariformis,  and  is 
inserted  into  the  handle  of  the  malleus  near  its  root.  Its  nerve-supply  is  from 
the  motor  root  of  the  trigeminal  nerve  by  way  of  the  otic  ganglion. 

The  Stapedius  (m.  stapedius)  (Fig.  775)  arises  from  the  side  of  a  conical  cavity 
hollowed  out  of  the  interior  of  the  pyramid ;  its  tendon  emerges  from  the  orifice 
at  the  apex  of  the  pyramid,  and,  passing  forward,  is  inserted  into  the  neck  of  the 
stapes.  Its  surface  is  aponeurotic,  its  interior  fleshy,  and  its  tendon  occasionally 
contains  a  slender  bony  spine,  which  is  constant  in  some  mammalia.  It  is 
supplied  by  the  tympanic  branch  of  the  facial  nerve. 

Actions. — The  Tensor  tympani  draws  the  handle  of  the  malleus  inward  and 
thus  heightens  the  tension  of  the  drum  membrane.  It  also  causes  slight  rotation 
of  the  bone  around  its  long  axis.  When  the  Stapedius  contracts  it  draws  the 
head  of  the  stirrup  backward,  and  in  consequence  the  anterior  end  of  the  foot- 
plate passes  outward  toward  the  tympanum,  and  the  posterior  end  inward  toward 
the  vestibule,  and  the  annular  ligament  is  made  tense. 

Movements  of  the  Ossicles  of  the  Tympanum. — The  chain  of  bones  is  a  lever-like 
arrangement,  by  means  of  which  the  vibrations  of  the  membrana  tympani  are 
transferred  to  the  membrane  covering  the  oval  window,  and  from  this  to  the  peri- 
lymph  in  the  labyrinth.  When  the  drum  membrane  moves  inward,  the  handle 
of  the  malleus  moves  with  it.  The  movement  of  the  malleus  moves  the  incus,  and 
the  movement  of  the  incus  drives  the  foot  of  the  stapes  toward  the  labyrinth. 
When  the  handle  of  the  malleus  moves  inward,  the  spur  on  the  head  becomes 
locked  with  the  body  of  the  incus.  During  outward  movement  it  is  unlocked. 
The  ordinary  outward  movement  of  the  drum  membrane  causes  the  above- 
described  movements  to  be  reversed.  When  there  is  overforcible  outward  move- 
ment the  incus  does  not  go  outward  quite  as  far  as  the  malleus,  but  slides  at  the 
joint  between  the  malleus  and  incus.  This  reluctance  of  the  incus  saves  the  foot 
of  the  stapes  from  being  pulled  away  from  the  oval  window. 


1172  THE    ORGANS    OF  SPECIAL   SENSE 

The  Mucous  Membrane  of  the  Tympanum  (tunica  mucosa  tympanicd). — The 
mucous  membrane  of  the  tympanum  is  continuous  with  the  mucous  membrane 
of  the  naso-pharynx  through  the  Eustachian  tube,  and  is  firmly  united  to  the 
periosteum.  It  invests  the  ossicula,  and  the  muscles  and  nerves  contained  in  the 
tympanic  cavity;  forms  the  internal  layer  of  the  membrana  tympani,  and  the  outer 
layer  of  the  membrana  tympani  secundaria,  and  is  reflected  into  the  mastoid 
antrum  and  air-cells,  which  it  lines  throughout.  It  forms  several  vascular  folds 
(plicae),  which  extend  from  the  walls  of  the  tympanum  to  the  ossicles.  In  these 
folds  the  ossicles  are  enveloped. 

The  anterior  malleolar  fold  (plica  malleolaris  anterior)  comes  off  from  the  mem- 
brana tympani  between  the  anterior  edge  of  the  notch  of  Rivinus  and  the  handle 
of  the  malleus,  envelops  the  processus  gracilis  of  the  malleus,  the  anterior  liga- 
ment of  the  malleus,  and  the  anterior  portion  of  the  chorda  tympani  nerve,  and 
terminates  in  a  free  concave  edge  (Spalteholz).  The  posterior  malleolar  fold  (plica 
malleolaris  posterior)  is  the  larger  of  the  two.  It  comes  off  from  the  margin  of  the 
notch  of  Rivinis,  envelops  the  external  ligament  of  the  malleus,  the  posterior  part 
of  the  chorda  tympani  nerve,  is  attached  to  the  handle  of  the  malleus,  and  ends 
in  a  free  concave  margin  (Spalteholz).  The  fold  of  the  incus  (plica  incudis)  takes 
origin  from  the  roof  of  the  epitympanic  recess  and  passes  to  the  body  and  short 
process  of  the  incus;  and  a  similar  fold  passes  from  the  head  of  the  malleus  to  the 
anterior  wall  of  the  epitympanic  recess.  The  entire  stapes,  with  its  obturator 
membrane,  is  enwrapped  by  the  fold  of  the  stapes  (plica  stapedis).  This  fold  also 
ensheaths  the  tendon  of  the  stapedius  muscle  and  often  reaches  to  the  posterior 
wall  of  the  cavity  of  the  tympanum.  The  mucous  membrane  over  the  round 
window  forms  the  membrana  tympani  secundaria.  These  folds  separate  off  pouch- 
like  cavities,  and  give  the  interior  of  the  tympanum  a  somewhat  honey-comb 
appearance.  One  of  these  pouches  is  well  marked — viz.,  the  pouch  of  Prussak, 
which  lies  between  the  neck  of  the  malleus  and  the  membrana  flaccida. 

The  inferior  external  pouch  of  the  tympanum  or  the  pouch  of  Prussak  (recessus 
membranae  tympani  superior)  is  between  the  flaccid  portion  of  the  membrana 
tympani,  the  external  ligament  of  the  malleus,  and  the  neck  of  the  mal- 
leus. The  anterior  and  posterior  malleolar  folds  with  the  tympanic  membrane 
form  two  pouches.  These  are  the  anterior  and  posterior  pouches  or  recesses  of 
Trbltsch  (recessus  membranae  tympani,  anterior  and  posterior) .  The  anterior  pouch 
is  blind  above  and  has  a  slit-like  opening  below.  The  posterior  pouch  is  con- 
tinued into  the  blind  superior  pouch  of  the  drum  membrane.  In  the  tympanum 
this  membrane  is  pale,  thin,  slightly  vascular,  and  covered  for  the  most  part  with 
columnar  ciliated  epithelium,  but  that  covering  the  pyramid,  ossicula,  and  mem- 
brana tympani  possesses  a  flattened,  non-ciliated  epithelium.  In  the  antrum  and 
mastoid  cells  its  epithelium  is  also  non-ciliated.  In  the  osseous  portion  of  the 
Eustachian  tube  the  membrane  is  thin;  but  in  the  cartilaginous  portion  it  is  very 
thick,  highly  vascular,  covered  with  ciliated  epithelium,  and  provided  with  numer- 
ous mucous  glands. 

The  Arteries  of  the  Tympanum. — The  arteries  supplying  the  tympanum  are  six 
in  number.  Two  of  them  are  larger  than  the  rest — viz.,  the  tympanic  branch  of 
the  internal  maxillary,  which  enters  by  way  of  the  Glaserian  fissure  and  supplies 
the  membrana  tympani ;  and  the  stylo-mastoid  branch  of  the  posterior  auricular, 
which  passes  through  the  stylo-mastoid  foramen  and  the  aqueduct  of  Fallopius, 
and  supplies  the  inner  wall  and  floor  of  the  tympanum,  the  mastoid  cells,  and 
antrum  and  the  Stapedius  muscle.  This  vessel  anastomoses  around  the  drum 
membrane  with  the  tympanic.  The  medidural  sends  a  small  branch  to  the  Tensor 
tympani  muscle  near  its  origin.  The  petrosal  branch  of  the  medidural  enters  the 
tympanum  by  way  of  the  hiatus  Fallopii.  Minute  branches  from  the  posterior 
branch  of  the  medidural  pass  through  the  petro-squamous  fissure  and  are  dis- 


THE  INTERNAL  EAR  OR  LABYRINTH  1173 

tributed  to  the  antrura  and  epitympanic  recess  (Cunningham).  Two  tympanic 
branches  come  oft'  from  the  internal  carotid  artery  in  its  course  through  the  carotid 
canal.  A  branch  from  the  ascending  pharyngeal  and  another  from  the  Vidian 
accompany  the  Eustachian  tube.  The  two  tympanic  branches  from  the  internal 
carotid  are  given  off  in  the  carotid  canal  and  perforate  the  thin  anterior  wall  of  the 
tympanum. 

The  Veins  of  the  Tympanum. — The  veins  of  the  tympanum  terminate  in  the 
ptervgoid  plexus,  the  medidural  vein,  and  the  superpetrosal  sinus. 

The  Nerves  of  the  Tympanum. — The  nerves  of  the  tympanum  constitute  the 
tympanic  plexus  (plexus  tympanicus  [Jacobsoni]) ,  which  ramifies  upon  the  surface 
of  the  promontory  (Fig.  775).  The  plexus  is  formed  by  (1)  the  tympanic  branch  of 
the  glosso-pharyngeal ;  (2)  the  small  deep  petrosal  nerve;  (3)  the  small  super- 
ficial petrosal  nerve;  and  (4)  a  branch  which  joins  the  great  superficial  petrosal. 

The  Tympanic  Branch  of  the  Glosso-pharyngeal  or  Jacobson's  Nerve  (n.  tympan- 
icus) enters  the  tympanum  by  an  aperture  in  its  floor  close  to  the  inner  wall  and 
divides  into  branches,  which  ramify  on  the  promontory  and  enter  into  the  forma- 
tion of  the  plexus.  The  small  deep  petrosal  nerve  (n.  petrosus  profundus),  from 
the  carotid  plexus  of  the  sympathetic,  passes  through  the  wall  of  the  carotid  canal, 
and  joins  the  branches  of  Jacobson's  nerve.  The  branch  to  the  great  superficial 
petrosal  passes  through  an  opening  on  the  inner  wall  of  the  tympanum  in  front 
of  the  fenestra  ovalis.  The  small  superficial  petrosal  nerve  (n.  petrosus  super- 
ficialis  minor),  derived  from  the  otic  ganglion,  passes  through  a  foramen  in  the 
middle  fossa  of  the  base  of  the  skull  (sometimes  through  the  foramen  ovale), 
passes  backward  and  enters  the  petrous  bone  through  a  small  aperture,  situ- 
ated external  to  the  hiatus  Fallopii  on  the  anterior  surface  of  this  bone;  it  then 
courses  downward  through  the  bone,  and,  passing  by  the  gangliform  enlargement 
of  the  facial  nerve,  receives  a  connecting  filament  from  it  (Fig.  779)  and  enters  the 
tympanic  cavity,  where  it  communicates  with  Jacobson's  nerve,  and  assists  in 
forming  the  tympanic  plexus. 

The  branches  of  distribution  of  the  tympanic  plexus  are  distributed  to  the 
mucous  membrane  of  the  tympanum;  one  special  branch  passing  to  the  fenestra 
ovalis,  another  to  the  fenestra  rotunda,  and  a  third  to  the  Eustachian  tube.  The 
small  superficial  petrosal  may  be  looked  upon  as  a  branch  from  the  plexus  to  the 
otic  ganglion. 

In  addition  to  the  tympanic  plexus  there  are  the  nerves  supplying  the  muscles. 
The  Tensor  tympani  is  supplied  by  a  branch  from  the  third  division  of  the  tri-' 
geminal  through  the  otic  ganglion,  and  the  Stapedius  by  the  tympanic  branch  of 
the  facial. 

The  chorda  tympani  (Figs.  771  and  774)  crosses  the  tympanic  cavity.  It  is  given 
off  from  the  facial  as  it  passes  vertically  downward  at  the  back  of  the  tympanum, 
about  a  quarter  of  an  inch  before  its  exit  from  the  stylo-mastoid  foramen.  It  passes 
from  below  upward  and  forward  in  a  distinct  canal,  and  enters  the  cavity  of  the 
tympanum  through  an  aperture,  iter  chordae  posterius,  already  described  (p.  1161), 
and  becomes  invested  with  mucous  membrane.  It  passes  forward,  through  the 
cavity  of  the  tympanum,  crossing  internal  to  the  membrana  tympani  and  over 
the  handle  of  the  malleus  to  the  anterior  inferior  angle  of  the  tympanum,  and 
emerges  from  that  cavity  through  the  iter  chordae  anterius  or  canal  of  Huguier 
(p.  1 162).  It  is  invested  by  the  fold  of  mucous  membrane  already  mentioned,  and 
therefore  lies  between  the  mucous  and  fibrous  layers  of  the  membrana  tympani. 


THE  INTERNAL  EAR  OR  LABYRINTH  (AURIS  INTERNA). 

The  internal  ear  is  the  essential  part  of  the  organ  of  hearing,  receiving  the 
ultimate  distribution  of  the  auditory  nerve.     It  is  called  the  labyrinth,  from  the 


1174  THE    ORGANS    OF   SPECIAL   SENSE 

complexity  of  its  shape,  and  consists  of  two  parts:  the  osseous  labyrinth,  a  series 
of  cavities  channelled  out  of  the  substance  of  the  petrous  bone,  and  the  membranous 
labyrinth,  the  latter  being  contained  within  the  former. 

The  Osseous  Labyrinth  (Labyrinthus  Osseus)  (Fig.  780). 

The  osseous  labyrinth  consists  of  three  parts:  the  vestibule,  semicircular  canals, 
and  cochlea.  These  are  cavities  hollowed  out  of  the  substance  of  the  bone,  and 
lined  by  periosteum.  A  clear  fluid  is  contained  in  the  space  between  the  osseous 
labyrinth  and  the  membranous  labyrinth.  The  space  is  called  the  perilymph 
space,  and  the  fluid  is  called  perilymph  or  liquor  Cotunnii. 

The  Vestibule  (vestibulum)  (Figs.  776  and  780). — The  vestibule  is  the  common 
central  cavity  of  communication  between  the  parts  of  the  internal  ear.  It  is  situated 
on  the  inner  side  of  the  tympanum,  behind  the  cochlea,  and  in  front  of  the  semi- 
circular canals.  It  is  somewhat  ovoidal  in  shape  from  before  backward,  flattened 
from  within  outward,  and  measures  about  one-fifth  of  an  inch  from  before  back- 


of  aqueductus  vestibuli. 
Bristle  passed  through  foramen  rotundum. 

Opening  of  aqueductus  cochleae. 
FIG.  780. — The  osseous  labyrinth  laid  open  (enlarged). 

ward,  as  well  as  from  above  downward,  and  about  one-eighth  of  an  inch  from  with- 
out inward.  On  its  outer  or  tympanic  wall  is  the  fenestra  ovalis  (fenestm  vestibuli), 
closed,  in  the  recent  state,  by  the  base  of  the  stapes,  and  its  annular  ligament. 
On  its  inner  wall,  at  the  forepart,  is  a  small  circular  depression,  fovea  hemi- 
sphaerica  or  spherical  recess  (recessus  spliaericus] ,  in  which  the  saccule  is  placed. 
This  recess  is  perforated,  at  its  anterior  and  inferior  part,  by  about  a  dozen  minute 
holes  (macula  cribrosa  media],  for  the  passage  of  filaments  of  the  auditory  nerve 
to  the  saccule.  Above  and  behind  this  depression  is  an  oblique  ridge,  the  crista 
vestibuli.  The  anterior  extremity  of  the  crista  vestibuli  is  the  shape  of  a  triangle, 
and  is  called  the  pyramid  (pyramis  vestibuli}.  This  ridge  bifurcates  posteriorly  to 
enclose  a  small  depression,  the  recessus  cochlearis  of  Reichert,  which  is  perforated 
by  eight  small  holes  for  the  passage  of  filaments  of  the  auditory  nerve  which 
supply  the  posterior  end  of  the  ductus  cochlearis.  An  oval  depression  is  placed 
in  the  roof  and  inner  wall  of  the  vestibule  above  and  behind  the  crista  vestibuli. 
It  is  called  the  fovea  hemielliptica,  elliptical  recess  or  spherical  recess  (recessus 
ellipticus],  and  receives  the  utricle.  The  pyramid  and  the  adjacent  elliptical 
recess  are  perforated  by  numerous  minute  foramina  (macula  cribrosa  superior], 


THE    OSSEOUS  LABYRINTH  1175 

The  openings  in  the  pyramid  transmit  filaments  from  the  vestibular  nerve  to  the 
utricle;  the  openings  in  the  elliptical  recess  transmit  filaments  from  the  vestibular 
nerve  to  the  ampullae  of  the  superior  and  external  semicircular  canals.  Below  and 
behind  the  elliptical  recess  is  a  groove  which  deepens  into  a  canal  and  is  called 
the  aquaeductus  vestibuli.  This  canal  passes  to  the  posterior  surface  of  the  petrous 
portion  of  the  temporal  bone  and  opens  as  a  mere  crack  between  the  internal 
auditory  meatus  and  the  groove  for  the  lateral  sinus.  It  transmits  a  small  vein, 
and  contains  a  tubular  prolongation  of  the  lining  membrane  of  the  vestibule, 
the  ductus  endolymphaticus,  which  ends  in  a  cul-de-sac  between  the  layers  of  the 
dura  within  the  cranial  cavity.  Behind,  the  semicircular  canals  open  into  the 
vestibule  by  five  orifices.  In  front  is  an  elliptical  opening,  which  communicates 
with  the  scala  vestibuli  of  the  cochlea  by  an  orifice,  apertura  scalae  vestibuli  cochleae. 
This  opening  is  bounded  below  by  a  thin  plate  of  bone  (lamina  spiralis  ossea), 
which  takes  origin  from  the  vestibular  floor  external  to  the  spherical  recess  and 
in  the  cochlea  forms  the  bony  portion  of  the  partition  between  the  scala  tympani 
and  the  scala  vestibuli.  In  the  anterior  portion  of  the  vestibular  floor  is  a  fissure 
(fissiira  vestibuli),  which  passes  into  the  bony  part  of  the  canal  of  the  cochlea. 
The  external  boundary  of  this  fissure  is  a  small,  thin  plate  of  bone  (lamina  spiralis 
secundaria). 

The  Semicircular  Canals  (canales  semicirculares  ossei)  (Fig.  780) . — The  semi- 
circular canals  are  three  bony  canals  situated  above  and  behind  the  vestibule.  They 
are  of  unequal  length,  compressed  from  side  to  side,  and  each  describes  the  greater 
part  of  a  circle.  They  measure  about  one-twrentieth  of  an  inch  in  diameter,  and 
each  presents  a  dilatation  at  one  end,  called  the  ampulla  ossea,  which  measures 
more  than  twice  the  diameter  of  the  tube.  These  canals  open  into  the  vestibule 
by  five  orifices,  one  of  the  apertures  being  common  to  two  of  the  canals. 

The  Superior  Semicircular  Canal  (canalis  semicircularis  superior). — The  superior 
semicircular  canal  is  vertical  in  direction,  and  is  placed  transversely  to  the  long 
axis  of  the  petrous  portion  of  the  temporal  bone,  on  the  anterior  surface  of  which 
its  arch  forms  a  round  projection.  It  describes  about  two-thirds  of  a  circle.  Its 
outer  extremity,  which  is  ampullated,  communicates  by  a  distinct  orifice  with  the 
upper  part  of  the  vestibule;  the  opposite  end  of  the  canal,  which  is  not  dilated, 
joins  with  the  corresponding  part  of  the  posterior  canal  to  form  the  cms  commune, 
which  opens  into  the  upper  and  inner  part  of  the  vestibule. 

The  Posterior  Semicircular  Canal  (canalis  semicircularis  posterior). — The  posterior 
semicircular  canal,  also  vertical  in  direction,  is  directed  backward,  nearly  parallel 
to  the  posterior  surface  of  the  petrous  bone ;  it  is  the  longest  of  the  three ;  its  ampul- 
lated end  commences  at  the  lower  arid  back  part  of  the  vestibule,  its  opposite  end 
joining  to  form  the  common  canal  already  mentioned.  In  the  wall  of  the  ampulla 
of  the  posterior  canal  are  a  number  of  small  openings  (macula  cribrosa  inferior) 
for  the  entrance  of  nerves  to  the  ampulla. 

The  External  or  Horizontal  Canal  (canalis  semicircularis  lateralis). — The  external 
or  horizontal  canal  is  the  shortest  of  the  three,  its  arch  being  directed  outward  and 
backward;  thus  each  semicircular  canal  stands  at  right  angles  to  the  other  two. 
Its  ampullated  end  corresponds  to  the  upper  and  outer  angle  of  the  vestibule,  just 
above  the  fenestra  ovalis,  where  it  opens  close  to  the  ampullary  end  of  the  superior 
canal;  its  opposite  end  opens  by  a  distinct  orifice  at  the  upper  and  back  part  of  the 
vestibule. 

The  Cochlea  (Figs.  780,78 1,782, and  783)  .—The  cochlea  bears  some  resemblance 
to  a  common  snail-shell ;  it  forms  the  anterior  part  of  the  labyrinth,  is  conical  in  form, 
and  placed  almost  horizontally  in  front  of  the  vestibule;  its  apex  is  directed  forward 
and  outward,  with  a  slight  inclination  downward,  toward  the  upper  and  front  part 
of  the  inner  wall  of  the  tympanum ;  its  base  corresponds  with  the  anterior  depression 
at  the  bottom  of  the  internal  auditory  meatus,  and  is  perforated  by  numerous 


1176 


THE    ORGANS    OF  SPECIAL    SENSE 


apertures  for  the  passage  of  the  cochlear  divisions  of  the  auditory  nerve.    It  meas- 
ures nearly  a  quarter  of  an  inch  (5  mm.)  from  base  to  apex,  and  its  breadth  across 


Fio.  781. — Osseous  cochlea  in  vertical  section.     The  broken,  white  lines  indicate  the  position  of  the  basilar 

membrane  of  the  canal  of  the  cochlea.     Semidiagrammatic.     (Testut.)  • 

the  base  is  somewhat  greater  (about  9  mm.).  It  consists  of  a  conical-shaped 
central  axis,  the  modiolus  or'columella ;  of  a  canal,  the  bony  canal  of  the  cochlea,  the 
inner  wall  of  which  is  formed  by  the  central  axis,  wound  spirally  around  it  for  two 


TRACTUS 

SPIRALIS 
FORAMINOSUS 


AREA 

COCHLEAE 


COMPACT  BONY 

CANAI.IS    CANALIS  LON-     SUBSTANCE  OF 

BASIS      SPIRALIS        GITUDINALIS     CAPSULE  OF       SULCUS  FOR   LA RGE  SUPER- 
MODIOLI        MODIOLI  MODOLI     LABYRINTH      /FICIAL  PETROSAL  N  ERV  E 

LAMINA  MODIOLI 

SULCUS  FOR  SMALL  SUPER- 
FICIAL PETROSAL  NERVE 


SEMICANAL 
.FOR  TENSOR 
TV M  PAN  I 
MUSCLE 
GLASERIAN 
FISSURb 


SEMICANAL  OF 

EUSTACHIAN 

TUBE 


LAMINA 

SPIRALIS 

OSSEA 


LAMINA  SPIRALIS 
SECUNDARIA 


FIG.  782. — Vertical  section  through  the  right  cochlea,  medial  portion,  viewed  from  the  lateral  side.    (Spalteholz.) 

turns  and  three-quarters,  from  the  base  to  the  apex,  and  of  a  delicate  lamina,  the 
lamina  spkalis  ossea,  which  projects  from  the  modiolus,  and,  following  the  windings 


THE  OSSEO  US  LAB  YRINTH  \  \  77 

of  the  canal,  partially  subdivides  it  into  two.  In  the  recent  state  certain  mem- 
branous layers  are  attached  to  the  free  border  of  this  lamina,  which  project  into 
the  canal  and  completely  separate  it  into  two  passages,  which,  however,  com- 
municate with  each  other  at  the  apex  of  the  modiolus  by  a  small  opening,  named 
the  helicotrema. 

The  Modiolus  (Figs.  782  and  783). — The  modiolus  or  columella  is  the  central  axis 
or  pillar  of  the  cochlea.  It  is  conical  in  form,  and  extends  from  the  base  to  the  apex 
of  the  cochlea.  Its  base  (basis  modioli]  is  broad,  and  appears  at  the  bottom  of  the 
internal  auditory  meatus,  where  it  corresponds  with  the  area  cochleae.  It  is  per- 
forated by  numerous  orifices,  which  transmit  filaments  of  the  cochlear  division 
of  the  auditory  nerve,  the  nerves  for  the  first  turn  and  a  half  being  transmitted 
through  the  foramina  of  the  tractus  spiralis  foraminosus;  the  fibres  for  the  apical 
turn  passing  up  through  the  foramen  centrale.  The  foramina  of  the  tractus 
spiralis  foraminosus  pass  up  through  the  modiolus  and  successively  bend  out- 
ward to  reach  the  attached  margin  of  the  lamina  spiralis  ossea.  Here  they  become 
enlarged,  and  by  their  apposition  form  a  spiral  canal  (canalis  spiralis  modioli), 
which  follows  the  course  of  the  attached  margin  of  the  lamina  spiralis  ossea  and 
lodges  the  ganglion  of  Corti  (ganglion  spirale  cochleae).  The  foramen  centrale  is 
continued  as  a  canal  up  the  middle  of  the  modiolus  to  its  apex,  and  from  this  canal 
numerous  minute  foramina  pass  outward  to  the  unattached  edge  of  the  lamina 
spiralis.  In  the  foramina  are  vessels  and  nerves.  The  axis  diminishes  rapidly 
in  size  in  the  second  and  succeeding  coil. 


FIG.  783. — The  cochlea  laid  open  (enlarged). 

The  Bony  Canal  or  the  Spiral  Canal  of  the  Cochlea  (canalis  spiralis  cochleae)  (Fig. 
783). — The  bony  canal  of  the  cochlea  takes  two  turns  and  three-quarters  round  the 
modiolus.  The  first  turn  of  the  canal  is  called  the  basal  coil,  the  second  is  called  the 
central  coil,  the  third  turn  is  called  the  apical  coil.  The  promontory  on  the  inner  wall 
of  the  tympanic  cavity  is  caused  by  the  basal  coil.  The  bony  canal  of  the  cochlea  is 
a  little  over  an  inch  in  length  (about  30  mm.),  and  diminishes  gradually  in  size  from 
the  base  to  the  summit,  where  it  terminates  in  a  cul-de-sac,  the  cupola  (cupula),  which 
forms  the  apex  of  the  cochlea.  The  commencement  of  this  canal  is  about  the 
tenth  of  an  inch  in  diameter;  it  diverges  from  the  modiolus  toward  the  tympanum 
and  vestibule,  and  presents  three  openings.  One,  the  fenestra  rotunda,  commu- 
nicates with  the  tympanum ;  in  the  recent  state  this  aperture  is  closed  by  a  mem- 
brane, the  membrana  tympani  secundaria.  Another  aperture,  of  an  elliptical  form, 
enters  the  vestibule.  The  third  is  the  aperture  of  the  aquaeductus  cochleae,  leading 
to  a  minute  funnel-shaped  canal,  which  opens  on  the  basilar  surface  of  the  petrous 
bone  internal  to  the  jugular  fossa,  and  transmits  a  small  vein,  and  also  forms 
a  communication  between  the  subarachnoidean  space  of  the  skull  and  the  peri- 
lymph  contained  in  the  scala  tympani. 

The  Lamina  Spiralis  Ossea. — The  lamina  spiralis  ossea  is  a  bony  shelf  or  ledge 
which  projects  outward  from  the  modiolus  into  the  interior  of  the  spiral  canal, 


1178 


THE    ORGANS    OF   SPECIAL    SENSE 


and,  like  the  canal,  takes  two  and  three-quarter  turns  around  the  modiolus.  It 
reaches  about  half-way  toward  the  outer  wall  of  the  spiral  tube,  and  partially 
divides  its  cavity  into  two  passages  or  scalae,  of  which  the  upper  is  named  the 
scala  vestibuli,  while  the  lower  is  termed  the  scala  tympani.  Near  the  summit  of 
the  cochlea  the  lamina  terminates  in  a  hook-shaped  process,  the  hamulus  (hamulus 
laminae  spiralis),  which  assists  in  forming  the  boundary  of  a  small  opening,  the 
helicotrema,  by  which  the  two  scalae  communicate  with  each  other.  From  the 
canalis  spiralis  modioli  numerous  foramina  pass  outward  through  the  osseous 
spiral  lamina  as  far  as  its  outer  or  free  edge.  In  the  lower  part  of  the  first  turn 
a  second  bony  lamina  (lamina  spiralis  secundaria)  projects  inward  from  the 
outer  wall  of  the  bony  tube;  it  does  not,  however,  reach  the  primary  osseous  spiral 
lamina,  so  that  if  viewed  from  the  vestibule  a  narrow  fissure,  the  fissura  vestibuli, 
is  seen  between  them. 

The  membrana  basilaris  (Fig.  781)  is  stretched  from  the  unattached  edge  of 
the  lamina  spiralis  ossea  to  the  outer  wall  of  the  cochlea.     The  lamina  spiralis 


NERVE  OF  AMPULLA 
OFSUPCRIOR  CANAL 


AMPULLA  OF  SUPERIOR 
MEMBRANOUS  CANAL 


SUPERIOR 

TERMINAL 

BRANCH  OF 

VESTIBULAR 

NERVE 


OUCTUS 
COCHLEARIS 


COCHLEAR 
NERVE 


ACOUSTIC 
NERVE 


VESTIBULAR 
NERVE 


VCSTIBULAR 
GANGLION 


DUCT  OF 
SUPERIOR 
SEMICIRCULAR 
CANAL 


AMPULLA  OF 
EXTERNAL 
MEMBRANOUS 
CANAL 


DUCT  OF 
EXTERNAL 
SEMICIRCULAR 
CANAL 


CRUS 

COMMUNE 

DUCT  OF 

POSTERIOR 

SEMICIRCULAR 

CANAL 


DUCTUS    EN  DO. 
LYMPHATICUS 


NERVE  OF        NERVE  OF  AMPULLA        SACCULE  AM  PU  LLA  OF  POSTERIOR 

SACCULE      OF   POSTERIOR   CANAL  MEMBRANOUS  CANAL 

FIG.  784. — The  right  membranous  labyrinth  of  an  adult,  isolated,  medial  and  posterior  view.     (Spalteholz.) 

makes  an  incomplete  septum  between  the  scala  tympani  and  scala  vestibuli;  the 
membrana  basilaris  completes  the  septum.  Even  with  the  perfected  septum  the 
two  scalae  communicate  at  the  apex  of  the  cochlea  by  means  of  the  helicotrema. 
The  Fundus  of  the  Internal  Auditory  Meatus  (fundus  meatus  acustici  interni) . — 
This  structure  is  the  inner  wall  of  the  vestibule  and  the  base  of  the  modiolus.  A 
transverse  ridge  (crista  transversa)  maps  it  off  into  two  parts,  the  fossula  superior 
and  the  fossula  inferior.  The  facial  area  (area  n.  facialis)  is  in  the  anterior  portion 
of  the  fossula  superior.  The  opening  seen  here  is  the  beginning  of  the  aqueduct 
of  Fallopius  (canalis  facialis)  for  the  transmission  of  the  facial  nerve.  The  superior 
area  of  the  vestibule  (area  vestibularis  superior)  is  the  posterior  portion  of  the  fossula 
superior.  Here  the  nerves  perforate  which  supply  the  utricle  and  the  ampullae  of 
the  superior  and  external  semicircular  canals  (Cunningham).  The  area  cochleae 
is  the  anterior  portion  of  the  fossula  inferior.  In  it  is  the  canalis  centralis  for  the 
nerve-fibres  to  the  apical  turn  of  the  cochlea;  and  the  tractus  spiralis  foraminosa 
for  the  transmission  of  nerves  to  the  first  turn  and  a  half  of  the  cochlea.  The 


THE    MEMBRANOUS    LABYRINTH 


1179 


inferior  area  of  the  vestibule  (area  vestibularis  inferior]  is  back  of  the  area  cochleae 
and  a  ridge  separates  the  two.  It  transmits  nerves  to  the  saccule.  At  the  posterior 
part  of  the  fossula  inferior  is  a  solitary  foramen,  the  foramen  singulare,  which 
transmits  nerves  to  the  ampulla  of  the  posterior  semicircular  canal. 

The  Membranous  Labyrinth  (Labyrinthus  Membranaceus)  (Figs.  784,  785). 

The  membranous  labyrinth  is  contained  within  the  bony  cavities  just  described, 
having  the  same  general  form  as  the  cavities  in  which  it  is  contained,  though 
considerably  smaller,  being  separated  from  the  bony  walls  by  a  quantity  of  fluid, 
the  perilymph  or  liquor  Cotunnii  (perilympha).  It  does  not,  however,  float  loosely 
in  this  fluid,  but  in  places  is  fixed  to  the  walls  of  the  cavity.  The  membranous 
sac  contains  fluid,  the  endolymph  (endolympha) ,  and  on  the  sac  the  ramifications 
of  the  auditory  nerve  are  distributed. 

Within  the  osseous  vestibule  the  membranous  labyrinth  does  not  quite  preserve 
the  form  of  the  bony  cavity,  but  presents  two  membranous  sacs,  the  utricle  and 
the  saccule. 


_       Ductus 
~Endolymphaticus 

FIG.  785. — The  membranous  labyrinth  (enlarged). 

The  Utricle  (utriculus). — The  utricle  is  the  larger  of  the  two,  of  an  oblong 
form,  compressed  laterally,  and  occupies  the  upper  and  back  part  of  the  vestibule, 
lying  in  contact  with  the  fovea  semi-elliptica  and  the  part  below  it.  The  highest 
portion  of  the  utricle  is  called  the  recess  (recessus  utriculi);  it  is  placed  in  the 
elliptical  recess,  and  opening  into  it  are  the  ampulla  of  the  superior  and  external 
semicircular  canals.  The  central  portion  of  the  recess  of  the  utricle  receives  upon 
the  side  the  external  semicircular  canal.  This  opening  has  not  an  ampulla.  The 
superior  sinus  is  a  prolongation  upward  and  backward  from  the  central  portion  of 
the  utricle  and  in  the  superior  sinus  the  crus  commune  and  the  superior  and 
posterior  semicircular  canals  open.  The  lower  and  inner  portion  of  the  utricle 
is  the  inferior  sinus,  and  into  it  the  ampulla  of  the  posterior  semicircular  canal 
opens.  The  floor  and  anterior  wall  of  the  recess  of  the  utricle  are  much  thicker 
than  elsewhere,  and  form  the  macula  acustica  utriculi,  which  receives  the  utricular 
filaments  of  the  auditory  nerve  and  has  attached  to  its  internal  surface  a  layer  of 
calcareous  particles  which  are  called  otoliths.  The  cavity  of  the  utricle  communi- 
cates behind  with  the  membranous  semicircular  canals  by  five  orifices.  From 
its  anterior  wall  is  given  off  a  small  canal  (ductus  utriculosaccularis) ,  which  joins 
with  a  canal  from  the  saccule,  the  ductus  endolymphaticus.  The  utricle  is  joined 
to  the  bony  wall  by  numerous  fibrous  bands. 


1180  THE    ORGANS    OF  SPECIAL   SENSE 

The  Saccule  (sacculus). — The  saccule  is  the  smaller  of  the  two  vesicular  sacs; 
it  is  globular  in  form,  lies  in  the  elliptical  recess  near  the  opening  of  the  scala 
vestibuli  of  the  cochlea.  Its  anterior  part  exhibits  an  oval  thickening,  the  macula 
acustica  sacculi,  to  which  are  distributed  the  saccular  filaments  of  the  auditory 
nerve.  Its  cavity  does  not  directly  communicate  with  that  of  the  utricle.  From 
the  posterior  wall  is  given  off  a  canal,  the  ductus  endolymphaticus.  This  duct 
passes  along  the  aquaeductus  vestibuli  and  ends  in  a  blind  pouch  on  the  posterior 
surface  of  the  petrous  portion  of  the  temporal  bone,  where  it  is  in  contact  with 
the  dura.  The  upper  extremity  of  the  saccule  looks  upward  and  backward 
and  forms  the  sinus  utricularis  sacculi.  This  lies  in  contact  with  but  is  not  a 
part  of  the  wall  of  the  utricle.  The  vestibule  contains  the  closed  end  of  the 
ductus  cochlearis.  This  is  known  as  the  caecum  vestibulare.  The  ductus  coch- 
learis lies  below  the  saccule  in  what  Reichert  described  as  the  recessus  cochlearis, 
and  it  enters  the  spiral  canal.  From  the  lower  part  of  the  saccule  a  short  tube, 
the  canalis  reunions  of  Hensen  (ductus  reuniens  [Henseni]),  passes  downward 
and  outward  to  open  into  the  ductus  cochlearis.  The  saccule  is  held  in  posi- 
tion by  numerous  fibrous  bands  which  pass  between  the  saccule  and  the  bony 
wall. 

The  Membranous  Semicircular  Canals  (ductus  semicircular  es}. — The  mem- 
branous semicircular  canals  are  about  one-third  the  diameter  of  the  osseous  canals, 
but  in  number,  shape,  and  general  form  they  are  precisely  similar,  and  present 
at  one  end  within  the  osseous  ampulla  a  membranous  ampulla.  These  ampullae 
are  called  ampullae  membranaceae.  The  canals  open  by  five  orifices  into  the  utricle, 
one  opening  being  common  to  two  canals.  In  the  ampullae  the  wall  is  thickened, 
and  projects  into  the  cavity  as  a  fiddle-shaped,  transversely  placed  elevation,  the 
septum  trans versum,  in  which  the  nerves  end. 

The  membranous  canals  are  attached  here  and  there  to  the  bone  by  numerous 
fibrous  bands,  the  so-called  ligaments  (ligamenta  labyrinthi  canaliculorum) . 

Structure. — The  walls  of  the  utricle,  saccule,  arid  membranous  semicircular 
canals  consist  of  three  layers.  The  outer  layer  is  a  loose  and  flocculent  struc- 
ture, apparently  composed  of  ordinary  fibrous  tissue,  containing  blood-vessels 
and  pigment-cells  analogous  to  those  in  the  pigment  coat  of  the  retina.  The 
middle  layer,  thicker  and  more  transparent,  bears  some  resemblance  to  the 
hyaloid  membrane,  but  it  presents  on  its  internal  surface,  especially  in  the  semi- 
circular canals,  numerous  papilliform  projections,  and,  on  the  addition  of  acetic 
acid,  presents  an  appearance  of  longitudinal  fibrillation  and  elongated  nuclei. 
The  inner  layer  is  formed  of  polygonal  nucleated  epithelial  cells.  The  raphe  of 
each  semicircular  canal  is  a  line  upon  the  concave  side  of  the  canal.  Along  the 
raphe  the  height  of  the  epithelial  cells  is  distinctly  increased.  In  the  ampullae 
adjacent  to  the  cristae  acusticae  the  cells  are  cylindrical  and  constitute  the 
plana  semilunata.  In  the  maculae  of  the  utricle  and  saccule,  and  in  the  trans- 
verse septa  of  the  ampullae  of  the  canals,  the  middle  coat  is  thickened  and  the 
epithelium  is  columnar,  is  increased  in  height,  and  passes  into  the  neuro-epithe- 
lium.  The  neuro-epithelium  consists  of  supporting  cells  and  hair-cells. 

1.  The  supporting  cells  are  long,  wider  at  the  ends  than  in  the  centre,  contain  an 
oval  nucleus,  and  the  lower  end  of  the  cell  is  fissured. 

2.  The  hair-cells  are  columnar,  with  bulged  lower  ends  and  free  upper  ends. 
The  bulged  lower  ends,  each  of  which  contains  a  spherical  nucleus,  do  not  reach 
higher  than  the  middle  of  the  epithelial  layer.    Each  free  upper  end  is  surmounted 
by  a  long,  tapering  filament.     These  filaments  constitute  auditory  hair,  and  they 
project  into  the  cavity.     The  filaments  of  the  auditory  nerve  enter  these  parts, 
and,  having  pierced  the  outer  and  thickened  middle  layer,  they  lose  their  medul- 
lary sheath,  and  their  axis-cylinders  divide  into  three  or  four  branches  at  the 
larger  and  deeper  ends  of  the  hair-cells.    These  branches  form  a  horizontal  plexus 


THE  MEMBRANOUS   LABYRINTH 


1181 


(stratum  plexi forme).  "These  surround  the  hair-cells  like  the  calyx  of  a  flower, 
and  give  off  ascending  branches,  which,  however,  do  not  reach  the  surface.  In 
this  way  one  branch  usually  comes  in  contact  with  many  hair-cells."1 


FIG.  786. — Floor  of  scala  media,  showing  the  organ  of  Corti,  etc. 

Numerous  small  prismatic  bodies  termed  statoliths,  otokonien  crystals  or  otoliths, 
and  consisting  of  a  mass  of  minute  crystalline  grains  of  carbonate  of  lime,  held 


COCHLEAR     NCRVE 
AND    GANGLION 


FIG.  787. — Cochlea  in  transverse  section.     Observe  especially  the  canal  of  the  cochlea,  which  is  a  part  of 
the  membranous  labyrinth.     (Testut.) 

together  in  a  rnesh  of  delicate  fibrous  tissue,  are  contained  in  the  walls  of  the 
utricle  and  saccule  opposite  the  distribution  of  the  nerves.     The  membrane  is 

1  Histology  and  Microscopic  Anatomy.     By  Dr.  Ladislaus  Szymonowicz.     Translated    and  edited  by  John 
Bruce  MacCallum,  M.D. 


1182  THE    ORGANS    OF  SPECIAL    SENSE 

called  the  otolith  membrane.  A  calcareous  material  is  also,  according  to  Bowman, 
sparingly  scattered  in  the  cells  lining  the  ampullae  of  the  semicircular  canals.  The 
conical  thickening  in  the  ampulla  corresponds  to  the  otolith  membrane  and  is 
called  the  cupola. 

The  Membranous  Cochlea,  Ductus  Cochlearis  or  Scala  Media  consists  of  a  spirally 
arranged  tube  enclosed  in  the  bony  canal  of  the  cochlea  and  lying  along  its  outer 
wall.  It  begins  as  a  blind  end  in  the  recessus  cochlearis  of  the  vestibule.  This 
beginning  is  the  caecum  vestibulare.  It  ascends  inside  the  bony  cochlea  and  termi- 
nates at  the  apex  of  the  cochlea  by  a  blind  end,  the  lagena  (caecum  cupulare).  The 
manner  in  which  it  is  formed  will  now  be  described. 

The  osseous  spiral  lamina,  as  above  stated,  extends  only  part  of  the  distance  be- 
tween the  modiolus  and  the  outer  bony  wall  of  the  cochlea.  A  membrane,  the  basilar 
membrane  (membrana  basilaris)  (Fig.  786) ,  stretches  from  its  free  edge  to  the  outer 
wall  of  the  cochlea, and  completes  the  roof  of  the  scala  tympani.  A  second  and  more 
delicate  membrane,  the  membrane  of  Reissner  (membrana  vestibularis  [Reissneri]) 
(Fig. 786), extends  from  the  thickened  periosteum  covering  the  lamina  spiralis  ossea 
to  the  outer  wall  of  the  cochlea,  to  which  it  is  attached  at  some  little  distance  above 
the  membrana  basilaris.  A  canal  is  thus  shut  off  between  the  scala  tympani  below 
and  the  scala  vestibuli  above;  this  is  the  membranous  canal  of  the  cochlea  (ductus 
cochlearis  or  scala  media]  (Fig.  787).  It  is  triangular  on  transverse  section,  its  roof 
being  formed  by  the  membrane  of  Reissner,  its  outer  wall  by  the  periosteum  which 
lines  the  bony  canal,  and  its  floor  by  the  membrana  basilaris,  and  the  outer  part 
of  the  lamina  spiralis  ossea,  on  the  former  of  which  is  placed  the  organ  of  Corti. 
Reissner's  membrane  is  thin  and  homogeneous,  and  is  covered  on  its  upper  and 
under  surfaces  by  a  layer  of  epithelium.  The  periosteum,  which  forms  the  outer 

wall  of  the  ductus  cochlearis,  is  greatly 

NERVE-FIBRES  PASSING  OUT  tViiVlr  p>nf»rl      nnrl      altf>rf>rl     in     r>Viarnr>tfr 

GANGLION      SPIRAL      BETWEEN  TH  E  TWO   LAY  E  RS  O  F  6F> 

SPIRALS   FIBRES   LA M i NA  spi R Ans  ossE  forming  what  is  called  the  spiral  liga- 

ment of  the  cochlea  (ligamentum  spirale 
cochleae)  (Fig.  786) .  It  projects  inward 
below  as  a  triangular  prominence,  the 
Crista  basilaris,  which  gives  attach- 
ment to  the  outer  edge  of  the  mem- 
brana basilaris, and  immediately  above 
which  is  a  concavity,  the  sulcus  spiralis 
externus  (Fig.  786).  The  upper  por- 
tion of  the  ligamentum  spirale  con- 

FIG.  788. — Part  of  the  cochlear  nerve,  highly  magnified.  .  ...          1.  , 

(Henie.)  tains    numerous  capillary  loops  and 

small  blood-vessels,  and  forms  what 

is  termed  the  stria  vascularis.  The  stria  is  limited  below  by  a  prominence  (promi- 
nentia  spiralis),  in  which  a  blood-vessel  (vas  prominens)  is  distinctly  visible. 

The  lamina  spiralis  ossea  (Fig.  787)  consists  of  two  plates  of  bone  extending 
outward;  between  these  are  the  canals  for  the  transmission  of  the  filaments  of  the 
auditory  nerve.  On  the  upper  plate  of  that  part  of  the  osseous  spiral  lamina 
which  is  outside  Reissner's  membrane  the  periosteum  is  thickened  to  form  the 
limbus  laminae  spiralis,  and  this  terminates  externally  in  a  concavity,  the  sulcus 
spiralis  internus,  which  presents,  on  section,  the  form  of  the  letter  C;  the  upper 
part  of  the  letter,  formed  by  the  overhanging  extremity  of  the  limbus,  is  named 
the  labium  vestibulare ;  the  lower  part,  prolonged  and  tapering,  is  called  the  labium 
tympanicum,  and  is  perforated  by  4000  foramina  (foramina  nervosa)  for  the  pass- 
age of  the  cochlear  nerves.  Externally,  the  labium  tympanicum  is  continuous 
with  the  membrana  basilaris.  The  upper  surface  of  the  labium  vestibulare  is 
intersected  at  right  angles  by  a  number  of  furrows,  between  which  are  numerous 
elevations;  these  present  the  appearance  of  teeth  along  the  free  margin  of  the 


THE    MEMBRANOUS    LABYRINTH 


1183 


labium,  and  have  been  named  by  Huschke  the  auditory  teeth.  There  are  7000 
auditory  teeth.  The  basilar  membrane  may  be  divided  into  two  areas,  inner  and 
outer.  The  inner  is  thin,  and  is  named  the  zona  arcuata  or  zona  tecta  (Fig.  786);  it 
supports  the  organ  of  Corti.  The  outer  is  thicker  and  striated,  and  is  termed 
the  zona  pectinata.  The  under  surface  of  the  membrane  is  covered  by  a  layer  of 

Outer  hair  cells. 
Membrana  tectona. 


Limbus. 


Cells  of  Deiters. 
Outer  rod. 
Basilar  membrane. 
FIG.  789. — Section  through  the  organ  of  Corti.     Magnified.     (G.  Retzius.) 


-'--S.RaBrAtti 


Nerve  fibres. 


vascular  connective  tissue.    One  of  these  vessels  is  somewhat  larger  than  the  rest, 
and  is  named  the  vas  spirale  (Fig.  789);  it  lies  below  Corti's  tunnel. 

Organ  of  Corti1  (organon  spirale  [Cortii])  (Figs.  786,  787,  789,  and  790).— The 
inner  part  of  the  membrana  basilaris — that  is,  the  part  directed  toward  the  canal 
of  the  ductus  cochlearis — is  covered  with  epithelium,  which  is  largely  neuro-epithe- 


INTERNAL  AUDI- 
TORY   CELLS 


BASILAR    MEMBRANE 


FIG.  790. — Organ  of  Corti.     Diagrammatic  view  of  a  small  portion.     (Testut.) 


Hum. 


nerve. 


It  forms  the  organ  of  Corti.  In  this  lie  the  terminations  of  the  cochlear 
It  appears  at  first  sight  as  a  papilla,  winding  spirally  throughout  the 
whole  length  of  the  ductus  cochlearis,  from  which  circumstance  it  has  been  desig- 
nated the  papilla  spiralis.  More  accurately  viewed,  it  is  seen  to  be  composed 
of  a  remarkable  arrangement  of  cells,  which  may  be  likened  to  the  keyboard  of  a 


1  Corti's  original  paper  is  in  the  Zeitschrift  f.  Wissen.  Zool.,  iii.,  109. 


1184 


THE    ORGANS   OF  SPECIAL    SENSE 


pianoforte.  The  organ  of  Corti  consists  of  an  inner  part  and  an  outer  part.  Each 
part  contains  auditory  cells  and  supporting  cells.  Of  these  cells,  the  two  central 
ones  are  rod-like  bodies  and  are  called  the  inner  and  outer  rods  of  Corti.  They  are 
placed  on  the  basilar  membrane,  at  some  little  distance  from  each  other,  but  are 
inclined  toward  each  other,  so  as  to  meet  at  their  opposite  extremities,  and  form 
a  series  of  arches  roofing  over  a  minute  tunnel,  the  canal  or  tunnel  of  Corti, 
between  them  and  the  basilar  membrane,  which  ascends  spirally  through  the 
whole  length  of  the  cochlea. 

The  inner  rods  (Fig.  789),  some  6000  in  number,  are  more  numerous  than  the 
outer  ones,  and  rest  on  the  basilar  membrane,  close  to  the  labium  tympanicum ; 
they  project  obliquely  upward  and  outward,  and  terminate  above  in  expanded 
extremities  which  resemble  in  shape  the  upper  end  of  the  ulna,  with  its  sigmoid 
cavity,  coronoid  and  olecranon  processes.  On  the  outer  side  of  the  rod,  in  the 
angle  formed  between  it  and  the  basilar  membrane,  is  a  nucleated  mass  of  proto- 
plasm; while  on  the  inner  side  is  a  row  of  epithelial  cells,  inner  hair-cells  (Fig. 
789),  surmounted  by  a  brush  of  fine,  stiff,  hair-like  processes.  On  the  inner  side 
of  these  cells  are  two  or  three  rows  of  columnar  supporting  cells,  which  are 
continuous  with  the  cubical  cells  lining  the  sulcus  spiralis  internus. 


FIG.  791. — Longitudinal  section  of  the  cochlea,  showing  the  relations  of  the  scalae,  the  ganglion  spirale,  etc. 
S.  V.,  Scala  vestibuli.  S.  T.,  Scala  tympani.  S.  M.,  Scala  media.  L.  S.,  Ligamentum  spirale.  G.  S.,  Ganglion 
spirale. 

The  outer  rods  (Fig.  789),  numbering  about  4000,  also  rest  by  a  broad  foot  on 
the  basilar  membrane;  they  incline  upward  and  inward,  and  their  upper  extremity 
resembles  the  head  and  bill  of  a  swan ;  the  back  of  the  head  fitting  into  the  con- 
cavity— the  analogue  of  the  sigmoid  cavity — of  one  or  more  of  the  internal  rods, 
and  the  bill  projecting  outward  as  a  phalangeal  process  of  the  membrana  reticu- 
laris,  presently  to  be  described. 

In  the  head  of  these  outer  rods  is  an  oval  portion,  where  the  fibres  of  which 
the  rod  appears  to  be  composed  are  deficient,  and  which  stains  more  deeply  with 
carmine  than  the  rest  of  the  rod.  At  the  base  of  the  rod,  on  its  internal  side- 
that  is  to  say,  in  the  angle  formed  by  the  rod  with  the  basilar  membrane— is  a 
similar  protoplasmic  mass  to  that  found  on  the  outer  side  of  the  base  of  the  inner 
rod;  these  masses  of  protoplasm  are  probably  the  undifferentiated  portions  of  the 
cells  from  which  the  rods  are  developed.  External  to  the  outer  rod  are  three  or 
four  successive  rows  of  epithelial  cells,  more  elongated  than  those  found  on  the 


THE  MEMBRANOUS  LABYRINTH  1185 

internal  side  of  the  inner  rod,  but,  like  them,  furnished  with  minute  hairs-or  cilia. 
These  are  termed  the  outer  hair-cells,  in  contradistinction  to  the  inner  hair-cells 
above  referred  to.  There  are  about  12,000  outer  hair-cells,  and  about  3500  inner 
hair-cells. 

The  hair-cells  are  somewhat  oval  in  shape;  their  free  extremities  are  on  a 
level  with  the  heads  of  Corti's  rods,  and  from  each  some  twenty  fine  hairlets 
project  and  are  arranged  in  the  form  of  a  crescent,  the  concavity  of  which  opens 
inward.  The  deep  ends  of  the  cells  are  rounded  and  contain  large  nuclei;  they 
reach  only  as  far  as  the  middle  of  Corti's  rods,  and  are  in  contact  with  the  rami- 
fications of  the  nervous  filaments.  Between  the  rows  of  the  outer  hair-cells 
are  rows  of  supporting  cells,  called  the  cells  of  Deiters;  their  expanded  bases  are 
planted  on  the  basilar  membrane,  while  their  opposite  ends  present  a  clubbed 
extremity  or  phalangeal  process.  Immediately  to  the  outer  side  of  Deiters's  cells 
are  some  five  or  six  rows  of  columnar  cells,  the  supporting  cells  of  Hensen.  Their 
bases  are  narrow,  while  their  upper  parts  are  expanded  and  form  a  rounded 
elevation  on  the  floor  of  the  ductus  cochlearis.  The  columnar  cells  lying  outside 
Hensen's  cells  are  termed  the  cells  of  Claudius.  A  space  is  seen  between  the 
outer  rods  of  Corti  and  the  adjacent  hair-cells;  this  is  called  the  space  of  Nuel. 

The  lamina  reticularis  or  membrane  of  Kblliker  is  a  delicate  framework  per- 
forated by  rounded  holes.  It  extends  from  the  inner  rods  of  Corti  to  the  external 
row  of  the  outer  hair-cells,  and  is  formed  by  several  rows  of  "minute  fiddle- 
shaped  cuticular  structures "  called  phalanges,  between  which  are  circular 
apertures  containing  the  free  ends  of  the  hair-cells.  The  innermost  row  of  phal- 
anges consists  of  the  phalangeal  processes  of  the  outer  rods  of  Corti;  the  outer 
rows  are  formed  by  the  modified  free  ends  of  Deiters's  cells. 

Covering  over  these  structures,  but  not  touching  them,  is  the  membrana  tectoria 
or  membrane  of  Corti  (Figs.  786  and  789),  which  is  attached  to  the  vestibular  sur- 
face of  the  lamina  spiralis  close  to  the  attachment  of  the  membrane  of  Reissner. 
It  is  thin  near  its  inner  margin,  and  overlies  the  auditory  teeth  of  Husch'ke.  Its 
outer  half  is  thick,  and  along  its  lower  edge,  opposite  the  inner  hair-cells,  is  a 
clear  band,  named  Hensen's  stripe.  Externally,  the  membrane  becomes  much 
thinner,  and  is  attached  to  the  outer  row  of  Deiters's  cells  (Retzius). 

The  fibres  from  the  cochlear  nerve  enter  the  organ  of  Corti  as  axis-cylinders, 
which  pass  directly  to  the  deepest  portions  of  the  inner  and  outer  hair-cells  by 
way  of  the  canal  of  Corti  or  by  the  space  of  Nuel.  The  terminations  arborize 
about  the  lower  portions  of  the  hair-cells  and  end  on  the  surfaces  of  the  hair-cells. 

The  inner  surface  of  the  osseous  labyrinth  is  lined  by  an  exceedingly  thin  fibro- 
serous  membrane,  analogous  to  a  periosteum,  from  its  close  adhesion  to  the 
inner  surfaces  of  these  cavities,  and  performing  the  office  of  a  serous  membrane  by 
its  free  surface.  It  lines  the  vestibule,  and  from  this  cavity  is  continued  into  the 
semicircular  canals  and  the  scala  vestibuli  of  the  cochlea,  and  through  the  helico- 
trema  into  the  scala  tympani.  A  delicate  tubular  process  is  prolonged  along  the 
aqueduct  of  the  vestibule  to  the  inner  surface  of  the  dura.  This  membrane  is 
continued  across  the  fenestra  ovalis  and  fenestra  rotunda,  and  consequently  has 
no  communication  with  the  lining  membrane  of  the  tympanum.  Its  attached 
surface  is  rough  and  fibrous,  and  closely  adherent  to  the  bone;  its  free  surface  is 
smooth  and  pale,  covered  with  a  layer  of  epithelium,  and  secretes  a  thin,  limpid 
fluid,  the  aqua  labyrinthi,  liquor  Cotunnii  or  perilymph  (Blainville). 

The  scala  media  is  closed  above  and  below.  The  upper  blind  extremity  is 
termed  the  lagena,  and  is  attached  to  the  cupola  at  the  upper  part  of  the  helico- 
trema;  the  lower  end  is  lodged  in  the  recessus  cochlearis  of  the  vestibule.  Near 
this  blind  extremity,  the  scala  media  receives  the  canalis  reunions  of  Hensen  (Fig. 
785),  a  very  delicate  canal,  by  which  the  ductus  cochlearis  is  brought  into  con- 
tinuity with  the  saccule. 


1186  THE   ORGANS   OF  SPECIAL    SENSE 

The  Arteries  of  the  Labyrinth. — The  arteries  of  the  labyrinth  are  the  internal 
auditory,  from  the  basilar,  and  the  stylo-mastoid,  from  the  posterior  auricular. 
The  internal  auditory  divides  at  the  bottom  of  the  internal  auditory  meatus 
into  two  branches,  cochlear  and  vestibular. 

The  cochlear  artery  divides  into  numerous  minute  branches,  which  enter 
foramina  in  the  tractus  spiralis  foraminosa  and  course  in  the  lamina  spiralis  ossea 
to  reach  the  membranous  structures.  The  largest  of  the  cochlear  branches  is  in 
the  canalis  centralis. 

The  vestibular  branches  accompany  the  nerves,  and  supply  the  membranous 
structures  in  the  vestibule  and  semicircular  canals.  Two  arteries  go  to  each 
canal.  The  two  vessels  enter  opposite  extremities  of  the  canal,  and  anastomose 
at  the  summit  of  the  canal.  The  vestibular  vessels  form  a  minute  capillary  net- 
work in  the  substance  of  each  membranous  labyrinth. 

The  Veins  of  the  Labyrinth. — The  veins  of  the  vestibule  and  semicircular  canals, 
the  auditory  veins,  accompany  the  arteries,  and  receive  those  of  the  cochlea  at  the 
base  of  the  modiolus,  to  form  the  internal  auditory  vein  (vv.  auditivae  internae), 
which  opens  into  the  posterior  part  of  the  inferior  petrosal  sinus  or  into  the  lateral 
sinus. 

The  Nerves  of  the  Labyrinth. — The  auditory  nerve  (n.  acusticus) ,  the  special  nerve 
of  the  sense  of  hearing,  divides,  at  the  bottom  of  the  internal  auditory  meatus, 
into  two  branches,  the  cochlear  and  vestibular. 

The  Vestibular  Nerve  (n.  vestibularis) ,  the  posterior  of  the  two,  presents,  as  it  lies 
in  the  internal  auditory  meatus,  a  ganglion,  the  vestibular  ganglion  or  the  ganglion 
of  Scarpa  (ganglion  vestibulare) ;  the  nerve  divides  into  three  branches  which  pass 
through  minute  openings  at  the  upper  and  back  part  of  the  bottom  of  the  meatus 
(area  vestibular  posterior),  and,  entering  the  vestibule,  are  distributed  to  the  utricle 
and  to  the  ampulla  of  the  external  and  superior  semicircular  canals. 

The  nerve  filaments  enter  the  ampullary  enlargements  opposite  the  septum 
transversum,  and  arborize  around  the  hair-cells.  In  the  utricle  and  saccule  the 
nerve-fibres  pierce  the  membrana  propria  of  the  maculae,  and  end  in  arborizations 
around  the  hair-cells. 

The  Cochlear  Nerve  (n.  cochlearis)  gives  off  the  branch  to  the  saccule,  the  fila- 
ments of  which  are  transmitted  from  the  internal  auditory  meatus  through  the 
foramina  of  the  area  vestibularis  inferior,  which  lies  at  the  lower  and  back  part 
of  the  floor  of  the  meatus.  It  also  gives  off  the  branch  for  the  ampulla  of  the 
posterior  semicircular  canal,  which  leaves  the  meatus  through  the  foramen  singulare. 

The  rest  of  the  cochlear  nerve  divides  into  numerous  filaments  at  the  base 
of  the  modiolus;  those  for  the  basal  and  middle  coils  pass  through  the  foramina 
in  the  tractus  foraminosus,  those  for  the  apical  coil  through  the  canalis  centralis, 
and  the  nerves  bend  outward  to  pass  between  the  lamellae  of  the  osseous  spiral 
lamina.  Occupying  the  spiral  canal  of  the  modiolus  is  the  spiral  ganglion  or  gan- 
glion of  Corti  (ganglion  spirale),  consisting  of  bipolar  nerve-cells,  which  really  con- 
stitute the  true  cells  of  origin  of  this  nerve,  one  pole  being  prolonged  centrally  to 
the  brain  and  the  other  peripherally  to  the  hair-cells  of  Corti's  organ.  Reaching  the 
outer  edge  of  the  osseous  spiral  lamina,  the  nerve  fibres  pass  through  the  foramina 
in  the  labium  tympanicum,  where  they  lose  their  axis-cylinders.  They  enter  the 
organ  of  Corti  and  pass  directly  to  the  deep  portions  of  the  inner  and  outer  hair-cells 
by  way  of  the  canal  of  Corti  and  the  space  of  Nuel.  The  terminations  arborize 
about  the  lower  portions  of  the  hair-cells  and  end  in  the  surfaces  of  the  cells. 

Surgical  Anatomy. — Malformations,  such  as  imperfect  development  of  the  external  parts, 
absence  of  the  meatus,  or  supernumerary  auricles,  are  occasionally  met  with.  Or  the  pinna  may 
present  a  congenital  fistula,  which  is  due  to  defective  closure  of  the  first  visceral  cleft,  or  rather 
of  that  portion  of  it  which  is  not  concerned  in  the  formation  of  the  Eustachian  tube,  tympanum, 
and  meatus.  In  some  cases  the  cephalo-auricular  angle  is  almost  absent;  in  others  it  is  nearly 


I  HE  MEMBRANOUS   LABYRINTH  1187 

a  right  angle.  Projecting  ears  and  long  ears  are  said  by  some  observers  to  be  more  common 
among  degenerates,  criminals,  and  the  insane  than  among  the  normal,  the  non-criminal,  and 
the  sane.  The  skin  of  the  auricle  is  thin  and  richly  supplied  with  blood,  but  in  spite  of  this  it 
is  frequently  the  seat  of  frost-bite,  due  to  the  fact  that  it  is  much  exposed  to  cold,  and  lacks  the 
usual  underlying  subcutaneous  fat  found  in  most  other  parts  of  the  body.  A  collection  of  blood 
is  sometimes  found  between  the  cartilage  and  perichondrium  (haematoma  auris},  usually  the 
result  of  traumatism,  but  not  necessarily  due  to  this  cause.  It  is  said  to  occur  most  frequently 
in  the  ears  of  the  insane.  Keloid  sometimes  grows  in  the  auricle  around  the  puncture  made  for 
ear-rings,  and  epithelioma  occasionally  affects  this  part.  Deposits  of  urate  of  soda  are  often  met 
with  in  the  pinna  in  gouty  subjects. 

The  external  auditory  meatus  can  be  most  satisfactorily  examined  by  light  reflected  down  a 
funnel-shaped  speculum;  by  gently  moving  the  latter  in  different  directions  the  whole  of  the 
canal  and  membrana  tympani  can  be  brought  into  view.  The  points  to  be  noted  are:  the  pres- 
ence of  wax  or  foreign  bodies,  the  size  of  the  canal,  and  the  condition  of  the  membrana  tympani. 
The  accumulation  of  wax  is  often  the  cause  of  deafness,  and  may  give  rise  to  very  serious  conse- 
quences, causing  ulceration  of  the  membrane  and  even  absorption  of  the  bony  wall  of  the  canal. 
Foreign  bodies  are  not  infrequently  introduced  into  the  ear  by  children,  and,  when  situated  in 
the  first  portion  of  the  canal,  may  be  removed  with  tolerable  facility  by  means  of  a  minute  hook 
or  loop  of  fine  wire,  the  parts  being  illuminated  with  reflected  light;  but  when  they  have  slipped 
beyond  the  narrow  middle  part  of  the  meatus,  their  removal  is  in  nowise  easy,  and  attempts  to  effect 
it,  in  inexperienced  hands,  may  be  followed  by  destruction  of  the  membrana  tympani  and  possibly 
injury  of  the  contents  of  the  tympanum.  The  calibre  of  the  external  auditory  canal  may  be  nar- 
rowed by  inflammation  of  its  lining  membrane,  running  on  to  suppuration;  by  periostitis;  by  polypi, 
sebaceous  tumors, and  exostoses.  The  membrana  tympani,  when  seen  in  a  healthy  ear,  "reflects 
light  strongly,  and,  owing  to  its  peculiar  curvature,  presents  a  bright  spot  of  triangular  shape  at  its 
lower  and  anterior  portion."  From  the  apex  of  this,  proceeding  upward  and  slightly  forward,  is 
a  white  streak  formed  by  the  handle  of  the  malleus,  while  near  the  upper  part  of  the  membrane 
may  be  seen  a  slight  projection,  caused  by  the  short  process  of  the  malleus.  In  disease  alterations 
in  color,  lustre,  curvature  or  inclination,  and  perforation  must  be  noted.  Such  perforations  may 
be  caused  by  a  blow,  a  loud  report,  a  wound,  or  as  the  result  of  suppuration  in  the  middle  ear. 

The  upper  wall  of  the  meatus  is  separated  from  the  cranial  cavity  by  a  thin  plate  of  bone; 
the  anterior  wall  is  separated  from  the  temporo-mandibular  joint  and  parotid  gland  by  the  bone 
forming  the  glenoid  fossa;  and  the  posterior  wall  is  in  relation  with  the  mastoid  cells;  hence 
inflammation  of  the  external  auditory  meatus  may  readily  extend  to  the  membranes  of  the  brain, 
to  the  temporo-mandibular  joint,  or  to  the  mastoid  cells;  and,  in  addition  to  this,  blows  on  the 
chin  may  cause  fracture  of  the  wall  of  the  meatus. 

The  nerves  supplying  the  meatus  are  the  auricular  branch  of  the  vagus,  the  auricula-temporal, 
and  the  auricularis  magnus.  The  connections  of  these  nerves  explain  the  fact  of  the  occurrence, 
in  cases  of  any  irritation  of  the  meatus,  of  constant  coughing  and  sneezing  from  implication  of  the 
vagus,  or  of  yawning  from  implication  of  the  auriculo-temporal.  No  doubt  also  the  association 
of  earache  with  toothache  in  cancer  of  the  tongue  is  due  to  implication  of  the  same  nerve,  a  branch 
of  the  trigeminal,  which  supplies  also  the  teeth  and  the  tongue.  The  vessels  of  the  meatus  and 
membrana  tympani  are  derived  from  the  posterior  auricular,  temporal,  and  internal  maxillary 
arteries.  The  upper  half  of  the  membrana  tympani  is  much  more  richly  supplied  with  blood 
than  the  lower  half.  For  this  reason,  and  also  to  avoid  the  chorda  tympani  nerve  and  ossicles, 
incisions  through  the  membrane  should  be  made  at  the  lower  and  posterior  part. 

The  principal  point  in  connection  with  the  surgical  anatomy  of  the  tympanum  is  its  relations 
to  other  parts.  Its  roof  is  formed  by  a  thin  plate  of  bone,  which,  with  the  dura,  is  all  that 
separates  it  from  the  temporal  lobe  of  the  brain.  Its  floor  is  immediately  above  the  jugular 
fossa  and  the  carotid  canal,  the  fossa  being  behind  and  the  canal  in  front.  Its  posterior  wall  pre- 
sents the  openings  of  the  mastoid  cells.  On  its  anterior  wall  is  the  opening  of  the  Eustachian 
tube.  Thus  it  follows  that  in  disease  of  the  middle  ear  we  may  get  subdural  abscess,  septic 
meningitis,  or  abscess  of  the  cerebrum  or  cerebellum  from  extension  of  the  inflammation  through 
the  bony  roof;  thrombosis  of  the  lateral  sinus,  with  or  without  pyjemia,  by  extension  through  the 
floor;  or  mastoid  abscess  by  extension  backward.  In  addition  to  this,  we  may  get  fatal  hemorrhage 
from  the  internal  carotid  in  destructive  changes  of  the  middle  ear;  and  in  throat  disease  we  may 
get  the  inflammation  extending  up  the  Eustachian  tube  to  the  middle  ear.  The  Eustachian  tube 
is  accessible  from  the  nose.  If  the  nose  and  mouth  be  closed  and  an  attempt  made  to  expire  air,  a 
sense  of  pressure  with  dulness  of  hearing  is  produced  in  both  ears,  from  the  air  finding  its  way  up 
the  Eustachian  tube  and  bulging  out  the  membrana  tympani.  During  the  act  of  swallowing,  the 
pharvngeal  orifice  of  the  tube,  which  is  normally  closed,  is  opened,  probably  by  the  action  of 
the  Dilator  tubea  muscle.  This  fact  was  employed  by  Politzer  in  devising  an  easy  method  of 
inflating  the  tube.  The  nozzle  of  an  india-rubber  syringe  is  inserted  into  the  nostril;  the  patient 
takes  a  mouthful  of  water  and  holds  it  in  his  mouth,  both  nostrils  are  closed  with  the  finger  and 
thumb  to  prevent  the  escape  of  air,  and  the  patient  is  then  requested  to  swallow;  as  he  does  so  the 


1188 


THE    ORGANS   OF  SPECIAL   SENSE 


surgeon  squeezes  the  bulb  and  the  air  is  forced  out  of  the  syringe  into  his  nose,  and  is  driven  into 
the  Eustachian  tube,  which  is  now  open.  The  impact  of  the  air  against  the  membrana  tympani 
can  be  heard  by  the  surgeon,  if  the  membrane  is  intact,  sound  being  conveyed  by  means  of  a 
piece  of  india-rubber  tubing,  one  end  of  which  is  inserted  into  the  meatus  of  the  patient's  ear,  the 
other  into  that  of  the  surgeon.  The  direct  examination  of  the  Eustachian  tube  is  made  by  the 
Eustachian  catheter.  This  is  passed  along  the  floor  of  the  nostril,  close  to  the  septum,  with 
the  point  touching  the  floor,  to  the  posterior  wall  of  the  pharynx.  When  this  is  felt,  the  catheter 
is  to  be  withdrawn  about  half  an  inch,  and  the  point  rotated  outward  through  a  quarter  of  a 
circle,  and  pushed  again  slightly  backward,  when  it  will  enter  the  orifice  of  the  tube,  and  will 
be  found  to  be  caught,  and  air  forced  into  the  catheter  will  be  heard  impinging  on  the  tympanic 
membrane  if  the  ears  of  the  patient  and  surgeon  are  connected  by  an  india-rubber  tube. 


THE  SKIN  (INTEGUMENTUM  COMMUNE). 

The  skin  covers  the  body  surface  and  is  continuous  with  the  mucous  membrane 
at  the  origin  and  termination  of  the  alimentary  canal  and  at  the  openings  of  other 
canals.  The  skin  is  a  protective  coat,  a  regulator  of  body-temperature,  contains 
multitudes  of  the  terminations  of  sensor  nerves,  and  is  the  seat  of  the  organ  of 
touch  (organon  tactus).  These  nerve-terminations  are  connected  with  nerve-fibres  of 
temperature,  pressure,  and  pain.  Connected  with  the  skin  are  sweat-glands  which 
have  important  excretory  functions  and  sebaceous  glands.  From  its  superficial  part 
come  appendages,  the  hairs,  and  nails.  The  skin  is  elastic  and  varies  in  thickness 
from  0.5  mm.  to  4  mm.  It  is  thinnest  in  the  eyelids  and  prepuce,  and  thickest  over 
the  back  of  the  neck,  back  of  the  shoulders,  palms  of  the  hands,  and  soles  of  the 
feet.  Its  color  depends  in  part  on  the  blood  within  it,  and  in  part  upon  pigment. 
The  deepest  hue  is  about  the  anus,  in  the  genital  region,  in  the  axillae,  over  the 
mammary  glands,  and  in  the  parts  exposed  to  air,  light,  and  varied  temperatures. 
The  color  varies  with  age,  being  pinkish  in  extreme  youth  and  becoming  yellow 
in  old  age.  It  varies  with  exposure  and  with  climate,  being  deepest  in  those  who 
;brave  all  weathers  and  temperatures  and  in  those  who  dwell  beneath  a  tropical  sun. 

It  also  varies  with  race,  and  this  is 
so  well  recognized  that  races  are  class- 
ified by  the  color  of  the  skin  into  the 
Black,  White,  Yellow,  and  Brown  races. 
The  color  of  the  skin  is  also  affected 
in  certain  diseases;  being  extremely 
pale  in  anaemia,  brown  in  Addison's 
disease,  yellow  in  jaundice,  etc. 

In  most  situations  the  skin  is  mova- 
ble, but  in  some  it  is  attached  closely 
to  underlying  structures,  and  is  con- 
sequently immovable  on  the  scalp, 
the  palms  of  the  hands,  the  soles  of 
the  feet,  and  the  outer  portion  of  the 
pinna  of  the  ear.  The  skin  is  fairly 
smooth,  but  close  examination  dis- 
closes multitudes  of  openings,  creases, 
furrows,  depressions,  folds,  and  hairs. 
Hair-follicles  open  upon  the  surf  ace, 
and  the  ducts  of  sebaceous  glands 
and  of  sweat-glands  perforate  the  skin. 
About  the  joints  are  folds  of  skin  (retinacula  cutis),  and  temporary  folds  or 
wrinkles  are  created  by  the  contraction  of  superficial  muscles.  The  facial  wrinkles 
of  advancing  years  are  due  to  habitual  expression  and  loss  of  skin  elasticity.  A 
dimple  is  a  permanent  pit  or  depression  due  to  adhesion  of  the  surface  to  parts 
beneath.  The  ridges  and  furrows  on  the  palms,  soles,  and  flexor  aspects  of  the 


•LONGITUDINAL 
FURROWS 


RIDGES  OF  SKIN 

INTERRUPTED   BY 

LONGITUDINAL 

FURROWS 


FURROWS 
OF  SKIN 


FLEXION    FURROWS 
OPPOSITE  THE 
FLEXURE  OF 
THE  JOINT 


FIG.  792. — The  furrows  and  ridges  of  the  surface  of  the 
skin  from  the  palm  or  surface  of  the  middle  finger.    (Toldt.) 


THE  SKIN 


1189 


digits  are  permanent,  and  over  the  palmar  surface  of  the  digits  they  are  arranged 
in  definite  forms  which  endure  through  life  and  are  so  distinctive  that  they  have 
been  utilized  by  police  officials  in  determining  the  identity  of  individuals.  These 
folds  are  due  to  the  papillae  of  the  skin  being  arranged  in  rows;  some  of  the  papillae 
proliferate,  and  linear  depressions  occur  in  the  horny  layer  (Philippson). 


FIG.  793. — Anterior  surface. 


FIG.  794. — Posterior  surface. 


The  general  course  of  the  connective-tissue  bundles  of  the  corium,  determined  by  the  direction  assumed  by  the 
linear  clefts  made  in  the  skin  when  it  is  punctured  by  a  round  awl.     (Langer.) 

Fig.  792  shows  skin  ridges  (cristae  cutis),  skin  furrows  (sidci  cutls),  furrows 
opposite  joints  due  to  acts  of  flexron,  and  called  flexure  furrows,  and  longitudinal 
furrows. 

When  the  skin  is  punctured  by  a  round  awl  it  tends  to  split  in  a  definite 
direction,  which  direction  varies  with  the  region  stabbed.  These  clefts  are  known 


1190 


THE  ORGANS  OF  SPECIAL  SENSE 


as  the  lines  of  cleavage  of  Langer  (Figs.  793  and  794),  and  depend  upon  the 
arrangement  of  the  connective-tissue  bundles  of  the  corium.  These  connective- 
tissue  bundles  certainly  influence  the  formation  of  folds  and  furrows.  In  many 
portions  of  the  body  the  cutaneous  surface  is  divided  by  linear  furrows  into  irregu- 
larly shaped  areas  (Fig.  795).  The  skin  consists  of  two  layers:  a  superficial  layer, 
the  epidermis,  and  a  deep  layer,  the  corium  or  dermis. 

The  Corium,  Cutis  Vera,  Dermis  or  True  Skin  (Figs.  796,  797,  and  799)  is  a 
connective-tissue  structure  which  arises  from  the  mesoderm.  It  consists  espe- 
cially of  connective  tissue  and  elastic  fibres;  it  contributes  elasticity  to  the  skin, 
and  is  the  seat  of  the  sensitive  layer.  The  corium  is  composed  of  two  layers, 
the  reticular  and  the  papillary. 


MOUTH  OF 

HAIR-FOLLICLES'- 


FIG.  795. — The  furrows  of  the  skin  and  the  areas  which  these  furrows  delimit,  reproduced  from  an  impression  of 

the  dorsal  surface  of  the  wrist.     (Toldt.) 

The  Deep  or  Reticular  Layer  or  Tunica  Propria  (stratum  reticulare)  rests  upon 
the  subcutaneous  tissue.  It  passes  superficially  into  the  papillary  layer,  and  at 
most  places  into  the  subcutaneous  tissue  without  a  sharp  line  of  differentiation. 
At  some  places,  for  instance  in  the  nipple,  the  deep  layer  of  the  corium  rests 
upon  a  layer  of  muscular  fibre.  In  the  face  this  muscle-fibre  is  striated  and  sends 


FURROWS   OF  SKIN 


TOUCH  CORPUSCLE 


I     STRATUM   CORNEUS 

EPIDERMIS^       STRATUM   LUCIDUM 

RETE  MUCOSUM 


(      STRATUM     PAPILLARE  | 


'STRATUM    RE 


TICULARE 


ORIFICE   OF 
SUDORIFEROUS 
DUCT 

;\SUDORI  FERGUS 
'DUCT 

CAPILLARY 
~  LOOP  OF 
PAPILUE 


BLOODVESSELS 
OF   CORIUM 

BODY  OF 

--^SUDORIFEROUS 
GLAND 


FIG.  796. — Vertical  section  through  the  skin  of  the  finger-tip.     The  layers  of  the  epidermis  and  of  the  corium. 
The  subcutaneous  areolar  tissue.     The  sudoriferous  or  sweat-gland.     (Toldt.) 

prolongations  to  the  papillary  layer;  in  the  nipple  and  scrotum  it  is  non-striated. 
The  reticular  layer  is  composed  of  bundles  of  white  fibrous  tissue,  arranged  in  a 
network.  In  the  meshes  of  the  network  are  fat,  blood-vessels,  lymphatics,  seba- 
ceous glands,  sweat-glands,  and  hair-follicles. 

The  Subcutaneous  Areolar  Tissue  or  Tela  Subcutanea  (panniculus  adiposus)  con- 
nects, the  skin  to  the  parts  beneath;  it  is  composed  o£  bundles  of  connective  tissue 


THE   8KIN 


1191 


ARRCCTOR 
PILI    MUSCLE 


EPIDERMIS 


which  cross  repeatedly  and  form  spaces.  In  almost  all  regions  the  spaces  contain  fat, 
but  in  the  scrotum  and  external  ear  they  do  not  contain  fat.  When  the  connective- 
tissue  fibres  of  the  panniculus  adiposus  are  long  and  nearly  parallel  to  the  skin- 
surface  the  skin  becomes  wrinkled;  when  they  are  short  and  nearly  at  right  angles 
to  the  surface,  the  skin  cannot  wrinkle. 

The  Superficial  or  Papillary  Layer  or  Corpus  Papillate  of  the  Corium  (stratum  papil- 
larc)  lies  just  beneath  the  epidermis,  contains  the  papillae,  and  is  composed  of  a 
network  of  fine  bundles  of  fibrous  tissue.  The  papillae  are  composed  of  fine 
strands  of  connective  tissue  and  elastic 
tissue.  They  project  from  the  corium 
beneath  the  epidermis  and  enter  into 
depressions  of  the  epidermis.  They  vary 
greatly  in  size,  averaging  pg-^  of  an  inch 
in  height  and  3-5-5-  of  an  inch  in  width  at 
the  base.  In  the  face,  especially  in  the 
eyelids,  they  are  insignificant.  On  the 
glans  penis,  the  palms  of  the  hands,  and 
the  soles  of  the  feet,  and  in  the  nipples, 
they  are  large.  In  the  palmar  surfaces 
of  the  hands  and  fingers  and  the  plantar 
surfaces  of  the  feet  and  toes  they  pro- 
duce permanent  ridges  (Fig.798) .  A  ridge 
is  composed  of  two  or  more  rows  of 

papillae,  and    the  ducts   of    SWeat-glands 

emerge  between  rows  of  papillae,  and 
open  on  the  curved  surface  ridges  (Fig. 
798).  Most  of  the  papillae  contain  loops  of  capillaries,  and  are  called  vascular 
papillae.  Some  contain  nerve-terminations  and  are  called  nervous  papillae.  Be- 
tween the  papillary  layer  of  the  corium  and  the  epidermis  is  a  very  thin  and 
structureless  membrane  called  the  basal  membrane. 


SUDORIFEROUS      SUBCUTANEOUS 
GLANDS      AREOLAR  TISSUE 

FIG.  797. — Vertical  section  through  the  skin  of  the 


PA  PILL*   OF 


SUDORIFEROUS 
DUCTS 


FURROWS 
OF  SKIN 


FIG.  798. — The  furrows  and  ridges  of  true  skin  on  the  palmar  surface  of  one  of  the  fingers,  the  epidermis 

having  been  removed.     (Toldt.) 

The  Cuticle,  Scarf  Skin  or  Epidermis  (Figs.  796,  797,  799,  and  800).— The 
cuticle,  scarf  skin  or  epidermis  is  composed  of  layers  of  epithelium  and  is 
derived  from  the  ectoderm.  The  epithelium  is  stratified,  and  there  are  no 
blood-vessels.  Two  layers  can  be  readily  made  out,  the  superficial  or  horny 
layer  and  the  deeper  or  Malpighian  layer. 

The  Horny  Layer  (stratum  corneum). — The  horny  layer  is  formed  by  several 
layers  of  non-nucleated  scaly  cells.  The  cells  consist  of  keratin.  The  surface 
cells  of  the  horny  layers  are  being  constantly  rubbed  off,  and  are  being  replaced 
by  cells  from  the  Malpighian  layer,  which  are  converted  into  keratin  as  they  near 
the  surface. 


1192 


THE    ORGANS    OF   SPECIAL   SENSE 


The  Malpighian  Layer. — The  Malpighian  layer  of  the  epidermis  is  divided  into 
four  layers,  named,  from  without  inward,  the  stratum  lucidum,  the  stratum  granu- 
losum,  the  stratum  mucosum,  and  the  stratum  germinativum. 

The  Stratum  Lucidum  is  not  classified  by  all  writers  as  part  of  the  Malpighian 
layer.  Some  anatomists  classify  it  as  a  separate  layer.  It  is  here  regarded  as  the 
most  superficial  part  of  the  Malpighian  layer.  It  consists  of  several  layers  of  flat 
cells,  the  nuclei  of  which  are  beginning  to  disappear.  The  cells  contain  eleidin 
granules.  In  regions  where  the  epidermis  is  thin  the  stratum  lucidum  is  absent. 

The  Stratum  Granulosum  consists  of  several  layers  of  nucleated  flat  cells,  con- 
taining keratohyaline  granules.  These  granules  are  probably  formed  from  the 
disintegrating  nucleus,  and  in  the  stratum  lucidum  are  converted  into  eleidin. 


Superficial 
layers 
Rete 

Mucosum 

f  Papilla 
( Corium 


i    Epidermis 


Cuticle 


Derma 


FIG.  799. — A  sectional  view  of  the  skin  (magnified). 

The  Mucous  Layer,  the  Stratum  Spinosum  or  the  Stratum  Mucosum  consists  of 
numerous  layers  of  nucleated,  polygonal,  spine-shaped  cells  known  as  prickle  cells 
or  finger  cells.  Between  the  cells  of  the  stratum  mucosum  are  spaces  containing 
pigment  granules  and  leukocytes.  Processes  from  the  prickle-cells  join  adjacent 
cells.  This  layer  contains  numerous  connective-tissue  fibres  arranged  in  a  net- 
work, and  known  as  epidermic  fibrils. 

The  Stratum  Cylindricum  or  Stratum  Germinativum  is  composed  of  cylindrical  or 
prickle-cells,  the  points  of  which  are  directed  downward.  Fine  fibrils  pass  up 
from  the  corium  between  the  cells,  and  there  is  cement-substance  as  well  between 
them. 

Pigmentation  of  the  Skin. — As  previously  stated,  in  certain  regions  the  skin  of  the 
white  race  is  brown  because  of  pigmentation  (areolae,  nipples,  around  the  anusr 
axillae,  scrotum,  labia  majora).  This  is  due  to  pigment  within  the  epithelial  and 


THE   SKIN 


1193 


connective-tissue  cells  of  the  papillary  layer  of  the  corium,  and  in  the  basal  cells 
of  the  epidermis.  There  are  few  or  none  of  these  pigmented  cells  in  the  stratum 
corneum  of  one  of  the  Caucasian  race. 


Stratum  corneum.  < 


Stratum  lucidum. 
Stratum  granuJosum. 


Stratum  mueosum/ 
Malpighii. ' 


Stratum  germinativum.  j 


-Nerve-fibrils. 


FIG.  800. — Section  of  epidermis.     (Ranvier.) 


"  In  negroes  and  other  colored  races  the  deep  pigmentation  is  due  to  a  similar 
distribution  of  the  pigment  granules  in  the  entire  epidermis;  but  even  here  the 
pigmentation  decreases  toward  the  surface,  although  the  uppermost  cells  of  the 


FIG.  801. — Microscopic  section  of  skin,  showing  the  epidermis  and  derma  ;  a  hair  in  its  follicle  ; 
the  Erector  pili  muscle  ;  sebaceous  and  sudoriferous  glands. 

stratum  corneum  always  contain  some  pigment.  The  nuclei  of  the  cells  are  always 
free  from  coloring  matter.  The  question  as  to  the  origin  of  the  pigment  is  as  yet 
unsolved."1 


1  A  Text-book  of  Histology.    By  A.  A.  Biihm  and  M.  von  Davidoff.    Translated  and  edited  by  G.  Carl  Huber. 


1194 


THE   ORGANS    OF  SPECIAL   SENSE 


The  Arteries  and  Veins  of  the  Skin  (Fig.  S02). — The  arteries  supplying  the  skin 
vary  in  number,  and  vary  much  in  size,  being  largest  in  regions  exposed  to 
pressure,  as  the  skin  of  the  palms,  soles,  and  buttocks.  The  arteries  enter  the 
skin  from  a  network  in  the  subcutaneous  tissue,  and  by  an  anastomosis  in  the 
deepest  part  of  the  corium  form  a  network  (rete  arteriosum  cutaneum}.  The  vessels 
send  branches  to  the  fat  and  to  the  sweat-glands.  Branches  from  the  network  just 
described  ascend  and  form  a  second  network  in  the  corium  beneath  the  papillae. 
This  is  called  the  subpapillary  network  (rete  arteriosum  subpapillare).  From  this  net- 
work fine  capillary  vessels  pass  into  the  papillae,  forming,  in  the  smaller  papillae, 
a  single  capillary  loop,  but  in  the  larger  a  more  or  less  convoluted  vessel.  From 
this  network  branches  go  to  the  hair-follicles  and  sebaceous  glands.  The  blood 
from  the  papillae  passes  into  a  plexus  (rete  venosum)  beneath  the  papillae.  This 


RETE 
VENOSUM 


SUBPAPILLARY 
NETWO 


EPIDERMIS 
—  PAPILLARY  LAYER- 


RETE 
VENOSUM 


SUBCUTANEOUS 
TISSUE 


FIG.  802. — The  distribution  of  the  blood-vesseis  in  the  skin  of  the  sole  of  the  foot.     (Spalteholz.) 

communicates  with  another  plexus  between  the  corium  and  subcutaneous  tissue. 
In  some  regions  one  or  more  retia  are  interposed  between  these  two.  The  veins 
from  the  sweat-glands,  sebaceous  glands,  superficial  fat,  and  hair-follicles  are 
received  by  the  retia  venosa.  From  the  deepest  rete  veins  pass  to  the  subcuta- 
neous tissue,  and  these  veins  enter  the  large  subcutaneous  veins. 

The  Lymphatics  of  the  Skin. — There  are  numerous  lymphatics  supplied  to  the 
skin  which  form  two  networks,  superficial  and  deep,  communicating  with  each 
other  and  with  the  lymphatics  of  the  subcutaneous  tissue  by  oblique  branches. 
They  originate  in  the  cell-spaces  of  the  tissue. 

The  Nerves  of  the  Skin. — The  nerves  of  the  skin  terminate  partly  in  the  epidermis 
(Figs.  796  and  800)  and  partly  in  the  cutis  vera  (Fig.  796).  The  former  are  pro- 
longed into  the  epidermis  from  a  dense  plexus  in  the  superficial  layer  of  the  corium 
and  terminate  between  the  cells  in  bulbous  extremities;  or,  according  to  some 
observers,  in  the  deep  epithelial  cells  themselves.  The  latter  terminate  in  end-bulbs, 
touch-corpuscles,  or  Pacinian  bodies  (Figs.  524  and  796),  in  the  manner  already 
described;  and,  in  addition  to  these,  a  considerable  number  of  fibrils  are  distrib- 
uted to  the  hair-follicles,  which  are  said  to  entwine  about  the  follicle  in  a  circular 


THE  NAILS 


1195 


manner.  Other  nerve-fibres  are  supplied  to  the  plain  muscular  fibres  of  the  hair- 
follicles  (arrectores  pili)  and  to  the  muscular  coat  of  the  blood-vessels.  These  are 
probably  amyelinic  fibres. 

The  Appendages  of  the  Skin. 

The  appendages  of  the  skin  are  the  nails,  the  hairs,  the  sudoriferous  and  seba- 
ceous glands,  and  their  ducts. 

The  nails  and  hairs  are  peculiar  modifications  of  the  epidermis,  consisting 
essentially  of  the  same  cellular  structure  as  that  tissue. 


Eponychium. 

Nail. 

Stratum 


Stratum  eo 
of  the  nail 
groove. 


granulosum. 
Corium. 


Blood-vessel. 


FIG.  803. — Longitudinal  section  through  human  nail  and  its  nail  groove  (sulcus).     (From  Biihm  and 

Davidoff's  Histology. 

The  Nails  (ungues)  (Figs.  803, 804,  805,  806, 807,  and  808).— The  nails  are  flat- 
tened, elastic  structures  of  a  horny  texture,  placed  upon  the  dorsal  surface  of  the 
terminal  phalanges  of  the  fingers  and  toes.  Each  nail  is  convex  on  its  outer  sur- 
face, concave  within.  Its  chief  mass,  called  the  body  (corpus  unguis),  lies  upon 
the  nail-bed.  The  free  edge  is  called  the  margo  liber.  Each  lateral  margin  (margo 
lateralis),  like  the  proxmial  short  edge  of  the  nail  (margo  occultus),  lies  in  a  groove 
of  the  cutis,  the  ungual  fold  (sulcus  matricis  unguis).  The  ungual  wall  (vallum 
unguis)  overlies  the  lateral  and  posterior  edges.  The  nail  is  implanted  by  means 
of  a  portion,  called  the  root  (radix  unguis),  into  a  groove  in  the  skin.  The  root  is 
beneath  the  ungual  wall  and  is  composed  of  cells  which  have  not  yet  become 

Nail. 

Stratum  Malpighii; 
Nail  wail. 

Nail  groove. 

Corium. 
hod-vessel. 


FIG.  804. — Transverse  section  through  human  nail  and  its  sulcus.     (From  Bohm  and  Davidoff's  Histology.) 

horny.  It  is  white  in  color.  The  nail  has  a  very  firm  adhesion  to  the  cutis  vera, 
being  accurately  moulded  upon  the  surface  of  the  true  skin,  as  the  epidermis  is  in 
other  parts.  The  part  of  the  cutis  beneath  the  body  and  root  of  the  nail  is  called 
the  matrix  (matrix  unguis),  because  it  is  the  part  from  which  the  nail  is  produced. 
Corresponding  to  the  body  of  the  nail,  the  matrix  is  thick,  and  raised  into  a  series 
of  longitudinal  ridges  (cristae  matricis  unguis},  which  are  very  vascular,  and  the 
color  is  seen  through  the  transparent  tissue.  Behind  this,  near  the  root  of  the 
nail,  the  papillae  are  small,  less  vascular,  and  have  no  regular  arrangement,  and 
here  the  tissue  of  the  nail  is  somewhat  more  opaque;  hence  this  portion  is  of  a 
whiter  color,  and  is  called  the  lunula  on  account  of  its  crescentic  shape. 


1196 


THE    ORGANS    OF  SPECIAL   SENSE 


The  cuticle,  as  it  passes  forward  on  the  dorsal  surface  of  the  finger  or  toe,  is 
attached  to  the  surface  of  the  nail,  a  little  in  advance  of  the  nail  root ;  at  the 
extremity  of  the  finger  it  is  connected  with  the  under  surface  of  the  nail  a  little 
behind  its  free  edge.  The  cuticle  and  the  horny  substance  of  the  nail  (both  epi- 
dermic structures)  are  thus  directly  continuous  with  each  other.  The  nails  con- 
sist of  a  greatly  thickened  stratum  lucidum,  the  stratum  corneum  forming  merely 


BODY 


HORNY 

"LAYER 


RIDGES  OF 
MATRIX 


NAIL-WALL 


MALPIGHIAN 

LAYER 


SULCUS  OF 
MATRIX 


LATERAL 
MARGIN 


RETINACULA 
OF  SKIN 


RIDGES^;' 
OF  SKIN 

PALMAR   SURFACE 
OF  FINGER 


FIG.  805. — Transverse  section  through  the  nail  and  the  terminal  portion  of  the  ring  finger.     (Toldt.) 

the  thin  cuticular  fold  (eponychium)  which  overlaps  the  lunula.  The  cells  have 
a  laminated  arrangement,  and  are  essentially  similar  to  those  composing  the 
epidermis.  The  deepest  layer  of  cells,  which  lie  in  contact  with  the  papillae 
of  the  matrix,  are  columnar  in  form  and  arranged  perpendicularly  to  the  surface; 
those  which  succeed  them  are  of  a  rounded  or  polygonal  form,  the  more  superficial 
ones  becoming  broad,  thin,  and  flattened,  and  so  closely  compacted  as  to  make  the 


MATRIX  OF  NAIL 


RIDGES  OF 
MATRIX 


SULCUS  OF 
MATRIX 


NAIL  FOLD 


CONCEALED  MARGIN 


FIG.  806. — The  finger  nail  com- 
pletely isolated,  seen  from  the  con- 
vex side.  (Toldt.) 


NAIL  WALL 


FIG,  807.— The  matrix  of 
the  nail  or  nail-bed,  with  the 
nail-fold  and  nail-walls  dis- 
played by  the  removal  of  the 
epidermic  portion  of  the  nail 
or  nail  proper  and  the  sur- 
rounding epidermis.  (Toldt  ) 


FIG.  808.— Matrix  of  the 
nail  with  partly  opened  mar- 
ginal groove  of  the  nail-bed. 
(Toldt.) 


limits  of  each  cell  very  indistinct.  It  is  by  the  successive  growth  of  new  cells  at 
the  root  and  under  surface  of  the  body  of  the  nail  that  it  advances  forward  and 
maintains  a  due  thickness,  while,  at  the  same  time,  the  growth  of  the  nail  in  the 
proper  direction  is  secured.  As  these  cells  in  their  turn  become  displaced  by 
the  growth  of  new  ones,  they  assume  a  flattened  form,  and  finally  become  closely 
compacted  together  into  a  firm,  dense,  horny  texture.  In  chemical  composition  the 


THE  HAIRS 


1197 


FIBROUS 
SUBSTANCE 


nails  resemble  the  upper  layers  of  the  epidermis,  containing,  however,  a  some- 
what larger  proportion  of  carbon  and  sulphur  (Mulder). 

The  Hairs  (pili)  (Figs.  797,  799, 801, 809, 810,  and  811).— The  hairs  are  peculiar 
modifications  of  the  epidermis,  and  consist  essentially  of  the  same  structure  as 
that  membrane.  They  are  found  on  nearly  every  part  of  the  surface  of  the  body, 
excepting  the  palms  of  the  hands,  soles  of  the  feet,  the  vermilion  borders  of  the 
lips,  the  dorsal  surfaces  of  the  phalanges,  the  nipples,  the  inner  surface  of  the 
prepuce,  and  the  glans  penis.  Hairs  include  hairs  of  the  head  (capilla) ;  of  the  eye- 
brows (snpercilia) ;  of  the  beard  (barba) ;  of  the  ears  (tragi) ;  of  the  nostrils (vibrissae) ; 
the  eyelashes  (cilia) ;  hairs  of  the  axilla  (hirci) ;  pubes  (pubes) ;  and  the  small  hairs 
of  the  skin  or  woolly  hairs  (lanugo}. 
They  vary  much  in  length,  thick- 
ness, and  color  in  different  parts  of 
the  body  and  in  different  races  of 
mankind.  In  some  parts,  as  in  the 
skin  of  the  eyelids,  they  are  so  short 
as  not  to  project  beyond  the  follicles 
containing  them;  in  others,  as  upon 
the  scalp,  they  are  of  considerable 
length;  again,  in  other  parts,  as  the 
eyelashes,  the  hairs  of  the  pubic  re- 
gion, and  the  whiskers  and  beard, 
they  are  remarkable  for  their  thick- 
ness. Straight  hairs  are  stronger 
than  curly  hairs,  and  present  on 
transverse  section  a  cylindrical  or  ROOT 

oval   outline;    curly  hairs,    on    the 
other  hand,  are  flattened.   The  hairs 

11  i    i«  OUTER 

are  usually  oblique  to  the  surface  "BROUS  LAYER 

from   which  they  arise  (Fig.  797).  INNER 

Their  direction   depends  upon  the  FIBROUS  LAVER 
region  from  which  they  spring,  being 


W^N^S'?'  MEDULLARY 
] SUBSTANCE 


NECK  OF 
HAIR-FOLLICLE 


INNER 
ROOT-SHEATH 


OUTER 
ROOT-SHEATH 


HYALINE 
LAYER 


FUNDUS  OF 
HAIR-FOLLICLE 


SEBACEOUS 
GLAND 


ARRECTOR 
PILI   MUSCLE 


HAIR-PAPILLA 


FIG.  809. — A  hair  of  the  head  still  in  the_   course  of  growth, 
with  hair-bulb  in  longitudinal  section      (Toldt.) 


fairly  regular  in  certain  regions. 
Thijs  are  formed  hair-streams  (flu- 
mina  pilorum)  and  hair-whirlpools 
(vortices  pilorum). 

A  hair  consists  of  the  root,  the 
part  implanted  in  the  skin ;  the  shaft 
or  stem,  the  portion  projecting  from 
its  surface;  and  the  point. 

The  Root  of  the  Hair  (radix  pili) 

r»rp<5pnt«   at    itc   *>Ytr*>rmtv  a    KulK/Mio 
llty  a    DUlbOUS 

enlargement,  the  hair-bulb  (bulbus 
pili)  (Figs.  799  and  809),  which  is  whiter  in  color  and  softer  in  texture  than  the  shaft, 
and  is  lodged  in  a  follicular  involution  of  the  epidermis  called  the  hair-follicle  (follic- 
ulus  pili)  (Figs.  797  and  801).  When  the  hair  is  of  considerable  length  the  follicle 
extends  into  the  subcutaneous  cellular  tissue  (Fig.  799).  The  hair-follicle  com- 
mences on  the  surface  of  the  skin  with  a  funnel-shaped  opening,  and  passes  inward 
in  an  oblique  or  curved  direction — the  latter  in  curly  hair — to  become  dilated  at 
its  deep  extremity  or  fundus  (fundus  folliculi  pili),  where  it  corresponds  with  the 
bulbous  condition  of  the  hair  which  it  contains.  It  has  opening  into  it,  near  its 
free  extremity,  the  orifices  of  the  ducts  of  one  or  more  sebaceous  glands  (Figs. 
799,  801,  809,  and  810).  At  the  bottom  of  each  hair-follicle  is  a  small  conical, 
vascular  eminence  or  papilla,  the  hair-papilla  (papilla  pili}  (Figs.  809  and  810), 


1198 


THE  ORGANS  OF  SPECIAL  SENSE 


similar  in  every  respect  to  the  papillae  found  upon  the  surface  of  the  skin;  it  is 
continuous  with  the  derraic  layer  of  the  follicle,  is  highly  vascular,  and  is  prob- 
ably supplied  with  nerve  fibrils.  In  structure  the  hair-follicle  consists  of  two 
coats — an  outer  or  dermic,  and  an  inner  or  epidermic  (Figs.  809  and  811). 

The  Outer  or  Dermic  Coat  is  formed  mainly  of  fibrous  tissue;  it  is  continuous 
with  the  corium,  is  highly  vascular,  and  is  supplied  by  numerous  minute  nerve 
filaments.  It  consists  of  three  layers.  The  most  internal,  the  cuticular  lining 
of  the  follicle,  consists  of  a  hyaline  basement-membrane,  the  hyaline  layer,  having 
a  glassy,  transparent  appearance,  which  is  well  marked  in  the  larger  hair-follicles, 
but  is  not  very  distinct  in  the  follicles  of  minute  hairs.  It  is  continuous  with  the 
basement-membrane  of  the  surface  of  the  corium.  External  to  this  is  the  inner 
fibrous  layer,  a  compact  layer  of  fibres  and  spindle-shaped  cells  arranged  circularly 
around  the  follicle.  This  layer  extends  from  the  bottom  of  the  follicle  as  high  as 
the  entrance  of  the  ducts  of  the  sebaceous  glands.  Externally  is  the  outer  fibrous 
layer,  a  thick  layer  of  connective  tissue,  arranged  in  longitudinal  bundles,  forming 
a  more  open  texture  and  corresponding  to  the  reticular  part  of  the  corium.  In  this 
are  contained  the  blood-vessels  and  nerves. 


EPIDERMIS. 


CORIUM-   -, 


SUBCUTANEOUS 
AREOLAR  TISSUE 


RETINACULA 
OF  SKIN 


OCCIPITO-FRONTAL 
APONEUROSIS 


ARRECTOR 
PILI   MUSCLE 


_SEBACEOUS 
GLAND 


SUDORIFEROUS 
GLAND 


— HAIR-FOLLICLE 
-ROOT 


HAIR-KNOB 


-HAIR-BULB 


FIG.  810. — Vertical  section  through  the  skin  of  the  head.     The  hairs  of  the  head  in  longitudinal  section.    (Toldt.) 

The  Inner  or  Epidermic  Layer  is  closely  adherent  to  the  root  of  the  hair,  so  that 
when  the  hair  is  plucked  from  its  follicle  this  layer  most  commonly  adheres 
to  it  and  forms  what  is  called  the  root-sheath.  It  consists  of  two  strata,  named 
respectively  the  outer  and  inner  root-sheaths ;  the  former  of  these  corresponds  with 
the  Malpighian  layer  of  the  epidermis,  and  resembles  it  in  the  rounded  form  and 
soft  character  of  its  cells;  at  the  bottom  of  the  hair-follicle  these  cells  become  con- 
tinuous with  those  of  the  root  of  the  hair.  The  inner  root-sheath  consists  of  a 
delicate  cuticle  next  the  hair,  composed  of  a  thin  layer  of  imbricated  scales  having 
a  downward  direction,  so  that  they  fit  accurately  over  the  upwardly  directed 
imbricated  scales  of  the  hair  itself;  then  of  one  or  two  layers  of  horny,  flattened 
nucleated  cells,  known  as  Huxley's  layer;  and  finally  of  a  single  layer  of  horny 
oblong  cells  without  visible  nuclei,  called  Henle's  layer. 

The  hair-follicle  contains  the  root  of  the  hair,  which  terminates  in  a  bulbous 
extremity,  and  is  excavated  so  as  to  exactly  fit  the  papilla  from  which  it  grows. 
The  bulb  is  composed  of  polyhedral  epithelial  cells,  which  as  they  pass  upward 
into  the  root  of  the  hair  become  elongated  and  spindle-shaped,  except  some  in  the 
centre  which  remain  polyhedral.  Some  of  these  latter  cells  contain  pigment- 


THE   HAIRS 


1199 


granules,  which  give  rise  to  the  color  of  the  hair.  It  occasionally  happens  that 
these  pigment-granules  completely  fill  the  cells  of  the  medullary  substance  in 
the  centre  of  the  bulb,  which  gives  rise  to  the  dark  tract  of  pigment  often  found, 
of  greater  or  less  length,  in  the  axis  of  the  hair. 

The  Stem  or  Shaft  of  the  Hair  (scapus  pili)  (Fig.  809),  consists  of  a  central  pith  or 
medulla,  the  fibrous  part  of  the  hair,  and  the  true  cuticle  externally.  The  medulla 
(substantia  medullaris  pili)  occupies  the  centre  of  the  shaft  and  ceases  toward  the 
point  of  the  hair.  It  is  usually  wanting  in  the  fine  hairs  covering  the  surface  of 
the  body,  and  commonly  in  those  of  the  head.  It  is  found  in  the  shafts  of  all  thick 
hairs  and  in  the  deeper  parts  of  the  root  of  most  hairs.  It  is  more  opaque  and 
deeper  colored  when  viewed  by  transmitted  light  than  the  fibrous  part;  but  when 
viewed  by  reflected  light  it  is  white.  It  is  composed  of  rows  of  polyhedral  cells, 
which  contain  granules  of  eleidin  and  frequently  air-bubbles.  The  fibrous  portion 
or  cortical  substance  of  the  hair  (substantia  corticalis  pili)  constitutes  the  chief  part 
of  the  shaft;  its  cells  are  elongated  and  unite  to  form  flattened  fusiform  fibres. 
Between  the  fibres  ape  found  minute  spaces  which  contain  either  pigment-granules 
in  dark  hair  or  minute  air-bubbles  in  white  hair.  In  addition  to  this  there  is  also  a 


CUTICLE  OF 
ROOT-SHEATH 


OUTER          . 

FIBROUS 

LAYER        /< 


HUXLEY'S 
^  LAYER 


\         OUTER 

-•* ROOT- SHEATH 


INNER 
ROOT-SHEATH 


MEDULLARY 
SUBSTANCE 


FIBROUS 
SUBSTANCE 


FIG.  811. — A  moustache  hair  with  its  hair-follicle  in  transverse  section.     (Toldt.) 


diffused  pigment  contained  in  the  fibres.  The  cells  which  form  the  outer  hair  mem- 
brane or  true  cuticle  (cuticula  pili)  consist  of  a  single  layer  which  surrounds  those  of 
the  fibrous  part;  they  are  converted  into  thin,  flat  scales,  having  an  imbricated 
arrangement. 

Connected  with  the  hair-follicles  are  minute  bundles  of  involuntary  muscular 
fibres,  termed  arrectores  pili  (mm.  arrectores  pilorum)  (Figs.  797  and  809).  They 
arise  from  the  superficial  layer  of  the  corium,  and  are  inserted  into  the  outer 
surface  of  the  hair-follicle,  below  the  entrance  of  the  duct  of  the  sebaceous  gland. 
They  are  placed  on  the  side  toward  which  the  hair  slopes,  and  by  their  action 
elevate  the  hair.1  When  the  hair  is  elevated  a  depression  forms  over  the  seat  of 
origin  of  the  muscle,  and  the  parts  about  the  hair  are  elevated.  This  condition  is 
known  as  goose-skin.  It  is  probable  that  the  contraction  of  these  muscles  aids  in 
emptying  sebaceous  glands. 

Blood-vessels  and  Nerves  (Fig.  799). — A  hair-follicle  possesses  a  rich  network  of 
capillaries  about  the  hyaline  membrane,  and  capillary  loops  pass  to  the  papilla. 

1  Arthur  Thomson  suggests  that  the  contraction  of  these  muscles  on  follicles  which  contain  weak,  flat  hairs 
will  tend  to  produce  a  permanent  curve  in  the  follicle,  and  this  curve  will  be  impressed  on  the  hair  which  is 
moulded  within  it,  so  that  the  hair,  on  emerging  through  the  skin,  will  be  curled.  Curved  hair-follicles  are 
characteristic  of  the  scalp  of  the  Bushman. —  ED.  of  15th  English  edition. 


1200  THE  ORGANS  OF  SPECIAL  SENSE 

We  have  little  knowledge  as  to  nerve-terminations  of  the  human  hair.  "In  other 
mammals  the  nerves  end  below  the  sebaceous  glands.  Myelinic  fibres  lose 
their  medullary  sheaths,  divide,  and  penetrate  to  the  hyaline  membrane.  Here 
some  of  the  branches  encircle  the  hair,  while  others  end  freely  on  the  hyaline 
membrane  as  naked  axis-cylinders.  These  branch  regularly  and  run  parallel  to 
the  long  axis  of  the  hair."1 

The  Sudoriferous  or  Sweat-glands  (glandulae  sudoriferae)  (Figs.  796,  797,  799, 
801,  and  810). — The  sudoriferous  or  sweat-glands  are  the  organs  by  which  a  large 
portion  of  the  aqueous  and  gaseous  materials  is  excreted  by  the  skin.  They  are 
found  in  almost  every  part  of  this  structure,  being  absent  on  the  red  border  of  the 
lips,  the  glans  penis,  and  inner  surface  of  the  prepuce.  On  the  eyelids  they  are  some- 
what modified,  and  are  called  ciliary  glands  (glandulae  ciliares  [Molli]) ;  about  the 
anus  they  are  extremely  large,  and  are  called  circumanal  glands  (glandulae  circum- 
anales).  The  sweat-glands  are  situated  in  small  pits  below  the  under  surface  of  the 
corium,  or,  more  frequently,  in  the  subcutaneous  areolar  tissue,  surrounded  by  a 
quantity  of  adipose  tissue.  They  are  small,  lobular,  reddish  bodies,  consisting  of 
a  single  convoluted  tube,  from  which  the  efferent  duct  (ductus  sudoriferus)  proceeds 
upward  through  the  corium  and  cuticle.  The  duct  in  the  corium  has  true  walls;  in 
the  epidermis  it  has  not  individual  walls,  but  is  simply  an  epidermic  tube.  It 
becomes  somewhat  dilated  at  its  extremity,  and  opens  on  the  surface  of  the  cuticle  by 
an  oblique  valve-like  aperture  (porus  sudoriferus).  The  duct,  as  it  passes  through 
the  epidermis,  presents  a  spiral  arrangement,  being  twisted  like  a  corkscrew,  in 
those  parts  where  the  epidermis  is  thick;  where,  however,  the  epidermis  is  thin,  the 
spiral  arrangement  does  not  exist.  In  the  superficial  layers  of  the  corium  the  duct 
is  straight,  but  in  the  deeper  layers  it  is  convoluted  or  even  twisted.  The  spiral 
course  of  these  ducts  is  especially  distinct  in  the  thick  cuticle  of  the  palm  of  the 
hand  and  sole  of  the  foot.  The  size  of  the  glands  varies.  They  are  especially 
large  in  those  regions  where  the  flow  of  perspiration  is  copious,  as  in  the 
axillae,  where  they  form  a  thin,  mamillated  layer  of  a  reddish  color,  which 
corresponds  exactly  to  the  situation  of  the  hair  in  this  region;  they  are  large  also  in 
the  groin.  Their  number  varies.  They  are  most  numerous  on  the  palm  of  the  hand, 
presenting,  according  to  Krause,  2800  orifices  on  a  square  inch  of  the  integument, 
and  are  rather  less  numerous  on  the  sole  of  the  foot.  In  both  of  these  situations 
the  orifices  of  the  ducts  are  exceedingly  regular,  and  open  on  the  curved  surface 
ridges.  In  other  situations  they  are  more  irregularly  scattered,  but  the  number 
in  a  given  extent  of  surface  presents  a  fairly  uniform  average.  In  the  neck  and 
back  they  are  least  numerous,  their  number  amounting  to  417  on  the  square  inch 
(Krause).  Their  total  number  is  estimated  by  the  same  writer  at  2,381,248,  and, 
supposing  the  aperture  of  each  gland  to  represent  a  surface  of  ^  of  a  line  in 
diameter,  he  calculates  that  the  whole  of  these  glands  would  present  an  evap- 
orating surface  of  about  eight  square  inches.  Each  gland  consists  of  a  single 
tube  intricately  convoluted,  terminating  at  one  end  by  a  blind  extremity,  and 
opening  at  the  other  end  upon  the  surface  of  the  skin. 

The  wall  of  the  tubercle  of  the  secreting  coil  is  lined  with  cubical  epithelial 
cells,  external  to  these  is  a  layer  of  smooth  muscle-cells,  and  more  externally  a 
layer  of  connective  tissue,  the  membrana  propria.  The  duct  in  the  corium,  in 
contrast  to  the  secreting  coil,  has  no  layer  of  muscle-cells,  but  instead  a  second 
layer  of  epithelial  cells  covered  by  connective  tissue.  As  previously  stated,  the 
duct  becomes  spiral  in  the  epidermis,  its  own  wall  disappears,  and  the  channel 
is  bounded  by  epidermic  cells. 

Blood-vessels  and  Nerves. — The  blood-vessels  are  branches  from  the  subcuta- 
neous vessels  and  the  arterial  plexus  of  the  deep  part  of  the  corium.  Numerous 

1  Histology  and  Microscopic  Anatomy.      By  Dr.  Ladislaus  Szymonowicz.     Translated  and  edited  by  John 
Bruce  MacCallum,  M.D. 


THE  SEBACEOUS  GLANDS.  1201 

ainyelinic  nerve-fibres  lie  upon  the  merrfbrana  propria  of  a  sweat-gland.    From 
them  fibrils  pass  inward  and  terminate  by  end-bulbs  upon  the  cells  of  the  gland. 

The  Sebaceous  Glands  (glandulaesebaceae). — The  sebaceous  glands  are  small, 
sacculated,  glandular  organs,  lodged  in  the  substance  of  the  corium.  They  are 
found  in  most  parts  of  the  skin,  and  are  usually  connected  with  hair-follicles. 
This  connection  is  so  common  that  they  are  sometimes  called  hair-follicle  glands. 
They  are  found  in  some  regions  which  are  devoid  of  hairs — the  vermilion  borders 
of  the  lips,  the  labia  minora,  the  glans  penis,  and  prepuce.  These  glands  are  espe- 
cially abundant  in  the  scalp  and  face;  they  are  also  very  numerous  around  the 
apertures  of  the  anus,  nose,  mouth,  and  external  ear;  but  are  wanting  in  the  palms 
of  the  hands  and  soles  of  the  feet.  Each  gland  consists  of  a  single  duct,  more  or 
less  capacious,  which  terminates  in  a  cluster  of  small  secreting  pouches  or  saccules. 
The  sacculi  connected  with  each  duct  vary,  in  number,  as  a  rule,  from  two  to  five, 
but  in  some  instances  may  be  as  many  as  twenty.  They  are  composed  of  a  trans- 
parent, colorless  membrane,  enclosing  a  number  of  epithelial  cells.  Those  of 
the  outer  or  marginal  layer  are  small  and  polyhedral,  and  are  continuous  with 
the  lining  cells  of  the  duct.  The  remainder  of  the  sac  is  filled  with  larger  cells, 
containing  fat,  except  in  the  centre,  where  the  cells  have  become  broken  up,  leav- 
ing a  cavity  containing  their  de*bris  and  a  mass  of  fatty  matter,  which  constitutes 
the  sebaceous  secretion.  The  orifices  of  the  ducts  open  most  frequently  into  the 
hair-follicles,  but  occasionally  upon  the  general  surface,  as  in  the  labia  minora  and 
the  free  margins  of  the  lips.  On  the  nose  and  face  the  glands  are  of  large  size, 
distinctly  lobulated,  and  often  become  much  enlarged  from  the  accumulation  of 
pent-up  secretion.  The  largest  sebaceous  glands  are  those  found  in  the  eyelids — 
the  Meibomian  glands. 


76 


THE  OEGANS  OF  DIGESTION. 


THE  Apparatus  for  the  Digestion  of  the  Food  (apparatus  digestorius}  consists 
of  the  alimentary  canal  and  of  certain  accessory  organs. 

THE  ALIMENTARY  CANAL. 

The  alimentary  canal  is  a  musculo-membranous  tube,  about  thirty  feet  in 
length,  extending  from  the  mouth  to  the  anus,  and  lined  throughout  its  entire 
extent  by  mucous  membrane.  It  has  received  different  names  in  the  various  parts 
of  its  course;  at  its  commencement,  the  mouth,  we  find  provision  made  for  the 
mechanical  division  of  the  food  (mastication},  and  for  its  admixture  with  a  fluid 
secreted  by  the  salivary  glands  (insalivation) ;  beyond  this  are  the  pharynx  and 
the  oesophagus,  the  organs  which  convey  the  food  (deglutition)  into  that  part  of 
the  alimentary  canal,  the  stomach,  in  which  the  principal  chemical  changes  occur, 
and  in  which  the  reduction  and  solution  of  the  food  take  place;  in  the  small  intes- 
tines the  nutritive  principles  of  the  food,  the  chyle,  are  separated,  by  its  admixture 
with  the  bile,  pancreatic  and  intestinal  fluids,  from  that  portion  which  passes  into 
the  large  intestine,  most  of  which  is  expelled  from  the  system. 

Alimentary  Canal. 

(  Duodenum. 

Mouth.  Small  intestine    <  Jejunum. 

Pharynx.  ( Ileum. 

Oesophagus.  f Caecum. 

Stomach.  Large  intestine  •<  Colon. 

(  Rectum. 

Accessory  Organs. 
Teeth. 

( Parotid.  Liver. 

Salivary  glands  <  Submaxillary.  Pancreas. 

(  Sublingual.  Spleen. 


THE  MOUTH,  ORAL  OR  BUCCAL  CAVITY  (CAVUM  ORIS). 

The  mouth  is  placed  at  the  commencement  of  the  alimentary  canal;  it  is  a 
nearly  oval-shaped  cavity,  in  which  the  mastication  and  insalivation  of  the  food 
take  place  (Figs.  812,  831,  and  837). 

The  aperture  of  the  mouth  (rima  oris]  is  bounded  by  the  lips.  The  angle  of  the 
mouth  (angulus  oris)  is  formed  on  each  side  by  the  meeting  of  the  upper  and 
lower  lips  (commissura  labiorum).  When  at  rest  with  the  lips  in  contact,  the  rima 
is  a  slightly  curved  line.  Every  movement  which  the  lips  make  alters  the  shape 
of  the  rima.  When  the  mouth  is  closed  the  floor  and  roof  are  usually  in  contact 
and  its  sides  are  approximated  to  the  dental  arches.  The  mouth  consists  of  two 

( 1203 ) 


1204 


THE    ORGANS    OF   DIGESTION 


MOUTH 


parts:  an  outer,  smaller  portion,  the  vestibule,  and  an  inner,  larger  part,  the  cavity 

proper  of  the  mouth. 

The  Vestibule  (vestibulum  oris). — The  vestibule  is  a  slit-like  space,  bounded 

in  front  and  laterally  by  the  lips  and  cheeks;  behind  and  internally  by  the  gums 

and  teeth.  Above  and  below  it  is  limited 
by  the  reflection  of  the  mucous  membrane 
from  the  lips  and  cheeks  to  the  gum  cover- 
ing the  upper  and  lower  alveolar  arch  re- 
spectively. It  receives  the  secretion  from  the 
parotid  glands,  and  communicates,  when  the 
jaws  are  closed,  with  the  cavum  oris  by  an 
aperture  on  each  side  behind  the  wisdom 
teeth. 

The  Cavity  of  the  Mouth  Proper  (cavum 
oris  proprium). — The  cavity  of  the  mouth 
proper  is  bounded  laterally  and  in  front 
by  the  alveolar  arches  with  their  contained 
teeth  ;  behind  it  communicates  with  the 
pharynx  by  a  constricted  aperture  termed 
the  isthmus  faucium.  It  is  roofed  in  by  the 
hard  and  soft  palate.  The  greater  part  of  the 
floor  is  formed  by  the  tongue,  the  remainder 
being  completed  by  the  reflection  of  the  mu- 
cous membrane  from  the  sides  and  under 
surface  of  the  tongue  to  the  gum  lining  the 
inner  aspect  of  the  mandible.  It  receives 
the  secretion  from  the  submaxillary  and 
sublingual  glands. 

The  Mucous  Membrane. — The  mucous 
membrane  lining  the  mouth  is  continuous 
with  the  integument  at  the  free  margin  of 
the  lips  and  with  the  mucous  lining  of  the 
pharynx  behind ;  it  is  of  a  rose-pink  tinge 

during  life,  and  very  thick  where  it  covers  the  hard  parts  bounding  the  cavity. 

It  is  covered  by  stratified  epithelium. 


SMALL 
INTESTINE 


ANUS 

FIG.  812. — Diagram  of  the  alimentary  tube  and 
its  appendages.     (Testut.) 


The  Lips  (Labia  Oris). 

The  lips  are  two  fleshy  folds  which  surround  the  orifice  of  the  mouth,  formed 
externally  by  integument  and  internally  by  mucous  membrane,  between  which  are 
found  the  Orbicularis  oris  muscle  (Fig.  263),  the  coronary  vessels  (Fig.  397),  some 
nerves  (Fig.  397),  areolar  tissue,  and  fat,  and  numerous  small  labial  glands. 
The  upper  lip  is  called  the  labium  superius;  the  lower  lip  is  called  the  labium 
inferius.  The  inner  surface  of  each  lip  is  connected  in  the  middle  line  to  the  gum 
of  the  corresponding  jaw  by  a  fold  of  mucous  membrane,  the  frenulum  (frenulum 
labii  superioris  and  frenulum  labii  inferioris).  The  frenulum  labii  superioris  is 
the  larger  of  the  two.  On  each  side,  external  to  the  angle  of  the  mouth,  the  lips 
become  continuous. 

The  Labial  Glands  (glandulae  labiales)  (Fig.  397)! — The  labial  glands  are  situated 
between  the  mucous  membrane  and  the  Orbicularis  oris  muscle  around  the  orifice 
of  the  mouth.  They  are  rounded  in  form,  about  the  size  of  small  peas,  and  their 
ducts  open  by  minute  orifices  upon  the  mucous  membrane.  In  structure  they 
resemble  the  salivary  glands. 


•/•///•;    TKKTH  1205 

The  Cheeks  (Buccae)o 

The  cheeks  form  the  sides  of  the  face  and  are  continuous  in  front  with  the  lips. 
They  are  composed  externally  of  integument,  internally  of  mucous  membrane, 
and  between  the  two  of  a  muscular  stratum,  besides  a  large  quantity  of  fat,  areolar 
tissue,  vessels,  nerves,  and  buccal  glands. 

The  Mucous  Membrane. — The  mucous  membrane  lining  the  cheek  is  reflected 
above  and  below  upon  the  gums,  where  its  color  becomes  lighter;  it  is  continuous 
behind  with  the  lining  membrane  of  the  soft  palate.  Opposite  the  second  molar 
tooth  of  the  upper  jaw  is  a  papilla,  the  summit  of  which  presents  the  aperture  of 
the  duct  of  the  parotid  gland  (ductus  parotideus  [Stenonis])  (Fig.  837).  The  prin- 
cipal muscle  of  the  cheek  is  the  Buccinator,  but  numerous  other  muscles  enter  into 
its  formation — viz.,  the  Zygomatici,  Risorius  Santorini,  and  Platysma  myoides. 

The  Buccal  Glands  (glandulae  buccales}. — The  buccal  glands  are  placed  in  the 
submucous  tissue  between  the  mucous  membrane  and  Buccinator  muscle;  they 
are  similar  in  structure  to  the  labial  glands,  but  smaller.  Four  or  five  glands  of 
larger  size  than  the  previously  mentioned  glands  are  placed  beneath  the  mucous 
membrane  in  the  neighborhood  of  the  last  molar  tooth.  They  are  called  the 
molar  glands  (glandulae  molares}.  Their  ducts  open  into  the  mouth  opposite  the 
last  molar  tooth. 

The  Gums  (Gingiva). 

The  gums  are  composed  of  a  dense  fibrous  tissue  closely  connected  to  the 
periosteum  of  the  alveolar  processes  and  surrounding  the  necks  of  the  teeth.  They 
are  covered  by  smooth  and  vascular  mucous  membrane,  which  is  remarkable  for 
its  limited  sensibility.  Around  the  necks  of  the  teeth  this  membrane  presents 
numerous  fine  papillae;  and  from  this  point  it  is  reflected  into  the  alveolus,  where 
it  is  continuous  with  the  periosteal  membrane  lining  that  cavity. 

The  Teeth  (Dentes). 

The  human  subject  is  provided  with  two  sets  of  teeth,  which  make  their  appear- 
ance at  different  periods  of  life.  The  first  set  appear  in  childhood,  and  are  called 
the  temporary,  deciduous  or  milk  teeth.  The  second  set  are  named  permanent. 

The  temporary  teeth  are  twenty  in  number — four  incisors,  two  canine,  and  four 
molars  in  each  jaw  (Figs.  813  and  830). 

The  permanent  teeth  are  thirty-two  in  number — four  incisors  (two  central  and  two 
lateral),  two  canines,  four  bicuspids,  and  six  molars  in  each  jaw  (Figs.  815  and  819). 

General  Characters  (Fig.  820). — Each  tooth  consists  of  three  portions;  the 
crown  or  body  (corona  dentis},  projecting  above  the  gum;  the  root  or  fang  (radix 
dentis},  entirely  concealed  within  the  alveolus;  and  the  neck  (collum  dentis},  the 
constricted  portion,  between  the  root  and  crown. 

Surfaces. — The  surfaces  of  a  tooth  are  named  thus:  that  which  comes  in  con- 
tact with  the  teeth  of  the  opposite  jaw  is  the  grinding  or  masticating  surface  (fades 
masticatoria} ;  that  which  touches  the  next  tooth  in  the  same  row  is  the  contact 
surface  (fades  contactus).  That  surface  which  is  toward  its  predecessor  is  called 
the  proximal  surface  (in  incisors  and  canines,  fades  medialis;  in  molars  and  pre- 
molars,  fades  anterior}.  That  surface  which  is  toward  its  successor  is  called  the 
distal  surface  (in  incisors  and  canines,  fades  lateralis;  in  molars  and  premolars, 
fades  posterior}.  That  which  looks  toward  the  lips  and  cheek  is  the  labial  or 
buccal  surface  (fades  labialis}.  That  toward  the  tongue  is  the  lingual  surface 
(fades  lingualis).  In  part  this  method  of  designation  applies  to  the  roots  as  well 
as  to  the  crowns  of  teeth. 


1206 


THE    ORGANS    OF  DIGESTION 


The  Roots  of  the  Teeth. — The  roots  of  the  teeth  are  firmly  implanted  within  the 
sockets  or  alveoli  of  the  jaws  (alveoli  dentales)  (see  pp.  109  and  124).  These  depres- 
sions are  lined  with  periosteum,  called  the  pericementum,  which  is  reflected  on  to  the 
tooth  at  the  point  of  the  root  and  covers  it  as  far  as  the  neck.  This  is  the  root 
membrane  (periosteum  alveolare).  At  the  margin  of  the  alveolus  the  periosteum 
becomes  continuous  with  the  fibrous  structure  of  the  gums. 


Right  upper. 


FIG.  813. — Deciduous  teeth.     Left  aide. 


FIG.  814. — Deciduous  teeth.      Lingual  view. 


Temporary,  Deciduous  or  Milk  Teeth  (denies  decidui)(Figs.  813, 814,  and  830). 
—The  temporary  or  milk  teeth  are  smaller,  but  resemble  in  form  those  of  the  per- 
manent set.  The  neck  is  more  marked,  owing  to  the  greater  degree  of  convexity 
of  the  labial  and  lingual  surfaces  of  the  crown.  The  hinder  of  the  two  temporary 
molars  is  the  largest  of  all  the  deciduous  teeth,  and  is  succeeded  by  the  second 
bicuspid.  The  first  upper  molar  has  only  three  cusps — two  labial,  one  lingual;  the 
second  upper  molar  has  four  cusps.  The  first  lower  molar  has  four  cusps;  the 
second  lower  molar  has  five.  The  roots  of  the  temporary  molar  teeth  are  smaller 
and  more  diverging  than  those  of  the  permanent  set,  but  in  other  respects  bear  a 
strong  resemblance  to  them. 


FIG.  815. — Permanent  teeth,  right  side.     (Burchard.) 


Permanent  Teeth  (denies  permanentes)  (Figs.  815,  816,  817,  and  819).  The 
Incisors  (denies  incisivi).—The  incisors  or  cutting  teeth  are  so  named  from  their 
presenting  a  sharp  cutting  edge,  adapted  for  incising  the  food.  They  are  eight  in 
number,  and  comprise  the  four  front  teeth  in  each  jaw. 

The  crown  is  directed  almost  vertically  and  is  spade-like  in  form ;  it  has  the  form 
of  a  truncated  cone  whose  top  has  been  compressed  into  a  sharp  horizontal  cutting 


THE    TEl'/ril 


1207 


edge.  Before  being  subjected  to  attrition  this  edge  presents  three  small  elevations. 
Titr  labial  surface  is  convex,  and  marked  by  free  longitudinal  ridges  extending 
from  the  edge  tubercles  toward  the  neck  of  the  tooth.  The  lingual  surface  is  con- 
cave, and  is  marked  by  two  marginal  ridges  extending  from  an  encircling  ridge 
at  the  neck  to  the  angles  of  the  cutting  edge  of  the  tooth.  The  ridge  at  the  neck 
is  termed  the  cingulum  or  basal  ridge.  The  mesal  and  distal  surfaces  arc  triangular, 
the  apex  of  the  triangle  being  at  the  cutting  edge.  The  neck  of  the  tooth  is 
constricted.  The  root  is  long,  single,  and  has  the  form  of  a  transversely  flattened 
cone,  thicker  before  than  behind.  The  root  may  be  curved. 

The  Incisors  of  the  Upper  Jaw  are  altogether  larger  and  stronger  than  those  of 
the  lower  jaw,  the  central  incisors  being  larger  and  flatter  than  the  lateral  incisors. 
They  are  directed  obliquely  downward  and  forward. 

The  Incisors  of  the  Lower  Jaw  are  smaller  and  flatter  than  the  upper,  and  the 
elevations  upon  their  lingual  faces  are  not  marked.  The  two  central  are  smaller 
than  the  two  lateral  incisors,  being  the  smallest  of  all  the  teeth.  The  roots  of  these 
teeth  are  flattened  laterally. 


FIG.  816. — Right  half  of  upper  jaw  (from  below), 
with  the  corresponding  teeth.  The  letters  and  numbers 
point  to  the  classes  of  teeth  and  the  numbers  in 
classes. 


FIG.  817. — Right  half  of  lower  jaw,  with  the  cor- 
responding teeth.  The  letter  and  numbers  point  to 
the  various  cusps  or  their  modifications  on  the  dif- 
ferent teeth.  (Burchard.) 


The  Canine  Teeth  or  Cuspidati  (denies  canini). — The  canine  teeth  are  four  in 
number,  two  in  the  upper,  two  in  the  lower  jaw — one  being  placed  distal  to  each 
lateral  incisor.  They  are  larger  and  stronger  than  the  incisors,  especially  in  the 
roots,  which  are  deeply  implanted  and  each  causes  a  well-marked  prominence 
of  the  process  at  the  place  of  insertion. 

The  crown  is  large,  of  spear-head  form,  and  its  very  convex  labial  surface  is 
marked  by  three  longitudinal  ridges.  The  concave  lingual  surface  is  also  marked 
by  three  ridges  which  unite  at  a  basal  ridge.  The  point  or  cusp  is  longer  than  in 
the  other  teeth,  and  is  the  point  of  division  between  a  short  mesal  and  a  long 
distal  cutting  edge.  These  two  edges  form  an  obtuse  angle  with  each  other. 

The  root  is  single,  oval,  or  elliptical  on  transverse  section,  and  is  longer  and  more 
prominent  than  the  roots  of  the  incisors. 

The  Upper  Canines  or  cuspids,  vulgarly  called  the  eye  teeth,  are  larger  and  longer 
than  the  two  lower,  and  in  occlusion  are  distal  to  them  to  the  extent  of  half  the 
width  of  the  crown. 

The  Lower  Canines,  vulgarly  called  the  stomach  teeth,  have  the  general  form  of 
the  upper  cuspids,  but  their  lingual  surfaces  are  much  more  flattened,  owing  to 


1208  THE    ORGANS    OF  DIGESTION 

the  absence  of  the  elevations  marking  the  upper.  Their  roots  are  more  flattened 
and  may  be  bifid  at  their  apices. 

The  Bicuspid  Teeth  or  the  Premolars  (denies  premolares). — The  bicuspid  teeth 
are  eight  in  number,  four  in  each  jaw;  they  are  placed  distal  to  the  cuspid  teeth, 
two  upon  each  side  of  the  jaw.  They  are  double  cuspids  in  form. 

The  crown  is  surmounted  by  two  cusps,  one  buccal  and  one  lingual,  separated 
by  a  groove,  the  buccal  being  more  prominent  and  larger  than  the  lingual.  The 
lower  bicuspids  are  not  truly  bicuspid,  the  first  having  but  a  primitive  lingual  cusp, 
the  second  having  the  lingual  cusp  divided  into  two  sections — i.  e.,  it  is  usually 
tricuspid.  The  necks  of  the  teeth  are  oval;  the  roots  are  single  and  laterally  com- 
pressed, that  of  the  first  upper  bicuspid  being  frequently  bifid.  The  first  upper 
bicuspid  is  usually  the  largest  of  the  series.  The  roots  of  the  lower  bicuspids  are 
less  compressed  and  more  rounded. 

The  Molar  Teeth,  the  Multicuspidati  or  Grinders  (denies  molar  es}. — The  molar 
teeth  are  the  largest  and  strongest  teeth  of  the  denture.  They  are  adapted  by 
their  forms  for  the  crushing  and  grinding  of  the  food.  They  are  twelve  in  number, 
six  in  each  jaw,  three  being  placed  posterior  to  each  second  bicuspid. 

The  crowns  are  cuboidal  in  form,  are  convex  buccally  and  lingually;  they  are 
flattened  mesally  and  distally.  They  are  formed  by  the  fusion  of  three  primitive 
cuspids  in  the  upper  and  four  in  the  lower.  To  these  are  added  in  the  first  and 
second  upper  molars  a  disto-lingual  tubercle,  and  in  the  first  and  third  molars  of 
the  lower  jaw  a  disto-buccal  tubercle.  The  unions  of  the  primitive  forms  are 
marked  by  sulci.  The  necks  of  these  teeth  are  large  and  rhomboidal  in  form. 
The  roots  of  the  upper  molars  are  three  in  number — one  large  lingual  or  palatal 
root,  and  two  smaller  buccal  roots.  In  the  lower  molars,  two  roots  are  found,  a 
mesal  and  a  distal,  each  of  which  is  much  flattened  from  before  backward. 

The  First  Molar  Teeth  are  the  largest  of  the  dental  series;  they  have  four  cusps 
on  the  upper  and  five  in  the  lower — three  buccal  and  two  lingual. 

The  Second  Molars  are  smaller;  the  crowns  of  the  upper  are  compressed  until  the 
disto-lingual  cusp  is  reduced.  The  crowns  of  the  lower  are  almost  rectangular, 
with  a  cusp  at  each  angle. 

The  Third  Molars  are  called  the  wisdom  teeth  or  dentes  sapientae  (denies  serotini), 
from  their  late  eruption;  they  have  three  cusps  upon  the  upper  and  five  upon  the 
lower.  The  three  roots  of  the  upper  are  frequently  fused  together,  forming  a 
grooved  cone,  which  is  usually  curved  backward.  The  roots  of  the  lower,  two 
in  number,  are  compressed  together,  and  curve  backward. 

Arrangement  of  the  Teeth.1 — The  human  teeth  are  arranged  in  two  parabolic 
arches,  the  upper  row  or  arch  (arcus  dentalis  superior}  being  larger,  its  teeth  over- 
lapping the  lower  row  or  arch  (arcus  dentalis  inferior}.  The  average  distance 
between  the  centres  of  the  condyles  of  the  inferior  maxillary  bones  is  about  four 
inches,  which  is  also  the  distance  from  either  of  these  points  to  the  line  of  junction 
between  the  lower  incisor  teeth.  Whether  the  jaw  be  large  or  small,  the  equilateral 
triangle  indicated  is  included  in  it;  .the  range  of  size  is  between  three  and  one-half 
and  four  and  one-half  inches. 

Owing  to  the  smaller  sizes  of  the  lower  incisors,  the  teeth  of  the  lower  jaw  are 
each  one-half  a  tooth  in  advance  of  its  upper  fellow,  so  that  each  tooth  of  the  dental 
series  has  two  antagonists,  with  the  exception  of  the  lower  central  incisors  and 
upper  third  molars  (Figs.  818  and  819). 

The  grinding  faces  of  the  upper  bicuspids  and  molars  curve  progressively  upward 
and  point  outward,  the  first  molar  being  at  the  lowest  point  of  the  curve,  the  third 
molar  at  the  highest.  The  curve  of  the  lower  dental  arch  is  the  reverse,  the  first 
molar  at  its  deepest  part,  the  third  molar  at  its  extremity.  The  greater  the  depth 

1  After  Dr.  W.  G.  A.  Bonwill. 


THE    TEETH 


1209 


to  which  the  upper  incisors  overlap  the  lower,  the  more  marked  this  curve  and 
the  more  pointed  are  the  cusps  of  the  grinding  teeth. 


FIG.  818. — View  of  teeth  in  situ,  with  the  external  plates  of  the  alveolar  processes  removed.     (Cryer.) 


FIG.  81ft. — Front  and  side  views  of  the  teeth  and  jaws.     (Cryer.) 

The  movement  of  the  human  mandible  is  forward  and  downward,  the  resultant 
of  these  directions  being  an  oblique  line,  upon  an  average  of  35  degrees  from 
the  horizontal  plane.1  When  the  lower  jaw  is  advanced  until  the  cutting  edges  of 


W.  E.  Walker,  Dental  Cosmos,  1896. 


1210 


THE    ORGANS    OF   DIGESTION 


the  incisors  are  in  contact,  the  jaws  are  separated,  but  at  the  highest  point  of  the 
lower  arch  its  third  molar  advances,  and  meets  and  rests  upon  a  high  point,  the 
second  molar  of  the  upper  arch,  and  thus  undue  strain  upon  the  incisors  is  obviated. 
In  the  lateral  movements  of  the  mandible  but  one  side  is  in  effective  action  at 
one  time;  the  oblique  positions  of  the  cusps  of  the  opposite  teeth  are  such  that 


Pulp 
cavity. 


Root. 


FIG.  820. — Vertical  section  of  a  molar  tooth. 

when  either  side  is  in  action  the  other 
is  balanced  at  two  or  more  points. 

There  is  an  anatomical  correspond- 
ence between  the  forms  and  arrange- 
ment of  the  teeth,  the  form  of  the  con- 
dyle  of  the  mandible,  and  the  muscular 
arrangement.  Individuals  who  have 
teeth  with  long  cusps  have  the  head  of 
the  bone  much  rounded  from  before 
backward,  and  have  a  preponderance 
of  the  direct  over  the  oblique  muscles 
of  mastication,  and  vice  versa;  teeth 
with  short  or  no  cusps  are  associated 
with  a  flattened  condyle  and  strong 
oblique  muscles. 

Very  great  aberrations  in  the  dental 
arrangement  are  frequently  followed  by 
accommodative  changes  in  the  heads  of 
the  mandible. 

Structure  of  the  Teeth.  The  Dental 
Pulp  (pulpa  dentis). —  A  longitudinal 
section  of  a  tooth  will  show  the  pres- 
ence of  a  central  chamber  having  the 
general  form  of  the  crown  of  the  tooth. 
Processes  of  the  chamber  pass  from  its 
body,  one  for  each  root  and  down  each 
root,  and  open  at  the  apex  by  a  minute 

orifice.  This  cavity  is  known  as  the  pulp-chamber  or  pulp-cavity  (cavum  dentis) 
(Figs.  820  and  821).  The  minute  canal  in  each  root  is  called  the  pulp-canal  or  root- 
canal  (canalis  radicis  dentis).  The  foramen  at  the  apex  of  the  root  is  the  apical 
foramen  (foramen  apicis  dentis).  The  cavity  contains  a  soft,  vascular,  and  sensitive 
organ  called  the  dental  pulp  (pulpa  dentis).  It  is  made  up  of  fibrous  cellular  con- 
nective tissue,  the  fibres  of  which  are  extremely  fine,  and  contains  numerous  blood- 
vessels and  nerves,  which  enter  by  way  of  the  apical  foramina.  It  has  not  been 
proved  that  there  are  lymphatics  in  the  dental  pulp,  although  some  authors  assert 
that  they  exist  (Wangermann  and  others).  It  seems  to  have  been  proved  that  the 
spaces  between  the  fibres  of  the  pulp  communicate  with  the  lymphatic  system.  The 
periphery  of  the  pulp  is  bounded  by  a  layer  of  cells  arranged  like  columnar  epithe- 
lium, each  cell  sending  one  or  more  branched  processes  through  the  basic  substance 


FIG.  821. —  Vertical  section  of  a  tooth  in  situ  (15 
diameters).  C  is  placed  in  the  pulp-cavity,  opposite 
the  cervix  or  neck  of  the  tooth  ;  the  part  above  is  tho 
crown,  that  below  is  the  root  (fang).  1.  Enamel  with 
radial  and  concentric  markings.  2.  Dentine  with 
tubules  and  incremental  lines.  3.  Cement  or  crusta 
petrosa,  with  bone  corpuscles.  4.  Dental  periosteum. 
5.  Bone  of  lower  jaw. 


777 /•;    T MTU 


1211 


of  the  dentine.  These  processes  constitute  the  dentine  fibres.  Other  processes  come 
off  from  the  cells  which  pass  in  the  direction  of  the  pulp  and  surround  it.  The 
cells  at  the  periphery  of  the  pulp  are  the 
dentine -forming  cells,  the  odontoblasts  of  Wal- 
deyer.  The  blood-vessels  break  up  into  in- 
numerable capillary  loops  which  lie  beneath 
the  layer  of  odontoblasts.  The  nerve-fibrils 
break  up  into  numberless  amyelinic  fila- 
ments, which  spread  out  beneath  the  odonto- 
blasts, and  probably  send  terminal  filaments 
to  the  extreme  periphery  of  the  pulp  outside 
the  odontoblasts. 

The  matrix  cells  and  their  processes  are 
irregularly  arranged  in  the  body  of  the  pulp, 
but  in  the  canal  portion  the  fibrillae  are  in  the 
direction  of  the  axis  of  the  root. 

The  Solid  Portion  of  the  Tooth.— The  sec- 
tion  will  exhibit  three  hard  tissues  in  a  tooth : 
one,  the  proper  dental  substance,  forming  the 
greater  mass  of  the  tooth;  hence  its  name 
dentine  or  ivory.  The  dentine  upon  the  ex- 
posed crown  is  sheathed  by  a  layer  called 
the  enamel  ;  the  dentine  of  the  root  is  en- 
closed in  a  distinct  tissue,  the  cementum  or 

crusta  petrosa;  both  cementum  and  enamel  are  thinnest  at  the  neck  and  thickest 
upon  their  distal  portions. 


FIG.  822.- — From  a  ground-section  through 
the  parts  of  a  dentine,  near  the  pulp,  of  a 
human  canine  tooth  which  has  been  impreg- 
nated with  pigment.  The  dental  canaliculi  are 
cut  across  and  are  joined  together  by  side 
branches.  X  400. 


Fir.  823. — Longitudinal  ground-section  through  the  apex  of  a  canine  tooth  from  a  three-and-a-half-year-o/d 
boy.  The  entrance  of  the  dental  canaliculi  between  the  enamel  prisms  and  the  course  taken  by  the  latter  are 
Shown.  X  135.  (.Szymonowicz.) 


1212 


THE    ORGANS    OF   DIGESTION 


The  Ivory  or  Dentine  (substantiate  eburnea)  (Figs.  821,822, 823,  and  S24)  forms 
the  principal  mass  of  a  tooth;  in  its  central  part  is  the  cavity  enclosing  the  pulp.  It 
is  a  modification  of  osseous  tissue,  from  which  it  differs,  however,  in  the  fact  that 
it  does  not  contain  cells  placed  in  cavities,  but  the  cells  lie  in  the  periphery  of  the 
pulp,  against  but  not  in  the  dentine.  The  dentine  contains  the  processes  of  the 
cells,  which  are  known  as  dental  or  dentinal  fibres.  On  microscopic  examination 
it  is  seen  to  consist  of  a  number  of  minute  wavy  and  branching  tubes  having 
distinct  parietes.  They  are  called  the  dentinal  tubuli  or  dental  canals,  and  are 
embedded  in  a  dense  homogeneous  substance,  the  intertubular  tissue. 

The  dentinal  tubuli  (canaliculi  dentales)  (Fig.  824)  are  placed  parallel  with  one 
another,  and  open  at  their  inner  ends  into  the  pulp-cavity.  In  their  course  to  the 
periphery  they  present  two  or  three  curves,  and  are  twisted  on  themselves  in  a  spiral 
direction.  The  direction  of  these  tubes  varies;  they  are  vertical  in  the  upper  por- 
tion of  the  crown,  oblique  in  the 
neck  and  Upper  part  of  the  root, 
and  toward  the  lower  part  of  the 
root  they  are  inclined  downward. 
The  tubuli,  at  their  commence- 
ment, are  about  4-5*5-5-  of  an  inch  in 
diameter;  in  their  course  they  di- 
vide and  subdivide  dichotomously, 
so  as  to  give  to  the  cut  surface  of 
the  dentine  a  striated  appearance. 
From  the  sides  of  the  tubes,  espe- 
cially in  the  root,  ramifications  of 
extreme  minuteness  are  given  off, 
which  join  together  in  loops  in  the 
intertubular  substance,  or  termin- 
ate in  small  dilatations,  from  which 
branches  are  given  off.  Near  the 
pulp  the  lateral  branches  are  few 
and  are  almost  at  right  angles  to 
the  canals.  Nearer  the  periphery 
the  lateral  branches  are  more  nu- 
merous, and  they  come  off  at 
acute  angles.  The  terminations  of 
the  chief  canals  at  the  periphery 
vary.  In  the  crown  they  break  up 
into  branches  like  fingers  just  be- 
neath the  enamel.  Some  of  these 
finger-like  branches  leave  the  den- 
tine and  enter  the  cement  substance  between  enamel  prisms.  The  majority  of 
the  chief  canals  end  in  blind  extremities  at  the  margin  of  the  enamel  and  do  not 
enter  this  structure.  In  the  lower  portion  of  the  tooth  the  chief  canals  do  not 
emerge  from  the  dentine,  but  end  at  the  margin  of  the  cement  in  blind  extremities. 
They  may  reach  the  spaces  of  the  granular  sheath.  Near  the  periphery  of  the 
dentine  of  the  crown  the  finer  ramifications  of  the  tubuli  pass  through  a  layer  of 
irregular  branched  spaces  which  communicate  with  each  other.  These  are  called 
the  interglobular  spaces  of  Czermak  (spatia  inter  globular  ia)  (Fig.  824,  J).  These 
spaces  are  gaps  in  the  dentine  due  to  failure  of  calcification  and  are  filled  with 
uncalcified  dentine.  The  outer  part  of  the  dentine  in  the  lower  portion  of  the 
tooth  contains  a  layer  of  interglobular  spaces  known  as  the  granular  layer  or 
granular  sheath  of  Tomes.  The  dentinal  tubuli  have  comparatively  thick  walls, 
and  contain  slender  cylindrical  prolongations  from  the  processes  of  the  cells  of 


\'.  \  '•   \ .  :    '     '         : 

FIG.  824. — Ground-section  through  the  root  of  a  human 
premolar.  D,  dentine  ;  K,  cement  corpusctes  ;  O,  osteoblasts  ; 
Ep.,  remains  of  Hertwig's  epithelial  sheath,  200  diameters  ; 
/,  interglobular  spaces.  (Rose.) 


THE    TEETH 


1213 


the  pulp-tissue  already  mentioned,  and  first  described  by  Mr.  Tomes  and  named 
Tomes's  fibres  or  dentinal  fibres.  These  dentinal  fibres  are  analogous  to  the  soft 
contents  of  the  canaliculi  of  bone.  Between  Tomes's  fibres  and  the  ivory  around 
the  canals  there  is  a  tissue  which  is  markedly  resistant  to  the  action  of  acids — the 
dentinal  sheath  of  Neumann. 

The  intertubular  substance  or  tissue  is  translucent  and  contains  the  chief  part 
of  the  earthy  matter  of  the  dentine.  After  the  earthy  matter  has  been  removed 
by  steeping  a  tooth  in  weak  acid  the  animal  basis  remaining  may  be  torn  into 
laminae  which  run  parallel  with  the  pulp-cavity  across  the  direction  of  the  tubules. 
These  laminae  show  the  method  of  growth  to  be  by  deposition  of  successive  strata 
of  dentine.  Fibrils  have  been  found  in  the  matrix  of  the  intertubular  substance, 
and  are  probably  continuous  with  the  dentinal  fibres  of  Tomes.  In  a  dry  tooth  a 
section  of  dentine  often  displays  a  series  of  lines — the  incremental  lines  of  Salter — 
which  are  parallel  with  the  laminae  above  mentioned.  These  lines  are  caused  by 
two  facts:  (1)  The  imperfect  calcification  of  the  dentinal  laminae  immediately 
adjacent  to  the  line.  (2)  The  drying  process,  which  reveals  these  defects  in  the 
calcification.  These  lines  are  wide  or  narrow  according. to  the  number  of  laminae 
involved,  and  along  their  course,  in  consequence  of  the  imperfection  in  the  calci- 
fying process,  little  irregular  cavities  are  left,  which  are  the  interglobular  spaces 
already  referred  to.  They  have  received  their  name  from  the  fact  that  they  are 
surrounded  by  minute  nodules  or  globules  of  dentine.  Other  curved  lines  may 
be  seen  parallel  to  the  surface.  These  are  the  concentric  lines  of  Schreger,  and  are 
due  to  the  optical  effect  of  simultaneous  curvature  of  the  dentinal  tubules. 


A 


FIG.  825. — Enamel  prisms  (350  diameters).     A,  fragments  and  single  fibres  of  the  enamel  isolated  by  the  action 
of  hydrochloric  acid.    B,  surface  of  a  small  fragment  of  enamel,  showing  the  hexagonal  ends  of  the  fibres. 

CHEMICAL  COMPOSITION. — According  to  Berzelius  and  Bibra,  dentine  consists 
of  twenty-eight  parts  of  animal  and  seventy-two  of  earthy  matter.  The  animal 
matter  is  resolvable  by  boiling  into  gelatin.  The  earthy  matter  consists  of  phos- 
phate and  carbonate  of  calcium,  with  a  trace  of  fluoride  of  calcium,  phosphate  of 
magnesia,  and  other  salts. 

The  Enamel  (substantia  adamantina)  (Figs.  821,  823,  and  825)  is  the  hardest  and 
most  compact  part  of  a  tooth,  and  forms  a  thin  crust  over  the  exposed  part  of 
the  crown  as  far  as  the  commencement  of  the  root.  It  is  thickest  on  the  grind- 
ing surface  of  the  crown  until  worn  away  by  attrition,  and  becomes  thinner  toward 
the  neck.  It  consists  of  a  congeries  of  minute  hexagonal  rods,  columns,  or  prisms 
known  as  enamel  fibres  or  enamel  prisms  (prismata  adamantina}  (Fig.  825).  In 
general,  they  lie  parallel  with  one  another,  resting  by  one  extremity  upon  the 
dentine,  which  presents  a  number  of  minute  depressions  for  their  reception,  and 


1214  THE    ORGANS    OF  DIGESTION 

forming  the  free  surface  of  the  crown  by  the  other  extremity.  There  are  occa- 
sional collections  of  prisms  which  run  diagonally.  The  prisms  are  directed 
vertically  on  the  summit  of  the  crown,  horizontally  at  the  sides;  they  are  about 
the  s-gVo"  of  an  inch  in  diameter,  and  pursue  a  more  or  less  wavy  course.  By 
reflected  light  radial  striations  are  visible.  These  are  Schreger's  lines,  and  are 
due  to  the  fact  that  the  prisms  take  an  undulatory  course  and  those  of  two  layers 
may  have  opposite  directions.  Another  series  of  lines,  having  a  brown  appear- 
ance from  pigmentation,  and  denominated  the  parallel  striae  or  brown  striae  of 
Retzius  or  the  colored  lines,  are  seen  on  a  section  of  the  enamel.  These  lines 
are  concentric  and  cross  the  enamel  rods.  They  are  caused  by  the  mode  of 
enamel  deposition.  Inasmuch  as  the  enamel  columns,  when  near  the  dentine, 
cross  each  other  and  only  become  parallel  farther  away,  a  series  of  radial  mark- 
ings, light  and  dark  alternately,  is  obtained  (Fig.  821).  The  enamel  prisms  are 
themselves  calcified  and  are  fixed  to  each  other  by  a  very  small  amount  of  cement 
substance.  Numerous  minute  interstices  intervene  between  the  enamel-fibres 
near  their  dentinal  surface.  It  is  noted  that  some  of  the  dentinal  canals  at  the 
crown  penetrate  a  certain  distance  between  the  rods  of  the  enamel  (Fig.  823).  No 
nutritive  canals  exist  in  the  enamel,  except  the  very  few  dentinal  canals  which  at 
the  crown  penetrate  a  short  distance,  and  these  are  found  only  in  a  small  area. 

CHEMICAL  COMPOSITION. — According  to  Bibra,  enamel  consists  of  96.5  per  cent, 
of  earthy  matter  and  3.5  per  cent,  of  animal  matter.  The  earthy  matter  consists 
of  the  phosphate  and  the  carbonate  of  calcium,  with  traces  of  fluoride  of  calcium, 
phosphate  of  magnesia,  and  other  salts. 

The  enamel  of  a  recently  erupted  tooth  is  covered  by  a  membrane,  the  thick- 
ness of  which  is  joTo"  °f  an  mcn-  It  is  known  as  enamel  cuticle  or  Nasmyth's  mem- 
brane (cuticula  dentis).  It  is  probably  the  most  recent,  and  hence  an  uncalcified, 
or  partly  calcified  enamel  layer.  Some  believe  it  to  be  a  product  of  the  outer  layer 
of  the  cells  of  the  enamel  organ. 

The  Cortical  Substance,  Cementum  or  Crusta  Petrosa  (substantia  ossea)  (Figs.  808 
and  81 1)  is  disposed  as  a  thin  layer  on  the  roots  and  neck  of  a  tooth,  from  the  termi- 
nation of  the  enamel  as  far  as  the  apex  of  the  root,  where  it  is  usually  very  thick.  At 
the  neck  it  overlays  a  slight  margin  of  enamel.  In  structure  and  chemical  com- 
position it  is  true  bone.  It  contains,  sparingly,  the  lacunae  and  canaliculi  which 
characterize  true  bone;  the  lacunae  placed  near  the  surface  have  the  canaliculi  radi- 
ating from  the  side  of  the  lacunae  toward  the  periodontal  membrane  or  dental 
periosteum,  and  those  more  deeply  placed  join  with  adjacent  dentinal  tubuli.  The 
teeth  of  the  young  usually  contain  Haversian  systems  in  the  thicker  portions  of 
the  cementum.  The  neck  of  the  tooth  does  not  contain  lacunae.  The  cementum 
is  occasionally  laminated.  Sharpey's  fibres  (p.  37)  are  very  numerous.  Some  of 
the  lacunae  of  the  cementum  receive  dentinal  tubes  from  the  dentine. 

As  age  advances  the  cement  increases  in  thickness,  and  gives  rise  to  those  bony  growths,  or 
exostoses,  so  common  in  the  teeth  of  the  aged;  the  pulp-cavity  becomes  also  partially  filled  up 
by  a  hard  substance  intermediate  in  structure  between  dentine  and  bone  (the  osteo-dentine  of 
Owen;  the  secondary  dentine  of  Tomes).  It  is  formed  by  the  odontoblasts,  the  dental  pulp 
lessening  in  volume. 

Development  of  the  Teeth  (Figs.  826,  827,  828,  and  829).— The  teeth  are  an 
evolution  from  the  dermoid  system,  and  not  of  the  bony  skeleton;  they  are  devel- 
oped from  two  of  the  blastodermic  layers,  the  epiblast  and  mesoblast.  From  the 
former  the  enamel  is  developed;  from  the  latter  the  dentinal  pulp,  dentine,  cemen- 
tum, and  pericementum.  It  is  customary  to  view  the  development  of  the  per- 
manent and  temporary  teeth  as  separate  studies. 

The  earliest  evidence  of  tooth-formation  in  the  human  embryo  is  observed 
about  the  seventh  week.  The  mucous  membrane  covering  the  embryonic  jaws  is 
seen  to  rise  as  a  longitudinal  ridge  along  the  summit  of  each  jaw.  This  ridge  is 


THE    TEETH 


121.') 


the  maxillary  rampart  of  Kblliker  and  Waldeyer.  A  transverse  section  through  the 
jaw  will  show  the  elevation  to  be  due  to  a  linear  and  outlined  activity  of  the 
germinal  epithelial  layer;  a  corresponding  epithelial  growth  is  seen  to  sink  as  a 
band  into  the  mesoblastic  tissue  beneath.  This  band  is  called  the  dental  lamina 
or  dental  band.  The  local  cell-activity  continues,  and  in  its  descent  the  band 
appears  to  meet  with  a  resistance  which 'causes  a  flattening  of  its  extremity  into  a 
continuous  lamina.  From  the  inner  (toward  the  tongue)  edge  of  the  lamina 
epithelial  cords  are  given  off,  ten  in  number,  one  for  each  temporary  tooth. 


FIG.  826. — Diagram  of  method  of  development  of  the  teeth.  1.  Early  stage.  4.  Later  stage.  2,  3.  Inter- 
mediate stages,  s.  Common  dental  germ.  o.  Special  dental  germ  (milk),  o'.  Special  dental  germ  (permanent). 
p.  Papilla,  e.  Dental  furrow.  (Gegenbauer.) 

The  growth  of  each  cord  continues,  and  each  expands  into  a  flask-like  form,  the 
walls  covered  by  a  layer  of  germinal  cells,  its  interior  by  swollen  mature  cells. 
The  ingrowing  bulb  is  now  seen  to  flatten  upon  its  lower  surface,  as  though  it  had 
met  with  an  outlined  resistance  from  the  mesoblastic  tissue  beneath.  The  epithelial 
ingrowth  assumes  the  general  form  of  the  several  teeth;  it  is  the  enamel-organ  of 
the  tooth  (Fig.  826).  The  cellular  tissue  of  the  jaw  beneath  the  cap  of  the  enamel- 
organ  grows  and  projects  into  the  cap.  This  projection  is  the  dentine  papilla 
(papilla  dentis).  At  this  period  the  mesoblastic  tissue  around  each  enamel-organ 
is  seen  to  become  differentiated  into  fibrous  tissue  surrounding  the  enamel-organs, 


Dental  furrow 


Remains  of  ' ' neck"  of 
enamel  organ,  or  of  the — 
common  dental  germ 


Permanent  special 
dental  germ 


Meckel's  cartilage. 


Dental  sac 


Enamel  pulp 
External  enamel 
layer 
Papilla 


Lover  jaw. 


FIG.  827. — Vertical  section  of  the  inferior  maxilla  of  an  early  human  foetus.     (Magnified  25  diameters.) 

but  at  some  distance  from  them.  Islets  of  bone  are  also  seen  to  be  forming  the 
beginning  of  the  bony  maxillae. 

The  indentation  of  the  base  of  the  enamel-organ  continues  until  it  assumes 
the  form  of  the  future  teeth.  The  cells  bounding  the  organ  assumes  a  cylindrical 
form;  the  cells  of  the  interior  become  much  expanded,  and  irregular  in  size  and 
form. 

The  mesoblastic  tissue  underlying  the  enamel-organ  is  much  condensed;  evi- 
dences of  cellular  differentiation  and  a  vascular  system  appear.  Bone  continues  to 


1216 


THE    ORGANS   OF  DIGESTION 


develop  until  all  of  the  tooth-follicles  are  embraced  in  a  gutter  of  bone.  From  the 
lingual  side  of  the  cords  of  the  temporary  teeth  epithelial  buds  are  given  off,  which 
sink  into  the  mesoblastic  tissue  and  form  the  enamel-organs  of  the  permanent 
teeth.  The  condensation  of  fibrous  tissue  continues  until  each  embryonic  tooth  is 
enveloped  in  a  sac,  the  dental  sac  (Fig.  827) ;  this,  together  with  all  of  its  contents, 
is  called  the  dental  follicle. 

The  tooth  which  is  undergoing  development  with  its  enamel-organ  and  dentine 
papilla  is  known  as  the  tooth  germ.  This  tooth  germ  is  encompassed  and  shut  off 
from  surrounding  structures  by  the  bag  of  membranous  structure  known  as  the 
dental  sac. 

The  cells  of  the  enamel-organ  now  undergo  a  series  of  differentiations:  the 
inner  layer,  arranged  as  columnar  epithelium,  are  the  enamel  cells,  or  ameloblasts. 
The  layer  is  called  the  ameloblastic  or  enamel-forming  layer  (Figs.  827  and  828). 
The  cells  of  the  outer  wall  remain  cuboidal ;  the  cells  which  lie  between  become 
much  distended,  and  on  account  of  their  appearance  when  seen  in  section  this 
portion  of  the  organ  is  called  the  enamel  jelly  or  the  stellate  reticulum.  The  layer  of 
cells  immediately  contiguous  to  the  ameloblasts  form  a  layer  called  the  stratum 
intermedium  (Fig.  828  A,  D). 


Dentine. 


Enamel. 


FIG.  828. — A.  Section  through  tooth-follicle — human  canine  seven  and  one-half  months.  A.  Follicular  wall. 
B.  Outer  epithelial  coat.  V.  Stellate  reticulum.  D.  Stratum  intermedium.  E.  Ameloblasts.  F.  Odonto- 
blasts. O.  Pulp. 

B.  Diagram  after  Williams  (Dental  Cosmos,  1896),  mode  of  enamel  deposition.  A.  Blood-supply  to  B,  secret- 
ing papillae.  C.  Layer  of  ameloblasts  containing  enamel  globules  and  droplets  of  calcoglobulin.  D.  Enamel- 
globules  deposited.  E.  Formed  dentine.  F.  Forming  dentine.  6.  Layer  of  odontoblasts.  H.  Blood-supply 
to  odontoblastic  layer. 


The  enclosed  mesoblastic  papilla  (the  future  dental  pulp)  has  its  peripheral  cells, 
which  are  called  odontoblasts,  differentiated  into  columnar  bodies  disposed  as  a 
layer,  each  cell  having  a  large  nucleus.  The  vascular  supply  of  the  pulp  is  now 
well  marked.  A  section  of  a  follicle  at  this  period  will  exhibit  the  follicular  wall 
springing  from  the  base  of  the  dental  papilla  and  having  a  well-marked  blood- 
supply.  The  bony  alveolar  walls  are  well  outlined,  and  evidences  of  a  periosteum 
appear  (Figs.  827  and  828). 

Development  of  Enamel  (Fig.  828  B). — In  point  of  time,  the  deposition  of  den- 
tine actually  begins  before  that  of  enamel,  so  that  the  first-formed  layer  of  enamel 
is  deposited  against  a  layer  of  immature  dentine.  The  enamel  is  built  up  of  two 
distinct  substances — globules  of  uniform  size  which  are  formed  by  the  amelo- 
blasts, and  a  cementing  substance,  probably  an  albuminate  of  calcium  (calco- 
globulin), the  basis  of  all  the  calcified  tissues.  At  the  ends  of  the  ameloblasts, 


THE   TEETH  1217 

next  to  the  dentine,  the  secretion  of  calco-globulin  is  deposited,  and  into  the 
plastic  mass  the  enamel-globules  are  extruded,  each  globule  remaining  con- 
nected with  the  ameloblasts  by  plasmic  strings,  which  also  join  the  globules 
laterally.1 

The  first  deposit  of  enamel  begins  in  the  tips  of  the  cusps,  and  is  quickly  fol- 
lowed by  a  disappearance  of  the  stellate  reticulum  at  that  point;  the  stellate  retic- 
ulum  appears  to  atrophy,  so  that  the  vascular  follicular  wall  is  brought  into 
direct  apposition  with  the  stratum  intermedium,  which  becomes  differentiated  into 
a  glandular  (secreting)  tissue  which  elaborates  the  calcic  albuminous  basis  of  the 
enamel.  The  secretion  passes  from  the  cells  of  the  stratum  intermedium  through  a 
membrane  into  the  ameloblasts,  where  it  is  in  part  combined  with  the  cellular 
globules,  and  irregular  masses  of  it  are  extruded  as  cementing  substance.  The 
deposition  continues  until  the  enamel-cap  has  its  typical  form.  The  deposition 
of  the  layers  of  globules  is  indicated  by  parallel  lines  transverse  to  the  axes  of  the 
enamel-rods.  At  the  completion  of  amelification  the  ameloblasts  are  partially 
calcified  and  form  the  enamel  cuticle  or  Nasmyth's  membrane  (cuticula  dentis). 

Formation  of  Dentine. — The  layer  of  columnar  cells  bounding  the  periphery  of 
the  pulp,  the  odontoblasts,  are  in  apposition  with  a  plexus  of  capillary  vessels 
(Fig.  829).  Each  cell  is  a  secreting  body  which  selects  the  material  for  dentine- 
building.  Against  the  layer  of  ameloblasts 
covering  the  dental  papilla  the  odontoblasts 
deposit  globules,  of  the  calcium  albuminate, 
and  receding  as  the  deposits  are  made,  leave 
one  or  more  protoplasmic  processes  in  the 
calcic  deposit.  These  are  known  as  Tomes 's 
fibres.  The  process  continues  until  the  normal 
dentine  thickness  is  formed.  The  deposit  is  ±1 
laid  down  in  a  scaffolding  of  finely  fibrillated 

tissue.     The  layer  of  formative  cells  remains      Flo  829._Part  of  section 
constant.    The  remains  of  the  dentine  papilla   tooth  of  young  rat,  showing  the  mode  of 

.                      i               •  deposition  of  the  dentine  (highly  magnified). 

Constitute    the    pulp    and    lie    in  the  pulp-Cavity  «•    Outer   layer    of     fully-calcified     dentine. 

1O1A\                                  '  Uncalcined  matrix  with  a  few  nodules  of 

(p.   I^IU).  calcareous    matter.       c.    Odontoblasts    with 

•n             ..            ,      „                                TT            •  processes  extending  into  the  dentine,  d.  Pulp. 

Formation    Of      CementUm. HertWlg    asserts  foe  section   is   stained   with  carmine,  which 

that  the  epithelial  edge  of  the  enamel  organ    cYfiedSparetuncal 

formed  by  the  inner  and  outer  epithelial  layers 

of  the  organ  grows  downward,  or  rather  the  developing  tooth  grows  upward  until 

the  future  root-form  of  the  tooth  is  outlined  by  a  double  layer  of  epithelial  cells, 

constituting  the  root-sheath  of  Hertwig.    The  growth  of  the  alveolar  process  is 

synchronous. 

Upon  the  pulp  side  of  the  sheath  a  layer  of  odontoblasts  is  developed;  upon 
the  outer  side  the  fibrous  encasement  becomes  closely  attached  to  the  sheath  and  a 
layer  of  osteogenetic  cells  is  differentiated.  These  cells  are  called  cementoblasts. 
The  growth  of  the  dentine  of  the  root  is  exactly  similar  to  the  growth  of  that  of 
the  crown.  The  epithelial  sheath  undergoes  atrophic  changes,  leaving  the  epithe- 
lial whorls  which  remain  in  the  pericementum.  The  cementum  is  developed  as 
subperiosteal  bone.  The  cementum  over  the  apex  of  the  root  is  not  formed  until 
after  the  eruption  of  the  tooth. 

Formation  of  Alveoli. — By  the  time  the  crowns  of  the  teeth  have  formed,  each 
is  enclosed  in  a  loculus  of  bone  which  has  developed  around  it  and  at  some  distance 
from  it;  the  loculus  is  open  at  the  top  toward  the  gums,  where  it  is  closed  by 
fibrous  tissue;  the  developing  permanent  tooth  is  contained  in  the  same  loculus, 
but  is  later  separated  from  the  temporary  tooth  by  a  growth  of  bone.  The  alveolar 

1  J.  L.  Williams,  Dental  Cosmos,  1896. 

77 


1218  THE    ORGANS    OF  DIGESTION 

process  is  not  completed  until  after  the  eruption  of  the  teeth.  During  eruption 
that  portion  of  the  process  overlying  the  crown  undergoes  absorption,  and  as  soon 
as  the  immature  tooth  has  erupted  the  alveolar  process  is  developed  about  the  root, 
whose  formation  is  also  completed  after  eruption. 

Development  of  the  Permanent  Teeth. — The  permanent  teeth  as  regards  their 
development  may  be  divided  into  two  sets:  (1)  those  which  replace  the  temporary 
teeth,  and  which,  like  them,  are  ten  in  number;  these  are  the  successional  perma- 
nent teeth;  and  (2)  those  which  have  no  temporary  predecessors,  but  are  super- 
added  at  the  back  of  the  dental  series.  These  are  three  in  number  on  either  side 
in  each  jaw,  and  are  termed  the  superadded  permanent  teeth.  They  are  the  three 
molars  of  the  permanent  set,  the  molars  of  the  temporary  set  being  replaced  by 
the  premolars  or  bicuspids  of  the  permanent  set. 

The  Development  of  the  Successional  Permanent  Teeth — the  ten  anterior  ones 
in  either  jaw — will  be  first  considered.  As  already  stated,  the  germ  of  each 
milk  tooth  is  a  special  thickening  of  the  "free"  edge  of  the  common  dental  germ 
or  dental  lamina.  In  like  manner  is  formed  the  special  dental  germ  of  each  of 
the  successional  permanent  teeth.  But  these  thickenings  are  not  at  the  "free" 
edge  of  the  dental  lamina,  but  occur  behind  and  lateral  to  each  of  the  milk-tooth 
germs  (Fig.  826).  There  are  ten  of  these,  and  they  appear  in  order,  about  the 
sixteenth  week,  on  each  side,  the  central  incisor  germs  being  the  first. 

These  special  dental  germs  now  go  through  the  same  transformations  as 
were  described  in  connection  with  those  of  the  milk  teeth,  and  the  changes  also 
eventuate  in  the  germs  becoming  enamel  organs;  that  is,  they  recede  into  the 
substance  of  the  gum  behind  the  germs  of  the  temporary  teeth.  As  they  recede 
they  become  flask-shaped,  form  an  expansion  of  their  distal  extremity,  and  finally 
meet  a  papilla,  which  has  been  formed  in  the  mesoblast,  just  in  the  same 
manner  as  was  the  case  in  the  temporary  teeth.  The  apex  of  the  papilla  inden- 
tates  the  dental  germ,  which  encloses  it,  and  forming  a  cap  for  it,  undergoes 
analogous  changes  to  those  described  in  the  development  of  the  milk  teeth,  and 
becomes  converted  into  the  enamel,  whilst  the  papilla  forms  the  dentine  of  the 
permanent  tooth.  In  its  development  it  becomes  enclosed  in  a  dentinal  sac  which 
adheres  to  the  back  of  the  sac  of  the  temporary  tooth.  The  sac  of  each  perma- 
nent tooth  is  also  connected  with  the  fibrous  tissue  of  the  gum  by  a  slender  band 
of  the  gubernaculum,  which  passes  to  the  margin  of  the  jaw  behind  the  correspond- 
ing milk  tooth  (see  above). 

The  Superadded  Permanent  Teeth — three  on  each  side  in  each  jaw— arise  from 
successive  extensions  backward — i.  e.,  along  the  line  of  the  jaw — of  the  common 
dental  germ  from  the  back  part  of  the  special  dental  germ  of  the  immediately 
preceding  tooth.  During  the  fourth  month  or  seventeenth  week,  in  that  portion 
of  the  common  dental  germ  which  lies  behind — i.  e.,  lateral  to  the  special  dental 
germ  of  the  last  temporary  molar  tooth,  and  which  has  hitherto  remained  unal- 
tered— there  is  developed  the  special  dental  germ  of  the  first  permanent  molar 
into  which  a  papilla  projects.  In  a  similar  manner,  about  the  fourth  month  after 
birth  the  second  molar  is  formed,  and  about  the  third  year  the  third  molar. 

Eruption. — When  the  calcification  of  the  different  tissues  of  the  milk  tooth 
is  sufficiently  advanced  to  enable  it  to  bear  the  pressure  to  which  it  will  be  after- 
ward subjected,  its  eruption  takes  place,  the  tooth  making  its  way  through  the 
gum.  The  gum  is  absorbed  by  the  pressure  of  the  crown  of  the  tooth  against  it, 
which  is  itself  pressed  up  by  the  increasing  size  of  the  fang.  At  the  same  time 
the  septa  between  the  dentinal  sacs,  at  first  fibrous  in  structure,  ossify  and  thus 
form  the  loculi  or  alveoli ;  these  firmly  embrace  the  necks  of  the  teeth  and  afford 
them  a  solid  basis. 

Previous  to  the  permanent  teeth  penetrating  the  gum,  the  bony  partitions 
which  separate  their  sacs  from  the  deciduous  teeth  are  absorbed,  the  roots  of 


THE    TEETH 


1219 


the  temporary  teeth  disappear  by  absorption  through  the  agency  of  particular 
multinucleated  cells,  called  odontoclasts,  which  are  developed  at  the  time  in  the 
neighborhood  of  the  root,  and  the  permanent  teeth  become  placed  under  the 
loose  crown  of  the  deciduous  teeth;  the  latter  finally  become  detached,  and  the 
permanent  teeth  take  their  place  in  the  mouth  (Fig.  830). 


FIG.  830. — The  milk-teeth  in  a  child  of  about  four  years.    The  permanent  teeth  are  seen  in  their  alveoli.    (Cryer.) 


Calcification  of  the  permanent  teeth  proceeds  in  the  following  order:  First 
molar,  soon  after  birth;  the  central  incisor,  lateral  incisor,  and  cuspid,  about  six 
months  afte~r  birth;  the  bicuspids,  at  the  second  year  or  later;  second  molar,  end 
of  second  year;  third  molar,  about  the  twelfth  year. 

The  Eruption  of  the  Temporary  Teeth  commences  at  the  seventh  month,  and  is 
complete  about  the  end  of  the  second  year. 

The  periods  for  the  eruption  of  the  temporary  set  are  (C.  S.  Tomes)— 


Lower  central  incisors 

Upper  incisors   .... 

Lower  lateral  incisors  and  first  molars 
Canines      ...... 

Second  molars    « 


6  to     9  months. 
8  to  10       " 

15  to  21       " 

16  to  20       " 
20  to  24       " 


The  Eruption  of  the  Permanent  Teeth  takes  place  at  the  following  periods,  the 
teeth  of  the  lower  jaw  preceding  those  of  the  upper  by  a  short  interval : 


6J  years,  first  molars. 
7th  year,  two  middle  incisors. 
8th  year,  two  lateral  incisors. 
9th  year,  first  bicuspid. 


10th  year,  second  biscuspid. 
llth  to  12th  year,  canine, 
J2th  to  13th  year,  second  molars. 
17th  to  21st  year,  third  molars, 


1220 


THE    ORGANS    OF   DIGESTION 


The  Palate  (Palatum). 


The  palate  forms  the  roof  of  the  mouth;  it  consists  of  two  portions,  the  hard 
palate  in  front,  the  soft  palate  behind. 

The  Hard  Palate  (palatum  durum)  (Figs.  831  and  832). — The  hard  palate  is 
bounded  in  front  and  at  the  sides  by  the  upper  alveolar  arches  and  gums.  In 
front  and  to  the  sides  it  is  continuous  with  the  gums;  behind,  it  is  continuous 
with  the  soft  palate.  It  is  formed  by  the  palate  processes  of  the  superior  maxil- 
lary bones  and  the  palate  processes  of  the  palate  bones  (Fig.  72) .  It  is  covered  by  a 
dense  structure  formed  by  the  periosteum  and  mucous  membrane  of  the  mouth, 
which  are  intimately  adherent,  particularly  to  the  front  and  sides,  by  means  of 


ANTERIOR 
PILLAR 


POSTERIOR 
PILLAR 


FIG.  831. — Antero-inferior  surface  of  the  soft  palate.     The  tongue  has  been  removed,  so  that  the  pharyngeal 
isthmus  is  distinctly  seen.     (Luschka.) 

a  layer  of  fibrous  tissue.  Along  the  middle  line  is  a  linear  ridge  or  raphe  (raphe 
palati),  which  terminates  anteriorly  in  a  small  papilla,  the  incisive  papilla  (papilla 
incisiva),  corresponding  with  the  inferior  opening  of  the  anterior  palatine  fossa. 
This  papilla  receives  filaments  from  the  naso-palatine  and  anterior  palatine 
nerves.  The  incisive  papilla  in  a  recently  born  child  is  continuous  with  the 
gum  and  the  frenulum  of  the  upper  lip.  On  either  side  and  in  front  of  the  raphe 
the  mucous  membrane  is  thick,  pale  in  color,  and  corrugated;  these  corruga- 
tions, which  are  composed  of  fibrous  tissue,  are  the  palatine  rugae  (plicae  pala- 
tinae  transversae).  In  very  young  children  the  rugae  are  distinct  and  definite. 
In  the  aged  they  are  indistinct.  Behind,  it  is  thin,  smooth,  and  of  a  deeper 
color;  it  is  covered  with  squamous  epithelium,  and  the  fibrous  tissue  beneath  it 


THE  PALATE 


1221 


contains  many  mucous  glands,  the  palatine  glands  (glandulae  palatinae).  The 
palatine  vessels  and  nerves  lie  in  the  fibrous  tissue  beneath  the  mucous  membrane. 
The  Soft  Palate  or  Velum  Pendulum  Palati  (palatum  molle)  (Figs.  831,  832, 
and  837). — The  soft  palate  is  a  movable  fold  suspended  from  the  posterior  border 
of  the  hard  palate,  and  forming  an  incomplete  septum  between  the  mouth  and 
pharynx.  It  consists  of  a  fold  of  mucous  membrane  enclosing  muscular  fibres, 
an  aponeurosis,  vessels,  nerves,  adenoid  tissue,  and  mucous  glands.  When 
occupying  its  usual  position  it  is  relaxed  and  pendent  and  its  oral  surface  is 
concave,  continuous  with  the  roof  of  the  mouth,  and  marked  by  a  median  ridge 
or  raphe,  which  indicates  its  original  separation  into  two  lateral  halves.  Its 
pharyngeal  surface  is  convex,  and  continuous  with  the  mucous  membrane  cover- 


ANTERIOR 
PALATINE  CANAL 


DESCENDING 

PALATINE 

ARTERY 


FIG.  832. — The  palatine  vault  on  the  right  side  of  the  mucous  membrane  has  been  removed.     The  left  side  shows 
the  mucous  membrane  and  the  glandular  layer.     (Poirier  and  Charpy  ) 

ing  the  floor  of  the  posterior  nares.  Its  anterior  or  upper  border  is  attached  to 
the  posterior  margin  of  the  hard  palate,  and  its  sides  are  blended  with  the 
pharynx.  Its  posterior  or  lower  border  is  free.  The  posterior  portion  of  the 
soft  palate  is  known  as  the  vail  of  the  palate  (velum  palatinum}  and  terminates 
posteriorly  and  externally  on  each  side  in  a  free  margin,  the  posterior  arch  of 
the  palate. 

Hanging  from  the  middle  of  its  lower  border  is  a  small,  conical-shaped,  pen- 
dulous process,  the  uvula  (uvula  palatina).  The  uvula  varies  greatly  in  length  ia 
different  individuals.  It  is  composed  of  glands  and  connective  tissue,  contains  a 
prolongation  of  the  Azjgos  uvulae  muscle  and  is  covered  with  mucous  membrane, 
and  arching  outward  and' down  ward  from  the  base  of  the  uvula  on  each  side  are 
two  curved  folds  of  mucous  membrane,  containing  muscular  fibres,  called  the 
arches  or  pillars  of  the  soft  palate  or  pillars  of  the  fauces  (arcus  palatini). 


1222  THE  ORGANS  OF  DIGESTION 

The  Anterior  Pillar  (arcus  glossopalatinus)  (Figs.  831  and  837).— The  anterior 
pillar  on  each  side  runs  downward,  outward,  and  forward  to  the  side  of  the  base 
of  the 'tongue.  These  pillars  are  formed  by  the  projection  of  the  Palato-glossi 
muscles,  covered  by  mucous  membrane. 

The  Posterior  Pillar  (arcus  pharyngopalatinus)  (Figs.  831  and  837). — The  pos- 
terior pillar  on  each  side  is  nearer  to  its  opposite  arch  than  is  the  anterior  pillar  to  its 
opposite.  These  pillars  are  larger  than  the  anterior;  they  run  downward,  outward, 
and  backward  to  the  sides  of  the  pharynx,  and  are  formed  by  the  projection  of  the 
Palato-pharyngei  muscles,  covered  by  mucous  membrane.  The  anterior  and  pos- 
terior pillars  are  separated  below  by  a  triangular  interval  in  which  the  tonsil  is  lodged. 

The  space  left  between  the  arches  of  the  palate  on  the  two  sides  is  called  the 
isthmus  of  the  fauces  (isthmus  faucium).  It  is  bounded,  above,  by  the  free  margin 
of  the  soft  palate;  below,  by  the  back  of  the  tongue;  and  on  each  side  by  the 
pillars  of  the  fauces  and  the  tonsils.  Through  this  isthmus  the  mouth  com- 
municates with  the  pharynx. 

The  Mucous  Membrane  of  the  Soft  Palate. — The  mucous  membrane  of  the  soft 
palate  is  thin,  and  covered  with  squamous  epithelium  on  both  surfaces,  excepting 
near  the  orifice  of  the  Eustachian  tube,  where  its  epithelium  is  columnar  and 
ciliated.1  Beneath  the  mucous  membrane  on  the  oral  surface  of  the  soft  palate 
is  a  considerable  amount  of  adenoid  tissue.  The  palatine  glands  form  a  con- 
tinuous layer  on  the  pharyngeal  surface  and  around  the  uvula. 

The  Aponeurosis  of  the  Soft  Palate. — The  aponeurosis  of  the  soft  palate  is  a  thin 
but  firm  fibrous  layer  attached  above  to  the  posterior  border  of  the  hard  palate, 
and  becoming  thinner  toward  the  free  margin  of  the  velum.  Laterally,  it  is  con- 
tinuous with  the  pharyngeal  aponeurosis.  It  forms  the  framework  of  the  soft 
palate,  and  is  joined  by  the  tendons  of  the  Tensor  palati  muscles. 

The  Muscles  of  the  Soft  Palate. — The  muscles  of  the  soft  palate  are  six  on  each 
side:  the  Levator  palati,  Tensor  palati,  Azygos  uvulae,  Palato-glossus,  Palato- 
pharyngeus  and  Salpingo-pharyngeus  (see  p.  407).  The  following  is  the  relative 
position  of  these  structures  in  a  dissection  of  the  soft  palate  from  the  posterior  or 
naso-pharyngeal  to  the  anterior  or  oral  surface :  Immediately  beneath  the  pharyn- 
geal mucous  membrane  is  a  thin  stratum  of  muscular  fibres,  the  posterior  fasciculus 
of  the  Palato-pharyngeus  muscle,  joining  with  its  fellow  of  the  opposite  side  in  the 
middle  line.  This  posterior  fasciculus  is  joined  by  the  Salpingo-pharyngeus 
muscle.  Beneath  this  are  the  Azygos  uvulae  and  Salpingo-pharyngeus  muscles, 
consisting  of  two  rounded  fleshy  fasciculi,  placed  side  by  side  in  the  median  line 
of  the  soft  palate.  Next  comes  the  aponeurosis  of  the  Levator  palati,  joining  with 
the  muscle  of  the  opposite  side  in  the  middle  line.  Fourthly,  the  anterior  fasciculus 
of  the  Palato-pharyngeus,  thicker  than  the  posterior,  and  separating  the  Levator 
palati  from  the  next  muscle,  the  Tensor  palati.  This  muscle  terminates  in  a  tendon 
which,  after  winding  around  the  hamular  process  of  the  internal  pterygoid  plate 
of  the  sphenoid  bone,  expands  into  a  broad  aponeurosis  in  the  soft  palate,  anterior 
to  the  other  muscles,  which  have  been  enumerated.  Finally,  we  have  a  thin  mus- 
cular stratum,  the  Palato-glossus  muscle,  placed  in  front  of  the  aponeurosis  of  the 
Tensor  palati,  and  separated  from  the  oral  mucous  membrane  by  adenoid  tissue. 

The  Blood-vessels  of  the  Palate  (Fig.  832). — The  palate  is  supplied  with  blood  by 
branches  of  the  posterior  or  descending  palatine  branch  of  the  internal  maxillary  artery 
(a.  palatina  descendens]  and  of  the  ascending  or  anterior  palatine  branch  of  the  facial 
artery  (a.  palatina  ascendens).  The  posterior  palatine  artery  divides  into  the  great 
and  small  palatine  arteries  (aa.  palatinae  major  et  minor),  which  run  through  the 

1  According  to  Klein,  the  mucous  membrane  on  the  nasal  surface  of  the  soft  palate  in  the  foetus  is  covered 
throughout  by  columnar  ciliated  epithelium,  which  subsequently  becomes  squamous;  and  some  anatomist! 
state  that  it  is  covered  with  columnar  ciliated  epithelium,  except  at  its  free  margin,  throughout  life. — ED.  of 
15th  English  edition. 


THE    TONSIL  1223 

palatine  canals  and  after  emerging  give  off  branches.  Branches  from  the  small 
palatine  go  to  the  soft  palate,  the  large  branch  passes  forward  on  the  hard  palate 
near  the  alveolar  margin.  The  ascending  palatine  branch  of  the  facial  lies  upon 
the  medial  surface  of  the  Tensor  palati  muscle  and  is  distributed  to  the  soft  palate 
and  pharynx.  A  palatine  vein  corresponding  to  the  descending  palatine  artery 
opens  into  the  anterior  facial  vein.  The  pharyngeal  veins  also  receive  palatine  veins. 

The  Nerves  of  the  Palate. — The  large  posterior  palatine  nerve  emerges  from  the 
posterior  palatine  canal  and  accompanies  the  posterior  palatine  artery.  The  naso- 
palatine  nerve  emerges  from  the  foramen  of  Scarpa  and  is  distributed  to  the  anterior 
portion  of  the  hard  palate.  The  soft  palate  is  supplied  by  the  small  posterior 
palatine  and  the  accessory  palatine  nerves. 

The  Tonsil  or  Amygdala  (tonsilla  palatina)  (Figs.  818  and  824). — The  tonsils 
or  amygdalae  are  two  prominent  bodies  situated  one  on  each  side  of  the  fauces, 
between  the  anterior  and  posterior  pillars  of  the  soft  palate.  They  are  of  a 
rounded  form,  and  vary  considerably  in  size  in  different  individuals.  A  recess, 
the  supra-tonsillar  fossa  (fossa  supratonsillaris),  may  be  seen,  directed  upward 
and  backward  above  the  tonsil.  His  regards  this  as  the  remains  of  the  lower  part 
of  the  second  visceral  cleft.  The  recess  is  covered  by  a  fold  of  mucous  mem- 
brane termed  the  plica  triangularis.  Externally  the  tonsil  is  covered  with  a  fibrous 
capsule  which  joins  the  aponeurosis  of  the  pharynx.  The  outer  surface  of  the 
capsule  is  in  relation  with  the  inner  surface  of  the  Superior  constrictor  muscle 
of  the  pharynx,  to  the  outer  side  of  which  is  the  Internal  pterygoid  muscle.  The 
ascending  palatine  artery  is  close  to  the  outer  surface  of  the  tonsil,  the  Superior 
constrictor  muscle  of  the  pharynx  and  the  tonsillar  capsule  intervening.  The 
tonsillar  artery,  which  is  sometimes  a  branch  of  the  ascending  palatine,  is  also 
close  to  the  outer  surface  of  the  tonsil.  The  internal  carotid  artery  lies  behind 
and  to  the  outer  side  of  the  tonsil,  and  nearly  an  inch  (20  to  25  mm.)  distant  from 
it.  It  corresponds  to  the  angle  of  the  lower  jaw.  The  surface  of  the  tonsil 
which  looks  toward  the  pharynx  presents  from  twelve  to  fifteen  orifices,  each 
leading  into  a  small  recess  or  crypt  (fossula  tonsiUaris).  From  the  crypts 
numerous  follicles  branch  out  into  the  substance  of  the  tonsil  by  means  of  very 
irregular  channels.  The  crypts  are  lined  with  stratified  pavement  epithelium. 
The  epithelium  of  the  crypts  exhibits  marked  degenerative  changes.  The 
degeneration  causes  the  formation  of  numerous  communicating  spaces,  which 
contain  leukocytes  and  lymphocytes.  The  crypts  are  surrounded  with  lymphoid 
tissue.  In  this  are  numerous  lymphoid  follicles  (noduli  lymphatici) ,  which  are 
placed  in  the  submucous  tissue.  These  follicles  are  analogous  to  those  of 
Peyer's  glands  and  consist  of  adenoid  tissue.  No  openings  from  the  capsules 
into  the  follicles  can  be  recognized.  They  contain  a  thick  grayish  secretion. 

The  Blood-vessels  of  the  Tonsil. — The  arteries  supplying  the  tonsils  are  the 
dorsalis  linguae  from  the  lingual,  the  ascending  palatine  and  tonsillar  from  the 
facial,  the  ascending  pharyngeal  from  the  external  carotid,  the  descending  palatine 
branch  of  the  internal  maxillary,  and  a  twig  from  the  parvadural.  The  veins 
terminate  in  the  tonsillar  plexus,  on  the  outer  side  of  the  tonsil,  and  the  tonsillar 
plexus  joins  the  pharyngeal  plexus,  which  communicates  with  the  pterygoid  plexus 
of  the  internal  jugular  or  facial  vein. 

Lymphatics  of  the  Tonsil. — Surrounding  each  follicle  is  a  close  plexus  of  lym- 
phatic vessels.  From  these  plexuses  the  lymphatic  vessels  pass  to  the  submaxillary 
lymph  glands  below  the  angle  of  the  jaw.  From  the  submaxilliary  glands  lymph 
passes  to  the  deep  cervical  glands. 

The  Nerves  of  the  Tonsil. — A  branch  from  the  glosso -pharyngeal  nerve  by  uniting 
with  branches  of  the  pharyngeal  plexus  forms  the  tonsillar  plexus.  The  pharyn- 
geal plexus  is  formed  by  the  pharyngeal  branches  of  the  glosso-pharyngeal  and 
superior  cervical  ganglia  of  the  sympathetic  and  the  pharyngeal  branch  of  the  vagus. 


1224 


THE  ORGANS  OF  DIGESTION 


The  Salivary  Glands  (Fig.  833). 

Numerous  glands  exist  in  the  lips,  cheeks,  palate,  and  tongue,  but  by  the  term 
salivary  glands  are  usually  understood  the  three  chief  glandular  masses  on  each 
side  of  the  face.  These  are  the  principal  salivary  glands.  They  communicate 
with  the  mouth,  pour  their  secretion  into  its  cavity,  and  are  named  respectively 
the  parotid,  submaxillary,  and  sublingual. 

The  Parotid  Gland  (glandulae  parotis). — The  parotid  gland,  so  called  from  being 
placed  near  the  ear  (nap A,  near;  o5c,  o»roc,  the  ear},  is  the  largest  of  the  three 
salivary  glands,  varying  in  weight  from  half  an  ounce  to  an  ounce.  It  lies  upon 
the  side  of  the  face  immediately  below  and  in  front  of  the  external  ear.  It  is  limited 
above  by  the  zygoma ;  below,  by  the  angle  of  the  jaw  and  by  a  line  drawn  between 
the  angle  and  the  mastoid  process:  anteriorly,  it  extends  to  a  variable  extent 
over  the  Masseter  muscle;  posteriorly,  it  is  bounded  by  the  external  meatus, 
the  mastoid  process,  and  the  Sterno-mastoid  and  Digastric  muscles,  slightly 
overlapping  the  two  muscles. 


FIG.  833.— The  salivary  glands. 

Its  anterior  surface  is  grooved  to  embrace  the  posterior  margin  of  the  ramus  of 
the  lower  jaw,  and  advances  forward  beneath  the  ramus,  between  the  two  Ptery- 
goid  muscles  and  superficial  to  the  ramus  over  the  Masseter  muscle.  Its  outer 
surface  is  triangular  and  convex,  slightly  lobulated,  is  covered  by  the  integument 
and  parotid  fascia,  and  has  one  or  two  lymphatic  glands  resting  on  it.  Its  inner 
surface  (processus  retromandibularis)  extends  deeply  into  the  neck  by  means  of 
two  large  processes,  one  of  which  dips  behind  the  styloid  process  and  projects 
beneath  the  mastoid  process  and  the  Sterno-mastoid  muscle ;  the  other  is  situated 
in  front  of  the  styloid  process,  and  passes  into  the  back  part  of  the  glenoid 
fossa,  behind  the  articulation  of  the  lower  jaw.  The  structures  passing  through 
the  parotid  gland  are — the  external  carotid  artery,  giving  off  its  three  terminal 


THE  SALIVARY   GLANDS  1225 

branches:  the  posterior  auricular  artery  emerges  from  the  gland  behind;  the  super- 
ficial temporal  artery  above;  the  transverse  facial,  a  branch  of  the  temporal,  in  front; 
and  the  internal  maxillary  winds  through  it  as  it  passes  inward,  behind  the  neck 
of  the  jaw.  Superficial  to  the  external  carotid  is  the  trunk  formed  by  the  union 
of  the  temporal  and  internal  maxillary  veins;  a  branch,  connecting  this  trunk 
with  the  internal  jugular,  also  passes  through  the  gland.  The  gland  is  also 
traversed  by  the  facial  nerve  and  its  branches,  which  emerge  at  its  anterior 
border;  branches  of  the  great  auricular  nerve  pierce  the  gland  to  join  the  facial, 
and  the  auriculo -temporal  branch  of  the  inferior  maxillary  nerve  emerges  from  the 
upper  part  of  the  gland.  The  internal  carotid  artery  and  internal  jugular  vein  lie 
close  to  its  deep  surface.  The  triangular  space  occupied  by  the  greater  part  of 
the  gland  is  bounded  in  front  by  the  posterior  margin  of  the  ramus  of  the  jaw 
and  the  internal  pterygoid  muscle,  and  behind  by  the  anterior  edge  of  the  Sterno- 
cleido-mastoid  muscle,  the  tympanic  portion  of  the  temporal  bone  and  the  car- 
tilaginous portion  of  the  external  auditory  meatus.  Its  floor  is  formed  by  the 
anterior  and  posterior  walls  of  the  space  which  meet  about  the  styloid  process. 
These  walls  are  composed  of  fascia  derived  from  the  deep  cervical  fascia.  The 
remaining  side  of  the  space  is  external  and  is  formed  by  fascia,  derived  from  the 
deep  cervical  fascia  and  called  the  parotid  fascia.  This  space  is  called  the  parotid 
recess.  Sir  Frederick  Treves1  denies  that  the  fascial  covering  of  the  space  is 
complete.  He  says  it  is  deficient  above  between  the  anterior  edge  of  the  styloid 
process  and  the  posterior  border  of  the  external  pterygoid  muscle.  A  portion 
of  the  gland  does  not  occupy  the  space,  but  projects  forward  over  the  Masseter 
muscle.  This  projecting  portion  is  the  facial  process. 

Lymph -glands,  known  as  the  parotid  lymph-glands,  are  in  and  about  the  parotid 
gland,  some  being  embedded  in  the  outer  surface  of  the  parotid  fascia,  others 
being  in  the  inner  surface  of  the  fascia,  others  in  the  gland  itself,  particularly 
along  the  temporo-maxillary  vein  and  external  carotid  artery.  They  receive 
lymph  from  the  anterior  and  lateral  portions  of  the  scalp,  both  eyelids,  a  portion 
of  the  cheek,  the  root  of  the  nose,  the  outer  portion  of  the  external  ear,  the  soft 
palate,  the  posterior  nares,  and  the  external  auditory  meatus.  The  vessels  from 
them  empty  into  the  superficial  cervical  glands  and  the  superior  deep  cervical 
glands.  Between  the  parotid  gland  and  the  pharynx  are  the  subparotid  glands. 
They  receive  lymph  from  the  nasal  fossae,  naso-pharynx,  and  Eustachian  tube,  and 
vessels  from  the  glands  take  lymph  to  the  deep  cervical  glands.2 

The  Duct  of  the  Parotid  Gland,  called  the  Parotid  Duct  or  Stenson's  Duct  (ductus 
parotideus  [Stenonis])  (Fig.  833). — The  duct  of  the  parotid  gland  is  about  two 
inches  and  a  half  in  length.  It  commences  by  numerous  branches  from  the  ante- 
rior part  of  the  gland,  crosses  the  Masseter  muscle,  and  at  its  anterior  border  dips 
down  into  the  substance  of  the  Buccinator  muscle,  which  it  pierces;  it  then  runs 
for  a  short  distance-  obliquely  forward  between  the  Buccinator  muscle  and  the 
mucous  membrane  of  the  mouth,  and  opens  upon  the  inner  surface  of  the  cheek 
by  a  small  orifice  opposite  the  second  molar  tooth  of  the  upper  jaw  (Fig.  824). 
Upon  the  beginning  of  Stenson's  duct  there  is  often  an  accessory  parotid  gland 
(glandulae  parotis  accessoria),  which  is  often  called  the  socia  parotidis.  It  is  a 
portion  of  the  facial  process.  It  is  a  detached  portion  of  gland,  and  has  a  duct 
which  opens  into  Stenson's  duct.  This  accessory  gland  occasionally  exists  as  a 
separate  lobe,  just  beneath  the  zygomatic  arch.  In  this  position  it  has  the  trans- 
verse facial  artery  above  it  and  some  branches  of  the  facial  nerve  below  it. 

Surface  Form. — The  direction  of  the  duct  corresponds  to  a  line  drawn  across  the  face  about 
a  finger's  breadth  below  the  zygoma;  that  is,  from  the  lower  margin  of  the  concha  to  midway 
between  the  free'  margin  of  the  upper  lip  and  the  ala  of  the  nose. 

1  Applied  Anatomy.  *  Poirier  and  Cun6o,  Human  Anatomy. 


1226  THE   ORGANS    OF  DIGESTION 

Structure  of  the  Parotid  Duct. — The  parotid  duct  is  dense,  it  is  of  considerable 
thickness,  and  its  canal  is  about  the  size  of  a  crowquill ;  but  at  ks  orifice  on  the 
inner  aspect  of  the  cheek  its  lumen  is  greatly  reduced  in  size.  The  duct  consists 
of  an  external  or  fibrous  coat,  of  considerable  density,  containing  contractile 
fibres,  and  of  an  internal  or  mucous  coat  lined  with  short  columnar  epithelium. 

Vessels  and  Nerves. — The  arteries  supplying  the  parotid  gland  are  derived  from, 
the  external  carotid,  and  from  the  branches  given  oft'  by  that  vessel  in  or  near  its 
substance.  The  veins  empty  themselves  into  the  external  jugular  through  some 
of  its  tributaries.  The  lymphatics  terminate  in  the  superficial  cervical  and  the 
deep  cervical  glands,  passing  in  their  course  through  several  lymphatic  glands 
placed  on  the  surface  and  in  the  substance  of  the  parotid.  The  nerves  are 
derived  from  the  plexus  of  the  sympathetic  on  the  external  carotid  artery,  the 
facial,  the  auriculo -temporal,  and  great  auricular  nerves.  It  is  probable  that  the 
branch  from  the  auriculo-temporal  nerve  is  derived  from  the  glosso-pharyngeal 
through  the  otic  ganglion.  At  all  events,  in  some  of  the  lower  animals  this  has 
been  proved  experimentally  to  be  the  case. 

The  Parotid  Capsule. — The  parotid  gland  is  enclosed  by  two  layers  of  the  parotid 
fascia  (fascia  parotideomasseterica) ,  which  almost  completely  encompass  the 
gland.  The  sheath  is  incomplete  at  one  area  toward  the  pharyngeal  wall  (see 
(p.  1225). 

The  parotid  fascia  comes  from  the  deep  cervical  fascia.  The  external  layer 
covers  the  gland.  The  internal  layer  lines  the  parotid  recess.  The  external  layer 
is  the  structure  usually  spoken  of  as  the  parotid  fascia.  Anteriorly  it  joins 
the  fascia  of  the  masseter;  below  it  is  continuous  with  the  deep  cervical  fascia; 
above  it  is  attached  to  the  zygoma;  behind  it  is  adherent  to  the  external  auditory 
meatus  and  sheath  of  the  Sternomastoid.  The  deep  layer  is  adherent  above  to  the 
external  auditory  meatus  and  back  of  the  glenoid  fossa;  internally  to  the  styloid 
process;  below  it  is  continuous  with  the  deep  cervical  fascia.  The  stylomaxillary 
or  stylomandibular  ligament  comes  off  from  the  parotid  fascia. 

The  Submaxillary  Gland  (glandula  submaxillaris)  (Fig.  833). — The  submax- 
illary  gland  is  situated  below  the  jaw,  in  the  anterior  part  of  the  submaxillary 
triangle  of  the  neck.  It  is  irregular  in  form  and  weighs  about  two  drachms 
(8  to  10  grammes).  It  is  covered  by  the  integument,  Platysma,  deep  cervical 
fascia,  and  the  body  of  the  lower  jaw,  corresponding  to  a  depression  on  the 
inner  surface  of  the  body  of  the  mandible,  and  lies  upon  the  Mylo-hyoid,  Hyo- 
glossus,  and  Stylo-glossus  muscles,  a  portion  of  the  gland  passing  beneath  the 
posterior  border  of  the  Mylo-hyoid.  In  front  of  it  is  the  anterior  belly  of  the 
Digastric  muscle;  behind,  it  is  separated  from  the  parotid  gland  by  the  stylo- 
maxillary  ligament,  and  from  the  sublingual  gland  in  front  by  the  Mylo-hyoid 
muscle.  The  facial  artery  lies  embedded  in  a  groove  in  its  posterior  and  upper 
border.  A  process  is  given  off  from  the  deep  surface  of  the  anterior  portion  of 
the  gland.  This  is  the  deep  process  (Cunningham),  and  it  passes  with  the  duct 
beneath  the  Mylo-hyoid  muscle. 

The  Duct  of  the  Submaxillary  Gland  or  Wharton's  Duct  (ductus  submaxillaris 
[Whartoni]). — The  duct  of  the  submaxillary  gland  is  about  two  inches  in  length, 
and  its  walls  are  much  thinner  than  those  of  the  parotid  duct.  It  commences  by 
numerous  branches  from  the  deep  portion  of  the  gland  which  lies  on  the  upper 
surface  of  the  Mylo-hyoid  muscle,  and  passes  forward  and  inward  between  the 
Mylo-hyoid  and  the  Hyo-glossus  and  Genio-hyo-glossus  muscles,  then  between  the 
sublingual  gland  and  the  Genio-hyo-glossus  muscle,  and  opens  by  a  narrow  orifice 
on  the  summit  of  a  small  papilla  (caruncula  sublingualis)  at  the  side  of  the  fraenum 
linguae.  On  the  Hyo-glossus  muscle  it  lies  between  the  lingual  and  hypoglossal 
nerves,  but  at  the  anterior  border  of  the  muscle  it  crosses  under  the  lingual  nerve, 
and  is  then  placed  above  it. 


THE  SALIVARY  GLANDS 


1227 


Vessels  and  Nerves. — The  arteries  supplying  the  submaxillary  gland  are  branches 
of  the  facial  and  lingual.  Its  veins  follow  the  course  of  the  arteries.  The  lymph- 
atics drain  into  the  submaxillary  lymph-glands.  There  are  no  lymphatic  glands 
in  this  salivary  gland.  The  nerves  are  derived  from  the  submaxillary  ganglion, 
through  which  it  receives  filaments  from  the  chorda  tympani  and  from  the  lingual 
branch  of  the  inferior  maxillary,  sometimes  from  the  mylo-hyoid  branch  of  the  inferior 
dental  and  from  the  sympathetic. 

The  Sublingual  Gland  (glandula  sublingualis}  (Fig.  833).— The  sublingual 
gland  is  the  smallest  of  the  salivary  glands.  It  is  situated  beneath  the  mucous 
membrane  of  the  floor  of  the  mouth,  at  the  side  of  the  fraenum  linguae,  in  contact 
with  the  inner  surface  of  the  lower  jaw,  close  to  the  symphysis.  It  is  narrow, 
flattened,  in  shape  somewhat  like  an  almond,  and  weighs  about  a  drachm.  It 
is  in  relation,  above,  with  the  mucous  membrane;  below,  with  the  Mylo-hyoid 
muscle;  in  front,  with  the  depression  on  the  side  of  the  symphysis  of  the  lower 
jaw,  and  with  its  fellow  of  the  opposite  side;  behind,  with  the  deep  part  of  the 
submaxillary  gland;  and  internally,  with  the  Genio-hyo-glossus,  from  which  it 
is  separated  by  the  lingual  nerve  and  Wharton's  duct.  Its  excretory  ducts  or 
ducts  of  Rivinus  (ductus  sublingualis  minores)  are  from  eight  to  twenty  in  number. 


Crescent  of  Gianuszi. 


Salivary  duct. 


FIG.  834. — A  highly  magnified  section  of  the  submaxillary  gland  of  the  dog,  stained  with  carmine.     (Kolliker.) 


They  open  separately  into  the  mouth  back  of  Wharton's  duct  and  upon  a  fold 
of  mucous  membrane  known  as  the  plica  sublingualis.  The  plica  sublingualis  is 
an  elevated  crest  of  mucous  membrane  caused  by  the  projection  of  the  gland  on 
either  side  of  the  fraenum  linguae.  One  or  more  ducts  sometimes  join  to  form 
a  tube  which  opens  into  the  Whartonian  duct  or  remains  independent,  opening 
close  to  Wharton's  duct  on  the  sublingual  papilla.  This  single  duct  is  called 
the  duct  of  Bartholin  (ductus  sublingualis  major). 

Vessels  and  Nerves. — The  sublingual  gland  is  supplied  with  blood  from  the 
sublingual  and  submental  arteries.  Its  nerves  are  derived  from  the  lingual. 

Structure  of  Salivary  Glands  (Fig.  834). — The  salivary  glands  are  compound 
racemose  glands,  consisting  of  numerous  lobes,  which  are  made  up  of  smaller 
lobules  connected  together  by  dense  areolar  tissue,  vessels,  and  ducts.  Each 
lobule  consists  of  the  ramifications  of  a  single  duct,  dividing  frequently  like  the 
branches  of  a  tree,  the  branches  terminating  in  dilated  ends  or  alveoli,  on  which 
the  capillaries  are  distributed.  These  alveoli,  however,  as  Pfliiger  points  out, 
are  not  necessarily  spherical,  though  sometimes  they  assume  that  form;  some- 
times they  are  perfectly  cylindrical,  and  very  often  they  are  mutually  com- 
pressed. The  alveoli  are  enclosed  by  a  basement  membrane  which  is  continuous 
with  the  membrana  propria  of  the  duct.  It  presents  a  peculiar  reticulated 


1228  THE    ORGANS    OF  DIGESTION 

structure,  having  the  appearance  of  a  basket  with  open  meshes,  and  consisting 
of  a  network  of  branched  and  flattened  nucleated  cells. 

The  alveoli  of  the  salivary  glands  are  of  two  kinds,  which  differ  both  in  the 
appearance  of  their  secreting  cells,  in  their  size,  and  in  the  nature  of  their  secre- 
tion. The  one  variety  secretes  a  ropy  fluid  which  contains  mucin,  and  such 
alveoli  have  therefore  been  named  the  mucous  alveoli,  whilst  the  other  secretes  a 
thinner  and  more  watery  fluid,  which  contains  serum-albumin,  and  alveoli  of 
this  variety  have  been  named  serous  or  albuminous  alveoli.  The  sublingual  gland 
may  be  regarded  as  an  example  of  the  former  variety,  the  parotid  of  the  latter. 
The  submaxillary  is  of  the  mixed  variety,  containing  both  mucous  and  serous 
alveoli,  the  latter,  however,  preponderating. 

Both  varieties  of  alveoli  are  lined  by  cells,  and  it  is  by  the  character  of  these 
cells  that  the  nature  of  the  gland  is  chiefly  to  be  determined.  In  addition,  how- 
ever, the  alveoli  of  the  serous  glands  are  smaller  than  those  of  the  mucous  ones. 

The  Mucous  Alveoli. — The  cells  in  the  mucous  alveoli  are  spheroidal  in  shape, 
glassy,  transparent,  and  dimly  striated  in  appearance.  The  nucleus  is  usually 
situated  in  the  part  of  the  cell  which  is  next  the  basement  membrane,  against 
which  it  is  sometimes  flattened.  The  most  remarkable  peculiarity  presented  by 
these  cells  is,  that  they  give  off  an  extremely  fine  process  which  is  curved  in  a 
direction  parallel  to  the  surface  of  the  alveolus,  lies  in  contact  with  the  membrana 
propria,  and  overlaps  the  process  of  neighboring  cells.  The  cells  contain  a  quan- 
tity of  inucin,  to  which  their  clear,  transparent  appearance  is  due. 

Here  and  there  in  the  alveoli  are  seen  peculiar  half-moon-shaped  bodies  lying 
between  the  cells  and  the  membrana  propria  of  the  alveolus.  They  are  termed 
the  crescents  of  Gianuzzi  or  the  demilunes  of  Heidenhain  (Fig.  834),  and  are  com- 
posed of  polyhedral  granular  cells,  which  Heidenhain  regards  as  young  epithelial 
cells  destined  to  supply  the  place  of  those  salivary  cells  which  have  undergone 
disintegration.  This  view,  however,  is  not  accepted  by  Klein. 

Serous  Alveoli. — In  the  serous  alveoli  the  cells  almost  completely  fill  the  cavity, 
so  that  there  is  hardly  any  lumen  perceptible.  Instead  of  presenting  the  clear, 
transparent  appearance  of  the  cells  of  the  mucous  alveoli,  they  present  a  granular 
appearance,  due  to  distinct  granules  of  an  albuminous  nature  embedded  in  a  closely 
reticulated  protoplasm.  The  ducts  which  originate  from  the  alveoli  are  lined  at 
their  commencement  by  epithelium  which  differs  little  from  the  pavement  type. 
As  the  ducts  enlarge,  the  epithelial  cells  change  to  the  columnar  type,  and  the  part 
of  the  cells  next  the  basement-membrane  is  finely  striated.  The  lobules  of  the 
salivary  glands  are  richly  supplied  with  blood-vessels  which  form  a  dense  network 
in  the  interalveolar  spaces.  Fine  plexuses  of  nerves  are  also  found  in  the  inter- 
lobular  tissue.  The  nerve-fibnls  pierce  the  basement-membrane  of  the  alveoli, 
and  end  in  branched  varicose  filaments  between  the  secreting  cells.  There  is  no 
doubt  that  ganglia  are  to  be  found  in  some  salivary  glands  in  connection  with  the 
nerve-plexuses  in  the  interlobular  tissue;  they  are  to  be  found  in  the  submaxillary, 
but  not  in  the  parotid. 

In  the  submaxillary  and  sublingual  glands  the  lobes  are  larger  and  more  loosely 
united  than  in  the  parotid. 

Mucous  Glands. — Besides  the  salivary  glands  proper,  numerous  other  glands 
are  found  in  the  mouth.  They  appear  to  secrete  mucus  only,  which  serves  to  keep 
the  mouth  moist  during  the  intervals  of  the  salivary  secretion,  and  which  is  mixed 
with  that  secretion  in  swallowing.  Many  of  these  glands  are  found  at  the  posterior 
part  of  the  dorsum  of  the  tongue,  behind  the  circumvallate  papillae,  and  also  along 
its  margins  as  far  forward  as  the  apex.1  Others  lie  around  and  in  the  tonsil 

pa. 

assist  in  the  more  rapid  di 

the  sense  of  taste  is  situated. — ED.  of  15th  English  edition. 


THE   SALIVARY   GLANDS  1229 

between  its  crypts,  and  a  large  number  are  present  in  the  soft  palate.  These 
glands  are  of  the  ordinary  compound  racemose  type.  Behind  the  tip  of  the 
tongue  on  each  side,  external  to  the  anterior  extremity  of  the  genio-glossus  muscle, 
is  a  mucous  gland,  the  gland  of  Nuhn  and  Blandin  (glandula  lingualis  anterior}. 
Its  lower  surface  is  partly  covered  by  muscular  fibres  from  the  inferior  lingualis 
and  styloglossus  muscles,  and  it  opens  by  several  ducts. 

Surface  Form.— The  orifice  of  the  mouth  is  bounded  by  the  lips,  two  thick,  fleshy  folds 
covered  externally  by  integument  and  internally  by  mucous  membrane,  and  consisting  of 
muscles,  vessels,  nerves,  arcolar  tissue,  and  numerous  small  glands.  The  size  of  the  orifice  of 
the  mouth  varies  considerably  in  different  individuals,  but  seems  to  bear  a  close  relation  to  the 
size  and  prominence  of  the  teeth.  Its  corners  correspond  pretty  accurately  to  the  outer  border 
of  the  canine  teeth.  In  the  Ethiopian  tribes  the  front  teeth  are  large  and  inclined  for- 
ward, the  mouth  is  large;  and  this,  combined  with  the  thick  and  everted  lips  which  appear  to 
be  associated  with  prominent  teeth,  gives  to  the  negro's  face  much  of  the  peculiarity  by  which 
it  is  characterized.  The  smaller  teeth  and  the  slighter  prominence  of  the  alveolar  arch  of  the 
more  highly  civilized  races  render  the  orifice  of  the  mouth  much  smaller,  and  thus  a  small 
mouth  is  an  indication  of  intelligence,  and  is  regarded  as  an  evidence  of  the  higher  civilization 
of  the  individual. 

Upon  looking  into  the  mouth,  the  first  thing  we  may  note  is  the  tongue,  the  upper  surface 
of  which  will  be  seen  occupying  the  floor  of  the  cavity.  This  surface  is  convex,  and  is  marked 
along  the  middle  line  by  a  raphe  which  divides  it  into  two  symmetrical  portions.  The  anterior 
two-thirds  is  rough  and  studded  with  papillae;  the  posterior  third  smooth  and  tuberculated, 
and  covered  by  numerous  glands  which  project  from  the  surface.  Upon  raising  the  tongue 
the  mucous  membrane  which  invests  the  upper  surface  may  be  traced  covering  the  sides  of  the 
under  surface,  and  then  reflected  over  the  floor  of  the  mouth  on  to  the  inner  surface  of  the 
lower  jaw,  a  part  of  which  it  covers.  As  it  passes  over  the  borders  of  the  tongue  it  changes  its 
character,  becoming  thin  and  smooth  and  losing  the  papillae  which  are  to  be  seen  on  the  upper 
surface.  In  the  middle  line  the  mucous  membrane  on  the  under  surface  of  the  tip  of  the  tongue 
forms  a  distinct  fold,  the  fraenum  linguae,  by  which  this  organ  is  connected  to  the  symphysis 
of  the  jaw.  Occasionally  it  is  found  that  this  fraenum  is  rather  shorter  than  natural,  and, 
acting  as  a  bridle,  prevents  the  complete  protrusion  of  the  tongue.  When  this  condition  exists 
and  an  attempt  is  made  to  protrude  the  organ,  the  tip  will  be  seen  to  remain  buried  in  the 
floor  of  the  mouth,  and  the  dorsum  of  the  tongue  is  rendered  very  convex,  and  more  or  less 
extruded  from  the  mouth;  at  the  same  time  a  deep  furrow  will  be  noticed  to  appear  in  the 
middle  line  of  the  anterior  part  of  the  dorsum.  Sometimes,  a  little  external  to  the  fraenum, 
the  ranine  vein  may  be  seen  immediately  beneath  the  mucous  membrane.  The  corresponding 
artery,  being  more  deeply  placed,  does  not  come  into  view,  nor  can  its  pulsation  be  felt  with  the 
finger.  On  either  side  of  the  fraenum,  in  the  floor  of  the  mouth,  is  a  longitudinally  elevation  or 
ridge,  produced  by  the  projection  of  the  sublingual  gland,  which  iies  immediately  beneath  the 
mucous  membrane.  And  close  to  the  attachment  of  the  fraenum  to  the  tip  of  the  tongue  may 
be  seen  on  either  side  the  slit-like  orifices  of  Wharton's  ducts,  into  which  a  fine  probe  may  be 
passed  without  much  difficulty.  By  everting  the  lips  the  smooth  mucous  membrane  lining  them 
may  be  examined,  and  may  be  traced  from  them  on  to  the  outer  surface  of  the  alveolar  arch. 
In  the  middle  line,  both  of  the  upper  and  lower  lip,  a  small  fold  of  mucous  membrane  passes 
from  the  lip  to  the  bone,  constituting  the  fraena;  these  are  not  so  large  as  the  fraenum  linguae. 
By  pulling  outward  the  angle  of  the  mouth,  the  mucous  membrane  lining  the  cheeks  can  be 
seen,  and  on  it  may  be  perceived  a  little  papilla  which  marks  the  position  of  the  orifice  of  Sten- 
son's  duct — the  duct,  of  the  parotid  gland.  The  exact  position  of  the  orifice  of  the  duct  will  be 
found  to  be  opposite  the  second  molar  tooth  of  the  upper  jaw.  The  introduction  of  a  probe 
into  this  duct  is  attended  with  considerable  difficulty.  The  teeth  are  the  next  objects  which 
claim  our  attention  upon  looking  into  the  mouth.  These  are,  as  stated  above,  ten  in  either  jaw 
in  the  temporary  set,  and  sixteen  in  the  permanent  set.  The  gums,  in  which  they  are  implanted, 
are  dense,  firm,  and  vascular. 

At  the  back  of  the  mouth  is  seen  the  isthmus  of  the  fauces,  or,  as  it  is  popularly  called,  "  the 
throat:"  this  is  the  space  between  the  pillars  of  the  fauces  on  either  side,  and  is  the  means 
by  which  the  mouth  communicates  with  the  pharynx.  Above,  it  is  bounded  by  the  soft  palate, 
the  anterior  surface  of  which  is  concave  and  covered  with  mucous  membrane,  which  is  con- 
tinuous with  that  lining  the  roof  of  the  mouth.  Projecting  downward  from  the  middle  of 
its  lower  border  is  a  conical-shaped  projection,  the  uvula.  On  either  side  of  the  isthmus  of  the 
fauces  are  the  anterior  and  posterior  pillars,  formed  by  the  Palato-glossus  and  Palato-pharyn- 
geus  muscles  respectively,  covered  over  by  mucous  membrane.  Between  the  two  pillars  on  eitner 
side  is  situated  the  tonsil.  The  extirpation  of  this  body  is  not  unattended  with  danger  of 
hemorrhage.  Dr.  Weir  has  stated  that  he  believes  that  when  hemorrhage  occurs  after  their 
removal  it  arises  from  one  of  the  palatine  arteries  having  been  wounded.  These  vessels  are 


1230  THE    ORGANS    OF  DIGESTION 

large:  they  lie  in  the  muscular  tissue  of  the  palate,  and  when  wounded  are  constantly  exposed 
to  disturbance  from  the  contraction  of  the  palatine  muscles.  The  vessels  of  the  tonsil,  Dr.  Weir 
states,  are  small  and  lie  in  the  soft  tissue,  and  readily  contract  when  wounded. 

When  the  mouth  is  wide  open  a  prominent  tense  fold  of  mucous  membrane  may  be  seen  and 
felt,  extending  upward  and  backward  from  the  position  of  the  fang  of  the  last  molar  tooth 
to  the  posterior  part  of  the  hard  palate.  This  is  caused  by  the  pterygo-maxillary  ligament, 
which  is  attached  by  one  extremity  to  the  apex  of  the  internal  pterygoid  plate,  and  by  the  other 
to  the  posterior  extremity  of  the  mylo-hyoid  ridge  of  the  lower  jaw.  It  connects  the  Buccinator 
with  the  Superior  constrictor  of  the  pharynx.  The  fang  of  the  last  molar  tooth  indicates  the 
position  of  the  lingual  (gustatory)  nerve  where  it  is  easily  accessible,  and  can  with  readiness 
be  divided  in  cases  of  cancer  of  the  tongue  (see  page  1043).  On  the  inner  side  of  the  last  molar 
tooth  we  can  feel  the  hamular  process  of  the  internal  pterygoid  plate  of  the  sphenoid  bone, 
around  which  the  tendon  of  the  Tensor  palati  plays.  The  exact  position  of  this  process  is  of 
importance  in  performing  the  operation  of  siaphylorrhaphy  .  About  one-third  of  an  inch  in 
front  of  the  hamular  process,  and  the  same  distance  directly  inward  from  the  last  molar  tooth, 
is  the  situation  of  the  opening  of  the  posterior  palatine  canal,  through  which  emerges  the  pos- 
terior or  descending  palatine  branch  of  the  internal  maxillary  artery  and  one  of  the  descending 
palatine  nerves  from  Meckel's  ganglion.  The  exact  position  of  the  opening  on  the  subject  may 
be  ascertained  by  driving  a  needle  through  the  tissues  of  the  palate  in  this  situation,  when  it 
will  be  at  once  felt  to  enter  the  canal.  The  artery  emerging  from  the  opening  runs  forward  in  a 
groove  in  the  bone  just  internal  to  the  alveolar  border  of  the  hard  palate,  and  may  be  wounded 
in  the  operation  for  the  cure  of  cleft  palate.  Under  these  circumstances  the  palatine  canal  may 
require  plugging.  By  introducing  the  finger  into  the  mouth  the  anterior  border  of  the  coronoid 
process  of  the  jaw  can  be  felt,  and  it  is  especially  prominent  when  the  jaw  is  dislocated.  By 
throwing  the  head  well  back  a  considerable  portion  of  the  posterior  wall  of  the  pharynx  may  be 
seen  through  the  isthmus  faucium,  and  on  introducing  the  finger  the  anterior  surface  of  the 
bodies  of  the  upper  cervical  vertebrae  may  be  felt  immediately  beneath  the  thin  muscular 
stratum  forming  the  wall  of  the  pharynx.  The  finger  can  be  hooked  around  the  posterior 
border  of  the  soft  palate,  and  by  turning  it  forward  the  posterior  nares,  separated  by  the 
septum,  can  be  felt,  or  the  presence  of  any  adenoid  or  other  growths  in  the  naso-pharynx  can 
be  ascertained. 

THE  PHARYNX  (Figs.  831,  837,  838). 


The  pharynx  (from  (pdpuys,  the  throat]  is  that  part  of  the  alimentary  canal 
which  is  placed  behind  and  communicates  with  the  nose,  mouth,  and  larynx.  It 
is  a  musculo-membranous  tube,  somewhat  conical  in  form,  with  the  base  upward 
and  the  apex  downward,  extending  from  the  under  surface  of  the  skull  to  the  level 
of  the  cricoid  cartilage  in  front  and  that  of  the  intervertebral  disk  between  the  fifth 
and  sixth  cervical  vertebrae  behind. 

The  pharynx  is  about  four  inches  and  a  half  in  length,  and  broader  in  the  trans- 
verse than  in  the  antero-posterior  diameter.  Its  greatest  breadth  is  opposite  the 
cornua  of  the  hyoid  bone  ;  its  narrowest  point,  at  its  termination  in  the  oesophagus. 
It  is  attached,  above,  to  the  periosteum  of  the  petrous  portion  of  the  temporal 
bone  and  of  the  basilar  process  of  the  occipital  bone.  To  the  pharyngeal  tubercle 
of  the  basilar  process  of  the  occipital  bone  the  raphe  of  the  Constrictor  muscles  is 
attached.  It  is  bounded  above  by  the  body  of  the  sphenoid  as  well  as  by  the  basilar 
process  of  the  occipital  ;  below,  it  is  continuous  with  the  oesophagus  ;  posteriorly,  it 
is  connected  by  loose  areolar  tissue  with  the  cervical  portion  of  the  vertebral 
column  and  the  Longi  colli  and  Recti  capitis  antici  muscles;  this  areolar  tissue  is 
contained  in  what  is  called  the  retro-pharyngeal  space  (spatia  retropharyngeus]  ; 
anteriorly,  it  is  incomplete,  the  gap  being  occupied  by  the  cavities  of  the  nose, 
mouth,  and  larynx.  Anteriorly,  it  is  attached  in  succession  to  the  Eustachian  tube, 
the  internal  pterygoid  plate,  the  pterygo-maxillary  ligament,  the  posterior  termi- 
nation of  the  mylo-hyoid  ridge  of  the  lower  jaw,  the  mucous  membrane  of  the 
mouth,  the  base  of  the  tongue,  hyoid  bone,  the  thyroid  and  cricoid  cartilages; 
laterally,  it  is  connected  to  the  styloid  processes  and  their  muscles,  and  is  in  con- 
tact with  the  common  and  internal  carotid  arteries,  the  internal  jugular  veins, 
and  the  glosso-pharyngeal,  vagus,  hypoglossal,  and  sympathetic  nerves,  and 
above  with  a  small  part  of  the  Internal  pterygoid  muscles.  When  the  pharynx 


THE  PHARYNX 


1231 


is  at  rest  the  anterior  and  posterior  walls  are  near  together.  Above  the  larynx 
they  do  not  come  in  contact,  but  leave  a  channel  for  air;  below  the  larynx  they 
lie  in  contact,  but  open  for  the  passage  of  food.  It  has  seven  openings  com- 
municating with  it — the  two  posterior  nares,  the  two  Eustachian  tubes,  the 
mouth,  larynx,  and  oesophagus.  The  pharynx  may  be  subdivided  from  above 
downward  into  three  parts,  nasal,  oral,  and  laryngeal. 

The  Nasal  Part  (pars  nasalis  pharyngis)  (Fig.  837). — The  nasal  part  of  the 
pharynx  or  naso-pharynx  lies  behind  the  nose  and  above  the  level  of  the  soft  palate; 
it  differs  from  the  two  lower  parts  of  the  tube  in  that  its  cavity  always  remains 
patent.  In  front  it  communicates  through  the  posterior  nares  (choanae)  (Fig.  838) 
with  the  nasal  fossae.  On  its  lateral  wall  is  the  pharyngeal  orifice  of  the  Eustachian 
tube  (ostium  pharyngeum  tubae  auditivae)  (Figs.  835  and  836),  which  presents  the 
appearance  of  a  vertical  or  triangular  cleft  bounded  above  and  behind  by  a  firm 
prominence.  The  anterior  portion  of  the  prominence (labium  anterius)is  the  smaller 
portion.  The  posterior  portion  (labium  posterius)  is  large  and  thick,  is  called  the 
Eustachian  cushion  (torus  tubarius),  and  is  caused  by  the  inner  extremity  of  the  car- 
tilage of  the  tube  impinging  on  the  deep  surface  of  the  mucous  membrane  (Fig. 836) . 
A  vertical  fold  of  mucous  membrane,  the  salpingo-pharyngeal  fold  (plica  salpingo- 


ORIFICE    OF 

EUSTACHIAN 

TUBE 

PHARYNGEAL 

BURSA 


FIG.  835. — Pharyngeal  tonsil  in  an  adult. 
(Eacat.) 


SALPINGO- 

NASAL  FOLD 

EUSTACHIAN 

CUSHION 

SALPINGO 
PALATINE  FOLD 


SALPINGO-PHARYN- 
GEAL FOLD 

FIG.  836. — The  posterior  lateral  cavity  of  the  naso- 
pharynx.    (Escat.) 


pharyngea)  (Fig.  836),  stretches  from  the  lower  part  of  the  cushion  to  the  pharynx; 
it  contains  the  Salpingo-pharyngeus  muscle.  A  second  and  smaller  mucous  fold 
may  be  seen  stretching  from  the  upper  part  of  the  cushion  to  the  palate,  the 
salpingo-palatine  fold  (plica  salpingopalatina)  (Fig.  836).  Behind  the  orifice  of  the 
Eustachian  tube  is  a  deep  recess,  the  lateral  recess  or  fossa  of  Rosenmtiller  (recessus 
pharyngeus)  (Fig.  836),  which  represents  the  remains  of  the  upper  part  of  the  sec- 
ond branchial  cleft.  The  posterior  wall  of  the  naso-pharynx  is  directed  upward  and 
forward,  and  it  meets  the  superior  wall  at  an  angle.  This  rounded  area  of  meet- 
ing is  the  vault  of  the  pharynx  (fornix  pharyngis).  On  the  posterior  wall,  at  the 
level  and  above  the  level  of  the  orifices  of  the  Eustachian  tubes,  there  is  a  col- 
lection of  lymphoid  tissue.  This  is  particularly  marked  in  children,  and  almost 
or  quite  disappears  in  the  aged.  Over  it  the  mucous  membrane  is  thick  and 
in  folds.  This  collection  of  lymphoid  tissue  is  the  pharyngeal  tonsil  (fonsilla 
pharyngea)  (Fig.  835).  The  naso-pharynx  communicates  with  the  oral  pharynx 
through  an  aperture  between  the  soft  palate  and  the  posterior  pharyngeal  wall. 
This  aperture  is  the  isthmus  of  the  pharynx  (isthmus  pharyngonasalis). 

The  Oral  Part  (pars  oralis  pharyngis). — The  oral  part  of  the  pharynx  reaches 
from  the  soft  palate  to  the  level  of  the  hyoid  bone.  It  opens  anteriorly,  through 
the  isthmus  faucium,  into  the  mouth,  while  in  its  lateral  wall,  between  the  two 


1232 


THE    ORGANS    OF  DIGESTION 


pillars  of  the  fauces,  is  the  tonsil.  A  triangular  area  on  the  lateral  wall  is  known  as 
the  sinus  tonsillaris  (Fig.  837) .  It  is  bounded  anteriorly  by  the  anterior  palatine 
arch,  posteriorly  by  the  posterior  palatine  arch,  and  below  by  the  side  of  the 
pharyngeal  portion  of  the  tongue. 

The  Laryngeal  Part  (pars  laryngea  pharyngis). — The  laryngeal  part  of  the 
pharynx  is  that  division  which  lies  behind  the  larynx ;  it  is  wide  above  where  it  is  con- 
tinuous with  the  oral  portion  while  below  at  the  lower  border  of  the  cricoid  cartilage 
it  becomes  continuous  with  the  oesophagus.  In  front  it  presents  the  triangular 
aperture  of  the  larynx,  the  base  of  which  is  directed  forward  and  is  formed  by  the 
epiglottis,  while  its  lateral  boundaries  are  constituted  by  the  aryteno-epiglottidean 
folds.  On  either  side  of  the  laryngeal  orifice  is  a  recess,  termed  the  sinus  pyri- 


OPENING   OF 

STENSON'S 

DUCT 


GENIO- 

HVOGLOSSUS 
MUSCLE 


BURSA  BENEATH 
HYOID  BONE 


THYROID 
CARTILAGE 


CRICOID 
CARTILAGE 


PHARYNGEAL 
BURSA 


ORIFICE    OF 
EUSTACHIAN  TUBE 


PHARYNGEAL 
TONSIL 


SOFT    PALATE 


NASOPHARYNX 


ANTERIOR   PALA- 
TINE ARCH 
POSTERIOR  PALA- 
TINE ARCH 
TONSIL 
CAVITY  OF 
PHARYNX 
TONSILLAR 
SINUS 


POSTERIOR  PALA- 
TINE ARCH 


EPIGLOTTIS 


SINUS 

-PYRIFORMIS 
ARYTENO- 
E  PI  GLOTTIC 
FOLD 

CUNEIFORM 
CARTILAGE 


ARYTENOID 
CARTILAGE 


OESOPHAGUS 


RING  OF 
TRACHEA 


FIG.  837. — Sagittal  median  section  of  the  head  and  neck.    The  head  is  thrown  backward  into  complete  extension, 
which  explains  the  relations  between  the  lower  jaw  and  the  hyoid  bone  as  seen  in  the  figure.     (Luschka.) 

formis  (recessus  piriformis)  (Fig.  837);  it  is  bounded  internally  by  the  aryteno- 
epiglottidean  fold,  externally  by  the  thyroid  cartilage  and  thyro-hyoid  membrane. 
In  the  anterior  part  of  the  sinus  pyriformis  is  a  fold  (plica  uervi  laryngei),  which 
passes  downward  and  inward.  Extending  outward  from  the  epiglottis  on  each 
side  is  a  fold,  the  pharyngo-epiglottic  fold  (plica  pharyngoepiglottica).  This  ascends 
in  the  lateral  wall  of  the  pharynx,  nearly  to  the  posterior  arch  of  the  fauces. 

Structure. — The  constrictors  of  the  pharynx  (see  p.  402)  are  surrounded  by 
a  sheath  of  thin  fascia,  the  bucco-pharyngeal  fascia  (Cunningham).    Forward  pro- 


THE   PHARYNX 


1233 


longations  of  this  fascia  overlay  the  Buccinator  muscles.  The  connective  tissue  of 
the  retro-pharyngeal  space  joins  the  bucco-pharyngeal  fascia  to  the  prevertebral 
fascia,  and  it  is  attached  by  areolar  tissue  to  the  other  structures  to  which  the 
pharynx  is  in  contact  (Cunningham).  The  pharynx  is  composed  of  three  coats 
— fibrous,  mucous  and  muscular. 

The  Pharyngeal  Aponeurosis  or  Fibrous  Coat  is  situated  between  the  mucous 
and  muscular  layers.  It  is  thick  above,  where  the  muscular  fibres  are  wanting,  and 
is  firmly  connected  to  the  periosteum  of  the  basilar  process  of  the  occipital  and 
petrous  portion  of  the  temporal  bones.  It  is  united  to  the  Eustachian  tube,  pos- 
terior nares,  and  other  points  which  the  pharynx  joins.  It  is  thicker  above  than 
below,  and  above  the  sinuses  of  Morgagni  there  is  no  muscular  coat,  and  the  wall 


FIG.  838. — The  anterior  surface  of  the  pharynx.     (Sappey.) 

of  the  pharynx  is  composed  of  aponeurosis  and  mucous  membrane.  As  it  descends 
it  diminishes  in  thickness,  and  is  gradually  lost.  It  is  strengthened  posteriorly  by 
a  strong  fibrous  band  which  is  attached  above  to  the  pharyngeal  spine  on  the  under 
surface  of  the  basilar  portion  of  the  occipital  bone,  and  passes  downward,  forming 
a  median  raphe,  which  gives  attachment  to  the  Constrictor  muscles  of  the  pharynx. 
The  Mucous  Coat  (tunica  mucosa). — The  mucous  coat  is  continuous  with  that 
lining  the  Eustachian  tubes,  the  nares,  the  mouth,  and  the 'larynx.  In  the  naso- 
pharynx it  is  covered  by  columnar  ciliated  epithelium;  in  the  buccal  and  laryngeal 
portions  the  epithelium  is  of  the  squamous  variety.  Beneath  the  mucous  membrane 
are  found  racemose  mucous  glands  (glandulae  pharyngeae) ;  they  are  especially 
numerous  at  the  upper  part  of  the  pharynx  around  the  orifices  of  the  Eustachian 
tubes.  Throughout  the  pharynx  are  also  numerous  crypts  or  recesses,  the  walls, 

;<  a 


1234  THE    ORGANS   OF  DIGESTION 

of  which  are  surrounded  by  lymphoid  tissue  similar  to  that  found  in  the  tonsils. 
Across  the  back  part  of  the  pharyngeal  cavity,  between  the  two  Eustachian  tubes, 
a  considerable  mass  of  this  tissue  exists,  and  has  been  named  the  pharyngeal  tonsil 
(Fig.  835).  Above  this  in  the  middle  line  is  an  irregular,  flask-shaped  depres- 
sion of  the  mucous  membrane,  extending  up  as  far  as  the  basilar  process  of  the 
occipital  bone.  It  is  known  as  the  pharyngeal  bursa  (bursa  pharyngea),  and  was 
regarded  by  Luschka  as  the  remains  of  the  diverticulum,  which  is  concerned  in 
the  development  of  the  anterior  lobe  of  the  pituitary  body.  Other  anatomists 
believe  that  it  is  connected  with  the  formation  of  the  pharyngeal  tonsils.  The 
muscular  coat  (tunica  muscularis  pharyngis)  has  been  already  described  (p.  402). 
The  sinuses  of  Morgagni,  referred  to  on  a  previous  page  (p.  404),  are  intervals 
between  the  Superior  constrictor  muscles  and  the  basilar  process  of  the  occipital 
bone. 

The  Lymphatic  Pharyngeal  Ring. — This  name  was  applied  by  Waldeyer  to  the 
lymphatic  structure  gathered  into  a  sort  of  ring  about  the  pharynx.  There  are 
three  chief  collections  of  this  tissue  on  each  side.  The  first  is  known  as  the  lingual 
tonsil  (p.  1098);  the  second  as  the  palatine  tonsil  (p.  1222);  and  the  third  as  the 
pharyngeal  tonsil  (p.  1231). 

Surgical  Anatomy  of  the  Mouth,  Cheeks,  Lips,  Gums,  Tonsils,  Palate,  Salivary  Glands, 
and  Pharynx. — The  duct  of  a  salivary  gland  may  be  blocked  by  a  calculus,  and  the  condition 
is  often  productive  of  severe  pain. 

A  wound  of  Stenson's  duct  or  of  the  parotid  gland  may  be  followed  by  a  salivary  fistula. 

The  parotid  recess  is  completely  lined  by  fascia,  except  above.  "Between  the  anterior  edge 
of  the  styloid  process  and  the  posterior  border  of  the  external  pterygoid  muscle  there  is  a  gap 
in  the  fascia,  through  which  the  parotid  space  communicates  with  the  connective  tissue  about 
the  pharynx."1 

This  explains  why  there  is  frequently  swelling  of  the  parotid  region  in  post-pharyngeal  abscess. 
A  parotid  abscess  rarely  bursts  through  the  skin;  it  may  pass  into  the  temporal  fossa,  may 
enter  the  zygomatic  fossa,  may  advance  toward  the  mouth,  pharynx,  or  neck.  Because  of  the 
situation  of  thj  gland,  a  parotid  abscess  may  cause  inflammation  of  the  temporo-mandibular 
joint  or  periostitis  of  the  bone  about  the  meatus,  and  may  even  burst  into  the  external  auditory 
meatus  (Treves). 

The  facial  nerve  passes  through  the  gland,  and  inflammation  or  tuberculosis  of  the  gland 
may  cause  facial  palsy.  Some  enlargements  of  the  parotid  region  are  due  to  inflammation  of 
the  parotid  lymph-glands,  and  these  glands  may  become  tuberculous. 

Mumps  is  characterized  by  acute  inflammation  of  the  parotid  gland. 

Various  tumors  occur  in  the  parotid  (fibroma,  sarcoma,  carcinoma,  enchondroma,  etc.). 
Most  parotid  tumors  contain  more  or  less  cartilage.  Complete  extirpation  of  the  parotid  gland 
surgically  is  certainly  extremely  difficult,  and  Treves  and  others  maintain  that  it  is  impossible. 

Ranula  is  a  salivary  cyst  of  the  floor  of  the  mouth,  due  to  occlusion  of  ducts  of  the  sublingual 
gland  or  the  duct  of  the  submaxillary  gland.  Mucous  cysts  occur  in  the  mouth.  A  mucous  cyst 
of  the  gland  of  Nuhn  and  Blandin  is  on  the  under  surface  of  the  tongue  near  the  apex.  A 
dermoid  cyst  of  the  base  of  the  tongue  is  occasionally  encountered.  It  is  of  congenital  origin. 

What  is  known  as  the  sublingual  bursa  is  an  epithelial-lined  space,  said  to  exist  between 
the  mucous  membrane  of  the  floor  of  the  mouth  and  the  Genio-hyo-glossus  muscle.  When 
acutely  inflamed,  it  produces  rapidly  a  marked  swelling  called  acute  ramda.  Incomplete 
closure  of  the  oral  end  of  the  thyro-glossal  duct  causes  thyro-glossal  fistula.  If  the  oral  end  closes, 
but  a  portion  of  the  duct  below  remains  unobl iterated,  a  thyro-glossal  cyst  forms.  Such  a  cyst 
or  fistula  is  always  in  the  median  line.  The  reader  will  remember  that  this  duct  runs  from  the 
foramen  caecum  to  the  isthmus  of  the  thyroid  gland. 

Hare-lip  is  considered  on  pp.  110  and  111. 

The  lower  lip,  more  commonly  than  any  other  structure,  gives  origin  to  cancer.  The  upper 
lip  is  not  nearly  so  often  affected.  Blocking  of  mucous  glands  of  the  lips  causes  mucous  cysts. 
A  scar  of  the  lip  or  about  the  lip  disturbs  this  structure  and  pulls  it  far  out  of  place.  Thus 
great  deformity  is  produced.  Burns  particularly  induce  hideous  cicatricial  contraction. 

Plastic  operations  in  this  region  are  often  successful,  because  of  the  great  vascularity  of  the 
parts,  and  because  adjacent  parts  admit -of  being  stretched  and  pulled  in. 

Cleft  palate  is  a  by  no  means  rare  congenital  deformity.  The  cleft  is  in  the  middle  line. 
It  may  be  a  mere  cleft  of  the  uvula,  it  may  be  limited  to  the  soft  palate,  or  it  may  involve 

1  Applied  Anatomy.      By  Sir  Frederick  Treves. 


THE    OESOPHAGUS  1235 

the  hard  palate  to  but  not  including  the  alveolus.  It  may  pass  through  the  alveolus,  but  if  it 
does  so  it  ceases  to  be  median  at  this  point,  and  follows  the  line  of  suture  between  the  incisive 
bone  and  the  superior  maxillary  (pp.  110  and  111).  In  a  complete  cleft  palate  there  is  apt 
to  be  hare-lip  at  the  end  of  the  palate  cleft.  This  cleft  in  the  lip  is  not  median,  but  is  at  the 
termination  of  the  palate  cleft.  If  the  cleft  of  a  cleft  palate  runs  along  each  side  of  the 
incisive  bone,  the  bone  is  isolated  from  the  superior  maxillary.  In  such  a  case  double  hare-lip 
results. 

When  a  tonsil  enlarges  it  projects  inward.  The  deafness  which  so  often  attends  hypertrophy 
of  the  tonsil  is  not  due  to  blocking  of  the  Eustachian  orifice  by  the  tonsil,  but  is  due  to  thicken- 
ing of  the  mucous  membrane  lining  the  tube  itself.  The  profuse  bleeding  which  sometimes 
follows  an  operation  for  the  removal  of  the  tonsil  is  very  seldom  due  to  injury  of  the  internal, 
carotid  artery,  but  is  due  to  injury  of  the  ascending  pharyngeal  artery  (p.  623)  or  one  of  the 
palatine  arteries. 

The  internal  carotid  artery  is  in  close  relation  with  the  pharynx,  so  that  its  pulsations  can 
be  felt  through  the  mouth.  It  has  been  occasionally  wounded  by  sharp-pointed  instruments 
introduced  into  the  mouth  and  thrust  through  the  wall  of  the  pharynx.  In  aneurism  of  this 
vessel  in  the  neck  the  tumor  necessarily  bulges  into  the  pharynx,  as  this  is  the  direction  in 
which  it  meets  with  the  least  resistance,  nothing  lying  between  the  vessel  and  the  mucous 
membrane  except  the  thin  Constrictor  muscle,  whereas  on  the  outer  side  there  is  the  dense 
cervical  fascia,  the  muscles  descending  from  the  styloid  process,  and  the  margin  of  the  Sterno- 
mastoid  muscle. 

The  mucous  membrane  of  the  pharynx  is  very  vascular,  and  is  often  the  seat  of  inflamma- 
tion, frequently  of  a  septic  character,  and  dangerous  on  account  of  its  tendency  to  spread  to  the 
larynx.  On  account  of  the  tissue  which  surrounds  the  pharyngeal  wall  being  loose  and  lax,  the 
inflammation  is  liable  to  spread  through  it  far  and  wide,  extending  downward  into  the  posterior 
mediastinum  along  the  oesophagus.  Abscess  may  form  in  the  connective  tissue  behind  the 
pharynx,  between  it  and  the  vertebral  column,  constituting  what  is  known  as  retro-pharyngeal 
abscess.  This  is  most  commonly  due  to  caries  of  the  cervical  vertebrae,  but  may  also  be  caused 
by  suppuration  of  a  lymphatic  gland  which  is  situated  in  this  position  opposite  the  axis,  and 
which  receives  lymphatics  from  the  nares,  or  by  gumma  or  by  acute  pharyngitis.  In  these 
cases  the  pus  may  be  easily  evacuated  by  an  incision,  with  a  guarded  bistoury,  through  the 
mouth,  but;  for  aseptic  reasons,  it  is  desirable  that  the  abscess  should  be  opened  from  the  neck. 
In  some  instances  this  is  perfectly  easy;  the  abscess  can  be  felt  bulging  at  the  side  of  the  neck 
and  merely  requires  an  incision  for  its  relief;  but  this  is  not  always  so,  and  then  an  incision 
should  be  made  along  the  posterior  border  of  the  Sterno-mastoid  and  the  deep  fascia  should 
be  divided.  A  director  is  now  to  be  inserted  into  the  wound,  the  forefinger  of  the  left  hand 
being  introduced  into  the  mouth  and  pressure  made  upon  the  swelling.  This  acts  as  a  guide, 
and  the  director  is  to  be  pushed  onward  until  pus  appears  in  the  groove.  A  pair  of  sinus  forceps 
are  now  inserted  along  the  director  and  the  opening  into  the  cavity  dilated. 

Foreign  bodies  not  infrequently  become  lodged  in  the  pharynx  and  most  usually  at  its  termi- 
nation at  about  the  level  of  the  cricoid  cartilage,  just  beyond  the  reach  of  the  finger,  as  the 
distance  from  the  arch  of  the  teeth  to  the  commencement  of  the  oesophagus  is  about  six  inches. 

Hypertrophy  of  the  adenoid  tissue  of  the  naso-pharynx  produces  groups  of  hypertrophic 
masses  known  as  adenoids.  A  child  with  adenoids  has  a  cough,  and  when  awake  or  asleep, 
breathes  noisily  and  with  the  mouth  open.  The  voice  is  muffled,  the  hearing  is  impaired,  the 
expression  is  vacant,  the  mind  is  dull,  and  the  tonsils  are  enlarged. 


THE  OESOPHAGUS  (Figs.  839,  840,  841,  842). 


The  oesophagus  (oi'to,  oi'oto,  I  carry;  <paf£iu,  to  eat}  or  gullet  is  a  muscular 
canal,  averaging  about  nine  or  ten  inches  in  length,  extending  from  the  pharynx 
to  the  stomach.  It  commences  at  the  upper  border  of  the  cricoid  cartilage,  oppo- 
site the  intervertebral  disk  between  the  fifth  and  sixth  cervical  vertebrae,  descends 
along  the  front  of  the  spine  through  the  posterior  mediastinum,  passes  through 
the  Diaphragm,  and,  entering  the  abdomen,  terminates  in  the  stomach  wall  at  the 
point  known  as  the  cardia  opposite  the  tenth  thoracic  vertebra  or  possibly  opposite 
the  intervertebral  disk  between  the  tenth  and  eleventh  thoracic  vertebrae.  The 
general  direction  of  the  oesophagus  is  vertical,  but  it  presents  two  or  three  slight 
curves  in  its  course.  At  its  commencement  it  is  placed  in  the  median  line,  but 
it  inclines  to  the  left  side  as  far  as  the  root  of  the  neck,  gradually  passes  to  the 
middle  line  again,  and  finally  again  deviates  to  the  left  as  it  passes  forward  to 


1236 


THE    ORGANS    OF   DIGESTION 


the  oesophageal  opening  of  the  Diaphragm  (hiatus  oesophageus) .  The  oesophagus 
also  presents  an  antero-posterior  flexure,  corresponding  to  the  curvature  of  the 
cervical  and  thoracic  portions  of  the  spine.  It  is  the  narrowest  part  of  the  alimen- 
tary canal,  being  most  contracted  at  its  commencement  and  at  the  point  where 
it  passes  through  the  Diaphragm. 

The  diameter  of  the  largest  portion  of  the  oesophagus  where  it  is  contracted  is 
about  half  an  inch;  when  it  is  fully  dilated,  an  inch  or  even  more. 

In  the  neck  the  oesophagus,  when  at  rest,  is  flattened,  the  anterior  and  posterior 
•  walls  approaching  each  other.  The  canal  in  the  neck  is  round  or  oval,  and  the 
lumen  is  stellate  (Cunningham).  The  oesophagus  is  somewhat  constricted  at  three 
points.  One  constriction  is  at  the  very  beginning  of  the  tube;  another  is  where 
the  left  bronchus  crosses  it;  another  is  at  the  point  where  the  oesophagus  passes 
through  the  Diaphragm.  The  tube  at  each  constricted  point  is  distinctly  flattened. 
The  diameter  of  each  of  these  constricted  parts  is  slightly  under  one-half  inch, 
the  diameter  of  the  rest  of  the  tube  when  contracted  is  one-half  inch,  but  when 
dilated  may  reach  or  exceed  one  inch.  The  average  distance  from  the  upper 


AZYGOS   VEIN 


FIG.  839.— Pleural  cul-de-sac  of  the  posterior  mediastinum. 

incisor  teeth  to  the  beginning  of  the  gullet  is  about  six  inches;  the  average  distance 
from  the  incisor  teeth  to  the  cardiac  opening  of  the  stomach  is  fifteen  or  sixteen 
inches.  The  portion  of  the  oesophagus  which  is  in  the  neck  is  called  the  cervical 
portion  (pars  cervicalis) ;  the  portion  in  the  thorax,  the  thoracic  portion  ( pars  thora- 
calis),  and  the  portion  which  lies  in  the  oesophageal  opening  of  the  Diaphragm, 
the  diaphragmatic  portion.  The  margin  of  the  oesophageal  orifice  in  the  Diaphragm 
is  narrow  in  front,  thicker  behind  and  to  the  sides.  Behind  and  to  the  sides  the 
diaphragmatic  portion  of  the  oesophagus  is  about  half  an  inch  in  length.  In 
front  there  is  only  a  thin  edge  of  Diaphragm  in  contact  with  the  gullet.  The 
oesophagus  is  connected  to  the  margins  of  the  diaphragmatic  orifice  by  connec- 
tive tissue.  The  so-called  abdominal  portion  of  the  oesophagus  (pars  abdominalis) 
is  not  over  half  an  inch  in  length,  and  is  limited  to  the  small  portion  of  the  ante- 
rior and  left  lateral  surface  observed  when  a  stomach  which  is  completely 
empty  is  drawn  downward  with  considerable  force.  The  abdominal  portion  of 
the  oesophagus  is  covered  with  peritoneum;  the  corresponding  portions  of  the 
right  lateral  and  posterior  walls  are  not  covered  by  peritoneum.  This  uncov- 
ered portion  of  the  oesophagus  runs  downward  and  to  the  left  and  lies  directly 


THE    OESOPHAGUS 


1237 


.OESOPHAGUS 


behind  the  oesophageal  groove  on  the  posterior  surface  of  the  left  lobe  of  the 
liver,  but  does  not  actually  touch  the  groove,  which  in  reality  holds,  the  thick, 
right  edge  of  the  oesophageal  opening  of  the  Diaphragm.  When  the  stomach  is 
distended  the  abdominal  portion  of  the  gullet  ceases  to  exist  and  becomes  part 
of  the  stomach  wall. 

Relations. — In  the  neck  the  oesophagus  is  in  relation,  in  front,  with  the  trachea, 
and  it  is  connected  to  the  posterior  wall  of  the  trachea  by  areolar  tissue.    At  the 
lower  part  of  the  neck,  where  it  projects  to  the  left 
side,  it  is  in  relation  in  front  with  the  thyroid  gland 
and  thoracic  duct;  behind,  it  rests  upon  the  vertebral 
column  and  Longi  colli  muscles;  on  each  side,  it  is  in 
relation  with  the  common  carotid  artery  (especially  the 
left,  as  the  gullet  inclines  to  that  side)  and  part  of  the 
lateral  lobes  of  the  thyroid  gland;  the  recurrent  laryn- 
geal  nerves  ascend  between  it  and  the  trachea. 

In  the  thorax,  it  is  at  first  situated  a  little  to  the  left 
of  the  median  line;  it  then  passes  behind  the  aortic 
arch,  being  separated  from  it  by  the  trachea,  and  de- 
scends in  the  posterior  mediastinum,  along  the  right 
side  of  the  aorta,  nearly  to  the  Diaphragm,  where  it 
passes  in  front  and  a  little  to  the  left  of  the  artery, 
previous  to  entering  the  abdomen.  It  is  in  relation, 
in  front,  with  the  trachea,  the  arch  of  the  aorta,  the 
left  common  carotid  and  left  subclavian  arteries,  which 
incline  toward  its  left  side,  the  left  bronchus,  the 
pericardium,  and  the  Diaphragm;  behind,  it  rests 
upon  the  vertebral  column,  the  Longi  colli  muscles, 
the  right  intercostal  arteries,  and  the  vena  azygos 
minor;  and  below,  near  the  Diaphragm,  upon  the  front 
of  the  aorta;  laterally,  it  comes  in  contact  with  both 
pleurae,  especially  with  the  left  pleura  above  and  the 
right  pleura  below;  it  overlaps  the  vena  azygos  major, 
which  lies  on  its  right  side,  while  the  descending  aorta 
is  placed  on  its  left  side.  The  vagus  nerves  descend 
in  close  contact  with  it,  the  right  nerve  passing  down 
behind,  and  the  left  nerve  in  front  of  it,  each  nerve 
spreading  out  into  a  plexus,  the  oesophageal  plexus, 
around  the  tube.  The  two  plexuses  are  joined  to  each 
other.  The  right  nerve  forms  the  posterior  oesophageal 
plexus  (plexus  oesophageus  posterior);  the  left  nerve 
the  anterior  oesophageal  plexus  (plexus  oesophageus 
anterior). 

In  the  lower  part  of  the  posterior  mediastinum  the 

thoracic  duct  lies  to  the  right  side  of  the  oesophagus;  higher  up,  it  is  placed 
behind  it,  and,  crossing  about  the  level  of  the  fourth  thoracic  vertebra,  is  continued 
upward  on  its  left  side. 

Above  the  aortic  arch  and  the  arch  of  the  great  azygos  vein  above  the  root 
of  the  right  lung,  the  pleurae  are  close  to  but  not  in  actual  contact  with  the 
oesophagus. 

Below  the  arch  of  the  great  azygos  vein  the  right  side  of  the  oesophagus  is 
covered  with  pleura  nearly  to  the  diaphragmatic  opening.  The  posterior  surface 
of  the  gullet  also  may  be  covered  with  pleura.  Below  the  arch  of  the  aorta  on 
the  left  side  the  pleura  covers  only  a  small  portion  of  the  oesophagus,  that  is,  a 
portion  of  the  left  wall,  a  little  above  the  diaphragmatic  opening, 


.DIAPHRAGM 


FIG.  840.— The  supports  of  the 
oesophagus  at  the  aorta  in  an  in- 
fant. (Poirier  and  Charpy.) 


1238 


THE    ORGANS    OF   DIGESTION 


Anomalies. — There  may  be  openings  of  the  oesophagus  into  the  trachea.  A 
diverticulum  or  pressure  pouch  may  exist.  Such  a  pouch  is  usually  placed  upon 
the  posterior  wall  near  the  pharynx.  There  may  be  congenital  constriction,  tubular 
or  annular. 

Structure. — The  oesophagus  is  fastened  to  adjacent  structures  by  connective 
tissue  called  the  tunica  adventitia.  The  tube  has  three  coats — an  external  or 
muscular,  a  middle  or  areolar,  and  an  internal  or  mucous  coat. 

The  Muscular  Coat  (tunica  muscularis}. — The  muscular  coat  is  composed  of  two 
planes  of  fibres  of  considerable  thickness,  an  external  plane  of  longitudinal  and 
an  internal  plane  of  circular  fibres. 


LEFT 

PULMONARY 
ARTERY 

LEFT  LUNG 
LEFT  BRONCHI 

THORACIC  CANAL' 


VAGUS    NERVE 


AZYGOS  VEIN 


SUPERIOR   LARYN- 
GEAL  NERVE 


INTERNAL 

JUGULAR  VEIN 
'       TRACHEA 
NFERIOR 
THYROID   ARTERY 

RECURRENT 
NERVE 

SUBCLAVICULAR 
ARTERY 

RIGHT  CEPHALIC- 
TRUNK 
•OESOPHAGUS 

VAGUS   NERVE 

AZYGOS  VEIN 

RONCHIAL 
ARTERY 

|  RIGHT  PUL- 
[—  MONARY  VEIN: 


FIG.  841. — The  position  and  relation  of  the  oesophagus  in  the  cervical  region  and  in  the  posterior  mediastinum. 

Seen  from  behind.    (Poirier  and  Charpy.) 

The  Longitudinal  Fibres  are  arranged,  at  the  commencement  of  the  tube,  in  three 
fasciculi:  one  in  front,  which  is  attached  to  the  vertical  ridge  on  the  posterior 
surface  of  the  cricoid  cartilage;  and  one  at  each  side,  which  is  continuous  with 
the  fibres  of  the  Inferior  constrictor  of  the  pharynx  ;  as  they  descend  they 
blend  together  and  form  a  uniform  layer,  which  covers  the  outer  surfaae  of  the 
tube. 

Accessory  slips  of  muscular  fibres  are  described  by  Cunningham  as  passing 
between  the  oesophagus  and  the  left  pleura  (m.  pleurooesophageus),  where  it  covers 
the  thoracic  aorta,  or  between  the  oesophagus  and  the  root  of  the  left  bronchus 
(m.  bronchooesophageus) ,  or  the  back  of  the  pericardium,  as  well  as  other  still  more 


THE    OESOPHAGUS 


1239 


rare  accessory  fibres.  In  Fig.  842,  taken  from  a  dissection  in  the  Museum  of  the 
Royal  College  of  Surgeons  of  England,  several  of  these  accessory  slips  may  be  seen 
passing  from  the  oesophagus  to  the  pleura,  and  two  slips  passing  to  the  back  of 
the  trachea  just  above  its  bifurcation.  These  slips  of  muscular  fibres  which  pass 
to  adjacent  structures  give  support  to  the  oesophagus.  Below,  the  longitudinal 
fibres  of  the  oesophagus  are  continued  into  the  longitudinal  fibres  of  the  stomach. 

The  Circular  Fibres  are  continuous  above  with  the  Inferior  constrictor  of  the 
pharynx;  their  direction  is  transverse  at  the  upper  and  lower  parts  of  the  tube, 
but  oblique  in  the  central  part.  Below,  the  circular  fibres  pass  into  the  circular 
and  oblique  fibres  of  the  stomach. 

The  muscular  fibres  in  the  upper  part  of  the  oesophagus  are  of  a  red  color,  and 
consist  chiefly  of  the  striped  variety,  but  below  they  consist  for  the  most  part  of 
involuntary  muscular  fibre.  At  the  cardia  they  act 
as  a  sphincter  to  solid  food.  Some  maintain  that 
this  sphincter  is  closed  tonically,  others  that  it  opens 
and  closes  rhythmically  during  gastric  digestion. 

The  Submucous  or  Areolar  Coat  (tela  submucosa).— 
The  submucous  or  areolar  coat  connects  loosely  the 
mucous  and  muscular  coats.  It  consists  of  dense 
connective  tissue  and  contains  blood-vessels,  nerves, 
and  oesophageal  glands  (glandulae  oesophageae).  The 
glands  are  mucous  glands  and  are  found  through- 
out the  length  of  the  gullet.  The  ducts  of  the  glands 
pass  through  the  muscularis  mucosae.  These  ducts 
are  surrounded  by  adenoid  tissue. 

The  Mucous  Coat  (tunica  mucosa). — The  mucous 
coat  is  thick,  of  a  reddish  color  above  and  pale 
below.  It  is  disposed  in  longitudinal  folds,  which 
disappear  on  distention  of  the  tube.  Its  surface  is 
studded  with  minute  papillae,  and  is  covered  through- 
out with  a  thick  layer  of  stratified  pavement  epithe- 
lium. The  mucous  coat  contains  glands  which  differ 
from  the  mucous  glands  of  the  submucous  tissue. 
They  are  branched  and  tubular  (Hewlett)  and  are 
called  the  superficial  glands.  There  are  two  chief 
groups  of  superficial  glands;  one  near  the  beginning, 
and  the  other  near  the  termination  of  the  oesophagus. 
The  ducts  of  the  superficial  glands  are  not  sur- 
rounded by  lymphoid  tissue  (Hewlett).  Beneath  the 
mucous  membrane,  between  it  and  the  submucous 
coat,  is  a  layer  of  longitudinally  arranged  non-striped 
muscular  fibres.  This  is  the  muscularis  mucosae 
(lamina  muscularis  mucosae) .  At  the  commencement 
it  is  absent,  or  only  represented  by  a  few  scattered 
bundles;  lower  down  it  forms  a  considerable  stratum. 

Vessels  of  the  Oesophagus. — The  larger  vessels  are  in  the  submucosa  and  send 
branches  to  the  mucosa  and  muscularis.  The  arteries  supplying  the  oesophagus 
are  derived  from  the  inferior  thyroid  branch  of  the  thyroid  axis  of  the  subclavian, 
from  the  descending  thoracic  aorta  and  the  bronchial  arteries,  and  from  the  gastric 
branch  of  the  coeliac  axis,  and  from  the  left  inferior  phrenic  of  the  abdominal  aorta. 
They  have  for  the  most  part  a  longitudinal  direction.  The  veins  are  gathered  into 
a  plexus  on  the  outer  surface  of  the  oesophagus.  This  plexus  receives  the  venous 
blood  from  the  walls  of  the  tube.  From  the  lower  portion  of  the  plexus  branches 
go  to  the  coronary  vein  of  the  stomach.  Higher  up  branches  go  to  the  azygos  veins 


FIG.  842. —  Accessory  muscular 
fibres  between  the  oesophagus  and 
pleura,  and  oesophagus  and  trachea. 
(From  a  preparation  in  the  Museum 
of  the  Royal  College  of  Surgeons  of 
England.) 


1240  THE  ORGANS  OF  DIGESTION 

and  thyroid  veins.  In  this  manner  a  communication  is  opened  between  the  portal 
veins  and  the  systemic  veins. 

Lymphatics  of  the  Oesophagus. — The  lymphatics  drain  into  the  inferior  deep 
cervical  glands  and  the  glands  of  the  posterior  mediastinum. 

Nerves  of  the  Oesophagus. — The  nerves  are  derived  from  the  vagus  and  from 
the  sympathetic;  they  form  a  plexus  in  which  are  groups  of  ganglion-cells  between 
the  two  layers  of  the  muscular  coats.  From  this  fibres  pass  to  supply  the  muscle, 
and  others  go  to  the  submucous  tissue  to  form  a  secondary  plexus.  It  is  usual 
to  regard  the  plexus  as  consisting  of  two  parts,  a  ventral  or  anterior  oesophageal 
plexus,  derived  from  the  left  vagus,  and  a  dorsal  or  posterior  oesophageal  plexus, 
derived  from  the  right  vagus.  These  two  plexuses  are  in  the  posterior  medias- 
tinum; they  communicate  with  each  other  and  contain  sympathetic  fibres. 

Movements  and  Innervation  of  the  Oesophagus. 

Movements. — When  liquid  is  swallowed  it  is,  as  pointed  out  by  Kronecker  and  Meltzer, 
suddenly  forced  into  the  gullet  by  the  contraction  of  the  Mylo-hyoid  muscle,  the  tube  playing 
a  practically  passive  part.1  In  the  passage  of  solid  and  semisolid  food  the  oesophagus  con- 
tracts. It  does  not  contract,  as  was  once  thought,  in  sections,  but  there  is  a  peristaltic  wave. 
"The  wave  at  a  given  point  lasts  in  the  neck  region, about  3.5  seconds,  and  from  five 
to  nine  seconds  in  the  thoracic  region.2  The  lower  end  of  the  oesophagus  or  cardia  has  a 
sphincter,  the  cardiac  sphincter.  It  is  usually  taught  that  this  sphincter  is  tonically  contracted. 
When  a  mouthful  of  food  is  swallowed  it  rests  above  the  sphincter  for  a  moment  and  is  then 
forced  through  by  muscular  contractions  (Kronecker  and  Meltzer).  If  several  acts  of  swallow- 
ing follow  each  other  rapidly  the  sphincter  relaxes  so  that  there  is  no  resistance  to  the  passage 
of  food.  In  cats  Dr.  Walter  B.  Cannon3  has  demonstrated  "rhythmical  relaxations  of  the 
cardia,  so  that  fluid  food  streams  from  the  stomach  into  the  oesophagus  even  above  the  level 
of  the  heart,  then  is  pressed  into  the  stomach  again  by  a  peristaltic  wave,  only  to  be  released 
a  moment  later  to  pour  into  the  oesophagus  anew." 

Innervation. — There  is  in  the  oesophagus  a  local  reflex,  but  peristalsis  is  dominated  by  the 
central  nerve  system.  "It  seems  probable  that  the  peristaltic  contractions  of  the  oesophagus, 
to  be  efficient,  must  be  supported  by  nervous  influences  from  outside.  In  this  respect  the 
oesophagus  is  different  from  the  remainder  of  the  alimentary  canal."4 

Surgical  Anatomy. — The  relations  of  the  oesophagus  are  of  considerable  practical  interest 
to  the  surgeon,  as  he  is  frequently  required,  in  cases  of  stricture  of  this  tube,  to  dilate  the  canal 
by  a  bougie,  when  it  is  of  importance  that  the  direction  of  the  oesophagus  and  its  relations 
to  surrounding  parts  should  be  remembered.  In  cases  of  malignant  disease  of  the  oesophagus, 
where  its  tissues  have  become  softened  from  infiltration  of  the  morbid  deposit,  the  greatest 
care  is  requisite  in  directing  the  bougie  through  the  strictured  part,  as  a  false  passage  may  easily 
be  made,  and  the  instrument  may  pass  into  the  mediastinum,  or  into  one  or  the  other  pleural 
cavity,  or  even  into  the  pericardium. 

The  student  should  also  remember  that  obstruction  of  the  oesophagus,  and  consequent 
symptoms  of  stricture,  are  occasionally  produced  by  aneurism  of  some  part  of  the  aorta  press- 
ing upon  the  tube.  In  such  a  case  the  passage  of  a  bougie  could  only  hasten  the  fatal  issue. 

In  passing  a  bougie  the  left  forefinger  should  be  introduced  into  the  mouth  and  the  epiglottis 
felt  for,  care  being  taken  not  to  throw  the  head  too  far  backward.  The  bougie  is  then  to  be 
passed  beyond  the  finger  until  it  touches  the  posterior  wall  of  the  pharynx.  The  patient  is 
now  asked  to  swallow,  and  at  the  moment  of  swallowing  the  bougie  is  passed  gently  down- 
ward, all  violence  being  carefully  avoided. 

It  occasionally  happens  that  a  foreign  body  becomes  impacted  in  the  oesophagus  and  can 
neither  be  brought  upward  nor  moved  downward.  When  all  ordinary  means  for  its  removal 
have  failed,  and  the  body  is  lodged  above  the  lower  one-third  of  the  gullet,  external  oesopha- 
gotomy  is  performed.  If  the  foreign  body  is  lodged  in  the  lower  one-third  of  the  gullet  the 
stomach  is  opened  (gaslrotomy)  and  the  foreign  body  is  extracted.  If  the  foreign  body  is 
allowed  to  remain  lodged  in  the  oesophagus,  extensive  inflammation  and  ulceration  may 
ensue.  In  one  case  the  foreign  body  ultimately  penetrated  the  intervertebral  substance,  and 
destroyed  life  t>y  inflammation  of  the  membranes  and  substance  of  the  cord. 

The  operation  of  oesophagotomy  is  thus  performed:  The  patient  being  placed  upon  his 
back,  with  the  head  and  shoulders  slightly  elevated,  an  incision,  about  four  inches  in  length, 

1  Recent  Advances  in  the  Knowledge  of  the  Movements  and  Innervation  of  the  Alimentary  Canal.    By  Walter 
B.  Cannon,  M.D.,  in  Medical  News,  May  20,  1905. 

2  Ibid.  3  Ibid.  «  Ibid. 


THE  ABDOMEN  1241 

should  be  made  on  the  left  side  of  the  trachea,  from  the  thyroid  cartilage  downward,  dividing 
the  skin,  Platysma,  and  deep  fascia.  The  edges  of  the  wound  being  separated,  the  Omo-hyoid 
muscle  should,  if  necessary,  be  divided,  and  the  fibres  of  the  Sterno-hyoid  and  Sterno-thyroid 
muscles  drawn  inward;  the  sheath  of  the  carotid  vessels,  being  exposed,  must  be  drawn  out- 
ward, and  retained  in  that  position  by  retractors:  the  oesophagus  will  now  be  exposed,  and 
should  be  divided  over  the  foreign  body,  which  can  then  be  removed.  Great  care  is  necessary 
to  avoid  wounding  the  thyroid  vessels,  the  thyroid  gland,  and  the  laryngeal  nerves. 

The  oesophagus  may  be  obstructed  not  only  by  foreign  bodies,  but  also  by  changes  in  its 
coats,  producing  stricture,  or  by  pressure  on  it  from  without  of  new-growths  or  aneurism,  etc. 

The  different  forms  of  stricture  are:  (1)  the  spasmodic,  occurring  in  neurotic  individuals,  and 
intermittent  in  character,  so  that  the  dysphagia  is  not  constant.  Spasmodic  stricture  of  the 
oesophagus  sometimes  occurs  in  cases  of  cancer  of  the  stomach  and  cancer  of  the  liver; 
(2)  fibrous,  due  to  cicatrization  after  injuries,  such  as  swallowing  corrosive  fluids  or  boiling 
water;  and  (3)  malignant,  usually  epitheliomatous,  in  its  nature.  Cancer  is  most  common 
either  at  the  upper  end  of  the  tube,  opposite  to  the  cricoid  cartilage,  or  at  its  lower  end  at  the 
cardiac  orifice.  Cicatricial  stricture  may  be  treated  by  gradual  dilatation.  If  a  stricture  is 
impassible  from  above,  the  stomach  may  be  opened,  an  instrument  passed  from  below,  and  a 
string  used  to  divide  the  stricture. 

The  operation  of  oesophagostomy  has  occasionally  been  performed  in  cases  where  the  stric- 
ture in  the  oesophagus  is  at  the  upper  part,  with  a  view  to  making  a  permanent  opening  below 
the  stricture  through  which  to  feed  the  patient,  but  the  operation  has  been  far  from  a  suc- 
cessful one,  and  the  risk  of  setting  up  diffuse  inflammation  in  the  loose  planes  of  connective 
tissue  deep  in  the  neck  is  so  great  that  it  wrould  appear  to  be  better,  if  any  operative  interference 
is  undertaken,  with  the  idea  of  forming  a  mouth  to  introduce  food,  to  perform  gastrostomy. 
The  operation  of  oesophagostomy  is  performed  in  the  same  manner  as  oesophagotomy,  but  the 
edges  of  the  opening  in  the  oesophagus  are  stitched  to  the  skin  incision.  Gastrostomy  is 
the  only  operation  to  be  thought  of  in  malignant  stricture. 


THE  ABDOMEN. 

The  abdomen  (from  abdo,  I  put  away  or  hide,  or  possibly  from  adeps,  fat)  is 
the  largest  cavity  in  the  body.  It  is  of  an  oval  form,  the  extremities  of  the  oval 
being  directed  upward  and  downward;  the  upper  one  being  formed  by  the  under 
surface  of  the  Diaphragm,  the  lower  by  the  upper  concave  surface  of  the  Levator 
ani  muscles.  In  order  to  facilitate  description,  it  is  artificially  divided  into  two 
parts:  an  upper  and  larger  part,  the  abdomen  proper;  and  a  lower  and  smaller 
part,  the  pelvis.  These  two  cavities  are  not  separated  from  each  other,  but  the 
limit  between  them  is  marked  by  the  brim  of  the  true  pelvis.  The  space  is  wider 
above  than  below,  and  measures  more  in  the  vertical  than  in  the  transverse 
diameter. 

The  abdomen  proper  differs  from  the  other  great  cavities  of  the  body  in  being 
bounded  for  the  most  part  by  muscles  and  fasciae,  so  that  it  can  vary  in  capacity 
and  shape  according  to  the  condition  of  the  viscera  which  it  contains;  but,  in 
addition  to  this,  the  abdomen  varies  in  form  and  extent  with  age  and  sex  (Fig. 
844).  In  the  adult  male,  with  moderate  distention  of  the  viscera,  it  is  oval  or 
barrel-shaped,  but  at  the  same  time  flattened  from  before  backward.  In  the  adult 
female,  with  a  fully  developed  pelvis,  it  is  conical  with  the  apex  above,  and  in 
young  children  it  is  conical  with  the  apex  below. 

Boundaries. — The  boundary  between  the  thorax  and  abdomen  is  the  Dia- 
phragm. This  muscle  forms  a  dome  over  the  abdomen,  and  the  cavity  extends 
high  into  the  bony  thorax,  reaching  to  the  level  of  the  junction  of  the  fourth  costal 
cartilages  with  the  sternum.  The  lower  end  of  the  abdomen  is  limited  by  the 
structures  which  clothe  the  inner  surface  of  the  bony  pelvis,  principally  the  Leva- 
tores  ani  and  Coccygei  muscles  on  either  side.  These  muscles  are  sometimes 
termed  the  Diaphragm  of  the  pelvis.  The  abdomen  proper  is  bounded  in  front  and 
at  the  sides  by  the  lower  ribs,  the  abdominal  muscles,  and  the  venter  ilii;  behind, 
by  the  vertebral  column  and  the  Psoas  and  Quadratus  lumborum  muscles;  above, 
by  the  Diaphragm;  below,  by  the  brim  of  the  pelvis.  The  muscles  forming  the 


1242 


THE    ORGANS    OF   DIGESTION 


boundaries  of  the  cavity  are  lined  upon  their  inner  surface  by  a  layer  of  fascia, 
differently  named,  according  to  the  part  which  it  covers. 


FIG.  843.; — Topography  of  thoracic  and  abdominal  viscera. 


THE  ABDOMEN 


1243 


The  abdomen  contains  (Fig.  843)  the  greater  part  of  the  alimentary  canal; 
some  of  the  accessory  organs  to  digestion — viz.,  the  liver  and  pancreas,  the  spleen, 
the  kidneys,  and  suprarenal  capsules.  Most  of  these  structures,  as  well  as  the 
wall  of  the  cavity  in  which  they  are  contained,  are  covered  by  an  extensive  and 
complicated  serous  membrane,  the  peritoneum  (Fig.  856). 

The  Apertures  in  the  Walls  of  the  Abdomen. — The  apertures  found  in  the  walls  of 
the  abdomen,  for  the  transmission  of  structures  to  or  from  it,  are  the  umbilicus,  for 
the  transmission  (in  the  foetus)  of  the  umbilical  vessels;  the  caval  opening  in  the 
Diaphragm,  for  the  transmission  of  the  postcava;  the  aortic  opening,  for  the 
passage  of  the  aorta,  vena  azygos  major,  and  thoracic  duct;  and  the  oesophageal 
opening,  for  the  oesophagus  and  vagus  nerves.  Below,  there  are  two  apertures 
on  each  side:  one  for  the  passage  of  the  femoral  vessels,  and  the  other  for  the 
transmission  of  the  'spermatic  cord  in  the  male,  and  the  round  ligament  in  the 
female. 


Male  Type 


Infantile  Type 


FIG.  844. — Schematic  outlines  of  the  abdomen. 


Regions  (Fig.  846). — For  convenience  of  description  of  the  viscera,  as  well  as 
of  reference  to  the  morbid  conditions  of  the  contained  parts,  the  abdomen  is  arti- 
ficially divided  into  nine  regions.  Thus,  if  two  circular  lines  are  drawn  around 
the  body,  the  one  through  the  extremities  of  the  ninth  ribs  where  they  join  their 
costal  cartilages,  and  the  other  through  the  highest  points  of  the  crests  of  the  ilia, 
the  abdominal  cavity  is  divided  into  three  zones — an  upper,  a  middle,  and  a 
lower.  If  two  parallel  lines  are  drawn  perpendicularly  upward  from  the  centre  of 
Poupart's  ligament,  each  of  these  zones  is  subdivided  into  three  parts — a  middle 
and  two  lateral.1 

The  middle  region  of  the  upper  zone  is  called  the  epigastric  (Im,  over;  faar^p^ 
the  stomach);  and  the  two  lateral  regions,  the  right  and  left  hypochondriac  (bno, 
under;  yovdpot,  the  cartilages}.  The  central  region  of  the  middle  zone  is  the 
mesogastric  or  umbilical;  and  the  two  lateral  regions,  the  right  and  left  lumbar.  The 
middle  region  of  the  lower  zone  is  the  hypogastric  or  pubic  region;  and  the  lateral 
regions  are  the  right  and  left  inguinal  or  iliac.  The  viscera  contained  in  these 
different  regions  are  the  following  (Fig.  846) : 

1  Anatomists  are  far  from  agreed  as  to  the  best  method  of  subdividing  the  abdominal  cavity.  Cunningham 
suggests  that  the  lower  line  should  encircle  the  body  on  a  level  with  the  highest  point  of  the  iliac  crest,  as  seen 
from  the  front — a  point  corresponding  with  a  prominent  tubercle  on  the  outer  lip  of  the  iliac  crest  about  two 
inches  behind  the  anterior  superior  spine.  Addison  (Journal  of  Anatonr"  and  Physiology,  vols.  xxxiv.  and 
xxxv.),  in  a  careful  analysis  of  the  abdominal  viscera  in  forty  subjects,  adopts  the  following  lines:  (1)  a 
median,  from  the  symphysis  pubis  to  the  ensiform  cartilage;  (2)  two  lateral  lines  drawn  vertically  through  a  point 
midway  between  the  anterior  superior  iliac  spine  and  the  symphysis  pubis  ;  (3)  an  upper  transverse  line  half-way 
between  the  symphysis  pubis  and  the  suprasternal  notch;  and  (4)  a  lower  transverse  line  midway  between  the 
last  and  the  upper  border  of  the  symphysis  pubis. — ED.  of  15th  English  edition. 

Joessel  draws  a  line  through  the  cartilaginous  ends  of  the  tenth  ribs:  a  line  through  the  two  anterior  superior 
spines  of  the  ilia.  On  each  side  he  carries  a  perpendicular  line  from  the  iliopectineal  eminence  to  the  hori- 
zontal line  connecting  the  tenth  ribs.  By  this  plan  the  highest  plane  is  subcostal. 


1244 


THE    ORGANS    OF  DIGESTION 


Right  Hypochondriac. 

The  greater  part  of  the 
right  lobe  of  the  liver, 
the  hepatic  flexure  of  the 
colon,  and  part  of  the 
right  kidney. 


Right  Lumbar. 

Ascending  colon,  part 
of  the  right  kidney,  and 
some  convolutions  of  the 
small  intestines. 


Right  Inguinal  or  Iliac. 

The  caecum  and  ver- 
miform appendix  and  a 
portion  of  the  ascending 
colon. 


Epigastric  Region. 

The  greater  part  of  the 
stomach,  including  both 
cardiac  and  pyloric  ori- 
fices, the  left  lobe  and 
part  of  the  right  lobe  of 
the  liver  and  the  gall- 
bladder, the  pancreas,  the 
duodenum,  the  supra- 
renal capsules,  and  parts 
of  the  kidneys. 

Umbilical  Region. 

The  transverse  colon, 
part  of  the  great  omentum 
and  mesentery,  transverse 
part  of  the  duodenum, 
and  some  convolutions  of 
the  jejunum  and  ileum, 
and  part  of  both  kidneys. 

Hypogastric  Region. 

Convolutions  of  the 
small  intestines,  the  blad- 
der in  children,  and  in 
adults  if  distended,  and 
the  uterus  during  preg- 
nancy. 


Left  Hypochondriac. 

The  fundus  of  the 
stomach,  the  spleen,  the 
extremity  of  the  pancreas, 
the  splenic  flexure  of  the 
colon,  and  part  of  the 
left  kidney. 


Left  Lumbar. 

Descending  colon,  part 
of  the  omentum,  part  of 
the  left  kidney,  and  some 
convolutions  of  the  small 
intestines. 


Left  Inguinal  or  Iliac. 

Sigmoid  flexure  of  the 
colon  and  a  portion  of 
the  descending  colon. 


The  regions  of  the  abdomen  as  described  in  the  new  nomenclature  are  shown 
in  Fig  845. 

If  the  anterior  abdominal  wall  is  reflected  in  the  form  of  four  triangular  flaps 
by  means  of  vertical  and  transverse  incisions — the  former  from  the  ensiform  car- 
tilage to  the  symphysis  pubis,  the  latter  from  flank  to  flank  at  the  level  of  the 
umbilicus — the  abdominal  or  peritoneal  cavity  is  freely  opened  into  and  the 
contained  viscera  are  in  part  exposed.1 

Above  and  to  the  right  side  is  the  liver,  situated  chiefly  under  the  shelter  of 
the  right  ribs  and  their  cartilages,  but  extending  across  the  middle  line,  and  reach- 
ing for  some  distance  below  the  level  of  the  ensiform  cartilage.  Below  and  to  the 
left  of  the  liver  is  the  stomach,  from  the  lower  border  of  which  an  apron-like  fold 
of  peritoneum,  the  great  omentum,  descends  for  a  varying  distance,  and  obscures, 
to  a  greater  or  lesser  extent,  the  other  viscera  (Fig.  874) .  Below  it,  however,  some 
of  the  coils  of  the  small  intestine  can  generally  be  seen,  while  in  the  right  and  left 
iliac  regions  respectively  the  caecum  and  the  sigmoid  flexure  of  the  colon  are  exposed. 
The  bladder  occupies  the  anterior  part  of  the  pelvis,  and,  if  distended,  will  project 
above  the  symphysis  pubis;  the  rectum  lies  in. the  concavity  of  the  sacrum,  but 
is  usually  obscured  by  the  coils  of  the  small  intestine. 

If  the  stomach  is  followed  from  left  to  right  it  will  be  found  to  be  continuous 
with  the  first  part  of  the  small  intestine,  or  duodenum,  the  point  of  continuity  being 
marked  by  a  thickened  ring  which  indicates  the  position  of  the  pyloric  valve. 


'  It  must  be  borne  in  mind  that,  although  the  term  abdominal  cavity  is  used,  there  is,  under  normal  con- 
ditions, only  a  potential  cavity  or  lymph-space,  since  the  viscera  are  everywhere  in  contact  with  the  parietes. — 
ED.  of  15th  English  edition. 


'«• 


.  LEW.S  EMERSON 


THE  ABDOMEN 


1245 


The  duodenum  passes  toward  the  under  surface  of  the  liver,  and  then,  curving 
downward,  is  lost  to  sight.  If,  however,  the  great  omentum  be  thrown  upward 
over  the  chest,  the  terminal  part  of  the  duodenum  will  be  observed  passing  across 
the  spine  toward  the  left  side,  where  it  becomes  continuous  with  the  coils  of  the 
small  intestine.  These  measure  some  twenty  feet  in  length,  and  if  followed  down- 
ward will  be  seen  to  end  in  the  right  iliac  fossa  by  opening  into  the  caecum,  the 
commencement  of  the  large  intestine.  From  the  caecum  the  large  intestine  takes 
an  arched  course,  passing  at  first  upward  on  the  right  side,  then  across  the  middle 
line  and  downward  on  the  left  side,  and  forming  respectively  the  ascending,  trans- 
verse, and  descending  parts  of  the  colon.  In  the  left  iliac  region  it  makes  still 
another  bend,  the  sigmoid  flexure,  and  then  follows  the  curve  of  the  sacrum  as 
far  as  the  rectum. 


REGIO  INGUINALIS 


FIG.  845. — Regions  of  the  abdomen  as  described  in  the  new  nomenclature. 

The  spleen  lies  behind  the  stomach  in  the  left  hypochondriac  region,  and  may 
be  in  part  exposed  by  pulling  the  stomach  over  toward  the  right  side. 

The  glistening  appearance  of  the  deep  surface  of  the  abdominal  wall  and  of 
the  exposed  viscera  is  due  to  the  fact  that  the  former  is  lined  and  the  latter  more 
or  less  completely  covered  by  a  serous  membrane,  the  peritoneum. 

Development  of  the  Alimentary  Canal,  Viscera  and  Peritoneum. — When 
the  paraxial  mesoblast  of  the  embryo  has  developed  a  series  of  transverse  seg- 
mentations it  becomes  converted  into  a  row  of  dark,  square  segments  known  as 
the  protovertebrae  or  the  mesoblastic  somites,  which  are  separated  by  clear,  trans- 
verse intervals.  They  appear  first  in  the  region  that  is  to  become  the  neck,  and 
from  there  extend  back  along  the  entire  length  of  the  trunk.  These  bodies  are 
not  solely  the  representatives  of  the  future  permanent  vertebrae,  but  differentiate 
partly  into  muscles  and  true  skin. 

On  each  side  of  the  protovertebrae  the  lateral  mesoblast  splits  into  two  layers. 
The  upper  layer  is  applied  to  the  epiblast,  and  forms  with  it  the  somatopleure  or 
body- wall.  The  lower  layer  becomes  adherent  to  the  hypoblast,  and  forms  the 
splanchnopleure  or  wall  of  the  alimentary  canal.  The  space  between  these  two 


1246 


THE  ORGANS  OF  DIGESTION 


layers  is  the  caelum  or  the  pleuroperitoneal  cavity.  This  body-cavity  is  of  large 
size  in  the  early  stages  of  the  development  of  the  embryo. 

Anteriorly — or,  if  the  body  is  in  the  erect  posture,  superiorly — there  is  developed 
a  comparatively  large  space  called  the  pericaxdiothoracic  cavity;  and  a  transverse 
fold  develops,  which  marks  off  this  cavity  from  the  future  abdominal  cavity.  This 
fold,  with  many  veins  of  large  size,  develops  into  the  primary  Diaphragm,  although 
its  dorsal  part  remains  incomplete.  The  dorsal  part  is  completed  at  a  later  period, 
constituting  the  Diaphragm  as  we  see  it  in  the  adult.  As  Dr.  Frederick  J.  Brock- 
way  expresses  it :  "The  Diaphragm  is  thus  made  up  of  a  ventral,  younger  part,  and 
a  dorsal,  older  part.  When  this  posterior  part  fails  to  develop,  there  is  opportunity 
for  a  congenital  diaphragmatic  hernia  to  be  present." 

The  pericardiothoracic  cavity  becomes  divided  into  three  cavities,  and  the  two 
lateral  ones  are  for  a  time  continuous  with  the  abdominal  cavity.  This  continuation 
is,  however,  but  temporary,  and  they  are  afterward  separated.  In  this  manner, 
four  large  serous  sacs  are  formed.  The  two  lateral  thoracic  sacs  are  known  as 


Limit 


FIG.  846. — The  regions  of  the  abdomen  and  their  contents.     Edge  of  costal  cartilages  in  dotted  outline. 


the  pleural  sacs,  and  are  lined  with  the  pleura;  the  median  thoracic  sac  is  the 
pericardial  sac,  and  is  lined  with  the  pericardium ;  and  the  abdominal  sac  forms  the 
abdominal  cavity,  and  is  lined  with  the  peritoneum. 

The  primitive  alimentary  canal,  which  was  formed  early  by  the  closure  within 
the  embryo  of  a  portion  of  the  blastodermic  vesicle,  consists  of  three  parts:  first, 
the  fore-gut,  within  the  cephalic  flexure,  dorsal  to  the  heart;  second,  the  mid-gut, 
opening  freely  into  the  yolk-sac;  and  third,  the  hind-gut,  within  the  caudal  flexure. 
In  the  fore-gut  are  developed  the  back  portion  of  the  mouth,  the  tongue,  the 
pharynx,  the  oesophagus,  the  stomach,  the  larger  part  of  the  duodenum,  and  the 


THE  ABDOMEN 


1247 


organs  that  have  grown  out  from  these  structures.  The  hind-gut  forms  a  portion 
of  the  colon  and  the  rectum,  with  the  exception  of  the  latter's  anal  end ;  and  the 
mid-gut  gives  rise  to  the  remainder  of  the  digestive  tube. 

Development  of  the  Alimentary  Canal. — The  fore-gut  and  hind-gut  end 
blindly,  there  being  at  first  neither  mouth  nor  anus  (Figs.  847  and  848).    The  upper 


ky 


FIG.  847. — Diagrammatic  outline  of  a  longitudinal  vertical  section  of  the  chick  on  the  fourth  day:  ep,  epi- 
blast;  am,  somatic  mesoblast;  hy,  hypoblast;  vm,  visceral  mesoblast;  af,  cephalic  fold;  pf,  caudal  fold;  am, 
cavity  of  true  amnion;  ys,  yolk-sac;  i,  intestine;  s,  fore-gut;  a,  future  anus,  still  closed;  TO,  the  mouth;  we,  the 
mesentery;  al,  the  allantoic  vesicle;  pp,  space  between  inner  and  outer  folds  of  amnion.  (From  Quain's  Anat- 
omy, Allen  Thomson.) 

part  of  the  fore-gut  becomes  dilated  to  form  the  pharynx,  in  relation  to  which  the 
branchial  arches  are  developed  (Fig.  850);  the  succeeding  part  remains  tubular, 
and  with  the  descent  of  the  stomach  is  elongated  to  form  the  oesophagus.  Soon 
a  fusiform  dilatation,  the  future  stomach,  makes  its  appearance,  and  beyond  this 
the  mid-gut  opens  freely  into  the  yolk-sac  (Figs.  850  and  851). 

This  opening  is  at  first  wide,  but,  as  the  body-walls  close  in  around  the  umbilicus, 
it  is  gradually  narrowed  into  a  tubular  stalk,  the  yolk-stalk  or  vitello-intestinal  duct. 


Amnion 


-Alluntois 
Hind-gut 


Fore-gut  /  Heart 

Chorda  Dorsalis 


FIG.  848. — Diagram  of  a  longitudinal  section  of  a  mammalian  embryo.     Very  early.     (After  Quain.) 

At  this  stage,  therefore  the  alimentary  canal  forms  a  nearly  straight  tube  in  front 
of  the  notochord  and  primitive  aorta  (Fig.  848).  From  the  stomach  to  the  rectum 
it  is  attached  to  the  notochord  bv  a  band  of  mesoblast,  from  which  the  common 


1248 


THE  ORGANS  OF  DIGESTION 


T, 


mesentery  of  the  gut  is  subsequently  developed.     The  stomach  undergoes  a  further 
dilatation,  and  its  two  curvatures  can  be  recognized   (Figs.  852  and  855),  the 

greater  directed  toward  the  verte- 
bral column  and  the  lesser  toward 
the  anterior  wall  of  the  abdomen, 
wThile  of  its  two  surfaces  one  looks 
to  the  right  and  the  other  to  the  left. 
The  mid-gut  also  undergoes  great 
elongation,  and  forms  a  V-shaped 
loop  which  projects  downward  and 
forward ;  from  the  bend  or  angle  of 
the  loop  the  vitello-intestinal  duct 
passes  to  the  umbilicus  (Fig.  855). 
For  a  time  a  part  of  the  loop  ex- 
tends beyond  the  abdominal  cavity 
into  the  umbilical  cord,  but  by 
the  end  of  the  third  month  this 
is  withdrawn.  With  the  length- 


ening of  the  tube,  the  mesoblast, 
which  attaches  it  to  the  future  ver- 
tebral column  and  which  carries  the 


FIG.  849. — Early  form  of  the  alimentary  canal.  In  A  a 
front  view  and  in  B  an  antero-posterior  section  are  repre- 
sented, a.  Four  pharyngeal  or  visceral  plates.  6.  The 
pharynx,  c,  c.  The  commencing  lungs.  d.  The  stomach. 

/  /    The  diverticula  connected   with   the  formation  of  the     •  i         i  i      »         .1  iJ!iU 

liver    g  The  yolk-sac  into  which  the  middle  intestinal  groove     blOOd-VCSSelS  tor  the   Supply  OI    ttie 

afPteerBischTohrTe)posteriorparto  ""'   gut,  is  thinned  and  drawn  out  to 

form  the  primitive  or  common  me- 
sentery. The  portion  of  this  mesentery  which  is  attached  to  the  greater  curva- 
ture of  the  stomach  is  named  the  mesogastrium,  and  the  parts  which  suspend 


Midbrain. 


Cerebellum.- ~, 

Pharyngeal  septum.— 

Pharynx.- 

Auditory  pitr 

Aortic  bulb.- 

Stomach.--\ J 


•Optic  vesicle. 


Stomodseum. 
Ventricle. 


Cloacal  dilatation- 
of  hind-gut. 


Allantoic  stalk." 
Umbilical  vein  •:. 


..Liver. 


^.Mid-gut  and  yolk 
stalk. 


^Hind-gut. 


FIG.  850. — Human  embryo,  about  fifteen  days  old.     Brain  and  heart  represented  from  right  side; 
alimentary  canal  and  yolk-sac  in  mesial  section.      (After  His.) 

the  colon  and  rectum  are  respectively  termed  the  mesocolon  and  mesorectum 
(Fig.  855).  About  the  sixth  week  a  lateral  diverticulum  makes  its  appear- 
ance a  short  distance  beyond  the  vitello-intestinal  duct,  and  indicates  the  future 


THE  ABDOMEN 


1249 


caecum  or  boundary  between  the  small  and  the  large  intestine.  This  caecal  divertic- 
ulum  has  at  first  a  uniform  calibre,  but  its  blind  extremity  remains  rudimentary 
and  forms  the  vermiform  appendix  (Figs.  855  and  856).  Changes  also  take  place 

Rathke's  pouch 
Notochord,        (pituitary  involution). 


Lung  diver-, 
ticulum. 
Stomach. 


Liver.  -I — 


Opening  into, 
yolk  sac. 


AQantoie.-r— 


-  .\-Blind  portion  of 
hind-gut.   ' 

'-Wolffian  duct. 
A 


Lung  diverticulum 
(Esophagus.  ^ 


Median  rudiment  of 
I  thyroid  gland. 

,Mandibular  arch. 


Rathke's 
pouch 
(pituitary 
involution). 


Allantois.  -  -\ 


Blind  portion  of 
hind-gut. 


_/  -Wolffian  duct. 


FIG.  851. — Sketches  in  profile  of  two  stages  in  the  development  of  the  human  alimentary  canal 
Fig.  A  X  30.     Fig.  B  X  20.     (His.) 

in  the  position  and  direction  of   the  stomach.      It  falls   over  on  its  right  sur- 
face, which  henceforth  is  directed  backward,  while  its  original  left  surface  looks 

79 


1250 


THE  ORGANS  OF  DIGESTION 


forward ;  further,  its  greater  curvature  is  drawn  downward  and  to  the  left,  away 
from  the  vertebral  column,  while  its  lesser  curvature  is  directed  .upward,  and  the 
commencement  of  ^he  duodenum  is  pushed  over  to  the  right  side  of  the  middle 
line.  The  mesogastrium,  being  attached  to  the  greater  curvature,  must  necessarily 
follow  its  movements,  and  hence  it  becomes  greatly  elongated  and  drawn  outward 
from  the  vertebral  column,  and,  like  the  stomach,  what  was  originally  its  right 
surface  is  now  directed  backward  and  its  left  forward.  In  this  way  a  pouch,  the 
bursa  omentalis,  is  formed  behind  the  stomach;  this  pouch  is  the  future  lesser  sac 
of  the  peritoneum,  and  it  increases  in  size  as  the  alimentary  tube  undergoes  further 
development;  the  entrance  to  the  pouch  constitutes  the  future  foramen  of  Winslow 
(Figs.  852,  856,  and  859).  The  remainder  of  the  mid-gut  becomes  greatly 
increased  in  length,  so  that  the  tube  is  coiled  on  itself,  and  this  increase  in  length 
demands  a  corresponding  increase  in  the  width  of  the  intestinal  attachment  of 
the  mesentery,  so  that  it  becomes  plaited  or  folded. 

At  this  stage  the  small  and  the  large  intestines  are  attached  to  the  vertebral 
column  by  a  common  mesentery,  the  coils  of  the  small  intestine  falling  to  the  right 
of  the  middle  line,  while  the  large  intestine  lies  on  the  left  side.1 


Trachea.- 


(Esophagus.- 


Stomach.- 


-Lung. 


-Trachea. 


-Pancreas. 


Bile  duct.. 


V-shaped  loop_ 
of  mid-gut. 

Vitello-intestinal  dnct- 
Cloaca.- 


Bile  duct. 
Pancreas. 


Lung. 
(Esophagus. 


Stomach. 


Csecum. 
Cloaca. 


FIG.  852. — Front  view  of  two  successive  stages  in  the  development  of  the  alimentary  canal.     (His.) 

The  gut  now  becomes  rotated  upon  itself,  so  that  the  large  intestine  is  carried 
over  in  front  of  the  small  intestine,  and  the  caecum  is  placed  immediately  below 
the  liver;  about  the  sixth  month  the  caecum  descends  into  the  right  iliac  fossa, 
and  the  large  intestine  now  forms  an  arch  consisting  of  the  ascending,  transverse, 
and  descending  portions  of  the  colon — the  transverse  portion  crossing  in  front 
of  the  duodenum  and  lying  just  below  the  greater  curvature  of  the  stomach; 
within  this  arch  the  coils  of  the  small  intestine  are  disposed  (Fig.  856).  Some- 
times the  downward  progress  of  the  caecum  is  arrested,  so  that  in  the  adult  it 
may  be  found  lying  immediately  below  the  liver  instead  of  in  the  right  iliac  region. 

Further  changes  take  place  in  the  bursa  omentalis  and  in  the  common  mesen- 
tery, and  give  rise  to  the  peritoneal  relations  seen  in  the  adult.  The  bursa  omen- 
talis, which  at  first  reaches  only  as  far  as  the  greater  curvature  of  the  stomach, 

1  Sometimes  this  condition  persists  throughout  life,  and  it  is  then  found  that  the  duodenum  does  not  cross 
from  the  right  to  the  left  side  of  the  vertebral  C9lumn,  but  lies  entirefy  on  the  right  side  of  the  mesial  plane, 
where  it  is  continued  into  the  jejunum;  the  arteries  to  the  small  intestine  (rami  intestini  tenuis)  also  arise  from, 
the  right  instead  of  the  left  side  of  the  superior  mesenteric  artery. 


THE  ABDOMEN 


1251 


grows  downward  to  form  the  great  omentum,  and  this  downward  extension  lies 

in  front  of  the  transverse  colon  and  the  coils  of  the  small  intestine.     The  anterior 

layer  of  the  transverse  mesocolon  is  at  first  quite 

distinct   from  the  posterior  wall   of  the  bursa 

omentalis,   but   ultimately  the  two   blend,  and 

hence  the  great  omentum  appears  as  if  attached  ,;,,,    >  g^  \        Right 

to  the  transverse  colon  (Figs.  859,  860,  and  861). 

The  mesentery  of  the  duodenum,  in  which  the 


_  rarenal 
capsule 


Liver 


ififfht 

suprarenal 

capsule 


Left 

suprarenal 

capsule 


FIG.  853. — Schematic  and  enlarged  cross-section  through 
the  body  of  a  human  embryo  in  the  region  of  the  mesogas- 
trium.  Beginning  of  third  month.  (Toldt.) 


Anterior  part  of  mesogastrium. 


Liver 


FIG.  854. — Same  section  as  in  Fig.  853,  at  end 
of  third  month.     (Toldt.) 


Aorta. 

Spleen. 

Mesogastrium. 
Codiac  axis. 

Pancreas. 


Superior  mesenteric 
artery. 


Mesentery. 


Inferior  mesenteric  artery. 


Hind-gut. 


rio.  855. — Abdominal  part  of  alimentary  canal  and  its  attachment  to  the  primitive  or  common  mesentery. 
Human  embryo  of  six  weeks.     (After  Toldt.)     (From  Kollmann's  Lntwickelungsgeschichte.) 


rudiment  of  the  pancreas  is  enclosed,  disappears,  and  so  this  part  of  the  gut 
becomes  fixed  to  the  posterior  abdominal  wall,  and  the  pancreas  lies  entirely 
behind  the  peritoneal  membrane.  The  mesenteries  of  the  ascending  and  descend- 


1252 


THE  ORGANS  OF  DIGESTION 


ing  parts  of  the  colon  disappear  in  the  majority  of  cases,  while  that  of  the  small 
intestine  assumes  the  oblique  attachment  characteristic  of  its  adult  condition. 

The  small  omentum  is  formed  by  a  thinning  of  the  mesoblast  or  anterior  primitive 
mesentery,  which  attaches  the  lesser  curvature  of  the  stomach  to  the  anterior 
abdominal  wall.  By  the  subsequent  growth  of  the  liver  this  leaf  of  mesobiast  is 


Duodenum. 
Mesentery. 


Small 
intestine. 

Yolk-stalk. 


Rectum. 


Duodenum. 


Mesocolon.  ~\  1 


Caecum. 
Vermiform 
appendix. 
Mesentery. 

Yolk-stalk. 


Greater 
curvature 
of  stomach. 
.Great  omen- 
tum. 

Point  where 
•  intestinal 
loops  cross 
each  other. 
•Mesocolon. 
Large  intes~ 

tine. 

•Small  intes- 
tine. 


Rectum. 
i 

FIG.  856. — Illustrating  two  stages  in  the  development  of  the  human  alimentary  canal  and  its  mesentery. 
The  arrow  indicates  the  entrance  to  the  bursa  omentalis.     (Hertwig.) 

divided  into  two  parts — viz.,  the  small  omentum  between  the  stomach  and  liver, 
and  the  falciform  ligament  between  the  liver  and  the  abdominal  wall  and  Dia- 
phragm (Fig.  858). 

The  anus  is  developed  as  a  slight  invagination  of  the  epiblast  a  short  distance 
in  front  of  the  posterior  end  of  the  hind-gut.     This  invagination  is  termed  the 

Septum  transversum. 


Liver. 


Mesogastrium 
(anterior  part) 


Umbilical  vein. 


Umbilical  cord. 


Aorta. 

Mesogastrium 
(posterior  part). 

Stomach. 


Intestinal 
V-shaped  loop. 

If- Mesentery. 

-Colon. 


FIG.  858. — The  primitive  mesentery  of  a  six  weeks'  human  embryo, 
half  schematic.      (Kollmann.) 

proctodaeum,  the  mesoblast  between  it  and  the  hypo- 
blastic  lining  of  the  hind-gut  is  thinned,  and  ultimately 
the  septum  breaks  down  and  disappears,  and  the  hind- 
gut  opens  on  the  surface;  into  this  part  of  the  hind- 
gut  the  urinary  and  generative  organs  open  for  a  time, 
and  so  constitutes  a  common  cloaca.  The  small  portion 
of  the  hind-gut  behind  the  orifice  of  the  anus  is  named 
the  caudal  or  post-anal  gut;  it  communicates  writh  the 
neural  tube  by  means  of  a  canal,  the  neurenteric  canal, 

already  referred  to.     Ultimately  the  post-anal  gut  becomes  obliterated,  and  itv 

together  with  the  neurenteric  canal,  finally  disappears. 


FIG.  857. — Final  disposition 
of  the  intestines  and  their  vas- 
cular relations:  A,  aorta;  H, 
hepatic  artery;  S,  splenic  artery; 
M,  Col,  branches  of  superior 
mesenteric  artery;  m,  m', 
branches  of  inferior  mesenteric 
artery.  (Jonnesco.) 


THE  ABDOMEN 


1253 


The  peritoneal  cavity  is  the  space  left  between  the  visceral  and  parietal  layers  of 
the  mesoblast,  and  the  serous  membrane  is  developed  from  these  layers. 

The  tongue  originates  from  the  floor  of  the  pharynx.  The  anterior  or  papillary 
portion  first  appears  as  a  rounded  elevation,  the  tuberculum  impar,  between  the 
ventral  ends  of  the  mandibular  and  hyoid  arches  (Fig.  862).  Between  the  third 
and  fourth  arches  a  second  larger  elevation  arises,  in  the  centre  of  which  is  a 
median  groove  or  furrow.  This  second  elevation  is  termed  the  furcula,  and  from 
it  the  epiglottis  is  developed,  while  the  median  furrow  becomes  the  entrance  to  the 
larynx  (Fig.  863).  The  tuberculum  impar  and  the  furcula  are  at  first  in  apposi- 
tion, but  are  soon  separated  by  a  ridge  produced  by  the  forward  growth  of  the 
second  and  third  arches.  This  ridge  gives  rise  to  the  posterior  part  of  the  tongue 
and  extends  forward  in  the  form  of  a  V,  so  as  to  embrace  between  its  two  limbs 
the  tuberculum  impar.  At  the  apex  of  the  V  there  is  a  pit-like  invagination  to 
form  the  middle  thyroid  rudiment,  and  this  depression  persists  as  the  foramen 
caecum  of  the  adult.  The  union  of  the  two  parts  of  the  tongue  is  indicated  even 
in  the  adult  by  a  V-shaped  depression,  the  apex  of  which  is  at  the  foramen  caecum, 
while  the  two  limbs  run  outward  and  forward  parallel  to  but  a  little  behind  the 
circumvallate  papillae,  which  are  therefore  developed  from  the  tuberculum  impar 
(Figs.  862,  863,  and  864).  The  tonsils  are  developed  from  the  second  branchial 
cleft,  and  make  their  appearance  between  the  fourth  and  fifth  months. 

The  liver  arises  in  the  form  of  two  diverticula  or  hollow  outgrowths  from  the 
ventral  surface  of  that  portion  of  the  fore-gut  which  afterward  becomes  the 


Mesogastrium 
anierius. 


Liver. 


Umbilical  vein. 


Border  of  the  anterior 
mesogastrium. 


Stomach 


ursa  omentalis. 


Pancreas. 

Mesogastrium 

posterius. 
Duodenum. 


Great  amentum. 

Transverse 
mesocolon. 

Transverse  colon. 


Fio.  859. — Schematic  figure  of  the  bursa  omentalw.  etc.      Human  embryo  of  eight  weeks.      (Kollmann.) 


duodenum  (Figs.  850  and  851).  The  outgrowths,  which  represent  the  right  and 
the  left  lobes,  respectively,  of  the  adult  liver,  give  off  solid  buds  of  cells,  which  grow 
into  columns  or  cylinders;  these  unite  with  one  another  in  every  direction  to  form 
a  close  network,  in  the  meshes  of  which  are  contained  the  capillary  blood-vessels. 
Some  of  these  columns  become  hollowed  out  and  form  the  bile-clucts,  while  the 
remainder  constitute  the  secreting  structure.  The  minute  ducts  thus  produced 
unite  to  form  the  right  and  left  hepatic  ducts;  while  the  common  bile-duct  is  devel- 
oped as  a  protrusion  from  the  duodenal  wall,  and  as  it  grows  the  liver  becomes 
shifted  away  from  the  duodenum.  The  gall-bladder  and  cystic  duct  are  formed  by 


1254 


THE    ORGANS    OF  DIGESTION 


a  hollow  evagination  from  the  wall  of  the  common  bile-duct.     About  the  third 
month  the  liver  almost  fills  the  abdominal  cavity.    From  this  period  the  relative 


Stomach 

Greater  curvature 

Anterior  lamella  of  greater  amentum 
Posterior  lamella  of  greater  amentum 

Transverse  colon 


Greater  amentum 


Diaphragm 

Liver 

Lesser  amentum 

Pancreas 

Transverse  mesocolon 
Duodenum 

Mesentery 
Small  intestine 


FIG.  860.  —  Illustrating  the  development  of  the  bursa  omentalis,  cavity  of  the  great  omentum  or  lesser  sac. 
Foetal  stage.     *  Lesser  sac.     (Hertwig.) 

Diaphragm 


Liver 


Stomach 

Greater  curvatun 

Posterior  lamella  of  greater  omentum 
Transverse  coloii 


Greater  omentum 


Leaser  omentum 

Pancreas 

Part  of  omentum  enclosing  pancreas 

Transverse  mesocolon 

Duodenum 


Mesentery 


Small  intestine 


FIG.  861. — Development  of  bursa  omentalis.     Infantile  stage.     Great  omentum  covers  the  intestines  and  has 
fused  with  the  transverse  mesocolon.     Pancreas  is  free  from  peritoneum  posteriorly.     (Hertwig.) 

development  of  the  liver  is  less  active,  more  especially  that  of  the  left  lobe,  which 
now  becomes  smaller  than  the  right;  but  up  to  the  end  of  foetal  life  the  liver 
remains  relatively  larger  than  in  the  adult. 


Mandibular  arch. 


Hyoid  arch. 


FIG.  862. — The  floor  of  the  pharynx  of  a  human  embryo  about  fifteen  days  old.     X  50.      (From  His.) 


The  pancreas  is  also  an  early  formation,  being  far  advanced  in  the  second 
month.  It  originates  as  a  hollow  projection  from  the  hypoblast  of  the  dorsal  wall 
of  the  duodenum  (Figs.  851  and  852),  opposite  the  hepatic  diverticula,  which,  as 
we  have  already  seen,  spring  from  its  ventral  wall.  This  hollow  process  grows 
between  the  two  layers  of  the  dorsal  mesentery  and  sends  out  offshoots,  which 


THE   PERITONEUM 


1255 


branch  abundantly  and  form  a  complicated  tubular  gland.  As  torsion  of  the 
stomach  takes  place,  the  pancreas  assumes  a  transverse  position  and  becomes  fixed 
across  the  dorsal  wall  of  the  abdomen,  the  posterior  layer  of  its  mesentery  under- 
going absorption.  Its  duct  ultimately  opens  into  the  duodenum  together  with  the 
common  bile-duct. 

The  spleen,  on  the  other  hand,  is  of  mesoblastic  origin,  for  there  is  never  any 
connection  between  the  intestinal  cavity  and  the  substance  of  this  organ.  It 
originates  in  the  mesenteric  fold  which  connects  the  stomach  to  the  vertebral 
column  (mesogastrium)  (Fig.  855). 

Tuberculum  impar  Posterior  part  of  tongue, 

(papillary  part  of  tongue). 

i 

Furcula. 

Mandibular  arch. 


Hyoid  arch. 


Entrance  to  larynx 

*• 


Third  arch. 
Fourth  arch. 


-  Lung. 

FIG.  863. — The  floor  of  the  pharynx  of  a  human  embryo  about  twenty-three  days  old.     X  30.      (From  His.) 
Papillary  portion  of  tongue. 


Mandibular  arch. 


Hyoid  arch. 


Foramen  csecum.     Posterior  part     Third  arch. 

of  tongue. 
FIG.  864. — Floor  of  mouth  of  an  embryo  slightly  older  than  that  shown  in  Fig.  863.      X  16.     (From  His.) 

THE  PERITONEUM  (TUNICA  SEROSA). 

During  life  and  in  the  uncut  corpse  the  peritoneal  cavity  (cavum  peritonaei)  is 
air-tight.  It  is  not  a  real  cavity,  as  muscular  tension  and  atmospheric  pressure 
permit  no  vacant  space  to  form.  When  the  surgeon  or  anatomist  opens  the 
abdomen,  the  peritoneal  cavity  is  at  that  moment  produced. 

The  peritoneum  (from  nepe,  about,  and  Tttoto,  I  stretch)  is  the  largest  serous 
membrane  in  the  body,  and  consists,  in  the  male,  of  a  closed  sac,  a  part  of  which 
is  applied  against  the  abdominal  parietes,  while  the  remainder  is  reflected  over 
the  contained  viscera.  In  the  female  the  peritoneum  is  not  a  closed  sac,  since  the 
free  extremities  of  the  Fallopian  tubes  open  directly  into  the  peritoneal  cavity. 
The  portion  of  the  peritoneum  applied  against  the  abdominal  parietes  consti- 
tutes the  parietal  peritoneum ;  the  portion  reflected  over  the  viscera,  the  visceral 
peritoneum.  The  free  surface  of  the  membrane  is  smooth,  covered  by  a  layer  of 
flattened  endothelium,  and  lubricated  by  a  small  cavity  of  serous  fluid.  Hence 
the  viscera  can  glide  freely  against  the  wall  of  the  cavity  or  upon  one  another  with 
the  least  possible  amount  of  friction.  Its  attached  surface  is  rough,  being  con- 


1256  THE  ORGANS  OF  DIGESTION 

nected  to  the  viscera  and  inner  surface  of  the  parieties  by  means  of  areolar  tissue 
termed  the  subserous  areolar  tissue  (tela  subserosa).  The  parietal  portion  is  loosely 
connected  with  the  fascia  lining  the  abdomen  and  pelvis,  but  more  closely  to  the 
under  surface  of  the  Diaphragm  and  also  in  the  middle  line  of  the  abdomen. 

The  peritoneum  differs  from  the  other  serous  membranes  of  the  body  in  pre- 
senting a  much  more  complex  arrangement — an  arrangement  which  can  only 
be  clearly  understood  by  following  the  changes  which  take  place  in  the  alimentary 
canal  during  its  development;  and  therefore  the  student  is  advised  to  preface  his 
study  of  the  peritoneum  by  reviewing  the  remarks  on  Embryology. 

Structure  of  the  Peritoneum. — It  is  a  thin,  glistening  serous  membrane  and 
consists  of  a  connective-tissue  layer  and  one  layer  of  flat  endothelial  cells  upon  the 
free  surface  of  the  membrane.  The  connective-tissue  layer  consists  of  bundles  of 
connective  tissue  which  contain  many  connective-tissue  cells  and  elastic  fibres. 
It  contains  a  multitude  of  lymph-spaces,  lymph-vessels,  and  lymph-capillaries. 
Beneath  the  peritoneum  is  a  layer  of  lax  and  spongy  connective  tissue  which  serves 
to  bind  the  serous  membrane  to  parts  beneath.  This  layer  is  called  the  subserous 
connective  tissue.  In  some  regions  it  is  plentiful;  in  others,  as  over  the  liver  and 
intestine,  it  is  very  scantily  developed.  The  endothelial  cells  are  flat  and  polyg- 
onal. Some  hold  that  they  are  joined  together  by  cement-substance.  Robinson 
asserts  that  there  is  no  cement-substance,  but  rather  an  organized  connection 
between  the  protoplasmic  processes  of  adjacent  cells. 

On  the  surface  of  the  endothelium  between  the  cells  numerous  apertures  or 
interruptions  are  to  be  seen.  These  openings  which  many  think  are  due  to  re- 
tracted epithelium  communicate  with  lymph-spaces  beneath  the  epithelial  layer. 
The  idea  is  held  by  some  that  the  openings  are  permanent  stomata  and  join 
lymphatic  capillaries.  Some  openings  which  are  noted,  the  stigmata  or  pseudo- 
stomata,  are  mere  interruptions  in  the  endothelial  layer,  and  are  occupied  by  pro- 
cesses of  the  branched  connective-tissue  corpuscle  of  the  subjacent  tissue. 

The  amount  of  fluid  contained  in  the  closed  sac  is,  in  most  cases,  only  sufficient 
to 'moisten  the  surface,  but  not  to  furnish  any  appreciable  quantity  of  free  liquid. 
When  a  small  quantity  can  be  collected,  it  is  found  to  resemble  lymph,  and,  like 
that  fluid,  coagulates  spontaneously;  but  when  present  in  large  quantities,  as 
in  dropsy,  it  is  a  more  watery  fluid,  but  still  contains  a  considerable  amount  of 
proteid  which  is  coagulated  on  boiling. 

The  peritoneum  contains  a  great  quantity  of  lymphatic  structures.  In  the 
subserous  tissue  the  numerous  lymph-spaces  obtain  fluid  from  the  peritoneal 
cavity.  The  subendothelial  interstitial  lymph-spaces  intercommunicate  and  can 
take  up  an  immense  quantity  of  fluid  from  the  peritoneal  cavity.  Normally  the 
spaces  contain  both  nutrient  material  and  waste  products.  Lymphatics  are  par- 
ticularly plentiful  in — 1,  the  tendinous  portion  of  the  Diaphragm;  2,  the  ligamenta 
lata;  3,  the  omentum;  4,  the  ventral  surface  of  the  small  intestine;  5,  the  liver  and 
spleen.1 

The  lymph  from  this  region  reaches  the  mediastinal  or  diaphragmatic  glands. 
The  serous  surface  of  the  Diaphragm  is  the  region  chiefly  efficient  in  absorption 
from  the  peritoneum,  and  there  is  a  current  in  the  peritoneal  cavity  directed  toward 
the  Diaphragm.2  Absorption  from  the  peritoneal  cavity  is  very  active.  Wegner 
has  shown  that  an  amount  of  fluid  equal  to  from  3  to  8  per  cent,  of  the  body 
weight  may  be  absorbed  in  one  hour.  Absorption  is  most  active  from  the  region 
of  the  Diaphragm  and  least  active  from  the  region  of  the  pelvis.  There  are  a 
multitude  of  nerves  in  the  peritoneum,  and  it  seems  probable  that  each  endothelial 
cell  receives  a  nerve  ending.  The  minute  arteries  of  the  peritoneum  are  surrounded 
by  nerve-plexuses.  According  to  Robinson,3  the  nerves  of  the  peritoneum  are: 

1  The  Peritoneum.     By  Byron  Robinson.  2  Ibid. 


THE  PERITONEUM  1257 

1.  Myelinic.  2.  Amyelinic.  3.  Fibres  of  Remak.  4.  The  Vater-Pacinian 
corpuscles  and  other  varieties  of  nerve  endings.  5.  Nerve-cells.  The  visceral 
peritoneum  contains  many  more  nerves  than  the  parietal  peritoneum. 

The  parietal  peritoneum  (peritonaeum  parietale)  lines  the  wall  of  the  abdominal 
cavity.  The  visceral  peritoneum  (peritonaeum  viscerale)  covers  the  viscera.  Back 
of  the  parietal  peritoneum  is  a  space,  the  retro-peritoneal  space  (spatium  retro- 
peritonaeale),  which  contains  the  great  vessels  and  nerves,  the  suprarenal  cap- 
sules, the  kidney,  and  ureters  (Figs.  866,  867,  868,  869,  and  870). 

We  describe  the  peritoneum  as  consisting  of  two  sacs,  a  greater  sac  and  a  lesser  sac 
(Fig.  866).  The  larger  part  of  the  abdominal  cavity  is  lined  by  the  greater  sac,  as  most 
of  the  viscera  are  covered  by  it.  The  lesser  sac  is  placed  largely  behind  the  stomach. 
These  two  sacs  are  not  two  distinct  cavities  which  communicate.  They' constitute 
one  cavity,  a  portion  of  which  has  been  formed  into  a  diverticulum  or  recess  by  a 
process  of  constriction,  the  result  of  changes  produced  in  the  position  of  adjacent 
viscera  by  development.  Prof.  Birmingham  says:  "If  the  great  sac  be  compared 
to  a  bag,  the  lesser  sac  might  be  represented  as  a  pocket  lying  behind,  and  open- 
ing into  it  by  a  narrow  orifice,  the  foramen  of  Winslow,  on  its  posterior  wall."1 
The  greater  sac  lines  the  walls  of  the  abdominal  cavity  and  covers  the  viscera 
which  are  invested  by  peritoneum,  except  the  posterior  portion  of  the  stomach, 
the  suprarenal  capsule  of  the  left  side,  the  superior  surface  of  the  pancreas,  the 
Spigelian  lobe  and  the  caudate  lobes  of  the  liver,  and  portions  of  the  spleen,  left 
kidney,  and  transverse  colon,  which  are  covered  by  peritoneum  of  the  lesser  sac.2 

To  trace  the  continuity  of  the  membrane  from  one  viscus  to  another,  and  from 
the  viscera  to  the  parietes,  it  is  necessary  to  follow  its  reflections  in  the  vertical 
and  horizontal  directions,  and  in  doing  so  it  matters  little  where  a  start  is  made. 

If  the  stomach  is  drawn  downward,  a  fold  of  peritoneum  will  be  seen  stretching 
from  its  lesser  curvature  to  the  transverse  fissure  of  the  liver  (Figs.  866  and  872). 
This  is  the  gastro-hepatic  or  lesser  omentum,  and  consists  of  two  layers;  these,  on 
being  traced  downward,  split  to  envelop  the  stomach,  covering  respectively  its 
anterior  and  posterior  surfaces.  At  the  greater  curvature  of  the  stomach  they 
again  come  into  contact  and  are  continued  downward  in  front  of  the  transverse 
colon,  forming  the  anterior  two  layers  of  the  great  or  gastro-colic  omentum  (Figs. 
866  and  874).  Reaching  the  free  edge  of  this  fold  they  are  reflected  upward  as 
its  two  posterior  layers,  and  thus  the  great  omentum  consists  of  four  layers  of 
peritoneum.  Followed  upward  the  two  posterior  layers  separate  so  as  to  enclose 
the  transverse  colon,  above  which  they  once  more  come  into  contact  and  pass 
backward  to  the  abdominal  wall  as  the  transverse  mesocolon  (mesocolon  trans- 
versum)  (Fig.  866).  Reaching  the  abdominal  wall  about  the  level  of  the  transverse 
part  of  the  duodenum,  the  two  layers  of  the  transverse  mesocolon  become  separated 
from  each  other  and  take  different  directions ;  the  upper  or  anterior  layer,  known 
as  the  ascending  layer  of  the  transverse  mesocolon,  ascends  in  front  of  the  pancreas, 
and  its  further  course  will  be  followed  presently  (Fig.  866).  The  lower  or  posterior 
layer  is  carried  downward,  as  the  anterior  layer  of  the  mesentery,  by  the  superior 
mesenteric  vessels  to  the  small  intestine,  around  which  it  may  be  followed  and 
subsequently  traced  upward  as  the  posterior  layer  of  the  mesentery  to  the  abdomi- 
nal wall.  From  the  posterior  abdominal  wall  it  sweeps  downward  over  the  aorta 
into  the  pelvis,  where  it  invests  the  first  part  of  the  rectum  and  attaches  it  to  the 
front  of  the  sacrum  by  a  fold  termed  the  mesorectum  (Fig.  866).  Leaving  first 
the  sides  and  then  the  front  of  the  second  part  of  the  rectum  it  is  reflected  on  to 
the  back  of  the  bladder,  and,  after  covering  the  posterior  and  upper  aspects  of 
this  viscus,  is  carried  by  the  urachus  and  obliterated  hypogastric  arteries  as  folds, 

1  Prof.  Cunningham's  Text-book  of  Human  Anatomy.  *  Ibid. 


1258  THE  ORGANS  OF  DIGESTION 

on  to  the  posterior  surface  of  the  anterior  abdominal  wall  (Fig.  865).  The  fold 
upon  the  urachus  is  the  plica  urachi  (plica  umbilicalis  media) ;  the  fold  on  each 
obliterated  hypogastric  artery  is  the  plica  hypogastrica  (plica  umbilicalis  lateralis). 
Between  the  rectum  and  bladder  it  forms  a  pouch,  the  recto-vesical  pouch  (exca- 
vatio rectovesicalis) ,  bounded  on  the  sides  by  two  crescentic  or  semilunar  folds 
(plicae  rectovesicales),  which  pass  from  the  posterior  surface  of  the  bladder  to  the 
sides  of  the  rectum;  the  bottom  of  this  pouch  is  about  on  a  level  with  the  middle 
of  the  vesiculae  seminales — i.  e.,  three  inches  or  so  from  the  orifice  of  the  anus. 
When  the  bladder  is  distended  the  peritoneum  is  carried  up  with  the  expanded 
viscus,  so  that  a  considerable  part  of  the  anterior  surface  of  the  latter  lies  directly 
against  the  abdominal  wall  without  the  intervention  of  the  peritoneal  membrane. 
When  the  bladder  is  empty  the  peritoneum  forms  a  transverse  fold  over  its  upper 
surface  (plica  vesicalis  transversa). 

In  the  female  the  peritoneum  is  reflected  from  the  rectum  on  the  upper  part 
of  the  posterior  vaginal  wall,  forming  the  recto-vaginal  pouch  or  pouch  of  Douglas 
(excavatio  rectouterina)  (Fig.  866).  In  the  pouch  of  Douglas  are  two  folds  of  peri- 
toneum (plica  rectouterinae) ,  which  begin  at  the  posterior  surface  of  the  cervix, 
extend  back  to  the  sides  of  the  rectum,  and  bound  above  the  deepest  portion  of  the 
pouch.  The  pouch  is  then  carried  over  the  posterior  aspect  and  fundus  of  the  uterus 
on  to  its  anterior  surface,  which  it  covers  as  far  as  the  junction  of  the  body  and 
cervix  uteri,  forming  here  a  second  but  shallower  depression,  the  utero-vesical 
pouch  (excavatio  vesicouterina) .  It  is  also  reflected  from  the  sides  of  the  uterus  to 
the  lateral  wall  of  the  pelvis  on  each  side  as  an  expanded  fold,  the  broad  ligament  of 
the  uterus  (ligamenum  latum  uteri) ,  in  the  free  margin  of  each  broad  ligament  can 
be  felt  a  thickened  cord-like  structure,  the  Fallopian  tube  (tuba  uterina  [Fallopii]). 

When  the  peritoneum  lining  the  anterior  abdominal  wall  is  examined  from 
behind,  it  is  noticed  that  certain  structures  which  lie  in  front  of  it  form  five  peri- 
toneal ridges  (Fig.  865).  The  structure  in  the  middle  line  is  the  urachus,  which  is 
the  remains  of  the  foetal  allantois.  In  the  adult  it  is  a  fibrous  cord  which  passes  from 
the  umbilicus  to  the  summit  of  the  bladder.  This  cord  is  slender  above,  but  broader 
below.  External  to  the  urachus  are  the  fibrous  cords  which  resulted  from  oblit- 
eration of  the  hypogastric  arteries  (arteriae  umbilicales) .  These  cords  become  more 
slender  as  they  ascend  toward  the  sides  of  the  urachus  and  pass  to  the  umbilicus. 
More  external  still  are  the  folds  formed  by  the  deep  epigastric  arteries.  The  fold 
over  each  epigastric  artery  is  the  plica  epigastrica;  the  fold  over  each  obliterated 
hypogastric  artery  is  the  plica  hypogastrica;  the  fold  over  the  obliterated  urachus 
is  the  plica  urachi. 

The  five  peritoneal  ridges  formed  by  the  above-named  structures  create  three 
peritoneal  fossae  on  each  side,  called  the  inguinal  fossae  or  pouches  (fovea  inguinales). 
The  external  inguinal  fossa  (fovea  inguinalis  lateralis)  is  external  to  the  deep  epi- 
gastric artery  and  corresponds  to  the  internal  abdominal  ring.  There  is  a  funnel- 
shaped  depression  in  its  floor  marking  the  point  at  which  the  inguinal  process 
passed  down.  This  depression,  if  marked,  predisposes  to  oblique  inguinal  hernia. 
The  middle  inguinal  fossa  (fovea  inguinalis  medialis)  is  placed  between  the  deep 
epigastric  arteries  and  the  obliterated  hypogastric  vessels.  The  internal  inguinal 
fossa  or  the  supravesical  fossa  (fovea  supravesicalis)  is  between  the  obliterated 
hypogastric  artery  and  the  urachus.  Just  beneath  the  inner  termination  of  Pou- 
part's  ligament  there  is  another  fossa,  the  femoral  or  crural  fossa  (fovea  femoralis), 
which  corresponds  to  the  situation  of  the  femoral  ring.  The  obliterated  hypo- 
gastric  artery  is  to  the  inner  side  of  this  fossa. 

On  following  the  parietal  peritoneum  upward  on  the  back  of  the  anterior 
abdominal  wall  it  is  seen  to  be  reflected  around  a  fibrous  band,  the  ligamentum 
teres  or  obliterated  umbilical  vein  (Figs.  868,  869,  and  870),  which  reaches  from  the 


THE  PERITONEUM 


1259 


umbilicus  to  the  under  surface  of  the  liver.  Here  the  membrane  forms  a  somewhat 
triangular  fold ,  the  falciform  or  suspensory  ligament  of  the  liver  (ligamentum  falciforme 
hepatis),  which  attaches  the  upper  and  anterior  surfaces  of  that  organ  to  the  Dia- 
phragm and  abdominal  wall.  With  the  exception  of  the  line  of  attachment  of  this 
ligament  the  peritoneum  covers  the  under  surface  of  the  anterior  part  of  the  Dia- 
phragm and  is  reflected  from  it  on  to  the  upper  surface  of  the  liver  as  the  anterior  or 
superior  layer  of  the  coronary  ligament  (ligamentum  coronarium  hepatis  anterior). 
Covering  the  upper  and  anterior  surfaces  of  the  liver  it  is  reflected  around  its  sharp 
margin  on  to  its  under  surface  as  far  as  the  transverse  fissure,  where  it  is  continuous 


M.  iliacus. 


External 
I       inguinal 
fossa. 


External, 
iliac 
artery. 


Extern 

Hiuc 
vein. 


Internal  inijtiiital 
fossa. 


Femoral 
fossa. 
Superior  vesical 

artery, 
fiddle  inguinal 
/MM. 


FIG.    865. — Posterior  view  of  the  anterior  abdominal  wall  in  its  lower  half.     The  peritoneum  is  in  place, 
and  the  various  cords  are  shining  through.     (After  Joessel.) 

with  the  anterior  layer  of  the  small  omentum  from  which  a  start  was  made  (Fig.  866) . 
The  posterior  layer  of  this  omentum  is  carried  backward  from  the  transverse  fissure 
over  the  under  surface  and  Spigelian  lobe  of  the  liver,  and  is  then  reflected,  as  the 
posterior  or  inferior  layer  of  the  coronary  ligament  (ligamentum  coronarium  hepatis 
posterior),  on  to  the  Diaphragm  and  is  prolonged  downward  over  the  pancreas  to 
become  continuous  with  the  ascending  layer  of  the  transverse  mesocolon  (Fig.  866). 
Between  the  two  layers  of  the  coronary  ligament  there  is  a  triangular  surface  of  the 
liver  which  is  devoid  of  peritoneum ;  it  is  named  the  bare  area  of  the  liver,  and  is 
attached  to  the  Diaphragm  by  connective  tissue.  If,  however,  the  two  layers  of  the 
coronary  ligaments  are  traced  toward  the  right  and  left  margins  of  the  liver,  they 
approach  each  other,  and,  ultimately  fusing,  they  form  the  right  and  left  lateral 
ligaments  of  the  liver  and  attach  its  right  and  left  lobes  respectively  to  the  Dia- 
phragm. 

If  the  small  omentum  is  followed  toward  the  right  side  it  is  seen  to  form  a 
distinct  free  edge  around  which  its  anterior  and  posterior  layers  are  continuous 


1260  THE  ORGANS  OF  DIGESTION 

with  each  other  and  between  which  are  situated  the  portal  vein,  hepatic  artery,  and 
bile-duct.  If  the  finger  is  introduced  behind  this  free  edge,  it  passes  through  a 
somewhat  constricted  ring,  the  foramen  of  Winslow  (foramen  epiploicum  [Wins- 
lowi])  (Figs.  866,  868,  and  871).  This  is  the  communication  between  what  are 
termed  the  greater  and  lesser  sacs  of  the  peritoneum  and  has  the  following  bound- 
aries: in  front,  the  free  edge  of  the  gastro-hepatic  omen  turn.  This  free  edge  is 
called  the  ligamentum  hepatoduodenale.  The  gastro-hepatic  omen  turn  has  the 
portal  vein,  hepatic  artery,  and  bile-duct  between  its  two  layers  (Fig.  872);  behind 
the  foramen  of  Winslow  is  the  postcava;  above,  are  the  Spigelian  and  caudate 
lobes  of  the  liver;  below,  the  duodenum  and  the  hepatic  artery,  as  the  latter  passes 
forward  and  upward  from  the  coeliac  axis. 

The  lesser  peritoneal  cavity  or  the  lesser  sac  of  the  peritoneum  (bursa  omentalis) 
(Figs.  866,  868,  and  871),  therefore,  lies  behind  the  small  omen  turn  and  has  the 
following  dimensions:  above,  it  is  limited  by  the  portion  of  the  liver  which  lies 
behind  the  transverse  fissure;  below,  it  extends  downward  into  the  great  omen  turn, 
reaching,  in  the  foetus,  as  far  as  its  free  edge  (Fig.  860);  in  the  adult,  however,  its 
vertical  extent  is  limited  by  adhesions  between  the  layers  of  the  omen  turn.  In  front, 
it  is  bounded  by  the  small  omentum,  stomach,  and  anterior  two  layers  of  the  great 
omen  turn;  behind,  by  the  two  posterior  layers  of  the  great  omentum,  the  transverse 
colon,  and  ascending  layer  of  the  transverse  mesocolon  which  passes  upward  in 
front  of  the  pancreas  as  far  as  the  posterior  surface  of  the  liver.  Laterally  the 
lesser  sac  reaches  from  the  foramen  of  Winslow  on  the  right  side  as  far  as  the 
spleen  on  the  left  (recessus  lienalis)  (Fig.  873),  where  it  is  limited  by  the  lieno-renal 
ligament.  The  extent  of  the  lesser  sac  and  its  relations  to  surrounding  parts  can 
be  definitely  made  out  by  tearing  through  the  small  omentum  and  inserting  the 
hand  through  the  opening  thus  made.  A  passage  (vestibulum  bursae  omentalis) 
leads  out  from  the  foramen  of  Winslow  over  the  head  of  the  pancreas  to  the  left  as 
far  as  the  median  vascular  gastro-pancreatic  fold  (plica  gastropancreatica)  (Fig.  871). 
This  fold  carries  the  gastric  artery  and  the  coronary  vein.  From  the  vestibule 
there  is  a  narrow  and  upward  prolongation  behind  the  lesser  omentum  and  cau- 
date lobe  of  the  liver  and  in  front  of  the  lumbar  portion  of  the  Diaphragm. 
This  prolongation  is  the  superior  omental  recess  (recessus  omentalis  superior). 
The  chief  part  of  the  lesser  peritoneal  cavity  extends  downward  from  the  gastro- 
pancreatic  fold  and  is  called  the  inferior  omental  recess  (recessus  omentalis  inferior). 
The  constriction  which  separates  the  two  recesses  is  due  to  the  passage  around 
the  lesser  sac  and  to  the  front  of  the  gastric  and  hepatic  arteries.  "The  former 
winds  around  its  left  side,  the  latter  around  its  right,  and  each  raises  up  a  fold 
of  peritoneum  which  projects  strongly  into  the  sac  and  partially  divides  it  into 
two"  (Cunningham).  A  small  projection  of  the  lesser  sac  passes  to  the  right  side 
behind  the  beginning  of  the  duodenum.  The  splenic  artery  in  its  course  to  the 
spleen  lies  back  of  the  posterior  layer  of  the  lesser  sac. 

It  should  be  stated  that  during  a  considerable  part  of  foetal  life  the  transverse 
colon  is  suspended  from  the  posterior  abdominal  wall  by  a  mesentery  of  its  own— 
the  two  posterior  layers  of  the  great  omentum  passing,  at  this  stage,  in  front  of  and 
above  the  colon  (Fig.  860).  This  condition  sometimes  persists  throughout  adult 
life,  but,  as  a  rule,  adhesion  occurs  between  the  mesentery  of  the  transverse  colon 
and  the  posterior  layer  of  the  great  omentum,  with  the  result  that  the  colon 
appears  to  receive  its  peritoneal  covering  by  the  splitting  of  the  two  posterior 
layers  of  the  latter  fold. 

In  addition  to  tracing  the  peritoneum  vertically,  it  is  necessary  to  trace  it  hori- 
zontally (Figs.  867,  868,  869,  and  870).  If  this  is  done  below  the  transverse  colon, 
the  circle  is  extremely  simple,  as  it  includes  only  the  greater  sac  of  the  peritoneum 
(Fig.  867).  Above  the  level  of  the  transverse  colon  the  arrangement  is  more  com- 
plicated, on  account  of  the  existence  of  the  two  sacs. 


THE  PERITONEUM 


1261 


Starting  from  the  linea  alba,  below  the  level  of  the  transverse  colon,  and  tracing 
the  continuity  in  a  horizontal  direction  to  the  right,  the  peritoneum  covers  the 
internal  surface  of  the  abdominal  wall  almost  as  far  as  the  anterior  border  of 
the  Quadratus  lumborum  muscle;  it  encloses  the  caecum,  and  is  reflected  over  the 


TRANSVERSE 
MCSOCOLON 


SMALL  SAC 

FORAMEN  OFWINSLOW, 
WITH   ARROW   PASSED 
THROUGH   IT 


PANCREAS 

THIRD   PART  OF 
DUODENUM 
TRANSVERSE 
COLON 


MESENTERY 


SMALL 
INTESTINE 


POUCH  OF 
DOUGLAS 


FIG.  866. — Diagrammatic  mesial  section  of  the  female  body,  to  show  the  peritoneum  on  vertical  tracing.  The 
great  sac  of  the  peritoneum  is  black  and  is  represented  as  being  much  larger  than  in  nature;  the  small  sac  is  very 
darkly  shaded;  the  peritoneum  on  section  is  shown  as  a  whjte  line,  and  a  white  arrow  is  passed  through  the  fora- 
men of  Wiuslow  from  the  great  into  the  small  sac.  (Cunningham.) 

sides  and  anterior  surface  of  the  ascending  colon,  fixing  it  to  the  abdominal  wall, 
from  which  it  can  be  traced  over  the  kidney  to  the  front  of  the  bodies  of  the  ver- 
tebrae. It  then  passes  along  the  mesenteric  vessels  to  invest  the  small  intestine, 
and  back  again  to  the  spine,  forming  the  mesentery,  between  the  layers  of  which 
are  contained  the  mesenteric  blood-vessels,  nerves,  lacteals,  and  glands.  Lastly, 
it  passes  over  the  left  kidney  to  the  sides  and  anterior  surface  of  the  descending 
colon,  and,  reaching  the  abdominal  wall,  is  continued  along  it  to  the  middle  line 
of  the  abdomen. 

Above  the  transverse  colon  (Fig.  868)  the  peritoneum  can  be  traced,  forming 
the  greater  and  lesser  cavities,  and  their  communication  through  the  foramen  of 
Winslowcan  be  demonstrated.  Commencing  in  the  middle  line  of  the  abdomen, 
the  membrane  may  be  traced  lining  its  anterior  wall,  and  sending  a  process  back- 
ward to  encircle  the  obliterated  umbilical  vein  (the  round  ligament  of  the  liver), 
forming  the  falciform  or  longitudinal  ligament  of  the  liver.  Continuing  its  course 
to  the  right,  it  is  reflected  over  the  front  of  the  upper  part  of  the  right  kid- 
ney, across  the  postcava  and  aorta,  and  over  the  left  kidney  to  the  hilum  of  the 
spleen,  forming  the  anterior  layer  of  the  lieno-renal  ligament,  the  posterior  layer 
being  formed  by  the  termination  of  the  cul-de-sac  of  the  greater  cavity  between 
the  kidney  and  spleen.  From  the  hilum  of  the  spleen  it  is  reflected  to  the 
stomach,  forming  the  posterior  layer  of  the  gastro-splenic  omentum  (lig amentum 


1262 


THE  ORGANS  OF  DIGESTION 


gastrolienale).     It  covers  the  posterior  surface  of  the  stomach,  and  from  its  lesser 
curvature  it  passes  around  the  portal  vein,  hepatic  artery,  and  bile-duct,  and  back 


Small      Lymphatic  Ascending 

Mesentery  Aorta        intestine        node       Postcava          colon 

j 


Peritoneum 


Mesocolon 
(imperfect) 


Psoas 

Right 
kidney 

Left  kidney 

FIQ.  867. — Peritoneal  reflection  in  transverse  section  of  lumbar  region  below  the  transverse  colon. 
Seen  from  above.     Schematic.     (Tillaux.) 

again  to  the  stomach,  as  the  lesser  omentum,  and  thus  it  forms  the  anterior  boun- 
dary of  the  foramen  of  Winslow.     It  now  covers  the  front  of  the  stomach,  and 


Vessels  in  lesser 
omentum 


Lig.  teres 


Aorta 


FIG.  868. — Transverse  section  of  peritoneum  above  the  transverse  colon.     The  arrow  points  to  the  lesser 
sac  and  passes  through  the  foramen  of  Winslow. 

upon  reaching  the  cardiac  extremity  it  passes  to  the  hilum  of  the  spleen,  form- 
ing the  anterior  layer  of  the  gastro-splenic  omentum.     From  the  hilum  of  the 


THE  PERITONEUM 


1263 


spleen  it  can  be  traced  over  the  surface  of  this  organ,  to  which  it  gives  a  serous 
covering;  it  is  then  reflected  from  the  posterior  border  of  the  hilum  on  to  the  left 
kidney,  forming  the  posterior  layer  of  the  lieno-renal  ligament. 


Vessels  in  lesser 
amentum 


Postcava 


FIG.  869. — Horizontal  section  through  the  abdomen  at  the  level  of  the  foramen  of  Winslow. 

(Modified  from  Godlee.) 

Lesser  amentum,  i     ROUND  LIGAMENT  OF  LIVER. 


Gastro-splenic 
amentum.  \ 


Hepatic  artery,  portal 
'vein,  and  hepatic  duct. 


LIENO-RENAL  LIGAMENT.     Abdominal  aorta.  Postcava 

FIG.  870. — Transverse  section  of  peritoneum. 


Numerous  folds,  formed  by  the  peritoneum,  extend  between  the  various  organs  or 
connect  them  to  the  parietes.  These  serve  to  hold  the  organs  in  position,  and  at  the 
same  time  enclose  the  vessels  and  nerves  proceeding  to  each  part.  Some  of  these 


1264 


THE  ORGANS  OF  DIGESTION 


folds  are  called  ligaments,  such  as  the  ligaments  of  the  liver  and  the  false  ligaments 
of  the  bladder.  Others,  which  connect  certain  parts  of  the  intestine  with  the 
abdominal  wall,  constitute  the  mesenteries;  and  lastly,  those  which  proceed  from 
the  stomach  to  certain  viscera  in  its  neighborhood  are  called  omenta. 


Papillary  tubercle 


Chit  edge  of  peritoneum 


Spleen  covered 
'by  peritoneum 


Descending 
duodenum 


Cut  edge  of  peritoneum 


FIG.  871. — Bursa  omentalis,  opened  from  the  front  by  an  incision  through  the  gastro-colic  omentum.     A  probe 
passes  through  the  foramen  of  Winslow  and  rests  on  the  gastro-pancreatic  fold.     (Henle.) 

The  Ligaments  of  the  Peritoneum. — The  ligaments,  formed  by  folds  of  the  peri- 
toneum, include  those  of  the  liver,  spleen,  bladder,  and  uterus.  They  will  be 
found  described  with  their  respective  organs. 

The  Omenta. — The  omenta  are:  the  lesser  omentum,  the  great  omentum,  and  the 
gastro-splenic  omentum. 

The  Lesser  or  Gastro-hepatic  Omentum  (omentum  minus]  (Figs.  866  and  871)  is  the 
duplicature  which  extends  between  the  transverse  fissure  of  the  liver  and  the  right 
side  of  the  abdominal  portion  of  the  oesophagus,  the  lesser  curvature  of  the  stomach, 
and  the  upper  portion  of  the  superior  surface  of  the  duodenum.  The  portion  going 
to  the  oesophagus  and  stomach  is  called  the  hepato-gastric  ligament  (ligamentum 
hepatogastricum).  The  division  of  the  ligament  which  goes  to  the  oesophagus  is 
strong  and  dense;  the  division  which  goes  to  the  lesser  curvature  of  the  stomach 
is  thin  and  relaxed.  The  portion  of  the  lesser  omentum  which  goes  to  the 
duodenum  is  continuous  with  the  first-named  portion.  It  is  called  the  hepato- 
duodenal  ligament  (ligamentum  hepatoduodenale) .  The  right  margin  of  this  liga- 
ment is  free  and  concave.  The  hepato-colic  ligament  (ligamentum  hepatocoli- 
cum)  is  not  invariably  present.  It  is  a  fold  of  the  hepato-duodenal  ligament  and 
runs  from  the  posterior  surface  of  the  gall-bladder  to  the  descending  portion  of 
the  duodenum  or  possibly  to  the  transverse  colon.  From  the  free  margin  of  the 
termination  of  the  hepato-duodenal  ligament  a  fold  often  passes  to  the  front 
of  the  right  kidney.  It  is  known  as  the  duodeno-renal  ligament  (ligamentum 
duodenorenale) .  The  lesser  omentum  is  extremely  thin,  and  consists  of  two  layers 
of  peritoneum;  that  is,  the  two  layers  covering  respectively  the  anterior  and 


THE  PERITONEUM 


1265 


posterior  surfaces  of  the  stomach.  The  posterior  layer  is  part  of  the  wall  of  the 
lesser  peritoneal  cavity;  the  anterior  layer,  of  the  greater  peritoneal  cavity.  When 
the  two  layers  reach  the  lesser  curvature  of  the  stomach,  they  join  together  and 
ascend  as  the  double  fold  to  the  transverse  fissure  of  the  liver;  to  the  left  of  this 


HEPATIC 
DUCT 


ROUND  OMENTAL 

LIGAMENT      TUBEROSITY    GASTRIC 

IMPRESSION 


POSTERIOR    LAYER 
OF  LESSER 
OMENTUM 

OESOPHAGUS 


CYSTIC  DUCT 


DUODENAL 
IMPRESSION 

FREE  EDGE 
OF  LESSER 
OMENTUM 


PORTAL 
VEIN 


COMMON 
BILE-DUCT 


PANCREATIC  DUCT 


PYLORUS 

RIGHT  GASTRO- 
EPIPLOIC  ARTERY 

SUPERIOR  PANCREATICO- 

DUODENAL  ARTERY 


FIG.  872. — Structure  between  the  layers  of  the  lesser  omentum.     The  liver  has  been  raised  up,  and  the 
anterior  layer  of  the  omentum  removed.     Semidiagrammatic.      (Cunningham.) 

fissure  the  double  fold  is  attached  to  the  fissure  of  the  ductus  venosus  as  far  as 
the  Diaphragm,  where  the  two  layers  separate  to  embrace  the  end  of  the  oesoph- 
agus. At  the  right  border  the  lesser  .omentum  is  free,  and  the  two  layers  of 
which  it  is  composed  are  continuous.  The  anterior  layer,  which  belongs  to  the 


RENAL  SURFACE 

POUCH  OF  GREATER  SAC 


LIENO-RENAL  LIGAMENT 

PHRENIC  SURFACE 

CASTRO-SPLENIC 

OMENTUM 

POUCH  OF  GREATER  SAC 


GASTRIC  SURFACE 


FIG.  873. — Horizontal  section  through  the  stomach,  pancreas,  spleen,  and  the  left  kidney  to  show  peritoneal 
reflections  at  the  hilum  of  the  spleen.     (G.  S.  H.) 

greater  sac,  turns  around  the  hepatic  vessels  to  become  continuous  with  the  poste- 
rior layer  belonging  to  the  lesser  one.  They  here  form  a  free,  rounded  margin, 
which  contains  between  its  layers  the  hepatic  artery,  the  common  bile-duct,  the 
portal  vein,  lymphatics,  and  the  hepatic  plexus  of  nerves  (Fig.  872) — all  these  struc- 

80 


1266  THE  ORGANS  OF  DIGESTION 

tures  being  enclosed  in  loose  areolar  tissue,  called  Glisson's  capsule.  Between  the 
layers  where  they  are  attached  to  the  stomach  lie  the  gastric  artery  and  the  pyloric 
branch  of  the  hepatic  artery,  anastomosing  with  it.  From  the  left  side  of  the 
greater  curvature  of  the  stomach  a  fold  passes  to  the  gastric  surface  of  the  spleen, 
covers  the  spleen,  and  passes  from  the  renal  surface  of  the  spleen  around  the 
left  kidney  to  the  Diaphragm.1  The  fold  passing  to  the  spleen  is  known  as  the 
gastro-splenic  ligament  or  the  gastro-splenic  omentum  (Fig.  873).  The  portion  pass- 
ing to  the  Diaphragm  is  known  as  the  spleno-phrenic  ligament  (ligamentum  phreni- 
colienale).  The  gastric  veins  or  vasa  brevia  pass  from  the  left  side  of  the  greater 
curvature  of  the  stomach  toward  the  spleen  in  the  gastro-splenic  omentum. 

The  Great  or  Gastro-colic  Omentum  (omentum  majus)  (Figs.  866  and  874)  is  the 
largest  peritoneal  fold.  It  consists  of  four  layers  of  peritoneum,  two  of  which 
descend  from  the  stomach,  one  from  its  anterior,  the  other  from  its  posterior 
surface,  and,  uniting  at  its  lower  border,  descend  in  front  of  the  small  intestines, 
sometimes  as  low  down  as  the  pelvis;  they  then  turn  upon  themselves,  and  ascend 
again  as  far  as  the  transverse  colon,  where  they  separate  and  enclose  that  part 
of  the  intestine.  These  separate  layers  may  be  easily  demonstrated  in  the  young 
subject,  but  in  the  adult  they  are  more  or  less  inseparably  blended.  At  the  free 
margins  the  two  outer  layers  and  the  two  inner  layers  become  continuous.  The 
left  border  of  the  great  omentum  is  continuous  with  the  gastro-splenic  omentum; 
its  right  border  extends  as  far  only  as  the  duodenum.  The  great  omentum  is 
usually  thin,  presents  a  cribriform  appearance,  and  always  contains  some  adipose 
tissue,  which  in  fat  subjects  accumulates  in  considerable  quantity.  Between  its 
two  anterior  layers  is  the  anastomosis  between  the  right  and  left  gastro-epiploic 
arteries.  In  opening  the  abdomen  the  great  omentum  is  rarely  found  spread  out 
evenly  over  the  intestines.  It  often  projects  between  intestinal  coils,  or  is  largely 
gathered  in  some  one  region,  or  is  pushed  in  front  of  the  stomach  by  distention 
of  the  colon. 

The  lower  portion  of  the  lesser  sac  of  the  peritoneum  continues  for  a  distance 
between  the  ascending  and  descending  layers  of  the  great  omentum  (Fig.  866). 
The  portion  of  the  lesser  peritoneal  cavity  within  the  great  omentum  is  more  or 
less  obliterated  in  the  adult  by  adhesion  between  its  opposing  layers.  At  birth 
the  omentum  is  very  short  and  barely  reaches  the  umbilicus.  In  adults  its  length 
varies  greatly.  In  some  individuals  it  is  very  short;  in  others  it  passes  into  the 
pelvis.  Mr.  Lockwood  points  out  that  in  persons  under  forty-five  years  of  age 
the  omentum  can  rarely  be  pulled  down  below  the  level  of  the  pubic  spine;  it 
generally  can  be  in  older  persons. 

The  Gastro-splenic  Omentum  is  the  fold  which  connects  the  margins  of  the 
hilum  of  the  spleen  to  the  cul-de-sac  of  the  stomach,  being  continuous  by  its  lower 
border  with  the  great  omentum.  It  was  described  as  the  gastro-splenic  liga- 
ment (Fig.  873). 

The  Mesenteries. — The  mesenteries  are:  the  mesentery  proper,  the  transverse 
mesocolon,  the  sigmoid  mesocolon,  the  mesorectum  (p.  1269),  and  the  mesentery  of 
the  vermiform  appendix.  In  addition  to  these  there  are  sometimes  present  an 
ascending  and  a  descending  mesocolon. 

The  Mesentery  (mesenterium)  (fjieaov  evre^ov)  (Figs.  866,  875,  and  876),  so  called 
from  being  connected  to  the  middle  of  the  cylinder  of  the  small  intestine,  is  the 
broad  fold  of  peritoneum  which  connects  the  convolutions  of  the  jejunum  and 
ileum  with  the  posterior  wall  of  the  abdomen.  It  consists  of  a  layer  of  connec- 
tive tissue,  each  side  of  which  is  covered  with  peritoneum.  In  the  connective 
tissue  there  are  fatty  masses.  Its  root  (radix  mesenterii) ,  the  part  connected  with 
the  vertebral  column,  is  narrow,  about  six  inches  in  length,  and  directed  obliquely 

1  Spalteholz,  Hand  Atlas  of  Human  Anatomy.     Translated  and  edited  by  Prof.  Lewellys  F.  Barker. 


THE  PERITONEUM 


1267 


from  the  left  side  of  the  second  lumbar  vertebra  to  the  right  sacro-iliac  symphysis 
(Fig.  876).  Its  intestinal  border  is  vastly  broader  (measures  about  twenty  feet); 
and  here  its  two  layers  separate  so  as  to  enclose  the  intestine,  and  form  its  peri- 
toneal coat.  Its  breadth,  between  its  vertebral  and  intestinal  border,  is  about 
eight  inches.  Its  upper  border  is  continuous  with  the  under  surface  of  the  trans- 
verse mesocolon;  its  lower  border,  with  the  peritoneum  covering  the  caecum  and 


FIG.  874. — The  great  omentum  as  seen  from  the  front.     (Testut.) 

ascending  colon.  The  origin  of  the  mesentery  above  is  just  beyond  the  termina- 
tion of  the  duodenum,  and  it  terminates  below  in  the  angle  formed  by  the  junction 
of  the  ileum  and  the  colon.  It  serves  to  retain  the  small  intestines  in  their  position, 
and  contains  between  its  layers  the  mesenteric  vessels  and  nerves,  the  lymphatic 
vessels  and  mesenteric  glands.  These  glands  number  from  50  to  150.  Occa- 
sionally congenital  mesenteric  openings  exist.  In  stout  individuals  the  mesentery 
contains  much  fat.  If  there  is  much  fat  the  mesentery  is  not  translucent;  if 
there  is  little  fat  it  is  translucent.  It  may  be  actually  transparent  above  and 
translucent  or  opaque  below.  The  thinnest  part  of  the  mesentery  is  above.  As 
we  descend  it  becomes  thicker,  because  of  the  presence  of  fat,  fibrous  ligament, 
and  muscular  tissue.1 

1  Intestinal  Localization.    By  Geo.  H.  Monks,  Annals  of  Surgery,  October,  1903. 


1268 


THE  ORGANS  OF  DIGESTION 


In  most  cases  the  peritoneum  covers  only  the  front  and  sides  of  the  ascending 
and  descending  parts  of  the  colon.  Sometimes,  however,  these  are  surrounded  by 
the  serous  membrane  and  attached  to  the  posterior  abdominal  wall  by  an  ascending 
mesocolon  (mesocolon  ascendens)  and  a  descending  mesocolon  (mesocolon  descendens) 


Mesentery 
(lejt  leaf) ' 


Root  of  mesen- 
tery 


Jleurr 

Sigmoid  flexure 
Cxcum 


Duodenum 


--•»sf 

FIG.  875. — Mesentery.     Small  intestine  pushed  to  the  right  and  above.     (Tillaux.) 

respectively.  At  the  place  where  the  transverse  colon  turns  downward  to  form  the 
descending  colon,  a  fold  of  peritoneum  is  continued  to  the  under  surface  of  the 
Diaphragm  opposite  the  tenth  and  eleventh  ribs.  This  is  the  phreno-colic  ligament 
(ligamentum  phrenicocolicum) ;  it  passes  below  the  spleen,  and  serves  to  support 
this  organ,  and  therefore  it  has  received  the  second  name  of  sustentaculum  lienis. 
The  Transverse  Mesocolon  (mesocolon  transversum)  (Fig.  876)  is  a  broad  fold, 
which  connects  the  transverse  colon  to  the  posterior  wall  of  the  abdomen.  It  is 
formed  by  the  two  ascending  or  posterior  layers  of  the  great  omentum,  which,  after 
separating  to  surround  the  transverse  colon,  join  behind  it,  and  are  continued 
backward  to  the  spine,  where  they  diverge  in  front  of  the  duodenum.  This  fold 
contains  between  its  layers  the  vessels  which  supply  the  transverse  colon. 


THE  PERITONEUM 


1269 


The  Sigmoid  Mesocolon  (mesocolon  sigmoideum)  (Fig.  876)  is  the  fold  of  peri- 
toneum which  retains  the  sigmoid  flexure  in  connection  with  the  left  iliac  fossa. 
This  portion  of  intestine  remains  always  freely  movable. 

The  Mesorectum  is  really  only  the  lower  portion  of  the  sigmoid  mesocolon.  It 
is  the  name  formerly  given  to  the  narrow  fold  which,  according  to  the  old  defini- 


Right  lateral          Falciform  ligt 
ligament  of  liver.  of  liver. 


Vena  cava  inferior. ?jj 

(Esophagus.— 
Right  phrenic  artery.  •• 

Coronary  artery. ~* 
Hepatic  artery.  — 

Splenic  artery....^ 
Pancreas. 

Inf.  pane. -duo.  artery. 
Colica  media. 

Superior  mesenteric. 

Duodenum  (3rd  part). 
Aorta. 

Duodenum  (2nd part). 

Right  and  left  kidneys. 

Superior  mesenteric. 

Aorta. 

Colica  sinistn 
Colica  dextri 


Sigmoid  artery. 

p.  hamorrhoidal  artery. 


Common  iliac  artery." 


Internal  iliac  artery.—— 

External  iliac  artery. " 

Epigastric  artery.  - 
Bladder.  •• 


Peritoneum. 
Extra-peritoneal  tissue. 

I    gastro- hepatic  omentun 
Gaitro-phrenic  ligament. 


Gattro-splenic  amentum. 
Foramen  of  Winslow. 
Duodenum  (tat  part). 


Costo-colic  ligament. 
Dot  between  two  anterior 
layers  of  great  omentum. 
Transverse  meso-colon. 

Bare  surface  for  descend- 
ing colon. 


The  two  layers  of  the 
mesentery  proper. 


Bare  surface  for  ascend- 
ing colon. 


Sigmoid  meso-colon. 


Bare  surface  for  caecum. 


Bare  surface  for  2nd  part 
.    of  rectum. 
5  Left  lateral  false  liga- 
(   ment  of  bladder. 


.MF 

FIG.  876. — Diagram  devised  by  Dr.  Del6pine  to  show  the  lines  along  which  the  peritoneum  leaves  the  w 

of  the  abdomen  to  invest  the  viscera. 


all 


tion  of  the  rectum,  connects  the  upper  part  of  the  rectum  with  the  front  of  the 
sacrum.     It  contains  the  superior  hemorrhoidal  vessels. 

The  Mesoappendix  or  Mesentery  of  the  Vermiform  Appendix  (mesenteriolum  pro- 
cessus  vermiformis)  (Fig.  880)  is  a  double  fold  of  peritoneum  which  usually  completely 
surrounds  the  vermiform  appendix.  It  is  usually  described  as  a  triangular  fold, 
and  at  a  glance  it  appears  so,  but  Jonnesco  points  out  that  it  has  four  borders:  a 
superior  or  mesenteric  border;  a  right  or  caecal;  a  left  or  free,  and  an  inferior 
or  appsndicular.  One  of  the  borders  is  often  extremely  short.  The  upper  sur- 
face of  the  mesoappendix  is  continuous  with  the  lower  surface  of  the  mesentery 
proper  and  with  the  left  or  internal  fold  of  the  peritoneum  covering  the  caecum. 
The  lower  surface  of  the  mesoappendix  is  continuous  with  the  right  or  external 


1270 


THE  ORGANS  OF  DIGESTION 


fold  of  peritoneum  covering  the  caecum.  As  a  rule,  the  entire  appendix  is  covered 
with  peritoneum;  sometimes  a  portion  of  the  base  is  uncovered,  and  this  portion  of 
the  diverticulum  is  then  extraperitoneal.  The  tip  is  never  extraperitoneal.  The 
mesoappendix  may  be  attached  to  the  entire  length  of  the  appendix,  but,  as  a 
rule,  the  tip  is  free.  In  fact,  one-third,  one-half,  or  two-thirds  may  be  free  and 
occasionally  the  mesoappendix  is  a  mere  vestige.  Between  the  two  peritoneal 
layers  of  the  mesoappendix  there  is  connective  tissue,  and  often  fat.  In  the 
connective  tissue  are  the  appendicular  blood-vessels,  lymph-vessels,  and  nerves. 

The  Appendices  Epiploicae  are  small  pouches  of  the  peritoneum  filled  with  fat 
and  situated  along  the  colon  and  upper  part  of  the  rectum.  They  are  chiefly 
appended  to  the  transverse  colon. 


t 


INFERIOR 

MCSENTCRIC 

VEIN 


SUPERIOR 
DUODENAL 
FOLD 


SUPERIOR 
DUODENAL 
FOLD 


INFERIOR 

DUODENAL 

FOLD 

INFERIOR 

DUODENAL 

FOLD 

ARTERIA 

COLICA 

SINESTRA 


FIG.  877. — Superior  and  inferior  duodenal  fossa.     (Poirier  and  Charpy.) 

Retro-peritoneal  Fossae. — In  certain  parts  of  the  abdominal  cavity  there  are 
recesses  of  peritoneum  forming  culs-de-sac  or  pouches,  which  are  of  surgical  inter- 
est in  connection  with  the  possibility  of  the  occurrence  of  retro-peritoneal  hernia. 
One  of  these,  which  was  previously  described,  is  the  lesser  sac  of  the  peritoneum 
(Figs.  866  and  868),  which  may  be  regarded  as  a  recess  of  peritoneum  through  the 
foramen  of  Winslow,  in  which  a  hernia  may  take  place,  but  there  are  several 
others,  of  smaller  size,  which  require  mention. 

These  recesses  of  fossae  may  be  divided  into  three  groups,  viz.:  (1)  the  duodenal 
fossae;  (2)  pericaecal  fossae;  and  (3)  the  intersigmoid  fossa. 

1.  Duodenal  Folds  and  Fossae. — Moynihan  has  described  no  less  than  nine  fossae 
as  occurring  in  the  neighborhood  of  the  duodenum.  Three  of  these  are  fairly 
constant.  Five  of  the  fossae  are  here  considered,  (a)  The  inferior  duodenal 
fossa  or  fossa  of  Treitz  (Fig.  877)  is  the  most  constant  of  all  the  peritoneal  fossae 
in  this  region,  being  present  in  from  70  to  75  per  cent,  of  cases.  It  is  situated 
opposite  the  third  lumbar  vertebra  on  the  left  side  of  the  ascending  portion  of  the 
duodenum.  The  opening  into  the  fossa  is  directed  upward,  and  is  bounded  by  a 
thin,  sharp  fold  of  peritoneum  with  a  concave  free  upper  margin.  This  fold  of 
peritoneum  is  called  the  inferior  duodenal  fold  (plica  duodenomesocolica) .  The 
tip  of  the  index  finger  introduced  into  the  fossa  under  the  fold  passes  some  little 
distance  up  behind  the  ascending  or  fourth  portion  of  the  duodenum.  One  margin 
of  the  fold  is  attached  to  the  ascending  portion  of  the  duodenum;  another  margin 
is  attached  to  the  parietal  peritoneum.  (&)  The  superior  duodenal  fossa  (Fig.  877) 
is  the  next  most  constant  pouch  or  recess,  being  present  in  from  40  to  50  per  cent, 
of  cases.  It  often  coexists  with  the  inferior  one,  and  its  orifice  looks  downward, 
in  the  opposite  direction  to  the  preceding  fossa.  It  lies  to  the  left  of  the  ascend- 


THE  PERITONEUM 


1271 


ing  portion  of  the  duodenum.     It  is  bounded  in  front  by  the  superior  duodenal  fold 
(plica  duodenojejunalis),  which  is  triangular  and  has  a  free  semilunar  base;  to  the 


RIGHT  RETRO- 
DUODENAL 
WALL 

INFERIOR 

DUODENAL 

ANGLE 


INFERIOR 

MESENTERIC 

VEIN 

PARIETAL   FOLD 
OF  DUODENUM 


LEFT   COLIC 
ARTERY 


INFERIOR   MESEN- 
TERIC ARTERY 


FIG.  878. — Retro-duodenal  fossa.     (Poirier  and  Charpy.) 

right  it  is  blended  with  the  peritoneum  covering  the  ascending  duodenum,  and  to 
the  left  with  the  peritoneum  covering  the  perirenal  tissues.  The  fossa  is  bounded 
in  front  by  the  superior  duodenal  fold;  behind  by  the  second  lumbar  vertebra;  to 
the  right  by  the  duodenum.  Its  depth  is  2  cm.,  and  it  terminates  in  the  angle 
formed  by  the  left  renal  vein  crossing  the  aorta.  This  fossa  is  of  importance,  as 
it  is  in  relation  with  the  inferior  mesenteric  vein;  that  is  to  say,  the  vein  almost 
always  corresponds  to  the  line  of  union  of  the  superior  duodenal  fold  with  the 
posterior  parietal  peritoneum,  (c)  The  duodeno-jejunal  fossa  or  mesocolic  fossa 
(recessus  duodenojejunalis}  is  formed  where  the  duodeno-jejunal  angle  enters  the 
root  of  the  transverse  mesocolon.  There  are  two  forms:  (1)  a  single  fossa  and  (2) 
a  double  fossa.  It  can  be  seen  by  pulling  the  jejunum  downward  and  to  the  right, 
after  the  transverse  colon  has  been  pulled  upward.  It  will  appear  as  an  almost 
circular  opening,  looking  downward  and  to  the  right,  and  bounded  by  two  free 
borders  or  folds  of  peritoneum,  the  duodeno-mesocolic  ligaments.  The  opening 
admits  the  little  finger  into  the  fossa  to  the  depth  of  from  2  to  3  cm.  The  fossa 
is  bounded  above  by  the  pancreas,  to  the  right  by  the  aorta,  and  to  the  left  by  the 
kidney;  beneath  is  the  left  renal  vein.  The  fossa  exists  in  from  15  to  20  per 
cent,  of  cases,  and  has  never  yet  been  found  in  conjunction  with  any  other  form 
of  duodenal  fossa,  (d)  Paraduodenal  fossa  or  the  fossa  of  Landzert  (recessus  duo- 
denojejunalis) is  most  distinct  in  the  infant,  and  is  to  the  left  of  the  ascending 
portion  of  the  duodenum.  The  fold  of  peritoneum  to  its  outer  side  and  above  is 
produced  by  the  inferior  mesenteric  vein.  Its  lower  limit  is  a  fold  called  the 
mesenterico-mesocolic  fold,  (e)  The  retroduodenal  fossa  (Fig.  878)  was  described 
in  1893  by  Jonnesco.  It  is  a  peritoneal  cul-de-sac,  sometimes  found  behind  the 
horizontal  and  ascending  portions  of  the  duodenum. 

2.  Pericaecal  Folds  and  Fossae.— There  are  at  least  three  pouches  or  recesses  to  be 
found  in  the  neighborhood  of  the  caecum,  which  are  termed  pericaecal  fossae.     (1) 


1272 


THE  ORGANS  OF  DIGESTION 


The  ileo-colic  fossa  or  superior  ileo-caecal  (recessus  ileocaecalis  superior)  (Fig.  879) 
is  formed  by  a  fold  of  peritoneum,  the  ileo-colic  fold,  arching  over  a  branch  of 
the  ileo-colic  artery,  which  supplies  the  ileo-colic  junction,  and  appears  to  be  the 
direct  continuation  of  the  artery.  The  fossa  is  a  narrow  chink  situated  between 
the  ileo-colic  fold  in  front,  and  the  mesentery  of  the  small  intestine,  the  ileum, 


ANTERIOR 

ILEOOECAL 

ARTCRY 

ANTERIOR  ILEO- 
OECAL  FOLD 


MESENTERY 


ANTERIOR 

ILEOC/ECAL 
FOSSA 


INFERIOR 

ILEOC/ECAL 
FOLD 


FIG.  879. — Anterior,  sometimes  called  superior,  ileo-cajcal  fossa.     (Poirier  and  Charpy.) 


ILEO-APPENDICULAR 
FOSSA 


MESENTERY 

APPENDICULAR 
ARTERY 

ILEO-APPENDICULAR 
ARTERY 


MESO-APPENDIX 


FIG.  880. — Ileo-appendicular  or  inferior  ileo-csecal  fossa.  The  caecum  and  ascending  colon  have  been 
rawn  outward  and  downward,  the  ileum  upward  and  backward,  and  the  appendix  downward.  (Poirier 
,nd  Charov.) 


and  Charpy.) 

and  a  small  portion  of  the  caecum  behind.  (2)  The  ileo-caecal,  inferior  ileo-caecal 
or  ileo-appendicular  fossa  (recessus  ileocaecalis  inferior)  (Fig.  880)  is  situated  behind 
the  angle  of  junction  of  the  ileum  and  caecum.  It  is  formed  by  a  fold  of  peritoneum, 
the  ileo-caecal  fold  (plica  ileocaecalis),  which  Treves  called  the  "bloodless  fold." 
Tuffier  denies  its  non-vascularity,  and  Lockwood  and  Rolleston  state  that  it  con- 
tains fat,  muscular  fibres,  and  arteries  and  veins  derived  from  the  appendicular  ves- 
sels and  the  anterior  and  posterior  ileo-caecal  vessels.1  The  upper  border  of  the  fold 
is  attached  to  the  ileum,  opposite  its  mesenteric  attachment,  and  the  lower  border, 
passing  over  the  ileo-crecal  junction,  joins  the  mesentery  of  the  appendix,  and 
sometimes  the  appendix  itself;  hence  this  fold  is  sometimes  called  the  ileo-appen- 
dicular fold.  Between  the  ileo-csecal  fold  and  the  mesentery  of  the  vermiform 
appendix  is  the  ileo-caecal  fossa.  It  is  bounded  above  by  the  posterior  surface  of 
the  ileum  and  the  mesentery;  in  front  and  below  by  the  ileo-csecal  fold,  and  behind 
by  the  upper  part  of  the  mesentery  of  the  appendix.  (3)  The  retro-caecal  or  retro-colic 

1  The  Caecal  Folds  and  Fossae.     By  Richard  J.  A.  Barry. 


THE  PERITONEUM 


1273 


fossae  (recessus  retrocaecalis)  (Fig.  881)  are  situated  behind  the  caecum  and  ascend- 
ing colon.  There  may  be  no  fossa  present.  There  may  be  one  fossa;  there  are 
usually  two  (external  and  internal  retrocolic  fossae) ;  occasionally  there  are  more 
than  two.1  The  fossae  are  brought  into  view  by  raising  the  caecum.  According  to 
Berry,  one  or  other  of  the  fossa  is  present  in  30  per  cent,  of  cases.  Treves  thinks 
the  retrocolic  fossae  are  extremely  rare.  There  may  be  one  fossa  (20  per  cent,  of 
cases)  or  two  fossae  (10  per  cent,  of  cases).  If  there  is  but  one  fossa  it  is  the 
internal  that  exists  three  times  as  often  as  the  external.  The  retro-colic  space, 
if  present,  varies  much  in  size  and  extent.  In  some  cases  it  is  sufficiently  large 
to  admit  the  index  finger  and  extends  upward  behind  the  ascending  colon  in 
the  direction  of  the  kidney;  in  others  it  is  merely  a  shallow  depression.  The 
external  retro-colic  fossa  is  bounded  and  formed  by  two  folds:  one,  the  external 
parieto-colic  fold  or  the  superior  caecal  fold,  which  is  the  outer  layer  of  the  ascend- 
ing mesocolon,  and  is  attached  by  one  edge  to  the  abdominal  wall  from  the 
lower  border  of  the  kidney  to  the  iliac  fossa  and  by  the  other  to  the  postero- 


ILEO-APPENDICULAR 


APPENOICULAR 
FOSSA 

MESO-APPENDIX 


INFERIOR 
C/CCAL  FOLD 


RETRO-OECAL 


FIG.  881. — The  retro-csecal  fossa.     The  ileum  and  csecum  are  drawn  backward  and  upward.     (Souligoux.) 

external  aspect  of  the  colon ;  and  the  other,  the  internal  parieto-colic  fold  or  inferior 
caecal  fold,  which  is  the  inner  layer  of  the  ascending  mesocolon.  The  internal 
retrocolic  fossa  is  bounded  externally  by  the  internal  parieto-colic  fold,  and  is 
bounded  internally  by  the  mesenterico-parietal  fold,  which  is  the  insertion  of  the 
mesentery  into  the  iliac  fossa. 

3.  The  Intersigmoid  Fossa  (recessus  intersigmoideus") . — The  intersigmoid  fossa 
is  constant  in  the  foatus  and  common  during  infancy,  but  disappears  in  a  large 
percentage  of  cases  as  age  advances.  Upon  drawing  the  sigmoid  flexure  upward, 
the  left  surface  of  the  sigmoid  mesocolon  is  exposed,  and  on  it  will  be  seen  a 
funnel-shaped  recess  of  the  peritoneum,  lying  on  the  external  iliac  vessels,  in  the 
interspace  between  the  Psoas  and  Iliacus  muscles.  This  is  the  orifice  leading  to 
the  fossa  intersigmoidea,  which  lies  behind  the  sigmoid  mesocolon,  and  in  front  of 
the  parietal  peritoneum.  This  fossa  is  produced  by  the  incomplete  fusion  in  the 
foetus  of  the  descending  mesocolon  with  the  parietal  peritoneum.  The  fossa  varies 


1  The  Caecal  Folds  and  Fossae.     By  Richard  J.  A.  Barry. 


1274  THE  ORGANS  OF  DIGESTION 

in  size;  in  some  instances  it  is  a  mere  dimple,  whereas  in  others  it  will  admit  the 
whole  of  the  index  finger. 

Any  of  these  fossae  may  be  the  site  of  a  retro  -peritoneal  hernia.  The  pericsecal 
fossae  are  of  especial  interest,  because  hernia  of  the  vermiform  appendix  frequently 
takes  place  into  one  of  them,  and  may  there  become  strangulated.  The  presence 
of  these  pouches  also  explains  the  course  which  pus  has  been  known  to  take  in 
cases  of  perforation  of  the  appendix,  where  it  travels  upward  behind  the  ascending 
colon  as  far  as  the  Diaphragm.1 

Surgical  Anatomy.  —  Study  of  the  peritoneum  by  Robinson  and  others  shows  that  absorption 
takes  place  most  rapidly  from  the  region  of  the  Diaphragm,  less  rapidly  but  still  very  actively  from 
the  region  of  the  small  intestine,  slowly  from  the  pelvic  region.  Clinically  we  know  that  pelvic 
peritonitis  is  not  nearly  so  dangerous  as  peritonitis  in  the  small  intestine  or  Diaphragm  areas,  and 
that  peritonitis  in  the  region  of  the  Diaphragm  is  the  most  fatal  form  of  the  infection.  After 
abdominal  operations  in  infected  cases,  it  is  well  to  elevate  the  head  of  the  bed  (Fowler's  position), 
so  as  to  obtain  the  aid  of  gravity  in  draining  septic  fluids  away  from  the  dangerous  region  and 
toward  the  safer  region.2  In  areas  in  which  absorption  is  rapid,  protective  exudation  is  not  apt  to 
form.  In  areas  in  which  absorption  is  slow,  inflammatory  exudation  is  apt  to  circumscribe  the 
area  and  prevent  diffusion.  After  an  operation  in  a  non-infected  case,  if  salt  solution  has  been 
left  in  the  abdominal  cavity  because  of  shock  or  hemorrhage,  raising  the  foot  of  the  bed  will  aid 
rapid  absorption  of  the  fluid  by  favoring  the  natural  current  toward  the  Diaphragm  and  hurrying 
the  fluid  to  a  region  in  which  absorption  is  rapid.  Dr.  John  B.  Murphy's  plan  of  treating  general 
peritonitis  has  proved  remarkably  successful.  He  does  not  remove  the  exudation  of  lymph  which 
is  seen  upon  the  peritoneum.  This  exudation  is  conservative,  blocks  up  lymph  spaces,  and  lessens 
the  absorption  of  dangerous  toxins.  He  inserts  a  drainage  tube  into  the  peritoneal  cavity  above 
the  pubes,  puts  the  patient  erect  or  semi-erect  in  bed  (Fowler's  position),  and  administers  salt 
solution  continuously  by  low  pressure  proctolysis.  According  to  Murphy  the  lymph  circulation 
is  reversed  and  the  peritoneum  becomes  a  secreting  surface.  Certain  it  is  that  the  salt  solution 
absorbed  from  the  rectum  reaches  the  peritoneal  cavity  in  large  amounts  and  flows  out  of  the 
drainage  tube. 

The  great  omentum  stores  up  fat,  and,  being  movable,  it  is  able  to  pass  to  different  parts  of 
the  peritoneal  cavity.  Dr.  Robinson,  in  his  work  on  the  Peritoneum,  describes  its  functions  as 
follows:  "The  omentum  is  the  great  protector  against  peritoneal  infectious  invasions.  It  builds 
barriers  of  exudates  to  check  infection.  It  is  like  a  man-of-war,  ready  at  a  moment's  notice  to 
move  to  invaded  parts.  It  circumscribes  abscesses;  it  repairs  visceral  wounds,  and  prevents 
adhesions  of  mobile  viscera  to  the  anterior  abdominal  wall.  It  resists  infectious  invasions  by 
typical  peritoneal  exudates,  and  not  by  succumbing  to  absorbed  sepsis.  It  is  a  director  of  peri- 
toneal fluids,  a  peritoneal  drain." 

In  abdominal  wounds  the  omentum  often  protrudes:  This  structure  frequently  constitutes 
or  is  part  of  a  hernia,  and  is  almost  invariably  present  in  umbilical  hernia.  As  a  result  of 
inflammation,  it  may  become  adherent  to  adjacent  structures.  Adhesions  may  be  of  service  by 
matting  together  the  intestines  and  circumscribing  infections.  They  may  be  harmful  by 
constricting  the  bowels  and  producing  obstruction.  A  portion  of  the  omentum  may  become 
adherent  to  some  other  part  and  form  a  band,  and  under  this  band  the  gut  may  be  caught  and 
strangulated.  Omentum  may  adhere  to  and  plug  a  perforation  in  a  hollow  viscus,  and  the  sur- 
geon may  utilize  it  for  the  same  purpose,  or  to  cover  a  raw  surface  or  overlie  a  suture  line.  The 
omentum  may  be  in  the  surgeon's  way  while  operating.  If  it  is,  the  patient  is  placed  in  the 
Trendelenburg  position  (pelvis  elevated). 

Any  tear  or  opening  found  by  the  surgeon  in  the  great  omentum  must  be  closed  with  sutures, 
because  of  the  danger  that  intestine  might  enter  and  be  caught  in  such  an  opening.  A  tumor 
cut  off  from  its  proper  blood-supply,  for  instance,  an  ovarian  cyst  with  a  twisted  pedicle,  may 
continue  to  receive  nourishment  from  adherent  omentum,  and  gangrene  may  thus  be  prevented. 

The  lax  character  and  shifting  tendency  of  the  subserous  tissue  explains  the  occurrence  of 
ptosis  of  the  abdominal  viscera  and  kidneys. 

The  vast  number  of  nerves  in  the  peritoneum  accounts  for  the  profound  shock  which  follows 
a  wound,  attends  an  intraperitoneal  calamity,  or  which  develops  from  infection.  An  infective 
process  of  any  portion  of  the  peritoneum  produces  pain  and  reflex  symptoms  (vomiting, 
abdominal  rigidity,  intestinal  paresis,  etc.). 

The  parietal  peritoneum  is  very  sensitive  to  pain,  but  not  to  touch;  hence,  after  injecting  a 
local  anaesthetic  and  opening  the  abdomen,  a  fairly  satisfactory  exploration  can  be  made  with 
the  finger. 

The  intestine,  the  mesentery,  the  stomach,  the  anterior  margin  of  the  liver,  and  the  gall-bladder 
are  insensitive,  and  may  be  cut  or  even  burned  without  pain.3 


1  On  the  anatomy  of  these  fossae,  see  the  Arris  and  Gale  Lectures  by  Moynihan,  1899. 

2  Geore  R.  Fowler,  in  Medical  Record,  April  14,  1900. 

E.  L.  Lennander,  in  Mittheilungen  aus  dem  Grenzgebieten  der  Medicin  und  Chirurgie,  Band  x., 


Heft  1,  2. 


THE  PERITONEUM 


1275 


FIG.  882 


FIG.  883 


Three  feet. 


Six  feet. 


FIG.  884 


FIG.  885 


Nine  feet. 


Twelve  feet. 


FIG.  886 


FIG.  887 


Seventeen  feet. 


Twenty  feet. 


FIGS.  882,  883,  884,  885,  886,  887. — Diagrams  showing  the  arrangement  and  variations  of  the  loops  of  the 
mesenteric  vessels  for  various  segments  of  the  small  intestine  of  average  length.  Nearest  the  duodenum  the 
mesenteric  loops  are  primary,  the  vasa  recta  are  long  and  regular  in  distribution  and  the  translucent  spaces 
(lunettes)  are  extensive.  Toward  the  ileo-colic  junction,  secondary  and  tertiary  loops  are  observed,  the  vessels 
are  smaller  and  become  obscured  by  numerous  fat-tabs.  (After  Monks.) 


1276  THE  ORGANS  OF  DIGESTION 

Viscera  which  obtain  their  innervation  purely  from  visceral  nerves  are  insensitive;  those  which 
receive  branches  from  somatic  nerves  are  sensitive  (Lennander). 

The  oblique  origin  of  the  mesentery  causes  this  structure  to  form  a  sort  of  shelf.  A  hemor- 
rhage or  extravasation  into  the  abdomen,  to  the  right  of  the  mesentery,  tends  to  flow  into  the 
right  iliac  fossa;  one  occurring  on  the  left  side  flows  into  the  pelvis.  Monks  points  out  that  in 
flushing  the  abdominal  cavity  the  tube  should  not  be  aimlessly  introduced,  but  should  utilize 
the  mesentery  on  each  side  of  an  intestinal  loop,  to  "conduct  the  tip  of  the  irrigating  tube  to  the 
bottom  of  the  two  fossae."1  Monks  also  shows  how  the  mesentery  can  be  utilized  to  determine 
the  direction  of  an  intestinal  loop: 

"  Now,  let  us  suppose  that  the  surgeon  has  between  his  fingers  a  loop  of  bowel,  and  wishes 
to  determine  its  direction.  He  knows  that  one  side  of  the  loop  is  the  left  side  of  the  intestine, 
and  that  the  corresponding  side  of  the  mesentery,  if  closely  followed  down  to  the  mesenteric 
root,  will  conduct  him  into  the  left  fossa;  he  also  knows  that  the  other  side  of  the  bowel  is  its 
right  side,  and  that  the  mesentery  on  that  side  will  conduct  him  into  the  right  fossa.  Now, 
if  his  finger  goes  into  the  great  fossa  on  the  left  side  of  the  abdomen,  after  having  closely  fol- 
lowed the  mesentery  down  to  its  root  and  arranged  his  loop  to  be  parallel  with  that  root,  he  then 
knows  that  the  left  and  right  sides  of  the  intestine  face  to  the  left  and  right  sides  of  the  abdomen 
respectively,  and  that  the  end  of  the  loop  which  points  downward  is  the  end  nearest  the  ileo- 
csecal  valve.  He  can  determine  the  direction  of  the  gut  in  a  similar  way  in  case  his  finger  enters 
the  right  fossa.  All  this  would  seem  very  simple  were  it  not  for  the  twists  in  mesentery  and 
intestine,  which  tend  to  mislead  one.  A  little  practice  will  usually  enable  one  to  recognize  a  twist 
in  the  mesentery.  This  should  be  untwisted  by  rotation  of  the  gut,  after  which  the  direction  is 
determined  by  another  palpation  of  the  mesenteric  root."2 

The  studies  made  of  the  arrangement  and  variations  of  the  loops  of  the  mesenteric  vessels  by 
Dr.  Thomas  Dwight3  have  been  utilized  and  expanded  by  Dr.  George  H.  Monks  in  laying  down 
rules  for  the  determination  of  the  exact  portion  of  small  intestine  which  may  be  in  the  surgeon's 
hand.4  His  views  are  as  follows: 

"General  Vascularity  of  the  Mesentery  near  the  Bowel. — Opposite  the  upper  part  of  the  bowel  the 
mesenteric  vessels  are  distinctly  larger  than  opposite  any  other  part  of  it.  These  vessels  grow 
smaller  and  smaller  as  we  pass  downward  until  the  lower  third  of  the  gut  is  reached,  where  they 
remain  about  the  same  size  as  far  as  the  ileo-caecal  valve.  The  arrangement  of  the  mesenteric 
vessels  has  some  features  which  intimately  concern  the  subject  in  hand,  and  which  I  shall  describe 
with  some  detail.  Diagrammatically  speaking,  the  main  branches  of  the  superior  mesenteric 
artery  unite  with  each  other  by  means  of  loops,  which  are  called  for  convenience  'primary  loops;' 
in  some  parts  of  the  tube,  'secondary  loops,'  and  even,  occasionally,  'tertiary  loops'  are  super- 
imposed upon  these.  From  these  loops  little  straight  vessels — the  vasa  recta  already  referred  to 
— run  to  the  bowel,  upon  which  they  ramify,  alternating,  as  a  rule,  as  to  the  side  of  the  intestine 
which  they  supply.  The  mesenteric  veins  are  arranged  in  a  manner  somewhat  similar  to  the 
arteries. 

"  The  Loops  of  the  Mesenteric  Vessels  (Figs.  882,  883,  884, 885,  and  886).— Opposite  the  upper 
part  of  the  bowel  there  are  only  primary  loops.  Occasionally  a  secondary  loop  appears,  but  it 
is  small  and  insignificant  as  compared  with  the  primary  loops,  which  are  large  and  quite  regular. 
As  we  proceed  down  the  bowel  secondary  loops  become  more  numerous,  larger,  and  approach 
nearer  to  the  bowel  than  the  primary  loops  in  the  upper  part.  As  a  rule,  secondary  loops 
become  a  prominent  feature  at  about  the  fourth  foot.'  As  we  continue  farther  downward,  the 
secondary  loops  (and,  possibly,  tertiary  loops)  become,  still  more  numerous  and  the  primary 
loops  smaller,  the  loops  all  the  time  getting  nearer  and  nearer  to  the  gut.  Opposite  the  lower 
part  of  the  gut  the  loops  generally  lose  their  characteristic  appearance,  and  are  represented  by 
a  complicated  network. 

"  The  Vasa  Recta. — Opposite  the  upper  part  of  the  intestine  the  vasa  recta  are  from  three  to 
five  centimetres  long,  when  the  loop  of  small  intestine  to  which  they  run  is  lifted  up  so  as  to 
put  them  gently  on  the  stretch.  They  are  straight,  large,  and  regular,  and  rarely  give  off  branches 
in  the  mesentery.  In  the  lower  third  they  are  very  short,  being  generally  less  than  one  centimetre 
in  length.  Here  they  are  less  straight,  smaller,  less  regular,  and  have  frequent  branches  in  the 
mesentery." 

The  translucency  of  the  mesentery  varies  greatly ;  in  some  parts  it  may  be  almost  transparent, 
in  others  almost  or  quite  opaque.  Its  thinnest  part  is  above.  It  is  thickened  below  by  fat,  fibrous 
tissue,  and  muscular  tissue.  In  very  fat  subjects  it  may  be  impossible  to  see  the  vessels  (Monks). 
According  to  Monks,  if  a  loop  is  raised  and  looked  at  against  the  light  close  to  the  gut  ''little 
transparent  spaces"  are  seen  between  the  vasa  recta,  and  even  in  the  thickest  mesentery;  some 
of  these  "lunettes"  exist  along  the  upper  portion  of  the  intestine.  As  we  descend  in  our  exam- 
ination, they  grow  smaller  and  become  fatty,  and  disappear  about  the  eighth  foot  of  the  intes- 

1  Intestinal  localization,  by  George  H.  Monks,  Annals  of  Surgery,  October,  1903.  2  Ibid. 

3  Reports  of  the  Meeting  of  American  Anatomists,  1897.  4  Annals  of  Surgery,  1903. 


THE  STOMACH  1277 

• 

tine  '  The  same  author  shows  that  the  mesentery  of  the  lower  third  of  the  intestine,  except  in 
the  thinnest  individuals,  contains  little  collections  of  fat  on  the  border  of  the  mesentery,  which 
project  toward  the  bowel  and  may  even  extend  upon  it. 

THE  STOMACH  (VENTRICULUS)   (Figs.  874,  888,  889,  891,  892). 

The  stomach  is  the  principal  organ  of  digestion.  It  is  the  most  dilated  part  of 
the  alimentary  canal,  and  is  situated  between  the  termination  of  the  oesophagus 
(cardid)  and  the  commencement  of  the  small  intestine.  Its  form  varies  because 
of  varied  conditions,  but,  as  a  rule,  it  is  somewhat  pyriform.  It  is  placed,  in 
part,  immediately  behind  the  anterior  wall  of  the  abdomen  and  beneath  the 
Diaphragm.  Viewing  the  stomach  from  in  front  it  appears  that  the  right  margin 
of  the  oesophagus  is  continued  downward  as  the  upper  two-thirds  of  the  lesser 
curvature  of  the  stomach,  the  remaining  third  of  this  border  bending  sharply 
backward  and  to  the  right,  to  complete  the  smaller  curvature  (Fig.  888).  The 
greater  curvature  begins  at  the  left  border  of  the  termination  of  the  oesophagus  in 
a  somewhat  acute  angle ;  it  then  passes  upward  and  to  the  left  to  the  under  surface 
of  the  Diaphragm,  with  which  it  lies  in  contact  for  some  distance,  and  then  sweeps 
downward  with  a  convexity  to  the  left,  and,  continued  across  the  middle  line  of  the 
body,  finally  turns  upward  and  backward,  to  terminate  at  the  commencement  of 
the  small  intestine.  It  will  thus  be  seen  that  the  stomach  may  be  divided  into  a 
fundus  (fundus  ventriculi)  and  a  middle  portion  or  body  (corpus  ventriculi).  The 
portion  of  the  body  adjacent  to  the  cardia  being  known  as  the  cardiac  portion  (pars 
cardiaca),  the  long  axis  of  which  is  directed  downward  with  a  slight  inclination 
forward  and  to  the  right;  and  the  portion  adjacent  to  the  pylorus  being  known  as 
the  pyloric  portion  (pars  pylorica),  the  long  axis  of  which  is  horizontal  or  rather 
upward  with  an  inclination  backward.  Of  the  two  openings,  the  cardiac  orifice,  by 
which  it  communicates  with  the  oesophagus,  is  situated  slightly  to  the  left  of  the 
middle  line  of  the  body  to  the  right  of  the  fundus,  or  dilated  upper  extremity  of  the 
stomach,  and  is  directed  downward ;  the  other, 

the  pyloric  orifice,  by  which  it  communicates  Fundus. 

with  the  small  intestine,  is  on  a  lower  plane, 
close  to  the  right  of  the  mid-line,  and  looks      Car 
directly  backward. 

Relations  Of    the  Stomach. — The  Stomach 

lies  in  a  space  or  chamber  called  the  stomach 

chamber  (Fig.  874) .  When  distended  the  viscus 

completely  fills  the  space.    When  the  stomach 

is  empty  it  lies  upon  the  floor  of  the  chamber,    pvlorus 

and  the  portion  it  has  vacated  is  occupied  by 

the  transverse  colon,  which  ascends  in  front  of 

the    Stomach    and    finally  gets   above    it.'    The          ^- 888.-Diaggrarnmatic  outline  of  the 

anterior  wall  of  the  stomach  chamber  is  formed 

by  the  anterior  abdominal  wall.  The  roof  is  formed  by  the  under  surface  of  the 
Diaphragm  and  the  under  surface  of  the  left  lobe  of  the  liver.  The  floor  is  formed 
by  the  left  suprarenal  capsule  and  the  summit  of  the  left  kidney,  the  gastric  face 
of  the  spleen,  the  upper  surface  of  the  pancreas,  the  transverse  mesocolon,  and 
the  colon.2 

Surfaces. — The  stomach  has  two  surfaces,  called  anterior  and  posterior  surfaces, 
and  two  borders,  termed  the  greater  and  lesser  curvatures. 

In  regard  to  the  so-called  anterior  and  posterior  surfaces  of  the  stomach,  it 
must  be  borne  in  mind  that  these  names  are  not  strictly  correct,  as  the  anterior 
surface  has  a  certain  amount  of  inclination  upward  and  the  posterior  downward . 

1  Annals  of  Surgery,  October,  1903. 

2  Prof.  Birmingham  in  Prof.  Cunningham's  Text-book  of  Anatomy. 


1278  THE  ORGANS  OF  DIGESTION 

• 

The  Anterior,  Upper  or  Parietal  Surface  (paries  anterior}. — The  anterior  surface 
is  directed  forward  and  to  the  right  side.  It  has  a  somewhat  flattened  appearance 
when  the  stomach  is  empty,  but  when  it  is  full  the  surface  becomes  convex.  It  is 
in  relation  with  the  Diaphragm ;  the  thoracic  wall  formed  by  the  anterior  parts  of 
the  seventh,  eighth,  and  ninth  ribs  of  the  left  side;  the  left  lobe  of  the  liver;  and 
the  anterior  abdominal  wall.  Between  the  part  covered  by  the  liver  and  that 
covered  by  the  left  ribs  there  is  a  triangular  segment  of  the  anterior  wall  of  the 
stomach,  which  is  in  contact  with  the  abdominal  wall  and  is  the  only  part  of  the 
stomach  which  is  visible  when  the  abdominal  wall  is  removed  and  the  viscera 
allowed  to  remain  in  situ.  Its  area  is  about  40  sq.  cm.,  and  it  is  of  great  impor- 
tance to  the  surgeon,  as  the  stomach  can  readily  be  reached  in  this  situation. 
Occasionally  the  transverse  colon  may  be  found  lying  in  front  of  the  lower  part 
of  the  anterior  surface  of  .the  stomach.  The  whole  of  this  surface  of  the  stomach 
is  covered  by  peritoneum. 

The  Posterior,  Lower  or  Visceral  Surface  (paries  posterior}. — The  posterior  sur- 
face of  the  stomach  is  directed  backward  and  to  the  left.  It  is  in  relation  with 
the  Diaphragm,  the  gastric  surface  of  the  spleen,  the  left  suprarenal  capsule,  the 
upper  part  of  the  left  kidney,  the  anterior  surface  of  the  pancreas,  the  splenic 
flexure  of  the  colon,  and  the  ascending  layer  of  the  transverse  mesocolon.  These 
structures  form  a  shallow  concavity  or  bed,  on  which  this  surface  of  the  stomach 
rests.  The  transverse  mesocolon  intervenes  between  the  stomach  and  the  duodeno- 
jejunal  junction  and  commencement  of  the  ileum.  Its  greater  curvature  is  in 
relation  with  the  transverse  colon  and  has  attached  to  it  the  anterior  two  layers 
of  the  great  omentum.  Almost  the  whole  of  this  surface  is  covered  with  peri- 
toneum, but  behind  the  cardiac  orifice  there  is  a  small  portion  of  the  stomach 
which  is  uncovered  by  peritoneum  and  is  in  contact  with  the  Diaphragm  and  fre- 
quently with  the  upper  portion  of  the  left  suprarenal  capsule. 

The  Lesser  Curvature  (curvatura  ventriculi  minor). — The  lesser  curvature  of  the 
stomach  extends  between  the  cardiac  and  pyloric  orifices  along  the  right  border 
of  the  organ.  It  descends  in  front  of  the  left  crus  of  the  Diaphragm,  along  the  left 
side  of  the  eleventh  and  twelfth  thoracic  vertebrae,  and  then  turning  to  the  right  it 
crosses  the  first  lumbar  vertebra  and  ascends  to  the  pylorus.  It  gives  attachment 
to  the  two  layers  of  the  gastro-hepatic  omentum,  between  which  blood-vessels  and 
lymphatics  pass  to  reach  the  organ. 

The  Greater  Curvature  (curvatura  ventriculi  major). — The  greater  curvature  of 
the  stomach  is  directed  to  the  left,  and  is  four  or  five  times  as  long  as  the  lesser 
curvature.  Starting  from  the  cardiac  orifice,  it  forms  an  arch  to  the  left  with  its 
convexity  upward,  the  highest  point  of  which  is  on  a  level  with  the  costal  cartilage 
of  the  sixth  rib  of  the  left  side.  It  then  passes  nearly  straight  downward,  with  a 
slight  convexity  to  the  left,  as  low  as  the  costal  cartilage  of  the  ninth  rib,  and  then 
turns  to  the  right  to  end  at  the  pylorus.  As  it  crosses  the  median  line  the  lowest 
edge  of  the  greater  curvature  is  about  two  fingers'  breadth  above  the  umbilicus. 
The  lower  part  of  the  greater  curvature  gives  attachment  to  the  two  anterior 
layers  of  the  great  omentum,  between  which  layers  vessels  and  lymphatics  pass 
to  the  organ. 

The  Cardia  (Fig.  889). — The  cardia  is  the  point  at  which  the  oesophagus  enters 
the  stomach  wall.  The  opening  is  called  the  cardiac  orifice  or  the  oesophageal 
opening.  At  the  cardia  the  circular  muscular  fibres  constitute  a  sphincter. 

The  Cardiac  Orifice  (Fig.  889). — The  cardiac  orifice  is  the  opening  by  which  the 
oesophagus  communicates  with  the  stomach.  It  is  therefore  sometimes  termed 
the  oesophageal  opening.  It  is  the  most  fixed  part  of  the  stomach,  and  is  situated 
about  two  inches  below  the  highest  part  of  the  fundus  on  a  level  with  the  body 
of  the  tenth  or  eleventh  thoracic  vertebra  to  the  left  and  a  little  in  front  of  the  aorta. 
This  would  correspond  on  the  anterior  surface  of  the  body  to  the  articulation  of 


THE  STOMACH 


1279 


the  seventh  left  costal  cartilage  to  the  sternum.  It  is  placed  far  off  from  the  surface 
and  is  at  least  four  inches  back  of  the  seventh  left  chondro-sternal  articulation. 

The  Pylorus  (Fig.  889).— The  pylorus  is  the  point  at  which  the  stomach  passes 
into  the  duodenum.  The  opening  of  communication  is  called  the  pyloric  orifice. 
At  the  pylorus  the  muscular  fibres  constitute  a  sphincter. 

The  Pyloric  Orifice  (Fig.  889). — The  pyloric  orifice  communicates  with  the  duod- 
enum, the  aperture  being  guarded  by  a  valve  (Fig.  890).  Its  position  varies  with 
the  movements  of  the  stomach.  When  the  stomach  is  empty  the  pylorus  is  situ- 
ated just  to  the  right  of  the  medium  line  of  the  body,  on  a  level  with  the  upper 
border  of  the  first  lumbar  vertebra.  On  the  anterior  surface  of  the  body  its  posi- 
tion would  be  indicated  by  a  point  one  inch  below  the  tip  of  the  ensiform  cartilage 
and  a  little  to  the  right.  As  the  stomach  becomes  distended  the  pylorus  moves  to 
the  right,  and  in  a  fully  distended  stomach  may  be  situated  two  or  three  inches 
to  the  right  of  the  median  line.  The  direction  of  the  pylorus  is  upward  and  to 


Cystic  duct. 


FIG.  889. — The  mucous  membrane  of  the  stomach  and  duodenum  with  the  bile-ducts. 

the  right,  which  position  prevents  "  the  weight  of  the  gastric  contents  bearing 
directly  on  the  sphincter  apparatus."1  The  pylorus  is  on  a  somewhat  higher  level 
than  the  lowest  point  of  the  stomach.  Near  the  pylorus  the  stomach  frequently 
exhibits  a  slight  dilatation,  which  is  named  the  antrum  of  the  pylorus  (antrum 
pyloricum).  The  pylorus  is  indicated  by  a  constriction,  the  direction  of  which 
is  circular.  The  pylorus  lies  upon  the  neck  of  the  pancreas  behind.  Above  it 
and  in  front  of  it  is  the  liver. 

The  size  of  the  stomach  varies  considerably  in  different  subjects.  When  mod- 
erately distended  its  greatest  length,  from  the  top  of  the  fundus  to  the  lowest  part 
of  the  greater  curvature,  is  from  ten  to  twelve  inches  and  its  diameter  at  the 

1  W.  J.  Mayo,  Medical  Record,  June  11,  1904. 


1280 


THE  ORGANS  OF  DIGESTION 


widest  part  from  four  to  five  inches.  The  distance  between  the  two  orifices  is  three 
to  six  inches,  and  the  measurement  from  the  anterior  to  the  posterior  wall  three 
and  a  half  inches.  Its  weight,  according  to  Clendinning,  is  about  four  ounces  and 
a  half,  and  its  capacity  in  the  adult  male  is  five  to  eight  pints.  The  stomach  of  a 
newborn  child  holds  about  one  ounce. 

Alterations  in  Position. — There  is  no  organ  in  the  body  the  position  and  connections  of  which 
present  such  frequent  alterations  as  the  stomach.  When  empty,  it  lies  at  the  back  part  of  the 
abdomen,  some  distance  from  the  surface,  and  is  in  the  left  hypochondriac  region  and  the  left 
portion  of  the  epigastric  region.  Its  fundus  is  directed  upward  and  backward  toward  the  Dia- 
phragm. The  long  axis  of  the  viscus  is  nearly  horizontal.  Its  pyloric  end  is  directed  upward 
and  backward,  is  situated  close  to  or  very  slightly  to  the  right  of  the  middle  line,  covered  in  front 
by  the  left  lobe  of  the  liver,  and  being  on  a  level  with  the  first  lumbar  vertebra.  When  empty, 
the  stomach  assumes  a  more  or  less  cylindrical  form,  especially  noticeable  at  its  pyloric  end.  The 
entire  viscus  is  small  and  contracted,  and  the  pyloric  region  resembles  the  intestine.  When  the 
stomach  is  distended,  its  surfaces,  which  are  flattened  when  the  organ  is  empty,  become  convex 
and  the  shape  becomes  pyriform.  The  viscus  becomes  very  oblique  and  approaches  the  vertical, 
its  long  axis  being  downward,  forward,  and  to  the  right.  The  greater  curvature  is  elevated  and 
carried  forward,  so  that  the  anterior  surface  is  turned  more  or  less  upward  and  the  posterior 
surface  downward,  and  the  stomach  is  brought  well  against  the  anterior  wall  of  the  abdomen.  Its 
fundus  expands  and  rises  considerably  above  the  level  of  the  cardiac  orifice;  in  doing  this  the 
Diaphragm  is  forced  upward,  contracting  the  cavity  of  the  chest;  hence  the  dyspnoea  complained 
of,  from  inspiration  being  impeded.  The  apex  of  the  heart  is  also  tilted  upward;  hence  the 
oppression  in  this  region  and  the  palpitation  experienced  in  extreme  distention  of  the  stomach. 
The  left  lobe  of  the  liver  is  pushed  to  the  right  side.  When  the  stomach  becomes  distended 
the  change  in  the  position  of  the  pylorus  is  very  considerable;  it  is  shifted  to  the  right,  some 
two  or  three  inches  from  the  median  line,  and  lies  under  cover  of  the  liver,  near  the  neck  of  the 
gall-bladder.  In  consequence  of  the  distention  of  the  stomach  the  lesser  cul-de-sac  bulges  over 
the  pylorus,  concealing  it  from  view,  and  causing  it  to  undergo  a  rotation,  so  that  its  orifice  is 
directed  backward.  When  the  stomach  is  greatly  distended  its  lower  border  may  enter  the 
umbilical  and  the  left  Irmbar  regions.  During  inspiration  the  stomach  is  displaced  downward 
by  the  descent  of  the  Diaphragm,  and  it  is  elevated  by  the  pressure  of  the  abdominal  muscles  dur- 
ing expiration.  Pressure  from  without,  as  from  tight  lacing,  pushes  the  stomach  down  toward  the 
pelvis.  In  fact,  in  the  female,  because  of  tight  lacing,  the  stomach  may  be  to  the  left  side  of  the 
vertebral  column  and  nearly  vertical  in  direction,  the  lower  portion  being  sharply  angled  upward 
toward  the  pylorus,  which  lies  underneath  the  liver.  Besides  the  angulation,  the  lower  end,  the 
stomach  may  have  a  median  constriction,  and  there  may  even  be  an  hour-glass  stomach.  The 
descent  of  the  stomach  from  tight  lacing  may  cause  the  pancreas  to  become  nearly  vertical.  In 
disease  the  position  and  connection  of  the  stomach  may  be  greatly  changed,  from  the  accumula- 
tion of  fluid  in  the  chest  or  abdomen,  or  from  alteration  in  size  of  any  of  the  surrounding  viscera. 

Variations  according  to  Age. — In  an  early  period  of  development  the  stomach  is  vertical,  and  in 
the  newborn  child  it  is  more  vertical  than  later  on  in  life,  as  owing  to  the  large  size  of  the  liver 
it  is  more  pushed  over  to  the  left  side  of  the  abdomen,  and  the  whole  of  the  anterior  surface  is 
covered  by  the  left  lobe  of  this  organ. 

On  looking  into  the  pyloric  end  of  the  stomach,  the  mucous  membrane  is  found 
projecting  inward  in  the  form  of  a  circular  fold,  the  pyloric  valve  (Fig.  890),  leaving 

a  narrow  circular  aperture,  about  half  an  inch  in 
diameter,  by  which  the  stomach  communicates  with 
the  duodenum. 

The  Pyloric  Valve  (valvula  pylori]  (Fig.  890). — The 
pyloric  valve  is  formed  by  a  reduplication  of  the  mucous 
membrane  of  the  stomach,containing  numerous  circular 
fibres,  which  are  aggregated  into  a  thick  circular  ring, 
the  pyloric  sphincter  (m.  sphincter  pylori) ;  the  longitu- 
dinal fibres  and  serous  membrane  being  continued 
FI<;.  890.— Diagrammatic  view  over  the  fold  without  assisting  in  its  formation  (Fig.  890) . 

of  the  coats  of   the   stomach,  duo-    rni  i  •  11      i  i         j    u      j.u  e 

denum,  and  pylorus.    The  ridge  is    1  he  pylorus  is  normally  kept  closed  by  the  action  or 

the  pyloric  valve.     (Allan  Thorn-     thjg  aggregation  Qf  circular  fibres  which'constitutes  the 

Sphincter  muscle.    During  the  early  stage  of  digestion 

it  remains  closed,  but  after  a  time  opens  now  and  then.  The  opening  becomes 
more  frequent  and  the  period  of  patency  is  prolonged  as  digestion  advances. 


THE  STOMACH 


1281 


The  diameter  of  the  pylorus  is  uncertain.  It  is  usually  said  to  be  half  an  inch. 
But  it  is  closed  when  the  pylorus  is  at  rest,  and  it  can  certainly  dilate  even  in 
a  child  to  at  least  an  inch  and  let  bodies  of  this  size  pass  through. 

The  Peritoneum. — The  great  omentum  comes  off  from  the  greater  curvature  of 
the  stomach  and  passes  to  the  transverse  colon.  The  lesser  omentum  comes  off 
from  the  lesser  curvature  and  passes  to  the  liver.  The  gastro -splenic  ligament  or 
omentum  passes  from  the  under  surface  of  the  stomach  just  below  the  greater 
curvature  to  the  spleen.  A  fold  of  peritoneum  passes  up  from  the  stomach  along 
the  left  side  of  the  oesophagus  to  the  Diaphragm.  This  is  the  gastro -phrenic 
ligament. 

Supports  of  the  Stomach. — The  stomach  lies  on  the  bed  of  the  stomach  cham- 
ber, which  was  described  on  p.  1277.  The  great  omentum  gives  no  support  to 
the  stomach,  neither  does  the  gastro-splenic  ligament,  because  of  the  movability 
of  the  spleen.  The  lesser  omentum  does  give  support  to  the  stomach  and  so  do 


FIG.  891. — The  superficial  muscular  layer  of  the  stomach,  viewed  from  above  and  in  front.     (Spalteholz.) 

the  gastro -phrenic  ligament  and  the  hepato -duodenal  ligament.  The  two  chief 
points  of  support  are  the  attachment  of  the  oesophagus  to  the  Diaphragm  and 
the  fixation  of  the  duodenum  to  the  front  of  the  vertebral  column. 

Structure. — The  wall  of  the  stomach  consists  of  four  coats:  serous,  muscular, 
areolar,  and  mucous,  together  with  vessels  and  nerves. 

The  Peritoneal  or  Serous  Coat  (tunica  serosa). — The  peritoneal  or  serous  coat 
covers  the  entire  surface  of  the  organ,  excepting  along  the  greater  and  lesser 
curvatures,  at  the  points  of  attachment  of  the  greater  and  lesser  omenta;  at 
each  curvature  the  two  layers  of  peritoneum  leave  a  small  triangular  space,  to 
which  the  peritoneum  is  not  attached,  although  it  is  attached  in  front  of  it  and 

81 


1282 


THE  ORGANS  OF  DIGESTION 


back  of  it.  Along  these  spaces  the  nutrient  vessels  and  nerves  pass.  On  the 
posterior  surface  of  the  stomach,  close  to  the  cardiac  orifice  and  below  and  to 
the  left  of  it,  there  is  a  smaller  triangular  area  uncovered  by  peritoneum,  where 
the  organ  is  in  contact  with  the  under  surface  of  the  Diaphragm,  and  it  may  be 
with  the  left  suprarenal  body  and  the  summit  of  the  left  kidney.  When  the 
stomach  is  moderately  distended  this  uncovered  area  measures  about  one  and  a 
half  inches  from  above  downward,  and  about  two  inches  from  before  backward. 
At  the  left  angle  of  this  uncovered  area  the  insertion  of  the  great  omentum 
begins.  At  the  right  angle  the  gastric  artery  reaches  the  stomach. 

The  Muscular  Coat  (tunica  muscularis)  (Figs.  891  and  892). — The  muscular  coat 
is  situated  immediately  beneath  the  serous  covering,  to  which  it  is  closely  connected. 
It  consists  of  three  sets  of  fibres — longitudinal,  circular,  and  oblique. 

The  Longitudinal  Fibres  (stratum  longitudinale)  are  most  superficial;  they  are 
continuous  with  the  longitudinal  fibres  of  the  oesophagus,  radiating  in  a  stellate 


FIG.  892. — The  middle  and  deep  muscular  layer  of  the  stomach,  viewed  from  above  and  in  front.    (Spalteholz.) 

manner  from  the  cardiac  orifice.  They  are  most  distinct  along  the  curvatures, 
especially  the  lesser,  but  are  very  thinly  distributed  over  the  surfaces.  At  the 
pyloric  end  they  are  more  thickly  distributed,  and  continuous  with  the  longitudinal 
fibres  of  the  small  intestine.  The  bundles  of  longitudinal  muscle-fibre  on  the  upper 
and  lower  surfaces  of  the  pylorus  are  particularly  firm  and  distinct,  and  are  called 
the"  pyloric  ligaments  (ligamenta  pylori). 

The  Circular  Fibres  (stratum  circulars)  form  a  uniform  layer  over  the  whole 
extent  of  the  stomach,  except  the  fundus,  beneath  the  longitudinal  fibres.  At  the 
pylorus  they  are  most  abundant,  and  are  aggregated  into  a  circular  ring  or  sphinc- 
ter, which  projects  into  the  cavity,  and  forms,  with  the  fold  of  mucous  membrane 
covering  its  surface,  the  pyloric  valve  (Fig.  890).  They  are  continuous  with  the 
circular  fibres  of  the  oesophagus. 


THE  STOMACH 


1283 


The  Oblique  Fibres  (fibrae  obliquae)  arise  at  the  left  side  of  the  cardia  from  the 
circular  fibres  of  the  oesophagus.  The  fibres  pass  down  in  the  anterior  and  pos- 
terior walls.  Those  of  the  anterior  wall  are  parallel  to  the  lesser  curvature  and 
almost  reach  the  pylorus.  Those  of  the  posterior  wall  are  more  nearly  transverse 
to  the  long  axis  of  the  stomach  (Spalteholz).  These  fibres  gradually  assume  the 
direction  of  the  circular  fibres  and  terminate  in  them.  The  layer  of  oblique  fibres 
is  beneath  the  circular  layer.  Certain  oblique  muscular  fibres  encircle  the  fundus 
of  the  stomach  in  a  series  of  rings. 

The  Areolar  or  Submucous  Coat  (tela  submucosa). — The  areolar  or  submucous 
coat  consists  of  loose,  filamentous,  areolar  tissue,  connecting  the  mucous  and 
muscular  layers.  It  supports  the  blood-vessels  previous  to  their  distribution  to 
the  mucous  membrane;  hence  it  is  sometimes  called  the  vascular  coat. 

The  Mucous  Membrane  (tunica  mucosa)  (Figs.  893,  894,  and  895). — The 
mucous  membrane  is  thick;  its  surface  smooth,  soft,  and  velvety.  In  the  fresh 
state  it  is  of  a  pinkish  tinge  at  the  pyloric  end,  and  of  a  red  or  reddish-brown 

Ridges  between  the  alveoli. 


Gastric  Areas. 


Rugae. 


FIG.  893.— Mucous  membrane  of  the  stomach,  from  the 
pars  pyiorica,  viewed  from  the  surface.     X  5.    (Spalteholz.) 


Gastric  alveoli. 


FIG.  894. — Mucous  membrane  of  the  stomach, 
from  the  pars  pyiorica,  viewed  from  the  surface. 
X  16.  (Spalteholz.) 


color  over  the  rest  of  the  surface.  In  infancy  it  is  of  a  brighter  hue,  the  vascular 
redness  being  more  marked.  It  is  thin  at  the  cardiac  extremity,  but  thicker  toward 
the  pylorus.  During  the  contracted  state  of  the  organ  it  is  thrown  into  numerous 
plaits  or  rugae  (plicae  mucosae)  (Figs.  893  and  895,  A),  which  for  the  most  part 
have  a  longitudinal  direction,  and  are  most  marked  toward  the  lesser  end  of  the 
stomach  and  along  the  greater  curvature,  and  which  contain  also  submucous  tissue. 
These  folds  are  entirely  obliterated  when  the  organ  becomes  distended.  A  constant 
fold  exists  at  the  pylorus  (Fig.  890).  It  is  called  the  pyloric  valve,  and  is  produced 
by  the  presence  beneath  it  of  the  Sphincter  muscle. 

Besides  the  large  folds  or  rugae  and  the  pyloric  valve,  there  are  numerous  small 
elevations  of  mucous  membrane  known  as  gastric  areas  (areae  gastricae),  which  are 
partly  separated  from  each  other  by  furrows  and  which  vary  greatly  in  shape 
(Fig.  893).  According  to  Spalteholz,  each  one  of  these  elevations  has  an  area  of 
several  square  millimetres. 


1284 


THE    ORGANS    OF  DIGESTION 


STRUCTURE  OF  THE  Mucous  MEMBRANE. — When  examined  with  a  lens  the 
inner  surface  of  the  mucous  membrane  presents  a  peculiar  honeycomb  appear- 


MAMMILUK 


MOUTHS  OF  GASTRIC 

GLANDS,   WITH   GLAND 

TUBES  AT  BOTTOM 


DEPRESSION  BETWEEN 
TWO  MAMMILLA 


MOUTH  OF 
GASTRIC  GLAND 


FIG.  895. — The  mucous  membrane  of  the  stomach.  A,  natural  size;  B,  magnified  25  diameters.  In  A  the 
rugae  and  the  mammillated  surface  are  shown.  In  B  the  gland  mouths  (fqveolae  gastricae),  with  the  gland  tubes 
leading  from  some  of  them,  and  the  ridges  separating  the  mouths  (plica  villosae)  are  seen.  (Cunningham.) 


FIG.  896. — Pyloric  gland. 


FIG.  897. — Peptic  gastric  glan 


ance,  from   being  covered   with   small   shallow  depressions  or  alveoli   (foveolae 
gastricae)  (Figs.  894  and  895,  B)  of  a  polygonal  or  hexagonal  form,  which  vary 


THE  STOMACH  1285 

from  y^  to  y^-g-  °f  an  inch  in  diameter,  and  are  separated  by  slightly  elevated 
ridges  (plicae  villosae).  The  ridges  are  most  distinct  at  the  pylorus.  These 
foveolae  are  within  the  areae  gastricae.  The  ridges  on  section  resemble  villi.  In 
the  bottom  of  the  alveola  are  seen  the  orifices  of  minute  tubes,  the  gastric  glands 
(Fig.  895  B),  which  are  placed  perpendicularly  side  by  side  throughout  the 
entire  substance  of  the  mucous  membrane.  The  surface  of  the  mucous  membrane 
of  the  stomach  is  covered  by  a  single  layer  of  columnar  epithelium;  it  lines  the 
alveoli,  and  also  for  a  certain  distance  the  mouths  of  the  gastric  glands.  This 
epithelium  commences  very  abruptly  at  the  cardiac  orifice,  where  the  cells  sud- 
denly change  in  character  from  the  stratified  epithelium  of  the  oesophagus.  The 
cells  are  elongated,  and  consist  of  two  parts,  the  inner  or  attached  portions 
being  granular,  and  the  outer  or  free  parts  being  clear  and  occupied  by  a  muco- 
albuminous  substance. 

The  Gastric  Glands. — The  gastric  glands  are  of  three  kinds:  the  true  gastric 
glands,  the  p^loiic  glands,  and  the  cardiac  glands. 

The  True  Gastric  Glands  (Fig.  897)  are  called  also  the  oxyntic  glands,  the  fundus 
glands,  and  the  peptic  glands  (glandulae  gastricae  propriae).  They  are  distributed 
throughout  the  entire  fundus  and  body,  and  may  be  found  even  at  the  pylorus.  They 
are  tubular  in  character,  and  are  formed  of  a  delicate  basement-membrane,  lined 
with  epithelium.  The  basement-membrane  consists  of  flattened  transparent  endo- 
thelial  cells,  with  processes  which  extend  between  and  support  the  epithelium.  Into 
the  crypt  of  a  true  gastric  gland  three  or  more  caecal  tubes,  branched  or  unbranched, 
empty.  The  duct,  however,  in  these  glands  is  shorter  than  in  the  other  variety, 
sometimes  not  amounting  to  more  than  one-sixth  of  the  whole  length  of  the  gland ; 
it  is  lined  throughout  by  columnar  epithelium.  At  the  point  where  the  terminal 
tubes  open  into  the  duct,  and  which  is  termed  the  neck,  the  epithelium  alters,  and 
consists  of  short  columnar  or  polyhedral,  granular  cells,  which  almost  fill  the  tube, 
so  that  the  lumen  becomes  suddenly  constricted,  and  is  continued  down  as  a  very 
fine  channel.  They  are  known  as  the  chiof  or  the  peptic  or  the  central  cells  of  the 
glands,  and  furnish  pepsin.  Between  these  cells  and  the  basement-membrane  are 
found  other  darker  granular-looking  cells,  studded  throughout  the  tubes  at  inter- 
vals, and  giving  it  a  beaded  or  varicose  appearance.  These  are  known  as  the 
parietal  or  oxyntic  cells.  Some  of  the  parietal  cells  empty  directly  into  the  lumen 
of  the  gland  by  secretory  capillaries;  others  empty  by  a  duct  which  divides  into 
secretory  capillaries.  The  parietal  cells  secrete  the  acid  of  the  gastric  juice. 
Between  the  glands  the  mucous  membrane  consists  of  a  connective-tissue  frame- 
work with  lymphoid  tissue.  In  places  this  latter  tissue,  especially  in  early  life,  is 
collected  into  little  masses,  which  to  a  certain  extent  resemble  the  solitary  glands 
of  the  intestine,  and  are  by  some  termed  the  lenticular  glands  of  the  stomach.  They 
are  not,  however,  so  distinctly  circumscribed  as  the  solitary  glands. 

The  Pyloric  Glands  (glandulae  pyloricae)  (Fig.  896)  are  the  branched  tubular 
glands,  and  secrete  mucus. 

They  are  placed  most  plentifully  about  the  pylorus,  but  between  the  fundus  and 
pylorus,  in  the  region  known  as  the  transitional  or  intermediate  zone,  both  true 
gastric  glands  and  pyloric  glands  are  found.  Each  pyloric  gland  consists  of  two 
or  three  short,  closed  tubes  opening  into  a  common  duct,  the  external  orifice  of 
which  is  situated  at  the  bottom  of  an  alveolus.  The  caecal  tubes  are  wavy,  and 
are  of  about  equal  length  with  the  duct.  The  tubes  and  duct  are  lined  through- 
out with  epithelium,  the  duct  being  lined  by  columnar  cells  continuous  with  the 
epithelium  lining  the  surface  of  the  mucous  membrane  of  the  stomach,  the  tubes 
with  shorter  and  more  cubical  cells,  which  are  finely  granular.  The  pyloric 
glands  branch  more  frequently,  are  more  curved  in  direction,  and  open  into 
deeper  foveolae  than  the  true  gastric  glands  (Szymonowicz).  They  contain  only 
chief  or  peptic  cells  and  do  not  possess  parietal  cells. 


1286 


THE    ORGANS    OF   DIGESTION 


PLEXUS 

iENCATH  THE 

EPITHELIUM 


GLANDULAR 
PLEXUS 


The  Cardiac  Glands  are  found  about  the  oesophageal  orifice.  They  resemble 
the  pyloric  glands. 

Beneath  the  mucous  membrane,  and  between  it  and  the  submucous  coat,  is  a 
thin  stratum  of  involuntary  muscular  fibre  (muscularis  mucosae),  which  in  some 
parts  consists  only  of  a  single  longitudinal  layer;  in  others,  of  two  layers,  an  inner 
circular,  and  an  outer  longitudinal. 

Vessels  and  Nerves. — The  arteries  supplying  the  stomach  are — the  gastric  or 
coronary,  the  pyloric  and  the  right  gastro-epiploic  branch  of  the  gastro-duodendal,  the 

left  gastro-epiploic  and  vasa  brevia  from 
the  splenic.  The  gastric  artery  passes  to  the 
lesser  curvature  just  below  the  cardia.  It 
gives  off  the  oesophageal  branch,  and  passes 
from  left  to  right  along  the  lesser  curva- 
ture of  the  stomach  beneath  the  perito- 
neum between  the  two  layers  of  the  lesser 
omentum  and  upon  the  wall  of  the  stomach. 
It  may  in  this  course  be  a  single  vessel,  or 
may  divide  into  two  branches,  which  run 
along  each  side  of  the  lesser  curvature  (Fig. 
899).  If  there  is  a  single  artery  it  gives  off 
six  or  seven  descending  branches  to  the  an- 
terior wall  and  about  the  same  number  to 

FIG.  888.-TenninationS~o7thI  blood-vessels  in   the  posterior  wall  of  the  stomach.     It  also 
and  chappy  )membrane  °f  the  stomach'    (p°irier  gives  branches  to  the  lesser  omentum.     If 

two  vascular  arches  form,  one  gives  branches 

to  the  anterior  wall  of  the  stomach,  the  other  to  the  posterior  wall,  and  both  to 
the  lesser  omentum.  The  termination  of  the  gastric  anastomoses  with  the 
pyloric  branch  or  two  rami  of  the  pyloric  branch  of  the  hepatic  artery.  From 
each  arch  six  or  seven  descending  branches  come  off  to  the  anterior  and  posterior 


ARTERIOLE 

PLEXUS  OF 

BLOODVESSELS 

IN  SUBMUCOUS 

TISSUE 


CASTRO- DUODENAL 
ARTERY 


RIGHT  GASTRO- 
EPIPLOIC  ARTERY 


LEFT  GASTRO- 
EPIPLOIC  ARTERY 


FIG.  899.  —The  arteries  of  the  anterior  surface  of  the  stomach.     (Poirier  and  Charpy.) 

walls  of  the  stomach.  The  gastro -duodenal  artery  is  given  off  by  the  hepatic. 
From  the  gastro-duodenal  comes  the  right  gastro-epiploic.  The  left  gastro- 
epiploic  comes  from  the  splenic.  The  right  gastro-epiploic  artery  passes  from 
right  to  left  in  the  gastro-colic  omentum  below  the  greater  curvature  of  the 


THE   STOMACH  1287 

stomach.  The  left  gastro-epiploic  artery  passes  forward  in  the  gastro-splenic 
ligament  to  below  the  greater  curvature  of  the  stomach,  and  passes  from  left  to 
right  along  that  curvature  in  the  gastro-colic  omentum,  and  joins  the  right  gastro- 
epiptoic  artery.  The  gastro-epiploic  arteries  are  not  upon  but  are  distinctly 
below  the  stomach  wall.  From  them  numerous  gastric  branches  are  sent  to  the 
anterior  and  posterior  walls  of  the  stomach,  and  they  anastomose  with  branches 
of  the  gastric  and  pyloric.  Vasa  brevia,  four  or  five  in  number,  arise  from  the 
splenic,  pass  forward  in  the  gastro-splenic  ligament,  and  supply  the  fundus. 
The  arteries  of  the  stomach  lie  first  beneath  the  peritoneum,  but  soon  enter  the 
muscular  coat,  supply  it,  pierce  it,  ramify  in  the  submucous  coat,  and  are  finally 
distributed  to  the  mucous  membrane.  The  arrangement  of  the  vessels  in  the 
mucous  membrane  is  somewhat  peculiar  (Fig.  898).  The  arteries  break  up  at 
the  base  of  the  gastric  tubules  into  a  plexus  of  fine  capillaries  which  run  upward 
between  the  tubules,  anastomosing  with  each  other,  and  ending  in  a  plexus  of 
larger  capillaries,  which  surround  the  mouths  of  the  tubes  and  also  form  hexagonal 
meshes  around  the  alveoli. 

The  capillary  networks  about  the  glands  give  origin  to  the  veins.  The  various 
small  veins  unite  and  form  a  plexus  in  the  submucous  tissue  (Fig.  898) .  From  this 
plexus  come  branches  which  pass  through  the  muscular  coat  and  terminate  in  the 
right  gastro-epiploic  branch  of  the  superior  mesenteric,  the  left  gastro-epiploic  branch 
of  the  splenic,  the  veins  to  the  splenic  which  correspond  to  the  vasa  brevia  arteries, 
and  the  gastric  or  coronary  branch  of  the  portal. 

The  lymphatics  (Figs.  505  and  506)  arise  in  the  mucous  membrane  and  terminate 
in  a  network  in  the  submucous  tissue.  From  this  network  trunks  arise  which 
perforate  the  muscular  coat  in  the  regions  of  the  curvatures  and  terminate  in  the 
sero-muscular  collecting  trunks.1 

According  to  Cune"o,  there  are  three  groups  of  these  collectors.  Those  from  the 
lesser  curvature  pass  to  the  point  where  the  gastric  artery  reaches  the  stomach  and 
enter  the  glands  along  the  gastric  artery.  Those  from  the  greater  curvature  pass 
from  left  to  right  and  enter  the  sub-pyloric  glands.  Those  from -the  fundus  pass 
from  right  to  left  and  end  in  the  splenic  glands.  Cuneo  further  pointed  out  that 
the  region  drained  by  the  collectors  of  the  lesser  curvature  is  divided  from  the 
others  by  the  line  shown  in  Fig.  506.  This  division  exists  on  both  surfaces  of 
the  stomach.  The  limit  between  the  collectors  which  drain  into  the  splenic 
glands  and  those  which  drain  into  the  sub-pyloric  glands  is  also  shown  in 
Fig.  506.  Along  the  lesser  curvature  the  lymph-glands  are  few  in  number  and 
are  limited  to  the  pyloric  region,  and  the  lymph- vessels  are  placed  directly  upon 
the  stomach  wall.  The  lymph-glands  and  vessels  are  not  upon  but  are  distinctly 
below  the  greater  curvature. 

The  subserous  and  submucous  lymphatic  networks  of  the  stomach  communi- 
cate with  the  corresponding  networks  of  the  oesophagus,  but  in  all  probability  do 
not  communicate  with  the  networks  of  the  duodenum. 

The  nerves  of  the  stomach  come  from  the  right  and  left  vagus  and  from  the  solar 
plexus  of  the  sympathetic.  The  left  vagus  passes  to  the  front  of  the  stomach,  and 
the  right  nerve  passes  to  the  back,  and  they  unite  with  the  fibres  of  the  sym- 
pathetic. The  fibres  thus  formed  are  mostly  amyelinic.  They  form  Auerbach's 
plexus  in  the  muscular  coat  between  the  circular  and  longitudinal  fibres  and 
Meissner's  plexus  in  the  submucous  coat,  the  latter  plexus  being  formed  by  fibres 
from  the  former.  Fibres  from  Meissner's  plexus  ramify  in  the  submucous  coat 
and  terminate  in  the  muscularis  mucosae  and  the  mucous  membrane,  branches 
passing  to  the  gastric  glands  and  to  just  beneath  the  epithelium. 

1  The  Lymphatics.     By  Poirier,  Cune'o,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


1288  THE    ORGANS    OF  DIGESTION 

Movements  and  Innervation  of  the  Stomach. 

Movements. — It  has  apparently  been  demonstrated  that  the  stomach  "consists  of  two  parts 
physiologically  distinct."1  The  cardiac  portion  of  the  stomach  is  a  food  reservoir  in  which 
salivary  digestion  continues;  the  pyloric  portion  is  the  seat  of  active  digestion.  Cannon  affirms 
that  there  are  no  peristaltic  waves  in  the  cardiac  portion,  but  that  as  the  food  passes  from  the 
pyloric  portion  into  the  intestines,  tonic  contraction  of  the  -muscles  of  the  fundus  squeezes  the 
contents  of  the  pyloric  portion.  Moritz,  Levan,  and  Cannon  assert  that  muscular  activity  is 
chiefly  manifested  in  the  pyloric  portion.  In  this  portion  during  digestion  there  is  a  succes- 
sion of  peristaltic  waves,  which  waves  in  the  human  being  pass  at  the  rate  of  three  per  minute 
(Moritz).  Cannon  .points  out  that  the  efficiency  of  peristalsis  in  mixing  the  food  depends 
upon  the  contraction  of  the  pyloric  sphincter.  So  long  as  the  sphincter  holds,  each  constric- 
tion-ring coursing  from  the  middle  to  the  end  of  the  stomach  presses  the  food  into  a  blind  pouch; 
the  food,  unable  to  escape  through  the  pyloric  opening,  has  as  its  only  outlet  the  opening  in 
the  advancing  ring.  This  is  an  admirable  device  for  bringing  the  food  under  the  influence  of 
the  glandular  secretions  of  the  pyloric  region.  For,  as  a  constriction  occurs,  the  secreting  sur- 
face enclosed  by  the  narrowed  muscular  ring  is  pressed  close  around  the  food  within  the  ring. 
As  the  constriction  advances  it  continually  presses  inward  fresh  glandular  tissue,  and  further- 
more, as  the  constriction  advances,  a  thin  stream  of  food  is  continuously  forced  back  through 
the  ring  and  thus  past  the  mouths  of  the  glands.  The  old  view  that  the  pyloric  sphincter  only 
opens  after  several  hours'  continuance  of  the  process  of  digestion  and  that  then  the  stomach 
empties  at  once  is  incorrect.  It  is  emptied  in  small  amounts  which  escape  at  frequent  intervals 
because  of  the  intermittent  opening  of  the  pylorus.  When  the  pylorus  is  open  a  wave  of  peri- 
stalsis forces  some  of  the  material  from  the  stomach  into  the  duodenum  (Cannon). 

Cannon  is  of  the  opinion  that  the  pyloric  sphincter  is  caused  to  relax  by  the  presence  of  free 
hydrochloric  acid  in  the  pyloric  portion  of  the  stomach.  When  the  pylorus  is  open  acid  chyme 
passes  into  the  duodenum  and  acid  in  the  duodenum  causes  the  pylorus  to  close.  The  acid 
in  the  duodenum  causes  a  flow  of  alkaline  pancreatic  juice  and  the  acid  is  neutralized.  "As 
the  neutralizing  proceeds  the  stimulus  closing  the  pylorus  is  weakened  until  the  acid  in  the 
stomach  again  opens  the  sphincter."2 

Innervation. — The  stomach,  as  previously  shown,  has  nerve  plexuses  in  its  walls  and  is 
connected  to  the  brain,  spinal  cord,  and  sympathetic  system.  It  is  probable  that  gastric  peri- 
stalsis is  due  to  a  local  reflex  from  Auerbach's  plexus  (Magnus),  the  local  reflex  being  inaugu- 
rated by  local  stimulation,  which  stimulation,  in  the  words  of  Bayliss  and  Starling,  "produces 
excitation  above  and  inhibition  below  the  excited  spot."3  Reversed  peristalsis  cannot  occur 
if  "the  reflex  mechanism  is  intact"  (Cannon).  Cannon  in  the  previously  quoted  article  states 
that  cutting  the  vagus  or  splanchnic  nerves  does  not  destroy  the  reflex  mechanism  of  the  pylorus, 
but,  nevertheless,  it  is  markedly  affected  by  the  central  nervous  system. 

Surface  Form  (see  p.  1280). — The  cardiac  orifice  corresponds  to  the  articulation  of  the 
seventh  left  costal  cartilage  with  the  sternum.  The  pyloric  orifice  of  the  empty  stomach  is  in 
a  vertical  line  drawn  from  the  right  border  of  the  sternum,  two  and  a  half  or  three  inches  below 
the  level  of  the  sterno-xiphoid  articulation.  According  to  Braune,  when  the  stomach  is  dis- 
tended, the  pylorus  moves  considerably  to  the  right,  as  much  sometimes  as  three  inches.  The 
fundus  of  the  stomach  reaches,  on  the  left  side,  as  high  as  the  level  of  the  sixth  costal  cartilage 
of  the  left  side,  being  a  little  below  and  behind  the  apex  of  the  heart.  The  portion  of  the  distended 
stomach  which  is  in  contact  with  the  abdominal  walls,  and  is  therefore  accessible  for  opening  in 
the  operations  of  gastrotomy  and  gastrostomy,  is  represented  by  a  triangular  space,  the  base  of 
which  is  formed  by  a  line  drawn  from  the  tip  of  the  tenth  costal  cartilage  on  the  left  side  to  the 
tip  of  the  ninth  costal  cartilage  on  the  right,  and  the  sides  by  two  lines  drawn  from  the  extremity 
of  the  eighth  costal  cartilage  on  the  left  side  to  the  ends  of  the  base  line. 

Surgical  Anatomy. — Operations  on  the  stomach  are  frequently  performed,  ulcers  are  excised, 
malignant  growths  are  removed  with  the  associated  lymphatic  involvement,  the  entire  stomach 
may  be  removed  for  cancer,  etc.  By  ''  gastrotomy"  is  meant  an  incision  into  the  stomach  for  the 
removal  of  a  foreign  body,  or  the  arrest  of  hemorrhage  or  for  exploration,  the  opening  being 
immediately  afterward  closed — in  contradistinction  to  "  gastrostomy,"  the  making  of  a  more  or 
less  permanent  fistulous  opening.  Gastrotomy  is  probably  best  performed  by  an  incision  in  the 
linea  alba,  especially  if  the  foreign  body  is  large.  The  cut  may  reach  from  the  ensiform  car- 
tilage to  the  umbilicus.  The  incision  may  be  made  over  the  body  itself,  where  this  can  be  felt, 
or  by  one  of  the  incisions  for  gastrostomy,  to  be  mentioned  shortly.  The  peritoneal  cavity 
is  opened,  and  the  point  at  which  the  stomach  is  to  be  incised  decided  upon.  This  portion  is 
then  brought  out  of  the  abdominal  wound  and  sponges  carefully  packed  around.  The  stomach 
is  now  opened  by  a  transverse  incision  and  the  foreign  body  extracted.  The  wound  in  the 
stomach  is  then  closed  by  Lembert  sutures — i.  e.,  by  sutures  passed  through  the  peritoneal, 

1  Walter  B.  Cannon,  Medical  News,  May  20,  1905,  -  Ibid.  3  Ibid. 


MOVEMENTS   AND  INNERVATION   OF   THE  STOMACH    1289 

muscular  and  submucous  coats  in  such  a  way  that  the  peritoneal  surfaces  on  each  side  of  the 
wound  are  brought  into  apposition,  (raxtroxfomij  was  formerly  done  in  two  stages  by  the  direct 
method.  The  first  stage  consisted  in  opening  the  abdomen,  drawing  up  the  stomach  into  the 
external  wound,  and  fixing  it  there;  and  the  second  stage,  performed  from  two  to  four  days 
afterward,  consisted  in  opening  the  stomach.  The  operation  is  now  done  by  a  valvular  method. 
The  following  plan  is  known  as  the  Ssabanejew-Frank  operation.  An  incision  is  commenced 
opposite  the  eighth  intercostal  space,  two  inches  to  the  left  of  the  median  line,  and  carried 
downward  for  three  inches.  By  this  incision  the  fibres  of  the  Rectus  muscle  are  exposed  and 
these  are  separated  from  each  other  in  the  same  line.  The  posterior  layer  of  the  sheath,  the 
transversalis  fascia  and  the  peritoneum,  are  then  divided,  and  the  peritoneal  cavity  is  opened. 
Instead  of  the  above  incision,  the  curved  incision  of  Fenger  can  be  made  at  the  margin  of  the 
left  costal  cartilages.  The  anterior  wall  of  the  stomach  is  now  seized  and  drawn  out  of  the 
wound  and  a  silk  suture  passed  through  its  submucous,  muscular,  and  serous  coats  at  the  point 
selected  for  opening  the  viscus.  This  is  held  by  an  assistant  so  that  a  long  conical  divertic- 
ulum  of  the  stomach  protrudes  from  the  external  wound,  and  the  parietal  peritoneum  and 
the  posterior  layer  of  the  sheath  of  the  rectus  are  sutured  to  the  base  of  the  cone.  A.  second 
incision  is  made  through  the  skin,  over  the  margin  of  the  costal  cartilage,  above  and  a  little  to  the 
outer  side  of  the  first  incision.  If  Fenger's  incision  were  used,  the  second  incision  should  be 
above  the  margin  of  the  cartilages.  With  a  pair  of  dressing  forceps  a  track  is  made  under  the 
skin  through  the  subcutaneous  tissue  from  the  one  opening  to  the  other  and  the  diverticulum  of 
the  stomach  is  drawn  along  this  track  by  means  of  the  suture  inserted  into  it;  so  that  its  apex 
appears  at  the  second  opening.  A  small  perforation  is  now  made  into  the  stomach  through 
this  protruding  apex  and  its  margin  carefully  and  accurately  sutured  to  the  margin  of  the 
external  wound.  The  remainder  of  this  incision  and  the  whole  of  the  first  incision  are  then 
closed  in  the  ordinary  way  and  the  wound  dressed. 

In  cases  of  gastric  ulcer,  perforation  sometimes  takes  place,  and  this  was  formerly  regarded 
as  an  almost  fatal  complication.  In  the  present  day,  by  opening  the  abdomen  and  closing 
the  perforation,  which  is  generally  situated  on  the  anterior  surface  of  the  stomach,  a  consider- 
able percentage  of  cases  are  cured,  provided  the  operation  is  undertaken  within  twelve  to  fifteen 
hours  after  the  perforation  has  taken  place.  The  opening  is  best  closed  by  bringing  the  peri- 
toneal surfaces  on  either  side  into  apposition  by  means  of  Lembert  sutures. 

Pylorectomy  or  excision  of  the  pylorus  is  performed,  particularly  for  early  cancer,  but  is  also 
done  for  cicatricial  stricture  and  for  ulcer.  The  mortality  after  operation  for  cancer  was,  until 
recently,  very  great,  but  of  late  years  it  has  been  notably  reduced,  though  it  is  still  much  higher 
than  that  which  follows  operation  for  any  non-malignant  condition. 

In  operating  for  cancer,  bear  in  mind  Cuneo's  study  of  the  lymphatics  (page  806).  These 
observations  indicate  that  the  fundus  and  two-thirds  of  the  greater  curvature  are  free  from 
lymphatic  involvement  in  pyloric  cancer.1  In  every  operable  case  of  cancer  of  the  pylorus  the 
entire  lesser  curvature  must  be  removed  up  to  the  gastric  artery  (Mikulicz's  point),  and  the 
greater  curvature  must  be  removed  to  the  left  of  the  involved  glands  (Hartmann's  rule). 

Gastro-enterostomy  is  an  operation  which  establishes  a  fistulous  communication  between  the 
stomach  and  jejunum.  The  operation  is  often  called  gastro-jejunostomy.  The  opening  may  be 
made  upon  either  the  anterior  or  the  posterior  wall  of  the  stomach,  between  the  cardia  and  the 
seat  of  pyloric  disease.  The  operation  is  employed  for  stricture  of  the  pylorus  (benign  or 
malignant),  and  occasionally  for  ulcer  of  the  stomach. 

Lorela's  operation  is  digital  divulsion  of  the  pylorus  for  cicatricial  stricture,  the  stomach  being 
incised  transversely  near  the  pylorus  to  admit  the  finger,  and  the  wound  in  the  stomach  being 
sutured  after  division  has  been  effected.  The  operation  has  been  abandoned,  because  contraction 
recurs. 

Pyloroplasty,  or  the  Heineke-Mikulicz  operation,  displaced  Loreta's  operation.  In  this  pro- 
cedure an  incision  is  made  through  the  stricture  in  the  direction  of  the  long  axis  of  the  stomach 
and  bowel.  By  making  traction  on  each  side  of  the  incision,  the  longitudinal  wound  assumes  a 
vertical  direction,  and  sutures  are  inserted  so  as  to  close  the  wound  in  a  vertical  line.  The  method 
of  pyloroplasty  devised  by  Finney,  of  Baltimore,  makes  a  large  permanent  opening  at  the 
most  dependent  part  of  the  stomach,  and  is  the  most  satisfactory  method  of  which  we  are 
possessed.2 

Total  gastrectomy  is  the  removal  of  the  entire  stomach.  It  is  only  used  for  cancer.  It  was  first 
performed  by  Conner,  of  Cincinnati.  The  first  successful  operation  was  done  by  Schlatter,  of 
Zurich,  in  1898.  A  number  of  successes  have  been  reported.  It  is  a  justifiable  operation  only  in 
a  case  in  which  almost  the  entire  stomach  is  cancerous,  in  which  the  viscus  is  movable,  in  which 
there  are  no  secondary  deposits,  and  no  irremovable  diseased  glands. 

Gastro-gastrostomy  is  an  operation  employed  in  hour-glass  stomach.  In  this  operation  an 
anastomosis  is  made  between  the  pyloric  and  cardiac  ends  of  the  stomach. 


1  William  J.  Mayo,  Annals  of  Surgery,  March,  1904. 

2  Johns  Hopkins  Hospital  Bulletin,  July,  1902. 


1290  THE    ORGANS    OF  DIGESTION 

Gastroplication  is  the  operation  of  suturing  the  stomach  wall  into  folds  or  reefs,  in  order  to 
lessen  its  size.  It  is  employed  in  some  cases  of  gastric  dilatation. 

Gastroptosis  is  a  condition  in  which  the  stomach  is  displaced  downward.  In  some  of  these 
cases  the  greater  curvature  almost  reaches  the  level  of  the  symphysis  pubis,  and  the  lesser  curva- 
ture is  midway  between  the  umbilicus  and  ensiform  cartilage.  The  condition  is  usually  associated 
with  enteroptosis  and  movable  kidney  (nephroptosis).  In  this  condition  the  gastro-hepatic 
omentum  and  the  gastro-phrenic  ligament  are  pulled  upon  and  lengthened.  The  best  operation 
for  gastroptosis  was  devised  by  Beyea.  He  applies  sutures  so  as  to  make  folds  in  and  thus  shorten 
the  stretched  ligament  and  omentum.  Thus  the  stomach  is  elevated  to  its  proper  position,  and 
its  mobility  is  not  lessened,  as  it  is  in  other  operations  which  suture  it  to  the  abdominal  wall. 


THE  SMALL  INTESTINE   (INTESTINUM  TENUE). 

The  small  intestine  is  a  convoluted  tube,  extending  from  the  pylorus  to  the 
ileo-caecal  valve,  where  it  terminates  in  the  large  intestine.  It  fills  up  the  greater 
part  of  the  abdominal  cavity  and  of  the  pelvic  cavity.  It  is  about  twenty  feet  in 
length,1  and  gradually  diminishes  in  size  from  its  commencement  to  its  termina- 
tion. The  diameter  of  the  duodenum  is  almost  two  inches;  the  diameter  of  the 
lower  portion  of  the  small  intestine  is  little  more  than  one  inch.  It  is  contained 
in  the  central  and  lower  part  of  the  abdominal  cavity,  and  is  surrounded  above 
and  at  the  sides  by  the  large  intestine;  a  portion  of  it  extends  below  the  brim  of 
the  pelvis  and  lies  in  front  of  the  rectum;  it  is  in  relation,  in  front,  with  the  great 
omentum  and  abdominal  parietes;  and  connected  to  the  spine  by  a  fold  of  peri- 
toneum, the  mesentery  (p.  1266).  The  small  intestine  is  divisible  into  three  portions 
—the  duodenum,  the  jejunum,  and  ileum. 

The  Duodenum  (Figs.  900,  905,  906,  907,  908). 

The  duodenum  has  received  its  name  from  being  about  equal  in  length  to  the 
breadth  of  twelve  fingers  (ten  inches).  It  is  the  shortest,  the  widest,  and  the  most 
fixed  part  of  the  small  intestine,  being  closely  and  firmly  attached  to  the  posterior 
abdominal  wall.  It  does  not  possess  a  mesentery.  Somewhat  more  than  the 
upper  half  of  the  duodenum  is  placed  in  the  epigastric  region ;  the  remainder  is  in 
the  umbilical  region.  The  duodenum,  with  the  exception  of  the  ascending  portion, 
is  to  the  right  of  the  median  line.  Its  course  presents  a  remarkable  curve,  which 
in  the  adult,  as  regards  the  greater  part  of  its  extent,  is  horseshoe-shaped,  though 
sometimes,  in  consequence  of  the  transverse  portion  being  very  short  or  alto- 
gether wanting,  it  partakes  more  of  the  character  of  the  letter  V.  The  opening 
of  the  horseshoe  being  directed  upward  and  to  the  left.  In  children  up  to 
the  age  of  about  seven  the  duodenum  is  annular.  The  two  extremities  of 
the  duodenum  are  nearly  on  the  same  level,  the  exit  being  slightly  lower  than  the 
entrance.  The  two  ends  are  about  two  inches  apart;  and  between  them  it 
describes  a  regular  curve  embracing  the  head  of  the  pancreas,  the  neck  of  which 
lies  between  the  two  extremities  of  the  ring. 

In  the  adult  the  course  of  the  duodenum  is  as  follows:  commencing  at  the 
pylorus  the  direction  of  the  first  portion  depends  upon  the  amount  of  distention 
of  the  stomach  and  therefore  upon  the  position  of  the  pylorus.  When  the  stomach 
is  empty  and  the  pylorus  is  situated  at  the  right  of  the  upper  border  of  the  first 
lumbar  vertebra,  it  is  nearly  horizontal  and  transverse ;  but  where  the  stomach  is 
distended,  in  consequence  of  the  alteration  of  the  position  of  the  pylorus  to  the 
right  the  proximal  end  of  the  duodenum  also  becomes  altered  in  position,  while  the 

1  Treves  states  that  in  one  hundred  cases  the  average  length  of  the  small  intestine  in  the  adult  male  was  22 
feet  6  inches,  and  in  the  adult  female  23  feet  4  inches  ;  but  that  it  varies  very  much,  the  extremes  in  the  male 
being  31  feet  10  inches  in  one  case  and  15  feet  6  inches  in  another,  a  difference  of  over  15  feet       He  states  that 
he  has  convinced  himself  that  the  length  of  the  bowel  is  independent,  in  the  adult,  of  age,  height,  and  weight. 
ED.  of  15th  English  edition. 


THE   DUODENUM 


1291 


distal  end  remains  fixed  and  the  direction  of  this  portion  of  the  bowel  is  now 
antero-posterior.    Whether  directed  transversely  or  antero-posteriorly,  it  reaches 


Tributary  to  vena  cara. 


Hepatic  artery,  portal^ 
vein,  and  bile  duct 


Supra-  renal 
capsule. 


'rura  of  Diaphragm. 
Gastric  artery. 


Eight 

renal 
Vessels 


Splenic 
artery. 

Splenic 
vein. 


FIG.  900. — Relations  of  duodenum,  pancreas,  and  spleen.     (From  a  cast  by  Professor  Birmingham.1) 
The  dotted  line  represents  the  line  of  attachment  of  the  transverse  mesocolon. 

the  under  surface  of  the  liver,  where  it  takes  a  sharp  curve  and  descends  along  the 
right  side  of  the  vertebral  column,  for  a  variable  distance,  generally  to  the  body  of 


1  In  the  subject  from  which  the  cast  was  taken  the  left  kidney  was  lower  than  normal. 


1292 


THE    ORGANS    OF   DIGESTION 


the  fourth  lumbar  vertebra.  It  now  takes  a  second  bend,  and  passes  across  the 
front  of  the  vertebral  column  from  right  to  left  and  finally  ascends  on  the  left  side 
of  the  vertebral  column  and  aorta  to  the  level  of  the  upper  border  of  the  second 
lumbar  vertebra  and  there  terminates  in  the  jejunum.  As  it  unites  with  the 
jejunum  it  often  turns  abruptly  forward,  forming  the  duodeno-jejunal  angle.  Prof. 


Omentum  Minus 


x    Lesser  Sac 


\0 


Hepatic 
Artery 


Portal 
Vein 


,  •  /'/  Greater  , 

Omeiitum      '{'' 
Majim     Transverse  Mesocolo 
FIG.  901. — Diagram  of  cross-section  of  the  first 


FIG.  902.—  Diagram  of  cross-section  of  the  second  part 


part   of    the  duodenum,   to   show  its    peritoneal          of     the    duodenum,   to     show    its    peritoneal    relations. 


relations. 


(Gerrish.) 


Birmingham  points  out  that  the  incomplete  ring  formed  by  the  duodenum  does 
not  lie  throughout  in  the  same  plane.  "Its  greater  part  is  placed  in  a  transverse 
vertical  plane ;  the  middle  portion  bends  strongly  backward,  around  the  right  side 
of  the  vena  cava,  and  lies  almost  in  a  sagittal  plane."1  From  the  above  descriotion 


FIG.  903. — Diagram  of  the  third  part  of  the 
duodenum,  to  show  its  peritoneal  relations. 
(Gerrish.) 


FIG.  904. — Diagram  of  the  fourth  part  of  the  duodenum, 
to  show  its  peritoneal  relations.     (Gerrish.) 


it  will  be  seen  that  the  duodenum  may  be  divided  for  purposes  of  description 
into  four  portions — superior,  descending,  transverse  and  ascending. 

The  First  or  Superior  Portion  (pars  superior)  (Figs.  900,  905,  and  907)  is 
very  variable  in  length,  but  is  usually  estimated  as  being  about  two  inches. 
Beginning  at  the  pylorus,  it  ends  at  the  level  of  the  neck  of  the  gall-bladder. 


1  Prof.  Cunningham's  Text-book  of  Anatomy. 


THE  DUODENUM  1293 

When  the  stomach  is  empty  this  portion  of  the  duodenum  is  horizontal  and 
transverse;  when  the  stomach  is  distended  it  extends  from  before  backward.  It 
is  the  most  movable  of  the  four  portions.  It  is  almost  completely  covered  by  peri- 
toneum derived  from  the  two  layers  of  the  lesser  omentum.  A  small  part  of  its 
posterior  surface  is  not  completely  covered  by  peritoneum  (Fig.  901).  The  first 
inch  of  the  superior  portion  of  the  duodenum  is  completely  covered  by  perito- 
neum; the  lesser  omentum  is  attached  above  and  the  greater  omentum  below 
(Fig.  901).  The  other  portion  has  only  its  anterior  wall  covered  by  peritoneum. 
The  posterior  and  lateral  surfaces  are  uncovered  by  peritoneum  and  are  near  the 
neck  of  the  gall-bladder  and  the  postcava.  The  first  portion  of  the  duodenum  is 
in  such  close  relation  with  the  gall-bladder  that  it  is  usually  found  to  be  stained 
by  bile  after  death,  especially  on  its  anterior  surface.  It  is  in  relation  above  and  in 
front  with  the  quadrate  lobe  of  the  liver,  lying  in  a  slight  concavity,  the  impressio 
duodenalis.  It  is  also  in  relation  above  in  part  with  the  gall-bladder;  behind  with 
the  gastro-duodenal  artery,  the  common  bile-duct,  and  the  portal  vein;  and 
below  with  the  head  of  the  pancreas.  The  superior  portion  of  the  duodenum 
crosses  the  transverse  fissure  of  the  liver,  and  by  means  of  the  superior  flexure 
of  the  duodenum  (flexura  duodeni  superior)  passes  into  the  second  or  descending 
portion  beneath  the  caudate  lobe. 

The  Second  or  Descending  Portion  (pars  descendens)  (Figs.  900,  905,  and  907) 
is  between  three  and  four  inches  in  length,  and  extends  from  the  neck  of  the  gall- 
bladder on  a  level  with  the  first  lumbar  vertebra  along  the  right  side  of  the  verte- 
bral column  as  low  as  the  body  of  the  fourth  lumbar  vertebra.  It  is  crossed  in 
its  middle  third  by  the  transverse  colon,  the  posterior  surface  of  which  is  uncovered 
by  peritoneum  and  is  connected  to  the  duodenum  by  a  small  quantity  of  connective 
tissue.  The  portions  of  the  descending  part  of  the  duodenum  above  and  below 
this  interspace  are  named  the  supracolie  and  infracolic  portions,  and  are  covered 
in  front  by  peritoneum  (Fig.  902).  The  right  side  of  the  supracolie  portion  is 
covered  by  peritoneum  derived  from  the  anterior  surface  of  the  right  kidney,  the 
left  side  of  the  same  portion  being  covered  by  the  peritoneum  forming  the  lesser 
sac.  The  infracolic  part  is  covered  by  the  right  leaf  of  the  mesentery.  Pos- 
teriorly the  descending  portion  of  the  duodenum  is  uncovered  by  peritoneum. 
The  descending  portion  of  the  duodenum  is  in  relation,  in  front,  with  the  trans- 
verse colon,  and  above  this  with  the  right  lobe  of  the  liver,  where  it  lies  in  the 
impressio  duodenalis  for  the  second  part  of  the  duodenum;  behind  with  the  front  of 
the  right  kidney,  to  which  it  is  connected  by  loose  areolar  tissue,  the  renal 
vessels  and  the  postcava;  at  its  inner  side  is  the  head  of  the  pancreas,  and  the 
ductus  communis  choledochus;  to  its  outer  side  is  the  hepatic  flexure  of  the  colon. 
The  common  bile-duct  passes  downward  behind  the  first  portion  of  the  duodenum, 
descends  to  the  inner  side  of  the  second  portion,  is  joined  by  the  pancreatic  duct, 
and  the  two  ducts  perforate  the  inner  side  of  this  portion  of  the  intestine  obliquely, 
and  empty  into  the  duodenum  by  a  common  opening  or  by  two  openings  at  the 
summit  of  a  papilla,  some  three  or  four  inches  below  the  pylorus.  The  relations 
of  the  second  part  of  the  duodenum  to  the  right  kidney  present  considerable 
variations.  The  descending  portion  passes  into  the  transverse  portion  by  means 
of  the  flexura  duodeni  inferior. 

The  Third,  Pre-aortic,  Horizontal  or  Transverse  Portion  (pars  horizontalis 
inferior)  (Figs.  900,  905,  and  907)  varies  much  in  length;  when  the  duodenum 
assumes  the  ordinary  horseshoe  form,  it  measures  from  two  to  three  inches;  but 
when  it  presents  the  rarer  V-shaped  form,  it  is  practically  wanting  or  very  much 
reduced  in  length.  The  transverse  portion  is  described  as  the  horizontal  part  of 
the  ascending  or  last  portion  by  those  authors  who  divide  the  duodenum  into  three 
parts  instead  of  four.  It  commences  at  the  right  side  of  the  fourth  lumbar  vertebra 
and  passes  from  right  to  left,  with  a  slight  inclination  upward,  in  front  of  the  great 


1294 


THE  ORGANS  OF  DIGESTION 


vessels  and  crura  of  the  Diaphragm,  and  ends  in  the  fourth  portion  in  front  of 
or  just  to  the  left  of  the  abdominal  aorta.  It  is  crossed  by  the  superior  mesen- 
teric  vessels  and  mesentery.  The  posterior  surface  rests  upon  the  aorta,  the  post- 
cava,  and  the  crura  of  the  Diaphragm.  By  its  upper  surface  this  portion  of  the 
duodenum  is  in  relation  with  the  head  of  the  pancreas.  The  front  of  the  third 
portion  of  the  duodenum  is  covered  by  peritoneum  except  where  the  mesenteric 
vessels  and  root  of  the  mesentery  cross  it  (Fig.  903).  The  left  side  of  the  termi- 
nation of  the  ascending  portion  is  also  covered  by  peritoneum,  and  in  this  region 
the  duodenal  fossae  are  found  (p.  1270). 

The  Fourth  or  Ascending  Portion  of  the  Duodenum  (pars  ascendens]  (Figs. 
900,  905,  and  907)  is  about  two  inches  long.  It  ascends  on  the  left  side  of  the 
vertebral  column  and  aorta,  as  far  as  the  level  of  the  upper  border  of  the  second 
lumbar  vertebra,  where  it  turns  abruptly  to  the  right  and  forward  to  become  the 
jejunum,  forming  the  duodeno-jejunal  angle  or  flexure  (flexura  duodenojejunalis) 


LOBE  OF 

SPIGELIUS 


CELLULAR    MEMBRANE 

CONNECTING  THE    PARTS 

OFTHE    DUODENAL  Rl NG 

BEHIND  THE   PANCREAS 


DIAPHRAGM 


CCELIAC  AXIS 


GANGLION  OF 
CCELIAC    PLEXUS 
SUPERIOR    MESEN- 
TERIC ARTE.RY 

SUSPENSORY 
MUSCLE  OF 
DUODENUM 


FIG.  905. — Suspensory  muscle  of  the  duodenum  or  muscle  of  Treitz.     (Poirier  and  Charpy.) 

(Fig.  905).  It  is  covered  entirely  in  front  and  partly  at  the  sides  by  peritoneum, 
derived  from  the  left  portion  of  the  mesentery  (Fig.  904) .  The  superior  mesen- 
teric artery  and  vein  are  in  front  of  it.  It  touches  the  left  kidney,  slightly  over- 
lapping its  inner  margin,  and  rests  upon  the  left  crus  of  the  Diaphragm. 

The  first  part  of  the  duodenum,  as  stated  above,  is  somewhat  movable,  but  the 
rest  is  practically  fixed  and  is  bound  down  to  neighboring  viscera  and  the  posterior 
abdominal  wall  by  the  peritoneum.  In  addition  to  this,  the  fourth  part  of  the 
duodenum  and  the  duodeno-jejunal  flexure  is  further  bound  down  and  fixed  by  a 
structure  called  the  Suspensory  muscle  of  the  duodenum  or  the  suspensory  ligament  of 
Treitz  (m.  suspensorius  duodeni)  (Fig.  905).  This  structure  commences  in  the  con- 
nective tissue  around  the  coeliac  axis  and  left  crus  of  the  Diaphragm,  and  passes 
downward  to  be  inserted  into  the  superior  border  of  the  duodeno-jejunal  curve  and 
a  part  of  the  ascending  duodenum,  and  from  this  it  is  continued  into  the  mesentery. 
It  possesses,  according  to  Treitz,  some  few  plain  muscular  fibres  mixed  with  the 


THE   DUODENUM 


1295 


fibrous  tissue,  of  which  it  is  principally  made  up.    It  is  of  little  importance  as  a 
muscle,  but  acts  as  a  suspensory  ligament. 


SOUND  IN   DUC-  CARUNCULA   MINOR 

TUS  CHOLEDOCHUS  OFSANTOR.NI 


VALVULAE 
CONNIVENTES 


CARUNCULA 
MAJOR 


SOUND  IN 
ACCESSORY 
PANCREATIC 
DUCT  OF 
SANTORINI 


LONGITUDINAL 
FOLD 


VALVULAE 
CONNIVENTE8 


.SOUND  IN  PANCREATIC 

DUCT  OF  WIRSUNG 
SOUND  IN 
DUCTU6  CHOLEDOCHUS 

FIG.  906. — The  interior  of  the  duodenum.     (Spalteholz.) 


Gastric  artery 


Lower  end  of  oesophagus 
Cceliac  axis 


VA, 

J5 


Portal  vein 

Hepatic  duct 

Cystic  duct 

Hepatic  artery 

Kight  suprarenal 

capsule 

Pyloric  orifice 
Right  gastro-epiplaic 
artery 

Superior  mesenteric 


•3>  ** 

<fl 

.CVS 


Spermatic  vessels  \Spermaticvessds 

Inferior  mesenteric  artery 

FIG.  907. — The  duodenum,  its  four  parts  marked  «,  I,  c,  d.     The  liver  is  lifted  up  ;  the  greater  part  of  the 
stomach  is  removed,  broken  lines  indicating  its  former  position.     (Testut.) 


1296  THE  ORGANS  OF  DIGESTION 

Interior  of  the  Duodenum  (Fig.  906). — In  the  beginning  of  the  duodenum  valvulae 
conniventes  are  absent.  They  begin  to  appear  in  the  lower  half  of  the  first  portion, 
being  at  first  trivial  elevations  irregularly  placed.  They  become  higher,  regular, 
and  more  numerous  lower  down,  and  near  the  termination  of  the  duodenum  are 
strongly  marked  and  closely  placed  transverse  or  spiral  folds  (Fig.  906  and 
p.  1299).  In  the  descending  portion  (Fig.  906)  to  the  side  and  rear  is  a  longi- 
tudinal fold  (plica  longitudinalis  duodeni),  which  is  formed  by  the  projection  of 
the  bile-duct  and  pancreatic  duct  beneath  the  mucous  membrane. 

The  caruncula  major  of  Santorini  or  the  bile  papilla  is  a  projection  or  tit  in  the 
lower  part  of  the  longitudinal  fold.  At  the  summit  of  this  papilla  are  seen  two 
openings,  if  the  bile-duct  and  pancreatic  duct  have  not  united,  or  one  common 
opening  for  both  of  them,  if  they  have  united.  One  inch  above  and  half  an  inch 
or  more  in  front  of  the  bile  papilla  is  a  much  smaller  papilla,  the  caruncula  minor 
of  Santorini  (papilla  duodeni  [Santorini]),  on  the  summit  of  which  the  accessory 
pancreatic  duct  of  Santorini  opens. 

Structure  of  the  Duodenum. — The  peritoneal  coat  (tunica  serosa)  has  been  de- 
scribed. The  muscular  coat  (tunica  muscularis)  is  practically  identical  with  the 
muscular  coat  of  the  balance  of  the  intestine.  The  bile-duct  and  pancreatic  duct 

FIRST  GASTRO-  GASTRO-  INFERIOR 

PART  OF  DUODENAL       DUODENAL      COZLIAC  PANCREATICO- 

DUODENUM          ARTERY  VEIN  A,xl^  DUODENAL 

VEIN 


PANCREATICO- 

DUODENAL 

SUPERIOR 

ARTERY 


DUCTUS 
CHOLEDOCHUS 


ANASTOMOSIS  OF  THE 
TWO  PANCREATICO- 
DUODENAL ARTERIES 


FIG.  908. — The  blood-vessels  of  the  duodenum.     (Poirier  and  Charpy.) 

pass  through  it.  The  submucous  coat  (tela  submucosa)  contains  lymph-nodes  and 
glands  of  Brunner  (glandulae  duodenales).  These  glands  are  particularly  plenti- 
ful in  the  first  half  of  the  duodenum  (p.  1303).  The  mucous  membrane  is 
thicker  in  the  duodenum  than  in  the  rest  of  the  small  intestine,  is  covered  with 
villi,  and  from  the  lower  half  of  the  first  portion  down  is  formed  into  circular 
folds  or  valvulae  conniventes.  In  the  descending  part  it  exhibits  the  previously 
described  longitudinal  fold. 

Vessels  and  Nerves. — The  arteries  (Fig.  908)  supplying  the  duodenum  are  the 
pyloric  and  pancreatico -duodenal  branches  of  the  hepatic,  and  the  inferior  pancreatico- 
duodenal  branch  of  the  superior  mesenteric.  The  veins  (Fig.  908)  correspond  to 
the  arteries.  The  superior  duodenal  vein  passes  into  the  superior  mesenteric,  and 
the  inferior  duodenal  vein  passes  into  the  portal.  The  lymphatics  pass  along  with 
the  pancreatico-duodenal  arteries,  glands  being  present  here  and  there,  and 
terminate  in  the  glands  about  the  coeliac  axis.  The  duodenal  fossae  are  described 
on  p.  1270.  The  nerves  are  derived  from  the  solar  plexus. 


THE  JEJUNUM  AND    ILEUM  1297 

The  Jejunum  and  Ileum  (Figs.  875,  877,  878, 880,  905). 

The  remainder  of  the  small  intestine  from  the  termination  of  the  duodenum 
comprises  the  jejunum  and  ileum;  the  former  name  being  given  to  the  upper  two- 
fifths  and  the  latter  to  the  remaining  three-fifths.  Spalteholz  and  others  call  all  of 
the  small  intestine  below  the  duodenum  the  intestinum  tenue  mesenteriale.  There 
is  no  morphological  line  of  distinction  between  the  jejunum  and  ileum,  and  the 
division  is  arbitrary;  but  at  the  same  time  it  must  be  noted  that  the  character  of 
the  intestine  gradually  undergoes  a  change  from  the  commencement  of  the  jeju- 
num to  the  termination  of  the  ileum,  so  that  a  portion  of  the  bowel  taken  from 
these  two  situations  would  present  characteristic  and  marked  differences.  These 
are  briefly  as  follows: 

Differences  between  the  Jejunum  and  Ileum. — If  the  jejunum  high  up  is  con- 
trasted with  the  ileum  low  down,  it  is  noted  that  the  former  is  thicker,  of  greater 
diameter,  contains  more  blood-vessels,  and  hence  is  more  distinctly  red,  has  well- 
marked  valvulae  conniventes,  but  a  few  small-sized  Peyer's  patches,  and  the  villi 
are  short  and  broad.  In  the  ileum  large  Peyer's  patches  are  present  in  numbers, 
and  the  villi  are  thin  (Prof.  Birmingham). 

The  Jejunum  (intestinum  jejunum). — The  jejunum,  which  derives  its  name 
from  the  Latin  word  jejunus  (empty),  because  it  was  formerly  supposed  to  be 
empty  after  death,  is  wider,  its  diameter  being  about  one  inch  and  a  half,  and  is 
thicker,  more  vascular,  and  of  a  deeper  color  than  the  ileum,  so  that  a  given  length 
weighs  more.  Its  valvulae  conniventes  are  large  and  thickly  set  and  its  villi  are 
larger  than  in  the  ileum.  The  glands  of  Peyer  are  almost  absent  in  the  upper  part 
of  the  jejunum,  and  in  the  lower  part  are  less  frequently  found  than  in  the  ileum, 
and  are  smaller  and  tend  to  assume  a  circular  form.  Brunner's  glands  are  only 
found  in  the  upper  part  of  the  jejunum.  By  grasping  the  jejunum  between  the 
finger  and  thumb  the  valvulae  conniventes  can  be  felt  through  the  walls  of  the 
gut;  these  being  absent  in  the  lower  part  of  the  ileum,  it  is  possible  in  this  way 
to  distinguish  the  upper  from  the  lower  part  of  the  small  intestine. 

The  Ileum  (intestinum  ileum). — The  ileum  (so  called  from  the  Greek  word 
ei'te'tv,  to  twist,  on  account  of  its  numerous  coils  and  convolutions)  is  placed 
below  and  to  the  right  of  the  jejunum.  It  is  narrower,  its  diameter  being  one  inch 
and  a  quarter,  and  its  coats  are  thinner  and  less  vascular  than  those  of  the  jejunum. 
It  possesses  but  few  valvulae  conniventes,  and  they  are  small  and  disappear  entirely 
toward  its  lower  end,  but  Peyer's  patches  are  larger  and  more  numerous.  The 
jejunum  for  the  most  part  occupies  the  umbilical  and  left  iliac  regions,  while  the 
ileum  occupies  chiefly  the  umbilical,  hypogastric,  right  iliac,  and  pelvic  regions, 
and  terminates  in  the  right  iliac  fossa  by  opening  into  the  inner  side  of  the  com- 
mencement of  the  large  intestine.  The  upper  portion  of  the  jejunum  passes  to 
the  left  of  the  duodeno-jejunal  flexure,  and  is  in  relation  with  the  under  surface 
of  the  pancreas  and  the  transverse  mesocolon.  The  lower  portion  of  the  ileum  is 
in  the  pelvis  and  rises  from  above  the  brim,  passing  upward,  backward,  and  to  the 
right  to  reach  the  ileo-caecal  opening.  Treves  points  out  that  another  portion  of 
the  small  intestine  may  be  in  the  pelvis,  viz.,  the  portion  with  the  longest  mesentery. 
This  is  a  portion  somewhere  between  a  point  six  feet  from  the  duodenum  and  a 
point  eleven  feet  from  the  duodenum.  The  jejunum  and  ileum  are  attached  to  the 
posterior  abdominal  wall  by  an  extensive  fold  of  peritoneum,  the  mesentery(p.  1266), 
which  allows  the  freest  motion,  so  that  each  coil  can  accommodate  itself  to  changes 
in  form  and  position.  The  mesentery  is  fan-shaped;  its  posterior  border,  about 
six  inches  in  length,  is  attached  to  the  abdominal  wall  from  the  left  side  of  the 
second  lumbar  vertebra  to  the  right  iliac  fossa  (Fig.  875).  Its  length  is  about  eight 
inches  from  its  commencement  to  its  termination  at  the  intestine,  and  it  is  rather 
longer  about  its  centre  than  at  either  end  of  the  bowel.  According  to  Lockwood, 

82 


1298  THE    ORGANS    OF  DIGESTION 

it  tends  to  increase  in  length  as  age  advances.  Between  the  two  layers  of  which 
it  is  composed  are  contained  blood-vessels,  nerves,  lacteals,  and  lymphatic  glands, 
together  with  a  variable  amount  of  fat. 

Meckel's  Diverticulum  (diverticulum  ilei). — Occasionally  there  may  be  found 
connected  with  the  lower  part  of  the  ileum,  on  an  average  about  three  feet  from 
its  termination,  a  blind  diverticulum  or  tube,  varying  in  length,  but  averaging 
about  two  inches,  and  being  of  about  the  same  diameter  as  the  piece  of- intestine  of 
which  it  is  a  part.  Sometimes  only  a  portion  of  the  proximal  end  is  open  and 
the  balance  of  the  structure  is  obliterated  and  shrunk  to  a  fibrous  cord.  In  other 
cases  the  diverticulum  is  actually  of  greater  diameter  than  the  intestine.  It 
usually  is  at  a  right  angle  to  the  intestine,  but  may  take  almost  any  direction. 
In  most  cases  it  has  a  mesentery.  It  is  attached  to  and  communicates  with  the 
lumen  of  the  bowel  by  one  extremity,  and  by  the  other  is  unattached  or  may  be 
connected  with  the  abdominal  wall  or  with  some  other  portion  of  the  intestine 
by  a  fibrous  band.  This  is  Meckel's  diverticulum,  and  represents  the  remains  of 
the  vitelline  or  omphalo-mesenteric  duct,  the  duct  of  communication  between  the 
umbilical  vesicle  and  the  alimentary  canal  in  early  foetal  life. 

Structure  of  the  Small  Intestine,  including  the  Duodenum.— The  wall  of 
the  small  intestine  is  composed  of  four  coats — serous,  muscular,  areolar  or  sub- 
mucous,  and  mucous. 

The  Serous  Coat  (tunica  serosa). — The  relation  of  the  peritoneum  to  the  duod- 
enum has  been  described.  The  remaining  portion  of  the  small  intestine  is  sur- 
rounded by  the  peritoneum,  excepting  along  its  attached  or  mesenteric  border; 
here  a  space  is  left  for  the  vessels  and  nerves  to  pass  to  the  gut. 

The  Muscular  Coat  (tunica  muscularis). — The  muscular  coat  consists  of  two 
layers  of  fibres,  an  external  or  longitudinal  layer  and  an  internal  or  circular 
layer. 

The  Longitudinal  Fibres  (stratum  longitudinale)  are  thinly  scattered  over  the 
surface  of  the  intestine,  and  are  more  distinct  along  its  free  border. 

The  Circular  Fibres  (stratum  circular -e)  form  a  thick,  uniform  layer;  they  sur- 
round the  cylinder  of  the  intestine  in  the  greater  part  of  its  circumference,  and  are 
composed  of  plain  muscle-cells  of  considerable  length.  The  muscular  coat  is 
thicker  at  the  upper  than  at  the  lower  part  of  the  small  intestine. 

The  Areolar  or  Submucous  Coat  (tela  submucosa). — The  areolar  or  submucous 
coat  connects  together  the  mucous  and  muscular  layers.  It  consists  of  loose, 
filamentous  areolar  tissue,  which  forms  a  bed  for  the  subdivision  of  the  nutrient 
vessels,  previous  to  their  distribution  to  the  mucous  surface. 

The  submucous  coat  contains  lymph-nodules  (noduli  lymphatici).  Each  nodule 
is  pyramidal  or  pear-shaped,  and  the  apex  lies  in  the  mucous  membrane  and  forms 
a  rounded  elevation.  These  rounded  elevations  mark  the  solitary  glands  and 
Fever's  patches  (Figs.  909,  911,  and  918),  and  in  nowise  resemble  villi.  In  the 
duodenum  the  submucous  tissue  contains  the  duodenal  glands.  The  submucous 
tissue  is  prolonged  into  the  valvulae  conniventes.  It  contains  blood-vessels,  Meiss- 
ner's  plexus  of  nerves,  and  lymph-vessels. 

The  Mucous  Membrane  (tunica  mucosa}. — The  mucous  membrane  is  thick  and 
highly  vascular  at  the  upper  part  of  the  small  intestine,  but  somewhat  paler  and 
thinner  below.  It  consists  of  the  following  structures:  next  the  areolar  or  sub- 
mucous  coat  is  a  layer  of  unstriped  muscular  fibres,  the  muscularis  mucosae ;  internal 
to  this  is  a  quantity  of  retiform  tissue,  enclosing  in  its  meshes  lymph-corpuscles, 
and  in  which  the  blood-vessels  and  nerves  ramify.  Lastly,  a  basement-membrane, 
supporting  a  single  layer  of  epithelial  cells,  which  throughout  the  intestines  are 
columnar  in  character.  They  are  granular  in  appearance,  and  each  possesses  a 
clear,  oval  nucleus.  At  their  superficial  or  unattached  end  they  present  a  distinct 
layer  of  highly  refracting  material,  marked  by  vertical  striae,  which  were  formerly 


THE   JEJUNUM   AND    ILEUM 


1299 


believed  to  be  minute  channels  by  which  the  chyle  was  taken  up  into  the  interior 
of  the  cell,  and  by  them  transferred  to  the  lacteal  vessels  of  the  mucous  membrane. 


MOUTHS    OF    GLANDS  SOLITARY  GLAND 

OF    LIEBERKUHN 

FIG.  909. — Free  surface  of  the  mucous  membrane  of  the  small  intestine,  showing  villi,  solitary  glands, 
and  openings  of  the  intestinal  glands.     Semidiagrammatic.     (Testut.) 

The  mucous  membrane  presents  for  examination  the  following  structures  con- 
tained within  it  or  belonging  to  it: 


Valvulae  conniventes. 

Villi. 

Simple  follicles. 


Duodenal  glands. 

...         j  i      f  Solitary  glands. 
Lymphatic  nodules  \  n        / 

(  reyer  s  or  agminate  glands. 


The  Valvulae  Conniventes  or  the  Valves  of  Kerkring  (plicae  circulares  [Kerkringi]) 
(Fig.  910)  are  large  folds  or  valvular  flaps  projecting  into  the  lumen  of  the  bowel. 
They  are  composed  of  reduplications  or  folds  of  the  mucous  membrane,  the  two 
layers  of  the  fold  being  bound  together  by  submucous  tissue;  they  contain  no 
muscular  fibres,  and,  unlike  the  folds  in 
the  stomach,  they  are  permanent,  and 
are  not  obliterated  when  the  intestine  is 
distended.  The  majority  extend  trans-, 
versely  across  the  cylinder  of  the  intestine 
for  about  one-half  or  two-thirds  of  its 
circumference,  but  some  form  complete 
circles,  and  others  have  a  .spiral  direc- 
tion; the  latter  usually  extend  a  little 
more  than  once  around  the  bowel,  but 
occasionally  two  or  three  times.  The 
spiral  arrangement  is  the  characteristic 
one  of  the  shark  family  of  fishes.  The 
larger  folds  are  about  one-third  of  an 
inch  in  depth  at  their  broadest  part;  but 
the  greater  number  are  of  smaller  size. 
The  larger  and  smaller  folds  alternate 

with  each  other.  They  are  not  found  at  the  commencement  of  the  duodenum, 
but  begin  to  appear  about  one  or  two  inches  beyond  the  pylorus.  In  the  lower 
part  of  the  descending  portion,  below  the  point  where  the  bile  and  pancreatic 
ducts  enter. the  intestine,  they  are  very  large  and  closely  approximated.  In 
the  transverse  portion  of  the  duodenum  and  upper  half  of  the  jejunum  they 


FIG.  910. — Valvulae  conniventes  in  the  upper  part 
of  the  small  intestine.     (Poirier  and  Charpy.) 


1300 


THE    ORGANS    OF   DIGESTION 


are  large  and  numerous;  and  from  this  point,  down  to  the  middle  of  the  ileum, 
they  diminish  considerably  in  size.  In  the  lower  part  of  the  ileum  they  almost 
entirely  disappear;  hence  the  comparative  thinness  of  this  portion  of  the  intes- 
tine as  compared  with  the  duodenum  and  jejunum.  The  valvulae  conniventes 
retard  the  passage  of  the  food  along  the  intestine,  and  afford  a  more  extensive 
surface  for  absorption. 

The  Villi  (villi  intestinales]  (Figs.  909,  911,  912,  913,  and  918)  are  minute,  highly 
vascular  processes,  never  larger  than  one  millimetre,  projecting  from  the  mucous 
membrane  of  the  small  intestine  throughout  its  whole  extent,  and  giving  to  its 
surface  a  velvety  appearance.  They  spring  from  the  valvulae  conniventes  and  also 
from  the  spaces  between  them.  In  shape,  according  to  Rauber,  they  are  short 
and  leaf-shaped  in  the  duodenum,  tongue-shaped  in  the  jejunum,  and  filiform 


MUCOUS   COAT 


PLANE    OF    MU- 
COUS   SURFACE 


FIG.  911. — Mucosa  of  small  intestine  in  ideal  vertical  cross-section.     (Testut,  after  Heitzmann.) 

in  the  ileum.  They  are  largest  and  most  numerous  in  the  duodenum  and 
jejunum,  and  become  fewer  and  smaller  in  the  ileum.  Krause  estimates  their 
number  in  the  upper  part  of  the  small  intestine  at  from  fifty  to  ninety  in  a  square 
line;  and  in  the  lower  part  from  forty  to  seventy,  the  total  number  for  the  whole 
length  of  the  intestine  being  about  four  millions. 

STRUCTURE  OF  THE  VILLI  (Figs.  912  and  913). — The  structure  of  the  villi  has 
been  studied  by  many  eminent  anatomists.  We  shall  here  follow  the  description 
of  Watney,1  whose  researches  have  a  most  important  bearing  on  the  physiology  of 
that  which  is  the  peculiar  function  of  this  part  of  the  intestine,  the  absorption  of  fat. 

The  essential  parts  of  a  villus  are — the  lacteal  vessel,  the  blood-vessels,  the 
epithelium,  the  basement-membrane  and  muscular  tissue  of  the  mucosa,  these 
structures  being  supported  and  held  together  by  retiform  lymphoid  tissue. 

1  Phil.  Trans.,  vol.  clxv.  part  ii. 


THE  JEJUNUM  AND  ILEUM 


1301 


These  structures  are  arranged  in  the  following  manner :  situated  in  the  centre 
of  the  villus  is  the  lacteal,  terminating  near  the  summit  in  a  blind  extremity; 


Tunica 


Blood  capillaries^^ 


Ciiticular  border 


r~     Epithelium 


Nucleus  of 
'wandering  cell 


jagi  _.  Nucleus  of  smooth 
muscle  cell 


lymph 
space 


f: 


V 


*V  -.f'": 
^4*          *'         » 

al»'lo 
o 


\ffitt 
if:-**  f  ^% 

^5»*'   •«-•/) 


SS^iSJ  „ 
/      ^^»     ?    " 

fW      /o       'J-Wlt        *   .    <S» 

'c_ A>.    .  -  ..    *lL 


•'-« 


•'*. 


oblet  cells 


««    w*  .g^^i 

,   «»««». 

iS. **JUr«g»  I 


FIG.  912. — Longitudinal  section  through  the  end  of  a  villus  from  the  small  intestine  of  a  cat.     X  450. 


Capillaries. 
Lymph  trunk.' 


'm — Lymph  trunk. 


m Capillaries. 


Small  artery.''  Lymphatic  plexus. 

FIG.  913. — Villi  of  small  intestine.     (Cadiat.) 


1302 


THE  ORGANS  OF  DIGESTION 


running  along  this  vessel  are  unstriped  muscular  fibres;  surrounding  it  is  a  plexus 
of  capillary  vessels,  the  whole  being  enclosed  by  a  basement-membrane,  and  cov- 
ered by  columnar  epithelium.  Those  structures  which  are  contained  within  the 
basement-membrane — namely,  the  lacteal,  the  muscular  tissue,  and  the  blood- 
vessels— are  surrounded  and  enclosed  by  a  delicate  reticulum  which  forms  the 
matrix  of  the  villus,  and  in  the  meshes  of  which  are  found  large,  flattened  cells 
with  oval  nuclei,  and,  in  smaller  numbers,  lymph-corpuscles.  These  latter  are 
to  be  distinguished  from  the  larger  cells  of  the  villus  by  their  behavior  with 
reagents,  by  their  size,  and  by  the  shape  of  the  nucleus,  which  is  spherical. 
Transitional  forms,  however,  of  all  kinds  are  met  with  between  the  lymph-cor- 
puscles and  the  proper  cells  of  the  villus.  Nerve-fibres  are  contained  within  the 
villi;  they  form  ramifications  throughout  the  reticulum. 

The  lacteals  are  in  some  cases  double,  and  in  some  animals  multiple.  Situated 
in  the  axis  of  the  villi,  they  commence  by  dilated  caecal  extremities  near  to,  but 
not  quite  at,  the  summit  of  the  villus.  The  walls  are  composed  of  a  single  layer 
of  endothelial  cells,  the  interstitial  substance  between  the  cells  being  continuous 
with  the  reticulum  of  the  matrix. 


CALCI  FORM 
CELL 


GLANDULAR 
CELL 


Fio.  914. — Section  of  a  gland  of  Lieberkiihn  in  the  mouse. 
(Paneth.) 


FIG.  915. — Transverse  section  of  crypts  of 
Lieberkflhn.     (Klein  and  Noble  Smith.) 


The  muscular  fibres  are  derived  from  the  muscularis  mucosae,  and  are  arranged 
in  bundles  around  the  lacteal  vessel,  extending  from  the  base  to  the  summit  of  the 
villus,  and  giving  off  laterally  individual  muscle-cells,  which  are  enclosed  by  the 
reticulum,  and  by  it  are  attached  to  the  basement-membrane. 

The  blood-vessels  form  a  plexus  between  the  lacteal  and  the  basement-mem- 
brane, and  are  enclosed  in  the  reticular  tissue;  in  the  interstices  of  the  capillary 
plexus,  which  they  form,  are  contained  the  cells  of  the  villus. 

These  structures  are  surrounded  by  the  basement-membrane,  which  is  made 
up  of  a  stratum  of  endothelial  cells,  and  upon  which  is  placed  a  layer  of  columnar 
epithelium.  The  reticulum  of  the  matrix  is  continuous  through  the  basement- 
membrane  (that  is,  through  the  interstitial  substance  between  the  individual 
endothelial  cells)  with  the  interstitial  cement  substance  of  the  columnar  epithelial 
cells  on  the  surface  of  the  villus.  Thus  we  are  enabled  to  trace  a  direct  continuity 
between  the  interior  of  the  lacteal  and  the  surface  of  the  villus  by  means  of  the 
reticular  tissue,  and  it  is  along  this  path  that  the  chyle  passes  in  the  process  of 
absorption  by  the  villi;  that  is  to  say,  it  passes  first  of  all  into  the  columnar 
epithelial  cells,  and,  escaping  from  them,  is  carried  into  the  reticulum  of  the  villus, 
and  thence  into  the  central  lacteal. 


THE  JEJUNUM  AND  ILEUM 


1303 


The  Simple  Follicles,  Intestinal  Glands,  Crypts  or  Glands  of  Lieberkiihn  (glandulae 
intestinales  [Lieberkiihni])  (Figs.  914,  915,  and  918)  are  found  in  considerable 
numbers  over  every  part  of  the  mucous  membrane  of  the  small  intestine.  They 
consist  of  minute  tubular  depressions  of  the  mucous  membrane,  arranged  per- 
pendicularly to  the  surface,  upon  which  they  open  by  small  circular  apertures. 
They  may  be  seen  with  the  aid  of  a  lens,  their  orifices  appearing  as  minute  dots 
scattered  between  the  villi  (Fig.  909).  Their  walls  are  thin,  consisting  of  a  base- 
ment-membrane lined  by  columnar  epithelium,  and  covered  on  their  exterior  by 
capillary  vessels. 

The  Duodenal  or  Brunner's  Glands  (glandulae  duodenales  [Brunneri])  are  limited 
to  the  duodenum  and  commencement  of  the  jejunum.  They  are  small,  flattened, 
granular  bodies  embedded  in  the  submucous  areolar  tissue,  and  open  upon  the 
surface  of  the  mucous  membrane  by  minute  excretory  ducts.  They  are  most 
numerous  and  largest  near  the  pylorus.  They  are  small,  compound,  acino-tubular 
glands,  and  much  resemble  the  small  glands  which  are  found  in  the  mucous  mem- 


...  -Capillary  network. 


FIG  916. — Transverse  section  through  the  equatorial  plane 
of  three  of  Peyer's  follicles  from  the  rabbit. 


FIG.  917. — Free  surface  of  a  Peyer's  patch. 
(After  Quain.) 


brane  of  the  mouth.  They  are  believed  by  Watney  to  be  direct  continuations  of 
the  pyloric  glands  of  the  stomach.  They  consist  of  a  number  of  tubular  alveoli, 
lined  by  epithelium,  and  opening  by  a  single  duct  on  the  inner  surface  of  the 
intestine. 

The  Lymph  Nodules  (nodidi  lymphatici)  are  small  pyriform  structures.  The 
bodies  of  the  nodes  are  in  the  submucous  coat;  the  apices  are  in  the  mucous  mem- 
brane, which  is  thrown  by  them  into  rounded  elevations.  They  are  divided  into 
solitary  glands  and  Peyer's  glands. 

The  solitary  glands  (noduli  lymphatici  solitarii)  (Figs.  909  and  911)  are  found 
scattered  throughout  the  mucous  membrane  of  the  small  intestine  and  the  large 
intestine.  In  the  small  intestine  they  are  most  numerous  in  the  lower  part  of  the 
ileum,  upon  and  between  the  valvulae  conniventes.  They  are  small,  round,  whitish 
bodies,  from  one-twenty-fourth  of  an  inch  to  one-quarter  of  an  inch  in  diameter. 
Their  free  surface  is  covered  with  villi,  and  each  gland  is  surrounded  by  the 
openings  of  the  follicles  of  Lieberkiihn.  They  are  now  recognized  as  lymph- 


1304 


THE  ORGANS  OF  DIGESTION 


nodules.  They  consist  of  a  dense  interlacing  retiform  tissue  closely  packed  with 
lymph-corpuscles  and  permeated  with  an  abundant  capillary  network.  The  inter- 
spaces of  the  retiform  tissue  are  continuous  with  larger  lymph-spaces  at  the  base 
of  the  gland,  through  which  they  communicate  with  the  lacteal  system.  They 
are  situated  partly  in  the  submucous  tissue,  partly  in  the  mucous  membrane, 
whence  they  form  slight  projections  of  its  epithelial  layer,  after  having  pene- 
trated the  muscularis  mucosae.  The  villi  situated  on  them  are  generally  absent 
from  the  very  summit  (or  "cupola,"  as  Frey  calls  it)  of  the  gland. 

Peyer's  glands,  Peyer's  patches,  the  agminated  glands  or  the  tonsillae  intestinales 
(noduli  lymphatici  aggregati  [Peyeri])  (Figs.  916,  917,  and  918)  may  be  regarded  as 
aggregations  of  solitary  glands,  forming  circular  or  oval  patches  from  twenty-five 
to  forty  in  number,  and  varying  in  length  from  half  an  inch  to  four  inches.  They 
are  largest  and  most  numerous  in  the  ileum.  In  the  lower  part  of  the  jejunum 
they  are  small,  of  a  circular  form,  and  few  in  number.  They  are  occasionally  seen 
in  the  duodenum.  They  are  placed  lengthwise  in  the  intestine,  and  are  situated 


INTESTINAL  VILLUS 


GLAND  OF  LIEBERKUHN 


CHYLI  FERGUS 
DUCT 


SUMMIT   OF 
FOLLICLE 


MIDDLE   FOLLICULAR 
ZONE 


PERIFOLLICULAR 
LYMPHATIC  ZONE 


INFERIOR   LYM- 
PHATIC PLEXUS 


FIG.  918. — Vertical  cell  of  a  Peyer's  patch  in  a  man  with  the  lymphatic  vessels  injected.     (Frey.) 


in  the  portion  of  the  tube  most  distant  from  the  attachment  of  the  mesentery. 
Each  patch  is  formed  of  a  group  of  the  above-described  solitary  glands  covered 
with  mucous  membrane,  and  in  almost  every  respect  are  similar  in  structure  to 
them.  They  do  not,  however,  as  a  rule,  possess  villi  on  their  free  surface.  Each 
patch  is  surrounded  by  a  circle  of  the  crypts  of  Lieberkiihn.  They  are  best  marked 
in  the  young  subject,  becoming  indistinct  in  middle  age,  and  sometimes  altogether 
disappearing  in  advanced  life.  They  are  largely  supplied  with  blood-vessels, 
which  form  an  abundant  plexus  around  each  follicle  and  give  off  fine  branches 
which  permeate  the  lymphoid  tissue  in  the  interior  of  the  follicle.  The  lacteal 
plexuses  which  are  found  throughout  the  small  intestine  are  especially  abundant 
around  these  patches;  here  they  form  rich  plexuses  with  sinuses  around  the  glands 
(Fig.  918),  In  typhoid  fever  there  is  ulceration  of  Peyer's  patches. 

Vessels  and  Nerves. — The  arteries  (vasa  intestini  tennis]  are  branches  of  the 
superior  mesenteric  (Fig.  423)  and  ascend  within  the  mesentery,  forming  single, 
double,  or  even  tertiary  loops  (Figs.  882,  883,  884,  885,  886,  887,  and  919).  The 
terminal  branches  reach  the  intestine,  and  each  branch  divides  into  two,  one  going 
to  each  side  of  the  intestine  and  passing  transversely  around  it.  At  first  they  are 


THE   JEJUNUM  AND    ILEUM 


1305 


directly  beneath  the  peritoneum,  but  after  a  time  they  pass  to  the  submucosa 
and  form  a  plexus,  from  which  branches  go  to  the  mucous  membrane.  Some 
of  these  enter  the  villi;  others  form  plexuses  about  the  glands  of  Lieberkiihn 
(Birmingham). 


FIG.  919. — A  loop  of  small  intestine,  showing  the  mode  of  distribution  of  the  arteries.     (Testut.) 

Dr.  George  H.  Monks1  points  out  that  opposite  the  upper  portion  of  the  bowel 
the  mesenteric  vessels  form  only  primary  loops ;  as  we  pass  down  secondary  loops 
appear,  become  larger  and  more  and  more  numerous,  and  actually  prominent 
features  about  the  fourth  foot.   As  we  descend  the  secondary 
loops  become  larger  and  more  numerous  and  the  primary 
become  smaller.     All  the  time  the  loops  get   nearer  and 
nearer  to  the  bowel.    Tertiary  loops  may  appear.    Opposite 
the  lower  part  of  the  ileum  the  loops  cease  to  be  character- 
istic and  they  form  a  network.     (Monks's  views  are  fully 
set  forth  on  p.  1276.)     In  the  upper  part  of  the  gut  the  vasa 
recta  are  from  3  to  5  cm.  long,  when  the  loop  of  small  intes- 
tine to  which  they  run  is  lifted  up  so  as  to  put  them  gently 
on  the  stretch.     They  are  straight,  large,  and  regular,  and 
rarely  give  off  branches  in  the  mesentery.     In  the  lower  third 
they  are  very  short,  being  generally  less  than  1  cm.  in  length. 
Here  they  are  less  straight,  smaller,  less  regular,  and  have 
frequent  branches  in  the  mesentery. 

The  veins  correspond  to  the  arteries,  and  the  venous 
blood  passes  to  the  superior  mesenteric  vein,  which,  it  will  be 
remembered,  unites  with  the  splenic  vein  to  form  the  portal 
vein.  The  mesenteric  veins  are  devoid  of  valves. 

The  lacteals   are   lymphatics   (Figs.   911,  912,   913,   and 
918)   which   arise  in  the  villi.     Lymphatics  also  begin  in 
sinuses  at  the  base  of  the  solitary  glands  and   as  li/nijtlt- 
nodes  in  the  submucous  coat.     Peyer's  patches  are  aggre-       ^^^BBBi^ 
gations  of  lymph-nodes.    There  is  an  extensive  lymphatic      FIG.  920.— Nerve  endings 

I  ,1  i  ,1         •      ,i  i     '  in  the  villi  of  the  small  in- 

plexus  in  the  submucous  coat,  another  in  the  muscular  coat,  testineof  arabbit.  (Muiier.) 
another  under  the  peritoneum.  The  submucous  plexus 

is  formed  by  lymphatics  from  the  villi  and  mucous  membrane.  This  plexus 
is  joined  by  lymphatics  from  the  bases  of  the  solitary  glands,  and  the  lymph 
passes  by  vessels  to  larger  vessels  at  the  mesenteric  border  of  the  gut.  The 
muscular  lymphatics  are  placed  between  the  two  muscular  layers.  They 

1  Annals  of  Surgery,  May,  1903. 


1306 


THE    ORGANS    OF  DIGESTION 


form  a  plexus  and  communicate  freely  with  the  lymphatics  from  the  mucous 
membrane,  and  empty  themselves  in  the  same  manner  into  the  commencement 


FIG.  921. — Meissner's  plexus.     (Ramon  y  Cajal.) 


Multipolar  ganglion-cells. 


Single  ganglion-cell. 


FIG.  922.— Meissner's  plexus.     (Klein  and  Noble  Smith.) 


THE  LARGE  INTESTINE 


1307 


of  the  lacteal  vessels  at  the  attached  border  of  the  gut.  The  vessels  from  all 
sources  of  lymphatic  supply  pass  up  between  the  two  layers  of  the  mesentery, 
being  connected  with  the  mesenteric  glands  (Fig.  507),  and  unite  to  form  a  trunk, 
the  intestinal  lymphatic  trunk,  which  opens  into  the  receptaculum  chyli,  or  the 
vessels  unite  to  form  several  trunks,  which  open  separately  into  the  receptaculum 
chyli. 

The  nerves  of  the  small  intestine  (Figs.  920,  921 ,  and  922)  are  derived  from  the 
coeliac  plexus  about  the  superior  mesenteric  artery,  which  is  one  of  the  divisions 
of  the  solar  plexus.  They  pass  along  within  the  mesentery  with  the  superior  mesen- 
teric artery  and  reach  the  intestine.  They  pass  to  the  plexus  of  nerves  and  ganglia 
situated  between  the  circular  and  longitudinal  muscular  fibres  (Auerbach's  plexus), 
from  which  the  nerve  branches  are  distributed  to  the  muscular  coats  of  the 
intestine.  From  this  plexus  a  secondary  plexus  is  derived  (Meissner's  plexus). 
It  is  formed  by  branches  which  have  perforated  the  circular  muscular  fibres 
(Fig.  922).  This  plexus  lies  between  the  muscular  and  mucous  coats  of  the  intes- 
tine. It  is  also  gangliated,  and  from  it  the  ultimate  fibres  pass  to  the  muscularis 
mucosae,  to  the  villi,  and  to  the  mucous  membrane.  The  nerves  of  the  intestine 
are  amyelinic,  and  some  of  the  fibres  are  derived  from  the  vagus. 


THE  LARGE  INTESTINE  (INTESTINUM  CRASSUM)  (Figs.  812, 874, 875, 923, 924). 

The  large  intestine  extends  from  the  termination  of  the  ileum  to  the  anus.    It 
is  about  five  feet  or  more  in  length,  being  one-fifth  of  the  whole  extent  of  the 


SACCULATIONS 


APPENDICES   EPIPIOICAE 


FIG.  923. — Large  intestine.     A  piece  of  transverse  colon  from  a  child  two  years  old.     The  three  chief  charac- 
teristics of  the  large  intestine — sacculation,  taeniae,  and  appendices  epiploicae — are  shown.     (Cunningham.) 


MUSCULAR    BAND 


intestinal  canal.  It  is  largest  at  its  com- 
mencement at  the  caecum,  and  gradually 
diminishes  as  far  as  the  rectum,  where 
there  is  a  dilatation  of  considerable  size 
just  above  the  anus.  The  diameter  of  the 
distended  caecum  is  usually  about  three 
inches;  the  diameter  of  the  descending 
colon  is  about  one  and  one-half  inches. 
The  large  intestine  differs  from  the  small 
intestine  in  its  greater  size,  its  more 
fixed  position,  its  sacculated  form  (Figs. 
923  and  924),  and  in  possessing  certain  ap- 
pendages to  its  external  coat,  the  appendices 
epiploicae  (Fig.  924).  The  appendices 

.      I      .  •  I  I  . 

epiploicae     are    peritoneal     pOUCheS    COn-    characteristic  features  of  its  structures. 

taining  fat,  unless  the  subject  is  greatly 

wasted;  they  protrude  here  and  there  from  the  peritoneal  coat  of  the  entire  large 

bowel,  except  the  rectum,  and  are  particularly  frequent  along  the  anterior  longi- 


MUSCULAR 
BAND 


MUSCULAR 
BAND 


FIG.  924. — Segment  of  large  intestine,  showing  the 

(Testut.) 


1308 


THE    ORGANS    OF  DIGESTION 


tudinal  band.  Further,  the  longitudinal  muscular  fibres  of  the  large  intestine  do 
not  form  a  continuous  layer  around  the  gut,  but  are  arranged  in  three  longitudinal 
bands  or  taeniae  (taeniae  coli]  (Fig.  924).  The  large  intestine,  in  its  course,  describes 
an  arch,  which  surrounds  the  convolutions  of  the  small  intestine.  It  commences 
in  the  right  inguinal  region,  in  a  dilated  part,  the  caecum.  It  ascends  through  the 
right  lumbar  and  right  hypochondriac  regions  to  the  under  surface  of  the  liver; 
it  here  takes  a  bend  to  the  left,  the  hepatic  flexure,  and  passes  transversely  across 
the  abdomen  on  the  confines  of  the  epigastric  and  umbilical  regions,  to  the  left 
hypochondriac  region;  it  then  bends  again,  the  splenic  flexure,  and  descends 
through  the  left  lumbar  region  to  the  left  iliac  fossa,  where  it  becomes  convoluted, 
and  forms  the  sigmoid  flexure;  finally  it  enters  the  pelvis,  and  descends  along  its 
posterior  wall  to  the  anus.  The  large  intestine  is  divided  into  the  caecum,  colon, 
and  rectum. 

The  Caecum  (Intestinum  Caecum)  (Figs.  925,  926). 

The  caecum,  the  commencement  of  the  large  intestine,  is  the  large  blind  pouch, 
or  cul-de-sac,  situated  below  the  ileo-caecal  valve.  Its  name  is  derived  from 
caecus,  blind.  Its  blind  end  or  fundus  is  directed  downward,  and  its  open  end 

upward,  communicating  directly  with  the 
colon,  of  which  this  blind  pouch  appears  to 
be  the  beginning  or  head,  and  hence  the  old 
name  caput  caecum  coli  was  applied  to  it. 
An  incomplete  groove  marks  the  upper  limit 
of  the  caecum.  This  groove  is  at  the  level 
of  the  opening  of  the  ileum.  When  the 
caecum  is  contracted  it  bends  on  this  groove 
as  on  a  hinge  and  forms  an  angle  with  the 
ascending  colon.  In  the  contracted  caecum 
sacculations  are  but  slightly  evident;  in  the 
distended  caequm  they  are  definite.  Its  size 
is  variously  estimated  by  different  authors, 
but  on  an  average  it  may  be  said  to  be  two 
and  a  half  inches  in  length  and  three  in 
breadth.  In  435  careful  autopsies,  Robinson 
found  the  caecum  and  appendix  congenitally 
absent  in  one  case.1  Sometimes  a  very  large, 
sometimes  an  exceedingly  small,  caecum  is 
encountered.  A  large  caecum  may  be  four 
inches  in  width,  entirely  surrounded  by  peri- 
toneum and  usually  is  excessively  mobile. 
An  adult  caecum  may  be  only  one  inch  in 
width  and  one-half  an  inch  in  length,  and  it 

Js  usually  devoid  of  mobility.  It  is  situated  in  the  right  iliac  fossa,  above  the  outer 
^ialf  of  Poupart's  ligament,  usually  rests  on  the  Ilio-psoas  muscle,  the  iliac  fascia 
intervening,  and  lies  immediately  behind  the  abdominal  wall.  The  right  side  of 
the  caecum  is  in  contact  with  the  outer  wall  of  the  abdomen,  and  the  outer  aspect 
of  the  anterior  wall  of  the  caecum  is  in  contact  with  the  anterior  abdominal  wall 
(Spalteholz).  When  the  caecum  is  full  the  small  intestine  lies  in  front  of  the  left 
side  and  lower  portion  of  the  anterior  caecal  wall.  If  the  caecum  is  empty  the 
small  intestine  lies  in  front  of  its  anterior  wall,  and  the  lower  end  is  on  a  higher 
ievel  than  when  this  portion  of  the  gut  is  full.  In  a  small  per  cent,  of  cases  the 


FIG.  925. — The  caecum  and  colon  laid  open 
to  show  the  ileo-caecal  valve. 


1  St.  Louis  Courier  of  Medicine,  October-December,  1902. 


THE  CAECUM  1309 

caecum  is  covered  by  the  omentum.  Robinson  describes  four  positions  of  the 
caecum:  1.  On  the  Psoas  muscle.  2.  To  the  right  of  the  Psoas  muscle.  3.  In  the 
pelvis.  4.  The  potential  position,  in  which  it  lies  free  in  the  abdominal  cavity. 
It  may  be  found  in  various  positions  in  the  abdomen,  because  of  elongation  of 
the  fixation  apparatus.  The  commonest  position  is  on  the  Psoas  muscle,  and 
this  position  is  even  more  common  in  men  than  in  women.  It  is  twice  as  often  in 
the  pelvis  in  women  as  in  men — 20  per  cent,  of  cases  in  the  former;  10  per  cent, 
in  the  latter.  As  a  rule,  it  is  entirely  enveloped  on  all  sides  by  peritoneum,  but  in 
a  certain  number  of  cases  (6  per  cent.,  according  to  Berry)  the  peritoneal  cover- 
ing is  not  complete,  so  that  a  small  portion  of  the  upper  end  of  the  posterior  surface 
is  uncovered  and  connected  to  the  iliac  fascia  by  connective  tissue.  As  a  matter 
of  fact,  there  is  no  real  mesocaecum— meaning  by  the  term  a  peritoneal  fold  which 
holds  the  caecum  to  the  dorsal  wall  of  the  abdomen — except  when  there  is  failure 
in  development.  Originally  the  caecum  receives  its  blood  along  a  single  peri- 
toneal fold,  the  ileo-caecal  fold,  which  is  a  simple  mesentery.  As  development 
advances,  this  simple  mesentery  becomes  a  double  fold  and  practically  bloodless, 
and  is  replaced  by  two  vascular  folds,  the  mesoappendix  to  the  left  and  the  mesen- 
terico-colicum  to  the  right.  The  mobility  of  the  caecum  varies.  Very  small  caeca 
are  fixed.  In  most  cases  the  caecum  lies  quite  free  in  the  abdominal  cavity  and 
enjoys  a  considerable  amount  of  movement.  Sometimes  it  is  excessively  mobile, 
and  in  such  cases  is  usually  also  of  large  size.  Such  mobility  is  due  to  a  stretched 
fixation  apparatus.  A  very  large  and  mobile  caecum  may  be  made  to  come  in 
contact  with  any  abdominal  viscus  and  may  enter  any  hernial  sac  on  either  side. 
It  is  to  be  remembered  that  a  mobile  caecum  carrying  with  it  the  appendix  may 
pass  to  almost  any  region  of  the  abdomen.  Sometimes  the  caecum  fails  to  descend 
or  only  descends  a  part  of  the  way  during  development,  the  axial  rotation  of  the 
intestinal  tract  having  been  arrested.  In  such  a  case  it  may  terminate  at  the 
level  of  the  gall-bladder,  and  the  ascending  colon  is  absent.  In  310  adult  males 
Robinson  found  8  per  cent,  with  undescended  caecum  and  appendix.  Non- 
descent  is  found  in  less  than  4  per  cent,  of  adult  females.  A  partly  descended 
caecum  usually  lies  upon  the  right  kidney. 

The  caecum  varies  in  shape,  but,  according  to  Treves,  in  man  it  may  be  classified 
under  one  of  four  types  (Fig.  926).  In  early  foetal  life  it  is  short,  conical,  and 
broad  at  the  base,  with  its  apex  turned  upward  and  inward  toward  the  ileo-caecal 
junction.  It  then  resembles  the  caecum  of  some  of  the  monkey  tribe,  e.  g.,  Man- 
gabey  monkey.  As  the  foetus  grows  the  caecum  increases  in  length  more  than  in 
breadth,  so  that  it  forms  a  longer  tube  than  in  the  primitive  form  and  without  the 
broad  base,  but  with  the  same  inclination  inward  of  the  apex  toward  the  ileo- 
caecal  junction.  This  form  is  seen  in  others  of  the  monkey  tribe,  e.  g.,  the  spider 
monkey.  As  development  goes  on,  the  lower  part  of  the  tube  ceases  to  grow  and 
the  upper  part  becomes  greatly  increased,  so  that  at  birth  there  is  a  narrow  tube, 
the  vermiform  appendix,  hanging  from  a  conical  projection,  the  caecum.  This  is 
the  infantile  form,  and  as  it  persists  throughout  life,  in  about  2  per  cent,  of 
cases,  it  is  regarded  by  Treves  as  the  first  of  his  four  types  of  human  caeca.  The 
caecum  is  conical  and  the  appendix  rises  from  its  apex.  The  three  longitudinal 
bands  start  from  the  appendix  and  are  equidistant  from  each  other.  In  the  second 
type,  the  conical  caecum  has  become  quadrate  by  the  growing  out  of  a  saccule  on 
either  side  of  the  anterior  longitudinal  band.  These  saccules  are  of  equal  size, 
and  the  appendix  arises  from  between  them,  instead  of  from  the  apex  of  a  cone. 
This  type  is  found  in  about  3  per  cent,  of  cases.  The  third  type  is  the  normal  type 
of  man.  Here  the  two  saccules,  which  in  the  second  type  were  uniform,  have 
grown  at  unequal  rates:  the  right  with  greater  rapidity  than  the  left.  In  conse- 
quence of  this  an  apparently  new  apex  has  been  formed  by  the  growing  downward 
of  the  right  saccule,  and  the  original  apex,  with  the  appendix  attached,  is  pushed 


1310 


1  HE  ORGANS  OF  DIGESTION 


over  to  the  left  toward  the  ileo-caecal  junction.  The  three  longitudinal  bands  still 
start  from  the  base  of  the  appendix,  but  they  are  now  no  longer  equidistant  from 
each  other,  because  the  right  saccule  has  grown  between  the  anterior  and  postero- 
external  bands,  pushing  them  over  to  the  left.  This  type  occurs  in  about  90  per 
cent,  of  cases.  The  fourth  type  is  merely  an  exaggerated  condition  of  the  third; 


FIG.  926. — The  four  types  of  caecum. 

the  right  saccule  is  still  larger,  and  at  the  same  time  the  left  saccule  has  been 
atrophied,  so  that  the  original  apex  of  the  caecum,  with  the  appendix,  is  close  to 
the  ileo-caecal  junction,  and  the  anterior  band  courses  inward  to  the  same  situa- 
tion. This  type  is  present  in  about  4  per  cent,  of  cases. 

Supports  of  the  Caecum. — According  to  Robinson,1  the  caecum  is  maintained 
in  position  by  the  mesocolon  and  a  peritoneal  fold,  the  right  phrenico-colic  liga- 
ment, which  arises  from  the  hepato-duodenal  and  hepato-renal  ligaments.  It  receives 
support  from  the  connective  tissue  about  vessels  and  nerves,  and  inconstantly 
from  folds  which  fixes  it  in  the  iliac  fossa  and  in  the  region  of  the  precava. 

The  Interior  of  the  Caecum. — In  the  interior  of  the  caecum  are  seen  depressions 
which  correspond  to  the  surface  haustra,  and  semilunar  folds  (plicae  semilunares 
coli)  (Fig.  925),  which  correspond  to  the  transverse  surface  constrictions.  There 
are  three  openings  in  the  caecum:  that  into  the  colon;  that  into  the  ileum,  which 
is  guarded  by  the  ileo-caecal  valve  (p.  1315) ;  and  that  into  the  appendix,  which 
may  be  guarded  by  the  valve  of  Gerlach. 

1  St.  Louis  Courier  of  Medicine,  October-December,  1902. 


THE  CAECUM  1311 

Pericaecal  Folds  and  Fossae. — See  p.  1272,  and  Figs.  879, 880,  and  881. 

The  Vermiform  Appendix  (processm  vermiformis)  (Figs.  879, 880, 881 , 926, 927, 
928,  929,  and  931). — The  vermiform  appendix  is  found  only  in  man,  the  higher 
apes,  and  the  wombat,  although  in  certain  rodents  a  somewhat  similar  arrangement 
exists.  In  carnivorous  animals  the  caecum  is  very  slightly  developed;  in  her- 
bivorous animals  (with  a  simple  stomach)  it  is,  as  a  rule,  extremely  large.  It  has 
been  suggested  that  the  vermiform  process  in  man  is  the  degenerated  remains  of  the 
herbivorous  caecum,  which  has  been  replaced  by  the  carnivorous  form.1  The 
vermiform  appendix  is  a  long,  narrow,  worm-shaped,  musculo-membranous  tube, 
which  starts  from  what  was  originally  the  apex  of  the  caecum.  After  development 
has  advanced  the  vermiform  appendix  comes  off,  as  a  rule,  from  the  inner  side  of 
the  posterior  wall  of  the  caecum  that  is  below  and  behind  the  termination  of  the 
ileum.  This  origin  usually  corresponds  to  McBurney's  point,  which  is  in  the 
abdominal  wall,  midway  between  the  umbilicus  and  the  anterior  superior  iliac 
spine,  and  which  is  the  usual  seat  of  the  greatest  tenderness  in  appendicitis.  The 
origin  of  the  appendix  varies  with  the  type  of  caecum  present.  These  variations 
are  shown  in  Fig.  926.  In  the  foetal  or  infantile  type  of  appendix  it  arises  from 
the  apex  of  the  caecum;  in  the  second  type  of  caecum  it  arises  between  the  two 
caecal  sacculi ;  in  the  third  type  it  arises  between  a  large  outer  and  a  small  inner  sac- 
culus;  and  on  the  posterior  wall  of  the  caecum,  the  excessive  growth  of  the  anterior 
wall  having  caused  the  appendix  to  originate  posteriorly;  in  the  fourth  type  there  is 
no  internal  sacculus,  and  the  appendix  arises  from  the  posterior  caecal  wall  behind 
the  ileo-caecal  junction  (p.  1310).  The  movable  portion  of  the  appendix  may  be 
met  with  in  different  situations.  It  may  pass  upward  and  in  front  of  the  caecum 
and  colon,  upward  and  behind  the  caecum,  and  even  behind  the  colon  between  the 
two  layers  of  the  mesocolon;  upward  and  to  the  inner  side,  or  upward,  and  to  the 
outer  side  of  the  caecum  and  colon.  It  may  pass  to  the  left  under  the  ileum  and 
mesentery,  upward  and  to  the  left  or  downward  and  to  the  left  into  the  true  pelvis. 
It  may  pass  directly  downward  under  the  caecum.  It  may  pass  to  the  right  in 
front  of  or  back  of  the  caecum.  It  may  occupy  any  one  of  the  caecal  fossae  (p.  1272), 
but  most  often  enters  the  ileo-caecal  fossa.  In  unusual  cases  the  appendix  is  found 
in  the  inguinal  canal  as  a  portion  of  or  the  sole  contents  of  a  hernia;  adherent  to 
the  parietal  peritoneum  in  front  of  or  to  the  side  of  the  caecum,  or  "behind  the 
peritoneum,  below  the  caecum,  adherent  to  the  under  surface  of  the  caecum  and  in 
contact  with  its  muscular  wall  and  covered  by  its  peritoneal  coat."2  When  the  cae- 
cum is  mobile  the  appendix  may  be  found  almost  anywhere  within  the  abdomen. 
When  the  caecum  is  undescended,  the  appendix  of  course  shares  in  the  failure  to 
descend,  and  may  be  below  the  gall-bladder  or  in  front  of  the  right  kidney,  and  may 
pass  in  several  directions:  upward  behind  the  caecum;  to  the  left  behind  the  ileum 
and  mesentery;  or  downward  and  inward  into  the  true  pelvis.  It  varies  from  one- 
half  an  inch  to  nine  inches  in  length,  its  average  being  about  three  inches.  Its  diam- 
eter is  from  one-eighth  inch  to  one-quarter  inch.  The  operating  surgeon  may 
occasionally  fail  to  find  an  appendix  buried  in  one  of  the  caecal  fossae,  and  may  con- 
clude that  the  diverticulum  is  absent.  As  a  matter  of  fact,  unless  the  colon  is  also 
absent,  it  seems  doubtful  if  the  appendix  is  ever  absent,  except  as  a  result  of  dis- 
ease. This  view  is  maintained  by  Lockwood  and  Rolleston,3  by  Kelynack,4  and 
others.  It  is  asserted  by  some  that  the  appendix  is  absent  5  times  out  of  10,000 
autopsies.  It  is  retained  in  position  by  a  fold  of  peritoneum  derived  from  the  left 
leaf  of  the  mesentery,  which  forms  a  mesentery  for  it,  and  is  called  the  meso- 
appendix  (p.  1269,  and  Figs.  879,  880,  and  881).  In  color  the  healthy  appendix  is 

1  Cunningham's  Text-book  of  Anatomy. 

2  Deaveps  Surgical  Anatomy. 

3  Journal  of  Anatomy  and  Physiology,  1891,  vol.  xxvi. 

4  A  Contribution  to  the  Pathology  of  the  Vermiform  Appendix. 


1312  THE  ORGANS  OF  DIGESTION 

yellowish-pink,  is  soft  and  smooth  to  the  touch,  and  the  "  subperitoneal  vessels 
are  barely  visible."1  The  canal  of  the  appendix  is  small  and  extends  throughout 
the  whole  length  of  the  tube.  The  walls  of  the  healthy  diverticulum  are  thick, 
and  the  diameter  of  the  lumen  is  usually  trivial  as  compared  with  the  diameter  of 
the  appendix  itself.  The  lumen  of  the  appendix  communicates  with  the  caecum 
by  an  orifice  which  is  placed  below  and  behind  the  ileo-caecal  opening  (Fig.  932). 
It  is  sometimes  guarded  above  and  to  the  left  side  by  a  semilunar  fold  of  mucous 
membrane,  the  valve  of  Gerlach  (valvula  processus  vermiformis) .  The  valve  is 
inconstant,  and  is  never  perfect.  It  is  stated  that  the  appendix  tends  to  undergo 
obliteration  as  an  involution  change  in  a  functionless  organ.  The  lumen  rarely 
contains  foreign  bodies  after  death,  but  often  contains  fecal  concretions.  Certain 
it  is  that  in  25  per  cent,  of  necropsies  upon  adults  or  elderly  people  the  lumen 
is  found  to  be  partially  or  completely  occluded. 


ILEOCOLIC    ARTtRY 


ANTERIOR    ILEO- 
CAECAL  ARTERY 


ANTERIOR  CAECAL 
ARTERY 


APPENDICULAR 
ARTERY 

APPENDIX 
VERMIFORMIS 


FIG.  927. — Arteries  of  the  csecum  and  of  the  appendix  vermiformis  and  of  the  terminal  portion  of  the  ileum. 

(Poirier  and  Charpy.) 

Structure  of  the  Appendix  (Fig.  930). — The  coats  of  the  appendix  correspond  to 
the  coats  of  the  bowel:  serous,  muscular  (the  outer  layer  of  longitudinal,  the  inner 
of  circular  fibres),  submucous,  and  mucous.  In  the  deepest  portion  of  the  mucous 
coat,  against  the  submucous  coat,  are  the  unstriated  fibres  constituting  the  mus- 
cularis  mucosae.  The  muscularis  mucosae  is  often  present  in  some  regions  and 
absent  in  others.  It  may  not  be  present  at  all. 

The  Outer  or  Serous  Coat  usually  completely  covers  the  appendix  and  has  a 
definite  mesentery,  the  mesoappendix  (p.  1269).  Occasionally  the  base  of  the 
appendix  is  not  surrounded  by  peritoneum,  but  is  extraperitoneal,  lying  in  the 
retroperitoneal  tissue.  The  appendiculo -ovarian  ligament  of  Olado  is  occasionally 
present  in  females.  It  is  a  prolongation  of  the  mesoappendix  which  passes  into 
the  broad  ligament,  and  is  extremely  thin,  and  its  fine  connective-tissue  fibres 
send  prolongations  into  the  longitudinal  muscle-fibres  of  the  appendix.  Lock- 
wood  points  out  that  the  subperitoneal  tissue  of  the  meso-appendix  and  "the 
blood-vessels,  nerves,  and  lymphatics  which  it  contains  are  very  intimately  con- 
nected with  the  submucosa.  This  union  takes  place  at  certain  large  gaps  in  the 
muscular  coats.  These  gaps  serve  for  the  transmission  of  blood-vessels,  nerves, 
and  lymphatics  from  the  mesoappendix  to  the  mucous  coat.  They  are  situated 
at  the  junction  of  the  mesoappendix  with  the  appendix."2 

The  Longitudinal  Muscular  Layer  is  thin  and  irregularly  distributed,  and  in  certain 
regions  may  be  excessively  thin  or  actually  absent,  and  between  the  fibres  are  the 
blood-vessels,  nerves,  and  lymphatics  passing  from  the  subperitoneal  tissue  to  the 
mucous  coat. 

1  Appendicitis,  its  Pathology  and  Surgery.     By  Charles  Barrett  Lockwood. 

2  Ibid. 


THE  CAECUM 


1313 


The  Circular  Fibres  are  much  better  developed  than  the  longitudinal  fibres,  and, 
according  to  Ix)ckwood,  the  layer  is  1  mm.  thick.  Large  gaps  are  found  here  and 
there  for  the  passage  of  vessels,  lymphatics,  and  nerves  to  and  from  the  meso- 
appendix  and  the  mucous  membrane,  and  a  few  vessels  pierce  the  fibres  at 
other  points  (Lockwood). 

The  Submucous  Coat  varies  greatly  in  thickness.  It  contains  blood-vessels, 
nerves,  and  lymphatics,  and  some  lymphoid  follicles. 

The  Mucous  Membrane  (Fig.  928)  is  covered  by  columnar 
epithelial  cells  and  contains  numerous  solitary  lymph- 
follicles,  some  glands  of  Lieberkiihn,  surrounded  by 
lymphoid  tissue,  blood-vessels,  lymphatics,  and  nerves. 

The  muscularis  mucosae  may  be  absent,  may  be  scanty, 
or  may  be  distinct.  The  lymphoid  follicles  are  visible  to 
the  naked  eye  (Fig.  928).  Some  of  them  are  in  the  sub- 
mucosa,  some  of  them  chiefly  in  the  mucosa,  the  bases  of 
the  latter,  however,  being  in  the  submucosa.  Lockwood 
estimates  that  an  appendix  three  and  a  half  inches  in 
length  contains  from  150  to  200  follicles. 

Blood-vessels  of  the  Caecum  and  Appendix  (Figs.  927,  929, 
945,  and  946). — The  ileo-colic  artery  in  the  ileo-colic  angle 
gives  off  the  anterior  and  posterior  ileo-caecal  arteries.  The 
anterior  ileo-caecal  runs  down  over  the  front  of  the  ileum 
and  supplies  the  ileum,  and  sends  off  a  terminal  branch, 
the  anterior  caecal  artery, which  supplies  the  anterior  surface 
of  the  caecum  and  of  a  portion  of  the  ascending  colon,  and 
to  the  upper  and  lower  margins  of  the  ileo-caecal  valve.  It 
sends  no  branch  to  the  appendix.  The  arteries  of  the  ap- 
pendix come  from  the  posterior  ileo-caecal  artery.  Tins 
vessel,  after  arising  from  the  ileo-colic  artery,  passes  back 
of  the  termination  of  the  ileum  and  gives  branches  to  the  face'of  the~ermiformnappen- 
lower  end  of  the  ileum  back  of  a  portion  of  the  ascending  dix-  <Bonamy  and  Broca-> 
colon  and  to  the  lower  margin  of  the  ileo-caecal  valve, 

where  they  anastomose  with  the  valvular  branches  from  the  anterior  ileo-caecal 
(Lockwood).  From  the  posterior  ileo-caecal  comes  the  posterior  caecal  branch, 
which  passes  over  the  posterior  and  inner  portion  of  the  caecum  near  the  base 
of  the  appendix  and  sends  one  or  two  branches  to  the  appendix.  The  chief  blood- 
supply  of  the  appendix  is  the  appendicular  artery,  which  comes  off  the  beginning 
of  the  posterior  ileo-caecal  or,  occasionally,  from  the  termination  of  the  ileo-colic. 
If  there  is  a  distinct  mesoappendix  the  largest  branch  of  the  artery  passes  along 
its  free  edge.  If  the  mesoappendix  is  absent  or  rudimentary  the  artery  usually 
lies  upon  the  appendix  from  base  to  tip  beneath  the  peritoneum. 

Lockwood  points  out  that  the  appendicular  artery  as  it  enters  the  mesoappen- 
dix divides  into  three  branches.  The  largest  branch  runs  along  the  free  edge, 
and  from  this  the  tip  of  the  appendix  obtains  its  blood-supply;  "the  other  two 
reach  the  appendix  at  intervals  of  half  an  inch."1  When  the  branches  reach 
the  appendix  they  divide  and  pass  around  it  in  the  subperitoneal  coat  and  send 
branches  through  the  muscular  gaps  to  enter  and  pass  through  the  submucous 
coat. 

In  females  there  is  occasionally  some  additional  blood-supply  through  a  branch 
of  the  ovarian  artery  in  the  appendiculo-ovarian  ligament. 

The  veins  of  the  appendix  are  numerous,  thin  walled,  and  large.  Veins  from 
the  submucous  plexus  pass  through  the  muscular  gaps  and  enter  the  subperi- 


1  Appendicitis,  its  Pathology  and  Surgery.      By  Charles  Barrett  Lockwood. 

83 


1314 


THE  ORGANS  OF  DIGESTION 


toneal  plexus.  Veins  from  the  subperitoneal  plexus  pass  into  veins  in  the  meso- 
appendix  which  correspond  to  but  do  not  really  accompany  the  arteries  (Lock- 
wood).  Most  of  the  veins  of  the  mesoappendix  pass  to  the  posterior  ileo-caecal 
vein,  though  some  pass  directly  to  the  caecal  vein.  These  veins  are  radicles  of 
the  portal  system. 


ILEOCOLIC  ARTERY 
AND  VEIN 


POSTERIOR 

ILEOCAECAL 

ARTERY 

AND    VEIN 

ILEAC    BRANCH 


APPENDICULAR 

ARTERY  AND 

VEIN 


ASCENDING 
COLON 


FIG.  929. — Arteries  and  veins  of  the  csecum  and  vermiform  appendix  seen  from  behind.     (Poirier  and  Charpy.) 

Lymphatic  System  of  the  Caecum  and  Appendix  (Fig.  930). — Surrounding  the  base 
of  each  lymph-follicle  in  the  submucous  tissue  of  the  appendix  is  a  lymph-space, 
which  Lockwood  calls  the  follicular  or  basilar  lymph-sinus.  This  sinus  communi- 
cates with  the  lymphatics  of  the  submucous  coat,  "which  again  communicate 
freely  through  the  hiatus  muscularis  with  those  of  the  peritoneum  and  of  the 
mesoappendix."1  The  collecting  trunks  from  the  caecum  and  appendix  follow  the 


EPITHELIUM 


MUSCULAR  LAYER 


FIG.  930. — Transverse  section  of  the  vermiform  appendix  of  man.      (Kolliker.) 

blood-vessels  (Fig.  931).  The  anterior  collecting  trunks  of  the  caecum  pass 
through  several  small  glands  in  the  anterior  ileo-caecal  fold,  and  terminate  in 
glands  along  the  ileo-colic  artery  (Fig.  931).  The  posterior  collecting  trunks 
pass  through  some  small  glands  and  terminate  in  glands  along  the  ileo-colic 
artery.  The  appendicular  collecting  trunks  enter  the  mesoappendix.  There  are 
usually  four  of  them,  sometimes  five.  Some  of  them  traverse  a  gland  constantly 
present  at  the  ileo-caecal  angle  (Clado).  Another  gland  is  constant.  It  is  situated 
beneath  the  ileo-colic  fossa  (Lockwood  and  Rolleston).  The  editor  subscribes  to 


1  Appendicitis,  its  Pathology  and  Surgery.     By  Charles  Barrett  Lockwood. 


THE  CAECUM 


1315 


Lockwood's  statement  that  in  appendicitis  there  is  often  a  chain  of  inflamed 
glands  along  the  inner  side  of  the  ascending  colon  behind  the  ascending  meso- 
colon.  Hence  this  is  one  road  taken  by  the  lymphatics  of  the  appendix.  The 
others  pass  to  the  mesenteric  glands. 


ANTERIOR 
LYMPHATICS 
OF  C/ECUM 


FIG.  931. — Lymphatics  of  the  caecum  and  appendix,  anterior  view.     (Pofrier  and  Charpy.) 

The  Heo-caecal  Valve  or  the  Valve  of  Bauhin  (valvuli  coli)  (Figs.  932,  933, 
934,  and  935). — The  lower  end  of  the  ileum  terminates  by  opening  into  the  inner 
and  back  part  of  the  large  intestine,  at  the  point 
of  junction  of  the  caecum  with  the  colon.     The 
opening  is  guarded  by  a  valve,  consisting  of 
two  semilunar  segments,  an  upper  or  colic  seg- 
ment (labium  superius)  and  a  lower  or  caecal 


ORIFICE   O 
APPEND 


FIG.  932. — Ileo-caecal  valve  of  the  circular  type. 
(Poirier.) 


FIG.  933. — Vertical  section  through  the  caecum 
and  ileo-caecal  valve.     (Gegenbaur.) 


segment  (labium  inferius),  which  project  into  the  lumen  of  the  large  intestine. 
The  upper  one,  nearly  horizontal  in  direction,  is  attached  by  its  convex  border  to 


1316 


THE  ORGANS  OF  DIGESTION 


the  point  of  junction  of  the  ileum  with  the  colon ;  the  lower  segment  which  is  more 
concave  and  longer,  is  attached  to  the  point  of  junction  of  the  ileum  with  the 
caecum.  At  each  end  of  the  aperture  the  two  segments  of  the  valve  coalesce,  and 
are  continued  as  a  narrow  membranous  ridge  around  the  canal  for  a  short  distance. 

Each  ridge  is  known  as  the 
retinaculum  or  frenulum  of 
the  valve  (frenulum  valvulae 
coli}.  The  left  or  ante- 
rior end  of  the  aperture  is 
rounded;  the  right  or  poste- 
rior is  narrow  and  pointed. 
In  the  formation  of  the  valve 
the  termination  of  the  small 
intestine  invaginates  for  a 
short  distance  into  the  lumen 
of  the  large  intestine  (Fig. 
933),  the  invaginated  portion 
of  the  wall  of  the  small  intes- 


SACCULUS 


SUPERIOR         J 
SEGMENT— £ 


INFERIOR 
SEGMEN 


ILEUM' 

LONG    MUSCU- 
LAR   FIBRES 
FROM    ILEUM 

ANTERIOR 
TXENIA 


POSTERIOR 


CUL-DE-SAC 

OF    C/ECUIV 


FIG.  934. — Caecum  and  vermiform  appendix.     (Sappey.) 


tine  uniting  with  a  corres- 
ponding portion  of  the  wall 
of  the  large  intestine. 

Each  segment  of  the  valve 
is  formed  by  a  reduplication 
of  the  mucous  membrane  and  of  the  circular  muscular  fibres  of  the  intestine,  the 
longitudinal  fibres  and  peritoneum  being  continued  uninterruptedly  across  from 
one  portion  of  the  intestine  to  the  other.  When  the  longitudinal  fibres  and  peri- 
toneum are  divided  or  removed,  the  ileum  may  be  drawn  outward,  and  all  traces 
of  the  valve  will  be  lost,  the  ileum  appearing  to  open  into  the  large  intestine  by  a 
funnel-shaped  orifice  of  large  size. 

The  surface  of  each  segment  of  the  valve  directed  toward  the  ileum  possesses 
villi,  and  presents  the  characteristic  structure  of  the  mucous  membrane  of  the 
small  intestine;  while  that  turned 
toward  the  large  intestine  is  desti- 
tute of  villi,  and  marked  with  the 
orifices  of  the  numerous  tubular 
glands  peculiar  to  the  mucous 
membrane  of  the  large  intestine. 
These  differences  in  structure  con- 
tinue as  far  as  the  free  margins  of 
the  valve.  When  the  caecum  is 
distended  it  is  supposed  that  the 
margins  of  the  opening  are  approxi- 
mated so  as  to  prevent  reflux  into 
the  ileum.  It  is  known,  however, 
that  a  very  large  enema  which  dis- 
tends the  caecum  and  colon  may  in 
part  enter  the  ileum,  being  driven 
there  by  waves  of  reversed  peris- 
talsis. The  valve  resists,  but  a 
certain  amount  of  pressure  over- 
comes it.  Some  believe  that  the  so-called  ileo-caecal  valve  is  not  a  valve,  but  a 
distinct  sphincter.  This  has  been  demonstrated  to  be  true  in  cats  and  dogs,  but 
lacks  demonstration  in  man  (p.  1331). 


ANTERIOR 

T/EN  IA 


EDGE    OF 

CJCCUM 

SUPERIOR 

SEGMENT 


POSTERIOR 
T/E  N  I  A' 


NTERNAL 
T/ENIA 


ORIFICE    OF 
VALVE 
INFERIOR 
SEGMENT 


FIG.  935. — Ileo-caecal  valve.     (Sappey.) 


THE  COLON  1317 


The  Colon. 

The  colon  is  divided  into  four  parts — the  ascending,  transverse  and  descending 
colon,  and  the  sigmoid  flexure. 

The  Ascending  Colon  (colon  ascendens}. — The  ascending  colon  is  smaller  than 
the  caecum,  with  which  it  is  continuous.  It  passes  upward,  from  its  commence- 
ment at  the  frenula  of  the  caecum,  opposite  the  ileo-caecal  valve,  to  the  under  sur- 
face of  the  right  lobe  of  the  liver,  on  the  right  of  the  gall-bladder,  where  it  is  lodged 
in  a  shallow  depression  on  the  liver,  the  impressio  colica;  here  it  bends  abruptly 
inward  to  the  left,  forming  the  hepatic  flexure  (flexura  call  dextra).  It  is  retained 
in  contact  with  the  posterior  wall  of  the  abdomen  by  the  peritoneum,  which  covers 
its  anterior  surface  and  sides,  its  posterior  surface  being  connected  by  loose  areolar 
tissue  with  the  Quadratus  lumborum  and  Transversalis  muscles,  and  with  the 
front  of  the  lower  and  outer  part  of  the  right  kidney  (Fig.  936).  Sometimes  the 
peritoneum  almost  completely  invests  it,  and  forms  a  distinct  but  short  meso- 
colon1  (p.  1269).  It  is  in  relation,  in  front,  with  the  convolutions  of  the  ileum  and 
the  abdominal  parietes. 

The  Transverse  Colon  (colon  transversum)  (Fig.  871). — The  transverse  colon, 
the  longest  part  of  the  large  intestine,  passes  transversely  from  right  to  left  across 
the  abdomen,  opposite  the  confines  of  the  epigastric  and  umbilical  zones,  into  the 
left  hypochondriac  region,  where  it  curves  downward  beneath  the  lower  end  of 
the  spleen,  forming  the  splenic  flexure  (flexura  coli  sinistra).  In  its  course  the 
transverse  colon  describes  an  arch,  the  concavity  of  which  is  directed  backward 
toward  the  vertebral  column  and  a  little  upward;  hence  the  name  transverse  arch 
of  the  colon.  This  is  the  most  movable  part  of  the  colon,  being  almost  completely 
invested  by  peritoneum,  and  connected  to  the  spine  behind  by  a  large  and  wide 
duplicature  of  that  membrane,  the  transverse  mesocolon  (Fig.  876).  The  trans- 
verse colon  is  in  relation,  by  its  upper  surface  with  the  liver  and  gall-bladder,  the 
great  curvature  of  the'stomach,  and  the  lower  end  of  the  spleen;  by  its  under  sur- 
face, with  the  small  intestines;  by  its  anterior  surface,  with  the  anterior  layers 
of  the  great  omentum  and  the  abdominal  parietes;  its  posterior  surface  on  the 
right  side  is  in  relation  with  the  second  portion  of  the  duodenum,  and  on  the  left 
side  is  in  contact  with  some  of  the  convolutions  of  the  jejunum  and  ileum. 

The  Descending  Colon  (colon  descendens). — The  descending  colon  passes 
downward  through  the  left  hypochondriac  and  lumbar  regions  along  the  outer 
border  of  the  left  kidney.  At  the  lower  end  of  the  kidney  it  turns  inward  toward 
the  outer  border  of  the  Psoas  muscle,  along  which  it  descends  to  the  crest  of  the 
ilium,  where  it  terminates  in  the  sigmoid  flexure.  At  its  commencement  it  is  con- 
nected with  the  Diaphragm  by  a  fold  of  peritoneum,  the  phreno-colic  ligament 
(see  p.  1268).  It  is  retained  in  position  by  the  peritoneum,  which  covers  its 
anterior  surface  and  sides,  its  posterior  surface  being  connected  by  areolar  tissue 
with  the  outer  border  of  the  left  kidney,  and  the  Quadratus  lumborum  and 
Transversalis  muscles  (Fig.  876).  It  is  smaller  in  calibre  and  more  deeply  placed 
than  the  ascending  colon,  and  is  more  frequently  covered  with  peritoneum  on  its 
posterior  surface  than  the  ascending  colon  (Treves). 

The  Sigmoid  Flexure,  Pelvic  Colon  or  Sigmoid  Colon  (colon  sigmoideum) 
(Figs.  937,  938,  939,  and  940)  is  the  narrowest  part  of  the  colon;  it  is  situated  in 
the  left  iliac  fossa,  commencing  from  the  termination  of  the  descending  colon,  at 
the  margin  of  the  crest  of  the  ilium,  and  then  forming  a  loop,  which  varies  in  length 

_!  Treves  states  that  after  a  careful  examination  of  one  hundred  subjects,  he  found  that  in  fifty-two  there  was 
neither  an  ascending  nor  a  descending  mesocolon.  In  twenty-two  there  was  a  descending  mesocolon,  but  no 
trace  of  a  corresponding  fold  on  the  other  side.  In  fourteen  subjects  there  was  a  mesocolon  to  both  the  ascend- 
ing and  the  descending  segments  of  the  bowel  ;  while  in  the  remaining  twelve  there  was  an  ascending  mesocolon, 
but  no  corresponding  fold  on  the  left  side.  It  follows,  therefore,  that  in  performing  lumbar  colostomy  a  meso- 
colon may  be  expected  on  the  left  side  in  36  per  cent,  of  all  cases,  and  on  the  right  in  26  per  cent.  (The  Anat- 
omy of  the  Intestinal  Canal  and  Peritoneum  in  Man,  1885,  p.  55.) — ED.  of  15th  English  edition. 


1318 


THE  ORGANS  OF  DIGESTION 


and  position,  and  which  terminates  in  the  rectum  at  the  level  of  the  attachment  of 
the  mesentery  upon  the  front  of  the  third  sacral  vertebra.     It  passes  downward 


Anterior 

1  n         f 

lamella  OJ 
lumbar  fascia. 


Posterior 

Middle  lamella  of 

lamella  of          iumoa  ,.  fascia. 
lumbar 


FIG.  936. — Diagram  of  the  relations  of  the  large  intestine  and  kidneys,  from  behind. 

about  two  inches  parallel  to  the  outer  border  of  the  Psoas  muscle,  then  taking  a 
transverse  direction  enters  the  cavity  of  the  pelvis,  crosses  this  cavity  from  left  to 
right  and  a  little  upward  to  the  lower  margin  of  the  right  iliac  fossa;  "from  this 


THE  COLON 


1319 


DESCENDING  COLON 


point  it  passes  downward,  backward,  and  inward  along  the  anterior  surface  of  the 
sacrum  to  its  junction  with  the  rectum."1  It  is  surrounded  with  the  peritoneum 
and  is  attached  to  the  posterior  abdominal  wall  by 
the  mesosigmoid,  a  continuation  of  the  mesocolon, 
but  which  greatly  exceeds  the  latter  in  length,  hence 
the  sigmoid  is  the  most  mobile  portion  of  the  large 
intestine.  Tuttle  divides  the  sigmoid  into  four  por- 
tions. The  first  or  vertical  portion;  the  second  or 
transverse  portion;  the  third  portion,  which  is  a  loop 
and  is  concave  upward  if  the  sigmoid  occupies  the 
pelvis,  and  is  concave  downward  if  it  occupies  the 
abdomen ;  the  fourth  portion,  which  is  curved  irregu- 
larly in  the  hollow  of  the  sacrum,  and  which  joins 
the  rectum  as  often  from  the  right  as  from  the  left. 
WThen  the  sigmoid  is  lifted  up  and  to  the  right  and 
the  mesosigmoid  is  put  slightly  upon  the  stretch,  an 
opening  is  seen  at  the  parietal  border  of  the  left 


FIG.  938. — Sigmoid  colon  and  rectum,  front  view.     The  broken  lines  indicate  the  situation  of  the  concealed  part 
of'the  sigmoid  colon.     The  small  intestine  is  drawn  away,  and  the  anus  is  turned  forward.     (Testut.) 

layer  of  the  mesosigmoid.     This  opening  leads  into  a  cul-de-sac,  the  intersigmoid 
fossa.     When  the  sigmoid  is  empty  most  of  it  falls  into  the  recto-vesical  or  recto- 

1  Tuttle,  Diseases  of  the  Anus,  Rectum,  and  Pelvic  Colon. 


1320 


THE  ORGANS  OF  DIGESTION 


vaginal  space  (Fig.  938).  When  distended  it  mounts  up  into  the  abdomen,  reaching 
to  or  even  above  the  umbilicus.  The  sigmoid  flexure  is  in  relation  in  front  with 
the  small  intestine  and  abdominal  parietes.  The  sigmoid  mesocolon  is  attached 
to  a  line  running  downward  and  inward  from  the  crest  of  the  ilium,  across  the 
Psoas  muscle  (Fig.  876). 


The  Rectum  (Intestinum  Rectum)  (Figs.  937,  938,  939,  940,  941,  942). 

The  rectum  is  the  terminal  part  of  the  large  intestine,  and  extends  from  the 
termination  of  the  sigmoid  flexure  to  the  level  of  the  semilunar  valves  of  Mor- 


PROSTATE 


TRANSVERSE 

PERINJEI 

MUSCLE 


EXTERNAL 

SPHINCTER 

MUSCLE 


FIG.  939.— Sagittal  section  in  the  median  line  of  the  pelvis.     (Poirier  and  Charpy.) 

gagni.  The  sigmoid  flexure  terminates  at  the  level  of  the  attachment  of  the 
mesentery  in  front  of  the  third  sacral  vertebra.  This  definition  is  practical  and 
useful.  It  was  suggested  by  Sir  Frederick  Treves.  "  It  gives  to  the  organ 
definite  limits;  it  separates  the  mobile  from  the  immobile  portion  of  the  gut;  it 
marks  the  line  where  the  course  of  the  blood-supply  changes;  it  indicates  the 
point  where  the  three  longitudinal  muscular  bands  of  the  colon  spread  out  and 
become  more  or  less  equally  distributed  arcund  the  gut;  and,  finally,  it  marks  a 
point  at  which  there  is  always  a  decided  narrowing  in  calibre,  indicating  the 
juncture  of  the  rectum  with  the  pelvic  colon."1  The  old  division  added  to  this 
the  so-called  first  part  of  the  rectum,  which  we  consider  as  part  of  the  sigmoid  colon. 
The  rectum  is  divided  into  two  portions,  a  superior  and  an  inferior.  The  supe- 
rior or  sacrococcygeal  portion  of  the  rectum  (ftexura  sacralis)  curves  downward 
with  the  concavity  forward  and  upward  in  front  of  the  sacrum  and  coccyx,  and 

1  A  Treatise  on  Diseases  of  the  Anus,  Rectum,  and  Pelvic  Colon.    By  James  P.  Tuttle. 


THE  RECTUM 


1321 


is  continued  as  far  as  the  apex  of  the  prostate  gland,  about  an  inch  in  front  of 
the  tip  c?  the  coccyx.  The  inferior  or  prostatic  portion  (flexura  perinealis)  begins 
at  this  point.  The  bowel  is  directed  downward  and  backward,  being  convex  in 
front,  and  terminates  at  the  beginning  of  the  anus  at  the  level  of  the  semilunar 
valves  of  Morgagni.  The  inferior  or  prostatic  portion  of  the  rectum  is  described 
by  Symington  as  the  anal  canal. 


HECTAL  FOLD 


VESICO-UTERINt 
CUL-DE-SAC 


CUL-DE-SAC 

OF.  DOUGLAS      \v'/\ 


FIG.  940. — Median  sagittal  section  of  the  female  pelvis.      (Luschka.) 

Curves  of  the  Rectum. — It  will  be  seen,  therefore,  that  the  rectum  presents  two 
antero-posterior  curves:  the  first,  with  its  convexity  backward,  is  due  to  the  con- 
formation of  the  sacro-coccygeal  column,  and  represents  the  arc  of  a  circle,  the 
centre  of  which  is  opposite  the  third  sacral  vertebra.  The  lower  one  has  its 
convexity  forward,  and  is  angular.  Its  centre  corresponds  to  a  line  drawn 
between  the  anterior  parts  of  the  ischial  tuberosities.  Two  lateral  curves  are  also 
described:  the  one  to  the  right,  opposite  the  junction  of  the  third  and  fourth  sacral 
vertebrae;  the  other  to  the  left,  opposite  the  sacro-coccygeal  articulation.  They 
are  of  little  importance. 

The  adult  rectum  as  here  described  has  a  length  of  from  four  to  six  inches  in  men, 
and  from  three  and  five-eighths  to  five  and  one-eighth  inches  in  women.  Accord- 
ing to  Tuttle  the  length  of  the  rectum  depends  to  some  degree  on  the  size  of  the 
subject,  and  is  some  what  greater  in  the  old  than  in  the  young.  The  prostatic  portion 
is  the  narrowest  portion  of  the  rectum.  The  widest  part  of  the  rectum  is  the  ampulla 
recti  just  above  the  anal  canal  (Figs.  939  and  940).  The  prostatic  portion  has  no 
peritoneal  investment  whatever  and  includes  the  lower  two  inches  of  the  superior 
portion  of  the  rectum.  When  the  rectum  is  empty  it  is  a  mere  slit,  the  anterior  and 
posterior  walls  being  in  contact.  When  distended  it  is  "irregularly  cylindrical" 
(Tuttle).  At  and  above  the  level  of  the  third  sacral  vertebra  the  gut  is  entirely  sur- 
rounded by  peritoneum,  and  there  is  a  mesosigmoid.  This  is  the  mesorectum  of 
those  who  describe  the  lower  pelvic  colon  as  the  first  part  of  the  rectum.  At  the  level 


1322 


THE  ORGANS  OF  DIGESTION 


FIG.  941. — Diagram  of  rectum,  showing  Hous- 
ton's valves  in  the  interior.     (Cunningham.) 


of  the  third  sacral  vertebra  the  true  rectum 
begins,  and  the  true  rectum  has  no  meso- 
rectum.  The  rectum  is  covered  in  front  and 
laterally  by  peritoneum  at  its  upper  part  ; 
gradually  the  peritoneum  leaves  its  sides, 
and  about  an  inch  above  the  prostate  is  re- 
flected from  the  anterior  surface  of  the  bowel 
on  to  the  posterior  wall  of  the  bladder  in 
the  male,  and  the  upper  fifth  of  the  posterior 
wall  of  the  vagina  in  the  female,  forming 
the  recto-vesical  or  recto-vaginal  pouch  (ex- 
cavatio  redovesicalis  and  excavatio  redoute- 
rina),  as  the  case  may  be  (Fig.  866).  The 
balance  of  the  rectum  has  no  peritoneal  cov- 
ering. The  level  at  which  the  peritoneum 
leaves  the  anterior  wall  of  the  rectum  to  be 
reflected  on  to  the  viscus  in  front  of  it  is  of 
considerable  importance  from  a  surgical 
point  of  view,  in  connection  with  removal  of  the  lower  part  of  the  rectum.  It  is 
higher  in  the  male  than  in  the  female.  In  the  former  the  height  of  the  recto- 
vesical  pouch  is  about  three  inches;  that  is  to  say,  the  height  to  which  an  ordinary 
index  finger  can  reach  from  the  anus.  In  the  female  the  height  of  the  recto- 
vaginal  pouch  is  about  two  and  a  quarter  inches  from  the  anal  orifice. 

The  upper  or  sacro-coccygeal  portion  of  the  rectum  is  in  relation,  in  front,  in 
the  male,  with  the  recto-vesical  pouch,  the  triangular  portion  of  the  base  of  the 
bladder,  the  vesiculae  seminales,  and  vasa  deferentia,  and  more  anteriorly  with 
the  under  surface  of  the  prostate.  In  the  female,  with  the  posterior  wall  of  the 
vagina  below,  and  the  recto-vaginal  pouch  above,  in  which  are  some  convolutions 
of  the  small  intestine  (Fig.  940).  To  the  sides  below  the  peritoneal  reflections, 
the  rectum  is  surrounded  by  cellular  tissue  in  which  on  each  side  lie  the  lateral 
sacral  artery  and  the  bifurcated  hypogastric  plexus.  This  portion  of  the  rectum  is 
separated  from  the  sacrum  and  coccyx  by  an  interval,  the  retro-rectal  space,  which 
is  filled  with  cellular  tissue.  The  superior  portion  of  the  distended  rectum  is  in  con- 
tact posteriorly  and  on  each  side  with  the  sacral  plexus,  ganglia  of  the  sympathetic, 
and  the  fascial  origin  of  the  pyramidalis  muscle  (Tuttle).  The  lower  or  prostatic 
portion  in  men  is  in  relation  anteriorly  with  the  prostate  gland  and  the  membranous 
urethra;  in  women  with  the  posterior  wall  of  the  vagina.  The  lower  end  of  the 
rectum  takes  a  backward  turn,  and  the  uro-genital  organs  turn  forward;  the  inter- 
vening space  is  called  the  perineum.  In  tlie  female,  the  fibro-fatty  and  muscular 
tissue  which  occupies  this  space  is  called  the  perineal  body.  The  prostatic  portion 
of  the  rectum  is  invested  by  the  Internal  sphincter,  supported  by  the  Levatores 
ani  muscles,  and  surrounded  at  its  termination  by  the  External  sphincter;  in  the 
empty  condition  it  presents  the  appearance  of  a  longitudinal  slit.  Posteriorly 
the  lower  part  of  the  rectum  is  in  contact  with  cellular  tissue,  which  separates  it 
from  the  coccygeal  gland  and  the  coccyx. 

Supports  of  the  Rectum. — The  rectum  as  it  has  been  described  in  these  pages  is  a 
fixed  tube.  The  upper  portion  of  the  rectum  is  supported  by  "the  inferior  mesen- 
teric  arteries  and  the  fibrous  sheaths  which  surround  them"  (Tuttle) ;  by  the  peri- 
toneal folds  which  attach  it  to  the  sacrum ;  and  by  the  peritoneal  folds  which  pass 
in  front  to  the  bladder  (plicae  rectovesicales) ,  or  to  the  uterus  (plicae  redouterinae) , 
and  laterally  to  the  pelvis.  The  middle  of  the  rectum  receives  some  support 
from  the  lateral  sacral  arteries  and  their  fibrous  sheaths.  The  lower  portion  of  the 
rectum  is  supported  by  the  Levator  ani,  External  sphincter,  and  Recto-coccygeus 
muscles. 


THE  RECTUM 


1323 


Blood-vessels  and  Lymphatics  of  Rectum. — See  pp.  1328  and  1329. 
Nerves  of  Rectum. — See  p.  1329. 
Structure  of  Rectum. — See  p.  1324. 


RECTAL  VALVES 


A  B  C 

FIG.  942. — The  anal  canal  and  lower  part  of  the  rectum  in  the  foetus.  A,  aged  four  to  five  months  ;  B,  six 
months  ;  C,  nine  months.  In  each  the  anal  canal  is  distinctly  marked  off  from  the  rectum  proper  ;  the  columns 
of  Morgagni  and  the  rectal  valves  are  distinct.  (Cunningham.) 

The  Common  Anal  Canal  (pars  analis  recti)  (Figs.  942  and  943).— The  anal 
canal  is  the  third  portion  of  the  rectum  of  the  older  descriptions.  It  begins 
where  the  true  rectum  ends.  This  canal  is  the  portion  of  the  intestinal  tract  which 


LONGITUDINAL 

FIBRES  OF 

RECTUM 


PART  OF 

LEVATOR  AN. 

INTERNAL 

SPHINCTER 


ANAL  CANAL 


RUG/E  OF 
MUCOUS 
MEMBRANE 

COLUMNS  OF 
MORGAGNI 


ANAL  VALVES 


FIG.  943.— The  interior  of  the  anal  canal  and  lower  part  of  the  rectum,  showing  the  columns  of  Morgagni  and 
the  anal  valves  between  their  lower  ends.  The  columns  were  more  numerous  in  the  specimen  than  usual. 
(Cunningham.) 

is  below  the  distribution  of  genuine  mucous  membrane,  and  is  just  posterior  to 
the  middle  of  a  line  drawn  from  one  tuberosity  to  the  other.  It  lies  between  the 
true  skin  and  the  upper  borders  of  the  semilunar  valves  of  Morgagni.  When  at 
rest  it  is  a  mere  slit  placed  antero-posteriorly.  The  external  opening  of  the  anal 
canal  is  the  anus.  The  skin  about  the  anus  is  pigmented,  is  thrown  into  radi- 
ating folds  by  the  contraction  of  the  External  sphincter  muscle,  and  contains 
hairs,  sebaceous  glands,  and  sudoriparous  glands  (glandulae  circumanales). 
Ascending  into  the  canal,  it  alters  its  character  and  becomes  muco-cutaneous, 
and  true  mucous  membrane  appears  at  the  rectum  proper.  Back  of  the  anus  is 
a  median  cutaneous  fold  passing  posterior  to  the  coccyx  and  called  the  anal  raphe. 
In  front  of  the  anus  is  a  median  fold  which,  in  the  female,  passes  forward  and 
merges  with  the  labia  major  and  in  the  male  continues  into  the  raphe"  of  the 
scrotum.  This  is  called  the  perineal  raphe.  The  length  of  the  anal  canal  is  three- 
quarters  to  one  inch.  "Its  circumference  varies  from  3  cm.  (one  and  three- 
sixteenths  inches)  in  normal  condition  to  15  cm.  (five  and  five-sixteenths  inches) 
in  disease,  following  injury  or  vicious  practices.  The  average  anus  will  admit  a 
cylinder  of  65  mm.  in  circumference  without  rupturing  the  mucous  membrane."1 


1  Diseases  of  the  Anus,  Rectum,  and  Pelvic  Colon.     By  James  P.  Tuttle. 


1324  THE  ORGANS  OF  DIGESTION 

Relations  of  the  Anal  Canal. — It  is  surrounded  by  the  external  and  internal 
sphincter  muscles,  and  above  by  the  Levatorcs  ani.  To  each  side  is  the  ischio- 
rectal  fossa  containing  fat.  Between  the  anal  canal  and  the  coccyx  is  a  collec- 
tion of  muscular  fibres  and  connective  tissue,  the  ano-coccygeal  body  of  Symington. 
In  front,  in  the  male,  is  the  bulb  of  the  urethra  and  the  base  of  the  triangular 
ligament  ;  in  the  female,  is  the  perineal  body,  which  separates  the  anus  from 
the  vagina.  There  are  three  layers  in  the  wall  of  the  anal  canal: 

1.  The  muco-cutaneous  layer,  which  contains  glands,  blood-vessels,  and  numer- 
erous  nerve-endings.     The  lower  portion  is  covered  with  pavement-epithelium, 
but  gradually  there  is  a  transition,  and  at  the  beginning  of  the  rectum  proper  the 
epithelium  is  entirely  columnar.  The  valves  of  Morgagni,  the  anal  valves  or  the  semi- 
lunar  valves  (Figs.  943  and  944)  are  in  the  upper  portion  of  the  anal  canal  between 
the  lower  ends  of  the  columns  of  Morgagni  (Figs.  943  and  944).    Above  the  valves 
the  canal  is  lined  by  transitional  mucous  membrane,  below  them  by  modified  skin. 

The  ano-rectal  line  is  not  straight,  but  is  irregularly  dentated  by  trivial  eleva- 
tions, each  of  which  is  papilliform  at  its  summit.  According  to  Tuttle,  these 
elevations  number  from  five  to  eight.  About  one-fifth  of  an  inch  below  the  ano- 
rectal  line  is  the  depression  known  as  Hilton's  white  line  (annulus  haemorrhoidalis) 
(Fig.  944).  This  line  is  somewhat  indistinct  to  sight,  but  can  always  be  felt  with 
the  finger.  It  marks  the  junction  of  the  External  with  the  Internal  sphincter. 
Above  Hilton's  line  are  some  mucous  crypts  and  also  dilatations  produced  by  the 
internal  haemorrhoidal  plexus  of  veins  (Fig.  944). 

2.  The  fibro-cellular  layer  is  beneath  the  mucous  membrane.     Above  Hilton's 
line  it  is  composed  of  cellular  tissue;  below  it  is  a  thin  fascia-like  layer  which  joins 
the  superficial  fascia. 

The  anal  canal  is  surrounded  by  longitudinal  fibres  from  the  rectum,  fibres  from 
the  Levator  ani,  the  lower  portion  of  the  Internal  sphincter,  and  particularly  by 
the  External  sphincter. 

Blood-vessels,  Lymphatics,  and  Nerves  of  Anus. — See  pp.  1328  and  1329. 

Structure  of  Large  Intestine  (including  the  Rectum  and  Anal  Canal). — The 
large  intestine  has  four  coats — serous,  muscular,  areolar  or  submucous  and  mucous. 

The  Serous  Coat  (tunica  serosa}. — The  serous  coat  is  derived  from  the  peritoneum, 
and  invests  the  different  portions  of  the  large  intestine  to  a  variable  extent.  The 
caecum  is  completely  covered  by  the  serous  membrane,  except  in  a  small  percent- 
age of  cases  (5  or  6  per  cent.),  where  a  small  portion  of  the  upper  end  of  the  pos- 
terior surface  is  uncovered.  The  ascending  and  descending  colon  are  usually 
covered  only  in  front  and  at  the  sides ;  a  variable  amount  of  the  posterior  surface 
is  uncovered.  The  transverse  colon  is  almost  completely  invested,  the  parts  corre- 
sponding to  the  attachment  of  the  great  omentum  and  transverse  mes~ocolon  being 
alone  excepted.  The  sigmoid  flexure  is  completely  surrounded,  except  along  the 
line  to  which  the  sigmoid  mesocolon  is  attached.  The  upper  two-thirds  of  the 
rectum  is  covered  in  front  and  laterally  by  the  peritoneum,  but  not  posteriorly, 
between  the  two  posterior  folds  of  peritoneum,  the  so-called  mesorectum;  later 
it  is  covered  only  on  its  anterior  surface;  and  the  lower  portion  is  entirely 
devoid  of  any  serous  covering.  In  the  course  of  the  colon  the  peritoneal  coat  is 
thrown  into  a  number  of  small  pouches  filled  with  fat,  called  appendices  epiploicae. 
They  are  chiefly  appended  to  the  transverse  colon,  and  are  particularly  numerous 
along  the  anterior  band. 

The  Muscular  Coat  (tunica  muscularis). — The  muscular  coat  consists  of  an 
external  longitudinal  and  an  internal  circular  layer  of  muscular  fibres. 

The  Longitudinal  Fibres,  although  found  to  a  certain  extent  all  around  the 
intestine,  do  not  form  a  uniform  layer  over  the  whole  surface  of  the  large 
intestine.  In  the  caecum  and  colon  they  are  especially  collected  into  three  flat 
longitudinal  bands  or  taeniae  (taeniae  coli)  (Figs.  923  and  924),  each  being  about 


THE  STRUCTURE  OF  THE  LARGE  INTESTINE  1325 

half  an  inch  in  width.  These  bands  commence  at  the  base  of  the  vermiform 
appendix,  which  structure  is  surrounded  by  a  uniform  layer  of  longitudinal 
muscular  fibres.  The  bands  pass  from  the  base  of  the  appendix  to  the  rectum. 
At  this  point  they  broaden,  fuse,  and  surround  the  rectum.  On  the  ascend- 
ing, descending,  and  sigmoid  colon  the  mesocolic  band  (taenia  mesocolica)  is 
posterior  and  internal;  the  omental  band  (taenia  omentalis)  is  posterior  and 
external;  the  free  band  (taenia  libera)  is  anterior.  On  the  transverse  colon  the 
taenia  libera  is  inferior;  the  taenia  mesocolica  is  posterior;  the  taenia  omentalis 
is  anterior  and  superior.  These  bands  are  one-sixth  shorter  than  the  other  coats 
of  the  intestine  to  which  they  are  applied,  and  serve  to  produce  the  sacculi  (Fig. 
924) .  which  are  characteristic  of  the  caecum  and  colon ;  accordingly,  when  they 
are  dissected  off,  the  tube  can  be  lengthened,  and  its  sacculated  character  becomes 
lost.  The  sacculations  are  called  haustra  coli.  There  are  three  rows  of  the  sac- 
culations  separated  from  each  other  by  the  longitudinal  bands.  These  pouches 
are  also  subdivided  by  transverse  furrows  which  correspond  to  concave  folds  of 
mucous  membrane,  called  semilunar  folds  (plicae  semilunares  coli).  In  the  sig- 
moid flexure  the  longitudinal  fibres  become  more  scattered;  but  upon  its  lower 
part,  and  around  the  rectum,  they  spread  out  and  form  a  layer  which  completely 
encircles  this  portion  of  the  gut,  but  is  thicker  on  the  anterior  and  posterior 
surfaces,  where  two  accentuations  exist,  than  on  the  lateral  surfaces.  In  the 
rectum  the  external  fibres  of  the  longitudinal  layer  descend  and  are  inserted  into 
the  fascia  covering  the  Levator  ani  muscle.  The  middle  fibres  are  mingled  with 
descending  fibres  of  the  Levator  ani  and  terminate  by  attachment  to  the  rectal 
wall.  The  internal  fibres  descend  between  the  External  and  Internal  sphincter 
muscles  and  are  inserted  into  the  superficial  fascia  around  the  anal  margin. 
The  lower  part  of  the  rectum  is  surrounded  by  the  Levator  ani  muscle  (p.  453). 
In  addition  to  the  muscular  fibres  of  the  bowels,  two  bands  of  plain  muscular 
tissue  are  to  be  noted.  They  arise  from  the  front  of  the  second  and  third  coccy- 
geal  vertebrae,  and  pass  downward  and  forward  to  blend  with  the  longitudinal 
muscular  fibres  on  the  posterior  wall  of  the  rectum.  Each  is  known  as  the  recto- 
coccygeal  muscle  (m.  rectococcygeus) . 

The  Circular  Fibres  form  a  thin  layer  over  the  caecum  and  colon,  being  especially 
accumulated  in  the  intervals  between  the  sacculi.  In  the  rectum  the  circular  fibres 
constitute  a  thick  coat  at  some  portions  of  the  circumference  and  a  thinner  coat 
at  others.  The  circular  fibres  are  thickened  at  every  flexure.  The  thickenings 
only  partly  surround  the  gut,  and  hence  are  not  to  be  considered  as  additional 
sphincters.  Tuttle  calls  them  the  semicircular  muscles  of  the  rectum.  These  semi- 
circular muscles  are  opposite  the  insertion  of  Houston's  valves.  At  the  lower  end 
of  the  rectum  the  circular  fibres  become  very  numerous  and  constitute  the  Internal 
sphincter  muscle  (m.  sphincter  ani  intermis)  (Fig.  943).  Tuttle  describes  it  as  fol- 
lows: "This  muscle,  composed  of  an  aggregation  of  circular  fibres,  begins  about 
4  cm.  above  the  anal  margin,  and  gradually  increases  in  thickness  until  it  reaches 
the  ano-rectal  line,  after  which  it  thins  out  again  and  disappears  about  the  middle 
of  the  anal  canal.  Its  width  from  above  downward  averages  1  to  3  cm.  (three-fifths 
of  an  inch  to  one  and  one-fifth  inches).  Its  thickness  is  so  variable  that  no  accurate 
measurement  can  be  given.  Its  lower  fibres  are  below  and  within  the  grasp  of  the 
External  sphincter,  from  which  it  is  separated  by  a  narrow  zone  of  connective 
tissue.  A  depressed  zone,  not  always  perceptible  to  the  eye,  but  appreciable 
by  digital  touch,  marks  the  line  of  division  between  these  two  muscles."1  The 
Internal  sphincter  is  an  involuntary  muscle.  The  external  sphincter  muscle  is 
not  a  portion  of  the  wall  of  the  bowel.  It  is  described  on  pages  450  and  451. 

The  Areolar  Coat  or  Submucous  Coat  (tela  submucosa). — The  areolar  or  sub- 
mucous  coat  connects  the  muscular  and  mucous  layers  closely  together.  This  coat 

1  Diseases  of  the  Anus,  Rectum,  and  Pelvic  Colon.     By  James  P.  Tuttle. 


1326 


THE  ORGANS  OF  DIGESTION 


is  thicker,  looser,  and  more  elastic  in  the  rectum  than  elsewhere.  In  this  coat  are 
the  blood-vessels,  nerves,  and  lymphatics. 

The  Mucous  Membrane  (tunica  mucosa). — The  mucous  membrane,  in  the  caecum 
and  colon,  is  pale,  smooth,  destitute  of  villi,  and  raised  into  numerous  crescentic 
folds  which  correspond  to  the  intervals  between  the  sacculi.  In  the  rectum  it  is 
thicker,  of  a  darker  color,  more  vascular,  and  connected  loosely  to  the  muscular 
coat,  as  in  the  oesophagus. 

The  rectum  contains  certain  horizontal  folds.  Most  of  them  disappear  when 
the  gut  is  distended,  but  some  of  them  do  not  disappear,  but  remain  as  distinct 


MUCOUS 
MEMBRANE 

DILATATION 

OF    VEINS 

COLUMNS   OF 

MORGAGNI 

VALVE    OF 

MORGAGNI 


HILTON'S 
WHITE  LINE 


MUSCULAR  WALL 
OF  RECTUM 


INTERNAL  HEMOR- 
RHOIDAL   PLEXUS 

DILATATION 
OF  VEIN 

COMMUNICATION    BE- 
TWEEN    INTERNAL ANt 
EXTERNAL  HEMOR- 
RHOIDAL    PLEXUS 
INTERNAL 
SPHINCTER 

EXTERNAL 
SPHINCTER 

LONGITUDINAL 
TENDINOUS  FIBRES 

SUBCUTANEOUS 
CELLULAR  TISSUE 


FIG.  944. — Inner  wall  of  the  lower  end  of  the  rectum  and  anus.  On  the  right  the  mucous  membrane  has 
been  removed  to  show  the  dilatation  of  the  veins  and  how  ihey  pass  through  the  muscular  wall  to  anastomose 
with  the  external  haemorrhoidal  plexus.  (Luschka.) 

folds  with  free  crescentic  edges.  These  permanent  folds  were  first  described  by 
Houston,  of  Dublin,  and  are  known  as  rectal  valves  or  Houston's  valves  (plicae 
transversales  recti)  (Figs.  941  and  942).  Each  fold  surrounds  more  than  one- 
third  of  the  gut,  and  is  composed  of  mucous  membrane,  submucous  tissue,  and 
a  layer  from  the  circular  muscular  layer  of  the  gut.  There  may  be  three,  four,  or 
five  of  these  folds.  Three  of  them  are  constant.  One  is  on  the  right  rectal  wall, 
about  the  point  of  peritoneal  reflection;  another  is  on  the  left  side,  about  one 
inch  above  the  margin  of  the  anal  canal.  A  third  is  on  the  rectal  wall,  either 
toward  the  right  or  left,  at  the  point  where  the  rectum  joins  the  front  of  the 
sigmoid.  These  shelf-like  valves  are  not  perfectly  flat,  for  on  the  superior  surface 
of  each  is  a  depression. 

The  borders  of  a  valve  are  thinner  than  its  base  and  are  very  flexible.  These 
valves  support  the  mass  of  faeces  as  it  descends,  and  give  to  it  a  rotary  motion 
(Tuttle).  In  the  lower  end  of  the  rectum  the  mucous  membrane  forms  longi- 
tudinal folds  known  as  the  columns  of  Morgagni  or  the  rectal  columns  (columnae 
rectales  [Morgagni])  (Figs.  943  and  944).  There  are  from  five  to  ten  of  these 
folds,  each  of  which  is  about  one-half  an  inch  long,  and  they  contain  longitudinal 
muscle-fibres.  They  are  most  prominent  when  the  sphincter  contracts.  The  base 
of  each  column  helps  to  form  the  upper  margin  of  the  anal  canal.  The  outer  angle 
of  each  column  below  passes  into  a  similunar  valve.  The  grooves  between  the 
columns  are  shallow  above  and  deeper  below,  and  end  in  the  semilunar  valves. 
The  semilunar  valves,  valves  of  Morgagni  or  anal  valves  (Figs.  943  and  944)  are  folds 
which  stretch  from  the  base  of  one  column  to  another,  and  form  the  anal  pockets 
or  crypts  of  Morgagni  (sinus  rectales).  These  pockets  are  about  5  mm.  in  depth. 
They  are  most  marked  pos'eriorly  (Ball),  but  none  exists  in  either  the  anterior 


THE  STRUCTURE  OF  THE  LARGE  INTE8TINE 


1327 


or  posterior  commissure  (Tuttle).  Below  the  sinuses  is  the  white  line  of  Hilton 
(Fig.  944),  which  reaches  to  the  region  where  hair  and  sebaceous  glands  appear. 

As  in  the  small  intestine,  the  mucous  membrane  consists  of  a  muscular  layer,  the 
muscularis  mucosae  (Fig.  948);  of  a  quantity  of  retiform  tissue  in  which  the  vessels 
ramify;  of  a  basement-membrane  and  epithelium,  which  is  of  the  columnar  variety, 
and  exactly  resembles  the  epithelium  found  in  the  small  intestine.  In  the  rectum 
the  epithelial  cells  are  columnar;  at  the  lower  end  of  the  tube,  however,  they  begin 
to  change  into  stratified  polyhedrons  and  prisms.  The  mucous  membrane  of  the 
large  intestine  presents  for  examination  simple  follicles  and  solitary  glands. 

The  Simple  Follicles,  Intestinal  Glands,  Crypts  or  Glands  of  Lieberkuhn  (glandulae 
intestinales  [Lieberkuhni])  (Fig.  948)  are  minute  tubular  prolongations  of  the 
mucous  membrane  arranged  perpendicularly,  side  by  side,  over  its  entire  sur- 
face; they  are  longer,  more  numerous,  and  are  placed  in  much  closer  apposition 
than  those  of  the  small  intestine;  and  they  open  by  minute  rounded  orifices  upon 
the  surface,  giving  it  a  cribriform  appearance. 


,  , 

D,  arteries  on  the  dorsal  surface  of  the  ileum.    (Robinson.) 


The  Solitary  Glands  (noduLi  lymphatici  solitarii)  (Fig.  948)  in  the  large  intes- 
tine are  most  abundant  in  the  caecum  and  vermiform  appendix,  but  are  irregu- 
larly scattered  also  over  the  rest  of  the  intestine.  They  are  similar  to  those  of  the 
small  intestine. 

Vessels  of  the  Large  Intestine.  —  The  arteries  supplying  the  large  intestine  give 
off  large  branches,  which  ramify  between  the  muscular  coats  supplying  them, 
and,  after  dividing  into  small  vessels  in  the  submucous  tissue,  pass  to  the 
mucous  membrane.  The  caecum,  the  appendix,  and  the  ileo-caecal  valve  are  sup- 
plied by  the  branches  from  the  anastomotic  loops  between  the  right  colic  and  ileo- 
colic  branches  of  the  superior  mesenteric  artery  (Figs.  945  and  946).  In  males  the 
sole  blood-supply  of  the  appendix  is  by  the  appendicular  artery  from  the  posterior 
ileo-caecal  branch  of  the  ileo-caecal  artery  (Fig.  946).  In  the  female  the  appendix 
occasionally  receives  an  additional  vessel  along  the  appendiculo-ovarian  ligament 


1328 


THE  ORGANS  OF  DIGESTION 


from  the  ovarian  artery.  The  ascending  colon  is  supplied  by  the  right  colic,  and  the 
transverse  colon  by  the  middle  colic  branch  of  the  superior  mesenteric.  The 
descending  colon  is  supplied  by  the  left  colic  branch  of  the  inferior  mesenteric, 
and  the  sigmoid  flexure  by  the  sigmoid  branches  of  the  inferior  mesenteric.  The 
rectum  (Fig.  947)  is  supplied  mainly  by  the  superior  haemorrhoidal  branch  of  the 
inferior  mesenteric,  but  also  at  its  lower  end  by  the  middle  haemorrhoidal  from 
the  internal  iliac,  and  the  inferior  haemorrhoidal  from  the  pudic  artery.  The  supe- 


FIG.  946. — The  arterial  blood-supply  of  the  anterior  (ventral)  surface  of  the  caecum  and  appendix.  .4  ileo- 
colio  artery;  B,  caecal-appendicular  artery;  D,  anterior  caecal  artery;  F  and  G,  appendicular  artery.  Note  that 
the  caecal  and  appendicular  arteries  anastomose  by  fine  capillaries,  both  ventrally  and  dorsally;  C,  iliac  artery; 
1,  right  colon;  2,  external  sacculus  of  caecum  (to  right  of  taenium  coli);  3,  appendix;  4,  Iliac,  and  5,  Psoas 
muscles.  (Robinson.) 

rior  haemorrhoidal,  'the  continuation  of  the  inferior  mesenteric,  divides  into  two 
branches,  which  run  down  either  side  of  the  rectum  to  within  about  five  inches 
of  the  anus;  they  here  split  up  into  about  six  branches,  which  pierce  the 
muscular  coat  and  descend  between  it  and  the  mucous  membrane  in  a  longi- 
tudinal direction,  parallel  with  each  other  as  far  as  the  Internal  sphincter,  where 
they  anastomose  with  the  other  haemorrhoidal  arteries  and  form  a  series  of  loops 
around  the  anus.  The  veins  of  the  large  intestine  correspond  to  the  arteries  and 
join  the  superior  and  inferior  mesenteric  veins  which  join  the  portal  vein.  The  veins 
of  the  rectum  (Fig.  947)  commence  in  a  plexus  of  vessels  which  surrounds  the  lower 
extremity  of  the  intestinal  canal.  In  the  vessels  forming  this  plexus  are  small 
saccular  dilatations  just  within  the  margin  of  the  anus  (Figs.  944  and  947); 
from  it  about  six  vessels  of  considerable  size  are  given  off.  These  ascend  between 
the  muscular  and  mucous  coats  for  about  five  inches,  running  parallel  to  each 
other;  they  then  pierce  the  muscular  coat,  and,  by  their  union,  form  a  single 


STRUCTURE  OF  THE  LARGE  INTESTINE  AND  RECTUM    1329 


SUPERIOR 

HEMORRHOIDAL 

VEIN 


SUPERIOR 

HEMORRHOIOAL 

ARTERY 


MIDDLE 

HEMORRHOIDAL 

ARTERY 


trunk,  the  superior  haemorrhoidal  vein,  which  empties  into  the  inferior  mesenteric 
branch  of  the  portal  vein.  This  arrangement  is  termed  the  haemorrhoidal  plexus 
(Fig.  473);  it  communicates  with  the  tributaries  of  the  middle  and  inferior 
haemorrhoidal  veins  at  its  commencement,  and  thus  a  communication  is  established 
between  the  systemic  and 
portal  circulations.  The  in- 
ferior haemorrhoidal  veins 
empty  into  the  internal  pudic 
veins,  and  the  middle  haemor- 
rhoidal veins  empty  into  the 
internal  iliac  veins. 

The  Lymphatics  of  the  Large 
Intestine. — The  lymphatics 
of  the  large  intestine  begin 
in  the  mucous  membrane  and 
form  an  extensive  plexus  in 
the  submucosa.  There  are 
also  lymphatics  more  deeply 
seated,  beneath  the  simple 
follicles.  Those  from  the 
ascending  colon  and  trans- 
verse colon  open  into  the 
glands  within  the  mesocolon 
and  behind  the  colon  (meso- 
colic  glands),  from  which 
glands  trunks  pass  to  the 
superior  mesenteric  glands. 
The  lymphatics  from  the 
transverse  colon  join  with 
lymph-vessels  of  the  great 
omentum,  and  hence  com- 
municate with  the  lymphatics 
of  the  greater  curvature  of 
the  stomach.  The  lymph 
from  the  descending  colon, 
from  the  sigmoid  and  from 
the  pelvic  colon  passes  to 
the  glands  ajong  the  inferior 
mesenteric  artery.  The  lym- 
phatics of  the  rectum  paSS  FIG.  947. — The  blood-vessels  of  the  rectum  and  anus,  snowing  the 
£  ,1  ill]  distribution  and  anastomosis  on  the  posterior  surface  near  the  termi- 

hrst     to     trie     rectal     glands,     nation  ot  the  gut.     (Poirier  and  Charpy.) 

which   lie   on  the   muscular 

coat  of  the  rectum,  next  to  the  glands  which  lie  back  of  the  rectum  along  the 
superior  haemorrhoidal  artery,  and  finally  to  the  sacral  glands.  Lymphatics  from 
the  skin  of  the  anus  pass  with  the  lymphatics  of  the  skin  to  the  superficial  inguinal 
glands.  Lymphatics  from  the  anus  between  the  skin  margin  and  Hilton's  white 
line  pass  to  the  hypogastric  glands. 

The  Nerves  of  the  Anus  and  Rectum. — The  nerves  of  the  anus  and  rectum  are 
derived  from  both  the  sympathetic  and  cerebro -spinal  system.  The  chief  supply 
of  the  rectum  is  from  the  mesenteric,  sacral,  and  hypogastric  plexuses  of  the  sympa- 
thetic. It  also  obtains  small  branches  from  the  third,  fourth,  and  fifth  sacral  nerves. 
The  lower  part  of  the  rectum  is  much  more  sensitive  than  the  upper  part. 
The  muscles  of  the  anus  and  rectum  are  supplied  "from  the  intricate  plexuses 
formed  by  the  second,  third,  fourth,  and  fifth  sacral  nerves"  (Tuttle).  The 

84 


INFERIOR 

HCMORRHOIDAL 

ARTERY 


1330 


THE  ORGANS  OF  DIGESTION 


External  sphincter  is  supplied  by  nerves  which  contain  motor,  sensor,  and 
sympathetic  fibres.  These  nerves  come  from  three  sources.  "Two  filaments 
from  the  branches  formed  by  the  third,  fourth,  and  fifth  sacral  nerves  extend 
transversely  across  the  ischio-rectal  fossa  and  distribute  themselves  to  the  middle 
portion  of  the  muscle  and  to  the  peri-anal  cutaneous  surface;  a  filament  which 
comes  off  from  the  internal  pudic  just  before  its  division  into  terminal  branches 
supplies  the  anterior  portion  of  the  muscle,  and  is  called  the  anterior  sphincterian 
nerve ;  while  a  filament  coming  off  from  the  fifth  and  sixth  sacral  nerves  passes 
down  into  the  hollow  of  the  sacrum,  between  the  Levator  ani  muscle  and  the  recto- 
coccygeus  ligament,  and  finally  reaches  the  posterior  superficial  surface  of  the 
External  sphincter."1  The  spinal  centre  for  the  nerves  of  the  anus  and  rectum  is 
opposite  the  first  lumbar  vertebra,  and  is  in  practically  the  same  region  as  the 
centre  for  the  genito-urinary  organs. 

Surface  of  mucous  membrane, 
with  openings  of  Lieberkiihn's 
follicles. 


Lieberkiihn's  follicles. 


=^=  Muscularis  mucosie  (two  layers). 


B="  Stibmucous  connective  tissue. 


Solitary  gland. 

FIG.  948. — Minute  structure  of  large  intestine. 

Movements  and  Innervation  of  the  Intestines. 

Movements. — As  the  small  intestine  is  devoid  of  any  sphincter  arrangement  peristalsis  cannot 
mix  the  food  as  it  does  in  the  pyloric  portion  of  the  stomach.  The  process  by  which  the  food  is 
mixed  with  the  secretions  and  is  brought  against  the  intestinal  wall  for  absorption  is  called 
by  Cannon  "rhythmic  segmentation."  Rhythmic  motions  "mix  the  food  and  expose  it  to  the 
mucosa  without  advancing  it  appreciatively  along  the  canal."2  In  this  process  constrictions  occur 
in  the  circular  fibres,  with  the  result  that  a  collection  of  stationary  food  is  divided  into  a  number 
of  segments.  In  the  middle  of  each  segment  constrictions  appear  and  the  earlier  constrictions 
relax.  Then  the  latter  constrictions  relax  and  the  earlier  reappear  and  so  on  until  the  food  is 
thoroughly  mixed  with  digestive  secretions.  Finally  the  food  is  driven  on  by  peristalsis  coming 
again  to  rest  and  being  again  subjected  to  "rhythmic  segmentation."  Cannon  says  that  in  the 
duodenum  "rhythmic  segmentation"  lasts  for  several  minutes,  but  in  other  parts  of  the  intestine 
it  may  continue  for  half  an  hour  or  more,  the  food  which  is  being  subjected  to  it  scarcely  moving 
along  the  canal.  It  is  probable  that  in  man  there  are  from  seven  to  eight  segmentations  per  minute 
in  a  given  area.  It  is  also  probable  that  there  is  a  sphincter  action  at  the  ileo-caecal  opening. 

Cannon  divides  the  large  intestine  into  two  parts:  a  distal  part,  in  which  the  material  is  hard 
and  lumpy  and  is  "advanced  by  rings  of  tonic  contraction,"  and  a  proximal  part,  in  which  the 
material  is  soft.  In  this  part  "the  common  movements  are  waves  of  constriction  running  back- 
ward toward  the  caecum."  The  resistance  of  the  valve  or  sphincter  enables  reversed  peristalsis 
or  antiperistalsis  to  mix  the  food.  When  more  food  enters  from  the  small  intestine,  antiperistalsis 
ceases,  tonic  contraction  of  the  caecum  and  proximal  portion  of  the  colon  occurs,  some  of  the  food 
is  merged  into  the  transverse  colon,  and  antiperistalsis  again  begins  to  act  on  what  remains.  The 
above  facts  have  been  observed  in  animals  and  are  probably  true  in  man. 

Innervation. — The  vagus  fibres  of  the  small  intestine  seem  to  excite  contraction  of  the  cir- 
cular fibres  after  a  brief  preliminary  period  of  inhibition.3  Some  observers  maintain  that  the 

1  Diseases  of  the  Anus,  Rectum  and  Pelvic  Colon.     By  James  P.  Tuttle. 

*  Medical  News,  May  20,  1905.  3  Bayliss  and  Starling,  Journal  cf  Physiology,  1899. 


SURGICAL  ANATOMY  OF  THE  INTESTINES  1331 

splanchnic  fibres  are  inhibitory,  but  others  claim  that  they  are  also  motor.  The  local  reflex  of  the 
small  intestine  is  in  Auerbach's  plexus.  Cannon  quotes  Bayliss  and  Starling  to  the  effect  that  the 
pelvic  visceral  nerves  to  the  large  intestine,  "arising  like  the  vagus  from  the  central  nerve 
system,  are  augmentary  nerves,  whereas  the  supply  from  the  sympathetic  system  is  purely 
inhibitory  in  its  action."  It  is  further  contended  that  the  pelvic  visceral  nerves  are  distributed 
to  the  distal  colon  only.  "The  region  of  antiperistalsis  does  not,  therefore,  receive  motor 
impulses  from  the  pelvic  nerves." 

Surface  Form. — The  coils  of  the  small  intestine  occupy  the  front  of  the  abdomen  below  the 
transverse  colon,  and  are  covered  more  or  less  completely  by  the  great  omentum.  For  the  most 
part  the  coils  of  the  jejunum  occupy  the  left  side  of  the  abdominal  cavity — i.  e.,  the  left  lumbar 
and  inguinal  regions  and  the  left  half  of  the  umbilical  region — whilst  the  coils  of  the  ileum  are 
situated  to  the  right,  in  the  right  lumbar  and  inguinal  regions,  in  the  right  half  of  the  umbilical 
region,  and  also  in  the  hypogastric  region.  The  caecum  is  situated  in  the  right  inguinal  region. 
Its  position  varies  slightly,  but  the  mid-point  of  a  line  drawn  from  the  anterior  superior  spinous 
process  of  the  ilium  to  the  symphysis  pubis  will  about  mark  the  middle  of  its  lower  border.  It  is 
comparatively  superficial.  From  it  the  ascending  colon  passes  upward  through  the  right  lumbar 
and  hypochondriac  regions,  and  becomes  more  deeply  situated  as  it  ascends  to  the  hepatic  flexure, 
which  is  deeply  placed  under  cover  of  the  liver.  The  transverse  colon  crosses  the  belly  trans- 
versely on  the  confines  of  the  umbilical  and  epigastric  regions,  its  lower  border  being  on  a  level 
slightly  above  the  umbilicus,  its  upper  border  just  below  the  greater  curvature  of  the  stomach. 
The  splenic  flexure  of  the  colon  is  situated  behind  the  stomach  in  the  left  hypochondrium,  and 
is  on  a  higher  level  than  the  hepatic  flexure.  The  descending  colon  is  deeply  seated,  passing 
down  through  the  left  hypochondriac  and  lumbar  regions  to  the  sigmoid  flexure,  which  is  situ- 
ated in  the  left  inguinal  region,  and  which  can  be  felt  in  thin  persons,  with  relaxed  abdominal 
walls,  rolling  under  the  fingers  when  empty,  and  when  distended  forming  a  distinct  bulge.  The 
usual  position  of  the  base  of  the  vermiform  appendix  is  indicated  by  a  point  on  the  cutaneous 
surface  two  inches  from  the  anterior  superior  spinous  process  of  the  ilium,  on  a  line  drawn  from 
this  process  to  the  umbilicus.  This  is  known  as  McBurney's  point.  Another  mode  of  defining  the 
position  of  the  base  of  the  appendix  is  to  draw  a  line  between  the  anterior  superior  spines  of  the 
ilia  and  marking  the  point  where  this  line  intersects  the  right  semilunar  line. 

Upon  introducing  the  finger  into  the  rectum,  the  membranous  portion  of  the  urethra  can 
be  felt,  if  an  instrument  has  been  introduced  into  the  bladder,  exactly  in  the  middle  line;  behind 
this  the  prostate  gland  can  be  recognized  by  its  shape  and  hardness  and  any  enlargement  detected; 
behind  the  prostate  the  fluctuating  wall  of  the  bladder  when  full  can  be  felt,  and  if  thought 
desirable  it  can  be  tapped  in  this  situation;  on  either  side  and  behind  the  prostate  the  vesiculae 
seminales  can  be  readily  felt,  especially  if  enlarged  by  tuberculous  disease.  Behind,  the  coccyx 
is  to  be  felt,  and  on  the  mucous  membrane  one  or  two  of  Houston's  folds.  The  ischio-rectal 
fossae  can  be  explored  on  either  side,  with  a  view  to  ascertaining  the  presence  of  deep-seated 
collections  of  pus.  Finally,  it  will  be  noted  that  the  finger  is  firmly  gripped  by  the  sphincter  for 
about  an  inch  up  the  bowel.  By  gradual  dilatation  of  the  sphincter,  the  whole  hand  can  be 
introduced  into  the  rectum  so  as  to  reach  the  descending  colon.  This  method  of  exploration  is 
not  at  the  present  day  employed  for  diagnostic  purposes. 

Surgical  Anatomy. — The  small  intestine  is  much  exposed  to  injury,  but,  in  consequence 
of  its  elasticity  and  the  ease  with  which  one  fold  glides  over  another,  it  is  not  so  frequently  rup- 
tured as  would  otherwise  be  the  case.  Any  part  of  the  small  intestine  may  be  ruptured,  bur 
probably  the  most  common  situation  is  the  transverse  duodenum,  on  account  of  its  being  more 
fixed  than  other  portions  of  the  bowel,  and  because  it  is  situated  in  front  of  the  bodies  of  the 
vertebrae,  so  that  if  this  portion  of  the  intestine  is  struck  a  sharp  blow,  as  from  the  kick  of  a 
horse,  it  is  unable  to  glide  out  of  the  way,  but  is  compressed  against  the  bone  and  lacerated. 
Wounds  of  the  intestine  sometimes  occur.  If  the  wound  is  a  small  puncture,  under,  it  is  said, 
three  lines  in  length,  there  may  be  no  extravasation  of  the  contents  of  the  bowel.  The  mucous 
membrane  becomes  everted  and  perhaps  plugs  the  little  opening.  The  bowels,  therefore,  may  be 
punctured  with  a  fine  capillary  trocar,  in  cases  of  excessive  distention  of  the  intestine  with  gas,  with- 
out much  danger  of  extravasation.  A  longitudinal  wound  gapes  more  than  a  transverse  wound, 
owing  to  the  greater  thickness  of  the  circular  muscular  coat.  In  closing  a  wound  of  the  intestine, 
use  Lembert's  inversion  sutures,  which  bring  the  peritoneal  surfaces  in  contact.  Halsted  showed 
us  that  these  sutures  must  include  the  tough  submucous  coat.  The  portions  of  intestine  which  lie 
in  the  pelvis  are  inflamed  in  pelvic  peritonitis  and  become  embedded  in  adhesions.  The  portions 
of  intestine  \vhich  may  be  present  are  the  termination  of  the  ileum,  the  portion  of  small  intestine 
with  the  largest  mesentery  (Treves),  the  rectum,  and  the  pelvic  colon.  The  small  intestine, .and 
most  frequently  the  ileum,  may  become  strangulated  by  internal  bands,  or  through  apertures, 
normal  or  abnormal.  The  bands  may  be  formed  in  several  different  ways:  they  may  be  old  peri- 
toneal adhesions  from  previous  attacks  of  peritonitis;  or  adherent  omentum  from  the  same 
cause;  or  the  band  may  be  formed  by  Meckel's  diverticulum,  which  has  contracted  adhesions  at 
its  distal  extremity;  or  the  band  may  be  the  result  of  the  abnormal  attachment  of  some  normal 
structure,  as  the  adhesion  of  two  appendices  epiploicae,  or  an  adherent  vermiform  appendix  or 


1332  THE  ORGANS  OF  DIGESTION 

Fallopian  tube.  Intussusception  or  invagination  of  the  small  intestine  may  take  place  in  any  part 
of  the  jejunum  ajid  ileum,  "but  the  most  frequent  situation  is  at  the  ileo-caecal  valve,  the  valve 
forming  the  apex  of  the  entering  tube.  This  form  may  attain  great  size,  and  it  is  not  uncom- 
mon in  these  cases  to  find  the  valve  projecting  from  the  anus.  Stricture,  the  impaction  of 
foreign  bodies,  and  twisting  of  the  gut  (volvulus)  may  lead  to  intestinal  obstruction.  Volvulus  is 
most  common  in  the  sigmoid  flexure.  MeckeFs  diverticulum  may  itself  become  twisted  and 
strangulated. 

Resection  of  a  portion  of  the  intestine  may  be  required  in  cases  of  gangrenous  gut;  in  cases 
of  intussusception;  for  the  removal  of  new  growth  in  the  bowel;  in  dealing  with  artificial  anus; 
and  in  cases  of  rupture.  The  operation  is  termed  enterectomy,  and  is  performed  as  follows:  the 
abdomen  having  been  opened  and  the  amount  of  bowel  requiring  removal  having  been  deter- 
mined upon,  the  gut  must  be  clamped  on  either  side  of  this  portion  in  order  to  prevent  the  escape 
of  any  of  the  contents  of  the  bowel  during  the  operation.  The  portion  of  bowel  is  then  separated 
above  and  below  by  means  of  scissors.  If  the  portion  removed  is  small,  it  may  be  simply  removed 
from  the  mesentery  at  its  attachment  and  the  bleeding  vessels  tied;  but  if  it  is  large,  it  will  be 
necessary  to  remove  also  a  triangular  piece  of  the  mesentery,  and  having  secured  the  vessels, 
suture  the  cut  edges  of  this  structure  together.  The  surgeon  then  proceeds  to  unite  the  cut 
ends  of  the  bowel  together.  He  may  do  it  by  the  operation  termed  end-to-end  anastomosis. 
There  are  many  ways  of  doing  this,  which  may  be  divided  into  two  classes:  one,  where  the  anas- 
tomosis is  made  by  means  of  some  mechanical  appliance,  such  as  Murphy's  button,  or  one  of 
the  forms  of  decalcified  bone  bobbins;  and  the  other,  where  the  operation  is  performed  by 
simply  suturing  the  ends  of  the  bowel  in  such  a  manner  that  the  peritoneum  covering  the  free 
divided  ends  of  the  bowel  is  brought  into  contact,  so  that  speedy  union  may  ensue. 

In  some  cases  after  resection  each  open  end  of  the  gut  is  closed,  the  side  of  the  terminal  portion 
is  sutured  to  the  side  of  the  initial  portion,  a  fistula  is  made  in  each,  and  the  suturing  is  com- 
pleted so  as  to  cause  the  two  fistulae  to  correspond.  A  permanent  side-to-side  opening  is 
thus  made.  Lateral  anastomosis  without  resection  may  be  practised  between  two  pieces  of 
intestine,  in  order  to  side-track  an  intervening,  portion,  which  is  the  seat  of  malignant  disease  or 
of  an  artificial  anus.  Complete  exclusion  of  a  portion  of  intestine  is  performed  for  irremovable 
tumors  or  persistent  faecal  fistulae  of  the  large  intestine.  The  intestine  is  cut  through  above  and 
below  the  diseased  area  and  the  ends  of  the  healthy  gut  are  united  to  each  other,  or  the  larger 
end  is  closed,  an  opening  is  made  into  the  side  of  the  larger  end  and  the  smaller  end  is  implanted 
in  it  (lateral  implantation).  The  two  ends  of  the  excluded  portion  are  fastened  to  the  skin  and 
are  left  open. 

In  ascites  resulting  from  cirrhosis  of  the  liver  benefit  occasionally  follows  the  performance  of 
Talma's  operation  (epiplopexy) .  The  abdomen  is  opened  and  the  omentum  is  sutured  to  the 
anterior  abdominal  wall  or  in  the  abdominal  wound  in  the  hope  of  establishing  a  more  free 
communication  between  the  portal  and  systemic  circulations,  thus  lowering  portal  pressure. 

External  hernia  is  considered  on  page  1333. 

By  the  term  internal  hernia,  we  mean  hernia  into  the  foramen  of  Winslow,  into  the  retro- 
duodenal  fossa,  into  the  retro-caecal  fossa,  6r  into  the  intersigmoid  fossa.  Such  a  hernia  produces 
the  symptoms  of  acute  strangulation  of  the  intestine. 

In  typhoid  fever  there  is  ulceration  of  Peyer's  patches.  One  of  these  ulcers  may  perforate. 
The  only  chance  for  life  is  immediate  laparotomy  and  closure  of  the  perforation.  This  saves 
one-fifth,  or  possibly  one-third,  of  the  cases.  The  incision  is  made  to  expose  the  lower  ileum,  as 
in  the  vast  majority  of  cases  the  perforation  is  in  this  portion  of  the  gut. 

Ulcer  of  the  duodenum  is  more  common  than  used  to  be  thought.  The  portion  of  the  duo- 
denum between  the  pylorus  and  the  bile  papilla  is  about  four  inches  in  length,  and  is  called  by 
the  Mayo  brothers  the  vestibule  of  the  duodenum.  Here  the  acid  gastric  juice  enters  and  may  pro- 
duce an  ulcer.  The  portion  of  the  duodenum  below  the  vestibule  is  not  liable  to  ulcer,  because 
it  is  protected  by  the  alkaline  bile  and  pancreatic  juice. 

A  duodenal  ulcer  may  perforate  a  large  duodenal  vessel  and  cause  death  from  hemorrhage, 
or  may  perforate  the  intestine  and  produce  septic  peritonitis.  A  perforated  ulcer  is  treated 
by  laparotomy  and  closure  of  the  perforation.  Occasionally  ulceration  of  the  duodenal  glands 
(Curling's  ulcer)  may  occur  in  cases  of  burns,  but  is  not  a  very  common  complication. 

The  vermiform  appendix  is  very  liable  to  become  inflamed,  the  condition  being  known  as 
appendicitis.  This  condition  may  be  set  up  by  a  catarrhal  inflammation  arising  in  the  appen- 
dix or  derived  from  the  colon.  It  may  remain  catarrhal  and  then  subside.  It  may  become 
purulent  or  may  be  purulent  from  the  beginning.  Anything  which  lessens  vital  resistance 
makes  the  appendix  a  ready  prey  to  bacteria.  Among  causes  which  lessen  resistance  are  fsecal 
concretions,  twists  of  the  mesoappendix  cutting  off  the  blood-supply,  bruises  inflicted  by  the  Psoas 
muscle  (Byron  Robinson),  blocking  of  the  outlet  of  the  appendix  by  catarrhal  exudate,  concre- 
tions, proliferated  lymphoid  tissue,  or  adhesions.  Appendicitis  may  arise  by  the  appendix  becom- 
ing twisted,  owing  to  the  shortness  of  its  mesentery,  in  consequence  of  distention  of  the  caecum. 
As  the  result  of  inflammation,  its  blood-supply,  which  is  mainly  through  one  large  artery  running 
in  the  mesoappendix,  becomes  interfered  with.  Again,  in  rarer  cases,  the  inflammation  is  set 
up  by  the  impaction  of  a  solid  mass  of  faeces  or  a  foreign  body  in  the  appendix.  The  inflammation 


SURGICAL  ANATOMY  OF  THE  INTESTINES  1333 

may  result  in  ulceration  and  perforation,  or  in  gangrene  of  the  appendix  the  appendix  may  be 
blocked  and  full  of  pus,  or  abscess  may  form  outside  of  it  (appendwular  abscess).  These  con- 
ditions require  prompt  operative  interference,  and  in  cases  of  recurrent  attacks  of  appendicitis  it 
is  advisable  to  remove  this  diverticulum  between  the  attacks.  In  external  hernia  the  ileum 
is  the  portion  of  bowel  most  frequently  herniated.  When  a  part  of  the  large  intestine  is 
involved,  it  is  usually  the  caecum,  and  this  may  occur  even  on  the  left  side.  In  some  few  cases 
the  vermiform  appendix  has  been  the  part  implicated  in  cases  of  strangulated  hernia,  and  has 
given  rise  to  serious  symptoms  of  obstruction.  The  diameter  of  the  large  intestine  gradually 
diminishes  from  the  caecum,  which  has  the  greatest  diameter  of  any  part  of  the  bowel,  to  the 
point  of  junction  of  the  sigmoid  flexure  with  the  rectum,  at  or  a  little  below  which  point  stricture 
most  commonly  occurs  and  diminishes  in  frequency  as  one  proceeds  upward  to  the  caecum. 
When  distended  by  some  obstruction  low  down,  the  outline  of  the  large  intestine  can  be  defined 
throughout  nearly  the  whole  of  its  course — all,  in  fact,  except  the  hepatic  and  splenic  flexures, 
which  are  more  deeply  placed;  the  distention  is  most  obvious  in  the  two  flanks  and  on  the  front 
of  the  abdomen  just  above  the  umbilicus.  The  caecum,  however,  is  that  portion  of  the  bowel 
which  is,  of  all,  most  distended.  It  sometimes  assumes  enormous  dimensions,  and  has  been 
known  to  give  way  from  the  distention,  causing  fatal  peritonitis.  The  hepatic  flexure  and  the  right 
extremity  of  the  transverse  colon  are  in  close  relationship  with  the  liver,  and  abscess  of  this  viscus 
sometimes  bursts  into  the  gut  in  this  situation.  The  gall-bladder  may  become  adherent  to  the 
colon,  and  gall-stones  may  find  their  way  through  into  the  gut,  where  they  may  become  impacted 
or  may  be  discharged  per  anum.  The  mobility  of  the  sigmoid  flexure  renders  it  more  liable  to 
become  the  seat  of  a  volvulus  or  twist  than  any  other  part  of  the  intestine.  It  generally  occurs 
in  patients  who  have  been  the  subjects  of  habitual  constipation,  and  in  whom,  therefore,  the 
mesosigmoid  is  elongated.  The  gut  at  this  part  being  loaded  with  faeces,  from  its  weight  falls 
over  the  gut  below,  and  so  gives  rise  to  the  twist. 

The  surgical  anatomy  of  the  rectum  is  of  considerable  importance.  There  may  be  congenital 
malformation  due  to  arrest  or  imperfect  development.  Thus,  there  may  be  no  invagination  of 
the  epiblast,  and  consequently  a  complete  absence  of  the  anus;  or  the  hind-gut  may  be  imper- 
fectly developed,  and  there  may  be  an  absence  of  the  rectum,  though  the  anus  is  developed; 
or  the  invagination  of  the  epiblast  may  not  communicate  with  the  termination  of  the  hind-gut 
from  want  of  solution  of  continuity  in  the  septum  which  in  early  foetal  life  exists  between  the 
two.  The  mucous  membrane  is  thick  and  but  loosely  connected  to  the  muscular  coat  beneath 
and  thus  favors  prolapse,  especially  in  children  The  vessels  of  the  rectum  are  arranged  as 
mentioned  above,  longitudinally,  and  are  contained  in  the  loose  cellular  tissue  between  the 
mucous  and  muscular  coats,  and  receive  no  support  from  surrounding  tissues,  and  this  favors 
varicosity.  Moreover,  the  veins,  after  running  upward  in  a  longitudinal  direction  for  about  five 
inches  in  the  submucous  tissue,  pierce  the  muscular  coats,  and  are  liable  to  become  constricted 
at  this  point  by  the  contraction  of  the  muscular  wall  of  the  gut.  In  addition  to  this  there  are  no 
valves  in  the  superior  hemorrhoidal  veins,  and  the  vessels  of  the  rectum  are  placed  in  a  depen- 
dent position,  and  are  liable  to  be  pressed  upon  and  obstructed  by  hardened  faeces.  The  anatom- 
ical arrangement,  therefore,  of  the  hemorrhoidal  vessels  explains  the  great  tendency  to  the 
occurrence  of  piles.  The  presence  of  the  Sphincter  ani  is  of  surgical  importance,  since  it  is  the 
constant  contraction  of  this  muscle  which  prevents  an  ischio-rectal  abscess  from  healing  and 
tends  to  cause  a  fistula.  Also,  the  reflex  contraction  of  this  muscle  is  the  cause  of  the  severe  pain 
complained  of  in  fissure  of  the  anus.  The  relations  of  the  peritoneum  to  the  rectum  are  of 
importance  in  connection  with  the  operation  of  removal  of  the  lower  end  of  the  rectum  for 
malignant  disease.  The  membrane  gradually  leaves  the  rectum  as  it  descends  into  the  pelvis; 
first  leaving  its  posterior  surface,  then  the  sides,  and  then  the  anterior  surface  to  become 
reflected  in  the  male  on  to  the  posterior  wall  of  the  bladder,  forming  the  recto-vesical  pouch,  and 
in  the  female  on  to  the  posterior  wall  of  the  vagina,  forming  Douglas's  pouch.  The  recto-vesical 
pouch  of  peritoneum  extends  to  within  three  inches  from  the  anus,  so  that  it  is  not  desirable 
to  remove  more  than  two  and  a  half  inches  of  the  entire  circumference  of  the  bowel,  for  fear 
of  the  risk  of  opening  the  peritoneum.  When,  however,  the  disease  is  confined  to  the  poste- 
rior surface  of  the  rectum,  or  extends  farther  in  this  direction,  a  greater  amount  of  the  poste- 
rior wall  of  the  gut  may  be  removed,  as  the  peritoneum  does  not  extend  on  this  surface  to  a 
lower  level  than  five  inches  from  the  margin  of  the  anus.  The  recto-vaginal  or  Douglas's  pouch 
in  the  female  extends  somewhat  lower  than  the  recto-vesical  pouch  of  the  male,  and  therefore 
it  is  advisable  to  remove  a  less  length  of  the  tube  in  this  sex.  Of  recent  years,  however,  much 
more  extensive  operations  have  been  done  for  the  removal  of  cancer  of  the  rectum,  and  in  these 
the  peritoneal  cavity  has  necessarily  been  opened.  If,  in  these  cases,  the  opening  is  plugged 
with  iodoform  gauze  until  the  operation  is  completed  and  then  the  edges  of  the  wound  in  the 
peritoneum  is  accurately  brought  together  with  sutures,  no  evil  result  appears  to  follow.  For 
cases  of  cancer  of  the  rectum  which  are  too  low  to  be  reached  by  abdominal  section,  and  too 
high  to  be  removed  by  the  ordinary  operation  from  below,  Kraske  has  devised  an  operation 
which  goes  by  his  name.  The  patient  is  placed  on  his  right  side  and  an  incision  is  made  from 
the  second  sacral  spine  to  the  anus.  The  soft  parts  are  now  separated  from  the  back  of  the 
left  side  of  the  sacrum  as  far  as  its  left  margin,  and  the  greater  and  lesser  sacro-sciatic  liga- 


1334 


THE  ORGANS  OF  DIGESTION 


ments  are  divided.  A  portion  of  the  lateral  mass  of  the  sacrum,  commencing  on  the  left  border 
at  the  level  of  the  third  posterior  sacral  foramen,  and  running  downward  and  inward  through 
the  fourth  foramen  to  the  cornu,  is  now  cut  away  with  a  chisel.  The  left  side  of  the  wound 
being  now  forcibly  drawn  outward,  the  whole  of  the  rectum  is  brought  into  view,  and  the  dis- 
eased portion  can  be  removed,  leaving  the  anal  portions  of  the  gut,  if  healthy.  The  two  divided 
ends  of  the  gut  can  perhaps  then  be  approximated  and  sutured  together.  Kraske's  operation  is 
in  many  cases  preceded  by  the  performance  of  iliac  colostomy.  In  cancer  high  up  in  the 
rectum  removal  of  the  growth  through  the  abdomen  is  sometimes  practised,  the  divided  lower 
end  of  the  rectum  being  sutured  to  the  divided  upper  end  (Weir's  operation). 

The  colon  frequently  requires  opening  in  cases  of  intestinal  obstruction,  and  by  some  sur- 
geons this  operation  is  performed  in  cases  of  cancer  of  the  rectum,  as  soon  as  the  disease  is 
recognized,  in  the  hope  that  the  rate  of  growth  may  be  retarded  by  removing  the  irritation  pro- 
duced by  the  passage  of  fecal  matter  over  the  diseased  surface.  The  operation  of  colostomy  may 
be  performed  either  in  the  inguinal  or  lumbar  region;  but  inguinal  colostomy  (Maydl's  opera- 
tion) has  at  the  present  day  superseded  the  lumbar  operation.  The  main  reason  for  preferring 
this  operation  is  that  a  spur-shaped  process  can  be  formed  which  prevents  any  fecal  matter  find- 
ing its  way  past  the  artificial  anus  and  becoming  lodged  on  the  diseased  structures  below.  The 
sigmoid  flexure  being  surrounded  by  peritoneum,  a  coil  can  be  drawn  out  of  the  wound,  and 
when  it  is  opened  transversely  a  spur  is  formed,  and  this  pre vents  any  fecal  matter  finding  its 
way  from  the  gut  above  the  opening  into  that  below.  The  operation  is  performed  by  making  an 
incision  two  or  three  inches  -in  length  from  a  point  one  inch  internal  to  the  anterior  superior 
spinous  process  of  the  ilium,  parallel  to  Poupart's  ligament.  The  various  layers  of  abdominal 
muscles  are  cut  through,  and  the  peritoneum  opened  and  sewed  to  the  external  skin.  The  sigmoid 
flexure  is  now  sought  for,  and  pulled  out  of  the  wound  and  fixed  by  pushing  a  glass  bar  through 
a  slit  in  the  mesocolon.  The  two  parts  of  the  loop  are  sutured  together.  The  intestine  is  now 
sutured  to  the  parietal  peritoneum.  The  wound  is  dressed,  and  either  immediately  or  between 
the  second  to  the  fourth  day,  according  to  the  requirements  of  the  case,  the  protruded  coil  of 
intestine  is  opened.  It  is  opened  transversely  with  the  Paquelin  cautery. 


THE  LIVER  (HEPAR)  (Figs.  949,  950,  951,  952). 

The  liver  is  the  largest  gland  in  the  body,  and  is  situated  in  the  upper  and 
right  part  of  the  abdominal  cavity,  occupying  almost  the  whole  of  the  right  hypo- 
chondrium,  the  greater  part  of  the  epigastrium,  and  extending  into  the  left  hypo- 
chondrium  as  far  as  the  mammary  line.  In  the  male  it  weighs  from  fifty  to  sixty 

Gall-bladder.  . 


RIGHT   LATERAL 
LIGAMENT. 


LEFT    LATERAL 
LIGAMENT. 


FIG.  949. — The  liver.      Upper  surface.     (Drawn  from  His'  method.) 


ounces;  in  the  female,  from  forty  to  fifty.  It  is  relatively  much  larger  in  the  foetus 
than  in  the  adult,  constituting,  in  the  former,  about  one-eighteenth,  and  in  the 
latter,  about  one-thirty-sixth  of  the  entire  body-weight.  Its  greatest  transverse 


THE  LIVER 


1335 


measurement  is  from  eight  to  nine  inches.     Vertically,  near  its  lateral  or  right 
surface,  it  measures  about  six  or  seven  inches,  while  its  greatest  antero-posterior 


Great  splanchnic 

nerve  piercing 

crus. 


Receptaculum 
chyli. 


Semilunar 
ganglion. 


nerve  piercing 
crus. 

Semilunar 
ganglion. 


FIG.  950. — The  relations  of  the  viscera  and  large  vessels  of  the  abdomen.     (Seen  from  behind, 
the  last  thoracic  vertebra  being  well  raised.) 

diameter  is  on  a  level  with  the  upper  end  of  the  right  kidney  and  is  from  four  to 
five  inches.  Opposite  the  vertebral  column  its  measurement  from  before  backward 
is  reduced  to  about  three  inches.  Its  consistence  is  that  of  a  soft  solid ;  it  is, 


1336  THE  ORGANS  OF  DIGESTION 

however,  friable  and  easily  lacerated;  its  color  is  a  dark  reddish7brown,  and  its 
specih'c  gravity  is  1.05. 

To  obtain  a  correct  idea  of  its  shape,  it  must  be  hardened  in  situ,  and  it  will 
then  be  seen  to  present  the  appearance  of  a  wedge,  the  base  of  which  is  directed 
to  the  right  and  the  thin  edge  toward  the  left.  Symington  describes  its  shape  as 
that  "of  a  right-angled  triangular  prism  with  the  right  angles  founded  off."  It 
possesses  five  surfaces,  viz.,  a  superior,  inferior,  anterior,  posterior,  and  a  right  lateral 
surface. 

The  superior  and  anterior  surfaces  are  separated  from  each  other  by  a  thick 
rounded  border,  and  are  attached  to  the  Diaphragm  and  anterior  abdominal  wall 
by  a  triangular  or  falciform  fold  of  peritoneum,  the  suspensory  or  falciform  liga- 
ment, which  divides  the  liver  into  two  unequal  parts,  termed  the  right  and  left 
lobes  (Figs.  949,  953,  and  954).  Except  along  the  line  of  attachment  of  this  liga- 
ment to  the  liver,  the  superior  and  anterior  surfaces  are  covered  by  peritoneum. 

The  Superior  Area  or  Surface  (fades  superior]  (Fig.  949). — The  superior 
area  or  surface  comprises  a  part  of  both  lobes.  Spalteholz  considers  as  parts  of 
the  superior  surface  the  right  surface  and  the  anterior  surface.  The  superior  sur- 
face is  convex,  and  fits  under  the  vault  of  the  Diaphragm ;  its  central  part,  however, 
presents  a  shallow  depression,  the  cardiac  depression  (impressio  cardiaca),  which 
corresponds  with  the  position  of  the  heart  on  the  upper  surface  of  the  Diaphragm. 
It  is  separated  from  the  anterior,  posterior,  and  lateral  surfaces  by  thick,  rounded 
borders.  Its  left  extremity  is  continued  into  the  under  surface  by  a  prominent 
sharp  margin. 

The  Anterior  Area  or  Surface. — The  anterior  area  or  surface  is  large  and 
triangular  in  shape,  comprising  also  a  part  of  both  lobes.  It  is  directed  forward, 
and  the  greater  part  of  it  is  in  contact  with  the  Diaphragm,  which  separates  it 
from  the  right  lower  ribs  and  their  cartilages.  In  the  middle  line  it  lies  behind 
the  ensiform  cartilage,  to  the  left  of  which  it  is  protected  by  the  seventh  and 
eighth  left  costal  cartilages.  In  the  angle  between  the  diverging  rib  cartilages 
of  opposite  sides  the  anterior  surface  is  in  contact  writh  the  abdominal  wall.  It 
is  continuous  with  the  inferior  surface  by  a  sharp  margin,  and  with  the  superior 
and  lateral  surfaces  by  thick  rounded  borders. 

The  Lateral  Right  Area  or  Surface  (Figs.  949  and  951). — The  lateral  or  right 
area  or  surface  is  convex  from  before  backward  and  slightly  so  from  above  down- 
ward. It  is  directed  toward  the  right  side,  forming  the  base  of  the  wedge,  and 
lies  against  the  lateral  portion  of  the  Diaphragm,  which  separates  it  from  the 
lower  part  of  the  left  pleura  and  lung,  outside  which  are  the  right  costal  arches 
from  the  seventh  to  the  eleventh  inclusive. 

The  Under  or  Visceral  Area  or  Surface  (fades  inferior)  (Figs.  951  and  952).— 
The  under  or  visceral  area  or  surface  is  uneven,  concave,  directed  downward  and 
backward  and  to  the  left,  and  is  in  relation  with  the  stomach  and  duodenum,  the 
hepatic  flexure  of  the  colon,  and  the  right  kidney.  The  surface  is  divided  by  a 
longitudinal  fissure  into  a  right  and  a  left  lobe,  and  is  almost  completely  invested 
by  peritoneum;  the  only  parts  where  this  covering  is  absent  are  where  the  gall- 
bladder is  attached  to  the  liver  and  at  the  transverse  fissure,  where  the  two  layers 
of  the  lesser  omentum  are  separated  from  each  other  by  the  blood-vessels  and 
duct  of  the  viscus.  The  under  surface  of  the  left  lobe  presents  to  the  right  and 
near  the  centre  a  rounded  eminence,  the  omental  tuberosity  (tuber  omentale]  (Fig. 
951),  which  is  in  contact  with  the  lesser  omentum.  It  is  surrounded  by  a  broad 
depression,  the  gastric  surface  or  impression  (impressio  gastrica),  with  which  the 
stomach  is  in  contact.  Between  the  gall-bladder  and  the  left  lobe  is  the  quad- 
rate lobe.  The  quadrate  lobe  is  bounded  to  the  left  by  the  umbilical  fissure  or  the 
fissure  of  the  umbilical  vein  (fossa  venae  umbilicalis],  which  is  the  anterior  portion 
of  the  longitudinal  fissure  and  lodges  the  round  ligament.  The  under  surface  of 
the  right  lobe  is  divided  into  two  unequal  portions  by  a  fossa,  which  lodges  the 


THE  LIVER  1337 

gall-bladder  and  is  called  the  fossa  vesicalis  (fossa- vesicae  felleae);  the  portion  to 
the  left,  the  smaller  of  the  two,  is  somewhat  oblong  in  shape,  its  antero-posterior 
diameter  being  greater  than  its  transverse.  It  is  known  as  the  quadrate  lobe, 
and  is  in  relation  with  the  pyloric  end  of  the  stomach  (impressio  pyloricd)  and  the 
first  portion  of  the  duodenum.  The  portion  of  the  under  surface  of  the  right 
lobe  to  the  right  of  the  fossa  vesicalis  presents  two  shallow  concave  impressions, 
one  situated  behind  the  other,  the  two  being  separated  by  a  ridge.  The  anterior 
of  these  two  impressions,  the  colic  impression  (impressio  colica) ,  is  produced  by  the 
hepatic  flexure  of  the  colon;  the  posterior,  the  renal  impression  (impressio  renalis}, 
is  occupied  by  the  upper  end  of  the  right  kidney  (Fig.  951).  To  the  inner  side  of 
the  latter  impression  is  a  third  and  slightly  marked  impression,  lying  between  it 
and  the  neck  of  the  gall-bladder.  This  is  caused  by  the  second  portion  of  the 
duodenum,  and  is  known  as  the  duodenal  impression  (impressio  duodenalis).  Just 
in  front  of  the  postcava  is  a  narrow  strip  of  liver  tissue,  the  caudate  lobe,  which 
connects  the  right  inferior  angle  of  the  Spigelian  lobe  to  the  under  surface  of  the 
right  lobe.  Immediately  below  it  is  the  foramen  of  Winslow. 

The  Posterior  Area  'or  Surface  (fades  posterior]  (Figs.  950  and  952).— The 
posterior  area  or  surface  is  rounded  and  broad  behind  the  right  lobe,  but  narrow 
on  the  left.  Over  a  large  part  of  its  extent  it  is  not  covered  by  peritoneum;  this 
uncovered  area  (Fig.  951)  is  about  three  inches  broad,  and  is  in  direct  contact  with 
the  Diaphragm,  being  united  to  it  by  areolar  tissue.  In  this  tissue  are  numerous 
small  veins  which  join  the  portal  circulation  to  the  systemic  circulation.  The 
uncovered  area  is  marked  oft'  from  the  upper  surface  by  the  line  of  reflection  of 
the  upper  or  anterior  layer  of  the  coronary  ligament.  It  is  in  the  same  way 
marked  oft'  from  the  under  surface  of  the  liver  by  the  line  of  reflection  of  the  lowrer 
layer  of  the  coronary  ligament  (Fig.  953).  In  its  centre  the  posterior  surface  is  deeply 
notched  for  the  vertebral  column  and  crura  of  the  Diaphragm,  and  to  the  right 
of  this  it  is  indented  for  the  postcava,  which  is  often  partly  embedded  in  its  sub- 
stance. Close  to  the  right  of  this  indentation  and  immediately  above  the  renal 
impression  is  a  small  triangular  depressed  area,  the  suprarenal  impression  (impressio 
suprarenalis)  (Fig.  951),  the  greater  part  of  which  is  devoid  of  peritoneum;  it 
lodges  the  right  suprarenal  capsule,  which  is  inserted  between  the  liver  and  Dia- 
phragm. To  the  left  of  the  fossa  for  the  postcava  is  the  Spigelian  lobe,  which  lies 
between  the  fissure  for  the  postcava  and  the  fissure  for  the  ductus  venosus.  Below 
and  in  front  it  projects  and  forms  part  of  the  posterior  boundary  of  the  transverse 
fissure.  Here,  to  the  right,  it  is  connected  with  the  under  surface  of  the  right  lobe 
of  the  liver  by  the  caudate  lobe,  and  to  the  left  it  presents  a  tubercle,  the  tuber- 
culum  papillare  (Fig.  951).  It  is  opposite  the  tenth  and  eleventh  thoracic  vertebrae, 
and  rests  upon  the  aorta  and  crura  of  the  Diaphragm,  being  covered  by  the  peri- 
toneum of  the  lesser  sac.  The  lobe  is  nearly  vertical  in  position,  and  is  directed 
backward;  it  is  longer  from  above  downward  than  from  side  to  side,  and  is  some- 
what concave  in  the  transverse  direction.  On  the  posterior  surface  to  the  left 
of  the  Spigelian  lobe  is  a  groove,  the  oesophageal  groove  (impressio  oesophagea), 
indicating  the  position  of  the  abdominal  portion  of  the  oesophagus  (Fig.  951). 

Prof.  Cunningham  divides  the  liver  into  two  surfaces,  a  visceral  and  a  parietal, 
and  subdivides  the  parietal  surface  into  a  posterior  area  and  superior  area,  an  ante- 
rior area  and  a  right  area.  The  parietal  surface  is  separated  from  the  visceral 
surface  by  the  inferior  border  or  margin. 

The  inferior  border  or  margin  (margo  inferioris),  posteriorly,  is  rather  ill  defined. 
It  is  the  lower  margin  of  the  posterior  surface;  it  follows  the  line  of  rib  and  is  in 
contact  with  the  right  kidney.  At  the  right  side  the  lower  margin  is  thick  and 
distinct,  and,  as  a  rule,  projects  slightly  below  the  thorax.  The  front  of  the 
inferior  margin  is  called  the  anterior  margin  (margo  anterior}.  It  is  a  sharp  edge 
which,  on  inspiration,  corresponds  to  an  oblique  line  on  the  abdominal  wall 


1338 


THE  ORGANS  OF  DIGESTION 


drawn  from  "a  point  half  an  inch  below  the  margin  of  the  ribs  (tip  of  tenth 
costal  cartilage),  on  the  right  side,  to  a  point  an  inch  below  the  nipple  on  the 
left,  and  extending  down  in  the  middle  line  to  a  point  half-way  between  the 
gladiolus  and  the  umbilicus."1 

In  men  the  anterior  margin  of  the  liver  often  corresponds  to  the  lower  margin 
of  the  ribs,  but  in  women  and  children  it  is  usually  below  the  ribs  in  the  line 


Sup 


rarenal 
impression 
(non-peritoneal). 

Suprarenal 
impression 
(peritoneal). 
Tuberculum 
caudatum. 


Tubercu 
papillare. 

7 

Umbilical  fissure.  Transverse  fissure. 

FIG.  951. — The  liver.     Posterior  and  inferior  surfaces.      (Drawn  from  His's  models.) 

indicated  above.  Opposite  the  attachment  of  the  falciform  ligament  the  anterior 
border  often  exhibits  a  deep  notch,  the  umbilical  notch  (incisura  umbilicalis}, 
which  is  the  anterior  end  of  the  fossa  venae  umbilicalis.  Another  notch,  some- 
times present,  corresponds  to  the  fundus  of  the  gall-bladder,  and  is  known  as  the 
notch  of  the  gall-bladder  (incisura  vesicae  felleae). 

The  left  extremity  of  the  inferior  margin  of  the  liver  is  thin  and  flattened  from 
above  downward.  The  margin  passes  posteriorly  around  the  free  end  of  the  left 
lobe  and  terminates  posteriorly  at  the  oesophageal  groove. 

Fissures. — Five  fissures  are  seen  upon  the  under  and  posterior  surfaces  of  the 
liver,  which  serve  to  divide  it  into  five  lobes.  They  are:  the  umbilical  fissure, 
the  fissure  of  the  ductus  venosus,  the  transverse  fissure,  the  fissure  for  the  gall-bladder, 
and  the  fissure  for  the  postcava.  They  are  arranged  in  the  form  of  the  letter  H. 
The  left  limb  of  the  H  is  known  as  the  longitudinal  fissure.  The  right  limb  is  formed 
in  front  by  the  fissure  for  the  gall-bladder,  and  behind  by  the  fissure  for  the  post- 
cava; these  two  fissures  are  separated  from  each  other  by  the  caudate  lobe.  The 
connecting  bar  of  the  H  is  the  transverse  or  portal  fissure.  It  separates  the  quad- 
rate lobe  in  front  from  the  caudate  and  Spigelian  lobes  behind. 

The  Longitudinal  Fossa  or  Fissure  (fossa  longitudinalis  sinistra}. — The  longi- 
tudinal fissure  is  a  deep  groove,  which  extends  from  the  notch  on  the  anterior 
margin  of  the  liver  to  the  upper  border  of  the  posterior  surface  of  the  organ.  It 
separates  the  right  and  left  lobes;  the  transverse  fissure  (Fig.  951)  joins  it,  at 
right  angles,  and  divides  it  into  two  parts.  The  anterior  part  is  called  the  um- 
bilical fossa  or  fissure  (fossa  venae  umbilicalis')  (Fig.  951);  it  is  deeper  than  the 
posterior,  and  lodges  the  umbilical  vein  in  the  foetus,  and  its  remains  (the  round 
ligament)  in  the  adult;  the  posterior  part  contains  the  ductus  venosus,  and  is 
known  as  the  fissure  of  the  ductus  venosus.  This  fissure  lies  between  the  quadrate 
lobe  and  the  left  lobe  of  the  liver,  and  is  often  partially  bridged  over  by 
prolongation  of  the  hepatic  substance,  the  pons  hepatis. 

1  Ambrose  Birmingham,  in  Cunningham's  Text-book  of  Anatomy. 


THE  LIVER 


1339 


The  Fissure  or  Fossa  of  the  Ductus  Venosus  (fossa  ductus  venosi)  (Fig.  951)  is 
the  back  part  of  the  longitudinal  fissure,  and  is  situated  mainly  on  the  posterior 
surface  of  the  liver.  It  lies  between  the  left  lobe  and  the  lobe  of  Spigelius.  It 
lodges  in  the  foetus  the  ductus  venosus,  and  in  the  adult  a  slender  fibrous  cord, 
the  obliterated  remains  of  that  vessel. 

The  Transverse  or  Portal  Fissure  (porta  hepatis)  (Fig.  951). — The  transverse  or 
portal  fissure  is  a  short  but  deep  fissure,  about  two  inches  in  length,  extending 
transversely  across  the  under  surface  of  the  left  portion  of  the  right  lobe,  nearer  to 
its  posterior  surface  than  its  anterior  border.  It  joins,  nearly  at  right  angles,  with 
the  longitudinal  fissure,  and  separates  the  quadrate  lobe  in  front  from  the  cau- 
date and  Spigelian  lobes  behind.  By  the  older  anatomists  this  fissure  was  con- 
sidered the  gateway  (porta)  of  the  liver;  hence  the  large  vein  which  enters  at  this 
fissure  was  called  the  portal  vein  (Fig.  952).  Besides  this  vein,  the  fissure  trans- 
mits the  hepatic  artery  and  nerves,  and  the  hepatic  duct  and  lymphatics.  At 
their  entrance  into  the  fissure,  the  hepatic  duct  lies  in  front  and  to  the  right, 
the  hepatic  artery  to  the  left,  and  the  portal  vein  behind  and  between  the  duct 
and  artery. 


CEsophageal  groove.         Portal  vein.         Suprarenal  impression. 


RIGHT    LATERAL 
LIGAMENT. 


LIGAMENTUM  — 
TERES. 


Hepatic  artery. 

Common  bile-duct. 
FIG.  952. — Posterior  and  under  surfaces  of  the  liver.    (From  Ellis.) 

The  Fossa  or  Fissure  for  the  Gall-bladder  (fossa  vesicae  felleae). — The  fossa  or 
fissure  for  the  gall-bladder  is  a  shallow,  oblong  fossa,  placed  on  the  under  surface 
of  the  right  lobe,  parallel  with  the  longitudinal  fissure.  It  extends  from  the 
anterior  free  margin  of  the  liver,  which  is  notched  for  its  reception,  to  the  right 
extremity  of  the  transverse  fissure. 

The  Fissure  or  Fossa  for  the  Postcava  (fossa  venae  cavae)  (Fig.  951). — The 
fissure  or  fossa  for  the  postcava  is  a  short,  deep  fissure,  in  some  cases  a  com- 
plete canal,  in  consequence  of  the  substance  of  the  liver  occasionally  surrounding 
the  postcava.  It  extends  obliquely  upward  from  the  lobus  caudatus,  which  sepa- 
rates it  from  the  transverse  fissure,  on  the  posterior  surface  of  the  liver,  and  sepa- 
rates the  Spigelian  from  the  right  lobe.  On  slitting  open  the  postcava  the  orifices 
of  the  hepatic  veins  will  be  seen  opening  into  this  vessel  at  its  upper  part,  after 
perforating  the  floor  of  this  fissure. 

Lobes. — The  lobes  of  the  liver,  like  the  ligaments  and  fissures,  are  five  in 
number — the  right  lobe,  the  left  lobe,  the  lobus  quadratus,  the  lobus  Spigelii,  and 
the  lobus  caudatus,  the  last  three  being  merely  parts  of  the  right  lobe. 


1340  THE  ORGANS  OF  DIGESTION 

The  Right  Lobe  (lobus  hepatis  dexter)  (Figs.  949  and  951). — The  right  lobe  is 
much  larger  than  the  left;  the  proportion  between  them  being  as  six  to  one.  It 
occupies  the  right  hypochondrium,  and  is  separated  from  the  left  lobe,  on  its  upper 
and  anterior  surfaces  by  the  falciform  ligament;  on  its  under  and  posterior  surfaces 
by  the  longitudinal  fissure;  and  in  front  by  the  umbilical  notch.  It  is  of  a  some- 
what quadrilateral  form,  its  under  and  posterior  surfaces  being  marked  by  three 
fissures — the  transverse  fissure,  the  fissure  for  the  gall-bladder,  and  the  fissure  for 
the  postcava,  which  separate  its  left  part  into  three  smaller  lobes — the  lobus 
Spigelii,  lobus  quadratus,  and  lobus  caudates.  On  it  are  seen  four  shallow  impres- 
sions: one  in  front,  for  the  hepatic  flexure  of  the  colon;  a  second  behind,  for 
the  right  kidney;  a  third  internal,  between  the  last-named  and  the  gall-bladder, 
for  the  second  part  of  the  duodenum;  and  a  fourth  on  its  posterior  surface,  for  the 
suprarenal  capsule. 

The  Lobus  Quadratus  or  Square  Lobe  (Figs.  951  and  952)  is  situated  on  the 
under  surface  of  the  right  lobe,  is  bounded  in  front  by  the  inferior  margin  of  the 
liver;  behind,  by  the  transverse  fissure;  on  the  right,  by  the  fissure  of  the  gall- 
bladder; on  the  left,  by  the  umbilical  fissure. 

The  Lobus  Spigelii  (lobus  caudatus  [Spigeli])  (Figs.  951  and  952)  is  situated 
upon  the  posterior  surface  of  the  right  lobe  of  the  liver.  It  looks  directly  back- 
ward, and  is  nearly  vertical  in  direction.  It  is  bounded,  above,  by  the  upper  layer 
of  the  coronary  ligament;  below,  by  the  transverse  fissure;  on  the  right,  by  the 
fissure  for  the  postcava;  and  on  the  left,  by  the  fissure  for  the  ductus  venosus. 
Its  left  upper  angle  forms  part  of  the  groove  for  the  oesophagus.  What  is  here 
called  the  lobus  Spigelii,  Spalteholz  calls  the  lobus  caudatus  of  Spigelius. 

The  Lobus  Caudatus  or  Tuberculum  Caudatum  (processus  caudatus)  (Fig.  951),  or 
tailed  lobe,  is  a  small  elevation  of  the  hepatic  substance  extending  obliquely  out- 
ward, from  the  lower  extremity  of  the  Spigelian  lobe  to  the  under  surface  of  the 
right  lobe.  It  is  situated  behind  the  transverse  fissure,  and  separates  the  fissure 
for  the  gall-bladder  from  the  commencement  of  the  fissure  for  the  postcava. 
What  is  here  called  the  lobus  caudatus,  Spalteholz  calls  the  processus  caudatus 
of  the  lobus  caudatus  of  Spigelius. 

The  Left  Lobe  (lobus  hepatis  sinister)  (Figs.  949  and  951). — The  left  lobe  is 
smaller  and  more  flattened  than  the  right.  It  is  situated  in  the  epigastric  and 
left  hypochondriac  regions.  Its  upper  surface  is  slightly  convex;  its  under  sur- 
face is  concave,  and  presents  a  shallow  depression  for  the  stomach,  the  gastric 
impression.  This  is  situated  in  front  of  the  groove  for  the  oesophagus,  and  is 
separated  from  the  longitudinal  fissure  by  the  omental  tuberosity,  which  lies  against 
the  small  omen  turn  and  lesser  curvature  of  the  stomach.  The  posterior  end  of 
the  left  lobe  frequently  exhibits  a  flat  projection,  composed  of  connective  tissue, 
and  called  the  appendix  fibrosus  hepatis.  In  the  adult,  portions  only  of  bile-ducts 
are  present  in  it.  In  the  newborn  it  is  a  definite  portion  of  secreting  liver  sub- 
stance, which  later  undergoes  connective-tissue  transformation. 

Ligaments. — The  liver  is  connected  to  the  under  surface  of  the  Diaphragm 
and  the  anterior  walls  of  the  abdomen  and  the  postcava  by  six  ligaments,  four 
of  which  are  peritoneal  folds;  the  other  two,  which  are  the  round  ligament  and 
the  ligament  of  the  ductus  venosus,  are  fibrous  cords,  resulting  from  the  obliteration 
of  foetal  vessels.  These  ligaments  are  the  falciform,  two  lateral,  coronary,  round, 
and  the  ligament  of  the  ductus  venosus.  It  is  also  attached  to  the  lesser  curvature 
of  the  stomach  by  the  gastro-hepatic  or  small  omen  turn. 

The  Falciform,  Broad  or  Suspensory  Ligament  (ligamentum  falciforme  hepatis) 
(Figs.  949,  953,  and  954). — The  falciform  or  suspensory  ligament  is  a  broad  and 
thin  antero-posterior  peritoneal  fold,  falciform  in  shape,  its  base  being  directed 
downward  and  backward,  its  apex  upward  and  backward.  It  is  attached  by  one 
margin  to  the  under  surface  of  the  Diaphragm,  and  the  posterior  surface  of  the 


THE  LIVER 


1341 


sheath  of  the  right  Recttis  muscle  to  within  one  inch  of  the  umbilicus;  by  its 
hepatic  margin  it  extends  from  the  notch  on  the  anterior  margin  of  the  liver,  as 
far  back  as  its  posterior  surface. 

The  free  edge  or  base  of  the  falciform  ligament  reaches  from  a  little  above  and  to 
the  right  of  the  umbilicus  to  the  umbilical  fissure  on  the  anterior  margin  of  the  liver. 
This  free  edge  contains  between  its  folds  the  round  ligament  of  the  liver.  On  the 
posterior  surface  of  the  liver  the  two  peritoneal  folds  which  constitute  the  falci- 
form ligament  separate,  the  right  fold  passing  into  the  upper  fold  of  the  coronary 
ligament,  the  left  fold  passing  into  the  upper  fold  of  the  left  lateral  ligament. 


CORONARY 
LIGAMENT 


RIGHT 
LATERAL  . 
LIGAMENT 


FALCIFORM 
LIGAMENT 


Fir,.  9o3. — The  peritoneal  ligaments  of  the  liver.    (Schematic.)    (Poirier  and  Charpy.) 

The  Lateral  Ligaments  (Figs.  949  and  953). — The  lateral  ligaments  are  two  in 
number,  and  are  called  the  right  and  left  lateral  ligaments. 

The  Right  Lateral  Ligament  (ligamentum  triangulare  dextrum)  (Figs.  949  and 
953)  is  in  reality  the  right  extremity  of  the  coronary  ligament.  This  ligament  is 
triangular  in  form,  runs  from  the  liver  to  the  Diaphragm,  and  is  forrfied  by  the 
apposition  of  the  upper  and  lower  layers  of  the  coronary  ligament.  It  is  attached 
to  the  liver  between  its  lateral  and  inferior  surfaces. 

The  Left  Lateral  Ligament  (ligamentum  triangulare  sinistrum)  (Figs.  949  and 
953)  is  also  formed  by  apposition  of  the  upper  and  lower  layers  of  the  coronary 
ligament.  It  is  triangular  in  form, 
runs  from  the  liver  to  the  Dia- 
phragm, and  is  longer  than  the  right 
lateral  ligament.  It  is  attached  to 
the  upper  surface  of  the  left  lobe, 
where  it  lies,  in  front  of  the  oesopha- 
geal  opening  in  the  Diaphragm. 

The  Coronary  Ligament  (ligamentum 
coronarium  hepatis)  (Figs.  949  and 
953). — The  coronary  ligament  con- 
nects the  posterior  surface  of  the  liver 
to  the  Diaphragm.  It  is  formed  by 
the  reflection  of  the  peritoneum  from 
the  Diaphragm  on  to  the  upper  and  NA< 
lower  margins  of  the  posterior  sur- 
face of  the  liver.  The  coronary  liga- 
ment Consists  of  tWO  layers,  which  FIG.  954.— Diagram  to  show  the  relations  of  the  falci- 
,•  i  •  i  •-!  ,1  form  or  suspensory  and  round  ligaments  to  the  liver  and 

are  COntinUOUS  On  each  Side  With  the     the  abdominal  wall.     (Gerrish.) 

lateral  ligaments,  and,  in  front,  with 

the  falciform  ligament.    Between  the  layers  a  large  triangular  area  is  left  uncovered 

by  peritoneum,  and  is  connected  to  the  Diaphragm  by  firm  areolar  tissue. 


1342  THE  ORGANS  OF  DIGESTION 

The  Round  Ligament  (ligamentum  teres  hepatis)  (Figs.  952  and  954). — The 
round  ligament  is  a  fibrous  cord  resulting  from  the  obliteration  of  the  foetal  umbil- 
ical vein.  It  ascends  from  the  umbilicus,  in  the  free  margin  of  the  falciform 
ligament,  to  the  notch  in  the  anterior  border  of  the  liver,  from  which  it  may  be 
traced  along  the  umbilical  fissure  on  the  under  surface  of  the  liver,  to  the  left 
branch  of  the  portal  vein. 

The  Ligament  of  the  Ductus  Venosus  (ligamentum  venosum  [Arantii])  is  com- 
posed of  slender  bundles  of  fibrous  tissue,  and  results  from  the  obliteration  of  the 
ductus  venosus  of  the  foetus.  It  arises  from  the  left  branch  of  the  portal  vein, 
almost  opposite  the  insertion  of  the  round  ligament,  passes  backward  in  the  fissure 
of  the  ductus  venosus,  and,  as  it  emerges  from  the  liver,  is  attached  to  the  postcava. 

Support  and  Movability  of  the  Liver. — The  liver  is  movable  within  certain 
narrow  limits.  It  moves  with  respiration.  On  inspiration  it  moves  down  with 
the  Diaphragm  to  distinctly  below  the  costal  arch  in  the  right  nipple  line. 
Much  discussion  has  taken  place  as  to  what  supports  the  liver  in  place.  Syming- 
ton asserted  that  the  ligaments  do  not  give  support,  because  they  lie  relaxed. 
Other  observers  (Graham,  Steele)  apparently  demonstrate  that  the  peritoneal 
ligaments  do  give  some  support  to  the  liver.  The  connective  tissue  which  unites 
the  uncovered  area  of  the  right  lobe  of  the  liver  to  the  Diaphragm  and  the  hepatic 
veins  which  join  the  postcava  (Faure)  do  give  distinct  support.  The  chief  factor 
in  the  support  of  the  liver  is  the  intra-abdominal  pressure  resulting  from  the 
tonic  contraction  of  the  abdominal  muscles.  When  abdominal  tension  is  normal 
the  intestines  are  driven  up  and  become  a  bed  for  the  liver.  Intrahepatic  vascular 
tension  aids  in  supporting  the  liver  (Glenard). 

Abnormalities  of  the  Liver. — The  liver  may  be  divided  into  many  lobules,  and 
such  lobulation  is  most  evident  on  the  parietal  surface  of  the  right  lobe.  Lobula- 
tion  is  probably  a  pathological  change.  Occasionally  the  right  lobe  is  small  and 
the  left  large. 

The  editor,  in  performing  an  abdominal  operation,  encountered  a  liver  the 
left  lobe  of  which  was  so  large  and  the  right  so  small  as  to  suggest  transposition 
or  rotation  of  the  organ.  Such  a  change  may  result  from  abnormality  of  the 
foetal  circulation  or  from  syphilitic  disease  of  the  right  lobe,  producing  cicatricial 
contraction.1  The  left  lobe  may  be  very  small;  sometimes  it  is  rudimentary. 
When  the  left  lobe  is  very  small  an  unusual  amount  of  stomach  is  visible,  and  the 
entire  gall-bladder  can  be  seen  from  the  front.  In  such  a  case  the  gall-bladder  is 
usually  displaced  and  it  may  actually  "lie  with  its  long  axis  in  the  transverse  axis 
of  the  body."2 

Atrophy  of  the  left  lobe  is  usually  a  congenital  defect,  but  may  result  from 
syphilis.  Small  accessory  lobes,  about  one  inch  in  length,  are  not  uncommon,  and 
they  are  most  often  met  with  on  the  visceral  surface  of  the  right  lobe.  "WTien 
markedly  pedunculated,  they  may  form  accessory  livers.  The  Spigelian  lobe  is 
sometimes  curiously  pedunculated."3 

Accessory  livers  are  fragments  of  hepatic  tissue  or  rests,  which  are  entirely 
separated  from  the  liver.  They  are  seldom  met  with.  When  they  do  exist  their 
most  common  situation  is  in  the  suspensory  ligament,  but  they  have  been  found 
in  the  great  omentum,  in  the  peritoneum,  wall  of  the  gall-bladder,  and  in  other 
situations.  They  may  be  congenital  or  may  be  due  to  atrophy  of  the  pedicle  of  an 
accessory  lobe  or  of  a  pedunculated  lobe.  Tight  lacing  alters  the  shape  and  posi- 
tion of  the  liver  (Fig.  955).  It  may  flatten  the  dome  and  increase  the  length  of 
the  anterior  surface,  this  change  being  especially  obvious  in  the  right  lobe,  and  a 
costal  groove  may  be  formed  by  the  pressure  of  a  rib.  "When  the  elongated 
right  lobe  passes  over  the  right  kidney,  there  is  atrophy  of  the  hepatic  substance 

1  H.  D.  Rolleston  on  Diseases  of  the  Liver.  -  Ibid.  3  Ibid. 


THE  LIVER 


1343 


and  thickening  of  the  capsule,  which  is  opaque  and  forms  a  hinge-like  ligament 
between  the  main  part  of  the  right  lobe  above  and  the  constricted  lower  portion. 
This  lobe  is  variously  termed  partial  hepatoptosis,  constriction  lobe,  or  the  sus- 
tentacular  formation  of  the  right  lobe  (Hertz).  The  constriction  furrow  is  pro- 
duced by  the  pressure  of  the  corset  in  front  and  the  resistance  of  the  kidney 
behind.  The  constriction  lobe  tapers  to  a  point,  so  that  the  shape  of  the  liver,  as 
seen  from  the  front,  is  that  of  a  right-angled  triangle,  with  the  apex  downward."1 
The  condition  resembles  Riedel's  lobe.  The  left  lobe  may  also  project  down, 


DIAPHRAGMATIC 
GROOVE 


FIG.  955.— Deformed  female  liver.     (Poirier  and  Charpy.) 

but  not  so  markedly.  Tight  lacing  may  cause  the  entire  organ  to  occupy  a  level 
higher  than  normal.  Such  a  liver  is  thick  and  excessively  convex  above  and 
thin  below,  and  reaches  to  or  laps  over  the  spleen.  In  severe  cases  the  superior 
surface  is  thrown  into  antero-posterior  creases  or  folds.  Linguifonn  or  tongue-like 
lobe,  Riedel's  lobe  or  floating  lobe  (Fig.  955),  may  be  congenital,  may  be  due  to  tight 
lacing,  or  may  arise  in  cholelithiasis  or  cholecystitis  from  the  traction  of  adhesions. 
Such  a  lobe  comes  off  from  the  right  lobe.  It  may  be  a  tapering  mass  of  liver 
tissue,  it  may  have  a  thin  pedicle  of  liver  tissue,  or  its  pedicle  may  be  merely  a 
double  fold  of  peritoneum.  The  gall-bladder  may  lie  upon  its  under  surface,  or 
may  be  placed  to  the  left  of  it. 

Vessels. — The  blood-vessels  connected  with  the  liver  are  the  hepatic  artery,  the 
portal  vein  and  the  hepatic  veins. 

The  Hepatic  Artery  and  Portal  Vein  (Figs.  421,  422,  488,  and  957),  accompanied 
by  numerous  lymphatics  and  nerves,  ascend  to  the  transverse  fissure  between  the 
layers  of  the  gastro-hepatic  omen  turn,  and  in  front  of  the  foramen  of  Winslow.' 
The  hepatic  duct,  lying  in  company  with  them,  descends  from  the  transverse  fissure 
between  the  layers  of  the  same  omentum.  The  relative  position  of  the  three 
structures  in  the  lesser  omentum  (Fig.  872)  is  as  follows:  the  hepatic  duct  lies  to 
the  right,  the  hepatic  artery  to  the  left,  and  the  portal  vein  behind  and  between 
the  other  two.  They  enter  the  transverse  fissure  in  the  above-described  order,  but 
in  that  fissure  undergo  rearrangement,  the  duct  being  in  front,  the  artery  in  the 

1  Rolleston,  on  Diseases  of  the  Liver. 


1344 


THE  ORGANS  OF  DIGESTION 


middle,  and  the  vein  behind.  The  artery,  the  vein,  and  the  duct  divide  into  a 
right  and  left  branch  and  several  smaller  branches,  and  within  the  organ  the 
vessels  from  the  three  sources  accompany  each  other  and  divide  at  the  same 
points;  so  each  branch  of  the  portal  vein  is  accompanied  by  a  branch  of  the 


FIG.  956. — Schematic  section  of  the  liver.    The  fibron  tunic  shown  in  black  and  the  capsule  of  Glisson  in  red. 


hepatic  artery  and  of  the  duct.  They  are  enveloped  in  a  loose  areolar  tissue,  the 
capsule  of  Glisson  (Fig.  956),  which  accompanies  the  vessels  in  their  course  through 
the  portal  canals  in  the  interior  of  the  organ. 

The  Hepatic  Veins  (Fig.  424). — The  hepatic  veins  convey  the  blood  from  the  liver. 
They  commence  in  the  substance  of  the  liver,  in  the  capillary  terminations  of  the 
portal  vein  and  hepatic  artery;  these  tributaries,  gradually  uniting,  usually  form 
three  veins,  which  converge  toward  the  posterior  surface  of  the  liver  and  open 
into  the  portion  of  the  postcava  situated  in  the  groove  at  the  back  part  of  this 
organ.  Of  these  three  veins,  one  from  the  right  and  another  from  the  left  lobe 
open  obliquely  into  the  postcava;  that  from  the  middle  of  the  organ  and  lobus 
Spigelii  having  a  straight  course. 


COMMON    DUCT 


FORAMEN    OF 
WINSLOW 


DUODENUM 


FIG.  957. — The  relations  of  the  vessels  as  they  pass  into  the  transverse  fissure  of  the  liver.     (Poirier  and  Charpy.) 


The  hepatic  veins  have  very  little  cellular  investment;  what  there  is  binds  their 
parietes  closely  to  the  walls  of  the  canals  through  which  they  run;  so  that,  on 
section  of  the  organ,  these  veins  remain  widely  open  and  solitary  (Fig.  959), 
and  may  be  easily  distinguished  from  the  branches  of  the  portal  vein  (Fig.  960), 


THE  LIVER 


1345 


which  are  more  or  less  collapsed,  and  always  accompanied  by  an  artery  and  duct, 
the  hepatic  veins  are  destitute  of  valves. 

Structure. — The  substance  of  the  liver  is  composed  of  lobules  held  together  by 
extremely  fine  areolar  tissue,  and  of  the  ramifications  of  the  portal  vein,  hepatic 
duct,  hepatic  artery,  hepatic  veins,  lymphatics,  and  nerves,  the  whole  being 
invested  by  a  serous  and  a  fibrous  coat. 

The  Serous  Coat  (tunica  serosa). — The  serous  coat  is  derived  from  the  perito- 
neum, and  invests  the  greater  part  of  the  surface  of  the  organ.  It  is  intimately 
adherent  to  the  fibrous  coat. 

The  Areolar  or  Fibrous  Coat  (capsula  fibrosa  [Glissoni]). — The  areolar  or  fibrous 
coat  lies  beneath  the  serous  investment  and  covers  the  entire  surface  of  the  organ. 
It  is  difficult  of  demonstration,  excepting  where  the  serous  coat  is  deficient.  At 
the  transverse  fissure  it  is  thick  and  evident,  is  known  as  the  capsule  of  Glisson, 
and  envelops  the  vessels  which  enter  the  liver  and  passes  with  them  along  the 
portal  canals.  The  areolar  tissue  which  surrounds  and  binds  together  the  liver 
lobules  is  continuous  with  the  areolar  coat. 

The  Lobules  (lobuli  hepatis)  (Fig.  962). — The  lobules  form  the  chief  mass  of 
the  hepatic  substance;  they  may  be  seen  either  on  the  surface  of  the  organ  or  by 
making  a  section  through  the  gland.  They  are  small  granular  bodies  about  the  size 
of  a  millet-seed,  measuring  from  one-twentieth  to  one-tenth  of  an  inch  in  diameter. 
In  the  human  subject  their  outline  is  very  irregular,  but  in  some  of  the  lower 
animals  (for  example,  the  pig)  they  are  well  defined,  and  when  divided  transversely 
have  a  polygonal  outline.  If  divided  longitudinally  they  are  more  or  less  foliated 
or  oblong.  The  bases  of  the  lobules  are  clustered  around  the  smallest  radicles 
of  the  hepatic  veins  (sublobular  veins),  to  which  each  is  connected  by  means  of  a 
small  branch  which  issues  from  the  centre  of  the  lobule  (intralobular  vein).  The 
remaining  part  of  the  surface  of  each  lobule  is  imperfectly  isolated  from  the  sur- 
rounding lobules  by  a  thin  stratum  of  areolar  tissue  in  which  are  ducts  and  a  plexus 


FIG.  958. — The  hepatic  cells  at  different  stages  of  digestion.     (Heidenhain.) 

of  vessels,  the  interlobular  plexus  (Figs..  961  and  962).  In  some  animals,  as  the 
pig,  the  lobules  are  completely  isolated  one  from  another  by  this  interlobular 
areolar  tissue. 

If  one  of  the  sublobular  veins  be  laid  open,  the  bases  of  the  lobules  may  be 
seen  through  the  thin  wall  of  the  vein  on  which  they  rest,  arranged  in  the  form 
of  a  tessellated  pavement,  the  centre  of  each  polygonal  space  presenting  a  minute 
aperture,  the  mouth  of  an  intralobular  vein  (Fig.  959). 

MICROSCOPIC  APPEARANCE. — Each  lobule  is  composed  of  a  mass  of  cells,  hepatic 
cells  (Fig.  958),  surrounded  by  a  dense  capillary  plexus,  composed  of  vessels  which 
penetrate  from  the  circumference  to  the  centre  of  the  lobule,  and  terminate  in  a 
single  straight  central  vein,  which  runs  through  its  centre,  to  open  at  its  base  into 
one  of  the  radicles  of  the  hepatic  vein.  Between  the  cells  are  also  the  minute  com- 
mencements of  the  bile-ducts.  Therefore  in  the  lobule  we  have  all  the  essentials  of 
a  secreting  gland;  that  is  to  say:  (1)  cells,  by  which  the  secretion  is  formed;  (2) 
blood-vessels,  in  close  relation  with  the  cells,  containing  the  blood  from  which 
the  secretion  is  derived;  and  (3)  ducts,  by  which  the  secretion,  when  formed,  is 
carried  away.  Each  of  these  structures  will  have  to  be  further  considered. 

85 


1346 


THE  ORGANS  OF  DIGESTION 


(1)  The  Hepatic  Cells  are  epithelial  in  nature  and  of  more  or  less  spheroidal  form, 
but  may  be  rounded,  flattened,  or  many-sided  from  mutual  compression.    They 
vary  in  size  from  the  j^Vo" to  the  WinF  °f  an  mcn  m  diameter.    They  consist  of  a 
honeycomb  network  (Klein)  without  any  cell-wall,  and  contain  one  or  sometimes 
two  distinct  nuclei.    In  the  nucleus  is  a  highly  refracting  nucleolus  with  granules. 
Embedded  in  the  honeycomb  network  are  numerous  yellow  particles,  the  coloring 
matter  of  the  bile,  and  oil-globules.    The  cells  adhere  together  by  their  surfaces  so 
as  to  form  rows,  which  radiate  from  the  centre  to  the  circumference  of  the  lobules.1 
As  stated  above,  they  are  the  chief  agents  in  the  secretion  of  the  bile. 

(2)  The  Blood-vessels. — The  blood  in  the  capillary  plexus  around  the  liver-cells 
is  brought  to  the  liver  principally  by  the  portal  vein,  but  also  to  a  certain  extent 
by  the  hepatic  artery.     For  the  sake  of  clearness  the  distribution  of  the  blood 
derived  from  the  hepatic  artery  may  be  considered  first. 

The  Hepatic  Artery,  entering  the  liver  at  the  transverse  fissure  with  the  portal 
vein  and  hepatic  duct,  ramifies  with  these  vessels  through  the  portal  canals.  It 
gives  off  vaginal  branches  which  ramify  in  the  capsule  of  Glisson,  and  appear  to 
be  destined  chiefly  for  the  nutrition  of  the  coats  of  the  large  vessels,  the  ducts, 
and  the  investing  membranes  of  the  liver.  It  also  gives  off  capsular  branches 
which  reach  the  surface  of  the  organ,  terminating  in  the  fibrous  coat  in  stellate 
plexuses.  Finally  it  gives  off  interlobular  branches  (rami  arteriosi  interlobular  es) 
which  form  a  plexus  on  the  outer  side  of  each  lobule,  to  supply  its  wall  and  the 
accompanying  bile-ducts.  From  this  plexus  lobular  branches  enter  the  lobule 


Hepatic 
artery. 


Portal  vein. 


Orifices  of  intralobular  veins. 


FIG.  959. — Longitudinal  section  of  an  hepatic 
vein.     (After  Kiernan.) 


rtion  of 
canal  from 
which  vein 
has  been 
removed. 


FIG.  960. — Longitudinal  section  of  a  small  portal 
vein  and  canal.     (After  Kiernan.) 


and  end  in  the  capillary  network  between  the  cells.     Some  anatomists,  however, 
doubt  whether  it  transmits  any  blood  directly  to  the  capillary  network. 

The  Portal  Vein  also  enters  at  the  transverse  fissure  and  runs  through  the 
portal  canals,  enclosed  in  Glisson's  capsule,  dividing  into  branches  in  its  course, 
which  finally  break  up  into  a  plexus,  the  interlobular  plexus,  in  the  interlobular 
spaces.  In  their  course  these  branches  receive  the  vaginal  and  capsular  veins, 
corresponding  to  the  vaginal  and  capsular  branches  of  the  hepatic  artery  (Fig. 


THE  LIVER 


1347 


960) .  Thus  it  will  be  seen  that  all  the  blood  carried  to  the  liver  by  the  portal  vein 
and  hepatic  artery,  except  perhaps  that  derived  from  the  interlobular  branches  of 
the  hepatic  artery,  directly  or  indirectly  finds  its  way  into  the  interlobular  plexus. 
From  this  plexus  the  blood  is  carried  into  the  lobule  by  fine  branches  which  pierce 
its  wall  and  then  converge  from  the  circumference  to  the  centre  of  the  lobule,  form- 


Intralobular  vein. 


Trunk  of  intralobular 
vein. 


FIG.  961. — Horizontal  section  of  liver  (dog.) 


ing  a  number  of  converging  vessels  which  are  connected  by  transverse  branches 
(Figs.  961  and  962).  In  the  interstices  of  the  network  of  vessels  thus  formed  are 
situated,  as  before  said,  the  liver-cells:  and  here  it  is  that  the  blood  is  brought  into 
intimate  connection  with  the  liver-^cells  and  the  bile  is  secreted.  Arrived  at  the 
centre  of  a  lobule,  all  these  minute  vessels  empty  themselves  into  one  vein,  of 
considerable  size,  which  runs  down  the  centre  of  the  lobule  from  apex  to  base 
and  is  called  the  intralobular  or  central  vein  (vein  interlobularis)  (Fig.  962).  At  the 


TT» 

FIG.  962. — Horizontal  section  of  a  liver  lobule:    1,  central  vein;  2,  converging  vessels;  3,  interlobular  plexus. 

(Poirier  and  Charpy.) 

base  of  the  lobule  this  vein  opens  directly  into  the  sublobular  vein,  with  which  the 
lobule  is  connected,  and  which,  as  before  mentioned,  is  a  radicle  of  the  hepatic  vein. 
The  sublobular  veins,  uniting  into  larger  and  larger  trunks,  end  at  last  in  the 
hepatic  veins,  which  do  not  receive  any  intralobular  veins.  Finally,  the  hepatic 
veins,  as  mentioned  on  page  767,  converge  to  form  three  large  trunks  which  open 
into  the  postcava,  while  that  vessel  is  situated  in  the  fissure  appropriated  to  it 
at  the  back  of  the  liver. 


1348 


THE  ORGANS  OF  DIGESTION 


(3)  The  Ducts. — Having  shown  how  the  blood  is  brought  into  intimate  relation 
with  the  hepatic  cells  in  order  that  the  bile  may  be  secreted,  it  remains  now  only 
to  consider  the  way  in  which  the  secretion,  having  been  formed,  is  carried  away. 


FIG.  963.  —  .Y-ray  picture  of  the  bile-ducts  and  the  pancreatic  ducts.    (Robinson.) 

Several  views  have  prevailed  as  to  the  mode  of  origin  of  the  hepatic  ducts;  it 
seems,  however,  to  be  clear  that  they  commence  by  little  passages  which  are 
formed  between  the  cells,  and  which  have  been  termed  intercellular  biliary  pass- 
ages, bile-capillaries  or  bile-canaliculi  (ductus  biliferi) .  These  passages  are  merely 
little  channels  or  spaces  left  between  the  contiguous  surfaces  of  two  cells  or  in  the 


INTER- 

LOBULAR 
BRANCHES 


Biliary  duct. 


FIG.  964. — Section  of  liver. 


FIG.  965. — A  transverse  section  of  a  small  portal  canal 
and  its  vessels.    (Kiernan.) 


angle  where  three  or  more  liver-cells  meet  (Fig.  964),  and  it  seems  doubtful 
whether  there  is  any  delicate  membrane  forming  the  wall  of  the  channel. 
Heidenhain,  however,  thinks  they  have  coats.  The  channels  thus  formed  radi- 
ate to  the  circumference  of  the  lobule,  and,  piercing  its  wall,  form  a  plexus 


THE  LIVER  1349 

(interlobular}  between  the  lobules.  From  this  plexus  interlobular  ducts  (ductus 
interlobular  es}  are  derived  which  pass  into  the  portal  canals,  become  enclosed  in 
Glisson's  capsule,  and,  accompanying  the  portal  vein  and  hepatic  artery  (Fig. 
952),  join  with  other  ducts  to  form  two  main  trunks,  the  right  and  left  branches  of 
the  hepatic  duct,  which  leave  the  liver  at  the  transverse  fissure,  and  by  their  union 
form  the  hepatic  duct. 

STRUCTURE. — The  coats  of  the  smallest  biliary  ducts,  which  lie  in  the  inter- 
lobular spaces,  are  a  connective-tissue  coat,  in  which  are  muscle-cells,  arranged 
both  circularly  and  longitudinally,  and  an  epithelial  layer,  consisting  of  short 
columnar  cells.  In  the  larger  ducts,  which  lie  in  the  portal  canals,  there  are  a 
number  of  orifices  disposed  in  two  longitudinal  rows,  which  were  formerly  regarded 
as  the  openings  of  mucous  glands,  but  which  are  merely  the  orifices  of  tubular 
recesses.  They  occasionally  anastomose,  and  from  the  sides  of  them  saccular 
dilatations  are  given  off. 

Lymphatics  of  the  Liver  (Fig.  504). — The  lymphatics  in  the  substance  of  the  liver 
commence  in  lymphatic  spaces  around  the  capillaries  of  the  lobules ;  they  accompany 
the  vessels  of  the  interlobular  plexus,  often  enclosing  and  surrounding  them, 
These  unite  and  form  larger  vessels,  which  run  in  the  portal  canals,  enclosed  in 
Glisson's  capsule,  and  emerge  at  the  portal  fissure  to  be  distributed  in  the  manner 
described.  Other  superficial  lymphatics  arise  from  the  superficial  lobules,  pass 
under  the  peritoneum,  and  form  a  close  plexus,  where  this  membrane  covers 
the  liver.  The  first-named  group  of  lymphatics  give  origin  to  the  deep  collecting 
trunks,  the  second  to  the  superficial  collecting  trunks.  According  to  Poirier, 
Cuneo  and  Delamare,1  one  group  of  deep  collecting  trunks  accompanies  the  portal 
vein,  there  being  fifteen  to  eighteen  of  them  emerging  from  the  transverse  fissure. 
They  empty  into  the  glands  of  the  hilum.  Another  group  accompanies  the  hepatic 
veins.  There  are  five  or  six  trunks  which  pass  through  the  Diaphragm  and  ter- 
minate in  the  glands  about  the  postcava  (intrathoracic  glands).  According  to  the 
above-cited  authorities,  the  superficial  trunks  of  the  superior  surface  are  divided 
into  posterior,  anterior,  and  superior  trunks.  Some  of  the  posterior  trunks  ter- 
minate in  the  glands  about  the  coeliac  axis,  others  in  the  glands  about  the  lower 
portion  of  the  postcava  in  the  thorax;  others  in  the  glands  about  the  abdominal 
portion  of  the  oesophagus.  The  anterior  trunks  which  are  limited  to  the  right 
lobe  pass  to  the  glands  of  the  hilum.  The  superior  trunks  ascend  in  the  suspen- 
sory ligament.  Some  pass  to  the  glands  about  the  postcava,  just  above  the 
Diaphragm;  others  to  the  hepatic  glands.  The  balance  unite  to  form  a  very  large 
trunk,  which  passes  through  the  Diaphragm  and  divides  into  branches  which  enter 
the  glands  back  of  the  base  of  the  ensiform  cartilage. 

Nerves  of  the  Liver. — The  nerves  of  the  liver  are  derived  from  the  left  vagus 
and  the  solar  plexus  of  the  sympathetic.  The  branches  of  the  vagus  ascend  from 
in  front  of  the  stomach  within  the  lesser  omentum.  The  sympathetic  nerves  pass 
along  the  hepatic  artery  from  the  coeliac  plexus.  The  nerves  enter  the  liver  at 
the  transverse  fissure  and  accompany  the  vessels  and  ducts  to  the  interlobular 
spaces.  Here,  according  to  Korolkow,  the  myelinic  fibres  are  distributed  almost 
exclusively  to  the  coats  of  the  blood-vessels;  while  the  amyelinic  fibres  enter  the 
lobules  and  ramify  between  the  cells. 

The  Excretory  Apparatus  of  the  Liver. 

The  excretory  apparatus  of  the  liver  consists  of  (1)  the  hepatic  duct,  which, 
as  we  have  seen,  is  formed  by  the  junction  of  the  two  main  ducts,  which  pass 
out  of  the  liver  at  the  transverse  fissure,  and  are  formed  by  the  union  of  the  bile- 
capillaries;  (2)  the  gall-bladder,  which  serves  as  a  reservoir  for  the  bile;  (3)  the 

1  The  Lymphatics.     Translated  and  edited  by  Cecil  H.  Leaf. 


1350 


THE  ORGANS  OF  DIGESTION 


cystic  duct,    which  is  the  duct  of  the  gall-bladder;  and  (4)  the  common  bile-duct, 
formed  by  the  junction  of  the  hepatic  and  cystic  ducts. 

The  Hepatic  Duct  (ductus  hepaticus)  (Figs.  961,  967,  and  969).— Two  main 
trunks  of  nearly  equal  size  issue  from  the  liver  at  the  transverse  fissure,  one  from 
the  right,  the  other  from  the  left  lobe;  these  unite  to  form  the  hepatic  duct,  which 
then  passes  downward  and  to  the  right  for  about  an  inch  and  a  half  or  two 
inches,  between  the  layers  of  the  lesser  omentum,  where  it  is  joined  at  an  acute 
angle  by  the  cystic  duct,  and  so  forms  the  ductus  communis  choledochus.  The 
hepatic  duct,  as  it  descends  from  the  transverse  fissure  of  the  liver,  between  the 
two  layers  of  the  lesser  omentum,  lies  in  company  with  the  hepatic  artery  and 
portal  vein  (Fig.  957). 

The  Gall-bladder  (vesica  fellea)  (Figs.  872,  874,  951,  957,  and  966).— The 
gall-bladder  is  the  reservoir  for  the  bile;  it  is  a  conical  or  pear-shaped  musculo- 
membranous  sac,  lodged  in  a  fossa  on  the  under  surface  of  the  right  lobe  of  the 
liver,  and  fixed  in  it  by  connective  tissue,  and  extending  from  near  the  right 
extremity  of  the  transverse  fissure  to  the  anterior  border  of  the  organ.  It  is 
about  four  inches  in  length,  one  inch  in  breadth  at  its  widest  part,  and  holds  from 
eight  to  ten  drachms.  It  is  divided  into  a  fundus,  body,  and  neck.  The  fundus 

(fundus  vesicae  felleae),  or  broad  extremity,  is 
directed  downward,  forward,  and  to  the  right, 
and  projects  beyond  the  anterior  border  of  the 
liver;  the  body  (corpus  vesicae  felleae)  and  neck 
(collum  vesicae  felleae}  are  directed  upward  and 
backward  to  the  left.  The  neck  of  the  gall- 
bladder is  on  a  slightly  higher  level  than  the 
lowest  point  of  the  gall-bladder;  thus  the  weight 
of  the  bile  is  away  from  rather  than  toward 
the  outlet.  The  upper  surface  of  the  gall- 
bladder is  attached  to  the  liver  by  connective 
tissue  and  vessels.  The  under  surface  is 
covered  by  peritoneum,  which  is  reflected  on  to 
it  from  the  surface  of  the  liver.  Occasionally 
the  whole  of  the  organ  is  invested  by  the  ser- 
ous membrane,  and  is  then  connected  to  the 
liver  by  a  kind  of  mesentery. 

Relations. — The  body  of  the  gall-bladder  is 
in  relation,  by  its  upper  surface,  with  the 
liver,  to  which  it  is  connected  by  areolar  tissue 
and  vessels ;  by  its  under  surface,  with  the 
commencement  of  the  transverse  colon  ;  and 
farther  back,  with  the  upper  end  of  the  de- 
scending portion  of  the  duodenum  or  some- 
times with  the  pyloric  end  of  the  stomach  or 
the  first  portion  of  the  duodenum.  The  fundus 
is  completely  invested  by  peritoneum  ;  it  is  in 
relation,  in  front,  with  the  abdominal  parietes, 
FIG.  966— The  gaii-biadder  and  bile-ducts,  immediately  below  the  ninth  costal  cartilage; 

cut  through.     (Spalteholz.)  .  J  .     . 

behind,  with  the  transverse  arch  ot  the  colon. 

The  neck  is  narrow,  and  curves  upon  itself  like  the  letter  S;  at  its  point  of 
connection  with  the  cystic  duct  it  presents  a  well-marked  constriction. 

When  the  gall-bladder  is  distended  with  bile  or  filled  with  calculi,  the  fundus  may  be  felt 
through  the  abdominal  parietes,  especially  in  an  emaciated  subject;  the  relations  of  this  sac  will 
also  serve  to  explain  the  occasional  occurrence  of  abdominal  biliary  fistulae,  through  which  biliary 
calculi  may  pass  out,  and  of  the  passage  of  calculi  from  the  gall-bladder  into  the  stomach,  duod- 
enum, or  colon,  which  occasionally  happens. 


THE  EXCRETORY  APPARATUS  OF  THE  LIVER 


1351 


Structure. — The  gall-bladder  consists  of  three  coats — serous,  fibrous  and  mus- 
cular, and  mucous. 

The  External  or  Serous  Coat  (tunica  serosa  vesicae  felleae)  is  derived  from  the  peri- 
toneum; it  completely  invests  the  fundus,  but  covers  the  body  and  neck  only  on 
their  under  surfaces. 

The  Fibro -muscular  Coat  (tunica  muscularis  vesicae  felleae)  is  a  thin  but  strong 
layer  which  forms  the  framework  of  the  sac,  consisting  of  dense  fibrous  tissue  which 
interlaces  in  all  directions  and  is  mixed  with  plain  muscular  fibres  which  are  dis- 
posed chiefly  in  a  longitudinal  direction,  a  few  running  transversely. 

The  Internal  or  Mucous  Coat  (tunica  mucosa  vesicae  felleae)  is  loosely  connected 
with  the  fibrous  layer.  It  is  generally  tinged  with  a  yellowish-brown  color,  and 
is  everywhere  elevated  into  minute  rugae,  by  the  union  of  which  numerous  meshes 
are  formed,  the  depressed  intervening  spaces  having  a  polygonal  outline.  The 
meshes  are  smaller  at  the  fundus  and  neck,  being  most  developed  about  the  centre 
of  the  sac.  Opposite  the  neck  of  the  gall-bladder  the  mucous  membrane  projects 
inward  in  the  form  of  oblique  ridges  or  folds,  forming  a  sort  of  screw-like  or  spiral 
valve  (Fig.  966). 

The  mucous  membrane  is  covered  with  columnar  epithelium,  and  secretes  an 
abundance  of  thick  viscid  mucus;  it  is  continuous  through  the  hepatic  duct  with 
the  mucous  membrane  lining  the  ducts  of  the  liver,  and  through  the  ductus  com- 
munis  choledochus  with  the  mucous  membrane  of  the  duodenum. 

The  Cystic  Duct  (ductus  cysticus). — The  cystic  duct,  the  smallest  of  the  three 
biliary  ducts,  is  about  an  inch  and  a  half  in  length.  It  passes  obliquely  downward 
and  to  the  left  from  the  neck  of  the  gall-bladder,  and  joins  the  hepatic  duct  to  form 
the  common  bile-duct.  It  lies  in  the  gastro-hepatic  ornentum  in  front  of  the  portal 


--% GALL-BLADDER 


_\ _  HEPATIC 

DUCT 


COMMON 
DUCT 


SPHINCTER  OF 
COMMON    DUCT 


PANCREATIC 
DUCT 


AMPULLA 
OF  VATER 


WALL  OF 
DUODENUM 


Fir,.  967. — The  biliary  ducts.     (Schematic.) 
(Poirier  and  Charpy.) 


FIG.  968. — The  sphincter  of  the  common  bile-duct. 
(Poirier  and  Charpy.) 


vein,  the  hepatic  artery  lying  to  its  left 
side.  The  mucous  membrane  lining  its  in- 
terior is  thrown  into  a  series  of  crescentic 
folds,  from  five  to  twelve  in  number,  similar 
to  those  found  in  the  neck  of  the  gall-blad- 
der. They  project  into  the  duct  in  regular 
succession,  and  are  directed  obliquely  round 
the  tube,  presenting  much  the  appearance 
of  a  continuous  spiral  valve  (valvula  spiralis 
[Heisteri])  (Fig.  966).  When  the  duct  is 
distended,  the  spaces  between  the  folds 
are  dilated,  so  as  to  give  to  its  exterior 
a  sacculated  appearance. 

The  Ductus  Communis  Choledochus  or 
Common  Bile-duct  (ductus  choledochus) 
Figs.  966  and  967) ,  the  largest  of  the  three, 


1352 


THE  ORGANS  OF  DIGESTION 


is  the  common  excretory  duct  of  the  liver  and  gall-bladder.  It  is  about  three 
inches  in  length,  is  of  the  diameter  of  a  goose-quill,  and  is  formed  by  the  junction 
of  the  cystic  and  hepatic  ducts. 

It  descends  within  the  two  layers  and  along  the  right  border  of  the  lesser  omen- 
turn  behind  the  first  portion  the  duodenum,  in  front  of  the  portal  vein,  and  to  the 
right  of  the  hepatic  artery  (Fig.  872);  then  passes  either  between  the  pancreas 
and  descending  portion  of  the  duodenum,  or  through  the  head  of  the  pancreas. 
In  fifty-eight  dissections  Prof.  Biingner  found  that  it  passed  through  the  pan- 
creas fifty-five  times  and  over  the  head  only  three  times.  Even  when  it  "passes 
through  the  pancreas  it  almost  always  joins  the  pancreatic  duct  outside  of  the 
gland.  It  descends  by  the  right  side  of  the  pancreatic  duct  and  passes  with  it 
obliquely  through  the  wall  of  the  descending  portion  of  the  duodenum  between 
the  mucous  and  muscular  coats  in  the  submucous  tissue  for  one-half  to  three- 


CIRCULAR 
MUSCULAR 

FIBRES 
MUCOUS 
COAT 


LONGITUDINAL 
MUSCULAR  FIBRES 

ACCESSORY 

PANCREATIC 

DUCTS 


BILE-DUCT 

PANCREATIC 
DUCT 


FIG.  970. — Diagram  showing  the  bile 
and  pancreatic  ducts  piercing  the  wall  of 
the  duodenum  obliquely.  (Cunningham.) 

quarters  of  an  inch.  The  two 
ducts  usually  unite  just  before 
opening  into  the  duodenum 
(Figs.  967,  968,  and  970),  but 
may  remain  independent 
throughout  (in  about  10  per 
cent,  of  individuals).  The 
diverticulum  ampulla  of  Vater 
(Fig.  967)  is  the  conical  cavity 
formed  by  the  fusion  of  the 
two  ducts,  and  is  much  larger 
than  the  opening  on  the  bile- 
papilla.  It  averages  3.9  mm. 

in  length.  The  average  'diameter  of  the  orifice  is  2.5  mm.  (Opie).  The  two 
ducts  open  by  a  common  orifice  if  there  is  an  ampulla,  or  by  two  separate  orifices 
if  there  is  no  ampulla,  upon  the  summit  of  a  papilla,  situated  at  the  inner  side  of 
the  descending  portion  of  the  duodenum,  a  little  below  its  middle  and  about  three 
or  four  inches  below  the  pylorus.  Circular  muscular  fibres,  continuous  with  the 
longitudinal  fibres  of  the  ducts,  surround  the  termination  of  the  two  ducts  in  the 
ampulla.  These  fibres  constitute  the  so-called  sphincter  of  Oddi  (Fig.  968). 

Structure. — The  coats  of  the  large  biliary  ducts  are  an  external  or  fibrous  and  an 
internal  or  mucous.  The  fibrous  coat  is  composed  of  strong  fibro-areolar  tissues, 
with  a  certain  amount  of  muscular  tissue  arranged,  for  the  most  part,  in  a  circular 
manner  around  the  duct.  The  mucous  coat  is  continuous  with  the  lining  mem- 


FIG.  969. — Part  of  the  bile-duct  and  the  pancreatic  ducts.  C 
and  B,  calculi;  Sa,  Santorini's  duct;  P,  pancreatic  duct;  ///  and 
IV,  ducts  from  the  right  and  left  lobes  of  the  liver;  //,  cystic  duct; 
C,  gall-bladder;  A,  common  duct.  (Robinson.) 


THE  EXCRETORY  APPARATUS  OF  THE  LIVER  1353 

brane  of  the  hepatic  ducts  and  gall-bladder,  and  also  with  that  of  the  duode- 
num; and,  like  the  mucous  membrane  of  these  structures,  its  epithelium  is  of  the 
columnar  variety.  It  is  provided  with  numerous  mucous  glands,  which  are  lobu- 
lated  and  open  by  minute  orifices  scattered  irregularly  in 'the  larger  ducts.  It  is 
questionable  if  the  smallest  biliary  ducts,  which  lie  in  the  interlobular  spaces,  have 
any  coats.  Heidenhain  thinks  they  have  a  connective-tissue  coat,  in  which  are 
muscle-cells  arranged  both  circularly  and  longitudinally,  and  an  epithelial  layer, 
consisting  of  short  columnar  cells. 

Dimensions  of  the  Bile-ducts. — The  hepatic  duct  is  about  two  inches  in  length, 
and  its  lumen  is  one-sixth  of  an  inch  in  diameter.  The  cystic  duct  is  about  one 
and  one-half  inches  in  length,  and  its  lumen  is  one-twelfth  of  an  inch  in  diameter. 
The  common  duct  is  about  three  inches  in  length,  and  its  lumen  is  one-quarter  of 
an  inch  in  diameter.  The  duodenal  opening  is  smaller  than  the  common  duct. 
The  ducts  are  capable  of  considerable  distention,  but  the  duodenal  opening  can- 
not be  dilated  (Hyrtl).. 

Blood-vessels,  Lymphatics,  and  Nerves  of  the  Gall-bladder  and  Bile-ducts. — The 
cystic  artery  (Fig.  421),  a  branch  from  the  right  division  of  the  hepatic,  supplies  the 
gall-bladder  and  cystic  duct  with  blood.  It  passes  along  the  cystic  duct,  and  on 
reaching  the  gall-bladder  divides  into  an  upper  branch  and  a  lower  branch.  The 
upper  branch  lies  between  the  gall-bladder  and  the  liver  and  sends  branches  to  each. 
The  lower  branch  is  between  the  peritoneum  and  the  wall  of  the  gall-bladder. 
The  cystic  veins  empty  into  the  portal  vein.  The  common  duct  receives  branches 
from  the  superior  pancreatico-duodenal  artery.  There  is  a  submucous  lymphatic  net- 
work and  a  muscular  lymphatic  network.  The  lymphatics  are  much  less  numer- 
ous at  the  fundus  of  the  gall-bladder  than  at  the  neck  or  in  the  extra-hepatic  ducts. 
The  collecting  trunks  (Fig.  504)  end  in  glands  along  the  cystic  and  common  ducts 
and  these  glands  are  in  communication  with  the  duodenal  lymphatics  and  the 
lymphatics  from  the  head  of  the  pancreas.  The  nerves  of  the  gall-bladder  and 
bile-ducts  come  from  the  coeliac  plexus  of  the  sympathetic.  The  adjacent  peri- 
toneum is  plentifully  supplied  with  nerves  (Robinson). 

The  Bile  (fel) . — The  bile  is  a  reddish-brown  or  greenish  fluid.  It  contains  pig- 
ments (bilirubin  and  biliverdin),  fats  and  soaps,  cholesterin,  sodium  salts  of  glyco- 
cholic  and  taurocholic  acid,  lecithin,  and  nucleo-albumin  furnished  by  the  mucous 
membrane.  There  are  also  present  CO2;  chlorides,  carbonates,  phosphates,  and 
sulphates  of  the  alkalies  and  of  calcium,  and  iron.  The  amount  normally 
secreted  is  from  one  pint  to  one  and  one-half  pints  in  the  twenty-four  hours. 

Surface  Relations. — The  liver  is  situated  in  the  right  hypochondriac  and  the  epigastric 
regions,  and  is  moulded  to  the  arch  of  the  Diaphragm.  In  the  greater  part  of  its  extent  it  lies 
under  cover  of  the  lower  ribs  and  their  cartilages,  but  in  the  epigastric  region  it  comes  in  con- 
tact with  the  abdominal  wall,  in  the  subcostal  angle.  The  upper  limit  of  the  right  lobe  of  the 
liver  may  be  defined  in  the  middle  line  by  the  junction  of  the  mesosternum  with  the  ensiform 
cartilage;  on  the  right  side  the  line  must  be  carried  upward  as  far  as  the  fifth  rib  cartilage 
in  the  line  of  the  nipple  and  then  downward  to  reach  the  seventh  rib  at  the  side  of  the  chest. 
The  upper  limit  of  the  left  lobe  may  be  defined  by  continuing  this  line  to  the  left  with  an  inclina- 
tion downward  to  a  point  about  two  inches  to  the  left  of  the  sternum  on  a  level  with  the  sixth 
left  costal  cartilage.  The  lower  limit  of  the  liver  may  be  indicated  by  a  line  drawn  half  an  inch 
below  the  lower  border  of  the  thorax  on  the  right  side  as  far  as  the  ninth  right  costal  cartilage, 
and  thence  obliquely  upward  across  the  subcostal  angle  to  the  eighth  left  costal  cartilage.  A 
slight  curved  line  with  its  convexity  to  the  left  from  this  point— i.  e.,  the  eighth  left  costal 
cartilage— to  the  termination  of  the  line  indicating  the  upper  limit  will  denote  the  left  margin  of 
the  liver.  The  fundus  of  the  gall-bladder  approaches  the  surface  behind  the  anterior  extremity 
of  the  ninth  costal  cartilage,  close  to  the  outer  margin  of  the  Right  rectus  muscle. 

It  must  be  remembered  that  the  liver  is  subject  to  considerable  alterations  in  position,  and 
the  student  should  make  himself  acquainted  with  the  different  circumstances  under  which  this 
occurs,  as  they  are  of  importance  in  determining  the  existence  of  enlargement  or  other  diseases 
of  the  organ. 


1354  THE  ORGANS  OF  DIGESTION 

Its  position  varies  according  to  the  posture  of  the  body.  In  the  erect  position  in  the  adult 
male  the  edge  of  the  liver  projects  about  half  an  inch  below  the  lower  edge  of  the  right  costal 
cartilages,  and  its  anterior  border  can  be  often  felt  in  this  situation  if  the  abdominal  wall  is  thin. 
In  the  supine  position  the  liver  gravitates  backward  and  recedes  above  the  lower  margin  of  the 
ribs,  and  cannot  then  be  detected  by  the  finger.  In  the  prone  position  it  falls  forward,  and  can 
then  generally  be  felt  in  a  patient  with  loose  and  lax  abdominal  walls.  Its  position  varies  also 
with  the  ascent  or  descent  of  the  Diaphragm.  In  a  deep  inspiration  the  liver  descends  below 
the  ribs;  in  expiration  it  is  raised  behind  them.  Again,  in  emphysema,  where  the  lungs  are 
distended  and  the  Diaphragm  descends  very  low,  the  liver  is  pushed  down;  in  some  other  dis- 
eases, as  phthisis,  where  the  Diaphragm  is  much  arched,  the  liver  rises  very  high  up.  Pressure 
from  without,  as  in  tight  lacing,  by  compressing  the  lower  part  of  the  chest,  displaces  the  liver 
considerably,  its  anterior  edge  often  extending  as  low  as  the  crest  of  the  ilium;  and  its  convex 
surface  is  often  at  the  same  time  deeply  indented  from  the  pressure  of  the  ribs.  Again,  its  posi- 
tion varies  greatly  according  to  the  greater  or  less  distention  of  the  stomach  and  intestines. 
When  the  intestines  are  empty  the  liver  descends  in  the  abdomen,  but  when  they  are  distended 
it  is  pushed  upward.  Its  relations  to  surrounding  organs  may  also  be  changed  by  the  growth  of 
tumors  or  by  collections  of  fluid  in  the  thoracic  or  abdominal  cavities. 

Surgical  Anatomy. — Movable  liver  or  hepatoptosis  is  a  rare  condition,  in  which  the  liver 
moves  or  can  be  moved  from  its  normal  position.  It  is  due  to  lessened  tone  of  the  abdominal 
muscles  and  relaxation  of  the  liver  supports.  In  movable  liver  the  organ  may  be  rotated  on  its 
vertical  axis  or  on  its  transverse  axis.  Tongue-like  lobes  have  been  referred  to.  On  account  of 
its  large  size,  its  fixed  position,  and  its  friability,  the  liver  is  more  frequently  ruptured  than 
any  of  the  abdominal  viscera.  The  rupture  may  vary  considerably  in  extent,  from  a  slight 
scratch  to  an  extensive  laceration  completely  through  its  substance,  dividing  it  into  two  parts. 
Sometimes  an  internal  rupture  without  laceration  of  the  peritoneal  covering  takes  place,  and 
such  injuries  are  most  susceptible  of  repair;  but  small  tears  of  the  surface  may  also  heal;  when, 
however,  the  laceration  is  extensive,  death  usually  takes  place  from  hemorrhage,  on  account 
of  the  fact  that  the  hepatic  veins  are  contained  in  rigid  canals  in  the  liver-substance  and  are 
unable  to  contract,  and  are  moreover  unprovided  with  valves.  The  liver  may  also  be  torn 
by  the  end  of  a  broken  rib  perforating  the  Diaphragm.  The  liver  may  be  injured  by  stabs 
or  other  punctured  wounds,  and  when  these  are  inflicted  through  the  chest-wall  both  pleural 
and  peritoneal  cavities  may  be  opened  up  and  both  lung  and  liver  be  wounded.  In  cases  of 
wound  of  the  liver  from  the  front,  protrusion  of  a  part  of  this  viscus  may  take  place,  but  can  gen- 
erally easily  be  replaced.  In  cases  of  laceration  of  the  liver,  when  there  is  evidence  that  bleeding 
is  going  on,  the  abdomen  must  be  opened,  the  laceration  sought  for,  and  the  bleeding  arrested. 
This  may  be  done  temporarily  by  introducing  the  forefinger  into  the  foramen  of  Winslow  and 
placing  the  thumb  on  the  gastro-hepatic  omentum  and  compressing  the  hepatic  artery  and  portal 
vein  between  the  two.  Any  bleeding  points  can  then  be  seen.  Bleeding  is,  if  possible,  arrested 
by  suture  ligatures.  The  edges  of  a  small  laceration  are  simply  brought  together  and  sutured  by 
means  of  a  blunt,  curved,  round  needle  passed  from  one  side  of  the  wound  to  the  other.  All  sutures 
must  be  passed  before  any  are  tied,  and  this  must  be  done  with  the  greatest  gentleness,  as  the  liver 
substance  is  very  friable.  If  suture  fails  the  actual  cautery  may  succeed.  When  the  laceration  is  ex- 
tensive, the  liver  is  sutured  to  the  abdominal  wall  to  hold  it  firm  when  pressure  is  applied,  and  then 
the  laceration  is  packed  with  a  piece  of  iodoform  gauze,  the  end  of  which  is  allowed  to  hang  out 
of  the  external  wound.  Abscess  of  the  liver  is  of  not  infrequent  occurrence,  and  may  open  in  many 
different  ways  on  account  of  the  relations  of  this  viscus  to  other  organs.  Thus  it  may  burst  into 
the  lung,  the  pus  being  coughed  up,  or  into  the  stomach;  the  pus  perhaps  being  vomited,  it  may 
burst  into  the  colon  or  into  the  duodenum,  or,  by  perforating  the  Diaphragm,  it  may  empty 
itself  into  the  pleural  cavity.  Frequently  it  makes  its  way  forward,  and  points  on  the  anterior 
abdominal  wall,  and  finally  it  may  burst  into  the  peritoneal  or  pericardiac  cavity.  Abscesses 
of  the  liver  require  opening,  and  this  must  be  done  by  an  incision  in  the  abdominal  wall,  in  the 
thoracic  wall,  or  in  the  lumbar  region,  according  to  the  direction  in  which  the  abscess  is  tracking. 
The  incision  through  the  abdominal  wall  is  to  be  preferred  when  possible.  The  abdominal  wall 
is  incised  over  the  swelling,  and  unless  the  peritorieum  is  adherent,  gauze  is  packed  all  around 
the  exposed  liver  surface  and  the  abscess  opened,  if  deeply  seated,  preferably  by  the  thermo- 
'  cautery.  Hydatid  cysts  are  more  often  found  in  the  liver  than  in  any  other  of  the  viscera.  The 
reason  of  this  is  not  far  to  seek.  The  embryo  of  the  egg  of  the  tsenia  echinococcus  being  liberated 
in  the  stomach  by  the  disintegration  of  its  shell,  bores  its  way  through  the  gastric  walls  and 
usually  enters  a  blood-vessel,  and  is  carried  by  the  blood-stream  to  the  hepatic  capillaries,  where 
its  onward  course  is  arrested,  and  where  it  undergoes  development  into  the  fully  formed  hydatid. 
Tumors  of  the  liver  have  recently  been  subjected  to  surgical  treatment  by  removal  of  a  portion 
of  the  organ.  The  abdomen  is  opened  and  the  diseased  portion  of  liver  exposed;  the  circulation 
is  controlled  by  compressing  the  portal  vein  and  the  hepatic  artery  in  the  gastro-hepatic  omen- 
tum and  a  wedge-shaped  portion  of  liver  containing  the  tumor  removed;  the  divided  vessels 
are  ligated  and  the  cut  surfaces  brought  together  and  sutured  in  the  manner  directed  above. 

When  the  gall-bladder  or  one  of  its  main  ducts  is  ruptured,  which  may  occur  independently 
of  laceration  of  the  liver,  death  usually  occurs  from  peritonitis.  If  the  symptoms  have  led  to 


THE  PANCREAS  1355 

the  performance  of  a  laparotomy  and  a  small  rent  is  found,  it  should  be  sutured;  if  an  exten- 
sive opening  is  found  the  gall-bladder  should  be  removed.  If  the  cystic  duct  is  torn,  its  intes- 
tinal end  must  be  closed  and  the  gall-bladder  removed.  In  rupture  of  either  of  the  other 
ducts,  simply  provide  for  free  drainage. 

The  gall-bladder  may  become  distended  with  bile  in  cases  of  obstruction  of  its  duct  or  of  the 
common  bile-duct,  or  it  may  become  distended  from  a  collection  of  gall-stones  within  its  interior, 
thus  forming  a  large  tumor.  The  swelling  due  to  distention  with  bile  is  pear-shaped,  and  pro- 
jects downward  and  forward  to  the  umbilicus.  It  moves  with  respiration,  since  it  is  attached  to 
the  liver.  To  relieve  a  patient  of  gall-xfom's,  the  gall-bladder  must  be  opened  and  the  gall-stones 
removed.  The  operation  is  performed  by  an  incision  two  or  three  inches  long  in  the  right  semi- 
lunar  line,  commencing  at  the  costal  margin.  The  peritoneal  cavity  is  opened,  and,  the  tumor 
having  been  found,  gauze  pads  are  packed  around  it  to  protect  the  peritoneal  cavity,  and  it  is 
aspirated.  When  the  contained  fluid  has  been  evacuated  the  flaccid  bladder  is  drawn  out  of 
the  abdominal  wound  and  its  wall  incised  to  the  extent  of  an  inch;  any  gall-stones  in  the 
bladder  are  now  removed  and  the  interior  of  the  sac  sponged  dry.  If  the  case  is  one  of 
obstruction  of  the  duct,  an  attempt  must  be  made  to  dislodge  the  stone  by  manipulation  through 
the  wall  of  the  duct;  or  it  may  be  crushed  from  without  by  the  fingers  or  carefully  padded  for- 
ceps. If  this  does  not  succeed,  the  safest  plan  is  to  incise  the  duct,  extract  the  stone,  close 
the  incision  in  the  duct  by  fine  sutures  in  two  layers  and  employ  drainage.  After  all  obstruction 
has  been  removed,  four  courses  are  open  to  the  surgeon:  1.  The  wound  in  the  gall-bladder 
may  be  at  once  sewed  up,  the  organ  returned  into  the  abdominal  cavity,  and  the  external  incision 
closed.  2.  The  edges  of  the  incision  in  the  gall-bladder  may  be  sutured  to  the  fascia  of  the  ex- 
ternal wound,  and  a  fistulous  communication  established  between  the  gall-bladder  and  the  exte- 
rior; this  fistulous  opening  usually  closes  in  the  course  of  a  few  weeks.  3.  The  gall-bladder  may 
be  connected  with  the  intestinal  canal,  preferably  the  duodenum,  by. means  of  a  lateral  anasto- 
mosis; this  is  known  as  cholecystenterostomy.  4.  The  gall-bladder  may  be  completely  removed 
(cholecystectomy).  Plan  2  is  usually  followed.  Plan  4  is  employed  when  the  coats  of  the 
gall-bladder  are  seriously  diseased.  Plan  2  is  employed  in  obstruction  of  the  common  duct  by 
malignant  disease. 

If  a  stone  blocks  the  diverticulum  of  Vater  and  if  the  common  bile-duct  and  the  pancreatic 
duct  empty  into  the  diverticulum,  it  is  evident  that  both  ducts  will  be  blocked.  It  has  been 
demonstrated  that  in  such  a  case  the  pressure  urging  the  bile  onward  is  sufficient  to  overcome 
the  pressure  in  the  pancreatic  duct  and  drive  bile  into  the  ducts  of  the  pancreas,  the  result,, 
perhaps,  being  disastrous  inflammation  of  the  pancreas. 

.  Septic  trouble  arises  more  rapidly  when  a  stone  is  blocked  in  the  duct  than  when  stones  merely 
block  the  gall-bladder,  because  the  first-named  part  is  richer  in  lymphatics  (Murphy). 


THE  PANCREAS  (Figs.  971,  972,  973,  974). 

Dissection. — The  pancreas  may  be  exposed  for  dissection  in  three  different  ways:  1.  By 
raising  the  liver,  drawing  down  the  stomach,  and  tearing  through  the  gastro-hepatic  omentum 
and  the  ascending  layer  of  the  transverse  mesocolon.  2.  By  raising  the  stomach,  the  arch  of 
the  colon,  and  great  omentum,  and  then  dividing  the  inferior  layer  of  the  transverse  mesocolon 
and  raising  its  ascending  layer.  3.  By  dividing  the  two  layers  of  peritoneum,  which  descend 
from  the  great  curvature  of  the  stomach  to  form  the  great  omentum;  turning  the  stomach 
upward,  and  then  cutting  through  the  ascending  layer  of  the  transverse  mesocolon  (see  Fig.  866). 

The  Pancreas  (xav-xpeaz,  all  flesh)  is  a  compound  racemose  gland,  analo- 
gous in  its  structure  to  the  salivary  glands,  though  softer  and  less  compactly 
arranged  than  those  organs.  It  is  long  and  irregularly  prismatic  in  shape,  and 
has  been  compared  to  a  human  or  a  dog's  tongue ;  it  is  of  reddish-white  color. 
Its  right  extremity  being  broad,  is  called  the  head.  The  right  half  of  the  head 
above  is  continuous  with  the  neck,  which  connects  the  head  to  the  main  portion 
of  the  organ,  the  body.  The  neck  is  a  slight  constriction  or  thin  part  of  the  gland, 
placed  in  front  of  the  portal  vein,  and  connecting  the  head  to  the  body.  The  left 
half  of  the  head  is  separated  from  the  neck  by  a  notch,  the  incisura  pancreaticus. 
The  body  of  the  gland  gradually  tapers  into  an  extremity  directed  to  the  left,  and 
called  the  tail.  The  pancreas  is  placed  transversely  across  the  posterior  wall  of 
the  abdomen,  at  the  back  of  the  epigastric  and  left  hypochondriac  regions.  Its 
length  varies  from  five  to  six  inches,  its  breadth  is  an  inch  and  a  half,  and  its  thick- 
ness from  half  an  inch  to  an  inch,  being  greater  at  its  right  extremity  and  along 


1356 


THE  ORGANS  OF  DIGESTION 


its  upper  border.     Its  weight  varies  from  two  to  three  and  a  half  ounces,  but  it 
may  reach  six  ounces. 


HEPATIC  DUCT 
CYSTIC  DUCT 


CANAL  OF 
SANTORINI 


SUPERIOR   MESENTERIC  VEIN 

FIG.  971. — Position  and  relations  of  pancreas. 


Gastric  artery 


Lower  end  of  oesophagus. 


Inferior  mesenteric 
artery. 


tpcrior  mesenteric 
artery. 


Spermatic  vessels. 


FIG.  972. — The  duodenum  and  pancreas.  The  liver  has  been  lifted  up  and  the  greater  part  of  the  stomach 
removed:  a}  portal  vein;  6,  hepatic  duct;  c,  cystic  duct;  d,  hepatic  artery;  e,  right  suprarenal  capsule; 
/,  pyloric  orifice  ;  g,  right  gastro-epiploic  artery  ;  h,  superior  mesenteric  vein  ;  i,  left  crus  of  diaphragm  ;  j,  left 
suprarenal  capsule  ;  k,  splenic  vein  ;  /,  splenic  artery;  m,  duodeno-jejunal  junction  ;  A,  B,  c,  D,  the  four  portions 
of  the  duodenum.  (Testut.) 


THE  PANCREAS  1357 

The  Right  Extremity  or  Head  of  the  Pancreas  (caput  pancreatis)  (Fig.  971) 
is  shaped  like  the  head  of  a  hammer,  being  elongated  both  above  and  below;  it 
is  flattened  from  before  backward,  and  conforms  to  the  whole  concavity  of  the 
duodenum,  which  is  slightly  overlapped  by  it.  The  anterior  surface  near  its  left 
border  exhibits  a  notch,  the  incisura  pancreatis,  which  contains  the  superior  mesen- 
teric  vessels.  The  notch  marks  the  separation  of  the  inferior  portion  of  the  head, 
which  is  known  as  the  uncinate  process  of  Winslow  (processus  uncinatus  [Winslowi]) , 
which  rests,  below,  upon  the  inferior  portion  of  the  duodenum,  and,  above,  is 
pushed  up  back  of  the  upper  portion.  The  lower  end  of  the  head  is  crossed  by 
the  transverse  colon  and  its  mesocolon.  Behind,  the  head  of  the  pancreas  is  in 
relation  with  the  postcava,  the  left  renal  vein,  the  right  crus  of  the  Diaphragm, 
and  the  aorta.  The  common  bile-duct  descends  behind,  between  the  duodenum 
and  pancreas,  or  in  the  substance  of  the  gland;  and  the  pancreatico-duodenal 
artery  descends  in  front  between  the  same  parts.  The  head  of  the  pancreas  is 
closely  adherent  to  the  duodenum. 


FIG.  973. — Duodenal  orifice  of  the  pancreatic  duct  and  of  the  canal  of  Santorini. 

The  Neck  of  the  Pancreas  is  about  an  inch  long,  and  passes  upward  and  for- 
ward to  the  left,  having  the  first  part  of  the  duodenum  above  it,  and  the  ter- 
mination of  the  fourth  portion  below.  It  lies  in  front  of  the  commencement  of 
the  portal  vein,  and  is  grooved  on  the  right  by  the  gastro-duodenal  and  superior 
pancreatico-duodenal  arteries.  The  pylorus  lies  just  above  it. 

The  Body  (corpus  pancreatis)  and  Tail  (cauda  pancreatis)  of  the  Pancreas  are 
somewhat  prismatic  in  shape,  and  have  three  surfaces:  anterior,  posterior,  and 
inferior. 

The  Anterior  Surface  (fades  anterior). — The  anterior  surface  is  somewhat  con- 
cave, and  is  covered  by  the  posterior  surface  of  the  stomach  which  rests  upon  it, 
the  two  organs  being  separated  by  the  lesser  sac  of  the  peritoneum.  At  its  right 
extremity  there  is  a  well-marked  prominence,  called  by  His  the  omental  tuberosity 
(tuber  omentale). 

The  Posterior  Surface  (fades  posterior). — The  posterior  surface  is  separated  from 
the  vertebral  column  by  the  aorta,  the  splenic  vein,  the  left  kidney  and  its  vessels, 
the  left  suprarenal  capsule,  the  pillars  of  the  Diaphragm,  and  the  origin  of  the 
superior  mesenteric  artery. 

The  Inferior  Surface  (fades  inferior)  (Fig.  972). — The  inferior  surface  is  narrow, 
and  lies  upon  the  duodeno-jejunal  flexure  and  on  some  coils  of  the  jejunum;  its  left 
extremity  rests  on  the  splenic  flexure  of  the  colon. 

The  Superior  Border  (margo  superior)  (Fig.  972). — The  superior  border  of  the 
body  is  blunt  and  flat  to  the  right;  narrow  and  sharp  to  the  left,  near  the  tail.  It 
commences  to  the  right  in  the  omental  tuberosity,  and  is  in  relation  with  the 
coeliac  axis,  from  which  the  hepatic  artery  courses  to  the  right  just  above  the  gland, 
while  the  splenic  branch  runs  in  a  groove  along  this  border  to  the  left. 


1358 


THE  ORGANS  OF  DIGESTION 


The  Anterior  Border  (margo  anterior). — The  anterior  border  is  the  position  where 
the  two  layers  of  the  transverse  mesocolon  separate;  the  one  passing  upward  in 
front  of  the  anterior  surface,  the  other  backward  below  the  inferior  surface 
(Fig.  866). 

The  lesser  end  or  tail  of  the  pancreas  is  narrow;  it  extends  to  the  left  as  far  as 
the  lower  part  of  the  inner  aspect  of  the  spleen,  and  its  end  is  directed  upward  and 
to  the  left  (Fig.  972). 

Birmingham  describes  the  body  of  the  pancreas  as  projecting  forward  as  a 
prominent  ridge  into  the  abdominal  cavity  and  forming  a  sort  of  shelf  on  which  the 
stomach  lies.  He  says:  "The  portion  of  the  pancreas  to  the  left  of  the  middle  line 
has  a  very  considerable  antero-posterior  thickness ;  as  a  result  the  anterior  surface 
is  of  considerable  extent,  it  looks  strongly  upward,  and  forms  a  large  and  important 
part  of  the  shelf.  As  the  pancreas  extends  to  the  left  toward  the  spleen  it  crosses 
the  upper  part  of  the  kidney,  and  is  so  moulded  on  to  it  that  the  top  of  the  kidney 
forms  an  extension  inward  and  backward  of  the  upper  surface  of  the  pancreas  and 
extends  the  bed  in  this  direction.  On  the  other  hand,  the  extremity  of  the  pan- 
creas comes  in  contact  with  the  spleen  in  such  a  way  that  the  plane  of  its  upper 
surface  runs  with  little  interruption  upward  and  backward  into  the  concave  gastric 
surface  of  the  spleen,  which  completes  the  bed  behind  and  to  the  left,  and,  running 
upward,  forms  a  partial  cap  for  the  wide  end  of  the  stomach."1  An  occasional 
anomaly  is  a  pancreas  prolonged  in  front  of  the  duodenum  or  actually  embracing 
it  (annular  pancreas). 


RECTUS    MUSCLE. 


f8th  Costal  Cartilage. 

7th  Costal  Cartilage. 


7th  Rib. 


8th  Rib. 


—9th  Rib. 


DIAPHRAGM. 


Abdominal  Aorta. 


mhRib.    nth  Rib. 


FIG.  974. — Transverse  section  through  the  middle  of  the  first  lumbar  vertebra,  showing  the  relations  of  the 

pancreas.      (Braune.) 

Peritoneal  Relations  (Fig.  866). — The  transverse  mesocolon  is  attached  to  the 
anterior  border  of  the  pancreas,  from  the  tail  to  the  neck  of  the  gland,  and  the  two 
layers  of  the  mesocolon  separate.  The  anterior  layer  which  comes  from  the  lesser 
peritoneum  covers  part  of  the  anterior  surface  and  the  superior  surface;  the  poste- 
rior layer,  which  comes  from  the  greater  omentum,  covers  the  rest  of  the  anterior 
surface  and  the  inferior  surface.  The  posterior  surface  is  devoid  of  peritoneum. 

1  Journal  of  Anatomy  and  Physiology,  vol.  xxxi.,  part  L,  p.  102. 


THE  PANCREAS  1359 

There  is  in  front  of  the  head  and  at  the  anterior  margin  a  narrow  strip  of  pancreas, 
which  remains  uncovered  by  peritoneum  and  which  corresponds  to  the  cellular 
tissue  of  the  mesocolon. 

The  principal  excretory  duct  of  the  pancreas,  called  the  pancreatic  duct  or  canal 
of  Wirsung  (ductus  pancreaticus  [Wirsungi])  (Figs.  969,  971,  and  973),  from  its 
discoverer,  extends  transversely  from  left  to  right  through  the  substance  of  the 
pancreas.  In  order  to  expose  it,  the  superficial  portion  of  the  gland  must  be 
removed.  It  commences  by  the  junction  of  the  small  ducts  of  the  lobules  situated 
in  the  tail  of  the  pancreas,  and,  running  from  left  to  right  through  the  body,  it  con- 
stantly receives  the  ducts  of  the  various  lobules  composing  the  gland.  Consider- 
ably augmented  in  size,  it  reaches  the  neck,  and  turning  obliquely  downward,  back- 
ward, and  to  the  right,  it  comes  into  relation  with  the  common  bile-duct,  lying  to 
its  left  side;  leaving  the  head  of  the  gland,  it  passes  very  obliquely  through  the 
mucous  and  muscular  coats  of  the  duodenum,  and  usually  terminates  by  an  orifice 
common  to  it  and  the  ductus  communis  choledochus  upon  the  summit  of  an  ele- 
vated papilla,  situated  at  the  inner  side  of  the  descending  portion  of  the  duodenum, 
three  or  four  inches  below  the  pylorus  (Figs.  967,  968,  and  970). 

Sometimes  the  pancreatic  duct  and  ductus  communis  choledochus  open  sep 
rately  into  the  duodenum  (Fig.  W)6):*  In  about  one-fifth  of  the  subjects  there  is  an 
accessory  duct,  which  is  given  off  from  the  canal  of  Wirsung  in  the  neck  of  the  pan-  /O 
creas  and  passes  horizontally  to  the  right  to  open  into  the  duodenum  about  an 
inch  above  the  orifice  of  the  main  duct.    This  is  known  as  the  duct  of  Santorini 
(ductus  pancreaticus  accessorius  [Santorini])  (Figs.  969.  970,  and  973). 

The  pancreatic  duct,  near  the  duodenum,  is  about  the  size  of  an  ordinary  quill; 
its  walls  are  thin,  consisting  of  two  coats,  an  external  fibrous  and  an  internal 
mucous ;  the  latter  is  smooth,  and  furnished  near  its  termination  with  a  few  scat- 
tered follicles. 

Structure. — In  structure,  the  pancreas  resembles  the  salivary  glands.  It  differs 
from  them,  however,  in  certain  particulars,  and  is  looser  and  softer  in  its  texture. 
It  is  not  enclosed  in  a  distinct  capsule,  but  is  surrounded  by  areolar  tissue,  which 
dips  into  its  interior,  and  connects  together  the  various  lobules  of  which  it  is  com- 
posed. Each  lobule,  like  the  lobules  of  the  salivary  glands,  consists  of  one  of  the 
ultimate  ramifications  of  the  main  duct,  terminating  in  a  number  of  caecal  pouches 
or  alveoli,  which  are  tubular  and  somewhat  convoluted.  The  minute  ducts  con- 
nected with  the  alveoli  are  narrow  and  lined  with  flattened  cells.  They  are  the 
secreting  end  tubules.  The  narrow  ducts  which  come  from  the  end  tubules  are 
lined  with  flat  epithelial  cells.  The  alveoli  are  almost  completely  filled  with  secret- 
ing cells,  so  that  scarcely  any  lumen  is  visible.  In  the  centre  of  the  end  tubules 
flat  cells  are  frequently  found.  They  are  continuations  into  the  tubules  of  the 
duct  epithelium.  These  cells  are  known  as  the  centro-acinar  cells  of  Langerhans. 
The  true  secreting  cells  which  line  the  wall  of  the  alveolus  are  very  characteristic. 
They  are  columnar  or  rounded  in  shape  and  present  two  zones:  an  outer  one 
clear  and  finely  striated  next  the  basement-membrane,  and  an  inner  granular 
one  next  the  lumen.  The  highly  refracting  granules  are  known  as  zymogen 
granules.  During  digestion  the  granules  gradually  disappear  and  the  cells  become 
clear.  During  fasting  the  granular  zone  occupies  more  than  one-half  of  the  cell 
(Szymonowicz).  In  some  secreting  cells  of  the  pancreas  is  a  spherical  mass, 
staining  more  easily  than  the  rest  of  the  cells;  this  is  termed  the  paranucleus,  and 
is  believed  to  be  an  extension  from  the  nucleus.  The  connective  tissue  among  the 
gland  tubules  and  alveoli  presents  in  certain  parts  collections  of  cells,  which  are 
termed  inter-alveolar  cell-islets,  intertubular  cell-masses  or  islands  of  Langerhans. 
Opie  points  out  that  they  are  most  common  in  the  splenic  end  of  the  pancreas. 
The  cells  of  the  islands  are  smaller  than  the  secreting  cells  of  the  alveoli,  and 
are  arranged  in  layers  with  intervening  spaces.  The  islands  are  surrounded  by 


1360  THE  ORGANS  OF  DIGESTION 

fine  connective  tissue.  The  spaces  in  the  islands  contain  capillaries.  There 
are  no  ducts  in  the  islands  of  Langerhans.  Their  function  is  to  furnish  the 
internal  secretion  of  the  pancreas. 

Blood-vessels,  Lymphatics,  and  Nerves. — The  arteries  of  the  pancreas  come  from 
the  superior  pancreatico -duodenal  branch  of  the  gastro -duodenal;  the  inferior  pan- 
creatico -duodenal  branch  of  the  superior  mesenteric;  the  inferior  pancreatic  branch  of 
the  superior  mesenteric;  pancreatic  branches  of  the  hepatic  and  pancreatic  branches 
of  the  splenic.  In  a  few  cases  a  large  artery,  the  pancreatica  magna,  accompanies 
the  pancreatic  duct.  In  most  cases  there  is  no  such  vessel.  The  veins  are  the 
anterior  pancreatico -duodenal  branch  of  the  superior  mesenteric;  the  posterior  pancre- 
atico-duodenal  branch  and  other  pancreatic  branches  of  the  portal;  and  pancreatic 
branches  of  the  splenic.  The  lymphatics  arise  in  a  network  about  the  lobules. 
Numerous  collecting  trunks  pass  to  the  surface  of  the  pancreas,  anastomose  with 
each  other,  and  enter  into  glands  about  the  pancreas.  The  splenic  glands  receive 
most  of  the  trunks.  Others  are  received  by  glands  along  the  aorta  (Sappey), 
glands  at  the  origin  of  the  superior  mesenteric  artery,  and  glands  along  the  pan- 
creatico-duodenal  vessels.1  The  nerves  come  from  the  coeliac,  superior  mesenteric, 
and  splenic  plexuses. 

The  Pancreatic  Juice. — The  pancreatic  juice  is  a  clear,  somewhat  viscid  alkaline 
liquid.  Its  specific  gravity  is  about  1030.  The  solid  .matter  consists  chiefly  of 
proteids,  and  amounts  to  about  10  per  cent,  of  a  sample  of  the  juice.2  The  juice 
contains  a  ferment  which  breaks  up  fat,  a  ferment  which  converts  starch  into 
sugar,  a  ferment  which  curdles  milk,  and  a  ferment  which  digests  proteid  material. 

Surface  Form. — The  pancreas  lies  in  front  of  the  second  lumbar  vertebra,  and  can  some- 
times be  felt,  in  emaciated  subjects,  when  the  stomach  and  colon  are  empty,  by  making  deep 
pressure  in  the  middle  line  about  three  inches  above  the  umbilicus. 

Surgical  Anatomy. — Of  late  years  our  knowledge  of  the  structure,  functions,  and  diseases 
of  the  pancreas  has  been  notably  increased,  and  surgeons  have  begun  to  operate  for  certain 
pancreatic  diseases.  It  is  occasionally  the  seat  of  cancer,  which  usually  affects  the  head  or 
duodenal  end,  and  therefore  often  speedily  involves  the  common  bile-duct,  leading  to  persistent 
jaundice.  Cancer  of  the  pancreas  may  be  primary  or  secondary.  Primary  sarcoma  is  very 
unusual;  secondary  sarcoma  is  more  common,  but  cancer  is  far  commoner  than  either  form  of 
sarcoma.  Adenoma  may  also  occur.  Cases  are  on  record  of  the  successful  removal  of  tumors  of 
the  pancreas,  but  the  operations  are  very  dangerous,  are  extremely  difficult,  and  are  seldom 
attempted.  The  pancreas  may  be  the  seat  of  syphilitic  or  tuberculous  disease.  As  a  result  of 
pancreatic  injury,  there  may  be  effusion  into  the  lesser  peritoneal  cavity.  The  lesser  cavity 
becomes  distended,  and  the  fluid  of  this  pseudo-cyst  may  contain  pancreatic  juice  (Jordan  Lloyd). 
True  cysts  of  the  pancreas  are  occasionally  found.  Pancreatic  cysts  may  result  from  blocking 
of  the  duct,  from  epithelial  proliferation,  from  traumatism  and  hemorrhage,  or  from  hydatid  dis- 
ease. Congenital  cysts  may  occur,  and  cystic  carcinoma  is  sometimes  encountered.  Cysts  of  the 
pancreas  may  present  in  the  epigastric  region  above  and  to  the  right  of  the  umbilicus.  The 
fluid  in  these  cysts  contains  some  of  the  pancreatic  secretion.  A  pancreatic  cyst  is  best  treated 
by  opening  the  abdomen,  suturing  the  cyst  to  the  skin,  opening  the  cyst  and  providing  for  drainage. 
Complete  extirpation  of  the  cyst  is  invariably  difficult  and  is  usually  impossible.  It  has  been 
said  that  the  pancreas  is  the  only  abdominal  viscus  which  has  never  been  found  in  a  hernia!  pro- 
trusion; but  even  this  organ  has  been  found,  in  company  with  other  viscera,  in  rare  cases  of 
diaphragmatic  hernia.  The  pancreas  has  been  known  to  become  invaginated  into  the  intestine, 
and  portions  of  the  organ  have  sloughed  pff.  In  cases  of  excision  of  the  pylorus  great  care  must 
be  exercised  to  avoid  wounding  the  pancreas,  as  the  escape  of  the  pancreatic  fluid  may  be  attended 
with  serious  and  even  with  fatal  results,  peritonitis  and  fat  necrosis,  and  gangrene  being  caused. 

Rupture  of  the  pancreas  as  a  solitary  result  of  traumatism  is  very  unusual,  but  is  more  common 
in  violent  injuries  which  rupture  the  liver  and  spleen  as  well.  An  injury  which  lacerates  the 
pancreas  and  permits  blood  and  pancreatic  juice  to  flow  into  the  lesser  peritoneal  cavity  is  usually 
rapidly  fatal,  but  may  not  be.  The  foramen  of  Winslow  may  be  occluded  by  inflammation,  and 
a  pseudo-cyst  may  form.  In  severe  laceration  of  the  pancreas  alone,  it  would  be  proper  to  open 
the  abdomen,  ligature  bleeding  vessels,  suture  the  pancreas,  and  drain  the  lesser  peritoneal  cavity 
posteriorly.  A  gunshot  wound  of  the  pancreas  requires  posterior  drainage.  Every  effort  must 

1  Poirier,  Cun6o,  and  Delamare  on  the  Lymphatics.     Edited  and  translated  by  Cecil  H.  Leaf. 
*  Robson  and  Moyniham  on  Diseases  of  the  Pancreas. 


THE  SPLEEN 


1361 


be  made  in  a  pancreatic  wound  to  rapidly  get  rid  of  pancreatic  fluid  by  drainage  from  jthe 
wound  area,  as  this  fluid  is  extremely  irritant  and  may  cause  gangrene. 

Inflammation  of  the  pancreas  is  due  to  infection.  Occasionally  it  seems  to  follow  the  entrance 
of  bile  into  the  pancreatic  duct,  because  of  plugging  of  the  ampulla  with  a  calculus  (Halsted, 
Opie).  Hemorrhage  into  the  pancreas  is  frequent  in  acute  pancreatitis,  and  fat  necrosis  is  common 
in  the  fat  of  the  mesentery,  subperitoneal  tissue,  omentum,  and  other  parts.  Acute  pancreatitis 
may  be  recovered  from  if  the  abdomen  is  opened,  the  pancreas  incised,  and  drainage  employed. 

In  chronic  interstitial  pancreatitis  of  the  head  of  the  pancreas  the  gall-duct  is  apt  to  become 
blocked,  and  the  disease  is  frequently  mistaken  for  cancer.  Cure  may  follow  opening  and  drain- 
age of  the  gall-bladder. 

•   THE  SPLEEN  (LIEN)  (Figs.  971,  972,  974). 

The  spleen  belongs  to  that  class  of  bodies  which  are  known  as  ductless  glands. 
It  is  probably  related  to  the  blood-vascular  system,  but  in  consequence  of  its 
anatomical  relationship  to  the  stomach  and  its  physiological  relationship  to  the 
liver  it  is  convenient  to  describe  it  in  this  section.  It  is  situated  principally  in  the 
posterior  portion 'of  the  left  hypochondriac  region,  its  upper  and  inner  extremity 
extending  into  the  epigastric  region;  lying  between  the  fundus  of  the  stomach 
and  the  Diaphragm.  If  the  abdomen  is  opened  a  spleen  of  ordinary  size  is  not 
visible  from  the  front,  as  it  is  placed  between  the  left  kidney,  Diaphragm,  and 
stomach.  It  moves  with  the  respiratory  movements  and  with  the  movements  of 
the  stomach.  It  is  the  largest  of  the  so-called  ductless  glands,  and  varies  greatly 
in  size.  Usually  it  measures  some  five  inches  in  length.  It  is  of  an  oblong, 
flattened  form,  soft,  of  very  brittle  consistence,  highly  vascular,  and  of  a  dark- 
purplish  color. 

Surfaces.     The  External  or  Phrenic  Surface  (Jades  diaphragmatica). — The  exter- 
nal or  phrenic  surface  is  convex,  smooth,  and  is  directed  upward,  backward,  and 
to  the  left,  except  at  its  upper  end,  where  it  is  directed  slightly  inward.     It  is  in 
relation  with  the  under  surface  of  the  Diaphragm,  which  separates  it  from  the 
eighth,  ninth,  tenth,  and  eleventh  ribs  of  the  left  side,  and  in  part  from  the  lower 
border  of  the  left  lung  and  pleura.      It  is 
to  be  remembered  that  not  only  are  the 
peritoneum  and  the  Diaphragm  between 
the  spleen  and  the  ribs,  but  also  the  cavity 
of  the  left  pleura  and  a  portion  of  the  left 
lung. 

The  Internal  Surface. — The  internal  sur- 
face is  concave,  and  divided  by  a  ridge 
into  an  anterior  or  larger,  and  a  posterior  or 
smaller  portion. 

The  Anterior  Portion  of  the  internal  sur- 
face or  the  gastric  surface  (fades  gastrica), 
which  is  directed  forward  and  inward,  is 
broad  and  concave,  and  is  in  contact  with 
the  posterior  wall  of  the  great  end  of  the 
stomach;  and  below  this  with  the  tail  of 
the  pancreas.  It  presents  near  its  inner 
border  a  long  fissure,  termed  the  hilum 
(hilus  lienis).  This  is  pierced  by  several 
irregular  apertures,  for  the  entrance  and 
exit  of  vessels  and  nerves. 

The  Posterior  Portion  of  the  internal 
surface  or  the  renal  surface  (fades  renalis] 
is  directed  inward  and  downward.  It  is 
somewhat  flattened,  does  not  reach  as  high 

86 


FIG.  975. — The  spleen,  showing  its  gastric  and 
renal  surfaces.     (Testut.) 


1362 


THE  ORGANS  OF  DIGESTION 


as^the  gastric  surface,  is  considerably  narrower  than  the  latter,  and  is  in  relation 
with  the  upper  part  of  the  outer  surface  of  the  left  kidney  and  occasionally  with 
the  left  suprarenal  capsule. 

The  upper  end  of  the  spleen  (extremitas  superior]  is  directed  inward,  toward  the 
vertebral  column,  where  it  lies  on  a  level  with  the  eleventh  thoracic  vertebra.  The 
lower  end  (extremitas  inferior) ,  sometimes  termed  the  basal  surface,  is  flat,  triangular 
in  shape,  and  rests  upon  the  splenic  flexure  of  the  colon  and  the  phreno-colic  liga- 
ment, and  is  generally  in  contact  with  the  tail  of  the  pancreas.  The  anterior  border 
(margo  anterior)  is  free,  sharp,  and  thin,  and  is  often  notched,  especially  below.  It 
separates  the  phrenic  surface  from  the  gastric  surface.  The  posterior  border  (margo 
posterior)  is  more  rounded  and  blunter  than  the  anterior.  It  separates  the  renal 
portion  of  the  internal  surface  from  the  phrenic  surface.  It  corresponds  to  the 
lower  border  of  the  eleventh  rib  and  lies  between  the  Diaphragm  and  left  kidney. 
The  internal  border  is  the  name  sometimes  given  to  the  ridge  which  separates  the 
renal  and  gastric  portions  of  the  internal  surface. 

The  spleen  is  surrounded  by  peritoneum,  except  at  the  hiluni  and  the  serous 
membrane,  is  firmly  adherent  to  its  capsule,  and  is  held  in  position  by  two  folds 
of  this  membrane:  one,  the  lieno-renal  ligament  (ligamentum  pfyrenicolienale)  (Figs. 
870  and  873),  is  derived  from  the  layers  of  peritoneum  forming  the  greater  and 
lesser  sacs,  where  they  come  into  contact  between  the  left  kidney  and  the  spleen. 
Between  its  two  layers  the  splenic  vessels  pass;  the  second,  the  gastro-splenic 
omentum  (ligamentum  gastrolienale) ,  also  formed  of  two  layers,  derived  from  the 
greater  and  lesser  sacs,  respectively,  where  they  meet  between  the  spleen  and 
stomach  (Fig.  873).  Between  these  two  layers  run  the  vasa  brevia  of  the 
splenic  artery  and  vein.  ,The  spleen  is  also  supported  by  the  phreno-colic  ligament 
(ligamentum  phrenicocolicum) ,  upon  which  its  lower  end  rests. 

The  size  and  weight  of  the  spleen  are  liable  to  very  extreme  variations  at  dif- 
ferent periods  of  life,  in  different  individuals,  and  in  the  same  individual  under 
different  conditions.  In  the  adult,  in  whom  it  attains  its  greatest  size,  it  is  usually 


FIG.  976. — Transverse  section  of  the  spleen,  showing  the  trabecular  tissue  and  the  splenic  vein  and 

its  tributaries. 


about  five  inches  in  length,  three  inches  in  breadth,  and  an  inch  or  an  inch  and  a 
half  in  thickness,  and  weighs  about  seven  ounces.  At  birth,  its  weight,  in  propor- 
tion to  the  entire  body,  is  almost  equal  to  what  is  observed  in  the  adult,  being  as 


THE  SPLEEN  1363 

1  to  350;  while  in  the  adult  it  varies  from  1  to  320  to  1  to  400.  In  old  age,  the  organ 
not  only  decreases  in  weight,  but  decreases  considerably  in  proportion  to  the 
entire  body,  being  as  1  to  700.  The  size  of  the  spleen  is  increased  during  and 
after  digestion,  and'  varies  considerably  according  to  the  state  of  nutrition  of  the 
body,  being  large  in  highly  fed,  and  small  in  starved  animals.  In  intermittent 
and  other  fevers  it  becomes  much  enlarged,  weighing  occasionally  from  eighteen 
to  twenty  pounds. 

Frequently  in  the  neighborhood  of  the  spleen,  and  especially  in  the  gastro- 
splenic  and  great  omenta,  small  nodules  of  splenic  tissue  may  be  found,  either 
isolated,  or  connected  to  the  spleen  by  thin  bands  of  splenic  tissue.  Every  such 
nodule  is  known  as  a  supernumerary  or  accessory  spleen  (lien  accessorius}.  Accessory 
spleens  vary  in  size  from  that  of  a  pea  to  that  of  a  plum. 

Support  and  Movability  of  the  Spleen. — The  spleen  is  normally  movable 
within  certain  narrow  limits.  It  moves  with  respiration  and  with  stomach  move- 
ments. It  is  supported  by  ligaments  (p.  1362).  An  unduly  movable  spleen  is 
called  a  movable  spleen.  In  order  that  a  spleen  shall  become  unduly  movable, 
the  ligaments  must  stretch,  and  this  stretching  is  often  effected  when  the  organ 
is  greatly  enlarged,  but  even  an  apparently  normal  spleen  may  become  movable. 
Movable  spleen  is  usually  associated  with  movable  left  kidney. 

Structure. — The  spleen  is  invested  by  two  coats — an  external  serous  and  an 
internal  fibro-elastic  coat. 

The  External  or  Serous  Coat  (tunica  serosa). — The  external  or  serous  coat  is 
derived  from  the  peritoneum;  it  is  thin,  smooth,  and  in  the  human  subject  is  inti- 
mately adherent  to  the  fibro-elastic  coat.  It  invests  the  entire  organ,  except  at 
the  places  of  its  reflection  on  to  the  stomach  and  Diaphragm  and  at  the  hilum. 

The  Fibro-elastic  Coat  (tunica  albuginea). — The  fibro-elastic  coat  forms  the 
framework  of  the  spleen.  It  is  composed  of  connective  tissue  containing  muscle- 
cells  and  elastic  fibres,  and  it  invests  the  organ  as  a  capsule,  and  at  the  hilum  is 
reflected  inward  upon  the  vessels  in  the  form  of  sheaths.  From  these  sheaths,  as 
well  as  from  the  inner  surface  of  the  fibro-elastic  coat,  numerous  small  fibrous 
bands,  trabeculae  (trabeculae  lienis)  (Figs.  976  and  977),  are  given  off  in  all  direc- 
tions; these  uniting,  constitute  the  framework  of  the  spleen.  This  framework 
resembles  a  sponge-like  material,  consisting  of  a  number  of  small  spaces  or 
areolae  formed  by  the  trabeculae,  which  are  given  off  from  the  inner  surface  of  the 
capsule,  or  from  the  sheaths  prolonged  inwardly  on  the  blood-vessels.  The  spaces 
or  areolae  contain  the  adenoid  material  known  as  splenic  pulp  (pulpa  lienis). 

The  proper  coat,  the  sheaths  of  the  vessels  and  the  trabeculae,  consist  of  a 
dense  mesh  of  white  and  yellow  elastic  fibrous  tissues,  the  latter  decidedly  pre- 
dominating. It  is  owing  to  the  presence  of  this  tissue  that  the  spleen  possesses 
a  considerable  amount  of  elasticity,  which  allows  of  the  very  great  variations  in 
size  that  it  presents  under  certain  circumstances.  In  addition  to  these  con- 
stituents of  this  tunic,  there  is  found  in  man  a  small  amount  of  non-striped  mus- 
cular fibre,  and  in  some  mammalia  (e.  g.,  dog,  pig,  and  cat)  a  very  considerable 
amount,  so  that  the  trabeculae  appear  to  consist  chiefly  of  muscular  tissue.  It  is 
probably  because  of  this  muscular  structure  that  the  spleen  exhibits,  when  acted 
upon  by  the  galvanic  current,  faint  traces  of  contractility. 

The  proper  substance  of  the  spleen  or  splenic-pulp  is  a  soft  mass  of  a  dark 
reddish-brown  color,  resembling  grumous  blood.  When  a  thin  section  is  exam- 
ined under  a  microscope,  it  is  found  to  consist  of  a  number  of  branching 
cells  and  an  intercellular  substance.  The  cells  are  connective-tissue  corpuscles, 
and  have  been  named  the  sustentacular  or  supporting  cells  of  the  pulp.  The 
processes  of  these  branching  cells  communicate  with  each  other,  thus  forming  a 
delicate  reticulated  tissue  in  the  interior  of  the  areolae  formed  by  the  trabeculae  of 
the  capsule;  so  that  each  primary  space  may  be  considered  to  be  divided  into  a 


1364  THE  ORGANS  OF  DIGESTION 

number  of  smaller  spaces  by  the  junction  of  these  processes  of  the  branching 
corpuscles.  These  secondary  spaces  contain  blood,  in  which,  however,  the  white 
corpuscles  are  found  to  be  in  larger  proportions  than  in  ordinary  blood.  The 
sustentacular  cells  are  either  small  uni-nucleated  or  larger  multi-nucleated  cells; 
they  do  not  stain  deeply  with  carmine,  like  the  cells  of  the  Malpighian 
bodies,  presently  to  be  described  (W.  Miiller),  but  like  them  they  possess  amce- 
boid  movements  (Cohnheim).  In  many  of  them  may  be  seen  deep  red  or 
reddish-yellow  granules  of  various  sizes  which  present  the  characters  of  the 
hsematin  of  the  blood.  Sometimes,  also,  unchanged  blood-disks  are  seen  included 
in  these  cells,  but  more  frequently  blood-disks  are  found  which  are  altered  both 
in  form  and  color.  In  fact,  blood-corpuscles  in  all  stages  of  disintegration  may 
be  noticed  to  occur  within  them.  Klein  has  recently  pointed  out  that  sometimes 
these  cells  in  the  young  spleen  contain  a  proliferating  nucleus;  that  is  to  say, 
the  nucleus  is  of  large  size,  and  presents  a  number  of  knob-like  projections, 
as  if  small  nuclei  were  budding  from  it  by  a  process  of  gemmation.  This  obser- 
vation is  of  importance,  as  it  may  explain  one  possible  source  of  the  colorless 
blood-corpuscles. 

The  interspaces  or  areolse  formed  by  the  framework  of  the  spleen  are  thus  filled 
by  a  delicate  reticulum  of  branched  connective-tissue  corpuscles,  the  interstices  of 
which  are  occupied  by  blood,  and  in  which  the  blood-vessels  terminate  in  the 
manner  now  to  be  described. 

Blood-vessels  of  the  Spleen. — The  splenic  artery  (Fig.  974)  is  remarkable  for  its 
large  size  in  proportion  to  the  size  of  the  organs,  and  also  for  its  tortuous  course. 
It  divides  into  six  or  more  branches,  which  enter  the  hilum  of  the  spleen  and 
ramify  throughout  its  substance,  receiving  sheaths  from  the  involution  of  the 
external  fibrous  tissue.  Similar  sheaths  also  invest  the  nerves  and  veins. 

Each  branch  runs  in  the  transverse  axis  of  the  organ  from  within  outward, 
diminishing  in  size  during  its  transit,  and  giving  off  in  its  passage  smaller  branches, 
some  of  which  pass  to  the  anterior,  others  to  the  posterior  part.  These  ultimately 


FIG.  977. — Transverse  section  of  the  humarr  spleen,  showing  the  distribution  of  the  splenic  artery  and  its 

branches. 

leave  the  trabecular  sheaths,  and  terminate  in  the  proper  substance  of  the  spleen 
in  small  tufts  or  pencils  of  minute  arterioles,  which  open  into  the  interstices 
of  the  reticulum  formed  by  the  branched  sustentacular  cells  (Figs  977,  978,  and 
979).  Each  of  the  larger  branches  of  the  artery  supplies  chiefly  that  region  of  the 
organ  in  which  the  branch  ramifies,  having  no  anastomosis  with  the  majority 
of  the  other  branches. 


THE  SPLEEN 


1365 


The  arterioles  (Fig.  979),  supported  by  the  minute  trabeculae,  traverse  the  pulp 
in  all  directions  in  bundles  or  pencilli  of  straight  vessels.  Their  external  coat,  on 
leaving  the  trabecular  sheaths,  consists  of  ordinary  connective  tissue,  but  it  grad- 
ually undergoes  a  transformation,  becomes  much  thickened,  and  is  converted  into 
a  lymphoid  material.1  This  change  is  effected  by  the  conversion  of  the  con- 
nective tissue  into  a  lymphoid  tissue,  the  bundles  of  connective  tissue  becoming 
looser  and  laxer,  their  fibrils  more  delicate,  and  containing  in  their  interstices 
an  abundance  of  lymph-corpuscles  (W.  Miiller).  This  lymphoid  material  is  sup- 
plied with  blood  by  minute  vessels  derived  from  the  artery  with  which  they  are 
in  contact,  and  which  terminates  by  breaking  up  into  a  network  of  capillary 
vessels. 

The  altered  coat  of  the  arterioles,  consisting  of  lymphoid  tissue  (Fig.  979),  pre- 
sents here  and  there  thickenings  of  a  spheroidal  shape,  the  Malpighian  bodies  of  the 
spleen  (noduli  lymphatici  lienales  [Malpighii]}  (Fig.  978)  These  bodies  vary  in  size 
from  about  the  y^  of  an  inch  to  the  -^  of  an  inch  in  diameter.  They  are  merely 
local  expansions  or  hyperplasiae  of  the  lymphoid  tissue  of  which  the  external  coat  of 
the  smaller  arteries  of  the  spleen  is  formed.  They  are  most  frequently  found  sur- 
rounding the  arteriole,  which  thus  seems  to  tunnel  them,  but  occasionally  they  grow 
from  one  side  of  the  vessel  only,  and  present  the  appearance  of  a  sessile  bud  grow- 
ing from  the  arterial  wall.  Klein,  however,  denies  this,  and  says  it  is  incorrect  to 
describe  the  Malpighian  bodies  as  isolated  masses  of  adenoid  tissue,  but  that  they 
are  always  formed  around  an  artery,  though  there  is  generally  a  greater  amount  on 
one  side  than  on  the  other,  and  that,  therefore,  in  transverse  sections  the  artery  in 
the  majority  of  cases  is  found  in  an  eccentric  position.  These  bodies  are  visible  to 
the  naked  eye  on  the  surface  of  a  fresh  section  of  the  organ,  appearing  as  minute 
dots  of  semi-opaque  whitish  color  in  the  dark 
substance  of  the  pulp.  In  minute  structure  they 
resemble  the  adenoid  tissue  of  lymphatic  glands, 
consisting  of  a  delicate  reticulum  in  the  meshes 
of  which  lie  ordinary  lymphoid  cells. 

The  reticulum  of  the  tissue  is  made  up  of  ex- 
tremely delicate  fibrils,  and  is  comparatively 
open  in  the  centre  of  the  corpuscle,  becoming 
closer  at  the  periphery  of  the  body.  The  cells 
which  it  encloses,  like  the  supporting  cells  of  the 
pulp,  are  possessed  of  amoeboid  movements,  but 
when  treated  with  carmine  become  deeply 
stained,  and  can  thus  easily  be  recognized  from 
those  of  the  pulp. 

The  arterioles  terminate  in  capillaries,  which 
traverse  the  pulp  in  all  directions;  their  walls 
become  much  attenuated,  lose  their  tubular 
character,  and  the  cells  of  the  lymphoid  tissue 
of  which  they  are  composed  become  altered ;  presenting  a  branched  appearance 
and  acquiring  processes  which  are  directly  connected  with  the  processes  of  the 
sustentacular  cells  of  the  pulp  (Fig.  979).  In  this  manner  the  capillary  vessels 
terminate,  and  the  blood  flowing  through  them  finds  its  way  into  the  interstices 
of  the  reticulated  tissue  formed  by  the  branched  connective-tissue  corpuscles  of 
the  splenic  pulp.  Thus  the  blood  passing  through  the  spleen  is  brought  into 
intimate  relation  with  the  elements  of  the  pulp,  and  no  doubt  undergoes  important 
changes. 

After  these  changes  have  taken  place  the  blood  is  collected  from  the  interstices 
of  the  tissue  by  the  rootlets  of  the  veins  (Fig.  976),  which  commence  much  in  the 

1  According  to  Klein,  it  is  the  sheath  of  the  small  vessel  which  undergoes  this  transformation,  and  forms  a 
"  solid  masa  of  adenoid  tissue  which  surrounds  the  vessel  like  a  cylindrical  sheath."  (Atlas  of  Histology,  p.  424.) 


FIG.  978. — Part  of  a  Malpighian  body 
of  the  spleen  of  man.  a,  arterial  branch 
in  longitudinal  section  ;  6,  adenoid  tissue, 
still  containing  the  lymph-corpuscles  ;  only 
their  nuclei  are  shown  ;  r,  adenoid  reticu- 
lum, the  lymph-corpuscles  accidentally  re- 
moved. (Klein  and  Noble  Smith.) 


1366 


THE  ORGANS  OF  DIGESTION 


same  way  as  the  arteries  terminate.  Where  a  vein  is  about  to  originate  the  con- 
nective-tissue corpuscles  of  the  pulp  arrange  themselves  in  rows  in  such  a  way  as  to 
form  an  elongated  space  or  sinus.  They  become  changed  in  shape,  being  elongated 
and  spindle-shaped,  and  overlap  each  other  at  their  extremities.  They  thus  form 
a  sort  of  endothelial  lining  of  the  path  or  sinus,  which  is  the  radicle  of  a  vein. 
On  the  outer  surface  of  these  cells  are  seen  delicate  transverse  lines  or  markings 
which  are  due  to  minute  elastic  fibrillae  arranged  in  a  circular  manner  around  the 
sinus.  Thus  the  channel  obtains  a  continuous  external  investment,  and  grad- 
ually becomes  converted  into  a  small  vein,  which  after  a  time  presents  a  coat  of 
ordinary  connective  tissue,  lined  by  a  layer  of  fusiform  endothelial  cells  which  are 
continuous  with  the  supporting  cells  of  the  pulp.  The  smaller  veins  unite  to  form 
larger  ones  which  do  not  accompany  the  arteries,  but  soon  enter  the  trabecular 
sheaths  of  the  capsule,  and  by  their  junction  form  from  six  or  more  branches  which 
emerge  from  the  hilum  and,  uniting,  form  the  splenic  vein,  the  largest  radicle  of 
the  portal  vein  (Figs.  971  and  975). 

The  veins  are  remarkable  for  their  numerous  anastomoses,  while  the  arteries 
hardly  anastomose  at  all. 

The  lymphatics  originate  in  two  ways — i  .e.,  from  the  sheaths  of  the  arteries 
and  in  the  trabeculae.  The  former  trunks  are  the  deep  collecting  trunks,  and 


Supporting  cell. 


Vessel  undergoing  lymphoid  change. 


Small 
artery." 


Vessel  continuous 
with  processes  of 
supporting  cells. 


Supporting  cell. 


Supporting- 
cell 
FIG.  979. — Section  of  spleen,  showing  the  termination  of  the  small  blood-vessels. 

accompany  the  blood-vessels;  the  latter  pass  to  the  superficial  lymphatic  plexust 
which  may  be  seen  on  the  surface  of  the  organ.  The  two  sets  communicate  in 
the  interior  of  the  organ.  The  deep  trunks  at  the  hilum  number  from  five  to 
ten,  and  terminate  in  the  splenic  glands.  The  superficial  trunks  also  pass  to  the 
hilum  and  terminate  in  the  splenic  glands. 

The  nerves  are  derived  from  the  splenic  plexus,  which  is  part  of  or  connected 
with  the  solar  plexus.  The  nerves  enter  the  spleen  with  the  vessels. 

Surface  Form. — The  spleen  is  situated  under  cover  of  the  ribs  of  the  left  side,  being  sepa- 
rated from  them  by  the  Diaphragm,  and  above  by  a  small  portion  of  the  lower  margin  of  the 
left  lung  and  pleura.  Its  position  corresponds  to  the  eighth,  ninth,  tenth,  and  eleventh  ribs. 
It  is  placed  very  obliquely.  "  It  is  oblique  in  two  directions— viz.,  from  above  downward  and 
outward,  and  also  from  above  downward  and  forward"  (Cunningham).  "Its  highest  and 
lowest  points  are  on  a  level  respectively  with  the  ninth  dorsal  and  first  lumbar  spines;  its  inner 
end  is  distant  about  an  inch  and  a  half  from  the  median  plane  of  the  body,  and  its  outer  end 
about  reaches  the  mid-axillary  line"  (Quain). 

Surgical  Anatomy. — Injury  of  the  spleen  is  less  common  than  that  of  the  liver,  on  account 
of  its  protected  situation  and  connections.  It  may  be  ruptured  by  direct  or  indirect  violence, 
torn  by  a  broken  rib,  or  injured  by  a  punctured  or  gunshot  wound.  When  the  organ  is  enlarged 
the  chance  of  rupture  is  increased.  The  great  risk  is  hemorrhage,  owing  to  the  extreme  vascu- 
larity  of  the  organ,  and  the  absence  of  a  proper  system  of  capillaries.  The  injury  is  not,  how- 


THE  SPLEEN  1367 

ever,  necessarily  fatal,  and  this  would  appear  to  be  due  in  a  great  measure  to  the  contractile 
power  of  its  capsule,  which  narrows  the  wound  and  thus  antagonizes  the  escape  of  blood.  In 
cases  in  which  the  symptoms  suggest  such  an  injury  and  indicate  danger  to  life,  laparotomy  must 
be  performed;  and  if  the  hemorrhage  cannot  be  arrested  by  ordinary  surgical  methods  the  spleen 
must  be  removed.  The  spleen  may  become  displaced,  producing  great  pain  from  stretching  of 
the  vessels  and  nerves,  and  this  dislocation  may  render  necessary  removal  of  the  organ.  The 
spleen  may  become  enormously  enlarged  in  certain  diseased  conditions,  such  as  ague,  leukaemia, 
syphilis,  valvular  disease  of  the  heart,  or  without  any  obtainable  history  of  previous  disease. 
It  may  also  become  enlarged  in  lymphadenoma  as  a  part  of  a  general  blood  disease.  In  these 
cases  the  mass  may  fill  the  abdomen  and  extend  into  the  pelvis,  and  may  be  mistaken  for 
ovarian  or  uterine  disease. 

The  spleen  is  sometimes  the  seat  of  cystic  tumors,  especially  hydatids,  and  of  abscess.  These 
cases  require  treatment  by  incision  and  drainage;  and  in  abscess  great  care  must  be  taken  if 
there  are  no  adhesions  between  the  spleen  and  abdominal  cavity,  to  prevent  the  escape  of  any 
of  the  pus  into  the  peritoneal  cavity.  If  possible,  the  operation  should  be  performed  in  two 
stages.  Sarcoma  and  carcinoma  are  occasionally  found  in  the  spleen,  but  very  rarely  as  a  primary 
disease.  In  movable  spleen,  if  the  organ  is  normal,  follow  the  advice  of  Rydygier  and  loosen 
the  parietal  peritoneum  to  make  a  pocket,  place  the  spleen  in  the  pocket,  and  pass  sutures  through 
the  parietal  peritoneum  and  the  splenic  ligaments.  A  movable  diseased  spleen  should  be  removed. 

Extirpation  of  the  spleen  has  been  performed  for  wounds  or  injuries,  floating  spleen,  simple 
hypertrophy,  and  leuksemic  enlargement;  but  in  the  latter  case  the  operation  is  now  regarded 
as  unjustifiable,  as  it  is  practically  certain  to  terminate  fatally.  The  incision  is  best  made  in 
the  left  semilunar  line:  the  spleen  is  isolated  from  its  surroundings,  and  the  pedicle  transfixed 
and  ligatured  in  two  portions,  before  the  tumor  is  turned  out  of  the  abdominal  cavity,  if  this  is 
possible,  so  as  to  avoid  any  traction  on  the  pedicle,  which  may  cause  tearing  of  the  splenic  vein  and 
which  inevitably  induces  grave  shock.  In  applying  the  ligatures  the  surgeon  must  not  include 
the  tail  of  the  pancreas,  and  in  lifting  out  the  organ  care  must  be  taken  to  avoid  rupturing  the 
capsule. 


THE  ORGANS  OF  VOICE  AND  RESPIRATION. 


THE  LARYNX. 

THE  Larynx  is  the  organ  of  voice,  placed  at  the  upper  part  of  the  air-passage. 
It  is  situated  between  the  trachea  and  base  of  the  tongue,  at  the  upper  and 
forepart  of  the  neck,  where  it  forms  a  considerable  projection  in  the  middle  line. 
On  either  side  of  it  lie  the  great  vessels  of  the  neck;  behind,  it  forms  part  of  the 
boundary  of  the  pharynx,  and  is  covered  by  the  mucous  membrane  lining  that 
cavity.  Its  vertical  extent  corresponds  to  the  fourth,  fifth,  and  sixth  cervical  ver- 
tebrae, but  it  is  placed  somewhat  higher  in  the  female  and  also  during  childhood. 
In  infants  between  six  and  twelve  months  of  age  Symington  found  that  the  tip  of 


OESOPHAGUS 

THYROID 

GLAND 

8TERNO-THYROID 
MUSCLE 
STERNUM 
THYROID 
BRANCH   OF 
CEPHALIC 
ARTERY 


FIG.  980. — Sagittal  section  of  a  man  twenty-one  years  of  age.     (After  W.  Braune.) 


the  epiglottis  was  a  little  above  the  level  of  the  cartilage  between  the  odontoid 
process  and  body  of  the  axis,  and  that  between  infancy  and  adult  life  the  larynx 
descends  for  a. distance  equal  to  two  vertebral  bodies  and  two  intervertebral  disks. 
The  movements  of  the  head  affect  the  position  of  the  larynx.  When  the  head  is 
drawn  back,  the  larynx  is  lifted,  and  when  the  chin  approaches  the  chest  the 
larynx  is  depressed.  During  swallowing  the  larynx  moves  distinctly;  during  sing- 
ing it  moves  slightly.  The  larynx  is  suspended  by  the  stylo-hyoid  ligament,  the 

(  1369  ) 


1370  THE   ORGANS   OF    VOICE  AND    RESPIRATION 

muscles  of  the  upper  border  of  the  hyoid  bone,  the  Stylo-pharyngeus  and  Palato- 
pharyngeus  muscles.  According  to  Sappey,  the  average  measurements  of  the  adult 
larynx  are  as  follows: 

In  males.  In  females. 

Vertical  diameter      .          .  .  .44  mm.  36  mm. 

Transverse  diameter          .  .  .     43     "  41  " 

Antero-posterior  diameter  .  .     36     "  26  " 

Circumference            .          .  .  .    136     "  112  " 

Until  puberty  there  is  no  marked  difference  between  the  larynx  of  the  male 
and  that  of  the  female.  In  the  latter  its  further  increase  in  size  is  only  slight, 
whereas  in  the  former  it  is  great;  all  the  cartilages  are  enlarged,  and  the  thyroid 
becomes  prominent  as  the  pomum  Adami  in  the  middle  line'  of  the  neck,  while 
the  length  of  the  glottis  is  nearly  doubled. 

The  larynx  is  broad  above,  where  it  presents  the  form  of  a  triangular  box, 
flattened  behind  and  at  the  sides,  and  bounded  in  front  by  a  prominent  vertical 
ridge.  Below,  it  is  narrow  and  cylindrical.  It  is  composed  of  cartilages,  which 
are  connected  together  by  ligaments  and  moved  by  numerous  muscles.  It  is  lined 
by  mucous  membrane,  which  is  continuous  above  with  that  lining  the  pharynx  and 
below  with  that  of  the  trachea. 

In  the  median  line  of  the  neck  the  larynx  has  in  front  of  it  the  skin  and  cer- 
vical fascia.  There  is  often  a  bursa  between  the  skin  and  fascia  over  the  most 
prominent  part  of  the  larynx.  It  is  called  -the  bursa  subcutanea  prominentiae 
laryngeae.  It  is  present  particularly  in  men,  and  is  seldom  found  in  the 
young  or  in  women.  The  larynx  is  covered  on  each  side  by  the  thyroid  gland, 
and  the  Sterno-hyoid,  Sterno-thyroid,  Thyro-hyoid,  and  Omo-hyoid  muscles,  and 
the  Inferior  constrictors  of  the  pharynx.  Posterior  is  the  laryngeal  portion  of  the 
pharynx. 

The  Cartilages  of  the  Larynx  (cartilagines  laryngis). — The  cartilages  of  the 
larynx  are  nine  in  number,  three  single,  and  three  pairs : 

Thyroid.  Two  Arytenoid. 

Cricoid.  Two  Cornicula  Laryngis. 

Epiglottis.  Two  Cuneiform. 

The  Thyroid  Cartilage  (cartilago  thyreoidea)  (Figs.  981  and  982). — The  thyroid 
cartilage  (from  #v/>£oc,  a  shield)  is  hyaline  cartilage  and  is  the  largest  cartilage 
of  the  larynx.  It  is  at  the  anterior  and  upper  portion  of  the  larynx.  It  con- 
sists of  two  lateral  lamellae  or  alae,  united  at  an  acute  angle  in  front,  forming  a 
vertical  projection  in  the  middle  line,  which  is  prominent  above  and  called  the 
pomum  Adami  (prominentia  laryngea).  This  projection  is  subcutaneous,  is  more 
distinct  in  the  male  than  in  the  female,  and  is  often  separated  from  the  integu- 
ment by  a  bursa,  the  bursa  subcutanea  prominentiae  laryngeae.  ' 

Each  lamella  is  quadrilateral  in  form.  Its  outer  surface  (Fig.  981)  presents 
an  oblique  ridge  (linea  obliqua),  which  passes  downward  and  forward  from  a 
tubercle  situated  near  the  root  of  the  superior  cornu,  the  superior  tubercle  (tuber- 
culwn  thyreoideum  superius),  to  a  small  tubercle  near  the  anterior  part  of  the 
lower  border,  the  inferior  tubercle  (tuberculum  thyreoideum  inferius).  This  ridge 
gives  attachment  to  the  Sterno-thyroid  and  Thyro-hyoid  muscles,  and  the  portion 
of  cartilage  included  between  it  and  the  posterior  border  gives  attachment  to 
part  of  the  Inferior  constrictor  muscle.  Just  below  each  superior  tubercle  there 
is  often  an  opening,  the  thyroid  foramen  (foramen  thyreoideum). 

The  anterior  borders  of  the  alae  of  the  thyroid  cartilage  which  are  continuous 
below  are  separated  above  by  a  V-shaped  notch,  the  thyroid  notch  (incisura  thy- 
reoidea  [superior]). 


THE  LARYNX 


1371 


The  Inner  Surface  (Fig.  982)  of  each  ala  is  smooth,  slightly  concave,  and 
covered  by  mucous  membrane  above  and  behind;  but  in  front,  in  the  receding 
angle  formed  by  their  junction,  are  attached  the  epiglottis,  the  true  and  false 
vocal  cords,  the  Thyro-arytenoid  and  Thyro-epiglottidean  muscles,  and  the 
thyro-epiglottidean  ligament. 

The  Upper  Border  or  Margin  of  the  Thyroid  Cartilage  (Fig.  982)  is  sinuously  curved, 
being  concave  at  its  posterior  part,  just  in  front  of  the  superior  cornu,  then  rising 
into  a  convex  outline,  which  dips  in  front  to  form  the  sides  of  the  thyroid  notch, 
in  the  middle  line,  immediately  above  the  pomum 
Adami.     This  border  gives  attachment  through- 
out its  whole  extent  to  the  thyro-hyoid  or  hyo- 
thyroid  membrane. 

The  Lower  Border  or  Margin  (Fig.  982)  is  nearly 
straight  in  front,  but  behind,  close  to  the  cornu, 
it  is  concave.  It  is  connected  to  the  cricoid  cartil- 
age, in  and  near  the  median  line,  by  the  middle 
portion  of  the  crico-thyroid  membrane  (membrana 
cricothyreoidea};  and,  on  either  side,  by  the 
Crico-thyroid  muscle. 

The  Posterior  Borders  (Fig.  982)  are  thick  and 
rounded,  and  each  terminates  above,  in  a  superior 
cornu  (cornu  superius),  and  below,  in  an  inferior 
cornu  (cornu  inferius).  The  two  superior  cornua 
are  long  and  narrow,  directed  upward,  backward, 
and  inward,  and  terminate  in  conical  extremities, 
which  give  attachment  to  the  lateral  thyro-hyoid 
ligaments.  The  two  inferior  cornua  are  short 
and  thick;  they  pass  downward,  with  a  slight 
inclination  forward  and  inward,  and  each  pre- 
sents on  its  inner  surface  a  small  oval  articular 
facet  for  articulation  with  the  side  of  the  cricoid 
cartilage  (Fig.  981 ).  The  posterior  border  receives 
the  insertion  of  the  Stylo-pharyngeus  and  Palato-pharyngeus  muscles  on  each  side. 

During  infancy  the  alae  of  the  thyroid  cartilage  are  joined  to  each  other  by  a 
narrow,  lozenge-shaped  strip,  named  the  intrathyroid  cartilage.  This  strip  extends 
from  the  upper  to  the  lower  border  of  the  thyroid  cartilage  in  the  middle  line, 
and  is  distinguished  from  the  alae  by  being  more  transparent  and  more  flexible. 

The  Cricoid  Cartilage  (cartilago  cricoidea)  (Figs.  981,  982,  and  984). — The  cri- 
coid cartilage  is  so  called  from  its  resemblance  to  a  signet  ring  (xpixot;,  a  ring}. 
It  is  smaller,  but  thicker  and  stronger  than  the  thyroid  cartilage,  and  forms  the 
lower  and*back  part  of  the  cavity  of  the  larynx.  It  is  hyaline  cartilage  and  con- 
sists of  two  parts:  a  quadrate  portion,  situated  behind,  and  a  narrow  ring  or 
arch,  one-fourth  or  one-fifth  the  depth  of  the  posterior  part,  situated  in  front. 
The  posterior  square  portion  rapidly  narrows  at  the  sides  of  the  cartilage,  at  the 
expense  of  the  upper  border,  into  the  anterior  portion. 

Its  Posterior  Portion  or  Lamina  (lamina  cartilaginis  cricoideae)  is  very  deep  and 
broad,  and  measures  from  above  downward  about  an  inch  (2  to  3  cm.) ;  it  presents, 
on  its  posterior  surface,  in  the  middle  line,  a  vertical  ridge  for  the  attachment  of 
the  longitudinal  fibres  of  the  oesophagus;  and  on  either  side  a  broad  depression 
for  the  Crico-arytenoideus  posticus  muscle. 

Its  Anterior  Portion  or  Arcus  (arcu*  cartilaginis  cricoideae)  is  narrow  and  convex, 
and  measures  vertically  about  one-fourth  or  one-fifth  of  an  inch  (5  to  7  cm.) ; 
it  affords  attachment  externally  in  front  and  at  the  sides  to  the  Crico-thyroid 
muscles,  and,  behind,  to  part  of  the  Inferior  constrictor.. 


FIG.  981. — Side  view  of  the  thyroid 
and  cricoid  cartilages. 


1372 


THE    ORGANS   OF    VOICE   AND    RESPIRATION 


Epiglottis. 


At  the  point  of  junction  of  the  posterior  quadrate  portion  with  the  rest  of  the 

cartilage  is  a  small  round  elevation,  for  articulation  with  the  inferior  cornu  of  the 

thyroid  cartilage. 

The  Lower  Border  of  the  cricoid  cartilage  is  horizontal,  and  connected  to  the 

upper  ring  of  the  trachea  by  fibrous  membrane  (Figs.  981  and  983). 

Its  Upper  Border  is  directed  obliquely  upward  and  backward,  owing  to  the 

great  depth  of  the  posterior  surface.    It  gives  attachment,  in  front,  to  the  middle 

portion  of  the  crico-thyroid  mem- 
brane ;  at  the  sides,  to  the  lateral 
portion  of  the  same  membrane 
and  to  the  lateral  Crico-arytenoid 
muscle;  behind,  it  presents,  in  the 
middle,  a  shallow  notch,  and  on 
each  side  of  this  is  a  smooth,  oval 
surface,  directed  upward  and  out- 
ward, for  articulation  with  the 
arytenoid  cartilage. 

The  Inner  Surface  of  the  cricoid 
cartilage  is  smooth,  and  lined  with 
mucous  membrane. 

The  Arytenoid  Cartilages  (cartil- 
agines  arytaenoideae)  (Figs.  982, 
985,  and  989).  — The  arytenoid 
cartilages  are  so  called  from  the 
resemblance  they  bear,  when  ap- 
proximated, to  the  mouth  of  a 
pitcher  (apuratva,  a  pitcher).  They 
are  two  in  number,  and  situated 
at  the  upper  border  of  the  cricoid 
cartilage,  at  the  back  of  the  larynx 
in  the  interval  between  the  poste- 
rior borders  of  the  alae  of  the  thy- 
roid cartilages.  Each  cartilage  is 
in  form  a  three-sided  pyramid,  and 
presents  for  examination  three  sur- 
faces, a  base,  and  an  apex. 

The  Posterior  Surface  is  trian- 
gular, smooth,  concave,  and  gives 
attachment  to  the  transverse  por- 


Thyroid. 


Cornicula  laryngis. 
Cuneiform  cartilage.  ^^^    ^      \ 

O 

Arytenoid. 


Insertion  of 

CRICO-ARYTENOIOEUS 
POSTICUS  ET  LATERALIS 


Posterior 
surface. 


Arytenoid  cartilages,  base. 


Cricoid. 

Articular  facet  for 
arytenoid  cartilage. 


Articular  facet  for 
inferior  cornu  of 
thyroid  cartilage. 


FIG.  982. — The  cartilages  of  the  larynx.     Posterior  view. 


tion  of  the  Arytenoid  muscle. 

The  Anterior  or  External  Surface 
is  somewhat  convex  and  rough.  It 
presents,  near  its  apex,  a  small 
elevation,  the  colliculus;  from  this  a 
ridge  (crista  arcuatd)  passes  back- 
ward and  then  forward  and  down- 
ward into  a  sharp-pointed  process,  the  vocal  process.  This  ridge  separates  a 
deep  depression  above,  the  fovea  triangularis,  from  a  broader  and  shallower  depres- 
sion below,  the  fovea  oblonga.  A  short  distance  above  the  base  a  small  tubercle 
gives  origin  to  the  ligament  of  the  false  vocal  cord,  the  superior  thyro-arytenoid 
ligament.  To  the  outer  part  of  the  ridge,  as  well  as  the  surface  above  and  below, 
is  attached  the  Thyro-arytenoid  muscle. 

The  Internal  Surface  is  narrow,  smooth,  and  flattened,  covered  by  mucous 
membrane,  and  forms  the  lateral  boundary  of  the  respiratory  part  of  the  glottis. 


THE   LARYNX  1373 

The  Base  (basis)  of  each  cartilage  is  broad,  and  presents  a  concave  smooth  sur- 
face, for  articulation  with  the  cricoid  cartilage.  Two  of  its  angles  require  special 
mention:  the  external  angle,  which  is  short,  rounded,  and  prominent,  projects 
backward  and  outward,  and  is  termed  the  muscular  process  (processus  muscularis), 
from  receiving  the  insertion  of  the  Posterior  and  Lateral  crico-arytenoid  muscles. 
The  anterior  angle,  also  prominent,  but  more  pointed,  projects  horizontally  forward, 
and  gives  attachment  to  the  inferior  thyro-arytenoid  ligament,  the  supporting  liga- 
ment of  the  true  vocal  cord.  This  angle  is  called  the  vocal  process  (processus  vocalis). 

The  Apex  of  each  cartilage  is  pointed,  curved  backward  and  inward,  and  sur- 
mounted by  a  small  conical,  cartilaginous-nodule,  the  corniculum  laryngis,  articu- 
lated with  or  united  to  the  arytenoid  cartilage. 

The  Cornicula  Laryngis  or  Caitilages  of  Santorini  (cartilagines  cornicuLatae)  (Figs. 
982  and  988). — The  cornicula  laryngis  are  two  small  conical  nodules,  consisting 
of  white  fibre-cartilage,  which  articulate  with  the  summit  of  the  arytenoid  carti- 
lages and  serve  to  prolong  them  backward  and  inward.  To  them  are  attached 
the  aryteno-epiglottidean  folds.  They  are  sometimes  united  to  the  arytenoid 
cartilages. 

The  Cuneiform  Cartilages  or  Cartilages  of  Wrisberg  (cartilagines  cuneijorm.es] 
(Figs.  982  and  984). — The  cuneiform  cartilages  are  two  small,  elongated,  carti- 
laginous bodies,  placed  one  on  each  side,  in  the  fold  of  mucous  membrane  which 
extends  from  the  apex  of  the  arytenoid  cartilage  to  the  side  of  the  epiglottis,  and 
is  called  the  aryteno-epiglottidean  fold  (plica  aryepiglottica)  (Fig.  984);  they  give 
rise  to  small  whitish  elevations  on  the  inner  surface  of  the  mucous  membrane, 
just  in  front  of  the  arytenoid  cartilages. 

The  Epiglottis  or  the  Cartilage  of  the  Epiglottis  (cartilago  cpiglcltica]  (Figs.  980,  982, 
983,  984,  985,  and  988). — The  epiglottis  is  a  thin,  flexible  lamella  of  fibro-cartilage, 
of  a  yellowish  color,  shaped  like  a  leaf,  and  placed  behind  the  tongue  in  front  of 
the  superior  opening  of  the  larynx.  Its  free  extremity,  which  is  directed  upward, 
is  broad  and  rounded,  and  often  notched;  its  attached  part  (petiolus  epiglottidis) 
is  long,  narrow,  and  connected  to  the  receding  angle  between  the  alae  of  the 
thyroid  cartilage,  just  below  the  median  notch,  by  a  long,  narrow  ligamentous 
band,  the  thyro-epiglottic  ligament  (Fig.  985).  It  is  also  connected  to  the  posterior 
surface  of  the  body  of  the  hyoid  bone  by  an  elastic  ligamentous  band,  the  hyo- 
epiglottic  ligament. 

Its  Anterior  or  Lingual  Surface  is  curved  forward,  toward  the  tongue,  and  cov- 
ered at  its  upper,  free  part  by  mucous  membrane,  which  is  reflected  on  to  the 
sides  and  base  of  the  organ,  forming  a  median  and  two  lateral  folds,  the  glcsso- 
epiglottidean  folds  (Fig.  984).  The  median  glosso-epiglottidean  fold  contains  the 
elastic  glosso-epiglottic  ligament  (ligamentum  glossocpiglotticum) .  Each  lateral 
glosso-epiglottidean  fold  runs  from  the  front  and  side  of  the  base  of  the  epiglottis 
to  the  side  of  the  tongue.  The  depression  between  the  epiglottis  and  the  base  of  the 
tongue  on  each  side  of  the  median  fold  is  named  the  vallecula  epiglottica.  The 
lower  part  of  the  anterior  surface  of  the  epiglottis  lies  behind  the  hyoid  bone, 
the  thyro-hyoid  membrane,  and  upper  part  of  the  thyroid  cartilage,  but  is  separated 
from  these  structures  by  a  mass  of  fatty  tissue. 

Its  Posterior  or  Laryngeal  Surface  is  smooth,  concave  from  side  to  side,  concavo- 
convex  from  above  downward;  its  lower  part  projects  backward  as  an  elevation, 
the  tubercle  or  cushion  (tuberculum  epiglotticum)(Fig.  983) ;  when  the  mucous  mem- 
brane is  removed,  the  surface  of  the  cartilage  is  seen  to  be  studded  with  a  number 
of  small  mucous  glands,  which  are  lodged  in  little  pits  upon  its  surface.  To  its 
sides  the  aryteno-epiglottidean  folds  are  attached  (Fig.  984). 

Structure. — The  cuneiform  cartilages,  the  epiglottis,  and  the  apices  of  the 
arytenoids  are  composed  of  yellow  elastic  cartilage,  which  shows  little  tendency  to 
calcification;  on  the  other  hand,  the  thyroid,  cricoid,  and  the  greater  part  of  the 


1374  THE    ORGANS    OF    VOICE   AND    RESPIRATION 

arytenoids  consist  of  hyaline  cartilage,  and  become  more  or  less  ossified  as  age 
advances.  Ossification  commences  about  the  twenty-fifth  year  in  the  thyroid  car- 
tilage, somewhat  later  in  the  cricoid  and  arytenoids;  by  the  sixty-fifth  year  these 
cartilages  may  be  completely  converted  into  bone.  The  cornicula  laryngis  consist 
of  white  fibre-cartilage,  which  becomes  osseous  about  the  seventieth  year. 

Ligaments,  Joints,  and  Membranes  of  the  Larynx. — The  ligaments  of  the  larynx 
are  extrinsic — i.  e.,  those  connecting  the  thyroid  cartilage  and  epiglottis  with  the 
hyoid  bone,  and  the  cricoid  cartilage  with  the  trachea;  and  intrinsic,  those  which 
connect  the  several  cartilages  of  the  larynx  to  each  other. 

The  ligaments  connecting  the  thyroid  cartilage  with  the  hyoid  bone  are  three 
in  number — the  thyro-hyoid  membrane,  and  the  two  lateral  thyro-hyoid  ligaments. 

The  Thyro-hyoid  or  Hyo-thyroid  Membrane  or  Ligament  (membrana  hyothyreoidea) 
(Fig.  985)  is  a  broad,  fibre-elastic,  membranous  layer,  attached  below  to  the 
upper  border  of  the  thyroid  cartilage,  and  above  to  the  posterior  border  of  the 
body  and  greater  cornua  of  the  hyoid  bone,  passing  behind  the  postero-inferior 
surface  of  the  hyoid,  and  being  separated  from  this  surface  by  a  synovial  bursa 
(bursa  m.  sternohyoidei) ,  which  facilitates  the  upward  movement  of  the  larynx 
during  deglutition.  The  membrane  is  thicker  in  the  middle  line  than  at  either 
side.  This  thickening  is  due  to  elastic  fibres,  and  constitutes  the  middle  thyro- 
hyoid  ligament  (ligamentum  hyothyreoideum  medium).  On  each  side  the  posterior 
extremity  of  the  membrane  is  thickened  by  elastic  fibres,  constituting  the  lateral 
thyro-hyoid  ligament  (ligamentum  hyothyreoideum  later  ale).  The  thyro-hyoid 
membrane  is  pierced  on  each  side  by  the  superior  laryngeal  .vessels  and  the 
internal  laryngeal  nerve.  The  anterior  surface  of  the  thyro-hyoid  membrane  is 
in  relation  with  the  Thyro-hyoid,  Sterno-hyoid,  and  Omo-hyoid  muscles  and  with 
the  body  of  the  hyoid  bone.  The  two  lateral  ligaments  are  rounded,  elastic  cords, 
which  pass  between  the  superior  cornua  of  the  thyroid  cartilage  and  the  extremi- 
ties of  the  greater  cornua  of  the  hyoid  bone.  A  small  cartilaginous  nodule  (car- 
tilago  triticea),  sometimes  bony,  is  frequently  found  in  each. 

The  Membrana  Quadrangularis  is  an  elastic  membrane  containing  numerous 
glands.  The  fibres  of  the  membrane  run  in  part  downward  and  in  part  down- 
ward and  backward.  The  membrane  on  each  side  arises  in  front  and  above  at 
the  lateral  margin  of  the  cartilage  of  the  epiglottis,  below  at  the  posterior  surface 
of  the  angle  of  the  thyroid  cartilage  and  becomes  attached  behind  to  the  cornicula 
laryngis  and  to  the  inner  margins  of  the  arytenoid  cartilages.1  The  membranes 
converge  below  and  medianward.  The  ligamentum  ventriculare  is  the  superior 
end  of  the  membrane  (Spalteholz) .  The  fibres  constituting  the  ligamentum  ven- 
triculare are  given  off  at  the  thyroid  cartilage  above  the  ligamentum  vocale  and 
pass  horizontally  backward  to  the  medial  margin  of  the  fovea  triangularis  of  the 
arytenoid  cartilage.2  The  epiglottis  is  connected  to  the  tongue  by  the  three 
glosso-epiglottidean  folds  of  mucous  membrane,  which  may  also  be  considered 
as  extrinsic  ligaments  of  the  epiglottis. 

The  Glosso-epiglottidean  Folds  or  Ligaments  (plicae  epiglotticae)  (Fig.  984)  num- 
ber three.  The  middle  glosso-epiglottidean  fold  (plica  glossoepiglottica  mediana) 
passes  from  the  middle  of  the  anterior  free  surface  of  the  epiglottis  to  the  base 
of  the  tongue.  It  contains  the  glosso-epiglottic  ligament.  The  lateral  glosso- 
epiglottidean  or  the  pharyngo-epiglottidean  fold  (plica  glossoepiglottica  lateralis) 
on  each  side  passes  from  the  side  of  the  epiglottis  to  the  side  of  the  base  of  the 
tongue  and  to  the  pharyngeal  wall.  On  each  side  between  the  median  and  lateral 
folds  is  a  depression,  the  vallecula  epiglottica. 

The  Hyo-epiglottic  Ligament  ((ligamentum  hyoepiglotticum)  is  an  elastic  band, 
which  extends  from  the  anterior  surface  of  the  epiglottis,  near  its  apex,  to  the 

1  Hand  Atlas  of  Human  Anatomy.     By  Werner  Spalteholz.     Translated  and  edited  by  Lewellys  F.  Barker. 

2  Ibid. 


THE  LARYNX 


1375 


upper  border  of  the  body  of  the  hyoid  bone.  The  epiglottis  is  attached  to  the 
thyroid  cartilage,  below  and  behind  the  superior  thyroid  notch,  by  the  strong 
and  elastic  thyro-epiglottic  ligament  (iigamentum  thyreoepiglotticum)  (Fig.  985). 
Between  the  epiglottis,  the  hyo-epiglottic  ligament,  and  the  thyro-hyoid  membrane 
is  a  triangular  space  containing  fat  on  each  side  of  the  median  line. 

The  ligaments  connecting  the  thyroid  cartilage  to  the  cricoid  are  also  three  in 
number — the  crico-thyroid  membrane  and  the  capsular  ligaments. 

The  Crico-thyroid  Membrane  (conus  elasticus)  (Figs.  971  and  988  is  an  elastic  mem- 
brane which  passes  radially  from  the  posterior  surface  of  the  angle  of  the  thyroid 
cartilage  to  the  upper  margin  of  the  arch  of  the  cricoid  cartilage  and  to  the  vocal 
processes  of  the  arytenoid  cartilages.  It  is  composed  mainly  of  yellow  elastic 
tissue.  It  consists  of  three  parts,  a  central  triangular  portion  and  two  lateral 
portions.  The  central  part  (Iigamentum  cricothyreoideum  medium)  is  thick  and 
strong,  narrow  above  and  broadening  out  below.  It  connects  together  the  con- 
tiguous margins  of  the  thyroid  and  cricoid  cartilages.  It  is  convex,  concealed  on 
each  side  by  the  Crico-thyroid  muscle,  but  subcutaneous  in  the  middle  line;  it  is 
crossed  horizontally  by  a  small  anastomotic  arterial  arch,  formed  by  the  junction 
of  the  two  crico-thyroid  arteries.  The  lateral  portions  are  thinner  and  lie  close 
under  the  mucous  membrane  of  the  larynx.  They  extend  from  the  superior 
border  of  the  cricoid  cartilage  to  the  inferior  margin  of  the  true  vocal  cords  with 
which  they  are  continuous.  On  each  side  are  the  uppermost  fibres  from  the 
inferior  thyro-arytenoid  ligament  (Iigamentum  vocale). 

The  lateral  portions  are  lined  internally  by  mucous  membrane,  and  are  sepa- 
rated from  the  thyroid  cartilage  by  the  lateral  Crico-arytenoid  and  Thyro-aryte- 
noid muscles.  This  membrane 
and  the  muscles  just  men- 
tioned reduce  greatly  the  inte- 
rior of  the  larynx.  The  crico- 
thyroid  membrane  with  the 
membrana  quadrangularis  con- 
stitute the  membrana  elastica 
laryngis. 

The  Crico-thyroid  Articulation 
(articulatio  cricothyreoidea)  (Fig. 
981),  on  each  side  of  the  inferior 
cornu  of  the  thyroid,  with  the 
cricoid  cartilage  on  each  side. 
A  loose  synovial  membrane  (cap- 
sula  articularis  cricothyreoidea) 
encloses  the  articulation. 

The  synovial  capsule  is 
strengthened  by  the  ligamenta 
ceratocricoidea,which  pass  from 
the  lesser  cornu  of  the  thyroid 
to  the  lamina  of  the  cricoid 
cartilage. 

The  Crico-arytenoid  Articula- 
tion (articulatio  cricoarytae- 

noidea)  (Fig.  982)  on  each  side  is  between  the  articular  surface  of  the  arytenoid 
cartilage  and  the  arytenoid  articular  surface  of  the  cricoid  cartilage. 

The  ligaments  connecting  the  arytenoid  cartilages  to  the  cricoid  are  on  each 
side  a  capsular  ligament  (capsula  articularis  cricoarytaenoidea)  and  a  posterior 
crico-arytenoid  ligament  (Iigamentum  cricoarytaenoideum  posterius).  The  capsular 
ligaments  are  thin  and  loose  capsules  attached  to  the  margin  of  the  articular 


ARYTENO- 
CPIGLOTTIDEUS 


CRICO- 
THYREOIDCUS 


LARYNGEAL 
SACCULE 


,   ,_  INFERIOR 
VOCAL    CORD 


FIG.  983. — Coronal  section  of  larynx,  rear  view  of  front  half. 
(Testut.) 


1376  THE    ORGANS   OF    VOICE  AND   RESPIRATION 

surfaces;  they  are  lined  internally  by  synovial  membrane.  The  posterior  crico- 
arytenoid  ligaments  extend  from  the  cricoid  to  the  inner  and  back  part  of  the  base 
of  the  arytenoid  cartilage. 

The  Crico-tracheal  Ligament  (ligamentum  cricotracheale)  connects  the  cricoid 
cartilage  with  the  first  ring  of  the  trachea.  It  resembles  the  fibrous  membrane 
which  connects  the  cartilaginous  rings  of  the  trachea  to  each  side. 

There  is  on  each  side  an  articulation  between  the  arytenoid  cartilage  and  the 
cartilage  of  Santorini  (synchondrosis  arycorniculala).  The  cartilage  of  Santo rini  is 
somewhat  movable  and  is  fixed  to  the  arytenoid  by  lax  connective  tissue.  From 
each  cartilage  of  Santorini  a  band  of  connective  tissue  runs  doAvn  to  the  lamina 
of  the  cricoid  cartilage  and  to  the  pharyngeal  mucous  membrane.  Beneath  the 
arytenoid  muscles  the  ligaments  from  the  two  sides  join  and  pass  down  together. 
Thus  is  formed  a  Y-shaped  ligament  called  the  ligamentum  corniculopharyngeum. 
The  portion  between  the  cricoid  cartilage  and  the  mucous  membrane  of  the 
pharynx  is  sometimes  called  the  ligamentum  cricopharyngeum. 

Interior  of  the  Larynx  (Figs.  983,  984,  and  985).— The  cavity  of  the  larynx 
(cavum  laryngis)  extends  fro  n  the  superior  aperture  of  the  larynx  to  the  lower 
border  of  the  cricoid  cartilage.  It  is  divided  into  two  parts  by  the  projection 
inward  of  the  true  vocal  cords,  between  which  is  a  narrow  triangular  fissure  or 
chink,  the  rima  glottidis.  It  is  further  subdivided  by  the  false  vocal  cords.  So 
we  consider  the  larynx  as  divided  into  a  portion  above  the  false  cords,  a  porT 
tion  between  the  false  and  true  vocal  cords,  and  a  portion  below  the  true  cords. 
The  entrance  of  the  first  compartment  is  the  superior  aperture  of  the  larynx. 

The  Superior  Aperture  of  the  Larynx  (aditus  laryngis}. — The  superior  aperture 
of  the  larynx  (Figs.  983  and  984)  is  a  triangular  or  cordiform  opening,  wide  in  front, 
narrow  behind,  and  sloping  obliquely  downward  and  backward.  It  is  bounded, 
in  front,  by  the  epiglottis;  behind,  by  the  apices  of  the  arytenoid  cartilages  and 
the  cornicula  laryngis;  and  laterally,  by  a  fold  of  mucous  membrane,  enclosing 
ligamentous  and  muscular  fibres,  stretched  between  the  sides  of  the  epiglottis 
and  the  apices  of  the  arytenoid  cartilages;  these  are  the  aryteno-epiglottidean 
folds  (Figs.  984  and  985),  on  the  margins  of  which  the  cuneiform  cartilages  form 
more  or  less  distinct  whitish  prominences. 

The  small  gap  between  the  cartilages  of  Santorini  is  called  the  incisura  inter- 
arytaenoidea.  On  the  pharynx,  on  either  side  of  the  posterior  portion  of  the  superior 
aperture  of  the  larynx,  is  a  recess,  called  the  sinus  pyriformis. 

Upper  Compartment  or  Vestibule  of  the  Laryngeal  Cavity  (vestibulum  laryngis)  (Figs. 
983  and  985). — The  vestibule  is  the  portion  between  the  superior  opening  and  the 
false  vocal  cords.  It  is  much  narrower  below  than  above.  It  is  bounded  anteriorly 
by  the  mucous  membrane-covered  epiglottis.  The  lower  part  of  the  epiglottis 
exhibits  a  prominence  called  the  cushion  or  tubercle  (Fig.  983).  The  lateral  wall  of 
the  vestibule  on  each  side  is  the  aryteno-epiglottidean  fold  (Fig.  985),  which  extends 
from  the  summit  of  the  arytenoid  cartilage  forward,  upward,  and  outward  to  the 
margin  of  the  epiglottis,  and  which  contains  fibres  of  the  Thyro-epiglottideus  and 
Arytenoideus  muscles  (musculus  arytaenoepiglottidean).  Near  the  posterior  end 
of  the  fold  are  two  trivial  elevations:  the  anterior  elevation  is  caused  by  the  promi- 
nence of  the  cuneiform  cartilage,  and  is  called  the  cuneiform  tubercle  of  Wrisberg 
(tuberculum  cuneiforme  [Wrisbergi]) ;  the  posterior  elevation  is  caused  by  the 
anterior  margin  of  the  arytenoid  cartilage  and  the  cartilage  of  Santorini,  and  is 
called  the  comical  tubercle  of  Santorini  (tuberculum  corniculatum  [Santorini]). 
Between  these  elevations  is  a  groove,  the  filtrum  ventriculi  of  Merkel,  which  passes 
into  the  space  between  the  false  and  true  vocal  cords.  The  anterior  elevation 
passes  into  the  false  vocal  cord,  the  posterior  elevation  into  the  true  vocal  cord. 
The  posterior  portion  of  the  laryngeal  vestibule  is  the  narrow  space  between 
the  upper  portions  of  the  arytenoid  cartilages. 


THE  LARYNX 


1377 


The  Middle  Compartment  of  the  Larynx  (Figs.  983  and  985). — This  lies  between  the 
false  vocal  cords  above  and  the  true  vocal  cords  below.  It  is  the  smallestof  the  laryn- 
geal  compartments.  It  opens  into  the  vestibule  by  way  of  the  gap  between  the 
false  vocal  cords,  which  is  called  the  false  glottis;  it  opens  into  the  lower  compart- 
ment of  the  larynx  by  way  of  the  space  between  the  true  vocal  cords,  the  true  glottis. 

The  True  Glottis. — The  true  glottis  is  the  apparatus  for  producing  tone  and  is 
formed  by  the  true  vocal  cords. 

The  Chink  of  the  Glottis  (rima  glottidis)  (Figs.  983  and  984).— The  chink  of  the 
glottis  is  the  elongated  fissure  or  chink  between  the  inferior  or  true  vocal  cords  in 
front,  and  between  the  bases  and  vocal  processes  of  the  arytenoid  cartilages  behind. 
It  is  therefore  frequently  subdivided  into  an  anterior,  interligamentous  or  vocal  por- 
tion, the  glottis  vocalis  (pars  intermembranacea) ,  and  a  posterior,  intercartilaginous 
or  respiratory  portion,  the  glottis  respiratoria  (pars  intercartilaginea).  Posteriorly  it  is 
limited  by  the  mucous  membrane  passing  between  the  arytenoid  cartilages.  The 
vocal  portion  averages  about  three-fifths  of  the  length  of  the  entire  aperture.  It 
is  the  narrowest  part  of  the  cavity  of  the  larynx,  and  its  level  corresponds  to  the 


APEX    OF   SUP.    HORN    OF 
THYROID    CARTILAGE 


INFERIOR 
VOCAL  CORD, 


CORNICULUM 
LARYNGIS 

CUNEIFORM 

CARTILAGE 
ARYTENO-EPIGLOT- 
TIDIAN   FOLD 
APEX    OF   GREAT 
HORN    OF   HYOID 


LATERAL   GLOSSO-  MIDDLE    GLOSSO- 

EPIGLOTTIDIAN    FOLD       EPIG  LOTTI  Ol  AN   FOLD 

FIG.  984.  —  Larynx,  viewed  from  above. 


(Testut.) 


bases  of  the  arytenoid  cartilages.  Its  length,  in  the  male,  measures  rather  less 
than  an  inch  (20  to  25  mm.);  in  the  female  it  is  shorter  by  5  or  6  mm.,  or  three 
lines.  The  width  and  shape  of  the  rima  glottidis  vary  with  the  movements  of  the 
vocal  cords  and  arytenoid  cartilages  during  respiration  and  phonation.  In  the 
condition  of  rest — i.  e.,  when  these  structures  are  uninfluenced  by  muscular  action, 
as  in  quiet  respiration,  the  glottis  vocalis  is  triangular,  with  its  apex  in  front  and 
its  base  behind,  the  latter  being  represented  by  a  line  about  8  mm.  long,  connect- 
ing the  anterior  extremities  of  the  vocal  processes,  while  the  inner  surfaces  of  the 
arytenoids  are  parallel  to  each  other,  and  hence  the  glottis  respiratoria  is  rectan- 
gular. During  extreme  adduction  of  the  cords,  as  in  the  emission  of  a  high  note, 
the  glottis  vocalis  is  reduced  to  a  linear  slit  by  the  apposition  of  the  cords,  while 
the  glottis  respiratoria  is  triangular,  its  apex  corresponding  to  the  anterior  extrem- 
ities of  the  vocal  processes  of  the  arytenoids,  which  are  approximated  by  the 
inward  rotation  of  the  cartilages.  Conversely  in  extreme  abduction  of  the  cords, 
as  in  forced  inspiration,  the  arytenoids  and  their  vocal  processes  are  rotated  out- 
ward, and  the  glottis  respiratoria  is  triangular  in  shape,  but  with  its  apex  directed 
backward.  In  this  condition  the  entire  glottis  is  somewhat  lozenge-shaped,  the 
sides  of  the  glottis  vocalis  diverging  from  before  backward,  those  of  the  glottis 

87 


1378 


THE  ORGANS  OF  VOICE  AND  RESPIRATION 


respiratoria  diverging  from  behind  forward,  the  widest  part  of  the  aperture  corre- 
sponding with  the  attachment  of  the  cords  to  the  vocal  processes.1 

The  Superior  or  False  Vocal  Cords  (plicae  ventricular es] (Figs. 983, 984,  and  985),  so 
called  because  they  are  not  directly  concerned  in  the  production  of  the  voice.  Each 
is  a  thick  fold  of  mucous  membrane,  enclosing  a  narrow  band  of  fibrous  tissue,  the 
superior  thyro-arytenoid  ligament,  which  is  attached  in  front  to  the  angle  of  the 
thyroid  cartilage  immediately  below  the  attachment  of  the  epiglottis,  and  behind 
to  the  anterior  surface  of  the  arytenoid  cartilage.  The  lower  border  of  this  liga- 
ment, enclosed  in  mucous  membrane,  forms  a  free  crescentic  margin,  which  con- 
stitutes the  upper  boundary  of  the  ventricle  of  the  larynx.  The  false  vocal  cord 
contains  the  lower  part  of  the  membrana  quadrangularis  with  the  ligamentum 
ventriculare,  the  muscle  ventricularis,  and  laryngeal  glands. 

The  Inferior  or  True  Vocal  Cords  (plicae  vocales)(F'}gs.  983,  984,  985,  and  989),  so 
called  from  their  being  concerned  in  the  production  of  sound.  Each  is  a  strong 


HYOID 


VHYRO-HYOIDEUS 


THYRO-EPIGLOT 
TIC    LIGAMENT 


ARYTENO-EPI- 
GLOTTIDIAN  FOLD 


CRICOID 
CARTILAGE 


FIG.  985. — Sagittal  section  of  larynx,  right  half.     (Testut.) 

band,  the  inferior  thyro-arytenoid  ligament  (ligamentum  vocale) ,  covered  on  its  sur- 
face by  a  thin  layer  of  mucous  membrane.  Each  ligament  consists  of  a  band  of 
yellow  elastic  tissue,  attached  in  front  to  the  depression  between  the  alae  of  the 
thyroid  cartilage,  and  behind  to  the  anterior  angle  of  the  base  of  the  arytenoid. 
This  angle  is  called  the  vocal  process.  Its  lower  border  is  continuous  with  the 
thin  lateral  part  of  the  crico-thyroid  membrane.  Its  upper  border  forms  the  lower 
boundary  of  the  ventricle  of  the  larynx.  Externally,  the  Thyro-arytenoideus 
muscle  lies  parallel  with  it.  It  is  covered  internally  by  mucous  membrane,  which  is 
extremely  pale,  thin,  and  closely  adherent  to  its  surface.  The  upper  margin  of 
the  true  vocal  cord  is  covered  with  mucous  membrane,  and  is  the  lower  boundary 
of  the  ventricle  of  the  larynx.  Over  the  vocal  process  it  is  yellowish  (macula 
flava).  The  true  vocal  cord  contains  the  upper  part  of  the  crico-thyroid  mem- 
brane with  the  ligamentum  vocale  and  the  muscle  vocalis. 


1  On  the  shape  of  the  rima  glottidis,  in  the  various  conditions  of  breathing  and  speaking,  see  Czermak.  On  the 
Laryngoscope,  translated  for  the  New  Sydenham  Society. — ED.  of  15th  English  edition. 


THE  LARYNX   ' 


1379 


The  Ventricle  of  the  Larynx  or  Laryngeal  Sinus  (ventriculus  laryngis  [Morgagnii]) 
(Figs.  970  and  972)  is  an  oblong  fossa,  situated  between  the  superior  and  inferior 
vocal  cords  on  each  side,  and  extending  nearly  their  entire  length.  This  fossa  is 
bounded,  above,  by  the  free  crescentic  edge  of  the  superior  vocal  cord;  below,  by 
the  straight  margin  of  the  inferior  vocal  cord;  externally,  by  the  mucous  mem- 
brane covering  the  corresponding  Thyro-arytenoideus  muscle.  The  anterior  part 
of  the  ventricle  leads  up  by  a  narrow  opening  into  a  caecal  pouch  of  mucous 
membrane  of  variable  size,  called  the  laryngeal  pouch. 

The  Laryngeal  Saccule  or  Pouch  (appendix  ventriculi)  (Fig.  983),  or  laryngeal 
pouch,  is  a  membranous  sac,  placed  between  the  superior  vocal  cord  and  the  inner 
surface  of  the  thyroid  cartilage,  occasionally  extending  as  far  as  its  upper  border 
or  even  higher;  it  is  conical  in  form,  and  curved  slightly  backward.  On  the  surface 
of  its  mucous  membrane  are  the  openings  of  sixty  or  seventy  mucous  glands,  which 
are  lodged  in  the  submucous  areolar  tissue.  This  sac  is  enclosed  in  a  fibrous  cap- 
sule, continuous  below  with  the  superior  thyro-arytenoid  ligament;  its  laryngeal 
surface  is  covered  by  the  Aryteno-epiglotticleus  inferior  muscle  (compressor  sacculi 
laryngis  of  Hilton);  while  its  exterior  is  covered  by  the  Thyro-arytenoideus  and 
Thyro-epiglottideus  muscles.  These  muscles  compress  the  sacculus  laryngis,  and 
discharge  the  secretion  it  contains  upon  the  Vocal  cords,  the  surfaces  of  which  it  is 
intended  to  lubricate. 


STERNO- 
'THYREOIDEUS 


FIG.  986. —Muscles  of  larynx,  front  view.  The  sterno- 
thyroids  and  right  thyro-hyoid  have  been  removed. 
(Testut.) 


FIG.  987. — Muscles  of  larynx,  from  behind. 
(Testut.) 


The  Lower  Compartment  of  the  Larynx  (Figs.  983  and  985). — This  space  is  just 
beneath  the  true  vocal  cords  and  leads  into  the  trachea.  It  is  called  the  additus  glot- 
tidis  inferior.  Above,  on  cross-section,  it  is  oval;  below,  it  is  round.  It  is  bounded 
by  the  inner  surface  of  the  crico-thyroid  membrane  and  the  cricoid  cartilage. 

Muscles  of  the  Larynx  (miLSculi  laryngis}. — We  do  not  consider  all  muscles 
which  are  attached  to  laryngeal  cartilages  as  laryngeal  muscles.  Some  muscles 
so  attached  in  reality  belong  to  other  regions,  for  instance,  the  Inferior  constric- 
tor, the  Stylo-pharyngeus,  the  Sterno-thyroid,  the  Thyro-hyoid,  and  the  Palato- 
pharyngeus.  The  muscles  which  really  belong  to  the  larynx  are  called  intrinsic. 

Four  muscles  of  the  vocal  cords  and  rima  glottidis  are  paired  and  one  is  single. 


1380 


THE  ORGANS  OF  VOICE  AND  RESPIRATION 


The  paired  musclas  are  the  crico-thyroid,  the  posterior  crico-arvtenoid,  the 
lateral  crico-arytenoid,  and  the  thyro-arytenoid.  The  single  muscle  is  the  aryte- 
noideus. 

A  Crico-thyroid  (m.  cricothyreoideus]  (Figs.  981,  983,  and  986)  is  placed  on  each 
side.  It  is  triangular  in  form,  and  situated  at  the  forepart  and  side  of  the  cricoid 
cartilage.  It  arises  from  the  front  and  lateral  part  of  the  cricoid  cartilage;  its 
fibres  diverge,  passing  obliquely  upward  and  outward  to  be  inserted  into  the  lower 
border  of  the  thyroid  cartilage  and  into  the  anterior  border  of  the  lower  cornu. 

The  inner  borders  of  these  two  muscles  are  separated  in  the  middle  line  by  a 
triangular  interval  occupied  by  the  central  part  of  the  crico-thyroid  membrane. 
The  Posterior  Crico-arytenoid  (m.  cricoarytaenoideus  posterior)  (Figs.  987,  988,  and 

989),  a  paired  muscle,  arises  from  the 
broad  depression  occupying  each  lat- 
eral half  of  the  posterior  surface  of  the 
cricoid  cartilage;  its  fibres  pass  up- 
ward and  outward,  converging  to  be 
inserted  into  the  outer  angle  (muscu- 


Cornicula 
laryngis 


Articular  facet  for 
inferior  cornu  of 
thyroid  cartilage. 


FIG.  988. — Muscles  of  larynx.    Side  view.    Eight  ala 
of  thyroid  cartilage  removed. 


FIG.  989. — Interior  of  the  larynx,  seen  from  above. 
(Enlarged.) 


lar  process)  of  the  base  of  the  arytenoid  cartilage.    The  upper  fibres  are  nearly 
horizontal,  the  middle  oblique,  and  the  lower  almost  vertical.1 

The  Arytenoideus  (Figs.  985,  987,  988,  and  989)  is  a  single  muscle  filling  up  the 
posterior  concave  surface  of  the  arytenoid  cartilages.  It  arises  from  the  posterior 
surface  and  outer  border  of  one  arytenoid  cartilage,  and  is  inserted  into  the  corre-. 
sponding  parts  of  the  opposite  cartilage.  It  consists  of  three  planes  of  fibres,  two 
oblique  and  one  transverse.  The  oblique  fibres  (m.  arytaenoideus  obliquus),  the 
most  superficial,  form  two  fasciculi,  which  pass  from  the  base  of  one  cartilage  to 
the  apex  of  the  opposite  one.  The  transverse  fibres  (m.  arytaenoideus  transversus), 
the  deepest  and  most  numerous,  pass  transversely  across  between  the  two  cartil- 
ages; hence  the  Arytenoideus  was  formerly  considered  as  three  muscles,  the  trans- 

1  Merkel,  of  Leipzig,  has  described  a  muscular  slip  which  occasionally  extends  between  the  outer  border  of  the 
sterior  surface  of  the  cricoid  cartilage  and  the  posterior  margin  of  the  inferior  cornu  of  the  thyroid  ;  this  he 


po 


calls  the  "  Musculus  kerato-cricoideus."  It  is  not  found  in  every  larynx,  and  when  present  exists  usually  only 
on  one  side,  but  is  occasionally  found  on  both  sides.  Sir  William  Turner  (Edinburgh  Medical  Journal,  February, 
1860)  states  that  it  is  found  in  about  one  case  in  five.  Its  action  is  to  fix  the  lower  horn  of  the  thyroid  cartilage 
backward  and  downward,  opposing  in  some  measure  the  part  of  the  Crico-thyroid  muscle,  which  is  connected  to 
the  anterior  margin  of  the  horn.  —  ED.  of  15th  English  edition. 


THE  LARYNX  1381 

verse  and  the  two  oblique.  A  few  of  the  oblique  fibres  are  around  the  outer  margin 
of  the  cartilage,  and  blend  with  the  Thyro-arytenoid  in  the  aryteno-epiglottidean 
fold,  and  are  called  the  Aryteno-epiglottideus  muscles. 

In  order  to  expose  the  rest  of  the  muscles  of  the  larynx  the  thyroid  cartilage 
of  one  side  must  be  removed.  Begin  by  taking  away  the  crico-thyroid  muscle, 
then  dividing  the  lateral  thyro-hyoid  ligament;  disarticulate  the  inferior  cornu  of 
the  thyroid  cartilage  from  the  cricoid  cartilage,  then  carefully  cut  through  the 
thyroid  cartilage  a  short  distance  from  its  union  with  its  twin.  The  following 
muscles  will  then  be  exposed  after  a  little  cleaning:  the  Lateral  crico-thyroid, 
the  Thyro-arytenoid,  the  Thyro-epiglottideus. 

The  Lateral  Crico-arytenoid  (m.  cricoarytenoidetis  lateralis]  (Figs.  988  and  989), 
a  paired  muscle,  is  smaller  than  the  preceding,  and  of  an  oblong  form.  It  arises 
from  the  upper  border  of  the  side  of  the  cricoid  cartilage,  and,  passing  obliquely 
upward  and  backward,  is  inserted  into  the  muscular  process  of  the  arytenoid 
cartilage  in  front  of  the  posterior  Crico-arytenoid  muscle. 

The  Thyro-arytenoid  (m.  thyroarytaenoideus)  (Figs.  988  and  989),  a  paired  muscle, 
is  broad  and  flat.  It  lies  parallel  with  the  outer  side  of  the  true  vocal  cord.  It 
arises  in  front  from  the  lower  half  of  the  receding  angle  of  the  thyroid  cartilage, 
and  from  the  crico-thyroid  membrane.  Its  fibres  pass  backward  and  outward,  to 
be  inserted  into  the  base  and  anterior  surface  of  the  arytenoid  cartilage.  This 
muscle  consists  of  two  fasciculi.1  The  inner  or  inferior  fasciculus  (m.  vocalis),  the 
thicker,  is  prismatic  in  shape  and  is  inserted  into  the  vocal  process  of  the  aryte- 
noid cartilage,  and  into  the  adjacent  portion  of  its  anterior  surface;  it  lies  parallel 
with  the  true  vocal  cord,  to  which  it  is  adherent.  This  fasciculus  on  its  deeper 
surface  gives  off  some  fibres  which  are  attached  to  the  true  vocal  cord.  These 
are  called  the  ary-vocalis  (Ludwig).  The  outer  or  superior  fasciculus,  the  thinner, 
is  inserted  into  the  anterior  surface  and  outer  border  of  the  arytenoid  cartilage 
above  the  preceding  fibres;  it  lies  on  the  outer  side  of  the  sacculus  laryngis,  imme- 
diately beneath  the  mucous  membrane.2 

The  muscles  of  the  epiglottis  are  the — 

Thyro-epiglottideus.  Aryteno-epiglottideus  superior. 

Aryteno-epiglottideus  inferior. 

The  Thyro-epiglottideus  (m.  thyroepiglotticus)  is  a  delicate  fasciculus,  which 
arises  from  the  inner  surface  of  the  thyroid  cartilage,  just  external  to  the  origin  of 
the  Thyro-arytenoid  muscle,  of  which  it  is  sometimes  described  as  a  part,  and 
spreads  over  the  outer  surface  of  the  sacculus  laryngis ;  some  of  its  fibres  are  lost 
in  the  aryteno-epiglottidean  fold,  while  the  others  are  continued  forward  to  the 
margin  of  the  epiglottis. 

The  Aryteno-epiglottideus  (Figs.  983  and  988)  is  properly  divided  into  two 
muscles,  a  superior  and  an  inferior. 

The  Aryteno-epiglottideus  superior  consists  of  a  few  delicate  muscular  fasciculi, 
which  arise  from  the  apex  of  the  arytenoid  cartilages,  and  become  lost  in  the 
fold  of  mucous  membrane,  the  aryteno-epiglottidean  fold,  extending  between  the 
arytenoid  cartilage  and  the  side  of  the  epiglottis. 

The  Aryteno-epiglottideus  inferior,  the  Compressor  sacculi  laryngis  of  Hilton,  arises 
from  the  arytenoid  cartilage,  just  above  the  attachment  of  the  superior  vocal  cord; 
passing  forward  and  upward, it  spreads  out  upon  the  anterior  surface  of  the  epiglot- 
tis. This  muscle  is  separated  from  the  preceding  by  an  indistinct  areolar  interval.3 

1  Henle  describes  these  two  portions  as  separate  muscles,  under  the  names  of  the  External  and  Internal  thyro- 
arytenoid.  —  ED.  of  15th  English  edition. 

2  Luschka  has  described  a  small  but  fairly  constant  muscle  as  the  Arytenoideus  rectus.      It  is  attached  below 
to  the  posterior  concave  surface  of   the  arytenoid  cartilage,   beneath  the  Arytenoideus  muscle,  and,  passing 
upward,  emerges  at  the  upper  border  of  this  muscle,  and  is  inserted  into  the  posterior  surface  of  the  cartilage  of 
Santorini  (Anatomy,  by  Hyrtl,  p.  718).  —  ED.  of  15th  English  edition. 

3  MusruLus  TRiTicEO-GLOSSOS.     Bochdalek,  Jr.  (Prager  Vierteljahrsschrift,  1866,  2d  part)  describes  a  muscle 
hitherto  entirely  overlooked,  except  by  Henle,  who  makes  a  brief  statement  in  his  Anatomy,  which  arises  from 
the  nodule  of  cartilage  (corpus  triticewn)  in  the  posterior  thyro-hyoid  ligament,  and  passes  forward  and  upward 
to  enter  the  tongue  along  with. the  Hyo-glossus  muscle.     He  met  with  this  muscle  eight  times  in  twenty-two  sub- 
jects.    It  occurred  in  both  sexes,  sometimes  on  both  sides,  at  others  on  one  only. — ED.  of  15th  English  edition. 


1382  THE    ORGANS    OF   VOICE  AND    RESPIRATION 

Actions. — In  considering  the  action  of  the  muscles  of  the  larynx,  they  may 
be  conveniently  divided  into  two  groups,  viz.:  1.  Those  which  open  and  close 
the  glottis.  2.  Those  which  regulate  the  degree  of  tension  of  the  vocal  cords. 

1.  The  muscles  which  open  the  glottis  are  the  two  Posterior  crico-arytenoids; 
and  those  which  close  it  are  the  Arytenoideus  and  the  two  Lateral  crico-arytenoids. 
2.  The  muscles  which  regulate  the  tension  of  the  vocal  cords  are  the  two  Crico- 
thyroids,  which  tense  and  elongate  them,  and  the  two  Thyro-arytenoids,  which 
relax  and  shorten  them.  The  Thyro-epiglottideus  is  a  depressor  of  the  epiglottis, 
and  the  Aryteno-epiglottideus,  superior  and  inferior,  constrict  the  superior  aper- 
ture of  the  larynx. 

The  Posterior  crico-arytenoids  separate  the  chordae  vocales,  and  consequently  open  the  glottis, 
by  rotating  the  arytenoid  cartilages  outward  around  a  vertical  axis  passing  through  the  crico- 
arytenoid  joints,  so  that  their  vocal  processes  and  the  vocal  cords  attached  to  them  become  widely 
separated. 

The  Lateral  crico-arytenoids  close  the  glottis  by  rotating  the  arytenoid  cartilages  inward  so 
as  to  approximate  their  vocal  processes. 

The  Arytenoideus  muscle  approximates  the  arytenoid  cartilages,  and  thus  closes  the  opening 
of  the  glottis,  especially  at  its  back  part. 

The  Crico-thyroid  muscles  produce  tension  and  elongation  of  the  vocal  cords.  This  is  effected 
as  follows:  the  thyroid  cartilage  is  fixed  by  its  extrinsic  muscles;  then  the  Crico-thyroid  muscles, 
when  they  act,  draw  upward  the  front  of  the  cricoid  cartilage,  and  so  depress  the  posterior  por- 
tion, which  carries  with  it  the  arytenoid  cartilages,  and  thus  elongate  the  vocal  cords. 

The  Thyro-arytenoid  muscles,  consisting  of  two  parts  having  different  attachments  and 
different  directions,  are  rather  complicated  as  regards  their  action.  Their  main  use  is  to  draw 
the  arytenoid  cartilages  forward  toward  the  thyroid,  and  thus  shorten  and  relax  the  vocal  cords. 
But,  owing  to  the  connection  of  the  inner  portion  with  the  vocal  cord,  this  part,  if  acting  sepa- 
rately, is  supposed  to  modify  its  elasticity  and  tension,  and  the  outer  portion,  being  inserted 
into  the  outer  part  of  the  anterior  surface  of  the  arytenoid  cartilage,  may  rotate  it  inward,  and 
thus  narrow  the  rima  glottidis  by  bringing  the  two  cords  together. 

The  T ' hyro-epiglottidei  may  depress  the  epiglottis;  they  assist  in  compressing  the  sacculi 
laryngis.  The  Aryteno-epiglottideus  superior  constricts  the  superior  aperture  of  the  larynx, 
when  it  is  drawn  upward,  during  deglutition.  The  aryteno-epiglottideus  inferior,  together  with 
some  fibres  of  the  Thyro-arytenoidei,  compress  the  sacculus  laryngis. 

The  Mucous  Membrane  of  the  Larynx  is  continuous  above  with  that  lining  the 
mouth  and  pharynx,  and  it  is  prolonged  through  the  trachea  and  bronchi  into  the 
lungs.  It  lines  the  posterior  surface  and  the  anterior  part  of  the  upper  surface  of 
the  epiglottis,  to  which  it  is  closely  adherent.  In  the  rest  of  the  larynx,  above  the 
true  vocal  cords,  it  is  lax  and  rests  upon  a  considerable  submucous  layer.  The 
mucous  membrane,  with  the  submucous  coat,  ligamentous  and  muscular  fibresr 
forms  the  aryteno-epiglottidean  folds,  which  folds  are  the  lateral  boundaries  of  the 
superior  aperture  of  the  larynx.  It  lines  the  whole  of  the  cavity  of  the  larynx; 
forms  by  its  reduplication  the  chief  part  of  the  superior  or  false  vocal  cord;  and, 
from  the  -ventricle,  is  continued  into  the  sacculus  laryngis.  It  is  then  reflected 
over  the  true  vocal  cords,  where  it  is  thin  and  very  intimately  adherent;  covers 
the  inner  surface  of  the  crico-thyroid  membrane  and  cricoid  cartilage;  and  is 
ultimately  continuous  with  the  lining  membrane  of  the  trachea.  The  forepart  of 
the  anterior  surface  and  the  upper  half  of  the  posterior  surface  of  the  epiglottis, 
the  upper  part  of  the  aryteno-epiglottidean  folds,  and  the  true  vocal  cords  are 
covered  by  stratified  squamous  epithelium;  the  rest  of  the  laryngeal  mucous 
membrane  is  covered  by  columnar  ciliated  cells. 

The  mucous  membrane  above  the  rima  glottidis  is  extremely  sensitive,  and 
during  life  the  lightest  touch  of  a  foreign  body  produces  cough. 

Glands. — The  mucous  membrane  of  the  larynx  is  furnished  with  numerous 
muciparous  glands,  the  orifices  of  which  are  found  in  nearly  every  part;  they 
are  very  numerous  upon  the  epiglottis,  being  lodged  in  little  pits  in  its  substance; 
they  are  also  found  in  large  numbers  along  the  posterior  margin  of  the  aryteno- 
epiglottidean  fold,  in  front  of  the  arytenoid  cartilages,  where  they  are  termed  the 


THE  LARYXX 


1383 


arytenoid  glands.    They  exist  also  in  large  numbers  upon  the  inner  surface  of  the 
sacculus  laryngis.    None  are  found  on  the  surface  of  the  true  vocal  cords. 

Vessels  and  Nerves. — The  arteries  of  the  larynx  (Fig.  990)  are  the  laryngeal 
branches  derived  from  the  superior  and  inferior  thyroid.  The  superior  laryngeal  artery 
from  the  superior  thyroid  courses  along  by  the  internal  laryngeal  nerve;  the  inferior 
laryngeal  artery  from  the  inferior  thyroid  courses  along  with  the  recurrent  laryngeal 
nerve.  The  veins  accompany  the  arteries;  those  accompanying  the  superior  laryn- 
geal artery  join  the  superior  thyroid  vein  which  opens  into  the  internal  jugular 
vein;  while  those  accompanying  the  inferior  laryngeal  artery  join  the  inferior 
thyroid  vein  which  opens  into  the  innominate  vein.  The  laryngeal  lymphatics  arise 
from  a  network  in  the  mucous  membrane.  This  network  is  divisible  into  two 
portions,  a  superior  and  an  inferior,  which  are  to  be  regarded  as  almost  inde- 
pendent areas.  The  superior  region  includes  all  of  the  "laryngeal  mucous 
membrane  above  the  glottis,  epiglottis,  aryteno-epiglottidean  folds,  interarytenoid 
region^  and  superior  vocal  cords."1  The  inferior  area  is  the  laryngeal  mucous 

Superior 

thyroid 

artery. 


Superior 
laryngeal 
artery. 


FIG.  990. — The  origin  and  distribution  of  the  arteries  of  the  larynx.     (Luschka.) 

membrane  below  the  glottis.  The  lymphatics  of  one-half  of  the  larynx  do  nut 
communicate  with  those  of  the  other  half  in  the  median  line  in  front,  but  do 
in  the  median  line  behind.  The  efferent  vessels  from  the  superior  network 
accompany  the  superior  laryngeal  artery,  pierce  the  thyro-hyoid  membrane, 
and  divide  into  three  sets.  One  or  two  lymphatic  vessels  pass  upward  and 
terminate  in  a  gland  slightly  below  the  posterior  belly  of  the  Digastric  muscle. 
A  group  of  vessels  passes  horizontally  outward  to  terminate  in  the  glands 
situated  on  the  internal  jugular  vein  on  a  level  with  the  bifurcation  of  the 
common  carotid  artery.  Another  group  descends  and  empties  into  the  internal 
jugular  group  of  glands  at  a  lower  level  than  the  horizontal  vessels.  Trunks  from 
the  inferior  network  of  the  laryngeal  mucous  membrane  form  two  groups.  The 
anterior  or  supracricoid  group  consists  of  three  trunks  which  pass  through  thecrico- 
thyroid  membrane,  to  empty  into  the  pre-laryngeal  glands,  the  pre-tracheal  gland, 
and  the  middle  and  lower  deep  cervical  glands.2  The  posterior  group  consists 


1  Philip  R.  W.  De  Santi  in  the  Lancet,  June  18,  1904. 


Poirier,  Cuntio,  Most,  De  Santi. 


1384  THE    ORGANS    OF    VOICE  AND    RESPIRATION 

of  "from  three  to  five  trunks,  which  pass  over  the  crico-tracheal  fascia  at  the 
junction  of  the  lateral  and  posterior  aspects  of  the  trachea,"1  and  terminate  in 
the  recurrent  glands  about  the  recurrent  laryngeal  nerve.  The  nerves  are  derived 
from  the  internal  and  external  laryngeal  branches  of  the  superior  laryngeal  nerve, 
from  the  inferior  or  recurrent  laryngeal,  and  from  the  sympathetic.  The  internal 
laryngeal  nerve  is  almost  entirely  sensor,  but  some  motor  filaments  are  said  to  be 
carried  by  it  to  the  Arytenoideus  muscle.  It  divides  into  a  branch  which  is  dis- 
tributed to  both  surfaces  of  the  epiglottis,  a  second  to  the  aryteno-epiglottidean 
folds,  and  a  third,  the  largest,  which  supplies  the  mucous  membrane  over  the 
back  of  the  larynx  and  communicates  with  the  recurrent  laryngeal.  The  external 
laryngeal  nerve  supplies  the  Crico-thyroid  muscle.  The  recurrent  laryngeal 
passes  upward  under  the  lower  border  of  the  Inferior  constrictor,  and  enters  the 
larynx  between  the  cricoid  and  thyroid  cartilages.  It  supplies  all  the  muscles  of 
the  larynx  except  the  Crico-thyroid  and  part  of  the  Arytenoideus.  The  sensor 
branches  of  the  laryngeal  nerves  form  subepithelial  plexuses,  from  which  fibres 
ascend  to  end  between  the  cells  covering  the  mucous  membrane. 

Over  the  posterior  surface  of  the  epiglottis,  in  the  aryteno-epiglottidean  folds, 
and  less  regularly  in  some  other  parts,  taste-buds,  similar  to  those  in  the  tongue, 
are  found. 

THE  TRACHEA  AND  BRONCHI  (Fig.  991). 

The  trachea  or  windpipe  is  a  cartilaginous  membranous,  elastic,  cylindrical 
tube,  flattened  posteriorly,  which  extends  from  the  lower  part  of  the  larynx,  on  a 
level  with  the  sixth  cervical  vertebra,  to  opposite  the  body  of  the  fourth,  or  some- 
times of  the  fifth,  thoracic  vertebra,  where  it  divides  (bifurcatio  tracheae)  into  two 
bronchi,  one  for  each  lung.  This  point  is  at  the  level  of  the  spine  of  the  fourth 
thoracic  vertebra.  The  trachea  is  found  to  be  more  deeply  placed  the  lower  down 
it  is  examined.  It  is  in  the  median  line,  deviating  below  a  very  little  to  the  right 
side.  When  a  cross-section  is  made  of  the  trachea  it  is  seen  that  its  anterior  and 
lateral  walls  are  rounded,  but  its  posterior  wall  is  flat  (Fig.  995).  The  largest 
diameter  of  the  tube  is  the  middle;  from  this  point  the  diameter  diminishes  toward 
the  bronchi  and  toward  the  laryngeal  end.  The  trachea  measures  about  four 
inches  and  a  half  in  length;  its  diameter  from  side  to  side  is  from  three-quarters 
of  an  inch  to  an  inch,  being  always  greater  in  the  male  than  in  the  female. 

Relations. — The  anterior  surface  of  the  trachea  is  convex,  and  covered  in  the 
neck,  from  above  downward,  by  the  isthmus  of  the  thyroid  gland,  the  inferior 
thyroid  veins,  the  arteria  thyroidea  ima  (when  that  vessel  exists),  the  Sterno-hyoid 
and  Sterno-thyroid  muscles,  the  cervical  fascia,  and  more  superficially,  by  the 
anastomosing  branches  between  the  anterior  jugular  veins:  in  the  thorax  it  is 
covered  from  before  backward  by  the  first  piece  of  the  sternum,  the  remains  of  the 
thymus  gland,  the  left  innominate  vein,  the  arch  of  the  aorta,  the  innominate  and 
left  common  carotid  arteries,  and  the  deep  cardiac  plexus.  Posteriorly,  it  is  in 
relation  with  the  oesophagus ;  laterally,  in  the  neck,  it  is  in  relation  with  the  com- 
mon carotid  arteries,  the  lateral  lobes  of  the  thyroid  'gland,  the  inferior  thyroid 
arteries,  and  recurrent  laryngeal  nerves;  and,  in  the  thorax,  it  lies  in  the  upper 
part  of  the  interpleural  space,  that  is,  in  the  superior  mediastinum,  and  is  in  relation 
on  the  right  to  the  pleura  and  right  vagus,  and  near  the  root  of  the  neck  to  the 
innominate  artery;  on  its  left  side  are  the  recurrent  laryngeal  nerve,  the  aortic 
arch,  the  left  common  carotid  and  subclavian  arteries. 

The  Right  Bronchus  (bronchus  dexter). — The  unbranched  portion  of  the  right 
.bronchus  is  wider,  shorter,  and  more  vertical  in  direction  than  the  left,  is  about 
an  inch  in  length,  and  enters  the  hilum  of  the  right  lung  opposite  the  fifth  thoracic 

i  De  Santi,  in  the  Lancet,  June  18,  1904. 


THE    TRACHEA    AND   BRONCHI 


1385 


vertebra.  It  forms  an  angle  to  the  median  plane  of  about  29  degrees.  The  vena 
azygos  major  arches  over  it  from  behind ;  and  the  right  pulmonary  artery  lies  below 
and  then  in  front  of  it.  About  three-quarters  of  an  inch  from  its  commencement 
it  gives  off  a  branch  to  the  upper  lobe  of  the  right  lung.  This  is  termed  the 
eparterial  branch  (ramus  bronchialis  eparterialis] ,  because  it  is  given  off  above 
the  right  pulmonary  artery.  The  bronchus  now  passes  below  the  artery,  and  is 


Superior 
Cornu. 


Inferior 
Cornu. 


FIG.  991. — Front  view  of  cartilages  of  larynx;  the  trachea  and  bronchi  (the  right  bronchus  is  not  shown  as 

steep  as  it  really  is. 

known  as  the  hyparterial   branch  (ramus   branchialis   hyparterialis).     It  divides 
into  two  branches  for  the  middle  and  lower  lobs. 

If  a  transverse  section  of  the  trachea  is  made  a  short  distance  above  its  point 
of  bifurcation,  and  a  bird's-eye  view  taken  of  its  interior  (Fig.  995),  the  septum 
placed  at  the  bottom  of  the  trachea  and  separating  the  two  bronchi  will  be  seen 
to  occupy  the  left  of  the  median  line,  and  the  right  bronchus  appears  to  be  a 
more  direct  continuation  than  the  left,  so  that  any  solid  body  dropping  into  the 
trachea  would  naturally  be  directed  toward  the  right  bronchus.  This  tendency  is 
aided  by  the  larger  size  of  the  right  tube  as  compared  with  its  fellow.  This  fact 


1386 


THE    ORGANS    OF    VOICE  AND    RESPIRATION 


serves  to  explain  why  a  foreign  body  in  the  trachea  more  frequently  falls  into  the 
right  bronchus  than  into  the  left.1 

The  Left  Bronchus  (bronchus  sinister}. — The  left  bronchus   is  smaller  and 
longer  than  the  right,  being  nearly  two  inches  in  length.    It  forms  an  angle  to  the 

median  plane  of  about  46  degrees.  It  is  slightly 
curved  and  enters  the  root  of  the  left  lung,  oppo- 
site the  sixth  thoracic  vertebra,  about  an  inch 
lower  than  the  right  bronchus.  It  passes  be- 
neath the  arch  of  the  aorta,  crosses  in  front  of 
the  oesophagus,  the  thoracic  duct,  and  the  de- 
scending aorta,  and  has  the  left  pulmonary  artery 
lying  at  first  above,  and  then  in  front  of  it.  The 
left  bronchus  has  no  branch  corresponding  to 
the  eparterial  branch  of  the  right  bronchus,  and 
therefore  it  has  been  supposed  by  some  that 
there  is  no  upper  lobe  to  the  left  lung,  but  that 
the  so-called  upper  lobe  corresponds  to  the 
middle  lobe  of  the  right  lung.  The  left  bron- 
chus does  have  an  hyparterial  branch. 

When  the  main  or  stem  bronchus  enters  the 
lung  on  each  side  it  appears  to  divide  into  nearly 
equal  branches  at  the  root  of  the  lung,  but  a 
somewhat  similar  arrangement  to  what  is  found 
in  many  animals  may  be  made  out  where  each 
main  bronchus  passes  downward  and  backward 
toward  the  extremity  of  the  lower  lobe,  and  ends 
near  the  posterior  surface  of  the  base  of  the  lung, 
a  portion  of  pulmonary  substance  which  is  be- 
tween the  Diaphragm  and  the  wall  of  the  chest. 
It  gives  off  four  branches,  or  lateral  bronchi 
(rami  bronchioles),  at  intervals  in  two  directions,  dorsally  and  ventrally,  and,  in 
addition,  accessory  branches,  which  arise  from  the  front  of  the  bronchus  and 
pass  mesally  and  dorsally  into  the  inferior  lobe.  In  the  right  bronchus  the 
first  ventral  branch  supplies  the  middle  lobe,  the  other  three  and  all  the  dorsal 
going  to  the  lower  lobe;  in  the  left  bronchus,  the  first  ventral  branch  sup- 
plies the  middle  lobe,  the  other  three  and  all  the  dorsal  going  to  the  lower 
lobe;  in  the  left  bronchus,  the  first  central  supplies  the  superior  lobe,  and  all  the 
others,  both  ventral  and  dorsal,  go  to  the  lower  lobe.  The  dorsal  and  ventral 
branches  divide  into  smaller  branches,  and  these  again  into  smaller  branches  or 
bronchioles  (Fig.  994).  Each  bronchiolus  divides  into  minute  branches  (bronchioli 
respiratorii)  (Fig.  994),  the  walls  of  which  show  numerous  areas  of  bulging  called 
alveoli  (Fig.  994).  From  the  bronchioli  respiratorii  come  the  terminal  branches 
of  the  bronchi.  These  terminal  branches  are  the  alveolar  ducts  (ductuli  alveolares), 
and  they  are  bulged  by  numerous  alveoli  (Fig.  994).  They  connect  by  openings 
at  their  termination  with  several  cavities  of  irregular  form,  which  are  called  atria. 
Each  atrium  is  connected  with  several  or  many  larger  cavities,  known  as  sacculi 
alveolares,  air-cells,  or  air-sacs  (infundibula).  The  entire  surface  of  the  air-sacs  is 
filled  with  small  cavities,  the  pulmonary  alveoli  (alveoli  pulmonis).  An  alveolar 
duct  with  its  branches  forms  a  pulmonary  lobule  (lobulus  pulmonis)  (Fig.  993). 

Structure  of  the  Trachea. — The  trachea  is  composed  of  imperfect  cartilagi- 
nous rings,  fibrous  membrane,  muscular  fibres,  mucous  membrane,  and  glands. 

The  Cartilages. — The  cartilages  vary  from  sixteen  to  twenty  in  number;  'each 
forms  an  imperfect  ring,  which  surrounds  about  two-thirds  of  the  cylinder  of  the 

1  Reigel  asserts  that  the  entrance  of  a  foreign  body  into  the  left  bronchus  is  by  no  means  so  infrequent  as  is 
generally  supposed.     See  also  Med.-Chir.  Transactions,  vol.  Ixxi.,  p.  121. — ED.  of  15th  English  edition. 


FIG.  992. — Internal  surface  of  the  bronchi. 
(Poirier  and  Charpy.) 


THE  TRACHEA  AND  BRONCHI 


1387 


trachea,  being  imperfect  behind,  where  the  tube  is  completed  by  fibrous  mem- 
brane. The  cartilages  are  placed  horizontally  above  each  other,  separated  by 
narrow  membranous  intervals.  They  measure  about  two  lines  in  depth,  and  half 
a  line  in  thickness.  Their  outer  surfaces  are  flattened,  but  internally  they  are 
convex,  from  being  thicker  in  the  middle  than  at  the  margins.  Two  or  more  of 
the  cartilages  often  unite,  partially  or  completely,  and  are  sometimes  bifurcated 
at  their  extremities.  They  are  highly  elastic,  but  sometimes  become  calcified  in 
advanced  life.  In  the  right  bronchus  the  cartilages  vary  in  number  from  six  to 

eight;  in  the  left,  from  nine  to  twelve.  They 
are  shorter  and  narrower  than  those  of  the 
trachea.  The  peculiar  cartilages  are  the  first 
and  the  last. 

The  First  Cartilage  is  broader  than  the  rest, 
and  sometimes  divided  at  one  end;  it  is  con- 
nected by  fibrous  membrane  with  the  lower 


NTERLOBULAR 


ALVEOLI 
DUCT 


BRONCHIOLE 


RESPIRATORY 
BRONCHIOLE 


FIG.  993. — A  pulmonary  lobule.     (Poirier  and 
Charpy.) 


FIG.  994. — The  terminal  bronchial  tubes.    The  respiratory 
bronchiole  and  alveoli.    (Poirier  and  Charpy.) 


Left. 


border  of  the  cricoid  cartilage,  with  which  or  with  the  succeeding  cartilage  it  is 
sometimes  blended. 

The  Last  Cartilage  is  thick  and  broad  in  the  middle,  in  consequence  of  its  lower 
border  being  prolonged  into  a  triangular  hook-shaped  process  which  curves  down- 
ward and  backward  between  the  two  bronchi.  It  terminates  on  each  side  in  an 

imperfect  ring  which  encloses  the  com- 
mencement of  the  bronchi.  The  cartil- 
age above  the  last  is  somewhat  broader 
than  the  rest  at  its  centre. 

The  Fibrous  Membrane. — The  cartil- 
ages are  enclosed  in  an  elastic  fibrous 
membrane  which  forms  a  double  layer, 
one  layer,  the  thicker  of  the  two,  passing 
over  the  outer  surface  of  the  ring,  the 
other  over  the  inner  surface;  at  the 
upper  and  lower  margins  of  the  cartilages 
these  two  layers  blend  together  to  form  a 
single  membrane,  which  connects  the  rings  one  with  another.  They  are  thus,  as 
it  were,  embedded  in  the  membrane.  In  the  space  behind,  between  the  extremi- 
ties of  the  rings,  the  membrane  forms  a  single  distinct  layer. 

The  Muscular  Fibres. — The  muscular  fibres  are  disposed  in  two  layers,  longi- 
tudinal and  transverse 


FIG.  995. — Transverse  section  of  the  trachea,  just 
above  its  bifurcation,  with  a  bird's-eye  view  of  the 
interior. 


1388 


THE    ORGANS    OF    VOICE   AND    RESPIRATION 


The  Longitudinal  Fibres  are  the  most  external,  and  consist  merely  of  a  few  scat- 
tered longitudinal  bundles  of  fibres. 

The  Transverse  Fibres  constitute  the  Trachealis  muscle  of  Todd  and  Bowman.  The 
most  internal  form  a  thin  layer  which  extends  transversely  between  the  ends  of 
the  cartilages  and  the  intervals  between  them  at  the  posterior  part  of  the  trachea. 
The  muscular  fibres  are  of  the  unstriped  variety. 

The  Mucous  Membrane. — The  mucous  membrane  is  continuous  above  with  that 
of  the  larynx,  and  below  with  that  of  the  bronchi.  Microscopically,  it  consists  of 
areolar  and  lymphoid  tissue,  and  presents  a  well-marked  basement-membrane, 
supporting  a  layer  of  columnar,  ciliated  epithelium,  between  the  deeper  ends  of 
which  are  smaller  triangular  cells,  the  bases  of  which,  often  branched,  are  attached 
to  the  basement-membrane.  These  triangular  cells  are  mucus-secreting,  and  may 
be  seen  as  goblet-cells  or  chalice-cells  when  their  contents  have  been  discharged. 
In  the  deepest  part  of  the  mucous  membrane,  and  especially  between  the  mucous 
and  subrnucous  layers,  longitudinally  arranged  fibres  are  very  abundant  and  form 
a  distinct  layer. 

The  Tracheal  Glands  (glandulae  tracheales). — The  trachea!  glands  are  found  in 
great  abundance  at  the  posterior  part  of  the  trachea.  They  are  racemose  glands, 
and  consist  of  a  basement-membrane  lined  by  columnar  mucus-secreting  cells. 
They  are  situated  at  the  back  of  the  trachea,  outside  the  layer  of  muscular  tissue, 
between  it  and  the  outer  fibrous  layer.  Their  excretory  ducts  pierce  the  muscular 
and  inner  fibrous  layers,  and  pass  through  the  submucous  and  mucous  layers  to 
open  on  the  surface  of  the  mucous  membrane.  Some  glands  of  smaller  size  are 
also  found  at  the  sides  of  the  trachea,  between  the  layers  of  fibrous  tissue  con- 
necting the  rings,  and  others  immediately  beneath  the  mucous  coat.  The  secre- 
tion from  these  glands  serves  to  lubricate  the  inner  surface  of  the  trachea. 


RIGHT  TRACHEAL 
LYMPH  GLAND 


RIGHT   SUPERIOR 
TRACHEO- 

BRONCHIAL 
LYMPH    GLAND 


LEFT  TRACHEAL 
LYMPH   GLAND 


LEFT  SUPERIOR 
TRACHEO- 
BRONCHIAL 
LYMPH   GLAND 

Vl 


BRONCHO- 
PULMONARY 
LYMPH  GLAND 


INFERIOR 

TRACHEO- BRONCHIAL 
LYMPH   GLAND 


FIG.  996.— The  tracheo-bronchial  and  broncho-pulmonary  lymphatic  glands,  seen  from  in  front.  The  pointed 
(?)  lymphatic  glands  and  lymph-vessels  are  not  visible  from  in  front:  d\,  rf.j,  first  and  second  dorsal  bronchial 
branches;  n,  ?>;,  first  and  second  ventral  bronchial  branches.  (Sukiennikow.) 

Vessels  and  Nerves. — The  trachea  is  supplied  with  blood  by  the  inferior  thy- 
roid arteries.  The  veins  terminate  in  the  thyroid  venous  plexus.  The  nerves 
are  derived  from  the  vagus  and  its  recurrent  branches  and  from  the  sympathetic. 


THE  TRACHEA   AND  BRONCHI  1389 

Lymphatic  Glands. — The  trachea  is  surrounded  by  lax  connective  tissue  which 
contains  numerous  lymph  glands,  known  as  the  peritracheo-bronchial  glands.  They 
are  divided  into  four  groups  (Bare"ty).  A  group  to  the  right  side,  in  the  angle 
between  the  trachea  and  right  bronchus  and  ascending  to  the  region  of  the  sub- 
clavian  vessels.  A  group  to  the  left  side,  in  the  angle  formed  by  the  trachea  and 
left  bronchus,  and  ascending  to  about  the  arch  of  the  aorta  a^d  the  recurrent 
laryngeal  nerve.  The  two  groups  just  described  are  usually  calle^  trackeal  glands 
(lymphoglandidae  tracheales).  A  third  group  is  in  the  angle  formea  by  the  bifur- 
cation of  the  trachea.  These  constitute  the  bronchial  glands  (lymphoglandidae 
bronchioles}.  They  number  ten  or  twelve  (Cune"o).  A  fourth  group,  the  inter- 
bronchial  glands,  are  found  in  angles  of  bifurcation  of  the  larger  bronchi  in  the 
lung  parenchyma.  Very  early  in  life  the  peritracheo-bronchial  glands  become 
dark  or  even  black  from  the  deposition  of  carbonaceous  substance  brought  by 
the  leukocytes  from  the  bronchial  tubes.  This  condition  is  called  anthracosis. 

Surface  Form. — In  the  middle  line  of  the  neck  some  of  the  cartilages  of  the  larynx  can  readily 
be  distinguished.  In  the  receding  angle  below  the  chin  the  hyoid  bone  can  easily  be  made 
out,  and  a  finger's  breadth  below  it  is  the  pomum  Adami,  the  prominence  between  the  upper 
borders  of  the  two  alae  of  the  thyroid  cartilage.  About  an  inch  below  this,  in  the  middle  line,  is 
a  depression  corresponding  to  the  crico-thyroid  space,  in  which  the  operation  of  laryngotomy  is 
performed.  This  depression  is  bounded  below  by  a  prominent  arch,  the  anterior  ring  of  the 
cricoid  cartilage,  below  which  the  trachea  can  be  felt,  though  it  is  only  in  the  emaciated  adult 
that  the  separate  rings  can  be  distinguished.  The  lower  part  of  the  trachea  is  not  easily  made 
out,  for  as  it  descends  in  the  neck  it  takes  a  deeper  position,  and  is  farther  removed  from  the 
surface.  The  level  of  the  vocal  cords  corresponds  to  the  middle  of  the  anterior  margin  of  the 
thyroid  cartilage. 

With  the  laryngoscope,  the  following  structures  can  be  seen:  The  base  of  the  tongue  and 
the  upper  surface  of  the  epiglottis,  with  the  glosso-epiglottic  ligaments;  the  superior  aperture  of 
the  larynx,  bounded  on  either  side  by  the  aryteno-epiglottidean  folds,  in  which  may  be  seen  two 
rounded  eminences  corresponding  to  the  cornicula  and  cuneiform  cartilages.  Beneath  these,  the 
true  and  false  vocal  cords,  with  the  ventricle  between  them.  Still  deeper,  the  cricoid  cartilage 
and  some  of  the  anterior  parts  of  the  rings  of  the  trachea,  and  sometimes,  in  deep  inspiration,  the 
bifurcation  of  the  trachea. 

Surgical  Anatomy. — Foreign  bodies  often  find  their  way  into  the  air-passages.  These  may 
be  either  large  soft  substances,  as  a  piece  of  meat,  which  may  become  lodged  in  the  upper  aper- 
ture of  the  larynx  or  in  the  rima  glottidis,  and  cause  speedy  suffocation  unless  rapidly  got  rid  of, 
or  unless  an  opening  is  made  into  the  air-passages  below,  so  as  to  enable  the  patient  to  breathe. 
Smaller  bodies,  frequently  of  a  hard  nature,  such  as  cherry-  or  plum-stones,  small  pieces  of  bone, 
buttons,  etc.,  may  find  their  way  through  the  rima  glottidis  into  the  trachea  or  bronchus,  or  may 
become  lodged  in  the  ventricle  of  the  larynx.  The  dangers  then  depend  not  so  much  upon  the 
mechanical  obstruction  as  upon  the  spasm  of  the  glottis  which  they  excite  from  reflex  irritation. 
When  lodged  in  the  ventricle  of  the  larynx,  they  may  produce  very  few  symptoms  beyond  sudden 
loss  of  voice  or  alteration  in  the  voice  sounds,  immediately  following  the  inhalation  of  the  foreign 
body.  When,  however,  they  are  situated  in  the  trachea,  they  are  constantly  striking  against 
the  vocal  cords  during  expiratory  efforts,  and  produce  attacks  of  dyspnoea  from  spasm  of  the 
glottis.  When  lodged  in  the  bronchus,  they  usually  become  fixed  there,  and,  occluding  the 
lumen  of  the  tube,  cause  a  loss  of  the  respiratory  murmur  on  the  affected  side,  which  is,  as  stated 
above,  more  often  the  right. 

Beneath  the  mucous  membrane  of  the  upper  part  of  the  air-passages  there  is  a  considerable 
amount  of  submucous  tissue  which  is  liable  to  become  much  swollen  from  effusion  in  inflamma- 
tory affections,  constituting  the  disease  known  as  "  oedema  of  the  glottis."  This  effusion  does 
not  extend  below  the  level  of  the  true  vocal  cords,  on  account  of  the  fact  that  the  mucous  mem- 
brane is  closely  adherent  to  these  structures,  without  the  intervention  of  any  submucous  tissue. 
So  that,  in  cases  of  this  disease  in  which  it  is  necessary  to  open  the  air-passages  to  prevent  suffo- 
cation, the  operation  of  laryngotomy  is  sufficient. 

Chronic  laryngitis  is  an  inflammation  of  the  mucous  glands  of  the  larynx,  which  occurs  in 
those  who  speak  much  in  public,  and  is  known  as  "  clergyman's  sore  throat."  It  is  due  to  the 
dryness  induced  by  the  large  amount  of  cold  air  drawn  into  the  air-passages  during  prolonged 
speaking,  which  incites  increased  activity  in  the  mucous  glands  to  keep  the  parts  moist,  and 
this  eventually  terminates  in  inflammation  of  these  structures. 

Ulceration  of  the  larynx  may  occur  from  syphilis,  either  as  a  superficial  ulceration,  or  from 
the  softening  of  a  gumma;  from  tuberculous  disease  (laryngeal  phthisis),  or  from  malignant 
disease  (epithelioma). 


1390  THE  ORGANS  OF  VOICE  AND  RESPIRATION 

The  air-passages  may  be  opened  surgically  in  two  different  situations:  through  the  crico- 
thyroid  membrane  (laryngotpmy) ,  or  in  some  part  of  the  trachea  (tracheotomy);  and  to  these 
some  surgeons  have  added  a  third  method,  by  opening  the  crico-thyroid  membrane  and 
dividing  the  cartilage  with  the  upper  ring  of  the  trachea  (laryn go-tracheotomy). 

Laryngotomy  is  anatomically  the  more  simple  operation:  it  can  readily  be  performed,  and 
should  be  employed  in  those  cases  where  the  air-passages  require  opening  in  an  emergency  for 
the  relief  of  some  sudden  obstruction  to  respiration.  The  crico-thyroid  membrane  is  very 
superficial,  being  covered  only  in  the  middle  line  by  the  skin,  superficial  fascia,  and  the  deep 
fascia.  On  each  side  of  the  middle  line  it  is  also  covered  by  the  Sterno-hyoid  and  Sterno-thyroid 
muscles,  which  diverge  from  each  other  at  their  upper  parts,  leaving  a  slight  interval  between 
them.  On  these  muscles  rest  the  anterior  jugular  veins.  The  only  vessel  of  any  importance 
in  connection  with  this  operation  is  the  crico-thyroid  artery,  which  crosses  the  crico-thyroid 
membrane,  and  which  may  be  wounded,  but  rarely  gives  rise  to  any  trouble.  The  operation 
is  performed  thus:  the  head  being  thrown  back  and  steadied  by  an  assistant,  the  finger  is  passed 
over  the  front  of  the  neck,  and  the  crico-thyroid  depression  felt  for.  A  vertical  incision  is  then 
made  through  the  skin,  in  the  middle  line  over  this  spot,  and  carried  down  through  the  fascia 
until  the  crico-thyroid  membrane  is  exposed.  A  cross-cut  is  then  made  through  the  membrane, 
close  to  the  upper  border  of  the  cricoid  cartilage,  so  as  to  avoid,  if  possible,  the  crico-thyroid 
artery,  and  a  tracheotomy  tube  is  introduced.  It  has  been  recommended,  as  a  more  rapid  way 
of  performing  the  operation,  to  make  a  transverse  instead  of  a  longitudinal  cut,  through  both  the 
superficial  and  deep  structures,  and  thus  to  open  at  once  the  air-passages.  It  will  be  seen, however, 
that  in  opening  in  this  way  the  anterior  jugular  veins  would  be  in  danger  of  being  wounded. 

Tracheotomy  may  be  performed  either  above  or  below  the  isthmus  of  the  thyroid  body,  or 
this  structure  may  be  divided  and  the  trachea  opened  behind  it. 

The  isthmus  of  the  thyroid  gland  usually  crosses  the  second  and  third  rings  of  the  trachea; 
along  its  upper  border  is  frequently  to  be  found  a  large  transverse  communicating  branch  between 
the  superior  thyroid  veins;  and  the  isthmus  itself  is  covered  by  a  venous  plexus  formed  between 
the  thyroid  veins  of  the  opposite  sides.  Theoretically,  therefore,  it  is  advisable  to  avoid  dividing 
this  structure  in  opening  the  trachea. 

Above  the  isthmus  the  trachea  is  comparatively  superficial,  being  covered  by  the  skin,  super- 
ficial fascia,  deep  fascia,  Sterno-hyoid  and  Sterno-thyroid  muscles,  and  a  second  layer  of  the 
deep  fascia,  which,  attached  above  to  the  lower  border  of  the  hyoid  bone,  descends  beneath  the 
muscles  to  the  thyroid  body,  where  it  divides  into  two  layers  and  enclose  the  isthmus. 

Below  the  isthmus  the  trachea  lies  much  more  deeply,  and  is  covered  by  the  Sterno-hyoid 
and  the  Sterno-thyroid  muscles  and  a  quantity  of  loose  areolar  tissue  in  which  is  a  plexus  of 
veins,  some  of  them  of  large  size;  they  converge  to  two  trunks,  the  inferior  thyroid  veins,  which 
descend  on  either  side  of  the  median  line  on  the  front  of  the  trachea  and  open  into  the  innomi- 
nate veins.  In  the  infant  the  thymus  gland  ascends  a  variable  distance  along  the  front  of  the 
trachea,  and  opposite  the  episternal  notch  the  windpipe  is  crossed  by  the  left  innominate  vein. 
Occasionally,  also,  in  young  subjects,  the  innominate  artery  crosses  the  tube  obliquely  above 
the  level  of  the  sternum.  The  thyroidea  ima  artery,  when  that  vessel  exists,  passes  from  below 
upward  along  the  front  of  the  trachea. 

From  these  observations  it  must  be  evident  that  the  trachea  can  be  more  readily  opened 
above  than  below  the  isthmus  of  the  thyroid  body. 

Tracheotomy  above  the  isthmus  is  performed  thus,  the  patient  should,  if  possible,  be  laid 
on  his  back  on  a  table  in  a  good  light.  A  pillow  is  to  be  placed  under  the  shoulders  and  the 
head  thrown  back  and  steadied  by  an  assistant.  The  surgeon  standing  on  the  right  side  of  his 
patient  makes  an  incision  from  an  inch  and  a  half  to  two  inches  in  length  in  the  median  line  of 
the  neck  from  the  top  of  the  cricoid  cartilage.  The  incision  must  be  made  exactly  in  the  middle 
line,  so  as  to  avoid  the  anterior  jugular  veins,  and  after  the  superficial  structures  have  been 
divided  the  interval  between  the  Sterno-hyoid  muscles  must  be  found,  the  raphe  divided,  and 
the  muscles  drawn  apart.  The  lower  border  of  the  cricoid  cartilage  must  now  be  felt  for,  and 
the  upper  part  of  the  trachea  exposed  from  this  point  downward  in  the  middle  line.  Bose  has 
recommended  that  the  layer  of  fascia  in  front  of  the  trachea  should  be  divided  transversely  at 
the  level  of  the  lower  border  of  the  cricoid  cartilage,  and,  having  been  seized  with  a  pair  of 
forceps,  pressed  downward  with  the  handle  of  the  scalpel.  By  this  means  the  isthmus  of  the 
thyroid  gland  is  depressed,  and  is  saved  from  all  danger  of  being  wounded,  and  the  trachea  is 
cleanly  exposed.  The  trachea  is  now  transfixed  with  a  sharp  hook  and  drawn  forward  in  order 
to  steady  it,  and  is  then  opened  by  inserting  the  knife  into  it  and  dividing  the  two  or  three  upper 
rings  from  below  upward.  If  the  trachea  is  to  be  opened  below  the  isthmus,  the  incicion  to 
expose  it  must  be  made  from  a  little  below  the  cricoid  cartilage  to  the  top  of  the  sternum. 

In  the  child  the  trachea  is  smaller,  more  deeply  placed,  and  more  movable  than  in  tho  adult. 
In  fat  or  short-necked  people,  or  in  those  in  whom  the  muscles  of  the  neck  are  prominently 
developed,  the  trachea  is  more  deeply  placed  than  in  others. 

A  portion  of  the  larynx  or  the  whole  of  it  has  been  removed  or  malignant  disease,  laryn- 
(jectomy. 


THE  PLEURAE 


1391 


Some  surgeons  do  preliminary  tracheotomy,  insert  a  Trendelenburg  cannula  to  prevent  the 
flow  of  blood  downward  into  the  lungs,  and  then  remove  the  larynx.  Other  surgeons  do  not 
employ  preliminary  tracheotomy. 

Perier's  method  of  laryngectomy  is  as  follows:  Make  a  vertical  incision  in  the  median  line 
from  the  level  of  the  hyoid  bone  to  below  the  level  of  the  cricoid  cartilage.  Make  a  transverse 
incision  at  each  end  of  the  vertical  incision.  This  makes  an  I-shaped  wound. 

Separate  the  soft  parts  from  the  larynx  and  upper  part  of  the  trachea,  and  separate  these  two 
structures  from  the  oesophagus.  After  arresting  bleeding,  divide  the  trachea  below  the  cricoid 
cartilage,  introduce  a  special  cinnula,  complete  the  removal  of  the  larynx,  suture  the  opening  of 
the  trachea  to  the  lower  nngleof  the  wound,  and  close  the  rest  of  the  wound  after  securing  drainage. 
In  malignant  disease  of  the  larynx  the  associated  lymphatic  glands  must  be  removed. 

Partial  laryngectomy,  according  to  Sir  F.  Semon,  is  the  removal  of  not  less  than  one  wing  of 
the  thyroid  cartilage.  Removal  of  a  lesser  piece  of  the  thyroid  or  of  a  bit  of  the  arytenoid  or 
cricoid  he  considers  with  the  operation  of  thyrotomy. 


THE  PLEURAE  (Figs.  997,  998,  999,  1000,  1001). 

Each  lung  is  invested,  upon  its  external  surface,  by  an  exceedingly  delicate 
serous  membrane,  the  pleura,  which  encloses  the  organ  as  far  as  its  root,  and  is 
then  reflected  upon  the  inner  surface  of  the  thorax.  The  portion  of  the  serous 
membrane  investing  the  surface  of  the  lung  and  dipping  into  the  fissures  between 
its  lobes  is  called  the  pulmonary  pleura  or  the  visceral  layer  of  the  pleura  (pleura 
pulmonalis)(Fig.  997),  while  that  which  lines  the  inner  surface  of  the  chest  is  called 
the  parietal  layer  of  the  pleura  (pleura  parietalis)  (Fig.  997).  The  two  layers  join  at 
the  hilum  of  the  lung.  The  space  between  these  two  layers  is  called  the  cavity  of  the 
pleura  (cavum  pleurae),  and  contains  a  very  little  clear  fluid.  It  must  be  borne 
in  mind  that  in  the  healthy  condition  the  two  layers  are  in  contact,  and  there 


TRIANGULARIS    STERN). 

Internal  Mammary  Vessels. 


Left  Phrenic  Nerve 


Pleura  Pulmonalis. 
Pleura  Costalis. 


Mediastinum 


\      Vena  A*yffO»  Major )  Pof(erior 
Vagus  Venn  > 


FIG.  997. — A  transverse  section  of  the  thorax,  showing  the  relative  position  of  the  viscera  and  the 

reflections  of  the  pleurae. 

is  no  real  cavity  until  the  lung  becomes  collapsed  and  separates  from  the  wall 
of  the  chest.  Each  pleura  is  therefore  a  shut  sac,  one  occupying  the  right,  the 
other  the  left  half  of  the  thorax,  and  they  are  perfectly  separate  from  each  other. 


1392 


THE  ORGANS  OF  VOICE  AND  RESPIRATION 


The  two  pleurae  do  not  meet  in  the  middle  line  of  the  chest,  excepting  anteriorly 
opposite  the  second  and  third  pieces  of  the  sternum — a  space  being  left  between 
them,  which  contains  all  the  viscera  of  the  thorax  excepting  the  lungs;  this  is  the 
mediastinum. 


SCALCNUS 
MINIMUS 


SYMPATHETIC 
GANGLION 


FIG.  998. — The  dome  of  the  pleura      (Poirier  and  Charpy.) 

Reflections  of  the  Pleurae  (Fig.  997).  The  Pleura  Pulmonalis  (Fig.  997).— The 
pleura  pulmonalis  is  closely  attached  to  the  surface  of  the  lung  and  enters  into  the 
depths  of  the  interlobar  fissures.  It  leaves  the  lung  surface  at  the  hilum,  covers  the 


COSTA PLED RAL 
LIGAMENT 


SCALENUS 
MINIMUS 
MUSCLE 


„       FIG.  999. — The  supports  of  the  pleural  dome.     The  oesophagus,  trachea,  and  arteries  have  been  cut  and  pulled 
aside  to  show  the  pleural  reinforcements.     (Poirier  and  Charpy.) 


root  of  the  lung  for  a  little  way  (Fig.  1004  and  1005),  and  then  passes  into  the  medi- 
astinal  pleura.  Between  the  hilum  and  the  mediastinal  pleura  there  is  a  thickened 
pleural  fold,  triangular  in  outline,  and  called  the  ligamentum  pulmonale  or  the 
ligamentum  latum  pulmonis  (Figs.  1004  and  1005).  It  is  formed  by  the  two  layers  of 


THE  PLEURAE 


1393 


the  pulmonary  pleura  coming  in  contact  below  the  root  of  the  lung.  This  fold 
passes  from  the  lower  part  of  the  inner  pulmonary  surface  to  the -pericardium, 
and  the  lower  border  is  free  or  attached  to  the  diaphragmatic  pleura.  In  the 
right  lung  the  origin  of  this  ligament  is  in  front  of  the  groove  for  the  azygos  vein; 
in  the  left  lung  it  is  in  front  of  the  groove  for  the  thoracic  aorta. 

The  Pleura  Parietalis. — The  pleura  parietalis  is  a  continuous  membrane,  but 
for  convenience  is  divided  into  the  cervical  pleura,  costal  pleura,  mediastinal  pleura, 
and  diaphragmatic  pleura. 

The  Cervical  Pleura  or  Dome  of  the  Pleura  or  Cupola  (cupula  pleurae}  (Fig.  1000)  is 
the  dome-shaped  roof  of  the  cavity  of  the  pleura.  It  projects  above  the  apex  of  the 
lung  to  the  neck  of  the  first  rib.  As  the  first  rib  is  placed  obliquely,  the  dome  of  the 
pleura  reaches  from  one  to  one  and  one-half  inches  above  the  anterior  extremity  of 
the  first  rib,  and  from  one-half  an  inch  to  one  inch  above  the  clavicle.  On  the 
outer  side  of  the  cervical  pleura  are  the  Scalenus  anticus  and  medius  muscles.  Just 


SYMPATHETIC 
GANGLION 


FIRST 

THORACIC 

NERVE 


SIXTH 
RIB 


I.ONGUS   COLL! 
MUSCLE 


.SIBSON'S 
APONEUROSIS 


HRENICO- 
OSTAL  SINUS 


CELLULAR 
TISSUE 


DIAPHRAGM 


^ 

FIG.  1001. — Section  of  the  wall  of  the 

FIG.  1000. — The  supports  of  the  pleural  dome.     (Poirier  and          thorax,  showing  the  phrenico-costal  sinus. 
Charpy.)  (Poirier  and  Charpy..) 


(Poirier  and  Charpy.) 

below  the  apex,  on  the  anterior  and  inner  surface,  is  a  groove  for  the  subclavian 
artery,  which  vessel  passes  over  it  in  an  arch  (Fig.  998).  A  little  below  the  groove 
for  the  subclavian  artery  is  a  broader  and  shallower  groove  for  the  innominate  and 
subclavian  veins.  Above  the  subclavian  artery  and  in  front  and  above  the  cervical 
pleura  are  the  cords  of  origin  of  the  brachial  plexus  and  the  inferior  cervical  gan- 
glion (Fig.  998).  The  dome  is  strengthened  and  kept  in  place  by  Sibson's  aponeu- 
rosis  or  the  vertebro-pleural  ligament  (Figs.  999  and  1000).  This  comes  from  a  little 
piece  of  muscle,  the  Scalenus  minimus  muscle,  which  originates  from  the  transverse 
process  of  the  seventh  cervical  vertebra,  broadens  and  becomes  aponeurotic  as  it 
descends,  and  is  inserted  into  the  inner  margin  of  the  first  rib  (Figs.  998  and  999). 
It  is  also  strengthened  by  the  costo-pleural  ligament  (Fig.  999),  from  the  inner  sur- 
face of  the  neck  of  the  first  rib  to  the  pleura,  and  by  fibrous  bands  which  pass  to  the 
tissue  about  the  subclavian  sheath,  trachea,  and  oesophagus  (Fig.  999). 

The  Costal  Pleura  (pleura  costalis]   (Fig.  997)  is  the  shortest  portion  of  the 
pleura  and  is  connected  to  the  parts  it  covers  by  the  endothoracic  fascia  (fascia 


1394  THE  ORGANS  OF  VOICE  AND  RESPIRATION 

endothoracica) ,  a  layer  of  connective  tissue  which  is  much  thicker  back  of  the  rib 
cartilages  than  it  is  posteriorly.  The  costal  pleura  covers  the  inner  surface  of  part 
of  the  sternum,  the  costal  cartilages,  ribs,  and  Intercostal  muscles,  and  the  sides 
of  the  bodies  of  the  thoracic  vertebrae.  This  layer  is  loosely  attached  except  as  it 
passes  from  the  heads  of  the  ribs  to  the  vertebrae,  where  it  is  firmly  adherent. 

The  Mediastinal  Pleura  (pleura  mediastinalis]  (Fig.  999)  covers  the  septum  of  the 
mediastinum,  which  intervenes  between  the  two  pleural  cavities.  The  mediastinal 
pleura  extends  from  the  inner  surface  or  the  anterior  wall  of  the  thorax  to  the 
vertebrae.  It  is  continuous  in  front  and  back  with  the  costal  pleura  of  the  same 
side,  the  lines  of  junction  being  known,  respectively,  as  the  anterior  line  of  pleural 
reflection  and  the  posterior  line  of  pleural  reflection.  Below  the  mediastinal  pleura 
passes  into  the  diaphragmatic  pleura  of  the  same  side.  The  portion  of  the  medi- 
astinal pleura  which  fuses  with  the  parietal  layer  of  the  pericardium  is  called  the 
pericardial  pleura  (pleura  pericardiaca). 

Above  the  root  of  the  lung  the  mediastinal  pleura  passes  back  directly  to  the 
vertebrae.  "  In  this  region  the  left  mediastinal  pleura  is  applied  to  the  arch  of  the 
aorta  and  the  phrenic  and  vagus  nerves;  to  the  left  innominate  vein,  the  left 
superior  intercostal  vein,  and.  the  left  common  carotid  and  left  subclavian  arteries; 
to  the  oesophagus  and  the  thoracic  duct.  The  right  mediastinal  pleura,  on  the  other 
hand,  is  applied,  above  the  level  of  the  root  of  the  lung,  to  the  upper  part  of  the 
precava  and  right  innominate  vein;  to  the  right  innominate  artery;  to  the  vena 
azygos  major,  as  it  hooks  forward  above  the  bronchus;  to  the  vagus  and  phrenic 
nerves;  and  to  the  right  side  of  the  trachea."1  Upon  the  pericardium  the  phrenic 
nerve  is  covered  by  the  pleura.  Back  of  the  root  of  the  lung  and  the  pulmonary 
ligament,  the  right  mediastinal  pleura  passes  back  to  the  vertebrae  to  the  left  of  the 
oesophagus;  the  left  mediastinal  pleura  passes  back  over  the  descending  aorta, 
and  just  above  the  Diaphragm  and  in  front  of  the  aorta  over  the  lower  end  of  the 
oesophagus. 

The  Diaphragmatic  Pleura  (pleura  diaphragmatica)  (Figs.  1001  and  1002)  covers 
the  upper  surface  of  the  Diaphragm  outside  of  the  base  of  the  pericardium,  but 
does  not  completely  cover  it;  for  it  does  not  pass  into  the  interval  between  the 
wall  of  the  thorax  and  Diaphragm,  and  before  this  point  is  reached  becomes 
continuous  with  the  costal  pleura. 

The  reflection  to  the  costal  pleura  begins  by  the  sternum,  at  the  lower  margin  of 
the  sixth  rib ;  takes  place  at  the  junction  of  the  cartilage  of  the  rib  with  the  seventh 
rib;  posteriorly,  it  takes  place  at  the  lower  margin  of  the  twelfth  thoracic  vertebra. 

In  the  front  of  the  chest,  where  the  parietal  layer  of  the  pleura  is  reflected  back- 
ward to  the  pericardium,  the  two  pleural  sacs  are  in  contact  for  a  considerable 
extent.  At  the  upper  part  of  the  chest,  behind  the  manubrium,  they  are  not  in 
contact;  the  point  of  reflection  being  represented  by  a  line  drawn  from  the  sterno- 
clavicular  articulation  to  the  mid-point  of  the  junction  of  the  manubrium  to  the 
body  of  the  sternum.  From  this  point  the  two  pleurae  descend  in  close  contact  to 
the  level  of  the  fourth  costal  cartilages  Here  the  line  of  reflection  on  the  right  side 
is  continued  downward  in  nearly  a  straight  line  to  the  lower  end  of  the  gladiolus  and 
then  turns  outward  behind  the  costal  cartilage  of  the  sixth  rib,  continuing  to 
descend  and  to  run  outward,  it  passes  behind  the  descending  part  of  the  seventh 
costal  cartilage,  and  meets  the  axillary  line  at  the  junction  of  the  eighth  rib  with 
the  cartilage.  The  line  of  reflection  continues  to  descend  till  it  reaches  its  lowest 
point  at  the  tenth  rib.  This  point  is  in  the  axillary  line,  while  on  the  left  side 
the  line  of  reflection  diverges  outward,  so  that  opposite  the  seventh  cartilage  it  is 
about  three-quarters  of  an  inch  from  the  left  border  of  the  sternum.  It,  how- 
ever, always  extends  considerably  farther  over  the  pericardium  than  the  corre- 
sponding lung.  From  this  joint  the  reflections  of  the  two  sides  are  practically 

1  Cunningham's  Text-book  of  Anatomy. 


THE  PLEURAE  1395 

• 

the  same.  The  lower  limit  of  the  pleura  is  on  a  considerably  lower  level  than 
the  lower  limit  of  the  lung,  but  does  not  extend  to  the  attachment  of  the  Dia- 
phragm, so  that  below  the  line  of  reflection  of  the  pleura  from  the  chest  wall 
on  to  the  Diaphragm  the  latter  is  in  direct  contact  with  the  rib  cartilages  and 
the  Internal  intercostal  muscles.  In  ordinary  inspiration  the  thin  margin  of  the 
base  of  the  lung  does  not  extend  as  low  as  the  line  of  pleural  reflection,  with  the 
result  that  the  costal  and  diaphragmatic  pleura  are  here  in  contact,  the  narrow 
slit  between  the  two  being  termed  the  phrenico-costal  sinus  (sinus  phrenicocos- 
talis)  (Fig.  1001).  A  similar  condition  exists  behind  the  sternum  and  rib  cartilages, 
where  the  anterior  thin  margin  of  the  lung  falls  short  of  the  line  of  pleural  reflec- 
tion, and  where  the  slit-like  cavity  between  the  two  layers  of  pleura  forms  what  is 
sometimes  called  the  costo-mediastinal  sinus  (sinus  costomediastinalis) . 

Along  the  line  of  reflection  of  the  diaphragmatic  pleura  a  dense  fascia  passes 
from  the  costal  cartilages  and  the  uncovered  portion  of  the  Diaphragm  to  the 
costal  pleura.  This  serves  to  hold  it  in  place.  It  is  named  by  Cunningham  the 
phrenico -pleural  fascia. 

The  inner  surface  of  the  pleura  is  smooth,  polished,  and  moistened  by  a  serous 
fluid;  its  outer  surface  is  intimately  adherent  to  the  surface  of  the  lung,  and  to  the 
pulmonary  vessels  as  they  emerge  from  the  pericardium;  it  is  also  adherent  to  the 
upper  surface  of  the  Diaphragm;  throughout  the  rest  of  its  extent  it  is  somewhat 
thicker,  and  may  be  separated  from  the  adjacent  parts  with  extreme  facility. 

The  right  pleural  sac  is  shorter,  wider,  and  reaches  higher  in  the  neck  than 
the  left. 

Structure  of  the  Pleura. — The  pleura  is  composed  of  connective  tissue  con- 
taining much  elastic  tissue,  its  free  surface  being  covered  with  flat  endothelial  cells. 
It  is  fastened  to  adjacent  structures  by  subserous  areolar  tissue.  The  subserous 
tissue  of  the  visceral  pleura  is  continuous  with  the  areolar  tissue  of  the  lung. 

Vessels  and  Nerves. — The  arteries  of  the  pleura  are  derived  from  the  intercostal, 
the  internal  mammary,  the  musculo-phrenic,  thymic,  pericardiac,  and  bronchial. 
The  veins  correspond  to  the  arteries.  The  lymphatics  are  very  numerous  in  the 
pleura  and  subserous  tissue.  Many  of  them  are  in  direct  communication  with  the 
pleural  cavity  by  stomata  between  the  endothelial  cells.  Stomata  are  absent  in 
the  mediastinal  pleura  and  over  the  ribs  (Dyskowsky).  The  lymphatics  of  the 
visceral  layer  empty  into  the  superficial  pulmonary  trunks ;  the  lymphatics  of  the 
costal  pleura  empty  into  the  intercostal  trunks;  of  the  diaphragmatic  pleura,  into 
the  diaphragmatic  trunks;  of  the  mediastinal  pleura,  into  the  posterior  mediastinal 
glands.1  The  nerves  are  derived  from  the  phrenic  and  sympathetic  (Luschka). 
Kolliker  states  that  nerves  accompany  the  ramification  of  the  bronchial  arteries 
in  the  pleural  pulmonalis. 

Surgical  Anatomy. — In  operations  upon  the  kidney  it  must  be  borne  in  mind  that  the  pleura 
may  sometimes  extend  below  the  level  of  the  last  rib,  and  may  therefore  be  opened  in  these 
operations,  especially  when  the  last  rib  is  removed,  in  order  to  give  more  room.  It  is  best  to 
keep  the  incision  at  least  one  inch  below  the  last  rib,  enlarging  the  wound  afterward,  when  the 
finger  can  be  introduced  as  a  guide. 

In  wounds  of  the  Diaphragm  the  pleura  may  be  injured.  In  operations  about  the  root  of 
the  neck,  especially  in  the  removal  of  glands  and  the  ligation  of  the  first  part  of  the  subclavian 
artery,  the  pleura  may  be  injured. 

Punctured  wounds  of  the  root  of  the  neck  are  apt  to  reach  the  pleura. 

Empyema  is  a  surgical  disease.  In  acute  empyema  the  treatment  is  drainage.  A  portion  of 
the  fifth  or  sixth  rib  in  the  axillary  line  is  removed  by  subperiosteal  resection,  the  pleura  is 
opened,  and  a  tube  is  introduced.  In  chronic  empyema  the  lung  is  contracted  and  adherent  and 
cannot  expand;  hence  drainage  will  not  cure  it.  It  is  necessary  to  perform  multiple  rib  resec- 
tion in  order  to  permit  the  chest-wall  to  sink  in  and  obliterate  the  cavity,  which,  as  the  lung 
is  unable  to  expand,  it  cannot  do.  The  necessary  operation  may  be  the  operation  of  Estlander, 
or  the  operation  of  Schede,  or  the  operation  of  Fowler  (page  168). 

,  '  Poirier,  Cune'o,  and  Delamare  on  the  Lymphatics.     Translated  and  edited  by  Cecil  H.  Leaf. 


1396  THE  ORGANS  OF  VOICE  AND  RESPIRATION 

If  a  large  wound  admits  suddenly  a  quantity  of  air  into  the  pleura,  dangerous  or  fatal  pneumo- 
thorax arises,  and  the  lung  collapses.  This  is  usually  met  during  operations  by  using  the  Fell- 
O1  Dwyer  apparatus  for  artificial  respiration  as  advised  by  Matas.1  This  apparatus  keeps  the 
lung  expanded,  in  spite  of  the  entrance  of  air  into  the  pleural  sac.  A  surgeon  can  open  the  pleura 
widely  without  any  fear  of  the  lung  collapsing  if  he  operates  in  a  Sauerbruch  chamber.  The 
pressure  within  this  chamber  is  negative.  The  patient's  head  is  outside  of  the  chamber,  his  body  is 
within  it.  The  bronchioles  are  distended  by  the  animal  inhaling  air  at  the  ordinary  pressure,  but 
the  exposed  lung  is  subjected  to  negative  pressure,  hence  the  lung  does  not  collapse  in  spite  of  a 
large  wound  in  the  pleura.  In  surgical  pneumothorax  the  lung  may  be  sutured  to  the  chest-wall, 
so  as  to  block  the  opening.  Sometimes,  in  order  to  arrest  dangerous  pulmonary  bleeding,  a  surgeon 
deliberately  induces  pneumothorax,  in  hope  that  the  collapse  of  the  lung  will  arrest  bleeding. 

When  an  abscess  of  the  liver  is  posterior  and  on  the  dorsum,  transpleural  hepatotomy  is  per- 
formed. A  portion  of  the  tenth  and  eleventh  ribs  below  the  angle  of  the  scapula  is  removed. 
As  a  rule,  the  pleura  is  found  obliterated  at  this  point.  If  it  is  opened,  it  is  at  once  sutured  or 
closed  with  gauze  packing.  The  exposed  Diaphragm  is  incised,  and,  as  it  is  usually  adherent 
to  the  liver,  the  abscess  cavity  is  entered.  If  it  is  not  adherent,  the  liver  is  exposed  and  the 
abscess  sought  for  with  an  aspirating-needle. 

THE  MEDIASTINAL  SPACE,  INTERPLEURAL  SPACE  OR 
MEDIASTINUM. 

The  mediastinum  is  the  space  left  in  the  median  portion  of  the  chest  by  the  non- 
approximation  of  the  two  pleurae.  It  extends  from  the  sternum  in  front  to  the 
spine  behind.  Within  it  are  the  contents  of  the  thorax  excepting  the  lungs.  The 
mediastinum  may  be  divided  for  purposes  of  description  into  two  parts — an 
upper  portion,  above  the  upper  level  of  the  pericardium,  which  is  named  the 
superior  mediastinum  (Struthers);  and  a  lower  portion,  below  the  upper  level  of 
the  pericardium.  This  lower  portion  is  again  subdivided  into  three — that  part 
which  contains  the  pericardium  and  its  contents,  the  middle  mediastinum;  that 
part  which  is  in  front  of  the  pericardium,  the  anterior  mediastinum;  and  that  part 
which  is  behind  the  pericardium,  the  posterior  mediastinum. 

The  Superior  Mediastinum  (Fig.  1003).— The  superior  mediastinum  is  that  por- 
tion of  the  interpleural  space  which  lies  above  the  upper  level  of  the  pericardium 
between  the  manubrium  sterni  in  front  and  the  upper  thoracic  vertebrae  behind.  It 
is  bounded  below  by  a  plane  passing  backward  from  the  junction  of  the  manubrium 
and  gladiolus  sterni  to  the  lower  part  of  the  body  of  the  fourth  thoracic  vertebra, 
and  laterally  by  the  lungs  and  pleurae.  It  contains  the  origins  of  the  Sterno-hyoid 
and  Sterno-thyroid  muscles  and  the  lower  ends  of  the  Longus  colli  muscles;  the 
arch  of  the  aorta;  the  innominate,  the  thoracic  portion  of  the  left  carotid  and  sub- 
clavian  arteries;  the  upper  half  of  the  precava  and  the  innominate  veins,  and  the 
left  superior  intercostal  vein;  the  vagus,  cardiac,  phrenic,  and  left  recurrent  laryn- 
geal  nerves;  the  trachea,  oesophagus,  and  thoracic  duct;  the  remains  of  the 
thymus  gland  and  some  lymphatic  glands. 

The  Anterior  Mediastinum  (Fig.  997).— The  anterior  mediastinum  is  bounded 
in  front  by  the  sternum,  on  each  side  by  the  pleura,  and  behind  by  the  pericardium. 
It  is  narrow  above,  but  widens  out  a  little  below,  and,  owing  to  the  oblique  course 
taken  by  the  left  pleura,  it  is  directed  from  above  obliquely  downward  and  to  the 
left.  Its  anterior  wall  is  formed  by  the  left  Triangularis  sterni  muscle  and  the 
fifth,  sixth,  and  seventh  left  costal  cartilages.  It  contains  a  quantity  of  loose 
areolar  tissue,  some  lymphatic  vessels  which  ascend  from  the  convex  surface  of  the 
liver,  two  or  three  lymphatic  glands  (anterior  mediastinal  glands),  and  the  small 
mediastinal  branches  of  the  internal  mammary  artery. 

The  Middle  Mediastinum  (Fig.  997).— The  middle  mediastinum  is  the 
broadest  part  of  the  interpleural  space.  It  contains  the  heart  enclosed  in  the 
pericardium,  the  ascending  aorta,  the  lower  half  of  the  precava,  with  the  vena 
azygos  major  opening  into  it,  the  bifurcation  of  the  trachea  and  the  two  bronchi, 

»  Annals  of  Surgery,  April,  1899. 


THE  MEDIASTINAL  SPACE  OR  MEDIASTINUM 


1397 


the  pulmonary  artery  dividing  into  its  two  branches  and  the  right  and  left  pul- 
monary veins,  the  phrenic  nerves,  and  some  bronchial  lymphatic  glands. 

The  Posterior  Mediastinum  (Figs.  997  and  1001).— The  posterior  mediastinum 
is  an  irregular  triangular  space  running  parallel  with  the  vertebral  column;  it  is 
bounded  in  front  by  the  pericardium  and  roots  of  the  lungs,  behind  by  the  verte- 


Fio.  1002. — The  posterior  mediastinum. 

braL  column  from  the  lower  border  of  the  fourth  thoracic  vertebra,  and  on  either 
side  by  the  pleura.  It  contains  the  descending  thoracic  aorta,  the  greater  and 
lesser  azygos  veins,  the  vagus  and  splanchnic  nerves,  the  oesophagus,  thoracic 
duct,  and  some  lymphatic  glands. 

Blood-vessels. — The  areolar  tissue  of  the  anterior  mediastinum  receives  numer- 
ous mediastinal  branches  from  the  internal  mammary  artery.     The  areolar  tissue 


1398 


THE  ORGANS  OF  VOICE  AND  RESPIRATION 


of  the  posterior  mediastinum  receives  mediastinal  branches  from  the  descending 
thoracic  aorta.  The  lowest  mediastinal  vessels  lie  upon  the  Diaphragm  and  are 
called  superior  phrenic  arteries.  The  precava  and  internal  mammary  veins  receive 
mediastinal  branches. 


Left  Inom- 
inate  Vein. 


Left  Carotid 
Artery. 


Thymus 
Gland. 


Vagus 
Nerve. 


Internal  Mammary 
Artery. 


Right  Innom- 
inate Vein. 


Vertebral 

Artery 

Left  SuUcaviun, 
Artery. 

Oesophagus.-'" 


V 

3rd  Rib. 

FIG.  1003. — Transverse  section  through  the  second  thoracic  vertebra.    (Braune.) 

The  anterior  mediastinal  lymphatic  glands  are  in  the  upper  portion  of  the  anterior 
mediastinum.  They  are  five  or  six  in  number  and  are  placed  in  front  of  the  trans- 
verse arch  of  the  aorta.  Chains  of  glands  run  up  from  them  to  the  root  of  the 
neck.  On  the  right  side  glands  are  in  front  of  the  right  innominate  vein,  between 
the  artery  and  vein  and  behind  the  artery.  On  the  left  side  they  are  around  the 
left  common  carotid  and  left  subclavian  arteries.1 

The  posterior  mediastinal  glands  are  around  the  oesophagus,  particularly  in  front 
of  it.  The  peritracheo-bronchial  glands  have  been  described. 


THE  LUNGS  (PULMONES)   (Figs.  997,  1004,  1005,  1006,  1007,  1008,  1009). 

The  lungs  are  the  essential  organs  of  respiration;  they  are  two  in  number, 
placed  one  on  each  side  of  the  chest,  separated  from  each  other  by  the  heart  and 
other  contents  of  the  mediastinum.  A  healthy  lung  hangs  free  within  the  pleural 
cavity.  It  is  suspended  by  the  root  and  by  the  ligamentum  pulmonis.  In  many 
cases  examined  the  lung  does  not  hang  free,  but,  as  a  result  of  former  pleurisy, 
an  area  of  the  pulmonary  pleura  is  adherent  to  the  parietal  pleura.  Each  lung  is 
conical  in  shape,  and  presents  for  examination  an  apex,  a  base,  two  borders,  and 
two  surfaces. 

The  Apex  (apex  pulmonis). — The  apex  forms  a  tapering  cone  which  extends 
into  the  root  of  the  neck  about  an  inch  to  two  inches  above  the  level  of  the  anterior 
extremity  of  the  first  rib.  The  brachial  plexus  is  in  close  proximity  to  (his  por- 
tion of  the  lung. 

The  Base  (basis  pulmonis). — The  base  is  broad,  concave,  and  rests,  by  its 
diaphragmatic  surface  (fades  diaphragmatica) ,  upon  the  convex  surface  of  the 

1  Poirier,  Cuneo,  and  Delamare  on  the  Lymphatics.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE  LUNGS 


1399 


Diaphragm,  which  separates  the  right  lung  from  the  upper  surface  of  the  right 
lobe  of  the  liver  and  the  left  lung  from  the  upper  surface  of  the  left  lobe  of  the 
liver,  the  fundus  of  the  stomach,  and  the  spleen;  its  circumference  is  thin,  and 


GROOVE   FOR 
INNOMINATE  VEIN 


HILUM 
OF  LUNG 


ANTERIOR 
BORDER 


LINE  OF  REFLECTION 
OF  PULMONARY 
PLEURA  ON  TO 
ROOT  OF  LUNG 


LIGAMENTUM 
LATUM   PULMONIS 


FIG.  1004. — The  right  lung.     The  inner  or  mediastinal  surface,  with  the  hilum  laid  bare  by  the  removal  of  the 
structures  forming  the  root  of  the  lung.     (Toldt.) 


SUBCLAVIAN 
GROOVE 


PULMONARY 
ARTERY 


BRONCHUS 


PULMONARY 
VEINS 


BRONCHIAL 
ARTERIES 


BRONCHIAL 

LYMPHATIC 

GLAND 


LIGAMENTUM 

LATUM 

PULMONIS 


CARDIAC 
DEPRESSION 


INFERIOR 
BORDER 


FIG.  1005. — The  left  lung.    The  inner  or  mediastinal  surface,  with  the  root  of  the  lung  cut  across.    (Toldt  ) 

projects  for  some  distance  into  the  phrenico-costal  sinus  of  the  pleura,  between 
the  lower  ribs  and  the  costal  attachment  of  the  Diaphragm,  extending  lower 
down  externallv  and  behind  than  in  front 


1400 


THE  ORGANS  OF  VOICE  AND  RESPIRATION 


Surfaces.  The  External,  Costal,  or  Thoracic  Surface  (fades  costalis]  (Figs.  1008 
and  1009). — The  external,  costal,  or  thoracic  surface  is  smooth,  convex,  of  con- 
siderable extent,  and  corresponds  to  the  form  of  the  cavity  of  the  chest,  being 
deeper  behind  than  in  front.  In  a  hardened  specimen  this  surface  has  grooves 
and  bulgings  on  it  corresponding  to  the  ribs  and  intercostal  spaces. 

The  Inner  or  Mediastinal  Surface  (Jades  mediastinalis)(Figs.l6Q4  and  1005). — The 


FIG.  1006. — Front  view  of  the  heart  and  lungs. 

inner  or  mediastinal  surface  is  concave.  It  presents  in  front  a  depression  corre- 
sponding to  the  convex  surface  of  the  pericardium,  and  behind  a  deep  fissure,  the 
hilum  (hilus  pulmonalis).  In  the  hilum  lie  the  bronchi,  vessels,  nerves,  and 
lymph-nodes,  which  together  constitute  the  root  of  the  lung.  On  the  inner  and 
anterior  surface,  a  little  below  the  apex,  is  a  groove,  the  subclavian  groove  (sulcus 
subdavius),  for  the  subclavian  artery.  A  little  lower  is  a  broader  and  shallower 
groove  for  the  innominate  and  subclavian  veins.  The  pleura  lies  between  the 
lungs  and  these  vessels.  .  In  front  of  the  hilum  and  below  it  is  a  depression  for 
the  heart  (impressio  cardiaca).  It  is  deeper  on  the  left  than  on  the  right  side. 
On  the  right  side  it  passes  into  the  groove  from  the  precava  and  the  vena  azygos 
major.  On  the  left  side,  behind  the  hilum,  is  a  groove  for  the  thoracic  aorta;  on 
the  right  side  a  groove  for  the  oesophagus. 

Borders.  The  Inferior  Border  (margo  inferior). — The  inferior  border  is  the  line 
of  junction  of  the  costal  and  diaphragmatic  surfaces.  Posteriorly,  it  is  rounded 
and  broad,  and  is  received  into  the  deep  concavity  on  either  side  of  the  spinal 
column.  It  is  much  longer  than  the  anterior  border,  and  projects,  below,  into 
the  phrenico-costal  sinus. 

The  Anterior  Border  (margo  anterior). — The  anterior  border  is  thin  and  sharp, 
overlaps  the  front  of  the  pericardium,  and  is  projected  into  the  costo-medi- 


THE  LUNGS 


1401 


astinal  sinus  of  the  pleura.      The  anterior  border  of  the  right  lung  is  almost 
vertical ;  that  of  the  left  presents,  below,  an  angular  notch,  the  incisura  cardiaca, 


ENTRANCE   OF 

VENA     AZYGOS 

BRANCH    OF   PUL- 
MONARY  ARTERY 


FIG.  1007. — Pulmonary  veins,  seen  in  a  dorsal  view  of  the  heart  and  lungs.  The  lungs  have  been  pulled 
away  from  the  median  line,  and  a  part  of  the  right  lung  has  been  cut  away  to  display  the  air-ducts  and  blood- 
vessels. (Testut.) 


FIG.  1008. — The  right  lung.    The  outer  or  costal 
surface.    (Toldt.) 


FIG.  1009. — The  left  lung.    The  outer  or  costal 
surface.    (Toldt.) 


into  which  the  heart  and  pericardium  are  received.     A  projection  from  the  upper 
lobe  comes  forward  beneath  the  cardiac  notch;  it  is  called  the  lingula  pulmonis. 

The  Lobes  of  the  Lungs  (Figs.  1008  and  1009).— Each  lung  is  divided  into  two 
lobes,  an  upper  (lobus  superior]  and  a  lower  (lobus  inferior},  by  a  long  and  deep 


1402  THE  ORGANS  OF  VOICE  AND  RESPIRATION 

fissure  (incisura  interlobaris),  which  extends  from  the  upper  part  of  the  posterior 
border  of  the  organ  about  three  inches  from  its  apex,  downward  and  forward  to 
the  lowest  part  of  the  lung  just  external  to  its  anterior  border.  This  fissure  pene- 
trates nearly  to  the  root.  The  upper  lobe  is  the  smaller;  the  lower  lobe  is  the 
larger.  In  the  right  lung  the  upper  lobe  is  partially  subdivided  by  a  second  and 
shorter  fissure,  which  extends  almost  horizontally  forward  from  the  middle  of 
the  preceding  to  the  anterior  margin  of  the  organ,  marking  off  a  small  triangular 
portion,  the  middle  lobe  (lobm  medius). 

The  right  lung  is  the  larger  and  heavier;  it  is  broader  than  the  left,  owing  to 
the  inclination  of  the  heart  to  the  left  side;  it  is  also  shorter  by  an  inch,  in  conse- 
quence of  the  Diaphragm  rising  higher  on  the  right  side  to  accommodate  the  liver. 

The  Root  of  the  Lung  (radix  pulmonis) (Figs.  1004,1005,  1006,  and  1007).— A 
little  above  the  middle  of  the  inner  surface  of  each  lung,  and  nearer  its  posterior 
than  its  anterior  border,  is  its  root,  by  which  the  lung  is  connected  to  the  heart 
and  the  trachea.  The  root  is  formed  by  the  bronchial  tube,  the  pulmonary 
artery,  the  pulmonary  veins,  the  bronchial  arteries  and  veins,  the  pulmonary 
plexus  of  nerves,  lymphatics,  bronchial  glands,  and  areolar  tissue,  all  of  which 
are  enclosed  by  a  reflection  of  the  pleura.  The  root  of  the  right  lung  lies  behind 
the  precava  and  ascending  portion  of  the  aorta,  and  below  the  vena  azygos  major. 
The  root  of  the  left  lung  passes  beneath  the  arch  of  the  aorta  and  in  front  of  the 
descending  aorta;  the  phrenic  nerve  and  the  anterior  pulmonary  plexus  lie  in 
front  of  each,  and  the  vagus  and  posterior  pulmonary  plexus  behind  each. 

The  chief  structures  composing  the  root  of  each  lung  are  arranged  in  a  similar 
manner  from  before  backward  on  both  sides — viz.,  the  two  pulmonary  veins  in  front; 
the  pulmonary  artery  in  the  middle;  and  the  bronchus,  together  with  the  bronchial 
vessels,  behind.  From  above  downward,  on  the  two  sides,  their  arrangement  differs, 
thus:  On  the  right  side  their  position  is — bronchus,  pulmonary  artery,  pulmonary 
veins;  but  on  the  left  side  their  position  is — pulmonary  artery,  bronchus,  pulmo- 
nary veins.  It  should  be  noted  that  the  entire  right  bronchus,  does  not  lie  above 
the  right  pulmonary  artery,  but  only  its  eparterial  branch  (see  p.  1385),  which 
passes  to  the  upper  lobe  of  the  right  lung;  the  divisions  of  the  bronchus  for  the 
middle  and  lower  lobes  lie  below  the  artery. 

The  true  weight  of  the  human  lungs  as  ascertained  in  the  bodies  of  criminals 
executed  by  electricity,  in  which  the  mode  of  death  is  attended  by  a  nearly  bloodless 
condition  of  the  lungs,  is  215  grams  (7^  ounces)  for  the  left  lung  and  240  grams 
(8£  ounces)  for  the  right  lung  (E.  A.  Spitzka,  Amer.  Jour,  of  Anat.,  iii.,  1,  p.  v.). 
Ordinarily,  with  the  vascular  channels  more  or  less  filled  with  blood  and  serum, 
the  two  lungs  together  weigh  about  42  ounces,  the  right  lung  being  2  ounces 
heavier  than  the  left,  but  much  variation  is  met  with  according  to  the  amount  of 
blood  or  serous  fluid  they  may  contain.  The  lungs  are  heavier  in  the  male  than 
in  the  female.  The  specific  gravity  of  the  lung-tissue  varies  from  0.345  to  0.746. 

The  color  of  the  lungs  at  birth  is  a  pinkish-white;  in  adult  life  a  dark  slate- 
color,  mottled  in  patches;  and  as  age  advances  this  mottling  assumes  a  black 
color.  The  coloring  matter  consists  of  granules  of  a  carbonaceous  substance 
deposited  in  the  areolar  tissue  near  the  surface  of  the  organ.  It  increases  in 
quantity  as  age  advances,  and  is  more  abundant  in  males  than  in  females.  The 
posterior  surface  of  the  lung  is  usually  darker  than  the  anterior. 

The  surface  of  the  lung  is  smooth,  shining,  and  marked  out  into  numerous 
polyhedral  spaces,  indicating  the  lobules  of  the  organ;  the  area  of  each  of  these 
spaces  is  crossed  by  numerous  lighter  lines. 

The  substance  of  the  lung  is  of  a  light,  porous,  spongy  texture;  it  floats  in 
water  and  crepitates  when  handled,  owing  to  the  presence  of  air  in  the  tissue;  it 
is  also  highly  elastic;  hence  the  collapsed  state  of  these  organs  when  they  are 
removed  from  the  closed  cavity  of  the  thorax. 

The  Foetal  Lung. — After  respiration  has  been  established,  the  lung  fills  the 
pleural  cavity.  In  the  foetus,  as  the  lung  has  never  been  distended  with  air 


THE  LUNGS  1403 

and  has  never  received  a  large  amount  of  blood,  it  is  gathered  into  a  small  mass 
at  the  back  of  the  thorax.  It  will  sink  in  water  and  feels  solid  to  the  touch. 

Structure. — The  structure  of  the  lung  is  such  that  the  blood  brought  by  the 
pulmonary  artery  comes  into  close  relation  with  the  air  which  enters  from  the 
bronchioles.  The  blood  gives  materials  to  the  air,  and  the  air  gives  elements  to 
the  blood,  and  the  process  of  respiration  causes  the  dark  blood  brought  from  the 
heart  by  the  pulmonary  artery  to  return  to  the  heart  as  red  blood  in  the  pulmonary 
vein.  The  lungs  are  composed  of  an  external  serous  coat,  a  subserous  areolar  tissue, 
and  the  pulmonary  substance  or  parenchyma. 

The  Serous  Coat. — The  serous  coat  is  thin,  transparent,  and  invests  the  entire 
organ  as  far  as  the  root.  It  is  known  as  the  pulmonary  pleura  (p.  1392). 

The  Subserous  Areolar  Tissue. — The  subserous  areolar  tissue  contains  a  large 
proportion  of  elastic  fibres;  it  invests  the  entire  surface  of  the  lung,  and  extends 
inward  between  the  lobules,  and  at  the  hilum  forms  the  pulmonary  scaffold  or 
framework. 

The  Parenchyma. — The  parenchyma  is  composed  of  lobules  which,  although 
closely  connected  together  by  an  interlobular  areolar  tissue,  are  quite  distinct  from 
one  another,  and  may  be  teased  asunder  without  much  difficulty  in  the  fretus. 
The  lobules  vary  in  size;  those  on  the  surface  are  large,  of  pyramidal  form,  with 
the  bases  turned  toward  the  surface;  those  in  the  interior  are  smaller  and  of  various 
forms.  Each  lobule  is  composed  of  one  of  the  ramifications  of  a  bronchial  tube 
and  its  terminal  air-cells,  and  of  the  ramifications  of  the  pulmonary  and  bronchial 
vessels,  lymphatics,  and  nerves,  all  of  these  structures  being  connected  together  by 
areolar  tissue. 

The  Bronchus  (pp.  1384  and  1386)  (Figs.  993,  994,  and  995).— The  bronchus, 
upon  entering  the  substance  of  the  lung,  divides  and  subdivides  bipinnately, 
throughout  the  entire  organ.  Sometimes  three  branches  arise  together,  and  occa- 
sionally small  lateral  branches  are  given  off  from  the  sides  of  a  main  trunk.  Each 
of  the  smaller  subdivisions  of  the  bronchi  enters  a  pulmonary  lobule,  and  is  termed 
a  lobular  bronchial  tube  or  bronchiole  (bronchioli).  Each  bronchiole  divides  into 
minute  branches  (bronchioli  respiratorii) ,  the  walls  of  which  now  begin  to  present 
irregular  dilatations,  bronchial  alveoli.  These  are  present  at  first  sparingly  and  on 
one  side  of  the  tube  only,  but  as  it  proceeds  onward  these  dilatations  become  more 
numerous  and  surround  the  tube  on  all  sides,  so  that  it  loses  its  cylindrical  char- 
acter. The  terminal  branches  come  from  the  bronchioli  respiratorii.  These 
terminal  branches  are  called  the  alveolar  ducts  or  alveolar  passages  (ductuli  alveo- 
lares).  The  alveolar  ducts  show  numerous  alveoli  (Fig.  994)  and  join  with  cav- 
ities called  atria.  Each  atrium  joins  several  larger  cavities,  the  air-cells  or  air-sacs 
(infundibula) .  The  numerous  small  cavities  on  the  surface  of  the  air-sacs  are 
the  pulmonary  alveoli  (alveoli  pidmonis) .  The  bronchiole  now  becomes  widened 
out  and  terminates  in  an  irregular  cul-de-sac,  the  air  cell,  air  sac  alveolus  or  infun- 
dibulum.  The  walls  of  the  infundibulum  are  closely  beset  in  all  directions  by  pul- 
monary alveoli  or  pulmonary  air  cells.  Professor  Gerrish  remarks  that  the  first  of 
the  alveoli  seen  on  the  bronchioles  before  the  coreal  ends  are  formed  would  seem 
an  effort  on  the  part  of  nature  to  form  an  infundibulum  before  all  the  necessary 
conditions  are  favorable. 

Changes  in  the  Structure  of  the  Bronchi  in  the  Lungs.— Within  the  lungs  the 
bronchial  tubes  are  circular,  not  flattened  (Fig.  995),  and  present  certain  pecu- 
liarities of  structure. 

In  the  Lobes  of  the  Lungs. — In  the  lobes  of  the  lungs  the  following  changes 
take  place:  The  cartilages  are  not  imperfect  rings,  but  consist  of  thin  laminae, 
of  varied  form  and  size,  scattered  irregularly  along  the  sides  of  the  tube,  being 
most  distinct  at  the  points  of  division  of  the  bronchi.  They  may  be  traced  into 
tubes,  the  diameter  of  each  of  which  is  only  one-fourth  of  a  line.  Beyond  this 
point  the  tubes  are  wholly  membranous.  The  fibrous  coat  is  continued  into  the 


1404  THE  ORGANS  OF  VOICE  AND  RESPIRATION 

smallest  ramifications  of  the  bronchi.  The  muscular  coat  is  disposed  in  the  form 
of  a  continuous  layer  of  annular  fibres,  which  may  be  traced  upon  the  smallest 
bronchial  tubes,  and  consists  of  the  unstriped  variety  of  muscular  tissue.  The 
mucous  membrane  lines  the  bronchi  and  their  ramifications  throughout,  and  is 
covered  with  columnar  ciliated  epithelium. 

In  the  Lobules  of  the  Lung. — In  the  lobular  bronchial  tubes  and  in  the  infun- 
dibula  the  following  changes  take  place:  The  muscular  tissue  begins  to  disap- 
pear, so  that  in  the  infundibula  there  is  scarcely  a  trace  of  it.  The  fibrous  coat 
becomes  thinner,  and  degenerates  into  areolar  tissue.  The  epithelium  becomes 
non-ciliated  and  flattened.  This  occurs  gradually;  thus,  in  the  lobular  bronchioles 
patches  of  non-ciliated  flattened  epithelium  may  be  found  scattered  among  the 
columnar  ciliated  epithelium;  then  these  patches  of  non-ciliated  flattened  epithe- 
lium become  more  and  more  numerous,  until  in  the  infundibula  and  air-cells  all 
the  epithelium  is  of  the  non-ciliated  pavement  variety.  In  addition  to  these  flat- 
tened cells,  there  are  small  polygonal  granular  cells  in  the  air-sacs,  in  clusters  of 
two  or  three,  between  the  others. 

The  air-cells  are  small,  polyhedral  recesses  composed  of  a  fibrillated  connec- 
tive tissue  and  surrounded  by  a  few  involuntary  muscular  and  elastic  fibres.  Free 
in  their  cavity  are  to  be  seen  under  the  microscope  granular,  rounded,  amoeboid 
cells  (eosinophile  leukocytes),  often  containing  carbonaceous  particles.  The  air- 
cells  are  well  seen  on  the  surface  of  the  lung,  and  vary  from  -%$-$  to  T\j-  of  an 
inch  in  diameter,  being  largest  on  the  surface  at  the  thin  borders  and  at  the  apex, 
and  smallest  in  the  interior. 

Mucous  Glands. — In  the  larger  bronchi  the  mucous  membrane  contains  goblet 
cells.  When  the  tubes  dimmish  to  1  mm.  in  diameter  the  glands  grow  fewer. 
In  the  smaller  bronchi  there  are  no  mucous  glands. 

Vessels  of  the  Lungs. — The  pulmonary  artery  (Figs.  1006  and  1007)  conveys  the 
venous  blood  to  the  lungs;  it  divides  into  branches  which  accompany  the  bronchial 
tubes,  and  terminates  in  a  dense  capillary  network  upon  the  walls  of  the  inter- 
cellular passages  and  air-cells.  In  the  lung  the  branches  of  the  pulmonary  artery 
are  usually  above  and  in  front  of  a  bronchial  tube,  the  vein  below. 

The  pulmonary  capillaries  form  plexuses  which  lie  immediately  beneath  the 
mucous  membrane  in  the  walls  and  septa  of  the  air-cells  and  of  the  infundibula. 
In  the  septa  between  the  air-cells  the  capillary  network  forms  a  single  layer.  The 
capillaries  form  a  very  minute  network,  the  meshes  of  which  are  smaller  than  the 
vessels  themselves;1  their  walls  are  also  exceedingly  thin.  The  arteries  of  neigh- 
boring lobules  are  independent  of  each  other,  but  the  veins  freely  anastomose 
together. 

The  pulmonary  veins  commence  in  the  pulmonary  capillaries,  the  radicles 
coalescing  into  larger  branches,  which  run  along  through  the  substance  of  the 
lung,  independently  from  the  minute  arteries  and  bronchi.  After  freely  commu- 
nicating with  other  branches  they  form  large  vessels,  which  ultimately  come  into 
relation  with  the  arteries  and  bronchial  tubes,  and  accompany  them  to  the  hilum 
of  the  organ.  Finally  they  open  into  the  left  auricle  of  the  heart,  conveying 
oxygenated  blood  to  be  eventually  distributed  to  all  parts  of  the  body  by  the  aorta. 

The  bronchial  arteries  supply  blood  for  the  nutrition  of  the  lung.  The  thoracic 
aorta  usually  gives  off  two  left  bronchial  arteries.  The  single  right  bronchial 
artery  usually  arises  from  the  first  right  aortic  intercostal,  but  sometimes  from 
the  superior  left  bronchial  artery,  or  from  the  aorta.  In  the  root  of  the  lung 
they  are  posterior  to  the  bronchus,  they  accompany  the  bronchial  tubes,  supply 
the  tubes  and  pulmonary  tissue,  and  give  branches  to  the  walls  of  the  larger 
pulmonary  vessels,  the  oesophagus,  pericardium,  and  bronchial  glands.  Those 

1  The  meshes  are  only  0.002'"  to  0.008'"  in  width,  while  the  vessels  are  0.003'"  to  0.005'"  (Kolliker,  Human 
Microscopic  Anatomy). — ED.  of  15th  English  edition. 


THE  LUNGS  1405 

supplying  the  bronchial  tubes  form  a  capillary  plexus  in  the  muscular  coat,  from 
which  branches  are  given  off  to  form  a  second  plexus  in  the  mucous  coat.  This 
plexus  communicates  with  branches  of  the  pulmonary  artery,  and  empties  itself 
into  the  pulmonary  vein.  Others  are  distributed  in  the  interlobular  areolar  tissue, 
and  terminate  partly  in  the  deep,  partly  in  the  superficial,  bronchial  veins.  Lastly, 
some  ramify  upon  the  surface  of  the  lung  beneath  the  pleura,  where  they  form  a 
capillary  network.  There  may  be  but  one  bronchial  artery;  there  may  be  three 
or  four. 

The  bronchial  veins  are  not  found  in  the  walls  of  the  very  small  bronchi.  The 
small  bronchial  veins  run  along  by  the  front  and  back  of  the  median  sized  and 
larger  tubes,  and  from  two  trunks  at  the  root  of  each  lung.  These  vessels  termi- 
nate on  the  right  side  in  the  vena  azygos  major,  and  on  the  left  side  in  the  superior 
intercostal  or  left  upper  azygos  vein.  Tracheal  and  posterior  mediastinal  veins 
open  into  the  bronchial  veins.  The  venous  blood  from  the  smaller  tubes  passes 
to  the  pulmonary  veins. 

The  lymphatics  begin  in  networks  about  the  lobules  and  form  networks  about 
the  bronchi  and  beneath  the  bronchial  mucous  membrane.  The  superficial  col- 
lecting trunks  arise  about  the  lobules  and  beneath  the  pleura.  According  to 
Sappey,  the  superficial  trunks  from  the  upper  lobe  begin  on  the  costal  surface; 
one  set  passes  around  the  anterior  border,  another  set  around  the  posterior 
border,  and  a  third  into  the  incisura  interlobaris.  The  same  observer  says  that  the 
superficial  trunks  from  the  middle  lobe  unites  with  the  trunks  from  the  upper  and 
lower  lobes;  and  the  superficial  trunks  from  the  lower  lobe,  like  those  of  the  upper 
lobe,  are  in  three  sets.  One  set  passes  around  the  posterior  margin,  one  around  the 
anterior  margin,  and  one  into  the  incisura  interlobaris.  All  of  the  superficial  trunks 
convey  lymph  to  the  glands  of  the  hilum.  Some  of  the  deep  collecting  trunks  begin 
by  the  sides  of  the  small  bronchi;  others  course  along  by  the  pulmonary  veins 
or  pulmonary  arteries.  All  of  them  pass  to  the  glands  of  the  hilum.  The  glands 
of  the  hilum  are  in  communication  with  the  peritracheo-bronchial  glands.1 

Nerves. — The  lungs  are  supplied  from  the  anterior  and  posterior  pulmonary 
plexuses,  formed  chiefly  by  branches  from  the  sympathetic  and  vagus.  The  fila- 
ments from  these  plexuses  accompany  the  bronchial  tubes,  and  are  lost  upon  them. 
Small  ganglia  are  found  upon  these  nerves. 

Surface  Form. — The  apex  of  the  lung  is  situated  in  the  neck,  behind  the  interval  between  the 
two  heads  of  origin  of  the  Sterno-mastoid  muscle.  The  height  to  which  it  rises  above  the  clavicle 
varies  very  considerably,  but  is  generally  about  one  inch.  It  may,  however,  extend  as  much  as 
an  inch  and  a  half  or  an  inch  and  three-quarters,  or,  on  the  other  hand,  it  may  scarcely  project 
above  the  level  of  this  bone.  In  order  to  mark  out  the  anterior  margin  of  the  lung,  a  line  is 
to  be  drawn  from  the  apex-point,  one  inch  above  the  level  of  the  clavicle,  and  rather  nearer  the 
posterior  than  the  anterior  border  of  the  Sterno-mastoid  muscle,  downward  and  inward  across 
the  sterno-clavicular  articulation  and  first  piece  of  the  sternum  until  it  meets,  or  almost  meets, 
its  fellow  of  the  other  side  opposite  the  articulation  of  the  manubrium  and  gladiolus.  From  this 
point  the  two  lines  are  to  be  drawn  downward,  one  on  either  side  of  the  mesial  line  and  close  to 
it,  as  far  as  the  level  of  the  articulation  of  the  fourth  costal  cartilages  to  the  sternum.  From 
here  the  two  lines  diverge;  the  left  is  to  be  drawn  at  first  passing  outward  with  a  slight  inclina- 
tion downward,  and  then  taking  a  bend  downward  with  a  slight  inclination  outward  to  the  apex 
of  the  heart,  and  thence  to  the  sixth  costo-chondral  articulation.  The  direction  of  the  anterior 
border  of  this  part  of  the  left  lung  is  denoted  with  sufficient  accuracy  by  a  curved  line  with  its 
convexity  directed  upward  and  outward  from  the  articulation  of  the  fourth  right  costal  cartilage 
of  the  sternum  to  the  fifth  intercostal  space,  an  inch  and  a  half  below  and  three-quarters  of  an 
inch  internal  to  the  left  nipple.  The  continuation  of  the  anterior  border  of  the  right  lung  is 
marked  by  a  prolongation  of  its  line  from  the  level  of  the  fourth  costal  cartilages  vertically 
downward  as  far  as  the  sixth,  when  it  slopes  off  along  the  line  of  the  sixth  costal  cartilage  to  its 
articulation  with  the  rib. 

The  lower  border  of  the  lung  is  marked  out  by  a  slightly  curved  line  with  its  convexity  down- 
ward from  the  articulation  of  the  sixth  costal  cartilage  to  its  rib  to  the  spinous  process  of  the 
tenth  thoracic  vertebra.  If  vertical  lines  are  drawn  downward  from  the  nipple,  the  mid-axillary 
line,  and  the  apex  of  the  scapula,  while  the  arms  are  raised  from  the  sides,  they  should  intersect 

1  The  Lymphatics,  by  Poirier,  Cunt5o,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


1406  THE  ORGANS  OF  VOICE  AND  RESPIRATION 

this  convex  line,  the  first  at  the  sixth,  the  second  at  the  eighth,  and  the  third  at  the  tenth  rib. 
It  will  thus  be  seen  that  the  pleura  extends  farther  down  than  the  lung,  so  that  it  may  be 
wounded,  and  a  wound  may  pass  through  its  cavity  into  the  Diaphragm,  and  the  abdominal 
viscera  may  be  injured  without  the  lung  being  involved. 

The  posterior  border  of  the  lung  is  indicated  by  a  line  drawn  from  the  level  of  the  spinous 
process  of  the  seventh  cervical  vertebra,  down  either  side  of  the  spine,  corresponding  to  the 
costo-vertebral  joints  as  low  as  the  spinous  process  of  the  tenth  thoracic  vertebra.  The  trachea 
bifurcates  opposite  the  spinous  process  of  the  fourth  thoracic  vertebra,  and  from  this  point  the  two 
bronchi  are  directed  outward. 

"The  position  of  the  great  fissure  of  the  lungs  may  be  indicated  by  a  line  drawn  from  the  third 
dorsal  spine  obliquely  downward  in  such  a  manner  as  to  reach  the  sixth  rib  close  to  the  mid- 
clavicular  line.  The  interlobar  fissure  between  the  upper  and  middle  lobes  of  the  right  lung 
corresponds  to  a  line  drawn  from  the  apex  of  the  axilla  almost  horizontally  to  the  sternum, 
reaching  the  latter  at  about  the  level  of  the  fourth  costal  cartilage"  (Erendrath). 

Surgical  Anatomy. — The  lungs  may  be  wounded  or  torn  in  three  ways:  (1)  By  compres- 
sion of  the  chest,  without  any  injury  to  the  ribs.  (2)  By  a  fractured  rib  penetrating  the  lung. 
(3)  By  stabs,  gunshot  wounds,  etc. 

The  first  form,  where  the  lung  is  ruptured  by  external  compression  without  any  fracture  of 
the  ribs,  is  very  rare,  and  usually  occurs  in  young  children,  and  affects  the  root  of  the  lung — 
i.  e.,  the  most  fixed  part — and  thus,  implicating  the  great  vessels,  is  frequently  fatal.  It  would 
seem  to  be  a  most  unusual  injury,  and  the  exact  mode  of  its  causation  is  difficult  to  understand. 
The  probable  explanation  is  that  immediately  before  the  compression  is  applied  a  deep  inspira- 
tion is  taken  and  the  lungs  are  fully  inflated;  owing  then  to  spasm  of  the  glottis  at  the  moment 
of  compression,  the  air  is  unable  to  escape  from  the  lung,  the  lung  is  not  able  to  recede,  and 
consequently  gives  way. 

In  the  second  variety,  when  the  wound  in  the  lung  is  produced  by  the  penetration  of  a  broken 
rib,  both  the  pleura  costalis  and  the  pleura  pulmonalis  must  necessarily  be  injured,  and  conse- 
quently the  air  taken  into  the  wounded  air-cells  may  find  its  way  through  these  wounds  into  the 
cellular  tissue  of  the  parietes  of  the  chest.  This  it  may  do  without  collecting  in  the  pleural  cavity; 
the  two  layers  of  the  pleura  are  so  intimately  in  contact  that  the  air  may  pass  straight  through 
from  the  wounded  lung  into  the  subcutaneous  tissue.  Emphysema  constitutes,  therefore,  an 
important  sign  of  injury  to  the  lung  in  cases  of  fracture  of  the  ribs.  Pneumothorax ,  or  air  in  the 
pleural  cavity,  is  much  more  likely  to  occur  in  injuries  to  the  lung  of  the  third  variety;  that  is 
to  say,  from  external  wounds,  from  stabs  and  gunshot  injuries,  in  which  cases  air  passes  either 
from  the  wound  of  the  lung  or  from  an  external  wound  into  the  cavity  of  the  pleura  dur- 
ing the  respiratory  movements.  In  these  cases  there  is  generally  no  emphysema  of  the  sub- 
cutaneous tissue  unless  the  external  wound  is  small  and  valvular,  so  that  the  air  drawn  into  the 
wound  during  inspiration  is  then  forced  into  the  cellular  tissue  around  during  expiration  because 
it  cannot  escape  from  the  external  wound.  Occasionally  in  wounds  of  the  parietes  of  the  chest 
no  air  finds  its  way  into  the  cavity  of  the  pleura,  because  the  lung  at  the  time  of  the  accident 
protrudes  through  the  wound  and  blocks  the  opening.  This  occurs  where  the  wound  is  large, 
and  constitutes  a  so-called  hernia  of  the  lung.  True  hernia  of  the  lung  occurs,  though  very 
rarely,  after  wounds  of  the  chest-wall,  when  the  wound  has  healed  and  the  cicatrix  sub- 
sequently yields  from  the  pressure  of  the  viscus  behind.  It  forms  a  globular,  elastic,  crepi- 
tating swelling,  which  enlarges  during  expiratory  efforts,  falls  during  inspiration,  and  disappears 
on  holding  the  breath.  Wounds  of  the  lung  may  produce  dangerous  or  fatal  hemorrhage  into 
the  pleural  sac.  In  many  cases  the  bleeding  is  spontaneously  arrested;  in  diners  the  surgeon 
must  interfere  to  save  life.  In  some  cases  air  has  been  admitted  by  intercostal  incision  and  the 
insertion  of  a  tube,  and  pulmonary  collapse  has  arrested  bleeding.  In  other  cases  it  is  necessary 
to  resect  portions  of  several  ribs,  and  stop  bleeding  by  ligatures  or  suture  ligatures.  In  one 
case  of  a  furious  secondary  hemorrhage  following  a  gunshot  wound,  the  editor  resected  several 
ribs,  packed  the  pleural  cavity  about  the  lung  with  sterile  gauze,  to  obtain  a  base  of  support,  and 
then  arrested  the  bleeding  by  packing  iodoform  gauze  against  the  firmly  supported  lung.  This 
patient  recovered. 

Incision  of  the  lung  (pneumotomy)  is  performed  for  pulmonary  abscess  (either  tuberculous  or 
pyogenic),  pulmonary  gangrene,  hydatid  cysts,  and  bronchiectasis.  In  pulmonary  abscess, 
locate  the  area  by  physical  signs  and  the  axray,  resect  a  portion  of  a  rib  over  it,  and  note  if  the 
pleura  is  adherent.  If  it  is  adherent,  continue  the  operation.  If  it  is  not  adherent,  insert  stitches 
of  catgut  through  the  two  layers  of  pleura  and  the  superficial  part  of  the  lung,  so  as  to  encircle 
a  considerable  area,  and  then  wait  several  days  for  adhesions  to  form.  Adhesions  protect  the 
pleura  from  infection,  and,  by  keeping  air  from  the  pleural  sac,  prevent  pneumothorax.  When 
ready  to  continue  the  operation,  locate  the  abscess  with  an  aspira ting-needle  and  syringe,  open 
it  with  a  cautery  at  a  dull-red  heat,  and  drain  by  means  of  a  tube. 

Pneumotomy  is  very  unsatisfactory  in  tuberculous  cavities  and  bronchiectasis.  In  tubercu- 
losis, excision  of  the  diseased  area  (pneumectomy)  has  been  employed,  but  it  is  not  to  be  advised. 

Operations  upon  the  lungs  can  be  most  safely  performed  with  the  patient  in  a  Sauerbruch 
chamber.  The  danger  of  collapse  of  the  lung  is  thus  eliminated. 


THE  DUCTLESS  GLANDS. 


fTIHESE  glands  do  not  possess  excretory  ducts.  They  furnish  materials  which 
-L  are  added  to  the  blood  or  lymph  as  it  passes  through  them.  The  material 
from  each  gland  is  known  as  an  internal  secretion.  Some  of  these  secretions  are 
powerful  materials  and  influence  profoundly  the  body  nutrition.  The  ductless 
glands  are  usually  given  as  follows:  the  spleen,  the  lymphatic  glands,  the  pineal 
gland,  the  pituitary  body,  the  suprarenal  capsules,  the  thyroid  gland,  the  para-thyroids, 
the  thymus,  the  carotid  body,  and  the  coccygeal  body.  The  lymphatic  glands  were 
described  in  a  special  section  (p.  772).  The  lymphatic  glands  are  not  con- 
sidered to  be  really  glands,  but,  nevertheless,  as  lymph  passes  through  the  lymph 
glands,  it  receives  a  product  of  the  glands,  namely,  lymphocytes.  There  is  no 
evidence  that  the  spleen  furnishes  an  active  internal  secretion,  and  this  organ 
has  been  studied  with  the  abdominal  viscera.  The  pineal  gland  (p.  915)  and 
pituitary  body  or  hypophysis  (p.  917)  were  considered  with,  the  brain.  The  supra- 
renal capsules  (p.  1437)  are  described  with  the  kidneys.  Some  glands,  for  instance, 
the  liver,  pancreas,  and  testicle,  have  an  external  secretion  and  also  an  internal 
secretion. 


THE  THYROID  BODY  OR  GLAND  (GLANDULA  THYREOIDEA) 

(Fig.  1010). 

The  thyroid  gland  is  an  extremely  vascular  body,  situated  at  the  front  and 
sides  of  the  neck,  and  extending  upward  upon  each  side  of  the  larynx.  It  is  a 
single  gland,  varying  greatly  in  size  in  different  individuals.  It  is  larger  relatively 
in  females  and  in  children  than  in  men.  It  is  frequently  asymmetrical.  In  early 
embryonal  life  the  gland  has  a  duct,  the  thyro-glossal  duct  (ductus  thyreoglossus) , 
which  passes  from  the  isthmus  of  the  thyroid  to  the  foramen  caecum  of  the  dorsum 
of  the  tongue.  The  lumen  of  this  duct  is  obliterated  early  and  becomes  a  cord  of 
epithelium.  The  lower  portion  of  the  duct  often  remains  open  for  a  little  way. 
The  upper  portion  remains  as  the  foramen  caecum.  The  situation  of  this  obliter- 
ated foetal  duct  may  be  marked  by  the  third  or  middle  lobe  of  the  thyroid  gland. 
The  thyroid  surrounds  the  upper  portion  of  the  trachea  like  a  horseshoe.  It  con- 
sists of  two  lateral  lobes  connected  across  the  middle  line  by  a  narrow  transverse 
portion,  the  isthmus. 

The  weight  of  the  gland  is  somewhat  variable,  but  is  usually  about  one  ounce. 
It  is  somewhat  heavier  in  the  female,  in  whom  it  becomes  enlarged  during  men- 
struation and  pregnancy.  As  age  advances  the  weight  of  the  thyroid  diminishes. 

The  color  of  the  thyroid,  as  seen  from  the  surface,  is  reddish-blue.  The  gland  is 
completely  surrounded  by  a  closely  adherent  thin  fibrous-tissue  capsule  of  the  pre- 
tracheal  layer  of  deep  cervical  fascia.  From  the  inner  surface  of  the  capsule  come 
delicate  septa,  which  enter  into  the  thyroid  body  and  separate  it  into  lobes  and  also 
separate  the  lobes  into  lobules.  The  blood-vessels  lie  beneath  the  capsule.  The 
anterior  and  lateral  portions  of  the  gland  are  covered  by  the  capsule.  "Passing 
around  the  side  of  the  gland  to  its  posterior  surface,  this  capsule  then  splits  into  two 
portions.  One  remains  in  contact  with  the  gland  and  invests  its  posterior  surface. 
The  other,  the  thicker  of  the  two,  passes  to  the  posterior  surface  of  the  pharynx 

( 1407 ) 


1408 


THE  DUCTLESS  GLANDS 


and  oesophagus,  thus  enclosing  them  with  the  larynx,  trachea,  and  thyroid  gland, 
in  a  common  sheath."1  There  is  also  a  layer  from  the  thyroid  capsule  which 
passes  between  the  trachea  and  oesophagus.2 

The  lateral  lobes  are  conical  in  shape,  the  apex  of  each  being  directed  upward 
and  outward  as  far  as  the  junction  of  the  middle  with  the  lower  third  of  the  thy- 
roid cartilage;  the  base  looks  downward,  and  is  on  a  level  with  the  fifth  or  sixth 
tracheal  ring.  The  summit  of  the  lateral  lobe  not  unusually  is  pointed  and  reaches 
to  the  level  of  the  oblique  line  upon  the  ala  of  the  thyroid  cartilage  or  even  higher. 
The  right  is,  as  a  rule,  somewhat  larger  than  the  left  lobe.  The  lower  portion  of 

the  gland,  when  the  head  is  extended,  is  about 
one  inch  above  the  upper  margin  of  the  ster- 
num; when  the  head  is  flexed,  it  is  at  the  level 
of  the  upper  border  of  the  sternum  or  even 
below  and  behind  it.  The  portion  of  the 
lateral  lobe  above  the  level  of  the  superior 
border  of  the  isthmus  is  called  the  upper  horn, 
the  portion  below  the  level  of  the  inferior  mar- 
gin of  the  isthmus  is  called  the  lower  horn.  The 
lower  horn  "is  usually  much  smaller  than  the 
upper  horn ;  frequently  it  is  altogether  absent."3 
At  the  inner  and  posterior  part  of  each  lateral 
lobe  is  the  hilum.  At  the  hilum  the  inferior 
thyroid  artery  passes  into  the  gland.  "Here 
the  recurrent  laryngeal  nerve  comes  into  close 
contact  with  the  gland,  lying  in  the  space  be- 
tween it  and  the  trachea  and  oesophagus."4 

The  external  or  superficial  surface  is  convex, 
and  covered  by  the  skin,  the  superficial  fascia, 
the  deep  fascia,  the  Sterno-mastoid,  the  anterior 
belly  of  the  Omo-hyoid,  the  Sterno-hyoid  and 
Sterno-thyroid  muscles,  and  beneath  the  last- 
named  muscles  by  the  pre-tracheal  layer  of  the 
deep  fascia,  which  forms  a  capsule  for  the 
gland. 

The  deep  or  internal  surface  is  moulded 
over  the  underlying  structures — viz.,  the  thy- 
roid and  cricoid  cartilages,  the  trachea,  the 
inferior  constrictor  and  posterior  part  of  the 
Crico-thyroid  muscles,  the  oesophagus  (par- 
ticularly on  the  left  side  of  the  neck),  the  supe- 
rior and  inferior  thyroid  arteries,  and  the  recurrent  laryngeal  nerves. 

The  deep  surface  of  each  lobe  is  fixed  by  bands  of  fibrous  tissue  passing  from 
the  capsule  of  the  isthmus  and  lateral  lobes  to  the  sides  of  the  cricoid  cartilage  and 
the  posterior  fascia  of  the  trachea.  These  bands  are  called  the  lateral  or  suspen- 
sory ligaments.  Because  of  this  fixation  to  the  larynx  and  trachea  by  the  capsule 
and  by  the  lateral  ligaments,  the  thyroid  gland  moves  with  the  trachea  and  ascends 
during  the  act  of  swallowing.  The  recurrent  laryngeal  nerve  on  each  side  is  in 
contact  with  the  outer  and  posterior  surface  of  the  suspensory  ligament. 

The  anterior  border  is  thin,  and  inclines  obliquely  from  above  downward  and 
inward  toward  the  middle  line  of  the  neck,  while  the  posterior  border  is  thick  and 
overlaps  the  common  carotid  artery.  Each  lobe  is  about  two  inches  in  length,  its 
greatest  width  is  about  one  inch  and  a  quarter,  and  its  thickness  about  three- 


FIG.  1010.— The  thyroid  gland.    (Spalteholz.) 


1  Diseases  of  the  Thyroid  Gland.    By  James  Berry. 

-  C.  H.  Mayo,  Surgery,  Gynecology,  and  Obstetrics,  July,  1907. 


3  Loc.  cit. 


<  Ibid. 


THE  THYROID  BODY  OR  GLAND  1409 

quarters  of  an  inch.  The  posterior  border  is  over  the  common  carotid  artery  and 
touches  the  oesophagus  and  pharynx.  The  carotid  artery  usually  makes  a  groove 
upon  the  gland. 

The  Isthmus  (isthmus  glandulae  thyreoidea}. — The  isthmus  connects  the  lower 
third  of  the  two  lateral  lobes;  it  measures  about  half  an  inch  in  breadth  and  the 
same  in  depth,  and  usually  covers  the  second  and  third  rings  of  the  trachea,  but 
sometimes  also  the  first  and  fourth  rings.  Its  situation  presents,  however,  many 
variations,  a  point  of  importance  in  the  operation  of  tracheotomy.  In  the  middle 
line  of  the  neck  it  is  covered  by  the  skin  and  fascia,  and  close  to  the  middle  line, 
on  either  side,  by  the  Sterno-hyoid  muscle.  Across  its  upper  border  run  branches 
of  the  superior  thyroid  artery  and  vein;  at  its  lower  border  is  a  branch  of  the 
inferior  thyroid  veins.  Sometimes  the  isthmus  is  altogether  wanting,  the  two 
lateral  lobes  being  completely  separate. 

The  third,  pyramidal  or  middle  lobe  is  called  the  pyramid  of  Lalouette.  It  is  not 
constant,  but  is  frequently  found.  Occasionally  it  arises  from  the  upper  part  of 
the  isthmus,  or  from  the  adjacent  portion  of  either  lobe,  but  most  commonly  from 
the  left  lobe,  and  ascends  in  front  of  the  thyroid  cartilage  in  the  direction  of  the 
middle  of  the  hyoid  bone.  It  may  reach  the  bone  or  may  not  reach  it.  If  it 
reaches  the  bone  it  is  attached  to  it.  If  it  does  not  reach  the  bone,  fibrous  tissue, 
which  often  contains  muscle,  is  prolonged  from  the  tip  of  the  pyramid  to  the 
back  of  the  bone  or  to  the  thyro-hyoid  membrane.  The  pyramid  is  occasionally 
quite  detached,  or  divided  into  two  or  more  parts,  or  altogether  wanting, 

A  few  muscular  bands,  derived  from  the  Thyro-hyoid  muscles,  are  occasionally 
found  attached,  above,  to  the  body  of  the  hyoid  bone,  and  below  to  the  isthmus 
of  the  gland  or  its  pyramidal  process.  These  form  a  muscle,  which  was  named 
by  Soemmerring  the  Levator  glandulae  thyreoidae. 

Accessory  Thyroids  (glandulae  thyreoideae  accessoriae) . — Frequently  small 
isolated  masses  of  thyroid  tissue  exist.  They  are  found  particularly  about  the 
lateral  lobes  of  the  thyroid  gland  in  the  sides  of  the  neck  or  just  above  the  hyoid 
bone,  and  are  called  accessory  thyroids.  Accessory  thyroids  may  also  exist  by  the 
side  of  the  pyramidal  lobe  or  upon  the  trachea,  as  low  even  as  the  level  of  the  arch 
of  the  aorta.  John  B.  Murphy1  says,  the  field  in  which  accessory  thyroids  "may 
be  found  can  be  roughly  represented  by  an  inverted  trapezoid,  the  larger  base 
being  a  line  running  from  one  apex  of  the  mastoid  process  to  the  other;  the  smaller 
base  is  a  line  tangential  to  the  arch  of  the  aorta,  and  the  sides  are  the  two  sterno- 
mastoid  muscles."  These  isolated  portions  of  gland  tissue  represent  isolated  por- 
tions of  the  median  thyroid  rudiment.  Sometimes  accessory  thyroid  tissue  is  found 
in  the  root  of  the  tongue  or  in  the  interior  of  the  larynx.  Berry  points  out  that  a 
distinction  must  be  made  between  true  congenital  accessory  thyroids  and  masses 
of  encapsuled  thyroid  tissue  which  "have  been  extruded  from  the  gland,"  and  still 
retain  a  connection  with  the  gland.  Such  masses  are  false  accessory  thyroids. 

Structure  of  the  Thyroid  (Fig.  1011). — The  thyroid  body  is  invested  by  a  thin 
capsule  of  connective  tissue  which  projects  into  its  substance  as  a  framework  and 
imperfectly  divides  it  into  masses  of  irregular  form  and  size,  known  as  lobules. 
More  slender  septa  separate  the  secretory  alveoli  from  one  another.  When  the 
organ  is  cut  into,  it  is  of  a  brownish-red  color,  and  is  seen  to  be  made  up  of  a 
number  of  closed  vesicles  or  alveoli  containing  a  yellow  glairy  fluid  and  separated 
from  each  other  by  intermediate  connective  tissue. 

According  to  Baber,  who  has  published  some  important  observations  on  the 
minute  structure  of  the  thyroid,2  the  vesicles  of  the  thyroid  of  the  adult  animal 
are  generally  closed  cavities;  but  in  some  young  animals  (e.g.,  young  dogs)  the 
vesicles  are  more  or  less  tubular  and  branched.  This  appearance  he  supposes 

1  Journal  of  the  American  Medical  Association,  December  16,  1905. 

*  Researches  on  the  Minute  Structure  of  the  Thyroid  Glands,  Phil.  Trans.,  part  Hi.,  1881. 

89 


1410 


THE  DUCTLESS  GLANDS 


to  be  due  to  the  mode  of  growth  of  the  gland,  and  merely  indicating  that  an 
increase  in  the  number  of  vesicles  is  taking  place.  Each  vesicle  is  lined  by  a  single 
layer  of  epithelium,  the  cells  of  which  are  cubical  or  cylindrical.  Between  the 
epithelial  cells  exists  a  delicate  reticulum.  The  vesicles  are  of  various  sizes  and 
shapes,  and  contain  as  a  normal  product  a  viscid,  homogeneous,  semi-fluid, 
slightly  yellowish  material  which  frequently  contains  blood,  the  red  corpuscles  of 
which  are  found  in  it  in  various  stages  of  disintegration  and  decolorization,  the 
yellow  tinge  being  probably  due  to  the  haemoglobin,  which  is  thus  set  free  from 
the  colored  corpuscles.  This  normal  product  is  known  as  colloid  material,  and  it 
is  secreted  by  the  epithelium.  What  part  if  any  the  colloid  plays  in  the  formation 
of  the  internal  secretion  of  the  gland  is  not  known.  It  is  quite  possible  that  the 
colloid  corresponds  to  the  external  secretion  of  glands  with  ducts  and  that  the 
true  internal  secretion  passes  directly  into  the  capillaries  which  form  a  network 
about  the  alveoli  (Szymonowicz),  or  passes  into  the  lymphatics.  In  the  thyroid 
gland  of  the  dog,  Baber  has  found  large  round  cells,  parenchymatous  cells,  each 
provided  with  a  single  oval-shaped  nucleus,  which  migrate  into  the  interior 
of  the  gland-vesicles.  Between  the  thyroid  vesicles  in  the  human  being  are  col- 
lections of  round  cells.  They  are,  in  reality,  miniature  vesicles,  and  are  much 
more  numerous  in  youth  than  in  old  age. 

The  capillary  blood-vessels  form  a  dense  plexus  in  the  connective  tissue  around 
the  vesicles,  between  the  epithelium  of  the  vesicles  and  the  endothelium  of  the 
lymph -spaces,  which  latter  surround  a  greater  or  smaller  part  of  the  circumference 


Vesicle. 


Lymphatic  vessel, 


Wall  of  gland-vesicle 


FIG.  1011. — Minute  structure  of  the  thyroid.     From  a  transverse  section  of  the  thyroid  of  a  dog.     Semi- 
diagrammatic.     (Baber.) 

of  the  vesicles.  These  lymph-spaces  empty  themselves  into  lymphatic  vessels 
which  run  in  the  interlobular  connective  tissue,  not  uncommonly  surrounding  the 
arteries  which  they  accompany,  and  communicate  with  a  network  in  the  capsule 
of  the  gland.  Small  glands  may  be  connected  with  this  network.  Baber  has 
found  in  the  lymphatics  of  the  thyroid  a  viscid  material  which  is  morphologically 
identical  with  the  normal  constituent  of  the  vesicle. 

Vessels  and  Nerves. — The  arteries  (Figs.  394  and  395;  see  also  p.  604)  supply- 
ing the  thyroid  are  the  superior  thyroid  from  the  external  carotid,  and  the  inferior 
thyroid  from  the  thyroid  axis  of  the  first  part  of  the  subclavian.  Sometimes  there 
is  an  additional  vessel,  the  thyroidea  media  or  ima,  usually  arising  from  the 


THE  THYROID  BODY  OR  GLAND  1411 

innominate  artery,  but  sometimes  from  the  arch  of  the  aorta  or  the  common  caro- 
tid. It  ascends  upon  the  front  of  the  trachea.  The  superior  thyroid  artery  reaches 
the  summit  of  the  upper  horn  of  the  gland,  and  usually  at  this  point  gives  off  a 
vessel  which  courses  down  the  posterior  surface  of  the  gland.  The  main  trunk 
passes  downward  and  inward  at  the  junction  of  the  inner  and  anterior  border  of 
the  upper  horn,  giving  branches  to  adjacent  structures  and  sending  branches  over 
the  anterior  surface  of  the  thyroid  gland.  It  reaches  the  isthmus  and  crosses 
the  isthmus  at  its  upper  border  to  anastomose  with  the  artery  from  the  other  side. 
The  inferior  thyroid  artery,  which  is  usually  larger  than  the  superior,  after  it 
has  passed  posterior  to  the  sheath  of  the  carotid  and  the  sympathetic  nerve,  reaches 
the  posterior  surface  of  the  gland.  At  this  point  branches  are  given  off;  some  pass 
into  the  hilum;  the  others  go  to  the  posterior  surface  of  the  gland.  The  relation 
of  the  artery  to  the  recurrent  laryngeal  nerve  is  very  important  to  the  surgeon. 
"Usually  the  main  trunk  of  the  artery  passes  behind  the  nerve;  sometimes  the 
artery  breaks  up  before  reaching  the  nerve ;  in  this  case  one  or  more  of  the  branches 
may  pass  in  front  of  it.  Much  less  commonly  the  main  trunk  or  all  its  branches 
will  be  found  to  lie  in  front  of  the  nerve."1  If  the  thyroidea  ima  is  present  it  goes 
to  the  lower  part  of  the  gland.  The  larger  branches  of  the  thyroid  arteries  are 
beneath  the  capsule  and  upon  the  surface  of  the  gland ;  smaller  branches  pass  to 
the  interior  of  the  gland  (Berry).  The  arteries  are  remarkable  for  their  large 
size  and  frequent  anastomoses. 

The  thyroid  veins  (Figs.  447  and  448;  see  also  p.  731)  form  a  plexus  upon  the 
surface  of  the  gland  and  beneath  the  capsule.  Here  and  there  veins  pass  through 
the  capsule  and  go  to  adjacent  venous  trunks.  Berry,  accepting  Kocher's  descrip- 
tion, notes  the  following  veins:  The  superior  thyroid  vein  runs  with  the  superior 
thyroid  artery  and  passes  to  the  internal  jugular  vein.  A  transverse  vein  of  the 
upper  border  of  the  isthmus  joins  the  two  superior  thyroid  veins.  A  single  vein, 
the  middle  thyroid,  sometimes  emerges  from  the  side  of  the  gland  and  passes  to 
the  internal  jugular.  Usually,  however,  instead  of  this  single  vein  there  are  two 
veins,  the  superior  and  inferior  accessory  thyroids.  The  superior  accessory  thyroid 
emerges  from  the  outer  side  of  the  upper  horn,  below  the  apex,  and  passes  to  the 
internal  jugular.  The  inferior  accessory  thyroid  emerges  from  the  posterior  and 
inferior  portion  of  the  gland  and  passes  to  the  internal  jugular.  The  veins  from  the 
lower  border  of  the  gland  vary  greatly.  A  vein  passes  vertically  down  on  each  side 
in  front  of  the  trachea  from  the  isthmus  and  from  the  inner  side  of  tho,  inferior  horn. 
It  is  called  by  Kocher  the  thyroidea  ima.  The  vein  of  the  left  side  passes  to  the  left 
innominate;  the  vein  of  the  right  side  passes  to  the  right  innominate  or  left  innom- 
inate. As  Berry  points  out,  the  vein  of  one  side  may  be  small  or  may  be  absent, 
or  the  two  veins  may  unite  and  form  one  vein  which  enters  the  left  innominate. 
An  inferior  thyroid  vein  is  often  present.  It  is  of  small  size,  emerges  at  the  inferior 
and  external  part  of  the  gland,  and  passes  to  the  corresponding  innominate  vein,2 

The  lymphatics  are  numerous  and  of  large  size.  Collecting  trunks  arise  from  a 
network  within  the  capsule.  Some  trunks  ascend  from  the  upper  margin  of  the 
isthmus  and  reach  the  gland  in  front  of  the  larynx ;  others  ascend  along  the  superior 
thyroid  artery  and  reach  the  glands  at  the  bifurcation  of  the  carotid.  Descending 
trunks  from  the  lower  margin  of  the  isthmus  reach  the  glands  in  front  of  the 
trachea;  trunks  from  the  side  of  the  gland  descend  to  the  glands  about  the  recur- 
rent laryngeal  nerve.3 

The  nerves  are  derived  from  the  middle  and  inferior  cervical  ganglia  of  the  sym- 
pathetic, and  from  the  inferior  laryngeal  nerves.  Probably  there  is  also  a  branch 
from  each  superior  laryngeal  nerve. 

Surgical  Anatomy. — The  thyroid  gland  may  be  congenitally  absent,  and  when  it  is  the  indi- 
vidual suffers  from  the  worst  form  of  cretinism.  One  lobe  may  be  congenitally  absent,  but 
this  will  provoke  no  trouble  unless  the  other  lobe  undergoes  atrophy. 

1  Diseases  of  the  Thyroid  Gland.    By  James  Berry.  2  Ibid. 

8  The  Lymphatics.    By  Poirier,  Cuneo,  and  Delamare,     Translated  and  edited  by  Cecil  H.  Leaf. 


1412 


THE  DUCTLESS  GLANDS 


Complete  removal  of  the  thyroid  and  parathyroids  will  produce  operative  myxoedema  (cachexia 
strumipriva),  unless  accessory  thyroids  enlarge  and  perform  the  functions  of  the  thyroid. 

The  thyroid  gland  may  be  congenitally  enlarged.  The  gland  tends  to  atrophy  in  old  age. 
It  is  atrophied  in  myxoedema  and  cretinisin.  Some  forms  of  thyroid  enlargement  are  called 
goitre. 

When  all  parts  of  the  gland  enlarge  the  condition  is  known  as  parenchymatous  goitre. 
Adenomatous  goitre  consists  of  an  adenoma  or  of  adenomata.    In  cystic  goitre  there  is  one 
or  more  cysts  due  to  cystic  degeneration  of  adenomata  or  to  fusion  of  adjacent  follicles. 

A  pulsating  goitre  is  one  which  receives  impulses  from  the  carotid  pulsations.  In  a  fibroid 
goitre  there  is  increase  of  interstitial  connective  tissue.  A  goitre  which  passes  back  of  the  sternum 
is  known  as  substernal  or  intrathoracic.  A  goitre  may  extend  back  of  the  trachea  or  back  of 
the  oesophagus. 

Exophthalmic  goitre,  Graves's  disease  or  Basedow's  disease,  is  a  remarkable  disease.  Its  three 
chief  symptoms  are  enlargement  of  the  thyroid,  or  goitre ;  prominence  of  the  eyeballs,  or  exoph- 
thalmos,  and  very  rapid  pulse,  or  tachycardia.  Dyspnoea,  tremor,  and  various  other  symptoms 
are  usually  found.  The  thyroid  gland  may  be  the  seat  of  a  carcinoma  or  sarcoma  (malignant 
goitre},  syphilitic  or  tuberculous  disease,  ordinary  inflammation,  suppuration,  or  hydatid  disease; 
For  the  relief  of  ordinary  goitre  various  methods  have  been  employed.  Tapping,  injection  of 
astringents,  simple  incision,  and  the  seton  are  obsolete.  Ligature  of  the  thyroid  arteries  is  rarely 
performed  as  a  curative  measure.  The  superior  and  inferior  thyroids  of  one  side  have  been  tied 
in  some  cases;  all  four  thyroids  in  other  cases.  Jaboulay  has  performed  exothyropexy.  In  this 
operation  the  gland  is  dislocated  from  its  bed,  brought  out  of  the  wound,  and  left  exposed,  in 
hope  that  it  will  atrophy 

Division  of  the  isthmus  is  occasionally  practised  to  relieve  dyspnoea.  The  operation  some- 
times succeeds,  but  often  fails. 

Extirpation  of  one-half  or  two-thirds  of  the  gland  is  a  very  successful  operation.    Removal  of 

the  entire  gland  will  be  followed  by  operative  myxoedema. 
Removal  or  injury  of  the  parathyroids  causes  tetany. 

In  extirpating  a  lobe  of  the  thyroid  by  the  method  until 
recently  in  vogue,  great  care  must  be  taken  to  avoid  tearing 
the  capsules,  as  if  this  happens  the  gland-tissue  bleeds 
profusely.  The  thyroid  arteries  should  be  ligatured  on  the 
diseased  side  before  an  attempt  is  made  to  remove  the 
mass,  and  in  ligaturing  the  inferior  thyroid  the  position  of 
the  recurrent  laryngeal  nerve  must  be  borne  in  mind,  so  as 
not  to  include  it  in  the  ligature.  In  order  to  preserve  the 
parathyroids  from  injury,  C.  H.  Mayo  recommends  that 
after  the  vessels  entering  and  leaving  the  thyroid  have  been 
double  clamped  and  divided,  the  entire  lobe  should  be 
elevated,  the  capsule  split  along  the  side  of  the  gland  and 
pushed  back  with  gauze,  and  the  gland  lifted  and  removed 
without  disturbing  the  posterior  portion  of  the  capsule  l 

A  cystic  or  solid  tumor  of  the  thyroid  may  be  removed 
by  intraglandular  enucleation.  If  operation  becomes  ne- 
cessary in  exophthalmic  goitre,  partial  extirpation  is  usu- 
ally preferred.  Bilateral  extirpation  of  the  cervical  ganglia 
of  the  sympathetic  (sympathectomy  or  Jonnesco's  operation) 
has  been  practised  by  some  surgeons  for  exophthalmic 
goitre.  The  value  of  the  procedure  is  uncertain. 

THE  PARATHYROID  GLANDS2  (Fig.  1012). 


FIG.  1012. — The  position  of  the  para- 
thyroid glands.  View  from  behind. 
(Zuckerkandl.) 


The  parathyroid  glands  or  the  epithelial  cor- 
puscles of  Kohn  were  first  described  as  anatomical 
entities  by  Sandstrom  in  1880.  Owen  had  seen 
the  parathyroids  in  the  rhinoceros  in  1862,  but  he  did  not  recognize  any  peculiarities 
of  structure.  Virchow  observed  them  in  man  in  1863  but  he  regarded  them  as  lymph- 
glands  or  detached  portions  of  thyroid  tissue.  Gley,  in  1891,  called  attention  to 
glands  within  the  body  of  the  thyroid.  In  1895  Kohn  affirmed  that  the  parathyroids 
are  separate  organs  and  not  a  part  of  the  thyroid  gland.  If  the  thyroid  gland  has 
been  carefully  detached,  two  round  bodies  of  stnall  size  may  be  found  embedded 


'  C.  H.  Mayo,  Surgery,  Gyneeology,  and  Obstetrics,  July,  1907. 

2  I  am  indebted  to  Dr.  F.  D.  Patterson  for  collecting  the  literature  upon  the  parathyroids. 


THE  PARATHYROID  GLANDS  1413 

upon  the  trachea  or  upon  the  surface  of  the  lateral  lobe  of  the  gland,  between 
the.  terminal  branches  of  the  inferior  thyroid  artery.  "These  are  the  parathy- 
roids, about  the  size  of  orange-seeds,  and  brownish-red  in  color."1  They  are 
smaller  in  infants  than  in  adults.  Welsh2  describes  them  in  adults  as  from 
6  to  7  mm.  in  length,  3  to  4  mm.  in  breadth,  and  1^  to  2  mm.  in  thickness. 
These  masses  are  constant  in  man.  There  is  no  record  of  a  case  in  which  they 
were  congenitally  absent.  Although  the  parathyroids  lie  on  or  in  the  thyroid, 
they  are  always  completely  separated  from  it  by  capsules  of  connective  tissue. 
Although  there  are  usually  four  parathyroids,  there  may  be  but  three,  or  there  may 
be  six  or  even  eight.  Parathyroid  tissue  may  exist  within  the  thyroid  gland  even 
when  the  superior  parathyroids  are  present.3  Accessory  parathyroids  may  be  found 
over  a  wide  area.  Rogers  and  Fergusson  found  one  in  the  middle  of  the  posterior 
portion  of  the  pharynx.  Ogle  found  a  gland  in  the  thorax  which  was  partly  para- 
thyroid. The  parathyroids  are  divided  from  their  situation  into  external  and 
internal.  The  former,  usually  two  in  number,  are  situated,  one  on  each  side,  in 
relation  to  the  postero-internal  surface  of  the  lateral  lobe  of  the  thyroid;  sometimes 
they  are  duplicated.  The  latter,  also  usually  two  in  number,  are  placed  one  in  or 
on  each  lateral  lobe  of  the  thyroid,  generally  near  its  mesal  surface. 

Structure. — The  structureof  thepara thyroids  is  different  from  that  of  the  thyroid. 
They  are  composed  of  solid  masses  of  epithelial  cells  arranged  in  a  more  or  less 
columnar  fashion  with  numerous  intervening  capillaries.  The  columns  of  the  para-* 
thyroids  anastomose.  There  is  a  certain  type  of  cell,  but  the  form  varies.  These 
variations  result  from  changes  due  to  episodes  of  rest  and  activity  (Verebely). 
MacCallum's  studies  seem  to  lead  to  the  same  conclusion.  Thompson4  states  that 
he  finds  only  one  type  of  cell  in  the  infant  gland,  and  that  in  the  adult  there  is 
primarily  but  one  type  of  cell,  the  other  cells  noted  being  modifications  of  the 
principal  cell  due  to  degeneration  or  hyp  erf  unction.  There  is  much  lymphoid 
tissue  connected  with  the  columns.  The  nerves  of  the  parathyroids  are  derived 
from  the  sympathetic  system.  Each  parathyroid  gland  is  supplied  by  a  para- 
thyroid artery.  The  inferior  parathyroid  artery  is  always  a  branch  of  the  inferior 
thyroid  artery  or  of  the  anastomosing  channel  between  the  superior  and  inferior 
thyroid  arteries  of  one  side  (Geist).  The  superior  parathyroid  artery  may  be  a 
branch  of  the  superior  thyroid  (Poole),  but  it  is  usually  a  branch  of  the  inferior 
thyroid  or  of  the  anastomosing  channel.  Ginsburg5  has  shown  that  each  of  the 
glands  has  an  accessory  blood  supply  by  anastomotic  channels  from  the  opposite 
side. 

Embryology. — The  parathyroids  develop  chronologically  in  advance  of  the 
thyroid.  They  are  derived  from  the  third  and  fourth  branchial  clefts  of  each  side. 
An  independent  accessory  parathyroid  may  develop  from  the  fifth  cleft  (Getzowa, 
Michand).  Some  have  regarded  the  parathyroids  as  embryonic  portions  of  the 
thyroid,  but,  as  MacCallum  says,  "  there  is  no  histological  proof  that  parathyroid 
tissue  can  ever  become  converted  into  thyroid  tissue."  Most  observers  regard  the 
parathyroids  as  distinct  glands  possessed  of  a  special  function.  Certain  it  is,  as 
Gley  and  others  have  shown,  removal  of  the  parathyroids  from  herbivora  leaving 
the  thyroid  intact  is  followed  by  spasms,  tetany,  etc.,  just  as  complete  thyroidec- 
tomy  is  followed  by  such  symptoms  in  carnivora.8 

Surgical  Anatomy. — Surgeons  have  become  convinced  that  removal  of  the  parathyroids  in  man 
causes  tetany,  and  that  damage  to  them  may  produce  serious  symptoms.  Because  of  this  dan- 
ger most  surgeons  now  prefer  to  remove  a  goitre  from  within  the  capsule  of  the  thyroid  gland 
after  the  plan  of  the  Mayos,  and  thus  avoiding  the  parathyroids. 

i  Practical  Anatomy.    By  Prof.  Alfred  W.  Hughes.  *  Journal  of  Anatomy  and  Physiology,  1897-1898. 

3  Getzowa,  Virchow's  Arch.,  1907,  clxxxvii.,  p.  181. 
'*  American  Journal  of  Medical  Sciences,  1907,  n.  s.,  cxxxiv.,  p.  562. 
6  University  of  Pennsylvania  Medical  Bulletin,  January,  1908. 
•  Internal  Secretions.     By  William  Hanria  Thomson.     New  York  Medical  Journal,  November  19,  1904. 


1414 


THE  DUCTLESS  GLANDS 


THE  THYMUS  GLAND  (Fig.  1013). 

The  thymus  gland  is  a  temporary  organ,  attaining  its  full  size  at  the  end  of  the 
second  year,  when  it  ceases  to  grow  and  remains  practically  stationary  until 
puberty,  at  which  period  it  rapidly  degenerates.  It  does  not  entirely  disappear, 
for  the  shrunken  and -degenerated  mass,  even  later  in  life,  maintains  a  likeness  to 
the  original  form  and  retains  within  its  substance  small  portions  of  thymus  tissue 
(Waldeyer).  If  examined  when  its  growth  is  most  active,  it  will  be  found  to  con- 


VAGUS 
NERVE 


FIG.  1013.  —The  thymus  gland  in  an  infant  two  months  old.     (Poiricr  and  Charpy.) 


sist  of  two  lateral  lobes  placed  in  close  contact  along  the  middle  line,  situated 
partly  in  the  superior  mediastinum,  partly  in  the  neck,  and  extending  from  the 
level  of  the  fourth  costal  cartilage  upward  as  high  as  the  lower  border  of  the 
thyroid  gland.  It  is  covered  by  the  sternum  and  by  the  origins  of  the  Sterno- 
hyoid  and  Sterno-thyroid  muscles.  Below,  it  rests  upon  the  pericardium,  being 
separated  from  the  arch  of  the  aorta  and  great  vessels  by  a  layer  of  fascia.  In  the 
neck  it  lies  on  the  front  and  sides  of  the  trachea,  behind  the  Sterno-hyoid  and 
Sterno-thyroid  muscles.  The  two  lobes  generally  differ  in  size;  they  are  occa- 
sionally united  so  as  to  form  a  single  mass,  and  are  sometimes  separated  by  an 
intermediate  lobe.  The  thymus  is  of  a  pinkish-gray  color,  is  soft  and  is  lobu- 
lated  on  its  surfaces.  It  is  about  two  inches  in  length,  one  and  a  half  inches 
in  breadth  below,  and  about  three  or  four  lines  in  thickness.  At  birth  it  weighs 
about  half  an  ounce. 

Structure  (Figs.  1014  and  1015). — Each  lateral  lobe  is  composed  of  numerous 
lobules  held  together  by  delicate  areolar  tissue,  the  entire  gland  being  enclosed  in 
an  investing  capsule  of  a  similar  but  denser  structure.  The  primary  lobules  vary 
in  size  from  a  pin's  head  to  a  small  pea,  and  are  made  up  of  a  number  of  small 
nodules  or  follicles  which  are  irregular  in  shape  and  are  more  or  less  fused 
together,  especially  toward  the  interior  of  the  gland.  Each  follicle  consists  of  a 


THE  THYMUS  GLAND 


1415 


medullary  and  cortical  portion,  which  differ  in  many  essential  particulars  from 
each  other.  The  cortical  portion  is  mainly  composed  of  lymphoid  cells  sup- 
ported by  a  delicate  reticulum.  In  addition  to  this  reticulum,  of  which  traces 
only  are  found  in  the  medullary  portion,  there  is  also  a  network  of  finely 
branched  cells  which  is  continuous  with  a  similar  network  in  the  medullary  por- 
tion. This  network  forms  an  adventitia  to  the  blood-vessels.  In  the  medullary 
portion  there  are  but  few  lymphoid  cells,  but  there  are,  especially  toward  the 
centre,  granular  cells  and  concentric  corpuscles.  The  granular  cells  are  rounded 
or  flask-shaped  masses  attached  (often  by  fibrillated  extremities)  to  blood-vessels 
and  to  newly  formed  connective  tissue.  The  concentric  corpuscles  are  com- 
posed of  a  central  mass  consisting  of  one  or  more  granular  cells,  and  of  a  capsule 
which  is  formed  of  epithelioid  cells  which  are  continuous  with  the  branched  cells 
forming  the  network  mentioned  above. 

Each  follicle  is  surrounded  by  a  capillary  plexus  from  which  vessels  pass  into 
the  interior  and  radiate  from  the  periphery  toward  the  centre,  and  form  a  second 
zone  just  within  the  margin  of  the  medullary  portion.  In  the  centre  of  the 
medulla  there  are  very  few  vessels,  and  they  are  of  minute  size. 


FIG.  1014. — Minute  structure  of  thymus  gland.  Upper  portion  of  the  thymus  of  a  foetal  pig  Of  2"  in  length, 
showing  the  bud-like  lobuli  and  glandular  elements:  2,  cells  of  the  thymus,  mostly  from  a  man;  a,  free  nuclei; 
b,  small  cells;  c,  larger;  d,  larger,  with  oil-globules,  from  the  ox;  e,  f,  cells  completely  filled  with  fat,  at  / 
without  a  nucleus;  g,  h,  concentric  bodies;  g,  an  encapsulated  nucleated  cell;  h,  a  composite  structure  of  a 
similar  nature. 

Watney  has  made  the  important  observation  that  haemoglobin  is  found  in  the 
thymus  either  in  cysts  or  in  cells  situated  near  to  or  forming  part  of  the  con- 
centric corpuscles.  This  haemoglobin  varies  from  granules  to  masses  exactly 
resembling  colored  blood-corpuscles,  oval  in  the  bird,  reptile,  and  fish;  circular 
in  all  mammals  except  in  the  camel.  Dr.  Watney  has  also  discovered  in  the 
lymph  issuing  from  the  thymus  similar  cells  to  those  found  in  the  gland,  and, 
like  them,  containing  haemoglobin  either  in  the  form  of  granules  or  masses. 
From  these  facts  he  arrives  at  the  physiological  conclusion  that  the  thymus  is 
one  source  of  the  colored  blood -corpuscles. 

Vessels  and  Nerves. — The  arteries  supplying  the  thymus  are  derived  from 
the  internal  mammary  and  from  the  superior  and  inferior  thyroid.  The  veins 
terminate  in  the  two  innominate  veins,  and  in  the  internal  mammary  and  the 
thyroid  veins.  The  lymphatics  are  of  large  size,  arise  in  the  substance  of  the 
gland,  and  are  said  to  terminate  in  the  internal  jugular  vein.  The  nerves  are 


1410 


THE  DUCTLESS  GLANDS 


exceedingly  minute;  they  are  derived  from  the  vagus  and  sympathetic.  Branches 
from  the  descendens  hypoglossi  and  phrenic  reach  the  investing  capsule,  but  do  not 
penetrate  into  the  substance  of  the  gland. 


Artery. 


Vein. 


Artery. 


FIG.  1015. — Minute  structure  of  the  thymus  gland.  Follicle  of  injected  thymus  from  a  calf,  four  days  old, 
slightly  diagrammatic,  magnified  about  50  diameters.  The  large  vessels  are  disposed  in  two  rings,  one  of  which 
surrounds  the  follicle,  the  other  lies  just  within  the  margin  of  the  medulla.  A  and  B,  from  thymus  of  camel, 
examined  without  addition  of  any  reagent.  Magnified  about  400  diameters.  A,  large  colorless  cell  containing 
small  oval  masses  of  haemoglobin.  Similar  ceils  are  found  in  the  lymph-glands,  spleen,  and  medulla  of  bone; 
B,  colored  blood-corpuscles.  (Watney). 


THE  CAROTID  GLAND  OR  CAROTID  BODY  (GLOMUS  CAROTICUM) 

This  body,  when  present,  lies  in  the  carotid  bifurcation,  to  the  inner  side  of  the 
common  carotid  below  the  bifurcation,  or  on  the  posterior  surface  of  the  internal  or 
of  the  external  carotid  artery.  Gomez1  finds  it "  most  commonly  between  the  internal 
and  external  carotid  arteries,  resting  posteriorly  on  the  bifurcation  of  the  common 
carotid."  It  is  often  absent.  Funke  found  it  absent  in  7  foetuses  out  of  8.  In  50 
human  cases  examined  by  Gomez  it  was  absent  in  5  cases.  In  4  of  Gomez's  cases 
it  was  found  only  on  one  side.  It  lies  in  fatty  tissue  and  is  surrounded  by  a  fibrous 
capsule  which  is  attached  to  the  carotid  sheath,  upon  which  it  lies  by  a  short  stump 
known  as  the  ligament  of  Mayer.  The  carotid  gland  is  about  the  size  of  a  grain  of 
corn;  it  is  oval  or  rounded  in  shape  and  reddish-brown  in  color.  The  capsule  of 
the  gland  sends  septa  inward.  The  septa  divide  the  organ  into  follicles  or  cell-balls. 
These  cell-balls  are  composed  of  endothelial  cells  and  are  associated  with  blood 
capillaries.  A  branch  (or  branches)  from  the  carotid  artery,  upon  which  the  gland 

1  American  Journal  of  Medical  Sciences,  July,  1908 


THE  PARASYMPATHETIC  BODIES  1417 

lies,  enters  the  carotid  gland  through  the  ligament  of  Mayer.  Many  nerve  fila- 
ments surround  the  carotid  gland,  and  they  usually,  but  not  always,  form  a  plexus, 
known  as  the  inter-carotid  plexus.  According  to  Poirier  and  Charpy  these  filaments 
come  from  the  superior  cervical  ganglion  of  the  sympathetic,  the  glosso-pharyngeal, 
the  hypoglossal,  the  superior  laryngeal,  and  the  nervi  molles  of  Haller.  (This 
structure  has  been  recently  studied  by  John  Funke,1  Reclus  and  Chevasson,2 
Paltauf,  Kartschenko,  Marchand,  and  Gomez.3) 

Surgical  Anatomy. —  Tumors  may  arise  from  this  structure.  Such  a  tumor  is  apt  to  be 
above  the  level  of  the  upper  margin  of  the  thyroid  cartilage,  and  in  most  cases  it  moves  with 
each  arterial  beat. 

THE  COCCYGEAL  GLAND  OR  COCCYGEAL  BODY  OR  LUSCHKA'S 
GLAND  (GLOMUS  COCCYGEUM). 

Lying  near  the  tip  of  the  coccyx  in  a  small  tendinous  interval  formed  by  the 
union  of  the  Levator  ani  muscles  and  just  above  the  coccygeal  attachment  of 
the  Sphincter  ani,  is  a  small  conglobate  body  about  as  large  as  a  lentil  or  a  pea, 
first  described  by  Luschka,4  and  named  by  him  the  coccygeal  gland.  Its  most 
obvious  connections  are  with  the  arteries  of  the  part.  It  is  similar  in  structure 
to  the  carotid  body. 

STRUCTURE. — It  consists  of  a  congeries  of  small  arteries  with  little  aneurismal 
dilatations  derived  from  the  middle  sacral  and  freely  communicating  with  each 
other.  These  vessels  are  enclosed  in  one  or  more  layers  of  polyhedral  granular 
cells,  and  the  whole  structure  is  invested  in  a  capsule  of  connective  tissue  which 
sends  in  trabeculae,  dividing  the  interior  into  a  number  of  spaces  in  which  the 
vessels  and  cells  are  contained.  Nerves  pass  into  this  little  body  from  the  sympa- 
thetic, but  their  mode  of  termination  is  unknown.  Macalister  believes  the  glom- 
erulus  of  vessels  "consists  of  the  condensed  and  convoluted  metameric  dorsal 
arteries  of  the  caudal  segments  embedded  in  tissue  which  is  possibly  a  small  per- 
sisting fragment  of  the  neurenteric  canal."  It  resembles  the  carotid  gland  in 
structure,  and  is  probably  one  of  the  ductless  glands. 

THE  PARASYMPATHETIC  BODIES  (ORGANA  PARASYMPATHETICA 

OF  ZUCKERKANDL). 

The  parasympathetic  bodies  were  discovered  in  1901  by  Zuckerkandl.  They  are 
from  one  to  four  in  number,  situated  retroperitoneally,  ventrad  of  the  abdominal 
aorta  at  the  level  of  the  third  and  fourth  lumbar  vertebrae.  Each  parasympathetic 
body  is  from  6  to  10  mm.  in  length  and  from  2  to  4  mm.  in  width.  These  bodies 
are  usually  supplied  by  fine  arterial  twigs  from  the  aorta.  They  are  best  developed 
in  the  foetus  and  in  infancy,  and  in  their  structure  they  resemble  the  carotid  and 
coccygeal  bodies. 

i  American  Medicine,  vol.  viii..  No.  3.  2  Bull,  et  me"m.  de  la  Soc.  de  chir.  de  Paris,  1903,  No.  18. 

3  American  Journal  of  Medical  Sciences,  July.  1908. 

«  Der  Hirnanhang  und  die  Steissdriise  des  Menschen,  Berlin,  I860;  Anatomic  des  Menschen,  Tubingen,  1864, 
vol.  ii.,  pt.  ii.,  p.  187. 


THE  UEINARY  OKGAN8. 


THE  KIDNEYS  (RENES)  (Figs.  1016, 1017,  1018). 

THE  Kidneys  are  large  glands.    They  are  two  in  number,  and  are  situated 
in  the  back  part  of  the  abdomen,  near  the  spinal  column.     Their  function  is 
to  separate  from  the  blood  certain  materials  which,  when  dissolved  in  a  quantity 
of  water,  also  separated  from  the  blood  by  the  kidneys,  constitute  the  urine. 


INFERIOR    PHRCNIC 
ARTERIES 


SUPERIOR     W  V  I 
MESENTERIC 
ARTERY 


INFERIOR 

MESENTERIC 

ARTERY 


COMMON 

ILIAC   ARTERY 

AND  VEIN 


CCELIAC 
ARTERY 


INTERNAL 
SPERMATIC 
ARTERY 
AND  VEIN 
INTERNAL 
ILIAC  ARTERY 
AND  URETER 


FIG.  1016.  —  Posterior  abdominal  wall,  after  removal  of  the  peritoneum,  showing  kidneys,  suprarenal 
capsules,  and  great  vessels.     (Corning.) 

They  are  placed  in  the  loins,  one  on  each  side  of  the  vertebral  column,  behind 
the  peritoneum,  and  are  surrounded  by  a  mass  of  fat  and  loose  areolar  tissue,  which 
constitutes  the  fatty  capsule  (capsula  adiposa]  (Figs.  1021  and  1022).  There  are 
two  distinct  layers  in  this  fatty  capsule.  The  superficial  fatty  layer  is  the  pararenal 
fat.1  Keen  calls  this  layer  the  transversalis  layer  of  fat,  because  it  is  derived  from  the 

1  See  Gerota,  Arch.  f.  Anatomie,  Leipzic,  1895;   Zuckerkandl,  Medizinische  Jahrbucher,  Vienna,  1883. 

(  1419) 


1420 


THE  URINARY  ORGANS 


transversalis  fascia.1  The  deeper  and  thicker  perirenal  layer  is  the  true  perinephric 
fat  (Fig.  1022).  The  deeper  layer  of  fat  completely  surrounds  the  kidney,  and  is 
somewhat  adherent  to  the  fibrous  renal  capsule.  The  fat  about  the  kidney  does 
not  look  like  fat  in  other  regions,  but  is  soft,  delicate,  and  of  a  canary  yellow 
color.  These  two  fatty  layers  are  separated  by  a  layer  of  connective  tissue,  which  is 
the  posterior  layer  of  the  perirenal  fascia,  and  is  called  by  Zuckerkandl  the  retro- 
renal  fascia  (fascia  retrorenalis)  (Fig.  1021).  The  true  capsule  of  the  kidney  (tunica 
fibrosa)  is  thin,  smooth,  and  glistening.  The  inner  part  of  this  capsule  (tunica 
muscularis)  contains  unstriated  muscle  fibres.  The  true  capsule  can  be  easily 
separated  from  the  underlying  glandular  structure.  The  upper  extremity  of  the 
kidney  is  on  a  level  with  the  upper  border  of  the  twelfth  thoracic  vertebra,the  lower 
extremity  on  a  level  with  the  third  lumbar  vertebra  (Fig.  1019).  The  right  kidney 
is  usually  on  a  slightly  lower  level  than  the  left,  probably  on  account  of  the  vicinity 
of  the  liver.  In  the  female  the  kidneys  are  a  little  lower  than  in  the  male. 

Each  kidney  is  about  four  and  a  half  inches  in  length,  two  to  two  and  a  half  in 
breadth,  and  rather  more  than  one  inch  in  thickness.  The  left  is  somewhat  longer, 
though  narrower,  than  the  right.  The  weight  of  the  kidney  in  the  adult  male  varies 
from  4^  ounces  to  6  ounces;  in  the  adult  female,  from  4  ounces  to  5^  ounces.  The 
combined  weight  of  the  two  kidneys  in  proportion  to  the  body  is  about  1  in  240. 


FIG.  1017. — Anterior  surface  of  the  kidney. 
(Bourgery.) 


FIG.  1018. — Posterior  surface  of  the  kidney. 
(Bourgery.) 


The  kidney  has  the  characteristic  form  of  a  "flattened  bean"  (Spalteholz).  It 
is  flattened  on  its  sides  and  presents  at  one  part  of  its  circumference  a  hollow. 
It  is  larger  at  its  upper  than  at  its  lower  extremity.  The  kidney  presents  for  exam- 
ination two  surfaces,  two  borders,  and  an  upper  and  lower  extremity. 

Surfaces.  The  Anterior  Surface  (fades  anterior)  (Figs.  1016  and  1017).— Its  ante- 
rior surface  is  convex,  looks  forward  and  outward,  and  is  partially  covered  by  peri- 
toneum. The  right  kidney  in  its  upper  three-fourths  is  in  contact  with  the  pos- 
terior part  of  the  under  surface  of  the  right  lobe  of  the  liver.  This  area  of  the  right 
kidney  is  flattened  (impressio  hepatica).  Toward  its  inner  border  it  is  covered  by 
the  second  part  of  the  duodenum,  while  its  lower  and  outer  part  is  in  relation  with 
the  hepatic  flexure  of  the  colon.  The  relation  of  the  second  part  of  the  duodenum 
to  the  front  of  the  right  kidney  is  a  varying  one.  The  left  kidney  is  covered  above 

1  W.  W.  Keen,  in  American  Medicine,  January  31,  1903. 


THE  KIDNEYS 


1421 


by  the  posterior  surface  of  the  stomach,  below  the  stomach  by  the  pancreas,  behind 
which  are  the  splenic  vessels.  The  region  in  contact  with  the  stomach  is  markedly 
depressed  (impressio  gastrica) .  Its  lower  half  is  in  contact  with  some  of  the  coils 


FIG.  1019. — Posterior  surface  of  the  kidneys.      (Poirier  and  Charpy.) 


Fio.  1020. — Relation  of  the  kidney  to  the  vertebral  column,  ribs,  muscles,  and  lumbo-costal  ligaments. 

(Poirier  and  Charpy.) 


1422 


THE  URINARY  ORGANS 


of  the  small  intestine  and  sometimes  with  the  third  part  of  the  duodenum.  Near 
its  outer  border  the  anterior  surface  lies  behind  the  spleen  and  the  splenic  flexure 
of  the  colon. 

The  kidneys  are  partly  covered  in  front  by  peritoneum  and  partly  uncovered. 
On  the  right  kidney,  the  hepatic  area,  that  is  to  say  that  portion  of  the  kidney 
which  produces  the  renal  impression  on  the  liver,  is  covered  by  peritoneum,  which 
therefore  separates  the  kidney  from  the  liver;  the  duodenal  and  colic  areas  are  not 
peritoneal,  and  these  structures  are  connected  to  the  kidney  by  loose  connective 
tissue;  at  the  lower  and  inner  extremity  is  a  small  area,  the  mesocolic  area,  which 
'is  covered  by  a  layer  of  peritoneum  of  the  greater  sac  and  by  the  colic  vessels. 
On  the  left  kidney  the  gastric  area  is  covered  by  the  peritoneum  of  the  lesser  sac; 
the  pancreatic  and  colic  areas  are  non-peritoneal;  while,  as  on  the  right  side,  at  the 
lower  and  inner  extremity,  is  an  area,  mesocolic  area,  which  is  covered  by  the 
peritoneum  of  the  greater  sac  and  by  the  colic  vessels. 

The  Posterior  Surface  (jades  posterior)  (Fig.  1018). — The  posterior  surface  of  the 
kidney  is  flatter  than  the  anterior  and  is  directed  backward  and  inward.  It  is 


ELEVENTH 
RIB 


TWELFTHJ 
RIB 


POSTERIOR 

LAMELLA  OF 

PER I  RENAL         | 
FASCIA 


FAT  BEHIND 

PERIRENAL 

FASCIA 


PERITONEUM 

ESSELS  OF 

ILUM    OF 
DNEY 


SECTION 
OF  COLON 


FIG.  1021. — Longitudinal  section,  showing  the 
arrangement  of  the  capsule  of  the  kidney. 
(After  Gerota.) 


ANTERIOR 
LAMELLA  O 
PERIRENAI 
FASCIA 


PERITONEUM 

TRUE 

PERINEPHRITIC 

FAT 


SACRO-LUMBALIS 
GROUP 


PARARCNAL 

FAT 

QUADRATUS  LUM- 
BOPUM   MUSCLE 


FIG.  1022. — Transverse  section,  showing  the  relations 
of  the  capsule  of  the  kidney  and  the  two  layers  of  fat. 
(After  Gerota.) 


entirely  devoid  of  peritoneal  covering,  being  embedded  in  areolar  and  fatty  tissue. 
It  lies  upon  the  Diaphragm,  the  anterior  layer  of  the  lumbar  aponeurosis,  the 
external  and  internal  arcuate  ligaments,  the  Psoas  and  Transversalis  muscles, 
one  or  two  of  the  upper  lumbar  arteries,  the  last  thoracic,  ilio-hypogastric,  and 
ilio-inguinal  nerves.  The  lumbo-costal  ligaments  overlie  the  posterior  surface  of 
the  kidney  (Fig.  1020).  The  right  kidney  rests  upon  the  twelfth  rib  (Fig.  1020), 
the  left  usually  on  the  eleventh  and  twelfth  ribs.  The  Diaphragm  separates  the 
kidney  from  the  pleura  as  the  pleura  dips  down  to  form  the  phrenico-costal  sinus 
(Fig.  1001),  but  frequently  the  muscular  fibres  of  the  Diaphragm  are  defective  or 
absent  over  a  triangular  area  immediately  above  the  external  arcuate  ligament, 


THE  KIDNEYS  1423 

* 

and  when  this  is  the  case  the  perirenal  areolar  tissue  is  in  immediate  apposition 
with  the  diaphragmatic  pleura.  In  the  lower  part  of  the  posterior  surface  of  the 
kidney  is  an  impression  produced  by  the  Quadratus  lumborum  muscle  and  called 

„ the  impressio  muscularis.  A  little  internal  to  this  a  flattening,  caused  by  the  Psoas 

muscle,  is  often  recognizable.  At  the  upper  part  of  the  posterior  surface  is  a  sulcus 
produced  by  contact  with  the  Diaphragm. 

Borders.  The  External  Border  (margo  lateralis)  (Figs.  1017  and  1018). — The 
external  border  is  convex,  and  is  directed  outward  and  backward,  toward  the 
postero-lateral  wall  of  the  abdomen.  On  the  left  side  it  is  in  contact,  at  its  upper 
part,  with  the  spleen  (Fig.  1016). 

The  Internal  Border  (margo  medialis)  (Figs.  1017  and  1018). — The  internal  bor- 
der is  concave,  and  is  directed  forward,  inward,  and  a  little  downward.  It  presents 
a  deep  longitudinal  fissure,  bounded  by  a  prominent  overhanging  anterior  and 
posterior  lip.  This  fissure  is  named  the  hilum  (hilus  renalis)  (Fig.  1023),  and 
allows  of  the  passage  of  the  vessels,  nerves,  and  ureter  into  and  out  of  the  kidney. 

Extremities.  The  Superior  Extremity  (extremitas  superior) (Figs.  101 7  and  1018) . 
—The  superior  extremity,  directly  slightly  inward  as  well  as  upward,  is  thick  and 
rounded,  and  is  surmounted  by  the  suprarenal  capsule  (Fig.  1023),  which  covers 
also  a  small  portion  of  the  anterior  surface. 

The  Inferior  Extremity  (extremitas  inferior)  (Figs.  101 7. and  1018). — The  inferior 
extremity,  directed  a  little  outward  as  well  as  downward,  is  smaller  and  thinner 
than  the  superior.  It  extends  to  within  two  inches  of  the  crest  of  the  ilium. 

At  the  hilum  of  the  kidney  the  relative  position  of  the  main  structures  passing 
into  and  out  of  the  kidney  is  as  follows:  the  vein  is  in  front,  the  artery  in  the 
middle,  and  the  duct  or  ureter  behind  and  toward  the  lower  part  (Fig.  1018).  By 
a  knowledge  of  these  relations  the  student  may  distinguish  between  the  right  and 
left  kidney.  The  kidney  is  to  be  laid  on  the  table  before  the  student  on  its 
posterior  surface,  with  its  lower  extremity  toward  the  observer — that  is  to  say, 
with  the  ureter  behind  and  below  the  other  vessels;  the  hilum  will  then  be  directed 
to  the  side  to  which  the  kidney  belongs. 

General  Structure  of  the  Kidney.— The  kidney  is  surrounded  by  a  distinct 
investment  of  fibrous  tissue,  which  forms  the  firm,  smooth  true  capsule  covering 
the  entire  organ.  The  capsule  passes  over  the  margins  of  the  hilum,  enters  the 
interior  of  the  kidney,  and  covers  the  wall  of  the  sinus.  The  true  capsule  is 
closely  and  firmly  adherent  to  the  renal  pelvis  where  it  is  attached  to  the  sinus. 
It  closely  invests  it,  but  can  be  easily  stripped  off,  in  doing  which,  however,  numer- 
ous fine  processes  of  connective  tissue  which  pass  to  the  intrarenal  connective 
tissue  and  numerous  small  blood-vessels  are  torn  through.  Beneath  this  fibrous 
layer  a  thin  wide-meshed  network  of  unstriped  muscular  fibre  forms  an  incom- 
plete covering  to  the  organ.  When  the  true  capsule  is  stripped  off,  the  surface  of 
the  kidney  is  found  to  be  smooth,  even,  and  of  a  deep-red  color. 

In  infants  fissures  extending  for  some  depth  may  be  seen  on  the  surface  of  the 
organ,  a  remnant  of  the  lobular  construction  of  the  gland  (Fig.  1040).  The  kid- 
ney is  dense  in  texture,  but  is  easily  lacerable  by  mechanical  force.  In  order  to 
obtain  a  knowledge  of  the  structure  of  the  gland,  a  vertical  section  must  be  made 
from  its  convex  to  its  concave  border,  and  the  loose  tissue  and  fat  removed 
around  the  vessels  and  the  excretory  duct  (Fig.  1023).  It  will  be  then  seen  that 
the  kidney  consists  of  a  central  cavity  surrounded  at  all  parts  but  one  by  the 
proper  kidney-substance.  This  central  cavity  is  called  the  sinus  (sinus  renalis), 
and  is  lined  by  a  prolongation  of  the  fibrous  coat  of  the  kidney,  which  enters 
through  a  longitudinal  fissure,  the  hilum  (Fig.  1023),  which  is  situated  at  that 
part  of  the  cavity  which  is  not  surrounded  by  kidney  structure.  Through  this 
fissure  the  blood-vessels  of  the  kidney  and  its  excretory  duct  pass,  and  there- 
fore these  structures,  upon  entering  the  kidney,  are  contained  within  the  sinus 


1424 


THE  URINARY  ORGANS 


(Fig.  1017).  The  excretory  duct  or  ureter,  after  entering,  dilates  into  a  wide, 
funnel-shaped  sac  named  the  pelvis  (pelvis  renalis]  (Figs.  1023  and  1024).  This 
divides  into  two  or  three  tubular  divisions,  which  subdivide  into  several  short, 
truncated  branches  named  calices  or  infundibula  (calyces  renales),  all  of  which 
are  contained  in  the  central  cavity  of  the  kidney  (Figs.  1023  and  1024).  The 
blood-vessels  of  the  kidney,  after  passing  through  the  hilum,  are  contained  in 
the  sinus  or  central  cavity,  lying  between  its  lining  membrane  and  the  excretory 
apparatus,  before  entering  the  kidney-substance  (Fig.  1024). 

This  central  cavity,  as  before  mentioned,  is  surrounded  on  all  sides  except  at 
the  hilum  by  the  substance  of  the  kidney,  which  is  at  once  seen  to  consist  of  two 
parts — viz.,  of  an  external  granular  investing  part,  which  is  called  the  cortical 
portion  (substantia  corticalis} ;  and  of  an  internal  part,  the  medullary  portion  (suh- 
stantia  medullaris),  made  up  of  a  number  of  dark-colored  pyramids,  with  their 
bases  resting  on  the  cortical  part  and  their  apices  converging  toward  the  centre, 
where  they  form  prominent  papillae,  the  renal  papillae  (papillae  renales),  which 
project  into  the  interior  of  the  calices  (Fig.  1023.) 


SUPERIOR 
EXTREMITY 


MAJOR 
ALICES 


CUT  SURFACE 
OF  KIDNEY 


INFERIOR 
EXTREMITY 


FIG.  1023. — Vertical  section  of  kidney. 


FIG.  1024. — The  right  kidney  with  its  pelvis  exposed,  view 
from  behind.   (Spalteholz.) 


The  cortical  substance  (Figs  1023  and  1030)  is  of  a  bright  reddish-brown  color, 
soft,  granular,  and  easily  lacerable.  It  is  found  everywhere  immediately  beneath 
the  capsule,  and  is  seen  to  extend  in  an  arched  form  over  the  base  of  each  medul- 
lary pyramid.  Prolongations  of  the  cortical  substance  pass  between  the  pyramids 
toward  the  renal  sinus.  These  prolongations  are  the  cortical  columns  or  the  columns 
of  Bertin  (columnae  renales]  (Fig.  1023,  B  B).  The  columns  contain  blood-vessels, 
nerves,  and  lymphatics.  The  base  of  each  pyramid  (basis  pyramidis)  is  known 
as  the  intermediate  zone.  That  portion  of  the  cortical  substance  which  stretches 
from  one  cortical  column  to  the  next,  and  intervenes  between  the  base  of  the 
pyramid  and  the  capsule  (marked  by  the  dotted  line  extending  from  A  to  A'  in  Fig. 
1023),  is  called  a  cortical  arch,  the  depth  of  which  varies  from  a  third  to  half  an  inch. 


THE  KIDNEYS 


1425 


The  medullary  substance  (Figs.  1023  and  1030),  as  before  stated,  is  seen  to  con- 
sist of  red-colored,  striated,  conical  masses,  the  pyramids  of  Malpighi  (pyramides 
renales)  (Fig.  1023),  the  number  of  which,  varying  from  eight  to  eighteen,  corre- 
sponds to  the  number  of  lobes  of  which  the  organ  in  the  foetal  state  is  composed. 
The  pyramids  are  composed  of  straight  tubes  which  pass  between  the  apices  of 
the  papillae  and  the  cortical  margin.  They  enter  the  cortex  in  masses  called  the 
pyramids  of  Ferrein  (see  below).  The  sides  of  the  pyramids  of  Malpighi  are  con- 
tiguous with  the  cortical  columns,  while  the  apices,  known  as  the  papillae  of  the 
kidney  (Figs.  1023  and  1027),  project  into  the  calices  of  the  ureter,  each  calyx 
receiving  two  or  three  papillae.  Radiating  from  the  bases  of  the  pyramids  of 
Malpighi  are  ridges  of  cortical  substance  with  distinct  depressions  between  them. 


CORTEX< 


MEDULLA 
AT  BASE  OF 


;E  OF< 

MID       I 


Cun  \  01  u  1 1  » 1     lumm   ,     &«i     <  i  ;u  i  >i  i  i' 'i  i  ui    »c^*Jim    uuuwiuvvu    tuuuic    MJ    wo    IAJUWUUIK    vlML/uaVf     Ad|     J.1,    cuncv: 

tubule,  joined  below  by  others  to  form  the  excretory  duct,  which  opens  at  the  apex  of  the  pyramid.      (Klein.) 


These  ridges  are  the  medullary  rays  (pars  radiata)  or  pyramids  of  Ferrein  (Figs. 
1026  and  1030).  The  labyrinth  of  the  cortex  (Fig.  1026)  is  constituted  by  the  kidney 
substance  between  the  rays.  The  pyramids  of  Ferrein  look  like  direct  continua- 
tions of  the  medullary  substance,  but,  in  reality,  they  are  in  the  cortex,  and  are 
formed  by  the  straight  tubes  extending  in  masses  into  the  cortex.  The  pyramids  of 
Ferrein  are  much  smaller  than  the  pyramids  of  Malpighi.  In  the  columns  of 

90 


1426 


THE  URINARY  ORGANS 


Bertin  blood-vessels,  nerves,  and  lymphatics  pass  to  and  emerge  from  the  sinus 
by  way  of  small  foramina.  The  summit  of  a  papilla  contains  a  number  of  orifices 
of  papillary  ducts.  Such  an  area  is  called  an  area  cribrosa  (Fig.  1027). 

These  two  parts,  cortical  and  medullary,  so  dissimilar  in  appearance,  are  very 
similar  in  structure,  being  made  up  of  urinary  tubes  and  blood-vessels  upited  and 
bound  together  by  a  connecting  matrix  or  stroma. 

Minute  Anatomy. — The  uriniferous  tubes,  urinary  canals  or  tubuli  uriniferi  (tubuli 
renales)  (Figs.  1025  and  1030),  of  which  the  kidney  is  for  the  most  part  made  up, 
commence  in  the  cortical  portion  of  the  kidney.  Each  tubule  begins  between  the 
medullary  rays  (Fig.  1026)  in  a  sac,  Bowman's  capsule  or  the  Malpighian  capsule 
(see  below).  The  tubules,  as  a  rule,  after  pursuing  a  very  circuitous  course 
through  the  cortical  and  medullary  parts  of  the  kidney,  finally  terminate  at  the 
apices  of  the  Malpighian  pyramids  by  open  mouths,  so  that  the  fluid  which  they 
contain  is  emptied  into  the  dilated  extremity  of  the  ureter  contained  in  the  sinus 
of  the  kidney.  If  the  surface  of  one  of  the  papillae  is  examined  with  a  lens,  it  will 


TUNICA 

AI.BUGINEA' 


LABYRINTH 
OF  CORTEX 


MEDULLARY 
RAYS 


INTERLOBULAR 
VEIN 


r-J-JS,,  CONVOLUTED 

•--•"•  -'TUBULES 


--.=.  .-     MALPIGHIAN 
///^-"CORPUSCLES 

lts& 


INTERLOBULAH 


^  STRAIGHT 
TUBULES 


FIG.  1026. — Part  of  a  section  through  the  cortex  of  the  kidney  in  the  direction  of  the  straight  tubules.    (Toldt.) 

be  seen  to  be  studded  over  with  a  number  of  small  depressions  (foramina  papil- 
laria),  from  sixteen  to  twenty  in  number,  and  in  a  fresh  kidney,  upon  pressure 
being  made,  fluid  will  be  seen  to  exude  from  these  depressions.  They  are  the 
orifices  of  the  tubuli  uriniferi,  which  terminate  in  this  situation.  The  tubuli  uri- 
niferi being  in  the  cortex  as  the  Malpighian  bodies  or  corpuscles  (corpuscula  rents) 
(Figs.  1025,  1026,  1028,  and  1031),  which  are  small  rounded  masses,  varying  in 
size,  but  average,  about  y^  of  an  inch  in  diameter.  They  are  of  a  deep-red  color, 
and  are  found  only  in  the  cortical  portion  of  the  kidney.  Each  of  these  little  bodies 
is  composed  of  two  parts — a  central  glomerulus  of  vessels,  called  a  Malpighian 
tuft,  and  a  membranous  envelope,  the  Malpighian  capsule  or  capsule  of  Bowman 
(capsula  glomeruli),  which  latter  is  a  small  pouch-like  commencement  of  a  urinif- 
erous tubule. 

The  Malpighian  Tuft  or  Vascular  Glomerulus  (Figs.  1028,  1030,  1035,  and  1036) 
is  a  network  of  convoluted  capillary  blood-vessels  held  together  by  scanty  con- 
nective tissue  and  grouped  into  from  two  to  five  lobules.  This  capillary  net- 
work is  derived  from  a  small  arterial  twig,  the  afferent  vessel,  which  pierces  the  wall 
of  the  capsule,  generally  at  a  point  opposite  that  at  which  the  latter  is  connected 


THE  KIDXEYS 


1427 


with  the  tube;  and  the  resulting  efferent  vessel  emerges  from  the  capsule  at  the  same 
point.  The  afferent  vessel  is  usually  the  larger  of  the  two  (Fig.  1028).  The  Mal- 
pighian  or  Bowman's  capsule  (capsula  glomeruli)  (Figs.  1028, 1029,  and  1030),  which 
surrounds  the  glomerulus,  is  formed  of  a  hyaline  membrane  supported  by  a  small 
amount  of  connective  tissue  which  is  continuous  with  the  connective  tissue  of  the 
tube.  It  is  lined  on  its  inner  surface  with  a  layer  of  squamous  epithelial  cells 
which  are  reflected  from  the  lining  membrane  on  to  the  glomerulus  at  the  point 
of  entrance  or  exit  of  the  afferent  and  efferent  vessels.  The  whole  surface  of 
the  glomerulus  is  covered  with  a  continuous  layer  of  the  same  cells  on  a  delicate 
supporting  membrance,  which  with  the  cells  dips  in  between  the  lobules  of  the 
glomerulus,  closely  surrounding  them.  Thus,  between  the  glomerulus  and  the 
capsule  a  space  is  left,  forming  a  cavity  lined  by  a  continuous  layer  of  cells,  which 
varies  in  size  according  to  the  state  of  secretion  and  the  amount  of  fluid  present 
in  it.  The  cells,  as  above  stated,  are  squamous  in  the  adult,  but  in  the  foetus  and 
young  subject  they  are  polyhedral  or  even  columnar. 


AREA  CRIBROSA 


EXCRETORY 
TUBULES 


WALL  OF  RENAL  CALYX 

FIG.  1027. — Area  cribrosa  of  renal  papilla.    (Toldt.) 


FIG.  1028. — Minute  structure  of  kidney. 


The  Tubuli  Uriniferi,  commencing  in  the  Malpighian  bodies,  in  their  course 
present  many  changes  in  shape  and  direction  (tubuli  renales  contorti),  and  are 
contained  partly  in  the  medullary  and  partly  in  the  cortical  portions  of  the 
organ. 

At  the  junction  of  a  tubule  with  the  Malpighian  capsule  there  is  a  somewhat 
constricted  portion  which  is  termed  the  neck  (Fig.  1031).  Beyond  this  the  tubule 
becomes  convoluted,  and  pursues  a  considerable  course  in  the  cortical  structure, 
constituting  the  proximal  or  first  convoluted  tubule  (Figs.  1030  and  1031).  After  a 
time  the  convolutions  disappear,  and  the  tubule  approaches  the  medullary  portion 
of  the  kidney  in  a  more  or  less  spiral  manner.  This  section  of  the  tubule  has 
been  called  the  spiral  tube  of  Schachowa  (Fig.  1031).  Throughout  this  portion 
of  their  course  the  tubuli  uriniferi  have  been  contained  entirely  in  the  cortical 
structure,  and  have  presented  a  pretty  uniform  calibre.  They  now  enter  the 
medullary  portion,  and  suddenly  become  much  smaller,  quite  straight  in  direction 
(tubuli  renales  recti},  and  each  tubule  dips  down  for  a  variable  depth  into  the 
pyramids,  constituting  the  descending  limb  of  Henle's  loop  (Figs.  1030  and  1031). 
Bending  on  itself,  it  forms  a  kind  of  loop  near  the  apex  of  the  pyramid,  the 
loop  of  Henle,  and,  reascending,  becomes  suddenly  enlarged  and  again  spiral 


THE  URINARY  ORGANS 


in  direction,  forming  the  ascending  limb  of  Henle's  loop  (Figs.  1030  and  1031), 
and  re-enters  the  cortical  structure.  This  portion  of  the  tubule  does  not  present 
a  uniform  calibre,  but  becomes  narrower  as  it  ascends  and  irregular  or  somewhat 
spiral  in  outline  (Fig.  1031).  As  a  narrow  tube  it  enters  the  cortex  and  ascends 
for  a  short  distance,  when  it  again  becomes  dilated,  irregular,  and  angular.  This 
section  is  termed  the  irregular  tubule  (Fig.  1031);  it  terminates  in  a  convoluted 
tubule  which  exactly  resembles  the  proximal  convoluted  tubule;  and  is  called  the 
distal  or  second  convoluted  tubule  (Figs.  1030  and  1031).  This  again  terminates 
in  a  narrow  curved  or  junctional  tubule,  which  enters  the  straight  or  collecting 
tube. 

Each  straight  collecting  or  receiving  tube  (Figs.  1030  and  1031)  commences 
by  a  small  orifice  on  the  summit  of  a  papilla,  thus  opening  and  discharging 
its  contents  into  the  interior  of  one  of  the  calices.  Traced  into  the  substance 


Afferent 

and 

efferent 

vessels          f  Convo- 
<  luted 
I  tubules 


Bowman's 
capsule, 
outer  part 

Blood- 


Beginning  of 

urinary 

tubule 


FIG.  1029. — A  section  through  the  cortex  of  an  ape's  kidney.    A  Malpighian  corpuscle,  together  with  the  beginning 

of  the  urinary  canal,  is  shown.     X350. 


of  the  pyramid,  these  tubes  are  found  to  run  from  apex  to  base,  dividing 
dichotomously  in  their  course  and  slightly  diverging  from  each  other.  Thus 
dividing  and  subdividing,  they  reach  the  base  of  the  pyramid,  and  enter  the 
cortical  structure  greatly  increased  in  number.  Upon  entering  the  cortical  por- 
tion they  continue  a  straight  course  for  a  variable  distance,  and  are  arranged  in 
groups,  several  of  these  groups  corresponding  to  a  single  pyramid.  The  tubes  in 
the  centre  of  the  group  are  the  longest,  and  reach  almost  to  the  surface  of  the  kid- 
ney, while  the  external  ones  are  shorter,  and  ad'.ance  only  a  short  distance  into 
the  cortex.  In  consequence  of  this  arrangement  the  cortical  portion  presents  a 
number  of  conical  masses,  the  apices  of  which  reach  the  periphery  of  the  organ, 
and  the  bases  are  applied  to  the  medullary  portion.  These  are  termed  the  medul- 


THE  KIDNEYS 


1429 


lary  rays  or  the  pyramids  of  Perrein  (Fig.  1026;  also  p.  1426).  As  they  run  through 
the  cortical  portion  the  straight  tubes  receive  on  either  side  the  curved  extremity 
of  the  convoluted  tubes,  which,  as  stated  above,  commence  at  the  Malpighian 
bodies.  Each  collecting  tube  receives  a  number  of  tubules,  and  several  collecting 
tubes  unite  together  to  form  a  papillary  duct  (Fig.  1030)  and  open  by  a  foramen 
(Fig.  1027)  at  the  surface  of  the  papilla. 


III. 


IV, 


Arteria  )  interlob- 
Ve.na  J  ularis 


Vena  )  interlob- 
Arteria  j  ularis 


FIG.  1030. — Diagrammatic  representation  of  the  course  of  the  urinary  canals  (left)  and  the  kidney  vessels 
(right).  The  arteries  are  red,  the  veins  blue:  capsules  of  Bowman,  convoluted  tubules  I.  order  and  loops  of 
Henle  are  black;  convoluted  tubules  II.  order  and  collecting  tubules  gray.  I..  II.,  III.,  IV.,  four  kidney 
lobules:  a,  vas  afferens;  e,  vas  efferens.  1,  Bowman's  capsule;  2,  convoluted  tubule  I.  order;  3,  descending 
limb  of  loop  of  Henle;  4,  ascending  limb  of  loop  of  Henle;  5,  convoluted  tubule  II.  order;  6,  7,  collecting 
tubules;  8,  papillary  duct.  (Szymonowicz.) 

It  will  be  seen  from  the  above  description  that  there  is  a  continuous  series 
of  tubes  from  their  commencement  in  the  Malpighian  bodies  to  their  termina- 
tion at  the  orifices  on  the  apices  of  the  pyramids  of  Malpighi,  and  that  the  urine, 


1430 


THE  URINARY  ORGANS 


Distal  Jnnctional] 
convo-       tubule, 
luted 


the  secretion  of  which  commences  in  the  capsule,  finds  its  way  through  these 
tubes  into  the  calices  of  the  kidney,  and  so  into  the  ureter.     To  recapitulate: 

the  tube  first  presents  a  con- 
stricted portion,  (1)  the  neck. 
2.  It  forms  a  wide  convoluted 
tube,  the  proximal  convoluted 
tube.  3.  It  becomes  spiral,  the 
spiral  tubule  of  Schachowa.  4.  It 
enters  the  medullary  structure 
as  a  narrow,  straight  tube,  the 
descending  limb  of  Henle's  loop. 

5.  Forming  a  loop  and  becom- 
ing dilated,  it  ascends  somewhat 
spirally,  and,  gradually  dimin- 
ishing in  calibre,  again  enters 
the   cortical   structure,  the  as- 
cending limb  of    Henle's    loop. 

6.  It   now  becomes   irregular 
and    angular    in    outline,    the 
irregular  tubule.    7.  It  then  be- 
comes   convoluted,    the    distal 
convoluted  tubule.   8.  Diminish- 
ing in  size,  it  forms  a  curve,  the 
curved  or  junctional  tubule.    9. 
Finally,  it  joins  a  straight  tube, 
the  straight  collecting  tube,which 
is  continued  downward  through 
the   medullary  substance    and 
joins   other    straight   tubes  to 
form    a  papillary   duct,    which 

FIG..  1031.— Uriniferous  tube.      For  the  sake  of  clearness  the  °PenS  in  a  foramen  »t  the 
epithelial  cells  have  been  represented  more  highly  magnified  than  nf  a   nvramifl 
the  tubes  in  which  they  are  contained.  d  HJrd      lu' 


Descending  limb  1  _ 
of  Henle's  loop,  j 


FIG.  1032.1 — Longitu-  FIG.  1033.—  Longjtu- 

dinal  section  of  Henle's  dinal  section  of  straight 

descending    limb:      a,  tube:    a,  cylindrical  or 

membrana  propria  ;   b,  cubical  epithelium  ;    b, 

epithelium.  membrana  propria. 


FIG.  1034. — Transverse  section  of  pyramidal  substance  of 
kidney  of  pig,  the  blood-vessels  of  which  are  injected:  n,  large 
collecting  tube  cut  across,  lined  with  cylindrical  epithelium; 
b,  branch  of  collecting  tube  cut  across,  lined  with  epithelium 
with  shorter  cylinders;  c  and  d.  Henle's  loops  cut  across  ;  e, 
blood-vessels  cut  across  ;  D,  connective-tissue  ground-sub- 
stance. 


THE  TUBULI  URINIFERI:  THEIR  STRUCTURE  (Figs.  1032,  1033,  and  1034).— 
The  tubuli  uriniferi  consist  of  basement-membrane  lined  with  epithelium.     The 


1  From  Handbook  for  the  Physiological  Laboratory. 


THE  KIDNEYS 


1431 


epithelium  varies  considerably  in  different  sections  of  the  uriniferous  tubes. 
In  the  neck  the  epithelium  is  continuous  with  that  lining  the  Malpighian 
capsule,  and,  like  it,  consists  of  flattened  cells  with  an  oval  nucleus.  The  cells 
are,  however,  very  indistinct  and  difficult  to  trace,  and  the  tube  has  here  the 
appearance  of  a  simple  basement-membrane  unlined  with  epithelium.  In  the 
proximal  convoluted  tubule  and  the  spiral  tubule  of  Schachowa  the  epithelium  is 
polyhedral  in  shape,  the  sides  of  the  cells  not  being  straight,  but  fitting  into 
each  other,  and  in  some  animals  so  fused  together  that  it  is  impossible  to  make 
out  the  lines  of  junction.  In  the  human  kidney  the  cells  often  present  an  angular 
projection  of  the  surface  next  the  basement-membrane.  These  cells  are  made 
up  of  more  or  less  rod-like  fibres,  which  rest  by  one  extremity  on  the  basement- 
membrane,  whilst  the  other  projects  toward  the  lumen  of  the  tube.  This  gives 
to  the  cells  the  appearance  of  distinct  striation.  In  the  descending  limb  of  Henle's 
loop  the  epithelium  resembles  that  found  in  the  Malpighian  capsule  and  the 
commencement  of  the  tube,  consisting  of  flat  transparent  epithelial  plates  with 
an  oval  nucleus  (Fig.  1032).  In  the  ascending  limb,  on  the  other  hand,  the 
cells  partake  more  of  the  character  of  those  described  ass  existing  in  the  prox- 
imal convoluted  tubule,  being  polyhedral  in  shape  and  presenting  the  same 
appearance  of  striation.  The 
nucleus,  however,  is  not  situ- 
ated  in  the  centre  of  the  cell, 
but  near  the  lumen  (Fig. 
1034).  After  the  ascending 
limb  of  Henle's  loop  becomes 
narrower  upon  entering  the 
cortical  structure,  the  stria- 
tion appears  to  be  confined 
to  the  outer  part  of  the  cell; 
at  all  events,  it  is  much  more 
distinct  in  this  situation,  the 
nucleus,  which  appears  flat- 
tened and  angular,  being  still 
situated  near  the  lumen.  In 
the  irregular  tubule  the  cells 
undergo  a  still  further  change, 
becoming  very  angular,  and 
presenting  thick  bright  rods 


a  A 

FIG.  1035. — Diagrammatic 


a  A 


FIG.  1036.— A  portion  of  Fig.  1035 
enlarged.  (The  references  are  the 
same.) 


or  markings,  which  render  the    sk*t'cGh'  Of  tfc  wSHSST.  of 
striation  much  more  distinct   thekldn?y- 

.  .  ,  .  .         A,  a,    interlobar  artery  and  vein,  the  former  giving  off  the  renal 

than    in    any   Other   Section    OI     afferent*,  the  latter  receiving  the  renal  efferents  ;  B,  6,  interlobular 

artery  and  vein,  the  latter  commencing  from  the  stellate  veins,  and 
receiving  branches  from  the  plexus  around  the  tubuli  contort!,  the 
former  giving  off  renal  afferents  ;  c,  straight  tube,  surrounded  by 
tubuli  contort!,  with  which  it  communicates,  as  more  fully  shown  in 
Fig.  1036;  D,  margin  of  medullary  substance  ;  E,  E,  E,  receiving  tubes 
cut  off;  F,  /,  arteriolae  et  venae  rectae,  the  latter  arising  from  (G)  the 
plexus  at  the  medullary  apex;  x,  vascular  glomerulus;  w,  the  arcuate 
artery  and  vein. 


the  urinary  tubules.  In  the 
distal  convoluted  tubule  the 
epithelium  appears  to  be 
somewhat  similar  to  that 
which  has  been  described  as 
existing  in  the  proximal  convoluted  tubule,  but  presents  a  peculiar  refractive 
appearance.  In  the  curved  tubule,  just  before  its  entrance  into  the  straight 
collecting  tube,  the  epithelium  varies  greatly  as  regards  the  shape  of  the  cells, 
some  being  angular  with  short  processes,  others  spindle-shaped,  others  poly- 
hedral. 

In  the  straight  tubes  the  epithelium  is  more  or  less  columnar;  in  its  papillary 
portion  the  cells  are  distinctly  columnar  and  transparent  (Fig.  1033),  but  as  the 
tube  approaches  the  cortex  the  cells  are  less  uniform  in  shape;  some  are  poly- 
hedral, and  others  angular  with  short  processes. 


1432 


The  Renal  Blood-vessels. — The  kidney  is  plentifully  supplied  with  blood  by 
the  renal  artery  (Figs.  1018  and  1024),  a  large  offset  of  the  abdominal  aorta.  Pre- 
viously to  entering  the  kidney,  each  artery  divides  into  four  or  five  branches, 
which  are  distributed  to  its  substance.  At  the  hilum  these  branches  lie  between 
the  renal  vein  and  ureter,  the  vein  being  in  front,  the  ureter  behind.  Each  vessel 
gives  off  a  small  branch  to  the  suprarenal  capsules,  the  ureter,  and  the  sur- 
rounding cellular  tissue  and  muscles.  It  has  been  pointed  out  by  Hyrtl  (p  680) 
that  the  renal  artery  gives  off  a  branch  which  divides  and  supplies  the  dorsal 
portion  of  the  kidney  and  a  branch  which  divides  and  supplies  the  ventral 
portion  of  the  kidney.  Between  these  two  vascular  systems  is  a  non-vascular 
zone,  called  by  Robinson  the  exsanguinated  renal  zone  of  Hyrtl.  It  "  is  one-half  inch 
dorsal  to  the  lateral  longitudinal  renal  border."  Frequently  there  is  a  second 
renal  artery,  which  is  given  off  from  the  abdominal  aorta  at  a  lower  level,  and  sup- 
plies the  lower  portion  of  the  kidney.  It  is  termed  the  inferior  renal  artery.  The 
branches  of  the  renal  arteries  pass  to  the  kidney  substance  between  the  pyramids 
and  are  known  as  interlobar  arteries  (arteriae  interlobares  renis]  (Figs.  1026,  1030, 
1037,  and  1038).  At  the^junction  of  the  cortical  and  medullary  portions  these  vessels 
turn  and  for  a  short  distance  pursue  a  course  parallel  to  the  kidney  surface. 
There  are  thus  formed  a  series  of  incomplete  vascular  arches  across  the  bases 
of  the  pyramids,  the  arcuate  arteries  (arteriae  arciformes)  (Figs.  1030,  1035,  and 
1036).  From  these  arches  two  sets  of  vessels  come.  The  vessels  of  one  set  go 
to  the  periphery  and  enter  the  labyrinth,  those  of  the  other  set  pass  toward  the 
centre  and  enter  the  intermediate  zone  of  the  medulla.  These  last  vessels  are 
the  arteriolae  recti  (Figs.  1030,  1035,  and  1036). 

Because  of  these  vessels  the  kidney  exhibits  stria-  6  m 

tions  on  section.  Each  of  the  arteriolae  recti 
in  the  medulla  divides  into  numerous  small 
branches  which  are  nearly  parallel  to  each  other 


FIG.  1039. — Diagrammatic  representation 
of  the  blood-vessels  in  the  substance  of  the 
cortex  of  the  kidney:  m,  region  of  the 
medullary  ray;  b.  region  of  the  tortuous 
portion  of  the  tubules;  ai,  interlobular 
artery;  vi,  interlobular  vein;  va,  vas  affer- 
ens;  gl,  glomerulus;  ve.  vas  efferens;  vz. 


FIG.  1037.— Lobar  circulation.      FIG.  1038. — Interlobar  circulation,    venous  twig  of  the  interlobularis.     (From 
(Poirier  and  Charpy.)  Ludwig,  in  Strieker's  Handbook.) 


and  supply  the  tubules  of  this  region.  The  arteries  which  arise  from  the  arches 
and  pass  to  the  periphery  are  the  interlobular  arteries  (arteriae  interlobulares] 
(Figs.  1030,  1035,  1036,  and  1039).  They  traverse  the  labyrinth  and  pass  toward 
the  surface  of  the  kidney.  A  number  of  short  branches,  the  vasa  afferentia,  are 
given  off  by  the  interlobular  arteries  (Figs.  1030,  1035,  1036,  and  1039).  Each 
afferent  vessel  passes  to  a  capsule  of  Bowman.  On  reaching  the  capsule  the 
vessel  forms  a  capillary  mass,  the  glomerulus,  which  is  within  the  invaginated 
capsule  (Figs.  1030, 1035,  and  1039). 

Emerging  from   each   glomerulus  is  a  small  vessel,   the  vas  efferens   (Figs. 


THE  KIDNEYS  1433 

1028,  1030,  1035,  and  1039).  This  vessel  divides  into  capillaries  which  are  dis- 
tributed to  the  tubules  of  the  labyrinth  and  medullary  rays.  Blood  is  gathered 
from  the  capillaries  about  the  tubules  by  veins  which  correspond  to  the  inter- 
lobular  arteries  and  arteriolae  recti.  These  veins  form  a  set  of  arches  across 
the  bases  of  the  pyramids.  From  the  arches  veins  arise  and  pass  between  the 
pyramids  to  the  sinus  of  the  kidney,  where  they  unite  and  form  branches  of 
the  renal  vein. 

Nerves  of  the  Kidney. — The  nerves  of  the  kidney,  although  small,  are  about 
fifteen  in  number.  They  have  small  ganglia  developed  upon  them,  and  are  derived 
from  the  renal  plexus,  which  is  formed  by  branches  from  the  solar  plexus,  the 
lower  and  outer  part  of  the  semilunar  ganglion  and  aortic  plexus,  and  from  the 
lesser  and  smallest  splanchnic  nerves.  They  communicate  with  the  spermatic 
plexus,  a  circumstance  which  may  explain  the  occurrence  of  pain  in  the  testicle  in 
affections  of  the  kidney.  So  far  as  they  have  been  traced,  they  seem  to  accompany 
the  renal  artery  and  its  branches,  but  their  exact  mode  of  termination  is  not 
known. 

The  Lymphatics. — The  lymphatics  consist  of  a  superficial  and  deep  set. 

The  superficial  lymphatics  are  just  beneath  the  capsule.    From  them  come  two 
sets  of  collecting  trunks  (Sappey).    One  set  joins  the  deep  collectors  by  entering 
the  kidney  substance  or  passing  to  the  hilum.    Another 
set  pass  into  the  lymphatics  of  the  fatty  capsule. 

The  deep  collectors  emerge  from  the  hilum  and  lie 
about  the  renal  artery  and  vein.  From  the  right  kidney 
some  of  the  trunks  pass  to  the  glands  about  the  post- 
cava  and  possibly  also  in  the  glands  in  front  of  the 
aorta.  Others  end  in  the  glands  back  of  the  postcava 
(Stahr). 

From  the  left  kidney  the  trunks  pass  to  the  glands 
which  lie  along  the  left  side  of  the  abdominal  aorta.1 
The  lymphatics  of  the  fatty  capsule  of  the  kidney  pass 
to  the  same  glands  as  do  the  deep  collectors  of  the 
kidney  (Stahr). 

Connective  Tissue  or  Intertubular  Stroma. — Although 
the  tubules  and  vessels  are  closely  packed,  a  certain 
small  amount  of  connective  tissue,  continuous  with  the 
capsule,  binds  them  firmly  together.     This  tissue  was  Fial040i^ta(Sutj showing 
first  described  by  Goodsir,  and  subsequently  by  Bow- 
man.   Ludwig  and  Zawarykin  have  observed  distinct  fibres  passing  around  the 
Malpighian  bodies,  and  Henle  has  seen  them  between  the  straight  tubes  com- 
posing the  medullary  structure. 

Variations  and  Abnormalities. — Congenital  absence  of  the  kidney  has  been 
observed.  Not  unusually  one  kidney  is  considerably  larger  than  the  other;  occa- 
sionally one  is  very  large  and  the  other  is  very  small,  from  atrophy,  the  large 
organ  having  become  large  in  response  to  a  functional  need,  which  causes  it  to 
compensate  for  the  insufficiency  of  the  small  kidney.  If  a  kidney  is  removed 
surgically,  the  other  kidney  enlarges.  As  previously  stated,  the  kidneys  of  the 
foetus  and  of  the  young  child  show  distinct  fissures  which  makes  each  organ 
lobulated  (Fig.  1040).  The  adult  kidneys  frequently  exhibit  remains  of  these 
fissures.  A  horseshoe  kidney  is  a  condition  in  which  the  lower  poles  of  the  two 
kidneys  are  united  by  kidney  structure,  the  bond  of  union  crossing  the  middle  line. 
The  strip  of  kidney  tissue  which  effects  the  junction  may  be  slight  in  amount, 

1  The  Lymphatics.    By  Poirier,  Cuneo,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


1434  THE  URINARY  ORGANS 

considerable,  or  extensive.     Sometimes  the  two  kidneys  are  completely   fused 
together  into  one  large  organ  with  two  ureters. 

Surface  Form. — The  kidneys,  being  situated  at  the  back  part  of  the  abdominal  cavity  and 
deeply  placed,  cannot  be  felt  unless  enlarged  or  misplaced.    They  are  situated  on  the  confines 


below  the  lower  edge  of  each  kidney.  2.  A  vertical  line  carried  upward  to  the  costal  arch  from 
the  middle  of  Poupart's  ligament  has  one-third  of  the  kidney  to  its  outer  side  and  two-thirds  to 
its  inner  side — i.  e.,  between  this  line  and  the  median  line  of  the  body."  In  adopting  these  lines 
it  must  be  borne  in  mind  that  the  axes  of  the  kidneys  are  not  vertical,  but  oblique,  and  if  con- 
tinued upward  would  meet  about  the  ninth  dorsal  vertebra.  Posteriorly:  The  upper  end  of  the 
left  kidney  would  be  defined  by  a  line  drawn  horizontally  outward  from  the  spinous  process  of  the 
eleventh  dorsal  vertebra,  and  its  lower  end  by  a  point  two  inches  above  the  iliac  crest.  The  right 
kidney  would  be  half  to  three-quarters  of  an  inch  below.  Morris  lays  down  the  following  rules 
for  indicating  the  position  of  the  kidney  on  the  posterior  surface  of  the  body:  "  1.  A  line  parallel 
with,  and  one  inch  from,  the  spine,  between  the  lower  edge  of  the  tip  of  the  spinous  process 
of  the  eleventh  dorsal  vertebra  and  the  lower  edge  of  the  spinous  process  of  the  third  lumbar 
vertebra.  2.  A  line  from  the  top  of  this  first  line  outward  at  right  angles  to  it  for  two  and  three- 
quarter  inches.  3.  A  line  from  the  lower  end  of  the  first  transversely  outward  for  two  and  three- 
quarter  inches.  4.  A  line  parallel  to  the  first  and  connecting  the  outer  extremities  of  the  second 
and  third  lines  just  described." 

The  hilum  of  the  kidney  lies  about  two  inches  from  the  middle  line  of  the  back,  at  the  level 
of  the  spinous  process  of  the  first  lumbar  vertebra. 

Surgical  Anatomy.— Cases  of  congenital  absence  of  a  kidney,  of  atrophy  of  a  kidney,  and 
of  horseshoe  kidney  are  of  great  importance,  and  must  be  duly  taken  into  account,  when  neph- 
rectomy  is  contemplated.  A  more  common  malformation  is  where  the  two  kidneys  are  fused 
together.  They  may  be  only  joined  together  at  their  lower  ends  by  means  of  a  thick  mass  of 
renal  tissue,  so  as  to  form  a  horseshoe-shaped  body,  or  they  may  be  completely  united,  forming 
a  disk-like  kidney,  from  which  two  ureters  descend  into  the  bladder.  These  fused  kidneys  are 
generally  situated  in  the  middle  line  of  the  abdomen,  but  may  be  misplaced  as  well. 

One  or  both  kidneys  may  be  misplaced  as  a  congenital  condition,  and  remain  fixed  in  this 
abnormal  position.  They  are  then  very  often  misshapen.  They  may  be  situated  higher  or  lower 
than  normal  or  removed  farther  from  the  spine  than  usual  or  they  may  be  displaced  into  the 
iliac  fossa,  over  the  sacro-iliac  joint,  on  to  the  promontory  of  the  sacrum,  or  into  the  pelvis 
between  the  rectum  and  bladder  or  by  the  side  of  the  uterus.  In  these  latter  cases  they  may 
give  rise  to  very  serious  trouble.  The  kidney  may  also  be  misplaced  as  a  congenital  condition, 
but  may  not  he  fixed.  It  is  then  known  as  a  floating  kidney.  It  is  believed  to  be  due  to  the 
fact  that  the  kidney  is  completely  enveloped  by  peritoneum,  which  then  passes  backward  to  the 
spine  as  a  double  layer,  forming  a  mesonephron,  which  permits  of  movement  taking  place.  The 
kidney  may  also  be  misplaced  as  an  acquired  condition;  in  these  cases  the  kidney  is  mobile  in 
the  tissues  by  which  it  is  surrounded,  either  moving  in  or  moving  with  its  fatty  capsule.  This 
condition  is  known  as  movable  kidney  (nephroptosis),  and  is  more  common  in  the  female  than 
in  the  male,  and  on  the  right  than  the  left  side.  If  a  displaced  kidney  becomes  fixed  in  an 
abnormal  position,  it  is  said  to  be  dislocated.  Movable  kidney  cannot  be  distinguished  from 
floating  kidney  until  the  kidney  is  exposed  by  incision.  Other  malformations  are  the  persist- 
ence of  the  foetal  lobulation;  the  presence  of  two  pelves  or  two  ureters  to  the  one  kidney.  In 
some  rare  instances  a  third  kidney  may  be  present. 

The  kidney  is  embedded  in  a  large  quantity  of  loose  fatty  tissue,  and  is  but  partially  covered 
by  peritoneum;  hence,  rupture  of  this  organ  is  not  nearly  so  serious  an  accident  as  rupture  of 
the  liver  or  spleen,  since  the  extravasation  of  blood  and  urine  which  follows  is,  in  the  majority 
of  cases,  outside  the  peritoneal  cavity.  Occasionally  the  kidney  may  be  bruised  by  blows  in  the 
loin  or  by  being  compressed  between  the  lower  ribs  and  the  ilium  when  the  body  is  violently 
bent  forward.  This  is  followed  by  a  little  transient  hccmaturia,  which,  however,  speedily  passes 
off.  Occasionally,  when  rupture  involves  the  pelvis  of  the  kidney  or  the  commencement  of  the 
ureter,  this  duct  may  become  blocked,  and  hy drone phrosis  follows. 

The  loose  cellular  tissue  around  the  kidney  may  be  the  seat  of  suppuration,  constituting 
perinephritic  abscess.  This  may  be  due  to  injury,  to  disease  of  the  kidney  itself,  or  to  extension 
of  inflammation  from  neighboring  parts.  The  abscess  may  burst  into  the  pleura,  causing 
empyema;  into  the  colon  or  bladder;  or  may  point  externally  in  the  groin  or  loin.  Tumors  of  the 
kidney,  of  which,  perhaps,  sarcoma  in  children  is  the  most  common,  may  be  recognized  by  their 
position  and  fixity;  by  the  resonant  colon  lying  in  front  of  it;  by  their  not  moving  with  respira- 
tion; and  by  their  rounded  outline,  not  presenting  a  notched  anterior  margin  like  the  spleen,  with 
which  they  are  most  likely  to  be  confounded.  The  examination  of  the  kidney  should  be  bimanual ; 
that  is  to  say,  one  hand' should  be  placed  in  the  flank  and  firm  pressure  made  forward;  while 


THE  KIDNEYS  1435 

the  other  hand  is  buried  in  the  abdominal  wall,  over  the  situation  of  the  organ.  Manipulation 
of  the  kidney  frequently  produces  a  peculiar  sickening  sensation  and  some  faintness. 

The  kidney  has,  of  late  years,  been  frequently  attacked  surgically.  It  may  be  exposed  and 
opened  for  exploration  or  the  evacuation  of  pus  (ncphrotomy);  it  may  be  incised  for  the  removal 
of  stone  (ncphro-lithotomy);  it  may  be  sutured  when  wounded  (nepkrorrhaphy);  it  may  be  fixed 
in  place  by  sutures  (nephropexy)  or  gauze  pads  when  movable  or  floating;  or  it  may  be  removed 
(ncphrectomy). 

The  kidney  may  be  exposed  either  by  a  lumbar  or  abdominal  incision.  The  operation  is 
best  performed  by  a  lumbar  incision,  except  in  a  case  of  very  large  tumor  or  of  wandering  kid- 
ney with  a  loose  mesonephron,  on  account  of  the  advantages  which  it  possesses  of  not  opening 
the  peritoneum  and  of  affording  admirable  drainage.  It  may  be  performed  either  by  an  oblique 
a  vertical,  or  a  transverse  incision.  A  common  incision  for  exposing  the  kidney  begins  an  inch 
below  the  twelfth  rib  at  the  margin  of  the  Erector  spinae  muscle  and  passes  obliquely  down- 
ward and  forward,  exposing  the  anterior  border  of  the  Latissimus  dorsi  and  the  posterior  border 
of  the  Internal  oblique.  The  surgeon  divides  the  posterior  leaflet  of  the  lumbar  fascia,  draws  aside 
or  incises  the  Quadratus  lumborum,and  cuts  the  anterior  leaflet  of  the  lumbar  fascia  and  also  the 
transversalis  fascia.  He  opens  the  fatty  capsule  down  to  the  kidney  and  strips  it  from  the  true 
capsule,  bringing  the  kidney  outside  of  the  body  for  inspection.  The  vertical  incision  at  the 
edge  of  the  Erector  spinae  muscle  is  frequently  used.  A  gridiron  or  muscle-splitting  operation 
is  used  by  some  in  order  to  avoid  the  division  of  nerves,  vessels,  and  muscular  fibre. 

The  abdominal  operation  is  best  performed  by  an  incision  in  the  linea  semilunaris  on  the 
side  of  the  kidney  to  be  removed,  as  recommended  by  Langenbuch;  the  kidney  is  then  reached 
from  the  outer  side  of  the  colon,  ascending  or  descending,  as  the  case  may  be,  and  the  vessels 
_of  the  colon  are  not  interfered  with.  If  the  incision  were  made  in  the  linea  alba,  the  kidney 
would  be  reached  from  the  inner  side  of  the  colon,  and  the  vessels  running  to  supply  the  colon 
would  necessarily  be  interfered  with.  The  incision  is  made  of  varying  length  according  to  the 
size  of  the  kidney,  and  commences  just  below  the  costal  arch.  The  abdominal  cavity  is  opened. 
The  intestines  are  held  aside,  and  the  outer  layer  of  the  mesocolon  incised,  so  that  the  fingers 
can  be  introduced  behind  the  peritoneum  and  the  renal  vessels  are  sought  for.  These  vessels 
are  then  to  be  ligatured:  if  tied  separately,  care  must  be  taken  to  ligature  the  artery  first.  The 
kidney  must  now  be  enucleated,  and  the  vessels  and  the  ureter  divided,  and  the  latter  disinfected 
and  tied,  and,  if  it  is  thought  necessary,  stitched  to  the  edge  of  the  wound. 

THE  URETER  (Figs.  1017,  1018,  1019,  1024,  1041,  1042). 

The  ureters  are  the  two  tubes  which  conduct  the  urine  from  the  kidneys  into 
the  bladder.  The  ureter  commences  within  the  sinus  of  the  kidney  by  a  number 
of  short  truncated  branches,  the  calices  or  infundibula,  which  unite  either  directly 
or  indirectly  to  form  a  dilated  pouch,  the  pelvis  (Fig.  1023),  from  which  the  ureter, 
after  passing  through  the  hilum  of  the  kidney,  descends  to  the  bladder.  The  calices 
are  cup-like  tubes  encircling  the  apices  of  the  Malpighian  pyramids;  but  inasmuch 
as  one  calyx  may  include  two  or  even  more  papillae,  their  number  is  generally 
less  than  the  pyramids  themselves.  The  calices  vary  in  number  from  eight  to 
eighteen.  These  calices  converge  into  two  or  three  tubular  divisions  which  by 
their  junction  form  the  pelvis  or  dilated  portion  of  the  ureter.  The  portion  last 
mentioned,  where  the  pelvis  merges  into  the  ureter  proper,  is  found  opposite 
the  spinous  process  of  the  first  lumbar  vertebra,  in  which  situation  it  is  accessible 
behind  the  peritoneum  (Fig.  1019). 

The  Ureter  Proper. — The  ureter  proper  is  a  cylindrical  membranous  tube, 
about  sixteen  inches  in  length  and  of  the  diameter  of  a  goosequill,  extending  from 
the  pelvis  of  the  kidney  to  the  bladder.  Its  course  is  obliquely  downward  and 
inward  through  the  lumbar  region  (pars  abdominalis)  (Fig.  1042),  into  the  cavity  of 
the  pelvis  (pars  pelvina)  (Fig.  1042),  where  it  passes  downward,  forward,  and  inward 
across  that  cavity  to  the  base  of  the  bladder,  into  which  it  then  opens  by  a  con- 
stricted orifice  (orificium  ureteris]  (Fig.  1059),  after  having  passed  obliquely  for 
nearly  an  inch  between  its  muscular  and  mucous  coats  (Fig.  1041).  The  lower 
part  of  the  abdominal  portion  of  the  ureter  exhibits  a  spindle-shaped  dilatation. 

Relations  (Fig.  1042). — In  its  course  it  rests  upon  the  Psoas  muscle,  being 
covered  by  the  peritoneum,  and  crossed  obliquely,  from  within  outward,  by  the 


1436 


URINARY  ORGANS 


spermatic  vessels;  the  right  ureter  is  crossed  by  the  branches  of  the  mesen- 
teric  arteries,  which  are  distributed  to  the  ascending  colon,  and  the  left  ureter  by 
those  for  the  descending  colon;  the  right  ureter  lying  close  to  the  outer  side  of 
the  postcava.  Opposite  the  first  piece  of  the  sacrum  it  crosses  either  the  common 

or  external  iliac  artery  and  vein,  lying  behind  the 
ileum  on  the  right  side  and  behind  the  sigmoid 
flexure  of  the  colon  on  the  left  side.  In  the  pelvis 
it  enters  the  posterior  false  ligament  of  the  bladder, 
below  the  obliterated  hypogastric  artery,  the  vas 
deferens  in  the  male  passing  between  it  and  the 
bladder.  In  the  female  the  ureter  is  to  the  inner 
side  of  the  uterine  artery  at  the  wall  of  the  pelvis, 
it  passes  forward  and  inward  below  the  posterior 
layer  of  the  broad  ligament  running  through  the 
parametrium,  passing  along  the  side  of  the  neck 
of  the  uterus  and  upper  part  of  the  vagina, 
beinff  in  contact  with  the  anterior  and  lateral 

,~    ,  ..  i     *     •  i  •       i        i 

vaginal  walls  and  being  crossed  anteriorly  by 
the  uterine  artery  (Fig.  1115).  At  the  base  of  the 

bladder  the  ureter  is  situated  about  two  inches  from  its  fellow:  lying,  in  the  male,- 

about  an  inch  and  a  half  from  the  vesical  orifice  of  the  urethra,  at  one  of  the 

posterior  angles  of  the  trigone  (Fig.  1059). 

Structure.  —  The  ureter  is  composed  of  three  coats  —  fibrous,  muscular,   and 

mucous. 


FIG.  1041.—  Diagram  showing  method 

of  entrance  of  the  ureter  into  the  blad- 

der.    (F.  H.  Gemsh.) 


RIGHT  URETER  PSOAS   MUSCLE 

LEFT  URETER 


ASCENDING 
COLON 


APPENDIX  (drawn 
up  under) 


ARTERIES  OF 


SUPERIOR 

HEMORRHOIDAL 

ARTERY 

ARTERY  TO 

SIGMOID 

FLEXURE 


FIG.  1042. — The  relations  of  the  pelvic  mesocolon  with  the  wall,  the  iliac  sigmoid  and  superior  hemorrhoidal 
arteries  and  the  ureter.      (Poirier  and  Charpy.) 

The  Fibrous  Coat  (tunica  adventitia). — The  fibrous  coat  is  the  same  throughout 
the  entire  length  of  the  duct,  being  continuous  at  one  end  with  the  fibrous  capsule 
of  the  kidney  at  the  floor  of  the  sinus,  while  at  the  other  it  is  lost  in  the  fibrous 
structure  of  the  bladder. 


THE  URETER  1437 

The  Muscular  Coat  (tunica  muscularis). — In  the  pelvis  of  the  kidney  the  mus- 
cular coat  consists  of  two  layers,  longitudinal  and  circular:  the  longitudinal  fibres 
become  lost  upon  the  sides  of  the  papillae  at  the  extremities  of  the  calices;  the 
circular  fibres  may  be  traced  surrounding  the  medullary  structure  in  the  same 
situation.  In  the  ureter  proper  the  muscular  fibres  are  very  distinct,  and  are 
arranged  in  three  layers — an  external  longitudinal  (stratum  externum),  a  middle 
circular  (stratum  medium),  and  an  internal  layer  (stratum  internum),  less  distinct 
than  the  other  two, .but  having  a  general  longitudinal  direction.  According  to 
Kolliker,  this  internal  layer  is  only  found  in  the  neighborhood  of  the  bladder. 

The  Mucous  Coat  (tunica  mucosa). — The  mucous  coat  is  smooth,  and  presents  a 
few  longitudinal  folds  which  become  effaced  by  distention.  It  is  continuous  with 
the  mucous  membrane  of  the  bladder  below,whilst  it  is  prolonged  over  the  papillae 
of  the  kidney  above.  Its  epithelium  is  of  a  peculiar  character,  and  resembles  that 
found  in  the  bladder.  It  is  known  by  the  name  of  transitional  epithelium.  It  con- 
sists of  several  layers  of  cells,  of  which  the  innermost — that  is  to  say,  the  cells  in 
contact  with  the  urine — are  quadrilateral  in  shape,  with  concave  margins  on  their 
outer  surface,  into  which  fit  the  rounded  ends  of  the  cells  of  the  second  layer. 
These,  the  intermediate  cells,  more  or  less  resemble  columnar  epithelium,  and  are 
pear-shaped,  with  a  rounded  internal  extremity  which  fits  into  the  concavity  of 
the  cells  of  the  first  layer,  and  a  narrow  external  extremity  which  is  wedged  in 
between  the  cells  of  the  third  layer.  The  external  or  third  layer  consists  of  conical 
or  oval  cells  varying  in  number  in  different  parts,  and  presenting  processes  which 
extend  down  into  the  basement-membrane. 

Vessels  and  Nerves. — The  arteries  supplying  the  ureter  are  branches  from  the 
renal,  spermatic,  internal  iliac,  and  inferior  vesical. 

The  nerves  are  derived  from  the  inferior  mesenteric,  spermatic,  and  pelvic  plexuses. 

Surgical  Anatomy. — Subcutaneous  rupture  of  the  ureter  is  not  a  common  accident,  but  occa- 
sionally occurs  from  a  sharp,  direct  blow  on  the  abdomen,  as  from  the  kick  of  a  horse.  The  ureter 
may  be  either  torn  completely  across,  or  only  partially  divided,  and,  as  a  rule,  the  peritoneum 
escapes  injury.  If  torn  completely  across  the  urine  collects  in  the  retroperitoneal  tissues;  if  it 
is  not  completely  divided,  the  lumen  of  the  tube  may  become  obstructed  and  hydro-nephrosis  or 
pyo-nephrosis  results.  The  ureter  may  be  accidentally  wounded  in  some  abdominal  operations; 
if  this  should  happen,  the  divided  ends  must  be  sutured  together,  or,  failing  to  accomplish  this, 
the  upper  end  must  be  implanted  into  the  bladder  or  the  intestine. 


THE  SUPRARENAL  CAPSULE  OR  GLAND  (GLANDULA 
SUPRARENALISj  (Figs.  1023,  1043,  1044). 

The  suprarenal  capsules  belong  to  the  class  of  ductless  glands.  They  are  two 
small  flattened  bodies,  of  a  yellowish  color,  situated  at  the  back  part  of  the  abdo- 
men, behind  the  peritoneum,  and  immediately  above  and  in  front  of  the  upper 
end  of  each  kidney;  hence  their  name.  The  right  one  (Fig.  1043)  is  somewhat 
triangular  in  shape,  bearing  a  resemblance  to  a  cocked  hat;  the  left  (Fig.  1044)  is 
more  semilunar,  usually  larger  and  placed  at  a  higher  level  than  the  right.  They 
vary  in  size  in  different  individuals,  being  sometimes  so  small  as  to  be  scarcely 
detected ;  their  usual  size  is  from  an  inch  and  a  quarter  to  nearly  two  inches  in 
length,  rather  less  in  width,  and  from  two  to  three  lines  in  thickness.  Their 
average  weight  is  from  one  to  one  and  a  half  drachms  each. 

Relations. — The  relations  of  the  suprarenal  capsules  differ  on  the  two  sides  oi 
the  body. 

The  Right  Suprarenal  (Fig.  1043).— The  right  suprarenal  is  roughly  triangular  in 
shape,  its  angles  pointing  upward,  downward,  and  outward.  It  presents  two  sur- 
faces for  examination,  an  anterior  and  a  posterior.  The  anterior  surface  (fades 


1438  THE  URINARY  ORGANS 

anterior)  presents  two  areas,  separated  by  a  furrow,  the  hilum  (hilus  glandulae 
suprarenatis] :  one  area  occupying  about  one-third  of  the  whole  surface,  is  situ- 
ated above  and  internally;  it  is  depressed,  uncovered  by  peritoneum,  and  is  in 
contact  in  front  with  the  posterior  surface  of  the  right  lobe  of  the  liver,  and  along 
its  inner  border  with  the  postcava;  the  remaining  area  is  elevated,  and  is  divided 
into  a  non-peritoneal  portion,  in  contact  with  the  hepatic  flexure  of  the  duodenum, 
and  a  portion  covered  by  peritoneum  forming  the  hepato-renal  fold.  The  pos- 
terior surface  (fades  posterior)  is  slightly  convex,  and  rests  upon  the  Diaphragm. 
The  base  (basis  glandulae  suprarenalis]  is  concave,  and  is  in  contact  with  the  upper 
end  and  the  adjacent  part  of  the  anterior  surface  of  the  kidney. 

The  Left  Suprarenal  (Fig.  1044). — The  left  suprarenal  is  crescentic  in  shape,  its 
concavity  being  adapted  to  the  upper  end  of  the  left  kidney.    It  presents  an  inner 


SUPRARENAL 


SUPRARENAL 
ARTERY 

SUPRARENAL 

SUPRARENAL  «pT  ^  9 ARTERY 

VEIN  " 


FIG.  1043. — The  right  suprarenal  gland.  FIG.  1044. — The  left  suprarenal  gland. 

(Spalteholz.)  (Spalteholz.) 

border  which  is  convex,  and  an  outer  which  is  concave ;  its  upper  border  is  narrow, 
and  its  lower  rounded.  Its  anterior  surface  (jades  anterior]  presents  two  areas:  an 
upper  one,  covered  by  the  peritoneum  forming  the  lesser  sac,  which  separates  it 
from  the  cardiac  end  of  the  stomach  and  to  a  small  extent  from  the  superior 
extremity  of  the  spleen;  and  a  lower  one,  which  is  in  contact  with  the  pancreas 
and  splenic  artery,  and  is  therefore  not  covered  by  the  peritoneum.  A  hilum  is 
present,  as  in  the  right  suprarenal.  Its  posterior  surface  (fades  posterior]  presents 
a  vertical  ridge,  which  divides  it  into  two  areas.  The  ridge  lies  in  the  sulcus 
between  the  kidney  and  crus  of  the  Diaphragm,  while  the  area  on  either  side  of 
it  lies  on  these  parts  respectively;  the  outer  area,  which  is  thin,  resting  on  the 
kidney,  and  the  inner  and  smaller  area  resting  on  the  left  crus  of  the  Diaphragm. 
The  surface  of  the  suprarenal  gland  is  surrounded  by  areolar  tissue  containing 
much  fat,  and  closely  invested  by  a  thin  fibrous  coat,  which  is  difficult  to  remove, 
on  account  of  numerous  fibrous  processes  and  vessels  which  enter  the  organ 
through  the  furrows  on  its  anterior  surface  and  base. 

Accessory  Suprarenal  Glands  (glandulae  suprarenales  accessoriae]. — Small 
accessory  suprarenals  are  often  to  be  found  in  the  connective  tissue  around  the 
suprarenals.  The  smaller  of  these,  on  section,  show  a  uniform  surface,  but  in 
some  of  the  larger  a  distinct  medulla  can  be  made  out. 

Structure  (Figs.  1045,  1046,  and  1047). — On  making  a  perpendicular  section 
(Fig.  1045),  the  suprarenal  gland  is  seen  to"  consist  of  two  substances — external  or 
cortical  and  internal  or  medullary.  The  former,  which  constitutes  the  chief  part  of 
the  organ,  is  of  a  deep- yellow  color.  The  medullary  substance  is  soft,  pulpy, 


THE  SUPRARENAL  CAPSULE  Oil  GLAND 


1430 


and  of  a  dark-brown  or  black  color,  whence  the  name  atrabiliary  capsules  formerly 
given  to  these  organs.  In  the  centre  is  often  seen  a  space,  not  natural,  but 
formed  by  breaking  down  after  death  of  the  medullary  substance. 

The  Cortical  Portion  (substantia  corticalis]  (Fig.  1045). — The  cortical  substance 
consists  chiefly  of  narrow  columnar  masses  placed  perpendicularly  to  the  surface. 
This  arrangement  is  due  to  the  disposition  of  the  capsule,  which  sends  into  the 
interior  of  the  gland  processes  passing  in  vertically  and  communicating  with  each 
other  by  transverse  bands  so  as  to  form  spaces 
which  open  into  each  other.  These  spaces  are 
of  slight  depth  near  the  surface  of  the  organ, 
so  that  there  the  section  somewhat  resembles  a 
net;  this  is  termed  the  zona  glomerulosa ;  but 
they  become  much  deeper  or  longer  farther  in, 
so  as  to  resemble  pipes  or  tubes  placed  endwise, 


'apsule. 

Zona 
glomerulosa. 


Zona 
fasciculata. 


Connective 
tissue. 


Gland 
cylinders. 


FIG.  1046. — Minute  structure  of  suprarenal 
capsule. 


Framework. 


Zona  reticularis. 


Medulla. 


Nuclei. 


Capillary. 


FIG.  1045. — Vertical  section  of  the  suprarenal  capsule.    (From 
Elberth,  in  Strieker's  Manual.) 


Gland 
cells. 


FIG.  1047. — Minute  structure  of  suprarenal 
capsule. 


the  zona  fasciculata.  Still  deeper  down,  near  the  medullary  part,  the  spaces 
become  again  of  small  extent;  this  is  named  the  zona  reticularis.  These  processes 
or  trabeculae,  derived  from  the  capsule  and  forming  the  framework  of  the  spaces, 
are  composed  of  fibrous  connective  tissue  with  longitudinal  bundles  of  unstriped 
muscular  fibres.  Within  the  interior  of  the  spaces  are  contained  groups  of  poly- 
hedral cells,  which  are  finely  granular  in  appearance,  and  contain  a  spherical 
nucleus,  and  not  infrequently  fat-globules.  These  groups  of  cells  do  not  entirely 
fill  the  spaces  in  which  they  are  contained,  but  between  them  and  the  trabeculae 
of  the  framework  is  a  channel  which  is  believed  to  be  a  lymph-path  or  sinus, 
and  which  communicates  with  certain  passages  between  the  cells  composing  the 


1440  THE  URINARY  ORGANS 

group.  The  lymph-path  is  supposed  to  open  into  a  plexus  of  efferent  lymphatic 
vessels  which  are  contained  in  the  capsule. 

The  Medullary  Portion  (substantia  medullaris)  (Fig.  1045). — In  the  medullary 
portion  the  fibrous  stroma  seems  to  be  collected  together  into  a  much  closer 
arrangement,  and  forms  bundles  of  connective  tissue  which  are  loosely  applied 
to  the  large  plexus  of  veins  of  which  this  part  of  the  organ  mainly  consists.  In 
the  interstices  lie  a  number  of  cells  compared  by  Frey  to  those  of  columnar  epithe- 
lium. They  are  coarsely  granular,  do  not  contain  any  fat-molecules,  and  some 
of  them  are  branched.  Luschka  has  affirmed  that  these  branches  are  connected 
with  the  nerve-fibres  of  a  very  intricate  plexus  which  is  found  in  the  oblongata;  this 
statement  has  not  been  verified  by  other  observers,  for  the  tissue  of  the  medullary 
substance  is  less  easy  to  make  out  than  that  of  the  cortical,  owing  to  its  rapid 
decomposition. 

Vessels  and  Nerves. — The  numerous  arteries  which  enter  the  suprarenal  bodies 
from  the  sources  mentioned  below  penetrate  the  cortical  part  of  the  gland,  where 
they  break  up  into  capillaries  in  the  fibrous  septa,  and  these  converge  to  the  very 
numerous  veins  of  the  .medullary  portion,  which  are  collected  together  into  the 
suprarenal  vein,  which  usually  emerge  as  a  single  vessel  from  the  centre  of  the 
gland. 

The  arteries  supplying  the  suprarenal  capsules  are  three  in  number  and  of  large 
size;  they  are  derived  from  the  aorta,  the  phrenic,  and  the  renal;  they  subdivide 
into  numerous  minute  branches  previous  to  entering  the  substance  of  the  gland. 

The  suprarenal  vein  returns  the  blood  from  the  medullary  venous  plexus, 
and  receives  several  branches  from  the  cortical  substance;  it  emerges  from  the 
hilum  and  opens  on  the  right  side  into  the  postcava,  on  the  left  side  into  the  renal 
vein. 

The  lymphatics  form  several  collections  which  are  about  the  beginning  of  the 
suprarenal  vein.  They  terminate  in  the  glands  to  the  corresponding  side  of  the 
aorta. 

The  nerves  are  exceedingly  numerous,  and  are  derived  from  the  solar  and 
renal  plexuses,  and,  according  to  Bergmann,  from  the  phrenic  and  vagus  nerves. 
They  enter  the  lower  and  inner  part  of  the  capsule,  traverse  the  cortex,  and  ter- 
minate about  the  cells  of  the  oblongata.  They  have  numerous  small  ganglia 
developed  upon  them,  from  which  circumstance  the  organ  has  been  conjectured 
to  have  some  function  in  connection  with  the  sympathetic  nerve  system. 


THE  CAVITY  OF  THE  PELVIS. 

The  cavity  of  the  pelvis  is  that  part  of  the  general  abdominal  cavity  which  is 
below  the  level  of  the  ilio-pectineal  lines  and  the  promontory  of  the  sacrum. 

Boundaries. — It  is  bounded  behind  by  the  sacrum,  the  coccyx,  the  Pyriformis 
muscles,  and  the  great  sacro-sciatic  ligaments;  in  front  and  at  the  sides  by  the 
portions  of  the  innominate  bones  below  the  ilio-pectineal  lines.  In  front  and 
to  the  sides  the  bony  sides  of  the  pelvic  cavity  are  partly  covered  by  the  internal 
Obturator  muscles,*  and  internal  to  these  muscles  by  the  parietal  part  of  the 
pelvic  fascia.  Above,  it  communicates  with  the  cavity  of  the  abdomen;  and 
below,  the  outlet  is  closed  by  the  triangular  ligament,  the  Levatores  ani  and 
Coccygei  muscles,  and  the  visceral  layer  of  the  pelvic  fascia,  which  is  reflected 
from  the  wall  of  the  pelvis  on  to  the  viscera. 

Contents. — The  viscera  contained  in  this  cavity  are — the  urinary  bladder,  the 
rectum,  and  some  of  the  generative  organs  peculiar  to  each  sex,  and  some  convo- 
lutions of  the  small  intestines.  The  pelvic  viscera  are  partially  covered  by  the 
Deritoneum,  and  supplied  with  blood-vessels,  lymphatics,  and  nerves. 


THE  URINARY  BLADDER 


1441 


THE  URINARY  BLADDER  (VESICA  URINARIA)  (Figs.  1050,  1051,  1069,  1070). 

The  urinary  bladder  is  the  reservoir  for  the  urine.  It  is  a  musculo-membranous 
sac  situated  in  the  pelvis,  behind  the  pubes,  and  in  front  of  the  rectum  in  the  male, 
the  cervix  uteri  and  vagina  intervening  between  it  and  that  intestine  in  the  female. 
The  shape,  position,  and  relations  of  the  bladder  are  greatly  influenced  by  age, 


FIG.  1048.— The  empty  bladder.     (Poirier  and  Charpy.) 


FIG.  1049.— M9difications  9f  form  of  the  blad- 
der during  distention  (Poirier  and  Charpy.) 


sex,  and  the  degree  of  distention  of  the  organ.  During  infancy  it  is  conical  in 
shape,  and  projects  above  the  symphysis  pubis  into  the  hypogastric  region.  In  the 
adult,  when  quite  empty  and  contracted  (Figs.  1048  and  1049),  it  is  cup-shaped, 
and  on  vertical  median  section  its  cavity,  with  the  adjacent  portion  of  the  urethra, 
presents  a  Y-shaped  cleft,  the  stem  of  the  Y  corresponding  to  the  urethra.  It  is 


PERITONEUM 


RECTO- 
VESICAL 
POUCH 


PROSTATE   AND 
SEMINAL  VESICLES 


FIG.  1050. — Mesal  section  through  pelvis  of  new-born  male.  (Corning.) 

placed  deeply  in  the  pelvis,  flattened  from  before  backward,  and  reaches  as  high  as 
the  upper  border  of  the  symphysis  pubis.  When  slightly  distended,  it  has  a  rounded 
form,  and  is  still  contained  within  the  pelvic  cavity  (Fig.  1049),  and  when  greatly 
distended  (Figs.  1049  and  1051),  it  is  ovoid  in  shape,  rising  into  the  abdominal 
cavity,  and  often  extending  nearly  as  high  as  the  umbilicus.  'It  is  larger  in  its  verti- 
cal diameter  than  from  side  to  side,  and  its  long  axis  is  directed  from  above 
obliquely  downward  and  backward,  in  a  line  directed  from  some  point  between 
the  symphysis  pubis  and  umbilicus  (according  to  its  distention)  to  the  end  of  the 
coccyx.  The  bladder,  when  distended,  is  slightly  curved  forward  toward  the 
anterior  wall  of  the  abdomen,  so  as  to  be  more  convex  behind  than  in  front.  In 
the  female  it  is  larger  in  the  transverse  than  in  the  vertical  diameter,  and  its 

91 


1442 


THE  URINARY  ORGANS 


capacity  is  said  to  be  greater  than  in  the  male.1  When  moderately  distended,  it 
measures  about  five  inches  in  length,  and  three  inches  across,  and  the  ordinary 
amount  which  it  can  contain  without  serious  discomfort  is  about  a  pint. 

The  bladder  is  divided  for  purposes  of  description  into  a  superior,  an  antero- 
inferior,  and  two  lateral  surfaces,  a  base  or  fundus,  and  a  summit  or  apex. 

Surfaces.  The  Superior  or  Abdominal  Surface  (Figs.  865,  1051,  1052,  and  1070). 
—The  superior  or  abdominal  surface  is  entirely  free,  and  is  covered  throughout  by 


Prostatic  p^ 
of  urethra. 
Ejaculatory  duct. 


CTER    AMI. 

Prostatic/ 
sinuses. 


Fossa 
-navicularis. 

Prepuce.-—-' 
FIG.  1051. — Vertical  section  of  bladder,  penis,  and  urethra. 

peritoneum.  It  looks  almost  directly  upward  into  the  abdominal  cavity,  and  extends 
in  an  antero-posterior  direction  from  the  apex  to  the  base  of  the  bladder.  It  is  in 
relation  with  the  small  intestine  and  sometimes  with  the  sigmoid  flexure,  and,  in 
the  female,  with  the  uterus.  On  each  side,  in  the  male,  a  portion  of  the  vas 
deferens  is  in  contact  with  the  hinder  part  of  this  surface,  lying  beneath  the 
peritoneum. 

The  Antero-inferior  or  Pubic  Surface  (Figs.  1051,  1052,  and  1070). — The  antero- 
inferior  or  pubic  surface  looks  downward  and  forward.  In  the  undistended 
condition  it  is  uncovered  by  peritoneum,  and  is  in  relation  with  the  Obturator 
internus  muscle  on  each  side,  with  the  recto-vesical  fascia,  and  anterior  true 
ligaments  of  the  bladder.  It  is  separated  from  the  body  of  the  pubis  by  a  tri- 
angular interval,  the  space  of  Retzius,  occupied  by  fatty  tissue.  As  the  bladder 
ascends  into  the  abdominal  cavity  during  distention  the  distance  between  its  apex 
and  the  umbilicus  is  necessarily  diminished,  and  the  urachus  (Fig.  865  and  1070) 
is  thus  relaxed;  so  that,  instead  of  passing  directly  upward  to  the  umbilicus,  it 
descends  first  on  the  upper  part  of  the  anterior  surface  of  the  bladder,  and  then, 

i  According  to  Henle,  the  bladder  is  considerably  smaller  in   the  female   than   in   the  male. — ED.  of   15th 
English  edition. 


THE  URINARY  BLADDER 


1443 


curving  upward,  ascends  on  the  back  of  the  abdominal  wall.  The  peritoneum, 
which  follows  the  urachus,  thus  comes  to  form  a  pouch  (plica  vesicalis  transversa) 
of  varying  depth  between  the  anterior  surface  of  the  viscus  and  the  abdominal 
wall  (Fig.  1052).  The  fold  passes  to  the  neighborhood  of  the  internal  abdom- 
inal rings.  Thus,  when  the  bladder  is  distended,  the  upper  part  of  its  anterior 
surface  is  in  relation  with  the  urachus  and  is  covered  by  peritoneum.  The  lower 
part  of  its  anterior  surface,  a  distance  of  about  two  inches  above  the  symphysis 
pubis,  is  devoid  of  peritoneum,  and  is  in  contact  with  the  abdominal  wall. 


AREOLO- 

TISSUE    CON 
TAINING    VEINS 


INTERNAL 
SPHINC- 
TER   ANI 
COM- 
PRESSOR 
URETHR/E 

EXTERNAL 
SPHINC- 
TER   ANI 


NOSUS    MUSCLE 


FIG.  1052. — Vertical  median  section  of  the  male  pelvis.     (Henle.) 

The  Lateral  Surfaces. — The  lateral  surfaces  are  covered  behind  and  above  by 
peritoneum,  which  extends  as  low  as  the  level  of  the  obliterated  hypogastric 
artery;  below  and  in  front  of  this,  these  surfaces  are  uncovered  by  peritoneum, 
and  are  separated  from  the  Levatores  ani  muscles  and  walls  of  the  pelvis  by  a 
quantity  of  loose  areolar  tissue  containing  fat.  In  front  this  surface  is  connected 
to  the  recto-vesical  fascia  by  a  broad  expansion  on  either  side,  the  lateral  true 
ligaments.  The  vas  deferens  crosses  the  hinder  part  of  the  lateral  surface  obliquely, 
and  passes  between  the  ureter  and  the  bladder.  When  the  bladder  is  empty  the 
peritoneum  descends  on  the  pelvic  wall  as  low  as  the  lateral  border  of  the  bladder 
and  enters  a  groove  known  as  the  paravesical  fossa.  The  lateral  surfaces,  the 
pubic  surface,  and  the  abdominal  surface  together  constitute  the  body  of  the 
bladder  (corpus  vesicae). 

The  Fundus  or  Base  (fundus  vesicae)  (Figs.  1052, 1067,  and  1070). — The  fundus 
or  base  is  directed  downward  and  backward,  and  is  partly  covered  by  peritoneum 


1444 


THE  URINARY  ORGANS 


and  is  in  part  not  covered  by  it.  In  the  male  the  upper  portion,  to  within  about 
an  inch  and  a  half  of  the  prostate,  is  covered  by  the  recto-vesical  pouch  of  peri- 
toneum (Fig.  868).  The  lower  part  is  in  direct  contact  with  the  anterior  wall  of 
the  second  part  of  the  rectum  and  the  vesiculse  seminales  and  vasa  deferentia 
(Figs.  1067  and  1069).  -  The  ureters  enter  the  bladder  at  the  upper  part  of  its 
base,  about  an  inch  and  a  half  above  the  base  of  the  prostate  gland  (Fig.  1059). 


Vermiform  appendix. 


External  iliac        Anterior  crural        External  oblique 
,  artery.  .  nerve.  muscle. 


V 
Profunda  vessels.    "-EVATOR  ANI.         Corpora         Urethra. 

FIG.  1053. — Frontal  section  of  the  lower  part  of  the  abdomen.     Viewed  from  in  front.     (Braune.) 

The  portion  of  the  bladder  in  relation  with  the  rectum  corresponds  to  a  trian- 
gular space,  bounded,  below,  by  the  prostate  gland;  above,  by  the  recto-vesical 
fold  of  the  peritoneum;  and  on  each  side,  by  the  vesicula  seminalis  and  vas 
deferens.  It  is  separated  from  direct  contact  with  the  rectum  by  (he  recto- 
vesical  fascia.  When  the  bladder  is  very  full,  the  peritoneal  fold  is  raised  with 
it,  and  the  distance  between  its  reflection  and  the  anus  is  about  four  inches;  but 
this  distance  is  much  diminished  when  the  bladder  is  empty  and  contracted.  In 
the  female,  the  base  of  the  bladder  is  connected  to  the  anterior  aspect  of  the  cervix 
uteri  by  areolar  tissue,  and  is  adherent  to  the  anterior  wall  of  the  vagina  (Fig. 
866).  Its  upper  surface  is  separated  from  the  anterior  surface  of  the  body  of 
the  uterus  by  the  utero-vesical  pouch  of  the  peritoneum  (Fig.  866). 

The  so-called  neck  or  cervix  of  the  bladder  (collum  vesicae)  is  the  point  of  com- 
mencement of  the  urethra;  there  is,  however,  no  tapering  part,  which  would 
constitute  a  true  neck,  but  the  bladder  suddenly  contracts  to  the  opening  of  the 
urethra  (Fig.  1052).  In  the  male  it  is  surrounded  by  the  prostate  gland  and  its 
direction  is  oblique  when  the  individual  is  in  the  erect  posture  (Figs.  1051  and 
1 052).  In  the  female  its  direction  is  obliquely  downward  and  forward. 


1445 


The  Summit  or  Apex  (vertex  vesicae). — The  summit  or  apex  is  the  portion 
of  the  bladder  which  when  that  organ  is  empty  or  nearly  empty  is  nearest  to 
the  upper  border  of  the  symphysis.  It  is  directed  upward  and  forward.  In  a 
distended  bladder  the  apex  is  well  above  the  pubes  in  the  abdominal  cavity. 

The  Urachus  or  Middle  Umbilical  Ligament  (ligamentum  umbilicale  medium) 
(Fig.  1070). — The  urachus  is  a  connective-tissue  cord  and  is  the  obliterated 
remains  of  the  tubular  canal  of  the  allantois,  which  existed  in  the  embryo,  and 
a  portion  of  which  expanded  to  form  the  bladder.  It  passes  upward,  from  the 
apex  of  the  bladder,  between  the  transversalis  fascia  and  peritoneum,  to  the 
umbilicus,  becoming  thinner  as  it  ascends.  It  is  composed  of  fibrous  tissue, 
mixed  with  plain  muscular  fibres.  The  urachus  causes  the  formation  of  a  peri- 
toneal fold,  the  plica  umbilicalis  media  (Fig.  865).  On  each  side  of  it  is  placed  a 
fibrous  cord,  the  obliterated  portion  of  the  hypogastric  artery,  which,  passing 
upward  from  the  side  of  the  bladder,  approaches  the  urachus  above  its  summit. 
Over  each  cord  is  the  fold  known  as  the  plica  umbilicalis  lateralis  (Fig.  865).  In 
the  infant,  at  birth,  the  urachus  is  occasionally  found  pervious,  so  that  the  urine 
escapes  at  the  umbilicus,  and  calculi  have  been  found  in  its  canal. 

Ligaments. — The  bladder  is  retained  in  its  place  by  ligaments,  which  are  divided 
into  true  and  false.  The  true  ligaments  are  five  in  number:  two  anterior,  two 
lateral,  and  the  urachus.  The  false  ligaments,  also  five  in  number,  are  formed  by 
folds  of  the  peritoneum. 

The  two  anterior  true  ligaments,  the  pubo-prostatic  or  pubo-vesical  ligaments  (liga- 
menta  puboprostatica)  extend  from  the  back  of  the  ossa  pubis,  one  on  each  side  of 
the  symphysis,  to  the  front  of  the  neck  of  the  bladder,  over  the  anterior  surface  of 
the  prostate  gland.  These  ligaments  are  formed  by  the  recto-vesical  fascia,  and 
contain  a  few  muscular  fibres  prolonged  from  the  bladder. 

The  two  lateral  true  ligaments,  formed  by  expansions  from  the  fascia  lining  the 
lateral  wall  of  the  pelvis,  are  broader  and  thinner  than  the  preceding.  They 
are  attached  to  the  lateral  parts  of  the  prostate  gland  and  to  the  sides  of  the  base  of 
the  bladder. 


Fir..  1054.— Fibres  of  the  external 
longitudinal  layer.  (Poirier  and 
Charpy.) 


FIG.  1055. — Fibres  of  the  middle 
or  circular  layer.  (Poirier  and 
Charpy.) 


FIG.  1056. — Fibres  of  the  inter- 
nal longitudinal  layer.  (Poirier 
and  Charpy.) 


The  urachus  or  middle  umbilical  ligament  is  the  fibro-muscular  cord  already  men- 
tioned, extending  between  the  summit  of  the  bladder  and  the  umbilicus.  It  is  broad 
below,  at  its  attachment  to  the  bladder,  and  becomes  narrower  as  it  ascends. 


1446  THE  URINARY  ORGANS 

The  two  posterior  false  ligaments  pass  forward,  in  the  male,  from  the  sides  of 
the  rectum  (plicae  rectovesicales) ;  in  the  female,  from  the  sides  of  the  uterus  (plicae 
rectouterinae)  to  the  posterior  and  lateral  aspect  of  the  bladder;  they  form  in 
the  male  the  lateral  boundaries  of  the  recto-vesical  pouch  (excavatio  rectovesicalis) 
(Figs.  939  and  1052) ;  they  form  in  the  female  the  lateral  boundaries  of  the  pouch  or 
cul-de-sac  of  Douglas  (excavatio  rectouterina  [Douglasi])  (Figs.  866  and  940).  The 
posterior  false  ligaments  contain  the  obliterated  hypogastric  arteries  and  the 
ureters,  together  with  vessels  and  nerves.  In  the  base  of  each  fold  is  smooth 
muscle-fibre,  the  Recto-vesical  muscle  (m.  rectovesicalis}. 

The  two  lateral  false  ligaments  are  reflections  of  the  peritoneum,  from  the 
iliac  fossae  and  lateral  walls  of  the  pelvis  to  the  sides  of  the  bladder.  Each 
lateral  false  ligament  (ligamentum  umbihcale  later  ale)  passes  in  front  into  the  plica 
umbilicalis  lateralis  over  the  corresponding  hypogastric  artery.  The  two  lateral 
reflections  of  peritoneum  are  continuous  in  front  of  the  apex  vesicae,  at  which 
point  the  peritoneum  passes  upon  the  urachus. 

The  superior  or  anterior  false  ligament  or  the  suspensory  ligament  (plica  umbilicalis 
media)  is  the  prominent  fold  of  peritoneum  extending  from  the  summit  of  the  blad- 
der to  the  umbilicus.  It  is  carried  off  from  the  bladder  by  the  urachus  and  the 
obliterated  hypogastric  arteries.  The  peritoneal  fold  over  each  obliterated  hypo- 
gastric  artery  is  called  the  plica  umbilicalis  lateralis  (Fig.  865),  and  is  the  pro- 
longation forward  of  the  ligamentum  umbilicale  laterale.  Besides  the  true  and 
false  ligaments,  the  bladder  receives  support  from  the  fibrous  tissue  and  unstriated 
muscle  about  the  seminal  vesicles,  and  terminations  of  the  ureters  and  vasa  defer- 
entia.  In  the  female  the  connection  with  the  anterior  vaginal  wall  supports  the 
base  of  the  bladder.  In  both  sexes  the  most  solidly  fixed  part  of  the  bladder  is 
about  the  orifice  of  the  urethra. 

Structure. — The  bladder  is  composed  of  four  coats — serous,  muscular,  sub- 
mucous,  and  mucous. 

The  Serous  Coat  (tunica  serosa). — The  serous  coat  is  partial,  and  derived  from  the 
peritoneum.  It  invests  the  superior  surface  and  the  upper  part  of  the  lateral  surfaces 
and  base,  and  is  reflected  from  these  parts  on  to  the  abdominal  and  pelvic  walls. 

The  Muscular  Coat  (tunica  muscularis)  (Figs.  1054,  1055,  and  1056). ^The  mus- 
cular coat  consists  of  three  layers  of  unstriped  muscular  fibre :  an  external  layer, 
composed  of  fibres  having  for  the  most  part  a  longitudinal  arrangement;  a  middle 
layer,  in  which  the  fibres  are  arranged,  more  or  less,  in  a  circular  manner;  and  an 
internal  layer,  in  which  the  fibres  have  a  general  longitudinal  arrangement. 

The  fibres  of  the  external  longitudinal  layer  (stratum  externum)  arise  from  the 
posterior  surface  of  the  body  of  the  os  pubis  in  both  sexes  (m.  pubovesicalis) ,  and 
in  the  male  arise  also  from  the  adjacent  part  of  the  prostate  gland  and  its  capsule. 
They  pass,  in  a  more  or  less  longitudinal  manner,  up  the  anterior  surface  of  the 
bladder,  over  its  apex,  and  then  descend  along  its  posterior  surface  to  its  base, 
where  they  become  attached  to  the  prostate  in  the  male  and  to  the  front  of  the  vagina 
in  the  female.  At  the  sides  of  the  bladder  the  fibres  are  arranged  obliquely  and 
intersect  one  another.  The  external  lorgitudinal  layer  has  been  named  the 
Detrusor  urinae  muscle. 

The  middle  circular  layers  (stratum  medium)  are  very  thinly  and  irregularly 
scattered  on  the  body  of  the  organ,  and,  though  to  some  extent  placed  transversely 
to  the  long  axis  of  the  bladder,  are  for  the  most  part  arranged  obliquely.  Toward 
the  lower  part  of  the  bladder,  around  the  neck  and  the  commencement  of  the 
urethra,  they  are  disposed  in  a  thick  circular  layer,  forming  the  sphincter  vesicae, 
which  is  continuous  with  the  muscular  fibres  of  the  prostate  gland. 

The  internal  longitudinal  layer  (stratum  internum)  is  thin,  and  its  fasciculi  have 
a  reticular  arrangement,  but  with  a  tendency  to  assume  for  the  most  part  a  longi- 
tudinal direction.  Two  bands  of  oblique  fibres,  originating  behind  the  orifices  of 
the  ureters,  converge  to  the  back  part  of  the  prostate  gland,  and  are  inserted,  by 


THE  URINARY  BLADDER  1447 

means  of  a  fibrous  process,  into  the  middle  lobe  of  that  organ.  They  are  the 
muscles  of  the  ureters,  described  by  Sir  C.  Bell,  who  supposed  that  during  the  con- 
traction of  the  bladder  they  served  to  retain  the  oblique  direction  of  the  ureters, 
and  so  prevent  the  reflux  of  the  urine  into  them. 

The  Submucous  Coat  (tela  submucosd). — The  submucous  coat  consists  of  a  layer 
of  areolar  tissue  connecting  together  the  muscular  and  mucous  coats,  and  inti- 
mately united  to  the  latter. 

The  Mucous  Coat  (tunica  mucosa). — The  mucous  coat  is  thin,  smooth,  and  of  a 
pale  rose  color.  It  is  continuous  above  through  the  ureters  with  the  lining  mem- 
brane of  the  uriniferous  tubes,  and  below  with  that  of  the  urethra.  Except  at  the 
trigone,  it  is  connected  very  loosely  to  the  muscular  coat  by  a  layer  of  areolar  tissue, 
and  is  therefore  thrown  into  folds  or  rugae  when  the  bladder  is  empty  (Fig. 
1060).  The  mucous  membrane  over  the  trigone  never  presents  rugae.  The 
epithelium  covering  it  is  of  the  transitional  variety,  consisting  of  a  superficial 
layer  of  polyhedral  flattened  cells,  each  with  one,  two,  or  three  nuclei  (Fig.  1057) ; 
beneath  these  is  a  stratum  of  large  club-shaped  cells  with  the  narrow  extremity  of 
each  cell  directed  downward  and  wedged  in  between  smaller  spindle-shaped  cells, 
each  an  oval  nucleus  (Fig.  1058).  There  are  no  true  glands  in  the  mucous  mem- 
brane of  the  bladder,  though  certain  mucous  follicles  which  exist,  especially  near 
the  neck  of  the  bladder,  have  been  regarded  as  such. 

Objects  Seen  on  the  Inner  Surface.— Upon  the  inner  surface  of  the  bladder  are 
seen  the  mucous  membrane,  orifices  of  the  ureters,  the  trigone,  and  the  commencement 
of  the  urethra. 


FIG.  1057.  — Superficial  layer  of  the  epithelium  of  FIG.  1058.  — Deep  layers  of  epithelium  of  bladder, 

the  bladder.     Composed  of  polyhedral  cells  of  vari-  showing  large  club-shaped  cells  above,  and  smaller, 

ous  sizes,  each  with  one,  two,  or  three  nuclei.     (Klein  more  spindle-shaped  cells  below,  each  with  an  oval 

and  Noble  Smith.)  nucleus.     (Klein  and  Noble  Smith.) 

The  Mucous  Membrane. — The  mucous  membrane  of  the  empty  bladder  is  thrown 
into  folds  or  rugae,  except  over  the  trigone,  where  it  is  firmly  adherent  to  the 
muscular  coat  and  is  smooth  (Figs.  1059  and  1060).  The  folds  disappear  when 
the  bladder  is  distended. 

The  Orifices  of  the  Ureters  (Figs.  1059  and  1060). — These  are  situated  at  the  base 
of  the  trigone,  being  distant  from  each  other  about  two  inches  when  the  bladder  is 
moderately  distended.  Each  orifice  is  about  an  inch  and  a  half  from  the  base  of  the 
prostate  and  the  commencement  of  the  urethra  in  the  moderately  distended  bladder. 

The  Vesical  Trigone  or  the  Trigonum  Vesicae  (Fig.  1060)  is  a  triangular  smooth 
surface,  with  the  apex  directed  forward,  situated  at  the  base  of  the  bladder,  imme- 
diately behind  the  urethral  orifice.  It  is  paler  in  color  than  the  rest  of  the 
interior,  and  never  presents  any  rugae,  even  in  the  collapsed  condition  of  the 
organ,  owing  to  the  intimate  adhesion  of  its  mucous  membrane  to  the  subjacent 
tissue.  It  is  bounded  at  each  posterior  angle  by  the  orifice  of  a  ureter,  and  in 
front  by  the  orifice  of  the  urethra.  Projecting  from  the  lower  and  anterior  part  of 
the  bladder,  and  reaching  to  the  orifice  of  the  urethra,  is  a  slight  elevation  of 
mucous  membrane,  particularly  prominent  in  old  persons,  called  the  uvula  vesicae. 
It  is  formed  by  a  thickening  of  the  submucous  tissue. 


1448 


Stretching  from  one  ureteral  opening  to  the  other  is  a  smooth,  slightly  curved 
ridge,  the  convexity  of  which  is  toward  the  urethra.  It  is  produced  by  transverse 
muscle-fibres  beneath  the  mucous  membrane.  The  outer  prolongations  of  this 
ridge  beyond  the  ureteral  orifices  are  called  the  ureteral  folds  (plicae  uretericae). 
They  are  created  by  the  ureters  as  they  traverse  the  bladder  wall.  About  the 
ureteral  orifice  are  slight  radial  folds  of  mucous  membrane,  which  are  continuous 
with  the  longitudinal  folds  of  the  prostatic  urethra.  "In  the  empty  bladder  the 
ureteral  orifice  and  the  openings  of  the  two  ureters  lie  at  the  angles  of  an  approxi- 
mately equilateral  triangle,  whose  sides  are  about  one  inch  in  length.  When  the 
bladder  is  distended  the  distance  between  the  openings  may  be  increased  to  one 
and  a  half  inches  or  more."1 


RIDGE    FORMrD  BY 
J-INTERURETERAL 
MUSCLE 


FIG.  1059.  —The  interior  of  the  bladder,  showing  the  vesical  trigone.      (Poirier  and  Charpy.) 


CIRCULAR 
FIBRES 


TRIGONE 

TRANSVERSE 

FIBRES  OF 

TRIGONE 

LONGITUDINAL 

FIBRES  OF 

TRIGONE 


EJACULATORY 
DUCT 


Fio.  1060. — The  internal  surface  of  the  bladder.     (Poirier  and  Charpy.) 
i  Professor  A.  Francis  Dixon,  in  Prof.  D.  J.  Cunningham's  Text-book  of  Anatomy. 


THE  URINARY  BLADDER  1449 

The  muscles  of  the  ureters  were  referred  to  on  p.  1447. 

The  internal  urethral  orifice  (orificium  urethrae  intcrnum)  is  sickle-shaped  and 
is  surrounded  by  a  circular  prominence  (annulus  urethralis},  which  is  most  distinct 
in  the  male. 

Vessels  and  Nerves. — The  arteries  (Fig.  427)  supplying  the  bladder  are  the 
superior,  middle,  and  inferior  vesical  in  the  male,  with  additional  branches  from 
the  uterine  and  vaginal  in  the  female.  They  are  all  derived  from  the  anterior 
trunk  of  the  internal  iliac.  The  obturator  and  sciatic  arteries  also  supply  small 
visceral  branches  to  the  bladder.  The  veins  form  a  complicated  plexus  around  the 
neck,  sides,  and  base  of  the  bladder  (Fig.  474).  The  veins  communicate  below 
with  the  plexus  about  the  prostate  and  terminate  in  the  internal  iliac  vein. 

The  lymphatics  form  two  plexuses,  one  in  the  muscular  and  another  in  the  sub- 
mucous  coat.  They  accompany  the  blood-vessels.  The  mucous  membrane  of 
the  bladder  contains  no  lymphatics  whatever  (Sappey).  The  muscular  tissue 
contains  a  few  lymphatics.  The  subperitoneal  tissues  contain  the  usual  number. 
The  collecting  trunks  from  the  anterior  surface  terminate  in  the  external  iliac 
glands.  The  trunks  from  the  posterior  surface  terminate  in  the  internal  iliac 
glands,  the  hypogastric  glands  and  the  glands  in  front  of  the  sacral  promontory. 

The  nerves  are  derived  from  the  pelvic  plexus  of  the  sympathetic  and  from  the 
third  and  fourth  sacral  nerves ;  the  former  supplying  the  upper  part  of  the  organ, 
the  latter  its  base  and  neck.  According  to  F.  Darwin,  the  sympathetic  fibres  have 
ganglia  connected  with  them,  which  send  branches  to  the  vessels  and  to  the 
muscular  coat. 

Surface  Form.— The  surface  form  of  the  bladder  varies  with  its  degree  of  distention  and 
under  other  circumstances.  In  the  young  child  it  is  represented  by  a  conical  figure,  the  apex 
of  which,  even  when  the  viscus  is  empty,  is  situated  in  the  hypogastric  region,  about  an  inch 
above  the  level  of  the  symphysis  pubis.  In  the  adult,  when  the  bladder  is  empty,  its  apex  does 
not  reach  above  the  level  of  the  upper  border  of  the  symphysis  pubis,  and  the  whole  organ  is 
situated  in  the  pelvis;  the  neck,  in  the  male,  corresponding  to  a  line  drawn  horizontally  backward 
through  the  symphysis  a  little  below  its  middle.  As  the  bladder  becomes  distended,  it  gradually 
rises  out  of  the  pelvis  into  the  abdomen,  and  forms  a  swelling  in  the  hypogastric  region,  which  is 
perceptible  to  the  hand  as  well  as  to  percussion.  In  extreme  distention  it  reaches  into  the  umbil- 
ical region.  Under  these  circumstances  the  lower  part  of  its  anterior  surface,  for  a  distance 
of  about  two  inches  above  the  symphysis  pubis,  is  closely  applied  to  the  abdominal  wall,  without 
the  intervention  of  peritoneum,  so  that  it  can  be  tapped  by  an  opening  in  the  middle  line  just 
above  the  symphysis  pubis,  without  any  fear  of  wounding  the  serous  membrane.  When  the 
rectum  is  distended,  the  prostatic  portion  of  the  urethra  is  elongated  and  the  bladder  lifted  out 
of  the  pelvis  and  the  peritoneum  pushed  upward.  Advantage  is  taken  of  this  by  some  surgeons 
in  performing  the  operation  of  suprapubic  cystotomy.  The  rectum  is  distended  by  an  India- 
rubber  bag,  which  is  introduced  into  this  cavity  empty,  and  is  then  filled  with  ten  or  twelve  ounces 
of  water.  If  now  the  bladder  is  injected  with  about  half  a  pint  of  some  antiseptic  fluid,  it  will 
appear  above  the  pubes  plainly  perceptible  to  the  sight  and  touch.  The  peritoneum  will  be 
pushed  out  of  the  way,  and  an  incision  three  inches  long  may  be  made  in  the  linea  alba,  from 
the  symphysis  pubis  upward,  without  any  great  risk  of  wounding  the  peritoneum.  Other  sur- 
geons object  to  the  employment  of  this  bag,  as  its  use  is  not  unattended  with  risk,  and  because 
it  causes  pressure  on  the  prostatic  veins  and  hence  produces  congestion  of  the  vessels  over  the 
bladder  and  a  good  deal  of  venous  hemorrhage. 

When  distended,  the  bladder  can  be  felt  in  the  male,  from  the  rectum,  behind  the  prostate, 
and  fluctuation  can  be  perceived  by  a  bimanual  examination,  one  finger  being  introduced  into  the 
rectum  and  the  distended  bladder  being  tapped  on  the  front  of  the  abdomen  with  the  finger 
of  the  other  hand.  This  portion  of  the  bladder — that  is,  the  portion  felt  in  the  rectum  by  the 
finger — is  uncovered  by  peritoneum. 

Surgical  Anatomy. — A  certain  defect  of  development  in  which  the  bladder  is  implicated  is 
known  under  the  name  of  extroversion  of  the  bladder.  In  this  condition  the  lower  part  of  the 
abdominal  wall  and  the  anterior  wall  of  the  bladder  are  wanting,  so  that  the  posterior  surface 
of  the  bladder  presents  on  the  abdominal  surface,  and  is  pushed  forward  by  the  pressure  of  the 
viscera  within  the  abdomen,  forming  a  red,  vascular  protrusion,  on  which  the  openings  of  the 
ureters  are  visible.  The  penis,  except  the  glans,  is  rudimentary  and  is  cleft  on  its  dorsal  sur- 
face, exposing  the  floor  of  the  urethra — a  condition  known  as  epispadias.  The  pelvic  bones 
are  also  arrested  in  development  (see  page  222). 

The  bladder  may  be  ruptured  by  violence  applied  to  the  abdominal  wall  when  the  viscus  is 


1450  THE  URINARY  ORGANS 

distended  without  any  injury  to  the  bony  pelvis,  or  it  may  be  torn  in  case  of  fracture  of  the 
pelvis.  The  rupture  may  be  either  intraperitoneal  or  extraperitoneal — that  is,  may  implicate  the 
superior  surface  of  the  bladder  in  the  former  case,  or  one  of  the  other  surfaces  in  the  latter. 
Rupture  of  the  antero-inferior  surface  alone  is,  however,  very  rare.  Until  recently  intraperi- 
toneal rupture  was  uniformly  fatal,  but  now  abdominal  section  and  suturing  the  rent  with  Lem- 
bert  sutures  often  saves  the  patient.  The  sutures  are  inserted  only  through  the  peritoneal  and 
muscular  coats  in  such  a  way  as  to  bring  the  serous  surfaces  at  the  margins  of  the  wound  into 
apposition,  and  one  is  also  inserted  just  beyond  each  end  of  the  wound.  The  bladder  should  be 
tested  as  to  whether  it  is  water-tight  before  closing  the  external  incision. 

The  muscular  coat  of  the  bladder  undergoes  hypertrophy  in  cases  in  which  there  is  any  per- 
sistent obstruction  to  the  flow  of  urine.  Under  these  circumstances  the  bundles  of  which  the 
muscular  coat  consists  become  much  increased  in  size,  and,  interlacing  in  all  directions,  give  rise 
to  what  is  known  as  the  fasciculated  bladder.  Between  these  bundles  of  muscular  fibres  the  mucous 
membrane  may  bulge  out,  forming  sacculi,  constituting  the  sacculated  bladder,  and  in  these 
little  pouches  phosphatic  concretions  may  collect,  forming  encysted  calculi.  The  mucous  mem- 
brane is  very  loose  and  lax,  except  over  the  trigone,  to  allow  of  the  distention  of  the  viscus. 

Various  forms  of  tumors  have  been  found  springing  from  the  wall  of  the  bladder.  The  inno- 
cent tumors  are  the  papilloma  and  the  mucous  polypus,  arising  from  the  mucous  membrane; 
the  fibrous  tumor,  from  the  submucous  tissue;  and  the  myoma,  originating  in  the  muscular 
tissue;  and,  very  rarely,  derrnoid  tumors,  the  exact  origin  of  which  it  is  difficult  to  explain. 
Of  the  malignant  tumors,  epitheliomata  are  the  most  common,  but  sarcomata  are  occasionally 
found  in  the  bladders  of  children. 

Puncture  of  the  bladder  is  performed  above  the  pubes  without  wounding  the  peritoneum. 
Puncture  by  the  rectum  is  not  now  performed,  as  a  permanent  fistula  may  be  left  from  abscess 
forming  between  the  rectum  and  the  bladder;  or  pelvic  cellulitis  maybe  set  up;  moreover,  it  is 
exceedingly  inconvenient  to  keep  a  cannula  in  the  rectum.  In  some  cases  in  performing  this 
operation  the  recto-vesical  pouch  of  peritoneum  has  been  wounded,  inducing  fatal  peritonitis. 
The  operation,  therefore,  has  been  abandoned.  Suprapubic  cystotomy  is  considered  above  under 
the  heading  of  Surface  Form.  This  operation  may  be  employed  to  permit  of  the  removal  of  a 
calculus  and  is  then  called  suprapubic  lithotomy. 

THE  MALE  URETHRA  (URETHRA  VIRILIS)  (Figs.  1061, 1062,  1063, 1064, 1069). 

The  urethra  in  the  male  extends  from  the  neck  of  the  bladder  at  the  internal 
orifice  of  the  urethra  (orificium  urethrae  internum)  to  the  meatus  urinarius,  the 
external  orifice  of  the  urethra  (orificium  urethrae  externum),  at  the  end  of  the  penis. 
The  internal  orifice  has  been  described  (p.  1449).  The  urethra  presents  a  double 
curve  in  the  flaccid  state  of  the  penis  (Fig.  1069),  but  in  the  erect  state  of  this 
organ  it  forms  only  a  single  curve,  the  concavity  of  which  is  directed  upward.  Its 
length  varies  from  eight  to  nine  inches;  and  it  is  divided  into  three  portions,  the 
prostatic,  membranous,  and  spongy,  the  structure  and  relations  of  which  are  essen- 
tially different.  Except  during  the  passage  of  the  urine  or  semen,  the  urethra  is  a 
mere  cleft  or  slit,  transverse,  T-shaped  or  crescentic  (Fig.  1063),  with  its  upper 
and  under  surfaces  in  contact.  At  the  meatus  urinarius  the  slit  is  vertical,  and 
in  the  prostatic  portion  somewhat  arched  (Fig.  1063). 

The  First  or  Prostatic  Portion  (pars  prostatica)  (Figs.  1051,  1061,  1062,  1070, 
and  1071). — The  first  or  prostatic  portion  is  the  widest  and  most  dilatable  part  of 
the  canal.  It  is  between  the  internal  orifice  of  the  urethra  and  the  superior  layer 
of  the  triangular  ligament  and  is  within  the  pelvic  cavity.  It  passes  between  the 
two  lateral  lobes  of  the  prostate  gland,  from  the  base  to  the  apex  of  the  gland, 
lying  nearer  its  anterior  than  its  posterior  surface.  The  gland  seems  to  completely 
surround  this  portion  of  the  urethra  (Fig.  1068),  but  the  glandular  matter  of  the 
gland  does  not  (Fig.  1066).  The  gland  is  like  a  buckle  open  in  front,  and  the  open 
part  of  the  buckle  is  closed  by  the  prostatic  muscle.  The  prostatic  urethra  is 
about  an  inch  and  a  quarter  in  length;  the  form  of  the  canal  is  spindle-shaped, 
being  wider  in  the  middle  than  at  either  extremity,  and  narrowest  below,  where  it 
joins  the  membranous  portion,  Except  during  the  passage  of  fluid,  the  canal  is  in 
a  collapsed  state,  the  anterior  wall  resting  upon  the  posterior  wall  (Fig.  1063),  and 
the  mucous  membrane  exhibiting  longitudinal  folds.  When  distended,  the  largest 
portion  of  the  prostatic  urethra  has  a  diameter  of  about  one-third  of  an  inch. 


THE  MALE  URETHRA 


1451 


A  transverse  section  of  the  canal  as  it  lies  in  the  prostate  is  horseshoe-shaped, 
the  convexity  being  directed  forward  (Figs.  1063  and  1066).  The  direction  of 
the  canal  is  nearly  vertical,  there  being  a  slight  curve,  which  is  concave  forward 
(Figs.  1051  and  1052). 

Upon  the  posterior  wall  or  floor  of  the  canal  is  a  narrow  longitudinal  ridge,  the 
crest  of  the  urethra  (crista  urethralis],  formed  by  an  elevation  of  the  mucous  mem- 
brane and  its  subjacent  tissue  (Fig.  1061).  This 
crest  begins  at  the  uvula  vesicae,  and  passes  Crest  of ^ 
through  the  prostatic  portion  and  into  the  mem- 
branous portion  of  the  urethra  (Fig.  1071),  and 
usually  bifurcates  at  its  distal  end;  it  contains, 
according  to  Kobelt,  muscular  and  erectile  tis- 
sues. On  this  longitudinal  ridge  is  an  enlarge- 
ment, the  verumontanum  or  caput  gallinaginis  CowPer 
(colliculus  seminalis)  (Figs.  1061  and  1071). 
When  distended,  it  may  serve  to  prevent  the 
passage  of  the  semen  backward  into  the  blad- 
der. On  each  side  of  the  verumontanum  is  a 
slightly  depressed  fossa,  the  floor  of  which  is 
perforated  by  numerous  apertures,  the  orifices 
of  the  prostatic  ducts  (Figs.  1061  and  1071),  from 
the  lateral  lobes  of  the  glands;  the  ducts  of  the 
middle  lobe  open  behind  the  verumontanum. ca 
At  the  forepart  of  the  verumontanum,  in  the 
middle  line,  is  a  depression,  the  prostatic  sinus, 
prostatic  utricle,  prostatic  vesicle,  uterus  mascu-  Corpus 
linus  or  sinus  pocularis  (utriculus  prostaticus) spon 
(Figs.  1052  and  1071);  and  upon  or  within  its 
margins  are  the  slit-like  openings  of  the  ejacu- 
latory  ducts  (ductus  ejaculatorii)  (Fig.  1071). 
The  sinus  pocularis  forms  a  cul-de-sac  about  a 
quarter  of  an  inch  in  length,  which  runs  upward 
and  backward  in  the  substance  of  the  prostate 
behind  the  transverse  band  of  prostatic  tissue 
which  joins  the  lateral  lobes  behind  the  poste- 
rior wall  of  the  urethra ;  its  prominent  anterioi 
wall  partly  forms  the  verumontanum.  Its  walls 
are  composed  of  fibrous  tissue,  muscular  fibres, 
and  mucous  membrane,  and  numerous  small 
glands  open  on  its  inner  surface.  It  has  been 
called  by  Weber,  who  discovered  it,  the  uterus 

masculinus,  from  its  being  developed  from  the  united  lower  ends  of  the  atrophied 
Miillerian  ducts,  and  therefore  being  homologous  with  the  uterus  and  vagina  in  the 
female. 

The  Second,  Muscular  or  Membranous  Portion  ( 'par 'smembranacea)  (Figs.  1061, 
1062,  and  1071)  extends  downward  and  forward  between  the  apex  of  the  prostate 
and  the  bulb  of  the  corpus  sppngiosum.  It  is  the  narrowest  part  of  the  canal(except- 
ing  the  meatus),  and  measures  three-quarters  of  an  inch  along  its  upper,  and  half 
an  inch  along  its  lower,  surface,  in  consequence  of  the  bulb  projecting  backward 
beneath  it.  Its  anterior  concave  surface  is  placed  about  an  inch  below  and  behind 
the  pubic  arch,  from  which  it  is  separated  by  the  dorsal  vessels  and  nerves  of  the 
penis,  and  some  muscular  fibres.  Its  posterior  convex  surface  is  separated  from 
the  rectum  by  a  triangular  space,  which  constitutes  the  perineum.  The  membra- 
nous portion  of  the  urethra  lies  chiefly  between  the  inferior  and  superior  layers  of 


Glans.  \™a"r  .f^H//   Fossa 


Meatus. 


FIG.  1061. — The  male  urethra,  laid  open  on 
its  anterior  (upper)  surface.    (Testut.) 


1452 


THE  URINARY  ORGANS 


the  triangular  ligament  (Fig.  308).  The  termination  of  this  part  of  the  urethra  is 
overlapped  by  the  bulb,  and  is  in  front  of  the  triangular  ligament  (Fig.  308).  As  it 
pierces  the  inferior  layer,  the  fibres  around  the  opening  are  prolonged  over  the 
tube  and  fix  the  two  structures  firmly  to  each  other.  The  membranous  urethra 
is  surrounded  by  cavernous  tissue  and  by  the  Compressor  urethrae  muscle  (m. 
sphincter  urethrae  membranaceae)  (Fig.  309).  On  the  floor  of  the  membranous 
urethra  is  the  anterior  extremity  of  the  crista  urethralis.  Behind  this  part  of  the 
urethra,  on  each  side  of  the  middle  line,  are  Cowper's  glands  (Figs.  307  and  1071). 
The  canal  enters  the  bulb  a  little  in  front  of  the  posterior  extremity,  and  the  an- 
terior wall  or  roof  of  the  membranous  urethra  is  a  little  longer  than  the  posterior 
wall  or  floor.  The  backward  projection  of  the  bulb  hangs  over  most  of  the  floor 
of  the  membranous  urethra  (Figs.  307,  308,  1061,  1071,  and  1073).  When  the 
urethra  is  empty  the  mucous  membrane  of  the  second  part  is  thrown  into  longitu- 
dinal folds,  which  are  obliterated  by  distention. 


MUSCULAR   WALL 
OF    BLADDER' 


PROSTATIC 
SINUS 


LONGITUDINAL  MUS- 
CLES OF  URETHRA 


FIG.  1062. — Proximal  portions  of  urethra  with  surrounding  parts.    (After  Testut.) 

The  Third,  Penile,  Pendulous,  Cavernous  or  Spongy  Portion  (pars  cavernosa) 
(Figs.  1051,  1061,  1062,  and  1064)  is  the  longest  part  of  the  urethra,  and  is  con- 
tained in  the  corpus  spongiosum.  It  is  about  six  inches  in  length,  and  extends 
from  the  termination  of  the  membranous  portion  to  the  meatus  urinarius.  It  is 
surrounded  throughout  its  entire  course  by  the  erectile  tissue  of  the  corpus  spon- 
giosum and  glans  penis.  Its  proximal  end  is  fixed  in  position  and  unchangeable 
in  direction.  Its  distal  end  is  movable  and  changeable  in  direction.  Commencing 
just  below  the  triangular  ligament  it  is  first  directed  forward  through  the  bulb; 
it  then  passes  downward  and  forward,  the  turn  beginning  at  the  seat  of  attachment 
of  the  suspensory  ligament  of  the  penis  (Fig.  1051).  The  direction  of  the  third  por- 
tion of  the  urethra  is  changed  by  alterations  in  the  position  of  the  penis.  When  the 
canal  is  closed  the  anterior  and  posterior  walls  are  in  contact  (roof  and  floor),  except 
in  the  glans  penis,  where  the  lateral  walls  come  together.  "  Thus  the  first  part  of 
the  canal  when  empty  is  represented  in  cross-section  by  a  transverse  slit,  and  the 
terminal  part  by  a  vertical  slit"1  (Fig.  1063).  The  calibre  of  the  spongy  urethra 
varies  in  different  portions  of  the  tube.  It  is  of  larger  diameter  in  the  bulb  (bul- 
bous portion  of  urethra)  and  in  the  glans  than  between  these  two  points.  In  the 


1  Professor  A.  Francis  Dixon,  in  Professor  D.  J.  Cunningham's  Text-book  of  Anatomy. 


THE  MALE  URETHRA 


1453 


body  of  the  penis  the  canal  is  of  uniform  size,  and  is  about  one-quarter  of  an  inch 
in  diameter.  The  fossa  navicularis  (fossa  navicularis  urethrae  [Morgagni])  is  an 
oblong  dilatation  of  the  terminal  portion  of  the  penile  urethra  (Figs.  1051,  1061, 
and  1075).  In  the  front  of  the  fossa  navicularis  there  is  a  transverse  fold  of 


PROBE  IN 

/LACUNA   MAQNA 
QLANS 


RlOHT    LIP  OF  MEATUS 


SKIN 

SIDE  OF   URETHRA 


LARGE    LACUNA 

SPONOY  BODY — cut  surface 


MEDIAN   LACUN/t 


SPONQIOSUM 

FIG.  1064. — The  distal  portion  of  the  male  urethra,  laid  open  on  its  posterior 
(under)  surface,  showing  the  lacunae.     (Testut.) 

mucous  membrane,  the  valve  of  Guerin  (valvulae  fossae  navicu- 
laris). It  is  part  of  a  distinct  depression  or  pocket.  The  fossa 
navicularis  opens  anteriorly  by  the  meatus  urinarius. 

The  meatus  urinarius  or  external  orifice  of  the  urethra  (orificium 
urethrae  externum)  (Figs.  1061  and  1074)  is  the  most  con- 
tracted part  of  the  urethra;  it  is  a  vertical  slit  (Fig.  1063), 
about  three  lines  in  length,  bounded  on  each  side  by  a  small 
lip  or  labium. 

The  inner  surface  of  the  lining  membrane  of  the  urethra, 
especially  on  the  floor  of  the  spongy  portion,  presents  the  ori- 
fices of  numerous  mucous  glands  (Fig.  1064)  situated  in  the 
submucous  tissue,  and  named  the  glands  of  Littre  (glandulae 
urethrales}.  A  number  of  little  recesses  or  follicles,  called 
lacunae  (lacunae  urethrales},  open  into  the  penile  urethra. 
Some  of  the  glands  of  Littre  open  into  the  lacunae;  some  do 
not.  They  vary  in  size,  and  their  orifices  are  directed  forward, 

FIG.      1063.— Cross-sec-  ,,      ,   .,    J  .,   .  .     ,  ,,  .     ,      »  ,,  .      .    ' 

ms  of  the  male  urethra  so  that  they  may  easily  intercept  the  point  ot  a  catheter  in  its 
118  end?"Cshow?n^  passage  along  the  canal.  One  of  these  lacunae,  larger  than 
the  rest,  is  situated  in  the  upper  surface  of  the  fossa  navicu- 
laris, about  half  an  inch  from  the  orifice;  it  is  called  the 
lacuna  magna  (Fig.  1075).  Into  the  bulbous  portion  are  found  opening  the  ducts 
of  Cowper's  glands. 

Structure. — The  urethra  is  composed  of  a  continuous  mucous  membrane, 
supported  by  a  submucous  tissue  which  connects  it  with  the  various  structures 
through  which  it  passes. 

The  Mucous  Coat. — The  mucous  coat  forms  part  of  the  genito-urinary  mucous 
membrane.  It  is  continuous  with  the  mucous  membrane  of  the  bladder,  ureters, 
and  kidneys;  externally  with  the  integument  covering  the  glans  penis;  and  is  pro- 
longed into  the  ducts  of  the  glands  which  open  into  the  urethra — viz.,  Cowper's 
glands  and  prostate  gland — into  the  vasa  differentia  and  the  seminal  vesicles 
through  the  ejaculatory  ducts,  The  mucous  membrane  is  arranged  in  longitudinal 


marked      alterations 
form.     (Testut.) 


1454  THE  URINARY  ORGANS 

folds  when  the  tube  is  empty.  Small  papillae  are  found  upon  it  near  the  orifice, 
and  its  epithelial  lining  is  of  the  columnar  variety,  excepting  near  the  meatus, 
where  it  is  squamous. 

The  Glands  and  Crypts  of  the  Urethral  Mucous  Membrane  (Fig.  1063) . — There  is  q, 
pocket,  the  lacuna  magna  (Fig.  1060) ,  opening  to  the  front  in  the  upper  wall  of  the 
fossa  navicularis.  The  fossa  is  bounded  by  the  valve  of  Guerin  (valvidae  fossa  navic- 
ularis) .  The  lacunae  of  Morgagni  are  in  the  spongy  urethra  back  of  the  valve  of 
Guerin.  The  lacunae  look  forward.  The  largest  of  them  is  on  the  roof  of  the  fossa 
navicularis,  one  and  one-half  inches  from  the  orifice  (see  above).  Some  of  the 
lacunae  receive  the  secretion  from  the  glands  of  Littre;  others  do  not,  because  some 
of  the  glands  open  on  the  free  surface.  The  larger  lacunae  are  one-third  of  an  inch 
deep  and  are  placed  in  a  longitudinal  row  upon  the  anterior  wall.  The  smaller 
lacunae  are  in  longitudinal  rows  at  the  sides  of  the  tube.  The  glands  of  Morgagni 
are  present  throughout  the  urethra,  except  in  its  most  anterior  part.  In  the  prostatic 
urethra  they  are  arranged  in  rows.  In  the  membranous  urethra  they  are  scat- 
tered irregularly.  In  the  spongy  portion  they  are  most  numerous  on  the  anterior 
wall  and  are  more  plentiful  on  the  sides  than  on  the  floor.  Besides  the  lacunae  and 
racemose  glands,  there  are  the  opening  of  the  prostatic  glands,  the  ejaculatory 
ducts,  Cowper's  glands,  and  the  opening  of  the  sinus  pocularis. 

The  Submucous  Tissue. — The  submucous  tissue  consists  of  a  vascular  erectile 
layer.  It  contains  the  glands  of  Littre,  especially  in  the  posterior  part.  These 
glands  are  lined  with  cylindrical  epithelium  and  enter  the  submucous  coat. 

The  Muscular  Layer. — The  muscular  layer  is  continuous  with  the  muscle  of  the 
prostate  and  bladder.  It  is  composed  of  non-striated  muscle  arranged  in  an 
outer  layer  of  circular  fibres  (stratum  circulars)  and  an  inner  layer  of  longitudinal 
fibres  (stratum  longitud.inale).  It  is  placed  external  to  the  submucous  coat.  In 
the  penile  urethra  there  is  only  a  thin  layer  of  longitudinal  fibres.  In  the  mem- 
branous urethra  and  the  prostatic  urethra  there  are  two  layers  of  muscle,  an  inner 
thin  layer  of  longitudinal  fibres  and  a  thicker  layer  of  circular  fibres.  The  longi- 
tudinal fibres,  when  contracted,  shorten  the  urethra  and  increase  its  diameter. 
The  circular  fibres  are  in  a  state  of  tonic  contraction  and  close  the  urethra.  In 
fact,  they  constitute  the  real  sphincter  (Zeissl,  Zuckerkandl).  -The  so-called 
sphincter  of  the  urethra,  the  Accelerator  urinae,  is  a  voluntary  muscle  and  is  not 
the  real  sphincter.  Outside  of  the  muscular  layer  of  the  urethra  is  the  tissue 
of  the  corpus  spongiosum. 

Surgical  Anatomy. — The  urethra  may  be  ruptured  by  the  patient  falling  astride  of  any  hard 
substance  and  striking  his  perinseum,  so  that  the  urethra  is  crushed  against  the  pubic  arch. 
Bleeding  will  at  once  take  place  from  the  urethra,  and  this,  together  with  the  bruising  in  the 
perinseum  and  the  history  of  the  accident,  will  at  once  point  to  the  nature  of  the  injury. 

Rupture  of  the  urethra  leads  to  extravasation  of  urine.  In  rupture  back  of  the  superior  layer 
of  the  triangular  ligament  the  urine  usually  follows  the  rectum  and  reaches  the  margin  of  the 
anus.  Rupture  between  the  two  layers  of  the  triangular  ligament  liberates  urine  between  the 
two  layers,  where  it  remains  until  a  path  of  exit  is  made  by  suppuration  or  the  surgeon's  knife. 
In  rupture  in  front  of  the  anterior  layer  of  the  ligament  the  urine  passes  into  the  scrotum  and 
may  mount  up  to  the  abdomen  between  the  symphysis  and  the  pubic  spine,  between  which 
points  the  deep  layer  of  the  superficial  fascia  is  not  attached.  It  cannot  pass  to  the  thigh  nor 
cross  the  mid-line,  because  the  fascia  is  attached  to  the  fascia  lata  and  at  the  mid-line. 

The  surgical  anatomy  of  the  urethra  is  of  considerable  importance  in  connection  with  the 
passage  of  instruments  into  the  bladder.  Otis  was  the  first  to  point  out  that  the  urethra  is 
capable  of  great  dilatation,  so  that,  excepting  through  the  external  meatus,  an  instrument  corre- 
sponding to  18  English  gauge  (29  French)  can  usually  be  passed  without  damage.  The  orifice 
of  the  urethra  is  not  so  dilatable,  and  therefore  may  require  slitting,  although  the  introduction 
of  the  Oberlander  dilator,  which  is  expanded  after  introduction,  renders  slitting  of  the  meatus 
seldom  necessary  in  cases  of  chronic  gonorrhoea.  A  recognition  of  this  dilatability  caused  Bige- 
low  to  very  considerably  modify  the  operation  of  lithotrity  and  introduce  that  of  litholapaxy. 
In  passing  a  fine  catheter,  the  point  of  the  instrument  after  it  has  passed  the  lacuna  magna 
should  be  kept  as  far  as  possible  along  the  upper  wall  of  the  canal,  as  the  point  is  otherwise 
very  liable  to  enter  one  of  the  lacunae.  Stricture  of  the  urethra  is  a  disease  of  very  common 


THE  MALE  URETHRA  14.-).") 

occurrence,  and  is  generally  situated  in  the  spongy  portion  of  the  urethra,  most  commonly  in 
the  bulbous  portion,  just  in  front  of  the  membranous  urethra,  but  in  a  very  considerable  num- 
ber of  cases  in  the  penile  or  ante-scrotal  part  of  the  canal.  Even  in  a  normal  urethra,  and  very 
markedly  in  an  inflamed  urethra,  a  bougie  encounters  resistance  behind  the  bulb.  This  is 
usually  supposed  to  be  due  to  spasm  of  the  Compressor  urethrae  muscle. 

In  irrigation  of  the  urethra  by  gravity  fluid  tends  to  block  at  the  same  point,  especially  if  it  is 
thrown  in  suddenly  or  forcibly.  If  a  reservoir  is  raised  seven  and  one-half  feet  from  the  floor, 
and  if  a  patient  sits  on  a  chair  or  lies  upon  a  bed,  fluid  can  be  readily  made  to  pass  by  hydraulic 
pressure  from  the  meatus  to  the  bladder.  Spasm  may  temporarily  prevent  the  inflow,  but  the 
weight  of  the  column  of  fluid  soon  tires  out  the  muscle  and  causes  it  to  relax.  Relaxation 
is  favored  by  having  the  patient  take  slow,  deep  breaths  and  make  efforts  at  urination 
(Valentine). 

Chronic  gonorrhoea  is  frequently  kept  up  by  persistent  inflammation  of  the  ducts  and  follicles  in 
the  mucous  membrane.  This  condition  is  known  as  chrome  glandular  urethritis  or  para- 
itrrfhritix.  In  these  crypts  and  glands  gonococci  may  remain  when  gonorrhoea  appears  to  have 
passed  away,  and  from  time  to  time  reinfection  of  the  urethra  may  arise  from  such  a  source. 

Median  urethrotomy  or  perineal  section  is  opening  of  the  membranous  urethra.  Through  such 
an  opening  the  bladder  can  be  drained  and  explored,  and  the  operation  is  sometimes  called 
median  cystotomy. 

In  lateral  lithotomy  the  knife  enters  the  membranous  urethra  and  strikes  the  groove  of  the 
staff.  Its  edge  is  then  turned  toward  the  left  ischial  tuberosity  and  is  carried  along  the  groove 
into  the  bladder,  dividing  the  membranous  urethra,  the  prostatic  urethra,  the  posterior  layer  of 
the  triangular  ligament,  the  Compressor  urethrae  muscle,  anterior  fibres  of  the  Levator  arii 
muscle  and  the  left  lobe  of  the  prostate  gland. 

THE  FEMALE  URINARY  BLADDER. 

The  female  bladder  is  situated  at  the  anterior  part  of  the  pelvis.  It  is  in  relation,  in 
front,  with  the  symphysis  pubis ;  behind,  with  the  utero-vesical  pouch  of  peritoneum, 
which  separates  it  from  the  body  of  the  uterus;  its  base  lies  in  contact  with  the 
connective  tissue  in  front  of  the  cervix  and  upper  part  of  the  vagina.  Laterally, 
is  the  recto-vesical  fascia.  The  bladder  is  said  by  some  anatomists  to  be  larger  in 
the  female  than  in  the  male.  At  any  rate,  it  does  not  rise  above  the  symphysis 
pubis  till  more  distended  than  in  the  male,  but  this  is  perhaps  owing  to  the  more 
capacious  pelvis  rather  than  to  its  being  of  actually  larger  size.  It  is  described 
in  the  section  on  the  Bladder  (p.  1441). 

THE  FEMALE  URETHRA  (URETHRA  MULIEBRIS). 

The  female  urethra  is  a  narrow  membranous  canal,  about  an  inch  and  a  half  in 
length,  extending  from  the  internal  urethral  orifice  (orificium  urethrae  internum) 
at  the  neck  of  the  bladder  to  the  vestibule  of  the  vagina,  where  it  ends,  being 
called  at  its  termination  the  external  orifice  of  the  urethra  or  the  meatus  urinarius 
(orificium  urethrae  externum).  The  meatus  is  usually  a  vertical  slit.  The 
urethra  is  placed  behind  the  symphysis  pubis,  embedded  in  the  anterior  wall 
of  the  vagina;  and  its  direction  is  obliquely  downward  and  forward,  its  course 
being  slightly  curved,  the  concavity  directed  forward  and  upward.  Its  diameter 
when  undilated  is  about  a  quarter  of  an  inch.  The  urethra  perforates  both 
layers  of  the  triangular  ligament,  and  its  external  orifice  is  situated  directly  in 
front  of  the  vaginal  opening  and  about  an  inch  behind  the  glans  clitoridis.  Except 
above,  the  posterior  wall  of  the  urethra  is  firmly  connected  to  the  anterior  wall 
of  the  vagina. 

Structure. — The  urethra  consists  of  three  coats:  muscular,  erectile,  and  mucous. 

The  Muscular  Coat  (tunica  muscularis). — The  muscular  coat  is  continuous  with 
that  of  the  bladder;  it  extends  the  whole  length  of  the  tube,  and  consists  of  an  , 
internal  layer  of  non-striated  longitudinal  fibres  (stratum  longitudinale)  and  an 
external  layer  of  non-striated  circular  fibres  (stratum  circulare).  Superficial  to  the 
circular  fibres  "lies  a  layer  of  cross-striped  muscle-fibres,  which  form  a  closed  ring 
near  the  bladder  only."1 

1  Hand  Atlas  of  Human  Anatomy.  By  Prof.  Werner  Spalteholz.  Translated  and  edited  by  Prof.  Lewellys  F 
Barker. 


1456 


THE  URINARY  ORGANS 


The  Submucous  Coat  (tunica  submucosa). — Internal  to  the  muscular  coat  is  the 
submucous  coat,  which  contains  a  venous  plexus,  networks  from  which  pass 
between  the  muscular  layers  and  impart  to  these  layers  an  erectile  or  spongy 
nature  (corpus  spongiosum  urethrae).  In  addition  to  this,  between  the  two  layers 
of  the  triangular  ligament,  the  female  urethra  is  surrounded  by  the  Compressor 
urethrae  muscle,  as  in  the  male. 


INTERNAL 

ORIFICE    OF 

URETHRA 


RECTO- 
UTERINE 
POUCH 

FOR  NIX 
OF  VAGINA 

RECTO- 
VAGINAL 
SEPTUM 


EXTERNAL 

ORIFICE    OF 

URETHRA 


FIG.  1065.— Mesal  section  through  the  pelvis  of  a  woman,  aged  cwenty-one  years. 

(Corning.) 


Peritoneum  in  blue. 


The  Mucous  Coat  tunica  mucosa) .—The  mucous  coat  is  pale,  continuous  exter- 
nally with  that  of  the  vulva,  and  internally  with  that  of  the  bladder.  It  is  thrown 
into  longitudinal  folds,  one  of  which,  placed  along  the  floor  of  the  canal,  extends 
from  the  vesical  trigone  almost  to  the  external  orifice  of  the  urethra.  It  is  called 
the  crest  (crate  urethralis).  The  outline  of  the  urethra  is  stellate  when  collapsed, 
because  of  the  formation  of  numerous  longitudinal  folds.  It  is  lined  by  laminated 
epithelium,  which  becomes  transitional  near  the  bladder.  Many  mucous  glands 
open  into  the  urethra,  and  there  are  numerous  lacunae.  External  to  the  external 
orifice,  on  each  side,  a  group  of  mucous  glands  opens  by  a  common  duct,  the 
ductus  para-urethralis. 

The  urethra,  because  it  is  not  surrounded  by  dense  resisting  structures,  as  in  the  male,  admits 
of  great  dilatation,  which  enables  the  surgeon  to  remove  with  considerable  facility  calculi  o: 
other  foreign  bodies  from  the  cavity  of  the  bladder. 


THE  MALE  ORGANS  OF  GENERATION. 


THE  PROSTATE  GLAND  (PROSTATA)   (Figs.  1062,  1066,  1067,  1068,  1069, 

1070,  1071,  1072). 


PROSTATIC 
MUSCLE 


GLANDULAR 
TISSUE 


THE  prostate  gland  (TipoiaTypc,  to  stand  before)  is  a  structure  accessory  to  the 
true  generative  organs  and  furnishes  a  viscid,  opalescent  secretion  in  which 
spermatozoids  will  live  (W.  G.  Richardson).  It  is  a  pale,  firm,  partly  glandular 
and  partly  muscular  body,  which  is 
placed  immediately  below  the  neck  of  the 
bladder  and  about  the  commencement  of 
the  urethra  in  the  male.  The  prostate 
appears  to  completely  surround  the  first 
portion  of  the  urethra  (Figs.  1068  and 
1072),  but  the  glandular  matter  does  not 
in  reality  completely  surround  the  tube 
(Figs.  1066  and  1072).  As  Spalteholz 
says,  it  partly  surrounds  it  as  a  broad 
clasp,  open  in  front.  This  opening  ir.  the 
glandular  tissue  is  closed,  and  a  com- 
plete ring  is  established  about  the  urethra 
by  the  prostatic  muscle  (m.  prostaticus) 

(Figs.  1066  and  1072).     This  muscle  below  is  composed  of  striated  fibres  and 
is  continuous  with  the  Compressor  urethrae  (m.  sphincter  urethrae  membranacea)  ; 


MUSCULAR 
LAYER  OF 
URETHRA 
URETHRA 


CJACULATORY 
UTRICLE  DUCT 

FIG.  1066. — Section  of  the  prostate.    (Jarjavay.) 


PROSTATIC 

,        MUSCLE 


TRANSVERSE 
PERINEAL  LIGAMENT 
FIG.  1067. — Side  view  of  the  position  of  the  prostate.     (Poirier  and  Charpy.) 

above  it  is  composed  of  non-striated  muscle,  and  is  continuous  with  the  circular 
muscular  fibres  of  the  bladder  which  surround  the  internal  urethral  orifice  and 

92  (  1457  ) 


1458 


THE   MALE    ORGANS    OF    GENERATION 


constitute  the  Sphincter  vesicae  (Fig.  1067).  The  general  course  of  the  fibres  is 
transverse,  with  radiations  into  the  gland  substance.  The  apex  of  the  gland  for 
about  one-quarter  of  an  inch  is  completely  surrounded  by  the  muscle  (Fig.  1067). 


VAS 
DEFERENS 


PROSTATE 

FIG.  1068. — Prostate  with  seminal  vesicles  and  seminal  ducts,  viewed  from  in  front  and  above.     (Spalteholz.) 

Ascending  from  the  apex  the  fibres  cover  for  a  short  distance  only  the  front  of  the 
gland  and  are  attached  at  the  sides  to  the  fascia  (Fig.  1067).    Higher  up  the  muscle 


AMPULLA 

OF  VAS 

DEFERENS 


VAS 
DEFERENS 

EJACULATORY 
DUCT 

PROSTATIC 
UTRICLE 

PROSTATE. 
GLAND 
COWPEFT 
GLAND 


PERITONEUM 


CORPUS 
SPONGIOSUM 


CORPUS 
CAVERNOSUM 


HYDATID  OF 
MORGAGNI 


FIG.  1069. — Diagrammatic  representation  of  the  male  reproduction  organs  and  their  relations  to  the  bladder 
and  the  urethra.     Lateral  view.     (Toldt.) 

passes  between  the  sheath  and  the  capsule  and  ascends  to  the  base  of  the  prostate, 
uniting  the  sheath  to  the  capsule  along  the  mid-line  in  front.  The  prostate  is  placed 
in  the  pelvic  cavity,  behind  the  lower  part  of  the  symphysis  pubis,  and  above  the 


THE  PROSTATE  GLAND 


1459 


deep  layer  of  the  triangular  ligament,  and  rests  upon  the  rectum,  through  which 
it  may  be  distinctly  felt,  especially  when  enlarged  (Fig.  1070). 

The  ejaculatory  ducts  (Figs.  1068, 1069,  and  1070)  enter  the  prostate  at  the  margin 
which  separates  the  base  fro'm  the  posterior  surface  of  the  gland ;  they  pass  down- 
ward, inward,  and  forward  through  the  prostate,  and  open  into  the  prostatic 
urethra.  The  prostate  when  surrounded  by  its  sheath  resembles  a  chestnut  in 
shape.  When  dissected  out  from  its  sheath  and  capsule  and  from  the  Prostatic 
muscle,  it  resembles  an  "open  clasp"  or  horseshoe.  The  sheath  of  the  prostate 


LEFT    COMMON 
ILIAC    VEIN 


FIG.  1070. — Sagittal  section  of  the  lower  part  of  a  male  trunk,  the  right  segment.     (Testut.) 

is  derived  from  the  recto- vesical  fascia.  It  is  called  the  prostatic  fascia  (fascia  pro- 
statae),  is  distinct  and  dense,  and  covers  the  entire  prostate,  except  at  the  apex  and 
at  the  attachment  of  the  base  of  the  prostate  to  the  neck  of  the  bladder.  The  pros- 
tatic fascia  is  a  distinct  structure,  though  it  is  thin.  The  veins  of  the  prostatic 
plexus  lie  in  the  layers  of  the  sheath,  "and  are  everywhere  separated  from  the 
prostatic  capsule  proper  by  a  layer  of  this  sheath."1  In  an  enlarged  prostate 
the  sheath  is  thick  and  fibrous.  It  is  very  difficult  to  shell  out  a  normal  prostate 
from  its  sheath,  but  it  is  easy  to  shell  out  an  enlarged  prostate.  Within  the  pros- 
tatic sheath  (which,  be  it  remembered,  carries  the  veins)  is  the  true  or  proper  capsule 

1  J.  W.  Thomson  Walker,  in  the  British  Medical  Journal,  July  9,  1904. 


H60 


THE   MALE    ORGANS    OF   GENERATION 


of  the  prostate.  The  true  capsule  is  a  continuous  investment  from  the  entrance 
of  the  urethra  above  to  the  triangular  ligament  below.  It  is  thin,  but  firm  and 
fibrous.  It  is  not  everywhere  absolutely  distinct  from  the  sheath,  but  may  be  fused 


MOUTH    OF    EJACU-_..gl=,] 

LATORY    DUCT 
VERUMONTANUM- — 


OPENINGS    OF 
PHOSTATIC  DUCTS 


MEMBRANOUS    URETHRA 


OUT  SURFACE 


DUCT    OF    COWPER'S 
GLAND— LAID   BARE 


A    RIDGE    OF 

MUCOSA 
BULBOUS 
URETHRA 

CORPUS    SPON- 
GIOSUM — CUT  SURFACE 


FIG.  1071. — Proximal  portion  of  the  urethra,  laid  open  by  a  median,  anterior  cut.     (Testut.) 

I 


FIG.  1072. — Transverse  section  of  normal  prostate  through  the  middle  of  the  verumontanum,  from  a  subject 
aged  nineteen  years:  a,  longitudinal  section  of  ducts  leading  from  the  lobules  of  the  prostatic  glands  ;  b,  veru- 
montanum ;  c,  sinus  pocularis  ;  d,  urethra  ;  e,  ejaculatpry  ducts  ;  /,  arteries,  veins,  and  venous  sinuses  in  sheath 
of  prostate  ;  g,  nerve  trunks  in  sheath  ;  h,  point  of  origin  of  fibro-muscular  bands  encircling  urethra  ;  i,  zone  of 
striated  voluntary  muscle  on  superior  surface.  (Drawn  from  Erdinger  projection  apparatus.)  (Taylor.) 


THE   PROSTATE    GLAND  1401 

with  it  here  and  there,  and  many  bands  of  fibres  run  from  the  sheath  to  the  capsule.1 
The  capsule  is  continuous  with  the  stroma  of  the  giand  and  cannot  be  stripped  off  as 
can  the  kidney  capsule.  Any  attempt  to  strip  off  the  capsule  tears  away  fragments 
of  gland.  The  capsule  is  composed  of  fibrous  tissue  and  unstriated  muscle-fibres. 
From  its  deep  surface  the  capsule  is  continuous  with  the  stroma  of  the  prostate  ( W.  G. 
Richardson).  Sir  Henry  Thompson,  half  a  century  ago,  pointed  out  the  distinction 
between  true  capsule  and  sheath,  and  suggested  these  names.  The  prostate  is  divided 
for  study  into  a  base,  apex,  posterior  surface,  anterior  surface,  and  lateral  surfaces. 

The  Base  (basis  prostatae}. — The  base  is  directed  upward,  and  is  situated 
immediately  below  the  base  of  the  bladder.  It  is  in  contact  with  and  supports  the 
base  of  the  bladder.  The  external  longitudinal  muscular  layer  of  the  bladder  is 
attached  to  the  posterior  portion  of  the  base  of  the  prostate,  and  some  of  the  fibres 
reach  and  adhere  to  the  true  capsule.  The  anterior  portion  of  the  base  is  called 
the  isthmus  (isthmus  prostatae)  (Fig.  1068). 

The  Apex  (apex  prostatae). — The  apex  is  directed  downward  and  rests  upon 
the  deep  layer  of  the  triangular  ligament.  The  apex  is  fixed,  except  for  the  slight 
mobility  of  the  triangular  ligament ;  the  rest  of  the  gland  is  somewhat  movable. 

Surfaces. — The  Posterior  Surface  (fades  posterior). — The  posterior  surface  is 
flattened,  marked  by  a  slight  longitudinal  furrow,  and  rests  on  the  second  part  of 
the  rectum,  and  is  distant  about  one  inch  and  a  half  from  the  anus.  At  the  upper 
and  posterior  border  of  the  gland  are  the  seminal  vesicles.  Their  direction  is 
downward  and  inward;  in  fact,  almost  transverse. 

The  Anterior  Surface  (fades  anterior). — The  anterior  surface  is  convex,  and  placed 
about  three-fourths  of  an  inch  behind  the  pubic  symphysis,from  which  it  is  separated 
by  a  plexus  of  veins  and  a  quantity  of  loose  fat.  It  is  connected  to  the  pubic  bone 
on  either  side  by  the  pubo-pro static  ligament.  It  is  shorter  than  the  posterior  surface. 

The  Lateral  Surfaces. — The  lateral  surfaces  are  prominent,  and  are  covered  by 
the  anterior  portions  of  the  Levatores  ani  muscles,  which  are,  however,  separated 
from  the  gland  by  a  plexus  of  veins. 

The  prostate  measures  about  an  inch  and  a  half  transversely  at  the  base,  an 
inch  in  its  antero-posterior  diameter,  and  an  inch  and  a  quarter  in  its  vertical 
diameter.  Its  weight  is  about  four  and  a  half  drachms.  It  is  held  in  position 
by  the  anterior  ligaments  of  the  bladder  (ligamenta  puboprostatica) ;  by  the  deep 
layer  of  the  triangular  ligament,  which  invests  the  commencement  of  the  mem- 
branous portion  of  the  urethra  and  prostate  gland ;  and  by  the  anterior  portions  of 
the  Levatores  ani  muscles,  which  pass  backward  from  the  os  pubis  and  embrace 
the  sides  of  the  prostate.  These  portions  of  the  Levatores  ani,  from  the  support 
they  afford  to  the  prostate,  are  named  the  Levator  prostatae. 

The  prostate  consists  of  two  lateral  lobes  and  a  middle  lobe. 

The  Lateral  Lobes  (lobus  dexter  et  sinister). — The  two  lateral  lobes  are  of 
equal  size,  separated  by  a  deep  notch  above,  and  by  a  furrow  upon  the  anterior 
and  posterior  surfaces  of  the  gland,  which  indicates  the  bilobed  condition  of  the 
organ  in  some  animals.  At  the  upper  and  posterior  portion  of  the  prostate  the 
two  lobes  are  united  by  two  bands  of  gland -tissue.  One  of  these  bands  is  in  front 
of  the  ejaculatory  ducts,  the  other  is  below  them.  "The  upper  limit  of  the  gland 
is  thus  in  the  form  of  a  horseshoe,  open  in  front."2  Below  the  level  of  the  prostatic 
ducts  the  prostate  and  urethra  are  in  relation,  but  are  not  closely  connected. 
Above  this  level  the  connection  is  intimate  (J.  W.  Thomson  Walker). 

The  So-called  Middle  Lobe  (lobus  medius). — The  middle  lobe  is  not  in  reality  a 
lobe,  and  the  name  is  usually  employed  to  describe  an  enlargement  of  the  region  of 
the  prostate  on  the  posterior  portion  of  the  urethra  in  front  of  the  ejaculatory  ducts. 
The  so-called  third  or  middle  lobe  is  an  abnormal  condition.  It  is  due  to  enlargement 
of  the  transverse  band  of  prostatic  tissue  which  joins  the  lateral  lobes  beneath  the 

1  W.  G.  Richardson  on  the  Development  and  Anatomy  of  the  Prostate  Gland. 

2  J.  W.  Thomson  Walker,  in  the  British  Medical  Journal,  July  9,  1904. 


1462  THE  MALE    ORGANS   OF    GENERATION 

base  of  the  bladder,  behind  the  posterior  wall  of  the  urethra  and  in  front  of  the  ejacu- 
latory  ducts.  This  mass  of  tissue  is  beneath  the  uvula  vesicae.  Walker  points  out 
that  frequently  nodules  of  enlarged  prostate  protrude  into  the  bladder,being  covered 
only  by  bladder  mucous  membrane.  This  is  accomplished  by  the  enlarging  pros- 
tate forcing  its  way  through  the  lumen  of  the  vesical  sphincter  and  dilating  it, 
and  separating  and  passing  between  the  strands  of  the  internal  longitudinal 
muscle  of  the  bladder.  "The  so-called  middle  lobe  is  formed  by  the  protrusion  of 
a  nodule  between  the  two  bands  of  muscle  which  pass  into  the  trigorie  from  the 
ureters,  and  unite  on  the  posterior  wall  of  the  prostatic  urethra."1 

The  urethra  passes  forward  between  the  lateral  lobes  of  the  prostate.  The 
prostate  is  perforated  by  the  ejaculatory  ducts.  The  urethra  usually  lies  on  the 
level  of  the  junction  of  the  anterior  and  middle  thirds  of  a  lateral  lobe.  The 
ejaculatory  ducts  pass  obliquely  downward  and  forward  through  the  posterior 
part  of  the  prostate,  and  open  into  the  prostatic  portion  of  the  urethra. 

Structure  (Fig.  1072). — As  previously  stated  (p.  1459),  the  prostate  is  surrounded 
by  a  sheath  from  the  recto-vesical  fascia,  and  possesses  also  a  true  capsule. 

The  glands  of  the  prostate  are  of  the  branched  tubular  variety  and  number 
forty  or  fifty.  Many  of  the  ducts  join  and  form  from  fifteen  to  twenty-five  smaller 
ducts,  which  empty  into  the  prostatic  urethra,  to  the  sides  of  the  verumontanum 
(Fig.  1071).  The  ducts  and  glands  are  lined  with  cubical  epithelium.  The 
prostatic  secretion  or  prostatic  fluid  (succus  prostaticus)  is  a  viscid,  opalescent, 
serous  secretion,  alkaline  in  reaction,  containing  a  ferment,  but  no  mucus.  The 
substance  of  the  prostate  is  of  a  pale,  reddish-gray  color,  of  great  density  and 
not  easily  torn.  It  consists  of  glandular  substance  and  muscular  tissue. 

The  muscular  tissue,  according  to  Kolliker,  constitutes  the  proper  stroma  of 
the  prostate,  the  connective  tissue  being  very  scanty,  and  simply  forming  thin 
trabeculae  between  the  muscular  fibres,  in  which  the  vessels  and  nerves  of  the 
gland  ramify.  The  true  capsule  is  continuous  with  the  stroma.  The  stroma  lies 
between  the  glandular  substance  and  strands  of  stroma  pass  in  convergent  lines 
toward  the  prostatic  urethra,  especially  toward  the  dorsum  of  the  urethra.  These 
strands  or  septa  divide  the  prostate  into  small  irregular  subdivisions  called  lobules. 
Next  to  the  urethra,  the  stroma  forms  a  thick  layer.  As  age  advances  the  inter- 
stitial tissue  of  the  prostate  increases  and  the  glandular  substance  shrinks. 

Vessels  and  Nerves. — The  arteries  supplying  the  prostate  are  derived  from  the 
internal  pudic,  inferior  vesical,  and  middle  haemorrhoidal.  Branches  of  the  vessels 
enter  the  gland  in  the  septa  between  the  lobules  and  send  off  minute  branches  to  the 
lobules  (Walker).  The  veins  form  a  plexus  around  the  sides  and  base  of  the  gland 
between  layers  of  the  fascial  sheath;  they  receive  in  front  the  dorsal  vein  ot  the 
penis,  and  terminate  in  the  internal  iliac  vein.  The  lymphatics  of  the  prostate 
begin  as  networks  about  the  acini  of  the  gland,  pass  to  beneath  the  capsule,  and 
form  another  network,  and  from  this  peripheral  network  collecting  trunks  arise. 
Several  trunks  pass  from  the  posterior  portion  of  the  gland.  One  trunk  passes  to 
the  external  iliac  glands,  one  to  the  internal  iliac  glands,  and  several  end  in  the 
lateral  sacral  glands,  and  the  glands  of  the  sacral  promontory.  An  anterior  trunk 
is  joined  by  lymphatics  from  the  membranous  urethra  and  prostatic  urethra  and 
passes  to  a  gland  on  the  internal  pudic  artery.2  The  nerves  are  derived  from  the 
hypogastric  plexus. 

Surgical  Anatomy. — The  relation  of  the  prostate  to  the  rectum  should  be  noted:  by  means  of 
the  finger  introduced  into  the  gut  the  surgeon  detects  enlargement  or  other  disease  of  the  prostate; 
he  can  feel  the  apex  of  the  gland,  which  is  the  guide  to  Cock's  operation  for  stricture;  he  is  enabled 
also  by  the  same  means  to  direct  the  point  of  a  catheter  when  its  introduction  is  attended  with 
difficulty  either  from  injury  or  disease  of  the  membranous  or  prostatic  portions  of  the  urethra. 
When  the  finger  is  introduced  into  the  bowel  the  surgeon  may,  in  some  cases,  especially  in  boys, 

1  J.  W.  Thomson  Walker,  in  the  British  Medical  Journal,  July  9,  1904. 

2  Poirier  and  Charpy.     Human  Anatomy. 


THE   PENIS  1463 

learn  the  position,  as  well  as  the  size  and  weight,  of  a  calculus  in  the  bladder.  In  the  operation 
for  the  removal  of  a  calculus,  if,  as  is  not  (infrequently  the  case,  the  storie  should  be  lodged 
behind  an  enlarged  prostate,  it  may  be  displaced  from  its  position  by  pressing  upward  the  base 
of  the  bladder  from  the  rectum.  The  prostate  gland  is  occasionally  the  seat  of  suppuration,  either 
due  to  injury,  gonorrhoea,  or  tuberculous  disease.  The  gland  is  enveloped  in  a  dense  unyield- 
ing capsule,  which  determines  the  course  of  an  abscess,  and  also  explains  the  great  pain  which  is 
present  in  acute  inflammation.  The  abscess  most  frequently  bursts  into  the  urethra,  the  direc- 
tion in  which  there  is  least  resistance,  but  may  occasionally  burst  into  the  rectum,  or  more  rarely 
in  the  perinseum.  In  advanced  life  the  prostate  often  becomes  considerably  enlarged,  and  may 
project  into  the  bladder  so  as  to  impede  the  passage  of  the  urine.  According  to  Dr.  Messer's 
researches,  conducted  at  Greenwich  Hospital,  it  would  seem  that  such  obstruction  exists  in  20 
per  cent,  of  all  men  over  sixty  years  of  age.  The  prostate  may  be  enlarged  by  the  growth  of 
innocent  tumors,  adenomata,  fibromata,  myomata,  and  myofibromata.  The  entire  gland  may 
be  hypertrophied.  A  tumor  may  be  encapsulated,  but  often  is  surrounded  by  an  area  of  hyper- 
plasia  of  prostatic  tissues,  and  usually  the  area  of  hyperplasia  is  much  more  extensive  than  the 
tumor.  A  tumor  may  be  beneath  the  mucous  membrane,  deep  in  the  gland,  or  beneath  the 
sheath.  The  growth  called  the  third  lobe  is  submucous.  In  some  cases  the  enlargement  affects 
principally  the  lateral  lobes,  which  may  undergo  considerable  enlargement  without  causing  much 
inconvenience.  In  other  cases  it  would  seem  that  the  nodule  forms  the  so-called  middle  lobe, 
and  even  a  small  enlargement  of  this  character  may  act  injuriously,  by  forming  a  sort  of  valve 
over  the  urethral  orifice,  preventing  the  passage  of  the  urine,  and  the  more  the  patient  strains, 
the  more  completely  will  it  block  the  opening  into  the  urethra.  In  consequence  of  the  enlarge- 
ment of  the  prostate  a  pouch  is  formed  at  the  base  of  the  bladder  behind  the  projection,  in  which 
urine  collects  and  cannot  entirely  be  expelled.  The  urine  becomes  decomposed  and  ammoniacal, 
and  leads  to  cystitis.  If  the  prostate  enlarges  the  urethra  is  lengthened,  often  dilated,  altered 
in  shape,  or  distorted. 

The  relation  of  the  enlarged  prostate  to  the  neck  of  the  bladder  is  greatly  altered  from  the 
relation  of  the  normal  prostate.  Normally,  it  is  extra vesical ;  when  enlarged  it  may  encapsule 
"the  neck  of  the  bladder  in  a  cuff-like  manner,  extending  several  inches  upward  on  its  wall," 
and  often  it  protrudes  "into  the  vesical  cavity,  carrying  on  its  surface  the  mucosa  vesicae."1  In 
many  cases  of  prostatic  enlargement  the  gland  should  be  removed  (prostatectomy).  One  method 
is  enucleation  through  a  suprapubic  incision;  another  method  is  enucleation  through  a  perineal 
incision;  another  method  is  carried  out  by  both  incisions  (the  combined  method). 

The  Bottini  operation  is  prostatotomy,  effected  by  a  special  instrument  for  the  purpose  of 
cauterizing  the  gland  and  thus  causing  shrinking. 

In  elderly  individuals  the  gland  tubules  may  form  round,  indurated,  and  sometimes  calcified 
masses,  about  1  mm.  in  diameter,  and  called  prostatic  stones. 

COWPER'S  GLANDS  (GLANDULAE  BULBO-URETHRALES) 

(Figs.  1071,  1078). 

Cowper's  glands  are  two  small,  rounded,  and  somewhat  lobulated  bodies  of 
a  yellow  color,  about  the  size  of  peas,  placed  behind  the  forepart  of  the  mem- 
branous portion  of  the  urethra,  between  the  two  layers  of  the  triangular  ligament. 
They  lie  close  above  the  bulb,  and  are  enclosed  by  the  transverse  fibres  of  the 
Compressor  urethrae  muscle.  Their  existence  is  said  to  be  constant,  they  gradually 
diminish  in  size  as  age  advances. 

Structure. — Each  gland  consists  of  several  lobules  held  together  by  a  fibrous 
investment.  Each  lobule  consists  of  a  number  of  acini  lined  by  columnar  epithe- 
lial cells,  opening  into  one  duct,  which,  joining  with  the  ducts  of  other  lobules 
outside  the  gland,  form  a  single  excretory  duct  (ductus  excretorius] .  The  excretory 
duct  of  each  gland,  nearly  an  inch  in  length,  passes  obliquely  forward  beneath 
the  mucous  membrane,  and  opens  by  a  minute  orifice  on  the  floor  of  the  bulbous 
portion  of  the  urethra. 

THE  PENIS  (Figs.  1073,  1074,  1075,  1076,  1077,  1078). 

The  penis  is  a  long  body  of  prismatic  shape  placed  below  and  in  front  of  the 
symphysis  pubis.  It  surrounds  the  greatest  length  of  the  urethra.  It  consists 
of  a  root,  body,  and  extremity  or  glans  penis.  The  root  and  the  posterior  portion 

1  John  B.  Murphy,  in  the  Journal  of  the  American  Medical  Association,  May  28,  1904. 


1464 


THE   MALE   ORGANS    OF    GENERATION 


of  the  body  lie  beneath  the  scrotum  and  the  integument  of  the  perinseum  (Fig. 

1069),  and  are  firmly  fixed  to  the  triangular  ligament,  the  pubic  bones,  and  the 

symphysis;  hence  this  portion  of  the  organ 
is  called  the  fixed  portion  (pars  fixa)  (Fig. 
309).  The  balance  of  the  organ  is  free 


FOSSA    OF 
FRAENUM 


PREPUCE 
RETRACTED 


MEDIAN    GROOVE 


NECK 


DISTAL   PART  OF  SEP- 
TUM PECTINIFORME' 


FIG.  1073. — The  penis,  proximal  portion,  seen 

from  below.     (Testut.)  FIG.  1074. — Glans  penis,  under  surface.     (Testut.) 

and  movable  (Fig.  1069),  and  is  called  the  mobile  portion  (pars  mobilis).  When 
the  penis  is  relaxed  there  is  an  angle  between  the  fixed  and  mobile  portions; 
when  the  penis  is  erect,  the  angle  disappears. 

The  Root  (radix  penis). — The  root  is  firmly  connected  to  the  rami  of  the  os 
pubis  and  ischium  by  two  strong  tapering,  fibrous  processes,  the  crura  (Figs.  1073, 
1077,  and  1078),  and  to  the  front  of  the  symphysis  pubis  by  the  suspensory  liga- 
ment (Fig.  1076),  a  strong  band 
of  fibrous  tissue  which  passes 
downward  from  the  front  of 
the  symphysis  pubis  to  the  root 
of  the  penis. 

The  extremity,  acorn,  or 
glans  penis  (Figs.  1074  and 
1075)  presents  the  form  of  an 
obtuse  cone,  flattened  from 
above  downward.  At  its  sum- 
mit is  a  vertical  fissure,  the 
external  orifice  of  the  urethra  or 
the  meatus  urinarius  (onficium 
urethrae  externum).  The  base 
of  the  glans  forms  a  rounded 
projecting  border,  the  corona 
glandis,  and  behind  the  corona 
is  a  deep  constriction,  the  cer- 
vix or  neck  (collum  glandis). 
Upon  both  the  corona  and  neck 
small  sebaceous 
glands  are  found,  the  glandulae 
Tysonii  odoriferae.1  They  secrete  a  sebaceous  matter  of  very  peculiar  odor, 
which  probably  contains  casein  and  becomes  easilv  decomposed. 


PREPUCE 
RETRACTED 


FOSSA    NAVIC- 
ULARIS 


'•  FRENUM 
_VALVE    OF  LA- 
CUNA   MAGNA 

LEFT  SIDE  OF  URETHRA 

•••FLOOR  OF  URETHRA 
LACUNA    MAGNA 


CORPUS 
CAVERNOSUM  CORPUS 

SPONGIOSUM 

FIG.  1075. — The  penis,  distal  end,  in  sagittal  section  one-twelfth  inch   numerous 
at  left  of  middle  line.     (Testut.) 


1  Stieda  (Comptes-rendus  du  XII.  Congres  International  de  Medecine,  Moscow,  1897)  asserts  that  Tyson's 
glands  are  never  found  on  the  corona  glandis,  and  that  what  have  hitherto  been  mistaken  for  glands  are  really 
large  papillae. — ED  of  15th  English  edition.  ' 


THE  PENIS 


1465 


The  Body  of  the  Penis  (corpus  penis). — The  body  of  the  penis  is  the  part 
between  the  root  and  extremity.  In  the  flaccid  condition  of  the  organ  it  is  cylin- 
drical, but  when  erect  it  has  a  triangular  prismatic  form  with  rounded  angles,  the 
broadest  side  being  turned  upward,  and  called  the  dorsum  penL>.  The  lower  sur- 
face of  the  body  of  the  penis  is  called  the  urethral  surface  (fades  urethralis).  The 
body  is  covered  by  integument,  and  contains  in  its  interior  a  large  portion  of  the 
urethra.  The  integument  covering  the  penis  is  remarkable  for  its  thinness,  its 
dark  color,  its  looseness  of  connection  with  the  deeper  parts  of  the  organ,  and  for 
the  absence  of  adipose  tissue.  At  the  root  of  the  penis  the  integument  is  contin- 
uous with  that  upon  the  pubes  and  scrotum,  and  at  the  neck  of  the  glans  it  leaves 
the  surface  and  becomes  folded  upon  itself  to  form  the  prepuce  (praeputium)  (Fig. 
1074).  The  internal  layer  of  the  prepuce  is  attached  behind  to  the  cervix  or  neck 
(Fig.  1074),  and  approaches  in  character  to  a  mucous  membrane;  from  the  cervix 
it  is  reflected  over  the  glans  penis,  and  at  the  meatus  urinarius  is  continuous  with 
the  mucous  lining  of  the  urethra. 

The  integument  covering  the  glans  penis  contains  no  sebaceous  glands,  but 
projecting  from  its  free  surface  are  a  number  of  small,  highly  sensitive  papillae. 


SUPERFICIAL 

FIBRES  OF 

SUSPENSORY 

LIGAMENT 

DEEP    FIBRES 

OF  SUSPENSORY 

LIGAMENT 

DORSAL  VEIN 

DORSAL  ARTERY 
DORSAL  NERVE 


PERITONEUM 


ANTERIOR 
LIGAMENT 
OF  BLADDER 

SUBPUBIC 
LIGAMENT 

ERECTA  PENIS 
MUSCLE 


FIG.  1076. — The  suspensory  ligament.      (Poirier  and  Charpy.) 

At  the  back  part  of  the  meatus  urinarius  a  fold  of  mucous  membrane  passes 
backward  to  the  bottom  of  a  depressed  raphe,  where  it  is  continuous  with  the 
prepuce ;  this  fold  is  termed  the  fraenum  (frenulum  praeputii).  The  skin  of  the  penis 
covers  the  mobile  parts  of  the  organ.  It  is  thin,  extremely  elastic,  and  contains  very 
few  hairs.  Beneath  the  skin  of  the  penis  is  the  dartos  layer  (Figs.  1076  and  1083), 
continuous  with  the  scrotal  dartos,  containing  chiefly  non-striated  muscular  fibres 
arranged  longitudinally.  It  passes  forward  to  the  orifice  of  the  prepuce,  and 
then  turns  backward,  growing  thinner  and  thinner,  and  finally  disappearing  at 
the  cervix.  Beneath  the  dartos  and  extending  forward  to  the  orifice  of  the  pre- 
puce is  a  sheath  of  areolar  tissue.  It  is  a  lax  sheath  rich  in  elastic  tissue  and 
containing  almost  no  fat.  The  superficial  vessels  and  nerves  are  in  the  areolar 
sheath.  Beneath  the  areolar  sheath  of  the  penis,  from  the  corona  to  the  root,  is 
the  fascia  of  the  penis  (fascia  penis)  (Fig.  1083).  It  covers  the  organ  from  the  root 
to  the  corona,  and  also  covers  the  dorsal  artery,  veins,  and  nerves.  It  is  continuous 
behind  with  the  superficial  perineal  fascia  and  suspensory  ligament.  It  is  com- 
posed chiefly  of  elastic  tissue. 

Structure  of  the  Penis. — The  penis  is  composed  of  a  mass  of  erectile  tissue 
enclosed  in  three  cylindrical  fibrous  compartments.     Of  these,  two,  the  corpora 


1466 


THE   MALE    ORGANS    OF    GENERATION 


cavernosa,  are  placed  side  by  side  along  the  upper  part  of  the  organ;  the  third,  or 
corpus  spongiosum,  encloses  the  urethra  and  is  placed  below. 

The  Two  Corpora  Cavernosa  (corpora  cavernosa  penis)  (Figs.  1077  and  1078). — The 
two  corpora  cavernosa  form  the  chief  part  of  the  body  of  the  penis.  They  consist  of 
two  fibrous  cylindrical  tubes,  placed  side  by  side,  and  intimately  connected  along 
the  median  line  for  their  anterior  three- 
fourths,  whilst  at  their  back  part  they 
separate  from  each  other  to  form  the 
crura  penis,  which  are  two  strong  taper- 
ing fibrous  processes  or  roots  firmly 
connected  to  the  rami  of  the  os  pubis 
and  ischium  (Figs.  1073,  1077,  and 
1078).  Each  cms  commences  by  a 


VAS 

DEFERENS 


CORONA. 
GLANDIS 


CORONA 
GLANDIS 


EXTERNAL  ORIFICE 
OF  URETHRA 


FIG.  1077. — The  penis,  with  the  puhic  bones,  seen 
from  before  and  below.     (Toldt.) 


FIG.  1078. — The  penis,  with  the  urethra,  Cowper  a 
glands,  the  prostate  gland, and  the  seminal  vesicles, 
seen  from  below  and  behind.  (Toldt). 


THE  PENIS 


1467 


blunt-pointed  process  in  front  of  the  tuberosity  of  the  ischium,  and  before  its  junc- 
tion with  its  fellow  to  form  the  body  of  the  penis  it  presents  a  slight  enlargement, 
named  by  Kobelt  the  bulb  of  the  corpus  cavernosum.  Just  beyond  this  point  they 
become  constricted,  and  retain  an  equal  diameter  to  their  anterior  extremity,  where 
they  form  a  single  rounded  end  which  is  received  into  a  fossa  in  the  base  of  the  glans 
penis  (Figs.  1075  and  1077).  A  median  groove  on  the  upper  surface  lodges  the 
dorsal  arteries,  nerves,  and  veins  of  the  penis  (Figs.  1081,  1082,  and  1083),  and  the 
groove  on  the  under  surface  receives  the  corpus  spongiosum  (Fig.  1077).  The 
root  of  the  penis  is  connected  to  the  symphysis  pubis  by  the  suspensory  ligament. 
Structure  (Fig.  1083). — Each  corpus  cavernosum  is  composed  of  erectile  tissue. 
The  erectile  tissue  is  surrounded  by  a  strong  fibrous  envelope,  the  tunica  albuginea, 
corporum  cavernosum,  consisting  of  two  sets  of  fibres — the  one,  longitudinal  in  direc- 
tion, being  common  to  the  two  corpora  cavernosa,  and  investing  them  in  a  com- 
mon covering;  the  other,  internal,  circular  in  direction,  and  being  proper  to  each 
corpus  cavernosum.  The  internal  circular  fibres  of  the  two  corpora  cavernosa 
form,  by  their  junction  in  the  mesial  plane,  an  incomplete  partition  or  septum, 
the  septum  penis,  between  the  two  bodies. 


SUSPENSORY 
LIGAMENT 


FIG.  1079.  —The  clartos.    (Poirier  and  Charpy.) 


FIG.  1080. — From  the  peripheral  portion  of  the  corpus 
cavernosum  penis  under  a  low  magnifying  power.  1,  a, 
capillary  network;  b,  cavernous  spaces;  2,  connection  of 
the  arterial  twigs  (a)  with  the  cavernous  spaces.  (Copied 
from  Langer.) 


The  septum  between  the  two  corpora  cavernosa  is  thick  and  complete  behind, 
but  in  front  it  is  incomplete,  and  consists  of  a  number  of  vertical  bands,  which  are 
arranged  like  the  teeth  of  a  comb,  whence  the  name  which  it  has  received,  septum 
pectiniforme.  These  bands  extend  between  the  dorsal  and  the  urethral  surface 
of  the  corpora  cavernosa.  The  fibrous -in vestment  of  the  corpora  cavernosa  is 
extremely  dense,  of  considerable  thickness,  and  consists  of  bundles  of  shining 
white  fibres,  with  an  admixture  of  well-developed  elastic  fibres,  so  that  it  is  pos- 
sessed of  great  elasticity. 

From  the  internal  surface  of  the  fibrous  envelope,  as  well  as  from  the  sides  of 
the  septum,  are  given  off  a  number  of  bands  or  cords  which  cross  the  interior  of 
each  crus  in  all  directions,  subdividing  it  into  a  number  of  separate  compart- 


1468  THE   MALE    ORGANS    OF    GENERATION 

merits,  and  giving  the  entire  structure  a  spongy  appearance.  These  bands  and 
cords  are  called  trabeculae  corponim  cavernosum,  and  consist  of  white  fibrous 
tissue,  elastic  fibres,  and  plain  muscular  fibres.  In  them  are  continued  numer- 
ous arteries  and  nerves. 

The  component  fibres  of  which  the  trabeculae  are  composed  are  larger  and 
stronger  around  the  circumference  than  at  the  centre  of  the  corpora  cavernosa; 
they  are  also  thicker  behind  than  in  front.  The  interspaces,  on  the  contrary,  are 
larger  at  the  centre  than  at  the  circumference,  their  long  diameter  being  directed 
transversely;  they  are  largest  anteriorly.  They  are  called  cavernous  spaces  and 
are  occupied  by  venous  blood,  and  are  lined  by  a  layer  of  flattened  cells  similar 
to  the  endothelial  lining  of  veins  (Fig.  1080). 

The  whole  of  the  structure  of  the  corpora  cavernosa  contained  within  the 
fibrous  sheath  consists,  therefore,  of  a  sponge-like  tissue  the  areolar  spaces  of 
which  freely  communicate  with  each  other  and  are  filled  with  venous  blood. 
The  spaces  may  therefore  be  regarded  as  large  cavernous  veins. 

The  arteries  bringing  the  blood  to  these  spaces  are  the  arteries  of  the  corpora 
cavernosa  and  branches  from  the  dorsal  artery  of  the  penis,  which  perforate  the 
fibrous  capsule,  along  the  upper  surface,  especially  near  the  forepart  of  the  organ. 

These  arteries  on  entering  the  cavernous  structure  divide  into  branches  which 
are  supported  and  enclosed  by  the  trabeculae.  Some  of  these  terminate  in  a 
capillary  network,  the  branches  of  which  open  directly  into  the  cavernous  spaces 
(Fig.  1080);  others  assume  a  tendril-like  appearance,  and  form  convoluted  and 
somewhat  dilated  vessels,  which  were  named  by  Mtiller  helicine  arteries  (arteriae 
helicinae).  They  project  into  the  spaces,  and  from  them  are  given  off  small 
capillary  branches  to  supply  the  trabecular  structure.  They  are  bound  down  in 
the  spaces  by  fine  fibrous  processes,  and  are  more  abundant  in  the  back  part  of  the 
corpora  cavernosa. 

The  blood  from  the  cavernous  spaces  is  returned  by  a  series  of  vessels,  some  of 
which  emerge  in  considerable  numbers  from  the  base  of  the  glans  penis  and  con- 
verge on  the  dorsum  of  the  organ  to  form  the  deep  dorsal  vein ;  others  pass  out  on  the 
upper  surface  of  the  corpora  cavernosa  and  join  the  dorsal  vein;  some  emerge  from 
the  under  surface  of  the  corpora  cavernosa, and,  receiving  branches  from  the  corpus 
spongiosum,  wind  around  the  sides  of  the  penis  to  terminate  in  the  dorsal  vein; 
but  the  greater  number  pass  out  at  the  root  of  the  penis  and  join  the  prostatic  plexus. 

The  Corpus  Spongiosum  (corpus  cavernosum  urethrae)  (Figs.  1075,  1077,  and 
1078). — The  corpus  spongiosum  encloses  the  urethra,  and  is  situated  in  the  groove 
on  the  under  surface  of  the  corpora  cavernosa  penis.  It  commences  posteriorly 
below  the  superficial  layer  of  the  triangular  ligament  of  the  urethra,  between 
the  diverging  crura  of  the  corpora  cavernosa,  where  it  forms  a  rounded  enlarge- 
ment, the  bulb  of  the  urethra,  and  terminates  anteriorly  in  another  expansion,  the 
glans  penis  (Figs.  1074, 1075,  1077,  and  1078),  which  overlaps  the  anterior  rounded 
extremity  of  the  corpora  cavernosa.  The  central  portion,  or  body  of  the  corpus 
spongiosum,  is  cylindrical,  and  tapers  slightly  from  behind  forward. 

The  Bulb  of  the  Urethra  (bulbus  urethrae')  (Figs.  1073,  1077,  and  1078)  varies 
in  size  in  different  subjects;  it  receives  a  fibrous  investment  from  the  superficial 
layer  of  the  triangular  ligament,  and  is  surrounded  by  the  Accelerator  urinae  mus- 
cle. The  urethra  enters  the  bulb  nearer  its  upper  than  its  lower  surface,  being  sur- 
rounded by  a  layer  of  erectile  tissue,  a  thin  prolongation  of  which  is  continued 
backward  around  the  membranous  and  prostatic  portions  of  the  canal  to  the  neck 
of  the  bladder,  lying  between  the  two  layers  of  muscular  tissue.  The  portion  of  the 
bulb  below  the  urethra  presents  a  partial  division  into  two  lobes  (hemisphaeria 
bulbi  urethrae),  being  marked  externally  by  a  linear  raphe,  whilst  internally  there 
projects,  for  a  short  distance,  a  thin  fibrous  median  septum  (septum  bulbi  urethrae), 
which  is  more  distinct  in  early  life. 


THE   PENIS 


1469 


Structure. — The  corpus  spongiosum  consists  of  a  strong  fibrous  envelope 
enclosing  a  trabecular  structure,  which  contains  in  its  meshes  erectile  tissue.  The 
fibrous  envelope  is  thinner,  whiter  in  color,  and  more  elastic  than  that  of  the  corpora 


CAVERNOUS 
BRANCH 


DORSAL  ARTERY 


CORPUS  CAVERNOSUM 


CLANS  PENIS 


SN 

INTERNAL  PUDIC 
ARTERY 


FIG.  1081. — Diagram  of  the  arteries  of  the  penis.     (Testut.) 


cavernosa  of  the  penis.  The  trabeculae  are  more  delicate,  more  nearly  uniform 
in  size,  and  the  meshes  between  them  smaller  than  in  the  corpora  cavernosa, 
their  long  diameter,  for  the  most  part,  corresponding  with  that  of  the  penis. 
The  external  envelope  or  outer  coat  of  the  corpus  spongiosum  is  formed  partly 
of  unstriped  muscular  fibre,  and  a 
layer  of  the  same  tissue  immediately 
surrounds  the  canal  of  the  urethra. 

Ligaments  of  the  Penis. — The  sus- 
pensory ligament  (ligamentum  sus- 
pensorium  penis}  (Fig.  1076)  is  firm 
and  fibrous.  It  passes  from  the  front 
of  the  symphysis  pubis  to  the  tunica 
albuguinea  of  the  corpora  cavernosa. 
The  ligamentum  fundiforme  penis 
(Fig.  1073),  formerly  called  the  sus- 
pensory ligament,  arises  from  the 
linea  alba,  sheath  of  the  rectus, 
superficial  fascia,  and  symphysis 
pubis,  and  surrounds  the  penis  in 
a  loop,  being  attached  more  distal- 
ward  than  is  the  suspensory  liga- 
ment, and  usually  passes  into  the 
scrotum.  It  is  composed  of  elastic 
tissue. 

Vessels  and  Nerves  of  the  Penis. — 
The  arteries  (Fig.  1081)  of  the  penis 
come  from  branches  of  the  internal 
pudic  artery.  The  deep  arteries  of 
the  penis  give  the  chief  supply  to 
the  erectile  tissue  of  the  corpora 
cavernosa,  and  the  dorsal  artery  also 
sends  branches  to  it ;  the  artery  of 
the  bulb  (p.  693)  supplies  the  erectile 
tissue  of  the  corpus  spongiosum.  The  chief  blood-supply  of  the  glans  is  from 
the  dorsal  artery  (p.  694).  In  the  trabeculae  the  arteries  are  very  small  and  often 
twisted.  The  twisted  vessels  are  called  helicine  arteries.  The  small  arteries 
open  directly  into  the  venous  spaces.  The  veins  of  the  penis  empty  directly  into 


SUPERFICIAL    DORSAL  VEIN 
EXTERNAL    PUDIC    VEIN 

OBTURATOR    VEIN 


FIG.  1082.— Veins  of  the  penis.      (Testut.) 


1470  THE  MALE  ORGANS  OF  GENERATION 

the  prostatic  plexus  or  into  the  deep  dorsal  vein,  which  empties  into  the  prostatic 
plexus.  On  each  side  of  the  deep  dorsal  vein  is  a  dorsal  artery  and  external 
to  each  dorsal  artery  is  a  dorsal  nerve  (Fig.  1083).  The  superficial  dorsal  vein 
(Figs.  1082  and  1083),  receiving  small  veins  from  the  prepuce,  passes  back 
beneath  the  skin,  reaches  the  symphysis  and  divides  into  two  branches,  each  of 
which  passes  to  the  corresponding  superficial  external  pudic  vein. 

The  lymphatics  of  this  region  have  been  studied  carefully  by  Poirier,  Cuneo, 
and  Delamare,1  which  book  I  have  freely  used. 

The  lymphatics  of  the  skin  of  the  penis  and  prepuce  are  continuous  (Fig.  499). 
Those  on  the  internal  surface  of  the  prepuce  are  continuous  with  those  of  the  glans. 
The  trunks  of  the  cutaneous  lymphatics  anastomose  with  each  other,  ascend  by 
the  dorsal  vein,  and  terminate  in  the  inguinal  glands.  The  trunks  'from  the  glans 

converge  toward  the  frsenum  ;  they 

SUPERFICIAL   DOR-  ,,  i      ,          ,,  i.  > 

SAL  VEIN  then  ascend  to  the  median  part  of 


DEEP 
FASCIA 


sides  unite.  Several  collectors  as- 
cend on  the  dorsum  to  the  inguinal 
and  femoral  glands. 

The  superior  wall  of  the  anterior 
portion  of  the  urethra  is  drained  by 
the  lymphatic  trunks  from  the  glans. 
From  the  rest  of  the  penile  urethra 

3ULBO-CAVERNOUS    ARTERY/~~-~LJ ^  il  1  1        j.'  '  ±  ' i.\       J.1  1 

-ANTERIOR  BRANCH          j  URETHRA  the  lymphatics  unite  with  the  trunks 

spoNoioluM  from  the  penis,  and  most  of  them  ter- 

FIG.  1083.— The  penis  in  transverse  section,  showing          ininate    ill    the    Same    Way,    although 

the  blood-vessels.     (Testut.)  „       .  . J 

one  of  them  passes  between  the 

Recti  muscles  and  terminates  in  the  deeper  external  iliac  glands  or  in  the 
"internal  retro-crural  gland."2 

The  trunks  from  the  bulb  and  membranous  urethra  terminate  in  the  external 
iliac  glands,  the  "internal  retro-crural  gland,"  and  the  glands  along  the  internal 
pudic  artery  (Poirier,  Cuneo,  and  Delamare).  The  trunks  from  the  prostatic 
urethra  join  the  trunks  from  the  prostate  gland. 

The  nerves  are  derived  from  the  internal  pudic  nerve  and  the  pelvic  plexus.  On 
the  glans  and  bulb  some  filaments  of  the  cutaneous  nerves  have  Pacinian  bodies 
connected  with  them,  and,  according  to  Krause,  many  of  them  terminate  in  a 
peculiar  form  of  end-bulb. 

Surgical  Anatomy. — It  is  occasionally  necessary  to  remove  a  penis  for  malignant  disease. 
Usually,  removal  of  the  ante-scrotal  portion  is  all  that  is  necessary,  but  sometimes  it  is  requisite 
to  remove  the  whole  organ  from  its  attachment  to  the  rami  of  the  ossa  pubis  and  ischia.  The 
former  operation  is  performed  either  by  cutting  off  the  whole  of  the  anterior  part  of  the  penis 
with  one  sweep  of  the  knife,  or,  what  is  better,  cutting  through  the  corpora  cavernosa  from  the 
dorsum,  and  then  separating  the  corpus  spongiosum  from  them,  dividing  it  at  a  level  nearer  the 
glans  penis.  The  mucous  membrane  of  the  urethra  is  then  slit  up,  and  the  edges  of  the  flap 
attached  to  the  external  skin,  in  order  to  prevent  contraction  of  the  orifice,  which  would  other- 
wise take  place.  The  vessels  which  require  ligature  are  the  two  dorsal  arteries  of  the  penis,  the 
arteries  of  the  corpora  cavernosa,  and  the  artery  of  the  septum.  When  the  entire  organ  requires 
removal  the  patient  is  placed  in  the  lithotomy  position,  and  an  incision  is  made  through  the 
skin  and  subcutaneous  tissue  around  the  root  of  the  penis,  and  carried  down  the  median  line  of 
the  scrotum  as  far  as  the  perinseum.  The  two  halves  of  the  scrotum  are  then  separated  from 
each  other,  and  a  catheter  having  been  introduced  into  the  bladder  as  a  guide,  the  spongy  por- 
tion of  the  urethra  below  the  triangular  ligament  is  separated  from  the  corpora  cavernosa  and 
divided,  the  catheter  having  been  withdrawn  just  behind  the  bulb.  The  suspensory  ligament 
is  now  severed,  and  the  crura  separated  from  the  bone  with  a  periosteum  scraper,  and  the  whole 
penis  removed.  The  membranous  portion  of  the  urethra,  which  has  not  been  removed,  is  now 
to  be  attached  to  the  skin  at  the  posterior  extremity  of  the  incision  in  the  perinseum.  The 
remainder  of  the  wound  is  to  be  brought  together,  free  drainage  being  provided  for. 

1  The  Lymphatics.     By  Poirier,  Cune'o,  and  Delamare.    Translated  and  edited  by  Cecil  H.  Leaf. 

2  Ibid. 


DESCENT   OF   THE    TESTIS 


1471 


THE   TESTICLES  (TESTES)  AND  THEIR  COVERINGS  (Figs.  1086,  1087). 

The  testicles  are  two  glandular  organs,  which  secrete  the  semen;  they  are  situ- 
ated in  the  scrotum,  being  suspended  by  the  spermatic  cords.  At  an  early  period 
of  foetal  life  the  testes  are  contained  in  the  abdominal  cavity,  behind  the  peri- 
toneum, but  they  subsequently  descend  into  the  scrotum. 


DESCENT  OF  THE  TESTIS  (DESCENDUS  TESTIS). 

Each  testis  at  an  early  period  of  foetal  life  is  placed  at  the  back  part  of  the 
abdominal  cavity,  behind  the  peritoneum,  in  front  and  a  little  below  the  kidney. 
The  anterior  surface  and  sides  are  invested  by  peritoneum.  At  about  the  third 
month  of  intra-uterine  life  a  peculiar  structure,  the  gubernaculum  testis,  makes  its 
appearance.  This  structure  is  at  first  a  slender  band  which  extends  from  the 
situation  of  the  internal  ring  to  the  epididymis  and  body  of  the  testicle,  and  is 
then  continued  upward  in  front  of  the  kidney  toward  the  Diaphragm.  As  devel- 
opment advances  the  peritoneum  covering  the  testicle  encloses  it  and  forms  a 
mesentery,  the  mesorchium,  which  also  encloses  the  gubernaculum  and  forms  two 
folds — one  above  the  testicle,  and  the  other  below  it.  The  one  above  the  testicle  is 


CREMASTER 


ANASTOMOSIS 
OF  VEINS 


FIG.  1084. — Vaginal  tunics  of  the  testicle. 
(Poirier  and  Charpy.) 


FIG.  1085. — Ligament  of  the  scrotum. 
(Poirier  and  Charpy.) 


the  plica  vascularis,  and  contains  ultimately  the  spermatic  vessels;  the  one  below, 
the  plica  gubernatrix,  contains  the  lower  part  of  the  gubernaculum,  which  has  now 
grown  into  a  thick  cord ;  it  terminates  below  at  the  internal  ring  in  a  tube  of  peri- 
toneum, the  processus  vaginalis,  which  now  lies  in  the  inguinal  canal.  The  lower 
part  of  the  gubernaculum  by  the  fifth  month  has  become  a  thick  cord,  whilst  the 
upper  part  has  disappeared.  The  lower  part  can  now  be  seen  to  consist  of  a  cen- 
tral core  of  unstriped  muscle-fibre,  and  outside  this  of  a  firm  layer  of  striped 
elements,  connected,  behind  the  peritoneum,  with  the  abdominal  wall.  Later  on, 
about  the  sixth  month,  the  lower  end  of  the  gubernaculum  can  be  traced  into  the 
inguinal  canal,  extending  to  the  pubes,  and,  at  a  later  period,  to  the  bottom  of 
the  scrotum.  The  fold  of  peritoneum  constituting  the  processus  vaginalis  pro- 
jects itself  downward  into  the  inguinal  canal,  forming  a  gradually  elongating 
depression  or  cul-de-sac,  which  eventually  reaches  the  bottom  of  the  scrotum.  This 
cul-de-sac  is  now  invaginated  by  the  testicle,  as  the  body  of  the  foetus  grows,  for  the 
gubernaculum  does  not  grow  commensurately  with  the  growth  of  other  parts,  and 
therefore  the  testicle,  being  attached  by  the  gubernaculum  to  the  bottom  of  the 


1472  THE  MALE    ORGANS    OF   GENERATION 

scrotum,  is  prevented  from  rising  as  the  body  grows,  and  is  drawn  first  into  the 
inguinal  canal,  and  eventually  into  the  scrotum.  By  the  eighth  month  the  tes- 
ticle has  reached  the  scrotum,  preceded  by  the  lengthened  pouch  of  peritoneum, 
the  processus  vaginalis,  which  communicates  by  its  upper  extremity  with  the 
peritoneal  cavity.  Just  before  birth  the  upper  part  of  the  pouch  usually  becomes 
closed,  and  this  obliteration  extends  gradually  downward  to  within  a  short  dis- 
tance of  the  testis.  The  process  of  peritoneum  surrounding  the  testis,  which  is  now 
entirely  cut  off  from  the  general  peritoneal  cavity,  constitutes  the  tunica  vaginalis.1 

Mr.  Jacobson2  says  that  the  attachments  of  the  gubernaculum  above  are  to 
the  vas,  the  epididymis,  and  afterward  to  the  testicle.  The  lower  attachments 
of  the  gubernaculum,  some  of  which  are  temporary,  are  the  abdominal  wall, 
pubes  and  root  of  the  scrotum,  Scarpa's  triangle,  perinseum  and  scrotum.  The 
remains  of  the  scrotal  fibres  constitute  a  so-called  ligament  of  the  scrotum  or 
the  mesorchium,  which  causes  adhesion  between  the  testicle  and  skin  (Fig.  1086). 

In  the  female,  a  small  cord,  corresponding  to  the  gubernaculum  in  the  male, 
descends  to  the  inguinal  region  and  ultimately  forms  the  round  ligament  of  the 
uterus.  A  pouch  of  peritoneum  accompanies  it  along  the  inguinal  canal,  analogous 
to  the  processus  vaginalis  in  the  male ;  it  is  called  the  canal  of  Nuck. 

Surgical  Anatomy. — Abnormalities  in  the  formation  and  in  the  descent  of  the  testicle  may 
occur.  The  testicle  may  fail  to  be  developed,  or  it  may  be  fully  developed  and  the  vas  deferens 
may  be  undeveloped  in  whole  or  in  part;  or,  again,  both  testicle  and  vas  deferens  may  be  fully 
developed,  but  the  duct  may  not  become  connected  to  the  gland.  The  testicle  may  fail  in  its 
descent  (cryptorchismus)  or  it  may  descend  into  some  abnormal  position  (ectopia  testis) .  Thus  it 
may  be  retained  in  the  position  where  it  was  primarily  developed,  below  the  kidney;  or  it  may 
descend  to  the  internal  abdominal  ring,  but  fail  to  pass  through  this  opening;  it  may  be  retained 
in  the  inguinal  canal,  which  is  perhaps  the  most  common  position;  or  it  may  pass  through  the 
external  abdominal  ring  and  remain  just  outside  it,  failing  to  pass  to  the  bottom  of  the  scrotum. 
On  the  other  hand,  it  may  get  into  some  abnormal  position;  it  may  pass  the  scrotum  and  reach 
the  perinseum,  or  it  may  fail  to  enter  the  inguinal  canal,  and  may  find  its  way  through  the  fem- 
oral ring  into  the  crural  canal,  and  present  itself  on  the  thigh  at  the  saphenous  opening.  Ectopia 
testis  is  due  to  the  absence,  overdevelopment  or  malposition  of  some  portion  of  the  gubernacu- 
lum. There  is  still  a  third  class  of  cases  of  abnormality  in  the  position  of  the  testicle,  where  the 
organ  has  descended  in  due  course  into  the  scrotum,  but  is  malplaced.  The  most  common  form 
of  this  is  where  the  testicle  is  inverted;  that  is  to  say,  the  organ  is  rotated,  so  that  the  epididymis 
is  connected  to  the  front  of  the  scrotum,  and  the  body,  surrounded  by  the  tunica  vaginalis,  is 
directed  backward.  In  these  cases  the  vas  deferens  is  to  be  felt  in  the  front  of  the  cord.  The 
condition  is  of  importance  in  connection  with  hydrocele  and  ha;matoeele,  and  the  position  of 
the  testicle  should  always  be  carefully  ascertained  before  performing  any  operation  for  these 
affections.  Again,  more  rarely,  the  testicle  may  be  reversed.  This  is  a  condition  in  which  the 
top  of  the  testicle,  indicated  by  the  globus  major  of  the  epididymis,  is  at  the  bottom  of  the 
scrotum,  and  the  vas  deferens  comes  off  from  the  summit  of  the  organ. 

THE  COVERINGS  OF  THE  TESTICLE  (Fig.  1088). 

The  coverings  of  the  testicle  are  the  following: 

Skin        )      0 

T>.  >     Scrotum. 

Dartos    j 

Intercolumnar  or  External  spermatic  fascia. 

Cremasteric  fascia. 

Infundibuliform  or  Fascia  propria  (Internal  spermatic  fascia). 

Tunica  vaginalis. 

The  Testicular  Bag  or  Scrotum  (Figs.  1086  and  1087). — The  testicular  bag  or 
scrotum  is  a  cutaneous  pouch  which  contains  the  testes  and  part  of  the  spermatic 
cords.  It  is  divided  on  its  surface  into  two  lateral  portions  by  a  median  line  or 

1  The  obliteration  of  the  process  of  peritoneum  which  accompanies  the  cord,  and  is  hence  called  the  funicular 
process,  is  often  incomplete.     See  section  on  Inguinal  Hernia. 

2  Diseases  of  the  Male  Organs  of  Generation. 


THE    COVERINGS    OF    THE    TESTICLE 


1473 


raphe*  (raphe  scroll),  which  is  continued  forward  to  the  under  surface  of  the  penis 
and  backward  along  the  middle  line  of  the  perinaeum  to  the  anus.  Of  these  two 
lateral  portions,  the  left  is  usually  longer  than  the  right,  and  corresponds  with  the 
usual  greater  length  of  the  spermatic  cord  on  the  left  side.  Its  external  aspect  varies 
under  different  circumstances:  thus  under  the  influence  of  warmth  and  in  old  and 
debilitated  persons  it  becomes  elongated  and  flaccid,  but  under  the  influence  of  cold 
and  in  the  young  and  robust  it  is  short,  corrugated,  and  closely  applied  to  the 
testes.  The  wrinkles  in  the  scrotum  are  called  rugae. 

The  scrotum  consists  of  two  layers,  the  integument  and  the  dartos. 


RIGHT    INGUINAL   CANAL 

(OPENED) 


CREMASTERIC   MUSCLE- 
AMD    FASCIA 
INTERCOLUMNAR 
FASCIA 


PERSISTENT  SEROUS 

CAVITY  AROUND 
CORD — EXCEPTIONAL 


TUNICA  VAQINALIS 

PARIETAL   LAYER 
—  -INFUNDIBULIFORM 

FASCIA 
NON-PEDUNCULATED 


RIGHT    HALF   OF   SCROTUM     SKIN 


LEFT    HALF   OF   SCROTUM 


FIG.  1086. — The  scrotum.     On  the  left  side  the  cavity  of  the  tunica  vaginalis  has  been  opened  ;  on  the 
right  side  only  the  layers  superficial  to  the  cremaster  have  been  removed.     (Testut.) 

The  Integument. — The  integument  is  very  thin,  of  a  brownish  color,  and  gen- 
erally thrown  into  folds  or  rugae.  It  is  provided  with  sebaceous  follicles,  the 
secretion  of  which  has  a  peculiar  odor,  and  is  beset  with  thinly-scattered,  crisp 
hairs,  the  roots  of  which  are  seen  through  the  skin. 

The  Dartos  (tunica  dartos)  (Figs.  1079  and  1086). — The  dartos  is  a  thin  layer,  of 
loose  tissue,  endowed  with  contractility;  it  forms  the  proper  tunic  of  the  scrotum, 
is  continuous  around  the  base  of  the  scrotum,  with  the  two  layers  of  the  super- 
ficial fascia  of  the  groin  and  perinaeum,  and  sends  inward  a  distinct  septum, 
the  septum  of  the  scrotum  (septum  scroll]  (Fig.  1086),  which  divides  it  into  two 
cavities  for  the  two  testes,  the  septum  extending  between  the  raphe'  and  the. 
under  surface  of  the  penis  as  far  as  its  root. 

The  dartos  is  closely  united  to  the  skin  externally,  but  connected  with  the 

93 


1474 


THE    MALE    ORGANS    OF   GENERATION 


subjacent  parts  by  delicate  areolar  tissue,  upon  which  it  glides  with  the  greatest 
facility.  The  dartos  is  very  vascular,  and  consists  of  a  loose  areolar  tissue  con- 
taining unstriped  muscular  fibre,  but  no  fat.  Its  contractibility  is  slow,  and 
excited  by  cold  and  mechanical  stimuli,  but  not  by  electricity. 

The  Intercolumnar  or  Spermatic  Fascia  (Fig.  1086). — The  intercolumnar 
fascia  is  a  thin  membrane  derived  from  the  margin  of  the  pillars  of  the  external 
abdominal  ring,  during  the  descent  of  the  testis  in  the  foetus,  which  is  prolonged 
downward  around  the  surface  of  the  cord  and  testis.  It  is  separated  from  the 


EXTERNAL 

ABDOMINAL 

RING 


ACCESSORY 

SLIP  OF 

ORIGIN  OF 

CREMASTER 

MUSCLE 


SPERMATIC 
CORD 


CREMASTER 
MUSCLE 


SEPTUM 
SCR01 


VAS 
DCFERENS 


SPERMATIC 
ARTERY 


•NERVE-FILAMENTS 
OF  SPERMATIC 
PLEXUS 
DEFERENTIAL 
ARTERY 


INFUNDIBULIFORM 
FASCIA 


SPERMATIC 
PLEXUS 

EPIDIDYMIS 
PARIETAL 
LAYER   OF 
TUNICA 
VAGINAL! 


dartos  by  loose  areolar  tissue,  which  allows  of  considerable  movement  of  the 
latter  upon  it,  but  is  intimately  connected  with  the  succeeding  layers. 

The  Cremasteric  Fascia  (fascia  cremasterica)  (Figs.  1086  and  1087). — The 
cremasteric  fascia  consists  of  scattered  bundles  of  muscular  fibres,  the  Cremaster 
muscle  (m.  cremaster)  (Figs.  1086  and  1087)  connected  together  into  a  continuous 
covering  by  intermediate  areolar  tissue.  The  muscular  fibres  are  continuous 
with  the  lower  border  of  the  Internal  oblique  muscle. 


THE  COVERINGS  OF  THE  TESTICLE 


1475 


The  Infundibuliform  Fascia  (tunica  vaginalis  communis)  [testis  etfuniculi  sper- 
matici])  (Figs.  1086  and  1087). — The  infundibuliform  fascia  is  a  thin  membranous 


Skin. 
Dartos. 

External  spermatic  fascia. 
Cremasteric  fascia. 
Infundibuliform  fascia 
Parietal  tunica  vayhtnli.i. 
Visceral  tunica  vaginalis.-.. 
Tunica  vasculosa. 
Tunica  albuginea. ... 

A  lobule  of  the  testicle..^ 


A  septum. J 

Mediastinum.. 

Digital  fossa.-. 

Spermatic  vein. 

Epididymis. 

Vas  deferens. . 

Artery  to  vas. 

Spermatic  artery. 

Internal  cremaster 

muscle. 


FIG.  1088. — Transverse  section  through  the  left  side  of  the  scrotum  and  the  left  testicle.     The  sac  of  the 
tunica  vaginalis  is  represented  in  a  distended  condition.     (Del6pine.) 

layer,  which  loosely  invests  the  surface  of  the  cord.  It  is  a  continuation  downward 
of  the  fascia  transversal  is.  Beneath  it  is  a  quantity  of  loose  connective  tissue  which 
connects  this  layer  of  fascia  with  the  spermatic  cord  and  posterior  parts  of  the  tes- 


SPERMATIC 
ARTERY 


.CHEMASTERIC 
ARTERY 


DEFERENTIAL 
"ARTERY 

SEMINAL 

"DUCT 


POSTERIOR 
"•GROUP  OF 
VEINS 


.ANASTOMOSIS 

OF  VEINS 


FIG.  1089.  — The  arteries  of  the  testicle  and  the  cord.     (Poirier'and  Charpy.) 

ticle.  This  connective  tissue  is  continuous  above  with  the  subserous  areolar  tissue  of 
the  abdomen.    These  two  layers,  the  infundibuliform  fascia  and  the  tissue  beneath 


1476 


THE    MALE    ORGANS    OF    GENERATION 


it,  are  known  collectively  as  the  fascia  propria.  The  infundibuliform  fascia  com- 
pletely encloses  the  testicle  and  epididymis  and  is  fused  with  the  parietal  lamina 
of  the  tunica  vaginalis  propria  testis. 

The  Tunica  Vaginalis  (tunica  vaginalis  propria  testis}. — The  tunica  vagi- 
nalis is  described  with  the  testis  (p.  1480). 

Vessels  and  Nerves. — The  arteries  supplying  the  coverings  of  the  testis  are: 
the  superficial  and  deep  external  pudic,  from  the  femoral;  the  superficial  perineal 
branch  of  the  internal  pudic;  and  the  cremasteric  branch  from  the  deep  epigastric. 
The  veins  follow  the  course  of  the  corresponding  arteries.  The  lymphatics  term- 
inate in  the  inguinal  glands.  The  nerves  are:  the  ilio-inguinal  branch  of  the 
lumbar  plexus,  the  two  superficial  perineal  branches  of  the  internal  pudic  nerve, 
the  inferior  pudendal  branch  of  the  small  sciatic  nerve,  and  the  genital  branch  of 
the  genito-f  emoral  nerve. 


TRANSVERSALIS 
FASCIA 


DEEP 

EPIGASTRIC 
ARTERY 


LIGAMENT 
OF  CLOQUET 


SPERMATIC 
ARTERY 

PAMPINIFORM 
PLEXUS 


SPERMATIC 
CORD 


FIG.  1090. — The  spermatic  cord  and  the  ligament  of  Cloquet.     (Poirier  and  Charpy.) 


THE    SPERMATIC    CORD    (FUNICULUS    SPERMATICUS) 

(Figs.  1086,  1087,  1090,  1091). 

The  spermatic  cord  extends  from  the  internal  abdominal  ring,  where  the 
structures  of  which  it  is  composed  converge,  to  the  back  part  of  the  testicle.  In 
the  abdominal  wall  the  cord  passes  obliquely  along  the  inguinal  canal,  lying  at 
first  beneath  the  Internal  oblique  muscle  and  upon  the  fascia  transversalis ;  but 
nearer  the  pubes  it  rests  upon  Poupart's  ligament,  having  the  aponeurosis  of 
the  External  oblique  in  front  of  it  and  the  conjoined  tendon  behind  it.  It  then 
escapes  at  the  external  ring,  and  descends  nearly  vertically  into  the  scrotum.  The 
left  cord  is  usually  rather  longer  than  the  right,  consequently  the  left  testis 
generally  hangs  somewhat  lower  than  its  fellow. 

Structure. — The  spermatic  cord  contains  the  spermatic  duct,  the  deferential 
artery  and  veins,  the  spermatic  artery,  the  pampiniform  plexus  of  veins,  the  sper- 
matic plexus,  and  the  deferential  plexus  of  the  sympathetic  nerve,  lymphatics,  and 
the  cord-like  remnant  of  the  funicular  process  of  peritoneum  called  the  ligament 


THE  SPERMATIC  CORD 


1477 


of  Gloquet  (Fig.  1090).  All  the  above  structures  are  held  together  by  connective 
tissue.  These  structures  are  ensheathed  by  the  infundibuliform  process  of  the  trans- 
versalis  fascia  (Fig.  1096  and  p.  1074).  This  fascia  is  thin  above  and  thicker  below, 
and  encloses  the  testicle  and  epididymis,  as  well  as  the  cord,  being  firmly  adherent 
to  the  parietal  layer  of  the  vaginal  tunic  of  the  testicle  and  with  the  posterior  portion 
of  the  testicle  and  epididymis.  Upon  this  fascia  are  the  fibres  of  the  Cremaster 
muscle,  which  spring  from  the  internal  oblique,  and  in  this  fascia  are  the  cremas- 
teric  artery,  the  genital  branch  of  the  genito-femoral  nerve,  and  external  sperma tic- 
veins.  This  fascia  is  surrounded  by  the  intercolumnar  or  spermatic  fascia,  which 
is  distinct  above,  but  not  below. 

Vessels  and  Nerves  of  the  Spermatic  Cord. — The  arteries  (Figs.  1089  and  1096)  of 
the  cord  are:  the  spermatic,  from  the  aorta;  the  artery  of  the  vas  deferens,  from 
the  superior  vesical;  the  cremasteric,  from  the  deep  epigastric. 


VAS 
DEFERENS 


SPERMATIC 
CORD 


FIG.  1091. — The  spermatic  cord  in  the  inguinal  canal.    (Poirier  and  Charpy.) 

The  spermatic  artery  (a.  spermatica  internd)  arises  from  the  abdominal  aorta 
below  the  renal  artery,  descends  by  the  Psoas  muscle,  crosses  the  ureter  and 
external  iliac  vessels,  meets  the  vas  deferens  at  the  internal  abdominal  ring, 
escapes  from  the  abdomen  at  the  internal  or  deep  abdominal  ring,  and  lying  in 
front  of  the  vas  deferens  accompanies  the  other  constituents  of  the  spermatic  cord 
along  the  inguinal  canal  and  through  the  external  abdominal  ring  into  the  scrotum. 
It  then  descends  to  the  testicle,  and,  becoming  tortuous,  divides  into  "several 
branches,  two  or  three  of  which,  the  epididymal  branches,  accompany  the  vas 
deferens  and  supply  the  epididymis,  anastomosing  with  the  artery  of  the  vas 
deferens  and  the  cremasteric  artery;  others,  the  glandular  branches,  pierce  the  back 
of  the  tunica  albuginea  and  supply  the  substance  of  the  testis. 

The  artery  of  the  vas  deferens,  a  branch  of  the  superior  vesical,  is  a  long  slender 
vessel  which  accompanies  the  vas  deferens,  ramifying  upqn  the  coats  of  that  duct, 
and  anastomosing  with  the  spermatic  artery  and  the  cremasteric  artery  near  the 
testis. 


1478 


THE   M4LE   ORGANS    OF    GENERATION 


The  cremasteric  artery  (a.  spermatica  externa)  is  a  branch  of  the  deep  epigas- 
tric artery.  It  accompanies  the  spermatic  cord  and  supplies  the  Cremaster 
muscle  and  other  coverings  of  the  cord,  anastomosing  with  the  spermatic  and 
deferential  arteries. 

The  spermatic  veins  (Figs.  1089, 1090, 1091,  and  1093)  emerge  from  the  back  of 
the  testis  and  receive  tributaries  from  the  epididymis;  they  unite  and  form  a  con- 
voluted plexus,  the  pampiniform  plexus  (plexus  .pampinif or  mis] ,  which  forms  the 
chief  mass  of  the  cord ;  the  vessels  composing  this  plexus  are  very  numerous,  and 
ascend  along  the  cord  in  front  of  the  vas  deferens;  below  the  external  or  super- 


CORPUS 
CAVERNOSUM 


COWPER'S 
GLAND 

BUtBO- 

CAVERNOSUS 

MUSCLE 


FIG.  1092. — Male  pelvic  organs    seen    from   right  side.    Bladder  and  rectum  distended;    relations  of  peritoneum 
to  the  bladder  and  rectum  shown  in  blue.    The  arrow  points  to  the  vesico-rectal  pouch.    (Corning.) 

ficial  abdominal  ring  they  unite  to  form  three  or  four  veins,  which  pass  along  the 
inguinal  canal,  and,  entering  the  abdomen  through  the  internal  or  deep  abdominal 
ring,  coalesce  to  form  two  veins.  These  again  unite  to  form  a  single  vein,  which 
opens  on  the  right  side  into  the  postcava  at  an  acute  angle,  and  on  the  left  side 
into  the  renal  vein  at  a  right  angle. 

The  lymphatic  vessels  of  the  scrotum  terminate  in  the  superficial  inguinal 
glands.'  The  lymphatics  of  the  testicle  join  the  lymphatics  of  the  epididymis  and  of 
the  visceral  layer  of  the  vaginal  tunic  of  the  testicle,  and  ascend  in  the  spermatic 
cord.  They  reach  the  lumbar  region  along  the  spermatic  blood-vessels  and  ter- 
minate in  the  juxta-aorta  glands,  and  sometimes  in  the  glands  in  front  of  the 
aorta.  The  lymphatics  of  the  seminal  duct  pass  to  the  external  iliac  glands. 

The  nerves  are  the  spermatic  plexus  from  the  sympathetic,  joined  by  filaments 
from  the  pelvic  plexus  which  accompany  the  artery  of  the  vas  deferens. 

The  Ligament  of  the  Scrotum. — See  Fig.  1085  and  p.  1472. 

Surgical  Anatomy. — The  scrotum  forms  an  admirable  covering  for  the  protection  of  the 
testicle.  This  body,  lying  suspended  and  loose  in  the  cavity  of  the  scrotum,  and  surrounded  by 


'/'///•;  TESTICLES 


1479 


a  serous  membrane,  is  capable  of  great  mobility,  and  can  therefore  easily  slip  about  within  the 
scrotum,  and  thus  avoid  injuries  from  blows  or  squeezes.  The  skin  of  the  scrotum  is  very 
elastic  and  capable  of  great  distention,  and  on  account  of  the  looseness  and  amount  of  subcu- 
taneous tissue  the  scrotum  becomes  greatly  enlarged  in  cases  of  (edema,  to  which  this  part  is 
especially  liable  on  account  of  its  dependent  position.  The  scrotum  is  frequently  the  seat  of 
epithelioma;  this  is  no  doubt  due  to  the  rugae  on  its  surface,  which  favor  the  lodgement  of  dirt, 
and  this,  causing  irritation,  is  the  exciting  cause  of  the  disease.  Cancer  was  especially  common 
in  chimney-sweeps  from  the  lodgement  of  soot.  The  scrotum  is  also  the  part  most  frequently 
affected  by  elephantiasis. 

On  account  of  the  looseness  of  the  subcutaneous  tissue  considerable  extravasations  of  blood 
may  take  place  from  very  slight  injuries.  It  is  therefore  generally  recommended  never  to  apply 
leeches  to  the  scrotum,  since  they  may  lead  to  considerable  ecchymosis,  but  rather  to  puncture 
one  or  more  of  the  superficial  veins  of  the  scrotum  in  cases  where  local  bloodletting  from  this 
part  is  judged  to  be  desirable.  The  muscular  fibre  in  the  dartos  causes  contraction  and  consider- 
able diminution  in  the  size  of  a  wound  of  the  scrotum,  as  after  the  operation  of  castration,  and 
is  of  assistance  in  keeping  the  edges  together  and  covering  the  exposed  parts. 


FIG.  1093. — Spermatic  veins.      (Testut.) 


THE  TESTICLES  (TESTES)  (Figs.  1084,  1086,  1087,  1094,  1095). 

The  testicles  are  suspended  in  the  scrotum  by  the  spermatic  cords.  As  the  left 
spermatic  cord  is  rather  longer  than  the  right  one,  the  left  testicle  hangs  somewhat 
lower  than  its  fellow.  Each  gland  is  of  an  oval  form,  compressed  laterally,  and 
having  an  oblique  position  in  the  scrotum,  the  upper  extremity  (extremitus  superior) 
being  directed  forward  and  a  little  outward,  the  lower  extremity  (extremitus  infe- 
rior],  backward  and  a  little  inward;  the  anterior  convex  border  (margo  anterior) 


1480 


THE  MALE  ORGANS  OF  GENERATION 


looks  forward  and  downward;  the  posterior  or  straight  border  (marcjo  posterior], 
to  which  the  cord  is  attached,  backward  and  upward. 

The  anterior  border  and  lateral  surfaces  (fades  latcralis  el  fades  medialis),  as  well 
as  both  extremities  of  the  organ,  are  convex,  free,  smooth,  and  invested  by  the 
visceral  layer  of  the  tunica  vaginalis.  The  posterior  border,  to  which  the  cord  is 
attached,  receives  only  a  partial  investment  from  that  membrane.  Lying  upon 
the  outer  edge  of  this  posterior  border  is  a  long,  narrow,  flattened  body,  named, 
from  its  relation  to  the  testis,  the  epididymis  (dido not;,  testis)  (Figs.  1094  and  1095). 
The  curve  of  the  epididymis  is  convex  outward  and  backward.  It  consists  of 
a  central  portion  or  body  (corpus  epididymidis) ;  an  upper  enlarged  extremity,  the 
head  or  globus  major  (caput  epididymidis) ;  and  a  lower  pointed  extremity,  the  tail 
or  globus  minor  (cauda  epididymidis}.  The  globus  major  is  directed  inward  and 
is  intimately  connected  with  the  upper  end  of  the  testicle  by  means  of  its  efferent 
ducts,  and  the  globus  minor  is  connected  with  its  lower  end  by  cellular  tissue  and  a 
reflection  of  the  tunica  vaginalis.  The  globus  minor  bends  suddenly  and  passes 
into  the  seminal  duct,  the  direction  of  which  is  upward  and  backward.  The  outer 
surface  and  upper  and  lower  ends  of  the  epididymis  are  free  and  covered  by 
serous  membrane;  the  body  is  also  completely  invested  by  it,  excepting  along  its 
posterior  border,  and  between  the  body  and  the  testicle  is  a  pouch  or  cul-de-sac, 
named  the  digital  fossa  (sinus  epididymidis) .  Above  this  fossa  is  a  fold  of  the 
tunica  vaginalis,  which  is  called  the  ligamentum  epididymidis  superior,  and  below 
it  is  another  fold,  the  ligamentum  epididymidis  inferior.  The  epididymis  is  con- 
nected to  the  back  of  the  testis  by  a  fold  of  the  serous  membrane.  Attached  to 
the  up^er  end  of  the  testis,  close  to  the  globus  major,  is  a  small  body.  It  is  oblong 
in  shape  and  has  a  broad  base.  Attached  to  the  globus  major  of  the  epididymis 
is  another  small  body,  which  is  pear-shaped  and  has  a  stalk.  These  bodies  are 
believed  to  be  the  remains  of  the  upper  extremity  of  the  Miillerian  duct,  and  are 
termed  the  hydatids  of  Morgagni;  some  observers,  however,  regard  the  stalked 
hydatid  as  being  a  rudiment  of  the  pronephros.  The  body  with  a  broad  base  is 
the  non-pedunculated  hydatid  (appendix  testis  [Morgagnii])  (Figs.  1086  and  1094) ; 


Spermatic  cord. 


Tunica  vaginalis, 
parietal  layer. 

Non-pedunculated 
hydatid. 
Digital 
fossa. 


Artery  of 
~  cord. 


MEDIASTINUM 
TESTIS 


ALBUGINEA 


FIG.  1094. — The  testis  in  situ,  the  tunica  vaginalis 
having  been  laid  open. 


FIG.  1095.  —Frontal  section  of    the  testicle  and 
epididymis.      (Poirier  and  Charpy.) 


the  pear-shaped  body  is  the  pedunculated  hydatid  (appendix  epididymidis) .     When 
the  testicle  is  removed  from  the  body,  the  position  of  the  vas  deferens,  on  the 


THE  TESTICLES 


1481 


Tunica  Vaginalis 


Tunica  Albug 
Its  Septa 


Tubuli 

seminiferi 

contorti. 


Ductuli 
efferentes. 


Tubuli 

seminiferi 

recti. 


posterior  surface  of  the  testicle  and  inner  side  of  the  epididymis,  marks  the  side 
to  which  the  gland  has  belonged. 

Size  and  Weight. — The  average  dimensions  of  this  gland  are  from  one  and  a 
half  to  two  inches  in  length,  one  inch  in  breadth,  and  an  inch  and  a  quarter  in 
the  antero-posterior  diameter,  and  the  weight  varies  from  six  to  eight  drachms, 
the  left  testicle  being  a  little  the  larger. 

The  Tunics  of  the  Testicle.— The  testis  is  invested  by  three  tunics— the  tunica 
vaginalis,  tunica  albuginea,  and  tunica  vasculosa. 

The  Proper  Sheath  of  the  Testicle  or  the  Tunica  Vaginalis  (tunica  vaginalis  propria 
testis)  (Figs.  1084, 1086, 1087,  1088,  and  1096)  is  the  serous  covering  of  the  testicle 
and  epididymis.  It  is  a  pouch 
of  serous  membrane,  derived 
from  the  peritoneum  (processus 
vaginalis  peritonaei)  during  the 
descent  of  the  testis  in  the  foetus 
from  the  abdomen  into  the  scro- 
tum. After  its  descent  that  por- 
tion of  the  pouch  which  extends 
from  the  internal  ring  to  near  the 
upper  part  of  the  gland,  the 
funicular  process,  becomes  oblit- 
erated, the  lower  portion  re- 
maining as  a  shut  sac,  which 
invests  the  outer  surface  of  the 
testis,  and  is  reflected  on  to  the 
internal  surface  of  the  scrotum; 
hence  it  may  be  described  as 
consisting  of  a  visceral  and 
parietal  portion. 

The  Visceral  Portion  (lamina 
visceralis)  of  the  tunica  vaginalis 
propria  covers  the  outer  surface 
of  the  testis,  as  well  as  the  epi- 
didymis, connecting  the  latter  to  the  testis  by  means  of  a  distinct  fold.    From  the 
posterior  border  of  the  gland  it  is  reflected  on  to  the  internal  surface  of  the  infun- 
dibuliform  process  of  the  transversalis  fascia,  and  between  the  tunic  and  the  fascia 
is  a  layer  of  unstriated  muscle  fibres,  the  Internal  cremaster  muscle  (Fig.  1088). 

The  Parietal  Portion  (lamina  parietalis)  of  the  tunica  vaginalis  propria  is  the 
reflected  portion.  It  is  far  more  extensive  than  the  visceral  portion,  extending 
upward  for  some  distance  in  front  and  on  the  inner  side  of  the  cord,  and  reaching 
below  the  testis.  The  inner  surface  of  the  tunica  vaginalis  is  free,  smooth,  and 
covered  by  a  layer  of  endothelial  cells.  The  interval  between  the  visceral  and 
parietal  layers  of  this  membrane  constitutes  the  cavity  of  the  tunica  vaginalis  and 
contains  a  small  amount  of  serous  fluid. 

The  obliterated  portion  of  the  pouch  may  generally  be  seen  as  a  fibro-cellular 
thread,  the  ligament  of  Cloquet  (rudimentum  processus  vaginalis}  (Fig.  1090),  lying 
in  the  loose  areolar  tissue  around  the  spermatic  cord;  sometimes  this  may  be  traced 
as  a  distinct  band  from  the  upper  end  of  the  inguinal  canal,  where  it  is  connected 
with  the  peritoneum,  down  to  the  tunica  vaginalis;  sometimes  it  gradually  becomes 
lost  on  the  spermatic  cord.  Occasionally  no  trace  of  it  can  be  detected.  In  some 
cases  it  happens  that  the  pouch  of  peritoneum  does  not  become  obliterated,  but 
the  sac  of  the  peritoneum  communicates  with  the  tunica  vaginalis.  This  may 
give  rise  to  one  of  the  varieties  of  oblique  inguinal  hernia;  or  in  other  cases  the 


FIG.  1096. --Vertical  section  of  the  testicle,  to  show  the  arrange- 
ment of  the  ducts. 


1482  THE  MALE  ORGANS  OF  GENERATION 

pouch  may  contract,  but  not  become  entirely  obliterated;  it  then  forms  a  minute 
canal  leading  from  the  peritoneum  to  the  tunica  vaginalis.1 

The  Tunica  Albuginea  (Figs.  1088, 1095,  and  1096). — The  tunica  albuginea  is  the 
fibrous  covering  of  the  testis.  It  is  a  dense  fibrous  membrane,  of  a  bluish-white 
color,  composed  of  bundles  of  white  fibrous  tissue,  which  interlace  in  every  direc- 
tion. Its  outer  surface  is  covered  by  the  tunica  vaginalis,  except  at  the  points  of 
attachment  of  the  epididymis  to  the  testicle,  and  along  its  posterior  border,  where 
the  spermatic  vessels  enter  the  gland.  This  membrane  surrounds  the  glandular 
structure  of  the  testicle,  and  at  its  posterior  border  forms  a  projection,  triangular 
in  shape  and  cellular  in  structure,  which  is  reflected  into  the  interior  of  the  gland, 
forming  an  incomplete  vertical  septum,  called  the  mediastinum  testis. 

The  Mediastinum  Testis  (corpus  Highmori)  (Figs.  1088,  1095,  and  1096)  extends 
from  the  upper,  nearly  to  the  lower,  extremity  of  the  gland,  and  is  wider  above 
than  below.  From  the  front  and  sides  of  this  septum  numerous  slender  fibrous 
cords  and  imperfect  septa,  called  the  trabeculae  (septula  testis]  (Fig.  1096),  are 
given  off,  which  radiate  toward  the  surface  of  the  organ,  and  are  attached  to  the 
inner  surface  of  the  tunica  albuginea.  This  scaffolding  of  connective  tissue  divides 
the  parenchyma  (parenchyma  testis)  of  the  organ  into  a  number  of  incomplete 
spaces,  which  are  somewhat  cone-shaped,  being  broad  at  their  bases  at  the  sur- 
face of  the  gland,  and  becoming  narrower  as  they  converge  to  the  mediastinum. 
The  mediastinum  supports  the  blood-vessels,  lymphatics,  and  ducts  of  the  testis 
in  their  passage  to  and  from  the  substance  of  the  gland,  and  contains  numerous 
fine  canals,  into  which  open  the  very  small  tubules  of  the  proper  substance  of 
the  testicle. 

The  Tunica  Vasculosa  (Fig.  1088). — The  tunica  vasculosa  is  the  vascular  layer  of 
the  testis,  and  consists  of  a  plexus  of  blood-vessels  held  together  by  a  delicate 
areolar  tissue.  It  covers  the  inner  surface  of  the  tunica  albuginea  and  the  dif- 
ferent septa  in  the  interior  of  the  gland,  and  therefore  forms  an  internal  invest- 
ment to  all  the  spaces  of  which  the  gland  is  composed. 

Structure  of  the  Testicle  and  Epididymis  (Fig.  1096). — The  glandular  struc- 
ture of  the  testis -consists  of  numerous  lobules  (lobuli  testis}.  Their  number,  in  a 
single  testis,  is  estimated  by  Berres  at  250,  and  by  Krause  at  400.  They  differ  in  size 
according  to  their  position, those  in  the  middle  of  the  gland  being  larger  and  longer. 
The  lobules  are  conical  in  shape,  the  base  of  each  being  directed  toward  the  circum- 
ference of  the  organ,  the  apex  toward  the  mediastinum.  Each  lobule  is  contained  in 
one  of  the  intervals  between  the  fibrous  cords  and  vascular  processes  which  extend 
between  the  mediastinum  testis  and  the  tunica  albuginea,  and  consists  of  from  one 
to  three  or  more  minute  convoluted  tubes,  which  anastomose  with  each  other,  the 
tubuli  seminiferi  contorti.  The  contorted  tubes  unite  at  the  apex  of  the  lobules  and 
form  the  straight  tubes  (tubuli  seminiferi  recii).  The  straight  tubes  pass  into  the 
mediastinum  testis  and  form  the  network  known  as  the  rete  testis  of  Haller  (Fig. 
1096).  The  rete  testis  is  lined  with  flattened  epithelium.  The  tubes  are  lined  with 
columnar  ciliated  epithelium.  The  efferent  ducts  (ductuli  efferentes  testis)(Fig.  1096), 
about  twelve  to  fifteen  in  number,  arise  from  the  rete.  The  contorted  tubes  may 
be  separately  unravelled  by  careful  dissection  under  water,  and  may  be  seen  to 
commence  either  by  free  caecal  ends  or  by  anastomotic  loops.  The  total  number  of 
tubes  is  considered  by  Munro  to  be  about  300  and  the  length  of  each  about  sixteen 
feet;  by  Lauth  their  number  is  estimated  at  840,  and  their  average  length  two  feet 
and  a  quarter.  The  diameter  varies  from  ^ru-  to  rsir  °f  an  mcn-  The  tubuli  are 
pale  in  color  in  early  life,  but  in  old  age  they  acquire  a  deep-yellow  tinge  from 
containing  much  fatty  matter.  Each  tube  consists  of  a  basement  layer,  formed 

1  It  is  recorded  that  in  the  post-mortem  examination  of  Sir  Astley  Cooper  a  minute  funicular  canal  was  found 
01  each  side  of  the  body.  Sir  Astley  Cooper  states  that  when  a  student  he  suffered  from  inguinal  hernia;  prob- 
ably this  was  of  the  congenital  variety,  and  the  canal  found  after  death  was  the  remains  of  the  one  down  which 
the  hernia  travelled  (Lancet,  1824,  vol.  ii.  p.  116). — ED.  of  15th  English  edition. 


THE  TESTICLES  1483 

of  epithelioid  cells  united  edge  to  edge,  outside  of  which  are  other  layers  of 
flattened  cells  arranged  in  interrupted  laminae,  which  give  to  the  tube  an  appear- 
ance of  striation  in  cross-section.  The  cells  of  the  outer  layers  gradually  pass 
into  the  interstitial  tissue.  Within  the  basement-membrane  are  epithelial  cells 
arranged  in  several  irregular  layers,  which  are  not  always  clearly  separated,  but 
which  may  be  arranged  in  three  different  groups.  Among  these  cells  may  be  seen 
the  spermatozoids  in  different  stages  of  development.  1.  Lining  the  basement- 
membrane  and  forming  the  outer  zone  is  a  layer  of  cubical  cells,  with  small 
nuclei;  these  are  known  as  the  lining  cells  or  spermatogonia.  The  nucleus  of  some 
of  them  may  be  seen  to  be  in  the  process  of  indirect  division  (karyokinesis),  and 
in  consequence  of  this  daughter  cells  are  formed,  which  constitute  the  second  zone. 
2.  Within  this  first  layer  is  to  be  seen  a  number  of  larger  cells  with  clear  nuclei, 
arranged  in  two  or  three  layers;  these  are  the  intermediate  cells  or  spermatocytes. 
Most  of  these  cells  are  in  a  condition  of  karyokinetic  division,  and  the  cells  which 
result  from  this  division  form  those  of  the  next  layer,  the  spermatoblasts  or  sperma- 
tids.  3.  The  third  layer  of  cells  therefore  consists  of  the  spermatoblasts  or  sperma- 
tids,  and  each  of  these,  without  further  subdivision,  becomes  a  spermatozoid.  They  • 
are  ill-defined  granular  masses  of  protoplasm,  of  an  elongated  form,  with  a  nucleus 
which  becomes  the  head  of  the  future  spermatozoid.  In  addition  to  these  three 
layers  of  cells  others  are  seen,  which  are  termed  the  supporting  cells,  or  cells  of 
Sertoli.  They  are  elongated  and  columnar,  and  project  inward  from  the  basement- 
membrane  toward  the  lumen  of  the  tube.  They  give  off  numerous  lateral  branches, 
which  form  a  reticulum  for  the  support  of  the  three  groups  of  cells  just  described. 
As  development  of  the  spermatozoids  proceeds  the  latter  group  themselves  around 
the  inner  extremities  of  the  supporting  cells.  The  nuclear  part  of  the  sperma- 
tozoid, which  is  partly  embedded  in  the  supporting  cell,  is  differentiated  to  form  the 
head  of  the  spermatozoid,  while  the  cell  protoplasm  becomes  lengthened  out  to 
form  the  middle  piece  and  tail,  the  latter  projecting  into  the  lumen  of  the  tube. 
Ultimately  the  heads  are  separated  and  the  spermatozoids  are  set  free. 

Spermatogenesis. — The  stages  in  the  development  of  the  spermatozoids  are  as 
follows:  The  spermatogonia  become  enlarged  to  form  the  spermatocytes,  and 
each  spermatocyte  subdivides  into  two  cells,  and  each  of  these  again  divides  into 
two  spermatids  or  young  spermatozoids,  so  that  the  spermatocyte  gives  origin  to 
four  spermatozoids. 

The  process  of  spermatogenesis  bears  a  close  relation  to  that  of  maturation  of 
the  ovum.  The  spermatocyte  is  equivalent  to  the  immature  ovum.  It  undergoes 
subdivision,  and  ultimately  gives  origin  to  four  spermatozoids,  each  of  which  con- 
tains, therefore,  only  one-fourth  of  the  chromatin  elements  of  the  nucleus  of  the 
spermatocyte.  In  the  process  of  maturation  of  the  ovum  its  nucleus  divides,  one- 
half  being  extended  as  the  first  polar  body.  The  remaining  half  of  the  nucleus 
again  subdivides,  one-half  being  extended  as  the  second  polar  body.  The  portion 
of  the  nucleus  which  is  retained  to  form  the  female  pronucleus  of  the  now  matured 
ovum  contains,  therefore,  only  one-fourth  of  the  chromatin  elements  of  the 
original  nucleus,  and  thus  the  spermatozoid  and  the  matured  ovurn,  so  far  as 
their  nuclear  elements  are  concerned,  may  be  regarded  as  of  the  same  morpho- 
logical value. 

The  tubules  are  enclosed  in  a  delicate  plexus  of  capillary  vessels,  and  are  held 
together  by  an  intertubular  connective  tissue,  which  presents  large  interstitial 
spaces  lined  by  endothelium,  which  are  believed  to  be  the  rootlets  of  lymphatic 
vessels  of  the  testis. 

The  Aberrant  Ducts  of  the  Epididymis  (ductuli  aberrantes)  are  tortuous  and  end 
in  blind  extremities.  The  superior  aberrant  duct  (ductus  abcrrans  superior)  is  in  the 
globus  major  and  joins  the  rete  testis.  The  inferior  aberrant  duct  (ductus  aberrans 
inferior)  (Fig.  1096)  is  in  the  tail  of  the  epididymis,  and  takes  origin  from  the 


1484  THE  MALE  ORGANS  OF  GENERATION 

duct  of  the  epididymis  or  the  seminal  duct.  It  is  a  persistent  canal  of  the  Wolffian 
body.  It  extends  up  the  cord  for  two  or  three  inches  and  terminates  by  a  blind 
extremity,  which  is  occasionally  bifurcated.  It  may  be  as  much  as  fourteen  inches 
in  length.  Its  structure  is  similar  to  that  of  the  seminal  duct. 

The  Seminal  Duct  or  Vas  Deferens  (ductus  deferens)  (Figs.  1089,  1090,  1091,  1096, 
1097,  and  1 135). — The  seminal  duct  or  vas  deferens,  the  excretory  duct  of  the  testis, 
is  the  continuation  of  the  epididymis.  Commencing  at  the  lower  part  of  the  globus 
minor,  it  ascends  along  the  posterior  border  of  the  testis  and  inner  side  of  the  epi- 
didymis, and  along  the  back  part  of  the  spermatic  cord,  through  the  inguinal  canal 
to  the  internal  or  deep  abdominal  ring.  From  the  ring  it  curves  around  the  outer 
side  of  the  internal  epigastric  artery  and  vein,  crosses  the  external  iliac  vessels,  and 
descends  into  the  pelvis  at  the  side  of  the  bladder;  it  arches  backward  and  down- 
ward to  its  base,  crossing  over  the  obliterated  hypogastric  artery  and  to  the  inner 
side  of  the  ureter.  At  the  base  of  the  bladder  it  lies  between  that  viscus  and  the 
rectum,  running  along  the  inner  border  of  the  seminal  vesicle.  Behind  the  bladder 
it  becomes  enlarged  and  sacculated,  forming  the  ampulla  (ampulla  ductus  deferentis) 
(Fig.  1097),  and  then,  becoming  narrowed  at  the  base  of  the  prostate,  unites  with 
the  duct  of  the  seminal  vesicle  to  form  the  ejaculatory  duct  (Fig.  1098).  From  the 
internal  abdominal  ring  to  the  middle  of  the  ampulla  the  seminal  duct  is  beneath 
the  peritoneum.  The  vas  deferens  offers  a  hard  and  cord-like  sensation  to  the 
fingers;  it  is  about  two  feet  in  length,  of  cylindrical  form,  and  about  a  line  and 
a  quarter  in  diameter.  Its  walls  are  dense,  measuring  one-third  of  a  line,  and  its 
canal  is  extremely  small,  measuring  about  half  a  line. 

Structure. — The  vas  deferens  consists  of  three  coats:  1.  An  external  or  areolar 
coat  (tunica  adventitia).  2.  A  muscular  coat  (tunica  muscularis) ,  which  in  the 
greater  part  of  the  tube  consists  of  two  layers  of  unstriped  muscular  fibre :  an  inner 
layer  of  thin  longitudinal  fibres  (stratum  internum)  existing  only  at  the  beginning, 
a  thick  layer  of  circular  fibres  (stratum  medium),  and  a  thick  external  layer  of 
longitudinal  fibres  (stratum  externum).  3.  An  internal  or  mucous  coat  (tunica 
mucosd),  which  is  pale,  and  arranged  in  longitudinal  folds;  its  epithelial  cells  are 
of  the  columnar  variety. 

Organ  of  Giraldes  (paradidi/mis). — This  term  is  applied  to  a  small  body  of 
rounded  shape  in  the  lower  end  of  the  spermatic  cord,  in  front  of  the  blood- 
vessels. It  consists  of  a  small  collection  of  minute  vesicles  and  a  small  collection 
of  convoluted  tubules.  These  tubes  are  lined  with  columnar  ciliated  epithelium, 
and  probably  represents  the  remains  of  a  part  of  the  Wolffian  body. 

Surgical  Anatomy. — Abnormalities  in  the  descent  and  position  of  the  testicle  have  been 
discussed  (p.  1472).  The  testicle  may  require  removal  for  malignant  disease,  tuberculous  disease, 
cystic  disease,  in  cases  of  large  hernia  testis,  and  in  some  instances  of  incompletely  descended  or 
misplaced  testicles.  The  operation  of  double  castration  has  also  been,  during  the  last  few  years, 
performed  for  enlargement  of  the  prostate  gland ;  for  it  has  been  found  that  removal  of  the  tes- 
ticles is  followed  by  very  rapid  and  often  considerable  diminution  in  the  size  of  the  prostate. 
The  operation  is,  however,  one  of  severity,  and  is  frequently  followed  by  death  in  these  cases, 
performed,  as  it  necessarily  is,  in  old  men.  Reginald  Harrison  has  proposed  to  substitute  for  it 
excision  of  a  portion  of  each  vas  deferens  (vasectomy).  The  operation  of  castration  is  a  com- 
paratively simple  one.  An  incision  is  made  into  the  cavity  of  the  tunica  vaginalis  from  the 
external  ring  to  the  bottom  of  the  scrotum.  The  coverings  are  shelled  off  the  organ,  and  the 
mesorchium,  stretching  between  the  back  of  the  testicle  and  the  scrotum,  divided.  The  cord  is 
then  isolated,  and  an  aneurism  needle,  armed  with  a  double  ligature,  passed  under  it,  as  high 
as  is  thought  necessary,  and  the  cord  tied  in  two  places,  and  divided  between  the  ligatures. 
Sometimes,  in  cases  of  malignant  disease,  it  is  desirable  to  open  the  inguinal  canal  and  tie  the 
cord  as  near  the  internal  abdominal  ring  as  possible. 

A  collection  of  serous  fluid  in  the  sac  of  the  vaginal  tunic  of  the  testicle  is  known  as  an  ordinary 
or  testicular  hydrocele.  In  congenital  hydrocele  a  communication  remains  between  the  tunica 
vaginalis  testis  and  the  peritoneal  cavity.  This  communication  should  have  closed  during 
development.  In  infantile  hydrocele  the  tunica  vaginalis  and  part  of  the  funicular  process  are 
distended  with  fluid,  but  the  funicular  process  is  closed  above  and  the  cavity  of  the  hydrocele 


THE  TESTICLES 


1485 


does  not  communicate  with  the  peritoneal  cavity.  In  encysted  hydroceleof  the  cord  the  funicular 
process  is  closed  above  and  below,  but  between  these  points  is  not  obliterated.  In  funicular 
hydrocele  the  funicular  process  is  closed  below  and  open  above.  Congenital  hydrocele  can 
usually  be  cured  by  the  application  of  a  truss.  This  obliterates  the  upper  end  of  the  funicular 
process,  and  the  obliteration  once  begun  may  proceed  to  completion.  If  it  does  not,  the  condi- 
tion has  become  an  infantile  hydrocele.  An  infantile  hydrocele  can  usually  be  cured  by  multiple 
punctures  or  tapping.  The  same  is  true  of  encysted  hydrocele  of  the  cord.  In  hydrocele  of  the 
funicular  process  wear  a  truss  for  a  time  and  then  tap.  In  ordinary  testicular  hydrocele  incise 
and  pack,  or  incise  and  suture,  the  cut  edge  of  the  parietal  layer  of  the  tunic  to  the  skin,  or  extir- 
pate the  parietal  layer  of  the  tunic.  A  successful  method  is  that  of  Longuet.  He  makes  an 
incision,  pulls  out  the  testicle,  and  allows  all  the  coats  except  the  skin  to  fall  behind  and  make 
a  sheath  for  the  cord.  These  coats  are  held  behind  by  one  catgut  suture.  A  bed  is  made  for 
the  testicle  beneath  the  skin  toward  the  septum  of  the  scrotum.  The  testicle  is  rotated  on  its 
long  axis  and  placed  in  the  bed,  and  the  skin  is  sutured  above  it.  This  operation  is  known 
as  extraserous  transposition.  If  a  portion  of  bowel  enters  an  open  vaginal  process  the  condition 
is  congenital  hernia. 

In  infantile  hernia  the  funicular  process  is  closed  above  but  not  below,  and  the  hernia  descends 
in  a  specfal  sac  back  of  the  vaginal  tunic.  If  the  hernia  pushes  down  on  the  vaginal  process  and 
causes  it  to  double  on  itself  the  condition  is  encysted  infantile  hernia. 


.Head 

Middle 
'  piece 


'Main  piece 


• 

Head — gfl 

Middle _l 

piece 


The  Semen  and  the  Spermatozoids. — Semen  consists  of  spermatozoids  with  liquids 
and  solids.  Part  of  the  semen  comes  from  the  testicles,  most  of  it  from  accessory 
glands — that  is,  from  the  glands  of  the  seminal  ducts,  the  seminal  vesicles,  the  pros- 
tate gland,  and  Cowper's  glands.  Semen  is  a  viscid, 
whitish  fluid,  of  alkaline  reaction  and  characteristic 
odor.  It  contains  water  and  about  18  per  cent,  of 
solid  matter.  In  this  solid  matter  are  fat,  choles- 
terin,  lecithin,  proteids,  nuclein,  xanthin,  chlorides, 
sulphates,  and  phosphates  of  sodium  and  potassium. 
Bottcher's  crystals,  which  can  be  obtained  from 
semen,  are  composed  of  phosphate  of  spermine. 
Spermine  is  a  nitrogenous  substance.  The  fluid 
portion  of  semen  carries  and  probably  nourishes  the 
living  cells  known  as  spermatozoids. 

The  spermatozoids  (Fig.  1097)  are  minute,  thread- 
like bodies,  which  constitute  the  essential  elements 
of  the  semen.  Each  consists  of  a  head,  a  middle 
piece  or  body,  and  an  elongated  filament  or  tail. 
The  head,  on  surface  view,  appears  oval  in  shape, 
but  if  seen  in  profile  it  is  narrow  and  pointed  at  its 
free  end.  It  represents  the  modified  nucleus  of  the 
spermatid,  and  consists  chiefly  of  chromatin,  and  so 
stains  readily  with  nuclear  reagents;  it  is  covered  by 
a  thin  cap  of  protoplasm.  The  body  is  a  short 
cylindrical  or  conical  piece,  intervening  between  the 
head  and  tail,  and  is  therefore  sometimes  spoken  of 
as  the  intermediate  segment.  The  tail  is  about  four 
times  the  combined  lengths  of  the  head  and  body;  its  terminal  part  is  extremely 
fine,  and  is  named  the  end-piece.  Contained  within  the  body  and  tail  is  an  axial 
filament,  surrounded,  except  in  the  end -piece,  by  a  thin  layer  of  protoplasm;  this 
axial  filament  terminates  just  below  the  head  in  a  rounded  knob  or  button.  In 
virtue  of  their  tails,  which  act  as  propellers,  the  spermatozoids,  in  the  fresh  con- 
dition, are  capable  of  free  movement,  and  if  placed  in  favorable  surroundings 
(e.  g.,  in  the  female  passages)  may  retain  their  vitality  for  some. days  or  even 
weeks.  • 


of 
the 
tail 


—End  piece 


FIG.  1097. — Spermatozoid  of  man. 
At  the  left  a  surface  view  is  shown; 
at  the  right  a  lateral  view.  X  1200. 
(Szymonowicz,  after  Retzius.) 


1486  THE  MALE  ORGANS  OF  GENERATION 


THE  SEMINAL  VESICLES  (VESICULAE  SEMINALES)  (Figs.  1098,  1099). 

The  seminal  vesicles  are  two  tabulated  membranous  pouches  placed  between 
the  base  of  the  bladder  and  the  rectum,  serving  as  reservoirs  for  the  semen,  and 
secreting  a  fluid  to  be  added  to  the  secretion  of  the  testicles.  Each  sac  is  some- 
what pyramidal  in  form,  the  broad  end  being  directed  backward  and  the  narrow 
end  forward  toward  the  prostate.  It  measures  about  two  and  a  half  inches  in 
length,  about  five  lines  in  breadth,  and  two  or  three  lines  in  thickness.  They 
vary,  however,  in  size,  riot  only  in  different  individuals,  but  also  in  the  same 
individual  on  the  two  sides.  The  upper  surface  is  in  contact  with  the  base  of 
the  bladder,  extending  from  near  the  termination  of  the  ureters  to  the  base  of 
the  prostate  gland.  The  under  surface  rests  upon  the  rectum,  from  which  it  is 
separated  by  the  recto-vesical  fascia.  -  Their  posterior  extremities  diverge  from 


VAS 
DEFERENS 


COWPER'S  EXCRETORY 

GLANDS  DUCT 

FIG.  1098. — The  urinary  bladder,  distended,  with  surrounding  structures,  viewed  from  behind.     (Spalteholz.) 

each  other.  Their  anterior  extremities  are  pointed,  and  converge  toward  the  base 
of  the  prostate  gland,  where  each  joins  with  the  corresponding  seminal  duct  to 
form  the  ejaculatory  duct.  Along  the  inner  margin  of  each  vesicle  runs  the 
enlarged  and  convolutsd  vas  deferens.  The  inner  border  of  the  vesicle  and  the 
corresponding  seminal  duct  form  the  lateral  boundaries  of  a  triangular  space, 
limited  behind  by  the  recto-vesical  peritoneal  fold;  the  portion  of  the  bladder 
included  in  this  space  rests  on  the  rectum. 

Each  vesicle  consists  of  a  single  tube,  coiled  upon  itself  and  giving  off  several 
irregular  caecal  diverticula  (Fig.  1098),  the  separate  coils,  as  well  as  the  diverticula, 
being  connected  together  by  fibrous  tissue.  When  uncoiled  this  tube  is  about  the 
diameter  of  a  quill,  and  varies  in  length  from  four  to  six  inches;  it  terminates  pos- 
teriorly in  a  cul-de-sac;  its  anterior  extremity  becomes  constricted  into  a  narrow 
straight  duct,  the  excretory  duct  (ductus  excretorius]  (Fig.  1099),  which  joins  with 
the  corresponding  seminal  duct,  and  forms  the  ejaculatory  duct. 


THE  TESTICLES 


1487 


The  Ejaculatory  Ducts  (ductus  ejaculatorii)  (Fig.  1099). — The  ejaculatory  ducts 
are  two  in  number,  oneon  each  side.  Each  duct  is  formed  by  the  junction  of  the  duct 
of  the  seminal  vesicle  with  the  seminal  duct.  Each  duct  is  about  three-quarters  of 
an  inch  in  length ;  it  commences  at  the  base  of  the  prostate,  and  runs  forward  and 
downward  between  the  middle  and  lateral  lobes  of  that  gland,  and  along  the  side 
of  the  sinus  pocularis,  to  terminate  by  a  separate  slit-like  orifice  close  to  or  just 
within  the  margins  of  the  sinus.  The  ducts  diminish  in  size  and  also  converge 
toward  their  termination. 

Structure. — The  seminal  vesicles  are  composed  of  three  coats:  an  external  or 
areolar  (tunica  adventitia) ;  a  middle  or  muscular  coat  (tunica  muscularis) ,  which 
is  thinner  than  in  the  seminal  duct,  and  is  arranged  in  two  layers,  an  outer, 
longitudinal,  and  inner,  circular;  an  internal  or  mucous  coat  (tunica  mucosa), 
which  is  pale,  of  a  whitish-brown  color,  and  presents  a  delicate  reticular  struc- 
ture, like  that  seen  in  the  gall-bladder,  but  the  meshes  are  finer.  The  epithelium 
is  columnar. 


VERUMONTANUM 


EXCRETORY 
DUCT 


EJACULATORY 
DUCT 


SINUS 
POCULARIS 


URETHRA 

FIG.  1099. — The  ejaculatory  ducts  viewed  from  in  front  and  above.     (Spalteholz.> 


The  coats  of  the  ejaculatory  ducts  are  extremely  thin.  They  are:  an  outer 
fibrous  layer,  which  is  almost  entirely  lost  after  the  entrance  of  the  duct  into  the 
prostate;  a  layer  of  muscular  fibres,  consisting  of  an  outer  thin  circular  and  an 
inner  longitudinal  layer;  and  the  mucous  membrane. 

Vessels  and  Nerves. — The  arteries  supplying  the  seminal  vesicles  are  derived 
from  the  middle  and  inferior  vesical  and  middle  haemorrhoidal.  The  veins  and 
lymphatics  accompany  the  arteries.  The  lymphatics  anastomose  on  the  surface 
of  the  vesicle.  The  trunks  from  this  network  anastomose  with  the  lymphatics 
of  the  bladder  and  prostate,  and  pass  to  the  external  and  internal  iliac  glands. 
The  nerves  are  derived  from  the  pelvic  plexus. 

Surgical  Anatomy. — The  seminal  vesicles  are  often  the  seat  of  an  extension  of  the  dis- 
ease in  cases  of  tuberculosis  of  the  testicle,  and  should  always  be  examined  through  the  rectum 
before  coming  to  a  decision  with  regard  to  castration  in  this  affection.  The  vesicles  have  been 
deliberately  extirpated  for  local  tuberculosis.  In  gonorrhoea  the  seminal  vesicles  may  become 
acutely  inflamed  (acute  seminal  vesiculitis) .  Chronic  seminal  vesiculitis  may  follow  the  acute 
form  or  may  arise  insidiously  during  gonorrhoea. 


THE  FEMALE  ORGANS  OF  GENERATION. 


EXTERNAL  ORGANS  (PARTES  GENITALES  EXTERNAL  MULIEBRES). 

THE  external  organs  of  generation  in  the  female  are:  the  mons  Veneris,  the 
labia  majora  and  minora,  the  vestibule,  the  clitoris,  the  vaginal  bulb,  and  the 
glands  of  Bartholin.  The  term  vulva  (pudendum  muliebre),  as  generally  applied, 
includes  all  of  these  parts.  In  examining  the  structures  entering  into  the  formation 
of  the  vulva  we  find  the  homologues  of  most  of  the  structures  which  make  up  the 
male  genitals. 


FALLOPIAN  TUBE 
PAROOPHORON 


UTERINE  ORIFICE 
OF  FALLOPIAN  TUBE 


INFUNDIBULUM  OF 
FALLOPIAN  TUBE 


PAVILION  OF 
FALLOPIAN  TUBE 


ORGAN  OF 
ROSENMULLCR 


PERITONEUM 


LABIUM 
MINUS 
LABIUM 
MAJUS 


VESTIBULE  OF  VAGINA 

FIG.  1100. — Diagrammatic  representation  of  the  female  reproductive  organs  and  their  relations  to  the  bladder 

and  urethra,  lateral  view.    (Toldt.) 


Labia  majora 
Clitoris 

Bulbus  vestibuli 
Vestibular  Glands 
(of  Bartholin). 


Scrotum. 

Corpora  cavernosa. 
Corpus  spongiosum. 
Bulbo-urethral  Glands 
(of  Cowper). 


THE  LARGE  LIPS  OR  LABIA  MAJORA  (LABIA  MAJORA  PUDENDI) 

'(Figs.  1101,  1102,  1103). 

The  labia  majora  are  two  prominent  longitudinal  cutaneous  folds,  narrow 
behind  but  fuller  and  larger  toward  the  mons  Verieris,  and  enclosing  the  pudendal 
slit  (rami  pudendi)  or  common  urino-genital  opening.  Each  labium  majus  (labium 

94  (  1489  ) 


1490 


THE  FEMALE  ORGANS  OJ  GENERATION 


majus  pudendi)  has  two  surfaces,  an  outer,  which  is  covered  by  pigmented  skin 
with  numerous  sebaceous  glands  and  strong,  crisp  hairs,  and  an  inner,  which  is 
smooth  and  moist,  and  is  continuous  with  the  gen i to-urinary  mucous  tract.  In 
the  subcutaneous  areolo-fatty  tissue  of  each  labium  majus  the  round  ligament  of 
the  uterus  ends.  The  labia  are  joined  with  each  other  anteriorly  by  the  mons 
Veneris  or  anterior  commissure  (commissura  labiorum  anterior).  Posteriorly  they 


MONS  VENERIS 


ANTERIOR 

OMMISSURE 
OF  VULVA 


PREPUCE  OF 
CLITORIS 


POSTERIOR 

COMMISSURE 

OF  VULVA 


VULVA  I. 
CLEFT 


-PERINEUM 


POST-ANAL. 
FURROW 


FIG.  1101. — The  female  pudendum  or  vulva  with  the  labia  majora.    (Toldt.) 

appear  to  become  lost  in  the  neighboring  integument,  although  sometimes  con- 
nected by  a  slight  transverse  fold  in  front  of  the  anus,  the  posterior  commissure 
(commissura  labiorum  posterior)  or  posterior  boundary  of  the  vulvar  orifice.  The 
interval  between  the  posterior  commissure  and  the  anus,  about  an  inch  in  length, 
constitutes  the  obstetric  perinaeum. 

Blood-vessels,  Nerves,  and  Lymphatics. — The  arteries  of  the  labia  majora  are 
derived  from  the  superficial  external  pudic  arteries  and  from  perineal  branches  of  the 
internal  pudic  arteries.  Homologous  with  the  scrotum,  the  nerve-supply  is  derived 
from  branches  of  the  ilio-inguinal,  internal  pudic,  and  perineal  branches  of  the  small 
sciatic.  The  lymphatics  drain  into  the  superficial  inguinal  and  internal  iliac  lymph- 
nodes. 


THE  SMALL  LIPS,  NYMPHAE  OR  LABIA  MINQRA   (LABIA  MINORA 
PUDENDI)    (Figs.  1101,  1102,  1103). 

The  labia  minora,  or  nymphae,  are  two  smaller,  narrower  longitudinal  folds, 
with  a  delicate  covering  of  modified  skin,  and  usually  hidden  from  view  unless  the 
labia  majora  are  separated.  They  end  posteriorly  by  gradually  joining  the  labia 


THE  CLITORIS 


1493 


THE  CLITORIS  (Figs.  1102,  1103,  1105). 

The  clitoris  is  an  erectile  structure  which  is  the  morphologic  homologue  of  the 
penis;  unlike  the  penis,  however,  it  is  not  traversed  by  the  urethra.  It  is  situated 
beneath  the  anterior  commissure  (or  mons  Veneris)  partially  hidden  between  the 
anterior  extremities  of  the  labia  minora.  It  is  composed  of  a  body  and  two  crura; 
the  extremity  of  the  body  is  surmounted  by  a  small  glans. 


SUSPENSORY 
LIGAMENT  OF  OVARY 


BROAD    LIGAMENT 

or UTERUS 


FIG.  1 104. — Female  pelvic  organs  in  situ,  seen  from  above.    (Bardeleben.) 


CRESCENTIC  FRINGED  BILABIAL  BIPERFORATE  CRIBRIFORM 

FIG.  1105.— Varieties  of  hymen.    (Testut,  after  Rose.) 

The  body  of  the  clitoris,  composed  of  erectile  tissue,  is  about  an  inch  and  a  quarter 
in  length,  bent  upon  itself  so  that  the  angle  opens  downward.  It  tapers  toward 
the  glans,  is  enclosed  by  a  dense  fibrous  coat,  and  is  divided  by  an  incomplete 


1494 


THE  FEMALE  ORGANS  OF  GENERATION 


septum  corporum  cavernosum  into  two  semi-cylindrical  corpora  cavernosa  clitoridis, 
homologous  with  the  corpora  cavernosa  of  the  male.  A  suspensory  ligament  passes 
from  the  pubic  symphysis  to  the  fibrous  coat  of  the  body  of  the  clitoris.  Each 
corpus  cavernosum  diverges  from  its  fellow  to  form  the  crus  clitoridis.  Each  crus 
is  attached  to  the  pubic  arch  (pubis  and  ischium)  and  covered  by  the  Ischio- 
cavernosus  muscle  (m.  erector  clitoridis}. 

To  each  crus  of  the  clitoris  goes  a  branch  from  the  internal  pudic  artery,  which 
branch  is  known  as  the  deep  artery  of  the  clitoris.  The  dorsal  arteries  of  the  clitoris 
(arteriae  dorsalis  clitoridis)  from  the  internal  pudic  send  branches  to  the  glans. 
The  nerves  of  the  clitoris  consist  of  the  dorsal  nerves  of  the  clitoris  from  the  internal 
pudic  nerve  and  sympathetic  fibres  from  the  hypogastric  plexus. 


SUSPENSORY   LIGAMENT 
OF    CLITORIS 


GLANS  OF 
CLITORIS 

SPHINCTER 
VAGINAE 
MUSCLE 

ERECTOR 

CLITORIDIS 

MUSCLE 

ORIFICE    OF 

URETHRA 

LABI  A. 
MINORA 

CARUNCULAE 
MYRTIFORMES 

SPHINCTER 
VAGINAE 
MUSCLE 


TRANSVERSE 
PERINEI 
MUSCLE 


EXCRETORY 
DUCT 


GLAND  OF 
BARTHOLIN 


OMPRESSOR 
URETHRAE  MUSCLE 


TRANSVERSE 
PERINEI   MUSCLE 


FIG.  1106. — The  female  external  organs  of  generation  dissected.    (Spalteholz.) 

The  glans  clitoridis  is  a  minute  mass  of  erectile  tissue,  surmounting  the  tapering 
apex  of  the  body  of  the  clitoris.  It  is  covered  by  a  very  sensitive  epithelium,  and 
its  erectile  tissue,  like  that  of  the  glans  penis,  is  continuous  with  the  erectile  tissue 
of  the  bulbus  vestibuli,  the  homologue  of  the  corpus  spongiosum  of  the  male.  The 
praeputium  clitoridis  and  the  frenulum  clitoridis  have  already  been  described  (p.  1491) 
as  divisions  of  the  labia  minora. 

Arteries  and  Nerves  of  the  Clitoris. — The  body  and  the  crura  of  the  clitoris  derive 
their  blood-supply  from  the  deep  artery  of  the  clitoris  (arteria  pro/undo,  clitoridis) 
from  the  internal  pudic  artery.  Another  branch  of  this  artery,  the  dorsal  artery  of 


THE  HYMEN  1495 

the  clitoris  (arteria  dorsalis  clitoridis)  supplies  the  glans.  The  nerve-supply  is 
derived  from  the  dorsal  nerve  of  the  clitoris,  from  the  internal  pudic,  and  from  the 
hypogastric  sympathetic  plexus. 

THE  VAGINAL  BULB  (BULBUS  VESTIBULI)    (Fig.  1106). 

The  bulbus  vestibuli  may  be  regarded  as  the  homologue  of  the  bulb  portions  of 
the  corpus  spongiosum  of  the  male.  The  principal  morphological  difference  lies 
in  the  fact  that  the  two  halves  are  fused  in  the  male,  but  remain  separated  in  the 
female.  The  bulbus  vestibuli  consists  of  a  mass  of  minute  convoluted  blood- 
vessels, of  such  plexiform  arrangement  as  to  be  often  called  erectile  tissue,  arranged 
in  two  halves  on  either  side  of  the  vaginal  and  urethral  orifices.  Each  half  is  thicker 
or  more  massive  posteriorly,  while  anteriorly  it  is  attenuated  and  joins  its  fellow 
of  the  opposite  side  to  form  the  pars  intermedia,  continuous  with  the  erectile  tissue 
of  the  glans  clitoridis.  Each  half  of  the  bulbus  vestibuli  rests  against  the  lateral 
wall  of  the  vagina  and  lies  superficial  to  the  triangular  ligament.  Externally  and 
inferiority  it  is  covered  by  the  Bulbo-cavernosus  muscle. 

Arteries  and  Nerves  of  the  Bulbus  Vestibuli. — The  blood  is  supplied  by  the  artery 
to  the  bulb  (arteria  bulbi  vestibuli) ,  a  branch  of  the  internal  pudic  artery.  The  nerve- 
supply  is  by  branches  of  the  hypogastric  sympathetic  plexus. 

GLANDS  OF  BARTHOLIN  (GLANDULA  VESTIBULARIS  MAJOR 
[BARTHOLINI])  (Fig.  1106). 

On  each  side  of  the  posterior  part  of  the  commencement  of  the  vagina  is  a 
round  or  oblong  body,  of  a  reddish-yellow  color,  and  of  the  size  of  a  horse-bean, 

analogous  to  Cowper's  gland  in  the  male.  It  is  called  the  gland  of  Bartholin,  the 
gland  of  Duverney,  the  vulvo-vaginal  gland  or  the  suburethral  gland.  Bartholin's 
gland  lies  partly  in  the  inferior  or  anterior  leaf  of  the  triangular  ligament.  The 
posterior  portion  of  the  bulbus  vestibuli  and  the  Bulbo-cavernous  muscle  partly 
cover  it.  Each  gland  opens  by  means  of  a  long  single  duct  immediately  external 
to  the  hymen,  in  the  angle  or  groove  between  it  and  the  nympha  (Fig.  1105). 

INTERNAL  ORGANS  (PARTES  GENITALES  INTERNAE  MULIEBRES). 

The  internal  organs  of  generation  are — the  vagina,  the  uterus  and  its  appendages, 
the  Fallopian  tubes,  the  ovaries  and  their  ligaments. 

THE  VAGINA  (Figs.  1100,  1103,  1109). 

The  vagina  extends  from  the  vulva  to  the  uterus.  It  is  situated  in  the  cavity 
of  the  pelvis,  behind  the  bladder  and  in  front  of  the  rectum.  Its  direction  is 
curved  upward  and  backward,  at  first  in  the  line  of  the  pelvic  outlet,  and  afterward 
in  that  of  the  axis  of  the  cavity  of  the  pelvis.  Its  walls  are  ordinarily  in  contact, 
and  its  usual  shape  on  transverse  section  is  that  of  an  H,  the  transverse  limb 
being  slightly  curved  forward  or  backward,  whilst  the  lateral  limbs  are  somewhat, 
convex  toward  the  median  line.  Its  length  is  about  two  and  a  half  inches  along 
its  anterior  wall  (paries  anterior),  and  three  and  a  half  inches  along  its  posterior 
wall  (paries  posterior).  It  is  constricted  at  its  commencement,  and  becomes 
dilated  medially,  and  narrowed  near  its  uterine  extremity;  it  surrounds  the  vaginal 
portion  of  the  cervix  uteri,  a  short  distance  from  the  os,  its  attachment  extending 
higher  up  on  the  posterior  than  on  the  anterior  wall  of  the  uterus  (Fig.  1112). 


1496  THE  FEMALE  ORGANS  OF  GENERATION 

The  vaginal  axis  forms  with  the  uterine  axis  an  obtuse  angle  opening  forward, 
and,  as  a  rule,  a  little  greater  than  a  right  angle  (Fig.  1110).  The  fact  that  the 
attachment  of  the  vagina  to  the  cervix  is  above  the  external  os  causes  the  forma- 
tion of  a  recess  between  the  cervix  and  vaginal  wall,  known  as  the  vaginal  fornix 
(fornix  vaginae).  This  recess  is  deeper  posteriorly  than  it  is  laterally  or  in  front. 
The  anterior  portion  of  the  fornix  is  called  the  anterior  fornix  (Fig.  1103). 
The  posterior  portion  is  called  the  posterior  fornix  (Fig.  1103).  The  right  and 
left  portions  are  called  the  right  and  left  lateral  fcrnices.  The  vagina  opens  into 
the  uro-genital  cleft,  between  the  labia  minora  and  back  of  the  urethra  and 
clitoris.  It  opens  by  the  vaginal  orifice  (orificium  vaginae)  (Fig.  1102).  In  the 
virgin  the  opening  is  partly  closed  by  the  hymen  (p.  1492).  After  rupture 
of  the  hymen  atrophied  fragments  of  the  torn  membrane  remain  around 
the  vaginal  orifice,  and  are  known  as  the  carunculae  myrtifcrmes  (carunculae 
hymenales). 

Relations  (Figs.  1100  and  1103). — The  upper  part  of  the  anterior  wall  of  the 
vagina  is  in  relation  with  the  base  of  the  bladder,  being  separated  from  that  viscus 
by  lax  connective  tissue.  Lower  down  the  middle  line  of  the  anterior  wall  and 
closely  joined  to  it  is  the  urethra.  The  upper  part  of  the  posterior  wall,  near 
the  middle  line,  is  covered  for  a  quarter  of  an  inch  or  more  with  peritoneum, 
which  forms  the  anterior  wall  of  the  depths  of  the  recto-vaginal  pouch  of  perito- 
neum or  pouch  of  Douglas  (excavatio  rectouterina  [Douglasi])  (Fig.  1112),  between 
the  uterus  and  vagina  and  the  rectum.  The  portion  of  the  posterior  wall  below 
the  level  of  the  pouch  of  Douglas  is  placed  close  to  the  rectum,  a  layer  of  pelvic 
fascia  intervening.  As  the  vaginal  orifice  is  neared,  the  rectum  and  vagina 
separate,  and  interposed  between  them  is  a  mass  of  fibro-fatty  tissue  called  the 
perinaeum  or  perineal  body.  Its  sides  are  enclosed  between  the  Levatores  ani 
muscles.  The  ureter  toward  its  termination  (Fig.  1113)  lies  near  the  lateral  wall 
of  the  vagina,  passing  at  this  point  in  a  direction  downward,  inward,  and  slightly 
forward  to  reach  the  bladder.  The  vagina  near  its  termination  passes  through 
the  triangular  ligament,  and  upon  its  sides  are  the  bulbs  of  the  vestibule,  the 
glands  of  Bartholin,  and  the  Bulbo-cavernous  muscle. 

Structure. — The  vagina  consists  of  an  internal  mucous  lining,  of  a  muscular  coat, 
and  between  the  two  of  a  layer  of  erectile  tissue. 

The  Mucous  Membrane  (tunica  mucosa)  (Fig.  1109). — The  mucous  membrane  is 
continuous  above  with  that  lining  the  uterus.  Its  inner  surface  presents,  along 
the  anterior  and  posterior  walls,  a  longitudinal  ridge  or  raphe,  called  the  rugous 
columns  of  the  vagina  (columna  rugarum  anterior  el  posterior).  The  anterior  col- 
umn extends  downward  as  far  as  the  external  orifice  of  the  urethra,  forming  the 
carina  urethralis  vaginae.  Numerous  transverse  ridges  or  rugae  (rugae  vaginales) 
extend  outward  from  the  raphe  on  either  side.  These  rugae  are  divided  by  fur- 
rows of  variable  depth,  giving  to  the  mucous  membrane  the  appearance  of  being 
studded  over  with  conical  projections  or  papillae;  they  are  most  numerous  near 
the  orifice  of  the  vagina,  especially  in  females  before  parturition.  The  epithelium 
covering  the  mucous  membrane  is  of  the  squamous  variety.  The  submucous  tissue 
is  very  loose  and  contains  numerous  large  veins,  which  by  their  anastomoses 
form  a  plexus,  together  with  smooth  muscular  fibres  from  the  muscular  coat;  it 
is  regarded  by  Gussenbauer  as  an  erectile  tissue  (see  p.  1497).  It  contains  a 
number  of  mucous  crypts,  but  no  true  glands. 

The  Muscular  Coat  (tunica  muscularis). — The  muscular  coat  consists  of  two 
layers :  an  external  longitudinal,  which  is  far  the  stronger,  and  an  internal  circular 
layer.  The  longitudinal  fibres  are  continuous  with  the  superficial  muscular  fibres 
of  the  uterus.  The  strongest  fasciculi  are  those  attached  to  the  recto-vesical  fascia 
on  each  side.  The  two  layers  are  not  distinctly  separable  from  each  other,  but 


THE    VAGINA 


1497 


are  connected  by  oblique  decussating  fasciculi  which  pass  from  the  one  layer  to 
the  other.  Above  the  triangular  ligament  the  fibres  are  non-striated ;  in  the  region 
of  the  ligament  they  show  striations.  In  addition  to  this  the  vagina  at  its  lower 
end  is  surrounded  by  a  band  of  striped  muscular  fibres,  the  sphincter  vaginae 
(p.  463).  External  to  the  muscular  coat  is  a  layer  of  connective  tissue  containing 
a  large  plexus  of  blood-vessels. 

The  Erectile  Tissue. — The  erectile  tissue  consists  of  a  layer  of  loose  connective 
tissue  situated  between  the  mucous  membrane  and  the  muscular  coat;  embedded 
in  it  is  a  plexus  of  large  veins,  and  numerous  bundles  of  unstriped  muscular  fibres 
derived  from  the  circular  muscular  layer.  The  arrangement  of  the  veins  is 
similar  to  that  found  in  other  erectile  tissues. 


EXTERNAL 
ILIAC  GLANDS 


INTERNAL 
ILIAC  GLANDS 


LATERAL 
SACRAL  GLANDS 


AFFERENTS 
TO  EXTERNAL 
ILIAC  GLANDS 


AFFERENTS 
TO  INTERNAL 
LIAC  GLANDS 


RETROVAGINAL 
NODULES 


FIG.  1107. — The  lymphatics  of  the  vagina.    Schematic.    (Poirier  and  Charpy.) 

Blood-vessels,  Nerves,  and  Lymphatics. — The  arteries  of  the  vagina  are  branches 
of  the  vesico- vaginal  artery;  the  vaginal  branch  of  the  uterine  artery  (p.  688),  and 
branches  of  the  internal  pudic  and  middle  haemorrhoidal.  The  veins  form  an  abun- 
dant plexus  around  the  wall  of  the  vagina  and  pass  to  the  internal  iliac  veins.  The 
lymphatics  (Fig.  1107)  arise  from  two  communicating  networks,  one  of  which  is 
below  the  mucous  membrane,  the  other  in  the  muscular  wall.  There  is  a  third  net- 
work around  the  vaginal  wall,  from  which  the  collectors  arise.  The  trunks  from  the 
upper  third  of  the  vagina  pass  to  the  external  iliac  glands;  those  from  the  middle 
third  pass  to  the  internal  iliac  glands ;  those  from  the  lower  third  terminate  in  the 
glands  at  the  promontory  of  the  sacrum  or  in  the  lateral  sacral  glands.1  The  nerves 
come  from  the  third  and  fourth  sacral  nerves  and  from  the  utero-vaginal  and 
vesical  plexuses  of  the  sympathetic. 


1  The  Lymphatics.    By  Poirier,  Cun6o,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


1498 


THE  FEMALE  ORGANS  OF  GENERATION 


THE  WOMB  OR  UTERUS  (Figs.  1100,  1103,  1104,  1108,  1113). 

The  uterus  is  the  organ  of  gestation,  receiving  the  fecundated  ovum  in  its  cavity, 
retaining  and  supporting  it  during  the  development  of  the  foetus,  and  becoming 
the  principal  agent  in  its  expulsion  at  the  time  of  parturition.  It  is  a  hollow 
muscular  organ.  The  non-pregnant  uterus  is  contained  in  the  cavity  of  the  pelvis 
between  the  bladder  and  rectum  (Figs.  1103  and  1104).  It  is  rarely  placed  exactly 
in  the  mid-line,  but  inclines  to  one  side  or  the  other,  more  often  to  the  left  than 
to  the  right.  The  walls  of  the  organ  are  extremely  thick.  The  uterus  is  movable 
as  a  whole,  and  the  body  of  the  uterus  is  movable  upon  the  neck.  Its  position 
varies  with  the  condition  of  adjacent  parts,  especially  the  bladder  and  rectum. 
The  cervix  is  more  firmly  fixed  than  the  body  and  fundus,  and  hence  the  latter 
vary  more  in  position  than  the  former.  Normally,  in  an  erect  individual,  with  the 
bladder  and  rectum  empty,  the  external  os  is  at  the  level  of  the  upper  surface  of 
the  pubic  symphysis  (Fig.  1100)  and  in  frontal  plane  passing  through  the  ischiatic 
spines.  The  long  axis  of  the  uterus  is  directed  forward  and  upward  (Fig.  1100), 
and  is  angled  where  the  body  and  cervix  join.  Hence,  normally,  with  the  bladder 


ANTERIOR        ISTHMUS  OF 
BORDER   OF      FALLOPIAN 
MESOVARIUM  OVARY  TUBE 


FALLOPIAN 
TUBE 


MCSOSALPINX 


OVARIAN 
FIMBRIA 


ABDOMINAL 
ORIFICE 


FIMBRIAE  OF 
FALLOPIAN  TUBE 


OVARIAN   ARTERY 
AND  VEIN 


TUBAL 

EXTREMITY 

OF  OVARY  UTERINE 

EXTREMITY 

OF  OVARY 


FORNIX  OF 
VAGINA 


VAGINAL 
PORTION  OF 
CERVIX 


ANTERIOR  LIP 
OF  CERVIX 


FIG.  1108. — The  uterus,  the  left  Fallopian  tube  and  the  left  ovary  in  their  connection  -with  the  broad  ligament  of 
the  uterus,  which  has  been  fully  unfolded.     Seen  from  behind.     From  a  virgin,  aged  nineteen  years.  (Toldt.) 

empty,  the  uterus  is  anteverted  and  anteflexed.  When  the  bladder  fills  the  ante- 
version  and  anteflexion  are  almost  abolished.  If  the  bladder  is  overdistended  and 
the  rectum  is  empty,  the  uterus  is  pushed  strongly  backward,  so  that  its  long  axis 
corresponds  to  the  long  axis  of  the  vagina;  in  other  words,  it  is  retroverted. 

In  the  virgin  state  it  is  pear-shaped,  flattened  from  before  backward,  and 
is  retained  in  its  position  by  the  round  and  broad  ligaments  on  each  side,  and 
projects  into  the  upper  end  of  the  vagina  below  (Figs.  1108  and  1109).  Its  upper 
end,  or  base,  is  directed  upward  and  forward;  its  lower  end,  or  apex,  downward 
and  backward,  in  the  line  of  the  axis  of  the  inlet  of  the  pelvis.  It  therefore 
forms  an  angle  with  the  vagina,  since  the  direction  of  the  vagina  corresponds  to 
the  axis  of  the  cavity  and  outlet  of  the  pelvis.  The  non-pregnant  adult  uterus 
measures  about  three  inches  in  length,  two  inches  in  breadth  at  its  upper  part,  and 
nearly  ait  inch  in  thickness,  and  it  weighs  from  an  ounce  to  an  ounce  and  a  half. 

It  consists  of  two  parts  (Fig.  1108):  (1)  An  upper  and  larger  portion,  consisting 
of  the  body  and  fundus.  This  portion  is  flattened  from  before  backward.  (2)  A 
lower,  smaller,  and  cylindrical  portion,  the  cervix. 


THE  WOMB  OR   UTERUS 


1499 


The  Fundus  (fundus  uteri)  (Fig.  1108). — The  funclus  is  the  upper  broad 
extremity  of  the  uterus.  If  a  line  is  drawn  from  the  uterine  opening  of  one 
Fallopian  tube  to  the  other,  the  portion  above  the  line  is  the  fundus.  The 
fundus  is  directly  continuous  with  the  body. 

The  Body  of  the  Uterus  (corpus  uteri)  (Fig.  1108). — The  body  of  the  uterus  is 
below  and  continuous  with  the  fundus.  In  outline,  when  seen  from  in  front  or 
behind,  it  resembles  a  triangle,  the  base  being  above  and  the  point  being  absent. 


PREPUCE  OF 
CLITORIS 


CLANS 
CLITORIOIS 


EXTERNAL 
ORIFICE  OF 
URETHRA 


PARA-URETHRAL 
DUCT 


ORIFICE    OF 
DUCT  OF 

BARTHOLIN'S 
GLAND 

BARTHOLIN'S 
'GLAND 


ANTERIOR 
VAGINAL 
COLUMN 

TRANSVERS 
RUGAE 


VAGINAL 
FORNIX 


VAGINAL 

PORTION  OF 

CERVIX 


MUSCULAR 
COAT 

ANTERIOR 
WALL 


ANTERIOR 
LIP  OF 
CERVIX 


OS   UTERI 
EXTERNUM 


POSTERIOR 
LIP  OF 
CERVIX 


SUPRAVAGINAL 
PORTION 

CERVIX 


Fio.  1109. — The  female  external  genital  organs  of  a  virgin  attached  to  the  vagina,  which  has  been  isolated 
and  opened,  and  a  portion  of  the  cervix  uteri.     (Toldt.) 


The  anterior  surface  (fades  vesicalis)  passes  on  each  side  into  the  posterior  surface 
(fades  intestinalis)  by  the  lateral  border  (margo  lateralis). 

The  body  gradually  narrows  from  the  fundus  to'the  neck.  Its  anterior  surface  is 
so  slightly  rounded  as  to  appear  flattened.  It  is  covered  by  peritoneum  (Fig.  1108), 
which  becomes  separated  from  it  at  its  union  with  the  cervix,  in  order  to  form  the 
utero-vesical  pouch,  which  lies  between  the  uterus  and  bladder  (Fig.  1112).  Its  pos- 
terior surface  is  more  rounded  than  the  anterior,  being  convex  transversely.  It  is 


1500 


THE  FEMALE  ORGANS  OF  GENERATION 


covered  by  peritoneum  throughout  (Fig.  1113),  and  separated  from  the  rectum  by 
some  convolutions  of  the  small  intestine  (Fig.  1 102).  The  peritoneum  which  covers 
the  posterior  surface  forms  most  of  the  anterior  wall  of  Douglas'  cul-de-sac  (Figs. 
866,  1112,  and  1113,  and  p.  1258).  Its  lateral  margins  (Figs.  1108  and  1113)  are 
concave,  and  each  gives  attachment  to  the  Fallopian  tube  above,  the  round  ligament 
below,  and  in  front  of  this  the  ligament  of  the  ovary;  behind  both  of  these  struc- 
tures, and  from  the  side  of  the  womb  the  broad  ligament  passes.  The  division 


GARTNER'S 
"DUCT 


FIG.  1110. — The  parovarium.    The  mesosalpinx  is  partly  removed.    (Poirier  and  Charpy.) 


between  the  body  and  the  cervix  is  indicated  externally  by  a  slight  constriction,  and 
by  the  reflection  ^of  the  peritoneum  from  the  anterior  surface  of  the  uterus  on  to  the 
bladder,  and  internally  by  a  narrowing  of  the  canal  called  the  internal  os  (Fig.  1111). 
The  Neck  or  Cervix  Uteri  (Figs.  1108  and  1111). — The  neck  or  cervix  uteri  is 
the  lower  constricted  segment  of  the  uterus;  around  its  circumference  is  attached 
the  upper  end  of  the  vagina  (Figs.  1103,  1108,  1109,  and  1112),  which  extends 
upward  a  greater  distance  behind  than  in  front.  The  neck  is  spindle-shaped  in 
those  who  have  had  no  children,  cylindrical  in  those  who  have  had  children. 


UTERINE 

ORIFICE    OF 

FALLOPIAN  TUBE 


O  K 
C  < 

MESOSALPINX    U  O 
ISTHMUS  OF 
UTERINE       FALLOPIAN 
PORTION    OF  TUBE 

FALLOPIAN  TUBE 


LONGITUDINAL 
O  O         <       FOLDS 


EPOOPHORON 

ABDOMINAL 
/ORIFICE 


HYDATID  OF 
MOROAGNI 


UTEROVAQINAL 

VENOUS 

PLEXUS 


SVAGINAL 

FORNIX 
OS    UTERI 
EXTERNUM 

FIG.  1111.—  The  uterus  and  the  right  Fallopian  tube  opened  from  behind.    (Toldt.) 

The  Supravaginal  Portion  (portio  supravaginalis  [cervicis])  (Figs.  1108  and  1112). 
— The  supravaginal  portion  is  not  covered  by  peritoneum  in  front;  a  pad  of  cellular 
tissue  is  interposed  between  it  and  the  bladder.  Behind,  the  peritoneum  is  extended 
over  it. 

The  Vaginal  Portion  (portio  vaginalis  [cervicis])  (Figs.  1103, 1108, 11 09,  and  1 
— The  vaginal  portion  is  the  lower  end  projecting  into  the  vagina.    It  is  round  or 


THE  WOMB  OR   UTERUS 


1501 


elliptical,  the  long  axis  of  the  elliptical  figure  being  transversely  placed.  On  its 
surface  is  a  small  aperture,  the  external  mouth  of  the  womb,  or  os  uteri,  or  external  os 
(orificium  externum  uteri)  (Figs.  1108, 1109, 1111,  and  1112),  generally  circular  in 
shape,  but  sometimes  oval  or  almost  linear.  If  a  woman  has  borne  children  the 
opening  is  transverse  and  the  margins  are  irregular.  The  margin  of  the  opening  is, 
in  the  absence  of  past  parturition  or 
disease,  quite  smooth.  This  aperture 
divides  the  vaginal  portion  of  the  cervix 
into  two  lips,  an  upper  or  posterior  lip 
(labium  posterius)  and  a  lower  or  an- 
terior lip  (labium  anterius).  On  each 
side  of  the  cervix  and  upper  portion  of 
the  vagina  there  is  a  space  containing 
bloodvessels  and  filled  with  loose  cellu- 
lar tissue.  This  loose  tissue  passes 
upward  between  the  layers  of  the  broad 
ligament  and  is  called  parametrium. 
On  each  side  of  the  cervix  and  three- 
quarters  of  an  inch  away  is  the  termi- 
nal portion  of  the  corresponding  ureter. 
Folds  and  Ligaments. — The  liga- 
ments of  the  uterus  are  eight  in  number.  Some  are  simple  folds  of  peritoneum; 
others  contain  connective  tissue  and  muscle.  The  ligaments  are  as  follows  :  one 


RECTAL    PERITONEUM 
OVAGINAL    POUCH 

INTERIOR  AND  POS- 
TERIOR LAYERS  OF 
BROAD  LIGAMENT 

VESICAL 
PERITONEUM 

UTERO-VCSICAL 
POUCH 

SUPRA-VAGINAL 
PORTION  OF 
CERVIX 


FIG.  1112. — The  cervix  uteri  and  upper  end  of  the 
vagina,  showing  their  relations  to  the  peritoneum. 
Diagrammatic.  (Testut.) 


ROUND 

.ICAMENT. 


nal  iliac 
artery. 


Apex  of  Douglas's 
pouch. 

External 

artery. 
FIG.  1113. — Douglas's  pouch.    (From  a  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 

anterior,  one  posterior,  two  lateral  or  broad,  two  sacro-uterine — all  these  being  formed 
of  peritoneum — and,  lastly,  two  round  ligaments. 


1502 


THE  FEMALE  ORGANS  OF  GENERATION 


The  Anterior  Ligament  or  the  Utero-vesical  Fold  or  Vesico-uterine  Ligament  is 
reflected  on  to  the  bladder  from  the  front  of  the  uterus,  at  the  junction  of  the 
cervix  and  body.  It  forms  the  utero-vesical  pouch  (excavatio  vesicouterina)  (Figs. 
1112andlll3). 

The  Posterior  Ligament  or  the  Recto-vaginal  Fold  passes  from  the  posterior  wall 
of  the  uterus  over  the  upper  fourth  of  the  vagina,  and  thence  on  to  the  rectum  and 
sacrum.  It  thus  forms  a  pouch,  called  the  recto-vaginal  pouch  or  Douglas'  pouch 
(Figs.  8G6,  1112,  and  1113),  the  boundaries  of  which  are,  in  front,  the  posterior 
wall  of  the  uterus,  the  supravaginal  portion  of  the  cervix,  and  the  upper  fourth  of 
the  vagina;  behind,  the  rectum  and  sacrum;  above,  the  small  intestine;  and, 
laterally,  the  folds  of  Douglas  or  recto-uterine  folds,  which  contain  the  sacro- 
uterine  ligaments. 

The  Lateral  or  Broad  Ligament  (ligamentum  latum  uteri)  '(Figs.  1104,  1114, 
and  1121)  is  a  peritoneal  fold  which  passes  from  each  side  of  the  uterus  to  the 
lateral  wall  of  the  pelvis  as  high  as  the  external  iliac  vein.  From  this  region 
comes  the  peritoneal  fold  called  the  suspensory  ligament  of  the  ovary  (Fig.  1114). 
The  two  broad  ligaments  form  a  septum  across  the  pelvis,  which  divides  that 
cavity  into  two  portions.  In  the  anterior  part  are  contained  the  bladder,  urethra, 
and  vagina;  in  the  posterior  part,  the  rectum.  In  the  uterus  normally  placed  the 
anterior  surface  of  the  broad  ligament  faces  forward  and  downward,  and  the  pos- 
terior surface  faces  upward  and  backward.  The  ligament  is  more  nearly  vertical 


FALLOPIAN 
TUBE 
CORPUS 
ALBICANS 


ESOSALPINX 
SEROUS 
MEMBRANE 


GRAAFIAN 
FOLLICLE 


GRAAFIAN 
FOLLICLE 


STROMA  Of 
OVARY 


LIGAMENT 
31   OF  OVARY 


MESOMETRIUM' 


FIG.  1114. — The  broad  ligament  of  the  uterus,  with 
the  mesoyarium,  the  mesosalpinx,  the  ovary,  and 
the  Fallopian  tube  in  transverse  section.  (Toldt.) 


FIG.  1115. — Longitudinal  section  through  the  ovary. 
(Toldt.) 


at  its  pelvic  insertion.  The  two  layers  of  the  broad  ligament  are  mostly  near 
to  each  other,  to  the  side  and  below  they  separate  and  pass  into  the  peritoneum 
of  the  lateral  pelvic  wall,  the  bladder  and  the  rectum.  Between  the  two  layers 
of  each  broad  ligament  are  contained — (1)  the  Fallopian  tube  superiorly;  (2)  the 
round  ligament;  (3)  the  ovary  and  its  ligament;  (4)  the  parovarium  or  organ  of 
Rosenmiiller,  and  the  paro-ophoron ;  (5)  loose  connective  tissue,  which  is  called 
parametrium;  (6)  unstriped  muscular  fibre;  and  (7)  blood-vessels  and  nerves.  The 
Fallopian  tube  is  in  the  free  edge  of  the  broad  ligament,  and  is  contained  in  a 
special  fold,  which  is  attached  to  the  part  of  the  ligament  near  the  ovary,  and  is 
known  by  the  name  of  the  mesosalpinx  (Tigs.  1110,  1114,  and  1121).  If  the 
mesosalpinx  is  spread  out,  it  is  seen  to  be  roughly  triangular;  the  base  of  the 
triangle  is  outward,  the  apex  at  the  upper  and  outer  angle  of  the  uterus;  the 
upper  boundary  is  the  Fallopian  tube,  and  the  lower  boundary  is  the  ovary  and 
its  ligament.  Between  the  two  layers  of  the  mesosalpinx  are  the  parovarium  and 
the  paro-ophoron.  Between  the  fimbriated  extremity  of  the  tube  and  the  lower 
attachment  of  the  broad  ligament  is  a  concave  rounded  margin,  called  the  infun- 
dibulo-pelvic  ligament  (Fig.  1120). 


THE   WOMB  OR   UTERUS  1503 

The  ovary  lies  in  a  depression  of  the  broad  ligament  called  the  ovarian  bursa 
(bursa  ovarii)  (Figs.  1114  and  1121),  and  is  joined  to  the  ligament  by  a  short  fold, 
the  mesovarium  (Fig.  1121). 

The  mesovarium  passes  upward  from  the  posterior  surface  of  the  broad  liga- 
ment (Fig.  1114).  Beneath  the  mesovarium  is  a  larger  and  thicker  portion  of 
the  broad  ligament,  called  the  mesometrium  (Fig.  1114). 

The  Sacro-uterine  or  Utero-sacral  Ligaments  (plicae  rectouterinae)  are  contained 
in  the  peritoneal  folds  of  Douglas.  They  pass  from  the  second  and  third  bones 
of  the  sacrum,  downward  and  forward  on  the  lateral  aspects  of  the  rectum  to  be 
attached  one  on  each  side  of  the  uterus  at  the  junction  of  the  supravaginal  cervix 
and  the  body,  this  point  corresponding  internally  to  the  position  of  the  os 
internum.  They  contain  fibrous  tissue  and  unstriated  muscle-fibre.  Muscular 
fibres  from  the  uterine  wall  to  the  rectal  wall  constitute  the  Recto-uterinus  muscle 
(musciilus  rectouterinus).  This  muscle  is  part  of  the  sacro-uterine  ligaments. 

A  Round  Ligament  (ligamentum  teres  uteri)  (Figs.  1104,  1113,  1116,  and  1121)  is 
attached  on  each  side  of  the  uterus.  The  two  ligaments  are  rounded  cords 
between  four  and  five  inches  in  length,  each  situated  between  the  layers  of  the 
broad  ligament  in  front  of  and  below  the  Fallopian  tube.  Commencing  at  the 
superior  angle  of  the  uterus,  this  ligament  passes  forward,  upward,  and  outward 
through  the  internal  abdominal  ring,  along  the  inguinal  canal,  to  the  labium 
majus,  in  which  it  becomes  lost.  The  round  ligament  consists  principally  of 
muscular  tissue  prolonged  from  the  uterus;  also  of  some  fibrous  and  areolar  tissue, 
besides  blood-vessels  and  nerves,  enclosed  in  a  duplicature  of  peritoneum,  which 
in  the  foetus  is  prolonged  in  the  form  of  a  tubular  process  for  a  short  distance  into 
the  inguinal  canal.  This  process  is  called  the  canal  of  Nuck.  It  is  generally  oblit- 
erated in  the  adult,  but  sometimes  remains  pervious  even  in  advanced  life.  It 
is  analogous  to  the  peritoneal  pouch  which  precedes  the  descent  of  the  testis. 

The  Cavity  of  the  Uterus  (cavum  uteri]  (Fig.  1111). — The  cavity  of  the  uterus 
is  small  in  comparison  with  the  size  of  the  organ,  because  of  the  great  thickness  of 
the  wall.  That  portion  of  the  cavity  which  corresponds  to  the  body  is  triangular, 
flattened  from  before  backward,  so  that  its  anterior  and  posterior  walls  are  closely 
approximated,  and  having  its  base  directed  upward  toward  the  fundus.  At  each 
superior  angle  is  a  funnel-shaped  cavity,  which  constitutes  the  remains  of  one 
division  of  the  body  of  the  uterus  into  two  cornua,  and  at  the  bottom  of  each  cavity 
is  the  minute  orifice  of  the  Fallopian  tube.  At  the  inferior  angle  of  the  uterine 
cavity  is  a  small  constricted  opening,  smaller  and  more  nearly  circular  than  the 
external  os  uteri,  the  internal  orifice  of  the  uterus  or  internal  os  uteri  (orificium 
internum  uteri)  (Fig.  1111),  which  leads  into  the  cavity  of  the  cervix. 

The  Cavity  of  the  Cervix  or  Cervical  Canal  (canalis  cervicis  uteri)  (Fig.  1111). 
—The  cavity  of  the  cervix  or  cervical  canal  extends  from  the  internal  os  uteri  to 
the  external  os  uteri.  It"  is  somewhat  fusiform,  flattened  from  before  backward, 
broader  at  the  middle  than  at  either  extremity,  and  communicates  below  with  the 
vagina.  The  wall  of  the  canal  presents,  anteriorly  and  posteriorly,  a  longitudinal 
column,  from  which  proceed  a  number  of  small  oblique  columns,  giving  the  appear- 
ance of  branches  from  the  stem  of  a  tree;  and  hence  the  name  uterine  arbor  vitae 
(plicae  palmatae)  applied  to  it.  These  folds  usually  become  very  indistinct  after 
the  first  labor. 

Structure. — The  uterus  is  composed  of  three  coats:  an  external  or  serous  coat,  a 
middle  or  muscular  coat,  and  an  internal  or  mucous  coat. 

The  Serous  Coat  or  Perimetrium  (tunica  serosa)  (Figs.  1103, 1108, 1112,  and  1113). 

—The  serous  coat  is  derived  from  the  peritoneum;  it  invests  the  fundus  and  the 

whole  of  the  posterior  surface  of  the  uterus;  but  covers  the  anterior  surface  only  as 

far  as  the  junction  of  the  body  and  cervix.     In  the  lower  fourth  of  the  posterior 

surface  the  peritoneum,  though  covering  the  uterus,  is  not  closely  connected  with 


1504  THE  FEMALE    ORGANS    OF    GENERATION 

it,  being  separated  from  it  by  a  layer  of  loose  cellular  tissue  and  some  large  veins. 
At  the  lateral  margins  of  the  uterus  the  serous  coat  passes  on  to  the  broad  liga- 
ments. The  serous  coat  adheres  closely  to  the  uterus,  and  it  is  very  difficult  to 
separate  it  from  the  muscle. 

The  Muscular  Coat  (tunica  muscularis}  (Fig.  1111)  .—The  muscular  coat  forms  the 
chief  bulk  of  the  substance  of  the  uterus.  In  the  unimpregnated  state  it  is  dense, 
firm,  of  a  grayish  color,  and  cutsalmost  like  cartilage.  It  is  thick  opposite  the  middle 
of  the  body  and  fundus,  and  thin  at  the  orifices  of  the  Fallopian  tubes.  It  consists 
of  bundles  of  unstriped  muscular  fibres,  disposed  in  layers,  intermixed  with  areolar 
tissue,  blood-vessels,  lymphatic  vessels,  and  nerves.  The  muscular  tissue  is  dis- 
posed in  three  layers — external,  middle,  and  internal. 

The  external  layer  is  placed  beneath  the  peritoneum,  disposed  as  a  thin  plane 
on  the  anterior  and  posterior  surfaces.  It  consists  of  fibres  which  pass  trans- 
versely across  the  fundus,  and,  converging  at  each  superior  angle  of  the  uterus, 
are  continued  on  the  Fallopian  tube,  the  round  ligament,  the  ligament  of  the 
ovary;  some  passing  at  each  side  into  the  broad  ligament,  and  others  running 
backward  from  the  cervix  into  the  sacro-uterine  ligaments.  The  fibres  of  the 
external  portion  of  the  outer  layer  (stratum  subserosum)  are  longitudinal.  The 
fibres  of  the  inner  portion  of  the  outer  layer  (stratum  supravasculare)  are  partly 
circular  and  partly  longitudinal. 

The  middle  layer  of  fibres  (stratum  vasculare),  which  is  thickest,  presents  bundles 
of  circular  fibres  closely  connected  with  blood-vessels.  In  this  layer  are  most  of 
the  blood-vessels.  The  circular  fibres  about  the  internal  os  form  a  distinct 
sphincter.  Those  which  surround  the  orifices  of  the  Fallopian  tubes  are  arranged 
in  the  form  of  two  hollow  cones,  the  apices  of  which  surround  the  orifices  of  the 
Fallopian  tubes,  their  bases  intermingling  with  one  another  on  the  middle  of  the 
body  of  the  uterus. 

The  internal  or  deep  layer  (stratum  mucosum)  consists  of  longitudinal  fibres. 
Some  consider  the  deeper  portion  of  the  muscular  tissue  of  the  uterus  to  be  the 
muscularis  mucosae.  But  the  deep  portion  of  the  muscular  substance  is  con- 
tinuous with  the  more  superficial  portion,  and  there  is  no  submucous  coat  between 
the  muscle  and  the  mucous  membrane.  The  deeper  layer  of  muscular  fibres  of 
the  uterus  contains  connective  tissue  and  elastic  fibres.  The  muscular  tissue  of 
the  cervix  contains  more  connective  and  elastic  tissue  than  does  the  body  of  the 
uterus;  hence,  the  cervix  is  harder  and  stiffer  than  the  body. 

The  Mucous  Membrane  (tunica  mucosa)  (Fig.  1111). — The  mucous  membrane 
is  thin,  smooth,  and  closely  adherent  to  the  subjacent  muscular  tissue.  .It  is 
continuous,  through  the  fimbriated  extremity  of  the  Fallopian  tubes,  with  the 
peritoneum,  and  through  the  os  uteri  with  the  lining  of  the  vagina. 

In  the  body  of  the  uterus  it  is  smooth,  soft,  of  a  pale-red  color  lined  with  columnar 
ciliated  epithelium,  and  presents,  when  viewed  with  a  lens,  the  orifices  of  numer- 
ous tubular  follicles  arranged  perpendicularly  to  the  surface.  It  is  unprovided 
with  any  submucosa,  but  is  intimately  connected  with  the  innermost  layer  of 
the  muscular  coat.  In  structure  its  corium  differs  from  ordinary  mucous  membrane, 
consisting  of  an  embryonic  nucleated  and  highly  cellular  form  of  connective  tissue, 
in  which  run  numerous  large  lymphatics.  In  it  are  the  tube-like  uterine  glands 
(glandulae  uterinae),  which  are  of  small  size  in  the  unimpregnated  uterus,  but 
shortly  after  impregnation  become  enlarged  and  elongated ,  presenting  a  contorted 
or  waved  appearance  toward  their  closed  extremities,  which  reach  into  the  mus- 
cularis, and  may  be  single  or  bifid.  The  uterine  glands  consist  of  a  delicate 
membrane,  lined  with  epithelium,  which  becomes  ciliated  toward  the  orifices. 

In  the  cervix  the  mucous  membrane  is  sharply  differentiated  from  that  of  the 
uterine  cavity.  It  is  thrown  into  numerous  oblique  ridges,  which  diverge  from  an 
anterior  and  posterior  longitudinal  raphe,  presenting  an  appearance  which  has 


1505 

received  the  name  of  arbor  vitae.  In  the  upper  two-thirds  of  the  canal  the  mucous 
membrane  is  provided  with  numerous  deep  glandular  follicles  (glandulae  cervicales 
uteri),  which  secrete  a  clear  viscid  alkaline  mucus;  arid  in  addition,  extending 
through  the  whole  length  of  the  canal,  are  a  variable  number  of  little  cysts,  pre- 
sumably follicles,  which  have  become  occluded  and  distended  with  retained  secre- 
tion. They  are  called  the  ovules  of  Naboth.  The  mucous  membrane  covering  the 
lower  half  of  the  cervical  canal  presents  numerous  papillae.  The  epithelium  of 
the  upper  two-thirds  is  cylindrical  and  ciliated,  but  below  this  it  loses  its  cilia,  and 
gradually  changes  to  squamous  epithelium  close  to  the  external  os. 

The  Uterus  at  Different  Ages. — The  uterus  of  the  foetus  is  in  the  abdominal  cavity 
projecting  above  the  brim  of  the  pelvis.  The  cervix  is  considerably  larger  than 
the  body.  At  birth  the  cervix  is  larger  relatively  than  in  the  adult;  there  is  no  dis- 
tinct internal  os  distinguish  ing  the  cavity  of  the  body  of  the  uterus  from  the  cavity  of 
the  cervix,  and  "  the  arbor  vitae  extends  throughout  the  whole  length  of  the  uterus."1 
The  growth  of  the  uterus  is  slow  until  puberty  is  almost  reached,  when  for  a  time 
the  growth  is  rapid.  The  growth  of  the  uterine  body  causes  the  mucous  mem- 
brane of  this  part  to  lose  its  folds,  hence  the  arbor  vitae  disappears  from  the  body. 
In  a  wroman  who  has  had  children  .the  uterine  cavity  is  larger  than  in  a  woman 
who  has  never  borne  a  child.  In  advanced  years  the  uterine  wall  becomes  paler 
and  hard  and  rigid  from  atrophic  fibrous  changes.  A  more  distinct  constriction 
separates  the  body  and  cervix.  The  internal  os  frequently  and  the  external  os 
occasionally  are  obliterated  in  old  age. 

Abnormalities. — Very  rarely  the  uterine  cavity  is  divided  into  two  by  a  septum. 
Occasionally  the  condition  known  as  bicornate  uterus  exists.  In  this  condition 
each  lateral  angle  is  prolonged  into  a  horn  or  cornu.  The  uterus  is  formed  by  the 
union  of  the  two  ducts  of  Miiller,  and  failure  of  fusion  of  these  ducts  makes  a 
double  uterus  or  a  bicornate  uterus. 

Changes  at  a  Menstrual  Period. — For  several  days  before  the  menstrual  flow 
begins  the  mucous  membrane  increases  in  thickness  and  vascularity  and  its  sur- 
face is  cast  into  folds.  After  these  preparatory  changes  the  superficial  portions 
of  the  mucous  membrane  break  down  and  are  cast  off,  and  bleeding  begins.  At 
the  termination  of  menstruation  the  mucous  membrane  rapidly  regenerates.  At 
each  menstrual  period  from  100  to  200  grammes  of  blood  are  discharged.  The 
meaning  of  menstruation  is  uncertain.  Pfliiger  believes  the  wall  of  the  uterus  is 
made  raw,  so  that  if  an  impregnated  ovum  arrives  it  will  adhere.  Reichert  believes 
that  menstruation  means  that  no  impregnated  ovum  has  arrived  in  the  womb,  and 
hence  no  bed  is  needed  for  one. 

Changes  Induced  by  Pregnancy. — The  muscular  fibres  hypertrophy  enormously 
and  become  vastly  longer  and  broader.  There  is  a  great  increase  in  connective 
tissue,  and  new  connective-tissue  fibres  pass  between  bundles  of  muscle.  The 
peritoneal  coat  undergoes  hyperplasia.  It  remains  closely  adherent  to  the  uterus, 
except  over  the  lower  segment,  from  which  region  it  can  be  easily  stripped.  The 
blood-vessels  become  large  and  tortuous.  The  nerves  are  increased  in  length  and 
new  filaments  form.  The  lymphatics  undergo  hypertrophy  and  hyperplasia 
(Prof.  Barton  Cooke  Hirst).  The  uterus  becomes  spherical,  and  after  the  fourth 
month  ovoidal.  Early  in  pregnancy  the  increase  in  weight  causes  the  uterus 
to  descend  in  the  pelvis.  After  the  third  month  it  rises  progressively,  and  during 
the  ninth  month  the  fund  us  reaches  the  epigastrium.  "  Before  term  (four  weeks 
in  primiparae,  ten  days  or  one  week  in  multiparae)  the  fund  us  sinks  again,  as 
the  presenting  part  and  lower  uterine  segment  become  engaged  in  the  pelvic 
cavity.  This  phenomenon  is  explained  by  contraction  of  the  overstretched 
abdominal  walls."2  The  womb  is  acutely  anteflexed  during  the  first  three  months 

1  Prof.  Francis  A.  Dixon  in  Prof.  Cunningham's  Text-book  of  Anatomy. 
8  A  Text-book  of  Obstetrics.     By  Prof.  Barton  Cooke  Hirst. 

95 


1506 


THE   FEMALE    ORGANS    OF    GENERATION 


of  pregnancy.  After  this  period,  as  the  womb  rises,  the  anteflexion  is  diminished, 
but  some  degree  remains,  because  the  abdominal  walls  are  too  lax  to  hold  the 
organ  straight.  The  uterus  passes  somewhat  to  the  right  side  and  undergoes  a 
rotation  on  its  longitudinal  axis,  so  that  the  anterior  surface  looks  front  and  to  the 

^~~Z^*sss**^>^   Branches  to  tube. 
Branches  to  f undue. 


Ovarian  artery 
Branch  to  round  ligament. 


ROUND    LIGAMENT. 

Uterine  artery. 
Arteries  of  cervix. 


Vaginal  arteries. 
FIG.  1116. — The  arteries  of  the  internal  organs  of  generation  of  the  female,  seen  from  behind.    (After  Hyrtl.) 

right.  These  changes  in  position  are  caused  by  fecal  distention  of  the  sigmoid. 
The  intestines  are  above  and  back  of  the  uterus.  During  the  first  four  months  the 
cervix  softens  and  enlarges  somewhat.  The  length  of  the  cervical  canal  is  not 


VESSELS    FROM 
BODY  OF  FUNDUS 


VESSELS 
FROM  TUBE 


ANASTOMOSIS 
OF  VESSELS 


VESSELS  OF 
ROUND    LIGAMENT 


VAGINAL 
LYMPHATICS 


FIG.  11 17. ^The  lymphatic  vessels  of  the  uterus.     (Poirier  and  Charpy.) 


altered  during  pregnancy,  and  the  canal  does  not  dilate  until  labor  begins.  During 
pregnancy  the  cervical  glands  secrete  thick  mucus,  which  coagulates  and  occludes 
the  cervical  canal ;  the  round  ligaments  become  stronger,  and  the  layers  of  the 
broad  ligament  are  separated  toward  their  inner  portions  by  the  enlarging  womb. 


THE    WOMB    OR     UTERUS 


1507 


After  parturition  the  uterus  nearly  regains  its  former  size,  usually  weighing 
something  over  one  and  a  half  ounces;  but  its  cavity  is  larger  than  in  the  virgin 
state,  the  external  orifice  is  more  marked,  its  edges  present  a  fissured  surface,  its 
vessels  are  very  tortuous,  and  its  muscular  layers  are  more  defined. 

Vessels  and  Nerves  (Fig.  1116). — The  arteries  of  the  uterus  are  the  uterine,  from 
the  internal  iliac,  and  the  ovarian,  from  the  aorta.  They  are  remarkable  for  their 
tortuous  course  in  the  substance  of  the  organ  and  for  their  frequent  anastomoses. 
The  uterine  artery  reaches  the  lower  part  of  the  uterus  at  the  side  and  is.  pro- 


JUXTA-AORTIC 
GLANDS 


VESSELS    FROM 
BODY  OF  UTERUS 


VESSELS    FROM 

NECK  OF  UTERUS 

TO  LATERAL 

SACRAL  GLAND 

VESSELS    FROM 

NECK  OF  UTERUS 

VESSELS  OF 
ROUND   LIGAMENT 


JUXTA-AORTIC 

GLANDS 


VESSEL  OF 
FALLOPIAN  TUBE 


UTERUS 


FIG.  1118. — The  lymphatics  of  the  internal  organs  of  generation  in  the  female.      (Poirier  and  Charpy.) 


longed  as  a  large  artery  to  the  body  and  fundus,  which  ascends  between  the 
layers  of  the  broad  ligament.  The  uterine  artery  gives  off  a  smaller  branch,  the 
cervical,  which  descends  to  supply  the  cervix  and  sends  cervico-vaginal  branches 
to  the  vagina.  The  azygos  arteries  of  the  vagina  come  from  the  cervico-vaginal 
reinforced  by  branches  of  the  vaginal  arteries  (Fig.  1121).  A  median  longitu- 
dinal vessel  is  formed  in  front  and  behind,  which  descends  in  the  vaginal  wall. 
The  termination  of  the  ovarian  artery  meets  the  termination  of  the  uterine 
artery,  and  forms  an  anastomotic  trunk  from  which  branches  are  given  off  to 
supply  the  uterus.  Dr.  Robinson,  instead  of  describing  the  uterine  and  ovarian 


1508 


THE  FEMALE  ORGANS  OF  GENERATION 


arteries  as  two  vessels,  describes  them  as  parts  of  one  vessel,  the  arteria  uterina 
ovarica  (p.  689).  The  veins  are  of  large  size,  and  correspond  with  the  arteries. 
In  the  impregnated  uterus  these  vessels  form  the  uterine  sinuses,  consisting  of 
the  lining  membrane  of  the  veins  adhering  to  the  walls  of  the  canals  channelled 
through  the  substance  of  the  uterus.  They  terminate  in  the  uterine  plexuses, 
which  empty  into  the  internal  iliac  veins.  The  lymphatics  (Figs.  1117  and  1118) 
originate  from  three  networks,  a  muscular  network,  a  peritoneal  network,  and  a 
network  in  the  stroma.  The  trunks  from  these  networks  anastomose,  and  thus 
form  another  network  beneath  the  peritoneum,  and  from  the  fourth  network  the 
collectors  arise.  The  network  of  the  cervix  is  continuous  with  that  of  the  body. 
The  collecting  trunks  from  the  cervical  region  number  from  five  to  eight.  Some 
terminate  in  the  external  iliac  glands,  some  in  the  internal  iliac  glands,  some  in  the 
lateral  sacral  glands,  or  the  glands  of  the  promontory.  The  collecting  trunks  from 
the  body  terminate  chiefly  in  the  juxta-aortic  or  pre-aortic  glands,  but  some  termi- 
nate in  the  external  iliac  glands,  and  some  in  the  inguinal  glands.1  The  nerves  come 
chiefly  from  the  utero-vaginal  plexus,  which  continues  into  the  hypogastric  plexus 
and  receives  filaments  from  the  third  and  fourth  sacral  nerves.  The  uterus  also 
receives  direct  fibres  from  the  hypogastric  plexus  and  from  the  vesical  plexus. 


FIG.  1119. — Relations  between  uterus,  ureter,  and  uterine  artery.     (Schematic.) 


Surgical  Anatomy.— Pelvic  cellulitis  (parametritis)  is  inflammation  of  the  pelvic  cellular 
tissue.  It  is  due  to  sepsis,  and  its  usual  antecedent  is  uterine  sepsis.  A  laceration  of  the  cervix 
may  admit  bacteria.  An  abscess  may  form.  If  it  points  in  the  vagina  it  should  be  incised  through 
the  vaginal  wall.  The  uterus  may  require  removal  (hysterectomy}  in  cases  of  malignant  disease 
or  for  fibroid  tumors.  Carcinoma  is  the  most  common  form  of  malignant  disease  of  the  uterus, 
though  cases  of  sarcoma  do  occur.  Carcinoma  may  show  itself  either  as  a  columnar  carcinoma 
or  as  a  squamous  carcinoma ;  the  former  commencing  either  in  the  cervix  or  body  of  the  uterus,  the 
latter  always  commencing  in  the  epithelial  cells  of  the  mucous  membrane  covering  of  the  vaginal 
surface  of  the  cervix.  The  columnar  form  may  be  treated  in  the  early  stage,  before  fixation  has 
taken  place,  by  removal  of  the  uterus,  either  through  the  vagina  or  by  means  of  abdominal 
section.  The  former  operation  is  attended  by  the  smaller  death-rate.  Vaginal  hysterectomy 
may  be  performed  in  any  case  in  which  the  uterus  or  the  uterus  and  tumor  are  not  too  large  to  be 
withdrawn  through  the  vagina.  It  is  difficult  in  this  operation  to  deal  with  adhesions  and  other 
complications  in  the  upper  part  of  the  pelvis,  and  for  this  reason  many  surgeons  prefer  the  abdom- 
inal operation.  Vaginal  hysterectomy  is  performed  by  placing  the  patient  in  the  lithotomy  position 
and  introducing  a  large  duckbill  speculum  into  the  vagina.  The  cervix  is  then  seized  with  a  vol- 
sellum  and  pulled  down  as  far  as  possible  and  the  mucous  membrane  of  the  vagina  incised  around 
the  cervix  as  near  to  it  as  the  disease  will  allow,  especially  in  front,  where  the  ureters  are  in 
danger  of  being  wounded.  A  pair  of  dressing  forceps  are  then  pushed  through  into  Douglas's 

1  The  Lymphatics.    By  Poirier,  Cuneo,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE  ADNEXA   OR  APPENDAGES  OF  THE  UTERUS         1509 

pouch  and  opened  sufficiently  to  allow  of  the  introduction  of  the  two  forefingers,  by  means  of 
which  the  opening  is  dilated  laterally  as  far  as  the  sacro-uterine  ligaments.  A  somewhat  similar 
proceeding  is  adopted  in  front,  but  here  the  bladder  has  to  be  separated  from  the  anterior  wall 
of  the  uterus  for  about  an  inch  before  the  vesico-uterine  fold  of  peritoneum  can  be  reached. 
This  is  done  by  carefully  burrowing  upward  with  a  director  and  stripping  the  tissues  off  the 
anterior  uterine  wall.  When  the  vesico-uterine  pouch  has  been  opened  and  the  opening  dilated 
laterally,  the  uterus  remains  attached  only  by  the  broad  ligaments,  in  which  are  contained  the 
vessels  that  supply  the  uterus.  Before  division  of  the  ligaments,  these  vessels  have  to  be  dealt 
with.  The  forefinger  of  the  left  hand  is  introduced  into  Douglas's  pouch  and  an  aneurism 
needle,  armed  with  a  long  silk  ligature,  is  inserted  into  the  vesico-uterine  pouch,  and  is  pushed 
through  the  broad  ligament  of  one  side  about  an  inch  above  its  lower  level  and  at  some  distance 
from  the  uterus.  One  end  of  the  ligature  is  now  pulled  through  the  anterior  opening,  and  in  this 
way  we  have  the  lowest  inch  of  the  broad  ligament,  in  which  is  contained  the  uterine  artery, 
enclosed  in  a  ligature.  This  is  tied  tightly,  and  the  operation  is  repeated  on  the  other  side.  The 
broad  ligament  is  then  divided  on  either  side,  between  the  ligature  and  the  uterus,  to  the  extent 
to  which  it  has  been  constricted.  By  traction  on  the  volsellum  which  grasps  the  cervix,  the  uterus 
can  be  pulled  considerably  farther  down  in  the  vagina,  and  a  second  inch  of  the  broad  ligament 
is  treated  in  a  similar  way.  This  second  ligature  will  embrace  the  pampiniform  plexus  of  veins 
and,  when  the  broad  ligament  has  been  divided  on  either  side,  it  will  be  found  that  a  third  liga- 
ture can  be  made  to  pass  over  the  Fallopian  tube  and  top  of  the  broad  ligament,  after  the  uterus 
has  been  dragged  down  as  far  as  possible.  After  the  third  ligature  has  been  tied  and  the  struc- 
tures between  it  and  the  uterus  divided,  this  organ  will  be  freed  from  all  its  connections  and  can 
be  removed  from  the  vagina.  This  canal  is  then  sponged  out  and  lightly  dressed  with  gauze, 
no  sutures  being  used.  The  gauze  may  be  removed  at  the  end  of  the  second  day.  In  squamous 
epithelioma,  amputation  of  the  cervix  is  done  by  some  in  those  cases  where  the  disease  is  recog- 
nized before  it  has  invaded  the  walls  of  the  vagina  or  the  neighboring  broad  ligaments.  The 
operation  consists  in  removing  a  wedge-shaped  piece  of  the  uterus,  including  the  cervix,  through 
the  vagina  and  attaching  the  cut  surfaces  of  the  stump  to  the  anterior  and  posterior  vaginal  walls, 
so  as  to  prevent  retraction.  In  view,  however,  of  the  continuity  of  the  lymphatic  network  of  the 
cervix  with  the  lymphatics  of  the  body,  the  operation  is  insufficient  and  should  be  condemned. 
Complete  abdominal  hysterectomy  is  rarely  necessary,  except  for  malignant  disease.  In  this  opera- 
tion the  entire  uterus  is  removed.  The  preliminary  introduction  of  bougies  into  the  ureters  as 
practised  by  Kelly  and  Clark  enables  the  surgeon  to  readily  recognize  the  situations  of  these  tubes. 
After  the  abdomen  has  been  opened  the  uterine  vessels  are  secured  and  the  broad  ligaments 
divided  in  a  similar  manner  to  that  employed  in  vaginal  hysterectomy,  except  that  the  proceeding 
is  commenced  from  above.  When  the  first  two  ligatures  have  been  tied  and  the  broad  ligament 
divided,  it  will  be  found  that  the  uterus  can  be  raised  out  of  the  pelvis.  A  transverse  incision 
is  now  made  through  the  peritoneum,  where  it  is  reflected  from  the  anterior  surface  of  the  uterus 
on  to  the  back  of  the  bladder  and  the  serous  membrane  peeled  from  the  surface  of  the  uterus 
until  the  vagina  is  reached.  The  anterior  wall  of  this  canal  is  cut  across.  The  uterus  is  now 
turned  forward  and  the  peritoneum  at  the  bottom  of  Douglas's  pouch  incised  transversely,  and 
the  posterior  wall  of  the  vagina  cut  across  until  it  meets  the  incision  on  the  anterior  wall.  The 
uterus  is  now  almost  free,  and  is  held  only  by  the  lower  part  of  the  broad  ligament  on  either 
side,  containing  the  uterine  artery.  A  third  ligature  is  made  to  encircle  this,  and,  after  having 
been  tied,  the  structures  are  divided  between  the  ligature  and  the  uterus.  The  organ  can  now 
be  removed.  The  vagina  is  plugged  with  gauze,  and  the  external  wound  closed  in  the  usual 
way.  The  vagina  acts  as  a  drain,  and  therefore  the  opening  into  it  is  usually  left  unsutured.  In 
some  cases  of  uterine  fibroid  the  abdomen  is  opened  and  the  tumor  is  removed,  but  the  uterus  is 
not  taken  away.  This  operation  is  called  myomectomy.  This  operation  is  suited  only  to  solitary 
subperitoneal  or  interstitial  tumors  (Penrose). 

The  common  operation  for  uterine  fibroids  is  supravaginal  amputation.  The  uterus  is 
cut  away  and  the  cervical  flaps  are  sutured.  Before  the  technique  of  hysterectomy  was  per- 
fected and  before  myomectomy  was  devised  the  favorite  operation  for  uterine  fibroids  was 
salpinfjo-odphorectomy,  and  by  it  a  large  majority  of  cases  operated  upon  were  cured.  W7hen  it 
succeeds  a  premature  menopause  is  induced  and  the  tumor  shrinks.  The  operation  is  useless  if 
a  woman  is  past  the  menopause,  and  is  apt  to  fail  if  the  tumor  is  very  soft  or  very  large. 

THE  ADNEXA  OR  APPENDAGES  OF  THE  UTERUS. 

The  appendages  of  the  uterus  are  the  Fallopian  tubes,  the  ovaries  and  ovarian 
ligaments,  and  the  round  ligaments.  They  are  placed  in  the  following  order:  in 
front  is  the  round  ligament;  the  Fallopian  tube  occupies  the  upper  margin  of  the 
broad  ligament;  the  ovary  and  its  ligament  are  behind  and  below  both. 


1510  THE  FEMALE  ORGANS  OF  GENERATION 


THE  FALLOPIAN  TUBE  (TUBA  UTERINA  [FALLOPII]) 

(Figs.  1108,  1113,  1114,  1120,  1121). 

The  Fallopian  tubes  or  oviducts  convey  the  ova  from  the  ovaries  to  the  cavity 
of  the  uterus.  They  are  two  in  number,  one  on  each  side,  situated  in  the  upper 
margin  of  the  broad  ligament,  extending  from  each  superior  angle  of  the  uterus  to 
the  sides  of  the  pelvis.  Each  tube  is  about  four  inches  and  a  quarter  in  length, 
and  is  placed  in  a  fold  of  peritoneum,  which  is  part  of  the  broad  ligament  and  is 
called  the  mesosalpinx  (Fig.  1114).  Each  tube  is  described  as  consisting  of  four 
portions:  (1)  the  isthmus  (isthmus  tub ae  uterinae)  (Fig.  1120), or  inner  constricted 
third ;  (2)  the  ampulla  (ampulla  tubae  uterinae)  (Fig.  1 120) ,  or  outer  dilated  portion, 
which  curves  over  the  ovary;  and  (3)  the  infundibulum  (infundibulum  tubae  uter- 
inae), the  funnel-like  expansion  of  the  tube,  at  the  bottom  of  which  is  the  abdominal 
orifice  or  pavilion  (ostium  abdominale  tubae  uterinae)  (Fig.  1120).  The  abdominal 
orifice  has  a  small  diameter  (2  mm.  when  relaxed  to  its  full  extent).  The  margin  of 
the  infundibulum  is  rendered  irregular  by  the  presence  of  numerous  small  pro- 
cesses, the  fimbriae  (fimbriae  tubae).  This  end  of  the  tube  is  called  the  fimbriated 
extremity  (Fig.  1120),  because  of  these  processes.  The  surfaces  of  the  fimbriae 
looking  into  the  cavity  of  the  infundibulum  are  covered  with  mucous  membrane 
continuous  with  the  tubal  mucous  membrane.  The  outer  surfaces  are  covered  with 
peritoneum.  One  of  the  fimbriae  is  attached  to  the  ovary  and  is  called  the  ovarian 
fimbria  (fimbria  ovarica)  (Fig.  1120).  (4)  The  uterine  portion  of  the  tube  (pars 
uterina)  (Fig.  1111)  is  in  the  uterine  wall.  The  opening  into  the  uterus  (ostium 
uterinum  tubae)  is  even  smaller  than  the  abdominal  opening,  and  will  admit  only  a 
small  bristle.  The  general  direction  of  the  Fallopian  tube  is  outward,  backward, 
and  downward.  In  connection  with  the  fimbriae  of  the  Fallopian  tube  or  with  the 
broad  ligament  close  to  them  there  is  frequently  one  or  more  small  vesicles  floating 
on  a  long  stalk  of  peritoneum.  These  are  termed  the  hydatids  of  Morgagni  (appen- 
dices vesiculosi).  They  are  representative  of  small  portions  of  the  upper  extremity 
of  the  Wolffian  duct. 

Course  Pursued  by  the  Fallopian  Tube  (Figs.  1104  and  1120). — The  tube  on  each 
side  begins  at  the  upper  and  outer  angle  of  the  uterus  and  passes  outward  in  a 
horizontal  direction  toward  the  uterine  extremity  of  the  ovary.  It  then  bends 
almost  to  a  right  angle  and  ascends  close  to  the  pelvic  wall  and  in  front  of  the 
anterior  margin  to  the  tubal  extremity  of  the  ovary.  At  this  point  it  turns  sharply 
downward  and  a  little  backward,  and  the  inner  surface  of  the  infundibulum  comes 
to  lie  upon  the  free  margin  and  the  posterior  portion  of  the  inner  surface  of  the 
ovary.  "The  fimbria  ovarica  thus  ascends  in  a  recurrent  direction  to  the  extrem- 
itas  tubaria."1 

Structure. — The  Fallopian  tube  consists  of  three  coats — serous,  muscular,  and 
mucous. 

The  external  or  serous  coat  (tunica  serosa)  (Fig.  1115)  is  peritoneal.  Beneath 
this  lies  the  tunica  adventitia,  composed  of  lax  connective  tissue. 

The  middle  or  muscular  coat  (tunica  muscularis)  consists  of  an  external  longi- 
tudinal layer  (stratum  longitudinale) ,  and  an  internal  circular  layer  (stratum  cir- 
cular e)  of  muscular  fibres  continuous  writh  those  of  the  uterus. 

The  internal  or  mucous  coat  (tunica  mucosa)  is  continuous  with  the  mucous  lining 
of  the  uterus  and,  at  the  free  extremity  of  the  tube,  with  the  peritoneum.  It  is 
thrown  into  longitudinal  folds  (plicae  tubariae),  which  in  the  outer,  larger  part  of 
the  tube  or  ampulla  (plicae  ampullares)  are  much  more  extensive  than  in  the 
narrow  canal  of  the  isthmus  (plicae  isthmicae).  The  lining  epithelium  is  columnar 
and  ciliated.  This  form  of  ephithelium  is  also  found  on  the  inner  surface  of  the 

1  Spalteholz's  Atlas.     English  edition  by  Barker. 


THE  FALLOPIAN  TUBE 


1511 


fimbriae,  while  on  the  outer  or  serous  surfaces. of  these  processes  the  epithelium 
gradually  merges  into  the  endothelium  of  the  peritoneum. 

Vessels  and  Nerves. — The  chief  artery  of  the  tube  is  the  tubal  branch  of  the 
uterine  artery  (ramus  tubarius]  (Fig.  1116).  It  also  receives  branches  from  the 
ovarian  (Fig.  1116).  Some  of  the  tubal  veins  empty  into  the  uterine  veins,  some 


Fimbrta  uvarica. 

FIG.  1120. — Uterine  appendages,  seen  from  behind.     (Henle.) 

into  the  ovarian  veins.  The  lymphatics  (Figs.  1117  and  1118)  coming  from  the 
tube  unite  with  the  trunks  coming  from  the  uterus  and  ovary  and  terminate  in 
the  juxta-aortic  glands.  The  nerves  come  from  the  same  plexuses  that  send 
branches  to  the  uterus  and  ovary. 

The  Epo-ophoron,  Parovarium  or  Organ  of  Rosenmiiller  (Figs.  1110, 11 11, 'and 
1120)  is  placed  in  the  mesosalpinx,  between  the  ovary  and  tube.  It  consists  of  a 
number  of  epithelial-lined  closed  tubes.  This  structure  can  be  readily  seen  if  the 

Fimbriated  extremity 
of  tube. 

Fallopian  tube. 


Broad  ligament, 
upper  part. 


Artery 
vein. 


Vagina,  anterior  wall. 

FIG.  1121. — The  uterus  and  its  appendages.  Posterior  view.  The  parts  have  been  somewhat  displaced  from 
their  proper  position  in  the  preparation  of  the  specimen,  thus  the  right  ovary  has  been  raised  above  the  Fallo- 
pian tube,  and  the  fimbriated  extremities  of  the  tubes  have  been  turned  upward  and  outward.  (From  a  prepa- 
ration in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 

mesosalpinx  is  stretched  and  held  in  front  of  the  light.  One  of  these  tubes  runs 
parallel  to  the  Fallopian  tube  and  is  called  Gartner's  duct  (ductus  epoophori  langitu- 
dinalis).  A  number  of  tubes  (ductuli  transversi)  ascend  from  near  the  ovary  and 


1512  THE  FEMALE  ORGANS  OF  GENERATION 

each  empties  into  Gartner's  duct  at  a  right  angle.  Gartner's  duct  is  a  portion  of 
the  Wolffian  duct,  which  has  persisted  and  is  lepresented  in  the  male  by  the  canal 
of  the  epididymis.  The  tubules  which  join  the  duct  "are  derived  from  the  meso- 
nephros  and  represent  the  vasa  eft'erentia  and  coni  vasculosi  of  the  testis,  and 
probably  also  the  ductuli  aberrantes  of  the  canal  of  the  epididymis."  (Cunningham.) 
The  Paro-ophoron  is  within  the  mesosalpinx,  but  is  nearer  to  the  uterus  than 
is  the  epo-ophoron.  It  consists  of  several  small  tubules,  which  can  be  seen  in  an 
adult  only  by  the  aid  of  a  pocket  lens.  They  are  visible  to  the  naked  eye  in  a  child 
at  birth.  It  represents  the  organ  of  Gisaldes  in  the  male  and  is  derived  from  the 
mesonephros. 

THE  OVARY  (OVARIA)  (Figs.  1104,  1108,  1110,  1111,  1113,  1114,  1115, 

1120,  1121). 

The  ovaries,  the  testes  muliebres  of  Galen,  are  two  in  number  and  are  analo- 
gous to  the  testes  in  the  male.  They  are  oval-shaped  bodies  of  an  elongated 
form,  flattened  from  above  downward,  situated  one  on  each  side  of  the  uterus, 
in  the  posterior  layer  of  the  broad  ligament  behind  and  below  the  Fallopian  tube. 
Each  ovary  is  connected  by  its  anterior  straight  margin  to  the  broad  ligament; 
by  its  lower  extremity  to  the  uterus  by  a  proper  ligament,  the  ligament  of  the 
ovary  (ligamentum  ovarii  proprium)  (Fig.  1120);  and  by  its  upper  end  to  the 
fimbriated  extremity  of  the  Fallopian  tube  by  the  ovarian  fimbria  (fimbria  ovarica) 
(Fig.  1120),  its  mesal  and  lateral  surfaces  and  posterior  convex  border  are  free 
(Fig.  1121).  The  ovaries  are  of  a  grayish-pink  color,  and  present  either  a  smooth 
or  a  puckered,  uneven  surface.  They  are  each  about  an  inch  and  a  half  in 
length,  three-quarters  of  an  inch  in  width,  and  about  a  third  of  an  inch  thick, 
and  weigh  from  one  to  two  drachms. 

The  exact  position  of  the  ovary  has  been  the  subject  of  considerable  difference 
of  opinion,  and  writers  are  in  conflict  as  to  what  is  to  be  regarded  as  the  normal 
position.  The  fact  appears  to  be  that  the  ovary  is  differently  placed  in  different 
individuals.  The  two  ovaries  are  seldom  placed  in  absolutely  identical  positions. 
Hasse  has  described  the  ovary  as  being  situated  with  its  long  axis  transverse,  or 
almost  transverse,  to  the  pelvic  cavity.  Schultze,  on  the  other  hand,  believes  that 
its  long  axis  is  antero-posterior.  Kolliker  asserts  that  the  truth  lies  between 
these  views,  and  that  the  ovary  is  placed  obliquely  in  the  pelvis,  its  long  axis 
lying  parallel  to  the  external  iliac  vessels,  with  its  surface  directed  inward  and  out- 
ward, and  its  convex  free  border  upward.  His  has  made  some  important  observa- 
tions on  this  subject,  and  his  views  are  largely  accepted.  He  teaches  that  the 
uterus  rarely  lies  symmetrically  in  the  middle  of  the  pelvic  cavity,  but  is  generally 
inclined  to  one  or  other  side,  most  frequently  to  the  left,  in  the  proportion  of  three 
to  two.  The  position  of  the  two  ovaries  varies  according  to  the  inclination  of  the 
uterus.  When  the  uterus  is  inclined  to  the  left,  the  ovary  of  this  side  lies  with 
its  long  axis  vertical  and  with  one  side  closely  applied  to  the  outer  wall  of  the 
pelvis,  while  the  ovary  of  the  opposite  side,  being  dragged  upon  by  the  inclina- 
tion of  the  uterus,  lies  obliquely,  its  outer  extremity  being  retained  in  close  appo- 
sition to  the  side  of  the  pelvis  by  the  infundibulo-pelvic  ligament.  When,  on 
the  other  hand,  the  uterus  is  inclined  to  the  right,  the  position  of  the  two 
ovaries  is  exactly  reversed,  the  right  'being  vertical  and  the  left  oblique.  In 
whichever  position  the  ovary  is  placed,  the  Fallopian  tube  forms  a  loop  around  it, 
the  uterine  half  ascending  obliquely  over  it,  and  the  outer  half,  including  the 
dilated  extremity,  descending  and  bulging  freely  behind  it.  From  this  extremity 
the  fimbriae  pass  upward  on  to  the  ovary  and  closely  embrace  it. 

Waldeyer1  states,  as  the  result  of  the  examination  of  fifty  female  .subjects, 

1  Journal  of  Anatomy  and  Physiology,  vol.  xxxii. 


THE  DESCENT  OF  THE  OVARY  1513 

ranging  from  early  childhood  to  advanced  age,  that  the  ovary  "lies  on  the  lateral 
pelvic  wall  and  vertically  when  the  woman  takes  the  erect  posture."  Its  tubal 
extremity  is  near  the  external  iliac  vein;  its  uterine  end  is  directed  downward, 
while  the  Fallopian  tube  overlies  it  so  as  to  cover  it  on  its  medial  face  entirely  or 
nearly  so.  Its  convex  margin  looks  downward  and  backward  toward  the  pelvic 
cavity  and  rectum,  while  its  straight  margin  or  hilum  lies  laterally  on  the  pelvic 
wall  attached  to  the  mesosalpinx.  He  also  finds  that  it  lies  in  a  distinct  but 
shallow  groove  (fossa  ovarii)  limited  above  by  the  hypogastric  artery  and  below 
by  the  ureter,  in  such  a  manner  that  the  ureter  lies  along  the  convex  margin 
of  the  ovary,  and  the  hypogastric  artery  passes  near  the  hilum  or  straight  margin. 
The  ovary  possesses  two  poles  or  extremities :  (1 )  An  outer,  superior  or  tubal 
extremity  (extremitas  tubaria  ovarii}.  (2)  An  inner,  inferior  or  uterine  extremity 
(extremitas  uterina  ovarii).  The  ovary  has  two  surfaces,  an  inner  surface  (fades 
medialis),  which  is  also  upper;  an  outer  surface  (fades  lateralis),  which  is  also 
lower.  The  posterior  or  free  border  (margo  liber)  is  markedly  convex.  The  anterior 
border  (margo  mesovaricus)  is  almost  straight  and  is  narrow.  The  anterior  border 
is  not  free,  but  is  joined  to  the  posterior  layer  of  the  broad  ligament  by  a  peritoneal 
fold  known  as  the  mesovarium.  There  is  a  groove  in  the  anterior  border  called  the 
hilum  (hilus  ovarii),  through  which  vessels  and  nerves  to  pass,  and  emerge  from 
the  ovary. 

Supports  and  Connections  of  the  Ovary. 

From  its  upper  extremity  a  peritoneal  fold  is  continuous  with  the  peritoneum 
over  the  iliac  vessels  and  Psoas  muscle.  It  is  called  the  ovario-pelvic  fold  or  the 
suspensory  ligament  (ligamentum  suspensorium  ovarii)  (Fig.  1104).  It  is  in  reality 
a  portion  of  the  broad  ligament,  and  within  it  are  the  ovarian  vessels  and  nerves. 
The  vessels  (Fig.  1121)  and  nerves  go  to  the  anterior  border  of  the  ovary  and  are 
surrounded  by  a  peritoneal  sheath  derived  from  the  posterior  layer  of  the  broad 
ligament;  it  is  thus  evident  that  the  anterior  border  of  the  ovary  is  connected  to 
the  posterior  portion  of  the  broad  ligament  by  a  very  short  mesentery,  the  meso- 
varium1 (Fig.  1114).  The  ligament  of  the  ovary  or  ovarian  ligament  (Figs.  1104 
and  1120)  is  a  round,  cord-like  structure,  composed  chiefly  of  non-striated  muscle- 
fibres,  which  passes  between  the  two  folds  of  the  broad  ligament  from  the  lower 
extremity  of  the  ovary  to  the  lateral  angle  of  the  uterus.  The  ovarian  fimbria 
(Fig.  1120),  as  previously  stated,  passes  to  the  upper  extremity  of  the  ovary 
from  the  extremity  of  the  Fallopian  tube. 

The  Descent  of  the  Ovary. 

In  the  female  there  is  a  gubernaculum  which  effects  a  considerable  change  in 
the  position  of  the  ovary,  though  not  so  extensive  a  change  as  is  effected  upon  the 
male  testicle.  The  gubernaculum  in  the  female,  as  it  lies  on  either  side  in  con- 
tact with  the  fundus  of  the  uterus  formed  by  the  union  of  the  Miillerian  ducts, 
contracts  adhesions  to  this  organ  and  thus  the  ovary  is  prevented  from  descending 
below  this  level.  The  remains  of  the  gubernaculum — that  is  to  say,  the  part 
between  the  attachment  of  the  cord  to  the  uterus  to  its  termination  in  the  labium 
majus — ultimately  forms  the  round  ligament  of  the  uterus.  A  pouch  of  peri- 
toneum accompanies  it  along  the  inguinal  canal,  analogous  to  the  funicular  process 
in  the  male;  it  is  called  the  canal  of  Nuck.  In  rare  cases  the  gubernaculum  fails 
to  contract  adhesions  to  the  uterus,  and  then  the  ovary  descends  through  the 
inguinal  canal  into  the  labium  majus,  extending  down  the  canal  of  Nuck. 
Under  these  conditions,  the  position  of  the  ovary  resembles  the  position  of  the 
testicle  in  the  male. 

The  Ovary  at  Different  Ages. — The  ovary  of  childhood  is  smooth  and 
even.  The  rupture  of  Graafian  follicles,  repeated  many  times,  causes  the  surface 

1  Prof.  Cunningham's  Text-book  of  Anatomy. 


1514 


THE  FEMALE  ORGANS  OF  GENERATION 


of  the  ovary  to  become  pitted,  puckered,  fibrous,  and  uneven  in  old  age.  The  sur- 
face of  the  ovary  is  grayish-red  in  color.  The  corpus  luteum  of  a  non-pregnant 
woman  slowly  degenerates  and  disappears.  The  corpus  luteum  of  an  impreg- 
nated woman  enlarges  during  pregnancy. 

Structure  (Figs.  1114,  1115,  1122,  and  1123).— The  ovary  consists  of  a  number 
of  Graafian  follicles  or  vesicles  embedded  in  the  meshes  of  a  stroma  or  framework, 
and  invested  by  a  serous  covering  derived  from  the  peritoneum. 

Serous  Covering. — Though  the  investing  membrane  of  the  ovary  is  continuous 
with  the  peritoneum  near  the  hilum  of  the  ovary  (the  point  of  junction  being 
indicated  by  a  narrow  white"  line),  it  differs  essentially  from  the  peritoneum, 
inasmuch  as  it  is  an  epithelial  structure  and  consists  of  a  single  layer  of  columnar 
epithelial  cells,  instead  of  the  flattened  endothelial  cells  of  other  parts  of  the 
membrane;  this  has  been  termed  the  germinal  epithelium  of  Waldeyer,  and  gives 
to  the  surface  of  the  ovary  a  dull-gray  aspect  instead  of  the  shining  smoothness 
of  serous  membranes  generally. 

Stroma. — The  stroma  is  a  peculiar  soft  tissue,  abundantly  supplied  with  blood- 
vessels, consisting  for  the  most  part  of  spindle-shaped  cells,  with  a  small  amount 
of  ordinary  connective  tissue.  These  cells  have  been  regarded  by  some  anatomists 
as  unstriped  muscle-cells,  which,  indeed,  they  most  resemble  (His);  by  others  as 
connective-tissue  cells  (Waldeyer,  Henle,  and  Kolliker).  On  the  surface  of  the 
organ  this  tissue  is  much  condensed,  and  forms  a  layer  composed  of  short  connec- 
tive-tissue fibres,  with  fusiform  cells  between  them.  This  was  formerly  regarded 
as  a  distinct  fibrous  covering,  and  was  termed  the  tunica  albuginea,  but  is  nothing 
more  than  a  condensed  layer  of  the  stroma  of  the  ovary. 

Graafian  Follicles  or  Vesicles  (folliculi  oophori  vesicidori  [Graafi])  (Figs.  1122  and 
1123). — Upon  making  a  section  of  an  ovary  numerous  round  transparent  vesicles 
of  various  sizes  are  to  be  seen;  they  are  the  Graafian  vesicles  or  ovisacs  containing 
the  ova.  Immediately  beneath  the  superficial  covering  is  a  layer  of  stroma,  in 
which  are  a  large  number  of  minute  vesicles  of  uniform  size,  about  yo-j-  of  an 
inch  in  diameter.  These  are  the  Graafian  vesicles  in  their  earliest  condition,  and 
the  layer  where  they  are  found  has  been  termed  the  cortical  layer.  They  are 
especially  numerous  in  the  ovary  of  the  young  child.  After  puberty  and  during  the 
whole  of  the  child-bearing  period  large  and  mature,  or  almost  mature,  Graafian 

vesicles  are  also  found  in  the  cortical 
layer  in  small  numbers,  and  also 
corpora  lutea,  the  remains  of  vesicles 
which  have  burst  and  are  undergoing 
atrophy  and  absorption.  Beneath 
this  superficial  stratum  other  large 
and  mature  Graafian  vesicles  are 


Ovum. 


Granular  zone. 


Peritoneum. 


FIG.  1122. — Section  of  the  ovary.  1,  outer  covering: 
1',  attached  border;  2,  central  stroma;  3,  peripheral 
stroma;  4.  blood-vessels;  5,  Graafian  follicles  in  their 
earliest  stage;  6,  7,  8,  more  advanced  follicles;  9,  an  almost 
mature  follicle;  9',  follicle  from  which  the  ovum  has 
escaped;  10,  corpus  luteum.  (After  Schron.) 


VJ    I      '[•-     Coats  of  the 
Stroma  of  the  ovary  '      »  Graaflan  vesicle, 
u'ith,  blood  vessels.    Membrana 
granulosa. 

FIG.  1 123. — Section  of  the  Graafian  vesicle. 
(After  von  Baer.) 


found  embedded  in  the  ovarian  stroma.  These  increase  in  size  as  they  recede 
from  the  surface  toward  a  highly  vascular  stroma  in  the  centre,  of  the  organ, 
termed  the  medullary  substance  (zona  vasculosa  [Waldeyeri]).  This  stroma  forms 


THE  DESCENT  OF  THE  OVARY  1515 

the  tissue  of  the  hilum  by  which  the  ovary  is  attached,  and  through  which  the 
blood-vessels  enter;  it  does  not  contain  any  Graafian  vesicles. 

The  larger  Graafian  follicles  consist  of  an  external  fibro- vascular  coat  connected 
with  the  surrounding  stroma  of  the  ovary  by  a  network  of  blood-vessels;  and  an 
internal  coat,  named  the  ovicapsule,  which  is  lined  by  a  layer  of  nucleated  cells, 
called  the  membrana  granulosa.  The  fluid  contained  in  the  interior  of  the  vesicles 
is  transparent  and  albuminous,  and  in  it  is  suspended  the  ovum.  In  that  part  of 
the  mature  Graafian  vesicle  which  is  nearest  the  surface  of  the  ovary  the  cells 
of  the  membrana  granulosa  are  collected  into  a  mass  which  projects  into  the 
cavity  of  the  vesicle.  This  is  termed  the  discus  proligerus,  and  in  this  the  ovum 
is  embedded. 

The  ova  are  formed  from  the  germinal  epithelium  on  the  surface  of  the  ovary. 
This  becomes  thickened,  and  in  it  are  seen  some  cells  which  are  larger  and  more 
rounded  than  the  rest;  these  are  termed  the  primordial  ova.  The  germinal  epi- 
thelium grows  downward  in  the  form  of  tubes  or  columns,  termed  the  egg  tubes 
of  Pfliiger,  into  the  ovarian  stroma,  which  grows  outward  between  the  tubes,  and 
ultimately  cuts  them  off  from  the  germinal  epithelium.  These  tubes  are  further 
subdivided  into  rounded  nests  or  groups  each  containing  a  primordial  ovum  which 
undergoes  further  development  and  growth,  while  the  surrounding  cells  of  the  nest 
form  the  epithelium  of  the  Graafian  follicle. 

The  development  and  maturation  of  the  Graafian  vesicles  and  ova  continue 
uninterruptedly  from  puberty  to  the  end  of  the  fruitful  period  of  woman's  life, 
while  their  formation  commences  before  birth.  Before  puberty  the  ovaries  are 
small,  the  Graafian  vesicles  contained  in  them  are  disposed  in  a  comparatively 
thick  layer  in  the  cortical  substance;  here  they  present  the  appearance  of  a  large 
number  of  minute  closed  vesicles,  constituting  the  early  condition  of  the  Graafian 
vesicle;  many,  however,  never  attain  full  development,  but  shrink  and  disappear. 
At  puberty  the  ovaries  enlarge  and  become  more  vascular,  the  Graafian  vesicles 
are  developed  in  greater  abundance,  and  their  ova  are  capable  of  fecundation. 

Discharge  of  the  Ovum.^-The  Graafian  vesicles,  after  gradually  approaching 
the  surface  of  the  ovary,  burst;  the  ovum  and  fluid  contents  of  the  vesicles  are 
liberated,  and  escape  on  the  exterior  of  the  ovary,  passing  thence  into  the  Fallopian 
tube.  This  is  effected  either  by  application  of  the  tube  to  the  ovary,  or  by  a 
curling  upward  of  the  fimbriated  extremity,  so  that  the  ovum  is  caught  as  it  falls. 

In  the  foetus  the  ovaries  are  situated,  like  the  testes,  in  the  lumbar  region,  near 
the  kidneys.  They  may  be  distinguished  from  those  bodies  at  an  early  period  by 
their  elongated  and  flattened  form,  and  by  their  position,  which  is  at  first  oblique 
and  then  nearly  transverse.  They  gradually  descend  into  the  pelvis. 

The  Round  Ligament  (p.  1503). 

Vessels  and  Nerves. — The  arteries  of  the  ovaries  (Figs.  1116  and  1121)  are  the 
ovarian  from  the  aorta,  corresponding  to  the  spermatic  arteries  in  the  male.  The 
ovarian  artery  on  each  side  enters  the  pelvis  in  the  fold  of  broad  ligament  known 
as  the  suspensory  ligament  of  the  ovary  and  enters  the  attached  border,  or  hilum, 
of  the  ovary.  The  ovarian  vessels  anastomose  about  the  hilum  with  branches  of 
the  uterine  artery.  The  veins  follow  the  course  of  the  arteries;  they  form  a  plexus 
near  the  ovarj,  the  pampiniform  plexus,  corresponding  to  a  like  structure  near  the 
male  testicle.  The  lymphatics  (Figs.  1117  and  1118)  terminate  in  the  glands  to 
the  corresponding  side  of  the  aorta,  and  they  anastomose  in  their  course  with 
trunks  from  the  uterine  fundus  and  Fallopian  tube.  The  nerves  come  from  the 
ovarian  plexus,  which  is  a  continuation  of  the  renal  plexus  along  the  ovarian  artery, 
and  from  the  aortic  plexus. 

Surgical  Anatomy  of  the  Appendages. — Extra-uterine  pregnancy  most  commonly  occurs 
in  the  ampulla  of  the  tube.  The  product  of  the  conception  may  escape  through  the  ostium 
abdominale  or  the  walls  of  the  tube  may  rupture,  a  violent  hemorrhage  resulting. 


1516  THE  FEMALE  ORGANS  OF  GENERATION 

Pelvic  peritonitis  is  a  not  uncommon  sequence  of  tubal  disease.  Salpingitis  is  inflammation 
of  the  mucous  coat  of  the  tube — interstitial  salpingitis  of  the  middle  coat,  perisalpingitis  of  the 
peritoneal  coat. 

If  inflammation  closes  the  uterine  and  the  abdominal  ends  of  the  tube,  mucus  gathers  and  dis- 
tends the  tube  (hydrosalpiruc).  If  purulent  matter  gathers,  the  condition  is  known  as  pyosalpinx. 

An  ovary  may  fail  to  descend  and  remain  well  above  the  pelvic  brim;  it  may  prolapse  into 
Douglas's  pouch;  it  may  enter  the  sac  of  a  hernia;  it  may  inflame;  a  tumor  or  cyst  may  arise  from 
it.  A  solid  tumor  of  the  ovary  may  be  a  fibroma,  a  sarcoma,  or  a  carcinoma.  "  Cysts  may  orig- 
inate in  any  part  of  the  tubo-ovarian  structure;  as  the  cortical,  medullary,  or  parenchymatous 
portions  of  the  ovary;  in  the  structure  between  the  tube  and  ovary  known  as  the  Rosenmiiller 
organ  or  parovarian  structures;  and  in  the  hydatid  of  Morgagni."1  Cysts  may  be  simple,  pro- 
liferating, or  dermoid;  unilocular  or  multilocular.  Glandular  proliferous  cysts,  papillary  pro- 
liferous cysts,  dermoid  cysts,  and  parovarian  cysts  may  attain  a  large  or  even  an  enormous  size. 
The  operation  for  the  removal  of  an  ovarian  cyst  is  one  of  the  most  successful  of  the  major 
procedures  of  surgery. 

THE  MAMMARY  GLAND  (MAMMA)  (Figs.  1124,  1125,  1126,  1127). 

The  breasts,  mammary  glands  or  mammae  secrete  the  milk,  and  are  accessory 
glands  of  the  generative  system.  They  develop  fully  in  the  female,  but  remain 
permanently  rudimentary  in  the  male.  There  are  two  of  these  glands,  and 
they  are  situated  in  the  superficial  fascia  of  the  anterior  portion  of  the  thorax. 
Between  the  two  glands  and  in  front  of  the  sternum  is  a  groove,  the  bosom. 

Description  of  a  Well-developed  Breast. — Each  gland  appears  as  a  hemispher- 
ical body  projecting  from  the  front  of  the  thorax  beneath  the  skin  and  lying  over 
a  portion  of  the  Pectoralis  major  muscle  and  a  smaller  portion  of  the  Serratus 
magnus  muscle.  The  hemispherical  projection  extends  usually  from  the  margin 
of  the  sternum  to  the  axilla  and  from  the  level  of  the  second  rib  to  the  level  of 
the  sixth  rib,  or  from  the  third  rib  to  the  seventh  rib,  but  this  does  not  represent 
the  real  size  of  the  gland.  The  gland  is  much  larger  than  this,  being  rendered 
so  by  tails  or  prolongations  of  breast  tissue,  which  will  be  described  later  (p.  1517). 

The  Nipple  (papilla  mammae)  (Figs.  1124, 1125, 1126,  and  1127). — The  nipple 
projects  from  a  little  below  and  to  the  median  side  of  the  summit  of  the  hemi- 
sphere at  or  above  the  level  of  the  fifth  rib,  and  is  covered  with  thin  skin.  The 
right  nipple  may  not  exactly  correspond  in  situation  and  direction  to  the  left 
nipple.  The  nipple  varies  considerably  in  height  and  shape.  In  the  virgin  it  is 
usually  cylindrical  and  is  directed  forward  and  slightly  upward  and  outward. 
The  apex  of  the  nipple  is  rendered  rough  by  fissures  (Fig.  1124),  it  exhibits  a 
depression  in  which  are  the  openings  of  the  milk  ducts  (Fig.  1126),  and  its  cir- 
cumference is  thrown  into  concentric  ridges  (Fig.  1126).  The  nipple  is  surrounded 
by  a  darker  circular  wrinkled  area,  the  areola  (areola  mammae)  (Figs.  1124  and 
1125),  in  which  are  sweat-glands  and  on  which  are  twelve  or  fifteen  small 
rounded  elevations.  These  elevations  are  caused  by  cutaneous  sebaceous  glands 
which  in  structure  represent  a  transition  between  sebaceous  and  mammary  glands. 
They  are  probably  rudimentary  portions  of  the  mammary  gland  and  are  known 
as  the  glands  of  Montgomery  (glandulae  areolares)  (Fig.  1126).  The  color  of  the 
nipple  and  areola  varies  with  the  complexion  of  the  individual.  In  brunettes  it  is 
darker  than  in  blondes.  The  usual  color  of  the  nipple  in  a  young  woman  is  rosy- 
pink,  the  areola  being  of  a  darker  shade.  During  the  early  months  of  pregnancy 
the  nipple  and  areola  become  dark  brown  in  color,  the  areola  becomes  larger  in 
circumference,  and  the  glands  of  Montgomery  increase  in  size  (Fig.  1127).  The 
nipple  contains  non-striated  muscle  and  mechanical  irritation  or  sexual  excitement 
makes  it  stiff  and  erect.  The  skin  covering  the  breast  is  clear,  soft,  and  delicate, 
and  subcutaneous  veins  are  often  visible.  The  skin  of  the  nipple  and  areola  is 
particularly  delicate. 

1  Text-book  of  Gynecology.     By  E.  E.  Montgomery. 


THE  MAMMARY  GLAND 


1517 


Variations  in  the  Mammae. — Before  puberty  the  glands  are  small,  of  the  infantile 
type,  grow  slowly,  and  differ  but  slightly  from  the  male  organs.  The  nipple  is 
small  and  flat  and  pale.  At  puberty  the  increase  in  the  size  of  the  breast  is  rapid 
and  considerable,  due  to  growth  of  gland  tissue  and  of  subcutaneous  fat.  During 
pregnancy  the  breasts  enlarge  greatly  and  remain  very  large  throughout  lactation. 
This  enlargement  is  due  to  new  gland  tissue  and  increased  vascularity.  Numerous 
blue  veins  are  visible  in  the  skin,  the  areola  darkens,  and  the  glands  of  Mont- 
gomery enlarge  (Fig.  1127).  During  lactation  the  associated  lymphatic  glands  may 
enlarge  (A.  Marmaduke  Sheild).  After  the  termination  of  lactation  the  breasts 
diminish  in  size.  They  do  not  become  as  small  as  the  virgin  breast,  are  apt  to  lose 
their  hemispherical  outlines,  and  cease  to  be  soft.  They  droop  as  flaccid  pendulous 
masses,  the  subcutaneous  fat  is  largely  gone,  and  the  outlines  of  the  lobular  breast 
tissue  can  be  seen  and  felt.  The  nipple  is  long  and  hangs  down  like  a  teat.  At 
the  menopause  the  breast  usually  shrinks.  In  some  cases,  however,  it  actually 
increases  in  size.  In  such  a  case,  although  the  gland  atrophies,  there  is  an  exten- 
sive deposit  of  fat.  In  old  age  the  glands  undergo  atrophy  and  largely  disappear, 
the  skin  is  flabby  and  thrown  into  wrinkles,  and  the  breasts  contain  very  little 
glandular  structure,  and  are  hard  from  the  presence  of  fibrous  tissue.  The  nipples 
become  pigmented  and  corrugated.  Women  vary  greatly  in  the  development  of 
the  breasts.  In  some  women  they  are  large,  firm,  and  well  proportioned;  in  others 
they  are  small,  flat,  or  atrophy  occurs  in  the  course  of  certain  bodily  diseases,  as 
phthisis,  and  certain  mental  diseases,  as  melancholia.  If  the  ovaries  are  ill- 
developed  the  breasts  remain  flat  and  small.  In  newly  married  women,  even 
though  pregnancy  does  not  exist,  the  breasts  often  develop  decidedly  and  rapidly. 
The  outline  and  direction  of  the  breast  and  also  of  the  nipple  may  be  altered  by 
corsets.  The  left  mamma  is  usually  somewhat  larger  than  the  right. 


Nipple. 


Areola. 


Fat 


Lobule  unravelled 


Lactiferous 
duct. 


Ampulla. 


Lobule.        "*^^^¥f  ]^  *'  ^^jj^^^^  Loculi  in  connective  tissue. 
FIG.  1124.— Dissection  of  the  lower  half  of  the  female  breast  during  the  period  of  lactation.     (From  Luschka.) 

One  gland  or  both  glands  may  be  entirely  absent,  the  nipple  being  also  absent. 
One  or  both  glands  may  be  absent,  one  or  both  nipples  being  present.  When  there 
is  only  one  nipple,  it  is  apt  to  be  the  left.  The  term  polymazia  (mammae  acces- 
soriae  muliebris)  means  the  presence  of  supernumerary  breasts,  with  or  without 


1518  THE  FEMALE  ORGANS  OF  GENERA  TION 

nipples.  Polythelia  means  the  presence  of  supernumerary  nipples,  the  associated 
glandular  structure  being  rudimentary.  There  may  be  one,  two,  or  several  super- 
numerary breasts,  and  when  more  than  one  exists,  are  usually  asymmetrical.  If 
one  is  functionally  active,  it  enlarges  during  pregnancy  and  furnishes  milk. 

Supernumerary  mammae  may  secrete  milk  or  may  be  without  function.  The 
most  common  situation  is  on  the  part  of  the  chest  below  and  to  the  inner  side  of 
the  normally  placed  gland.  They  may  also  exist  in  the  axilla,  the  abdomen,  the 
groin,  the  back,  and  the  thigh.  Many  cases  of  supposed  supernumerary  glands 
have  been  really  instances  in  which  moles,  warts,  or  sebaceous  cysts  have  been 
mistaken  for  breast  tissue,  but  some  cases  are  undoubted. 

Prolongations  of  Mammary  Tissue. — As  previously  stated,  the  outlines  of 
the  breast  are  not  regular,  but  here  and  there  tails,  prolongations,  or  cusps  come  off 
from  and  are  true  portions  of  the  gland.  Two  or  even  more  prolongations  pass  to 
the  edge  of  the  sternum ;  others  pass  toward  the  axilla,  the  clavicle,  and  the  origin 
of  the  external  oblique  muscle  from  the  ribs.  Underneath  the  mammary  gland 
prolongations  of  mammary  tissue  penetrate  the  pectoral  fascia  (Heidenhain) . 
If  one  of  the  glandular  cusps  is  of  considerable  size  it  is  called  an  outlying 
lobule. 

Structure  of  Mammary  Gland  and  Nipple  (Figs.  1124  and  1 125).— The  glands  of 
the  breast  (corpus  mammae)  rest  by  a  smooth  posterior  surface  upon  the  loose  pectoral 
fascia,  which  fastens  the  breast  to  the  muscle  beneath,  but  so  loosely  that  the  breast 
is  movable.  The  mamma  consists  of  gland-tissue;  of  fibrous  tissue,  connecting  its 
lobes,  of  fatty  tissue  in  the  intervals  between  the  lobes,  of  retinacula,  and  of  skin. 
The  gland-tissue,  when  freed  from  fibrous  tissue  and  fat,  is  of  a  pale  reddish  color, 
firm  in  texture,  in  general  circular  in  form,  with  prolongations  here  and  there,  flat- 
tened from  before  backward,  thicker  in  the  centre  than  at  the  circumference,  and 
presenting  several  inequalities  on  its  surface,  especially  in  front.  On  the  anterior 
surface  there  are  many  irregular  elevated  processes  with  deep  spaces  between 
them.  From  the  summits  of  the  elevations  connective-tissue  strands  (retinacula 
cutis)  pass  to  the  true  skin.  The  glandular  structure  consists  of  numerous  lobes 
(lobi  mammae),  and  these  are  composed  of  lobules  (lobuli  mammae),  connected 
together  by  areolar  tissue,  blood-vessels,  and  ducts.  The  smallest  lobules  con- 
sist of  a  cluster  of  rounded  alveoli  (Fig.  1124),  which  open  into  the  smallest 
branches  of  the  excretory  ducts;  these  ducts,  uniting,  form  larger  ducts,  which 
terminate  in  single  canals.  Each  canal  is  called  a  lactiferous,  galactophorous  or 
mammillary  duct  (ductus  lactiferw)  (Fig.  1124).  Each  lobe  possesses  one  lac- 
tiferous duct.  This  passes  to  the  apex  of  the  lobe  and  then  into  the  nipple. 
The  lactiferous  ducts  are  white  and  cord-like,  and  contrast  with  the  yellowish- 
red  tissue  of  the  gland  itself.  The  number  of  excretory  ducts  varies  from  fifteen 
to  twenty.  They  converge  toward  the  areola,  beneath  which  each  duct  forms 
a  spindle-shaped  dilatation,  the  ampulla  (sinus  lactiferans)  (Fig.  1124).  The 
ampullae  serve  as  reservoirs  for  the  milk.  At  the  base  of  the  nipple  the  ducts 
become  contracted  and  pursue  a  straight  course  to  its  summit,  perforating  it  by 
separate  orifices  considerably  narrower  than  the  ducts  themselves.  Each  orifice 
(porus  lactiferus)  is  the  orifice  of  a  tube  which  drains  an  individual  lobe.  The 
ducts  are  composed  of  areolar  tissue,  with  longitudinal  and  transverse  elastic 
fibres;  muscular  fibres  are  entirely  absent;  their  mucous  lining  is  continuous,  at 
the  point  of  the  nipple,  with  the  integument.  The  epithelium  of  the  mammary 
gland  differs  according  to  the  state  of  activity  of  the  organ.  In  the  gland  of  a  woman 
who  is  not  pregnant  or  nursing  the  alveoli  are  very  small  and  solid,  being  filled 
with  a  mass  of  granular  polyhedral  cells.  During  pregnancy  the  alveoli  enlarge 
and  the  cells  undergo  rapid  multiplication.  At  the  commencement  of  lactation 
the  cells  in  the  centre  of  an  alveolus  undergo  fatty  degeneration,  and  are  elim- 
inated in  the  first  milk  as  colostrum-corpuscles.  The  peripheral  cells  of  the  alveolus 
remain,  and  form  a  single  layer  of  granular,  short  columnar  cells  lining  the  limit- 


THE  MAMMARY  GLAND 


1519 


ing  membrana  propria.     The  single  nucleus  of  each  cell  divides  and  forms  two. 
In  the    protoplasm,  especially,  in  the   end    of   the   cells    toward    the   alveolus, 


FIBROUS    SEPTUM 
GLAND    SUBSTANCE 

ADIPOSE   TISSUE 


AREOLA 
NIPPLE 


FIRST 
RIB 


SECOND 

RIB 
PtCTORALIS 

MINOR 

INTERCOSTALES 
SHEATH  OF  PEC- 
TORALIS  MAJOR 

THIRD    RIB 
AREOLAR    TISSUE 


SUPERFICIAL 
FASCIA 


FOURTH    RIB 


LUNG 

ADIPOSE    TISSUE 

.HORIZONTAL    PLANE 

OF    NIPPLE 


FIFTH    RIB 


FIG.  1125. — Right  breast  in  sagittal  section,  inner  surface  of  outer  segment.     (Testut.) 


drops  of  fat  appear,  and  the  nucleus  toward  this  end  of  the  cell  also  becomes 
fattv. 


SECONDARY    ARtOLA 


;:,  CONCENTRIC 
RIDGES 


FIG.  1126. — Nipple  and  areola  of  a  virgin.     (Testut.) 


FIG.  1127. — Nipple  and  areolae  of  a  preg- 
nant woman.     (Testut.) 


The  end  of  the  cell  toward  the  alveolus  breaks  down,  and  the  liberated  mate- 
rial constitutes  "  the  albuminous  ingredients  of  the  milk,  while  the  drops  of  fat 
become  the  milk-globules.  The  portion  of  the  cell  which  remains  forms  new 


1520 


THE  FEMALE  ORGANS  OF  GENERATION 


cytoplasm,  and  the  same  process  is  repeated  over  and  over  again.  The  cells 
also  secrete  water  and  the  salts  which  are  found  in  the  milk."1 

The  fibrous  tissue  (Fig.  1125)  invests  the  entire  surface  of  the  breast,  and  sends 
down  septa  between  its  lobes,  connecting  them  together. 

The  fatty  tissue  (Figs.  1124  and  1125)  surrounds  the  surface  of  the  gland  and 
occupies  the  interval  between  its  lobes.  It  usually  exists  in  considerable  abun- 
dance, and  determines  the  form  and  size  of  the  gland.  There  is  no  fat  immediately 
beneath  the  areola  and  nipple. 


FIG.  1128. — The  lymphatic  vessels  of  the  anterior  surface  of  the  bieast;  the  subareolar  plexus  and  the 
trunks  which  run  from  it.     (Sappey.) 

Vessels  and  Nerves. — The  arteries  supplying  the  mammary  gland  are  derived 
from  the  perforating  branches  of  the  internal  mammary,  long  thoracic  branches  of  the 
axillary,  and  branches  from  the  intercostals.  The  veins  describe  an  anastomotic 
circle  around  the  base  of  the  nipple,  called  by  Haller  the  circulus  venosus.  From 
this  large  branches  transmit  the  blood  to  the  circumference  of  the  gland  and  end 
in  the  axillary  and  internal  mammary  veins.  The  lymphatics  of  the  mammary 
gland  (Figs.  1128  and  1129)  and  mammary  region  have  been  previously  described 
(pp.  810  and  811).  The  nerves  are  derived  from  the  fourth,  fifth,  and  sixth 
intercostal  nerves,  and  sympathetic  filaments  from  the  dorsal  cord  pass  to  the  breast 
along  the  branches  of  the  intercostal  nerves. 

Surgical  Anatomy. — Occasionally  the  mammary  gland  undergoes  enormous  hypertrophy. 
This  may  occur  at  any  age,  even  in  the  virgin.  The  physiological  enlargement  of  puberty  may 
become  excessive  or  the  physiological  enlargement  of  pregnancy  and  lactation  may  continue 
and  increase  after  the  termination  of  lactation.  The  chief  elements  in  the  enlargement  are  fat 
and  connective  tissue,  and  it  is  doubtful  if  there  is  extensive  reproduction  of  glandular  tissue. 

Abscess  of  the  breast  may  occur  at  any  age,  but  is  most  common  by  far  in  nursing  women. 
The  portals  are  opened  to  infection  by  a  crack  in  the  nipple  and  bacteria  are  carried  inward 
by  the  lymph- vessels.  In  some  cases  the  pus  gathers  beneath  the  skin  (supra-mammary  abscess), 
in  others  in  the  breast  tissue  (intra-mammary  abscess).  In  rare  cases  pus  gathers  beneath  the 
breast  (retro-mammary  abscess).  In  intra-mammary  abscess  the  pus  burrows  through  the 

1  Human  Physiology.     By  Joseph  Howard  Raymond. 


THE  MAMMARY  GLAND 


1521 


fibrous  septa  or  fascia  and  forms  numerous  channels,  and  such  a  channel  is  constricted  at  the 
point  where  it  passes  through  fascia  or  a  fibrous  septum,  as  an  hour-glas?  is  constricted. 

In  every  patient  suffering  from  abscess  the  nipple  should  be  examined  for  a  sore  or  crack,  and 
the  area  when  found  should  be  treated  antiseptically.  A  supra-mammary  abscess  should  be 
opened  by  an  incision  radiating  from  the  nipple. 

In  intra-mammary  abscess  follow  the  advice  of  Sheild:  open  the  abscess  by  an  incision  radiating 
from  the  nipple,  insert  the  index  finger,  and  when  possible  pass  it  to  the  bottom  of  the  abscess 
and  carry  the  tip  from  the  depths  of  the  abscess  to  as  near  the  surface  as  possible.  At  this  point 
make  a  counter  opening.  The  finger  breaks  down  septa  which  cause  constriction  and  thus  con- 
verts the  tracking  sinuses  into  one  large  cavity.1  Drain  by  tubes. 

A  retro-mammary  abscess  is  opened  by  an  incision,  following  the  outline  of  the  breast  at  the 
thoraco-mammary  junction,  the  finger  being  pushed  through  the  incision  and  up  under  the  gland. 

Tuberculosis  of  the  breast  may  occur,  and  if  it  does,  cold  abscess  is  apt  to  form.  The  best 
treatment  is  removal  of  the  gland  and  the  associated  lymph  glands. 

Chronic  mastitis  is  a  condition  of  mammary  fibrosis,  most  common  in  neurotic  single  women, 
and  apt  to  be  associated  with  ovarian  or  uterine  disease. 

Meuignant  dermatitis  or  Paget's  disease  of  the  nipple  is  a  chronic  condition  consisting  of 
epithelial  proliferation,  induration,  desquamation,  and  ulceration,  and  it  is  apt  to  be  followed 
by  epithelioma. 

Chancre  of  the  nipple  is  occasionally  met  with. 

Secondary  and  tertiary  syphilitic  lesions  are  seen  upon  the  skin  of  the  breast,  the  nipple,  and 
the  areola. 

Cysts  and  tumors  are  common  in  the  breast. 


DELTA-PECTORAL     HUMCAAL  CHAIN 


CENTRAL- 
GROUP 
SCAPULAR 
CHAIN 


THORACIC 
CHAIN 


CUTANEOUS  COLLECTING 

TRUNK  FROM  THE 

THORACIC  WALL 


MAMMARY  LYMPHATIC 
ENDING  IN  SUB- 
CLAVIAN  GLANDS 


THORACIC 
CHAIN 

MAMMARY  COL- 
LECTING TRUNKS 


8UBAREOLAR 
PLEXUS 


CUTANEOUS  COL- 
LECTING TRUNKS 


I 

COLLECTING  TRUNKS 
PASSING  TO  INTERNAL 
MAMMARY  GLANDS 


MAMMAF 

FIG.  1129.— Lymphatics  of  the  breast  and  axillary  glands.     (Poirier  and  Charpy.) 


There  may  be  cystic  degeneration  of  the  gland  in  women  near  the  menopause  (involution 
cysts);  a  lacteal  cyst;  a  hydatid  cyst;  an  adenoma  may  become  cystic. 

The  nipple  may  suffer  from  epithelioma,  myoma,  myxoma,  angioma,  papilloma,  or  fibroma. 

The  innocent  tumors  of  the  breast  are  fibro-adenoma,  cystic  adenoma,  myxoma,  and  angioma. 

The  skin  of  the  breast  majj  suffer  from  any  form  of  growth  or  cyst  which  could  arise  from 
the  skin  of  another  part.  Malignant  tumors  of  the  glandular  structure  are  ten  times  as  frequent 
as  innocent  tumors.  Sarcoma  is  rare;  carcinoma  is  very  common. 

Carcinoma  of  the  breast  has  occupied  much  of  the  attention  of  surgeons  during  recent  years. 
The  old  operation  was  uniformly  followed  by  recurrence.  The  modern  radical  operation  has 
been  evolved  from  the  studies  of  Moore,  the  younger  Gross,  Heidenhain,  Stiles,  Banks,  Halsted, 
and  others.  The  modern  operation  always  removes  at  least  the  skin  and  subcutaneous  tissue 
over  the  hemispherical  portion  of  the  breast,  the  outlying  lobules  of  the  breast,  the  pectoral  fascia, 


1  Diseases  of  the  Breast.     By  A.  Marmaduke  Sheild. 
96 


1522  THE  FEMALE  ORGANS  OF  GENERATION 

and  the  sternal  portion  of  the  great  Pectoral  muscle,  the  lymphatic  tracts  from  the  breast,  the 
lymphatic  glands  and  cellular  tissue  from  the  axilla,  and  from  beneath  the  ktissimus  dorsi  muscle. 
The  pectoral  fascia  and  the  sternal  portion  of  the  great  Pectoral  muscle  must  corne  away  in  every 
case,  because  breast  tissue  may  pass  through  the  fascia.  The  entire  breast  must  be  removed, 
because  even  in  a  recent  case  the  entire  breast  is  regarded  as  infected.  The  clavicular  portion 
of  the  great  Pectoral  muscle  is  anatomically  distinct  from  the  sternal  portion  and  its  removal  is 
not  imperative.  Some  operators  remove  the  lesser  Pectoral  muscle.  To  leave  it  is  of  no  value  to 
the  arm,  and  it  frequently  causes  an  annoying  rigid  band  anterior  to  the  axilla.  To  take  it  away 
gives  ready  access  to  the  axillary  vessels  at  a  desirable  point  above.  The  sheath  of  the  axillary 
vein  should  be  removed  with  the  glands  and  cellular  tissue  of  the  axilla.  The  glands  receiving 
lymph  from  the  cancerous  area  must  be  removed,  of  course.  In  view  of  the  fact  that  in  an 
undetermined  percentage  of  cases  a  lymph  tract  passes  direct  to  the  subclavian  glands,  it  is 
evident  that  these  glands  may  become  infected  by  this  route  instead  of,  as  is  more  usual,  secondarily 
to  axillary  infection ;  hence  it  seems  wiser  in  every  case  to  remove  the  cellular  tissue  and  glands 
from  the  subclavian  triangle.  All  of  these  structures  should  be  removed  as  one  piece,  in  order 
to  avoid  cutting  across  lymph  tracts  and  flooding  the  wound  with  carcinoma  cells  which  might 
adhere,  grow,  and  reproduce  cancer. 

Halsted's  operation  is  the  method  adopted  by  most  surgeons.  The  wound  cannot  be  com- 
pletely closed,  and  the  raw  spot  is  covered  at  once  or  later  with  Thiersch  skin  grafts.  (For  sur- 
gical considerations  regarding  the  lymphatics  in  mammary  carcinoma  see  page  811.) 

The  Male  Breast  (mamma  virilis). — The  male  breast  is  a  small  flat  struc- 
ture, consisting  chiefly  of  connective  tissue,  but  containing  some  branched  tubules. 
Under  normal  circumstances  it  remains  permanently  of  the  infantile  type.  It 
possesses  a  nipple  which  is  much  smaller  than  that  of  the  female  breast,  and 
which  usually  lies  over  the  fourth  intercostal  space,  but  may  lie  over  the  fourth  or 
fifth  rib.  The  nipples  of  the  two  sides  are  rarely  placed  quite  symmetrically. 
Accessory  glands  and  accessory  nipples  are  as  common  among  males  as  females. 
The  male  breast  may  exhibit  some  evidence  of  temporary  functional  activity  at  birth 
and  at  puberty.  Cases  have  been  recorded  of  actual  lactation  by  the  male  breast. 

Surgical  Anatomy. — The  male  breasts  may  undergo  enormous  hypertrophy  (gynaecomazia). 
In  these  cases  the  penis  is  often  small  and  the  testicles  may  be  atrophied.  The  breasts  may 
be  absent  in  the  male.  Disease  of  the  male  breast  is  not  nearly  so  frequent  as  disease  of  the 
female  breast.  The  organ  may  be  the  seat  of  syphilis,  tuberculosis,  acute  or  chronic  mastitis, 
abscess  or  tumor.  A  number  of  cases  of  cancer  of  the  male  breast  have  been  recorded. 


THE  SURGICAL  ANATOMY  OF  INGUINAL 
HERNIA  AND'  FEMORAL  HEENIA. 


Dissection  (Fig.  287). — For  dissection  of  the  parts  concerned  in  inguinal  hernia  a  male 
subject,  free  from  fat,  should  always  be  selected.  The  body  should  be  placed  in  the  supine 
position,  the  abdomen  and  pelvis  raised  by  means  of  blocks  placed  beneath  them,  and  the  lower 
extremities  rotated  outward,  so  as  to  make  the  parts  as  tense  as  possible.  If  the  abdominal  walls 
are  flaccid,  the  cavity  of  the  abdomen  should  be  inflated  through  an  aperture  made  at  the  umbil- 
icus. An  incision  should  be  made  along  the  middle  line  from  a  little  below  the  umbilicus  to 
the  symphysis  pubis,  and  continued  along  the  front  of  the  scrotum,  and  a  second  incision  from 
the  anterior  superior  spine  of  the  ilium  to  just  below  the  umbilicus.  These  incisions  should 
divide  the  integument,  and  the  triangular-shaped  flap  included  between  them  should  be  reflected 
downward  and  outward,  when  the  superficial  fascia  will  be  exposed. 

The  Superficial  Fascia  of  the  Abdomen  (p.  434). — This,  over  the  greater  part  of 
the  abdominal  wall,  consists  of  a  single  layer  of  fascia,  which  contains  a  variable 
amount  of  fat;  but  as  it  approaches  the  groin  it  is  easily  divisible  into  two  layers, 
between  which  are  found  the  superficial  vessels  and  nerves  and  the  superficial 
inguinal  lymphatic  glands. 

The  Superficial  Layer  of  the  Superficial  Fascia  or  the  Fascia  of  Camper  is  thick, 
areolar  in  texture,  containing  adipose  tissue  in  its  meshes,  the  quantity  of  which 
varies  in  different  subjects.  Below,  it  passes  over  Poupart's  ligament,  and  is  con- 
tinuous with  the  outer  layer  of  the  superficial  fascia  of  the  thigh.  In  the  male  this 
fascia  is  continued  over  the  penis  and  over  the  outer  surface  of  the  cord  to  the 
scrotum,  where  it  helps  to  form  the  dartos.  As  it  passes  to  the  penis,  and  over  the 
cord  to  the  scrotum  it  changes  its  character,  becoming  thin,  destitute  of  adipose 
tissue,  and  of  a  pale  reddish  color;  and  in  the  scrotum  it  acquires  some  involuntary 
muscular  fibres.  From  the  scrotum  it  may  be  traced  backward,  to  be  continuous 
with  the  superficial  fascia  of  the  perinseum.  In  the  female  this  fascia  is  continued 
into  the  labia  majora. 

The  hypogastric  branch  of  the  ilio -hypo gastric  nerve  perforates  the  aponeurosis 
of  the  External  oblique  muscle  about  an  inch  above  and  a  little  to  the  outer  side  of 
the  external  abdominal  ring,  and  is  distributed  to  the  integument  of  the  hypogas- 
tric region. 

The  ilio-inguinal  nerve  escapes  at  the  external  abdominal  ring,  and  is  distributed 
to  the  integument  of  the  upper  and  inner  part  of  the  thigh,  to  the  scrotum  in  the 
male  and  to  the  labium  in  the  female. 

The  superficial  epigastric  artery  arises  from  the  femoral  about  half  an  inch 
below  Poupart's  ligament,  and,  passing  through  the  saphenous  opening  in  the  fascia 
lata,  ascends  on  to  the  abdomen,  in  the  superficial  fascia  covering  the  External 
oblique  muscle,  nearly  as  high  as  the  umbilicus.  It  distributes  branches  to  the 
superficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and  the  integument, 
anastomosing  with  branches  of  the  deep  epigastric  and  internal  mammary 
arteries. 

The  superficial  circumflex  iliac  artery,  the  smallest  of  the  cutaneous  branches, 
arises  close  to  the  preceding,  and,  piercing  the  fascia  lata,  runs  outward,  parallel 
with  Poupart's  ligament,  as  far  as  the  crest  of  the  ilium,  dividing  into  branches 
which  supply  the  superficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and 

(  1523  ) 


1524 


THE  SURGICAL    ANATOMY   OF   HERNIA 


the  integument,  anastomosing  with  the  deep  circumflex  iliac  and  with  the  gluteal 
and  external  circumflex  arteries. 


POUPARTS  INTERCOLUMNAR 

LIGAMENT  FIBRES 


GIMBERNAT'S 
LIGAMENT 


SAPHENOUS 
OPENING 


LONG 

SAPHENOUS 
VEIN 


EXTERNAL 

ABDOMINAL 

RING 


FIG.  1130. — Right  external  abdominal  ring  and  saphenous  opening  in  the  male.    (Spalteholz.) 


EXTERNAL  OBLIQUE 

(reflected  downward) 


EXTERNAL  OBLIQU 

(reflected  inward) 


POSTERIOR  WALL  OF 
INGUINAL  CANAL 


INTERNAL    ORIGIN 
OF  CRENASTER 


FIG.  1131. — Right  inguinal  canal  in  the  male.     Second  layer  viewed  from  in  front.     (Spalteholz.) 


APONEUROSIS    OF   THE  EXTERNAL    OBLIQUE   MUSCLE     1525 


The  superficial  external  pudic  (superior)  artery  arises  from  the  inner  side  of 
the  femoral  artery  close  to  the  preceding  vessels,  and,  after  passing  through  the 
saphenous  opening,  courses  inward  across  the  spermatic  cord,  to  be  distributed  to 
the  integument  on  the  lower  part  of  the  abdomen,  the  penis  and  scrotum  in  the  male, 
and  the  labium  in  the  female,  anastomosing  with  branches  of  the  internal  pudic. 

The  Superficial  Veins. — The  veins  accompanying  these  superficial  vessels  are 
usually  much  larger  than  the  arteries;  they  terminate  in  the  internal  saphenous  vein. 

The  superficial  inguinal  lymphatic  glands  are  placed  immediately  beneath  the 
.integument,  are  of  large  size,  and  vary  from  ten  to  twenty  in  number  (p.  791). 


INTERNAL  OBLIQUE 

(reflected  inward) 


INTERNAL 
OBLIQUE 


EXTERNAL  OBLIQUE 
reflected  inward) 


POSTERIOR 
WALL 


TRIANGULAR 
FASCIA 


FIG.  1132. — The  right  inguinal  canal  in  the  male.     Third  layer  viewed  from  in  front.     (Spalteholz.) 

The  Deep  Layer  of  the  Superficial  Fascia,  the  Fascia  of  Scarpa  or  the  Fascia  of  Cooper 
p.  435)  is  thinner  and  more  membranous  in  character  than  the  superficial  layer. 
In  the  middle  line  it  is  intimately  adherent  to  the  linea  alba;  above,  it  is  continuous 
with  the  superficial  fascia  over  the  rest  of  the  trunk;  below,  it  blends  with  the  fascia 
lata  of  the  thigh  a  little  below  Poupart's  ligament ;  below  and  internally,  in  the  male, 
it  is  continued  over  the  penis  and  over  the  outer  surface  of  the  cord  to  the  scrotum, 
where  it  helps  to  form  the  dartos.  From  the  scrotum  it  may  be  traced  backward 
to  be  continuous  with  the  base  of  the  triangular  ligament  of  the  urethra.  In  the 
female  it  is  continuous  with  the  labia  majora. 

The  scrotum  is  a  cutaneous  pouch  which  contains  the  testes  and  part  of  the 
spermatic  cords,  and  into  which  an  inguinal  hernia  frequently  descends. 

The  Aponeurosis  of  the  External  Oblique  Muscle  (Fig.  1130). — This  is  a  thin 
but  strong  membranous  aponeurosis,  the  fibres  of  which-  are  directed  obliquely 
downward  and  inward.  That  portion  of  the  aponeurosis  which  extends  between 


1526  THE  SURGICAL  ANATOMY  OF  HERNIA 

the  anterior  superior  spine  of  the  ilium  and  the  spine  of  the  os  pubis  is  a  broad 
band,  folded  inward  and  continuous  below  with  the  fascia  lata;  it  is  called  Poupart's 
ligament  (Figs.  288, 1130, 1133, 1134, 1135, 1141,  and  1142).  The  portion  which  is 
reflected  from  Poupart's  ligament  at  the  spine  of  the  os  pubis,  along  the  pectineal 
line,  is  called  Gimbernat's  ligament  (Fig.  296,  338,  1130,  1141,  and  1142).  A  thin 
fibrous  band  extends  from  the  inner  end  of  Poupart's  ligament  and  Gimbernat's 
ligament  upward  and  inward  behind  the  inner  pillar  of  the  external  ring  to  the 
anterior  layer  of  the  rectus  sheath.  The  fibres  diverge  as  they  ascend.  This 
band  is  known  as  the  triangular  fascia  or  Colles's  fascia  or  the  triangular  ligament 
of  Colles  (Figs.  1132  and  1136). 

The  External  or  Superficial  Abdominal  Ring  (annulus  inguinalis  subcutaneus) 
(Figs.  288  and  1130). — Just  above  and  to  the  outer  side  of  the  crest  of  the  os  pubis 
an  interval  is  seen  in  the  aponeurosis  of  the  External  oblique,  called  the  external 
abdominal  ring.  This  aperture  is  oblique  in  direction,  somewhat  triangular  in 
form,  and  corresponds  with  the  course  of  the  fibres  of  the  aponeurosis.  It  usually 
measures  from  base  to  apex  about  an  inch,  and  transversely  about  half  an  inch. 
It  is  bounded  below  by  the  crest  of  the  os  pubis;  above,  by  a  series  of  curved 
fibres,  the  intercolumnar  fibres,  which  pass  across  the  upper  angle  of  the  ring,  so  as 
to  increase  its  strength;  and  on  either  side  by  the  margins  of  the  opening  in  the 
aponeurosis,  which  are  called  the  columns  or  pillars  of  the  ring. 

The  External  Pillar,  which  at  the  same  time  is  inferior  (crus  inferius),  from  the 
obliquity  of  its  direction,  is  the  stronger;  it  is  formed  by  that  portion  of  Poupart's 
ligament  wrhich  is  inserted  into  the  spine  of  the  os  pubis ;  it  is  curved,  so  as  to  form 
a  kind  of  groove,  upon  which  the  spermatic  cord  rests. 

The  Internal  or  Superior  Pillar  (crus  superius)  is  a  broad,  thin,  flat  band,  which 
is  attached  to  the  front  of  the  body  of  the  os  pubis,  interlacing  with  its  fellow  of 
the  opposite  side  in  front  of  the  symphysis  pubis,  that  of  the  right  side  being 
superficial. 

The  external  abdominal  ring  gives  passage  to  the  spermatic  cord  in  the  male 
and  round  ligament  in  the  female;  it  is  much  larger  in  men  than  in  women,  on 
account  of  the  large  size  of  the  spermatic  cord,  hence  the  great  frequency  of  inguinal 
hernia  in  men. 

The  Intercolumnar  Fibres  (fibrae  intercrurales)  (Fig.  1130)  are  a  series  of  curved 
tendinous  fibres  which  arch  across  the  lower  part  of  the  aponeurosis  of  the  Exter- 
nal oblique.  They  have  received  their  name  from  stretching  across  between  the 
two  pillars  of  the  external  ring;  they  increase  the  strength  of  the  lower  part  of  the 
aponeurosis  and  prevent  the  divergence  of  the  pillars  from  one  another.  They 
are  thickest  below,  where  they  arise  from  Poupart's  ligament,  and  they  are 
inserted  into  the  linea  alba,  describing  a  curve,  with  the  convexity  downward. 
They  are  much  thicker  and  stronger  at  -the  outer  angle  of  the  external  ring  than 
internally,  and  are  more  strongly  developed  in  the  male  than  in  the  female. 
These  intercolumnar  fibres,  as  they,  pass  across  the  external  abdominal  ring,  are 
themselves  connected  together  by  delicate  fibrous  tissue,  thus  forming  a  fascia 
which,  as  it  is  attached  to  the  pillars  of  the  ring,  covers  it  in,  and  is  called  the 
intercolumnar  fascia.  This  intercolumnar  fascia  is  continued  downward  as  a 
tubular  prolongation  around  the  outer  surface  of  the  cord  and  testis,  and  encloses 
them  in  a  distinct  sheath;  hence,  it  is  also  called  the  external  spermatic  fascia. 
The  sac  of  an  inguinal  hernia  in  passing  through  the  external  abdominal  ring 
receives  an  investment  from  the  intercolumnar  fascia. 

If  the  finger  is  introduced  a  short  distance  into  the  external  ring  and  the  limb 
is  then  extended  and  rotated  outward,  the  aponeurosis  of  the  External  oblique, 
together  with  the  iliac  portion  of  the  fascia  lata,  will  be  felt  to  become  tense  and 
the  external  ring  much  contracted;  if  the  limb  is,  on  the  contrary,  flexed  upon  the 
pelvis  and  rotated  inward,  this  aponeurosis  will  become  lax,  and  the  external  ring 


THE    TRIANGULAR    FASCIA    OF    THE   ABDOMEN 


1527 


sufficiently  enlarged  to  admit  the  finger  with  comparative  ease;  hence  the  patient 
should  always  be  put  in  the  latter  position  when  the  taxis  is  applied  for  the  reduc- 
tion of  an  inguinal  hernia,  in  order  that  the  abdominal  walls  may  be  relaxed  as 
much  as  possible. 

The  aponeurosis  of  the  External  oblique  should  be  removed  by  dividing  it  across  in  the  same 
direction  as  the  external  incisions,  and  reflecting  it  downward  and  outward;  great  care  is  requisite 
in  separating  it  from  the  aponeurosis  of  the  muscle  beneath.  The  lower  part  of  the  Internal 
oblique  and  the  Cremaster  are  then  exposed,  together  with  the  inguinal  canal,  which  contains 
the  spermatic  cord  (Fig.  1133).  The  mode  of  insertion  of  Poupart's  and  Gimbernat's  ligaments 
into  the  os  pubis  should  also  be  examined. 

Poupart's  Ligament  (ligamentum  inguinale  [Pouparti])  (Figs.  288,  1130,  1133, 
1 134, 1 135, 1141 ,  and  1 142)  or  the  crural  arch  is  the  lower  border  of  the  aponeurosis 
of  the  External  oblique  muscle,  which  extends  from  the  anterior  superior  spine  of 
the  ilium  to  the  spine  of  the  os  pubis.  From  this  latter  point  it  is  reflected  out- 
ward to  be  attached  to  the  pectineal  line  for  about  half  an  inch,  forming  Gimber- 
nat's ligament.  Its  general  direction  is 
curved  downward  toward  the  thigh, 
where  it  is  continuous  with  the  fascia 
lata.  Its  outer  half  is  rounded  and 
oblique  in  direction ;  its  inner  half  grad- 
ually widens  at  its  attachment  to  the  os 
pubis,  is  more  horizontal  in  direction, 
and  lies  beneath  the  spermatic  cord. 

Gimbernat's  Ligament  (ligamentum 
lacunare  [Gimbernati])  (Figs.  288,  296, 
338,  1130,  1141,  and  1142)  is  that  por- 
tion of  the  aponeurosis  of  the  External 
oblique  muscle  which  is  reflected  up- 
ward and  outward  from  the  spine  of 
the  os  pubis  to  be  inserted  into  the 
pectineal  line.  It  is  about  half  an 
inch  in  length,  larger  in  the  male  than 
in  the  female,  almost  horizontal  in 
direction  in  the  erect  posture,  and  of  a 
triangular  form,  with  the  base  directed 
outward.  Its  base  or  outer  margin  is 
concave,  thin,  and  sharp,  and  lies  in 
contact  with  the  femoral  sheath,  form- 
ing the  inner  boundary  of  the  femoral 
ring  (Fig.  1141).  Its  apex  corresponds 
to  the  spine  of  the  os  pubis.  Its  pos- 

tprinr    maro-in    i<?    nttarVipd    to  rhp    npr-        FIG.  1133.— Inguinal  hernia.    Dissection  showing  the 
margin  Internal  oblique  and  Cremaster. 

tineal  line,  and  is  continuous  with  the 

pubic  portion  of  the  fascia  lata.    Its  anterior  margin  is  continuous  with  Poupart's 

ligament. 

The  Triangular  Fascia  of  the  Abdomen,  Colles's  Fascia  or  the  Triangular  Ligament 
of  Colles  (ligamentum  inguinale  reflexum  [Collesi])  (Figs.  1132, 1133,  and  1136)  is  a 
band  of  tendinous  fibres,  of  a  triangular  shape,  which  is  attached  by  its  apex  to 
the  inner  end  of  Poupart's  ligament  and  to  Gimbernat's  ligament.  It  passes 
inward  beneath  the  spermatic  cord,  and  expands  into  a  somewhat  fan-shaped 
fascia,  lying  behind  the  inner  pillar  of  the  external  abdominal  ring  and  in  front 
of  the  conjoined  tendon,  and  interlaces  with  the  ligament  of  the  other  side  at  the 
linea  alba  in  the  anterior  layer  of  the  sheath  of  the  Rectus  muscle. 


1528  THE  SURGICAL  ANATOMY  OF  HERNIA 

The  Ligament  of  Cooper. — See  Fig.  296  and  p.  439. 

The  Internal  Oblique  Muscle  (Figs.  1131,  1132,  and  1133)  has  been  previously 
described  (p.  439).  The  part  which  is  now  exposed  is  partly  muscular  and  partly 
tendinous  in  structure.  Those  fibres  which  arise  from  Poupart's  ligament,  few  in 
number  and  paler  in  color  than  the  rest,  arch  downward  and  inward  across  the 
spermatic  cord,  and,  becoming  tendinous,  are  inserted,  conjointly  with  those  of 
the  Transversalis,  into  the  crest  of  the  os  pubis  and  pectineal  line,  forming  what 
is  known  as  the  conjoined  tendon  of  the  Internal  oblique  and  Transversalis  (Figs. 
1133  and  1134).  This  tendon  is  inserted  immediately  behind  the  inguinal  .canal 
and  external  abdominal  ring,  serving  to  protect  what  would  otherwise  be  a  weak 
point  in  the  abdominal  wall.  The  conjoined  tendon  is  sometimes  divided  into 
an  outer  and  an  inner  portion,  the  former  being  called  the  ligament  of  Hessel- 
bach  (ligamentum  interfoveolare)  (Fig.  291),  and  the  latter  the  ligament  of  Henle 
(Fig.  291).  Sometimes  the  conjoined  tendon  is  insufficient  to  resist  the  pressure 
from  within,  and  is  carried  forward  in  front  of  the  protrusion  through  the  exter- 
nal ring,  forming  one  of  the  coverings  of  direct  inguinal  hernia,  or  the  hernia 
forces  its  way  through  the  fibres  of  the  conjoined  tendon. 

The  Cremaster  (Figs.  1131  and  1133)  is  derived  from  the  lower  margin  of  the 
Internal  oblique,  of  which  muscle  it  is  in  reality  a  portion.  It  is  a  thin  muscular 
layer  composed  of  a  number  of  fasciculi.  It  arises  by  a  thick  external  bundle  of 
fibres  from  the  upper  portion  of  Poupart's  ligament,  being  connected  with  the 
Internal  oblique  muscle  and  also  occasionally  with  the  Transversalis.  It  arises 
also  by  a  thin  inner  bundle  of  fibres  from  the  anterior  layer  of  the  rectus 
sheath. 

The  thick  bundle  of  origin  is  on  the  lateral  surface ;  the  thin  bundle  is  on  the 
medial  surface  of  the  spermatic  cord.  The  Cremaster  passes  along  with  the 
spermatic  cord,  and  descends  with  it  through  the  external  ring.  Upon  the  front  and 
sides  of  the  cord  both  bundles  spread  out  upon  the  vaginal  tunic  of  the  testicle 
and  epididymis,  and  form  a  series  of  loops  which  differ  in  thickness  and  length 
in  different  subjects.  These  loops  are  united  together  by  areolar  tissue,  and 
form  a  thin  covering  over  the  cord  and  testis,  the  cremasteric  fascia  (fascia 
cremaster  ica} . 

It  will  be  observed  that  the  Cremaster  is  a  separated  portion  of  the  Internal 
oblique.  This  fact  affords  an  easy  explanation  of  the  manner  in  which  the  testicle 
and  cord  are  invested  by  this  muscle.  At  an  early  period  of  foetal  life  the  testis  is 
placed  at  the  lower  and  back  part  of  the  abdominal  cavity,  but  during  its  descent 
toward  the  scrotum,  which  takes  place  before  birth,  it  passes  beneath  the  arched 
border  of  the  Internal  oblique.  In  its  passage  beneath  this  muscle  some  fibres 
are  derived  from  its  lower  part,  which  accompany  the  testicle  and  cord  into  the 
scrotum. 

It  occasionally  happens  that  the  loops  of  the  Cremaster  surround  the  cord,  some 
lying  behind  as  well  as  in  front.  It  is  probable  that  under  these  circumstances 
the  testis  in  its  descent  passes  through,  instead  of  beneath,  the  fibres  of  the  Internal 
oblique. 

In  the  descent  of  an  oblique  inguinal  hernia,  which  takes  the  same  course  as 
the  spermatic  cord,  the  Cremaster  muscle  forms  one  of  its  coverings.  This  muscle 
becomes  largely  developed  in  cases  of  hydrocele  and  large  old  scrotal  herniae.  No 
such  muscle  exists  in  the  female,  but  an  analogous  structure  is  developed  in  those 
cases  where  an  oblique  inguinal  hernia  descends  beneath  the  margin  of  the  Internal 
oblique. 

The  Internal  oblique  should  be  detached  from  Poupart's  ligament,  separated  from  the  Trans- 
versalis to  the  same  extent  as  in  the  previous  incisions,  and  reflected  inward  on  to  the  sheath 
of  the  Rectus  (Fig.  11 34).  The  deep  circumflex  iliac  vessels,  which  lie  between  these  two  muscles, 
form  a  valuable  guide  to  their  separation. 


THE  INGUINAL  OR  SPERMATIC  CANAL 


1529 


The  Transversalis  Muscle  (Figs.  1132  and  1134)  has  been  previously  described 
(p.  444).  The  part  which  is  now  exposed  is  partly  muscular  and  partly  tendinous 
in  structure;  it  arises  from  the  outer  third  of  Poupart's  ligament,  its  fibres  curve 
downward  and  inward,  and  are  inserted,  together  with  those  of  the  Internal 
oblique,  into  the  lower  part  of  the  linea  alba,  into  the  crest  of  the  os  pubis  and 
the  pectineal  line,  forming  what  is  known  as  the  conjoined  tendon  of  the  Internal 
oblique  and  Transversalis  (Figs.  1133  and  1134).  The  falx  aponeurotica  [inguinalis] 
is  a  collection  of  fibres  of  tendinous  consistence  in  the  inner  side  of  the  Trans- 
versalis insertion.  Between  the  lower  border  of  this  muscle  and  Poupart's 
ligament  a  space  is  left  in  which  is  seen  the  transversalis  fascia. 

The  Inguinal  or  Spermatic  Canal  (canalis  inguinalis)  (Figs.  1131,  1132,  and  1134) 
contains  the  spermatic  cord  in  the  male  and  the  round  ligament  in  the  female.  It 
is  an  oblique  canal,  about  an  inch  and  a  half  in  length,  directed  downward  and 
inward  and  placed  parallel  with,  and  a  little  above,  Poupart's  ligament.  It  com- 
mences above  at  the  internal  or  deep  abdominal  ring,  which  is  the  point  where 


Internal  . 
abdominal  ring. 


Epigastric  artery. 


FIG.  1134. — Inguinal  hernia. 


Dissection  showing  the  Transversalis  muscle,  the  transversalis  fascia, 
and  the  internal  abdominal  ring. 


the  cord  enters  the  inguinal  canal,  and  terminates  below  at  the  external  or  super- 
ficial ring.  It  is  bounded,  in  front,  by  the  integument  and  superficial  fascia,  by 
the  aponeurosis  of  the  External  oblique  throughout  its  whole  length,  and  by  the 
Internal  oblique  for  its  outer  third;  behind,  by  the  triangular  fascia,  the  conjoined 
tendon  of  the  Internal  oblique  and  Transversalis,  transversalis  fascia,  and  the 
subperitoneal  fat  and  peritoneum;  above,  by  the  arched  fibres  of  the  Internal 
oblique  and  Transversalis;  below,  by  the  union  of  the  transversalis  fascia  with 
Poupart's  ligament.  That  form  of  hernia  in  which  the  intestine  follows  the  course 
of  the  spermatic  cord  along  the  inguinal  canal  is  called  oblique  inguinal  hernia. 

On  the  posterior  wall  of  the  inguinal  canal  is  seen  the  band  of  fibres  known  as 
the  ligament  of  Hesselbach  (ligamentum  interfoveolare  [Hesselbachi])  (Fig.  291). 
It  is  placed  in  front  of  the  deep  epigastric  artery.  The  fibres  come  from  the 
external  portion  of  the  lower  fibres  of  the  conjoined  tendon  (Fig.  1133)  and  pass 


1530  THE   SURGICAL   ANATOMY    OF  HERNIA 

downward  for  a  distance,  some  of  them  then  passing  outward  and  upward,  some 
of  them  downward  and  inward  to  the  inner  surface  of  Poupart's  ligament. 

The  Transversalis  Fascia  (Figs.  296, 1134,  and  1142)  is  a  thin  aponeurotic  mem- 
brane which  lies  between  the  inner  surface  of  the  Transversalis  muscle  and  the 
peritoneum.  It  forms  part  of  the  general  layer  of  fascia  which  lines  the  interior 
of  the  abdominal  and  pelvic  cavities,  and  is  directly  continuous  with  the  iliac 
and  pelvic  fasciae. 

In  the  inguinal  region  the  transversalis  fascia  is  thick  and  dense  in  structure, 
and  joined  by  fibres  from  the  aponeurosis  of  the  Transversalis  muscle;  but  it 
becomes  thin  and  cellular  as  it  ascends  to  the  Diaphragm.  Below,  it  has  the 
following  attachments;  external  to  the  femoral  vessels  it  is  connected  to  the 
posterior  margin  of  Poupart's  ligament,  and  is  there  continuous  with  the  iliac 
fascia.  Internal  to  the  vessels  it  is  thin,  and  attached  to  the  os  pubis  and  pectineal 
line  behind  the  conjoined  tendon,  with  which  it  is  united;  and,  corresponding  to 
the  points  where  the  femoral  vessels  pass  into  the  thigh,  this  fascia  descends  in 
front  of  them,  forming  the  anterior  wall  of  the  femoral  sheath.  The  spermatic  cord 
in  the  male  and  the  round  ligament  in  the  female  pass  through  this  fascia;  the 
point  where  they  pass  through  is  called  the  internal  or  deep  abdominal  ring.  This 
opening  is  not  visible  externally,  owing  to  a  prolongation  of  the  transversalis  fascia 
on  the  structures  forming  the  infundibuliform  fascia. 

The  Internal  or  Deep  Abdominal  Ring  (annulus  inguinalis  abdominalis)  (Figs.  296 
and  1134)  is  situated  in  the  transversalis  fascia,  midwyay  between  the  anterior  superior 
spine  of  the  ilium  and  symphysis  pubis,  and  about  half  an  inch  above  Poupart's 
ligament.  It  is  of  an  oval  form,  its  long  diameter  being  directed  upward  and 
downward;  it  varies  in  size  in  different  subjects,  and  is  much  larger  in  the  male 
than  in  the  female.  It  is  bounded  above  and  externally  by  the  arched  fibres  of 
the  Transversalis  muscle,  below  and  internally  by  the  deep  epigastric  vessels.  It 
transmits  the  spermatic  cord  in  the  male  and  the  round  ligament  in  the  female. 
From  its  circumference,  a  thin,  funnel-shaped  membrane,  the  infundibuliform  fascia, 
is  continued  around  the  cord  and  testis,  enclosing  them  in  a  distinct  pouch  (Fig. 
1134).  When  the  sac  of  an  oblique  inguinal  hernia  passes  through  the  internal  or 
deep  abdominal  ring,  the  infundibuliform  fascia  constitutes  one  of  its  coverings. 

The  Subperitoneal  Areolar  Tissue  or  the  Fascia  Propria  of  Cooper. — Between  the 
transversalis  fascia  and  the  peritoneum  is  a  quantity  of  loose  areolar  tissue.  In 
some  subjects  it  is  of  considerable  thickness  and  loaded  with  adipose  tissue. 
Opposite  the  internal  ring  it  is  continued  around  the  surface  of  the  cord,  forming 
a  loose  sheath  for  it. 

The  Deep  Epigastic  Artery  (Figs.  291  and  1135)  arises  from  the  external  iliac 
artery  a  few  lines  above  Poupart's  ligament.  It  at  first  descends  to  reach  this  liga- 
ment, and  then  ascends  obliquely  along  the  inner  margin  of  the  internal  or  deep 
abdominal  ring,  lying  between  the  transversalis  fascia  and  the  peritoneum,  and 
passing  upward  pierces  the  transversalis  fascia  and  enters  the  sheath  of  the  Rectus 
muscle  by  passing  over  the  semilunar  fold  of  Douglas.  Consequently  the  deep 
epigastric  artery  bears  a  very  important  relation  to  the  internal  abdominal  ring 
as  it  passes  obliquely  upward  and  inward  from  its  origin  from  the  external  iliac. 
In  this  part  of  its  course  it  lies  along  the  lower  and  inner  margin  of  the  internal 
ring  and  beneath  the  commencement  of  the  spermatic  cord.  At  its  commence- 
ment it  is  crossed  by  the  vas  deferens  in  the  male  and  by  the  round  ligament  in 
the  female. 

The  Peritoneum  (Fig.  1135),  corresponding  to  the  inner  surface  of  the  internal 
ring,  presents  a  well-marked  depression,  the  depth  of  which  varies  in  different 
subjects.  A  thin  fibrous  band  is  continued  from  it  along  the  front  of  the  cord 
for  a  variable  distance,  and  becomes  ultimately  lost,  the  ligament  of  Cloquet. 
This  is  the  remains  of  the  pouch  of  peritoneum  which,  in  the  foetus,  precedes 


THE   PERITONEUM 


1531 


the  cord  and  testis  into  the  scrotum,  the  obliteration  of  which  commences  soon 
after  birth.  In  some  cases  the  fibrous  band  can  only  be  traced  a  short  distance, 
but  occasionally  it  may  be  followed,  as  a  fine  cord,  as  far  as  the  upper  end  of  the 
tunica  vaginalis.  Sometimes  the  tube  of  peritoneum  is  closed  only  at  intervals 
and  presents  a  sacculated  appearance,  or  a  single  pouch  may  extend  along  the 
whole  length  of  the  cord,  which  may  be  closed  above,  or  the  pouch  may  be  directly 
continuous  with  the  peritoneum  by  an  opening  at  its  upper  part. 

In  the  female  fo?tus  the  peritoneum  is  also  prolonged  in  the  form  of  a  tubular 
process  for  a  short  distance  into  the  inguinal  canal.  This  process  is  called  the 
canal  of  Nuck.  It  is  generally  obliterated  in  the  adult,  but  sometimes  it  remains 
pervious  even  in  advanced  life. 


If.  iliacus. 


External 
inguinal 
fossa. 


External 
iliac 
artery. 


External 
iliac 
vein. 


Femoral 


Internal  inguinal 
fossa. 


Superior  vesical 

artery, 
'iddle  inguinal 
fossa. 


FIG.  1135. — Posterior  view  of  the  anterior  abdominal  wall  in  its  lower  hah.     The  peritoneum  is  in  place, 
and  the  various  cords  are  shining  through.     (After  Joessel.) 

In  order  to  understand  the  relation  of  the  peritoneum  to  inguinal  hernia,  it  is 
necessary  to  view  the  anterior  abdominal  wall  from  its  internal  aspect,  when  it  will 
be  seen  as  shown  in  Fig.  1135.  Between  the  upper  margin  of  the  front  of  the 
pelvis  and  the  umbilicus,  the  peritoneum,  when  viewed  from  behind,  will  be  seen 
to  be  raised  into  five  vertical  folds,  with  intervening  depressions,  by  more  or  less 
prominent  bands  which  converge  to  the  umbilicus.  One  of  these  is  situated  in  the 
median  line,  and  is  caused  by  the  urachus,  the  remnant  of  the  allantois;  it  extends 
from  the  summit  of  the  bladder  to  the  umbilicus.  The  fold  of  peritoneum  covering 
it  is  known  as  the  fold  of  the  urachus  or  the  plica  urachi  (plica  umbilwalis  media). 
On  either  side  of  this  is  a  prominent  band,  caused  by  the  obliterated  hypogastric 
artery,  which  extends  from  the  side  of  the  bladder  obliquely  upward  and  inward 
to  the  umbilicus.  This  is  covered  by  a  fold  of  peritoneum  which  is  known  a«  the 


1532  THE   SURGICAL    ANATOMY    OF  HERNIA 

hypogastric  fold  or  the  plica  hypogastrica  (plica  umbilicalis  lateralis).  To  either 
side  of  these  three  cords  is  the  deep  epigastric  artery,  which  ascends  obliquely 
upward  and  inward  from  a  point  midway  between  the  symphysis  pubis  and  the 
anterior  superior  spine  of  the  ilium  to  the  semilunar  fold  of  Douglas,  in  front  of 
which  it  disappears.  It  is  covered  by  a  fold  of  peritoneum  which  is  known  as  the 
plica  epigastrica.  Between  these  raised  folds  are  depressions  of  the  peritoneum, 
constituting  so-called  fossae.  The  most  internal,  between  the  plica  urachi  and  the 
plica  hypogastrica,  is  known  as  the  internal  inguinal  fossa  (fovea  supravesicalis). 
The  middle  one  is  situated  between  the  plica  hypogastrica  and  the  plica  epigas- 
trica, and  is  termed  the  middle  inguinal  fossa  (fovea  inguinalis  mesialis).  The 
external  one  is  external  to  the  plica  epigastrica,  and  is  known  as  the  external 
inguinal  fossa  (fovea  inguinalis  lateralis).  Occasionally  the  deep  epigastric  artery 
corresponds  in  position  to  the  obliterated  hypogastric  artery,  and  then  there  is  but 
one  fold  on  each  side  of  the  middle  line,  and  the  two  external  fossae  are  merged 
into  one.  In  the  usual  condition  of  the  parts  the  floor  of  the  external  inguinal 
fossa  corresponds  to  the  internal  abdominal  ring,  and  into  this  fossa  an  oblique 
inguinal  hernia  descends.  To  the  inner  side  of  the  plica  epigastrica  are  the 
two  internal  fossae,  and  through  either  of  these  a  direct  hernia  may  descend,  as 
will  be  explained  in  the  sequel  (p.  1535).  The  whole  of  this  space,  that  is  to 
say,  the  space  between  the  deep  epigastric  artery,  the  margin  of  the  Rectus  and 
Poupart's  ligament,  is  commonly  known  as  Hesselbach's  triangle.  These  three 
depressions  or  fossae  are  situated  above  the  level  of  Poupart's  ligament,  and  in 
addition  to  them  is  another  below  the  ligament,  corresponding  to  the  position  of 
the  femoral  ring,  and  into  which  a  femoral  hernia  descends. 


INGUINAL  HERNIA. 

Inguinal  hernia  is  that  form  of  protrusion  which  makes  its  way  through  the 
abdomen  in  the  inguinal  region. 

There  are  two  principal  varieties  of  inguinal  hernia — external  or  oblique,  and 
internal  or  direct. 

External  or  oblique  inguinal  hernia,  the  more  frequent  of  the  two,  takes  the 
same  course  as  the  spermatic  cord.  It  is  called  external  from  the  neck  of  the  sac 
being  on  the  outer  or  iliac  side  of  the  deep  epigastric  artery. 

Internal  or  direct  inguinal  hernia  does  not  follow  the  same  course  as  the  cord, 
but  protrudes  through  the  abdominal  wall  on  the  inner  or  pubic  side  of  the  deep 
epigastric  artery. 

Oblique  Inguinal  Hernia. 

In  oblique  inguinal  hernia  (Fig.  1135)  the  intestine  or  omentum  escapes  from  the 
abdominal  cavity  at  the  internal  ring.  Before  it  is  a  pouch  of  peritoneum,  which 
forms  the  hernial  sac  (Fig.  1137,  /I).  This  pouch  of  peritoneum  is  invested  by  the 
subserous  areolar  tissue,  and  is  enclosed  in  the  infundibuliform  process  of  the  trans- 
versalis  fascia,  which  it  receives  as  it  enters  the  inguinal  canal.  In  passing  along  the 
inguinal  canal  the  hernia  displaces  upward  the  arched  fibres  of  the  Transversalis  and 
Internal  oblique  muscles,  and  is  imperfectly  surrounded  by  the  fibres  of  the  Cre- 
master  muscles,  the  coat  being  completed  by  the  cremasteric  fascia.  It  then  passes 
along  the  front  of  the  cord,  and  escapes  from  the  inguinal  canal  at  the  external 
ring,  receiving  an  investment  from  the  intercolumnar  fascia.  Lastly,  it  descends 
into  the  scrotum,  receiving  coverings  from  the  superficial  fascia  and  the  integument. 

The  coverings  of  this  form  of  hernia,  after  it  has  passed  through  the  external 
ring?  are,  from  without  inward,  the  integument,  superficial  fascia,  intercolumnar 


OBLIQUE   INGUINAL    HERNIA 


1533 


fascia,  Cremaster  muscle  and  fascia,  infundibuliform  fascia,  subserous  areolar 
tissue,  and  peritoneum. 

This  form  of  hernia  lies  in  front  of  the  vessels  of  the  spermatic  cord  and  seldom 
extends  below  the  testis,  on  account  of  the  intimate  adhesion  of  the  coverings 
of  the  cord  to  the  tunica  vaginalis  (Fig.  1137,  A}. 

The  seat  of  stricture  in  a  strangulated  oblique  inguinal  hernia  is  either  at  the 
external  ring,  in  the  inguinal  canal,  caused  by  the  fibres  of  the  Internal  oblique 
or  Transversalis;  or  at  the  internal  ring,  most  frequently  in  the  latter  situation. 
If  it  is  situated  at  the  external  ring,  the  division  of  a  few  fibres  at  one  point  of 
its  circumference  is  all  that  is  necessary  for  the  replacement  of  the  hernia.  If 
in  the  inguinal  canal  or  at  the  internal  ring,  it  may  be  necessary  to  divide  the 


Flo.  1136. — Oblique  inguinal  hernia,  showing  its  various  coverings.     (From  a  preparation  in  the 
Museum  of  the  Royal  College  of  Surgeons.) 


In 


aponeurosis  of  the  External  oblique  so  as  to  lay  open  the  inguinal  canal, 
dividing  the  stricture  the  direction  of  the  incision  should  be  upward. 

When  the  hernia  passes  along  the  inguinal  canal  and  escapes  from  the  external 
ring  into  the  scrotum,  the  condition  is  called  complete  oblique  inguinal  or  scrotal 
hernia  (Fig.  1137,  A).  If  the  hernia  does  not  escape  from  the  external  ring,  but  is 
retained  in  the  inguinal  canal,  the  condition  is  called  incomplete  inguinal  hernia  or 
bubonocele.  In  each  of  these  cases  the  coverings  which  invest  the  intestine  or 
omentum  will  depend  upon  the  extent  to  which  it  descends  in  the  inguinal  canal. 

There  are  some  other  varieties  of  oblique  inguinal  hernia  depending  upon  con- 
genital defects  in  the  processus  vaginalis.  The  testicle  in  its  descent  from  the 
abdomen  into  the  scrotum  is  preceded  by  a  pouch  of  peritoneum,  which  about 


1534 


THE   SURGICAL    ANATOMY   OF   HERNIA 


the  period  of  birth  becomes  shut  off  from  the  general  peritoneal  cavity  by  a  closure 
of  that  portion  of  the  pouch  which  extends  from  the  internal  abdominal  ring  to 


Sac  of  hernia. 


Tunica 
vaginalis.''' 

A.  Common  scrotal  hernia. 


Tunica 
--  -vaginalis. 


B.  Congenital  hernia. 


Sac  of  ^^ 
hernia. 


Sac  of  hernia. 

Tunica 
'vaginalis. 


Tunica  vaginalis.-]- «*? 


— 1 — Sac  of  hernia. 


E   Hernia  into  the  funicular  process. 
FIG.  1137. — Varieties  of  oblique  inguinal  hernia 


near  the  upper  part  of  the  testicle,  the  lower  portion  of  the  pouch  remaining  per- 
sistent as  the  tunica  vaginalis.     It  would  appear  that  this  closure  commences  at 


DIRECT  INGUINAL    HERNIA  1535 

two  points — viz.,  at  the  internal  abdominal  ring  and  at  the  top  of  the  epididymis 
— and  gradually  extends  until,  in  the  normal  condition,  the  whole  of  the  inter- 
vening portion  is  converted  into  a  fibrous  cord.  From  failure  in  the  completion 
of  this  process  variations  in  the  relation  of  the  hernial  protrusion  to  the  testicle 
and  tunica  vaginalis  are  produced,  which  constitute  distinct  varieties  of  inguinal 
hernia,  and  which  have  received  separate  names  and  are  of  surgical  importance. 
These  are  congenital,  infantile,  encysted,  and  hernia  of  the  funicular  process. 

Congenital  Hernia  (Fig.  1137,  B). — Where  the  congenital  pouch  of  peritoneum 
which  precedes  the  cord  and  testis  in  its  descent  remains  patent  throughout  and 
is  unclosed  at  any  point,  the  cavity  of  the  tunica  vaginalis  communicates  directly 
with  the  cavity  of  the  peritoneum.  The  intestine  descends  along  this  pouch  into 
the  cavity  of  the  tunica  vaginalis,  which  constitutes  the  sac  of  the  hernia,  and  the 
gut  lies  in  contact  with  the  testicle. 

Infantile  and  Encysted  Hernia. — Where  the  congenital  pouch  of  peritoneum 
is  occluded  at  the  internal  ring  only,  but  remains  patent  throughout  the  rest  of 
its  extent,  two  varieties  of  oblique  inguinal  hernia  may  be  produced,  which  have 
received  the  names  of  infantile  and  encysted  hernia.  In  the  infantile  form  (Fig. 
1137,  C)  the  septum  which  closed  the  congenital  sac  above  and  the  peritoneum 
in  its  immediate  neighborhood  yields  and  forms  a  sac,  which  descends  behind  the 
tunica  vaginalis,  so  that  in  front  of  the  bowel  there  are  three  layers  of  perito- 
neum, the  two  layers  of  the  tunica  vaginalis  and  the  layer  of  the  proper  hernial 
sac.  In  the  encysted  form  (Fig.  1137,  D)  yielding  occurs  in  the  same  position  as 
in  the  infantile  form — namely,  at  the  occluded  spot  in  the  pouch — and  a  sac  forms 
which  projects  into  and  not  behind  the  tunica  vaginalis,  as  in  the  infantile  form, 
and  thus  it  constitutes  a  sac  within  a  sac,  so  that  in  front  of  the  bowel  there  are  two 
layers  of  peritoneum — one  layer  of  the  tunica  vaginalis  and  one  of  true  hernial  sac. 

Hernia  into  the  Funicular  Process  (Fig.  1137,  E). — Where  the  congenital 
pouch  of  peritoneum  is  occluded  at  the  lower  point  only — that  is,  just  above  the 
testicle — the  intestine  descends  into  the  pouch  of  peritoneum  as  far  as  the  testicle, 
but  is  prevented  from  entering  the  sac  of  the  tunica  vaginalis  by  the  septum  which 
has  formed  between  it  and  the  pouch,  so  that  it  resembles  the  congenital  form  in 
all  respects,  except  that,  instead  of  enveloping  the  testicle,  that  body  can  be  felt 
below  the  rupture. 

Direct  Inguinal  Hernia. 

In  direct  inguinal  hernia  the  protrusion  makes  its  way  through  some  part  of 
the  abdominal  wall  internal  to  the  epigastric  artery. 

At  the  lower  part  of  the  abdominal  wall  is  a  triangular  space,  Hesselbach's 
triangle,  bounded  externally  by  the  deep  epigastric  artery,  internally  by  the 
margin  of  the  Rectus  muscle,  below  by  Poupart's  ligament  (Fig.  1135).  The  con- 
joined tendon  is  stretched  across  the  inner  two-thirds  of  this  space,  the  remaining 
portion  of  the  space  having  only  the  subperitoneal  areolar  tissue  and  the  trans- 
versalis  fascia  between  the  peritoneum  and  the  aponeurosis  of  the  External  oblique 
muscle. 

In  some  cases  the  hernial  protrusion  escapes  from  the  abdomen  on  the  outer 
side  of  the  conjoined  tendon,  pushing  before  it  the  peritoneum,  the  subserous 
areolar  tissue,  and  the  transversalis  fascia.  It  then  enters  the  inguinal  canal, 
passing  along  nearly  its  whole  length,  and  finally  emerges  from  the  external  ring, 
receiving  an  investment  from  the  intercolumnar  fascia.  The  coverings  of  this 
form  of  hernia  are  precisely  similar  to  those  investing  the  oblique  form,  with  the 
insignificant  difference  that  the  infundibuliform  fascia  is  replaced  by  a  portion 
derived  from  the  general  layer  of  the  transversalis  fascia. 

In  other  cases — and  this  is  the  more  frequent  variety — the  hernia  is  either  forced 
through  the  fibres  of  the  conjoined  tendon  or  the  tendon  is  gradually  distended  in 


1536  THE   SURGICAL    ANATOMY    OF  HERNIA 

front  of  it  so  as  to  form  a  complete  investment  for  it.  The  intestine  then  enters 
the  lower  end  of  the  inguinal  canal,  escapes  at  the  external  ring  lying  on  the 
inner  side  of  the  cord,  and  receives  additional  coverings  from  the  superficial  fascia 
and  the  integument.  This  form  of  hernia  has  the  same  coverings  as  the  oblique 
variety,  excepting  that  the  conjoined  tendon  is  substituted  for  the  Cremaster,  and 
the  infundibuliform  fascia  is  replaced  by  a  portion  derived  from  the  general  layer 
of  the  transversalis  fascia. 

The  difference  between  the  position  of  the  neck  of  the  sac  in  these  two  forms 
of  direct  inguinal  hernia  has  been  referred,  with  some  probability,  to  a  difference 
in  the  relative  positions  of  the  obliterated  hypogastric  artery  and  the  deep  epi- 
gastric artery.  When  the  course  of  the  obliterated  hypogastric  artery  corre- 
sponds pretty  nearly  with  that  of  the  deep  epigastric  the  projection  of  these 
arteries  toward  the  cavity  of  the  abdomen  produces  two  fossae  in  the  peritoneum. 
The  bottom  of  the  external  fossa  of  the  peritoneum  corresponds  to  the  position  of 
the  internal  abdominal  ring,  and  a  hernia  which  distends  and  pushes  out  the  peri- 
toneum lining  this  fossa  is  an  oblique  hernia.  When,  on  the  other  hand,  the 
obliterated  hypogastric  artery  lies  considerably  to  the  inner  side  of  the  deep  epi- 
gastric artery,  corresponding  to  the  outer  margin  of  the  conjoined  tendon,  it  divides 
the  triangle  of  Hesselbach  into  two  parts,  so  that  three  depressions  will  be  seen  on 
the  inner  surface  of  the  lower  part  of  the  abdominal  wall — viz.,  an  external  one  on 
the  outer  side  of  the  deep  epigastric  artery;  a  middle  one,  between  the  deep  epi- 
gastric and  the  obliterated  hypogastric  arteries;  and  an  internal  one,  on  the  inner 
side  of  the  obliterated  hypogastric  artery  (pp.  1531  and  1532).  In  such  a  case 
a  hernia  may  distend  and  push  out  the  peritoneum  forming  the  bottom  of  either 
fossa.  These  fossae  are  the  inguinal  fossae.  When  the  hernia  distends  and 
pushes  out  the  peritoneum  forming  the  bottom  of  the  external  fossa,  it  is  an 
oblique  or  external  inguinal  hernia. 

When  the  hernia  distends  and  pushes  out  the  peritoneum  forming  the  bottom 
of  either  the  middle  or  the  internal  fossa,  it  is  a  direct  or  internal  hernia. 

The  anatomical  difference  between  these  two  forms  of  direct  or  internal  inguinal 
hernia  is  that,  when  the  hernia  protrudes  through  the  middle  fossa — that  is, 
the  fossa  between  the  deep  epigastric  and  the  obliterated  hypogastric  arteries — 
it  will  enter  the  upper  part  of  the  inguinal  canal ;  consequently  its  coverings  will  be 
the  same  as  those  of  an  oblique  hernia,  with  the  insignificant  difference  that  the 
infundibuliform  fascia  is  replaced  by  a  portion  derived  from  the  general  layer  of 
the  transversalis  fascia,  whereas  when  the  hernia  protrudes  through  the  internal 
fossa  it  is  either  forced  through  the  fibres  of  the  conjoined  tendon  or  the  tendon  is 
gradually  distended  in  front  of  it  so  as  to  form  a  complete  investment  for  it.  The 
intestine  then  enters  the  lower  part  of  the  inguinal  canal,  and  escapes  from  the 
external  abdominal  ring  lying  on  the  inner  side  of  the  cord. 

This  form  of  hernia  has  the  same  coverings  as  the  oblique  variety,  excepting 
that  the  conjoined  tendon  is  substituted  for  the  Cremaster,  and  the  infundibuli- 
form fascia  is  replaced  by  a  portion  derived  from  the  general  layer  of  the  fascia 
transversalis. 

The  seat  of  stricture  in  strangulation  in  both  varieties  of  direct  hernia  is  most 
frequently  at  the  neck  of  the  sac  or  at  the  external  ring.  In  that  form  of  hernia 
which  perforates  the  conjoined  tendon  it  not  unfrequently  occurs  at  the  edges  of 
the  fissure  through  which  the  gut  passes.  In  dividing  the  stricture  the  incision 
should  in  all  cases  be  directed  upward.1 

If  the  hernial  protrusion  passes  into  the  inguinal  canal,  but  does  not  escape 

1  In  all  cases  of  inguinal  hernia,  whether  oblique  or  direct,  it  is  proper  to  divide  the  stricture  directly  upward: 
the  reason  of  this  is  obvious,  for  by  cutting  in  this  direction  the  incision  is  made  parallel  to  the  deep  epigastric 
artery — either  external  to  it  in  the  oblique  variety,  or  internal  to  it  in  the  direct  form  of  hernia — and  thus  all 
chance  of  wounding  the  vessel  is  avoided.  If  the  incision  was  made  outward,  the  artery  might  be  divided  if  the 
hernia  was  direct;  and  if  made  inward,  the  vessel  would  stand  an  equal  chance  of  injury  ifthe  case  was  one  of 
oblique  inguinal  hernia. — ED.  of  15th  English  edition. 


FEMORAL    HERNIA  1537 

from  the  external  abdominal  ring,  it  forms  what  is  called  incomplete  direct  hernia. 
This  form  of  hernia  is  usually  of  small  size,  and  in  corpulent  persons  is  very 
difficult  of  detection. 

Direct  inguinal  hernia  is  of  much  less  frequent  occurrence  than  the  oblique, 
their  comparative  frequency  being,  according  to  Cloquet,  as  one  to  five.  It  occurs 
far  more  frequently  in  men  than  in  women,  on  account  of  the  larger  size  of  the 
external  ring  in  the  former  sex.  It  differs  from  the  oblique  in  its  smaller  size  and 
globular  form,  dependent  most  probably  on  the  resistance  offered  to  its  progress 
by  the  transversalis  fascia  and  conjoined  tendon.  It  differs  also  in  its  position, 
being  placed  over  the  os  pubis  and  not  in  the  course  of  the  inguinal  canal.  The 
deep  epigastric  artery  runs  on  the  outer  or  iliac  side  of  the  neck  of  the  sac,  and  the 
spermatic  cord  along  its  external  and  posterior  side,  not  directly  behind  it,  as  in 
oblique  inguinal  hernia. 

FEMORAL  HERNIA. 

The  dissection  of  the  parts  comprised  in  the  anatomy  of  femoral  hernia  should  be  performed, 
if  possible,  upon  a  female  subject  free  from  fat.  The  subject  should  lie  upon  the  back;  a  block 
is  first  placed  under  the  pelvis,  the  thigh  everted,  and  the  knees  slightly  bent  and  retained  in 
this  position.  An  incision  should  then  be  made  from  the  anterior  superior  spinous  process  of 
the  ilium  along  Poupart's  ligament  to  the  symphysis  pubis;  a  second  incision  should  be  carried 
transversely  across  the  thigh  about  six  inches  beneath  the  preceding;  and  these  are  to  be  con- 
nected together  by  a  vertical  one  carried  along  the  inner  side  of  the  thigh  (Fig.  338).  These 
several  incisions  should  divide  merely  the  integument;  this  is  to  be  reflected  outward,  when  the 
superficial  fascia  will  be  exposed. 

The  Superficial  Fascia  forms  a  continuous  layer  over  the  whole  of  the  thigh, 
consisting  of  areolar  tissue,  containing  in  its  meshes  much  fat,  and  capable  of  being 
separated  into  two  or  more  layers,  between  which  are  found  the  superficial  vessels 
and  nerves.  It  varies  in  thickness  in  different  parts  of  the  limb.  In  the  groin 
it  is  thick,  and  the  two  layers  are  separated  from  one  another  by  the  superficial 
inguinal  lymphatic  glands,  the  internal  saphenous  vein,  and  several  smaller 
vessels.  One  of  these  layers,  the  superficial,  is  continuous  with  the  superficial 
fascia  of  the  abdomen. 

The  superficial  layer  should  be  detached  by  dividing  it  across  in  the  same  direction  as. the 
external  incisions;  its  removal  will  be  facilitated  by  commencing  at  the  lower  and  inner  angle  of 
the  space,  detaching  it  at  first  from  the  front  of  the  internal  saphenous  vein,  and  dissecting  it 
off  from  the  anterior  surface  of  that  vessel  and  its  tributaries;  it  should  then  be  reflected  out- 
ward in  the  same  manner  as  the  integument.  The  cutaneous  vessels  and  nerves  and  superficial 
inguinal  glands  are  then  exposed,  lying  upon  the  deep  layer  of  the  superficial  fascia.  These  are 
the  internal  saphenous  vein  and  the  superficial  epigastric,  superficial  circumflex  iliac,  and  super- 
ficial external  pudic  vessels,  as  well  as  numerous  lymphatics,  ascending  with  the  saphenous  vein 
to  the  inguinal  glands. 

The  internal  or  long  saphenous  vein  (Figs.  1138, 1139,  and  1140)  ascends  along 
the  inner  side  of  the  thigh,  and,  passing  through  the  saphenous  opening  in  the 
fascia  lata,  terminates  in  the  femoral  vein  about  an  inch  and  a  half  below  Poupart's 
ligament  (Fig.  1130).  This  vein  receives  at  the  saphenous  opening  the  superficial 
epigastric,  the  superficial  circumflex  iliac,  and  the  superficial  external  pudic  veins. 

The  superficial  external  pudic  artery  (superior)  arises  from  the  inner  side  of 
the  femoral  artery,  and,  after  passing  through  the  saphenous  opening,  courses 
inward  across  the  spermatic  cord,  to  be  distributed  to  the  integument  on  the 
lower  part  of  the  abdomen,  the  penis  and  scrotum  in  the  male  and  the  labium  in 
the  female,  anastomosing  with  branches  of  the  internal  pudic. 

The  superficial  epigastric  artery  arises  from  the  femoral  about  half  an  inch 
below  Poupart's  ligament,  and,  passing  through  the  saphenous  opening  in  the 
fascia  lata,  ascends  on  to  the  abdomen,  in  the  superficial  fascia  covering  the 
External  oblique  muscle,  nearly  as  high  as  the  umbilicus.  It  distributes  branches 

97 


1538 


THE    SURGICAL    ANATOMY    OF  HERNIA 


to  the  superficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and  the  integu- 
ment, anastomosing  with  branches  of  the  deep  epigastric  and  internal  mammary 
arteries. 

The  superficial  circumflex  iliac  artery,  the  smallest  of  the  cutaneous  branches, 
arises  close  to  the  preceding,  and,  piercing  the  fascia  lata,  runs  outward,  parallel 
with  Poupart's  ligament,  as  far  as  the  crest  of  the  ilium,  dividing  into  branches 
which  supply  the  superficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and 
the  integument  of  the  groin,  anastomosing  with  the  deep  circumflex  iliac,  and  with 
the  gluteal  and  external  circumflex  arteries. 

The  Superficial  Veins  (Fig.  1138). — The  veins  accompanying  these  superficial 
arteries  are  usually  much  larger  than  the  arteries;  they  terminate  in  the  internal 
or  long  saphenous  vein  at  the  saphenous  opening. 

The  superficial  inguinal  lymphatic  glands. — See  p.  791. 


FIG.  1138. — Femoral  hernia.     Superficial  dissection. 

The  ilio-inguinal  nerve  arises  from  the  first  lumbar  nerve.  It  escapes  at  the 
external  abdominal  ring,  and  is  distributed  to  the  integument  of  the  upper  and 
inner  part  of  the  thigh — to  the  scrotum  in  the  male  and  to  the  labium  in  the 
female.  The  size  of  this  nerve  is  in  inverse  proportion  to  that  of  the  ilio-hypo- 
gastric  nerve.  Occasionally  it  is  very  small,  and  ends  by  joining  the  ilio-hypogastric ; 
in  such  cases  a  branch  of  the  ilio-hypogastric  takes  the  place  of  the  ilio-inguinal, 
or  the  latter  nerve  may  be  altogether  absent.  The  crural  branch  of  the  genito- 
femoral  nerve  passes  along  the  inner  margin  of  the  Psoas  muscle,  beneath  Pou- 
part's ligament,  into  the  thigh,  entering  the  sheath  of  the  femoral  vessels,  and  lying 


FEMORAL  HERNIA 


1539 


superficial  and  a  little  external  to  the  femoral  artery.  It  pierces  the  anterior  layer 
of  the  sheath  of  the  vessels,  and,  becoming  superficial  by  passing  through  the  fascia 
lata,  it  supplies  the  skin  of  the  anterior  aspect  of  the  thigh  as  far  as  midway 
between  the  pelvis  and  knee.  On  the  front  of  the  thigh  it  communicates  with 
the  outer  branch  of  the  middle  cutaneous  nerve,  derived  from  the  femoral. 

The  Deep  Layer  of  the  Superficial  Fascia  is  a  very  thin  fibrous  layer,  best  marked 
on  the  inner  side  of  the  long  saphenous  vein  and  below  Poupart's  ligament.  It  is 
placed  beneath  the  subcutaneous  vessels  and  nerves,  and  upon  the  surface  of  the 
fascia  lata,  to  which  it  is  intimately  adherent  at  the  lower  margin  of  Poupart's 
ligament.  It  covers  the  saphenous  opening  in  the  fascia  lata,  is  closely  united  to 
its  circumference,  and  is  connected  to  the  sheath  of  the  femoral  vessels  corre- 


Fio.  1139. — Femoral  hernia,  showing  fascia  lata  and  saphenous  opening. 

spending  to  its  under  surface.  The  portion  of  fascia  covering  this  aperture  is 
perforated  by  the  internal  saphenous  vein  and  by  numerous  blood-  and  lymphatic 
vessels;  hence  it  has  been  termed  the  cribriform  fascia,  the  openings  for  these 
vessels  having  been  likened  to  the  holes  in  a  sieve.  The  cribriform  fascia  adheres 
closely  both  to  the  superficial  fascia  and  to  the  fascia  lata,  so  that  it  is  described 
by  some  anatomists  as  a  part  of  the  fascia  lata,  but  it  is  usually  considered  (as  in 
this  work)  as  belonging  to  the  superficial  fascia.  It  is  not  till  the  cribriform  fascia 
has  been  cleared  away  that  the  saphenous  opening  is  seen,  so  that  this  opening 
does  not  in  ordinary  cases  exist  naturally,  but  is  the  result  of  dissection  (p.  515).  A 
femoral  hernia  in  passing  through  the  saphenous  opening  receives  the  cribriform 
fascia  as  one  of  its  coverings. 


1540 


THE   SURGICAL    ANATOMY   OF   HERNIA 


The  deep  layer  of  superficial  fascia,  together  with  the  cribriform  fascia,  having 
been  removed,  the  fascia  lata  is  exposed. 

The  Fascia  Lata  has  been  already  described  with  the  muscles  of  the  front  of 
the  thigh  (p.  515).  At  the  upper  and  inner  part  of  the  thigh,  a  little  below 
Poupart's  ligament,  a  large  oval-shaped  aperture  is  observed  after  the  superficial 
fascia  has  been  cleared  away;  it  transmits  the  internal  saphenous  vein  and  other 
smaller  vessels,  and  is  called  the  saphenous  opening  (Fig.  1130).  In  order  the 
more  correctly  to  consider  the  mode  of  formation  of  this  aperture,  the  fascia  lata  in 
this  part  of  the  thigh  is  described  as  consisting  of  two  portions,  an  iliac  portion  and 
a  pubic  portion. 


FIG.  1140. — Femoral  hernia.     Iliac  portion  of  fascia  lata  removed,  and  sheath  of  femoral  vessels  and 

femoral  canal  exposed. 

The  iliac  portion  (Fig.  1139)  is  all  that  part  of  the  fascia  lata  on  the  outer  side  of 
the  saphenous  opening.  It  is  attached  externally  to  the  crest  of  the  ilium  and  its 
anterior  superior  spine;  to  the  whole  length  of  Poupart's  ligament;  and  to  the 
pectineal  line  in  conjunction  with  Gimbernat's  ligament.  From  the  spine  of  the 
os  pubis  it  is  reflected  downward  and  outward,  forming  an  arched  margin,  the 
outer  boundary  or  falciform  process  or  superior  cornu  (cornu  superius]  (Fig.  1139) 
of  the  saphenous  opening.  This  margin  overlies  and  is  adherent  to  the  anterior 
layer  of  the  sheath  of  the  femoral  vessels;  to  its  edge  is  attached  the  cribriform 
fascia,  and  below  it  is  continuous  with  the  pubic  portion  of  the  fascia  lata. 

The  pubic  portion  of  the  fascia  lata  or  the  pectineal  fascia  (Fig.  1139)  is  situated 
at  the  inner  side  of  the  saphenous  opening;  at  the  lower  margin  of  this  aperture 
it  is  continuous  with  the  iliac  portion;  traced  upward,  it  covers  the  surface  of 
the  Pectineus,  Adductor  longus,  and  Gracilis  muscles;  and,  passing  behind  the 


FEMORAL   HERNIA  1541 

sheath  of  the  femoral  vessels,  to  which  it  is  loosely  united,  is  continuous  with 
the  sheath  of  the  Psoas  and  Iliacus  muscles,  and  is  attached  above  to  the  ilio- 
pectineal  line,  where  it  becomes  continuous  with  the  fascia  covering  the  Iliacus 
muscle.  From  the  description  it  may  be  observed  that  the  iliac  portion  of  the 
fascia  lata  passes  in  front  of  the  femoral  vessels  and  the  pubic  portion  behind 
them,  so  that  an  apparent  aperture  consequently  exists  between  the  two,  through 
which  the  internal  saphenous  vein  joins  the  femoral  vein. 

The  Saphenous  Opening  (fossa  ovalis)  (Figs.  1130,  1138,  1139,  and  1140)  is  an 
oval-shaped  aperture  measuring  about  an  inch  and  a  half  in  length  and  half  an 
inch  in  width.  It  is  situated  at  the  upper  and  inner  parts  of  the  front  of  the 
thigh,  below  Poupart's  ligament,  and  is  directed  obliquely  downward  and  out- 
ward. It  is  covered  by  the  cribriform  fascia  (fascia  cribrosa),  a  portion  of  the 
deep  layer  of  the  superficial  fascia  of  the  thigh,  and  which  extends  from  the 
falciform  margin  to  the  pubic  portion  of  the  fascia  lata  or  the  pectineal  fascia. 

The  outer  margin  of  the  saphenous  opening  is  of  a  semilunar  form,  thin,  strong, 
sharply  defined,  and  lies  on  a  plane  considerably  anterior  to  the  inner  margin. 
If  this  edge  is  traced  upward,  it  will  be  seen  to  form  a  curved  elongated  process, 
the  falciform  process  or  superior  cornu  (Fig.  1139),  which  ascends  in  front  of  the 
femoral  vessels,  and,  curving  inward,  is  attached  to  Poupart's  ligament  and  to  the 
spine  of  the  os  pubis  and  pectineal  line,  where  it  is  continuous  with  the  pubic  por- 
tion. If  traced  downward,  it  is  found  continuous  with  another  curved  margin, 
the  concavity  of  which  is  directed  upward  and  inward;  this  is  the  inferior  cornu 
of  the  saphenous  opening,  and  is  blended  with  the  pubic  portion  of  the  fascia 
lata  covering  the  Pectineus  muscle. 

The  inner  boundary  of  the  opening  (Figs.  1130  and  1139)  is  on  a  plane  posterior 
to  the  outer  margin  and  behind  the  level  of  the  femoral  vessels;  it  is  much  less 
prominent  and  defined  than  the  outer,  from  being  stretched  over  the  subjacent 
Pectineus  muscle.  It  is  through  the  saphenous  opening  that  a  femoral  hernia 
passes  after  descending  along  the  crura!  canal. 

If  the  finger  is  introduced  into  the  saphenous  opening  while  the  limb  is  moved 
in  different  directions,  the  aperture  will  be  found  to  be  greatly  constricted  on 
extending  the  limb  or  rotating  it  outward,  and  to  be  relaxed  on  flexing  the  limb 
and  inverting  it;  hence  the  necessity  for  placing  the  limb  in  the  latter  position  in 
employing  the  taxis  for  the  reduction  of  a  femoral  hernia. 

The  iliac  portion  of  the  fascia  lata,  but  not  its  falciform  process,  should  now  be  removed  by 
detaching  it  from  the  lower  margin  of  Poupart's  ligament,  carefully  dissecting  it  from  the  sub- 
jacent structures,  and  turning  it  inward,  when  the  sheath  of  the  femoral  vessels  is  exposed, 
descending  beneath  Poupart's  ligament  (Fig.  1140). 

Poupart's  Ligament  (ligamentum  inguinale  [Pouparti])  (Figs.  288,  1130,  1133, 
1134,  1136,  1139,  1140,  1141,  and  1142)  is  the  lower  border  of  the  aponeurosis 
of  the  External  oblique  muscle,  which  extends  from  the  anterior  superior  spine 
of  the  ilium  to  the  spine  of  the  os  pubis.  From  this  latter  point  it  is  reflected 
outward,  to  be  attached  to  the  pectineal  line  for  about  half  an  inch,  forming 
Gimbernat's  ligament.  Its  general  direction  is  curved  downward  toward  the  thigh, 
where  it  is  continuous  with  the  fascia  lata.  Its  outer  half  is  rounded  and 
oblique  in  direction.  Its  inner  half  gradually  widens  at  its  attachment  to  the 
os  pubis,  is  more  horizontal  in  direction,  and  lies  beneath  the  spermatic  cord. 
Nearly  the  whole  of  the  space  included  between  Poupart's  ligament  and  the 
innominate  bone  is  filled  in  by  the  parts  which  descend  from  the  abdomen  into 
the  thigh  (Figs.  296,  338,  and  1141).  The  outer  half  of  the  space  (lacuna  muscu- 
lorum)  is  occupied  by  the  Iliacus  and  Psoas  muscles,  together  with  the  external 
cutaneous  and  femoral  nerves.  The  pubic  half  of  the  space  (lacuna  vasorum) 
is  occupied  by  the  femoral  vessels  included  in  their  sheath,  a  small  oval-shaped 
interval  existing  between  the  femoral  vein  and  the  inner  wall  of  the  sheath, 


1542 


THE  SURGICAL  ANATOMY  OF  HERNIA 


which  is  occupied  merely  by  a  little  loose  areolar  tissue,  a  few  lymphatic  vessels, 
and  occasionally  by  a  small  lymphatic  gland;  this  is  the  femoral  ring,  through 
which  the  gut  descends  in  femoral  hernia.  The  part  of  Poupart's  ligament  in 
front  of  the  femoral  or  crural  ring  is  called  the  superficial  crural  arch. 

Gimbernat's  Ligament  (ligamentum  lacunare  [Gimbernati])  (Figs.  296,  338,  1130, 
1141,  and  1142)  is  that  part  of  the  aponeurosis  of  the  External  oblique  muscle 
which  is  reflected  backward  and  outward  from  the  spine  of  the  os  pubis,  to  be 
inserted  into  the  pectineal  line.  It  is  about  half  an  inch  in  length,  larger  in  the 
male  than  in  the  female,  almost  horizontal  in  direction  in  the  erect  posture,  and 
of  a  triangular  form,  with  the  base  directed  outward.  Its  base  or  outer  margin 
is  concave,  thin,  and  sharp,  and  lies  in  contact  with  the  femoral  sheath.  Its 
apex  corresponds  to  the  spine  of  the  os  pubis.  Its  posterior  margin  is  attached  to 
the  pectineal  line,  and  is  continuous  with  the  pubic  portion  of  the  fascia  lata.  Its 
anterior  margin  is  continuous  with  Poupart's  ligament. 


Crural 

Poupart's  ligament.      iranch     Femoral 
of  genito- 
femoral. 


External 
cutaneous  nerve. 


Iliac  portion  of 
fascia  lata. 


Femoral  vein. 
Femoral  ring. 

Gimbernat's 


Femoral  arterji. 
FIG.  1141. — Structures  which  pass  beneath  the  crural  arch. 

Femoral  Sheath  (Fig.  1141). — The  femoral  or  crural  sheath  is  a  continuation  down- 
ward of  the  fasciae  that  line  the  abdomen,  the  transversalis  fascia  passing  down  in 
front  of  the  femoral  vessels,  and  the  iliac  fascia  descending  behind  them;  these 
fasciae  are  directly  continuous  on  the  iliac  side  of  the  femoral  artery,  but  a  small 
space  exists  between  the  femoral  vein  and  the  point  where  they  are  continuous  on 
the  pubic  side  of  that  vessel,  which  constitutes  the  femoral  or  crural  canal  (Fig.  1130). 
The  femoral  sheath  is  closely  adherent  to  the  contained  vessels  about  an  inch 
below  the  saphenous  opening,  being  blended  with  the  areolar  sheath  of  the  vessels, 
but  opposite  Poupart's  ligament  it  is  much  larger  than  is  required  to  contain  them; 
hence  the  funnel-shaped  form  which  it  presents.  The  outer  border  of  the  sheath 


FEMORAL  HERNIA  1543 

is  perforated  by  the  femoral  nerve.  Its  inner  border  is  pierced  by  the  internal 
saphenous  vein  and  numerous  lymphatic  vessels.  In  front  it  is  covered  by  the 
iliac  portion  of  the  fascia  lata;  and  behind  it  is  the  pubic  portion  of  the  same 
fascia. 

If  the  anterior  wall  of  the  sheath  is  removed  (Fig.  1130),  the  femoral  artery  and 
vein  are  seen  lying  side  by  side,  a  thin  septum  separating  the  two  vessels,  while 
another  septum  may  be  seen  lying  just  internal  to  the  vein,  and  cutting  off  a  small 
space  between  the  vein  and  the  inner  wall  of  the  sheath.  The  septa  are  stretched 
between  the  anterior  and  posterior  walls  of  the  sheath,  so  that  each  vessel  is 
enclosed  in  a  separate  compartment.  The  interval  left  between  the  vein  and  the 
inner  wall  of  the  sheath  is  not  filled  up  by  any  structure,  excepting  a  little  loose 
areolar  tissue,  a  few  lymphatic  vessels,  and  occasionally  by  a  small  lymphatic 
gland;  this  is  the  femoral  or  crural  canal  (Fig.  1130),  through  which  the  intestine 
descends  in  femoral  hernia. 

Deep  Crural  Arch. — Passing  across  the  front  of  the  femoral  sheath  on  the  abdom- 
inal side  of  Poupart's  ligament,  and  closely  connected  with  it,  is  a  thickened  band 
of  fibres  of  the  transversalis  fascia,  called  the  deep  crural  arch.  It  is  apparently  a 
thickening  of  the  transversalis  fascia,  joining  externally  to  the  centre  of  Poupart's 
ligament,  and  arching  across  the  front  of  the  crural  sheath,  to  be  inserted  by  a 
broad  attachment  into  the  pectineal  line  behind  the  conjoined  tendon.  In  some 
subjects  this  structure  is  not  very  prominently  marked,  and  not  infrequently  it  is 
altogether  wanting.  The  superficial  crural  arch  is  the  portion  of  Poupart's  liga- 
ment in  front  of  the  femoral  ring. 

The  Femoral  or  Crural  Canal  (canalis  jemoralis)  (Figs.  296,  338,  and  1130)  is  the 
narrow  interval  between  the  femoral  vein  and  the  inner  wall  of  the  femoral  sheath. 
It  exists  as  a  distinct  canal  only  when  the  sheath  has  been  separated  from  the  vein 
by  dissection  or  by  the  pressure  of  a  hernia  or  tumor.  Itsjength  is  from  a  quarter 
to  half  an  inch,  and  it  extends  from  the  femoral  ring  to  the  upper  part  of  the 
sa|5nTnbTis  openingT 

Its  anterior  wall  is  very  narrow,  and  formed  by  a  continuation  downward  of 
the  transversalis  fascia,  under  Poupart's  ligament,  covered  by  the  falciform 
process  of  the  fascia  lata. 

Its  posterior  wall  is  formed  by  a  continuation  downward  of  the  iliac  fascia  cover- 
ing the  pubic  portion  of  the  fascia  lata. 

Its  outer  wall  is  formed  by  the  fibrous  septum  separating  it  from  the  inner  side 
of  the  femoral  vein. 

Its  inner  wall  is  formed  by  the  junction  of  the  processes  of  the  transversalis 
and  iliac  fasciae,  which  form  the  inner  side  of  the  femoral  sheath,  and  lies  in 
contact  at  its  commencement  with  the  outer  edge  of  Gimbernat's  ligament. 

This  canal  has  two  orifices — an  upper  one,  the  femoral  or  crural  ring,  closed  by 
the  septum  crurale ;  and  a  lower  one,  the  saphenous  opening,  closed  by  the  cribri- 
form fascia. 

The  femoral  or  crural  ring  (annulus  femoralis)  (Figs.  1130,  1141,  and  1142)  is 
the  upper  opening  of  the  femoral  canal,  and  leads  into  the  cavity  of  the  abdomen. 
It  is  bounded  in  front  by  Poupart's  ligament  and  the  deep  crural  arch;  behind, 
by  the  os  pubis,  covered  by  the  Pectineus  muscle  and  the  pubic  portion  of  the  fascia 
lata;  internally,  by  the  base  of  Gimbernat's  ligament,  the  conjoined  tendon,  the 
transversalis  fascia,  and  the  deep  crural  arch;  externally,  by  the  fibrous  septum 
lying  on  the  inner  side  of  the  femoral  vein.  The  femoral  ring  is  of  an  oval  form; 
its  long  diameter,  directed  transversely,  measures  about  half  an  inch,  and  it  is 
larger  in  the  female  than  in  the  male,  which  is  one  of  the  reasons  of  the  greater 
frequency  of  femoral  hernia  in  the  former  sex. 

POSITION  OF  PARTS  AROUND  THE  RING. — The  spermatic  cord  in  the  male  and 
round  ligament  in  the  female  lie  immediately  above  the  anterior  margin  of  the 


1544 


THE   SURGICAL    ANATOMY    OF   HERNIA 


femoral  ring,  and  may  be  divided  in  an  operation  for  femoral  hernia  if  the  incision 
for  the  relief  of  the  stricture  is  not  of  limited  extent.  In  the  female  this  is  of  little 
importance,  but  in  the  male  the  spermatic  artery  and  vas  deferens  may  be  divided. 

The  femoral  vein  lies  on  the  outer  side  of  the  ring. 

The  deep  epigastric  artery  in  its  passage  upward  and  inward  from  the  external 
iliac  artery  passes  across  the  upper  and  outer  angle  of  the  crural  ring,  and  is 
consequently  in  danger  of  being  wounded  if  the  stricture  is  divided  in  a  direction 
upward  and  outward. 

The  communicating  branch  between  the  deep  epigastric  and  obturator  lies  in 
front  of  the  ring. 

The  circumference  of  the  ring  is  thus  seen  to  be  bounded  by  vessels  in  every 
part,  excepting  internally  and  behind  (Fig.  1142).  It  is  in  the  former  position  that 
the  stricture  is  divided  in  cases  of  strangulated  femoral  hernia. 

The  obturator  artery  (p.  689),  when  it  arises  by  a  common  trunk  with  the  deep 
epigastric  (p.  690),  which  occurs  once  in  every  three  subjects  and  a  half,  bears 
a  very  important  relation  to  the  crural  ring.  In  most  cases  it  descends  on  the 


FIG.  1142. — Hernia.     The  relations  of  the  femoral  and  internal  abdominal  rings,  seen  from  within  the 

abdomen.     Right  side. 

inner  side  of  the  external  iliac  vein  to  the  obturator  foramen,  and  will  consequently 
lie  on  the  outer  side  of  the  crural  ring,  where  .there  is  no  danger  of  its  being 
wounded  in  the  operation  for  dividing  the  stricture  in  femoral  hernia  (Fig.  429  A, 
p.  690).  Occasionally,  however,  the  obturator  artery  curves  along  the  free  margin 
of  Gimbernat's  ligament  in  its  passage  to  the  obturator  foramen;  it  would  conse- 
quently skirt  along  the  greater  part  of  the  circumference  of  the  crural  ring,  and 
could  hardly  avoid  being  wounded  in  the  operation  (Fig.  4295,  p.  690). 

The  Crural  Septum  or  Septum  Crurale  (septum  femorale  musculus)  (Fig.  296).— 
The  femoral  ring  is  closed  by  a  thin  process  of  transversalis  fascia  containing  fat 
and  called,  by  J.  Cloquet,  the  septum  crurale.  This  serves  as  a  barrier  to  the 
protrusion  of  a  hernia  through  this  part.  Its  upper  surface  is  slightly  concave, 
and  supports  a  small  lymphatic  gland  (Fig.  1142),  by  which  it  is  separated  from 
the  subserous  areolar  tissue  and  peritoneum.  Its  under  surface  is  turned  toward 
the  femoral  canal.  The  septum  crurale  is  perforated  by  numerous  apertures  for 
the  passage  of  lymphatic  vessels  connecting  the  deep  inguinal  lymphatic  glands 
with  those  surrounding  the  external  iliac  artery. 


FEMORAL    HERNIA  1545 

The  size  of  the  femoral  canal,  the  degree  of  tension  of  its  orifices,  and  conse- 
quently the  degree  of  constriction  of  a  hernia,  vary  according  to  the  position  of 
the  limb.  If  the  leg  and  thigh  are  extended,  abducted,  or  everted,  the  femoral 
canal  and  its  orifices  are  rendered  tense  from  the  traction  on  these  parts  by  Pou- 
part's  ligament  and  the  fascia  lata,  as  may  be  ascertained  by  passing  the  finger 
along  the  canal.  If,  on  the  contrary,  the  thigh  is  flexed  upon  the  pelvis,  and  at 
the  same  time  adducted  and  rotated  inward,  the  femoral  canal  and  its  orifices 
become  considerably  relaxed;  for  this  reason  the  limb  should  always  be  placed  in 
the  latter  position  when  the  application  of  the  taxis  is  made  in  attempting  the 
reduction  of  a  femoral  hernia. 

The  subperitoneal  areolar  tissue  is  continuous  with  the  subserous  areolar  tissue 
of  surrounding  parts.  It  is  usually  thickest  and  most  fibrous  where  the  iliac  ves- 
sels leave  the  abdominal  cavity.  It  covers  over  the  femoral  ring,  the  small  interval 
on  the  inner  side  of  the  femoral  vein.  In  some  subjects  it  contains  a  considerable 
amount  of  adipose  tissue.  In  such  cases,  where  it  is  protruded  forward  in  front 
ofJke_§ac^of  a Jemoral  hernia,  it  may  be  migfa.kpn  fr>r  a  portion  of  omentum.  The 
peritoneum  lining  the  portion  of  the  abdominal  wall  between  Poupart's  ligament 
and  the  brim  of  the  pelvis  is  similar  to  that  lining  any  other  portion  of  the  abdom- 
inal wall,  being  very  thin.  Here  there  is  no  natural  aperture  for  the  escape  of 
intestine. 

Descent  of  the  Hernia. — From  the  preceding  description  it  follows  that  the 
femoral  ring  must  be  a  weak  point  in  the  abdominal  wall;  hence  it  is  that  when 
violent  or  long-continued  pressure  is  made  upon  the  abdominal  viscera  a  portion 
of  intestine  may  be  forced  into  it,  constituting  a  femoral  hernia;  and  the  changes 
in  the  tissues  of  the  abdomen  which  are  produced  by  pregnancy,  together  with  the 
larger  size  of  this  aperture  in  the  female,  serve  to  explain  the  frequency  of  this 
form  of  hernia  in  women. 

When  a  portion  of  the  intestine  passes  through  the  femoral  ring,  a  pouch  of 
peritoneum  lies  before  it,  which  forms  what  is  called  the  hernial  sac;  it  is  cov- 
ered by  the  subserous  areolar  tissue,  receives  an  investment  from  the  septum 
crurale,  and  descends  vertically  along  the  crural  canal  in  the  inner  compartment  of 
the  sheath  of  the  femoral  vessels  as  far  as  the  saphenous  opening;  at  this  point  it 
changes  its  course,  being  prevented  from  extending  farther  down  the  sheath  on 
account  of  the  narrowing  of  the  sheath  and  its  close  contact  with  the  vessels,  and 
also  from  the  close  attachment  of  the  superficial  fascia  and  crural  sheath  to  the 
lower  part  of  the  circumference  of  the  saphenous  opening;  the  hernia  is  conse- 
quently directed  forward,  pushing  before  it  the  cribriform  fascia,  and  then  curves 
upward  on  to  the  falciform  process  of  the  fascia  lata  and  lower  part  of  the  tendon 
of  the  External  oblique,  being  covered  by  the  superficial  fascia  and  integument. 
While  the  hernia  is  contained  in  the  femoral  canal  it  is  usually  of  small  size, 
owing  to  the  resisting  nature  of  the  surrounding  parts;  but  when  it  has  escaped 
from  the  saphenous  opening  into  the  loose  areolar  tissue  of  the  groin,  it  becomes 
considerably  enlarged.  The  direction  taken  by  a  femoral  hernia  in  its  descent  is 
at  first  downward,  then  forward  and  upward;  this  should  be  borne  in  mind,  as 
in  the  application  of  the  taxis  for  the  reduction  of  a  femoral  hernia  pressure  should 
be  directed  in  the  reverse  order. 

Coverings  of  the  Complete  Hernia. — The  coverings  of  a  femoral  hernia,  from 
within  outward,  are — peritoneum,  subserous  areolar  tissue,  the  septum  crurale, 
crural  sheath,  cribriform  fascia,  superficial  fascia,  and  integument.1 

1  Sir  Astley  Cooper  has  described  an  investment  for  femoral  hernia,  under  the  name  of  " fascia  jpropria."  lying 
immediately  external  to  the  peritoneal  sac,  but  frequently  separated  from  it  by  more  oFTess  adipose  tissue. 
Surgically,  it  is  important  to  remember  the  existence  (at  any  rate,  the  occasional  existence)  of  this  layer,  on 
account  of  the  ease  with  which  an  inexperienced  operator  may  mistake  the  fascia  for  the  peritoneal  sac  and  the 
contained  fat  for  omentum.  Anatomically,  this  fascia  appears  identical  with  what  is  called  in  the  text  "sub- 
nerous  argofar  flssue,"  the  areolar  tissue  being  thickened  and  caused  to  assume  a  membranous  appearanclTBy 
the  •pressure-  ofTtWbernia. — ED.  of  15th  English  edition. 


1 


1546  THE  SURGICAL    ANATOMY    OF   HERNIA 

Varieties  of  Femoral  Hernia. — If  the  hernia  descends  along  the  femoral  canal  only 
as  far  as  the  saphenous  opening,  and  does  not  escape  from  this  aperture,  the  con- 
dition is  called  incomplete  femoral  hernia.  The  small  size  of  the  protrusion  in  this 
form  of  hernia,  which  is  due  to  the  firm  and  resisting  nature  of  the  canal  in 
which  it  is  contained,  renders  it  an  exceedingly  dangerous  variety,  from  the 
extreme  difficulty  of  detecting  the  existence  of  the  swelling,  especially  in  corpulent 
subjects.  The  coverings  of  an  incomplete  femoral  hernia,  named  from  without 
in  ward,  are  as  follows :  the  integument,  superficial  fascia,  iliac  portion  of  fascia  lata, 
crural  sheath,  septum  crurale,  subserous  areolar  tissue,  and  peritoneum.  When, 
however,  the  hernia  protrudes  through  the  saphenous  opening  and  directs  itself 
forward  and  upward,  it  forms  a  complete  femoral  hernia,  the  coverings  of  which 
have  been  given  (p.  1533).  Occasionally  the  hernial  sac  descends  on  the  iliac 
side  of  the  femoral  vessels  or  in  front  of  these  vessels,  or  even  sometimes  behind 
them. 

The  seat  of  stricture  in  a  strangulated  femoral  hernia  varies;  it  may  be  in  the 
peritoneum  at  the  neck  of  the  hernial  sac;  in  the  greater  number  of  cases  it  would 
appear  to  be  at  the  point  of  junction  of  the  falciform  process  of  the  fascia  lata 
with  the  lunated  edge  of  Gimbernat's  ligament,  or  at  the  margin  of  the  saphenous 
opening  in  the  thigh.  The  stricture  should  in  every  case  be  divided  in  an  inward 
direction,  or  upward  and  inward,  and  the  extent  of  the  necessary  cut  in  the 
majority  of  cases  is  about  two  or  three  lines.  By  these  means  all  vessels  or 
other  structures  of  importance  in  relation  with  the  neck  of  the  hernial  sac  will 
be  avoided. 


SUEGICAL  ANATOMY  OF  THE  PEBDLEUM. 


Dissection. —The  student  should  select  a  well-developed  muscular  subject,  free  from  fat, 
and  the  dissection  should  be  commenced  early,  in  order  that  the  parts  may  be  examined  in  as 
recent  a  state  as  possible.  A  staff  having  been  introduced  into  the  bladder  and  the  subject 
placed  in  the  position  shown  in  Fig.  1143,  the  scrotum  should  be  raised  upward,  and  retained  in 
that  position,  and  the  rectum  moderately  distended  with  tow. 

The  Perinasum  corresponds  to  the  inferior  aperture  or  outlet  of  the  pelvis.  Its 
deep  boundaries  are,  in  front,  the  pubic  arch  and  subpubic  ligament;  behind, 
the  tip  of  the  coccyx;  and  on  each  side,  the  rami  of  the  os  pubis  and  ischium,  the 
tuberosities  of  the  ischium,  and  great  sacro-sciatic  ligaments.  The  space  included 
by  these  boundaries  is  somewhat  lozenge-shaped,  and  is  limited  on  the  surface  of 


FIG.  1143. — Dissection  of  perinseum  and  ischio-rectal  region. 

the  body  by  the  scrotum  in  front,  by  the  buttocks  behind,  and  on  each  side  by  the 
inner  side  of  the  thigh.  A  line  drawn  transversely  between  the  anterior  parts  of 
the  tuberosities  of  the  ischium,  on  each  side,  in  front  of  the  anus,  divides  this  space 
into  two  portions.  The  anterior  portion  contains  the  penis  and  urethra,  and  is 
called  the  perinaeum  proper  or  genito -urinary  region.  The  posterior  portion  con- 
tains the  termination  of  the  rectum,  and  is  called  the  ischio-rectal  or  anal  region. 


ISCHIO-RECTAL  REGION. 

The  ischio-rectal  region  contains  the  termination  of  the  rectum  and  a  deep  fossa, 
filled  with  fat,  on  each  side  of  the  intestine,  between  it  and  the  tuberosity  of  the 
ischium;  this  is  called  the  ischio-rectal  fossa. 

The  ischio-rectal  region  presents  in  the  middle  line  the  aperture  of  the  anus; 
around  this  orifice  the  integument  is  thrown  into  numerous  folds,  which  are 
obliterated  on  distention  of  the  anus.  The  integument  is  of  a  dark  color,  con- 
tinuous with  the  mucous  membrane  of  the  rectum,  and  is  provided  with  numerous 

( 1547  ) 


1548  SURGICAL    ANATOMY    OF    THE   PERINEUM 

follicles,  which  occasionally  inflame  and  suppurate,  and  may  be  mistaken  for 
h'stulae.  The  veins  around  the  margin  of  the  anus  are  occasionally  much  dilated, 
forming  a  number  of  hard  pendent  masses,  of  a  dark  bluish  color,  covered  partly 
by  mucous  membrane  and  partly  by  the  integument.  These  tumors  constitute  the 
disease  called  external  piles. 

Dissection  (Fig.  1143). — Make  an  incision  through  the  integument,  along  the  median  line, 
from  the  base  of  the  scrotum  to  the  anterior  extremity  of  the  anus:  carry  it  around  the  margins 
of  this  aperture  to  its  posterior  extremity,  and  continue  it  backward  to  about  an  inch  behind 
the  tip  of  the  coccyx.  A  transverse  incision  should  now  be  carried  across  the  base  of  the  Scrotum, 
joining  the  anterior  extremity  of  the  preceding;  a  second,  carried  in  the  same  direction,  should 
be  made  in  front  of  the  anus;  and  a  third  at  the  posterior  extremity  of  the  first  incision.  These 
incisions  should  be  sufficiently  extensive  to  enable  the  dissector  to  raise  the  integument  from 
the  inner  side  of  the  thighs.  The  flaps  of  skin  corresponding  to  the  ischio-rectal  region  should 
now  be  removed.  In  dissecting  the  integument  from  this  region  great  care  is  required,  otherwise 
the  Corrugator  cutis  ani  and  External  sphincter  will  be  removed,  as  they  are  intimately  adherent 
to  the  skin. 

The  Superficial  Fascia  is  exposed  on  the  removal  of  the  skin;  it  is  very  thick, 
areolar  in  texture,  and  contains  much  fat  in  its  meshes.  In  it  are  found  ramifying 
two  or  three  branches  of  the  perforating  cutaneous  nerve;  these  turn  around  the 
inferior  border  of  the  Gluteus  maximus  and  are  distributed  to  the  integument 
around  the  anus. 

In  this  region,  and  connected  with  the  lower  end  of  the  rectum,  are  four  muscles : 
the  Corrugator  cutis  ani;  the  two  Sphincters,  External  and  Internal;  and  the 
Levator  ani. 

These  muscles  have  been  already  described  (p.  451). 

The  Ischio-rectal  Fossa  (fossa  ischiorectalis)  (Figs.  299  and  303)  is  situated 
between  the  end  of  the  rectum  and  the  ischial  tuherosity.  It  is  triangular  in  shape; 
its  base,  directed  to  the  surface  of  the  body,  is  formed  by  the  integument  of  the 
ischio-rectal  region ;  its  apex,  directed  upward,  corresponds  to  the  point  of  division 
of  the  obturator  fascia  and  the  thin  membrane  given  off  from  it,  which  covers  the 
outer  surface  of  the  Levator  ani  (ischio-rectal  or  anal  fascia).  Its  dimensions  are 
about  an  inch  in  breadth  at  the  base  and  about  two  inches  in  depth,  being  deeper 
behind  than  in  front.  It  is  bounded,  internally,  by  the  Sphincter  ani,  Levator 
ani,  and  Coccygeus  muscles;  externally,  by  the  tuberosity  of  the  ischium  and  the 
obturator  fascia,  which  covers  the  inner  surface  of  the  Obturator  internus  muscle; 
in  front,  it  is  limited  by  the  line  of  junction  of  the  superficial  fascia  with  the  base 
of  the  triangular  ligament;  and  behind,  by  the  margin  of  the  Gluteus  maximus 
muscle  and  the  great  sacro-sciatic  ligament.  This  space  is  filled  with  a  large  mass 
of  adipose  tissue,  which  explains  the  frequency  with  which  abscesses  in  the  neigh- 
borhood of  the  rectum  burrow  to  a  considerable  depth. 

If  the  subject  has  been  injected,  on  placing  the  finger  on  the  outer  wall  of  this 
fossa  the  internal  pudic  artery,  with  its  accompanying  veins  and  the  two  divisions 
of  the  nerve,  will  be  felt  about  an  inch  and  a  half  above  the  margin  of  the  ischiatic 
tuberosity,  but  approaching  nearer  the  surface  as  they  pass  forward  along  the 
inner  margin  of  the  pubic  arch.  These  structures  are  enclosed  in  a  sheath,  the 
fascial  canal  or  canal  of  Alcock  (Figs.  303  and  1148),  formed  by  the  obturator  fascia, 
the  pudic  nerve  lying  below  the  artery  and  the  dorsal  nerve  of  the  penis  above  it. 
Crossing  the  space  transversely,  about  its  centre  are  the  inferior  hemorrhoidal 
vessels  and  nerves,  wrhich  are  distributed  to  the  integument  of  the  anus  and  to  the 
muscles  of  the  lower  end  of  the  rectum.  These  vessels  are  occasionally  of  large 
size,  and  may  give  rise  to  troublesome  hemorrhage  when  divided  in  the  operation 
of  lithotomy  or  in  that  for  fistula  in  ano.  At  the  back  part  of  this  space,  near 
the  coccyx,  may  be  seen  a  branch  of  the  fourth  sacral  nerve,  and  at  the  forepart  of 
the  space  the  superficial  perineal  vessels  and  nerves  can  be  seen  for  a  short  distance. 


THE  PERINEUM  PROPER   IN    THE   MALE  1549 


THE  PERINEUM  PROPER  IN  THE  MALE. 

The  perineal  space  is  of  a  triangular  form;  its  deep  boundaries  are  limited, 
laterally,  by  the  rami  of  the  pubic  bones  and  ischia,  meeting  in  front  at  the  pubic 
arch;  behind,  by  an  imaginary  transverse  line  extending  between  the  anterior 
parts  of  the  tuberosities  of  the  ischia.  The  lateral  boundaries  are,  in  the  adult, 
from  three  inches  to  three  inches  and  a  half  in  length,  and  the  base  from  two  to 
three  inches  and  a  half  in  breadth,  the  average  extent  of  the  space  being  two 
inches  and  three-quarters. 

The  variations  in  the  diameter  of  this  space  are'  of  extreme  interest  in  connection  with  the 
operation  of  lithotomy  and  the  extraction  of  a  stone  from  the  cavity  of  the  bladder.  In  those 
cases  where  the  tuberosities  of  the  ischia  are  near  together  it  would  be  necessary  to  make  the 
incisions  in  the  lateral  operation  of  lithotomy  less  oblique  than  if  the  tuberosities  were  widely 
separated,  and  the  perineal  space  consequently  wider.  The  perinseum  is  subdivided  by  the 
median  raphe"  into  two  equal  parts.  Of  these,  the  left  is  the  one  in  which  the  operation  of  lith- 
otomy is  performed. 

In  the  middle  line  the  perinseum  is  convex,  and  corresponds  to  the  bulb  of  the 
urethra.  The  skin  covering  it  is  of  a  dark  color,  thin,  freely  movable  upon  the 
subjacent  parts,  and  covered  with  sharp  crisp  hairs,  which  should  be  removed 
before  the  dissection  of  the  part  is  commenced.  In  front  of  the  anus  a  prominent 
line  commences,  the  raphe",  continuous  in  front  with  the  raphe  of  the  scrotum. 
The  skin  of  the  raphe'  is  adherent  to  the  deep  layer  of  the  superficial  fascia. 

Upon  removing  the  skin  and  the  superficial  layer  of  the  superficial  fascia,  in  the 
manner  shown  in  Fig.  1143,  a  plane  of  fascia  will  be  exposed,  covering  in  the 
triangular  space  and  stretching  across  from  one  ischio-pubic  ramus  to  the  other. 
This  is  the  deep  layer  of  the  superficial  fascia  or  fascia  of  Colles  (fascia  superficialis 
perinaei}.  It  has  already  been  described  (p.  458).  It  is  a  layer  of  considerable 
strength,  and  encloses  and  covers  a  space  in  which  are  contained  muscles,  vessels, 
and  nerves.  It  is  continuous  in  front  with  the  fascia  of  the  penis  and  the  dartos 
of  the  scrotum;  on  each  side  it  is  firmly  attached  to  the  margin  of  the  ischio-pubic 
ramus  and  to  the  tuberosity  of  the  ischium;  and  posteriorly  it  curves  down  behind 
the  Transversalis  perinaei  muscles  to  join  the  base  of  the  triangular  ligament. 

It  is  between  this  layer  of  fascia  and  the  triangular  ligament  of  the  urethra  that  extravasa- 
tion of  urine  most  frequently  takes  place  in  cases  of  rupture  of  the  urethra.  The  triangular 
ligament  of  the  urethra  (p.  461)  is  attached  to  the  ischio-pubic  rami,  and  in  front  to  the  subpubic 
ligament.  It  is  clear,  therefore,  that  when  extravasation  of  fluid  takes  place  between  these 
two  layers,  it  cannot  pass  backward,  because  the  two  layers  are  continuous  with  each  other 
around  the  Transversi  perinaei  muscles :  it  cannot  extend  laterally,  on  account  of  the  connection 
of  both  these  layers  to  the  rami  of  the  os  pubis  and  ischium ;  it  cannot  find  its  way  into  the  pelvis 
because  the  opening  into  this  cavity  is  closed  by  the  triangular  ligament,  and,  therefore,  so 
long  as  these  two  layers  remain  intact,  the  only  direction  in  which  the  fluid  can  make  its  way 
is  forward  into  the  areolar  tissue  of  the  scrotum  and  penis,  and  then  on  to  the  anterior  wall  of 
the  abdomen. 

When  the  deep  layer  of  the  superficial  fascia  is  removed  (Fig.  1144),  a  space  is 
exposed,  between  this  fascia  and  the  triangular  ligament,  in  which  are  contained  the 
superficial  perineal  vessels  and  nerves  and  some  of  the  muscles  connected  with  the 
penis  and  urethra — viz.,  in  the  middle  line,  the  Accelerator  urinae;  on  each  side, 
the  Erector  penis;  and  behind,  the  transversus  perinaei;  together  with  the  crura 
of  the  corpora  cavernosa  and  the  bulb  of  the  corpus  spongiosum.  Here  also  is  seen 
the  central  tendinous  point  of  the  perinaeum.  This  is  a  fibrous  point  in  the  middle 
line  of  the  perinfeum  between  the  urethra  and  the  rectum,  being  about  half  an  inch 
in  front  of  the  anus.  At  this  point  four  muscles  converge  and  are  attached — viz., 
the  External  sphincter  ani,  the  Accelerator  urinae,  and  the  two  Transversi  perinaei 


1550 


SUMGICAL    ANATOMY   OF    THE   PERINEUM 


muscles;  so  that  by  the  contraction  of  these  muscles,  which  extend  in  opposite 
directions,  it  serves  as  a  fixed  point  of  support. 

The  Accelerator  urinae,  the  Erector  penis,  and  the  Superficial  transversus 
perinaei  muscles  have  been  already  described  (p.  459).  They  form  a  triangular 
space  (Fig.  1144).  bounded,  internally,  by  the  Accelerator  urinae;  externally,  by 
the  Erector  penis;  and  behind,  by  the  Transversus  perinaei.  The  floor  of  this 
space  is  formed  by  the  triangular  ligament  of  the  urethra;  and  running  from 
behind  forward  in  it  are  the  superficial  perineal  vessels  and  nerves,  and  the 
transverse  perineal  artery  coursing  along  the  posterior  boundary  of  the  space, 
on  the  Transversus  perinaei  muscle. 

The  Accelerator  urinae  and  Erector  penis  should  now  be  removed,  when  the  triangular  liga- 
ment of  the  urethra  will  be  exposed,  stretching  across  the  front  of  the  outlet  of  the  pelvis.  The 
urethra  is  seen  perforating  its  centre,  just  behind  the  bulb;  and  on  each  side  is  the  crus  penis, 
connecting  the  corpus  cavernosum  with  the  rami  of  the  ischium  and  os  pubis. 


Transversus  perinei 
superficialis. 


GREAT   SACRO- 
SCIATIC    LIGAMENT 


Superficial  perineal  artery. 
Superficial  perineal  nerve. 
Internal  pudic  nerve. 
Internal  pudic  artery. 


FIG.  1144. — The  superficial  muscles  and  vessels  of  the  perineum. 

The  Triangular  Ligament  or  the  Deep  Perineal  Fascia  (trigonum  urogenitale  or 
diaphragma  urogenitale)  (Figs.  308,  309,  and  1145),  which  has  been  already 
described  (p.  461),  consists  of  two  layers,  the  inferior  anterior  or  superficial  layer 
(fascia  trigoni  urogenitalis  inferior)  of  which  is  now  exposed.  It  is  united  to  the 
superior  or  deep  layer  behind,  but  is  separated  in  front  by  a  subfascial  space  in 
which  are  contained  certain  structures. 

The  inferior  layer  of  the  triangular  ligament  (Figs.  304  and  309)  consists  of  a 
strong  fibrous  membrane,  the  fibres  of  which  are  disposed  transversely,  which 
stretches  across  from  one  ischio-pubic  ramus  to  the  other  and  completely  fills  in 
the  pubic  arch;  it  is  attached  in  front  to  the  subpubic  ligament,  except  just  in  the 
centre,  where  a  small  interspace  is  left  for  the  dorsal  vein  of  the  penis.  In  the  erect 
position  of  the  body  it  is  almost  horizontal.  It  is  perforated  by  the  urethra  in  the 
middle  line,  and  on  each  side  of  the  urethral  opening  by  the  ducts  of  Cowper's 
glands  and  by  the  arteries  of  the  bulb;  in  front,  and  external  to  this,  by  the  artery 


THE  PERINEUM  PROPER  IN  THE  MALE 


1551 


of  the  corpus  cavernosum,  immediately  before  this  vessel  enters  the  crus  penis. 
Near  its  apex  the  ligament  is  perforated  by  the  termination  of  the  pudic  artery  and 
by  the  dorsal  nerve  of  the  penis.  The  apex  of  the  triangular  ligament  is  known  as 
the  transverse  perineal  ligament.  The  crura  penis  are  exposed,  lying  superficial  to 
this  ligament.  They  will  be  seen  to  be  attached  by  blunt-pointed  processes  to  the 
rami  of  the  os  pubis  and  ischium,  in  front  of  the  tuberosities,  and  passing  forward 
and  inward,  joining  to  form  the  body  of  the  penis.  In  the  middle  line  the  bulb  and 
corpus  spongiosum  are  exposed  by  the  removal  of  the  Accelerator  urinae  muscle. 
If  the  inferior  layer  of  the  triangular  ligament  is  detached  on  either  side, 
the  deep  perineal  interspace  will  be  exposed  and  the  following  parts  will  be  seen 
between  it  and  the  deep  layer  of  the  ligament:  the  subpubic  ligament  in  front, 
close  to  the  symphysis  pubis ;  the  dorsal  vein  of  the  penis ;  the  membranous  por- 
tion of  the  urethra  and  the  Compressor  urethrae  muscle;  Cowper's  glands  and 
their  ducts;  the  pudic  vessels  and  the  dorsal  nerve  of  the  penis;  the  artery  and 
nerve  of  the  bulb  and  a  plexus  of  veins. 


Anterior  layer  of 

deep  perineal  fascia  removed, 

shoiving 

,    COMPRESSOR    URETHR/C. 

Internal  pudic  artery. 
•Artery  of  the  buU). 
-Cowper's  gland. 


FIG.  1145. — Deep  perineal  fascia.    On  the  left  side  the  anterior  layer  has  been  removed. 

The  superior,  deep,  or  posterior  layer  of  the  triangular  ligament  or  deep  perineal 
fascia  (fascia  trigoni  urogenitalis  superior)  (Fig.  304)  is  derived  from  the  obturator 
fascia,  and  is  continuous  with  it  along  the  pubic  arch.  Behind,  it  joins  with  the 
inferior  layer  of  the  triangular  ligament,  and  is  continuous  with  the  anal  fascia. 
Above  it  is  the,  prostate  gland  (Fig.  1146),  supported  by  the  anterior  fibres  of 
the  Levator  ani,  which  act  as  a  sling  for  the  gland  and  form  the  Levator  prostatae 
muscle.  The  superior  layer  of  the  triangular  ligament  is  continuous  around  the 
anterior  free  edge  of  this  muscle  with  the  layer  of  recto-vesical  fascia  covering 
the  prostate  gland.  The  superior  layer  of  the  triangular  ligament  is  perforated 
by  the  urethra.  Between  the  two  layers  of  the  triangular  ligament  are  situated 
the  membranous  part  of  the  urethra,  enveloped  by  the  Compressor  urethrae 
muscle  (Fig.  309);  the  ducts  of  Cowper's  glands;  the  arteries  to  the  bulb;  the 
pudic  vessels  and  the  dorsal  nerve  of  the  penis.  The  membranous  part  of  the 
urethra  is  about  three-quarters  of  an  inch  in  length,  and  passes  downward  and 


1552 


SURGICAL    ANATOMY   OF   THE   PERINEUM 


forward  behind  the  symphysis  pubis,  from  which  it  is  distant  about  an  inch.  It 
is  the  narrowest  part  of  the  tube,  and  is  enveloped,  as  has  already  been  stated, 
by  the  Compressor  urethrae  muscle. 

The  Compressor  urethrae  has  already  been  described  (p.  460).  In  addition  to 
this  muscle,  and  immediately  beneath  it,  circular  muscular  fibres  surround  the 
membranous  portion  of  the  urethra  from  the  bulb  in  front  to  the  prostate  behind, 
and  are  continuous  with  the  muscular  fibres  of  the  bladder.  These  fibres  are 
involuntary. 

Cowper's  glands  (Figs.  302,  1145,  and  1146)  are  situated  immediately  below 
the  membranous  portion  of  the  urethra,  close  behind  the  bulb,  and  below  the 
artery  of  the  bulb. 

The  Pudic  Vessels  (Figs.  1145  and  1146)  and  Dorsal  Nerve  of  the  Penis  (Fig.  309) 
are  placed  along  the  inner  margin  of  the  pubic  arch  (p.  1548). 

The  Artery  of  the  Bulb  (Figs.  1145  and  1146,  and  p.  692)  passes  transversely 
inward,  from  the  internal  pudic  artery  (p.  690)  along  the  base  of  the  triangular 


Avtery  of  corpus  cavernosum 
Dorsal  artery  of  penis 


Artery  of  bulb. 
Internal  pudic  artery. 

Cowper's  gland. 


FIG.  1146. — A  view  of  the  position  of  the  viscera  at  the  outlet  of  the  pelvis. 

ligament,  between  its  two  layers,  accompanied  by  a  branch  of  the  pudic  nerve. 
If  the  superior  layer  of  the  triangular  ligament  is  removed  and  the  crus  penis  of 
one  side  detached  from  the  bone,  the  under  or  perineal  surface  of  the  Levator 
ani  muscle,  covered  by  the  anal  fascia,  is  brought  fully  into  view  (Figs.  301, 
302,  and  303).  This  muscle,  with  the  triangular  ligament  in  front  and  the  Coc- 
cygeus  and  Pyriformis  behind,  closes  the  outlet  of  the  pelvis. 

The  Levator  ani  and  Coccygeus  muscles  have  already  been  described  (p.  453). 

Position  of  the  Viscera  at  the  Outlet  of  the  Pelvis.—  Divide  the  central  tendinous  point 
of  the  perinseum,  separate  the  rectum  from  its  connections  by  dividing  the  fibres  of  the  Levator 
ani,  which  descend  upon  the  sides  of  the  prostate  gland,  and  draw  the  gut  backward  toward  the 
coccyx,  when  the  under  surface  of  the  prostate  gland,  the  neck  and  base  of  the  bladder,  the 
vesiculse  seminales,  and  the  vasa  deferentia  will  be  exposed. 

The  Prostate  Gland  (p.  1141)  is  a  pale,  firm,  glandular  body  which  is  placed 
immediately  below  the  neck  of  the  bladder,  around  the  commencement  of  the 


THE   PERINsEUM  PROPER   IN   THE   MALE  1553 

urethra.  It  is  placed  in  the  pelvic  cavity,  behind  the  lower  part  of  the  sym- 
physis  pubis,  above  the  superior  layer  of  the  triangular  ligament,  and  rests  upon 
the  rectum,  through  which  it  may  be  distinctly  felt,  especially  when  enlarged.  In 
shape  and  size  it  resembles  a  chestnut.  Its  base  is  directed  upward  toward  the 
neck  of  the  bladder.  Its  apex  is  directed  downward  to  the  deeper  layer  of  the 
triangular  ligament,  which  it  touches. 

Its  posterior  surface  is  smooth,  marked  by  a  slight  longitudinal  furrow,  and  rests 
on  the  second  part  of  the  rectum,  to  which  it  is  connected  by  areolar  tissue.  Its 
anterior  surface  is  flattened,  marked  by  a  slight  longitudinal  furrow,  and  placed 
about  three-quarters  of  an  inch  below  the  pubic  symphysis.  It  measures  about 
an  inch  and  a  half  in  its  transverse  diameter  at  the  base,  an  inch  in  its  antero- 
posterior  diameter,  and  three-quarters  of  an  inch  in  depth.  Hence  the  greatest 
extent  of  incision  that  can  be  made  in  it  without  dividing  its  substance  completely 
across  is  obliquely  backward  and  outward.  This  is  the  direction  in  which  the 
incision  is  made  in  it  in  the  lateral  operation  x>f  lithotomy.  The  prostate  has  a 
sheath  derived  from  the  recto- vesical  fascia  (p.  1459). 

Above  the  prostate  a  small  triangular  portion  of  the  bladder  is  seen  (Fig.  1147), 
bounded,  in  front  and  below,  by  the  prostate  gland;  above,  by  the  recto-vesical  fold 
of  the  peritoneum;  on  each  side,  by  the  seminal  vesicle  and  the  vas  deferens.  It  is 
separated  from  direct  contact  with  the  rectum  by  the  recto-vesical  fascia.  The 
relation  of  this  portion  of  the  bladder  to  the  rectum  is  of  extreme  interest  to  the 
surgeon.  In  cases  of  retention  of  urine  this  portion  of  the  organ  is  found  pro- 
jecting into  the  rectum,  between  three  and  four  inches  from  the  margin  of  the 
anus,  and  may  be  easily  perforated  without  injury  to  any  important  parts.  This 
portion  of  the  bladder  was  consequently  selected  in  the  old  days  for  the  perform- 
ance of  the  now  obsolete  operation  of  tapping  the  bladder. 

Surgical  Anatomy.  MEDIAN  LITHOTOMY. — As  the  incision  is  in  the  raphe",  the  hemor- 
rhage is  trivial,  and  there  is  but  slight  risk  of  injuring  the  pelvic  fascia.  But  the  operation  gives 
little  room  for  manipulation  and  is  inadmissible  in  children,  because  in  them  dilatation  of  the 
wound  may  tear  the  bladder  loose  from  the  urethra.  A  risk  of  median  lithotomy  is  division  of 
the  artery  of  the  bulb. 

In  median  lithotomy  a  grooved  staff  is  introduced,  the  groove  being  median.  The  knife  is 
introduced  in  the  mid-line,  just  in  front  of  the  anal  margin,  and  hits  the  staff  near  the  apex 
of  the  prostate;  the  entire  length  of  the  membranous  urethra  is  cut  as  the  instrument  is  with- 
drawn. 

PARTS  DIVIDED. — Skin,  superficial  fascia,  sphincter  ani  muscle,  central  tendon  of  the 
perinseum,  inferior  leaf  of  the  triangular  ligament,  membranous  urethra,  and  the  Compressor 
urethrse  muscle. 

LATERAL  LITHOTOMY.— -The  operation  is  performed  on  the  left  side  of  the  perinseum,  as  this 
is  most  convenient  for  the  right  hand  of  the  operator.  A  grooved  staff  having  been  introduced 
into  the  bladder,  the  first  incision  is  commenced  midway  between  the"  anus  and  the  back  of 
the  scrotum  (i.  e.,  in  an  ordinary  adult  perinaeum  about  an  inch  and  a  half  in  front  of  the  anus) 
a  little  on  the  left  side  of  the  raphe*,  and  is  carried  obliquely  backward  and  outward  to  midway 
between  the  anus  and  tuberosity  of  the  left  ischium.  The  incision  divides  the  integument  and 
superficial  fascia,  the  inferior  hemorrhoidal  vessels  and  nerves,  and  the  superficial  and  trans- 
verse perineal  vessels.  If  the  forefinger  of  the  left  hand  is  thrust  upward  and  forward  into 
the  wound,  pressing  at  the  same  time  the  rectum  inward  and  backward,  the  staff  may  be  felt  in 
the  membranous  portion  of  the  urethra.  The  finger  is  fixed  upon  the  staff,  and  the  structures 
covering  the  staff  are  divided  with  the  point  of  the  knife,  which  must  be  directed  along  the  groove 
toward  the  bladder,  the  edge  of  the  knife  being  turned  outward  and  backward,  dividing  in  its 
course  the  membranous  portion  of  the  urethra  and  part  of  the  left  lobe  of  the  prostate  gland 
to  the  extent  of  about  an  inch.  The  knife  is  then  withdrawn,  and  the  forefinger  of  the  left  hand 
passed  along  the  staff  into  the  bladder.  The  position  of  the  stone  having  been  ascertained,  the 
staff  is  to  be  withdrawn,  and  the  forceps  is  introduced  over  the  finger  into  the  bladder.  If  the 
stone  is  very  large,  the  opposite  side  of  the  prostate  may  need  to  be  -notched  before  the  forceps 
is  introduced;  the  finger  is  now  withdrawn,  and  the  blades  of  the  forceps  opened  and  made  to 
grasp  the  stone,  which  must  be  extracted  by  slow  and  cautious  undulating  movements. 

Paris  Divided  in  the  Operation. — The  various  structures  divided  in  this  operation  are  as 
follows:  the  integument,  superficial  fascia,  inferior  hemorrhoidal  vessels  and  nerves,  and  prob- 


1554  SURGICAL    ANATOMY    OF    THE   PERINEUM 

ably  the  superficial  perineal  vessels  and  nerves,  the  posterior  fibres  of  the  Accelerator  urinae 
muscle,  the  Transversus  perinaei  muscle  and  artery,  the  triangular  ligament,  the  anterior  fibres  of 
the  Levator  ani  muscle,  part  of  the  Compressor  urethrae  muscle,  the  membranous  and  pros- 
tatic  portions  of  the  urethra,  and  part  of  the  prostate  gland. 

Parts  to  be  Avoided  in  the  Operation. — In  making  the  necessary  incisions  in  the  perinseum  for 
the  extraction  of  a  calculus  the  following  parts  should  be  avoided :  The  primary  incision  should 
not  be  made  too  near  the  middle  line,  for  fear  of  wounding  the  bulb  of  the  corpus  spongiosum 
or  the  rectum;  nor  too  far  externally,  otherwise  the  internal  pudic  artery  may  be  implicated  as  it 
ascends  along  the  inner  border  of  the  pubic  arch.  If  the  incisions  are  carried  too  far  forward, 
the  artery  of  the  bulb  may  be  divided;  if  carried  too  far  backward,  the  entire  breadth  of  the  pros- 
tate and  neck  of  the  bladder  may  be  cut  through,  which  allows  the  urine  to  become  infiltrated 
behind  the  pelvic  fascia  into  the  loose  areolar  tissue  between  the  bladder  and  rectum,  instead 
of  escaping  externally;  diffuse  inflammation  is  consequently  set  up,  and  peritonitis,  from  the 
close  proximity  of  the  recto-vesical  peritoneal  fold,  is  the  result.  If,  on  the  contrary,  only  the 
anterior  part  of  the  prostate  is  divided,  the  urine  makes  its  way  externally,  and  there  is  less 
danger  of  infiltration  taking  place. 

During  the  operation  it  is  of  great  importance  that  the  finger  should  be  passed  into  the  bladder 
before  the  staff  is  removed ;  if  this  is  neglected,  and  if  the  incision  made  in  the  prostate  and  neck 
of  the  bladder  is  too  small,  great  difficulty  may  be  experienced  in  introducing  the  finger  afterward; 
and  in  the  child,  where  the  connections  of  the  bladder  to  the  surrounding  parts  are  very  loose, 
the  force  made  in  the  attempt  is  sufficient  to  displace  the  bladder  upward  into  the  abdomen, 
out  of  the  reach  of  the  operator.  Such  a  proceeding  has  not  unfrequently  occurred,  producing 
the  most  embarrassing  results  and  total  failure  of  the  operation. 

It  is  necessary  to  bear  in  mind  that  the  arteries  in  the  perinseum  occasionally  take  an  abnormal 
course.  Thus  the  artery  of  the  bulb,  when  it  arises,  as  sometimes  happens,  from  the  pudic 
opposite  the  tuber  ischii,  is  liable  in  its  passage  forward  to  the  bulb  to  be  wounded  in  the 
operation  of  lithotomy.  The  accessory  pudic  may  be  divided  near  the  posterior  border  of  the 
prostate  gland,  if  this  gland  is  completely  cut  across;  and  if  the  prostatic  veins  are  of  large  size, 
and  give  rise,  when  divided,  to  troublesome  hemorrhage.  In  men  advanced  in  years  the  pros- 
tatic veins  are  very  apt  to  be  enlarged. 

EXTRAVASATION  OF  URINE. — Extravasation  most  commonly  occurs  from  urethral  rupture, 
between  Colles's  fascia  and  the  triangular  ligament  of  the  urethra  (extravasation  in  front  of 
the  triangular  ligament).  The  adherence  of  these  two  fascial  layers  posteriorly  prevents  the 
urine  from  passing  backward.  The  urine  cannot  find  a  way  laterally,  because  both  layers  on 
each  side  are  attached  to  the  rami  of  the  pubes  and  ischium.  It  cannot  reach  the  pelvis,  because 
the  triangular  ligament  bars  the  way.  It  can  only  go  forward  if  the  two  fascial  layers  remain 
intact,  and  consequently  the  urine  passes  into  the  areolar  tissue  of  the  scrotum  beneath  the 
superficial  fascia  of  the  penis  and  of  the  anterior  abdominal  wall. 

Pus  and  blood  would  pursue  the  same  course  in  this  space.  Effusions  in  this  space  causes 
much  pain,  because  the  space  contains  the  three  long  scrotal  nerves. 

In  rupture  of  the  urethra  between  the  two  layers  of  the  triangular  ligament,  the  urine  remains 
in  this  situation  as  long  as  fascia  remains  intact.  If  suppuration  occurs,  destruction  of  fascia 
liberates  the  urine. 

In  rupture  behind  the  superior  layer  of  the  triangular  ligament  (extravasation  back  of  the 
triangular  ligament),  the  urine  passes  into  the  ischio-rectal  fossa  and  upward  and  backward 
into  the  pelvis. 


THE  FEMALE  PERINEUM. 

The  female  perinaeum  presents  certain  differences  from  that  of  the  male,  in 
consequence  of  the  whole  of  the  structures  which  constitute  it  being  perforated 
in  the  middle  line  by  the  vulvo-vaginal  passage. 

The  Superficial  Fascia,  as  in  the  male,  consists  of  two  layers,  of  which  the 
superficial  one  is  continuous  with  the  superficial  fascia  over  the  rest  of  the  body, 
and  the  deep  layer,  corresponding  to  the  fascia  of  Colles  in  the  male,  is,  like  it, 
attached  to  the  ischio-pubic  rami,  and  in  front  is  continued  forward  through 
the  labia  majora  to  the  inguinal  region.  It  is  of  less  extent  than  in  the  male, 
in  consequence  of  being  perforated  by  the  aperture  of  the  vulva. 

On  removing  this  fascia  the  muscles  of  the  female  perinreum,  which  have 
already  been  described  (p.  463),  are  exposecl  (Figs.  310  and  1147).  The  Sphincter 
vaginae,  corresponding  to  the  Accelerator  urinae  in  the  male,  consists  of  an  atten- 


THE   FEMALE   PERINEUM 


1555 


uated  plane  of  fibres,  forming  an  orbicular  muscle  around  the  orifice  of  the 
vagina,  instead  of  being  united  in  a  median  raphe,  as  in  the  male.  The  Erector 
clitoridis  is  proportionately  reduced  in  size,  but  differs  in  no  other  respect  from 
the  erector  penis,  and  the  Transversus  perinaei  is  similar  to  the  muscle  of  the 
same  name  in  the  male. 

The  triangular  ligament  (Fig.  1147)  is  not  strongly  marked  as  in  the  male. 
It  transmits  the  urethra  and  the  tube  of  the  vagina. 

The  Compressor  Urethrae  corresponds  with  the  Compressor  urethrae  in  the  male. 
It  arises  from  the  ischio-pubic  ramus,  and,  passing  inward,  its  anterior  fibres  blend 
with  the  muscle  of  the  opposite  side,  in  front  of  the  urethra;  its  middle  fibres,  the 
most  numerous,  are  inserted  into  the  side  of  the  vagina,  and  the  posterior  fibres 
join  the  central  point  of  the  perinseum. 


Suspensory  ligament 
of  clitoris 


Glans  clitoris 


Greater  gland 
of  vestibule, 
or  gland  of 
Bartholini 


Erector 

clitoridie 

muscle 


Sphincter 

vaginae 

muscle 


Deep  perineal 
muscle,  with 
its  under 
layer  of  fascia 
(the  triangular 
ligament) 


External 
obturator 
muscle 


Sacro- 
sciatic 
ligament 


Glutens  maximus 

muscle 
FIG.  1147. — The  female  perinaeum  after  removal  of  the  skin  and  superficial  fascia. 


External  sphincter 
ani  muscle 


(Bardeleben.) 


The  distribution  of  the  internal  pudic  artery  is  the  same  as  in  the  male  (p. 1552), 
and  the  pudic  nerve  has  also  a  similar  arrangement,  the  dorsal  nerve  being, 
however,  very  small  and  supplying  the  clitoris. 

The  corpus  spongiosum  is  divided  into  two  lateral  halves,  which  are  represented 
by  the  bulbi  vestibuli  and  partes  intermediates. 

The  Perineal  Body  fills  up  the  interval  between  the  lower  part  of  the  vagina 
and  the  rectum.  Its  base  is  covered  by  the  skin  lying  between  the  anus  and 


1556 


SURGICAL    ANATOMY    OF    THE   PERINEUM 


vagina  on  what  is  called  the  perinaeum.  Its  anterior  surface  lies  behind  the  pos- 
terior vaginal  wall,  and  its  posterior  surface  lies  in  front  of  the  anterior  rectal 
wall  and  the  anus.  It  measures  about  an  inch  and  a  quarter  from  before  back- 
ward, and  laterally  extends  from  one  tuberosity  of  the  ischium  to  the  other.  In  it 
are  situated  the  muscles  belonging  to  the  external  organs  of  generation.  Through 
its  centre  runs  the  transverse  perineal  septum,  which  is  of  great  strength  in  women, 
and  forms  on  either  side,  behind  the  posterior  commissure,  a  hard,  ill-defined 
body,  consisting  of  connective  tissue,  with  much  yellow  elastic  tissue  and  inter- 
lacing bundles  of  involuntary  muscular  fibres,  in  which  the  voluntary  muscles  of 
the  perinseum  are  inserted. 

THE  PELVIC  FASCIA  (FASCIA  PELVIS)   (Figs.  303  and  1149). 

The  pelvic  fascia  strengthens  the  floor  of  the  pelvis,  fastens  pelvic  structures 
together,  and  supports  the  nerves,  blood-vessels,  and  lymphatics.  It  is  connected 
above  with  the  transversalis  fascia  and  the  iliac  fascia.  It  is  at  first  a  thin  membrane 


Internal  pudic  vessels_\Ji 
and  nerve. 


Tuberosity  of 
ischium. 

Fia.  1148. — A  transverse  section  of  the  pelvis,  showing  the  pelvic  fascia  from  behind. 

and  covers  the  inner  surface  of  the  pelvis,  being  attached  to  the  brim  for  a  short 
distance  at  the  side  of  the  cavity  and  to  the  inner  surface  of  the  bone  around  the 
attachment  of  the  Obturator  internus.  At  the  posterior  portion  of  this  muscle  it  is 
continued  backward  as  a  very  thin  membrane  in  front  of  the  Pyriformis  muscle  to 
the  front  of  the  sacrum.  In  front,  as  it  descends,  it  gives  off  the  parietal  layer  of  the 
pelvic  fascia,  which  continues  as  the  obturator  fascia.  It  then  becomes  thicker  and 
covers  the  inner  and  upper  surface  of  the  Diaphragm  of  the  pelvis  as  far  as  the  white 
line  (arcus  tendineits  fasciae  pelvis).  The  portion  covering  the  superior  and  upper 
surface  of  the  pelvic  Diaphragm  is  the  inner  sheath  of  the  Levator  ani  muscle  and 
is  called  the  visceral  layer  of  the  pelvic  fascia  or  the  recto-vesical  fascia  (fascia 
diaphragmatis  pelvis  superior).  The  white  line  is  a  rough  band  of  fascial  thick- 
ening, seen  in  the  pelvic  fascia  of  each  side.  It  indicates  the  line  of  separation 
between  the  pelvic  cavity  ami  the  ischio-rectal  fossa.  It  passes  from  the  lower 


1557 

portion  of  the  symphysis  pubis  outward  and  backward  to  the  spine  of  the  ischium. 
It  makes  the  attachment  of  the  Levator  ani  muscle  to  the  pelvic  fascia.  At  the  white 
line  the  chief  mass  of  the  pelvic  fascia  passes  upon  the  pelvic  viscera  and  is  known 
as  the  fascia  endo-pelvica.  It  covers  portions  of  the  vagina,  rectum,  and  urinary 
bladder,  becomes  thinner  and  thinner,  and  is  gradually  lost.  Other  bands  of  fascia 
begin  at  the  white  line,  descend  on  the  inner  surface  of  the  recto-vesical  fascia,  and 
in  the  male  pass  to  the  tip  of  the  prostate  and  become  the  prostatic  fascia.  Between 
the  anterior  ends  of  the  two  white  lines  the  level  of  the  fascia  is  lower,  and  it  forms 
a  fossa,  bounded  on  the  sides  in  the  male  by  the  pubo-pro static  ligaments  (liga- 
mt-nta  puboprostatica  lateralia),  and  in  the  female  by  the  pubo-vesical  ligaments 
(ligamenta  pubovesicalia  lateralia).  These  ligaments  are  called  the  lateral  true 
ligaments  of  the  bladder.  In  the  base  of  this  fossa  in  the  male  runs  the  anterior  true 
ligament  of  the  bladder  or  the  pubo-prostatic  ligament  (ligamentum  puboprostaticum 


FIG.  1149. — Side  view  of  the  pelvic  viscera  of  the  male  subject,  showing  the  pelvic  and  perineal  fasciae. 

medium),  and  in  the  female  the  anterior  true  vesical  ligament  (ligamentum  pubo- 
vesicale  medium).  These  ligaments  arise  from  the  lowest  portion  of  the  symphysis 
and  pass  to  the  urinary  bladder  and  prostate  in  the  male,  and  urinary  bladder  and 
urethra  in  the  female  (Spalteholz).  The  outer  surface  of  the  pelvic  Diaphragm  is 
covered  by  the  anal  fascia  or  the  ischio-rectal  fascia  (fascia  diaphragmatis  pelvis 
inferior}.  It  is  the  lower  or  outer  sheath  of  the  Levator  ani  muscle,  and  is  derived 
from  the  obturator  fascia.  The  space  between  the  obturator  fascia  and  the  anal 
fascia  is  pyramidal  and  is  called  the  ischio-rectal  fossa  (fossa  ischiorectalis) . 

The  pelvic  fascia  does  not  completely  invest  the  bladder,  although  the  neck  and 
lateral  walls  lie  upon  the  Levator  ani  muscles,  and  the  lateral  true  ligaments  and 
the  anterior  ligament  ascend  upon  the  sides  and  front  of  the  bladder  and  are  lost 
upon  the  fibrous  coat  of  that  viscus.  The  sides  and  anterior  wall  have  a  fascial 
investment.  The  sheath  of  the  prostate  has  already  been  discussed  (p.  1459).  It  is 


1558  SURGICAL    ANATOMY   OF   THE   PERINEUM 

continuous  with  the  recto-vesical  fascia  and  the  anterior  true  ligament  of  the 
bladder. 

The  pelvic  fascia  is  composed,  according  to  Hughes,  of:  1.  The  fibrous  cap- 
sules of  the  pelvic  viscera.  2.  The  sheaths  of  the  Levator  ani  and  Coccygei 
muscles  (recto-vesical  and  anal  fasciae).  3.  The  sheath  of  the  Obturator  internus 
(obturator  fascia).  4.  Sheath  of  the  Compressor  urethrae  muscle  (the  triangular 
ligament).  5.  The  sheath  of  the  pelvic  aspect  of  the  Pyriformis  muscle.  The 
sacral  plexus  is  outside  this  sheath,  the  internal  iliac  vessels  inside  of  it.1  As  pre- 
viously stated,  the  pelvic  fascia  gives  off  the  obturator  fascia  and  the  recto-vesical 
fascia. 

The  Obturator  Fascia  (fascia  obturatoria)  descends  and  covers  the  Obturator 
internus  muscle.  It  is  a  direct  continuation  of  the  parietal  pelvic  fascia  below 
the  white  line  above  mentioned,  and  is  attached  to  the  pelvic  arch,  the  ischial 
tuberosities,  and  to  the  margin  of  the  great  sacro-sciatic  ligaments.  This  fascia 
forms  a  canal  for  the  pudic  vessels  and  nerve  in  their  passage  forward  to  the 
perinaeum,  and  gives  off  a  thin  membrane  which  covers  the  perineal  aspect  of  the 
Levator  ani  muscle,  and  is  called  the  anal  or  ischio-rectal  fascia.  It  forms  the  inner 
boundary  of  the  ischio-rectal  fossa.  From  its  attachment  to  the  rami  of  the  os 
pubis  and  ischium  a  process  is  given  off  which  is  continuous  with  a  similar  process 
from  the  opposite  side,  so  as  to  close  the  front  part  of  the  outlet  of  the  pelvis,  form- 
ing the  deep  layer  of  the  triangular  ligament. 

The  Recto-vesical  Fascia  or  the  Visceral  Layer  of  the  Pelvic  Fascia 
(fascia  endopelvica)  descends  into  the  pelvis  upon  the  upper  surface  of  the  Levator 
ani  muscle,  and  invests  the  prostate,  bladder,  and  rectum.  From  the  inner  sur- 
face of  the  symphysis  pubis  a  short  rounded  band  is  continued,  on  each  side  of 
the  middle  line,  to  the  upper  surface  of  the  prostate  and  neck  of  the  bladder,  form- 
ing the  pubo-prostatic  or  anterior  true  ligaments  of  the  bladder.  At  the  side  this 
fascia  is  connected  to  the  side  of  the  prostate,  enclosing  this  gland  and  the  vesico- 
prostatic  plexus  of  veins,  and  is  continued  on  to  the  side  of  the  bladder,  forming 
the  lateral  true  ligaments  of  the  organ.  Another  prolongation  invests  the  seminal 
vesicle,  and  passes  across  between  the  bladder  and  rectum,  being  continuous 
with  the  same  fascia  of  the  opposite  side.  Another  thin  prolongation  is  reflected 
around  the  surface  of  the  lower  end  of  the  rectum.  The  Levator  ani  muscle  arises 
from  the  point  of  division  of  the  pelvic  fascia,  the  visceral  layer  of  the  fascia 
descending  upon  and  being  intimately  adherent  to  the  upper  surface  of  the  muscle, 
while  the  under  surface  of  the  muscle  is  covered  by  a  thin  layer  derived  from  the 
obturator  fascia,  called  the  ischio-rectal  or  anal  fascia.'  In  the  female  the  vagina 
perforates  the  recto-vesical  fascia  and  receives  a  prolongation  from  it. 

1  A  Manual  of  Practical  Anatomy.     By  Prof.  Alfred  W.  Hughes;  edited  and  completed  by  Dr.  Arthur  Keith. 


CHRONOLOGICAL  TABLE 

OF 

THE  DEVELOPMENT  OF  THE  FCETUS. 

(FROM  BEATJNIS  AND  BOUCHARD.) 

First  Week. — During  this  period  the  ovum  is  in  the  Fallopian  tube.  Having  been  fertilized  in 
the  upper  part  of  the  tube,  it  slowly  passes  down,  undergoing  segmentation,  and  reaches 
the  uterus  probably  about  the  end  of  the  first  week.  During  this  time  it  does  not  undergo 
much  increase  in  size. 

Second  Week. — The  ovum  rapidly  increases  in  size  and  becomes  imbedded  in  the  decidua,  so 
that  it  is  completely  enclosed  in  the  decidua  reflexa  by  the  end  of  this  period.  An  ovum 
believed  to  be  of  the  thirteenth  day  after  conception  is  described  by  Reichert.  There  was 
no  appearance  of  any  embryonic  structure.  The  equatorial  margins  of  the  ovum  were  beset 
with  villi,  but  the  surface  in  contact  with  the  uterine  wall  and  the  one  opposite  to  it  were 
bare.  In  another  ovum,  described  by  His,  believed  to  be  of  about  the  fourteenth  day, 
there  was  a  distinct  indication  of  an  embryo.  There  was  a  medullary  groove  bounded  by 
folds.  In  front  of  this  a  slightly  prominent  ridge,  the  rudimentary  heart.  The  amnion 
was  formed  and  the  embryo  was  attached  by  a  stalk,  the  allantois,  to  the  inner  surface  of 
the  chorion.  It  may  be  said,  therefore,  that  these  parts,  the  amnion  and  the  allantois.  and 
the  first  rudiments  of  the  embryo,  the  medullary  groove,  and  the  heart,  are  formed  at  the 
end  of  the  second  week. 

Third  Week. — By  the  end  of  the  third  week  the  flexures  of  the  embryo  have  taken  place,  so 
that  it  is  strongly  curved.  The  protovertebral  disks,  which  begin  to  be  formed  early  in  the 
third  week,  present  their  full  complement.  In  the  nervous  system  the  primary  divisions 
of  the  brain  are  visible,  and  the  primitive  ocular  and  auditory  vesicles  are  already  formed. 
The  primary  circulation  is  established.  The  alimentary  canal  presents  a  straight  tube  com- 
municating with  the  yolk-sac.  The  branchial  arches  are  formed.  The  limbs  have  appeared 
as  short  buds.  The  Wolffian  bodies  are  visible.  . 

Fourth  Week. — The  umbilical  vesicle  has  attained  its  full  development.  The  caudal  extremity 
projects.  The  upper  and  the  lower  limbs  and  the  cloaca!  aperture  appear.  The  heart  sep- 
arates into  a  right  and  left  heart.  The  special  ganglia  and  anterior  roots  of  the  spinal 
nerves,  the  olfactory  fossae,  the  lungs  and  the  pancreas  can  be  made  out. 

Fifth  Week. — The  allantois  is  vascular  in  its  whole  extent.  The  first  traces  of  the  hands  and 
feet  can  be  seen.  The  primitive  aorta  divides  into  aorta  and  pulmonary  artery.  The  duct 
of  Miiller  and  genital  gland  are  visible.  The  ossification  of  ttie  clavicle  and  the  lower  jaw 
commences.  The  cartilage  of  Meckel  occupies  the  first  post-oral  arch. 

Sixth  Week. — The  activity  of  the  umbilical  vesicle  ceases.  The  pharyngeal  clefts  disappear. 
The  vertebral  column,  primitive  cranium,  and  ribs  assume  the  cartilaginous  condition.  The 
posterior  roots  of  the  nerves,  the  membranes  of  the  nervous  centres,  the  bladder,  kidney, 
tongue,  larynx,  thyroid  body,  the  germs  of  teeth,  and  the  genital  tubercle  and  folds 
are  apparent. 

Seventh  Week. — The  muscles  begin  to  be  perceptible.  The  points  of  ossification  of  the  ribs, 
scapula,  shaft  of  humerus,  femur,  tibia,  palate,  and  upper  jaw  appear. 

Eighth  Week.— The  distinction  of  arm  and  forearm,  and  of  tnigh  and  leg,  is  apparent,  as  well  as 
the  interdigital  clefts.  The  capsule  of  the  lens  and  pupillary  membrane,  the  interventricu- 
lar  and  commencement  of  the  interauricular  septum,  the  salivary  glands,  the  spleen,  and 
suprarenal  capsules  are  distinguishable.  The  larynx  begins  to  become  cartilaginous.  All 
the  vertebral  bodies  are  cartilaginous.  The  points  of  ossification  for  the  ulna,  radius,  fibula, 
and  ilium  make  their  appearance.  The  two  halves  of  the  hard  palate  unite.  The 
sympathetic  nerves  are  now  for  the  first  time  to  be  discerned. 

1  [Eternod  (Anal.  Anzeiger,  Band  xv.,  1898)  described  an  ovum  which  he  reconstructed.  It 
had  a  precise  history,  from  which  he  concluded  that  it  must  have  belonged  to  the  end  of  the  second 
or  the  beginning  of  the  third  week.  Including  the.  villi  it  measured  10  X  8.2  X  6  mm.  It  was 
flattened  on  its  embryonal  side,  and  the  embryo  measured  1.3  ram.  The  amnion  was  completely 
formed  and  the  allantois  existed  as  a  long  canal.  The  vitelline  circulation  was  established  and  the 
villi  of  the  chorion  were  beginning  to  be  vascularized.  The  blastopore  still  opened  into  the  amniotic 
cavity,  with  the  primitive  groove  behind  it  and  the  rudimentary  groove  in  front.  The  notochord 
was  closing  in  and  all  three  layers  of  the  blastoderm  were  distinct,  except  around  the  blastopore,  where 
they  formed  an  undivided  mass. — ED.  of  loth  English  edition.] 

(  1559  ) 


1560  THE  FCETUS. 

Ninth  Week. — The  corpus  striatum  and  the  pericardium  are  first  apparent.  The  ovary  and 
testicle  can  be  distinguished  from  each  other.  The  genital  furrow  appears.  The  osseous 
nuclei  of  the  bodies  and  arches  of  the  vertebrae,  of  the  frontal,  vomer,  and  malar  bones  of  the 
shafts  of  the  metacarpal  and  metatarsal  bones,  and  of  the  phalanges  appear.  The  union  of 
the  hard  palate  is  completed.  The  gall-bladder  is  seen. 

Third  Month. — The  formation  of  the  foetal  placenta  advances  rapidly.  The  projection  of  the 
caudal  extremity  disappears.  It  is  possible  to  distinguish  the  male  and  female  organs  from 
each  other.  The  cloacal  aperture  is  divided  into  two  parts.  The  cartilaginous  arches  on  the 
dorsal  region  of  the  spine  close.  The  points  of  ossification  for  the  occipital,  sphenoid, 
lachrymal,  nasal,  squamous  portion  of  temporal  and  ischium  appear,  as  well  as  the  orbital 
centre  of  the  superior  maxillary.  The  pons  Varolii  and  fissure  of  Sylvius  can  be  made  out. 
The  eyelids,  the  hair,  and  the  nails  begin  to  form.  The  mammary  gland,  the  epiglottis, 
and  prostate  are  beginning  to  develop.  The  union  of  the  testicle  with  the  canals  of  the 
Wolffian  body  takes  place. 

Fourth  Month. — The  closure  of  the  cartilaginous  arches  of  the  spine  is  complete.  Osseous 
points  for  the  first  sacral  vertebra  and  os  pubis  appear.  The  ossification  of  the  malleus  and 
incus  takes  place.  The  corpus  callosum,  the  membrana  lamina  spiralis,  the  cartilage  of 
the  Eustachian  tube,  and  the  tympanic  ring  are  seen.  Fat  is  first  developed  in  the  sub- 
cutaneous cellular  tissue.  The  tonsils  are  seen,  and  the  closure  of  the  genital  furrow  and 
the  formation  of  the  scrotum  and  prepuce  take  place. 

Fifth  Month. — The  two  layers  of  the  decidua  begin  to  coalesce.  Osseous  nuclei  of  the  axis  and 
odontoid  process,  of  the  lateral  points  of  the  first  sacral  vertebra,  of  the  median  points  of 
the  second,  and  of  the  lateral  masses  of  the  ethmoid  make  their  appearance.  Ossification 
of  the  stapes  and  the  petrous  bone  and  ossification  of  the  germs  of  the  teeth  take  place. 
The  germs  of  the  permanent  teeth  and  the  organ  of  Corti  appear.  The  eruption  of  hair  on 
the  head  commences.  The  sudoriferous  glands,  Brunner's  glands,  the  follicles  of  the  tonsil 
and  base  of  the  tongue,  and  the  lymphatic  glands  appear  at  this  period.  The  differentiation 
between  the  uterus  and  vagina  becomes  apparent. 

Sixth  Month. — The  points  of  ossification  for  the  anterior  root  of  the  transverse  process  of  the 
seventh  cervical  vertebra,  the  lateral  points  of  the  second  sacral  vertebra,  the  median  points 
of  the  third,  the  manubrium  sterni  and  the  os  calcis  appear.  The  sacro-vertebral  angle 
forms.  The  cerebral  hemispheres  cover  the  cerebellum.  The  papillae  of  the  skin,  the 
sebaceous  glands,  and  Peyer's  patches  make  their  appearance.  The  free  border  of  the 
nail  projects  from  the  cqrium  of  the  dermis.  The  walls  of  the  uterus  thicken. 

Seventh  Month. — The  additional  points  of  the  first  sacral  vertebra,  the  lateral  points  of  the 
third,  the  median  point  of  the  fourth,  the  first  osseous  point  of  the  body  of  the  sternum, 
and  the  osseous  point  for  the  astragalus  appear.  Meckel's  cartilage  disappears.  The 
cerebral  convolutions,  the  island  of  Reil,  and  the  tubercula  quadrigemina  are  apparent.  The 

•  pupillary  membrane  atrophies.  The  testicle  passes  into  the  vaginal  process  of  the 
peritoneum. 

Eighth  Month. — Additional  points  for  the  second  sacral  vertebra,  lateral  points  for  the  fourth 
and  median  points  for  the  fifth  sacral  vertebrae,  can  be  seen. 

Ninth  Month. — Additional  points  for  the  third  sacral  vertebra,  lateral  points  for  the  fifth, 
osseous  points  for  the  middle  turbinated  bone,  for  the  body  and  great  cornu  of  the  hyoid, 
for  the  second  and  third  pieces  of  the  body  of  the  sternum,  and  for  the  lower  end  of  the 
femur  appear.  Ossification  of  the  bony  lamina  spiralis  and  axis  of  the  cochlea  takes  place. 
The  eyelids  open,  and  the  testicles  are  in  the  scrotum. 


INDEX. 


ABDOMEN,  1241 

boundaries  of,  1241 
fascia  of,  deep,  435 
superficial,  435,  1523 
triangular,  1527 
lymphatics  of,  795,  799 
muscles  of,  434 
deep,  451 
dissection  of,  434 
superficial,  434 
surface  form  of,  450 
nerves  of,  cutaneous,  1014 
anterior,  1013 
lateral,  1013 
ventral,  1013 
.  intercostal,  1013 
regions  of,  1243 
veins  of,  755 
viscera,  1245 

walls  of,  apertures  in,  1243 
lymphatic  vessels  of,  799 
Abdominal  aorta,  670 
branches  of,  673 
relations  of,  671 
surface  marking  of,  672 
surgical  anatomy  of,  672 
aortic  plexus,  1089,  1094 
intercostal  nerves,  1013 
muscles,  434 

portion  of  oesophagus,  1236 
ring,  external,  437,  1526 
internal,  448,  1530 

pillars  of,  1526 
sacs,  1246 

surface  of  bladder,  1442 
viscera,  position  of,  1244 
Abdomino-aortic  glands,  797 
Abdomino-thoracic  arch,  166 
Abducent  nerve,  1057 
branches  of,  1057 
nuclei  of,  894 
relations  of,  1058 
surgical  anatomy  of,  1058 
Abductor  hallucis  muscle,  547 
indicis  muscle,  501 
minimi  digiti  muscle,  foot,  548 

hand,  500 
pollicis  muscle,  497 

relations  of,  498 
Aberrant  ganglia  of  spinal  nerves, 

983 

Absorbent  glands,  774 
Absorbents,  772 
Accelerator  urinae  muscle,  459 
Accessorius  ad  ilio-costalem  mus- 
cle, 421 
Accessory  chains  to  deep  cervical 

glands,  785 
cuneate  nucleus,  884 
descending  palatine  canals,  1 16 
femoral     'nerve    of     Winslow, 

1020 

ganglia  of  spinal  nerves,  983 
gland  of  Rosenmiiller,  1151 
ligament  of  atlas,  278 


Accessory  nerve,  1073 

accessory  portion  of,  1073 
bulbar  portion  of,  1073 
nuclei  of,  890 
spinal  portion  of,  1074 
surgical  anatomy  of,  1074 
vagal  accessory  part  of,  1073 
obturator  nerve,  1020 
olivary  nuclei,  885 
parotid  gland,  1225 
posterior  palatine  canals,  116, 

135 

processes,  57 
quadrate  cartilage,  1107 
suprarenal  glands,  1438 
thyroid  glands,  1409 

veins,  731 
Acetabulum,  220 
fossa  of,  220 

ligaments  of,  transverse,  332 
Acoustic  canal,  external,  1158 
nerve,  1064 
nuclei  of,  892 
surgical  anatomy  of,  1065 
Acrocephalic  skull,  146 
Acromial  angle,  178 
region,  fascia  of,  472 
muscles  of,  472 

surgical  anatomy  of,  473 
thoracic  artery,  653 
Acromio-clavicular    articulation, 

301 

surface  form  of,  303 
surgical  anatomy  of,  303 
ligament,  inferior,  301 

superior,  301 
Acromion  process,  175 
Additus  glottidis  inferior,  1379 
Adductor  brevis  muscle,  523 
canal,  699 
longus  muscle,  522 
magnus  muscle,  523 
minimus  muscle,  523 
obliquus  hallucis  muscle,  549 

pollicis  muscle,  499 
transversus    hallucis    muscle, 

551 

pollicis  muscle,  499 
tubercle,  227 

Adipose  tissue,  pads  of,  265 
Aditus  ad  antrum,  87,  1160 
Adminiculum  linea;  albte,  439 
Afferent  nerve,  827 

neurone,  peripheral  axone  of, 

819 

root  of  spinal  cord,  836 
vessels  of  kidneys,  1432 
Agminated  glands,  1304 
Air  cells,  1403 

sinus,  82 
Ala  cinerea,  880 

nuclei  of,  891 
lobuli  central!*,  897 
nasi,  1106 

artery  of,  609 
Ala?  cinerea?,  nuclei  of,  891 
of  ethmoid,  99 


Ala?  of  sacrum,  64 

of  vomer,  121,  143 
Alar  cartilage,  greater,  1107 

lesser,  1107 
ligaments,  280 
thoracic  artery,  653 
Albicantia,  867,  916 
Alcock's  canal,  1028,  1548 
Alimentary  canal,  1203 

development  of,  1247 
Alveolar  artery,  617 
inferior,  616 
superior,  617 
ducts,  1386 
hare-lip,  111 
point  of  skull,  150 
processes,  140 

of  superior  maxillary,  109 
Alveoli,  mucous,  1228 
pulmonary,  1386 
serous,  1228 

of  teeth,  development  of,  1217 
Alveus,  937 
Amacrine  cells,  820 
of  retina,  1135 
Amceblasts,  1216 
Ammon's  horn,  937 
Amphiarthrosis,  266 
Ampulla?  of  Fallopian  tube,  1510 
membranacea?,  1180 
ossea,  1175 
tubuli  lactiferi,  1518 
of  Vater,  1352 
Amygdala,  871,  954 
Amygdaline  fissure,  932,  933 
Amygdaloid  tubercle,  945 
Anal  canal,  1323 

areolar  coat  of,  1325 
mucous  membrane  of,  1326 
muscular  coat  of,  1324 
relations  of,  1326 
serous  coat  of,  1324 
structure  of,  1326 
submucous  coat  of,  1325 
fascia,  456,  1558 
pockets,  1326 
valves,  1326 
Anastomosis  of  arteries,  585 

circumpatellar,  710 
Anastomotic  vein  of  Trolard,  735 
Anastomotica  magna  of  brachial, 

658 

of  femoral,  706 
Anatomical  neck  of  humerus,  179 

of  scapula,  176 
Anconeus  muscle,  489 
Andersch,  ganglion  of,  1066 
Angle,  acromial,  178 
cephalo-auricular,  1 1 54 
of  jaw,  124 
lateral,  inferior,  63 
of  Luclwig,  166 
nasal,  105 
of  os  pubis,  219 
of  ribs,  163 
Rolandic,  926 
sacro- vertebral,  61 

( 1561  ) 


1562 


INDEX 


Angle  of  skull,  147 
of  sternum,  157 
subscapular,  173 
Angular  artery,  609 
convolution,  931 
gyre,  931 
process,  external,  80,  140 

internal,  80,  140 
vein,  726 
Ankle  bone,  246 
bursae  of,  546 

Ankle-joint,  articulations  of,  I 
ligaments  of,  349 
surface  form  of,  353 
surgical  anatomy  of,  353 
Annular  ligament  of    ankle,  an- 
terior, 544 
external,  545 
internal,  545 
of  radius  and  ulnar,  316 
of  stapes,  1171 
of  wrist,  anterior,  493 

posterior,  495 
plexus,  1121 
Annul  us  ciliaris,  1125 

ovalis,  569 
Ano-coccygeal  body  of  Syming- 
ton, 1324 

Ansa  hypoglossi,  1077 
lenticularis,  914,  957 
peduncularis,  914,  957 
of  Vieussens,  1086 
Ante-cubital  glands,  787 
Anterior  angle  of  ribs,  163 

annular  ligament  of  ankle,  544 

of  wrist,  493 

atlanto-axial  ligament,  276 
atlo-axoid  ligament,  276 
auricular  artery,  613 

nerves,  1052 
bicipital  ridge,  181 
branches   of   superior   cervical 

ganglion,  1085 
cardiac  plexus,  1090 
carpal  arch,  661 

of  ulnar,  665 
cerebral  artery,  628 
chamber  of  eye,  1139 
chondro-sternal  ligament,  290 
chondro-xiphoid  ligament,  290 
choroid  artery,  630 
ciliary  arteries,  627 
clinoid  process,  131 
common  ligament,  271 
communicating    artery   of   ul- 
nar, 664 
condyloid  foramen,  73, 133, 136 

fossa,  136 

coronary  plexus,  1090 
costo-vertebral  ligament,  286 
costo-xiphoid  ligament,  290 
crescentic  lobe  of  cerebellum, 

897 

crucial  ligament,  339 
crural    nerve.       Sec    Femoral 

nerve. 

deep  cervical  vein,  733 
dental  canal,  107 
divisions    of    cervical    nerves, 

988 

of  coccygeal  nerves,  1025 
of  lumbar  nerves,  1015 
of  thoracic  nerves,  1010 
ethmoidal  canal,  82,  100 
cells,  101 

foramen,  82,  130,  141 
sinuses,  101 
extremity  of  ribs,  162 
facial  vein,  726 

femoral  region,  muscles  of,  514 
fontanelle,  78,  103 


Anterior  fossa  of  skull,  130 
gluteal  line,  216 
humeral    region,    muscles    of 

476 
inferior  cerebellar  artery,  642 

spinous  process  of  ilium,  217 
intercostal  arteries,  646 

veins,  752 

internal  frontal  artery,  628 
interosseous    artery    of    ulnar 
664 

nerve,  1004 

intersternal  ligament,  292 
intertrochanteric  line,  225 
jugular  vein,  728 
ligament  of  Helmholtz,  1170 

of  malleus,  1170 

of  wrist,  320 
longitudinal  ligament,  271 

spinal  veins,  754 
marginal  fasciculus,  854 
median  vein,  736 
mediastinal  glands,  808 
mediastinum,  1396 
medullary  velum,  901 
meningeal  artery,  623 
nares,  142,  1108 
nasal  spine,  111,  139,  143 
occipito-atlantal  ligament,  278 
palatine  canal,  143 

fossa,  110,  133 

nerve,  1049 

parolfactory  sulcus,  935 
perforated  space,  935 
perforating  arteries,  646 
peroneal  artery,  717 
phreno-pericardial      ligament, 

561 
pillars  of  fornix,  950,  951 

of  soft  palate,  1222 
pubic  ligament,  298 
pulmonary  nerves,  1072 

plexus,  1069,  1072, 1091 
radial  carpal  artery,  661 
radio-ulnar  ligament,  317 

region,  muscles  of,  481 
recurrent  tibial  artery,  713 
region  of  skull,  139 
root  of  spinal  nerves,  982 
sacral  foramina,  62 
sacro-coccygeal  ligament,  296 
sacro-iliac  ligament,  294 
sacro-sciatic  ligament,  295 
scapular    region,    muscles    of, 

473 

spinal  artery,  640 
sterno-clavicular  ligament,  300 
sterno-costal  ligament,  290 
subarachnoid  space,  978 
superior  dental  nerve,  1048 

ligament,  287 

spinous  process  of  ilium,  216 
surface  of  liver,  1336 

of  stomach,  1277 
temporal  artery,  613,  642 

diploic  vein,  734 
thoracic  nerve,  1001 
tibial  artery,  710 

gland,  794 

nerve,  1033 

veins,  758 
tibio-fibular  region,  muscles  of, 

534 

tibio-tarsal  ligament,  349 
triangle  of  neck,  618 
tubercle  of  cervical  vertebra, 

50 
tympano-malleolar     ligament, 

1166 
ulnar  recurrent  artery,  664 

vein,  745 


Anterior    vertebral  region,  mus- 
cles of,  408 
vein,  733 

wall  of  tympanum,  1163 
Antero-lateral  fontanelle,  103 

ganglionic  arteries,  629 
Antero-median   ganglionic    arte- 
ries, 628 
Antero-posterior      diameter      of 

pelvis,  210 
Antihelix,  1154 

fossa  of,  1154 
Antitragicus  muscle,  1157 
Antitragus,  1155 
Antrum  of  Highmore,  108 

mastoid,  87 

opening  of,  1163 

of  pylorus,  1279 

tympanic,  87 
Anus,  1323 

arteries  of,  1327 

lymphatics  of,  807,  1329 

nerves  of,  1329 

veins  of,  1328 
Aorta,  589 

abdominal,  670 

arch  of,  593 

branches  of,  595 
peculiarities  of,  594,  595 
relations  of,  594 
surgical  anatomy  of,  594 

ascending,  590  . 

descending,  676 

sinus  of,  great,  591 

thoracic,  667 

transverse,  592 
Aortic  isthmus,  593 

opening  of  diaphragm,  431 
of  heart,  568 

semilunar  valves,  574 

sinus  of  Valsalva,  575 

spindle,  593 

vestibule  of  Sibson,  574 
Apertura  scalar  vestibuli  cochleae, 
1175 

tympanica   canaliculi   chordae, 

1163 
Aperture   of   nose,    cartilage   of, 

1107 
Apical  coil  of  cochlea,  1177 

glands,  1101 

Aponeurosis  of  external  oblique, 
435,  1525 

of  internal  oblique,  441 

palatine,  406 

pharyngeal,  404,   1233 

Sibson 's,  1393 

of  soft  palate,  1222 

supra-hyoid,  396 

vertebral,  413,  418 
Apophysis,  34 
Appendages  of  eye,  1 147 

of  skin,  1195 

of  uterus,  1509 
Appendices  epiploicse,  1270 
Appendicular  artery,  678 

vein,  768 
Appendiculo-ovarian  ligament  of 

dado,  1312 

Appendix  of  auricle,  left,  570 
right,  567 

ensiform,  159 

vermiform,    1311 

xiphoid,  159 
Aqueduct  of  mid-brain,  907 

central  gray,  907 
Aquaeductus  cochleae,  89,  136 
1177 

Fallopii,  89 

eminence  of,  1162 

vestibuli,  89,  133,  1175 


INDEX 


1563 


Aqueous  chamber,  1138 

humor,  1138 
Arachnoid  of  brain,  976 

structure  of,  978 
of  cord,  858 

structure  of,  859 
villi,  979 

Arangi,  body  of,  573 
Arbor  vita;  cerebelli,  895,  899 

of  uterus,  1505 
Arboriform  cells,  821 
Arch  of  aorta,  593 
of  atlas,  51 

axillary,  415,  466,  648 
carpal,  anterior,  661 

posterior,  661 
crural,  deep,  450,  1543 
superficial,  438,  1541 
palmar,  deep,  660 
superficial,  666 
plantar,  719 
pubic,  211 
supraorbital,  80 
tarsal,  inferior,  625 

superior,  625 
of  vertebra,  48 
zygomatic,  138 
Arched  commissure  of  Gudden, 

905 

Arcuate  ligaments,  429,  451 
internal,  429 
middle,  429 
Arcus  senilis,  1120 
Area  cribrosa  media,  89 

superior,  89 
of  oblongata,  875 
dorsal,  876 
lateral,  876 
vestibularis,  inferior,  1186 

superior,  1186 
Areolffi  of  bone,  primary,  44 

secondary,  45 
of  mamma,  1516 
Areolar  coat  of  anal  canal,  1325 
of  intestine,  large,  1325 

small,  1298 
of  liver,  1345 
of  oesophagus,  1239 
of  rectum,  1325 
of  stomach,  1283 
tissue,  subcutaneous,  1190 

subserous,  1256 
Arm,  arteries  of,  639 
bones  of,  179 
fascia?  of,  476 
deep,  472 
superficial,  472 
lymphatics  of,  787 
muscles  of,  472,  476 
dissection  of,  471,  476 
surgical  anatomy  of,  480 
nerves  of,  994 
veins  of,  744 
Arnold's  ganglion,  1053 

branches  of,  1053 
nerve,  1070 

canal  for,  90 
Arteria  centralis  retinae,  627 

magna,  589 
Arterise  hallucis,  715 
princeps  cervicis,  611 
receptaculi,  623 
uterina  ovarica,  689 
Artery  or  arteries,  585 
alveolar,  617 
inferior,  616 
superior,  617 
anastomosis  of,  585 
anastomotica  magna  of  brach- 

ial,  658 
of  femoral,  706 


Artery  or  arteries,  angular,  609 
antero-lateral  ganglionic,  629 
antero-median  ganglionic,  628 
aorta,  589 

abdominal,  670 

arch  of,  593 

ascending,  590 

descending,  667 

thoracic,  667 
appendicular,  678 
arterise  receptaculi,  623 
articular,  of  knee,  710 
auditory,  641,  1186 
auricular,  anterior,  613 

posterior,  611 
axillary,  649 
azygos,  of  knee,  710 

of  vagina,  688 
basilar,  641 
brachial,  654 
of  brain,  630 
bronchial,  668 
buccal,  616 
of  bulb,  692 
bulbar,  641 
calcanean,  external,  718 

internal,  718 
carotid,  common,  598 

external,  602 

internal,  620 

carpal  arch,  anterior,  661 
posterior,  661 

radial,  anterior,  661 
posterior,  661 

ulnar,  anterior,  665 

posterior,  665 

central  ganglionic  system,  632 
centralis  retinae,  627 
cerebellar,  anterior  inferior,  642 

posterior  inferior,  641 

superior,  642 
cerebral,  anterior,  628 
of  cerebral  hemorrhage,  630 

middle,  629 

posterior,  642 
cervical,  ascending,  643 

deep,  647 

superficial,  644 

transverse,  644 
choroid,  anterior,  630 

posterior,  642 
ciliary,  627 
circle  of  Willis,  642 
circumflex,  of  arm,  653 

iliac,  deep,  698 
superficial,  704 

of  thigh,  705 
coccygeal,  694 
cochlear,  1186 
coeliac,  673 
colic,  left,  680 

middle,  678 

right,  677 

comes  nervi  ischiadici,  694 
mediana,  665 
phrenici,  646 

communicating,  anterior  cere- 
bral, 628 

to  deep  palmar  arch,  666 

posterior  cerebral,  630 

of  ulnar,  anterior,  664 
coronary,  673 

of  heart,  592 

of  lip,  inferior,  609 

superior,  609 

of  corpus  cavernosum,  692 
cortical  system  of,  632 
cremasteric,  697 
cri co-thyroid,  605 
cystic,  676 
dental,  anterior,  617 


Artery  or  arteries,  inferior,  616 

posterior,  617 
digital,  plantar,  661 

of  ulnar,  666 
dorsalis  hallucis,  715 

indicis,  661 

lingua;,  606 

nasi,  626 

pedis,  713 

pollicis,  661 

scapulae,  653 
dural,  611,  612,  974 
epigastric,  deep,  697 

internal,  697 

superficial,  704 

superior,  647 
ethmoidal,  625 
facial,  607 

transverse,  613 
femoral,  698 

common,  700 

deep,  704 

fibular,  superior,  712 
of  foot,  713 
frontal,  613 

from       anterior       cerebral, 
628 

from  middle  cerebral,  630 

from  ophthalmic,  625 
ganglionic,  postero-lateral,  642 

postero-median,  642 
gastric,  673,  676 
gastro-duodenalis,  675 
gastro-epiploica  dextra,  675 

sinistra,  676 
gluteal,  695 

inferior,  694 
hsemorrhoidal,  inferior,  691 

middle,  688 

superior,  680 
of  head,  598 
of  heart,  580 
hepatic,  674 
histology  of,  586 
hyoid  branch  of  lingual,  606 
of  superior  thyroid,  605 
hypogastric,  685 

in  fret  us,  685 
ileo-colic,  677 
iliac,  circumflex,  deep,  698 
superficial,  704 

common,  683 

external,  695 

internal,  685 
ilio-lumbar,  694 
infra-hyoid  branch  of  superior 

thyroid,  605 
infraorbital,  617 
innominate,  596 
inosculation  of,  585 
intercostal,  669 

anterior,  646 

superior,  647 
interlobar,  1432 
interosseous,  of  foot,  715 

of  hand,  662 

ulnar,  664 
anterior,  664 
posterior,  665 
labial,  inferior,  609 
lachrymal,  624 
laryngeal,  inferior,  643 

superior,  605 
lateralis  nasi,  609 
lenticulo-striate,  630 
lingual,  605 

deep,  606 

of  lower  extremity,  698 
lumbar,  682 
lymphatics  of,  588 
malar  from  lachrymal,  625 


1564 


INDEX 


Artery    or     arteries,     malledlar 

713,  718 

mammary,  internal,  645 
maridibular,  616 
marginal,  592 
masseteric,  616 
mastoid,  611,  612 
maxillary,  external,  607 

internal,  613 
mecliastinal,  646 

posterior,  668 
medicerebellar,  642 
medicerebral,  629 
medidural,  615 
meningeal,  611,  612 

anterior,  623 

middle,  615 

from  occipital,  611 

from  pharyngeal,  612 

from  vertebral,  640 

posterior,  640 

small,  616 
mesenteric,  inferior,  679 

superior,  677 
metatarsal,  715 
of  muscle,  364 
musculo-phrenic,  646 
mylo-hyoid,  616 
nasal,  from  ophthalmic,  626 

of  septum,  609 
naso-palatine,  617 
of  neck,  598 
nerves  of,  588 
nutrient,  of  femur,  706 

of  fibula,  717 

of  humerus,  658 

of  tibia,  718 
obturator,  689 
occipital,  610 
resophageal,  643,  668 
ophthalmic,  624 
orbital,  613 

internal,  629 
ovarian,  682 
palatine,  ascending,  608 

descending,  617 

inferior,  608 

posterior,  617 
palmar  arch,  deep,  660 

superficial,  666 
palpebral,  625 
pancreatic,  676 

pancreatico-duodenalis,      infe- 
rior, 677 
superior,  676 
parietal,  613 

ascending,  630 
parieto-sphenoidal,  630 
parieto-temporal,  630 
parvidural,  616 
of  penis,  dorsal,  691,  1468 
perforating,  anterior,  646 

of  foot,  719 

of  hand,  662 

of  thigh,  706 
pericardiac,  646,  668 
of  pericardium,  563 
perineal,  superficial,  691 

transverse,  692 
peroneal,  717,  718 
pharyngeal,  ascending,  612 
phrenic,  inferior,  682 

superior,  646 
of  pi  a  of  brain,  982 
plantar,  718,  719 
popliteal,  707 
postcerebellar,  641 
postce'rebral,  642 
postchoroid,  642 
postcomniunicant,  630 
postdural,  612 


Artery      or      arteries,     postero- 

lateral  ganglionic,  642 
postero-median  ganglionic,  630 
precerebellar,  642 
precerebral,  628 
prechoroid,  630 
precommuiiicant,  628,  629 
predural,  623 
prevertebral,  612 
princeps  hallucis,  715 

pollicis,  662 
profunda,  of  arm,  inferior,  658 
superior,  657 

femoris,  704 
pterygo-palatine,  617 
pterygoid,  616 
pudic,  accessory,  691 

external,  704 

internal,  in  female,  693 

in  male,  690 
pulmonary,  589 
pyloric,  inferior,  675 

superior,  675 
radial,  659 
radialis  indicis,  662 
ranine,  606 
recurrent,  palmar,  662 

radial,  661 

tibial,  anterior,  713 
posterior,  712 

ulnar,  anterior,  664 

posterior,  664 
renal,  680 

inferior,  1432 
of  round  ligament,  689 
sacral,  lateral,  694 

middle,  683 

scapular,  posterior,  644 
sciatic,  693 
sigmoid,  680 
spermatic,  681 
spheno-palatine,  617 
spinal,  anterior,  640 

dorsal,  641 

lateral,  640 

posterior,  641 

rami,  640 

ventral,  640 
splenic,  676 
sternal,  646 

sterno-mastoid,  605,  611 
stylo-mastoid,  611 
subclavian,  633 
subcostal,  669 
sublingual,  606 
submaxillary,  608 
submental,  608 
subscapular,  653 
superficialis  volse,  661 
supra-acromial,  644 
supra-hyoid,  606 
supraorbital,  625 
suprarenal,  680 
suprascapular,  643 
suprasternal,  644 
sural,  709 
tarsal,  714 
temporal,  612,  613 

anterior,  613,  642 

deep,  616 

middle,  613 

posterior,  613,  642 
terminal,  632 
thoracic,  acromial,  653 

alar,  653 

long,  653 

superior,  651 
thyroid  axis,  642 

inferior,  643 

superior,  604 
of  thyroid  gland,  605 


Artery     or     arteries,    thyroidea 

ima,  596 
tibial,  anterior,  710 

posterior,  715 

recurrent,  anterior,  713 

posterior,  712 
tonsillar,  608 
tracheal,  643 
transversalis  colli,  644 

humeri,  643 
of  trunk,  667 

tympanic,       from      ascending 
pharyngeal,  612 

from  internal  carotid,  623 

from  internal  maxillary,  615 
ulnar,  662 

recurrent,  anterior,  664 

posterior,  664 

umbilical,  in  foetus,  583,    686 
of  upper  extremity,  633 
uterine,  688 
vaginal,  688 
of  vas  deferens,  687 
vasa  brevia,  676 

intestini  tenuis,  677 

vasorum  of,  588 
vertebral,  639 
vesical,  inferior,  688 

middle,  688 

superior,  687 
Vidian,  617 
Arthrodia,  268 
Arthrology,  261 
Articular  arteries  of  knee,  710 
inferior,  710 
superior,  710 
cartilage,  262 
circumference  of  ulna,  191 
corpuscles,  830 

eminence  of  temporal  bone,  84 
lamella  of  bone,  261 
processes  of  a  vertebra,  49 
synovial  membrane,  264 
Articulations,  261 

acromio-clavicular,  301 
of  ankle-joint,  349 
astragalo-scaphoid,  356 
atlanto-axial,  276 
of  atlas  with  axis,  276 

with  occipital  bone,  278 
biaxial,  267 

.calcaneo-astragaloid,  354 
calcaneo-cuboid,  355 
calcaneo-scaphoid,  355 
carpo-metacarpal,  323 
of  carpus,  321 
chondro-sternal,  290 
coccygeal,  296 
condyloid,  267 
costo-central,  285 
costo-chondral,  292 
costo-sternal,  289 
costo-transverse,  287 
costo- vertebral,  285 
crico-arytenoid,  1375 
crico-thyroid,  1375 
of  cuboid  with  cuneiform,  358 

with  scaphoid,  357 
of  elbow-joint,  310 
femoro-tibial,  337 
of  hip,  327 
immovable,  266 
interchondral,  291 
interneural,  274 
of  knee,  336 
of  lower  extremity,  327 

jaw,  282 

metacarpo-phalangeal,  326 
metatarso-phalangeal,  361 
mixed,  266 
movable,  267 


INDEX 


1565 


Articulations,    occipito-atlantal 

278 

occipito-axial,  280 
of  ossa  pubis,  298 
of  ossicles  of  tympanum,  1170 
of  pelvis,  294 
of  phalanges  of  foot,  361 

of  hand,  327 
radio-carpal,  319 
radio-ulnar,  315 
inferior,  317 
middle,  316 
superior,  316 

by  reciprocal  reception,  267 
of  ribs  with  vertebrae,  285 
sacro-coccygeal,  266 
sacro-iliac,  294 
sacro-sciatic,  294 
sacro- vertebral,  292 
of  sacrum  with  coccyx,  296 
and  ilium,  294 
and  ischium,  294 
scapulo-clavicular,  301 
of  shoulder-joint,  305 
of  spine  with  cranium,  278 
sterno-clavicular,  299 
of  sternum,  292 
tarso-metatarsal,  359 
of  tarsus,  354 
temporo-mandibular,  282 
temporo-maxillary,  138 
tibio-fibular,  347 
tibio-tarsal,  349 
of  trunk,  271 
of  upper  extremity,  299 
of  vertebral  column,  271 

with  pelvis,  292 

of  wrist,  319 

Articuli,  954 

Aryteno-epiglottidean  folds,  1373 

Aryteno-epiglottideus        muscle, 

1381 

Arytenoid  cartilages,  1372 
apex  of,  1373 
base  of,  1373 
surfaces  of,  1372 
glands,  1383 
muscles,  1380 
Arytenoideus  muscle,  1380 
Ascending  aorta,  590 
•    branches  of,  592 
relations  of,  591 
cervical  artery,  643 
colon,  1317 

hepatic  flexure  of,  1317 
frontal  artery,  630 
lumbar  vein,  753,  765 

right,  752 
mesocolon,  1268 
oblique    muscle    of    abdomen, 

439 

palatine  artery,  608 
parietal  artery,  630 
pharyngeal  artery,  612 
projection  nerve  fibres,  963 
ramus  of  ischium,  218 

of  pubis,  219 
root  of  fifth  nerve,  1042 
vena  cava,  764 
Association  fibres  of  cerebellum, 

902,  961 

Asterion,  75,  138,  150 
Astragalo-scaphoid    articulation, 

356 

ligament,  superior,  356 
Astragalus,  246 

articulations  of,  248 
body  of,  246 
head  of,  246 
neck  of,  246 
surfaces  of,  246,  247 


Astrocytes,  832 

Atlanto-axial  ligament,  anterior, 

276 

posterior,  277 
Atlanto-odontoid    joint  of    Cru- 

veilhier,  276 
Atlas,  50 
arches  of,  51 

attachment  of  muscles  to,  60 
development  of,  59 
lateral  masses  of,  51 
processes  of,  51 
transverse  ligament  of,  277 
Atlo-axoid     ligament,     anterior, 

276 

posterior,  277 
Atrabiliary  capsules,  1439 
Atria  of  left  bronchus,  1386 
Atrium,  1160 

of  nasal  fossae,  1110 

meat  us,  145 
Attic,  1160 

tympanic,  87 

Attollens  auriculam  muscle,  371 
Attrahens  auriculam  muscle,372 
Auditory  arteries,  641,  1186 
canal,  external,  1158 
meat  us,  external,  138,  1158 
arteries  of,  1159 
cartilaginous    portion    of, 

1158 

lymphatics  of,  1160 
nerves  of,  1160 
osseous  portion  of,  1159 
relations  of,  1159 
skin  of,  1159 
surface  form  of,  1160 
veins  of,  1160 
internal,  133 

fundus  of,  1178' 
nerve,  1064,  1186 

surgical  anatomy  of,  1065 
nuclei,  dorsal,  892 

ventral,  892 
process,  88 
radiation,  956 
teeth,  1183 
veins,  1186 

Auerbach's  plexus,  1307 
Aula,  917 
Aulix,  916 
Auricle  of  ear,  1154 
of  heart,  fibres  of,  577 
left,  570 

sinus  of,  570 
right,  567 

sinus  of,  567 

Auricular  appendices,  567 
appendix,  left,  570 

right,  567 
artery,  anterior,  613 

posterior,  611 

branch  of  vagus  nerve,  1070 
fissure,  90,  136 
nerves,  anterior,  1052 
great,  989 
posterior,  1062 
point  of  skull,  150 
region,  muscles  of,  371 
dissection  of,  371 
surface  of  sacrum,  63 
vein,  727 

Auriculo-temporal  nerve,  1052 
Auriculo- ventricular  fasciculus  of 

heart,  579 

groove  of  heart,  567 
opening,  left,  571 

right,  568 
Axes  of  pelvis,  211 
Axilla,  dissection  of,  465 
surgical  anatomy  of,  647 


Axilla,    suspensory   ligament  of, 

466 

Axillary  arch,  415,  466,  648 
artery,  649 

branches  of,  652 

peculiarities  of,  651 

relations  of,  650 

surface  marking  of,  651 

surgical  anatomy  of,  651 
border  of  scapula,  176 
fascia,  465,  648 
glands,  787 
space,  647 
veins,  747 

surgical  anatomy  of,  748 
Axis,  52 
apex  of,  52 

attachment  of  muscles  to,  60 
body  of,  52 
cerebro-spinal,  833 
coeliac,  673 
cylinder  process,  820 
medullated,  824 
development  of,  59 
ligament  of  malleus,  1171 
odontoid  process  of,  52 
optic,  1115 
pedicles  of,  52 
processes  of,  53 
thoracic,  653 
thyroid,  642 
visual,  1116 
Axone  of  cord,  myelinization%of, 

855 

myelinic,  824,  826 
of  nerve-cells,  816,  820,  823 
peripheral,    of     afferent    neu- 
rone, 819 

termination  of,  828 
varieties  of,  824 
Azygos  arteries,  articular,  710 

of  vagina,  688 
uvulae  muscle,  407 
veins,  752 

larger,  752 

left  lower,  753 
upper,  753 

right,  752 

smaller,  753 

surgical  anatomy  of,  753 


B 


BACK,  fascia  of,  deep,  413 

superficial,  413 
muscles  of,  dissection  of,  422 
fifth  layer,  422 
first  layer,  412 
fourth  layer,  419 
second  layer,  416 
surface  forms  of,  426 
third  layer,  417 
Baillarger,  fibre  band  of,  959 
Band,  fibre,  of  Baillarger,  959 
of  Bechterew,  959 
of  Gennari,  959 
of  Meckel,  1170 
of  Vicq  d'Azyr,  939 
Bartholin,  duct  of,  1227 

glands  of,  1495 
Basal  ganglia,  867,  952 
Base  of  sacrum,  64 
of  skull,  130 

surfaces  of,  130 
Basi-hyal  of  hyoid  bone,  155 
Basil  coil  of  cochlea,  1177 
Basilar  artery,  641 

branches  of,  641 
groove,  75 
of  pons,  877 


1566 


INDEX 


Basilar  lymph-sinus,  1314 

membrane  of  cochlea,  1182 

process,  71 

sinus,  743 

suture,  128 

vein,  735 
Basilic  vein,  746 
median,  746 
Basion,  73,  150 
Basis  vertebrarum,  venae,  753 
Basisylvian  fissure,  924 
Basket-cells  of  cerebellum,  902 
Bauhin,  valve  of,  1315 
Beaunis   et    Bouchard,    table   of 

development  of  fostus,  1559 
Bechterew,  fibre  band  of,  959 
Bell,  respiratory  nerve  of,  exter- 
nal, 1000 
internal,  992 
Bertin,  bones  of,  97 

columns  of,  1424 

ligaments  of,  330 
Biaxial  articulation,  267 
Biceps  flexor  cubiti  muscle,  477 

muscles,  477,  532 

bursa  of,  477 
Bicipital  fascia,  478,  746 

groove,  179 

ridges,  181 

tuberosity,  191 
Bicornate  uterus,  1505 
Bicuspid  teeth,  1208 

yalve,  574 

cusps  of,  574 
Bigelpw,  ligament  of,  330 
Bile,  1353 

Bile-canaliculi,  1348 
Bile-capillaries,  1348 
Bile-duct,  common,  1351 
arteries  of,  1353 
dimensions  of,  1353 
lymphatics  of,  803,  1353 
nerves  of,  1353 
structure  of,  1352 
surgical  anatomy  of,  1355 
veins  of,  1353 

papilla,  1296 

Bipeiiniform  muscles,  365 
Bipolar  cells,  820 
"Bird's     nest"     of     cerebellum, 

898 

Biventer  cervicis  muscle,  422 
Bi ventral  lobe  of  cerebellum,  898 
Bladder,  1441 

apex  of,  1445 

arteries  of,  1449 

base  of,  1443 

body  of,  1443 

cervix  of,  1444 

female,  1455 

fundus  of,  1443 

ligaments  of,  1445 

lymphatics  of,  800,  1449 

mucous  coat  of,  1447 
membrane  of,  1447 

muscular  coat  of,  1446 

neck  of,  1444 

nerves  of,  1449 

serous  coat  of,  1446 

structure  of,  1446 

submucous  coat  of,  1447 

summit  of,  1445 

surface  form  of,  1449 

surfaces  of,  1442 
inner,  1447 

surgical  anatomy  of,  1449 

trigone  of,  1447 

veins  of,  1449 
Blade  bone,  172 
Blind  spot,  1131 
Blood-vascular  system,  557 


Bochdalek,  ganglion  of,  1048 
Bodies,  parasympathetic,  1417 
Body,  carotid,  1416 

cavernous,  artery  of,  692 
coccygeal,  1417 
of  lungs,  915 
pineal,  915 
pituitary,  917 
thyroid,'  1407 
of  a  vertebra,  49 
Bones,  acetabulum,  220 
apophysis  of,  34 
areolse  of,  primary,  44 

secondary,  45 
astragalus,  246 
atlas,  50 
axis,  52 
of  Bertin,  97 
blood-vessels  of,  39 
breast,  157 
calcaneum,  242 
canaliculi  of,  46 
cancellous,  35 
carpus,  195 

chemical  composition  of,  41 
clavicle,  169 
coccyx,  65 
compact,  35 
cranial,  71 
cuboid,  248 
cuneiform  of  foot,  249 

of  hand,  199 
diploe  of,  34 
ear,  1168 
eminences  and  depressions  of, 

34 

epactal,  103 
epicteric,  103 
epiphysis  of,  34 
ethmoid,  98 
of  face,  104 
femur,  223 
fibula,  239 
flat,  34 
of  foot,  244 
frontal,  79 
growth  of,  42 

of  hand,  195 
Haversian  canals  of,  38 

systems  of,  38 
humerus,  179 
hyoid,  155 
ilium,  214 
incus,  1169 
inter-maxillary,  110 
irregular,  34 
ischium,  217 
of   jaw,    changes  produced  in, 

by  age,  112 
lachrymal,  112 
lacunae  of,  38 
lamella  of,  38 

articular,  261 
of  leg,  233 
lingual,  155 
long,  33 

lymphatics  of,  41 
malar,  113 
malleus,  1168 
marrow  of,  36 
maxillary,  inferior,  122 

superior,  105 
medullary  spaces  of,  45 
metacarpal,  200 
metatarsal,  252 
mixed,  34 
nasal,  104 
navicular,  197,  249 
nerves  of,  41 
occipital,  71 
orbicular,  1169 


Bones,  os  calcis,  244 

innominatum,  213 

magnum  of  carpus,  201 
ossification  of,  42 

intracartilaginous,  43 

intramembranous,  43 
palate,  115 
parietal,  76 
patella,  233 
pelvic,  209 
periosteum  of,  37 
phalanges  of  foot,  255 

of  hand,  206 
pisiform,  199 
ploughshare,  120 
pre-maxillary,  110 
pubis,  219 
radius,  192 
ribs,  161 
sacrum,  61 
scaphoid  of  foot,  249 

of  hand,  197 
scapula,  172 
semilunar,  198 
sesamoid,  259 
short,  33 
sphenoid,  92 
spongy,  97 
sternum,  157 
structure,  34 
supernumerary,  103 
surface  of,  34 
sutural,  103 
tarsus,  244 
temporal,  83 
thigh,  223 
tibia,  234 
trapezium,  200 
trapezoid,  200 
turbinated,  inferior,  119 

middle,  101 

sphenoidal,  143 

superior,  101 
tympanic,  91 
ulna,  186 
unciform,  201 
veins  of,  41 

vertebra  prominens,  53 
vertebra,  cervical,  49 

lumbar,  56 

thoracic,  53  . 

vomer,  120 
wedge,  249 
Wormian,  103 
Bony  canal  of  cochlea,  1177 
Bosom,  1516 
Bowman's  capsule,  1427 
glands,  1111 
membrane,  1119 
muscle,  1125 

Brachia  of  quadrigemina,  905 
Brachial  artery,  654 

branches  of,  657 

peculiarities  of,  655 

relations  of,  654 

surface  marking  of,  656 

surgical  anatomy  of,  656 
lymphatic  glands,  787 
plexus,  994 

branches  of,  998 

relations  of,  998 

surgical  anatomy  of,  1009 
region,  anterior,  muscles  of,  481 

posterior,  muscles  of,  488 
veins,  747 

Brachialis  anticus  muscle,  478 
Brachio-cephalic  vein,  750 
Brachycephalic  skull,  146 
Brain,"  860 

adult  human,  descriptive  an- 
atomy of,  873 


INDEX 


1567 


Brain,  arachnoid  of,  976 
villi  of,  975) 

areas  of  localization  of,  966 

blood-vessels  of,  630 

convolutions  of,  922 

cortex  of,  871 

development  of,  863 

dimensions  of,  862 

dura  of,  972 

fissures  of,  922,  923 

fore-,  911 

ganglionic  vessels  of,  632 

gyres  of,  922 

hemispheres  of,  989 

hind-,  874 

laminae  of,  870 

little,  895 

lobes  of,  923 

localization  of  function  of,  966 

meninges  of,  972 

mill-,  904 

Pacchionian  bodies  of,  979 

pia  of,  980 

sand,  915 

smell-,  920 

topography  of,  860 

tube,  flexures  of,  869 

ventricles  of,  869,  878 

vesicles  of,  864 

weight  of,  965 

zones  of,  longitudinal,  870 
Breast  bone,  157 
Bregma,  129,  150 
Bregmatic  fontanelle,  103 
Breschet,  canals  of,  733 
Brim  of  pelvis,  209 
Broad  ligaments  of  liver,  1340 

of  uterus,  1502 
Broca,  "cap"  of,  925 

diagonal  band  of,  936 
Bronchi,  1384 
Bronchial  arteries,  668 

branch  of  innominate,  596 

glands,  1389 

septum,  1389 

veins,  753 
Bronchus,  left,  1386 

right,  1384 

Brown  striae  of  Retzius,  1214 
Bruce   and   Campbell's   tract   of 

cord,  853 

Bruch,  membrane  of,  1124 
Brunner's  glands,  1303 
Bubonocele,  1533 
Buccal  artery,  616 

cavity,  1203 

glands,  1205 

lymphatic  glands,  781 

nerve,  1051,  1063 
Buccinator  crest,  124 

glands,  781 

muscle,  382 

nerve,  1051 

veins,  726 
Bucco-pharyngeal     fascia,     383, 

390,  403,  1232 
Bulb,  artery  of,  692 

surgical  anatomy  of,  692 

of  cornu,  946 

of  corpus  cavernosum,  1467 
spongiosum,  1468 

of  internal  jugular  vein,  729 

nerve  to,  1030 

occipital,  946 

olfactory,  867,  934 

spinal,  874 

of  urethra,  male,  1468 

vaginal,  1495 
Bulbar  arteries,  641 

portion    of    accessory    nerve, 
1073 


Bulbar   portion   of    conjunctiva 

1150 

Bulbo-cavernous  muscle,  459 
Bulboid  corpuscles,  830 
Bulbous  vestibuli,  1495 
Bulla  ethmoiclalis,  145,  1109 
Bundle  of  Helwig,  886 
of  His,  579 

of  Vicq  d'Azyr,  914,  916 
Burdach,  column  of,  840,  850 
Burns,  falciform  margin  of,  517 

space  of,  389 
Bursae  of  ankle,  546 
anserina,  533 
of  biceps  muscle,  477 
of    coraco-brachialis      muscle 

477 

of  elbow,  313 
of  extensor  carpi  radialis  bre- 

vior  muscle,  488 
of  foot,  546 

of  gastrocnemius  muscle,  537 
of  great  trochanter,  333 
gluteo-femoral,  333 
of  hand,  494 
of  hip,  332 
iliac,  333 
ilio-pectineal,  332 
infrapatellar,  342 
infraspinatus,  307,  475 
ischio-gluteal,  333 
of  knee,  342 
of      latissimus     dorsi    muscle 

476 
obturator,  333 

internus  muscle,  528 
olecranon,  313 
patellar,  521 
pharyngeal,  1234 
prepatellar,  342 
of  pyriformis  muscle,  528 
of    semimembranous     muscle, 

534 

of  shoulder,  307 
sterno-hyoid,  394 
subacromial,  307,  473 
subcutanea  prominentiae  laryn- 

geae,  1370 
subcutaneous  acromial,  307 

olecranon,  479 

synovial,  265 

tibial,  342 

trochanteric,  333 
subdeltoid,  307,  473 
subscapular,  307,  473 
subtendinous  iliac,  333 

synovial,  265 
suprapatellar,  342 
of  tendo  Achillis,  538 
theca  synovial,  265 
of  tibialis  anticus  muscle,  535 
wrist,  494 
Bursal  synovial  membrane,  265 


CACUMINAL  lobe  of  cerebellum 

898 
Csecal  fold,  inferior,  1273 

superior,  1273 
Caecum,  1308 

arteries  of,  1315 

interior  of,  1310 

lymphatics  of,  1314 

supports  of,  1310 

veins  of,  1313 

vestibulare,  1180 
Ca-lurn,  1246 

Cajal,  horizontal  cells  of,  1135 
Calamus  scriptorius,  879 


Calcaneal  nerves,  lateral,  1031 

medial,  1031 
Calcanean  artery,  external,  718 

internal,  718 
Calcaneo-astragaloid     ligament, 

external,  354 
internal,  354 
posterior,  354 

Calcaneo-cuboid  ligament,  inter- 
nal, 355 
long,  355 
short,  355 
superior,  355 

Calcaneo-navicular  ligament,  355 
Calcaneo-plantar  nerve,  1031 
Calcaneo-scaphoid  ligament,  ex- 
ternal, 355 
inferior,  356 
internal,  356 
superior,  355 
Calcaneus,  244 

articulations  of,  246 
attachment  of  muscles  to,  246 
body  of,  244 
extremities  of,  244 
processes  of,  245 
surfaces  of,  244,  245 
tuberosity  of,  246 
Calcar,  946 

femorale,  229 
Calcarine  fissure,  926 
Calf  bone,  239 
Calices  of  kidney,  1424 
Callosal  gyre,  928,  930 
Callosum,  920,  939 
body  of,  940 
development  of,  941 
genu  of,  940 
peduncles  of,  936 
splenium  of,  920 
tapetum  of,  945 
Calvaria,  71 
Camper,  fascia  of,  435 
Canaliculi  of  bone,  46 
Canaliculus  tympanicus,  1161 
Canalis  centralis  cochleae,  89 
reuniens  of  Hensen,  1180 
spiralis  modioli,  1177 
Canals,  acoustic,  external,  1158 
adductor,  699 
Alcock's,  1028,  1548 
alimentary,  1203 
anal,  1323 
of  appendix,  1312 
for  Arnold's  nerve,  90 
auditory,  external,  1158 
of  Breschet,  733 
carotid,  136 
cervical,  1503 
of  Cloquet,  1139 
of  cochlea,  1177 

membranous,  1182 
of  cord,  central,  845 
cranio-pharyngeal,  917 
crural,  1543 
dental,  1212 
anterior,  107 
inferior,  124 
posterior,  106 
diploic,  733 
ethmoidal,  82,  100 
for  Eustachian  tube,  1164 
fascial,  1548 
femoral,  511,  1543 
Haversian,  38 
of  Huguier,  84,  1062 
Hunter's,  524,  699 
hyaloid,  1139 
incisor,  110 
infraorbital,  107,  140 
inguinal,  450,  1529 


1568 


INDEX 


Canals  for  Jacobson's  nerve,  90 
lachrymal,  1152 
malar,  114 
naso-palatine,  121 
neurenteric,  1252 
of  Xuck,  1472,  1513 
obturator,  528 
palatine,  anterior,  143 
posterior,  107,  116 

accessory,  116,  135 
palato-maxillary,  107 
of  Petit,  1140 
pterygo-palatine,  135 
pterygoid,  135 
sacral,  6.4 

of  Schlemm,  1118,  1121 
semicircular,  1 175 
spermatic,  450,  1529 
spinal,  69 
of  Stilling,  1139 
for  tensor  tympani,  91,  1163 
vertebral,  49 
Vidian,  96,  135 
Volkmann's,  38 
of  Wirsung,  1359 
Cancellous  bone,  35 

lamellae  of,  39 
Canine  eminence,  106 
fossa,  106,  140 
teeth,  1207 

Canthi  of  eyelids,  1148 
"Cap"  of  Broca,  925 
Capillaries,  histology  of,  586 
Capitellum  of  humerus,  183 
Capsular     liaments.       See    Indi- 
vidual joints. 

Capsules,  atrabiliary,  1439 
Bowman's,  1427 
cartilage,  262 
external,  957 

of  Glisson,  770,  1266,  1344 
internal,  955 
of  kidneys,  fatty,  1419 

true,  1423 
of  lens,  1140 
parotid,  1226 
of  prostate  gland,  1459 
suprarenal,  1437 
of  Tenon,  1113 
Caput  gallinaginis,  1451 
Cardia,  1278 

Cardiac  depression  of  liver,  1336 
ganglion  of  Wrisberg,  1090 
glands,  1286 
lymphatics,  812 
muscular  fibres,  363 
nerve,  cervical,  1072 
great,  1086 
inferior,  1086 
middle,  1086 
minor,  1086 
plexus  of,  1090 
anterior,  1090 
deep,  1090 
great,  1090 
superficial,  1090 
superior,  1085 
thoracic,  1072 
orifice  of  stomach,  1278 
portion  of  stomach,  1277 
veins,  770 
anterior,  771 
great,  770 
left,  771 
middle,  771 
posterior,  771 
right,  771 

Cardio-motor  nerves,  1081 
Carina  urethralis  vaginae,  1496 
Carotico-tympanic  nerve,  1083 
Carotid  arteries,  common,  598 


Carotid        arteries,         common 

branches  of,  601 
peculiarities  of,  601 
relations  of,  600 
surface  form  of,  601 
surgical  anatomy  of,  601 
external,  602 

branches  of,  604 
relations  of,  603 
surface  form  of,  603 
surgical  anatomy  of,  603 
internal,  620 

branches  of,  623 
cavernous  portion,  622 
cerebral  portion,  623 
cervical  portion,  621 
peculiarities  of,  623 
petrous  portion,  622 
relations  of,  622 
surgical  anatomy  of,  623 

body, 1416 

canal,  136 

foramen,  external,  89 
internal,  88 

ganglion,  1083 

gland,  785,  1416 

surgical  anatomy  of,  1407 

groove,  93 

nerves,  1067 
plexus  of,  1083 

sheath,  390 

triangle,  inferior,  618 
superior,  396,  619 

tubercle,  51 

Carpal  arch,  anterior,  661 
posterior,  661 

artery,  radial,  anterior,  661 

posterior,  661 

ulnar,  anterior,  665 

posterior,  665 

bones,  development  of,  207 
Carpo-metacarpal    articulations, 

323 
Carpus,  195 

articulations  of,  321 

common  characters  of,  195 

ligaments  of,  321 

surface  form  of,  206 

surgical  anatomy  of,  207 
Cartilage,  261 

accessory  quadrate,  1107 

alar,  1107 

of  aperture  of  nose,  1107 

articular,  262 

arytenoid,  1372 

capsule,  262 

costal,  164 

cricoid,  1371 

cuneiform,  1373 

of  ear,  1156 

elastic,  262 

ensiform,  157 

of  epiglottis,  1373 

epiphyseal,  36,  44 

fibro-,  262 

hyaline,  262 

intrathyroid,  1371 

of  Jacobson,  1107 

of  larynx, 1370 

of  nose,  1106 

permanent,  261 

of  pinna,  1156 

of  Santorini,  1373 

sesamoid,  1107 

spaces,  262 

temporary,  261 

thyroid,  1370 

of  "trachea,  1386 

triangular,  of  septum  of  nose, 
1107 

yomerine,  1107 


Cartilage  of  Wrisberg,  1373 

xiphoid,  157 

Cartilaginous  isthmus  of   pinna, 
1156 

portion    of    Eustachian    tube, 

1164 
of  external  auditorv  meatus, 

1158 

Cartilago  triticea,  1373 
Caruncle,  lachrymal,  1150,  1152 
Caruncula  lacrimalis,  1150,  1152 

of  Santorini,  1296 
Caruncula?  mystiforma?,  1492 
Casserius,    perforating   nerve  of, 

1002 
Cauda  equina,  836,  1023 

helicis,  1156 
Caudal  gut,  1252 
Caudate  lobe  of  liver,  1340 

nucleus,  953 
Cauda  turn,  953 
Cava,  ascending,  764 

inferior,  764.     See  Postcava. 

superior,  752.     See  Precava. 
Cave  of  Meckel,  973,  1042 
Cavernous  body,  artery  of,  692 

groove,  93 

nerves  of  penis,  1095 

plexus,  1083 

portion  of  internal  carotid  ar- 
tery, 622 
of  urethra,  1452 

sinus,  739 

surgical  anatomy  of,  740 
Cavity,  buccal,  1203 

of  cervix  uteri,  1503 

cotyloid,  220 

glenoid,  176 

of  larynx,  1376 

of  Meckel,  973 

of  mouth,  143 

nasal,  142 

oral,  1203 

of  pelvis,  1440 

pericardiothoracic,  1246 

of  pleura,  1391 

pleuroperitoneal,  1246 

sigmoid,  of  radius,  193 
of  ulna,  188 

of  thorax,  558 

of  tunica  vaginalis,  1481 

tympanic,  1160 

of  uterus,  1503 
Cavum  conchse,  1155 

Meckelii,  1042 

oris  proprium,  1204 
Cells,  amacrine,  820 

arboriform,  821 

basket,  902 

bipolar,  820 

body,  nerve,  820 

centro-aeinar,   of   Langerhans, 
1359 

ciliated  endymal,  818 

of  Claudius,  1185 

of  cord,  commissural,  856 
horn,  dorsal,  856 
lateral,  856 
ventral,  856 

tract,  contra-lateral,  855 
homo-lateral,  855 

of  Deiters,  1185 

ectal  polymorphous,  958 

enamel,  1216 

endymal,  832 

ental  polymorphous,  959 

ethmoidal,  82,  100 
posterior,  145 

ganglion,  820 

germinal,  818 

giant,  959 


IXDKX 


Cells,  glia-,  832 
of  Golgi,  821,  902 
gustatory,  1101 
of  Hensen,  1185 
hepatic,  1338 
horizontal,  of  Cajal,  1135 
of  Marti  not  ti,  960 
mastoid,  86 
mitral,  960 
molecular,  958 
multipolar,  820 
nerve,  820 

axone  of,  823 

dcndrites  of,  822 
olfactory,  1111 
oxyntic,  1285 
parietal,  1285 
peptic,  of  glands,  1285 
prickle,  1119 
Purkinjean,  902 
pyramidal,  958 
of  Sertoli,  1483 
sphenoidal,  94 
stellate,  821 
unipolar,  820 
Cementum  of  teeth,  1214 

development  of,  1216 
Central  canal  of  cord,  845 
coil  of  cochlea,  1177 
fissure,  926 
ganglionic  system   of   arteries, 

632 

lobe  of  cerebrum,  933 
pathway,  964  . 

sulcus  of  Rolando,  926 
tendon  of  diaphragm,  431 
Centrifugal  nerves,  827 
Centripetal  nerves,  827 

fibre,  823 

neurones,  peripheral  nerve  be- 
ginnings of,  828 
Centro-acinar    cells    of    Langer- 

hans,  1359 
Centrum  medianum,  914 

vertebra,  48 

Cephalic  flexure  of  brain,  869 
index  of  skull,  147 
vein,  747 

median,  746 

Cephalo-auricular  angle,  1154 
Cerato-hyals  of  hyoid  bone,  155 
Cerebellar   arteries,    anterior   in- 
ferior, 642 

posterior  inferior,  641 

superior,  642 

cortex,     microscopic     appear- 
ance of,  902 
peduncle,  900 
prepeduncles,  888 
tract  of  cord,  direct,  852 
veins,  deep,  736 

superficial,  736 
Cerebello-olivary  fibres,  886 
Cerebello-spinal  tract  of  cord,  853 
Cerebellum,  895 

amygdala  of,  871,  954 
dentatum  of,  900 

hilum  of,  900 
embolus  of,  900 
falcula  of,  895 
fastigium  of,  879,  900 
fibres  of,  902 

association,  902 

clinging,  903 

commissural,  902 

moss,  902 

proper,  902 

tendril,  903 
fissures  of,  896 
folia  of,  895 
fra-nulum  of,  902 

99 


Cerebellum,  glohulus  of,  900 
gray  masses  of,  899 
hemispheres  of,  896 
internal  structure  of,  899 
lobes  of,  896 
nuclei  of,  899 
peduncles  of,  900 
postraimis  of,  899 
prepeduncles  of,  909 
preramus  of,  899 
vallecula  of,  895 
valvula  of,  895 
velum  of,  895 
vermis  of,  895 
weight  of,  903 
worm  of,  895 
Cerebral  artery,  anterior,  628 

branches  of,  628 
middle,  629 

branches  of,  629 
posterior,  642 

convolutions,  922.      See  Gyre. 
cortex,  939 

nerve  cells  of,  958 

fibres  of,  959 
structure  of  internal,  958 
cranium,  71 
fibre  system,  961 
fissures,  922,  923 
gyres,  922 
hemispheres,  919 

configuration  of,  922 
external  morphology  of,  919 
gray  masses  of,  952 
internal     configuration     of, 

938 

hemorrhage,  arteries  of,  630 
lobes,  923 
localization,  926 
lymphatic  vessels,  778 
nerves,  1036 
portion     of     internal     carotid 

artery,  623 
veins,  734 
cortical,  735 
deep,  735 
inferior,  735 
median,  735 
superficial,  735 
superior,  735 
Cerebro-spinal  axis,  833 
fasciculus,  lateral,  853 
fluid,  859 

Cerebrum.     See  Cerebral. 
Ceruminous  glands,  1159 
Cervical  artery,  ascending,  643 
deep,  647 
superficial,  644 
transverse,  644 
canal,  1503 
cardiac  nerves,  1072 
enlargement  of  spinal  cord,  836 
fascia,  deep,  389 
superficial,  388 
surgical  anatomy  of,  391 
flexure  of  brain,  869 
ganglion,  inferior,  1086 

branches,  central  commu- 
nicating, 1086 
peripheral,  1086 
middle,  1085 

branches  of,  central  com- 
municating, 1086 
peripheral,  1086 
superior,  1081 

branches  of,  1083 

central  communicating, 

1083 

peripheral,  1083 
surgical  anatomy  of,  1087 
glands,  deep,  785 


Cervical  glands,  deep,  accessory 

chains  to,  785 
lower,  785 
upper,  785 
superficial,  783 
anterior,  784 
nerves,  986 

divisions  of,  anterior,  988 
dorsal,  986 

from  facial  nerve,  1063 
eighth,   division  of,     dorsal, 

987 

ventral,  989 
fifth,  division  of.  dorsal,  987 

ventral,  989 
first,  division   of,  dorsal,  986 

ventral,  988 
root  of,  dorsal,  986 
fourth,    division    of,    dorsal, 

987 

ventral,  988 
posterior,  986 
ventral,  988 
roots  of,  986 
second,  division   of,    dorsal, 

986 

ventral,  988 
trunk  of,  986 
seventh,  division   of,  dorsal, 

987 

ventral,  989 
sixth,  division  of,  dorsal,  987 

ventral,  989 
superficial,  990 
third,  division  of,  dorsal,  987 

ventral,  988 
pleura,  1393 
plexus,  989 

branches  of,  deep,  992 

superficial,  989 
posterior,  987 
surgical  anatomy  of,  994 
portion     of     internal     carotid 

artery,  621 
of  oesophagus,  1236 
region,  superficial   muscles   of, 

388 

rib,  53,  167 
veins,  anterior  deep,  733 

posterior  deep,  733 
vertebra^,  49 
lamina*  of,  49 
body  of,  49 
pedicles  of,  49 
processes  of,  50 
seventh,  53 

Cervicalis  ascendens  muscle,  421 
Cervico-facial  nerve,  1063 
Cervix  of  bladder,  1444 
uteri,  1500 

cavity  of,  1503 
Chassaignac's  tubercle,  69 
Check  ligaments,  280 

of  eve,  1115 
Cheeks,  1205 

mucous  membrane  of,  1205 
surgical  anatomy  of,  1234 
Chemical  composition  of  bone,  41 
Chest,  156 

articulations  of,  161 
attachment  of  muscles  to,  161 
boundaries  of,  156 
development  of,  159 
structure  of,  159 
surface  form  of,  166 
surgical  anatomy  of,  167" 
Chiasm,  919,  1038 
Chiasma    or    optic    commissure, 

1038 

Chink  of  glottis,  1377 
Choamc,  146 


1570 


INDEX 


Chondro-glossus  muscle,  399 
Chondro-sternal  ligament,   ante- 
rior, 290 

interarticular,  290 
posterior,  290 
Chondro-xiphoid  ligament,  ante- 
rior, 290 
posterior,  290 
Chondroblasts,  262 
Chorda  tympani  nerve,  1061 
Chordae  .tendinese    of    left    ven- 
tricle, 575 

of  right  ventricle,  572 
Willisi,  737 
Choroid  arteries,  anterior,  630 

posterior,  642 
coat  of  eye,  1121 

structure  of,  1122 
fissure,  946 
nerves  of,  1130 
plexus.     See  also  Paraplexus. 
of  fourth  ventricle,  881 
of  lateral  ventricle,  943 
of  third  ventricle,  947 
vein,  735 

Chromatophile  granules,  822 
Chyli  receptaculum,  775 
Cilia,  or  ej'elashes,  1148 
Ciliary  arteries,  anterior,  627 
long,  627 
short,  627 
body,  1125 
ganglion,  1040 

long  root  of,  1045 
glands,  1200 
ligament,  1126 
margin,  1127 
muscles,  1125 
nerves,  long,  1045 

short,  1045 
processes  of  eye,  1125 

structure  of,  1125 
Ciliated  endymal  cells,  818 
Cimbia,  906 
Cingulum,  962 
Circle  of  Willis,  631,  642 
Circular  sinus,  742 
Circulus,  642 
of  iris,  627 
tonsillaris,  1050 
Circumanal  glands,  1200 
Circumduction,  276 
Circumflex  arteries  of  arm,  653 

of  thigh,  705 
iliac  artery,  deep,  698 

superficial,  704 
vein,  deep,  759 

superficial,  756 
nerve,  1002 

lower  branch,  1002 
upper  branch,  1002 
vein,  deep,  758 
Circumflexus  muscle,  406 
Circuminsular  fissure,  925 
Circumpatellar  anastomosis,  710 
Circumvallate  papillae  of  tongue, 

1099 

Cistern  of  Pecquet,  775 
Cisterna  basalis,  977,  978 
crural,  978 
pontis,  978 

Clado,  appendiculo-ovarian  liga- 
ment of,  1312 
Clarke,  vesicular  column  of,  844, 

847 

Claudius,  cells  of,  1185 
Claustrum,  954 

gray  substance  of,  961 
Clavi-pectoral  fascia,  469 
Clavicle,  169 

articulations  of,  172 


Clavicle,  attachment  of    muscles 
to,  172 

development  of,  172 

peculiarities  of,   in  sexes   anc 
individuals,  171 

structure  of,  171 

surface  form  of,  172 

surgical  anatomy  of,  172 
Clavicular  facet,  157 
Cleft,  intercerebral,  921 

sylvian,  development  of,  925 
Clinoid  process,  anterior,  131 
middle,  93,  132 
posterior,  93,  132 
Clitoris,  1493 

arteries  of,  1494 

body  of,  1493 
.  fraenum  of,  1494 

muscles  of,  463 

nerves  of,  1494 
dorsal,  1030,  1495 

prepuce  of,  1494 
Clival  lobe  of  cerebellum,  898 
Clivus,  93 
Cloquet,  canal  of,  1139 

gland  of,  794,  795 

ligament  of,  1476,  1477 

septum  crurale  of,  511 
Coccygeal  artery,  694 

body, 1417 

gland, 1417 

ligament,  857 

nerve,  divisions  of,  dorsal, 1025 
ventral,  1025 

plexus,  1034 
Coccygeus  muscle,  457 
Coccyx,  65 

apex  of,  66 

articulation  of,  67 

attachment  of  muscles  to,  67 

base  of,  66 

borders  of,  66 

cornua  of,  66 

development  of,  66 

surfaces  of,  66 
Cochlea,  1175 

canal  of,  bony,  1177 
membranous,  1182 
spiral,  1177 

lamina  spiralis  of,  1177 

ligament  of,  spiral,  1182 
Cochlear  artery,  1186 

nerve,  1064,*  11 86 
nuclei  of,  892 

window,  1162 
Coaliac  artery,  673 

axis,  673 

glands,  798 

plexus,  1072,  1094 
Colic  area  of  kidnevs,  1422 

artery,  left,  680 
middle,  678 
right,  677 

glands,  806 

impression  of  liver,  1337 

plexus,  1094 
Collar  bone,  169 
Collateral,  823 

eminence,  944 

fissure,  932 

intercostal  artery,  670 
Colles'  fascia,  458,  1527 

ligament,  439 
Colloid  material,  1412 
Colon,  1317 

ascending,  1317 

descending,  1317 

pelvic,  1317 

sigmoid,  1317 

surgical  anatomy  of,  1334 

transverse,  1317 


Colostrum  corpuscles,  1519 
Columella  cochleae,  1176 
Columna  nasi,  1106 
Columnas  carnese  of  left  ventricle, 

575 

of  right  ventricle,  572 
Columns  of  Berlin,  1424 
of  Burdach,  840 
of  Goll,  839,  840 
of  Morgagni,  1326 
of  spinal  cord,  839 

Clarke's,  844,  847 
dorsal,  839 

dorso-lateral,  839,  840 
dorso-median,  839 
lateral,  840 
ventral,  840 
of  vagina,  1496 

Comes^nervi  ischiadici  artery, 694 

mediana  artery,  665 

phrenici  artery,  646 

Comma  tract  of  Schultze,  851 

Commissura  hippocampi,  896 

ventralis  alba,  844 
Commissural  cells  of  cord,  856 
nerve  fibres,  963 

of  cerebellum,  902 
Commissure  of  cord,  gray,  844 

white,  ventral,  854 
Gudden's,  905,  1038 
habenal,  915 
hippocampal,  951 
of  Kolliker,  919 
of  Meynert,  919 
optic,"l31,  1038 
Common  carotid  artery,  598 
facial  vein,  726 
femoral  artery,  700 
iliac  arteries,  683 
glands,  796 
vein,  764 

temporal  vein,  727 
ulnar  vein,  745 
Communicantes  hvpoglossi  nerve, 

988 
Communicating  arteries,  anterior 

cerebral,  629 
posterior  cerebral,  630 
of  ulnar,  anterior,  664 
Compact  bone,  35 

longitudinal  section  of,  39 
transverse  section  of,  38 
Complexus  muscle,  422 
Compressor  narium  minor  mus- 
cle, 378 

sacculi  laryngis,  1381 
urethras  muscle  in  female,  464 

in  male,  462 

Concentric  lines  of  Schreger,  1213 
Concha  auriculas,  1155 
Condyles  of  bones.     See  Bones. 
Condylic     portion     of     occipital 

bone,  71 

Condyloid  articulation,  267 
foramen,  anterior,  73,  133,  136 

posterior,  73,  133,  136 
fossa,  anterior,  136 

posterior,  136 
glands  of  Leaf,  794 
process,  125 
Cone-bipolars,  1135 
Cone-granules  of  retina,  1136 
Cones  of  retina,  1136 
Congenital  hernia,  1535 
Conglobate  glands,  774 
Conical  papillae,  1100 
Conjugate  diameter  of  pelvis,  210 
Conjunctiva,  1150 

bulbar  portion  of,  1150 
fornix  of,  1150 
glands  of,  1150 


INDEX 


1571 


Conjunctiva,  nerves  of,  1150 
palpebral  portion  of,  1150 
surgical  anatomy  of,  1154 
Connective      tissue,      subserous 

1256 
Conoid  ligament,  302 

tubercle,  169 

Constriction  lobe  of  liver,  1343 
Constrictor  isthrni  fkucium  mus- 
cle, 400,  407 
muscles,  inferior,  402 
middle,  403 
superior,  403 
urethrae  muscle  in  female,  464 

in  male,  462 
Contra-lateral  tract-cells  of  cord 

855 

Conus  arteriosus,  571 
of  spinal  cord,  837 
Convolutions.     See  Gyre. 
Cooper,  ligament  of,  439,  450 
Copula,  920 

Coraco-acromial  ligament,  303 
Coraco-brachialis  muscle,  477 

bursa  of,  477 

Coraco-clavicular  ligament,  302 
Coraco-humeral  ligament,  306 
Coracoid  ligament,  304 

process,  176 
Cord,  gangliated,  1081 

cervical  portion  of,  1081 
lumbar  portion  of,  1081 
pelvic  portion  of,  1089 
sacral  portion  of,  1089 
thoracic  portion  of,  1087 
spermatic,  1476 
spinal,  834.     See  Spinal  cord, 
vocal,  1378 
Cordiform  tendon  of  diaphragm, 

431 
Corium,  1190 

corpus  papillare  of,  1191 
of  tongue,  1099 
Cornea,  1118 
arteries  of,  1121 
nerves  of,  1121 
structure  of,  1119 
Corneal  endothelium,  1121 

spaces,  1120 
Comical    tubercle    of    Santorini, 

1376 

Cornicula  laryngis,  1373 
Cornu  ammonis,  937 

bulb  of,  946 
Cornua  of  coccyx,  66 
of  hyoid  bone,  155 
sacral,  62 

Corona  ciliaris,  1125 
glandis,  1464 
radiata,  914,  955 
Coronal  suture,  78,  127 
Coronary  artery,  673 
of  heart,  592 
descending,  592 
infundibular,  593 
marginal,  592 
peculiarities  of,  593 
transverse,  592 
of  lip,  inferior,  609 

superior,  609 

of  stomach,  673 

ligament  of  knee,  342 

of  liver,  1341 
plexus,  1094 
anterior,  1090 
left,  1090 
posterior,  1090 
right,  1090 
sinus,  569,  771 
valve,  569 
vein,  768 


Coronary  vein,  left,  770 

small,  771 
Con  moid  fossa,  183 
process  of  jaw,  125 

of  ulna,  188 
Corpora  Arantii,  575 
cavernosa,  1465,  1466 
arteries  of,  1468 
bulb  of,  1466 
structure  of,  1467 
trabeculae  of,  1467 
veins  of,  1468 
quadrigemina,  905.    See  Quad 

rigemina. 
Corpus  Arantii,  573 

callosum,  939.     SecCallosum. 
cavernosum,  artery  of,  692 
hypothalamicus,  915 
papillare  of  corium,  1191 
spongiosum,  1468 

structure  of,  1469 
striatum,  952 
Corpuscles,  articular,  830 
bulboid,  830 

epithelial,  of  Kohn,  1412 
genital,  830 
of  Herbst,  830 
lamellated,  830 
Malpighian,  of  kidney,  1426 

of  spleen,  1365 
Pacinian,  830 
tactile,  826,  830 
touch,  830 
of  Vater,  830 
Corrugator  cutis  ani  muscle,  451 

supercilii  muscle,  373 
Cortex,  939 
of  brain,  871 

cerebellar,  microscopic  appear- 
ance of,  902 
cerebral,  cells  of,  958 
nerve  fibres  of,  959 
structure  of,  internal,  958 
Corti,  membrane  of,  1185 
organ  of,  1183 
rods  of,  1184 
tunnel  of,  1184 
Cortical  arterial  system,  632 
cerebral  veins,  735 
localization     of      function     of 

brain,  966 
portion  of  kidney,  1424 

of  suprarenal  capsule,  1439 
of  thymus  gland,  1415 
substance  of  teeth,  1214 
Cortico-thalamic  fibres,  914 
Coruna,  horns  of,  dorsal,  844 
lateral,  844 
ventral,  844 
Costal  cartilages,  165 

attachment   of    muscles    to, 

166 

borders  of,  166 
extremities  of,  166 
surfaces  of,  165 
facet,  170 
pleura,  1393 
process,  50 

surface  of  lungs,  1400 
Costo-axillary  vein,  748 
Costo-central  articulations,  285 
Costo-chondral  articulations,  292 
Costo-clavicular  ligament,  300 
Costo-coracoid  ligament,  469 

membrane,  469 
Costo-mediastinal  sinus,  1395 
Costo-sternal  articulations,  289 
Costo-transverse       articulations, 

287 

foramen,  50 
ligament,  long,  287 


Costo-transverse   ligament,  mid- 
dle, 288 
posterior,  288 
Costo-vertebral  articulations,  285 

ligament,  anterior,  286 
Costo-xiphoid  ligament,  anterior, 

290 

posterior,  290 
Cotunnis,  nerve  of,  1050 
Cotyloid  cavity,  220 
ligament,  331 
notch,  220 

Cowper's  glands,  1463 
structure  of,  1463 
Cranial  bones,  71 
fossa,  143 
nerves,  1036 

arising    in    mid-brain,    deep 

origin  of,  910 
region,  dissection  of,  368 
fascia  of,  superficial,  368 
lymphatics  of,  778 

vessels  of,  781 
sutures,  127 

Cranio-cerebral  topography,  970 
Cranio-pharyngeal  canal,  917 
Cranium,  71 

capacity  of,  147 
cerebral,  71 
development  of,  102 
differences  in  size  and  form  of, 

146 

fasciae  of,  367 
lymphatics  of,  778 
membranous,  102 
muscles  of,  367 
shape  of,  146 

Cremaster  muscle,  441,  1528 
Cremasteric  artery,  697 

fascia,  1474,  1528 
Crescentic    lobe    of    cerebellum, 

anterior,  897 
posterior,  898 

Crescents  of  Gianuzzi,  1228 
Crest,  buccinator,  124 
ethmoidal,  94 
falciform,  89 
frontal,  80,  130 
incisor,  111 
infratemporal,  95 
lachrymal,  113 

bone,  141 
nasal,  111,  116 
obturator,  220 
occipital,  external,  72,  136 

internal,  74,  133 
sphenoidal,  94 
supramastoid,  84,  137 
temporal,  76,  80,  84 
of  tibia,  237 
turbinated,  inferior,  107,  117 

superior,  117 

Cribriform  fascia,  514,  1539 
lamina,  1118 
plate,  130 

of  ethmoid,  99 

Crico-arytenoid  articulation,  1375 
ligaments,  1375 
muscle,  lateral,  1381 

posterior,  1380 
Crico-thyroid  artery,  605 
articulation,  1375 
membrane,  1375 
muscle,  1380 
Crico-tracheal  ligament,  1376 
Cricoid  cartilage,  1371 
borders  of,  1372 
surfaces  of,  1372 
Crista  falciformis,  89 
galli,  99,  130 
terminalis,  567 


1572 


INDEX 


Crista  vestibuli,  1174 
Crucial  ligaments  of  knee,  339 
Cruciform  ligament,  277 
Crura,  869 

cerebri,  904,  905 

pes  of,  905,  910 
of  diaphragm,  429 
fornicis,  951 
of  penis,  1454 
Crural  arch,  deep,  450,  1543 

superficial,  438,  1541 
canal,  511,  1543 
cisterna,  978 

nerve.     See  Femoral  nerve, 
ring,  439,  511,  1544 
septum,  1544 
sheath,  511 
Crureus  muscle,  520 
nerve  to,  1022 
Crus  of  helix,  1155 
Crusta,  910 

petrosa  of  teeth,  1214 
Cruveilhier,          atlanto-odontoid 

joint  of,  276 
glenoid  ligament  of,  361 
Crypts  of  Lieberkiihn,  1303 

of  Morgagni,  1326 
Crystalline  lens,  1140 
capsule  of,  1140 
substance  of,  1140 
structure  of,  1141 
Cuboid  bone,  248 

articulations  of,  248 
attachment    of    muscles    to, 

248 

surfaces  of,  248 

tuberosity  of,  248 

Culminal  lobe  of  cerebellum,  897 

Cuneal  fissure,  931 

Cuneate  nucleus,  accessory,  884 

tubercle,  876 

Cuneiform  bone,  foot,  249 
external,  251 

articulations  of,  251 
attachment  of  muscles 

to,  251 

surfaces  of,  251 
internal,  249 

articulations   of,   250 
attachment  of  muscles 

to,  250 

surfaces  of,  250 
middle,  250 

articulations  of,  251 
attachment  of  muscles 

to,  251 

surfaces  of,  250 
of  hand, 199 

articulations  of,  199 
surfaces  of,  199 
cartilages,  1373 
tubercle  of  Wrisberg,  1376 
Cupola  of  cochlea,  J177,  1182 
Cushion  of  epiglottis,  1373 
Cusps  of  bicuspid  valve,  574 

of  tricuspid  valve,  572 
Cutaneous  nerve,  external,  1002, 

1018 

first  ventral,    1011 
internal,  1003,  1021 
.  lateral,  1018 
middle,  1021 
palmar,  1004 
perforating,  1028 
Cuticle  of  skin,  1191 
Cutis  vera,  1190 
Cuvier,  duct  of,  563 
Cylindro-dendrites,  823 
Cymba  conchsfe,  1155 
Cystic  artery,  676 
duct,  1351 


Cystic  plexus  of  nerves,  1094 

vein,  769 
Czermak,  interglobular  spaces  of 

1212 


DACRYON,  141,  150 
Dartos  of  scrotum,  1473 
Darwin,  tubercle  of,  1155 
Deciduous  teeth,  1206 
Decussatio    nervorum    trochlea- 

rium,  1041 
Decussation  of  lemnisci,  882 

of  pyramids,  875,  881 
Deep    anterior     thoracic     nerve 

1001 
branches    of    cervical    plexus 

992,  993 

cardiac  plexus,  1090 
cerebral  veins,  735 
cervical  artery,  647 
fascia,  389 ' 
glands,  785 
circumflex  iliac  artery,  698 

vein,  759 

crural  arch,  450,  1543 
dorsal  vein  of  penis,  762 
epigastric  artery,  697 

vein,  759 

external  pudic  artery,  704 
fascia,  367 

of  arm,  472,  476 

of  back,  413 

of  femoral  region,  anterior, 

515 

of  forearm,  480 
of  leg,  535 

transverse,  540 
of  shoulder,  472 
of  thoracic  region,  anterior, 

465 
femoral  artery,  704 

lymphatic  glands,  794 
inguinal  lymphatic  glands,  794 
lymphatic  glands  of  upper  ex- 
tremity, 787 
vessels   of   abdominal    wall, 

799 

of  lower  extremity,  795 
of  upper  extremity,  790 
muscles  of  abdomen,  451 
palmar  arch,  660 
fascia,  495 
veins,  747 

parotid  lymphatic  glands,  780 
patellar  bursa,  521 
pectoral  fascia,  466 
perineal  fascia,  1550 
petrosal  nerve,  1083 
radial  veins,  747 
superficial   external   pudic   ar- 
tery, 704 

temporal  artery,  616 
nerves,  1051 
veins,  727 
ulnar  veins,  747 
veins  of  foot,  758 

of  lower  extremity,  758 
of  upper  extremity,  747 
Deiters,  cells  of,  1185 
nucleus  of,  853 
process,  820 
Deltoid  eminence,  181 
impression,  181 
muscle,  472 
tubercle,  169 

Demilunes  of  Heidenhain,  1228 
De'mours,  membrane  of,  1120 
Dendraxones,  823 
Den'drites,  816,  820,  822 


Dendrites,  monopolar,  821 
Dental  artery,  inferior,  616 
posterior,  617 

band,  1215 

canal,  1212 
anterior,  107 
inferior,  124 
posterior,  106 

fibres,  1212 

follicle,  1216 

lamina,  1215 

nerves,  anterior  superior,  1048 
inferior,  1053 
middle  superior,  1047 
posterior  superior,  1047 

periosteum,  1214 

plexus,  superior,  1048 

pulp,  1210 

sac,  1216 
Dentate  gyre,  938 

gray  substance  of,  960 

ligament,  860 

nucleus  of  cerebellum,  900 
Dentato-fascicolar  groove,  937 
Dentatum  of  cerebellum,  900 

hilum  of,  900 

Dentinal    sheath    of    Neumann^ 
1213 

tubuli,  1212 
Dentine,  1212 

formation  of,  1217 

papilla,  1215 
Depression,  pterygoid,  125 

trigeminal,  88 
Depressions  of  bone,  34 
Depressor  alae  nasi  muscle,  378 

anguli  oris  muscle,  380 

labii  inferioris  muscle,  380 
Dermic  coat  of  hair-follicle,  1198 
Dermis,  1190 

Descemet,  membrane  of,  1120 
Descendens     hvpoglossi     nerve, 

988 
Descending  aorta,  667 

branch    of    superior    cervical 
ganglion,  1084 

colon,  1317 

mesocolon,  1268 

oblique    muscle    of    abdomen, 
435 

palatine  artery,  617 

projection  nerve  fibres,  963 

ramus  of  ischium,  218 
of  pubis,  220 

root  of  fifth  nerve,  1042 
Descen^ of  ovary,  1513 

of  testicles,  1471 

surgical  anatomy  of,  1472 
Detrusor  urina?  muscle,  1446 
Development  of    alimentary  ca- 
nal, 1247 

of  alveoli  of  teeth,  1217 

of  atlas,  59 

of  axis,  59 

of  brain,  863 

of  callosum,  941 

of  carpal  bones,  207 

of  cementum,  1217 

of  clavicle,  172 

of  coccyx,  66 

of  cranium,  102 

of  dentine,  1217 

of  enamel,  1216 

of  ethmoid  bone,  101 

of  femur,  231 

of  fibula,  241 

of  foot,  255 

of  frontal  bone,  82 

of  humerus,  184 

of  hyoid  bone,  156 

of  inferior  turbinated  bone,  120 


INDEX 


1573 


Development  of  lachrymal   bone, 
113 

of  liver,  1253 

of    maxillary    bone,     inferior, 

125 
superior,  112 

of  mesentery,  1 248 

of  metacarpal  bones,  207 

of  metatarsal  bones,  255 

of  nasal  bones,  105 

of  nerve  tissue,  818 

of  occipital  bone,  75 

of  omentum,  1250 

of  organs,  chronological  table 
of,  1559 

of  os  innominatum,  221 

of  palate  bone,  119 

of  pancreas,  1254 

of  parietal  bone,  78 

of  patella,  234 

of  peritoneal  cavity,  1253 

of  peritoneum,  1254 

of  permanent  teeth,  1218 

of  phalanges  of  foot,  256 
of  hand,  208 

of  radius,  194 

of  ribs,  165 

of  sacrum,  64 

of  scapula,  177 

of  sphenoid  bone,  97 

of  spinal  cord,  840 

of  spleen,  1255 

of  sternum,  159 

of  tarsal  bones,  255 

of  teeth,  1214 

of  temporal  bone,  91 

of  tibia,  238 

of  tongue,  1253 

of  tonsils,  1253 

of  ulna,  191 

of  vertebra?,  58 

of  viscera,  1245 

of  vomer,  122 

Wormian  bone,  104 
Diagonal  fissure,  928 
Diameter  of  pelvis,  210 
Diaphragm,  429 

actions  of,  432 

crura  of,  429 

lymphatics  of,  808 

nerves  of,  432 

openings  of,  431 
aortic,  431 
cesophageal,  432 
for  vena  cava,  432 

of  pelvis,  1241 

pillars  of,  429 

serous  membranes  of,  432 

tendons  of,  central,  431 
Diaphragma  sellse,  976 
Diaphragmatic  ganglion,  1092 

hernia,  429 

lymphatics,  808 

pleura,  1394 

portion  of  ccsophagus,  1236 
Diaphysis,  34 
Diaplexus,  946 
Diarthrosis,  267 
Diatela,  912 
Diaxonic  cells,  823 

neurones,  823 
Diencephalon,  911 
Digastric  branch  of  facial  nerve, 
1062 

f6ssa,  86,  123,  136 

muscle,  396 

Digestion,  organs  of ,  1203 
Digital  arteries,  dorsal,  661 
of  ulna,  666 

fossa,  225 

nerves  of  foot,  1032 


Digital  nerves  of  hand,  1005 
Digitations,  hippocampal,  947 
Dilator  naris  anterior  muscle,  378 

posterior  muscle,  378 
tuba?  muscle  of  Rudinger,  1 1 65 
Dimensions  of  skull,  147 
Diploe,  34 

veins  of,  733 
Diploic  canals,  733 
veins,  frontal,  734 
occipital,  734 
parietal,  external,  734 
temporal,  anterior,  734 

posterior,  734 

Direct  inguinal  hernia,  1535 
Disk,  interpubic,  298 
intervertebral,  272 
optic,  1131 

Dissection  of  axilla,  465 

of  cord,  856 

of  internal  oblique  muscle,  439 

of  meninges  of  brain,  972 

of  muscles  of  abdomen,  434 

of  arm,  471,  476 

of  auricular  region,  371 

of  back,  412,  416,  417,  419 

of  cranial  region,  368 

of  femoral  region,  anterior, 

514 

internal,  522 
posterior,  532 
of  fibular  region,  542 
of  forearm,  480,  484 
of  gluteal  region,  525 
of  hand, 493 
of  iliac  region,  510 
of  infra-hyoid  region,  393 
of  intermaxillary  region,  381 
'  of  lingual  region,  399 
of  mandibular  region,  380 
of  orbital  region,  374 
of  palatal  region,  405 
of  palpebral  region,  372 
of  pectoral  region,  465 
of  pharyngeal  region,  402 
of  plantar  region,  547,  548, 

549 

of    pterygo-mandibular    re- 
gion, 386 

of  radial  region,  486 
of  scapular  region,  anterior, 

473 

posterior,  474 
of  shoulder,  471 
of  superficial  cervical  region, 

388 

of  supra-hyoid  region,  396 
of  tibio-fibular  region,  ante- 
rior, 535 

posterior,  537,  540 
of  pancreas,  1355 
of  perinamm,  1547 
of  popliteal  space,  707 
of  rectus  abdominis  muscle,  444 
of  sole  of  foot,  545 
of  temporal  muscle,  384 
of  transversalis  muscle,  443 
Diverticulum,  Meckel's,  1290 
Dolichocephalic  skull,  146 
Dorsal  accessory  olivary  nuclei, 

885 

area  of  oblongata,  876 
artery  of  penis,  693 
cervical  plexus  of  nerves,  984 
columns  of  spinal  cord,  839 
coronary  plexus,  1090 
digital  arteries,  661 

veins,  745 
divisions    of    cervical    nerves, 

986 
of  coccygeal  nerve,  1025 


Dorsal      divisions      of      lumbar 

nerves,  1015 
branches,   lateral,    1015 

medial,  1015 
of  sacral  nerves,  1023 
lower,  1023 
upper,   1023 

branches,      lateral, 

1023 

medial,  1023 
of  thoracic  nerves,  1010 

branches,        cutaneous, 

1010 

lateral,  1010 
medial,  1010 
fissure  of  oblongata,  875 
horn  of  cornua,  844 
horn-cells  of  cord,  856 
interosseous  arteries,  661,  715 

nerve,    1008 
lamina  of  brain,  870 
nerves,  1010 

of  clitoris,  1030 
of  penis,  1030 
roots  of,  1010 
pulmonary  nerves,  1072 

plexus,  1070, 1072, 1091 
region,  muscles  of,  546 
root  of  spinal  cord,  836 

nerves,  983 

sacral  plexus  of  nerves,  984 
spinal  artery,  641 
ulnar  vein,  745 
veins  of  penis,  deep,  762 

superficial,  762 
vertebra?,  53.     See  Thoracic. 
Dorsalis  hallucis  artery,  715 
indicis  artery,  661 
linguae  artery,  606 
nasi  artery,  626 
pedis  artery,  713 

branches  of,  714 
peculiarities  of,  713 
relations  of,  713 
surface  marking  of,  714 
surgical  anatomy  of,  714 
pollicis  arteries,  661 
scapula?  artery,  653 
Dorsi-lumbar  nerve,  1016 
Dorsi-spinal  veins,  753 
Dorso-lateral  columns  of  spinal 

cord,  839,  840 
fissure  of  oblongata,  875 

of  spinal  cord,  839 
Dorso-median  columns  of  spinal 

cord,  839 

fissure  of  oblongata,  875 
veins,  736 
Dorso-paramedian      fissure       of 

spinal  cord,  839 
Dorso-spino-cerebellar     tract    of 

cord,  852 

Dorsum  ephippii,  93,  132 
of  penis,  1465 
of  scapula,  173 
sellse,  93 
Douglas,  fold  of,  semilunar,  441, 

446 

pouch  of,  1502 
Drumhead,  1165 
Duct  or  ducts,  alveolar,  1386 
of  Bartholin,  1227 
biliary,  1348 
of  Cuvier,  563 
cystic,  1351 

efferent  of  epididymis,  1482 
ejaculatory,  1487 
galactophorus,  1518 
Gartner's,  1511 
hepatic,  1350 
interlobular.  1349 


1574 


INDEX 


Duct  or  ducts  of  kidney,  1429 
lactiferous,  1518 
of  liver,  1348 
lymphatic,  right,  777 
mammillary,  1518 
nasal,  1152 
pancreatic,  1359 
parotid,  1225 
of  Rivinus,  1227 
seminal,  1484 
Stenson's,  1225 
of  submaxillary  gland,  1226 
thoracic,  775 
thyroglossal,  1100,  1407 
Wharton's,  1226 
Ductless  glands,  1407 
Ductus  arteriosus,  582 

communis  choledochus,  1351 
endolymphaticus,  89,  1175 
venosus,  fissure  of,  1338 

fossa  of,  1339 

Duodenal  area  of  kidney,  1422 
folds,  1270 
fossae,  1270 
glands,  1303 
impression  of  liver,  1337 
Duodeiio-jejunal  fossa,  1271 
Duodeno-mesocolic       ligaments 

1271 

Duodeno-renal  ligament,  1264 
Duodenum,  1290 
arteries  of,  1296 
ascending  portion  of,  1294 
descending  portion  of,  1293 
first  portion  of,  1292 
flexure  of,  superior,  1293 
fourth  portion  of,  1294 
horizontal  portion  of,  1293 
interior  of,  1296 
lymphatics  of,  1296 
muscular  coat  of,  1296 
nerves  of,  1296 
peritoneal  coat  of,  1296 
pre-aortic  portion  of,  1293 
second  portion  of,  1293 
structure  of,  1296 
submucous  coat  of,  1296 
superior  portion  of,  1292 
surgical  anatomy  of,  1332 
suspensory  muscle  of,  1294 
third  portion  of,  1293 
transverse  portion  of,  1293 
veins  of,  1296 
Dura  of  brain,  972 
arteries  of,  974 
lymphatics  of,  974 
nerves  of,  974 
processes  of,  975 
structure  of,  972 
veins  of,  974 
mater  of  brain,  972 
of  cord,  856 
sinuses  of,  736 
spinal,  856 

structure  of,  858 
Dural  artery,  611,  612 
nerves,  1046 
veins,  730,  734 
Duverney,  gland  of,  1495 


EAR,  1154 

auditory      meatus,      external, 

1158 

auricle  of,  1154 
bones  of,  1168 
cartilages  of,  1156 
cochlea,  1175 
external,  1154 


Ear,  external,  auricle  of,  1154 

lobule  of,  1155 
internal,  1173 
labyrinth,  1173 

membranous,  1179 
osseous,  1174 
middle,  1160 
muscles  of  auricle,  1157 

of  tympanum,  1171 
ossicula  of,  1168 
pinna  of,  1154 
semicircular  canals  of,  1175 
surgical  anatomy  of,  1186 
trumpet,  1163 
tympanum,  1160 
Ear-drum  membrane,  secondary 

1162 

Ebner,  von,  glands  of,  1101 
Ectal    arcuate   fibres   of   postob 

longata,  886 
polymorphous  nerve  cells,  958 
Efferent  nerve,  827 

root  of  spinal  cord,  836 
Egg  tubes,  1515 
Eighth  nerve,  1064 

surgical  anatomy  of,  1065 
Ejaculator  seminis  muscle,  459 

urinaj  muscle,  459 
Ejaculatory  ducts,  1487 
Elastic  cartilage,  262 
tissue,  yellow,  264 
Elbow,  bend  of,  surgical  anatomy 

of,  655 
bone,  186 
bursa  of,  313 
ligament  of,  anterior,  311 

posterior,  311 
Elbow-joint,  articulations  of,  310 
surface  form  of,  314 
surgical  anatomy  of,  314 
Eleventh  nerve,  1073 

surgical  anatomy  of,  1074 
thoracic  vertebra,  56 
Ellipsoid  of  Krause,  1137 
Elliptical  recess,  1174 
Embolus  of  cerebellum,  900 
Eminence,  articular,  of  temporal 

bone,  84 
of  bone,  34 
canine,  106 
deltoid,  181 
frontal,  79 

ilio-pectineal,  217,  220 
of  Jacobson,  1110 
nasal,  79 
olivary,  93 
parietal,  76 

Eminentia  abduceritis,  880 
articularis,  84,  135 
concha?,  1156 
fossa?  triangularis,  1156 
Emissary  veins,  743 

surgical  anatomy  of,  743 
Emulgent  vein,  766 
Enamel  cells,  1216 
cuticle,  1214 
fibres,  1213 
jelly,  1216 
prisms,  1213 
of  teeth,  1213 

development  of,  1216 
Enamel-organ  of  tooth,  1215 
Enarthrosis,  268 
Encephalon,  860 
Encysted  hernia,  1535 
End-bulb  of  Krause,  826,  830 
Endocardium,  576 
Endo-exo-gnathion  suture,  111 
Endo-gnathion  suture,  111 
Endolymph,  1179 
Endo-meso-gnathion  suture,  111 


Endomysium,  364 
Endoneurium,  826 
Endosteum,  36 
Endothelium,  corneal,  1121 
Endothoracic  fascia,  1393 
End-plates,  motor,  828 
Endyma,  881 
Endymal  cells,  832 

ciliated,  818 
Ensiform  appendix,  159 

surfaces  of,  159 
cartilage,  156 
Ental   arcuate  fibres  of   postob- 

longata,  886 

polymorphous  nerve-cells,  959 
Eosinophiles,  36 
Epactal  bones,  103 
Eparterial   branch   of   bronchus,. 

1385 

Epencephalon,  860 
Epicardium,  576 
Epicondyles,  182 
Epicondylic  ridge,  181 
Epicteric  bone,  103 
Epidermic    coat   of   hair-follicle, 

1198 
Epididymis,  1480 

structure  of,  1482 
Epidural  space,  857,  973 
Epigastric  artery,  deep,  697 
peculiarities  of,  697 
surgical  anatomy  of,  698 
internal,  697 
superficial,  704 
superior,  647 
glands,  superior,  800 
plexus,  1091 
vein,  deep,  759 
Epiglottis,  1373 
cartilage  of,  1373 
cushion  of,  1373 
surfaces  of,  1373 
Epimysium,  364 
Epineurium,  826 
Epiotic  portion  of  temporal  boner 

91 
Epiphyseal  cartilage,  36,  867,  915 

recess,  915 
Epiphysis,  867,  915 
albicantia  of,  916 
of  bone,  34 

postcommissure  of,  915 
postperi'oration  of,  916 
structure  of,  915 
Episylviari  ramus,  925 
Epithalamus,  916 
Epithelial  corpuscles  of    Kohn,. 

1412 

Epithelium.    See  Various  organs, 
germinal,  of  Waldeyer,  1513 
lens,  1140 
transitional,  1437 
Epitrochlea,  183 
Epitympanic  recess,  87,  1160 

space,  87 

Epo-ophoron,  1511 
Erectile  tissue  of  penis,  1467 

of  vagina,  1497 
Erector  clitoridis  muscle,  463 
penis  muscle,  460 
spina?  muscle,  419 
Crythroblasts,  36 
Cthmo-frontal  suture,  130 
Cthmo-sphenoidal  suture,  130- 
Cthmoid  bone,  98 

articulations  of,  102 
cribriform  plate  of,  99 
development  of,  101 
horizontal  lamina  of,  99 
infundibulum  of,  101 
lateral  mass  of,  100 


JATZ>/:A 


1575 


Ethmoid  bone,  os  plammi  of.  1(K) 
perpendicular  plate  <>t'.   ino 
unciform  process  of,  100 
Ethmoidal  arteries,  625 
canals,  82,  100 
cells,  82,  100 

posterior,  145 
crest,  94 
foramina,  82 

anterior,  130,  141 
posterior,  130,  141 
notch,  82 
process  of    inferior   turbinated 

bone,  120 
sinuses,  101 
spine,  93,  130 
Eustachian  cushion,  1231 
tube,  1163 

canal  for,  1164 
cartilaginous      portion       of, 

1164 

osseous  portion  of,  1164 
valve,  569 

in  foetus,  581 

Excito-glandular  neurones,  816 
Excito-motor  neurones,  816 
Excretory    apparatus    of    liver, 

1342 

Exo-gnathion  suture,  111 
Expiration,  muscles  of,  434 
Expression,  muscles  of,  387 
Exsanguinated     renal     zone     of 

Hyrtl,  680,  1423 

Extensor  brevis  digitorum  mus- 
cle, 546 

pollicis  muscle,  491 
carpi  radialis  brevior  muscle, 

487 

bursa  of,  488 
longior  muscle,  487 
ulnaris  muscle,  489 
coccygeus  muscle,  424 
communis    digitorum    muscle, 

488 

indicis  muscle,  492 
longus  digitorum  muscle,  536 

pollicis  muscle,  491 
minimi  digiti  muscle,  489 
ossis  metacarpi  pollicis  muscle, 

491 

primi  internodii  pollicis   mus- 
cle, 491 

proprius  hallucis  muscle,   535 
secundi  internodii  pollicis  mus- 
cle, 491 
External    abdominal    ring,    437, 

1526 

acoustic  canal,  1158 
angular  process,  80,  140 
annular  ligament,  545 
anterior  thoracic  nerve,  1001 
arcuate  ligament,  429,  451 
auditory  canal,  1158 
meatus,  138,  1158 
bicipital  ridge,  181 
calcanean  artery,  718 
calcaneo-astragaloid  ligament , 

354 
calcaneo-scaphoid       ligament, 

355 

capsule  of  brain,  957 
carotid  artery,  602 

foramen,  89 
circumflex     artery    of    thigh, 

705 

condyle  of  femur,  228 
crucial  ligament,  339 
cutaneous  nerve,  1002,  1018 
ear,  1154 
epicondyle,  182 
hiemorrhoidal  veins,  760 


Kxti-rnal  iliac  artery,  695 
glands,  795 
vein,  759 
inguinal  fossa,  1532 

hernia,  1532 

interchondral  ligament,  292 
intercostal  muscle,  427 
jugular  vein,  728 
lateral  ligament,  2S2,  312 
malleolus,  241 

ligament  of,  1170 
mammary  artery,  653 
maxillary  artery,  607 
oblique  line,  123 
muscle,  435 

aponeurosis  of,  1525 
occipital  crest,  72,  136 

protuberance,  71,  136 
orbital  foramina,  95 
os,  1501 

palatine  nerve,  1050 
palpebral  arteries,  625 
parietal  diploic  vein,  734 
plantar  artery,  719 

nerve,  1032 
popliteal  nerve,  1033 
pterygoid  muscle,  386 
nerve,  1051 
plate,  96 

pudic  artery,  deep,  704 
superficial,  704 

deep,  704 
saphenous  gland,  794 

vein,  756 

semicircular  canal,  1175 
semilunar  fibrocartilage,  341 
spermatic  fascia,  438,  1526 

nerve,  1018 

sphincter  ani  muscle,  452 
supracondylar  ridge,  181 
tarsal  ligament,  373 
tuberosity  of  tibia,  236 
Extracranial  lymphatics,  778 
Extrinsic     muscles    of     tongue, 

400 
Eye,  1113 

appendages  of,  1147 
aqueous  humor  of,  1138 
choroid,  1121 
ciliary  muscle,  1125 
conjunctiva,  1150 
cornea,  1118 
crystalline  lens,  1140 
globe  of,  arteries  of,  1142 
lymphatics  of,  1143 
nerves  of,  1144 
veins  of,   1143 
iris,  1127 

lachrymal  apparatus,  1151 
glands,  1151 
sac,  1152 
nasal  duct,  1152 
pupil  of,  1127 
refracting  media  of,  1138 
retina,  1130 
sclera,  1117 

surgical  anatomy  of,  1144 
tunics  of,  1117 
uveaof,  1128 
vitreous  body  of,  1139 
Eyeball,  coverings  of,  377 
Eyebrow,  1147 
Eyelashes,  1148 
Eyelid,  1147 

Meibomian  glands  of,  1149 
orbital  portion  of,  1147 
structure  of,  1148 
surface  form  of,  1152 
surgical  anatomy  of,  1153 
tarsal  portion  of,  1147 
Eye-teeth,  1207 


F 


FACE,  arteries  of,  607 
bones  of,  104 
fasciie  of,  367 
lymphatics  of,  778 
muscles  of,  367 

surface  form  of,  387 
nerves  of,  1059 
veins  of,  725 
Facet,  clavicular,  157 

costal,  170 
Facial  artery,  607 

branches  of,  608 

relations  of,  608 

surgical  anatomy  of,  610 

transverse,  613 
bones,  104 
index  of  skull,  147 
nerve,  1059 

branches  of,  1060 

nuclei  of,  893 
afferent,  894 
efferent,  894 

surgical    anatomy    of,    1064 
>inus,  738 

suture,  transverse,  128 
vein,  anterior,  726 

common,  726 

surgical  anatomy  of,  726 

transverse,  727 
Falciform  crest,  89 
ligament,  295 

of  liver,  1340 
process       of       fascia      lata, 

517 

Falcula,  895,  976 
Fallopian  tube,  1510 

ampulla  of,  1510 

artery  of,  1511 

course  pursued  by,  1510 

fimbriffl  of,  1510 

infundibulum  of,  1510 

isthmus  of,  1510 

lymphatics  of,  801,  1511 

nerve  of,  1511 

structure  of,  1510 

uterine  portion  of,  1510 

vein  of,  151 1 
False  pelvis,  209 
ribs,  161 

vocal  cords,  1378 
Falx,  922,  975 
cerebelli,  976 
cerebri,  975 
inguinalis,  450 
Fascia  or  fasciae,  363 
of  abdomen,  deep,  435 

superficial,  435,  1523 

triangular,  1527 
of  acromial  region,  472 
anal,  456,  1558 
of  arm,  476 

deep,  472,  476 

superficial,  472 
axillary,  465,  648 
of  back,  deep,  413 

superficial,  413 
bicipital,  478,  746 
bucco-pharyngeal,     383,     390, 

403,  1232 
of  Camper,  435 
cervical,  deep,  389 

superficial,  388 
clavi-pectoral,  469 
of  Colics,  458,  1527 
costo-coracoid,  469 
of  cranial  region,  368 
of  cranium,  367 
cremasteric,  1474,  1528 
cribriform,  514,  1539 


1576 


INDEX 


Fascia  or  fasciae,  deep,  367 
dentate,  938 
endo-pelvica,  1556 
endothoracic,  1393 
of  face,  367 
of    femoral     region,     anterior 

deep,  515 
superficial,  514 
of  foot,  544 
of  forearm,  480 
of  hand,  493 
of  hip,  525 
iliac,  510 

infraspinatus,  474 
infundibuliform,  448,   1475 
intercolumnar,  438,  1474,  1526 
intercostal,  426 
ischio-rectal,  456,  1558 
lata,  515,  1539 

falciform  process  of,  1540 

iliac  portion,  517,  1540 

pubic  portion,  517,  1540 
of  leg,  535 

transverse,  540 
of  lower  extremity,  509 
masseteric,  383 
of  neck,  387 
obturator,  1558 
of  orbit,  377 
palmar,  deep,  495 
palpebral,  1149 
parotid,  389,  1225 
parotideo-masseterica,   389 
pectoral,  deep,  466 
pelvic,  1556 
of    perinteum    in    male,    deep, 

460,  1550 
superficial,  457 
phrenico-pleural,  1395 
plantar,  545 
pre-tracheal,  391 
prevertebral,  390 
of  quadratus  lumborum,  451 
recto-vesical,  1558 
retro-renal,  1420 
salpingopharyngea  of  Troltsch, 

1165 

of  Scarpa,  435 
semilunar,  478 
of  shoulder,  deep,  472 

superficial,  472 
spermatic,  1474 

external,  438,  1526 

internal,  448 

middle,  442 
subseapular,  473 
superficial,  366 
supraspinatus,  474 
temporal,  384 
of  thigh,  514 
of    thoracic    region,    anterior, 

deep,  465 
superficial,  465 
of  thorax,  426 
transversalis,  447,  1529 
triangular,  439 
of  trunk,  412 
of  upper  extremity,  464 
Fascial  canal,  1548 
Fasciculi,  264 
proprii,  849 

Fasciculus  albicantiothalami,  914 
archiformis    pedis,    906 
longitudinal,  inferior,  962 

superior,  962 
marginalis,  849     . 
pedunculomammillaris,  916 
perpendicular,  962 
rectus,  962 
retroflexus,  908 
thalamomammillaris,  914,  916 


Fasciculus  of  Tiirck,  854 

uncinate,  962 
Fasciola,  938 

Fastigatum  of  cerebellum,  900 
Fastigium  of  cerebellum,  879 
Fauces,  isthmus  of,  1222 

pillars  of,  1221 
Female  bladder,  1455 

organs  of  generation,  1489 
perinaeum,  1554 
urethra,  1455 
Femoral  artery,  698 

anastomotica  magna  of,  706 
branches  of,  704 
common,  700 
deep,  704 

peculiarities  of,  702 
superficial,  701 
surface  marking  of,  702 
surgical  anatomy  of,  702 
canal,  511,  1543 
cutaneous  nerves,  1028 
hernia,  1537 
complete,  1546 
coverings  of,  1545 
descent  of,  1545 
incomplete,  1545 
varieties  of,  1545 
ligament,  517 

lymphatic  glands,  deep,  794 
nerve,  1021 
region,  anterior,  fascia  of,  deep 

515 

superficial,  514 
surgical  anatomy  of,  517 
muscles  of,  514 
dissection  of,  514 
surgical      anatomy    of, 

521 

internal,  muscles  of,  522 
dissection  of,  522 
surgical     anatomy     of, 

525 

posterior  muscles  of,  532 
dissection  of,  532 
surgical     anatomy     of, 

534 

ring,  439,  511,  1544 
sheath,  511,  1542 
spur,  229 
vein,  758 
Femur,  223 

articulations  of,  231 
attachment  of  muscles  to,  231 
condyles  of,  227 
development  of,  231 
lower  extremity  of,  227 
shaft  of,  226 
borders  of,  227 
linea  aspera,  226 
surfaces  of,  227 
spiral  line  of,  225 
structure  of,  228 
surface  form  of,  231 
surgical  anatomy  of,  232 
trochlea  of,  227 
tubercle  of,  225 
tuberosities  of,  228 
upper  extremity  of,  223 
head  of,  223 
neck  of,  223 
trochanters  of,  225 
Fenestra  ovalis,  1162 

rotunda,  1162,  1177 
Fenestrated  membrane  of  Henle, 

587 

space,  posterior,  859 
Ferrein,  pyramids  of,  1425 
Fibre-baskets,  1137 
Fibres,  arcuate,  of  postoblongata, 
886 


Fibres  of  auricles  of  heart,  577 
cardiac  muscular,  363 
cerebello-olivary,  886 
of  cerebellum,  association,  902 
clinging,  903 
commissural,  902 
moss,  902 
proper,  907 
tendril,  903 

of  cerebral  cortex,  959  ' 
of  cord,  longitudinal,  848 
cortico-thalamic,  914 
dental,  1212 
enamel,  1213 
intercolumnar,  438 
lens,  1140 
muscle,  363 
nerve,  association,  961 
commissural,  963 
projection,  963 
thalamo-frontal,  956 
thalamo-striate,  956 
olivo-cerebellar,  886 
of  pons,  longitudinal,  887 

transverse,  887 
preanal,  of  levator  ani,  455 
pr£-rectales,  456 
of  Purkinje,  577 
of  Sharpey,  37 
sustentacular,  1131 
of    tegmentum    of    mid-brain, 

908 

thalamo-cortical,  914 
of  ventricles  of  heart,  577 
Fibre-tracts     in     pre-oblongata, 

888 

cere.bellar  prepeduncle,  888 
lateral  lemniscus,  888 
medial  lemniscus,  888 

longitudinal  bundle,  888 
Fibrils,  side,  823 
FibrillaD,  terminal,  830 
Fibro-cartilage,  262 
circumferential,  263 
connecting,  263 
interarticular,  283,  300,  302 

triangular,  317 
intervertebral,  272 
semilunar,  339 
stratiform,  263 

Fibro-elastic  coat  of  spleen,  1363 
Fibro-muscular     coat     of     gall- 
bladder, 1351 
Fibrous  coat  of  liver,  1345 
of  pharynx,  1233 
of  ureter,  1436 
layer  of  pericardium,  560 
membrane  of  trachea,  1387 
rings  of  heart,  576 
septum  of  tongue,  400 
sheaths  of  flexor  tendons,  548 
tissue,  white,  263 
Fibula,  239 

articulations  of,  241 
attachment  of  muscles  to,  241 
development  of,  241 
lower  extremity  of,  241 
nutrient  artery  of,  717 
oblique  line  of,  240 
shaft  of,  240 
styloid  process  of,  239 
surface  form  of,  241 
surgical  anatomy  of,  244 
upper  extremity  of,  239 
Fibular  artery,  superior,  712 
region,  muscles  of,  542 
actions  of,  543 
dissection  of,  542 
surgical  anatomy  of     544 
Fifth  lumbar  vertebra,  57 
nerve,  1041 


1577 


Fifth    nerve,  scmilunar  ganglion 
of,  1042 

surface  marking  of,  1055 

surgical  anatomy  of,  1055 
ventricle,  920,  921 ',  941 
Filiform  papilla1  of  tongue,  1100 
Filtrum     ventriculi     of     Merkel, 

1376 

Fihini  <lur:i>  spinalis,  857 
externum,  837 
intornuin,  837 

Fimbria,  937,  938,  945,  950 
Firnbriae  of  Fallopian  tube,  1510 

of  ovary,  1512 
Finger,   index,   metacarpal  bone 

of,  204 
ligaments  of,  324 

superficial  transverse,  496 
little,  metacarpal  bone  of,  205 
middle,    metacarpal    bone    of, 

204 

ring,  metacarpal  bone  of,  205 
veins  of,  superficial,  745 
First  nerve,  1037 

thoracic  vertebra,  55 
Fissura  antitragohelicina,  1156 

vi-stibuli,  117S 
Fissure  or    fissures,  amvgdaline, 

932, 933 

antitrasiohelioina,  1156 
auricular,  90,  136 
bivsisylvian,  924 
of  brain,  922,  923 
calcarine,  926 
central,  926 
of  cerebellum,  896 
cerebral,  922,  923 
choroid,  946 
circuminsular,  925 
collateral,  932 
of  cord,  838 
cuneal,  931 
diagonal,  928 
of  ductus  venosus,  1338 
of  frontal  lobe,  920 
of  gall-Madder,  1338 
dlaserian,   84,    1162 
inflected,  928 
insular,  933 

central,  933 
intereerebral,  921 
interlobar,  924 
intermedial,  931 
of  liver,  1338 

longitudinal,  1338 

transverse,  1338 
of  lung,  1402 
mammary,    prolongations    of, 

1518 

medifrontal,  927 
meditemporal,  932 
of  oblongata,  874 

dorsal,  875 

dorso-lateral,  875 

dorso-median,  875 

ventral,  874 

ventro-lateral,  875 

ventro-median,  874 
occipital,  926 

inferior,  931 

lateral,  931 

lobe,  931 
olfactory,  928 
orbital,  96 
or bi to-frontal,  927 
paracentral,  928 
paramesal,  927 
parietal  lobe,  930 
paroccipital,  930 
petro-tympanic,  84,  1162 
portal,  "1338 


Fissure    or    fissures,    post-calca- 

rinc,  926 
post-central,   930 
precrntral,  927 
superior,  927 
prccuneal.  931 
pterygo-maxillary,  139 
pterygoid,  96 
radiate,  928 
rhinal,  933 
rhinica,  933 
of  Rolando.  926 
rostral,  928 

spheno-maxillary,  115,  138 
sphenoidal,  96,  132 
.    of  Santorini,  1156,  1158 
of  spinal  cord,  838 

dorso-lateral,  839 
dorso-paramedian,  839 
ventro-paramedian,  839 
subfrontal,  927 
suboccipital,  931 
subrostral,  928 
subtemporal,  932 
supercentral,  927 
superfrontal,  927 
supertemporal,  932 
sylvian,  924 
temporal  lobe,  931 
of  tragus,  1156 
transinsular,  933 
transorbital,  929 
transparietal,  931 
transprecentral,  928 
transtemporal,  932 
umbilical,  1338 
Flat  bones,  34  \ 

Flechsig,  nucleus  semilunaris  of, 

914 

oval  bundle  of,  851 
Flexor  accessorius  muscle,  549 
brevis  digitorum  muscle,  547 
hallucis  muscle,  549 
minimi   digiti   muscle,   foot, 

550 

hand,  500 
pollicis  muscle,  499 
carp   radialis  muscle,  481 

ulnaris  muscle,  482 
longus  digitorum  muscle,  541 
hallucis  muscle,  541 
pollicis  muscle,  484 
ossis   metacarpi    pollicis    mus- 
cle, 498 
profundus    digitorum    muscle, 

484 

sublimis  digitorum  muscle,  i83 
tendons,  fibrous  sheaths  of,  548 
Flexure  of  brain  tube,  869 
cephalic,  869 
cervical,  869 
pontile,  869 
of  colon,  hepatic,  1317 
sigmoid,  1317 
splenic,  1317 

of  duodenum,  superior,  1293 
of  large  intestine,  hepatic,  1308 
sigmoid,  1308 
splenic,  1308 

Floating  lobe  of  liver,  1343 
Floccular  fossa,  89,  133 
Hood's  ligament,  306 
Flower's  gnathic  index  of  skull, 

148 

Fluid,  cerebro-spinal,  859 
Postal  circulation,  583 

lung,  1402 
Fold  of  Douglas,  semilunar,  441, 

446 

duodenal,  1270 
hypogastric,  1531 


Fold,  ovario-pelvic,  1512 
recto-vaginal,  1502 
of  urachus,  1531 
utero-vesical,  1502 
of  uterus,  1501 
Folia,  895 

linguae,  1097 
Follicle,  dental,  1216 
simple,  1303,  1327 
Folliculv  lymph-sinus,  1314 
I'ontana,  spaces  of,  1120 
Fontanelles,  102 
anterior,  78,  103 
antero-lateral,  103 
bregmatic,  103 
posterior,  103 
postero-lateral,  103 
Foot,  arteries  of,  713 
bones  of,  244 
bursae  of,  546 
development  of,  255 
fasciae  of,  544 
ligaments  of,  544 
muscles  of,  544 
nerves  of,  1031 
phalanges  of,  255 

articulations  of,  361 
sole  of,  dissection  of,  545 
surface  form  of,  257,  362 
surgical  anatomy  of,  257,  362 
veins  of,  758 
Foramen,  96 

cascum,  80,  130,  874 
carotid,  external,  89 

internal,  88 
condyloid,  anterior,  73, 133, 136 

posterior,  73,  133,    136 
costo-transverse,  50 
dental,  inferior,  124 
ethmoidal,   anterior,    130,    141 

posterior,  130,  141 
of  Huschke,  92 
infraorbital,  106,  140 
jugular,  73,  133 
of  Key  and  Retzius,  978 
lacerum  anterius,  96,  132 

medium,  132 

posterius,  133 
of  Langer,  466,  648,  790 
of  Luschka,  978 
magnum,  72,  133 
of  Majendie,  859,  881,  978 
malar,  113 
mastoid,  85,  138 
mental,  123,  140 
of  Monro,  866,  913 
obturator,  220 
optic,  93,  131,  142 
ovale,  95,  132,  569 

in  fostus,  581 
palatine,  great,  116 

posterior,  135 
parietal,  76 
pterygo-palatine,  95 
quadratum  of  diaphragm,  432 
rotundum,  95,  132 
sacro-sciatic,  great,  218,  296 
singulare,  89,  1179 
of  Somm erring,  1131 
spheno-palatine,  119,  143 
spinal,  49,  132 
sternal,  159 
stylo-mastoid,  90,  135 
supraorbital,  80,  140 
supratrochlear,  183 
temporo-malar,  115 
thyroid,  220 
vertebral,  49 
vertebrarterial,  50 
Vesalii,  95,  132 
Foramina  of  diaphragm,  432 


1578 


INDEX 


Foramina,  ethmoidal,  82 

incisor,  110 

intervertebral,  49 

of  Key  and  Retzius,  859 

Luschkae,  881 

malar,  113 

olfactory,  143 

orbital,  external,  95 

sacral,  anterior,  62 
posterior,  63 

of  Scarpa,  110,  135,  1050 

of  Stenson,  1 10 

Thebesii,  569,  570,  771 
Forearm,  arteries  of,  659 

bones' of,  186 

fascia?  of,  480 

interosseous  veins  of,  747 

lymphatics  of,  787 

muscles  of,  480 

dissection  of,  480,  484 

nerves  of,  1000 

veins,  744 
Fore-brain,  865,  911 

epiphysis  of,  915 

structure  of,  external,  911 

thalami  of,  912 

third  ventricle  of,  916 

vesicles  of,  secondary,  866 
Fore-chambers  of  heart,  5C7,  57C 
Fore-gut,  1246 
Form  of  bones,  33 
Formatio    reticularis,    882,    884 

910 

alba,  884 
grisea,  884 
Fornicolumns,  951 
Fornicommissure,  951 
Fornix,  921,  943,  949 

body  of,  949,  951 

of  conjunctiva,  1150 

periphericus,  962 

pillars  of,  950 

vaginal,  1496 

Fossa   or   fossae   of   acetabulum, 
220 

of  antihelix,  1154 

canine,  106,  140 

condyloid,  anterior,  136 
posterior,  136 

coronoid,  183 

cranial,  143 

digastric,  86,  123,  136 

digital,  225 

duodenal,  1270 

duodeno-jejunal,  1271 

floccular,  89,  133 

glenoid,  84,  135 

of  helix,  1154 

hypophyseos,  917 

ileo-appendicular,  1272 

ileo-cracal,  1272 

ileo-colic,  1272 

iliac,  216 

incisive,  106,  123,  139 

incudis,  1163 

mfraspinous,  174 

inguinal,  1258,  1532 

intersigmoid,  1319 

ischio-rectal,  1548 

jugular,  91 

lachrymal,  81 

of  Landzert,  1271 

longitudinal,  of  liver,  1338 

mandibular,  84 

mastoid,  86 

mesocolic,  1271 

myrtiform,  106 

nasal,  142,  1108 

navicularis  of  urethra,  1453 

occipital,  133 

olecranori,  183 


Fossa  or  fossa?,  orbital,  143 
ovalis,  569 
palatine,   110,  133 
paraduodenal,  1271 
patellaris,  1139 
pericsecal,  1271 
pituitary,  93 
pterygoid,  96,  115 
radial,  183 
retro-csecal,  1272 
retro-colic,  1272 
retro-duodenal,  1271 
retro-peritoneal,  1270 
of  Rosenmuller,  1231 
of  Scapha,  1155 
scaphoid,  97,  135,  1154 
sigmoid,  86 
of  skull,  anterior,  130 
infratemporal,  138 
middle,  130 
orbital,  140 
posterior,  132 
pterygo-palatine,  139 
spheno-maxillary,  139 
temporal,  137 
zygomatic,  138 
spheno-maxillary,  115 
sublingual,  123 
submaxillary,  123 
subscapular,  172 
supra-tonsillar,  1223 
supraspinous,  174 
temporal,  76 
of  Treitz,  1270 
trochanteric,  225 
trochlear,  82 
umbilical,  1338 
Fossula  inferior,  1178 

superior,  1178 
Fountain  decussation,  910 
Fourchette,  1490 
Fourth  nerve,  1041 
ventricle,  878 

choroid  plexuses  of,  881 
floor  of,  879 
roof  of,  881 
Fovea    centralis    retinae,     1131, 

1138 

hemielliptica,  1174 
hemispherica,  1174 
inferior,  880 
inguinalis  lateralis,  1532 

mesialis,  1532 
mediana,  880 
oblonga,  1372 
superior,  880 
supra-vesicularis,  1532 
triangular  is,  1372 
Foveolse,  Howship's,  38 
Framulum  of  cerebellum,  902 
Giacomini,  938 
of  ileo-cfflcal  valve,  1316 
Fraenum  of  clitoris,  1494 

labii    superioris    et    inferioris, 

1204 

linguae,  1097 
of  penis,  1465 
Frontal  air  sinus,  82 
artery,  613 

from  anterior  cerebral,  ante- 
rior internal,  628 
inferior  internal,  628 
middle   internal,   629 
posterior  internal,  629 
from    middle    cerebral,    as- 
cending, 630 
inferior  external,  630 
from  ophthalmic,  625 
bone,  79 

horizontal  portion  of,  81 
articulations  of,  83 


Frontal  bone,  horizontal  portion 
of,     attachment       of 
muscles  to,  83 
border  of,  82 
development  of,  82 
structure  of,  82 
orbital  portion  of,  81 
articulations  of,  83 
attachment  of  muscles. 

to,  83 

border  of,  82 
development  of,  82 
structure  of,  82 
vertical  portion  of,  79 
border  of,  81 
structure  of,  81 
crest,  80,  130 
diploic  vein,  734 
eminence,  79 
lobe,  926 

fissures  of,  926 
gyres  of,  929 
nerve,  1043 
process  of  malar,  114 
spine,  80 
suture,  79,  127 
vein,  725 

Frontalis  muscle,  369 
Fronto-malar  suture,  1 28 
Fronto-parietal    operculum,    925- 

suture,  127 

Fronto-pontile  tract,  910 
Fronto-sphenoidal  suture,  128 
Fundament  of  cerebellum1,  869 
Fundamental  plexus,  1121 
Fundiform  ligament  of  Retzius, 

544 
Furidus  glands,  1285 

of   internal    auditory    meat  us, 

1178 

tympani,  1161 
of  uterus,  1499 
Fungiform    papillae    of    tongue, 

1100 
Funicular     process,     hernia     of,, 

1535 

Fuiiiculus  cuneatus,  876 
gracilis,  876 
lateralis,  876,  884 
separans,  879 
Furcula,  1253 
Furrow,  interauricular,    567 

sternal,  166 
Fusiform  muscles,  365 


A.LACTOPHORTJS   duct,    1518 

Galen,  testes  muliebres  of,  1511 

veins  of,  735,  771 
Gall-bladder,  1350 

arteries  of,  1353 

body  of,  1350 

fibro-muscular  coat  of,  1351 

fissure  for,  1338 

fundus  of,  1350 

lymphatics  of,  1353 

mucous  coat  of,  1351 

neck  of,  1350 

nerves  of,  1353 

notch  of,  1338 

relations  of,  1350 

serous  coat  of,  1351 

structure  of,  1351 

surgical  anatomy  of,  1354 

veins  of,  1353 
anglia,  basal,  867,  952 

of  nerves,  827 
spinal,  983 
aberrant,  983 


INDEX 


1579 


Ganglia  of  nerves,  spinal,  acces- 
sory, 983 

semilunar,  of  abdomen,  1091 
Gangliated  cord,  1081 

cervical  portion   of,  1081 
lumbar  portion  of,  1089 
pelvic  portion  of,  1089 
sacral  portion  of,  1089 
thoracic  portion  of,  1087 
Ganglion  of  Andersch,  1066 

Arnold's,  1053 

of  Bochdalek,  1048 

cardiac,  of  Wrisberg,    1090 

carotid,  1083 

cell,  820 

cervical,  inferior,  1086 
middle,  1085 
superior,  1081 

ciliary,  1045 

long  root  of,  1045 

diaphragmatic,  1092 

of  facial  nerve,  1059 

of  fifth  nerve,  1045 

Gasserian,  1042 

geniculate,  1013,  1059 

of  glossu-pharyngeal,   1066 

impar,  1078 

inferior,  1086 

interpeduncular,  908 

jugular,  1086 

lenticular,  1040 

lumbar,  1089 

.Mockers,  1048 

mesenteric,  1094 

ophthalmic,  1045 

otic,  1053 

peripheral,  1083 

petrous,  1066 

pharyngeal,  1070 

phrenic-,  1092 

of  Ribes,  1077 

of  Scarpa,  1065 

semilunar,  of  abdomen,  1091 
of  fifth  nerve,  1042 

spheno-palatine,  1048 

of  spinal  nerves,  983 

submaxillary,  1054 

superior,  1066 

of  sympathetic  nerves,  1080 

thoracic,  1087 

thyroid,  1085 

of  vagus,  1069 

of  Valentin,  1047 

vestibular,  1065 
Ganglionic     arteries,     postero- 

lateral,  642 
postero-median,  642 

branch  of  nasal  nerve,  1045 

system  of  arteries,  central,  632 

vessels  of  brain,  central,  631 
Gartner's  duct,  1511- 
Gasserian  ganglion,  1042 
Gastric  area  of  kidney,  1422 

artery,  673,  676 

glands,  798,  1285 

impression,  1340 

nerves,  1072 

plexus,  1094 

surface  of  liver,  1336 
of  spleen,  1361 

veins,  768 

Castro-colic  omentum,  1266 
Gastro-duodeiial   plexus,   1094 
Gastro-duodenalis  artery,  675 
Gastro-epiploic  plexus,  1094 
left,  1094 

vein,  768 

Gastro-epiploica    dextra    artery, 
675 

sinistra  artery,  676 
Gastro-hepatic  omentum,  1264 


( iastro-spleiiif    ligament,    1266 

omentum,  1266 
Gastrocnemiua  muscle,  537 

bursa  of,  537 
Gemellus  muscle,  inferior,  530 

superior,  529 
Gemmules,  S23 

Generation,  organs  of,  develop- 
ment of,  1559 
female,  1489 
male,  1457 
Genial  gland,  781 

tubercles,  123 

ganglion,  1048,  1059 

tract,  956 

Genio-glossus  muscle,  399 
Genio-hyo-glossus  muscle,  399 
Genio-hyoid  muscle,  397 
Genital  corpuscles,  830 
Genito-crural  nerve.     See  Genito- 

femoral. 

Genito-femoral  nerve,  1018 
femoral  branch,  1018 
genital  branch,  1018 
Gennari,  fibre  band  of,  959 
Genu  splenium  of  callosum,  920 
Gerlach,  valve  of,  1310 
Germinal  cells,  818 

epithelium  of  Waldeyer,  1514 
Giant  cells,  959 
Gianuzzi,  crescents  of,  1228 
Gimbernat's  ligament,  439,  1527 
Gingival     branches     of     dental 

nerves,  1047 
Ginglymus,  267 
Giraldes,  organ  of,  1484 
Girdle  shoulder,  168 
Glabella,  150 

of  frontal  bone,  80,  139 
Gladiolus,  157 

borders  of,  159 

surfaces  of,  159 
Glands,  absorbent,  774 

agmiriated,  1304 

apical,  1101 

arytenoid,  1385 

of  Bartholiii,  1495 

of  biliary  ducts,  1349 

of  Bowman,  1111 

bronchial,  1389 

Brunner's,  1303 

buccal,  1205 

cardiac,  1286 

carotid,  1416 

ceruminous,  1159 

ciliary,  1200 

circumanal,  1200 

coccygeal,  1417 

conglobate,  774 

Cowper's,  1453 

ductless,  1407 

duodenal,  1303 

of  Duverney,  1475 

epiglottis,  1382 

fundus,  1285 

gastric,  1285 

infralaryngeal,  785 

interbronchial,  1389 

intestinal,  1303,  1327 

labial,  1204 

lachrymal,   1151 

of  larynx,  1382 

lenticular,  of  stomach,  1285 

of  Lieberkuhn,  1303,  1327 

lingual,  1101 

of  Littre\  1453 

Luschka's,  1417 

lymphatic,  774 

mammary,  1516 

Meibomian,  1149 

molar,  1205 


Glands  of  Moll,  1148 

of  Montgomery,  1516  « 

mucilaginous,  265 

mucous,  1228 

of  Nuhn  and  Blandin,  110L 

odoriferae,  1464 

oesoph:igcal,  1239 

oxyiitic,  1285 

of  Pacchioni,  737 

palatal,  1221 

parathyroid,  1412 

parotid,  1224 

peptic,  1285 

peritracheo-bronchial,  138& 

Peyer's,  1304 

pharyngeal,  1233 

prelaryngeal,  785 

prostate,  1457 

pyloric,  1285 

of      Rosenmuller,      accessory, 
1151 

salivary,  1224 

sebaceous,  1148,  1201 

solitary,  1303,  1327 

sublingual,  1227 

submaxillary,  1226 

subparotid,  1225 

suburethral,  1495 

sudoriferous,  1200 

suprarenal,  1437 

sweat,  1200 

tarsal,  1149 

thymus,  1414 

thyroid,  1407 
arteries  of,  605 
lymphatic  vessels  of,  782 
veins  of,  731 

of  tongue,  1101 

tracheal,  1389 

of  Tyson,  1464 

of  v.  Ebner,  1101 

vulvo-vaginal,  1495 
Glandulae  Pacchioni,  737 

Tysonii  odoriferae,  1464 
Glans  clitoridis,  1494 

penis,  1464 

Glaserian  fissure,  84,  1162 
Gleno-humeral  ligament,  307 
Glenoid  cavity,  176 

fossa,  84,  135 

ligament,  176 

of  Cruveilhier,  361 

point  of  skull,  150 
Glia-cells,  832 
Gliosa,  882 

centralis,  843,  847 

cornualis,  843,  848,  852 
Glisson,    capsule    of,    770,    1266 

1337 

Globulus  of  cerebellum,  900 
Globus  of  epididymis,  1480 
Glomeruli  olfactorii,  964 
Glosso-epiglottic   ligament,    1373 
Glosso-epiglottidean  folds,  1374 
Glosso-pharyngeal  nerve,  1066 
nuclei  of,  890 
surgical  anatomy  of,  1067 
Glottis,  chink  of,  1377 

false,  1377 

respiratoria,  1377 

true,  1377 

vocalis,  1377 
Gluteal  artery,  695 
inferior,  694 

cutaneous  nerve,  1028 

glands,  794 

line,  anterior,  216 
inferior,  216 
posterior,  216 

nerve,  inferior,  1027 
superior,  1027 


1580 


INDEX 


Gluteal  region,  lymphatic  vessel 

of,    799 

muscles  of,  525 
dissection  of.  525 
surgical  anatomy  of,  531 
ridge,  226 
veins,  761 

Gluteo-femoral  bursa,  333 
Gluteus  maximus  muscle,  525 
medius  muscle,  526 
minimus  muscle,  526 
Gnathic  index  of  skull,  148 
Golgi,  cells  of,  821,902 

organ  of,  831 

Goll,  column  of,  839,  840,  850 
Gomphosis,  266 
Gonion,  124,  150 
Gowers'  tract,  901 
Graafian  follicles,  1514 
vesicles,  1514 

membrana      granulosa      of, 

1515 

ovicapsule  of,  1515 
Gracile  lobe  of  cerebellum,  898 
Gracilis  muscle,  522 
Granular  sheath  of  Tomes,  1212 
Gray  commissure   of    cord,  844, 

'845 

substance  of  cord,  843,  855 
Great  auricular  nerve,  989 
cardiac  nerve,  1086 
plexus,  1090 
vein,  770 

deep  petrosal  nerve,  1049 
occipital  nerve,  986 
omentum,  1266 
sacro-sciatic  foramen,  296 

ligament,  294 
sciatic  nerve,  1030 
sinus  of  aorta,  591 
superficial  petrosal  nerve,  1048 
Greater  alar  cartilage,  1107 

wings  of  sphenoid,  95 
Grooves,  auriculo-ventricular,  of 

•  heart,  5G7 
basilar,  75 

of  pons,  877 
bicipital,  179 
carotid,  93 
cavernous,  93 
dentato-fascic-olar,  937 
infraorbital,  107,  141 
interventricular,  570 

of  heart,  507 
intervertebral,  49 
lachrymal,  107,  109,  141,  143 
musculo-spiral,  181 
mylo-hyoidean,  124 
naso-palatine,  121 
obturator,  217,  220 
occipital,  86 
optic,  93,  130,  131 
peroneal,  248 
popliteal  228 
pterygopalatiiie,  116 
sacral,  63 
of  spinal  cord,  837 
subclavian,  170 
subcostal,  163 
ulnar,  183 
vertebral,  156 

Ground  bundle  of  cord,  849 
dorsal  column,  852 
lateral  column,  853 
ventral  column,  854 
Gubernaculum  testis,  1471 
Gudden's  commissure,  905,  1038 
infracommissure  of,  919 
tractus  peduncularis  transver- 

sus,  906 
•  Guerin,  valve  of,  1454 


Gulf  of  internal  jugular  vein,  729 
Gullet,  1235 
Gums,  1205 

surgical  anatomy  of,  1234 
Gustatory  cells,  1101 

hair,  1101 

nerve,  1052 

path,  1067 

pore,  1100 
Gyre,  angular,  931 

callosal,  928,  930 

cerebral,  922 

dentate,  928 

of  frontal  lobe,  929 

hippocampal,  932 

marginal,  931 

medifrontal,  929 

meditemporal,  932 

mesorbital,  928,  930 

olfactory,  935 

paracentral,  929 

parietal,  931 
lobe,  931 

paroccipital,  931 

postcentral,  931 

postparietal,  931 

precentral,  929 

preinsula,  933 

subcalcarine,  932 

subcallosal,  867 

subcollateral,  932 

subfrontal,  929 

subtemporal,  932 

superfrontal,  928,  929,  930 

supertemporal,  932 

supramarginal,  931 

temporal  lobe,  932 

transtemporal,  932 

uncinate,  932 
Gyri  Andrese  Retzii,  938 
Gyrus  ambiens,  935 

dentatus,  937 

epicallosus,  938 

fasciolaris,  938 

intralimbicus,  937 

semilunaris,  935 

subcallosus,  936 


H.VBENAL  commissure,  915 
Haemorrhoidal    artery,     inferior 

691 

middle,  688 
superior,  680 
gland,  middle,  796 
nerve,  inferior,  1028 
plexus,  inferior,  1095 

superior,  1095 
veins,  external,  760 
inferior,  760 
middle,  760 
superior,  768 
surgical  anatomy  of,  761 
Hair,  1197 

blood-vessels  of,  1199 
coats  of,  dermic,  1198 

epidermic,  1198 
cortical  substance  of,  1199 
gustatory,  1101 
nerves  of,  1199 
olfactory,  1110 
Hair-bulb,  1197 
Hair-follicle,  1197 
Hair-papilla,  1197 
root  of,  1197 
shaft  of,  1199 
stem  of,  1199 
Hair-streams,  1197 
Hair-whirlpools,  1197 


Haller,  rete  testis  of,  1482 
Hamstring  muscles,  532 
Hamular    process    of  lachrymal, 

113 

of  sphenoid,  90 
Hamulus,  1178 
Hand,  arteries  of,  6G2 

bones  of,  195 

development  of,  207 

bursa  of,  494 

fasciae  of,  493 

ligaments  of,  321 

muscles  of,  493 
dissection  of,  493 

nerves  of,  from  median,  1004 
from  radial,  1008 
from  ulnar,  1006 

phalanges  of,  206 

veins  of,  745 
Hard  palate,  1220 
Harmonia,  266 
Hastier,  valve  of,  1152 
Ilaustra  coli,  1325 
Ilaversian  canal,  38 
Head,  arteries  of,  598 

lymphatic  glands  of,  778 

muscles    of,    surface   form   of, 
387 

veins  of,  725 
Heart,  564 

arteries  of,  580 

auricles  of,  fibres  of,  577 
left,  570 

sinus  of,  570 
right,  567 

auriculo-ventricular  fasciculus 
of,  579 

cavities  of,  capacity  of,  566 

component  parts  of,  567 

endocardium,  576 

fat  upon,  566 

fibrous  rings  of,  576 

fore-chambers  of,  567,  570 

grooves  of,   auriculo-ventricu- 
lar, 567 
interventricular,  567 

infundibulum  of,  571 

lymphatics  of,  580 

muscular  fibres  of,  577 

myocardium,  576 

nerves  of,  580 

position  of,  564 

size  of,  566 

structure  of,  576 
muscular,  577 

surface  form  of,  580 

surgical  anatomy  of,  580 

veins  of,  580 

ventricle  of,  fibres  of,  577 
right,  571 

ventricular  portion  of,  570 

vortex  of,  578 

weight  of,  566 
Heel  bone,  244 
Heidenhain,        demilunes       of, 

1228 

Helicine  arteries,  1468 
Helicis  major  muscle,  1157 

minor  muscle,  1157 
Helicotrema  of  cochlea,  1177 
Helix,  1154 

crus  of,  1155 

fossa  of,  1155 

muscles  of,  1157 

spine  of,  1156 

Helmholtz,  ligaments  of,  1170 
Helwig,  bundle  of,  886 
Hemiseptum,  921,  941 
Hemispheres  of  cerebellum,  896 

cerebral,  919 
Hemolymph  nodes,  774 


INDEX 


15X1 


Henle,  fenestrated  membrane  of 
587 

ligament  of,  440,  444 

loop  of,  1427 

spine  of,  88 
llcnsi'ii,  canalis  reunions  of,  118( 
'    cells  of,  1185 

stripe,  1185 
Hepatic  area  of  kidneys,  1422 

artery,  674,  1346 

cells,*1346 

ducts,  1350 

flexure  of  colon,  1317 
of  large  intestine,  1308 

glands,  798 

plexus,  1094 

veins,  767 

Hepato-colic  ligament,  1 264 
Hepa to-duodenal  ligament,  1264 
1 1  rpato-gastric  ligament,   1264 
Herbst,  corpuscles  of,  830 
Hernia,  congenital,  1535 

diaphragmatic,  429 

encysted,  1535 

femoral,  1537 

of  funicular  process,  1535 

infantile,  1535 

inguinal,  1532 
direct,  1535 
external,  1532 
oblique,  1529,  1532 

scrotal,  1533 

surgical  anatomy  of,  1523 
Hesselbach,  ligament  of,  440,  444 
1529 

triangle,  1532 
Hey,  ligament  of,  517 
Hiatus  Fallopii,  88 

sacralis,  62 

semilunar,  747,  1110 

tendineus,  524 
Highmore,  antrum  of,  108 
Hilton,  compressor  sacculi  laryn- 
gis  muscle  of,  1381 

white  line  of,  1327 
Hilum  of  dentatum  of  cerebellum, 
900 

of  kidney,  1423 

of  ovary,  1513 

of  spleen,  1361 
Hind-brain,  869 

central   connection   of   cranial 
nerves,  888 

external  morphology  of,  874 
Hind-gut,  1246 
Hinge-joint,  267 
Hip,  articulations  of,  327 

bursa  of,  332 

fasciae  of,  525 

ligaments  of,  328 

muscles  of,  525 

surface  form  of,  335 

surgical  anatomy  of,  335 
Hippocampal  commissure,  951 

digitations,  947 

gyre,  932 
Hippocampus,  936,  937,  947 

gray  substance  of,  960 
His,  bundle  of,  579 

peripheral  veil  of,  818 

sulcus  terminalis  of,  568 
Histology  of  arteries,  586 

of  capillaries,  586 
Homo-lateral  tract-cells  of  cord, 

855 

Hook  bone,  201 
Horizontal  cells  of  Cajal,  1135 

lamina  of  ethmoid,  99 

plate  of  palate  bone,  116 

semicircular  canal,  1175 
Horn  cells  of  cord.  856 


Horn  cells  of  cord,  lateral,  845 
of  cornua,  dorsal,  844 

ventral,  844 
Horner's  muscle,  373 
Horny  layer  of  skin,  1191 
Horseshoe  kidney,  1433 
Houston's  valves,  1326 
llmvship's  lacunae,  38 
Huguier,  canal  of,  84,  1062 
Humeral   region,    anterior,    mus- 
cles of,  476 

posterior,  muscles  of,  479 
Humerus,  179 

articulations  of,  185 
attachment     of     muscles     to 

185 

capitellum  of,  183 
development  of,  184 
lower  extremity  of,  182 
nutrient  canal  of,  181 
pressure  curves  of,  183 
shaft  of,  181 
structure  of,  183 
surface  form  of,  185 
surgical  anatomy  of,  185 
trochlea  of,  183 
tuberosities  of,  179 
upper  extremity  of,  179 
Humors  of  eye,  1138 
Hunter's  canal,  524,  699 
Huschke,  foramen  of,  92 
Hyaline  cartilage,  262 
Hyaloid  canal  of  eye,  1 139 
membrane  of  eye,  1139 
Hydatids  of  Morgagni,  1480 
non-pedunculated,    1480 
pedunculated,  1480 
Hymen,  1492 

Hyo-epiglottic  ligament,  1373 
Hyo-glossus  muscle,  399 
Hyo-thyroid  membrane,   1374 
Hyoid  artery  of  lingual,  606 
of  superior  thyroid,  604 
bone,  155 

attachment   of   muscles    to, 

156 

basi-hyal  of,  155 
body  of,  155 
borders  of,  155 
surfaces  of,  1 55 
cornua  of,  greater,  155 

lesser,  155 
development  of,  156 
region,  infra-,  muscles  of,  393 

supra-,  muscles  of,  396 
surface  form  of,  156 
surgical  anatomy  of,  156 
tubercle  of,  155 
Hyparterial  branch  of  bronchus, 

1385 

Hypochondriac  region,  1243 
Hypbgastric  artery,  685 

in  foetus,  685 
fold,  1531 
nerve,  1017 
plexus,  1089,  1095 
region,  1243 
vein,  760 
Hypoglossal  nerve,  1074 

branches  of,  1075,  1076 
nuclei,  889 

surgical  anatomy  of,  1077 
Hypophysis,  917 

posthypophysis,  917 
prehypophysis,  917 
Hyposylvian  ramus,  925 
rlypotnalamus,  867 

optic      portion      of,     external 

morphology  of,  917 
hypophysis,  917 
optic  tract,  917 


Hypothalamus,  optic  portion  of, 

terma,  917 
tuber,  917 

Hypothalamic     tegmental     sub- 
stance, 915 

Hyrtl,  exsanguinated  renal  zone 
of,  680,  1432 


ILEO-APPENDICULAR     fold,     1272 

fossa,  1272 
Ileo-caecal  fossa,  1272 
valve,  1315 

fraenulum  of,  1316 
Ileo-colic  artery,  677 
fold,  1272 
fossa,  1272 
Ileum,  1297 
Iliac   arteries,    circumflex,   deep, 

698 

superficial,  704 
common,  683 

branches  of,  683 
compression  of,  685 
peculiarities  of,  684 
surface  marking  of,  684 
surgical  anatomy  of,  684 
external,  695 
branches  of,  697 
surface  marking   of,  684, 

696 

surgical  anatomy  of,  696 
internal,  685 

branches  of,  687 
peculiarities  of,  686 
surface  form  of,  695 
surgical  anatomy  of,  687 

695 

bursa,   subtendinous,   333 
fascia,  510 
fossa,  216 
furrow,  222 
glands,  795 
common,    796 
external,  795 
internal,  796 
nerve,  1017 

portion  of  fascia  lata,  1540 
region,  muscles  of,  510 

surgical  anatomy  of,  513 
vein,  circumflex,  deep,  759 
common,  764 
external,  759 
internal,  760 
Iliacus  muscle,  512 
tlio-capsularis  muscle,  513 
Ilio-coccygeus  muscle,  456 
Qio-costalis  muscle,  421 
tlio-femoral  ligament,  330 
[lio-hypogastric  nerve,  1017 
[lio-inguinal  nerve,  1018 
Qio-lumbar  artery,  694 
ligament,  293 
veins,  764 

[lio-pectineal  bursa,  332 
eminence,  217,  220 
ligament,  510 
line,  216 

[lio-pelvic  glands,  795 
flio-sciatic  notch,  217 
;iio-tibial  band,  237,  516 
;iio-trochanteric  ligament,  331 
Ilium,  215 

borders  of,  217 
crest  of,  216 
dorsum  of,  215 
processes  of,  217 
spine  of,  217 
surfaces  of,  217,  216 


1582 


INDEX 


Ilium,  venter  of,  216 
Impar  ganglion,  1078 
Impression,  deltoid,  181 

gastric,  1340 

Incisive  fossa,  106,  123,  139 
Incisor  canal,  110 
crest,  111 
foramina,  110 
nerve,  1053 
teeth,  1206 

Incisura  cardiaca,  1401 
inter-arytsenoidea,  1376 
pancreatis,  1355 
Incisures      of      Schmidt-Lauter 

mann,  824 

Incremental  lines  of  dentine,  121 
Incus,  1169 
body  of,  1169 
ligaments  of,  1171 
processes  of,  1169 
Indices  of  skull,  147 
Indusium,  938,  940 
Infantile  hernia,  1535 
Inferior  acromio-clavicular  liga 

ment,  301 

alveolar  artery,  616 
branch    of    superior    cervica 

ganglion,  1084 
calcaneo-scaphoid       ligament 

356 

cardiac  nerve,  1086 
carotid  triangle,  618 
cerebral  veins,  735 
cervical-ganglion,  1086 
constrictor  muscle,  402 
coronary  artery  of  lip,  609 
dental  artery,  616 
canal,  124 
foramen,  124 
nerve,  1053 
ethmoidal  turbinate  bone,  101 
external  frontal  artery,  630 
gemellus  muscle,  530 
gluteal  artery,  694 
line,  216 
nerve,  1027 

hajmorrhoidal  artery,  691 
nerve,  1028 
plexus,  1095 
veins,  760 

internal  frontal  arteries,  628 
labial  artery,  609 
lachrymal  gland,  1151 
laryngeal  artery,  643 

veins,  751 
lateral  angle,  63 
lingualis  muscle,  401 
longitudinal  fasciculus,  962 

sinus,  738 
maxilla  bone,  122 

horizontal  portion  of,  122 
maxillary    bone,    articulations 

of,  125 
attachment  of  muscles  to, 

125 

development  of,  125 
horizontal  portion  of,  bor- 
ders of,  124 
perpendicular  portion  of, 

124 

borders  of,  124 
processes  of,  125 
surfaces  of,  124 
nerve,  1050 
meatus  of  nose,  145 
medullary  velum,  901 
mesenteric  artery,  679 
plexus,  1094 
vein,  768 
nuchal  line,  72 
obliquus  oculi  muscle,  376 


Inferior  occipital  fissure,  931 

fossae,  133 
olivary  nucleus,  885 
ophthalmic  vein,  741 
orbito-palpebral  sulcus,   1147 
palatine  artery,  608 
pancreatico-duodenal     arter 

677 

petrosal  sinus,  742 
phrenic  arteries,  682 

veins,  767 

profunda  artery,  658 
pubic  ligament,  298 
pudendal  nerve,  1028 
pyloric  artery,  675 
radio-ulnar  articulation,  317 
ramus  of  ischium,  218 

of  pubis,  220 
rectus  oculi  muscle,  375 
renal  artery,  1432 
sacro-seiatic  foramen,  296 
stephanion,  76,  150 
sterno-pericardiac    ligament, 

560 

superficial  cerebellar  veins,  73 
tarsal  arch,  625 
thyroid  artery,  643 

veins,  751 

transverse  ligament,  304 
turbinated  bone,  119 

articulations  of,  120 
borders  of,  120 
development  of,  1 20 
processes  of,  120 
surfaces  of,  120 
crest,  107,  117 
vena  cava,  764.     See  Postcava 
vesical  artery,  688 

plexus,  762 
vocal  cords,  1378 
.nflected  fissure,  928 
infraclavicular  plexus,  790 
nfracommissure  of  Gudden,  91f 
nf  racostales  muscle,  427 
nfraglenoid  margin  of  tibia,  237 

tubercle,  176 
^nfrahyoid  artery,  604 

region,  muscles  of,  393 
^nfralaryngeal  glands,  785 
nframandibular  nerve,  1064 
nframaxillary  glands,  781 

nerve,  1064 
nfraorbital  artery,  617 
canal,  107,  140 
foramen,  106,  140 
groove,  107,  141 
nerves,  plexus  of,  1063 
nfrapatellar  bursa,  342 
nfraspinatus  bursa,  307 
fascia,  474 
muscle,  474 

bursa  of,  475 
nfraspinous  fossa,  174 
nfrasternal  depression,  166 
nfratemporal  crest,  95 

fossa,  138 

iifratrochlear  nerve,  1045 
nfundibula  of  kidney,  1424 
nfundibular  artery,  593 

recess  of  third  ventricle,  917 

nfundibuliforni  fascia,  448,  1475 

nfundibulo-pelvic  ligament,  1502 

nfundibulum  of  brain,  917 

of  ethmoid,  101 

of  Fallopian  tube,  1510 

of  heart,  571 

ngrassias,  processes  of,  96 
nguinal  canal,  450,  1529 
fossa,  1258 

external,   1532 
internal,  1532 


Inguinal  fossa,  middle,  1332 
hernia,  1532 
direct,  1535 

-  incomplete,  1536 
oblique,  1529,  1532 
lymphatic  gland,  deep,  794    . 
superficial,  791 

surgical     anatomv     of 

794 

region,  1243 
Inion,  71,  150 
Inlet  of  pelvis,  209 
Inner  condyle  of  femur,  228 
Innominate  artery,  596 
branches  of,  596 
peculiarities  of,  597 
surgical  anatomy  of   597 
bone,  213 
vein,  750 
left,  750 
right,  750 

Inosculation  of  arteries,  585 
Insertion  of  muscles,  366 
Inspiration,  muscles  of  434 
Insula,  933 
apex  of,  933 
development  of,  925 
fissure  of,  933 
pole  of,  933 

Integument  of  scrotum,  1473 
Inter-alveolar  cell  islets,  1359 
Interarticular  chondro-sternal 

ligament,  290 
fibro-cartilage,  283,  300,  302 

triangular,  317 
ligament,  286,  331 
sterno-costal  ligament,  290 
Interauricular  furrow,  567 

septum,  567 
Inter-brain,  911 
Intercalatum,  907 
Intercarotid  body,  602 
Intercavernous  sinus,  742 
Intercellular     biliary     passages, 

1348 
Intercerebral  cleft,  921 

fissure,  921 

Interchondral  articulations,  291 
ligament,  external,  292 

internal,  292 

[nterclavicular  ligament,  300 
Intercolumnar  fascia,  438,  ]  474 

1526 

fibres,  438 

!ntercondyloid  notch,  227 
intercostal  arteries,  669 
anterior,  646 
collateral,  670 
superior,  647 
surgical  anatomy  of,  670 
fascia,  426 
glands,  807 
muscles,  427 
external,  427 
internal,  427 
nerves,  1011 

abdominal,  1013 
first,  1011 
pectoral,  1011 
surgical  anatomy  of,  1014 
space,  156,  161 
veins,  752 
anterior,  752 
posterior,  752 
superior,  left,  752 

right,  752 

ntercosto-humeral  nerve,  1013 
ntercrural  space,  904 
iterglobular  spaces  of  Czermak, 
1212 


INDI:X 


Interlobar  arteries,  1432 

lU.Mires,  924 
Interlobular  biliary  plexus,  1345 

ducts,  1349 

Inter-maxillary  bone,  110 
region,  muscles  of,  381 
suture,  139 

Intenuecliul  Insure,  931 
Intermediate    dorsal    cutaneous 

nerve,  1034 
glands,  790 
zone  of  kidney,  1424 
Intormedio-lateral  tract  of  cord, 

853 
Internal    abdominal    ring,    448, 

1530 

angular  process,  80,  140 
annular  ligament,  545 
anterior  thoracic  nerve,  1001 
arcuate  ligament,  429 
auditory  artery,  641 

meat  us,  133 
bicipital  ridge,  181 
branches   of  superior   cervical 

ganglion,  1084 
calcaneal  nerve,  1031 
calcanean  artery,  718 
calcaneo-astragaloid  ligament, 

354 

calcaneo-cuboid  ligament,  355 
calcaneo-scaphoid    ligament, 

356 

capsule,  955 
carotid  artery,  620 

foramen,  88 

plexus,  1083 

circumflex  artery  of  thigh,  70 
condyle  of  femur,  228 
crucial  ligament,  339 
cutaneous  nerve,  1003,  1021 
ear,  1173 
«picoiidyle,  182 
epigastric  artery,  697 
femoral  region,  muscles  of,  522 
iliac  artery,  685 

glands,  796 

vein,  760 

inguinal  hernia,  1532 
interchondral  ligament,  292 
Intercostal  muscle,  427 
jugular  glands,  785 

vein,  729 

bulb  of,  729 

lateral  ligament,  282,  312 
malleolar  artery,  718 
malleolus,  238 
mammary  artery,  645 

vein,  750 
maxillary  artery,  613 

lymphatic  glands,  781 

vein,  727 
•oblique  line,  123 

muscles,  439, 1528 
•occipital  crest,  74,  133 

protuberance,  73 
•orbital  arteries,  628 
«s,  1500 

palpebral  arteries,  625 
plantar  artery,  718 

nerve,  1031 
popliteal  nerve,  1030 
pterygoid  muscle,  386 

nerve,  1051 

plate,  96 

pudic  artery  in  female,  693 
in  male,  690 

vein,  760 

rectus  oculi  muscle,  375 
respiratory  nerve  of  Bell,  992 
saphenous  nerve,  1022 

vein,  756 


Internal  semiluiiarfibro-cartilage 

340 

spermatic  fascia,  448 
sphincter  am  muscle,    \~>:\ 
structure  of  cerebellum,  899 
supracondylar  ridge,  1S1 
tarsal  ligament,  372 
tuberosity  of  tibia,  236 
wall  of  tympanum,  1162 
Internasal  suture,  139 
Interneural  articulations,  274 
Internoclia  or  phalanges,  206 
Interossei  muscles  of  foot,  551 
dorsal,  551 
plantar,  551 
of  hand, 501 

Interosseous  artery  of  ulnar,  664 
anterior,  664 
posterior,  665 
arteries,  dorsal,  661,  715 

palmar,  662 
ligament,  288 
nerve,  anterior,  1004 
dorsal,  1008 
posterior,  1008 
volar,  1004 

sacro-iliac  ligament,  294 
veins  of  forearm,  747 
Tnterpalpebral  slit,  1148 
Interparietal  sulcus  of  Turner, 

930 

suture,  127 

Interpeduncular  ganglion,  908 
Interpleural  space,  1396 
Interpubic  disk,  298 
Intersigmoid  fossa,  1319 
Interspinales  muscle,  423 
Interspinous  ligaments,  275 
Intersternal    ligament,    anterior, 

292 

posterior,  292 

Intertransversales  muscle,  424    [ 
laterales  muscle,  424 
mediates  muscle,  424 
Intertrarisverse    ligaments,    275, , 

297 
Intertrochanteric   line,    anterior, 

225 

posterior,  225 
Intertubular     cell-masses,     1359 

tissue,  1213 
Interventricular  grooves,  570 

of  heart,  567 
septum,  571 

Inter  vertebral  disks,  272 
fibro-cartilages,  272 
foramina,  49 
grooves,  49 
notches,  49 
substances,  272 
veins,  755 

Intestinal  glands,  1303,  1327 
Intestine,  large,  1307 

areolar  coat  of,  1325 
arteries  of,  1327 
flexure  of,  hepatic,  1308 
sigmoid,-1308 
splenic,  1308 
lymphatic    glands    of,    806, 

1328 

vessels  of,  806 
mucous  membrane,  1326 
muscular  coat  of,  1324 
serous  coat  of,  1324 
structure  of,  1324 
submucous  coat  of,  1325 
veins  of,  1328 
innervation  of,  1330 
movements  of,  1330 
small,  1290 

areolar  coat  of,  1298 


Intestine,  small,  arteries  of,  1304 
lymphatic    ghuids    of,    805, 

1305 

vessels  of,  806 

mucous  membrane  of,  1298 
muscular  coat  of,  1298 
nerves  of,  1307 
serous  coat  of,  1298 
|          structure  of,  1298 

submucous  coat  of,  1298 
veins  of,  1305 
villi  of,  1300 
surface  form  of,  1331 
surgical  anatomy  of,  1331 
Intestinurn    tenue    mesenteriale, 

1297 

liitracapsular  fracture,  232 
Intracartilaginous  ossification,  43 
L  ntraepithelial  plexus,  1121 
Intralobular  veins,  767 
Intramembranous  ossification,  43 
Intraspinal  venous  plexuses,  732 
Intrathyroid  cartilage,  1371 
Intrinsic  muscles  of  tongue,  400 
Intumescentia     ganglioformis, 

1059 

Involuntary  muscles,  363 
Iris,  1127 

arteries  of,  1130 
muscular  fibres  of,  1128 
nerves  of,  1130 
pigment  of,  1129 
stroma  of,  1128 
structure  of,  1128 
Iregular  bones,  34 
Ischiatic  lymphatic  glands,  795 
Ischio-capsular  ligament,  330 
Ischio-gluteal  bursa,  333 
Ischio-rectal  fascia,  456,  1558 
fossa,  1548 
region,  muscles  of,  451 

surgical  anatomy  of,  1547 
Ischium,  217 
body  of,  217 
ramus  of,  ascending,  218 

descending,  218 
spine  of,  218 
tuberosity  of,  218 
Island  of  Langerhans,  1359 

of  Reil,  933 
Isthmus,  aortic,  593 
of  auditory  canal,  1158 
of  Fallopian  tube,  1510 
of  fauces,  1222 
faucium,  1204 
gyri  hippocampi,  932 
of  pharynx,  1231 
of  prostate  gland,  1461 
rhombencephali,  869 
of  thyroid  gland,  1409 
Iter  chorda;  anterius,  1162 

posterius,  1161 
Ivory  of  teeth,  1212 


JACOB'S  membrane,  1136 
Jacobsori,  cartilage  of,  1107 
eminence  of,  1110 
nerve,  1067 

canal  for,  90 

organ  of,  rudimentary,  1110 
Jaw,  angle  of,  124 

lower,  articulations  of,  282 
changes  produced  in,  by  age, 

125 

upper.      See    Maxillary    bone. 
Jejunum,  1297 
Joints.     See  Articulations. 
Jugular  foramen,  73,  133 


1584 


INDEX 


Jugular  fossa,  91 
ganglion,  1066 
glands,  internal,  785 
lymphatic,  trunk,  785 
nerve,  1083 
process,  73 
tubercle,  74 
vein,  anterior,  728 
external,  728 

sinus  of,  728 
internal,  729 
bulb  of,  729 
sinus  of,  729 
surgical  anatomy  of,  732 
posterior  external,  728 
Juxta-aortic  glands,  left,  798 

right,  797 

Juxta-cervical    lymphatic    knot, 
801 


KERKRING,  valves  of,  1299 
Key    and    Retzius,    foramen    of, 

859,  978 
Kidneys,  1418 

abnormalities  of,  1433 

areas  of,  1422 

arteries  of,  1432 

borders  of,  1423 

calices  of,  1424 

capsule  of,  fatty,  1419 
true,  1423 

connective  tissue  of,  1433 

cortical  substance  of,  1424 

ducts  of,  1429 

hilum  of,  1423, 

horseshoe,  1433 

infundibula  of,  1424     ^ 

intermediate  zone  of,  1424 

lymphatic  vessels  of,  802,  1433 

Malpighian  bodies  of,  1426 
capsule,  1426 
tuft  of,  1426 

medullary  substance  of,  1425 

minute  anatomy  of,  1426 

nerves  of,  1433 

papillae  of,  1425 

pelvis  of,  1424 

pyramids  of  Ferrein,  1425 
of  Malpighi,  1425 

sinus  of,  1423 

structure  of,  1423 

surface  form  of,  1434 

surfaces  of,  1420 

surgical  anatomy  of,   1434 

tubuli  uriniferi,  1429 

variations  of,  1433 

veins  of,  1433 
Knee,  bursse  of,  342 

ligaments  of,  337 
Knee-cap,  233 
Knee-joint,  surface  form  of,  345 

surgical  anatomy  of,  345 
Kohn,    epithelial    corpuscles   of, 

1412 
Kolliker,  commissure  of,  919 

membrane  of,  1185 
Krause,  ellipsoid  of,  1137 

end-bulbs  of,  826,  830 
Kiihne,  muscle-spindle  of,  830 


LABIA  pudendi  majora,  1489 

minora,  1490 
Labial  artery,  inferior,  609 

glands,  1204 

nerves,  1048 
Labium  tympanicum,  1182 


Labium  vestibulare,  1182 
Labyrinth,  1173 
arteries  of,  1186 
membranous,   1 1 79 
nerves  of,  1186 
osseous,  1174 
veins  of,  1186 

Lachrymal  apparatus,  1151 
artery,  624 

peculiarities  of,  625 
bone,  112 

articulations  of,  113 
attachment    of    muscles    to, 

113 

borders  of,  113 
crests  of,  141 
development  of,  113 
lesser,  113 
surfaces  of,  113 
canaliculi,  1152 
canals,  1152 
caruncle,  1152 
crest,  113 
fossa,  81 
glands,  1151 

structure  of,  1151 
surface  form  of ,  1152 
surgical  anatomy  of,  1154 
groove,  107,  109,  141,  143 
nerve,  1043 
notch, 107 
papilla,  1148,  1152 
process  of  inferior  turbinated, 

120 
sac,  1152 

surface  form  of,  1152 
surgical  anatomy  of,  1153 
sulcus,  113 
tubercle,  109 
Lactiferous  duct,  1518 
Lacuna  magna,  1453 
Lacuna;,  1120 
of  bone,  38 
Howship's,  38 
Lacus  lacrimalis,  1148 
Lagena,  1182 

Lalouette,  pyramid  of,  1409 
Lambda,  129,  150 
Lambdoid  suture,  75,  78,  123 
Lamella  of  bone,  articular,  251 
Lamellated  corpuscles,  830 
Lamina  basalis,  1124 
of  brain,  dorsal,  870 

ventral,  870 
of  cornea,  1119 
cribrosa,  89 
cribriform,  1118 

of  sclerotic,  1118 
dental,  1215 

of  ethmoid,  horizontal,  99 
perpendicular,  100 
vertical,  100 
fusca,  1118 
periclaustral,  954 
reticularis,  1185 
spiralis  ossea  of  cochlea,  1177 
suprachorioidea,  1122 
vasculosa,  1122 
of  vertebra,  34 
Lancisi,  nerve  of,  940 
Landzert,  fossa  of,  1271 
Langer,  foramen  of,  466,  648,  790 

lines  of  cleavage  of,  1190 
Langerhans,    centro-acinar    cells 

of,  1359 
islands  of,  1359 
Large,  deep  petrosal  nerve,  1049 

1083 

intestine,  1307 
palatine  nerve,  1049 
superficial  petrosal  nerve,  1048 


Laryngeal  artery,  inferior,  643 

superior,  605 
nerve,  superior,  1071 
external,  1071 
internal,  1071 
pouch,  1379 
saccule,  1379 
sinus,  1379 

surface  of  epiglottis,  1373 
veins,  751 
Larynx,  1369 

aperture  of,  superior,  1376 
arteries  of,  1383 
cartilages  of,  1380 
cavity  of,  1376 
compartments  of,  1376 

lower,  1379 
.    middle,  1377 
glands  of,  1382 
joints  of,  1374 
ligaments  of,  1374 
lymphatics  of,  782,  1383 
membranes  of,  1374 
mucous  membrane  of,  1382 
muscles  of,  1379 
nerves  of,  1384 
rima  glottidis,  1377 
structure  of,  1373 
veins  of,  1383 
ventricle  of,  1379 
vocal  cords  of,  false,  1378 

true,  1377 

Lateral  angle,  inferior,  63 
area  of  oblongata,  876 
calcaneal  nerves,  1031 
cell  column,  846 
cerebro-spinal  fasciculus,  853 
column  of  spinal  cord,  840 
fissures  of  cord,  845 
horn-cells  of  cord,  856 
ligament,  external,  282 

internal,  282 

of  liver,  1341 

of  wrist,  320 
masses  of  atlas,  51 

of  ethmoid,  100 
occipital  fissure,  931 
odontoid  ligaments,  280 
patellar  ligaments,  337 
phreno-pericardial     ligaments, 

561 

plantar  nerve,  1032 
region  of  skull,  136 
sacral  artery,  694 

veins,  760 

sacro-coccygeal  ligament,  297 
sinus,  738 

surgical  anatomy  of,  739 
spinal  arteries,  640 
surface  of  liver,  1336 
thoracic    region,    muscles    of, 

471 

ventricle  of  brain,  941 
body  of,  941,  943 
cells  of,  941 
choroid  plexus  of,  943 
cornua  of,  941 
vertebral    region,    muscles    of, 

410 
vestibulo-spinal  tract  of  cord, 

853 

Lateralis  nasi  artery,  609 
Latissimus  dorsi  muscle,  415 

bursa  of,  476 
Leaf,    intercondyloid    glands    of. 

794 

supracondyloid  glands  of,  794 
Left  bronchus,  1386 
cardiac  vein,  771 
colic  artery,  680 

plexus,  1095 


INDEX 


1585 


Left  coronary  artery,  593 
plexus,  1090 
vein,  770 

fore-chamber  of  heart,  570 
gastro-epiploic  plexus,  1094 
innominate  vein,  750 
juxta-aortie  glands,  798 
lobe  of  liver,  1340 
lower  azygos  vein,  753 
marginal  vein,  771 
superior  intercostal  vein,  7.YJ 
upper  azygos  vein,  753 
Leg,  arteries  of,  710 
bones  of,  233 
fasciae  of,  534 
ligaments  of,  327 
muscles  of,  534 
nerves  of,  1019 
veins  of,  755 

Lemnisci,  decussation  of,  882 
Lens,  crystalline,  1140 
epithelium,  1140 
fibres,  1140 

suspensory  ligament  of,  1139 
Lenticula,  867,871,954 
Lenticular  ganglion,  1040 
Lenticulo-striate  arteries,  630 
Lesser  internal  cutaneous  nerve 

1003 

omentum,  1264 
sacro-sciatic  foramen,  296 

ligament,  295 
sciatic  nerve,  1027 
wing  of  sphenoid,  96 
Levator  anguli  oris  muscle,  379 

scapula?  muscle,  416 
ani  muscle,  453 

preanal  fibres  of,  455 
glandulse     thyroidea?    muscle 

1409 

labii  inferioris  muscle,  380 
superior  alaeque  nasi  muscle, 

378 

superioris  muscle,  379 
menti  muscle,  380 
palati  muscle,  405 
palpebrse  muscle,  373 

superioris  muscle,  375 
prostatae,  456 
urethra?,  456 

Levatores  costarum  muscle,  428 
Lieberkiihn,  crypts  of,  1303 

glands  of,  1303,  1327 
Lieno-renal  ligament,  1261,  1362 
Ligamenta  alaria,  342 

sacro-coccygea,  anterior,  454 
subflava,  274 

suspensoria  of  mamma,  465 
Ligamentous  action  of  muscles, 

270 
Ligaments,  263 

accessory,  of  atlas,  278 

of  acetabulum,  transverse,  332 

acromio-clavicular,    inferior, 

301 

superior,  301 
of  ankle,  349 
anmilar,  anterior,  544 
external,  545 
internal,  545 
of  radius,  316 
of  stapes,  1171 
anterior  common,  271 
longitudinal,  271 
superior,  287 
appendiculo-ovarian  of  Clado, 

1312 

arcuate,  external,  429,  451 
internal,  429 
middle,  429 
astragalo-scaphoid,  356 

100 


Ligaments,    atlanto-axial,     ante- 
rior, 276 

posterior,  277 
atlo-axoid,  anterior,  276 

posterior,  277 
of  axilla,  suspensory,  466 
of  Bertin,  330 
of  Rigelow,  330 
of  bladder,  false,  1446 

true,  1445 
broad,  of  liver,  1340 

of  uterus,  1502 
calcaneo-astragaloid,  external, 
354 

internal,  354 

posterior,  354 
calcaneo-cuboid,  internal,  355 

long,  355 

short,  355 

superior,  355 
calcaneo-navicular,  355 
calcaneo-scaphoid,    external, 
355 

inferior,  356 

internal,  356 

superior,  355 
capsular.     See    Individual 

joints. 

carpo-metacarpal,  323 
of  carpus,  321 
check,  280,  1115 
chondro-sternal,  anterior,  290 

interarticular,  290 

posterior,  290 
chondro-xiphoid,  anterior,  290 

posterior,  290 
ciliary,  1126 
of  Cloquet,  1476,  1477 
coccygeal,  857 
Colles',  439 
conoid,  302 
of  Cooper,  439,  450 
coraco-acromial,  303 
coraco-clavicular,  302 
coraco-humeral,  306 
coracoid,  304 
costo-clavicular,  300 
costo-coracoid,  469 
costo-transverse,  long,  287  • 

middle,  288 

posterior,  288 

costo- vertebral,  anterior,  286 
costo-xiphoid,  anterior,  290 

posterior,  290 
cotyloid,  331 
crico-arytenoid,  1375 
crico-tracheal,  1376 
cruciform,  277 
deltoid,  350 
dentate,  860 

dorsal.     See  Individual  joints, 
duodeno-mesocolic,  1271 
duodeno-renal,  1264 
of  elbow,  anterior,  311 

posterior,  311 
femoral,  517 
of  fingers,  324 

superficial,  transverse,  496 
Flood's,  306 
of  foot,  544 

fundiform  of  Retzius,  544 
gastro-splenic,  1266 
Gimbernat's,  439,  1527 
gleno-humeral,  307 
glenoid,  176,  307 

of  Cruveilhier,  361 
glosso-epiglottic,  1374 
of  hand,  321 
of  Helmholtz,  1170 
of  Henle,  440,  444 
hepato-colic,  1264 


Ligaments,  hepato-duodenal,  1204 
nepato-gMtric,  1264 
of  Hesselbach,  440,  444,  1529 
of  Hey,  517 
of  hip',  328 
hyo-epiglottic,  1373 
ilio-femoral,  330 
ilio-lumbar,  293 
ilio-pectirieal,  510 
ilio-troL-hanteric,  331 
of  incus,  1171 
infundibulo-pclvic,  1502 
interarticular,  28(3,  331 
interchondral,  external,  292 

internal,  292 
interclavicular,  300 
interosseous.      See     Individual 

joints. 

interspinous,  275 
intersternal,  anterior,  292 

posterior,  292 
inter  trans  verse,  275,  297 
intervertebral,  272 
ischio-capsular,  330 
of  jaw,  282 
of  knee,  337 

alar,  342 

anterior,  347 

coronary,  342 

crucial,  339 

mucosum,  342 

posterior,  337 

transverse,  342 
of  larynx,  1374 

lateral.     See  Individual  joints, 
of  leg,  327 

lieno-renal,  1261,  1362 
of  liver,  1340 

coronary,  1341 

falciform,  1340 

lateral,  1341 

round, 1342 

suspensory,  1340 
lumbo-sacra'1,293 
of  Luschka,  560 
of  malleus,  1170 
of  Mayer,  1416 
metacarpal,  326 
metacarpo-phalangeal,  326 
metatarsal,  361 
metatarso-pharyngeal,  361 
nuchffi,  275,  415 
oblique,  316 
obturator,  298 
occipito-atlantal,  anterior,  278 

posterior,  278 
occipito-axial,  280 
odontoid,  lateral,  280 

middle,  281 
orbicular,  316 
orbito-tarsal,  1149 
of  ossicula,  1170 
palpebral,  1149 
of  patella,  337 
pelvis,  falciform,  295 

transverse,  461 
of  penis,  1469 

suspensory,  439 
perineal,  transverse,  461 
of  peritoneum,  1264 
of  phalanges  of  foot,  361 

of  hand,  327 
phreno-colic,  1268 
phreno-pericardial,  561 
plantar,  long,  355 

short,  355 
posterior  common,  272 

longitudinal,  272 
Poupart's,  438,  1527 
pterygo-mandibular,  383 
pterygo-maxillary,  383 


1586 


INDEX 


Ligaments,  pubic,  anterior,  298 
inferior,  298 
posterior,  298 
superior,  298 
pubo-capsular,  330 
pubo-femoral,  330 
pubo-prostatic,  1445,  1461 
pubo-vesical,  1445 
radio-carpal,  320 
radio-ulnar,  annular,  316 

anterior,  317 

oblique,  316 

orbicular,  316 

round,  316 

posterior,  317 
rhomboid,  300 
sacro-coccygeal,   anterior,   29( 

lateral,  297 

posterior,  296 
sacro-iliac,  anterior,  296 

interosseous,  294 

long,  294 

oblique,  294 

posterior,  294 

short,  294 
sacro-sciatic,  anterior,  295 

great,  294 

lesser,  295 

posterior,  294 
sacro-uterine,  1502 
sacro-vertebral,  293 
of  scapula,  303 
Srhlemm's,  307 
of  shoulder,  305 
spirio-glenoid,  304 
spiral,  of  cochlea,  1182 
spleno-phrenic,  1266 
sterno-clavicular,  anterior,  300 

posterior,  300 
sterno-costal,  anterior,  290 

interarticular,  290 

posterior,  290 
sterno-costo    pericardial,    560, 

561 

sterno-pericardiac,  560 
of  stapes,  1171 
of  sternum,  292 
stylo-hyoid,  397 
stylo-mandibular,  283,  389 
stylo-maxillary,  283 
subpubic,  298 
superior,  of  incus,  1171 
suprascapular,  304 
supraspinous,  275 
suspensory,  of  clitoris,  439 

of  eye,  1115 

of  lens,  1139 

of  liver,  1340 

of  mamma,  465 

of  ovary,  1513 

of  penis,  439 

of  Treitz,  1294 
sutural,  261 
synovial,  264 
tarsal,  external,  373 

internal,  373 
of  thumb,  323 
thyro-epiglottic,  1375 
thyro-hyoid,    1374 
tibio-tarsal,  anterior,  349 

posterior,  349 
transverse,  of  atlas,  277 

humeral,  307 

inferior,  304 

of  knee,  342 

superior,  of  scapula,  304 
trapezoid,  302 
tympano-malleolar,  1166 
utero-sacral,  1502 
of  uterus,  1501 

round, 1503 


Ligaments  of  vertebra?,  271 
vertebro-pericardial,  560 
vertebro-pleural,  1393 
vesico-uterine,  1502 
of  Winslow,  337 
of  Wrisberg,  341 
of  wrist,  320 
anterior,  320 
dorsal,  320 
lateral,  320 
posterior,  320 
volar,  320 

xipho-pericardial,  561 
Y-,  330 
of  Zinn,  375 
Ligamentum     arcuatum     exter- 

num,  429,  451 
internum,  429 
arteriosum,  589 
conjugate,  286 
corniculopharyngeum,  1376 
crico-pharyngeum,    1376 
epididymidis,  1480 
hepatoduodenale,  1260 
latum  pulmonalis,  1392 
mucosum,  342 
nuchse,  275,  415 
patella;,  337 

posticum  Winslowii,  337 
pulmonale,  1392 
spirale,  1182 
suspensorium,  281 
teres,  331 
ventriculare,  1374 
Light  stimuli,  path  of,  1137 
Limbic  lobe,  936 
Limbus  alveolaris,  124 
laminse  spiralis,  1182 
Limen  insula%  933 
Linea  alba,  446 
aspera,  226 
quadrati,  226 
Lina?  semilunares,  447 

transverse,  of  abdomen,  447 
Line,  gluteal,  anterior,  216 
inferior,  216 
posterior,  216 
ilio-pectineal,  216 
nuchal,  inferior,  72 

superior,  72 
temporal,  76,  80 
Lingual  artery,  605 
branches  of,  606 
deep,  606 

surgical  anatomy  of,  606 
bone,  155 
glands,  1101 
nerve,  1052,  1067 

branches  of,  1052 
region,  muscles  of,  398 
dissection  of,  399 
tonsil,  1096 
veins,  729 

Lingualis  muscle,  inferior,  401 
superior,  401 
transverse,  401 
vertical,  401 
Lingula,  93,  282,  897 

pulrronis,  1392 
Lips,  1204 

surgical  anatomy  of,  1234 
Liquor  Cotunnii,  1174 
Lissauer,  tract  of,  851 
Little  brain,  895 
Littre,  glands  of,  1453 
Liver,  1334 

abnormalities  of,  1342 
accessory,  1342 
areolar  coat  of,  1345 
arteries  of,  1343 
development  of,  1253 


Liver,  ducts  of,  1348 

excretory  apparatus  of,  1349 
fibrous  coat  of,  1345 
fissures  of,  1338 
hepatic  arteries,  1343 
ducts,  1343 
vein,  1344 
ligaments  of,  1340 
lobes  of,  1339 
lobules  of,  1345 
lymphatics  of,  802,  1349 
margins  of,  1337 
movability  of,.  1342 
nerves  of,  1349 
portal  vein,  1343 
serous  coat  of,  1345 
structure  of,  1345 
support  of,  1342 
surface  relations  of,  1353 
surfaces  of,  1336 
surgical  anatomy  of,  1354 
veins  of,  1343 
Lobe  or  lobes  of  brain,  923 
central,  933 

of  cerebellum,  896,  897,  898 
cerebral,  923 
frontal,  926 

fissures  of,  926 
gyres  of,  929 
of  kidney, 1423 
limbic,  936 
of  liver,  1339 
of  lungs,  1403 
occipital,  931 
fissures  of,  931 
gray  substance  of,  959 
olfactory,  934 
orbital,  926 
parietal,  930 
fissures  of,  930 
gyre  of,  931 
of  prostate  gland,  1461 
temporal,  931 
fissures  of,  931 
gyres  of,  932 
of  testicle,  1482 
of  thymus  gland,  1414 
of  thyroid  gland,  1409 
Lobule  of  ear,  1155 
of  kidney,  1423 
of  liver,  ~1345 
of  lungs,  1404 
of  mamma,  1518 
Lobuli  testis,  1482 
Locus  cseruleus,  880 
Long  bones,  33 

calcaneo-cuboid  ligament,  355 
ciliary  arteries,  627 

nerves,  1045 
plantar  ligament,  355 
sacro-iliac  ligament,  294 
saphenous  nerve,  1022 

vein,  756 

scrotal  nerve,  1028 
subscapular  nerve,  1002 
thoracic  artery,  653 
nerve,  lOOO' 
vein,  748 

Longissimus  dorsi  muscle,  421 
Longitudinal  fibres  of  cord,  848 

of  pons,  887 
sinus,  inferior,  738 

superior,  78, 130,  736 
zones  of  brain,  870 
Longus  capitis  muscle,  408 

colli  muscle,  409 
Looped  tubes  of  Henle,  1428 
Louis,  angle  of,  157 
Lowenthal's  tract  of  cord,  854 
Lower  deep  cervical  glands,  785 
extremity,  arteries  of,  698 


INDEX 


1587 


Lower    extremity,     articulations 

of,  327 
bones  of,  208 
fasciae  of,  509 
ligaments  of,'  327 
lymphatic  vessels  of,  794 
deep,  795 
superficial,  795 
muscles  of,  509 

surface  form  of,  552 
surgical  anatomy  of,  554 
nerves  of,  1019 
veins  of,  7-V> 
deep,  758 
superficial,  756 
jaw,  articulation  of,  282 
subscapular  nerve,   1001 
Ludovic,  angle  of,  .157 
Lumbar  arteries,  682 

enlargement  of  spinal  cord,  836 
fascia,  418 
ganglia,  1089 
glands,  797 
nerves,  1015 

divisions  of,  dorsal,  1015 

ventral,  1015 
roots  of,  1015 
plexus,  1016 
branches,  1017 
surgical  anatomy  of,  1034 
portion    of    gangliated     cord, 

1089 

region,  1243 
veins,  765 

ascending,  753,  765 

right,  752 
vertebra:,  56 
body  of,  56 
fifth,  57 
laminae  of,  56 
pedicles  of,  56 
processes  of,  57 
Lumbo-iliac  ligament,  293 
Lumbo-inguinal  nerve,  1018 
Lumbo-sacral  ligament,  293 

plexus,  1015 
Lumbricales  muscle,  foot,  549 

hand, 501 
Lungs,  1398 

air-cells  of,  1403 
apex  of,  1398 
arteries  of,  1404 
base  of,  1398 
borders  of,  1400 
bronchus  of,  1403 
capillaries,  1404 
color  of,  1402 
fissures  of,  1402 
foetal,  1402 
lobes  of,  1403 
lobules  of,  1404 
lymphatics  of,  1405 
nerves  of,  1405 
parenchyma  of,  1403 
root  of,  1402 
serous  coat  of,  1403 
structure  of,  1403 
subserous  areolar  coat  of,  1403 
svibstance  of,  1402 
surface  form  of,  1405 
surfaces  of,  1400,  1402 
surgical  anatomy  of,  1406 
veins  of,  1405 
weight  of,  1402 
Lunula  of  nails,  1195 
Luschka,  foramen  of,  881 ,  978 
gland  of,  1417 
ligament  of,  560 
Luys,  body  of,  915 

centrum  medianum  of,  914 
Lymph  canalicular  system,  772 


Lymph-capillaries,  772 
Lymph-glands,  parotid,  1225 
Lymph-nodes,  774 
Lymph-spaces,  772 
perivascular,  772 
Lymphatic  or  lymphatics,  772 
of  arm,  787 
of  arteries,  588 
of  bone,  41 
of  cranial  region,  778 
duct,  right,  777 

tributaries  of,  778 
of  dura  of  brain,  974 
extracranial,  778 
of  face,  778 
glands,  774 

of  abdomen,  195 
abdomino-aortic,  797 
along     mesenteric     arteries, 

798 

of  anus,  807 
axillary,  787 
brachial,  787 
bronchial,  1389 
buccal,  781 
buccinator,  781 
carotid,  785 
cervical,  deep,  785 

superficial,  783 
of  Cloquet,  794,  795 
coeliac,  798 
colic,  806 

condyloid  of  Leaf,  794 
connected  with  coeliac  axis 

and  branches,  798 
diaphragmatic,    808 
epigastric,  superior,  800 
of  face,  778 
femoral,  deep,  794 
gastric,  798 
genial,  781 
gluteal,  794 

hsemorrhoidal,  middle,  796 
of  head, 778 
hepatic,  798 
hypogastric,  796 
iliac,  795 

common,  796 

external,  795 

internal,  796 
ilio-pelvic,  795 
infralaryngeal,  785 
inframaxillary,  781 
inguinal,  deep,  794 

superficial,  791 
intercostal,  808 
intermediate,  790 
of  intestine,  large,  806 

small,  805 
ischiatic,  794 
jugular,  external,  783 

internal,  785 
juxta-aortic,  left,  798 

right,  797 

of  lower  extremity,  791 
lumbar,  797 
malar,  781 

mammary,  internal,  807 
mastoid,  779 
maxillary,  internal,  781 
mediastinal,  anterior,  808 

posterior,  808 
middle,  of  Stahr,  784 
of  neck,  783 
obturator,  795 
occipital,  779 
paramammary,  811 
parietal,  807 
parotid,  779 

deep,  780 

superficial,  779 


Lymphatic  or  lymphatics  glands, 
pectoral,  788 

of  pelvis,  795 

peritracheo-bronchial,  809 

popliteal,  794 

post-pharyngeal,  784 

posterior     auricular     retro- 
auricular,  779 

pre-aortic,  797 

pre-auricular,  779 

prelaryngeal,  785 

pretracheal,  786 

rectal,  806 

retro-aortic,  798 

retro-crural,  795 

retro-pharyngeal,  784 

of  Rosenmiiller,  794 

sacral,  797 

saphenous,  external,  794 

scapular,  788 

splenic,  798 

sterno-mastoid,  785 

subclavian,  790 

submaxillary,  784 

submental,  784 

suboccipital,  779 

suborbital,  781 

subparotid,  781 

substerno-mastoid,  785 

supraclavicular,  785 

supraconclyloid    of     Leaf, 
794 

supra-epitrochlear,  787 

suprahyoid,  lateral,  784 
median,  784 

supramaxillary,  781 

supratrochlear,  787 

surgical  anatomy  of,  775 

of  thoracic  wall,  807 

tibial,  anterior,  794 

tracheal,  786 

of  upper  extremity,  787 
deep,  787 
superficial,  787 

visceral,  808 

zygomatic,  781 
pharyngeal  ring,  1234 
vessels  of  abdomen,  799 
walls  of,  deep,  799 
superficial,  799 

of  bile-ducts,  803 

of  bladder,  800 

cardiac,  812 

cerebral,  778 

of  cranial  region,  781 

of  face,  782 

of  Fallopian  tube,  801 

of  gluteal  region,  799 

of  head,  781 

of  heart,  580 

of  intestines,  large,  806 
small,  806  ' 

of  kidney,  802 

of  larynx,  782 

of  leg,  794 

of  liver,  802 

of  lower  extremity,  794 
deep,  795 
superficial,  795 

of  lung,  812 

meningeal,  778 

of  mouth,  782 

of  neck,  778,  786 

of  nose,  interior  of,  782 

of  oesophagus,  813 

of  ovary,  801 

of  pancreas,  804 

of  pelvis,  799 

of  penis,  799 

of  perineum,  799 

of  peritoneum,  800 


1588 


INDEX 


Lymphatic  or  lymphatics  vessels 

of  pharynx,  782 
pleural,  812 
of  prostate  gland,  800 
pulmonary,  812 
of  scrotum,  799 
of  seminal  vesicles,  802 
of  spleen,  804 
of  stomach,  804 
of  suprarenal  capsule,  802 
of  testicle,  802 
of  thoracic  trachea,  813 

wall,  810 
thymic,  813 
of  thyroid  gland,  782 
of  tongue,  782 
of  umbilicus,  799 
of  upper  extremity,  790 
deep,  790 
superficial,  790 
of  ureter,  802 
of  urethra,  female,  801 

male,  801 
of  uterus,  801 
of  vagina,  802 
of  vas  deferens,  802 
Lyra,  951 

M 

McBuRNEY's  point,  1311 
Macula  acustica  sacculi,  1180 
cribrosa,  1174 
lutea,  1138 

Magnum  of  carpus,  201 
Majendie,  foramen  of,  859,  881, 

978 
Malar  bone,  113 

articulations  of,  115 
attachment   of    muscles    to, 

115 

borders  of,  115 
development  of,  115 
processes  of,  114 
surfaces  of,  113 
canal,  114 
foramen,  113 
glands,  781 
nerve,  1046,  1062 
point  of  skull,  150 
process  of  superior  maxillary, 

109 
Male  breast,  1522 

surgical  anatomy  of,  1522 
organs  of  generation,  1457 
perinseum,  1549 
urethra,  1450 
Malleolar  artery,  713,  718 
Malleolus,  external,  241 

internal,  238 
Malleus,  1168 
handle  of,  1168 
head  of,  1168 
ligaments  of,  1170 
manubrium  of,  1168 
neck  of,  1168 
processes  of,  1168 
spur  of,  1168 

Malpighi,  pyramids  of,  1425 
Malpighian    bodies     of    kidney, 

1426 

of  spleen,  1365 
capsule,  1426 
layer  of  skin,  1192 
tuft,  1426 
Mamma,  1516 
areola  of,  1516 
arteries  of,  1520 
ligament  of,  suspensory,  465 
lobule  of,  1518 
lymphatics  of,  1520 


Mamma,  nerves  of,  1520 
variations  in,  1517 
veins  of,  1520 

Mammary  artery,  external,  653 
internal,  645 

branches  of,  646 
surgical  anatomy  of,  647 
glands,  1516 

description  of,  1516 
internal,  807 
lymphatics  of,  810 

surgical  anatomy  of,  811 
structure  of,  1518 
surgical  anatomy  of,  1520 
tissue,  prolongations  of,  1518 
vein,  internal,  750 
Mammillary  duct,  1518 

process  of  lumbar  vertebra,  57 
Mandible,  122 
Mandibular  artery,  616 
fossa,  84 
nerve,  1050 
region,  muscles  of,  380 
dissection  of,  380 
Manubrium  of  malleus,  1168 

of  sternum,  157 
Marchi  and  Lowenthal,  tract  of 

cord,  853 
Marginal  artery,  592 

fasciculus,  anterior,  854 
gyre,  931 
tract  of  cord,  851 
vein,  left,  771 
Marrow  of  bone,  36 
Marshall,  vein  of,  oblique,  771 

vestigial  fold  of,  563 
Martinotti,  nerve-cells  of,  960 
Masseter  muscle,  383 
Masseteric  artery,  616 
fascia,  383 
nerve,  1051 
vein,  727 
Mast-cells,  36 

Masto-occipital  suture,  75,  128 
Masto-parietal  suture,  128 
Mastoid  air-cells,  1163 
antrum,  87 
artery,  611,  612 
cells,  86 

foramen,  85,  138 
fossa,  86 

lymphatic  glands,  779 
nerves,  990 
process,  86,  138 
vein,  728 

Matrix  of  nails,  1195 
Maxillary  antrum,  orifice  of,  145 
artery,  external,  607 

internal,  613 
bone,  inferior,  122 

articulation  of,  125 
attachment  of  muscles  to, 

125 

development  of,  125 

horizontal  portion  of,  122 

borders  of,  124 

surfaces  of,  122 

perpendicular  portion   of, 

124 

borders  of,  124 
processes  of,  125 
surfaces  of,  124 
superior,  105 

articulations  of,  112 
attachment  of  muscles  to, 

112 
body  of,  105 

siu  faces  of,  106 
development  of,    112 
processes  of,  109 
hiatus,  107 


Maxillary  lymphatic   glands,  in- 
ternal,781 
nerve,  inferior,  1050 
superior,  1046 

branches  of,  1046 
process  of  inferior    turbinated 

bone,  120 
of  malar  bone,  115 
of  palate  bone,  118 
region,  superior,  muscles  of,  379 
sinus,  108 
tuberosity,  106 
vein,  internal,  727 
Mayer,  ligaments  of,  1416 
Meatus,    auditory,   external,   88, 

138,  1158 
internal,  89,  133 
of  nose,  inferior,  145 
middle,  145 
superior,  101,  144 
urinarius,  male,  1453 

female,  1492 
Meckel,  band  of,  1170 
cave  of,  973 
diverticulum,  1298 
ganglion,  1048 

branches  of,  1048 
Medial  accessory  olivary  nuclei, 

885 

calcaneal  nerve,  1031 
dorsal  cutaneous  nerve,  1034 
plantar  nerve,  1031 
Median  nerve,  1004 

branches  of,  1004 
vein,  745 
basilic,  746 
cephalic,  746 
cerebral,  735 
Mediastinal  arteries,  646 

posterior,  668 
glands,  anterior,  808 

posterior,  808 
pleura,  1394 

subpleural,  646 
space,  1396 
surface  of  lungs,  1399 
Mediastinum,  1396 
anterior,  1396 
arteries  of,  1397 
lymphatics  of,  1398 
middle,  1396 
posterior,  1396 
superior,  1396 
testis,  1482 
veins  of,  1398 
Medicerebellar  artery,  642 
Medicerebral  artery,  629 

branches  of,  629. 
veins,  735 
Medicornu,  945 
Medidural  artery,  615 

veins,  734 
Medifrontal  fissure,  927 

gyre,  929 

Medio-tarsal  joint,  352,  357 
Medipeduncles  of  cerebellum,  901 
Meditemporal  fissure,  932 

gyre,  932 
Medulla     oblongata,     874.     See 

Oblongata. 
Medullary  portion  of  suprarenal 

capsule,  1440 
of  thymus  gland,  1416 
sheath  of  Schwann,  824 
spaces  of  bone,  45 
substance  of  kidneys,  1425 
vela,  901 
velum,  901 

Medullated      axis-cylinder     pro- 
cesses, 824 
Medulli-spinal  veins,  755 


INDEX 


1589 


Megacephalic    skull,  capacity  of 

147 

Meibomian  glands,  1149 
structure  of,  1150 
surgical  anatomy  of,  1153 
Meissner      and       Wagner,      touch 

corpuscles  of,  830 
Membrana  basilaris,  1182 

cochlea  cluctus  cochlearis,  1 182 
elastica  laryngis,  1375 
flaccida  of  Shrapnell,  1166 
limitans  externa  of  retina,  1136 

interim,  1132 
nietitans,  1151 
pupillaris,  1'130 
quadrangularis,  1374 
sacciformis,  319 
tectoria,  1185 
tymparii,  1165 
arteries  of,  1167 
lymphatics  of,  1168 
nerves  of,  1168 
secundaria,  1177 
structure  of,  1167 
veins  of,  1167 
Membrane,  basilar,  1182 
Bowman's,  1119 
of  brain,  arachnoid,  976 

meningeal,  972 
of  Bruch,  1124 
of  choroid,  1122 
of  Corti,  1185 
costo-coracoid,  469 
crico-thyroid,  1375 
of  Demours,  1120 
of  Descemet,  1120 
fenestrated,  of  Henle,  587 
hyaloid,  1139 
hyo-thyroid,  1374 
of  Jacobs,  1136 
of  Kolliker,  1185 
Nasmyth's,  1214 
obturator,  528 
occipito-atlantal,  anterior,  278 

posterior,  278 
otolith,  1182 
of  Reissner,  1182 
of  Scarpa,  1162 
of  Shrapnell,  1166 
of  spinal  cord,  856 
arachnoid,  858 
surgical  anatomy  of,  860 
sutural,  236,  973 
synovial,  264 
tliyro-hyoid,  1374 
Membranous    canal    of    cochlea, 

1182 

cranium,  102 
labyrinth,  1179 
portion  of  urethra,  1451 
semicircular  canals,  1180 
Meningeal  artery,  611,  612 
anterior,  623 
middle,  615 

surgical  anatomy  of,  615 
posterior,  640 
small,  616 

lymphatic  vessels,  778 
membranes  of  brain,  972 
veins,  730,  734 
Meuinges  of  brain,  972 
Meningo-rachidian  veins.  754 
Meiiisco-femoral  joint,  344 
Menisco-tibial  joint,  344 
Meniscus,  283 
Mental  foramen,  123,  140 
nerve,  1053 
point  of  skull,  150 
process,  122,  140 
protuberance,  122 
spines,  123 


Mental  tubercles,  122 

.Merkel,     filtrum     ventriculi     of, 

1376 

Mesenrrphalon,  904 
Mesenteric  arteries,  glands  along, 
798 

artery,  inferior,  679 
superior,  677 

ganglion,  1094 

plexus,  inferior,  1094 
superior,  1094 

vein,  inferior,  768 

superior,  768 

Mesenterico-mesocolic  fold,  1271 
Mesenterico-parietal  fold,  1273 
Mesentery,  1266 

development  of,  1248 

glands,  805 

of  vermiform  appendix,  1269 
Meso-exo-gnathion  suture,  111 
Meso-gnathous    skull,    index    of, 

148 

Mesoappendix,  1269 
Mesoblastic  somites,  1245 
MesocEecum,  1309 
Mesncele,  907 
Mesochorium,  1471 
Mesocolic  area  of  kidney,  1422 

band,  1325 

fossa,  1271 
Mesocolon,  ascending,  1268 

descending,  1268 

sigmoid,  1269 

transverse,  1268,  1317 
Mesogastrium,  1248 
Mesognathion  suture,  111 
Mesophalic  skull,  capacity  of,  147 
Mesorbital  gyre,  928,  930 
Mesorectum,  1269 
Mesosalpinx,  1502 
Mesosternum,  157 
Mesovarium,  1502,  1512 
Metacarpal  bones,  202 

ligament,  transverse,  326 

spaces,  203 

Metacarpo-phalangeal      articula- 
tions, 326 

surface  form  of,  327 
Metacarpus,  202 

articulations  of,  206 

common  character  of,  202 

development  of,  207 

peculiar  characters  of,  203 
Metaplexuses,  881 
Metapore,  859,  881,  978 
Metasternum,  159 
Metatarsal  artery,  715 

bones,  252 
fifth,  254 
first,  252 
fourth,  254 

peculiar  characters  of,  252 
second,  252 
third,  253 

ligament,  transverse,  361 
Mctatarso-phalangeal      articula- 
tions, 361 
Metatarsus,  252 

articulations  of,  254 

common  characters  of,  252 

development  of,  255 
Metatela,  879,  902,  981 
Metathalamus,  914 
Metopic  suture,  83,  127 
Meynert,  commissure  of,  919 

fasciculus  retroflexus,  908 
Microcephalic  skull,  capacity  of, 

147 
Mid-brain,  869,  904 

aqueduct  of,  907 

crusta  of,  910 


Mid-brain,   deep  origin  of   cranial 
nerves  in,  910 

gray  masses  of,  910 

intercalatum  of,  907 

pes  of,  910 

pyramidal  tract  of,  910 

structure  of,  external,  905 
internal,  906 

substantia  nigra  of,  907 

tegmentum  of,  908 

fibre  tracts  of,  908 
Middle  arcuate  ligament,  429 

cardiac  nerve,  1086 

cerebral  artery,  629 

cervical  ganglion,  1085 

clinoid  processes,  93,  132 

colic  artery,  678 

constrictor  muscle,  403 

costo-trans verse  ligament,  288 

cutaneous  nerve,  1021 

ear,  1160 

fossa  of  skull,  130 

hsemorrhoidal  artery,  688 
gland,  796 
veins,  760 

inguinal  fossa,  1532 

internal  frontal  artery,  629 

meatus  of  nose,  145 

mediastinum,  1396 

meningeal  artery,"  615 
veins,  734 

odontoid  ligament,  52,  281 

palatine  nerve,  1050 

sacral  artery,  683 
veins,  764 

spermatic  fascia,  442 

subscapular  nerve,  1002 

superior  dental  nerve,  1047 

temporal  artery,  613 
vein,  727 

thyroid  vein,  730 

turbinated  bone,  101 

vesical  artery,  688 
Mid-gut,  1246 
Milk  teeth,  1206 
Minor  cardiac  nerve,  1086 
Mitral  nerve-cells,  960 

orifice,  570 
Mixed  bones,  34 
Mobile  septum,  1107 
Moderator  band,  572 
Modiolus,  1177 
Molar  glands,  1205 

teeth,  1208 

Molecular  nerve-cells,  958 
Moll,  glands  of,  1148 
Monakow's  tract  of  cord,  853 

tractus  rubrospinalis,  908,  909 
Monaxonic  neurones,  823 
Monopolar  dendrites,  821 
Monro,  foramen  of,  866,  913 

sulcus  of,  916 
Mons  Veneris,  1490 
Montgomery,  glands  of,  1516 
Monticulus  cerebelli,  896 
Morgagni,  columns  of,  1326 

crypts  of,  1326 

hydatids  of,  1480 

sinus  of,  404 

valves  of,  1326 
Motor  end-plates,  828 

neurones,  816 

root  of  spinal  cord,  836 
Mouth,  1203 

angle  of,  1203 

aperture  of,  1203 

cavity  of,  143 
proper,  1204 

floor  of,  lymphatic  vessels  of, 
782 

mucous  membranes  of,  1204 


1590 


INDEX 


Mouth,  muscles  of,  379 
surface  form  of,  1229 
surgical  anatomy  of,  1234 
vestibule  of,  1204 
Movable  spleen,  1363 
Movements   admitted   in   joints, 

268 

Mucilaginous  glands,  265 
Mucous  alveoli,  1228 
coat  of  bladder,  1447 
of  gall-bladder,  1351 
of  oesophagus,  1239 
of  pharynx,  1233 
of  urethra,  1453, 1456 
glands  of  tongue,  1228 
Miiller's  muscle,  376 

"ring"  muscle,  1126 
Multifidus  spina;  muscle,  423 
Multipolar  cells,  820 
Muscle  or  muscles,  363 
of  abdomen,  434 
deep,  451 
superficial,  434 
abductor  hallucis,  547 
indicis,  501 
minimi  digiti,  foot,  548 

hand,  500 
pollicis,  497 
accelerator  urinse,  459 
accessorius    ad    ilio-costalem, 

421 

of  acromial  region,  472 
adductor  brevis,  523 
longus,  522 
magnus,  523 
minimus,  523 
obliquus  hallucis,  549 

pollicis,  499 
transversus  hallucis,  551 

pollicis,  499 
anconeus,  489 
antitragicus,  1157 
of  arm,  472,  476 
arteries  of,  364 
aryteno-epiglottideus,  1381 
arytenoid,  1383 
arytenoideus,  1380 
attollens  auriculam,  371 
attrahens  auriculam,  371 
of  auricular  region,  371 
azygos  uvulae,  407 
of  back,  412 
biceps,  arm,  477 
flexor  cubiti,  477 
thigh,  532 
bipenniform,  365 
biventer  cervicis,  422 
Bowman's,  1125 
brachialis  anticus,  478 
buccinator,  382 
bulbo-cavernous,  459 
bundles,  363 
cervicalis  ascendens,  421 
chondro-glossus,  399 
ciliary  of  eye,  1125 
circumflexus,  406 
coccygeus,  457 
complexus,  422 
compressor  narium  minor,  378 
nasi,  378 

sacculi  laryngis,  1381 
urethras  in  female,  464 

in  male,  462 
constrictor,     isthmi     faucium, 

400,  407 

pharyngeus,  inferior,  402 
middle,  403 
superior,  403 
urethrte,  in  female,  464 

in  male,  462 
coraco-braehialis,  477 


Muscle    or    muscles,    corrugator 

cutis  ani,  451 
supercilii,  373 
of  cranium,  367 
cremaster,  441,  1528 
crico-arytenoid,  posterior,  1380 
crico-thyroid,  1380 
crureus,  520 
deltoid,  472 
depressor  alae  nasi,  378 
anguli,  oris,  380 
labii  inferioris,  380 
detrusor  urinas,  1446 
diaphragm,  429 
digastric,  396 
dilator  naris  anterior,  378 

posterior,  378 
of  dorsal  region,  546 
ejaculator  seminis,  459 

urinse,  459 

erector  clitoridis,  463 
penis,  460 
spinae,  419 
of  expiration,  434 
of  expression,  387 
extensor  brevis  digitorum,  546 

pollicis,  491 
carpi  radialis  brevior,  487 

longior,  487 
ulnaris,  489 
coccygeus,  424 
communis  digitorum,  488 
indicis,  492 
longus  digitorum,  536 

pollicis,  491 
minimi  digiti,  489 
ossis  metacarpi  pollicis,  491 
primi  internodii  pollicis,  491 
proprius  hallucis,  535 
secundi    internodii    pollicis, 

491 

of  face,  367 

of  femoral  region,  anterior,  514 
internal,  522 
posterior,  532 
fibres,  363 

structure  of,  364 
of  fibular  region,  542 
flexor  accessorius,  549 
brevis  digitorum,  547 
hallucis,  549 
minimi  digiti,  foot,  550 

hand,  500 
pollicis,  499 
carpi  radialis,  481 

ulnaris,  482 
longus  digitorum,  541 
hallucis,  541 
pollicis,  484 
ossis  metacarpi,  500 

pollicis,  498 

profundus  digitorum,  484 
sublimis  digitorum,  483 
of  foot,  544 
of  forearm,  480 
frontalis,  369 
fusiform,  365 
gastrocnemius,  537 
gemellus,  inferior,  530 

superior,  529 
genio-glossus,  399 
genio-hyo-glossus,  399 
genio-hyoid,  397 
of  gluteal  region,  525 
gluteus  maximus,  525 
medius,  526 
minimus,  526 
gracilis,  522 
hamstring,  532 
of  hand, 493 
of  head, 367 


Muscle  or  muscles,  helicis  major, 
1157 

minor,  1157 
Hilton's,  1381 
of  hip,  525 
Horner's,  373 
of    humeral    region,    anterior, 

476 

posterior,  479 
hyo-glossus,  399 
of  iliac  region,  510 
iliacus,  512 
ilio-capsularis,  513 
ilio-coccygeus,  456 
ilio-costalis,  421 
of  infra-hyoid  region,  393 
infracostales,  427 
infraspinatus,  474 
insertion  of,  366 
of  inspiration,  434 
intercostal,  427 

external,  427 

internal,  427 

of  intermaxillary  region,  381 
interossei  of  foot,  551 

of  hand,  501 
interspinales,  423 
intertransversales,  424 

lateralis,  424 

mediates,  424 
involuntary,  363 
of  ischio-rectal  region,  451 
of  larynx,  1381 
latissimus  dorsi,  415 
of  leg,  534 

levator  anguli  oris,  380 
scapulae,  416 

ani,  453 

glandulce  thyroideas,  1409 

labii  inferioris,  380 
superioris,  379 
alaeque  nasi,  378 

menti,  380 

palati,  405 

palpebrae,  373 
superioris,  374 

prostatae,  456 

urethra;,  456 
levatores  costarum,  428 
ligamentous  action  of,  270 
of  lingual  region,  398 
lingualis,  inferior,  401 

superior,  401 

transverse,  401 

vertical,  401 
longissimus  dorsi,  421 
longus  capitis,  408 

colli,  409 

of  lower  extremity,  509 
lumbricales,  foot,  549 

hands,  499 

of  mandibular  region,  380 
masseter,  383 
of  maxillary  region,  379 
Miiller's,  376 
multifidus  spin®,  423 
mylo-hyoid,  397 
naso-labialis,  381 
of  natal  region,  378 
of  neck,  387 
nerves  of,  364 
oblique,  ascending,  439 

descending,  435 

external,  435 

internal,  439,  1528 
obliquus  auriculae,  1157 

capitis  inferior,  424 
superior,  424 

oculi,  inferior,  376 

superior,  376 
obturator  externus,  531 


1591 


Muscle     or    muscles,    obturator 

hit  emus,  528 
occipitalis,  369    . 
occipito-frontalis,  369 
omo-hyoid,  395 
opponens  minimi  digiti,  500 

pollicisj  498 
orbicular,  365 
orbicularis  oris,  381 

palpebrarum,  372 
orbital,  376 

region,  374 
of  palatal  region,  405 
palato-glossus,  400,  407 
palato-pharyngeus,  407 
of  palmar  region,  middle,  501 
palmaris  brevis,  500 

longus,  482 

of  palpebral  region,  372 
pectineus,  522 
pectoralis  major,  466 

minor,  470 
of  pelvic  outlet,  451 
penniform,  365 
of  perinaeum  in  female,  462 

in  male,  457 
peroneus  brevis,  543 

longus,  542 

tertius,  537 

of  pharyngeal  region,  402 
pharyngo-glossus,  400 
of  plantar  region,  547 
plantaris,  539 
platysma  myoides,  388 
popliteus,  540 
pronator  quadratus,  485 

radii  teres,  481 
psoas  magnus,  512 

parvus,  512 
of  pterygo-mandibular  region, 

385 
pterygoid,  external,  386 

internal,  386 
pubococcygeus,  454 
pyramidalis  abdominis,  446 

nasi,  378 
pyriformis,  527 
quadratus  femoris,  530 

lumborum,  451 

menti,  380 

quadriceps  extensor,  518 
quadrilateral,  365 
of  radial  region,  486,  497 
of    radio-ulnar    region,    poste- 
rior, 488 

recto-urethralis,  456 
recto-uterinus,  1503 
rectus  abdominis,  444 

capitis  anticus  major,  408 

minor,  409 
lateralis,  409 
posticus  major,  424 
minor,  424 

femoris,  518 

oculi,  external,  375 
inferior,  375 
internal,  375 
superior,  375 
retrahens  auriculum,  371 
rhomboidal,  365 
rhomboideus  major,  416 

minor,  416 

"ring"  of  Miiller,  1126 
risorius,  383 
rotatores  spinae,  423 
sacro-lumbalis,  421 
salpingo-pharyngeus,  407 
Santorini's,  383 
sartorius,  518 
scalenus  anticus,  410 

medius,  410 


Muscle  or  muscles,  scalenus  pos- 
ticus, 411 
of    scapular    region,    anterior 

473 

posterior,  474 

semicircular,  of  rectum,  1325 
semimembranosus,  533 
semispinalis  colli,  423 

dorsi,  423 

semitendinosus,  533 
serratus  magnus,  471 

posticus  inferior,  417 

superior,  417 
of  shoulder,  472 
skeletal,  363 
of  sole  of  foot,  547 
soleus,  538 
sphincter,  365 

ani,  external,  452 
internal,  453 

vagina?,  463 
spinalis  colli,  422 

dorsi,  421 

spindle  of  Kiihne,  830 
splenius,  418 

capitis,  418 

colli,  418 

sterno-cleido-mastoid,  391 
sterno-hyoid,  394 
sterno-mastoid,  391 
sterno-thyroid,  394 
striated,  363 
striped,  363 
stylo-glossus,  399 
stylo-hyoid,  397 
stylo-pharyngeus,  405 
subanconeus,  480 
subclavius,  470 
subcrureus,  521 
subscapularis,  473 
of   superficial   cervical   region, 

388 
supinator  longus,  486 

radii  brevis,  489 
of  supra-hyoid  region,  396 
supraspinales,  423 
supraspinatus,  474 
suspensory,  of  duodenum,  1294 
temporal,  384 
of  temporo-mandibular  region 

383 
tensor  fasciae  femoris,  517 

palati,  406 

tarsi,  373 

tympani,  1171 
teres  major,  475 

minor,  475 
of  thigh,  514 
of  thoracic  region,  anterior, 

465 

lateral,  471 
of  thorax,  426 
thyro-arytenoid,  1381 
thyro-epiglottideus,  1381 
thyro-hyoid,  395 
tibialis  anticus,  535 

posticus,  541 

of  tibio-fibular  region,  534 
of  tongue,  400 

extrinsic,  400 

intrinsic,  400 
trachelo-mastoid,  421 
tragicus,  1157 

transversalis   abdominis,    444, 
1528 

cervicis,  421 

colli,  421 
transversus  auriculae,  1157 

menti,  380 

perinei    superficialis,    in    fe- 
male, 462 


Muscle  or  muscles,  transversus 
perinei  superficialis,  in  male, 
459 

trapezius,  413 
triangular,  365 
triangularis  menti,  380 

sterni,  427 
triceps,  479 

extensor  cubiti,  479 
of  trunk,  412 
of  ulnar  region,  500 
unstriated,  363 
unstriped,  363 
of  upper  extremity,  464 
of  ureters,  1446 
vastus  externus,  520 

internus,  520 
vegetative,  363 
veins  of,  364 
of   vertebral    region,    anterior, 

408 

lateral,  410 
voluntary,  363 
zygomaticus  major,  379 
'  minor,  379 
Muscular    coat  of     anal    canal, 

1324 

of  bladder,  1446 
of  duodenum,  1296 
of  intestine,  large,  1324 

small,  1298 
of  o?sophagus,  1238 
of  rectum,  1324 
of  stomach,  1282 
of  vermiform  appendix, 1312 
fibres,  cardiac,  363 
portion  of  urethra,  1451 
structure  of  heart,  577 
substance  of  tongue,  400 
Musculi    papillares   of    ventricle, 

left,  575 
right,  572 
pectinati   of  auricle,   left,   570 

right,  568 

pubo-vesicalis,  1446 
Musculo-cutaneous   nerve,    1002, 

1034 

Musculo-phrenic  artery,  646 
Musculo-spiral  groove,  181 
nerve,  1007 

branches  of,  1007 
Myelencephalon,  874 
Myelin  sheath,  824 
Myelinic  axones,  824,  826 
Myelinization  of  axones  of  cord, 

855 

Myelocele,  845 
Myelon,  834 
Mylo-hyoid  artery,  616 
muscle,  397 
ridge,  123 

Mylo-hyoidean  groove,  124 
Myocardium,  576 
Myrtiform  fossa,  106 


N 

NABOTH,  ovules  of,  1505 
Nails,  1195 

body  of,  1195 

edge  of,  1195 

lunula  of,  1195 

matrix  of,  1195 

ridges  of,  1195 

ungual  fold  of,  1195 

wall  of,  1195 
Nares,  anterior,  142,  1108 

posterior,  142,  1108 

septum  of,  142 
Nasal  angle,  105 


1592 


INDEX 


Nasal  artery   from  internal  max- 
illary, 617 

from  ophthalmic,  626 
of  septum,  609 
transverse,  626 
bones,  104 

articulations  of,  105 
attachment    of    muscles    to 

105 

borders  of,  105 
development  of,  105 
surfaces  of,  105 
cartilages,  1106 
cavity,  142 
crest,' 111,  116 
duct,  1152 
fossae,  142,  1108 
arteries  of,  1111 
atrum  of,  1110 
inner  wall  of,  1110 
lymphatics  of,  1112 
mucous  membrane  of,  1110 
nerves  of,  1112 
outer  wall  of,  1109 
surgical  anatomy  of,  1112 
veins  of,  1111 
groove,  105 
nerve,  1044 

branches  of,  1045 
notch,  80 

portion  of  pharynx,  1231 
process,  80 

of  superior  maxillary,  109 
region,  muscles  of,  378 
slit,  143 
spine,  80 

anterior,  111,  139,  143 
posterior,  116,  135,  143 
venous  arch,  725 
Nasion,  80,  139,  150 
Nasmyth's  membrane,  1214 
Naso-frontal  vein,  740 
Naso-labial  ridge,  380 
Naso-labialis  muscle,  381 
Naso-maxillary  suture,  139 
Naso-palatine  artery,  617 
canal,  121 
groove,  121 
nerve,  1050 
Naso-pharynx,  1231 
Nates  of  quadrigemina,  905 
Navicular  bone,  249 

articulations  of,  249 
attachment    of    muscles    to, 

249 

surfaces  of,  249 
tuberosity  of,  249 
Neck,  arteries  of,  598 
fascise  of,  387 
lymphatic  glands  of,  778,  783 

vessels  of,  786 
muscles  of,  387 
triangles  of,  posterior,  620 

surgical  anatomy  of,  618 
veins  of,  724,  728 
Nelaton's  line,  232 
Nerve  or  nerves,  825 
abducent,  1057 
accessory,  1073 
acoustic,  1064  . 
afferent,  827 
ansa  hypoglossi,  1077 
of  arm,  994 
Arnold's,  1070 
of  arteries,  588 
articular,    of    anterior     tibial 

1033 

of  auriculo-temporal,   1052 
of  great  sciatic,  1030 
of  internal  plantar,  1032     • 
popliteal,  1031 


Nerve   or   nerves,    articular,    oi 
peroneal,  1033 

of  posttibial,  1031 

of  ulnar,  1006,  1186 
auditory,  1064 
auricular,  anterior,  1052 

posterior,  1062 

of  vagus,  1070 
auriculo-temporal,  1052  - 
beginnings,  peripheral,  828 
of    centripetal     neurones 

828 

blood-vessels  of,  826 
of  bones,  41 
buccal,  1051 

from  facial,  1063 
buccinator,  1051 
calcaneal,  lateral,    1031 

medial,  1031 
calcaneo-plantar,  1031 
cardiac,  cervical,  1072 

great,  1086 

inferior,  1086 

middle,  1086 

minor,  1086 

superior,  1085 

thoracic,  1072 
cardio-motor,  1081 
carotico-tympanic,  1083 
carotid,  1067 
cavernous,  large,  1095 

small,  1095 
centrifugal,  827 
centripetal,  827 
cerebral,  1036 
cervical,  986 

superficial,  990 
cervico-facial,  1063 
chorda  tympani,  1052,  1061 
ciliary,  long,  1045 

short,  1045 
circumflex,  1002 
coccygeal,  1023 
cochlear,  1064,  1186 
communicantes  hypoglossi,  988 
communicating,  fibular,  1031 

tibial,  1031 
of  Cotunnius,  1050 
cranial,  1036 
crural,  anterior,  1021 

accessory    of    Winslow, 

1020  ' 
cutaneous,  of  abdomen,  1013 

external,  1002,  1018 

intermediate  dorsal,   1034 

internal,  1003,  1021 
plantar,  1032 

lateral,  1018 

medial  dorsal,  1034 

middle,  1021 

of  musculo-cutaneous,  1034 

musculo-spiral,    1008 

of  obturator,  1020 

palmar,  1004 

of  perineal,  1028 

of  peroneal,  1033 

of    small    sciatic,     femoral, 

1028 

gluteal,  1028 
perineal,  1028 

of  supraorbital,  1044 

of  thorax,  1012 

of  ulnar,  1006 
dorsal,  1006 

palmar,  1006 
dental,  anterior  superior,  1048 

inferior,  1053 

middle  superior,  1047 

posterior  superior,  1047 
descendens  hypoglossi,  988 

norii,  1076 


Nerve  or  nerves,  digastric,    from 

facial,  1062 
digital,  foot,  1032 

hand,  1005 
dorsal,  1010 

of  clitoris,  1030, 

of  penis,  1030 
dorsi-lumbar,  1016 
of  dura  of  brain,  974 
dural,  1046 

from  hypoglossal,  1076 

of  inferior  maxillary,  1051 

of  vagus,  1070 
efferent,  827 
eighth,  1064 
eleventh,  1073 
of  eyeball,  1038 
facial,  1059 
femoral,  1021 
fifth,  1041 
first,  1037 

ventral  cutaneous,  1011 
of  foot,  1032 
fourth,  1041 
frontal,  1043 
ganglia  of,  827 

spinal,  983 
ganglion  of  ciliary,  1040 

lenticular,  1040 

of  Scarpa,  1065 

vestibular,  1065 
gastric,  1072 
genito-crural,  1018 

femoral,  1016 
glosso-pharyngeal,  1066 
gluteal,  inferior,  1027 

superior,  1027 
gustatory,  1052 
huemorrrioidal,  inferior,  1028 
of  heart,  580 
hypogastric,  1018 
hypoglossal,  1074 
iliac,  1017 

ilio-hypogastric,  1017 
ilio-inguinal,  1018 
ncisor,  1053 
nframandibular,  1064 
nframaxillary,  1064 
nfraorbital,  1062 
nfratrochlear,  1045 
ntercostal,  1011 
intercosto-humeral,  1013 
interosseous,   anterior,   1004 

dorsal,  1008 

posterior,  1008 

of  tibial,  1034 

volar,  1004 
Jacobson's,  1067 
jugular,  1083 
labial,  1048 
of  labyrinth,  1186 
lacrimal,  1043 
of  Lancisi,  940 
laryngeal,    of    vagus,    inferior, 

1071 

superior,  1071 
external,  1071 
internal,  1071 
lingual  of  fifth,  1052 

of  glosso-pharvngeal,   1067 
lumbar,  1015 
lumbo-inguinal,  1018 
malar,  1062 

of  superior  maxillary,  1046 
mandibular,  1050 
masseteric,  1051 
mastoid,  990 
maxillary,  inferior,  1050 

superior,  1046 
median,  1004 
mental.  1053 


INDEX 


1593 


Nerve  or  nerves,  muscular,  of  ex- 
ternal   plantar,  1033 

of  great  sciatic.   KYM 

of  hypoglossal,  1077 

of  internal  plantar,  1032 
popliteal,  1031 

of  musculo-cutaneous,   103-4 

of  musculo-spiral,   1007 

of  perineal,   1030 

of  posttibial,  1031 

of  sciatic  plexus,  1027 

of  tibial,  1033 

of  ulnar,  1006 
museulo-cutaneous,  1002,  1034 
musculo-spiral,  1007 
mylo-hyoid,  1053 
nasal,  1044 

from  Meokel's  ganglion,  1048 

ganglionie  hraneli  of,  1045 
na>o-palatine,  1050 
ninth,  1066 
obturator,  1020 

accessory,  1020 
occipital,  from  facial,  1062 

great,  986 

small.  989 
oculomotor,  1039 

nucleus  of,  911 
<esophageal,  1072 
olfactory,  1037 
ophthalmic,  1043 
optic,  1038 
orbital,  of  superior  maxillary, 

1046 

origin  of,  827,  828 
palatine,  anterior,  1049 

external,  1050 

large,  1049 

middle,  1050 

posterior,  1050 

small,  1050 
palmar,  of  ulnar,  1006 
palpebral,  1048 
parotid,  1052 

perforating,  of  Casserius,  1002 
of  pericardium,  563 
pericrania!,  1044 
perineal,  1028 
peroneal,  1030 

common,  1033 

deep,  1033 
petrosal,  deep,  1083 

great  deep,  1049 
superficial,  1048 

large  deep,  1049,  1083 

superficial,  1048 
pharyngeal,  1050,  1067,  1070 
phrenic,  992 
of  pia  of  brain,  982 
plantar,  lateral,  1032 

medial,  1031 
plexus  of,  826 

abdominal  aortic,    1094 

adrenal,  1092 

annular,  1121 

brachial,  994 

cardiac,  1090 

carotid,  internal,  1083 

cavernous,  1083 

cervical,  989 
dorsal,  984 

coccygeal,  1034 

cceliac,  1072,  1094 

colic,  left,  1095 

coronary,  1090,  1094 

cystic,  1094 

of  dental,  superior,  1048 

epigastric,  1091 

fundamental,  1121 

gastric,  1094 

gastro-duodenal,  1094 


Nerve  or  nerves,  plexus  of,  gastro- 

epiploic,  ID!)  I 
left,  1094 

luemorrhoiclal,  inferior,  109; 
superior,  1095 

hepatic,  1094 

hvpogastric,  1095 

infraorbital,  1062 

int  fa-epithelial,  1121 

lumbar,  1016 

mesenteric,  inferior,   1094 
superior,  1094 

oesophageal,     1069,     1072, 
1091 

ovarian,  1094 

pancreatic,  1095 

patellar,  1021 

pelvic,  1095 

pharyngeal,  1067 

phrenic,  1092 

prostatic,  1095 

pudendal,  1026 

pudic,  1026 

pulmonary,  1091 
dorsal,  1069,  1072 
ventral,  1069,  1072 

pyloric,  1094 

renal,  1072,  1093 

sacral,  1026,  1095 
dorsal,  984 

sciatic,  1026 

sigmoid,  1095 

solar,  1091 

spermatic,  1094 

splenic,  1072,  1094 

subclavian,  1086 

subepithelial,  1121 

suprarenal,  1092 

thoracic  aortic,  1087 

tympanic,  1067 

uterine,  1095 

utero-vaginal,  1095 

vaginal,  1095 

vertebral,  1086 

vesical,  1095 
pneumogastric,  1068 
popliteal,  external,  1033 

internal,  1030 
portio  dura,  1059 

mollis,  1060 
posttibial,  1031 
pterygoid,  external,  1051 

internal,  1051 
pterygo-palatine,  1050 
pudendal,  inferior,  1028 
pudic,  1028 
pulmonary,  dorsal,  1072 

ventral,"  1072 
radial,  1008 

recurrent,    of    internal    maxil- 
lary, 1051 

laryngeal,  of  vagus,  1071 
respiratory,  of  Bell,   external, 

1000 

internal,  992 
sacral,  1023 
saphenous,  1222 

external,  1031 

internal,  1022 

long, 1022 

short,  1031 

scapular,  posterior,  999 
of  Scarpa,  1050 
sciatic,  great,  1030 

small,  1027 
scrotal,  long,  1028 
second,  1038 

seventh, 1059 

sixth,  1057 

spermatic,  external,   1018 

spheno-palatine,  1047 


Xervc  or  nerves,  sphenoidal,  1054 
spinal,  982 

accessory,  1073 
splanchnic,  1087 

renal,  1088 
stylo-hyoid,  1062 
subcutaneous  mala?,  1047 
suboccipital,  986 
subscapular,  1001 
superficial  colli,  990 
supra-acromial,  992 
supraclavicular,  991 
supramandibular,  1063 
supramaxillary,  1063 
supraorbital,  1044 
suprascapular,  1000 
suprasternal,  991 
supratrochlear,  1044 
sural,  1033 
sympathetic,  827 
system,  815 

cell-element  of,  816 

development  of,  816 

structure  of,  819 

supporting    tissue    elements 

of,  832 

temporal,    of    auriculo-tempo- 
ral,  1052 

deep,  1051 

from  facial,  1062 

of  superior  maxillary,   1046 
temporo-malar,  1046 
tenth,  1068 
termination  of,  828 
third,  1039 
thoracic,  1010 

anterior,  1001 

long,  1009 

posterior,  1001 
thoracico-lumbar,  1014 
thyro-hyoid,  1077 
thyroid!  1086 
tibial,  1030 

tissue,    chemical    composition 
of,  833 

development  of,  818 
tonsillar,  1067 
trifacial,  1041 
trigeminal,  1041 
trochlear,  1041 

nucleus  of,  910 
twelfth,  1074 
tympanic,  1067 

from  facial,  1061 
ulnar,   1005 
vagus,  1068 
vasomotor,  1081 
vestibular,  1065 
Vidian,  1048 
Nerve-cells,  820 

axone  of,  823 

body    external   morphology, 

'  of,  820 

internal    morphology    of, 
822 

of  cerebral  cortex,  958 

dendrites  of,  822 

of  Martinotti,  960 

mitral,  960 

Nerve-endings  in  muscle,  364 
Nerve-fibre,  axis-cylinder  of,  823 
Nerve-fibres,  825 

centrifugal,  827 

centripetal,  823 

cerebral,  961 
cortex,  959 

commissural,  963 

projection,  963 

thalamo-frontal,  956 

thalamo-striate,  956 

vasomotor,  826 


1594    ' 


INDEX 


Nerve-paths,  825 
Nervi  nervorum,  826 
Nervous  papilla?,  1191 
Nervus  cutaneus  patellae,  1022 

intermedius,  894 

superficialis  cordis,  1085 
Neumann,    dentinal    sheath    of, 

1213 
Neural  arch,  34 

tube,  817 
Neuraxone,  820 
Neurenteric  canal,  1252 
Neuri lemma  of  cord,  824 

amyelinic  axones  with,  825 

without,  825 
nucleus  of,  825 
Neurite,  820 
Neuroblasts,  818 
Neuro-central  suture,  59 
Neuro-muscular  spindles,  830 
Neuro-tendinous  spindles,  830 
Neuroglia  of  cord,  818,  832 
Neurones,  816,  820 

afferent,   peripheral  axone  of, 
819 

centripetal,    peripheral    nerve, 
beginnings  of,  828 

diaxonic,  823 

excito-glandular,  816 

excito-motor,  816 

forms  of,  820 

monaxonic,  823 

motor,  816 

polyaxonic,  823 

sensor,  816 

peripheral  axone  of,  819 

theory  of,  831 
Neuropore,  863 

Nexal  root  of  eighth  nerve,  1065 
Nidus  avis  of  cerebellum,  898 

larvngei,  890 

pharyngei,  890,  892 
Ninth  nerve,  1066 

surgical  anatomy  of,  1067 
Nipple,  1516 

structure  of,  1518 
Nissl's  bodies,  822 
Nodal  point,  1116 
Nodes,  hemolymph,  774 
Nodular  lobe  of  cerebellum,  898 
Nose,  1105 

aperture  of  cartilage  of,  1107 

arteries  of,  1108 

cartilage  of,  1106 

dorsum  of,  1106 

fossa;  of,  142,  1108 

integument  of,  1107 

interior  of,  lymphatic  vessels 
of,  782 

lymphatics  of,  1108 

meatus  of,  inferior,  145 
middle,  145 
superior,  101,  144 

mucous  membrane  of,  1108 

muscles  of,  1107 

nerves  of,  1108 

outer,  1106 

septum  of,  142 

cartilage  of,  triangular,  1107 

structure  of,  1106 

veins  of,  1108 
Notch,  cotyloid,  220 

ethmoidal,  82 

ilio-sciatic,  217 

intercondyloid,  227 

intervertebral,  49 

lachrymal,  107 

nasal,  80 

popliteal.  236 

pre-occipital,  922 

pre-sternal,  157 


Notch,  ptervgoid,  96 

of  Rivinus,  1161 

sacro-sciatic,  211 
great,  217 
lesser,  218 

scapular,  great,  175 

sigmoid,  125 

spheiio-palatine,  118 

supraorbital,  80,  140 

suprascapular,  175 

suprasternal,  411 

thyroid,  1370 
Nuchal  line,  inferior,  72 
superior,  72 

plane,  72 

Nuck,  canal  of,  1472,  1513 
Nuclei  of  abducent  nerve,  894 

of  accessory  nerve,  890 

of  acoustic  nerve,  892 

of  cerebellum,  899 

of  cochlear  nerve,  892 

of  facial  nerve,  893 

of  glosso-pharyngeal  nerve,  890 

of  hypoglossal  nerve,  889 

of  origin,  889 

pontius,  887 

of  termination,  889 

of  trigeminal  nerve,  894 

of  vagus  nerve,  890 

vestibular  nerve,  893 
Nucleus,  accessory  cuneate,  884 

alae  cinerea?,  891 

ambiguus,  890,  892 

arcuatus,  886 

dentate  of  cerebellum,  900 

emboliformis,  900 

fastigii,  900 

funiculi  cuneati,  876 
teretis,  886 

globosus,  900 

incertus,  888 

intercalatus,  886 

lateralis,  886 

lentis,  1142 

of  oculomotor  nerve,  911 

of  olive,  885 
superior,  887 

postremus,  886 

ruber,  908 

semilunaris,  914 

of  Stilling,  847 

tegmenti,  908 

trochlear  nerve,  910 
Nuel,  space  of,  1185 
Nuhn    and    Blandin,    glands    of, 

1101 

Nutrient  artery  of  femur,  706 
of  fibula,  717 
of  humerus,  658 
of  tibia,  718 
Nymphse,  1490 


OBELION,  129,  150 
Obex,  881 

Oblique  diameter  of  pelvis,  210 
inguinal  hernia,  1529,  1532 
complete,  1533 
incomplete,  1533 
ligament,  316 
line  of  clavicle,  169 
of  fibula,  240 
of  radius,  192 
of  tibia,  237 
muscles,  ascending,  439 
aponeuiosis  of,  441 
descending,  435 
external,  435 

aponeurosis  of,  435 


Oblique  muscles,    internal,    439. 

1528 

aponeurosis  of,  441 
dissection  of,  443 
ridges  of  scapula,  172 
of  trapezium,  200 
of  ulna,  190 

sacro-iliac  ligament,  294 
sinus  of  pericardium,  562 
vein  of  Marshall,  771 
Obliquus  auriculas  muscle,   1157 
capitis  inferior  muscle,  424 

superior  muscle,  424 
oculi  muscle,  inferior,  376 

superior,  376 
Oblongata,  874 
areas  of,  875 
fissures  of,  874 
funiculus  cuneatus  of,  876 
gracilis,  876 
lateralis  of,  876 
olive  of,  876 
pyramids  of,  875 
restis  of,  876 

tuberculum  cinereum  of,  876 
veins  of,  736 

Obstetric  perinseum,  1490 
Obturator  artery,  689 

peculiarities  of,  690 
bursa,  333 
canal.  528 
crest,  220 

externus  muscle,  531 
fascia,  1558 
foramen,  220 
groove,  217,  220 
internus  muscle,  528 

bursa  of,  528 
ligament,  298 
membrane,  528 
nerve,  1020 

accessory,  1020 
vein,  761 
Occipital  artery,  610,  642 

branches  of,  611 
bone,  71 

angles  of,  75 
articulations  of,  76 
attachment  of  muscles  to,  76 
borders  of,  75 
development  of,  75 
structure  of,  75 
surfaces  of,  71 
bulb,  946 
crest,  external,  72,  136 

internal,  74,  133 
diploic  vein,  734 
fissures,  926,  931 
inferior,  931 
lateral,  931 
fossa;,  inferior,  133 
groove,  86 
lobe,  931 

fissures  of,  931 
gray  substance  of,  959 
lymphatic  glands,  779 
nerve  of  facial,  1062 
great,  986 
small,  989 
point  of  skull,  150 
protuberance,  external,  71, 136 

internal,  73 
sinus,  739 
triangle,  620 
vein,  727 

Occipitalis  muscle,  369 
Occipito-atlantal  ligament,  ante- 
rior, 278 
posterior,  278 

Occipito-axial    ligament,    poste- 
rior, 280 


INDEX 


1595 


Occipito-frontalis  muscle,  369 
surgical  anatomy  of,  369 
Oecipito-parietal  suture,   128 
Occipito-pontile  tract,  956,  957 
Occiput,  arteries  of,  610 
Oculomotor  nerve,  1039 
nucleus  of,  911 
sulcus,  904 

surgical  anatomy  of,  1040 
Odontoblasts,  1216 
ofWaldeyer,  1211 
Odontocla-sts,  1219 
Odontoid  ligaments,  lateral,  280 

middle,  52,  281 
process  of  axis,  52 
CEsophageal  arteries,  643,  668 
nerves,  1072 
opening  of  diaphragm,  432 

of  stomach,  1278 
plexus,  1069,  1072,  1091 
veins,  751 
(Esophagus,  1235 

abdominal  portion  of,  1236 
anomalies  of,  1238 
areolar  coat  of,  1239 
arteries  of,  1239 
cervical  portion  of,  1236 
diaphragmatic  port  ion  of,  1236 
innervation  of,  1240 
lymphatics  of,  813,  1240 
movements  of,  1240 
mucous  coat  of,  1239 
muscular  coats  of,  1238 
nerves  of,  1240 
relations  of,  1237 
structure  of,  1238 
submucous  coat  of,  1239 
surgical  anatomy  of,  1240 
thoracic  portion  of,  1236 
veins  of,  1239 
Olecranon  bursa,  313 

subcutaneous,  479 
fossa,  183 
process,  186 
Olfactory  bulb,  867,  934 

gray  substance  of,  960 
cells,  1111 
fissure,  928 
foramina,  143 
gyre,  935 
hair,  1111 
lobe,  934 

postolfactory  division  of,  935 
preolfactory  division  of,  934 
nerve,  1037 

surgical  anatomy  of,  1038 
pathways,  964 
striae,  935 
tract,  867,  934,  935 
tubercle,  935,  1037 
Olivary  body,  876.     See  Olive, 
eminence,  93 
nucleus  superior,  887 
process,  93,  131 
Olive,  885 

nucleus  of,  885 

accessory,  885 
of  oblongata,  876 
Olivo-cerebellar  fibres,  886 
Olivo-spinal  tract  of  cord,  853 
Omenta,  1264 
Omental  band,  1325 

tuberosity,  1336 

Omentum,  development  of,  1250 
gastro-colic,  1266 
gastro-hepatic,  1264 
gastro-splenic,  1266 
great,  1266 
lesser,  1264 

Omo-hyoid  muscle,  395 
Opercula  of  insula,  925 


Operculum,  925 
Ophryon,  80,  150 
Ophthalmic  artery,  624 
ganglion,  i o  \.~> 
nerve,  1043 
veins,  740 
inferior,  741 
superior,  740 
Opisthion,  150 
Opisthotic   portion   of   tempora 

bone,  91 
Opponens  minimi  digiti  muscle 

foot,  550 
hand,  500 
pollicis  muscle,  498 
Optic  axis,  1115 
chiasm,  1038 
commissure,  131,  1038 
cup,  1131 
disk,  1131 

foramen,  93,  96,  131,  142 
groove,  93,  130,  131 
nerve,  1038 

surgical  anatomy  of,  1038 
papilla,  1131 
path, 1038 
radiations,  914,  956 
tract,  1038 

central  connections  of,  917 
vesicles,  865 
Ora  serrata,  1130 
Oral  cavity,  1203 

portion  of  pharynx,  1231 

of  tongue,  1097 
Orbicular  bone,  1169 
ligament,  316 
muscles,  365 

Orbicularis  oris  muscle,  381 
palpebrarum  muscle,  372 

external  portion  of,  372 
internal  portion  of,  372 
orbital  portion  of,  372 
palpebral  portion  of,  372 
Orbiculus  ciliaris,  1125 
Orbit,  140 

arteries  of,  624 
fasciae  of,  377 
margin  of,  106 
muscles  of,  376 
Orbital  artery,  613 

internal,  628 

branch  of  facial  nerve,  1046 
cavities,  140 
fascia,  377 
fissure,  96 
foramina,  95 
fossse,  140,  143 
index  of  skull,  147 
muscle,  376 
nerve,  1046 
operculum,  925 
plates,  81 
process  of  malar  bone,  114 

of  palate  bone,  1 18 
region,  muscles  of,  374 
dissection  of,  374 
surgical  anatomy  of,  377 
septum,  1149 
sinus,  118 
vein,  727 

Orbito-frontal  fissure,  927 
Orbito-palpebral  sulcus,  inferior, 

1147 

superior,  1147 

Orbito-tarsal  ligament,  1149 
Orbits,  140 
Organ  of  Corti,  1183 
of  Jacobson,  1110 
Organs  of  digestion,  1203 
of  generation,  female,  1489 
male,  1457 


Organs  of  Giraldes,  1484 
of  Golgi,  831 
of  respiration,  1369 
of  Rosenmiiller,  1511 
of  special  sense,  1097 
of  voice,  1369 
Orifice,  mitral,  570 

of  prostatic  ducts,  1451 
tricuspid,  569 
of  ureters,  1447 
Ortho-gnathous  skull,  index  of, 

148 

Os  acetabulum,  220 
external,  1501 
incae,  76 

innominatum,  213 
articulations  of,  222 
attachment    of    muscles   to, 

222 

development  of,  221 
ilium,  214 
ischium,  217 
pubis,  219 
structure  of,  221 
internal,  1500 
magnum  of  carpus,  201 
articulations  of,  201 
attachment  of  muscles  to, 

201 

surfaces  of,  201 
planum  of  ethmoid,  100 
trigonum,  247 
uteri,  1501 

Osborn,  supracommissure  of,  915 
Ossa  pubis,  articulations  of,  298 

angle  of,  219 
unguis,  113 
Osseous  labyrinth,  1174 

portion    of    Eustachian    tube. 

1164 
of  external  auditory  meatus, 

1159 

Ossicle,  pterion,  103 
Ossicles  of  tympanum,  1168 
articulations  of,  1170 
ligaments  of ,  1170 
movements  of,  1171 
Oss'fication  of  bone,  42 
centre  of,  44 
intracartilaginous,  43 
intramembranous,  43 
of  spine,  60 

Osteo-dentine  of  Owen,  1214 
Osteoclasts,  36 
Osteology,  33 
Ostium  abdominale  of  Fallopian 

tube,  1510 
Otic  ganglion,  1053 

branches  of,  1053 
Otokonien,  1181 
Otolith,  1179 

membrane,  1182 
Outer  condyle  of  femur,  228 
Outlet  of  pelvis,  21 1 
3va,  primordial,  1515 
Ovarian  arteries,  681 
plexus,  1094 
veins,  766 
>vary,  1512 
arteries  of,  1515 
connections  of,  1513 
descent  of,  1513 
at  different  ages,  1513 
fimbria  of,  1512 
hilum  of,  1513 
lymphatic  vessels  of,  801 
lymphatics  of,  1515 
nerves  of,  1515 
serous  covering  of,  1514 
stroma  of,  1514 
structure  of,  1514 


1596 


INDEX 


Ovary,  supports  of,  1513 

surgical  anatomy  of,  1515 

veins  of,  1515 
Ovicapsule  of  Graafiaii  follicles 

1514 

Ovules  of  Naboth,  1505 
Ovum,  discharge  of,  1515 
Oxyntie  cells,  1285 

glands,  1285 


PACCHIONIAN  bodies,  979 
depressions,  78 
glands,  737 

Pacinian  corpuscles,  830 
Pads  of  adipose  tissue,  265 
Palatal  index  of  skull,  147 
region,  muscles  of,  405 
dissection  of,  405 
surgical  anatomy  of,  408 
Palate,  1220 
bone,  115 

articulations  of,  119 
attachment   of   muscles    to, 

119 

development  of,  119 
horizontal  plate  of,  116 
perpendicular  plate  of,  117 
processes  of,  118 
tuberosity  of,  117,  135 
vertical  plate  of,  117 
hard, 1220 
muscles  of,  405 
soft,  1221 

surgical  anatomy  of,  1234 
vail  of,  1221 

Palatine  aponeurosis,  406 
artery,  ascending,  608 
descending,  617 
inferior,  608 
posterior,  617 
surgical  anatomy  of,  617 
•canal,  anterior,  143 
posterior,  107,  116 

accessory,  116,  135 
foramen,  great,  116 

posterior,  135 
fossa,  anterior,  110,  133 
glands,  1221 
nerve,  anterior,  1049 
external,  1050 
large,  1049 
middle,  1050 
posterior,  1050 
small,  1050 
process  of  superior    maxillary 

bone,  110 
spine,  116 
veins,  727 

Palato-glossus  muscle,  400,  407 
Palato-maxillary  canal,  107 
Palato-pharyngeus  muscle,  407 
Palmar  arch,  deep,  660 
superficial,  666 
surface  marking  of,  667 
surgical  anatomy  of,  667 
cutaneous  nerve,  1004 
fascia,  deep,  495 

surgical  anatomy  of,  496 
interosseous  arteries,  662 
plexus  of  nerves,  745 
recurrent  arteries,  662 
region,  middle,  muscles  of,  501 
veins,  747 
Palmaris  brevis  muscle,  500 

longus  muscle,  482 
Palpebral  arteries,  external,  625 

internal,  625 
fasciae,  1149 


Palpebral  ligaments,  1149 

nerves,  1048 

portion  of  conjunctiva,  1150 

region,  muscles  of,  372 
dissection  of,  372 
Pampiniform  plexus  of  veins,  765 
Pancreas,  1355 

arteries  of,  1360 

body  of,  1357 

borders  of,  1357 

development  of,  1254 

dissection  of ,  1355 

head  of,  1357 

lymphatic  vessels  of,  804 

lymphatics  of,  1360 

neck  of,  1357 

nerves  of,  1360 

peritoneal  relations  of,  1358 

structure  of,  1359 

surface  form  of,  1360 

surfaces  of,  1357 

surgical  anatomy  of,  1360 

tail  of,  1358 

veins  of,  1360 
Pancreatic  area  of  kidney,  1414 

artery,  676 

duct,  1359 

juice,  1360 

plexus  of  nerves,  1094 
Pancreatica  magna  artery,  676 
Pancreatico-duodenal     artery, 

inferior,  677 
superior,  676 

plexus  of  nerves,  1094 

vein,  768 
Papilla,  bile,  1296 

dentine,  1215 

lachrymal,  1152 

spiralis,  1183 
Papilla?  circumvallate,  1099 

conical,  1100 

filiform,  1100 

fungiform,  1100 

maximae,  1099 

mediae,  1100 

minimse,  1100 

simple,  1100 

structure  of,  1100 

of  tongue,  1099 
Papillary  layer  of  skin,  1191 
Paracentral  fissure,  928 

gyre,  930 

Paraduodenal  fossa,  1271 
Paramammary  gland,  811 
Paramastoid  process,  73 
Paramesal  fissure,  927 
Parametrium,  1501 
Paranucleus,  1359 
Paraplexus,.943,  945,  946 
Parasympathetic  bodies,  1417 
Parathyroid  glands,  1412 
embryology  of,  1413 
structure  of,  1413 
surgical  anatomy  of,  1413 
Paraxones,  823 
Parenchyma  of  lungs,  1403 

of  testicle,  1482 
Paries  carotica,  1163 

jugularis,  1161 

labyrinthica,  1162 

mastoidea,  1162 

tegmentalis,  1161 
Parietal  artery,  613 

arteries,  ascending,  630 

bone,  76 

articulations  of,  79 
attachment    of    muscles   to, 

79 

development  of,  78 
surfaces  of,  76 
borders  of,  78 


Parietal  cells   of  gastric   glands, 

1285 

diploic  vein,  external,  734 
eminence,  76 
fissure,  930 
foramen,  76 
gyre,  931 

layer  of  pleura,  1393 
lobe,  930 

fissures  of,  930 
gyre  of,  931 
lymphatics,  807 
peritoneum,  1257 
surface  of  liver,  1337 
of  stomach,  1278 
Parieto-colic  fold,  external,  1273 

internal,  1273 

Parieto-sphenoidal  artery,  630 
Parieto-temporal  artery,  630 
Paro-ophoron,  1512 
Paroccipital  fissure,  930 

gyre,  931 
Parolfactory  sulcus  anterior.  935 

posterior,  935 
Parotid  capsule,  1226 
duct,  1225 

structure  of,  1226 
surface  form  of,  1225 
fascia,  389,  1225 
gland,  1224 

accessory,  1225 
arteries  of,  1226 
duct  of,  1225 
lymph,  1225 
lymphatics  of,  1226 
nerves  of,  1226 
veins  of,  1226 
lymphatic  glands,  779    • 
deep,  780 
superficial,  779 
nerves,  1052 
recess,  1225 

Parotideo-masseterica  fascia,  389 
Parovarium,  1511 
Pars  ciliaris  retinas,  1125,  1130 
intermedia  of  Wrisberg,  1059 
iridica  retinae,  1130 
Parvidural  artery,  616 
Patella,  233 
apex  of,  234 
articulations  of,  234 
attachment  of  muscles  to,  234 
borders  of,  234 
development  of,  234 
ligaments  of,  337 
structure  of,  234 
surface  form  of,  234 
surfaces  of,  233 
surgical  anatomy  of,  234 
Patellar  bursa,  deep,  521 

plexus,  1021 

Path  of  light  stimuli,  1137 
Paths,  gustatory,  1067 

optic,  1038 

Pecquet,  reservoir  of,  775 
Pecten  ossis  pubis,  219 
Pectineus  muscle,  522 

nerve  to,  1022 
Pectoral  fascia,  deep,  466 
gland,  788 

intercostal  nerve,  1011 
region,  dissection  of,  465 
ridge,  181 
Pectoralis  muscle,  major,  46& 

minor,  470 

Peduncles  of  callosum,  936 
cerebellar,  900 

medi  peduncle,  901 
postpeduncle,  900 
prepeduncle,  901 
Pelvic  colon,  1317 


IX  DUX 


1597 


Pelvic  fascia.   1. '>."><> 

ligament,  transverse,  461 
plexus,  1  ()<>.-> 
portion     of    gangliated     cord 
1089 

Pelvis,  209 

axes  of,  211 

brim  of,  209 

cavity  of.  210,  1440 
boundaries  of.   1  I  Id 
contents  of,  1440 

diameters  of,  210 

diaphragm  of,  1241 

differences  between   male  anc 
female,  212 

false.  2119 

of  kidney,  1424 

lower  circumference  of,  211 

lymphatic  vessels  of,  799 

lymphatics  of,  795 

muscles  of,  451 

outlet  of,  211 

position  of,  211 

surface  form  of,  222 

surgical  anatomy  of,  222 

true,  209 
inlet  of,  209 
superior    circumference    of, 
209 

veins  of,  755 
Pendulous    portion    of    urethra, 

1452 

Penile  portion  of  urethra,  1452 
Penis,  1463 

arteries  of,  1469 
dorsal,  693 

body  of,  1465 

corpora  cavernosa  of,  1465 

corpus  spongiosum,  1468 

crura  of,  1464 

dorsum  of ,  1465 

frcenum  of,  1465 

ligaments  of ,  1469 

lymphatic  vessels  of,  799 

lymphatics  of,  1469 

nerves  of,  1030,  1470 
dorsal,  1030 

prepuce  of,  1465 

root  of,  1464 

septum  of,  1467 

structure  of,  1465 

surgical  anatomy  of,  1470 

veins  of,  1469 

dorsal,  deep,  762 
superficial,  762 
Penniform  muscles,  365 
Peptic  cells  of  glands,  1285 

glands,  1285 

Perforated  space,  anterior,  935 
Perforating  arteries,  anterior,  646 
of  hand,  662 
of  thigh,  706 

cutaneous  nerve,  1028 

nerve  of  Casserius,  1002 
Pericsecal  folds,  1271 

fossse,  1271 

Pericardiac  arteries,  646,  668 
Pericardial  pleura,  1394 

sac,  1246 

Pericardiothoracic  cavity,  1246 
Pericardium,  559 

arteries  of,  563 

fibrous  layer  of,  560 

nerves  of,  563 

serous,  562 

sinus  of,  oblique,  562 
transverse,  562 

structure  of,  560 

surgical  anatomy  of,  563 

vestigial  fold  of,  563 
Pericementum,  1206 


Perichondnum,  2<il,  262 
Periclioroidal  space,   111-8 
Penelaustral  lamina.  054 
Pericrania!  nerves,  1044 
Perilymph  space,  1174 
Perimysimn,  '.M>  1 
Perineal  artery,  superficial,  691 

transverse,  692 
body,  1322,  1496,  1555 
cutaneous  nerve,  1028 
fascia,  deep,  1550 
ligament,  transverse,  461 
nerve,  1028 
Perineum,  1322,  1496 
dissection  of,  1547 
in  female,  1554 

muscles  of,  462 
lymphatic  vessels  of,  799 
in  male,  1549 

central   tendinous  point  of, 

1549 

fascia3  of,  457 
muscles  of,  457 
obstetric,  1490 
surgical  anatomy  of,  1547 
Perineurium,  826 
Periosteum,  37 
dental,  1214 
Peripheral     axone     of     afferent 

neurone,  819 
branches  of  lumbar  portion  of 

gangliated  cord,  1089 
of  middle  cervical  ganglion, 

1086 

of  pelvic  portion  of  gangli- 
ated cord,  1089 
of  sacral  portion  of  gangli- 
ated cord,  1089 
of    superior     cervical     gan- 
glion, 1083 
of  thoracic  portion  of  gan- 
gliated cord,  1087 
nerve  beginnings,  828 

of    centripetal    neurones, 

828 

pathway,  964 
veil  of  His,  818 
Peritoneal    coat    of    duodenum, 

1296 

of  stomach,  1281    . 
relations  of  pancreas,  1358 
Perisclerotic  lymph-space,  1113 
Peritoneum,  1255 

development  of,  1245,  1252 
ligaments  of,  1264 
lymphatic  vessels  of,  800 

surgical  anatomy  of,  800 
mesenteries  of,  1266 
omenta  of,  1264 
parietal,  1257 
structure  of,  1256 
surgical  anatomy  of,  1274 
visceral,  1257 
Peritracheo-bronchial     glands, 

809 

Perivascular  lymph-spaces,  772 
Permanent,  teeth,  1206 

development  of,  1218 
eruption  of,  1219 
superadded,  1218 
Peroneal  artery,  717 
anterior,  717 
branches  of,  717 
peculiarities  of,  717 
posterior,  718 
groove,  248 
nerve,  1033 
common,  1033 
deep,  1033 
spine,  246 
tubercle,  246 


Peroneus  brevis  muscle,  543 
longus  muscle,  542 
tertius  muscle,  537 
Perpendicular  fasciculus,  962 
line  of  ulna,  I '.Ml 
plate  of  ethmo:d  bone,  100 

of  palate  bone,  117 
Pes  anserinus,  1060 

of  crura  cerebri,  905,  910 
hippocampi,  947 
leonis,  947 
Petit,  canal  of,  1140 

triangle  of,  437 

Petro-mastoid    portion    of    tem- 
poral bone,  91 
Petro-occipital  fissure,  128 

suture,  75,  133 
Petro-sphenoidal  fissure,   128 

suture,  136 
Petro-squamous  sinus,  739 

suture,  88 

Petro-tympanic  fissure,  84,  1162 
Petrosal  nerve,  deep,  1083 
great  deep,  1049 

superficial,  1048 
large  deep,  1049,  1083 

superficial,  1048 
process,  93 
sinus,  inferior,  742 

superior,  742 
Petrous  ganglion,  1066 
branches  of,  1067 
portion     of     internal     carotid 

artery,  622 

of  temporal  bone,  136 
Peyer's  glands,  1304 

patches,  1304 
Phalanges  of  foot,  255 

articulations  of,  255,  361 
attachment    of    muscles    of, 

255 

development  of,  255 
of  hand,  206 

articulations  of,  206,  327 
attachment  of  muscles,  206 
development  of,  208 
ligaments  of,  327 
Pharyngeal      aponeurosis,      404. 

1233 

arter}',  ascending,  612 
branches  pf,  612 
surgical  anatomy  of,  612 
branch  of  vagus  nerve,  1070 
bursa,  1234 
glands,  1233 
nerve,  1050,  1067 
plexus  of,  1067 
portion  of  tongue,  1097 
region,  muscles  of,  402 
dissection  of,  402 
ring,  lymphatic,  1234 
spine,  73,  135 
tonsil,  1231,  1234 
tubercle,  73 
veins,  730 

plexus  of,  730 

Pharyngo-epiglottic  fold,  1232 
Pharyngo-glossus  muscle,  400 
Pharynx,  1230 

aponeurosis  of,  1233 
arteries  of,  612 
fibrous  coat  of,  1233 
isthmus  of,  1231 
laryngeal  part  of,  1 232 
lymphatic  vessels  of,  782 
mucous  coat  of,  1233 
muscles  of,  402 
nasal  part  of,  1231 
oral  part  of,  1231 
structure  of,  1232 
surgical  anatomy  of,  1234 


1598 


INDEX 


Pharynx,  vault  of,  1231 
Philtriim,  381 
Phleboliths,  762 
Phrenic  arteries,  inferior,  682 

superior,  646 
ganglion,  1092 
hernia,  429 
nerve,  992 

plexus  of,  1092 
surface  of  spleen,  1361 
veins,  767 
Phrenico-costal  sinus,  1395,  1422 
Phrenico-pleural  fascia,   1395 
Phreno-colic  ligament,  1268 
Phreno-pericardial  ligament,  561 
Physiological  retina,  1130 
Pia  of  brain,  980 
arteries  of,  982 
nerves  of,  982 
veins  of,  982 
spinal,  859 

structure  of,  860 

Pigmentary  layer  of  retina,  1137 
Pileums,  896 
Pillars  of  fauces,  1221 

of  fornix,  950 
Pineal  body,  915 

gland, 915 
Pinna  of  ear,  1154 
arteries  of,  1157 
cartilage  of,  1156 
integument  of,  1156 
ligaments  of,  1156 
lymphatics  of,  1157 
muscles  of,  1157 
nerves  of,  1158 
structure  of ,  1156 
veins  of,  1157 
Pisiform  bone,  199 

articulations  of,  199 
attachment   of    muscles    to, 

199 

surfaces  of,  199 
Pit  of  stomach,  166 
Pituitary  body,  917 
fossa,  93 
membrane,  1110 
Pivot-joint,  267 
Plane,  nuchal,  72 
Plantar  arch,  719 

arteries,  external,  719 
branches  of,  719 
surface  marking  of,  719 
surgical  anatomy  of,  719 
internal,  718 

branches  of,  719 
surface  marking  of,  719 
surgical  anatomy  of,  719 
fascia,  545 

surgical  anatomy  of,  546 
ligaments,  long,  355 
superficial,  355 
^hort,  355 

nerves,  external,  1032 
internal,  1031 
lateral,  1032 
medial,  1031 
region,  muscles  of,  547 
dissection  of,  547 
veins,  758 

Plantaris  muscle,  539 
Planum  temporale,  76 
Plate,  cribriform,  of  ethmoid,  99 
horizontal,  of  palate  bone,  116 
perpendicular,  of  ethmoid,  100 

of  palate  bone,  117 
pterygoid,  external,  96 

internal,  96 
vertical,  of  ethmoid,  100 

of  palate  bone,  117 
Platysma  myoides  muscle,  388 


Pleurae,  1391 
arteries  of,  1395 
cavity  of,  1391 
cervical,  1393 
costal,  1393 
diaphragmatic,  1394 
dome  of,  1393 
lymphatics  of,  1395 
mediastinal,  1394 
nerves  of,  1395 
parietal  layer  of,  1393 
pericardia!,  1394 
pulmonary,  1392 
reflections  of,  1392 
structure  of,  1395 
surgical  anatomy  of,  1395 
veins  of,  1395 
visceral  layer  of,  1391 
Pleural  lymphatics,  812 

sacs,  1246 

Pleuroperitoneal   cavity,    1246 
Plexus,  Auerbach's,  1307 

choroid  of  fourth  ventricle,  881 
interlobular,  1346 
of  nerves,  826 

abdominal  aortic,  1089,  1094 

adrenal,  1092 

annular,  1121 

brachial,  994 

cardiac,  1090 
deep,  1090 
great,  1090 
superficial,  1090 
ventral,  1090 

carotid,  internal,  1083 

cavernous,  1083 

cervical,  989 

coccygeal,  1034 

creliac,  1072,  1094 

colic,  left,  1095 

coronary,  1094 

cystic,  1094 

dental  superior,  1048 

dorsal  cervical,  984 
sacral,  984 

epigastric,  1091 

fundamental,  1121 

gastric,  1094 

gastro-duodenal,  1094 

gastro-epiploic,  1094 
left,  1094 

hsemorrhoidal,  inferior,  1095 
superior,  1095 

hepatic,  1094 

hypogastric,  1089,  1095 

irifraorbital,  1062 

intra-epithelial,  1121 

lumbar,  1016 

lumbo-sacral,  1016 

magnus  profunda,  1090 

mesenteric,  inferior,   1094 
superior,  1094 

cesophageal,     1069,     1072, 
1091 

ovarian,  1094 

pancreatic,  1095 

pancreatico-duodenal,  1094 

patellar,  1021     . 

pelvic,  1095 

pharyngeal,  1067 

phrenic,  1092 

prostatic,  1095 

pudendal,  1026 

pudic,  1026 

pulmonary,  1091 
dorsal,  1069,  1072 
ventral,  1069,  1072 

pyloric,  1094 

renal,  1072,  1093 

sacral,  1026,  1095 

sciatic,  1026 


Plexus  of  nerves,  sigmoid,  1095 
solar,  1091 
spermatic,  1094 
splenic,  1072,  1094 
subclavian,  10S6 
subepithelial,  1121 
suprarenal,  1092 
thoracic  aortic,  1087 
tympanic,  1067 
uterine,  1095 
utero-vaginal,  1095 
vaginal,  1095 
vertebral,  1086 
vesical,  1095 

of  veins,  infraclavicular,  790 
palmar,  745 
pharyngeal,  730 
prostatic,  761 
prostatico-vesical,  761 
pterygoid,  727 
spermatic,  765 
spinal,  753 

subpleural  mediastinal,  646 
uterine,  763 
vaginal,  763 
venous,  intraspinal,  732 
on  thyroid  body,  751 
vesical,  inferior,  762 

superior,  761 
Plica,  epigastrica,  1532 
fimbriata,  1097 
gubernatrix,  1471 
hypogastrica,  1531 
salpingopalatine,  1231 
salpingopharyngea,  1231 
semilunaris,  1150 
sublingualis,  1227 
triangularis,  1223 
urachi,  1531 
vascularis,  1471 
Pneumatic  spaces,  1113 
Pneumogastric  nerve,  1068 
Poles  of  eye,  1115 
Polyaxonic  neurones,  823 
Polymazia,  1517 
Polymorphous  nerve  cells,  ectal, 

958 

ental,  959 
Polythelia,  1518 
Pomum  Adami,  1370 
Pons,  877 

basilar  groove  of,  877 
fibres  of,  longitudinal,  887 

transverse,  887 
internal  structure  of,  887 
nuclei  pontis,  887 
Varolii,  877.      Sec  Pons. 
veins  of,  736 
ventral  surface  of,  877 
Pontal  arteries,  641 
Ponticulus,  1156 
Pontile  flexure  of  brain,  869 
Popliteal  artery,  707,  708 
branches  of,  709 
peculiarities  of,  708 
surface  marking  of,  709 
surgical  anatomy  of,  709 
groove,  228 
line,  237 

lymphatic  glands,  794 
nerve,  external,  1033 
internal,  1030 

branches,  1031 
notch,  236 
space,  707 

boundaries  of,  707 
contents  of,  708 
dissection  of,  707 
position  of  contained  parts, 

708 
vein,  758 


INDEX 


1599 


Popliteus  muscle,  540 
Pore,  gustatory,  1100 
IWta,  866,  913 
Portal  sinus,  769 
vein,  769 

system  of,  768 
Portio  dura    of    seventh    nerve, 

1059 

ganglia  of,  1059 
mollis  of  auditory  nerve,  1059 
Post -anal  gut,  1252 
Post-central  fissural  complex,  930 
H-sure,  930 
gyro,  931 

Poet-glenoid  process,  84 
Posi-pharyngeal  gland,  784 
Poetbrachium,  905 
P<  ist  ralrariiie  fissure,  926 
Postcava,  764 

peculiarities  of,  764 
relations  of,  764 
surgical  anatomy  of,  766 
Postcerebellar  artery,  641 
Post  cerebral  artery,  642 

branches  of,  642 
Postchoroid  artery,  642 
Postcisterna,  978 
Po-t  commissure  of  epiphysis,  915 
I  'ost  communicant  artery,  630 
Postcornu,  945 
Postdural  artery,  612 
Posterior  auricular  artery,  611 
nerve,  1062 
vein,  727 

bicipital  ridge,  181 
calcaneo-astragaloid  ligament, 

354 
carpal  arch,  661 

artery  of  ulnar,  665 
cerebral  artery,  642 
cervical  plexus,  987 
chondro-stemal  ligament,  290 
chondro-xiphoid  ligament,  290 
choroid  artery,  642 
clinoid  process,  93,  132 
common  ligament,  272 
condyloid    foramen,    73,    133 

136 

t'n-sa,  136 

costo-transverse  ligament,  288 
costo-xiphoid  ligament,  290 
crucial  ligament,  339 
deep  cervical  vein,  733 
dental  canals,  106 
divisions    of     cervical    nerves, 

986 

ethmoidal  canal,  82,  100 
cells,  101,  145 
foramen,  82,  130,  141 
sinuses,  101 

external  jugular  vein,  728 
extremity  of  ribs  1(il 
head  of,  161 
neck  of,  161 
tuberosity  of,  162 
femoral  region,  muscles  of,  532 
fenestrated  space,  859 
fontanelle,  75,  103 
fossa  of  skull,  132 
gluteal  line,  216 
humeral  region,  muscles  of,  479 
inferior  cerebellar  artery,  641 

spinous  process  of  ilium,  217 
intercostal  veins,  752 
internal  frontal  artery,  629 
interosseous  artery  of  ulna,  665 

nerve,  1008 

intersternal  ligament,  292 
intertrochanteric  line,  225 
ligament  of  incus,  1171 
of  Winslow,  337 


Posterior  ligament  of  wrist,  320 
longitudinal  ligament,  272 

spinal  veins,  755 
median  ganglionic  arteries,  642 

vein,  736 
mediastinal  arteries,  668 

glands,  808 
mediastinum,  1397 
medullary  velum,  '.'ill 
meningeal  artery,  640 
nares,  142,  1108 
nasal  spine,  116,  135,  143 
occipito-atlantal  ligament,  278 
occipi to-axial  ligament,  280 
palatine  artery,  617 
canal,  107,  116 
canals,  accessory,  116,  135 
foramen,  135 
nerve,  10  10 

parolfactory  sulcus,  935 
peroneal  artery,  718 
pillar  of  soft  palate,  1222 
pillars  of  fornix,  950,  951 
pubic  ligament,  298 
radial  carpal  artery,  661 
radio-ulnar  ligament,  317 

region,  muscles  of,  488 
recurrent  tibial  artery,  712 
root  of  spinal  nerves,  983 
sacral  foramina,  63 
sacral-coccygeal  ligament,  296 
sacro-iliac  ligament,  294 
sacro-sciatic  ligament,  294 
scapular  artery,  644 
nerve,  999 

region,  muscles  of,  474 
semicircular  canal,   1167 
spinal  artery,  641 
sterno-clavicular  ligament,  3001 
sterno-costal   ligament,    290 
surface  of  liver,  1337 

of  stomach,  1278 
superior  dental  nerves,  1047 

spinous  process  of  ilium,  216 
temporal  artery,  613,  642 

diploic  vein,  734 
thoracic  nerve,  1000 
tibial  artery,  715 

veins,  758 
tibio-fibular  region,  muscles  of,  | 

537 

tibio-tarsal  ligament,  349 
triangle  of  neck,  620 
tubercle  of  cervical   vertebra,  j 

50 

tympano-malleolar     ligament, 
"  1166 
ulnar  recurrent  artery,  664 

vein,  745 

vertebral  vein,  733 
wall  of  tympanum,  1162 
Postero-lateral  fontanelles,   103   j 

ganglionic  arteries.  642 
Postero-median  ganglionic   arte-; 

ries,  630,  642 
Post  forceps,  940 
Postgemina,  905 
Postgeniculum,  905 
Post  hypophysis,  867,  917 
Postirisula,  933 
Postoblongata,     arcuate    fibre     i 

systems  of,  886 
decussation  of  lemnisci,  882 
gray  masses  of,  886 
internal  structure  of,  881 
pyramidal  decussation  of,  881 
raphe  of,  885 
rest  is  of,  885 
of  Wilder,  874 
Postoperculum.  925 
Postorbital  limbus,  930 


Postparietal  gyre,  931 
Post  peduncle  of  cerebellum,  900 
Postperforatum,  908,  916 
Postpontile  recess,  874 
Postramus  of  cerebellum,  899 
Postrhinal  fissure,  933 
Posttibial  nerve,  1031 
Postvermis,  896 
Pouch,  Douglas's,  1502 

of  Prussak,  1172 

recto-vaginal,  1502 

utero-vesical,  1499,  1502 
Poupart's  ligament,  438,  1527 
Pre-anal  fibres  of  levator  ani,  455 
Pre-aortic  glands,  798 
Pre-auricular  lymphatic  glands, 

779 
Pre-oblongata,  878 

fibre-tracks  in,  888 

gray  masses  in,  888 

internal  structure  of,  887 

nucleus  incertus,  888 

superior  olivary  nucleus,  887 
Pre-occipital  notch,  922 
Pre-operculum,  925 
Pre-sternal  notch,  157 
Pre-sternum,  157 
Prebrachium,  905 
Precava,  752 

relations  of,  752 

surgical  anatomy  of,  753 
Precentral  fissure,  927 
superior,  927 

gyre,  929 

Precerebellar  artery,  642 
Precerebral  artery,  628 

branches  of,  628 
Prechoroid  artery,  630 
Precommissure,  952 
Precommunicant  artery,  628,  629 
Precornu,  943 
Precuneal  fissure,  931 
Predural  artery,  623 
Preforceps,  940 
Pregemina,  905 
Pregeniculum,  913,  914 
Prehypophysis,  917 
Preinsula,  933 

gyres,  933 

Prelaryngeal  glands,  785 
Premaxillary  bones,  110 
Prepatellar  bursa,  342,  521 
Prepeduncles,  879 

cerebellar,  888,  901,  909 
Preperforation,  867,  935 
Prepuce  of  clitoris,  1494 

of  penis,  1465 

Prepyramidal  tract  of  cord,  853 
Preramus  of  cerebellum,  899 
Pressure  curves  of  humerus,  183 
Presylviari  ramus,  924 
Pretracheal  fascia,  391 

glands,  786 
Prevermis,  896 
Prevertebral  fascia,  390 
Prickle  cells,  1119 
Primordial  ova,  1514 
Princeps  hallucis  artery,  715 

pollicis  artery,  662 
Pro-gnathous  skull,  index  of,  148 
Pro-otic     portion     of     temporal 

bone,  91 

Process  or  processes,   acromion, 
175 

alveolar,  140 

angular,  80 
external,  14O 
internal,  140 

of  atlas,  55 

auditory,  88 

basilar,  73 


1600. 


IXDEX 


Process    or    processes,    of    calca- 
neus,  greater,  245 

lesser,  245 
clinoid,  anterior,  131 

middle,  93,  132 

posterior,  93,  132 
cochleariform,  91,  1163 
condyloid  of  lower  jaw,  125 
coracoid,  176 
coronoid,  of  jaw,  125 

of  ulna,  188 
costal,  50 
ethmoidal,  of  inferior  turbin- 

ated,  120 
falciform,  517 
hamular,  of  lachrymal,  1 13 

of  sphenoid,  90 
of  inferior  turbinated  bone,  120 
of  Ingrassias,  96 
jugular,  73 
lachrymal,  of  inferior  turbin- 
ated, 120 

of  malar  bone,  114 
mammillary,  of  lumbar  verte- 
brae, 57 

mastoid,  86,  138 
mental,  122,  140 
nasal,  80 

odontoid,  of  axis,  52 
olecranon,  186 
olivary,  93,  131 
orbital,  118 

of  malar,  114 
of  palate  bone,  118 
petrosal,  93 
postglenoid,  84 
pterygoid,  of  palate  bone,  117 

of  sphenoid  bone,  96 
sphenoidal,  1107 

of  palate  bone,  118 
spinous,  of  ilium,  217 

of  sphenoid,  95 

of  tibia,  236 
stylohyal,  92 
styloid,  of  fibula,  239 

of  temporal  bone,  90 

of  ulna,  191 

of  superior  maxillary,  109,  110 
tympanohyal,  92 
unciform,  202 

of  ethmoid,  100 
vaginal,  of  sphenoid,  95 

of  temporal  bone,  90 
of  vertebra,  articular,  49 
zygomatic,  84 

Processus  brevis  of  malleus,  1 1 69 
cochleariformis,  91,  1163 
gracilis  of  malleus,  1 168 
tubarius,  1165 
vaginalis,  1471 
Proctodseum,  1252 
Profunda  artery,  inferior,  658 

superior,  657 
femoris  artery,  704 

vein,  759 
Projection    fibres    of    cerebrum, 

963 

Prominentia  styloide*,  1163 
Promontory  of  sacrum,  61 

of  tympanum,  1162 
Pronator  quadratus  muscle,  485 
radii  teres  muscle,  481 

surgical  anatomy   of, 

481 

ridge,  190 

Prosencephalon,  91 1 
Prostate  gland,  1457 

apex  of,  1461 

arteries  of,  1462 

base  of,  1461 

capsule  of,  1459 


Prostate  gland,  isthmus  of,  1461 
lobes  of,  1461 
lymphatic  vessels  of,  800 
lymphatics  of,  1462 
nerves  of,  1462 
sheath  of,  1459 
structure  of,  1462 
surfaces  of,  1461 
surgical  anatomy  of,  1462 
veins  of,  1462 

Prostatic  ducts,  orifices  of,  1451 
plexus  of  nerves,  1095 

of  veins,  761 
portion  of  rectum,  1321 

of  urethra,  1450 
secretion,  1462 
sinus,  1451 
vesicle,  1451 

Prostatico-vesical  plexus,'  761 
surgical  anatomy  of,  762 
Proton,  869 
Proto  vertebra,  1245 
Protuberance,  mental,  122 
occipital,  external,  71,  136 

internal,  73 

Prbtuberantia  annularis,  877 
Prussak,  pouch  of,  1172 
Psalterium,  951 
Pseudocele,  920,  921,  941 
Pseudostomata,  1256 
Psoas  magnus  muscle,  512 

parvus  muscle,  512 
Pterion,  137,  150 
ossicle,  83,  103 
Pterygoid  artery,  616 
canal,  135 
depression,  125 
fissure,  96 
fossa  of  jaw,  115 

of  sphenoid,  96 
muscles,  external,  386 

internal,  386 
nerve,  external,  1051 

internal,  1051 
notch,  96 
plate,  external,  96 

internal,  96 
plexus  of  veins,  727 
process  of  palate  bone,  117 

of  sphenoid  bone,  96 
ridge,  95,  137 
tubercle,  97 
Pterygo-mandibular    ligament, 

383 

region,  dissection  of,  385 
muscles  of,  385 
nerves  of,  387 
Pterygo-maxillary  fissure,  139 

ligament,  383 

Pterygo-palatine  artery,  617 
canals,  135 
fossa,  139 
groove,  116 
nerve,  1050 
Pubic  arch,  211 

ligament,  anterior,  298 
inferior,  298 
posterior,  298 
superior,  298 

portion  of  fascia  lata,  1540 
surface  of  bladder,  1442 
Pubis,  219 
angle  of,  219 
body  of,  219 

ramus  of,  ascending,  219 
descending,  220 
inferior,  220 
superior,  219 
spine  of,  219 

Pubo-capsular  ligament,  330 
Pubo-coccygeus  muscle,  454 


Pubo-femoral  ligament,  330 
Pubo-prostatic    ligament,     1445, 

1461 
Pubo-vesical  ligament,  1445 

muscle,  1446 
Pudendal  nerve,  inferior,  1028 

plexus  of,  1026 
slit,  1489 
Pudendum,  1489 
Pudic  artery,  accessory,  691 
external  deep,  704 
superficial,  704 
internal,  in  female,  693 
in  male,  690 

branches  of,  691 
peculiarities  of,  691 
surgical  anatomy  of,  691 
nerve,  1028 

plexus  of,  1026 
vein,  internal,  760 
Pulmonary  alveoli,  1386 
artery,  589 
left,  589 
opening  of,  571 
right  of,  589 
branches    of    thoracic    portion 

of  gangliated  cord,  1087 
lymphatics,  812 
nerves,  dorsal,  1072 

ventral,  1072 
pleura,  1392 
plexus,  1091 

dorsal,  1069,  1072,  1091 
ventral,  1069,  1072,  1091 
sinuses  of  Valsalva,  573 
veins,  723 

Pulmonic  semilunar  valves,  573 
Pulp,  dental,  1210 
Pulvinar  of  optic  thalamus,  913 
Puncta  lacrimalia,  1152 
Punctum  lacrimale,  1148 
Pupil  of  eye,  1127 
Pupillary  margin,  1127 
Purkinje,  cells  of,  902 

fibres  of,  577 
Putamen,  954 
Pyloric  artery,  inferior,  675 

superior,  675 
glands,  1285 
orifice  of  stomach,  1279 
plexus,  1094 

portion  of  stomach,  1277 
sphincter,  1280 
valve,  1280 
Pylorus,  1279 

antrum  of,  1279 
Pyramid  of  Ferrein,  1425 
of  Lalouette,  1411 
of  Malpighi,  1425 
of  oblongata,  875 

decussation  of,  875 
of  tympanum,  1163 
of  vestibule  of  ear,  1174 
Pyramidal    lobe   of     cerebellum, 

898 

nerve  cells,  958 
tract,  956 
crossed,  853 
of  crusta,  910 
direct,  854 
Pyramidalis  muscle,  446 

nasi  muscle,  378 
Pyramido-oliviary  groove,  876 
Pyriformis  muscle,  527 
bursa  of,  528 


QUADRATE  lobe  of  liver,  1340 
Quadratus  femoris  muscle,  530 


IXDKX 


1601 


Quadratus  hunhorum,  fascia  of, 

451 
muscle,  451 

mrnti  muscle,  380 
Quadriceps  extensor  muscle,  518 
Quudrigemina,  869,  005,  907 

brachia  of,  905 

nates  of,  905 

postgemina  of,  905,  907 

pregemina  of,  905,  907 

structure  of,  905 

testes  of,  905 
Quadrilateral  muscles,  365 


RADIAL  artery,  659 
branches  of,  661 
peculiarities  of,  660 
relations  of,  659 
surface  marking  of,  660 
surgical  anatomy  of,  660 
fossa,  183 

head  of  humerus,  183 
nerve,  1008 
recurrent  artery,  661 
region,  muscles  of,  486,  497 

dissection  of,  486 
vein.  745 

Radialis  indicis  artery,  662 
Radiate  fissure,  928 
Radio-carpal  articulations,  319 
surface  form  of,  320 
surgical  anatomy  of,  320 
Radio-ulnar  articulation,  315 
inferior,  317 

surface  form  of,  319 
middle,  316 
superior,  316 

surface  form  of,  316 
surgical  anatomy  of,  316 
ligaments,  annular,  316 
anterior,  317 
oblique,  316 
orbicular,  316 
posterior,  317 
round, 316 
region,  anterior,  muscles  of,  481 

surgical  anatomy  of,  486 
posterior  muscles  of,  488 

surgical  anatomy  of,  493 
Radius,  192 

articulations  of,  194 
attachment  of  muscles  to,  19-1 
development  of,  194 
lower  extremity  of,  193 
shaft  of,  192 

borders  of,  192,  193 
surfaces  of,  193 
sigmoid  cavity  of,  193 
structure  of,  194 
surface  form  of,  194 
surgical  anatomy  of,  194 
upper  extremity  of,  192 
Rami  of  lower  jaw,  124 
Ramus  episylvian,  925 
hyposylvian,  925 
of  isehimn,  ascending,  218 

descending,  218 
presylvian,  924 
of  pubis,  ascending,  219 
descending,  220 
inferior,  220 
superior,  219 
subsylvian,  924 
Ranine  artery,  606 

vein,  729 

Raph6  of  perineum,  1549 
of  poetoblongata,  885 
of  scrotum,  1473 

101 


Raph6  of  tongue,  1097 
Receptaculum  chyli,  775 
Recess,  epitympanic,  87 

infundibular  of  third  ventricle, 

917 

postpontile,  874 
Recessus  cochlearis  of   Reichert. 

1174 

tecti,  902 

Reciprocal    reception,     articula- 
tion by,  267 
Rectal  columns,  1326 
glands,  snr, 
valves,  1326 

Recto-urethralis  muscle,  456 
Recto-uterinus  muscle,  1503 
Recto-vaginal  fold,  1502 

pouch,  1322,  1502 
Recto-vesical  fascia,  1558 

pouch, 1322 
Rectum.  1320 

areolar  coat  of,  1325 
arteries  of,  1327 
curves  of,  1321 
lymphatics  of,  807,  1329 
mucous  membrane  of,  1326 
muscular  coat  of,  1324 
nerves  of,  1329 
prostatic  portion  of,  1321 
sacrococcygeal  portion  of,  1320 
serous  coat  of,  1324 
structure  of,  1324 
submucous  coat  of,  1325 
supports  of,  1322 
surface  form  of,  1331 
surgical  anatomy  of,  1331 
veins  of,  1328 

Rectus  abdominis  muscle,  444 
capitis  anticus  major  muscle. 

408 

minor  muscle,  409 
lateralis  muscle,  409 
posticus  major  muscle.  424 

minor  muscle,  424 
femoris  muscle,  518 
oculi  muscle,  external,  375 
inferior,  375 
internal,  375 
superior,  375 

Recurrent  artery,  palmar,  662 
radial,  661 
tibial,  anterior,  713 

posterior,  712 
ulnar,  anterior,  664 

posterior,  664 
laryngeal  nerve,  1071 
Reflections  of  pleurae,  1392 
Refracting  media  of  eye,  1138 
Reichert,  recessus  cochlearis  of, 

1174 

Reil,  island  of,  933 
Reissner,  membrane  of,  1182 
Renal  artery,  680 
inferior,  1432 
bloodvessels,  1432 
impression  of  liver,  1337 
plexus,  1072,  1093 
surface  of  spleen,  1361 
veins,  767 
zone  of  Hyrtl,  exsanguinated, 

1432 

Reservoir  of  Pecquet,  775 
Respiration,  muscles  of,  433 

organs  of,  1369 

Respiratory  nerve  of  Bell,  exter- 
nal, 1000 
internal,  992 
Rest  is  of  oblongata,  876 
of  postoblongata,  885 
HHe  test  is  of  Haller,  1482 
Reticular  formation  of  cord,  845 


Retina,  1130 

nerve-fibres  of,  1 1 32 
physiological,  1130 
pigmentary  layer  of ,  1137 
rods  of,  1135 
structure  of,  1131 
supporting  framework  of,  1137 
Retinacula  of  capsular  ligament 

of  hip,  329 
patellae  mediale,  520 
Retrahens  auriculam  muscle,  371 
Retro-aortic  glands,  797 
Retro-csecal  fossa,  1272 
Retro-colic  fossa>,  1272 
Retro-crural  glands,  795 
Retro-duodenal  fossa,  1271 
Retro-peritoneal  lossa?,  1270 

space,  1257 
Retro-pharyngeal  glands,  784 

space,  391,  1230 
Retro-rectal  space,  1322 
Retro-renal  fascia,  1420 
Retro-sternal  glands,  807 
Retzius,  brown  striae  of,  1214 
fundiform  ligament  of,  544 
gyrus  fasciolaris  of,  938 
intralimbicus  of,  937 
space  of,  1 442 
Rhinencephalon,  920,  934 
central  part  of,  936 
cortical  part,  of,  936 
Rhodopsin,  or  visual  purple,  1130 
Rhombencephalon,  874 
Rhombocaele,  845 
Rhomboid  impression,  170 

ligament,  300 
Rhomboidal  muscles,  365 
Rhomboideus  major  muscle,  416 

minor  muscle,  416 
Rlbes,  ganglion  of,  1077 
Ribs,  163 

anterior  extremity  of,  162 
articulations  of,  285 
attachment  of  muscles  to,  165 
cervical,  53,  167 
common  characters  of,  161 
development  of,  165 
false,  161 
floating,  161 
peculiar,  163 

posterior  extremity  of,  161 
shaft  of,  162 
structure  of,  165 
true,  161 

Ridges,  bicipital,  181 
epicondylic,  181 
gluteal,  226 
mylo-hyoid,  123 
naso-labial,  380 
.  oblique,  of  trapezium,  200 

of  ulna,  190 
pectoral,  181 
pronator,  190 
pterygoid,  95,  137 
superciliary,  80 
supracpndylar,  external,   181 

internal,  181 
supraorbital,  140 
temporal,  76,  80 
trapezoid,  169 
Riedel's  lobe  of  liver,  1343 
Right    ascending    lumbar    vein, 

752 

azygos  vein,  752 
bronchus,  1384 
cardiac  vein,  771 
colic  artery,  677 
coronary  artery,  592 

plexus,  1090 

forechamber  of  heart,  567 
innominate  vein.  750 


1602 


INDEX 


Right  juxta-aortic  glands,  797 

lobe  of  liver,  1340 

lymphatic  duct,  777 

superior  intercostal  vein,  752 
Rima  glottidis,  1377 
Ring,  abdominal,  internal,  448 

crural,  439,  1544 

femoral,  439,  511,  1544 

fibrous,  of  heart,  576 

muscle  of  Miiller,  1126 
Ripa,  912 

Risorius  muscle,  383 
Risus  sardonicus,  383 
Rivinus,  ducts  of,  1227 

notch  of,  1161 
Rod-bipolars,  1135 
Rod-cells,  1136 
Rod-fibre,  1136 
Rod-granules,  1135 
Rods  of  Corti,  1184 

of  retina,  1135 
Rolandic  angle,  926 
Rolando,  fissure  of,  926 
Roots  of  cervical  nerves,  986 

of  fifth  nerve,  ascending,  1042 
descending,  1042 

•of  lumbar  nerve,  1015 

of  lung,  1402 

of  penis,  1464 

of  sacral  nerves,  1023 

of  spinal  nerves,  983 
dorsal,  983 
ventral,  983 

of  thoracic  nerves,  1010 

of  tongue,  1097 

of   vagus   nerve,    ganglion    of, 

1069 
Rosenmuller,  fossa  of,  1231 

gland  of,  794 
accessory,  1151 

organ  of,  1511 
Rostral  fissure,  928 
Rostrum,  920 

of  sphenoid  bone,  94,  135 
Rotary  joint,  287 
Rotatores  spinsc  muscle,  423 
Round  ligament,  artery  of,  689 
of  liver,  1342 
of  uterus,  1503 

Roux's  amputation  of  foot,  259 
Rubro-spinal  tract  of  cord,  853 
Rudimentary  organ  of  Jacobson, 

1110 
Rudinger,    dilator   tubse   muscle 

of,  1165 
Rugse  of  scrotum,  1473 

of  stomach,  1283 

of  vagina,  1496 
Ruysch,  tunic  of,  1123 


S 

SACS,  abdominal,  1246 

dental,  1216 

lachrymal,  1152 

pericardia!,  1246 

pleural,  1246 
Saccule  of  "vestibule,  1180 
Sacculi  alveolares,  1386 
Sacculus  laryngis,  1379 
Sacral  artery,  lateral,  694 
middle,"  683 

canal,  64 

cornua,  62 

foramina,  anterior,  62 
posterior,  63 

groove,  63 

lymphatic  glands,  797 

nerve.  1023 


Sacral  nerve,  division  of,  dorsa 

1023 

ventral,  1025 
roots  of,  1023 
plexus,  1026,  1095 
portion     of    gangliated     rord 

1089 
veins  lateral,  760 

middle,  764 
Sacro-coccygeal   ligament,   ant 

rior,  296 
lateral,  297 
posterior,  296 
portion  of  rectum,  1320 
symphisis,  66 

Sacro-iliac  ligament,  anterior,  294 
interosseous,  294 
long,  294 
oblique,  294 
posterior,  294 
short,  294 

Sacro-lumbalis  muscle,  421 
Sacro-sciatic  foramen,  great,  218, 

296 

inferior,  296 
lesser,  218,  296 
superior,  296 
ligament,  anterior,  295 
great,  294 
lesser,  295 
posterior,  294 
notches,  211 
great,  217 
lesser,  218 

Sacro-uterine  ligaments,   1502 
Sacro- vertebral  angle,  61 
Sacrum,  61 
ala  of,  64 
apex  of,  64 
articulations  of,  65 
attachment  of  muscles  to,  65 
base  of,  64 
development  of,  64 
differences    in    the    male    and 

female,  64 
peculiarities  of,  64 
promontory  of,  61 
structure  of,  64 
surfaces  of,  61 
tuberosity  of,  63 
Saddle-joint,  267 
Sagittal  axis,  1115 
sulcus,  73,  80 
suture,  78,  127 
Salivary  glands,  1224 
structure  of,  1227 
surgical  anatomy  of,  1234 
Salpingo-palatine  fold,  1231 
Salpingo-pharyngeal  fold,  1231 
Salpingo-pharyngeus  muscle,  40" 
Salter,      incremental      lines      o! 

1213 

Santorini,  cartilages  of,  1373 
comical  tubercle  of,  1376 
fissures  of,  1156,  1158 
muscle  of,  383 
Saphenous  gland,  external,  794 
opening,  516,  1541 
nerve,  1022 
external,  1031 
internal,  1022 
long,  1022 
short,  1031 
vein,  external,  756 
internal,  756 
long,  756 
short,  756 

surgical  anatomy  of,  757 
Sarcolemma,  364 
Sardonic  laugh,  383 
Sartorius  muscle,  518 


Sartorius  muscle,  nerve  to,  1022 
St-ala  media,  1182 

tympani  of  cochlea,  1178 
vestibuli  of  cochlea,  1178 
Scalenus  muscles,  anticus,  410 
medius,  410 
posticus,  411 
Scalp,  skin  of,  368 
Scapha,  fossa  of,  1155 
Scaphoid  bone  of  foot,  249 
articulations  of,  249 
attachment  of  muscles  to, 

249 

surfaces  of,  249 
tuberosity  of,  249 
of  hand,  197 

articulations  of,  198 
attachment  of  muscles  to, 

198 

surfaces  of,  198 
fossa,  97,  135,  1154 
skull,  146 
Scapula,  172 
angles  of,  175 
articulations  of,  178 
attachment  of  muscles  to,  178 
base  of,  176 
borders  of,  175.  176 
development  of,  177 
dorsum  of,  173 
head  of,  176 
ligaments  of,  303 
spine  of,  175 
structure  of,  177 
surface  form  of,  178 
surgical  anatomy  of,  178 
venter  of,  172 

Scapular  arteries,  posterior,  644 
glands,  788 
nerve,  posterior,  999 
notch,  great,  175 
region,    anterior,    muscles    of, 

473 

dissection  of,  473 
posterior,  muscles  of,  474 

dissection  of,  474 
Scapulo-clavicular     articulation, 

301 

Scarf  skin,  1191 
Scarpa,  fascia  of,  435 

foramina  of,  110,  135,  1050 
ganglion  of,  1065 
membrane  of,  1162 
nerve  of,  1050 
triangle  of,  518,  698 
Schachowa,  spiral  tube  of,  1427 
Schindylesis,  266 
Schlemm,  canal  of,  1118,  1121 

ligament,  307 
Schmidt-Lautermann,     incisures 

of,  824 

Schneiderian  membrane,  1110 
Schreger,  concentric  lines  of,  1213 
Schultze,  comma  tract  of,  851 
Schwann,   medullary   sheath  of, 

824 

Sciatic  artery,  693 
nerve,  great,  1030 

branches  of,  1030 
small,  1027 

branches  of,  1028 
notch,  great,  217 
plexus,  1026 
veins,  761 
Sclera,  1117 

structure  of,  1118 
Scleral  sulcus,  1115 
Sclerotic  coat,  1117 
Scrotal  hernia,  1533 
nerve,  long,  1028 
Scrotum,  1472 


Scrotum,  arteries  of,  1476 
dartos  of,  1473 
integument  of,  1473 
lymphatic  vessels  of,  799 
lymphatics  of,  1470 
nerves  of,  1476 
raphe  of,  1473 
rugae  of,  1473 
septum  of,  1473 
surgical  anatomy  of,  1478 
veins  of,  1476 

Sebaceous  glands,  1148,  1201 
Second  nerve,  1038 
Secondary  ear-drum  membrane 

1162 

Sella  turcica,  93, 131 
Semen,  1485 

Semicircular  canals,  1175 
external,  1175 
horizontal,  1175 
membranous,  1180 
posterior,  1175 
superior,  1175 
muscles  of  rectum,  1325 
Semilunar  bone,  198 

articulations  of,  199 
surfaces  of,  198 
fascia,  478 
nbro-cartilages,  339 
external,  341 
internal,  340 
folds  of  colon,  1325 

of  Douglas,  441,  446 
ganglion  of  abdomen,  1091 

of  fifth  nerve,  1042 
hiatus,  145,  747 
valves,  aortic,  574 

pulmonic,  573 
."Semimembranosus  muscle,  533 

bursa  of,  534 
Seminal  duct,  1484 
vesicles,  1486 
arteries  of,  1487 
lymphatic  vessels  of,  802 
lymphatics  of,  1487 
nerves  of,  1487 
structure  of,  1487 
surgical  anatomy  of,  1487 
veins  of,  1487 
'Semispirialis  colli  muscle,  423 

dorsi  muscle,  423 
Semitendinosus  muscle,  533 
Sensor  neurones,  816 

peripheral  axone  of,  819 
root  of  spinal  cord,  836 
Septum  atriorum,  569 
crurale,  1544 

of  Cloquet,  511 
interauricular,  567 
intervenrioular,  751 
lucidum,  941,952 
of  nose,  142 

cartilage  of,  triangular,  1107 
orbital,  1149 
pectiniforme,  1467 
pellucidum,  921 
of  scrotum,  1473 
of  tongue,  fibrous,  400 
transversum,  1180 
Serous  coat  of  anal  canal,  1324 
of  bladder,  1446 
of,  gall-bladder,  1351 
of  large  intestine,  1324 
of  lungs,  1362 
of  rectum,  1324 
of  small  intestine,  1298 
of  spleen,  1363 
of  stomach,  1281 
of    vermiform     appendix, 

1312 
•covering  of  ovary,  1513 


INDEX 

Serous  pericardium,  562 
Sorratus  inagnus  muscle,  471 

posticus  inferior  muscle,  417 

superior  muscle,  417 
Sertoli,  cell  of,  1483 
Sesamoid  bones,  259 

cartilage,  1107 
Seventh  nerve,  1059 

surgical  anatomy  of,  1004 
Shaft  of  bone,  its  structure,  33 

of  hair,  1199 

of  ribs,  162 
Sharpey,  fibres  of,  37 
Sheath,  carotid,  390 

dentinal,  of  Neumann,  1213 

femoral,  511,  1542 

of  flexor  tendons,  fibrous,  548 

granular,  of  Tomes,  1212 

myelin,  824 

of  prostate,  1459 

of  rectus  muscles,  445 

synovial,  265 
Shin  bone,  234 
Short  bones,  33 

calcaneo-cuboid  ligament,  355 

ciliary  arteries,  627 

plantar  ligament,  355 

sacro-iliac  ligament,  294 

saphenous  vein,  756 
Shoulder,  fascia  of,  deep,  472 
superficial,  472 

girdle,  168 

muscles  of,  472 
Shoulder-joint,    articulations   of, 
305 

bursse  of,  307 

surface  form  of,  309 

surgical  anatomy  of,  309 
Shrapnell,  membrana  flaccida  of, 

1166 
Sibson,  aortic  vestibule  of,  574 

aponeurosis,  1393 
Sigmoid  arteries,  680 

cavity  of  radius,  193 
of  ulna,  186 

colon,  1317 

flexure  of  colon,  1317 
of  large  intestine,  1308 

fossa,  86 

rnesocolon,  1269 

notch  of  lower  jaw,  125 

plexus,  1095 

sinus,  739 

sulcus,  86 
Sinus  or  sinuses,  air,  82 

alse  parvsc,  740 

of  aorta,  great,  591 

basilar,  743 

cavernous,  739 

circular,  742 

confluence  of,  737 

coronary  vein,  569,  771 

costo-mediastinal,  1395 

of  dura,  736 

ethmoidal,  101 

falcial,  738 

frontal,  80 

of  heart,  auricle  of,  left,  570 
right,  567 

intercavernous,  742 

of  jugular  vein,  external,  728 
internal,  729 

ot  kidney,  1423 

laryngeal,  1379 

lateral,  738 

longitudinal,  inferior,  738 
superior,  78,  130,  736 

maxillary,  108 

of  Morgagni,  404 

of  nose,  80 

occipital,  739 


1603 

Sinus  or  sinuses,  orbital,  118 
of  pericardium,  oblique,  562 

transverse,  562 
petrosal,  inferior,  742 

superior,  742 
petro-squamous,  739 
phrenico-costal,  1395,  1422 
pocularis,  1451 
portal,  769 
prostatic,  1451 
pyriformis,  1232,  1376 
sigmoid,  739 
spheno-parietal,  740 
sphenoidal,  94,  143 
straight,  738 
subpetrosal,  742 
superpetrosal,  742 
tentorial,  738 
terminalis,  845 
tonsillaris,  1232 
transverse,  743 

peric»rdial,  562 
utricularis  sacculi,  1180 
of  Valsalva,  aortic,  575 

pulmonary,  573 
venosus,  567 
Sixth  nerve,  1057 

surgical  anatomy  of,  1058 
Skeletal  muscles,  363 
Skin,  1188 

appendages  of,  1195 
arteries  of,  1194 
cuticle  of,  1191 
epidermis,  1191 
folds  of,  1188 
furrows,  1189 
horny  layer  of,  1191 
lymphatics  of,  1194 
Malpighian  layer  of,  1192 
nerves  of,  1194 
papillary  layer  of,  1191 
pigmentation  of,  1192 
ridges,  1189 
of  scalp,  368 
scarf,  1191 
stratum  cylindricum,  1192 

germinativum,  1192 

granulosum,  1192 

lucidum,  1192 

mucosum,  1192 

spinosum,  1192 
true,  1190 
veins  of,  1 1 94 
Skull,  acrocephalic,  146 
angles  of,  147 
anterior  region  of,  139 
base  of,  130 
brachycephalic,  146 
at  different  ages,  102 
dimensions  of,  147 
dolichocephalic,  146 
fixed  point  for  measurement  of, 

150 
fossa  of,  anterior,  130 

infratemporal,  138 

middle,  130 

orbital,  140 

posterior,  132 

pterygo-palatine,  139 

spheno-maxillary,   139 

temporal,  137 

zygomatic,  138 
index  of,  147 

cephalic,  147 

facial,  147 

gnathic,  148 

of  height,  147 

mesognathous,  148 

nasal,  147 

orbital,  147 

ortho-gnathous,  148 


1604 


INDEX 


Skull,  index  of,  palatal,  147 

prognathous,  148 
lateral  regions  of,  136 
megacephalic  capacity  of,  147 
mesocephalic  capacity  of,  147 
microcephalic  capacity  of,  147 
scaphoid,  146 
sexual  differences  in,  102 
shape  of,  146 
surface  form  of,  148 
surgical  anatomy  of,  150 
tables  of,  33 

vitreous,  34 
vertex  of,  129 
Small  coronary  vein,  771 
intestine,  1290 
occipital  nerve,  989 
palatine  nerve,  1050 
sciatic  nerve,  1027 
Smell-brain,  920 
Socia  parotidis,  1225 
Soft  palate,  1221 

aponeurosis  of,  1222 

arches  of,  1221 

arteries  of,  1222 

mucous  membrane  of,  1222 

muscles  of,  1222 

nerves  of,  1223 

pillars  of,  1221 

veins  of,  1223 
Solar  plexus,  1091 
Soleus  muscle,  538 
Solitary  glands,  1303,  1327 
Somatopleure,  1245 
Sommerring,  foramen  of,  1131 

yellow  spot  of,  1131 
Space  or  spaces,  axillary,  647 
of  Burns,  389 
cartilage,  262 
corneal,  1120 
epidural,  857,  973 
epitympanic,  87 
fenestralia,  859 
of  Fontana,  1120 
intercostal,  161 
intercrural,  904 
interglobular,    of    Czermak, 

1212 

interpleural,  1396 
mediastinal,  1396 
of  Nuel,  1185 
perichoroidal,  1118 
perisclerotic,  1113 
pneumatic,  1113 
popliteal,  707 
retro-peritoneal,  1257 
retro-pharyngeal,  391,  1230 
of  Retzius,  1442 
subarachnoid,  858,  977 

anterior,  978 
subdural,  858,  973 
suprascleral,  1113 
suprasternal,  389 
Special  sense,  organs  of,  1097 
Spermatic  arteries,  681 
canal,  450,  1529 
cord,  1476 

arteries  of,  1477 

lymphatics  of,  1478 

nerves  of,  1478 

structure  of,  1476 

surgical  anatomy  of,  1478 

veins  of,  1477 
fascia,  1464 

external,  1526 

internal,  448 

middle,  442 
nerve,  external,  1018 

plexus  of,  1094 
vein,  765     . 

plexus  of,  765 


Spermatic  vein,  surgical  anatomv 

of,  766 

Spermatids,  1483 
Spermatoblasts,  1483 
Spermatocysts,  1483 
Spermatogenesis,  1483 
Spermatogonia,  1483 
Spermatozoid,  1483 
Spheno-ethmoidal  recess,  145 
Spheno-maxillary     fissure,     115 

138 

fossa,  115,  139 
Spheno-palatine  artery,  617 
foramen,  119,  143 
ganglion,  1048 
nerves,  1047 
notch,  118 
Spheno-parietal  sinus,  740 

suture,  128 

Spheno-phrenic  ligament,  1266 
Sphenoid  bone,  92 

articulations  of,  98 
attachment   of    muscles   to 

98 
body  of,  92 

surfaces  of,  93 
development  of,  97 
greater  wings  of,  95 
circumference  of,  95 
surfaces  of,  95 
hamular  process  of,  96 
lesser  wings  of,  96 
pterygoid  process  of,  96 
rostrum  of,  94,  135 
Sphenoidal  cells,  94 
crest,  94 
fissure,  96,  132 
process,  1107 

of  palate  bone,  118 
sinuses,  94,  143 
spine,  95 
spongy  bones,  97 
turbinated  bones,  143 
Spherical  recess,  1174 
Sphincter  ani   muscle,   external, 

452 

internal,  453 
muscles,  365 
pyloris,  1280 
vaginae  muscle,  463 
Spigelian  lobe  of  liver,  1337 
Spina  tympanica  major,  1161 

minor,  1161 
Spinal     accessory     nerve,     1073. 

See  Accessory  nerve, 
arachnoid,  858 
arteries,  anterior,  640 
dorsal,  641 
lateral,  640 
posterior,  641 
ventral,  640 
branch  of  vertebral  artery,  640 
bulb,  874 
canal,  69 
column,  48 
cord,  834 

arachnoid,  858 

axones  of,  myelinization  of, 

855 

canal  of,  central,  845 
cells  of,  855 
columns  of,  839 

dorsal,  ground  bundle    of, 

852 
lateral,  ground  bundles  of, 

853 
ventral,    ground   bundles 

of,  854 
commissure  of,  844,  845 

white,  ventral,  854 
conus  of,  837 


Spinal   cord,   cornua    of,    dorsal 

horn,  844 
lateral  horn,  845 
•ventral  horn,  845 
development  of,  840 
dissection  of,  856 
dura  of,  856 
enlargement  of,  836 
cervical,  836 
lumbar,  836 

external  morphology  of,  835 
fibres,  longitudinal,  848 
filum  of,  837 
fissures  of,  837 
gliosa  of,  847 
grooves  of,  837 
ground  bundles  of,  849 
internal  structure  of,  843' 
membranes  of,  856 
muscular  supply  from  motor 

segments  of,  843 
pia  of,  859 

reticular  formation  of,  845 
roots  of,  836 
afferent,  836 
dorsal,  836 
efferent,  836 
motor,  836 
sensor,  836 
ventral,  836 
substances  of,  gray,  843,  855 

white,  848,  856' 
surgical  anatomy  of,  860 
tracts    of,     cerebello-spinal, 

853 

conducting,  841 
direct  cerebellar,  852 
dorso-lateral      spino-cere- 

bellar,  852    • 
functions  of,  844 
intermedio-lateral,    853 
lateral    vestibulo-spinal, 

853 

marginal,  851 
olivo-spinal,  853 
prepyramidal,  853 
pyramidal,  853 

direct,  854 
rubro-spinal,  853 
spino-mesencephalic,    852 
spino-olivary,  853 
spino-thalamic.,  852 
sulco-marginal,  854 
superficial     ventro-lateral 

spino-cerebellar,    852 
ventral   cerebello-spinal, 

854 

vestibulo-spinal,  854 
veins  of,  755 
ventral    column   of,   ground 

bundle  of,  854 
weight  of,  835 
dura,  856 
foramen,  49 
nerves,  982 

accessory,  1073 
distribution  of,  984 
ganglia  of,  983 
gray  ramus  communicans  of, 

985 

points  of  emergence  of,  985 
roots  of,  dorsal,  982 

ventral,  982 

visceral  branches  of,  985 
white    ramus    communicans 

of,  985 

portion  of  accessory  nerve,  1074 
veins,  753 

longitudinal,  anterior,  754 

posterior,  755 
plexus  of,  753 


1M)EX 


1605 


Spinalis  colli  muscle,  422 

dorsi  muscle,  421 
Spindle,  aortic,  593 
Spindles,  neuro-muscular,  830 

neuro-tendinous,  831 
Spine,  articulations  of,  278 

ethmoidal,  93,  130 

frontal,  80 

of  helix,  1156 

of  Henle,  88 

of  ilium,  217 

of  ischium,  218 

mental,  123 

nasal,  SO 

anterior,  111,  139,  143 
posterior,  116,  135,  143 

palatine,  116 

peroneal,  246 

pharyngeal,  73,  135 

progress  of  ossification  in,  60 

of  pubis,  219 

of  scapula,  175 

spheiioidal,  95 

suprameatal,  88 
Spino-cerebellar    tract,    ventral, 

901 

Spino-glenoid  ligament,  304 
Spino-mesencephalic    tract    of 

cord,  852 

Spino-olivary  tract,  853,  886 
Spino-thalamic  tract  of  cord,  852 
Spinous  processes  of  ilium,  217 
of  tibia,  236 
of  vertebrae,  49 
Spiral  canal  of  cochlea,  1177 

ligament  of  cochlea,  1182 

line  of  femur,  225 

tube  of  Schachowa,  1427 
Spitzka,  marginal  tract  of,  852 
Splanchnic  nerves,  1087 
Splanchnopleure,  1245 
Spleen,  1361 

accessory,  1363 

arteries  of,  1364 

development  of,  1255 

fibre-elastic  coat  of,  1363 

hilum  of,  1361 

lymphatics  of,  804,  1366 

Malpighian  bodies  of,  1365 

movability  of,  1363 

movable,  1363 

nerves  of,  1366 

serous  coat  of,  1363 

.structure  of,  1363 

supernumerary,  1363 

support  of,  1363 

surface  form  of,  1366 

surgical  anatomy  of,  1366 

veins  of,  1366 
Splenic  artery,  676 

flexure  of  colon,  1317 
of  large  intestine,  1308 

glands,  798 

plexus,  1072,  1094 

pulp,  1363 

vein,  768 

Splenium,  920,  940,  941 
Splenius  muscle,  418 
Spongioblasts,  818 
Spongiosa,  847 
Spongy  portion  of  urethra,  1452 

tissue  of  bone,  33 
Spur,  femoral,  229 
Squamo-parietnl  suture,  128 
Squamo-sphenoidal  suture,  128 
Squamous    portion    of    occipital 
bone,  71 

suture,  85,  128 
Square  lobe  of  liver,  1340 
Stahr,  middle  fdand  of,  784 
Stapedius  muscle,  1171 


Stapes,  1170 

base  of,  1170 

crura  of,  1170 

foot-plate,  1170 

head  of,  1170 

ligament  of,  1171 

neck  of,  1170 
Statoliths,  1181 
Stellate  cells,  821 

ligament,  286 

reticulum,  1216 
Stenson,  duct  of,  1225 

foramina  of,  110 
Stephanion,  137 

inferior,  76,  150 

superior,  76,  150 
Sternal  arteries,  646 

foramen,  159 

furrow,  166 

glands,  807 

ribs,  161 
Sterno-clavicular      articulations, 

299 

surface  form  of,  301 
surgical  anatomy  of,  301 
Sterno-cleido-mastoid  muscle,391 
Sterno-costal  ligament,  anterior, 

290 

interarticular,  290 
posterior,  290 
Sterno-costo  pericardial  ligament, 

560 

Sterno-hyoid  muscle,  394 
Sterno-mastoid  artery,  605,  611 

glands,  785 

muscle,  391 

surface  form  of,  393 
surgical  anatomy  of,  393 
Sterno-pericardiac  ligaments,  560 
Sterno-thyroid   muscle,   394 
Sternum,  157 

angle  of,  157 

articulations  of,   161,  292 

attachment  of  muscles  to,  161 

development  of,  159 

ensiform  appendix  of,  159 

gladiolus,  157 

ligaments  of,  292 

manubrium  of,  157 

structure  of,  159 

surface  form  of,  166 

surgical  anatomy  of,  167 

xiphoid  appendix  of,  159 
Stigmata,  1256 
Stilling,  canal  of,  1139 

nucleus  of,  847 
Stomach,  1277 

alterations  in  position  of,  1280 

areolar  coat  of,  1283 

arteries  of,  1286 

body  of,  1277 

cardiac  orifice  of,  1278 
portion  of,  1277 

chamber,  1277 

curvatures  of,  1278 

fundus  of,  1277 

innervation  of,  1288 

lymphatic  vessels  of,  804,  1287 

movements  of,  1288 

mucous  membrane  of,  1283 

muscular  coat  of,  1282 

nerves  of,  1287 

oesophageal  opening  of,  1278 

peritoneal  coat  of,  1281 

pit  of,  166 

pyloric  orifice  of,  1279 
portion  of,  1277 

relations  of,  1277 

rugae  of,  1283 

serous  coat  of,  1281 

structure  of,  1281 


Stomach,    submucous     coat    of, 
1283 

supports  of,  1281 

surface  form  of,  1288 

surfaces  of,  1277 

surgical  anatomy  of,  1288 

vascular  coat  of,  1283 

veins  of,  1287 
Stomach  teeth,  1207 
Stomata,  1256 
Straight  sinus,  738 
Stratum  cinereum,  907 

opticum,  907 

zonale,  907,  912 
Stria  medullaris,  912 

terminalis,  913 

vascularis,  1182 
Striae,  olfactory,  935 
Striated  muscle,  363 

structure  of,  364 
Striatum,  952 

connections  of,  964 
Striped  muscle,  363 
Stroma  of  iris,  1128 

of  ovary,  1514 

plexus  of,  1121 
Stylo-glossus  muscle,  399 
Stylo-hyal  process,  92 
Stylo-hyoid  ligament,  397 

muscle,  396 

nerve  from  facial,  1062 
Stylo-mandibular  ligament,  283, 

389 
Stylo-mastoid  artery,  611 

foramen,  90,  135 
Stylo-maxillary  ligament,  283 
Stylo-pharyngeus  muscle,  405 
Styloid  process  of  fibula,  239 
of  temporal  bone,  90 
of  ulna,  191 

Subacromial  bursa,  307,  473 
Subanconeus  muscle,  480 
Subarachnoid  cisternae,  978 

space,  859,  977 
anterior,  978 

tissue,  859 
Subarachnoidean   areolar   tissue, 

977 

Subcalcarine  gyre,  932 
Subcallosal  gyre,  867 
Subcerebellar  veins,  736 
Subcerebral  veins,  735 
Subclavian  artery,  633 
branches  of,  639 
first  part  of  left,  635 

right,  633 

peculiarities  of,  636 
second  part  of,  635 
surface  form  of,  637 
surgical  anatomy  of,  637 
third  part  of,  636 

glands,  790 

groove,  170 

loop,  1086 

plexus  of  nerves,  1086 

triangle,  620 

vein,  749 

Subclavius  muscle,  470 
Subcollateral  gyre,  932 
Subcostal  artery,  669 

groove,  163 

Subcrureus  muscle,  521 
Subcutaneous     acromial     bursa, 
307 

areolar  tissue,  1190 

olecranon  bursa,  479 

synovial  bursa,  265 

tibial  bursa,  342 

trochanteric  bursa,  333 
Subdnltoid  bursa,  307,  473 
Subdural  space,  858,  973 


1606 


INDEX 


Subepithelial  plexus,  1121 
Subfrontal  fissure,  927 

gyre,  929 
Sublingual  artery,  606 

fossa,  123 

gland,  1227 
Sublobular  veins,  767 
Submaxillary  artery,  608 

fossa,  123 

ganglion,  1054 
branches  of,  1054 

gland,  784,  1226 
arteries  of,  1227 
ducts  of,  1226 
lymphatics  of,  1227 
nerves  of,  1227 
veins  of,  1227 

triangle,  396,  619 

vein,  727 
Submental  artery,  608 

glands,  784 

Subnasal  point  of  skull,  150 
Suboccipital  fissure,  931 

lymphatic  glands,  779 

nerves,  986 

triangle,  425 
Suboperculum,  925 
Suborbital  glands,  781 
Subparotid  glands,  1225 

lymphatic  glands,  781 
Subpetrosal  sinus,  742 
Subpleural    mediastinal    plexus 

646 

Subpubic  ligament,  298 
Subrostral  fissure,  928 
Subscapular  angle,  173 

artery,  653 

bursa,  307 

fascia,  473 

fossa,  172 

nerves,  1001 

Subscapularis  muscle,  473 
Subserous  areolar  coat  of  lungs 

1403 
tissue,  1256 

connective  tissue,  1256 
Substance  of  cord,  gray,  855 

white,  856 
Substantia  ferruginea,  880 

nigra,  906,  907 

propria  of  cornea,  1120 

reticularis  alba,  933 
Substerno-mastoid  glands,  785 
Subsylvian  ramus,  924 
Subtemporal  fissure,  932 

gyre,  932 
Subtendinous  iliac  bursa,  333 

synovial  bursa,  265 
Suburethral  gland,  1495 
Sucking  pad,  383 
Suctorial  pad,  383 
Sudoriferous  glands,  1200 
Sulco-marginal  tract  of  cord,  854 
Sulcus  intraparietal  of    Turner, 
930 

lachrymal,  113 

lateralis  mesencephali,  905 

lunatus,  931 

of  Monro,  916 

oculomotorius,  904 

orbito-palpebral,  inferior,  1147 
superior,  1147 

parolfactory  anterior,  935 
posterior,  935 

sagittal,  73,  80 

scleral,  1115 

sigmoid,  86 

spiralis  externus,  1182 
internus,  1182 

terminalis  of  His,  568,  1097 

tympanic,  1159 


Sulcus  tympanicus,  1161 
Supercentral  fissure,  927 
Supercerebellar  veins,  736 
Supercerebral  veins,  735 
Superciliary  ridge,  80 
Superficial     anterior     thoracic 

nerve,  1001 
branches    of    cervical    plexus 

989 

cardiac  .plexus,  1090 
cerebellar  veins,  736 
cerebral  veins,  735 
cervical  artery,  644 
fascia,  388 
glands,  783 
nerve,  990 

region,  muscles  of,  388 
circumflex  iliac  artery,  704 

vein,  756 

crural  arch,  438,  1541 
dorsal  veins  of  penis,  762 
epigastric  artery,  704 
external  pudic  artery,  704 
fascia,  366 

of  abdomen,  434,  1523 
of  arm,  472 
of  back,  413 
of  cranial  region,  368 
of  femoral  region,  514 
of  perinaeum  in  male,  457 
of  shoulder,  472 
of  thoracic  region,  465 
femoral  artery,  701 
inguinal  lymphatic  glands,  791 
long  plantar  ligament,  355 
lymphatic  glands  of  upper  ex- 
tremity, 787 
vessels  of  gluteal  region,  799 
of  lower  extremity,  794 
of  penis,  799 
of  perinaeum,  799 
of  scrotum,  799 
of  upper  extremity,  790 
of  walls  of  abdomen,  799 
muscles  of  abdomen,  434 
palmar  arch,  666 
parotid  lymphatic  glands,  779 
perineal  artery,  691 
sural  artery,  710 
sylvian  vein,  735 
temporal  artery,  612 
nerves,  1052 
vein,  727 
transverse  ligament  of  fingers, 

496 

veins  of  fingers,  745 
of  foot,  756 
of  hand,  745 
of  lower  extremity,  756 
of  upper  extremity,  745 
ventro-lateral  spino-cerebellar 

tract,  852 
Superficialis  colli  nerve,  990 

volse  artery,  661 
Superfrontal  fissure,  927 

gyre,  928,  929,  930 
Superior   acromio-clavicular   lig- 
ament, 301 
astragalo-scaphoid      ligament, 

356 
branch    of    superior    cervical 

ganglion,  1083 

calcaneo-cuboid  ligament,  355 
calcaneo-scaphoid       ligament, 

355 

cardiac  nerve,  1085 
carotid  triangle,  396 
cerebellar  artery,  642 
cerebral  veins,  735 
cervical  ganglion,  1081 
constrictor  muscle,  403 


Superior  coronary  artery  of   lip, 

609 

dental  plexus,  1048 
epigastric  artery,  647 

glands,  800 
fibular  artery,  712 
flexure  of  duodenum,  129a 
gemellus  muscle,  529 
gluteal  nerve,  1027 
hsemorrhoidal  artery,  680 
plexus  of  nerves,'  1095 
veins,  768 
intercostal  artery,  647 

veins,  752 

lachrymal  gland,  1151 
laryngeal  artery,  605 

nerve,  1071 
ligament  of  incus,  1171 

of  malleus,  1170 
lingualis  muscle,  401 
longitudinal  fasciculus,  962 

sinus,  78,  130,  736 
maxillary  bones,  105 
nerve,  1046 

region,  muscles  of,  379 
meatus  of  nose,  101,  144 
mediastinum,  1396 
medullary  velum,  901 
mesenteric  artery,  677 
plexus  of  nerves,  1094 
vein,  768 
nuchal  line,  72 
obliquus  oculi  muscle,  376 
olivary  nucleus,  887 
ophthalmic  vein,  740 
orbito-palpebral  sulcus,  1147 
petrosal  sinus,  742 
phrenic  artery,  646 

veins,  767 

precentral  fissure,  927 
profunda  artery,  657 
pubic  ligament,  298 
pyloric  artery,  675 
radio-ulnar  articulation,  316 
ramus  of  ischium,  218 

of  pubis,  219 
rectus  oculi  muscle,  375 
sacro-sciatic  foramen,  296 
semicircular  canal,  1175 
stephanion,  76,  150 
sterno-pericardiac    ligament. 

560 
superficial  cerebellar  veins,  736 

external  pudic  artery,  704 
surface  of  liver,  1336 
tarsal  arch,  625 
thoracic  artery,  652 
thyroid  artery,  604 

vein,  730 

transverse  ligament,  304 
turbinated  bone,  101 

crest,  117 

vena  cava,  752.     See  Precava. 
vesical  artery,  687 

plexus  of  veins,  761 
vocal  cords,  1378 
Supernumerary  bones,  103 

spleens,  1363 
Superpetrosal  sinus,  742 
Supertemporal  fissure,  932 

gyre,  932 
Supinator  longus  muscle,  486 

radii  brevis  muscle,  489 
Supporting  cells  of  Hensen,  1185 
Supra-acromial  artery,  644 

nerves,  992 
Supraclavicular  glands,  785 

nerves,  991 

Supracommissure  of  Osborn,  915 
Supracondylar    ridge,    external,. 
181 


1607 


Supracondylar     ridge,     internal 

181 
Supracondyloid  glands  of   Leaf 

794 

Supraepitrochlear  glands,  787 
Supraglenoid  tubercle,  176 
Suprahyoid  aponeurosis,  396 
artery,  606 
glands,  lateral,  784 

median,  784 
region,  muscles  of,  396 
Supramandibular  nerves,  1063 
Supramarginal  gyre,  931 
Supramastoid  crest,  84,  137 
Supramaxillary     lymphatic 

glands,  781 
nerves,  1063 
Suprameatal  spine,  88 

triangle,  85 
Supraorbital  arch,  80 
artery,  625 
foramen,  80,  140. 
nerve,  1044 
notch,  80,  140 
ridge,  140 
vein,  726 

Suprapatellar  bursa,  342,  521 
Suprarenal  artery,  680 
capsule,  1437 
arteries  of,  1440 
left,  1438 

lymphatic  vessels  of,  802 
lymphatics  of,  1440 
nerves  of,  1440 
relations  of,  1437 
right,  1437 
structure  of,  1438 
veins  of,  1440 
glands,  1437 

accessory,  1438 
impression  of  liver,  1337 
plexus  of  nerves,  1092 
veins,  767 

Suprascapular  artery,  643 
ligament,  304 
nerve,  1000 
notch,  175 

Suprascleral  lymph-space,  1113 
Supraspinales  muscle,  423 
Supraspinatus  fascia,  474 

muscle,  474 
Supraspinous  fossa,  174 

ligament,  275 
Suprasternal  artery,  644 
nerves,  991 
notch, 411 
space,  389 

Supratonsillar  fossa.  1223 
Supratrochlear  foramen,  183 
glands,  787 
nerve,  1044 
Supravaginal  portion  of  uterus, 

1500 
Surface  form  of  abdominal  aorta, 

672 

of  acromio-clavicular  artic- 
ulation, 303 
of  ankle-joint,  353 
of  axillary  artery,  651 
of  bladder,  1449 
of  bones,  34 
of  brachial  artery,  656 
of  carotid  arteries,  common, 

601 

external.  603 
of  carpus,  206 
of  clavicle.  172 
of    common    iliac    arteries, 

684 

of  dorsalis  pcdis  artery,  714 
of  elbow-joint,  314 


Surface  form  of  external  auditory 

meatus,  1160 
iliac  artery,  684,  696 

of  eyelids,  1152 

of  femoral  artery,  702 

of  femur,  231 

of  fibula,  241 

of  fifth  nerve,  1055 

of  foot,  257,  362 

of  heart,  580 

of  hip,  335 

of  humerus,  185 

of  hyoid  bone,  156 

of  inferior  radio-ulnar  artic- 
ulation, 319 

of  internal  iliac  artery,  695 

of  intestines,  1331 

of  kidney,  1434 

of  knee-joint,  345 

of  lachrymal  gland,  1153 
sac,  1153 

of  liver,  1353 

of  lungs,  1405 

of  metacarpo-phalangeal  ar- 
ticulation, 327 

of  mouth,  1229 

of  muscles  of  abdomen,  450 
of  back,  426 
of  face,  387 
of  head,  387 
of  lower  extremity,  552 
of  upper  extremity,  502 
of  vertebral  region,  411 

of  pancreas,  1360 

of  parotid  duct,  1225 

of  patella,  234 

of  pelvis,  222 

of  plantar  arteries,  719 

of  popliteal  artery,  709 

of  radial  artery,  660 

of  radio-carpal  articulation, 
320 

of  radius,  194 

of  rectum,  1331 

of  scapula,  178 

of  shoulder-joint,  309 

of  skull,  148 

of  spleen,  1366 

of   sterno-clavicular    articu- 
lation, 301 

of  sterno-mastoid   muscle, 
393 

of  sternum,  166 

of  stomach,  1288 

of  subclavian  artery,  637 

of   superior   radio-ulnar   ar- 
ticulation, 316 

of   temporo-mandibular   ar- 
ticulations, 284 

of  tibial  artery,  anterior,  711 
posterior,  716 

of  trachea,  1389 

of  trifacial  nerve,  1055 

of  trigeminal  nerve,  1055 

of  ulnar  artery,  663 

of  vermiform  appendix,  1331 

of  vertebral  column,  69 
Surgical  anatomy  of  abdominal 
aorta,  672 

of  abducent  nerve,  1058 

accessory  nerve,  1074 

of  acromio-clavicular  articu- 
lation, 303 

of  ankle-joint,  353 

of  arch  of  aorta,  594 

of  artery  of  bulb,  692 

of  ascending  pharyngeal  ar- 
tery, 612 

of  auditory  nerve,  1065 

of  axilla,  647 

of  axillary  artery,  651 


Surgical    anatomy     of     axillary 

vein,  748 

of  azygos  veins,  753 
of  bend  of  elbow,  655 
of  bile-duct,  1354 
of  bladder,  1449 
of  brachial  artery,  656 

plexus,  1009 
of  carotid  arteries,  common, 

601 

external,  603 
internal,  623 

gland,  1064 
of  carpus,  207 
of  cavernous  sinus,  740 
of  cervical  fascia,  391 

ganglion,  1087 

plexus,  994 
of  cheeks,  1234 
of  clavicle,  172 
of  colon,  1334 
of    common    iliac    arteries, 

684 

of  conjunctiva,  1154 
of    deep    epigastric    artery, 

698 

of  -descent  of  testicles,  1 472 
of  dorsalis  pedis  artery,  714 
of  duodenum,  1332 
of  ear,  1186 
of  eighth  nerve,  1065 
of  elbow-joint,  314 
of  eleventh  nerve,  1074 
of  emissary  veins,  743 
of  external  iliac  artery,  696 
of  eye,  1144 
of  eyelashes,  1153 
of  eyelids,  1153 
of  facial  artery,  610 

nerve,  1064" 

veins,  726 
of  fascia  of  femoral  region, 

anterior,  517 
of  femoral  artery,  702 
of  femur,  232 
of  fibula,  244 
of  foot,  258,  362 
of  gall-bladder,  1354 
of  glosso-pharyngeal  nerve, 

1067 

of  gums,  1234 
of  hffimorrhoidal  veins,  761 
of  heart,  580 
of  hernia,  1523 
of  hip,  335 
of  humerus,  185 
of  hyoid  bone,  156 
of  hypoglossal  nerve,  1077 
of  inferior  calcaneo-scaphoid 
ligament.  356 

thyroid  artery,  643 
of  innominate  artery,  597 
of  intercostal  artery,  670 

nerves,  1014 

of  internal  iliac  artery,  687, 
695 

jugular  vein,  732 

mammary  artery,  647 

pudic  artery  in  male,  691 
of  intestines,  1331 
of  ischio-rectal  region,  1547 
of  kidney,  1434 
of  knee-joint,  345 
of  lachrymal  gland,  1154 

sac,  1154 

of  lateral  sinus,  739 
of  ligaments  of  vertebra,  281 
of  lingual  artery,  606 
of  lips,  1234 
of  liver,  1354 
of  lumbar  plexus,  1034 


H.OS 


INDEX 


Surgical  anatomy  of  lungs,  1406 
of  lymphatic  glands,  775 
of  lymphatics  of  mammary 

'gland,  811 
of  neck,  786 

of  upper  extremity,  791 
vessels  of  peritoneum,  80( 

of  stomach,  804 
of  male  breast,  1522 
of  mammary  gland,  1520 
of   maxillary   artery,   exter- 
nal, 610 

of  Meibomian  glands,  1 153 
of  membranes  of  cord,  860 
of  middle  meningeal  artery, 

615 

of  mouth,  1234 
of   muscles   of   acromial   re- 
gion, 473 
of  arm,  480 
of  femoral  region,  anterior, 

521 

internal,  525 
posterior,  534 
of  gluteal  region,  531 
of  iliac  region,  513 
of  lateral  thoracic  r.egion, 

471 

of  leg,  544 

of  lower  extremity,  554 
of  orbital  region,  377 
of  palatal  region,  408 
of  radio-ulnar  region,  an- 
terior, 486 
posterior,  493 
of  tongue,  402 
of  upper  extremity ,  505 
of  nasal  fossm,  1112 
of  ninth  nerve,  1067 
of  occipito-frontalis  muscle, 

371 

of  oculomotor  nerve,  1040 
of  oesophagus,  1240 
of  olfactory  nerve,  1038 
of  optic  nerve,  1038 
of  ovary,  1515 
of  palate,  1234 
of  palatine  artery,  617 
of  palmar  fascia,  deep,  496 
of  pancreas,  1360 
of  parathyroid  glands,  1413 
of  patella,  234 . 
of  pelvis,  222 
of  penis,  1470 
of  pericardium,  563 
of  perinseum,  1547 
of  peritoneum,  1274 
of  pharynx,  1234 
of  phrenic  nerve,  993 
of  plantar  arteries,  719 

fascia,  546 
of  pleura,  1395 
of  popliteal  artery,  709 
of  postcava,  766 
of  precava,  753 
of  pronator  radii  teres  mus- 
cle, 481 

of  prostate  gland,  1462 
of  prostatico-vesical  plexus, 

762 

of  radial  artery,  660 
of  radio-carpal  articulation, 

320 

of  radius,  194 
of  rectum,  1333 
of  salivary  glands,  1234 
of  saphenous  veins,  757 
of  scapula,  178 
of  scrotum,  1478 
of  seminal  vesicles,  1487 
of  seventh  nerve,  1064 


Surgical    anatomy  of    shoulder 

joint,  309 

of  sixth  nerve,  1058 
of  skull,  150 
of  spermatic  cord,  1478 

veins,  766 
of  spinal  cord,  860 
of  spleen,  1366 
of  sterno-clavicular  articula- 
tion, 301 
of    sterno-mastoid     muscle 

393 

of  sternum,  167 
of  stomach,  1288 
of  subclavian  artery,  637 
of  superficial  fascia  of  cra- 
nial region,  369 
inguinal  lymphatic  glands 

794 

of  superior  radio-ulnar  artic- 
ulation, 316 
of  synovial  tendons  at  wrist, 

494 

of  tarsal  joint,  358 
of  tarsus,  257 
of  temporal  artery,  613 
of   temporo-mandibular   ar- 
ticulations, 284 
of  tenth  nerve,  1072 
of  testicles,  1484 
of  thoracic  aorta,  668 
of  thyroid  artery,  superior, 

605 

gland,  1411 
of  tibia,  244 
of  tibial  artery,  716 

anterior,  711 
of  tongue,  1103 
of  tonsils,  1234 
of  trachea,  1389 
of  triangles  of  neck,  618 
of  trochlear  nerve,  1041 
of  twelfth  nerve,  1077 
of  ulna,  194 
of  ulnar  artery,  663 
of  ureter,  1437 
of  urethra,  male,  1454 
of  utero-ovarian  artery,  689 
of  uterus,  1508 
of  vagus  nerve,  1072 
of     vermiform     appendix, 

1332 
of  vertebral  artery,  641 

column,  69 
neck  of  humerus,  179 

of  scapula,  173 
Suspensory    ligament    of    axilla, 

466 

of  clitoris,  439 
of  eye,  1115 
of  lens,  1139 
of  liver,  1340 
of  malleus,  1170 
of  mamma,  465 
of  ovary,  1513 
of  penis,  439 
of  Treitz,  1294 
muscle  of  duodenum,  1294 
Sustentacular  cells  of  spleen,  1363 

fibres,  1131 
Sustentaculum  lienis,  1268 

tali,  257 
Sutura,  266 
dentata,  266 
harmonia,  266 
limbosa,  266 
notha,  266 
serrata,  266 
squamosa,  266 
vera,  266 
Sutural  bones,  103 


Sutural  ligament,  261 
membrane,  266,  973 
Suture  or  sutures,  basilar,  128 
coronal,  78,  127 
cranial,  127 
endo-exo-gnathion,  111 
endo-gnathion,  111 
endo-meso-gnathion,  111 
ethmo-frontal,  130 
ethmo-sphenoidal,  130 
exo-gnathion,  111 
frontal,  79,  127 
fronto-malar,  128 
fronto-parietal,  127 
fronto-sphenoidal,    128,    130 
intermaxillary,  139 
internasal,  139 
interparietal,  127 
lambdoid,  75,  78,  128 
masto-occipital,  75,  128 
masto-parietal,  128 
meso-exo-gnathion,  111 
meso-gnathion,  111 
metopic,  83,  127 
naso-maxillary,  139 
occipito-parietal,  128 
petro-occipital,  75,  128,  133 
petro-sphenoidal,  128,  136 
petro-squamous,  88 
sagittal,  78,  127 
spheno-parietal,  128 
squamo-parietal,  128 
squamo-sphenoidal,  128 
squamous,  85,  128 
transverse,  128 

facial,  128 
Sweat-glands,  1200 
Sylvian  cleft,  development  of,  925 
fissure,  924 
vein,  superficial,  735 
Symington,   ano-coccygeal  body 

'  of,  1324 

Sympathetic  nerve,  827 
ganglion  of,  1067 
plexuses  of,  1090 
structure  of,  1079 
Symphysis,  266,  269 
'  of  jaw,  122 

sacro-coccygeal,  66 
Synarthrosis,  266 
Synchondrosis,  266 
Syndesmo-odontoid  joint,  276 
Syndesmosis,  267 
Synovial  bursa,  265 

thecal,  265 
ligaments,  264 
membranes,  264 
articular,  264 
bursal,  265 
of    flexor    tendon    at    wrist, 

494 
surgical  anatomy  of, 

494 

vaginal,  265.     See  also  Indi- 
vidual joints, 
sheaths,  265 
villi,  264 

Systemic  arteries,  585 
veins,  724 


TABLES  of  skull,  33 

Tabular  portion  of  occipital  bone, 

71 

Tactile  corpuscle,  826,  830 
Tsenia  pontis,  906 

semicircularis,  913,  943,  954 

thalami,  912 
Talipes,  541 
Tapetum  of  callosum,  945 


Tapetum  of  choroid,  1124 
lucidum,  1137 
nigrum,  1137 
Tarsal  arch,  625 
artery,  714 

bones,  development  of,  255 
glands,  1149 
joint,    surgical    anatomy    of, 

358 
ligament,  external,  372 

internal,  372 
plates  of  eyelid,  1149 
Tarso-metatarsal      articulations, 

359 
Tarsus,  244 

articulations  of,  354 
surface  form  of,  257 
surgical  anatomy  of,  257 
synovial  membrane  of,  354 
Taste-buds,  1100 
Teeth,  1205 

arrangement  of,  1208 

auditory,  1183 

bicuspid,  1208 

•canine,  1207 

«ementum  of,  1214 

cortical  substance  of,  1214 

deciduous,  1206 

•development  of,  1214 

•enamel  of,  1213 

eruption  of,  1218 

eye,  1207 

general  characters  of,  1205 

grinders,  1208 

incisors,  1207 

Ivory  of,  1212 

milk,  1206 

molar.  1208 

permanent,  1206 

superadded,  1218 
premolars,  1208 
roots  of,  1206 
solid  portion  of,  1211 
stomach,  1207 
structure  of,  1210 
surfaces  of,  1205 
temporary,  1206 
Tegmen  tympani,  87 
Tegmental  tract,  central,  910 
Tegmentum,  hypothalamic  sub- 
stance of,  915 
of  mid-brain,  908 

nucleus  of,  908 
Tela  chorioidea  inferior,  981 

superior,  981 

subcutanea,  1190 

Telancephalon,  911 

Telodendria,  823,  828 

Temporal  artery,  613 

anterior,  613,  642 

from  internal  maxillary,  615 

middle,  613 

posterior,  613,  642 

surgical  anatomy  of,  613 
bone,  83 

articulations  of,  92 
.    attachment    of    muscles    to, 
92 

development  of,  91 

mastoid  portion  of,  85 

petrous  portion  of,  88,  136 
•      squamous  portion  of,  83 
crest,  76,  80,  84 
diploic  vein,  734 
fascia,  384 
fossa,  76,  137 
lines,  76,  80 
lobe,  931 

fissures  of,  931 

gyre  of,  932 
muscle,  384 


INDEX 

Temporal  nerves  from  auriculo- 

temporal,   1052 
deep,  1051 
from  facial,  1046,  1062 

ridges,  76,  80 

veins,  727 

Temporary  teeth,  1206 
eruption  of,  1219 
Temporo-facial  nerve,  1062 
Temporo-malar  filaments,  115 

foramen,  115 

nerve,  1046 

Temporo-mandibular    articula- 
tions, 282 

surface  form  of,  284 
surgical  anatomy  of,  284 

region,  muscles  of,  383 
Temporo-maxillary   articulation, 
138 

vein,  727 

Temporo-pontile  tract,  910,  957 
Tendo  Achillis,  538 
bursa  of,  538 

oculi,  372 
Tendons,  366 

of  diaphragm,  central,  431 
cordiform,  431 

flexor,  fibrous  sheaths  of,  548 
Tenon,  capsule  of,  113 
Tensor  fascia!  femoris  muscle,  517 

palati  muscle,  406 

tarsi  muscle,  373 

tympani  muscle,  1171 

canal  for,  1163 
Tenth  nerve,  1068 

surgical  anatomy  of,  1072 

thoracic  vertebra,  56 
Tentorial  sinus,  738 
Tentorium,  975 
Teres  major  muscle,  475 

minor  muscle,  475 
Terma,  867,  917 
Terminal  arteries,  632 
Testes  gubernaculum,  1471 

muliebres  of  Galen,  1511 

of  quadrigemina,  705 
Testicles,  1471 

coverings  of,  1472 

descent  of,  1471 

gubernaculum  testis,  1471 

lobes  of,  1482 

lymphatic  vessels  of,  802 

mediastinum  testis,  1481 
.    parenchyma  of,  1482 

rete  testis,  1482 

sheaths  of,  proper,  1481 

size  of,  1481 

structure  of,  1482 

surgical  anatomy  of,  1484 

trabeculaj  of ,  1482 

tubuli  seminiferi  of,  1482 

tunica  albuginea,  1482 
vaginalis,  1481 
vasculosa,  1482 

tunics  of,  1481 

weight  of,  1481 
Testicular  bag.  1472 
Thalamencephalon,  911 
Thalami,  867,  912 
Thalamo-cortical  fibres,  914 
Thalamo-frontal  fibres,  956 
Tlialamo-olivary   tract,   886 
Thalamo-striate  fibres,  956 
Thalamus,  912 

connections  of,  914 

fibres  of,  914 

structure  of,  internal,  914 
Thalamic  radiation,  914 
Thebesian  valve,  569,  771 
Thecal  synovial  bursa,  265 
Thigh,  bones  of,  223 


1609 

Thigh,  fascia  of,  514 

muscles  of,  514 
Third  nerve,  1039 

ventricle  of  brain,  869,  916 
Thoracic  aorta,  667 
branches  of,  668 
surgical  anatomy  of,  668 
aortic  plexus,  1087 
artery,  acromial,  653 
alar,  653 
long,  653 
superior,  652 
axis,  653 

cardiac  nerves,  1072 
duct,  775 

structure  of,  777 
ganglion,  1087 
nerves,  1010 

branches  of,  1010 
divisions  of,  1010 
roots  of,  1010 
portion    of    gangliated     cord, 

1087 

of  oesophagus,  1236 
region,  anterior,  fascia  of,  deep, 

465 

superficial,  465 
muscles  of,  465 
lateral,  muscles  of,  471 

surgical  anatomy  of,  471 
surface  of  lungs,  1400 
trachea,  lymphatic  vessels  of, 

813 

vein,  long,  748 
vertebra?,  53 
bodies  of,  53 
eleventh,  56 
first,  55 
laminae  of,  54 
ninth,  55 
peculiar,  55 
pedicles  of,  54 
processes  of,  54 
tenth,  56 
twelfth,  56 
wall,  lymphatic  glands  of,  807 

vessels  of,  810 

Thoracico-epigastric  vein,  748 
Thoracico-lumbar  nerve,  1014 
Thorax,  156 

boundaries  of ,  156 

cavity  of,  558 

fascise  of,  426 

lymphatics  of,  807 

muscles  of,  426 

nerves  of,  cutaneous,  1012 

openings  of,  lower,  558 

upper,  558 
veins  of,  744 
Thumb,  ligaments  of,  323 
metacarpal  bone  of,  203 
muscles  of,  486 
Thymic  artery,  596 

lymphatic  vessels,  813 
Thymus  gland,  1414 
arteries  of,  1415 
lobes  of,  1414 
Ivmphatics  of,  1415 
nerves  of,  1415 
structure  of,  1414 
veins  of,  1415 

Thyro-arytenoid  ligament,    infe- 
rior, 1378 
superior,  1378 
muscle,  1381 

Thyro-epiglottic  ligament,  1375 
Thyro-epiglottideus  muscle,  1381 
Thyro-glossal  duct,  1100,  1407 
Thyro-hyals  of  hyoid  bone,  155 
Thyro-hyoid  ligaments,  1374 
membrane,  1374 


1610 


INDEX 


Thyro-hyoid  muscle,  395 

nerve,  1077 
Thyroid  artery,  inferior,  643 

surgical  anatomy  of,  643 
superior,  604 

surgical  anatomy  of,  605 
axis,  642 
body, 1401 

venous  plexus  on,  751 
cartilage,  1370 
foramen,  220 
ganglion,  1085 
gland,  1407 

accessory,  1409 
arteries  of,  605,  1410 
color  of,  1407 
isthmus  of,  1409 
lobes  of,  1408 
lymphatic  vessels  of,  782 
lymphatics  of,  1411 
nerves  of,  1411 
structure  of,  1409 
surgical  anatomy  of,  1411 
veins  of,  731,  1411 
weight  of,  1407 
nerve,  1086 
notch,  1370 
veins,  accessory,  731 
inferior,  751 
middle,  730 
superior,  730 
Thyroidea  ima  artery,  596 

vein,  751 
Tibia,  234 

articulations  of,  238 
attachment  of  muscles  to,  238 
crest  of,  237 
development  of,  238 
lower  extremity  of,  238 

surfaces  of,  238 
nutrient  artery  of,  7i8 
oblique  line  of,  237 
shaft  of,  237 

surfaces  of,  237 
spinous  process  of,  236 
structure  of,  238 
surface  form  of,  239 
tubercle  of,  236 
tuberosities  of,  236 
upper  extremity  of,  236 
Tibial  artery,  anterior,  710 
branches  of,  712 
peculiarities  of,  711 
relations  of,  711 
surface  marking  of,  711 
surgical  anatomy  of,  711 
posterior,  715 
branches  of,  716 
peculiarities  of,  716 
relations  of,  715 
surface  marking  of,  716 
surgical  anatomy  of,  716 
recurrent,  anterior,  713 

posterior,  712 
bursa,  subcutaneous,  342 
gland,  anterior,  794 
nerve,  1030 

branches  of,  1031,  1033 
veins,  anterior,  758 

posterior,  758 
Tibialis  anticus  muscle,  535 

bursa  of,  535 
posticus  muscle,  541 
Tibio-fibular  articulation,  347 
region,  anterior,  muscles  of,  534 

posterior,  muscles  of,  537 
Tibio-tarsal  ligament,  anterior, 

349 

posterior,  349 

Tissue,  adipose,  pads  of,  265 
areolar,  subserous,  1256 


Tissue,    connective,      subserous 

1256 

elastic,  yellow,  264 
fibrous,  white,  263 
intertubular,  1213 

subarachnoid ,  859 
Tomes'  fibres,  1213 

granular  sheath  of,  1212 
Tongue,  1097 

anterior  portion  of,  1097 

apex  or  tip  of,  1 097 

arteries  of,  1102 

base  or  root  of,  1097 

body  of,  1097 

cerium  of,  1099 

development  of,  1253 

dorsum  of,  1097 

fibrous  septum  of,  400 

fraenum  of,  1097 

glands  of,  1101 

lymphatic  vessels  of,  782 

lymphatics  of,  1103 

margin  of,  1097 

mucous  membrane  of,  1098 

muscles  of,  400,  1102 
extrinsic,  400 
intrinsic,  400 
surgical  anatomy  of,  402 

nerves  of,  1103 

oral  portion  of,  1097 

papillae  of,   1099 

pharyngeal  portion  of,  1097 

posterior  portion  of,  ]  097 

raph^of,  1097 

structure  of,  1098 

surface  of,  1 097 

surgical  anatomy  of,  1103 

veins  of,  1102 

Tongue-like  lobe  of  liver,  1343 
Tonsil,  1223 

arteries  of,  1223 

development  of,  1253 

lingual,  1098 

lymphatics  of,  1223 

nerves  of,  1223 

pharyngeal,  1231,  1234 

surgical  anatornv  of,  1234 

veins  of,  1223 
Tonsillar  artery,  608 

nerves,  1067 
Tooth  germ,  1216 
Torcular,  74,  737 
Touch-corpuscles      of      Meissner 

and  Wagner,  830 
Trabeculse    corpus    cavernosum, 
1468 

of  spleen,  1363 

of  testicle,  1482 
Trachea,  1384 

arteries  of,  643,  1388 

cartilages  of,  1386         v 

fibrous  membrane  of,  1387 

lymphatics  of,  1389 

mucous  membrane  of,  1388 

muscular  fibres  of,  1386 

nerves  of,  1388 

relations  of,  1384 

structure  of,  1386 

surface  form  of,  1389 

surgical  anatomy  of,  1389 

thoracic,  Ivmphatic  vessels  of, 
813 

veins  of,  751,  1388 
Tracheal  arteries,  643 

glands,  786,  1388 

veins,  751 

Trachelo-mastoid .  muscle,  421 
Tract  cells  of  cord,  855 

of  cord,  cerebello-spinal,  853 
conducting,  841 
direct  cerebellar,  852 


Tract  of  cord,  dorso-lateral  spino- 

cerebellar,  852 
functions  of,  844 
intermedio-lateral,    853 
lateral  vestibulo-spinal,  853. 
marginal,  851 
olivo-spinal,  853 
prepyramidal,  853 
pyramidal  crossed,  853 

direct,  854 
rubro-spinal,  853 
spino-mesencephalic,    852. 
spino-olivary,  853 
spino-thalamic,  852 
sulco-marginal,  854 
superficial     ventro-lateral 

spino-cerebellar,  852 
ventral  cerebello-spinal,  854' 

vestibulo-spinal,  854 
fronto-pontile,  910 
geniculate,  956 
of  Cowers,  901 
marginal  of  Spitzka  and  Lis— 

sauer,  852 
motor,  956 

occipito-pontile,  956,  957 
olfactory,  867,  934,  935,  1037 
optic,  1038 

central  connections  of,  917 
pyramidal,  956 
of  crusta,  910 

spino-cerebellar,    ventral,    901 
spino-olivary,  886 
tegmental,  910 
temporo-pontile,  910,  957 
thalamo-olivary,  886 
Tractus    cerebello-tegmentalis, 

901 

peduncularis  transversus,  906 
rubrospinalis,  908,  909 
spino-tectalis    et     thalamicus., 

853 

spiralis  foraminosus,  89 
Tragicus  muscle,  1157 
Tragus,  1155 
Transinsular  fissure,  933 
Transitional  epithelium,  1437 
Transorbital  fissure,  929 
Transparietal  fissure,  931 
Transprecentral  fissure,  928 
Transtemporal  fissure,  932 
gyre,  932 

gray  substance  of,  960 
Transversalis  cervicis  muscle,  421 
colli  artery,  644 

muscle,  421 
fascia,  447,  1529 
humeri  artery,  643 
muscle,  444,  1528 
Transverse   cervical   artery,   644 
colon,  1317 

flexure  of,  splenic,  1317 
diameter  of  pelvis,  210 
facial  artery,  613 
suture,  128 
vein,  727 
fibres  of  pons,  887 
foramen,  50 
humeral  ligament,  307 
ligament  of  acetabulum,  332 
of  atlas,  277 
inferior,  304 
of  knee,  342 
superior,  304 
lingualis  muscle,  401 
mesocolon,  1268,  1317 
metacarpal  ligament,  326 
pelvic  ligament,  461 
perineal  artery,  692 

ligament,  461 
processes  of  a  vertebra,  49> 


1XDEX 


1611 


Transverse  sinus,  743 

of  pericardium,  562 
suture,  128 
Transversus     auricula*     muscle, 

1157 

menti  muscle,  380 
perinei     superficialis     muscle, 

459, 462 
Trapezium,  887 
bone,  200 

articulations  of,  200 
attachment   of   muscles   to, 

200 

surfaces  of,  200 
Trapezius  muscles,  413 
Trapezoid  bone,  200 

articulations  of,  201 
surfaces  of,  200 
ligament,  302 
ridge,  169 
TreiU,  fossa  of,  1270 

suspensory  ligament  of,  1294 
Triangle,  carotid,  inferior,  618 

superior,  396,  619 
of  elbow,  655 
of  election,  619 
Hesselbach's,  1532 
of  necessity,  618 
of  neck,  anterior,  618 
posterior,  620 
surgical  anatomy  of,  618 
occipital,  620 
Petit's,  437 
Scarpa's,  518,  698 
subclavian,  620 
submaxillary,  396,  619 
suboccipital,  425 
suprameatal,  85 
Triangular  cartilage  of  septum  of 

nos«,  1107 
fascia  of  abdomen,  439,  1527 

of  urethra,  460 
interarticular      fibro-cartilage, 

317 

ligament  of  urethra,  460 
muscles,  365 
Triangularis  menti  muscle,  380 

sterni  muscle,  427 
Triceps  extensor   cubiti  muscle, 

479 
Tricuspid  orifice,  569 

valve,  572 
Trifacial  nerve,  1041 

surface  marking  of,  1055 
surgical  anatomy  of,  1055 
Trigeminal  depression,  88 
nerve,  1041 

distribution  and  connections 

of,  1055 
nuclei  of,  894 
afferent,  894 
efferent,  894 

surface  marking  of,  1055 
surgical  anatomy  of,  1055 
Trigone  of  bladder,  1447 
Trigonum  habemi-,  912,  915 
hypoglossi,  880 
lemnisci,  905 
olfactorium,  935 
vagi,  880 
vrntriculi,  944 
vesicse,  1447 
Trigoid  bodies,  822 
Trochanter,  great,  225 

bursa  of,  333 
lesser,  225 

rudimental,  third,  226 
Trochanteric  fossa,  225 
Trochlea  of  femur,  227 

of  humerus,  183 
Trochlear  fossa.  82 


Trochlear  nerve,  1041 
nucleus,  910 
surgical  anatomy  of,  1041 

surface  of  astragalus,  246 
Trochoid,  267 

Trolard,  anastomotic  vein  of,  735 
Troltsch,  recessus  of,  1172 
True  vocal  cords,  1378 
Trunk,  arteries  of,  667 

articulations  of,  271 

fascia*  of,  412 

muscles  of,  412 

of   vagus   nerve,    ganglion   of, 

1069 
Tube  or  tubes,  bronchial,  1384 

egg,  1515 

Eustachian,  1163 

Fallopian,  1510 

lymphatic  vessels  of,  801 

neural,  817 

spiral,  of  Schachowa,  1427 

tonsil,  1165 
Tuber,  867,  917 

cinereum,  917 

Tuberal  lobe  of  ferebellum,  898 
Tubercle,  adductor,  227 

amygdaloid,  945 

carotid,  51 

of  cervical  vertebra,  anterior, 

50 
posterior,  50 

Chassaignac's,  69 

conoid,  169 

comical,  of  Santorini,  1376 

cuneate,  876 

cuneiform,  of  Wrisberg,  1376 

of  Darwin,  1155' 

deltoid,  169 

of  epiglottis,  1373 

of  femur,  225 

genial,  123 

of  hyoid  bone,  155 

infraglenoid,  176 

jugular,  74 

lachrymal,  109 

mental,  122 

of  navicular  bone,  249 

olfactory,  935 

peroneal,  246 

pharyngeal,  73 

pterygoid,  97 

of  quadratus,  226 

of  ribs,  162 

^of  scaphoid,  198 

supraglenoid,  176 

of  tibia,  236 

of  ulna,  188 

of  zygoma,  84 
Tuberculum  acusticum,  880 

anterius,  913 

caudatum,  1340 

cinereum,  876,  884 

impar,  1253 

vestibularis,  880 
Tuberosity,  bicipital,  192 

of  calcaneus,  246 

of  cuboid,  248 

of  femur,  inner,  228 
outer,  228 

of  humerus,  179 

of  ischium,  218 

maxillary,  106 

of  navicular  bone,  249 

of  palate  bone,  117,  135 

of  radius,  192 

of  ribs,  162 

of  sacrum,  63 

of  scaphoid  bone,  249 

of  tibia   external,  236 

internal,  236 
Tubuli,  lactiferi,  1519 


Tubuli  seminiferi,  1482 

uriniferi,  1427 
Tunic  of  Ruysch,  1123 
Tunica  adventitia,  1238 
albuginea,  376,  1467,  1482 
interna,  1130 
propria,  1190 

vaginalis,  1472,  1475,  1481 
cavity  of,  1481 
parietal  portion  of,  1481 
visceral  portion  of,  1481 
vasculosa  testis,  1482 
Tunics  of  eye,  1117 

of  testicle,  1481 

Turbinated  bone,  inferior,  119 
articulations  of,  120 
development  of,  120 
surfaces  of,  120 
middle,  101 
sphenoidal,  143 
superior,  101 
crest,  107,  117 
Tiirck,  bundle  of,  910.     Note. 

fasciculus  of,  854 
Turner,   intraparietal   sulcus   of, 

930 
Twelfth  nerve,  1074 

surgical  anatomy  of,  1077 
thoracic  vertebra,  56 
Tympanic  antrum,  87 
aperture,  1161 

artery  from  ascending  pharyn- 
geal, 612 
from  internal  carotid,  623 

maxillary,  615 
attic,  87 
cavity,  1160 
nerve,  1067 

from  facial,  1061 
plexus  of,  1067 
sulcus,  1159 

Tympanohyal  process,  92 
Tympanomalleolar    ligaments, 

1166 

Tympanum,  1160 
arteries  of,  1172 
cavity  of,  1160 
floor  of,  1161 
fundus  of,  1161 
mucous  membrane  of,  1172 
muscles  of,  1171 
nerves  of,  1173 
ossicles  of,  1168 
pyramid  of,  1163 
roof  of,  1161 
veins  of,  1173 
walls  of,  1163 


ULNA,  186 

articulations  of,  191 

attachment  of  muscles  to,  191 

development  of,  191 

lower  extremity  of,  191 

shaft  of,  190 

structure  of,  191 

surface  form  of,  191 

surgical  anatomy  of,  194 

tubercle  of,  188 

upper  extremity  of,  186 

coronoid  process  of,  186 
olecranon  process  of,  186 
sigmoid  cavities  of,  188 
Ulnar  artery,  662 

peculiarities  of,  663 
surface  marking  of,  663 
surgical  anatomy  of,  663 
groove,  183 
nerve,  1005 


1612 


INDEX 


Ulnar  region,  muscles  of,  500 

veins,  745 
Umbilical  arteries  in  foetus,  583 

686 

fissure  of  liver,  1338 
fossa  of  liver,  1338 
notch,  1338 

region,  contents  of,  1244 
Umbilicus,  lymphatic  vessels  of, 

799 

Umbo,  1167 
Unciform  bone,  201 

articulations  of,  201 
attachment    of    muscles    to, 

201 

process  of  ethmoid,  100 
Uiicinate  fasciculus,  962 
gyre,  932 

process  of  Winslow,  1357 
Uncus,  932,  937 
Ungual  phalanges,  206 
Unipolar  cells,  820 
Unstriated  muscle,  363 
Unstriped  muscle,  363 
Upper  deep  cervical  glands,  785 
extremity,  arteries  of,  633 
articulations  of,  299 
bones  of,  169 
fasciae  of,  464 
lymphatic  glands  of,  787 

vessels  of,  790 
muscles  of,  464 

surface  form  of,  502 
veins  of,  744 
subscapular  nerve,  1001 
Urachus,  1445 
fold  of,  1531 
Ureter,  1435 

arteries  of,  1437 
fibrous  coat  of,  1436 
lymphatic  vessels  of,  802 
mucous  coat  of,  1436 
muscular  coat  of,  1436 
nerves  of,  1436 
orifices  of,  1447 
relations  of,  1435 
structure  of,  1435 
surgical  anatomy  of,  1437 
Ureteral  folds,  1448 
Urethra,  female,  1455 

lymphatic  vessels  of,  801 
mucous  coat  of,  1456 
muscular  coat  of,  1455 
orifice  of,  1493 
structure  of,  1455 
submucous  coat  of,  1456 
male,  1450 
bulb  of,  1468 

cavernous  portion  of,  1452 
crest  of,  1451 
fossa  navicularis  of,  1453 
lymphatic  vessels  of,  801 
membranous  portion  of, 

1451 

mucous  coat  of,  1453 
muscular  layer  of,  1454 

portion  of,  1451 
pendulous  portion  of,  1452 
penile  portion  of,  1452 
prostatic  portion  of,  1450 
spongy  portion  of,  1452 
structure  of,  1453 
submucous  tissue  of,  1454 
surgical  anatomy  of,  1454 
Urinary  bladder.    See  Bladder. 

organs,  1419 
Uterine  artery,  688 

portion     of     Fallopian     tube 

1510 

plexus  of  nerves,  1096 
veins,  763 


Uterine  veins,  plexus  of,  763 
Utero-sacral  ligaments,   1502 
Utero-vaginal  plexu.s,  1095 
Utero-vesical  fold,  1502 

pouch,  1499,  1502 
Uterus,  1498 

abnormalities  of,  1505 

appendages  of,  1509 

arbor  vitse  of,  1505 

arteries  of,  1507 

bicornate,  1505 

body  of,  1499 

cavity  of,  1503 

changes  induced  by  pregnancy 

1505 
at  menstrual  period,  1505 

at  different  ages,  1505 

folds  of,  1501 

fundus  of,  1499 

ganglia  of,  1096 

ligaments  of,  1501 

lymphatic  vessels  of,  801,  150£ 

masculinus,  1451 

mucous  membrane  of,  1504 

muscular  coat  of,  1504 

neck  of,  1500 

nerves  of,  1096,  1508 

after  parturition,  1507 

structure  of,  1503 

supravaginal  portion  of,  1500 

surgical  anatomy  of,  1508 

vaginal  portion  of,  1500 

veins  of,  1508 
Utricle  of  vestibule,  1179 
Uvea,  1128 
Uvula  of  throat,  1221 

vesicse,  1447 
Uvular  lobe  of  cerebellum,  898 


VAGAL,     accessory      portion      of 

accessory  nerve,  1073 
Vagina,  1495 
arteries  of,  1497 
azygos  arteries  of,  688 
columns  of,  1496 
erectile  tissue  of,  1497 
lymphatic  vessels  of,  802,  1 49 
mucosa  intertubercularis,  306 

membrane  of,  1496 
muscular  coat  of,  1496 
nerves  of,  1497 
orifice  of,  1493 
relations  of,  1496 
rugse  of,  1496 
structure  of,  1496 
veins  of,  1497 
vestibule  of,  1493 
Vaginal  artery,  688 
bulb,  1495 
fornix,  1496 
plexus  of  nerves,  1096 
portion  of  uterus,  1 500 
process  of  temporal  bone,  90 
synovial  membrane,  265 
veins,  763 

plexuses  of,  763 
Vagus    nerve,    ganglion    of    root 

of,  1069 

of  trunk  of,  1069 
nuclei  of,  890 
afferent,  890 
efferent,  891 

surgical  anatomy  of,  1072 
Valentin,  ganglion  of,  1047 
Vallecula,  895 
epiglottica,  1373 
sylvii,924 
Vallev  of  cerebellum,  890,  891 


Valsalva,  sinuses  of,  aortic,  575 

pulmonary,  573 
Valve  or  valves,  anal,  1326 
of  Bauhin,  1315 
bicuspid,  574 
coronary,  569 
Eustachian,  569 

in  foetus,  581 
of  Gerlach,  1301 
of  Guerin,  1453 
of  Hasner,  1152 
Houston's,  1326 
ileo-CEecal,  1315 
of  Kerkring,  1299 
of  Morgagni,  1326 
pyloric,  1280 
rectal,  1326 
semilunar,  1326 

aortic,  574 

pulmonic,  573 
Thebesian,  569,  771 
tricuspid,  572 
Valvula,  879,  895,  901 
Valvulze  conniventes,  1299 
Vas  deferens,  1482 

artery  of,  687 

lymphatic  vessels  of,  802 

structure  of,  1483 
spirale,  1183 
Vasa  brevia  arteries,  676 
intestini  tenuis  artery,  677 
vasorum  of  arteries,  588 
Vascular  papillae,  1191 

system  at  birth,  changes  in, 
584 

in  foetus,  581 
Vasomotor  fibres,  826 

nerves,  1081 
Vastus  externus  muscle,  520 

internus  muscle,  520 
Vater,  ampulla  of,  1352 

corpuscles  of,  830 
Vegetative  muscle,  363 
Veins,  721 

of  abdomen,  755 
anastomotic,  of  Troland,  735 
angular,  726 
appendicular,  768 
of  arm,  744 
auditory,  1186 
auricular,  727 
axillary,  747 
azvgos,  752 

larger,  752 

left  lower,  753 
upper,  753 

right,  752 

smaller,  753 
basilar,  735 
basilic,  746 

median,  746 
of  bones,  41 
brachial,  747 
brachio-cephalic,  750 
bronchial,  753 
buccal,  726 
cardiac,  770 
cava,  inferior,  764 

superior,  752 
cephalic,  747 

median,  746 
cerebellar,  736 
cerebral,  734 
cervical,  anterior,  deep,  733 

posterior,  deep,  733 
choroid,  735 
circumflex,  iliac,  759 

superficial,  756 
companion,  747 
coronary,  768 
costo-axillary,  748 


INDEX 


1613 


Veins,  cystic,  7ti!> 
digital,  hand,  745 
of  diploe,  733 
dorsal,  of  penis,  762 
dorsi-spinal,  7V! 
dorso-meilian,  736 
of  dura  of  brain.  974         g 
dural,  730,  7*1 
emissary,  743 
emulgent,  766 
epigastric,  deep,  759 

superficial,  756 
of  face,  exterior  of,  725 
facial,  726 
femoral,  758 

of  fingers,  superficial,  745 
of  foot,  758 
frontal,  725 
of  Galen,  735 
gastric,  768 
gluteal,  761 
ha-morrhoidal,  external,  760 

inferior,  760 

middle,  760 

superior,  768 
of  hand,  superficial,  745 
of  head,  724 
of  heart,  580 
hepatic,  767 
histology  of,  722 
hvpogastric,  760 
iliac,  circumflex,  deep,   759 

common,  764 

external,  759 

internal,  760 
ilio-lumbar,  7(>4 
innominate,  750 
intercostal,  752 
interosseous,  of  forearm,  747 
intervertebral,  755 
intralobular,  767 
jugular,  728 
laryngeal,  inferior,  751 
lingual,  729 

longitudinal,  inferior,  738 
of  lower  extremity,  755 
lumbar,  765 

ascending,  753,  765 

right,  752 

mammary,  internal,  750 
masseteric,  727 
maxillary,  internal,  727 
median,  745 

anterior,  736 

posterior,  736 
medicerebral,  735 
medidural,  734 
medulli-spinal,  755 
meningeal,  730,  734 
meningo-rachulian,  754 
mesenteric,  768 
of  muscle,  364 
naso-frontal,  740 
of  neck,  724 
of  oblongata,  736 
obturator,  761 
occipital,  727 
oeaophageai,  751 
ophthalmic,  740 
orbital.  727 
ovarian,  766 
palatine,  727 
palmar,  deep,  747 
pancreatic,  768 
of  pelvis,  755 
pharyngeal,  730 
phrenic,  767 
of  pia  of  brain,  982 
plantar,  758 
plcstis  of,  palmar,  745 

paropinniform,  765 


Veins,  plexus  of,  pharyngeal,  730 

prostatic,  761 

prostatico-vesical,  761 

pterygoid,  727 

spermatic,  765 

spinal,  753  ' 

on  thyroid  body,  751 

uterine,  763 

vaginal,  763 

vesical,  inferior,  763 

superior,  761 
popliteal,  758 
portal,  769 

system  of,  768 
postcava,  764 
precava,  752 
profunda  femoris,  759 
pterygoid  plexus,  727 
pudic,  760 
pulmonary,  723 
pyloric,  768 
radial,  745 

deep,  747 
ranine,  729 
renal,  767 
sacral,  lateral,  760 

middle,  764 
saphenous,  756 
sciatic,  761 
spermatic,  765 
spinal,  753 
splenic,  768 
subcerebellar,  736 
subcerebral,  735 
subclavian,  749 
sublobular,  767 
submaxillary,  727 
supercerebellar,  736 
supercerebral,  735 
supraorbital,  726 
suprarenal,  767 
sylvian,  superficial,  735 
systemic,  724 
temporal,  727 
temporo-maxillary,  727 
thoracic,  long,  748 
thoracico-epigastric,  748 
of  thorax,  744 
thyroid,  accessory,  731 

gland,  731 

inferior,  751 

middle,  730 

superior,  730 
thyroidea  ima,  751 
tibial,  758 
tracheal,  751 
ulnar,  745 

of  upper  extremity,  744 
uterine,  763 
vaginal,  763 
velar,  735 
ventricular,  735 
ventro-median,  736 
vennian,  735 

of  vertebrae,  bodies  of,  755 
vertebral,  732,  751 
Vidian,  730 
Vela,  medullary,  901 
Velar  veins,  735 
Velum,  881,  895,  902,  946,  981 
interpositum,  912,  946 
medullary,  901 

anterior,  901 

inferior,  901 

posterior,  901 

superior,  901 
pendulum,  palati,  1221 
Vena  azygos  major,  752 

minor,  753 

basis  vertebra?,  49,  755 
cava,  ascending,  764 


Vena    cava,    inferior,    764.     See 

Postcava. 

superior,  752.     See  Precava. 
magna  Galeni,  735 
Vena?  basis  vertebrarum,  755 
comites,  723,  747 
corporis  striati,  735 
interlobulares  of  kidney,  1432 
Thebesii,  771 
vorticosse,  1123 
Venesection,  746 
Venous  arch,  nasal,  725 
plexus,  intraspinal,  732 
on  thyroid  body, 751 
Venter  ilii,  216 

of  scapula,  172 
Ventral  cerebello-spinal   tract  of 

cord,  854 

column  of  spinal  cord,  840 
crusta,  905 

fissure  of  oblongata,  874 
horn-cells  of  cord,  856 

of  cornua,  844 
lamina  of  brain,  870 
root  of  spinal  cord,  836 

nerve,  982  • 

spinal  artery,  640 
spino-cerebellar  tract,  901 
vestibulo-spinal  tract  of  cord, 

854 

white  commissure  of  cord,  854 
Ventricle  of  brain,  fifth,  920,  921 , 

941 

fourth,  878 
lateral,  941 
third,  869,  916 

infundibular  recess  of,  917 
Verga's  951 
of  heart,  fibres  of,  577 

left,  chordae  tendinese  of,  575 

columnar  carnea;  of,  575 
right,  571 

chordae  tendineae  of,  572 
columnar  carneae  of,  572 
of  larynx,  1379 
Ventricular  portion  of  heart,  570 

veins,  735 

Ventro-lateral  fissure,  875 
Ventro-median  fissure,  874 
Ventro-paramedian     fissure    of 

spinal  cord,  839 
vein,  736 

Verga's  ventricle,  951 
Vermian  vein,  735 
Vermiform  appendix,  1311 
arteries  of,  1313 
canal  of,  1312 
lymphatics  of,  1314 
mesentery  of,  1269 
mucous  membrane  of.  1313 
muscular  coat  of,  1312 
'  serous  coat  of,  1312 
structure  of,  1312 
subjnucous  coat  of,  1313 
surface  form  of,  1331 
surgical  anatomy  of,  1332 
veins  of,  1313 
Vermis,  895 

Verrucas  gyri  hippocampi,  933 
Vertebras,  48 

bodies  of,  veins  of,  755 
centrum  of,  48 
cervical,  49 

seventh,  53 
coccygeal,  61 
development  of,  58 
dorsal,  53 
false,  61 

general  characters  of,  48 
immovable,  61 
ligaments  of,  272 


DR.  M.  LEWIS  h  MER: 
1614  INDEX 


Vertebrae,  lumbar,  56 

fifth,  57 

process  of,  articular,  49 
spinous,  49 
transverse,  49 
prominens,  53 
sacral,  61 
structure  of,  58 
thoracic,  53 

peculiar,  55 

Vertebral  aponeurosis,  413,  418 
artery,  639 

surgical  anatomy  of,  641 
border  of  scapula,  176 
canal  49 
column,  48 

articulations  of,  271 
surface  form  of,  69 
surgical  anatomy  of,  69 
foramen,  49 
groove,   156 
ligaments,  272 
plexus  of  nerves,  1086 
region,    muscles    of,    anterior, 

408,  411 
lateral,  410 
ribs,  161 
vein,  732,  751 

Vertebrarterial  foramen,  50 
Vertebro-chondral  ribs,  161 
Vertebro-pericardial  ligaments. 

560 

Vertebro-pleural  ligament,   139C 
Vertebro-sternal  'ribs,'  101 
Vertex  of  skull,  129,  150 
Vertical  lingualis  muscle,  401 

plate  of  palate  bone,  117 
Verumontanum,  1451 
Vesical  arteries,  687,  688 
plexus  of  nerves,  1095 
of  veins,  inferior,  762 

superior,  761 
trigone,  1447 
Vesicle,  prostatic,  1451 
Vesicles  of  brain,  864 

optic,  865 
Graafian,  1514 
seminal,  1486 

Vesico-uterine  ligament,   1502 
Vesicula  prostatica,  1450 
Vestibular  artery,  1186 
ganglion,  1065 
nerve,  1065 

branches  of,  1065 
nuclei  of,  893 
window,  1162 
Vestibule,      aortic,     of      Sibson, 

574 

of  ear,  1174 
of  mouth,  1204 
of  nose,  1109 


Vestibule  of  vagina,  1491 
Vestibulo-spinal   tract,  of    cord, 

lateral,  853 
ventral,  854 
Vestigial  fold  of  pericardium,  563 
Vibrissse,  1106 
Vicq  d'Azyr,  band  of,  939 

bundle  of,  914,  916 
Vidian  artery,  617 

canal,  96,  135 

nerve,  1049 

veins,  730 

Vieussens,  ansa  of,  1086 
Villi  of  small  intestine,  1300 

synovial,  264 

Viscera,  development  of,  1245 
Visceral  cranium,  71 

layer  of  pleura,  1391 

lymphatics,  808 

peritoneum,  1257 

portion    of    tunica    vaginalis, 
1481 

surface  of  liver,  1336 

of  stomach,  1278 
Visual  axis,  1116 

purple,  1130 
Vitreous  body,  1139 

humor  of  eye,  1139 

table  of  skull,  34 
Vocal  cords,  false,  1378 
true,  1378 

process,  1373       > 
Voice,  organs  of,  1369 
Volar  interosseous  nerve,  1004 
Volkmann's  canals,  38 
Voluntary  muscle,  363 
Vomer,  120 

alse  of,  121,  143 

articulations  of,  122 

development  of,  122 

surfaces  of,  121 
Vomerine  cartilage,  1107 
Vortex  of  heart,  578 
\Vilvo-vaginal  gland,  1495 


W 

WALDEYER,  germinal  epithelium 
of,  1513 

odontoblasts  of,  1211 
Wedge  bones,  249 
Wharton's  duct,  1226 
White  commissure  of  cord,  854 

fibrous  tissue,  263 

line  of  Hilton,  1327 

substance  of  cord,  848,  856 
W ilder,  post-oblongata  of,  874 
Willis,  circle  of,  631,  642 
Winslow,  accessory  anterior  cru- 
ral nerve  of,  1020 


Winslow,  ligament  of,  posterior, 
337 

uncinate  process  of,  1357 
Wirsung,  canal  of,  1359 
Wornb,  1498 
Worm  of  cerebellum,  895 
Wormian  bones,  103 

development  of,  104 
Wrisberg,    cardiac    ganglion    of. 
1090 

cartilages  of,  1373 

cuneiform  tubercle  of,  1376 

ligament  of,  341 

nerve  of,  1003 

pars  intermedia  of,  1059 
Wrist,  articulations  of,  319 

bursa  of,  494 
Wrist-joint,  319 

ligament  of,  320 

surface  form  of,  320 

surgical  anatomy  of,  320 


XIPHO-PERICARDIAL    ligament, 

561 

Xiphoid  appendix,  159 
surfaces  of,  159 

cartilage,  157 


Y-LJGAMENT,  330 

Yellow  elastic  tissue,  264 
spot  of  Sommerring,  1131 

Z 

ZINN,  ligament  of,  375 

zonule  of,  1139 
Zona  arcuata,  1183 

fasciculata,  1439 

glomerulosa,  1439 

orbicularis,  329 

pectinata,  1183 

reticularis,  1439 

tecta,  1183 

Zones  of  brain,  longitudinal,  870 
Zonula  ciliaris,  1139 
Zonule  of  Zinn,  1139 
Zygoma,  84 
Zygomatic  arch,  138 
'fossa,  138 

lymphatic  glands,  781 

process  of  malar,  115 

of  temporal  bone,  84 
Zygomaticus  major  muscle,  379 

minor  muscle,  379 
Zymogen  granules,  1352 


f 


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